Methane Sorption Research Articles

Ligand Tailoring Strategy of a Metal-Organic Framework for Optimizing Methane Storage Working Capacities.

Methane, as the main component of natural gas, shale gas, and marsh gas, is regarded as an ideal clean energy to replace traditional fossil fuels and reduce carbon emissions. Porous materials with superior methane storage capacities are the key to the wide application of adsorbed natural gas technology in vehicle transportation. In this work, we applied a ligand tailoring strategy to a metal-organic framework (NOTT-101) to fine-tune its pore geometry, which was well characterized by gas and dye sorption measurements. High-pressure methane sorption isotherms revealed that the methane storage performance of the modified NOTT-101 can be effectively improved by decreasing the unusable uptake at 5 bar and increasing the total uptake under high pressures, achieving a substantially high volumetric methane storage working capacity of 190 cm3 (STP) cm-3 at 298 K and 5-80 bar.

Shale’s Pore Structure and Sorption-Diffusion Characteristics: Effect of Analyzing Methods and Particle Size

The delineation of pore size and surface area distribution and methane sorption-diffusion capacity in gas shale reservoirs is crucial for the estimation of storage capacity, anticipating flow characteristics, and field development. A systematic approach and guidelines are needed for the analysis of the pore size and surface area distribution of shale formations. The effect of shale sample size on the gas sorption and diffusion properties is not well understood either. The low-pressure nitrogen adsorption technique is a prevalent method for pore characterization of nanoporous shale formations. Although researchers adopted some corrections to the classical method for the analysis of pore size and surface area distribution, there is a significant mismatch between different approaches in depicting fine mesopore size and surface area (2–10 nm). In this study, the classical methods and density functional theory are employed to comparatively analyze the pore characteristics of some shale and clay samples for their applicability, efficacy, and consistency issues. Furthermore, the effect of shale particle size on the methane sorption capacity and diffusion is being investigated. It seems that confinement stress has less of a considerable effect on methane sorption (6% decrease). However, crushing shale rocks into smaller particles can significantly overestimate the methane adsorption capacity. The methane diffusion coefficient also increases with increasing the shale particle size by more than an order of magnitude.

Multi-Parameter Analysis of Gas Losses Occurring during the Determination of Methane-Bearing Capacity in Hard Coal Beds

The content of natural methane in hard coal seams, called methane-bearing capacity, is the basic parameter that enables the level of methane hazard to be determined in hard coal mines. This parameter is also used to determine the potential quantities of methane that can be collected and used for energy purposes and the amount of its harmful emission to the atmosphere. Direct methods are most often used to determine methane-bearing capacity. An important aspect that has a great influence on the final result of the research is the gas losses generated at the stage of sampling. Under the conditions of the Polish mining industry, the direct drill cuttings method is used to determine the methane-bearing capacity. Gas losses are compensated for in this method with the use of the coefficient 1.12, by which the obtained result is multiplied. In this paper, a multi-parameter analysis of gas loss in the determination of methane-bearing capacity in hard coal seams has been carried out. Several experiments were performed to identify the most important aspects to be taken into account to obtain a correct result. A methane-bearing capacity test was conducted using two direct methods: the direct drill cuttings method, otherwise known as the single-phase vacuum degassing method, and a method based on the United States Bureau of Mines standards. Sorption studies, such as methane sorption kinetics tests, were also conducted in which sorption properties, such as sorption capacity, effective diffusion coefficient, and half sorption time, were determined. Methane sorption isotherms were also determined, and pore structure was analysed. Based on the obtained test results, an analysis was carried out which made it possible to present appropriate conclusions concerning the gas losses during the methane-bearing capacity test, generated at the stage of sampling. The final result of the work was the proposal of a new gas loss coefficient for the direct drill cuttings method of methane-bearing capacity determination.

Silver and copper modified zeolite imidazole frameworks as sustainable methane storage systems

The effective sorption of methane with mesoporous adsorbents is one of the most sought-after methods of energy storage. The constant development of organometallic networks and the synthesis of new materials increases the efficiency of methane sorption, reaching new record amounts of gas adsorbed per gram of adsorbent. In this study, we present the optimised in-situ synthesis preparation method of Ag and Cu-modified zeolite imidazole frameworks by using ultrasonic irradiation. We proved that silver is present in ZIFs in the form of nanoparticles in the case of silver-modified materials. In contrast, in the case of copper-modified materials, the copper is present in ionic form. We also found that incorporating PVP as a stabilising agent and the modification with Ag and Cu changes the structural parameters of the prepared materials. The methane sorption results confirmed that the developed materials exhibit enhanced sorption capacity by over 100% (based on ZIF-8) and by 20% (based on ZIF-67). The highest methane adsorption at 1.6 MPa was achieved by Cu-PVP/ZIF-8 and Cu-PVP/ZIF-67, and Ag-PVP@ZIF-67 samples, and was equal to 112 cm3 CH4/g, 96 cm3 CH4/g and 97 cm3 CH4/g, respectively. The developed sonochemically assisted synthesis method allowed to obtain Ag and Cu modified zeolite imidazole frameworks which may be considered as efficient materials for sustainable methane storage systems.

Inorganic geochemical, mineralogical and methane sorption capacities of Paleozoic shale formations from Western Peninsular Malaysia: Implication of shale gas potential

An experimental study comprising methane sorption capacity (MSC), inorganic geochemical and mineralogical analysis was conducted to assess the shale gas potential, depositional environments, and tectonic settings in the Western Peninsula (WP) Malaysia. Here, we report 146 shale samples from seven Paleozoic formations in WP Malaysia, divided into four groups based on their ages. The results indicate MSC ranging between 0.054 and 0.065, 0.034 and 0.109, 0.032 and 0.069 and 0.021 and 0.100 mmol/g rock for Silurian-Devonian (S-D), Devonian, Carboniferous, and Permian shales, respectively. By comparison, the MSC of the WP Malaysia shale is close to obtainable values for Longmaxi (China) and Barnett (USA) shales. Geochemical characterization reveals that the studied Paleozoic shales were deposited mainly in continental island arc and active continental margin (ACM) under a reducing marine depositional environment. Sr/Cu, Rb/Sr,Sr/Ba ratios, and C-values reveal warm, humid to hot arid paleoclimate for the S-D and Carboniferous shale samples, and warm, humid paleoclimate for the Devonian and Permian shales. The PIA, CIW, and CIA values indicate the source rocks have been subjected to moderate to strong chemical weathering. Al2O3/TiO2, Zr/TiO2, and LREE/HREE ratio, Eu anomalies, and the binary plot of Zr/Sc and Th/Sc denote that the shales from WP Malaysia are derived from intermediate to felsic igneous source rock. Mineralogical analysis reveals that S-D and Permian shales generally possess less clay and more siliceous minerals than the Devonian and Carboniferous shales. Comparatively, the mineral content of the Paleozoic shales is close to the mineralogy of Niutitang and Longmaxi shales. The geochemical analysis indicates that the pyrobitumen reflectance of Paleozoic shale samples is overmatured. Overall, based on the derived geological data and comparative analysis with hot gas shale reservoirs around the world, high, moderate and low shale gas potentials were obtained for the Devonian and Permian shales, S-D shales and Carboniferous shales in WP Malaysia, respectively.

Quantitative Gas‐in‐place Comparison of Original and Bitumen‐free Lacustrine Shale

AbstractResidual bitumen in organic‐rich shale of oil windows exists widely, and its effect on the gas storage capacity of shale could be two‐fold. Bitumen could occupy and block the nanopores of shale, thereby reducing the gas storage capacity. On the other hand, gas could be dissolved in bitumen in shale gas reservoirs, leading to enhanced gas storage capacity. To quantify the effect of bitumen on the gas‐in‐place (GIP) estimation of lacustrine organic‐rich shale, the micropore characteristics and methane sorption capacity of original and bitumen‐free shale from the Triassic Yangchang Formation of the Ordos Basin, combined with the methane dissolution capacity for the isolated bitumen, were analyzed and compared. GIP for the original and bitumen‐free shale in the depth range of 500–2500 m was evaluated. The results show that micropores in the shale samples were mainly related to organic matter. Clay mineral‐hosted pores contributed slightly to microporosity. Bitumen significantly reduced the micropore surface area and volume of the original shale, with average percentages of 28.09% and 51.26%, respectively. The methane sorption capacity decreased after bitumen removal. When normalized to the original shale mass, the sum of the methane sorption capacity for bitumen‐free shale and the methane dissolution capacity for isolated bitumen was similar to the methane sorption capacity of the original shale, indicating that the lack of methane absorbed on bitumen is the main reason for the decrease in methane sorption capacity after bitumen removal. The contribution of absorbed methane on bitumen to sorbed methane in shale could be higher than 36.23%. Dual effects of bitumen on shale GIP were observed. A high content of bitumen (1.12%) increased the GIP of the shale samples, with an average percentage of 23.5% in the depth range of 500–2500 m, while a low content of bitumen (0.06%) decreased the GIP, with an average percentage of 13.6%.

Effect of pore structure on competitive sorption and diffusion of mixed methane and carbon dioxide in anthracite, South Qinshui Basin, China

A deep understanding of the competitive adsorption and diffusion of methane (CH4) and carbon dioxide (CO2) in coal is significant for implementing the CO2-ECBM project. For three high-rank coal samples, industrial analysis, coal maceral, and vitrinite reflectance (RO) determination, mercury injection test, and low-temperature nitrogen/carbon dioxide specific surface test were carried out, and the composition and pore structure of coal samples were studied systematically. Meanwhile, through the three mixed gases (75%CH4 + 25%CO2, 50%CH4 + 50%CO2, 25%CH4 + 75%CO2) adsorption and desorption test, the absolute adsorption amount, free phase and adsorption phase of CH4 and CO2 under different equilibrium pressures, and the equivalent diffusion coefficients of gas migration in the process of adsorption/desorption equilibrium were calculated. Finally, the relationship among the coal composition, pore structure, and the competitive adsorption and diffusion characteristics of methane and carbon dioxide mixture in coal were studied. The results show that: (1) the composition of coal has an important influence on the development of coal pore structure and the adsorption and transport of gas in coal. Supermicropore (<2 nm in size) is the prominent adsorption place. Furthermore, its development, which essentially determines the adsorption capacity of coal samples, is positively correlated with fixed carbon content, vitrinite content, and vitrinite reflectance. (2) When the pores >100 nm in size relatively developed, the coal samples have higher porosity, lower micropore diffusion, and a smaller desorption hysteresis index. Because the pore's connectivity is limit, its content has no apparent correlation with the permeability of coal samples and most of the adsorption and diffusion parameters. (3) The desorption hysteresis is mainly caused by the opposite migration direction of gas in the process of adsorption and desorption and the resulting dislocation of coal matrix swelling and shrinkage. The competitive adsorption of CH4 or CO2 and their separation index (SCO2/CH4) in coal samples decreases with the increase of adsorption equilibrium pressure. Also, the desorption process often shows a higher SCO2/CH4 value than that of the adsorption process. (4) During the adsorption process, the equivalent macro-diffusivities of the coal sample decrease as a power function with increasing pressure and increase with the carbon dioxide content increasing in the mixed gas. However, the equivalent micro-diffusivities change little with the different CH4 and CO2 mixtures migration in different coal samples. The equivalent diffusion coefficient of coal is positively correlated with macropore, mesopore, transitional and micropore content in coal samples.

Experimental and simulation investigations of the impact of polyacrylamide on CBM ad-/desorption

Slickwater is commonly used during hydraulic fracturing in coalbed gas well, which is often prepared with polyacrylamide as the friction reducer. To investigate the impact of polyacrylamide on CBM ad-/desorption after a fracturing operation, slickwater with different concentrations of polyacrylamide were prepared and used to treat Illinois coal samples. Both isothermal ad-/desorption experiments and molecular simulations were conducted to investigate the impact of slickwater. Nuclear magnetic resonance measurements were performed to analyse the evolution of surface functional groups of coal during slickwater treatment. The results show that there is no significant chemical reaction between the coal component and polyacrylamide. Because of the porosity of the polyacrylamide coating adhered onto the surface of the pore, polyacrylamide has a significant sorption capacity of methane. The methane sorption amount of the ‘coal-slickwater’ system is higher than that of raw coal. However, with the increase of the amount of residue entering the pores, the porous structure of the polyacrylamide coating becomes denser, blocking some pores and the pore surface area is reduced; thus, the overall sorption capacity of the ‘coal-polyacrylamide’ system decreases.

Pore evolution in siliceous shales and its influence on shale gas-bearing capacity in eastern Sichuan-western Hubei, China

The Upper Permian siliceous shale reservoir, which was less studied before, is considered to be a successor target of marine Wufeng-Longmaxi shale gas in Sichuan Basin. To deeply explore pore characteristics, evolution process, formation mechanism and their influences on shale gas capacity, we performed a comprehensive multiscale characterization on siliceous shales with different maturities from Dalong and Wujiaping Formations using low-pressure N2 adsorption (N2GA), mercury injection pressure (MIP), field emission scanning electron microscopy (FE-SEM), and methane sorption capacity. Results indicate that shale pore development, especially OM pore development, and physical property are strictly controlled by thermal maturation levels. OM pores are seldom in low-mature shales but are well-developed in high-to over-mature shales. Pore structures in shales with different maturities are determined by different factors. The high TOC content is conducive to developing OM micropores for high-to over-mature shales. High content of brittle minerals is conducive to developing interparticle (interP) pores and dissolved mesopores at high-mature stage. In terms of the data and published articles, we established a general pore evolution model in siliceous shales to illustrate shale pore development process and formation mechanism. Similar to OM pore development, methane sorption capacity is controlled firstly by thermal maturation and secondly by TOC content. It's pointed out that over-mature shales have smaller-sized OM pores compared with high-mature shales, and therefore they have higher specific surface areas and methane sorption capacities normalized to TOC. This indicates that siliceous shales with extremely high maturity still have good shale gas potential, which further expand shale gas exploration in over-mature shale gas reservoir, as well as provide exploration suggestion for the siliceous shale gas reservoirs in south China.

Analysis of the Influence of Coal Petrography on the Proper Application of the Unipore and Bidisperse Models of Methane Diffusion

The analysis of phenomena related to gas transport in hard coal is important with regard to the energetic use of coal bed methane (CBM), the reduction of greenhouse gas emissions to the atmosphere (CO2) and the prevention of natural hazards such as methane hazards and gas and rock outbursts. This article presents issues concerning the feasibility and scope of applying the unipore and bidisperse diffusion models to obtain knowledge concerning the kinetics of methane sorption and its diffusion in the carbon structure, depending on its petrography. Laboratory tests were carried out on coal samples which varied in terms of petrography. Quantitative point analyses were carried out, based on which content of groups of macerals was determined. The degree of coalification of coal samples was also determined based on measurements of vitrinite reflectivity R0 and the volatile matter content Vdaf. Sorption kinetics were also investigated, and attempts were made to adjust the unipore and bidisperse models to the real sorption kinetic courses. This allowed the identification of appropriate coefficients controlling the course of sorption in mathematical models. An attempt was also made to assess the possibility of applying a given model to properly describe the phenomenon of methane sorption on hard coal.

Influence of active water on gas sorption and pore structure of coal

Active water fracturing is one of the commonly used technologies in area for enhanced coalbed methane (CBM) extraction. However, after the fracturing process, active water residues may block the pore of coal and ultimately reduce the production of CBM. To address this limitation, pore structures of Dongtan (DT) and Houwenjialiang (HW) coal samples were subjected to active water fracturing effect using active water with different concentrations of PAM prepared using polyacrylamide (PAM). Methane adsorption experiment was conducted to probe the effect of active water on the adsorption of methane in coal samples. Additionally, low-temperature nitrogen-adsorption experiments (LT-NAT) and nuclear magnetic resonance (NMR) were probed to characterize the discrepancies in the pore structure and chemical composition surface functional groups of the two coal-sample types. The results showed that considerable discrepancies existed in the pore structures of the two coal-sample types; however, their surface functional groups were similar. The active water treatment had contrasting effects on the adsorption behavior of methane features of the two coal-sample types, that is, as concentration of PAM in the active water increased, the methane adsorption of the treated HW coal sample increased whereas that of the treated DT coal sample gradually decreased. The PAM molecules in the active water residue could adsorb methane, and blockage of pores by the residue will reduce the amount of methane adsorption. The combined effect of the two dominated the influence of active water fracturing on methane sorption. Further optimizing the active water formulation to improve the flowback effect can be a very useful channel of reducing damage to the coal seam.

Sorption characteristics in coal and shale: A review for enhanced methane recovery

The exploration and exploitation of hydrocarbon resources within coal and shale reservoirs is an engineering challenge. Well-developed internal micro-pore structures, complex sorption mechanism as well as numerous influencing factors affecting the gas flow are generally not well-accounted in the commercial life-cycle of shale gas and coalbed methane wells. Although large number of studies have been conducted to propose improved sorption models and study the influencing factors on adsorption and desorption characteristics of methane and CO2 in coal and shale reservoirs, a systematic review of such studies for efficient understanding of the accumulated literature is missing, especially with a focus towards coal and shale reservoirs. In that context, this study presents a review of sorption characteristics of methane in coal and shale. Firstly, theoretical mechanisms for methane sorption are introduced, followed by description of sorption models. Further, three factors influencing the sorption of gas in coal and shale are described: total organic carbon and clays, pore structures, and reservoir conditions. Finally, the preferential sorption characteristics of hydrocarbons and carbon dioxide are described, and the methods to promote methane desorption for enhanced recovery are discussed, which include technologies such as gas injection, microwave heating, and hydraulic fracturing. Cited as: Qin, X., Harpreet, S., Cai, J. Sorption characteristics in coal and shale: A review for enhanced methane recovery. Capillarity, 2022, 5(1): 1-11. https://doi.org/10.46690/capi.2022.01.01

Sorption and Micro-Scale Strength Properties of Coals Susceptible to Outburst Caused by Changes in Degree of Coalification.

Coals from the south-western part of the Upper Silesian Coal Basin have a strong outburst susceptibility. The objective of this study was to identify the influence of coalification degree on methane sorption and micro scale strength properties of 24 coals from Jastrzębie Zdrój. Coal samples showed a reflectance Ro between 0.98 and 1.25%. Sorption measurements were carried out by gravimetric method. Sorption capacities were determined at mean deposit temperature of 35 °C. Using the unipore model and solution of Fick’s second law, the effective diffusion coefficients of methane in the studied coals were obtained. The Vickers method was used to study the microhardness and the modulus of elasticity. It has been shown that the increase in the coalification degree reduces the sorption capacity of coal and also reduces the rate of methane emission. Coals the most susceptible to outbursts, were the most brittle. With the increase in Ro, the methane seam pressure p increased as well as desorbable methane content DMC, both due to the reduction in the sorption capacity of coal. The increased dp index is a warning sign indicating an increased total methane content of coal seam, an increased seam pressure or an alternation of coal structure.

Experimental study on the adverse effect of gel fracturing fluid on gas sorption behavior for Illinois coal

Hydraulic fracturing is an effective technology for coal reservoir stimulation. After fracturing operation and flowback, a fraction of fracturing fluid will be essentially remained in the formation which ultimately damages the flowability of the formation. In this study, we quantified the gel-based fracturing fluid induced damages on gas sorption for Illinois coal in US. We conducted the high-pressure methane and CO2 sorption experiments to investigate the sorption damage due to the gel residue. The infrared spectroscopy tests were used to analyze the evolution of the functional group of the coal during fracturing fluid treatment. The results show that there is no significant chemical reaction between the fracturing fluid and coal, and the damage of sorption is attributed to the physical blockage and interactions. As the concentration of fracturing fluid increases, the density of residues on the coal surface increases and the adhesion film becomes progressively denser. The adhesion film on coal can apparently reduce the number of adsorption sites for gas and lead to a decrease of gas sorption capacity. In addition, the gel residue can decrease the interconnectivity of pore structure of coal which can also limit the sorption capacity by isolating the gas from the potential sorption sites. For the low concentration of fracturing fluid, the Langmuir volume was reduced to less than one-half of that of raw coal. After the fracturing fluid invades, the desorption hysteresis of methane and CO2 in coal was found to be amplified. The impact on the methane desorption hysteresis is significantly higher than CO2 does. The reason for the increasing of hysteresis may be that the adsorption swelling caused by the residue adhered on the pore edge, or the pore blockage caused by the residue invasion under high gas pressure. The results of this study quantitatively confirm the fracturing fluid induced gas sorption damage on coal and provide a baseline assessment for coal fracturing fluid formulation and technology.

A comparison of potential functions for molecular dynamic simulation of methane sorption in the silicalite

A comparison of potential functions for molecular dynamic simulation of methane sorption in the silicalite

Effect of depth on the sorption capacity of coals affected by outburst hazard

The aim of the presented research was a quantitative evaluation of the burial depth impact on the methanesorption capacity of outburst coals inrelation to present-day temperatures and coalification degrees. Theavailable for sampling coal seams of Zofiówka mine in the Upper Silesian Coal Basin (USCB) were tested. Coal samples of R0 from 0.98% to 1.25% were taken from average burial depths between 678 and 863 [m] which covered a range of deposit temperatures from 33.0 to 38.4 [°C]. Methane sorption isotherms were performed for all the samples at temperature from 25 °C to 55 °C with interval of 10 °C. Sorption results up to apressure of 1.2 MPa were approximated with the Langmuir model. Overlapping effects with increasing depth were measured: (i) an increase in deposit temperature and (ii) an increase in degree of coalification. Within the considered depths, the sorption capacity of coal decreases together with depth increase. It was shown that degree of coalification havea dominant effect (about 89%) on the reduction of the sorption capacity and the effect of geothermal gradient is only slightly more than 10%. Reduction of the sorption capacity with depth was shown to be unfavourable from the point of view of the risk of outbursts. It contributes to an increase in the seam methane pressure and an increase in free methane content in total methane content (the value of w/TMC). Reduction of the sorption capacity with depth leads to the increase of desorbable methane content (DMC) and thus influences the scale of the potential outburst.

Sorption and Diffusion of Methane, Carbon Dioxide, and Their Mixture in Amorphous Polyethylene at High Pressures and Temperatures

Molecular dynamics (MD) simulations are performed to study the sorption and transport properties of CH4 and CO2 in amorphous polyethylene at temperatures from 350 to 600 K and pressures up to 500 bar. The uptake of CH4 and CO2 by polyethylene generally increased with increasing pressure and decreasing temperature. However, at high pressures, for example, the uptake of methane by polyethylene increases with temperature. The self-diffusion coefficients of methane and carbon dioxide generally increase with pressure. These results are, in general, consistent with the swelling behavior of the polymer. Interestingly, for the penetrants, the activation barrier of diffusion decreases with pressure. MD simulations are also carried out for the CH4/CO2 mixture in amorphous polyethylene. Here, the overall sorption and transport properties were similar to those reported for pure CH4 and pure CO2 in polyethylene. The sorption selectivity of CO2/CH4 decreases with increasing pressure and temperature and was mostly independent of the bulk mole fraction of methane. Importantly, at high pressures, the mobility of methane found here is higher than that of the corresponding pure methane in polyethylene and the opposite trend is observed in the case of carbon dioxide. These results might be due to the fact that the swelling of the polymer in the presence of carbon dioxide is significantly higher than that in the presence of methane, especially at high pressures. The diffusion and membrane selectivities of carbon dioxide/methane show a similar trend to the sorption selectivity data. Furthermore, the simulation data were in good agreement with the theoretical calculations based on the PC-SAFT equation of state.

Dynamic in situ imaging of methane hydrate formation in coal media

Fast 3D X-ray imaging has proved to provide crucial insights into multi-phase dynamic processes in various geo-materials. In particular, many in situ imaging experiments have been made to study gas-hydrate formation in porous sandy samples. Such imaging is challenging for the methane gas-hydrate formation in coal samples because of the coal micro-porosity structure and lower X-ray contrast. Here we present results of the first dynamic in situ micro-computed tomography experiment of methane-hydrate formation in coal samples. Synchrotron phase-contrast tomography techniques allowed to achieve necessary contrast levels to separate all the materials of interest (gas, water, coal, and gas hydrate) in reconstructed images with high spatial and temporal resolution. The imaging results are compared to the ones from a similar tomographic experiment with sand samples. Methane-hydrate formation is accompanied by the water movements caused by cryogenic water suction that happens in sequences of short fast movements with longer equilibrium states in between. Only one type of the hydrate formation was observed in coal (growth as shells on grain boundaries) as opposed to three types in sand (shells, growth into gas pockets, and inside water volumes). In particular, this leads to a slower hydrate-formation speed in coal. For the coal sample, we also observed water extraction from grains, and interpreted it as competitive sorption of methane. We visualized the dynamic behavior of this water extraction via micro-channels inside the coal grains, and performed nano-tomography imaging of these channels for a better understanding of this phenomenon.

Comparative study of conventional steam-methane-reforming (SMR) and auto-thermal-reforming (ATR) with their hybrid sorption enhanced (SE-SMR & SE-ATR) and environmentally benign process models for the hydrogen production

The paper presents a comparison of steam methane reforming (SMR), sorption enhanced steam methane reforming (SE-SMR), auto-thermal reforming (ATR), and sorption enhanced auto-thermal reforming (SE-ATR) in a fixed bed reformer for hydrogen production. A one-dimensional, unsteady-state heterogeneous reactor model for each process which includes mass and thermal dispersion in the direction of flow and axial pressure distribution, has been simulated using gPROMS® 4.0.1 model builder, while CEA and Aspen Plus® have been employed to analyze the equilibrium performance and simulate the process flowsheets of individual process respectively. The performance of the individual hydrogen production process has been analyzed in terms of CH4 conversion (%), H2 yield (wt. % of CH4), H2 purity and CO2 capture under the various operating conditions of temperature (773–1473 K) and pressure (5–40 bar). The simulation results were also compared with the thermodynamic calculations and literature data. An excellent agreement was observed between our reactor modelling outputs and literature data. The operating conditions of 923 K, 30 bar and S/C of 3.0, O2/CH4 of 0.45 have been chosen. At these conditions, the CH4 conversion for SMR, SE-SMR, ATR, and SE-ATR was found to be 32%, 66%, 51%, and 76% respectively while the composition of hydrogen produced on a dry basis was 55%, 87%, 55%, and 92% respectively. It has been concluded that there are significant advantages of both sorption enhanced processes over conventional reforming in terms of CH4 conversion, H2 purity and the amount of H2 energy produced per unit CH4 energy consumed (MJ).

Determination of methane sorption capacity using microstructural analysis in coal of Jharia Coalfield, India

Micrometer-scale pore and fracture structures of coal seams are the crucial parameters for the adsorption of coalbed methane (CBM) and recovery. This paper deals with the microstructure’s influence on coal methane sorption behavior obtained from the Jharia Coalfield, India. Coal samples were collected from different seams to study the variability and heterogeneity of the reservoir parameters. Proximate and ultimate analysis of coal samples were determined to predict the rank of the coal. Microstructural parameters like pore size distribution, surface morphology, and infrared spectroscopy (FT-IR) were studied to predict the extent of gas sorption in the coal. The excess amount of methane sorption was determined using a volumetric method at 47 °C temperature and variable pressure. The identified pore volume varied from 0.2 to 3.07 m3/g. The surface morphology indicated inter- and intraparticle pores with spongy surfaces. The pore volume and surface morphology confirmed the favorable sorption of methane in coal samples. The FT-IR study showed the formation of hydrogen bond and methane sorption in coal. The maximum sorption capacity varied from 5.08 to 9.01 cc/g at 400 to 580 m depth. A strong, positive, and nonlinear correlation was observed with pore volume. The results showed that the presence of meso- and micropores and the spongy surface morphology are vital in defining its methane sorption capacity. As a whole, these coals have a higher porosity from 4.9 to 5.64% and meso- and micropores and are suitable for methane sorption.