Abstract A system and process is described for treating the effluent chemicals from an air pollution control system for fossil fuel fired equipment. The air pollution control system involves the addition of magnesium-containing additives such as dolomite to the equipment followed by the wet scrubbing of the flue gases resulting in the reaction of the sulfur oxides with the additive. The treatment involves the addition of ammonium hydroxide to the solution removed from the scrubber to convert the soluble magnesium sulfate to soluble ammonium sulfate and precipitate magnesium hydroxide. The ammonium sulfate solution is removed from the magnesium hydroxide and either used for fertilizer or further reacted with calcium oxide to precipitate calcium sulfate and form ammonium hydroxide which is recycled for reaction with the scrubber effluent.
A method as recited in claim 1 wherein said hydroxide material in step (e) is calcium hydroxide and said precipitated sulfate is calcium sulfate.
Claim 2
Dependent Claim
25 words
A method as recited in claim 1 wherein another portion of said magnesium sulfate solution together with additional makeup water is employed for wet scrubbing.
Claim 3
Independent Claim
228 words
A method of reducing pollution caused by the combustion of sulfur-containing fuel comprising the steps of: a. burning said sulfur-containing fuel to form hot products of combustion containing sulfur oxides; b. introducing into said hot products of combustion an additive containing magnesium carbonate and calcium carbonate which decompose to magnesium oxide and calcium oxide when subjected to the heat of said products of combustion which will react with said sulfur oxides; c. wet scrubbing said products of combustion containing said additive with water whereby dissolved magnesium sulfate and precipitated calcium sulfate are formed in said scrubber water; d. separating said precipitated calcium sulfate from said scrubber water containing said dissolved magnesium sulfate; e. recycling a first portion of said separated scrubber water together with additional makeup water for said wet scrubbing; f. introducing ammonium hydroxide into a second portion of said separated scrubber water and thereby reacting said ammonium hydroxide with said dissolved magnesium sulfate to form ammonium sulfate solution and precipitated magnesium hydroxide; g. separating said precipitated magnesium hydroxide from said ammonium sulfate solution; h. reacting said separated ammonium sulfate solution with calcium hydroxide so as to produce an ammonium hydroxide solution and precipitated calcium sulfate; i. separating said ammonium hydroxide solution from said precipitated calcium sulfate; and j. recycling said ammonium hydroxide solution together with additional ammonium hydroxide solution for reaction with said magnesium sulfate solution.