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Acoustic emission and sorptive deformation induced in coals of various rank by the sorption-desorption of gas

Majewska Z., Ziętek J.

Acta Geophysica

2007

Vol. 55, no. 3

324-343

Simultaneous measurements of acoustic emission (AE) and expansion/ contraction of coal samples subjected to gas sorption-desorption processes were conducted on high- and medium-rank coal. The aim of this study was to examine the influence of the coal rank and type of sorbate on measured AE and strain characteristics. The experimental equipment employed in this study consisted of a pressure vessel and associated pressurisation and monitoring units. The arrangement of pressure-vacuum valves permitted the coal sample to be pressurised and depressurised. Carbon-dioxide and methane were used as sorbats. Acoustic emission and strains were recorded continuously for a period of 50 hours during sorption and for at least 12 hours during the desorption process. Tests were conducted on cylindrical coal samples at 298 K. The experimental data were presented as plots of AE basic parameters versus time and in strain diagrams. These studies lead to the following conclusions: 1. There are significant differences in AE and strain characteristics for the two sys-tems (coal-CO2 and coal-CH4); 2. There is a direct influence of rank and type of coal on its behaviour during the sorption-desorption of gas. An attempt has been made to interpret the results obtained on the grounds of the copolymer model of coal structure. More research is needed into this topic in order to get a quantitative description of the observed facts.

Wpływ rozdrobnienia próbek węgli kamiennych na niskotemperaturową sorpcję azotu i ditlenku węgla w temperaturze pokojowej

Cygankiewicz J., Dudzińska A., Żyła M.

Przemysł Chemiczny

2006

T. 85, nr 11

1505-1509

Przedstawiono wyniki własnych badań sorpcji azotu (77,5 K) i ditlenku węgla (293 K) na czterech klasach ziarnowych rozdrobnionego węgla kamiennego. Wykazano istotną zależność sorpcji azotu od stopnia rozdrobnienia węgla, której nie obserwowano w przypadku sorpcji ditlenku węgla. Cząsteczki CO2, podobnie jak H2O i CH3OH, wnikają do najdrobniejszych porów, powodując pęcznienie polimerycznej struktury węgla kamiennego. Sorpcja azotu ma miejsce na zewnętrznych powierzchniach węgla i prawdopodobnie w zewnętrznych makroporach.

Sorption isotherms of N2 and CO2 were detd. at 77.5 and 293 K, resp., on 65–85% C bituminous coals (type 32) in relation to particle size (0.063–0.075, 0.075–0.125, 0.125– 0.25, and 0.25–0.355 mm), volatiles, and origin. N2 sorbed only on the external surface, at best on the 0.063–0.075mm grade (1.18–3.53 m2/g in sp. surface). CO2 penetrated very easily into the micro and submicro porous structure (so that it could displace other gases, e.g. CH4) and thus enabled the micropore vol. and the sp. surface of the coals to be detd. The porous structure was as accessible to CO2 as it was to H2O and MeOH.