Bench-Scale Testing on 02/C02 Combustion for C02 Recovery

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8 and/ or duct fabricated by normal materials. Accordingly. we may refer this design cri terion, if we do not use high-grade materials such as stainless steel on ducting from an economical point of view. Consequently. we decided an allowable upper limit of 02 conc. in the 02/C02 mixture to be 35% or so, roughly esitimating the difference of the reactivity between 02/C02 and 02/N2 mixtures. For the limitation of 02 conc. in the secondary stream. an additional pure 02 injection to flame region .was expected to be a practical measure enhancing flame stability with improving char burnout efficiency. Effect of 02 injection in tertiary stream Increasing the flow rate of the tertiary stream -pure 02 injection to burner throat in separate from secondary stream- has a simi lar effect as increasing 02 conc. in the secondary stream, on elevating f lame temperature, when 02 conc. in the secondary stream kept constant. Fig.9 shows the adiabatic flame temperature against the flow rate of the tertiary stream (pure 02) on this experimental research. The adiabatic flame temperature will be affected little by the preheat temperature of tertiary stream. If more than 70m3N/h of the tertiary stream was fed to a burner, the flame temperature on 02/C02 combustion will be beyond that on air combustion. Actually as shown in Fig.10. the increase of the tertiary stream elevated flame temperature profile along burner axis and eventually unburnt carbon also decreased. This data were obtained by using a multi-hole type 02 injection nozzle. Fig.ll also shows the comparison of both 02 injection nozzles on the combustion performance for NOx vs unburnt carbon. It was noted that the multi-hole type 02 injection nozzle gave better performance. Pure 02 may be distributed , more homogeneously and mixed with pulverized coal dust. at the exit of the coal nozzle, using a multi-hole type