Sazal K Kundu | RMIT University (original) (raw)

Papers by Sazal K Kundu

Research paper thumbnail of Explosion characteristics of methane–air mixtures in a spherical vessel connected with a duct

With the aim of exploring explosion characteristics of methane–air explosive mixtures in a ducted... more With the aim of exploring explosion characteristics of methane–air explosive mixtures in a ducted vessel, a 20 l spherical vessel connected with a 2813 mm long duct was employed. The experimental setup was comprised of a wafer check valve, which kept the methane–air mixture initially confined and opened at the time of explosion. The system introduced turbulence to the gas mixture during operation and pyrotechnic igniters were employed in the investigation. This approach assisted to obtain data that can be correlated with real world ducted explosion accidents where the explosion initiates in the presence of strong ignition energies and in turbulent states of methane–air mixtures. This study shows that the explosion severity can be very high in the turbulent field of methane–air mixture and in the presence of strong ignition energies. The pressure rise in the vessel and the flame speed along the length of the duct were found to be higher in the present study when compared to data obtained with quiescent methane–air mixtures and low ignition energies. The impact of the duct length and pyrotechnic igniters’ energy on reduced peak explosion pressure was characterised. The rate of pressure rise, a parameter linked to the burning rate, increased from the ducted to the vented configurations of the explosion test units.

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Research paper thumbnail of Reaction of dichloromethane under non-oxidative conditions in a dielectric barrier discharge reactor and characterisation of the resultant polymer

This paper presents the results of dichloromethane (DCM) decomposition to polymers utilising diel... more This paper presents the results of dichloromethane (DCM) decomposition to polymers utilising dielectric barrier discharge under non-oxidative reaction conditions. The conversion levels, mass balance, reaction mechanism and polymer characterisation in relation to DCM reaction are presented in this paper. Reaction pathways describing the decomposition of DCM and subsequent formation of the major products are outlined. Speculation of the mechanism of formation of CHCl3 and C2HCl3 are supported by quantum chemical calculations. In addition, the effect of introducing methane in the reaction feed on the conversion level of DCM and the polymer structure is also examined in this paper.

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Research paper thumbnail of Investigations into Physicochemical Changes in Thermal Coals during Low-Temperature Ionic Liquid Treatment

Two Australian thermal coals were treated with four different ionic liquids (ILs) at temperatures... more Two Australian thermal coals were treated with four different ionic liquids (ILs) at temperatures as low as 100 °C. The ILs used were 1-butylpyridinium chloride ([Bpyd][Cl]), 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCM]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), and 1-butyl-3-methylimidazolium tricyanomethanide ([Bmim][TCM]). Visual comparisons were made between the raw and IL-treated coals via optical microscopy. Changes in thermal behavior of these treated coals were compared against raw coals via pyrolysis experiments in a thermogravimetric analyzer (TGA). Changes in functional group composition in the treated coals were probed via Fourier transform infrared (FTIR) spectroscopy. The recovered ILs were also analyzed via FTIR and nuclear magnetic resonance (NMR) spectroscopies to observe any changes after recovery. Low-temperature IL treatment of each of the coals resulted in fragmentation and fracturing, reducing the average particle size. An increase in mass loss in the treated coals was also observed when compared to each raw coal, indicating an increase in lower molecular weight fragments after treatment. This was corroborated by a large increase in aliphatic hydrocarbons being observed in the treated coals, along with a decrease in oxygenated functional groups and mineral matter in one coal. The recovered ILs were shown to be unchanged by this treatment process, indicating their potential recyclability. These results indicate the potential for ILs to be implemented as solvent treatments for coal conversion processes.

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Research paper thumbnail of Modification of lignites via low temperature ionic liquid treatment

Two lignite samples (150–212 μm) were treated with four ionic liquids (ILs); 1-butylpyridinium ch... more Two lignite samples (150–212 μm) were treated with four ionic liquids (ILs); 1-butylpyridinium chloride ([Bpyd][Cl]), 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCA]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) and 1-butyl-3-methylimidazolium tricyanomethanide ([Bmim][TCM]) at 100 °C for 3 h to establish the utility of ILs for lignite pre-treatment in conversion processes. ILs are room temperature molten salts that have remarkable physical and chemical properties including high thermal and electrochemical stabilities, low vapour pressures and, critically for this work, the capacity to solubilise a diverse range of materials. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and optical microscopy were employed in this study to gain insight into the physical and chemical interactions occurring between lignite and ILs at low temperatures. The FTIR results indicate that the majority of the ILs employed were able to break apart the macro-structure of coal resulting in an increase in short chain aliphatic hydrocarbons. Additionally, FTIR analysis revealed a significant decrease in the presence of COOH and CO groups for lignites treated with [Emim][DCM]. The TGA data revealed that the IL treated lignites had significantly lower devolatilisation temperatures than the untreated lignite, indicating an increase in lower molecular weight species after treatment. Microscopy showed a sizeable decrease in particle size after IL treatment due to fragmentation, and these coals appeared to be considerably swollen. Analysis of the recovered ILs showed no denaturing after the treatment process, indicating their recyclability potential in the treatment process.

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Research paper thumbnail of Effect of Methane and coal dust Concentrations on Explosion Pressure Rise

Australian Combustion Symposium, 2015

Explosion pressure rate rise (dp/dt) experiments for coal dust and methane-coal dust-air hybrid m... more Explosion pressure rate rise (dp/dt) experiments for coal dust and methane-coal dust-air hybrid mixtures in a modified 20 L explosion apparatus were conducted to provide data on explosion characteristics in Ventilation Air Methane (VAM) systems. Coal dust concentrations of 10, 25, 50 and 100 g.m-3; methane concentrations of 0.75, 1.25, 2.5 and 5%; and initial igniter energies of 1, 5 and 10 kJ were investigated. The dp/dt of dilute coal dust-methane-air hybrid mixtures were strongly affected by the igniter energy. The potential of higher energy boosting the fuel combustion from the flammable to the explosion phase was demonstrated. There was no observed influence on dp/dt at 10 g.m-3 coal dust concentration. In contrast, 25 g.m-3 of coal dust concentration had significant influence on the dp/dt for methane-coal dust-air hybrid mixtures.

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Research paper thumbnail of Pyrolysis characteristics of ionic liquid and solvent treated coals

Australian Combustion Symposium, 2015

Two coals, one lignite and one sub-bituminous, were treated at low temperatures with four differe... more Two coals, one lignite and one sub-bituminous, were treated at low temperatures with four different ionic liquids (ILs), 1-butylpyridinium chloride [Bpyd][Cl], 1-ethyl-3-methylimidazolium dicyanamide [Emim][DCA], 1-butyl-3-methylimidazolium chloride [Bmim][Cl] and 1-butyl-3-methylimidazolium tricyanomethanide [Bmim][TCM]. These IL treated coals were then washed with n-methyl-2-pyrrolidone (NMP). The pyrolysis characteristics of the treated coals were probed via thermogravimetric analysis (TGA) with the aim of investigating the differences among the raw coal, the IL treated coal and the IL & NMP treated coals. After low temperature IL treatment, all coal samples lost more mass during pyrolysis in comparison to the raw coal. This indicated that IL treatment had broken the macrostructure of the coal apart; resulting in an increase in the volatilization of lower molecular weight species during pyrolysis. The pyrolysis characteristics of the IL & NMP treated coals, saw some samples, specifically those treated by [Bpyd][Cl] lose less mass after NMP treatment, indicating that the lower molecular weight species may have been extracted by the NMP treatment. Other samples showed little to no difference after NMP treatment, and in the case of coal P treated [Emim][DCM], an increase in mass loss was observed after NMP treatment. The observed differences in pyrolysis characteristics appeared to be coal and IL specific, with [Bpyd][Cl] appearing to be the most effective in liberating lower molecular weight species to be extracted by NMP. These results are promising for utilising lower grade coals as feedstocks for valuable chemicals and tars, and producing coals with less volatile matter and a higher carbon content.

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Research paper thumbnail of Pre-treatment of thermal and lignite coals with ionic liquids

International Conference on Coal Science & Technology, 2015

Ionic liquids are room temperature molten salts that have remarkable physical and chemical proper... more Ionic liquids are room temperature molten salts that have remarkable physical and chemical properties including high thermal and electrochemical stabilities, vanishingly low vapour pressures and, critically for this work, the capacity to solubilize a diverse range of materials. The interactions of four ionic liquids with four coal samples (2 thermal and 2 lignite) at 100°C has been probed to establish the utility of ionic liquids for coal pre-treatment in coal conversion processes. Fourier Transform Infrared Spectroscopy (FTIR) and Optical Microscopy were employed in this study to understand the physicochemical interactions between coal and ionic liquids at low temperatures. The FTIR results indicate that the majority of the ionic liquids employed were able to break apart the macro-structure of coal resulting in an increase in short chain aliphatic hydrocarbons. It was also observed that the treated coals were highly fragmented and had a lower average particle size, with the lignite coals appearing to be significantly swollen after IL treatment. The changes in coal morphology and composition following treatment with the ionic liquids, varied with both the coal and the ionic liquid types. The recyclability of the ionic liquid over multiple treatment cycles has been demonstrated, which makes coal pre-treatment processes with these solvents more economically viable.

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Research paper thumbnail of A Review on Understanding Explosions from Methane-Air Mixture

This review examines existing knowledge on the genesis and flame acceleration of explosions from ... more 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.

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Research paper thumbnail of Experimental investigation of the reaction of HCFC-22 and methane in a dielectric barrier discharge non-equilibrium plasma

A dielectric barrier discharge non-equilibrium plasma was employed to study the reaction of HCFC-... more A dielectric barrier discharge non-equilibrium plasma was employed to study the reaction of HCFC-22 (CHClF2) with methane (in an argon bath gas) at atmospheric pressure and in the absence of oxygen and nitrogen. The reaction produced a fluorine-containing polymeric product, as well as gaseous species including H2, HF, HCl, CHF3, C2H3F, CH3Cl, CH2ClF, C2HClF4, CHCl2F, CH2Cl2 and CCl2F2. While the main polymeric fraction is non-crosslinked, a small portion of the solid product is crosslinked. The polymers contain a wide range of functional groups including CH3, CH2, CHCl, CHF, CHClF, CHF2, CF2 and CF3. The conversion level of CHClF2 increased from 53% to 78%, with an increment in input energy density from 3 kJ L−1 to 13 kJ L−1. A reaction mechanism is proposed explaining the formation of gaseous as well as polymeric products.

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Research paper thumbnail of Experimental Study on the Reaction of CCl3F and CH4 in a Dielectric Barrier Discharge Nonequilibrium Plasma Reactor

The reaction of CCl3F (CFC-11) with CH4 (in an argon bath gas) in a dielectric barrier discharge ... more The reaction of CCl3F (CFC-11) with CH4 (in an argon bath gas) in a dielectric barrier discharge nonequilibrium plasma was examined. Oxygen and nitrogen were excluded from the feed stream and the reactions resulted in the production of fluorine-containing polymers, as well as a range of gaseous products including H2, HCl, HF, C2H3F, C2H3Cl, C2H2ClF, CHCl2F, CCl2F2, CH3Cl, CH2Cl2, CHCl3, and C2Cl4. The polymeric material synthesized during reaction is characterized as being non-cross-linked and random in nature, containing functional groups including CH3, CH2, CHCl, CHF, CF2, and CF3. The conversion level of CCl3F increased from 37% to 63% as the input energy density increased from 3 to 13 kJ L–1 (the applied voltage range was 14.1 to 15.2 kV, peak–peak). The electrical discharge was characterized and found to be a slight modification of filamentary discharge toward a diffuse discharge due to the presence of the relatively low concentration of CCl3F and CH4 (less than 2% each) in argon. A reaction mechanism is proposed describing the formation of gas phase, as well as polymeric products.

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Research paper thumbnail of Effect of Methane on the Conversion of HFC-134a in a Dielectric Barrier Discharge Non-equilibrium Plasma Reactor

The effect of methane on the conversion of HFC-134a (CF3CH2F) in a dielectric barrier discharge n... more The effect of methane on the conversion of HFC-134a (CF3CH2F) in a dielectric barrier discharge non-equilibrium plasma reactor was examined. Reactions were conducted in an argon bath gas and in the absence of oxygen and nitrogen. The products of the reaction include H2, HF, CHF3, CH2F2, C2H6, C3H8, C2H3F, CHF2CHF2, C2H4F2, C3H7F as well as a polymeric solid deposit. The polymeric materials are predominantly fluorine containing random copolymers, which can be categorised as fluoropolymers, constituted from various functional groups including CF3, CF2, CHF, CHF2, CH2F, CH2 and CH3. While the presence of methane in the feed stream reduces the conversion level of CF3CH2F, it also modifies the polymer architecture. The addition of 1.25% methane with 1.25% CF3CH2F in an argon bath gas at 100 cm3 min−1 feed rate reduces the conversion of CF3CH2F from 74.5% to 46.8% and increases the formation of HF from 1500 μmol h−1 to 2640 μmol h−1. The effect of methane addition on the electrical discharge and the reaction pathways are discussed.

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Research paper thumbnail of Comparative study of the decomposition of CH4 in a nonequilibrium plasma and under high temperature pyrolytic conditions

Australian Combustion Symposium, 2013

In this study, the decomposition of methane in a nonequilibrium plasma, where nitrogen and oxygen... more In this study, the decomposition of methane in a nonequilibrium plasma, where nitrogen and oxygen were excluded from the feed mixture, was investigated. The major product species formed under conditions where the conversion level of methane was relatively high (up to 50 %) were determined. Hydrogen, acetylene, ethylene, ethane and propane were the primary gaseous species identified, and a liquid fraction was detected, which was characterised by 1H NMR and gel permeation chromatography. The product spectrum formed in the nonequilibrium plasma is compared to the species profile predicted from methane pyrolysis, where the feed composition, residence time and methane conversion levels used in the high temperature pyrolysis simulation matched those in the nonequilibrium plasma experimental reactor.

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Research paper thumbnail of Conversion of HFC 134a to non cross-linked fluoropolymer in a non thermal plasma

Nonequilibrium Processes in Plasma, Combustion and Atmosphere, 2012

The reaction of HFC-134a (CF3CH2F) in an argon bath gas has been studied using a dielectric barri... more The reaction of HFC-134a (CF3CH2F) in an argon bath gas has been studied using a dielectric barrier discharge non-thermal plasma at atmospheric pressure. Oxygen and nitrogen have been excluded in the reaction. It has been found that CF3CH2F can be converted into a non-crosslinked polymer under the reaction conditions studied. Other products include CHF3, CH2F2, C2H3F, C3H3F5, H2, HF and an oligomeric product fraction. The discharge characteristics of argon diluted CF3CH2F has been discussed, which is in the transition region between filamentary and homogeneous glow. The conversion of CF3CH2F ranges from 52% to 82 % for the applied voltage range of 13.4 – 15 kV (peak-peak) and input energy density range of 2 - 12 kJ/L. A simplified reaction mechanism has been proposed. Gel permeation chromatography analysis show two fractions with top molecular weights (Mp) of 2400 and 105,000 g/mol respectively, produced at an input energy density of 8 kJ/l.

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Research paper thumbnail of Conversion of a Waste Refrigerant Mixture containing CFC-12, HCFC-22 and HFC-134a to Non-Crosslinked Fluoropolymer in a Non-Thermal Plasma

21st International Symposium on Plasma Chemistry (ISPC-21), 2013

The reaction of a waste refrigerant mixture of CFC-12, HCFC-22 and HFC-134a (in an argon/methane ... more The reaction of a waste refrigerant mixture of CFC-12, HCFC-22 and HFC-134a (in an argon/methane bath gas) in a dielectric barrier discharge non-thermal plasma reactor has been studied. The conversion of the major refrigerant, CFC-12, ranged from 59–76 % for an input energy density range of 3–13 kJ/L. The reaction results in the formation of a range of gaseous products as well as non-crosslinked polymers of two distinct fractions.

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Research paper thumbnail of Experimental study of the reaction of 1, 2-dichloroethane in a non-thermal plasma–effect of methane addition

21st International Symposium on Plasma Chemistry (ISPC-21), 2013

This paper examines the effect of methane on the reaction of 1, 2-dichloroethane in a non-thermal... more This paper examines the effect of methane on the reaction of 1, 2-dichloroethane in a non-thermal plasma in a double dielectric barrier discharge (DBD) reactor, under non oxidative conditions and at atmospheric pressure. Commercially important products such as vinyl chloride and polyvinyl chloride were produced. The addition of CH4 to the feed stream reduces the concentration of unsaturation in the polymeric material.

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Research paper thumbnail of Reaction of chloroform in a non-oxidative atmosphere using dielectric barrier discharge

IEEE Pulsed Power & Plasma Science Conference – PPPS 2013, 2013

This paper investigates the reaction of chloroform under non oxidative conditions in a quartz die... more This paper investigates the reaction of chloroform under non oxidative conditions in a quartz dielectric barrier discharge reactor. A non thermal plasma is generated in the dielectric barrier discharge reactor at atmospheric pressure where argon functions as a carrier gas and is mixed with chloroform and fed into the plasma zone. Parameters such as chloroform conversion, product distribution, reactor temperature and polymer characterisation are studied in this paper. A reaction mechanism outlining the reaction steps leading to the formation of major products is presented

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Research paper thumbnail of Reaction of carbon tetrachloride with methane in a non-equilibrium plasma at atmospheric pressure, and characterisation of the polymer thus formed

In this paper we focus on the development of a methodology for treatment of carbon tetrachloride ... more In this paper we focus on the development of a methodology for treatment of carbon tetrachloride utilising a non-equilibrium plasma operating at atmospheric pressure, which is not singularly aimed at destroying carbon tetrachloride but rather at converting it to a non-hazardous, potentially valuable commodity. This method encompasses the reaction of carbon tetrachloride and methane, with argon as a carrier gas, in a quartz dielectric barrier discharge reactor. The reaction is performed under non-oxidative conditions. Possible pathways for formation of major products based on experimental results and supported by quantum chemical calculations are outlined in the paper. We elucidate important parameters such as carbon tetrachloride conversion, product distribution, mass balance and characterise the chlorinated polymer formed in the process.

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Research paper thumbnail of Characterization of Polymer Synthesized from the Nonequilibrium Plasma Conversion of CFC-12 and Methane in a Dielectric Barrier Discharge Reactor

A dielectric barrier discharge (DBD) nonequilibrium plasma reactor was employed to polymerize CFC... more A dielectric barrier discharge (DBD) nonequilibrium plasma reactor was employed to polymerize CFC-12 (CCl2F2, dichlorodifluoromethane) at atmospheric pressure. The plasma polymerization of this saturated halogenated hydrocarbon was conducted in the presence of methane as reactant, in an argon bath gas and where the reaction environment was free from oxygen and nitrogen. The reaction resulted in the formation of non-cross-linked polymer product and whereby the non-cross-linked nature of the polymer enabled its characterization by solution state 13C and 19F nuclear magnetic resonance (NMR) spectroscopic analysis. The generated polymer was also analyzed by Fourier transform infrared (FTIR) spectrometry, and the spectra thus obtained were consistent with the analysis by NMR. The analyses of NMR and FTIR spectroscopy reveal the formation of fluoropolymers from the conversion of CFC-12.

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Research paper thumbnail of Non-thermal plasma polymerization of HFC-134a in a dielectric barrier discharge reactor; Polymer characterization and understanding the mechanism of polymer formation

IEEE Pulsed Power & Plasma Science Conference – PPPS 2013, 2013

The plasma polymerization of HFC-134a (CF3CH2F) has been investigated in a non-thermal plasma die... more The plasma polymerization of HFC-134a (CF3CH2F) has been investigated in a non-thermal plasma dielectric barrier discharge reactor. HFC-134a is a green house gas and it has a global warming potential of 1410 with respect to CO2 and 100-year time horizon. Its release is regulated in many countries and its manufacture is likely to be controlled in the near future. A dielectric barrier discharge reactor, constructed from concentric alumina tubes was used for the investigation. The polymer generated from reaction was soluble in tetrahydrofuran solvent which suggests that it is non-crosslinked. The polymer was characterized using various NMR spectroscopic techniques (e.g., 13C, 19F) which reveal that the functional groups in the polymer include CHF, CF2 and CF3 groups. Based on these data, a detailed reaction mechanism has been developed which is similar but not identical to those available in the open literature. We previously reported the conversion of HFC-143a, the characterization of plasma discharge and the molecular weight of the polymers. This work is focused on a detailed structural analysis of the polymers and a proposed mechanism for their formation.

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Research paper thumbnail of Non-Oxidative Conversion of 1,2-Dichloroethane in a Non-Thermal Plasma and Characterisation of the Polymer Formed

ABSTRACT This paper focuses on the conversion of 1,2-dichloroethane (EDC) using non-thermal plasm... more ABSTRACT This paper focuses on the conversion of 1,2-dichloroethane (EDC) using non-thermal plasma under reaction conditions that can decompose EDC and yield a value-added product. A cylindrical double dielectric barrier discharge system has been used to generate non-thermal plasma and quartz has been used as a dielectric. Our findings show that under non-oxidative reaction conditions employed in this study, vinyl chloride, a commercially important compound, is the major gas phase product produced. This paper also encompasses a preliminary characterisation of polymer during the reaction. Possible mechanisms for gaseous product formation and polymerisation are presented.

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Research paper thumbnail of Explosion characteristics of methane–air mixtures in a spherical vessel connected with a duct

With the aim of exploring explosion characteristics of methane–air explosive mixtures in a ducted... more With the aim of exploring explosion characteristics of methane–air explosive mixtures in a ducted vessel, a 20 l spherical vessel connected with a 2813 mm long duct was employed. The experimental setup was comprised of a wafer check valve, which kept the methane–air mixture initially confined and opened at the time of explosion. The system introduced turbulence to the gas mixture during operation and pyrotechnic igniters were employed in the investigation. This approach assisted to obtain data that can be correlated with real world ducted explosion accidents where the explosion initiates in the presence of strong ignition energies and in turbulent states of methane–air mixtures. This study shows that the explosion severity can be very high in the turbulent field of methane–air mixture and in the presence of strong ignition energies. The pressure rise in the vessel and the flame speed along the length of the duct were found to be higher in the present study when compared to data obtained with quiescent methane–air mixtures and low ignition energies. The impact of the duct length and pyrotechnic igniters’ energy on reduced peak explosion pressure was characterised. The rate of pressure rise, a parameter linked to the burning rate, increased from the ducted to the vented configurations of the explosion test units.

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Research paper thumbnail of Reaction of dichloromethane under non-oxidative conditions in a dielectric barrier discharge reactor and characterisation of the resultant polymer

This paper presents the results of dichloromethane (DCM) decomposition to polymers utilising diel... more This paper presents the results of dichloromethane (DCM) decomposition to polymers utilising dielectric barrier discharge under non-oxidative reaction conditions. The conversion levels, mass balance, reaction mechanism and polymer characterisation in relation to DCM reaction are presented in this paper. Reaction pathways describing the decomposition of DCM and subsequent formation of the major products are outlined. Speculation of the mechanism of formation of CHCl3 and C2HCl3 are supported by quantum chemical calculations. In addition, the effect of introducing methane in the reaction feed on the conversion level of DCM and the polymer structure is also examined in this paper.

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Research paper thumbnail of Investigations into Physicochemical Changes in Thermal Coals during Low-Temperature Ionic Liquid Treatment

Two Australian thermal coals were treated with four different ionic liquids (ILs) at temperatures... more Two Australian thermal coals were treated with four different ionic liquids (ILs) at temperatures as low as 100 °C. The ILs used were 1-butylpyridinium chloride ([Bpyd][Cl]), 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCM]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), and 1-butyl-3-methylimidazolium tricyanomethanide ([Bmim][TCM]). Visual comparisons were made between the raw and IL-treated coals via optical microscopy. Changes in thermal behavior of these treated coals were compared against raw coals via pyrolysis experiments in a thermogravimetric analyzer (TGA). Changes in functional group composition in the treated coals were probed via Fourier transform infrared (FTIR) spectroscopy. The recovered ILs were also analyzed via FTIR and nuclear magnetic resonance (NMR) spectroscopies to observe any changes after recovery. Low-temperature IL treatment of each of the coals resulted in fragmentation and fracturing, reducing the average particle size. An increase in mass loss in the treated coals was also observed when compared to each raw coal, indicating an increase in lower molecular weight fragments after treatment. This was corroborated by a large increase in aliphatic hydrocarbons being observed in the treated coals, along with a decrease in oxygenated functional groups and mineral matter in one coal. The recovered ILs were shown to be unchanged by this treatment process, indicating their potential recyclability. These results indicate the potential for ILs to be implemented as solvent treatments for coal conversion processes.

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Research paper thumbnail of Modification of lignites via low temperature ionic liquid treatment

Two lignite samples (150–212 μm) were treated with four ionic liquids (ILs); 1-butylpyridinium ch... more Two lignite samples (150–212 μm) were treated with four ionic liquids (ILs); 1-butylpyridinium chloride ([Bpyd][Cl]), 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCA]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) and 1-butyl-3-methylimidazolium tricyanomethanide ([Bmim][TCM]) at 100 °C for 3 h to establish the utility of ILs for lignite pre-treatment in conversion processes. ILs are room temperature molten salts that have remarkable physical and chemical properties including high thermal and electrochemical stabilities, low vapour pressures and, critically for this work, the capacity to solubilise a diverse range of materials. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and optical microscopy were employed in this study to gain insight into the physical and chemical interactions occurring between lignite and ILs at low temperatures. The FTIR results indicate that the majority of the ILs employed were able to break apart the macro-structure of coal resulting in an increase in short chain aliphatic hydrocarbons. Additionally, FTIR analysis revealed a significant decrease in the presence of COOH and CO groups for lignites treated with [Emim][DCM]. The TGA data revealed that the IL treated lignites had significantly lower devolatilisation temperatures than the untreated lignite, indicating an increase in lower molecular weight species after treatment. Microscopy showed a sizeable decrease in particle size after IL treatment due to fragmentation, and these coals appeared to be considerably swollen. Analysis of the recovered ILs showed no denaturing after the treatment process, indicating their recyclability potential in the treatment process.

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Research paper thumbnail of Effect of Methane and coal dust Concentrations on Explosion Pressure Rise

Australian Combustion Symposium, 2015

Explosion pressure rate rise (dp/dt) experiments for coal dust and methane-coal dust-air hybrid m... more Explosion pressure rate rise (dp/dt) experiments for coal dust and methane-coal dust-air hybrid mixtures in a modified 20 L explosion apparatus were conducted to provide data on explosion characteristics in Ventilation Air Methane (VAM) systems. Coal dust concentrations of 10, 25, 50 and 100 g.m-3; methane concentrations of 0.75, 1.25, 2.5 and 5%; and initial igniter energies of 1, 5 and 10 kJ were investigated. The dp/dt of dilute coal dust-methane-air hybrid mixtures were strongly affected by the igniter energy. The potential of higher energy boosting the fuel combustion from the flammable to the explosion phase was demonstrated. There was no observed influence on dp/dt at 10 g.m-3 coal dust concentration. In contrast, 25 g.m-3 of coal dust concentration had significant influence on the dp/dt for methane-coal dust-air hybrid mixtures.

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Research paper thumbnail of Pyrolysis characteristics of ionic liquid and solvent treated coals

Australian Combustion Symposium, 2015

Two coals, one lignite and one sub-bituminous, were treated at low temperatures with four differe... more Two coals, one lignite and one sub-bituminous, were treated at low temperatures with four different ionic liquids (ILs), 1-butylpyridinium chloride [Bpyd][Cl], 1-ethyl-3-methylimidazolium dicyanamide [Emim][DCA], 1-butyl-3-methylimidazolium chloride [Bmim][Cl] and 1-butyl-3-methylimidazolium tricyanomethanide [Bmim][TCM]. These IL treated coals were then washed with n-methyl-2-pyrrolidone (NMP). The pyrolysis characteristics of the treated coals were probed via thermogravimetric analysis (TGA) with the aim of investigating the differences among the raw coal, the IL treated coal and the IL & NMP treated coals. After low temperature IL treatment, all coal samples lost more mass during pyrolysis in comparison to the raw coal. This indicated that IL treatment had broken the macrostructure of the coal apart; resulting in an increase in the volatilization of lower molecular weight species during pyrolysis. The pyrolysis characteristics of the IL & NMP treated coals, saw some samples, specifically those treated by [Bpyd][Cl] lose less mass after NMP treatment, indicating that the lower molecular weight species may have been extracted by the NMP treatment. Other samples showed little to no difference after NMP treatment, and in the case of coal P treated [Emim][DCM], an increase in mass loss was observed after NMP treatment. The observed differences in pyrolysis characteristics appeared to be coal and IL specific, with [Bpyd][Cl] appearing to be the most effective in liberating lower molecular weight species to be extracted by NMP. These results are promising for utilising lower grade coals as feedstocks for valuable chemicals and tars, and producing coals with less volatile matter and a higher carbon content.

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Research paper thumbnail of Pre-treatment of thermal and lignite coals with ionic liquids

International Conference on Coal Science & Technology, 2015

Ionic liquids are room temperature molten salts that have remarkable physical and chemical proper... more Ionic liquids are room temperature molten salts that have remarkable physical and chemical properties including high thermal and electrochemical stabilities, vanishingly low vapour pressures and, critically for this work, the capacity to solubilize a diverse range of materials. The interactions of four ionic liquids with four coal samples (2 thermal and 2 lignite) at 100°C has been probed to establish the utility of ionic liquids for coal pre-treatment in coal conversion processes. Fourier Transform Infrared Spectroscopy (FTIR) and Optical Microscopy were employed in this study to understand the physicochemical interactions between coal and ionic liquids at low temperatures. The FTIR results indicate that the majority of the ionic liquids employed were able to break apart the macro-structure of coal resulting in an increase in short chain aliphatic hydrocarbons. It was also observed that the treated coals were highly fragmented and had a lower average particle size, with the lignite coals appearing to be significantly swollen after IL treatment. The changes in coal morphology and composition following treatment with the ionic liquids, varied with both the coal and the ionic liquid types. The recyclability of the ionic liquid over multiple treatment cycles has been demonstrated, which makes coal pre-treatment processes with these solvents more economically viable.

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Research paper thumbnail of A Review on Understanding Explosions from Methane-Air Mixture

This review examines existing knowledge on the genesis and flame acceleration of explosions from ... more 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.

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Research paper thumbnail of Experimental investigation of the reaction of HCFC-22 and methane in a dielectric barrier discharge non-equilibrium plasma

A dielectric barrier discharge non-equilibrium plasma was employed to study the reaction of HCFC-... more A dielectric barrier discharge non-equilibrium plasma was employed to study the reaction of HCFC-22 (CHClF2) with methane (in an argon bath gas) at atmospheric pressure and in the absence of oxygen and nitrogen. The reaction produced a fluorine-containing polymeric product, as well as gaseous species including H2, HF, HCl, CHF3, C2H3F, CH3Cl, CH2ClF, C2HClF4, CHCl2F, CH2Cl2 and CCl2F2. While the main polymeric fraction is non-crosslinked, a small portion of the solid product is crosslinked. The polymers contain a wide range of functional groups including CH3, CH2, CHCl, CHF, CHClF, CHF2, CF2 and CF3. The conversion level of CHClF2 increased from 53% to 78%, with an increment in input energy density from 3 kJ L−1 to 13 kJ L−1. A reaction mechanism is proposed explaining the formation of gaseous as well as polymeric products.

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Research paper thumbnail of Experimental Study on the Reaction of CCl3F and CH4 in a Dielectric Barrier Discharge Nonequilibrium Plasma Reactor

The reaction of CCl3F (CFC-11) with CH4 (in an argon bath gas) in a dielectric barrier discharge ... more The reaction of CCl3F (CFC-11) with CH4 (in an argon bath gas) in a dielectric barrier discharge nonequilibrium plasma was examined. Oxygen and nitrogen were excluded from the feed stream and the reactions resulted in the production of fluorine-containing polymers, as well as a range of gaseous products including H2, HCl, HF, C2H3F, C2H3Cl, C2H2ClF, CHCl2F, CCl2F2, CH3Cl, CH2Cl2, CHCl3, and C2Cl4. The polymeric material synthesized during reaction is characterized as being non-cross-linked and random in nature, containing functional groups including CH3, CH2, CHCl, CHF, CF2, and CF3. The conversion level of CCl3F increased from 37% to 63% as the input energy density increased from 3 to 13 kJ L–1 (the applied voltage range was 14.1 to 15.2 kV, peak–peak). The electrical discharge was characterized and found to be a slight modification of filamentary discharge toward a diffuse discharge due to the presence of the relatively low concentration of CCl3F and CH4 (less than 2% each) in argon. A reaction mechanism is proposed describing the formation of gas phase, as well as polymeric products.

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Research paper thumbnail of Effect of Methane on the Conversion of HFC-134a in a Dielectric Barrier Discharge Non-equilibrium Plasma Reactor

The effect of methane on the conversion of HFC-134a (CF3CH2F) in a dielectric barrier discharge n... more The effect of methane on the conversion of HFC-134a (CF3CH2F) in a dielectric barrier discharge non-equilibrium plasma reactor was examined. Reactions were conducted in an argon bath gas and in the absence of oxygen and nitrogen. The products of the reaction include H2, HF, CHF3, CH2F2, C2H6, C3H8, C2H3F, CHF2CHF2, C2H4F2, C3H7F as well as a polymeric solid deposit. The polymeric materials are predominantly fluorine containing random copolymers, which can be categorised as fluoropolymers, constituted from various functional groups including CF3, CF2, CHF, CHF2, CH2F, CH2 and CH3. While the presence of methane in the feed stream reduces the conversion level of CF3CH2F, it also modifies the polymer architecture. The addition of 1.25% methane with 1.25% CF3CH2F in an argon bath gas at 100 cm3 min−1 feed rate reduces the conversion of CF3CH2F from 74.5% to 46.8% and increases the formation of HF from 1500 μmol h−1 to 2640 μmol h−1. The effect of methane addition on the electrical discharge and the reaction pathways are discussed.

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Research paper thumbnail of Comparative study of the decomposition of CH4 in a nonequilibrium plasma and under high temperature pyrolytic conditions

Australian Combustion Symposium, 2013

In this study, the decomposition of methane in a nonequilibrium plasma, where nitrogen and oxygen... more In this study, the decomposition of methane in a nonequilibrium plasma, where nitrogen and oxygen were excluded from the feed mixture, was investigated. The major product species formed under conditions where the conversion level of methane was relatively high (up to 50 %) were determined. Hydrogen, acetylene, ethylene, ethane and propane were the primary gaseous species identified, and a liquid fraction was detected, which was characterised by 1H NMR and gel permeation chromatography. The product spectrum formed in the nonequilibrium plasma is compared to the species profile predicted from methane pyrolysis, where the feed composition, residence time and methane conversion levels used in the high temperature pyrolysis simulation matched those in the nonequilibrium plasma experimental reactor.

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Research paper thumbnail of Conversion of HFC 134a to non cross-linked fluoropolymer in a non thermal plasma

Nonequilibrium Processes in Plasma, Combustion and Atmosphere, 2012

The reaction of HFC-134a (CF3CH2F) in an argon bath gas has been studied using a dielectric barri... more The reaction of HFC-134a (CF3CH2F) in an argon bath gas has been studied using a dielectric barrier discharge non-thermal plasma at atmospheric pressure. Oxygen and nitrogen have been excluded in the reaction. It has been found that CF3CH2F can be converted into a non-crosslinked polymer under the reaction conditions studied. Other products include CHF3, CH2F2, C2H3F, C3H3F5, H2, HF and an oligomeric product fraction. The discharge characteristics of argon diluted CF3CH2F has been discussed, which is in the transition region between filamentary and homogeneous glow. The conversion of CF3CH2F ranges from 52% to 82 % for the applied voltage range of 13.4 – 15 kV (peak-peak) and input energy density range of 2 - 12 kJ/L. A simplified reaction mechanism has been proposed. Gel permeation chromatography analysis show two fractions with top molecular weights (Mp) of 2400 and 105,000 g/mol respectively, produced at an input energy density of 8 kJ/l.

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Research paper thumbnail of Conversion of a Waste Refrigerant Mixture containing CFC-12, HCFC-22 and HFC-134a to Non-Crosslinked Fluoropolymer in a Non-Thermal Plasma

21st International Symposium on Plasma Chemistry (ISPC-21), 2013

The reaction of a waste refrigerant mixture of CFC-12, HCFC-22 and HFC-134a (in an argon/methane ... more The reaction of a waste refrigerant mixture of CFC-12, HCFC-22 and HFC-134a (in an argon/methane bath gas) in a dielectric barrier discharge non-thermal plasma reactor has been studied. The conversion of the major refrigerant, CFC-12, ranged from 59–76 % for an input energy density range of 3–13 kJ/L. The reaction results in the formation of a range of gaseous products as well as non-crosslinked polymers of two distinct fractions.

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Research paper thumbnail of Experimental study of the reaction of 1, 2-dichloroethane in a non-thermal plasma–effect of methane addition

21st International Symposium on Plasma Chemistry (ISPC-21), 2013

This paper examines the effect of methane on the reaction of 1, 2-dichloroethane in a non-thermal... more This paper examines the effect of methane on the reaction of 1, 2-dichloroethane in a non-thermal plasma in a double dielectric barrier discharge (DBD) reactor, under non oxidative conditions and at atmospheric pressure. Commercially important products such as vinyl chloride and polyvinyl chloride were produced. The addition of CH4 to the feed stream reduces the concentration of unsaturation in the polymeric material.

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Research paper thumbnail of Reaction of chloroform in a non-oxidative atmosphere using dielectric barrier discharge

IEEE Pulsed Power & Plasma Science Conference – PPPS 2013, 2013

This paper investigates the reaction of chloroform under non oxidative conditions in a quartz die... more This paper investigates the reaction of chloroform under non oxidative conditions in a quartz dielectric barrier discharge reactor. A non thermal plasma is generated in the dielectric barrier discharge reactor at atmospheric pressure where argon functions as a carrier gas and is mixed with chloroform and fed into the plasma zone. Parameters such as chloroform conversion, product distribution, reactor temperature and polymer characterisation are studied in this paper. A reaction mechanism outlining the reaction steps leading to the formation of major products is presented

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Research paper thumbnail of Reaction of carbon tetrachloride with methane in a non-equilibrium plasma at atmospheric pressure, and characterisation of the polymer thus formed

In this paper we focus on the development of a methodology for treatment of carbon tetrachloride ... more In this paper we focus on the development of a methodology for treatment of carbon tetrachloride utilising a non-equilibrium plasma operating at atmospheric pressure, which is not singularly aimed at destroying carbon tetrachloride but rather at converting it to a non-hazardous, potentially valuable commodity. This method encompasses the reaction of carbon tetrachloride and methane, with argon as a carrier gas, in a quartz dielectric barrier discharge reactor. The reaction is performed under non-oxidative conditions. Possible pathways for formation of major products based on experimental results and supported by quantum chemical calculations are outlined in the paper. We elucidate important parameters such as carbon tetrachloride conversion, product distribution, mass balance and characterise the chlorinated polymer formed in the process.

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Research paper thumbnail of Characterization of Polymer Synthesized from the Nonequilibrium Plasma Conversion of CFC-12 and Methane in a Dielectric Barrier Discharge Reactor

A dielectric barrier discharge (DBD) nonequilibrium plasma reactor was employed to polymerize CFC... more A dielectric barrier discharge (DBD) nonequilibrium plasma reactor was employed to polymerize CFC-12 (CCl2F2, dichlorodifluoromethane) at atmospheric pressure. The plasma polymerization of this saturated halogenated hydrocarbon was conducted in the presence of methane as reactant, in an argon bath gas and where the reaction environment was free from oxygen and nitrogen. The reaction resulted in the formation of non-cross-linked polymer product and whereby the non-cross-linked nature of the polymer enabled its characterization by solution state 13C and 19F nuclear magnetic resonance (NMR) spectroscopic analysis. The generated polymer was also analyzed by Fourier transform infrared (FTIR) spectrometry, and the spectra thus obtained were consistent with the analysis by NMR. The analyses of NMR and FTIR spectroscopy reveal the formation of fluoropolymers from the conversion of CFC-12.

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Research paper thumbnail of Non-thermal plasma polymerization of HFC-134a in a dielectric barrier discharge reactor; Polymer characterization and understanding the mechanism of polymer formation

IEEE Pulsed Power & Plasma Science Conference – PPPS 2013, 2013

The plasma polymerization of HFC-134a (CF3CH2F) has been investigated in a non-thermal plasma die... more The plasma polymerization of HFC-134a (CF3CH2F) has been investigated in a non-thermal plasma dielectric barrier discharge reactor. HFC-134a is a green house gas and it has a global warming potential of 1410 with respect to CO2 and 100-year time horizon. Its release is regulated in many countries and its manufacture is likely to be controlled in the near future. A dielectric barrier discharge reactor, constructed from concentric alumina tubes was used for the investigation. The polymer generated from reaction was soluble in tetrahydrofuran solvent which suggests that it is non-crosslinked. The polymer was characterized using various NMR spectroscopic techniques (e.g., 13C, 19F) which reveal that the functional groups in the polymer include CHF, CF2 and CF3 groups. Based on these data, a detailed reaction mechanism has been developed which is similar but not identical to those available in the open literature. We previously reported the conversion of HFC-143a, the characterization of plasma discharge and the molecular weight of the polymers. This work is focused on a detailed structural analysis of the polymers and a proposed mechanism for their formation.

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Research paper thumbnail of Non-Oxidative Conversion of 1,2-Dichloroethane in a Non-Thermal Plasma and Characterisation of the Polymer Formed

ABSTRACT This paper focuses on the conversion of 1,2-dichloroethane (EDC) using non-thermal plasm... more ABSTRACT This paper focuses on the conversion of 1,2-dichloroethane (EDC) using non-thermal plasma under reaction conditions that can decompose EDC and yield a value-added product. A cylindrical double dielectric barrier discharge system has been used to generate non-thermal plasma and quartz has been used as a dielectric. Our findings show that under non-oxidative reaction conditions employed in this study, vinyl chloride, a commercially important compound, is the major gas phase product produced. This paper also encompasses a preliminary characterisation of polymer during the reaction. Possible mechanisms for gaseous product formation and polymerisation are presented.

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