Numerical Evaluation of Potential Catalyst Savings for Ventilation Air Methane Catalytic Combustion in Helical Coil Reactors with Selective Wall Coating

Abstract

During active mining operation of a gassy underground mine, large amounts of methane will be released from the mine ventilation shaft. To eliminate the harmful effects of this ventilation air methane and minimize the wastage of this potential energy resource, considerable effort has been devoted to converting this alternative fuel using catalytic combustion. This study numerically investigated the reaction performance of ventilation air methane (VAM) in helical coil tubes of various configurations utilizing a computational fluid dynamics (CFDs) approach. Several key factors affecting the catalytic combustion performance such as curvature, inlet Reynolds number, and cross-section aspect ratio were evaluated. Recalling the high cost of the catalyst used in this reaction—platinum—optimization of catalyst usage by implementing selective catalyst coating was conducted and investigated. For evaluation purposes, the reaction performance of the helical coil tube was compared to its straight counterpart. The results gave a firm confirmation of the superior performance of the helical coil tube compared to the straight one. In addition, it was found that the selective inner wall coating in the circular cross-section at a higher Reynolds number gave rise to the highest figure of merit (FoM), defined as the net energy produced per mg of catalyst platinum.

Numerical Investigation of Ventilation Air Methane Catalytic Combustion in Circular Straight and Helical Coil Channels with Twisted Tape Insert in Catalytic-Monolith Reactors

“…As revealed in our previous study [35], higher methane concentration is observed in straight channels, by approximately 60%, as compared to helical channels, suggesting lesser methane reaction. Moreover, it can be seen that incorporation of twisted tape insert does enhance the reaction performance, indicated by lower methane concentration for all reactors with a twisted tape insert.…”

“…These geometries are illustrated in Figure 9. The assumptions taken in developing this model are a premix inlet condition, the reaction occurs at the reactor wall, Newtonian fluid steady, and laminar flow [24,25,35]. Table 3 summarizes details geometric and operating parameters considered in this study.…”

“…where η pg denotes the efficiency of the power generation, ∆H c,cH4 is the methane combustion enthalpy, V is the volumetric flow rate, and ∆p is the pressure drop. Currently, VAM is utilized as fuel for steam power plant utilizing catalytic oxidation [35]. Typical steam power plant has efficiency within 38% to 45% [36].…”

Performance Evaluation of Liquid Mixing in a T-Junction Passive Micromixer with a Twisted Tape Insert

“…Meanwhile, streamline is defined as the line along which the stream function is constant and is tangent to the velocity field. By adopting a similar concept, the massline function is defined as where where M x and M y are the x- and y- components of the total (convection and conduction) mass flux, respectively.…”