Interaction between energy integration and control performance of hydrodealkylation process

Abstract

The use of energy integration is to improve thermodynamic efficiency of a process. This translates into a reduction in utility cost. Thus, it is common practice to install feed-effluent desing 2-6 exchangers around reactors and distillation columns as Hydrodealkylation of Toluene (HAD) process (alternative 6). Positive feedback can occur and make the plants more difficult to control. The objective of this research was to study the effect of levels of energy integration and energy maintained within the process on control performance of energy integrated Hydrodealkylation of toluene (HAD) process. The ideas of Luyben's heat pathways were taken into account in order to get insight of the roles of heat pathways and their effects on the control performance. These ideas helped us to design several levels of energy maintained within the process (third pathway, Q3) for HDA process and evaluate the control performance quantitatively. Design Alternative 6 was chosen for our case studies. The performances of those designed processes were evaluated dynamically with two different control structures. The corrected overall effectiveness was used to relate with energy maintained within the process (Q3). Results showed that the designed process maintaining most of energy within the process gave poorer control performance and the lowest ratio of IAE/Q3 was referred to indicate optimum Q3 in this work. Having FEHEs could attenuate the disturbances because it behaved like buffer tanks. The corrected overall effectiveness was used to evaluate the design and control more accurately. When ratio control (CS2) was used to keep hydrogen/toluene constant, gave the same trend of the effect of energy maintained within the process on control performance and also gave the smoother operations in control loop relating to the those reactants.