By David Reed, UT EditorLeverkusen, Germany-Bayer MaterialScience has developed a new process for making chlorine from hydrochloric acid which, it claims, uses less electricity, yields chlorine that is pure enough to use without extra processing, and can be operated flexibly, in line with actual demand. Chlorine is a vital part of processes for making polyurethane raw materials and polycarbonates, the firm points out.Bayer has already installed a unit using the new process at its Brunsbüttel, Germany, site-where it operates plants for making TDI (toluene diisocyanate) and MDI (methylene diphenyl diisocyanate)-and says it will also license the process to third parties.The new process uses a purely metallic electrolysis cell with an ion exchanger membrane and an "oxygen-depolarised cathode"; this electrode is fed with oxygen and yields water rather than hydrogen. As a result, Bayer explains, the electrolysis can be operated at a significantly reduced voltage at the same current density, which leads to lower energy consumption.In addition, the ODC process yields pure chlorine which can be recycled directly without the need for extra clean-up. Finally, the unit can be kept in stand-by mode and can start supplying chlorine of high quality at short notice, even after brief standstills. This means chlorine production can be much more flexibly adjusted to the actual requirement, Bayer points out.The firm adds that its new unit at Brunsbüttel was developed and brought to industrial maturity through a three-way programme of cooperation between Bayer AG, UHDENORA - a joint venture between UHDE based in Dortmund, Germany, and De Nora of Milan, Italy - and De Nora North America.For further details, contact Bayer at Fax: +49 221 9902 160."
