| The opposed multi-burner(OMB)entrained-flow coal-water slurry(CWS)gasification technology is the key technology for the clean and efficient utilization of coal.The thermal atomization of CWS and the thermal behaviors of high-temperature particle groups in different spatial regions are closely related to the smooth operation and gasification efficiency of the gasifier.Therefore,it is urgent to study the thermal atomization characteristics of CWS and the thermal behavior of high-temperature particle groups deeply and systematically in the gasifier.Based on the bench-scale OMB entrained-flow CWS gasification thermal state experimental platform,an optimized visualization imaging system was used to conduct experimental research on the air-blast thermal atomization characteristics of coal-water slurry,the particle motion behaviors during coal-water slurry atomization,and the thermal behaviors of high-temperature particles below the burner plane in the gasifier.(1)In order to deeply grasp the air-blast thermal atomization characteristics of CWS in the gasifier,an optimized visualization imaging system was used to collect the image sequence of air-blast thermal atomization of CWS during the thermal operation of the gasifier.Based on the research results of cold-state atomization of CWS and morphological classification method,combined with the behavior characteristics of air-blast thermal atomization of CWS,the primary and secondary atomization modes of CWS in gasifier are discussed and classified in detail;The image processing method was used to obtain the atomization angle and breakup length during the air-blast thermal atomization process of CWS;Combined with the statistical analysis method,the particle size distribution in the statistical area during the air-blast thermal atomization of CWS is analyzed in detail;The influence of oxygen-CWS relative velocity on the air-blast thermal atomization characteristics of CWS is discussed.The results show that the primary atomization modes of CWS in the gasifier can be divided into two types:Rayleightype atomization mode and superpulsating atomization mode,which are highly dependent on the oxygen-CWS relative velocity;The atomization efficiency of the Rayleigh-type atomization mode is relatively low.The secondary atomization modes of CWS in the gasifier can be divided into deformation mode,tensile breakup atomization mode,shear breakup atomization mode and synergistic atomization mode;Compared with the cold-state experiment,the shear breakup atomization mode of CWS in the gasifier is always accompanied by deflagration phenomenon.Statistical analysis shows that with the increase of oxygen-CWS relative velocity,the distribution of small-sized CWS particles gradually increases,while the distribution of largesized CWS particles gradually decreases,and the atomization angle and breakup length gradually decrease.(2)The optimized radial visualization imaging system was used to study the characteristics of particle motion behaviors in the jet zone and the non-jet zone during the air-blast thermal atomization of CWS under three O/C operating conditions.Based on the image sequence of the particle motion behaviors during CWS atomization,the particle motion behavior patterns are discussed and divided in detail according to the particle motion behavior characteristics;The particle tracking algorithm and statistical analysis method were used to obtain the particle trajectory and particle size distribution during CWS atomization,particle velocity and angle were further analyzed;The particle trajectory tracking in the gasifier was preliminarily realized;The distribution characteristics of particle motion trajectories in the jet zone and the non-jet zone are analyzed.The particle trajectories during the air-blast thermal atomization of CWS show that the motions of CWS particles in jet zone are simple straight lines,but the motions of CWS particles in non-jet zone are irregular and unevenly distributed.The determinant factors of particle motion behaviors in jet zone and non-jet zone are different.Particle motion behaviors in the jet zone can be divided into three types:rotation,deformation,and fragmentation.Statistical analysis of the particle trajectories shows the proportion of particle trajectories in the non-jet zone is larger than that in the jet zone under three O/C operating conditions;With the increase of O/C ratio,the proportion of particle trajectories distributed in jet zone decreases.(3)In order to realize the in-depth study of the thermal behaviors of high-temperature particles in the region below the burner plane of the gasifier,the bench-scale opposed multiburner entrained-flow gasifier CWS gasification thermal state experimental platform was reformed.Two sets of imaging systems are used to capture the image sequences of the particle evolution process in the recirculation-flow zone and the impinging-flow zone below the burner plane of the gasifier,respectively;The image post-processing algorithms and statistical methods are used to analyze and discuss the particle velocity,particle size distribution and particle spatial distribution of the high-temperature particle group,as well as the volatile flame area and shape of the single particle.The particle trajectory distribution shows that most of the particles in the recirculation-flow zone and the impinging-flow zone move downward along the axial direction of the gasifier.Some of the particles in the recirculation-flow zone move obliquely upwards.Statistical analysis shows that the velocity of particles in the jet recirculation-flow zone and the impinging-flow zone is mostly distributed in the range of 0-2m/s.The average velocity of particles in the impinging-flow zone is slightly greater than that in the recirculation-flow zone.The particle size of different axial regions in the recirculation-flow zone and the impingingflow zone of the gasifier is mostly distributed in the range of 225-475μm,the SMD of particles and the particle concentration in the impinging-flow zone are smaller.The particle distribution in the recirculation-flow zone is more uniform.As the particles move downward along the axial direction of the gasifier,the occurrence frequency of particles in the impinging-flow zone increases.The volatile flame form of single coal particles presents two forms:diffusion flame and detached flame;The volatile flame area gradually increases with the increase of particle size. |
PDF Full Text Request