Development of CO2 Selective Poly(Ethylene Oxide)-Based Membranes: From Laboratory to Pilot Plant Scale

Membrane gas separation is one of the most promising technologies for the separation of carbon dioxide (CO₂) from various gas streams. One application of this technology is the treatment of flue gases from combustion processes for the purpose of carbon capture and storage. For this application, poly(ethylene oxide)-containing block copolymers such as Pebax^® or PolyActive™ polymer are well suited. The thin-film composite membrane that is considered in this overview employs PolyActive™ polymer as a selective layer material. The membrane shows excellent CO₂ permeances of up to 4 m³(STP)·(m²·h·bar)⁻¹ (1 bar = 10⁵ Pa) at a carbon dioxide/nitrogen (CO₂/N₂) selectivity exceeding 55 at ambient temperature. The membrane can be manufactured reproducibly on a pilot scale and mounted into flat-sheet membrane modules of different designs. The operating performance of these modules can be accurately predicted by specifically developed simulation tools, which employ single-gas permeation data as the only experimental input. The performance of membranes and modules was investigated in different pilot plant studies, in which flue gas and biogas were used as the feed gas streams. The investigated processes showed a stable separation performance, indicating the applicability of PolyActive™ polymer as a membrane material for industrial-scale gas processing.     

新型CO2捕获材料研究进展

高效、经济、环境友好的CO2捕获技术的开发与应用将是未来发展的趋势.本文概括了对CO2的吸附分离技术以及捕获机理,总结了传统CO2捕获材料的研究与不足,重点讨论了新型CO2捕获材料的发展状况和研究进展,新型CO2捕获材料的研发与应用将大大缓解全球气候变暖.     

Carbon dioxide absorption by ammonia intensified with membrane contactors

Membrane gas absorption technology is a promising alternative for CO₂ removal from post-combustion coal-fired flue gases. This study examines an alternative which consists in absorbing carbon dioxide by ammonia aqueous solution in a membrane contactor to improve the capture processes and to intensify the gas–liquid transfer. Absorption measurements through a membrane contactor have been made. The influence of the material nature constituting the membrane and operating parameters on the capture efficiency has been studied. The potentialities of dense skin membrane contactors are discussed with regard to both increased CO₂ mass transfer performances and mitigation of ammonia volatilization. The results have shown that it is possible to capture CO₂ from ammonia through a membrane with capture efficiency greater than 90 %. The membrane limits ammonia losses but does not eliminate it. The experimental results are used to calculate an intensification factor of 5, which represents the comparison between the membrane overall absorption rate to that of the column.     

Production of methanol and organic carbonates for chemical sequestration of CO2 from an NGCC power plant

Global economic development anticipates a growth in demand of the energy sector whose supply in the coming decades will remain achieved by burning fossil fuels. The need to stabilize the CO₂ atmospheric concentration requires technologies for capturing and reutilization of this greenhouse gas. Such scenario motivates feasibility analysis of power generation with post-combustion capture of CO₂ from the flue gas associated with its transformation into chemical commodities. Specifically, the economic performance of an integrated NGCC with post-combustion capture and utilization is evaluated to balance aggregated revenues with energy penalty. The proposed CO₂ reutilization is the production of methanol (MeOH), organic carbonates—dimethyl carbonate (DMC) and ethylene carbonate (EC), and ethylene glycol (EG). The study uses CO₂ capture with MEA (monoethanolamine), including compression of the captured gas followed by its conversion to methanol and organic carbonates, and separation of products with recycle of reactants. Three scenarios were evaluated corresponding to the capture of 30, 50, and 80 % of the CO₂ present in the flue gas. The comparative analysis includes definition of design premises followed by synthesis of process flowsheet, process simulation in the three scenarios, with sizing of the main pieces of process equipments for economic analysis—capital and operational expenditures (CAPEX and OPEX). Results indicated economic feasibility for the three scenarios. Furthermore, energy and mass balances showed that the emissions from energy demand to drive reactions and separations surpasses the proposed sequestration of CO₂ by chemical utilization in the scenarios of 30 and 50 % of CO₂ capture from NGCC emissions. In reality, CO₂ accounting for cases 1 and 2 reveals a “carbon debt” while for case 3 a net positive abatement of CO₂ occurs which increases process revenue by 1.7 % and reduces ROI in 1 year.     

BDAF-PMDA型聚酰亚胺炭膜的制备及其气体分离性能的研究

以2,2-双[4-(4-氨基苯氧基苯基)]六氟丙烷(BDAF)为二胺单体,均苯四酸二酐(PMDA)为二酐单体,采用两步法制备了BDAF-PMDA型聚酰亚胺,进一步高温热解制备炭膜.采用红外、热重、X射线衍射分析其结构变化,并测试炭膜对纯组分及混合气体的渗透性能和分离选择性.结果表明,BDAF-PMDA型炭膜具有较高的气体渗透性,在CO2/H2体系中可优先渗透CO2.提高炭化温度,炭膜孔径减小,气体的渗透性能降低,选择性提高,并使得BDAF-PMDA型炭膜的分离机理由表面扩散为主逐渐变为表面扩散和分子筛分共同控制.     

Valuing Metal–Organic Frameworks for Postcombustion Carbon Capture: A Benchmark Study for Evaluating Physical Adsorbents

The development of practical solutions for the energy‐efficient capture of carbon dioxide is of prime importance and continues to attract intensive research interest. Conceivably, the implementation of adsorption‐based processes using different cycling modes, e.g., pressure‐swing adsorption or temperature‐swing adsorption, offers great prospects to address this challenge. Practically, the successful deployment of practical adsorption‐based technologies depends on the development of made‐to‐order adsorbents expressing mutually two compulsory requisites: i) high selectivity/affinity for CO₂ and ii) excellent chemical stability in the presence of impurities. This study presents a new comprehensive experimental protocol apposite for assessing the prospects of a given physical adsorbent for carbon capture under flue gas stream conditions. The protocol permits: i) the baseline performance of commercial adsorbents such as zeolite 13X, activated carbon versus liquid amine scrubbing to be ascertained, and ii) a standardized evaluation of the best reported metal–organic framework (MOF) materials for carbon dioxide capture from flue gas to be undertaken. This extensive study corroborates the exceptional CO₂ capture performance of the recently isolated second‐generation fluorinated MOF material, NbOFFIVE ‐1‐Ni, concomitant with an impressive chemical stability and a low energy for regeneration. Essentially, the NbOFFIVE ‐1‐Ni adsorbent presents the best compromise by satisfying all the required metrics for efficient CO₂ scrubbing.     

Removal of carbon tetrafluoride from nitrogen trifluoride by gas hydrate crystallization

This paper examines the separation of gas mixtures based on nitrogen trifluoride and carbon tetrafluoride by different versions of gas hydrate crystallization. We calculate the distribution coefficient and separation factor of the major components of the mixture in the temperature range 253–273 K for different pressures and gas mixture compositions. The results demonstrate that gas hydrate crystallization ensures efficient separation of mixtures containing nitrogen trifluoride and carbon tetrafluoride. Directional crystallization allows nitrogen trifluoride to be separated more completely, whereas crystallization at constant pressure ensures a larger yield of the purified material.     

分离氧化亚氮和二氧化碳的变压吸附方法研究

介绍了使用变压吸附方法分离氧化亚氮和二氧化碳的实验研究,使用自制的改性吸附剂TK-103,在0.2MPa的吸附压力下,可将实验配制的含N_2O混合气中的CO_2脱除至20×10-6以下,且净化气中的N_2O收率达到约80%,该方法具有操作压力低、CO_2脱除精度高、N_2O回收率高、设备投资低及操作能耗省的优点,特别适用于从己二酸尾气中回收提纯氧化亚氮。     

In silico screening of carbon-capture materials

One of the main bottlenecks to deploying large-scale carbon dioxide capture and storage (CCS) in power plants is the energy required to separate the CO(2) from flue gas. For example, near-term CCS technology applied to coal-fired power plants is projected to reduce the net output of the plant by some 30% and to increase the cost of electricity by 60-80%. Developing capture materials and processes that reduce the parasitic energy imposed by CCS is therefore an important area of research. We have developed a computational approach to rank adsorbents for their performance in CCS. Using this analysis, we have screened hundreds of thousands of zeolite and zeolitic imidazolate framework structures and identified many different structures that have the potential to reduce the parasitic energy of CCS by 30-40% compared with near-term technologies.     

A partially interpenetrated metal-organic framework for selective hysteretic sorption of carbon dioxide

The selective capture of carbon dioxide in porous materials has potential for the storage and purification of fuel and flue gases. However, adsorption capacities under dynamic conditions are often insufficient for practical applications, and strategies to enhance CO(2)-host selectivity are required. The unique partially interpenetrated metal-organic framework NOTT-202 represents a new class of dynamic material that undergoes pronounced framework phase transition on desolvation. We report temperature-dependent adsorption/desorption hysteresis in desolvated NOTT-202a that responds selectively to CO(2). The CO(2) isotherm shows three steps in the adsorption profile at 195?K, and stepwise filling of pores generated within the observed partially interpenetrated structure has been modelled by grand canonical Monte Carlo simulations. Adsorption of N(2), CH(4), O(2), Ar and H(2) exhibits reversible isotherms without hysteresis under the same conditions, and this allows capture of gases at high pressure, but selectively leaves CO(2) trapped in the nanopores at low pressure.     

Life cycle assessment of membrane-based carbon capture and storage

Many investigations have conducted life cycle assessments (LCA) of the most commonly discussed routes of carbon capture and storage (CCS): post-combustion with amine wash separation; oxyfuel using cryogenic air separation and pre-combustion by integrated gasification combined cycle (IGCC) using physical separation. A research alliance developed corresponding separation systems using different types of membranes to allow a more energy efficient separation process: polyactive polymeric membranes for post-combustion, ceramic membranes for oxyfuel and metallic membranes for IGCC separation. By conducting an LCA, the study examines the actual greenhouse gas emissions and other environmental impacts of the new membrane separation technologies, together with concepts implementing the more common technologies. The reference systems represent today’s state-of-the-art supercritical coal fired power plant in Germany, together with a more advanced ultra-supercritical plant operating at 700 °C without CO₂ capture. The results demonstrate that among the three reference power plants the IGCC is the superior concept due to the highest efficiency. Regarding climate change, the IGCC power plants with CO₂ capture are still the best concepts. When other environmental impacts are considered, the capture technologies are inferior. The membrane concepts show the overall better results in comparison to the conventional capture technologies. The environmental impacts for membrane applications add a new range of findings to the field of CCS LCAs. Now the results for several different approaches can be compared directly for the first time.     

Optimization of cryogenic carbon dioxide capture from natural gas

Cryogenic carbon dioxide removal from natural gas requires accurate thermodynamic phase study of the natural gas mixture and individual components. Thermodynamic data generation of carbon dioxide‐methane mixture having 90 % carbon dioxide for cryogenic carbon dioxide capture from natural gas using Peng Robinson equation of state is discussed in this research work. Golden section search technique along with Eureqa optimizing tool is then used to optimize the pressure‐temperature conditions for the cryogenic carbon dioxide capture in the solid‐vapour two‐phase region. Cost optimization is done for the carbon dioxide capture system at atmospheric pressure and 20 bar. Temperature ranges for optimization were obtained from the predicted thermodynamic data for the mixture. The optimum temperatures obtained in this research work for the cryogenic carbon dioxide capture at atmospheric pressure and the 20 bar are ?103.8 °C and ?60.90 °C respectively. For atmospheric pressure at ?103.8 °C the worth of methane, carbon dioxide, and energy is 114 $/h, 9 $/h, and 53 $/h respectively, while at 20 bar and ?60.9 °C the worth of carbon dioxide, methane, and the energy are found to be 129 $/h, 46 $/h, 52 $/h, respectively.     

中空纤维膜接触器分离烟气中CO2试验研究

在中空纤维膜接触器分离CO2试验台上,对模拟烟气进行分离CO2试验,采用MEA、MDEA和氨基酸盐3种吸收液,考察了吸收液流速、浓度、温度以及气体流速和入口CO2浓度对CO2的脱除效率和系统阻力的影响。试验结果表明采用氨基酸盐吸收液,CO2的脱除效率可达90％以上,而气相阻力小于150Pa。因此该技术满足了锅炉烟气大、压力小的特点,非常适合于烟气中CO2的分离与回收,是一种很有前途的分离CO2的方法。     

CO2/N2分离中水合物膜形成的影响因素研究

温室效应是如今人类所面临的一个重大问题,而二氧化碳对温室效应的"贡献"最大,因此发展研究捕集CO2的新型高效节能技术及相关理论,对避免温室效应,保护环境具有极其重要的意义.本文提出了将膜分离法和水合物法结合起来即水合物膜法,并利用自行组建的水合物膜法分离二氧化碳实验系统初步探索了多孔陶瓷管的孔径,体系的压力、温度、气体...     

Hydrates in the ocean and evidence for the location of hydrate formation

There is substantial evidence that the oceans of the world will pose the most important challenges in the area of hydrate formation. This work indicates three areas of concern for hydrate formation in the ocean: (1) deposits of natural gas in ocean hydrates, which will serve as an energy resource and environmental concern in the next tnillenium, (2) a recent proposal for the ocean storage of carbon dioxide in the form of hydrates, and (3) the prevention of hydrate formation in ocean pipelines. To address such applications, fundamental knowledge on the site of hydrate formation was determined. Results are presented for quiescent, high-pressure experiments done in a sapphire tube to determine the site of hydrate formation in deionized water and in mixtures with amorphous silica and sodium dodecyl sulfate. Visual (microscope aided) results are presented for formation with a typical gas mixture and with carbon dioxide.Invited paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, USA.     

基于Herriott吸收池的固定源二氧化碳浓度测量研究

准确的碳排放计量是实现“碳峰化、碳中和”目标的重要一步。在所有碳排放源中,固定排放源排放的CO2是温室效应的主要因素。因此,精确测量固定排放源CO2的浓度尤为重要。基于近红外分子吸收光谱原理并结合多次反射直接吸收光谱技术,利用35% CO2/N;2混合物,建立了精确测量CO2浓度的方法,测量了293K和0,4.1,8.1,13.3kPa下,CO2在6359.97cm-1的(30012)←(00001)R16e和6361.25cm-1的(30012)←(00001)R18e跃迁谱线,计算了R18e的谱线强度,通过比较35% CO2/N2混合物和其它CO2/N;2混合物的吸收面积,可以得到15%,10%,5%的CO2/N;2混合物的浓度。结果表明所建立的理论方法和实验结果能够较好地表征待测气体的浓度,测量不确定度与基于天平的称重法相当。     

Low-temperature CO2 capture technologies – Applications and potential

CO₂ capture by chemical or physical sorption and membrane separation have been the dominant fields of research within post- and pre-combustion CO₂ capture from power cycles and industrial processes. Except for oxy-combustion capture applications, limited attention has been given to low-temperature capture from flue gas and synthesis gas by phase separation. This paper gives an overview of common CO₂ capture conditions for a broad range of different power cycles and industrial processes. For a selected range of capture conditions, potential applications for low-temperature CO₂ capture have been evaluated with respect to energy consumption and CO₂ capture ratio. For all applications of low-temperature capture, specific power consumption and obtainable CO₂ capture ratio are sensitive to flue-gas or synthesis-gas feed CO₂ concentration. However, for certain applications such as synthesis gas from coal gasification, low-temperature capture shows promising potential and highly competitive energy figures compared to baseline technology.     

二氧化碳水合物形成原因分析

从万金塔二氧化碳气田向气站内输送原料二氧化碳过程中,经常发生二氧化碳与水形成水合物堵塞输气管道的现象,给二氧化碳的净化提纯生产带来不利的影响。研究人员在参阅相关文献的基础上,提出应用统计热力学方法来求取二氧化碳形成水合物的具体条件,并且基于实践的基础上分析了防止水合物形成的预防方法,对二氧化碳气田的开发具有一定的借鉴意义。     

Optimum synthesis of solvent-based post-combustion CO2 capture flowsheets through a generalized modeling framework

A generalized framework for the optimal design of post-combustion CO₂ capture processes based on a systemic and flexible equilibrium separation model that employs orthogonal collocation on finite elements techniques is proposed. Within this context, a column section of adaptive separation capability and functionality serves as the fundamental structural block for the identification of efficient separation schemes. Separation column sections in combination with heat transfer blocks, as well as stream splitters and mixers enable the generation and evaluation of alternative flowsheet configurations within a nonlinear optimization program. The main objectives for the flowsheet evaluation involve separation and thermal efficiency that eventually impact the economics of the overall process. Vapor–liquid equilibrium calculations are performed using statistical associating fluid theory for potentials of variable range (Mac Dowell et al., Ind Eng Chem Res 49:1883–1899, 2010). The proposed design framework is used for the optimal design of five alternative flowsheet configurations for the separation of CO₂ from a flue gas stream using a 30 % weight monoethanolamine aqueous solution. These flowsheets illustrate the various connection patterns between the process units and indicate suitable distribution of process-driving forces through which the overall efficiency can be drastically enhanced.     

Emission characteristics of coal combustion in different O2/N2, O2/CO2 and O2/RFG atmosphere

This study investigates the emission characteristics of CO(2), SO(2) and NOx in the flue gas of coal combustion by varying the compositions and concentrations of feed gas (O(2)/CO(2)/N(2)) and the ratios of recycled flue gas. The differences between O(2)/recycled flue gas (O(2)/RFG) combustion and general air combustion are also discussed. Experimental results indicate that the maximum concentration of CO(2) in O(2)/CO(2) combustion system is 95% as the feed gas is 30% O(2)/70% CO(2). The average concentration of CO(2) in the flue gas of O(2)/CO(2) coal combustion system is higher than 90% and much higher than that of O(2)/N(2) coal combustion system. This high concentration of CO(2) is beneficial for the separation of CO(2) from the flue gas by adsorption or absorption technologies. The maximum concentration of CO(2) in O(2)/N(2) combustion system is only 34% at the feed gas 50% O(2)/50% N(2), the concentration of CO(2) is increased with the concentration of O(2) in feed gas. By O(2)/CO(2) combustion technology, higher concentration of SO(2) is produced as the feed gas is 30% O(2)/70% CO(2) or 40% O(2)/60% CO(2), while higher concentration of NOx is produced as the feed gas is 20% O(2)/80% CO(2) or 50% O(2)/50% CO(2). The mass flow rates of CO(2), SO(2) and NOx in the flue gas are all increased with the ratio of recycled flue gas except for the feed gas 20% O(2)/80% CO(2). The enhanced mass flow rates of air pollutants in such O(2)/RFG combustion system are also beneficial for improving the control efficiencies of air pollution control devices. By O(2)/N(2) combustion technology, higher concentrations of SO(2) and NOx are produced as the feed gas is 21% O(2)/79% N(2). The results also indicate that the formation of NOx in general air combustion system is higher than that in O(2)/RFG or O(2)/CO(2) combustion system.