SVP-GLS A Novel Method of Producing Salt Cake Free Chlorine Dioxide, 1996 Pulping Conference Proceedings

Göran Sundström, Roy Hammer-Olsen, Helena Falgén, Johan Landfors

EKA Chemicals AB

John Sokol

ERA Chemicals INC.

During recent years, the forestry industry has become increasingly aware of environmental issues. This has resulted in a fast conversion from chlorine to chlorine dioxide as the most used bleaching chemical. This current development is driven by stricter regulations as well as marketing reasons. There is a strong trend towards closed loop mills where by-products can be converted internally into useful products or transformed into substances that can take part in the ecological cycles. One remaining issue for chlorine dioxide technology is the formation of by-product sodium sulfate, which cannot be used as a make-up chemical in a more closed pulp mill. We have studied different alternatives of salt splitting to solve this problem and at the same time get valuable sodium hydroxide that can be used in the mill. Our results from lab and pilot tests show that a chlorine dioxide generator can be integrated with a salt splitter to get an efficient process that is easy to control and has low operating costs. In the Generator Liquor Split, GLS, process the generator liquor is electrochemically acidified. The GLS process, internally generates all acid necessary for the process, and produces simultaneously 0,6 ton caustic per ton of chlorine dioxide With chlorate, reducing agent and electrical energy as the only raw materials, SVP-GLS is able to produce chlorine dioxide without by-product sodium sulfate. SVP-GLS also provides superior performance with respect to energy balance, production capacity, production economy and ease of operation compared with other salt-free chlorine dioxide alternatives.