煤粉气力输送管道压降的工艺模拟

Simulation and analysis for pressure drop of pneumatic conveying of pulverized coal

  • 摘要: 管道压降是煤粉气力输送系统最重要的参数之一。对管道压降的研究目前主要采用试验和数值模拟,将工艺模拟应用在气力输送研究中是一种既能快速模拟管道压降特性又能满足工程应用精度的研究方法。采用流程模拟软件Aspen Plus,首先通过7组试验数据对水平直管气力输送模型的参数进行校准,并对与校准工况相似和非相似工况进行模拟计算,比较分析模型的模拟精度;然后应用校准模型,分析煤粉输送量、输送压力对管道压降的影响规律;最后对Shell煤气化中内径54 mm的煤粉气力输送管线进行压降计算,绘制煤粉输送管线压力分布图,并对各管件的压降占比进行对比分析。结果表明:Aspen Plus的模拟计算可以获取输送相图中的最小压降及经济气速,水平直管压降的模拟值与试验值误差小于35%,当模拟条件与校准工况相近时,压降计算误差减小至20%以内;当气速一定时,随着煤粉输送量的增大压降逐渐增大。当煤粉输送量一定时,随着表观气速的增大,水平直管的总压降逐渐降低,压降曲线随气速增大逐渐变得平缓;输送压力对压降的影响规律在不同气速条件下有所不同。在低气速区,水平直管压降随输送压力增大而增大,而在高气速区则输送压力越大,水平直管压降越小;Shell气化的煤粉输送管线中,压降最大为垂直段管线,高达51.7%,水平管压降为27.6%,弯头1和弯头2占据总压降的8%和13%。输送管道内表观气速和经济速度沿煤粉流动方向缓慢增大,其均值分别为8.8和7.1 m/s,超过1.5 m/s的速度差使得煤粉输送过程既保持了足够大的颗粒浓度又避免发生颗粒沉降堵塞管道的问题。

     

    Abstract: Pipe pressure drop is one of the most important parameters of pulverized coal pneumatic conveying system.At present, the research on pipeline pressure drop mainly adopts experiment and numerical simulation.The application of process simulation in the study of pneumatic conveying is a research method which not only can quickly simulate the pressure drop characteristics of pipeline, but also meet the engineering application accuracy.This paper uses Aspen Plus, a process simulation software, to conduct the simulation.Firstly, the parameters of the horizontal straight pipe pneumatic conveying model are calibrated through seven groups of experimental data, and the simulations of similar and non-similar conditions with the calibration condition are carried out, and the simulation accuracy of the model is compared and analyzed.Secondly, the influence of pulverized coal conveying capacity and conveying pressure on the pipeline pressure drop is analyzed by using the calibration model.Finally, the coal with inner diameter of 54 mm in Shell coal gasification is analyzed.The pressure drop of pneumatic conveying pipeline is calculated, the pressure distribution diagram of pulverized coal conveying pipeline is drawn, and the proportion of pressure drop of each pipe fitting is compared and analyzed.The minimum pressure drop and economic gas velocity in the conveying phase diagram can be obtained by the simulation.The error between the simulation value and the experimental value of the pressure drop in the horizontal straight pipe is less than 35%.When the simulation conditions are similar to the calibration conditions, the model calculation error is reduced to less than 20%.When the gas velocity is constant, the pressure drop increases gradually with the increase of pulverized coal conveying capacity.When the conveying capacity of pulverized coal is constant, the total pressure drop of horizontal straight pipe gradually decreases with the increase of apparent gas velocity, and the pressure drop curve gradually becomes gentle with the increase of gas velocity, and the influence law of conveying pressure on pressure drop is different under different gas velocity conditions.In the low gas velocity region, the pressure drop of the horizontal straight pipe increases with the increase of the conveying pressure.In the high gas velocity region, the pressure drop of the horizontal straight pipe increases with the increase of the conveying pressure.In the pulverized coal conveying pipeline of Shell gasification, the maximum pressure drop is the vertical section pipeline, up to 51.7%,the horizontal pipe pressure drop is 27.6%,and the bend head 1 and elbow 2 account for 8% and 13% of the total pressure drop.The apparent gas velocity and economic gas velocity increase slowly along the direction of pulverized coal flow, and their average values are 8.8 m/s and 7.1 m/s, respectively.When the velocity difference exceeds 1.5 m/s, the conveying process of pulverized coal can not only maintain sufficient particle concentration, but also avoid the problem of particle settlement blocking the pipeline.

     

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