Selective Catalytic Reduction for NO Removal: Comparison of Transfer and Reaction Performances among Monolith Catalysts

One of the available technologies that can effectively control the emission of NOx is the selective catalytic reduction (SCR) of NOx with ammonia (NH3). Monolith catalysts are widely used in this technology due to their unique advantages that they offer, like low pressure drop, high external geometric surface area, and resistance to deposition of carbon, dust, and metals from combustion process. But the configuration of monolith catalysts has prominent influence on transfer and reaction performances of SCR for NO removal. This work tries to provide an easy-to-read and comprehensive comparison of momentum transfer, heat transfer, mass transfer, and reaction performance between two types of monolith catalysts with five kinds of channel shapes for SCR for NO removal, and to address the issues specific to SCR applications as to (i) whether or not monolith catalysts can improve the transfer and reaction performances compared to traditional pellet packed-bed reactors; (ii) which type of monolith catalysts and (iii) which kind of channel shapes for each type are optimum from the viewpoint of chemical reaction engineering. It was found that monolith catalysts have a much lower pressure drop and higher effectiveness factor than traditional pellet packed-bed reactors, and a coating catalyst seems more suitable than an extruded catalyst for SCR for NO removal. Although a round channel brings the best heat and mass transfer, a triangle-shaped channel of coating catalyst possesses the highest NOx conversion due to the chemical reaction being the controlling step.