Method for recycling silicon cutting sand by utilizing countercurrent washing of silicon cutting waste sand cake

Abstract

The invention relates to a method for recycling silicon cutting sand by utilizing countercurrent washing of a silicon cutting waste sand cake, and belongs to the fields of circular economy and energy-saving emission reduction. The method is mainly characterized in that washing and separation functions of a cyclone group are utilized, and a multi-stage countercurrent washing technological process is formed according to purity requirements of a recycled silicon cutting material. The technological process is continuously carried out in closed pipeline equipment, so as to eliminate a recontamination risk of intermediate products; a washing agent is in gradient utilization in different stages, a washing function of the washing agent is fully played, the washing agent is recycled by solid-liquid separation, and thus cyclic utilization of the washing agent is achieved; an alkali washing operation is replaced, consumption of chemical resources is reduced, and thus zero pollution emission is achieved; and the constructed process device has compact structure. Through industrial tests, the purity of the silicon cutting sand recycled by four-stage countercurrent washing reaches more than 80%, the purity of the silicon cutting sand recycled by six-stage countercurrent washing reaches more than 96%, and the purity of the silicon cutting sand can be also improved through further increasing the stage number.

Description

technical field [0001] The invention relates to a method for recycling silicon crystal cutting sand by countercurrent washing of silicon crystal cutting waste sand cake, which belongs to the field of circular economy and energy saving and emission reduction, and in particular relates to the continuous production of silicon crystal cutting waste sand cake countercurrent washing recovery of silicon crystal cutting sand , Recycling of detergent, zero pollution discharge, and a green process that meets the requirements of silicon crystal cutting sand. Background technique [0002] Silicon wafers are an important foundation for the solar industry. With the rapid development of the global solar energy industry, the demand and processing volume of silicon wafers has increased sharply. In 2010, China's silicon wafer production has accounted for more than 50% of the world's total. Silicon wafer production currently usually adopts silicon crystal cutting fluid (also known as cutting ...

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Problems solved by technology

[0003] The resource recovery of silicon crystal cutting waste mortar is carried out from two aspects: cutting fluid recovery and silicon crystal cutting sand recovery: generally, the silicon crystal cutting waste mortar is replaced by pressure filtration to obtain cutting fluid containing pollutants and silicon crystal cutting waste sand The contaminated cutting fluid is purified by distillation to realize the regeneration of the silicon crystal cutting fluid; while the silicon crystal cutting waste sand cake is dissolved in NaOH alkali to dissolve the silicon powder, and then pickled after being washed with pure water , produces a large amount of alkaline sewage and acid sewage, which not only causes great environmental pressure to the sustainable development of production, but also consumes a large amount of chemical resources, increasing the cost of silicon crystal cutting sand recycling

At present, there is also a washing method that uses a cyclone group to configure a stirring tank, but it consumes a large amount of water and the process cycle is long, which belongs to intermittent production. The washing effect cannot meet the purity required for silicon crystal cutting sand, and acid and alkali are required. deal with

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