Simplified efficient process for reducing NOx, SOx, and particulates

摘要

The removal of SOx and particulates, and preferably also NOx, from the combustion gases of a large boiler, is simplified while efficiency is improved. In a primary treatment zone, a slurry comprising an alkaline SOx-reducing composition and preferably a nitrogen-containing composition effective to reduce NOx, is introduced into combustion gases at a temperature of from about 900 DEG to about 1300 DEG C. The gases are cooled by initial contact with steam-generating means, and then by contact with an gas-to-gas heat exchanger. Cooled gases are then subjected to a secondary treatment in which they are first humidified and further cooled by introduction of a water spray or aerosol to reduce the temperature to 100 DEG C. or below. Contact between the SOx-reducing composition and the humidified gases is maintained for a reaction period of at least 2 seconds. Particulate solids are then separated from the gases with a fabric filter. The cleaned gases are reheated by the gas-to-gas heat exchanger prior to discharge to the atmosphere. Reductions of SOx of greater than 80% are achieved, preferably 90 to 95%.