A case study on suspended particles in a natural gas urban transmission and distribution network

Suspended particles in the natural gas transmission and distribution network of the city of Kerman, Iran were investigated. Particle concentration and size distribution were measured in different locations of the natural gas pipeline network. Particle samplings were carried out in two seasons: summer, when there is the lowest consumption, and winter, when there is the highest consumption of natural gas. Additional particle characterization was carried out by scanning electron microscopy coupled with energy dispersion X-ray (SEM/EDX) and X-ray diffraction(XRD) analyses. Particle concentration was found to be significantly higher in winter as compared to summer. The range of particle concentrations in summer was from 0.12 mg/Nm³ at the end of the pipeline to 4.7 mg/Nm³ at the network entrance, and from 0.30 mg/Nm³ to 22.1 mg/Nm³ in winter. Particle size distribution showed a higher frequency of smaller particles in winter than in summer. Larger particles were more likely to exist at the network entrance as compared to the exit. The average particle size ranged from 181 μm at the network end to 253 μm at the entrance in summer, and from 74 μm to 209 μm in winter. Particle characterization confirmed the presence of corrosion products in the suspended particles.     

高压天然气管道内粉尘在线检测方法

针对高压天然气管道分输站场用过滤分离设备性能评价和设备选型的要求,利用小孔节流效应设计了适合高压管道取样用减压装置,在此基础上提出了高压天然气管道内粉尘在线检测方法。采用数值计算与现场试验相结合的方法,验证了粉尘在线检测方法,结果表明减压装置减压过程中无液滴析出、对粉尘浓度和粒度分布影响小,在线检测方法检测结果准确可靠。     

四氢呋喃和一氟二氯乙烷水合物颗粒聚结特性

实验研究了四氢呋喃（THF）水合物和一氟二氯乙烷（HCFC-141b）水合物颗粒聚结特性,将实验得到的水合物颗粒聚结粒度分布（PSD）与正态分布、对数正态分布、伽马分布、威布尔分布拟合曲线对比,探讨了初始四氢呋喃溶液和一氟二氯乙烷溶液浓度以及搅拌速度对水合物颗粒聚结的影响,并对四氢呋喃水合物和一氟二氯乙烷水合物颗粒特性进行了对比。结果表明,四氢呋喃水合物和一氟二氯乙烷水合物颗粒聚结粒径符合对数正态分布;初始溶液浓度越低、搅拌速度越大,水合物颗粒聚结粒径越小,可以起到防治水合物颗粒聚结的作用;四氢呋喃水合物颗粒粒径是一氟二氯乙烷水合物颗粒粒径的1.3倍左右,从成浆输送的角度来说,一氟二氯乙烷水合物颗粒更易于在管道中输送。     

高压天然气管道内颗粒物在线检测结果校正方法

采用在线检测装置对天然气管道内颗粒物进行了实验测定,该装置可在操作压力12 MPa下无需减压装置直接对高压天然气内的颗粒物浓度和粒径分布进行检测. 在6.3 MPa压力下,对国内某天然气站管道内颗粒物的特性进行了检测,分析了影响在线测量结果的因素,以离线测量数据为基准,提出了修正方法,对在线测量所得粉尘颗粒物的粒径分布和浓度进行了修正,在线检测所测粒径范围由0.65~9.5 mm修正为0.55~7.2 mm. 修正前在线测量浓度为4.04 mg/m3,离线测量浓度为2.76 mg/m3,二者偏差约为46%,修正后在线检测平均浓度约为2.83 mg/m3,与离线测量浓度的偏差小于5%.     

Solids behaviour in a gas-solid two-phase mixture flowing through a packed particle bed

This paper reports the solids behaviour in a dilute gas-solid two-phase mixture flowing through a packed bed. The positron emission particle tracking (PEPT) technique was used in the work, which allowed investigation of three-dimensional solids motion at the single suspended particle level. Processing of the data gave solids velocity, the residence time of suspended particles, bed tortuosity in terms of solids motion, as well as solids occupancy in the cross-section of the packed bed. The results suggest that the wall effect on the motion of suspended particles is limited to approximately one packed particle diameter under the conditions of this work. Both the average axial and radial velocities of suspended particles, normalised by the superficial gas velocity, change periodically with radial position, but the periodicity does not correspond exactly to the packed particle diameter. The peak and trough values of the average axial velocity of the suspended particles in the bulk region are, respectively, ∼25% and ∼15% of the superficial gas velocity under the conditions of this work and the superficial gas velocity shows little effect. The peak and trough values of the average radial velocity of the suspended particles in the bulk region are, respectively, +5% (positive) and -5% (negative) of the superficial gas velocity. The results of the residence time and tortuosity of the suspended particles show an approximately Gaussian distribution with the peak residence time and tortuosity increasing with decreasing superficial gas velocity. The occupancy data suggest that particles spend more time in an annular region close to the wall, indicating a non-uniform particle distribution across the packed bed cross-section.     

天然气储气库往复式压缩机异常磨损分析和控制

“十四五”期间全国天然气管网已形成了互联互通,但管输气质更加复杂,一定量的粉尘广泛存在于天然气管道中,导致储气库往复式压缩机压缩缸发生异常磨损。基于切向撞击能量模型,结合现场测量和计算流体力学动网格方法,明确了压缩缸磨损特性。结果表明,压缩缸内润滑油与粉尘混合后形成研磨膏,随着粉尘质量浓度从0.01%增至3.00%,研磨膏黏度从4.51×105 mPa?s增加至1.27×106 mPa?s,密度从890 kg/m3增至980 kg/m3;压缩缸磨损多发生在其12点和6点钟方向,当活塞在行程的两侧时,压缩缸内剪切应力和磨损速率最小,当活塞位于行程中点时,压缩缸内剪切应力和磨损速率最大;发现对于每1000 h运行不需修复压缩缸(磨损量小于0.13 mm),粉尘质量浓度宜控制在0.60%以下,每5000 h和每10 000 h运行不需更换压缩缸(磨损量小于1.16 mm),粉尘质量浓度应分别控制在1.30%和0.40%以下;当粉尘质量浓度为0.01%时,磨损速率随润滑油黏度降低而降低,当粉尘质量浓度为0.51%和1.00%时,当润滑油黏度在2.59×105, 2.21×105, 1.97×105 mPa?s时,计算磨损速率随黏度降低陡然增大。     

Calculation of the efficiency of coagulation of a fine suspension in a flow

The change in the grain size distribution of very small particles suspended in a gas flow is investigated under the assumption that the evolution of the powder dispersity is caused by particle coagulation. It is supposed that the mixture being investigated is under quasi-equilibrium conditions and the volumetric concentration of the solid phase is low.     

悬浮物直径和含量对岩心渗透率的影响

通过定量滤膜调整现场污水的粒度分布,采取岩心流动试验模拟方法,研究了浓度和直径不同的悬浮物注入水对地层所造成的渗透率伤害。室内岩心流动实验结果表明：岩心的物理特征大致接近时,给定悬浮物粒径,颗粒浓度越大,引起的渗透率损失越大;悬浮颗粒浓度一定时,颗粒粒径越大,引起的渗透率损失越大;以渗透率伤害15％为界,确定渗透率70 mD左右的地层,注入水中悬浮物控制标准为粒度中值2．6μm,含量3 mg／L。     

城市燃气管道小孔泄漏数值仿真研究

随着城市天然气管网建设的飞速发展,城市天然气输送管网越来越复杂。城市燃气管道泄漏会造成重大的经济损失和人员伤亡,并影响到人们的日常生活。为探究城市燃气管道的泄漏规律,建立了城市天然气管道泄漏最为常见的小孔泄漏扩散模型,应用MATLAB软件编制了相应程序,对气体泄漏浓度和泄漏范围进行数值仿真,探究管内压力、风速、地形条件对气体扩散范围、扩散浓度的影响。结果表明,风速、管内压力直接影响泄漏浓度值和泄漏范围。相比于城市地形,郊区地形条件下,风速对扩散范围的影响更大,充分证明了郊区的地形更利于燃气扩散。     

Calculating the aggregation of particles being dehydrated in an air flow

Change in the grain-size distribution of a small-particle collective suspended in a steady-state gas flow is studied under the assumption that the evolution of particle dispersity results from the phenomena of evaporation (drying) and coagulation of a suspension. It is assumed that the suspension under consideration is in quasi-equilibrium low-temperature conditions and the volume concentration of particles is slight.     

高温烟气颗粒物在线检测装置性能评价

为评价高温工况下颗粒物在线检测装置的性能,在催化裂化高温烟气过滤实验装置上使用光学在线颗粒物检测装置测定了过滤器下游烟气中的催化剂浓度及粒径分布,同时用离线式粉尘等动采样装置和Coulter粒径分析仪测量过滤器上游与下游的催化剂浓度和粒径分布,对在线式的测量结果进行验证。考虑了温度对在线式测量结果的影响。实验结果表明:在线式检测装置可以在操作温度320~465℃,操作压力0.21 MPa工况下实现稳定的测量,在线式测量结果和离线式测量结果吻合很好,实验和计算模拟结果表明操作温度对实验测量的影响可以忽略。在此基础上,针对煤化工行业的实际工况,提出了利用迭代方式来获得在线测量结果修正值的方法,该方法对煤化工工艺中高温气体管道内颗粒物的在线测定同样具有指导意义。     

Modeling and Simulation of a Bubbling SO2 Absorber with Granular Limestone Slurry and an Organic Acid Additive

The absorption of SO₂ into limestone slurry containing suspended reactive particles was performed in a bubble reactor with continuous feeding of both gas and liquid phases at a constant pH and high temperature (50 °C). An absorption model with a reaction plane based on the film model was developed. The effect of limestone particle size, concentration, acetic acid additives, and inlet SO₂ concentration on the concentration distribution of chemical species in the liquid film and SO₂ absorption rate were simulated. Increasing the concentration of limestone slurry, adding acetic acid additives into the system or decreasing the limestone particle size or inlet SO₂ concentration caused the reaction plane in the liquid film to shift towards the gas‐liquid interface. Model and experimental results were compared, and it was shown that the model fits the experimental data well.     

燃煤超细颗粒物团聚促进机制的实验研究

煤粉燃烧排放大量超细颗粒物对大气环境和人类健康造成了严重的危害。提出一种燃后区烟尘团聚促进新方法，通过在燃后区烟道喷射团聚促进剂，利用絮凝理论，增加超细颗粒之间的液桥力和固桥力，促使超细颗粒物团聚长大，进而被现有除尘装置捕获，减少超细颗粒的排放。在自行设计搭建的团聚实验台上进行了系统的实验研究，分析了团聚促进剂溶液的pH值、流量、浓度，团聚室的温度以及模拟烟气中粉尘浓度等因素对超细颗粒物团聚效率的影响。结果表明，化学团聚对于超细颗粒物的脱除具有显著的作用，喷入团聚促进剂后的烟尘排放浓度远比无团聚和喷水的情况要低；团聚促进剂的高分子链对超细颗粒的吸附絮凝作用促进超细颗粒团聚，显著降低烟尘排放浓度，实现超细颗粒物经济高效脱除，达到国家新的烟尘排放标准。     

天然气管道泄漏扩散规律的数值模拟

近年来,由于天然气管道泄漏而导致火灾、爆炸的风险,对群众的安全、企业财产和环境等造成极大的威胁,因此,通过分析管道的泄漏模型,制定相应的对策保障天然气管道系统的安全、可靠的运行是非常有意义的。本文利用FLUENT对天然气管道泄漏扩散规律迚行了数值模拟,得到了甲烷的扩散规律及浓度分布规律,为有效预测天然气泄漏扩散的影响范围提供了依据。     

Removal of micron-size particles from gases by turbulent deposition and diffusiophoresis

When one gaseous or vapour component diffuses across a space occupied by another component, there is a tendency to entrain and remove particles in the micron size range suspended in that space. This phenomena is called diffusiophoresis. The object of this work was to study the application of this phenomenon as a means of air pollution control when pollutant particles are suspended in a gas stream in turbulent flow. Under these conditions turbulent deposition also results in removal of particles from the gas stream. The test system chosen for study was sulfuric acid droplets suspended in air, with water vapour as the diffusing component. A concentration gradient was established by passing the mixture through a vertical tube whose walls were cooled. Experimental particle collection efficiencies agreed with efficiencies calculated from a theoretical model of the system. The energy requirement of this pollution control technique was analyzed.     

Removal of micron-size particles from gases by turbulent deposition and diffusiophoresis

When one gaseous or vapour component diffuses across a space occupied by another component, there is a tendency to entrain and remove particles in the micron size range suspended in that space. This phenomena is called diffusiophoresis. The object of this work was to study the application of this phenomenon as a means of air pollution control when pollutant particles are suspended in a gas stream in turbulent flow. Under these conditions turbulent deposition also results in removal of particles from the gas stream. The test system chosen for study was sulfuric acid droplets suspended in air, with water vapour as the diffusing component. A concentration gradient was established by passing the mixture through a vertical tube whose walls were cooled. Experimental particle collection efficiencies agreed with efficiencies calculated from a theoretical model of the system. The energy requirement of this pollution control technique was analyzed.     

Effects of particle properties on flow structure in a 2-D circulating fluidized bed: Solids concentration distribution and flow development

The effects of particle properties (particle density, size and sphericity) on solids concentration in a 2-D riser were comprehensively investigated by measuring the axial and lateral solids concentration with an optical fiber probe. In this study, solids concentration of different types of particles shows that heavier particles have higher solids concentration laterally and axially than lighter particles; larger particles result in more compact solids distribution and such size effect is more evident at the riser bottom; more spherical particles lead to higher solids concentration. Various forces acting on particles and the change in the slip velocity between gas and particles were used to explain the effects of particle properties on solids distribution.     

On the problem of laminar flame propagation in a gas with an inert dust

This paper presents a mathematical model and the results of calculation of the velocity of propagation of the flame front in a fuel gas with suspended inert particles taking into account the thermal expansion of the gas and the dynamic relaxation of particles. Dependences of the steady-state flame velocity on the particle size and mass concentration are obtained.     

气田地面集输管网参数优化设计

气田集输管网参数优选是气田地面工程规划设计的关键,开展集输管网参数优化可以有效降低集气系统投资。针对气田常用管网结构和工艺流程,考虑伴热带传热对于管道工艺计算的影响,建立了以管网建设费用最小为目标,以温压平衡、经济流速、节点流量平衡等为约束条件的气田集输管网参数优化数学模型,根据模型的结构特点设计了粒子群智能求解算法,结合C#语言和Access数据库开发了优化设计软件。实例验证得出,模型及算法正确,粒子群求解算法可靠性和收敛性良好,优化软件稳定高效。     

大型快速流化床内颗粒浓度和速度分布的实验研究

采用压力巡检仪和光纤测量仪,对直径300 mm的快速流化床反应器内气固两相流动特性进行了研究,考察了操作条件对快速床轴、径向催化剂颗粒浓度、颗粒速度、筛分分布等的影响. 结果表明,当操作气速提高到2.0~2.6 m/s,相应的催化剂循环强度在60~160 kg/(m2×s),床层密度可保持在50~650 kg/m3;催化剂颗粒浓度在径向上呈中心低、边壁高的不均匀分布,轴向上各径向位置在颗粒加速区逐渐降低、在充分发展区趋于稳定、随表观气速增大或催化剂循环强度减小而减小,且径向均匀性变好,在r/R<0.7的中心区域趋于一致;颗粒速度在径向上呈中心高、边壁低的抛物线形分布,且随操作气速增大或催化剂循环强度增大而更加明显.