Method and device for preparing basic magnesium carbonate from heavy magnesium carbonate water by pyrolysis

Abstract

The invention relates to a method for preparing basic magnesium carbonate from heavy magnesium carbonate water by pyrolysis, which comprises the following steps: mixing a magnesium bicarbonate water solution, of which the temperature is 20-60 DEG C and the mass concentration is 3.5-100g / L, and a saturated basic magnesium carbonate or saturated basic magnesium carbonate solution containing small amount of solid crystals, of which the temperature is 40-90 DEG C, in a volume ratio of 1:(0.05-29); carrying out heat exchange in a 40-90 DEG C pyrolyzer for 10-240 minutes; carrying out solid-liquid separation on the reaction liquid to obtain solid basic magnesium carbonate crystals and a filtrate; and drying the solid basic magnesium carbonate crystals to obtain the heavy magnesium carbonate. The method provided by the invention can overcome the defects of high fuel consumption, high power consumption, high scaling tendency of the pyrolyzer or boiler, short operating cycle, incapability of long-cycle smooth operation, and the like in the existing methods.

Description

technical field [0001] The invention belongs to the technical field of magnesium carbonate production, and in particular relates to a method for preparing basic magnesium carbonate by pyrolyzing heavy magnesium water. Background technique [0002] Heavy magnesium water is the aqueous solution of magnesium bicarbonate. The solubility of magnesium bicarbonate in water is: 120g / (100g water) at 20°C, 80g / (100g water) at 40°C, and 20g / (100g water) at 80°C. The data is based on MgO saturated CO 2 Solubility meter in water. Magnesium bicarbonate is an unstable weak acid salt. When magnesium bicarbonate is heated in water, it undergoes a decomposition reaction, that is, pyrolysis. The reaction process absorbs heat. The main reaction formula is as follows: [0003] 5Mg(HCO 3 ) 2 + nH 2 O = 4MgCO 3 ·Mg(OH) 2 4H 2 O↓+6CO 2 ↑ + nH 2 O-Q [0004] It can be seen from the reaction formula that rising temperature and reducing the partial pressure of carbon dioxide inside and on...

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Problems solved by technology

[0006] Disadvantages of the first type of method: 1) The utilization rate of heat energy is low, and a boiler needs to be specially set up for pyrolysis, and the steam generated by the boiler is used to heat the heavy magnesium water, or the boiler is used to directly heat the heavy magnesium water. In this method, the fuel burns at 600 The heat energy in the high temperature area above ℃ and the heat radiation area is not effectively utilized, and the heat exchange process between steam and heavy magnesium water is more heat loss and more fuel consumption

2) The basic magnesium carbonate precipitate generated in the pyrolysis process of heavy magnesium water is precipitated from the water in the form of crystallization, and the supersaturation of basic magnesium carbonate crystals produced by the decomposition reaction increases too quickly during the crystallization and growth, which is easy to Scabs form on the surface of the pyrolyzer or boiler, block the pyrolyzer or boiler, cause low heat transfer efficiency of the pyrolyzer or boiler, short operating cycle (10-20 days), cannot continue production, and the system cannot run smoothly for a long period of time

The disadvantage of the second type of method is that the power (electricity) consumption for generating negative pressure or positive pressure is large

[0007] Conventional methods generally have the disadvantages of high fuel consumption, high power consumption, easy scarring of pyrolyzers or boilers, short operating cycle (10-20 days), inability to produce continuously, and the system cannot run smoothly for a long period of time

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