ACARP ACARP ACARP ACARP
Mine Site Greenhouse Gas Mitigation

Toward the Development of an Improved Methodology For Estimating Fugitive Seam Gas Emissions From Open Cut Mining

Mine Site Greenhouse Gas Mitigation » Mine Site Greenhouse Gas Mitigation

Published: February 03Project Number: C9063

Get ReportAuthor: Abouna Saghafi, S Day, David Williams, D Roberts, A Quintanar, John Carras | CSIRO Energy Technology

The project goal was to develop a method for estimating fugitive emissions such that an individual mine could estimate its own emissions based on data related to coal gas properties and mining method. In the proposal for this work it was intended that the method would be based on:

  • gas content of the mined coal
  • gas content of uneconomic seams and neighbouring strata sent to spoil piles and
  • coal production and mining method used.

In the course of project C9063 work was carried out at seven open-cut mines in the Hunter Valley and three in the Bowen Basin where measurements of surface emission and gas content of coal were made. Numerous direct measurements of emissions from uncovered coal seams as well as gas released in coal blast holes and exploration surface holes were made. Fresh coal samples from blasted coal seams were also collected and measured for their gas content and composition. Some samples were allowed to release their gas over periods up to 2 months to investigate the kinetics of gas release.

Measurements of the gas contents in the pit for coal collected from blasted seams in the Hunter Valley mines showed seam gas content of ~0.1 m3/t to more than 1.6 m3/t. Seam gas compositions for these samples varied from almost pure CO2 to 30% CO2, with the remaining gas being CH4. For some coal samples the rates of gas desorption were also measured over a period of a few weeks. For one coal with lump size of 100 mm 50% of the gas was still present after a time period of 6 weeks and 10% still present after ~4.5 months. This suggests that there may be significant amounts of seam gas in the coal leaving the mine. Further work is required to determine the full significance of this observation.

For the Bowen Basin results, measurements of the gas contents of coal seams in pit for the three mines studied varied from almost unmeasurable quantities to 1.5 m3/t. The higher gas contents corresponded to the seams with higher methane composition.

During the course of sample collection and measurement of gas content it was clear that sampling methodology and knowledge of the length of time since the coal seams were uncovered would have significant impacts on the results. Extended time periods from coal being uncovered, to being mined, allow seam gas to desorb. This is an important consideration in the rate of release of seam gas from the uncovered yet unblasted coal seam.

Measurements of the surface emissions from Hunter Valley and Bowen Basin mines showed a wide range of emission rates. For example at one mine the emission rates varied from 0.02 to 0.45 mgs-1m-2 (CO2 equivalents) over essentially similar surfaces.

The surface emissions data generally showed wide variability in the emission rate. This is because the surface emission rates depend on

  1. The initial gas content of the coal
  2. The elapsed time from when the overburden and coal was disturbed and the measurements made
  3. The permeability of the layer over which the measurements were made which is in turn influenced by the mining method and blasting of the coal and overburden

Also the emissions can be expected to decrease with time as the gas desorbs from the target coal seam. Consequently it is not possible, at present, to generalise the above results in a manner so as to arrive at emission factors for the mines studied.

During the final phase of the project, effort concentrated on studying a purposely-drilled surface borehole at a Hunter Valley operation. Gas content of in-situ virgin coal seams up to a depth of 100 m was measured. The gas contents varied from ~0.4 to 3.7 m3/t. As expected, the smaller gas contents corresponded to the shallower seams. The seam gas composition also varied from almost pure CO2 near the surface up to almost 90% CH4 for the deepest seam at 95 m below the surface.

The results demonstrated the significance of water in the boreholes and the necessity to dewater these holes in order to measure gas emission rates. The borehole emissions approximate the emissions likely from a highwall on mine closure. This suggests a method whereby post mining emissions (after mine closure) can be estimated. Further work is required for this methodology to be developed to a stage where it can be used routinely to estimate the fugitive emissions after mine closure.

The fresh borecore samples also provided the opportunity to investigate the kinetics of gas release from fresh coal. For example a sample of the Vaux seam was allowed to desorb for a period over ~2 months. From the desorption history it was concluded that it would take 15 months in order for the coal to release 90% of its gas.

Based on the results of the current study it is clear that sampling coal from open cut operations on an opportunistic basis as attempted during this project is insufficient to allow the appropriate data to be obtained for a Tier 3 methodology to be determined. A dedicated borehole if required so that detailed gas content data can be obtained. These data could then be used, along with data from an extension of the exploration drilling program to include a limited number of gas content measurements, in order to develop a Tier 3 methodology. In addition further work on the emission rates from boreholes could see this approach developed into a method for estimating emissions from final highwalls after mining has ceased.

Underground

Health and safety, productivity and environment initiatives.

Recently Completed Projects

C26047Real Time Dust Monitor

The aim of this project was to develop a real time respirable dust m...

C29034Integrated Roadway Development: A Strategic Industry Review

This report describes the outcomes of a strategic review of Australi...

C26062New Outburst Risk Determination Measures Along With Data Gathering And Analysis For Coal Burst Assessment

Bursts are events that expel material at velocity at the time of eje...

Underground

Open Cut

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

Recently Completed Projects

C27009Tailings Revegetation Project Through “The Vegetative Water Pump”

This project aimed to greatly reduce the water trapped below the cru...

C29043Design, Construction And Commissioning Of Tyre Handler Test Apparatus

C29030Mapping Of Elemental Coal Content For Exploration And Mining

This project has analysed the concentrations of 50 elements not typi...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C26010Multi-Sloped Screening Efficiency With Changing Strokes, Frequencies, Feed Solids And Feed Rates-Pilot Plant Study

Optimising multi-sloped screens is often described as an art and the...

C28059Impact Of Water Quality In Coal Handling And Preparations Plants

The objective of this project was to deliver a concise reference do...

C27026Ultra-Low Ash Coal By 3D Binder Flotation

The objective of this project was to investigate the potential to pr...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C28067Characterisation Of Complex Coal Blends, And Methodology To Investigate Thermal Coals Based On Compositional Analysis

This project built on the outcomes from project C25049 (Fusibility ...

C28066Influence Of Coal Blending On Coke Nanoporosity And CO2 Reactivity

Reactivity of coke is one of the most important parameters that defi...

C29077The Effects Of Ash Minerals On Coke Reactivity At High Temperatures

An investigation into how coke mineralogy affects coke reactivity ha...

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement

This multi‐phase project is concerned with the mitigation of m...

C27054Optimisation Of A Thermal Flow Reversal Reactor For Ventilation Air Methane Mitigation

Ventilation air methane (VAM) generally accounts for 50-85% of the t...

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...

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

NERDDC

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

NERDDC