Desalting and reusing method of high-salinity heavy ash mother liquor in combined-soda system

The invention discloses a desalting and reusing method of high-salinity heavy ash mother liquor in a combined-soda system, which comprises the following steps that (1) when the sodium chloride content of heavy ash mother liquor is higher than 60 g/L, a part of high-salinity heavy ash solution is required to be discharged, and the discharged solution is conveyed to an evaporator to evaporate; (2) the discharged high-salinity heavy ash solution is evaporated to the co-saturated point of sodium carbonate and sodium chloride, so that monohydrate sodium carbonate crystals are precipitated out, and the monohydrate sodium carbonate crystals are separated from residual mother liquor after evaporating; and (3) the separated crystals are dissolved, so that a solution with a sodium chloride content of less than 20 g/L is obtained, and the solution is returned to a heavy ash system to reuse; and the residual mother liquor is applied to a salt-leaching process of a vacuum salt manufacturing device. In a solution which can be reused in the system and obtained by using the method disclosed by the invention, the sodium chloride content of is less than 20 g/L, and the sodium carbonate content is about 310 g/L, so that the solution can meet the index requirements of the heavy ash system.