Combustion efficiency of oil shale and lignite mixtures in atmospheric fluidized combustion bed

Abstract

Experiments in combustion of oil shale and lignite mixtures of various ratios were carried out in an atmospheric fluidized bed with the inside diameter of 15 cm to investigate the influences of oil shale to lignite ratio and air to fuel ration on combustion efficiency, using Mae Sot oil shale possessing 1,598 cal/gm heating value and average particle sizes of 1.44 and 2.67 mm, and Mae Moh lignite of 2,970 cal/gm and 2.61 mm. Furthermore, the effects of the above two ratios on desulfurization efficiency and sulfur dioxide, carbon monoxide and nitric oxide emissions were also studied. In the experiments, bed height was kept at 30 cm and air to fuel mass ratios were between about 7.5 to 12.5. Conclusions can be drawn, from the experiments, that atmospheric fluidized bed combustion using oil shale and lignite mixture as fuel, with combustion and desulfurization efficiencies above 95% is possible. Combustion and desulfurization efficiencies increase with oil shale to lignite ratio until the ratio is about 3. Moreover, combustion efficiency decreases as air to fuel ratio and oil shale size increase while desulfurization efficiency is effected in the reverse direction.