Abstract
M.Tech. (Chemical Engineering)
Laboratory and pilot plant trials were carried out on a modified carbonatation process to reduce overall refining costs. Sulphur dioxide dosages of less than 250ppm on brix
were added to carbonatated liquors. The resultant filtered liquor had an additional 4,6% colour removal and a 10% ash gain relative to factory liquors. Reducing sugars and
filterability were not affected. Additional colour removal of 14% was noted in the affinated crystal colour of crystals grown from the resultant brown liquors in the SMRI pilot pan.
The failure of the combined carbonatation - sulphitationLaboratory and pilot plant trials were carried out on a modified carbonatation process to reduce overall refining
costs. Sulphur dioxide dosages of less than 250ppm on brix were added to carbonatated liquors. The resultant filtered liquor had an additional 4,6% colour removal and a 10% ash gain relative to factory liquors. Reducing sugars and filterability were not affected. Additional colour removal of 14% was noted in the affinated crystal colour of crystals grown from the resultant brown liquors in the SMRI pilot pan.
The failure of the combined carbonatation - sulphitation process to remove the ash that the carbonatation process does, negates the cost benefits of the additional colour removals. The reason for the ash "gain" is that the sulphur dioxide partially dissolves the calcium carbonate, releasing the adsorbed ash and colour. The colour is then adsorbed onto the calcium sulphite. process to remove the ash that the carbonatation process
does, negates the cost benefits of the additional colour removals.