The invention discloses a production method of heavy soda ash. The production method comprises the following steps: adding light soda ash and a
sodium carbonate saturated solution into a hydration crystallizer; introducing
crystal mush into a thickener to adjust the
solid-to-
liquid ratio after the reaction, separating the
crystal mush in the thickener in a centrifugal
machine, and introducing thesupernatant of the thickener into a
mother liquor barrel; separating, washing with washing water, removing salt and impurities on the surface of
crystal mush, and feeding centrifugate into the motherliquor
barrel; treating the centrifuged
solid to obtain a heavy soda ash product; evaporating the 20-50%
mother liquor until the common saturation point of
sodium carbonate and
sodium chloride is reached to separate out
sodium carbonate monohydrate crystals, mixing the
sodium carbonate monohydrate crystals and steam condensate, recycling the mixture into a hydration crystallizer, and feeding the residual sodium
chloride and
sodium carbonate co-saturated solution into a combined-soda
system vacuum salt making device; enabling 50-80%
mother liquor to enter a clarification device, adding
sodium sulfide, removing iron impurities, and enabling clarified liquor to enter a hydration crystallizer to continue to prepare heavy soda ash. According to the method, sodium
chloride and iron impurities inthe
sodium bicarbonate mother liquor in the current
sodium bicarbonate production process can be removed,
discharge of the
sodium bicarbonate mother liquor is reduced, and the quality of the sodium
bicarbonate product is improved.