Efficiency analysis of air-fuel and oxy-fuel combustion in a reheating furnace

This study numerically verified the enhanced efficiency of a steel reheating furnace when applying oxyfuel combustion instead of air-fuel combustion. Only radiation heat transfer was considered to analyze the periodically transient slab heating for an axial-fired furnace. The radiation field was computed without flow field calculation by dividing the entire furnace into ten subzones of which the temperatures were calculated by taking the overall heat balance for all the subzones. A total of five cases, 2 for air fuels and 3 for oxy-fuels, was analyzed to compare the slab heating behavior between air-fuel and oxy-fuel combustion. The modified 5-gas WSGGM was used for oxy-fuel combustion cases to fulfill the characteristics of CO2 and H2O enriched medium, while ordinary 4-gas WSGGM was used for air-fuel combustion cases. From the efficiency analysis for the total of five cases, it was predicted that oxy-fuel combustion gave an approximately 50% enhancement in efficiency compared to air-fuel combustion. (C) 2018 Elsevier Ltd. All rights reserved.