SU950684A1 - Method for purifying fluorinaceous effluents from phosphorous production - Google Patents

Description

The invention relates to a technology for purifying fluorine-containing wastewater / phosphate raw materials obtained during acid processing (apatite concentrate, phosphate ores), phosphoric acid and mineral fertilizers (downtime and double superphosphate, ammophos, etc.) and various phosphoric salts.

In the process of preparing these products, compounds in the form of SiF and HF are released into the gas phase.

At present, fluoride compounds are collected from the gas phase by water, which leads to the formation of wastewater, from which it is necessary to separate fluoride compounds.

A known method of wastewater treatment in the production of phosphorus and phosphate fertilizers, which is reduced to trapping the gas phase containing Si4 and HF, with water and then treating the resulting fluorine-containing water with calcium components CaCOj, -CaCON), CAP.

The disadvantage of this method is the low degree of purification of fluorine from solution, which is 95% and, consequently, the high consumption of the calcium component Llj.

The closest to the proposed technical essence and the achieved result is a method of purification of fluorine-containing wastewater of phosphorus production, including the processing of calcium-silicate material, settling and separation of the clarified solution f2.

Metallurgical slag is used as calcium-silicate material, 50% of which is dicalcium silicate 2 CaO SiO. To increase the activity of the mechanical mixture, in addition to the sludge, chalk (CaCO) is introduced into 15 water.

The disadvantage of this method is insufficient purification from fluorine.

The purpose of the invention is to increase the degree of cleaning.

The goal is achieved by that; According to the method of purification of fluorine-containing wastewater of phosphorus industries, including the treatment of calcium silicate materials, the removal and separation of the clarified solution, in which c. As a calcium-calcium silicate mate.p., compounds of CaO .SiOjj®® composition of 0.1-2.0 are used with a weight ratio of them to the sum of wastewater components (F + 2.0 + SiOji) equal to (2-20). stop fluorine-containing water with calcium silicates, the latter decomposes into its constituent parts (by the example of dicalcium silicate) 2CaO-SiO, t 2HiP ZCa + Il., SiO + + 20IG “Calcium ions formed react with F, Р04. , Ca2 - + - + F-CaPj + Ca, (PO.) 2, Ca2-- + H, j.SiOi (CaSlFfc with the formation of hardly soluble compounds of fluoride, phosphate and calcium silicate hydroxide. The CaO introduced with silicates is sufficient to form Calcium fluoride CaF-j, Calcium Phosphate Saz (ROD) 2 and CaO 510.2 KjO. An excess of SiO | f ion, resulting from the decomposition of calcium silicates in waste water, is discharged as calcium hydrosilicate of CaO-SiOi -pH jp. At the same time, the end of the process responds in a solution of pH 11-12. This ensures a more complete elimination of phosphates and calcium fluorides. A feature of this process is that soluble silica binds to calcium hydrosilicates, which have an alkaline environment. The presence of these compounds, in addition, causes an additional withdrawal of a part of fluorine and phosphorus from the solution. The method is carried out as follows. silicate-calcium material is introduced at 2 ° C. The resulting pulp is settled and sent to a slurry separator, where the pulp is separated into a clarified solution and a condensed product. Example. The acidic production currents of extraction phosphoric acid contain, mg / g: F SiOj 1300 1400 300 For wastewater treatment, dicalcium silicate containing 65.1% CaO and 34.9% Si02 is used. (XCaOySiOir X 2, in 1J. Dosage calculation the dicalcium silicate is effected on the basis of the weight ratio xCaO.ySiOi / K to the sum of F. V.Ci and SiO2 equal to 2. The dicalcium silicate is introduced into the wastewater at 20 ° C. The resulting slurry is kept for 12 minutes and then sent to the sludge separator where the separation takes place pulp on the clarified solution and condensed product. The speed of clarification the solution is 3 m / h, and W: T of the condensed product is 1: 1. The degree of purification of the solution from fluorine is 99.0%; Pj 0ff99.2%; 5102.70%. The final pH of the solution is 10.5. Example 2. For wastewater treatment, the composition of which is given in example 1, uses SCaO-SiOi tri-calcium silicate containing 73.7% CaO and 26.3% SiO, 2 (xCaOySi02; x 3, y 1) .The weight ratio of CaO to the sum (F - + SiO.) Is equal to 10. At the same time, the consumption of tricalcium silicate amounts to 15 kg / m of wastewater. The resulting slurry, after administration of SCaOySiOj, is maintained at 10 minutes. After concentration, the solid product has a F: T ratio of 1: 1, and the rate of clarification of the solution is 3 m / h. The degree of purification of the solution is 99.9% of F; 99.9% of PjiO; 86.6% of SiO-j. The final pH of the solution is 10.1. Example 3. Calcium monosilicate CaO is used to purify acidic effluents of which the composition is given in Example 1. Si0.2, containing 48.2% CaO and 51.8% SiO, .j (xCaOySi02; X 1, y 1). Weight ratio хСаО ySiOo. to the sum of the components of the F + + SiOi solution is equal to 20. The consumption of monocalcium silicate is 20 kg / m of waste water. After entering monocalcium silicate into wastewater, the pulp is kept for 20 min at 40 ° C. The degree of purification of the solution from F is 99.5%; from R2.05- - 99.1%; SiOg - 80%. The final pH of the purified solution is 11.2, the rate of clarification is 1.8 m / h, W: T of the condensed product 1: 1. The results of the comparative analysis of the prototype and the proposed method are shown in the table.

Initial data

The composition of the solution, mg / l

F1300

R Ou1400

, SiO, j -300

pH of solution

1300

1400

300

2.1

Claims (1)

Claim A method for purifying fluorine-containing wastewater from phosphorus production, including treatment with calcium-silicate materials, settling and separating a clarified solution, characterized in that, in order to increase the degree of purification, compounds of the composition xCaOySiO ^ are used as calcium-calcium materials, where x = 1- 3, y = 0.1-0.2 with a weight ratio of them to the sum of wastewater components (F + ⁺ SiO ₄ equal to (2-20): 1.