SIMULATION AND OPTIMIZATION OF A SET OF CATALYTIC REACTORS USED FOR DEHYDROGENATION OF BUTENE INTO BUTADIENE

The simulation and optimization of a set of industrial fixed bed catalytic reactors is presented. The reactors are operating in deactivation-regeneration cycles. Dynamic mathematical models for the four stages of the process are included, i.e. dehydrogenation (deactivation by coking), steam purge, oxidative regeneration and evacuation. An iterative method was used to simulate an autothermal process, which is common in the industrial practice. To prevent the permanent loss of the catalyst activity by sintering, an upper limit of temperature has been imposed. The cycle time, temperature and composition of the feed during the regeneration stage are selected as optimization variables. Under autothermal conditions, the four stages of the cycle start with markedly non-uniform thermal profiles in the catalytic bed, which have considerable influence on the maximum temperature of the cycle. In this way, the production rate of butadiene has been substantially improved as both the maximum allowable temperature and the inert-catalyst ratio increase, The higher the oxygen molar fraction at the regeneration stage, the shorter is the optimal duration of the cycle.