RESIDENCE TIME DISTRIBUTIONS IN CONFINED SWIRLING FLAMES

The objective of this work was two-fold: to determine the residence ti me distribution (RTD) in swirling pulverised coal flames and to develo p a simple configuration of ideal chemical reactors, able to simulate the RTD. The work was performed using the solution of a mathematical m odel for a 2.2 MWth and a 12 MWth pulverised coal flame. Both flames a re type II, resulting in high NOx emissions. From the mathematical sol ution the RTD was simulated by tracing a number of fluid particles or inert particles. The simulations showed that about 30% (dependent of t he flame) of the fluid had a significantly lower residence time compar ed to the mean residence time. Based on RTD simulations and particle t rajectories a simple configuration of ideal chemical reactors, able to simulate the main how of the gas phase in the furnaces, was developed . The configuration consists of a plug Bow reactor representing the je t centre, a well-stirred reactors representing the external recirculat ion zone, and a combination of well-stirred reactors representing the down stream region of the furnaces. The parameters in the ideal chemic al reactor model were shown to be related to distinct zones in the fur naces. Finally, the ideal chemical reactor model was verified against experimental RTD data of a 2.5 MWth confined swirling natural gas flam e.