HF/hydrofluoric acid filter

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Thinning is a process in which TFT glass reacts chemically with HF to remove the excess thickness of the glass, thereby achieving a thinner profile. Thinning is divided into two types: slot thinning and wafer-thinning. General thinning process: Incoming material inspection → Pre-cleaning → Drying → Pre-treatment for thinning → Thinning → Post-cleaning → Drying → Polishing → Thinning completed. Thinning is primarily used in screen displays; after thinning, the thickness of LCD screens falls between 0.3 and 0.5 mm, which saves a significant amount of space compared to the 1 mm thickness after assembly, resulting in a more natural and realistic display quality. A large amount of etching acid is used in production, which also results in a significant amount of waste acid. The main chemical reaction involved in etching is: 4HF + SiO2 = SiF4 (gas) + 2H2O. Since there is an excess of HF, the SiF4 produced can react further with HF: 2HF + SiF4 = H2. The remaining waste acid, due to its strong corrosiveness and containing a large amount of etching residues, cannot be discharged carelessly ； It can either be sent to the wastewater treatment plant for neutralization and disposal, or it can be recycled and reused, and then disposed of after being used to a certain extent ； The main methods of recovery include: precipitation to extract the supernatant, bag filtration for recovery, and plate filter press filtration for recovery. Advantages and disadvantages comparison: A. Precipitation method: The advantage is that it requires almost no investment; tanks or sedimentation ponds are used for purification through layering, with the clear liquid on top being manually removed for reuse, while about 15% of the concentrated acid at the bottom is discharged ； The disadvantages include its unsuitability for situations with large amounts of waste acid; human intervention poses risks to health; the recovered acid is not pure as fine particles cannot be settled, resulting in a low recovery rate and significant amounts of acid being discharged. The wastewater treatment facility has to handle large volumes of waste, requiring large quantities of neutralizing agents, which increases operational costs and environmental risks, and hinders modern management of production sites ； B. Bag filtration for recovery: Its advantages include easy installation, low investment costs, a much cleaner filtering effect compared to the sedimentation method, and it requires less space ； The disadvantages include frequent replacement of the filter bags, which means they cannot be reused; more consumables are required over time. Additionally, the filter bags need to be replaced manually every day, resulting in low efficiency. Workers have to deal with acidic gases directly, and the bags require manual cleaning as well as daily maintenance ； C. Recovery using plate and frame filter presses: The advantages include nearly semi-automatic filtering, a longer service life for the filter cloth compared to filter bags, and higher filtration efficiency than bag filters ； The disadvantages are that open-type operation tends to cause the acid to evaporate, manual cleaning of the filter cake is required, making it difficult to manage the site; it gets dirty and messy easily, the numerous moving parts are prone to failure, and the filter cloth also needs to be replaced frequently and cleaned manually. This poses safety risks to the workers on site and is not conducive to the modern \"6S\" management practices in factories. 2. What is the technical problem to be solved by this invention? It helps enterprises improve the efficiency of acid waste recovery, replacing traditional and outdated recovery methods; it reduces factory operating costs as well as the workload associated with wastewater treatment facilities. Its automated and sealed operation prevents secondary environmental pollution and reduces the need for excessive manual labor, thereby improving environmental management on site. Technical Support: Qingrui Environmental Protection