Process for treating sulphur-containing spent liquor using multi-stage carbonization

摘要

PCT No. PCT/AT94/00038 Sec. 371 Date Oct. 5, 1995 Sec. 102(e) Date Oct. 5, 1995 PCT Filed Mar. 31, 1994 PCT Pub. No. WO94/23124 PCT Pub. Date Oct. 13, 1994To recover the sodium-sulphur compounds following sodium-based pulp processing, e.g. the ASAM process or basic or acidic sodium sulphite processes, the waste liquor is burnt in a lye burning vat (1) with liquid slag extraction and the exhaust gases are subjected to multi-stage purification with dry fly-ash recovery and the gaseous sulphur compounds are also separated in a multi-stage washing process. The water-soluble components of the fly-ash are taken to the waste liquor to be burnt and thus the sulphur to be recovered in the slag is increased. The slag is dissolved in water and the dissolved sodium compounds are converted by multi-stage carbonisation with a part of the purified flue gas into sodium bicarbonate and H2S. The H2S is burnt and finally converted into sodium sulphite so that the desired lye for pulping cellulose can be made up from sodium sulphite and carbonate.