The desalination and crystallization unit at Guoneng Yulin Chemical produces sodium chloride

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The desalination and crystallization unit at Guoneng Yulin Chemical Industry produces sodium chloride. Author/Source: Shaanxi Petrochemical News Network. Date: April 29, 2022. Clicks: 7. On April 27, the desalination and crystallization unit of Energy Group Yulin Chemical Industry Co., Ltd. began producing high-quality sodium chloride, achieving continuous and stable operation for one month. This marked the first application of the low-temperature critical freezing combined with vacuum heating method for desalination in the treatment of coal chemical industry wastewater, filling a gap in China and setting a benchmark for wastewater treatment in this industry. Compared with the traditional nanofiltration membrane method for salt separation, the low-temperature critical freezing combined with vacuum heating technique for salt separation features lower investment costs, a shorter process flow, and reduced operating expenses. However, the patented technology introduced by a domestic company involves numerous key indicators and control points related to its design and operation, covering areas such as water treatment, salt chemical industry, and inorganic chemical industry, which demands very high standards in terms of design and operation. Since its commissioning, the salt separation and crystallization unit has encountered issues such as short operation cycles of the evaporator, unstable operation of the mirabilite freezing system, low processing capacity, frequent crystal blockages in the coolers, and long thawing times for those coolers. As a result, mirabilite leaks into the sodium chloride system; organic substances in the sodium chloride crystallizer cannot be effectively separated and removed, and the quality parameters of the incoming water remain unstable and fail to meet the required standards. To address these challenges, Yulin Chemical Company established a technical task force, despite having no prior experience in engineering design or operational procedures. Adhering to the principles of independent innovation, overcoming difficulties, and transformation and upgrading, the company carried out numerous technological innovations and improvements. They gradually overcame challenges such as short operation cycles of the evaporators and the mirabilite freezing system, and formulated measures such as increasing the salt-nitrate ratio and the concentration multiple of the evaporators, thereby determining clear adjustment ranges. At present, the evaporator is able to operate stably over long periods of time; the mirabilite system has gradually stabilized as well. The processing capacity has increased from less than 5 t/h to 18 t/h, the temperature difference in the cooler has decreased from 2.4°C to below 1.6°C, the thawing time has been reduced from 36 hours to less than 4 hours, and the period during which crystallization occurs in the cooler has extended from 3–5 days to longer durations. There is almost no loss of mirabilite suspended particles, and all operational parameters are gradually becoming stable. The purity of sodium chloride is over 99.4%, and the production volume in the past month has reached more than 150 tons.