Computational particle fluid dynamics modeling and design of in-situ catalytic deNOx in an industrial CFB boiler

In-situ catalytic deNOx is a promising NOx control technology for circulating fluidized bed (CFB) boilers. In this application, matching the conditions between the catalyst and gaseous species is crucial. To under-stand this, a comprehensive computational particle fluid dynamics (CPFD) model was established; flow, combustion, and NOx emission characteristics in an industrial CFB boiler were elaborated; 20 catalysts with various sizes and densities were designed, and their degree of matching with the gaseous species was evaluated. The simulation results indicated that NOx was gradually produced at the bottom of the furnace and attained its maximum concentration at the elevation of secondary air; CO showed a high concentration in the bottom dense-phase zone; and the homogeneous NO-CO reaction is too weak to effectively reduce NOx. With catalyst application, the NO-CO reaction was evidently enhanced and the in-furnace NOx concentration decreased significantly. The 20 evaluated catalysts can be categorized as dipleg deposition, fluidization circulating, furnace suspension, and furnace deposition types. While the last three types of catalysts could match the spatial and temporal distribution of CO and NOx species well, the furnace suspension-type catalyst produced an optimal matching degree and maximum deNOx efficiency.(c) 2023 Elsevier Ltd. All rights reserved.