Evaluating dynamics and plantwide control of hydrodealkylation process

Abstract

With the increasing interest in and the need for plant-wide design and control, it is desirable to develop rigorous models for realistic with recycle streams, energy integration and non-ideal systems, and use them for evaluating plantwide control schemes. In this study, a rigorous model for the hydrodealkylation of toluene (HAD) process is developed using the commercial software, HYSYS.PLANT. A simulation-based methodology for evaluating these phenomena and finding the best control structure is reported from a controllability point of view. Staedy-state and dynamic simulations are combined with controllability analysis tools, both steady-state and dynamic simulations are combined with controllability analysis tools, both steady-state and in the frequency domain, which cxtracts more value from simulation than the usual sensitivity studies. The case of HAD process, The reference control structure designed by Luuyben (1998) and the two control structures designed by Kietawarin (2002) are considered. The steady-state analysis is confirmed that the second control structure should be controlled. For using the controllability analysis it appeared that the problems mainly come from the interaction between the different units in the flowsheet. Controllability analysis described by PRGA and CLDG. For PRGA, the response of the control stucture2 can give the result into satisfied bound. That means the effect of changing setpoint is less than the reference structure and the first one. However, for CLDG gives the result that the reference structure and the control structure, can reject the disturbance better than the second one. The considered disturbances are the temperature of Ftoluene stream and pressure of FFH2 stream.