United States Office of Water and SW 176C.9
Environmental Protection Waste Management October 1979
Agency Washington, D.C. 20460
Solid Waste
<&EPA European Refuse Fired
Energy Systems
Evaluation of Design Practices
Volume 9
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fan EPA
and State. Solid Wa&te. Management
EUROPEAN REFUSE FIRED ENERGY SYSTEMS
EVALUATION OF DESIGN PRACTICES
Gothenbu^g-Savanas Plant
Sweden
(SW-776c..9)
the. 0|J(J A.ep/todaced OA /Lecex.ued ijtom ^e conxfLac^o^.
The <5^.ncttng4 AkouZd be. att>u,bute.d to tne. contsia.c£ofi
and not to tke. O^ce. o£ Sotid Wa&te..
Copies will be available from the
National Technical Information Service
U.S. Department of Commerce
Springfield, VA 22161
Volume 9
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.9) in the solid waste
management series.
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TRIP REPORT
to
GOTHENBURG-SAVENAS PLANT, SWEDEN
on the contract
EVALUATION OF EUROPEAN REFUSE-FIRED
STEAM GENERATOR DESIGN PRACTICES
to
U.S. ENVIRONMENTAL PROTECTION AGENCY
September 22-23, 1977
EPA Contract No. 68-01-^376
EPA RFP No. WA-76-B146
February, 1978
by
Richard Engdahl and Philip Beltz
BATTELLE
Columbus Laboratories
505 King Avenue
Columbus, Ohio i»3201
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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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11
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
Bengt Rundqwist Director, Gothenburg (Savenas)
Plant
Gian-Rudlinger Chief Operating Engineer,
Gothenburg (Savenas) Plant
Beat C. Ochse Project Engineer, Von Roll, Ltd.,
Zurich
Kurt Spillman Project Engineer, Von Voll, Ltd.,
Zurich
The authors are glad to acknowledge the very kind and competent
assistance of these men in providing the information presented in this
report.
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TABLE OF CONTENTS
Page
SUMMARY 2
GOTHENBURG STATISTICAL SUMMARY 3
OVERALL SYSTEM SCHEMATIC 6
COMMUNITY DESCRIPTION 9
SOLID WASTE PRACTICES. 11
Solid Waste Generation 11
Solid Waste Collection 11
Solid Waste Disposal 19
DEVELOPMENT OF THE SYSTEM 20
Beginning of the SaVenas Facility 22
PLANT ARCHITECTURE 23
REFUSE-FIRED STEAM GENERATOR 24
Weighing Operation 25
Provisions to Handle Bulky Wastes 26
Refuse Storage and Retrieval 26
Furnace Hoppers and Feeders 30
Burning Grate 30
Furnace Wall 33
Second Pass 37
Furnace Heat Release 37
Superheater 38
Boiler 38
Primary Air 38
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TABLE OF CONTENTS
(Continued)
Page
Secondary Air 39
Boiler Water Treatment 39
ENERGY UTILIZATION EQUIPMENT 40
POLLUTION CONTROL EQUIPMENT 43
Chimney 43
Wastewater Discharge 46
Noise 46
Residue Disposal 46
POLLUTION CONTROL ASSESSMENT 47
EQUIPMENT PERFORMANCE ASSESSMENT 48
PERSONNEL AND MANAGEMENT . 52
ENERGY MARKETING 54
ECONOMICS 56
Revenues 57
FINANCE 58
REFERENCES 59
LIST OF TABLES
Table 11-1. Sources and Quantities of Refuse Handled in 1976 for 53
Week Period December 29, 1975 to January 2, 1977 12
Table 11-2. Energy Produced by Savenas Plant in 1976 41
Table 11-3. 1976 Operating Results for Savenas Plant 49
Table 11-4. Savenas Annual Results 1974-1976 51
Table 11-5. Operating Budget for 1977 at Gothenburg 57
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LIST OF FIGURES
Figure 11-1. Topview of Savenas Waste-to-Energy Plant Showing
Traffic Pattern, Weigh Stations and Distinctive Square
4-Flue Chimney. Only Three Flues in Use. Chimney
Equipped with Two-Passenger Elevator 7
Figure 11-2. Savenas Plant East of Gothenburg 8
Figure 11-3. Collection Area for Gothenburg Waste Handling System
Total Area Served is About 1000 km2 (386 square
miles) 10
Figure 11-4. Chart of Data Shown in Table 11-1 13
Figure 11-5. Trend of Weekly Receipts of Refuse for Years 1975-1976,
Thousands of Metric Tons 14
Figure 11-6. Trend of Annual Totals of Refuse Handled 1972-1976,
Thousands of Metric Tons 15
Figure 11-7. Transfer Vehicle. The Cylindrical Chamber Holds About
50 m^ (538 ft^) Compressed at the Transfer Station by a
Factor of about 3.3 to 1 16
Figure 11-8. Cross Section and Plan View of Transfer Station 18
Figure 11-9. Transfer Truck in Unloading Position at Savenas
Plant 27
Figure 11-10. Cross Section of Nominal 900 Tonne Per Day Refuse
Fired Steam-to-Hot Water Heating Plant at Savenas,
Gothenburg. Plant Started Up March 1, 1972 28
Figure 11-11. Refuse Pit with 2 of the 14 Doors Open to Receive
Refuse 29
Figure ll-12a. Two Views of New Q-L Type Grate Bar 30a
Figure 11-12. View Forward in Furnace Showing Two Grate Steps and
Slag Accumulation on Wall at Left 32
Figure 11-13. Lower Portion of First Pass Showing 18 Original
Sidewall Jets, Now Abandoned, Rear Nose Formed of
Refractory Covered Bent Tubes, and Manifolds for New
Front and Rearwall Secondary Air Jets Aimed Downward
About 30 Degrees 36
Figure 11-14. Monthly Trend for 1976 of Heat Production and
Utilization 42
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LIST OF FIGURES
(Continued)
Page
Figure 11-15. Unusual Square Chimney 44
Figure 11-16. Neighborhood of Savenas Plant Viewed from Top of
Chimney Looking Between Two Chimney Flues 45
Figure 11-17. Control Room at Savenas Plant. The Foliage Plants
at Left Decorate the Coffee and Rest Area 53
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2
SUMMARY
The 900 tonnes/day (990 tons/day) Savenas plant at Gothenburg
(Goteborg), Sweden is owned and operated by the Goteborgsregionens
Avfallsaktiebolag-GRAAB (Gothenburg Regional Refuse Management Company).
The heat recovered is used in district heating. There is no electricity
generation. Maximum burning capacity of each of three furnaces was
originally rated as 15 tonnes/hr or a total of 1,080 tonnes/day (1,188
tons/day). However, the Gothenburg refuse has turned out to have an
unusually high heat value and therefore the normal capacity is now about
14th in the year 1975 corosions in the first pass of the boiler gave in all
three units operating stops and therefore the utilisation is shorter.
Modifications of furnace configuration and of operation have been effective
in bringing these problems under control.
transfer stations and 30 specially built, large transfer vehicles.
The refuse is collected over a broad area through the use of five
transfer stations and 30 specially built, large transfer vehicles.
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GOTHENBURG STATISTICAL SUMMARY
Community Description:
Area (square kilometers) 1,000
Population (number of people) 670,000
Key terrain feature Hilly, coastal
Solid Waste Practices:
Total waste generated (tonnes/year) 254,000 (1976)
Waste generation rate (kg/person/year) 380 kg
Lower heating value of waste (Kcal/kg) 2600 * 2700
Collection period (days/week)
Cost of collection (local currency/tonne) Not in GRAAB responsibility
Use of transfer and/or pretreatment (yes or no) Yes
Distance from generation centroid to:
Local landfill (kilometers) 8
Refuse-fired steam generator (kilometers) 6
Waste type input to system Res., com., ind.
Cofiring of sewage sludge (yes or no) Contemplated
Development of the System:
Date operation began (year) March 1, 1972
Plant Architecture:
Material of exterior construction Anodized aluminum
Stack height (meters) 120
Refuse-Fired Steam Generator Equipment:
Mass burning (yes or no) Yes
Waste conditions into feed chute:
Moisture (percent) about 23
Lower heating value (Kcal/kg) 2,600 - 2700
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Volume burned:
Capacity per furnace (tonnes/day) (max) 360
Number of furnaces constructed 3
Capacity per system (tonnes/day) (max.) 1,080
Actual per furnace (tonnes/day) 300-3*10
Number of furnaces normally operating 3
Actual per system (tonnes/day) 900* 1020
Use auxiliary reduction equipment (yes or no) Bulky waste
shears
Pit capacity level full:
(tonnes) 2,500
6,000
(12,000 max)
(m3) 6,000
Crane capacity (2):
(tonnes) 11,4
(m3) GRAB Capacity 6
Drive method for feeding grate Hydraulic cylinders
Burning grate:
Manufacturer Von Roll
Type Reciprocating/transversal
Number of Grates 3
Length overall (m) 5.U25
Width overall (m) 3.HO
Primary air-max (Nnr/hr) 60,000
Secondary air-overfire air-max (Nnr/hr) 33,000
Furnace volume (m ) Approx. 320
320
Boiler wall tube diameter (cm) 7.6
2
Furnace heating surface (m ) proj. surface 160 m2
Auxiliary fuel capability (yes or no) Yes
Use of superheater (yes or no) Yes
Boiler:
Manufacturer Generator AB, Gothenburg
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Type Eckrohr
Number of boiler passes 3
Steam production per boiler (kg/hr) (max) 52,500
Total plant steam production (kg/hr) (max) 157,500
Steam temperature ( C) 21U
Steam pressure (bar) 20-22
Use of economizer (yes or no) No
Use of air preheater (yes or no) Yes
Use of flue gas reheater (yes or no) No
Cofire (fuel or waste) input startup and emergency burn Oil
Use of electricity generator (yes or no) No
Energy Utilization:
Medium of energy transfer
Temperature of medium ( C)
Population receiving energy (number)
Pressure of medium ( bar )
Energy return medium
Hot water
(max) 180
10,000 flats/and one hospital
14,5 bar
Condensate from
heat exchanger
Pollution Control:
Air:
Furnace exit conditions:
Gas flow rate (Nnr/hr)
Furnace exit loading (mg/Nm )
100,000
Less than 150
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OVERALL SYSTEM SCHEMATIC
Figure 11-1 shows a top-view sketch of the Savenas plant which is
located about 6 km (3-7 mi) from downtown Gothenburg. The site is amply
sized to accommodate the large transfer trucks that are an important
feature of the system.
Figure 11-2 shows a view of the plant looking toward the west.
The unusual multicolored wall is anodized aluminum. The tipping hall is
the dark mass on the right. The elevated entrance ramp crosses the width
of the main building from left to right. The chimney is 120 m (391* ft)
tall. The main building is 36.1 m (118.4 ft) high. The site is 18.6 m (61
ft) above sea level.
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FIGURE 11-1.
TOPVIEW OF SAVENAS WASTE-TO-ENERGY PLANT SHOWING.TRAFFIC
PATTERN, WEIGH STATIONS AND DISTINCTIVE SQUARE 4-FLUE
CHIMNEY. ONLY THREE FLUES IN USE. CHIMNEY EQUIPPED WITH
TWO-PASSENGER ELEVATOR. (COURTESY GRAAB)
1. Entrance gate - monitored by television.
2. Classification lanes for large and small trucks.
3. Weigh station.
A. Traffic control area.
5. Entrance ramp.
6. Entrance to enclosed tipping hall.
7. Bunker doors.
8. Exit door.
9. Exit lanes.
10. Exit weigh station.
11. Automatic exit gate.
12. Cafeteria (open 9 am to 2 pm).
13. Washroom (Drivers only)
14. Parking.
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FIGURE 11-2. SAVENAS PLANT EAST OF GOTHENBURG.
(Courtesy Von Roll, Ltd.)
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COMMUNITY DESCRIPTION
Gothenburg is a relatively "new" port city founded in 1619 on the
hilly southwest coast of Sweden about 120 km (75 mi) across the Kattegat
from the northern tip of Denmark. It is the most important industrial
center in Sweden.
The Savenas plant is on the border of Partille adjacent to a large
railway yard between the river Savean and the main highway to the east
called Europawag 3. Figure 11-3 shows the area served which originally
involved about 36 other towns. Owing to rapid consolidation of communities
throughout Sweden, the number of towns now served is nine.
The Gothenburg population is 440,000. The total population served
by the Savenas plant is 670,000. About 220,000 tonnes (242,000 tons) of
refuse are received annually which is collected within a radius of about
17 km (10 mi) from the plant.
There are many manufacturing facilities in the area and a
considerable fraction of the refuse received is industrial.
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10
Klovsten
FIGURE 11-3.
f Savenas incinerator.
^ New landfill at Tagene. (for ash only)
• Existing transfer stations.
O Future transfer station
Dist. SSvenSs to Tagene *v6 mi.
COLLECTION AREA FOR GOTHENBURG WASTE HANDING SYSTEM.
TOTAL AREA SERVED IS ABOUT 1000 km2 (386 square miles)
(Courtesy of GRAAB) .
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11
SOLID WASTE PRACTICES
Solid Waste Generation
Refuse from the community residential, commercial, and industrial
sources is received at the plant and at the five transfer stations shown
in Figure 11-3. As of January, 1973, a separate facility, GRAAB-KEMI, was
activated to receive chemical wastes.
Table 11-1 and Figure 11-1 show the proportions of waste received
from the various sources.
Figure 11-5 shows the trend of weekly receipts of refuse for 1975
and 1976. The 15 to 20 percent drop in July and August reflects the effect
of vacation time in Sweden.
Figure 11-6 shows the trend of total annual amount handled since
1972.
Solid Waste Collection
In 1971, the GRAAB organization established the first of five
transfer stations and began acquiring specially-built transfer trucks as
shown in Figure 11-7. The cylindrical chamber is 13.60 m (44.6 ft) long
and 2.5 m (8.2 ft) in diameter, volume is 50 m^ (538 f t^), and overall
height is 3.83 m (12.5 ft). Total weight is 33.40 tonnes (36.7 tons).
Carrying capacity is 17.40 tonnes (19.1 tons). Overall length, including
tractor, is 15.86 m (52 ft).
There are 30 of these transfer vehicles in the system bringing
refuse to the plant from the five transfer stations. In 1972, each vehicle
cost 250,000 skr ($62,500, 4 skr/$). Also, over 100 other trucks deliver
directly to the Savenas plant. Total collections and deliveries to the
transfer stations are made by the individual districts. There are about
300 truck loads per day delivered between 7:00 a.m. and 3:00 p.m., 5
days/week.
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12
TABLE 11-1. SOURCES AND QUANTITIES OF REFUSE HANDLED
IN 1976 FOR 53 WEEK PERIOD DECEMBER 29,
1975 TO JANUARY 2, 1977
(From 1976 GRAAB Annual Report)
THE GRAAB-REGION
Community
Ale
Goteborg, incl. "dckerC
HUrryda
Kungsbacka
Kungalv
Lerum
MSlndal
Patille
Private haulers
Sa'ven'a's plant
Hogsbo Transfer Station
Kunga'lv Transfer Station
Lerum Transfer Station
Mb'lndal Transfer Station
Kungsbacka Transfer Station
Total GRAAB region
Misc. haulers
Ton
5,100
184,800
5,600
8,600
8,700
6,700
11,700
6,800
6,000
1,900
200
1,900
2,700
2,300
253,000
800
Population
1/1 1976
22,000
453,900
20,700
38,400
28,300
28,200
47,300
27,200
—
—
—
—
—
—
666,000
kg per
1975
234
396
304
220
297
233
245
234
-
-
-
-
-
—
374
person
1976
232
407
271
225
307
237
247
252
-
-
-
-
-
-
380
Total 253,800
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13
FIGURE 11-4. CHART OF DATA SHOWN IN TABLE 11-1.
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1A
Vi
01
o.
m
o
o
•H
at
m
TJ
«
a
o
u..
jan mar
—— 1976
--- 1975
jul sep nov
FIGURE 11-5.
TREND OF WEEKLY RECEIPTS OF REFUSE FOR YEARS 1975-1976,
THOUSANDS OF METRIC TONS. (From GRAAB 1976 Annual Report)
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15
223
135
D
240
1972 1973 1974 1975 1976
•« ••
Delivered to Savenas plant.
Delivered directly to landfill area at Tagene.
FIGURE 11-6. TREND OF ANNUAL TOTALS OF REFUSE HANDLED 1972-1976,
THOUSANDS OF METRIC TONS. (From GRAAB 1976 Annual Report)
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16
W5S
FIGURE 11-7.
TRANSFER VEHICLE. THE CYLINDRICAL CHAMBER HOLDS
ABOUT 50 m3(l,765 ft3) COMPRESSED AT THE TRANSFER
STATION BY A FACTOR OF ABOUT 3.3 to 1
(Courtesy GRAAB)
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17
Figure 11-8 shows one transfer station. The lower plan view shows
two compactor trucks and one large truck delivering simultaneously to two
hoppers.
Mr. Bengt Rundqwist, Works Director, described the operation of
the system in a leaflet prepared for visitors in 1972:
"The transfer stations are as centrally positioned as
possible within each generation area in relation to local
transport, since this method generally requires short distances
for good economy. The central position requires high operational
reliability to prevent health hazards. For the stations further
away from the incineration plant, this means that irrespective of
capacity requirements these are designed with double compactors ,
whilst the other stations are constructed as single stations.
The waste is received basically in the same way and with the
same type of weighing instruments and equipment as in the main
plant. However, only one weighing machine is provided, which is
why in tare weighing the vehicles must drive over the entrance
weigher another time when leaving.
Referring again to Figure 11-8, after weighing incoming
refuse, the vehicles are backed into the emptying bay (1). The
refuse is dumped into a funnel-shaped bunker with two pockets
(2). Two compactors are placed under the bunker in the compactor
room (3).
In the unloading bay CO, trailer cars are coupled to the
compactors, which force the refuse into the trailer containers
against counter pressure. In the control room (7)» a good view is
obtained of the unloading and loading operations. From here,
everything happening inside and outside the plant can be
monitored. A station equipped with two compactors has a capacity
of about 50,000 tons/annum and costs about 2 million kroner
($500,000 6 1* skr/$).
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18
FIGURE 11-8.
CROSS SECTION AND PLAN VIEW OF TRANSFER STATION.
(Courtesy GRAAB)
1. Tipping Hall
2. Bunker
3. Compactor
4. Vehicle Hall
5. Stairway
6. Washroom
7. Control Room
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19
The transfer trailer is equipped with a hydraulic plate
which, when loading, serves as a back-stop to obtain correct load
distribution and compression ratios (about 1:3)« On
emptying—which takes M to 5 minutes—the plate serves as an
explusion plate."
Solid Waste Disposal
Noncombustibles, incinerated residue, and sewage sludge go to the
new Tagene sanitary landfill about 10 km (6 mi) from the Savenas plant.
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20
DEVELOPMENT OF THE SYSTEM
Prior to 1971, about 10 percent of the refuse disposal in the
region was handled in 10 small local incinerators, seven of which
recovered heat for district heating and the rest went to uncontrolled
landfills. Air pollution from the incinerators was sometimes a problem. In
1955, discussions began of better ways of doing it. The concensus
developed that a central facility would be desirable but siting was
difficult. At one point, consideration was given to building some large
landscaped hills of refuse as is now being done at the Hogdalen plant just
south of Stockholm.
Mr. Bengt Rundqwist, who was quoted earlier, wrote in 1972:
"According to a special report on refuse prepared by the
Greater Gothenburg Cooperation Committee in 1965, the 23-member
districts formed a community of interests, Goteborgsregionens-
Avfallsaktiebolag-GRAAB, with the task of solving associated
problems.
The responsibilities of the districts and the regulations
governing cooperation were laid down in a consortial agreement
valid for a period of 30 years. The agreement describes the
method whereby expenses shall be calculated, stipulates that
costs for refuse treatment shall be the same throughout the
region when the refuse is deposited at the incineration plant or
any of the transfer stations, and how the shares amounting to 4.5
million kronor and the bonds amounting to 120 million kroner
shall be distributed.
GRAAB also played a leading part in constructing GRAAB-KEMI,
a receiving station for chemical wastes. This consists of a
chemical storage, toxic storage, and an oil reception plant.
Furthermore, a wet chemical line was planned with the task of
treating diluted solutions and those chemicals which are
unsuitable for storage. The wet chemical line will form the basis
for decisions on the region's own treatment plants. The operation
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21
of this reception station is also GRAAB-KEMI task. The
company has equipment for work in practically the entire chemical
refuse sector. Detailed discussions were held with the Gothenburg
Cleaning Dept., GRAAB on the company's cooperation within the
monopoly as a whole, which began to operate the Gothenburg district
in January, 1973."
GRAAB also installed a cremation furnace for dead animals.
Although at the beginning of the discussions, 36 communities were
involved. Later, consolidation of communities, which has been nationwide,
reduced the number first to 23» then to 13» and now to nine large
communities. These are all involved in GRAAB. Some of these extend partly
into other counties. They have ownership in the entire system as follows:
Shares Percent
Ale 1,530 3.4
Goteborg 33,396 7M.2
Harryda 762 1.7
Kungsbacka 1,239 2.8
Kungalv 2,03^ U.5
Lerum 1,101 2.U
Molndal 3,066 6.8
Partille 1,551 3-5
Ockero 321 0.7
TOTAL 45,000 100.0
The nine communities are represented on a Board of Directors,
which meets 10 times/year. A working committee of the Board meets about
twice a month.
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22
Beginning of the Savenas Facility
Eight bids were received in 1967 for the Savenas plant. Von Roll,
Ltd. was selected because, although it was not the lowest bidder, it
appeared to have experience with many similar large plants and had built
or was building plants at Linkoping, Bollmora, and Umea in Sweden.
In 1965, the estimated price was 65 x 106 skr ($16.25 x 106 g 4
skr/$).* The contract was signed in October, 1969. By the time the plant
and its ancillary stations were built in 1972, the total cost had risen to
120 x 10 skr ($30 x 106 § 4 skr/$). This included five transfer stations,
trucks, Tagene landfill and the transport equipment for residue and sewage
sludge. Three boiler-furnace units were installed with building space
provided for a fourth unit.
Inflation was the primary cause of the increase in cost although
the national environmental authorities caused some increase by requiring
some enlargement of pollution control equipment. GRAAB management feels
that 88 percent of the increase was beyond their control. For example,
unexpected clay under the site required 3,000 m more piling than
expected. For this same reason, the refuse pit is not as deep as planned.
Normal plant operation began March 1, 1972. It operates 7
days/week.
* The report uses two monetary conversion factors: (1) 1965 to 1972 estimates,
bids, capital investment costs, etc. @ 4 skr/$; and (2) 1975 to 1977 expense
and revenue figures @ 5 skr/$.
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23
PLANT ARCHITECTURE
The plant structure was designed by the Gothenburg firm of Sten
Ericssons Arkitektkontor AB. As seen earlier in Figure 11-2, the main
plant facade presents an unusual aspect produced by random vertical strips
of different colors of anodized aluminum panels.
Figure 11-1 has earlier shown the plot plan with ample roadways
for orderly traffic flow.
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24
REFUSE-FIRED STEAM GENERATOR
Heat Input
Because of the considerable industrial activity in the Gothenburg
region, the lower heat value of the refuse is comparatively high. At
present, it is estimated to average between 2,600 and 2,700 Kcal/kg (4,689
to 4,870 Btu/lb) (10,885 to 11,304 kJ/kg). Estimated moisture content is
about 23 percent'. Design figures in 1967 were 15 t/h and 2200 kcal/kg-33Gcal/h.
Plant staff are certain that when the plant started in 1972, the heat value
was even higher because then it was found difficult to burn.more than 12
tonnes/hr without overheating the boilers, but now it is possible to burn 15
tonnes/hr. This apparent trend in heat value ot Swedish retuse is borne
out by data published by Feindler '•*•' for Stockholm as follows;
Lower Heat Value
Btu/lb
1964
1965
1966
1971
1972
1973
1974
1975
A puzzling contrast with these values are the comparative maximum
lower heat values at Duesseldorf, a highly industrialized area, through
1972 to 1975, of only 1,800 Kcal/kg. Their average values were 1,700
Kcal/kg.
It is likely that Gothenburg's refuse reached a higher peak in
1972 than the value shown above for Stockholm because of the probably
higher proportion of industrial waste. Plant staff surmise that the
reduced heat value at Gothenburg in recent years has occurred because of
increased Swedish activity in paper recycling. In all of this discussion
Btu/lb
3,546
3,942
4,050
4,545
4,950
4,680
4,500
4,410
Kcal/kg
1,970
2,190
2,250
2,525
2,750
2,600
2,500
2,450
kJ/kg
8,248
9,169
9,420
10,572
11,514
10,885
10,467
10,158
-------
25
of heat values, it must be borne in mind that it is notoriously difficult
to obtain reliable samples of heterogenous refuse for analysis. Small
differences in heat values are not significant.
If the high values at Stockholm from 1971 to 1975 were actually
exceeded at Gothenburg, this would help to explain some of the
difficulties experienced in 1972 and 1973 with furnace tube failures to be
discussed later. However, later it will be shown that the weight ratio of
steam produced to refuse fired is still (1976) relatively high at Gothenburg
and still increasing slightly every year which indicates a continuing high
heat value of refuse.
Weighing Operation
All refuse is weighed at the entrance to the plant area shown
earlier in Figure 11-1. The weighing procedure is automated whenever
possible. Most suppliers use customer cards and need no service therefore.
The weighing plant is equipped with four electronic weighing
machines and a data recording system, which, besides supplying continuous
information to operational management, also enables automatic debiting and
invoicing to be carried out. In addition, statistical information is
received. Traffic inside the area and the emptying bay is monitored by a
traffic controller—stationed in the emptying bay—who directs arriving
vehicles by means of TV and traffic signals. In low traffic periods,
monitoring can be transferred to the central plant control room. Incoming
vehicles pass to the closed emptying bay via ramps, the bay being
separated frors the waste bunker by 1H bunker gates. After emptying, the
vehicles again PL r the weighing room where tare weighing is carried out
on certain vehicles «nf* trfiere any cash is paid.
The weighing equipment and data system have required little
servicing, an estimated down-time of once per year. The scale is of
Swedish make, by Stathmos. The data system is by General Automation Co. of
Anaheim, California, U.S.A.
-------
26
Provisions to Handle Bulky Wastes
When the crane operator stationed in the podium near the top of
the bunker observes oversize waste being delivered, he can lift it to one
of two Von Roll Model 13/310 shears situated between two of the furnace
feed hoppers to have it cut to smaller size. The cut pieces fall from the
shears into the refuse pit. The rated shear capacity is 120 m3/hr.
Refuse Storage and Retrieval
Figure 11-9 shows a transfer truck backing toward an open pit
door to which the driver has been directed by signal lights.
Figure 11-10 shows a cross-section of the Savenas plant. The pit
extends 9 m below the tipping floor. It holds approximately 6,000 nr
o
(7.8M3 yd ). By closing half of the 14 bunker doors and piling the waste
high against the opposite wall, the storage capacity can be doubled.
The pit is served by two bridge cranes built by Kone with
capacities of 11,4 and 4,8 f net. weight. One has a polyp-type bucket of
6m^ capacity.
Figure 11-11 shows the pit with two of the m doors open to
receive waste. The two crane operators can be seen in the glass walled
podium in the upper right. Beneath them is a platform supporting a
high-pressure water cannon which can inject water at 1 m /min for control
of pit fires. Because of a dangerous fire when two drums of solvent were
cut open in a shear, new foam nozzles have been added a: the pit sides
which can cover the pit with foam 1 m deep in 10 minuses
The weight of refuse in each bucket load is read from two
calibrated watt meters on the cranes with digital readout in the crane
podium and readout and recording in the control room. The total weights
are checked frequently against the truck scale totals. The watt-meter
weights are claimed to be accurate within 5 kg (11.1 lb).
-------
27
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-------
29
FIGURE 11-11
REFUSE PIT WITH
RECEIVE REFUSE
2 OF THE 14 DOORS OPEN TO
(Baftelle Photograph)
-------
30
To reduce crane cable wear, the cable drums have been enlarged to
24 times the wire diameter and wire size has been increased from 23 to 27
mm (0.9 to 1.1 in).
Furnace Hoppers and Feeders
The top of the three furnace feed hoppers is 3.5 by 2.5 m (11.5
by 8.1 ft) each. At the hopper bottom is a sloping vibrating table built
by Schenk and having an amplitude of 8 mm (0.3 in). The feeders are
controlled by radioactive level indicators in the water-cooled feed
chutes. The indicators use radiation from Cesium 136. They were made by
Endress and Hauser of Lorrach, Germany.
The vibrating feeder has been satisfactory. The chief engineer
pointed out that the use of a vibrating feeder to feed the vertical chute
1.2 by 3.4 m (4 by 11 ft) requires about a 3 m (10 ft) height of refuse in
the chute to assure a tight air seal and avoid burnbacks in the chute. If
a hydraulic ram feeder were used just above the grate to maintain a seal,
apart of the 10-ft chute height could be eliminated, thus reducing
overall building height by about 1-2 meters. However, the tall chute does
provide a simple, easily managed seal that has effectively minimized
burnback.
Burning Grate
From the chute, the refuse falls on to a Von Roll reciprocating
/transversal feed grate which drops it down along a refractory wall to the
main burning grate. The feed grate is 2.625 m (8.6 ft) long and 3.4 m
(11.2 ft) wide. The length of the main grate and outburning grate is 5.425 m
(17.8 ft) each and their width is alsc 3.4 m (11.2 ft).
-------
30a
FIGURE ll-12a.
TOO VIEWS OF NEW Q-L TYPE GRATE BAR
(Courtesy Von Roll)
-------
31
Figure 11-12 shows a view upward into one of the furnaces. The
main burning grate in the foreground carries some clinker. Above the
cooled refractory grate step wall in the rear of the platform (front of the
furnace) is the feed grate. Secondary combustion air introduced through the
cooled refractory step wall to improve the distribution of combustion. The
slag shown on the wall will be discussed later.
p
The burning and burnout grates have a total area of 36.9 m (397
2
ft ). For a nominal daily throughput of 300 tonnes/day, this provides an
average burning rate of 339 kg/m2/hr (69 Ib/ft2/hr). At the maximum
throughput of 360 tonnes/day, the burning rate increases 20 percent to HOT
2 2
kg/m /hr (83 Ib/ftVhr). These are moderately high rates which, with
unusually "hot" refuse, could require maximum furnace cooling to avoid
slag melting problems.
In Figure 11-10, introduced earlier, grate "knives" are shown in
both burning grates which were intended to break up the fuel mass and
allow better air distribution. Because of maintenance problems, and no need
of them anymore with the high lower heat value, these have been removed
successively. The new Q-L grate is shown on enclosed photos.
The original grate was the early style Von Roll grate in which
alternating rows of grate bars reciprocate causing rapid wear on the sides
of the bars. The design GJ eararice between bars was 2 or 3 mm (0.080 to
0.18 in). After 25,000 hours, this had increased to 15 ffl (0.59 in) at the
tops of the bars. This a.llows unburned material and ash to drop through
and inhibits firm control of the distribution of primary air flow. Von
Roll feels that much of the wear was caused by abrasion from small, hard
steel machine screws and similar matter which cowe in the industrial wastes.
With the new grate, the undergrate air pressure is 110 to 12C mm water
(1.08 to 1.18 k Pa). With old worn grates, it was onJy 10 to 50 mm (0.29 to
0.4 k Pa)
The feed grate has been no problem, Sixty to 70 percent of the
main burning grate bars had to be replaced over a period of 5 years. The
burnout grate bars required some replacement but only toward the upper end
near the drop from the main grate- The cost of grate repairs over 5 years
was about 250,000 to ?1'0,OCO skr ($^0,000 tc $60,000?..
-------
32
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-------
33
In 1973> after 2-1/2 years of operation, a test showed 3 percent
unburned carbon in the residue. The guarantee was 7 percent. Guaranteed
putrescible content was 0.3 percent. Actual content was O.OH percent.
These results would indicate good combustion at that time. Nevertheless,
because the wear of grate bars would continue, in December, 1976, the old
grate in Boiler 3 was replaced by the new Von Roll arrangement where each
transverse assembly of grates reciprocates in unison, thus eliminating the
wear from relative motion between adjacent bars. Similar replacements were
made on Boilers 1 and 2 between June and August, 1977. The basic
undergrate construction remains the same.
Furnace Wall
Referring back to Figure 11-10, showing the plant cross section,
it can be observed that most of the main furnace is not water-tube walled
but is refractory, 0.58 m (1.9 ft) thick. In the upper part of the combustion
chamber, the front and rear arch surfaces are partially covered with a
castable refractory lining, applied on special studys as a protection
against the furnace gases. The water tube front wall is seen to begin
near the top of the furnace at about the level of the top of the refuse
feed entrance. The carbon steel tubes are tangent welded, 76 mm (3 in)
in diameter and A mm (0.16 in) thick.
The front and rear walls are spaced water tubes covered with
cast. Above the nose of the front wall can be seen a separate water-tube-
walled combustion chamber for burning oil. Half of the rated heat output
of each boiler can be generated using low-sulfur, No. 5 fuel oil.
Although these boilers generate saturated steam at only 22 bar
(323 psia) (2,229 Pa) and 217 C (U23 F), which is well below the usual
tube-corrosion threshold, the lower one third of the water-tube walled
first pass was equipped with welded studs holding in place a 50 mm (2 in)
thick layer of high alumina plastic refractory. This was a successful
effort to protect those tubes from chloride attack, which occurs when the
chlorides deposited against the tube metal and sealed in by other ash
deposits became hot enough to decompose under the reducing conditions
-------
34
existing within the deposit, thus liberating chlorine which attacks the
tube metal.
As already stated, the alumina covering over the lower one third
of the first pass was successful in protecting those wall tubes, but in
July, 1975, immediately above that coating, a tube began to leak in Boiler
2 after 20,830 hours of operation. Three weeks later, a similar leak
appeared in Boiler 1. Up to that time, no routine checks had been made of
tube thickness. After that experience, checks have been made twice a year
at specific locations throughout the boiler. The wastage rates in the
first and second passes now range between 0.1 and 0.2 mm per year (0.004
to 0.008 in).
In retrospect, it now appears that the tube wastage was caused by
the following:
• High refuse input rates
• High heat value of refuse
• Uneven distribution of air and combustion
• Excessive soot blowing.
Originally, each boiler was equipped with 21 soot blowers. There
were two sets in the first pass. Although the plant is for district
heating only (hence, does not need high-temperature steam), a small
superheater was placed in the third pass to generate superheated steam up
to 300 C (572 F) for soot blowing only. When the soot blowers were not in
use, the superheated steam was condensed in a heat exchanger in the boiler
drum. The soot blowers thus were assured of dry steam so as to avoid any
erosive impact on the boiler tubes by water droplets. However, they
probably cleaned the tubes too well and too often with the result that the
bare tubes were exposed to corrosion and probably erosion. In 1971*, it had
been first noted that the first pass blowers were cleaning exceptionally
well. Accordingly, 11 of the 21 blowers have now been removed and the 10
remaining are used once per shift.
-------
35
Another change was to add more refractory coating above that
originally in the first pass. That was done in three successive steps
until the coating extended upward to cover the lower two thirds of the
first pass water-tube wall.
Figure 11-13 shows more changes that were made at GRAAB expense
to reduce tube wastage. The 18 sidewall air jets on each side just below
the wall tube header were blocked and replaced by downward angled jets in
front and back. Also, a rear nose formed of refractory-covered tubes was
added to direct the flame flow away from the rear wall. A sloping dotted
line above that rear nose shows how the slope of the tubes was later
modified to discourage buildup of loose ash deposits. Also, later the
location of the rearwall jets was moved farther forward toward the top of
the nose. The first rear wall nose was installed in Boiler 2 in December,
1975 (Week No. 48). The second was in Boiler 1 in March, 1976 (Week No.
10). The third was in November, 1976 (Week No. 46).
These measures plus the apparent reduction in refuse heat value
have reduced the tube corrosion rate to a point where plant staff
estimates that 30,000 hours of operation can be expected before some tube
replacements may be needed.
The cost of the boiler-furnace repairs and modifications in 1975
was about 5 million skr ($1 million). Ordinarily the staff expects repairs
to cost 10 skr/tonne.
Some wastage has occurred in the roof tubes of both the first and
second pass. This is being countered by a sprayed-on coating of silicon
carbide about 8 mm (0.31 in) thick. The same coating has been sprayed
opposite the soot blowers in the second pass. The durability of this
coating appears good after 1 year but has not yet been fully determined.
Ten sections of alloy-clad steel tubes are being tried in the
upper middle position of the wall of the second pass. These "sandwich"
tubes, made by Sandviken, have a wall thickness of 7.1 mm (0.28 in) coated
with an extruded stainless steel layer 1.6 mm (0.063 in) thick. Although these.
tubes cost 10 times as much as carbon steel tubes, experience with an
-------
-------
37
entire pass formed of these tubes at the Hogdalen plant built by Vereinigte
Kesselwerke south of Stockholm indicates that for conditions at that plant
they are worth it in minimizing tube wastage.
To monitor first pass gas temperature, thermocouples have been
placed about 7 m (23 ft) above the grate.
In the third pass which contains the boiler convection sections
and superheater, some tube erosion by soot blowers has occurred. This was
first countered by means of alloy half-round shields 1 mm (0.04 in) thick
made of Swedish steel designated 23-43. The shields were tack welded to
the tubes directly opposite the soot blowers. For simplicity, these were
later replaced by alloy angle irons strapped to the tubes. The angles are
made of 20 percent chromium and 10 percent nickel steel. This material
costs 40 skr/kg ($3.60/lb). They are fully successful in protecting the
tubes from soot-blower action and appear to survive about 6 months before
needing replacement.
Second Pass
All of the wall coatings, roof coatings, and convection-bank
shielding have impaired somewhat the total boiler heat absorption. To
counter this loss, it is planned shortly to install in the second pass
three vertically suspended plattens of water tubes to increase heat
absorption in that pass
Furnace Heat Release
Von Roll considers the entire furnace and first pass as effective
combustion volume which it estimates at 310 m (3,336 ft^). However, if
only that two thirds of the pass which is now refractory coated is
considered as part of the combustion volume, we estimate this volume,
together with the furnace, is 263 m3 (2,830 ft3). In this smaller volume,
with 300 tonnes (330 tons) per day being burned having a lower heat value
of 2,500 Kcal/kg (4,500 Btu/lb) (10,467 kJ/kg), the volume heat release
rate is approximately 118,821 Kcal/m3-hr (13,325 Btu/ft3) (498
-------
38
mJ/m -hr). These are moderately high heat release rates.
Figure 11-12, discussed earlier, showed some evidence of slag
accumulation on the refractory walls. As changes were made in wall-tube
coatings and secondary air direction, this slag appeared to accumulate
higher up on the walls. Some thought is being given to the possible use of
air-cooled wall blocks low in the furnace to help alleviate this problem.
i
Superheater
As explained before, the only reason for a superheater in this
heating plant is to provide dry 300 C (572 F) steam for the soot blowers.
It is formed in two in-line banks of 35 tubes of carbon steel designated
as composition 35.8. These tubes are 32.8 mm (1.25 in) in diameter and 3
mm (0.118 in) thick. The two banks are located in the lower portion of the
third pass just after the first convection bank.
Some erosion of the superheater tubes was caused by fly ash
concentrating against the wall of the third pass. This has been countered
by steel shields on the tubes where they pass through the wall.
Boiler
The three boilers are of the Eckrohr type built by Generator AB
of Gothenburg under license from Dr. Verkauf of Berlin. Rated steam
capacity is 52.5 tonnes/hr (115,500 Ib/hr) of saturated steam at 22 bar
(313 psia) (2,157 kPa). Overall height is 13 m (42 ft), width is 4.5 m
(14.8 ft), and depth is 15-5 m (51 ft). There is no economizer.
Primary Air
Originally there was a steam-to-air preheater and a tubular flue-
gas to air preheat. The steam to air preheater has been removed in 1974-75.
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39
The tubular flue gas to air preheater will be removed, the first unit (No. 3)
in September 1978 as the heat value of the refuse is so high that preheated
air is unnecessary.
The primary air is drawn from the front of the tipping floor
and passes the bunker to the inlet. The blowers were made by Svenska Flakt-
fabriken. Maximum blower capacity is approximately 90,000 Nm^/hr (34,718 scfm)
at 400 mm water (3.9 kPa) maximum pressure. The original air preheat was 250 C
(482 F) but this is being discontinued as unnecessary. The air originally went
to five zones under the grates, but the air to the feed grate has been stopped,
so there are now four zones, manually controlled.
Secondary Air
•2
The three secondary air blowers can each deliver 33,000 Nm /hr
(19,420 scfm) at 280 mm water (2.74 kPa).
The estimated velocity in the air nozzles is 35 m/sec (115 fps). As explained
earlier in connection with Figure 11-13, the 18 jets on each side were replaced
by seven jets in the front and nine in the back. All of these are 80 mm (3.1
in) in diameter except three larger ones in the front wall which are 150
mm (5-9 in) in diameter.
The blowers take moist air from above the residue quench channel
to which, in winter, warm air taken from the top of the furnace room is
supplied.
Boiler Water Treatment
City water is used for boiler water makeup. Hydrazine and
trisodium phosphate are added. The makeup is required by blowdown of 9 to
10 tonnes/day (2,378 to 2,642 gals/day) from each boiler plus use of a
total of 15 to 20 m3/day (9,511 to 10,OUO gals/day) for soot blowing.
Every 8 to 12 weeks, the boilers are emptied for maintenance and cleaning
and then refilled. Since the energy of the steam is transferred at the plant
to hot water for the district heating system, there are no problems with
condensate return from outside the plant.
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40
ENERGY UTILIZATION EQUIPMENT
Gothenburg has the largest hot water district heating system in
Europe, most of it heated by oil-fired boilers. The longest pipeline is 20
km (12.3 mi) one way. The steam produced from refuse at the Savenas plant
is used to heat water to 150 C (F) at 14,5 kg/m2 (207 psia) (1.423 kPa).
The temperature drop in the district system is 80 C (176 F) and the hot
water flow rate is about 200 tn-Vhr (881 gpm) in the summer and 700 m^/hr
(3083 gpm) in the winter.
Table 11-2 shows the monthly results.for 1976 on production and
utilization of the energy from refuse as published in the GRAAB Annual
Report. Figure 11-14 from the same report shows the monthly trends in heat
recovery and utilization.
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41
TABLE 11-2. ENERGY PRODUCED BY SAVENAS PLANT IN 1976
(Courtesy GRAAB)
(2)
January
February
March
April
May
June
July
August
September
October
November
December
Total
Electrical
Refuse
Quantity
Tonnes
20,500
18,900
21,900
21,600
21,400
21,000
17,000
19,800
22,500
21,600
22,200
21,100
249,500
Equivalent
(1) Includes about 15
Heat (1)
Recovered
Gcal
28,300
27,700
33, 4 JO
31,800
31,900
26,400
26,400
25,900
31,900
29,100
28,900
33,400
355,100
(413,000 MWh)
Heat
Utilized
Gcal
23,300
23,900
27,600
22,100
14,700
9,900
7,900
13,700
19,000
19,600
22,600
28,500
232,800
(271,000 MWh)
percent as internally used heat.
Proportion
of Heat
Utilized
Percentage
97
99
97
82
54
44
35
62
70
79
92
98
77
(1 Gcal =
(2) Utilities consumed:
1.163 MWh)
• Industrial Water - 0.64 m /tonne waste
• City Water - 0.26 m /tonne waste
• Electricity - 13,300 MWh; 53 KWh/tonne waste
• Residue Disposed - 73,000 tonne
• Residue Disposed - 29.3 percent of weight of waste
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42
I
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Energy to district heating system.
Unused heat sent to air-cooled condensers.
FIGURE 11-14.
MONTHLY TREND FOR 1976 OF HEAT PRODUCTION
AND UTILIZATION. (Courtesy GRAAB)
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43
POLLUTION CONTROL EQUIPMENT
The three electrostatic precipitators were built by Svenska
Flaktfabriken for a flow rate of 100,000 Nm3/hr (58,850 scfm). Flow model
tests were not used in the design. Average velocity was 1.15 m/sec (3-8
fps). Particle residence time was 4.8 sec. There are two fields.
When the precipitators were tested in 1973, the guaranteed
emission limit of 150 mg/Nnr (0.0*11 gr/scf) corrected to 10 percent CO
was exceeded. Accordingly, the manufacturer provided an additional smaller
precipitator besides the three others to which a portion of the gas is
bypassed. The result is lower velocity, longer residence time, and the
o
combination now meets the 150 mg/Nm design limit. For this size of plant,
the allowable legal limit is 180 mg/Nm3 at 10% C02 and dry gas.
Regulations require that the precipitators be tested twice per year.
Some corrosion has been found near the top of the last field
caused by excessive temperatures. Attempts are made to hold it to 250 C
(482 F), but at times it reaches 300 C (572 F). Hopefully the planned
installation of additional heat absorbing surface in the second pass of
the boilers will help to reduce the precipitator temperature (These
installations are ordered for units and operation start is expected in
November 1978).
Chimney
Figure 11-15 shows the unusual square concrete chimney 120 m (394
ft) tall, which contains three mineral-wool insulated corten-steel flues,
1.6 m (5.25 ft) in diameter. There is room for another flue if the fourth
boiler is added in the space provided in the plant. The chimney also
contains a two-passenger industrial elevator which facilitates the
testing or flue gas and changing of aircraft warning lights from platforms
located every 20 m (65 ft) within the chimney. Slight corrosion has been
observed in welds at the top.
Figure 11-16 shows a view of a nearby residential area from the
top of the chimney. The interior of the top of one flue is visible at the
left. A very thin deposit of fine, white ash coats the interior.
-------
FIGURE 11-15. UNUSUAL SQUARE CHIMNEY (Battell- Photograph)
-------
45
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46
Wastewater Discharge
There is no wastewater discharge from the plant except sanitary
waste water. Process water from the quench tank and slaggunker is collected
in a pump pit and recirculated to the hot quench tank.
Noise
To suppress the noise of the large fans which supply air to the
air-cooled condensers, they are enclosed in perforated louvered walls.
This has reduced the noise level 100 m (328 ft) from the plant from 58 to
50 dB. Noise regulations now for new plants require M5 dB(A) in the day
and 35 at night.
Residue Disposal
The new Tagene landfill which receives the residue has a clay
base from which drainage is collected and piped to the city wastewater
treatment plant. When the system was planned, there were tentative plans
for metal recovery from the residue. The planned metal recovery has not
been implemented to date.
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47
POLLUTION CONTROL ASSESSMENT
The clean appearance of the plant and the data indicate that it
is achieving a high degree of environmental acceptability in its
operations. By achieving its design particle emission limit of 150 mg/Nm ,
(9.066 gr/scf)it is well within the 180 mg legally allowed for furnaces burning
over 15 tonnes/hr (16.5 tons/hr). Smaller plants are allowed up to 250 mg/Nm3
(0.109 gr/scf).
A new regulation of the national environmental control agency,
Statens Naturvord Verket (SNV) is that if a plant is emitting more than 40
mg/Nm of total acid, equivalent, studies must be undertaken to seek
feasible means for control. The acid equivalent emissions from Savenas
were not stated.
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48
EQUIPMENT PERFORMANCE ASSESSMENT
The system is achieving its goals of useful energy recovery while
disposing of the industrial and community solid wastes from 670,000
inhabitants in nine communities. Various equipment problems have been
encountered as already described and as solutions have been found, overall
performance is improving. Final costs per unit of waste handled have
increased due to inflation and equipment modification.
Table 11-3 summarizes the plant input and output in 1976. The
refuse monthly input data are a few percent lower than those shown in the
previous Table 11-2, apparently because the plant receipts did not include
some bulky noncombustibles that entered the system but were diverted from
the plant because they had no fuel value.
The total length of time that each unit operated for the year
corresponds to the following availabilities of total houres per year on 7-
day week plant operation:
Unit 1 76 percent
Unit 2 84 percent
Unit 3 72 percent
These are typical availabilities for this type of plant.
The heat utilized—235,869 Goal—amounts to 0.9725 Goal/tonne of
refuse (3-508 M Btu/ton). Assuming the current estimated average heat
value of 2,350 Kcal/kg, this represents a final annual use of 41.4 percent
of the potentially available energy in the refuse. Assuming a
boiler-furnace efficiency of 70 percent, this corresponds to an effective
use of 59 percent of the energy generated as steam. As seen in Figure
11-14, introduced earlier, a significant block of the energy liberated
must be dissipated in the air-cooled condensers in the 4 months May
through August because little district heating is needed then.
-------
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-------
50
Table 11-H summarizes the plant performance for the 3 years,
1974-1976. The major changes to the water-tube walls and secondary air
system in 1975 caused a loss of operation, particularly with Unit 2. All
of the units increased operation in 1976, particularly Unit 2, which is a
hopeful sign that many of the early problems have been solved.
-------
51
TABLE 11-4. SAVENAS ANNUAL RESULTS 1974-1976
Furnace start-up: 1972
Capacity: t/24 h 3 x 300
Operating Personnel
Day Personnel
Shift Personnel
Total
Refuse Fired
Residue
Operating Hours
Furnace 1
Furnace 2
Furnace 3
Total
Availability
Steam Production
Steam Production/t Refuse
Heat Supply
Power Consumption x 1000
Power Consumption/t Refuse
Water Consumption
Total Water Consumption
Industrial Water
Water Consumption/t Refuse
Boiler Feed Water
tonne
tonne
h
h
h
percent
tonne
tonne
Gcal
kWh
kWh/t
m3
m3
m3/t
m3
1974
22
20
42
214,885
66,133
6,242
5,700
5,852
17,794
67
663,906
3.09
178,922
10,248
47.69
217,660
185,091
1.01
32,569
1975
28
20
48
187,319(1)
56,165
5,484(2)
4,751
6,035
16,270
62
586,668
3.13
184,068
10,537
56.25
173,963
141,698
0.93
32,265
1976
242,536
6,686
7,360
6,351
20,397
77
771,995
3.18
235,869
13,296
54.82
186,110
158,791
0.77
27,319
(1) Total stop about 15 days.
(2) Boiler revision and repair.
-------
52
PERSONNEL AND MANAGEMENT
Mr. Bengt Rundqwist, the Plant Director, reports to the Board of
GRAAB. He prepares the agenda for the Board's working committee which
meets about twice per month. His total staff in 1975 is 48. There are five
shifts, four workers per shift: foreman, crane operator, furnace man, and
control room operator. Formerly, the work-week for shift workers was 40
hours. Now it is 32.3 hours because it is demanding work and requires six
shifts. The maintenance staff works a 40-hour week.
The salary of the shift foreman is 5,600 to 5,800 skr/mo ($1,120
to $1,160 § 5 skr/$), including social benefits. The crane operator earns
4,800 skr/mo. Workers receive free working clothes, special shoes once per
year, subsidized cafeteria service and coffee, and use of the sports club
equipment, maintenance of which costs 3,000 to 4,000 skr/yr. Free classes
and training are provided. The plant participates in a cooperative
education program.
Many workers are recruited from the navy and merchant marine and
nearby refineries. All workers have had 9 years normal schooling. A boiler
operator must have 1 year of special schooling plus 40 weeks of practice.
The workers' union has the right to review all questions that
affect workers before they go to the Board for consideration. If the
planned-for eventual fourth unit is considered, it must have union
approval.
Figure 11-17 shows the spacious control room with comfortable
rest center at rear left.
-------
53
w
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-------
54
ENERGY MARKETING*
The entire energy output is hot water which is supplied to the
large district heating system which serves about 200,000 flats and a
nearby new hospital. The bulk of the 660 Gcal/h (2,620 G Btu/h) (2,763
GJ/h) produced for the system comes from the exhaust of back-pressure
turbo-generators powered by oil-fired boilers.
In winter months, as seen earlier in Figure 11-14, the Savenas
plant sends about 23,000 Gcal/mo to the system, an average of about 32
Gcal/h (127 G Btu/h) (13*1 GJ/h).
The Savenas plant wholesales the energy to the district heating
system at about 40 skr/Gcal ($2.02/106 Btu) (9-55 skr/GJ) (0.03^
skr/kw-hr thermal) § 5 skr/$. The retail price of this energy delivered to
the customers is about 60 skr/Gcal ($3-03/10 Btu).
Ten years ago in 1967, the system purchased 1 percent sulfur, No.
5 oil for 57 skr/m3, about 63-3 skr./tonne ($.04/gal). In 1976, it had
o
increased to 450 skr/nr or 500 skr/tonne ($.34/gal § 5 skr/$).
The total heating system serves 200,000 flats each of which
s 100 m2 (1 ,076 ft
calculated from the following:
2 2
averages 100 m (1,076 ft ) in living areas. The monthly bill is
Cost of heat = 0.129 x W x B + 18,000 E x -—-
in which
W = energy, Goal
B = oil cost, skr/m
E = capacity of the individual heat exchanger, Gcal/hr
k = cost of living index which was 400 in late 1977.
* To repeat, this report uses 1975 to 1977 expense and revenue figures @
5 skr/$.
-------
55
2
For a 100 m flat, the value of E is about 0.085, which is based on a heat
2 2
load of 0.085 Mcal/h-m (31-3 Btu/h-ft ). Thus, the maximum monthly cost
to heat a flat if the heat operated at full capacity all month would be
3.1I11* skr ($682 § 5 skr/$). Even operated at half capacity this would be
$3111/mo.
In arranging to serve a suburb city (BERGSJO), 1 and 2 km (0.6 to
1.2 mi) away, the Savenas plant paid one third of the cost, 3.5 x 106 Skr
skr ($700,000), for the pipeline that had to go through hilly terrain.
-------
56
ECONOMICS
Construction of the Savenas plant, which was completed in 1971,
cost about 98 million skr ($24.5 million § 4 skr/$) not including the cost
of land which is leased for 105,000 skr/year. The rest of the waste
handling system, including the transfer stations, the new Tagene landfill,
and the 30 transfer trucks, cost an additional 22 million skr ($5-5
million § 4 skr/$).
In 1976, the approximate operating costs including depreciation
are shown in Table 11-5.
For the 1976 input of 242,536 tonnes, this results in an
operation and maintenance cost, including depreciation, of 84.5 skr/tonne
($l6.90/ton). About one fourth of this, $4.64, is for interest and $2.14
is for depreciation.
An added one-time cost in 1976 was 3.5 million skr paid to the
district heating system for a one-third share of the cost of a 1.5 km
heating line to Bergsjo.
Revenues
The operating budget (expected results) for 1977 is shown
in Table 11-6.
-------
57
TABLE L-24. OPERATING BUDGET FOR 1977 AT GOTHENBURG
COST ALLOCATIONS (Estimated for a Waste
Quantity of 250,000 ton)
Annual Cost
1000 skr
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Capital costs
Administration
Incinerator, operating cost
Incinerator, repair and maint. cost
Transfer stations, operating cost
Transfer stations, repair and maint.
Landfill, operating cost
Landfill, repair and maint. cost
Refuse hauling
Residue hauling
Total Costs
Income from district heating
Income from tipping fee
15
2
6
5
1
cost
2
35
8
27
,171 (18,721)
,119
,558
,888
,411
710
679
232
,208
685
,661 (39,211)
,161
,500 (31,050)
Cost per tonne,
skr /tonne
60.
8.
26.25
23.55 49.
5.65
2.85 8.
2.70
0.95 3.
8.
2.
142.
32.
110.
70
45
80
50
65
85
75
70
70
00
(74.9)
(156.9)
(124.2)
Note: The data are from the annual report for 1976 "Aresredovisning"
which served as the basis for the 1977 budget.
Conversion example: 2,100,000 S.Kr. 1 U.S. $ 1 Year 1 Tonne = $1.91/Ton
1 Year 4.127 S.Kr. 242,536 Tonnes 1.1 Ton
i.e., Multiply all S.Kr. numbers by .0000009082316
-------
58
FINANCE
The cost of the system in 1972 was about 120 million skr ($48
million § H skr/$). In 1969, the communities represented in GRAAB raised
H.5 million skr ($1.125 million § U skr/$). On the basis of this
commitment, GRAAB borrowed 90 million skr for 20 years from a major
pension fund at 7-3 percent interest. After 10 years, this interest can be
adjusted depending on interest trends at that time. Communities which
borrow such large sums must first have approval of the Swedish government.
Because the final cost of the system nearly doubled over the
early estimates, additional money was borrowed on similar terms in order
to complete construction.
The financial condition of GRAAB is published in detail in the
Annual Report.
-------
59
REFERENCES
(1) Feindler, Klaus S., "Refuse Power Plant Technology - A State of
the Art Review", Paper presented in New York, December 16, 1976,
to the Energy Bureau, Inc.
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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, So. 4, Published by the International Monetary Fund.
18281
*OS. GOVERNMENT PRINTING OFFICS: 1979 620-007/6317 1-3
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