Crystallization system and crystallization method for generating sodium fluoroaluminate crystals from hydrofluoric acid waste liquid

Abstract

The invention discloses a crystallization system and a crystallization method for generating sodium fluoroaluminate (Na3AlF6) crystals by utilizing a hydrofluoric acid waste liquid. The crystallization system is characterized in that a given-flow-rate and uniformly-dispersed medication section is arranged in a notch of a reaction trough, so that chemicals can be quantitatively controlled in different batches and uniformly dispersed into the hydrofluoric acid waste liquid to be reacted, and the crystallization method which is matched with the crystallization system comprises the steps: feeding the hydrofluoric acid waste liquid, charging sodium aluminate, crystallizing, precipitating the sodium fluoroaluminate crystals, filtering and discharging the water, the hydrofluoric acid waste liquid is purified by adopting a crystallization operation mode to substitute the well-known chemical coagulation operation mode, the reaction efficiency of the hydrofluoric acid waste liquid and the chemicals and the crystallization purity can be improved, and the purposes for effectively recycling the fluoride, reducing the size of chemical sludge and generating the high-economic-benefit sodium fluoroaluminate crystals can be realized.

Description

technical field [0001] The invention relates to a crystallization system for generating sodium fluoroaluminate crystals from hydrofluoric acid waste liquid, in particular to a crystallization system capable of effectively crystallizing fluoride ions in hydrofluoric acid waste liquid into sodium fluoroaluminate crystals system; the present invention also relates to a crystallization method of the crystallization system. Background technique [0002] High-concentration hydrofluoric acid (HF, 49%) or hydrofluoric acid mixed acid is widely used in etching technology for semiconductor (IC), liquid crystal display panel (TFT-LCD), solar cells and other technology industries, so the output concentration is as high as 49% % or as low as 0.5% of hydrofluoric acid waste acid with various concentrations and bulky volume, it needs to be treated with waste liquid. [0003] The current hydrofluoric acid waste treatment method is to add such as CaO, Ca(OH) 2 , CaCl 2 Such calcium-contai...

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Problems solved by technology

[0008] However, in the fluorosilicate production method of this patent, there must be an operating limit of 5 to 15 wt% of the hydrofluoric acid-containing waste liquid and the fluorosilicate waste liquid. If it is too low or too high, the output will not be economical Benefits of fluorosilicate and increase operating costs, especially the neutralization of fluorosilicate with sodium or potassium-containing alkali or alkali metal salt is an exothermic reaction, so that the reaction temperature in the operation process forms another control parameter, resulting in an increase in the Operational Difficulty of Patents

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