Simulation and control of recycle systems

Recycle streams are widely used in the chemical industry. As the industry moves towards higher yield and low (or zero) discharge, more recycle loops will be put in place. Unfortunately, recycle introduces equipment interactions which slow the system response and increase the sensitivity to disturbances. The use of conventional methods such as Laplace domain to analyze recycle systems may be difficult. Frequency response analysis is used to study recycle dynamics. The effect of different model parameters (such as gains and time constants) is examined. The recycle function is explicitly studied.