At RUSAL’s alumina plants, excess process water is removed in a specialized production stage known as evaporation. At RUSAL Achinsk JSC, in the soda ash calcination shop, a direct-flow evaporator train with forced-circulation units is used to remove excess water and recover the product-anhydrous soda ash. In 2021-2022, specialists at RUSAL Engineering & Technology Center LLC developed a mathematical model of the evaporator train, including material and heat balances derived from statistical data on the operation of the plant’s potash and soda sections. The computer model, which included computational and graphical diagrams, fully replicated the layout of the existing evaporator train and served as the basis for developing design solutions to improve its energy efficiency. Based on the developed mathematical model, 14 layout variants of the evaporator train were calculated, involving the installation of additional heat exchange equipment, changes to the brine heating schemes after each vessel, modifications to the heat exchange surfaces, the installation of self-evaporators for brine and condensate, and changes to the brine and steam flow schemes. The effectiveness of the solutions, based on the calculation results, was determined through an expert technical assessment that included the costs of implementing the evaporator bank modernization project, the energy efficiency of the evaporator bank after modernization, and the technical feasibility of implementing the measures. Based on the results of the assessment of the balance and thermal calculations, technical solutions were developed involving the installation of two solution evaporators, one heat exchanger to preheat the initial sulfate mother liquor entering the evaporator train, and the conversion of the evaporator train from a co-current flow regime for the solution and steam to a counter-current flow regime. In 2023, specialists from RUSAL Engineering & Technology Center LLC (St. Petersburg) and Chemical Systems Design Bureau LLC (Yekaterinburg) developed the technical package and carried out construction and installation work. In 2024-2025, pilot-scale tests were conducted at RUSAL Achinsk JSC, confirming the results obtained from calculations in the mathematical mode
EVAPORATION, EVAPORATOR TRAIN, DIAGRAM, SODA, SODA SOLUTION, MATHEMATICAL MODEL
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