Study On Producing Combustible Gas From Biomass Pyrolysis With The Three-stage Reactor

In order to improve the useful life of catalysts for cracking tar in the process ofbiomass gasification and produce synthetic gas of high purity, a three-stage reactorwas employed in this paper and the using life of Ni/char and the effect of pyrolysisand cracking conditions on compositions of gasification gas were investigated. Thethree-stage reactor contains the three regions, including upper, middle and bottomstages. The bottom region was used for biomass pyrolysis. While the middle andupper stages were used to crack small molecular production of biomass pyrolysis.The effect of the cracking temperature in the upper and middle regions on the finalproducts was studied by using the three-stage reactor. At the same time,the components of the gas product were online analyzed with GC and themicroscopic structure of Ni/char before and after reusing was characterized by XRDand SEM.The results showed that the change in the weight of Ni/char depended on thetwo roles: the carbon deposited on the catalyst by the thermal cracking and carbonlost by oxidation in the cracking process of fir wood sawdust. But the carbondeposited on the Ni/char catalyst was more difficult to be oxidized than the charused as the carrier. The deposited carbon predominated in a form of carbonnanofibres. The Ni/char catalyst could be reused for more times in the three-stagereactor than in the two-stage one. As a result, the three-stage reactor wasrecommended to apply in the process of biomass gasification because it may reduceremarkably the cost of biomass gasification.Using Ni/char catalyst which used in thermal cracking of Chinese firsawdust can produce the synthetic gas of high purity. Rising temperaturewas beneficial to cracking tar and reforming gases. Reforming reactions about CH4and CO2on Ni/char catalyst become more intense in900oC, which resulted into anobvious improvement of the purity of synthesis gas.The increase in the cracking temperature of the upper stage where Ni/char waslocated was beneficial to cracking tar. When the cracking temperature of the upperstage reached900oC, the cracking temperature in the middle stage produced a littleeffect on the products of biomass pyrolysis. A synthesis gas of high purity can beproduced in the three-stage reactor, where the upper stage was900oC and the middle stage was700oC.