溢流管结构对天然气水合物用旋流器分离性能的影响

建立了主直径100 mm的旋流器模型,采用计算流体力学(CFD)方法研究了溢流管内径、插入深度及壁厚对旋流器分离天然气水合物性能的影响规律。结果表明,入口流速为9 m/s时,随溢流管内径增大,水合物分离效率增大,砂的分离效率降低,旋流器的压力降逐渐减小;随溢流管壁厚增大,水合物和砂的分离效率稍有增大,旋流器的压力降先增大后减小;随溢流管插入深度增大,水合物分离效率先减小后增大,砂的分离效率先增大后减小,旋流器的压力降波动较小。溢流管内径对旋流器分离天然气水合物性能的影响最大,插入深度次之,壁厚的影响最小。     

纯化天然气水合物螺旋分离器流场与性能分析

基于海洋天然气水合物固态流化开采方法的井下原位除砂提纯回填工艺,本文结合试采所得水合物浆体特征,设计用于解决设备磨损、储层坍塌等问题的井下除砂螺旋分离器,利用CFD数值模拟方法研究了入口速度和水合物体饱和度对井下除砂螺旋分离器流场和性能的影响,得到了随着入口速度增加,流场中流体的速度急剧增大,特别是切向速度、分离效率增加。当分离效率为70%以上,分离器内压降急剧增大,表明分离器内部的能量损耗不断增加;随着入口水合物体积分数的增加,螺旋分离器内流场变化微小,水合物分离效率降低,砂分离效率增加;分离效率为80%以上,压降逐渐降低。说明该分离器的最佳操作区为入口速度范围为3～5m/s,水合物入口体积分数15%以下。研究结果表明：本螺旋分离器具有极佳的除砂效果;切向速度是决定分离器分离性能的关键速度,处理量的增大有利于水合物的提纯;海底水合物储层中水合物饱和度变化对螺旋分离器分离效率具有一定的影响,但螺旋分离器对其具有一定的适应能力;揭示了水合物井下螺旋分离器除砂的分离机理,为其设计提供了一定的依据,为海洋水合物储层开采防砂提了一种新的技术及装备。     

天然气水合物提纯螺旋分离器性能数值模拟

针对海底浅层天然气水合物开采中产砂量大而造成管路堵塞、设备磨损的问题,基于固态流化开采方法,提出天然气水合物原位分离的思路,结合水合物混合浆体物性参数设计井下原位螺旋分离器,采用CFD-Fluent商业软件建立分析模型并进行模型正确性验证,考察了固相水合物体积浓度、固相砂体积浓度和入口流速对分离装置性能的影响。结果表明,研究范围内砂去除率和水合物回收率均约为80%,随水合物体积分数增大,砂去除率和水合物回收率变化非常小,分离器压降变化很小;随砂体积分数增大,砂去除率急剧降低,而水合物回收率急剧增加,压降急剧增大;随入口速度增加,砂去除率和水合物回收率不断增大,分离器压降不断增大。设计的螺旋分离器在水合物原位除砂提纯中性能优异,水合物饱和度对分离器性能影响不大,但粉砂浓度对分离器性能影响较明显,工程应用中需要重点考虑;入口速度对分离器分离性能起关键性作用,决定了分离器的处理能力,适当提高入口速度可一定程度提高分离器的分离效率。     

用双锥-内锥型水力旋流器提纯海洋天然气水合物浆体

针对水合物混合浆体中存在少量天然气的问题,设计了一种适合水合物混合浆体除气除砂的新型水力旋流器?双锥?内锥型水力旋流器,采用有限体积数值模拟方法研究了颗粒粒径、锥角组合、进口压力对固体颗粒和天然气分离效率的影响. 结果表明,固体颗粒粒径为50?90 ?m、天然气气泡直径为400?800 ?m、进口压力为4.3?7.3 MPa时分离效率最佳,最优的锥角组合为10o–5o.     

旋流分离对天然气水合物除砂提纯的影响

针对固态流化开采方法开采海底天然气水合物含砂量大导致开采效率低的问题,提出原位分离工艺,设计了旋流分离装置,基于该装置利用CFD数值模拟方法研究了固相(砂和水合物颗粒)直径、入口浆体流量及浆体中砂浓度对装置分离性能的影响。结果表明,在研究范围内,砂和水合物分离效率大部分高于60%,最高达98.72%,压降大部分低于0.5 MPa,最低至0.03 MPa。砂粒分离效率随固相粒径增大先增大后趋于平稳,随浆体入口流量增大先增大后减小,随砂浓度增大而降低;水合物分离效率随固相粒径增大先增大后趋于平稳,随浆体入口流量增大先增大后减小,随砂浓度增大而降低。溢流口和底流口压降几乎不随固相粒径变化,随砂浓度和浆体入口流量增大而增大。固相粒径、入口流量、砂浓度对分离性能有较大影响,在砂粒径大于20 ?m、水合物粒径大于40 ?m、浆体入口流量约5 m3/h、入口砂浓度不超过25vol%的条件下分离性能良好。     

CFD Study on the Effect of Hydrocyclone Structure on the Separation Efficiency of Fine Particles

Abstract

Effects of geometric structure parameters of 10 mm-diameter hydrocyclones on the particle separation efficiency are studied using computational fluid dynamics (CFD). The fluid velocity profiles and particle trajectories are simulated using RFLOW software with a standard isotropic k-ε turbulent model. The JIS standard CaCO₃-17 particles are adopted as a particulate sample in simulations and experiments. Comparing the simulated results with experimental data, a maximum deviation about 20% in partition curves occurs for 5–10 µm particles. However, fairly good agreements for the cut-size predictions and the fish-hook phenomenon are obtained. The simulated cut-size d ₅₀ is only 2 µm larger than that measured in experiments, while the value of d ₁₀₀ can be accurately predicted. An increase in overflow diameter or a decrease in underflow diameter leads to a lower separation efficiency but a clearer separation sharpness due to lower fluid underflow rate. A short-and-wide rectangular inlet is more efficient for particle separation than a tall-and-narrow one. An inclined inlet conduit plays an inessential role on the efficiency improvement but gains a 2 µm reduction in d ₁₀₀. Comparing the simulated results, the hydrocyclone used in the experiments of this study exhibits a higher separation sharpness than the Rietema type and a higher efficiency than the Bradley type based on the same operation capacity and hydrocyclone size.     

Gas–liquid mass transfer and bubble size distribution in a multi-Cyclone separator

This article discusses the use of a multi-cyclone separator, which is a simplified form of a degassing hydrocyclone, in the separation of sweeping nitrogen bubbles and dissolved oxygen from water. The motion of the nitrogen bubbles and mass transfer of dissolved oxygen is discussed. It was observed that the Sauter mean diameter and gas volume in the swirling flow region as well as the total gas holdup increased as the volumetric ratio of gas to liquid flow increased. Almost all bubbles were found to exit through the gas outlet, indicating optimum performance of the bubble-separation process. The multi-cyclone separator was found to achieve good performance for the mass transfer of oxygen from water to nitrogen. This work is important in predicting the destination of bubbles and dissolved gas in swirling flow. © 2018 American Institute of Chemical Engineers AIChE J, 65: 215–223, 2019     

基于旋转分相单元的电容式气液两相流含液率测量

为提高电容器对含水率测量的能力,设计与其相匹配的旋转分相单元,以实现气液两相流含水率的起旋分相式电容测量。在电容传感器的测量单元基础上,增加旋转分相单元,利用气液两相流体力学理论对其结构进行设计优化,并根据实际应用条件确定分离圈数,保证气液分相效率。旋转分相单元克服了气液两相流流动形态的多样性,将体积含水率信息转换成液膜厚度信息及截面含水率信息进行测量。经实验验证,Lockhart-Martinelli截面含气率模型与实验中电容器测量截面含气率具有良好的一致性,其能够实现对体积含水率20%以内的气液两相流有效测量,体积含水率的绝对误差在±2%以内。     

Investigations on various characteristics of novel cyclone separator with helical square fins

ABSTRACT

Cyclone separators are very energy intensive devices primarily used in power and process industries to separate the particles from hot gases. Hence in the present study, the barrel wall of the cyclone separator was modified by fixing the helical square fins of sizes 5, 7.5, and 10 mm, with 30 and 50 mm pitch variations to improve its separation efficiency. Hence in the present study, various fluid dynamic characteristics which affect the separation efficiency such as axial and tangential velocities, axial pressure drops were investigated. Computational results were validated using the published experimental data for the non-finned cyclone separator and further CFD simulations were performed for novel finned cyclone separators. It was observed that for the particles’ sizes below 3 µm, finned cyclone separator with fin size 10 mm and pitch 50 mm was giving separation efficiency more than other 5 finned cyclone separators. Also 5 to 10% improvement in the separation efficiency was observed over the separation efficiency of the non-finned cyclone separator. Since main function of separating the particles from gas was unaffected rather it was improved using finned cyclone separator(s) which is important in a view of reducing serious fine particulate matter (PM2.5) emissions causing serious health issues.     

旋流分离技术在甲醇制烯烃工艺废水处理中的应用

旋流分离技术在液-固分离和油水分离方面有广泛的应用,针对甲醇制烯烃废水处理中存在的问题,分别研究了急冷水旋液分离器和水洗水旋流除油器,应用于急冷水中催化剂微粉的脱除及水洗水中的油蜡类物质的分离。研究成果应用于某化工企业180万吨/年DMTO装置的水处理系统,并对其急冷水和水洗水水质进行了长期的监测,主要监测指标为急冷水旋液分离器进出口悬浮物含量和水洗水旋流除油器进出口油含量。工业运行结果表明：急冷水一级旋液分离器和二级旋液分离器的效率分别能达到50%和80%,对急冷水进行了有效的澄清,同时对外排相进行了有效的提浓;水洗水除油器的分离效率可达到60%,对油蜡类物质具有较好的分离效果。旋流分离技术的应用,减少了水系统中管路及设备堵塞,保证了装置的稳定运行。     

脱气除油旋流系统流场分布及分离特性

目前我国大部分油田已进入高含水阶段，且采出液中常带有大量伴生气，采用旋流分离法实现采出液高效分离对于简化陆上油田地面处理工艺及提升海上平台经济环保的采出液处理技术具有重要意义。脱气除油旋流系统由GLCC型气液分离器和油滴重构旋流器串联组成，设计的目的是在保证高效脱气的同时进一步改善对小油滴的去除效果，实现油气水三相高效分离。本文基于计算流体动力学（computational fluid dynamics，CFD）方法，利用种群平衡模型（population balance model，PBM）模拟油滴破碎与聚结，对脱气除油旋流系统内部流场特性及粒度分布进行模拟分析，并采用数值模拟与试验相结合的研究方法，对比分析不同含气体积分数和气相出口分流比对脱气除油旋流系统分离性能的影响规律。结果表明：含气体积分数与气相出口分流比对脱气除油旋流系统分离效率的交互作用较显著，在研究范围内综合脱气效率和除油效率可以得到，含气10%、20%、30%的最佳分流比分别为25%、30%、35%，数值模拟结果与试验结果吻合良好，验证了数值模拟方法的可靠性。另外，含气体积分数越大，油滴重构旋流器的油滴分层重构现象越明显，油滴重构旋流器可以在一定程度上改善含气情况下油水分离效果差的现象，脱气除油旋流系统对油气水三相分离的适用性较好。     

脉动进料气液旋流分离器分离性能分析

为提高钻井液振动筛的气、固、液分离能力,一种以振动筛形成的脉动真空与压缩空气注入相结合的固液分离钻井方法被提出,在此基础上出现了一种采用脉动进料边界的旋流器。为分析旋流器的气液分离性能,需要探究其脉动进料条件下的最佳气液分离效率及其影响参数。为此,采用Fluent对稳定、脉动进料状态下不同结构参数的旋流分离器进行流动模拟,通过UDF函数设置脉动进料边界,并分析效率曲线得到脉动进料状态下分离器的最优参数。结果表明,脉动进料状态下的流场可以较好地实现稳定;采用频率为0.4 Hz的正弦脉冲进料气液分离效率最高,可达85.5%;在脉动进料状态下,其脉动不连续性会导致流场湍动能变大,径向压力降梯度降低,切向速度峰值降低。     

水合物法快速脱除天然气中二氧化碳

水合物法脱除天然气中CO2是一种新的天然气脱碳分离技术,可用于初步大量脱除高含CO2天然气和沼气中的CO2.为天然气脱碳提供一种工艺简单、流程快和环保的方法.笔者用CO2(摩尔分数为33.00％)/CH4混合气模拟高含CO2的天然气,在1L的反应釜内,研究混合气水合过程随压力和气水体积比的变化,分析水合过程的温度、压力...     

Xenon recovery from natural gas by multiple gas hydrate crystallization: a theory and simulation

ABSTRACT

For efficient xenon (Xe) recovery from natural gas (NG), multiple gas hydrate crystallization was considered. The optimal stages’ number for effective Xe recovery from model gas mixtures with close composition to NG one was determined. Gas hydrate distribution’s coefficients are defined for these gases at each stage, and each iterations of the multiple gas hydrate crystallization. In CH₄+ H₂S+CO₂+ Xe gas mixture that is closest to NG composition, the maximum average Xe concentration in the gas hydrate phase was observed at the second stage of the multiple gas hydrate crystallization.     

Swirling flow of natural gas in supersonic separators

The supersonic swirling separator is a new apparatus for offshore and subsea natural gas separation, due to its lightweight and the viability of unmanned operation. A new supersonic swirling separator was designed for the numerical calculation, in which a central body was inserted based on the principle of conservation of angular momentum. Axial and radial distribution of the main parameters of natural gas flow was investigated with RNG K-? turbulence model. The effects of the shock waves on the natural gas flow fields were analyzed in the supersonic separator. The results show that water and heavy hydrocarbons can be separated from natural gas due to the low temperature and high centrifugal field. The non-uniformity of radial distribution of the gas dynamic parameters significantly affects the gas/liquid separation. The position of the shock wave determines the distribution of the temperature, which has a great influence on the re-evaporation of liquid droplets.     

Study on the influence of SDS and THF on hydrate-based gas separation performance

Hydrate additives can be used to mitigate hydrate formation conditions, promote hydrate growth rate and improve separation efficiency. CO₂ + N₂ and CO₂ + CH₄ systems with presence of sodium dodecyl sulfate (SDS) or tetrahydrofuran (THF) are studied to analyze the effect of hydrate additives on gas separation performance. The experiment results show that CO₂ can be selectively enriched in the hydrate phase. SDS can speed up the hydrate growth rate by facilitating gas molecules solubilization. When SDS concentration increases, split and loss fraction increase initially and then decrease slightly, resulting in a decreased separation factor. The optimum concentration of SDS exists at the range of 100–300 ppm. As THF can be easily encaged in hydrate cavities, hydrate formation condition can be mitigated greatly with its existence. Additionally, THF can also strengthen hydrate formation. The THF effect on separation performance is related to feed gas components. CO₂ occupies the small cavities of type II hydrate prior to N₂. But the competitiveness of CO₂ and CH₄ to occupy cavities are quite fair. The variations of split fraction, loss fraction and separation factor depend on the concentration of THF added. The work in this paper has a positive role in flue gas CO₂ capture and natural gas de-acidification.     

天然气脱蜡旋风分离器分离效率的模拟

旋风分离器分离效率高,不易堵塞,用于天然气脱蜡效果显著。通过CFD软件Fluent模拟CYG-S型天然气脱蜡旋风分离器的两相流场,得到了旋风分离器内的压力、切向速度、轴向速度分布。对比了不同入口速度下的模拟与理论计算的分割粒径x50,发现具有很好的吻合度,两相模拟有一定的可靠性。结果表明：在旋风分离器锥段底部靠近壁面处的石蜡液滴质量浓度较高;随着进口流量的增加,旋风分离器分离效率提高,当进口流量为1000 m3/h时,x50可以达到5.3 μm;大粒径液滴的分离效果明显,但在所研究的进口流量范围内,进口流量的变化不能明显地影响粒径小于5 μm液滴的分离效率;柱段和锥段长度的增加使得旋风分离器的整体长度增加,延长了液滴在旋风分离器内的停留时间,提高了旋风分离器的分离效率。     

Prediction of induction time for natural gas components during gas hydrate formation in the presence of kinetic hydrate inhibitors in a flow mini‐loop apparatus

The objective of this work is the prediction of induction time (t_i) for simple gas hydrate formation in the presence or absence of kinetic hydrate inhibitors at various conditions based on the Kashchiev and Firoozabadi model in a flow mini‐loop apparatus. For this purpose, the t_i model is developed for simple gas hydrate formation in batch system for natural gas components during hydrate formation in a flow mini‐loop apparatus. A laboratory flow mini‐loop apparatus is designed and built up to measure the t_i for simple gas hydrate formation when a hydrate former (such as C₁, C₃, CO₂ and i‐C₄) is contacted with water in the absence or presence of dissolved inhibitor, such as poly vinylpyrrolidone, PVCap and L ‐tyrosine. In each experiment, a water blend saturated with pure gas is circulated up to a required pressure. Pressure is maintained at a constant value during experimental runs by means of the required gas make‐up. The average absolute deviation (AAD) of the predicted t_i values from the corresponding experimental data are found to be about 11% and 9.4% for gas hydrate formation t_i in the presence or absence of kinetic hydrate inhibitors, respectively. © 2012 Canadian Society for Chemical Engineering     

Effects of Operating Variables on the Yeast Separation Process in a Hydrocyclone

This work involved the use of a hydrocyclone to separate yeast from alcoholic fermentation suspensions. The performance of the hydrocyclone was quantified using empirical models that describe the capacity, total separation efficiency, flow ratio, and reduced separation efficiency as a function of the concentration of the suspension and the operating pressure drop. The results showed capacities of 0.1283 to 0.1820 m³/h, total separation efficiencies of 81.96% to 92.19%, reduced separation efficiencies of 0.63% to 58.44%, and flow ratios ranging from 81.05% to 84.85%.     

Development of a new type high-efficient inner-cone hydrocyclone

Performance of a hydrocyclone can be influenced by many factors, such as structural type, geometric parameters and operation parameters, among which the structural type plays a very important role. The separation principle of a typical hydrocyclone was introduced. Focused on a gas–liquid separation, numerical simulation of the typical hydrocyclone was carried out. The gas phase fraction distribution was analysed. It is shown that the separation effect was not satisfactory. A revising idea was thus proposed and developed step by step, so a new inner-cone hydrocyclone (ICH) was designed. The inner-cone structure was thought to provide a more stable flow field for phase separation. It functions like a gas carrier that is beneficial for radially separated gas congregating on and growing into larger gas bubbles. It also produces an upward pushing force to gas bubbles, so as to enhance the gas–liquid separation performance, although the ICH has lower inner tangential velocities than the typical hydrocyclone. Numerical simulation and experimental study verified the analysis. Pressure drop of the ICH is much lower than that of the typical hydrocyclone; and the ICH has a wider scope for the change of liquid split ratio or inlet gas–liquid ratio. Development of the ICH would provide a new thought for the design of other separators.