JPS597645B2 - Manufacturing method of carbonated soda - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing soda carbonate and ammonium chloride by using the effluent from a diaphragm electrolyzer in the process of producing ammonia soda which co-produces ammonium chloride.

The method for producing soda carbonate from the effluent of a diaphragm electrolyzer is as follows:
Sodium carbonate is produced by direct carbonation and precipitation separation as ferric acid cedar monohydrate, sodium carbonate decahydrate, bicarbonate, or sesquicarbonate, or by a combination of diaphragm method electrolytic cell effluent and ammonia soda method. There is a manufacturing method.

Regarding the manufacturing method of soda carbonate in combination with the ammonia soda manufacturing method, in Japanese Patent Publication No. 46-26104, the electrolytic solution flowing out from the diaphragm method electrolytic cell is divided into two parts, and one is divided into two before the ammonia absorption stage of the soda manufacturing process. A method is described in which one is carbonated in advance with carbon dioxide gas, the other is used to recover ammonia in the soda production process, and the effluent from the recovery device is circulated to an electrolytic cell.

Furthermore, in Japanese Patent Publication No. 47-41236, ammonium chloride contained in the mother liquor is obtained by mixing the crystallized mother liquor obtained after separating sodium bicarbonate and ammonium chloride obtained in the process of the ammonia soda method with the effluent of a diaphragm method electrolytic cell. at least partially decomposing and supplementing the resulting solution with common salt,
Recycling to the ammonia soda process and/or the electrolysis process is described.

Furthermore, in JP-A No. 49-51199, it is disclosed that the number of moles of sodium hydroxide in the effluent of the diaphragm electrolytic cell is crystallized in the crystallization mother liquor after separating ammonium chloride in the production of ammonium chloride soda from the effluent of the diaphragm electrolytic cell. A continuous method for producing soda carbonate, ammonium chloride, and chlorine, which comprises adding ammonium chloride in an amount equivalent to or less than the number of moles of ammonium chloride in the mother liquor, and further adding ammonia to the mixed solution, and carbonating it as brine. is listed.

The present inventor has discovered that when using the effluent from a diaphragm electrolytic cell as a raw material in the ammonium chloride co-producing ammonia soda production process, by adopting a certain method, it is possible to improve the Na utilization rate and to improve the Na utilization rate in the ammonia absorber. It has been found that the amount of ammonia blown can be reduced and the amount of mother liquor distilled can be reduced.

That is, in the present invention, when using the electrolytic cell cathode effluent in the diaphragm method brine electrolysis process as a raw material in the ammonium chloride co-producing ammonia soda production process, the cathode effluent is carbonated in advance, and then solid ammonium chloride and ammonium chloride crystals are formed. This is a method for producing soda carbonate and ammonium chloride, which is characterized in that the mother liquor is added and used.

Generally, when chlorine ions are not replenished to the soda process solution, the Na utilization rate in the effluent of the diaphragm electrolyzer is approximately 70%.
(Na as alkali and salt) is low.

On the other hand, by increasing the chlorine ion concentration by replenishing it, the Na utilization rate can be improved to, for example, 85%.

Furthermore, according to the present invention, by supplementing the chloride ion concentration by using ammonium chloride instead of common salt,
The Na utilization rate can be further increased.

Furthermore, as an advantage of using ammonium chloride,
Compared to the case where common salt is used as in No. 7-41236, the amount of ammonia injected for the amount of supplementary salt and alkali in the effluent of the diaphragm electrolyzer can be reduced, and furthermore, the amount of ammonia that is responsible for the above does not need to be distilled. This is the result.

In addition, in the present invention, by carbonating the cathode effluent in advance, that is, pre-carbonating the cathode effluent, not only can a dilute gas such as exhaust gas be used as a carbon dioxide gas source, but also pre-carbonation can be carried out as in the following reaction. When carbonation is performed (reaction 2), the back pressure of ammonia in the ammonia absorber is lower than when preliminary carbonation is not performed (reaction 1), so there is an advantage that ammonia is easily absorbed.

(Reaction 1) (Reaction 2) The present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a process diagram of one embodiment of carrying out the invention.

First, the effluent 1 from the diaphragm electrolytic cell is introduced into the pre-carbonation equipment 100, and is pre-carbonated with CO2 gas 2a.

At this time, the degree of carbonation of the carbonated liquid is (number of moles of CO2)/(
It is desirable that the value of the number of moles of alkali does not exceed 0.5.

When the degree of carbonation exceeds 0.5, sesquicarbonate soda (Na2
CO3, NaHC03, 2H20) is likely to precipitate and the absorption tower can become clogged, causing operational problems.

Note that the reference numeral 19 indicates an inert gas path.

Next, the pre-carbonated liquid 3 and the brine 4 are mixed with the ammonium chloride separated mother liquor 16 and the solid ammonium chloride 17 in a mixing tank 200.

At this time, irrigation is not necessarily required.

Furthermore, solid ammonium chloride is used to increase the chloride ion concentration.

The solid ammonium chloride prevents the formation of solid matter in the mixing tank effluent55. 3 mol/'A or less (30℃)
It is preferable to add it so that

The mixing tank effluent 5 is led to an ammonia absorber 300, and generally (NH3)/(CI) = 1. 1~
Absorb ammonia so that the concentration is 1.2 to obtain stock solution 6.

The stock solution 6 is carbonated by blowing carbon dioxide gas 2b into it in a carbonation tower 400 to precipitate sodium bicarbonate.

Next, the finishing liquid 7 containing bicarbonate of soda is applied to a separator 500 to separate bicarbonate of soda crystals 8, and then calcined to form soda ash.

On the other hand, part of the sodium bicarbonate separated mother liquor may be
0 is distilled in a distillation column 600 to recover ammonia.

The recovered ammonia 11a is recycled to the ammonia absorber 300 together with the ammonia 1lb supplied from the outside, and the distillation mother waste liquid 12 is sent to the calcium chloride manufacturing process.

All of the sodium bicarbonate separated mother liquor or the remainder 9 sent to the distillation column 600 is converted into ammonia by an ammonia absorber 700.
After absorbing ie to a ratio of (NH40H)/(Co2)〉2.5, preferably 3 or more, it is introduced into an ammonium chloride reaction tank 800 via route 13, and solid salt 14 is introduced to perform salting out. At the same time, it is cooled by a refrigerator 900 to precipitate ammonium chloride.

This ammonium chloride slurry 15 is introduced into a separator 1000 to separate ammonium chloride crystals 18.

The separated ammonium chloride mother liquor 16 and a portion 17 of the separated ammonium chloride crystals are recycled to the mixing tank 200 for use.

As described above, the present invention generally provides a solution in which solid ammonium chloride is supplemented and mixed with the crystallized mother liquor after ammonium chloride separation in the ammonium chloride co-producing ammonia soda production process by carbonating the effluent of a diaphragm electrolytic cell in advance. Then, the number of moles of alkali in the preliminary carbonation solution does not exceed the number of moles of ammonium chloride in the mixture, and the mixture is made to absorb ammonia, which is then introduced into a carbonation tower and carbonated. This is a method for producing sodium carbonate and ammonium chloride.

At this time, solid ammonium chloride may be added at the same time as the ammonium chloride crystallization mother liquor is mixed with the effluent of the diaphragm electrolytic cell, or in a separate step from the mother liquor.

Further, the solid ammonium chloride may be used in a form in which the ammonium chloride is not completely crystallized and the mother liquor is a slurry liquid containing the solid ammonium chloride.

For example, in FIG. 1, the slurry liquid 15 containing solid ammonium chloride may be directly circulated to the mixing tank 200.

Examples and comparative examples are given below, but the present invention is not limited to these examples.

Example The process was carried out according to the process diagram shown in FIG.

First, a diaphragm electrolyzer cathode effluent having the following composition is sent to the preliminary carbonation tower 100.

This diaphragm method electrolyzer cathode effluent is treated with carbon dioxide in a preliminary carbonation tower 100.
O.

It is carbonated and has the following composition. This pre-carbonated liquid was sent to the mixing tank 200, and NH4C l containing 5 g of water was sent to the mixing tank 200.
120P and NH4Cl crystallization mother liquor having the following composition are added and mixed thoroughly.

A solution having the following composition is sent from the mixing tank 200 to the ammonia absorber 300.

When 2151NH3 is absorbed in an ammonia absorber, a stock solution with the following composition is obtained.

This stock solution is sent to a carbonation tower 400 and carbonated with CO2.

The effluent taken out from the bottom of the carbonation tower 400 is sent to a separator 500, where 18 g of bicarbonate of soda having absorbed 170 g of water is added.
71I? A bicarbonate of soda separated mother liquor having the following composition is obtained.

Of this separated mother liquor, a solution having the following composition is sent to an ammonia absorber 700 to absorb 123 ammonia.

On the other hand, the composition of the remaining separated mother liquor is as follows:
17 oz of N}{3 is sent to the distillation column 600 and recovered, and is recycled and used in the ammonia absorber 300.

The composition of the solution that absorbed ammonia in the ammonia absorber 700 is as follows.

This solution is sent to the salting-out reaction tank 800 and 41'? Solid NaCl 828P which has occluded water of
690 g of ammonium chloride occluded and an ammonium chloride separated liquid having the following composition were obtained.

This separated mother liquor is sent to the mixing tank 200 and used for circulation.

At this time, the Na utilization rate was 95.1%, and the ammonia absorber 3
Ammonia absorption amount in 00 215? Met.

Comparative Example 1 When the same procedure as in Example was carried out except that the chlorine ions were supplemented with common salt instead of solid ammonium chloride, bicarbonate of soda 2015P which absorbed 183 g of water was obtained.
and water 61? A barrel containing 668 grams of ammonium chloride.

At this time, the Na utilization rate was 92.9%, and the amount of ammonia absorbed by the ammonia absorber 300 was 252 g.

Comparative Example 2 By performing the same operation as in Example without using the solid ammonium chloride supplementary salt in Example, other conditions were the same as in Example, 1617P of bicarbonate of soda which occluded 1471 g of water and 446 g of ammonium chloride which occluded 41 g of water were obtained. Ta.

At this time, the Na utilization rate was 89.8%, and the ammonia absorber 3
The ammonia absorption amount in 00 was 2341.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing one aspect of carrying out the method of the present invention. 1 is the tank effluent, 2a and 2b are carbon dioxide gas, 3 is the preliminary carbonation liquid, 4 is brine, 5 is the mixing tank effluent, 6 is the stock solution, 7
is finishing liquid containing bicarbonate of soda, 8 is bicarbonate of soda, 9,
10 is sodium bicarbonate separated mother liquor, 11a, 1lb, 11c
is ammonia, 12 is distillation mother waste liquid, 13 is route, 14 is salt, 15 is ammonium chloride sura! J-, 16 is ammonium chloride separated mother liquor, 1T is solid ammonium chloride,
18 is ammonium chloride crystal, 19 is inert gas, 1
00 is preliminary carbonation equipment, 200 is mixing tank, 300 and 7
00 is an ammonia absorber, 400 is a carbonation tower, 500 and 1000 are separators, 600 is a distillation tower, 800 is an ammonium chloride reaction tank, and 900 is a refrigerator.

Claims (1)

[Claims] 1 When using the electrolytic cell cathode effluent in the diaphragm method salt electrolysis process as a raw material in the ammonium chloride co-producing ammonia soda production process, the cathode effluent is carbonated in advance, and then solid ammonium chloride and ammonium chloride crystallization mother liquor are added and mixed. A method for producing soda carbonate and ammonium chloride, characterized in that the method is used as a method of producing sodium carbonate and ammonium chloride.