Mine Site Greenhouse Gas Mitigation

Estimation Of The Residual Gas Content In Mined Coal And Coal Waste

Mine Site Greenhouse Gas Mitigation » Mine Site Greenhouse Gas Mitigation

Published: February 12Project Number: C20004

Get ReportAuthor: L Connell, M Lu, Z Chen, D Chen | CSIRO Advanced Coal Technology

This report presents the results of a project on the behaviour of residual gas in mined coal and waste components after mining. The objective of the project is to estimate the residual gas content in product and waste coal at the point of disposal as this may represent an important factor in the calculation of a mine's fugitive gas emissions.


Coal in the sub-surface often naturally contains methane mostly as an adsorbed gas. The quantity of methane stored in the coal is a function of the pore pressure. Once mined the coal and other carbon rich geologic waste material, such as low grade coals and carbonaceous shales, will involve a broad range of fragment sizes within which will be residual gas. The mechanisms that could drive migration of the residual from the mined material will be a combination of the pore and partial pressure gradients between the gas within the fragments, the void space between the fragments and then the surrounding atmosphere. When initially mined, gas contents could be expected to be relatively high and thus provide a pore pressure gradient to drive gas flow into the void space between the coal fragments. Over time the pore pressure will become equilibrated with atmospheric pressure and gas will diffuse out of the coal driven by the partial pressure or concentration differences, such as the difference between a coal rich in methane and air where almost no methane is present.


Existing measurements of the gas content of mined coal are extremely limited. Only one study was available to the project; measurements made by Day et al. (2007) for ACARP C15077, where samples of product coal were collected from a number of mines shortly after processing. In these samples there was a distinct contrast between the low gas contents found with open cut mines and the high methane contents with samples from gassy underground mines. However this is a complex problem influenced by a wide range of operating conditions and coal properties, including storage times and processing practices.


The analyses presented in this report focus on the diffusion limited stage after pore pressure has equilibrated with atmospheric pressure and used published information on product coal particle size distribution but also examined the sensitivity of the predictions of the residual to the coal fragment particle size. The physical arrangement of the product coal is also an important aspect of this problem as it determines the diffusion lengths that gas must travel and thus the rates of gas emission. In the analyses presented in this report two scenarios were considered; product coal within a hypothetical stockpile and within a rail transport hopper.


The predictions were performed by deriving a set of differential equations to describe the gas migration process (based on accepted approaches to describing gas migration in coal) and then implementing these in the computational multi-physics package, COMSOL. This provided an efficient approach to investigating the various physical processes and arrangements operating. The physical properties were estimated from the literature, in particular, ACARP reports. However an important step which was not possible within the scope of the project was testing of the predictions against observations of the residual gas content with time. As a result these predictions should be treated as rough guides as to the behaviour of the residual gas content with time.


It is assumed here that during and shortly after processing the run of mine coal into smaller fragments the pore pressure within the coal fragments will rapidly equilibrate to atmospheric pressure. This means that the initial residual gas content is the gas content at atmospheric pressure calculated directly from the adsorption isotherm; thus any gas within the coal above this is assumed to become fugitive during processing. This important point should be noted in calculating the fugitive emissions.


As expected the large size of the stockpile, involving longer gas migration pathways, meant that the rate at which the residual gas content decreased with time was much slower than for coal within the much smaller rail hopper. In addition, while the particle size of the product coal was important for gas migration from the coal hopper, it was much less important for coal within the stockpile, since gas diffusion within the coal void space played a more important role.


Health and safety, productivity and environment initiatives.


Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C19024Establishing Ecologically Sustainable Mine Water Release Criteria In Seasonally Flowing Streams

Extreme rainfall conditions in the Fitzroy Catchment over an approxi...

C25030Coal Mine Open Pit Final Void Closure And Relinquishment - Addressing Uncertainty In Coal Mine Environmental Planning

This report addresses uncertainties faced by coal mine operators whe...

C27046Estimation Of True Deformation Vector From Slope Radar Monitoring

Slope deformation radar monitors are now widely used in open cut coa...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27004Improving Coal Flotation With Oscillatory Air Supply

This report provides detailed information on coal flotation with os...

C25018Improving Solids Recovery And Moisture Reduction In Ultrafine Coal Dewatering

This report provides detailed information on fine coal dewatering in...

C27028Lab Froth Flotation Testing Guide With Coal Quality

Correct outcomes from laboratory froth flotation testing in coal bor...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C26039Nanoporosity In Cokes: Their Origin, Control And Influence On CO2 Reactivity

This project using the outcomes of previous project C24060, examine...

C28063A Comprehensive Technical Review Of High-Efficiency Low-Emission (HELE) Pulverised Coal Combustion Technologies For Power Generation

Research and development has been undertaken worldwide to realise co...

C28064Carbon Structure Transformation During Coking Of Australian Coking Coals: Better Understanding The Coke Formation

Carbon structures of coke that are formed during the plastic layer a...

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C28076Selective Absorption Of Methane By Ionic Liquids (SAMIL) - Phase 2 Demonstration In A Packed Bed Reactor

An alternative approach to high temperature oxidation of ventilation...

C26004CFD Modelling Of Reverse Thermal Oxidisers For VAM Abatement - CFD Modelling Of Fixed-Bed RTO Devices

The project is part of a larger multi‐phase program of study a...

C27058Technological Assessment Of A Recycle Reactor For VAM Abatement

Underground coal mining emits high volumes of methane, diluted in ve...

Mine Site Greenhouse Gas Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community


National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook