An Investigation On Heat Exchange Between Ceramic Beads And Biomass Chars In A V-shaped Down-flow Tube

The process of utilizing the down flow tube reactor to produce the bio-oil is to use high temperature ceramic beads to heat the biomass in the down-flow tube, and the biomass is vaporized and condensed into bio-oil in a few seconds. The investigation of the heat transfer contributes to the pyrolysis mechanism of biomass. But people has made a progress in the principle of heat transfer within the down flow tube. Since the biomass powders are changed into biomass chars very quickly as they enter the tube, it is more practical to study the heat transfer between ceramic beads and biomass chars. TheⅤ-shaped down flow tube apparatus was used to study the heat transfer mechanism of ceramic beads and biomass chars.The study included the following aspects:First, based on the down flow tube reactor used for the pyrolysis of biomass, aⅤ-shaped tube experimental apparatus was designed and the feeding rate of biomass char was measured. Second, he heat exchange between ceramic beads (50℃,60℃, and 70℃) and the tube system was studied;. Then, the heat exchange between ceramic beads and the biomass char with differing ceramic temperature (50℃,60℃, and 70℃) and char flow rate(32,40,53.3 g/min) was studied. Last, the ratio of input and output heat flow of granular was studied.By integrating the results, the conclusions have been drawn:The total heat output of ceramic beads increase with increase of the initial temperature of ceramic beads linearly, and the heat flow across the wall of the tube and the heat flow across the air increase with the increase of the initial temperature of heat carriers similarly at steady state. The final temperature of ceramic beads, the temperature of air,and temperature difference of the wall of the tube increase with the time exponentially, and the coefficient of heat exchange between ceramic beads and air increases with the increase of initial temperature of ceramic beads linearly. The heat conduction is the majority of the heat flux of biomass chars. The ratio of input and output heat flow of granular increases with the increase of the flow rate of granular.