Numerical Investigation of the Effect of CO2/H2O Composition in Oxidizer on Flow Field and Combustion Behavior of Oxy-pulverized Coal Combustion

Abstract

ABSTRACT Oxy-coal combustion is the most promising technology for the reduction of greenhouse gases from pulverized coal-fired power plants. Oxy-coal combustion employs recirculated flue gas mainly consisting of CO2 and water vapor as a diluent. Thus, the pulverized coal particles are surrounded and burned under steam rich atmosphere. The addition of H2O would have a significant impact on the combustion characteristics of oxy-coal combustion. The chemical and physical properties of steam are different than the CO2, replacement of CO2 with steam will alter heat capacity, gasification, and radiation properties considerably. The present article numerically compares ideal dry recycle oxy-coal combustion (0% H2O) with wet recycle oxy-coal (10-50% H2O) and oxy-steam combustion (H2O replaces whole CO2 from oxidant) in terms of flow field, temperature distribution, oxidizer distribution, radiative heat transfer, char consumption, and species concentration. Higher flame temperatures under enriched steam oxy-coal combustion cases were found due to lower volume heat capacity of H2O than CO2. Steam enrichment also enhanced char gasification reaction, which has affected temperature distribution and incident radiation profile inside the combustion chamber. Peak temperature obtained under oxy-steam case is around 10% higher than ideal dry recycle case (0% H2O) and 2-5% higher than the wet oxy-coal combustion cases having 50-10% H2O in the oxidizer.