Study On Lumpy Coal Particle Fracture Behavior During Pyrolysis And Gasification In Fixed Bed

Influenced by thermal stress or other factors,the lumpy coal particle in fixed bed gasification is easily fractured to produce a large amount of dust.The generation of dust not only increases the resistance of bed,but also causes problems such as pipeline wear and blockage,which affecting the long-term stable operation of gasification system.Therefore,it is of great significance to study the fracture behavior of coal particles during pyrolysis and gasification in fixed bed.In this study,Jincheng anthracite(JC),Shenhua bituminous(SH),Antaibao bituminous(ATB9#,ATB10#,ATB12#),Majialiang lignite(MJL)and Jincheng coke(JCC),Shenhua coke(SHC),Majialiang coke(MJLC)were chosen as the experiment samples,the particle fracture behaviors during fast pyrolysis and gasification were investigation with fixed bed reactor.First of all,the proximate analysis,ultimate analysis,carbon structure,specific surface area and pore size distribution of lumpy coal and coke were investigated by the coal proximate analyzer,ultimate analyzer,Raman spectrometer,surface area and porosity analyzer.Results showed that after pyrolysis,the order degree of JC,SH and ATB10#coke decreased,and the content of amorphous carbon increased;the order degree and the content of amorphous carbon of ATB9#coke both decreased;the order degree and the amorphous carbon content of ATB12#coke both increased;MJLC's amorphous carbon content increased.Compared with raw coal,the pore volume and specific surface of SHC decreased,the average pore diameter increased,while the pore volume and average pore diameter of MJLC increased,and the specific surface area decreased.Then based on the rapid pyrolysis experiments of 6 coals with different particle sizes,the fracture behaviors of different coal particles in the process of fast pyrolysis was studied.Results showed that the fracture and spalling of JC and SH coal particles occurred simultaneously during the fast pyrolysis at 900?.As for ATB9#,ATB10#,ATB12#and MJL coal particles,the fracture behavior was dominated by spalling at the size less than 15mm,while the fragmentation was dominant at the size larger than 15mm.The fragmentation index If increased with the increase of coal particle size da.Additionally,the fragmentation index was also affected by the ash content,carbon content and amorphous carbon content in the coal.The relationship between fragmentation index If and physical and chemical properties of coal was established.Finally,CO2 gasification experiment of different cokes at 1200? were conducted in fixed bed reactor to study the fracture behavior during gasification.Results showed that for the gasification semi-cokes of JCC,SHC and MJLC,with the increase of carbon conversion,the probability of fragmentation Rf increased and the particle size change rate Fd decreased,which indicated that the fragmentation and spalling behavior of cokes were enhanced,and there was a positive linear correlation between If and carbon conversion.At the same carbon conversion,the differences in the fragmentation index of coke were mainly influenced by ash content and volatile content of cokes.