9 pilot plant was built to evaluate the economic potentialities of' producing glycerol from si1ga.r by the bisulphit,e fermenta.tion process. The design of this small unit was based on information collected from benchscale studies of the fermentation a,nd recovery processes taking advantage of new separation techniques.
A beer containing 5 per cent of glycerol is protluced in a continuous fermentat.ion in which the free bisulphit,e level is itiitoinatically controlled. The effluent from the fermentor is centrifuged, ant1 the yeast is ret urnetl t o the fermentat,ion. The dilut,e clarified beer is aciditietl ; sulpliru* dioxide, acetaldehyde, and alcohol are removed ; anti the stripped solution is neutralized and concentrated until i t contains 45 per cent of glycerol. This concentrated glycerol stock is pnrified by using a combinat,ion of ionexclusion and ion-exchange.
Good fermentation control results in a beer that has a low solida-toglycerol ratio, low organic acid content, and low residual sugar. The met.hod of glycerol purification results in a high glycerol recovery, since no distillation of glycerol is involved. The sulphur dioxide removed from t,he beer is recycled through the fermenhtion so t.hat the chief raw materials used in the process are sugar, sulphtiric acid, and sodium carbonate. The yields of products based on sugar charged are: glycerol, 25 per cent; alcohol, 17 per cent, ; and acetaldehyde, 1 1 per cent.
The economic success of the process depends to a large extent upon the price of sugar. I'nder present conditions it is felt thnt the process is competit ive. * Presented a t the ilmerican Chemical Society meeting in A4tlantic City, N.J. t This report is based on work supported by U.S. Army Ordnance under Maintained at Madison, Wis., in cooperation with the University of Wisconsin. September 1959.