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Process for producing magnesium hydroxide and calcium carbonate by dolomite conversion method

A technology of magnesium hydroxide and calcium hydroxide, applied in the direction of magnesium hydroxide, calcium carbonate/strontium/barium, etc., can solve the problems of not being able to obtain pure calcium carbonate products, high production costs, and a large amount of acid, and achieve a good social environment Benefits and economic benefits, no discharge of three wastes, and reduced energy consumption

Inactive Publication Date: 2011-10-26
HEBEI UNIVERSITY OF SCIENCE AND TECHNOLOGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0014] The above patents and documents divide the process of preparing calcium-magnesium salt products from dolomite into three cases. The first case is to carry out acid hydrolysis treatment on dolomite or calcined dolomite, and the acid used is sulfuric acid or hydrochloric acid. , and then adding a precipitant to separate the calcium and magnesium in the dolomite to prepare calcium and magnesium products; the second case is to use kiln gas carbonization treatment to obtain basic magnesium carbonate products and magnesium-containing calcium carbonate products through pyrolysis of heavy magnesium water; The disadvantage of the solution is that a large amount of acid is required, which brings certain problems to transportation and safety. The carbonization method is due to the limitation of the solubility of magnesium bicarbonate. Generally, the solubility of magnesium bicarbonate is 10g / l (equivalent to magnesium oxide), so the energy consumption is high, resulting in The production cost of the product is high, and calcium carbonate products with relatively high purity cannot be obtained

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0039] a. Crush 300g of dolomite (containing MgO ≥ 19%) to 50-80mm, then put it into a muffle furnace for calcination, the temperature is controlled at 950°C, and the calcination time is 8 hours.

[0040] b. Add the calcined dolomite obtained in step a above into a digestion reactor, then add 720ml of water to carry out the digestion reaction, and obtain dolomite milk containing calcium hydroxide and magnesium hydroxide, and pass through a 325-mesh vibrating sieve to remove the dolomite containing Acid-insolubles such as silicon dioxide and aluminum oxide are obtained to obtain calcium hydroxide with a concentration of 12.8%, and a refined dolomite milk with a concentration of magnesium hydroxide of 10%.

[0041] c. by the refining dolomite milk that above-mentioned step b makes, squeeze into ammonia distillation reactor with pump, carry out metathesis reaction with the ammonium chloride aqueous solution that is 1mol / l with concentration. The temperature was controlled at 90°C...

Embodiment 2

[0045] a. Crush 300g of dolomite (containing MgO≥19%) to 50-80mm, put it into a muffle furnace, control the calcination temperature at 980°C, and calcine for 6 hours.

[0046] b. Add the calcined dolomite obtained in step a above into the digestion reactor, then add 720ml of water to carry out the digestion reaction to obtain dolomite milk containing calcium hydroxide and magnesium hydroxide, and pass through a 325-mesh vibrating sieve to remove Containing acid-insoluble matter such as silicon dioxide and aluminum oxide, the refined dolomite milk whose calcium hydroxide concentration is 12.8% and magnesium hydroxide concentration is 10% is obtained.

[0047] c. by the refining dolomite milk that above-mentioned step b makes, pump into ammonia distillation reactor, be that 1.5mol / l ammonium chloride solution carries out metathesis reaction with concentration. The temperature was controlled at 95°C. The feeding ratio is the molar ratio of ammonium chloride to calcium hydroxide ...

Embodiment 3

[0052] a. Crush 300g of dolomite (containing MgO≥19%) to 50-80mm, put it into a muffle furnace, control the calcination temperature at 1000°C, and calcine for 3 hours.

[0053] b. Add the calcined dolomite obtained in step a above into a digestion reactor, then add 720ml of water to carry out the digestion reaction, and obtain dolomite milk containing calcium hydroxide and magnesium hydroxide, and pass through a 325-mesh vibrating sieve to remove the dolomite containing Acid-insolubles such as silicon dioxide and aluminum oxide are obtained to obtain calcium hydroxide with a concentration of 12.8%, and a refined dolomite milk with a concentration of magnesium hydroxide of 10%.

[0054] c. by the refining dolomite milk that above-mentioned step b makes, pump into ammonia distillation reactor, be that 2mol / l ammonium chloride solution carries out metathesis reaction with concentration. The temperature was controlled at 100°C. The feeding ratio is 1:1 molar ratio of ammonium chl...

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Abstract

The invention provides a process for producing magnesium hydroxide and calcium carbonate by the dolomite conversion method. The process comprises the following steps: calcining dolomite, carrying out a digestion reaction on dolomite and water and refining so as to obtain a refined slurry of calcium hydrate and magnesium hydroxide; reacting the slurry with an ammonium chloride solution to enable calcium hydrate to react with ammonium chloride; carrying out ammonia evaporation so as to obtain a fluid suspension of a calcium chloride solution, ammonia gas and magnesium hydroxide; carrying out filtering and washing so as to obtain a magnesium hydroxide product; carrying out a carbonization reaction on the calcium chloride aqueous solution which has absorbed ammonia gas with kiln gas generated by the calcination of dolomite so as to obtain calcium carbonate; carrying out filtering and washing so as to obtain a calcium carbonate product. In the invention, washing water is used for the digestion of dolomite ashes so as to totally separate magnesium from calcium in dolomite and produce magnesium hydroxide and calcium carbonate products, thereby fully utilizing dolomite. The process provided in the invention enables cyclic utilization of the intermediate product ammonium chloride and no discharge of the three wastes, being in accordance with the developmental requirements for green chemicals in modern society.

Description

technical field [0001] The invention belongs to the field of chemical industry, and in particular relates to a method for producing magnesium hydroxide and calcium carbonate by a dolomite conversion method. Background technique [0002] Dolomite is a calcium-magnesium composite non-metallic mineral, the main components are calcium carbonate and magnesium carbonate, and it is one of the main raw materials for the preparation of calcium-magnesium products. my country's dolomite resources are very rich, and the national proven reserves are more than 4 billion tons, distributed in Liaoning, Jilin, Hebei and other provinces. [0003] At present, the utilization methods of dolomite mainly include direct crushing method, carbonization method, acid hydrolysis method and so on. Among them, the dolomite powder obtained by the direct pulverization method has a narrow application range and can only be used as a low-end filler in rubber; the carbonization method can produce basic magnes...

Claims

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Application Information

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IPC IPC(8): C01F5/16C01F11/18
Inventor 刘润静
Owner HEBEI UNIVERSITY OF SCIENCE AND TECHNOLOGY
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