Shin-Etsu Chemical Co., Ltd. has developed an innovative new system to recover and recycle salt water from the combustion of exhaust gas and waste water, and it began full-scale operation of the system from July 2005 at the companyfs Naoetsu Plant (Joetsu City, Niigata Prefectures).
The Shin-Etsu Group has been making strenuous efforts to promote environmental protection, and with the operation of this new system it will be able to achieve a large reduction in waste products, an objective the company has been working on as a major theme.
This system recovers salt water derived in the batch processing of exhaust gas and waste water generated in the production process of methylcellulose, one of the main products produced at the Naoetsu Plant. Then, the salt water is treated using an electrolysis process so as to be able to use it as a raw material in the manufacturing of caustic soda, which is another key product of the Naoetsu Plant. This system is an innovative recycling system that establishes a series of closed processes, which consist of processing, recovering and reusing stages.
In the production of methylcellulose, methylchloride is used as a raw material, and the exhaust gas that is generated in the manufacturing process contains methylchloride and VOC (volatile organic compound). Shin-Etsu Chemical has been working independently to both reduce and effectively utilize these waste products. By burning together the exhaust gas and waste water generated in the process of methylcellulose production, this new system recovers energy and high-purity salt water (NaCl) and recycles them using an electrolysis process. The salt water collected is more highly purified by far than raw salt, and without the need of any special treatment process it is possible to reuse it in the electrolysis process.
As a result of the adoption of this system, the exhaust amount of methylchloride and VOC at the Naoetsu Plant is expected to be reduced to less than one-tenth of the previous level. In addition, as a next step, an improvement in the combustion system for burning together the waste water that is generated at different production lines of methylcellulose is under study. After the improvements are made, it is expected that an amount that will be equivalent to about 10% of the salt presently used at the Naoetsu Plant can be collected through this system.
The Shin-Etsu Group will continue to pursue the achievement its global goal of reducing emissions to as close to zero as possible at all of its facilities around the world.