Das Projekt "Energiesparendes Rauchgasentschwefelungsverfahren" wird vom Umweltbundesamt gefördert und von Walther & Cie AG durchgeführt. Objective: The development and construction of a Walther flue gas desulphurization demonstration plant to prove that this process permits the reheating of cleaned gas as well as the spray drying of the ammonium sulphate solution produced during the scrubbing sequence. By the reheating of scrubbed flue gases using a regenerative heat exchanger, +/- 1,800 Kg/h of fuel oil is saved under full load operation. General Information: The flue gas desulphurization plant consists of the following systems and/or main components: - ammonia storage and evaporator station; - flue gas scrubbing and reheating; - oxidization and spray drying; - product treatment. The system has other important advantages apart from those already noted: - no waste water; - production of the marketable nitrogen fertilizer ammonium sulphate. The Walther desulphurisation system is connected to a new 475 Mwe coal fired plant for combined heat/ electricity production, and is located in the Grosskraftwerk (Mannheim). The system is designed for a flue gas SO2 content of 150-200mg/m3 and for demonstration, 50 per cent of one boiler's flue gas (750,000m3/h) will be desulphurized. The system consists of a rotating regenerative heat exchanger, two SO2 washing towers, oxidization tank, spray dryer and equipment for treatment of the fertilizer end-product. The heat exchanger serves both to cool and to reheat flue gas entering and leaving the FGD plant. When ammonia is added to the flue gas before entry into the heat exchanger, a reaction occurs in the first washing tower producing ammonium-sulphate-bisulphate. The flue gases are then subjected to another fresh water wash in the second tower to eliminate salt solution particles and any ammonia remaining. Concentrated washing liquid is extracted from the washing circuit of the first washing tower, pumped to an oxidization tank where the ammonium-sulphite and bisulphite are converted to ammonium sulphate. This is then pulverised in a spray dryer by hot flue gases extracted from the boiler off-gas in front of the air heater, and collected in a tank. The product is then sent to a granulator. It is then transferred to a moving-bed dryer, and subsequently sieved, milled and stored in a tank prior to transportation. Achievements: Difficulties were almost exclusively in the conventional part of the plant and related to the 'flowability' of the ammonium sulphate powder. The rubber coated steel scrubbing system consists of two scrubbers arranged in series. In the upper part, the scrubbing solution containing ammonia is injected into the flue gas in order to absorb SO2, which is absorbed in the first scrubber. The second serves to bind the ammonia gas still contained in the flue gas, thus preventing exhaust of gaseous ammonia from the plant. Scrubbing solution PH value in scrubber 1 is 5.6-6.2 and between 4-4.5 in scrubber 2. The scrubbing process is such that SO2/ammonia ratio is over-stoichiometric up stream of the last scrubber so that, due to ...