RU1801948C - Method for calcium fluoride production - Google Patents

Abstract

SUMMARY OF THE INVENTION: phosphogypsum is mixed with a mixture of ammonium fluoride and ammonium cream oil fluoride, in a ratio of 1: (O., 6-0.8), in a weight ratio of 1: 1.1-1.2. The heat treatment is carried out in two stages: for 1.5-2 hours at a temperature of 150-200 °; Siv for 2-2.5 hours at a temperature of 600-650 ° C. The content of calcium fluoride in the product is up to 97% 1 tab.

Description

The invention relates to the chemical industry, in particular to the production of fluoride compounds and can be used to process phosphogypsum waste production. Extraction phosphoric acid (EPA) to calcium fluoride.

The aim of the invention is to increase the content of the basic substance in the product when calcium phosphogypsum is used as calcium sulfate.

The goal is achieved in that in the known method, which consists in heat treatment of a mixture of phosphogypsum with fluoride compounds, the latter use a dry mixture of ammonium fluoride with ammonium silicofluoride taken in an amount of 110-120 kg per 100 kg of phosphogypsum, the ratio of ammonium fluoride to ammonium fluoride in the mixture fluorides are maintained within 1: (0.6 -0.8), and heat treatment is carried out in 2 stages: for 1.5-2 hours at a temperature of 150-200 ° C and for 2-2.5 hours at a temperature 600-650 ° C.

 The lower limit for the ratio of ammonium fluoride and silicofluoride 1: 0.6 is chosen because a lower content of silicofluoride leads to a sharp increase in the content of residual calcium sulfate in the product.

The upper limit on the ratio of ammonium fluoride to ammonium silicofluoride 1: 0.8 is chosen due to the fact that a higher content of silicofluoride in the mixture leads to a sharp increase in silicon dioxide in the product.

The lower limit on the rate of a mixture of ammonium fluoride and ammonium silicofluoride 110 kg per 100 kg of phosphogypsum is chosen because the use of smaller amounts of fluoride compounds leads to an increase in the content of impurities of silicon dioxide and calcium sulfate in the product.

The upper limit on the norm of a mixture of ammonium fluoride and ammonium silicofluoride 120 kg per 100 kg of phosphogypsum is chosen due to the fact that the use of large amounts of fluoride reagents leads to a significant increase in heat treatment time and to a sharp increase in energy consumption.

Two-stage heat treatment is used in connection with the fact that in one-step heat treatment significantly higher norms of ammonium fluoride and ammonium silicofluoride are required to achieve the objective of the invention.

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The lower limit on the temperature of the first heat treatment stage of 150 ° C was chosen because of this. that heat treatment at lower temperatures dramatically slows down the formation of ammonium silicofluoride and the reaction of the latter with calcium sulfate.

The upper limit on the temperature of the first heat treatment stage of 200 ° C is chosen due to the fact that at higher temperatures the resulting silicofluoride decomposes, and the quality of the product deteriorates.

The lower temperature limit of the second heat treatment stage of 600 ° C is chosen due to the fact that at lower temperatures the reaction rate is slow and, accordingly, gases are poorly sublimated.

The upper limit for heat treatment of the second stage of 650 ° C is chosen due to the fact that at higher temperatures the quality of the product deteriorates and energy costs increase.

The significance of the differences is confirmed by the fact that any excess of the proposed technological limits leads to a sharp deterioration in the quality of the product (see table of experimental data).

When testing was used: phospho-gypsum containing mass. %: CaO - 32.5, 50s -46.5, P20-total 1.6. P20z, 5; P20z - 0.3, F - 0.4, SI02 - 17, ammonium fluoride, ammonium cremne fluoride, x. hours (B / P - water soluble).

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Example. A dry mixture of fluorides is prepared in the ratio of ammonium fluoride to ammonium silicofluoride 1: 0.65 and mixed with phosphogypsum in the ratio of the mixture of fluorides to phosphogypsum 1.1: 1. The mixture is heated at 150-200 ° C for 2 hours, then kept at 600 ° C for 2.5 hours.

The resulting cake was dissolved in hot water, T: W ratio of 1: 3. The insoluble precipitate was filtered off and dried. The resulting product contains mass. %: CaRz - 94.58, CaZSm - 3.85, 5U2 - 0.77, others - 0.8.

The research results are summarized in table.

Claims (1)

The claims A method of producing calcium fluoride, including heat treatment of a mixture of solid calcium sulfate and a fluorine-containing compound at 600-650 ° C and washing the product, characterized in that, in order to increase the content of the main substance in the product when using phosphogypsum as calcium sulfate, a fluorine-containing compound is used a mixture of ammonium fluoride and silicofluoride, which is taken in an amount of 110-120 kg per 100 kg of phosphogypsum, the ratio of ammonium fluoride and silicofluoride in the mixture is maintained equal to 1: 0.6-0.8, respectively, before By heat treatment, the mixture of starting reagents is kept at 150-200 ° С for 1.5-2.0 hours, and heat treatment is carried out for 2.0-2.5 hours.