Crystallization and drying integrated method for heptahydrate magnesium sulfate preparation

Abstract

The invention provides a crystallization and drying integrated method for a heptahydrate magnesium sulfate preparation. The method is characterized in that a magnesium sulfate solution is pumped into an atomization plant of a crystallization and drying tower through a liquid phase pipe and atomized to form small liquid drops, and the small liquid drops and airflow moving upwards are mixed and exchange heat; as downward moving of the small liquid drops, the liquid temperature decreases gradually, the heptahydrate magnesium sulfate crystals are separated out gradually, meanwhile, redundant moisture is volatilized and discharged through an air vent; the concentration of the magnesium sulfate solution is controlled in the range of from 38 w% to 45 w%, the temperature of the magnesium sulfate solution is controlled in the range of from 70 DEG C to 80 DEG C, the wind speed of an induced draught fan is controlled in the range of from 2 m / s to 30 m / s, the negative pressure in the tower is controlled in the range of from -10 pa to -1000 pa, and the yield of the heptahydrate magnesium sulfate crystals with the large particle size ranging from 0.2 mm to 5 mm is controlled to be over 80% the full yield. The crystallization and drying integrated method used in the process of preparing heptahydrate magnesium sulfate through magnesium desulphurization byproducts has the advantages of being not prone to scaling, free of mother solution circulation and a drying system, simple in process, small in occupied area, low in energy consumption, high in efficiency, low in investment, environmentally friendly and free of pollution.

Description

technical field [0001] The invention belongs to crystallization technology from a solution, in particular to magnesium sulfate heptahydrate, in particular to an integrated method of crystallization and drying in the process of preparing magnesium sulfate heptahydrate from by-products of magnesium desulfurization, and belongs to the field of inorganic chemical industry. Background technique [0002] Magnesium desulfurization technology is a commonly used flue gas treatment process in industrial enterprises, and the by-product is magnesium sulfite. In order to reduce the operating cost of this desulfurization process and eliminate the environmental impact caused by the accumulation of a large amount of magnesium sulfite, companies usually continue to use the by-products to prepare magnesium sulfate products. There are many processes for preparing magnesium sulfate products by using magnesium sulfite, a by-product of desulfurization, such as direct aeration, adding industrial w...

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Problems solved by technology

[0003] In the current cooling crystallization method, jacket cooling crystallization and coil cooling crystallization, the heat exchange surface is easy to scale and consumes a lot of water resources; evaporation crystallization consumes a lot of water because of high energy consumption; the patent "production of large particles of heptahydrate with magnesium sulfate solution The method of magnesium sulfate and magnesium sulfate monohydrate " (publication number is CN101214980A), discloses a kind of method that desulfurization by-product produces magnesium sulfate product, wherein mentions that solution adopts high-temperature autoclaving to prepare magnesium sulfate product, and ambient temperature in this method It can reach 105-115°C and the pressure can reach 0.3-0.4MPa. Although it does not require a large amount of cooling water, the energy consumption is relatively high; the patent "Air Cooling Crystallization Tower" (publication number CN201543264U) discloses a cooling system using air as the medium Crystallization tower, without cooling water and steam, low energy consumption, but the crystallization tower needs mother liquor circulation and drying system, long process flow and low efficiency

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