Accurate testing coal isotherm can play a significant role in the areas of coal seam gas drainage, outburst control, CO 2 geo-sequestration, coalbed methane (CBM) and enhanced coalbed methane recovery (ECBM) etc. The effect of particle size on the CO 2 and CH 4 sorption capacity of bituminous coal from Illawarra, Australia was investigated at 35°C and at pressure up to 4 MPa. A unique indirect gravimetric apparatus was used to measure the gas adsorption and desorption isotherms of coal of different particle sizes ranging from around 150 μm to 16 mm. Langmuir model was used to analysis the experimental results of all gases. Coal particle size was found to have an apparent effect on the coal ash content and helium density results. Coal with larger particle size had higher ash content and higher helium density. The sorption isotherm was found to be highly sensitive with helium density of coal which was determined in the procedure of testing the void volume of sample cell. Hence, coal particle size had a significant influence on the coal sorption characteristics including sorption capacity and desorption hysteresis for CO 2 and CH 4 , especially calculated with dry basis of coal. In this study, the 150-212 μm (150 μm) coal samples achieved higher sorption capacity and followed by 2.36-3.35 mm (2.4 mm), 8-9.5 mm (8 mm) and 16-19 mm (16 mm) particle size samples. However, the differences between different coal particles were getting smaller when the sorption isotherms are calculated with dry ash free basis. Test with 150 μm coal samples were also found to have relatively smaller desorption hysteresis compared with the other larger particle size samples. The different results including adsorption/desorption isotherm, Langmuir parameters and coal hysteresis were all analysed with the CO 2 and CH 4 gases.Keywords: coal adsorption, desorption, coal particle size, isotherm, Langmuir volume Dokładne zbadanie izoterm sorpcji na węglu odgrywa kluczową rolę w takich dziedzinach jak odgazowanie pokładów węgla, zapobieganie wybuchom, sekwestracja geologiczna CO 2 , odzysk metanu ze złoża. Wpływ wielkości ziaren na pojemność sorpcyjną bitumicznego węgla z Illawara (Australia) względem CO 2 i CH 4 zbadano w temperaturze 35°C przy ciśnieniu do 4 MPa. Wykorzystano oryginalną aparaturę do badań grawimetrycznych do zmierzenia izoterm adsorpcji i desorpcji na węglu w którym rozmiar ziaren wahał się od 150 μm do 16 mm. Analizę wyników doświadczalnych dla wszystkich gazów przeprowadzono w oparciu o model Langmuira. Stwierdzono, że rozmiary ziaren węglowych w znacznym stopniu warunkują zawartość popiołu i gęstość helową. Węgiel grubiej uziarniony charakteryzował się wyższą zawartością popiołu i większą gęstością helową. Wykazano, że izoterma sorpcji wykazuje wysoką wrażliwość na zmiany gęstości helowej, co stwierdzono na podstawie badania martwej przestrzeni ampułki w której umieszczono próbkę. Wnioskować stąd można, że rozmiar ziaren węgla w dużym stopniu wpływa na charakterystyki sorpcyjne węgla, w tym także na chłonność sorpcyjną i hi...

No abstract

Permeability refers to the ability of coal to transmit gas when a pressure or concentration gradient exists across it. The permeability of coal is dependent upon factors that include effective stress, gas pressure, water content, disturbance associated with drilling and matrix swelling/shrinkage due to adsorption/desorption. A programme of laboratory tests were conducted on coal samples from the Bulli seam for evaluating the permeability and drainability of coal. Two different types of permeability apparatus were used in this study. The methods of permeability testing of coal under different triaxial conditions are discussed. Permeability testing of the Bulli seam coal with N 2 is described. The laboratory test results were found to be in agreement with the calculated permeability values.

Thin spray-on liners (TSLs) have been attracting increasing attention as an alternative to steel mesh in underground roadway support. In order to investigate the shear strength of glass fibre reinforced TSLs, an improved punch test was developed: the steel ring is replaced by TSL plates and four screws are used to tighten the TSL sample between the clamping plates to ensure stable and symmetrical loading. Four different glass fibre contents were tested to evaluate the effect of glass fibre reinforcement on the shear strength of TSLs. The effect of loading rate was studied. The results suggest that the steel punch can shear through the polymer sheet well and the failure mode can be easily identified. The results are consistent and easily calculated. The shear strength increases with glass fibre content. The TSL material samples showed good linear behaviour prior to reaching ultimate load and ductile behaviour that reflects the fibre reinforcement of failed resin during the yielding stage of the sample, which is beneficial to support in underground mines. Although there may be some impact of the shearing rate on the shear strength, the effect is negligible for the loading rates used. Shear strength testing of glass fibre reinforced thin spray-on liner Q. QIAO*, J. NEMCIK* and I. PORTER* Thin spray-on liners (TSLs) have been attracting increasing attention as an alternative to steel mesh in underground roadway support. In order to investigate the shear strength of glass fibre reinforced TSLs, an improved punch test was developed: the steel ring is replaced by TSL plates and four screws are used to tighten the TSL sample between the clamping plates to ensure stable and symmetrical loading. Four different glass fibre contents were tested to evaluate the effect of glass fibre reinforcement on the shear strength of TSLs. The effect of loading rate was studied. The results suggest that the steel punch can shear through the polymer sheet well and the failure mode can be easily identified. The results are consistent and easily calculated. The shear strength increases with glass fibre content. The TSL material samples showed good linear behaviour prior to reaching ultimate load and ductile behaviour that reflects the fibre reinforcement of failed resin during the yielding stage of the sample, which is beneficial to support in underground mines. Although there may be some impact of the shearing rate on the shear strength, the effect is negligible for the loading rates used. INTRODUCTIONThin spray-on liners (TSLs) are a relatively new form of rock support in underground coal mines. As an active support technique, it is known that a TSL is able to take action even if only small rock movement occurs, which is desirable for rock support. As steel mesh is of a passive nature and does not contribute to roadway skin reinforcement, TSLs are currently being investigated as an effective technology. ToughSkin, a fibre glass reinforced polymeric material liner developed at the University of Wollongong, has properties that sati...

Mine roadways developed in highly stressed strata are subject to roof shear, which under severe conditions may manifest as the well known symptom of guttering, particularly at the roadway edge leading into the major horizontal stress. This roof shear can progressively reduce the effectiveness of bolt confinement of the strata within the lower roof horizon affecting stability of the immediate roof. This paper presents the results of a study to investigate the effectiveness of polymers as skin reinforcement in highly stressed coal mine roadways, as they may provide better roadway skin support than the currently used steel mesh. A large concrete block intercepted with artificial joints and reinforced with steel bolts without skin support, was loaded until significant slip occurred along the joints. Upon loading, a roof cavity resembling a gutter developed, as some of the jointed concrete parted from the free surface. In addition to bolts, subsequent models with identical fracture planes were supported with steel mesh or with glass reinforced polymer skin bonded to the free side. Loads and displacements were compared for models with and without skin reinforcement. As expected the skin support helped resist gutter formation, to various degrees, while increasing the residual strength of the concrete block. It was found that there was significantly less bedding displacements in models with the polymer skin, when compared with both steel mesh and no skin reinforcement. This suggests that there would be benefits to using a spray on polymeric skin as surface support in roofs subject to severe roof shear.