Flow Characteristics of Dense Phase Pneumatic Conveying of Pulverized Coal through the Bend
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摘要: 在自主搭建的工业级管径（内径50 mm）气力输送实验平台上，开展了密相气力输送实验，对气固两相通过弯管的流动特性进行了研究。借助电容层析成像技术分析弯管出口截面流型特征，发现煤粉流经弯管时管道截面浓度存在明显径向分布，外壁浓度相对较高。采用附加压降法，并结合对实验数据的回归分析，建立了精度±10%以内弯管压降模型。并基于微元分析和弯管压降分布的基本规律，获得了煤粉浓度沿弯管流动方向的分布特征。Abstract: Experiments on dense phase pneumatic conveying of pulverized coal were carried out in the self-built pneumatic conveying facility with a Industrial pipe diameter of 50 mm. The gas-solid two-phase flow characteristics through the bend were studied. Firstly, With the help of Enick and Klinzing model, the entrance length of gas-solid two-phase flow in a bend outlet is calculated. It is found that electrical capacitance tomography (ECT) is in the underdeveloped area, where the flow is affected by the bend. The flow patterns of the outlet section of the bend were analyzed in the means of ECT, and it was found that the flow pattern changed from the packed bed flow to the unstable/stable plug flow with the increase of the superficial gas velocity. Due to the influence of inertial force and centrifugal force, there was an obvious radial distribution in the concentration of the pipe section when the pulverized coal flowed through the bend, while the coal concentration on lateral wall surface was relatively high. Next, regression analysis of experimental data is carried out by using pressure drop model and dimensional analysis method, a pressure drop model of pulverized coal dense phase pneumatic conveying bend was established by providing errors most smaller than ±10%. Finally, based on micro element analysis and pressure drop distribution along the bend, the distribution characteristics of pulverized coal concentration along the bend were obtained. The research in this work can provide important guiding significance in reducing the wear of bend.
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Key words:
- dense phase pneumatic conveying /
- bend /
- flow pattern /
- concentration /
- pressure drop
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图 1 实验装置图
1-空气压缩机，2,4-缓冲罐，3-冷冻干燥机；5-气体分配器；6-气体流量计；7-除尘器；8-发料罐；9-压差变送器；10-固体质量流量计；11-电容层析成像系统；12-接料罐；13-称重传感器；14-压力传感器
Figure 1. Diagram of experimental equipment
图 2 表观气速与固气比关系图
Figure 2. Relationship between superficial gas velocity and the ratio of solid and gas
图 3 ECT处流型以及平均截面浓度分布图
Figure 3. Flow pattern and distribution profile of average cross section at ECT
图 4 弯管压降实验值与计算值比较
Figure 4. Comparison of experimental value and calculated value of pressure drop of bend
图 5 弯管结构示意图及压力的沿程变化图
Figure 5. Schematic diagram of bend pipe structure and trend of pressure drop along the distance
图 6 压力、浓度沿管道变化趋势图
Figure 6. trend diagram of pressure and concentration along the pipeline
表 1 煤粉的物料性质
Table 1. Material properties of pulverized coal
dv/μm ds/μm d10/μm d50/μm d90/μm ρp/(kg·m-3) MC/% 40.30 4.83 2.07 17.42 115.30 1627.50 1.15 
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表 2 实验工况表
Table 2. Experimental condition
Case Q2/(m3·h−1) Q3/(m3·h−1) Ws/(kg·h−1) PT/kPa Ug/(m·s−1) ∆P1/kPa $ \frac{{\Delta {P_2}}}{{\rm{L}}}$ /(kPa·m−1)
P/kPa μ/(kg·kg−1) 1 15.75 0.00 4659.85 68.22 1.09 10.21 5.64 39.79 328.23 2 16.34 5.73 4161.88 62.15 1.76 8.61 3.90 49.65 170.14 3 16.07 16.41 3980.70 91.63 2.20 7.30 2.94 79.34 110.92
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表 3 Le计算表
Table 3. Calculation of Le
Case Ug/(m·s−1) ρg/(kg·m−3) Re Le/mm 1 1.09 1.80 5480.45 2506.37 2 1.76 1.93 9488.27 1731.07 3 2.20 2.31 14195.53 1115.49
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