| Summary: | 碩士 === 逢甲大學 === 化學工程學所 === 96 === This thesis aims at the characterization of the dynamic behavior of the runaway phenomena and the investigation of the conversion control problem for fixed-bed reactors. To reach this goal, a new mathematical model which is able to take into consideration the interaction between the reaction system and the cooling system is presented. The dynamic simulation is done with the finite element software named COMSOL Multiphysics. With setting the partial differential equations with boundary conditions in the simulation model, one can characterize the runaway phenomena visually. It was found that the efficiency of the outer loop heat exchanger can affect the operation of the fixed-bed reactor. There is a great tendency to runaway as the efficiency is lowered. To circumvent the runaway phenomena of the hot spot temperature and to achieve the stable conversion control, a direct adaptive control strategy as well as a cascade control framework is suggested for the operation of a highly exothermic fixed-bed reactor. In both schemes, a bounded single neuron controller (SNC) associated with a simple yet stable parameter tuning algorithm is implemented in the control system. Extensive simulation results show that both the control schemes can handle well the exit conversion control system of the highly exothermic fixed reactor. However, the cascade control scheme outperforms the conventional SNC adaptive control scheme, especially when facing with unexpected process variations and unknown disturbances.
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