摘要 :
Australia has developed a number of gas drainage technologies over the last twenty years and achiered significant success in gas and outburst control．The majority of coal seams in Australian coal basins are regarded as medium to ...
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Australia has developed a number of gas drainage technologies over the last twenty years and achiered significant success in gas and outburst control．The majority of coal seams in Australian coal basins are regarded as medium to highly gassy，and are prone to coal and gas outbursts．To prevent these outbursts in coal mines,Australia uses extensive gas pre-drainage techniques to reduce the virgin seam gas content below the outburst threshold levels．One of the major developments in this field in Australia is the development of directional drilling technology，which significantly increased the targeted pre-drainage capability of the coal industry．These developments have led to the prevention of outbursts and significant improvements in gas drainage performance and productivity in the coal mining industry．Goaf gas control is another major issue in most of the gassy underground coal mines due to its direct impact on safety，production delays and cost of production．Analysis of the gas data from different collieries in Australia showed that longwall gas emissions have increased substantially over the years．Simply drilling a surface goal hole into the longwall goal or increasing the number of goal holes in the panel or reducing goaf hole spacing does not seem to be effective in controlling high goal gas emissions．A number of developments have taken place in the recent years to achieve a step-change improvement in goaf gas drainage performance．A brief summary of various gas drainage technologies and practices being used in Australia and the recent developments in goal gas control strategies are summarised in this paper.
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摘要 :
In German underground hard coal mining，extraction has had to be moved to ever-greater depths，using the multi-seam mining method．On the one hand this requires high quality longwall entries，which are normally used twice．On the ...
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In German underground hard coal mining，extraction has had to be moved to ever-greater depths，using the multi-seam mining method．On the one hand this requires high quality longwall entries，which are normally used twice．On the other hand successful control of gas emissions is a decisive factor if longwall mining is to be productive．Despite extremely difficult geological conditions with winning depths of more than 1，100 m，rock temperatures of over 60℃ and releasable gas contents in the working seams up to 9 m3/t coal and in the surrounding strata (for 1 ton saleable coal)up to 40 m3/t,it has been possible to implement high-performance longwall mining operations．Several factors are important for this success today and in the future：a program for advance calculation of gas emissions developed on the basis of practical experience，modern gas drainage and monitoring technology，supporting and sealing off the seam edge areas using innovative construction material machinery-and last but not least，a carefully trained and experienced mining team．
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摘要 :
The paper presents potential increased afterburst hazard in the case of working in the seams prone to afterbursts．Chosen airing systems of longitudinal longwalls pplied in the afterburst hazard conditions were also discussed．Sub...
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The paper presents potential increased afterburst hazard in the case of working in the seams prone to afterbursts．Chosen airing systems of longitudinal longwalls pplied in the afterburst hazard conditions were also discussed．Substitute airing systems-their potential and range of use aiming at limiting insufficiently aired zones，which can result from afterbursts，were pointed out．
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摘要 :
The effective management of longwall goaf gas emission，spontaneous heating and goal inertisation is paramount to the sustained productivity and safety of underground coal mines．Understanding of the airflow and gas characteristic...
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The effective management of longwall goaf gas emission，spontaneous heating and goal inertisation is paramount to the sustained productivity and safety of underground coal mines．Understanding of the airflow and gas characteristics helps the development of innovative strategies for gas capture and the suppression of self-heating hazards behind the face．CSIRO has been engaged in the investigation of gas flow migration dynamics within longwall goaf areas with the objective of improving gas capture，minimising the risk of spontaneous combustion and developing effective goaf inertisation strategies．Three dimensional Computational Fluid Dynamics(CFD)models have been developed to study the goaf gas dynamics under the influence of various mining and geological parameters including ventilation layouts，face orientation and gas emission rates．The simulation results provide new insights into the fundamental process of gas flow motion taking place within the goaf as well as the subsequent impact of goaf gas drainage and inert gas injection for goal inertisation．In combination with field work，this approach not only helps the design of innovative gas management strategies but also the implementation of optimum goaf inertisation strategies for both seal-off and active longwall panels．
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摘要 :
Current research and development on mine methane mitigation and utilisation focuses on methane emitted from underground coal mines，in particular ventilation air methane (VAM)．This is because (1) it represents most of the methane...
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Current research and development on mine methane mitigation and utilisation focuses on methane emitted from underground coal mines，in particular ventilation air methane (VAM)．This is because (1) it represents most of the methane emitted from coal mines;and (2) it is most difficult to capture and use，as the air volume is large and the methane resource is dilute and variable in both concentration and flow rate．It is estimated in China that over 70﹪ of the drainage gas has a methane concentration of less than 30﹪，and this should be targeted for the mitigation and utilisation as well．VAMmitigation/utilisationrequireseither treatmentinits dilutestate，or concentration up to levels that can be used in conventional gas fuelled engines．This paper reviews most of the existing and developing VAM technologies,and discusses potential technical issues for their applications at mine sites．Then，based on fundamental thermodynamic laws the paper analyses methods for the concentration and oxidisation of methane in mine ventilation air to gain insight into the effect of methane concentration．They are simplified as far as possible to allow conclusions to be drawn as to the limits of what is possible with ventilation air methane．The analytic results are summarised to provide a guide on thermodynamic limitations for each technical process．
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摘要 :
Reliable mine gas prediction is not only essential for effective gas drainage and control，improvement of mining safety and reduction of coal production costs，but also important to mine gas production assessment for gas utilisati...
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Reliable mine gas prediction is not only essential for effective gas drainage and control，improvement of mining safety and reduction of coal production costs，but also important to mine gas production assessment for gas utilisation evaluation and planning．An integrated mine gas simulation system has been developed to predict strata conditions and methane gas emission during longwall mining．The system is used to assist selection and planning of suitable mining，gas management and utilisation strategies for new and existing mines．Several key mine gas assessment processes，such as mine site gas and geotechnical characterisation,and fully coupled mechanical deformation-fluid flow computer simulation，have been integrated in the simulation system．Gas flow during mining is controlled by in situ gas content and geotechnical conditions，as well as the mining induced changes in the strata such as those of stress，fracture，pore pressure and permeability.The central part of the integrated simulation system is the new 3D code called COSFLOW that simulates the complex behaviour of rock，water and gas flow，and predicts gas emission during longwall development and retreat．The code is also capable of simulating gas drainage performance and estimating gas production．This system was developed from a recently completed collaborative project entitled “Predevelopment Studies for Mine Methane Management and Utilisation”，between the New Energy and Industrial Technology Development Organization (NEDO) of Japan，the Japan Coal Energy Center (JCOAL)，and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) of Australia．The integrated simulation approach is described in this paper and examples of mine site application are presented．
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摘要 :
Gas emissions and problems in the Australian coal mines have lncreased significantly in recent years as mines reach greater depths and increase longwall production levels and panel sizes.Traditionally，the main objective of gas dr...
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Gas emissions and problems in the Australian coal mines have lncreased significantly in recent years as mines reach greater depths and increase longwall production levels and panel sizes.Traditionally，the main objective of gas drainage operations was to meet the safety requirements of the underground coal mines with respect to outburst and frictional ignition.However，with the recent focus on reducing greenhouse gas(GHG) emissions from the mining industry，gas drainage and improved gas capture has become one of the critical GHG mitigation strategies．It was identified that the wider application of gas drainage as a mitigation strategy depends on achieving drainage costs that are less than the combined value of the associated safety，greenhouse and gas revenue benefits．The technique of surface-to-inseam drainage (SIS) also known as Medium Radius Drilling (MRD) technology is gaining acceptance in the coal mining industry as an acceptable means of pre draining virgin underground areas prior to mining operations，although the design and application of the MRD technology is still being developed based on our ever increasing knowledge of coal seam gas behaviour．MRD techniques offer the most promising alternative to Conventional Inseam drilling or‘CIS’drilling．Numerous improvements in drilling techniques have allowed MRD drilling to become more productive and cost effective not the least of which is the management of bottom hole pressures during drilling operations．The control of pressure has improved drilling rates and minimised near surface damage to coal seams which is known to effect drainage performance．Studies by CSIRO have identified the major parameters effecting MRD performance as a result of a two year ACARP funded study into MRD techniques．These parameters are outlined in the following paper．
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Methane (CH4) forms a significant component of coal seam gas and is extracted as a preventative measure before or during the mining of coal，as well as for a resource in its own right．As part of a major collaborative project with...
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Methane (CH4) forms a significant component of coal seam gas and is extracted as a preventative measure before or during the mining of coal，as well as for a resource in its own right．As part of a major collaborative project with the aim of extracting gasses for low-emission energy from deep or otherwise difficult seams，an explicit fracture computer model of coal seam methane extraction is being developed．The aim of the model is to assist and verify the continuous models in predicting the rate of coal gas extraction by simulating the deformation of coal and the flow of gas through fractures and natural joints．Initial studies to investigate the influence on computer run times of fluid and material properties and the ratio of mechanical to fluid cycles in the computer program are presented．The paper then presents initial results from a multi-seam model of coal．Results indicate that extraction of methane into a borehole changes the local pore pressure distribution leading to shrinkage of the coal while injection of fluid into a borehole inhibits this deformation．With two coal seams separated by five metres，the modelling results indicate that methane extraction is enhanced if fluid is injected into the borehole in the adjacent seam in comparison with the case of extracting gas from both holes simultaneously.These results，while still preliminary，offer the potential to optimise the extraction of coal seam gas by developing optimal staged injection and extraction scenarios．
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