Magnesium chloride is one of the substances that are abundant in brine and have high added value. In addition to its own use, other magnesium products produced from magnesium chloride are also very widely used. High purity magnesium oxide is one of them. At present, there are many methods to produce high purity magnesium oxide, magnesium chloride pyrolysis is one of the most popular methods in recent years, especially it does not need any additives, low production cost, no pollution to the environment, simple process and other advantages to become the best choice for many enterprises trying to put into large-scale production.
Hebei Messi Biology Co., Ltd. has prepared high quality magnesium chloride hexahydrate crystals by using Qinghai Salt Lake. Magnesium chloride pyrolysis was used to prepare magnesium oxide products with high purity and stable properties. The process parameters for the preparation of high purity magnesium oxide were explored in three main parts. The effects of pyrolysis time and pyrolysis temperature on the purity and activity of magnesium oxide and the decomposition rate of magnesium chloride were investigated in the magnesium chloride pyrolysis stage, and the relationship between magnesium oxide activity and its microstructure was explored. The study showed that with the increase of magnesium chloride pyrolysis temperature and time, the magnesium oxide purity and magnesium chloride decomposition rate kept increasing, the magnesium oxide activity kept decreasing, and the grain size kept increasing.
By investigating the reaction mechanism and kinetic parameters of magnesium chloride pyrolysis, Hebei Messi Biology Co., Ltd. provides the theoretical basis for the production of high-purity magnesium oxide by magnesium chloride pyrolysis. The optimized conditions of magnesium chloride pyrolysis and calcination were investigated to provide optimized design parameters for the industrial production of high-purity magnesium oxide.
From the perspective of the relationship between magnesium oxide activity and grain size, the pyrolysis temperature and time affect the crystallinity of magnesium oxide, with the increase of temperature and time, the magnesium oxide crystalline shape tends to be complete and the surface activation site decreases, which shows a decrease of activity.
In the impurity purification stage, the effects of univariate variables of washing temperature, washing time, stirring rate and solid-liquid ratio on the removal of chloride ions and the purity of magnesium oxide were investigated, and the optimal purification parameters were obtained by designing an orthogonal test: washing temperature 80°CC, washing time 40 min, stirring rate 830 r/min and solid-liquid ratio 0.05 g/ml. The calcination stage was treated by controlling the sample after washing. Calcination conditions such as calcination temperature and calcination time were controlled, and the conditions were analyzed to obtain the optimized process parameters.
The calcination temperature was chosen to be 650℃ and the calcination time to be 1 hour, and the content of magnesium oxide in the product made was more than 99%, which met the requirement of high purity magnesium oxide and achieved the experimental purpose.
The apparent activation energy and frequency factor of magnesium chloride pyrolysis reaction were obtained by TG-DTG analysis method and Doyle method: E1=68.26KJ/mol, A1=7.59x105s-1E2=123.99KJ/mol, A2=1.38x1012s-1;E3=138.70KJ/mol,A3=6.70×1012s-1;E4=176.06KJ/mol,A4=3.41×1015s-1.