A hierarchical computational approach is introduced that combines materials screening with process optimization. This approach leads to novel materials for cost-effective CO2 capture. Zeolites are screened using shape, size, and adsorption selectivities. Next, process optimization is introduced to generate a rank-ordered list based on total cost of capture and compression. We not only select the most cost-effective materials, but we also attain the optimal process conditions while satisfying purity, recovery, and other process constraints. The top ten zeolites (AHT, NAB, MVY, ABW, AWO, WEI, VNI, TON, OFF and ITW) can capture and compress CO2 to 150 bar from a mixture of 14% CO2 and 86% N2 at less than $30 per ton of CO2 captured. Several zeolites have moderate selectivities, yet they cost-effectively capture CO2 with 90% purity and 90% recovery using a 4-step adsorption process. Such nonintuitive selection demonstrates the necessity of combining materials-centric and process-centric viewpoints.

This paper reports studies on CO2 capture technologies and presents the mathematical modeling, simulation, and optimization of adsorption-based process alternatives, namely, pressure swing adsorption (PSA) and vacuum swing adsorption (VSA). Each technology includes feed dehydration, capture of at least 90% of CO2 from the feed, and compression to almost pure CO2 for sequestration at 150 bar. Each process alternative is optimized over a range of feed CO2 compositions and flow rates. A superstructure of alternatives is developed to select the optimum dehydration strategy for feed to each process. A four-step process with pressurization, adsorption in multiple columns packed with 13X zeolite, N2 purging, and product recovery at moderate to low vacuum is configured. A nonlinear algebraic and partial differential equation (NAPDE) based nonisothermal adsorption model is used, which is fully discretized and solved via a kriging model. Explicit expressions for costs as functions of feed flow rate and CO2 composition are also developed for the PSA- and VSA-based CO2 capture and compression for the first time. Furthermore, a cost-based comparison of four leading CO2 capture technologies, namely, absorption-, membrane-, PSA-, and VSA-based processes, is presented over a range of flue gas compositions and flow rates. This enables selection of the most cost-effective CO2 capture and storage (CCS) technology for diverse emission scenarios. Results indicate that CO2 can be captured with the least cost using a MEA-based chemical absorption when the feed CO2 composition is less than 15–20%. For higher CO2 compositions, VSA is the preferred process.

Studies on leading technologies for industrial CO2 capture are performed. Each technology includes flue gas dehydration, capture of at least 90% of CO2 from the feed, and compression to almost pure CO2 for sequestration at 150 bar. This paper presents the modeling, simulation, optimization, and energy integration of a monoethanolamine (MEA)-based chemical absorption process and a multistage membrane process over a range of feed compositions (1–70% CO2, 5.5–15% H2O, 5.5% O2, and the balance N2) and flow rates (0.1, 1, 5, and 10 kmol/s). A superstructure of process alternatives is developed to select the optimum dehydration strategy for the feed to each process. A rigorous simulation-based optimization model is proposed to determine the minimum annualized cost of the MEA-absorption process. The MEA-absorption process is energy integrated through heat exchanger network optimization. A novel mathematical model is developed for the optimization of multistage and multicomponent separation of CO2 using membranes, which can be also used for a range of membrane-based gas separation applications. The results showing the optimum investment, operating, and total costs provide a quantitative approach toward technology comparison and scaling up the absorption- and membrane-based CO2 capture from various CO2 emitting industries. Explicit expressions for the investment and operating costs of each alternative postcombustion CO2 capture process as functions of feed flow rate and CO2 composition are also developed for the first time. This may assist the decision-makers in selecting the cost-appropriate technology for comprehensive carbon management by taking the diverse emission scenarios into consideration.

We design a CO 2 Capture, Utilization, and Sequestration (CCUS) supply chain network with minimum cost to reduce stationary CO 2 emissions and their adverse environmental impacts in the United States. While doing so, we consider simultaneous selection of source plants, capture technologies, capture materials, CO 2 pipelines, locations of utilization and sequestration sites, and amounts of CO 2 storage. The CCUS costs include the costs of flue gas dehydration, CO 2 capture, compression, transportation and injection, and revenues from CO 2 utilization through enhanced oil recovery (CO 2 -EOR). The dehydration, capture, and compression costs are derived using advanced modeling, simulation, and optimization of leading CO 2 capture processes. Our results suggest that it is possible to reduce 50−80% of the current CO 2 emissions from the stationary sources at a total annual cost ranging $58.1−106.6 billion. Furthermore, it is possible to generate $3.4−3.6 billion of revenue annually through supplying CO 2 for CO 2 -EOR. Overall, the optimal CCUS supply chain network would correspond to a net cost of $35.63−43.44 per ton of CO 2 captured and managed. Such a cost-effective network for CO 2 management is attained due to (i) using novel materials and process configurations for CO 2 capture, (ii) simultaneous selection of materials and capture technologies, (iii) CO 2 capture from diverse emission sources, (iv) CO 2 utilization for enhanced oil recovery, and (v) nationwide CO 2 storage. Results for the regional and statewide (Texas) CCUS are also favorable.

in Wiley Online Library (wileyonlinelibrary.com) An efficient computational screening approach is proposed to select the most cost-effective materials and adsorption process conditions for CH 4 /CO 2 separation. The method identifies eight novel zeolites for removing CO 2 from natural gas, coalbed methane, shale gas, enhanced oil recovery gas, biogas, and landfill gas sources. The separation cost is minimized through hierarchical material screening combined with rigorous process modeling and optimization. Minimum purity and recovery constraints of 97 and 95%, respectively, are introduced to meet natural gas pipeline specifications and minimize losses. The top zeolite, WEI, can recover methane as economically as $0.15/MMBTU from natural gas with 5% CO 2 to $1.44/MMBTU from natural gas with 50% CO 2 , showing the potential for developing natural gas reservoirs with higher CO 2 content. The necessity of a combined material selection and process optimization approach is demonstrated by the lack of clear correlation between cost and material-centric metrics such as adsorption selectivity. V C 2014 American Institute of Chemical Engineers AIChE J, 60: 1767-1785, 2014 Keywords: zeolites, adsorption/gas, process synthesis, optimization, computational screening IntroductionThere are vast reserves of natural gas worldwide that are uneconomical to develop due to high CO 2 content, which can be as high as 70% by volume.1 About 10% of natural gas in the United States contains significant quantities of CO 2 that must be removed prior to pipeline transportation to meet the typical specification on CO 2 of 3%.2,3 Typical specifications on composition for U.S. pipelines are provided in Table 1. Even for natural gas sources with low to moderate CO 2 content that is separated before pipeline transport, the CO 2 is often vented into the atmosphere, which contributes to global climate change. In fact, natural gas production is the second-largest source of CO 2 emissions in the United States (after fossil fuel consumption). 5 Even more of an environmental concern is methane, which is the most potent greenhouse gas (GHG) with about 21 times the GHG warming potential than CO 2 . It is, therefore, important to minimize methane losses during natural gas purification for both economic and environmental reasons.Major methane sources in the United States that may require CO 2 separation are illustrated in Figure 1. Shale gas sources typically contain 0-10% CO 2 , but the CO 2 content can increase during the life of a well to up to 30%. 6 Coalbed methane is a type of natural gas found in unmineable coal areas, which is typically extracted through the addition of CO 2 that is selectively adsorbed in the coal bed. As a result, coalbed methane typically contains 30-50% CO 2 . 7 The gases resulting from enhanced oil recovery may contain 20-80% CO 2 in addition to CH 4 . 8 Biogas is the result of anaerobic decomposition of organic waste, such as animal products (e.g., manure), agricultural residues, municipal solid waste, and municipal wastewat...

Natural gas (NG) is the cleanest fossil fuel, which is most popular and economical after crude oil. Liquefied natural gas (LNG) is the most economical way of transporting NG over long distances. Because of LNG transportation and storage at -163 °C, boil-off losses are an unavoidable reality. While these are significant, few systematic studies on boil-off exist in the literature. In this work, we perform rigorous, realistic, detailed, and extensive dynamic simulation of boil-off during various steps of LNG transportation, study the effects of various factors such as nitrogen content, tank pressure, ambient temperature, voyage length, etc., and analyze the results. On the basis of our simulations, we determine optimal heels for several scenarios of lean LNG transportation. Our analysis shows that heel can be reduced by up to 40% for a typical long voyage of 20 days, compared to the usual industrial practice of 5% of the cargo, and the reduction is significantly more for the shorter voyages. Our computations suggest savings of millions of dollars from heel optimization alone in LNG transportation.

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