RU2542310C2 - Method of purifying mother waters of sodium azide synthesis - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods of multi-stage processing of industrial and circulating mother waters from organic and nitrogen-containing pollutants of different origin and can be applied at factories of chemical industry, predominantly in technology of purifying mother water of synthesis of toxic and explosive compounds of substances, which contain hydrazine, azides and ethanol. Hydrazine oxidation is carried out by hydrogen peroxide in mother waters, with ethyl alcohol and sodium azide in form of volatile compound being blown by air from mother waters with the following oxidation of steam-air mixture on catalyst; oxidation of hydrazine with hydrogen peroxide is carried out at pH=10 and temperature t=60°C for 2 hours; conversion of sodium azide into volatile compound is carried out by acidifying of mother waters by sulphuric acid to pH=1.65; blowing of ethanol and nitrogen hydride from mother waters is carried out by acidification of mother waters with sulphuric acid to pH=1.65; flowing of ethyl alcohol and nitrogen hydride from mother waters by air is carried out at temperature t=60°C, oxidation of ethyl alcohol steam and nitrogen hydride is carried out by air oxygen on aluminium-copper-chrome catalyst at temperature t=300-350°C and W=10000 h^-1.

EFFECT: complex purification of mother waters, which contain hydrazine, sodium azide and ethyl alcohol with minimal expenditures for process realisation.

5 cl, 1 dwg, 1 ex

Description

The present invention relates to methods for multi-stage treatment of industrial and recycled mother water from organic and nitrogen-containing pollutants of various origins and can be used in chemical industry enterprises, mainly in the technology for treating mother water of the synthesis of toxic and explosive compounds of substances containing hydrazine, azides and ethyl alcohol.

A known method is the adsorption purification of aqueous solutions of hydrazine, based on the absorption of hydrazine by a chemical sorbent containing hydrated acidic chromium and aluminum tripolyphosphates [USSR Author's Certificate No. 1551655 IPC ⁷ C02F 1/28. The method of purification of aqueous solutions of hydrazine. Publ. 03/23/1990].

The disadvantage of this method is the difficulty of regeneration of the sorbent, which is accompanied by the formation of toxic products that require disposal.

There is a method of neutralizing hydrazine in mother waters with air oxygen during sparging using iron, cobalt and copper ions as catalysts. [Gogolashvili E.L., Molgacheva I.V., Isakov A.A. Neutralization of hydrazine in mother waters. - Heat power engineering. - 2001. - No. 11. - S. 937-944].

The disadvantage of this method is the low oxidation rate of hydrazine due to the poor solubility of oxygen in water.

A known method for the disposal of water effluents containing nitrous-hydrogen acid, including its oxidation with sodium nitrite in a strongly acidic medium to gaseous products [Study of the processes of oxidation of nitric acid in relation to the technology of SNF processing: Report / RIAN. - Zilberman B.Ya. et al. Inv. 11647 t. - St. Petersburg, 1995].

The disadvantages of this method include the use of sodium nitrite, which increases the salt content of effluents, as well as the process only in strongly acidic environments.

A known method of fire neutralization of mother water containing combustible organic substances at a temperature of t = 1300-1350 ° C [Bernadiner M.N., Shurygin A.P. Fire processing and disposal of industrial waste. - M .: Chemistry, 1990].

The disadvantages of this method are the high fuel consumption for the evaporation of the mother water, as well as the need to clean high-temperature gases.

The closest in technical essence is the method of oxidation of hydrazine with hydrogen peroxide [Audrit L., Ogg B. Chemistry of hydrazine. - Per. from English. - M.: Mir. - 1954. - S. 125].

The disadvantage of this method is the impossibility of oxidation of azides and ethyl alcohol present in the mother water.

The technical problem to be solved by the claimed invention is directed is the comprehensive purification of mother waters containing hydrazine, sodium azide and ethyl alcohol, with minimal costs for the implementation of the process.

List of drawings and tables

Figure 1 shows the technological scheme of the integrated treatment of mother water synthesis of sodium azide.

SUMMARY OF THE INVENTION

The solution to the technical problem is ensured by the fact that according to the proposed method, hydrazine is oxidized with hydrogen peroxide in the mother water, and ethyl alcohol and sodium azide in the form of a volatile compound are blown off from the mother water with the subsequent oxidation of the vapor-air mixture on the catalyst; oxidation of hydrazine with hydrogen peroxide is carried out at pH = 10 and a temperature of t = 60 ° C for 2 hours; the conversion of sodium azide to a volatile compound — hydrogen nitride is carried out by acidification of the mother liquor with sulfuric acid to pH = 1.65; ethanol and hydrogen nitride are blown out of the mother water by air at a temperature of t = 60 ° C, ethanol and hydrogen nitrogen vapors are oxidized with air oxygen on an aluminum-chromium catalyst at a temperature of t = 300-350 ° C and W = 10,000 h ^-1 .

Hydrazine reacts quite effectively with hydrogen peroxide at pH = 10 and a temperature of t = 60 ° C.

Hydrogen nitrogen and ethyl alcohol have low boiling points (t _bales HN ₃ 37 ° C and t _bales C ₂ H ₅ OH 78.37 ° C), which allows them to be blown with air from aqueous solutions.

Blowing off vapors of ethyl alcohol and hydrogen nitride from the mother water with air at a temperature of t = 60 ° C allows purification of the mother water from the synthesis of azides with optimal ablation of water vapor.

Catalytic oxidation is more efficient and economical than thermal oxidation in a burner flame.

Information confirming the possibility of carrying out the invention

The method is illustrated by the following example using the mother water of industrial synthesis of sodium azide.

Example. The method of purification of mother water synthesis of sodium azide according to the proposed method

Hydrazine Oxidation

In the wastewater of industrial synthesis of sodium azide containing 12 g / l of hydrazine, 290 g / l of ethyl alcohol and 1.5 g / l of sodium azide, a 25% solution of hydrogen peroxide (H ₂ O ₂ ) in an amount of 20% vol. . Hydrazine is oxidized with hydrogen peroxide at pH = 10, for which a 10N sodium hydroxide solution is added to the solution, the exposure time at a temperature of t = 60 ° C is 2 hours. Gas purge containing ethyl alcohol vapor is sent for purification on an IKT-12-8 alumina-chromium catalyst.

Blowing off vapors of ethyl alcohol and hydrogen nitrogen

To convert sodium azide to a volatile compound - hydrogen nitrogen, the mother liquors are adjusted with a solution of concentrated sulfuric acid to pH = 1.65. Blowing off vapors of ethyl alcohol and hydrogen nitrogen from the mother water is carried out with air in a mass transfer apparatus (stripper) at a temperature of t = 60 ° C. Gas purge containing vapors of ethyl alcohol and hydrogen nitrogen is sent for purification on an IKT-12-8 alumina-chromium catalyst.

Catalytic oxidation of vapors of ethyl alcohol and hydrogen nitrogen

Deep oxidation of ethyl alcohol and hydrogen nitride vapors is carried out with atmospheric oxygen on an IKT-12-8 alumina-chromium catalyst at a temperature of t = 300-350 ° C and W = 10,000 h ^-1 with minimal NO _x generation. The purified gases are emitted by the fan into the atmosphere.

Adjustment of the pH of the mother water and discharge to the industrial collector

The treated wastewater, in which there is no hydrazine, sodium azide and ethyl alcohol, is adjusted by adding 10N sodium hydroxide solution to pH = 8-9. Next, the wastewater is sent for discharge to the industrial collector.

Thus, the inventive method allows for the purification of the mother water of industrial production of sodium azide from the main pollutants: hydrazine, ethyl alcohol and azides.

The proposed solution meets the criteria of industrial applicability, novelty and inventive step.

Claims (5)

1. The method of purification of mother waters of the synthesis of sodium azide containing hydrazine, ethyl alcohol and sodium azide, including their oxidation, characterized in that the oxidation of hydrazine is carried out with hydrogen peroxide in the mother water, and ethyl alcohol and sodium azide in the form of a volatile compound blow air from the mother water, followed by oxidation of the vapor-air mixture on the catalyst. 2. The method according to claim 1, characterized in that the oxidation of hydrazine with hydrogen peroxide is carried out at pH = 10 and a temperature of t = 60 ° C for 2 hours. 3. The method according to claim 1, characterized in that the conversion of sodium azide into a volatile compound - hydrogen nitrogen is carried out by acidification of the mother liquor with sulfuric acid to pH = 1.65. 4. The method according to claim 1, characterized in that the blowing of ethyl alcohol and hydrogen nitrogen from the mother water by air is carried out at a temperature of t = 60 ° C. 5. The method according to claim 1, characterized in that the oxidation of vapors of ethyl alcohol and hydrogen nitrogen is carried out with atmospheric oxygen on an aluminum-chromium catalyst at a temperature of t = 300-350 ° C and W = 10000 h ^-1 .

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