径向流吸附器流体流动特性及其结构参数优化

径向流吸附器通常存在流体沿轴向床层分布不均匀,从而导致吸附剂利用率下降和空分系统运行安全性问题。通过对表征Z型径向流吸附器流动特性的微分控制方程中包含的结构参数进行量纲1化,系统地研究了各结构参数对吸附器内流体分布的影响。同时针对实验室已有的一台Z型径向流吸附器,采用理论求解和实验数据对照的方法验证了模型的可靠性。结果表明,减小吸附床层轴向高度和吸附剂颗粒直径能显著提高Z型径向流吸附器内流体分布的均匀性;当空气的运动黏度和其他结构参数不变时,吸附器的空气处理量在一定范围内变化对吸附床层内流体的均匀性影响不大。     

立式径向流吸附器中流体均布的理论分析

为提高空分用吸附器吸附效率,通常在内分布流道布置一锥体使内外分布流道沿轴向压降梯度相等以保证空气在吸附剂中流场均匀。通过对立式径向Z型吸附器内的压降分析,推导出一个可表征当空气在吸附剂中均匀分配时吸附器各参数应满足的量纲1微分控制方程。同时对一个实验径向吸附器进行设计,利用该量纲1微分控制方程获得了锥体截面半径随轴向高度的变化规律,为该类径向吸附器的设计提供了理论依据。     

π型向心径向流吸附器变质量流动特性研究

对径向流吸附器内变压吸附(PSA)制氧的变质量流动规律进行研究,有助于准确掌握吸附过程及床层内的变量因素对制氧性能的影响。对π型向心径向流吸附器建立气固耦合的两相吸附模型,并对其PSA制氧过程进行了数值模拟研究,得到了床层内氧气浓度分布、温度分布以及产品气浓度的变化规律。结果表明：首次循环结束时床层内氧气最高摩尔分数可达66.02%,回收率29.2%。非稳定循环期间,氧气摩尔分数从66.02%升高至 97.5%,回收率从29.2%提高至38.5%。循环达到稳定后,床层内氧气摩尔分数最高可达98.6%,回收率38.9%左右,且达到稳定状态后床层内气固两相温差减小,逐渐达到热平衡。获得了吸附器内部气体与吸附剂两相间的传质、传热过程,为π型向心径向流吸附器用于PSA制氧提供技术支持。     

π型向心径向流吸附器变质量流动特性研究

对径向流吸附器内变压吸附(PSA)制氧的变质量流动规律进行研究,有助于准确掌握吸附过程及床层内的变量因素对制氧性能的影响。对π型向心径向流吸附器建立气固耦合的两相吸附模型,并对其PSA制氧过程进行了数值模拟研究,得到了床层内氧气浓度分布、温度分布以及产品气浓度的变化规律。结果表明:首次循环结束时床层内氧气最高摩尔分数可达66.02%,回收率29.2%。非稳定循环期间,氧气摩尔分数从66.02%升高至97.5%,回收率从29.2%提高至38.5%。循环达到稳定后,床层内氧气摩尔分数最高可达98.6%,回收率38.9%左右,且达到稳定状态后床层内气固两相温差减小,逐渐达到热平衡。获得了吸附器内部气体与吸附剂两相间的传质、传热过程,为π型向心径向流吸附器用于PSA制氧提供技术支持。     

立式分层并联径向流吸附器流场数值模拟

为降低径向流吸附器高度对均布的影响,提出了径向流吸附器的分层并联设计方法,并建立了径向流分层并联吸附器的数值计算模型。应用计算流体力学方法对分层并联式径向流吸附器中流体在床层内的流场进行了数值模拟计算,并在相同条件下与增高改进后的径向流吸附器的流场分布进行对比。结果表明,分层并联设计方法的均匀度相比于增高方法的均匀度提高了80%,有效清除了径向流吸附器过高对床层内流体均布的负面影响,且对分层并联径向流吸附器上部单元床层厚度进一步优化,达到了上下单元同时穿透的目的。     

空气预纯化的技术研究进展

空气预纯化在空分设备流程中起着保障整套设备安全运行的重要作用。本文综述了近年来国内、外空气预纯化技术的研究和应用情况。指出目前目前存在的问题是:工艺流程大多通过增加均压、多塔循环等工艺步骤来提高空气预纯化效果,但系统尺寸较大、流程较复杂;吸附剂大多采用单一吸附剂、几种混合吸附剂或复合吸附剂来纯化气体,但纯化效果不理想且成本较高;吸附器大多采用立式轴向流、卧式垂直流、立式径向流等结构,通过改进气流分布器、改善分子筛布局及装填方式等提高吸附效率,但受到场地、能耗等因素限制。未来的研究重点应放在工艺流程的改进及开发新型模块式流程系统、原有吸附剂的改性及寻找新型吸附剂材料、原有吸附器结构的改进及开发新型吸附器结构等方面。     

多床层径向反应器中床层的流场行为

在直径3m、高5m的大型多床层径向反应器冷模装置上,通过测定流体在流道和各分床层内的静压分布,考察了各分床层的流体流动行为和特征.结果表明,当流道静压差的均方根偏差小于1%时,各分床层静压差的均方根偏差小于5%,流体在各分床层的径向流速沿轴向分布均匀,流速最大偏差小于5%;当流道静压差沿轴向的差别大于10%时,则其沿轴向分布显著不均匀,且靠近流道静压变化梯度大的分床层的径向流速均匀性最差,床层上下端流速偏差达70%.Π型流动形式是动量交换型径向反应器的最佳选择,适宜的两流道静压差设计可实现径向流速沿床层轴向完全均匀分布。     

径向流固定床反应器的流动特性研究及结构参数的合理选择

径向流固定床反应器的操作状态和反应效果在很大程度上取决于反应器内穿越催化剂床层径向气流沿反应器轴向分布的均匀程度，亦即床层内催化剂负荷的均布程度。本文对此类反应器内的流动特性进行了研究，对立了描述反应器内流动规律的基本运动方程。研究结果表明，径向气流的轴向分布情况与反应器的流动结构型式、反应器内分流流道与合流流道截面积的比值、催化剂床层的阻力系数以及反应器的高径比等参数有关。并提出了如何合理选择反     

立式径向流吸附器床层泄漏问题处理

神华榆林能源化工有限公司配用的空分装置立式双层径向流吸附器在运行过程中出现了内、外层床层泄漏,吸附剂损失的问题,造成吸附器出口空气中CO_2含量超标,板式换热器进、出口温差增大,影响空分装置安全、满负荷运行。本文总结空分装置配合设备制造厂家处理吸附器床层泄漏问题的原因分析、施工准备、施工过程、整改措施等相关工作,为同类型吸附器运行维护提供借鉴。     

径向流反应器流场分布的数值模拟分析

径向流反应器是一种高效节能反应器。为了深入研究四种不同流动类型的径向流反应器的流场分布特征,在验证模拟可行性的基础上,引入多孔介质模型,运用FLUENT软件对不同类型的径向流反应器内的流场进行数值模拟。在边界条件设置一定时,模拟分析四种类型径向流反应器内分流流道与集流流道间的压降沿轴向的变化程度,结果说明:离心流动的流体分布均匀度优于向心流动,П型离心的径向流反应器内部流场分布最均匀,其次是Z型离心流动、П型向心流动、Z型向心流动。     

A Mathematical Model for Designing Optimal Shape for the Cone Used in Z-flow Type Radial Flow Adsorbers

Nonuniform flow distribution along the radial direction usually exists in a Z-flow type radial flow adsorber, which will decrease the utilization of adsorbent and the switching time and may result in operating safety problems in cryogenic air separation. In order to improve the uniformity of the flow distribution along the radial direction in the adsorber, a differential equation is derived through pressure drop analysis in the Z-flow type radial adsorber with a cone in the middle of the central pipe. The differential equation determines the ideal cross-sectional radii of the cone along the axis. The result shows that the cross-sectional radius of the cone should gradually decrease from 0.3 m to zero along the axis to ensure that the process air is distributed uniformly in the Z-flow type radial flow adsorber and the shape of the cone is a little convex. The flow distribution without the cone in the central pipe is compared under different bed porosities. It is demonstrated that the proposed differential equation can provide theoretical support for designing Z-flow type radial flow adsorbers.     

Investigation on a vertical radial flow adsorber designed by a novel parallel connection method

Due to the increasing global demand for industrial gas,the development of large-scale cryogenic air separation systems has attracted considerable attention in recent years.Increasing the height of the adsorption bed in a vertical radial flow adsorber used in cryogenic air separation systems may efficiently increase the treatment capacity of the air in the adsorber.However,uniformity of the flow distribution of the air inside the adsorber would be deteriorated using the height-increasing method.In order to reduce the non-uniformity of the flow distribution caused by the excessive height of adsorption bed in a vertical radial flow adsorber,a novel parallel connection method is proposed in the present work.The experimental apparatus is designed and constructed;the Computational Fluid Dynamics (CFD) technique is used to develop a CFD-based model,which is used to analyze the flow distribution,the static pressure drop and the radial velocity in the newly designed adsorber.In addition,the geometric parameters of annular flow channels and the adsorption bed thickness of the upper unit in the parallelconnected vertical radial flow adsorber are optimized,so that the upper and lower adsorption units could be penetrated by air simultaneously.Comparisons are made between the height-increasing method and the parallel connection method with the same adsorber height.It is shown that using the parallel connection method could reduce the difference between the maximum and minimum radial static pressure drop by 86.2％ and improve the uniformity by 80％ compared with those of using the height-increasing method.The optimal thickness ratio of the upper and lower adsorption units is obtained as 0.966,in which case the upper and lower adsorption units could be penetrated by air simultaneously,so that the adsorbents in adsorption space could be used more efficiently.     

真空变压吸附制氧径向流吸附器的流动特性模拟

真空变压吸附制氧是一个复杂的动态过程,深入了解真空变压吸附制氧过程中吸附器内的流动特性是吸附器设计与完善的基础.基于Fluent中的多孔介质模型,通过用户自定义函数功能,建立了真空变压吸附制氧用径向流吸附器的二维轴对称模型,研究了真空变压吸附首次和第二次循环中径向流吸附器的流动特性,对比分析了吸附剂颗粒直径、流道截面积...     

Optimization design research of air flow distribution in vertical radial flow adsorbers

Non-uniform flow distribution usually exists in a vertical radial flow adsorber, which significantly decreases the utilization of adsorbents. We adopted numerical simulation methods based on the ANSYS Fluent 15.0 software to study the flow pattern in vertical radial flow adsorber, where programs of user-defined functions (UDF) were set up to interpret component equation, momentum equation and energy equation. To solve the problem of non-uniform air distribution, the relationship between the radial pressure drop across the bed and the ratio of cross-sectional area of the central pipe to that of the annular channel was studied, and optimization design of the distributor inserted in the central channel was given by parametric method at the same time. Through comparative analysis in the given experimental condition, the uniformity reached about 99.1% and the breakthrough time extended from 564 s to 1,175 s under the present optimized design method.     

折流式旋转床出口气相流场研究

采用实验的方法对折流式旋转床气体出口流场进行研究。实验在旋转床壳体直径为724mm,气体出口直径为152mm的折流式旋转床中进行,在常温常压空气单相的情况下采用5孔探针测量了不同转速和气量下旋转床出口位置的气相流场。实验得到了不同转速不同气量下气相切向、径向和轴向速度随无因次半径变化的流场分布情况,从而为折流式旋转床的设计提供理论基础。     

Numerical Investigation of Integrated Design on Uniform Fluid Distribution for Radial Flow Adsorber

Theoretical Foundations of Chemical Engineering - Non-uniform distribution of air in radial flow adsorber restricts the development of large-scale air separation units (ASUs). The cross-sectional...     

两段循环流化床吸附有机气体实验

以Ambersorb 600为吸附剂,甲苯为吸附质,在两级循环流化床吸附装置内进行了吸附特性的实验. 采用PGM-7600型VOCs分析仪测量甲苯的浓度,得到两段循环流化床的压力和空隙率分布及浓度随床高的分布;研究了气体进口浓度和表观气速对吸附效率的影响. 在实验条件下吸附装置效率为95%~98%.     

循环流化床气固传质实验研究

This study is devoted to gas-solid mass transfer behavior in heterogeneous two-phase flow. Experiments were carried out in a cold circulating fluidized bed of 3.0m in height and 72mm in diameter with naphthalene particles. Axial and radial distributions of sublimated naphthalene concentration in air were measured with an online concentration monitoring system HP GC-MS. Mass transfer coefficients were obtained under various operating condition, showing that heterogeneous flow structure strongly influences the axial and radial profiles of mass transfer coefficients. In the bottom dense region, mass transfer rate is high due to intensive dynamic behavior and higher relative slip velocity between gas and clusters. In the middle transition region and the upper diluter region, as a result of low mass transfer driving force and the influence of flow structure, mass transfer rate distribution becomes non-uniform. In conclusion, among the operating parameters influencing mass transfer coefficients, the superficial gas velocity is the most important factor and the solid circulation rate should be also taken into account.