My country is rich in salt lake resources. The magnesium resources in the Chaerhan Salt Lake in Qinghai and the Lop Nur Salt Lake in Xinjiang are in urgent need of development. Therefore, the development of salt lake magnesium resources to prepare magnesium oxide can not only promote the comprehensive utilization of salt lakes, but also solve the current dilemma of the depletion of solid magnesium ore and the declining grade of magnesium products in my country. At the same time, it can alleviate the magnesium produced by the development of potash industry and bring social and economic benefits.
Using the sulfate subtype salt lake brine of the Lop Nur Salt Lake in Xinjiang as raw material, the ammonia method is used to prepare the magnesium oxide precursor, and high-purity light magnesium oxide is prepared after carbonization and calcination. A new three-stage process of ammonia precipitation of magnesium-ammonium bicarbonate carbonization-calcination is established. Experiments show that ammonium bicarbonate carbonization of magnesium oxide can effectively reduce the content of S and B in magnesium oxide products and improve the apparent specific volume and purity of magnesium oxide. Under the process conditions, the purity of the high-purity light magnesium oxide product is 99%, the apparent specific volume reaches 10mL/g, and the main indicators meet the requirements.
The precursor of magnesium oxide was prepared by using CL magnesium stone from the Chaerhan Salt Lake in Qinghai as raw material and lime water as precipitant. High-purity light magnesium oxide was obtained after carbonization and calcination. A new three-stage process of lime water method magnesium precipitation-ammonium bicarbonate carbonization-calcination was established. The CaCl2 -Ca(OH)2-H2 O system involved in the preparation of magnesium oxide by lime water method was theoretically studied. The thermodynamic equilibrium log c-pH diagram of the Ca(OH)2-H2O system at 273.15K was drawn. The effects of pH and CaCl2 concentration on the solubility of Ca(OH)2 in lime water were found. The relationship between CaCl2 concentration and calcium hydroxide concentration was calculated using the Debye-Huckel law, and the experimental value was found to be consistent with the calculated value.
When the concentration of CaCl2 mother liquor was 2.5720mol/L, CaClOH phase was generated. At this time, it could not be used to prepare lime water. According to calculation, CaCL mother liquor can be circulated to prepare lime water 132 times. The experiment shows that the two-way bottom liquid synthesis method is good, and the increase in the mass percentage concentration and volume of the CaCl2 bottom liquid are conducive to reducing the supersaturation of the reaction system. The lime water method is significantly better than the traditional lime method. The impurity content in the prepared magnesium oxide is much lower than that of the traditional lime method, and the purity can reach more than 99% after washing. The magnesium oxide prepared by the continuous experiment has good sedimentation performance and stable product quality. The apparent specific volume of the magnesium oxide prepared by carbonization and calcination is effectively improved, the purity is high, the crystal shape is complete, and the product quality meets the requirements.