Anti-scaling method for calcium chloride production

Abstract

The invention discloses an anti-scaling method for calcium chloride production. The method comprises the steps of taking soda distilled ammonia waste liquid with a calcium chloride concentration of not less than 15%(wt) as a raw material solution, performing evaporation and concentration on the raw material solution via a triple-effect evaporation device to form a salt calcium intermediate mothersolution with the calcium chloride concentration of 38-42%(wt), performing physical separation on the salt calcium intermediate mother solution to remove a byproduct, sodium chloride, then performingheat preservation and sedimentation to form a purer calcium solution and a calcium mother solution containing a calcium sulfate crystal, mixing and returning the calcium mother solution containing thecalcium sulfate crystal and the raw material solution to the above mentioned steps, conveying into a primary feeding evaporator after controlling the calcium chloride concentration to be greater than18%(wt), and performing the evaporation and concentration, sheeting and drying on the purer calcium solution obtained after the heat preservation and the sedimentation via a double-effect evaporationdevice to form a finished product, namely sheeted calcium chloride dihydrate. The method solves the problem of 2mm scaling after production for 30 days in the prior art, achieves an effect of scalingthickness not exceeding 0.5mm after continuous production operation for 105 days, lowers cleaning cost, improves device vaporization efficiency and greatly prolongs an operation cycle of the evaporators.

Description

Technical field [0001] The invention relates to a method for preventing scaling in the production of calcium chloride. Background technique [0002] At present, most of the domestic calcium chloride production processes are based on the ammonia-soda waste liquid produced in the soda production process of the ammonia-soda soda plant as the raw material, and the multi-effect vacuum evaporation device is the operating unit, and the chlorine is removed by multi-effect evaporation concentration and sedimentation separation. Sodium sulfide is used to obtain the evaporated liquid, and then the evaporated liquid is subjected to the production process of evaporative concentration and flake drying. The final product is dihydrate flake calcium chloride. The main production equipment is multiple forced circulation evaporators, and the efficient long-period continuous operation of the evaporator is the key to energy saving and consumption reduction in calcium chloride production. Because the...

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Problems solved by technology

Because the raw material liquid used in this process is ammonia distilled waste liquid produced by ammonia-soda method soda ash, which contains a large amount of SO42-, resulting in calcium sulfate scaling on the inner wall of the evaporator heating tube during the evaporation and concentration process, which seriously reduces the evaporation efficiency. When the scale layer thickens to more than 2mm within a few days, it is necessary to mechanically clean the heating tube to completely remove the scale to resume production. The time for cleaning the scale is 3 to 4 days, which has become a major bottleneck restricting the production of calcium chloride.

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