RU1784580C - Process for producing solution of ammonium silicofluoride - Google Patents

Abstract

A method of producing a solution of ammonium silicofluoride. 40-54% Technical Hydrochloric Acid, a waste product of hydrogen fluoride production, is neutralized with a weak ammonia solution of the composition, May.%: МНз 3.2-4.3: МЩРО.б-2.4, a waste product of the production of acid ammonium fluoride. Get a production solution with a concentration of 12-18%, used as a wood preservative. 2 tab.

Description

The invention relates to the chemical technology of inorganic substances, in particular to a method for producing ammonium silicofluoride, which is widely used as an antiseptic for wood impregnation.

A known method for producing ammonium silicofluoride by absorption of silicon tetrafluoride from exhaust gases by a circulating aqueous solution of ammonium silicofluoride. Solutions from the absorption stage, containing 17-22% hydrofluoric acid and 10% ammonium fluoride, are neutralized with 25% ammonia water to a residual acidity of 1% (free hydrofluoric acid content) and precipitated ammonium fluoride crystals are separated.

A method is known for producing ammonium silicofluoride by neutralizing 10-12% hydrofluoric acid with ammonia to a pH of 2-3, evaporating the resulting solution to a concentration of 28-30%, crystallizing the latter, separating and drying it.

The disadvantages of this method are the high energy intensity due to the cost of evaporating low-concentrated solutions of ammonium silicofluoride, as well as the use of expensive raw materials - ammonia, the cost of equipment for crystallization, separation and drying of crystals of ammonium silicofluoride

The purpose of the invention is to obtain a production solution with a concentration of 12-18% used as a wood preservative, cheaper process and reduced energy costs.

The goal is achieved by excluding from the prototype method the last three stages, evaporation, separation, drying; using cheap raw materials as production reagents, production reagents. The reagents in the proposed method are 40-54% technical fluorosilicic acid (TU-113-08-555-84) - hydrogen fluoride production waste (GOST 7618-83), and a weak ammonia solution of the composition, wt.%: MNZ (3.2-4.3), MNDR

cl

with

VI 00 N SL

with

about

(0.6-2.4) - waste of the production of acid ammonium fluoride (TU 113-08-544-83).

The use of more concentrated hydrofluoric acid makes it possible to obtain, at the stage of neutralization, an ammonium cream oil concentration of May 12-18,%, ready for use as a wood antiseptic.

A comparative analysis of the claimed solution with the prototype shows that the claimed method differs from the prototype in that three stages are excluded from the scheme, i.e. evaporation of the solution, separation of the crystals, and drying of the crystals. The difference from the prototype in the claimed method is the concentration of the starting hydrofluoric acid - 40-54% wt.%, As well as the replacement of the neutralizing agent - ammonia with a solution of the composition, wt.% MH 3,2-4.3; NH4F (0.6-2.4).

A comparative analysis of the production of ammonium silicofluoride at cost and energy costs of the proposed method and prototype are given in table 1,

The method is tested in a pilot installation.

Example 1 In a reactor with a stirrer from storage tanks load 1000 kg of an aqueous ammonia solution containing, wt.%: Ammonium fluoride 0.6; ammonia 3.9, after which hydrofluoric acid with a molar ratio of fluorine to silicon of 5.84 and a concentration of 45 wt.% in the amount of 385.4 kg is fed.

The process is carried out with stirring.

Get 1385.4 kg of a production solution of the following composition, wt.%: Ammonium silicofluoride 15.77; silica 0.03; hydrofluoric acid 0.05; the rest is water

In Examples 2-5, the process is the same. The results are shown in table.2.

Using artificially prepared solutions of the starting reagents with a concentration that goes beyond the boundary conditions, we obtained solutions of ammonium cremne fluoride with a concentration of more than 18%. while precipitation of ammonium cremofluoride was observed, or with a concentration of less than 12%. Transportation

An antiseptic with such a low concentration is not economically beneficial to the consumer.

The method is simple to implement, waste-free, does not require special equipment. Using the proposed method

provides the following advantages over existing methods.

Due to the high concentration of hydrofluoric acid, a concentrated solution of ammonium silicofluoride is obtained; therefore, there is no need for its subsequent evaporation, which greatly reduces the energy consumption of the process and the cost of equipment,

economy production areas.

Due to the use of chemical wastes as reagents, the cost of raw materials is significantly reduced, waste dumping is stopped

into wastewater, which is very important for environmental protection.

Currently, technical hydrofluoric acid and weak solutions of ammonia and ammonium fluoride

goes into industrial wastewater.

Claims (1)

SUMMARY OF THE INVENTION A method for producing a solution of ammonium silicofluoride, comprising neutralizing hydrofluoric acid with an ammonia solution, characterized in that, in order to obtain a production solution with a concentration of 12-18% used as a wood preservative, To reduce the cost of the process and reduce energy costs, hydrofluoric acid is taken at a concentration of 40-54%. and as the ammonia solution, a waste product is used for the production of acid ammonium fluoride containing, wt.%; ammonia 3.2-4.3; ammonium fluoride - 0.6-2.4; water is the rest. Table Table 2