Principle Of Particle Movement In Incline Down Flow Tube Reactor

Fast biomass pyrolysis is a popular international technology to process and utilize the biomass waste. The down flow tube reactor heated by ceramic balls solid heat carrier is a new type reactor for biomass pyrolysis and it has been patented in China. In a high heating rate, biomass becomes biomass-char (residual carbon) by fast pyrolysis, so the heat transfer occurs between the biomass-chars and ceramic balls in the reaction tube.In the down flow tube reactor, biomass pyrolysis is controlled not only by pyrolysis kinetics but also by the particle flow and heat transfer, so to study the law of biomass pyrolysis in the down flow tube reactor, it must be study the law of particle flow.The paper studied the principles of ceramic balls and biomass-char particles mixed flow behavior through experiments, theoretical analysis and numerical simulation in the 45°inclined down flow tube reactor, and revealed the movement mechanism of mixed granular. These studies would contribute to the design and increase system efficiency.In this paper, a 45°inclined down flow tube reactor cold experimental apparatus was designed, and the feeding system of the experimental devices were experimentally investigated, results show that the volume of feed and feeding time into a linear relationship, to satisfy the experimental needs. While establishing a camera automatic control system with mobile error of less than 1mm that makes the experiments more precise, convenient and fast.For the PIV system, the test results of a pipe with square cross-section are better than a circular pipe. So in this paper, a square, semicircle and a semi circular-square channels were tested and the results showed that a square or semi circular-square tubes could not take place of a circular tube to do experiments in the down flow tube reactor.It studies the concentration distribution of mixed particles by the "flapper method" in the inclined down flow tube reactor, and obtains the concentration distribution of ceramic ball and biomass-chars particles. It provides data to support the determination of concentration distribution n in the particle collision model.Ceramic balls collision rate is studied by PTV combined with the "particle size analysis," PIV combined with the "direction of velocity discrimination law" and theoretical model of random collisions of particles of Sommerfeld and Oesterle proposed in the down flow tube reactor, and amend the random particle collision model according to the experimental values. Collision can calculate the heat transfer f·Q by the collision in biomass pyrolysis.Using fluorescence technique measured the velocity of ceramic balls in the cross-section of 690mm and 1190mm away from entrance and received the speeds, it proves the feasibility of this method.Axial mean velocity distribution of biomass-char were divided into three parts in the entire pipeline, the beginning section of the fluid control, transition section of particle/fluid control and the stable section of the particle control; radial mean velocity changed little.In the fluid control section, the axial mean velocity distribution of biomass-char is similar to the jet gas, the maximum speed in the center of the tube; with the decline in the distance increases, the role of particles in the pipe more and more obvious, the maximum speed position down, move to the bottom of the pipe, and finally stabilized at around the bottom of the tube (y/d=0.2); In the pipe cross-section of the particle control section, from the top to the bottom of the tube is also divided into three parts:near the top tube (y/d=0.9～1) is the viscous sublayer of "Newtonian fluid", the middle part (y／d=0.1～0.9) and close to the bottom of the tube (y/d=0～0.1) is the "plug flow."Studies of the ceramic balls and biomass-char velocity distribution show that the straight pipe length 590mm range is more conductive to heat.Residence time of biomass-char granular is affected most by the amount of exhaust, followed by the ceramic particle size, and largely unaffected by the mixed mass ratio. Studies of particle residence time provide data to support the design of the total length of the pipe.According to the flow phenomena and motion laws of ceramic ball and biomass-char in inclined down flow tube reactor, established general mathematical model of Lagrange and Euler to describe the mixed particles flow laws of the down flow tube reactor. Using Fluent to simulate flow laws of ceramic ball and biomass-char in inclined down flow tube reactor.At the cross-section of 90mm away from entrance, the axial mean averaged velocity distribution of the experimental is closer to the simulated; at the cross-section of 1190mm away from entrance, due to the amount of saturation entrainment is overestimated, making large differences between the experimental and simulated axial mean velocity distribution.