PLANTWIDE CONTROL AND DYNAMICS BEHAVIOR OF AN INTEGRATED PLANT COUPLING NITROBENZENE HYDROGENATION AND METHYL-CYCLOHEXANE DEHYDROGENATION

Coupling of exothermic and endothermic processes is an application of process intensification where two or more processes can be combined in single unit for better utilization of material and energy. Nitrobenzene hydrogenation and dehydrogenation of Methyl cyclohexane in a single adiabatic reactor was investigated and found efficient, stable and economical in the previous study. The scope of this research is to implement plantwide control structure to analyze the dynamics behavior of an integrated system using Aspen Dynamics. Integrated plants where un-reacted reactants are recycled have high sensitivity towards disturbances. The complexity of the plant is reduced by fixing flow rates of reactants at reactor inlet using feedback control strategy. On introduction of individual and combined disturbances in flow rates of reactants ±10%, the system showed robust behavior and achieved stable operation. The system allows production rate changes keeping high purity of products

Integrated Production of γ-butyrolactone through Coupling of Maleic Anhydride Hydrogenation and 1,4-butanediol Dehydrogenation

Design and plantwide control of an integrated plant for the hydrogenation of maleic anhydride and the dehydrogenation of 1,4-butanediol has been studied for the synthesis of γ-butyrolactone in an adiabatic reactor, under different conditions of reaction temperatures and hydrogen to feed ratio, realizing optimal hydrogen utilization and better energy efficiency. Compared to stand-alone processes, the integrated process has several advantages, e.g., easy temperature control, improved γ-butyrolactone yield, good energy efficiency and optimal hydrogen utilization. The stability and robustness of the process is checked by rigorous dynamic simulation in AspenDynamics

Design and Control of Di n-Pentyl Ether Process

Recycle of un-converted reactants is a common practice in industrial chemical processes. However, the material recycle induces a non-linear behaviour of the plant which often manifests as high sensitivity of the recycle flow rates with respect to disturbances such as changes in raw material quality, production rate and uncertain design parameters. This non-linear behaviour of the system is often the source of control difficulties. Thus the importance of appropriate control structure in reactor-separation-recycle is evident. The case study of di n-pentyl ether production illustrates two control strategies that can be applied to processes involving one reactant and one recycle. The strategy based on self-regulating reactant inventory uses the plant-inlet flow rate as the dominant variables which significantly affects the production rate. The strategy based on inventory feedback control uses the reactor inlet flow rate, the reactor holdup or the reaction temperature / pressure as throughput manipulator. For the di n-pentyl ether process, both strategies are applicable, as demonstrated by rigorous dynamic simulation