SU1721015A1 - Method for obtaining sodium carbonate - Google Patents

Abstract

This invention relates to ammonia processes for the preparation of soda ash and can be used in the chemical industry in the production of soda ash by the ammonia method. The aim of the invention is to reduce the specific steam consumption for distillation by reducing the volumes to be processed. The method involves the separation of the original brine into two streams in a volume ratio of 60-85; 14-40, a smaller part of which is evaporated to obtain solid sodium chloride, mixing the obtained sodium chloride with the remaining amount of pre-ammoniated and precarbonized brine, carbonizing the resulting mixture together with ammonia-containing liquid formed in the distillation gas cooler and previously saturated with ammonia by contacting it with a distillation gas, separating the sodium bicarbonate formed, calcining it, regenerating ammonia from the filter liquid by distilling it steam to form a distillation in the refrigerator and in the condenser the distillation of ammonia-containing liquid and distillation gas. Moreover, the ammoniacontaining liquid formed in the refrigerator of the distillation gas and the distillation preliminarily saturated with ammonia is fed to carbonization, and the ammoniacontaining liquid produced in the distillation condenser is mixed with filter liquid in a ratio of 1: 0.7 and served for additional distillation. Thereafter, the distillate liquid formed is directed to the lime slaking. The resulting lime suspension before serving for the decomposition of ammonium chloride is subjected to concentration. The method according to the invention makes it possible to reduce the volume of distillate liquid from 7.72 to 6.63 m3 and, as a result, to reduce the heat consumption for evaporation and distillation from 0.99 to 0.92 Gcal compared with the prototype. 1 tab., 1 Il. s te GO O SP

Description

The invention relates to ammonia processes for producing soda ash and can be used in the chemical industry in the production of soda ash by the ammonia method.

The aim of the invention is to reduce the specific steam consumption for distillation for

by reducing the amount of recycled.

The drawing shows the technological scheme of the proposed method for the production of soda ash.

The scheme includes the steps of absorbing 1 ammonia and carbon dioxide with purified sodium chloride brine, a preliminary

carbonization 2 ammonia-treated brine, washing 3 carbonation gases, evaporation -4 parts of purified brine, mixing 5 pre-carbonated liquid with condensed sodium chloride precipitate, carbonization 6, filtration 7 to separate sodium bicarbonate precipitate, calcining 8 to obtain salable soda, distillation 9 filter liquid vapor in the distiller and the distillation heat exchanger, condensation in the distillation condenser 10 of the vapor-gas mixture of distillation, cooling in the refrigerator of the distillation gas 11, mixing 12 to after condensation of the vapor-gas mixture of distillation with filter liquid, additional distillation of filter liquid 13, lime calcining 14, concentration of lime lime 15, mixing 16 concentrated lime suspension with carbon dioxide degassed carbon dioxide in a heat exchanger of distillation 9, saturating 17 Ammonia containing ammonia liquids after the distillation gas cooler.

The method for producing soda ash is carried out as follows.

The original purified sodium chloride brine is divided into two unequal streams. One stream in the amount of 60-85% by volume is directed to the absorption stage of 1 ammonia and carbon dioxide, and the rest (15-10% by volume) is fed to the evaporation stage - sediment 4.

After the absorption stage 1, the ammoniated brine enters the preliminary carbonization stage 2 and washing 3 gas to the carbonation stage 6, where partial absorption of carbon dioxide occurs. The precarbonized liquid is then fed to the mixing stage 5, where condensed sodium chloride is supplied from the evaporation stage-4. The liquid mixture obtained in mixing stage 5 is fed to the carbonation stage 6, where ammonia-saturated ammonia obtained in the subsequent stages of the process is also introduced. containing liquid. In the carbonation stage 6, the liquid mixture is saturated with carbon dioxide, resulting in a suspension of sodium bicarbonate. The sodium bicarbonate precipitate is separated in the filtration stage 7 and then sent to the calcination stage 8 to obtain salable soda ash.

The mother liquor (filter) after filtration is fed to the distillation stage 9, 10, where ammonia and carbon dioxide are regenerated from it. Steam-gas mixture

The distillations are condensed in the distillation condenser 10. The condensate formed in condenser 10 is mixed at the mixing stage 12c with filter liquid in a ratio of 1: 0.7 and, after the additional distillation at stage 13, is fed to the quenching stage 14 of lime, where to form a lime slurry and quality water is additionally supplied.

After the slaking stage 14 lime lime suspension with a CaO content of 0.22-0.26 May. shares and not more than 0,022 May. the CaCIa fractions are directed to the concentration stage 15 by CaO (partially dehydration in a centrifuge or hydrcyclone), after which the concentrated lime suspension with a CaO content of at least 0.29 May. the fraction enters the mixing stage 16 with the distilled carbon dioxide gas degassed by filter liquid 9. As a result of the mixing, ammonium chloride decomposes in the filter liquid to form calcium chloride and release ammonia.

The ammonia-containing liquid formed during cooling of the distillation gases at the cooling stage 11 (ammoniacondensation condensate of the distillation cooler) is cooled at atmospheric pressure to 40-42 ° C and saturated in ammonia at stage 17 by contacting with uncondensed condensation under these conditions. gas distillation cooling stage 11, and then served on the stage of carbonization 6.

Below is a specific example of the implementation of the proposed method (given the specific cost per 1 ton of soda).

Approx. 5.1 m3 of purified brine of sodium chloride is divided into two streams. One stream in the amount of 1232 kg (1.03 m3), which is 20% by volume of the total amount of the initial solution, is sent to the evaporation stage — approximately 4. The second stream of purified brine in the amount of 5006 kg (4.1 m3) is served at the absorption stage 1, where the brine absorbs 423 kg MNZ and 160 kg C02. Further, the ammoniated brine passes through the pre-carbonation column 2 and the washer 3 of the gas of the carbonation columns 6, where it additionally absorbs 157 kg CO2.

5820 kg (4.87 m3) of precarbonized liquid contains 0.068 May. MNZ shares, 0.05 May. shares of COA and 0.216 May. at the mixing stage 5, a wet precipitate of NaCl in the amount of 325 kg obtained with evaporation-sedimentation 4 is added to this liquid. As a result of dissolution at the stage of displacement of 5 solid NaCI, 6,140 (5.16 m3) of a liquid mixture containing 0.255 may be supplied to the carbonization column of the carbonization stage b. fractions of NaCI, 0.065 May, fractions MNZ and 0.048 May. share of C02.

In the carbonization column of the carbonization stage 6, in the area of the second gas inlet, the condensate of the distillation cooler concentrated in ammonia at stage 17, obtained by cooling the distillation gases at stage 11, is 210 kg (0.2 m3) containing 0.21 May . MNZ and 0.21 May C02. An ammonia-containing liquid with a temperature of 42 ° C is saturated with ammonia: at atmospheric pressure.

In the carbonization process, the ammoniated and precarbonated solution is saturated with carbon dioxide, resulting in the formation of sodium bicarbonate, which precipitates in an amount of 1614 kg.

After separating the sodium bicarbonate from the filtration stage 7 on the filters and washing it, the amount of filter liquid formed is 5994 kg (5.33 m3) and it contains 0.017 May. shares, 0,0147 May. MNZ, 0,025 May. share of C02. May 0.062 share NaCI.

The condensate formed in the distillation condenser at stage 10 in the amount of 525 kg is withdrawn into the mixer at the mixing stage 12, where 384 kg of filter liquid is fed.

The ratio of condensate: filter fluid 1: 0.7. Thereafter, the mixture is fed to an additional distillation 13, and the remaining filter liquid is distilled in the heat exchanger and distiller of the main distillation column 9. After additional distillation, 13 distillate liquid in the amount of 1155 kg (1.07 kg) containing 0.049 May . shares of CaC12 and 0,026 May. share NaCI, comes to the lime slaking 14, which also serves 692 kg of water. As a result of the slaking of lime, a lime slurry is formed in the amount of 2597 kg, containing 0.22 May. share of Cao. 0.022 May. share of CaCl2. The resulting lime suspension is sent to concentration 15 by partial dehydration in a centrifuge, where 619 kg of clarified solution is separated,

1978 kg (1.54 m3) of a condensed lime suspension containing 0.29 May. of CaO, is fed to mixing 16 with carbon dioxide gas degassed by carbon dioxide distillation heat exchanger 9. When mixed, ammonium chloride decomposes to form calcium chloride and ammonia.

As a result of the main distillation process 9, a distillation liquid in the amount of 7653 kg (b, 63 m3) is formed, and the steam consumption for the distillation of the filter liquid 5 is 0,8385 Gcal, or 1290 kg.

Steam consumption for evaporation of 1,232 kg of purified brine of sodium chloride to obtain 325 kg of NaCI precipitate amounted to 1032 kg, and the amount of secondary vapor forming 0,912 kg.

Thus, out of 1,290 kg of steam fed to the distillation of the filter liquid, 912 kg is the secondary steam after the evaporation step. Taking into account the required amount of heat for the evaporation process, the total heat consumption is 0.9165 Gcal. In the known method, the total heat consumption of 0.9864 Gcal.

0 The main parameters of the proposed method are tabulated (example 1), and examples 5-6 of the table show the main indicators 5 achieved in the well-known and industrial methods for producing soda ash.

Thus, when using the proposed method, the amount of dysgillary fluid is reduced to 6.63 m3 (7653 kg) versus 7.72 m3 (8908 kg) by lime. This method, and the total heat consumption for evaporation and distillation does not exceed 0.9165 Gcal versus 0.9864 Gcal by a known method.

Claims (1)

Invention Formula 5 Method of obtaining calcined soda, including the separation of the original brine into two streams in a volume ratio of 60-85: 15-40, a smaller part of which is evaporated to obtain a solid 0 sodium chloride, mixing the resulting solid sodium chloride with the remaining pre-ammoniated and predkarbonizovannogo brine carbonization gas soda and izvestko5 O furnaces resulting mixture together with an ammonia-liquid separation of the resulting bicarbonate solution on the filters, calcination of sodium hydrogencarbonate, slaked lime, regeneration ammi0 aka of filter liquid by steam distillation and decomposition of ammonium chloride with lime suspension to form distillate gas in the refrigerator and in the distillation condenser of the ammoniax-containing liquid and gas of distillation, which is due to the fact that, in order to reduce the specific steam consumption for the distillation of filter liquids by reducing the processed volumes, the lime kilns ammonia-containing liquid formed in the distillation gas cooler, preliminarily saturated in ammonia by contacting it with the distillation gas, and emmiax-containing liquid formed in the distillation condenser is mixed with the filter liquid at a ratio of 1: 0.7 and is fed to an additional distillation, after which the distillation liquid formed is sent to the lime quenching, and the lime suspension thus obtained is concentrated before being fed to the decomposition of ammonium chloride. 1 Proposal 1: 0,70,29 2 Exit for claimed values of 1: 0,60,29 ratios of condensate after 3 condensation of steam-gas 1: 0,80,29 mixture of distillation to filter fluid and preferred concentrate P g 0.9165 0.9195 26 25 A slurry of lime slurry is observed.