Technology of membrane distillation treatment for highly-mineralized mine water in western mining area

A considerable proportion of mine water in western coal mines is high salinity mine water. Product water quality of typical treatment process meets the requirements of recycled water. But there are some problems with typical treatment process such as high up-front investment, complex process and high treatment cost. Statistics show that the solar energy and geothermal resources of the seven large-scale coal bases in the west are rich or relatively rich. In order to realize the large-scale and low-cost treatment of high-salinity mine water, the advantages of western solar energy, geothermal energy and industrial waste heat can be fully utilized, and membrane distillation technology can be used for treatment. Its advantages are mainly reflected in: low-cost heat source, high concentration ratio, short process flow, good water quality, and low degree of membrane fouling (wetting). The combination process of membrane distillation, solar energy and geothermal energy were described in detail, and it is pointed out that solar membrane distillation can be used for deep concentration of reverse osmosis concentrated water on the ground; eothermal membrane distillation could directly treat mine water with high salinity underground. The produced water can be reused underground or on the ground. Concentrated water can be sealed underground, resulting in significant cost reduction of “zero discharge” of mine water. Taking the 100 t/h mine water treatment in Ningdong Area as an example, the photothermal area required for solar membrane distillation and the heat exchanger length required for geothermal membrane distillation were measured. The results show that the photothermal area required for the treatment of 100 m3/h mine water by reverse osmosis series membrane distillation is about 8 257 m2, which can make full use of the space at the top of the treatment station and the reservoir, and basically do not occupy new land. Besides, the length of the heat exchanger required for direct treatment of 100 m3/h mine water under the geothermal membrane distillation is about 9 435 m. Vast rock and soil of underlying layer can meet the heat exchange space required for geothermal membrane distillation.