Identification of hard coal surface structure using polar and apolar small molecule substances

Abstract

The paper presents a numerical approach to the analysis of the statistical effect of functional groups on the sorption of methanol and water on hard coal samples. The material used for the analysis was obtained from numerous samples of hard subbituminous and bituminous coals up to anthracite from different Polish coal mines and includes sorption isotherms of water and methanol vapors, as well as carbon dioxide and methane on these samples. Measurements were made of the sorption isotherms of water and methanol vapors and the data set has been supplemented with the sorption isotherms of water, methane and carbon dioxide taken from the literature for the precise estimation of the model parameters. More precise estimation is reached by using a strong setting of the coal structure parameters for a bigger number of sorption system, and in each case the same parameters of coal geometry are constant with an exact fitting of sorption isotherm. The adsorption-absorption model of the sorption in coal (Multiple Sorption Model-MSM) is used in the numerical experiments and the parameters of hard coal structure and the sorption systems are estimated. It has been stated that water as a polar substance together with methanol, as well as carbon dioxide and methane give good estimates of coal structure and let us quantify the polar effect of surface groups present in hard coal. The polar effect is introduced in the model in the range of adsorption and expansion subprocesses. The presence of oxygen groups in the bulk of coal matter has no significant effect and can be neglected. A weak decreasing tendency of polar factors ratio for water and methanol is discovered.

Application of multiple sorption model to estimation of CO2sequestration capacity or CH4recovery in polish hard coals

“…Sorption isotherms of CO2 and CH4 measured up to 3.4 MPa were used for evaluation of the computed set of isotherms. The MSM model was described in previous articles [12][13][14]. The results that were obtained are presented on Figures and Tables 2 and 3.…”

“…[12] Arene domains and crosslinked chains constitute a limitedly rigid macromolecular phase which simultaneously constitutes the network and enables non-crosslinked chains to flow (crawl) between cells of the network. The participation and structure of the above-mentioned components of carbon structure are the input parameters of the model.…”

Characterization of hard coal properties applying multiple sorption model with parameters determined from qualitative approach to adsorption mechanism identification

“…Finally, correction factors accounting for an interactions polarity are C pa and C pA . More detailed see (Jodłowski et al 2016).…”

“…Concerning the proposed description of each of the three-stage processes, the overall thermodynamic description of the energy change due to sorption may be expressed by unit-less term (Jodłowski et al 2016;Milewska-Duda and Duda 1997): is the initial holes fraction in the coal matter and parameter χ ac is a generalization of a Flory-Huggins parameter for porous sorbents (i.e., assumption 0 h = 0 leads to the description of purely absorptive system).…”

“…For these reasons, the author's team is currently working on continuous development of multiple sorption model (MSM) aimed at hard coal structure identification and sorption system properties characterization (Jodłowski et al 2016). The applicability of MSM to identify of various sorption systems parameters is examined, as well as its use for estimation of coal deposits capacity in carbon dioxide sequestration.…”