Dr Jafar Zanganeh

There has been a surge of interest from the extractive industries in the application of mechanical means to the mitigation of flame deflagration. To verify the implementation and performance of passive and active mitigation protection, a comprehensive experimental investigation has been conducted on a large scale detonation tube, 30¿m long and 0.5¿m in diameter, with two mitigation valves (passive and active) and a burst panel venting system. The valves were used alternately to mitigate the flame deflagration of methane in concentrations ranging from 1.25% to 7.5%. The experimental work revealed that locating the passive mitigation valve at 22¿m distance from the ignition source mitigates the flame by fully isolating the tube. However, closing the valve structure in the axial direction generated another pressure wave upstream, which was approximately the same value as for the original pressure wave upstream. In the case of the active mitigation system, the system perfectly isolated upstream from downstream with no further pressure wave generation. When the vent was located at 6.5¿m from the ignition source, the total pressure was reduced by 0.48¿bar. Due to the counter flow of the reflected pressure wave the flame was extinguished at 12.5¿m from the ignition source.

This paper is concerned about a detailed techno-economic assessment of a hypothetical 500 MWe coal-fired power plant in New South Wales, Australia, for oxy-fuel conversion using integrated chemical looping air separation (ICLAS) technology and cryogenic air separation unit (CASU). The key objectives of this study are to (i) investigate and compare the detailed integration options for oxy-fuel conversion using ICLAS and CASU and (ii) determine the technical merits of the above integration options and the conditions at which the technologies become economically feasible. The study produced scientific evidence that confirms the viability of the CLAS process from both technical and economic points of view under certain conditions. The detailed technical analysis revealed that ICLAS with natural gas integration is energy-efficient compared to CASU running on parasitic load. This is primarily due to the fact that ICLAS needs less auxiliary power compared to CASU. Despite the fact that ICLAS natural gas integration has resulted in higher efficiencies than CASU running on parasitic load, from a series of detailed economic analyses, it was observed that both ICLAS and CASU may not be viable under the present operating and economic conditions. Nevertheless, from sensitivity analysis, it was concluded that ICLAS can become feasible if economic conditions are improved, e.g., a low natural gas market price (<$3.5/GJ), a high electricity wholesale price (>$59/MWh), and/or a high carbon tax (>$33/tonne).

The fires and explosions caused by flammable hydrocarbon air mixtures are a major safety concern in the chemical and processing industries. The thermo-physical and chemical properties of the flammable fuels in a hybrid form appear to have a significant impact on the combustion process. This usually occurs due to substantial changes in the flammability concentration regimes. The aim of this study is to investigate the fire and explosive properties of hybrid fuels in the chemical and process industries. In addition, it examines the impact of the ignition energy and vessel geometry on the magnitude of the pressure rise and flame propagation velocity. The experimental work was conducted on a cylindrically shaped explosion chamber constructed as part of this study at The University of Newcastle, Australia. The chamber was made of mild steel and was 30 m in length and 0.5 in diameter. It included a series of high resolution pressure transducers, a pyrometer, as well as a high speed video camera. Methane and coal dust were used as fuels and chemical igniters with a known energy were used to ignite the fuels.The results obtained from this study showed that both the ignition energy and the diluted combustible fuel dust have significant impacts on the Over Pressure Rise (OPR) in an explosion chamber. The significant findings included that the OPR doubled when 30 g m-3 of coal dust was added to a 6% methane/air mixture, and it increased by 60% when 10 kJ was used instead of a 1 kJ ignition source. The initial ignition energy was observed to considerably enhance the speed of both the pressure wave and the flame front, where the pressure wave speed doubled when using a 5 kJ instead of a 1 kJ ignition source. However, the pressure wave speed increased by five times when a 10 kJ was used instead of a 1 kJ ignition source. Additionally, the maximum flame front velocity observed for the ignition source with 5 kJ energy was twice the flame front velocity for the 1 kJ ignition source. Finally, it was observed that the time needed for the initial methane ignition was reduced by about 50% when using a 10 kJ instead of a 1 kJ ignition source.

Ventilation Air Methane (VAM) abatement technology is recognized as a promising and value adding technique for reducing fugitive methane emissions, however, it also increases the potential fire and explosion risks of overheated coal dust. To eliminate these risks from the abatement systems it is necessary to determine the critical combustion characteristics of the minimum auto ignition temperature (MAIT) for a coal dust layer. This study investigates the auto-ignition behavior of coal dust layers in a humid environment with Relative Humidity (RH) >80%. The MAIT of four different coal dust samples (Australian coal) with particle sizes below 212 µm and dust layer thicknesses of 5, 12 and 15 mm were measured using a dust layer auto ignition temperature apparatus in accordance with the ASTM E2021 standard. It was concluded that the MAIT of the coal dust layer significantly decreases with decreasing particle size. The MAIT for the coal samples with a smaller D50 size were observed to be lower in comparison with samples with a larger D50 size. The dust layer thickness was shown to significantly impact on the MAIT. The MAIT increased proportionally with the increasing thickness of the coal dust layer. The effect of the coal dust moisture content and humidity on the MAIT for compacted dust layers was noticeable, whereas, this effect was less important with loose dust layers. In addition, this work investigated and compared the MAIT for a typical coal dust sample based on the existing ASTM and International Electrotechnical Commission (IEC) standard procedures for ignition of coal dust layers.

This article presents a numerical study of the explosive wave propagations from a 40¿cm long and 10.8¿cm diameter cylinder to smaller 1.7¿m and 2.6¿m long cylinders with 36¿mm diameters. Initially, the 40¿cm long cylinder was filled with 4% propane-air mixtures and ignited with a 1¿kJ sparking energy until the maximum temperature near the ignition source reached 2400/3000¿K. In the study, a 3D numerical model was established by combining compressible four-step reduced propane oxidation reaction kinetics with the k-¿ shear-stress transport (SST) turbulent model. In order to resolve the thin detonation wave front, a dynamically refined mesh near the high pressure gradient was adopted. The pressure gradient profiles, velocity magnitude contours, temperature contours and compressible wave propagation speeds across the tubes were then predicted using this 3D model.

Present study aims to examine the dynamics of maturation and qualification indicators in various vermicompost treatments and selection of the best treatment along with best maturation time in this regard. In this empirical study, dynamics of chemical (pH, electrical conductivity (EC), total nitrogen (TN), phosphorous, lignin, water soluble carbon (WSC), C/N, NH4/NO3) and biological (dehydrogenase enzyme (DEH) and DEH/WSC) properties were investigated in four various treatments, including various ratios of compost produced from municipal solid waste (MSW) and carbonaceous materials (50:50, 70:30, 85:15 and 100:0) over 100 days. Results showed a significant fluctuation in EC, DEH and DEH/WSC proportions over the process. In addition, a noticeable increase was observed for the dynamics of TN, phosphorous and lignin. In contrast, the C/N, NH4/NO3 and WSC values gradually decreased during the process. Moreover, it was observed that the length of 75 days for the process is an appropriate time for maturation of all treatments. However, the first and second treatments resulted in better outcomes compared with the other types of treatments. From the point of view of quality obtained vermicompost was nitrogen enriched product in all treatments. Whereas, for the phosphorous elements this method is appropriate for the first treatment only.

This review examines existing knowledge on the genesis and flame acceleration of explosions from methane-air mixtures. Explosion phases including deflagration and detonation and the transition from deflagration to detonation have been discussed. The influence of various obstacles and geometries on explosions in an underground mine and duct have been examined. The discussion, presented here, leads the readers to understand the considerations which must be accounted for in order to obviate and/or mitigate any accidental explosion originating from methane-air systems.

This paper conducts a numerical study of detonation wave propagations in 30 m and 73 m long straight/varying angle bending detonation tubes with inner diameters of 0.5 m and 1.05 m, respectively, which are filled with varying stoichiometric methane-air mixtures. In the study a 3D numerical model was established by combining a compressible one-step global reaction hot model with the k-¿ shear-stress transport (SST) turbulent model. In order to resolve the thin detonation wave front, a dynamically refined mesh near the high pressure gradient is adopted. The initial conditions of the model are obtained from the 1D detonation model. The present model was first verified by comparing the numerical results against the published measurements. The pressure distributions and detonation wave speeds across the tubes and bends were then predicted by using this 3D model.

Deflagration explosions of coal dust clouds and flammable gases are a major safety concern in coal mining industry. Accidental fire and explosion caused by coal dust cloud can impose substantial losses and damages to people and properties in underground coal mines. Hybrid mixtures of methane and coal dust have the potential to reduce the minimum activation energy of a combustion reaction. In this study the Minimum Explosion Concentration (MEC), Over Pressure Rise (OPR), deflagration index for gas and dust hybrid mixtures (Kst) and explosive region of hybrid fuel mixtures present in Ventilation Air Methane (VAM) were investigated. Experiments were carried out according to the ASTM E1226-12 guideline utilising a 20 L spherical shape apparatus specifically designed for this purpose. Results: obtained from this study have shown that the presence of methane significantly affects explosion characteristics of coal dust clouds. Dilute concentrations of methane, 0.75-1.25%, resulted in coal dust clouds OPR increasing from 0.3 bar to 2.2 bar and boosting the Kst value from 10 bar m s-1 to 25 bar m s-1. The explosion characteristics were also affected by the ignitors' energy; for instance, for a coal dust cloud concentration of 50 g m-3 the OPR recorded was 0.09 bar when a 1 kJ chemical ignitor was used, while, 0.75 bar (OPR) was recorded when a 10 kJ chemical ignitor was used.For the first time, new explosion regions were identified for diluted methane-coal dust cloud mixtures when using 1, 5 and 10 kJ ignitors. Finally, the Le-Chatelier mixing rule was modified to predict the lower explosion limit of methane-coal dust cloud hybrid mixtures considering the energy of the ignitors.

This experimental study was conducted to investigate the rate of flame spread over an inclined porous solid (sand) wetted with finite quantities of fuel (iso-propanol). The study comprised experiments that were conducted over 15° and 30° inclined beds with depths ranging from 13.3 mm to 39.9 mm and consisting of average sand particle diameters ranging from 0.5 mm to 5 mm under quiescent, assisted and opposed airflow conditions. Analysis of the resulting data indicate that the rate of flame spread is significantly decreased by increasing the bed inclination angle or the airflow velocity and is applicable for both assisted and opposed directions. Furthermore, the rate of flame spread is decreased to the minimum value and actually ceased halfway along the bed with a 30° inclination angle. This behaviour was observed mainly for beds containing coarse sand particles. The rate of flame spread was higher for thinner beds rather coarse beds under any given airflow conditions. Finally, the rate of flame spread in upward direction was relatively quicker in comparison with downward direction counterpart. © 2014 Elsevier Ltd. All rights reserved.

Fires caused by accidental spillage of flammable liquids have been a major safety concern in industries and urban areas. There has been a recent surge of interest in the research concerning the combustion and flame spread over an inert porous media soaked with flammable liquid. This interest has been driven by the need to better understand fire and its behaviour under these conditions and improve the relevant fire safety and prevention technologies. A review of key studies in this subject area has been conducted and summarised, focussing mainly on the theory plus a notable experimental findings about combustion and the flame spread phenomena of fuel-soaked porous media. The review covers topics such as flame spread behaviour, physical flame propagation aspects, heat transfer, temperature distribution; and fuel consumption over inert porous media. The review concludes with some practical safety and environmental considerations for decontamination of land soaked with flammable liquid. © 2013 Elsevier Ltd. All rights reserved.

An experimental investigation was conducted to explore the rate of flame spread over an unconsolidated porous bed of sand wetted with 2-propanol under a range of operating conditions. Video cinematography was employed to determine the rate of flame spread and characterise the combustion behaviour of the system. The rate of flame spread strongly correlated with: (i) the ratio of fuel volume to the weight of the sand bed, referred to as FR, and (ii) the flame initiation delay, referred to as FID. The rates of flame spread associated with no initiation delay cases were found to rise with increasing FR while for cases associated with any given flame initiation delay the rate of flame spread was found to decrease with increasing FR. In addition, the rate of change in flame spread was observed to be different for beds containing finer particles in comparison to those containing coarser ones. © 2013 Elsevier Ltd.