PREVENTION OF PLUME IN STACK EMISSION FROM SULPHUR DIOXIDE SCRUBBER

摘要

1458057 Removal of sulphur oxides from gases AIR PRODUCTS & CHEMICALS Inc 8 Feb 1974 [26 Feb 1973 12 Sept 1973 2 April 1973] 05911/74 Heading C1A In a process for the scrubbing of combustion gases with aqueous ammoniacal solution for the removal of contained sulphur oxides, the formation of smoke discharged from the stack is reduced or eliminated by controlling the concentration of the components within the scrubber such that the logarithm to the base 10 of the product of the partial vapour pressures of SO 2 , NH 3 and H 2 O does not exceed the value 31À2-(17,300/T) wherein the partial pressure is expressed in millimetres of mercury and T is the absolute temperature in degrees Rankine. The gas is preferably washed with water prior to contact with the ammoniacal scrub liquor to saturate the gas with water vapour and to reduce the hydrogen chloride content to less than 10 p.p.m. The scrubbing is preferably carried out in several stages and the scrubbing liquid is recycled. Prior to discharging the effluent into the atmosphere it is preferably re-heated, suitably to 35‹ to 70‹ F., above the absorption temperature. The gases are preferably also, or alternatively, washed with an aqueous acidic solution, preferably of pH less than 3, prior to discharge of the gases. The acidic solution may suitably be provided by a portion of the solution obtained by water washing of the gas in the initial stage.