SU1096236A1 - Method for purifying waste liquors contaning fluorides and ammonia - Google Patents

Abstract

1. A METHOD FOR CLEANING WASTE WATER CONTAINING FLUORIDES AND AMMONIA, including two stages of lime water treatment with intermediate separation of calcium fluoride precipitate, carbonation of water and ammonia removal, characterized in that, in order to increase the degree of purification from fluoride and ensure the possibility of using water, manure is recycled, mercury in circulation should be used. The removal of ammonia is carried out after the first stage of water treatment with lime at a ratio of concentrations of fluoride ions and calcium 1:

Description

The invention relates to methods for the purification of industrial wastewater from fluoride and ammonia and can be used in the chemical, metallurgical and other industries that have wastewater contaminated by these components.

The closest to the proposed technical essence and the achieved result is a method of purification of wastewater containing fluoride and ammonia, including two-stage treatment of water with lime, followed by the separation of calcium fluoride precipitate, carbonation of water and removal of ammonia.

According to this method, the water purification process is achieved in that the water in several stages is treated with an excessive amount (relative to the total fluoride content) of the milk of lime, filtering the precipitated calcium fluoride, precipitating calcium ions by adding ammonium carbonate to it and removing the ammonia from it by evaporation. The degree of water purification from fluoride ions is 90%, its residual concentration is 1.56 g / l. The residual concentration of calcium ions is less than 1 mg / l t1.

However, this method is characterized by an insufficient degree of purification from fluoride ion (from 15.6 to 1.56 g / l which does not allow further use of purified water in circulating water supply systems. Or for transfer to municipal sewage treatment plants (maximum allowable concentrations of fluoride ions not more than 0.75 mg / l).

The purpose of the invention is to increase the degree of purification of wastewater from fluoride and to ensure the possibility of disposal of BOj№f in the circulating water supply

The goal is achieved by the fact that according to the method of purification of wastewater containing fluoride and ammonia, including a two-stage water treatment with lime with intermediate separation of calcium fluoride precipitate, carbonization of water and removal of ammonia, the latter is carried out after the first stage of water treatment with lime at a ratio of fluorine ion concentrations and calcium 1: (1.2-2.0 and precipitation of calcium fluoride precipitate.

The removal of ammonia is prevented by blowing it out with air for 40-90 minutes at 80-90 ° C and a compressed air feed rate of 4.9-5.1 l / min.

The method is carried out as follows.

Sewage water containing fluorides and is treated with lime at the co: oxidation of fluorine and calcium in solution 1 :( 1.2-2.0). The solution is stirred and the precipitated precipitate of calpe-cn fluoride is separated by filtration.

From the formed filtrate, ammonia is removed by stripping it with air for 40-90 minutes at 80-90 ° C and a compressed air feed rate of 4.9-5.1 g / min. After the ammonia is distilled off, the purified water is again treated with lime milk and a stream of carbon dioxide is passed through it. A new portion of milk of lime is introduced so that the concentration of calcium ions in addition to those present in the solution is 1.5-1.6 g / l. Carbon dioxide is passed at a rate of 2 l / h for 30-60 ivniH until the water is neutralized to a pH value of 6.5-8.5, at a temperature of room temperature, and continuous mechanical stirring of the solution.

The residual concentration of calcium ions is no more than 180 mg / l, which satisfies the requirements for treated water according to the standards of the technological regime of working cycles, in which the residual cr concentration of calcium ions should not exceed 245 mg / l, and the value of the solutions should be pH range 6.5-8.5.

After filtering off the calcium carbonate precipitate, the purified water in all respects satisfies the requirements for recycled water and the g / s to be returned to the circulating production water supply cycle or transferred to the municipal sewage treatment plant.

Example. Sewage water containing fluorides and is treated in a known manner according to the scheme:

0 treatment of the purified water with a 10% solution of lime at a ratio of Ca2 concentrations 1 :; removal of sediment Sar2; re-treatment with lime; carbonization; deletion

5 sediment CaCO and Ca F; bringing the pH of the filtrate with alkali to 12.0-12.5; distilling off the ammonia by air; neutralization of purified water to a pH of 6.5-8.0.

Sewage water containing fluorides and ammonia is treated by the proposed method according to the scheme; treatment of treated water with 10% lime solution at a concentration ratio

5 removal of sediment (CaFj, 5 i Oj and others,); distilling off the ammonia by air; secondary treatment of water with 10% lime solution; carbonization of the solution with a current of carbon dioxide gas to a pH of 6.5-8.0; sediment removal (CaCOe and CaF.L

The results of purification of industrial water from fluorides according to the copyright scheme are presented in Table.

Table

From the data of Table 1 it can be seen that when purifying water by this method, residual concentration of fluoride is necessary, equal to 0.75 mg / l, is not reached, the best result. From the data given in Table 2 it can be seen that the proposed scheme of purification

by purification from fluoride is 0.96 mg / l. /

The results of the purification of industrial waters from fluorides by the proposed method are given in table. 2

Table ki water more efficiently, as achieved the required degree of purification

industrial water from fluorides Sufficient concentrations of fluoride ions 10.75 mg / l.)

EXAMPLE 2 To clean from fluoride and ammonia, take 1 liter of wastewater containing from 7170 up to. 58680 mg / l of fluoride ions and from 7550 to 55640 mg / l of ammonia with a purity within the pH range of 7.09, 0 are placed in a reactor and treated with 10% lime milk solution with continuous stirring.

The amount of lime is added so that the ratio of the concentration of ions in the solution corresponds to FlCa 1:: (1.5-2, .0). The solution is stirred for 20 minutes, then filtered from the precipitated precipitate.

The filtrate is placed in a flask with a reflux condenser, heated to 80-90s, and compressed air is passed through it at a rate of 5 liters / min for 60 minutes. In this way, ammonia is removed from the water to be purified. After the ammonia has been removed, the waste water is again treated with a 10% solution of milk of lime. Lime is added to the solution so that the concentration of calcium ions in addition to that contained in the solution is 1.5-1.6 g / l. The solution is stirred and a stream of carbon dioxide gas is passed through it for 30-60 minutes at a rate of 2 l / h. Carbon dioxide neutralizes the water to be purified to a pH of 6.5-850 and binds calcium ions to poorly soluble calcium carbonate.

The dependence of the purification results on the ratio of fluorine and calcium ions in the treatment of water with lime at stage I is presented in Table 3.

T a

l and c

Note. In industrial wastewater being treated, pH 8.08, fluoride concentration is 11380 mg / l.

From table 3 it follows that when going beyond the lower limit in the proposed ratio, the residual content of fluoride ions in the solution increases. The upper limit in the proposed ratio is determined by the economic value of tvsh, the residual content of fluoride ions remains unchanged.

Cy t the results of the cleaning of the treated wastewater using the proposed method are presented in table 4.

From the analysis data given in Table 4 it can be seen that the proposed method allows purifying industrial wastewater to residual fluoride concentrations of not more than 0.75 mg / l, ammonia — not more than 3.0 mg / l, calcium ions — not more than 180 mg / l, i.e. Purified waters meet all the requirements for water from the circulating water supply cycle and can be reused in production.

The technical and economic advantages of the proposed method consist in the fact that it permits a more complete purification of wastewater from fluorides and thereby ensures the possibility of their use in circulating water supply. The organization of such closed drainless production cxeNbj eliminates environmental pollution by harmful fluorine and ammonia containing emissions.

Claims (2)

1. METHOD FOR CLEANING WASTE WATER CONTAINING FLUORIDES AND AMMONIA, including two-stage treatment of water with lime with an intermediate separation of calcium fluoride sludge, carbonization of water and removal of ammonia, characterized in that, in order to increase the degree of purification from fluorides and ensure the possibility of using water in recycled water supply, the removal of ammonia is carried out after the first stage of water treatment with lime at a ratio of concentration of fluorine ions and calcium 1: (1.2-2.0) and separation of the precipitate of calcium fluoride. 2. The method of pop. 1, characterized in that the removal of ammonia is carried out by blowing it with air for 40-90 minutes at 80-90 ° C and a compressed air supply rate of 4.9-5.1 l / min.