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[Display omitted] • Cryogenic CO 2 capture and storage (CCS) reduces power generation efficiency penalty. • Power consumption during natural gas liquefaction decreases by up to 67.17%. • Liquefied natural gas (LNG) supply chain with cryogenic CCS reduces energy waste. • Natural gas liquefaction and regasification are integrated based on cryogenic CCS. • The exergy efficiency in the LNG supply chain is increased from 18.18 to 46.39%. Natural gas combined cycle power plants generate substantial amounts of CO 2. Also, since natural gas is produced in limited sites, the liquefied natural gas (LNG) supply chain consumes considerable energy in transporting natural gas overwide. Herein, advanced natural gas liquefaction and regasification processes using an LNG supply chain with cryogenic CO 2 capture and storage (CCS) are proposed using Aspen Plus® V11. This solves three significant problems associated with conventional LNG supply chains. First, through the utilization of LNG cold energy, the cryogenic CCS process reduces the efficiency penalty of power generation from 14.34 to 4.45%. Second, solid CO 2 from cryogenic CCS is used as an additional cold source in the natural gas liquefaction process by conveying it to the liquefaction site via the returning LNG ship. As a result, the power consumption in the refrigerant cycle is reduced by up to 67.17% than single mixed refrigerant (SMR) process. Finally, the LNG supply chain with cryogenic CCS minimizes the sustained energy waste between the natural gas liquefaction and regasification stages owing to the geographical separation. LNG cold energy from the regasification stage is utilized in the form of solid CO 2 in the CCS and liquefaction stages. Consequently, the exergy efficiency in the overall LNG supply chain increases from 18.18 to 46.39%. The findings of this study can potentially provide environmentally friendly design guidelines for various LNG processes that use LNG cold energy in CCS and natural gas liquefaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxy-fuel combustion-based blue hydrogen production process. • Integrates fossil fuel-based hydrogen production and electrolysis processes. • Proposed processes are SMR + SOEC and SMR + PEMEC. • SMR + SOEC shows highest thermal efficiency (85.2%) and exergy efficiency (80.5%) • SMR + SOEC shows lowest levelized cost of hydrogen and life cycle GHG emissions. Blue hydrogen is gaining attention as an intermediate step toward achieving eco-friendly green hydrogen production. However, the general blue hydrogen production requires an energy-intensive process for carbon capture and storage, resulting in low process efficiency. Additionally, the hydrogen production processes, steam methane reforming (SMR) and electrolysis, emits waste heat and byproduct oxygen, respectively. To solve these problems, this study proposes an oxy-fuel combustion-based blue hydrogen production process that integrates fossil fuel-based hydrogen production and electrolysis processes. The proposed processes are SMR + SOEC and SMR + PEMEC, whereas SMR, solid oxide electrolysis cell (SOEC), and proton exchange membrane electrolysis cell (PEMEC) are also examined for comparison. In the proposed processes, the oxygen produced by the electrolyzer is utilized for oxy-fuel combustion in the SMR process, and the resulting flue gas containing CO 2 and H 2 O is condensed to easily separate CO 2. Additionally, the waste heat from the SMR process is recovered to heat the feed water for the electrolyzer, thereby maximizing the process efficiency. Techno-economic, sensitivity, and greenhouse gas (GHG) analyses were conducted to evaluate the efficiency and feasibility of the proposed processes. The results show that SMR + SOEC demonstrated the highest thermal efficiency (85.2%) and exergy efficiency (80.5%), exceeding the efficiency of the SMR process (78.4% and 70.4% for thermal and exergy efficiencies, respectively). Furthermore, the SMR + SOEC process showed the lowest levelized cost of hydrogen of 6.21 USD/kgH 2. Lastly, the SMR + SOEC demonstrated the lowest life cycle GHG emissions. In conclusion, the proposed SMR + SOEC process is expected to be a suitable technology for the transition from gray to green hydrogen. [ABSTRACT FROM AUTHOR]

[Display omitted] • On-site hydrogen refueling stations require efficient catalysts/reactors. • Intrinsic kinetics of Ru catalysts were estimated using a parametric estimation. • New multistage (two- and three-stage) reactor designs were proposed. • Multistage reactors showed less temperature drop (better reactor stability). • Three-stage reactor can improve hydrogen production and conversion. In recent years, interest in the development of a hydrogen economy has increased, and the steam methane reforming (SMR) reaction, which yields so-called "gray" hydrogen, is expected to play a key role in hydrogen refueling stations (HRSs) in the interim before "green" hydrogen process is developed. For this purpose, compact and economical designs for small- to medium-scale SMR processes for HRSs are required. Herein, we investigated the intrinsic kinetics of a Ru-based catalyst using catalyst experiments and parametric estimation. In addition, reactor modelling was performed using a kinetic model with a special focus on multistage reactor configurations. The proposed reactor design showed an increase in the reactor energy supplied rate from 6.98 to 7.55 kW compared to the base case (single-stage reactor), and the conversion increased from 86.2% to 91.2%. Further, the drastic temperature drop owing to the strongly endothermic nature of the SMR reaction was reduced, and, thus, reactor stability was improved. The proposed novel design of a multistage reactor using a Ru-based catalyst will advance the development of the hydrogen economy. [ABSTRACT FROM AUTHOR]

• DNN data-driven model for steam methane reforming is developed. • Data preprocessing techniques were applied to improve the quality of datasets. • Four hyperparameters were optimized to obtain an accurate prediction model. • Process optimization was conducted with 387,320,489 cases under five constraints. • The operating conditions were optimized to achieve a thermal efficiency of 85.6%. The production and application of hydrogen, an environmentally friendly energy source, have been attracting increasing interest of late. Although steam methane reforming (SMR) method is used to produce hydrogen, it is difficult to build a high-fidelity model because the existing equation-oriented theoretical model cannot be used to clearly understand the heat-transfer phenomenon of a complicated reforming reactor. Herein, we developed an artificial neural network (ANN)-based data-driven model using 485,710 actual operation datasets for optimizing the SMR process. Data preprocessing, including outlier removal and noise filtering, was performed to improve the data quality. A model with high accuracy (average R 2 = 0.9987) was developed, which can predict six variables, through hyperparameter tuning of a neural network model, as follows: syngas flow rate; CO, CO 2 , CH 4 , and H 2 compositions; and steam temperature. During optimization, the search spaces for nine operating variables, namely the natural gas flow rate for the feed and fuel, hydrogen flow rate for desulfurization, water flow rate and temperature, air flow rate, SMR inlet temperature and pressure, and low-temperature shift (LTS) inlet temperature, were defined and applied to the developed model for predicting the thermal efficiencies for 387,420,489 cases. Subsequently, five constraints were established to consider the feasibility of the process, and the decision variables with the highest process thermal efficiency were determined. The process operating conditions showed a thermal efficiency of 85.6%. [ABSTRACT FROM AUTHOR]

[Display omitted] • LP-HTL and MSP increased gas yield & achieved high monomer recovery. • LP-HTL and MSP achieved ethylene and propylene yield of 53.07 %. • Energy requirements reduced by 95.82 % by eliminating refrigerants from the process. • GTP100 and GWP100 values were 90 % lower than those of the reference process. • The olefins, monomers of plastics, can be used to manufacture circular plastics. Plastics pose environmental challenges in landfills, persisting for extended periods spanning thousands to millions of years. Consequently, research into plastic depolymerization has gained significance, aiming to address the problem of plastic waste management and the increasing demand for plastics. This study proposes a novel process for recovering olefins, specifically ethylene and propylene, from waste polyethylene (PE) and polypropylene (PP) through low-pressure hydrothermal liquefaction (LP-HTL) and microwave steam pyrolysis (MSP) chemical recycling. Mixed waste PE and PP undergo LP-HTL to produce gas and oil. Subsequently, the oil from the LP-HTL undergoes cracking via MSP to enhance olefin recovery. Olefin compounds produced through distillation serve as refrigerants. The results demonstrated the production of 39.75 wt% C 2 H 4 and 13.32 wt% C 3 H 6 , achieving a total recovery of 53.07 wt% of olefin materials. The levelized cost of ethylene (LCOE) in the proposed process was calculated at 0.89 USD/kg C 2 H 4 , equating to a 72.86 % reduction compared with that in flash pyrolysis. Furthermore, the life cycle assessment (LCA) results indicated reduced 100-year global temperature potential and global warming potential (GTP100 and GWP100) emissions of 2.46 and 2.55 kg CO 2 eq/kg C 2 H 4 , respectively, approximately 90 % lower than that in the flash process. Thus, the proposed process, with its energy efficiency and high recovery rates, can serve as a benchmark for future plastic depolymerization endeavors aimed at achieving a circular carbon economy. [ABSTRACT FROM AUTHOR]

[Display omitted] • A sustainable conversion of plantation waste into syngas was achieved using CO 2 (key greenhouse gas). • CO 2 served a partial oxidant reacting with volatile pyrogenic products evolved from rubber tree residue, leading to enhancement of syngas, especially CO. • Oxidative functionality of CO 2 on syngas production was intensified in the presence of a nickel-based catalyst (Ni/Al 2 O 3). • Integrated process of catalytic pyrolysis and water–gas shift reaction notably increased H 2 productivity. This study introduces the sustainable recovery of energy from plantation waste by converting rubber tree residue (RTR) into syngas through carbon dioxide (CO 2)-assisted pyrolysis. The investigation centers on elucidating the specific impact of CO 2 on the pyrolysis of rubber tree residue, emphasizing its significant influence on enhancing syngas production. At temperatures ≥ 500 °C, CO 2 engages with volatile matters (VMs) released during the thermolysis of rubber tree residue, increasing carbon monoxide (CO) yields. To further optimize the process, catalytic pyrolysis setups incorporating additional heat (600 °C) and a nickel-based catalyst (Ni/Al 2 O 3) were implemented. These experimental configurations substantially increased syngas production from 19.51 to 24.24 mmol g−1, particularly amplifying CO yields under CO 2 conditions 2.58-fold compared to nitrogen (N 2) conditions. This enhancement is attributed to the partial oxidation of volatile matters facilitated by CO 2. Additionally, the Ni/Al 2 O 3 catalyst played a pivotal role in expediting the gas-phase homogeneous reaction of CO 2 with volatile matters, leading to further improved syngas production. Indeed, the syngas yield in the catalytic pyrolysis in the presence of CO 2 was 24.24 mmol g−1, which increased by 1.24 times in reference to the result under the N 2 environment. The identified functional role of CO 2 presents an opportunity to enhance the sustainability of waste management by optimizing carbon utilization and generating value-added products. [ABSTRACT FROM AUTHOR]

• Novel waste energy recovery process for carbon capture and storage was developed. • Waste cold and hot energy from liquefied natural gas plant is recovered. • Net power generation can increased by 16% compared to base process. • Net profit can increased by 75% compared to base process. In an liquefied natural gas (LNG) power plant, the amine scrubbing and CO 2 liquefaction process are generally employed for CO 2 capture and storage (CCS) because it is suitable for large-scale plants. However, a large amount of hot and cold energy is required for CO 2 absorption, regeneration and liquefaction. As a solution, the waste LNG cold energy from the LNG regasification process and waste hot energy from natural gas combined cycle (NGCC), which are generally disposed into the seawater, can be recovered and utilized for the abovementioned purposes. Hence, this study suggested a novel process for waste hot and cold energy recovery of the LNG power plants for CCS. The suggested process model consists of the following four steps: LNG regasification, natural gas combined cycle, CO 2 capture and regeneration and CO 2 liquefaction. In the process model, the waste LNG cold energy is recovered at the lean amine cooler in the CO 2 capture process and each heat exchanger in the CO 2 liquefaction process. Furthermore, for CO 2 regeneration, the waste hot energy from NGCC is recovered at the stripper reboiler. The exergy and economic analyses were addressed to evaluate the economic feasibility of energy conversion of the proposed process. As a result, compared to the base process, the net power generation and exergy efficiency of the proposed process increased by 16% and 8%, respectively. In addition, the net profit of the proposed process increased by 75%, indicating high economic feasibility. The overall energy efficiency and economic feasibility using waste cold and hot energy were observed to increase, which resulted in decreased fuel usage. Therefore, we believe that the proposed approach can contribute significantly to the economic improvements and environmental protection efforts. [ABSTRACT FROM AUTHOR]

• Oxygen gas produced from the PEMEC is used for biogas ATR reforming for large-scale hydrogen production. • Continuous oxygen supplied is available using intermediate oxygen storage system. • The LCOH of the proposed system is distributed between 4 $/kg H2 and 10 $/kg H2 under uncertainties. • Robust optimization reduces mean and variance of the LCOH by 11.96 % and 37.81% on average. • The proposed system could provide low LCOH in current green hydrogen market. The oxygen gas produced from electrolysis is both a good heat supplier and an oxidizing agent for the autothermal reforming (ATR) process. Thus, green hydrogen production could be achieved by integrating the biogas ATR and electrolysis processes directly with renewable power sources. Under the natural fluctuation of renewable power, the oxygen produced from electrolysis can be stored in a compressed or liquid state in an intermittent storage tank to buffer its production rate for steady-state operation of biogas ATR process. In this study, integrated systems have been newly proposed using compressed gas and liquid oxygen storage methods, which are denoted as PEMCOAR and PEMLOAR systems, respectively. Using the surrogate model based on polynomial chaos expansion methodology (PCE), the statistical moments of levelized cost of hydrogen (LCOH) of both proposed systems were optimized considering the uncertainties of renewable power, biogas composition, and electricity tariff. As a result, the mean and variance of LCOH is reduced by 11.9% and 37.8%, respectively. In case of renewable power and biogas price of 0.06 $/kWh and 5.58 $/MMBTU, it was observed that the average LCOH below the current green hydrogen market price at a renewable power scale of over 55 MW. In conclusion, the study suggests the optimal operating condition under uncertainties and simultaneously, prove the economic feasibility of integrating electrolysis and biogas ATR systems. [ABSTRACT FROM AUTHOR]