中间气两步充压对快速真空变压吸附制氧的影响

针对快速变压吸附制氧浓度和回收率低问题,提出了用于提高产氧浓度和回收率的中间气两步充压的快速真空变压吸附流程,并对该流程进行了研究。结果表明：在快速真空变压吸附制氧过程中,中间气先在出气端充压可以有效提高产氧浓度,之后再在进气端充压可提高氧气回收率。出气端充压前中间气压力及氧浓度和进气端充压后床层压力是影响产氧浓度和回收率提高的关键参数。当吸附和解吸压力分别为240、60 kPa时,循环氧气回收率为34.57%,且每天产单位吨氧需吸附剂量为61.18 kg·TPD^-1。     

用于乙醇脱水的生物质吸附性能

The adsorption capability of paddy flour and maize flour for gaseous phase selective adsorption for ethanol dehydration was investigated via a bench-test fixed-bed adsorber at constant temperature. Ethanol concentration in the feed was 93.4% (mass) and each of the dried biomass was used as adsorbent, and breakthrough curves and temperature distribution in adsorptive bed were obtained for different bed depths,superficial velocities, granularities of adsorbent and temperatures. Bed pressure drop curves for different bed depths and superficial velocities were also measured. A product of ethanol purity of 99.5% (mass) could be obtained through both kinds of biomass adsorbent. When 99.5% (mass) of ethanol purity is defined as the breakthrough point, the production capacity for either adsorbent was within 0.0915-0.2256 (gram product/gram adsorbent). Tests on pure ethanol adsorption were also performed to extrapolate the selectivity of both adsorbents.     

Evaluation of pressure-temperature swing adsorption for sulfur hexafluoride (SF<Subscript>6</Subscript>) recovery from SF<Subscript>6</Subscript> and N<Subscript>2</Subscript> gas mixture

The separation/concentration of SF₆, a strong greenhouse gas, of 1.3% in N₂ was investigated using pressure-temperature swing adsorption (PTSA) with activated carbon. To screen an effective adsorbent to be used for PTSA, adsorption isotherms on the selected adsorbents were obtained. Among the studied adsorbents, AC-1, a coconut-shell based commercial activated carbon, showed the largest adsorption amount of 3.5 mmol-SF₆/g-carbon at 303.65 K and 3 atm and the highest selectivity among the adsorbents tested. Its adsorption isotherm was well fit into Langmuir-Freundlich model. Before feasibility test of PTSA, a series of experiments were performed to investigate the effect of operating parameters including adsorption pressure, feed flow rate, desorption temperature and evacuation time on the PTSA performance using the 3-step PTSA cycle (pressurization, adsorption and regeneration-recovery). As the adsorption pressure, desorption temperature and evacuation time were increased, respectively, purity and recovery increased. Increasing the feed flow rate resulted in low purity and recovery. The maximum purity of 19.5% and recovery of 50.1% were obtained with adsorption pressure of 2.5 atm, desorption temperature of 200 °C and evacuation of 1 hour.     

Enrichment of coal‐bed methane by PSA complemented with CO2 displacement

A PSA cycle complemented with CO₂ displacement was studied for enriching coal‐bed methane (CBM). The column was first pressurized to the adsorption pressure with feed gas, and then N₂ was produced at column top in step 2. The feed gas switched to CO₂ at the end of step 2, and the adsorbed CH₄ was displaced and pushed to column top by CO₂ becoming the second column‐top product in step 3. The CO₂ stream was shut off before it broke through the sorption bed. Then bed regeneration followed. A series of CH₄/N₂ mixtures containing 17.62 to 51.33% CH₄ was used for feed gas. It was experimentally shown that the product concentration was higher than 90%, and methane recovery was higher than 98% even for the feed of low‐methane concentration. Displacement at ambient pressure was shown more efficient than the displacement at adsorption pressure for the enrichment. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

快速变压吸附制氢工艺的模拟与分析

目前工业上主要通过变压吸附技术从蒸汽甲烷重整气中制取氢产品气。然而,能源需求量的快速增加使得传统变压吸附技术在产量方面的不足越发明显。为此,进行了快速变压吸附从蒸汽甲烷重整气中制取氢气的模拟研究。采用活性炭和5A分子筛作为吸附剂,并以测得的原料气中各组分在两种吸附剂上的吸附数据为基础,进行了六塔快速变压吸附工艺的数值模拟与分析。在分析了塔内温度、压力和固相的浓度分布后,探究了进料流量、双层吸附剂高度比以及冲洗进料比三个操作参数对于快速变压吸附工艺性能的影响,结果表明：原料气组成为H₂/CH₄/CO/CO₂=76%/3.5%/0.5%/20%,吸附压力为22 bar（1 bar=10⁵ Pa）,解吸吹扫压力为1.0 bar,处理量为0.8875 mol·s^-1,吸附剂床层高度比为0.5∶0.5,冲洗进料比为22.37%时,可获得H₂纯度99.90%,回收率69.88%,此时H₂产量为0.4713 mol·s^-1。相比之下,氢气纯度为99.90%时,尽管PSA工艺回收率为83.40%,但处理量只有0.39 mol·s^-1,因此H₂产量仅为0.2472 mol·s^-1。     

Novel design and performance of a medical oxygen concentrator using a rapid pressure swing adsorption concept

A novel design of a compact rapid pressure swing adsorption system consisting of a single adsorber enclosed inside a product storage tank is proposed for application as a medical oxygen concentrator (MOC). A self‐contained test unit for the process is constructed which is capable of directly and continuously producing 1–3 sl/m of 90% O₂ from compressed air. Pelletized LiLSX zeolite is used as the air separation adsorbent. Steady state process performance data [bed size factor (BSF) and O₂ recovery (R) as functions of total cycle time (t_c)], as well as transient, cyclic, adsorber pressure, and temperature profiles are presented. A four‐step Skarstrom‐like pressure swing adsorption cycle was used. Two options for column pressurization, (a) using compressed feed air cocurrently or (b) using a part of the oxygen‐enriched product gas counter‐currently were evaluated. Option (b) exhibited superior performance. The optimum total cycle time for option (b) was 5–6 s where the BSF was lowest (～45 kgs/TPD O₂) and the corresponding R was ～29.3%. These numbers indicate that the adsorbent inventory of a MOC can be potentially reduced by a factor of three while offering a ～10–20% higher O₂ recovery compared to a typical commercial unit. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3330–3335, 2014     

流化床用树脂基球形活性炭及其VOCs吸附性能

以聚苯乙烯树脂为原料,采用水蒸气活化、氯化锌活化及水蒸气?氯化锌协同活化方法制备了3种流化床用树脂基球形活性炭,采用固定床反应器考察了活性炭对乙酸乙酯的动态吸附行为,对比了其传质区长度,并利用Yoon?Nelson模型对实验数据进行了拟合. 结果表明,3种活性炭的摩擦磨损指数均小于0.1%,耐磨性能出色,物理、化学协同活化活性炭比表面积高达1702.49 m2/g,对二甲苯的静态吸附容量达0.86 g/g.     

气源温度与解吸过程对变压吸附制氧效果的影响

研究了气源温度和解吸条件对制氧效果的影响,结果表明：细长解吸管路会导致吸附塔内氧浓度波前沿在吸附周期内极易穿透床层,在产氧期及间歇期都会有低浓度氧流入储氧罐,造成氧浓度和流量下降;较高的气源温度有利于分子筛解吸再生,在15～65 ℃内,平均每升高10 ℃,产氧体积分数可以提高1.2%。     

Production of argon free oxygen by adsorptive air separation on Ag‐ETS‐10

The purification of different components of air, such as oxygen, nitrogen, and argon, is an important industrial process. Pressure swing adsorption (PSA) is surpassing the traditional cryogenic distillation for many air separation applications, because of its lower energy consumption. Unfortunately, the oxygen product purity in an industrial PSA process is typically limited to 95% due to the presence of argon which always shows the same adsorption equilibrium properties as oxygen on most molecular sieves. Recent work investigating the adsorption of nitrogen, oxygen and argon on the surface of silver‐exchanged Engelhard Titanosilicate‐10 (ETS‐10), indicates that this molecular sieve is promising as an adsorbent capable of producing high‐purity oxygen. High‐purity oxygen (99.7+%) was generated using a bed of Ag‐ETS‐10 granules to separate air (78% N₂, 21% O₂, 1% Ar) at 25°C and 100 kPa, with an O₂ recovery rate greater than 30%. © 2012 American Institute of Chemical Engineers AIChE J, 59: 982–987, 2013     

基于双回流变压吸附工艺的空气分离模拟及分析

双回流变压吸附是一种在吸附塔中间位置进料,塔顶和塔底分别采用轻、重组分回流的变压吸附过程,能够同时生产两种高纯度、高回收率的产品气。以实验室自主合成的LiLSX分子筛为吸附剂,利用Aspen Adsorption模拟软件,对进料组成为78%N₂/21%O₂/1%Ar的实际空气进行了两塔双回流变压吸附的模拟研究。模拟结果表明：当原料气为78%N₂/21%O₂/1%Ar,吸附压力为2 bar(1 bar=10⁵ Pa),解吸压力为0.3 bar,进料量为0.4 m³/h,轻组分回流流量为0.095 L/min,重组分回流流量为5.22 L/min时,能够得到体积分数为95.67%的O₂和体积分数为98.25%的N₂,回收率分别为94.60%和99.91%。并且进一步探究了进料位置、吸附时间、轻组分回流流量、重组分产品气流量等因素对O₂和N₂两种产品气纯度和回收率的影响。     

Performance Comparison of Different Separation Systems for H2 Recovery from Catalytic Reforming Unit Off‐Gas Streams

The performance of pressure swing adsorption (PSA), membrane separation, and gas absorption systems for H₂ recovery from refinery off‐gas stream was studied by simulation‐based data. The PSA process was simulated using adsorbents of silica gel and activated carbon for removing heavy and light hydrocarbons. The mole fraction profiles of all components and the relationship between hydrogen purity and recovery as a function of feed pressure were examined. The solution‐diffusion model was applied for modeling and simulation of a one‐stage membrane process. The gas absorption process with a tower tray was simulated at sub‐zero temperature and the correlation between hydrogen purity and recovery as a function of tower pressure and temperature was evaluated at different solvent flow rates.     

Characteristics of a Pressurized Gas‐Solid Magnetically Fluidized Bed

The hydrodynamic, heat and mass transfer characteristics of a pressurized co‐current gas‐solid magnetically fluidized bed (MFB) were systematically investigated considering major influence factors, such as magnetic field strength, superficial gas velocity, and operating pressure. It was shown that this pressurized gas‐solid MFB has the advantages of a wider operation range of the superficial gas velocity under bubble‐free particulate fluidization, a larger bed voidage with smaller pressure drop across the bed, and larger heat transfer efficiency, compared with a conventional fluidized bed. Moreover, the minimum bubbling velocity, gas‐solid mass, and heat transfer coefficients were correlated at high accuracy within the investigated range of operating conditions.     

Optimal design of a four‐zone simulated moving bed process for separation of homoharringtonine and harringtonine

A simulated moving bed (SMB) technology was applied to the separation of homoharringtonine (HHT) and harringtonine (HT), which were known to have the potentiality of being used as anti‐cancer agents. First, a series of pulse injection experiments were performed for estimation of the adsorption isotherm and mass‐transfer parameters of HHT and HT. The estimated parameters were utilised in the SMB optimisation tool based on the standing wave design method. From the optimisation tool prepared, the SMB operating parameters (zone flow rates and step time) that led to the highest throughput were obtained under the constraints of product purities (=99.0%) and pressure drop (≤1000 psi). Such an optimisation work was then extended to determine an optimal size of the adsorbent particle for the SMB of interest. The results showed that a particle size of 29 µm was the optimal one for maximising the SMB throughput under the conditions that the column configuration was 2–2–2–2 and the length of each column was 25 cm. If the SMB had the particle size other than 29 µm, its throughput was limited by either the maximum operating pressure or the mass‐transfer efficiency. Finally, an efficient procedure of removing a mobile‐phase additive (ammonium formate) from the product stream of the aforementioned SMB system was developed using a liquid–liquid extraction (LLE) technique. From the results of this study, it was confirmed that the SMB process coupled with a LLE procedure could be highly effective in separating HHT and HT with high throughout and high purity.     

Effect of bed void volume on pressure vacuum swing adsorption for air separation

The effects of a poorly packed bed on the pressure vacuum swing adsorption (PVSA) process were investigated experimentally and theoretically by a five-step two-bed PVSA system. At first, the adsorption dynamics of a zeolite LiX bed for air separation (78 mol% N₂, 21 mol% O₂ and 1 mol% Ar) was studied at various adsorption pressures and flow rates. In breakthrough results, the effect of adsorption pressure on variations in bed temperature was greater than that of the feed flow rate. A combined roll-up of Ar and O₂ by N₂ propagation was observed and the roll-up plateau reached about 4 mol%. The fluid dynamic behavior of the poorly packed bed was simulated at each step in the PVSA process. The pressure and velocity profiles in the non-isobaric steps were clearly different from those of a normally packed bed. The two-bed PVSA process using one poorly packed bed with additional 1% void volume in feed end of bed could produce a purity of 92.3mol% O₂ from air, which was almost 1% purity lower than the PVSA with normal two beds. Even small asymmetry between beds, due to poor bed packing, could greatly reduce the product purity in the PVSA process.     

颗粒直径对吸附分离影响的数值模拟

基于Fluent的多孔介质模型,建立了变压吸附制氧发生器的立式填充床模型。采用用户自定义函数功能,以反映吸附传质、传热,并将多孔介质单相模型整合为更精确的气固两相耦合模型。在此基础上,模拟了吸附颗粒直径对气相压力、速度、床层压降以及氧气分离浓度、回收率等参数的影响情况。结果表明：床层压降随颗粒直径的增大而减小;床层对入口急流的抗穿透性能随颗粒直径的增大而减小;相同条件下,采用较小颗粒直径能够提高氧气分离浓度、回收率,原因在于小颗粒直径降低了床层内气体的流速,增加了吸附时间,促进了吸附的进行。     

Vacuum pressure swing adsorption process for coalbed methane enrichment

The enrichment of low concentration coalbed methane using adsorption process with activated carbon adsorbent was studied in this work.Adsorption isotherms of methane,nitrogen and carbon dioxide on activated carbon were measured by volumetric method,meanwhile a series of breakthrough tests with single component,binary components and three components feed mixture has been performed for exploring dynamic adsorption behaviors.Moreover,a rigorous mathematical model of adsorption bed containing mass,energy,and momentum conservation equation as well as dual-site Langmuir model with the Linear driving force model for gas-solid phase mass transfer has been proposed for numerical modeling and simulation of fixed bed breakthrough process and vacuum pressure swing adsorption process.Furthermore,the lumped mass transfer coefficient of methane,nitrogen and carbon dioxide on activated carbon adsorbent has been determined to be 0.3 s~(-1),1.0 s~(-1) and 0.06 s~(-1) by fitting the breakthrough curves using numerical calculation.Additionally,a six bed VPSA process with twelve step cycle sequence has been proposed and investigated for low concentration coalbed methane enrichment.Results demonstrated that the methane molar fraction in feed mixture ranged from 10% to 50% could be enriched to 32.15% to 88.75% methane in heavy product gas with a methane recovery higher than 83%under the adsorption pressure of 3 bar(1 bar=10~5 Pa) and desorption pressure of 0.1 bar.Energy consumption of this VPSA process was varied from 0.165 kW·h·m~(-3) CH_4 to 0.649 kW·h·m~(-3) CH_4.Finally,a dual-stage VPSA process has been successfully developed to upgrade a low concentration coalbed methane containing 20% methane to a target product gas with methane purity higher than 90%,meanwhile the total methane recovery was up to 98.71% with a total energy consumption of 0.504 kW·h·m~(-3) CH_4.     

节能型 VPSA 富氧工艺优化模拟

根据变压吸附分离原理,建立数学模型,并利用Aspen Adsim软件对三塔VPSA富氧工艺过程进行模拟。通过调整模拟参数考查了循环周期、均压时间等对富氧效果的影响。为了降低工艺能耗,一方面在保证产品气氧气浓度以及回收率的基础上尽量降低吸附压力与解吸压力比,另一方面当吸附塔压力低于大气压力时,借助于压降驱动力采取常压进气方式。结果表明：在本模拟工艺中,当循环时间75 s,均压时间4 s,吸附、解吸压力比为2.88时,得到产品气氧气体积分数为94.6%,回收率为56.6%。     

Linking micro‐scale predictions of capillary forces to macro‐scale fluidization experiments in humid environments

The effects of increasing relative humidity (RH) on fluidization/defluidization are investigated experimentally and understood via particle‐level predictions for the resulting capillary force. Experimentally, defluidization is found to be more sensitive to small changes in RH than fluidization. This sensitivity is captured by a new defluidization velocity U_df, which characterizes the curvature of the defluidization plot (pressure drop vs. velocity) observed between the fully‐fluidized (constant pressure drop) and packed‐bed (linear pressure drop dependence on velocity) states; this curvature is indicative of a partially‐fluidized state arising from humidity induced cohesion. Plots of U_df vs. RH reveal two key behaviors, namely U_df gradually increases with a relatively constant slope, followed by an abrupt increase at RH ～55%. Furthermore, the bed transitions from Group A to Group C behavior between RH of approximately 60–65%. From a physical standpoint, these macro‐scale trends are explained via a theory for capillary forces that, for the first time, incorporates measured values of particle surface roughness. Specifically, a model for the cohesive energy of rough surfaces in humid environments shows the same qualitative behavior as U_df vs. RH for RH <55%, unlike predictions of the cohesive force. Furthermore, the abrupt transition at RH ～60–65% is explained via the previously observed onset of liquid‐like water adsorption, rather than crystal/ice‐like adsorption, onto glass surfaces. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3585–3597, 2016     

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。     

Heterogeneous Reactor Modeling of an Industrial Multitubular Packed‐Bed Ethylene Oxide Reactor

The one‐dimensional heterogeneous model of an industrial multitubular packed‐bed ethylene oxide (EO) reactor was developed using the equation‐oriented platform Aspen Custom Modeler. Reactor operation was optimized in terms of maximized EO production and selectivity and enhanced safety related to the presence of oxygen in the EO reactor. Good agreement was found between the model results during validation against the available information under identical operating conditions. The model predicts the behavior of the EO reaction and demonstrates the extent of catalyst utilization with product distribution, product yield, by‐product formation, temperature and concentration profiles, over time and along the length of the reactor or catalyst bed. The model sensitivity studies compute the optimum feed flow, oxygen concentration, feed pressure, etc. and suggest the best operational philosophy.