耦合膜分离的新型CO2低温捕集系统性能优化

CO₂捕集作为温室气体排放控制的有效手段已成为重要研究课题。作为新兴捕集技术之一,低温CO₂捕集因产品纯度高、无附加污染等优势受到关注。然而,该技术能耗和捕集率对于气体中CO₂浓度十分敏感,对于高CO₂浓度气体可获得较高的CO₂捕集率和较低能耗水平。基于此,本文提出了耦合膜分离的新型CO₂低温捕集系统,通过膜材料选择渗透性实现待捕集气体CO₂浓度主动调控,并在最优浓度下进行CO₂低温捕集。首先基于不同传统低温捕集系统特点,对比分析了不同耦合系统模式,从而确定了最优耦合系统结构。针对最优耦合系统进行了运行参数优化,并分别基于实现系统捕集能耗最低与捕集率最高的目标,获得了膜渗透侧CO₂浓度与进气CO₂浓度间的关系式,为该耦合系统中膜组件选型提供指导。研究表明,本文提出的耦合系统捕集能耗为1.92MJ/kgCO₂,相比于传统单一低温系统捕集能耗可降低16.5%。     

CO2捕集技术的研究现状

针对目前主要的CO2捕集技术进行了综述,总结了各种技术的优缺点,并阐述了各种方法目前存在的问题,指出了可能的改进方法,并提出未来CO2捕集技术研究的重点以及方向.     

燃烧后二氧化碳捕集技术与应用进展

二氧化碳是主要的温室气体之一，其大量排放已对全球的气候环境造成严重影响，迫切需要开发经济有效的碳捕集技术。目前，碳捕集技术主要有吸收分离法、吸附分离法、膜分离法和低温分离法。首先，介绍了碳捕集技术的发展现状、应用研究进展和未来发展趋势；总结了国内外碳捕集示范项目；重点对比了各碳捕集技术的优势与缺点，同时强调了捕集技术面临的困难与挑战；指出目前主要的碳捕集技术均难以独立实现高效、节能、经济的碳捕集分离，需针对不同的应用场景，选择适合的分离技术，并提出了适用分离场景的应用建议；最后，简要介绍了混合捕集技术的研究成果，提出混合捕集技术可能是一种突破单一捕集技术瓶颈的可行方法。     

膜技术用于CO2回收和捕集的研究进展

综述了近年来膜技术在CO2回收和捕集中的应用,分别介绍了高分子膜、无机膜、有机-无机杂化膜、促进传递膜、膜生物反应器用于回收和捕集CO2的研究现状和优缺点。针对目前膜技术用于回收和捕集CO2中的不足,提出了今后研究工作的发展方向。     

温室气体CO2的捕集和分离--分离技术面临的挑战与机遇

介绍了采用溶剂吸收、膜分离和变压吸附等方法捕集和分离温室气体CO2的最新进展,并对技术发展动向进行了讨论。     

有机多孔聚合物CO2捕集及分离性能的研究进展

有机多孔聚合物（porous organic polymers,POPs）是一类由有机构建单元连接而形成的新型多孔材料。由于其优异的物理化学稳定性以及CO₂吸附能力,近年来有关POPs在CO₂捕集和分离的研究成为一大研究热点。大量具有优异孔性质（比表面积和孔容）的POPs通过不同有机合成反应被成功地开发出来应用于CO₂吸附分离过程。本文介绍了POPs材料的CO₂捕集与分离性能的研究现状,总结了提高POPs材料CO₂分离性能的合成策略,重点分析了可以通过功能化增强吸附剂与二氧化碳分子之间的相互作用,来提高材料的CO₂分离能力的方法。     

CO2的捕集及资源化利用

新型吸附材料对CO₂进行吸附分离并催化转化为高附加值产品,具有绿色清洁的优点,是未来全球应对气候变化的重要技术选择之一,但在复杂环境CO₂的捕集过程中存在无法高效吸附分离以及成本较高的问题。本文简述了CO₂吸附材料最新研究进展以及资源化利用的有效途径,主要介绍了金属有机骨架（MOF）、分子筛、多孔碳材料、共价有机骨架（COF）等吸附材料的物化性质等对吸附量和选择性的影响,从催化转化的角度对合成甲酸、甲醇以及烯烃等小分子化合物进行了论述。基于含CO₂废气的综合治理问题,探讨了将钢铁行业中的烟道气以及高炉煤气等进行加氢的可行性,在CO₂捕集和转化的科学技术进步上开拓了新思路,对CO₂更加清洁高效利用,实现低碳化、智能化多能融合进行展望。     

低分压CO2回收新技术捕集燃煤电厂烟气CO2

基于分子模拟和设计,开发了以一乙醇胺(MEA)为主溶剂,优选添加了活性胺、抗氧化剂和缓蚀剂组成了适用于回收低分压CO2的优良复合吸收剂,在华能北京热电厂建立了我国第1套燃煤电站烟气CO2捕集示范装置,并完成了运行测试。结果表明:CO2回收装置出来的CO2纯度为99.5%(体积分数),每tCO2蒸汽消耗为3.5GJ,每tCO2溶液消耗小于1.5kg。该套装置的建成和各项指标试验的进行将为我国大规模推广电站CO2捕集奠定基础。     

碳质吸附剂对CO2的吸附、捕集和分离

温室效应日渐显著,如何减少温室气体CO2的排放以及如何将大气中的CO2富集、分离并加以应用逐渐成为科学研究的热点.碳质吸附材料因其优良的吸附性能和发达的孔隙结构,在气体分离领域起着重要的作用;同时碳质材料的化学性质稳定,可以在很广的工作条件下应用.由此,碳质材料作为CO2的分离和捕集介质在许多方面都具有很大的优势.本文简要介绍近年来运用碳质材料吸附、捕集和分离CO2的研究进展.     

跨临界CO2热泵系统的喷射器特性

在自行研制的跨临界CO₂热泵热水器实验台上,通过调节系统中阀门开度控制喷射器的进出口压力和温度,研究喷射器的流量、喷射系数、压缩比和效率的变化规律。实验结果表明:同时增大工作流体压力和引射流体压力可以提高喷射器的工作性能,减小工作流体压力或者增大引射流体压力可以提高喷射器的工作完善度。高效率喷射器的研制是优化跨临界CO₂热泵系统的关键要素。     

Partial O2-fired coal power plant with post-combustion CO2 capture: A retrofitting option for CO2 capture ready plants

In the work presented in this paper, an alternative process concept that can be applied as retrofitting option in coal-fired power plants for CO₂ capture is examined. The proposed concept is based on the combination of two fundamental CO₂ capture technologies, the partial oxyfuel mode in the furnace and the post-combustion solvent scrubbing. A 330 MW_el Greek lignite-fired power plant and a typical 600 MW_el hard coal plant have been examined for the process simulations. In a retrofit application of the ECO-Scrub technology, the existing power plant modifications are dominated by techno-economic restrictions regarding the boiler and the steam turbine islands. Heat integration from processes (air separation, CO₂ compression and purification and the flue gas treatment) can result in reduced energy and efficiency penalties. In the context of this work, heat integration options are illustrated and main results from thermodynamic simulations dealing with the most important features of the power plant with CO₂ capture are presented for both reference and retrofit case, providing a comparative view on the power plant net efficiency and energy consumptions for CO₂ capture. The operational characteristics as well as the main figures and diagrams of the plant’s heat balances are included.     

Properties of char particles obtained under O2/N2 and O2/CO2 combustion environments

Pulverized coal combustion in O₂/N₂ and O₂/CO₂ environments was investigated with a drop tube furnace. Results present that the reaction rate and burn-out degree of O₂/CO₂ chars (obtained in O₂/CO₂ environments) are lower than that of O₂/N₂ chars (obtained in O₂/N₂ environments) under the same experimental condition. It indicates that a higher O₂ concentration in O₂/CO₂ environment is needed to achieve the similar combustion characteristic to that in O₂/N₂ environment. The main differences between O₂/N₂ and O₂/CO₂ chars rely on the pore structure determined by N₂ adsorption and chemical structure measured by FT-IR. For O₂/CO₂ char, the surface is thick and the pores are compact which contribute to the fragmentation reduction of particles burning in O₂/CO₂ environment. The organic functional group elimination rate from the surface of O₂/CO₂ chars is slower or delayed. The present research results might have important implications for further understanding the intrinsic kinetics of pulverized coal combustion in O₂/CO₂ environment.     

Thermodynamic performance of O2/CO2 gas turbine cycle with chemical recuperation by CO2-reforming of methane

This paper proposes a novel power cycle system composed of chemical recuperative cycle with CO₂–NG (natural gas) reforming and an ammonia absorption refrigeration cycle. In which, the heat is recovered from the turbine exhaust to drive CO₂–NG reformer firstly, and then lower temperature heat from the turbine exhaust is provided with the ammonia absorption refrigeration system to generate chilled media, which is used to cool the turbine inlet gas except export. In this paper, a detailed thermodynamic analysis is carried out to reveal the performance of the proposed cycle and the influence of key parameters on performance is discussed. Based on 1 kg s⁻¹ of methane feedstock and the turbine inlet temperature of 1573 K, the simulation results shown that the optimized net power generation efficiency of the cycle rises up to 49.6% on the low-heating value and the exergy efficiency 47.9%, the new cycle system reached the net electric-power production 24.799 MW, the export chilled load 0.609 MW and 2.743 kg s⁻¹ liquid CO₂ was captured, achieved the goal of CO₂ and NO_x zero-emission.     

木质素磺酸钠在TiO2/水界面的吸附特性

木质素磺酸钠在固体表面的吸附特性决定了其应用性能,利用红外和紫外分光光度仪,采用剩余质量分数法研究了温度、pH值、无机盐和氢键破坏剂脲对木质素磺酸钠在TiO₂/水界面吸附动力学和等温吸附性能的影响,初步探讨了其在固液界面的吸附作用机理。结果表明,该吸附为单层多点式吸附,随着温度升高和pH值减小,木质素磺酸钠在TiO₂/水界面的吸附速率常数和饱和吸附量均增大,而离子强度的增大和脲的加入却使吸附速率常数减小;木质素磺酸钠在TiO₂/水界面的吸附驱动力为静电、疏水和氢键作用,疏水作用力可显著增加其吸附量。     

CO2 capture by adsorption with nitrogen enriched carbons

The success of CO₂ capture with solid sorbents is dependent on the development of a low cost sorbent with high CO₂ selectivity and adsorption capacity. Immobilised amines are expected to offer the benefits of liquid amines in the typical absorption process, with the added advantages that solids are easy to handle and that they do not give rise to corrosion problems. In this work, different alkylamines were evaluated as a potential source of basic sites for CO₂ capture, and a commercial activated carbon was used as a preliminary support in order to study the effect of the impregnation. The amine coating increased the basicity and nitrogen content of the carbon. However, it drastically reduced the microporous volume of the activated carbon, which is chiefly responsible for CO₂ physisorption, thus decreasing the capacity of raw carbon at room temperature.     

UV/H2O2氧化联合Ca(OH)2吸收同时脱硫脱硝

在小型紫外光-鼓泡床反应器中,对UV/H₂O₂氧化联合Ca(OH)₂吸收同时脱除燃煤烟气中NO与SO₂的主要影响因素[H₂O₂浓度、紫外光辐射强度、Ca(OH)₂浓度、NO浓度、溶液温度、烟气流量以及SO₂浓度]进行了考察。采用烟气分析仪和离子色谱仪分别对尾气中的NO₂和液相阴离子作了检测分析。结果显示:在本文所有实验条件下,SO₂均能实现完全脱除。随着H₂O₂浓度、紫外光辐射强度和Ca(OH)₂浓度的增加,NO的脱除效率均呈现先大幅度增加后轻微变化的趋势。NO脱除效率随烟气流量和NO浓度的增加均有大幅度下降。随着溶液温度和SO₂浓度的增加,NO脱除效率仅有微小的下降。离子色谱分析表明,反应产物主要是SO₄^2-和NO₃^-,同时有少量的NO₂^-产生。尾气中未能检测到有害气体NO₂。     

Cyclic CO2 capture behavior of KMnO4-doped CaO-based sorbent

This study examines the CO₂ capture behavior of KMnO₄-doped CaO-based sorbent during the multiple calcination/carbonation cycles. The cyclic carbonation behavior of CaCO₃ doped with KMnO₄ and the untreated CaCO₃ was investigated. The addition of KMnO₄ improves the cyclic carbonation rate of the sorbent above carbonation time of 257 s at each carbonation cycle. When the mass ratio of KMnO₄/CaCO₃ is about 0.5-0.8 wt.%, the sorbent can achieve an optimum carbonation conversion during the long-term cycles. The carbonation temperature of 660-710 °C is beneficial to cyclic carbonation of KMnO₄-doped CaCO₃. The addition of KMnO₄ improves the long-term performance of CaCO₃, resulting in directly measured conversion as high as 0.35 after 100 cycles, while the untreated CaCO₃ retains conversion less than 0.16 at the same reaction conditions. The addition of KMnO₄ decreases the surface area and pore volume of CaCO₃ after 1 cycle, but it maintains the surface area and pores between 26 nm and 175 nm of the sorbent during the multiple cycles. Calculation reveals that the addition of KMnO₄ improves the CO₂ capture efficiency significantly using a CaCO₃ calcination/carbonation cycle and decreases the amount of the fresh sorbent.     

Microporous phenol-formaldehyde resin-based adsorbents for pre-combustion CO2 capture

Different types of phenolic resins were used as precursor materials to prepare adsorbents for the separation of CO₂ in pre-combustion processes. In order to obtain highly microporous carbons with suitable characteristics for the separation of CO₂ and H₂ under high pressure conditions, phenol-formaldehyde resins were synthesised under different conditions. Resol resins were obtained by using an alkaline environment while Novolac resins were synthesised in the presence of acid catalysts. In addition, two organic additives, ethylene glycol (E) and polyethylene glycol (PE) were included in the synthesis. The phenolic resins thus prepared were carbonised at different temperatures and then physically activated with CO₂. The carbons produced were characterised in terms of texture, chemical composition and surface chemistry. Maximum CO₂ adsorption capacities at atmospheric pressure were determined in a thermogravimetric analyser. Values of up to 10.8 wt.% were achieved. The high-pressure adsorption of CO₂ at room temperature was determined in a high-pressure magnetic suspension balance. The carbons tested showed enhanced CO₂ uptakes at high pressures (up to 44.7 wt.% at 25 bar). In addition, it was confirmed that capture capacities depend highly on the microporosity of the samples, the narrow micropores (pore widths of less than 0.7 nm) being the most active in CO₂ adsorption at atmospheric pressure. The results presented in this work suggest that phenol-formaldehyde resin-derived activated carbons, particularly those prepared with the addition of ethylene glycol, show great potential as adsorbents for pre-combustion CO₂ capture.     

Reactivation and remaking of calcium aluminate pellets for CO2 capture

CaO-based pellets supported with aluminate cements show superior performance in carbonation/calcination cycles for high-temperature CO₂ capture. However, like other CaO-based sorbents, their CO₂ carrying activity is reduced after increasing numbers of cycles under high-temperature, high-CO₂ concentration conditions. In this work the feasibility of their reactivation by steam or water and remaking (reshaping) was investigated. The pellets, prepared from three limestones, Cadomin and Havelock (Canada) and Katowice (Poland, Upper Silesia), were tested in a thermogravimetric analyzer (TGA). The cycles were performed under realistic CO₂ capture conditions, which included calcination in 100% CO₂ at temperatures up to 950 °C. Typically, after 30 cycles, samples were hydrated for 5 min with saturated steam at 100 °C in a laboratory steam reactor (SR). Moreover, larger amounts of pellets were cycled in a tube furnace (TF), hydrated with water and reshaped, and tested to determine their CO₂ capture activity in the TGA. It was found that, after the hydration stage, pellets recovered their activity, and more interestingly, pellets that had experienced a longer series of cycles responded more favorably to reactivation. Moreover, it was found that conversion of pellets increased after about 70 cycles (23%), reaching 33% by about cycle 210, with no reactivation step. Scanning electron microscope (SEM) analyses showed that the morphology of the low-porosity shell formed at the pellet surface during cycles, which limits conversion, was eliminated after a short period (5 min) of steam hydration. The nitrogen physisorption analyses (BET, BJH) of reshaped spent pellets from cycles in the TF confirmed that sorbent surface area and pore size distribution were similar to those of the original pellets. The main alumina compound in remade pellets as determined by XRD was mayenite (Ca₁₂Al₁₄O₃₃). These results showed that, with periodic hydration/remaking steps, pellets can be used for extended times in CO₂ looping cycles, regardless of capture/regeneration conditions.