Refinery vacuum pan energy efficiency optimisation

As part of Harwood Mill and Refinery's energy efficiency opportunities (EEO) program process improvements have been implemented at the Refinery to optimise the consumption of energy and water in the refinery pans. Limited refined sugar grading capacity exists within the factory and this has required intense focus on accurate vacuum pan boiling to achieve tight control of refined sugar grain size and regularity. Previous pan control included a constant temperature slurry graining and 'check' process that used significant quantities of water to control the supersaturation of the pan contents and achieve the required grain specification. The improved 'vacuum-checking' process controls supersaturation with minimal use of water by manipulating the content's temperature by adjusting and regulating the vacuum in the head space. Whilst this concept is certainly not new, this paper gives an insight into the history of pan boiling at Harwood Refinery, and the effective implementation of this concept into normal operations. Calculations predict an annual energy saving of approximately 34 TJ (equivalent to about 2500 t of coal each year assuming 50% thermal efficiency) and water saving of 13,320 t across the pan stage based on an annual refined sugar production output (RSO) of 220,000 t.