Adiabatic oven testing for spontaneous combustion assessment has been a primary method used by the Australian and New Zealand coal industries for input to the development of Principal Hazard Management Plans for mining operations. Consistency of results is important to ensure that the ratings obtained are accurate and reliable for maintaining the integrity of the database used to compare between mines and for obtaining site specific relationships. This paper presents the results from commissioning tests of four new adiabatic ovens at two different laboratories, which show the high level of reproducibility and repeatability needed for confidence in planning of future mining operations. The results cover a range of coal self-heating rates to show the validity of the testing and the reliability of the adiabatic ovens

Beamish, B.

Levi, T.

Saurat, J.

Theiler, J.

University of Queensland eSpace

Commissioning adiabatic oven testing - an inter-laboratory comparison

Research Online

University of Wollongong Research Online Coal Operators' Conference Faculty of Engineering and Information Sciences 2014 Commissioning Adiabatic Oven Testing – an Inter-Laboratory Comparison B. Beamish B3 Mining Services Pty Ltd J. Theiler CB3 Mine Services Pty Ltd J. Saurat CRL Energy Ltd T. Levi CRL Energy Ltd Follow this and additional works at: https://ro.uow.edu.au/coal Recommended Citation B. Beamish, J. Theiler, J. Saurat, and T. Levi, Commissioning Adiabatic Oven Testing – an Inter-Laboratory Comparison, in Naj Aziz and Bob Kininmonth (eds.), Proceedings of the 2014 Coal Operators' Conference, Mining Engineering, University of Wollongong, 18-20 February 2019 https://ro.uow.edu.au/coal/527 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: research-pubs@uow.edu.au 2014 Coal Operators’ Conference The University of Wollongong    324 12 – 14 February 2014 COMMISSIONING ADIABATIC OVEN TESTING – AN INTER-LABORATORY COMPARISON B Beamish1,2, J Theiler3, J Saurat4 and T Levi4 ABSTRACT: Adiabatic oven testing for spontaneous combustion assessment has been a primary method used by the Australian and New Zealand coal industries for input to the development of Principal Hazard Management Plans for mining operations. Consistency of results is important to ensure that the ratings obtained are accurate and reliable for maintaining the integrity of the database used to compare between mines and for obtaining site specific relationships. This paper presents the results from commissioning tests of four new adiabatic ovens at two different laboratories, which show the high level of reproducibility and repeatability needed for confidence in planning of future mining operations. The results cover a range of coal self-heating rates to show the validity of the testing and the reliability of the adiabatic ovens. INTRODUCTION Adiabatic oven testing has been used routinely by Australian and New Zealand coal mine operations since the early 1980’s to rate the propensity of coal to spontaneously combust (Humphreys, Rowlands and Cudmore, 1981). The parameter obtained from these tests is known as the R70 initial self-heating rate and is simply a measure of the temperature rise rate of the coal as it reacts with oxygen under adiabatic conditions from a start temperature of 40 °C until it reaches 70 °C. The higher the R70 value the higher the intrinsic reactivity of the coal and therefore the more prone it is to spontaneous combustion. R70 values are strongly rank dependent (Beamish and Arisoy, 2008a,2008b; Beamish and Beamish, 2012), with low rank coals having high R70 values (up to 99 °C/h for lignite) and high rank coals having low R70 values (less than 0.5 °C/h for medium and low volatile bituminous coals). Other coal properties such as mineral matter and coal type (dull or bright) can also affect the R70 value (Beamish and Blazak, 2005; Beamish and Clarkson, 2006; Beamish and Sainsbury, 2008). To gain a proper perspective of the overall propensity of a particular coal for spontaneous combustion it is therefore important to obtain a reliable result for R70 as an input to management planning.  Unlike other coal quality tests, there are no established repeatability and reproducibility limits for R70 testing. This is partly due to the fact that the test is very specialised and only a limited number of laboratories are available to do the test and partly due to the fact that this would be a costly exercise in terms of time and resources. To date there has been no published inter-laboratory comparison of R70 results. This paper provides an insight into the reliability of the R70 test by presenting the results of inter-laboratory comparisons during the commissioning of four adiabatic ovens at two new laboratories. Results from a decommissioned third laboratory are used for comparison to validate a seamless transition for the coal industry into the future. ADIABATIC OVEN TESTING Laboratories and coal samples  Two new laboratories have recently been established in Australia (LAB A) and New Zealand (LAB B) to provide testing capabilities for spontaneous combustion assessment. At each laboratory, two adiabatic ovens have been commissioned and comparison of the test results from each laboratory has been performed to establish repeatability for the ovens and reproducibility between the laboratories. In addition, a comparison has also been possible with previous results from a decommissioned third laboratory (LAB C) using a stored (frozen) block of coal from one particular mine. Other comparisons with previous mine results are on-going as new testing is performed for compliance at existing mines.                                             1 B3 Mining Services Pty Ltd, PO Box 1565, Toowong BC QLD 4066, basil@b3miningservices.com, M: +61 488 708 949 2 School of Mechanical and Mining Engineering, The University of Queensland, Brisbane QLD 4072 3 CB3 Mine Services Pty Ltd, PO Box 1089, Mt Ommaney QLD 4074 4 CRL Energy Ltd, PO Box 31-244, Lower Hutt, New Zealand 2014 Coal Operators’ Conference The University of Wollongong    12 –14 February 2014 325 The samples used in this inter-laboratory comparison cover a range of reactive high volatile bituminous and sub-bituminous coals from several mining regions.  R70 self-heating test procedure  The R70 testing procedure essentially involves drying a 150 g sample of <212 m crushed coal at 110 C under nitrogen for approximately 16 hours (Beamish, 2005). Whilst still under nitrogen, the coal is cooled to 40 C before being transferred to an adiabatic oven. Once the coal temperature has equilibrated at 40 C under a nitrogen flow in the adiabatic oven, oxygen is passed through the sample at 50 mL/min. A data logger records the temperature rise due to the self-heating of the coal. The time taken for the coal temperature to reach 70 C is used to calculate the initial self-heating rate for the rise in temperature due to adiabatic oxidation. This is known as the R70 index, which is in units of C/h and is a good indicator of the intrinsic coal reactivity towards oxygen. ADIABATIC TESTING RESULTS AND DISCUSSION Oven repeatability and reproducibility tests at LAB A  The R70 self-heating curves for a Newcastle high volatile bituminous coal are shown in Figure 1. These tests were conducted over consecutive days in the same oven. This comparison shows that Oven 1 at LAB A obtained R70 values of 4.73 °C/h and 4.90 °C/h, indicating excellent repeatability that is well within the limits of ±5% reported by Beamish, Barakat and St George (2000). The same sequence of repeat testing was applied to an Australian and US sub-bituminous coal and the results are shown in Figures 2 and 3, which confirm the same excellent repeatability for the adiabatic oven testing of a higher reactivity coal. In addition, the R70 value obtained by Oven 2 at LAB A for the US sub-bituminous coal (Figure 3) shows good reproducibility between the two different ovens.    Figure 1 - Adiabatic self-heating curves for a Newcastle high volatile bituminous coal showing consistency of results between tests performed on consecutive days in oven 1 at LAB A  Oven repeatability and reproducibility tests at LAB B   The R70 self-heating curves for a New Zealand sub-bituminous coal are shown in Figure 4. The repeatability for Oven 1 and the repeatability for Oven 2 are almost identical for this highly reactive coal and both are within the limits of ±5% reported by Beamish, Barakat and St George (2000). The reproducibility between the two ovens is also very high as the average R70 value for Oven 1 is 204060801001201401600 1 2 3 4 5 6 7 8 9 10Temperature (oC)Time (hours)LAB A (Oven 1) LAB A (Oven 1)R70 = 4.73 oC/hR70 = 4.90 oC/h2014 Coal Operators’ Conference The University of Wollongong    326 12 – 14 February 2014 18.45 °C/h and for Oven 2 it is 17.98 °C/h. The R70 self-heating curves for a New Zealand high volatile bituminous coal are shown in Figure 5 for tests conducted in Oven 1 and Oven 2 at LAB B. Again there is good reproducibility between the two ovens.    Figure 2 - Adiabatic self-heating curves for an Australian sub-bituminous coal showing consistency of results between tests performed in oven 1 at LAB A    Figure 3 - Adiabatic self-heating curves for a US sub-bituminous coal showing consistency of results between tests performed on consecutive days in oven 1 at LAB A and a test in oven 2 at LAB A on the same coal  Reproducibility between LAB A and LAB B  R70 test results for US sub-bituminous coal sample tested at both LAB A and LAB B are shown in Figure 6. There is excellent reproducibility between the R70 values obtained, which indicates that the sample preparation procedures as well as the oven performance at each laboratory are working very effectively. 204060801001201401600.0 0.5 1.0 1.5 2.0Temperature (oC)Time (hours)LAB A (Oven 1) LAB A (Oven 1)R70 = 33.42 oC/hR70 = 34.27 oC/h204060801001201401600.0 0.5 1.0 1.5 2.0 2.5Temperature (oC)Time (hours)LAB A (Oven 1) LAB A (Oven 1) LAB A (Oven 2)R70 = 21.38 oC/hR70 = 21.15 oC/hR70 = 22.35 oC/h2014 Coal Operators’ Conference The University of Wollongong    12 –14 February 2014 327 Consequently, there is a considerable degree of confidence in comparing results between these two laboratories.    Figure 4 - Adiabatic self-heating curves for a New Zealand sub-bituminous coal showing consistency of results between ovens    Figure 5 - Adiabatic self-heating curves for a New Zealand high volatile bituminous coal showing consistency of results between ovens  Comparison between results from LAB A and previous results from LAB C  The block of Newcastle high volatile bituminous coal tested at LAB A in 2013 was also tested at LAB C in 2007. Figure 7 shows that the self-heating test results overlap, indicating excellent reproducibility between these two laboratories. These results provide on-going confidence in the continuity of spontaneous combustion assessment at the mine extracting this particular coal. Test results from other 204060801001201401600.0 0.5 1.0 1.5 2.0 2.5Temperature (oC)Time (hours)LAB B (Oven 1) LAB B (Oven 1) LAB B (Oven 2) LAB B (Oven 2)R70 = 18.56 oC/hR70 = 17.39 oC/hR70 = 17.84 oC/hR70 = 19.05 oC/h204060801001201401600 1 2 3 4 5 6 7 8Temperature (oC)Time (hours)LAB B (Oven 1) LAB B (Oven 2)R70 = 5.30 oC/hR70 = 5.84 oC/h2014 Coal Operators’ Conference The University of Wollongong    328 12 – 14 February 2014 mines previously tested at LAB C are also showing good overlap with results from LAB A, thus maintaining the integrity of the large database across a range of mining operations around the world.    Figure 6 - Adiabatic self-heating curves for a US sub-bituminous coal showing reproducibility between LAB A and LAB B    Figure 7 - Adiabatic self-heating curves for a Newcastle high volatile bituminous coal showing continuity of results over a long period of time CONCLUSIONS The coal mining industry expects reliable and accurate results to be available for spontaneous combustion assessment as an input to the development of an appropriate Principal Hazard 204060801001201401600.0 0.5 1.0 1.5 2.0 2.5Temperature (oC)Time (hours)LAB A (Oven 2) LAB B (Oven 2)R70 = 17.82 oC/hR70 = 18.47 oC/h204060801001201401600 1 2 3 4 5 6 7 8 9 10Temperature (oC)Time (hours)LAB A (2013) LAB A (2013) LAB C (2007) LAB C (2007)R70 = 4.73 oC/hR70 = 4.47 oC/hR70 = 4.95 oC/hR70 = 4.90 oC/h2014 Coal Operators’ Conference The University of Wollongong    12 –14 February 2014 329 Management Plan. No published data exists to establish the reproducibility of R70 self-heating rates between laboratories. As part of the due diligence process in establishing two new laboratories an inter-laboratory comparison has been performed that shows the high degree of repeatability and reproducibility that can be obtained for this parameter. The results obtained provide the industry with confidence when comparing results across mining operations and also in terms of establishing site specific relationships that can be used for developing a hazard map model. Comparison of results with a laboratory that is no longer in operation shows a good degree of consistency that provides continuity for future mining operations. ACKNOWLEDGEMENTS The authors would like to thank the Coal Industry for their continued support of spontaneous combustion benchmarking, along with The University of Queensland for allowing the comparison with LAB C. REFERENCES Beamish, B B, 2005. Comparison of the R70 self-heating rate of New Zealand and Australian coals to Suggate rank parameter, International Journal of Coal Geology, 64(1-2):139-144. Beamish, B B and Arisoy, A, 2008a. Effect of intrinsic coal properties on self-heating rates, in Proceedings 12th US/North American Mine Ventilation Symposium (ed: K G Wallace Jr), pp 149-153 (The Society of Mining, Metallurgy and Exploration Inc., Littleton, USA). Beamish, B B and Arisoy, A, 2008b. Effect of mineral matter on coal self-heating rate, Fuel, 87:125-130. Beamish, B and Beamish, R, 2012. Testing and sampling requirements for input to spontaneous combustion risk assessment, in Proceedings of the Australian Mine Ventilation Conference (eds: B Beamish and D Chalmers), pp 15-21 (The Australasian Institute of Mining and Metallurgy: Melbourne). Beamish, B B and Blazak, D G, 2005. Relationship between ash content and R70 self-heating rate of Callide coal, International Journal of Coal Geology, 64(1-2):126-132. Beamish, B and Clarkson, F, 2006. Self-heating rates of Sydney Basin coals – The emerging picture, in Proceedings of the 36th Sydney Basin Symposium, pp 1-8 (University of Wollongong). Beamish, B B and Sainsbury, W, 2008. Development of a site specific self-heating rate prediction equation for a high volatile bituminous coal, in Proceedings 8th Coal Operator’s Conference (ed: N Aziz), pp 161-165, (University of Wollongong and The Australasian Institute of Mining and Metallurgy). http://ro.uow.edu.au/coal/16/. Beamish, B B, Barakat, M A and St George, J D, 2000. Adiabatic testing procedures for determining the self-heating propensity of coal and sample ageing effects, Thermochimica Acta, 362 (1-2):79-87. Humphreys, D, Rowlands, D and Cudmore, J F, 1981. Spontaneous combustion of some Queensland coals, in Proceedings of Ignitions, Explosions and Fires in Coal Mines Symposium, pp 5-1 - 5-19 (The AusIMM Illawarra Branch). 

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Commissioning Adiabatic Oven Testing – an Inter-Laboratory Comparison

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Commissioning adiabatic oven testing - an inter-laboratory comparison

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