Ammonia-limestone scrubbing with by-product for use in agriculture

A method of wet flue gas desulfurization comprising the steps of:

• (a) passing a sulfur containing flue gas through a scrubber tower having upper and lower zones separated by a perforated tray;
• (b) injecting an ammonia based liquid reagent into said upper zone of said scrubber tower for desulfurization in said upper zone via said ammonia based liquid reagent;
• (c) collecting a bottoms product in a lower region of said scrubber tower;
• (d) forcibly oxidizing said bottoms product, thereby forming gypsum and ammonium sulfate compounds;
• (e) supplying a calcium based reagent to said forcibly oxidized bottoms product;
• (f) recycling said oxidized bottoms product from said lower region of said scrubber tower and spraying same onto the flue gas for desulfurization in said lower zone of said tower via said calcium based reagent;
• (g) delivering a portion of said oxidized bottoms product to a primary dewatering assembly;
• (h) generating a liquid stream in said primary dewatering assembly containing un-used or under-used said ammonia based reagent and said calcium based reagent and a separate solid/slurry stream containing gypsum and ammonium sulfate compounds;
• (i) returning said liquid stream to said tower and spraying same onto the flue gas for desulfurization in both said upper and lower zones of said tower;
• and,
• (j) concentrating said solid/slurry stream in a secondary dewatering assembly for the subsequent removal therefrom of said gypsum and ammonium sulfate compounds.