Development of an oxycoal swirl burner operating at low O2 concentrations

This work is to clarify the underlying mechanisms of burning pulverised coal in a mixture of CO2/O2CO2/O2. The performance of two different burner designs, single central orifice-type (SCO) and single annular orifice-type (SAO), under oxycoal conditions was examined in a down-fired test facility. Based on detailed in-flame measurements, combined with numerical simulations, the main parameters influencing the stability of a CO2/O2CO2/O2 pulverised coal swirl flame were investigated. The oxycoal flame was stabilised at the burner quarl by: increasing the O2 concentration above 34 vol% without changes to the air-firing burner design and by modifications of the burner geometry thus changing its aerodynamics. The modification of the burner allowed a decrease of the O2 concentrations to 23 vol% for SCO burner and to less than 21 vol% for SAO burner. Comprehensive measurement data for axial and tangential velocity, flue gas temperature and oxygen concentration for stable oxy-firing at 21 vol% O2 is presented. The results reported can be used as a guideline for a development of an industrial swirl burner capable of stable operation in both regimes, namely: air and oxycoal.