Abstract

The design and plantwide control of an integrated plant, where the endothermic dehydrogenation of 1,4-butanediol leading to g-butyrolactone and the exothermic hydrogenation of furfural leading to furfural alcohol and 2-methyl furan are simultaneously performed in a single reactor, is presented. Analysis of the reactorseparation-recycle system shows that the reactions can be carried out using small hydrogen excess, in an adiabatic reactor, with reduced parameter sensitivity. The plant is flexible, allowing different production rates and a wide range of ratios between the furfural alcohol and 2-methyl furan products. The additional separation of g-butyrolactone from the reaction mixture is easy. The conclusions are supported by rigorous steady-state and dynamic simulations performed in Aspen-Plus and AspenDynamics.

The scope of this study is to emphasize the possibility and benefits of direct coupling of exothermic and endothermic reactions. Simultaneous production of aniline by exothermic nitrobenzene hydrogenation and endothermic dehydrogenation of methyl-cyclohexane to toluene is investigated. Instead of multitubular reactor, the reaction is carried out in an adiabatic reactor eliminating the requirement of complex setup of the hydrogenation reactor. Additionally, large amount of hydrogen needed to avoid reaction runaway is no longer needed. Nonlinear analysis of reactor-separation-recycle shows difficulty in controlling integrated plants where unreacted reactant is recycled.Details of the plant design, obtained by Aspen Plus simulation, are given. The new integrated system is feasible with the benefits of simple reactor and reduce hydrogen requirement. Economic analysis shows that the total annual cost of coupled system is reduced by 20%. The results obtained here are also applicable to other chemical processes of practical relevance.

Abstract-The scope of this research is to emphasize the importance, possibility and benefits about the coupling of exothermic and endothermic reactions. Coupling could be hydration with dehydration, oxidation with reduction and hydrogenation with dehydrogenation. Nonlinear analysis of reactor-separation-recycle shows difficulties in controlling integrated plants when un-reacted reactant is recycled. As a case study simultaneous hydrogenation of Nitrobenzene to Aniline with dehydrogenation of Methyl-cyclohexane to Toluene is investigated. Instead of multi-tubular reactor, the coupled reaction is carried out in a single tube adiabatic reactor, therefore the complex set-up for hydrogenation and large amount of hydrogen to avoid reaction run-away are no longer required. The steady state and dynamic state behaviour of an integrated plant is analysed using AspenPlus and AspenDynamics respectively. On implementing plantwide control structure the change in production rate is studied. The new system is simpler, stable and robust to feed disturbances. The results obtained here are also applicable to other chemical processes of practical relevance.

Recycle of un-converted reactants is a common practice in