prevention and control of spontaneous combustion - Mining and

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Examination of chemical constituents • Rank • Petrological classification • Moisture • Volatiles • Oxygen (DAF basis) • Sulphur content. Thermal studies • Initial temperature • Crossing point temperature • Crossing and ignition point • Modified CPT • DTA method • Russian tests of ignition temp • Olpinski index • Adiabatic calorimetry. Oxygen avidity • Glasser test • Peroxy complex analysis • Rate studies • Russian U index • Wet oxidation method • H2O2 methods • Other oxidation methods (KMnO4 method). Based on extrinsic characteristics • Risk mapping • Risk indexing. Preventing spontaneous combustion Spontaneous combustion is a time-dependent phenomenon. Early attention to the potential sources of problems may prevent occurrences of heating progressing to full-scale spontaneous 7
combustion. Examples of commonly used methods of dealing with spontaneous combustion in different circumstances are detailed below. Tailings (plant rejects) – Tailings dams should be capped with at least one metre of inert (noncarbonaceous) material, topsoil should be added and the whole area revegetated. Coarse reject (discard) – Problem material should be placed in layers and compacted using a roller, particularly on the edges of the dump, so that the infiltration of oxygen is minimal. The total layer thickness should be no greater than 5m and each layer should be covered by a 1m thick layer of inert (non-carbonaceous) material. The final landform should be such that erosion and runoff is minimised and new areas of discard coal are not exposed to the atmosphere. Spoil heaps in strip-mining – The sequence of spoiling should result in accumulations of coal material, particularly if pyritic, being buried under inert spoil. Although difficult to achieve, the most reactive material should be enclosed within less reactive material using the principles developed at Grootegeluk Mine. If this is not possible then rehabilitation of the spoil heaps should take place as soon as possible and a thick layer of softs should be used before topsoil is added. Product (coal) – Product stockpiles and coal inventory in the cut should not be left longer than the incipient heating period. There is considerable variation in the time taken for heatings to occur, but most mines have an understanding, based on experience, of the time limits for their product. An indication of the length of this period can be obtained from specific tests, such as the CSIR Bunker Test. Both run-of-mine (RoM) and saleable product coal have been known to be susceptible to spontaneous combustion. Particular caution should be taken where there is segregation of material sizes because of the stockpiling/dumping technique. A layer of coarser particles at the base and edges of stockpiles may result in increased ventilation passing through the coal. The situation is particularly aggravated by prevailing hot, moist winds and this may lead to a higher risk of spontaneous combustion in the summer months. Shape and orientation of stockpiles and dumps – The height of stockpiles and dumps may be a critical site-specific consideration. When the technique is feasible, considerable benefit can be obtained by building dumps in relatively thin compacted layers. Longer-term stockpiles, particularly of product coal, can be further safeguarded by spraying the surfaces with a thin (bituminous) coating to exclude air. Highwalls at surface mines – Coal spalling from the seams should not be allowed to remain against the highwall. If the coal is liable to spontaneous combust, loose coal should be cleared away promptly and/or the highwall reinforced with soft, spoil material if it is to be left for an extended period. At the end of the life of mine complete rehabilitation and closing of the final void should take place. If this is not undertaken the highwall should be effectively sealed with water, clay or a thick blanket of inert spoil. Detecting spontaneous combustion Spontaneous combustion fires can be detected fairly early in their development, i.e. before any obvious smoke and/or flame. Any of the following may assist in early detection, depending upon the particular circumstances. 8
Page 1 and 2: PREVENTION AND CONTROL OF SPONTANEO
Page 3 and 4: The guidelines have also built upon
Page 5 and 6: Case study 3 (ATCOM Colliery) .....
Page 7 and 8: How to use the best practice guidel
Page 9 and 10: temperature is raised and, accordin
Page 11: on a complex relationship of a rang
Page 15 and 16: Other gases, all of which are flamm
Page 17 and 18: ank of coal, (3) weathering, (4) mo
Page 19 and 20: literature but probably the most im
Page 21 and 22: In addition to heatings during mini
Page 23 and 24: • Mono-valents such as sodium chl
Page 25 and 26: Approximately 87% of the sand is re
Page 27 and 28: • Burning spoils • General prob
Page 29 and 30: Control of spontaneous combustion a
Page 31 and 32: • The use of a pre-split blasting
Page 33 and 34: Control of spontaneous combustion a
Page 35 and 36: within the time taken for spontaneo
Page 37 and 38: Appendix 1 ATCOM Colliery Hot Hole
Page 39 and 40: • The survey department will desi
Page 41 and 42: Hot hole area preparation • Areas
Page 43 and 44: DRILL RIG BIT SIZE Revision Date: S
Page 45 and 46: DATE : ………………………
Page 47 and 48: BLAST TYPE: PRESPLIT PARTING OVERBU
Page 49 and 50: FROM : BLASTING SUPERVISOR TO : MAG
Page 51: Appendix 2 Kleinkopje Colliery Spon
Page 54 and 55: All of the mines experiencing serio
Page 56 and 57: During the top coal removal, the in
Page 58 and 59: etween the pillars, are drilled 0.5
Page 60 and 61: When buffer blasting is not practic
Page 62 and 63:
Appendix 4 Definitions 57
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Cladding - Covering of the highwall
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Water cannon - Water cannons are us
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Appendix 5 COALTECH 2020 A literatu
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Table of contents Preface .........
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1 Introduction Spontaneous combusti
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Pyrites The oxidation of pyrites ha
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Exogenous factors 5 Temperature in
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of extraction, in that the producti
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They also identified the factors fo
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Initially the coal sample and vesse
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Gouws and Wade 27 found with their
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Figure 3.1.2: ESSH expert system ar
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and larger meet this criterion. How
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• The base should be reasonably l
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gases at different stages during th
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on remote sensing by ITC. Two case
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3) SPOT Band 3 and TM Bands 5 and 7
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6 Control of spontaneous combustion
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Liquid phase: Cools by conduction a
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6.1.2.3 Biotechnological methods In
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Accessing hot spots is usually a pr
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17 Guney, M., Equilibrium Humiditie
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48 Anonymous 1, Biological Oxidatio
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27. Bardocz V, A New Hypothesis Con
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59. Chakravorty R N, Kolada R J, Pr
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89. Drakeley T J, The Liberation of
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120.Gill F S, Browning E J, Spontan
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149.Haldane J S, Makgill R H, The S
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179.Kim AG, Laboratory Determinatio
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208.Singh R N, Denby B, Ren T X, A
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236.Francart W J, Beiter D A, Barom
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266.Gaofeng K, Environmental Monito
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290.Langer G, Hermulheim W, Bresser
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Premature detonations and blasting
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Samples of minerals for testing mus
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isks. There are numerous publicatio
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