New method for processing fluorine-containing tail gas in production of calcium superphosphate

Abstract

The invention discloses a mew method for processing a fluorine-containing tail gas in the production of calcium superphosphate, which considers practical cases of the production of calcium superphosphate and needs of the environmental protection processing of the tail gas and adopts a tail gas segment absorption mode to process wastewater and waste gases. The method of the invention is characterized in that: the fluorine-containing tail gas generated in the production process of calcium superphosphate is processed in a three-segment absorption mode; ammonium fluoride is adopted as an absorption liquid in the first segment and the second segment, and water is adopted as an absorption liquid in the third segment; ammonium fluorosilicate which is well absorbed in the first segment and the second segment is cooled and crystallized to obtain an ammonium fluorosilicate product, and can also be directly ammonified as needed to obtain an over 40% ammonium fluoride solution which can be evaporated and concentrated to obtain an ammonium fluoride product or can be used to prepare other fluorine chemical engineering products; and water is used as an absorption washing liquid in the third segment, and an obtained mixed solution is added with a mother solution (a dilute ammonium fluorosilicate solution) according to the needed concentration amount when the fluorine-containing tail gas which is not completely absorbed in a first absorbing tower and a second absorbing tower or ammonia, or volatilized ammonium fluoride and an ammonium fluorosilicate liquid foam which escape because of the over high temperature of the first absorbing tower and the second absorbing tower is absorbed and washed by water.

Description

technical field [0001] The invention discloses a new method for treating fluorine-containing tail gas in calcium superphosphate production. Considering the actual situation of calcium superphosphate production and the need for environmental protection treatment of tail gas, the tail gas can be absorbed in stages to treat both waste water and waste gas. Background technique [0002] In the past production process of calcium superphosphate, when sulfuric acid decomposes phosphate rock to produce calcium superphosphate, the fluorine in the phosphate rock will escape in the form of silicon tetrafluoride. For a long time, various manufacturers have used water to absorb this Fluorine-containing tail gas is used to produce low-concentration fluosilicic acid, which is then further processed into sodium fluosilicate products for sale. When this treatment method produces sodium fluorosilicate, a large amount of waste water will be generated, forming secondary pollution. [0003] Chin...

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Problems solved by technology

However, although this method can eliminate the secondary pollution caused by waste water, since ammonium fluoride is used as the absorption liquid and there is some free ammonia in the ammonium fluoride, the temperature of the absorption liquid reaches 40-- 80°C

Under the above conditions, free ammonia, ammonium fluoride and ammonium fluorosilicate in the absorption liquid are easy to escape at high temperature, resulting in the increase of new pollutants ammonia and nitrogen emissions in the process of tail gas emission.

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