Quality of Chinese Solar Salt and Composition of Mother Liquid in Concentrating and Crystallizing Ponds
Studies on Mother Liquid in Salt-Manufacturing Process (Part 29)
1976 Volume 30 Issue 3 Pages 124-132
Details
1976 Volume 30 Issue 3 Pages 124-132
To study the relationship between the quality of Chinese solar salt and the composition of mother liquid in concentrating and crystallizing ponds, an analysis was conducted on the brine of concentrating ponds, the mother liquid of crystallizing ponds, and the solar salt taken from Tangku Salt Field in China in May, 1975. The results of the analysis were as follows:
1. The weight ratio of Na/Mg of the brine and mother liquid was eight from the stage of sea water to the stage of the second concentrating pond, but it began to decrease at the middle stage of the second concentrating pond and came down to three at the stage of the crystallizing pond. In addition, the chemical composition of the solution differed from the concentrating process line of sea water. This showed that the mother liquid circulated between the second concentrating pond and the crystallizing pond.
2. When the total impurities of the solar salt taken for the current analysis were compared with those of the solar salt mentioned in previous papers, the content of sodium chloride was 1.5% more than before, while the content of water and insoluble matters was 1.0% and 0.2% less, respectively.
3. As the result of the comparison made on the impurities in the crystals of the solar salt between the current and previous analyses, the content of impurities excluding potassium ions in the crystals was 20-50% of the previous case. Judging from the contents of the total impurities and of the impurities in the crystals, the solar salt samples taken for the current analysis were of better quality.
4. The calculated concentration of magnesium ions of the solar salt was higher than that of the mother liquid in the crystallizing pond. This suggested that in the early part of the growth-stage the crystals of the solar salt grew in the more-concentrated mother liquid being contained in the crystals, but in the later part of the growth-stage they were placed in the less-concentrated mother liquid attaching to the surface of the crystals.
5. To make a comparison on the impurities of the outer and the inner sides of the crystals, 10-20mm polycrystals of the solar salt were crushed into 4-5mm unit-crystals, and about 80% of the total was resolved in water and analyzed. The amount of the impurities of the outer side was 4-6 times more in potassium ions and 6-12 times more in magnesium ions than the inner side.
6. The total water content of the solar salt was 2.3g/100g, of which 11%(0.26g/100g) was in the cavities of the crystals, 30%(0.67g/100g) among 10-20mm polycrystals (aggregates of 4-5mm unit-crystals), and 59%(1.37g/100g) on the surface of the crystals.
