Method for decreasing content of sodium chloride impurities in recovered sodium formate

Abstract

The invention relates to a method for decreasing the content of sodium chloride impurities in recovered sodium formate, which is applicable for recovering the sodium formate from a rongalite mother solution. According to the method, sodium chloride is separated out in the concentrating working procedure of a rectified raffinate, and the method comprises the following steps of A. heating the concentrated rectified raffinate to the temperature of 105-110 DEG C under the vacuum degree of -0.08 to -0.09Mpa to separate out the sodium chloride from the raffinate; B. closing the vacuum, emptying, and continuously heating to the temperature of 130-135 DEG C to dissolve the sodium formate which is separated out through crystallization in the vacuum concentrating process of the raffinate; and C. after the temperature reaches to 130-135 DEG C, placing a material into a filter with a jacket, and carrying out vacuum filtration to separate the sodium chloride which is separated out of the material from a material solution; and placing the material solution which is obtained through the filtration into a crystallization kettle, and adding methanol with the volume accounting for about 1 / 4 of that of the material solution to obtain the recovered sodium formate with the low-content sodium chloride impurities through filter-pressing and drying processes after extraction and crystallization. The content of the sodium formate in a recovered sodium-formate product which is obtained by the method is higher than 88 percent, and the content of the sodium chloride impurities is lower than 5 percent.

Description

technical field

[0001] The invention relates to a method for reducing the impurity content of sodium chloride in recovered sodium formate, and the method is suitable for recovering sodium formate from sodium hydrosulfite mother liquor. technical background

[0002] After nearly 20 years of development, the sodium formate method has gradually replaced the zinc powder method as the most important method for hydrosulfite production. Sodium formate is one of the main raw materials for the production of sodium hydrosulfite by the sodium formate method. In the process of producing hydrosulfite by the sodium formate method, the process of excessive sodium formate is generally used. Only a part of the mother liquor produced by each reaction is recycled for the next synthesis reaction. The excess mother liquor needs Carry out comprehensive recycling. In addition to the solvent methanol, the treated mother liquor also contains inorganic salts such as sodium bisulfite, sodium thiosulf...