Plate evaporators in British Sugar – An update

Plate evaporators are a cost effective technology for increasing the heating surface of existing evaporators or for providing new evaporators up to 2,000 m2 heating surface. At British Sugar 12 units are in operation. In case of a booster system a simple series connected system can be used without a juice pump, this provides more favourable heat transfer by allowing larger flow rates and in some cases flash vapor to enter the plate evaporator. Juice quality should benefit from the small residence times of 50 s per evaporator found in practice. Operational stability is improved by recirculation of juice to maintain a minimum flow rate per channel on larger heating surfaces (> 500 m2) and by using restrictor gaskets. The requirement for maintaining a minimum flow is greater at higher juice inlet dry substance contents although the peripheral wetting rate required is one tenth that of a tubular falling film evaporator. A GEA CT193 evaporator installed in a series flow configuration achieved similar levels of heat transfer coefficient to that expected of an Alfa Laval EC500 in a similar system.