Device and method for recycling waste acid liquid produced in polycrystalline silicon texturing

Abstract

The invention relates to a device and a method for recycling waste acid liquid produced in polycrystalline silicon texturing. According to the method, in a secondary chemical reaction precipitation section, hydrofluoric acid is neutralized through a primary reaction, a fluorosilicate precipitate is generated through a secondary reaction, and the precipitate can be sold; in a rectification and purification section, rectification and purification can be performed on dilute nitric acid to generate concentrated nitric acid; the nitric acid is evaporated and concentrated to obtain about 65% of dilute nitric acid through a dehydrating agent reduced-pressure rectification process, and the dilute nitric acid can be directly reused in a texturing liquid system, so the cyclic utilization of nitric acid is achieved, and reagent cost is reduced; and in a dehydrating agent regeneration section, a certain amount of magnesium oxide is added into a solution containing a small amount of dilute magnesium nitrate for neutralization, and then evaporation is carried out so as to obtain high-concentration concentrated magnesium nitrate which can be directly used as a dehydrating agent and applied to therectification and purification section. According to the invention, resource utilization and recycling of waste water and solid waste are realized, the operation cost and production cost of enterprises are further reduced, and the requirements of energy conservation, high efficiency and environmental protection are met.

Description

technical field [0001] The invention relates to the technical field of environmental protection treatment, in particular to the technical field of waste liquid recovery and reuse, in particular to a device and method for recycling waste acid liquid used in polysilicon texturing. Background technique [0002] During the texturing of polysilicon, a large amount of waste acid will be produced, including nitric acid, hydrofluoric acid and fluosilicic acid. At present, there are mainly five methods for the treatment of this waste mixed acid: neutralization method, evaporation process, direct incineration, membrane separation and resin adsorption technology. [0003] There are certain defects in the above five methods: [0004] One is the neutralization method, which not only needs to consume a large amount of alkaline substances, but also wastes the recyclable nitric acid and hydrofluoric acid in the waste acid. In addition, because the waste acid contains heavy metal ions, nit...

AI Technical Summary

Problems solved by technology

However, due to the thermal decomposition of nitric acid and nitrate into nitrogen oxides, it is necessary to increase the tail gas nitrogen oxide purification system and increase investment.

At the same time, the recovery rate of nitric acid is only about 30%, and the equipment is seriously anti-corrosion.

[0007] The fourth is membrane separation. The advantage of membrane separation is small investment and relatively simple device structure. The disadvantage is that it will produce an equal volume of dilute waste acid, and the separation effect for low-concentration metal ions is not good, and the technology is immature

[0008] The fifth is resin adsorption, which is to use special resin for the adsorption treatment of waste acid. Although the special resin adsorption process can achieve the purpose of recycling waste acid without consuming heat energy, its disadvantage is that after the resin adsorption treatment reaches saturation, it will consume at least the same amount of pure water for resin regeneration

As a result, the investment in the pure water system and the wastewater treatment system will be increased, and the residual metal ions in the recovered acid are still about 20%.

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