The Repeatability of Sorption Processes Occurring in the Coal-Methane System during Multiple Measurement Series

Abstract

Abstract:The aim of this paper was to investigate the repeatability of sorption processes occurring in the coal-methane system during multiple measurement series. For research purposes, three granular samples of coal sorbent were used. The samples were subjected to a series of three measurements, each time performed under the same conditions. During each series of measurements, the following stages took place: outgassing the sample in a vacuum, and then saturating it with methane under the pressure of 1, 3, and 10 bar. Sorption capacities and the values of effective diffusion coefficients were compared. The studies into the repeatability of measurements of sorption capacities, conducted by means of the IGA-001 (Intelligent Gravimetric Analyzer) gravimetric instrument for three measurement cycles, showed that the obtained measurement discrepancies in relation to the mean value did not exceed 1.23%. The discrepancies in question approximated the measurement uncertainty of the IGA-001 device. The evaluation of the recurrence of determining the values of effective diffusion coefficients showed that the obtained discrepancies were no larger than 10%, which might have resulted from problems with fulfilling most of the assumptions of the applied unipore diffusion model. The authors did not observe any changes of the sorption parameters of hard coal during consecutive cycles of methane saturation.

Insights into Multifractal Characterization of Coals by Mercury Intrusion Porosimetry

“…where ∆Vpi, ∆Vd(pi) and ∆Vm(pi) are the changes of filling pore volume, detected mercury volume, and matrix compression volume when pressure increases from P0 to Pi, respectively; Vd(pi) represents the Assuming ∆V c /∆P is independent of mercury intrusion pressure, in this case, dV c /dP can be replaced by ∆V c /∆P. Hence, the matrix compressibility coefficient can be calculated by combining Equations (13) and (16). In this study, the calculated matrix compressibility coefficient for the selected coal samples is in the range of 0.89-2.47 × 10 −10 m 2 /N ( Table 1), averaging at 1.21 × 10 −10 m 2 /N, which is consistent with previous researches, such as Cai et al [2] (1.55-2.37 × 10 −10 m 2 /N), Guo et al [23] (0.35−2.91 × 10 −10 m 2 /N), and Shao et al [40] (1.13-3.06 × 10 −10 m 2 /N).…”

“…Direct observation methods are, for example, scanning electron microscopy (SEM) [5,6], X-ray computerized tomography (X-CT) [7,8] and atomic force microscope (AFM) [9,10], which can be used 2 of 18 to characterize the two-or three-dimensional distribution of coal PSDs. Indirectly inferred methods include mercury intrusion porosimetry (MIP) [11,12], gas adsorption (N 2 and CO 2 ) [13][14][15][16] and nuclear magnetic resonance (NMR) [17][18][19]. Among of these methods, MIP measurement has been proven as an effective method to estimate the PSD of coals.…”

Methane Emission during Gas and Rock Outburst on the Basis of the Unipore Model

“…Review of the literature on the subject reveals that almost all the described outbursts took place in regions of geological disturbances [17,[23][24][25]. The outburst hazard is particularly high when the thickness of the tectonically deformed layer exceeds 0.8 m [26].…”

Predicting long term coal seam gas concentrations from multi-component sorption

“…This chapter explains gas transport modelling works on unipore and bidisperse diffusion models (theoretical details of which are referenced to previous researchers' extensive work [55][56][57][58]…”

“…Before utilizing experimental data in the numerical models to determine diffusion coefficients, some additional information on gas transport mechanism and its relationship with coal heterogeneity from previous research works are provided to discuss the importance of selecting an adequate model for coal seam gas transport mechanism [55][56][57][58].…”