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Fernwarme - Thermal Waste Treatment Plant

The following is adapted from the public brochure published by the Spittelau Thermal Waste Treatment Plant visited by Dr. Ophardt in the summer of 2003.

Introduction:

In Vienna, Austria the word "incinerator for solid waste disposal" does not generate the kind of reaction that it would get in the U.S. The Fernwarme Wein is even a tourist attraction because of the abstract and whimsical design by the famous architect Friedensreich Hunderwasser.

In Vienna, much of the water and space heating for 4,400 commercial properties is based upon an interconnected network of 10 heating plants with 900 km of pipes, and is one of the largest in Europe. It is located right in the city in a mixed use neighborhood.

The plant at Spittelau, Fernwarme Wein, was designed to burn municipal waste and provide the heat for New General Hospital about 2 km away. It is the second largest of the heating plants in Vienna, rated at 460 MW. It is designed to burn 250,000 tons of waste per year. The plant is also designed to generate its own electricity and provides 15 MW of electricity to the main electrical grid.

Solid domestic and non-hazardous commercial waste is delivered to the Thermal Waste Treatment plant by 250 trucks daily. The loads are weighed and tipped at 8 docks. The waste is thoroughly mixed before a crane transfers it to one of two incineration lines. The exit gases lines are shown in the graphic on the left by the silver pipes at the bottom of the tall stack.


Incineration:
 
Only during start-up and shut-down procedures is natural gas used to insure a greater than 800 degree Celsius operating temperature. Once started the waste has enough heating value to maintain this temperature.
 
The energy balance sheet is as follows:
Energy output 71%, internal energy consumption 4 %, and losses 25 %.
 
The 850 C flue gas gives off heat to the surfaces of the waste heat boiler to generate steam which is used to generate electricity and the left over heat is further used to heat water for distribution.
 
Flue Gas Treatment:
 
The flue gas is treated with a series of scrubbers to remove ash and other air pollutants.
 
The flue gas is initially cleaned of solid particles by a three stage electrostatic precipitator to remove dust.
 
The gas then enters the first scrubber with water at pH 1 to remove, HCl, HF, residual dust, particle bound heavy metals, and gaseous heavy metals. The second scrubber operates at pH 7 to remove sulfur dioxide.
 
Then the gas is moved through a final electrostatic precipitator to remove the last amounts of dust down to a very small value.

 

 Final deNOx and Dioxin destruction:

The final treatment of the flue gas is in a DeNOx facility. The flue gas is subjected to selective catalytic reduction by mixing with vaporized water-ammonia and heated to 280 C. By passing through three catalytic converter stages, the nitrogen oxides react with the ammonia and oxygen in the flue gas to form nitrogen gas and steam. This also results in the destruction of dioxin. The flue gas is finally released to the 126 meter stack. The emission of residual gases and solids are well below the permissible amounts. A billboard electronic display outside of the plant gives the current emissions to the public.

Solids and Water Waste Treatment:

All waste water from the scrubbers is treated, to removed the solids into something called filter cake, before being released to the Danube River.

All solids (about 600 lbs per 2000 lbs of trash) of slag, iron scrap, and filter cake are further processed. The slag is mixed with cement and used for construction, and iron scrap is recycled to make steel. The filter cake is bagged and transported to Germany as in fill in an unused slat mine.

Conclusion:

In the right environment, it is possible to operate a state of the art incinerator plant that disposes of solid waste, generates electricity and heat, and meets very strict environmental standards.