A New Process for Producing K_2SO_4 from Bittern

摘要

Bittern brine is an excellent raw material for chemical products processing. It is the mother liquid after evaporating sea water in the sun to make salt, and contains six kinds of main chemical ions such as Na~+, K~+, Mg~(2+), SO_4~(2-), Ch~- and Br. Many domestic coastal salt factories have been draincing bittern into the sea for a long time, and have wasted resources and polluted sea water. Some salt gactories have been producing MgCl_2(H_2O)_6, bromine, and KCl by use of bittern brine. A large part of high temperature salt wastes has been still draining to the environment. Furthermore, the value of KCI is quite low, so that the economic benefit of these enterprises is not so good. We have successfully developed a comprehensive utilization technology of producing K_2SO_4 with bittern brine. The technological process parts are: (1) evaporating and concentrating the bittern brine, separating NaCI and sulfates in solid form from KCI and MgCl_2 in the remaining liquid,; (2) physically separating NaCI from sulfates in the solid part, obtaining K_2SO_4 via two-step transformation of the sulfates with KCI; (3) cooling the liquid part and separating carnallite in solid form from the mother liquid (4) wholly changing the mother liquid into MgCI_2(H_2O)_6 after extracting bromine, and using KCI obtained from carnallite decompositing with water to produce K_2SO_4. All components in the bittern brine are fullu used in this process and a so-called closed-circuit circulation without any chemical additives and envirenrnental pollution is realized. This technology will be spread in all domestic coastal salt factories to resolve sea water pollution problems caused by bittern brine draining, especially to reform the existing bittern brine chemical factories which produce KCI. It can get rid of the waste pollution, change products structure, and remarkably increase the profits of the bittern factories.