Absorption of sulfur oxides from hot gases

A continuous process for removing sulfur oxides from hot gases containing the same comprising

• (a) providing first and second zones,
• (b) providing a source of an aqueous scrubbing medium containing an absorbent selected from the group consisting of alkali metal carbonates, alkali metal bicarbonates and mixtures thereof,
• (c) passing the hot gas containing sulfur oxides sequentially through said first and second zones,
• (d) withdrawing a stream of the aqueous scrubbing medium containing the selected absorbent from said source provided in step (b) and introducing the stream in a finely dispersed spray into the first zone in an amount to provide an equivalent weight ratio of absorbent to sulfur oxide contained in the hot gas passing therethrough of about 0.8:1,
• (e) contacting the hot gas with said finely dispersed spray and forming
• (1) a substantially water-unsaturated gaseous reaction product of reduced sulfur oxide content and
• (2) a dry powder reaction product containing alkali metal sulfates and sulfides substantially free of unreacted absorbent,
• (f) withdrawing another stream of the aqueous scrubbing medium containing the selected absorbent from said source provided in step (b) and introducing it into said second zone into intimate contact with the hot gas passing therethrough in an amount to provide an equivalent weight ratio of absorbent to sulfur oxide of at least 1.5:1 to form
• (1) an aqueous solution of alkali metal sulfates, sulfides, and unreacted absorbent, and
• (2) a gaseous reaction product substantially free of sulfur oxides,
• (g) returning at least a portion of the aqueous solution formed in (f) to said source of aqueous scrubbing medium,
• (h) discharging the gaseous reaction products substantially free of sulfur oxides from said second zone,
• (i) adding additional absorbent to said source (b) in about the stoichiometric amount required to react with all the sulfur oxides initially contained in the hot gas being processed, and
• (j) adding makeup water in an amount about equal to that required to cool the hot gas entering the process to its temperature of adiabatic saturation.

A continuous process for removing sulfur oxides from hot gases containing the same, comprising the steps of:

• (a) introducing the hot gas containing sulfur oxides into a first zone;
• (b) introducing into the first zone a finely dispersed aqueous scrubbing medium containing an absorbent from a source to be provided in step (g);
• (c) contacting the hot gas with said aqueous scrubbing medium and forming (1) a substantially water-unsaturated gaseous reaction product of reduced sulfur oxide content and (2) a dry powder reaction product containing alkali metal sulfites and sulfates, and substantially free of unreacted absorbent;
• (d) transferring the gaseous reaction products from the first zone into a second zone;
• (e) introducing into the second zone an aqueous scrubbing medium containing an absorbent selected from the group consisting of alkali metal carbonates, alkali metal bicarbonates and mixtures thereof, said absorbent being provided in an amount to provide an equivalent weight ratio of absorbent to sulfur oxide contained in the gaseous reaction product transferred from the first zone of at least 1.5:1;
• (f) contacting the gas in the second zone with said aqueous scrubbing medium and forming (1) an aqueous solution of alkali metal sulfates, sulfites and unreacted and partially reacted absorbent, and (2) a gaseous reaction product substantially free of sulfur oxides;
• and
• (g) utilizing a portion of said aqueous solution formed in the second zone as said source of aqueous scrubbing medium introduced into the first zone, said aqueous solution being introduced into the first zone in an amount to provide an equivalent weight ratio of absorbent to sulfur oxide contained in the gas introduced therein of about 0.8:1.