Chlor-alkali electrolysis technologies applied in Japan

The Japanese chlor-alkali industry originated in 1881, when caustic soda was produced by Le Blanc process. Thereafter, mercury, diaphragm, and ammonia-soda processes were developed and applied. After the second world war, mercury process was further developed and mainly applied. However, in 1973, mercury pollution problem was disclosed by a newspaper. Two thirds of mercury process capacity was converted to diaphragm in the phase I process conversion and the balance to ion exchange membrane process in the phase II, which was developed in Japan urgently to meet with the process conversion. About 80% of diaphragm cells, installed in the first stage, were re-converted to new or retrofit type of ion exchange membrane cells. Now in Japan 90% of caustic soda is produced by ion exchange membrane process, 10% by diaphragm process.