Process of manufacture of phosphoric acid with recovery of co-products

Abstract

An improved process for the wet-acid process for manufacture of phosphoric acid with recovery of valuable co-products is provided. Phosphate rock is digested in a sulfuric acid/phosphoric acid mixture. Phosphoric acid is filtered from the digested rock, the gypsum thus formed, and sludge from the phosphoric acid, are second-stage acid treated, washed, and heated in a drier-calciner at 900.degree. to 1300.degree. C. Sulfur dioxide evolved from the gypsum and the fossil fuel is used to replenish the sulfuric acid. The hot impure lime remaining is fused in an electric furnace to form valuable calcium aluminum silicate products, which are then tapped, cooled, stored, and sold. The only waste products from the process are common, sulfur dioxide free combustion gases from the high sulfur content fossil fuel. Nearly 100% recovery of all phosphorus and fluorine values is claimed.

Dependencies are inferred from the claim text.