FI66293C - FOER REFRIGERATION FOR RELEASE AV ENTITY AND GASFORM OF MATERIAL FREON - Google Patents

Description

---- m ri ADVERTISEMENT zr / roOT

Vftg) W ^ UTLÄGCHINGSSRRIFT 6 6293 ^ ^ (51) Kv.N ^ / IM.CL3 B 01 D 3/00 FINLAND —FINLAND (21) P · * · "**» »· * ·" "· - PiMncmOkitlitg 800082 (22) Hak * mtap * hrt — Ant5kning «i * | 11.01.80 '' (23) Allnpdvt — GikiglMtadag 1 1.01.80 (41) Tulkit fvlkJMfcsI - Uhrit ^ 2 07 8 1

Pram-ed. rvhMntynta. W 5Ϊ2? ^. & ΪΚ £! Γ ^ ΖΛ 23.06.84 (32) (33) (31) »* yr <*« «T« woHw »ί» | Μ prtorttac (71) (72) Grigory Zakharovich Bljum, ulitsa Kominterna 32/5, kv. 23, Moscow, Evgeny Alexandrovich Ryabenko, ulitsa B. Cheremushkinskaya, 2, building 2, kv. 26, Moscow, Gennady Georgievich Vinogradov,

Izmailovskaya Ploschad, 4, building 1, sq. Km. 71, Moscow,

Aron Izrailevich Goikhrakh, Novogireevskaya ulitsa 16, building 1, sq. Km. 39, Moscow, Sofia Isaakovna Khainson, Graivoronovskaya ulitsa, 16, building 1, kv. 28, Moscow, Sergei Alexeevich Nazarov, ulitsa Shishkina, 6, kv. 28, Perm, Leonid Petrovich Kleinburd, ulitsa 8 March, 2/10, building 3, sq. M. 14, Moscow,

Yulia Vladimirovna Vasilieva, Komsomolskaya ulitsa, 5, sq. Km. 49, Moskovskoi oblasti, USSR (SU) (74) Oy Kolster Ab (54) The present invention relates to methods for purifying an aqueous solution of a gaseous substance from impurities, and to a method for purifying an aqueous solution of a gaseous substance from impurities.

Purified aqueous solutions of gaseous substances such as hydrogen fluoride, hydrogen chloride and ammonia are widely used in the manufacture of semiconductor devices with high electrophysical performance.

Depending on the method by which the aqueous stock solutions of gaseous substances are prepared, they may contain various impurities of organic and inorganic origin.

The average impurity concentrations in gaseous effluent solutions are shown in the table.

2 66293

Impurity Hydrogen fluoride Hydrogen chloride Aqueous ammonia solution aqueous solution aqueous solution 12 3 4 Al 2,1Q-3 5.10 ~ 4 3.10 ~ 4

Fe 1.10-3 5.10 ~ 3 2.10_3

Ca 1.10-3 4.1Q-3 3.10-3

Mg 1.10-4 5.10-4 2.10-4

Cu 2.10-4 3.10 ~ 4 2.10-4 -4 -4 -4

Pb 3.10 5.10 1.10

Mn 1.10-4 3.10 ~ 4 1.10-4

Zn 4.10-3 5.10 ~ 3 2.10 ~ 3 K 2.10 ~ 3 3.10-3 4.10-4

Na 5.10-4 3.10-4 1.10 ~ 4

As 5.10 ~ 2 1.10-2 5.10-3 P 5.10-3 4.10-3 1.10-3 organic _ _ impurities 3.10 5.10 4.10

It can be seen from the table that the starting aqueous solutions of gaseous substances (technical products) are contaminated with heavy, alkali and alkaline earth metals as well as arsenic, phosphorus and other impurities. As a result, in order to produce highly pure products, the starting materials must be purified using efficient methods.

Various processes for purifying aqueous solutions of gaseous substances are known. Thus, processes based on ion exchange technology are widely used for the purification of hydrohalic acids (cf. E.I. Kazantsev et al., Coll., Of Art of Uralsky Politekhnichesky Institut (in Russian). Purification of aqueous solutions occurs due to the ability of the ion exchange resin to sorb complex ions.

-4 -5

However, removal of many elements to a concentration of 10-10% is only possible from dilute solutions.

The most widely used are processes based on distillation (cf. SNTL Invention No. 379533 and U.S. Patent No. 3199642). The use of such a technique for gas and liquid mixtures is due, on the one hand, to the ability of gaseous substances to form azeotropes with liquids, i.e. solutions that boil without changing the composition, and on the other hand to the azeotrope volatility of impurities present in aqueous solutions of gaseous substances. Hardly volatile impurities are usually more easily separated than easily volatile impurities even in the case where there is only a slight difference in vapor pressure.

The possibilities offered by the ordering method for purification from volatile impurities can be greatly expanded by the use of chemically active additives, since the volatility of the impurities then increases, which increases the separation ratio (cf. Japanese Patent No. 16407 15 B 34); Polish Patent No. 49615). Purification of aqueous solutions of hydrogen fluoride and hydrogen chloride by distillation in the presence of chemically active additives and purification of aqueous solutions of ammonia under pressure (German Patents Nos. 858894 and 1467198) make it possible to prepare very pure products containing 10 ^ - 10 ®% of metallic impurities, 10 ^ - 10 ®% arsenic and -7 5. 10% phosphorus. However, these purification methods do not guarantee the production of concentrated end products. s *

A process for purifying an aqueous solution of hydrogen chloride is known in the art, which is also based on distillation but involves the desorption of a gaseous substance in excess in the starting solution (excess gaseous substance relative to the azeotropic mixture) (cf. Chemical Processing, Vol. XIII, No. 11, 1967). In the process, 36% of the starting solution is fed to the distillation vessel of the packed column at a rate of 1 kg / h. The distillation vessel of the column is heated with a circulating heat carrier. The stock solution is heated to boiling. The violent release of hydrogen chloride present in excess of the azeotropic composition occurs under such conditions from the starting solution at a rate of 0.16 kg / h and the vigorous formation of acid vapor having an azeotropic composition due to /B.

Azeotropic acid vapor and desorbed hydrogen chloride rise to the packing column. The acid vapor is fed to a condensing condenser where condensation takes place at a rate of 0.74 kg / h, and the desorbed hydrogen chloride is fed to an adsorption apparatus. The hydrochloric acid prepared by condensation is fed at a concentration of 20% 66293 for injection in an adsorption device. 36% hydrochloric acid is removed from the adsorption device at a rate of 0.9 kg / h.

-4 -5

The concentration of impurities in the acid obtained is 1. 10 -1.10%.

This relatively poor quality of the final product is due to the fact that the boiling of the effluent solution to be purified and the vigorous release of its hydrogen chloride in excess of the composition of the azeotropic mixture are associated with significant splash and mist losses which contaminate the gas and acid to be condensed. This is because during the boiling of the liquid, the gas bubble bursts when it comes to the surface and does not have time to grow due to membrane defects and forms several fine droplets (mist) or a stable aerosol phase. This mist penetrates through the columns of the apparatus together with the vapor phase, settling very little.

The object of the present invention is to eliminate the above-mentioned disadvantages.

The invention is based on changing the conditions in a process for purifying aqueous solutions of a gaseous substance from impurities so that very pure products are produced due to the maximum possible elimination of spatter and mist losses.

This object is achieved by saturating an aqueous solution of a gaseous substance from impurities, desorbing the excess gaseous substance present in the starting solution, distilling the liquid remaining after desorption and boiling without a change in composition, saturating the distillate with a desorbed gaseous substance, according to the invention, the desorption of the excess gaseous substance from the starting aqueous solution is carried out by heating the solution from a temperature which ensures at least 95% desorption of the excess gaseous substance present in the starting aqueous solution to a temperature 1 ° C below the boiling point of the liquid.

Aqueous solutions of gaseous substances may contain aqueous solutions of mineral acids (HF, HCl, I 2 SO 4) and aqueous ammonia solution. Such aqueous solutions are either azeotropic acids of composition containing the corresponding gaseous substance (in excess of the azeotropic composition) or aqueous ammonia solution containing 25-27% dissolved gas. After the excess gaseous substance present in the effluent solution is 5 66293 desorbed, liquids which boil without changing the composition are formed in both cases; either an azeotropic acid or a liquid containing 3-5% ammonia.

In the process according to the invention, the desorption of the excess gaseous substance present in the starting aqueous solution is carried out under "sub-heated boiling" conditions, whereby the release of gas from the liquid takes place peacefully. Heating an aqueous solution of gaseous substances to temperatures equal to or near their boiling points involves a significant increase in the pressure of the dissolved gas. In the case where the liquid is not yet boiling, there are no defects in the membrane of the gas bubble. It stretches, its thickness decreases, and the membrane breaks when a gas bubble appears on the surface, forming a large drop of liquid.

According to the invention, "underheated boiling" conditions are provided due to the fact that the desorption of excess gaseous matter from the gaseous stock solution is carried out at a temperature which guarantees 95% desorption of the excess gaseous substance present in the starting water solution to a temperature below 1 ° C. composition without change.

The process according to the invention for purifying aqueous solutions of gaseous substances makes it possible to finely purify solutions of the above type from impurities and to prepare aqueous solutions of mineral acids such as hydrofluoric acid, hydrochloric acid and sulfuric acid and ammonia in high purity containing 10% iron, heavy metals, phosphorus and arsenic. The substances obtained are very concentrated products: hydrofluoric acid - at least 50%; hydrochloric acid - at least 36-38%; sulfuric acid - at least 95.6%; ammonia solution- at least 25%.

The process is simple to manufacture and is performed as follows.

The aqueous solution of the gaseous substance is fed to the top of the membrane column device 2, where the heat exchange area is 1-1.8 m, at normal pressure in the form of a continuous flow. The distillation vessel of the column is equipped with a heating device. The starting solution is heated to a temperature below 1 ° C 6 66293 below the boiling point of the corresponding boiling liquid of the corresponding composition. As a result of the heating, the gaseous substance is desoped and this substance is fed to the bottom of the absorber. The degassed liquid, which boils without changing the composition, is removed from the bottom of the apparatus and collected in a collecting vessel from which it is fed for distillation in a fractionation column.

After distillation, the purified product (distillate) is removed and fed for injection at the top of the absorber. Normal-quality concentrated, very pure product is recovered from the ab-absorption apparatus.

The invention will be better understood from the following examples. Example 1 36% technical hydrochloric acid was fed at a rate of 50 kg / h under normal pressure in the form of a continuous flow to the upper end of a membrane column 2 with a heat exchange area of 1 m and the temperature of the acid in the column distillation vessel was maintained between 107-109 ° C. Under these conditions, gaseous hydrogen chloride was released from the liquid at a rate of 7.6 kg / h (desorption) and fed to an absorber.

42.5 kg / h hydrochloric acid containing 25% hydrogen chloride was removed from the bottom of the apparatus (azeotropic hydrochloric acid).

The acid was fed into a collecting vessel from which it was fed for distillation. For this purpose, 25% hydrochloric acid was fed in a continuous flow at a rate of 42.5 kg / h to the distillation vessel of the fractionator. The distillation process was performed with a reflux to product ratio of 1. About 10% (of the starting charge) of the distillation vessel liquid was removed every hour. The vapor pressure in the distillation vessel was maintained between 50 and 100 millimeter. As a result of the distillation, 38 kg / h of purified acid (distillate) was removed and fed to be injected into a plate-type absorber for impregnation with purified hydrogen chloride to a concentration of 36-38%. As a result of the boiling of hydrogen chloride, a large amount of heat was released, which was recovered by means of external water-cooled heat exchangers.

The obtained hydrochloric acid (45.6 kg / h) had a concentration of 36-38% and was a very pure product. The concentration of each critical impurity -7-8 in the acid was 10-10%.

7 66293

Example 2

Technical hydrofluoric acid with a total hydrogen fluoride content of 70% was fed in the form of a continuous flow at a rate of 25 kg / h at normal pressure to the top of a membrane-type column apparatus 2 with a heat exchange surface of 1.8 m and an acid temperature of 108-109 ° C. Under these conditions, gaseous hydrogen fluoride was released from the liquid at a rate of 11 kg / h (desorption) and fed to an absorber. 14 kg / h of hydrofluoric acid containing 40-41% hydrogen fluoride (azeotropic acid) was removed from the bottom of the column apparatus. The acid was collected in a collecting vessel and then fed to the distillation. For this purpose, 40-41% of hydrofluoric acid was fed at a rate of 14 kg / h from the collecting vessel to the distillation vessel of the fractionator in a continuous stream. Fractionation was performed at a reflux to product ratio of 1. Every hour, 10% (from the starting charge) of the distillation vessel liquid was drained. The vapor pressure in the distillation vessel was maintained between 100-150 mmH 2 O.

As a result of the distillation, 12.6 kg / h of purified acid (distillate) was removed and fed for injection into a plate-type absorber to be impregnated with purified gaseous fluorohydrogen to a concentration of 70-72%. As a result of the dissolution of hydrogen fluoride, a large amount of heat was released, which was recovered by means of external water-cooled heat exchangers.

The resulting hydrofluoric acid (23 kg / h) was 70-72% concentrated and was a very pure product. The concentration of critical - 7-8 impurities was 10-10%.

Example 3 1 kg of technical or reactive oleum containing 65% free sulfuric anhydride was fed to the evaporator under normal pressure. The temperature of the oleum during evaporation was maintained at 280 ° C. 0.61 kg / h of sulfuric anhydride was released under these conditions and fed to an absorber.

0.39 kg / h of sulfuric acid having a specific gravity of 1.870 and containing 4.13% of free dissolved sulfuric acid hydride (total SO 2 content 82.6%) was discharged from the bottom of the evaporator. The acid was fed to a collection vessel where it was treated with 1% by weight of chromium oxide to oxidize the organic compounds present in the starting product and then fed to the distillation. For this purpose, 0.39 kg / h of acid was fed in a continuous stream to the distillation vessel of the fractionator. Distillation was performed at a reflux to product ratio of 1. Every hour, about 10% (of the starting charge) of the distillation vessel liquid was removed.

As a result of the distillation, 0.35 kg / h of purified acid was removed and fed to an absorber for injection to saturate with purified sulfuric anhydride to a concentration of 66%.

As a result of the dissolution of the sulfuric anhydride in the sulfuric acid, heat was released, which was recovered by external water-cooled heat exchangers.

The gas oleum (0.96 kg / h) had a concentration of 66% and was a very pure product. The concentration of each critical impurity was 10-10%.

Example 4 25-27% technical ammonia liquid was fed in a continuous flow to the top of a membrane-type column apparatus with a heat exchange surface area of 1.8 m at a rate of 20 kg / h at normal pressure and the temperature of the solution was maintained at 97 ° C. Under these conditions, gaseous ammonia was released from the solution at a rate of 4.5 kg / h (desorption) and fed to an absorber. 15.5 kg / h of ammonia solution containing 3% ammonia was removed from the bottom of the apparatus (ammonia solution which boiled without changing the composition). The ammonia solution was fed into a collecting vessel and then distilled. For this purpose, 15.5 kg / h of a 3% ammonia solution was fed in a continuous flow into the distillation vessel of the fractionator.

Distillation was performed at a reflux to product ratio of 1. About 10% (of the starting charge) of the distillation vessel liquid was drained off every hour. The vapor pressure in the distillation vessel was maintained between about 50-70 mmH 2 O. As a result of the distillation, 18 kg / h of purified liquid containing 0.5-1% ammonia was removed and fed for injection to a plate-type absorber to be impregnated with purified ammonia to a concentration of 26-27%.

The concentration of the ammonia solution obtained (18 kg / h) was 25-27% and was a very particularly pure product. The concentration of each critical impurity was -7%.