Hebei Messi Biology Co., Ltd. stated that my country is rich in salt lake resources, and the magnesium resources in Qinghai Chaerhan Salt Lake and Xinjiang Lop Nur Salt Lake 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 predicament of my country’s solid magnesium ore depletion and declining magnesium product grade. At the same time, it can greatly alleviate the “magnesium harm” caused by the development of potassium salt industry, and bring great social and economic benefits.
Using the sulfate subtype salt lake brine of Xinjiang Lop Nur Salt Lake as raw material, the ammonia method is used to prepare magnesium oxide precursors, 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 optimal process conditions, the purity of high-purity light magnesium oxide products 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 the water bischofite from the Chaerhan Salt Lake in Qinghai as raw material and lime water as precipitant. After carbonization and calcination, high-purity light magnesium oxide was obtained. A new three-stage process of magnesium precipitation by lime water method-ammonium bicarbonate carbonization-calcination was established. The CaCl2-Ca(OH)2-H2O system involved in the circulation of calcium chloride mother liquor to prepare lime water in the process of preparing 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, and the effects of pH and CaCl2 concentration on the solubility of Ca(OH)2 in lime water were found. The relationship between calcium chloride concentration and calcium hydroxide concentration was calculated using the Debye-Huckel limiting law, and it was found that the experimental value was consistent with the calculated value.
Hebei Messi Biology Co., Ltd. stated that when the concentration of calcium chloride mother liquor was >2.5720 mol/1, CaClOH phase was generated. At this time, it could not be used to prepare lime water. According to calculations, the calcium chloride mother liquor can be circulated to prepare lime water 132 times. The experiment shows that the two-way bottom liquid synthesis method is the best. The increase in the mass percentage concentration and volume of the calcium chloride bottom liquid are conducive to the reduction of the supersaturation of the reaction system. The lime water method is significantly better than the traditional lime milk method. The impurity content of the prepared magnesium oxide is much lower than that of the traditional lime milk 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.