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The sudden increase in the concentration of carbon dioxide (CO2) in the atmosphere due to the high dependency on fossil products has created the need for an urgent solution to mitigate this challenge. Global warming, which is a direct result of excessive CO2 emissions into the atmosphere, is one major issue that the world is trying to curb, especially in the 21st Century where most energy generation mediums operate using fossil products. This investigation considered a number of materials ideal for the capturing of CO2 in the post-combustion process. The application of aqueous ammonia, amine solutions, ionic liquids, and activated carbons is thoroughly discussed. Notable challenges are impeding their advancement, which are clearly expatiated in the report. Some merits and demerits of these technologies are also presented. Future research directions for each of these technologies are also analyzed and explained in detail. Furthermore, the impact of post-combustion CO2 capture on the circular economy is also presented. [ABSTRACT FROM AUTHOR]

This paper investigates the relationships among the important process parameters that impact Post-combustion Carbon Capture (PCC) carbon dioxide (C O 2) separation. A better understanding of the complex relationships among those parameters can support optimization and performance enhancement of the separation process. Being able to precisely predict the process parameters will enable the operator to determine the current state of the process, forecast any potential changes or events, and adjust process parameters to enhance the plant's performance. With the objective of studying the process parameters' correlations in the amine-based PCC process, we modeled the multi-year historical production data of the Clean Energy Technologies Research Institute (CETRi) (formerly known as the International Test Center for PCC or ITC) in Regina, Saskatchewan, Canada, using a Decision Forest approach. The model validation process revealed that the Decision Forest model produced higher predictive accuracy than previous efforts. The Decision Forest models we developed also represent knowledge about the importance of parameters involved in the capture process, and such knowledge is useful for further optimization of the capture process in the future. • Modeling the parameters of the Carbon Capture process with machine learning (ML). • The ML models used Decision Forest with Gradient Boosting and Oblique Split. • The ML models achieved superior predictive accuracy compared to past efforts. • The ML models support interpretability by visualizing weights and prediction paths. [ABSTRACT FROM AUTHOR]

Intensive energy penalty caused by CO2 separation process is a critical obstacle for retrofitting power plant with carbon capture technology. Therefore, the concept of utilizing solar energy to assist solvent regeneration for post-combustion carbon capture power plant is proposed recently as a promising pathway to compensate the efficiency reduction derived from CO2 capture process. However, the feasibility of solar-assisted post-combustion technologies largely depends on the types of CO2 absorbent, categories of solar thermal collectors, areas of solar field, and the integration of thermal energy storage system. Therefore, this paper conducts a comparative analysis on monoethanolamine-based and NH3-based solar-assisted post-combustion power plants employing two types of solar collectors, i.e the vacuum tube and the parabolic through collector, with climate data of Tianjin City, China. Levelized costs of electricity and cost of CO2 removed are comparatively studied for both solar-assisted post-combustion configurations. Results show that the proposed solar-assisted post-combustion configurations are economically viable when the price of vacuum tube is lower than 86.64 $/m2 and 117.29 $/m² for the monoethanolamine-based and NH3-based solar-assisted postcombustion power plant, respectively. Meanwhile, the price of parabolic through collector should be less than 111.12 $/m² for the monoethanolamine-based and 114.51 $/m² for the NH3-based solar-assisted post-combustion power plant. It is indicated that employing the vacuum tube for chilled NH3-based solar-assisted post-combustion power plant offers a promising approach to reduce the energy penalty with attractive economic performance. [ABSTRACT FROM AUTHOR]

There is a wide range of resources for CO2 emissions. The net amount of CO2 emissions in the cement industry due to the consumption of fossil fuels and the chemical processes of cement production under heating raw materials is reported to be in the range of 15–25%; this industry, among all the industries and after the power plants and refineries, is the largest CO2 gas producer throughout the world. Using CO2 capture and storage (CCS), it can reduce greenhouse gas emissions in a short time. In this study, the technical feasibility study of recycling CO2 in Abyek Cement Company, with a cement production capacity of about 12,500 tons per day in two production lines, has been studied as one of the largest cement industries throughout the world. Fuel oil (Mazut) is used as the primary fuel for furnaces in this industry. Affected by combustion, the emissions emitted from the five-stage preheater contain 5/24% vol% of CO2, 7.6% H2O, 4.8% vol% of O2, and 63.1% N2. [ABSTRACT FROM AUTHOR]

• The steady operation of the methane/ammonia free-piston engine was achieved. • Effects of ammonia addition on the engine operating characteristics were studied. • Combustion and emission characteristics of the engine were studied numerically. • Obvious post combustion phenomenon occurred under the ammonia addition condition. In this paper, experimental and numerical studies of the methane-ammonia dual-fuel glow-ignition free-piston engine generator (FPEG) are carried out, with emphasis on its operation stability, performance and combustion characteristics. The ammonia in FPEG operates at different energy substitution rates (ESRs), including 100 %CH 4 , 90 %CH 4 +10 %NH 3 , 80 %CH 4 +20 %NH 3 , and 70 %CH 4 +30 %NH 3. The experimental results show that the FPEG can achieve stable operation in the methane/ammonia dual-fuel combustion mode. However, the operation stability of the FPEG becomes worse with the increase of the ESR. Especially when ESR = 30 %, engine shutdown accident will occur due to the high cycle-to-cycle variation caused by ignition delay. The peak pressure and heat release rate (HRR) decrease significantly because the additive ammonia weakens the combustion activity and reduces the combustion rate of mixture. In the case of pure methane, the indicated power and indicated thermal efficiency reach 319 W and 11.33 %, respectively. However, when ESR = 10 %, 20 % and 30 %, the corresponding values decrease significantly to 210 W, 7.48 %, 189 W, 6.72 % and 139 W, 4.95 %, respectively. The high-speed flame images show that with the increase of ESR, the flame structure becomes less wrinkled, because the addition of ammonia reduces the flame speed and weakens the combustion reaction, leading to the weakening of turbulent combustion intensity. In addition, the ammonia addition will also lead to post combustion phenomenon. The simulation results show that the start of combustion (SOC) is delayed and the crank angle (CA) 0–10 and CA10-50 are prolonged with the increase of ESR, because the ammonia addition reduces the amount of key radical, such as OH and H, which reduces the mixture reaction rate. The NOx emission decreases with the increase of ESR due to the low combustion temperature. Soot emissions from the pure methane remain extremely low, and the CO emissions gradually increase with the increase of ESR due to the incomplete combustion of mixture. In addition, the amount of unburned ammonia increases with the increase of ESR. [ABSTRACT FROM AUTHOR]

In this paper, optimization of a post combustion carbon capture process based on two different objective functions of energy and utility requirements and associated costs is presented. CO 2 residual mole fraction of the regenerated solution, solution circulation rates and lean solution temperature were selected as three most important variables of the process for optimization. One at a time method is adopted for optimization of the process variables. The results show that for a post combustion carbon capture process using monoethanolamine (MEA), lowest costs of the process are associated with the highest CO 2 residual mole fraction of regenerated solution, lowest solution circulation rate and highest lean solution temperature. Based on the results of this research, having a general view of energy and utility requirements of the process leads to finding the lowest possible process costs. However, if a component oriented view is adopted for energy requirements, the worst possible choices of operational parameters are likely to be made. [ABSTRACT FROM AUTHOR]

Carbonate looping promises low energy penalties for postcombustion CO2-capture and is particularly suited for retrofitting existing power plants. To further improve the process, a new concept with an indirectly heated calciner using heat pipes was developed, offering even higher plant efficiencies and lower CO2 avoidance costs than the oxy-fired standard carbonate looping process. The concept of the indirectly heated carbonate looping (1HCL) process was tested at sufficient scale in a 300 kWth pilot plant at Technische Universität Darmstadt. The paper presents a technical overview of the process and shows first test results of the pilot plant. Furthermore, the concept is economically evaluated and compared to other carbon capture processes. [ABSTRACT FROM AUTHOR]

Stirling machines present a forthcoming potential for substituting the internal combustion engine as an auxiliary power unit in future series hybrid electric powertrains. Different Stirling thermodynamic configurations can be found in the literature. Among them, the recuperative reheat Stirling thermodynamic cycle offers high net specific work and high efficiency, resulting in reduced system's weight, size and integration complexity, as well as reduced vehicle's fuel consumption. This paper presents an experimental investigation of the impact of Stirling combustion reheat process on the system performance and emissions. For that purpose a Stirling combustion chamber was modified and a post combustion chamber was added. The new configuration of the designed combustion chamber was manufactured and tested. The effect of reheating process on pollutant emissions was evaluated by measuring the NO x emissions and compared to the fuel quantity injected in both reheat and no reheat configurations. The test results demonstrate the high importance of reheating process in decreasing the NO x emission. The obtained reduction was more than 50% in comparison to the original construction. Consequently, the recuperative reheat Stirling thermodynamic configuration was selected as the best candidate for replacing the internal combustion engine. • Stirling combustion chamber was modified to enable the reheating process. • Recuperative reheat Stirling machine was tested, NO x emissions were analysed and compared. • This recuperative reheat thermodynamic configuration offers higher efficiency and higher net specific work. • The NO x emissions can be reduced by more than 50% compared to no-reheat thermodynamic configuration. [ABSTRACT FROM AUTHOR]

Abstract: A concept of coal-fired power plant built around a supercritical CO2 Brayton power cycle and 90% post-combustion CO2 capture have been designed. The power cycle has been adapted to the coal-fired boiler thermal output, this boiler has been roughly designed in order to assess the power cycle pressure drop and its cost, an adapted CO2 capture process has been designed and finally the overall heat integration of the power plant has been proposed. Due to the high complexity of such as plant, this paper does not intend to provide definitive evaluation of the concept but to explore its potential. A coal power plant with CO2 power cycle without carbon capture could achieve a net efficiency of 50% (LHV) with a maximal temperature and pressure of 620 °C and 300 bar, these performances has to be validated but the first results on pilot plant are encouraging. The CO2 capture process use monoethanolamine as solvent and is equipped with vapor recompression systems in order to reduce the heat needed from the CO2 cycle. It achieves around 2.2 GJ/ of specific boiler duty with 145 kWh/ of electrical auxiliary consumption including compression to 110 bar. The energetic evaluation of the overall power plant carried out highlights the promising potential of CO2 supercritical cycle. A net power plant efficiency of 41.3% (LHV), with carbon capture and CO2 compression to 110 bar, seem to be achievable with available or close-to-available equipment. A technical-economic evaluation of the designed power plant has been performed. It shows a levelized cost of electricity reduction of 15%, and a cost of avoided CO2 reduction of 45%, without transport and storage, compared to a reference supercritical coal-fired power plant equipped with standard carbon capture process. [Copyright &y& Elsevier]

Abstract: This paper addresses the issue of unburnt carbon in fly ashes from coal-fired power stations. It has been shown that carbon-in-ash has much lower combustion reactivity than the original coal, because of the extensive thermal annealing experienced in the boiler. Thermal annealing reduces the rate of the first reaction step of which carbon combustion is composed, namely oxygen chemisorption. In the present work experiments have been carried out in order to verify if a preconditioning stage consisting of mild pre-oxidation with air is able to promote oxygen chemisorption thus increasing the combustion reactivity of ashes. Fly ashes with high LOI have been exposed to air at temperature <400°C for times up to 300min. Results show that a satisfactory extent of oxygen chemisorption can be attained at 300–400°C with 1–2h holding time. After this conditioning, samples have been tested to check their combustion reactivity by means of non isothermal thermogravimetric analysis. Additionally, combustion experiments have been carried in a purposely designed suspension reactor at temperatures up to 1000°C. Results confirm that ash pre-conditioning reduces the burn-out time of carbon in ash. The concept has been finalized into an international patent application. [Copyright &y& Elsevier]

This study takes place in an engineering global study of incineration process (rotary kiln, post-combustion room, smoke treatment), which has as objective the identification of the aero-thermal and chemical behaviour of the reactive flow in the post combustion room. The work developed here, in an engineering approach, focuses in particular on the verification of the three T rule (Temperature, Turbulence and Time stay of gases) in the first treatment smoke unity. The study is done through numerical simulation in reactive flow of a post-combustion room. The incineration unity works with a rotary kiln of 1.5 MW and consuming gas fuel. Phoenics is used to achieve simulation, taking into account turbulence and combustion interaction through the Eddy Break Up model coupled with the turbulence model K-ε. [ABSTRACT FROM AUTHOR]

• Provides key performance metrics for gas separation in electrochemical reactors. • Bench-scale demonstration of continuous operation for flue gas CO 2 capture. • Offers performance metrics to assess amine regeneration energy at scale. • Offers flexible and modular amine regeneration for 'plug-and-play' CO 2 capture. The electrochemically-mediated amine regeneration (EMAR) process uses electrons to modulate amine capacity to achieve CO 2 separation from flue gas as an alternative to the traditional thermal regeneration process for CO 2 capture. The EMAR separation scheme is validated in a batch system designed to evaluate efficiency losses. Current and voltage responses of the electrochemical process were analyzed in a flow system operated continuously for up to 50 h. An isothermal EMAR system can achieve separation efficiencies above 80% from a 15% CO 2 feed, which is representative of the CO 2 composition in a flue gas. This bench scale continuous system can operate at 40–80 kJ e /mol CO 2 with an amine regeneration of between 0.12 and 0.62 mol CO 2 /mol amine. The ability to separate CO 2 at high electron utilization and moderate electrical energy consumption will prompt future research into optimization of the electrochemical separation unit to obtain long-term and stable operations for flue gas scrubbing. [ABSTRACT FROM AUTHOR]