A new \"membrane\" method for treating soda ash ammonia-evaporation waste liquid

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According to Sinochem News, recently the technology for producing concentrated calcium chloride from ammonia-vaporization waste liquid, along with refined brine as a by-product, which was independently developed by Shandong Haili Group Co., Ltd., passed the evaluation of scientific and technological achievements organized by the China Petroleum and Chemical Industry Federation. The evaluation committee, chaired by Dou Jinliang, Secretary-General of the China Soda Ash Industry Association, unanimously agreed that this achievement is highly innovative and that its overall technology has reached an internationally advanced level. 　　This technology achieves multiple innovations by making efficient use of the ammonia vapor waste liquid generated in the production of soda ash via the ammonia-alkali process as a resource. Firstly, this technology uses membrane methods to separate and concentrate Ca2+ and Na+ from the ammonia evaporation waste liquid, producing products such as calcium chloride concentrate, brine, and fresh water, thereby achieving effective separation of various components in the ammonia evaporation waste liquid ； Concentrated calcium chloride is used as a raw material for producing products such as calcium chloride dihydrate, while the brine is reused in the production of soda ash, thereby enabling the resource utilization of ammonia-evaporation waste liquid. Secondly, by making comprehensive use of ammonia vaporization waste liquid, this technology reduces the discharge of waste liquid generated in the production of soda ash via the ammonia-alkali method, thereby lowering the ecological burden. It also allows for a significant reduction in the area required for waste liquid treatment, saving land resources. Thirdly, this technology utilizes the principle of confined mass transfer; through the strategic arrangement of special separation nanofiltration membranes, it prevents scaling on these membranes, thereby increasing the system’s recovery rate. It also provides valuable insights for designing anti-scaling solutions in the separation of divalent ions from high-salt concentration wastewater. Two patents have been granted for this technology, including 1 invention patent and 1 utility model patent. 　　The treatment of ammonia evaporation wastewater in the ammonia-alkali industry is a global challenge. The pH value of the ammonia-vaporization waste liquid is around 11, with a solid content of approximately 15% to 20%. The main components of the liquid phase are calcium chloride and sodium chloride. The conventional treatment method involves separating the solids from the liquids, after which the waste residues and the liquid are stored separately; this approach requires a large amount of land and can have an adverse impact on the surrounding environment. A few companies manage to meet the ammonia nitrogen standards before discharging the wastewater by adjusting the pH value, but the treatment effect remains unsatisfactory. To address this challenge, Haihua has spent over a decade working intensively on it, overcoming key technical hurdles such as membrane fouling control, scale prevention, membrane module selection, and process system integration optimization. By relying on its independently developed pure membrane separation process, it has achieved precise and efficient separation of Ca+ and Na+ from ammonia-evaporation waste liquid. It has also pioneered the stable low-pressure, high-flux filtration of high-concentration wastewater, successfully enabling the recycling and reuse of wastewater resources. 　　This result has been verified in an experimental setup designed to handle 6 cubic meters per hour of ammonia vaporization waste water. Currently, this technology has entered the stage of industrial deployment, and can be widely applied to the comprehensive treatment of waste liquids generated by the ammonia-alkali process, thereby reducing enterprises’ environmental protection costs.