Sodium Carbonate Monohydrate → Sodium Carbonate Decahydrate

Participants

Reaction Steps

The neutralized brine stream from line 20 which is combined with recycled mother liquor from the sodium carbonate monohydrate crystallizer from line 45, discussed below, is removed from the combined feed tank 20A through line 21 at a temperature of from about 90° C. to about 110° C. It is then cooled by heat exchange means not shown to a temperature of about 70° C. to about 90° C. and introduced into the first of two sodium carbonate decahydrate crystallizers identified as 21A. The stream from line 21 entering crystallizer 21A normally has a sodium carbonate concentration of about 20% to about 30% with only trace amounts, not above about 1/2% of sodium bicarbonate. In crystallizer 21A, sodium carbonate decahydrate crystals are formed by evaporative cooling of the solution and water vapor is removed via line 22. Evaporative cooling is preferred because it both concentrates the liquor in the crystallizer and this evaporation also cools the solution to crystallize sodium carbonate decahydrate. The crystal slurry formed in crystallizer 21A is then passed via line 24 into an initial centrifuge 24A to separate the decahydrate crystals from their mother liquor. The mother liquor is separated from the decahydrate crystals in centrifuge 24A and sent via line 26 to a second decahydrate crystallizer 26A. The crystals in centrifuge 24A are washed with water which enters through line 25. This is desired to get good separation of impurities from the crystals by washing the sodium carbonate decahydrate crystals to remove the impurities contained in the residual mother liquor remaining on the crystals. This assures obtaining crystals of higher purity.

Provenance & Evidence