John Carras

Self-heating of coal and related materials: Models, application and test methods

Abstract The current understanding of the phenomenon of self-heating of coal and coal mine waste dumps is discussed along with the status of a number of numerical models developed to predict self-heating behaviour. Within this framework the commonly used industrial tests to predict the self-heating propensity of coal are assessed and their limitations identified. Future work requires further elucidation of the role of water on the oxidation rate of coal and other carbonaceous materials, as well as validation of numerical models on commercial size coal stockpiles.

Measurements of trace gases emitted by Australian savanna fires during the 1990 dry season

During 18–23 July 1990, 31 smoke samples were collected from an aircraft flying at low altitudes through the plumes of tropical savanna fires in the Northern Territory, Australia. The excess (above background) mixing ratios of 17 different trace gases including CO2, CO, CH4, several non-methane hydrocarbons (NMHC), CH3CHO, NOx (− NO + NO2), NH3, N2O, HCN and total unspeciated NMHC and sulphur were measured. Emissionratios relative to excess CO2 and CO, and emissionfactors relative to the fuel carbon, nitrogen or sulphur content are determined for each measured species. The emission ratios and factors determined here for carbon-based gases, NOx, and N2O are in good agreement with those reported from other biomass burning studies. The ammonia data represent the first such measurements from savanna fires, and indicate that NH3 emissions are more than half the strength of NOx emissions. The emissions of NOx, NH3, N2O and HCN together represent only 27% of the volatilised fuel N, and are primarily NOx (16%) and NH3 (9%). Similarly, only 56% of the volatilised fuel S is accounted for by our measurements of total unspeciated sulphur.

Measurement and modelling of pollutant emissions from Hong Kong

Abstract During November 1997 a detailed airborne investigation of air pollution in the Hong Kong region was undertaken. The airborne investigation formed part of a larger study funded by the Hong Kong Environmental Protection Department (EPD) and included the development of a state of the art numerical air quality modelling system to simulate air pollution in the Hong Kong region. The system consisted of a numerical weather prediction module, a prognostic air–chemistry/transport model, an emissions inventory system and a Graphical User Interface for display of results and preparation of simulations. The purpose of the airborne investigations was to provide data on the fluxes of selected pollutants arising from or entering the Hong Kong airshed as a check on the inventory. In addition the aircraft was to provide data on other pollutants of interest particularly with respect to the formation of photochemical smog. This paper describes the inventory data obtained from the aircraft and makes comparisons between the predictions of the model and the aircraft data for one of the days when the aircraft was able to be used to estimate the total fluxes of NMHC and NOx from the study area.

A comparison of three methods for the quantification of greenhouse gas emissions from spontaneous combustion in open-cut coal mines

Greenhouse gas emissions from spontaneous combustion in coal mines are currently excluded from national inventories by the United Nations Framework Convention on Climate Change because there are no robust methods available to quantify the emissions. This article reports on investigations of three approaches being pursued with the aim of developing methods which are sufficiently robust to enable these emissions to be included in inventories. The first method was based on the use of airborne thermal infrared photography coupled with chamber measurements of emissions from hot mine spoil pile surfaces. In the second method, crosswind traverses of the plume using an instrumented vehicle were used to estimate the emission fluxes. The third method was based on inverse atmospheric modelling using stationary CO2 monitors. All three methods showed considerable scatter in their estimates but also showed appreciable overlap. While the three methods used in this study have shown convergence, there is still considerable uncertainty associated with any single approach.

Chapter 1 – Spontaneous Combustion in Open-Cut Coal Mines: Australian Experience and Research

Spontaneous combustion results from self-heating caused mainly by low temperature oxidation of coal and other carbonaceous materials. In open-cut coal mines large quantities of carbonaceous waste material are disposed of in spoil piles within the mine site. Some of this material may be sufficiently reactive to begin to self-heat which can ultimately lead to spontaneous combustion in the spoil piles if not properly managed. Uncontrolled fires in spoil piles present a number of problems including safety hazards for mine personnel, the production of toxic gases, damage to rehabilitated land, and emission of greenhouse gases. Although a great deal of research into spontaneous combustion in coal has been conducted over many years, there has been comparatively little investigation of carbonaceous materials in spoil piles. In this chapter, some research aimed specifically at understanding self-heating and spontaneous combustion in spoil materials is reviewed, especially in the context of Australian open-cut coalmines. The principal conclusions of this work and resultant mine site management practices developed to minimize the occurrence of self-heating are discussed.