Carbon Dioxide Separation from Nitrogen/Hydrogen Mixtures over Activated Carbon Beads: Adsorption Isotherms and Breakthrough Studies
Carbon Dioxide Separation from Nitrogen/Hydrogen Mixtures over Activated Carbon Beads: Adsorption Isotherms and Breakthrough Studies
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DOI：
10.1021/acs.energyfuels.5b00164
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发表时间：
2015-06-01
期刊：
影响因子：
5.3
通讯作者：
Woodt, Joseph
中科院分区：
文献类型：
--
作者：
Caldwell, Simon J.;Al-Duri, Bushra;Woodt, Joseph
在两种酚醛树脂衍生的活性炭珠样品上进行了二氧化碳/氮气和二氧化碳/氢混合物的高压分离研究：一种是由酚醛树脂前驱体制成的未改性活性炭，另一种是先用硝酸再用氨处理的改性材料。用二氧化碳和氮气对材料进行了高压容量法的平衡测试。使用固定床试验台测试了分离的动态响应，以产生几种二氧化碳进料馏分(0.1、0.2、0.3、0.4和0.5)在氮气中的二氧化碳穿透曲线。这项研究是为数不多的关于平衡能力与高压二氧化碳捕获应用中填充床操作中实现的突破能力相关的研究之一，也是第一次应用理想吸附溶液理论(IAST)模型。平衡实验表明，在纯组分吸附研究中，Langmuir-Freundlich等温式和双位Langmuir等温式比单独用Langmuir等温式更好地拟合了所有数据。发现了基于动态分离的材料的容量，在25巴和25℃下，氮气中的0.5个二氧化碳的摩尔分数导致在未改性的活性碳上捕获6.09摩尔千克(-1)的二氧化碳，而在改性的活性碳上捕获7.48摩尔千克(-1)的二氧化碳。根据纯组分等温线参数，改性后的活性碳在相同温度下对0.5摩尔分数二氧化碳的高压体积吸附容量符合Langmuir-Freundlich方程，未改性材料的饱和容量为8.06 moL kg(-1)，改性材料的饱和容量为7.68 molkg(-1)。对0.1-0.5范围内的二氧化碳进料馏分也发现了突破能力。动态容量与等温线预测值的比较表明，纯组分数据不一定代表动态多组分系统。因此，多组分等温线模型被拟合到数据中，并与使用IAST的预测进行了比较。多组分双点朗缪尔方程对二元组分数据的拟合效果最好。据报道，二氧化碳在氢气中的穿透曲线也超过了改性活性碳，碳珠由于其物理强度，显示出在发电厂燃烧前分离装置中应用于碳捕获的相当大的潜力，这意味着它们在填充床中的使用不需要进一步团聚粉末样品。
The high-pressure separation of carbon dioxide/nitrogen and carbon dioxide/hydrogen mixtures was investigated over two phenolic-resin-derived activated carbon bead samples: an unmodified activated carbon made from a phenolic resin precursor and a modified material manufactured by treating the former activated carbon with first nitric acid and then ammonia. Equilibrium tests on the material were performed with a high-pressure volumetric analysis with carbon dioxide and nitrogen. The dynamic response of the separation was tested using a fixed-bed rig to produce carbon dioxide breakthrough curves with several carbon dioxide feed fractions (0.1, 0.2, 0.3, 0.4, and 0.5) in nitrogen. This study represents one of the few studies that equilibrium capacities have been related to the breakthrough capacities achieved in packed-bed operation for high-pressure carbon dioxide capture applications and the first to apply the ideal adsorbed solution theory (IAST) model. The equilibrium tests showed that the Langmuir-Freundlich isotherm and the dual-site Langmuir isotherm gave a closer fit to all of the data than the Langmuir isotherm alone in the pure component adsorption studies. The capacity of the material based on the dynamic separation was found with mole fractions of 0.5 carbon dioxide in nitrogen leading to 6.09 mol kg(-1) carbon dioxide being captured over the unmodified activated carbon and 7.48 mol kg(-1) being captured over the modified activated carbon at 25 bar and 25 degrees C. By comparison, the saturation capacity of the modified activated carbon in the Langmuir-Freundlich fit to the high-pressure volumetric adsorption data for 0.5 mole fraction carbon dioxide at the same temperature was 8.06 mol kg(-1) for the unmodified material and 7.68 mol kg(-1) for the modified material based on the pure component isotherm parameters. The breakthrough capacities were also found for feed fractions of carbon dioxide in the range of 0.1-0.5. A comparison between the dynamic capacities and those predicted by the isotherm show that pure component data are not necessarily representative of a dynamic multi-component system. Therefore, multi-component isotherm models were fitted to the data and compared to predictions using the IAST. A multi-component dual-site Langmuir equation was found to give the best fit to the binary component data. Breakthrough curves were also reported for carbon dioxide in hydrogen over the modified activated carbon, with the carbon beads showing considerable potential for application for carbon capture in pre-combustion separation units of power plants, because of their physically strength, meaning no further agglomeration of powdered samples is required for their use in packed beds.