Page 58 - Waste-to-Energy in the Danube Strategy Region. Challenges and Prospects
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can haul up to 10 m of waste. From here, waste is fed to the grates in three incineration lines
(EVN Abfallverwertung 2015).
Natural gas is used within the start-up phase to achieve the initial temperature for grate
firing (850 C). The waste is then burned on its own at a temperature over 1,000 C, during which
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most of the pollutants are destroyed. The products of the combustion process are flue gas, ash,
and an inert, rock-like slag. The grate is built from movable bars set in an overlapping arrangement
enabling garbage to move slowly across the grate until everything is burned. Throughout this
process, air is injected through the grate bars to promote incineration (EVN Abfallverwertung
2015).
During the fifth phase, flue gas generated during the grate firing phase is processed in the
waste heat recovery boiler, equipped with gas-tight tubing walls designed for constant circulation
of water. The flue gas transfers its heat to the circulating water, generating approximately 260
tonnes of steam per hour. This steam is delivered to the nearby Dürnrohr power plant where it is
used for electricity production. The flue gas is also cooled to 170 C during this process, after
which it is ready to be cleaned (EVN Abfallverwertung 2015).
The last step consists of three cleaning stages: fabric filters, scrubber, and DeNOx system.
The first constitutes a dry cleaning stage using fabric filters to extract dust particles and separate
heavy metals together with dioxins and furans. The filtered ash is stored in silos and later
deposited to landfill. The next stage is wet cleaning wherein hydrogen chloride and sulphur
dioxide are scrubbed from the flue gas by adding a limestone suspension. The resulting
wastewater is subsequently cleaned and discharged into the Danube. The filter cake is deposited,
and the resulting gypsum can be later used in the construction industry. The last cleaning stage,
the DeNOx system, converts NOx gases to steam and nitrogen (two normal compounds in the air)
by adding an ammonium solution. Before the gas is released, it passes through several measuring
points where continuous measurements are taken for dust, hydrogen chloride, sulphur dioxide,
carbon monoxide, carbon dioxide, nitrogen oxides, mercury and mercury compounds together
with total organic carbon (EVN Abfallverwertung 2015).
11 Combustion exhaust gas produced from combustible elements of waste.
Project co-funded by the European Union
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