On the exergy efficiency of CO2 capture: The relation between sub-process and overall efficiencies

Berstad, David; Gundersen, Truls

doi:10.1016/j.ccst.2023.100111

Cited by 9 publications

(4 citation statements)

References 21 publications

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“…This exclusion is due to their relatively low impact, deemed insignificant, and the fact that these utility streams are typically configured based on theoretical heat energy inputs, rather than their exergy content. The net rational efficiency is the ratio between the theoretical exergy inputdefined as the difference in exergy between the product and feed streamsand the actual net exergy input required to produce the specified product streams. ,, Thus, only the primary inlet and outlet streams as well as process input energies such as compression work are considered for evaluation. Similarly, the liquefaction exergy efficiency for both the Linde–Hampson process and the proposed process with a recycling loop is confined to the inflow and outlet exergies within the refrigeration cycle.…”

Section: Comparison Methodsmentioning

confidence: 99%

Utilization of Cold Energy of LNG for Carbon Dioxide Capture and Liquefaction in Amine-Based SMR

Jeong,

Nguyen,

Wang

et al. 2024

Ind. Eng. Chem. Res.

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Hydrogen is widely produced by a steam methane reforming (SMR) process, but CO 2 that is produced as a byproduct needs to be captured. For this purpose, amine absorption, one of the main carbon capture and utilization (CCU) techniques, is commonly integrated with the SMR process. A drawback of the amine absorption process is that captured CO 2 is recovered in the gas phase and must be liquefied or solidified to be suitable for transportation and storage. Traditionally, the liquefaction of CO 2 is achieved by a series of compression-cooling and expansions (e.g., the Linde−Hampson process), which is a costly and energy-intensive process. This study proposes using liquefied natural gas (LNG) not only as the source for hydrogen production and heat supply for the SMR reaction, but also to provide the necessary thermal energy requirement for the liquefaction of CO 2 using plate-fin heat exchangers. Aspen HYSYS is used to simulate a 300 Nm 3 /h scale SMR process, the amine absorber, and CO 2 Liquefaction processes. Energy, exergy, and cost efficiencies for a conventional Linde−Hampson process and two novel setups utilizing LNG cold energy are studied and compared. In summary, our results show the significant advantages of the proposed nonrecycling process over the conventional Linde−Hampson system. Specifically, it offers up to a 39.38% enhancement in overall exergy efficiency, achieves a net rational exergy efficiency as high as 95.72%, and reduces total capital costs by 30.83%.

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Section: Comparison Methodsmentioning

confidence: 99%

Utilization of Cold Energy of LNG for Carbon Dioxide Capture and Liquefaction in Amine-Based SMR

Jeong,

Nguyen,

Wang

et al. 2024

Ind. Eng. Chem. Res.

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“…As discussed and exemplified in previous publications, such as [34], there are different ways to define and assess exergy efficiency from the exergy balance of processes. In [3], it is argued that a rigorous definition of exergy efficiency is the ratio between the minimum exergy requirement, . E in,min , and the actual exergy input to the process, .…”

Section: Exergy Analysis Of Low-temperature Co 2 Separation Processesmentioning

confidence: 99%

“…Chemical solvents, despite being a mature technology, are arguably inefficient energy-wise and can even have negative exergy efficiency in pre-combustion applications [3]. To better exploit the high CO2 concentrations that reforming processes can provide, an innovative solution was proposed by Straus et al [4], in which a PSA unit is combined with a low-temperature tail gas separation process for CO2 capture and recirculation of CO, methane, and hydrogen to the upstream water-gas shift reactors and reformer.…”

mentioning

confidence: 99%

CO2 Capture and Enhanced Hydrogen Production Enabled by Low-Temperature Separation of PSA Tail Gas: A Detailed Exergy Analysis

Berstad,

Straus,

Gundersen

2024

Energies

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Hydrogen from natural gas reforming can be produced efficiently with a high CO2 capture rate. This can be achieved through oxygen-blown autothermal reforming as the core technology, combined with pressure-swing adsorption for hydrogen purification and refrigeration-based tail gas separation for CO2 capture and recirculation of residual hydrogen, carbon monoxide, and methane. The low-temperature tail gas separation section is presented in detail. The main objective of the paper is to study and quantify the exergy efficiency of this separation process in detail. To achieve this, a detailed exergy analysis is conducted. The irreversibilities in 42 different process components are quantified. In order to provide transparent verification of the consistency of exergy calculations, the total irreversibility rate is calculated by two independent approaches: Through the bottom-up approach, all individual irreversibilities are added to obtain the total irreversibility rate. Through the top-down approach, the total irreversibility rate is calculated solely by the exergy flows crossing the control volume boundaries. The consistency is verified as the comparison of results obtained by the two methods shows a relative deviation of 4 · 10−7. The exergy efficiency of the CO2 capture process is calculated, based on two different definitions. Both methods give a baseline exergy efficiency of 58.38%, which indicates a high degree of exergy utilisation in the process.

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“…Exergy analysis provides a comprehensive assessment of energy systems: Exergy analysis not only considers the efficiency of energy conversion but also takes into account the loss of energy quality. By conducting an Exergy analysis on each component within the system, it is possible to determine which components or processes need improvement or replacement to enhance the overall energy efficiency of the system [19]. In this paper, the thermodynamic efficiency of the Carnot battery system proposed through Exergy efficiency evaluation is assessed.…”

Section: Exergy Modelmentioning

confidence: 99%

Non-Saturated 3E (Energy, Exergy, and Economic) Analysis of Carnot Battery Systems Based on Organic Rankine Cycle

Ma,

Yang

2023

J. Adv. Therm. Sci. Res.

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Artificial activities, environmental factors, and industrial production lead to periodic fluctuations in electricity consumption, necessitating peak-shaving measures to ensure efficient and stable operation of the power grid. The Carnot battery system represents an effective solution due to its high efficiency and convenience. In this paper, we propose a novel Carnot battery system based on a dual-function unit and establish thermodynamic and economic models. This paper proposed a simple reversible heat pump-organic Rankine cycle Carnot battery system, where a compression and expansion dual-function unit was developed to simplify the system and reduce investment costs. Subsequently, considering the unsaturated operating conditions that occur during practical operation, a comprehensive performance analysis of the system is conducted by varying pressure and temperature parameters. Afterward, an exergy analysis is performed on the proposed system to determine the exergy losses of its components for subsequent optimization. The results indicate that pressure drop has a detrimental effect on the system. When the pressure drop is 15 kPa, the system achieves a power-to-power ratio (P2P), levelized cost of storage (LCOS), and exergy efficiency of 27.57%, 0.66 $/kW∙h, and 62.8%. However, this also leads to increased exergy losses in the evaporator, resulting in decreased exergy efficiency. The evaporator exhibits the highest exergy loss, with a maximum loss of 21.16 kW among all components. Undercharging mode, the condenser shows the lowest exergy efficiency of 64.43%.

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On the exergy efficiency of CO2 capture: The relation between sub-process and overall efficiencies

Cited by 9 publications

References 21 publications

Utilization of Cold Energy of LNG for Carbon Dioxide Capture and Liquefaction in Amine-Based SMR

Utilization of Cold Energy of LNG for Carbon Dioxide Capture and Liquefaction in Amine-Based SMR

CO2 Capture and Enhanced Hydrogen Production Enabled by Low-Temperature Separation of PSA Tail Gas: A Detailed Exergy Analysis

Non-Saturated 3E (Energy, Exergy, and Economic) Analysis of Carnot Battery Systems Based on Organic Rankine Cycle

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