带循环的二阶变压吸附碳捕集工艺模拟、实验及分析

针对日益严重的温室效应及传统CO₂捕集和储存技术的不足,设计带循环的二阶四塔变压吸附装置捕集电厂烟道气中的二氧化碳,采用炭分子筛作为第一阶二塔处理装置吸附剂,采用13X作为第二阶二塔处理装置的吸附剂。建立上述工艺的数学模型,通过实验验证数学模型和模拟结果的准确性。模拟结果表明,本工艺可以将烟道气中的CO₂（15%）富集为纯度95%的产品气,收率为93.92%,工艺处理量为4.576 mol CO₂·h^-1·kg^-1,能耗为0.847 MJ·（kg CO₂）^-1,通过对比,本工艺具有处理量大、回收率高、纯度高的优点。在此基础上,根据数学模型分析二阶床层在一个周期内的压力变化、温度分布、固相和气相组成分布、能耗组成、生产能力。     

烟道气低浓度二氧化碳的变压吸附法富集研究

建立了3塔变压吸附分离装置,对烟道气中的低浓度二氧化碳(体积分数12%左右)的富集进行了实验研究,考察了吸附压力和吸附时间、置换压力和置换时间及解吸压力对产品气浓度和回收率的影响.结果表明:基于硅胶的PSA技术能够对炉窑尾气中的低浓度二氧化碳气体进行浓缩;吸附压力和吸附时间对变压吸附回收浓缩烟道气中低浓度的二氧化碳有着重要的影响,为了得到较高浓度的二氧化碳气体,吸附压力不能太低,不同的吸附压力下有着不同的最佳吸附时间;一定条件下提高置换气的流量和压力会提高二氧化碳气体的浓度,但是回收率会下降.     

13X-APG沸石真空变压变温耦合工艺吸附捕集烟道气中CO2

采用13X-APG沸石吸附捕集烟道气中CO2,并研发了五步循环真空变压变温(VTSA)耦合吸附捕集工艺. 实验测定了循环吸附/解吸过程中吸附剂再生率、烟道气中CO2回收率、产品气量及产品气中CO2纯度,并与传统的真空变压吸附工艺(VSA)和变温吸附工艺(TSA)比较. 由于VTSA在真空解吸的同时加热吸附剂,减少了真空泵的电耗,可在较温和的真空下(约3′103 Pa)操作,附加的吸附剂再生温度也不高,90~150℃下吸附剂再生率达97%以上,CO2回收率达98%以上. 吸附剂捕集CO2的量可提高到1.8 mol/kg,是VSA工艺产品气量的2倍,且产品气中CO2纯度提高到90%以上.     

膜分离-变压吸附协同捕集低浓度烟气二氧化碳工艺模拟研究

利用软件PROⅡ和Aspen Adsorption分别模拟协同工艺中膜分离和变压吸附过程,通过引入气体流量修正系数解决气体流量不匹配问题,提高膜-变压吸附协同碳捕集工艺模拟的准确性。案例研究表明,引入流量修正系数解决了协同工艺模拟过程中出现的气体流量不匹配问题,实现了稳态膜分离和动态循环变压吸附过程的耦合。与以往的膜-变压吸附协同工艺模拟方法相比较,更好地识别了能耗降低和捕集率提升的技术途径。     

真空变压吸附捕集烟道气中二氧化碳的模拟、实验及分析

采用工业硅胶作为吸附剂,利用两塔变压吸附装置进行了烟道气变压吸附碳捕集实验。利用gPROMS软件建立两塔变压吸附模型对实验过程进行模拟,对比了实验和模拟的结果,验证了模型的准确性。通过两塔变压吸附可将15%的CO_2富集到74%,收率为91.52%。在模型基础上考察了变压吸附碳捕集过程中进料量、吸附时间、顺放压力与二氧化碳收率、纯度和能耗的关系,定性分析了吸附塔压力和进料量对压缩机能耗的影响。结果表明:增大进料量、延长吸附时间、降低顺放压力,可以有效提高产品气中CO_2浓度,但同时也导致收率的下降,前两者还会造成单位能耗的增加;吸附压力越高,进料流量越大,压缩机能耗越大。     

真空变温吸附捕集干烟道气中CO2的模拟研究

为减缓气候变化,减少CO₂的排放,对真空变温吸附(TVSA)从干烟道气中捕集CO₂进行了系统的研究。以沸石13X为吸附剂,设计了实验室规模的4塔连续进料的TVSA工艺,并建立数学模型进行数值模拟。模拟结果表明,通过四塔TVSA可获得纯度为97.54%,回收率为96.79%的CO₂产品气,其产率为1.7 mol· ( \mathrm{k} \mathrm{g} \text{?} \mathrm{a} \mathrm{d} \mathrm{s} ) ^-1·h^-1,能耗为3.14 \mathrm{M} \mathrm{J} · ( \mathrm{k} \mathrm{g} \text{?} \mathrm{C} {\mathrm{O}}_{\mathrm{2}} {)}_{}^{-\mathrm{1}} 。此外,考察了进料量、循环回流步骤时间、真空度对产品气纯度、回收率、吸附剂产率和工艺能耗的影响,并且分析了塔内压力与温度变化,详细探讨了塔内气固相浓度随轴向的分布。良好的工艺效果表明,TVSA有潜力成为一种能够生产高纯度高回收率的CO₂产品气,并具有良好经济效益的捕碳工艺。     

变温吸附碳捕集机组标准化测试方案探讨及性能实验

变温吸附（TSA）碳捕集技术是控制碳排放进而实现“双碳”目标的有效保障手段之一。然而,由于目前缺乏相对完善的计量体系和可执行的标准化测试方案,导致机组性能的测试结果差别较大,缺乏规律性所造成的趋势和性能迭代困难不利于TSA产业化发展。本文初步提出了包含测试工况、性能评价指标、数据的测量与采集三个方面的标准化测试方案,并对样机规模的实物机组进行了性能测试。结果表明,该套方案的可执行度高,可为相关机组的性能评价工作提供借鉴。此外,机组的性能测试结果显示,该机组的运行状态容易控制,纯度和回收率最高均能达到90%以上,但是能源效率在3.5%～6.5%之间,提升潜力大。对标分析发现机组内的管道等部件损失的能耗占比30%～40%,所以需要通过优化管道线路布置、提高吸附腔内换热效率、优化解吸温度和真空压力等运行参数等方式来进一步降耗提效。     

二氧化碳捕集技术研究进展

随着全球工业的快速发展,二氧化碳的大量排放被认为是造成气候变暖最主要原因,二氧化碳的捕集和封存已经成为研究的热点,本文综述了近年来CO2捕集技术的研究进展,主要有燃烧后捕集、燃烧前捕集和富氧燃烧三条技术路线,最后提出了可以提高二氧化碳捕集能力的策略与展望。     

二氧化碳捕集技术研究进展

在“碳达峰、碳中和”的双重任务下,CO₂捕集已经成为今后工业发展的必然趋势。分别介绍了燃烧前捕集、燃烧后捕集以及富氧燃烧技术,并总结了相关技术还存在的问题。同时,系统地总结了国内外主要的CO₂捕集方法,分析了不同捕集方法的优缺点,并针对不同行业提出了合理的捕集方法。其中,重点介绍了溶液吸收法,通过对现有吸收液存在的能耗高、易挥发、毒性大的问题,提出了今后溶液吸收法的主要发展方向,并针对现有吸附法存在的问题提出开发新型低温、低压、低成本的固体吸附材料及相关工艺的研究思路。     

变电吸附二氧化碳捕集技术研究进展

基于变电吸附的碳捕集技术,通过“通电-断电”实现摆荡模式,利用电能焦耳效应产生热能,驱动吸附剂实现连续地吸附与再生。相对于变温吸附,其输入高品位电能,因此可驱动碳源、碳汇之间的大浓度差富集,近年来备受关注。然而,目前限制变电吸附碳捕集技术应用的主要问题是较高的能耗与较低的产率。据此,本文总结了近年来国内外变电吸附碳捕集技术的研究进展并提出了技术展望。首先讨论了变电吸附碳捕集的基本原理,其次综述了近十年变电吸附碳捕集技术中吸附剂、循环结构的研究进展及发展趋势,应用热力学第二定律效率对变电吸附碳捕集系统展开评价。最后,对变电吸附碳捕集技术发展趋势进行展望,变电吸附技术具备规模化竞争力的关键为：在改善吸附剂导电和捕集性能的基础上,改进吸附剂制备工艺,关注吸附剂的加热形式以及吸附腔体内的电阻分配,尝试与其他碳捕集技术耦合进行分级捕集,与可再生能源进行集成。     

Design and experiment of high-productivity two-stage vacuum pressure swing adsorption process for carbon capturing from dry flue gas

A two-stage vacuum pressure swing adsorption (VPSA) process that coupled kinetically controlled and equilibrium controlled separation process with reflux has been investigated for capturing carbon dioxide from dry flue gas (85% N₂/15% CO₂). In the first enriching stage, carbon molecular sieve (CMS), which shows kinetic selectivity for CO₂/N₂, is adopted as the adsorbent to remove most N₂ in feed gas, thereby upgrading CO₂ and significantly reducing the amount for further refinement. The second stage loads zeolite 13X as adsorbent to purify the CO₂-rich flow from the first stage for meeting the requirements of National Energy Technology Laboratory. Series of experiments have been conducted for adsorption isotherms measuring and lab-scale experimental validation as well as analysis. The effect of feed composition on the separation performance of the PSA system was studied experimentally and theoretically here. The optimal results achieved 95.1% purity and 92.9% recovery with a high CO₂ productivity (1.89 mol CO₂·h^-1·kg^-1) and an appropriate energy consumption of 1.07 MJ·(kg CO₂)^-1. Further analysis has been carried out by simulation for explicating the temperature, pressure, and concentration distribution at cyclic steady state.     

CO2 capture from dry flue gas by vacuum swing adsorption: A pilot plant study

The capture and concentration of CO₂ from a dry flue gas by vacuum swing adsorption (VSA) has been experimentally demonstrated in a pilot plant. The pilot plant has the provision for using two coupled columns that are each packed with approximately 41 kg of Zeochem zeolite 13X. Breakthrough experiments were first carried out by perturbing a N₂ saturated bed with 15% CO₂ and 85% N₂ feed, which is representative of a dry flue gas from coal‐fired power plants. The breakthrough results showed long plateaus in temperature profiles confirming a near adiabatic behavior. In the process study, a basic four‐step vacuum swing adsorption (VSA) cycle comprising the following steps: pressurization with feed, adsorption, forward blowdown, and reverse evacuation was investigated first. In the absence of any coupling among the steps, a single bed was used. With this cycle configuration, CO₂ was concentrated to 95.9 ± 1% with a recovery of 86.4 ± 5.6%. To improve the process performance, a four‐step cycle with light product pressurization (LPP) using two beds was investigated. This cycle was able to achieve 94.8 ± 1% purity and 89.7 ± 5.6% recovery. The Department of Energy requirements are 95% purity and 90% recovery. The proposed underlying physics of performance improvement of the four‐step cycle with LPP has also been experimentally validated. The pilot plant results were then used for detailed validation of a one‐dimensional, nonisothermal, and nonisobaric model. Both transient profiles of various measured variables and cyclic steady state performance results were compared with the model predictions, and they were in good agreement. The energy consumptions in the pilot plant experiments were 339–583 ± 36.7 kWh tonne^?1 CO₂ captured and they were significantly different from the theoretical power consumptions obtained from isentropic compression calculations. The productivities were 0.87–1.4 ± 0.07 tonne CO₂ m^?3 adsorbent day^?1. The results from our pilot plant were also compared with available results from other pilot plant studies on CO₂ capture from flue gas. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1830–1842, 2014     

Strategies for CO2 capture from different CO2 emission sources by vacuum swing adsorption technology☆

Different VSA(Vacuum Swing Adsorption) cycles and process schemes have been evaluated to find suitable process configurations for effectively separating CO2 from flue gases from different industrial sectors. The cycles were studied using an adsorption simulator developed in our research group, which has been successfully used to predict experimental results over several years. Commercial zeolite APGIII and granular activated carbon were used as the adsorbents. Three-bed VSA cycles with- and without-product purge and 2-stage VSA systems have been investigated. It was found that for a feed gas containing 15% CO2(representing flue gas from power plants), high CO2 purities and recoveries could be obtained using a three-bed zeolite APGIII VSA unit for one stage capture, but with more stringent conditions such as deeper vacuum pressures of 1–3 k Pa. 2-stage VSA process operated in series allowed us to use simple process steps and operate at more realistic vacuum pressures. With a vacuum pressure of 10 k Pa, final CO2 purity of 95.3% with a recovery of 98.2% were obtained at specific power consumption of 0.55 MJ·(kg CO2)-1from feed gas containing15% CO2. These numbers compare very well with those obtained from a single stage process operating at1 k Pa vacuum pressure. The feed CO2 concentration was very influential in determining the desorption pressure necessary to achieve high separation efficiency. For feed gases containing N 30% CO2, a singlestage VSA capture process operating at moderate vacuum pressure and without a product purge, can achieve very high product purities and recoveries.     

Efficient capture of CO2 from flue gas at high temperature by tunable polyamine-based hybrid ionic liquids

For an ideal absorbent for CO₂ capture from flue gas, there are some key features including easy preparation, high stability, low absorption enthalpy, high capacity at high temperature and excellent reversibility. Herein, several polyamine-functionalized ionic liquids (ILs) were easily prepared from cheap polyamines and lithium salts, which exhibited significantly improved stability due to the presence of multisite coordinating interactions. The viscosity was reduced by introducing polyalcohol-based ILs, leading to polyamine-based hybrid ILs. Interestingly, these polyamine-based hybrid ILs exhibited high CO₂ capacity (4.09 mmol/g, 0.1 bar) at high temperature (80°C) and excellent reversibility in the presence of H₂O and O₂, which is superior to many other good absorbents. Moreover, these ILs also showed good performance for CO₂ capture from stimulated air (2.10 mmol/g, 380 ppm). We believe that this method with easy preparation, low cost, high efficiency and excellent reversibility has a great potential in the industrial capture of CO₂ from flue gas.     

Application of high‐pressure swing adsorption process for improvement of CO2 recovery system from flue gas

Although the super cold separator applied to the system for CO₂ recovery from flue gas can produce pure CO₂ liquid, the CO₂ recovery efficiency is low. Therefore, the addition of a PSA plant was considered for the secondary CO₂ recovery from the noncon‐densing gas to improve the efficiency. The PSA plant was operated for adsorption at the same pressure as that of the super cold separator and for desorption at the atmospheric pressure. From both the simulation and the experimental data, it was confirmed that CO₂ could be concentrated from 50% in the noncondensing gas to 70% in the recovery gas by the PSA plant and the CO₂ recovery efficiency of the plant was about 90%.     

Development of silica‐gel‐supported polyethylenimine sorbents for CO2 capture from flue gas

In order to reduce the sorbent preparation cost and improve its volume‐based sorption capacity, the use of an inexpensive and commercially available silica gel was explored as a support to prepare a solid polyethylenimine sorbent (PEI/SG) for CO₂ capture from flue gas. The effects of the pore volume and particle size of the silica gels, molecular weight of polyethylenimine and amount of polyethylenimine loaded, sorption temperature and moisture in the flue gas on the CO₂ sorption capacity of PEI/SG were examined. The sorption performance of the developed PEI/SG was evaluated by using a thermogravimetric analyzer and a fixed‐bed flow sorption system in comparison with the SBA‐15‐supported polyethylenimine sorbent (PEI/SBA‐15). The best PEI/SG sorbent showed a mass‐based CO₂ sorption capacity of 138 mg‐CO₂/g‐sorbent, which is almost the same as that of PEI/SBA‐15. In addition, the PEI/SG gave a high volume‐based sorption capacity of 83 mg‐CO₂/cm³‐sorbent, which is higher than that of PEI/SBA‐15 by a factor of 2.6. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2495–2502, 2012     

变温吸附碳捕集系统能效性能实验研究

燃烧后CO₂捕集技术（PCC）因易于与既有电厂结合而被认为是一项减少二氧化碳排放的重要技术。化学吸收、吸附和膜分离是PCC的主流技术。在CO₂吸附技术类中,变温吸附（TSA）是一种有效的吸附方法。近年来,TSA技术的能源消耗和能源转换效率问题成为人们对其大规模部署的关注焦点。然而,大多数的研究都是将数学模型和仿真方法应用于TSA的性能评估,缺乏足够的实验研究支持。为了对TSA系统的能源转化效率进行实验分析,开发了一套四步法TSA系统,能效性能是基本分离性能外的主要考察指标。实验采用沸石13X-APG作为吸附剂材料,根据实验测得的两组吸附等温线,计算了CO₂/N₂的吸附选择性系数。通过进气CO₂浓度、解吸时间、吸附温度和解吸温度对纯度、回收率、单位能耗和第二定律效率的影响分析,得到了4组实验结果。结果表明,第二定律效率的范围为3.24%～9.23%,回收率和纯度最高分别为83.97%和94.70%。解吸温度和进气CO₂浓度的升高,吸附温度的降低有利于分离及能效性能提升。延长解吸时间有利于分离和能效提升,但过长的操作时间反而使得效果变差,这会对工程中的运行策略优化产生积极的指导意义。     

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.