A major breakthrough occurred recently in the engineering of de-nitration by membrane method, which is organized by State Environmental Protection Membrane Engineering Technology Center and co-undertaken by BlueStar (Beijing) Chemical Machinery Co., Ltd., China Haohua Engineering Co., Ltd. and Hangzhou Development Center of Water Treatment Technology.
The project, intended to handle 30,000 tons of caustic soda in Huanghua, a city of Hebei Province, and whose capacity can be expanded to 80,000 tons, has finished material balance calculation, heat balance calculation, flow chart and equipment list, providing a process package.
Barium method is the traditional way to remove sulfate ion from primary brine, but considering environmental protection and the toxicity and cost of barium chloride, de-nitration by membrane method, a system in which sodium sulfate is removed by means of membrane, is a better choice. It relies on the selective isolation of the membrane to separate surplus sulfate ion from the brine circulation system in the form of sodium sulfate, so the circulation only contains up-to-standard brine. Highly advanced and automated, the de-nitration device by membrane method recycles all the brine and mirabilite and will not produce a large amount of waste salt slurry as in the traditional method. A typical case of patent in China, the new method is estimated to save chlor-alkali enterprises several billion yuan every year in energy consumption, chemical input and safe production.