SU141861A1 - The method of obtaining granulated magnesium oxide and hydrogen chloride - Google Patents

Description

The method of hydrolytic decomposition of magnesium chloride, for example, in the form of bischofite by the reaction: MgCls-eHsO - MgO + 2HCl + 5H20 can be used to obtain various grades of magnesium oxide, including highly pure magnesium oxide, used to produce superneufeors.

Several processes are known for producing magnesium oxide by the indicated method.

Thus, in the USSR, the process of hydrolysis of magnesium chloride was developed, consisting of the following operations:

a) blending chloromagnesium solutions (bischofite) with retum magnesium oxide to form an intermediate magnesia cement;

b) drying and grinding of magnesia cement;

c) hydrolytic decomposition of magnesian cement in retort or rotary kilns with internal heating (Compiled. "Solikamsk carnallites, 1935). This method has not found practical application due to the need to use expensive and cumbersome equipment.

In 1955-1957 in the United States by International Minerals a.Chem. C ° industrial hydrolysis of magnesium oxide was carried out. The raw materials used are waste chlorine magnesium brines, obtained in the production of potassium sulfate from the mineral langbeinig (Kj504 2MgSO4) to potassium chloride. After separation from brines of chlorides and sulphates of potassium and sodium, bischofite is obtained, which is sent to a rotary kiln with internal heating.

The hydrolysis is carried out at a temperature of 600 ° with direct flow of gases and raw materials.

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The method of hydrolytic decomposition of chlorophyll by the mono of f, eden: south of the potash brine wastes:

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 .r ezirzhi.va, shle-x-Lrmagnicheskih liquor in a spray dryer to obtain a mixture of four - and sixth of magnesium chloride;

2. decomposition of magnesium chloride hydrate in the suspended layer. The resulting fine magnesium oxide is carried along with the gases from the apparatus and separated in a dust collecting plant.

According to the proposed method, the initial brines, containing magnesium chloride or bishofit, are partially dewatered with hot gases, the output of the second stage, where the partially dehydrated material is subjected to thermohydrolysis with fresh hot gases from burning fuel. The process is carried out in an apparatus with a skull, a layer divided into two sections (see drawing).

In the first section of the apparatus, dehydration of the chlorine – magnesium solution or biphofite occurs (as a melt or crystalline product) in a boiling bed. The supply of solutions to the dewatering apparatus is carried out through a coarse-sprayed mechanical nozzle located above the cue front of the bed, at a height of 300-400 mm from the upper boundary of the layer. The temperature of the bed is maintained between 180-200 °. This forms a mixture of 1,5- and 2-water hydrates of magnesium chloride in the form of granules of an average diameter of 1-2 mm. Dehydration is carried out by hot, gases leaving the second section. The gases leaving the apparatus are directed to the production of hydrochloric acid, the concentration of which depends on the moisture content of the feedstock. In the USA, commercial hydrochloric acid contains 31.5% HCI.

The granules of low-moisture magnesium chloride hydrates are continuously transferred to the second section of the apparatus, where thermohydrolysis takes place with the help of fresh hot gases obtained from burning fuel.

Conducting hydrolysis in a fluidized bed makes it possible to reduce the reaction rate to 500–550 °. Reaction time 7-10 minutes (according to laboratory experiments); while the degree of hydrolysis reaches 97-. At a temperature of 300-320 °, the degree of hydrolysis is 92%.

In the process of hydrolysis, the coolant is in-line gases, which, when passing through the bed, bring the latter into a fluidized state. The resulting magnesium oxide granules are continuously discharged from the apparatus.

The main advantages of the proposed method are as follows:

1. Simplification and cheapening of equipment, since the high intensity of the process makes it possible to significantly reduce the reaction volume of the apparatus.

2. Reduction by 35-40% of specific fuel consumption. In a two-stage process, the heat of the reaction gases is used to pre-dewater the feedstock.

3. In the fluidized bed apparatus, granular magnesium oxide is obtained; at the same time, the removal from the bed of the dust-like fraction to be captured does not exceed 7-1C%. Therefore, the installation of bulky dust collecting devices is not required.

4. As a result of a reduction in the specific fuel consumption in a fluid bed apparatus, the content of hydrogen chloride in the reaction gases is significantly increased compared to a floating furnace or a suspended bed apparatus.

Subject invention

The method of obtaining granulated magnesium oxide and hydrogen chloride by thermal decomposition of magnesium chloride raw material in a fluidized bed apparatus, characterized in that the initial saltwaters or bishofit are subjected to partial dehydration with hot gases leaving the second stage, where the partially dehydrated material is subjected to thermohydrolysis hot gases from fuel combustion.

- 3 No. 141861

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Magnesia oxide