CN1475443A - Method of producing neutral high quality anhydrous sodium sulfate using natucal salt lake sodium sulfate decahydrate - Google Patents

Abstract

A process for preparing the refined neutral sodium sulphate from the sodium mirabilite of natural salt lake includes dissolving raw material, sand filtering, adding ammonium sulfate, forced evaporation, centrifugal separation, hot-air drying and magnetically removing iron. Its advantages are high purity (more than 99.3%), high whiteness (90%) and pH value 6-8.

Description

Method for producing neutral fine anhydrous sodium sulphate from natural salt lake sodium sulfate

The technical field is as follows:

a method for producing neutral fine anhydrous sodium sulphate from natural salt lake sodium sulphate, belonging to the field of chemical industry.

Background art:

the industrial anhydrous sodium sulfate is as early as 1658 years after the mirabilite is invented by the method of Chinese Grounder, with the progress of scientific technology, the anhydrous sodium sulfate with very high purity is gradually produced, and the latter is called high-purity anhydrous sodium sulfate as anhydrous sodium sulfate. At present, the scale of the anhydrous sodium sulphate production in China is the first place in the world. The raw materials for producing the anhydrous sodium sulphate comprise three kinds of salt lake mirabilite, seawater sodium sulfate and mirabilite ores, and the production method mainly comprises seven kinds of methods including a by-product method, a conversion method, a weathering drying method, a hot-melt salting-out method, a hot-tower evaporation method, a full-hot-melt evaporation method and the like. The total thermal solution evaporation method is a method which is adopted at present. The method comprises the following processes: the finished product is prepared by the working procedures of raw material dissolution, forced evaporation, centrifugal separation and hot air drying. The purity, whiteness and alkali content of the anhydrous sodium sulphate produced by the method are not ideal.

The invention content is as follows:

the invention aims to further improve the purity and whiteness of the anhydrous sodium sulphate and reduce the alkali content of the anhydrous sodium sulphate by improving the traditional total-heat evaporation process.

The method for producing neutral fine glauber salt from natural salt lake glauber salt also comprises the steps of raw material dissolution, forced evaporation, centrifugal separation and hot air drying to obtain the finished product, wherein the clear liquid of the glauber salt is subjected to two steps of sand filtration refining and ammonium sulfate alkali reduction neutralization before the forced evaporation, and in addition, the iron is removed by a magnet after the hot air drying.

The method can effectively improve the purity and whiteness of the finished product of the anhydrous sodium sulphate and reduce the alkali content of the finished product of the anhydrous sodium sulphate by the procedures of sand filtration refining, alkali reduction neutralization, magnet iron removal and the like of the nitrate cleaning liquid. The method aims to reform the traditional technical process of the anhydrous sodium sulphate production industry, so that the product fully highlights low salt, low iron, low water insoluble substances, low pH value (6-8), high main content (more than or equal to 99.3%), high whiteness (more than or equal to 90%), high added value is a product which is not in line with the market supply, and the product conforms to GB 6009-92. Compared with the traditional neutralization method by adding sulfuric acid, the alkali reduction method has the advantages of low cost, easy control, small investment for overall process improvement and high added value of the obtained product. The method not only greatly improves the scientific and technological added value of the traditional product, but also can meet the production requirements of special fine chemical industry, and has guiding significance for the development and utilization of the natural salt lake sodium sulfate resource in the same industry or the same type, thereby promoting the development of the traditional industry in China.

Drawings

The figure is a process flow chart of the method for producing neutral fine anhydrous sodium sulphate from natural salt lake sodium sulphate.

Detailed Description

Example (b): (see the figure)

Salt lake glauber salt resource (salt-alkali-saltpeter paragenic ore) is prepared by using crystallized saltpeter as a raw material through a cold-hot bittern making process and a saltpeter day sun drying process, wherein the content of sodium sulfate is more than 40%, the content of sodium chloride is 8-12%, and the content of sodium carbonate is 5-10%; dissolving the sodium sulfate with water to ensure that the concentration of the clear nitrate solution is 350 g/L at 250-; filtering and refining the nitrate solution by a sand bed to ensure that the turbidity of the filtered nitrate solution is less than 10ppm, wherein the thickness of the sand bed is 0.6-0.7 m, and the diameter of sand grains is 0.45-0.6 mm; adding ammonium sulfate into the filtered clear nitrate solution for alkali reduction and neutralization: the adding amount of the ammonium sulfate is 80 to 90 percent of the total amount of the sodium carbonate in the clear nitrate solution; and (3) entering a forced evaporation process, wherein the temperature in the process is 150-160 ℃, and ammonium carbonate (the decomposition temperature is 134 ℃) generated in the previous process is heated and decomposed: the discharged ammonia gas and carbon dioxide gas are recovered for other use, and the pH value of the nitrate cleaning liquid after forced evaporation is 6-8, which is controlled by the amount of ammonium sulfate added in the alkali-reducing neutralization process; carrying out centrifugal separation; drying with hot air; the magnet is used for removing iron, the dried semi-finished product anhydrous sodium sulphate passes through a cylindrical magnet to remove iron filings contained in the dried semi-finished product anhydrous sodium sulphate, and the cylindrical magnet is a permanent magnet made of neodymium iron boron magnet, and the magnetic strength is 3500-5000 oersted.

Claims (6)

1. A process for preparing high-quality neutral anhydrous sodium sulfate from natural sodium sulfate in salt lake includes such steps as dissolving raw materials, forced evaporation, centrifugal separation and hot-air drying.

2. The method for producing neutral refined glauber salt from natural salt lake glauber salt according to claim 1, wherein the salt lake glauber salt resource is prepared from crystal saltpeter prepared by a cold-hot bittern preparation process and a saltpeter solarization process, wherein the sodium sulfate content is more than 40%, the sodium chloride content is 8-12%, and the sodium carbonate content is 5-10%; sodium sulfate is dissolved by water, so that the concentration of the clear liquid is 350 g/l at 250-.

3. The method of claim 1, wherein the sand filtration refining is performed by filtering the saltpeter solution through a sand bedto obtain a filtrate with a turbidity of less than 10ppm, wherein the thickness of the sand bed is 0.6-0.7 m, and the diameter of the sand is 0.45-0.6 mm.

4. The method for producing neutral fine anhydrous sodium sulphate from Nature salt lake Nature sodium sulphate according to claim 1, characterized in that the adding amount of ammonium sulphate during alkali reduction and neutralization is 80-90% of the total amount of sodium carbonate contained in the liquid of nitrate cleaning.

5. The method for producing neutral high-quality anhydrous sodium sulphate from Nature salt lake Natrii sulfas as claimed in claim 1, wherein the pH of the clear solution after forced evaporation is 6-8, which is controlled by the amount of ammonium sulphate added in the alkali reduction neutralization process.

6. The method for producing neutral fine anhydrous sodium sulphate according to claim 1, wherein the step of removing iron from the magnet is to pass the dried semi-finished anhydrous sodium sulphate through a cylindrical magnet to remove iron filings contained therein, wherein the cylindrical magnet is a permanent magnet made of neodymium iron boron magnet, and the magnetic strength is 3500-5000 oersted.