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Since hydrogen (H2) demand in the transportation field has increased as a result of efforts to reduce carbon emissions, the number of H2 refueling stations has been increasing as well. However, the transportation of H2 itself requires a lot of energy due to the low volumetric density of H2 necessitating energy-intensive processes of compression or liquefaction. In this context, ammonia (NH3) has been emerging as an efficient H2 carrier with several beneficial characteristics such as a large weight fraction of H2 (17.65%), and liquefaction at ambient temperature and moderate pressures which allows for the utilization of existing fossil fuel infrastructure. Thus, NH3 can be utilized as an H2 transport medium as well as a raw material for remote H2 refueling stations. In this study, a comparative 4E (energy, exergy, economic, and environmental) analysis of an H2 refueling station supplied from an on-site NH3 reforming using a packed bed reactor (PBR) and a membrane reactor (MR) is performed. Due to the higher H2 recovery in the MR, a greater H2 production rate is observed resulting in lower H2 production cost. Compared to the PBR, energy and exergy efficiency in the MR-based process are improved by 3.6%p and 2.7%p reaching 82.7% and 78.7%, respectively, and greenhouse gas emissions are reduced by ∼17% from 5.4 to 4.5 kgCO2-eq kgH2−1. The break-even price of H2 in the MR-based process at present is 8.1– 9.2 USD kgH2−1 (at scale of 900 kgH2 d−1) and the break-even points with the H2 selling price of 12.5 USD kg H2−1 are 7.8–8.9 y whereas the corresponding values are 9.4–10.5 USD kgH2−1 and 10.2–12.3 y in the process using the PBR. At an H2 selling price of 7.5 USD kgH2−1, most cases (90.6%) of the net present value in the MR-based process were positive in 2040 indicating an economically feasible process, while cases with lower H2 selling price (2.5 and 5.0 USD kgH2−1) were not deemed profitable under current technological level.

Real-time performance is important in rule-based continuous spatiotemporal query processing for risk analysis and decision making of target objects collected by sensors of combat vessels. The existing Rete algorithm, which creates a compiled node link structure for executing rules, is known to be the best. However, when a large number of rules are to be processed and the stream data to be performed are large, the Rete technique has an overhead of searching for rules to be bound. This paper proposes a hashing indexing technique for Rete nodes to the overhead of searching for spatiotemporal condition rules that must be bound when rules are expressed in a node link structure. A performance comparison evaluation experiment was conducted with Drool, which implemented the Rete method, and the method that implemented the hash index method presented in this paper. For performance measurement, processing time was measured for the change in the number of rules, the change in the number of objects, and the distribution of objects. The hash index method presented in this paper improved performance by at least 18% compared to Drool.

Accurate prediction of the hydrodynamic profile is important for circulating fluidized bed (CFB) reactor design and scale-up. Multiphase computational fluid dynamics (CFD) simulation with interphase momentum exchange is key to accurately predict the gas-solid profile along the height of the riser. The present work deals with the assessment of six different drag model capability to accurately predict the riser section axial solid holdup distribution in bench scale circulating fluidized bed. The difference between six drag model predictions were validated against the experiment data. Two-dimensional geometry, transient solver and Eulerian&ndash, Eulerian multiphase models were used. Six drag model simulation predictions were discussed with respect to axial and radial profile. The comparison between CFD simulation and experimental data shows that the Syamlal-O&rsquo, Brien, Gidaspow, Wen-Yu and Huilin-Gidaspow drag models were successfully able to predict the riser upper section solid holdup distribution with better accuracy, however unable to predict the solid holdup transition region. On the other hand, the Gibilaro model and Helland drag model were successfully able to predict the bottom dense region, but the upper section solid holdup distribution was overpredicted. The CFD simulation comparison of different drag model has clearly shown the limitation of the drag model to accurately predict overall axial heterogeneity with accuracy.

The well-established Haber-Bosch (HB) process (industrial ammonia production) is a significant contributor to the world’s carbon emissions as it is a major consumer of natural gas as well as being energy-intensive in general. This work addresses the challenge of decarbonizing the HB process in a novel way as it, for the first time, presents a conceptual process integration with a supercritical CO2 Allam power cycle, therefore transforming gaseous CO2 emissions into a valuable side product in a form of liquid CO2. Detailed process design and flowsheet simulation using Aspen Plus ® was used as a basis for scale-up and techno-economic assessment of two cases (electrical grid dependent and independent). The results indicated that using this process design NH3 production reaches profitability at scales larger than 2 ton h−1 to 5.4 ton h−1 and at current global NH3 prices, the cost of manufacturing decrease, due to scale-up stabilizes at ∼ 30 ton h−1. Finally, this novel process integration achieves a significant reduction in gaseous CO2 emissions (compared to conventional HB process) of 68 % to 96 %, which indicates great potential for economically feasible green NH3.

Hydrogen produced by the electrochemical water splitting is essential for expanding and utilizing renewable power sources and establishing a sustainable energy society. As renewable energy network widely established, the produced hydrogen can be utilized by connecting the energy demand and energy supply. The proton exchange membrane (PEM) water electrolyser technology is one of the ideal candidates for direct coupling with renewable energy sources. In recent years, bench-scale experiments, and computational fluid dynamics (CFD) simulation-based approaches are used to accelerate the advances in performance and cost of the technology. We studied the influence of the key performance parameter of a PEM water electrolyser, and a single channel-based three-dimensional CFD model was developed. The PEM water electrolyser CFD model is validated against in-house experiments, where the developed model successfully predicts the current–voltage polarization curve. The developed CFD model is then used to analyze the influence of temperature, cathode pressure, membrane thickness, porous transport layer porosity and water feed rate. The main observation from the numerical study was discussed to provide insight into the factors affecting the PEM water electrolyser performance.

This study comprehensively investigates hydrogen production from green ammonia reforming, including synthesis of catalysts, reactor development, process integration, and techno-economic analysis. In-house developed Ru/La–Al2O3 pellet catalyst having perovskite structure showed high catalytic activity of 2827 h−1 at 450 °C and stability over 6700 h at 550 °C, exceeding the performance of the majority of powder catalysts reported in the literature. A scalable 12-faceted reactor adopting the as-produced catalyst was designed to enhance heat transfer, producing over 66 L min−1 of hydrogen with state-of-the-art ammonia reforming efficiency of 83.6 %. Near-zero CO2 emission of hydrogen extraction from green ammonia was demonstrated by-product gas recirculation as a combustion heat source. A techno-economic assessment was conducted for system scales from 10 kW to 10 MW, demonstrating the effect of reduced minimum hydrogen selling prices from 7.03 USD kg−1 at small modular scales to 3.98 USD kg−1 at larger industrial scales. Sensitivity analyses indicate that hydrogen selling prices may reduce even further (up to 50 %). The suggested hydrogen production route from green NH3 demonstrates superior CO2 reduction ranging from 78 % to 95 % in kg CO2 (kg H2)−1 compared to biomass gasification and steam methane reforming. These findings can be used as a basis for following economic and policy studies to further validate the effectiveness of the suggested system and process for H2 production from NH3.

As many countries have tried to construct a hydrogen (H2) society to escape the conventional energy paradigm by using fossil fuels, methane pyrolysis (MP) has received a lot of attention owing to its ability to produce H2 with no CO2 emission. In this study, a techno-economic analysis including a process simulation, itemized cost estimation, and sensitivity and scenario analysis was conducted for the system of thermal-based and catalyst-based MP (TMP-S1 and CMP-S2), and the system with the additional H2 production processes of carbon (C) gasification and water–gas shift (WGS) reaction (TMPG-S3 and CMPG-S4). Based on the technical performance expressed by H2 and C production rate, the ratio of H2 combusted to supply the heat required and the ratio of reactants for the gasifier (C, Air, and water (H2O)), unit H2 production costs of USD 2.14, 3.66, 3.53, and 3.82 kgH2−1 from TMP-S1, CMP-S2, TMPG-S3, and CMPG-S4, respectively, were obtained at 40% H2 combusted and a reactants ratio for C-Air-H2O of 1:1:2. Moreover, trends of unit H2 production cost were obtained and key economic parameters of the MP reactor, reactant, and C selling price were represented by sensitivity analysis. In particular, economic competitiveness compared with commercialized H2 production methods was reported in the scenario analysis for the H2 production scale and C selling price.

With the growing concern about environmental issues including high CO2 emission, which is the main contributor to global warming resulting in climate change, CO2 utilization technologies have received much attention. Among diverse technologies, renewable methanol synthesis using H2 generated from the water electrolysis and the CO2 captured from various industrial processes as well as the atmosphere has received significant attention. In this context, the technical and economic feasibility analysis of renewable methanol synthesis was conducted in this study. Using a commercial process simulation program, Aspen HYSYS®, parametric studies were conducted to investigate the effects of diverse operating parameters, such as the reaction pressure, temperature, and H2/CO2 ratio, on the technical performance of this process. Under the optimum conditions of 100 bar and 493 K derived from thermodynamic studies, an economic analysis was performed to estimate the unit methanol production costs at different methanol production capacities using itemized cost estimation, sensitivity analysis, and predictive cost analysis. Predictive cost analysis was conducted to determine how the unit methanol production cost could be rendered reasonable compared to the existing one, which indicated that decreasing the renewable H2 production cost as well as increasing in the CO2 tax credit for a methanol production capacity of 100 ton per day would make the renewable methanol synthesis an economically feasible process.

Background: The negative pressure of the pleural cavity is critical to maintain lung expansion. However, the actual values of pleural pressure according to the phase of respiration after various types of pulmonary resection have not been well reported. The aim of this study was to measure the pleural pressure directly and to compare the results according to the extent of pulmonary resection. Methods: We manufactured a high-resolution digital manometer with which pleural pressure can be measured directly. A total of 43 patients who underwent thoracic surgery (lobectomy in 23, minimal resections in 20) were enrolled. The maximum, minimum, and mean pleural pressure was recorded during normal quiet breathing, forced breathing, and coughing, separately. Results: During normal quiet breathing, the average values of pleural pressure at end inspiration, end expiration, and the mean pleural pressure were −17.7, −7.0 and −11.2 cmH 2 O in lobectomy group, and −14.3, −4.6, −8.3 cmH 2 O in the minimal/no-resection group, respectively. The mean pleural pressure was significantly lower in lobectomy group compared to the minimal/no-resection group (P=0.026). During forced respiration, the same values were −44.0, −4.2 and −18.9 cmH 2 O in the lobectomy group, and −29.8, −0.1 and −12.7 cmH 2 O in the minimal/no-resection group. All of the pleural pressure values in lobectomy group were significantly lower compared to minimal/no-resection group (P=0.029, P=0.015, P=0.019, respectively). The maximal pressures during coughing were not statistically different between the two groups (38.4 vs . 34.4 cmH 2 O, P=0.687). Conclusions: We reported the actual pleural pressure changes according to the phase of respiration and type of surgery using a digital manometer. In lobectomy patients, the pleural pressure was highly negative compared to the minimal/no-resection group, especially during deep inspiration.