European Refuse Fired Energy Systems Evaluation Of Design Practices Volume 10 The Hague Refuse Fired Power Plant, The Hague, Netherlands


United States        Office of Water and      SW 176C.10
Environmental Protection     Waste Management      October 1979
Agency          Washington, D.C. 20460

Solid Waste	



European Refuse Fired



Energy Systems
Evaluation of Design  Practices


Volume  10

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Pne.pu.bLLccuti.on -ci.4ue &on EPA LLbiaiieA
and State. SoLLd Woiie Management Age.nc.iu
EUROPEAN REFUSE FIRED ENERGY SYSTEMS

EVALUATION OF DESIGN PRACTICES
The Hague Refuse Fired Power Plant
The Hague, Netherlands
tiip -le-pott (SW-776c.J0) cfeici-tb&i wcife pe.fL&c"une.d
the. 0^-Lcn o& ScLLd Wcu>te under contract no. 6&-01-4376
and -u> reproduced ai
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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.lO) in the solid waste
management series. *« ,'
r
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TRIP REPORT
to
THE HAGUE REFUSE-FIRED POWER PLANT
THE HAGUE, NETHERLANDS
on the contract
EVALUATION OF EUROPEAN REFUSE-FIRED
STEAM GENERATOR DESIGN PRACTICES
September 14, 15, 16, 1977
to
U.S. ENVIRONMENTAL PROTECTION AGENCY

EPA Contract No. 68-01-4376
EPA RFP No. WA-76-B146

January 20, 1978

Richard Engdahl and Philip Beltz
BATTELLE
Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
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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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LIST OF PERSONS CONTACTED
Johan G. Postma The Hague, Plant Manager, Gemeentelijk
Energiebedrijf Vuilverbranding, The
Hague, Netherlands

John M. Kehoe, Jr. Wheelabrator-Frye, Inc., Vice President
Energy Systems Division,
Hampton, New Hampshire, U.S.A.

Beat C. Ochse Von Roll, Ltd., Project Engineer,
Environmental Eng.,
Zurich, Switzerland Div.

Richard Scherrer Von Roll, Ltd., Project Engineer,
Environmental Eng.,
Zurich, Switzerland Div.
The authors are greatly indebted to the above experts for

their very helpful assistance in gathering the information for this

trip report.
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TABLE OF CONTENTS

Page

SUMMARY 1

STATISTICAL SUMMARY 2

OVERALL SYSTEM SCHEMATIC 5

COMMUNITY DESCRIPTION 7

Geography 7

Industry and Government 7

SOLID WASTE PRACTICES 9

Solid Waste Generation 9

Solid Waste Collection 9

Solid Waste Transfer or Pretreatment 9

Solid Waste Disposal 9

DEVELOPMENT OF THE SYSTEM 13

PLANT ARCHITECTURE 14

REFUSE-FIRED STEAM GENERATOR 16

Waste Input 16

Weighing Operation , 18

Provisions to Handle Bulky Wastes 18

Furnace Hoppers and Feeders 20

Burning Grate 22

Furnace Wall 30

Superheater (Units 1-3) 35

Superheater (Unit 4) 35

Boiler (Units 1-3) 38

Boiler (Unit 4) 38
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TABLE OF CONTENTS
(Continued)

Page

Economizer 39

Air Preheater (Units 1-3) 39

Air Preheater (Unit 4) 39

Primary Air 40

Secondary Air 41

Heat Release Rate 43

Boiler Water Treatment 45

Start-up Procedure 45

ENERGY UTILIZATION EQUIPMENT . 46

POLLUTION CONTROL EQUIPMENT 47

Chimney 47

Wastewater Discharge 48

Noise 48

Residue Processing . 48

POLLUTION CONTROL ASSESSMENT . . 50

EQUIPMENT PERFORMANCE ASSESSMENT 50

PERSONNEL AND MANAGEMENT 54

ENERGY MARKETING 55

ECONOMICS 56

FINANCE 57

REFERENCES 58
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LIST OF TABLES
Page
Table 9-1. Refuse Received and Residue Produced at the Hague Plant,
1976, Tonnes 12

Table 9-2. Dimensions of Grates and Rated Burning Rates Used at the
Hague Plant 31

Table 9-3. Estimated Combustion Rates at The Hague 44

Table 9-4. Refuse Burning Summary, The Hague, 1976 (Compared to
1975) 51

Table 9-5. The Hague Plant Annual Operating Results Over Seven Year
Period. (Furnace 4 Began Operation Early 1974) .... 53

LIST OF FIGURES

Figure 9-1. Artists View of The Hague Plant (Courtesy Gemeentelijk
Energie Bedrijf Vuilverbranding) 6

Figure 9-2. Map of Central City of The Hague Showing the Waste
Burning Plant and International Peace Palace Near Cen-
ter. The Strand (North Sea Beach) is Less Than 2 km
(1.2 mi) Northwest of the Plant at the Resort of
Schevenigen 8

Figure 9-3. Annual Refuse Generation in The Hague Since 1936 ... 10

Figure 9-4. The Hague Plant Situated Near the Center of The Hague.
The Four Chimneys in the Background Serve the 200 mw
Oil-Fired Municipal Power Plant (Courtesy GE Vuilver-
branding) 15

Figure 9-5. Seasonal Variation of Lower Heat Value and Moisture
Content of Refuse at The Hague, 1964-65 17

Figure 9-6. Private Hauler Delivering Very Dry Bulky Waste to the
Hague Plant 19

Figure 9-7. Cross-Section of Boiler Systems, 1-3 The Hague (Courte-
sy of Gemeentelijke Reinigindienst) 21

Figure 9-8. Polyp Bucket Dropping a Charge of Municipal REfuse into
a Furnace Hopper at The Hague Plant 23

Figure 9-9. Mirror Above a Furnace Hopper to Enable Crane Operator
to Determine When the Hopper Needs to be Replenished -
The Hague Plant 24
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LIST OF FIGURES
(Continued)
Figure 9-10.

Figure 9-11.

Figure 9-12.

Figure 9-13.
Figure 9-14,

Figure 9-15.
Figure 9-16,
Figure 9-17,
Crane Operator's Cabin at The Hague Plant With Empty
Furnace Hopper and a Portion of the Floor Plate of
the Vibrating Feeder in the Foreground
Two Steps of Von Roll Grate Using Reciprocating For-
ward-Feed Design
Kiinstler Grate (at Basel) (Courtesy K&K AG)
25

28
Comparative Cross-Sections of the Two Boiler-Furnace
Systems at the Hague Plant. Units 1-3 were Designed
in 1965. Unit 4 was Designed in 1971. (Courtesy of
Gemeentelijk Energiebedrijf Vuilverbranding) [Waste-
burning Energy Utility]
29
Sketch of Air Flows Through Kunstler Air Blocks
(Courtesy of Widmer & Ernst)
Water-Tube Wall Portion of Boilers in Units 1-3, The
Hague, Showing Suspended Platten-Type Superheater at
Top of Radiation Pass, Screen Tubes at Outlet From
Radiation Pass, Sinuous Tube Convection-Type Super-
heater at Top of Second Water-Tube Walled Pass, Boiler
Convection Sections, Economizer, and Tubular Air
Heaters 36
Exterior View of Tubes for Secondary Air Jets on Side
of Unit 4. Ten Jets are Spaced Horizontally and Two
are Located Along a Slanting Vertical Line at Left.
Note Spring-Loaded Cap on Each Tube to Facilitate In-
spection and Cleaning
Conveyors and Magnetically Separated Scrap and Pile
of Sized Residue Accumulated by Nev Resource Recovery
System Adjacent to The Hague Plant
42
49
Figure 9-14a. Perforated Air-Cooled Refractory Wall Blocks by Dider
as Installed by Von Roll at the Solingen Plant, West
Germany 34a
Figure 9-14b. Construction Photograph Showing Air Supply Chambers
For the Refractory Wall Blocks Shown in Figure 9-14a
34a
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SUMMARY

The Hague plant, ten years old, is unique among large plants
(1440 t/d) in that the four furnaces are not water cooled. This feature
was a natural result of the original design assumption that the plant,
handling no industrial refuse, would receive relatively wet refuse with
a low heat value (1800 kcal/kg) [3240 Btu/lb] [7535 kJ/kg]. However,
over the nearly ten years of operation, the refuse heat value has in-
creased causing wall-slagging problems.
From the beginning, boiler wall-tube and superheater corrosion
has been a problem requiring significant maintenance in the first three
units, which started up in 1968. However, in Unit 4, started in 1971,
a drastic modification of superheater design and location has prevented
significant corrosion there to date. Also, in the first three units,
partial refractory covering of the radiation pass wall tubes and reduced
firing rates have nearly eliminated tube wastage.
The plant is operated as a 23 Mw electrical production component
of a municipal energy facility dominated by a 200 Mw oil-fired plant which
also serves a district heating network. At present, the waste plant
turbines operate condensing but some thought is being given to modify the
turbines so as to make the exhaust heat available for district heating.
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STATISTICAL SUMMARY
Community description:
Area (square kilometers)
Population (number of people)
Key terrain feature
70
550,000
Flat, coastal
Solid waste practices:
Total waste generated per day (tonnes/day)
Waste generation rate (Kg/person/day)
Lower heating value of waste (Kcal/kg)
Collection period (days/week)
Cost of collection (local currency/tonne)
Use of transfer and/or pretreatment (yes or no)
Distance from generation centroid to:
Local landfill (kilometers)
Refuse fired steam generator (kilometers)
Waste type input to system
Cofiring of sewage sludge
575
1.14
1800 - 2300
5

4
0
Residential
No
Development of the system:
Date operation began (year)
1968
Plant architecture:
Material of exterior construction
Stack height (meters)
steel
100
Refuse fired steam generator equipment
Mass burning (yes or no)
Waste conditions into feed chute:
Moisture (percent)
Lower heating value (Kcal/kg)
Yes

35%
1800 - 2300
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Volume burned:
Capacity per furnace (tonnes/day)
Number of furnaces constructed (number)
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

Pit capacity level full:
(tonnes)
(m3)
Crane capacity: (two)
(tonnes )

Feeder drive method
1,440
4
1,440
360
3
1,080
No
10,000

10 each
4 each
mechanical, vibrating
Burning grate:
Manufacturer
Type
Number of sections (number)
Length overall (m)
Width overall (m)
3
Primary air-max (Mm /hr
3
Secondary air-overfire air-max (m /min)
3
Furnace volume (m )
Furnace wall tube diameter (mm)
2
Furnace heating surface (m )
Auxiliary fuel capability
Use of superheater
Boiler
Manufacturer
Type
Number of boiler passes (number)
Von Roll
3-step, sloping, recipro.
3
13, 14.5
3
71,000
350

63.5

No
Yes

Bronswerk
Eckrohr - (corner-tube)
3
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Steam production per boiler (kg/hr)
Total plant steam production (kg/hr)
Steam temperature (° C)
Steam pressure (bar)
Use of economizer
Use of air preheater
Use of flue gas reheater
Cofire (fuel or waste) input (verbal)
Use of electricity generator
Type of turbine (verbal)
Number of turbines (number)
Steam consumption (kg/hr)
Electrical production capacity per turbine (kw)
Total electrical production capacity (kw)
Turbine back pressure
User of electricity ("Internal" and/or "External")
3 x 37,000 1 x 41,500
125,500
425
40
Yes
Yes
No
No
Yes
11.5 mw each
23,000

Both
Pollution control:
Air:
Furnace exit conditions
3
Gas flow rate (m /hr)
3
Furnace exit loading (mg/Nm )
89,000
(1-3)557(4)19
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OVERALL SYSTEM SCHEMATIC

Figure 9-1 is an artist's sketch of the overall system. Bulky
refuse is delivered at the upper left and is processed for the furnaces.
Community refuse arrives at the right. Ash and residue is removed for
processing at the lower left and electricity leaves at the lower right
for the G.E. (Gemeentelijk Energiebedrijf) [The Community Energy System
which supplies fuel gas, electricity, and district heating for the
Hague and its suburbs].
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COMMUNITY DESCRIPTION

Geography

The Hague is situated on the North Sea on very flat coastal
land.
The plant, located in the southwest part of The Hague, is
completely surrounded by old residential communities. The plant is
adjacent to a large oil-burning municipal power plant and is less than
one km (0.6 mi) from the International Peace Palace. Figure 9-2 shows
the concentrated urban location of the plant.
A population of 550,000 is served: 500,000 of these in The
Hague and 50,000 in four small neighboring communities. The population
served in 1968 was 450,000 when the plant was built. At present the
population of The Hague is not growing, but is decreasing slightly, and
the annual tonnage of refuse received has about stabilized around 210,000
tonnes per year (231,000 t/y). The collection area for this plant ex-
tends over a radius of about 15 km (9.3 mi) from the plant.

Industry and Government
There is no heavy industry. The city is a government center
and, because of its location on the sea, is also visited by many
tourists during the summer.
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Peace
Palace
Waste burning
plant
FIGURE 9-2. MAP OF CENTRAL CITY OF THE HAGUE SHOWING THE WASTE BURNING
PLANT AND INTERNATIONAL PEACE PALACE NEAR CENTER. THE
STRAND (NORTH SEA BEACH) IS LESS THAN 2 KM (1.2 MI) NORTH-
WEST OF THE PLANT AT THE RESORT OF SCHEVENIGEN.
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SOLID WASTE PRACTICES

Solid Waste Generation

The plant receives little industrial waste. Chemical wastes are
sent to the Botlek plant at Rotterdam, which has a rotary kiln specific-
ally for chemical wastes. Along with typical community refuse, The
Hague plant receives much government waste paper and some boxes from
department stores. Figure 9-3 shows the curve of annual refuse gener-
ation.

Solid Waste Collection

There are 55 municipal packer trucks which collect twice per
week on weekdays except Wednesday when the crews are assigned to bulky
refuse pickup. They do this in two alternate sections of town on alter-
nate Wednesdays, using open trucks.
Private haulers also deliver refuse to a separate bunker and
pay cash for the privilege on a weight basis. If a load is mostly
metallic, such as appliances, it is placed in a collection yard at the
plant for later processing by a new residue processing plant, privately
operated.

Solid Waste Transfer or Pretreatment

There is no transfer or pretreatment of waste before it reaches
the plant. There have been some experiments with separate collection
of glass but the results were that most of those participating preferred
not to separate.

Solid Waste Disposal

Non-combustibles and incinerated residue goes to a sanitary
landfill at Rijswijk, about four km (2.5 mi) south of The Hague plant.
No household refuse goes directly to the Rijswijk landfill.
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10
Thousands
Tonnes/year

250

230

210

190

170

150

130

110

70
Actual Total 1976
229,000 tonnes
f_ HONGERWINTER (Winter of starvation)

36 '38 40 42 44 46 48 50 52 54 56 58 60 '62 64 66 68 70 ' 72 74 76 78 80
t
-started Units 1-3
-ordered Units 1-3
FIGURE 9-3. ANNUAL REFUSE GENERATION IN THE HAGUE SINCE 1936
(1)
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11
For six years the incinerated residue was used to build dikes
for land reclamation but this was stopped because of concern over in-
creased cadmium and silver content of local drinking water.
Very recently, August 1977, a private contractor began a resource
recovery processing system for the plant residue at the plant property.
Table 9-1 shows the monthly refuse receipts at The Hague plant
in 1976.
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13
DEVELOPMENT OF THE SYSTEM

In 1919, the city built an incinerator but it was met by a
storm of protest by those favoring utilization of wastes for recoverv of land,
As a result, on June 18, 1929, an agreement was reached whereby the
incinerator continued to operate at a low rate but a distant landfill
site was selected.
Later, for over 30 years, before the present plant was contrac-
ted for in November 1964, refuse from The Hague was sent by rail to a
landfill and compost plant at Wijster in the region of Drente, 200 km
(120 mi) away in the northeast part of Holland. Other cities, such as
Amsterdam also sent refuse to Wijster, which had the largest compost
plant in Holland. Much of the compost was sold in five and ten kg
(11 to 22 Ib) sacks. The dedicatory brochure for The Hague plant,
published in March 1968, stated that from the opening of the Wijster
site on February 23, 1932, until the end of 1967, 154,984 rail car loads
of refuse from The Hague were shipped to Wijster.
However, the cost of the long rail haul increased over the
years and the demand for compost for land reclamation decreased.
Accordingly, a study was begun on alternate methods for refuse disposal.
In 1958, the conclusion was reached that a modern waste-burning facil-
ity should be planned. The planning extended from 1960 through 1964 in
cooperation with the "Gemeentelijk Energiebedrif" (municipal utilities).
One of the principal considerations was the need to meet high hygienic
standards and to avoid nuisance factors inherent in other solutions.
At the time when the decision was made, fuel prices were high, and the
possibility to recover heat energy from refuse promised attractive
revenues. This led to the combination of combustion and power genera-
tion. The final plant design included a total of four furnace-boiler
units with an incineration capacity of 360 tonnes/day (400 tons/day) each.
In November 1964, the order was issued for three of them. The first
three began operation in January 1968.
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14
PLANT ARCHITECTURE

The plant, shown in Figure 9-4, presents a clean and impressive
facade to the residential area which is very close. It stands on the
site of a former gasworks - hence, the street address: Gaslaan. An older
and larger 200 mw municipal power plant stands adjacent to this plant.
The two plants are separated by the Afvoer Canal and a busy street railway
line.
The structure is steel, enclosed in coated aluminum panels.
The tallest portion is 29 m (95 ft) tall. The main structure is 47.72 m
(156 ft) and 46.45 m (152 ft) deep.
Generously sized roadways on the plant property provide room
for trucks to line up without affecting traffic on the surrounding streets,
This is an old gasworks site and there is no landscaping. Several of the
old gasworks service building are now shops for the refuse plant.
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15
H^^T^^i^*
FIGURE 9-4. THE HAGUE PLANT SITUATED NEAR THE CENTER OF THE HAGUE.
THE FOUR CHIMNEYS IN THE BACKGROUND SERVE THE 200 MW
OIL-FIRED MUNICIPAL POWER PLANT (Courtesy GE Vuilver-
branding)
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16

REFUSE-FIRED STEAM GENERATOR

Waste Input

Since The Hague is not a highly industrialized community, this
plant receives very little industrial refuse. The supply of refuse is
principally residential plus some commercial waste, such as boxes and
much governmental paper.
Figure 9-5 shows the seasonal variations in lower heat value
and moisture content of the local refuse as measured in 1964-65, when
the annual average lower heat value was only about 1800 kcal/kg (3240 Btu/
Ib) [7535 kJ/kg]. However, as with all European refuse, the heat value
has been increasing, so that in 1972-73 at The Hague, it reached 2300 kcal/
kg (4140 Btu/lb) [9630 kJ/kg]. However, during the oil embargo in 1973-74,
apparently many of the citizens found ways to recover heat by burning some
of their dry combustible wastes and the heat value of the waste delivered
to the plant dropped to about 1800 kcal/kg. An analysis of a refuse
sample during that period produced the following:
Carbon 7%
Volatile 34%
Ash 24%
Moisture 35%
Heat Value 1800 kcal/kg (3240 Btu/lb)
However, in 1976-77 the heat value had again reached 2300 kcal/kg. The
furnaces in Units 1-3 were designed for a maximum heat value of 2066 kcal/kg
(3270 Btu/lb) [8,653 kJ/kg]. However, some dry, bulky waste such as
wooden crates and cardboard boxes can have much higher heat value, up to
4000 kcal/kg (7200 Btu/lb [16,750 kJ/kg], and wetting of such refuse to
protect the furnaces and boilers will be discussed later. Unit 4 was
designed for a heat value of 2500 kcal/kg (4500 Btu/lb [10,467 kJ/kg].
There are 55 city trucks which deliver refuse eight hours per
day, 8:00 a.m. to 4:00 p.m., five days per week. Also, the plant accepts
deliveries by private trucks. An estimated 20-30 percent of the total of
approximately 210,000 tonnes/yr (231,000 tons/yr) is delivered by private
haulers who pay cash on a weight basis.
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17
00
n)
o
2500
0)
3
2000
1500
OJ
0)
ffi
o 1000
50

s-s 40

8 30
.u
•H 20
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2 10

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Seasonal variation

Lower heat value of
community waste
JAN,
'64
JUL.
'64
JAN.
'65
JUL.
'65
Seasonal variation

Moisture content of
community refuse
JAN.
'64
JUL.
'64
JAN.
'65
JUL.
'65
FIGURE 9-5. SEASONAL VARIATION OF LOWER HEAT VALUE AND
MOISTURE CONTENT OF REFUSE AT THE HAGUE,
196A-65(1)
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18
Normally the plant operates 5-1/2 days per week and normally
only three of the four furnaces are operating. Startup time is usually
3:00 p.m. on Sunday and operation continues until about 8:00 a.m. Saturday.

Weighing Operation

The weigh station is not operated by the plant. Instead, it
is operated by the municipal waste collection department. In 1976, the
station was relocated and modernized. It is situated between two scales,
one for city trucks, one for private. The scale operator regulates
traffic flow by means of a manually controlled red-green signal light on
the approach to the scale house. Private trucks weigh in and then out.
City trucks weigh in by insertion of a coded magnetic card into a slot
at the scale which identifies the truck and causes immediate machine
recording of the loaded weight, known tare weight, and by difference the
net weight delivered.

Provisions to Handle Bulky Wastes

This plant is unusual in that it has two bunkers: a large one
of about 10,000 m3 (13,080 yd ) capacity (level full) for community
refuse which, with the hinged lift type doors, can be piled up to about
•3 o
16,000 m (20,930 yd ) f plus a smaller one for private haulers which
often receives mainly bulky refuse. The two bunkers were shown earlier
in the upper left and right center of Figure 9-1. The tendency for the
privately delivered refuse in the smaller bunker to be very dry and highly
combustible is so great that water sprays located high on the bunker wall
are turned on much of the time to keep that waste dampened.
Figure 9-6 shows a private hauler delivering very dry, bulky
waste.
Where the scale operator observes non-combustible bulky waste,
such as steel appliances being delivered, he directs the driver to unload
the objects in a walled-in yard near the new waste processing facility
for later processing and reclamation and disposal.
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The original plant design included a 15 tonne/hr Von Roll shear
shown earlier in the upper left of Figure 9-1. This shear received bulky
waste from the small bunker which receives primarily bulky waste from
private haulers. However, owing to the light construction of this early
shear design, much maintenance was required. Also, some explosions were
experienced within the shear. Accordingly, in 1970 the use of the shear
was discontinued and the crane operators are instructed to try to smash
bulky objects in the bunker by dropping the crane bucket on them. Also,
as shown near the upper center of Figure 9-1, there is a holding pit which
is positioned to receive either sheared material or bulk refuse that can
be by-passed over the shear. From that pit, the operators of the main
bunker cranes can lift refuse directly to the furnace hoppers or it can
be deposited in the main bunker for mixing with conventional refuse. This
complex arrangement requires good judgment and skill on the part of the
crane operators to assure a well-mixed and reasonably sized supply of
refuse to the four furnaces.
If four of the main bunker doors are closed, the estimated stor-
age capacity is about 4500 tonnes (4950 tons) which is nearly one week's
supply for three furnaces.
There are two crane control rooms high on the outside of the
main bunker wall controlling two cranes. Usually only one crane operates
at a time. The smaller bunker is served by one crane controlled by an
operator riding the crane in a cab. Each of the main cranes, made by
Heemat of Holland, is of nine tonne capacity carrying a polyp-type bucket
3
of 4 m each. Fire control in the main bunker is by both fire hose and
fixed water spray. To obtain a measure of firing rate, the operators re-
cord the number of buckets charged to each furnace per hour.

Furnace Hoppers and Feeders

Figure 9-7 shows a cross-section of boiler/furnaces 1-3 which
were built in 1967. Each of the four furnace hoppers has a top opening
of five by 3.7 m (16.4 by 12.1 ft). Immediately beneath the hopper is a
large vibrating feeder which feeds into a water-cooled chute about 3.4 by
-------
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1 m (11 by 3.3 ft). The feeder, made by Schenck of Darmstadt, West Germany,
is vibrated by rotating eccentric weights automatically controlled by a
radioactive chute-level indicator made by Endress and Hauser. The radio-
active source is Cesium 37 with an intensity of 75 milliroentgens.
Burnback in the chute never occurs on start-up or shut-down,
only if the chute jams, preventing full flow or refuse. A flap damper
can be used to seal off the top of the chute in case of burnback. Jamming
in a hopper can be released by the force of a railroad tie dropped in by
the bucket. The vibrating feeders have been trouble-free for nearly ten
years. It is expected that the steel floor-plate of the feeders will need
replacement after about 12 years of service.
Figure 9-8 shows a polyp bucket in the act of dropping a charge
into a furnace hopper opening.
Figure 9-9 shows a mirror positioned above the furnace hopper to
provide the crane operator with a view of the_inside of the hopper so that
he can know when the hopper has been emptied by the vibrating feeder.
Figure 9-10 shows, in the background, one of- the two crane
control cabins on the bunker wall. In the foreground an empty hopper
with a portion of the floor plate of the vibrating feeder showing at the
bottom of the hopper can be seen.

Burning Grate

Figure 9-11 shows the improved grate which Von Roll has been
developing in recent years. The older grate, as installed on all four
units at this plant, involves the alternating forward motion of adjacent
grate "plates." This naturally caused wear by the abrasive action of ash
and clinker particles sifting between the plates as they slide relative
to each other. As a result, the air gaps between the grate plates, origin-
ally 3 mm (0.12 in) increased in nearly ten years to, in some cases, 40 mm
(1.6 in). This has impaired control of the distribution of primary air
and, at times, the air-flow resistance through portions of the grate and
fuel bed is so low that the air pressure below the grate becomes less than
atmospheric. However, there has been little grate repair work done in nearly
ten years of operation except for annual renewal of the sliding plates
attached to the bottom of the grate bars.
-------
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FIGURE 9-10.
CRANE OPERATOR'S CABIN AT THE HAGUE PLANT WITH EMPTY FURNACE
HOPPER AND A PORTION OF THE FLOOR PLATE OF THE VIBRATING
FEEDER IN THE FOREGROUND (Battelle Photograph)
-------
26
FIGURE 9-11.
TWO STEPS OF VON ROLL GRATE USING RECIPROCATING
FORWARD-FEED DESIGN. (Courtesy of Von Roll)
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27
For smaller furnaces, that is five tonnes per hour or less, Von
Roll began 15 years ago to install the improved grate composed of alternate
fixed and moving rows in which each entire moving row of grate plates
moves forward and backward together, thus eliminating the relative motion
and grinding action between adjacent grate blocks. There is still a
wearing action then due to the relative motion of each moving row on the
stationary row beneath it, but the air gap there is kept minimal by the
gravitational force holding each upper row tightly against the next row
below.
Von Roll is now applying this grate as shown in Figure 9-11 to
all new furnaces regardless of size. At this plant the grate drive is
hydraulic. Some drive failures have occured.
At The Hague No. 2 furnace, after about 55,000 hours operation,
is now being converted to use a Kiinstler grate manufactured by K & K
Ofenbau AG, Zurich. This type of grate, shown in Figure 9-12, which has been
used in a number of plants, similar to improved Von Roll grate, con-
sists of horizontal rows of grate blocks which are moved forward in unison,
thus eliminating relative motion between adjacent blocks. At the same time,
the Kiinstler air wall system has been installed in the walls near the
grate. This will be discussed later under Furnace Wall.
Figure 9-13 shows comparative cross-sections of the two boiler
furnace systems at The Hague: Units 1-3 started up in 1968; Unit 4 started
up in early 1974.
Primary air is supplied through seven controlled zones under the
Von Roll grate for Units 1-3. There are six zones on Unit 4. Initially,
this air was preheated as described later. There is a manually set damper
controlling flow to each zone. Also, an automatically controlled main
damper controls the total supply of air from the blower. Three thermocouples
attached to each grate enable indication of grate temperatures in the control
room.
As can be seen in Figure 9-13 and also earlier in Figure 9-7,
in Units 1-3 there was a large drying grate because it was anticipated
that often the refuse would be very wet. Also, directly above the drying
grate there was a gas burning chamber so that hot flue gas could be forced
directly downward against wet refuse on the drying grate. However, the
refuse has not been as wet as expected. Accordingly, in Unit 4 the gas (or oil)
burning chamber was eliminated and the size of the drying grate was
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28
FIGURE 9-12.
KUNSTLER GRATE
(Courtesy of K & K AG)
-------
29
THE HAGUE UNITS 1, 2, 3
LONGITUDINAL SECTION
1 Refuse pit
2 Vibrating hopper
3 Feed chute
4 Feed grate
5 Main grate
6 Burnout grate
7 Clinker channel
THE HAGUE UNIT 4
1 Refuse pit
2 Vibrating hopper
3 Feed chute
4 Feed grate
5 Main grate
8 Clinker pit
9 Settling tank
10 Combustion chamber
11 Boiler
12 Electrostatic precipitator
13 Stack
14 Feed water tank
15 Additional water tank
16 Condensate tank
17 Forced draft fan
18 Induced draft fan
19 Flue gas recycling
fan
6 Burnout grate
7 Clinker pit
8 Settling tank
9 Clinker channel
10 Boiler
11 Electrostatic precipitator
12 Induced draft fan
13 Stack
14 Forced draft fan
15 Overfire air fan
FIGURE 9-13.
COMPARATIVE CROSS-SECTIONS OF THE TWO BOILER-FURNACE
SYSTEMS AT THE HAGUE PLANT. UNITS 1-3 WERE DESIGNED
IN 1965. UNIT 4 WAS DESIGNED IN 1971. (Courtesy of
Gemeentelijk Energiebedrijf Vuilverbranding)[Waste-
burning Energy Utility]
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30
reduced. The drying or feed grate, Item 4 in Figure 9-13, is seen to be
shorter in Unit 4 and the burnout grate, Item 6, is longer. Table 9-1
shows the grate dimensions for all four furnaces. In this table the in-
tensity of utilization or burning rate is seen to be significantly less
in Unit 4 than in Units 1-3.
In addition to the grate change, many other improvements can
be seen to have evolved during the six years, 1965-L971, that elapsed
between the beginning of these two designs.
The residue handling system was unchanged when Unit 4 was built.
Each stoker discharges to a concrete quench tank from which the residue
is continuously removed by a submerged drag conveyor shown in both parts
of Figure 9-13. The conveyor delivers the residue, partially drained,
to the residue bunker from which it is lifted by crane into trucks or onto
a conveyor leading to the ash recovery process. The same crane serves the
adjacent flyash settling tank.

Furnace Wall

In terms of predominant current practice for large furnaces,
The Hague plant is noteworthy in that the furnace sLdewalls are not water-
cooled. What water-tube walled surface is used begins above the furnace and
extends from there upward to the top of the radiation chamber (first boiler
pass). The sloping rear roof of the furnace is water-cooled but the tubes
are completely covered by formed refractory block supported between the
tubes. Thus, there is very little cooling of the predominantly refractory
furnace. The furnace sidewall construction consists of one layer of high-
alumina firebrick plus insulation and a steel casing. The full wall thick-
ness is about 50 cm (20 in). This wall is modified alongside the drying
grate where the alumina brick is replaced by silicon carbide brick to re-
sist abrasion by the moving refuse. This refractor/ wall has required
little maintenance in nearly ten years' operation. The refractory stops
at about the level of the top of the feed opening. A horizontal header
for the higher wall tubes is located at that level and the wall tubes
extend upward from that level.
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At first, in Units 1-3, the wall tubes in the radiation pass
were bare. The tubes in Units 1-3 are 63.5 mm (2.5 in) in diameter, 4 mm
(0.160 in) thick, on 85 mm (3.4 in) centers and joined by a welded fin.
However, within the first year, significant wastage of the wall tubes was
observed as well as in the radiant superheater suspended through the top
of the radiation pass. Accordingly, that superheater was shortened by 70 cm
(2.3 ft) and the wall tubes were studded with 10 mm (0.4 in) long studs and
then coated with 12 mm thick (0.5 in) silicon carbide. This coating was
carried up to just above the bottom of the shortened superheater.
Another unique feature of The Hague plant is that it began
operation without any overfire air jets. Because of the early corrosion
problems referred to earlier, sidewall jets were added. However, the
plant experience is that front and rear-wall jets would be better.
At first there was little slag accumulation on the refractory
sidewalls. However, in 1971 and 1972, after about three of four years'
operation, thick accumulation of slag developed on the sidewalls, es-
pecially where the burning was intensified when the burning refuse dropped
from the drying grate onto the burning grate. Attempts were made to re-
move this slag mass by means of water lances but this was deleterious to
the refractory wall. The thermal shock to the hot refractory wall caused
it to tilt inward. Then, continuous air injection was tried along the wall
but the build-up of slag continued. It is believed that this growing
problem of slag build-up was caused by a substantial rise in the heat
value of Dutch community refuse in that period. The relatively high grate
burning intensities calculated in Table 9-2 were contributory to the problem.
The solution to the problem of sidewall slag accumulation at
that time was to reduce the load on each furnace. Instead of carrying
the average daily plant load of about 700 to 750 tonnes per day in two
units, each nominally rated at 360 tonnes/day (400 tons/day); the third
or spare unit was brought into regular operation so that each unit had
to handle only about 230 to 250 tonnes per day (260 to 275 tons/day).
However, it is well established that, in this technology, normal wear
and tear usually requires a plant to have one spare unit so that each unit
in turn can benefit from a well-established preventive maintenance program.
It appears that such considerations led, in 1971, to the order for Unit 4
which began operation early in 1974. The wisdom of this expansion is
-------
33
attested by the fact, mentioned earlier, that the refractory furnace walls
of Units 1-3 have required essentially no maintenance except slag removal
in nearly ten years' use. Operation of Units 1-3 at reduced rate has
eliminated the slag accumulations.
The annual waste input to the plant reached a peak of 229,000
tonnes in 1976. If Unit 4 had not been available that year, Units 1-3
would have been overloaded which certainly would have caused much diffi-
culty in added maintenance costs and reduced availability. Assuming 5-1/2
days per week operation, the 229,000 tonnes burned in 1976 in 52 weeks
in three units, (one spare), nominally rated at 360 tonnes/day each
results in an estimated operating rate of 800 tonnes/day or 105 percent
of rated capacity. Although no mention was made by plant staff of any
recent return of problems from sidewall slag build-up, its imminence may
have encouraged a decision to plan to install air-cooled Kunstler wall
blocks in Unit 2 in 1978.
It is notable that the SIC covering on the studded wall tubes
requires little maintenance. During each year approximately four square
meters of coating is replaced in each boiler.
Figure 9-14 shows, schematically, the arrangement of the air
flow through the patented, cast steel, Kunstler blocks which will soon be
added on Unit 2. Kunstler of Zurich has added this modified air-cooled
wall construction to over a dozen European plants since 1972. It is also
now being incorporated into some new plants as original construction.
The system does appear to provide relatively cool sidewalls so that sticky
slag particles that may touch it are chilled and solidified before they
have time to fuse to the wall. The installation in Unit 2 at The Hague
will provide an interesting test of block durability in a large, heavily-
loaded furnace.
Figure 9-14a and 9-14b show a similar wall cooling system using
perforated refractory blocks by Didier-Werke AG, Weisbaden, Germany, which
Von Roll is now applying at other plants. The installation shown in these
figures is at Solingen, West Germany.
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FIGURE 9-14a.
PERFORATED AIR-COOLED REFRACTORY WALL BLOCKS
BY DIDIER AS INSTALLED BY VON ROLL AT THE
SOLINGEN PLANT, WEST GERMANY (COURTESY
VON ROLL)
FIGURE 9-14b.
CONSTRUCTION PHOTOGRAPH
SHOWING AIR SUPPLY CHAM
FOR THE REFRACTORY WALL
BLOCKS SHOWN IN FIGURE
9-l4a.
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35
Superheater (Units 1-3)

Figure 9-15 shows the original superheater and boiler arrangement
for Units 1-3, as designed in 1965. The superheater was in two sections.
The first section was a platen-type radiant superheater which was inserted
about 3.6 m (11.8 ft) downward from the water-cooled roof into the radiation
chamber (first pass). Subsequent experience at many plants has revealed
that this was a particularly vulnerable location for a superheater. The
designer estimated that the flue gas temperature, as it rose in the
radiation chamber toward the superheater, would be about 955 C (1751 F).
With a steam temperature leaving the superheater of 425 C (797 F) the
temperature of potentially corrosive chloride salts on the superhe'ater
surface could thus rise well over 500 C (932 F) both from contact by surges
of high temperature flame and from intense radiation from the incandescent
gases in the furnace below. Thus, in hindsight, it is not surprising that
the pendant superheaters in Units 1-3 had tube wastage within the first
year of operation. The solution to this attack was to shorten the platten
by about 70 cm (2.3 ft) and to increase the tube thickness from 2.9 to
5 mm (0.12 to 0.2 in). After about five years and about 25,000 to 30,000
hours operation, the pendant superheater was replaced at a cost of
DG 60,000 ($24,600 @ 2.44/$).
The second superheater section, a sinuous convection type, is
shown in Figure 9-15 at the top of the second pass. A spray-type de-
superheater (attemperator) is between the sections. The designer estimated that
the gases entering the second superheater section would be about 900 C
(1652 F) and leaving it would be 807 C (1485 F). In this section, corrosion
was observed two or three years after startup. However, the steam temper-
ature there is lower and the corrosion rate is apparently not rapid. This
superheater section will also soon be replaced.

Superheater (Unit 4)

During the three years between 1968, when Units 1-3 were started
up, and 1971, when Unit 4 was ordered, much had been learned both at this
plant and elsewhere about some of the causes of superheater corrosion. One
-------
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FIGURE 9-15.
WATER-TUBE WALL PORTION OF BOILERS IN UNITS 1-3, THE HAGUE, SHOWING
SUSPENDED PLATTEN-TYPE SUPERHEATER AT TOP OF RADIATION PASS, SCREEN
TUBES AT OUTLET FROM RADIATION PASS, SINUOUS TUBE CONVECTION-TYPE
SUPERHEATER AT TOP OF SECOND WATER-TUBE WALLED PASS, BOILER CON-
VECTION SECTIONS, ECONOMIZER, AND TUBULAR AIR HEATERS.
(Courtesy of Von Roll)
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37
emerging lesson was that the superheater should be as far removed as possi-
ble from the furnace flames. In this way any potentially corrosive chloride
deposits on the tubes would not be overheated by sudden surges of flames
extending far above the furnace. Also, the deposits would not be heated
by intense radiation from the furnace.
Accordingly, as seen in Figure 9-13, the horizontal superheater
sections in Unit 4 are far removed from the furnace. Also, the entirely
open second pass, completely water-tube walled, provides cooling of the
gases before they reach the first superheater section at the bottom,
beginning, of the third pass. Thus, instead of an estimated gas temperature
of 955 C (1751 F) approaching the pendant superheater in Units 1-3, in
Unit 4 the partially cooled gas entering the horizontal superheater bundle
is estimated to range from 530 to 630 C (986 F to 3166 F).
Another improvement helping to alleviate corrosive conditions
was to add secondary air jets in the sidewalls in Units 1-3 and to include
them in the initial design for Unit 4. These jets are located high in the
refractory sidewalls of the furnace, just below the. coated water-tube wall
of the first (radiant) pass.
The steam flow through the first (bottom) superheater section is
counter flow so that the hottest steam (425 C) [797 F] "meets" the hottest
gas. In the second superheater section of Unit 4 the steam and gas flows
are cocurrent.
The boiler redesign and air jets just described have eliminated
superheater corrosion in Unit 4 except for some wastage in the vicinity
of the soot blowers. This is being satistactorily controlled by means of
carbon steel shields covering the affected tubes. It is estimated that
the shields will need replacement every four years.
In Unit 4 the superheater tubes are made of 15 Mo 3 steel, 38 mm
(1.5 in) diameter and 3.6 mm (0.14 in) thick. The spacing between the in-
line rows is 150 mm (5.9 in). In Units 1-3 this spacing was only 80 mm
(3.1 in). With this wider spacing, it is estimated that the unit could run
8000 hours (about two years) before chemical cleaning of the tube deposits
would be necessary. However, tube thickness is checked once per year, hence
cleaning is needed each year before the thickness measurements are made.
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38
At first in Unit 4 the soot blowers were operated once per shift.
This caused tube erosion; hence the 20 bar (290 psia) blowers are no
longer used. Instead, the entire boiler system is cleaned about every three
months by a Dutch contractor: FA Conservator of Rotterdam. They use
high pressure jets of a solution of sodium carbonate to clean the ash
deposits from the tubes.

Boiler (Units 1-3)

The overall boiler system was built by Bronswerk Amersfoort of
Holland under a license for the Eckrohr design by Dr. Vorkauf of Berlin.
The boilers are designed for a steam flow range of 18.8 to 37 tonnes/hr
(41,360 to 81,400 Ib/hr) at 40 bar (580 psia) and 425 C (797 F). The top
of the steam drum is 20.9 m (68.4 ft) above the ground floor.
As can be observed in Figures 9-13 and 9-15, the arrangement
of the boiler convection tube bundles is unique in that the gas, as it
flows upward out of the first inclined tube bundle at an estimated 600 C
(1112 F), is divided into two streams as it continues upward in the third
pass. Part of the gas flows into the second convection bundle, also in-
clined, and then into the economizer. The remainder flows upward through
two passes of a tubular air heater. The amount of gas that flows along
each path can be controlled by two sets of multiple vane dampers, one
located at the outlet of the economizer and the other after the air heater.
The design estimate was that the gas leaving the economizer would be about
315 C (600 F) and leaving the air heater it would at 220 C (428 F).
Actually these temperatures will vary depending on the damper settings.

Boiler (Unit 4)

This boiler is slightly larger and much taller than the first
three, having a steam range of 18.8 to 40 tonnes/hr (41,360 to 88,000 Ib/hr).
However, the maximum firing rate, 15 tonnes per hour, is the same as units 1-3.
The higher rating comes from an expected higher heat value in the refuse. The
top of the steam drum is 24.3 m (79.7 ft) above the ground floor.
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39
The convection section for Unit 4 is quite different from Units
1-3 as can be seen by comparing them in Figure 9-13. The second pass is
a completely open water-tube-walled down-pass with the superheater banks
horizontal across the bottom of the third pass and thus far removed from
the furnace. The air heater was eliminated in Unit 4 and the third pass
contains not only the superheaters but also the two evaporator bundles
and two tubular economizers.

Economizer

The tubular economizers have given trouble-free service except
at the beginning of operation of Units 1-3, leakage developed that was
caused by an error in installation which was corrected.

Air Preheater (Units 1-3)

Consistent with the design concept in 1965 that the refuse from
this community would be very wet due to the rainy Holland climate and thus
need special provisions for drying, tubular air heaters were installed parallel
to the economizers as seen in Figure 9-13. A separate steam heated air heater
using 4.3 bar (62.4 psia) steam at 146 C (295 F) was provided ahead of the
tubular gas-to-air heater to help prevent condensation from the flue gases in
the cold end of the tubular heaters. However, when both the steam heater and
gas-to-air heaters were operating, the primary air temperature reached 300 C
(572 F), and the grates became overheated. But, operation without the steam
pre-heat caused dewpoint corrosion in the tubular air heaters. Furthermore,
as the heat value of the community refuse increased, there became less need
for drying it on the grate by means of preheated air.

Air Preheater (Unit 4)

Because of the numerous difficulties in Units 1-3 with air
preheating by extracting heat from the flue gas, Unit 4 has simply a steam
heated air heater using high pressure steam.
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40
Primary Air

The primary combustion air supply for all four units is similar
with a few important variations for Unit 4. Each unit is supplied with
preheated air from a radial type blower made by Pollrich of Mdnchengladbach,
2
Germany. The maximum primary air pressure to Units 1-3 is 400 kg/m (3930
Pa) [15.8 in w] and to Unit 4 is 365 kg/m (3585 Pa) [14.4 in w]. Maximum
air preheat temperature for Units 1-3 was originally 300 C (572 F) but,
as explained earlier under "Air Preheater" this involved various diffi-
culties and now, using steam-heated heat exchangers only, the primary
air is heated to about 80 C (178 F). On Unit 4 steam is used to heat
the primary air to 150 C (302 F).
The air is supplied to the grate in six or seven zones, each
controlled by a manually set damper.
Because of the dust content in the primary air which is drawn
from near the top of the main refuse bunker, a 1 mm (0.040 in) thick
deposit of dust builds up on the blowers each year. The deposit is re-
2
moved once per year by means of high pressure water jets at 350,000 kg/m
(500 psi) [3433 kPa] and 90 C (195 F).
The induced draft fan accumulates deposits much faster, hence,
it is similarly washed for two hours every three weeks.
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41
Secondary Air

Furnaces 1-3 were originally installed without secondary air jets.
This was consistent with the original design concept for this plant which
was expected to be faced with the problems of burning high-moisture, low-
calorific-value waste. Thus, the potential cooling effect of secondary
air jets was probably deemed of greater disadvantage than any gain that
would accrue from the mixing action of the air jets.
However, as pointed out in the discussion of wall-tube and
superheater corrosion, within the first year of operation, wastage of both
areas was observed and it was concluded that the temperatures in the
radiation pass (first pass) were, at times, excessive. Accordingly, after
one year's operation, nine secondary air jets were added on each side of
each of Furnaces 1-3. They are about 50 mm (2 in) diameter and are located in
one horizontal row in the refractory sidewall just below the beginning
of the water-tube wall of the radiation pass. The jets are supplied with
3
a maximum of 21,000 Nm /h (12348 scfm) biler room air by a radial blower
producing a maximum static pressure of 390 mm (3834 Pa) [15.4 in w].
When Unit 4 was built, it was supplied with a similar horizontal
row of nine jets on each side close to the main burning grate. Figure
9-16 shows the secondary air manifold on the side of Furnace 4. In addi-
tion to the ten jets in the horizontal row there are two additional jet
tubes visible on a sloping line at the left. These are probably directly
above the step in the grates between the feed grate and the main burning
grate with the slope of the line of jets conforming approximately to the
slope of the angle of repose of the refuse as it flovs into the furnace.
A useful detail of the jet tubes shown in Figure 9-16 is that each tube
is lightly capped by a spring-loaded cover which can be easily lifted
aside for inspection of the jet and, if the jet entry into the furnace is
observed to be clogged by ash or slag, the buildup can be readily poked
into the furnace by means of a rod inserted through the tube.
It is not clear whether the addition of these secondary air jets
was beneficial. The plant staff appeared to prefer future application of
front-wall and rear-wall jets in view of the predominant experience else-
where that such jets appear to provide better mixing.
-------
42
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43
As has been described earlier under Furnace Wall, the walls of
Unit 2 will shortly be modified to incorporate Ktinstler air-cooled wall
blocks as shown in Figure 9-17. Presumably, this method of introducing
low-velocity secondary air will replace the present wall jets. That
furnace may then once more be operating without the mixing action of
moderate-velocity air jets. Whether this lack will affect furnace perform-
ance remains to be seen.

Heat Release Rate

An estimate has been made in Table 9-3 of the combustion volumes
and burning and heat release rates in the two types of boiler-furnaces in
this plant. To estimate combustion volume it was assumed that combustion
is complete when it reaches the top of the Silicon Carbide-coated walls
of the radiation pass (first pass). If the flames normally never reach
that high then the true combustion volume is less and the true heat re-
lease rates are actually somewhat greater than estimated here.
For Units 1-3 it is assumed that only half of the drying grate
2 2
is active with combustion, or approximately 31.5 m (339 ft ) total
burning area. For Unit 4 the feed grate is not considered as combustion
2 2
surface leaving a total of approximately 40.5 m (439 ft ) burning area.
In all cases combustion volume was considered only that volume vertically
above active grate area. The grate dimensions were given earlier in
Table 9-1.
The conditions indicated by the estimated rates in Table 9-3
are that the initially designed grate burning rate for Units 1-3 of
2 2
476 kg/m -hr (97.3 Ib/ft -hr) was rather high, but that with 1800 kcal/kg
heat value of the refuse, the heat release rates on the grate and in the
furnace were moderate. Even when the heat value rose to 2300 kcal/kg the
heat release rates were not excessive. On the other hand, Unit 4, with
a larger furnace (combustion volume) and a much larger effective grate,
was much more conservatively designed. In addition, in Unit 4 the super-
heater was not placed at the top of the radiation pass but was moved
-------
44
TABLE 9-3. ESTIMATED COMBUSTION RATES AT THE HAGUE
Unit 1-3 Unit 4

Year Unit began operation 1968 1974
3
Combustion Volume, m 232 258
3
Combustion Volume, ft 8192 9110
2
Grate area, m 31.5 40.8
2
Grate area, ft 339 439

Burning Rate:

Per boiler, tonnes/hr 15 15

Per boiler, tons/hr 16.5 16.5

Total Heat Release per Boiler, Gcal/hr

at 1800 kcal/kg (3240 Btu/lb) 27 27

at 2300 kcal/kg (4140 Btu/lb) 34.5 34.5
2
Grate burning rate, kg/m -hr 476 367
o
Grate burning rate, Ib/ft -hr 97.3 75.2
o
Grate heat release (at 1800 kcal/kg) kcal/m -hr 856,800 660,000
o
Grate heat release (equiv), Btu/ft -hr 315,252 243,648

Grate heat release (equiv), MJ/m -hr 3,587 2,766
2
Grate heat release (at 2300 kcal/kg) Kcal/m -hr 1,094,800 844,100

Grate heat release (equiv), Btu/ft2-hr 402,822 311,328
7
Grate heat release (equiv), MJ/m -hr 4,584 3,534

Volume heat release (at 1800 kcal/kg) kcal/m3-hr 116,379 104,651

Volume heat release (equiv), Btu/ft -hr 13,052 11,736
3
Volume heat release (equiv), MJ/m -hr 487 438

Volume heat release (at 2300 kcal/kg) kcal/m -hr 148,707 133,721
3
Volume heat release (equiv), Btu/ft -hr 16,677 14,997
3
Volume heat release (equiv), MJ/m -hr 623 560
-------
45
beyond the second radiation pass to the third (convection) pass. This,
too was a much more conservative design policy. As a consequence it is
not surprising that Unit 4 has suffered none of the corrosion problems
that came to Units 1-3 from probable overheating of the potentially
corrosive deposits on the wall tubes and superheaters.

Boiler Water Treatment

The waste-burning plant receives its treated makeup water from
the adjacent 200 mw municipal power plant. It is fully demineralized
and deoxidized.

Start-up Procedure

The Von Roll organization provides each plant with a detailed
operating guide including specific procedures for startup to avoid over-
heating and damage to the system. At this plant the operator is also
required to follow established curves showing the rate of rise of furnace
temperature, economizer outlet temperature, and steam flow rate. Through-
out the period of startup of a unit which normally will take 18-24 hours
the operator plots the critical parameters on a startup chart so that the
active curve for each parameter is plotted alongside the prescribed
startup curve which has been established from experience. Thus, the start-
up chart serves as a guide to the operator and, when completed, provides
a record of any excursions that may have occurred during the process.
This is one more indication of careful management at this plant that is
reflected in relatively low maintenance and operating costs.
-------
A6
ENERGY UTILIZATION EQUIPMENT

The energy available from this plant is electrical only.
Internally, a small amount of steam at 4.3 bar (62 psi)
[427 kPa] is extracted from the turbines for use in plant water heating
and space heating. The electricity is generated in two 11.5 Mw 10,000
volt condensing turbogenerators operating at 40 bar (580 psia) [4000 kPa].
About 15 percent of the power generated in 1975 was used internally. The
remainder was supplied to the municipal network which is supplied principally
by the large oil-fired power plant just across the Afvoer Canal from the
waste plant. Because there is always ample cooling water available in the
adjacent canal, the condensers are water cooled. There are, however, some
plans to eventually use the turbine exhaust heat in the adjacent community.
During weekdays the contract with the municipal electrical
organization requires the waste plant to generate for distribution at least
5.5 Mw between the hours of 6:00 a.m. and 10:00 to 11:00 p.m. If pro-
duction falls below that level the waste plant loses a bonus of DG 30,000
per month ($12,300@ 2.44/$). Accordingly, considerable attention is given
to preventive maintenance throughout the plant to enable reliable operation.
The plant, as a whole, achieves 74 to 76 percent availability.
-------
47
POLLUTION CO_NTROL EQUIPMENT

Each unit is equipped with an electrostatic precipitator. Those
for Units 1-3 vere made by a Swedish company. No. 4 was built by
Rothemiihle of West Germany. Gas flow rate is 90,000 Nm /h (52,965 scfm) .
There are two electrical fields per precipitator. Preliminary
model flow tests were made for the Unit 4 precipitator only. Average
velocity is 2 m/sec (6.5 fps). Entering flow is distributed across the
passage by a perforated plate. There are 204 plates per field, each 7 m
by 0.3 m (23 ft by 1 ft). Plate spacing is 0.3 m (1 ft). Cleaning of the
plates is by mechanical rapping. Rectifier output is 40,000 volts at 50 ma.
The pyramidal flyash hoppers for Units 1-3 are covered with 15 cm
(6 in) of insulation but are unheated. The hopper for Unit 4 is heated
electrically. The collected ash is sluiced to the flyash setting tank
shown at the right in Figure 9-7.
The precipitators for Units 1-3 were guaranteed to achieve an
emission level of 100 mg/Nm (0.0437 grn/scf) corrected to 7% CO . They
have been tested twice in ten years. The last test showed an emission of
3 3
only 55 mg/Nm (0.024 grn/scf). Unit 4 was guaranteed for 80 mg/Nm and
3
in September 1974, when tested emitted only 19 mg/Nm (0.008 grn/scf).
Its efficiency was stated to be 99.6% with two fields and 85% with one field.
As has been explained under Furnace Wall and Superheater, the
refuse burned in Units 1-3 had a much higher heat value than expected with
the result that there were times when the gases leaving the economizers
were as high as 330-350 C (626-662 F), far above the safe operating tem-
perature for the precipitators. As a result, the plates rapidly corroded
and had to be replaced. Because of that experience the temperature enter-
ing the precipitators is now held below 270-280 C (518-536 F). When the
economizer exit temperature begins to exceed about 225 C (437 F) plans are
made to clean the boiler heating surfaces. These practices have almost
eliminated plate corrosion.

Chimney
The two concrete stacks, 100 m (328 ft) tall are brick lined. The
inside diameter of the outer shell is 5 m (16.4 ft). The liner is 2.7 m
(8.9 ft) inside.
-------
48
Between the stack wall and liner is space to permit annual inspection and repair.
Some major cracks needed repair after six years operation.

Wastewater Discharge

There is no wastewater discharge from the plant except sani-
tary wastes and moisture in the quenched residue and sluiced flyash.

Noise

The plant is completely enclosed and except for the barely
noticeable sound of trucks coming and going is not a source of annoying
noise to the numerous nearby residents. Dutch regulations permit no
more than 45 decibels at the plant boundary day and night.

Residue Processing

Until very recently, the quenched furnace residue and wet fly-
ash have been hauled to the Rijswijk landfill without any processing for
resource recovery. However, in August 1977 the processing equipment
shown in Figure 9-17 was installed adjacent to the plant by a private
company which evidently hopes to benefit from resource recovery. The
magnetically separated steel scrap piled in the foreground is to be sent
to a steel plant. The conical pile of sized cinders in the background
will be used for fill and road building. This processing plant is too
new to have produced any data on its costs and revenues.
-------
49
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-------
50
POLLUTION CONTROL ASSESSMENT

The location of this plant, as illustrated in Figure 9-4,
close to the center of this city surrounded by quiet rov housing has
naturally imposed a severe requirement that its operation be nuisance-
free. The plant presents a very clean appearance and the stack
emissions are only slightly visible. Emission tests reported earlier
were well within the allowable limits. Very little wastewater is discharged.
EQUIPMENT PERFORMANCE ASSESSMENT

In 1976 the plant produced 85,028,300 kw-hr, 71,930,500 kw-hr of
which was delivered to the municipal electric system, thus earning, at
DG 0.03/kw-hr, DG 2,157,915 ($884,391(3 2.44/$). To achieve this per-
formance the two 11.5 mw steam turbogenerators operated 5710 and 5698 hours
respectively, and average overall plant availability for generating of
82.9% based on a 5.5 day week of operation (6883 hr/yr). As explained
earlier, good plant reliability is achieved by having one of the four units
available for repair and preventive maintenance.
Of the total energy delivered, 35.7 x 10 kw-hr was delivered
during the days, 36.2 x 10 kw-hr at night. Maximum 5-minute average
peak production rate was 19,160 kw at 2:25 p.m. on December 10, 1976.
Table 9-4 shows an annual summary sheet prepared by the staff
each year to depict overall plant performance. In that table the final
chart and the final column both have to do with the electrical contract
with the parent organization, Gemeentelijk Energiebrijf (municipal
utility). That contract provides a monthly bonus if the waste plant
delivers at least 5.5 mw continuously during the 5.5 days of operation
each week. Table 9-4 shows that in 1976 that monthly bonus was won in all
months except April, August, and October because on a total of 26 days the
minimum rate was not maintained.
In addition to the annual plant performance tabulation, every
month the staff produces a monthly summary of availability of all major
plant components showing for each boiler-furnace, turbine, crane, and
-------
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52
pump the period of operation, time required for maintenance, repair, or
modification. Also, a hand-recorded daily table is included showing, by
coded symbols, which days of the month which components did or did not
operate and why. Thus, management can tell at a glance over several
months of these coded tables which particular components are trending
toward decreasing availability and hence should receive appropriate
maintenance.
Table 9-5 shows the annual plant performance results for the
seven years 1970-1976. The most notable item in this extensive record
is steam produced, tonnes per tonne of refuse. Although this plant, as
all waste-to-energy plants, must contend with a highly variable source
of energy, it shows a remarkably consistent production rate. That rate
ranged for 1.92 to 2.02, a maximum variation over seven years of + 2.5%.
The decided drop in rate in 1974 is attributed to the severe energy crisis
caused by the Arab oil embargo beginning in October 1973. Plant staff
surmised that many householders found ways to reduce the amount of com-
bustible materials discarded.
-------
53

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-------
PERSONNEL AND MANAGEMENT
The plant was built by the city and is under the overall
management of the Director of Utilities who also oversees the operation
of the adjacent 200 Mw power plant and gas and district heating facil-
ity. That combined facility has a staff of 1500 workers. The refuse
plant has a staff of 54. However, major repairs of the refuse plant
are handled by the maintenance staff from the main power plant. Mr.
Postma, plant manager, gives a report each day on his plant's operation
to the manager of the utilities plant.
The plant staff numbers 54, including the manager and assistant
There are 33 operating personnel divided over four shifts as
manager
follows:
4 mechanics
4 machinist-turbines
4 boiler operators
4 crane operators
8 relief mechanics
4 laborers
5 reserve shiftworkers
The work week is 40 hours
2 slag crane operators
2 electricians
2 meter and control technicians
3 pipefitters
2 operators for hospital refuse burner
1 janitor
-------
55
Although marine training is obviously not crucial to the oper-
ation of a waste-burning power plant, this type and extent of experience
is essential in preparing the principal operating staff for successfully
coping with the problems of waste handling and burning.
ENERGY MARKETING

The refuse plant receives DG 0.03/kw-hr ($0.012/kw-hr@ 2.44/$)
from the city utility department of which it is a part. Thus, if both
turbines are operating to produce a total of 23 Mw, the income would be
DG 690/hr ($282.79/hr(§ 2.44/$). If a base supply rate of 5.5 Mw is main-
tained throughout a month the plant is paid an additional bonus of
DG 30,000 ($12,295.08). If this minimum energy delivery rate cannot be
maintained the bonus is lost for that month.
-------
56
ECONOMICS

The capital cost for the plant as it stands today, not including
land cost, was DG 62 million ($15.5 million in terms of 1969 guilders at
4.00/$). However, this included Units 1-3, built in 1967-68, and the
entire building for DG 45 million plus Unit 4 added within that building
in 1972-74 at a cost of DG 17 million.
At present, the approximate amortization cost is DG 28/tonne
of refuse fired ($10.43/ton @ 2.44/$). This and other operational charges
for 1976 were as follows:
Guilders/tonne
Principal and interest 28.0
Maintenance 16.5
Operation 10.0
Water use and ash disposal 3.0
Total cost 57.5
Revenues are:
Sale of electricity 15.0 5.59
Tipping fee (The Hague) 6.3 2.35
Tipping fee (Suburbs) 3.0 1.12
Total Revenue 24.3 9.06
Net Cost 33.2 12.37
The net waste generation per inhabitant per year is estimated to be 417 kg
or 0.417 tonne (917 Ib). Thus the per capita cost of disposal is DG 13.84
per year ($5.67/yr per capita). This is a relatively low figure compared
to most large cities. It reflects good management, reliable equipment,
and a very alert and busy staff.
-------
57

FINANCE

All of the funds needed to build the plant were borrowed by the
city on a 25-year loan with uniform payment and declining balance. The
equipment life is estimated at 25 years, building at 40 years.
-------
58
REFERENCES
1. Vuilverbranden in 's-Gravenhage, Dedicatory brochure for The Hague
plant published March, 1968.
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TABLE EXCHANGE RATES FOR SIX EUROPEAN COUNTRIES.
(NATIONAL MONETARY UNIT PER U.S. DOLLAR)
1948 TO FEBRUARY, 1978(a)

1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
'1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978 (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
6.886
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.)
2.662
3.490
3.499
3.500
3.500
3.500
3.500
3.500
3.500
4.199
4.906
4.909
4.903
4.900
4.900
4.902
4.900
4.902
4.952
4.908
4.948
5.558
5.520
5.224
5.125
4.708
4.444
4.486
4.970
4.705
4.766
W . Germany
Deutsch Mark
(D.M.)
3.333
4.200
4.200
4.200
4.200
4.200
4.200
4.215
4.199
4.202
4.178
4.170
4.171
3.996
3.998
3.975
3.977
4.006
3.977
3.999
4.000
3.690
3.648
3.268
3.202
2.703
2.410
2.622
2.363
2.105
2.036
Netherlands
Guilders
(Gl.)
2.653
3.800
3.800
3.800
3.800
3.786
3.794
3.829
3.830
3.791
3.775
3.770
3.770
3.600
3.600
3.600
3.592
3.611
3.614
3.596
3.606
3.624
3.597
3.254
3.226
2.824
2.507
2.689
2.457
2.280
2.176
Sweden
Kroner
(S.Kr.)
3.600
5.180
5.180
5.180
5.180
5.180
5.180
5.180
5.180
5.173
5.173
5.181
5.180
5.185
5.186
5.200
5.148
5.180
4.180
5.165
5.180
5.170
5.170
4.858
4.743
4.588
4.081
4.386
4.127
4.670
4.615
Switzerland
Francs
(S.Fr.)
4.315
4.300
4.289
4.369
4.285
4.288
4.285
4.285
4.285
4.285
4.308
4.323
4.305
4.316
4.319
4.315
4.315
4.318
4.327
4.325
4.302
4.318
4.316
3.915
3.774
3.244
2.540
2.620
2.451
2.010
1.987
(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.
ya 1828J
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