| Based on a bench-scale Opposed Multi-Burner(OMB) gasifier, thermal behaviour of coal-water slurry(CWS) gasification was studied. Particle size and composition were characterized by Malvern laser particle size analyzer, infrared coal analyzer and SEM/EDS. Then particle distribution and formation in gasifier was analysed at different position and experimental condition. In addition, the feasibility of hot oxygen technology applied for gasification was preliminary researched through its flame image and properties of particles.For OMB CWS gasification, the clear flame is restricted in the gasifier center. With the increase of mole ratio of oxygen to carbon, the brightness of impinging flame region and whole gasifer increase. Temperature difference is significant at different position downwards the axis of gasifier. The temperature at impinging flame region is much higher than plug flow region, while the temperatue above the burner plane is slightly higher than below. The total content of CO and H2maximize at the oxygen to carbon ratio of1.0.The size of particles in gasifier is generally higer than parent coal because of the poor burner atomization. Char fragment and carbon reaction result in that the fixed carbon content and average size decrease downwards the axis of gasifier while mineral fragment have little contribution on particle size decrease. The fragment during impinging flame region to plug flow region is more intense than plug flow region. The combustion and gasification take place in both impinging flame region and plug flow region, and the mass ratio of burned fixed carbon in the two region is about2:1. Compared with two burners, gasification with four burners lead to clearer impinging flame region and higher fixed carbon burnout. Based on fixed mole ratio of oxygen to carbon and fixed burner outlet speed of oxygen, with the increase of CWS flow rate, the area of impinging flame region increased as well as the fixed carbon burnout of particles.In open space, only partial CWS can be ignited. Compared with open space, closed space in gasifier reduce the influence of temperature and concentration decay of hot oxygen on the combustion of diesel and CWS. As a result, change in oxygen flow rate have more signigificant influence on flame. With the increase of oxygen flow rate, hot oxygen flame length of diesel decreases while length of CWS increases. Compared with the ambient oxygen, the flame of hot oxygen is more stable, and fixed carbon content and average size of particles are smaller in the same distance from burner during hot oxygen gasification. The differene in fixed carbon content and average size between hot oxygen and ambient oxygen reduces with the increased distance from burner. |
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