Summary
Flash fires and explosions in areas containing an enriched combustible dust atmosphere are a major safety concern in industrial processing. An experimental study was conducted to analyse the ...effects of atmospheric coal dust particle sizes and concentrations on the minimum auto‐ignition temperature (MAIT) of a dust cloud. Two different coal samples from Australian coal mines were used. The coal dust particles were prepared and sized in 3 ranges, of below 74 μm, 74 to 125 μm and 125 to 212 μm, by using a series of sieves and a sieve shaker. A humidifier was used to increase the moisture content of the particles to the required level. All the experiments were conducted in accordance with the ASTM E1491‐06 method in a calibrated Goldbert‐Greenwald furnace.
The results from this study indicate that coal dust properties, such as the chemical nature (H/C), concentration, particle size (D50), and moisture content, impact on the MAIT. For coal dust concentrations less than 1000 g.m−3, the MAIT decreases with increasing coal dust concentrations. On the other hand, for low concentrations of 100 to 15 g.m−3, the MAIT becomes more reliable for particle size D50 rather than for volatile matters.
This paper describes the development of a novel stone dust looping process that relates to the removal of ventilation air methane using stone dust. The working principle behind the stone dust looping ...process is incredibly simple which involves the catalytic oxidation of methane followed by carbonation and calcination reactions. In the current work, laboratory scale fluidized bed experiments and process simulations were conducted to evaluate the feasibility of the stone dust looping process. The experimental work concluded that oxidation of ventilation air methane in the stone dust looping process can be successfully achieved at temperatures between 500 and 650°C. The experimental results indicated that oxidation of methane was found to increase at higher temperatures while carbon dioxide capture efficiency showed a declining trend with increasing temperature. Furthermore, higher methane conversion and optimum (thermodynamic) carbon dioxide capture efficiency were observed for lower ventilation air methane flow rates and higher bed inventory. The concentration of methane in ventilation air methane and stone dust particle size did not have a significant effect on methane conversion or carbon dioxide capture. Also, comparison with synthetically prepared CuO and Fe2O3 catalysts has been made with CaO for VAM oxidation. CaO was found to be comparable to Fe2O3 and superior to CuO. From the process simulations, it was concluded that thermal energy generation in the carbonator was increased with higher methane and carbon dioxide concentrations. However, at the same time for higher methane and carbon dioxide concentrations, a greater CaO flux was required in the carbonator and hence a larger amount of goaf gas was required for the calcination reaction. The higher thermal energy generation in the carbonator was expected to improve the autothermicity of the stone dust looping process at concentrations of methane in the ventilation stream <0.2 vol.% (thermodynamic limit).
•The paper discusses the development of a stone dust looping process.•Fluidized bed experiments and process simulations were performed.•Effect of process parameters on conversion and energy generation has been studied.•It has been found that methane oxidation can occur at 500–650°C.•The self-sustainability limit is found to be less than 0.2 vol.% of methane.
Fugitive methane emissions from the mining industry, particularly so-called ventilation air methane (VAM) emissions, are considered among the largest sources of greenhouse gas (GHG) emissions. VAM ...emissions not only contribute to the global warming but also pose a significant hazard to mining safety due to the risk of accidental fires and explosions. This research presents a novel approach that investigates the capture of CH4 in a controlled environment using 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide BMIMTF2N ionic liquid (IL), which is an environmentally friendly solvent. The experimental and modelling results confirm that CH4 absorption in BMIMTF2N, in a packed column, can be a promising technique for capturing CH4 from point sources, particularly the outlet streams of ventilation shafts in underground coal mines, which typically accounts for <1% v/v of the flow. This study assessed the effectiveness of CH4 removal in a packed bed column by testing various factors such as absorption temperature, liquid and gas flow rates, flow pattern, packing size, desorption temperature, and desorption pressure. According to the optimisation results, the following parameters can be used to achieve a CH4 removal efficiency of 23.8%: a gas flow rate of 0.1 L/min, a liquid flow rate of 0.5 L/min, a packing diameter of 6 mm, and absorption and desorption temperatures of 303 K and 403.15 K, respectively. Additionally, the experimental results indicated that ILs could concentrate CH4 in the simulated VAM stream by approximately 4 fold. It is important to note that the efficiency of CH4 removal was determined to be 3.5-fold higher compared to that of N2. Consequently, even though the VAM stream primarily contains N2, the IL used in the same stream shows a notably superior capacity for removing CH4 compared to N2. Furthermore, CH4 absorption with BMIMTF2N is based on physical interactions, leading to reduced energy requirements for regeneration. These findings validate the method’s effectiveness in mitigating CH4 emissions within the mining sector and enabling the concentration of VAM through a secure and energy-efficient procedure.
Ventilation air methane is low concentration methane (below 1 vol. %) emitted from an underground coal mine. High ventilation air volumes circulated through the mine, ensure that the methane remains ...at a safe concentration. In 2016, the Australian Government reported fugitive emissions of methane from underground coal mines at approximately 19.0 million tonnes (CO
2
-equivalent) which was about 4.0% of Australia's national greenhouse gas emissions. Therefore, an optimised process of heat recovery from a fluidised-bed VAM abatement reactor, to produce power and cooling was studied. For a ventilation flow rate of 20 m
3
/s, the minimum methane concentration for a direct gas turbine was 0.45 vol. % at a reactor temperature of 630°C and compressor pressure of 1.5 bar. An indirect gas turbine process operated with a minimum methane concentration was 0.4 vol. % at a reactor temperature of 630°C, compressor pressure of 4.0 bar and turbine flow rate of 2.2 kg/s.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•The pyrolysis behaviors of coconut shells up to 700°C were systemically investigated.•The effect of pyrolysis temperature on the grindability of coconut shell chars was revealed.•The separation ...factor of CH4/N2 of the coconut shell-based carbon adsorbent is 6.18.•The VAM consisted of 0.42% CH4 was enriched to 1.09% by VPSA with the carbon adsorbent.
Coconut shell-based carbon adsorbents were prepared and applied to vacuum pressure swing adsorption (VPSA) process for ventilation air methane (VAM) enrichment. The preparation procedure consists simply of pulverization of the coconut shell chars, pelletization with phenolic resin as binder, and carbonization of the pellets under N2 flow. The pyrolysis characteristics of coconut shells, including the composition of gas products at different pyrolysis temperature interval, the porous characteristics, the proximate and ultimate analyses, the surface functional groups, and the grindability of the chars from varied pyrolysis temperature, were systematically investigated. So that the reasonable pyrolysis temperature for coconut shell chars production was determined. The ratio of phenolic resin to char powder was optimized in regarding of the compressive strength, packing density, textural characteristics, and CH4/N2 separation factor of the carbon adsorbents. The performance of the carbon adsorbent prepared under optimum condition for VAM enrichment by VPSA was examined, and it merits the need for flow-reversal reactor or lean-burn combustion turbine to generate power.
Between 1997 and 2016 we observed important changes in hard coal extraction and methane emission in the Upper Silesian Coal Basin. Hard coal extraction in the near future will be very dangerous ...because it will be necessary to reach deeper methane-rich coal seams. Permanent monitoring of the volume of emitted and captured methane is necessary to combat the methane hazard. The predictability of gaseous hazards are important in order to keep underground work safe. We gathered and analysed data from three coal companies: Katowice Coal Holding, the Coal Company, Jastrzębie Coal Company and in the whole of the Upper Silesian Coal Basin for the last twenty years and this allowed us to notice changes and CH
trends in ventilation emission and demethanation. There is a decrease in the extraction of hard coal from year to year. At the same time there is an increase in the total methane emissions which forces actions aimed to effective contracting the methane hazard. Specifically, methane emission has been increasing for years, making hard coal extraction very dangerous. We observed increases in CH
vent emission and volume of methane coming from underground drainage systems. Much more methane is released during hard coal extraction at deeper mine levels. Throughout the entire research period the methane hazard increased. Therefore, the development of modern technologies for methane capturing should contribute to improvement of hazardous conditions for coal mining in the basin.
Ventilation Air Methane (VAM) refers to the release of fugitive methane (CH4) emissions into the atmosphere during underground coal mining operations. Growing concerns regarding the greenhouse ...effects of CH4 have led to a worldwide effort in developing efficient and cost-effective methods of capturing CH4. Among these, absorption-based processes, particularly those using Ionic Liquids (ILs) are appealing due to their advantages over conventional methods. In this study, the solubility of CH4 in various ILs, expressed by Henry’s law constant, is first reviewed by examining a wide range of experimental techniques. This is followed by a review of thermodynamic modelling tools such as the extended Henry’s law model, extended Pitzer’s model, Peng–Robinson (PR) equation of state, and Krichevsky−Kasarnovsky (KK) equation of state as well as computational (Artificial Neural Network) modelling approaches. The comprehensive analysis presented in this paper aims to provide a deeper understanding of the factors that significantly influence the process of interest. Furthermore, the study provides a critical examination of recent advancements and innovations in CH4 capture by ILs. ILs, in general, have a higher selectivity for methane compared to conventional solvents. This means that ILs can remove methane more effectively from VAM, resulting in a higher purity of the recovered methane. Overall, ILs offer several advantages over conventional solvents for the after treatment of VAM. They are more selective, less volatile, have a wider temperature range, are chemically stable, and can be made from renewable materials. As a result of their many advantages, ILs are becoming increasingly popular for the after treatment of VAM. They offer a more sustainable, efficient, and safe alternative to conventional solvents, and they are likely to continue gaining market share in the coming years.
In a catalytic combustion of ventilation air methane, one of the key factors determining the reactor performance is the geometry of the reactor. It should be designed to provide maximum energy ...conversion at minimum catalyst usage and operating cost. This numerical study is conducted to investigate the catalytic combustion of ventilation air methane from a gassy underground mine in a circular straight and helical reactor channel with twisted tape insert. A three-dimensional computational fluid dynamics model which considers conservation of mass, momentum, energy, and species together with chemical reactions, and constitutive relations for species properties and reactions kinetics was developed and validated against the previously published data. The effect of several key factors affecting the catalytic combustion performance such as inlet Reynolds number, twisted tape ratio, and reactor length are evaluated to obtain the optimum reactor parameters. For evaluation purpose, the reaction performance of the studied reactors will be compared to the straight reactor without twisted tape which is set as a baseline. The results give a firm confirmation on the superior performance of the reactors with twisted tape insert as compared to those without. In addition, it is found that helical reactors generate higher net power as compared to their respective straight reactor counterpart despite having lower FoM due to larger catalyst area. Interestingly, the higher twisting ratio offers better performance in terms of net power as well as FoM. Overall, the results highlight the potential of twisted tape insert application in catalytic combustion.
•Dynamic modelling using heterogeneous one-dimensional models.•Design and simulation of regenerative thermal oxidizer and heat storage system.•Feedback control determines the heat ...extracted/introduced in the oxidizer.•Demonstration for a real coal mine ventilation air emission.
Regenerative oxidizers are very useful for combustion of methane–air lean mixtures (<1vol.% and as low as 0.15%), as those generated in coal mines (ventilation air methane, VAM). However, the performance of the oxidizer is unstable, leading to overheating or extinction, when methane concentration varies. We propose a new procedure for overcoming this problem, using the heat storage concept. Thus, this issue is addressed by proposing the use of an external sensible heat storage system, added to the regenerative oxidizer, capable of storing the excess of heat released in the oxidizer during rich concentration periods, and using it to heat the feed as needed during lean concentration periods. The performance of the heat storage system has been studied by simulating the behaviour of a regenerative thermal oxidizer designed to operate at 0.25vol.% nominal feed methane concentration. It was found that the regenerative oxidizer, provided with the heat storage system together with a feedback controller that regulates the heat extracted/introduced in the oxidizers can operate satisfactory, dealing with the variations in methane concentration found in ventilations of coal mines.
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