Research On Producing High Purity Magnesium Hydroxide By Sodium Hydroxide And Bischofite

Magnesium hydroxide is an important chemical products and intermediate products. High purity magnesium hydroxide is produced by reaction crystallization using sodium hydroxide and bischofite as raw material. This can not only solve the "magnesium harm", but also use magnesium resources effectively. The mother liquor can be used in the chlor-alkali process after refined, which can realize the comprehensive utilization of salt lake resources, and promote the development of circular economy.The reactive crystallization kinetics of magnesium hydroxide was investigated in a MSMPR crystallizer by continuous method. Based on the population balance theory, it is determined that magnesium hydroxide growth conforms to the ASL model, crystal nucleation and growth rate eqautions wereB0=324×1015exp(-1.23×104/RT)ΔC4.12MT0.16n0.52G=3.00×103exp (-1.59×104/RT)ΔC1.33High-purity magnesium hydroxide which is low water content (<30%), easy to filter, and the average particle size greater than 10μm was produced, and the influence of parameters on the performance of magnesium hydroxide was investigated. The optimal experimental conditions was got by the orthogonal regression method, which is temperature 92.8℃, speed 2.61 m/s, magnesium chloride concentration 3.7 mol/L, feed rate 1.1 mL/min.The continuous process of crystallization and draft tube on the performance of magnesium hydroxide was researched with MSMPR crystallizer, which shown that high-purity magnesium hydroxide which average particle size was greater than 20μm was produced with MSMPR crystallizer, and the system can be mixed well under a smaller pressure head by installing draft tube.A large number of basic physical properties were measured during the process of magnesium hydroxide production, such as raw materials, slurry, filtrate andproduction.A conceptual design of preparation of 140000 t/y magnesium hydroxide was made based on the experimental results and theoretical analysis. The material balance and energy balance of the process were carried. The effective volume of the mold and the floating zone volume were calculated.