IMPROVING THE QUALITY OF C SUGAR MAGMA FOR USE AS SEED CRYSTAL MATERIAL

摘要

The sugar crystals produced by continuous C massecuite centrifugals typically comprise large numbers of crystal chips and broken grain, as well as the main crystal population. Consequently, the C sugar magma produced from this material is of poor quality for use as crystal seed for subsequent crystal growth, unless washing is undertaken firstly to dissolve and remove the chips and small crystals. Generally mills undertake this magma preparation step in batch pans, but the washing step is one of the most difficult to control on the pan stage due to the rapid crystal dissolution that occurs. A magma preparation system has been developed that involves the continuous flow of magma through a mixer where controlled dissolution is undertaken, and then through a specially designed cooling crystalliser where the dissolved sucrose is recrystallised onto the remaining crystals. Condong Mill has operated the SRI designed magma preparation system since 1995, with good results. The prepared magma, which is stored in a buffer tank prior to use in a batch pan for seed development, typically is of 25% crystal content, has a mean size of 0.25 mm, and contains very few small crystals. No washing of the prepared magma is undertaken in the batch pan prior to the commencement of crystal growth. The main benefits to Condong Mill from implementing the system have been a boost of about 9% to the production capacity of the pan stage and improved quality of the sugar produced by the factory. The paper describes the design of the system and the control functions, together with the results from Condong Mill. The application of the system to other raw sugar factory arrangements, e.g. as the seed supply to continuous pans, is also discussed.