Experimental study on gas uniformity at the inlets of six cyclones in a CFB with multi-tracer gas method

To investigate the non-uniform distribution of different gases passing through the parallel cyclones, experiments were conducted on a circulating fluidized bed (CFB) equipped with six asymmetrical cyclones. A multi-tracer gas method was used, with CO, O₂, and CO₂ chosen to represent gases with different properties in the flue gas at the inlets of the cyclones. The uniformity of multi-gas distribution was evaluated by measuring the concentration deviations of each tracer gas passing through individual cyclones. The results indicate that the concentrations of multi-tracer gases are higher in the middle cyclone among the three, which are located on the tracer gas injection side during the test of single-side secondary air (SA) tracing. The maximum concentration deviation of tracer gases is for CO₂, while the minimum is for CO. At the three cyclone inlets on the opposite side, the tracer gas with higher density exhibits a more uniform distribution, and the gas uniformity decreases as the density decreases. The effects of superficial velocity, SA ratio, bed inventory, and tracer gas injection region on the uniformity of gas distribution were studied. The results show that superficial velocity and SA ratio primarily affect the uniformity of higher density gases, while bed inventory has a greater influence on lower density gases. The gas distributions are most non-uniform, especially for CO₂, when the tracer gas injection region is near the rear wall closer to the induced draft fan during the test of regional SA tracing.