Experience of using ammonium bisulphite in extraction at British Sugar

Trials were carried out using ammonium bisulphite (ABS) as a biocide in extraction at two British Sugar factories during the 1994/1995 campaign. It was demonstrated that bacterial activity during extraction can be controlled effectively by maintaining the level of sulphur dioxide in raw juice at 150-200 mg/kg and the extraction temperature above 70 °C. There was a reduction in the pressed pulp dry substance content which decreased from 29.1% when formalin was used in extraction to 25.7% when ABS was substituted. There were also several incidents of high ash sugar (> 0.02%) resulting in white sugar returning for reprocessing. Analysis showed that the increase in ash was due to an increase in the concentrations of potassium, calcium and sulphate. It was postulated that this was due to the precipitation of a double salt of potassium and calcium sulphate, Kalussite.