Abstract
Thermal design and optimization for reverse water gas shift (RWGS) reactors is particularly important to fuel synthesis in naval or commercial scenarios. The RWGS reactor with irreversibilities of heat transfer, chemical reaction and viscous flow is studied based on finite time thermodynamics or entropy generation minimization theory in this paper. The total entropy generation rate (EGR) in the RWGS reactor with different boundary conditions is minimized subject to specific feed compositions and chemical conversion using optimal control theory, and the optimal configurations obtained are compared with three reference reactors with linear, constant reservoir temperature and constant heat flux operations, which are commonly used in engineering. The results show that a drastic EGR reduction of up to 23% can be achieved by optimizing the reservoir temperature profile, the inlet temperature of feed gas and the reactor length simultaneously, compared to that of the reference reactor with the linear reservoir temperature. These optimization efforts are mainly achieved by reducing the irreversibility of heat transfer. Optimal paths have subsections of relatively constant thermal force, chemical force and local EGR. A conceptual optimal design of sandwich structure for the compact modular reactor is proposed, without elaborate control tools or excessive interstage equipment. The results can provide guidelines for designing industrial RWGS reactors in naval or commercial scenarios.
Highlights
The footsteps of human industrialization are always accompanied by massive levels of energy consumption
By solving the optimal control problem with different boundary conditions, the optimal configurations for the minimum total entropy generation rate (EGR) involving heat transfer, chemical reaction and viscous flow are found by optimizing the heat reservoir temperature and the reactor length, subjected to given feed compositions and a fixed chemical conversion at the outlet of the reactor
The results show that there is a great potential for the EGR reduction in the reverse water gas shift (RWGS) reactor
Summary
The footsteps of human industrialization are always accompanied by massive levels of energy consumption. C and a more generalized one xA yB zC considering orders of the chemical reactions with the maximum yield of B [37,38] and the minimum entropy generation rate (EGR) [39] as objective functions, respectively. The chemical engineering processes, including ideal reactors, and the units both upstream and downstream, are optimized with the minimum EGR as the objective function. The optimal design of the industrial process units is driven by some objective functions related to cost, products and energy [55,56]. Optimization results based on EGM are independent of the current socio-political environment and markets, and the improvements for the chemical process units such as chemical reactors with the minimum EGR as objective function are related to the reduction of energy quality loss. The engineering application of the optimal reactor design will be discussed based on the optimization results
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