Coal Mine Waste Utilisation in NSW and Qld

This report gives an assessment of options to utilise coal mine wastes (carboniferous, drainage gas and ventilation air) for electricity generation.

The main objectives of the study were to understand the basis for potential savings in greenhouse gas emissions, and overall economics.

The approach has been to use hypothetical mining-generation-waste management scenarios that represent a range of technology combinations. For the purposes of comparison, the existing Queensland grid and a new supercritical pf power station have been used as benchmarks. Generic 2 Mtpa underground Class A and Class B, and open cut mines were used, giving a matrix of 23 technology-mine combinations using the following technologies:

• Supercritical pf (base)
• Fluidised bed combustion (eg Redbank)
• IGCC (eg US proposal, anthracite waste to liquid fuels)
• AIDG (a variant of IGCC particularly suited to waste coals)
• Gas engines (eg Appin/Tower)
• VOCSIDISER (BHPB pilot/proposed)
• Liquatech (CSIRO process, NSW and Chinese proposals)
• Combined Cycle Gas Turbine

Main findings

• The flaring/utilisation of gaseous wastes from the Class A mine reduces the GGE substantially. The power generation greenhouse gas intensity is decreased by approximately 170 kg/MWh.
• Spoil oxidation has only a very small impact on overall GGE - around 0.5% even assuming oxidation rates 20 times higher than the assumed base case.
• The lowest greenhouse gas intensity scenarios are for new gasification technologies that can utilise more mine gases and have a slightly higher overall thermal efficiency than for supercritical pf.
• FBC (eg Redbank-type options) can only achieve a reduction in GGE when mine gases are used. In all other cases FBC utilising rejects increases the overall GGE.
• For the Class A ROM cases the cost of carbon abatement is below $10/t CO2-e, and in some cases negative (ie lower generation cost and lower GGE).
• The imposition of NGAC's significantly reduces the cost of generation for cases with a lower GGE intensity (AIDG and IGCC).
• Uncertainties remain with some aspects for the most attractive technologies. Further studies are required at a proposal/semi-engineered level of detail, for a specific location. This study should be carried out with close involvement of the technology providers and potential backers, and needs to include other benefits/avoided costs not considered in the present analysis (eg associated liabilities).
• There are major uncertainties with the use of high ash, high moisture fuels in gasification. These aspects could be economically investigated in partnership with the technology providers.
• Unlike FBC, the utilisation of coal rejects alone in gasification type power generation systems can achieve greenhouse gas emission reductions over currently available technologies. The use of coal rejects in conjunction with mine gases would give further reductions. Given that the preliminary economics of these new technologies are approaching that of new pf plant, it is considered that further more detailed investigation is warranted.