Wet-process phosphoric acid technology and fluosilicic acid processing method free of fluorine-containing exhaust gas emission

Abstract

The invention discloses a wet-process phosphoric acid and fluosilicic acid production method free of fluorine-containing exhaust gas and waste heat emission. The method is suitable for a technology for decomposing phosphate ore to prepare a wet-process phosphoric acid of which the P2O5 content is 18-43% through phosphoric acid and a technology for preparing a concentrated phosphoric acid of which the P2O5 content does not exceed 54% through wet-process phosphoric acid evaporation and concentration. According to the method, a wet-process phosphoric acid technology system is isolated from a water environment, a heat source is provided for phosphoric acid concentration by using a clean heat-carrying working medium gasification-condensation cycle or heat pump recovery reaction heat or condensation heat, a fluosilicic acid of which the concentration is greater than 15% is produced by the method of coupling fluorine-containing steam condensation and fluosilicic acid concentration, so that closed wet-process phosphoric acid production is achieved, no fluorine-containing exhaust gas or waste heat is generated, and the concentrated phosphoric acid of which the P2O5 content does not exceed 54% and the fluosilicic acid of which the concentration is not lower than 15% can be produced without an external heat supply source.

Description

technical field [0001] The invention relates to the technical field of wet-process phosphoric acid produced by decomposing phosphate rock with sulfuric acid, in particular to an environmentally friendly and energy-saving process for recycling exhaust gas and waste heat. Background technique [0002] The wet process phosphoric acid process uses sulfuric acid to decompose phosphate rock (the main chemical components are calcium fluorophosphate, Ca 5 F(PO 4 ) 3 ) produced by the acidolysis reaction of dilute phosphoric acid and a large amount of reaction heat must be removed from the reactor in time. Scrubbing of flue gas", Chemical Industry Press, 1987: pp.124~129). Blast cooling is to inject a large amount of cold air into the reactor to carry the fluorine-containing gas and heat, and the resulting process tail gas is washed with cooling water and discharged up to the standard; the tail gas washing effect depends on the water volume and water temperature, resulting in a wa...

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Problems solved by technology

[0003] During the wet phosphoric acid evaporation and concentration process, more fluorine escapes from the acid with the secondary steam. The current treatment method is to install a fluorine scrubber between the phosphoric acid concentration evaporator and the atmospheric condenser to absorb fluorine and make fluorosilicic acid (H 2 SiF 6 ) products, the incompletely absorbed fluorine-containing tail gas is also absorbed with cooling water in the atmospheric condenser, and the above-mentioned waste heat discharge and air pollution problems also exist

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