NSF/EPA Partnership for Environmental Research: New Methods for Carbon Dioxide Separation and Recovery [TSE01-F]

CTS-0124445二氧化碳分离和回收的新方法M.Rakowski DuBois和R.D.NobleUniversity of Colorado，Boulder，CO摘要该项目的主要目标是开发一种高效的电化学泵送工艺，用于从排放源中分离酸性气体，并将其浓缩用于回收和/或处置。电化学泵方法正被应用于从稀薄气流中去除和回收二氧化碳的具体问题。研究活动包括鉴定和合成适合二氧化碳的分子载体。目前正在对三种不同类型的二氧化碳分子载体进行评估，它们的优缺点各不相同。在一种方法中，氧化还原活性的苯二酚被还原，以产生足够强度的碱，以在吸收来自废物流源的二氧化碳时直接结合。在以这种方式捕获二氧化碳之后，对苯二酚-二氧化碳络合物进行电化学氧化，以释放浓缩的二氧化碳并再生被氧化的载体形式。第二种方法是开发具有氧化还原活性的金属络合物，这些络合物的功能与碳酸氢根离子类似。它们的优点是空气稳定，易溶于水。第三种方法是研究能产生电化学控制的pH摆动的苯醌载体。在高pH条件下，苯二酚还原生成的氢氧根离子与CO2络合，在低pH条件下，由苯二酚氧化生成的氢氧化物离子释放出CO2。对每个载体系统的工作包括对二氧化碳的反应吸收速率和结合常数作为载体氧化态的函数的电化学研究，以及对电化学泵送系统的研究，以确定适当的操作参数、重复性和稳定性以及能量效率。此外，正在对吸收/解吸和相关的质量传输现象进行过程建模研究和调查。目前大气中的二氧化碳浓度已显著高于工业化前的水平，随着化石燃料的继续使用，二氧化碳水平将继续上升。在这种情况下，气候模型预测了显著的全球变暖和严重的环境影响。必须开发有效的方法，捕获和储存二氧化碳以供将来使用，或以稳定的形式进行隔离。最容易捕获二氧化碳的点是在二氧化碳被与大气混合稀释之前，从发电厂、化工厂等大型生产商的废气中捕获二氧化碳。然而，据估计，在当今最好的技术下，从发电厂的废气中回收二氧化碳将导致其整体效率降低20%-30%。基于先前研究和模型研究的估计表明，使用合适的分子载体的电化学泵送过程可以比目前的传统方法更有效地回收二氧化碳。随着合适的载体的开发，这一过程应该可以应用于有效地去除工业工厂废气中的二氧化碳和其他酸性气体。

CTS-0124445New Methods for Carbon Dioxide Separation and Recovery M. Rakowski DuBois and R. D. NobleUniversity of Colorado, Boulder, CO AbstractThe broad objective of this project is to develop an efficient electrochemical pumping process for separating an acid gas from emission sources and concentrating it for recovery and/or disposal. The electrochemical pumping approach is being applied to the specific problem of removing and recovering CO2 from dilute gas streams. The research activities include the identification and synthesis of appropriate molecular carriers for CO2. Three different types of molecular-based carriers for CO2, which differ in their advantages and disadvantages, are being evaluated. In one approach, a redox-active quinone is reduced to produce a base of sufficient strength to bind CO2 directly in absorption from the waste-stream source. After CO2 is captured in this manner, the quinone-CO2 complex is oxidized electrochemically to release concentrated CO2 and to regenerate the oxidized form of the carrier. A second approach develops redox-active metal complexes that function in a similar cycle with bicarbonate ion. These have the advantage of being air-stable and water-soluble. A third approach investigates quinone carriers that produce an electrochemically controlled pH swing. CO2 is complexed at high pH by hydroxide ions generated by quinone reduction and released at low pH produced by quinone oxidation. Work on each carrier system includes electrochemical studies of the reaction-absorption rates and binding constants of CO2 as functions of carrier oxidation state and studies of the electrochemical-pumping systems to determine appropriate operating parameters, characteristics of reproducibility and stability, and energy efficiencies. In addition, process-modeling studies and investigations of absorption/desorption and related mass transport phenomena are being carried out. Current CO2 concentrations in the atmosphere have increased significantly from pre-industrial levels, and as the use of fossil fuels continues, CO2 levels will continue to rise. In this scenario, climate models predict a significant global warming with serious environmental impacts. Efficient methods must be developed in which CO2 is captured and stored for future use or sequestered in a stable form. The easiest point to capture CO2 is from the waste streams of large producers such as power plants, chemical plants, etc. before the CO2 is diluted by mixing with the atmosphere. It is estimated, however, that with today's best technology the recovery of CO2 from the exhaust of power plants will result in a 20-30% reduction in their overall efficiency. Estimates based on prior research and modeling studies suggest that an electrochemical pumping process with appropriate molecular carriers can be much more efficient than current conventional approaches for CO2 recovery. As appropriate carriers are developed, this process should find application in the efficient removal of CO2 as well as other acid gases from waste streams of industrial plants.