System and method for co-production of ammonium sulfate and calcium carbonate from desulfurization and decarbonization mineralized phosphogypsum by ammonia process

Abstract

A system and method for ammonia-based desulfurization and decarbonization of phosphogypsum and co-production of ammonium sulfate and calcium carbonate is disclosed. This system removes over 98% of SO₂ from flue gas, reduces CO₂ emissions by 10-20%, and converts over 95% of calcium sulfate dihydrate (the main component of phosphogypsum) into calcium carbonate usable as cement raw material, while also co-producing ammonium sulfate for fertilizer. Ammonia emissions in the tail gas are less than 10 mg / m³. This invention utilizes waste heat from flue gas to deammonize and desorb ammonia-containing slurry, saving energy required for evaporation and improving mass transfer efficiency during desulfurization and decarbonization due to lower flue gas temperature. By recycling the deammoniation-treated slurry as a washing liquid for escaping ammonia and replacing process water with ammonium sulfate solution to prepare the phosphogypsum, the ammonia escape problem is effectively solved, while reducing energy consumption for subsequent ammonium sulfate crystallization and evaporation treatment by approximately 35%. Employing a structural design similar to traditional limestone-gypsum desulfurization towers, this system achieves a technological upgrade of ammonia-based desulfurization and decarbonization without altering the existing main structure of the desulfurization tower, significantly reducing investment costs for technological upgrades. This invention successfully overcomes the technical pain points of ammonia desulfurization and decarbonization technology, such as severe ammonia escape, large washing water volume leading to high energy consumption in subsequent product processing and high equipment modification costs, resulting in significant energy saving, water saving, emission reduction and increased revenue benefits.

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