狭缝型分布板流化床提高核桃壳颗粒的流化效果  被引量:10

Fluidization effect of walnut shell particles in fluidized bed with slotted gas distributor

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作  者:李占勇[1,2] 王少铁[1] 王娟[1] 张建国[1,2] 

机构地区:[1]天津科技大学机械工程学院,天津300222 [2]天津市轻工与食品工程机械装备集成设计与在线监控重点试验室,天津300222

出  处:《农业工程学报》2016年第9期225-232,F0003,共9页Transactions of the Chinese Society of Agricultural Engineering

基  金:天津市人才引进与科技合作计划国际科技合作项目(14RCGFGX00850);国家农业科技成果转化项目(2014GB2A100526)

摘  要:为了提高Geldart D类大颗粒物料在流化床中的流化效果,该文设计了一种结构简单的狭缝型气体分布板,进行了核桃壳颗粒(2~2.8 mm)的流态化试验,结果表明狭缝型分布板比传统多孔分布板提高床层膨胀率约5%,降低最小流化速率约8%。在欧拉-欧拉法的双流体模型和颗粒动力学理论基础上,建立流化床内气固两相流的数学模型并对模型进行验证,模拟值与试验值的误差在8%以内。利用数学模型对2种分布板流化床内大颗粒流化过程进行数值模拟,比较了2种分布板结构对流化床内床层压降、床层膨胀率、颗粒相体积分数及气固两相的流化速度的影响。模拟结果表明:狭缝型分布板的"V"型气流通道结构,使得气流易于集束向上运动,形成大气泡对床层造成扰动,从而增大床层压降波动幅度,提高床层膨胀率,并在流化床内形成4个小环流,促进气体相和颗粒相之间的混合,使得核桃壳颗粒流化均匀。该研究为大颗粒物料处理过程中流化床分布板的设计和选用提供参考。Gas distributor is a key component in fluidized beds. Various gas distributors for practical application have been successfully developed and studied in depth. Fluidization of coarse particles is still a challenge for good gas-solid contacting. In this study, a slotted gas distributor with simple structure was proposed for the fluidized bed processing coarse particles. The fluidization characteristics of the Geldart D type large particles(2-2.8 mm walnut shell) were investigated experimentally in a 285 mm × 190 mm × 700 mm fluidized bed with the slotted gas distributor whose opening rate was 5.6%. The experimental results were compared with the ones obtained from the traditional perforated distributor. It was found that the bed expansion ratio increased by about 5% and the minimum fluidization velocity reduced by about 8% when using the slotted gas distributor, indicating that the slotted gas distributor had better fluidization characteristics for the large-sized particles. To explain the better fluidization performance of the slotted gas distributor, a computational fluid dynamics(CFD) model was developed based on the Eulerian-Eulerian model, the particle kinetic theory, the standard k-ε turbulence model and the SIMPLE algorithm. The CFD model was used to simulate the behaviors of the gas particle flow in the fluidized bed of walnut shell particles with slotted gas distributor or traditional perforated distributor, and the results of experiment and simulation were agreed well. The simulations were conducted under such operation conditions: The physical two-dimensional model of the rectangular fluidized bed was 285 mm × 700 mm with slotted gas distributor or traditional perforated distributor in which the opening rate was 5.6%. Particles packed in the fluidized bed had the volume fraction of 0.6 and the height of the bed was 200 mm. The superficial gas velocity of inlet was selected as operation parameter, which ranged from 0.615 to 1.128 m/s. The simulation results were compared on the bed pressure

关 键 词:流态化 模型 设计 气体分布板 大颗粒 模拟 

分 类 号:TH69[机械工程—机械制造及自动化] TS04[轻工技术与工程]

 

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