重质大颗粒在非均匀布风流化床内停留时间

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清华大学辅仁网/2017-07-07

重质大颗粒在非均匀布风流化床内停留时间

蔡容容,张衍国(

),蒙晨玮,李清海,蒙爱红

Residence time of a large heavy object in a fluidized bed with an uneven air distribution

Rongrong CAI,Yanguo ZHANG(

),Chenwei MENG,Qinghai LI,Aihong MENG

Department of Thermal Engineering, Tsinghua University, Beijing 100084, China

摘要:

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文章导读

摘要用电容层析成像(ECT)示踪法研究了单个球形重质大颗粒在流化床密相区的停留时间分布特性及随流化风速变化时运动状态的演化过程。通过对实验结果的概率统计分析和对大颗粒受力特征的分析,揭示了大颗粒在床内运动行为的统计规律性和随机性。研究发现: 大颗粒在床内的平均停留时间随流化风速的降低先缓慢增大,当流化风速低于某一临界值后,停留时间急剧增大,并过渡到以一定的概率到达布风板低侧,直至最终滞留在床中间; 大颗粒密度越大,演变过程对应的流化风速越大。由于周围两相流压力场、速度场随时间的随机脉动性,大颗粒在床内的停留时间分布很宽。

关键词 ：流化床,重质大颗粒,停留时间,非均匀布风,概率分布

Abstract：The influence of the superficial gas velocity on the residence time distributions (RTDs) of large spherical objects of different densities in the dense phase of a fluidized bed was studied using electrical capacitance tomography (ECT) tracing technique. The regularity and randomness of the motion of a large object were decided by a probabilistic statistical analysis to investigate the mechanical characteristics of an object in a bed. The results show that decreasing the fluidization velocity first slowly reduces the residence time. When the gas velocity is lower than a critical value, the residence time sharply increases until the object does not reach the low side of the air distributor. Heavier objects have higher critical gas velocities. The RTD curves are very broad due to the stochastic pressure and velocity pulsations in the fluidization bed.

Key words：fluidized bed large heavy object residence time uneven air distribution probability distribution

收稿日期: 2013-04-28 出版日期: 2015-03-17

基金资助:国家“九七三”重点基础研究项目(2011CB201502)

引用本文:

蔡容容,张衍国,蒙晨玮,李清海,蒙爱红. 重质大颗粒在非均匀布风流化床内停留时间[J]. 清华大学学报（自然科学版）, 2014, 54(6): 775-780.
Rongrong CAI,Yanguo ZHANG,Chenwei MENG,Qinghai LI,Aihong MENG. Residence time of a large heavy object in a fluidized bed with an uneven air distribution. Journal of Tsinghua University(Science and Technology), 2014, 54(6): 775-780.

链接本文:

http://jst.tsinghuajournals.com/CN/或 http://jst.tsinghuajournals.com/CN/Y2014/V54/I6/775

图表:

实验系统

倾斜布风板和定向风帽

ρ_o/(g·cm^-3)	D/cm	外壳	内填充物
0.90	3/4/5	硝化纤维塑料,PE	纯净水、无水乙醇
1.63	3/4/5		001×7聚甲基丙烯酸甲酯颗粒、一氧化铅粉末
3.00	3/4/5		一氧化铅粉末

球体大颗粒的性质

大颗粒运动图谱

流化风速对平均停留时间的影响 (ρ_o/ρ_b =1.9, D/L=0.143)

流化风速对平均停留时间的影响 (ρ_o/ρ_b =3.5, D/L=0.143)

流化风速对平均停留时间的影响 (ρ_o/ρ_b =6.4, D/L=0.143)

停留时间分布(D/L=0.143)

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