Process for preparing low-salt heavy soda ash

Abstract

The invention relates to a method for preparing low-salt heavy soda ash by applying a multi-temperature phase diagram of a Na2CO3-NaHCO3-H2O ternary system, utilizing the feature that the system can precipitate anhydrous sodium carbonate crystals at the appropriate temperature and the composition and adopting the anhydrous sodium carbonate flow process. The method comprises the following steps: carrying out pressure wet decomposition on mixed solution of the heavy soda ash which is rich in sodium bicarbonate or refined natural alkali halide, leading the content of the sodium bicarbonate and the content of sodium carbonate in the solution to achieve the corresponding proportion, further leading the solution to enter into a multi-effect evaporator for evaporation and concentration, controlling the crystallization temperature to be above the phase transition point from anhydrous sodium carbonate to sodium carbonate monohydrate, and ensuring that the precipitated solid phase is the anhydrous sodium carbonate; and taking out a magma by self-pressure, carrying out thermal insulation and separation, obtaining a filter cake which mainly contains the anhydrous sodium carbonate, and drying the filter cake for preparing the low-salt heavy soda ash. The process can change the traditional two-step dry calcination to one-step wet calcination, simplify and shorten the process flow, reduce the area occupied by devices, improve the operation environment, simultaneously improve the quality of a product and reduce the energy consumption.

Description

technical field [0001] The invention relates to a method for preparing soda ash. Specifically, it relates to a method for preparing low-salt heavy soda ash with sodium bicarbonate. Background technique [0002] Heavy soda ash has the characteristics of high bulk density, uniform particle size, not easy to fly, good fluidity, etc., and is very popular with downstream users of soda ash, especially heavy soda ash with low salt content and uniform particle size. The production method of heavy soda ash, except that all the United States adopts trona through monohydrate process, most other countries use light soda ash produced by ammonia soda or combined soda as raw material for reprocessing. There are three processing methods: solid phase hydration, liquid phase hydration and extrusion. Among them, solid phase hydration is the most common method. Among the three processes, the extrusion method is the lowest in production cost, and the other two methods are basically the same; ...

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Problems solved by technology

[0007] Chinese patent application CN1111214A (Yu Zhongfu. The preparation method of heavy soda ash and the fixed decomposition reaction furnace used therefor. 1995-11-08.) Propose, produce heavy soda ash by sodium bicarbonate wet decomposition under the situation that catalyst exists, this The method uses a fixed device, which cannot be operated continuously and cannot realize large-scale industrial production

This process combines wet decomposition and decahydrate crystallization, avoiding the incomplete residual NaHCO of wet decomposition 3 The influence brought by the process of using sodium carbonate monohydrate avoids the need to evaporate a large amount of water and increase energy consumption, but the process is complicated and the equipment is more

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