Spittelau.The thermal waste treatment plant.

Spittelau.The thermal waste treatment plant.

distant, with district heating.With its total output of 460MW the Spittelau plant is thesecond-largest generator inthe City of Viennas districtheating network.

The thermal waste treatmentplant integrated in the workshas a throughput capacity ofmore than 250,000 tonnes perannum and is part of the sup-ply network, feeding in anannual average of 60 MW(basic load coverage).

In addition, five further gas- orgas/oil-fired hot water boilerscan produce 400 MW of ther-mal output to cover peakdemand.

The ongoing updating to thestate of the art in flue gascleaning technology hasmeant continuous modernisa-tion of the thermal waste

treatment plant with a flue gas wet scrubber (1986/1989)and a deNOx and dioxin destruction system (1989).

History of the Spittelau thermal waste treatment plant.In 1969 the newly-foundedFernwrme Wien GmbH (for-merly Heizbetriebe Wien) wascommissioned by the City ofVienna to secure the citysdistrict heating supply. Withthe operation of the Sipttelauthermal waste treatment plantwhich was under constructionat that point in time Fern-wrme Wien also assumedresponsibility for the orderlydisposal of municipal wastes.

Today, the successively expan-ded district heating network isfed by a total of ten generatingplants with an installed outputof more than 2,800 MW, andits pipeline length of over1,000 km makes it one of thelargest in Europe.

More than 262,000 dwellingsand over 5,300 industrial con-sumers are currently suppliedwith district heating for spaceheating and water heating. The Spittelau thermal waste treatment plant was erected at its current location in orderto supply the new General Hospital, some two kilometres

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At the time of the modernisa-tion of the Spittelau thermalwaste treatment plant thefamous painter and architectFriedensreich Hundertwassercompletely redesigned thefaade of the whole works.The previously sober, func-tional building became aninternationally unique, spec-tacular work of art: a succes-sful example of a harmonioussymbiosis of technology, eco-

logy and art together with an important contribution to thereduction of the optical environmental pollution in theurban living space.

Friedensreich Hundertwasser on the design of faades:Einstein said: if the formula is not neat, it can also not becorrect. That is precisely the opposite of what the functionalists, rationalists and technocrats preach. Todaywe are experiencing the triumph of rationalism and thedepressing, aggressive and soulless monotony and are confronted simultaneously with nothingness. The sins areparticularly prominent in industrial construction. More sinned-against than the cities were the people who spendmore time in sterile, inhumane industrial buildings than at

Friedensreich Hundertwasser.home. The example of the Spittelau thermal waste treat-ment plant is proof that, rather than the existing rational,impersonal architecture under which we all suffer, a creativespirit in harmony with nature can be inspired. It should be astatement against the anonymity in our cities. I know, thatfuture-oriented action demands courage to implement thatwhich is still derided and opposed by the establishmenttoday.

In the meantime, a familiar Viennese sight,widely admired by tourists and locals alike:

the Spittelau thermal waste treatment plant.

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Layout of the Spittelau thermal waste treatment plant.

Firstly the delivered waste arrives at the waste bunker. Twobridge cranes feed the feeding hoppers (filling shafts) of theplant. A dispatcher thrusts the waste onto the grate of thecom-bustion chamber. From the overhead stream boiler theflue gases flow through an electrostatic precipitator and athree-stage flue gas scrubber into the catalytic deNOx anddioxin destruction system. They finally leave the works viathe chimney. The in-house waste water treatment plant cle-anses the waste water resulting from the flue gas cleaning process. The remaining solid residues are disposed of in anorderly manner.

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Waste bunker

Feeding hopper

Grate

Combustion chamber

Waste heat boiler

Wet slag remover

Electrostatic precipitator

Flue gas wet scrubber

(two-stage)

Fine dust separator

(electrodynamic Venturi)

SCR deNOx system

Chimney

Magnetic separator

Slag bunker

Filter ash silo

Emission control

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Waste delivery.

The main delivery of Viennese municipal waste (domesticwaste and industrial wastes similar to household waste) tothe Spittelau thermal waste treatment plant takes placefrom Monday to Friday between 7.00 am and 3.00 pm. Up to250 delivery vehicles pass over one of the two weighbridgesdaily. After weighing, they empty their contents at one ofthe total of eight dumping stations into the waste bunkerwhich has a capacity of some 7,000 m3.

Following thorough mixing in the bunker in order to keepthe heating value constant, two bridge cranes, each ofwhose polyp grabs have a capacity of some 4 m3, transferthe waste to the two incinerators.

Orange-coloured transporters of Vienna City Council (the 48er) unloading municipal waste

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Thermal waste treatment.The thermal waste treatment plant consists of two incinera-tors, each with a flue gas cleaning system as well a commondeNOx and dioxin destruction system that serves both in-cinerators. Connected to this is a treatment plant for thewaste water from the flue gas wet scrubber.

Via the feeding hopper and the hydraulic dispatcher thewaste is moved from the bunker to the grate at the lowerend of the combustion chamber. Up to 17 tonnes of wasteper hour can be thermally treated on the sloping, 35 m2 areaof the two-track reverse-acting stocker grate.

During the start-up and run-down phase of a boiler two 9 MW gas burners ensure the necessary combustion chamber temperature and thus the burn-off of the fluegases required by law. In normal operation the use of thegas burners is not necessary: the average waste heatingvalue of 9,500 kJ/kg is more than sufficient to ensure self-combustion of the waste.

The crane transports the waste to the feeding hopper

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Waste bunker

Feeding hopper

Grate

Combustion chamber

Waste heat boiler

Wet slag remover

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Annual energy balance 2006of the Spittelau thermal waste treatment plant

Flue gas losses126,000 MWh

Waste water losses67,900 MWh

In-house heat demand5,700 MWh

Net heat479,000 MWh

Natural gas for deNOx plant50,400 MWh

Natural gas for auxiliary firing3,400 MWh

Natural gas252,607 t waste665,300 MWh

Effective energy 525,200 MWh

In-house power demand22,600 MWh

Net current17,900 MWh

27 % Losses69 % Energy output

4 % Energy demand

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District heating and power generation.Waste combustion creates hot flue gases. These give offtheir heat content to the boiler heating surfaces of the incinerators. The two incinerators generate a total of 90 ton-nes of saturated steam (33 bar) per hour. For power genera-tion this steam volume is first reduced to 4.5 bar in a back-pressure turbine. In the downstream heat exchanger groupthe return water from the district heating network is re-heated by condensation.

The non-combustible waste components (slag) that arriveat the end of the grate fall into the wet slag remover. Fromthere the cooled slag is transported to the slag bunker by aconveyor belt, with ferrous scrap being removed before-hand for recycling by overhead electromagnets. In thewaste bunker there is constant negative pressure caused bythe extraction of the necessary fresh air for the combustionprocess, thus minimising the escape of odours and dust viathe dumping stations into the ambient air. In addition, theuse of a complex combustion control system which has beendeveloped over many years ensures an optimum combustionprocess on the grate and thus maximum burn-out of slagand flue gas.

In an average year large amounts of power are generatedfrom domestic waste and household-like wastes: approxi-mately 6 MW of power to meet in-house requirements andfeeding into the public grate as well as 60 MW district heating. This amount of energy is equivalent to a space heating equivalent of some 60,000 dwellings with 80 m2

floor area.

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Waste bunker

Feeding hopper

Grate

Combustion chamber

Waste heat boiler

Wet slag remover

1st heat exchanger

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Flue gas cleaning. Dust separation and wet scrubbing.

The thermal waste treatment plant has had a highly effi-cient dust separation system (electrostatic precipitator)since initial commissioning in 1971. This was augmented in1986 by a two-stage flue gas wet scrubber with attachedfine dust separator (electrodynamic Venturi). With themodification of these three treatment stages as well as theinstallation of the Europes first SCR deNOx system down-stream from a wet scrubber in 1989 the Spittelau plant wasthe international pioneer in the field of flue gas cleaningand emission reduction relating to thermal waste treat-ment. The emission limit values in accordance with theWaste Incineration Directive that apply today relating todomestic waste-fired steam boil