STEAG'S OPERATING EXPERIENCE WITH FLUE GAS DESULFURIZATION PLANTS

摘要

STEAG is an independent power producer in Germany and is operating more than 5,400 MWe mainly bituminous coal fired power stations. As a result of the 1983 Large Combustion Plants Directive (LCPD) about 46,000 MW of thermal power station capacity in Germany has been equipped with desulfurization facilities to date. Small furnaces of between 35 and 110 MW will also have been equipped with such facilities. Existing and new units in East Germany mostly lignite fired must be retrofitted until July 1996. Approximately 66% of FGD capacity in the unified Germany is for bituminous coal fired plants (Steags share 13 %), 32.5 % for lignite and 1.5 % for residual oil. Wet desulfurization processes, and in particular limestone scrubbing with gypsum as the end product account for greater than 90% of the installed scrubber capacity. The operation of these facilities, has reduced the annual SO_2 emissions in West Germany from 1.5 million tons to 0.2 million tons. Due to the enactment of the environmental regulations program all of STEAG's power stations are fitted with flue gas cleaning installations for SO_2-abatement and NOx-reduction. According to the Large Combustion Plants Directive (LCPD) the SO_2-concentration in the treated flue gas must be below 400 mg/Nm~3 and the SO_2-removal efficiency above 85 %. Time constraints for LCPD compliance, the existing experience and economic benefits resulted in major use of commonplace, wet lime/limestone scrubbing, but a number of other FGD processes have been applied in Germany. These include the Wellman Lord process, wet ammonia scrubbing, dry activated-carbon absorption process and dry limestone injection. Moreover, a number of semi-dry type scrubbing systems using spray dryers or circulating-fluidbed scrubbers have been installed. Many technical problems have caused set backs on the Walther(Ammonia)-, Wellman Lord- and Activated-carbon process and therefore limited the number of installed facilities. Earliest wet FGD installation in STEAG's power stations were slip stream facilities with treatment of 30 - 60 % of the total flue gas volume. Such plants began operation at Bergkamen in October 1981 and at Voerde in October 1982. This report concentrates primarily on the operating experience gained with the wet limestone/gypsum desulfurization process. Until today STEAG has gained operating experience from more than 800,000 FGD operating hours. STEAG's experience is more diverse than that from most other German power plant operators, because the coal quality used in STEAG's power stations varies in a broad range. Approximately 40 % of the units are fired with high grade (calorific value 25-30 MJ/Kg and low sulfur content) and 60 % of the units are fired with low grade coal (calorific value 19-22 MJ/kg, middling coal) with high sulfur ash- and chloride-content, resulting in SO_2 flue gas concentrations up to