1504393 Sodium bicarbonate RHONE-POULENC INDUSTRIES 20 May 1975 [22 May 1974 28 Feb 1975] 21589/75 Heading C1A A continuous method of obtaining sodium bicarbonate in crystals of a size larger than those produced by the ammonia-soda process comprises treating sodium chloride diaphragm cell liquor in a first zone with CO 2 -containing gas to produce Na 2 CO 3 which remains in solution, subjecting this solution to the action of CO 2 -containing gas in a second zone to precipitate NaHCO 3 at a temperature below 70‹ C., passing the suspension obtained to a third zone to complete the bicarbonation by the action of CO 2 -containing gas and cooling the suspension to no more than 45‹ C. and separating the precipitated NaHCO 3 . Some of the resulting mother liquor or the suspension may be recycled from the third zone to a point upstream of the point of maximum temperature of the second zone, thus allowing lower maximum temperatures to be used in the second zone, e.g. 40-60‹ C.
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