The control of low raw crystallization is greatly influenced by the much slower crystallization rate at the purity at which this crystallization step is conducted. Depending on the purity of the massecuite being processed, the mass crystallization rate is about 1/15 that in white crystallization and about 3/10 that in high raw crystallization. The lower the massecuite purity, the lower the crystallization rate. Unlike white or high raw crystallization, a low purity low raw strike virtually never reaches a point where the mass crystallization rate exceeds the potential evaporation rate. As a result, if optimal performance is to be achieved, a low raw strike demands strict control of mother syrup DS concentration from the time the strike is seeded until it is discharged from the vacuum pan. Therein lies the subject of this short discussion.Complicating matters is that the purity of the molasses produced is nearly directly proportional to the purity of the low raw massecuite. Of course, other factors such as sucrose solubility and equipment capacity do influence the purity of molasses produced but none so much as the purity of the feed to the low raw crystallization and the purity of the final massecuite regardless of these other factors. So, for a truly efficient sugar end operation achieving the highest recovery of sucrose from the thick juice being processed, it is essential to operate the low raw crystallization at as low a massecuite purity as possible.
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