International Journal of Coal Geology, Jul 1, 2010
This paper presents experimental investigations on CO 2 /CH 4 binary gas flow in bulk coal under ... more This paper presents experimental investigations on CO 2 /CH 4 binary gas flow in bulk coal under controllable stress conditions, focusing on sorption-induced swelling/shrinkage and gas permeability associated with CO 2-sequestration enhanced coalbed methane (CO 2-ECBM) recovery. The gas flush tests with carbon dioxide were conducted on a specially designed true tri-axial stress coal permeameter (TTSCP) using a large coal sample pre-adsorbed methane. These tests simulate the in-situ conditions of CO 2-ECBM recovery from coal and provided experimental information for better understanding of the gas transport in coals. The swelling/ shrinkage coefficients of coal associated with CO 2-ECBM process have been evaluated using the experimental data. The results show that adsorption and desorption of gases CH 4 and CO 2 can significantly affect the volumetric change of micro-and macropores in coal, leading to coal swelling/shrinkage and fluctuation of permeability, and hence controlling the transport and flow of gases through coal.
Arc dynamics in a vortex-stabilized non-transferred plasma torch with a tangential gas feed
Journal of Physics D, Sep 17, 2021
The mode of anode arc attachments in a thermal plasma torch, such as constricted arc, multi-arc o... more The mode of anode arc attachments in a thermal plasma torch, such as constricted arc, multi-arc or diffused arc attachment, has operational as well as economic consequences on the use of plasma torches in industrial applications. The mode of arc attachment is strongly dependent on the gas flow dynamics, gas vortex formation and wall energy exchange. To gain more insight into arc attachment behaviour, this article presents a transient flow plasma model implemented using OpenFOAM computational fluid dynamics code to study the effect of gas swirl and arc rotation on modes of arc attachments. A tangentially fed plasma gas creates a gas swirl that helps to induce the arc rotation. The investigations were carried out at arc currents between 200–450 A and input gas flow rates in the range of 5–20 slpm. High gas swirl and low arc currents are found to favour constricted attachment on the anode surface. The local gas vortex driven by the plasma swirl creates hot spots inside the torch that dictate the arc attachment. The transition of arc attachment from the diffuse to constricted mode was simulated by imposing a step-change in the gas flow which shows the evolution of different arc attachment behaviour. During the transition from constricted to diffused attachment, the arc tends to undergo a transitionary multi-attachment mode at specific selected current and flow parameters.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Simulation of Salt Transport Above a Shallow Saline Watertable
Recommendations for the reclamation of saline and sodic soils in Queensland are based on simple e... more Recommendations for the reclamation of saline and sodic soils in Queensland are based on simple empirical relations. To accurately determine the quantity of gypsum, water and time needed a model that can simulate the complex chemical and physical processes involved in the reclamation of saline and sodic soils is required. UNSATCHEM [6,7] is a software package for simulating water, heat, carbon dioxide and solute movement in one-dimensional variably saturated media (nutrient levels are assumed to be adequate for optimum plant growth). The model is unique in that it predicts the impacts of salinity and sodicity on soil hydraulic conductivity. To the authors' knowledge it is the only model that links both soil chemical and physical properties. The use of UNSATCHEM to predict changes in salinity and sodicity was recently advocated [5]. This study found the model was able to simulate salt movement within the range of natural variations found at the Darbalara field trial and therefore may be used to evaluate the feasibility of reclamation and management practices for salinity and sodicity control.
International Journal of Applied Science and Engineering, Aug 1, 2015
Sequestration of carbon dioxide in geological formations has been recognised as one of the most p... more Sequestration of carbon dioxide in geological formations has been recognised as one of the most promising ways to cope with greenhouse gas emissions, and saline aquifers are one of the potential storage target. This study evaluates feasibility of CO 2 storage in saline aquifers under different conditions. Simulation studies are carried out based on a homogeneous aquifer model. Compositional reservoir simulator (CMG-GEM) was used to simulate 10 years of CO 2 injection phase and simulate the fate of CO 2 post injection from hundreds to thousands of years. Different subsets of sensitive parameters are independently investigated to understand the impact of various parameter son different trapping mechanisms. Simulation results are also compared with other published research studies to provide additional insight of factors affecting CO 2 sequestration process.
The arc behaviour within a vortex stabilised argon plasma torch is investigated by a transient fl... more The arc behaviour within a vortex stabilised argon plasma torch is investigated by a transient fluid dynamic modelling. The simulation was carried out to mimic a plasma torch operating at a current of 200A, and the gas flow rate in the range of 5 and 15 slpm. Simulations show that the gas flow rate has a major impact on the arc attachment behaviour on the anode surface. At low gas flow rates a diffusive arc attachment is observed on the anode surface, however increasing the gas flow rate changes the attachment to partially diffusive or single spot. Higher gas flow rates increase the thickness of the cold boundary layer around the anode giving a high resistance for diffusive current transfer thus consolidating the current within a narrow column and consequently creating a spot attachment on the anode.
Characterisation of Readily Bioavailable Compounds in Surat Basin Walloon Coals for Biomethane Production Using Exogenous Culture
This experimental study aims to characterize the bioavailability of six Surat Basin Walloon coals... more This experimental study aims to characterize the bioavailability of six Surat Basin Walloon coals to exogenous methanogenic consortia, and the possible compositional and environmental factors that control bioavailability. Finely crushed coal cores samples were inoculated with digested sludge culture sourced from domestic wastewater treatment plants in biomethane potential bottles (BMP bottles) maintained at mesophilic temperature. Degradation of coal compounds was demonstrated via GC-MS characterization of methanol and dichloromethane (DCM) extracts of coals, as well as analysis of volatile fatty acids and alcohols and total dissolved organic carbon (TOC) in water eluents of coals conducted before and after biodegradation. The resulting methane yields ranged from 14 to 33 μmol/g, with an average of 21 μmol/g (0.515 m3/t) achieved within 30 days. Organic solvent-extractable materials accounted for 3.8 to 12% of coal weight. Aliphatic compounds, primarily medium-long-chain n-alkanes, n-alcohols and esters dominated the solvent extracts. Aromatics were detected up to three fused rings, and are rich in dibenzofuran, alkyl benzene, alkyl polyaromatic hydrocarbons, and acetyl diphenyl. The abundance of solvent-extractable matter was found to rely on liptinite content, particularly suberinite. Preservation of these compounds was thought to be facilitated by vitrinite, such as telinite and collotelinite that are rich in micropores, serving as storage for the hydrocarbons. On the other hand, environmental factors, such as microbes-carrying groundwater might compromise coal extractability by converting coal hydrocarbons to biogas. The study has revealed three levels of dependence regarding coal bioavailability: 1) Water solubility - An average 98% of aqueous compounds (based on TOC) was eliminated via biodegradation. These were mainly volatile fatty acids and alcohols, and to a lesser degree, medium-chain n-alcohols, esters and aliphatic amine; 2) Solvent extractability – approximately 35% of solvent-extractable compounds were biodegraded on average, with aliphatics being more bioavailable than aromatics; 3) Heterogeneous moieties, particularly aliphatic hydroxyl, ester bond, ether bond and C-N bond in aliphatic amine - These functional groups are characteristics of compounds that were heavily degraded. The study is to our knowledge, the first coal bioavailability research that demonstrated a detailed linkage between biomethane generation and bio-elimination of coal extractable compounds with connections to petrographic composition and possible environmental factors.
Coal-bed methane (CBM) production behaviour is difficult to predict or analyse due to its highly ... more Coal-bed methane (CBM) production behaviour is difficult to predict or analyse due to its highly intricate reservoir characteristics. Gas production from (CBM) reservoirs is governed by complex interaction of diffusion from the matrix to fractures and two phase gas and water flows through the fracture system to the production wells. The parameters that control the flow physics of these two systems are highly variable during the fluid production process. Generally CBM reservoir performance is evaluated using simulation software which requires experimental or/and field data to parametize the various governing equations that determine performance. Amongst the parameters that affect simulation outcomes, coal absolute permeability and relative permeability are key factors controlling CBM productivity.
Measurements of gas-liquid relative permeability of Queensland coals
The feature of water-gas two-phase flow through coal seams determines the water depletion and gas... more The feature of water-gas two-phase flow through coal seams determines the water depletion and gas production associated in coal seam gas recovery. Therefore, coal relative permeability is crucial for studies of two-phase flow behaviour in coal, which is greatly influenced by water/gas saturation and coal ranks. In this study, a permeability model incorporated with cleat size distribution and cleat tortuosity was developed to predict the relative permeability of gas and water in coals. An unsteady-state method has been applied to investigate the relative permeability of gas and water in coal samples from Surat Basin through water replacement with gas. A series of relative permeability curves for selected coals have been obtained. The measured pore size distribution, porosity and irreducible water saturation percentage are used to correlate the permeability of gas and water with gas saturation by modelling.
Transactions of the Indian Institute of Metals, Jan 4, 2017
Abstract Two phase emulsion is widely used to increase the reaction efficiency. Slag–metal emulsi... more Abstract Two phase emulsion is widely used to increase the reaction efficiency. Slag–metal emulsion is used widely in metallurgy to increase the efficiency of the process. Previously, Pb–salt emulsion system at high temperature has been studied experimentally and mathematically. In this work the study has been extended to Al–salt and Sn–salt systems to cover wider physical properties at much higher temperature, both experimentally as well as mathematically. Further the mathematical model has been verified against various published emulsion systems, having a wide variety of physical properties. Using this model, the effect of various physical properties of slag and iron, such as viscosity, density and drop size, on the iron–slag emulsion system has been studied. It is found that the iron droplets of the size of 100 µm or lesser may be entrapped in the slag if sufficient time is not allowed to settle them into the metal phase.
International Journal of Coal Geology, Jul 1, 2010
This paper presents experimental investigations on CO 2 /CH 4 binary gas flow in bulk coal under ... more This paper presents experimental investigations on CO 2 /CH 4 binary gas flow in bulk coal under controllable stress conditions, focusing on sorption-induced swelling/shrinkage and gas permeability associated with CO 2-sequestration enhanced coalbed methane (CO 2-ECBM) recovery. The gas flush tests with carbon dioxide were conducted on a specially designed true tri-axial stress coal permeameter (TTSCP) using a large coal sample pre-adsorbed methane. These tests simulate the in-situ conditions of CO 2-ECBM recovery from coal and provided experimental information for better understanding of the gas transport in coals. The swelling/ shrinkage coefficients of coal associated with CO 2-ECBM process have been evaluated using the experimental data. The results show that adsorption and desorption of gases CH 4 and CO 2 can significantly affect the volumetric change of micro-and macropores in coal, leading to coal swelling/shrinkage and fluctuation of permeability, and hence controlling the transport and flow of gases through coal.
Arc dynamics in a vortex-stabilized non-transferred plasma torch with a tangential gas feed
Journal of Physics D, Sep 17, 2021
The mode of anode arc attachments in a thermal plasma torch, such as constricted arc, multi-arc o... more The mode of anode arc attachments in a thermal plasma torch, such as constricted arc, multi-arc or diffused arc attachment, has operational as well as economic consequences on the use of plasma torches in industrial applications. The mode of arc attachment is strongly dependent on the gas flow dynamics, gas vortex formation and wall energy exchange. To gain more insight into arc attachment behaviour, this article presents a transient flow plasma model implemented using OpenFOAM computational fluid dynamics code to study the effect of gas swirl and arc rotation on modes of arc attachments. A tangentially fed plasma gas creates a gas swirl that helps to induce the arc rotation. The investigations were carried out at arc currents between 200–450 A and input gas flow rates in the range of 5–20 slpm. High gas swirl and low arc currents are found to favour constricted attachment on the anode surface. The local gas vortex driven by the plasma swirl creates hot spots inside the torch that dictate the arc attachment. The transition of arc attachment from the diffuse to constricted mode was simulated by imposing a step-change in the gas flow which shows the evolution of different arc attachment behaviour. During the transition from constricted to diffused attachment, the arc tends to undergo a transitionary multi-attachment mode at specific selected current and flow parameters.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Simulation of Salt Transport Above a Shallow Saline Watertable
Recommendations for the reclamation of saline and sodic soils in Queensland are based on simple e... more Recommendations for the reclamation of saline and sodic soils in Queensland are based on simple empirical relations. To accurately determine the quantity of gypsum, water and time needed a model that can simulate the complex chemical and physical processes involved in the reclamation of saline and sodic soils is required. UNSATCHEM [6,7] is a software package for simulating water, heat, carbon dioxide and solute movement in one-dimensional variably saturated media (nutrient levels are assumed to be adequate for optimum plant growth). The model is unique in that it predicts the impacts of salinity and sodicity on soil hydraulic conductivity. To the authors' knowledge it is the only model that links both soil chemical and physical properties. The use of UNSATCHEM to predict changes in salinity and sodicity was recently advocated [5]. This study found the model was able to simulate salt movement within the range of natural variations found at the Darbalara field trial and therefore may be used to evaluate the feasibility of reclamation and management practices for salinity and sodicity control.
International Journal of Applied Science and Engineering, Aug 1, 2015
Sequestration of carbon dioxide in geological formations has been recognised as one of the most p... more Sequestration of carbon dioxide in geological formations has been recognised as one of the most promising ways to cope with greenhouse gas emissions, and saline aquifers are one of the potential storage target. This study evaluates feasibility of CO 2 storage in saline aquifers under different conditions. Simulation studies are carried out based on a homogeneous aquifer model. Compositional reservoir simulator (CMG-GEM) was used to simulate 10 years of CO 2 injection phase and simulate the fate of CO 2 post injection from hundreds to thousands of years. Different subsets of sensitive parameters are independently investigated to understand the impact of various parameter son different trapping mechanisms. Simulation results are also compared with other published research studies to provide additional insight of factors affecting CO 2 sequestration process.
The arc behaviour within a vortex stabilised argon plasma torch is investigated by a transient fl... more The arc behaviour within a vortex stabilised argon plasma torch is investigated by a transient fluid dynamic modelling. The simulation was carried out to mimic a plasma torch operating at a current of 200A, and the gas flow rate in the range of 5 and 15 slpm. Simulations show that the gas flow rate has a major impact on the arc attachment behaviour on the anode surface. At low gas flow rates a diffusive arc attachment is observed on the anode surface, however increasing the gas flow rate changes the attachment to partially diffusive or single spot. Higher gas flow rates increase the thickness of the cold boundary layer around the anode giving a high resistance for diffusive current transfer thus consolidating the current within a narrow column and consequently creating a spot attachment on the anode.
Characterisation of Readily Bioavailable Compounds in Surat Basin Walloon Coals for Biomethane Production Using Exogenous Culture
This experimental study aims to characterize the bioavailability of six Surat Basin Walloon coals... more This experimental study aims to characterize the bioavailability of six Surat Basin Walloon coals to exogenous methanogenic consortia, and the possible compositional and environmental factors that control bioavailability. Finely crushed coal cores samples were inoculated with digested sludge culture sourced from domestic wastewater treatment plants in biomethane potential bottles (BMP bottles) maintained at mesophilic temperature. Degradation of coal compounds was demonstrated via GC-MS characterization of methanol and dichloromethane (DCM) extracts of coals, as well as analysis of volatile fatty acids and alcohols and total dissolved organic carbon (TOC) in water eluents of coals conducted before and after biodegradation. The resulting methane yields ranged from 14 to 33 μmol/g, with an average of 21 μmol/g (0.515 m3/t) achieved within 30 days. Organic solvent-extractable materials accounted for 3.8 to 12% of coal weight. Aliphatic compounds, primarily medium-long-chain n-alkanes, n-alcohols and esters dominated the solvent extracts. Aromatics were detected up to three fused rings, and are rich in dibenzofuran, alkyl benzene, alkyl polyaromatic hydrocarbons, and acetyl diphenyl. The abundance of solvent-extractable matter was found to rely on liptinite content, particularly suberinite. Preservation of these compounds was thought to be facilitated by vitrinite, such as telinite and collotelinite that are rich in micropores, serving as storage for the hydrocarbons. On the other hand, environmental factors, such as microbes-carrying groundwater might compromise coal extractability by converting coal hydrocarbons to biogas. The study has revealed three levels of dependence regarding coal bioavailability: 1) Water solubility - An average 98% of aqueous compounds (based on TOC) was eliminated via biodegradation. These were mainly volatile fatty acids and alcohols, and to a lesser degree, medium-chain n-alcohols, esters and aliphatic amine; 2) Solvent extractability – approximately 35% of solvent-extractable compounds were biodegraded on average, with aliphatics being more bioavailable than aromatics; 3) Heterogeneous moieties, particularly aliphatic hydroxyl, ester bond, ether bond and C-N bond in aliphatic amine - These functional groups are characteristics of compounds that were heavily degraded. The study is to our knowledge, the first coal bioavailability research that demonstrated a detailed linkage between biomethane generation and bio-elimination of coal extractable compounds with connections to petrographic composition and possible environmental factors.
Coal-bed methane (CBM) production behaviour is difficult to predict or analyse due to its highly ... more Coal-bed methane (CBM) production behaviour is difficult to predict or analyse due to its highly intricate reservoir characteristics. Gas production from (CBM) reservoirs is governed by complex interaction of diffusion from the matrix to fractures and two phase gas and water flows through the fracture system to the production wells. The parameters that control the flow physics of these two systems are highly variable during the fluid production process. Generally CBM reservoir performance is evaluated using simulation software which requires experimental or/and field data to parametize the various governing equations that determine performance. Amongst the parameters that affect simulation outcomes, coal absolute permeability and relative permeability are key factors controlling CBM productivity.
Measurements of gas-liquid relative permeability of Queensland coals
The feature of water-gas two-phase flow through coal seams determines the water depletion and gas... more The feature of water-gas two-phase flow through coal seams determines the water depletion and gas production associated in coal seam gas recovery. Therefore, coal relative permeability is crucial for studies of two-phase flow behaviour in coal, which is greatly influenced by water/gas saturation and coal ranks. In this study, a permeability model incorporated with cleat size distribution and cleat tortuosity was developed to predict the relative permeability of gas and water in coals. An unsteady-state method has been applied to investigate the relative permeability of gas and water in coal samples from Surat Basin through water replacement with gas. A series of relative permeability curves for selected coals have been obtained. The measured pore size distribution, porosity and irreducible water saturation percentage are used to correlate the permeability of gas and water with gas saturation by modelling.
Transactions of the Indian Institute of Metals, Jan 4, 2017
Abstract Two phase emulsion is widely used to increase the reaction efficiency. Slag–metal emulsi... more Abstract Two phase emulsion is widely used to increase the reaction efficiency. Slag–metal emulsion is used widely in metallurgy to increase the efficiency of the process. Previously, Pb–salt emulsion system at high temperature has been studied experimentally and mathematically. In this work the study has been extended to Al–salt and Sn–salt systems to cover wider physical properties at much higher temperature, both experimentally as well as mathematically. Further the mathematical model has been verified against various published emulsion systems, having a wide variety of physical properties. Using this model, the effect of various physical properties of slag and iron, such as viscosity, density and drop size, on the iron–slag emulsion system has been studied. It is found that the iron droplets of the size of 100 µm or lesser may be entrapped in the slag if sufficient time is not allowed to settle them into the metal phase.
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