Updated: July 2002Solvent Recovery System for Stripper
1. Overview of Apparatus
The solvent recovery system for stripper regenerates solvent after removing and dissolving photo-resist to reuse as the stripper. The apparatus comprises a distillation unit and accessory units such as utility supply units. First, the charged waste stripper is indirectly heated by steam under vacuum boiling, vaporizing the solvent for recovery target components together the low boiling impurities. The photo-resist does not vaporize but remains in the liquid phase with other nonvolatile components. Second, the continuous distillation unit separates low boiling impurities consisting of H2O. The mixed vapor of H2O and stripper solvent is charged from the separator to the distillation unit center. The low boiling point waste liquid consisting of H2O is distilled from the top of the tower, and the recycled stripper free of impurities is recovered from the bottom of the tower. The distillation tower separates each component with differences in vapor pressure.
By connecting the photo-resist enriching section with H2O removing distillation section using a vapor pipe, the advantages are described as follows:
(1) Stable operation with simple pressure control
(2) Energy saving with vapor feed to distillation
(3) Avoidance of clogging risk with vapor feed
The stripper recovery system aims at the recycled stripper quality. Quantitative expression is referred to variation in component, metallic ion concentrations, and the number of particles along with the H2O and photo-resist content. System design suitable to the H2O content is not difficult, thus considering initial cost and running cost. For resist separation, the effect of the mist separation system is signified. Variation of component concentration means a change in the ratio of two components after distillation and reclamation. This change occurs in the recycled stripper according to difference in vapor pressure and material balance of concentration and discharge rates of waste liquid. The concentration adjustment is performed after recovered the target materials as far as possible, by followed by a sufficient quantity of component.
4. Application Fields and Processing
TFT-LCD (Thin Film Transistor-Liquid Crystallize Display) is widely used as computer monitors and other applications. In recent years, TFT-LCD is seen anywhere within automobiles and on armrests in the aircraft, while the production scale is expected to rise in the near future, because the TFT-LCD production process employs many kinds of chemicals. Meantime, it is a concern of great significance to reduce the amount of chemicals consumption from the viewpoint of stripper resource and environmental conservation.
Many kinds of solvent is used for photo-resist in the TFT-LCD production process. Relating to these solvents, we can provide the recovery system for MEA (mono-ethanol-amine) based organic stripper.
Economic merits of introduction of the apparatus for the solvent recovery system for stripper will be related to various factors such as stripper cost, disposal method for waste liquid, and utility unit price. It is a concern of great significance for the first step to the zero-emission concept that KIMURA CHEMICAL PLANTS has recovered the stripper with internal circulation of resources.