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Utilization of waste fluosilicic acid (in two sections). 1. Laboratory investigations. 2. Cost evaluation.
Blake-HE Jr.; Thomas-WS; Moser-KW; Reuss-JL; Dolezal-H
Albany, OR: U.S. Department of the Interior, Bureau of Mines, RI 7502, 1971 Jan; :1-60
This report describes two processes for utilizing the waste fluosilicic acid (H2SiF6) generated by the manufacture of phosphatic fertilizers. The first process involves conversion of fluosilicic acid to an acid-grade fluorspar (CaF2) by first precipitating the silica with ammonia and filtering, and then reacting the ammonium fluoride (NH4F) filtrate with Ca(OH)2. Over 95 percent of the fluoride is converted to CaF2. The second process involves neutralizing the H2SiF6 with Ca(OH)2 and silica and filtering and then volatilizing HF from the dry precipitate by pyrohydrolytic action at 1,050C. By this method, over 80 percent of the fluoride in H2SiF6 is recovered as anhydrous HF. Preliminary tests on the synthesis of cell-grade aluminum fluoride (AlF3) from the rotary reactor offgases and activated alumina showed that an 82-percent AlF3 product could be produced. An evaluation was made to determine the economics of utilizing waste fluosilicic acid for production of (1) calcium fluoride, and (2) anhydrous hydrogen fluoride. The evaluation showed that both products could be produced and marketed competitively.
Fertilizers; Hydrogen fluoride; Calcium fluorides; Production; Materials recovery; Silicates; Fluorides; Chemical industry; Cost estimates; Fluorite; Capitalized costs; Ammonia; Operating costs; Hydrogen hexafluorosilicate; Silicate/hexafluoro; Waste gas recovery
IH; Report of Investigations
NTIS Accession No.
Albany, OR: U.S. Department of the Interior, Bureau of Mines, RI 7502
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division