Dynamic coupling of reactor and heat exchanger network considering catalyst deactivation

Abstract

Catalyst activity decreases with time. Identifying the variation of optimal system parameters along with the catalyst deactivation can alleviate the effects of catalyst deactivation and reduce energy consumption. A graphic method is established to integrate reactor and HEN, considering the catalyst deactivation. Based on the reaction kinetics, the catalyst deactivation kinetics, and the material and energy balances, the relations among running time, catalyst activity, reactor temperatures, and heat load are deduced for different reactors. Their influences on energy consumption are studied by pinch analysis and algebraic reasoning. The heat load variation of each heat exchanger in the path/loop is analyzed, and the load-shift laws are proposed. A Reactor-HEN coupling diagram is constructed to illustrate the variation of system parameters with running time and determine the catalyst's optimal replacement node. The proposed method can be applied to guide the operation of the practical process and evaluate the process through the catalyst replacement cycle in the design stage. An alkylation process of benzene to ethylbenzene is studied by the proposed method, and the optimal catalyst replacement node is identified to be 5.2 months.