Quantitative comparison of reactive distillation with conventional multiunit reactor/column/recycle systems for different chemical equilibrium constants

Recent advances in technologies based on process intensification offer different design alternatives for chemical processes including reaction and separation units. An excellent example of process intensification is reactive distillation, which combines reaction and separation units in one piece of equipment. This paper studies the steady-state economic optimum design of a chemical process with a generic exothermic reversible reaction A + B <----> C + D for two different process flowsheets: a conventional multiunit reactor/separator/recycle structure and a reactive distillation column. Each system is optimized in terms of the total annual cost for a wide range of chemical equilibrium constants, K-EQ. In the conventional system, the design optimization variables include the reactor temperature, reactor size, and recycle flow rate. In the reactive distillation system, the design optimization variables include the pressure, number of reactive trays, and number of total trays. The two systems are designed for identical feeds and identical products. Results show that reactive distillation is significantly less expensive (by a factor of up to 3) than the conventional process for all values of the chemical equilibrium constant.