The invention relates to the technical field of salt extraction and
recovery of
sodium-process desulfurization waste liquid, in particular to a method and device for extracting product-grade
sodium thiocyanate from
sodium-process desulfurization waste liquid, and the method comprises the following steps: step a, primary decoloring treatment, step b, primary concentration
crystallization, step c, secondary decoloring treatment, step d, freezing
crystallization, step e, precise desalting, and step f, secondary concentration
crystallization. A stepped
process design of two-time decoloration, fractional crystallization and precise
desalination is adopted, aiming at the physicochemical property difference of three core salts of
sodium sulfate,
sodium thiosulfate and
sodium thiocyanate in the sodium-process desulfurization waste liquid, efficient separation is realized by accurately controlling process parameters, the
sodium sulfate is preferentially separated out by utilizing the characteristic that the
solubility of the
sodium sulfate is relatively low at high temperature, and the
sodium thiosulfate is separated out by utilizing a high-temperature crystallization method. The
sodium thiocyanate is separated out in a targeted manner on the premise of ensuring that the
sodium thiocyanate is in an unsaturated state, so that the technical problem that the sodium
thiocyanate is easy to co-crystallize at low temperature is solved.