AN EVALUATION OF MECHANICAL STIRRING IN V ACUUM PANS

This paper sets out to evaluate the relative advantages of mechanical stirring and natural circulation in vacuum pans. Fundamental to this e valuation is an economic appraisal of steam usage and energy rationali sation. With low steam pressures the longer boiling times call be sign ificantly reduced by mechanical stirring. At normal operating pressure s, the use of mechanical stirring reduces boiling lime by 45% in the c ase of B-massecuite and 53% for C-massecuite. In addition, mechanical stirring is shown to improve crystal yield. An economic analysis based on a factory with a 5000 t cane/day throughput is carried out. It is demonstrated that possible savings can be achieved in the boiling hous e by using low pressure steam from a 5-effect evaporator. In a 5000 t cane/day mill, these savings could reach US$ 250,000 a year.