A Superstructure-Based Optimal Synthesis of PSA Cycles for Post-Combustion CO2 Capture
A Superstructure-Based Optimal Synthesis of PSA Cycles for Post-Combustion CO2 Capture
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DOI：
10.1002/aic.12107
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发表时间：
2010-07-01
期刊：
影响因子：
3.7
通讯作者：
Zitney, Stephen E.
中科院分区：
文献类型：
--
作者：
Agarwal, Anshul;Biegler, Lorenz T.;Zitney, Stephen E.
最近的发展表明，变压/真空吸附 (PSA/VSA) 是有效捕获烟道气流中二氧化碳的一种有前景的选择。在大多数商业变压吸附循环中，混合物中弱吸附的组分是所需的产物，富集强吸附的二氧化碳不是问题。另一方面，有必要将CO2浓缩至高纯度，以降低CO2封存成本并最大程度地降低安全和环境风险。因此，有必要开发专门针对获得纯强吸附组分的PSA工艺。文献中已经开发了多种 PSA/VSA 循环，用于从二氧化碳浓度较低的原料中捕获二氧化碳。然而，尚未提出系统的方法来开发、评估和优化用于高纯度二氧化碳捕获的 PSA 循环。本研究提出了一种基于系统优化的配方，用于针对给定应用合成新型 PSA 循环。特别是，提出了一种新颖的 PSA 上部结构，用于设计最佳的 PSA 循环配置并评估二氧化碳捕获策略。上层建筑足够丰富，可以预测许多不同的 PSA 操作步骤。上部结构中的床连接由与时间相关的控制变量控制，可以改变这些控制变量以实现大多数 PSA 操作步骤。通过利用 PSA 系统的偏微分方程和代数方程以及循环稳态条件制定最优控制问题，可以实现操作步骤的最优序列。大规模优化能力使我们能够采用完整的离散化方法，使用非线性优化求解器IPOPT将最优控制问题作为大规模非线性程序来求解。上层建筑方法在与燃烧后二氧化碳捕获相关的案例研究中得到了证明。特别是，合成了最佳的 PSA 循环，可最大限度地提高给定纯度的二氧化碳回收率，并最大限度地降低总体功耗。结果表明，上层建筑具有预测 PSA 循环的潜力，二氧化碳纯度和回收率高达 98%。此外，这些循环可以从大气、烟气中回收二氧化碳，回收率约为85%，纯度超过90%，能耗仅为465千瓦时/吨(-1)二氧化碳。因此，所提出的方法对于评估不同吸附剂、原料和 PSA 操作策略的适用性以及评估其二氧化碳捕集的有效性非常有前景且非常有用。出版 (C) 2009 美国化学工程师学会 AIChE J, 56: 1813-1828, 2010
Recent developments have shown pressure/vacuum swing adsorption (PSA/VSA) to be a promising option to effectively capture CO2 from flue gas streams. In most commercial PSA cycles, the weakly adsorbed component in the mixture is the desired product, and enriching the strongly adsorbed CO2 is not a concern. On the other hand, it is necessary to concentrate CO2 to high purity to reduce CO2 sequestration costs and minimize safety and environmental risks. Thus, it is necessary to develop PSA processes specifically targeted to obtain pure strongly adsorbed component. A multitude of PSA/VSA cycles have been developed in the literature for CO2 capture from feedstocks low in CO2 concentration. However, no systematic methodology has been suggested to develop, evaluate, and optimize PSA cycles for high purity CO2 capture. This study presents a systematic optimization-based formulation to synthesize novel PSA cycles for a given application. In particular, a novel PSA superstructure is presented to design optimal PSA cycle configurations and evaluate CO2 capture strategies. The superstructure is rich enough to predict a number of different PSA operating steps. The bed connections in the superstructure are governed by time-dependent control variables, which can be varied to realize most PSA operating steps. An optimal sequence of operating steps is achieved through the formulation of an optimal control problem with the partial differential and algebraic equations of the PSA system and the cyclic steady state condition. Large-scale optimization capabilities have enabled us to adopt a complete discretization methodology to solve the optimal control problem as a large-scale nonlinear program, using the nonlinear optimization solver IPOPT. The superstructure approach is demonstrated for case studies related to post-combustion CO2 capture. In particular, optimal PSA cycles were synthesized, which maximize CO2 recovery for a given purity, and minimize overall power consumption. The results show the potential of the superstructure to predict PSA cycles with up to 98% purity and recovery of CO2. Moreover, for recovery of around 85% and purity of over 90%, these cycles can recover CO2 from atmospheric,flue gas with a low power consumption of 465 kWh tonne(-1) CO2. The approach presented is, therefore, very promising and quite useful for evaluating the suitability of different adsorbents, feedstocks, and operating strategies for PSA, and assessing its usefulness for CO2 capture. Published (C) 2009 American Institute of Chemical Engineers AIChE J, 56: 1813-1828, 2010