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Method for recovering polyethylene glycol and silicon carbide from silicon crystal cutting waste liquid

A technology of polyethylene glycol and silicon carbide, which is applied in the field of waste liquid recovery, can solve the problems of fluorine pollution, loss of use value, ineffective separation of silicon carbide and silicon, etc., to reduce the amount of addition, reduce the cost of environmental protection treatment, and improve the production process Proven and Reliable Effects

Inactive Publication Date: 2012-06-20
ZHEJIANG YUANSHENG SILICON MATERIALS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This method is easy to control, simple equipment, and low cost, but its existing problems are: one is that silicon carbide and silicon cannot be effectively separated; the other is that HNO 3 The mixed acid liquid treatment method composed of +HF is likely to cause fluorine pollution; the above process needs to be further improved. If polyethylene glycol is to be evaporated, the temperature must be about 200°C under vacuum conditions, and the polyethylene glycol has deteriorated at this time Redness, loss of use value

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0032] Take 50 kg of silicon crystal cutting waste liquid, add 50 kg of water, stir, the mixture is ultrasonically treated, and the iron in the mixture is sucked out with a magnet; 0.03 kg of flocculant is added, and after the reaction, a centrifuge is used for solid-liquid separation to obtain a solid One, solid two and liquid. Solids II can be sold directly.

[0033] Take 10 kg of solid matter, add 10 kg of water to dilute it into a silicon carbide suspension, add a 30% sodium hydroxide solution to the suspension until the pH value is 12, and heat it to 80°C for reaction. After the reaction is completed , washed with water until the pH value reached 7.5, then added a 30% sulfuric acid solution by mass percentage to reach the pH value of 3, and washed with water until the pH value reached 7 to obtain a crude silicon carbide. A scraper centrifuge is used for separation, and the separated solid is heated and dried until the water content is not more than 0.4%, and the silicon ...

Embodiment 2

[0036] Take 50 kg of silicon crystal cutting waste liquid, add 100 kg of water, stir, the mixture is ultrasonically treated, and the iron in the mixture is sucked out with a magnet; 0.05 kg of flocculant is added, and after the reaction, a centrifuge is used for solid-liquid separation to obtain a solid One, solid two and liquid. Solids II can be sold directly.

[0037] Take 10 kg of solid matter, add 15 kg of water to dilute it into a silicon carbide suspension, add a 40% sodium hydroxide solution to the suspension until the pH value is 11, and heat it to 90°C for reaction. After the reaction is completed , wash with water until the pH value reaches 7, then add a 25% hydrochloric acid solution by mass percentage until the pH value is 1, wash with water until the pH value reaches 6.5, and obtain a crude silicon carbide. A scraper centrifuge is used for separation, and the separated solid is heated and dried until the water content is not more than 0.5%, so as to obtain a fini...

Embodiment 3

[0040] Take 50 kg of silicon crystal cutting waste liquid, add 25 kg of water, stir, the mixture is ultrasonically treated, and the iron in the mixture is sucked out with a magnet; 0.01 kg of flocculant is added, and after the reaction, a centrifuge is used for solid-liquid separation to obtain a solid One, solid two and liquid. Solids II can be sold directly.

[0041] Take 10 kg of solid matter, add 5 kg of water to dilute it into a silicon carbide suspension, add a 10% sodium hydroxide solution to the suspension until the pH value is 13, and heat it to 60°C for reaction. After the reaction is completed , washed with water until the pH value reached 7, then added a 20% sulfuric acid solution by mass percentage to reach the pH value of 4, washed with water until the pH value reached 7, and obtained crude silicon carbide. A scraper centrifuge is used for separation, and the separated solid is heated and dried until the water content is not more than 0.3%, so as to obtain a fin...

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Abstract

The invention discloses a method for recovering polyethylene glycol and silicon carbide from silicon crystal cutting waste liquid. The method comprises the following steps of: A) diluting the cutting waste liquid with water and stirring, extracting metal scarp iron from the mixture by using a magnet after ultrasonic processing; B) adding a flocculating agent into the mixture for centrifugal separation; C) diluting solid I with water, adding sodium hydroxide into the solution, heating the mixture to perform reaction, cleaning the mixture with the water, adding an acid into the mixture, and cleaning the mixture with the water to obtain a crude silicon carbide product; D) performing centrifugal separation on the crude silicon carbide product, and drying the crude product to obtain a finishedsilicon carbide product; and E) filtering the liquid, heating, evaporating and dehydrating the filtered liquid to obtain a finished polyethylene glycol product. In the scheme, the mixture is diluted first, so the recovery rate of the polyethylene glycol is improved. The silicon and iron content of the crude silicon carbide product and the consumption level of the acid and alkali are reduced by ultrasonic processing and iron removal. The method has the characteristics of reasonable process, environmental protection and the like.

Description

technical field [0001] The invention relates to a method for recovering waste liquid, more specifically a method for recovering polyethylene glycol and silicon carbide from silicon crystal cutting waste liquid. Background technique [0002] In the process of multi-wire cutting of silicon wafers, the functions of cutting fluid are mainly to disperse, suspend, lubricate, cool, improve cutting efficiency, and reduce cutting consumption. The main components of existing silicon wafer cutting fluids are polyethylene glycol and silicon carbide, so the main components of the cutting waste liquid produced by silicon wafer cutting are polyethylene glycol and silicon carbide, and also include a small amount of silicon chips (generally 2-2 5%) and traces of metallic iron. The existing recovery of polyethylene glycol and silicon carbide in silicon crystal cutting waste liquid often has problems such as low recovery rate and low purity of recovered polyethylene glycol and silicon carbide...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B31/36
Inventor 罗其洋陈云根
Owner ZHEJIANG YUANSHENG SILICON MATERIALS
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