Gas flow in a pressurized fluidized-bed combustor

The residence time distribution (RTD) of gas in a pressurized fluidized-bed combustor and in the freeboard have been measured with 41Ar as radioactive tracer. The procedure of normalisation of measured impulse responses could be used to evaluate the RTD in the whole combustor. A deconvolution method using Laguerre functions was successfully used for the analysis of RTD in the freeboard. In the whole combustor and in the freeboard region a tendency to decreasing mean gas residence time with increasing pressure has been found. A simple method for estimation of fast bubble flow is presented. The bubble flow rate and rise velocity were estimated from the various RTDs of gas measured for the same operating conditions. The expected tendency for bubble flow to decrease with pressure has been confirmed. The results agree with values for bubble rise velocity measured independently with an impedance probe.