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Modeling of solids segregation in circulating fluidized bed boilers |
Xuan YAO1, Tao WANG1, Jia ZHAO2, Hairui YANG1( ), Hai ZHANG1 |
| 1. Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China; 2. Department of Mathematics and Applied Science, School of Applied Science, University of Science and Technology Beijing, Beijing 100083, China |
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Abstract Segregation always occurs in a circulating fluidized bed (CFB) because of the wide distribution of particle size and density of the bed material. Terminal velocity has a significant influence on solids segregation; thus, it is convenient to describe the segregation tendency using single particle terminal velocity ut. This paper proposes a segregation model in CFB boilers based on the Cell Model. In each cell along the riser, varied-sized particles have different tendencies toward segregation; finer particles are carried out more easily, while coarser ones tend to sink into the cell. It is assumed that the average terminal velocity ut ˉ, corresponding to the mean particle size in the cell, has a segregation index of x = 1.0 as the reference point. The segregation index of particles with higher terminal velocity is lower than 1.0, while that for finer particles is larger than 1.0. The empirical formulae of segregation parameters, namely x0 and k1, are derived by optimizing experimental data in published literature. The test result of ash size distribution in a 220 t/h CFB boiler validates the reasonableness of the model.
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| Keywords
segregation
model
terminal velocity
circulating fluidized bed (CFB)
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Corresponding Author(s):
YANG Hairui,Email:yhr@mail.tsinghua.edu.cn
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Issue Date: 05 March 2011
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