Methods to reduce the salinity of mine water

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This post was last edited by sdwfsgyykai on 2015-7-21 at 17:38. The development of technologies for treating and reusing water from coal mines in our country started relatively late, and the efficiency of such treatment is low. However, as awareness of energy conservation and environmental protection grows, more attention is being paid to these technologies for treating and reusing water from coal mines. Coal mine water is both a pollution source with industry-specific characteristics and a valuable water resource. At present, many coal mines in our country suffer from a severe water shortage; at the same time, the water is discharged directly without treatment, resulting in massive waste of water resources and environmental pollution. The reuse of treated coal mine water is an urgent necessity, and desalination is the most critical step in this process. Methods for reducing the salt content in mine water include: (1) Thermal methods – Both high-temperature (distillation) and low-temperature (freezing) treatment processes fall under thermal desalination. Distillation is an effective method for thermally desalinating saline water. At the cost of heat energy consumption, this method is generally suitable for the treatment of mine water with a salt content exceeding 3000 mg/L. The former Soviet Union’s Coal Environmental Protection Research Institute developed a distillation unit for the desalination of mine water, designed for treating mine water with a salt content of over 5 g/L; the water produced could be used for domestic and industrial purposes in coal mines, with the cost of fresh water at 50 kopecks per m3. The insulated evaporator installed in the Chernovsk mines is capable of reducing the salinity level, which ranges from 7800 to 9000 mg/L, to 25 to 200 mg/L. The Jebeńska mine in Poland has installed an adiabatic evaporation desalination unit with a production capacity of 100 m3/h, which can reduce the salt content in the feed water from 100 g/L to 100 mg/L. The main problem with distillation is preventing scaling on the heat exchange surfaces. 　　(2) Chemical methods The ion exchange method is the main approach for chemical desalination; it involves using cation and anion exchangers to remove ions from water, thereby reducing its salt content. This method is cost-effective when the salt content in the feed water is less than 500 mg/L, and can be used as an additional desalination step after membrane separation of highly mineralized water. 　　(3) Membrane separation methods Both electrodialysis and reverse osmosis technologies belong to membrane separation techniques, and they are the two main methods used in China for desalinating brackish water at present. In particular, the former has many application examples and experiences in China’s coal mining industry.