brief introduction
Because of the high concentration of salt, coal chemical wastewater can not be treated by biochemical treatment or other methods, so it can only be treated by evaporation; Some waste water can be evaporated and concentrated to turn waste into treasure. The process of evaporation and crystallization is used to treat coal chemical wastewater, so that the water after evaporation can be recycled and the wastewater can be discharged in zero.
technological process
For coal chemical wastewater, we use multi effect evaporation for treatment. Multi effect evaporation is a process in which two or more evaporators are connected in series. The secondary steam generated in the former evaporator can be used as the heating steam of the latter evaporator. As long as the pressure and boiling point of the solution in the latter evaporator are lower than those in the original evaporator, the secondary steam can be used as the heating source. Each evaporator is called one effect. By recycling steam, the heat energy is reused, thus reducing the cost of energy consumption.
The reverse osmosis concentrated brine is heated by 0.4MPa low-pressure saturated steam, and then enters the first effect evaporator, the second effect evaporator and the third effect evaporator in turn for evaporation. The steam from the former evaporator can be used as the heat source of the latter evaporator. Finally, the steam is cooled into condensed water through the condenser and enters the fresh water tank. The conductivity of recovered condensate is less than 200 μ S / cm, COD < 10mg / L, NH4 + - N < 2mg / L, meet the requirements of water quality reuse. On the other hand, the saturated material discharged from the three effect evaporator enters the cyclone thickener, in which the dilute solution is recycled, while the concentrated material enters the crystallizer and centrifuge, and finally transforms into solid salt mud. Because the energy consumption of multi effect evaporation process mainly comes from steam, and in most coal chemical enterprise projects, steam is a by-product, easy to get, low cost, so multi effect evaporation technology is very suitable for coal chemical wastewater treatment.
