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1、 1 气气-固射流流化床的燃烧模拟固射流流化床的燃烧模拟 Ruoyu Hong Chemical Engineering Department, Soochow University, Suzhou, 215006, China, E-mail: rhong Hongzhong Li Multiphase Reaction Lab., Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100080, China ABSTRACT Related referential studies of the te
2、mperature influence on hydrodynamics in gas-solid fluidized beds were reviewed. Two-dimensional (2-D) numerical modeling and simulation based on a two-fluid model for gas-solid fluidization was conducted. The modified IMF algorithm was employed to solve the governing equations expressed in the conse
3、rvative form in the 2-D Cartesian/Cylindrical coordinates. The solid-phase pressure was modeled via the local sound speed. The gas-phase turbulence was described using the - two-equation turbulence model. A 2-D fluidized bed with a cold vertical jet was simulated first to verify the numerical model
4、and the developed computer code. Then, a 2-D fluidized bed with a hot vertical jet was simulated. The jet penetration height was obtained numerically using the computer code based on the two-fluid model. The temperature effect on jet penetration height was investigated numerically. Keywords: Fluidiz
5、ation; Jet penetration; Two-fluid model. INTRODUCTION Bubbly gas-solid flows are widely encountered in many unit operations in the chemical, petroleum, agricultural, biochemical, and power-generation industries. It is essential to understand and predict gas-solid flows, and bubble formation mechanis
6、m and bubble motion behavior for better design and operation of a fluidized-bed reactor 1-20. Yates 20 made a comprehensive review of the temperature (and pressure) effects on the gas-solid fluidization. The minimum fluidization velocity, minimum bubbling conditions, gas bubble dynamics, terminal fa
7、ll velocity, entrainment and elutriation, and choking at different temperatures were reviewed. The temperature influence on jet penetration was also discussed briefly. Werther 19 reviewed the measurement techniques that can be used to study the temperature influence on fluidization behavior in fluid
8、ized beds. Experimental investigation Up to now, most of the related investigations were made experimentally. Marco et al. 17 carried the experiments on the fluidization of agglomerating particles at high temperature. The minimum fluidization velocity was estimated in the 700900 temperature range an
9、d was compared with the measured values. Llop et al. 16 presented experimental results for the expansion of a fluidized bed operating at high temperature (20600) using Geldart groups B and D particles. A semi-empirical model was developed to predict the bed expansion. Lettieri et al. 13 reported the
10、 experimental results of the temperature influence on the fluidization behavior with the temperature range from ambient conditions up to 650. The pressure drop versus gas velocity at high temperature, bed collapse time versus temperature were measured. Later, Lettieri et al. 14 reported their experi
11、mental observations on the homogeneous bed expansion of three FCC catalysts with increasing temperature from ambient up to 650 . The parameters of the RichardsonZaki equation were estimated and were compared with data reported in the literature. Formisani et al. 10 measured the temperature influence
12、 on the voidage both at rest and at incipient fluidization from ambient temperature to 800. Later, Formisani et al. 11 analyzed the influence of operating temperature on the dense phase properties of bubbling fluidized beds. The experimental temperature ranges from room level to 700 . High temperatu
13、re changes significantly the fluidization dynamics, the solid-phase voidage, dense phase velocity and bubble hold-up. Lin et al. 15 studied the temperature effect on minimum fluidization velocity (Umf) with different-sized particles as bed material. The experimental results revealed a minimum in Umf
14、 near 800, and the reason was interpreted. By measuring the onset velocity of slugging, slug rising velocity and slug frequency at different temperature, Choi et al. 2 studied the temperature effect on slug properties. A correlation between slug rising velocity and bed temperature was proposed. Guo
15、et al. 3 investigated the minimum fluidization velocity and flow dynamics at bed temperature up to 1000. Pressure fluctuation signals were analyzed by using power spectral density function, chaos, and wavelet analysis, and some interesting results were obtained. Mathematical modeling and simulation
16、Mathematical modeling and simulation are very useful to study the temperature effects on fluidization. Abba et al. 1 proposed a generalized fluidized-bed reactor model and extended it to cases with different temperatures (and pressures). The reactor performance and gas transfer between two phases can be predicted using the model. Kuwagi et al. 12 numerically investigated the high temperature fluidization of iron particles using the discrete element m
