Method and system for recovering fluorine from waste acid produced in thinning production of solar cells or glass

Abstract

The invention discloses a method and a system for recovering fluorine from waste acid produced in thinning production of solar cells or glass and belongs to the technical field of environmental protection. The method comprises the following steps: the waste acid is collected by a production line source; sodium fluosilicate or potassium fluosilicate is obtained through primary fluorine recovery; calcium fluoride is obtained through secondary fluorine recovery; wastewater is treated. The system comprises a fluorine-containing waste acid storage tank, a middle water tank, two stages of fluorine recovery units and a wastewater treatment station, wherein an outlet of the fluorine-containing waste acid storage tank is connected with an inlet of the primary fluorine recovery unit, a waste acid outlet of the primary fluorine recovery unit is connected with an inlet of the middle water tank, an outlet of the middle water tank is connected with an inlet of the secondary fluorine recovery unit, a wastewater outlet of the secondary fluorine recovery unit is connected with the wastewater treatment station, and the two stages of fluorine recovery units are provided with recovery product outlets respectively. With adoption of the method, fluorine resources can be recovered efficiently, and the discharge amount of fluorine-containing sludge and fluorine pollution of the wastewater can be reduced remarkably; with adoption of the system, capacity and quantity of equipment can be reduced, and the production cost can be saved.

Description

technical field [0001] The invention belongs to the technical field of environmental protection, and in particular relates to the recycling and harmless treatment technology of wastes discharged from the production of crystalline silicon solar cells and glass thinning industries. technical background [0002] The production of crystalline silicon solar cells is an important link in the photovoltaic industry chain, and a relatively large amount of hydrofluoric acid is used in the production processes of texturing, pickling and etching. Glass thinning production is an important raw material manufacturing process in liquid crystal panel production, and a large amount of hydrofluoric acid is also used in chemical glass thinning production. The hydrofluoric acid used in the production of crystalline silicon solar cells and the production of glass thinning both causes high concentration of fluorine ions in the discharged wastewater, causing serious pollution and waste of fluorine ...

AI Technical Summary

Problems solved by technology

[0004] 1. The consumption of chemicals is large, and the treatment cost is high: it is often necessary to add a large amount of lime or calcium chloride, etc., and a large amount of coagulants such as aluminum sulfate, polyaluminum chloride, polyacrylamide, etc. The flocculant can reduce the concentration of fluoride ion to below the allowable discharge standard. Studies have shown that the direct cost of fluorine-containing wastewater treatment is usually 10 yuan / m 3 above, while the treatment cost of fluorine-containing waste acid is often as high as 300-500 yuan / m 3

These wastewater treatment causes heavy economic pressure on production enterprises

[0005] 2. A large amount of fluorine-containing sludge is produced, causing serious environmental hazards and high disposal costs: a large amount of fluoride-containing sludge is produced after the fluoride-containing wastewater is defluorinated by reaction. In the treatment of solar cell production wastewater, the amount of fluoride-containing sludge is about 6t / MW, taking a company with an annual output of 1GW of solar cells as an example, its annual discharge of dehydrated fluorine-containing sludge is about 6,000 tons or more

However, this kind of sludge has high moisture content, low content of effective fluoride on a dry basis, and poor purity. It has basically no use value and methods, and can only be disposed of as sludge waste.

Sludge landfill not only causes land occupation, but also may pollute soil, groundwater or surface water due to sludge leaching, etc.

In most areas, this kind of fluorine-containing sludge cannot be properly stacked or disposed of, causing serious environmental hazards

In some areas, it has been classified as hazardous waste, and the disposal cost is high, which brings great economic pressure to the production enterprises

[0006] 3. Serious waste of resources: a large amount of fluoride ions are discharged with wastewater or sludge after treatment, and resources are not recycled and reused, resulting in serious waste of resources

[0007] 4. Poor stability of wastewater treatment: During the treatment of fluorine-containing wastewater, the volume and quality of wastewater fluctuate greatly due to fluorine-containing waste acid, the dosage of chemicals is large, and the control stability of the fluoride removal process is poor, resulting in that the treatment effect of fluoride-containing wastewater cannot be stably up to the standard

At present, there are no technical reports on the recovery of fluorine resources in this industry at home and abroad

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