Abstract: CO2 and CH4 Sorption Kinetics on Coal: Experiments and Potential Application in CBM/Ecbm Modeling (original) (raw)
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CO2 and CH4 sorption kinetics on coalAn experimental and modeling approach
Greenhouse Gas Control Technologies 7, 2005
Apart from thermodynamic data on equilibrium sorption capacity and selective sorption, numerical modeling of CBM processes requires information on the kinetics (rates, characteristic times) of sorption processes. In order to cover this issue which is of relevance in different EU-projects (ICBM, RECOPOL), the kinetics of CO 2 and CH 4 sorption on dry and moist Carboniferous coals have been investigated in a systematic study. Data have been compared in a qualitative way as well as by use of a simple, 1 st-order rate model. The goal was to provide simple, semi-empirical approaches applicable in reservoir models for CBM production and CO 2 injection.
Sorption Kinetics of CH 4 and CO 2 Diffusion in Coal: Theoretical and Experimental Study
Experimental and theoretical analyses with empirical correlations were framed for diffusion of gas species CH 4 and CO 2 in coal samples from Jharia coal fields, India, considering the intrinsic pore parameters. Coefficient of diffusion (D) and diffusivity (D eff) for a single and binary component coal−gas system were estimated by adopting unipore gas kinetic models for gas flow on the integration of Fick's law and Langmuir relation. The rigorous study was carried out in estimating crossover pressure, which is dominant in distinguishing the flow regime for two primary types of diffusion: Knudsen and molecular as well as the transition between two regimes. Investigation reveals that experimental values of coefficients of diffusion of CH 4 and CO 2 in random homogeneous isotropic sphere packing of coal samples are in good agreement with the results of theoretical calculations. For the pressure range investigated, variation of coefficient of diffusion was found to follow a dual nature with a stable trend at pressures above 3500 kPa and an increasing trend for lower pressures. The practical implication of the investigation for the pressures that are characteristically encountered in the Jharia coalfields is a positive finding for the concomitant recovery of coalbed methane with CO 2 sequestration. Additionally, the dynamic relation between sorption−diffusion reveals that the coefficient of diffusion significantly depends on the pore structure and pore size distribution, exhibiting a negative relationship with pressure variation.
Sorption rate of CH4 and CO2 in coal at different pressure ranges
IOP Conference Series: Materials Science and Engineering, 2018
The aim of this study was to verify the dynamic factor, that is the diffusion rate, which can directly affect the efficiency of CO2 injection and as a consequence-storage. A manometric setup was used for experiments on two hard coals from Upper Silesian Coal Basin in Poland. A model combining two firs-order rate functions with different rate constants was used to plot normalized equilibration curves. Diffusion curves were plotted at three pressure ranges 5-6 MPa, 3.5-4 MPa and 1.5-2 MPa. Result show that fast adsorption rate is higher at 5.5-6 MPa than at lower pressure range with highest fast adsorption rate fraction both for CH4 and CO2. Lower (1.5-2 MPa) pressure range allows achieving sorption equilibrium in less time for both gases. Diffusion rates are lower for CO2 than for methane the CH4 desorption rate has a slight impact on the CO2 adsorption and as a consequence CO2 storage capacity.
The aim of the study is to estimate the theoretical capacity of coal deposits in terms of carbon dioxide storage and methane recovery estimate during the injection of carbon dioxide. The Multiple Sorption Model was used for this purpose. The range of sorption measurement data on which the simulations were based does not exceed the critical point for both methane and carbon dioxide. The model allows to calculate absorption, adsorption, expansion and total theoretical sorption. For further consideration absorption was used as the process of the percolation of the gas in the bulk of the coal matter as well as the total theoretical sorption, the occurrence of which is possible due to the presence of fractures in the coal seam. Calculated levels of absorption and the total theoretical adsorption were applied to estimate the possible storage capacity of carbon dioxide based on the data associated with the content of coal in the mining fields of individual Polish coal mines. Moreover, MSM development for the gas mixture sorption can be used to roughly assess the recovery of methane naturally occurring in coal deposits during such a process.
Methane and Carbon Dioxide Sorption and Transport Rates in Coal at In-situ Conditions
Energy Procedia, 2009
Geologic sequestration of carbon dioxide is an option for the mitigation of industrial emissions. However, considerable effort remains to shift this technology from its current status as potential solution to a safe, effective and trusted foundation to the global energy system. Characterization of gas movement and sorption capacity of coal at in-situ conditions is required. Using the volumetric method, measurements of CH 4 and CO 2 sorption and diffusion in coal have been made on powder and non-powder confined coal. Results obtained, emphasized that the sorption capacity and the kinetics of gas in coal are both influenced by the stress state of the sample. The application of 6.9 MPa confining stress contributed to about 30% and 80% of sorption capacity reduction for CO 2 and CH 4 respectively. The sorption and diffusion of CO 2 in confined coal follow two distinct rates described with diffusion coefficients of 2.3 x 10-6 m 2 /s and 9.4 x 10-12 m 2 /s respectively. In contrast, the flow of methane is characterized by a continuous process with a diffusion coefficient of 3.8 x 10-7 m 2 /s. These observations confirms the complex interaction of CO 2 with the coal structure and stressed that CH 4 and CO 2 sorption and transport in coal should be characterized differently, specifically when dealing with non-powder confined samples. Consequently, the use of information collected on pulverized coal samples for the simulation and prediction of long term underground sequestration and enhanced coalbed methane is not justified.
Modeling of CO2 sorption on coal
Fuel, 2008
This paper discusses moderate pressure CO 2 sorption behavior of Illinois coals. The results fit the Langmuir and Dubinin-Astakhov (D-A) sorption models satisfactorily although the fit is better for D-A equation. Since factors like swelling of coal with CO 2 sorption and CO 2 dissolution in coal matrix contribute to uncertainties in estimating the void volume in and around the sample, an attempt was made to account for these by modifying the conventional adsorption equation. Re-fitting the experimental data using the modified equation results in improved fit for both models. The adsorption capacities of coals tested, as predicted by the equations, also reduce by 7% to 32%. The effect of volumetric uncertainty is more in lower rank coals than the higher rank ones. Furthermore, it explains the excess sorption behavior observed by others when extrapolated beyond the experimental pressure range.
Study on CO 2 Sorption Capacity of Coal – An Experimental Approach
In the present situation of global warming, the percentage of í µí° ¶í µí± 2 in atmospheric air is increasing very rapidly, which will create major problem for the future generation. Storage of í µí° ¶í µí± 2 is gaining widespread interest as a potential method of controlling greenhouse gas emissions as suggested by Intergovernmental Panel on Climate Change (IPCC). This study includes methane desorption mechanism from coal bed, and suggests that the desorbed methane can be used as a pure fuel for many purposes. It is generally acknowledged that coal beds are an important rock medium with regard to their capacity to act as a reservoir for í µí° ¶í µí± 2 gas. In this paper, í µí° ¶í µí± 2 sorption capacity of coal under different temperatures has been investigated by experimental approach and also explains the effect of cracks on coal surface in its sorption capacity. As temperature and pressure increases, with the depth of seam from surface level, the mathematical relation derived from this experiment will be helpful in determination of total amount of í µí° ¶í µí± 2 that can be stored in a coal seam at various reservoir temperature. The results will be helpful to use enhanced production of methane as additional benefit and also to use coal seam as a permanent sink for anthropogenic í µí° ¶í µí± 2 emission.
Implications of carbon dioxide sorption kinetics of low rank coal
Journal of Physics: Conference Series, 2019
This study appraises the dynamic of porosity and permeability measurement of the coal for reservoir modelling during gas production. Known as one of the main target areas for coalbed methane (CBM) production and potentially in integrating testing methodology, these measurements were carried out on low rank coals. During the testing, the pore pressure was varied at each pressure in stepwise with the adsorption equilibration. The gas content of the core sample was estimated until equilibration of the system and the sample of swelling in response to adsorption was measured. By employing newly achieved measurements, CT scan and acoustic emission wave methods, this study determines the porosity and permeability evolution which acts an important role in the dynamic changes in CO2 sorption kinetics of coal. Permeability can be calculated by applying a pressure difference between both end sides of inlet-outlet of a certain direction according to Darcy's law. While the Kozeny-Carman is an empirical equation influenced by several parameters such as total porosity, specific surface area, pore shape, tortuosity, and porosity to determine the permeability. By merging both approaches, empirical and laboratory method, the sorption kinetics of coals and other controlling factors are also counteracted. High isotherm interval low swelling capacity Low isotherm interval Peak swelling area Adsorption Isotherm Change of Coal A2 Adsorption Isotherm Change of Coal B1 (a) (b) High swelling Capacity
Sorption behavior of coal for implication in coal bed methane an overview
International journal of mining science and technology, 2017
CBM has been recognized as a significant natural gas resource for a long time. Recently, CO 2 sequestration in coalbeds for ECBM has been attracting growing attention because of greater concerns about the effects of greenhouse gases and the emerging commercial significance of CBM. Reservoir-simulation technology, as a useful tool of reservoir development, has the capability to provide us with an economic means to solve complex reservoir-engineering problems with efficiency. The pore structure of coal is highly heterogeneous, and the heterogeneity of the pores depends on the coal type and rank.
International Journal of Coal Geology, 2012
High-pressure sorption experiments with methane (CH 4) and carbon dioxide (CO 2) were performed on coals from different mines in the SW Upper Silesian Basin in the Czech Republic. The coals were of high-to low-volatile bituminous rank, representing the late stage of catagenesis. The influence of different factors on the sorption capacity of these coals was evaluated by varying the experimental conditions. Excess sorption capacities of moisture-equilibrated coals ranged from 0.3 to 0.8 mmol/g daf for CH 4 and from 0.8 to 1.2 mmol/g, daf for CO 2. Excess sorption capacities of as-received (air dried) coals were on average 34% higher for CH 4 and 17% higher for CO 2 as compared to the moisture equilibrated state. Sorption capacity shows a weak positive correlation with coal rank and a negative correlation with temperature. The CO 2 /CH 4 sorption capacity ratio is larger for moisture-equilibrated coal, while it decreases with increasing pressure as well as increasing coal rank. From the experimental data, correlations were derived between sorption capacity, and coal rank and temperature. These correlations were used to estimate the "static" variation of sorption capacity with coal seam depth. Estimated sorption capacities increase towards a maximum value between 600 and 1000 m depth, followed by a decrease due to the predominance of the temperature effect. Temperature and pressure data derived from the reconstructed (1D) burial history were used to calculate the "dynamic" variation of sorption capacity during basin evolution. These computations show that initial sorption capacity was significantly higher than the one estimated from present day pressure and temperature gradients. Uplift of coal seams resulted in under-saturation of the coal.