Abstract: A system for precipitation of pollutants from an off-gas, wherein the off-gas is cooled in a smooth-tube heat exchanger (13). The off-gas flows through a bundle of tubes (19) which extend vertically or tilted inside the heat exchanger. Cold water is introduced at a secondary side connection (43) of the heat exchanger (13). An air stripper (36) and a mist eliminator (26), and an optional electrostatic filter (27), are installed downstream of the heat exchanger (13). In the heat exchanger (13) and the air stripper (36), a portion of the condensable pollutants condenses out and a portion of the water-solubles and solids are precipitated. The system can be cleaned automatically and requires only a small placement area.

Abstract: A steam boiler (2) including a fire tube (21) and convection heating surfaces (22) is preceded by a combustion chamber (30) including a surface burner (34) for high excess air. The combustion chamber (30) and the fire tube (21) are internally thermally insulated (33). The combustion air supply opening (37) of the burner (34) is connected by way of a blower (40) with an exhaust air source (1). A fuel control valve (36) is controlled as a function of the boiler load. A plurality of heat exchangers (47, 48, 49) are incorporated in the flue gas channel (45) following the convection heating surfaces (22). The most upstream heat exchanger (47) is connected on the water inlet side by way of a pump (51) to the water chamber (23) and on the water outlet side by way of a baffle (53) to the water-steam circuit of the boiler (2). With this system it is possible to purify all of the exhaust air from the exhaust air source (1) over a broad boiler (2) load range.

Abstract: The exhaust air from the tenterframe (1) conveyed by a fan (7) is fed as combustion air to the burner (13) of a steam boiler (21). The burner (13) is operated with a variable and high excess of air of .lambda.=1,5 to .lambda.=3,5. The boiler output is regulated by the fuel supply. The excess of air is increased at low boiler load. The boiler exhaust gas is cooled down below the dew point via three heat exchangers (29,30,31). Thus complete combustion of the organic noxious substances in the tenterframe exhaust air and at the same time recovery, which can be readily utilized, of the tenterframe waste heat and a lowering of the fuel requirement of the steam boiler are achieved. The same method is also suitable for purifying the exhaust air from singers.