Trace metals - their distribution and modes of occurrence
There are environmental issues associated with the production and utilisation of fossil fuels. This research programme aims to mitigate the impacts of trace metals associated with coal utilisation by understanding the factors that determine their distributions throughout coal seams and using that understanding as the basis for a robust modelling tool. In addition to identifying where they occur, the model also takes account of their modes of occurrence (in what form they are present). This factor is also crucial in determining their environmental impact.
Geotechnical Research
This research aims to reduce risks from rock instability in coal and gold mining operations. It assesses rock stability as it relates to sedimentological regime - a unique and important concept because when it comes to modelling of deposits, knowledge of sedimentology allows mapping and better risk assessment to be made than from models based on rock characteristics alone.
Coal Gasification
The major objective of this recently concluded programme was to establish the suitability or otherwise, of a wide range of New Zealand coals for the new advanced clean coal gasification technologies being demonstrated and commercialised internationally. These technologies are at the heart of many of the new high efficiency electricity generation processes. It was found that many of our coals (over 90% of known reserves) are well suited to low temperature fluidised bed gasification while high temperature entrained flow gasification was well suited to approximately half of the coals trialled. The research on fluidised bed gasification also showed a propensity toward good yields of hydrogen on the product gas and this finding lead directly to the new hydrogen energy research programme.
Solid Fuel Combustion
This research evaluates the combustion performance of a wide range of New Zealand coals and biomass fuels in terms of efficiencies and environmental impacts. Over 100 full evaluations have been carried out on the 50 kW scale rig at the CRL Energy Gracefield site. Evaluation parameters include ash slagging and fouling deposition and emission levels of particulates, PM10, dioxins, trace metals, SOx, NOx, CO2, methane, CO, acid halide gases, volatile and semi-volatile organics including polyaromatic hydrocarbons. Ash mineralogy changes are also identified and found to have a major effect on combustion performance. This is particularly the case in some incidences where coal and biomass are co-fired.
Spontaneous combustion
This research showed that the commonly held three step series of reactions required for coal to undergo self-heating from room temperature up to around 180°C was more complex than necessary. A single step process involving oxygen attack on certain sites within the coal structure was sufficient to explain all the observed behaviours along the pathway to spontaneous combustion. The research also showed that the factors controlling the rate of oxygen attack are extremely sensitive to a variety of influences. This explains why spontaneous combustion is notoriously hard to predict - and suggests it will remain so.
Coking coal research
This research identified the underlying reasons for the fact that some (by no means all) certain coking coals may loose certain of their coking properties on exposure to air and developed and easy test for predicting those coals most prone to sudden loss. This is particularly useful for mine planning - a coal with a short "shelf-life" needs to be handled differently from one with a much greater ability to retain its coking abilities.
For more information contact Dr Tony Clemens.
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