Process Economics Program Report 8a
Wet Process Phosphoric Acid
Published: July 1967
During 18 months since the last report there has been an acceleration of the rate of new developments and growth in the wet process phosphoric acid industry. New capacity and production have continued to expand at near-record rates. New processes for phosphoric acid manufacture are appearing and bringing with them a greater understanding of the calcium sulfate crystal system.
Changing markets and costs and a widening sulfur shortage are forcing the wet process phosphoric acid industry to look closely at other raw materials, other products, and other associated or complementary operations. The object of this supplementary report is to recognize and summarize these latest developments in the wet process phosphoric acid industry and, where possible, to provide some indication of their significance relative to existing phosphoric acid plants. New semihydrate and semihydrate-dihydrate processes, as represented by the Tennessee Valley Authority's foam distribution scheme and Singmaster and Breyer's semihydrate-dihydrate variation are evaluated. Phosphoric acid processes based on nitric rather than sulfuric acids have been examined with particular attention to a nitric acid-ion exchange. Recent literature on the recovery and use of by-product gypsum is reviewed, and capital and operating costs are estimated for its conversion to ammonium sulfate. A previous estimate of investment and production costs for the conventional, widely used dihydrate process has been revised.