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[Display omitted] • The production of heat and hydrogen gas by water splitting was investigated. • AA6061 pellets and Al beverage can scraps were oxidized in aqueous NaOH solutions. • The aluminum-alkali reaction system is applicable in the district heating field. The production of heat and hydrogen gas by water splitting was experimentally investigated in a circulating flow reactor. Aluminum (Al) alloy pellets (i.e., AA6061; 10 mm long and 0.5 mm in diameter) and aluminum beverage can scraps (10 mm wide by 10 mm long and 0.24 mm thick) were used as the energy source, while sodium hydroxide (NaOH; 98 % purity) pellets were used to make aqueous alkali solutions. The temperature, mass flow rate, and molar concentration of NaOH solutions were varied in the range of 25 ∼ 85 ℃, 4.4 ∼ 21.4 g sol /s, and 1 ∼ 4 M NaOH , respectively, to conduct a parametric study. The experimental results showed an increase in hydrogen (H 2) production rate with increasing solution temperature and NaOH molar concentration, whereas the H 2 evolution rate was not reduced significantly with increases in the amount of AA6061 pellets charging the reactor or the mass flow rate of the NaOH solution. From the one-cycle operation results, the average heat generation rate and hydrogen production rate for AA6061 pellets and aluminum beverage can scraps were 3.26 Wh th /g AA6061 , 2.06 Wh th /g Alcan , 3.54 Wh H2 /g AA6061 , and 2.72 Wh H2 /g Alcan , respectively. Generation of a combination of heat and power for next-generation district heating was deemed possible using the combination of common AA6061 pellets, Al beverage can scraps, and aqueous NaOH solutions in a circulating flow reactor. [ABSTRACT FROM AUTHOR]

• Experimental Evaluation of the effectiveness of the immiscible CO2-AGD process in water-wet reservoirs with bottom water drive. • Used a Hele-Shaw model with two parallel glass plates and silica sand to visually assess process performance. • Investigated the process's effectiveness in reducing water cut and delaying cresting. • Evaluated the impact of bottom water drive intensity, water cut, and gas breakthrough time on CO2-AGD process performance. • Evidence shows that aquifer strength improves breakthrough and ultimate oil recovery. Mature oil reservoirs surrounded with strong edge and bottom water drive aquifers experience pressure depletion and water coning/cresting. This laboratory research investigated the effects of bottom water drive and gas breakthrough on immiscible CO 2 -Assisted Gravity Drainage (CO 2 -AGD), focusing on substantial bottom water drive. The CO 2 -AGD method vertically separates the injected CO 2 to formulate a gas cap and Oil. Visual experimental evaluation of CO2-AGD process performance was performed using a Hele-Shaw model. Water-wet sand was used for the experiments. The gas used for injection was pure CO 2 , and the "oleic" phase was n-decane with a negative spreading coefficient. The aqueous phase was deionized water. To evaluate the feasibility of the CO 2 -AGD process without any bottom water drives, it was first used. The experimental results demonstrated that existence of bottom water drive affected oil recoveries due to pressure support. Oil recovery before gas breakthrough increases proportionally with bottom water drive intensity. The gas breakthrough time recoveries for CO 2 -AGD1, CO 2 -AGD2, and CO 2 -AGD3 runs were 38.68%, 50.70%, and 60.85% of OOIP. The pressure gradient along the physical model decreases as bottom water drive intensity increases. The CO 2 -AGD approach delayed gas breakout by 72 min. As aquifer strength increases, gas breakthrough is delayed. In the three CO 2 -AGD runs and after breakthrough occurrence, the injector-producer pressure difference decreased due to the residual heads of oil and water columns above the horizontal well. As long as oil and water exist in the model, the pressure differential will not be zero, and the relative permeability and capillary trapping also control this phenomenon. Finally, it was demonstrated that there is a direct correlation between the strength of the aquifer and the oil recovery factor. The strength of the aquifer positively affects the oil recovery at breakthrough and the ultimate oil recovery. [ABSTRACT FROM AUTHOR]

• The coupling deposition and plugging of wax and hydrate were systematically investigated. • The coupling solid phase of hydrate and wax is bulk aggregations arch bridge deposition. • The effect of wax on the coupling deposition with different water content is opposite. • The coupling deposition and plugging of wax and hydrate in gas-annular flow has four stages. The coupling deposition and plugging caused by hydrate formation and wax precipitation during the development of deep water natural gas resources bring new industrial challenges and theoretical difficulty. We designed a single-pass pipeline with two types to investigate deposition behavior and systematically performed the coupling deposition and plugging of hydrate and wax experiments in gas–liquid annular flow. The experimental results illustrate that the single solid phase of hydrate is covered layer sheet deposition, while the coupling solid phase of hydrate and wax is bulk aggregations arch bridge deposition. Meanwhile, the natural eddy zone in reducing pipeline accelerates coupling solid particles deposition. Our finds provided the first knowledge on the double effect that wax crystals inhibit particles adhesion and gel network increases aggregations arch bridge blockage. For the low water content in emulsion system, the gel network provides gathering place for hydrate particles, and the arch bridge structure formed by aggregations accelerates the pipeline blockage. The plugging time is shortened by up to 72.6% with the wax concentration increase from 0 wt% to 3 wt%. For the high water content in emulsion system, the majority of wax crystals adsorbed on the hydrate particles and reduce particles cohesion force, which increase the plugging time. Combined with the microscopic morphology evolution perspective of hydrate particles coupled wax, the coupling deposition of hydrate and wax in gas–liquid annular flow has four stages: gas–liquid flow, coupling solid phase formation, coupling solid phase deposition and sloughing, and coupling solid phase plugging. This study can provide theoretical support and design basis for flow assurance program of deep water gas fields and low temperature natural gas transportation pipelines. [ABSTRACT FROM AUTHOR]

• Wall-protection isolated dual-active sites of Fe-Co catalysts were fabricated. • A controllable distribution of active Fe and Co sites in 3D structure was realized. • Catalyst with wall-protection could increase the specific surface area apparently. • The ordered distribution sequence of Fe and Co favored the formation of C 5+. Carbon dioxide hydrogenation into valuable chemicals is an attractive strategy for CO 2 fixation. Constructing bimetallic Fe-Co catalysts achieves high selectivity of heavy hydrocarbons instead of undesired methane is challenging, owing to the high methanation of cobalt. Herein, we develop an isolated dual-active sites of Fe-Co catalyst that separates Fe and Co via a carbon shell by multi-step impregnation combination with hydrothermal synthesis strategy. Fe-Co catalyst (C/FeCo 3) with an intimate contact presents a high CH 4 selectivity and low selectivity of C 5+ hydrocarbon. However, C 5+ hydrocarbon selectivity climbs from 19.8 % to 39.7 % over the cleverly designed wall-protection isolated dual-active sites of Fe-Co catalyst (C/Co 3 @C/Fe). The designed isolated structure between different active sites is conducive to chain propagation reaction by suppressing methanation reaction. As verified by in situ DRIFTS, more –CH 2 – species is enriched in the structure of C/Co 3 @C/Fe catalyst, which is considered as intermediate ingredient in the chain growth process. The designed structure catalyst strengthens the cascade reaction process of reverse water gas reaction and chain growth, and its combination with bimetallic catalysts may be a very potential measure for the preparation of bimetallic catalysts in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Inverse Nb-CeO 2 /Cu samples were separately prepared by four methods. • Their structures and activities in low-temperature water-gas shifts were compared. • The coprecipitation sample exhibited the highest CO conversion and H 2 selectivity. • Nano Nb-CeO 2 /Cu promotes active nanointerfaces and sintering resistance. • Results of this study should help researchers develop new environmental catalysts. A comparative investigation of inverse Nb–CeO 2 /Cu catalysts obtained via sol–gel, coprecipitation, hydrothermal, and incipient wetness impregnation methods was performed against a normal configuration for hydrogen production through a water–gas shift reaction. Exposed oxygen-deficient Nb–CeO 2 (1 1 1) facet sites deposited on Cu (1 1 1) facets with enhanced densities of Ce3+, Cu+, and O v species for high reducibility were confirmed using X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Nb–CeO 2 /Cu catalyst prepared by coprecipitation exhibited the highest activity of 68 % CO conversion, 100 % H 2 selectivity at 360 °C, and gas hourly space velocity of 43,535 h−1. The lowest activation energy (39.67 kJ/mol) and high turnover frequency illustrate facilitated water dissociation and CO oxidation in close vicinity across nanointerfaces. For the Nb–CeO 2 /Cu catalyst prepared by the coprecipitation method, nanosized Nb–CeO 2 stabilized over the porous Cu support was optimum for generating interfaces and facilitating catalytic performance. It is to underscore that the catalyst prepared by coprecipitation exhibited constant H 2 production under realistic conditions for 102 h, demonstrating the robust structural features of the configuration Nb–CeO 2 /Cu. [ABSTRACT FROM AUTHOR]

• With regard to the imbibition effect, the soaking process is introduced to the CO 2 foam flooding process in the fractured low-permeability reservoirs. • CO 2 foam flooding experiments are carried out using various injection techniques in order to maximize the simulation of fluid exchange between the fracture-matrix system. • The influencing factors on the CO 2 foam flooding impact in fractured low-permeability reservoirs are experimentally investigated. • Combined with microscopic flooding experiments and core experiments, the EOR mechanism of CO 2 foam injection in fractured low-permeability reservoirs is revealed. Fractured low-permeability reservoirs are characterized by poor reservoir physical properties, strong interlayer heterogeneity and the existence of natural and artificial fractures, resulting in significant water or gas channeling during flooding development. CO 2 foam can effectively control the mobility of CO 2 and ensure a more stable flooding front. In this study, taking into account the imbibition effect of the flooding process, the flooding performance under different injection methods and the influencing factors of foam pre-injection volume, back pressure and fracture complexity on CO 2 foam flooding were systematically analyzed using fractured low-permeability core flooding experiments. In addition, the mechanism of CO 2 foam flooding enhanced oil recovery (EOR) in low-permeability fractured reservoirs was obtained in combination with microscopic flooding experiments. The results show that the maximum recovery of 59.36 % can be obtained by soaking the core samples for 12 h with pre-injection of 0.4 PV CO 2 foam followed by CO 2 foam flooding, which adequately considers the imbibition effect during the flooding process. The pressure difference and oil recovery increases with increasing foam pre-injection amount, and the oil recovery with back pressure (2 MPa and 4 MPa) is significantly higher than that without back pressure; however, a further increase in back pressure has less impact on the recovery. The oil recovery rate of the fracture-free core is lower than that of the multiple fracture core during CO 2 foam flooding but higher than that of the single fracture core, and the fracture complexity of the fractured cores has less impact on the final oil recovery. Microscopic experiments show that CO 2 foam can effectively prevent channeling and improve the sweep efficiency. Soaking during the CO 2 foam flooding process makes foam enter the matrix through the fracture, and CO 2 dissolves after the foam breaks to increase the mobility of the crude oil, while the surfactant solution emulsifies the crude oil and changes the rock wettability. The unbroken foam can increase the sweep range, and the crude oil that flows into the fracture is carried by the subsequent injected foam to be recovered as foamy oil. [ABSTRACT FROM AUTHOR]

• Inhibition characteristics of mist on gas/dust explosions was studied by experiment. • Pressure, flame temperature, propagation characteristics and products were analyzed. • Relationship between mixture explosion parameter under mist condition was clarified. • Effects of mist and methane concentrations on explosion inhibition were obtained. • Effective engineering suggestion was proposed and inhibition mechanism was reveale. Inhibition of water mist on the gas/dust two-phase explosions and its influence factor were studied inside the vessel. The effects of mist and methane concentrations on the pressure and its rise rate, flame propagation characteristics and its temperature were explored. Especially the explosion products were analyzed by the infrared spectroscopy. The weakening effect was revealed based on the corresponding relationship and changing rule of explosion parameters. As the flame developed and changed, the pressure rise showed the same correspondence. However, the corresponding moment was evidently prolonged compared with the case no mist. The mist could effectively inhibit the intensity of mixture explosions, causing a dark-irregular structure in the early stage and accelerating its extinction in the later stage. After the mist concentration increased, the explosion parameter was evidently reduced. As the methane concentration increased (4% ≤ c ≤ 10%), the explosion parameters appeared a trend of firstly rising and then reducing. As c = 6%, the explosion intensity was the greatest. After adding mist, the explosion parameter exhibited the same change regular. And the weakening effect of mist on the weaker flame was more outstanding and was constantly enhanced as the rise of mist concentration. Besides, the mist could effectively inhibit the pyrolysis and combustion reactions of macromolecular functional groups, further leading to evident increase in the functional group content inside the coal dust as the mist concentration increased. [ABSTRACT FROM AUTHOR]

• Effect of gas to water ratio and nano-Cu dosage on hydrate formation was revealed. • The conductivity was calculated by the Green-Kubo approach and EMD simulations. • The relationship among various process factors was identified by PCC. • The performance of formation system was evaluated by design factor. Natural gas hydrate (NGH) is a highly promising alternative for gas storage and transportation. Nevertheless, the artificial generation of gas hydrates faces considerable obstacles for large-scale commercial implementation, primarily due to its slow formation rate and inadequate storage density. This study delves into the effects of gas to water ratios and metal nanoparticle dosages on the synthesis of NGH. Molecular dynamics (MD) simulations were employed to examine the formation of CH 4 hydrate under varying gas to water ratios and metal nanoparticle concentrations. The investigation assessed critical parameters of the gas–water system, such as radial distribution function, carbon storage ratio, hydrate cages, potential energy, diffusion coefficient, and thermal conductivity. For the first time, Pearson's correlation coefficient analysis was utilized to discern the interrelationships among these factors. The results demonstrated that medium gas to water ratios led to increased carbon storage, a higher number of cages, and augmented energy consumption. The nano-Cu dosage impacted the stability of hydrates and the thermal conductivity of the gas–water system, particularly at elevated gas to water ratios. Drawing on the MD simulation findings, a design factor was introduced to appraise the performance of the multicomponent system, which in turn, informs the development of a high-performance NGH formation system. The effectiveness of the design factor was corroborated through laboratory experiments, revealing its robust potential for designing high-performance NGH systems. This research paves the way for the practical realization of efficient hydrate-based production in real-world applications. [ABSTRACT FROM AUTHOR]

• Inflatable temperature–sensitive hydrogel (HPMC–CS–EM) was prepared to prevent coal spontaneous combustion. • The HPMC–CS–EM (A 50 , B 50) prepared with Hydroxypropyl Methyl Cellulose viscosity of 50 mPa∙s and Expanded Microsphere content of 0 %, 0.5 %, had good stability, expansibility and fluidity. • The inhibition effect of B 50 gel was obvious in the initial mass loss stage of coal, and the inhibition effect of A 50 gel was mainly manifested in the slow oxidation stage. A serious of inflatable temperature–sensitive hydrogel (HPMC–CS–EM) were prepared to prevent coal spontaneous combustion (CSC). Through performance tests, it was found that gel of 50 mPa∙s HPMC had good fluidity, the addition of EM can increase the water loss in the early pyrolysis stage. A 50 , B 50 prepared by 50 mPa∙s HPMC and 0 %, 0.5 % EM had good performance which were suitable for the prevention of CSC. The inhibition of A 50 , B 50 on CSC was tested by means of paramagnetic resonance spectroscopy and thermogravimetry. Inhibition experiments revealed that more water and hydrocarbon gas were released from B 50 gel, thereby significantly reducing the concentration and amount of free radicals, the maximum water loss rate temperature and the dry crack temperature. The more carbon residue of A 50 gel made it have better inhibition effect in the slow oxidation stage. The average apparent activation energy was obtained by the combination of universal integral and differential at multiple heating rates, indicating that these two gels remarkably reduced the tendency of CSC. [ABSTRACT FROM AUTHOR]

• Influence of material composition on reservoir property and gas enrichment. • Differences in the storage potential of various states of methane. • Differential accumulation rule of methane in lignite. The significant variation in production in different blocks has seriously restricted the large-scale breakthrough of China's low-rank coalbed methane industry for a long time. This study describes in detail the effects of lignite composition on reservoir structure, gas-bearing characteristics, and methane enrichment in the Erlian Basin, thus providing a theoretical basis for accurate exploration of lignite methane. Homogenization of huminite-rich lignite results in the disappearance of cellular structure, closure of cell cavity, small pore size, and low proportion of macropore. The cell wall of inertinite-rich lignite is thin, the cell structure is well preserved, and many cellular pores are developed, providing abundant macropore space. The inertinite-rich lignite contains larger pores and throats, and the content of high coordination number pores is also more abundant. Reservoir characteristics further control the occurrence, migration, and preservation of methane. The inertinite bands provide good seepage space and channels for lignite. The inertinite-rich lignite has high permeability and a low proportion of adsorbed methane, so methane has high mobility in it. The huminite-rich lignite has an excellent "self-sealing" effect on the gas. Overall, huminite-rich lignite in the stagnant area and inertinite-rich lignite in the regional structural culmination are potential favorable positions for the enrichment of lignite methane. Moreover, the interbedded thick coal seam of huminite-rich lignite and inertinite-rich lignite can provide advantageous conditions for water infiltration and gas preservation, thus forming a complete combination of "source, reservoir, and cap rock" in the thick lignite itself. [ABSTRACT FROM AUTHOR]

• Increasing water content in coal can reduce the elastic modulus and coal strength. • Water in coal reduces the initial gas diffusion speed and change adsorption constant. • Loosening blasting before water injection can promote cracks and water infusion. • Water injection after blasting reduces the gas outburst potential greatly. Gas outburst is a serious disaster in deep mining. In this paper, we first study the effect of water content on gas outburst, and found that increasing the water content of coal can significantly reduce the elastic modulus and uniaxial compressive strength, which is beneficial in reducing the peak stress concentration in the roadway and pushing the peak stress deeper. We also found that by increasing the water content of the coal seam, the firmness coefficient increases, while the initial speed of gas diffusion decreases simultaneously. Increasing the water content of the coal seam can also change the Langmuir adsorption constant of coal, reduce the a value of the limit adsorption capacity, increase the b value of the adsorption capacity, and reduce the amount of desorption gas in the coal. These studies indicate that increasing the water content of coal can significantly reduce the risk of gas outbursts. To increase the water injection volume, the technology of promoting coal seam infusion by blasting has been proposed. Blasting promotes equilibrium distribution in the stress field and generate new fractures, which promotes the water injection. In the 8th coal mine in the Pingdingshan coal field, the test results indicate that after loosening blasting, the water injection of a single borehole increased by an average of 54.6 times under the injection pressure of 3–7 MPa. The water content of coal is improved significantly, and the prediction index value of the gas outburst is reduced significantly. This technology is important for gas control in similar coal mines. [ABSTRACT FROM AUTHOR]

Highlights • Steam reforming is poisoned by H 2 S only and not effected by HCl. • WGS activity is poisoned by both H 2 S and HCl. • The poisoning of reforming activity by H 2 S is only partially reversible. • The poisoning of WGS activity by H 2 S and HCl can be completely restored. • The stronger NiO-Al 2 O 3 interactions provided beneficial effect to catalytic activity. Abstract H 2 S and HCl are common impurities in raw syngas produced during gasification of biomass and municipal solid waste. The purpose of this study was to investigate the poisoning effect of H 2 S and HCl on synthesized and commercial catalysts during steam reforming of naphthalene. Four synthesized catalysts with different loadings of Ni and Fe on alumina support and two commercial catalysts were selected and evaluated in a fixed bed reactor at 790, 850 and 900 °C. The obtained results revealed that reforming and water-gas shift (WGS) activities of catalysts did not benefit from the Fe addition. The activities were influenced differently by H 2 S and HCl indicating that the reactions were catalyzed by different active sites on the nickel surface. In the presence of H 2 S and HCl, the poisoning of naphthalene reforming activity was caused by H 2 S and was not affected by HCl when both compounds were present in the gas. H 2 S chemisorbs on nickel surface forming NiS and decreasing the accessibility of active sites to hydrocarbons. The poisoning effect was only partially reversible. On the contrary, the poisoning of WGS activity could be caused by both H 2 S and HCl, and the activity could be completely restored when H 2 S and HCl were removed from the gas. Unlike naphthalene reforming activity, which was comparable for catalysts with similar Ni loadings, WGS activity depended on the catalyst structure and was less susceptible to poisoning by H 2 S and HCl in case of the catalyst with strong NiO-support interactions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The reactor gaseous media affects the upgrading process. • Water-gas shift reaction plays a significant role in the upgrading. • The choice of by-product may influence the selection of gaseous media. • Hydrogen media was shown to promote gases, while Nitrogen encourages coke. Abstract Ni-Co/γ-alumina catalyst was prepared and tested in upgrading of heavy crude oil. The parameter studied was the type of the pressurising gas and especially its effect on the water-gas shift reaction on the upgrading. The preliminary results suggested that a combination of the cracking reaction and the original water-in-oil which triggered a low temperature water-gas shift reaction generated hydrogen in-situ for the hydrogenation reaction. To further explore this, four major experimental runs were conducted; amongst which two were without catalysts and reactor inner liner in hydrogen and nitrogen environments, two were catalytically driven with and without a liner. The experimental conditions were 380 °C, 32 bar and residence time of 2 h with a catalyst/oil ratio of 0.01. The results show that API gravity, Hydrogen/Carbon ratio and light oil yields were slightly higher for the reaction in nitrogen atmosphere without liner as compared to hydrogen with liner– 15.8°, 0.138, and 40.2 g respectively for the latter with 18.2°, 0.177, and 45 g for the former. The catalytic reaction in hydrogen environment however; produced no coke as against the 0.2 wt% coke recorded with nitrogen. Meanwhile, the reduction in sulphur content and viscosity of the nitrogen experiment were higher compared to that of hydrogen. [ABSTRACT FROM AUTHOR]

[Display omitted] • The hydrogenation path of dibenzyl ether under WGSR is obtained by combining experiments with DFT. • Heavy water is utilized to participate in WGSR for in-situ hydrogen tracing. • Excessive water hinders the transfer of hydrogen. • The hydrogen produced by WGSR preferentially attacks the C atom on the ether bond. The hydrogenation properties of dibenzyl ether (an oxygenated model compound of lignite) via the water–gas shift reaction (WGSR) were studied in a subcritical CO-H 2 O system. The result showed during the hydrogenation process, the C-O bond was broken, and the fragments of dibenzyl ether were stabilized by the hydrogen generated by WGSR, generating benzene, toluene, benzyl alcohol and benzaldehyde. The presence of excess water inhibited the hydrogen transfer, largely reducing the conversion of dibenzyl ether. However, the inhibition effect was substantially reduced when the reaction environment reached the critical temperature and subcritical pressure of water. The hydrogen and deuterium generated by H 2 O and D 2 O via WGSR were utilized to label and analyze the hydrogenation position of the product, respectively. The results showed that the hydrogen generated by WGSR was added to the methylene after the break of dibenzyl ether, and this hydrogen appeared on the benzene ring structure via hydrogen transfer. The bond dissociation energy and energy required for the hydrogenation process of dibenzyl ether under aqueous condition were calculated by utilizing density functional theory (DFT). First, hydrides (H−) are formed by the WGSR under alkaline conditions. Then, the formation energy (140.81 kJ/mol) of hydrides and the energy (15.54 kJ/mol) of hydrides attacking the dibenzyl ether to form the transition state were lower than the bond dissociation energy (259.26 kJ/mol) of the dibenzyl ether. That is, the hydrogenation of dibenzyl ether via WGSR prefers to be a nucleophilic reaction rather than a pyrolysis reaction. In the coal liquefaction process, the hydrides produced by WGSR under the catalysis of alkali is conducive to the hydrocracking of oxygen containing functional groups. [ABSTRACT FROM AUTHOR]

• A digital core was reconstructed using thin sections of a reservoir-collected rock. • Conducted 3D multiphase flow simulations for performance evaluations of CO 2 EOR strategies. • Agreements in history match confirmed cyclic CO 2 injection as the most effective scheme in a tight core. • Operational parameters were optimized for a better performance of CO 2 EOR. In this study, a three-dimensional tight sandstone core was reconstructed digitally using serials thin sections cut from a core sample used in laboratory carbon dioxide (CO 2) flooding experiments. Based on the digital core, multiphase flow simulations were carried out to evaluate the performance of three prior laboratory-tested injection strategies: CO 2 continuous injection, water alternative gas (WAG: CO 2) injection, and cyclic CO 2 injection. The chosen image-based reconstruction led to a close porosity and permeability match with the sampled core in an economical way. The numerical evaluation closely replicated the laboratory-tested procedures, thus providing realistic fluid distributions before CO 2 injection. To determine saturation functions for CO 2 injection after water flooding, sensitivities of endpoint relative permeability and capillary pressure to CO 2 continuous injection were quantified. Water relative permeability was identified as a key factor. The saturation functions were used in a history match between simulations and laboratory data where close agreements were observed for all three CO 2 injection strategies. Then critical enhanced oil recovery (EOR) operational parameters (soaking time, slug ratio, cycle size, and test duration) were optimized to maximize CO 2 displacement performance, which led to the following observations: (1) While extended soaking after CO 2 continuous injection increased incremental oil recovery, such increase was limited due to concurrent soaking during low-rate CO 2 injection. (2) In WAG injection, CO 2 and brine slug sizes and ratios were optimized: increasing the cycle size performed better than adjusting the slug ratio for favorable mobility control and efficient CO 2 EOR. (3) For cyclic CO 2 injection, the total CO 2 injection volume was the most important factor, followed by the number of cycles, to allow CO 2 diffusion into tight core to maximize the swept pore volumes. The history-matched simulations suggest that both WAG and cyclic CO 2 injection can achieve high displacement effectiveness for the tight reservoir, compared with that achieved with slight soaking after CO 2 continuous injection. The injected brine slugs in the WAG injection reduced the CO 2 needed at the expense of reduced storage capacity. Compared to WAG, cyclic CO 2 injection, though realizing the highest oil recovery and gas storage, requires more CO 2. [ABSTRACT FROM AUTHOR]

• Effects of H2 co-injection via tuyere and shaft on the performance of an industrial scale blast furnace are quantified. • Impacts of water gas shift reaction on blast furnace performance are studied. • Interrelation between utilisation efficiencies of H2 and CO on isothermal lines is identified. • Operation strategies for H2-rich operation of blast furnaces are explored. Hydrogen (H 2) can be co-injected into the tuyere and shaft into a blast furnace (BF) for reducing CO 2 emissions. However, the feasible co-injection schemes and their effects on in-furnace phenomena are not well understood. In this study, a multi-fluid industrial-scale BF model is further developed to investigate the impacts of H 2 co-injection through the shaft and/or tuyere on the BF internal state and overall performance in terms of temperature field, H 2 and CO utilisation efficiency, and species distributions. The results show that the proposed H 2 co-injection through tuyere and shaft allows H 2 to be better utilized and the overall BF temperature field can be improved, compared to respective tuyere or shaft injection cases. Further, the effects of high hydrogen injection rate at tuyere (i.e., low hydrogen injection rate at shaft) are studied. It is found that with increasing H 2 injection ratio at tuyere, the water gas reaction and water gas shift reaction are intensified; the temperature is decreased and the H 2 utilization efficiency is suppressed; the raceway adiabatic flame temperature (RAFT) gradually decreases; the lowest coke rate is 285.8 kg-C/t-HM is found when the distribution ratio of injected H 2 is 4:6 at tuyere and shaft, and the highest coke replacement ratio is 4.1 kg-C/kg-H 2. Then, the possible operation strategies for H 2 -rich operation of blast furnaces are explored. This paper provides a cost-effective tool to understand the flow-thermal-chemical behaviours inside a BF when H 2 co-injection schemes are employed. [ABSTRACT FROM AUTHOR]

• Ni nanoparticles (2 nm) are active for the reverse water gas shift; • Superior activity for Ni/Co 3 O 4 due to metal-support interaction; • Carbon nanotubes formed in situ promote Ni/Co 3 O 4. Ni nanoparticles (NPs) supported on Al 2 O 3 , ZnO, Fe 2 O 3 and Co 3 O 4 activate CO 2 for the reverse water–gas shift (RWGS) reaction at ambient pressure. The highly dispersed Ni NPs at a loading of 0.02 g g−1 minimized agglomeration and hydrogen adsorption to the surface, thus CO hydrogenation. Irreducible (Al 2 O 3 , ZnO) and reducible (Fe 2 O 3 , Co 3 O 4) supports promoted the catalytic properties of Ni. The metal-support interaction (MSI) between Ni and semi-conductors ZnO and Co 3 O 4 suppresses CH 4 formation, increases the selectivity towards the RWGS, and promotes the catalytic activity and stability of Ni. Carbon nanotubes (CNTs) formed during the reaction dispersed Ni/Co 3 O 4 and promoted its catalytic properties by forming a synergistic relationship between Ni/Co 3 O 4 and CNTs. Ni/Co 3 O 4 converted the most CO 2 among all catalysts at ∼ 36 % of CO 2 with traces of CH 4 , while Ni/Al 2 O 3 converted ∼ 33 % with a ∼ 96 % CO selectivity at 600 °C. Furthermore, we demonstrate that Ni/Co 3 O 4 converts 4 % of the CO 2 in the feed with a 95 % CO selectivity at 300 °C due to the reducibility of Co 3 O 4 promoting the catalytic properties of Ni. [ABSTRACT FROM AUTHOR]

• An experimentally validated CLG model has been used to evaluate incorporation of electrolysis in BtL process. • Syngas conditioning with electrolyzers results in higher biofuel yield. • Due to WGS reaction in MCEC, less biogenic carbon ends up in the biofuel compared to PEM. • Tar reforming improves the biogenic carbon efficiency. • The study predicts better economic performance for future electricity price scenarios. The second-generation bio aviation fuel production via Chemical Looping Gasification (CLG) of biomass combined with downstream Fischer-Tropsch synthesis is a possible way to decarbonize the aviation sector. Although CLG has a higher syngas yield and conversion efficiency compared to the conventional gasification processes, the fraction of biogenic carbon which is converted to biofuel is still low (around 28%). To increase carbon utilization and biofuel yield, incorporation of two types of electrolyzers, Polymer Electrolyte Membrane (PEM) and Molten Carbonate Electrolysis Cell (MCEC), for syngas conditioning has been investigated. Full chain process models have been developed using an experimentally validated CLG model in Aspen Plus for Iron sand as an oxygen carrier. Techno-economic parameters were calculated and compared for different cases. The results show that syngas conditioning with sustainable hydrogen from PEM and MCEC electrolyzers results in up to 11.5% higher conversion efficiency and up to 8.1 % higher biogenic carbon efficiencies in comparison to the syngas conditioning with water gas shift reactor. The study shows that the lowest carbon capture rates are found in the configurations with the highest biogenic carbon efficiency which means up to 14% more carbon ends up in FT crude compared to the case with conventional WGS conditioning. Techno-economic analysis indicates that syngas conditioning using PEM and MCEC electrolyzers would result in an increase of the annual profit by a factor of 1.4 and 1.7, respectively, when compared to using only WGS reactors. [ABSTRACT FROM AUTHOR]

The characteristics of Na 2 CO 3 -catalyzed water-gas shift reaction (WGSR) under coal liquefaction conditions were investigated. The reactivity of WGSR could be enhanced by improving water content and initial pressure of CO, owing to the reduced activation energy for WGSR in the high water density and subcritical state. The Na 2 CO 3 had a promoting effect on WGSR, and a synergistic effect between Na 2 CO 3 and water occurred obviously. HCOONa and NaHCO 3 as intermediate products were generated for CO consumption, and subsequently decomposed into CO 2 and H 2 , which can be a hydrogen source further. A major catalyzed mechanisms in WGSR about intermediate products under coal liquefaction conditions was investigated preliminarily. [ABSTRACT FROM AUTHOR]

Methane production using syngas is a feasible way for overcoming the shortage of natural gas supply and a clean utilization of coal. The full-loop circulating fluidized bed will be a good choice to improve the methane production and extend the catalyst lifetime. This work is the first attempt to adopt the full-loop reactor for producing methane, and also the ready for industrial application. Methanation process is investigated numerically in full-loop fluidized bed over Ni/Al 2 O 3 catalyst. The influences of operation parameter on reactants conversion and CH 4 yield are evaluated. Meanwhile, the performance of water gas shift reaction is taken into consideration during reactions to improve the conversion rate. The fluidization behavior and reaction characteristic are analyzed for better understanding the methanation process. [ABSTRACT FROM AUTHOR]

• Effect of recycling of the exhaust emissions from internal combustion engines inside the air-blown gasification system is investigated. • A 2D CFD model is investigating the novel research idea and further study the combined effects on the gasifier performance. • A new parameter – CB ratio – is defined, which is the exhaust/emissions from ICE gases to the feedstock mass ratio. Optimum values of CB are recommended between (0.05–0.25). • The proposed design helps in preserving the environment, reducing CO 2 and GHG emissions, and increasing the gasifier performance. • The significant outcomes of the study are applicable for different scales of air-blown gasifiers. The current research presents a proposed system for the recycling of the exhaust emissions from internal combustion engines (ICE) inside the air-blown gasification system. A 2D Computational Fluid Dynamics (CFD) model is investigating the novel research idea and further study the combined effects on the gasifier performance. To this end, the numerical model will be validated against wide range of operating conditions. Additionally, the effect of exhaust emissions injection along with air (the gasifying medium) on gasification, carbon conversion, system performance, syngas composition, and yield will be investigated. A new parameter – CB ratio – is defined, which is the exhaust/emissions from ICE gases to the feedstock mass ratio. Optimum values of CB are recommended between (0.05–0.25). The research idea resulted in boosting the yield of H 2 , and CO by 10.3, and 3.3 mol.% respectively, and correspondingly, higher heating values by 5.8% within the optimum range of CB. For the same range, N 2 , and CO 2 emissions are found to decrease within the gasifier. The exhaust emissions stream with high temperature and rich content of CO 2 , and H 2 O resulted in higher turbulence, velocity, and mixing inside the gasifier. Thus, enhanced the gasification reactions i.e., boudouard, and water gas reactions. Moreover, producer gas yield, carbon conversion and gasification efficiencies are found to be 28, 10, and 11% higher than air gasification under the same working conditions respectively. The proposed design (20 kW gasifier) – i.e., small scale industrial gasification unit – is found to consume around 3.5 kg/hr of the ICE emissions. Thus, preserving the environment, reducing CO 2 and GHG emissions, and increasing the gasifier performance. The significant outcomes of the study are applicable for different scales of air-blown gasifiers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thin foils of Cu–Ce alloy were fabricated for highly efficient hydrogen production. • Catalysts were prepared by oxidative/reductive heat treatments of the thin foils. • Cu 80 Ce 20 exhibited a particularly high activity for the water–gas shift reaction. • The foil catalysts have a multilayered Cu/(CeO 2 + Cu 2 O)/Cu structure. • The structure has many Cu 2 O–CeO 2 interfaces and a large specific surface area. Metallic plate-type catalysts exhibit higher thermal conductivity, greater compactness, and lower pressure drop per catalyst volume than those of granular catalysts. In this study, Cu-based thin-foil catalysts—that is, Cu–Ce alloy thin-foils with compositions ranging from Cu 75 Ce 25 to Cu 87.5 Ce 12.5 (at%)—were fabricated by single-roller rapid quenching of a melted Cu–Ce alloy, followed by oxidative and reductive heat treatments (at 500 °C in air and at 430 °C under hydrogen flow, respectively). The Cu–Ce foil catalysts showed composition-dependent activity for the water–gas shift (WGS) reaction, with Cu 80 Ce 20 and Cu 83.3 Ce 16.7 exhibiting particularly noteworthy catalytic behavior. Morphological and microstructural analyses indicated that the foil samples subjected to the oxidative and reductive treatments have a Cu/(CeO 2 + Cu 2 O)/Cu sandwich structure with numerous Cu 2 O–CeO 2 interfaces and a large specific surface area (>10 m2 g−1), which enabled the foils to exhibit high catalytic activity for the WGS reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Non-catalytic innovative CO 2 conversion via reverse water gas shift reaction. • Up to 75 % CO 2 conversion in a single pass with gas residence time of <0.03 s. • A hydrogen oxyflame which supports the reaction is at the core of the process. • Reactor operating range studied by a systematic experimental design method. • Metal wall effects were shown to have limited impact on reactor performance. Climate change concerns demand for drastic measures to mitigate greenhouse gas (GHG) emissions from fossil resources particularly those of CO 2. Effective conversion of CO 2 into syngas (a mixture of CO and H 2) via reverse water gas shift (RWGS) reaction requires high temperatures (> 900 °C) to overcome thermodynamic limitations. Challenges may arise in commercial catalytic reactors in achieving close to equilibrium efficiencies due to physical barriers such as maximum catalyst operating temperature and associated operating costs. Herein, a simple and novel approach is presented to produce syngas from CO 2 via RWGS reaction using a high temperature hydrogen oxyflame. Test results from a tubular laboratory reactor show that a CO 2 conversion of up to 75 % is achievable in a single pass with a gas residence time of < 0.03 s. Lower than equilibrium CO 2 conversions are observed due to non-adiabatic temperatures in the reactor. Heat integration and reactor insulation at industrial scale would help in a closer to equilibrium performance. Systematic analysis of reactor performance supported by empirical modelling revealed that there is an optimum economical point where hydrogen consumption can be minimized (< 1.0 mol H 2 /mol CO 2). A trade-off must be made to identify an optimum operating point depending on required syngas quality. Relatively small effect of reactor wall material (within 10 % in CO 2 conversion) may indicate an enhancing effect of hydrogen oxyflame as the main contributor to the reactor performance. [ABSTRACT FROM AUTHOR]

• The gasification of high wet sludge mixed with sawdust was explored based on Fe-based oxygen carrier. • The in-situ adsorption of carbon dioxide improved the quality hydrogen-rich syngas. • The role and route of water in sludge in gasification process was investigated. In this study, chemical looping gasification (CLG) of high wet sludge (HWS) mixed with sawdust was carried out based on red mud and Fe/Al composite oxygen carrier (OC) prepared by impregnation method. Further, the optimal gasification conditions in a fixed-bed reactor and the migration path of water from HWS were investigated for the preparation of hydrogen-rich syngas. Results show that the reaction temperature significantly affects gasification, and the higher temperature is conducive to the progress of sludge gasification. Addition of sawdust changes the volatile content of mixture fuel, thus affecting the composition of syngas. Utilization of appropriate amount of OC can promote the gasification rate. The syngas with calorific value of 11.16 MJ⋅Nm−3 was obtained under conditions including temperature of 800 °C, ratio of sludge to sawdust of 3:1, and O/C ratio of 1:10. Owing to the catalyst and adsorbent dual function, addition of CaO into bed material led to the significant increase in the H 2 /CO ratio of syngas; however, addition of excessive CaO affected the contact between sludge volatile and OC, resulting in the increase of CO 2 fraction and the decrease of the calorific value of syngas. A proportion of the vapor released from HWS reacted with carbon and OC and water–gas shift reaction with CO in gas to produce more H 2 and improved the syngas quality, which thus proves the advantages of wet sludge CLG to obtain higher energy yield than those of the dried sludge. [ABSTRACT FROM AUTHOR]

[Display omitted] • DFT and microkinetic simulation were performed to study WGSR on oxygen-deficient TiO 2 supported copper cluster catalysts with different sizes and Cu(1 1 1) crystal planes. • DFT and microkinetic simulation results showed that WGSR activities follow the order of Cu 4 > Cu 2 ≈ Cu 8 > Cu 1 > Cu(1 1 1). • The redox pathway cannot proceed due to the lack of active sites on Cu 1 and Cu 2 clusters. • The active center structure of the copper cluster is composed of 3 copper atoms in which the Cu-Cu coordination number is ca. 2 ∼ 3. • The low-coordination copper atoms determined by the geometry structure promote the WGSR activity of the copper clusters. The water–gas shift reaction (WGSR) is of great significance in industrial hydrogen production. In this paper, Cu n /TiO 2 (n = 1,2,4,8) and Cu (1 1 1) crystal planes were studied to explore the effect of size effect on the activity of WGSR. Density functional theory (DFT) calculations showed that the adsorption energy of H 2 O molecule was significantly enhanced on the surface of Cu 1 and Cu 2 clusters compared with Cu 4 and Cu 8 clusters, while CO adsorption strength first increased and then decreased. Among many copper clusters of different sizes, the redox pathway cannot proceed due to the lack of active sites on Cu 1 and Cu 2 clusters. According to the analysis of the microkinetic model, the order of WGSR activity on the surface of copper clusters of different sizes is: Cu 4 > Cu 2 ≈ Cu 8 > Cu 1 > Cu (1 1 1). The active center structure of the copper cluster is composed of 3 copper atoms in which the Cu-Cu coordination number is ca. 2 ∼ 3, and the active center is partially oxidized copper. Essentially, the low-coordination copper atoms determined by the geometry structure promote the WGSR activity of the copper clusters. This work not only reveals the copper cluster size effect on WGSR, but also provides the guidance for the size design and control of other supported metal catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pyrolysis-CO 2 gasification-WGS process of oil sludge based on CaL is proposed. • H 2 production and in-situ CO 2 capture are achieved through this process. • H 2 yield and CO 2 capture efficiency are 0.34 Nm3/kg-oil sludge and 98%, respectively. • Energy conversion efficiency and exergy efficiency are 36% and 32%, respectively. The treatment of oil sludge (OS) from petrochemical industry is a challenge. Traditional OS gasification process has the disadvantages such as low H 2 yield and high CO 2 emission. In this work, a novel pyrolysis-CO 2 gasification-water gas shift process of OS for efficient H 2 production based on calcium looping was proposed, which includes four stages: drying, pyrolysis, char gasification with recycled CO 2 and water gas shift reaction for H 2 production by in-situ CO 2 capture using CaO. The pyrolysis-CO 2 gasification-water gas shift process of OS was thermodynamically simulated by Aspen Plus. The effects of the mass ratio of steam/OS, temperature, mass ratio of CaO/OS, the proportion of CO 2 reused on H 2 generation and efficiencies of CO 2 capture, energy conversion, and exergy were analyzed. The OS pyrolysis and CO 2 gasification of char were also studied by experiment. Compared with direct steam gasification of OS process, H 2 yield (0.32 Nm3/kg-OS) and efficiencies of energy conversion (36%) and exergy (32%) increase by 0.28 Nm3/kg-OS, 13.62%, and 17.16%, respectively. The novel process is promising for energy recovery from OS. [ABSTRACT FROM AUTHOR]

• A Development of techno-economic greenhouse gas (GHG) life cycle assessment (LCA) incorporated CO 2 -EOR optimization model. • Impact assessment of different energy sources on emission factors and project NPV. • Analysis of tax incentives and oil price on CO 2 storage, oil recovery and project NPV. Optimizations of CO 2 Water Alternating Gas(WAG)- systems with multi-objectives of incremental recovery and maximization of CO 2 storage are challenging. The incorporation of a total Greenhouse gas (GHG) life cycle assessment is mostly ignored leading to inaccurate estimation of overall net carbon emissions of their operations. In this study, the effect of a total GHG life cycle assessment on a multi-objective CO 2 -WAG optimization with integrated techno-economic assessment (TEA) which factors carbon tax credit is conducted. A life cycle assessment (LCA) was conducted utilizing a 20 -year optimized post history matched data from a high fidelity reservoir simulation model. Using data generated from the optimum result, a techno-economic life cycle analysis was further conducted. The first scenario classified as the base model had an estimated 81% of purchased CO 2 sequestered. The results through a comprehensive techno-economic LCA model yielded a net estimate of 73% of purchased CO 2. The optimized forecasted model which considered key operational and reservoir factors such as WAG ratio, injection rates and periods, and well specification resulted in an improved sequestration of 92% of purchased CO 2. However, this also dropped to 84% after taking it through LCA. These results clearly indicate a significant amount of net CO 2 is not accounted for when operations are not analyzed through LCA. From the LCA, direct flaring volumes of CO 2 , energy consumption and efficiency of unit equipment were noticed to be the major causes of these reductions. Considering ten main sources of energy as source of energy generation, a comparative techno-eco LCA was conducted. The results confirmed a lower net volume and NPV for energy sources with higher carbon footprints and vice versa. Thus, a total LCA of CO 2 -WAG greatly influences net storage factor of purchased CO 2 and hence project NPV where tax credit/incentives per ton of CO 2 sequestered is considered. Although operational conditions are optimized for best results, there are significant factors that leads to minimization of net storage factor. This study therefore provides an insightful information for optimizing CO 2 -WAG multi-objectives to achieve minimum GHG emission. [ABSTRACT FROM AUTHOR]

• We developed a hydrocyclone desanding experimental device for high-viscosity oil. • We found the range of operating parameters for high-viscosity oil desanding. • We found some methods to resist the interference of dissolved gas. Crude oil containing sand brings serious safety hazards to the surface gathering system, and wellhead sand removal could basically eliminate the sand threat to the pipelines and equipment. We developed a hydrocyclone desanding experimental device, using high-viscosity industrial white oil to simulate the high-viscosity crude oil on site to carry out the hydrocyclone desanding experiment, and explored the factors such as the oil viscosity, water content and gas injection on the hydrocyclone separation. The range of operating parameters for efficient hydrocyclone desanding of high-viscosity oil was found. The results showed that the hydrocyclone is not suitable for de-sanding of pure oil, but adding water could significantly improve the inefficient desanding state caused by the increase of oil viscosity. And the higher the viscosity of white oil, the more water is needed. Feed stream containing gas would cause a significant increase in pressure drop, which would waste excess pressure energy. Therefore, it is recommended that the dissolved gas should be removed before hydrocyclone desanding on site. Increasing the inlet flow rate, reducing the oil viscosity and increasing the water content could enhance the resistance to the interference of the gas. [ABSTRACT FROM AUTHOR]

In coal-bed methane (CBM) field development plan, more attention is paid to production forecasting, well spacing optimization, pressure transient analysis and adsorption/desorption mechanism within coal matrix. Few studies were carried out to investigate the expansion of drainage and desorption area based on the characteristics of pressure propagation in CBM reservoir. Moreover, the production rate and bottom-hole pressure (BHP) are usually variable, while the production system in current analytical models are either at constant production rate or constant BHP. When optimizing the production system of CBM well, the knowledge of expansion principle of drainage and desorption area can help obtain the critical time of interference and its intensity, which are both key factors for efficient development of CBM reservoirs. In this paper, a comprehensive method for drainage and desorption area expansion during coal-bed methane production is proposed, in which the variable rate and BHP in different production stages and saturation distribution are considered. The coal seam is divided into two areas, namely desorption and without-desorption area, and the production life is divided into five stages. The pressure profiles at different production stages are detailed investigated utilizing diffusivity equation which is solved by the continuous succession of steady states. By assuming the desorption area with low water-gas ratio and without-desorption area with high water-gas ratio, the pressure-squared approach is applied in desorption area and pressure approach is employed in without-desorption area. Finally, a model for predicting drainage and desorption area is developed by generating pressure profile and material balance equation. The proposed semi-analytical model is verified by numerical simulation with excellent agreement with the simulation data. Results show that the drainage area expands much faster at early production stage than that at late stage when desorption area starts expanding in the coal-bed reservoir. In addition, the production system of CBM well is found to play a significant role in the expansion characteristics of desorption area. Considering these characteristics of CBM, we shed light on the production system optimization in different production stages and apply the developed production system to a CBM well in Qinshui field, China. In summary, this method only requires BHP, gas and water production, and turns out to be simple, reliable and powerful in application. [ABSTRACT FROM AUTHOR]

Coal fines are generated during both the dewatering and Coal Seam Gas (CSG) production stages. This is due to the interaction between the fluid flow and the coal solids affixed to coal cleat surfaces. The generated coal fines may plug gas flow paths and reduce coal permeability. Although some investigations of the impact of water flow on coal fines generation were conducted, little research has been conducted into the generation of coal fines under water-gas two-phase flow condition. This is a typical flow type in the late dewatering and early CSG production phases. Two-phase flow requires higher pressure to initiate the fluid movement. Therefore, coal fines generation in two-phase flow conditions is expected to be very different from that in single-phase flow. In this work, a fully coupled numerical model was developed, which integrated different flow regimes and the generation of coal fines. Coal cleat geometries were constructed using the Scanning Electron Microscopy (SEM) images taken from a set of coal samples collected from the Bowen Basin, Australia. The two-phase flow was simulated based on the Phase Field Method (PFM). Different flow regimes were examined, including water flow, gas flow, gas-drive-water and water-drive-gas scenarios. The coal fines generation was evaluated according to the combination of shear and tensile failure criteria. The simulation results revealed that more coal fines were generated in two-phase flow compared to single-phase flow. The majority of coal fines were generated around the regions where residual phase was observed. This was attributed to the substantial force induced by significant pressure difference between the residual fluid and mobile fluid. Among different flow regimes, the gas-wet gas-drive-water scenario generated the greatest amount of coal fines, with over one order of magnitude more than any other scenarios. It was observed that the change of fluid phase composition inside the cleat created considerable pressure fluctuations (up to several kPa), which was unfavourable in controlling the production of coal fines. Based on the dimensional analysis, two dimensionless numbers, namely Capillary number ( Ca ) and Euler number ( Eu ) were found to define the coal fines generation process. A new criterion that could be used to evaluate coal fines generation was obtained. The findings from this study deliver a comprehensive knowledge of coal fines generation under different flow regimes, which provides useful guideline as to how to implement effective mitigation strategies to minimize coal fines induced production delays. [ABSTRACT FROM AUTHOR]

Wettability of CO 2 /water/coal systems is a fundamental petro-physical parameter, which governs the fluid flow and distribution in coal seams and thus directly affects CO 2 -storage and methane recovery from unmineable coal seams. The recognition of wettability of coal/CO 2 /brine systems help to de-risk CO 2 -storage and enhanced methane recovery projects in coal seams. To understand the factors influencing the wetting characteristics of coals, a detailed examination and characterization of coal surface chemistry is essential and literature data in this context is missing. We thus measured zeta potentials as a function of temperature (298–343 K), brine salinity (0 wt% NaCl–5 wt% NaCl) and salt type (NaCl, CaCl 2 and MgCl 2 ) for coals of low, medium and high ranks. Further, we measured water advancing and receding contact angles as a function of temperature and salinity for the same experimental matrix in order to associate wettability changes to the surface charge at the coal/brine interface. Moreover, coal surfaces were investigated by Fourier transformed infrared (FTIR) spectroscopy and the surface functional groups responsible for a particular wetting behaviour were identified. We found that zeta potential increased with temperature, salinity and cation valency. Both advancing and receding contact angles decreased with temperature, and increased with salinity and cation valency irrespective of the coal rank. Finally the XRD measurements and infrared spectra revealed that the presence of polar surface functional groups (e.g. Si OH and carboxylic acid groups) which is responsible for the hydrophilic behaviour of low rank coals and the absence of these groups in high rank coal is responsible for their hydrophobic behaviour even at lower pressure. The high rank coal seams at high pressure are better for CO 2 storage and methane recovery. [ABSTRACT FROM AUTHOR]

• The woody biomass air gasification was performed to produce H 2 -rich gas. • Acid mine drainage sludge showed a high catalytic effect on H 2 production. • Increasing temperature enhanced the gas yield and H 2 selectivity. • Raising ER increased the gas yield, but was not conductive for H 2 production. • Ex-situ contact mode was more effective than in-situ case for H 2 production. In this study, the feasibility of employing acid mine drainage sludge (AMDS), mainly consisting of iron oxide (Fe 2 O 3), as a novel catalyst for the air gasification of woody sawdust to produce H 2 -rich gas was evaluated for the first time. The effects of temperature, equivalence ratio (ER), and contact mode of the feedstock and catalyst on gas yield and H 2 selectivity were investigated. Using the AMDS catalyst, a comparably higher gas yield (56.79 wt%) and higher content of H 2 (18.31 vol%) and CO 2 (36.45 vol%) were obtained compared to those obtained in the non-catalytic case owing to stimulated water–gas shift and steam–methane reforming reactions caused by the redox cycle of Fe 2 O 3 within the gasification process. Gas yield and H 2 concentration were enhanced by increasing the temperature from 750 to 850 ℃ (up to 65.11 wt% and 21.73 vol%, respectively) due to promoted endothermic reactions. Although increasing the ER from 0.1 to 0.3 dramatically increased the gas yield, it was not conducive to the promotion of H 2 production, primarily because of the stimulated hydrogen oxidation reaction. The ex situ contact mode, where feedstock and catalyst were placed in the reactor and catalyst bed, respectively, resulted in a higher gas yield and H 2 selectivity compared to those achieved by the in situ case, in which a mixture of feedstock and catalysts was located in the same reactor. Overall, the gasification of woody sawdust over an AMDS catalyst in an air medium has the potential to mitigate the challenges of AMDS treatment along with the production of valuable H 2 -rich gas. [ABSTRACT FROM AUTHOR]

[Display omitted] • A crossflow tube reactor system is designed for hydrogen production from ethanol. • The crossflow tube reaction system consists of ethanol steam reforming and water gas shift reaction. • The steam/ethanol (S/E) ratio of 3 is optimal for hydrogen production and CO reduction. • The effect of the tube diameter on catalyst cost is higher than that of the catalyst thickness. • The optimized system intensifies H 2 yield by 1.05 times and improves CO reduction by 27.38%. Crossflow tube reactors with crossflow configuration are considered a special design for hydrogen production via ethanol steam reforming with less catalyst than conventional packed bed reactors. However, the results showed that crossflow tube reactors would produce an elevated concentration of carbon monoxide, which has a detrimental effect on further applications of the product gas from steam reforming, such as hydrogen purification. This drawback can be diminished by integrating a water gas shift reaction unit into the steam reformer. This study's combined system is numerically investigated for hydrogen production and enrichment. The results show that low reaction temperatures are favorable for hydrogen production. The steam/ethanol (S/E) ratio of 3 is optimal for hydrogen production and CO reduction in the system combined with ethanol steam reforming and water gas shift reaction. Both variations in the catalytic tube diameter and the catalyst thickness positively affect hydrogen production. However, the effect of the tube diameter is higher than that of the catalyst thickness. This study also uses a parametric sweep associated with the evolutionary computation of bound optimization by quadratic approximation (BOBYQA) method to optimize the system's tube arrangement. The optimized system intensifies H 2 yield by 1.05 times and improves CO reduction by 37.71% compared to ethanol steam reforming alone. [ABSTRACT FROM AUTHOR]

• The injection of different syngas in blast furnaces (BF) was assessed. • The syngas come from biomass, plastic, CO 2 electrolysis, and RWGS reaction. • Air-blown BF, oxygen BF, and advanced oxygen BF were considered. • An Aspen Plus model based on the extended operating line methodology was used. • The lowest net CO 2 emissions were achieved in oxygen BF with RWGS syngas. This paper assesses the injection of different syngas in air-blown blast furnaces, oxygen blast furnaces, and advanced oxygen blast furnaces. The selected types of syngas come from biomass gasification, plastic gasification, CO 2 electrolysis, and reverse water–gas shift reaction. An Aspen Plus model, based on the new extended operating line methodology, was used for the simulation. This methodology is a generalization of the conventional Rist diagram, to extend its application to cases in which the injected gases have large contents of CO 2 and H 2 O, and also to cases in which injections take place at the middle or upper zone of the blast furnace. The base cases were elaborated and validated with data from literature, with a discrepancy below 3.5%. A total of 7 key performance indicators were defined for the study (mass flow of syngas, coke replacement ratio, gas utilization, percentage of direct reduction, blast furnace gas temperature, flame temperature, and net CO 2 emissions). In practice, the amount of syngas that can be injected is limited to 92 – 264 kg syngas /tHM because of the drop in the flame temperature. The lowest net CO 2 emissions are achieved in oxygen blast furnace with injection of syngas from reverse water–gas shift reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ACM was developed for the water gas shift reaction in a high-temperature shift reactor. • The simulation results of the ACM were compared with those obtained by the PCM and PRCFD. • The ACM exhibited equivalent accuracy as the PRCFD but comparative efficiency as the PCM. • The ACM is suitable for the simulation of high-temperature shift with internal mass transfer. The packed bed reactor with the high-temperature shift reaction has been a competitive industrial device for the production of hydrogen fuel. While the temperature distribution in the packed bed plays an important role in improving the reaction efficiency, and numerical simulation is a powerful way to recover the heat transfer inside the reactor. Nevertheless, the current simulation methods are either high computational cost or low accuracy for the high-temperature shift. To accomplish the effective computational cost and accuracy simultaneously, we developed a two-dimensional anisotropic continuum model with modified space-dependent effectiveness factor and anisotropic thermal conduction based on the pseudo continuum model. Meanwhile, the simulation results were compared with those by the particle-resolved 3D computational fluid dynamics to validate the model accuracy. Due to the overestimation of the radial thermal conductivity by the pseudo continuum model, the axial temperature rise in the packed bed was only 10 K, but a significant temperature rise of 50 K was presented by the other two methods, suggesting the coordinate computational accuracy of the anisotropic continuum model. However, the computational time consumed by the particle-resolved 3D computational fluid dynamics was up to 1320 min, which exceeds a thousand times more than that in current advanced model. All the comparisons indicate the anisotropic continuum model can predict the heat transfer through the packed bed with sufficient computational accuracy and efficiency, making a powerful and time-saving method to conduct the effective heat management in packed bed reactors for actual industrial applications. [ABSTRACT FROM AUTHOR]

• DCLS is an effective method that can convert low-rank coals into fuels. • The effects of coal, catalyst, and solvent on liquefaction behaviors are summarized. • The coal liquefaction mechanisms (especially WGSR mechanisms) in DCLS are reviewed. • The potential challenges for the development and application of DCLS are discussed. With the increasing demand for energy and raw materials, the importance of effective utilization of low-rank coals has been emphasized. The utilization of low-rank coals in direct liquefaction is limited by their high oxygen and moisture contents because large amounts of hydrogen and energy are required for oxygen removal and drying, respectively. Direct coal liquefaction in the system containing water and syngas or CO (DCLS) is an economical and effective method that can convert low-rank coals into fuels and value-added chemicals in the conditions of no pure hydrogen (or hydrogen-poor gas) and drying, thus resulting in the whole cost reduction for the utilization of DCLS. This review presents the latest development of DCLS, focusing on critical liquefaction behaviors (mainly the effects of various parameters such as coals, catalysts, solvents, as well as appropriate reaction temperatures and pressures on the liquefaction behaviors), widely recognized catalytic liquefaction mechanisms (especially water–gas shift reaction), and liquefaction technological processes. On the basis of the above inductions, analyses and discussions, the potential opportunities and challenges for the development and application of DCLS are emphasized. This review aims at discussing valuable technologies to provide more solutions for the efficient utilization of low-rank coals. [ABSTRACT FROM AUTHOR]

• We study the reburning characteristics of pre-oxidized coal formed in low-oxygen and high-temperature environment. • PT and POC have different effects on each characteristic temperature. • The optimal critical POC and optimal PT affect each other. The secondary oxidation of residual coal during re-mining in goaf will seriously endanger mine safety production. To investigate the influence of the formation process of PC(pre-oxidized coal) in goaf on the secondary oxidation of coal, This paper utilized the TG-DSC analysis method to study the burning characteristics of PC under different pre-oxidized temperatures and different pre-oxidized oxygen concentrations. The results showed that both PT(pre-oxidation temperature) and POC(pre-oxidation oxygen concentration) have effects on the burning process of oxidized coal, and there is an optimal POC and the best PT. Both PT and POC only have significant effects on the characteristic temperatures before ignition temperature, and fewer effects on the ignition temperature and the characteristic temperatures after ignition temperature, and thus PT and POC only have effects on the first three stages of the secondary oxidation process of PC, i.e., water evaporation and gas desorption stage, oxygen absorption stage of weight gain, and thermal decomposition stage. The effects of PT and POC are different from each characteristic temperature, thus the effects of PT and POC are different in the first three stages. In general, the secondary oxidation process of PC Y-18 %-100 is the most dangerous when re-mining the residual coal in the goaf. However, different pre-oxidized coals have different risks in different stages of the secondary oxidation process, because the types of active structures mainly involved in the coal-oxygen reaction in each stage are different, and the PT and POC during the formation of pre-oxidized coals will affect the number of active structures involved in the coal-oxygen reaction during the secondary oxidation of pre-oxidized coals. The DSC curves of PC at 300 °C showed no obvious plateau of heat uptake, which was because the too high PT would decompose the steady aromatic ring structures in the coal samples. The research results can be used as the theoretical basis for the re-mining of goaf, and ensure the safety of workers and the smooth progress of re-mining. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of initial MH saturation on hydrate accumulation in a flow system is studied. • Amount of MH reformation decreased with water mass fraction and hydrate saturation. • Onset time of blockage is delayed 0.7 times when MH saturation is elevated 1.8 times. • MH reformation accumulation act as a barrier to prevent gas overflow from reservoirs. Pressure gradient is established in reservoirs when the depressurization method is applied to decompose natural gas hydrates (NGHs). When the local reservoir pressure is in the thermodynamically stable area, hydrate reformation and blockage may occur and lead to incomplete hydrate exploitation. However, studies have so far not focused on the effect of hydrate saturation change and multiphase flow at the different exploitation stages on NGHs production behaviors, thus, it was the research priority in this study. The NGHs saturation at different exploitation stages is characterized by controlling the initial hydrate saturation, and the multiphase flow in reservoirs is simulated by controlling the water–gas flowrate. The results show that the onset time of blockage and amount of hydrate reformation were negatively associated with initial hydrate saturation (S hi) at a given water–gas flowrate. When the S hi elevated 1.8 times, the onset time of blockage and increment of hydrate saturation decreased by 0.7 times in the flow system. However, when the S hi < 12 %, the hydrate accumulation, and flow blockage were avoided with the water–gas flowrate of 10–1 mL/min. Other conditions being the same, the onset time of blockage was increased with the water phase fraction, while the increment of hydrate saturation was decreased with the water mass fraction. At a given gas flowrate of 1 mL/min and initial hydrate saturation of 40 %, when the water flowrate improved 7.5 times, a factor of 2.6 decreases in the increment of hydrate saturation was confirmed, from around 33.73 % to 12.95 %. Furthermore, the hydrate reformation and accumulation can prevent the gas overflow by forming the hydrate barrier, thus, a stable pressure was observed after flow blockage. [ABSTRACT FROM AUTHOR]

• N 2 O formation by injecting ammonia gas and UWS in cu-zeolite SCR is studied. • Ammonia gas injection produces more N 2 O emissions than UWS. • N 2 O formation is increased by increasing the NH 3 /NOx (α) ratio. • N 2 O formation shows a bimodal profile by increasing the exhaust gas temperature. In this study, the N 2 O emission formation from heavy-duty diesel engine was studied by injecting ammonia gas and urea water solution (UWS) in Cu-zeolite SCR. Furthermore, the effect of exhaust gas temperature and NH 3 /NOx (α) ratio on the N 2 O formation were investigated. The ammonia was supplied using an ammonium carbamate (AC) based ammonia generating system. Experiments were performed under the European stationary cycle (ESC), world harmonized transient cycle (WHTC), and non-road transient cycle (NRTC). Ammonia gas injection produced a higher amount of tailpipe N 2 O than UWS injection for all test conditions. Compared with UWS an increment of 27% in N 2 O formation for ammonia gas was observed during the ESC test. The N 2 O emissions of ammonia gas injection in the WHTC and NRTC were increased compared with that of UWS during the cold phase by 63% and 55%, respectively, and during the hot phase by 57% and 74%, respectively. Meanwhile, NO and NO 2 emissions were decreased by injecting ammonia gas compared with UWS. The higher NH 3 /NOx (α) ratio led to higher tailpipe N 2 O and lower NO and NO 2 emissions. For each reductant test, the concentration of N 2 O formation was high at the exhaust gas temperature of 200–250 °C. These presented results provide useful information about the N 2 O formation from after-treatment systems of diesel engines when ammonia gas is used. [ABSTRACT FROM AUTHOR]

• The inlet temperature played an important role in the formation of N 2 O and NH 3. • The maximum N 2 O concentration and NH 3 formation raised with the increase of H 2 O content. • The formation of N 2 O decreased with the increase of CH 4 concentration, which was contrary for NH 3. • The emission of N 2 O and NH 3 decreased to zero by controlling the exhaust gas temperature and O 2 concentration. To investigate the effects of inlet temperature and exhaust gas composition on the formation characteristics of nitrous oxide (N 2 O) and ammonia (NH 3) for stoichiometric natural gas engines with Pd-only three-way-catalyst (TWC) , a global model of Pd-only TWC by constructing a comprehensive catalytic reaction mechanism was established and a simulation investigation of the effect of inlet temperature, H 2 O content, oxygen (O 2) concentration and methane (CH 4) concentration on the formation of N 2 O and NH 3 was conducted. The results showed that the inlet temperature played an important role in the formation of N 2 O and NH 3. N 2 O was easy to generate N 2 through secondary reduction under high temperatures·NH 3 was formed by the reduction of nitric oxide (NO) through hydrogen (H 2). The H 2 required for the reduction came from the reactions of steam reforming and water gas shift on the Pd surface. The formation of NH 3 by the reduction of NO through H 2 at a temperature above 750 K. Secondly, the maximum N 2 O concentration and NH 3 formation raised with the increase of H 2 O content. In addition, the emission of N 2 O and NH 3 decreased to zero by controlling the exhaust gas temperature and O 2 concentration. Finally, the formation of N 2 O decreased with the increase of CH 4 concentration, which was contrary to NH 3. The emission of N 2 O and NH 3 declined to zero by controlling the exhaust gas temperature in the range of 700 K–750 K under 1500 × 10−6 CH 4. [ABSTRACT FROM AUTHOR]

[Display omitted] • <2 nm Pt, Ru and Rh NCs were anchored over CeO 2 /MCF17. • Supported metal NCs exhibited excellent catalytic performance for CO 2 reduction. • Ru NCs/CeO 2 exhibited ∼ 99% selectivity to CH 4. • Effect of two entirely different supports (CeO 2 and MCF 17) was evaluated. Efficient conversion of CO 2 into CH 4 and CO brings an important opportunity to get valuable feedstock for a variety of industrially important reactions as both CH 4 and CO are widely used as starting materials for the synthesis of valuable fuels and chemicals. Herein, we synthesized sub-nanometer (<2nm) Platinum (Pt), Ruthenium (Ru) and Rhodium (Rh) nanoclusters (NCs) via colloidal method; successfully decorated over mesoporous CeO 2 and high surface area (HSA) siliceous meso -cellular foam (MCF 17) and tested for high-pressure CO 2 reduction at lower temperature range (220–340 °C). Pt and Ru NCs exhibited typical reverse water gas shift (RWGS) and methanation catalytic performance respectively with minimal influence of the nature of support however, Rh NCs showed drastic variations in the product selectivity which exhibited strong influence of the support over the product distribution. Furthermore, Ru NCs (with a relatively lower metal loading ∼ 1 wt%) were found to be highly selective to CH 4 (∼99 %) and stable (upto 40 hr time on stream) with either CeO 2 /MCF 17 at 340 °C; also Ru NCs exhibited comparatively the highest CO 2 conversion (∼93 % in case of Ru NCs/CeO 2) among the supported metal NCs. HRTEM results showed that metal NCs were homogeneously dispersed with a controlled and uniform particle size (<2nm); no substantial agglomeration of Ru NCs were observed after reaction. Beside the stable dispersion of NCs, Near Ambient Pressure (NAP) in situ XPS of Ru/CeO 2 showed that the dynamic Ce3+/Ce4+ ratio of CeO 2 can attribute to the high activity and selectivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Increase of propane conversion by shifting the equilibrium through RWGS over PtZn alloy. • The synergistic effect of PtZn alloy plays a key role on both PDH and RWGS. • A high catalytic activity with TOF of 1.82 × 104h−1 was obtained from PtZn alloy catalyst. • Insights into the mechanistic aspects of CO 2 -assisted PDH over PtZn alloy. CO 2 -assisted propane dehydrogenation has been developed in propylene production technology to deal with thermodynamic equilibrium limitations. However, the rational design of catalysts is a crucial challenge in achieving high catalytic performances. Herein, we report the successful fabrication of highly dispersed PtZn alloy on hierarchical zeolites for CO 2 -assisted propane dehydrogenation through the reverse water–gas shift reaction (RWGS). Compared with monometallic Pt, the synergistic effect of PtZn plays a crucial role in both direct propane dehydrogenation and RWGS, resulting in an outstanding catalytic performance with a high turnover frequency (TOF) of 1.82 × 104h−1. From the catalytic point of view, Pt-Zn alloy surfaces facilitate the equilibrium shift in propane conversion by consuming produced H 2 through RWGS with weakening CO-metal surface interaction revealed by operando studies and DFT calculations. These findings illustrate the conceptual design of alloy catalysts and allow insights into the mechanistic details of CO 2 -assisted alkane dehydrogenation. [ABSTRACT FROM AUTHOR]

• Profitability analysis of green hydrogen production from biogas. • Prices could be competitive versus electrolysis hydrogen production. • Subsidies could boost the hydrogen market in the short-medium term. • Costs reduction strategies are envisaged. Hydrogen is not only considered as a cornerstone within renewable energy portfolio but it is also a key enabler for CO 2 valorisation being a central resource for industrial decarbonization. This work evaluates the profitability of hydrogen production via combined biogas reforming and water–gas shift reaction, based on a real case scenario for landfill biogas plant in Seville (Spain). A techno-economic model was developed based on a process model and the discounted cash-flow method. A biogas flow of 700 m3/h (input given by the landfill biogas plant) was used as plant size and the analysis was carried out for two different cases: (1) use of already available energy sources at the industrial plant, and (2) solar energy generation to power the process. The economic outputs obtained showed that under the current circumstances, this hydrogen production route is not profitable. The main reason is the relatively low current hydrogen prices which comes from fossil fuels. A revenues analysis indicates that hydrogen from biogas selling prices between 2.9 and 5.7 €/kg would be needed to reach profitability, which are considerably higher than the current hydrogen cost (1.7 €/kg). A subsidy scheme is suggested to improve the competitiveness of this hydrogen production process in the short-medium term. A cost analysis is also performed, revealing that electricity prices and investment costs have a high impact on the total share (23–40% and 8–22%, respectively). Other potential costs reduction such as catalyst, labour and manteinance & overhead are also evaluated, showing that cutting-down production costs is mandatory to unlock the potential of hydrogen generation from biogas. Our work showcases the techno-economic challenge that green energy policies face in the path toward sustainable societies. [ABSTRACT FROM AUTHOR]

The low temperature water–gas-shift reaction (LT-WGS) has been assessed by means of a hybrid sorption-enhanced membrane reactor (HSEMR) that combines both CO 2 and H 2 removal from the reaction zone. The performance of this reactor has been compared with that obtained by (i) a traditional and (ii) a sorption-enhanced (only CO 2 is removed) reactor operating in the same operational conditions. Cu/ZnO–Al 2 O 3 and K 2 CO 3 -promoted hydrotalcite materials have been used as a catalyst and CO 2 sorbent, respectively. A self-supported Pd–Ag membrane tube has been used in order to selectively separate the H 2 . The CO 2 sorption capacity, in the presence and absence of water vapour, of the potassium-promoted hydrotalcite has been determined by means of breakthrough experiments. The presence of water vapour enhanced the sorption capacity of the hydrotalcite in the experimental conditions used. Concerning the performance of the HSERM, results clearly show that when both CO 2 and H 2 are removed from the reaction zone, the hydrogen production through the reversible LT-WGS reaction is enhanced compared to either a traditional or a sorption-enhanced reactor, allowing overcoming equilibrium limitations and obtain a pure H 2 stream. [ABSTRACT FROM AUTHOR]

Understanding the time of water/gas breakthrough has a prominent role in cost effective oil production, improve oil recovery and extension the reservoir production time. The importance lies in the fact that once water or gas has broken through, the fluid distribution and the fluid relative permeabilities in the system will change. Accordingly, applying robust predictive models in this area to arrive at a proper estimation of breakthrough times as well as optimal horizontal well placement in heterogeneous and homogeneous reservoirs as a function of density difference ratio and rate is of great interest in oil and gas production system. The current study plays emphasis on applying the predictive model with the aim of the LSSVM (least square support vector machine) to estimate breakthrough time and optimum fractional well placement. Genetic algorithm (GA) was utilized to choose and optimize hyper parameters ( γ and σ 2 ) which are embedded in LSSVM model. Utilization of this model showed high competence of the applied model in terms of correlation coefficient ( R 2 ) of 0.9999 and 0.9999, mean squared error (MSE) of 0.000000142 and 0.000000622 from actual values for estimated dimensionless breakthrough time and optimum fractional well placement, respectively. [ABSTRACT FROM AUTHOR]

This paper reports the development of a catalytic gasification process to gasify low rank coals to produce FT-suitable synthesis gas in a single direct step using K 2 CO 3 as a catalyst and a mixture of steam and CO 2 as a gasifying agent. A small laboratory scale continuous catalytic gasification unit was developed and experiments were carried out at 700 °C. Effect of CO 2 addition on the synthesis gas composition was investigated. Synthesis gas with H 2 /CO = 1, 2 and 3 was produced by changing the steam/CO 2 ratio of the gasifying agent. Calculated gas compositions were found to be in good agreement with the experimental gas compositions suggesting that the water–gas shift reaction was in thermodynamic equilibrium. K 2 CO 3 was also very effective for tar cracking. The results showed that the synthesis gas suitable for the FT synthesis process can be produced in a single step at 700 °C by steam/CO 2 gasification process. [ABSTRACT FROM AUTHOR]

Partially sharing of active sites on char particle by multicomponent gasifying agent and detailed chemistry of water–gas-shift reaction are modeled and implemented. A three-dimensional RANS-based simulation with these models is also performed to investigate effects of a CO 2 injection on gasification characteristics within an entrained flow coal gasifier. Results show that the gasification performance such as carbon conversion, product gas composition and gaseous temperature distribution is precisely captured by the present simulation. The reaction inhibition by the product gas and the reaction suppression by the multicomponent gasifying agent’s partially sharing active sites are reasonably predicted. The effects of the CO 2 injection on the gasification characteristics are also discussed in detail with considering contributions of reaction pathways to the gasification performance. It is revealed that it is essential to locally control exothermic gaseous reactions and endothermic heterogeneous reactions in order to take advantage of the CO 2 injection. [ABSTRACT FROM AUTHOR]

• Water-gas relative permeability in hydrate-bearing porous media is studied by LBM. • Relationship between relative permeability and fluid distribution is characterized. • Effect of hydrate on water-gas relative permeability is revealed at a pore scale. The water-gas relative permeability is an important parameter to characterize multiphase flow in sediments. To study the water-gas relative permeability of hydrate-bearing porous media, multiphase flow simulations were carried out at the pore scale using the lattice Boltzmann method. The effects of hydrate saturation and hydrate-growth habits on the water-gas relative permeability, which is scaled by the relative permeability considering the hydrate only, were evaluated in a two-dimensional porous medium. Results show that the increase of hydrate saturation causes the decrease of water-gas effective permeability as expected. However, the effect of hydrate saturation on the water-gas relative permeability is different from that of hydrate saturation on the water-gas effective permeability. The water-gas relative permeability increases with the increase of hydrate saturation in the pore-filling case. The water-gas relative permeability decreases with the increase of hydrate saturation in the grain-coating case. The wettability of solid phase has a different effect on the relative permeability of wetting phase and nonwetting phase. The Jamin effect (phase blocking) was observed and may exist in the production of gas from natural gas hydrate reservoirs. This seriously affects the multiphase flow characteristics. The changes of microscale fluid distribution effect the changes of water-gas relative permeability. The relationship between the water-gas relative permeability and the characterization parameters of microscale fluid distribution was analyzed. [ABSTRACT FROM AUTHOR]

• The dissociation characteristics of CH4-rich and CO2-rich hydrates were studied. • Three critical parameters were examined to correlate with production parameters. • Maximized enhancement of both CH4 recovery and CO2 storage was recorded. • Hydrate reformation and simultaneous dissociation occurred during the shut-in period. • Resistance variation was dependent on shut-in period and residual water saturation. Early studies show that multistep depressurization of CH 4 /CO 2 mixed hydrates generates additional CH 4 while storing CO 2 in hydrate-bearing sediments. There are many critical factors that could affect the production and storage efficiency of this method. However, it is unclear how to achieve high efficiency in both CH 4 production and CO 2 storage by controlling these critical parameters. In this experimental work, we identified three critical parameters (CH 4 /CO 2 ratio in mixed hydrates, residual water saturation (S rw), and shut-in period) and investigated their effects on production parameters (CH 4 molar fraction in the gas phase (XCH 4), CH 4 recovery percentage (RCH 4), and CO 2 storage ratio (SCO 2)). Experiments were performed on sandstone cores using a high-pressure core flooding system equipped with pressure, temperature, and electrical resistivity measurements. Gas composition was analyzed by gas chromatography. The results showed that the optimal production parameters were determined at low S rw of 43.7–47.4% and higher CH 4 /CO 2 ratio of 1.76–2.06 in CH 4 /CO 2 mixed hydrates. The optimized values were obtained at the equilibrium pressure of CH 4 /CO 2 hydrate system at a specific reservoir temperature without water production during pressure release. In addition, the period between two pressure releases had a direct effect on the production and storage performances, and the most efficient production and storage was measured at 4-hour shut-in period of pressure release. The measured percent changes in normalized resistivity (ΔNR 2) were dependent on S rw and shut-in period. Positive increase of ΔNR 2 indicated increased hydrate saturation or improved water gas distribution in the sediment during multistep depressurization. The results demonstrated the importance of three critical parameters in designing an effective production and storage scheme after CO 2 injection into CH 4 hydrates. [ABSTRACT FROM AUTHOR]

• A new method for effectively identifying CO 2 from water, oil, and hydrocarbon gases is proposed. • The slopes between different formation parameters are used to amplify the difference between CO 2 and hydrocarbon gases. • The CO 2 identification method is less affected by environmental factors such as porosity, lithology, and shale content. The use of carbon dioxide to enhance oil and gas recovery (CO 2 -EOR) plays an important role in carbon capture, utilization, and storage (CCUS). CO 2 monitoring is of great significance for understanding CO 2 migration mechanisms, leakage pathways, and storage effect, and it is help for optimizing the performance of CO 2 -EOR and risk assessment. Moreover, oil and gas fields involving CO 2 also need to monitor and identify CO 2 layers to support decisions on oil and gas exploration and development. The purpose of this study is to use nuclear logging methods to distinguish CO 2 from other fluids, including hydrocarbon gases, and to monitor and identify CO 2. Based on the differences in the formation properties of CO 2 and other fluids, a slope method is proposed. The slopes related to different formation properties are calculated by the Monte Carlo method. The sensitivity of various slopes in distinguishing CO 2 from hydrocarbon gases (hereinafter referred to as "sensitivity") is analyzed. The cross-plot of slopes with high sensitivity is used to identify CO 2 from other fluids. The effects of various environmental factors on the cross-plot and the applicability of the cross-plot method are analyzed. The results indicate that the positions of CO 2 points in the cross-plot are greatly different from the positions of water, oil, and CH 4 , and the cross-plot can effectively identify CO 2 from other fluids. Lithology and shale content have little effect on the performance of the cross-plot in identifying CO 2 from other fluids. Comparatively, gas density and water saturation have greater impacts on such performance. The results of interpretation of field data obtained with the new method are basically consistent with the sample results, indicating that the new method is effective. This method can provide strong support for making decision on the exploration and development of oil and gas fields and has promising prospects for application in CO 2 monitoring in CO 2 -EOR. [ABSTRACT FROM AUTHOR]