1.DETECTION AND PREVENTION OF SPONTANEOUS COMBUSTION GOVERNMENT ENGINEERING COLLEGE- BHUJ PREPAREDBY: SUJITSURENDRAN KATARIYAPRASHANTRAMESHBHAI SAROJRAJRAMNARESH

2. DETECTION AND PREVENTION OF SPONTANEOUS COMBUSTION A PROJECT REPORT Submitted by 1. SUJIT SURENDRAN (100150122039) 2. KATARIYA PRASHANT RAMESHBHAI (100150122095) 3. SAROJ RAJ RAMNARESH (100150122033) UNDER THE GUIDENCE OF C.H.THAKER In fulfilment for the award of the degree of BACHELOR OF ENGINEERING in MINING DEPARTMENT 3. INTRODUCTION 4. Fires in coal mines can be categorised into two groups, Viz. A) Fires resulting from spontaneous combustion of coal and B) Open fires which are accidental in nature and are caused because of ignition of combustion materials. Here, in this paper we are going to discuss for group A) kind of fires its detection, prevention techniques and newly developed ideas which can bring about a revolutionary change in the face 5. WHAT IS SPONTANEOUS COMBUSTION ??? SPONTANEOUS COMBUSTION OF COAL DEFINED AS THE PROCESS OF SELF- HEATING RESULTING EVENTUALLY IN ITS IGNITION WITHOUT THE APPLICATION OF EXTERNAL HEAT. MAINLY CO, CO2, WATER VAPOR ALONG WITH THE EVOLUTION OF HEAT DURING THE CHEMICAL REACTION. THE PROCESS TAKES PLACE AT NORMAL TEMPERATURE, BUT IT IS SLOW AND THE HEAT EVOLVED IS NOT PERCEPTIBLE AS IT IS CARRIED AWAY BY AIR UNLESS AIR IS STAGNANT. 6. How spontaneous combustion leads to fire? OXIDATION OF COAL (FUEL) AND HENCE PRODUCTION OF HEAT IF HEAT NOT DISSIPATED, TEMPERATURE OF COAL INCREASES IF HEAT NOT DISSIPATED, TEMPERATURE OF COAL INCREASES FIRE 7. MYTH & FACT ABOUT SPONTANEOUS COMBUSTION FACT : Coal is a macro-molecule which has many different components, each with their own reactivity It shows that coal contains a wide range of functional groups including those containing purely carbon and hydrogen as well as many including oxygen, such as aldehyde, alcohol, ketone, ether, ester, carboxylic acid. These latter functional groups are much more reactive than the pure hydrocarbon groups. (Kalema and Gavalas, 1987). CONVENTIONALLY : Spontaneous combustion is thought of as simply coal reacting with oxygen to form carbon dioxide and carbon monoxide which reduces the coal to a simple uniform molecule, which of course it is not. 8. AN EXAMPLE SHALL CLEAR OUR DOUBTS REGARDING COAL AND ITS SPONTANEOUS HEATING. . . . . Consider the oxidation of methane to carbon dioxide. 2CH4 + O2 = 2CH3OH CH3OH + O2 = CH2O + H2O 2CH2O + O2 = 2HCOOH 2HCOOH + O2 = 2CO2 + 2H2O ACTIVATION ENERGY REQUIRED DECREASES From the given reaction series, the latter coals in the reaction chain will generate more heat when they react with oxygen.Figure 1.3 Coal Model (Wells and Smoot 1991) 9. HOW ACTIVATION ENERGY EFFECTS THE SUSCEPTIBILITY OF SPONTANEOUS COMBUSTION? Basic Principle - The activation energy required to break aromatic hydrocarbon bonds is even higher than for aliphatic hydrocarbon bonds. High rank coals are low in oxygen content and have few reactive functional groups, they are the most aromatic. Therefore generally they are not highly prone to spontaneous combustion and produce the most heat when burnt. Low rank coals, contain more oxygen than high rank coals, and have significant concentrations of oxygenated functional groups. These are generally more reactive and prone to spontaneous combustion but do not generate as much heat when burnt. 10. LITERATURE REVIEW 11. Factors Responsible for Spontaneous Combustion A. Seam Factors : 1. Rank 7. Bacteria 2. Temperature 8. The effect of previous oxidation 3. Available air 9. Physical properties 4. Particle size 10. Heating due to earth movement 5. Moisture 11. Bacteria 6. Sulphur 12. Other minerals 12. Factors Responsible for Spontaneous Combustion (contd.) B. Geological factors: 1. Seam thickness 5. Coal outbursts 2. Seam gradient 6. Friability 3. Caving characteristics 7. Depth of cover 4. Faulting 13. Factors Responsible for Spontaneous Combustion (contd.) C. Mining Factors: 1. Mining methods 9. Multi-seam working 2. Rate of advance 10. Coal losses 3. Pillar conditions 11. Main roads 4. Roof condition 12. Worked out areas 5. Crushing 13. Heat from machines 6. Packing 14. Stowing 7. Effect of timber 15. Ventilating pressure 8. Leakage 16. Change in humidity 14. THEORIES ON SPONTANEOUS COMBUSTION Pyrite theory: Heating of coal can be caused by iron pyrites (when present in considerable proportion) and in finely powdered and dispersed state in the presence of moisture. The reaction of iron pyrites with oxygen and moisture is exothermic yields products of greater volume than the original pyrite thus opening more pore area for oxygen. The reaction can be given as - Fe S2+ 702+ 16 H2O = 2 H2SO4+ 2 Fe S04.7 H2O + 316 kcal Fe S2+ 15/4 O2+ 9/2 H2O = Fe O.OH + 2 H2SO4 The equations indicate that both oxygen and moisture, two prime weathering agents, contribute to pyrite alteration and the sulphuric acid is formed as a by-product of the alteration. 15. THEORIES OF SPONTANEOUS COMBUSTION(contd.) Bacterial theory: Different evidences showed that bacteria were capable of living on coal and in some cases such bacteria caused a slight rise in temperature of the coal. Graham observed that sterilized coal oxidized at the same rate as the un sterilized coal and concluded that mechanism of oxidation did not include bacterial activity. Finally, Fuchs however concluded that bacteria could cause only a slight heating which may not play any significant role. There is no conclusive proof to authenticate or discard this theory. 16. THEORIES ON SPONTANEOUS COMBUSTION(contd.) Phenol theory: Experiments have shown that phenolic hydroxyls and poly phenols oxidize faster than many other groups. This theory is interesting because it offers a method of determining liability of coal to spontaneous heating. Electro-chemical theory: It explains auto-oxidation of coals as oxidation-reduction processes In micro galvanic cells formed by the coal components. Coal-oxygen complex theory: Oxidation of coal is believed to be initiated at native radical sight. Formation of peroxyl radical and hydro peroxides is commonly to be thought to be they mechanism by which oxygen and moisture are initially in corporate into organic matrix. These species may react, rearrange or decomposed to form wide range of oxygen functionality in the matrix or gaseous product. 17. THEORIES ON SPONTANEOUS COMBUSTION(contd.) Humidity theory: Quantity of heat liberated by atmospheric oxidation of coal is much less than the quantity of heat required removing water from the coal. Thus it can be concluded that if the evaporation of water can be induced at the seat of heating, then the temperature of heating would decrease. Mukherjee and Lahiri (1957) proposed the following mechanism of the reaction between water and coal at 100C. (Brackets indicate chemisorptions): H2O - (H) (OH) - (H2) (0) -- (H2) +02 C + 0 --- (CO) --- CO (CO) + (0) --- (CO2) --- CO2 When it is recalled that water is an oxidation product of low temperature oxidation of coal, the above scheme well explains other possible sources of CO and CO2 in low temperature reaction between coal and oxygen. 18. PROBLEM DISCUSSION 19. Summary of problems due to spontaneous combustion The problems due to spontaneous combustion of coal can be categorized according to the method of working adopted i.e. (1) Underground, (2) Opencast (1) Underground: The universal problem due to spontaneous combustion in an underground mine is fire or precisely coal seam fire. Coal seam fires can be divided into, near-surface fires, in which seams extend to the surface and the oxygen required for their ignition comes from the atmosphere, and Fires in deep underground mines, where the oxygen comes from the ventilation. 20. Summary of problems due to spontaneous combustion (contd.) Subsidence Induced due spontaneous combustion occur due to ignition the coal closer to the surface or entrance. The smoldering fire can spread through the seam, creating subsidence that may open further seams to oxygen and spawn future wildfires when the fire breaks to the surface. Example: JCF is prone to subsidence and formation of pot holes or cracks reaching up to surface. Around 34.97 sq. km. area of the JCF is under subsidence. 21. Summary of problems due to spontaneous combustion (contd.) (2) Opencast /Surface: Fire in overburden is are noticeable in many quarries in Jharia, Raniganj, West Bokarao (Kedla Jharkhand) and other coalfields. Such dumps are on cracked surface of a goaf area the heat travels to underground through cracks resulting in ignition of coal left in underground during depillaring. Stockpiles are prone to spontaneous combustion especially when large quantities are stored for extended periods. Slope failures induced by spontaneous combustion Example, Singrauli Coalfields. 22. Summary of problems due to spontaneous combustion (contd.) (3) Other Problems: Uncontrollable fire in of coal storage in the power plant and during coal transport. Spontaneous heating can result into catastrophic in damage to power plant equipments. ENVIRONMENT IMPACT AND ECONOMIC LOSS: Greenhouse gas emissions (CO2 and CH4) from low temperature oxidation and spontaneous combustion in coal mines. Land acquisition as become the greatest challenge to BCCL and other subsidiaries of CIL post Jharia fires. India has to bear the loss of 453 million tons of coal which is locked up in 70 fires in the Jharkhand due to spontaneous heating. 23. HISTORY OF SPONTANEOUS COMBUSTION IN INDIA History of coal mines fires due to spontaneous heating can be traced back to the year 1865, when the first fire was reported in Raniganj Coalfields. Critical-investigations reveal that fires due to Endogenous cause i.e., spontaneous heating, are more severe than Exogenous one. Further it is observed that the occurrence of spontaneous heating in underground workings got reduced considerably in 1969 to 1972, 'thereafter start in- creasing giving the peak maxima in 1977 24. Dangerous occurrences due to spontaneous heating between 1960 and 1974 Sl. No. Cause 1975 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 1. Spontaneous Heating Underground 18 17 23 12 14 18 8 8 19 13 19 19 19 12 9 14 2. Spontaneous Heating Surface 19 19 12 2 0 4 - 3 3 1 5 1 1 1 - - 3. Spontaneous Heating O.C Workings 1 2 5 1 2 - 1 2 2 2 3 2 2 1 2 - TOTAL 38 38 40 15 16 22 9 13 24 16 27 22 22 14 11 14 25. Sr. No. Cause 1960 61 62 63 64 65 66 67 68 69 70 71 72 73 74 1. Spontaneous Heating Underground 9 5 10 12 8 10 10 11 10 8 6 3 6 11 11 2. Spontaneous Heating Surface 10 22 11 22 26 10 19 9 14 9 13 11 16 17 20 3. Spontaneous Heating O.C Workings 3 6 2 3 7 2 4 2 1 4 1 4 3 1 1 TOTAL 22 33 23 37 41 22 33 22 25 21 20 18 25 29 32 Dangerous occurrences due to spontaneous heating between 1975 and 1990 26. SLOPE FAILURES AT SINGRAULI DUE TO SPONTANEOUS HEATING Date of Failure Description of Events 10 February 1997 A slope failure affected the lower section of the steepest part of the dragline dumps, to a height of 48 m. The total height of the tip before failure was inclined at 54 . The rotational slide was 140 m wide and the coal underwent translational shift by 5 m Along the floor of the seam, in the dip direction. The collapsed material accumulated Up to 15 m in the mined out section of the workings. 28 May 1997 A slope failure affected the lower 52 m of the dump material. The total height of the tip Before failure was 82 m and was inclined at 51. The width of the slide was 51 m, and The tip material accumulated 18 m into the workings. 3 October 1997 The total pre-slide dump height was 106 m and the overall slope was 48, steeping to 76 in the lower 50m of the slope. Failure affected the dragline dump 50 m high and 220 m long. The collapsed material accumulated on the floor of the mine where the Turra seam was being extracted. The coal pillar underwent translational shift by 7 m towards the high wall face. 19 September 1998 A slope failure involved the failure of a 94 m high, 47, dragline tip. This created a scar 75 m high and 250 m long and caused the down-dip translational shift of the coal pillar by 65 m, stopping just short of the high wall. 27. DETECTION AND PREVENTION OF SPONTANEOUS COMBUSTION 28. Detection Methods: 1 Principal Techniques: By Physical Indications By Chemical Indications 1) PHYSICAL INDICATIONS The different odors at different stages can alarm about spontaneous heating At initial stage we find faint haze, moisture deposition on roof, side and timber and smells like gob-stink Petrol like odor at intermediate stage. Fire stink at last stage approaching ignition. 29. Detection Methods (contd.) Keeping systematic records of dry and wet bulb temperatures may also alarm about spontaneous combustion. A Whirling Hygrometer Drawbacks: The odors may be interrupted by Decay of wood in warm damp places, Tarred brattice cloth, Lubricating oil. Strata temperature in deep mines can and percolation of ground water can result in high dry and wet bulb temperatures(as observed during training in Moonidih Colliery). 30. Detection methods (contd.) 2) Chemical Indications The method includes detection by collection and interpretation of mine samples. Graham's Ratio is most conventionally used which detects spontaneous heating by oxygen deficiency ratio . Grahams Ratio = / 0.1 -0.5% is normal to the coal mine 1% indicate existence of spontaneous heating 2% indicates heating in advanced stage approaching active fire. 3% or more indicates active fire. 31. Detection methods (contd.) Drawbacks: It cant be always assumed that oxygen is consumed due to oxidation. The use of the fresh air nitrogen concentration of 79.02% includes argon (Ar) in the amount. Use of this equation is only valid for samples where the initial gas has the same oxygen to nitrogen ratio as fresh air.Dragger Multigas detector for detection of percentages of CO and CO2 32. Other Techniques and Work by CMRI 1) Tele monitoring system : This system essentially comprises of temperature sensors, toxic and combustible gas analyzers placed in underground workplace environment and other fire prone areas and connected to the pit top computer through a data acquisition system. IMPEMENTED IN : Kotadih Colliery (ECL) & New Manjari Colliery (WCL). In reopening a sealed of area at VK7 incline, SCCL this system worked successfully. 33. Other Techniques and Work by CMRI (contd.) 2) Thermal Oxidation Of Coal CMRI It is a laboratory technique suggested by CMRI which uses thermo- decompositional analysis of coal sample. The coal sample is kept in a reaction vessel and temperature of which is measured by thermocouple and regulated with a programmable temperature controller. Air samples are collected through water displacement methods and interpreted with a chromatograph at every 20C.Apparatus For thermal oxidation of coal 34. Prevention Methods 1) Control measures to reduce or eliminate oxygen from the process: i. Sealing of the fire If the fire is inaccessible, e.g. in a goaf area and there are chances of spontaneous combustion, it has to be sealed off. The stoppings are constructed to seal a fire area are of the following types depending upon the purpose they serve 1. Preparatory Stoppings 2. Emergency stopping or temporary stopping 3. Permanent Stoppings. ii. Dozing over This can done to douse fire in opencast mine. 35. Prevention Methods (contd.) iii. Cladding of the high wall. Cladding refers to Covering of the highwall or the overburden surface with a layer of inert material, usually sand or soft soil excavated during the removal of overburden. 2) Control measure to reduce the temperature and hence the reaction rate: i. Water Flushing with bitumen. Water is flooded in worked out area in u/g mines where there is propensity of heating. If the area to be doused is large it can cause gas explosions. 36. Prevention Methods (contd.) ii. Nitrogen Injection : The mine we visited during our vocational training (Moonidih Colliery BCCL) had faced spontaneous heating in F1 longwall caving panel of XVI combined seam was detected in August 1993 in, a degree III gassy mine. The ratio of goaf-volume and quantity of N2 pumped was 1:1.65. N2 injection helped in salvaging the longwall equipment. N2 flushing has a drawback that the cost of liquid N2 is high. In 1982, during the firefighting operations at Laikdih deep colliery, the cost of N2 gas was estimated at $ 11,628 per million m3 and this cost rose to $ 18,605 per million m3 in 1986. Nitrogen Injection in u/g mine 37. Prevention Methods (contd.) 3) Removal of the fuel: Excavation of hot or burning material. This is possible if the igniting materials are not spread in a wide area. Work done by CMRI : Development techniques for immediate halting of advancing fire by gel infusion through coal massive; Development of high expansion foam and its application technology for combating mine fires in the mine roadways; Development of fire protective coating material for preventing spontaneous heating in coal mines ; 38. Prevention Methods (contd.) Development of pressure balancing techniques for controlling fire in underground coal mines; Development of fire gallery model for studying the different conditions which take part in occurrence of fire; Material development research like grouting material, remote sealing, inhibitors for controlling for controlling and preventing fire. 39. Future Prospects Our work in next semester 40. Future Prospects Use of Radioactivity For early detection of Spontaneous Heating Use of Infra-red techniques for detection. Use of remote sensing for monitoring fires in surface , subsurface fires and subsidence induced by spontaneous heating. Colloid injection and other better techniques that can prove better than nitrogen and water injection. 41. Thank You !!!