Steady and Transient Characteristics of Catalytic Flow Reverse Reactor Integrated with Central Heat Exchanger

Abstract

A Pd/Al 2 O 3 monolith catalyst was prepared by wet impregnation. Its excellent performance was demonstrated in the removal of lean methane. After 1000 h of operation, a higher catalytic activity can be sustained. On this basis, a pilot-scale catalytic flow reversal reactor (CFRR) coupled with a central heat exchanger was designed for catalytic removal of ventilation air methane. Experiments showed high methane destruction ratios were achieved at elevated reactor temperatures maintained by reverse flow operations. Transient and steady characteristics of the reactor were also studied experimentally and analyzed under various operating parameters involving methane concentration, cycle period, and heat transfer flux. The coupling of central heat exchanger caused the complex quasi-periodic states and the significant divergences on the reactor behaviors compared with the results in the literature. To further verify the robustness of the heat recovery method, the experimental unit was operated in a long-time course. The lean methane can be efficiently eliminated and utilized.

Reverse flow reactors as sustainable devices for performing exothermic reactions: Applications and engineering aspects

“…As shown in Table 3, different types of catalysts have been studied in RFR, being Pd the most popular [41][42][43][44][45][46][47][48], the main reason being that Pd provides higher activity [49]. Kinetic studies on Pd-based catalysts showed a 0.5-1.0-order dependence for lower alkanes, whereas a very weak or zero-order dependence was observed for oxygen [50][51][52][53].…”

“…Autothermal operation for the lower boundary of the range is only attainable by the more active precious-metal catalysts. The higher boundary of the range corresponds to studies where the heat extraction from the reactor was tested [42,[55][56][57][58]. This topic will be discussed in a separate section.…”

“…These particles usually are porous with a high internal surface area that allows high dispersion of the catalytic active phase. Structured beds, made of honeycomb monoliths, and ceramic foams, have been proposed and tested for reverse flow reactors [42][43][44]46,131]. Honeycomb monoliths are blocks formed by parallel channels that allow the gas flow with very low pressure drop.…”

“…a shell and tube or compact heat exchanger) [141,143]. Wang et al [42] demonstrated the technical feasibility of this heat exchange procedure using a spiral heat exchanger refrigerated by water. The amount of heat extracted was adjusted by the temperature difference between the hot gas and the coolant.…”

“…One of the advantages of hot gas withdrawal is that this way of heat extraction does not cause a direct decrease of temperature in the reactor, like those based on heat exchangers. Therefore, the dynamic behaviour of the reverse flow reactor is disturbed to a least extent (for the same amount of energy extracted) [42,56,141].…”