Method for preparing basic magnesium chloride and magnesium oxide by pyrolyzing bischofite

Abstract

The invention relates to a method for preparing basic magnesium chloride and magnesium oxide by pyrolyzing bischofite. The method is characterized by adopting section calcining, recovering HCl in a section manner, particularly pressurizing and spraying the hot solution of refined bischofite under the temperature of 130 to 150 DEG C to a reaction kettle, carrying out primary calcining under the 250 to 300 DEG C after removing parts of crystal water with the calcining time of 1 to 3 hours, and obtaining the product of basic magnesium chloride (MgOHCl); absorbing the tail gas with water to obtain hydrochloric acid; the washing the calcining product which contains little amount of undecomposed magnesium chloride hydrate to obtain the basic magnesium chloride (MgOHCl); carrying out secondary calcining on the obtained MgOHCl under a temperature of 450 to 500 DEG C with the calcining time for 1 to 3 hours to obtain MgO, and cooling and recovering the produced HCl to obtain hydrochloric acid. The method has the advantages of low calcining temperature, little equipment corrosion, little energy consumption, high HCl recovery rate, simple technique, high product purity and low cost.

Description

【Technical field】 [0001] The invention relates to the technical field of magnesium compounds, in particular to a method for preparing basic magnesium chloride and magnesium oxide by pyrolyzing bischofite. 【Background technique】 [0002] Magnesium oxide is an important inorganic chemical product with a wide range of uses, mainly for the preparation of refractory materials, and secondly for pulp, uranium extraction, building materials, animal food, fertilizers, rubber, plastics and adhesives. There are three main sources of magnesium oxide: magnesium-containing ores (magnesite and dolomite, etc.), brine, and seawater. Magnesium oxide series products include light magnesium oxide, active magnesium oxide, heavy magnesium oxide, electrical grade magnesium oxide, silicon steel grade magnesium oxide, medical magnesium oxide, high-purity magnesium oxide, etc. [0003] Basic magnesium chloride (Mg x (OH) y Cl z mH 2 O, 2x-y-z=0, 0≤m≤6) is an excellent flame retardant and filler,...

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Problems solved by technology

[0006] (1) Magnesite Calcination Method—my country has large reserves of magnesite. This method is simple in process and low in cost, but the purity of the obtained magnesium oxide is low, generally lower than 95%, difficult to reach 99%, and will produce a large amount of Carbon dioxide, polluting the environment;

[0007] (2) The carbonization method is to calcinate solid ores such as magnesite into powder, pass into carbon dioxide and water, heat to generate magnesium bicarbonate, and then burn to obtain magnesium oxide; this method has low cost, but the process flow is long and the equipment investment is large. The magnesium oxide obtained has low purity;

[0019] (4) Lime method - cheap raw materials, low cost, if the by-products are fully utilized, the cost can be reduced, but the production process of this method is long, the filtration performance of magnesium hydroxide in the production process is poor, the energy consumption is high, and the requirement for lime activity is high , suitable for treating low-concentration brine;

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