United States . ^ Office of Water and SW 176C.16
Environmental Protection" Waste Management October 1979
Agency Washington, D.C. 20460
Solid Waste '
v>EPA European Refuse Fired
Energy Systems
Evaluation of Design Practices
Volume 16
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faon EPA
and State. SoLLd Wo/i^e Management
EUROPEAN REFUSE FIRED ENERGY SYSTEMS
EVALUATION OF DESIGN PRACTICES
Duesseldorf-Fli'ngern Plant
West Germany
tke. 0^-ic.n o{> So Lid (titutu undzi contract no. 6&-01-4376
and iA rep reduced 'tece-tved ^fiom the. c.ont-iacton.
The. ^ndA,nQ^> Ahoutd be. at&u_bute.d to tke.
and not to tke. Oi-ce. o SoLLd
Copies will be available from the
National Technical Information Service
U.S. Department of Commerce
Springfield, VA 22161
Volume 16
U.S. ENVIRONMENTAL PROTECTION AGENCY
1979
-------
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.l6) in the solid waste
management series.
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TABLE OF CONTENTS
Page
PREFACE i
ACKNOWLEDGEMENTS 1
SUMMARY 2
STATISTICAL SUMMARY A
DEVELOPMENT OF THE SYSTEM 8
COMMUNITY DESCRIPTION 9
Geography 9
Government and Industry 9
SOLID WASTE COLLECTION PRACTICES ... 10
Solid Waste Generation and Collection Activities 10
Solid Waste Transfer and/or Preteatment . 10
Solid Waste Disposal 10
REFUSE-FIRED STEAM GENERATOR EQUIPMENT 14
Furnace Hoppers and Feeders 20
Burning Grate 22
Furnace Wall (Combustion and First Pass Radiation
Chambers) 24
First Open Boiler Pass, Units No. 1-4 29
Furnace Wall in Unit No. 5 33
Wall Construction in Unit No. 5 36
Wall Protection 36
Superheater 36
Experiences with Superheater Corrosion 37
Causes of the Corrosion 39
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TABLE OF CONTENTS (Continued)
Boiler (Convection Section) ................ 42
Economizer ......................... 43
Boiler Water Treatment ................... 43
Primary Air Supply ..................... 43
Secondary Air ....................... 44
Co-Firing Equipment .................... 45
Heat Release Rate ..................... 45
Energy Utilization Equipment ........... ..... 46
Plant Start-Up Procedure ............... 47
Shut Down ....................... 48
Emergency Shut Down , ................. 49
POLLUTION CONTROL EQUIPMENT ................... 50
Wastewater Discharge .................... 54
Stack Construction . . ........... ........ 54
EQUIPMENT PERFORMANCE ASSESSMENT ........ . ....... 55
POLLUTION CONTROL ASSESSMENT ........ ......... , 59
Noises ........................... 60
PERSONNEL AND MANAGEMENT .................. . . 61
Training ........ ..... . ......... 61
Crane Operator .................. 61
Boiler Operator ................. 61
ENERGY MARKETING ........................ 64
ECONOMICS ............................ 64
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TABLE OF CONTENTS (Continued)
Page
Capital Investment 64
Operating Costs 66
Revenues 72
REFERENCES 77
LIST OF FIGURES
FIGURE 3-1. REFUSE INCINERATION PLANT AT DUESSELDORF
FIGURE 3-2. WASTE COLLECTION AREA SERVED BY DUESSELDORF
PLANT (1) 11
FIGURE 3-3. PLAN OF DUESSELDORF WASTE-TO-ENERGY PLANT 15
FIGURE 3-4. CROSS SECTION OF DUESSELDORF PLANT 16
FIGURE 3-5. MAIN STORAGE PIT. THERE ARE TWO CRANE OPERATOrS
OPERATING PULPIT FOR ONE IS AT UPPER LEFT ... - 18
FIGURE 3-5a. NEW POLYP BUCKET BEING PREPARED FOR INSTALLATION . . 19
FIGURE 3-6. SIDE VEIW OF BOILER NO. 4 21
FIGURE 3-7. SIX DRUM WALZENROST (ROLLER GRATE); ALSO COMMONLY
KNOWN AS THE DUESSELDORF GRATE 23
FIGURE 3-8. FIRST TEST INSTALLATION OF REFUSE ON BARREL GRATE
ADDED TO EXISTING COAL-BURNING TRAVELING GRATE AT
FLINGERN POWER PLANT 28
FIGURE 3-9. CROSS SECTION OF ONE OF BOILERS NO. 1-4 30
FIGURE 3-10. DIAGRAM OF LOCATION OF GUIDING WALL AT TOP OF FUR-
NACE OUTLET SHOWING EFFECT ON OXYGEN DISTRIBUTION
IN GASES 32
FIGURE 3-11. CROSS SECTION OF BOILER NO. 5 WITH ROLLER GRATE
"SYSTEM DUESSELDORF" 34
FIGURE 3-lla. HARD COATING ON BENDS OF SUPERHEATER TUBES TO BE
INSTALLED IN THE SECOND PASS OF BOILER NO. 5 ... 41
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LIST OF FIGURES (Continued)
Paee
FIGURE 3-12. SAMPLE DATA CARDS AS USED IN PLANT SYSTEM AT
DUESSELDORF 53
FIGURE 3-13. INCLINED CONVEYORS REMOVING BALED SCRAP 74
FIGURE 3-14. CLOSE-UP OF BALED STEEL SCRAP 75
FIGURE 3-15. VISITORS DISCUSSING FINE ASH RESIDUE USES NEAR
STORAGE AREA 76
LIST OF TABLES
TABLE 3-1. REFUSE COLLECTION AND DEPOSITING IN DUESSELDORF,
1975 12 to 13
TABLE 3-2. HEATING VALUES FOR MIXED MUNICIPAL REFUSE IN REFUSE
POWER PLANTS 26 to 27
TABLE 3-3. RESULTS OF TWO PERFORMANCE TESTS BY TUV ON A
PRECIPITATIOR AT THE DUESSELDORF REFUSE PLANT ... 51
TABLE 3-3a. DUESSELDORF WASTE-BURNING FACILITYOPERATING RESULTS
- 1976 56 to 58
TABLE 3-4. STAFF ORGANIZATION AT STADTWERKE DUESSELDORF WASTE-TO-
ENERGY PLANT 62
TABLE 3-5. DUESSELDORF WASTE-BURNING FACILITY - 1975 67
TABLE 3-6. COSTS OF THE WASTE BURNING FACILITY, 1975 68
TABLE 3-7. COSTS FOR WASTE COLLECTION AND TRANSPORT INCLUDING
BULKY WASTE HAULED BY FOUR SIZES OF VEHICLE .... 69
TABLE 3-8. COST SUMMARY OF REFUSE HANDLING INCLUDING COSTS OF
BURNING AND LANDFILL DISPOSAL, 1975 70
TABLE 3-9. DUESSELDORF WASTE BURNING FACILITY, 1966-1976 ... 71
TABLE 3-10. INCOME TO THE WASTE BURING FACILITY IN 1975 .... 73
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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.
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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
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ACKNOWLEDGEMENTS
We are pleased to acknowledge the very competent, earnest, and
generous assistance which we received from the following without whose help
this descriptive report and analysis would have been impossible:
Stadtwerke Duesseldorf
Dr. Maruct, Member of the Board
Karl-Heinz Thoemen, Works Manager
Uwe Andresen, Assistant Works Manager
Vereinigte Kesselwerke
- Dir. Werner Schlottman
Grumman Ecosystems, Inc.
- Klaus Feindler
Stadtreinung u. Fuhramt
- Dir. Helmut Orth, Retired
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SUMMARY
This 13-year old plant, Figure 3-1, is a pioneer in the sense that
it utilizes a unique burning grate that was developed at Duesseldorf between
1961 and 1965. Also this full-scale plant was the first large application
of this new methodthe Duesseldorf roller grate, now used all over the
world. It utilizes the slow rotary motion of six or seven horizontal drums
to move and gently agitate the burning refuse on a downward sloping path
through the furnace.
This single plant, enlarged in 1972, and anticipating a further
expansion, is an obviously successful venture by the city of Duesseldorf
and surrounding communities toward solving their solid xvaste problem.
Another unique feature of this plant is that for 13 years, it has
been supplying 930 F (500 C) steam to its "parent" Flingern Power Plant.
This has not been without its corrosion problems but the management and
staff have experimented and developed corrective measures which have reduced
their corrosion losses to within acceptable limits. In numerous publications,
the plant manager has generously shared this experience with all who are
interested.
The plant serves a population of 800,000 of these, 600,000 are in
Duesseldorf. In 1976, it burned 284,185 tonnes (312,603 tons) and produced
564,091 tonnes (620,500 tons) of high pressure, 80 bar (1160 psig), high
temperature, 500°C (932 F) steam for power generation and for making hot water
for district heating. Baled iron scrap and sized ash is also sold from the
residue. The net burning cost after allowing for all income is now averaging
about 30 DM per tonne (11.43 per ton) in 1976.
During the visit, there was discussion of a sixth unit to be
installed around 1980.
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FIGURE 3-1. REFUSE INCINERATION PLANT AT DUESSELDORF
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STATISTICAL SUMMARY
Corrj-iunity descript ion:
Area (square- kilometers)
Population (number of people)
Key terrain feature
R - 20 km -- 7,250 knT
800.000 hah. (Duesseldorf: 600.OOC
Rhein Vallev, flat
Solid waste practices:
Total waste generated per day (tonnes/day)
Waste generation rate (Kg/person/yr)
Lower heating value of waste (Kcal/kg)
Collection period (days/week)
Cost of collection (local currency/tonne)
778.6 t/d (1976)
0.973 (1976)
1700 *-> 2000
5
95 DM/tonne
..,-,/ , % ,. shredder i
Use of transfer and/or pretreatmcnt (yes or no) transfer: no - ml j yes
Distance from generation centroid to:
Local landfill (kilometers)
Refuse fired steam generator (kilometers)
Waste type input to system
Cofiring of sewage sludge (yes or no)
shear
10
<7
MSW-lndustrial-Bulky
No
Development of the system:
Date operation began (year)
1965
Plant architecture:
Material of exterior construction
Stack height (meters)
Concrete
100 m
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)
Number of furnaces constructed (number)
Yes
25-28 Percent
1850 kcal/kg
Furnaces 1 to 4:
5
240 t/d; Furnace
5:300
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Capacity per system (tonnes/day)
Actual per furnace (tonnes/day)
Number of furnaces normally operating (number)
Actual per system (tonnes/day)
Use auxiliary reduction equipment (yes or no)
Pit capacity level full:
(Tonnes)
(m3)
Crane capacity:
(tonnes)
(m3)
Feeder drive method
Burning grate:
Manufacturer
Type
Number of sections (number)
Length overall (m) effective #1-4:16, 57m
Width overall
Drum diameter
Primary air-max
Secondary 'air-overf ire air-max (m /min)
, .
Furnace volume (m )
#1-4: 167m
^, OQ7 3
10 : zy /m
Furnace wall tube diameter (mm)
2
Furnace heating surface (m )
Auxiliary fuel capability (yes or no)
Use of superheater (yes or no)
Boiler
Manufacturer
Type
Number of boiler passes (number) #1-4:2
Steara production per boiler (kg/hr)
Total plant steam production (kg/hr)
Steam temperature ( C)
Steara pressure (design)
#1-4:
#5
1260 t/d
#1-4:8.5-lOtphr/#5:12.5tphr
4 out of 5
850-960
Yes
4000
10'500
lOt - Bucket capacity: 4 m3
#1-4: mechanical; #5: hydraulic
Vereinigte Kessel Werke
Duesseldorf roller grate
Boilers No. 1-4: 7; Boiler No. 5: 6
#5:14.21m
3m
1.5m
75*000 Nm3/h Boiler No. 5
40,000 NmJ/h Boiler No.1-4
#1-4 - 200 m^/min
#5 - 250 m-Vmin (without boiler
volume)
70
52
Boilers 1-4: 100m2; Boiler 5: 146m2
Yes
Yes
DUrr (1.2,5) - VKW 3,4 1-4:
Steilrohrkessel
#5+4
Boilers 1-4: 16/20x103 Boiler 5:
25/30x103
-89/llOxlO3 kg/h = 89-110t/h
480 -500°C
(1500 psia)
105/112 atm. - 1491-1590 psig
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Use of feed water heater
Use of economizer (yes or no)
Use of air prchcater (yes or no)
Use of flue gas rcheater (yes or no)
Cofire (fuel or waste) input
Use of electricity generator (yes or no)
Type of turbine
Number of turbines (number)
Steam consumption (KS/KWh)
Electrical production capacity per turbine
Total electrical production capacity
2
Yes
Yes
No
No
In neighboring plant
BBC-HP; AEG-LP
2+2
at 4,
HP-13+32 MW
LP-30+53 MW
125 MW
Turbine back pressure (kg/m')
User of electricity ("Internal" and/or "External") External
Energy utilization: Electricity generation and District Heating
Medium of o-H energy transfer Hot water
Temperature of medium ( C)
Customers/receiving energy (number)
Pressure of medium (bar) Q ,,
o i n
Energy return medium
Hot water
Winter: 130°; return 70°C
Summer: 80°; return 65°C
132
Pollution control:
Air:
Furnace exit conditions
Gas flow rate (Nm^/hr)
3
Furnace exit loading (mg/Nm )
#1-4:45000,
11-13
#5:60000
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Equipment:
Mechanical cyclone collector (yes or no)
Electrostatic precipitator (yes or no)
Manufacturer
3
Inlet loading on precipitator (mg/Nm )
j
'Exit - loading on precipitator (mg/Nm )
Legislative requirement (mg/Nm )
Scrubber (yes or no)*
Inlet loading:
H Cl (mg/Nm3)
H F (mg/Nm3)
Exit loading:
H Cl (mg/NM3)
H F (rag/Nra3)
Legislative requirements (mg/Nm )
Other air pollution control equipment (yes or no)
No
Yes
Lurgi/Rothemuhle
5,000-15,000
36-85
100
No
7.5 mg/Nm at the exit
HCL 100 mg/Nm3 - HF-5 mg/Nm3 CO-ls/Nm3
No
Water:
Total volume of waste water (liters/hr) 50-70xl03 l/m
Ash:
Volume of ash (tonnes/day) . 300-385
Volume of metal recovered (tonnes/per working day) 40
* However, if a 6th line is installed, scrubbers may be required on all six units,
#1-5 for the first time.
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DEVELOPMENT OF THE SYSTEM
Organized waste management by the city of Duesseldorf began in
1862. As early as 1897, the growing problems with solid waste disposal
led to some consideration of incineration. However, not until 1957-1958
did an active search begin for some "new way" to process solid wastes.
In 1960, it was decided to erect an experimental heat-recovery type of
furnace in the existing coal-fired Flingern municipal power plant near
the center of the city.
The plant is owned by "Das Stradtreinigungs und Fuhramt (Department
of Sanitation and Streets) of which Helmut Orth was the Director prior
to his recent retirement. That department has assigned operation of the
Miillverbrennungsanlage (MVA) (Refuse Buring Plant) to the Stadtwerke
Diisseldorf AG", the utility company for Dusseldorf, Dr. Marnet, member
of the board and department head of the department for electricity
generation is the legal operator.
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COMMUNITY DESCRIPTION
Geography
Duesseldorf is a densely populated, highly industrialized city
of about 600,000 people located on the very busy Rhine River. The terrain
is very flat and many smaller industrial cities are located nearby along
the river. Land costs are very high.
Government and Industry
Duesseldorf is a major industrial center and river port with a
broad variety of manufacturing activities.
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10
SOLID WASTE COLLECTION PRACTICES
Solid Waste Generation and Collection Activities
Over the more than 100 years that Duesseldorf has been collecting
and disposing of community refuse, the methods and equipment for collection
have evolved into a variety of vehicles. Outside of Duesseldorf, a popu-
lation of over 200,000 are served in suburbs and in towns within a 20-km
(12 mile) radius, as shown in Figure 3-2. In 1976, the daily per capita waste
generation rate was 0.973 kg per person (2.1 Ib). Table 3-1 shows the
waste characteristics and flow for 1975.
Solid Waste Transfer and/or Pretreatment
Transfer stations are not used. Originally the only pretreatment
arranged was a Lindenmann shear for bulky waste only. In 1972, when Unit
No. 5 was installed, a 45 tonne/hr (49 ton/hr) Lindenmann shredder was
installed to reduce the large amount of cardboard boxes and similar shred-
dable bulky waste that could not be cut up by the shear. (Lack of capacity)
Solid Waste Disposal
Plant residue and noncombustibles tabulated in Table 3-1 are sent
to two landfillsHamm and K31.
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tCCTTtv/G
KBCFELO
FIGURE 3-2. WASTE COLLECTION AREA SERVED BY DUESSELDORF PLANT
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12
TABLE 3-1. REFUSE COLLECTION AND DEPOSITING IN DUESSELDORF,
1975, TONNES*
Incineration
Landfill/Hamm Landfill, K-31
Household Wastes, 110 128,872.51
liter containers
Household Wastes, 1,100 42,586.82
liter containers
4.4 cbm containers 11,590.67
6.0 cbm containers 1,769.70
8.0 cbm containers 6,208.64
Fairgrounds 2,355.25
Supermarkets 2,290.10
Karlplatz 931.33
Special Waste 110.03
Bulky Waste 6,464.49
Tires 1,090.03
Household Waste From Out- 30,557.04
side Duesseldorf
Bulky Waste 2,549.12
Industrial Waste From 36,187.71
Duesseldorf Plus
Other Non-Combustible
Waste
Bulky Industrial Waste 11,357.59
Rubbish 10,969.14
Oil polluted soil 1,668.29
Agricultural Refuse ^
Combustible Waste 297,358.36
16,431.44
854.32
1,976.00
207.00
9,130.00
28,599.26
1,727.09
4,125.86
12,423.19
24,895.17
43,171.32
Building Construction Waste
Excavated Earth
Dust
Foundry Sand
60,718.65
12,009.92
469.00
6,510.99
* Data provided by plant manager.
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13
TABLE 3-1. (Continued)
Rubbish
Glass
Ash From Waste Burning
Industrial Wastes
Total Non-Combustible Wastes
4,252.50
5,010.00
74,299.87
3,237.73
166,508.68
To K-31 Landfill
Non-Combustibles
Total Non-Combustible
43,171.32
166,508.68
209,680.00
Total Fired
Landfill Hamm
Landfill K-37
Non-Combustible Waste
Total
297,358.56
28,599.26
43,171.32
166,506.68
535,637.82
Combustibles to Plant
Discard to Hamm Landfill
Discard to K-31 Landfill
Total
Deductions
297,358.56
28,599.26
43,171.32
369,129.14
24,895.17
344,233.97
Total Non-Combustible 209,680.00
To Hamm Landfill 28,599.26
Total Refuse
Amount Burned
535,637.82
297,358.56
238,279.26
Ash Not Sold
40,282.49
1975
344,233.97 Discarded Ash , 15,579.22
319,621.62 Total Ash 55,861.71
24,612.35 Total Non-Combustible 294,140.97
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14
REFUSE-FIRED STEAM GENERATOR EQUIPMENT
Six to 7,000 tonnes of refuse are delivered to the pit per week
by 700 to 800 public and private trucks between 7:00 a.m. to 2:00 p.m., 5
days per week. On a 7-day week basis, hospital and hotel wastes are received.
A 15 tonne/hr shear is available in a separate building to cut
up bulky wastes and since May, 1973, a 45 tonne/hr shredder has been used to
shred bulky wastes. It will be explained later that the plant management
feels that the concentration in the pit of this highly combustible, dry,
shredded waste has been a major cause of high-temperature corrosion in the
newest boiler, No. 5, which appears to receive most of that waste.
Figure 3-3 shows the plant property which is located in a concen-
trated industrial area well inside the city.
Figure 3-4 shows a cross-section of the plant as it was built in
1965.
The weigh scale is to the right of Figure 3-3. Two scales are
providedone on each side of the scale buildingso that two trucks can
be weighed simultaneously. The scales were built by Schenck of Darmstadt.
Normally there is one scale operator. At peak times, there are two. Peak
times are from 8:30 a.m. to 10:30 a.m., 12:00 to 1:30 p.m., and 2:30 p.m. to
3:00 p.m.
The scale reading and tare are punched automatically on data
cards. Also, an automatic typewriter logs the readings.
The scale service has been good with little maintenance. Calibrations
are made every 3 years. The scale data-recorder has caused difficulty.
The electrical system requires repair 10 times per year.
When the scale operator observes bulky waste in a truck, he directs
it to either the shredder or the shear. The standard refuse container in
Duesseldorf takes up to 0.6 m (2 ft) pieces; larger pieces are cut or shredded.
The Lindenmann shear is a hydraulically driven knife and bar machine usually
operated 3 to 4 hours per day. At times of heavy use, the operator is
assisted by a scale operator. The shear produces pieces about 0.6 m by 0.5 m
(2 ft by 1.6 ft). Rubber tires are usually cut to 0.25 m square (0.8 ft).
Shear load is indicated by the current input to the hydraulic-driven motor.
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15
Shredder
\
~~\T
&*J
Cafeteria '.:..
and Office '
Repair-Shop
Dress & Showe
1 Residue fl
1 Process:
Scrap ] I
""~~^ Iron
-j _ ~"~- =- - *
r=
rs^"
;,{
llf
c
Refuse Bunker
Boilerhouse
i_l L\ i i
~ ~. J1
V Railroad
Steam Line to
Flingern Power
Plant and Condensate
- Return Line, 700 m
Conveyor
Total Area:
Buildings:
Streets:
Trees,
Shrubbery, Grass
30,831 sq. meters
7,000 sq. meters
15,831 sq. meters
8,000 sq. meters
FIGURE 3-3. PLAN OF DUESSELDORF WASTE-TO-ENERGY PLANT
(COURTESY STADTWERKE DUESSELDORF)
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16
1 Refuse feed hopper
2 Refuse push feeder
3 "Dusseldotf System"
roller grate
4 Humidifying worm conveyoi
5 Wet type ash extractor
6 Ash belt conveyors
7 Roof light-off humei
8 Evaporator heating surfaces
9 Platen superheater
10 Nos 1 and 2 spray attemperators
15 No 2 primary superheater
12 No 1 primary superheater
13 Evaporator coils
14 Continuous loop economizer
FIGURE 3-4. CROSS SECTION OF DUESSELDORF PLANT (Units 1-4)
(COURTESY VEREINIGTE KESSELWERKE)
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17
Shear stroke can be manually adjusted by the operator. Operating time is
recorded. Shear blades are turned over every 3 months and are replaced
once per year. The hydraulic seals must be replaced 1-2 times per
year
The Lindemann shredder was added in May, 1973. It is a horizontal-
shaft, belt-driven machine which operates about 6 hours per day. No one is
permitted in the shredder building during operation owing to explosion
hazards. The size of pieces produced is relatively large0.3 m by 0.5 m
(1 ft by 1.6 ft)although rubber tires may pass through essentially intact.
The output is conveyed to the main plant pit by a belt conveyor. Maintenance
on the shredder is minor which the management attributes to the relatively
large size of the product. The first set of shredder hammers lasted 4,000
hours during which 40,000 tonnes (44,000 tons) were shredded. The second
set lasted 3,000 hours.
Much more difficulty has been experienced with the feed and output
conveyors for the shredded refuse. The oil mist lubrication for the conveyor
has been ineffective.
Figure 3-5 shows the main bunker which has a storage capacity of
10,500 m3 (370,313 ft3 or 13,734 yd3). At a compressed and settled density
3 3
of 645 Ib/yd (0.383 tonnes/m ), this represents a storage volume of 4,022
tonnes (4,424 tons), about 3 days supply. Fire control is by means of six
nozzles at the operator's level plus a spray system.
There are three MSchiess" cranes (now part of Demag), 120 tonnes or
(132 tons) each. One crane is stored as a spare on a track in a loft above
the boiler top level. Also, the crane can be quickly hoisted onto this storage
track for repairs. One of the two crane operator's posts can be seen on
the left in Figure 3-5. Both cranes operate simultaneously during the
day, alternately at night.
Each crane bucket is the polyp type with a capacity of 4 m3 (141
2
ft ). Figure 3-5a shows a new bucket in preparation for installation.
For boiler tests, the crane motor electrical input was calibrated
in terms of weight lifted. During the tests, this current was recorded
continuously. In routine operation, the crane operator records the number
of bucket loads charged to each furnace per shift. From this, an approxi-
mate average furnace load is calculated.
-------
IS
FIGURE 3-5. MAIN STORAGE PIT. THERE ARE TWO CRANE OPERATORS
OPERATING PULPIT FOR ONE IS AT UPPER LEFT
(Courtesy Vereinigte Kesselwerke AG)
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c
12
O
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20
The lifting cables on the cranes last about 6 months. The bucket-
closing cables last on the average 4 to 5 weeks although at times, they may
fail in 3 days. On weekends, cable inspection may reveal near failure which
is immediately remedied.
Furnace Hoppers and Feeders
Some modification of the original 5 m by 5 m (16.3 ft by 16.3 ft)
hoppers has been required to prevent bridging in the pyramidal hopper. The
remedy was to raise one side of the sloping hopper wall so that less material
could crowd downward into the feed chute. This crowding caused the bridging.
Also, the feed chute, 3 m by 1.8 m (10 ft by 5.9 ft), is tapered
outward from top to bottom at the rate of 150 mm (5.9 in) in 5 m (16.3 ft)
to relieve the tendency to jam in the chute. Two years ago, the height of
the opening (see Figure 3-4) , where the refuse is pushed from the bottom of
the chute into the furnace, was reduced somewhat on three of the boilers
to prevent burnback. Also, about 1 year ago, water cooling was added to
the lower 2.5 m (8 ft) on some of the feed chutes. On those chutes, which
are not water cooled, burnback during shutdown is prevented by use of
guillotine doors covering the opening between furnace and chute.
Four of the reciprocating refuse feeders are mechanically driven and
one drive is hydraulic. They feed horizontally under the automatic control
of boiler steam flow but are limited by furnace temperature and excess oxygen.
If temperature is too high or oxygen is too low, feed rate is reduced. The
reciprocating feeder plate is water cooled. The forward stroke is
faster than the return stroke. Operators prefer the four mechanically
driven feeders because they require less maintenance than the hydraulic
drive. Also, any hydraulic fluid leakage constitutes a fire hazard. The
feeders used were developed at this plant.
Figure 3-6 is a side view of Boiler No. 4. The feed chute and
feeder are at the right.
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FIGURE 3-6. SIDE VIEW OF BOILER NO. 4 (Courtesy of
Vereinigte Kesselwerke)
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22
Burning Grate
Figure 3-7 shows the essential characteristic of the "walzenrost"
(roller grate) which was developed in 1961 at the neighboring Flingern Power
Plant, using a four-roller pilot grate which has since been dismantled.
It is manufactured by the Vereinigte Kesselwerke in Duesseldorf and is
generally known as the "Duesseldorf Grate". It provides a sloping fuel bed
as do most European mass-burning grates for refuse. But instead of using
oscillating or reciprocating grate bars to agitate the burning material and
to move the incombustible residues down the slope, the walzenrost moves the
bed by slow rotation of the 1.5 m (4.92 ft) diameter drums which are formed of
cast iron grate sections. Thus, there is opportunity for a slow tumbling
action of the refuse which helps to keep the fibrous mass loose, thus allowing
for upward flow of primary air throughout the bed.
The drums rotate at an adjustable speed of about three to six
revolutions per hour. Instead of being continuously exposed to the hot
fuel bed, each grate bar rotates through a cool zone about half of the time.
Thus, for minor repairs to the grates, the temperature on the underside of
the grate is low enough to enable workmen to repair it while the unit is on line.
Each grate roll is formed of 10 sections, each of which contains
60 curved grate bars. The bars at each side which rub against the air seal
plates are cast of chrome-nickel alloy to resist abrasion. Out of a total
of 600 bars per roll, 20 are cast alloy» Boilers No. 1-4 have seven rolls
each but in No. 5 and later designs, there are six rolls per furnace.
The gap between adjacent rolls is filled by a cast iron wiper bar.
This bar is strong enough to shear off refuse that may become attached to
the grate. The only grate bar failures that have been experienced was the
replacement of the first roll in two different furnaces when scrap containing
considerable magnesium was charged. In one case, 20,000 dry cells containing
magnesium damaged the first roll so that replacement was necessary. Similar
loss of the first roll has occurred on three separate occasions since 1965.
The remainder of the grate rolls have operated 30,000 hours without major
repairs. In 1976, total down time for repairing all 34 rolls in the plant
was 650 hours. Some rolls were repaired simultaneously during this period.
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23
FIGURE 3-7. SIX DRUM WALZENROST (ROLLER GRATE); ALSO COMMONLY KNOWN
AS THE DUESSELDORF GRATE. NOTE THE CAST IRON WIPER SEALS
BETWEEN ADJACENT ROLLS WHICH PREVENT LARGE PIECES OF
REFUSE FROM FALLING OUT OF THE FURNACE (Courtesy of
Vereinigte Kesselwerke)
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24
The wiper seals are repaired three times a year. Normal wear of
the seal gradually widens the gap which allows larger and larger pieces of
residue to fall through. A screw conveyor removes such residue from under-
neath the grate.
The hollow steel roller shafts have never been replaced. Asbestos
air seals at each end of the shaft require replacement every 5 or 6 years.
Each roller constitutes a separate supply zone for primary air.
The air enters the interior of the roll from both ends and flows through
the many small gaps between the interlocking grate bars. The amount of air
flow through each roll can be adjusted.
As the burning refuse moves down the slope, the rotative speed of
each successive roll is adjusted so as to keep the fuel bed thickness approx-
imately uniform.
This is an extremely rugged type of grate. The first roll is sub-
ject occasionally to severe impact from heavy objects being fed in by the
feed ram and then dropping 1.8 m (5.9 ft) to the first roll. No damage
has occurred as a result of such impacts.
Furnace Wall (Combustion and First
Pass Radiation Chambers)
The five furnaces at this plant comprise an interesting example
of the evolution of water-tube wall furnaces for mass burning over the past
12 years. When the first pilot furnace was built in 1961, the
use of water-tube walled furnaces for refuse was still in its infancy. There
were good reasons for that. The heat value of European refuse was very low.
This was caused by three factors. Many homes used coal for heating and the
resulting ash and clinkers were discarded with other household refuse.
Probably also dry, combustible wastes tended to be burned in the domestic
coal stoves for their heat value. Thus, the moisture in any remaining house-
hold wastes, such as food scraps, tended to raise the moisture content of
the collected waste. In addition, Europeans economized in their shopping
by use of a minimum of paper bags and other packaging. Then in the 1950's,
many homes were converted to oil, thus eliminating much ash from municipal
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25
refuse. Also, paper packaging came into widespread use and the heat value
of European refuse increased rapidly. Table 3-2 shows that from 1961 to
1975 at the Duesseldorf plant, the average lower heat value of refuse
increased 70 percent, 4,292kJ/kgto 7,314 kJ/kg (1,025 kcal/kg to 1,747
kcal/kg) [1,845 Btu/lb to 3,145 Btu/lb].
Thus, so long as wet, high-ash refuse often made combustion very
difficult, designers were understandably reluctant to depart from the use
of hot refractory-walled furnaces. However, as the heat value of refuse
increased, furnace refractories were damaged by excessive furnace temperatures
and the merits of water cooling the furnace and thus of adding it to the
heat recovery loop became more and more attractive. However, the pilot plant
at Duesseldorf, burning 8 tonnes per hour, utilized an old refractory-walled
furnace, shown in Figure 3-8, which had originally burned coal on a traveling
grate at the Flingern Power Plant. This pilot unit was operated inter-
mittently for a total of 22,000 hours from 1961 to 1965 and provided the
design basis for a plant started up at Rosenheim in 1964, and for the
first four full size units at Duesseldorfthe first of which was started
in November, 1965.
For the reasons cited earlier, when the design transition was
made in 1964-1965 from the old refractory-walled pilot furnace to the new,
full-scale units, No. 1 through 4, there was an understandable reluctance
to use a fully water-tube walled furnace. Although the lower heat value
of Duesseldorf refuse shown in Table 3-2 had risen to 1,220 kcal/kg (5,108
kJ/kg [2,196 Btu/lb] by 1963, that was still a relatively low level; hence,
the need for some refractory in the main furnace to reflect heat to the raw
refuse so as to facilitate rapid ignition and burning.
Accordingly, the front and rear water tube walls of the furnace
itself in Units No. 1 through 4 were protected by a 50 percent aluminum oxide
refractory curtain 250 mm (10 in) thick and spaced by a dead air space 50 mm
(2 in) wide in front of the vertical wall tubes. The tubes are 70 mm (2.75 in)
diameter with 5 mm (0.2 in) wall thickness. The distance between tubes is
about 70 mm.
This type of unique wall construction was not used in Furnace
No. 5 built in 1972, which will be described later.
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26
TABLE 3-2. HEATING VALUES FOR MIXED MUNICIPAL REFUSE
IN REFUSE POWER PLANTS (COURTESY OF
KLAUS S. FEINDLER)
Year
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
Duesseldorf (2)
Minimum Average Maximum
Btu/lb. Btu/lb. Btu/lb.
(kcal/kg) (kcal/kg) (kcal/kg)
1,845
(1,025)
1,530
( 850)
2,196
(1,220)
2,468
(1,371)
2,621
(1,456)
2,792
(1,551)
2,882
(1,601)
2,948
(1,638)
3,087
(1,715)
2,911 3,164 3,299
(1,617) (1,758) (1,832)
2,803 3,037 3,242
(1,557) (1,687) (1,801)
Stockholm^3)
Average
Btu/lb.
(kcal/kg)
3,546
(1,970)
3,942
(2,190)
4,050
(2,250)
4,545
(2,525)
4,950
(2,750)
4,680
(2,600)
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27
TABLE 3-2. (Continued)
Year
1974
1975
V
N
Average
I
Minimum
Btu/lb.
(kcal/kg)
2,666
(1,481)
2,954
(1,641)
11,334
4
2,834
(1,574)
Duesseldorf (2)
Average
Btu/lb.
(kcal/kg)
2,855
(1,586)
3,145
(1,747)
34,570
13
2,659
(1,477)
Maximum
Btu/lb.
(kcal/kg)
3,203
(1,779)
3,374
(1,874)
13,118
4
3,280
(1,822)
Stockholm^3)
Average
Btu/lb.
(kcal/kg)
4,500
(2,500)
4,410
(2,450)
34,623
8
(2^404)
(1) Annual Averages of the Lower or Net Heating Value LHV in Btu/
Ib.
(2) Source: Operator of MVA Duesseldorf.
(3) Source: Vereinigte Kesselwerke A.G., Duesseldorf.
(4) Stockholm refuse reportedly contains a fairly high percentage
of plastics.
(5) To convert from kcal/kg to KJ/kg multiply by 4.1868.
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28
^^.-J.i^j 1, V
FIGURE 3-8. FIRST TEST INSTALLATION OF REFUSE ON BARREL GRATE
ADDED TO EXISTING COAL-BURNING TRAVELING GRATE
AT FLINGERN POWER PLANT
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29
The sloping roof of furnaces No. 1 through 4 is in two parts as
seen in Figure 3-9. The front roof is cooled by water tubes, as well as
the longer rear roof. In these four furnaces, the total heating surface
2 2
in each furnace is 100 m (861 ft ). The volume of Furnaces 1-4 was
3 3
estimated to be 167 m and in Furnace 5, 297 m .
First Open Boiler Pass, Units No. 1-4
With a furnace configuration as shown in Figure 3-9 it can be
expected that burning is not complete as the gas flows upward out of the
main furnace. This means that the ash particles carried in the burning gases
are usually hot enough, over 982 C (1800 F), to be sticky. Accordingly,
enough volume must be provided and that volume must be cooled for two reasons:
Allow time for combustion to be completed, about 50 to 200
milliseconds
Cool the gases so that deposits of ash particles will be dry
and will be below the corrosive range.
Mr. K-H Thoemen, plant manager, has described the design of the
(2)
first four boilers as follows:
"For different reasons, among others' economy, the construction
and operation of large incinerator plants in Germany has been
put into the hands of municipal power plants or similar insti-
tutions. This had the result that in the design of the
incinerator plants, the same design elements have been used
as in the design of coal-fired power plant steam boiJers. For
example, to save construction costs and volume, the incinerator
steam generator was built directly on top of the furnace, instead
of separating the furnace from the so-called waste heat boiler
as practiced in former times. In addition, it was desired to
utilize the steam for power generation and district heating.
Therefore, the steam conditions were matched to those of the
power plants.
In 1967, after tube failures had been reported at other incin-
erator plants, in Dusseldorf the tubes just above the furnace
were inspected and at the lower area of the side walls, the
first indications of corrosion were found (Figure 3-9).
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30
[
^-rr
- 1
1 ' 1 "I I -J
1 - : , --,,- 11
FIGURE 3-9.
CROSS SECTION OF
STADTREINUNGS UND
1. Refuse hopper
2. Refuse feeder and roller
grate "system Duesseldorf"
3. Ignition burner
4. Oil burner (one side)
5. Economizer
6. Steam drum
7. Radiant water-tube-wall boiler
8. Boiler convection section
ONE OF BOILERS NO. 1-4 (COURTESY OF
FUHRAMT DUESSELDORF)
9. First and second stage super-
heater
10. High-temperature superheater
11. Steam discharge
12. Exhaust gas duct to electro-
static precipitator
13. Ash siftings removal
14. Wet residue conveyor
15. Residue removal to processing
plant
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31
As a means of protection, additional secondary air nozzles were
installed to build up a curtain of excess air in front of the
tubes. Furthermore, the endangered area was studded and
covered with a 1/2-inch layer of silicon carbide refractory.
In other plants, this method of protection already has been
applied, with similar good results.
In 1968, a tube rupture occurred in one of our boilers. The
cause was investigated and found to be corrosion by the flue
gas. Subsequent extensive inspections of the boilers demon-
strated that corrosion observed the year before had continued
and reached the tube surface above the protected area (Location
3). Not only the side walls but now the front wall was
affected. Ultrasonic measurements showed that it was necessary
to renew about 30 to 40 tubes in each boiler for a length of
about 7 feet. A considerable number of the remaining tubes had
to be reinforced by welding. Moreover, an extended area of
tube surface was studded and concealed."
In a futher endeavor to stop wall tube wastage in the lower part
of the first boiler pass, more secondary air was added in the furnace roof
and a refractory arch or "guiding wall".was evolved at the top of the furnace
outlet (see Figure 3-10). Thoemen explains this evolution as follows:
"To guarantee a better burn-out and mixture of the flue gases
in the exisLing units, the following changes were accomplished.
The overfire secondary air was increased to about 25-30 percent
of the total air. But the experience is, that with the overfire
air by itself a complete mixture of the gases cannot be obtained.
The relatively cold air does not blend with the gas but pushes
it aside.
The first step to change the configuration of the furnace was
done by the construction of a fire guiding wall. This is an
arch-like wall of firebrick, built in at the end of the furnace
front-roof. This guiding-wall hinders the direct flow of the
gases along the roof into the first flue. Furthermore, it is
a contraction of the profile of the furnace throat by which
part of the gas with high excess air from the end of the grate
is forced into the front part of the furnace. Because the
secondary air nozzles are located directly in front of the
wall, a better vortical intermixture of air and gas is achieved.
The arch-like configuration of the wall contracts the gas flow
in the center of the first flue which results in a more uniform
directed gas stream.
The experience with this guiding-wall is very good. Since its
erection in the years 1968 and 1969, tube corrosion in the first
pass has not continued or spread out. Stream tests with a water-
tank model and extensive gas analyses have proved the efficiency
for the uniformity and burn-out of the gases."
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32
fleasur/ng
Pleasuring {.eve/ /
fleasur/nq
teref 7 \ '-
Setondary
o/r nozzles
t1easurinq\ . , " ''" / ''''
y \ <-- '^- r>'' ^ »<
FIGL'RE 3-10.
DIAGRAM OF LOCATION OF GUIDING WALL
AT TOP OF FURNACE OUTLET SHOWING
EFFECT ON OXYGEN DISTRIBUTION IN
GASES
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33
This guiding wall in Furnaces 1 through 4 was formed of high alumina
content refractory and was not air cooled. Now these are made of silicon
carbide. Because of the high temperature to which these refractories are sub-
jected, they are now being air-cooled. Uncooled, their life was about 23,000
hours. The air cooling arrangement is discussed later under "Secondary Air".
No. 4 was converted in early 1976, No. 3 in early 1977, and Nos. 1 and 2 will
be converted to air cooling later (completed 1978).
Furnace Wall in Unit No. 5
The furnace for Unit No. 5, built in 1972, was altered in accordance
with the experience gained in about 6 years' operation of Units 1-4. Also,
the flow pattern in No. 5 was radically altered because of the rising heat
value of Dusseldorf refuse. Instead of having the burning gases flow upward
at an angle toward the furnace outlet as in Units 1-4, a sloping water-
cooled baffle was built in No. 5 above the fuel bed as shown in Figure 3-11,
in such a way that the gases first flow nearly parallel to the fuel bed, then
at the end of the baffle, they turn and flow upward toward the furnace outlet.
This provides a longer flame path and residence time for the hot gases
resulting from the higher heat value of refuse.
One desirable achievement of this new design is that by the time
the gases reach the top of the furnace and pass into the first pass, they
are well mixed and cool enough to reduce corrosion. In late 1976, at the
(3)
Engineering Foundation Conference at Hueston Woods, Ohio, Thoemen stated
regarding this new furnace in Boiler No. 5:
"Although the tubes of the first pass have not at all been
protected by ceramic lining, after more than 1 year of
operation not any corrosion attack of the former kind was
detected..." "The construction forms a true combustion
chamber in the front part of the furnace. It is evident
that in this combustion chamber, higher temperatures are
generated than in the elder units; hence, the danger of
slagging in the furnace had to be taken in to account...
so that the furnace roof and the later fire-guiding wall
were designed as steam generating water-walls, to carry
off certain amounts of heat from the furnace.
-------
Boiler C rrrp o r. r -. t s
1. Welded Fin Water Tube Walls
2. Superbtat or
3. SIC.IID DruTr
4. Boiler Convert ion Section
5. Econocizcr
iL'-' - '~ : I < T- jj 1 ' | i
»--=_rti 8 yT ~ * f ',,,
I
FIGURE 3-11. CROSS SECTION OF BOILCR NO. 5 WITH ROLLER GRATE "SYSTEM
DUESSELDORF" (Courtesy Stadtwerke Duesseldorf Kraftwerke)
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35
For the sidewalls, the choice between water-walls and uncooled
refractory lining was discussed. Water-walls would have
solved the problem of slagging, but these tube surfaces need
special care and maintenance. To protect them against cor-
rosion and erosion, they must be covered with plastic refractory
lining, which must be checked at frequent intervals, and if
necessary, be amended. An uncooled lining of the sidewalls
was chosen, under consideration that the ignition of refuse
with low heating values must be supported. The refractory
material, which is most suited is SiC (silicon carbide) on
account of its slag repellent property. On the other hand,
it is known that the use of SiC materials in furnaces is
problematic, when temperatures of 900 C (1650 F) to 1010 C
(1850 F) exist and the flue gas contains considerable amounts
of 02 and H20. Experience of American operators communicated
to the manufacturers of the refractory materials in Germany
had indicated unsatisfactory performance. Accordingly, after
6,000 operating hours, the SiC lining of the front part of
the furnace was totally damaged. The furnace had to be recon-
structed with plastic refractory on an AL203 base. Now the
slagging problem appeared again, and during the following
operation period several times heavy slag formation occurred
at the side walls, which made it necessary to shut the boiler
down and remove the slag. In order to achieve a further
undisturbed operation, the combustion was shifted to the end
of the grate. Instead of air, recycled flue gas was injected
under the first roll of the grate. Due to the oxygen
reduction in the forward combustion chamber, the main com-
bustion zone moved one roll downward along the grate.
Consequently, the burnout time for the flue gas was
shortened, and after an. operation time of about 1 year,
the- first corrosion on the tube surfaces of the front wall
of the first pass occurred.
Because of the unsolved problems with the furnace, the
endangered area, about 2m (6.5 ft) in height, was studded
and lined with plastic refractory. Later no further corrosion
was found in this zone.
In 1974, a new composition of SiC material was offered by
"CARBORUNDUM1'j a manufacturer of refractory, which was
supposed to withstand the forementioned attacks. Two test
areas of this material were incorporated at the zone with the
highest heat load. After 11,000 hours of operation, it can be
said 'that this material promised to give sufficient life and to
have satisfactory slag repellent capacity.
No further damage of 'the first furnace lining occurred. Only
a minor attack and waste of the brick surface was observed.
Resting upon this experience, the lower halves of the side-
walls were rebuilt with the previously mentioned SiC bricks.
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36
Moreover, this part of the lining is air cooled by the use
of hollow bricks. The secondary air is employed as cooling
medium and is then finally injected into the furnace through
three horizontal groups of sidewall nozzles. Similar designs
are known in American plants."
Wall Construction in Unit No. 5
While the walls in Units 1-4 were either refractory or spaced
water tubes backed by high-temperature insulation, the non-refractory water-
tube walls in Unit No. 5 are "membrane walls"; that is, each tube has two
welded fins, 10 to 12 mm (0.4 to 0.5 in) facing the adjacent tubes. The joint
between the fins is also welded forming a solid, water-cooled membrane wall.
Wall Protection
When the first plastic-refractory coating was applied to water-
tube walls at Dusseldorf, the 10 mm (0.4 in) diameter studs were welded
2 2
to the wall tubes at a density of 2,800 per m (260 per ft ). Later this
density was reduced to 2,200 (204).
To cover the studs, a moldable form of silicon carbide is preferred
if an accumulation of slag is expected because SiC tends to repel the adherence
of sticky slag. Where slag is little problem, a plastic refractory such
as Plibrico, 75 mm (2.9 in) thick is used.
Superheater
In all boilers at this plant, the high-temperature section of
superheater is a suspended platen type located at the top of the first open
boiler pass as shown in Figures 3-9 and 3-10. Experience at many plants
has indicated that it would be desirable to position the superheater at a
greater distance from the main furnace. For one thing, the gas cooling
rate is relatively slow as it rises in the first open pass toward the super-
heater. Thus, if there are frequent bursts of high temperature gas leaving
the furnace because of the inhomogeneity of the refuse causing erratic
burning, there are then likely to be moments of excessive gas temperature
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37
striking the exposed bends of the suspended platens. Also, in the case of
Units No. 1-4, there is direct radiation from the furnace to the platens
which may contribute to overheating any ash deposits on the platens.
The rest of the superheater sections in this plant are horizontal
type at the top of the second pass. Thus, the flow of steam through the
superheater sections is counter flow, with the steam first meeting partially
cooled gases as they pass through the horizontal sections in the second pass.
Then the partially superheated steam flows to the suspended platen section
in the first pass where it meets hotter gas in a range of 700-800 C (1292-
1472 F) .
The superheater for Units No. 1-4 is made up of three sections
having the following heating surface: 83, 91, 52 m2 (893, 929, 560 ft2).
The superheater for No. 5 is in two sections. Material in these five units
and dimensions are as follows:
Unit 5
Units 1-4 First Section Second Section
Carbon: 0.12 - 0.20 0.1 - 0.18 <0.15
Silicon: 0.15 - 0.35 0.15 - 0.35 0.15 - 0.5
Manganese: 0.5 - 0.7 0.4 - 0.7 0.4 - 0.6
Phosphorus: <0.04 <0.04 <0.04
Molybdenum: 0.25 - 0.35 0.4 - 0.5 0.9 - 1.1
Chromium: None 0.7-1.0 2.0-2.5
Tube Diameter: 33.7 mm (1.33 in) 38 mm (1.5 in)
38 mm (1.5 in) 38 mm (1.5 in)
31.8 mm (1.25 in) 44.5 mm (1.75 in)
31.8 mm (1.25 in)
Tube Spacing: 150 mm (5.9 in)
150 mm (5.9 in)
600 mm (23.6 in)
Experiences with Superheater Corrosion
(3)
Thoemen has recently published a review of corrosion:
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38
"In the time from 1970 to 1972, fireside qorrosions of a con-
siderable rate appeared on the final state platen superheaters
on Boilers No. 1-4, which are installed at the upper end of the
first flue. The tube side, being directed against the gas flow,
showed a rapid material wastage at a rate up to 4,5 x 10"^ m/n
(0.00018 in/hr). At first, this corrosion was interpreted as
chlorine corrosion under lack of oxygen. Gas analyses, however,
showed, that in these parts of the boiler, sufficient oxygen
is present at any time. Only extensive analyses of the deposits
of the tubes have shown a chlorine-corrosion released by the trans-
formation of alkalichlorides into sulphates within the deposits.
As a partial remedy, the endangered tube parts were provided with
protective shields in form of flat steel. This proved to be
sufficient, but as these steel bars are cooled insufficiently,
an inspection and eventually a partial renewal has to be made
at every shut-down of the boiler, approximately every 3 months.
To cut down the maintenance costs, another tube material was
sought for better resistance against this corrosion. This is an
austenitic steel which has the German standard specification:
XSCrNi Nb 1613,
Its composition is:
C = (equal or smaller than) 0,08£
Si = 0,25 - 0,55%
Mn = 1,10 - 1,4%
Cr = 15 - 17%
Ni = 12 - 14%
Nb = (more than) 10 times C
In 1972, platens of this material were installed. On occasion of
a boiler inspection, after 16,000 hr, no substantial material
wastage could be found. But lately (1976), the first failure of
these platen tubes happened. The loss of material is strictly
limited to the outside surface of the 90° bend of the U-shaped
tube. The horizontal and vertical parts of the tubes are completely
unharmed. By the appearance of this damage, it can perhaps be
concluded that by bending the tubes not only a reduction of the
thickness of the outer wall occurs, but a structural change of
the material occurs too, which makes it sensitive to corrosion.
Tests about this matter are running, but not yet concluded, so
that final statements cannot be made. In relation to the corrosion
rate of 1970, these tubes have been a significant improvement,
although no protective shields have been used on these tubes.
Returning to the boiler which is in service since 1972, No. 5,
it must be said, that similar good experience with this unit has
not been achieved. Contrary to the anticipated effect of a
reduced suspectibility for corrosion, considerable difficulty
arose with this new unit too. There occurred corrosion phenomena
of kinds not known before.
-------
39
Although the corrosions of the wall tubes of the first boiler
pass in No. 5 are under control, a totally different picture is
presented in the superheater area. Both the final stage super-
heater and the convection superheater were affected by numerous
attacks and damages since startup. The tube failures of the
superheaters have been as follows:
22 failures of convection superheater tubes (see No. 2
of Figure 3-11)
13 failures of final superheater tubes (see No. 3 of
Figure 3-11).
An accumulation of that kind of tube failures caused by corrosions
has not been observed in former years. The final (suspended
platen) superheater which is of nearly the same design and
arrangement as in Boilers No. 1-4, had to be renewed in two steps
in the years 1973 and 1974. The cause of this failure was a fault
in the design. The 14 tubes of each platen superheater had been
welded together instead of being clamped. Hereby the tubes were
hindered in their expansion so that after a short operation period,
they were completely twisted and no longer hung vertical at the
leading edge of the tubes, not only the outward tubes were
endangered, but the superheater platens presented larger surfaces
to the corrosion attack. With the renewal of the first half of
this superheater, the first four outer tubes of each platen
were made of the same austenitic steel mentioned earlier. But
after about 6,000 hours of operation, one of these tubes failed
and the others showed considerable attack too. Investigations
were made in order to trace the cause of this short tube life,
compared to that of the same tubes in the other boilers. A new
phenomenon was found not known up to that date. On the presuper-
heater too, being located at the upper end of the second gas pass
as a convection tube bundle, corrosion occurred to an extent
not known from the other boilers. Not only the tube bends were
affected, but at the middle section of the tube bends, the material
was carried away at the top side, the material loss at the middle
sections occurred at both sides of the tubes at an angle of about
30° to the vertical axis as a longfaced erosion. In addition, not
only the first or second row of the tubes is affected, but the
damages continued throughout the whole upper tube bundle."
Causes of the Corrosion
"By search for the possible reasons of this intensified corrosion,
it was found that in 1973 about 1 year after the start of operation
of Boiler No. 5 a new situation had come up in the method of
operation. In May, 1973, a shredder-installation for bulky refuse
(wood of any kind, furniture, boxes, crates, etc.) was started.
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40
Due to space arrangements between the shredder and the boiler,
most of the shredded material is fed into this unit."
Mr. Thoemen believes this is caused by a concentration of potassium
chloride in the tube deposits.
Thoemen's conclusions regarding corrosion protection for super-
heaters is:
Good mixing of refuse to avoid concentration of corrosive
salts in one boiler
Clamp protective metallic shields on tubes at vulnerable
locations. He finds that a convenient alloy for this purpose(similar
to 1.0% Mn) Sicromal 8 plus because it can be formed and welded is:
Carbon: 0.1%
- Silicon: 1.0%
Aluminum: 0.8%
- Manganese: 1.0%
- Chromium: 6.5%.
The shield lasts 3 to 12 months.
Use alloy steels in tubes
Plasma-gun coating by metallic or ceramic materials. This
will be tried at Duesseldorf.
Figure 3-lla shows a hard coating applied in 1977 on bends of super-
heater tubes to be installed in the second pass of Boiler No. 5 to determine
its usefulness in reducing tube wastage.
Soon after Boilers No. 1-4 began operation in 1965, a limited amount
of corrosion appeared in the top tube row of the horizontal superheater
sections in the second pass. However, as soon as a protective deposit
developed there, corrosion almost ceased. Thoemen described this situation
in 1972(2):
"For the first time after about 1,000 hours of operation time, we
experienced comparatively severe corrosion on the tubes of the
first stage superheater at the side of the direction of gas flow.
The uppermost rows of tubes of the superheater carried, under a
relatively small scale of deposits, a heavy layer of corrosion
products. By the thickness of this layer, it had to be concluded
that rapid wastage of these tubes could be expected. However, as
operations continued, the corrosion rate declined and has reached
a level which causes a barely measurable waste of material. The
tubes now are covered with a hard layer of deposits."
-------
41
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-------
42
The importance of a protective deposit is thus emphasized. Also
the deleterious effect of any action, such as excessive soot blowing, is
emphasized. However, at this plant, excessive tube wastage because of soot
blowing has not occurred. Mr. Thoemen emphasized the importance of the
following in safe soot blowing:
Steam lines must be well drained to avoid blasting slugs
of water against the tubes. Tubes are blown once per shift.
Protective shields are very successfully used to guard
against soot blower erosion.
Steam jet pressure must not be too high.
A thermocouple in the steam line can be used as an operating
guide. The temperature should be well above saturation
temperature to avoid blowing slugs of water when the soot
blower is turned on.
Boiler (Convection Section)
The convection section of the boiler is located in the lower
portion of the second pass as seen in Figure 3-9. Some erosion by fly ash
has been experienced in this area. In Boilers No. 1-4, this occurred only
at the outside of the first row of tubes where the gas flow pattern caused
a concentrated stream of fly ash to impinge against the metal. In Boiler
No. 5, after 28,000 hours, steel cladding was added to shield these tubes
against erosion.
The boilers in No. 1 and No. 2 were built by Duerr. Those in
Nos. 3 and 4 were built by Vereinigte Kesselwerke. No. 5 was built in joint
responsibility of both firms. Both companies are now a part of Deutsche
Babcock. No. 1-4 are rated at 20 t/hr. No. 5 is rated at 30 t/hr.
The entire boiler is water cleaned in Units No. 1-4 every 2,000
hours. No. 5 is similarly cleaned every 5,000 hours. At first, the tubes
o
are sprayed for 10-12 hours at the rate of 10 m /hr (44.0 gpm) to soak the
deposits. Then the weakened deposits are removed the next morning by means
of a high pressure water jet.
-------
43
Economizer
The plain tubular economizer generates about 5 percent of the
steam produced in each unit. The gas temperature entering is 525 C (980 F)
and leaving is 237 C (459 F). Excessive soot blower operation in the
economizer has caused some tube failure.
Boiler Water Treatment
Because this plant feeds its output of high-pressure, high-
temperature steam to the turbines at the nearby Flingern power plant, it
receives all of its feedwater from that plant. It is fully demineralized
and deoxidized.
Primary Air Supply
The primary air to each of the five boilers is supplied by one
axial flow fan built by Buttner-Schilde-Haas. For Boilers No. 1-4, the
3
maximum volume is 11 m /sec at 110 C (23,304 cfm at 230 F) at 180 mm (7 in)
water. The preheated air is heated by means of heat exchangers heated by
condensate returning from the Flingern Power Plant 600 m (1,970 ft) away.
3 3
For Boiler No. 5, the primary air rate is 52,800 Nm /hr (14.67 Nm /sec or
31,080 cfm) at a pressure of 240 mm (9.5 in) water.
The air flow to each of the seven grate rolls in Boilers No. 1-4
is controlled by a separate damper which is adjustable manually. The vane
position of the fan is controlled automatically from excess air as measured
approximately 1 to 2 m (3.3 to 6.5 ft) up into the first pass above the
furnace. An effort is made to control the 0_ at that point to between 6
and 8 percent. A similar system controls the air to the six rolls in Boiler
No. 5.
A membrane type manometer connected to each grate roll zone
provides an indication in place. The condition of the main and secondary
air flow is indicated in the control room. The total primary and secondary
air flow to each boiler is measured bv means of a venturi.
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44
As already indicated, there is no redundancy in the , 'r supply
to each boiler but performance for 12 years has been excellent. However,
the zone control dampers require lubrication and have a tendency to bind.
Secondary Air
This plant provides an interesting view of the evolution in the
application of overfire air to maintain complete combustion. Apparently
the experience with the first small pilot furnace from 1961 to 1965 led
the designers of Boilers No. 1-4 to specify only a nominal secondary air
3
flow per boiler of 4,000 Nm /hr (2,354 scfm) at a moderate pressure of 280 mm
(11 in) water. This air was supplied to a total of 44 nozzles in each boiler
distributed as follows:
18 pointing nearly downward in the water-cooled front roof
20 pointing at an angle down and forward in the water-cooled
rear roof
Six in each refractory sidewall.
As had already been discussed under the topic "First Open Boiler
Pass", in 1967 an inspection of the water-tube walls in the first open
boiler pass immediately above the furnace revealed tube wastage in the
front wall (Figure 3-9) which appeared to be caused by the flow against
these tubes of high-temperature flame having low oxygen content. To obtain
a higher oxygen content at that point, the number of secondary air nozzles
was increased. Also, the secondary air pressure was increased from 280 mm
(11 in) water to 500 mm (23.6 in) water and the available air volume was
increased from 4,000 Nm3/hr (2,354 scfm) to 10,172 Nm3/hr (5,988 scfm).
In addition, in 1976, more secondary air was introduced in Boilers
No. 1-4 through the air cooled refractory arch or guiding wall which has
been described earlier. The air cooling system for this silicon carbide
arch has now been evolved to contain 62 air holes in two rows of 31 each.
Sixteen of the holes are 30 mm (1.2 in) diameter and 46 of them are 60 mm
(2.4 in) diameter. The secondary air flowing into the furnace through this
arch cooling system becomes heated to about 300 C (572 F).
-------
45
o
Boiler No. 5 has a larger secondary air supply: 15,000 Nm /hr
(8,828 cfm); and a considerably higher air pressure: 800 nun (31.5 in) water.
In addition to nozzles in the front and rear roof similar to Boilers No. 1-4,
there are three rows of six sidewall nozzles each, the lowest row about 1.5 m
(4.9 ft) above and parallel to the sloping grate line.
These overfire air systems have operated satisfactorily except that
at first there was insufficient air supply. In the air piping systems, the
individual nozzles have been connected to the air manifolds by flexible steel
hoses. Because of overheating of some of these connections, they are being
converted to stainless steel hoses.
Co-Firing Equipment
The only auxiliary fuel used at this plant is No. 2 fuel oil
which is used only for start-up or in an emergency. There is a legal
requirement on incinerators that the combustion gases must attain a level
of 800 C (1,472 F) . If there is very wet refuse or some other cause for
the furnace temperature to fall below that limit, the oil burners can be
used to raise the temperature. Originally, Boilers No. 1-4 had three oil
burners at the top-front-center of the furnace between the feed chute and
the arch. Now there is only one burner per unit. The burner for No. 5
is on one side. Maximum oil capacity per burner is 0.4 tonnes/hr (130 gal/hr)
Heat Release Rate
The following approximate heat release rates have been estimated
based on the grate areas and furnace volumes calculated from dimensions
scaled from available diagrams. The combustion volume in Furnaces No. 1-4
was taken as 167 m3 (5,285 ft3) and for No. 5 was 297 m (10,487 ft ). The
2 2
corresponding grate burning areas were taken as 49.71 m (527 ft ) and
2 2
42.63 m (458 ft ), respectively. The lower heat value was assumed to be
1,850 kcal/kg (7,746 KJ/kg or 3,330 Btu/lb).
-------
46
Boilers No. Boiler No,
Burning Rate, per boiler, tonnes/day
Burning Rate, per boiler, tons/day
2
Burning Rate, on grate, kg/m -hr
Burning Rate, on grate, Ib/ft -hr
2
Burning Rate, on grate, Kcal/m -hr
2
Burning Rate, on grate, MJ/m -hr
2
Burning Rate, on grate, Btu/ft -hr
3
Heat Release Rate, Kcal/m -hr
3
Heat Release Rate, MJ/m -hr
Heat Release Rate, Btu/ft -hr
1-4
240
264
201.4
41.17
372,220
1,558
137,350
110,778
464
12,449
5
300
330
293.
60.
542,420
2,271
200,155
77,862
326
8,750
2
0
The inclusion of a portion of the first pass as active furnace
volume may increase that volume by 21 percent in the case of Furnaces No. 1-4
and 18 percent for Furnace No. 5. Thus, the above volume heat release
rates would be 18 to 21 percent higher if the burning were considered to be
entirely contained in the main furnace.
The above burning rates and heat release rates are conservatively
low, especially for the relatively low heating value refuse obtained in
Duesseldorf.
Energy Utilization Equipment
Because this refuse to energy plant was built adjacent to and
connected to the Flingern power plant, the entire output from the burning
of refuse goes 700 m (2,300 ft) to the turbines at the Flingern plant in
the form of high pressure, 80 bar (1,500 psig or 104 atm) high temperature
steam, 500 C (932 F). Here it is utilized in two double shaft condensing
steam turbines, two high perssure generating about 32 mw and 11 mw and 2 low
pressure generating about 53 and 30 mw. Steam extracted from the 50 mw turbine
is used to produce hot water at a maximum of 130 C (266 F) for district
heating. Early this year (1977), the Federal government issued regulations
permitting 180 C (356 F).
-------
47
In the summer, the refuse-burning plant supplies practically all
of the energy needed for district heating. On such days with an outdoor
temperature of 20 C (68 F), the district supply water temperature is 80 C
(176 F) and the system return temperature is 65 C (149 F). The system water
flow rate is then 800 m /hr (3,520 gpm). In the winter at an outdoor
temperature of -10 C (14 F), the flow rate is 1,400 m3/hr (6,160 gpm) at
supply and return temperatures of 130 C (266 F) and 70 C (158 F).
The district heating loop is 15.9 km (10 mi) long and serves 133
buildings included in which are 8,000 apartments. The peak heat demand is
110 Gcal/hr (460.6 GJ/hr or 27.72 MBtu/hr). For comparison, the maximum
rated output of the five boilers at the refuse burning plant is 110 tonnes/hr
(121 tons/hr), equivalent to approximately 88.5 Gcal/hr (371.7 GJ/hr or 22.3
M Btu/hr). However, this full capacity, 963,600 tonnes per year, is never
available all at one time.
In 1975, this plant burned 297,359 tonnes of refuse (327,095 tons)
and delivered 560,002 tonnes (617,570 tons) of steam (1.89 ton/ton) to the
Flingern Power Plant, which is 58.1 percent of full rated capacity. The
income from this output was 8,125,629.02 DM ($3,412,764.20) a rate of
14.5 DM/tonne ($5.53/ton) or $2.76/1,000 Ib (approximately $2.76/106 Btu).
In addition, some steam is used internally for turbine-driven feedwater and
condenser cooling water pumps.
Plant Start-Up Procedure
The following start-up procedure as described by Mr. Thoemen is
used:
Check all access ports, assure that all workers are outside,
that internal equipment appears in order. This check takes
1 hour.
Fill the boiler with feedwater. Preheat the boiler with steam
from the intermediate pressure line and build the pressure to
20 atm (275 psig). This takes 4 to 8 hours.
-------
Adjust the steam flow to blow out any condensate from super-
heater and set valve about 40 percent open.
Start primary air fan at minimum flow, start grate rollers
and start hot condensate flow through air preheater.
Over the next 45 minutes, complete the following:
Fill refuse feedchute
- Start refuse feeder
Cover first two rollers with refuse
- Light oil burner
- Increase feed gradually at rate governed by rate
of rise of superheat temperature and drum pressure
- Start flow of steam to Flingern Power Plant.
The total elapsed time for this start-up procedure is usually
8 to 10 hours.
Shut Down
Crane stops filling chute.
Empty chute onto grate over a period of 2 to 3 hours.
Increase furnace draft to maximum.
Reduce primary air.
Complete burnout of refuse on bed over a period of 1 to
1-1/2 hours.
Stop steam flow to main line.
Vent steam to intermediate line.
Continue primary air fan for 4 to 6 hours.
Turn off fans to allow final cooling by natural draft.
After 24 hours, begin repair work on unit.
-------
49
Emergency Shut Down
If a tube fails, shut off steam flow to main line.
Shut off primary and secondary air.
Extinguish fire with fire hoses.
Complete extinguishment takes 5 to 6 hours.
Turn grate off.
Stop feedwater pumps.
Empty grate.
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50
POLLUTION CONTROL EQUIPMENT
The four original boilers were equipped with two Lurgi Electrostatic
Precipitators having a design efficiency of 99+ percent. In each precipitator,
the gas flow is divided into 28 passages, each 0.226 m (8.5 in) wide. The
height of the passage is 6.27 m (20.6 ft) and its flow length is 5.75 m
2
(18.9 ft). Total projected collection area in each precipitator is 2020 m
(20,800 ft2). The inlet flow area is 37.6 m2 (406 ft2) and the design
velocity is 1.1 m/s (3.7 ft/s). Design flow rate was 39,000 Nm /hr (22,952
scfm).
(4)
Table 3-3 by Konopka gives the results of two precipitator tests
at this plant in 1967 by the government testing organization, Technische
Uberwachungs Verein Rheinland, e.v. (TUV). The report indicated that in one
test, the combustible content of the collected dust was 6.6 percent and its
resistivity at 220 C (432 F) was 6 x 10 ohm-cm. Konopka recorded similar
measurements by TUV at other plants that gave similar values.
Boilers No. 3 and 4 are served by an identical precipitator to
that serving Nos. 1 and 2. Boiler No. 5 is served by a third precipitator.
All three precipitators are connected by a manifold to a single chimney.
By means of multi-vane butterfly dampers, the flow from any boilers can
be fed to either of the three precipitators. The damper blades are 574 mm
(22 in) wide and are shaped to present a "knife edge" to upstream and down-
stream flow when open. This shape helps to minimize deposition of ash on
the blades. The upstream edge of each blade is made of manganese steel.
To further discourage deposition and erosion, each blade is shielded upstream
by a manganese steel I-bar positioned 20 mm (0.79 in) upstream. The damper
assembly was made by Warmekraft-Gesellschaft Stobert Morlock of Recklinghausen,
Germany.
The installation of precipitator No. 3 for Boiler No. 5 by RothemUhle
in 1972 was preceded by a flow model study although the approaching flow
pattern produced by the flue gas manifold was not modeled. It has two fields
and 30 rows of collector plates spaced 300 mm (11.8 in) apart. The plates
are 10 m (32.8 ft) high and each field is 3 m (9.8 ft) long. Effective
2 2
projected collector surface is 3,600 m (38,730 ft ). Perforated distributor
-------
51
TABLE 3-3. RESULTS OF TWO PERFORMANCE TESTS BY TUV ON A PRECIP-
ITATOR AT THE DUESSELDORF REFUSE PLANT
Test Number 1 2
Firing Mode Refuse Refuse
Rated Gas Volumes M3/S °C 44.00 260 44.00 260
FT3/S °F (V Design) 15502 500 15500 500
Actual Gas Volume M3/S °C (Measured at Pptr. Outlet) 43.00 235 43.50 242
FT3/S °F (V Actual) 15205 455 15350 460
1000 ACFM °F (4) 91.0 455 92.0 405
Percent of Rating (Percent) 97.7 98.9
Actual (Test) Pptr. Inlet Dust Cone. (gm/Nm3) 11.0 13.1
(gr/SCF) 4.31 5.69
Actual (Test) Pptr. Outlet Dust Cone. (gm/Nm3) 0.036 0.042
(gr/SCF) 0.0158 0.0184
Guarantee Collection Efficiency (Corrected for Actual 98.35 98.95
Test Conditions per Manufacturer's Corrosion
Factors (Percent)
Actual (Test Collection Efficiency) (Percent) 99.67 99.68
Pptr. Design Gas Velocity at Rated Volume (in/sec) 1.16 1.16
(ft/sec) 3.82 3.82
Pptr. Actual (Test) Gas Velocity (v) (in/sec) 1.14 1.15
(ft/sec) 3.74 3.77
Design Migration Velocity (ft/sec) .408 .319
Actual Migration Velocity (ft/sec) .399 .406
Pptr. Electrical Energization Data
Secondary Kilovolts Inlet (KV) (Inlet/Outlet) 31.5/29 31/29
Secondary Mill-amps (MA) (Inlet/Outlet) 265/267 313/310
Input Power (AXB) (Kilowatts) (Inlet/Outlet) 8.3/7.7 9.7/9.0
Power Density-Watts per 1000 ACFM (Inlet/Outlet) 91.7/85 105/97.7
Power Density-Watts per Ft2 C.E. (Inlet/Outlet) .401/.372 .466/.432
Field Strength-Kilovolts per Inch (Inlet/Outlet) 0.74/0.68 0.73/0.68
Note: No = corrected to 0°C and 760 nun Hg; 0.0736 mm Hg. water vapor pressure.
pressure.
-------
52
plates produce an excellent velocity flow distribution entering the first
field at an average velocity of 0.834 m/s (2.74 f/s). Residence time is
7.2 seconds.
A power supply of 95.5 KVA is available to each field at 55 KV.
No-flow voltage is 78 KV. Normal current is 600 ma, maximum 900 ma. Power
consumption per field is 33 Kw.
Rapping is by means of gravity hammers operated automatically in
a prescribed sequence. Unlike many outdoor precipitators, these hoppers
are not heated. They are covered with 100 mm (3.9 in) of insulation.
There is no problem of condensation causing sticking of the ash in the
hoppers because there is no storage of fly ash there.
Originally, the ash removal system was pneumatic but this was
abandoned after 2 years and was replaced by screws. Some modification of
the fitting of the screws to the hoppers was needed to facilitate ash removal.
One 24-hour test by TUV showed the particulate emission rate to
3
range from 80 to 100 mg/Nm corrected to 11 percent CO. (0.0352 to 0.044
o
grains/ft ).
The applied voltage on the precipitators must be continuously
recorded as required by the county licensing board. The record must be
stored for 5 years.
The availability for service of the individual precipitators is
shown by the record for the last 2 years:
Availability, Percent
1975 1976
Precipitator No. 1 99.3 99.2
Precipitator No. 2 99.6 100.0
Precipitator No. 3 100.0 92.7
Figure 3-12 is an example of two of the operation and maintenance
computer cards which are used at the plant to maintain systematic records
on the precipitators and other components.
-------
53
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-------
54
Wastewater Discharge
Wastewater from boiler blowdown and ash disposal go to a
settling tank and then to the city combined sewer system.
Stack Construction
The chimney 100 m tall (328 ft) is 80 m concrete and 20 m bricks,
with a firebrick lining surrounded by 150 mm (5-9 in) foamed glass insulation.
In 1971 after 6 years service, some of this insulation had to be replaced.
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55
EQUIPMENT PERFORMANCE ASSESSMENT
The product of this plant is high-pressure, high-temperature steam.
In 1975 it delivered 58.1 percent of its rated steaming capacity. Actually
since the plant design philosophy is to have one boiler always in reserve
this output was nearer to 70 percent of nominal operational capacity. Con-
sidering the inherent difficulty involved in handling wastes as fuel with all
these problems the neat and well-maintained appearance of this plant and its
grounds, 70 percent of nominal capacity is excellent. The performance is
even more remarkable in terms of the pioneering nature of the plant; this
particular type of stoker was invented only 16 years ago and this is the
first large plant ever built using this principle.
Table 3-3a is a summary of the year's operating data for 1976 as
printed from the data storage and analysis system.
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56
TABLE 3-3a. DUESSELDORF WASTE-BURNING FACILITYOPERATING RESULTS - 1976
Waste Input
Residential Waste 180,462.80 Tonnes
Industrial Waste 65,795.35 Tonnes
Bulky Waste (Residential and Industrial) 25,250.79 Tonnes
Rubbish 10,844.80 Tonnes
Waste Oil 1,831.54 Tonnes
Total 284,185.37 Tonnes
Heating Oil 20.81 Tonnes
Consumption
Waste 284,185.37 Tonnes
Heating Oil 3.40 Tonnes
Storage
Waste 2,475.00 Tonnes
Heating Oil 26.84 Tonnes
Heat Value
Waste 1,815.98 kcal/kg
Heating Oil 10,155.03 kcal/kg
Sulfur
Heating Oil 0.43 Percent
Wet Residue
Fine 78,706.30 Tonnes
Discarded 19,650.28 Tonnes
Total Residue 98,356.58 Tonnes
Total Residue Shipped 97,641.58 Tonnes
Storage 935.00 Tonnes
Residue Analysis
Water 18.89 Percent
Combustible 5.03 Percent
Scrap Iron
Total 8,492.42 Tonnes
Bulky Scrap 531.51 Tonnes
-------
57
TABLE 3-3a. (Continued)
Electricity Consumption
Total Received
Maximum Electrical Demand
Consumption
City Water
Well Water
Total Water
Time of Operation of all Boilers
Waste Feed
Number of Crane Loads Charged
Live Steam
Pressure
Temperature
Amount
Enthalpy of Steam
Enthalpy of Feedwater
Flue Gas Temperature
Oxygen (02) Content
Left Side of Furnace
Right Side of Furnace
Air Temperature
Ambient
Entering Preheater
Leaving Preheater
Heat Balance
Live Steam
Exhaust Gas
Combustible in Residue
Sensible Heat in Residue
Piping and Radiation Loss
Total
14,521.00
2,445.00
99,253.00
507,671.00
606,924.00
30,963.00
125,939.00
MWH
KW
Cubic Meter
Cubic Meter
Cubic Meter
Hours
81.26
471.90
592,265.00
795.06
130.71
270.00
8.88
8.88
11.00
25.00
87.00
470,885.32
94,749.74
18,673.44
12,702.76
13,322.98
610,334.24
Bar
°C
Tonnes
kcal/kg
kcal/kg
°C
Percent
Percent
°C
°C
°C
Gcal
Gcal
Gcal
Gcal
Gcal
Gcal
-------
58
TABLE 3-3a. (Continued)
Heat Input
Heat in Feedwater
Heat in Combustion Air
Heat From Heating Oil
Heat From Waste
Boiler Efficiency
Energy Losses
Exhaust Gas
Unburned Combustible
Sensible Heat in Residue
Piping and Radiation Loss
Consumption and Operating Rates
Heating Oil
Waste (aver, per unit operating)
Crane Lift Rate
Heat Release
Live Steam Rate
Total
Produced From Oil
Produced From Waste
Production Rates
Steam Per Unit Fuel
Steam Per Unit Waste
Steam Per Unit Oil
Residue Per Unit Waste
Total Water Consumption
Electricity Consumption
Per Tonne Total Waste
Per Tonne Steam
Steam Sold *
77,414.96
16,810.26
34.53
516,074.50
73.83
17.78
3.50
2.38
2.50
0.11
9.18
2.26
16.67
19.13
1.34
19.13
2.08
2.08
12.19
0.37
2.14
51.10
24.52
564,091.00
gcal
gcal
gcal
gcal
Percent
Percent
Percent
Percent
Percent
kg /hour
tonnes/hour
tonnes/grab
Gcal/hour
tonnes/hour
kg /hour
tonnes/hour
kg /kg
kg /kg
kg /kg
kg /kg
Cubic Meter/tonne
kwh/ tonne
kwh/ tonne
Tonnes
* Corrected to 807 Kcal/kg
-------
59
POLLUTION CONTROL ASSESSMENT
The stack plume from this plant was usually slightly visible as a
very light, thin gray cloud against a clear blue sky. It dissipated quickly
and did not appear to be objectionable. The emission appeared to be within
the allowable limit.
In 1974 a new Federal regulation of atmospheric emissions was
enacted known as TA Luft (Technischen Anleitung zur Reinhaltung der Luft).
It reduced the allowable particulate emission for plants over 100,000m /h
(58,850 cfm) to 100 mg/Nm corrected to 11 percent CC>2. For new plants it
also specifies limits for emission of CO, N0? and S0~. For plants which
expand by adding new capacity, all of the old and new equipment must meet
following new limits on gases (at o C, 32F) :
HC1: 100 mg/Nm3 (62 ppm) [0.083 lb/1000 Ib gas]
HF: 5 mg/Nm3 (11 ppm) [0.008 lb/1000 Ib gas]
S02: 100 mg/Nm3 (2175 ppm) [0/46 lb/1000 Ib gas].
CO: Ig/Nm3
Requirements for SO reduction are made according to ambient air quality. In
3
case that S07 reduction is necessary the limit is 100 mg/Nm .
Since 1973 the gaseous emissions from this plant have been checked
periodically. The most recent average is as follows (all corrected to
11 percent C0?):
mg/Nm ZEE. (by Vol at o c, 32."I
HC1 1000 623
HF 9 10
S02 500 175
S03 5 2
NO (as N0?) 9 4
X ^
Oxygen 11 percent
Evidently if Boiler No. 6 were to be installed the levels of HC1
and HF now produced would require that all 6 boilers be equipped with
scrubbers to remove most of these gases. This poses a difficult dilemma
for this and similar existing plants. Although both HC1 and HF are readily
-------
60
soluble in water, the operation of large scrubbers to remove these gases
reliably has yet to be demonstrated. Corrosion by the acids formed is still
a major problem with the few such scrubbers that have been tried on a large
scale. Hopefully the new plants which are encountering major problems with
their scrubbers will in a few years find practical answers which will show
the way for older and future plants. Meanwhile, since ambient air measure-
ments of HC1 and HF are not usually made it would seem that the regulation
is premature both from the standpoints of demonstrated need and demonstrated
control technology.
Noises
This plant is located in an industrial area adjacent to a major
railroad line, hence its noise is not a major problem. However, in 1972
because of complaints over noise from the outdoor induced axial flow fans,
the fans were replaced by sound treated ones at a cost of 300,000 DM each
($129,000 at 2.32 DM/$ in 1973).
-------
51
PERSONNEL AND MANAGEMENT
Table 3-4 shows the organization of the 83 persons who constitute
the plant staff. The plant operates on a 4-shift per day basis with the
average work week 43 hours. Normally there are 9 workers handling the
operation per shift. Job descriptions are published annually and key workers
have an organization handbook.
The following principal operators are connected by an inter-
communication system:
Crane operator
Boiler operator
Shear operator
Shredder operator
Tipping Floor (2 locations).
Training
Crane Operator. One year general plant training plus one year
special training followed by examination for an operators license. No
special prior education or experience is required.
Boiler Operator. An effort is made to recruit those having
mechanical training from a 3-year apprenticeship. At this plant he starts
as a boiler operator's apprentice for 2 years. Their additional training
is given 6 hours per week. Then the Technischer Uberwachungs Verein (lt)V)
provides a 6-month course, 3 hours per week to prepare for examination
for a boiler operator's license.
Separately the VGB (Association for Large Power Plant Operators), conducts
an on-the-job training program for power plant operators. Prerequisite
for this training is 6 years experience on boilers, turbines, coal handl-
ing, water treatment or similar power-oriented work.
-------
V.-62
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-------
63
The VGB course totals 1500 hours. Without prior training this
course must be matched by 8 years experience. Then successful completion
of a VGB-administered examination qualifies him as a Kraftwerker (Power
Plant Worker). Shift foremen must have this rank. After one year of
additional experience he may become eligible for a one-year course at the
VGB school in Essen, at the successful conclusion of which he becomes a
Kraftwerkmeister (Master Power Plant Worker).
Pay scales are developed in negotiation with the workers union.
Following are the approximate monthly pay rates including 28 to 30 percent
for pension and taxes:
DM 4600
DM 3300
DM 3300
DM 3400
DM 3200
Shift supervisor
Shift workers
Crane operator
Foreman
Boiler cleaner
Senior boiler operator DM 3050
Apprentice boiler
operator
Power plant operator
Ash handler
Electrician
Shop foreman
DM 2800
DM 3150
DM 2600-2800
DM 2300
DM 2600
The Boiler Cleaner is paid a relatively high rate because it is
difficult, odd time work.
For the average worker at DM 3000/month, less 30 percent for
pension and taxes, his annual takehome pay is 25,000 DM ($10,584 at $0.42/DM)
-------
64
ENERGY MARKETING
Although the refuse plant does no marketing because it has only
one customer, Stadtwerke Dusseldorf AG, the latter does advertise and has an
appliance sales outlet. Aside from selling electricity it also sells distric
heating, gas and water. There are about 50 in its sales force. The Stadtwer
Dusseldorf AG was converted to a stock company in 1972.
In the district heating system the customer is billed annually
but pays on a monthly budget plan. The contract for heating is reviewed
annually. The rate is reduced if the customer helps reduce peak demands by
installing a heated rock heat storage tank.
The district heating loop in Garath, a new housing area, was in-
stalled and paid for by Stadtwerke Dusseldorf as was also the loop for the nev
Dusseldorf University but customers contribute to loop costs. The supply
comes from the base load power station "Lansword" on the river Rhine.
ECONOMICS
Capital Investment
The first four units and associated structures built in 1965 cost
106 ($8.63 x 106 at 4.0
This cost was divided as follows:
DM 34.5 x 106 ($8.63 x 1Q6 at 4.00 DM/$-1965)[$14.5 x 106 at 2.35 DM/$-1977].
Mechanical equipment DM15.5 x 10
Electrical 1.6
Structures, roads, landscaping 12.0
29.7
Construction financing 5.4
over 2 years and site
development
TOTAL DM 34.5 x 1Q6
When the larger unit No. 5, was added within the existing building
in 1972 it cost 11.7 x 106 DM ($3.67 x 106 at 3.19 DM/$-1972)[$4.91 x 106
at 2.38 DM/$-1977]. Part of this proportionately higher cost was the result
of a new precipitator and shredder installed at that time. The cost breakdown
in 1972 was:
-------
65
Mechanical equipment DM6.5 x 10
Electrical (including precipitator) 1.77
Structural changes 0.41
Shredder 1.6
Engineering fee (2.5%) 0.22
Escalation cost 1.3
DM11.70 x 106
Mr. Thoemen estimated if No. 5 were built today (1977) it would
cost 20 x 10 DM ($8.4 x 10 ) because of inflation. If all five units were
built today the plant would cost 80-90 x 1Q6 DM ($34-38 x 106). If No. 6
were built today in the space already available for it in the existing building
with a maximum capacity of 360 tonnes/day it would cost an estimated 27 x 10 DM
($11.3 x 10 ) including a fourth precipitator and a flue-gas scrubber system
for the entire plant composed of 4 scrubber modules in parallel. Mr. Thoemen's
experience is that no one plant unit should be designed for more than 15 tonnes/hr,
(360 tonnes/day) [396 tons/day) because if a breakdown reduces plant capacity,
the accumulation in storage of more than 360 tonnes per day will rather quickly
force hauling the excess to distant landfills, a fairly expensive operation.
The above costs expressed per tonne (ton) day of capacity were as
follows:
DM per $ per $ per
tonne-day ton-day ton-day
in DM for in $ for ^f built
year built year built in 1977
1965 No. 1-4 (includ. building 35,938 8,990 15,109
1972 No. 5 (without building) 39,000 12,233 16,367
1977 If NO. 6*were built(est) 75,000 31,390 31,390
Because this plant generates only high-pressure steam and not
electricity these costs are low for most plants of this size which do have
the equipment to generate electricity. It appears that the German requirement
for removal of HC1 and HF by means of scrubbers will raise plant costs sub-
stantially.
* Including 1 el. precipitator and scrubbing system for all 6 units.
-------
66
The land area required for this operation is as follows:
2
Structures 7,000 m
2
Landscape 8,000 m
Roads 15,331 m2
30,831 m2 (331,862 ft2)[7.5 acres]
The value of this property is estimated in 1977 terms as 7.7 x 10 DM
($3,234,000). It is of considerable significance that if this same expensive
industrial property were utilized as a sanitary landfill, it would have .
become filled in about 2 or 3 years at the average rate this plant is now
operating (290,000 tonnes/yr or 319,000 tons/yr).
Operating Costs
In 1975, the operation and maintenance costs, not including
amortization or interest on debt, totalled 9.066 x 10 DM ($3.808 at 2.38
DM/$). This consisted of 4.215 x 10 DM for operation and 4.85 x 106 DM
for maintenance.. Maintenance was divided as follows:
Millions Millions
DM 1977 Dollars
Maintenance by plant staff 1.139
Maintenance by outside contractors 2.481
Maintenance materials 1.231
TOTAL 4.851
Added to these costs is a 5 percent management fee, which the uStadtwerke
DUsseldorf" charges the department of Sanitation as a management fee, and
5 percent debt cost. Thus, the total charge to the owner for the operation
and maintenance in 1976 was 10.822x 10 DM ($4.545 x 10 at 2.38 DM/$).
Including capital costs and misc. expenses 1976 total gross costs per tonne
of refuse were: DM - 63,86. Net costs (revenues are included) were:
DM - 30,67 per tonne. The total refuse burned in 1976 was 286, 185 tonnes
(312,604 tons).
Tables 3-5 through 3-9 showing the operating costs (and revenues)
for the plant in 1975 were provided by Dr. Helmut Orth, Direktor, Stadtreinigungs-
und Fuhramt (Deaprtment of Sanitation and Streets).
-------
57
TABLE 3-5. DUESSELDORF WASTE-BURNING FACILITY- 1975
Type of Waste
Residentual
Bulky
Rubbish
Industrial
Contaminated Oil
Total Waste
Residues From Burning
Ash
Baled Scrap
Loose Scrap
Total Residue
Amount
in Tonnes
201,816
9,014
10,024
74,837
1,668
297,359
Percent of
Throughput
67.87
3.03
3.37
25.17
0.56
100.00
Percent of Weight,
Input Tonnes
35.3 105,092
3.1 5,986
3,192
38.4 114,278
-------
68
TABLE 3-6. COSTS OF THE WASTE BURNING FACILITY, 1975
Operating Expense Including 80 Percent Overhead
on Salaries and Wages and 10 Percent Overhead
on Other costs
Maintenance Expense with Overhead
Miscellaneous Expense with Overhead
Operational Fee Surcharge of 5 Percent Without
Electricity, Water, or Fuel
Management Fee of Sanitation Department
Insurance
Electricity, Water
Fuel
Ash and Scrap Hauling
Amortization
TOTAL
DM
2,707,858.03
4,216,217.39
763,636.37
256,511.93
321,157.70
130,190.00
1,267,719.68
2,152.85
126,695.16
6,944,611.78
16,736,650.89
Percent
16.19
25.19
4.56
1.53
1.92
0.78
7.57
0.01
0.76
41.49
-------
69
TABLE 3-7. COSTS FOR WASTE COLLECTION AND TRANSPORT INCLUDING
BULKY WASTE HAULED BY FOUR SIZES OF VEHICLE
Salaries
Operating Wages
Materials
Motor Fuel
Special Charges
Interest
Repair Wages
Repair Supplies
Contracted Repair
Amortization
DM
DM
DM
DM
DM
DM
DM
DM
DM
DM
DM
1,759.173.24
17.302.664.26
845.009.56
488.747.19
2.694.862.82
597.459.89
680.020.98
416.634.60
180.231.16
2.134.280-09
27.099.083.79
6.49%
63.85%
3.12%
1.80%
9.94%
2.20%
2.51%
1-54%
0.67%
7.88%
100.00%
-------
70
TABLE 3-8. COST SUMMARY OF REFUSE HANDLING INCLUDING
COSTS OF BURNING AND LANDFILL DISPOSAL, 1975
Collection and Transport DM 27.099.083.79 80.73%
Burning DM 6.324.975.06 18.84%
Landfill DM 143.375-00 Q.43%
TOTAL DM 33.567.443.85 100.00%
-------
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72
For private haulers who deliver refuse to the plant, the following
charges apply:
DM/Tonne $/Ton
Residential Waste 26 9.90
Industrial Waste 30 11.40
Bulky Waste 35 13.40
Tires 41 15.70
Oil contaminated soil 52 19.90
Revenues
Income to the plant comes from the sale of steam, residue, and
scrap iron.
The city power system considers the value of the steam received
is 1.017 times the cost of the coal that would be needed to generate that
steam. In 1977, that amounts to <§ 15 DM/tonne ($6.30/ton) of steam ($2.86/
1,000 Ib).
Table 3-10 shows the plant income in 1975.
Figure 3-13 shows two inclined conveyors removing baled scrap
from the processing plant. Figure 3-14 is a close-up of the baled scrap
which, according to Table 3-10, sold in 1975 for an average of 107.50 DM
per tonne ($45.18 per ton at 2.38 DM/$).
Figure 3-15 pictures Mr. Thoemen, in white helmet, answering
questions of the visiting team while standing in the sized residue storage
area. As shown in Table 3-10, this fines residue was sold in 1975 for an
average price of 1.01 DM/tonne ($0.39/ton). The affiliated company-sells
a portion of the residue for 9 DM/tonne ($3.44/ton).
-------
-. -73
TABLE 3-10. INCOME TO THE WASTE BURNING FACILITY IN 1975
Steam
Scrap
Ash
TOTAL INCOME
GROSS WEIGHT
TONNES
590.814
105.092
NET WEIGHT
TONNES
560.002
9.180
48.000
COST PER
TONNE, DM
14,51
107.52
1,01
COST, DM
8.125.629.02
986.987.75
48,596.25
9,161.213.02
-------
74
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TABLE . EXCHANGE RATES FOR SIX EUROPEAN COUNTRIES,
(NATIONAL MONETARY UNIT PER U.S. DOLLAR)
1948 TO FEBRUARY, 1978(a)
1943
1949
1950
1951
1952
1953
1954
1955
1956
1957
1953
1959
1960
1961
1962
1963
1964
1965
1966
1967
1963
1969
1970
1971
1972
1973
1974
1975
1976
1977
1973 (Feb.)
Denmark
Kroner
(D.Kr.)
4.810
6.920
6.920
6.920
6.920
6.920
6.914
6.914
6.914
6.914
6.906
6.908
6.906
6.386
6.902
6.911
6.921
6.891
6.916
7.462
7.501
7.492
7.489
7.062
6.843
6.290
5.650
6.178
5.788
5.778
5.580
France
Francs
(F.Fr.)
2.
3.
3.
3.
3.
3.
3.
3.
3.
4.
4 .
4 .
4.
4 .
4 .
4.
4 .
4.
4.
4.
4.
5.
5.
5.
5.
4.
4.
4.
4.
4.
4 .
662
490
499
500
500
500
500
500
500
199
906
909
903
900
900
902
900
902
952
908
948
558
520
224
125
708
444
486
970
705
766
W. Germany
Deutsch Mark
(D.M.)
3
4
4
4
£
4
4
4
4
4
4
4
4
3
3
3
3
4
3
3
4
3
3
3
3
2
2
2
2
2
2
.333
.200
.200
.200
.200
.200
.200
.215
.199
.202
.178
.170
.171
.996
.998
.975
.977
.006
.977
.999
.000
.690
.648
.268
.202
.703
.410
.622
.363
.105
.036
Netherlands
Guilders
(Gl.)
2.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
2.
2.
2.
2.
2.
2.
653
800
800
800
800
786
794
829
830
791
775
770
770
600
600
600
592
611
614
596
606
624
597
254
226
824
507
689
457
280
176
Sweden
Kronor
(S.Kr.)
3.
5.
5.
5.
5.
5.
5.
5.
5.
5.
5.
5.
5.
5.
5.
5.
5.
5.
!t.
5.
5.
5.
5.
it.
4.
4.
4 .
4 .
4.
4.
4 .
600
180
180
180
180
180
180
180
180
173
173
181
180
185
186
200
148
180
180
165
180
170
170
858
743
588
081
386
127
670
615
Switzerland
Francs
(S.Fr.)
4.
4.
4.
4.
4.
4.
4.
4.
4.
4 .
4.
4 .
4.
4.
4.
4.
4.
4.
4 .
4.
4.
4.
4.
3.
3.
3.
2.
o t
*>
2.
1.
315
300
289
369
285
288
285
285
285
285
308
323
305
316
319
315
315
318
327
325
302
318
316
915
774
244
540
620
451
010
987
(a) Exchange Rate at end of period.
Line "ae" Market Rate/Par or Central Rate.
Source: International Financial Statistics: 1972 Supplement; April, 1978, Volume
XXXI, No. 4, Published by the International Monetary Fund.
1828p
-------
76
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77
REFERENCES
(1) Das Stadtreinigungs und Fuhramt de Laudeshaupt Duesseldorf (1969).
(2) Thoemen, K-H., Contribution to the Control of Corrosion Problems on
Incinerators with Water-Wall Steam Generators, Proceedings, 1972
National Incinerator Conference, New York, New York (June 4-7, 1972)
pp 310-318.
(3) Thoemen, K-H., Review of 4 Years of Operation with an Incinerator
Boiler of the Second Generation, Proceedings, "Present Status and
Research Needs in Energy Recovery from Wastes", Hueston Woods Cant. Sep.
1976, ASME, New York, New York (1977) pp 171-181.
(4) "Report of Dust Collector Performance Tests", Stadtwerke Duesseldorf
(March, 1967) (Confidential Document). Quoted by Konopka, A. P.,
"Systems Evaluation of Refuse as a Low-Sulfur Fuel", Part 3Air
Pollution Aspects, ASME Paper No. 71-WA/Inc-l (December, 1971).
(5) Fiendler, Klaus S., "Refuse Power Plant Technology-State Of The
Art Reviewed", unpublished paper presented to the Energy Bureau,
Inc., New York, December 16, 1976.
(6) Feindler, Klaus, S., and Thoemen, K-H., "308 Billion Ton-Hours
of Refuse Power Experience", Presented to ASME 8th National Waste
Processing Conference, Chicago, Illinois, May 7-10, 1978.
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