Industrial production generates various types of wastewater with diverse characteristics, and there are multiple methods available for its treatment. Some wastewater contains high concentrations of salts (such as sodium chloride, sodium sulfate, ammonium chloride, zinc sulfate, etc.) and organic compounds, making it unsuitable for biological or other conventional treatments. In such cases, the only viable option is to use evaporation to remove the salts and meet the required emission standards. Additionally, some wastewater can be concentrated through evaporation, allowing the recovery and reuse of valuable substances.

    Sulfate-containing wastewater typically consists of components like ammonium sulfate, zinc sulfate, and sodium sulfate. The primary sources of sulfate-containing wastewater are the mining industry and the fermentation pharmaceutical industry. During mining processes, sulfur and sulfides present in ores are oxidized to form sulfate salts, resulting in wastewater with high sulfate concentrations and low organic content. In the fermentation pharmaceutical industry, sulfate in wastewater mainly originates from the addition of auxiliary materials such as sulfuric acid and sulfurous acid in the production process, leading to wastewater with low sulfate concentrations but generally higher organic content.

   Both Mechanical Vapor Recompression (MVR) evaporation and Multiple-Effect Evaporation (MEE) processes are suitable for evaporating and crystallizing sodium sulfate solutions. The choice between the two depends on various factors of actual condition, including but not limited to processing capacity, types of components, mother liquor concentration, and emission concentration. Due to the solubility characteristics of sodium sulfate, its solubility changes significantly with temperature. Therefore, when designing the evaporator, considerations should be given to preventing blockages, and the pipelines and systems should be designed with various flushing measures in mind.

    A triple-effect forced circulation evaporator is adopted for the sodium sulfate wastewater treatment, and the overall process flow is: the sodium sulfate wastewater was concentrated by a triple-effect forced circulation evaporator till oversaturated, and then the oversaturated liquor was transferred into a centrifuge for liquor-solid separation, and the solids separated were treated in further, and the mother liquor were returned to the evaporator to be concentrated again.

    The forced circulation pump equipped can effectively prevent the crystal solids from setting and caking which would lead to tube blockage, and can slow the formation of scaling on the heat exchange surface at the mean time, improve the heat transfer efficiency, increase the continuous operation time of equipment, and reduce the cleaning frequency.

    This evaporator-crystallizer is suitable for evaporating and crystallizing inorganic salts and organic compounds, including sodium chloride, phenylalanine, sodium sulfate, glycine, barium chloride, zinc sulfate, calcium chloride, ammonium sulfate, etc. It mainly applies in the food industry, chemical industry, metallurgical industry, as well as for treating pickling wastewater in large steel plants and wet desulfurization wastewater in power plants.