JPS6259525A - Production of sodium bicarbonate - Google Patents

Abstract

PURPOSE:To produce high-purity sodium bicarbonate having low ammonium content, by controlling the pH of an aqueous solution of a sodium salt to a specific level and introducing carbon dioxide gas into the solution to precipitate sodium bicarbonate. CONSTITUTION:Sodium bicarbonate is precipitated by introducing carbon dioxide gas into an aqueous solution of a sodium salt having a pH controlled to 6.0-6.5. The aqueous solution of the sodium salt is usually a saturated aqueous solution of sodium chloride similar to the brine preparation process of general ammonia soda process, however, an aqueous solution of neutral sodium salt such as sodium nitrate, etc., can be used for the purpose. The control of pH of the reaction liquid to 6.0-6.5 is carried out usually by adding an ammonium carbonate such as NH4HCO3, (NH4)2CO3, etc., to the reaction liquid, however, it can be easily achieved also by the addition of ammonia such as NH3 gas, NH4OH, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for easily producing high purity sodium bicarbonate, particularly with a low ammonia content.

[Prior Art and its Problems] Conventionally, high-purity sodium bicarbonate has been produced by a method in which an aqueous solution of sodium hydroxide or sodium carbonate is bicarbonated by passing carbon dioxide gas, and crystals are precipitated, separated, and dried. However, in these methods, since sodium hydroxide or sodium carbonate is used as a raw material, there is a problem that the cost of the raw material is high, and the manufacturing cost of the obtained sodium bicarbonate is also high.

On the other hand, sodium bicarbonate is produced in large quantities as an intermediate product in the production of sodium carbonate by the ammonia-soda method using industrially inexpensive sodium chloride as a raw material, but it contains about 1% ammonia as an impurity. Even if sodium bicarbonate is dried, the ammonia content is 200 p.
l) It only decreases to about II. Therefore, in order to obtain highly pure sodium bicarbonate with even lower ammonia content, additional post-treatments such as purification of the above-mentioned sodium bicarbonate from an aqueous solution by recrystallization are required, which increases the production cost.

[Means for Solving the Problems] In view of the problems described in L, the inventors of the present invention have conducted intensive research on a method for easily obtaining high-purity sodium bicarbonate from inexpensive sodium salts as raw materials.

As a result, when introducing carbon dioxide gas into a saturated aqueous solution such as sodium chloride to precipitate sodium bicarbonate, ammonia carbonate etc. are added to the aqueous solution and reaction p;
．． By controlling the sodium bicarbonate to 0 to 6.5, high purity sodium bicarbonate with extremely low ammonia content can be obtained by normal drying of the produced sodium bicarbonate, and the present invention has been provided. It is something that III. In the present invention, when introducing carbon dioxide gas into an aqueous solution of sodium salt to precipitate sodium bicarbonate, the p of the aqueous solution is
This is a method for producing tatorium bicarbonate, characterized by controlling H to 5.0 to 6.5.

In the present invention, as the aqueous solution of sodium salt, a saturated aqueous solution of sodium chloride similar to that prepared by the ammonia-soda method is generally used, but in addition, an aqueous solution of a neutral sodium salt such as mirabilite is also used. It will be done.

In addition, in the reaction of the present invention, it is preferable that the carbon dioxide gas introduced into the aqueous solution of sodium salt be as concentrated as possible; Approximately 4 obtained by pyrolysis
About 0% is used.

In the present invention, when carbon dioxide gas is introduced into the aqueous solution of sodium salt to perform the bicarbonation reaction, the pH of the solution is set to 6.0 to 6.0.
The desired high purity sodium bicarbonate fi! It is extremely important to obtain That is, it is not preferable to increase the pH of the reaction solution above 6.5 because the ammonia content of the resulting sodium bicarbonate increases. Similarly, if the pH of the reaction solution is lower than 8-1, the bicarbonation reaction of the sodium salt will not proceed sufficiently, making it impossible to efficiently obtain sodium bicarbonate. The method of controlling the pH of the reaction solution according to the present invention to 6.0 to 6.5 generally involves adding NH4t (C03) to the reaction solution.

(This is preferably achieved by adding an ammonia carbonate such as Nt(4)zcO3, but in addition, NH
3 gas, by adding ammonia such as NH4OH? Achieved with precision.

In the present invention, since the rate of dissolution of carbonate scum in an aqueous solution of sodium salt is reaction rate-determining, it is preferable to carry out the reaction system under low temperature and/or pressurized conditions. Generally reaction temperature is 0-30℃, pressure is 0-10 kg
/eva2G range.

[Function] Compared to the conventional ammonia-soda method, the present invention eliminates carbon dioxide by normal drying without any special post-treatment.
, it is possible to obtain highly pure sodium bicarbonate with extremely low ammonia content, and the reason for this is speculated as follows.

Under the conditions for precipitation of sodium tNKH in the ammonia-soda method, the pI of the reaction solution is generally as high as ? The production reaction of sodium carbamate proceeds.

N a (IJ + CO2+ 2 N H3 + N a
cOz .N)I 2 +N H4cQ."-(1) The decomposition reaction of sodium carbamate proceeds as shown in the following formulas (2) and (3).

NaC02-NH2+2H20 -eNaHcO3+NH4OH・”・(2)2NaCO
2φNH2+28zO →N a 2 CO3+ (NH4) z CO3・
...(:]) Therefore, if a large amount of sodium carbamate coexists in the produced sodium bicarbonate, the sodium carbamate will have the corresponding water present in the above formulas (2) and (3). Otherwise, there will be no decomposition in the container and sufficient deammonification will not be achieved by normal drying.

On the other hand, in the method of the present invention, the p of the reaction solution is
By controlling H to 6.0 to 6.5, the reaction of the above formula (1) does not proceed at all or proceeds only slightly. Therefore, the sodium bicarbonate produced by the present invention In this method, there is little coexistence of sodium bicarbonate, and as a result, highly pure sodium bicarbonate with an extremely low ammonia content can be obtained using ordinary dry agglomerates.

[Effects of the Invention] As explained above, according to the present invention, sodium bicarbonate with a low ammonia content is produced directly from the raw materials and the inexpensive sodium salt in 1), and the sodium bicarbonate is treated with a special treatment. High purity sodium bicarbonate with an ammonia content of generally less than 10 ppm can be obtained by conventional drying without further treatment. Therefore, the present invention can greatly reduce the production cost compared to the conventional method and easily obtain highly pure sodium bicarbonate, which can be used as a food additive and for mulberry crops. Can be fully adopted.

[Example] Examples of the present invention are shown below, but the present invention is not particularly limited to these Examples4. Example 1 90 wt% sodium chloride saturated fU aqueous solution was added.
While blowing 9% carbon dioxide gas, 25wt% ammonium bicarbonate aqueous solution was added, and the reaction solution was heated to 6.0~
It was controlled to 6.5. The reaction temperature was maintained at approximately 20°C.

After filtering and washing the formed sodium bicarbonate crystals,
It was dried at a temperature of 60° C. for 3 hours. The ammonia (NH3)-containing acid content of the resulting sodium bicarbonate was 7 ppm.

Comparative Example] The same procedure as in Example 1 was carried out except that the pH of the reaction solution was controlled to 8.5 to 9.2.

Ammonia (N■(3) in the resulting sodium bicarbonate
The content was 2560 ppm.

Example 2 Na (io%N H401) was added while blowing 90voi% CO2 gas into a Q-saturated rail, and pH=
It was controlled to be 6.0 to 6.5. The produced sodium carbonate crystals were filtered, washed, and dried in the same manner as in Example 1. The reaction temperature was maintained at approximately 20°C.

The N1(3 content) in the obtained sodium bicarbonate was 8
It was Fltlm.

Comparative Example 2 The same processing operations as in Example 2 were performed except that the pH+;υ1i311 was set to 8.5 to 2.

At this time, the N83 content in the sodium bicarbonate obtained was lE)≦]Oppm.

Claims (1)

[Claims] 1) When introducing carbon dioxide gas into an aqueous solution of sodium salt to precipitate sodium bicarbonate, the pH of the aqueous solution is adjusted to 6.0.
A method for producing sodium bicarbonate, characterized by controlling the sodium bicarbonate to 6.5. 2) The manufacturing method according to claim 1, wherein ammonia or an ammonium salt is added to control the pH of the aqueous solution to 6.0 to 6.5. 3) The manufacturing method according to claim 2, wherein the ammonium salt is ammonium bicarbonate or ammonium carbonate.