The scheme proposed by rousset et al. (1989a,b) was based on a series of feedforward/feedback controllers. The results from this system were very promising , althouah a high degree of instrumentation was required on the plant. Lee and Newell(1989) proposed generic model control as a means of controlling a single effect recirculation evaporator . the study was confined to simulation studies, and although the control system gave impressive results, constraints could not be handled diretly,not anticipated (Harris and mclellan,1990).