DESIGN AND OPERATING CRITERIA FOR MAXIMISING THE BENEFIT OF CONTINUOUS VACUUM PANS

Abstract CONTINUOUS vacuum pans provide significant advantages in achieving more effective use of installed volumetric capacity than batch pans. Other advantages are reduced supervision, benefits to steam economy and consistency in the composition of the product massecuite. However, in order to maximise the benefits, continuous pans must be operated at high sucrose deposition rates and be able to minimise the effects of any shortcomings such as time off line for cleaning. The paper discusses several important design and operating criteria for maximising the benefits of continuous pans to overall factory operation. Data are presented from operating continuous pans to highlight the importance of these criteria. Such data include circulation velocity measurements for the massecuite flow, residence time distribution data, massecuite exhaustion and crystal quality data. Consideration is given to design changes for future installations of continuous pans and ways to minilnise the effects of downtime. Introduction Continuous vacuum pans achieve more effective use of the installed volumetric capacity than batch pans. This benefit, coupled with other advantages of improved exhaustion performance, consistent operation, reduced supervision by operators and reduced steam consumption makes continuous vacuum pans an economically attractive proposition for raw sugar crystallisation. However, there are potential pitfalls in the design and operation which must be avoided if the full benefits are to be achieved. Current installations of continuous pans in Australian factories Continuous vacuum pans are employed in 13 of the 28 sugar factories in Australia and are used for all massecuite production duties, as specified in 3