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Highlights • A CO 2 de-SOx and de-NOx process was simulated for full oxy-fuel cement plants. • A comprehensive chemical mechanism has been elucidated and implemented in Aspen. • Results of a parametric study were presented for a single-column configuration. • Optimizations depending on purity targets were achieved by economic evaluations. Abstract The purpose of the present work was to investigate, for a gas issued from a full oxy-fuel combustion in the cement industry, a CO 2 de-SOx and de-NOx process, called "Sour-Compression Unit" (SCU), thanks to simulations with Aspen PlusTM. An important stage necessary for the SCU modeling has been the construction of an accurate chemical mechanism. Two-column and single-column configurations have been evaluated and compared. A parametric study and a Design Of Experiments have been conducted on a single-column process to study the influence of the operating parameters on the SOx and NOx abatement ratios. As a demonstration of the effectiveness of the model, three SOx and NOx purity specifications (depending on the further applications of the CO 2) were applied to the purified gas. The feature of the investigated model lies on optimizing the way to reach the purity target in order to decrease installation costs (CAPEX) and energy requirements (OPEX). [ABSTRACT FROM AUTHOR]

Carbon Capture Utilization or Storage (CCUS) has gained widespread attention as an option for reducing CO 2 emissions from power plants but specific developments are still needed for the application to cement plants. More precisely, the post-combustion CO 2 capture process by absorption-regeneration is the more mature technology but its cost reduction is still necessary. The present study is focusing on Aspen Hysys™ simulations of different CO 2 capture process configurations (namely “Rich Solvent Recycle” (RSR), “Solvent Split Flow” (SSF), “Lean/Rich Vapor Compression” (L/RVC)) applied to the flue gas coming from the Norcem Brevik cement plant (taken as case study) and using three different solvents, namely: monoethanolamine (MEA), piperazine (PZ) and piperazine-methyldiethanolamine (MDEA) blend. For each configuration and solvent, different parametric studies were carried out in order to identify the operating conditions ((L/G) vol. , split fraction, flash pressure variation, etc.) minimizing the solvent regeneration energy. Total equivalent thermodynamic works and utilities costs were also analyzed. It was shown that the configurations studied allow regeneration energy savings in the range 4–18%, LVC and RVC leading to the higher ones. As perspectives, other configurations and combination of configurations will be considered in order to further reduce the energy consumption of the process. [ABSTRACT FROM AUTHOR]

In order to reduce the operating costs of post-combustion CO 2 capture process by absorption-regeneration using amine based solvents for its application in the cement industry, the present study was focused on the Aspen Hysys TM simulation of different CO 2 capture process configurations (namely conventional configuration, “Rich Solvent Recycle” (RSR), “Solvent Split Flow” (SSF) and “Lean/Rich Vapor Compression” (L/RVC)) applied to the flue gas coming from the Norcem Brevik cement plant in Norway and using three different solvents, namely: monoethanolamine (MEA), piperazine (PZ) and piperazine-methyldiethanolamine (MDEA) blend. For each configuration and solvent, a parametric study was carried out in order to identify the specific operating conditions (flow rates ratio (L/G), split fraction, injection stage in the columns, flash pressure, etc.) minimizing the solvent regeneration energy and highlighting the energetical interest of such configurations. Energy savings of almost 30% were estimated with the RVC configuration and MDEA+PZ blend. A decrease of the condenser cooling energy was also noted. As perspectives, other configurations (such as InterCooled Absorber (ICA)) and combination of configurations will be considered in order to further reduce the energy consumption of the process. In addition to OPEX calculations, the consequence in terms of CAPEX of implementing each process configuration will have to be estimated for evaluating more precisely the global economic interest of using alternative process configurations for the application to cement plant flue gases. [ABSTRACT FROM AUTHOR]

The present work was focused on the application in the cement industry of the post-combustion CO 2 capture technology using amine-based chemical absorption. Besides conventional conditions, investigations were performed on a concept called “partial oxy-fuel combustion” applied to cement kilns leading to more CO 2 -concentrated flue gas (y CO2 up to 60%) and allowing to reduce the solvent regeneration energy consumption. The purpose of the study was to highlight and evaluate this reduction. Firstly, the performances of several solvents were evaluated thanks to screening tests at lab (results with a cables-bundle contactor) and micro-pilot (absorption-regeneration unit) scales considering different CO 2 contents (y CO2,in = 20-60 vol.%). Simple and blended solvents were tested in such conditions, such as primary and secondary alkanolamines (benchmark Monoethanolamine (MEA), Diethanolamine (DEA) and cyclical di-amine (Piperazine (PZ)). It was shown that the use of activated solutions (such as DEA 30 wt.% + PZ 5 wt.%) presented particularly high absorption performances both in conventional and high CO 2 contents conditions. Secondly, Aspen Hysys TM simulations were carried out considering cement plant flue gas. For MEA 30 wt.% an increase of y CO2 from 20% to 44% leads to a 26% decrease of the regeneration energy (from 3.36 to 2.48 GJ/t CO2 ), which is clearly encouraging. As perspectives, new absorption-regeneration tests at micro-pilot scale and simulations will be performed with other solvents in order to have a more global evaluation of the interest of partial oxy-fuel conditions for the cement industry. [ABSTRACT FROM AUTHOR]

In the context of Carbon Capture Storage (CCS) or Utilization (CCU), the application of a CO 2 Purification Unit (CPU) previously developed for oxyfuel power plants is here tested on flue gases coming from oxyfuel cement plants thanks to simulations with Aspen Plus TM . The CPU block is divided into three CO 2 purification steps. The compressed gas is firstly desulfurized and denitrified in a double-column (operating at 15 bar for the first column and 30 bar for the second one) unit called “Sour-Compression Unit” (SCU) where it is purified counter-currently with water to remove SO x and NO x components by a reactive absorption. Further treatments include a water adsorption step, and finally a separation step using either a distillation column or a double flash unit, to remove the residual inert gases. The present communication will be focused on the first step of the CPU, the “Sour-Compression Unit”. For this purpose, an accurate chemical mechanism was constructed based on literature reviews and critical comparison of various sources in order to represent properly the removal of SOx and NOx components and evaluate the performances of the SCU. Simulation results of this quite innovative application to cement plant flue gases are given and discussed. Future works will include an energetic and economic optimization of the SCU for the cement plant case. [ABSTRACT FROM AUTHOR]

Carbon Capture and Utilization (CCU) is one of the most widely studied technology to reduce anthropogenic CO 2 emissions and particularly the ones coming from power plants and cement plants which are currently among the world's main industrial sources of carbon dioxide. As a result, this study focuses on the optimization of an overall CCU process that should be applied to an oxyfuel cement plant, and including the CO 2 capture from flue gases and its purification in order to obtain a rich CO 2 stream that will be further converted into methane, methanol, or other chemically valuable compounds. To investigate the feasibility of such as process, two units (namely sour compression and cryogenic units) have been modeled and simulated on Aspen Plus software. These simulations were conducted considering flue gases compositions coming from both power and cement oxyfuel plants in order to compare their respective energy demands with regard to the CO 2 purity of the end-of-pipe product and to the CO 2 recovery of the overall process. It was observed that such process applied to simulated oxyfuel cement plant flue gases has a global CO 2 recovery range of 75.8 – 93.8% and that the CO 2 molar purity of the final stream is between 94.8 and 98.4%. This process appears to be completely applicable for the treatment of oxyfuel cement plant flue gases with CO 2 recovery and CO 2 molar purity in agreement with requirements for the chemical conversion of carbon. [ABSTRACT FROM AUTHOR]

• Process modeling and conceptual design are implemented using Aspen Plus. • Techno-economic and environmental analyses are conducted for performances evaluation. • Thermal energy self-sufficiency is achieved through an optimized integrated process. • Overall energy efficiency reaches 89.5 % on a LHV basis. • Drastic reductions in terms of net CO 2 emissions and fossil depletion are observed. Carbon Capture Utilization and Storage (CCUS) technologies are receiving increasing interest and its implementation at world scale appears to be crucial to reduce CO 2 emissions. In this context, Power-to-Gas technologies (PtG) are very promising, allowing to store renewable electricity and valorize captured CO 2 to produce Synthetic Natural Gas (SNG), among other. The present work simulates an integrated CO 2 capture and conversion process to SNG, and investigates its techno-economic and environmental performances. Different scenarios are defined considering the application to a cement plant flue gas and the production of renewable hydrogen. An advanced CO 2 capture unit is implemented, considering a configuration (Rich Vapor Compression and Inter Cooling) and a solvent (MDEA + PZ) allowing to minimize its specific energy consumption (35 % regeneration energy savings in comparison with a conventional amine-based CO 2 capture system). The excess heat released by the catalytic conversion is recovered for the solvent regeneration maximizing the amount of captured CO 2. From the scenarios analyses, it is shown that integrating the CO 2 capture and conversion steps is beneficial for reducing both the net CO 2 emission to the atmosphere, by 45 %, and the contribution to fossil depletion, by 81 %, in comparison with the non-integrated one, as the production of fossil-based natural gas is replaced by renewable SNG. The proposed process leads to a cost of 2.39 € per kg Raw-SNG, with expected revenues of 0.87 € per kg Raw-SNG. Significant subsidies and incentives would thus be needed to compete with conventional energy prices for natural gas (0.55 € per kg). [ABSTRACT FROM AUTHOR]

• Power-to-gas has a strong potential in the transition to a renewable network. • Advanced CO 2 capture process allows to reduce the energy consumption. • Heat integration improves the competitiveness of the global Power-to-Gas chain. • Attractiveness of Power-to-gas is economically sensitive to electricity cost. The Power-to-Gas strategy has become a mainstream topic for decarbonization and development of renewables and flexibility in energy systems. One of the key arguments for decarbonizing the gas network is to take advantage of existing network infrastructure, gradually transitioning to lower fossil carbon sources of methane from Power-to-Gas. This work proposes the techno-economic investigation of an integrated system considering an advanced CO 2 capture process, in terms of solvent and process configuration, to treat about 10% of a cement plant's flue gas and convert the captured CO 2 into synthetic natural gas using renewable hydrogen generated from a large-scale wind powered electrolyzer. An optimized heat recovery system is proposed, drastically decreasing the external hot utility demand of the CO 2 capture unit. In addition, it leads to the production of complementary electricity (about 1.06 MW), reducing thus also the electrical demand of the integrated process. The synthetic natural gas produced has a composition (CH 4 92.9 mol.%, CO 2 3.7 mol.%, and H 2 3.4 mol.%) and a Wobbe index (46.72 MJ/m3), corresponding to specification for gas grid injection at 50 bar in Germany. With an overall system efficiency of 72.6%, the process produces 0.40 ton synthetic natural gas per ton of captured CO 2. The cost of the synthetic natural gas produced is higher when compared to the present natural gas market price, but cost reductions and possible commercial use of coproducts like oxygen, represent a likely alternative. Costs are mainly driven by high capital investments (the electrolyzer), and the price of renewable electricity, which is expected to decrease in the coming years. [ABSTRACT FROM AUTHOR]

• High CO 2 contents flue gases. • Both simple and activated solutions investigated in partial oxy-fuel conditions. • Simulation of absorption-regeneration CO 2 capture process. • Aspen Hysys™ simulations validated thanks to micro-pilot experimental results. • Significant energy savings. The present study is focusing on the investigation, for the cement industry, of the post-combustion CO 2 capture process using amine(s)-based solvents. The novel aspect of the work is the flue gas considered, namely the high CO 2 contents (between 20 and 60 vol.%), representative of flue gases coming from oxygen-enriched air combustion process (also called partial oxy-fuel combustion). Using the results of preliminary solvents screening tests at laboratory scale, absorption-regeneration micro-pilot experiments were carried out for the best solvents in order to characterize their respective absorption and regeneration performances. The use of the activated solution of DEA (diethanolamine) 30 wt.% with PZ (piperazine) 5 wt.% led to particularly high absorption performances in all CO 2 concentration range. Besides the experimental measurements, Aspen Hysys™ simulations of the micro-pilot tests were performed for three solvents (monoethanolamine (MEA) as the reference case, then PZ and DEA + PZ) to validate the models implemented. Finally, the validated models were used to perform industrial scale simulations. These simulations confirmed that both the regeneration energy, the equivalent work and the operating costs are reduced when the absorption-regeneration process is implemented to flue gases with high CO 2 contents. [ABSTRACT FROM AUTHOR]

The carbon capture, utilisation and storage (CCUS) process chain is subject to increasing interest, and its overwhelming implementation on the industrial scale appears to be one of the main ways to reduce CO 2 emissions. In this context, the optimisation of a CO 2 purification process for oxy-combustion cement plant flue gases is proposed. This optimisation is based on a multidimensional study on the energy, exergy, economy, and environmental impacts of the process. The results of the optimisations carried out show that it is more favourable to increase the CO 2 recovery above 90%, from an energy, exergy and economic point of view. The analysis of the evolution of the capture cost as a function of the CO 2 recovery shows that for a given carbon tax, there is a minimum for the total cost which includes the sum of the carbon tax contributions for the uncaptured CO 2 and the capture cost. As the unit uses only electrical energy, the cost and the electricity generation will directly impact the capture cost as well as the overall balance in terms of CO 2 avoided. As the electricity price increases from 50 to 250 €/MWh, the CO 2 capture cost increases by almost 250%. An analysis of the parameter uncertainties allows to observe their impacts on the results, and to define a standard deviation from the optimised points and show the robustness of these. Considering the technical parametric uncertainties, the standard deviation on the electrical consumption (3.65 kWh/t CO2), CO 2 recovery (0.09%) and exergy efficiency (0.92%) is limited. • Study of hybrid CO 2 capture system combining cryogenic and membrane technologies. • 4E analyses considering recovery, energy consumption, exergy yield and capture cost. • Maximum exergy efficiency for the cases where the CO 2 recovery is above 90%. • High sensitivity of the electricity price on the CO 2 capture cost. • Uncertainty quantification of modelling assumptions and impact on 4E analyses. [ABSTRACT FROM AUTHOR]

Tris-copper centers are present at the active site of multicopper oxidases (MCO) which couple the four-electron reduction of molecular oxygen to water with the oxidation of substrates. Modelling these sites with small molecular complexes has thus attracted the interest of many groups in the (bio)inorganic community over the past three decades and still appears a challenge. These enzymes and their model complexes presently enjoy a renewed interest as potential non-precious metal catalyst for the Oxygen Reduction Reaction. Moreover recent work has revealed that tris-copper centers can catalyze methane oxidation. Therefore the elaboration of tris-copper system constitutes an important and timely issue. The aim of the present review is to analyze the various attempts at preparing tris-copper complexes in terms of strategy of ligand design. Of course the challenge to be met is to force three independent binding sites to converge and react in concert. Three main approaches have been developed to anchor these binding sites based on the use of (i) a node either (a) a single atom node (tren-based systems and related), or (b) an hexa -atom node (mesityl-based systems and derivatives), (ii) macrocyclic systems, and (iii) combination of mono- and dinuclear sites. The structures of the different systems will be described and analyzed accordingly. Then the various reactivities exhibited by these systems will be presented so as to evaluate how the ligand design influences the reactivity and to discern promising future directions. [ABSTRACT FROM AUTHOR]

Abstract Chemically tuned pillared graphene structures show ability to limit restacking of graphene sheets for electrochemical energy storage in SCs. A comprehensive electrochemical characterization using various ion sizes allowed identification of ion-sieving in the cross-linked galleries of reduced pillared graphene materials (RPs). The access to the cross-linked galleries, which provide additional ion sorption sites, offered slightly increased capacitances in RPs compared to completely restacked sheets in reduced graphene oxide (RGO). We performed electrochemical impedance analyses on RPs and RGO to understand the ion transport inside the cross-linked graphene galleries. RGO adsorbs ions in the inter-particle micro/meso pores and the ion access to such sites from the bulk electrolyte occurs with relative ease. RPs sieve ions into their inter-layer gallery pores based on effective ion sizes and the ion transport process is resistive compared to RGO. A control study using 3D pillared graphene hydrogel with improved macro porosity assigns this resistive behavior and the moderate capacitances to limited ion access to the active sites due to excess number of pillars. The obtained results on the ion transport dynamics between graphene layers provide perspectives towards further optimization of these graphene materials for SCs. Graphical abstract Ion transport inside the inter-layer galleries of pillared graphene materials is impeded by the pillars. Image 1 [ABSTRACT FROM AUTHOR]

Direct Air Capture (DAC) technologies are gaining interest in the concept of carbon utilization and Power-to-Gas (PtG), as the economic valorization of the CO 2 into methane provides a viable pathway to allow DAC systems to mature. However, research on DAC mainly focuses on isolated systems, and the system performance depends on parameters that are highly uncertain. To study the integration of DAC in PtG, we developed a DAC-PtG model, performed an Energy, Exergy, Economic and Environmental (4E) analysis and implemented uncertainty quantification to consider the uncertain environment. The results illustrate that the DAC-PtG system is autothermal when introducing a two-stage mechanical vapor recompression unit at the DAC outlet. The exergy efficiency ranges between 51.3% and 52.6% within 3 standard deviations, for which the uncertainty is driven by the ambient conditions and the uncertain heat of desorption. The methane issued from DAC-PtG has a lower carbon footprint than fossil methane when the carbon footprint of the electricity supply is below or equal to 0.12 kg˙CO˙2-eq /kWh. The Levelized Cost of Synthetic Natural Gas (LCSNG) ranges between 130 €/ MWh and 744 €/ MWh, following an uncertain electricity price and uncertain expenses related to DAC and electrolysis. Therefore, bulk manufacturing, further maturing of these technologies and more demonstration projects are required to reduce the uncertainty of the LCSNG. Future works will consider intermittent renewable energy sources to supply power. • Integrated direct air capture and CO 2 methanation are investigated. • Exergy efficiency ranges between 51.3% and 52.6% within three standard deviations. • The levelized cost of synthetic natural gas ranges between 130 €/MWh and 744 €/MWh. • Electricity emission intensity below 0.12 kg CO2-eq /kWh results in carbon reduction. • To reduce uncertainty, bulk manufacturing and more pilot projects are needed. [ABSTRACT FROM AUTHOR]