Pneumatic Classification And Pyrolysising Char With Wucaiwan Non-Caking Coal In Xinjiang

In order to widen the range of particles size for pyrolysising raw coal, the divid-ing pyrolysis technology, a new thermal conversion process for low-rank coal, was proposed by Institute of Process Engineering, Chinese Academy of Sciences. The process equipment consists of a bottom-fluidized transport column coupled with a moving bed. It was able to pyrolyze the widespread coal particles below 50mm owing to the difference of settling velocity for different particle size. The pneumatic classi-fication behavior of coal in a bottom-fluidized transport column and a bot-tom-fluidized transport column coupled with a moving bed were carried out. And py-rolysis conditions were investigated for large particles in 20~50mm.The pneumatic classification behavior of coal sample below 10mm was investi-gated in the bottom-fluidized transport column. The influential factors have superfi-cial gas velocity in the transport column, dimensionless velocity of particles, feed-ing position and rate, and internal baffle in the fluidized bottom. The classification was analyzed by measuring the mass partitions and size distributions of the elutriated particles, overflowed particles from the fluidized bed and the particles remaining in the bottom of the column. The Newton classification efficiency was employed to quantitatively evaluate the classification performance. Results clarified that there was an optimal dimensionless velocity for separating a fraction of particles below a given size. With the increase of targeted size, its optimal dimensionless velocity reduced. The Newton classification efficiency was being a maximum value for different tar-geted size and the optimal targeted size was 4mm for this setup. The coal feeding from the transport column at low feeding rate could facilitate the classification per-formance for a cut size in 1~4mm. The particle elutriation and the classification effi-ciency for a fraction below a given size both decreased when a vertical baffle was mounted in the inside of fluidized particles at the bottom.The pneumatic classification behavior of coal below 50mm was investigated in a bottom-fluidized transport column coupled with a moving bed. The tested influential parameters mainly included superficial gas velocity of moving bed. The classification was analyzed by measuring the mass partitions and size distributions of the elutriated particles, overflowed particles from the fluidized bed and the particles remaining in the bottom of the column. Results clarified that the pneumatic classification behavior was well for this setup when the superficial gas velocity of moving bed was 0.42 and 0.48m·s~-1. With the increase of height, pressure drop linearity increased in moving bed but steady in fluidized bed and transport column.The pyrolysis conditions for larger particles in 20~50mm was investigated in a fluidized bed reactor. The tested influential parameters included temperature, resi-dence time, oxygen concentration, particles size, and medium. The pyrolysis was analyzed by measuring the yield, fixed carbon, ash, volatile and specific reactivity of pyrolytic char. Results clarified that ash content of the raw coal is low, so the ash content of pyrolytic char made in experimental conditions were less than 14%. With the increase of temperature, residence time and oxygen concentration, core tempera-ture of the pyrolytic particle increased, yield and volatile decreased, fixed carbon and ash content increased, and specific reactivity of pyrolytic char decreased. With the increase of particles size, core temperature of the particle decreased, yield and volatile increased, fixed carbon and ash content decreased, and specific reactivity of pyrolytic char increased. With Al2O3 the medium, core temperature of the particle was lower but specific reactivity of pyrolytic char was higher.