Silvio J. Spigolon Ph.D.
Engineering in Memphis, TN

4312842, Jan 26, 1982

Feb 12, 1980

6/120825

Eddie K. Wilson - Memphis TN
Silvio J. Spigolon - Memphis TN

C01F 100, C01F 510, C01B 2516

423178

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.

4608238, Aug 26, 1986

Jul 27, 1984

6/634965

Eddie K. Wilson - Germantown TN
Silvio J. Spigolon - Memphis TN

C01F 100, C01F 510, C01F 2516

423178

This disclosure concerns an improved phospho-gypsum recovery process in which phospho-gypsum waste product and coke are first heated to remove moisture, some SO. sub. 2 and other vaporous matter, then heated to a higher temperature in a reducing atmosphere to remove and separately recover SO. sub. 2, then further heated in an oxidizing atmosphere to about 1200. degree. to 1250. degree. C. to remove any unreacted carbon and calcium sulfide before entering an electric furnace. The disclosure also concerns passing the gas stream from the condenser-heat exchanger over the clinker from the electric furnace to scrub SO. sub. 2 from said gas stream. The essence of the invention is the unique absorber system used to remove any and all remaining fluorine in the gases from the calciner/furnace. If not removed, the fluorine will severely harm the catalyst used in the contact sulfuric acid plant to which the gases are sent for recovery of sulfur values. The absorber system uses a sulfuric acid absorber folowed by a water absorber.

4415543, Nov 15, 1983

Jan 25, 1982

6/342474

Eddie K. Wilson - Memphis TN
Silvio J. Spigolon - Memphis TN

C01F 100, C01F 510, C01B 2516

423178

This disclosure concerns a process for treating phospho-gypsum waste product from the wet process method of making phosphoric acid including the steps of water washing the phospho-gypsum to remove all but an acceptable level of fluorine before the phospho-gypsum is calcined. The process allows the use of high sulfur coal for the production of steam if desired for use in the overall process. The process also allows for production of SO. sub. 3 from part of the phospho-gypsum in an electric furnace to enrich the SO. sub. 2 stream for making sulfuric acid.

4734272, Mar 29, 1988

Aug 25, 1986

6/899987

Eddie K. Wilson - Germantown TN
Silvio J. Spigolon - Memphis TN

C01F 100, C01F 510, C01F 2516

423178

This disclosure involves a process for treating wet phospho-gypsum, a by-product from wet phosphoric acid manufacture, to remove fluorine values so as to make the sulfur values in the phospho-gypsum usable in making sulfuric acid in a contact sulfuric acid plant. The process involves drying the phospho-gypsum at 400. degree. -600. degree. C. to vaporize the fluorine values, the P. sub. 2 O. sub. 5 values and water and reacting the hot vapors with lime or limestone to remove the fluorine values as fluorspar. The P. sub. 2 O. sub. 5 values are subsequently condensed and used in a phosphoric acid plant. The dry phospho-gypsum is heated to 1200. degree. -1250. degree. C. under reducing conditions to produce SO. sub. 2 gas and siliceous lime. The SO. sub. 2 is then passed through a lime or limestone scrubber to eliminate any remaining fluorine values, dried and utilized in a contact sulfuric acid plant.