共查询到15条相似文献,搜索用时 140 毫秒
1.
导向管喷流床的最小喷动速度的研究 总被引:1,自引:0,他引:1
在内径92mm的有机玻璃床内,使用四种没的物料,以空气作为喷动相流气体,综合考虑了床层的几何尺寸,以及气体和固体本身的物性,研究了导向管喷流床的最小喷动速度,得出了导向管喷流床的最小喷动速度的经验公式,以便对其设计和操作提供参考 相似文献
2.
1前言在普通喷动床的环形区底部额外引入一股辅助气体,由于喷动气体和辅助气体各自独立地改变,气固系统将出现下列几种体系或操作状态:①固定床;②充气喷动床;③喷流床;④带射流的流化床。长期以来对充气喷动床与喷流床的区别不是很清楚的[1~5]。张怀清等[6... 相似文献
3.
在内径120 mm的半圆柱型声场导向管喷动流化床中,以平均粒径290 nm的TiO_2颗粒为原料,高速空气射流为喷动气,考察了操作条件、声参数(频率和声压)对纳米颗粒在声场导向管喷流床中的流态化特性的影响。结果表明:声波可以有效抑制沟流,改善环隙流化质量,防止射流旁路,从而促使粉体稳定循环,加快循环速率;同时声波可以显著地降低纳米TiO_2颗粒的最小喷动速度,声波频率一定时,最小喷动速度随声压的增加而减小;声压一定时,最小喷动速度在声波频率为80 Hz时达到最小值,低于或者高于80 Hz,最小喷动速度都会增大。 相似文献
4.
狭缝式矩型喷动床中多粒度颗粒体系的最小喷动速度 总被引:6,自引:1,他引:5
在150 mm×50 mm×1100 mm的矩形喷动床中,采用宽度为2, 4, 6 mm 的3种狭缝式气体分布板,研究了单一粒度组成和多粒度组成玻璃珠的最小喷动速度. 实验证明,矩形喷动床的最小喷动速度与物料的粒度和组成有关. 给出了最小喷动速度与颗粒粒径和粒度组成的关联式,作出了多粒度组成颗粒体系最小喷动速度的相图. 相似文献
5.
6.
7.
8.
导向管喷动床是较为常见的一种喷动床改进床型,通过阻断喷动区与环隙区气固接触来提高颗粒循环的规律性与稳定性。本文采用计算颗粒流体力学(CPFD)方法对于直径150mm的柱锥式导向管喷动床进行了数值模拟研究,考察了导向管直径对于喷动床内颗粒流动特性的影响,从环隙区死区分布、颗粒速度分布、固体循环量等方面分析了具有不同直径导向管喷动床的运行状态。结果表明,加入导向管在减少床内死区的同时也降低了运行时的固体循环量,对于本次采用的喷动床结构尺寸与运行参数,只有在导向管直径为40~60mm时才能保证床内具有良好喷动状态,综合考虑各因素,选用直径50~55mm的导向管最为合适。对于具有类似结构与运行条件的柱锥喷动床,导向管直径可考虑选为无导向管运行时喷动区直径的1.2~1.375倍。 相似文献
9.
10.
11.
12.
A cylindrical gas-liquid-solid spouted bed, driven exclusively by gas flow, has been developed with a high potential for use in biochemical processes, such as a biological wastewater treatment. A plexiglass column with a 152 mm inner diameter was used in combination with a 53 mm inner diameter plexiglass draft tube. Three particle types were studied with densities ranging from 1044 kg/m3-1485 kg/m3 and average particle sizes ranging from 0.7-2.5 mm. Four flow regimes were observed when increasing the gas velocity, including fixed bed, semispouted bed, full spouted bed, and internal circulating fluidized bed. The transition gas velocities between those regimes were experimentally measured and termed as minimum spouting velocity, full spouting velocity, and minimum circulating velocity, respectively. A measurement of the downward particle flux in the annulus was used to identify the minimum spouting velocity, while the particle velocity and dense phase retraction in the annulus were monitored for the full spouting and minimum circulating velocities. All regime transition velocities increased with more dense particles and longer draft tubes. The minimum spouting velocity and full spouting velocity were not affected when varying the nozzle-tube gap, while the minimum circulating velocity increased with longer nozzle-tube gaps. Experiments without a draft tube were carried, though the spouting stability was significantly reduced without the draft tube. 相似文献
13.
《Drying Technology》2008,26(3):308-314
A study has been conducted on the performance of a draft tube conical spouted bed for drying fine particles. Batch operation has been performed with nonporous, porous, and open-sided draft tubes in order to ascertain the optimum configuration of this internal device. The nonporous draft tube requires the lowest minimum spouting velocity. Nevertheless, the solid circulation rate and the drying efficiency of the open-sided draft tube are superior to any other spouted bed configuration. Moreover, it allows for reducing the height of the fountain and, consequently, the height of the drying equipment. 相似文献
14.
A study has been conducted on the performance of a draft tube conical spouted bed for drying fine particles. Batch operation has been performed with nonporous, porous, and open-sided draft tubes in order to ascertain the optimum configuration of this internal device. The nonporous draft tube requires the lowest minimum spouting velocity. Nevertheless, the solid circulation rate and the drying efficiency of the open-sided draft tube are superior to any other spouted bed configuration. Moreover, it allows for reducing the height of the fountain and, consequently, the height of the drying equipment. 相似文献
15.
In order to properly design and scale up spouted beds, one needs to predict the minimum spouting velocity of specific systems having different bed dimensions, and properties of particle and spouting gas. Because of inherent complexity of predicting minimum spouting velocity, the prevailing approach has been to use empirical correlations, a number of which are available in the literature. Central jet distributors are commonly used in the experimental studies reported in the literature. Circular slit distributor is a new concept in which air is supplied to the bed of particles through a circular slit. This paper presents results of an experimental study on the hydrodynamics of central jet and circular slit distributors. In this paper a fully connected feed-forward neural network model was used to predict the minimum spouting velocity of central jet and circular slit spouted beds. A neural network model was also developed to predict minimum fluidization velocity. The actual experimental data obtained from published literature and from the experiments carried out in this study were used for training and validating the models. The minimum spouting and fluidization velocities predicted using the neural network models developed in this study show a better approximation to the actual experimental values than those obtained from correlations available in the open literature. The position of flow regime of circular slit spouted bed was also established relative to the flow regimes of central jet spouted bed and fluidized bed. 相似文献