2 results listed
Physical properties of coal particles have influence on combustion characteristics. Particle size is one of these physical properties that causes dramatic effect on the surface reaction rate and hence on the residence time required for complete combustion. In the present paper, the particle size influence on coal combustion is investigated for Tunçbilek lignite under two selected size cuts: 106-125 µm and 180-212 µm. Particle size effect on coal combustion is studied both experimentally and theoretically. Experiments are conducted by using a drop tube furnace (DTF). Computational Fluid Dynamics (CFD) analysis is carried out by using Fluent software. Moreover, two analytic methods namely D2 law and two- film model is used to model char combustion. The experimental tests are performed in a drop tube furnace at high temperature (1000 ºC) and high heating rate (~104 ºC s-1). CFD simulations using Fluent are performed using the Coupled algorithm, both discrete and continuum phases are solved in a 3D steady-state formulation. On the other hand, the analytical methods solve the discrete phase to obtain burnout; diffusion limited model is used in D2 calculations, while two-film model relates the surface reaction kinetics with the diffusion of the gaseous species around the particle. The burnout values from experimental and CFD analysis are similar (100 and 94%, respectively) for small particles, while for large particles values are 85 and 97%, respectively. Results obtained from analytical methods agreed on the complete combustion (100% burnout) for both particle size ranges.
International Combustion Symposium
INCOS2018
Feyza Kazanc
Burak Ozer
Duarte Magalhaes
This work investigated the particulate matter (PM) formation during the combustion of a Turkish lignite. The fuel studied was Tunçbilek lignite in a size cut of 106-125 µm. Tests were performed in a drop tube furnace at high temperature (1000 ºC), high heating rate (~104 ºC s-1), and short residence time (~3 s). The experimental setup consists of a drop tube furnace, a feeding system, and a collection unit. A syringe pump feeding system was calibrated to ensure a constant fuel feeding rate. Fuel was fed into the furnace at a low mass rate of 10 g h-1 by means of the syringe pump. Ash particles were collected at the outlet of the drop tube furnace using a three-stage stack impactor and a vacuum pump. Particle sizes were categorized into PM2.5, PM2.5-10, and above PM10 (PM>10). PM from each collection stage was analysed in terms of burnout, morphology, size distribution, and concentration. Burnout was approximately constant and always above 96% for all collected particle sizes. Optical microscopy revealed that PM was quasi-spherical for PM2.5-10 and PM>10, whereas PM2.5 was perfectly spherical. Concentrations of PM2.5 and PM2.5-10 were similar, although the contribution of PM2.5 to PM10 was higher. Values of PM2.5 and PM10 were within those found in literature.
International Combustion Symposium
INCOS2018
Feyza Kazanc
Duarte Magalhaes