Utilization Of Coalbed Methane Research Articles

Selective adsorption of coalbed methane on multilayer defective graphene nanostructures and their Mn-modified nanostructures: A DFT study

Coalbed methane (CBM) is an unconventional natural gas with CH4 as the main component. It is found in coal seams and surrounding rocks. The development and exploitation of CBM is a promising approach to ensure the safety of coal mine production, reduce greenhouse effects, and increase clean energy resources. Based on the first-principles calculations in conjunction with a grand canonical Monte Carlo (GCMC) simulation, this paper aims to examine the effects of interlayer spacing and Mn modification on CBM and CO2 adsorption. We assess the CH4 storage performance in multilayered defective graphene nanostructures (MDGNs). Using density functional theory in conjunction with the Grimm correction method (DFT-D approach), both the adsorption energy and charge distribution between CBM components and extended line defects (ELD) are appropriately evaluated in the presence or lack of Mn modification (Mn-ELD). The GCMC simulation is implemented to investigate CH4 adsorption isotherms of MDGN and Mn-MDGN configurations at 298.15 K. The selective adsorption capabilities of MDGNs and Mn-MDGNs for CO2, N2, and CH4 are also systematically analyzed. The obtained results reveal that an Mn-MDGN configuration with an interlayer spacing of dGL=1.02 nm is effective in sequestering CO2 from CBM. In contrast, MDGN configurations with interlayer spacings of dGL=0.68 and 1.02 nm are more effective for the storage of purified CBM. In continuing, the CH4 purification mechanism in Mn-MDGNs and the CH4 storage mechanism in MDGNs are also methodically explored at the molecular level. The research work reported here can serve as a crucial guide for the future development and utilization of CBM.

Система совместного использования обедненного метана угольных пластов и биогаза для выработки электроэнергии в угольных шахтах

Purpose: Justification and development of new resource-saving technologies aimed at utilization of coal bed methane. The problem of low efficiency of utilization of lean methane-air mixtures is primarily due to the low content of methane itself, which varies significantly depending on the type of coal or concentration. This paper discusses the concept of a co-production system that mixes low-methane methane-air mixtures and biogas to generate power. Methods: Analysis of the possible volumes of utilized methane, biogas requirements and the suitability of the primary feedstock for co-generation of heat and electricity. Selection of appropriate parameters for the processes of utilization of mine methane. Analysis of the merits of the proposed method of utilization of lean coal mine methane. Results: It is recommended that biogas produced by agriculture and forestry in the vicinity of the mines be added to the dry methane stream to obtain the necessary gas concentration for electricity generation. Potential electricity production and greenhouse gas emission reductions have also been evaluated. The result shows that the co-production system can significantly improve the efficiency of poor methane-air mixtures in coal mines. Practical significance: The joint use of lean methane and biogas from straw offers practical advantages both economically, ensuring sufficient energy supply in mines, and as a foundation for broad future prospects. It allows for energy cost reduction and environmental pollution reduction, such as decreasing carbon dioxide emissions.

Research and application of dual tube gas lift technology in coal bed methane well

ABSTRACT Coal bed methane (CBM) is a gas resource associated with and symbiotic with coal, which refers to the hydrocarbon gas stored in the coal seam, with methane as the main component, which belongs to unconventional natural gas. The development and utilization of CBM has the effect of achieving multiple things in one fell swoop: clean energy, commercialization can produce huge economic benefits. At present, rod pump, screw pump and other lifting technologies commonly used in CBM drainage and production have poor adaptability, short pump inspection period, and it is difficult to enter horizontal section in horizontal well. Aiming at this problem, a new method of efficient CBM lifting is proposed by adopting dual-pipe gas lift technology. In this paper, the basic principle of double tube gas lift is analyzed, the optimization design of gas injection volume, coiled tubing size and coiled tubing running depth is carried out, and the field technology application of vertical and horizontal Wells is carried out. The results show that the dual tube gas lift technology has good adaptability in the deliquification of CBM, and the field application has achieved good production results. After the process modification, gas production of CBM Wells increases continuously, while water production decreases gradually, with the maximum gas rate exceeding 2400 m3/d. According to the latest production data, well L31 has been in steady production for more than 9 months, with an average gas rate of 1294.56 m3/d, which greatly exceeds the capacity before the transformation. Because there are no moving parts in the wellbore, the pump inspection period is greatly improved, and it has the potential to be widely applied in CBM.

Experimental Study of the Influence of Moisture Content on the Pore Structure and Permeability of Anthracite Treated by Liquid Nitrogen Freeze-Thaw.

The liquid nitrogen freeze–thaw (LN2-FT) method has been widely used to improve the coal permeability in the coalbed methane (CBM) production. However, the influence of moisture content on the permeability of coal treated by LN2-FT remains unclear, limiting the broad application of this technique. A novel seepage system was proposed to analyze the permeability evolution of anthracite coal samples treated by LN2-FT. Moreover, variations of the pore structure were analyzed using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and low-field NMR. The results showed that pores and fractures appeared on the coal surface after the LN2-FT treatment. As the moisture content of the coal increased, more pores and fractures tended to be formed during the LN2-FT treatment. The total pore volume, porosity, and average pore diameter of the anthracite coal after the treatment were 1.77, 2.44, and 5.58 times higher, respectively, than that of the raw coal. The change in the specific surface area exhibited three trends as the moisture content of the coal samples increased: a slow descent, a steady increase, and a rapid descent. Moreover, it was found that the LN2-FT treatment increased the connections between pores and fractures, improving gas migration in the coal. Furthermore, the LN2-FT treatment significantly increased the permeability of the anthracite coal samples. The higher the coal moisture, the higher the permeability of the coal samples after the LN2-FT treatment. Hence, the LN2-FT technique can substantially improve the permeability of coal reservoirs, providing essential information for the efficient utilization of CBM.

Mechanical responses of coals under the effects of cyclical liquid CO2 during coalbed methane recovery process

Liquid CO2 fracturing technology has been introduced to enhance coalbed methane (CBM) recovery for the decades, under its multiple-effects of phase transition and flooding, by complicating the crack distribution and improving the reservoir permeability. When huge amounts of cryogenic fluids were cyclically injected into the reservoirs, the accompanying effects of temperature shock and adsorption might have some potential impacts on the fracturing results, and their influence degree and the related mechanical deterioration were required to systematically studied. Three different rank coals were chosen and cyclically treated by liquid CO2, and the uniaxial compression behaviors of these affected coals were studied to investigate the destruction patterns, the evolutions of mechanical parameters, and the mechanism of damage failure. Compared to the raw coals, the ones affected by temperature-adsorption coupling effects of liquid CO2 displayed a more complex “separation + spallation” destruction pattern, while the ones treated by the sole effect had a destruction pattern of “spallation” and “separation” respectively. The more complex the destruction pattern, the larger the fractal dimension, and the greater the structure degradation. The affected coals exhibited diverse mechanical responses, for example, the compression strength σc and elastic modulus E had negative correlations with the increasing cyclical parameters, while Poisson’s ratio μ and damage variable Dv positively correlated with the increasing affecting parameters, respectively, which manifested that the accompanying cyclical temperature shock could facilitate the crack growth and the CO2 adsorption aggravated the strength deterioration, finally destroying the coals with the smaller yield strength. A new damage model was established by jointly considering the grain anisotropy from the microscopic aspect and the diversity of mechanical responses from the macroscopic perspective, and the induced unrecoverable deformations greatly weakened the cohesive stress among the grains or matrix skeleton, finally destroying the coal structure by producing amounts of new cracks. Furthermore, the produced new-raw cracks provided amounts of adsorption sites for CO2 molecules, which further decreased the surface energy and accelerated shear failure. The results were helpful to the injection parameters optimization, the low-cost of CO2 injection invests and the potential profit maximization of CBM utilization.

The use of coal bed methane to fabricate diamonds

The use of coal bed methane (CBM) to fabricate diamonds by chemical vapor deposition (CVD) is proposed. The method uses a closed-loop system composed of CBM mining, CBM purification, the production of hydrogen from CBM for use in diamond growth, diamond fabrication and waste gas recovery. The requirements for the fabrication of diamonds of different grades for use in cutting tools, thermal management, and optical lens and field emission transistors are introduced as examples of the efficient utilization of CBM to produce different quality diamonds.

Research on forecasting coal bed methane demand and resource allocation system based on time series

The mining area is the main place for the development and utilization of Coalbed Methane (CBM), and there are a series of systems for the development and utilization of CBM. However, owing to lack of a clear understanding of demand-side gas consumption rules and a reasonable resource allocation system, a large amount of CBM resources in the mining area are wasted. In order to predict the demand for CBM dynamically, the Seasonal Auto Regressive Integrated Moving Average (SARIMA) model, Additive Holt-Winters (AHW) model and Multiplicative Holt-Winters (MHW) model based on time series are used to predict the monthly demand for CBM in Yangquan Mine Area in 2020, respectively. Then the predicted results are evaluated by using the prediction model parameters combined with the characteristics of actual demand for CBM. Finally, a resource allocation system under different supply and demand conditions is built to reduce the waste of resources. In this paper, it is found that the information of the actual data is not sufficiently extracted in the MHW model while the SARIMA model can reflect the cyclical trend of monthly demand for CBM under ideal conditions. Furthermore, the AHW model can reasonably predict the demand for CBM under the influence of COVID-19, with a mean relative error of 0.099. The supply and demand distribution system built based on the proposed models can solve the problem of seasonal unevenness of CBM demand in mining areas and ensure the economic benefits of mining areas.

A gas outburst prevention and control strategy for single thick coal seams with high outburst risk: A case study of Hudi Coal Mine in Qinshui Basin

AbstractCoal and gas outburst is one of the most harmful natural disaster in coal mine production. The frequency and scope of outburst are closely related to the metamorphic degree of coal seam, the depth of coal seam, and the complexity of geological structure. In general, the use of traditional along‐seam borehole or cross‐seam borehole can meet the needs of gas control. However, for the coal seams with high outburst risk, these methods fail to meet the demands of high‐yield and high‐efficiency coal recovery as well as safe, green, and economical coal mining. Although pressure‐relief gas extraction in the protective seam and coalbed methane (CBM) pre‐extraction can eliminate outburst risk in coal seams, these methods can hardly help realize the green development trend of coal and CBM co‐extraction because they cannot guarantee the current situation of highly mechanized mining. In this study, a three‐dimensional coal and CBM co‐extraction strategy was proposed. The strategy includes three levels of three‐dimensional gas prevention and control methods. The first level is the combination of ground and underground gas extraction methods, to achieve joint extraction of ground and underground gas. The second level is the full‐coverage extraction of the coal resources to be mined, to achieve joint extraction through upper and lower cross‐seam borehole and along‐seam borehole. The third level is the optimization of ground and underground extraction and utilization systems, to realize the full utilization of CBM and to achieve the goal of coal and CBM co‐extraction. The three‐dimensional gas prevention and control method constructs a new gas control model for single thick coal seams with high gas outburst risk and realizes the all‐round coordination and unity of different gas control methods spatially and temporally. The gas control strategy completely eliminates the high gas outburst risk of a single thick coal seam and has been successfully applied in Hudi Coal Mine. The application results verify that the method can effectively guarantee the operation safety during highly mechanized mining, realize extraction and full utilization of separate‐source gas, and provide guidance and direction for coal and CBM co‐extraction with similar extraction conditions.

Reservoir characteristics and coalbed methane resource evaluation of deep-buried coals: A case study of the No.13–1 coal seam from the Panji Deep Area in Huainan Coalfield, Southern North China

The Panji Deep Area in Huainan Coalfield, Southern North China is a newly discovered deep coal-bearing block with abundant coalbed methane (CBM) resources. To date, systematic geological studies regarding CBM reservoir in this region are still deficient, thereby seriously hindering the further exploitation and utilization of CBM in Huainan Coalfield. Results indicate that No.13–1 coal seam in the Panji Deep Area has good material conditions for CBM accumulation and preservation. All the coal samples from the No.13–1 coal seam are medium ash and medium−high volatile bituminous coals (Ro,max, 0.72–0.82%), which have different proportions of macerals and minerals. Pore structure and morphology analyses indicate that No.13–1 coal samples have various pore types and complex pore structures. Among them, the ink-bottle shaped pores are mainly observed with a pore size diameter of 4 nm. The gas content of No.13–1 coal samples is 16.11–21.83 m3/t (avg. 18.16 m3/t), which is strongly affected by the effective thickness of coal reservoir, reservoir pressure and temperature. Gas content is significantly positively correlated with burial depth, reservoir pressure, and temperature below 700 m, 6 MPa, and 34 °C, respectively. However, the upward trend tends to be constant after these demarcation points. Numberous micropores hold the retention capacity of coal matrix to methane molecules, thus the residual gas content increases along with the volume and surface area of micropores. By contrast, the correlations between gas content and coal thickness and roof thickness are not obvious. The total CBM resource of No.13–1 coal seam is approximately reserve of 205.36 × 108 m3. Moreover, the total CBM resources in the northern and southern parts of the Panji Deep Area are 73.83 × 108 m3 and 131.53 × 108 m3, respectively. On the basis of multi-level fuzzy model and the evaluated factors, the most favorable areas for CBM development of the No.13–1 coal seam were predicted to be around Zhutuan and south Gugou town in the Panji Deep Area.

Estimation of hydrogen release and conversion in coal-bed methane from roof extraction in mine goaf

In order to effectively utilize the coal bed methane (CBM) resources extracted from underground coal mines, an evaluation method of hydrogen production capacity from CBM is established by means of experiments and theoretical models. The main components of CBM collected from coal working face are measured by gas chromatography, and the release law of trace hydrogen is obtained. Considering gas extraction technology in goaf roof, a computational fluid dynamics model for seepage problem in porous media is presented. The law of gas migration in goaf under extraction conditions is obtained by simulation, and the extraction rate of CBM and methane/hydrogen content are predicted. The technology of producing hydrogen from CBM extracted from goaf under low gas concentration is discussed, and the effect of methane content on auto-thermal conversion efficiency is analyzed. Under the condition of this study case, the theoretical estimation of pure hydrogen produced from goaf extraction can reach more than 10,000 m3 per day. The presented results could provide a new route for the utilization of CBM by underground extraction.

Enhanced separation of coal bed methane via bioclathrates formation

The separation and utilization of coal bed methane have great research and economic significances. Consequently, we investigated the two-stage separation of CH4/N2 binary gas mixture, an analogue of coal bed methane, using hydrate separating method in this work. In order to realize green environmental protection and promote the popularization of hydrate separation method, two biological additives, i.e., tea polyphenol and catechin, were applied to recovery CH4 by forming bioclathrates. The influences of tea polyphenol and catechin on hydrates thermodynamic phase equilibria, kinetic hydration rate, gas storage capacity and separation effects were systematically studied. The results show that these two bio-additives could significantly increase the formation rate and gas storage capacity of hydrates in comparison with pure water system. In addition, the recovery of CH4 and separation factor are also enhanced in the presence of bio-promoters. Therefore, the formation of bioclathrates is helpful to protect environment, and promote the industrial application of the hydrate separation technology.

Enhanced activity and stability of La-doped CeO2 monolithic catalysts for lean-oxygen methane combustion.

Effective utilization of coal bed methane is very significant for energy utilization and environment protection. Catalytic combustion of methane is a promising way to eliminate trace amounts of oxygen in the coal bed methane and the key to this technology is the development of high-efficiency catalysts. Herein, we report a series of Ce1-xLaxO2-δ (x = 0-0.8) monolithic catalysts for the catalytic combustion of methane, which are prepared by citric acid method. The structural characterization shows that the substitution of La enhance the oxygen vacancy concentration and reducibility of the supports and promote the migration of the surface oxygen, as a result improve the catalytic activity of CeO2. M-Ce0.8La0.2O2-δ (monolithic catalyst, Ce0.8La0.2O2-δ coated on cordierite honeycomb) exhibits outstanding activity for methane combustion, and the temperature for 10 and 90% methane conversion are 495 and 580°C, respectively. Additionally, Ce0.8La0.2O2-δ monolithic catalyst presents excellent stability at high temperature. These Ce1-xLaxO2-δ monolithic materials with a small amount of La incorporation therefore show promises as highly efficient solid solution catalysts for lean-oxygen methane combustion. Graphical abstract ᅟ.

Determination of Hydrogen Gas Emitted from Coal by Gas Chromatography and its Significance

Methane in coal mine gas is the research focus about the prevention of gas hazard and the development and utilization of coal bed methane. There have been more researches on heavy hydrocarbon in coal mine gas and a consensus has been formed about heavy hydrocarbon. Compared with methane and heavy hydrocarbon in coal mine gas, the research on hydrogen in coal mine gas is few and just unfolding. In this paper, 1097 gas samples are prepared based on 1097 coal samples. And, the hydrogen in gas samples is tested by Gas Chromatography. The research reveals that: the hydrogen contents in all gas samples can be detected, and the maximum value of hydrogen is 4.8% while the mean value is 0.645%, so the presence of hydrogen in gas is universal. 2 contents of hydrogen exceed 4%, 47 contents are between 2%-4% and 206 contents are between 1%-2%, thus, the content of hydrogen in gas is roughly the same with the content of heavy hydrocarbon in gas. It is suggested that: more attentions should be given to the hydrogen in gas to be an important index of coal and gas outburst and to be an important index of gas explosion, safety of coal storage and transportation.

Transient Modeling and Simulation of Coal Bed Methane Transmission Pipeline

The coal bed methane is methane mainly and it has less heavier than conventional natural gas, thus coal bed methane has a slightly higher value than natural gas. Developing and utilization of coal bed methane is an important way to release contraction between supply and demand of natural gas in China. The pipeline is principle way of transporting the coal bed methane from sources to end-users. In view of the characteristics of coal bed methane, equation of state BW RS is used to calculate the thermodynamic parameters. Then based on continuity equation, momentum equation, characteristic equations of non-pipe elements and flow quantity balance equation, the transient simulation mathematic model of coal bed methane transmission pipeline is built. Considering the slow transient characteristic of gas flowing, the implicit central difference method is used to transform partial differential equations of the model into finite difference equations. Aiming at non- linear characteristics of differential equations, Newton iteration format is constructed and the model's solution method is discussed. Finally, MS Visual C++ is utilized to develop a simulation software name coal bed methane pipeline emulation system, and the practical applications are carried out. The results show the mathematic model built in the paper and its solving method are both feasible. They provide technical supports for reasonable design and operation of the coal bed methane pipelines.

Catalytic performance of La1−xErxCoO3 perovskite for the deoxidization of coal bed methane and role of erbium in a catalyst

The effective utilization of coal bed methane (CBM) is very significant for energy utilization and environmental protection, reducing significantly greenhouse gas methane emission. In this paper, La1−xErxCoO3 perovskite (0 ≤ x ≤ 0.4) catalysts for the catalytic deoxidization of CBM were prepared by a co-precipitation method and were characterized by X-ray diffraction (XRD), laser Raman spectroscopy (LRS), H2 and CH4 temperature-programmed reduction (H2, CH4-TPR), CO pulse and N2adsorption/desorption techniques. The results show that the amount of Er affects obviously the physicochemical and catalytic properties of La1−xErxCoO3, and when x = 0.2, La0.8Er0.2CoO3 exhibits the best activity for deoxidization of CBM, because Er doping promotes the activity and migration of the lattice oxygen of La0.8Er0.2CoO3. The influences of the operation parameters (methane concentration, oxygen concentration and space velocity) on the catalytic deoxygenation of CBM and the kinetics behaviours were investigated. The reaction order of removing oxygen is 0.9 for methane partial pressure and −0.6 for oxygen partial pressure.

Stress relief coalbed methane drainage by surface vertical wells in China

Abstract This paper summarizes the status of engineering practice, technology and research related to stress relief coalbed methane (CBM) drainage using surface wells in China during the past 10 years. Comments are provided on the theory and technical progress of this method. In high gas mining areas, such as the Huainan, Huaibei and Tiefa mining areas, characterized by heavily sheared coals with relatively low permeability, stress relief CBM surface well drainage has been successfully implemented and has broad acceptance as a CBM exploitation technology. The fundamental theories underpinning stress relief CBM surface well drainage were established in China, and include elements relating to: (1) rock layer deformation theory, vertical zoning and horizontal partitioning, and the change in the stress condition in mining stopes; (2) a theory regarding an Abscission Circle in the development of mining horizontal abscission fracture and vertical broken fracture in overlaying rocks; and (3) the theory of stress relief inducing permeability increase in protected coal seams during mining; and the gas migration–accumulation theory of stress relief CBM surface well drainage. Three kinds of technical drainage modes are described: protected seam surface well drainage in areas influenced by mining represented mainly in the Huainan mining area; gob surface well drainage most prominently in the Tiefa mining areas; and the multipurpose surface well drainage used in the Huaibei mining areas. Serial well allocation in which wells are used for different purposes as extraction and mining proceeds, and well bore configurations and designs suitable for this purpose, are described. The development and utilization of CBM is significant to energy-saving, emission-reduction and to ensure safety in coal production.

A Community Model for Coalbed Methane Utilization: ABSTRACT

The University of Alabama at Tuscaloosa provides a model for community utilization of coalbed methane and energy independence. A feasibility study for coalbed methane development has been completed through a grant from the U. S. Department of Energy. The total resource available beneath the 760-acre (310-ha.) campus is estimated to be nearly 10 bcf. The Mary Lee Coal Group alone contains more than 3.4 mcf of gas, assuming 75% recovery. As a result of an economic analysis, two exploration/research wells have been completed to depths of 2,289 and 2,760 ft (698 and 841 m) respectively. The university is currently in the process of unitizing with Bryce and Partlow Hospitals. The combined acreage is approximately 2,000 acres (800 ha.). It is anticipated that coalbed methane could meet the gas demands of all three facilities for many decades. The methane will be used for space heating, domestic hot water, and for compressed natural gas (CNG) to operate the university's vehicle fleet. Recently the university, along with Southern Company Services, Kaneb Services, and the Gas Research Institute, has embarked on a demonstration project to evaluate the feasibility of using coalbed methane as a primary fuel source for a fuel-cell power plant. A 40-kW fuel cell will be utilized to provide both electricity and hot water for the student recreation building. These coalbed methane utilization activities should provide planning information for communities located over coal lands to develop independent resources and provide long term energy alternatives. End_of_Article - Last_Page 457------------