Method for preparing anhydrous magnesium chloride from bischofite

A technology of anhydrous magnesium chloride and bischofite, which is applied in the direction of magnesium chloride and magnesium halide, can solve the problems of high construction investment cost, high operating cost, and cannot be completely prevented, and achieve a wide range of process conditions, reduce circulation, and improve The effect of uniformity

Active Publication Date: 2009-06-24
INST OF PROCESS ENG CHINESE ACAD OF SCI
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Problems solved by technology

The main problems of this method are: hydrogen chloride is a corrosive gas, and the requirements for equipment materials are relatively high; side reactions can only be suppressed, but not completely prevented; the composition of salt lake brine and salt field bittern is relatively complicated, and it is difficult to completely separate or remove impurities. Removal affects the purity of the anhydrous magnesium chloride product, and at the same time the construction investment cost is very high and the operating cost is high
However, there are the following problems in the preparation of anhydrous magnesium chloride by ammonification of bischofite raw materials at present: (1) the circulation consumption of anhydrous organic medium per unit product is large, and the efficiency still needs to be improved; (2) the dehydration energy consumption per unit product is relatively high

Method used

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  • Method for preparing anhydrous magnesium chloride from bischofite
  • Method for preparing anhydrous magnesium chloride from bischofite
  • Method for preparing anhydrous magnesium chloride from bischofite

Examples

Experimental program
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Effect test

example 1

[0048] Get 500g bischofite (MgCl 2 ·6H 2 (0), drying and dehydration at a temperature of 180°C, the weight after drying is 245g, and the weight loss is 255g. Bischofite is dried at 180°C and partially hydrolyzed, and the composition of the dried product is MgCl 2 ·H 2 O and Mg(OH)Cl, where MgCl 2 ·H 2 O accounts for 71.2wt%.

example 2

[0050] Dry the bischofite at 180°C and keep it sealed. Take 150g of dried bischofite and dissolve it in 1000ml of ethylene glycol solvent, and add 33g of ammonium chloride at the same time. The water content of the solution was measured by the Karl Fischer method, and the measurement result showed that the water content was 1.60%. Put the prepared solution into a 2000ml three-necked distillation flask, carry out intermittent vacuum distillation and dehydration operation in the distillation tower for 200min. under the conditions of vacuum degree of 660mmHg, temperature 150°C, and reflux ratio of 5:1, and measure the vacuum distillation dehydration. The water content of the solution is 0.20%. Take out the ethylene glycol solution of 800ml magnesium chloride from the tower kettle and cool it down, add 100ml liquid ammonia, then pass through ammonia gas, generate white precipitate of hexaammoniated magnesium chloride in the fluidized bed reaction crystallizer, filter it, and use ...

example 3

[0052] Get 100g of bischofite, directly dissolve in 1000ml of ethylene glycol for dissolving without drying, adopt the Karl-Fisher method to measure the water content of the solution, and the measurement result shows that the water content is 5.3%. The prepared magnesium chloride hydrate ethylene glycol solution does not go through the step of vacuum distillation and dehydration, and directly carries out the reaction crystallization process. Other steps (reaction crystallization, filtration, washing and drying process) are identical with example 2, and the scanning electron microscope figure of the crystal obtained as a result is as attached image 3 As shown, it can be seen that magnesium chloride hexaammoniate is impure (magnesium chloride hexaammoniate crystal form is an octahedral structure).

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Abstract

The invention relates to a method for preparing anhydrous magnesium chloride from bischofite, which uses the bischofite as a raw material for preparing the anhydrous magnesium chloride. The method comprises the following technical processes: (1) firstly, drying the bischofite for dewatering most crystallization water; (2) dissolving the dried magnesium chloride in glycol for preparing a glycol solution of the magnesium chloride and using a vacuum distillation method for dewatering water in the glycol solution of the magnesium chloride; (3) reacting the dewatered glycol solution of the magnesium chloride with ammonia for crystallizing so as to generate magnesium chloride hexammoniate crystals; (4) washing, filtering and drying for obtaining the magnesium chloride hexammoniate crystals; and (5) heating, decomposing and deaminating the dried magnesium chloride hexammoniate crystals for preparing the anhydrous magnesium chloride. In each process, ammonia gas, detergent and a crystallization mother liquor are recycled. The process has the characteristics of convenient operation, easy large-scale production, low energy consumption, low product cost and no pollution to environment and the prepared anhydrous magnesium chloride can be used as a raw material for producing magnesium metal by an electrolysis method.

Description

technical field [0001] The invention relates to a method for preparing anhydrous magnesium chloride from bischofite. Background technique [0002] There are generally two methods for producing magnesium metal: thermal reduction method and electrolytic anhydrous magnesium chloride method. The thermal reduction method has simple process and low investment cost, but it has high energy consumption, low resource utilization rate and serious environmental pollution. The method of electrolyzing anhydrous magnesium chloride has many procedures and high cost, but compared with the thermal reduction method, it has lower energy consumption and less pollution to the environment. It is a green, environmentally friendly and sustainable production method of metal magnesium . [0003] The raw material for the production of metal magnesium by electrolysis is high-purity anhydrous magnesium chloride, and the preparation of anhydrous magnesium chloride is the key to the production of metal m...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F5/34C25C3/04
Inventor 卢旭晨闫岩王体壮
Owner INST OF PROCESS ENG CHINESE ACAD OF SCI
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