Experimental study of particle evolution characteristics in an opposed multi-burner gasifier

Abstract

Based on a bench-scale opposed multi-burner (OMB) gasifier and advanced visualization techniques, the particle evolution characteristics in the gasifier was studied. Particle images of different focusing planes were obtained by optical sectioning tomography (OST) method. Particle types and the principles of transformation between them, particle shape and particle size distribution (PSD), particle fragmentation characteristics were statistically analyzed after image processing. The results show that the burner plane contains all of the particle types, most of them are high temperature particle without wake (HTP), low temperature particle without wake (LTP), high temperature particle with high temperature wake (HTP-HTW) and low temperature particle with high temperature wake (LTP-HTW). Particle shapes in the burner plane are mainly round or round-like. The particle fragmentation process in the burner plane is violent and usually accompanied by sudden bursts that would result in the change of particle motion status, but the probability of which is relatively low (only about 7%). The space between 100mm and 300mm above the burner plane is the main regions of particle pyrolysis, particle types are mainly the low temperature particle with low temperature wake (LTP-LTW). Particles at 100mm above the burner plane have a higher fragmentation probability (10.53%) than that at 200mm (9.51%) and 300mm (8.73%) above the burner plane because of the more intense pyrolysis. In these regions, particle shapes become more irregular and the median particle diameter (D50) are slightly increased. There are plenty of LTP in the space between 400mm above the burner plane to the refractory dome. The probability of fragmentation around 400mm (16.84%), 500mm (11.35%) and 580mm (9.32%) above the burner plane are all higher than the probability around 100mm, 200mm and 300mm above the burner plane, which indicates that the particle fragmentation has more probability to take place in the char gasification stage than in the pyrolysis stage in the OMB gasifier. The closer to the refractory dome, the less the number of large particle is and the smaller the D50 is. About 85% of the particles near the refractory dome have a diameter less than 500μm.