In the chemical-process industries, dilute streams containing valuable ingr
edients are generated in several unit operations. Mechanical vapor-recompre
ssion is the best available technology for vaporization that may be used fo
r concentrating such dilute solutions. Energy consumption for vaporization
by compression and membrane technology is 350 and 90 kJ/kg, respectively. I
n order to save additional energy by recycling water, this study explored t
he use of membranes for processing a hot feed (70-80 degrees C) containing
small amounts of food ingredients. Pilot tests report the effects of experi
mental parameters on membrane performance. The impact of pretreatment of th
e feed and membrane-cleaning procedures to maintain performance will also b
e discussed. Initial results indicate that the use of a membrane to preconc
entrate, prior to the final concentration with mechanical vapor recompressi
on, has the potential to save significant amounts of energy. Furthermore, t
he use of membranes would increase plant capacity by reducing the load on t
he vapor-compression unit. In this study, it was estimated that a plant pro
cessing 15 metric tonnes of feed every day and using membrane technology fo
r concentrating to twice the concentraiton would save about 2 GJ of energy.
(C) 1999 Published by Elsevier Science Ltd. All rights reserved.