5A分子筛分离工业异己烷中低含量正己烷

采用5A分子筛对工业异己烷进行吸附分离,既可纯化异己烷,又可得到高纯的正己烷。测定了吸附穿透曲线,分析了吸附温度对穿透吸附量、传质区长度以及床层利用率的影响,探讨了水置换法脱附再利用吸附剂的方法。试验结果表明:常压下,在60~90℃,5A分子筛对正己烷的吸附穿透曲线均为"S"型;70℃时正己烷的穿透吸附量及饱和吸附量最高;对于低浓度正己烷,温度对吸附传质区长度、床层利用率影响不大;采取水置换脱附法可以有效多次再生5A分子筛。5A分子筛对2-甲基戊烷、3-甲基戊烷吸附作用很小,吸附分离中异己烷的损失量小。     

5A沸石分子筛低温变压吸附CO2/CH4实验研究

采用静态容积法测量5A沸石分子筛对CO_2和CH_4的单组份等温吸附曲线,采用低温变压测量不同实验参数对5A沸石分子筛分离CH_4/CO_2混合气体的能力影响。静态实验表明,CO_2和CH_4吸附量随温度的降低而上升,-30℃时CO_2和CH_4在吸附剂上的饱和吸附量最高:分别为4.94 mmol/g和3.0 mmol/g;动态试验表明,增加吸附压力会降低分离效果,减小混合气体分离系数;降低吸附温度有利于CH_4/CO_2分离,提高混合气体分离系数。     

吸附床在封闭气流循环中的除湿传质动力学研究

用硅胶和4A分子筛吸附剂进行气流封闭循环实验,对吸附床的除湿传质动力学进行了研究。由湿度随时间的微分规律拟合了吸附床的除湿传质系数与吸附剂表面平衡湿度。除湿传质系数主要受操作条件的影响而随吸附剂种类变化不大,表明吸附床的除湿过程主要受外扩散控制。在层流状态下,吸附床的除湿传质系数随雷诺数近似线性增大。     

膨胀珍珠岩负载碳纳米管膜的表征及其对甲苯吸附性能初探

为了解决传统颗粒型吸附剂压降过大,传质效率低等问题,采用化学气相沉积法(CVD),以樟脑为前驱体在膨胀珍珠岩表面成功合成了碳纳米管(CNT)膜,构成了具有梯度多孔结构的膨胀珍珠岩碳纳米管膜(CNTs/Perlite)复合材料。结果表明,当生长温度和时间分别为800℃和40 min,樟脑用量为2 g时,合成的CNT生长密度高、热稳定性强、表面缺陷结构少。同时系统研究了甲苯在不同CNT与CNTs/Perlite比例下构成的结构化床层上的吸附透过行为。结果表明,结构化固定床层(1.5 cm CNT+0.5 cm CNTs/Perlite)的无效床层厚度由1.028降低为0.984 cm,床层利用率从48.6%提高为50.8%,传质速率k’从0.041 6提高到0.059 6 min^-1。作为一种梯度孔结构材料,膨胀珍珠岩碳纳米管膜能够显著降低床层阻力,提高传质速率,为工业应用提供了一种新思路。     

13X沸石分子筛对低浓度CO2动态吸附

目前对于吸附分离技术应用于高压、低浓度CO₂脱除的研究还较少,在进行相应吸附脱碳工艺设计时也缺少相关的参考数据。为探究13X沸石分子筛对低浓度CO₂的动态吸附性能,本文利用动态吸附实验的方法,探究不同条件下低浓度（摩尔分数3%）CO₂气体在13X分子筛上的动态吸附性能,得到不同压力、温度、气体流量、填料高度及分子筛规格（尺寸、形状）等因素影响下的13X分子筛对于CO₂气体的动态吸附规律及相应的性能指标参数。结果表明：随着吸附压力的升高,13X分子筛的CO₂吸附量增加但增量逐渐减小;降低吸附温度、减小气体流量和增加填料高度均有利于增强13X分子筛的动态CO₂吸附性能,提高吸附脱碳效果,其中温度及填料高度的变化对于CO₂吸附的影响程度最大;实验还发现小尺寸及条状13X分子筛的动态吸附脱碳性能优于其他规格,并根据其特定条件下的出口CO₂浓度为50mL/m³时的CO₂吸附量指标,给出吸附剂用量与液化天然气（LNG）脱碳工艺处理量的关系系数。     

活性炭吸附提取氰化亚金离子的数学模拟

以含金工业废水的处理装置为研究对象及镍离子代替氰化亚金离子,对Φ0.2 m×0.5 m吸附柱中活性炭吸附氰化亚金离子进行数学模拟,得到不同条件下氰化亚金离子的吸附柱穿透曲线和吸附负荷分布曲线. 结果表明,当氰化亚金离子的进料流量为0.001 m3/s,进料浓度为 7.614′10-5 kmol/m3,传质系数为0.001 s-1时,吸附床层开始穿透时间为47.61 h,完全被穿透时间为124.14 h;增大进料流量和进料浓度可提高床层被穿透的速度,而当传质系数≥0.001 s-1时,氰化亚金离子吸附穿透曲线不再随传质系数增大而变化.     

脉动流变压吸附分离CH_4/CO_2实验研究

为解决变压吸附脱碳工艺过程中气体流动与吸附不均匀、存在流动死区与疏松畅流区等问题,改善吸附效果,将脉动流与变压吸附工艺结合设计脉动流变压吸附脱碳设备,以验证该吸附方式的可行性。利用动态脉动变压吸附实验检测不同条件下脉动吸附分离CH_4/CO_2的穿透曲线,进一步计算吸附量、分离系数等表征吸附分离效果。实验结果表明,随着脉动频率的增加,吸附分离效果先改善后变差;随着流量与压力增大,脉动吸附对应最佳吸附效果的脉动频率也随之增大;脉动吸附对于不同吸附剂的效果也不同,实验检测了13X沸石分子筛、椰壳活性炭、5A分子筛三种吸附剂,脉动吸附对13X分子筛效果较明显,分离系数与吸附量变化较大。     

氢同位素气体的新型动力学吸附模型

将氢同位素气体在多孔吸附剂表面上的吸附脱附过程假设为简单对峙反应,提出了一个适用于体积法计算气体动力学吸附速率常数的数学模型。模型可考察温度与初始压力对动力学吸附速率的影响,且能较好地计算不同压力下氢气与氘气在微孔分子筛4A,5A,Y,10X与介孔分子筛CMK-3,SBA-15上的动力学吸附速率常数。当分子筛孔径为0.5 nm时动力学吸附选择性最大,可高达2.48。介孔分子筛的动力学吸附选择性则较小,表明大孔径的吸附剂不利于氢同位素气体混合物的分离。     

5A分子筛的改性制备及其对汞的吸附研究

以5A分子筛为原料,Ce(NO3)3.6H2O为改性试剂,通过一步浸渍法并结合干燥、焙烧与研磨过程,制备CeO2/5A分子筛吸附剂,研究了5A分子筛在改性前后及不同温度下对汞的吸附性能,由表征和吸附热力学分析的结果可知:改性后的5A分子筛与改性前相比,吸附能力提高将近一倍,穿透时间延长;CeO2/5A分子筛对汞的最佳去除温度是175℃,去除率为90％,吸附量是6.25 μg/g;改性后的5A分子筛孔径增大,比表面积减小,有利于对汞的吸附;TG结果表明CeO2成功的负载到5A分子筛上,使5A分子筛对汞的吸附能力增强;热力学研究发现Langmuir吸附模型的拟合结果比Freundlich模型要好;CeO2/5A分子筛对汞的吸附过程是一个多层吸附过程.     

CO_2在13x分子筛上的吸附分离——总传质系数及数学模型

以CO_2在分子筛和活性炭上的吸附平衡理论为基础,用微分床层测定CO_2在13x分子筛上的吸附与解吸总传质系数K_0,对描述吸附柱操作的偏微分方程组,分别用Laplace变换和有限差分法直接求解,计算所得透过曲线与实验结果相近似。     

Predictive equations in gas adsorption kinetics

The experimental method of determining the operative parameters of adsorptive capacity and rate in the gas adsorption kinetics of packed bed sorbents relies upon the linear relationship between gas breakthrough time and sorbent weight. The slope and intercept of the straight line, resulting from such a plot, yields values for the gas saturation capacity and adsorption rate constant of the adsorbent. This relationship is shown in the modified Wheeler adsorption equation, originally derived from a continuity equation of mass balance between the gas entering an adsorbent bed and the sum of the gas adsorbed by plus that penetrating through the bed. We have found that for wellpacked adsorbent beds, the Dubinin-Polanyi equations for predicting adsorption space at equilibrium, based upon prior characterization of an adsorbent with a reference gas, could also be applied to gas flow conditions, and the kinetic capacity of the adsorbent predicted within close limits. Although no theoretical relationship exists for prediction of the adsorption rate constant, recent gas tests at high linear flow velocities have shown experimental evidence of the mass transfer limiting value for the rate constant. The functionalities of the kinetic saturation capacity and the mass transfer limited value for the adsorption rate constant have been incorporated into the modified Wheeler adsorption equation to provide an expanded equation permitting prediction by calculation of the breakthrough time of a gas through a well-packed bed of adsorbent granules.     

Optimum structured adsorbents for gas separation processes

Recent developments in separation technology by adsorption have included the development of new structured adsorbents which offer some attractive characteristics compared to a typical packed bed. These improved features include lower energy consumption, higher throughput and superior recovery and purity of product. However, the exact combination of structural, geometric parameters which yields optimum performance is unknown. This study formulates a methodology for comparison based on a variety of analytical and numerical models and uses it to examine the performance of different adsorbent configurations. In particular, monolithic, laminate and foam structures are evaluated and compared to a packed bed of pellets. The effects of physical adsorbent parameters which govern the performance of a PSA process are considered during model development. Comparisons are carried out based on mass transfer kinetics, adsorbent loading and pressure drop of a PSA system for CO₂/N₂ separation. The results indicated that structured adsorbents can provide superior throughput to packed beds provided their geometrical parameters exceed certain values. For example, laminate structures can offer superior performance to a packed bed of pellets only if the critical sheet thickness and spacing are less than about 0.2 mm. Each adsorbent structure should be designed to operate at its “optimal” velocity. When operating at velocities higher than the “optimal” value, the increase in pressure drop and length of the mass transfer zone more than offsets gains accrued through reduction in cycle time.     

Studies on Dynamic Adsorption Behaviour of Ethyl Acetate from Air on 5A and 13X Molecular Sieves

Experimental data for dynamic adsorption of ethyl acetate present in air using 5A and 13X molecular sieves are generated with variations of inlet adsorbate concentration, inlet velocity and bed diameter to bed length ratio to study their effects on the adsorber bed performance. Mathematical model based on Linear Driving Force approximation is validated with experimental data and simulated to understand effects of other pertinent parameters such as overall mass transfer coefficient, saturation capacity and bed to wall heat transfer coefficient. 13X molecular sieve with higher capacity than 5A shows closer to ideal adsorption behaviour. Mass transfer rate is controlled by pore diffusion.     

规整复合吸附剂真空变压吸附分离CH4/N2工艺模拟与分析

为减少甲烷排放,实现低浓度煤层气有效资源化利用,探究了使用规整复合吸附剂真空变压吸附富集低浓度煤层气的工艺。采用静态容积法测定了甲烷、氮气在规整复合吸附剂上的吸附等温线,同时建立了包括质量、热量和动量守恒在内的严格吸附床数学模型,设计了三塔连续进料的真空变压吸附工艺并进行模拟。分析了工艺达到循环稳态后吸附床层轴向温度分布和压力变化,并且探究了进料量、解吸压力、原料气中甲烷浓度和吸附压力对纯度、回收率、工艺能耗和吸附剂产率等工艺性能的影响。模拟结果表明,在进料量为100 L·min^-1,解吸压力为0.1 bar（1 bar=0.1 MPa）,原料气甲烷浓度为30%,吸附压力为3 bar时可以生产纯度为59.07%,回收率为93.64%的富CH₄产品气,同时单位能耗为18.70 kJ·mol^-1,吸附剂产率为4.56 mol·h^-1·kg^-1。表明规整吸附剂对CH₄/N₂具有良好的吸附分离效果,能够实现低浓度煤层气中甲烷高效富集。     

真空变压吸附提纯沼气的实验

以煤基碳分子筛为沼气净化吸附剂,借助扫描电镜观察了碳分子筛的表面形貌,并通过物理化学吸附仪表征了碳分子筛的孔径分布。基于静态容积法测定了CO₂与CH₄在碳分子筛的静态吸附量,并估算了CO₂与CH₄在碳分子筛的动力学扩散系数。单塔穿透实验考察了吸附压力与进料流量对原料气中CO₂穿透曲线的影响,选取吸附压力为0.3 MPa,进料流量为4 L·min-1进行两塔六步真空变压吸附提纯沼气的实验研究,并考察了吸附步骤时长与产品气冲洗率对CH₄富集效果的影响。实验结果表明,吸附步骤时长为140 s,冲洗率为0.05时,产品气中CH₄纯度可达98%,收率可达82%。     

Effects of Adsorbent Characteristics on Adiabatic Vacuum Swing Adsorption Processes for Solvent Vapor Recovery

The effects of the adsorbent characteristics on the performance parameters and periodic state behavior of the vacuum swing adsorption (VSA) solvent vapor recovery (SVR) processes are examined and optimized. The adsorbent characteristics studied were the adsorbent particle's porosity, density, radius and heat capacity, the packed bed void fraction, the isosteric heat of adsorption, the monolayer saturation limit of the solvent molecules on the adsorbent, the adsorbent's affinity to adsorb the solvent molecules and the mass transfer coefficient for the adsorption of the solvent molecules. It was found that the best VSA‐SVR process performances can be obtained using adsorbents characterized by the minimum possible packed bed void fraction and particle porosity, with the maximum possible adsorbent heat capacity and density, adsorption monolayer saturation capacity and mass transfer coefficient, and at intermediate adsorption affinity and isosteric heat of adsorption of the solvent molecules.     

A kinetic study of the adsorption and desorption process of two commercial molecular sieves

A mathematical model and its numerical solution is presented to describe adiabatic adsorption—desorption processes in a fixed bed when the mass and heat transfer can be described by external film transfer coefficients only, which is especially interesting in the case of non-uniform, irregular particles. A new method to measure such rates is presented, based on continuous weighing of a through-circulated bed. The measured rates can be checked against the difference in humidity and temperature between the outlet and inlet air in order to minimize errors.The comparison between experimental results and calculations showed that the adsorption process in a bed of molecular sieve pellets can not be described with a constant mass transfer coefficient; the desorption process is better described although not entirely satisfactorily. In the case of a honeycomb molecular sieve, a constant mass transfer coefficient described both the adsorption and desorption processes satisfactorily.     

VOCs在分子筛上吸附性能的研究进展

简单介绍了一些常见分子筛的构型及特点,讨论了不同构型分子筛对各种VOCs废气吸附效果的研究进展。总结了各类分子筛对VOCs的吸附特性,发现立方构型的分子筛对VOCs废气的吸附效果最佳。小结了影响分子筛吸附性能的因素,发现分子筛的比表面积、孔容、硅铝比、表面官能团等自身性质都会对吸附VOCs废气的性能产生一定的影响。另外,分子筛的吸附容量还与吸附时的进气流速、入口气体浓度、吸附剂床层高度等工况有关。最后,对现有研究做了总结与展望,为分子筛吸附VOCs的合理应用提供了理论支持。     

Air separation by pressure swing adsorption on a carbon molecular sieve

A simplified dynamic model for a PSA air separation process is developed based on linearized mass transfer rate expressions and binary Langmuir equilibrium. Constant pressure is assumed during adsorption and desorption steps but the variation in flow rate through the column due to adsorption is accounted for. The model predictions, using independently measured kinetic and equilibrium data are compared with experimental results obtained in a simple two-bed air separation PSA system packed with a carbon molecular sieve adsorbent. The model is shown to provide a good representation of the experimentally observed behaviour over a wide range of conditions.     

Sensitivity analysis of adsorption bed behavior: Examination of pulse inputs and layered-bed optimization

A mathematical model is developed to examine the sensitivity of the breakthrough of adsorption beds to system parameters. As the process model is integrated a single time, sensitivities are simultaneously calculated. The impact of mass and energy transfer effects and adsorbent layer thicknesses are determined by calculating the derivatives of the outlet concentration and outlet temperature. Several examples are considered. To establish a basis, the breakthrough of single beds is considered first. The adsorption of hexane on BPL activated carbon is contrasted with the adsorption of nitrogen on carbon molecular sieve, and combined mass and energy effects are considered by studying the adsorption of nitrogen on BPL activated carbon. The sensitivity data are then applied to determine the optimum bed layering of a two-layer, two-bed PSA system. The solution method presented can be adapted for the sensitivity analysis and subsequent optimization of a large number of adsorption systems.