Effects of Diluent Gases on Combustion of Coal Gasification Gas: Comparison Between N2 and CO2 Dilutions

Abstract

Combustion properties of coal gasification gas with CO2 dilution were investigated for a newly proposed IGCC power generation system with CO2 capture. In this system, the gasification gas was burned under high CO2 concentration atmosphere. In order to clarify the properties of the flames under such atmosphere, the laminar and turbulent burning velocities were investigated for outwardly propagating stoichiometric H2/O2/CO2 and H2/O2/N2 flames under the two conditions, 1: the same amount of diluent of CO2 or N2, 2: the constant flame temperature irrespective of diluents. Under the condition1 of the same amount of diluents, the unstretched laminar burning velocities, ul of CO2 diluted flames were smaller than those of N2 diluted flames. The ratios of the turbulent burning velocity at the flame radius 30mm, utn(30mm) to ul of the CO2 diluted flames were found to be larger than those of N2 diluted flames. Under the condition2 of the constant flame temperature, it was set to 1300, 1500, 1700, and 2135 degrees Celsius. At the flame temperatures except for 2135 degrees Celsius, ul of CO2 diluted flames were slightly smaller than those of N2 diluted flames. The ratios, utn(30mm) / ul of CO2 diluted flames were larger than those of N2 diluted flames. Increase in the turbulence Karlovitz number and decrease in the Markstein number by the CO2 dilution might cause the increase in utn(30mm) / ul of CO2 diluted flames in both conditions.