United States Office of Water and SW 176C.8
Environmental Protection Waste Management October 1979
Agency Washington, D.C. 20460
Solid Waste
&EPA European Refuse Fired
Energy Systems
Evaluation of Design Practices
Volume 8
-------
Pizpubtication >t64ae rfo*. EPA
and State. Sotid Wa&te. Management Agencies
EUROPEAN REFUSE FIRED ENERGY SYSTEMS
EVALUATION OF DESIGN PRACTICES
Zurich: Hagenholz
Switzerland
Thit> tsu.p tiupoit. (SW-176c.8}
A the. 0^4.c.e. o£ Sotid Watte. undeA c.ont^act no. 68-01-4376
and -ta n.ep>wdu.c.e.d a& lece/tved ^om the. contSLactoi.
The. |J>cw£cng4 bkouLd. be. att>u.bute.d to the. contsiactoi
and not to the, O^-tce o£ Sotid
Copies will be available from the
National Technical Information Service
U.S. Department of Commerce
Springfield, VA 22161
Volume 8
U.S. ENVIRONMENTAL PROTECTION AGENCY
1979
I'.1 rr.vlro-rr.rr.t:! Bisection
-------
This report was prepared by Battelle Laboratories, Columbus, Ohio,
under contract no. 68-01-4376.
Publication does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of commercial products constitute endorsement by the U.S.
Government.
An environmental protection publication (SW-176c.8) in the solid waste
management series.
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TRIP REPORT
to
ZURICH: HAGENHOLZ, SWITZERLAND
(FEATURING UNIT #3 AND COMMENTING ON
THE NEW JOSEFSTRASSE PLANT)
on June 8, 9, and 10, 1977
on the contract
EVALUATION OF EUROPEAN
REFUSE FIRED STEAM GENERATOR
DESIGN PRACTICES
to
U.S. ENVIRONMENTAL PROTECTION AGENCY
December 20, 1977
EPA Contract Number: 68-01-4376
Battelle Project Number: G-6590
EPA-RFP Number: WA-76-B146
Philip R. Beltz
and
Richard B. Engdahl
BATTELLE
Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
-------
1
PREFACE
This trip report is one of a series of 15 trip reports on
European waste-to-energy systems prepared for the U.S. Environmental
Protection Agency. The overall objective of this investigation is to
describe and analyze European plants in such ways that the essential
factors in their successful operation can be interpreted and applied
in various U.S. communities. The plants visited are considered from
the standpoint of environment, economics and technology.
The material in this report has been carefully reviewed by the
European grate or boiler manufacturers and respective American licensees.
Nevertheless, Battelle Columbus Laboratories maintains ultimate responsi-
bility for the report content. The opinions set forth in this report are
those .of the Battelle staff members and are not to be considered by EPA
policy.
The intent of the report is to provide decision making in-
formation. The reader is thus cautioned against believing that there is
enough information to design a system. Some proprietary information has
been deleted at the request of vendors. While the contents are detailed,
they represent only the tip of the iceberg of knowledge necessary to de-
velop a reliable, economical and environmentally beneficial system.
The selection of particular plants to visit was made by Battelle,
the American licensees, the European grate manufacturers, and EPA. Pur-
posely, the sampling is skewed to the "better" plants that are models of
what the parties would like to develop in America. Some plants were selected
because many features envolved at that plant. Others were chosen because
of strong American interest in co-disposal of refuse and sewage sludge.
The four volumes plus the trip reports for the 15 European
plants are available through The National Technical Information Service,
Springfield, Virginia 22161. NTIS numbers for the volumes and ordering
information are contained in the back of this publication. Of the 19
volumes only the Executive Summary and Inventory have been prepared for
wide distribution.
-------
ii
ORGANIZATION
The four volumes and 15 trip reports are organized the the
following fashion:
VOLUME I
A EXECUTIVE SUMMARY
B INVENTORY OF WASTE-TO-ENERGY PLANTS
C DESCRIPTION OF COMMUNITIES VISITED
D SEPARABLE WASTE STREAMS
E REFUSE COLLECTION AND TRANSFER STATIONS
F COMPOSITION OF REFUSE
G HEATING VALUE OF REFUSE
H REFUSE GENERATION AND BURNING RATES PER PERSON
I DEVELOPMENT OF VISITED SYSTEMS
VOLUME II
J TOTAL OPERATING SYSTEM RESULTS
K ENERGY UTILIZATION
L ECONOMICS AND FINANCE
M OWNERSHIP, ORGANIZATION, PERSONNEL AND TRAINING
VOLUME III
P REFUSE HANDLING
Q GRATES AND PRIMARY AIR
R ASH HANDLING AND RECOVERY
S FURNACE WALL
T SECONDARY (OVERFIRE) AIR
VOLUME IV
U BOILERS
V SUPPLEMENTARY CO-FIRING WITH OIL, WASTE OIL AND SOLVENTS
W CO-DISPOSAL OF REFUSE AND SEWAGE SLUDGE
X AIR POLLUTION CONTROL
Y START-UP AND SHUT-DOWN
Z APPENDIX
-------
LIST OF PERSONS CONTACTED
Max Baltensperger Chief of Waste Disposal and Cleaning (Abfuhrwesen)
for City of Zurich
Erich Moser Technical Assistant Chief
R. Hirt Professor at Zurich Technical Institute
(conducted study of ash disposal)
Herr Lackmann Hagenholz Operations Manager
Herr Widmer Hagenholz Engineering Manager or Administration
Manager
Heinz Kauffmann Projects Manager, Martin, Munich, West Germany
George Stabenow Consultant to UOP, East Stroudsburg, Pennsylvania, U.S.A.
Herr Puli Hagenholz Assistant Operations Manager
The authors are glad to acknowledge the skilled assistance
and kind hospitality provided by these representatives.
-------
TABLE OF CONTENTS
Page
SUMMARY 1
STATISTICAL SUMMARY 5
OVERALL SYSTEM SCHEMATIC 9
COMMUNITY DESCRIPTION 9
Geography 9
SOLID WASTE PRACTICES 14
Solid Waste Generation 14
Solid Waste Collection 21
Solid Waste Transfer Activity 21
Source Separation Programs 22
DEVELOPMENT OF THE SYSTEM 23
Background 23
Beginning of Subject System 27
Building the Subject System 28
Next System Under Construction (Josefstrasse) 28
PLANT ARCHITECTURE AND AESTHETICS 29
Plant Design 29
Rendering Plant Gases (see also Secondary Air section) . 29
Comment 32
TOTAL OPERATING SYSTEM 34
The 4,000 Hour Cycle Between Boiler Cleanings ... 39
REFUSE FIRED STEAM GENERATOR EQUIPMENT 43
Waste Input 43
Weighing Operation 43
Provisions to Handle Bulky Waste 44
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TABLE OF CONTENTS
(Continued)
Page
Waste Storage and Retrieval 47
Furnace Hoppers 50
Feeders 50
Primary (Underfire) Air Source and Air Preheater .... 51
Secondary (Overfire) Air 52
Burning Grate 56
Complete Boiler 58
One Day's Flue Gas Temperature, C0? Level and Steam
Production Recordings 60
Furnace Walls (Combustion Chamber—First, Second, and
Third Passes) 63
Screen Tubes 66
Superheater (and Attemperator) 67
Boiler Cleaning 69
Convection Section 72
Economizer 72
Boiler Water Treatment 73
Boilers for Firing With Fuel Oil, Waste Oil, and
Solvents 73
LITTLE OR NO CORROSION AT ZURICH: HAGENHOLZ UNIT #3 78
27 Design Steps Taken at Hagenholz to Reduce Metal Wastage . . 78
Management . 79
Automatic Control • 79
Start-up Procedures 79
Refuse Handling . 79
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TABLE OF CONTENTS
(Continued)
Page
Secondary Air 80
Furnace Walls 80
Superheater 81
Economizer 81
Theory of Corrosion Supplied by Richard Tanner Formerly
of Von Roll 83
General Theory of Temperature and Chloride Corrosion as
Supplied by Dale Vaughan of Battelle 83
ENERGY UTILIZATION 87
Hagenholz Refuse Fired Steam Generator 87
New Oil Fired Energy Plant 87
Electricity Generation 91
District Heating 91
ENERGY MARKETING 100
POLLUTION CONTROL EQUIPMENT 101
Mechanical Collectors 101
Electrostatic Precipitators . . 101
Stack Construction 104
Fly Ash 105
War-'. Water Discharge 105
Noise , 106
Air Cooled Steam Condensers 106
ASH RECOVERY 108
PERSONNEL AND MANAGEMENT 120
Start-up Procedure 123
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TABLE OF CONTENTS
(Continued)
Page
ECONOMICS 126
Capital Investment 117
Annual Costs 126
Annual Revenues 126
FINANCE 135
REFERENCES 136
LIST OF TABLES
Table 8-1. Solid Waste Delivered to Zurich: Hagenholz in 1976
(Volume and Weight) 17
Table 8-2. Composition of Municipal Solid Waste in Switzerland,
U.S.A., and Britain 18
Table 8-3. Energy Values of Selected Waste Types (Dry) 19
Table 8-4. Average Chemical Composition of Municipal Solid Waste
in Switzerland 20
Table 8-5. Comparison of Zurich: Hagenholz Incinerator Perform-
ance, 1974 35
Table 8-6. Report of Operations 1974 and 1976 36
Table 8-8. Capital Investment Cost (1969) for Units #1 and #2 and
Other Buildings at Zurich: Hagenholz 127
Table 8-9. Capital Investment Costs (1972) for Unit #3 ard the
Water Deaeration Tanks and Room at Zurich: Hagenholz . 128
Table 8-10. Annual 1976 Operating, Maintenance, Interest, and
Other Costs for Zurich: Hagenholz Units #1, #2, and #3 129 to 130
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LIST OF TABLES
(Continued)
Page
Table 8-11. Annual 1976 Revenues for Zurich: Hagenholz Units
#1, #2, and #3 132
LIST OF FIGURES
Figure 8-1. Facility Cross-Sectional View of the Designs at
Zurich: Hagenholz 10
Figure 8-2. Furnace/Boiler Cross-Sectional View of the Zurich:
Hagenholz Unit #3 13
Figure 8-3. Refuse Burned at the Zurich Josefstrasse and
Hagenholz Plants from 1905 to 1976, Tonnes per Year . 15
Figure 8-4. 1976 Weekly Refuse Collections in Zurich 16
Figure 8-5. Artist Sketch of the 1904 Refuse Fired Steam and
Electricity Generator as Manufactured by Horsfall-
Destructor Co. at its Location on Josefstrasse in
Zurich 24
Figure 8-6. Views of the Zurich: Hagenholz Refuse Fired Steam
Generator 30
Figure 8-7. Horizontal Ventilation Air Pipe from Rendering Plant
to Zurich: Hagenholz Plant 31
Figure 8-8. Overhead View of Zurich: Hagenholz 33
Figure 8-9. Steam Production, Flue Gas Temperatures and CO- Levels
(Weekly Average) During the 4000 Hour Operating Cycle
Between Cleaning at Zurich: Hagenholz Unit #3 .... 40
Figure 8-10. Steam Production, Flue Gas Temperatures, and C0? Levels
(Weekly Average) During the 4000 Hour Operating Cycle
Between Cleaning at Zurich: Hagenholz Unit #3 .... 41
Figure 8-11. (a) Von Roll Shear Opening at Zurich: Hagenholz ... 45
Figure 8-11. (b) Elevation and Plan Views of Von Roll Shear .... 46
Figure 8-12. Tipping Floor 48
Figure 8-13. Refuse Receiving Pit Zurich: Hagenholz 48
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LIST OF FIGURES
(Continued)
Page
Figure 8-14. Anonymous Furnace Where Secondary Overfire Air
is Very Little or Totally Lacking 53
Figure 8-15. Hagenholz Unit #3 Where Secondary Overfire is
Plentiful 55
Figure 8-16. Martin Burning Grate (not Zurich: Hagenholz) ... 57
Figure 8-17. Furnace/Boiler Cross-Sectional View of the Zurich:
Hagenholz Unit #3 59
Figure 8-18. Boiler Tube Sections Layout at Zurich: Hagenholz #3 61
Figure 8-19. First Pass Walls Covered with Silicon Carbide over
Welded Studs: Shows Rejection of Slag from Walls at
Zurich: Hagenholz 65
Figure 8-20. Superheater Flue Gas and Steam Temperature and
Flow Patterns at Zurich: Hagenholz 68
Figure 8-21. Superheater Flue Gas and Steam Temperature and Flow
Patterns at the New Zurich: Josefstrasse Plant and
at the Yokohama, Japan Martin Plant 70
Figure 8-22. Water Consumption per tonne of Refuse Consumed in
1976 76
Figure 8-23. Corrosion Threat on Plain Carbon Steel 84
Figure 8-24. (a) Electrical Power Generation Room 89
Figure 8-24. (b) Steam and Boiler Feedwater Flow Pattern Exter-
nal to the Zurich: Hagenholz Boiler 89
Figure 8-25. Tonne Steam Produced per tonne of Refuse Consumer
(1976 Average was 2.41) 90
Figure 8-26. KWH Electrical Sales per tonne of Refuse Consumed . 90
Figure 8-27. 1976 Heat Delivery to Kanton and Rendering Plant
and Steam to EWZ from Zurich: Hagenholz 93
Figure 8-28. Kanton District Heating System (5.3 km long) Using
260 C (500 F) Steam at Zurich, Switzerland .... 94
Figure 8-29. Entrance to Walk-Through District Heating Tunnel at
Zurich: Hagenholz 95
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LIST OF FIGURES
(Continued)
Page
Figure 8-30. Cross-Section Schematic of Pipes in the District
Heating Supply and Return Tunnel at Zurich:
Hagenholz 96
Figure 8-31. General View of Energy Distribution from Zurich:
Hagenholz 97
Figure 8-32. 1976 Energy Delivery (Warmeabgabe) to the Railroad
Station, the KZW and EWZ 99
Figure 8-33. Cooling Tower at Hagenholz 107
Figure 8-34. Partially Processed Residue at Hagenholz 109
Figure 8-35. Segregated Bulky Residue From Furnaces at Hagen-
holz 112
Figure 8-36. Truck Discharing Plant Residue at Hagenholz .... 113
Figure 8-37. Front-End Loader Delivering Residue To Hagenholz
Processing System 114
Figure 8-38. Worker Removing Wire From Waste Processing Conveyor
At Hagenholz 115
Figure 8-39. Small Size Metal From Hagenholz Residue-Processing
Plant 116
Figure 8-40. Medium and Large Metallics From Hagenholz Residue-
Processing Plant 117
Figure 8-41. Non-Ferrous Sized Residue For Roadbuilding at Hagen-
holz 118
Figure 8-42. Test Slabs At Hagenholz Containing Sized Residue. . 119
Figure 8-43. Organization Chart For Municipal Functions In The
City of Zurich: Switzerland 121
Figure 8-44. Organization Chart For Waste Collection And Disposal
In Zurich, Switzerland 122
Figure 8-45. Total Personnel (Collecting and Disposal) Working
For Abfuhrwesen: The City of Zurich 125
Figure 8-46. Cost of Zurich Cleansing Department Since 1928 . . 131
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SUMMARY
This report discusses the Zurich: Hagenholz refuse fired steam
generation plant. Units #1 and #2 are only occasionally mentioned. Unit #3
was manufactured by Martin and is featured in the discussion. The report
also refers to the two older Josefstrasse plants (now demolished) and the
new Josefstrasse plant by Martin due to begin operations in 1979. All
plants and units are described to present the picture of the refuse fired
steam generation (RFSG) technology as it evolved in Zurich.
The Hagenholz plant is located in the Zurich suburb of that
name. In 1976, all three units burned about 218,342 tonnes (240,176 tons)
as collected from a 560,000 person area. It was a surprise to many that
the lower heating value had doubled since the end of World War II. This
has had both negative and positive effects on plant operations.
The plant is owned and operated by Abfuhrwesen, the City of
Zurich's Department for Refuse Collection and Disposal.
Abfuhrwesen collects about 56% of the plants input while 18%
comes from other municipalities and 26% from private haulers and businesses.
In addition to municipal solid waste, the plant also receives
waste oil, waste solvents, and other chemicals.
Ajoining the RFSG plant is a new rendering plant also under the
control of Abfuhrwesen. A delightful feature is that odiferous rendering
gases are collected and injected into the RFSG furnaces as secondary air.
No objectional odor is thus emitted from either plant.
Zurich began converting waste to energy almost 75 years ago (1904)
at Josefstrasse. A second Josefstrasse plant was built in 1927. Hagenholz
Units #1 and #2 were operational in 1969. Hagenholz Unit #3 started in
1973. Now the third Josefstrasse unit is due to begin in 1979.
Unit #3 is routinely stopped every 1000 hours for eight hours to
conduct inspections. The unit is also stopped every 4,000 hours for major
inspection and repair. An excellent set of steam and temperature readings
over the 4000 hour cycle have been provided by the plant personnel.
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ZURICH-HAGENHOLTZ
While the entire Hagenholz plant burns 570 to 700 tonnes per day,
Unit #3 burns 240 to 450 tonnes per day. Household waste and bulky waste
that has been sheared are fed into the furnaces.
Both the primary (underfire) air and the secondary (overfire)
air are injected into the furnace at very high pressures, overfire air at
500 to 700 mmWs (20 to 28 inches) . This produces an intense flame.
The Martin reverse action reciprocating grate has performed well
and still has 70% of the original grate bars intact after 30,000 hours
(3-1/2 years).
The " boiler" can also be described as a "one-drum
natural circulation boiler with welded water tube walls". The layout of
superheaters is routine compared to Martin's layout at Josefstrasse that
has the hottest steam superheater bundle in the second position behind
another superheater section.
Readings are provided for much of one day when a bulky load
greatly reduced flue gas temperatures and the quantity of steam produced.
However, steam temperature and pressure remained perfectly constant.
The furnace water tube walls, which are part of the boiler, are
2
covered with small steel studs (2,000 studs/m ) and then coated with plastic
silicon carbide. This is only one of the 33 discussed ways in which plan-
ners designed Hagenholz so that metal wastage could be reduced. The com-
bined efforts have been most successful in preventing corrosion and erosion.
After 30,000 hours, the water tube walls have suffered only 0.1 to 0.2 mm
wastage. The superheater tube readings taken in April, 1977 showed 0.3 mm
wastage.
The superheater is equipped with an attemperator or desuperheater
to reduce temperatures when the superheated steam becomes too hot. Among
the boiler cleaning techniques are compressed air soot blowing, falling
steel shot, pneumatic vibrators, manual alkali washing and sandblasting.
Each technique is apparently used properly at its unique location. Detailed
water quality measurements are taken.
In addition to the three refuse fired units, there is also a
No. 2 fuel oil unit to provide start-up steam and to reduce dew point
-------
corrosion. Finally, there is a separate waste oil boiler to consume the
community's automobile waste oil and to produce energy.
The energy utilization picture is most complex. High temperature
steam passes through a steam extraction-condensing turbo generator.
Medium temperature steam and hot water are used for three-district heating networks,
Electricity is used internally and sold to the two electricity networks.
The plant produces 2.41 tonnes of steam per tonne of refuse.
District heating has a priority over electricity production. Therefore,
electrical production peaks in the Summer.
All three units have electrostatic precipitators (ESP). Units
//I and #2 have somewhat ineffective multi-cyclone mechanical collectors
to supplement their ESP's. Unit //3 was last measured at 42 mg/Nm which
2
is substantially under the 100 mg/Nm requirement of the Swiss government.
Ash recovery is advanced at Hagenholz. Unprocessed ash was
25.8% of the refuse input in 1976. Of the unprocessed ash, only 4% is
eventually landfilled. This means that of the refuse received, about 99%
is recovered in some fashion. In other words, the landfill life is in-
creased 100 fold with the RFSG and the ash recovery program.
The strong management at Hagenholz is outstanding and memorable.
The care devoted to specifying Unit #3 has been rewarded by a most suc-
cessful plant. There has been a reduction of 100 people in the last
seven years from the entire Abfuhrwessen collection and disposal staff.
The entire Hagenholz facility has been built at a capital cost
of SF 59,700,000. Of this, the Martin chute-to-stack capital cost in 1972-73
was SF 11,430,000.
The accounting formula for this "not-for-profit" activity defines
expenses to equal revenues and for 1976 they both equaled SF 14,424,262.
In 1976, U.S. dollars assuming one dollar equals SF 2.50, the plant had
expenses and revenues of $24,11 per ton.
The tipping fees accounted for about 53% while the energy sales
represented 42% of total revenue. As is often the case, a plant (Hagenholz)
that can manufacture energy for both district heating and electrical
purposes finds the energy economics much better if it concentrates on
district heating and makes electricity as a secondary product.
-------
The plant was financed at three government levels—City (70%),
State (15%), and Federal (15%). The Federal 15% carried a stipulation
that the plant must successfully pass environmental tests before the
Federal share could be released.
-------
STATISTICAL SUMMARY
Community description:
Area
Population (number of people)
Key terrain feature
City Zurich
388,165 in Zurich, 560,000 total
hills
Solid waste practices:
Total waste generated per day (tonnes/day) (610 t/d: total)
Waste generation rate (Kg/person/year) 295
Lower heating value of waste (Kcal/kg) Design data (Unit #3); 1600-3300 Kcal/kg
Collection period (days/week)
Cost of collection (local currency/tonne)
Use of transfer and/or pretreatment (yes or no)
Distance from generation centroid to:
Refuse fired steam generator (kilometers)
Waste type input to system
Cofiring of sewage sludge (yes or no)
Shear for bulky wastes
municipal solid waste
No
Development of the system:
Date operation began (year)
Plant architecture:
Material of exterior construction
Stack height (meters)
Von-Roll furnaces: July 1969 Units //1&//2
Martin : July 1973 Unit #3
concrete
91
Refuse fired steam generator equipment:
Mass burning (yes or no)
Waste conditions into feed chute:
Moisture (percent)
Lower heating value (Kcal/kg)
Volume burned:
Capacity per furnace (tonnes/day) design.'
Number of furnaces constructed (number)
Yes
20-25%
2200-2400
Martin 473 t/d at LEV = 1600 kcal/hg
360 t/d at LHV = 2200 " "
264 t/d at LHV = 3000 " "
240 t/d at LHV = 3300 " "
2 Von Roll
1 Martin
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STATISTICAL SUMMARY (Continued)
Capacity per system (tonnes/day) 570 to 700 tonnes/day
Actual per furnace (tonnes/day) Unit #3: 240 to 450 tonnes/day
Number of furnaces normally operating (number) 3
Actual per system (tonnes/day) 610 tonnes/day
Use auxiliary reduction equipment (yes or no) Yes-shear
Pit capacity level full:
(m3) 5000
Crane capacity:
(tonnes) 3.3 tonnes
(m ) bucket: 3 m
Feeder drive method hydraulic
Burning grate:
Manufacturer Joseph Martin Feuerungsbau GmbH
Type Reverse Action Reciprocating Grate
Number of sections (number) 3
Length overall (m) 8.35
Width overall (m) 5.57
Primary air-max (Nm /hour) 62,000
3
Secondary air-overfire air-max (Nm /hour) 16,000
o
Furnace volume (m ) 472
Furnace wall tube diameter (cm) 5.7
2
Furnace heating surface (m ) 1,349
Auxiliary fuel capability (no)
Use of superheater (yes or no) Yes
Boiler
Manufacturer EVT Stuttgart
Type one-drum natural circulating boiler with welded water
tube walls
Number of boiler passes (number) 4
Steam production per boiler (kg/hr) Max: 38,200 (in 1976: 34,430)
Total plant steam production (kg/hr) 72,000
Steam temperature (° C) 420
Steam pressure bar 38
-------
STATISTICAL SUMMARY (Continued)
Use of convection section (yes or no)
Use of economizer (yes or no)
Use of air preheater (yes or no)
Use of flue gas reheater (yes or no)
Cofire (fuel or waste) input
Use of electricity generator (yes or no)
Type of turbine
Number of turbines (number)
Steam consumption (kg/hr)
Electrical production capacity per turbine (kw)
Total electrical production capacity (kw)
2
Turbine back pressure (kg/m )
User of electricity ("Internal" and/or "External")
Energy Utilization:
Medium of energy transfer
Temperature of medium (° C)
Population receiving energy (number)
2
Pressure of medium (kg/m )
Energy return medium
No
Yes
Yes
No
No
Yes
condensation, extraction
2
2 x 30 tonnes/hour
2 x 6 MW
12 MW
Internal: 36%
External: 64%
Steam Hot water
260-280 130
Condensate
Warm water
-100° C
Pollution control:
Air:
Furnace exit conditions
3
Gas flow rate (m /hr)
3
Furnace exit loading (mg/Nm )
95,580 Nm /hr
Equipment:
Mechanical cyclone collector (yes or no)
Electrostatic precipitator (yes or no)
No
Yes
-------
STATISTICAL SUMMARY (Continued)
Manufacturer ELEX
3
Inlet loading to precipitator (mg/Nm )
3 3
Exit - loading from precipitator (mg/Nm ) 62-75 mg/Nm (7% CO,)
3 3
Legislative requirement (mg/Nm ) 100 mg/Nm (7% CO,)
Scrubber (yes or no) No
3 3
Legislative requirements (mg/Nm ) 75 mg/Nm adjusted to 7% CO-
Other air pollution control equipment (yes or no)
Water:
Total volume of waste water (liters/day) 32,400
Ash: (1976)
Volume of ash (tonnes/year) 56,271
Volume of metal recovered (tonnes/year) 6,494
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OVERALL SYSTEM SCHEMATIC
The overall schematic for Zurich: Hagenholz is shown in Figure
8-1. This page shows cross-sectional views of both the Von Roll Units
#1 and #2 as well as the Martin Unit #3. A detailed picture of the Martin
Unit #3 furnace and boiler follows in Figure 8-2.
COMMUNITY DESCRIPTION
Geography
The Zurich metropolitan area is located in the Northern foot-
hills of the Swiss Alps. The land is thus gently rolling except near the
suburb of Hagenholz where the terrain is relatively flat.
The City of Zurich has a population of 388,000 people. The
Hagenholz plant serves 560,000 people, not only in Zurich but also other
neighboring suburbs. The population has recently decreased because
Mediterranian workers went home after the "Swiss for the Swiss"
referendum. The concurrent world recession has also contributed to a
return to family farms and the countryside.
Industry and other employment activities are well diversified.
There were no mentionable unique generators of waste that would affect
Hagenholz plant operations. Hagenholz is much overloaded as the City
refuse collection (Abfuhrwesen) increases; hence, the city is completely
rebuilding the Josefstrasse facility closer to downtown Zurich.
-------
-------
ijjSJfl^ Ijjii
lii'iiSMidili^/i.killiliitil^X'!, !
£ >l I i n"l|' '| ll 'i ,, r, V'.'l ', ,|M • I I | , L__J *' . I t W^." I "I"
• 4 'Lit..it ilii'iiiiJI' ',M't!( 'i! •' ii11 I ''''•' 'I'1' l*TTT*n • ' T^' -Vi] i"2>. '> '•.""
S^^i'SMl'^iv^llJX^ '"i-i '' : K^ W:i
"!!:&:' ^;:>fr:!i I YA -'H ti'i\ W":
FIGURE 8-2 . FURNACE/BOILER CROSS-SECTIONAL VIEW OF
THE ZURICH: HAGENHOLZ UNIT #3
-------
14
SOLID WASTE PRACTICES
Solid Waste Generation
Not all waste generated in the Zurich area was collected under
Abfuhrwesen control until recent years. Figure 8-3 portrays the recorded
history of collection from 1905 until the present. The 400 percent
increase from 1969 to 1974 reflects the scope of record keeping more
than it reflects true generation and collection of solid waste. The
weekly pattern of refuse treatment is shown in Figure 8-4.
Sources of waste during 1976 are shown in Table 8-1. Note the
importance of non-Abfuhrwesen collection and the receipt of waste oils,
solvents, and cliemicals. The waste oils are burned. The chemicals,
however, are collected and transferred to an industrial and hazardous waste
treatment center.
The city provided several tables describing solid waste composi-
tion. Table 8-2 shows physical component percentages, for studies that have
been made in Switzerland, the U.S.A. and the U.K. The first Swiss column
is what was used in planning Hagenholz Martin Unit #3. Calorific values
*
are shown in Table 8-3 for common components in waste. A 1969 study by
EWAG (a testing service) and Von Roll showed values between 1950 and 2150 kcal/
kg (3510 to 3870 Btu/pound). Since 1965, the lower heating value has risen
only modestly. Plastic percentages are not rising very fast. Unit #3 was
designed for calorific values ranging from 1600 to 3300 kcal/kg (2880 to 5940
Btu/pound). Presently, the calorific value with 20 to 2.5 percent moisture
ranges from 2200 to 2400 kcal/kg (3960 to 4320 Btu/pound). Elemental percen-
tages for Swiss municipal solid waste are shown in Table 8-4.
At Hagenholz, slightly over 800 tonnes (880 tons) per day of
solid waste are received on a five day collection basis. This converts
to slightly over 600 tonnes (660 tons) per day on a seven day burning
basis. The plant gates are open Saturday mornings to receive trash from
private vehicles.
Every reference to refuse calorific value relates to the lower heating
value commonly used in Europe (and not the higher heating value used in
the U.S.A).
-------
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-------
18
TABLE 8- 2. COMPOSITION OF MUNICIPAL SOLID
WASTE IN SWITZERLAND, U.S.A.,
AND BRITAIN
Composition by Weight Percent (%)
(Location and
Switzerland U.S
Constituents
Food waste
Textiles
Paper
Plastics
Leather and rubber
Wood
Glass
Ferrous and nonferrous
metals
Street sweepings and
garden waste
Stones, dust, and other
debris
123
20 12 14.5
4 2.5 3.0
36 30 33.5
47 2
2 -
4 6 2.5
8 5 8.5
67 5
6 -
10 33.5 31
1
6
3
40
4
2
2
17
9
5
12
Source)
.A. Britain
4
14
-
55
1
-
4
9
9
5
3
5 6
26 13
2 2.5
37 51.5
1.5 1.0
-
-
8 6.5
8.5 6.5
2 3
15 16
Sources: 1. National averages as published by EAWAG (1971) (used for
planning Hagenholz)
2. Municipal solid waste of Geneva (1972)
3. Municipal solid waste of Zurich (1963/1964)
4. USA (1970 - 72)
5. London (1972)
6. Birmingham (1972)
-------
19
TABLE 8-3 . ENERGY VALUES OF SELECTED
WASTE TYPES (DRY)
kcal/kg
Average waste
Constituents (in relation to the
dried products)
paper
plastic, leather, rubber
food waste
textiles
wood
Forest and wood industry residues
Agriculture and food industry waste
Tires
Bituminous coal
Gasoline
Methanol
1600 - 3400
4160 - 4460
5600 - 6450
4775
4500
4820
4090
2780
8230
5600 - 8100
11400
5420
Source: Various sources.
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20
TABLE 8-4 . AVERAGE CHEMICAL COMPOSITION
OF MUNICIPAL SOLID WASTE
IN SWITZERLAND
Composition^
Constituent in weight %
Water 32.90
Material containing organics
Decomposable material 36.20
Carbon 20.20
Hydrogen 2.60
Chlorine 0.34
Nitrogen 0.57
Phosphorus 0.12
Organic material total 41.00
Material containing minerals
Carbonate 0.86
Potassium 0.11
Calcium 2.40
Sodium 0.54
Magnesium 0.24
Ferrous 2.35
Mineral material total 26.10
The table is not composed for totals to be
summed.
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21
Solid Waste Collection
Solid waste collection is performed by the City of Zurich, Depart-
ment of Streets and Sanitation, (Abfuhrwesen) by private collectors and by
other communities. The 130 Abfuhrwesen vehicles typically make four trips
per day carrying about five tonnes per truck per day.
Beginning in 1970, Abfuhrwesen began using plastic and paper sacks
in place of metal containers. This has had a very positive effect on re-
ducing collection personnel and hence costs as seen in the later Figure 8-35.
The previous Table 8-1 infers more information about collection
activities. Considering only the solid waste, the collection activities
are performed in 1976 by the three types of collectors in the following
manner:
Abfuhrwesen (City of Zurich) 56
Other municipalities 18
Private haulers and businesses 26
100% by weight
Solid Waste Transfer Activity
The Hagenholz facility is used as a location for anyone to dispose
of properly containerized hazardous (non-radioactive) wastes and in-
dustrial chemical waste. In Europe, as compared to the U.S.A., there is
a much greater emphasis on municipal responsibility for treatment and
disposal of such wastes.
Private haulers simply bring their containers to a rear area
of the plant for temporary storage. When enough waste of a certain
category is stored, then a truck load of material is taken to the rele-
vant treatment center. Presumably, some of the material is taken to the
privately operated hazardous waste processing plant adjacent to the Baden-
Brugg refuse fired steam generator (RFSG) that was discussed in a separate
trip report.
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22
Source Separation Programs
The community has just started three voluntary recycling
centers for glass, cans, and waste paper.
Abfuhrwesen has had seven centers for collection of used
crank case oil. Garages and private individuals bring their waste oil
•
to the centers. However, no money changes hands.
-------
23
DEVELOPMENT OF THE SYSTEM
Background
Zurich began its long history of converting waste into energy
back in 1904 at the unit pictured in Figure 8-5 on Josefstrasse. In fact, efforts
are now proceeding to develop a 75-year anniversary brochure that will be
released in 1979.
Operations continued until 1927 when the plant was temporarily
closed for rebuilding. The plant reopened in 1928. Refuse consumption
rose from 30,000 tonnes (33,000 tons) per year to 70,000 tonnes (77,000 tons)
per year in 1959. Between 1959 and 1968, the overloading results became
pronounced as corrosion repairs increased. During the period, extra
waste had to be landfilled on farm land. By 1969, tonnage consumption had
dropped to 50,000 tonnes (55,000 tons).
By 1965 a long range plan had been developed where two large
RFSG units would be built, one on each side of the Limmat River (the
river flowing through the old city's centrum). Because Josefstrasse was
south of the river, officials decided to build a 520 tonne (572 ton)
per day facility at Hagenholz, a northern suburb. This was one of the
few remaining open industrial spaces in the city.
Partially because of Von Roll's local presence and because of
their excellent reputation throughout Europe, Von Roll was chosen to
build two 260-tonne (286 ton) per day units with room set aside for
a third unit later on. The construction begun in 1966 was completed in
1969. Waste consumption immediately jumped to about 170,000 tonnes (187,000
tons) per year at both plants.
NOTE: These first two furnace/boilers at Hagenholz have
experienced considerable problems. Battelle decided
to visit Hagenholz, not because of these first two
units but because of the later added excellent Martin unit
that has experienced almost no corrosion. Nevertheless,
the general history of the first two units needs to be
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24
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25
explained because of its philosophical impact on the
design of the third unit and because of a most important
lesson to be learned.
This report has been carefully reviewed by both Von Roll,
Martin, and their American representatives.
The basic problem with the first two units is that the refuse
calorific value rose much more than expected. The 1945 values of 1000 kcal/
kg (1800 Btu/pound) were known to have risen, but how much was apparently
unknown. Likely, no one in the City Administration nor at Von Roll ex-
pected the 1969 value to be 1950 to 2150 kcal/kg (3510 to 3870 Btu/pound) as
was later measured by Von Roll and EWAG, the Government's testing service.
Thus, the plant (well designed for rather low calorific value waste) had
to burn waste that was 50% to 100% hotter.
The gas flow passages between the boiler tubes were properly designed
to be small - assuming the "cool" waste. But the result with the "hot"
waste was excessive sticking of hot, fused flyash on boiler tubes causing
eventual blockage. The sticking is caused by the flyash fusion tempera-
ture being often exceeded as temperatures in the boiler convection section
were around 600 C (1112 F). These sticky deposits interfered with heat
transfer hence the flue gas leaving the boiler was very high. These high
temperatures corroded the boiler tubes and the electrostatic precipitators.
To reduce sticking and corrosion, less waste was fed and
primary and secondary air was reduced. Elsewhere, the rubbing action of
the grate bars against each other had worn away grate metal so that
the air.spaces were larger. With the lower volume and pressure of
underfire air, objects fell between the bars and down into the siftings
removal system. Fires under the grate became common.
The net effect on energy delivery was negative. The city had
specified 28 tonnes (31 tons) steam per hour per furnace. Unfortunately, to
run the system, about 17 to 19 tonnes (19 to 21 tons) steam per hour per
furnace could be produced as shown below:
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26
1974 1976
Furnace/Boiler #1 23.7 tonnes 18.7 tonnes
Furnace/Boiler #2 18 tonnes 17 tonnes
Original Rated Steaming Capacity 28 tonnes 28 tonnes
Moving ahead to total operating Tables 8-5 and 8-6, notice
that the long overdue rebuilding of Units #1 and #2 was done in 1974.
These units now operate a normal set of hours per year as also shown below
when compared to the Unit #3.
1974 1976
Furnace/Boiler //I (Von Roll) 4,766 hours 7,463 hours
Furnace/Boiler #2 (Von Roll) 4,561 hours 7,289 hours
Furnace/Boiler #3 (Martin) 7,004 hours 7,596 hours
Total Hours in 365 day year 8,760 hours 8,760 hours
At Hagenholz most parties back in the early 1960's underestimated
"the heating value in 1965 and grossly underestimated the value for the
1970"s." As a result, the system (1) was grossly overheated, (2) had been
designed for low furnace wall tube surface area for heat removal prior to
the superheater, (3) had small boiler passes designed, (4) suffered with
slagging on furnace walls and tubes, (5) developed corrosion on boiler tubes,
(6) developed high temperature corrosion in the electrostatic precipitator,
(7) suffered reduced air pressure under the grate, (8) increased number of
fires in the siftings hoppers, (9) reduced production of steam, etc.
This report mentions at several places management's emphasis
is on energy production. This has been contributory to some of the
Unit #1 and #2 problems. The original contract specified operation
at the "continuous maximum load." The term was never clearly defined
as to whether this meant "peak" or "average" or "maximum average load
over the long running time."
Plant officials interpreted the rated 28 tonnes of steam per hour
to be the maximum average load over the long-running time. Von Roll had,
however, designed the plant assuming that the 28 tonnes of steam would be
permissible for short periods as a holdable peak—but not for continuous
operation.
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27
Going back to the energy emphasis, plant staff began a cam-
paign to increase the volume of high calorific value industrial waste.
The vendor, of course, claimed that (to paraphrase) "It's not fair to
ask Von Roll to build a unit for 1200-1500 Kcal/kg refuse and then
purposely try to load it with high calorific value refuse at 2200 to
2400 Kcal/kg. Of course it will have problems."
The experience at Hagenholz and other similar experiences in
Europe have sensitized system designers to push for an accurate current
estimate of calorific values. More searching for accurate forecasts of
calorific values is needed as well.
The concern about Hagenholz Units #1 and //2 resulted in the
design of a later unit at Hamburg: Borsigstrasse to be over-compensated.
So much heat was extracted by the boiler that plant operators would
worry about keeping the refuse properly burning. The writers
now believe that all parties involved have carefully studied the parameters
and that such problems will not recur at future installations—if
designers and system purchasers will respect the calorific value of waste.
The Hagenholz full story will not be described in this report.
Contracts, guarantees, politics, personalities, etc., could be the
subject of a book and are not that relevant to this report. The item
that is relevant is:
LEARN THE PRESENT COMPOSITION OF WASTE AND ESTIMATE FUTURE TRENDS.
Beginning of Subject System
The technical problems experienced on Units #1 and #2 and the
inability of the City and Von Roll to agree and then resolve the problems
led to a prej aced view of the firm for Unit #3. By 1970, other firms
had improved their technologies and reputations.
Martin assigned one of its top project managers, Heinz Kauffmann,
to work with the City. Max Baltensperger opened his pre-bid discussions
to all vendors. Apparently, Martin seized the opportunity with more vigor and
apparent thoroughness.
-------
28
Erich Moser explained the City's philosophy that "this plant
is not at a price but rather the City asked what can we build that will
be most reliable." Another comment was, "The biggest (most important)
thing is the grate."
Another philosophical comment, "Some people spend so much
(money) on architecture . . . and then skimp on the (furnace/boiler)
equipment. (Another plant) has a very nice entrance but can't make money."
They wanted "maximum reliability with mimimum maintenance, a
o
4000 hour guarantee, a minimum of 1-1/2 m waste water hour,
3
particulate emissions under 75 mg/Nm ," etc.
Three bids were received: Martin, Von Roll, and VKW. The VKW
chute-to-stack bid of SF 9,000,000 was lower than the SF 11,430,000 bid of
Martin. Yet Martin was chosen due to the City's confidence in Martin's
ability to produce an excellent system.
Building the Subject System
The result of this unusual attention to design details is a unit
that is one of the finest in Europe. Construction was finished in early
Fall of 1973. There were no appreciable construction delays. The bid
was fixed price and there were no appreciable financing problems.
Next System Under Construction (Josefstrasse)
Once the Martin Unit #3 had successfully passed its 4000 hour
compliance test in 1973, the City began discussions about replacing the
second generation (1927-1976) Josefstrasse plant with a third generation
(1979) Martin plant. This plant is now (1977) under construction at the
original site.
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29
PLANT ARCHITECTURE AND AESTHETICS
Plant Design
The plant is located on the "last available site of sufficient
size" considering the City of Zurich and the suburb of Hagenholz. It
seemed to be near the far end of an industrial park. As a result, trucks
must drive back on an industrial road that sometimes becomes overloaded
with traffic.
Being in a secluded portion of an industrial park, the land-
scaping is appropriately modest. This is also consistent with managements'
continued emphasis of putting money into the furnace/boiler and not into
pleasantries and "frills."
The plant design (see Figure 8-6) might be characterized as blocky
concrete. Very few windows were allowed, thus reducing noise. Regarding
noise limitations, the plant seems to be meeting the 45 decibel rating for
100 meters.
The entire front wall of the control room faces the discharge
portion of the furnace.
The basic building is 26 meters (85 feet) high. The 91 meter (300
feet) tall stack is built on a platform several meters from the building.
The plant operates under negative pressure so any odors generated
in the pit are collected in the primary air system for combustion in the furnace.
Rendering Plant Gases (see also Secondary Air section)
The most noteworthy, aesthetic feature of the Zurich-Hagenholz
plant is its consumption of rendering plant gases. Max Baltensperger is
responsible not only for recovering energy from municipal waste but also
for manufacturing flesh-meal and industrial oils and fats from animal carcasses.
In the careful design of the new rendering plant, room air collection vents
and process vents are placed to suck, under negative pressure, all of the
gases into a common pipe. This horizontal pipe is extended from the rendering
plant (see Figure 8-7) to the refuse fired steam generator for use as
secondary air. As a result, virtually all unpleasant gases associated with
the normal rendering plant never enter the environment.
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30
FIGURE 8-6 . VIEWS OF THE ZURICH: HAGENHOLZ
REFUSE FIRED STEAM GENERATOR
(Courtesy City of Zurich)
-------
31
FIGURE 8-7. HORIZONTAL VENTILATION AIR PIPE FROM RENDERING PLANT TO
ZURICH: HAGENIiOLZ PLANT (Battelle Photograph;
-------
32
For years, the U.S. EPA has investigated means of controlling
these organic gases. Absolute control would entail expensive use of
natural gas afterburners. A former president of the National Renderers
Association now working at the Columbus, Ohio, Inland Products plant
has been retrofitting his plant with suction equipment around selected
processes. The gas is then injected to the plant's oil fired boiler as
combustion air. This procedure could be most important and relevant to the
U.S. EPA's philosophy of non-degradation of the atmosphere. During 1977,
the U.S. Congress has been discussing an environmental control philosophy
that would permit construction of a new source generating a given pollutant
if an old source is either better controlled or closed.
The Hagenholz example is not quite the same thing. There, the
combination of plants may have minor air particulate emissions from the
RFSG stack, but has eliminated non-particulate odors from the old render-
ing plant.
For the complete story on rendering gases the reader should read
the later appearing section on secondary air.
Comment
Battelle believes that the spirit (but not the precise words) of
the Congressional discussions could be served in a community now having an
odoriferous rendering plant and a municipal solid waste disposal problem.
We would suggest consideration of a Sanitary Park with at least two
occupants: (1) the rendering plant and (2) the refuse fired steam generator.
We are also wondering whether.the components of various
reduced sulfur rendering gases could be contributing to elimination of the tube
corrosion threat. This has been suggested by corrosion researchers at
Battelle and is being investigated at a U.S. plant.
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33
^
4a
l^<-
- /L 4b
1
! JL !
, 10 ,
ts
13
,; 7
11
12
1. Tipping Floor
2. Refuse Bunker
3. Bulky Waste Shear
Aa Furnace/Boiler (Martin)
4b Furnace/Boiler (Von Roll)
5. Control Room
6. Ash Discharger
7.
8.
9.
10.
11.
12.
Ash Bunker
Chimney
Storage
Turbogenerators
Fuel Oil Boiler
Waste Oil Processing Plant
Solvent Receiving Station
FIGURE 8-8. OVERHEAD VIEW OF ZURICH: HAGENHOLZ
-------
34
TOTAL OPERATING SYSTEM
Any visitor to the Zurich-Hagenholz plant will soon be discussing
the Von Roll #1 and #2 units and the Martin #3 unit. This report is in-
tended to fully discuss the Martin #3 unit. Nevertheless, we feel that
certain operating data for all three units should be presented, but in
proper perspective.
To repeat from a previous section, most of the problems of units
#1 and #2 derived from a design for "somewhat over 1000 kcal/kg (1800 Btu/
pound) waste" instead of waste actually over 2000 kcal/kg ( 3600 Btu/pound)
as has been the case in the 1970's.
Table 8-5 presents some operating figures for 1974 which reflect
poorly on units #1 and #2. But, as mentioned before, 1974 was the year
for major overhauling that could not be accomplished before.
By 1976, all three units were operating on a more normal
schedule as shown in Table 8-6 . Figures are also presented for the
entire Sanitary Park complex including these buildings and energy customers.
• Car and truck repair shop (1,000,000 SF ($400,000) worth of
spare parts in basement)
• Office building
• Workers social hall and cleanup area
• Truck garage for storage
• Rendering plant
• FEW
• City's district heating network
• Electric utility's district heating network
The units are shut down for about eight hours every 1000 hours
for routine inspection and minor maintenance. Every 4000 hours or twice
a year, the unit is down for about one week or two for boiler cleaning and
major overhaul if needed.
During 1976, the Martin #3 unit was shut down seven (7) times
for less than one day for planned 1000 hour routine inspections. In total,
the unit was out of service for six (6) weeks.
Zurich used to have an instrument service contract but that be-
came too expensive. Their own staff now repair the instruments.
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35
TABLE 8-5 . COMPARISON OF ZURICH-HAGENHOLZ
INCINERATOR PERFORMANCE, 1974
Incinerator boiler #
Make of incinerator
Maximum throughput of solid
waste Sh.T/D
Maximum Burning Rate Sh.T/Hr
Average Burning Rate Sh.T/Hr
Average Performance Rate %
Total Operating Hours Hr/Yr.
Availability %
Average Steam Output Sh.T/Hr
Rated Steaming Capacity Sh.T/Hr
Average Steam Output Rate %
#1
Von Roll
286.52
11.93
9.18
76.90
4,766.00
54.40
23.675
28.00
48.60
#2
Von Roll
286.52
11.93
9.18
60.70
4,561.00
52.10
18.672
28.00
66.70
#3
Martin
521.0
21.7
15.7
72.5
7,004.0
80.0
40.5
42.1
96.4
Source: Information obtained from data given by Mr. Max Baltensperger,
Director, Department of Streets and Sanitation, City of Zurich.
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36
TABLE 8-6. REPORT OF OPERATIONS 1974 AND 1976
Annual Totals
icinerator boiler #1 operating hours (h)
Incinerator boiler #2 operating hours (h)
incinerator boiler #3 operating hours (h)
Number 2 fuel oil fired 3-pass boiler #1 operating hours (h)
Waste oil fired 3-pass boiler #2 operating hours (h)
Incinerator boiler #1 Steam Generation (tonnes)
Incinerator boiler #2 Steam Generation (tonnes)
Incinerator boiler #3 Steam Generation (tonnes)
Total steam produced from solid waste (tonnes)
Steam generation per ton of solid waste, unit #1
unit #2
unit #3
average (t/t)
Fossil fuel fired 3-pass boiler #1 - steam generation (tonnes)
Fossil fuel fired 3-pass boiler #2 - steam generation (tonnes)
3-pass boiler total - steam generation
(tonnes)
Total steam generation (tonnes)
Quantity of solid waste burned (tonnes)
Quantity of waste oil burned (tonnes)
Quantity of waste solvents burned (tonnes)
Quantity of crude oil burned (3-pass boilers) (tonnes)
Total weight burned (tonnes)
Quantity of solid waste collected (tonnes)
Quantity of waste oil collected (tonnes)
Quantity of waste solvents collected (tonnes)
Total waste collected (tonnes)
1974
4,766
4,561
7,004
201
1,486
112,891
85,118
284,255
482,264
2.579
1,413
11,244
12.658
494,922
186,968
794
71
109
187,942
186,146
1,654
71
187,871
1976
7,463
7,289
7,596
182
2,099
139,930
125,306
261,515
526,751
2.41
1,404
13,192
14.596
541,347
218,342
1,102
113
108
219,665
217,503
1,801
113
219,417
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37
Make-up for feedwater treatment (Gals.) 6,961,926 6,798,528
Steam turbine #1 operating hours (h) 6,090 6,565
Steam turbine #2 operating hours (h) 5,351 6,160
Steam turbine #1 electric power generated KWH 18,677,670 22,376,817
Steam turbine #2 electric power generated KWH 16,155,350 20,626,620
Total electric current generated KWH 34,697,540 43,003,437
Electric current used for incineration plant KWH 11,540,878 14,276,322
Car and truck repair shop KWH 45,373 47,791
Office building KWH 148,550 131,702
Garage building KWH 39,819 27,406
Flesh-meal plant KWH 24,456 767,760
District heating system KWH 160,668 185,378
Community service KWH 12,740
Residue processing plant KWH 30,225
Community uses KWH 6,090
Total consumed for plant system (kWh) 11,973,563 15,466,584
Electric current fed to utility grid (kWh) 23,151,000 28,374,000
Electric current used from utility grid (kWh) 549,700 781,000
Water used for incineration plant kg 197,668,901 125,334,528
Car and truck repair shop kg 829,796 933,240
Office building kg 1,853,945 1,721,016
Garage building kg 114,386 37,488
Flesh meal plant kg 8,145,720
Total water consumption kg 200,772,370 136,171,992
Water consumed per ton of solid waste (kg/S. T.) 1,162 *kg/Sh.T 686
63.3 gals/S. T. 37.3
*Normal Water Consumption Per ton of solid waste for Martin System = 20 Gals/Sh.T
-------
38
Wet Residue Sh. T
Note * not weighed after June 30, 1974
Heat consumed by car and truck repair shop
Heat consumed by office building
Heat consumed by garage building
Flesh meal plant
Hot water to local factory
District heating system
City EWZ (investor-owned public utility)
Total Heat supplied by hot water and steam
Operational hours for bulky waste shear
47,594,551
1,296 x 10 Btu
2,772 x 106 Btu
1,623 x 106 Btu
1.090 x 10" Btu
2.895 x 10 Btu
1.623 x 10 Btu
304 x 10 Btu
26,425 x 10° Btu
287 x 106 Btu
531,742 x 106 Btx
489,700 x 106 Btu 65,687 x 106 Btx
495,695 x 106 Btu 629,749 x 106 Btv
2,931
2,809
[(NOTE: The causes of wide fluctuations in system energy consumption were not
determined.)
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39
The 4.000 Hour Cycle Between Boiler Cleanings. Readings of key
variables on Hagenholz Unit #3 furnace/boiler have been averaged for each of 26
weeks (4,300 hours) between July 1, 1973 and February 23, 1974 (when the
unit was stopped for planned cleaning) and are displayed in Figure 8- 9 .
The following Figure 8-10 is similar. It starts February 17,
1977 and goes to June when this visit was made. The unit was not
stopped for cleaning. The two figures present results of the plants
first half year (1973) and its latest half year of operation (1977 after
30,000 hours). For most of the 1973 period, steam production had hovered
around 37.5 tonnes (41.3 tons) per hour. Four years later the figure
had decreased to about 35 tonnes (38.5 tons) per hour.
Notice the steady rise in flue gas temperatures during the first
1000 or 2000 hours. The low initial readings reflect excellent heat
transfer rates due to rather clean tubes. After the tubes have accumulated
deposits, the heat transfer levels out as is indicated by the flat tem-
perature and steam profiles.
The superheater and the economizer tubes are stacked (and not
staggered). During the first 1000 hours, deposits are beginning to
accumulate vertically between close tubes as shown in this diagram by
Martin's Heinz Kauffman. Eventually, the space between the close tubes
becomes filled with deposits.
o o o
o o o
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efficiency remains consistent for the remaining 2000 hours of the cycle.
The economizer is especially large to both recover energy and
to reduce flue gas temperatures entering the electrostatic precipitator as
seen in the earlier Figure 8-1. In 1973, the flue gas temperature leaving the
economizer was around 250 C (482 F) but always below 275 C (527 F) on a weekly
average. Four years later, the average temperatures had risen to 290 C
-------
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(554 F) with occasional excursions to 300 C (572 F) the temperature con-
sidered by many to be the temperature above which ESP high temperature
corrosion occurs.
Should stack gas temperatures rise 90 C (162 F) above normal,
then overall plant efficiency would fall by 5%, i.e., not enough energy was
absorbed by the boiler tubes from the flue gas stream.
-------
43
REFUSE FIRED STEAM GENERATOR EQUIPMENT
Waste Input
Normal sized refuse in garbage trucks and bulky waste is
defined as pieces entering the hopper less than Imx Imx3m(3ftx
3 tt x y tt).
The previous Tables 8-2, 8-3, and 8-4 should be referred to
understand the waste composition. With a moisture percentage of 20 to 25%,
the lower heating value is now 2,200 to 2,400 kcal/kg (3960 Btu to 4320 Btu/
pound). The later Martin #3 unit was designed to accept waste with lower
heating values from 1600 to 3300 kcal/kg (2880 Btu to 5940 Btu/pound).
Waste is received at Hagenholz five (5) days per week amounting
to 4,000 to 5,000 tonnes (4,400 to 5,500 tons), i.e., 570 to 700 tonnes/
day (627 to 770 tons/day) on a seven (7) day burning basis.
The Unit #3 burns 240 to 450 tonnes (264 to 495 tons) of refuse
per day. Animal horns and hoofs from the adjoining rendering plant are dumped
into the bunker.
Sewage sludge is not permitted as an input because the City con-
siders its ash recovery program to be very important. Tests by R. Hirt
have shown that incinerator ash, contaminated by the heavy metals in
sewage sludge cause the processed incinerator ash to be less desirable as a
road building material.
Weighing Operation
The scale at the plant entrance has performed very well. The
scale is recalibrated once per year. Now, there are two men at the scale.
Two men are assigned to direct tipping and to encourage truck drivers to
clean up any spillage. Later, when the new Josefstrasse plant is operational,
only one man will be at the Hagenholz scale and one on the tipping floor.
The reader may wish to review the later section on Waste Storage
and Retrieval to read about why the crane scale was abandoned.
-------
44
Provisions to Handle Bulky Waste
A scissor shear, manufactured by Von Roll operates from 6 a.m.
to 8 p.m. five days per week. This unit operated 2,931 hours in 1974 and
2,809 hours in 1976. Normally this type of shear does not need an operator
in residence because it is in motion all the time. It can process one to
ten tonnes per hour.
The bulky waste shears (see Figures 8— lla and 8-llb) operate like
multiple scissors, cutting and crushing the bulky refuse between its shear
beams. Seven fixed and six moveable shear beams are connected at their lower
end through shaft and bearings. Each beam is equipped with double edged
blades of highly wear-resistant alloy steel which can easily be turned once
and reused. The moving beams are arranged in two groups of three, each
group being opened and closed by a hydraulic working cylinder.
The sheared material falls through the spaces between the fixed
shear beams and down into the pit. The crane operator must then carefully
distribute this usually higher calorific waste over the entire pit.
The unit operates either fully or semi-automatically, with
remote-control by the crane operator. Control can otherwise be exercised
at the main control panel installed near the hydraulic power pac. A pre-
set pressure switch at a limited pressure of approximately 120 bars is provided
in the hydraulic circuit and combined with a back-up pressure relief valve,
limits is reached, the forward thrust stops and the six moveable shears
retract so that more refuse can fall into the V-shaped hopper. Thus,
the unit is protected against damage when the shearing resistance should
grow too high.
In contrast to many other size reduction methods, the Von Roll
Hagenholz unit has been almost 100% reliable. Routine inspections are con-
ducted and repairs made three (3) times per year and the expected life is at
least 20 years.
The knives are completely changed every 16 months. But during
that period, the edges are rotated four (4) times, i.e., once every four
(4) months.
Once per week, the knives are cleaned. Bed springs and large
tires can be a problem and may need to be extracted with a long hook.
-------
45
FIGURE 8-lla. VON ROLL SHEAR OPENING AT
ZURICH: HAGENHOLZ
(Courtesy City of Zurich)
-------
46
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FIGURE 8-llb. ELEVATION AND PLAN VIEWS OF VON ROLL SHEAR
-------
47
Originally, the shear was not strong enough and was later rein-
forced. There will be no shear at the new Josefstrasse plant because the
chute will be larger, i.e. 1.5 x 6 m.
Waste Storage and Retrieval
3 3
The refuse pit holds about 5,000 m (6540 yds ) or 3,000 tonnes
(3,300 tons) when filled to the level of the tipping floor (see Figure 8-12).
and 8-11.) When three or four doors are closed out of a total of doors, refuse
can be piled up to 9,000 m3(11,772 yd3). During our visit, material was so piled
up that the closed doors were bowed outward.
There are fire hoses above the pit to fight small fires. Once,
since 1969, they did have to call the fire department.
The two three-tonne (3.3 ton) cranes manufactured by Haushahn
of Stuttgart are double bridge. The crane operator is in a position that
is often faced with a problem of judging waste content (for calorific
value and bulky items) because of the obstructed view of the opened,
bended knee door that extends out into the refuse pit (see the previous
Figure 8-13). As a result, the new plant at Josefstrasse will have
vertically rising guillotine doors as shown below:
Existing Hagenholz
New Josefstrasse
-------
48
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49
Josefstrasse will have the semi-automatic crane feature that
accurately places the bucket over the hopper. (The Hagenholz system is
manually operated only). Hagenholz uses the less expensive clam shell
buckets. However, at Josefstrasse, polyps will be used. The clam shell,
while large in volume capacity does not compact well and is itself very
heavy. The polyp, however, is lighter and can compact more. This re-
sults in a bigger refuse load lifted per horsepower expanded. The crane
capacity at Hagenholz is 38.7 tonnes (42.6 tons) per hour while at
Josefstrasse it will be 44 tonnes (48.4 tons) per hour.
The load cell on the crane failed and has intentionally not
been repaired. When asked why, the response given was something like the
following:
"We don't care how much refuse we are burning. Our concern is
how much steam we are producing. Hagenholz is an energy plant
and not primarily a refuse disposal plant. If we repair the
load cells, people may begin paying too much attention to
refuse burning and not enough to energy production."
The reader is referred back to Tables 8-5 and 8-6. In no
way is it possible to determine how many tons of refuse were burned per
furnace in 1976.
Comment; It appears to be sophisticated to say, after everyone
has been discussing energy from waste for a time, "Let's
remember that these are primarily refuse disposal plants
and that energy production is a secondary consideration."
Plant managers at Nashville, Tennessee and at Zurich,
Switzerland would likely not agree with this statement
for their own systems.
We believe that the emphasis is totally a matter of
local circumstances. Norfolk, Virginia has a waste
disposal plant while Nashville, Tennessee has in fact
an energy facility.
Some might argue with (post construction) emphasis on
energy production on Units #1 and #2 with higher heat-
containing waste. However, with the predeclared emphasis
on energy from Unit #3, there has been no problem at
all.
-------
50
Furnace Hoppers
The hopper dimensions are 5.517 m (18.1 feet) by 7.056 m
(23.1 feet). The hopper tapers down to the feed chute that has dimen-
sions of 1.5 m (4.9 feet) by 5.486 m (18.0 feet). The chute is sur-
rounded by a water jacket.
Burnback has only occurred once in four (4) years in Martin's
#3 unit. While not certain, operators suspect that superheater tubes
might have become plugged enough such that not all of the combustion
gases could escape. Another reason might be that the I.D. fan was not
functioning properly. For whatever reason, pressure likely built up
and fire eventually went up the chute.
An explanation was made for the excessive burnback experience
at Paris: Issy - les - Moulineaux, Issy has a very high chute. As a
result, an induced draft pulls the flame back up the chute in 90% of
all start-ups.
Hagenholz is thus fortunate to have a stubby chute and wide
enough spaces between boiler tubes.
Feeders
Unit #3 has three (3) runs. Each run has upper and lower
Martin feeders with the following specifications. Stroke frequency is a
function of steam temperature, steam pressure, and temperature entering
the electrostatic precipitator.
Upper Lower
Stroke (maximum) 600 mm 1000 mm
Stroke (normal) 180 mm 300 mm
Frequency (strokes/minute) 2 to 5 2 to 5
-------
51
The feeders are hydraulically driven. As with many other com-
ponents, preventive maintenance is performed on the units. The feeders
are almost 100% reliable. On one occasion, a waste container of acetone
spilled down the chute, leaked out of the chute and onto the rubber
hydraulic lines. The acetone entering the furnace caught fire and the
rubber tubes outside the chutes were destroyed. Consequently, they were
replaced with steel flex hoses.
The feeders are controlled by the Martin "black box" that is ex-
tensively discussed in the Paris: Issy and the Hamburg: Stellinger Moor
reports in this same series.
Zurich officials are pleased with the hopper and feeder per-
formance and Martin will use the same design at Josefstrasse.
Primary (Underfire) Air Source and Air Preheater
Primary air is drawn from the top of the bunker, above the cranes
and away from hopper discharge dust. The centrifugal forced draft fan, made
by Pollrich of West Germany, produces a static air pressure after the fan
3
of 580 mmWs. Volume maximum is 62,000 Nm /hour.
The primary air temperature would average around 20 C ( 68 F) if
the GEA air preheater were not being used. With the steam air preheater
on, temperatures are raised to 80 to 150 C (176 to 302 F). Hagenholz #3
(in contrast to Hamburg: Stellinger Moor or Paris: Issy, whose existing
preheaters are seldom used) was properly designed for hotter waste and
also hotter primary air. As a result, the preheater is almost always on
and consumes 2.1 to 2.5 tonnes (2.2 to 2.8 tons) of steam per hour depending
on the refuse heating value as shown below:
Lower heating value (cal/kg) 1800 1600
Exiting air temperature (C) 80 300
Refuse quantity (tonnes/hr) 15 15
Heat output (Gcal/hr) 0.985 1.160
Steam consumption (tonnes/hr) 2.120 2.500
Upon start-up, the steam used by the air preheater is not raised in
the RFSG but rather it is raised in the package fuel oil boiler or from the
RFSG //I or #2. The heat produced is about 0.985 to 1.16 Gcal/hour (up to 4.7)
MBtu/hr) assuming^ a lower beating^ value of 1600 + 1800 kcal/ke (2880 to 3240
Btu/pound).
-------
52
Neither the fan nor the preheater have experienced maintenance
problems. The fan V-belt has been changed once in 30,000 hours. The Unit
#3 preheater has bare "flat" tubes through which steam passes. Units #1 and
#2, instead, had "finned" tubes which caused cleaning problems. During each
anticipated 4000 hour inspection, cleaning and repair activity, compressed
air is used to blow off accumulated dust.
The primary air, thus preheated, passes down and into the five
zone plenums under each of the three runs, i.e., 15 zones. The pressure
just under the grate bars is fairly high at 50 to 150 mmWs.
The underfire air pressure is held constant. The air damper
settings are rarely changed and only if the refuse is very very wet.
At the plenum hopper bottom, a siftings damper opens and closes
according to an automatic timer. When open, the siftings fall and are
pneumatically blown down to the bottom ash hopper.
Readings of underfire air pressure are recorded every two hours.
If absolutely necessary, the pressure and flow can be changed in the
control room.
Secondary (Overfire) Air
Again, Pollrich centrifugal fans are used. As discussed in
the previous Plant Architecture and Aesthetics section, rendering plant
gases are the exclusive source of secondary overfire air.
Of the total combustion air, roughly 80% is primary underfire air
and 20% is secondary overfire air. Roughly 91 kw are required to pull a
maximum of 10 Nm /second from the rendering plant.
There is no secondary air preheating and rendering gas temperatures
3
average around 20 C (68 F). The maximum air volume is 16,000 Nm /hour.
The static pressure is 730 mmWs (mm of water). The front wall air
pressure is 300 mmWs while the back wall air pressure is 540 mmWs. These
very high secondary air pressures create extreme turbulence within the
furnace.
Figure 8-14 shows an anonymous furnace where secondary air
pressure is very low. Notice the clearly shaped flame and details of the
opposite furnace wall. Turbulence is very low.
-------
53
FIGURE 8- , ANONYMOUS FURNACE WHERE SECONDARY OVERFIRE AIR IS VERY
LT^LE OR TOTALLY LACKING
-------
54
Figure 8-15, however, presents a red ball - a glow with no dis-
cernable shape. We suspect that any carbon monoxide (CO) formed could only
exist instantaneously before conversion to CO,,. This turbulence virtually
eliminates CO. CO, if present in appreciable amounts, is thought to
contribute boiler tube corrosion in RFSG.
The unusual fact is that Zurich: Hagenholz Martin #3 super-
heaters have experienced only .3 mm metal wastage in 30,000 operating
hours. This amazing lack of corrosion exists despite the 732 C (1350 F)
flue gas temperature entering the superheater and the 427 C (800 F)
steam temperature leaving the superheater. The water tube walls have a
most acceptable 0.1 mm metal wastage for the same time period. This
high turbulence along with many other factors share the credit for no
corrosion. See page 83 for a comprehensive discussion on corrosion.
Martin and Hagenholz personnel emphasized their rejection of any
sidewall secondary air jets. Any sidewall jets, they claim, would cause
CO to develop in the middle of the furnace.
The secondary air passes 22 nozzles in a single row of the front
wall and a similar 22 nozzle row in the rear wall.
Readings of C0? are taken by using an instrument built by Landis
and Gyr of Zug, Switzerland. The instrument is recalibrated every two
weeks using a sample of known CO- concentration. Every year, the instrument
is cleaned and the filter is changed. On June 8-10, 1977, the C02 readings
varied between 8.2% and 11% (see the data - Page 62).
Reliability of the secondary air system has been excellent. The
V-belts have not even been replaced after 30,000 hours. The nozzle jets
have remained open and clear despite slag buildup on the rear wall.
-------
55
FIGURE 8-15. HAGENHOLZ UNIT #3 WHERE SECONDARY OVERFIRE IS PLENTIFUL
-------
56
Burning Grate
The Martin #3 furnace is equipped with its unique reverse action
reciprocating grate as depicted in Figure 8-16. The furnace, with its three
parallel runs, is wide but quite typical for Martin installations. The
unit is rated 21 tonnes (23.1 tons) per hour of refuse input.
The reader is referred to a previous discussion on Waste Storage
and Retrieval where little concern is expressed for knowing exactly how much
refuse is being fired at any one time. Nevertheless, for a period, pre-
cise measurements were taken and ratios were developed. One of these
ratios is 2.41 tonnes of steam produced per 1.00 tonne of refuse con-
sumed. This, by definition, is also 2.41 tons of steam produced per 1.00
ton of refuse consumed.
In a typical hour, 34 to 39 tonnes of steam are produced.
Assuming 37 tonnes steam means that about 15.3 tons refuse was consumed.
Grate bars are made from 18% chromium steel. They are designed
and assembled so that no more than two percent of the grate area is open
for air flow. Thus, with separate air flow control in each of the fifteen
air plenums and with the many small air holes, the air pressure drop can
be kept at a very high level for maximum turbulence.
The total furnace width is 5.57 m (18 feet) and the length is
2 2
8.35 m ( 27 feet) for a total area of 44.9 m (483 ft ).
The first sign of bar breakage is usually sittings discharge
problems. After a bar breaks, larger material falls into the plenum
and eventually enough will plug the hopper.
Non-anticipated inspections are made upon breakdowns. Cursory-,
anticipated quick inspections are made every 1,000 hours. But the de-
tailed anticipated grate inspections are made every 4,000 hours or twice
per year.
In four years of running, grate bars caused emergency shutdown
twice, resulting in five grate bars total to be repaired under emergency
conditions. After three of the anticipated inspections, grate bars were
replaced. In total, about 30% of the grate bars have been replaced
leaving 70% of the original grate bars intact after 30,000 hours.
-------
57
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Complete Boiler
Before presenting details of the EVT (of Stuttgart, W.Germany)
boiler, some general boiler items should be described. Figure 8-17 shows
the furnace/boiler cross-sectional view of Unit #3. For those not familiar
with this technology, it should be mentioned that all parts of the boiler
are connected. Some would call this a "one-drum natural circulating
boiler with welded water tube walls." (A similar type of boiler had been
designed by Dr. Vorkauf of Berlin many years ago. In Europe it is called
the Eckrohr boiler and in the U.S. it is often known as an econotube boiler.
"Eckrohr" translated means "corner-tube." These corner-tube boilers use
very large, hollow, and heavy steel columns for two purposes. First, they
support the entire boiler. Secondly, they carry water down from the sfceam
drum to the bottom of the water walls.) The Hagenholz-EVT-boiler is definitely
not an "Echrohr-boiler"! This boiler is topsupported from a steelstructure
and not corner-tube-supported! The boilers #1 and #2 are Echrohr boilers!
This boiler is a natural circulating boiler and not a forced circulating
boiler!
Boiler water entering from the boiler feedwater system passes
through the following sets of tubes in the below order. The ordering is
not necessarily correlated with the passage of flue gases. In fact,
city officials have learned enough from Hagenholz experiences so that
the third generation Josefstrasse unit will have a slightly different
ordering.
Portions of Zurich Hagenholz Boiler #3
Economizer bundle at bottom of 4th Pass 1
" " " middle " " " 2
II II II II II II II O
It II II II II II II /
II I. It top tl II II 5
Water tube walls combustion chambers 6a
Water tube walls first pass 6b
-------
FIGURE 8-17. FURNACE/BOILER CROSS-SECTIONAL VIEW OF
THE ZURICH: HAGENHOLZ UNIT #3
At Josefstraeae, the hottest superheater will be at position 10
in between two other superheaters.
-------
60
Water tube walls second pass 6c
Screen tubes at bottom entrance to 3rd pass 6d
Superheater supporting tubes 7
Superheater bundle at top of 3rd pass 8
Superheater bundle at middle of 3rd pass 9
Superheater bundle at middle of 3rd pass 10
Superheater bundle at bottom of 3rd pass 11
At Josefstrasse (Figure 8-17), positions 11 and 12 will be reversed.
This change will permit slightly cooler flue gases to hit the hottest steam
temperature superheater.
Figure 8-13 shows the spacing and key dimensions of all of the
tubes used.
Considering the complete boiler, the height is 28.7 m ( 94 feet),
the width is 7.88 m (25.8 feet) and the depth is 15.9 m ( 52 feet). The
final'output is 38,200 kg/hr (84,216 Ibs/hour) of steam at 38 bar (551 psi)
at 420 to 427 C (788 to 800 F).
Assuming that the refuse energy input rate is 33 Gcal ( 131 MBtu) per
hour, the volume heat release rate is 117 Gcal/m^ - hour ( 13100 Btu/ft3 - hour),
The heating surface is as follows:
o
• Water tube walls, Passes 1,2, and 3 1,349 m
2
• Screen tubes 42 m
2
• Superheater 703 m
2
• Economizer 951 m
3,045 m2
One Day's Flue Gas Temperature. CO^ Level and Steam Production Recordings
During our visit on June 9, 1977, several hours were spent in
the control room. The steam flow (volume) chart showed relatively steady
readings of 34.5 to 39 tonnes (38 to43 tons) steam per hour. Actually,
much of the time the readings were closer at 35 to 37.5 tonnes (38 to 41
tons) steam per hour. All readings are shown in Table 8-7.
-------
61
Water Tube Walls 1st and 2na Passes
O (
300
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mm
1st Pass 57
2nd Pass 57
70
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mm
4.0
4.0
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Maximum Average
4.38 4.10
6.66 6.40
5.55 5.55
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FIGURE 8-18. BOILER TUBE SECTIONS LAYOUT AT ZURICH: HAGENHOLZ #3
-------
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At 4:50 a.m. to 5:10 a.m., the flow suddenly dropped to 24.1
tonnes ( 26 tons) steam per hour owing to bulky waste which reduced the
energy input. By 5:15 a.m. the steam flow rate had returned to 36.1 tonnes
( 40 tons) per hour. In a few minutes it peaked at 41.1 tonnes (43 tons)
per hour; but only for a few minutes.
Later in the morning, between 9:00 a.m. and 10:00 a.m., there was
a similar drop to 26 tonnes ( 29 tons) per hour and subsequent recovery.
All this time, the steam pressure and temperature held a perfectly steady
position; the pressure at an unchanging 62% of full scale.
Flue gas temperatures, C0_ levels, and two-hour steam flows are
shown in Table 8-7 . These readings are for Unit #3 that has operated
about 3,000 hours since the last cleaning.
Boiler Walls (Combustion Chamber—First, Second, and Third Passes)
The total boiler wall heat adsorption area is 1,349 m^ (14,515 ft^ )
2 2
Another 42 m (452 ft ) could be added if one considers the large screen
tubes to be part of the wall. Data were available on furnace volume up to
the screen tubes (and not the third pass) that indicate a volume of
472 (16,670 ft3). Considering the first pass alone, the volume is 340 m3
(12,000 ft3) and the heating surface is 330 (3550 ft2).
The wall tubes are 57 mm (2.2 in) in diameter and are 4 mm (0.16 in)
thick. The center-to-center spacing is 75 mm (2.9 in). In the first pass,
the maximum flue gas velocity is 4.38 m (14.3ft)/second with 4.10 m (13.5 ft)/
second being more normal. Following in the second pass, the maximum flue gas
velocity increases due to its smaller cross-sectional area, to 6.66 (22 ft)/
second with 6.40 m ( 21 ft)/second being normal.
The wall construction is termed "welded fin". The fins connecting
the tubes are extruded with the tube. The procedure was developed by EVT of
Stuttgart. At the factory small steel studs are welded to the furnace
side of the tubes to a density of 2000 studs/m (186 studs/ft2). The stud
orientation is radially out from the tube center. Therefore, with respect
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to the relatively flat wall, the stud angles are different and result in a
better adhering surface; as shown below:
Note: All dimensions
in millimeters
57 did
8 dia
Each stud is 12 mm (0.5 in) long and 8 mm (0.3 in) in diameter.
After the studded tubes had been installed at Hagenholz, plastic
silicon carbide (SiC) was covered over the studs to a thickness of 12-15 mm
(0.5 to 0.6 in). The use of studs covered with SiC is only in the
combustion chamber and the lower 2/3 of the first pass as depicted in the
previous Figure 8-2. Mr. Baltensperger commented that the SiC should
extend one or two meters beyond where flames might be expected.
Figure 8-19 is a picture taken of the studded SiC-covered walls
taken from across the active combustion chamber in Unit #3. As can be
seen, slag very seldom adheres to the SiC. Small amounts of slag will
accumulate but will fall off.
Sootblowers are not used in the first and second passes so that
any chance of a sootblower malfunction causing a tube rupture is eliminated.
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65
FIGURE 8-19.
FIRST PASS WALLS COVERED WITH SILICON CARBIDE OVER WELDED
STUDS: SHOWS REJECTION OF SLAG FROM WALLS OF ZURICH: HAGEN-
HOLZ (Battelle Photograph)
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66
Officials have been most pleased with results. After 30,000
hours, the combustion chamber wall tubes have experienced only .1 - .2
mm (0.004 to 0.008 in) metal wastage. Finally in 1978, after about
40 000 hours operation and no tube bursts, the superheater was replaced,
"to be on the safe side".
The temperature at the end of the flame tips is 1000 C
(Ilc2 F). Two-thirds up the first pass (where the SiC stops), the flue
gse * emperature falls to 800 C (.1472 F) . Using the highly-thermally
3
e.'Ucient SiC, a heat release rate of 117,OOOKcal/m is possible based on
a heat input rate of 33 Gcal/hour.
The SiC surface is rarely repaired on the 1000 hour inspections.
SiC might be repaired on the 4000 hour planned inspections. Studs and
SiC might be repaired once per year during major overhaul.
An additional design recommendation to reduce wall tube corro-
sion is to place the vertical man-hole doors flush with the inside surface
of the furnace wall. Eliminating the recessed cavity will reduce dust
erosion.
gas flow
Screen Tubes
The normal function of screen tubes is to facilitate water
circulation and to hold the walls in alignment.
However, at Hagenholz, screen tubes have a third important
function. To further reduce corrosion, flue gases pass through large, gent-
ly sloping screen tubes at the. base of the third pass. These circulating boiler-water
carrying tubes provide a modest chill to the flue gases. Flue gas tempera-
tures are reduced slightly to the benefit of superheater life. To some ex-
tent, these easy-to-replace screen tubes might be called "sacrifice screen tubes."
The tubes have a diameter of 70 mm (2.7 in) and a thickness of
4.5 mm (0.18in). They are spaced 300 mm (12 in) apart. The maximum design
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67
and the average flue gas velocities are both 5.55 m/sec (18.2 feet/
sec).
Superheater (and Attemperator)
The superheater placement can be seen in either the previous
Figure 8-18 or in the following Figure 8-20. Four horizontal tube
bundles are connected as shown on the following figure.
The interview turned again to the differences between the
evolving Paris: Issy plant and the mature Zurich: Hagenholz Unit #3.
In Paris, the superheater tubes were hung vertically in a "harp" design.
.f
Paris: Issy
I
&
o
of of
Zurich: Hagenholz
The Paris design, (built in 1961) it is theorized, would develop water droplets
in the bottom of the loop that would act as an insulation blanket.
Proper heat transfer could not take place and metal temperatures would rise further
in the high temperature corrosion range.
At Zurich: Hagenholz, however, (designed in 1971) the steam flow
is always downward such that nothing can become trapped. Heat transfer
2
thus takes place and corrosion is reduced. The heat transfer area is 703 m .
The lower and hotter bundles are made from 15 Mo 3 steel while
the upper and cooler bundles are made from 35.8 II steel. The tube diameter
is 31.8 mm(1.2 in)while the thickness is 4 mm (0.15 in). The horizontal
centerline spacing is 150 mm (5.9 in) and the vertical spacing within a
bundle is 50/100 mm.
The lower hottest first bundle has a maximum flue gas velocity
of 6.65 m/sec (22 feet/sec) and average velocity slightly less at 6.45 m/sec
( 21 feet/sec). The top three bundles, however, have a slower velocity at
a maximum of 6.25 m/sec ( 20 feet/sec) and an average velocity slightly
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68
Flue Gas Exit Temperature
500 C (932 F)
Steam Entrance Temperature
260 C (500 F)
8 XI PKainyCarbjzfn Stofeel
Plain £arb/n S/eel
302 C
(575 F)Steara
343 C
(650 F)Steara
Location of soot-
^ blower when its
nozzle failed
after 8,000 hours
385 C
(725 F)Steam
643 C (1190 F)
T
1
V
O
o
15/Mo /Low
7 / /
teej
732 C (1350 F)
Flue Gas Entrance Temperature
O
Attemperator
Pure Water
420 - 427 C
(788 - 800 F)
Steam Exit Temperature
FIGURE 8-20. SUPERHEATER FLUE GAS AND STEAM TEMPERATURE AND
FLOW PATTERNS AT ZURICH: HAGENHOLZ
* The last and lowest loop of the 3rd bundle and the entire 4th
bundle are made with 15 Mo 3 low alloy steel.
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69
less at 5.75 m/sec. The reason for the lower velocity with the same cross-
sectional area of flow is the cooling of the flue gases.
To better control boiler exit steam temperature (plus and minus
5° C), an attemperator injects varying amounts of deionized, deaerated,
and demineralized pure water. In general this must be even more pure
than boiler feedwater. The injected water must be pure; otherwise, scale
is likely to build up in the superheater tubes. The point of injecting is shown
in Figure 8-16 as being between the lowest and the next bundle.
One might ask why the attemperator (desuperheater) water must be
even cleaner than the very clean boiler feedwater. The answer is that the
attemperator water (under 100 C, 212 F) must suddenly convert to steam (at
400 C, 788 F). As a result, the minerals formerly dissolved in the water
suddenly become solid particles. The higher concentration of these parti-
cles will accumulate on the downstream superheater tubes.
About 38,200 kg/hr (84,276 Ib/hr) of steam at 38 kp/cm2 (551.psi)
are produced.* Nute that the steam enters the superheater at 260 C (500 F)
and then exits with a temperature of 420-427 C (788 to 800 F) at the very
bottom of the third pass. In a later design, Martin tried a slightly
different configuration as shown in Figure 8-17. In this design, the
hottest tubes are the upper row of tubes in the first bundle. This
design was likely motivated by the excessively high percentage of total
plastics, being 10 to 15 percent of the refuse input.
The advantage is that a slightly cooler temperature flue gas
hits the hottest steam tube. Thus, the metal and tube deposit temperature
is less and there will be less corrosion. Zurich and Martin
officials apparently believe that a slight reduction in exit steam temperature
is more than compensated by a reduction in superheater metal wastage. Hence,
the new Josefstrasse plant under construction will use this design.
Boiler Cleaning. As mentioned previously, there has (with one
sootblower incident exception) been virtually no corrosion of superheater
tubes in 30,000 hours. At 30,000 hours, metal wastage was determined to be
only .3 mm (0.013 in) at many points around the tubes.
*kp is translated "kilogram force"
1 kp| 2 = 1 bar = 14.504 psi = 10,000 Newtons/m2
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70
Flue Gas Exit Temperature
500 C (932 F)
t
Steam Entrance Temperature
Q 4 260 C (500 F)
302 C (575 F)
343 C (650 F)
380 C (715 F)
highest temperature steam
Steam Exit Temperature
385 C (725 F)
^.427 C (800 F)
Attemperator
Pure Water
JT 732 C (1350 F) Flue Gas Entrance Temperature
t
FIGURE 8-21. SUPERHEATER FLUE GAS AND STEAM TEMPERATURE
AND FLOW PATTERNS AT THE NEW ZURICH:
JOSEFSTRASSE PLANT
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71
The one exception occured after only 8,000 hours. The soot-
blower was manufactured by Forest and Bergaman of Brisstol, Belgium. A
nozzle on a fixed position, rotary sootblower fell off. As a result, high
pressure compressed air blew directly onto the tube sides. The nozzle
failure was detected and the tubes were inspected. None of the superheater
tubes were burst but they had sufficient metal wastage to motivate replace-
ment. Thus, after 8,000 hours, twenty (20) tube sections, averaging 5 m
( 16 feet) per tube each, were replaced. There have been no sootblower
problems since.
The compressed air sootblowers are used daily. The two air
compressors supply two storage air tanks each 15-* with air at a 30 bar
(450 psig). The air released at the sootblower nozzle is at 15 bar
(225 psig). Officials expressed their preference for superheater soot-
blowing with compressed air over steam even though the air compressor
costs about SF 250,000. As an official stated, "We use air for sootblowing.
If we used 10 tonnes steam per hour for sootblowing, we wouldn't be able
to sell it."
Once (or twice) per year, each Hagenholz boiler is manually
cleaned by the Hutte Company of Recklinghausen, West Germany (near Essen).
Four or five (4 or 5) men spend seven or eight (7 or 8) days cleaning one
boiler. An alkali chemical is used. Sandblasting may be used for selected
hard to dissolve deposits. The procedure is basically as follows for most
deposit areas.
1. Spray alkali (soak, no pressure)
2. Rinse with water
3. Spray alkali (second soak)
4. Rinse with water
5. Scrub with brushes and other tools
6. Sandblast difficult deposits
Cleaning all the tubes (walls and bundles) in all four passes normally costs
about 25,000 SF ($10,000). The dirty water coming out at the boiler bottom
has a Ph of about 2 so lime must be added.
Plant staff have been experimenting with an "unbalanced compressed
air vibrator" for cleaning the superheater. Every two minutes, the upper
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72
three bundles are vibrated. Every second or third months, they perform
a variation and interrupt the procedure for a half day.
At the Hamburg: Borsigstrasse plant, the bundle wall anchors
are hit with a sledge hammer once per week.
Convection Section
Hagenholz Unit #3 does not have a regular boiler convection
section because of the extensive four bundle superheater, the five bundle
economizer, and the four passes of water tube walls.
Economizer
The five economizer bundles are made of 35.8 II plain carbon
steel. The centerline spacing in both directions is 100 mm ( 4 in).
Each tube is 38 mm (1.5 in) in diameter and 4.0 mm (0.16in) thick. The
maximum flue gas velocity is 6.1 m/sec (20 feet/sec) while the average
velocity is 5.5 m/sec (18 feet/sec).
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73-74
Boiler Water Treatment
Boiler water is carefully monitored and treated. Detailed
water tests are made once per month. For deoxidation, N-H, (Hydrazine)
is used. Sometimes Levaxin, manufactured by Bayer Chemical, is used
rather than Hydrazine.
Water usage per refuse tonne handled over 52 weeks is shown in
Figure 8-22. The primary water use is the ash quench. Presumably,
the ash content rises in the Spring and Summer as vegetation, earth
and construction material waste increases.
Boilers for Firing With Fuel Oil, Waste Oil, and Solvents
Hagenholz is equipped with two Sulzer (of Zurich) fossil fuel
boilers; one for virgin Number 2 fuel oil and another boiler for both
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2
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w
CO
8
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77
waste oil and waste solvents. Some operating figures previously appearing
in Table 8-6 are repeated below:
Annual Totals
1974 1976
Number 2 fuel oil fired boiler #1 (operating hours)
Waste oil and solvent fired boiler #2 ( " )
Total (boiler - operating hours)
Number 2 fuel oil fired boiler #1 (tons of steam) 1,413 1,404
Waste oil and solvent fired boiler #2 ( " ) 11.244 13.192
Total 12,657 14,596
Number 2 fuel oil burned (tons) 109 108
Waste oil burned (tons) 794 1,102
Waste solvents burned (tons) 71 113
Total 974 1,323
Waste oil collected (tons) 1,654 1,801
It would be incorrect to label these activities as co-firing.
The refuse burning areas are not connected at all to the oil burning
areas. Max Baltensperger feels very strongly that no other fuel should
be fired in the same combustion chamber as refuse because of inevitable
problems of ash deposits on boiler tubes.
The Number 2 fuel oil boiler is only used to preheat the boiler
and the air preheater (for the benefit of the electrostatic precipitator).
The waste oil, however, is a completely separate system devoted to waste
oil destruction and energy recovery.
Readings of CO- and opacity (Ringleman scale) are used to
control these oil burning systems. There have been corrosion problems
in the steel stack of these boilers.
The previous Figure 8-8 shows the general layout of the
solvent and waste oil preparation area. The waste oil is heated and
decanted. The oil, water, and sludge are pulled off separately. The
sludge at the bottom of the decanting tank is mixed with the municipal
solid waste in the pit. The oil overflow goes to the boiler.
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78
LITTLE OR NO CORROSION AT ZURICH; HAGENHOLZ UNIT //3
The occurrence of little or no corrosion at the Zurich: Hagenholz
Unit #3 has been of interest to professionals as the 30,000 operating
hours since original construction in 1973 continue to increase. From
1973 to June-5 3977, not a singlp. br>ilpi tube in any section has failed.
The most serious incident was when a superheater section fixed
rotary sootblower nozale failed and sent too much compressed air directly
onto superheater tubes. The nozzle failure was discovered after 8,000 hours and
the area was examined for metal thickness. They replaced 20 tubes of an
average 5 m (15 feet) length.
A recent check in April, 1977, showed that the original
superheater tubes had metal wastage of only 0".3 mm. The water tube walls
of the second pass had only 0.1 to 0.2 mm metal wastage on the original
tubes.
What accounts for this amazing Ir.ck of corrosion despite a
relatively high steam temperature? In summary, the threat of corrosion
was well known before construction began and many steps (27 were discussed
with Battelle staff while in Zurich) were taken to minimize the metal
wastage. Metal wastage can occur chemically in the form of corrosion or
physically through erosion.
This section describes these 33 steps, discusses Mr. Richard
Tanner's theory, Battelle's general theory and finally Dale Vaughan's
explanation of chloride actions as a reason for no metal wastage at Hagenholz.
33 Design^Steps Taken at Hagenholz to Reduce Metal Wastage
Four general causes of met?il wastage are important: dew point
corros.'.on, high temperature corrosion, chlorine corrosion and physical erosion.
They will be referred to often in the following listing of how Max
Baltensperger and Heinz Kauffman cooperatively designed the unit for most
successful operating results.
At a social gathering, Walter Martin was asked, "Why doesn't
Hagenholz Unit #3 corrode?" His initial casual remark was "Good Management".
Later upon reflection, he added nine ether leasons. Other reasons came out
of the normal .'ntervieving process.
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79
Management
1. The original design spirit at Zurich was that there was a no set
limit as to spending for the best (efficient and reliable) boiler
that "icney could buy.
2. The refuse input averages 72.4% of the maximum burning rate. "You
ought to build the best [.lent possible and then run it at 80% of
capacity".
3. Excellent management ensures that the properly designed plant is observed,
monitored, and controlled as it is intended.
4. Rotating job positions for each man enhances his understanding of
the complex plant and his spirit to run it properly.
Automatic Control
5. The Martin "black box" sends instantaneous furnace roof temperature
readings to the feeder and grate controls. As a result, flue gas, metal
surface, and steam temperatures are kept within limits and high temperature
corrosion is avoided.
Start-up Procedures
6, The standby boiler (Number 2 oil or waste oil) is; always started
before the refuse is fired and the steam heats primary underfire air
in the steam air preheater to 150 C—above the dev point temperature.
7. This same standby oil-boiler supplies steam to the refuse boiler
to preheat the tubes above the dew point temperature.
The effect of the oil-fired steam is to raise the boiler surface
temperatures sbo'/? the dew point temperature so that this type of
corrosion dees not affect either the boiler, the electrostatic
precipitator, or the stack.
Refuse Handling
8. Refuse is thoroughly mixed by the crane operators so that a more
uniform refuse fuel is available that will not cause wide swings in
flue gas temperatures.
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80
9. The feeders are designed to introduce controlled amounts of refuse into
the furnace and not permit uncontrolled cascading that would cause poor
burning and formation of harmful CO.
10. The Martin grate, with its reverse action motion, gently (without
cascading—except for tires and stumps) rotates the refuse for
exposure to flame and combustion air.
Secondary Air
11. The front and rear-wall secondary overfire-air jets are properly
aimed to develop the desired turbulent pattern. Flame lengths are
kept short and few rise into the first pass.
12. No side wall air is permitted where inadequate mixing might allow
CO to form. (However, this is not meant to criticize Kunstler or
Didier air wall blocks).
13. Secondary air at 500 to 600 mmWs causes intense turbulence so that
virtually all CO is eliminated before the flue gases leave the
combustion chamber. Alternating reducing - oxidizing atmospheres
are eliminated.
14. The secondary (overfire air) from the neighboring rendering plant
"may" contain reduced sulfurs, etc., that may reduce corrosion by
forming sulfate deposits on the tube, thus reducing chlorine tube
deposits. However, the concentration of sulfur is believed to
be low and more investigation is needed to confirm any hypothesis.
The ammonia ppm is often high and its effect, if any, on corrosion
is not known.
Furnace Walls
15. The walls of the combustion chamber and the lower 2/3 of the walls
in the first pass are coated with Silicon Carbide (instead of bare
plain carbon steel) that was properly applied and bonded. No flame
passes beyond this point.
16. The second pass is very large so that more heat is absorbed into the
walls.
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81
17. The flue gases flowing in the large second pass are at a lower
velocity which reduces the erosive effect of the particulates in
the gas as it hits the first row of superheater tubes.
Superheater
18. The superheater is positioned in the third pass (and not the first or
second passes) so that cooler flue gases, with little or no CO, hit
the tubes.
19. The superheater tubes are horizontal flowing downward (and not verti-
cally hanging). Thus, stagnant water pockets cannot form •
to interrupt heat transfer.
20. The superheater tubes are in line (and not staggered) so that flue
gases can more easily pass.
21. The superheater metallurgy is 13 Mo 3 in the lower two bundles and
35.8 II in the upper three bundles instead of plain carbon steel,
35.8 I.
22. The atteroperator (desuperheater) between the lowest superheater
bundle and the next bundle Inserts pure demineralized water when
steam temperature rises above a certain limit. Thus, steam tempera-
ture and pressure (but not flow rate) can be kept constant plus or
minus 5° C.
23. The entire boiler is designed so that the average superheater
exit steam temperature is 420 C (788 F).
Economizer
24. The economizer originally equipped with a shield on the first tube
row of the first bundle, was later augmented with more shielding on
the second row of the first bundle.
25. The economizer is especially large to both recover energy and to
reduce flue gas temper?tures entering the electrostatic precipitator.
26. The plant used for test purposes is an "unbalanced compressed air
pneumatic hammering vibrator".
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82
27. No sootblowers are used in the first and second passes.
28. Compressed air (and not steam) sootblowers are used in the superheater
section. Thus, injurious slugs of water lying in inactive soot-
blower pipelines cannot harm the tubes upon startup.
29. The sootblowers in superheater section are fixed-rotary (and not
retractable). Hence, the nozzles are always oriented properly and
not directed right on the steam tubes. The, sootblower jets are
fixed just underneath the tube"bundle.
30. The boiler is manually cleaned with an alkali every 4,000 hours.
31. Sandblasting is limited to removing only difficult tube deposits.
32. With the lower flue gas temperatures in the first 1000 hours after
cleaning, a ferrous sulfate FeSO. might have formed instead of the
more harmful FeCl_.
33. The economizer is cleaned with falling steel shot (and not by soot-
blowers) thus avoiding potential problems.
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83
Theory of Corrosion Supplied by Richard Tanner Formerly of Von Roll
Figure 8-23 was supplied to Battelle by Mr. Tanner, Von Roll's
top refuse-fired steam generator expert for many years before retiring. It
shows corrosion threat (abstractly without any numerical reading) on
plain carbon steel as a function of tube metal temperature.
General Theory of Temperature and Chloride Corrosion
as Supplied by Dale Vaughan of Battelle
Early in this project, Dale Vaughan was asked to summarize his
theory of how gases, metal salts, chlorine and sulfur react at different
temperatures to cause corrosion. The following is his reply so carefully
worded that it may have to be reread.
"The boiler tubes are exposed to the normal
combustion gases C02, CO, HC1, small amounts
of sulfur oxides and organics, excess air,
plus vapors and solids of inorganic compounds.
The initial reaction is undoubtedly the forma-
tion of a thin oxide layer on the boiler tube
which is quickly coated with a deposit con-
taining large amounts of chlorine identified
as a. mixture of potassium and sodium chloride
with smaller amounts of heavy metals. Hence,
the tube metal is no longer exposed to the
gaseous combustion products but instead is
exposed to the deposit and/or the products
of its reaction with the gases.
Studies of deposits after long exposure to
incinerator combustion products have shown
that the chlorides are converted to sulfates
and that the chlorine content is thus reduced
significantly except at the metal surface when
Fed- has formed. The iron oxide layer is no
longer in contact with the metal surface, but
instead chlorine is now the corrosive species.
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85
Battelle's corrosion data show that wastage of
carbon steel increases rapidly at about 400 F
and again at 800 F. The first increase is
attributed to chloridation and the second to
sulfidization. The first increase coincides
with the rapid attack of iron by elemental Cl
as shown by Brown, DeLong and Auld. Further-
more, their studies show that rapid attack of
iron by HC1 does not occur until a temperature
of about 900 F. Therefore, it is doubtful that
the HC1 content of the combustion products is a
significant contributor to metal wastage in the
temperature range where chlorine is the corro-
sive species.
However, as expected, Cl^ has not been detected
in combustion gases but this does not eliminate
its existence as a product of the conversion of
MC17* to M SO,. This occurs mainly in deposits
which are retained on boiler tubes and exposed
for sufficient time to the hot gases containing
low concentrations of sulfur oxides. When the
CL_ is released from the MC1? deposits at the
metal surface the attack is very rapid. The
Battelle studies have shown that by increasing
the sulfur in the fuel M SO^ forms rather than
MCI in the fuel bed and combustion chamber,
little or no chlorine is found in the deposit
and the metal wastage is markedly decreased
even though the HC1 in the combustion gases is
the same or perhaps increased some. SO
emission increases some but not rapidly."
* The letter "M" refers to any metal that might
bond with CL. or SO,.
2 4
V,
Upon return to Battelle from Zurich, Mr. Vaughan was presented with
specific data regarding conditions at Hagenholz Unit #3. He had the following
response as summarized below:
He examined the charts showing weekly average
temperatures for July 1, 1973, to February 23,
1974 (Figure 8-9 ), and the period February 17,
1977 to June, 1977 (Figure 8-10). He believes
the important factor is that early in both
periods, namely, the first 1000 hours after tube
cleaning, all flue gas temperatures were lower
than later on in the 4000 hour cycle. Figures
are summarized below.
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86
Hours
100 1000 2000 4000
Flue Gas Temperature Leaving Furnace 610°C 675°C 800°C 780°C
Flue Gas Temperature Entering Superheater 510 575 675 750
Flue Gas Temperature Entering Economizer 400 470 490 600
Flue Gas Temperature Leaving Economizer 225 265 250 260
The metal temperatures are, of course, much lower. The result
is that the metal temperatures were low enough so any FeCl~ that has been
formed had time to convert to a ferrous sulfate, FeSO,, thus, providing
a protective coating immediately adjacent to the tube. The later high
temperatures were thus not harmful because the sulfate coating shielded
the tube from any later deposition and decomposition of chlorides.
The remarkable freedom from corrosion on Unit 3 appears to
confirm Vaughans theory which has been discussed earlier. It was deve-
loped by Vaughan and his colleagues in laboratory and field research
sponsored by EPA at Battelle since 1969.
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87
ENERGY UTILIZATION
Energy utilization at Zurich: Hagenholz is among the most ad-
vanced in Europe. Max Baltensperger repeatedly pointed out that Hagenholz
is primarily an energy plant. The plant is integrated with the other
conventional fossil fuel district heating and electricity plants. A new
oil fired energy plant is located nearby. The total story involves follow-
ing energy media:
Hagenholz Refuse Fired Steam Generator
High temperature steam for electricity production
(steam extraction - condensing turbo generators) 420 C (788 F)
Medium temperature steam for district heating
(Kanton, the municipal district heating system) 260 C (500 F)
Hot water for district heating (EWZ, the investor-
owned public utility for electricity and district
heating) 130 C (266 F)
Hot water for a State hospital (sterilizing), small
factory in Hagenholz, the railroad station, and
perhaps the Technical University (5 km/line) 130 C (266 F)
Electricity for the two networks (Kanton and EWZ) 11,000 volts
Electricity for internal use, truck garage, and
workshop 220 v and 380 v
High temperature steam for the rendering plant 420 C (788 F)
New Oil Fired Energy Plant
Hot water for district heating (Kanton, the
municipal owned district heating system) 180 C (356 F)
Figure 8-24a shows the electrical power generation room and some of
its equipment. The full energy product schematic for the plant is shown on
the same page i,i Figure 8-24b.
Fig 8-25 and 8-26 are also two separate figures on one page.
Figure 8-25 pre^nCs c relatively flat picture of total steam produced per
ton of refuse consumed during the 52 week year. The average is 2.41 tonnes
of steam produced per one tonne of refuse input.
-------
88
Figure 8-26, showing kWh electrical sales per tonne of refuse
consumer, however, does have a substantial seasonal pattern that compli-
ments the district heating pattern. The philosophy is that district
heating demand is the first priority and electrical production is second.
The two electrical networks can absorb as much refuse produced electricity
as can be generated. The reverse pattern for district heating appears
later in Figure 8-26.
-------
89
FIGURE 8-24a. ELECTRICAL POWER GENERATION ROOM
1.
2.
3.
4.
5.
Furnace/Boilers 6.
High pressure distribution valve 7.
Governing valve 8.
Medium pressure distribution valve 9.
Low pressure distribution valve 10.
Turbogenerator
Air condenser
Feedwater storage and deaerator
Feedwater pump
Steam for district heating
FIGURE 8-24b. STEAM AND BOILER FEEDWATER FLOW PATTERN
EXTERNAL TO THE ZURICH: HAGENHOLZ BOILER
-------
90
J976
J_
\ i r
FIGURE 8-25. TONNE STEAM PRODUCED PER TONNE OF REFUSE CONSUMER (1976 AVERAGE WAS 2.4i;
.i..... I.
FIGURE 8-26. KWH ELECTRICAL SALES PER TONNE OF REFUSE CONSUMED
-------
91
Electricity Generation
High temperature/pressure steam from all three Hagenholz units
is fed into two Escher-Wyss (since acquired by Sulzer of Zurich) steam
extraction-condensing turbines. Each consumes 30 tonnes (33 tons) of
steam per hour for a total of 60 tonnes (66 tons).
Each then produces 6 raw for a 12 mw total average 5.25 for a
10.5 mw total) at 11,000 volts which is equal to the local network
voltage. Actually there are two electricity customers: the Kanton (local
government) and EWZ (a public utility). The turbine speed is 6800 rpm.
A large gear box between them connects it to the generator having
a 3000 rpm speed. There has been very little trouble with the turbo-
generator set. Once produced, the voltage can be lowered to 220 v and
380 v for internal use.
The new Josefstrasse plant will be equipped with two 40 tonne
steam per hour Brown-Boveri turbo generator sets. Each will produce 8 mw
for a 16 mw total.
District Heating
The Hagenholz refuse fired plant and the nearby oil
fired energy plant provide steam and hot water for three different dis-
trict heating networks. Most of the district heating piping has been in
place for many years.
The investor-owned public utility EWZ plant receives hot water
from Hagenholz which is added to the larger EWZ supply. This hot water,
at 130 C (266 F), is then distributed to many customers in Zurich.
The weekly load is shown in Figure 8-27.
-------
92
The second, a Kanton-owned district heating system, (see the
map Figure 8-28) has only a few large customers and has a limited po-
tential as listed below:
Kanton municipal hospital (current)
Ramibuhl Factory (current)
Railroad station (current)
Post office (potential)
University (potential)
Municipal museum (potential)
This system uses about 15 tonnes (16.5 tons) of steam per hour in the Winter
and 10 tonnes (11 tons) per hour in the Summer.
The third district heating system has many apartments and other
buildings as customers and is also owned by the Kanton. It is basically
the system that the Josefstrasse plant supplied which is now supplied by
Hagenholz while Josefstrasse is being rebuilt.
These three district heating networks are supplied by several
energy plants. Two of the energy plants are in the Hagenholz suburb;
(1) the Hagenholz refuse fired steam generator, and (2) the oil fired
energy plant. The supply and return pipelines connecting the two plants
with the three networks are in a ground-level, walk-through tunnel covered
with earth as shown in Figure 8-29. Figure 8-30 is a cross-section
schematic of the tunnel showing the supply and return lines for water,
steam, and condensate. This researcher walked about 500 m (1500 feet)
into the tunnel with the general overhead plan shown in Figure 8-28.
-------
93
' FIGURE 8-27. 1976 HEAT DELIVERY TO KANTON AND RENDERING PLANT AMP STEAM TO EWZ FROM ZURICH; HAGENHOLZ
1 t t la
cal/week< » 3 « I *
/boo
f *
fooo
3000
1000
2000
-------
94
Technical University
^sSJ^Kr^xW
^^^P
Small Factory Using' Hot Water
Major Access to
Tunnel
State Hospital
Ramibuhl Factory
FIGURE 8-28. KANTON DISTRICT HEATING SYSTEM (5.3 km long)
USING 260 C (500 ?) STEAM AT ZURICH, SWITZERLAND
-------
95
FIGURE 8-29. ENTRANCE TO WALK-THROUGH DISTRICT HEATING TUNNEL AT
ZURICH: HAGENHOLZ
-------
96
t
Energy
Media
Supply
Energy
Media
Return
1. Steam condensate return from Kanton district heating network to
Hagenholz 70-80 C.
2. Warm water return from Kanton district heating network to new oil
energy plant.
3. Hot water supply from oil energy plant to Kanton district heating
network for apartments 180 C.
4. Hot water supply from Hagenholz to EWZ plant to EWZ district heating
network 130 C.
5. Warm water return from EWZ district heating network to EWZ plant to
Hagenholz 100 C.
6. Condensate return from steam purge conditioning tank to Hagenholz
(5 atmospheres).
7. Cooling water from City to pump for EWZ plant
8. Total purge condensate return from Kanton district heating network
to conditioning tank 200 C (12-14 atmospheres).
9. Steam from Hagenholz to Kanton district heating network 5 km away
260-280 C (12-14 atmospheres).
FIGURE 8-30.
CROSS-SECTION SCHEMATIC OF PIPES IN THE DISTRICT
HEATING SUPPLY AND RETURN TUNNEL AT ZURICH:
HAGENHOLZ
-------
97
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-------
98
The purge system for outbound steam pipes is used when the
steam is being turned off or being turned on. Pipe number 8 travels
the distance of the tunnel collecting condensate from the cooled steam
pipe (not to be confused with the return condensate pipes). The con-
densate is collected in the purge tanks and then added to the return
condensate tanks. One pipe (number 6) then returns the combined liquid
condensate to the Hagenholz plant.
The steam and purge line pressures are limited to a slight
superheat of 260 C (500F) and 12 to 14 atmosphere (175 to 200psi) because of
local regulations relating to pipeline expansion problems. The pipe from
the condensate return collection tank back to the RFSG plant is at five
atmospheres (73 psi) pressure.
The hot water and steam supply and return lines are inspected
and reconditioned once per year in the summer.
The electricity sells for SF 0.06/kwh in the Winter and SF 0.04/
kwh in the Summer.
The charge for district heating steam is SF 35 to SF 60/Gcal
depending on who the customer is and how much of the pipeline capital
cost the customer is paying for.
Figure 8-32 shows the weekly pattern of steam sales to the
railroad central station (SBB), KZW and to EQZ.
There has been almost no corrosion of pipes in these walk-through
tunnels. The district heating system is stopped once per year for valve
repairs where necessary.
There is five to seven percent loss in "refuse-derived condensate"
returned to the plant by the district heating networks. However, more
HJD by weight is returned because a disproportionate amount of "oil-
derived condensate" is returned to the RFSG plant.
-------
99
SBB und A'Ztt 1976
n
r
SBB
i
J
Lr
KZW
T_ r
EWZ
.r i .r
FIGURE 8-32.
Sflf)
KlVf
CKi
f
J
r
r
-\.f
" -<-L ,—J-
1976 ENERGY DELIVERY (WARMEABGABE) TO THE RAILROAD STATION,
THE KZW AND EWZ
-------
100
ENERGY MARKETING
Obtaining new publicly or privately owned large-volume customers
is an art or skill practiced by several of Abfuhrwesen's management people.
There is no formal plan. However, management is very careful to seek po-
tential customer contacts. Sales calls are made. No fixed rate schedule
is used.
The energy plants are operated as profit centers that happen to
be owned by the City. Each contract is negotiated. If the City must
put in a large pipeline that will be depreciated over 40 years, a higher
price will have to be charged for a unit of energy. As an example,
Hagenholz sells its steam, at its own plant boundary, at a low rate to the
Kanton district heating network. However, Josefstrasse (1904, 1928, and 1979)
has always owned and maintained its pipeline network; hence, its rates are
higher. To lower the customer's price, quantity discounts are possible.
There are attempts by the Kanton district heating system (Heizamt,
a sister organization to Abfuhrwesen) to sell to large apartment complex
owners. No attempt is made to encourage individual homeowners to purchase
steam.
Officials gave Battelle an eight (8) page contract and finan-
cial worksheet as an example of a negotiated offer. This most interesting
document between Abfuhrwesen and Migros (the leading food warehouse) is
written in German and can be made available to interested parties.
-------
101
POLLUTION CONTROL EQUIPMENT
Mechanical Collectors
Units #1 and #2 have Rothemuehle multi-cyclone mechanical col-
lectors following the electrostatic precipitators (ESP). However, Unit #3
does not have a mechanical collector. The cyclones were always difficult
to clean. The cyclones on the first two units performed well until they
were corroded by the high flue gas temperatures. Eventually, the spirals
were removed and now the gas flows through the empty cyclone. See the
following page for more details.
While Unit #3 does not have a mechanical collector, it does
have an open chamber and hopper immediately before the ESP. The larger
flue gas cross-sectional area causes some of the heavier particles to
fall out, thus reducing the load into the ESP.
Electrostatic Precipitators
o
Unit #3 has a maximum gas flow rate of 95,580 Nm /hour or
26.55 Nm /sec assuming that the refuse lower heating value is 2800 kcal/kg
(5040 Btu/pound) and that 11,800 kg per hour (13 tons per hour) are com-
busted. The mean velocity is 0.814 m/sec. The furnace/boiler emits
3
flue gas with 2500 mg/Nm of particulate.
The electrostatic precipitator was manufactured and installed
by the Elex organization. It contains two (2) fields and has a cross-
secional area of 74.1 m2 (797 ft ). The effective surface collection
area is 3560 m2 (38,306 ft2).
Elex felt that it had enough experience and a flow-model study
was not performed. Mr. Erick Moser, the technical assistant lamented
that, "There is never enough information on (inlet) gas and dust compo-
sition."
Flue gases must pass through a perforated plate and a series of
baffles before entering the electric field. The output voltage is 78 kv
with an effective output current of 2,430 ma.
-------
102
The unit is cleaned by mechanical rapping with a hammer. Flyash
falls through pyramidal hoppers and is removed by a feedscrew.
The insulation is 80 mm (3.1 in) thick. In the Winter, the
hopper is electrically heated.
The flue gas temperature entering the ESP is usually 280 C
(536 F). See the previous Table 8-10. If it rises to above 300 C (572 F),
there is serious danger of high temperature corrosion from Zinc. Chloride
deposits. The chemical attacks the steel until it becomes spongy and short
circuits become common.
Plant staff .cautioned about closing the plant every weekend.
They have observed other plants that develop dew point corrosion at the
150 C (302 F) flue gas temperature level. When the unit is shut down
eight (8) hours for the 1000 hour planned inspection, the ESP is kept
warm by the 150 C (342 F) steam from the (Number 2 fuel oil or waste oil)
boiler. The ESP is thus cooled only twice per year - during the 4000 hour
planned inspections.
Whenever the ESP falls below 78 kv and cannot maintain a 65 kv
charge across the fields, then operators know the excessive short circuiting
is occuring and that inspection and maintenance should soon follow.
When Units //I and #2 were built, the Swiss air pollution law
3
limited emissions to 150 mg/Nm corrected to 7 percent (X^. The
3
Zurich request for proposals (RFP) specified a 100 mg/Nm limit. The
two-field Elex ESP followed by the Rothemuehle multi-cyclone more than
met the requirements and average 70-90 mg/Nm during compliance tests.
Later, after the units had been operating over the critical 300 C
2
(572 F) limit, corrosion began and later readings changed to 120 mg/Nm .
!
The original compliance test for one of the first units produced the
following: Units #1 and #2
Particulates - total
*
Particulates - over 30 u
co2
°2
H20 (or H2)
SO
£,
HC1
72 mg/Nm"'
3
15 mg/Nm
7.7%
9.2%
15.7%
219 mg/Nm3
531 mg/Nm3
(currently about 120 mg/Nm
-------
103
When Unit //3 was built, the regulation had been tightened to
5
3
3 3
100 mg/Nm for particulates. The RFP thus specified 75 mg/Nm . During
the compliance test, conducted by EMPA, an excellent reading of 42 mg/Nm"
was recorded as well as these other figures. Assuming an inlet loading
3
of 2500 mg/Nm and an output reading of 42 mg/Nm3 means that the unit
operates at 98.3 percent efficiency.
-------
104
Unit #3
Particulates - total
co2
H2°
so2
HG1
HF
ZnO
Pb
42 mg/Nm3
8.4%
12.0%
220 mg/Nm3
840 mg/Nm
11 mg/Nm
3
4.7 mg/Nm
0.37 mg/Nm3
Now that the third generation Josefstrasse is being built
(Martin is the designer), the RFP specification has been tightened further
to 50 mg/Nm . As of this writing, the plant is under construction and
thus no compliance test has been made. Officials have been so pleased
with the Elex precipitator (marketed by American Air Filter in the U.S.),
that it was easily chosen for Hagenholz.
The Federal Switzerland Government had a financial incentive
program several years ago that motivated construction of many refuse
fired steam generators. A condition for the Federal money was that
the plant pass its compliance test. Prior to passing the test, vendors
would have to wait for their money or the city would have to obtain a
short term bank loan. As compared to several other countries, this
policy has done much to ensure plants with well controlled emissions.
This program still exists on paper, but funds have not been
nearly as plentiful as in years before. In many Swiss regions there has
been pverbuilding of these plants and several persons have mentioned
that Switzerland is "saturated" with RFSG's.
Stack Construction
The single Hagenholz chimney is a single flue brick-lined stack
9l m (300 feet) tall with a top inside diameter of 3.8 m ( 12 feet).
Inspections are made twice per year. So far (since 1969), there have
been no chimney repairs. However, a galvanized ladder has exhibited
some corrosion. The chimney is expected to last 20 to 70 years. The
original 1904 Josefstrasse stack was used for 70 years.
-------
105
Unfortunately, with three furnaces supplying flue gas to a
single flue chimney, the flue gas velocity may be reduced by 1/3 or 2/3
depending on how many units are in operation. Therefore, the new
Josefstrasse will have a three flue steel-lined chimney. Since each
furnace will have its own flue, flue gas velocity will thus be independent
of how many furnaces are operating, i.e. the plume will generally behave
as is desired. Another feature of Josefstrasse is that when upper sec-
tions become corroded, a ground level hydraulic system can raise all
other sections. The deteriorated top section can be removed and another
new steel section, 5 m (16 feet) long can be inserted at the bottom.
Fly Ash
To prevent blowing dust from flyash, it needs to be wetted.
This is most difficult in the Summer and with freezing, almost impossible
in the Winter. As a result, the screw conveyors transport all flyash to
the ash discharger where it is inserted 1 m (3 feet) above the water level.
Some dust is recycled through the furnace/boiler/ESP but that is no real
problem. The flyash and bottom ash are later recycled for roadbuilding.
Waste Water Discharge
Generally speaking, the higher the refuse calorific content,
the less amount of water per hour is needed to operate the system. Hence,
there is less waste water. The following demonstrates assuming a heat
release rate of 33,000 Gcal/hr:
Lower Heating Value (kcal/kg) 1800 2400 3000
Waste Water (liter/hour) 1500 1200 900
Waste Water (Gallons/hour) 396 317 238
-------
106
Hagenholz waste is around 2100 to 2200 kcal/kg so about 1350
liters per hour is added to the ash quencher. There is no overflow of
water from the quench tank to the sewer. Only toilet waste water and
used boiler blowdown water are put in the sewer.
Noise
During the day, noise must be kept under 45 decibels at dis-
tances further than 100 m (328 feet) from the plant fences. At night,
after 8:00 p.m., the turbine windows must be closed to abate noise.
Air Cooled Steam Condensers
Large vertical louvers, made by GEA of Bochum, West Germany,
are installed on the roof wall around the air-cooled steam condenser
fan bottoms to abate noise.
Separately, the V-belt drive on the condenser fans started
squealing at low speeds. They now have two-speed motors.
The condensing capacity is 75 tonnes (82.5 tons) per hour.
At present they condense about 40 tonnes (44 tons) per hour from the
extraction condensing turbines.
Previously, Hagenholz had freezing problems in the Winter.
They now feed steam first to what would otherwise be the coldest part of
the condenser.
Figure 8-33 shows the cooling tower.
-------
K>7
FIGURE 8-33. COOLING TOWER AT HAGENHOLZ (Battelle Photograph)
-------
108
ASH RECOVERY
Ash recovery is very advanced at Hagenholz. Credit for this
accomplishment is to be shared among several parties that have funded and
guided the research and development. The entire program is outlined in
an excellent 50-page report written by Professor R. Hirt, a professor of
forest engineering at the Technical University in Zurich. His publication
is titled, "Die Verwendung von Kehrichtschlacke als Baustoff fuer den
Strassenbav", dated October, 1975. The German title translated is "Use
of Processed Incinerator Ash for Road Building". The report is available
through Mr. Hirt or Battelle.
The analysis mentions many Swiss cities. But for the City of
Zurich alone the following general 1974 data are presented:
Population
Refuse (generated )
Refuse per person (kg basis)
Refuse per person (pounds basis)
Refuse per person (365 days basis)
*
Ash generated by incinerators
Ash per person (kg basis)
Ash per person (pounds basis)
Ash per person (365 days basis)
Ash as % of Refuse
City of
Zurich
421,650
216,000
512
1,126
3.08
61,800
147
323
0.88
28.6
14 Large Swiss Cities
2,314,100 people
812,485 tonnes/year
351 kg/person/year
772 pounds/person/year
2.12 pounds/per day
271,260 tonnes/year
117 kg/person/year
257 pourids/person/year
0.70 pounds/person/day
33.4 tonnes/tonnes
* Josefstrasse and Hagenholz both in 1974.
-------
109
FIGURE 8-34. PARTIALLY PROCESSED RESIDUE AT HAGENHOLZ (Battelle Photo)
-------
110
The ash residue (slag), when removed from the ash bunker, is
stored in a pile for two months for these several reasons:
• moisture reduction
• stop fires
• chemical reactions
•• heat hydration of free lime
•• water and calcium carbonate
These exothermic reactions result in an internal temperature of
80 C (176 F). The bottom ash and flyash combined residue has a Ph of 11
or 12. Interestingly, the dirty water removed during the semiannual boiler
cleaning to remove flyash deposits has a Ph of 2 or 3—an alkali is the
cleaning agent.
In 1976, the actual following figures were reported:
Quantity of solid waste burned 218,342 tonnes 100.0%
Quantity of raw ash generated 56,271 tonnes 25.8%
Quantity of metal recovered 6,494 tonnes 3,05
The following are percentage ranges for output from the ash recovery
process:
Roadbuilding material 80%
Ferrous metals 8-9% (before recession 10-12%)
Non-ferrous mediums re-
turned to furnace 3-5%
Stumps and tires sent
to landfill 3-5%
Except for uncaptured particulates and gases, the only materials
leaving the plant in an unrecycled mode are the tree stumps and tires.
This amounts to 3 to 5% of ash and ash is 25.8% of the total waste input.
This means that 98.75 to 99.25'% is the volume reduction for purposes of
calculating necessary landfill requirements.
The copper is manually pulled out and sold as scrap when con-
veniently seen and removable. Aluminum is recycled indefinitely until
oxidized.
-------
Ill
In 1974, before the recession, ferrous incinerator scrap sold
for SF 30-90 per tonne depending on the season and strikes in Italy and
France. In 1977, the price range from SF 30-35 per tonne F.O.B. Zurich.
The roadbuilding ash (or slag as most Europeans call it) sells
for 10% under the competitive price for gravel. Mr. Hirt believes that
the long term price is bound to rise substantially as gravel pits become
scarce. The 1974 price of SF 12 had fallen to SF 6 in 1977 dye to the
recession.
Most of the slag is used for secondary roads. They can operate
in rain and freezing weather due to the exothermic reactions.
There is a new plant that is planned to mix the material as
aggregate with cement to serve the Zurich and Winterthur areas.
Because the material can also be used as road base for paved
roads, several tests have been conducted. Tubes made of PVC, cement, zinc,
rubber, etc. have been inbedded in the processed ash to determine corrosion
effects.
Three people, not employees of Abfuhrwesen, operate the facility
for a joint venture owned by the Bless and the Muldenzentrale companies.
Figure 8-35 through 8-42 show the various stages of residue
processing.
-------
112
FIGURE 8-35,
SEGREGATED BULKY RESIDUE FROM FURNACE AT HAGENHOLZ
(Battelle Photograph)
-------
113
FIGURE 8-35. TRUCK DISCHARGING PLANT RESIDUE AT HAGENHOLZ (Battelle Photo)
-------
114
FIGURE 8-37.
FRONT-END LOADER DELIVERING RESIDUE TO HAGENHOLZ PROCESSING
SYSTEM (Battelle Photograph)
-------
115
FIGURE 8-38.
WORKER REMOVING WIRE FROM WASTE PROCESSING CONVEYOR AT
HAGENHOLZ (Battelle Photograph)
-------
116
FIGURE 8-39.
SMALL SIZE METAL FROM HAGENHOLZ RESIDUE-PROCESSING PLANT
(Battelle Photograph)
-------
117
FIGURE 8-40.
MEDIUM AND LARGE METALLICS FROM HAGENHOLZ RESIDUE
PROCESSING PLANT (Battelle Photograph
-------
118
FIGURE 8-41.
NON-FERROUS SIZED RESIDUE FOR ROADBUILDING AT
HAGENHOLZ (Battelle Photograph)
-------
119
FIGURE b TE^T SLABS AT HAGENHOLZ CONTAINING SIZED RESIDUE
.-tejlc Photograph)
-------
120
PERSONNEL AND MANAGEMENT
Figure 8-43 displays the City of Zurich's organization.
The Hagenholz plant itself is part of the Abfuhrwesen (Waste Disposal
Organization) which reports to Gesundheits - und WirtschafIsamt
(Health and Cleansing Department). Note that the Heizamt (City's heat-
ing organization) and the Elekrizitatswerk (electric works) are each
in different departments. This makes more impressive the attitude of
Max Baltensperger, Chief of the Waste Disposal Organization, that the
Hagenholz RFSG is primarily an energy facility and secondarily a waste
disposal facility.
The waste collection, Hagenholz, Josefstrasse, and rendering
plant relationships are shown in the Abfuhrwesen organization chart:
Figure 8-44. The activities above the dash line are performed at City
Hall.
Compared to other European RFSG plants, the plant level
organization chart is less precise. There are no shift specialists.
Each man gets to do all the jobs around the plant. The philosophy is
that the men should take more interest in the overall plant operation.
Changing assignments also tend to inhibit formation of cliques and
selfish attitudes.
Each of the 39 men work a 44 hour week. There are four
operators per shift as follows: shift foreman, crane operator, mainten-
ance man, and control room operator. Service contracts with outside
firms permit a limited staff size.
Each supervisory and management person in the plant must
submit a written report weekly to his supervisor. This i:t-lv,des Max
Baltensperger's report to the nine (9) member Council.
While the plant staff has walkie talkies, ic.hu> are seldom
used. The crane operators and the control room operators frequently
talk by telephone.
-------
121
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Switzerland, being a landlocked nation, does not have as many
former seamen running their boilers. Instead, some of the people come
from industry such as Brown Boveri, Sulzer, etc. Often a young man will
start as an apprentice machinist or pipefitter. Training is primarily
on the job as compared with the rigorous schooling/experience program in
Germany. Accordingly, promotion is based on merit and actual contribution
to the plant operations and not based on formal progression through a
schooling/experience program.
The total number of personnel (collection, disposal, adminis-
tration, rendering plant, etc.) since 1911 is shown in Figure 8-35.
Plant staff stated that the change from garbage cans to paper
and plastic bags greatly reduced the manpower requirements for collectors.
The third reason for keeping manpower levels low, costs low, and efficiency
high, is the bonus. In 1976, management shared SF 2,737 while the plant
people shared SF 17,617. A fourth reason is that 50% of the people are
in the local union.
Start-up Procedure
The Number 2 fuel oil boiler produces 150 C (342 F) steam that
is put into the boiler. This helps eliminate dew point corrosion. Steam
from this oil boiler is also used to heat tubes in the air preheater, also
to 150 C (342 F). The electrostatic precipitator is turned on after about
1/2 hour. Whenever they shut-down for the 1000 hour checks, the ESP is
kept hot.
At one point, a comparison was made between Hamburg: Stellinger
Moor and Zurich: Hagenholz—both plants operated by municipal governments.
The main difference was that the Stellinger-Moor is causually operated
as a well run municipal department. Hagenholz, however, leanly and
efficiently, is operated as if it were private energy-generating enter-
prise. At Hamburg, the primary objective is clean disposal of waste.
-------
124
1/2-hour. After about 1-1/2 hours, fairly dry and high calorific value
waste is fed into the furnace and the charge is lit.
When the unit is stopped for its 1000 hour inspection, the
ESP is kept hot to prevent dew point corrosion.
-------
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-------
126
ECONOMICS
Capital Investment
The first two units and the administration, social, truck repair,
truck storage, bicycle storage, and space parts areas were built in 1969
at a total cost of SF 56,000,000. Of this total, about SF 45,694,000 was
for the refuse fired steam generator (RFSG) building itself. Von Roll's
chute-to-stack price was SF 23,000,000. Later, in 1973, an additional
SF 14,000,000 was spent for Unit #3 and water deaeration. Out of this,
the Martin contract was SF 11,430,000. This brings the total for all
three RFSG units to SF 59,700,000.
Details of the first Von Roll construction period are shown
in Table 8-8 • Similar details for the last Martin construction period
follow in Table 8-9 .
Annual Costs
A separation of annual costs to operate Units #1 and #2 from
operation costs for Unit #3 is impossible. Annual 1976 costs, totaling
SF 14,414,893, include costs of operations, maintenance, interest, and
other costs, and are portrayed in Table 8-11. The costs are for all three
RFSG units. Excluded are costs to inspect and repair the fleet of garbage
collection trucks. The cost pattern since 1928 is shown in Figure
8-^fi. Notice the excellent control over salaries and wages and hence the
total personnel costs.
Annual Revenues
Annual 1976 revenues, totaling SF 14,424,262, include tipping
fees; sale of steam, hot water, electricity and ferrous; a large insurance
settlement for a turbine, rent of a tire shredder, credit for repairs to
other City of Zurich vehicles, and other incomes.
Dividing the tipping fee, charged to non-Abfuhrwesen trucks,
of SF 2,210,966 by the annual tonnage of 94,000 tonnes, yields a SF 23.46/
tonne tipping fee. However, the public tipping fee charged, and the sub-
sidy later paid total of SF 5,417,988, divided by 121,559 tonnes, yields
a public Abfuhrwesen collection tipping fee per ton of SF 44.57/tonne.
-------
127
TABLE 8-8. CAPITAL INVESTMENT COST (1969) FOR
UNITS II AND #2 AND OTHER BUILDINGS
AT ZURICH: HAGENHOLZ
Building costs
(excavation, foundation, structure, stack,...)
Equipment (Von Roll contract chute to stack)
(boiler, furnace,...)
Outfit
Administrative building
Workshop
Trucks-garage
Connection-way (alley)
Scale house
Bicycle house
Grading
Environment (garden, fences , . . . )
Streets and parking places
Oil storage tank
Others
Land
Construction management fee
Engineering fees
Interest during construction
Others Total
Capital Investment
Total
Complex
(SF)
11,000,000
23,000,000
20,000
2,500,000
2,200,000
700,000
1,200,000
350,000
100,000
750,000
600,000
1,300,000
115,000
12,000,000
59,700,000
RFSG
Only
(SF)
11,000,000
23,000,000
20,000
1,250,000
440,000
—
—
350,000
50,000
375,000
300,000
650,000
115,000
8,144S000
45,694,000
(SF 6,000,000 value of land previously purchased)
-------
128
TABLE 8-9. CAPITAL INVESTMENT COSTS (1972*) FOR
UNIT #3 AND THE WATER DEAERATION
TANKS AND ROOM AT ZURICH: HAGENHOLZ
Furnaces and boiler (Martin contract chute to stack) SF 11,430,437
Spare parts 11,374
Deaeration tanks (2) 339,837
Foundation work 548,281
Piling 43,894
Temporary office building 17,776
Scaffolding rental 9,415
Demolition and boring 96,242
Front wall, trusses, insulation 95,734
Steel structure 110,574
Heating/cooling/electrical/plumbing 125,628
Inside finishing 97,767
Miscellaneous 43,323
Photography and brochures 6,294
Engineering fee 107,453
Architect fee 58,373
Other expert fees 1,605
Interest during construction 800,015
Water treatment room 62,314
Total Capital Investment for Unit #3 SF 14,006,335
Reserve 650,000
Miscellaneous 521,665
Total Amount Financed 15,178,000
75% of the capital costs were paid in 1972.
**However, the spare parts inventory stored in the basement under the
truck repair garage now totals about SF 1,000,000.
-------
3.29
TABLE 8-10. ANNUAL 1976 OPERATING, MAINTENANCE, INTEREST,
AND OTHER COSTS FOR ZURICH;.HAGENHOLZ
UNITS #1, if2, AND #3
Component
Totals
Interest
Plant Amortization
Office Equipment Amortization
Spare Parts Amortization
Total Amortization
Office Wages
Managerial Wages
Part-time Wages
Plant Wages
Total Wages
Managerial Bonus
Plant Bonus
Total Bonus
Overalls and Clothing
Cafeteria Subsidy
Cost of Living Pension Adj.
Planned Pension
Makeup Pension
Social Security Pension
Total Pension
Accident and Sickness Insurance
Office Supplies
Ash Research and Treatment (net cost)
Other Dept. Services
Studies
Building
Chute to Stack
Ash Truck (1)
Landscape on Old Landfill
Workman Clean-Up Room
Plant Controls (est.)
Boiler Cleaning (est,)
Cafeteria Repairs and Cleaning
Total Repairs (no wages)
2,365,967
6,731,680
19,186
110,205
148,323
162,278
4,146
1,576,561
2,737
17,617
79,258
124,798
99,198
92,405
60,271
680,809
1,077
60,697
4,989
42,629
80,000
5,008
2,365,967
6,861,071
1,891,307
20,354
8,306
16,540
395,659
35,748
422
1,374,782
14,825
994
935,483
-------
130
TABLE 8-10. (Continued)
Component Totals
Janitorial Service (est.)
Heating (est.)
Office and Repair Shops
Cleaning Supplies
Fuel Oil
Electricity Purchase
Water
Electricity for Office
Total Utilities
Truck TEA and Diesel Oil
Oil and Lubricants for Plant
Electrical Replacements (Lamps)
Chemicals for Water Treatment
Office Costs Burden
Property and Liability Insurance
Tax Overpayment
Hospitality
Damages not covered by Insurance
GRAND TOTAL COSTS
3,000
2,973
5,973
11,861
19,217
105,949
201,821
184
327,173
790
11,223
10,440
15,332
30,773
75,151
(3,465)
2,849
4.098
SF 14,414,893
-------
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The question was asked, "Why would you charge outsiders only
SF 23.46/refuse tonne and charge your own taxpayers SF 44.57/refuse tonne-
almost twice as much?" The answer was three-fold and is paraphrased as
follows:
Answer 1. "Hagenholz is an energy plant and we need as much
fuel as possible. Even though the tipping fee is half, we
are still being paid to accept fuel."
Answer 2. "The non-Abfuhrwesen waste typically has a de-
sirable higher heating value" (bad for Units #1 and #2, good
for Unit #3)
Answer 3. With more waste, our fixed costs are spread
over more refuse tonnes and total unit costs will be less.
The SF 44,57/tonne figure would be higher if others were to
not bring waste to Hagenholz.
The scrap iron collected in plant containers before burning
is sold for about SF 3.50 to SF 4.00 per ton which is about one cubic
meter.
The revenue table has no entry for sale of ash residue—
either ferrous or road building material. This is because the ash
processing is operated separately. The result is a "net cost" and
that is recorded in the annual cost table.
Both the 1976 annual costs and revenues are summarized below:
Annual Revenue SF 14,424,262
Annual Cost 14,414.893
Net Profit SF 9,369
A net profit figure is somewhat ficticious because of the
subsidy calculation designed to make net profit come out to near zero.
This deductive subsidy figure appears in the revenue table as "portion
of general tax to dispose of household refuse".
As is typical of RFSG plants that manufacture both electricity
and district heating; most of the energy revenues come from district
heating-35% less from electricity-7% and very little from scrap metal
pulled from the refuse stream before burning.
-------
134
Comment: As Battelle staff has viewed systems in many countries,
usually energy economics strongly favors sale of energy
for district heating (and perhaps cooling for the summer
load). This is in contrast to the competitive electricity
prices normally held down by economical production at
very large (100 times the mw size) hydro, fossil, or
nuclear power plants.
-------
135
FINANCE
The original 1969 development of SF 56 million was financed
by three sources of funds as follows:
70% by the City of Zurich
15% by the Kanton (state) of Zurich
15% by the Federal Switzerland Government
The City of Zurich for its 70% portion put up cash on hand
and also borrowed money from local banks as general obligation bonds.
Usually the term is five years. The interest rate varies. Having
started at 4-1/2% in 1973 for Unit #3, it was 4-3/4 in 1976. The
building is amortized over 25 years and the mechanical equipment is
amortized in 14 years.
Borrowing from the Swiss Federal Government carries a small
but important risk. The only way that the Fede.ral funds will be re-
leased to the City is after the plant has been built and the environmen-
tal portion of the compliance test has been successfully passed.
At Hagenholz, the acceptance test was run after 4,000 hours and
before cleaning to ensure performance even under adverse conditions. As
was stated, and we paraphrase again, "Anyone can make a unit be acceptable
immediately after cleaning. The trick is to make it acceptable after a
half year's operation with no cleaning and overhaul."
-------
136
REFERENCES
1. Kehricht - verbrennungsanlaze der Stadt Zurich (Brochure distributed
at the public opening of Zurich: Hagenholz in 1969) printed by
Afbuhrwesen der Stadt Zurich Walchestrasse 33 Zurich 800 6.
2. Stadt Zurich Geschaftsbericht 1976 Gesundheits - und Wirtschaftsomt
(Annual 1976 Report for the City of Zurich's Health and Cleansing
Department).
3. Bauabrechnung (Construction costs breakdown for Hagenholz Unit #3
submitted by the architect Baerlocher and Ungerv March 20, .1974).
4. Vertrag (Contract for Hagenholz RFSG to sell energy to the Migros
food warehouse as a district heating customer, dated April 4 s 1977).
5. Die entscheIdenden Kriterien bei der Wahl des Energie - erzeugung
sprozesses beim Heizkraftwerk "Aubrugg" des Kontons Zurich in
Wallisellen, an article appearing in Fernwarme International
Sonderdruck No. 2742 FWI 4 (1975) H.3. S. 91-98 (an article discussing
future plans for Hagenholz and other Zurich energy matters).
6. Die Verwendung von aufbereeteter Kehrichtschlache im Strassenbau,
Reprint article from Strasse und Verkehr (Streets and Traffic),
October, 1975, publisher Vogt-Schild AG 4500 SoJothurn [7 pages]
(Use of processed incinerator ash for road building).
7. Die Verwendung Von Kehrichtschlacke Als Baustaff Fuer den Strassenbau,
Final report on use of processed incinerator ash for roadbuilding.
A 50 page report written by Professor R. Hirt of The Technical
University of Zurich, October 1975.
8. Was Geschieht Hit Unseven Siedlungsa bfaellen? (S.pecial article in) i
Energie aus Kehricht (Energy from Waste), a chapter by Max
Baltensperger, pages 18, 19 and 20, appearing in Issue No. 65
November, 1976, Mitteilungsblatt Schweizerischer Stadtererband,
Bern, Switzerland.
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-------
-------
United States Office of Water and SW 176C.8
Environmental Protection Waste Management October 1979
Agency Washington, D.C. 20460
Solid Waste
&EPA European Refuse
Energy Systems
Evaluation of Design Practices
Volume 8
-------
Pie-pubLication xi^ue ^on EPA.
and State. SotLd Watte. Management Agenc/teA
EUROPEAN REFUSE FIRED ENERGY SYSTEMS
EVALUATION OF DESIGN PRACTICES
Zurich: Hagenholz
Switzerland
(SW-176c,.B)
the. 0^4.c.e. o£ SoLLd. Watte, wide*, contract no. 6B-01-4376
and 'id ie.ptu)du.ce.d a& Aececved faom the. c.ontMicto>L.
The. fcnding* Ahoutd be. attru,bute.d to the. contsiactox.
and not to the. 06c.e. o& Sotid Watte,.
Copies will be available from the
National Technical Information Service
U.S. Department of Commerce
Springfield, VA 22161
Volume 8
U.S. ENVIRONMENTAL PROTECTION AGENCY
1979
!0. rrAiro-mcr-t-J RtitecttoS ftc6
-------
This report was prepared by Battelle Laboratories, Columbus, Ohio,
under contract no. 68-01-4376.
Publication does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of commercial products constitute endorsement by the U.S.
Government.
An environmental protection publication (SW-176c.8) in the solid waste
management series.
pnrr.ontjj Protection rc^r-"
*»<..'.
-------
TRIP REPORT
to
ZURICH: HAGENHOLZ, SWITZERLAND
(FEATURING UNIT #3 AND COMMENTING ON
THE NEW JOSEFSTRASSE PLANT)
on June 8, 9, and 10, 1977
on the contract
EVALUATION OF EUROPEAN
REFUSE FIRED STEAM GENERATOR
DESIGN PRACTICES
to
U.S. ENVIRONMENTAL PROTECTION AGENCY
December 20, 1977
EPA Contract Number: 68-01-4376
Battelle Project Number: G-6590
EPA-RFP Number: WA-76-B146
Philip R. Beltz
and
Richard B. Engdahl
BATTELLE
Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
-------
i
PREFACE
This trip report is one of a series of 15 trip reports on
European waste-to-energy systems prepared for the U.S. Environmental
Protection Agency. The overall objective of this investigation is to
describe and analyze European plants in such ways that the essential
factors in their successful operation can be interpreted and applied
in various U.S. communities. The plants visited are considered from
the standpoint of environment, economics and technology.
The material in this report has been carefully reviewed by the
European grate or boiler manufacturers and respective American licensees.
Nevertheless, Battelle Columbus Laboratories maintains ultimate responsi-
bility for the report content. The opinions set forth in this report are
those .of the Battelle staff members and are not to be considered by EPA
policy.
The intent of the report is to provide decision making in-
formation. The reader is thus cautioned against believing that there is
enough information to design a system. Some proprietary information has
been deleted at the request of vendors. While the contents are detailed,
they represent only the tip of the iceberg of knowledge necessary to de-
velop a reliable, economical and environmentally beneficial system.
The selection of particular plants to visit was made by Battelle,
the American licensees, the European grate manufacturers, and EPA. Pur-
posely, the sampling is skewed to the "better" plants that are models of
what the parties would like to develop in America. Some plants were selected
because many features envolved at that plant. Others were chosen because
of strong American interest in co-disposal of refuse and sewage sludge.
The four volumes plus the trip reports for the 15 European
plants are available through The National Technical Information Service,
Springfield, Virginia 22161. NTIS numbers for the volumes and ordering
information are contained in the back of this publication. Of the 19
volumes only the Executive Summary and Inventory have been prepared for
wide distribution.
-------
ii
ORGANIZATION
The four volumes and 15 trip reports are organized the the
following fashion:
VOLUME I
A EXECUTIVE SUMMARY
B INVENTORY OF WASTE-TO-ENERGY PLANTS
C DESCRIPTION OF COMMUNITIES VISITED
D SEPARABLE WASTE STREAMS
E REFUSE COLLECTION AND TRANSFER STATIONS
F COMPOSITION OF REFUSE
G HEATING VALUE OF REFUSE
H REFUSE GENERATION AND BURNING RATES PER PERSON
I DEVELOPMENT OF VISITED SYSTEMS
VOLUME II
J TOTAL OPERATING SYSTEM RESULTS
K ENERGY UTILIZATION
L ECONOMICS AND FINANCE
M OWNERSHIP, ORGANIZATION, PERSONNEL AND TRAINING
VOLUME III
P REFUSE HANDLING
Q GRATES AND PRIMARY AIR
R ASH HANDLING AND RECOVERY
S FURNACE WALL
T SECONDARY (OVERFIRE) AIR
VOLUME IV
U BOILERS
V SUPPLEMENTARY CO-FIRING WITH OIL, WASTE OIL AND SOLVENTS
W CO-DISPOSAL OF REFUSE AND SEWAGE SLUDGE
X AIR POLLUTION CONTROL
Y START-UP AND SHUT-DOWN
Z APPENDIX
-------
LIST OF PERSONS CONTACTED
Max Baltensperger Chief of Waste Disposal and Cleaning (Abfuhrwesen)
for City of Zurich
Erich Moser Technical Assistant Chief
R. Hirt Professor at Zurich Technical Institute
(conducted study of ash disposal)
Herr Lackmann Hagenholz Operations Manager
Herr Widmer Hagenholz Engineering Manager or Administration
Manager
Heinz Kauffmann Projects Manager, Martin, Munich, West Germany
George Stabenow Consultant to UOP, East Stroudsburg, Pennsylvania, U.S.A.
Herr Puli Hagenholz Assistant Operations Manager
The authors are glad to acknowledge the skilled assistance
and kind hospitality provided by these representatives.
-------
TABLE OF CONTENTS
Page
SUMMARY 1
STATISTICAL SUMMARY 5
OVERALL SYSTEM SCHEMATIC 9
COMMUNITY DESCRIPTION 9
Geography 9
SOLID WASTE PRACTICES 14
Solid Waste Generation 14
Solid Waste Collection 21
Solid Waste Transfer Activity 21
Source Separation Programs 22
DEVELOPMENT OF THE SYSTEM 23
Background 23
Beginning of Subject System 27
Building the Subject System 28
Next System Under Construction (Josefstrasse) 28
PLANT ARCHITECTURE AND AESTHETICS 29
Plant Design 29
Rendering Plant Gases (see also Secondary Air section) . 29
Comment 32
TOTAL OPERATING SYSTEM 34
The 4,000 Hour Cycle Between Boiler Cleanings ... 39
REFUSE FIRED STEAM GENERATOR EQUIPMENT 43
Waste Input 43
Weighing Operation 43
Provisions to Handle Bulky Waste 44
-------
TABLE OF CONTENTS
(Continued)
Page
Waste Storage and Retrieval 47
Furnace Hoppers 50
Feeders 50
Primary (Underfire) Air Source and Air Preheater .... 51
Secondary (Overfire) Air 52
Burning Grate 56
Complete Boiler 58
One Day's Flue Gas Temperature, CO^ Level and Steam
Production Recordings 60
Furnace Walls (Combustion Chamber—First, Second, and
Third Passes) 63
Screen Tubes 66
Superheater (and Attemperator) 67
Boiler Cleaning 69
Convection Section 72
Economizer 72
Boiler Water Treatment 73
Boilers for Firing With Fuel Oil, Waste Oil, and
Solvents , 73
LITTLE OR NO CORROSION AT ZURICH: HAGENHOLZ UNIT #3 78
27 Design Steps Taken at Hagenholz to Reduce Metal Wastage . . 78
Management 79
Automatic Control 79
Start-up Procedures 79
Refuse Handling 79
-------
TABLE OF CONTENTS
(Continued)
Page
Secondary Air 80
Furnace Walls 80
Superheater 81
Economizer 81
Theory of Corrosion Supplied by Richard Tanner Formerly
of Von Roll 83
General Theory of Temperature and Chloride Corrosion as
Supplied by Dale Vaughan of Battelle 83
ENERGY UTILIZATION 87
Hagenholz Refuse Fired Steam Generator 87
New Oil Fired Energy Plant 87
Electricity Generation 91
District Heating 91
ENERGY MARKETING 100
POLLUTION CONTROL EQUIPMENT 101
Mechanical Collectors 101
Electrostatic Precipitators 101
Stack Construction 104
Fly Ash 105
War- « Water Discharge 105
Noise , 106
Air Cooled Steam Condensers 106
ASH RECOVERY 108
PERSONNEL AND MANAGEMENT 120
Start-up Procedure 123
-------
TABLE OF CONTENTS
(Continued)
Page
ECONOMICS 126
Capital Investment 117
Annual Costs 126
Annual Revenues 126
FINANCE 135
REFERENCES 136
LIST OF TABLES
Table 8-1. Solid Waste Delivered to Zurich: Hagenholz in 1976
(Volume and Weight) 17
Table 8-2. Composition of Municipal Solid Waste in Switzerland,
U.S.A., and Britain 18
Table 8-3. Energy Values of Selected Waste Types (Dry) 19
Table 8-4. Average Chemical Composition of Municipal Solid Waste
in Switzerland 20
Table 8-5. Comparison of Zurich: Hagenholz Incinerator Perform-
ance, 1974 35
Table 8-6. Report of Operations 1974 and 1976 36
Table 8-8. Capital Investment Cost (1969) for Units #1 and #2 and
Other Buildings at Zurich: Hagenholz 127
Table 8-9. Capital Investment Costs (1972) for Unit #3 ard the
Water Deaeration Tanks and Room at Zurich: Hagenholz . 128
Table 8-10. Annual 1976 Operating, Maintenance, Interest, and
Other Costs for Zurich: Hagenholz Units #1, #2, and #3 129 to 130
-------
LIST OF TABLES
(Continued)
Page
Table 8-11. Annual 1976 Revenues for Zurich: Hagenholz Units
#1, #2, and #3 132
LIST OF FIGURES
Figure 8-1. Facility Cross-Sectional View of the Designs at
Zurich: Hagenholz 10
Figure 8-2. Furnace/Boiler Cross-Sectional View of the Zurich:
Hagenholz Unit #3 13
Figure 8-3. Refuse Burned at the Zurich Josefstrasse and
Hagenholz Plants from 1905 to 1976, Tonnes per Year . 15
Figure 8-4. 1976 Weekly Refuse Collections in Zurich 16
Figure 8-5. Artist Sketch of the 1904 Refuse Fired Steam and
Electricity Generator as Manufactured by Horsfall-
Destructor Co. at its Location on Josefstrasse in
Zurich 24
Figure 8-6. Views of the Zurich: Hagenholz Refuse Fired Steam
Generator 30
Figure 8-7. Horizontal Ventilation Air Pipe from Rendering Plant
to Zurich: Hagenholz Plant 31
Figure 8-8. Overhead View of Zurich: Hagenholz 33
Figure 8-9. Steam Production, Flue Gas Temperatures and CO- Levels
(Weekly Average) During the 4000 Hour Operating Cycle
Between Cleaning at Zurich: Hagenholz Unit #3 .... 40
Figure 8-10. Steam Production, Flue Gas Temperatures, and C0_ Levels
(Weekly Average) During the 4000 Hour Operating Cycle
Between Cleaning at Zurich: Hagenholz Unit #3 .... 41
Figure 8-11. (a) Von Roll Shear Opening at Zurich: Hagenholz ... 45
Figure 8-11. (b) Elevation and Plan Views of Von Roll Shear .... 46
Figure 8-12. Tipping Floor 48
Figure 8-13. Refuse Receiving Pit Zurich: Hagenholz 48
-------
LIST OF FIGURES
(Continued)
Figure 8-14. Anonymous Furnace Where Secondary Overfire Air
is Very Little or Totally Lacking 53
Figure 8-15. Hagenholz Unit #3 Where Secondary Overfire is
Plentifiil 55
Figure 8-16. Martin Burning Grate (not Zurich: Hagenholz) ... 57
Figure 8-17. Furnace/Boiler Cross-Sectional View of the Zurich:
Hagenholz Unit #3 59
Figure 8-18. Boiler Tube Sections Layout at Zurich: Hagenholz #3 61
Figure 8-19. First Pass Walls Covered with Silicon Carbide over
Welded Studs: Shows Rejection of Slag from Walls at
Zurich: Hagenholz 65
Figure 8-20. Superheater Flue Gas and Steam Temperature and
Flow Patterns at Zurich: Hagenholz 68
Figure 8-21. Superheater Flue Gas and Steam Temperature and Flow
Patterns at the New Zurich: Josefstrasse Plant and
at the Yokohama, Japan Martin Plant 70
Figure 8-22. Water Consumption per tonne of Refuse Consumed in
1976 76
Figure 8-23. Corrosion Threat on Plain Carbon Steel 84
Figure 8-24. (a) Electrical Power Generation Room 89
Figure 8-24. (b) Steam and Boiler Feedwater Flow Pattern Exter-
nal to the Zurich: Hagenholz Boiler 89
Figure 8-25. Tonne Steam Produced per tonne of Refuse Consumer
(1976 Average was 2.41) 90
Figure 8-26. KWH Electrical Sales per tonne of Refuse Consumed . 90
Figure 8-27. 1976 Heat Delivery to Kanton and Rendering Plant
and Steam to EWZ from Zurich: Hagenholz 93
Figure 8-28. Kanton District Heating System (5.3 km long) Using
260 C (500 F) Steam at Zurich, Switzerland .... 94
Figure 8-29. Entrance to Walk-Through District Heating Tunnel at
Zurich: Hagenholz 95
-------
LIST OF FIGURES
(Continued)
Figure 8-30. Cross-Section Schematic of Pipes in the District
Heating Supply and Return Tunnel at Zurich:
Hagenholz 96
Figure 8-31. General View of Energy Distribution from Zurich:
Hagenholz 97
Figure 8-32. 1976 Energy Delivery (Warmeabgabe) to the Railroad
Station, the KZW and EWZ 99
Figure 8-33. Cooling Tower at Hagenholz 107
Figure 8-34. Partially Processed Residue at Hagenholz 109
Figure 8-35. Segregated Bulky Residue From Furnaces at Hagen-
holz 112
Figure 8-36. Truck Discharing Plant Residue at Hagenholz .... 113
Figure 8-37. Front-End Loader Delivering Residue To Hagenholz
Processing System 114
Figure 8-38. Worker Removing Wire From Waste Processing Conveyor
At Hagenholz 115
Figure 8-39. Small Size Metal From Hagenholz Residue-Processing
Plant 116
Figure 8-40. Medium and Large Metallics From Hagenholz Residue-
Processing Plant 117
Figure 8-41. Non-Ferrous Sized Residue For Roadbuilding at Hagen-
holz 118
Figure 8-42. Test Slabs At Hagenholz Containing Sized Residue. . 119
Figure 8-43. Organization Chart For Municipal Functions In The
City of Zurich: Switzerland 121
Figure 8-44. Organization Chart For Waste Collection And Disposal
In Zurich, Switzerland 122
Figure 8-45. Total Personnel (Collecting and Disposal) Working
For Abfuhrwesen: The City of Zurich 125
Figure 8-46. Cost of Zurich Cleansing Department Since 1928 . . 131
-------
SUMMARY
This report discusses the Zurich: Hagenholz refuse fired steam
generation plant. Units #1 and #2 are only occasionally mentioned. Unit #3
was manufactured by Martin and is featured in the discussion. The report
also refers to the two older Josefstrasse plants (now demolished) and the
new Josefstrasse plant by Martin due to begin operations in 1979. All
plants and units are described to present the picture of the refuse fired
steam generation (RFSG) technology as it evolved in Zurich.
The Hagenholz plant is located in the Zurich suburb of that
name. In 1976, all three units burned about 218,342 tonnes (240,176 tons)
as collected from a 560,000 person area. It was a surprise to many that
the lower heating value had doubled since the end of World War II. This
has had both negative and positive effects on plant operations.
The plant is owned and operated by Abfuhrwesen, the City of
Zurich's Department for Refuse Collection and Disposal.
Abfuhrwesen collects about 56% of the plants input while 18%
comes from other municipalities and 26% from private haulers and businesses.
In addition to municipal solid waste, the plant also receives
waste oil, waste solvents, and other chemicals.
Ajoining the RFSG plant is a new rendering plant also under the
control of Abfuhrwesen. A delightful feature is that odiferous rendering
gases are collected and injected into the RFSG furnaces as secondary air.
No objectional odor is thus emitted from either plant.
Zurich began converting waste to energy almost 75 years ago (1904)
at Josefstrasse. A second Josefstrasse plant was built in 1927. Hagenholz
Units #1 and #2 were operational in 1969. Hagenholz Unit #3 started in
1973. Now the third Josefstrasse unit is due to begin in 1979.
Unit #3 is routinely stopped every 1000 hours for eight hours to
conduct inspections. The unit is also stopped every 4,000 hours for major
inspection and repair. An excellent set of steam and temperature readings
over the 4000 hour cycle have been provided by the plant personnel.
-------
ZURICH-HAGENHOLTZ
While the entire Hagenholz plant burns 570 to 700 tonnes per day,
Unit #3 burns 240 to 450 tonnes per day. Household waste and bulky waste
that has been sheared are fed into the furnaces.
Both the primary (underfire) air and the secondary (overfire)
air are injected into the furnace at very high pressures, overfire air at
500 to 700 nnnWs (20 to 28 inches). This produces an intense flame.
The Martin reverse action reciprocating grate has performed well
and still has 70% of the original grate bars intact after 30,000 hours
(3-1/2 years).
The " boiler" can also be described as a "one-drum
natural circulation boiler with welded water tube walls". The layout of
superheaters is routine compared to Martin's layout at Josefstrasse that
has the hottest steam superheater bundle in the second position behind
another superheater section.
Readings are provided for much of one day when a bulky load
greatly reduced flue gas temperatures and the quantity of steam produced.
However, steam temperature and pressure remained perfectly constant.
The furnace water tube walls, which are part of the boiler, are
2
covered with small steel studs (2,000 studs/m ) and then coated with plastic
silicon carbide. This is only one of the 33 discussed ways in which plan-
ners designed Hagenholz so that metal wastage could be reduced. The com-
bined efforts have been most successful in preventing corrosion and erosion.
After 30,000 hours, the water tube walls have suffered only 0.1 to 0.2 mm
wastage. The superheater tube readings taken in April, 1977 showed 0.3 mm
wastage.
The superheater is equipped with an attemperator or desuperheater
to reduce temperatures when the superheated steam becomes too hot. Among
the boiler cleaning techniques are compressed air soot blowing, falling
steel shot, pneumatic vibrators, manual alkali washing and sandblasting.
Each technique is apparently used properly at its unique location. Detailed
water quality measurements are taken.
In addition to the three refuse fired units, there is also a
No. 2 fuel oil unit to provide start-up steam and to reduce dew point
-------
corrosion. Finally, there is a separate waste oil boiler to consume the
community's automobile waste oil and to produce energy.
The energy utilization picture is most complex. High temperature
steam passes through a steam extraction-condensing turbo generator.
Medium temperature steam and hot water are used for three-district heating networks,
Electricity is used internally and sold to the two electricity networks.
The plant produces 2.41 tonnes of steam per tonne of refuse.
District heating has a priority over electricity production. Therefore,
electrical production peaks in the Summer.
All three units have electrostatic precipitators (ESP). Units
//I and #2 have somewhat ineffective multi-cyclone mechanical collectors
to supplement their ESP's. Unit #3 was last measured at 42 mg/Nm which
•j
is substantially under the 100 mg/Nm requirement of the Swiss government.
Ash recovery is advanced at Hagenholz. Unprocessed ash was
25.8% of the refuse input in 1976. Of the unprocessed ash, only 4% is
eventually landfilled. This means that of the refuse received, about 99%
is recovered in some fashion. In other words, the landfill life is in-
creased 100 fold with the RFSG and the ash recovery program.
The strong management at Hagenholz is outstanding and memorable.
The care devoted to specifying Unit #3 has been rewarded by a most suc-
cessful plant. There has been a reduction of 100 people in the last
seven years from the entire Abfuhrwessen collection and disposal staff.
The entire Hagenholz facility has been built at a capital cost
of SF 59,700,000. Of this, the Martin chute-to-stack capital cost in 1972-73
was SF 11,430,000.
The accounting formule for this "not-for-profit" activity defines
expenses to equal revenues and for 1976 they both equaled SF 14,424,262.
In 1976, U.S. dollars assuming one dollar equals SF 2.50, the plant had
expenses and revenues of $24,11 per ton.
The tipping fees accounted for about 53% while the energy sales
represented 42% of total revenue. As is often the case, a plant (Hagenholz)
that can manufacture energy for both district heating and electrical
purposes finds the energy economics much better if it concentrates on
district heating and makes electricity as a secondary product.
-------
The plant was financed at three government levels—City (70%),
State (15%), and Federal (15%). The Federal 15% carried a stipulation
that the plant must successfully pass environmental tests before the
Federal share could be released.
-------
STATISTICAL SUMMARY
Community description:
Area
Population (number of people)
Key terrain feature
City Zurich
388,165 in Zurich, 560,000 total
hills
Solid waste practices:
Total waste generated per day (tonnes/day) (610 t/d: total)
Waste generation rate (Kg/person/year) 295
Lower heating value of waste (Kcal/kg) Design data (Unit #3); 1600-3300 Kcal/kg
Collection period (days/week)
Cost of collection (local currency/tonne)
Use of transfer and/or pretreatment (yes or no)
Distance from generation centroid to:
Refuse fired steam generator (kilometers)
Waste type input to system
Cofiring of sewage sludge (yes or no)
Shear for bulky wastes
municipal solid waste
No
Development of the system:
Date operation began (year)
Plant architecture:
Material of exterior construction
Stack height (meters)
Von-Roll furnaces: July 1969 Units //1&//2
Martin : July 1973 Unit #3
concrete
91
Refuse fired steam generator equipment:
Mass burning (yes or no)
Waste conditions into feed chute:
Moisture (percent)
Lower heating value (Kcal/kg)
Volume burned:
Capacity per furnace (tonnes/day)design:
Number of furnaces constructed (number)
Yes
20-25%
2200-2400
Martin 473 t/d at LHV - 1600 kcal/hg
360 t/d at LHV = 2200 " "
264 t/d at LHV - 3000 " "
240 t/d at LHV = 3300 " "
3
2 Von Roll
1 Martin
-------
STATISTICAL SUMMARY (Continued)
Capacity per system (tonnes/day) 570 to 700 tonnes/day
Actual per furnace (tonnes/day) Unit #3; 240 to 450 tonnes/day
Number of furnaces normally operating (number) 3
Actual per system (tonnes/day) 610 tonnes/day
Use auxiliary reduction equipment (yes or no) Yes-shear
Pit capacity level full:
(m3) 5000
Crane capacity:
(tonnes) 3.3 tonnes
3 3
(m ) bucket: 3 m
Feeder drive method hydraulic
Burning grate:
Manufacturer Joseph Martin Feuerungsbau GmbH
Type Reverse Action Reciprocating Grate
Number of sections (number) 3
Length overall (m) 8.35
Width overall (m) 5.57
3
Primary air-max (Nm /hour) 62,000
3
Secondary air-overfire air-max (Nm /hour) 16,000
o
Furnace volume (m ) 472
Furnace wall tube diameter (cm) 5.7
2
Furnace heating surface (m ) 1,349
Auxiliary fuel capability (no)
Use of superheater (yes or no) Yes
Boiler
Manufacturer EVT Stuttgart
Type one-drum natural circulating boiler with welded water
tube walls
Number of boiler passes (number) 4
Steam production per boiler (kg/hr) Max: 38,200 (in 1976: 34,430)
Total plant steam production (kg/hr) 72,000
Steam temperature (° C) 420
Steam pressure bar 38
-------
STATISTICAL SUMMARY (Continued)
Use of convection section (yes or no)
Use of economizer (yes or no)
Use of air preheater (yes or no)
Use of flue gas reheater (yes or no)
Cofire (fuel or waste) input
Use of electricity generator (yes or no)
Type of turbine
Number of turbines (number)
Steam consumption (kg/hr)
Electrical production capacity per turbine (kw)
Total electrical production capacity (kw)
2
Turbine back pressure (kg/in )
User of electricity ("Internal" and/or "External")
Energy Utilization:
Medium of energy transfer
Temperature of medium (° C)
Population receiving energy (number)
2
Pressure of medium (kg/m )
Energy return medium
Pollution control:
Air:
Furnace exit conditions
Gas flow rate (m /hr)
3
Furnace exit loading (mg/Nm )
No
Yes
Yes
No
No
Yes
condensation, extraction
2
2 x 30 tonnes/hour
2 x 6 MW
12 MW
Internal: 36%
External: 64%
Steam Hot water
260-280 130
Condensate
Warm water
~100° C
95,580 Nm /hr
Equipment:
Mechanical cyclone collector (yes or no)
Electrostatic precipitator (yes or no)
No
Yes
-------
STATISTICAL SUMMARY (Continued)
Manufacturer ELEX
3
Inlet loading to precipitator (mg/Nm )
3 3
Exit - loading from precipitator (mg/Nm ) 62-75 mg/Nm (7% CO,)
3 3
Legislative requirement (mg/Nm ) 100 mg/Nm (7% C02)
Scrubber (yes or no) No
3 3
Legislative requirements (mg/Nm ) 75 mg/Nm adjusted to 7% C02
Other air pollution control equipment (yes or no)
Water:
Total volume of waste water (liters/day) 32,400
Ash: (1976)
Volume of ash (tonnes/year) 56,271
Volume of metal recovered (tonnes/year) 6,494
-------
OVERALL SYSTEM SCHEMATIC
The overall schematic for Zurich: Hagenholz is shown in Figure
8-1. This page shows cross-sectional views of both the Von Roll Units
#1 and #2 as well as the Martin Unit #3. A detailed picture of the Martin
Unit #3 furnace and boiler follows in Figure 8-2.
COMMUNITY DESCRIPTION
Geography
The Zurich metropolitan area is located in the Northern foot-
hills of the Swiss Alps. The land is thus gently rolling except near the
suburb of Hagenholz where the terrain is relatively flat.
The City of Zurich has a population of 388,000 people. The
Hagenholz plant serves 560,000 people, not only in Zurich but also other
neighboring suburbs. The population has recently decreased because
Mediterranian workers went home after the "Swiss for the Swiss"
referendum. The concurrent world recession has also contributed to a
return to family farms and the countryside.
Industry and other employment activities are well diversified.
There were no mentionable unique generators of waste that would affect
Hagenholz plant operations. Hagenholz is much overloaded as the City
refuse collection (Abfuhrwesen) increases; hence, the city is completely
rebuilding the Josefstrasse facility closer to downtown Zurich.
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12-13
FIGURE 8-2 . FURNACE/BOILER CROSS-SECTIONAL VIEW OF
THE ZURICH: HAGENHOLZ UNIT #3
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14
SOLID WASTE PRACTICES
Solid Waste Generation
Not all waste generated in the Zurich area was collected under
Abfuhrwesen control until recent years. Figure 8-3 portrays the recorded
history of collection from 1905 until the present. The 400 percent
increase from 1969 to 1974 reflects the scope of record keeping more
than it reflects true generation and collection of solid waste. The
weekly pattern of refuse treatment is shown in Figure 8-4.
Sources of waste during 1976 are shown in Table 8-1. Note the
importance of non-Abfuhrwesen collection and the receipt of waste oils,
solvents, and chemicals. The waste oils are burned. The chemicals,
however, are collected and transferred to an industrial and hazardous waste
treatment center.
The city provided several tables describing solid waste composi-
tion. Table 8-2 shows physical component percentages for studies that have
been made in Switzerland, the U.S.A. and the U.K. The first Swiss column
is what was used in planning Hagenholz Martin Unit #3. Calorific values
*
are shown in Table 8-3 for common components in waste. A 1969 study by
EWAG (a testing service) and Von Roll showed values between 1950 and 2150 kcal/
kg (3510 to 3870 Btu/pound). Since 1965, the lower heating value has risen
only modestly. Plastic percentages are not rising very fast. Unit #3 was
designed for calorific values ranging from 1600 to 3300 kcal/kg (2880 to 5940
Btu/pound). Presently, the calorific value with 20 to 25 percent moisture
ranges from 2200 to 2400 kcal/kg (3960 to 4320 Btu/pound). Elemental percen-
tages for Swiss municipal solid waste are shown in Table 8-4.
At Hagenholz, slightly over 800 tonnes (880 tons) per day of
solid waste are received on a five day collection basis. This converts
to slightly over 600 tonnes (660 tons) per day on a seven day burning
basis. The plant gates are open Saturday mornings to receive trash from
private vehicles.
Every reference to refuse calorific value relates to the lower heating
value commonly used in Europe (and not the higher heating value used in
the U.S.A).
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FIGURE 8-4. 1976 WEEKLY REFUSE COLLECTIONS IN ZURICH
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17
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From other community (175
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Total waste oil
Other waste (solvents, che
GRAND TOTAL
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Source: Stadt Zurich Gesc
Gesundheits - und
pages 32 and 33
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18
TABLE 8- 2. COMPOSITION OF MUNICIPAL SOLID
WASTE IN SWITZERLAND, U.S.A.,
AND BRITAIN
Composition by Weight Percent (%)
(Location and
Switzerland U.S
Constituents
Food waste
Textiles
Paper
Plastics
Leather and rubber
Wood
Glass
Ferrous and nonferrous
1
20
4
36
4
2
4
8
6
2
12
2.5
30
7
-
6
,5
7
3
14.5
3.0
33.5
2
-
2.5
8.5
5
1
6
3
40
4
2
2
17
9
Source)
.A. Britain
4
14
-
55
1
-
4
9
9
5 6
26 13
2 2.5
37 51.5
1.5 1.0
-
-
8 6.5
8.5 6.5
metals
Street sweepings and
garden waste
Stones, dust, and other
debris
10 33.5
31
12 3
15
16
Sources: 1. National averages as published by EAWAG (1971) (used for
planning Hagenholz)
2. Municipal solid waste of Geneva (1972)
3. Municipal solid waste of Zurich (1963/1964)
4. USA (1970 - 72)
5. London (1972)
6. Birmingham (1972)
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19
TABLE 8-3 . ENERGY VALUES OF SELECTED
WASTE TYPES (DRY)
kcal/kg
Average waste
Constituents (in relation to the
dried products)
paper
plastic, leather, rubber
food waste
textiles
wood
Forest and wood industry residues
Agriculture and food industry waste
Tires
Bituminous coal
Gasoline
Methanol
1600 - 3400
4160 - 4460
5600 - 6450
4775
4500
4820
4090
2780
8230
5600 - 8100
11400
5420
Source: Various sources.
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20
TABLE 8-4 . AVERAGE CHEMICAL COMPOSITION
OF MUNICIPAL SOLID WASTE
IN SWITZERLAND
Composition^
Constituent in weight %
Water 32.90
Material containing organics
Decomposable material 36.20
Carbon 20.20
Hydrogen 2.60
Chlorine 0.34
Nitrogen 0.57
Phosphorus 0.12
Organic material total 41.00
Material containing minerals
Carbonate 0.86
Potassium 0.11
Calcium 2.40
Sodium 0.54
Magnesium 0.24
Ferrous 2.35
Mineral material total 26.10
The table is not composed for totals to be
summed.
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21
Solid Waste Collection
Solid waste collection is performed by the City of Zurich, Depart-
ment of Streets and Sanitation, (Abfuhrwesen) by private collectors and by
other communities. The 130 Abfuhrwesen vehicles typically make four trips
per day carrying about five tonnes per truck per day.
Beginning in 1970, Abfuhrwesen began using plastic and paper sacks
in place of metal containers. This has had a very positive effect on re-
ducing collection personnel and hence costs as seen in the later Figure 8-35.
The previous Table 8-1 infers more information about collection
activities. Considering only the solid waste, the collection activities
are performed in 1976 by the three types of collectors in the following
manner:
Abfuhrwesen (City of Zurich) 56
Other municipalities 18
Private haulers and businesses 26
100% by weight
Solid Waste Transfer Activity
The Hagenholz facility is used as a location for anyone to dispose
of properly containerized hazardous (non-radioactive) wastes and in-
dustrial chemical waste. In Europe, as compared to the U.S.A., there is
a much greater emphasis on municipal responsibility for treatment and
disposal of such wastes.
Private haulers simply bring their containers to a rear area
of the plant for temporary storage. When enough waste of a certain
category is stored, then a truck load of material is taken to the rele-
vant treatment center. Presumably, some of the material is taken to the
privately operated hazardous waste processing plant adjacent to the Baden-
Brugg refuse fired steam generator (RFSG) that was discussed in a separate
trip report.
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22
Source Separation Programs
The community has just started three voluntary recycling
centers for glass, cans, and waste paper.
Abfuhrwesen has had seven centers for collection of used
crank case oil. Garages and private individuals bring their waste oil
«
to the centers. However, no money, changes hands.
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23
DEVELOPMENT OF THE SYSTEM
Background
Zurich began its long history of converting waste into energy
back in 1904 at the unit pictured in Figure 8-5 on Josefstrasse. In fact, efforts
are now proceeding to develop a 75-year anniversary brochure that will be
released in 1979.
Operations continued until 1927 when the plant was temporarily
closed for rebuilding. The plant reopened in 1928. Refuse consumption
rose from 30,000 tonnes (33,000 tons) per year to 70,000 tonnes (77,000 tons)
per year in 1959. Between 1959 and 1968, the overloading results became
pronounced as corrosion repairs increased. During the period, extra
waste had to be landfilled on farm land. By 1969, tonnage consumption had
dropped to 50,000 tonnes (55,000 tons).
By 1965 a long range plan had been developed where two large
KFSG units would be built, one on each side of the Limmat River (the
river flowing through the old city's centrum). Because Josefstrasse was
south of the river, officials decided to build a 520 tonne (572 ton)
per day facility at Hagenholz, a northern suburb. This was one of the
few remaining open industrial spaces in the city.
Partially because of Von Roll's local presence and because of
their excellent reputation throughout Europe, Von Roll was chosen to
build two 260-tonne (286 ton) per day units with room set aside for
a third unit later on. The construction begun in 1966 was completed in
1969. Waste consumption immediately jumped to about 170,000 tonnes (187,000
tons) per year at both plants.
NOTE: These first two furnace/boilers at Hagenholz have
experienced considerable problems. Battelle decided
to visit Hagenholz, not because of these first two
units but because of the later added excellent Martin unit
that has experienced almost no corrosion. Nevertheless,
the general history of the first two units needs to be
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24
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25
explained because of its philosophical impact on the
design of the third unit and because of a most important
lesson to be learned.
This report has been carefully reviewed by both Von Roll,
Martin, and their American representatives.
The basic problem with the first two units is that the refuse
calorific value rose much more than expected. The 1945 values of 1000 kcal/
kg (1800 Btu/pound) were known to have risen, but how much was apparently
unknown. Likely, no one in the City Administration nor at Von Roll ex-
pected the 1969 value to be 1950 to 2150 kcal/kg (3510 to 3870 Btu/pound) as
was later measured by Von Roll and EWAG, the Government's testing service.
Thus, the plant (well designed for rather low calorific value waste) had
to burn waste that was 50% to 100% hotter.
The gas flow passages between the boiler tubes were properly designed
to be small - assuming the "cool" waste. But the result with the "hot"
waste was excessive sticking of hot, fused flyash on boiler tubes causing
eventual blockage. The sticking is caused by the flyash fusion tempera-
ture being often exceeded as temperatures in the boiler convection section
were around 600 C (1112 F). These sticky deposits interfered with heat
transfer hence the" flue gas leaving the boiler was very high. These high
temperatures corroded the boiler tubes and the electrostatic precipitators.
To reduce sticking and corrosion, less waste was fed and
primary and secondary air was reduced. Elsewhere, the rubbing action of
the grate bars against each other had worn away grate metal so that
the air.spaces were larger. With the lower volume and pressure of
underfire air, objects fell between the bars and down into the siftings
removal system. Fires under the grate became common.
The net effect on energy delivery was negative. The city had
specified 28 tonnes (31 tons) steam per hour per furnace. Unfortunately, to
run the system, about 17 to 19 tonnes (19 to 21 tons) steam per hour per
furnace could be produced as shown below:
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26
1974 1976
Furnace/Boiler #1 23.7 tonnes 18.7 tonnes
Furnace/Boiler #2 18 tonnes 17 tonnes
Original Rated Steaming Capacity 28 tonnes 28 tonnes
Moving ahead to total operating Tables 8-5 and 8-6, notice
that the long overdue rebuilding of Units #1 and #2 was done in 1974.
These units now operate a normal set of hours per year as also shown below
when compared to the Unit #3.
1974 1976
Furnace/Boiler #1 (Von Roll) 4,766 hours 7,463 hours
Furnace/Boiler #2 (Von Roll) 4,561 hours 7,289 hours
Furnace/Boiler #3 (Martin) 7,004 hours 7,596 hours
Total Hours in 365 day year 8,760 hours 8,760 hours
At Hagenholz most parties back in the early 1960's underestimated
"the heating value in 1965 and grossly underestimated the value for the
1970's." As a result, the system (1) was grossly overheated, (2) had been
designed for low furnace wall tube surface area for heat removal prior to
the superheater, (3) had small boiler passes designed, (4) suffered with
slagging on furnace walls and tubes, (5) developed corrosion on boiler tubes,
(6) developed high temperature corrosion in the electrostatic precipitator,
(7) suffered reduced air pressure under the grate, (8) increased number of
fires in the sittings hoppers, (9) reduced production of steam, etc.
This report mentions at several places management's emphasis
is on energy production. This has been contributory to some of the
Unit #1 and #2 problems. The original contract specified operation
at the "continuous maximum load." The term was never clearly defined
as to whether this meant "peak" or "average" or "maximum average load
over the long running time."
Plant officials interpreted the rated 28 tonnes of steam per hour
to be the maximum average load over the long-running time. Von Roll had,
however, designed the plant assuming that the 28 tonnes of steam would be
permissible for short periods as a holdable peak—but not for continuous
operation.
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27
Going back to the energy emphasis, plant staff began a cam-
paign to increase the volume of high calorific value industrial waste.
The vendor, of course, claimed that (to paraphrase) "It's not fair to
ask Von Roll to build a unit for 1200-1500 Kcal/kg refuse and then
purposely try to load it with high calorific value refuse at 2200 to
2400 Kcal/kg. Of course it will have problems."
The experience at Hagenholz and other similar experiences in
Europe have sensitized system designers to push for an accurate current
estimate of calorific values. More searching for accurate forecasts of
calorific values is needed as well.
The concern about Hagenholz Units #1 and #2 resulted in the
design of a later unit at Hamburg: Borsigstrasse to be over-compensated.
So much heat was extracted by the boiler that plant operators would
worry about keeping the refuse properly burning. The writers
now believe that all parties involved have carefully studied the parameters
and that such problems will not recur at future installations—if
designers and system purchasers will respect the calorific value of waste.
The Hagenholz full story will not be described in this report.
Contracts, guarantees, politics, personalities, etc., could be the
subject of a book and are not that relevant to this report. The item
that is relevant is:
LEARN THE PRESENT COMPOSITION OF WASTE AND ESTIMATE FUTURE TRENDS.
Beginning of Subject System
The technical problems experienced on Units #1 and #2 and the
inability of the City and Von Roll to agree and then resolve the problems
led to a prej -iced view of the firm for Unit #3. By 1970, other firms
had improved their technologies and reputations.
Martin assigned one of its top project managers, Heinz Kauffmann,
to work with the City. Max Baltensperger opened his pre-bid discussions
to all vendors. Apparently, Martin seized the opportunity with more vigor and
apparent thoroughness.
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28
Erich Moser explained the City's philosophy that "this plant
is not at a price but rather the City asked what can we build that will
be most reliable." Another comment was, "The biggest (most important)
thing is the grate."
Another philosophical comment, "Some people spend so much
(money) on architecture . . . and then skimp on the (furnace/boiler)
equipment. (Another plant) has a very nice entrance but can't make money."
They wanted "maximum reliability with mimimum maintenance, a
4000 hour guarantee, a minimum of 1-1/2 m waste water hour,
particulate emissions under 75 mg/Nm ," etc.
Three bids were received: Martin, Von Roll, and VKW. The VKW
chute-to-stack bid of SF 9,000,000 was lower than the SF 11,430,000 bid of
Martin. Yet Martin was chosen due to the City's confidence in Martin's
ability to produce an excellent system.
Building the Subject System
The result of this unusual attention to design details is a unit
that is one of the finest in Europe. Construction was finished in early
Fall of 1973. There were no appreciable construction delays. The bid
was fixed price and there were no appreciable financing problems.
Next System Under Construction (Josefstrasse)
Once the Martin Unit #3 had successfully passed its 4000 hour
compliance test in 1973, the City began discussions about replacing the
second generation (1927-1976) Josefstrasse plant with a third generation
(1979) Martin plant. This plant is now (1977) under construction at the
original site.
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PLANT ARCHITECTURE AND AESTHETICS
Plant Design
The plant is located on the "last available site of sufficient
size" considering the City of Zurich and the suburb of Hagenholz. It
seemed to be near the far end of an industrial park. As a result, trucks
must drive back on an industrial road that sometimes becomes overloaded
with traffic.
Being in a secluded portion of an industrial park, the land-
scaping is appropriately modest. This is also consistent with managements'
continued emphasis of putting money into the furnace/boiler and not into
pleasantries and "frills."
The plant design (see Figure 8-6) might be characterized as blocky
concrete. Very few windows were allowed, thus reducing noise. Regarding
noise limitations, the plant seems to be meeting the 45 decibel rating for
100 meters.
The entire front wall of the control room faces the discharge
portion of the furnace.
The basic building is 26 meters (85 feet) high. The 91 meter (300
feet) tall stack is built on a platform several meters from the building.
The plant operates under negative pressure so any odors generated
in the pit are collected in the primary air system for combustion in the furnace.
Rendering Plant Gases (see also Secondary Air section)
The most noteworthy, aesthetic feature of the Zurich-Hagenholz
plant is its consumption of rendering plant gases. Max Baltensperger is
responsible not only for recovering energy from municipal waste but also
for manufacturing flesh-meal and industrial oils and fats from animal carcasses.
In the careful design of the new rendering plant, room air collection vents
and process vents are placed to suck, under negative pressure, all of the
gases into a common pipe. This horizontal pipe is extended from the rendering
plant (see Figure 8-7) to the refuse fired steam generator for use as
secondary air. As a result, virtually all unpleasant gases associated with
the normal rendering plant never enter the environment.
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30
FIGURE 8-6 . VIEWS OF THE ZURICH: HAGENHOLZ
REFUSE FIRED STEAM GENERATOR
(Courtesy City of Zurich)
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31
FIGURE 8-7. HORIZONTAL VENTILATION AIR PIPE FROM RENDERING PLANT TO
ZUSICh: HAGENUOLZ PLANT (Battelle Photograph)
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32
For years, the U.S. EPA has investigated means of controlling
these organic gases. Absolute control would entail expensive use of
natural gas afterburners. A former president of the National Renderers
Association now working at the Columbus, Ohio, Inland Products plant
has been retrofitting his plant with suction equipment around selected
processes. The gas is then injected to the plant's oil fired boiler as
combustion air. This procedure could be most important and relevant to the
U.S. EPA's philosophy of non-degradation of the atmosphere. During 1977,
the U.S. Congress has been discussing an environmental control philosophy
that would permit construction of a new source generating a given pollutant
if an old source is either better controlled or closed.
The Hagenholz example is not quite the same thing. There, the
combination of plants may have minor air particulate emissions from the
RFSG stack, but has eliminated non-particulate odors from the old render-
ing plant.
For the complete story on rendering gases the reader should read
the later appearing section on secondary air.
Comment
Battelle believes that the spirit (but not the precise words) of
the Congressional discussions could be served in a community now having an
odoriferous rendering plant and a municipal solid waste disposal problem.
We would suggest consideration of a Sanitary Park with at least two
occupants: (1) the rendering plant and (2) the refuse fired steam generator.
We are also wondering whether.the components of various
reduced sulfur rendering gases could be contributing to elimination of the tube
corrosion threat. This has been suggested by corrosion researchers at
Battelle and is being investigated at a U.S. Slant.
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33
13
12
1. Tipping Floor
2. Refuse Bunker
3. Bulky Waste Shear
4a Furnace/Boiler (Martin)
Ab Furnace/Boiler (Von Roll)
5. Control Room
6. Ash Discharger
7. Ash Bunker
8. Chimney
9 Storage
10. Turbogenerators
11, Fuel Oil Boiler
12, Waste Oil Processing Plant
13. Solvent Receiving Station
FIGURE 8-8- OVERHEAD VIEW OF ZURICH: HAGENHOLZ
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34
TOTAL OPERATING SYSTEM
Any visitor to the Zurich-Hagenholz plant will soon be discussing
the Von Roll #1 and #2 units and the Martin #3 unit. This report is in-
tended to fully discuss the Martin #3 unit. Nevertheless, we feel that
certain operating data for all three units should be presented, but in
proper perspective.
To repeat from a previous section, most of the problems of units
#1 and #2 derived from a design for "somewhat over 1000 kcal/kg (1800 Btu/
pound) waste" instead of waste actually over 2000 kcal/kg ( 3600 Btu/pound)
as has been the case in the 1970's.
Table 8-5 presents some operating figures for 1974 which reflect
poorly on units #1 and #2. But, as mentioned before, 1974 was the year
for major overhauling that could not be accomplished before.
By 1976, all three units were operating on a more normal
schedule as shown in Table 8-6 . Figures are also presented for the
entire Sanitary Park complex including these buildings and energy customers.
• Car and truck repair shop (1,000,000 SF ($400,000) worth of
spare parts in basement)
• Office building
• Workers social hall and cleanup area
• Truck garage for storage
• Rendering plant
• FEW
• City's district heating network
• Electric utility's district heating network
The units are shut down for about eight hours every 1000 hours
for routine inspection and minor maintenance. Every 4000 hours or twice
a year, the unit is down for about one week or two for boiler cleaning and
major overhaul if needed.
During 1976, the Martin #3 unit was shut down seven (7) times
for less than one day for planned 1000 hour routine inspections. In total,
the unit was out of service for six (6) weeks.
Zurich used to have an instrument service contract but that be-
came too expensive. Their own staff now repair the instruments.
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35
TABLE 8-5 . COMPARISON OF ZURICH-HAGENHOLZ
INCINERATOR PERFORMANCE, 1974
Incinerator boiler #
Make of incinerator
Maximum throughput of solid
waste Sh.T/D
Maximum Burning Rate Sh.T/Hr
Average Burning Rate Sh.T/Hr
Average Performance Rate %
Total Operating Hours Hr/Yr.
Availability %
Average Steam Output Sh.T/Hr
Rated Steaming Capacity Sh.T/Hr
Average Steam Output Rate %
11
Von Roll
286.52
11.93
9.18
76.90
4,766.00
54.40
23.675
28.00
48.60
#2
Von Roll
286.52
11.93
9.18
60.70
4,561.00
52.10
18.672
28.00
66.70
#3
Martin
521.0
21.7
15.7
72.5
7,004.0
80.0
40.5
42.1
96.4
Source: Information obtained from data given by Mr. Max Baltensperger,
Director, Department of Streets and Sanitation, City of Zurich.
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36
TABLE 8-6. REPORT OF OPERATIONS 1974 AND 1976
Annual Totals
icinerator boiler #1 operating hours (h)
Incinerator boiler #2 operating hours (h)
incinerator boiler #3 operating hours (h)
Number 2 fuel oil fired 3-pass boiler #1 operating hours (h)
Waste oil fired 3-pass boiler #2 operating hours (h)
Incinerator boiler #1 Steam Generation (tonnes)
Incinerator boiler #2 Steam Generation (tonnes)
Incinerator boiler #3 Steam Generation (tonnes)
Total steam produced from solid waste (tonnes)
Steam generation per ton of solid waste, unit #1
unit #2
unit #3
average (t/t)
Fossil fuel fired 3-pass boiler #1 - steam generation (tonnes)
Fossil fuel fired 3-pass boiler #2 - steam generation (tonnes)
3-pass boiler total - steam generation
(tonnes)
Total steam generation (tonnes)
Quantity of solid waste burned (tonnes)
Quantity of waste oil burned (tonnes)
Quantity of waste solvents burned (tonnes)
Quantity of crude oil burned (3-pass boilers) (tonnes)
Total weight burned (tonnes)
Quantity of solid waste collected (tonnes)
Quantity of waste oil collected (tonnes)
Quantity of waste solvents collected (tonnes)
Total waste collected (tonnes)
1974
4,766
4,561
7,004
201
1,486
112,891
85,118
284,255
482,264
2.579
1,413
11,244
12,658
494,922
186,968
794
71
109
187,942
186,146
1,654
71
187,871
1976
7,463
7,289
7,596
182
2,099
139,930
125,306
261,515
526,751
2.41
1,404
13,192
14,596
541,347
218,342
1,102
113
108
219,665
217,503
1,801
113
219,417
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37
Make-up for feedwater treatment (Gals.) 6,961,926 6,798,528
Steam turbine #1 operating hours (h) 6,090 6,565
Steam turbine #2 operating hours (h) 5,351 6,160
Steam turbine #1 electric power generated KWH 18,677,670 22,376,817
Steam turbine #2 electric power generated KWH 16,155,350 20,626,620
Total electric current generated KWH 34,697,540 43,003,437
Electric current used for incineration plant KWH 11,540,878 14,276,322
Car and truck repair shop KWH 45,373 47,791
Office building KWH 148,550 131,702
Garage building KWH 39,819 27,406
Flesh-meal plant KWH 24,456 767,760
District heating system KWH 160,668 185,378
Community service KWH 12,740
Residue processing plant KWH 30,225
Community uses KWH 6,090
Total consumed for plant system (kWh) 11,973,563 15,466,584
Electric current fed to utility grid (kWh) 23,151,000 28,374,000
Electric current used from utility grid (kWh) 549,700 781,000
Water used for incineration plant kg 197,668,901 125,334,528
Car and truck repair shop kg 829,796 933,240
Office building kg 1,853,945 1,721,016
Garage building kg 114,386 37,488
Flesh meal plant kg 8,145,720
Total water consumption kg 200,772,370 136,171,992
Water consumed per ton of solid waste (kg/S. T.) 1,162 *kg/Sh.T 686
63.3 gals/S. T. 37.3
*Normal Water Consumption Per ton of solid waste for Martin System = 20 Gals/Sh.T
-------
38
Wet Residue Sh. T
Note * not weighed after June 30, 1974
Heat consumed by car and truck repair shop
Heat consumed by office building
Heat consumed by garage building
Flesh meal plant
Hot water to local factory
District heating system
City EWZ (investor-owned public utility)
Total Heat supplied by hot water and steam
Operational hours for bulky waste shear
47,594,551
1,296 x 10° Btu
2,772 x 106 Btu
1,623 x 106 Btu
1.090 x 10" Btu
2.895 x 10 Btu
1.623 x 10 Btu
304 x 10 Btu
26,425 x 10° Btu
287 x 106 Btu
531,742 x 106 Btv
489,700 x 106 Btu 65,687 x 106 Bti
495,695 x 106 Btu 629,749 x 106 Bti
2,931
2,809
|(NOTE: The causes of wide fluctuations in system energy consumption were not
determined.)
-------
39
The 4.000 Hour Cycle Between Boiler Cleanings. Readings of key
variables on Hagenholz Unit #3 furnace/boiler have been averaged for each of 26
weeks (4,300 hours) between July 1, 1973 and February 23, 1974 (when the
unit was stopped for planned cleaning) and are displayed in Figure 8- 9 .
The following Figure 8-10 is similar. It starts February 17,
1977 and goes to June when this visit was made. The unit was not
stopped for cleaning. The two figures present results of the plants
first half year (1973) and its latest half year of operation (1977 after
30,000 hours). For most of the 1973 period, steam production had hovered
around 37.5 tonnes (41.3 tons) per hour. Four years later the figure
had decreased to about 35 tonnes (38.5 tons) per hour.
Notice the steady rise in flue gas temperatures during the first
1000 or 2000 hours. The low initial readings reflect excellent heat
transfer rates due to rather clean tubes. After the tubes have accumulated
deposits, the heat transfer levels out as is indicated by the flat tem-
perature and steam profiles.
The superheater and the economizer tubes are stacked (and not
staggered). During the first 1000 hours, deposits are beginning to
accumulate vertically between close tubes as shown in this diagram by
Martin's Heinz Kauffman. Eventually, the space between the close tubes
becomes filled with deposits.
o o o
O O o
o
0
o
e>
GOO
After the loss of heat transfer from the initial deposit, the increasing
deposit has little effect on further lowering heat transfer and the
efficiency remains consistent for the remaining 2000 hours of the cycle.
The economizer is especially large to both recover energy and
to reduce flue gas temperatures entering the electrostatic precipitator as
seen in the earlier Figure 8-1. In 1973, the flue gas temperature leaving the
economizer was around 250 C (482 F) but always below 275 C (527 F) on a weekly
average. Four years later, the average temperatures had risen to 290 C
-------
40
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-------
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-------
42
(554 F) with occasional excursions to 300 C (572 F) the temperature con-
sidered by many to be the temperature above which ESP high temperature
corrosion occurs.
Should stack gas temperatures rise 90 C (162 F) above normal,
then overall plant efficiency would fall by 5%, i.e., not enough energy was
absorbed by the boiler tubes from the flue gas stream.
-------
43
REFUSE FIRED STEAM GENERATOR EQUIPMENT
Waste Input
Normal sized refuse in garbage trucks and bulky waste is
defined as pieces entering the hopper less than Imx Imx3m(3ftx
3 tt x 9 tt).
The previous Tables 8-2, 8-3, and 8-4 should be referred to
understand the waste composition. With a moisture percentage of 20 to 25%,
the lower heating value is now 2,200 to 2,400 kcal/kg (3960 Btu to 4320 Btu/
pound). The later Martin #3 unit was designed to accept waste with lower
heating values from 1600 to 3300 kcal/kg (2880 Btu to 5940 Btu/pound).
Waste is received at Hagenholz five (5) days per week amounting
to 4,000 to 5,000 tonnes (4,400 to 5,500 tons), i.e., 570 to 700 tonnes/
day (627 to 770 tons/day) on a seven (7) day burning basis.
The Unit #3 burns 240 to 450 tonnes (264 to 495 tons) of refuse
per day. Animal horns and hoofs from the adjoining rendering plant are dumped
into the bunker.
Sewage sludge is not permitted as an input because the City con-
siders its ash recovery program to be very important. Tests by R. Hirt
have shown that incinerator ash, contaminated by the heavy metals in
sewage sludge cause the processed incinerator ash to be less desirable as a
road building material.
Weighing Operation
The scale at the plant entrance has performed very well. The
scale is recalibrated once per year. Now, there are two men at the scale.
Two men are assigned to direct tipping and to encourage truck drivers to
clean up any spillage. Later, when the new Josefstrasse plant is operational,
only one man will be at the Hagenholz scale and one on the tipping floor.
The reader may wish to review the later section on Waste Storage
and Retrieval to read about why the crane scale was abandoned.
-------
44
Provisions to Handle Bulky Waste
A scissor shear, manufactured by Von Roll operates from 6 a.m.
to 8 p.m. five days per week. This unit operated 2,931 hours in 1974 and
2,809 hours in 1976. Normally this type of shear does not need an operator
in residence because it is in motion all the time. It can process one to
ten tonnes per hour.
The bulky waste shears (see Figures 8— lla and 8-llb) operate like
multiple scissors, cutting and crushing the bulky refuse between its shear
beams. Seven fixed and six moveable shear beams are connected at their lower
end through shaft and bearings. Each beam is equipped with double edged
blades of highly wear-resistant alloy steel which can easily be turned once
and reused. The moving beams are arranged in two groups of three, each
group being opened and closed by a hydraulic working cylinder.
The sheared material falls through the spaces between the fixed
shear beams and down into the. pit. The crane operator must then carefully
distribute this usually higher calorific waste over the entire pit.
The unit operates either fully or semi-automatically, with
remote-control by the crane operator. Control can otherwise be exercised
at the main control panel installed near the hydraulic power pac. A pre-
set pressuie switch at a limited pressure of approximately 120 bars is provided
in the hydraulic circuit and combined with a back-up pressure relief valve,
limits is reached, the forward thrust stops and the six moveable shears
retract so that more refuse can fall into the V-shaped hopper. Thus,
the unit is protected against damage when the shearing resistance should
grow too high.
In contrast to many other size reduction methods, the Von Roll
Hagenholz unit has been almost 100% reliable. Routine inspections are con-
ducted and repairs made three (3) times per year and the expected life is at
least 20 years.
The knives are completely changed every 16 months. But during
that period, the edges are rotated four (4) times, i.e., once every four
(4) months.
Once per week, the knives are cleaned. Bed springs and large
tires can be a problem and may need to be extracted with a long hook.
-------
FIGURE 8-Ha. VON ROLL SHEAR OPENING AT
ZURICH: HAGENHOLZ
(Courtesy City of Zurich)
-------
46
7965
U83
U83
FIGURE 8-llb. ELEVATION AND PLAN VIEWS OF VON ROLL SHEAR
-------
47
Originally, the shear was not strong enough and was later rein-
forced. There will be no shear at the new Josefstrasse plant because the
chute will be larger, i.e. 1.5 x 6 m.
Waste Storage and Retrieval
3 3
The refuse pit holds about 5,000 m (6540 yds ) or 3,000 tonnes
(3,300 tons) when filled to the level of the tipping floor (see Figure 8-12).
and 8-11.) When three or four doors are closed out of a total of doors, refuse
can be piled up to 9,000 m3(11,772 yd3). During our visit, material was so piled
up that the closed doors were bowed outward.
There are fire hoses above the pit to fight small fires. Once,
since 1969, they did have to call the fire department.
The two three-tonne (3.3 ton) cranes manufactured by Haushahn
of Stuttgart are double bridge. The crane operator is in a position that
is often faced with a problem of judging waste content (for calorific
value and bulky items) because of the obstructed view of the opened,
bended knee door that extends out into the refuse pit (see the previous
Figure 8-13). As a result, the new plant at Josefstrasse will have
vertically rising guillotine doors as shown below:
t rn
Existing Hagenholz
New Josefstrasse
-------
48
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-------
49
Josefstrasse will have the semi-automatic crane feature that
accurately places the bucket over the hopper. (The Hagenholz system is
manually operated only). Hagenholz uses the less expensive clam shell
buckets. However, at Josefstrasse, polyps will be used. The clam shell,
while large in volume capacity does not compact well and is itself very
heavy. The polyp, however, is lighter and can compact more. This re-
sults in a bigger refuse load lifted per horsepower expanded. The crane
capacity at Hagenholz is 38.7 tonnes (42.6 tons) per hour while at
Josefstrasse it will be 44 tonnes (48.4 tons) per hour.
The load cell on the crane failed and has intentionally not
been repaired. When asked why, the response given was something like the
following:
"We don't care how much refuse we are burning. Our concern is
how much steam we are producing. Hagenholz is an energy plant
and not primarily a refuse disposal plant. If we repair the
load cells, people may begin paying too much attention to
refuse burning and not enough to energy production."
The reader is referred back to Tables 8-5 and 8-6. In no
way is it possible to determine how many tons of refuse were burned per
furnace in 1976.
Comment; It appears to be sophisticated to say, after everyone
has been discussing energy from waste for a time, "Let's
remember that these are primarily refuse disposal plants
and that energy production is a secondary consideration."
Plant managers at Nashville, Tennessee and at Zurich,
Switzerland would likely not agree with this statement
for their own systems.
We believe that the emphasis is totally a matter of
local circumstances. Norfolk, Virginia has a waste
disposal plant while Nashville, Tennessee has in fact
an energy facility.
Some might argue with (post construction) emphasis on
energy production on Units #1 and #2 with higher heat-
containing waste. However, with the predeclared emphasis
on energy from Unit #3, there has been no problem at
all.
-------
50
Furnace Hoppers
The hopper dimensions are 5.517 m (18.1 feet) by 7.056 m
(23.1 feet). The hopper tapers down to the feed chute that has dimen-
sions of 1.5 m (4.9 feet) by 5.486 m (18.0 feet). The chute is sur-
rounded by a water jacket.
Burnback has only occurred once in four (4) years in Martin's
#3 unit. While not certain, operators suspect that superheater tubes
might have become plugged enough such that not all of the combustion
gases could escape. Another reason might be that the I.D. fan was not
functioning properly. For whatever reason, pressure likely built up
and fire eventually went up the chute.
An explanation was made for the excessive burnback experience
at Paris: Issy - les - Moulineaux, Issy has a very high chute. As a
result, an induced draft pulls the flame back up the chute in 90% of
all start-ups.
Hagenholz is thus fortunate to have a stubby chute and wide
enough spaces between boiler tubes.
Feeders
Unit #3 has three (3) runs. Each run has upper and lower
Martin feeders with the following specifications. Stroke frequency is a
function of steam temperature, steam pressure, and temperature entering
the electrostatic precipitator.
Stroke (maximum)
Stroke (normal)
Frequency (strokes/minute)
-------
51
The feeders are hydraulically driven. As with many other com-
ponents, preventive maintenance is performed on the units. The feeders
are almost 100% reliable. On one occasion, a waste container of acetone
spilled down the chute, leaked out of the chute and onto the rubber
hydraulic lines. The acetone entering the furnace caught fire and the
rubber tubes outside the chutes were destroyed. Consequently, they were
replaced with steel flex hoses.
The feeders are controlled by the Martin "black box" that is ex-
tensively discussed in the Paris: Issy and the Hamburg! Stellinger Moor
reports in this same series.
Zurich officials are pleased with the hopper and feeder per-
formance and Martin will use the same design at Josefstrasse.
Primary (Underfire) Air Source and Air Preheater
Primary air is drawn from the top of the bunker, above the cranes
and away from hopper discharge dust. The centrifugal forced draft fan, made
by Pollrich of West Germany, produces a static air pressure after the fan
of 580 mmWs. Volume maximum is 62,000 Nm /hour.
The primary air temperature would average around 20 C ( 68 F) if
the GEA air preheater were not being used. With the steam air preheater
on, temperatures are raised to 80 to 150 C (176 to 302 F). Hagenholz #3
(in contrast to Hamburg: Stellinger Moor or Paris: Issy, whose existing
preheaters are seldom used) was properly designed for hotter waste and
also hotter primary air. As a result, the preheater is almost always on
and consumes 2.1 to 2.5 tonnes (2.2 to 2.8 tons) of steam per hour depending
on the refuse heating value as shown below:
Lower heating value (cal/kg) 1800 1600
Exiting air temperature (C) 80 300
Refuse quantity (tonnes/hr) 15 15
Heat output (Gcal/hr) 0.985 1.160
Steam consumption (tonnes/hr) 2.120 2.500
Upon start-up, the steam used by the air preheater is not raised in
the RFSG but rather it is raised in the package fuel oil boiler or from the
RFSG //I or #2. The heat produced is about 0.985 to 1.16 Gcal/hour (up to 4.7)
MBtu/hr) assuming^ a lower heating^ value of 1600 + 1800 kcal/ke (2880 to 3240
Btu/pound).
-------
52
Neither the fan nor the preheater have experienced maintenance
problems. The fan V-belt has been changed once in 30,000 hours. The Unit
#3 preheater has bare "flat" tubes through which steam passes. Units #1 and
#2, instead, had "finned" tubes which caused cleaning problems. During each
anticipated 4000 hour inspection, cleaning and repair activity, compressed
air is used to blow off accumulated dust.
The primary air, thus preheated, passes down and into the five
zone plenums under each of the three runs, i.e., 15 zones. The pressure
just under the grate bars is fairly high at 50 to 150 mmWs.
The underfire air pressure is held constant. The air damper
settings are rarely changed and only if the refuse is very very wet.
At the plenum hopper bottom, a siftings damper opens and closes
according to an automatic timer. When open, the siftings fall and are
pneumatically blown down to the bottom ash hopper.
Readings of underfire air pressure are recorded every two hours.
If absolutely necessary, the pressure and flow can be changed in the
control room.
Secondary (Qverfire) Air
Again, Pollrich centrifugal fans are used. As discussed in
the previous Plant Architecture and Aesthetics section, rendering plant
gases are the exclusive source of secondary overfire air.
Of the total combustion air, roughly 80% is primary underfire air
and 20% is secondary overfire air. Roughly 91 kw are required to pull a
3
maximum of 10 Nm /second from the rendering plant.
There is no secondary air preheating and rendering gas temperatures
3
average around 20 C (68 F). The maximum air volume is 16,000 Nm /hour.
The static pressure is 730 mmWs (mm of water). The front wall air
pressure is 300 mmWs while the back wall air pressure is 540 mmWs. These
very high secondary air pressures create extreme turbulence within the
furnace.
Figure 8-14 shows an anonymous furnace where secondary air
pressure is very low. Notice the clearly shaped flame and details of the
opposite furnace wall. Turbulence is very low.
-------
53
FIGURE 8- . ANONYMOUS FURNACE WHERE SECONDARY OVERFIRE AIR IS VERY
LT^'LE OR TOTALLY LACKING
-------
54
Figure 8-15, however, presents a red ball - a glow with no dis-
cernable shape. We suspect that any carbon monoxide (CO) formed could only
exist instantaneously before conversion to C0_. This turbulence virtually
eliminates CO. CO, if present in appreciable amounts, is thought to
contribute boiler tube corrosion in RFSG.
The unusual fact is that Zurich: Hagenholz Martin #3 super-
heaters have experienced only .3 mm metal wastage in 30,000 operating
hours. This amazing lack of corrosion exists despite the 732 C (1350 F)
flue gas temperature entering the superheater and the 427 C (800 F)
steam temperature leaving the superheater. The water tube walls have a
most acceptable 0.1 mm metal wastage for the same time period. This
high turbulence along with many other factors share the credit for no
corrosion. See page 83 for a comprehensive discussion on corrosion.
Martin and Hagenholz personnel emphasized their rejection of any
sidewall secondary air jets. Any sidewall jets, they claim, would cause
CO to develop in the middle of the furnace.
The secondary air passes 22 nozzles in a single row of the front
wall and a similar 22 nozzle row in the rear wall.
Readings of CO are taken by using an instrument built by Landis
and Gyr of Zug, Switzerland. The instrument is recalibrated every two
weeks using a sample of known C02 concentration. Every year, the instrument
is cleaned and the filter is changed. On June 8-10, 1977, the CO readings
varied between 8.2% and 11% (see the data - Page 62).
Reliability of the secondary air system has been excellent. The
V-belts have not even been replaced after 30,000 hours. The nozzle jets
have remained open and clear despite slag buildup on the rear wall.
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55
FIGURE 8-15. HAGENHOLZ UNIT #3 WHERE SECONDARY OVERFIRE IS PLENTIFUL
-------
56
Burning Grate
The Martin #3 furnace is equipped with its unique reverse action
reciprocating grate as depicted in Figure 8-16. The furnace, with its three
parallel runs, is wide but quite typical for Martin installations. The
unit is rated 21 tonnes (23.1 tons) per hour of refuse input.
The reader is referred to a previous discussion on Waste Storage
and Retrieval where little concern is expressed for knowing exactly how much
refuse is being fired at any one time. Nevertheless, for a period, pre-
cise measurements were taken and ratios were developed. One of these
ratios is 2.41 tonnes of steam produced per 1.00 tonne of refuse con-
sumed. This, by definition, is also 2.41 tons of steam produced per 1.00
ton of refuse consumed.
In a typical hour, 34 to 39 tonnes of steam are produced.
Assuming 37 tonnes steam means that about 15.3 tons refuse was consumed.
Grate bars are made from 18% chromium steel. They are designed
and assembled so that no more than two percent of the grate area is open
for air flow. Thus, with separate air flow control in each of the fifteen
air plenums and with the many small air holes, the air pressure drop can
be kept at a very high level for maximum turbulence.
The total furnace width is 5.57 m (18 feet) and the length is
o ?
8.35 m (27 feet) for a total area of 44.9 m (483 ft ).
The first sign of bar breakage is usually siftings discharge
problems. After a bar breaks, larger material falls into the plenum
and eventually enough will plug the hopper.
Non-anticipated inspections are made upon breakdowns. Cursory--
anticipated quick inspections are made every 1,000 hours. But the de-
tailed anticipated grate inspections are made every 4,000 hours or twice
per year.
In four years of running, grate bars caused emergency shutdown
twice, resulting in five grate bars total to be repaired under emergency
conditions. After three of the anticipated inspections, grate bars were
replaced. In total, about 30% of the grate bars have been replaced
leaving 70% of the original grate bars intact after 30,000 hours.
-------
57
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58
Complete Boiler
Before presenting details of the EVT (of Stuttgart, W.Germany)
boiler, some general boiler items should be described. Figure 8-17 shows
the furnace/boiler cross-sectional view of Unit #3. For those not familiar
with this technology, it should be mentioned that all parts of the boiler
are connected. Some would call this a "one-drum natural circulating
boiler with welded water tube walls." (A similar type of boiler had been
designed by Dr. Vorkauf of Berlin many years ago. In Europe it is called
the Eckrohr boiler and in the U.S. it is often known as an econotube boiler.
"Eckrohr" translated means "corner-tube." These corner-tube boilers use
very large, hollow, and heavy steel columns for two purposes. First, they
support the entire boiler. Secondly, they carry water down from the steam
drum to the bottom of the water walls.) The Hagenholz-EVT-boiler is definitely
not an "Echrohr-boiler"! This boiler is topsupported from a steelstructure
and not corner-tube-supported! The boilers #1 and #2 are Echrohr boilers!
This boiler is a natural circulating boiler and not a forced circulating
boiler!
Boiler water entering from the boiler feedwater system passes
through the following sets of tubes in the below order. The ordering is
not necessarily correlated with the passage of flue gases. In fact,
city officials have learned enough from Hagenholz experiences so that
the third generation Josefstrasse unit will have a slightly different
ordering.
Portions of Zurich Hagenholz Boiler #3
Economizer bundle at bottom of 4th Pass 1
" middle " " " 2
II II II II II II I* O
II II II tl II II II A
ii it ii top .1 ii it 5
Water tube walls combustion chambers 6a
Water tube walls first pass 6b
-------
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^-.iiLi.hLily*L-r-*fqiqiri»rjMW>rt';>!^UWm^"*B^ ->• T ^ f ^ t 't ' '"
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SB^iffita^
FIGURE 8-17. FURNACE/BOILER CROSS-SECTIONAL VIEW OF
THE ZURICH: HAGENHOLZ UNIT t3
At Josefstrae3e> the hottest superheater will be at position 10
in between two other sunerheaters.
-------
60
Water tube walls second pass 6c
Screen tubes at bottom entrance to 3rd pass 6d
Superheater supporting tubes 7
Superheater bundle at top of 3rd pass 8
Superheater bundle at middle of 3rd pass 9
Superheater bundle at middle of 3rd pass 10
Superheater bundle at bottom of 3rd pass 11
At Josefstrasse (Figure 8-17), positions 11 and 12 will be reversed.
This change will permit slightly cooler flue gases to hit the hottest steam
temperature superheater.
Figure 8-13 shows the spacing and key dimensions of all of the
tubes used.
Considering the complete boiler, the height is 28.7 m ( 94 feet),
the width is 7.88 m (25.8 feet) and the depth is 15.9 m ( 52 feet). The
final'output is 38,200 kg/hr (84,216 Ibs/hour) of steam at 38 bar (551 psi)
at 420 to 427 C (788 to 800 F).
Assuming that the refuse energy input rate is 33 Gcal ( 131 MBtu) per
hour, the volume heat release rate is 117 Gcal/m-* - hour ( 13100 Btu/ft3 - hour)
The heating surface is as follows:
• Water tube walls, Passes 1,2, and 3 1,349 m
2
• Screen tubes 42 m
2
• Superheater 703 m
2
• Economizer 951 m
3,045 m^
One Day's Flue Gas Temperature, C0? Level and Steam Production Recordings
During our visit on June 9, 1977, several hours were spent in
the control room. The steam flow (volume) chart showed relatively steady
readings of 34.5 to 39 tonnes (38to43 tons) steam per hour. Actually,
much of the time the readings were closer at 35 to 37.5 tonnes (38 to 41
tons) steam per hour. All readings are shown in Table 8-7.
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61
Water Tube Walls 1 and 2
Tube
Diameter
mm
1st Pass 57
2nd Pass 57
Tube
Thickness
4.0
4.0
Flue Gas Velocity
Maximum
4.38
6.66
Average
4.10
6.40
Screen Tube
O O O
300
70
4.5
5.55
5.55
a.
/
150 (
•>
-^- o
o o
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Superheater (Lower first bundle)
O o o
o o o
serpentine tubes
Superheater (Top three bundles)
o o o
0 O O
serpentine tubes
®_
^
f
f
150
\
-- o
O 0
31.8
31.8
4.0
4.0
6.65
6.25
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At 4:50 a.m. to 5:10 a.m., the flow suddenly dropped to 24.1
tonnes ( 26 tons) steam per hour owing to bulky waste which reduced the
energy input. By 5:15 a.m. the steam flow rate had returned to 36.1 tonnes
( 40 tons) per hour. In a few minutes it peaked at 41.1 tonnes (43 tons)
per hour; but only for a few minutes.
Later in the morning, between 9:00 a.m. and 10:00 a.m., there was
a similar drop to 26 tonnes ( 29 tons) per hour and subsequent recovery.
All this time, the steam pressure and temperature held a perfectly steady
position; the pressure at an unchanging 62% of full scale.
Flue gas temperatures, CO levels, and two-hour steam flows are
shown in Table 8-7 . These readings are for Unit #3 that has operated
about 3,000 hours since the last cleaning.
Boiler Walls (Combustion Chamber—First, Second, and Third Passes)
The total boiler wall heat adsorption area is 1,349 m2 (14,515 ft2).
2 2
Another 42 m (452 ft ) could be added if one considers the large screen
tubes to be part of the wall. Data were available on furnace volume up to
the screen tubes (and not the third pass) that indicate a volume of
472 (16,670 ft3). Considering the first pass alone, the volume is 340 m3
(12,000 ft3) and the heating surface is 330 (3550 ft^).
The wall tubes are 57 mm (2.2 in) in diameter and are 4 mm (0.16 in)
thick. The center-to-center spacing is 75 mm (2.9 in). In the first pass,
the maximum flue gas velocity is 4.38 m (14.3ft)/second with 4.10 m (13.5 ft)/
second being more normal. Following in the second pass, the maximum flue gas
velocity increases due to its smaller cross-sectional area, to 6.66 (22 ft)/
second with 6.40 m ( 21 ft)/second being normaJ .
The wall construction is termed "welded fin". The fins connecting
the tubes are extruded with the tube. The procedure was developed by EVT of
Stuttgart. At the factory small steel studs are welded to the furnace
side of the tubes to a density of 2000 studs/m2 (186 studs/ft2). The stud
orientation is radially out from the tube center. Therefore, with respect
-------
to the relatively flat wall, the stud angles are different and result in a
better adhering surface; as shown below:
Note: All dimensions f I \—I I V—/ I l«57dio
in millimeters
8 dio
Each stud is 12 mm (0.5 in) long and 8 mm (0.3 in) in diameter.
After the studded tubes had been installed at Hagenholz, plastic
silicon carbide (SiC) was covered over the studs to a thickness of 12-15 mm
(0.5 to 0.6 in). The use of studs covered with SiC is only in the
combustion chamber and the lower 2/3 of the first pass as depicted in the
previous Figure 8-2. Mr. Baltensperger commented that the SiC should
extend one or two meters beyond where flames might be expected.
Figure 8-19 is a picture taken of the studded SiC-covered walls
taken from across the active combustion chamber in Unit #3. As can be
seen, slag very seldom adheres to the SiC. Small amounts of slag will
accumulate but will fall off.
Sootblowers are not used in the first and second passes so that
any chance of a sootblower malfunction causing a tube rupture is eliminated.
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65
FIGURE 8-19.
FIRST PASS WALLS COVERED WITH SILICON CARBIDE OVER WELDED
STUDS: SHOWS REJECTION OF SLAG FROM WALLS OF ZURICH: HAGEN-
HOLZ (Battelle Photograph)
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66
Officials have been most pleased with results. After 30,000
hours, the combustion chamber wall tubes have experienced only .1 - .2
mm (0.004 to 0.008 in) metal wastage. Finally in 1978, after about
40 000 hours operation and no tube bursts, the superheater was replaced,
"tc be on the safe side".
The temperature at the end of the flame tips is 1000 C
(lfe;2 F). Two-thirds up the first pass (where the SiC stops), the flue
giv? 'emperature falls to 800 C (.1472 F) . Using the highly-thermally
3
efficient SiC, a heat release rate of 117,OOOKcal/m is possible based on
a heat input rate of 33 Gcal/hour.
The SiC surface is rarely repaired on the 1000 hour inspections.
SiC might be repaired on the 4000 hour planned inspections. Studs and
SiC might be repaired once per year during major overhaul.
An additional design recommendation to reduce wall tube corro-
sion is to place the vertical man-hole doors flush with the inside surface
of the furnace wall. Eliminating the recessed cavity will reduce dust
erosion.
gas rlow
Screen Tubes
The normal function of screen tubes is to facilitate water
circulation and to hold the walls in alignment.
However, at Hagenholz, screen tubes have a third important
function. To further reduce corrosion, flue gases pass through large, gent-
ly sloping screen tubes at the base of the third pass. These circulating boiler-water
carrying tubes provide a modest chill to the flue gases. Flue gas tempera-
tures are reduced slightly to the benefit of superheater life. To some ex-
tent, these easy-to-replace screen tubes might be called "sacrifice screen tubes."
The tubes have a diameter of 70 mm (2.7 in) and a thickness of
4.5 mm (9.18in). They are spaced 300 mm (12 in) apart. The maximum design
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67
and the average flue gas velocities are both 5.55 m/sec (18.2 feet/
sec) .
Superheater (and Attemperator)
The superheater placement can be seen in either the previous
Figure 8-18 or in the following Figure 8-20. Four horizontal tube
bundles are connected as shown on the following figure.
The interview turned again to the differences between the
evolving Paris: Issy plant and the mature Zurich: Hagenholz Unit #3.
In Paris, the superheater tubes were hung vertically in a "harp" design.
I
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Paris: Issy
Zurich: Hagenholz
The Paris design, (built in 1961) it is theorized, would develop water droplets
in the bottom of the loop that would act as an insulation blanket.
Proper heat transfer could not take place and metal temperatures would rise further
in the high temperature corrosion range.
At Zurich: Hagenholz, however, (designed in 1971) the steam flow
is always downward such that nothing can become trapped. Heat transfer
2
thus takes place and corrosion is reduced. The heat transfer area is 703 m .
The lower and hotter bundles are made from 15 Mo 3 steel while
the upper and rooler bundles are made from 35.8 II steel. The tube diameter
is 31.8 mm(1.2 in)while the thickness is 4 nan (0.15 in). The horizontal
centerline spacing is 150 mm (5.9 in) and the vertical spacing within a
bundle is 50/100 mm.
The lownr hottest first bundle has a maximum flue gas velocity
of 6.65 m/sec (22 feet/sec) and average velocity slightly less at 6.45 m/sec
( 21 feet/sec). The top three bundles, however, have a slower velocity at
a maximum of 6.25 m/sec ( 20 feet/sec) and an average velocity slightly
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68
Flue Gas Exit Temperature
500 C (932 F)
Steam Entrance Temperature
260 C (500 F)
302 C
(575 F)Steam
35/8 Vt PL4in /arb/n S/eel,
Li/C
5.8/11 Plait/CaEfcon 2tee
15/140 / Low A^loy /tee;
343 C
1650 F)Steam
Location of soot-
— blower when its
nozzle failed
after 8,000 hours
385 C
(725 F)Steam
643 C (1190 F)
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732 C (1350 F)
Flue Gas Entrance Temperature
Attemperator
Pure Water
420 - 427 C
(788 - 800 F)
Steam Exit Temperature
FIGURE 8-20. SUPERHEATER FLUE GAS AND STEAM TEMPERATURE AND
FLOW PATTERNS AT ZURICH: HAGENHOLZ
* The last and lowest loop of the 3rd bundle and the entire 4th
bundle are made with 15 Mo 3 low alloy steel.
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69
less at 5.75 m/sec. The reason for the lower velocity with the same cross-
sectional area of flow is the cooling of the flue gases.
To better control boiler exit steam temperature (plus and minus
5° C), an attemperator injects varying amounts of deionized, deaerated,
and demineralized pure water. In general this must be even more pure
than boiler feedwater. The injected water must be pure; otherwise, scale
is likely to build up in the superheater tubes. The point of injecting is shown
in Figure 8-16 as being between the lowest and the next bundle.
One might ask why the attemperator (desuperheater) water must be
even cleaner than the very clean boiler feedwater. The answer is that the
attemperator water (under 100 C, 212 F) must suddenly convert to steam (at
400 C, 788 F). As a result, the minerals formerly dissolved in the water
suddenly become solid particles. The higher concentration of these parti-
cles will accumulate on the downstream superheater tubes.
About 38,200 kg/hr (84,276 Ib/hr) of steam at 38 kp/cm2 (551.psi)
are produced.* Nute that the steam enters the superheater at 260 C (500 F)
and then exits with a temperature of 420-427 C (788 to 800 F) at the very
bottom of the third pass. In a later design, Martin tried a slightly
different configuration as shown in Figure 8-17. In this design, the
hottest tubes are the upper row of tubes in the first bundle. This
design was likely motivated by the excessively high percentage of total
plastics, being 10 to 15 percent of the refuse input.
The advantage is that a slightly cooler temperature flue gas
hits the hottest steam tube. Thus, the metal and tube deposit temperature
is less and there will be less corrosion. Zurich and Martin
officials apparently believe that a slight reduction in exit steam temperature
is more than compensated by a reduction in superheater metal wastage. Hence,
the new Josefstrasse plant under construction will use this design.
Boiler Cleaning. As mentioned previously, there has (with one
sootblower incident exception) been virtually no corrosion of superheater
tubes in 30,000 hours. At 30,000 hours, metal wastage was determined to be
only .3 mm (0.013 in) at many points around the tubes.
*kp is translated "kiloferam force"
1 kpl 2 - 1 bar = 14.504 p_si - 10,000 Newtons/m2
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70
Flue Gas Exit Temperature
500 C (932 F)
Steam Entrance Temperature
260 C (500 F)
302 C (575 F)
343 C (650 F)
380 C (715 F)
highest temperature steam
•e-
-^•427 C (800 F)
Steam Exit Temperature
385 C (725 F)
Attemperator 1 732 C (135° F) Flue Gas Entrance Temperature
Pure Water
t
FIGURE 8-21. SUPERHEATER FLUE GAS AND STEAM TEMPERATURE
AND FLOW PATTERNS AT THE NEW ZURICH:
JOSEFSTRASSE PLANT
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71
The one exception occured after only 8,000 hours. The soot-
blower was manufactured by Forest and Bergaman of Brisstol, Belgium. A
nozzle on a fixed position, rotary sootblower fell off. As a result, high
pressure compressed air blew directly onto the tube sides. The nozzle
failure was detected and the tubes were inspected. None of the superheater
tubes were burst but they had sufficient metal wastage to motivate replace-
ment. Thus, after 8,000 hours, twenty (20) tube sections, averaging 5 m
( 16 feet) per tube each, were replaced. There have been no sootblower
problems since.
The compressed air sootblowers are used daily. The two air
compressors supply two storage air tanks each 153 with air at a 30 bar
(450 psig). The air released at the sootblower nozzle is at 15 bar
(225 psig). Officials expressed their preference for superheater soot-
blowing with compressed air over steam even though the air compressor
costs about SF 250,000. As an official stated, "We use air for sootblowing.
If we used 10 tonnes steam per hour for sootblowing, we wouldn't be able
to sell it."
Once (or twice) per year, each Hagenholz boiler is manually
cleaned by the Hutte Company of Recklinghausen, West Germany (near Essen).
Four or five (4 or 5) men spend seven or eight (7 or 8) days cleaning one
boiler. An alkali chemical is used. Sandblasting may be used for selected
hard to dissolve deposits. The procedure is basically as follows for most
deposit areas.
1. Spray alkali (soak, no pressure)
2. Rinse with water
3. Spray alkali (second soak)
4. Rinse with water
5. Scrub with brushes and other tools
6. Sandblast difficult deposits
Cleaning all the tubes (walls and bundles) in all four passes normally costs
about 25,000 SF ($10,000). The dirty water coming out at the boiler bottom
has a Ph of about 2 so lime must be added.
Plant staff have been experimenting with an "unbalanced compressed
air vibrator" for cleaning the superheater. Every two minutes, the upper
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72
three bundles are vibrated. Every second or third months, they perform
a variation and interrupt the procedure for a half day.
At the Hamburg: Borsigstrasse plant, the bundle wall anchors
are hit with a sledge hammer once per week.
Convection Section
Hagenholz Unit #3 does not have a regular boiler convection
section because of the extensive four bundle superheater, the five bundle
economizer, and the four passes of water tube walls.
Economizer
The five economizer bundles are made of 35.8 II plain carbon
steel. The centerline spacing in both directions is 100 mm ( 4 in).
Each tube is 38 mm (1.5 in) in diameter and 4.0 mm (0.16in) thick. The
maximum flue gas velocity is 6.1 m/sec (20 feet/sec) while the average
velocity is 5.5 m/sec (18 feet/sec).
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73-74
Boiler Water Treatment
Boiler water is carefully monitored and treated. Detailed
water tests are made once per month. For deoxidation, N-H. (Hydrazine)
is used. Sometimes Levaxin, manufactured by Bayer Chemical, is used
rather than Hydrazine.
Water usage per refuse tonne handled over 52 weeks is shown in
Figure 8-22. The primary water use is the ash quench. Presumably,
the ash content rises in the Spring and Summer as vegetation, earth
and construction material waste increases.
Boilers for Firing With Fuel Oil, Waste Oil, and Solvents
Hagenholz is equipped with two Sulzer (of Zurich) fossil fuel
boilers; one for virgin Number 2 fuel oil and another boiler for both
-------
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77
waste oil and waste solvents. Some operating figures previously appearing
in Table 8-6 are repeated below:
Annual Totals
1974 1976
Number 2 fuel oil fired boiler #1 (operating hours)
Waste oil and solvent fired boiler #2 ( " )
Total (boiler - operating hours)
Number 2 fuel oil fired boiler #1 (tons of steam) 1,413 1,404
Waste oil and solvent fired boiler #2 ( " ) 11.244 13.192
Total 12,657 14,596
Number 2 fuel oil burned (tons)
Waste oil burned (tons)
Waste solvents burned (tons)
Total
Waste oil collected (tons) 1,654 1,801
It would be incorrect to label these activities as co-firing.
The refuse burning areas are not connected at all to the oil burning
areas. Max Baltensperger feels very strongly that no other fuel should
be fired in the same combustion chamber as refuse because of inevitable
problems of ash deposits on boiler tubes.
The Number 2 fuel oil boiler is only used to preheat the boiler
and the air preheater (for the benefit of the electrostatic precipitator).
The waste oil, however, is a completely separate system devoted to waste
oil destruction and energy recovery.
Readings of CO^ and opacity (Ringleman scale) are used to
control these oil burning systems. There have been corrosion problems
in the steel stack of these boilers.
The previous Figure 8-8 shows the general layout of the
solvent and waste oil preparation area. The waste oil is heated and
decanted. The oil, water, and sludge are pulled off separately. The
sludge at the bottom of the decanting tank is mixed with the municipal
solid waste in the pit. The oil overflow goes to the boiler.
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78
LITTLE OR NO CORROSION AT ZURICH; HAGENHOLZ UNIT //3
The occurrence of little or no corrosion at the Zurich: Hagenholz
Unit #3 has heen of interest to professionals as the 30,000 operating
hours since original construction in 1973 continue to increase. From
1973 to June, 3977, not a single boiler tube in any section has failed.
The most serious incident was when a superheater section fixed
rotary sootblower nozzle failed and sent too much compressed air directly
onto superheater tubes. The nozzle failure was discovered after 8,000 hours and
the area was examined for metal thickness. They replaced 20 tubes of an
average 5 m (15 feet) length.
A recent check in April, 1977, showed that the original
superheater tubes had metal wastage of only 0'. 3 mm. The water tube walls
of the second pass had only 0.1 to 0.2 mm metal wastage on the original
tubes.
What accounts for this amazing Ir.ck of corrosion despite a
relatively high steam temperature? In summary, the threat of corrosion
was well known before construction began and many steps (27 were discussed
with Battelle staff while in Zurich) were taken to minimize the netal
wastage. Metal wastage can occur chemically in the form of corrosion or
physically through erosion.
Ttis section describes these 33 steps, discusses Mr. Richard
Tanner's theory, Battelle's general theory and finally Dale Vaughan's
explanation of chloride actions as a reason for no metal wastage at Hagenholz.
33 Design Steps Taken at Hagenholz to Reduce Metal Wastage
Four general causes of metal wastage are important: dew point
corros.'.on, high temperature corrosion, chlorine corrosion and physical erosion.
They will be referred to often in the following listing of how Max
Baltensperger and Heinz Kauffman cooperatively designed the unit for most
successful operating results.
At a social gathering, Walter Martin was asked, "Why doesn't
Hagenholz Unit #3 corrode?" His initial casual remark was "Good Management".
Later upon reflectior, he added nine ether 7easons. Other reasons came out
of the normal .interviewing process.
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79
Management
1. The original design spirit at Zurich was that there was a no set
limit as to spending for the best (efficient and reliable) boiler
that "icuey could buy.
2. The refuse input averages 72.4% of the maximum burning rate. "You
ought to build the best ['lent possible and then run it at 80% of
capacity".
3. Excellent management ensures that the properly designed plant is observed,
monitored, and controlled as it is intended.
4. Rotating job positions for each man enhances his understanding of
the complex plant and his spirit to run it properly.
Automatic Control
5. The Martin "black box" sends instantaneous furnace roof temperature
readings to the feeder and grate controls. As a result, flue gas, metal
surface, and steam temperatures are kept within limits and high temperature
corrosion is avoided.
Start-up Procedures
6. The standby boiler (Number 2 oil or waste oil) is; always .started
before the refuse is fired and the steam heats primary underfire air
in the steam air preheater to 150 C—above the dev point temperature.
7. This same standby oil-boiler supplies steam to the refuse boiler
to preheat the tubes above the dew point temperature.
The effect of the oil-fired steam is to raise the boiler surface
temperatures sbo'."? Lhe dew point temperature so that this type of
corrosion dots not affect either the boiler, the electrostatic
preen*pltator, or the stack.
Refuse Handling
8. Refuse is thoroughly mixed by the crane operators so that a more
uniform refuse fuel is available that will not cause wide swings in
flue gas temperatures.
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80
9. The feeders are designed to introduce controlled amounts of refuse into
the furnace and not permit uncontrolled cascading that would cause poor
burning and formation of harmful CO.
10. The Martin grate, with its reverse action motion, gently (without
cascading—except for tires and stumps) rotates the refuse for
exposure to flame and combustion air.
Secondary Air
11. The front and rear-wall secondary overfire-air jets are properly
aimed to develop the desired turbulent pattern. Flame lengths are
kept short and few rise into the first pass.
12. No side wall air is permitted where inadequate mixing might allow
CO to form. (However, this is not meant to criticize. Runs tier or
Didier air wall blocks).
13. Secondary air at 500 to 600 mmWs causes intense turbulence so that
virtually all CO is eliminated before the flue gases leave the
combustion chamber. Alternating reducing - oxidizing atmospheres
are eliminated.
14. The secondary (overfire air) from the neighboring rendering plant
"may" contain reduced sulfurs, etc., that may reduce corrosion by
forming sulfate deposits on the tube, thus reducing chlorine tube
deposits. Hovever, the concentration of sulfur is believed to
be low and more investigation is needed to confirm any hypothesis.
The ammonia ppm is often high and its effect, if any, on corrosion
is not known.
Furnace Walls
15. The walls of the combustion chamber and the lower 2/3 of the walls
in the first pass are coated with Silicon Carbide (instead of bare
plain carbon steel) that was properly applied and bonded. No flame
passes beyond this point.
16. The second pass is very large so that more heat is absorbed into the
walls.
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81
17. The flue gases flowing in the large second pass are at a lower
velocity which reduces the erosive effect of the participates in
the gas as it hits the first row of superheater tubes.
Superheater
18, The superheater is positioned in the third pass (and not the first or
second passes) so that cooler flue gases, with little or no CO, hit
the tubes.
19. The superheater tubes are horizontal flowing downward (and not verti-
cally hanging). Thus, stagnant water pockets cannot form-
to interrupt heat transfer.
20. The superheater tubes are in line (and not staggered) so that flue
gases can more easily pass.
21. The superheater metallurgy is 15 Mo 3 in the lower two bundles and
35.8 II in the upper three bundles instead of plain carbon steel,
35.8 I.
22. The attemperator (desuperheater) between the lowest superheater
bundle and the next bundle inserts pure demineralized water when
steam temperature rises above a certain limit. Thus, steam tempera-
ture and pressure (but not flow rate) can be kept constant plus or
minus 5° C.
23. The entire boiler is designed so that the average superheater
exit steam temperature is 420 C (788 F).
Economizer
24. The economizer originally equipped with a shield on the first tube
row of the first bundle, was later augmented with more shielding on
the second row of the first bundle.
25. The economizer is especially large to both recover energy and to
reduce flue gas temper?trres entering the electrostatic precipitator.
26. The plant used for test purposes is an "unbalanced compressed air
pneumatic hammering vibrator".
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82
27. No sootblowers are used in the first and second passes.
28. Compressed air (and not steam) sootblowers are used in the superheater
section. Thus, injurious slugs of water lying in inactive soot-
blower pipelines cannot harm the tubes upon startup.
29. The sootblowers in superheater section are fixed-rotary (and not
retractable). Hence, the nozzles are always oriented properly and
not directed right on the steam tubes. The, sootblower jets are
fixed just underneath the tube bundle.
30. The boiler is manually cleaned with an alkali every 4,000 hours.
31. Sandblasting is limited to removing only difficult tube deposits.
32. With the lower flue gas temperatures in the first 1000 hours after
cleaning, a ferrous sulfate FeSO, might have formed instead of the
more harmful ^.
33. The economizer is cleaned with falling steel shot (and not by soot-
blowers) thus avoiding potential problems.
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83
Theory of Corrosion Supplied by Richard Tanner Formerly of Von Roll
Figure 8-23 was supplied to Battelle by Mr. Tanner, Von Roll's
top refuse-fired steam generator expert for many years before retiring. It
shows corrosion threat (abstractly without any numerical reading) on
plain carbon steel as a function of tube metal temperature.
General Theory of Temperature and Chloride Corrosion
as Supplied by Dale Vaughan of Battelle
Early in this project, Dale Vaughan was asked to summarize his
theory of how gases, metal salts, chlorine and sulfur react at different
temperatures to cause corrosion. The following is his reply so carefully
worded that it may have to be reread.
"The boiler tubes are exposed to the normal
combustion gases C02, CO, HC1, small amounts
of sulfur oxides and organics, excess air,
plus vapors and solids of inorganic compounds.
The initial reaction is undoubtedly the forma-
tion of a thin oxide layer on the boiler tube
which is quickly coated with a deposit con-
taining large amounts of chlorine identified
as a mixture of potassium and sodium chloride
with smaller amounts of heavy metals. Hence,
the tube metal is no longer exposed to the
gaseous combustion products but instead is
exposed to the deposit and/or the products
of its reaction with the gases.
Studies of deposits after long exposure to
incinerator combustion products have shown
that the chlorides are converted to sulfates
and that the chlorine content is thus reduced
significantly except at the metal surface when
FeCl2 has formed. The iron oxide layer is no
longer in contact with the metal surface, but
instead chlorine is now the corrosive species.
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Battelle's corrosion data show that wastage of
carbon steel increases rapidly at about 400 F
and again at 800 F. The first increase is
attributed to chloridation and the second to
sulfidization. The first increase coincides
with the rapid attack of iron by elemental Cl.
as shown by Brown, DeLong and Auld. Further-
more, their studies show that rapid attack of
iron by HC1 does not occur until a temperature
of about 900 F. Therefore, it is doubtful that
the HC1 content of the combustion products is a
significant contributor to metal wastage in the
temperature range where chlorine is the corro-
sive species.
However, as expected, Cl has not been detected
in combustion gases but this does not eliminate
its existence as a product of the conversion of
MCI * to M SO,. This occurs mainly in deposits
which are retained on boiler tubes and exposed
for sufficient time to the hot gases containing
low concentrations of sulfur oxides. When the
CL_ is released from the MC1? deposits at the
metal surface the attack is very rapid. The
Battelle studies have shown that by increasing
the sulfur in the fuel M SO^ forms rather than
MCI in the fuel bed and combustion chamber,
little or no chlorine is found in the deposit
and the metal wastage is markedly decreased
even though the HC1 in the combustion gases is
the same or perhaps increased some. SO
emission increases some but not rapidly."
* The letter "M" refers to any metal that might
bond with CL. or SO,.
2 4
Upon return to Battelle from Zurich, Mr. Vaughan was presented with
specific data regarding conditions at Hagenholz Unit #3. He had the following
response as summarized below:
He examined the charts showing weekly average
temperatures for July 1, 1973, to February 23,
1974 (Figure 8-9 ), and the period February 17,
1977 to June, 1977 (Figure 8-10). He believes
the important factor is that early in both
periods, namely, the first 1000 hours after tube
cleaning, all flue gas temperatures were lower
than later on in the 4000 hour cycle. Figures
are summarized below.
-------
86
Hours
100 1000 2000 4000
Flue Gas Temperature Leaving Furnace 610°C 675°C 800°C 780°C
Flue Gas Temperature Entering Superheater 510 575 675 750
Flue Gas Temperature Entering Economizer 400 470 490 600
Flue Gas Temperature Leaving Economizer 225 265 250 260
The metal temperatures are, of course, much lower. The result
is that the metal temperatures were low enough so any FeCl_ that has been
formed had time to convert to a ferrous sulfate, FeSO,, thus, providing
a protective coating immediately adjacent to the tube. The later high
temperatures were thus not harmful because the sulfate coating shielded
the tube from any later deposition and decomposition of chlorides.
The remarkable freedom from corrosion on Unit 3 appears to
confirm Vaughans theory which has been discussed earlier. It was deve-
loped by Vaughan and his colleagues in laboratory and field research
sponsored by EPA at Battelle since 1969.
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87
ENERGY UTILIZATION
Energy utilization at Zurich: Hagenholz is among the most ad-
vanced in Europe. Max Baltensperger repeatedly pointed out that Hagenholz
is primarily an energy plant. The plant is integrated with the other
conventional fossil fuel district heating and electricity plants. A new
oil fired energy plant is located nearby. The total story involves follow-
ing energy media:
Hagenholz Refuse Fired Steam Generator
High temperature steam for electricity production
(steam extraction - condensing turbo generators) 420 C (788 F)
Medium temperature steam for district heating
(Kanton, the municipal district heating system) 260 C (500 F)
Hot water for district heating (EWZ, the investor-
owned public utility for electricity and district
heating) 130 C (266 F)
Hot water for a State hospital (sterilizing), small
factory in Hagenholz, the railroad station, and
perhaps the Technical University (5 km/line) 130 C (266 F)
Electricity for the two networks (Kanton and EWZ) 11,000 volts
Electricity for internal use, truck garage, and
workshop 220 v and 380 v
High temperature steam for the rendering plant 420 C (788 F)
New Oil Fired Energy Plant
Hot water for district heating (Kanton, the
municipal owned district heating system) 180 C (356 F)
Figure 8-24a shows the electrical power generation room and some of
its equipment. The full energy product schematic for the plant is shown on
the same page i.i Figure 8-24b.
Fig 8-25 and 8-26 are also two separate figures on one page.
Figure 8-25 prer.^nts •-:. relatively flat picture of total steam produced per
ton of refuse consumed during the 52 week year. The average is 2.41 tonnes
of steam produced per one tonne of refuse input.
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88
Figure 8-26, showing kWh electrical sales per tonne of refuse
consumer, however, does have a substantial seasonal pattern that compli-
ments the district heating pattern. The philosophy is that district
heating demand is the first priority and electrical production is second.
The two electrical networks can absorb as much refuse produced electricity
as can be generated. The reverse pattern for district heating appears
later in Figure 8-26.
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89
FIGURE 8-24a. ELECTRICAL POWER GENERATION ROOM
8
-I 1
gfc
1. Furnace/Boilers
2. High pressure distribution valve
3. Governing valve
4. Medium pressure distribution valve
5. Low pressure distribution valve
6. Turbogenerator
7. Air condenser
8. Feedwater storage and deaerator
9. Feedwater pump
10. Steam for district heating
FIGURE 8-24b. STEAM AND BOILER FEEDWATER FLOW PATTERN
EXTERNAL TO THE ZURICH: HAGENHOLZ BOILER
-------
90
a_
r 4 f r f *tl
*17
FIGURE 8-25. TONNE STEAM PRODUCED PER TONNE OF REFUSE CONSUMER (1976 AVERAGE WAS 2.4i;
FIGURE 8-26. KWH ELECTRICAL SALES PER TONNE OF REFUSE CONSUMED
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91
Electricity Generation
High temperature/pressure steam from all three Hagenholz units
is fed into two Escher-Wyss (since acquired by Sulzer of Zurich) steam
extraction-condensing turbines. Each consumes 30 tonnes (33 tons) of
steam per hour for a total of 60 tonnes (66 tons).
Each then produces 6 mw for a 12 mw total average 5.25 for a
10.5 mw total) at 11,000 volts which is equal to the local network
voltage. Actually there are two electricity customers: the Kanton (local
government) and EWZ (a public utility). The turbine speed is 6800 rpm.
A large gear box between them connects it to the generator having
a 3000 rpm speed. There has been very little trouble with the turbo-
generator set. Once produced, the voltage can be lowered to 220 v and
380 v for internal use.
The new Josefstrasse plant will be equipped with two 40 tonne
steam per hour Brown-Boveri turbo generator sets. Each will produce 8 mw
for a 16 mw total.
District Heating
The Hagenholz refuse fired plant and the nearby oil
fired energy plant provide steam and hot water for three different dis-
trict heating networks. Most of the district heating piping has been in
place for many years.
The investor-owned public utility EWZ plant receives hot water
from Hagenholz which is added to the larger EWZ supply. This hot water,
at 130 C (266 F), is then distributed to many customers in Zurich.
The weekly load is shown in Figure 8-27.
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92
The second, a Kanton-owned district heating system, (see the
map Figure 8-28) has only a few large customers and has a limited po-
tential as listed below:
Kanton municipal hospital (current)
Ramibuhl Factory (current)
Railroad station (current)
Post office (potential)
University (potential)
Municipal museum (potential)
This system uses about 15 tonnes (16.5 tons) of steam per hour in the Winter
and 10 tonnes (11 tons) per hour in the Summer.
The third district heating system has many apartments and other
buildings as customers and is also owned by the Kanton. It is basically
the system that the Josefstrasse plant supplied which is now supplied by
Hagenholz while Josefstrasse is being rebuilt.
These three district heating networks are supplied by several
energy plants. Two of the energy plants are in the Hagenholz suburb;
(1) the Hagenholz refuse fired steam generator, and (2) the oil fired
energy plant. The supply and return pipelines connecting the two plants
with the three networks are in a ground-level, walk-through tunnel covered
with earth as shown in Figure 8-29. Figure 8-30 is a cross-section
schematic of the tunnel showing the supply and return lines for water,
steam, and condensate. This researcher walked about 500 m (1500 feet)
into the tunnel with the general overhead plan shown in Figure 8-28.
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93
FIGURE 8-27. 1976 HEAT DELIVERY TO KANTON AMP RENDERING PLANT AND STEAM TO EW2 FROM ZURICH; HAGENHOLZ
cal/week*
-------
94
Technical University-
Small Factory Using" Hot Water
Major Access to
Tunnel
State Hospital
Ramibuhl Factory
FIGURE 8-28. KANTON DISTRICT HEATING SYSTEM (5.3 km long)
USING 260 C (500 F) STEAM AT ZURICH, SWITZERLAND
-------
95
FIGURE 8-29.
ENTRANCE TO WALK-THROUGH DISTRICT HEATING TUNNEL AT
ZURICH: HAGENHOLZ
-------
96
t
Energy
Media
Supply
Energy
Media
Return
1. Steam condensate return from Kanton district heating network to
Hagenholz 70-80 C.
2. Warm water return from Kanton district heating network to new oil
energy plant.
3. Hot water supply from oil energy plant to Kanton district heating
network for apartments 180 C.
4. Hot water supply from Hagenholz to EWZ plant to EWZ district heating
network 130 C.
5. Warm water return from EWZ district heating network to EWZ plant to
Hagenholz 100 C.
6. Condensate return from steam purge conditioning tank to Hagenholz
(5 atmospheres).
7. Cooling water from City to pump for EWZ plant
8. Total purge condensate return from Kanton district heating network
to conditioning tank 200 C (12-14 atmospheres).
9. Steam from Hagenholz to Kanton district heating network 5 km away
260-280 C (12-14 atmospheres).
FIGURE 8-30.
CROSS-SECTION SCHEMATIC OF PIPES IN THE DISTRICT
HEATING SUPPLY AND RETURN TUNNEL AT ZURICH:
HAGENHOLZ
-------
97
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-------
98
The purge system for outbound steam pipes is used when the
steam is being turned off or being turned on. Pipe number 8 travels
the distance of the tunnel collecting condensate from the cooled steam
pipe (not to be confused with the return condensate pipes). The con-
densate is collected in the purge tanks and then added to the return
condensate tanks. One pipe (number 6) then returns the combined liquid
condensate to the Hagenholz plant.
The steam and purge line pressures are limited to a slight
superheat of 260 C (500F) and 12 to 14 atmosphere (175 to 200psi) because of
local regulations relating to pipeline expansion problems. The pipe from
the condensate return collection tank back to the RFSG plant is at five
atmospheres (73 psi) pressure.
The hot water and steam supply and return lines are inspected
and reconditioned once per year in the summer.
The electricity sells for SF 0.06/kwh in the Winter and SF 0.04/
kwh in the Summer.
The charge for district heating steam is SF 35 to SF 60/Gcal
depending on who the customer is and how much of the pipeline capital
cost the customer is paying for.
Figure 8-32 shows the weekly pattern of steam sales to the
railroad central station (SBB), KZW and to EQZ.
There has been almost no corrosion of pipes in these walk-through
tunnels. The district heating system is stopped once per year for valve
repairs where necessary.
There is five to seven percent loss in "refuse-derived condensate"
returned to the plant by the district heating networks. However, more
H?0 by weight is returned because a disproportionate amount of "oil-
derived condensate" is returned to the RFSG plant.
-------
99
«ea_
JOO--
SBB unct KZW 1976
r
SBB
Lr
KZW
-F i .r
EWZ
L-JTr
\
r-
Sflfl
new
l
J"
J~
J
' ~l I /—J
FIGURE 8-32. 1976 ENERGY DELIVERY (WARMEABGABE) TO THE RAILROAD STATION,
THE KZW AND EWZ
-------
100
ENERGY MARKETING
Obtaining new publicly or privately owned large-volume customers
is an art or skill practiced by several of Abfuhrwesen's management people.
There is no formal plan. However, management is very careful to seek po-
tential customer contacts. Sales calls are made. No fixed rate schedule
is used.
The energy plants are operated as profit centers that happen to
be owned by the City. Each contract is negotiated. If the City must
put in a large pipeline that will be depreciated over 40 years, a higher
price will have to be charged for a unit of energy. As an example,
Hagenholz sells its steam, at its own plant boundary, at a low rate to the
Kanton district heating network. However, Josefstrasse (1904, 1928, and 1979)
has always owned and maintained its pipeline network; hence, its rates are
higher. To lower the customer's price, quantity discounts are possible.
There are attempts by the Kanton district heating system (Heizamt,
a sister organization to Abfuhrwesen) to sell to large apartment complex
owners. No attempt is made to encourage individual homeowners to purchase
steam.
Officials gave Battelle an eight (8) page contract and finan-
cial worksheet as an example of a negotiated offer. This most interesting
document between Abfuhrwesen and Migros (the leading food warehouse) is
written in German and can be made available to interested parties.
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101
POLLUTION CONTROL EQUIPMENT
Mechanical Collectors
Units #1 and #2 have Rothemuehle multi-cyclone mechanical col-
lectors following the electrostatic precipitators (ESP). However, Unit #3
does not have a mechanical collector. The cyclones were always difficult
to clean. The cyclones on the first two units performed well until they
were corroded by the high flue gas temperatures. Eventually, the spirals
were removed and now the gas flows through the empty cyclone. See the
following page for more details.
While Unit #3 does not have a mechanical collector, it does
have an open chamber and hopper immediately before the ESP. The larger
flue gas cross-sectional area causes some of the heavier particles to
fall out, thus reducing the load into the ESP.
Electrostatic Precipitators
o
Unit #3 has a maximum gas flow rate of 95,580 Nm /hour or
3
26.55 Nm /sec assuming that the refuse lower heating value is 2800 kcal/kg
(5040 Btu/pound) and that 11,800 kg per hour (13 tons per hour) are com-
busted. The mean velocity is 0.814 m/sec. The furnace/boiler emits
flue gas with 2500 mg/Nm of particulate.
The electrostatic precipitator was manufactured and installed
by the Elex organization. It contains two (2) fields and has a cross-
2 2
secional area of 74.1 m (797 ft ). The effective surface collection
area is 3560 m2 (38,306 ft2).
Elex felt that it had enough experience and a flow-model study
was not performed. Mr. Erick Moser, the technical assistant lamented
that, "There is never enough information on (inlet) gas and dust compo-
sition."
Flue gases must pass through a perforated plate and a series of
baffles before entering the electric field. The output voltage is 78 kv
with an effective output current of 2,430 ma.
-------
102
The unit is cleaned by mechanical rapping with a hammer. Flyash
falls through pyramidal hoppers and is removed by a feedscrew.
The insulation is 80 mm (3.1 in) thick. In the Winter, the
hopper is electrically heated.
The flue gas temperature entering the ESP is usually 280 C
(536 F). See the previous Table 8-10. If it rises to above 300 C (572 F),
there is serious danger of high temperature corrosion from Zinc Chloride
deposits. The chemical attacks the steel until it becomes spongy and short
circuits become common.
Plant staff . cautioned about closing the plant every weekend.
They have observed other plants that develop dew point corrosion at the
150 C (302 F) flue gas temperature level. When the unit is shut down
eight (8) hours for the 1000 hour planned inspection, the ESP is kept
warm by the 150 C (342 F) steam from the (Number 2 fuel oil or waste oil)
boiler. The ESP is thus cooled only twice per year - during the 4000 hour
planned inspections.
Whenever the ESP falls below 78 kv and cannot maintain a 65 kv
charge across the fields, then operators know the excessive short circuiting
is occuring and that inspection and maintenance should soon follow.
When Units #1 and #2 were built, the Swiss air pollution law
3
limited emissions to 150 mg/Nm corrected to 7 percent CC^- The
Zurich request for proposals (RFP) specified a 100 mg/Nm limit. The
two-field Elex ESP followed by the Rothemuehle multi-cyclone more than
3
met the requirements and average 70-90 mg/Nm during compliance tests.
Later, after the units had been operating over the critical 300 C
2
(572 F) limit, corrosion began and later readings changed to 120 mg/Nm .
The original compliance test for one of the first units produced the
following: Units #1 and #2
Particulates - total
Particulates - over 30 u
co2
°2
H20 (or H2)
so2
HC1
72 mg/Nm
15 mg/Nm3
7.7%
9.2%
15.7%
219 mg/Nm3
531 mg/Nm3
(currently about 120 mg/Nm
•3r
-------
103
When Unit #3 was built, the regulation had been tightened to
r
' 3
100 mg/Nm for particulates. The RFP thus specified 75 mg/Nm . During
the compliance test, conducted by EMPA, an excellent reading of 42 mg/Nm"
was recorded as well as these other figures. Assuming an inlet loading
3
of 2500 mg/Nm and an output reading of 42 mg/Nm3 means that the unit
operates at 98.3 percent efficiency.
-------
104
Unit #3
Particulates - total
co2
H»0
so2
HC1
HF
ZnO
Pb
42 mg/Nrn3
8.4%
12.0%
220 mg/Nm3
840 mg/Nm3
3
11 mg/Nm
4.7 mg/Nm
0.37 mg/Nm3
Now that the third generation Josefstrasse is being built
(Martin is the designer), the RFP specification has been tightened further
3
to 50 mg/Nm . As of this writing, the plant is under construction and
thus no compliance test has been made. Officials have been so pleased
with the Elex precipitator (marketed by American Air Filter in the U.S.),
that it was easily chosen for Hagenholz.
The Federal Switzerland Government had a financial incentive
program several years ago that motivated construction of many refuse
fired steam generators. A condition for the Federal money was that
the plant pass its compliance test. Prior to passing the test, vendors
would have to wait for their money or the city would have to obtain a
short term bank loan. As compared to several other countries, this
policy has done much to ensure plants with well controlled emissions.
This program still exists on paper, but funds have not been
nearly as plentiful as in years before. In many Swiss regions there has
been pverbuilding of these plants and several persons have mentioned
that Switzerland is "saturated" with RFSG's.
Stack Construction
The single Hagenholz chimney is a single flue brick-lined stack
9l m (300 feet) tall with a top inside diameter of 3.8 m ( 12 feet).
Inspections are made twice per year. So far (since 1969), there have
been no chimney repairs. However, a galvanized ladder has exhibited
some corrosion. The chimney is expected to last 20 to 70 years. The
original 1904 Josefstrasse stack was used for 70 years.
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105
Unfortunately, with three furnaces supplying flue gas to a
single flue chimney, the flue gas velocity may be reduced by 1/3 or 2/3
depending on how many units are in operation. Therefore, the new
Josefstrasse will have a three flue steel-lined chimney. Since each
furnace will have its own flue, flue gas velocity will thus be independent
of how many furnaces are operating, i.e. the plume will generally behave
as is desired. Another feature of Josefstrasse is that when upper sec-
tions become corroded, a ground level hydraulic system can raise all
other sections. The deteriorated top section can be removed and another
new steel section, 5 m (16 feet) long can be inserted at the bottom.
Fly Ash
To prevent blowing dust from flyash, it needs to be wetted.
This is most difficult in the Summer and with freezing, almost impossible
in the Winter. As a result, the screw conveyors transport all flyash to
the ash discharger where it is inserted 1 m (3 feet) above the water level.
Some dust is recycled through the furnace/boiler/ESP but that is no real
problem. The flyash and bottom ash are later recycled for roadbuilding.
Waste Water Discharge
Generally speaking, the higher the refuse calorific content,
the less amount of water per hour is needed to operate the system. Hence,
there is less waste water. The following demonstrates assuming a heat
release rate of 33,000 Gcal/hr:
Lower Heating Value (kcal/kg) 1800 2400 3000
Waste Water (liter/hour) 1500 1200 900
Waste Water (Gallons/hour) 396 317 238
-------
106
Hagenholz waste is around 2100 to 2200 kcal/kg so about 1350
liters per hour is added to the ash quencher. There is no overflow of
water from the quench tank to the sewer. Only toilet waste water and
used boiler blowdown water are put in the sewer.
Noise
During the day, noise must be kept under 45 decibels at dis-
tances further than 100 m (328 feet) from the plant fences. At night,
after 8:00 p.m., the turbine windows must be closed to abate noise.
Air Cooled Steam Condensers
Large vertical louvers, made by GEA of Bochum, West Germany,
are installed on the roof wall around the air-cooled steam condenser
fan bottoms to abate noise.
Separately, the V-belt drive on the condenser fans started
squealing at low speeds. They now have two-speed motors.
The condensing capacity is 75 tonnes (82.5 tons) per hour.
At present they condense about 40 tonnes (44 tons) per hour from the
extraction condensing turbines.
Previously, Hagenholz had freezing problems in the Winter.
They now feed steam first to what would otherwise be the coldest part of
the condenser.
Figure 8-33 shows the cooling tower.
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T'7
FIGURE 8-33. COOLING TOWER AT HAGENHOLZ (Battelle Photograph)
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108
ASH RECOVERY
Ash recovery is very advanced at Hagenholz. Credit for this
accomplishment is to be shared among several parties that have funded and
guided the research and development. The entire program is outlined in
an excellent 50-page report written by Professor R. Hirt, a professor of
forest engineering at the Technical University in Zurich. His publication
is titled, "Die Verwendung von Kehrichtschlacke als Baustoff fuer den
Strassenbav", dated October, 1975. The German title translated is "Use
of Processed Incinerator Ash for Road Building". The report is available
through Mr. Hirt or Battelle.
The analysis mentions many Swiss cities. But for the City of
Zurich alone the following general 1974 data are presented:
Population
Refuse (generated )
Refuse per person (kg basis)
Refuse per person (pounds basis)
Refuse per person (365 days basis)
Ash generated by incinerators
Ash per person (kg basis)
Ash per person (pounds basis)
Ash per person (365 days basis)
Ash as % of Refuse
City of
Zurich
421,650
216,000
512
1,126
3.08
61,800
147
323
0.88
28.6
14 Large Swiss Cities
2,314,100 people
812,485 tonnes/year
351 kg/person/year
772 pounds/person/year
2.12 pounds/per day
271,260 tonnes/year
117 kg/person/year
257 pourids/person/year
0.70 pounds/person/day
33.4 tonnes/tonnes
* Josefstrasse and Hagenholz both in 1974.
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109
FIGURE 8-34. PARTIALLY PROCESSED RESIDUE AT HAGENHOLZ (Battelle Photo)
-------
110
The ash residue (slag), when removed from the ash bunker, is
stored in a pile for two months for these several reasons:
• moisture reduction
• stop fires
• chemical reactions
•• heat hydration of free lime
•• water and calcium carbonate
These exothermic reactions result in an internal temperature of
80 C (176 F). The bottom ash and flyash combined residue has a Ph of 11
or 12. Interestingly, the dirty water removed during the semiannual boiler
cleaning to remove flyash deposits has a Ph of 2 or 3—an alkali is the
cleaning agent.
In 1976, the actual following figures were reported:
Quantity of solid waste burned 218,342 tonnes 100.0%
Quantity of raw ash generated 56,271 tonnes 25.8%
Quantity of metal recovered 6,494 tonnes 3.05
The following are percentage ranges for output from the ash recovery
process:
Roadbuilding material 80%
Ferrous metals 8-9% (before recession 10-12%)
Non-ferrous mediums re-
turned to furnace 3-5%
Stumps and tires sent
to landfill 3-5%
Except for uncaptured particulates and gases, the only materials
leaving the plant in an unrecycled mode are the tree stumps and tires.
This amounts to 3 to 5% of ash and ash is 25.8% of the total waste input.
This means that 98.75 to 99.25>% is the volume reduction for purposes of
calculating necessary landfill requirements.
The copper is manually pulled out and sold as scrap when con-
veniently seen and removable. Aluminum is recycled indefinitely until
oxidized.
-------
Ill
In 1974, before the recession, ferrous incinerator scrap sold
for SF 30-90 per tonne depending on the season and strikes in Italy and
France. In 1977, the price range from SF 30-35 per tonne F.O.B. Zurich.
The roadbuilding ash (or slag as most Europeans call it) sells
for 10% under the competitive price for gravel. Mr. Hirt believes that
the long term price is bound to rise substantially as gravel pits become
scarce. The 1974 price of SF 12 had fallen to SF 6 in 1977 due to the
recession.
Most of the slag is used for secondary roads. They can operate
in rain and freezing weather due to the exothermic reactions.
There is a new plant that is planned to mix the material as
aggregate with cement to serve the Zurich and Winterthur areas.
Because the material can also be used as road base for paved
roads, several tests have been conducted. Tubes made of PVC, cement, zinc,
rubber, etc. have been inbedded in the processed ash to determine corrosion
effects.
Three people, not employees of Abfuhrwesen, operate the facility
for a joint venture owned by the Bless and the Muldenzentrale companies.
Figure 8-35 through 8-42 show the various stages of residue
processing.
-------
112
FIGURE 8-35.
SEGREGATED BULKY RESIDUE FROM FURNACE AT HAGENHOLZ
(Battelle Photograph)
-------
113
FIGURE 8-35. TRUCK DISCHARGING PLANT RESIDUE AT HAGENHOLZ (Battelle Photo)
-------
114
FIGURE 8-37.
FRONT-END LOADER DELIVERING RESIDUE TO HAGENHOLZ PROCESSING
SYSTEM (Battelle Photograph)
-------
115
FIGURE 8-38.
WORKER REMOVING WIRE FROM WASTE PROCESSING CONVEYOR AT
HAGENHOLZ (Battelle Photograph)
-------
116
FIGURE 8-39.
SMALL SIZE METAL FROM HAGENHOLZ RESIDUE-PROCESSING PLANT
(Battelle Photograph)
-------
117
FIGURE 8-40.
MEDIUM AND LARGE METALLICS FROM HAGENHOLZ RESIDUE-
PROCESSING PLANT (Battelle Photograph
-------
118
FIGURE 8-41.
NON-FERROUS SIZED RESIDUE FOR ROADBUILDING AT
HAGENHOLZ (Battelle Photograph)
-------
119
FIGURn 8 T'E^T SLABS AT HAGENHOLZ CONTAINING SIZED RESIDUE
.. ieile Photograph)
-------
120
PERSONNEL AND MANAGEMENT
Figure 8-43 displays the City of Zurich's organization.
The Hagenholz plant itself is part of the Abfuhrwesen (Waste Disposal
Organization) which reports to Gesundheits - und Wirtschaflsamt
(Health and Cleansing Department). Note that the Heizamt (City's heat-
ing organization) and the Elekrizitatswerk (electric works) are each
in different departments. This makes more impressive the attitude of
Max Baltensperger, Chief of the Waste Disposal Organization, that the
Hagenholz RFSG is primarily an energy facility and secondarily a waste
disposal facility.
The waste collection, Hagenholz, Josefstrasse, and rendering
plant relationships are shown in the Abfuhrwesen organization chart:
Figure 8-44. The activities above the dash line are performed at City
Hall.
Compared to other European RFSG plants, the plant level
organization chart is less precise. There are no shift specialists.
Each man gets to do all the jobs around the plant. The philosophy is
that the men should take more interest in the overall plant operation.
Changing assignments also tend to inhibit formation of cliques and
selfish attitudes.
Each of the 39 men work a 44 hour week. There are four
operators per shift as follows: shift foreman, crane operator, mainten-
ance man, and control room operator. Service contracts with outside
firms permit a limited staff size.
Each supervisory and management person in the plant must
submit a written report weekly to his supervisor. This ijeludes Max
Baltensperger's report to the nine (9) member Council,
While the plant staff has walkie talkies, cr,;y are seldom
used. The crane operators and the control room operators frequently
talk by telephone.
-------
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Switzerland, being a landlocked nation, does not have as many
former seamen running their boilers. Instead, some of the people come
from industry such as Brown Boveri, Sulzer, etc. Often a young man will
start as an apprentice machinist or pipefitter. Training is primarily
on the job as compared with the rigorous schooling/experience program in
Germany. Accordingly, promotion is based on merit and actual contribution
to the plant operations and not based on formal progression through a
schooling/experience program.
The total number of personnel (collection, disposal, adminis-
tration, rendering plant, etc.) since 1911 is shown in Figure 8-35.
Plant staff stated that the change from garbage cans to paper
and plastic bags greatly reduced the manpower requirements for collectors.
The third reason for keeping manpower levels low, costs low, and efficiency
high, is the bonus. In 1976, management shared SF 2,737 while the plant
people shared SF 17,617. A fourth reason is that 50% of the people are
in the local union.
Start-up Procedure
The Number 2 fuel oil boiler produces 150 C (342 F) steam that
is put into the boiler. This helps eliminate dew point corrosion. Steam
from this oil boiler is also used to heat tubes in the air preheater, also
to 150 C (342 F). The electrostatic precipitator is turned on after about
1/2 hour. Whenever they shut-down for the 1000 hour checks, the ESP is
kept hot.
At one point, a comparison was made between Hamburg: Stellinger
Moor and Zurich: Hagenholz—both plants operated by municipal governments.
The main difference was that the Stellinger-Moor is causually operated
as a well run municipal department. Hagenholz, however, leanly and
efficiently, is operated as if it were private energy-generating enter-
prise. At Hamburg, the primary objective is clean disposal of waste.
-------
124
1/2-hour. After about 1-1/2 hours, fairly dry and high calorific value
waste is fed into the furnace and the charge is lit.
When the unit is stopped for its 1000 hour inspection, the
ESP is kept hot to prevent dew point corrosion.
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ECONOMICS
Capital Investment
The first two units and the administration, social, truck repair,
truck storage, bicycle storage, and space parts areas were built in 1969
at a total cost of SF 56,000,000. Of this total, about SF 45,694,000 was
for the refuse fired steam generator (RFSG) building itself. Von Roll's
chute-to-stack price was SF 23,000,000. Later, in 1973, an additional
SF 14,000,000 was spent for Unit #3 and water deaeration. Out of this,
the Martin contract was SF 11,430,000. This brings the total for all
three RFSG units to SF 59,700,000.
Details of the first Von Roll construction period are shown
in Table 8-8 • Similar details for the last Martin construction period
follow in Table 8-9 .
Annual Costs
A separation of annual costs to operate Units #1 and #2 from
operation costs for Unit #3 is impossible. Annual 1976 costs, totaling
SF 14,414,893, include costs of operations, maintenance, interest, and
other costs, and are portrayed in Table 8-11. The costs are for all three
RFSG units. Excluded are costs to inspect and repair the fleet of garbage
collection trucks. The cost pattern since 1928 is shown in Figure
8-^fi. Notice the excellent control over salaries and wages and hence the
total personnel costs.
Annual Revenues
Annual 1976 revenues, totaling SF 14,424,262, include tipping
fees; sale of steam, hot water, electricity and ferrous; a large insurance
settlement for a turbine, rent of a tire shredder, credit for repairs to
other City of Zurich vehicles, and other incomes.
Dividing the tipping fee, charged to non-Abfuhrwesen trucks,
of SF 2,210,966 by the annual tonnage of 94,000 tonnes, yields a SF 23.46/
tonne tipping fee. However, the public tipping fee charged, and the sub-
sidy later paid total of SF 5,417,988, divided by 121,559 tonnes, yields
a public Abfuhrwesen collection tipping fee per ton of SF 44.57/tonne.
-------
127
TABLE 8-8. CAPITAL INVESTMENT COST (1969) FOR
UNITS #1 AND #2 AND OTHER BUILDINGS
AT ZURICH: HAGENHOLZ
Building costs
(excavation, foundation, structure, stack,...)
Equipment (Von Roll contract chute to stack)
(boiler , furnace , . . . )
Outfit
Administrative building
Workshop
Trucks -gar age
Connection-way (alley)
Scale house
Bicycle house
Grading
Environment (garden, fences , . . . )
Streets and parking places
Oil storage tank
Others
Land
Construction management fee
Engineering fees
Interest during construction
Others Total
Capital Investment
Total
Complex
(SF)
11,000,000
23,000,000
20,000
2,500,000
2,200,000
700,000
1,200,000
350,000
100,000
750,000
600,000
1,300,000
115,000
12,000,000
59,700,000
RFSG
Only
(SF)
11,000,000
23,000,000
20,000
1,250,000
440,000
—
—
350,000
50,000
375,000
300,000
650,000
115,000
8,144,000
45,694,000
(SF 6,000,000 value of land previously purchased)
-------
128
TABLE 8-9. CAPITAL INVESTMENT COSTS (1972 ) FOR
UNIT #3 AND THE WATER DEAERATION
TANKS AND ROOM AT ZURICH: HAGENHOLZ
Furnaces and boiler (Martin contract chute to stack)
**
Spare parts
Deaeration tanks (2)
Foundation work
Piling
Temporary office building
Scaffolding rental
Demolition and boring
Front wall, trusses, insulation
Steel structure
Heating/cooling/electrical/plumbing
Inside finishing
Miscellaneous
Photography and brochures
Engineering fee
Architect fee
Other expert fees
Interest during construction
Water treatment room
Total Capital Investment for Unit #3
Reserve
Miscellaneous
Total Amount Financed
SF 11,430,437
11,374
339,837
548,281
43,894
17,776
9,415
96,242
95,734
110,574
125,628
97,767
43,323
6,294
107,453
58,373
1,605
800,015
62,314
SF 14,006,335
650,000
521,665
15,178,000
75% of the capital costs were paid in 1972.
**However, the spare parts inventory stored in the basement under the
truck repair garage now totals about SF 1,000,000.
-------
329
TABLE 8-10. ANNUAL 1976 OPERATING, MAINTENANCE, INTEREST,
AND OTHER COSTS FOR ZURICH:-HAGENHOLZ
UNITS #1, s*2, AND //3
Component
Totals
Interest
Plant Amortization
Office Equipment Amortization
Spare Parts Amortization
Total Amortization
Office Wages
Managerial Wages
Part-time Wages
Plant Wages
Total Wages
Managerial Bonus
Plant Bonus
Total Bonus
Overalls and Clothing
Cafeteria Subsidy
Cost of Living Pension Adj .
Planned Pension
Makeup Pension
Social Security Pension
Total Pension
Accident and Sickness Insurance
Office Supplies
Ash Research and Treatment (net cost)
Other Dept. Services
Studies
Building
Chute to Stack
Ash Truck (1)
Landscape on Old Landfill
Workman Clean-Up Room
Plant Controls (est.)
Bciler Cleaning (est,,)
Cafeteria Repairs and Cleaning
Total Repairs (no wages)
2,365,967
6,731,680
19,186
110,205
148,323
162,278
4,146
1,576,561
2,737
17,617
79,258
124,798
99,198
92,405
60,271
680,809
1,077
60,697
4,989
42,629
80,000
5,008
2,365,967
6,861,071
1,891,307
20,354
8,306
16,540
395,659
35,748
422
1,374,782
14,825
994
935,483
-------
130
TABLE 8-10. (Continued)
Component
Totals
Janitorial Service (est.)
Heating (est.)
Office and Repair Shops
Cleaning Supplies
Fuel Oil
Electricity Purchase
Water
Electricity for Office
Total Utilities
Truck TEA and Diesel Oil
Oil and Lubricants for Plant
Electrical Replacements (Lamps)
Chemicals for Water Treatment
Office Costs Burden
Property and Liability Insurance
Tax Overpayment
Hospitality
Damages not covered by Insurance
GRAND TOTAL COSTS
3,000
2,973
19,217
105,949
201,821
184
5,973
11,861
327,173
790
11,223
10,440
15,332
30,773
75,151
(3,465)
2,849
4,098
SF 14,414,893
-------
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The question was asked, "Why would you charge outsiders only
SF 23.46/refuse tonne and charge your own taxpayers SF 44.57/refuse tonne-
almost twice as much?" The answer was three-fold and is paraphrased as
follows:
Answer 1. "Hagenholz is an energy plant and we need as much
fuel as possible. Even though the tipping fee is half, we
are still being paid to accept fuel."
Answer 2. "The non-Abfuhrwesen waste typically has a de-
sirable higher heating value" (bad for Units #1 and #2, good
for Unit #3)
Answer 3. With more waste, our fixed costs are spread
over more refuse tonnes and total unit costs will be less.
The SF 44.57/tonne figure would be higher if others were to
not bring waste to Hagenholz.
The scrap iron collected in plant containers before burning
is sold for about SF 3.50 to SF 4.00 per ton which is about one cubic
meter.
The revenue table has no entry for sale of ash residue—-
either ferrous or road building material. This is because the ash
processing is operated separately. The result is a "net cost" and
that is recorded in the annual cost table.
Both the 1976 annual costs and revenues are summarized below:
Annual Revenue SF 14,424,262
Annual Cost 14,414.893
Net Profit SF 9,369
A net profit figure is somewhat ficticious because of the
subsidy calculation designed to make net profit come out to near zero.
This deductive subsidy figure appears in the revenue table as "portion
of general tax to dispose of household refuse".
As is typical of RFSG plants that manufacture both electricity
and district heating; most of the energy revenues come from district
heating-35% less from electricity-7% and very little from scrap metal
pulled from the refuse stream before burning.
-------
134
Comment: As Battelle staff has viewed systems in many countries,
usually energy economics strongly favors sale of energy
for district heating (and perhaps cooling for the summer
load). This is in contrast to the competitive electricity
prices normally held down by economical production at
very large (100 times the mw size) hydro, fossil, or
nuclear power plants.
-------
135
FINANCE
The original 1969 development of SF 56 million was financed
by three sources of funds as follows:
70% by the City of Zurich
15% by the Kanton (state) of Zurich
15% by the Federal Switzerland Government
The City of Zurich for its 70% portion put up cash on hand
and also borrowed money from local banks as general obligation bonds.
Usually the term is five years. The interest rate varies. Having
started at 4-1/2% in 1973 for Unit #3, it was 4-3/4 in 1976. The
building is amortized over 25 years and the mechanical equipment is
amortized in 14 years.
Borrowing from the Swiss Federal Government carries a small
but important risk. The only way that the Federal funds will be re-
leased to the City is after the plant has been built and the environmen-
tal portion of the compliance test has been successfully passed.
At Hagenholz, the acceptance test was run after 4,000 hours and
before cleaning to ensure performance even under adverse conditions. As
was stated, and we paraphrase again, "Anyone can make a unit be acceptable
immediately after cleaning. The trick is to make it acceptable after a
half year's operation with no cleaning and overhaul."
-------
136
REFERENCES
1. Kehricht - verbrennungsanlaze der Stadt Zurich (Brochure distributed
at the public opening of Zurich: Hagenholz in 1969) printed by
Afbuhrwesen der Stadt Zurich Walchestrasse 33 Zurich 800 6.
2. Stadt Zurich Geschaftsbericht 1976 Gesundheits - und Wirtschaftsomt
(Annual 1976 Report for the City of Zurich's Health and Cleansing
Department).
3. Bauabrechnung (Construction costs breakdown for Hagenholz Unit #3
submitted by the architect Baerlocher and Unger9 March 20, 1974).
4. Vertrag (Contract for Hagenholz RFSG to sell energy to the Migros
food warehouse as a district heating customer, dated April 4, 1977).
5. Die entsche-denden Kriterien bei der Wahl des Energie - erzeugung
sprozesses beim Heizkraftwerk "Aubrugg" des Kontons Zurich in
Wallisellen, an article appearing in Fernwarme International
Sonderdruck No. 2742 FWI 4 (1975) H.3. S. 91-98 (an article discussing
future plans for Hagenholz and other Zurich energy matters).
6. Die Verwendung von aufbereeteter Kehrichtschlache im Strassenbau,
Reprint article from Strasse und Verkehr (Streets and Traffic),
October, 1975, publisher Vogt-Schild AG 4500 Solothurn [7 pages]
(Use of processed incinerator ash for road building).
7. Die Verwendung Von Kehrichtschlacke Als Baustaff Fuer den Strassenbau,
Final report on use of processed incinerator ash for roadbuilding.
A 50 page report written by Professor R, Hirt of The Technical
University of Zurich, October 1975.
8. Was Geschieht Mit Unseven Siedlungsa bfaellen? (S.pecial article in) i
Energie aus Kehricht (Energy from Waste), a chapter by Max
Baltensperger, pages 18, 19 and 20, appearing in Issue No. 6S
November, 1976, Mitteilungsblatt Schweizerischer Stadtererband,
Bern, Switzerland.
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«Oi GOVERNMENT PRINTING OFFICE: 1979 620-007/6305
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