CHAPTER 1 INTRODUCTION TO COAL MINING INDUSTRY

Transcription

1 CHAPTER 1 INTRODUCTION TO COAL MINING INDUSTRY Economic growth world over is driven by energy, whether in the form of finite resources such as coal, oil and gas or in renewable forms such as hydroelectric, wind, solar and bio-mass or its converted form, electricity(power). Increased energy consumption (especially of electricity) is inevitable with higher GDP growth. Coal was created by the fossilised remains of plants and has high carbon content. Coal is the world's most abundant and widely distributed fossil fuel. Coal is still the primary energy source for several countries world-wide and provides between 25% and 28% of the world's primary energy. Worldwide, coal is the main fuel for the generation of electricity as the price of coal is cheap compared to other fuels. It is also the highest polluting source of electricity. The other major uses of coal are in the production of steel and synthetic fuels. Singareni Collieries Company Limited (SCCL) is the only coal mining company in south India. Bulk of coal production in India is from government - owned mines managed by Coal India Limited (CIL) and Singareni Collieries Company Limited (SCCL). SCCL is a public sector mining organization is the largest producer of coal in India after coal India Limited (CIL) with manpower of 77,000 and catering the energy needs of southern part of India. The company is now operating 42 Underground (UG) mines and 15 Open Cast (OC) mines. 1.1 Global Coal Mining Industry Top Hard Coal producers: Over 5845 million tonnes (Mt) of hard coal is currently produced worldwide and 951Mt of brown coal/lignite. The largest coal producing countries are not confined to one region - the top five hard coal producers are China, the USA, India, Australia and South Africa. Much of global coal production is used in 1

2 the country in which it was produced; only around 16% of hard coal production is destined for the international coal market. Tablel.l Top Hard Coal producers in world Top Ten Hard Coal Producers 2009 China 276 lmt Indonesia 246Mt USA 1007Mt South Africa 236Mt India 490Mt Kazakhstan 104Mt Australia 325Mt Poland 84Mt Russia 247Mt Colombia 79Mt Source: International Energy Agency Coal in Electricity Generation Coal is the major fuel used for generating electricity worldwide - countries [108] heavily dependent on coal for electricity. Electricity demand grows more rapidly than for any other end-use fuel, at an average annual rate of 2.7%. Its projected share in world final energy consumption increases from 17% today to 20% by 2020.Coal provides for around 22% of global primary energy needs and is generating around 41% of world s electricity at present shown in fig 1.1.Coal is likely to maintain its position as the world s largest source of electricity generation through to China and India, with ample coal reserves and rising electricity demand, will contribute more than two-thirds to the increase in world demand over the projection period. 2

3 Tablel.2 worldwide - countries heavily dependent on coal for electricity South Africa 94% Israel 71% Morocco 57% Poland 93% Kazakhstan 70% Greece 55% China 81% India 68% USA 49% Australia 76% Czech Rep 62% Germany 49% Coal & Electricity Other* 2% Coal 41% Hydro 16% Oil 6% Nuclear 15% Gas 20% Figl.l Total World Electricity Generation by Fuel Coal Reserves worldwide Coal reserves are available in almost every country worldwide, with recoverable reserves in around 70 countries. At current production levels, proven coal reserves are estimated to last 122 years. In contrast, proven oil and gas reserves are equivalent to around 42 and 60 years at current production levels respectively. Over 67% of oil and 66% of gas reserves are concentrated in the Middle East and Russia. 3

4 1.1.4 World Coal Consumption by Region ( ) Percentage of coal consumption by the different countries in the world is shown in figl.2. Figl.2 World Coal Consumption by Region 1.2 Coal mining industry - Indian scenario Coal is the most important and abundant fossil fuel in India. It accounts for 55% of the country's energy need. The country's industrial heritage was built upon indigenous coal. Commercial primary energy consumption in India has grown by about 700% in the last four decades. The current per capita commercial primary energy consumption in India is about 350 kgoe/year is well below that of developed countries. Driven by the rising population, expanding economy and a quest for improved quality of life, energy usage in India is expected to raise around 450 kgoe/year in Considering the limited reserve potentiality of petroleum & natural gas, eco-conservation restriction on hydel project and geo-political perception of nuclear power, coal will continue to occupy centre-stage of India s energy scenario. 4

5 With hard coal reserves around 246 billion tonnes, of which 92 billion tonnes are proven, Indian coal offers a unique ecofriendly fuel source to domestic energy market for the next century and beyond. Hard coal deposit spread over 27 major coalfields, are mainly confined to eastern and south central parts of the the country. About 88% of the total coal production in the country is produced by various subsidiaries (a total of 390 mines) of Coal India Ltd. which is the largest supplier of coal (and one of the largest taxpayers) in the country The only other major producer outside of CIL,is the Singerani Collieries Company that is located in Andhra Pradesh. Singerani has 37 underground and 19 opencast mines, and produced 50.4 million tonnes of coal in The state-wise distribution of coal resources As a result of exploration carried out up to the depth of 1200m by the GSI, CMPDI and MECL etc, a cumulative total of Billion tonnes of Geological Resources of Coal have so far been estimated in the country. The state-wise distribution of coal resources and its categorisation are as follows: Tablel.3 The state-wise distribution of coal resources and its categorisation State Geological Resources of Coal (in Million Tonnes) Proved Indicated Inferred Total Andhra Pradesh Arunachal Pradesh Assam Bihar Chhattisgarh Jharkhand Madhya Pradesh Maharashtra Meghalaya

6 Nagaland Orissa Sikkim Uttar Pradesh West Bengal Total 1E Status of Coal Resources in India during Last Five Years: As a result of Regional, Promotional and Detailed Exploration by GSI, CMPDI and SCCL etc, the estimation of coal resources of India has reached to Bt. the estimates of coal resources in the country during last 5 years are given below: Table 1.4 Coal resources in the country during last 5 years Year Geological Resources of Coal(in Million Tonnes) Proved Indicated Inferred Total Indian Coal Occurrences Coal resources of the country are mainly reported from two different stratigraphic levels (geological period) and basinal set-up - Permian sediments deposited in intra-cratonic Gondwana basins and Early Tertiary coal and lignite occurrences in peri-cratonic near shore basins and shelf. Gondwana basins of Peninsular India are generally restricted in the eastcentral part of the country along some well defined linear belts namely - Damodar-Koel, Son- Mahanadi, Satpura, and Pranhita-Godavari valleys besides the Rajmahal basin. In addition rocks belonging to Gondwana 6

7 Formation are also reported beneath the Ganga and Brahmaputra alluvium in Bengal basin and also below the Deccan Trap. Report of coal occurrences (mostly of academic importance) is also available from Foot Hills of the Eastern Himalaya. Economic deposits of Tertiary coals occur in two distinct geotectonic domains of the Northeastern India - one in the shelf sediments of Meghalaya and Assam and the other is in the intricately thrusted belt (Schuppen Belt) of Assam, Nagaland and Arunachal Pradesh. Lignite occurrences of economic importance are found within the Tertiary sediments, occurring along the pericratonic basins of the southeastern and western Peninsular Region. Geographically coalfields of economic viability are distributed mainly in the states of Orissa, Jharkhand, Madhya Pradesh, Chhattisgarh, West Bengal, Maharashtra. Andhra Pradesh, Uttar Pradesh, Assam, Arunachal Pradesh, Meghalaya, Nagaland and Sikkim. Figl.3 Coal Fields of India 7

8 STATEWISE COAL RESOURCE (. b.lb» tonne) Figl.4 State wise Coal Resources 1.3 Coal Mining at A.P (Singerani Collieries Company Limited) The Singareni Collieries Company Limited (SCCL) is a Government coal mining company jointly owned by the Government of Andhra Pradesh and Government of India on a 51:49 equity basis. The Singareni coal reserves stretch across 350 Km of the Pranahita - Godavari Valley of Andhra Pradesh with a proven geological reserves aggregating to whopping 8791 million tonnes. SCCL is currently operating 14 opencast and 36 underground mines in 4 districts of Andhra Pradesh [105] with manpower around 70,000. Table 1.5 Overview of SCCL Mines Linder Ground - 36 : Opencast - 14 Manpower (as on ) 68,451 Targetted Production( ) 51.3 Million tonnes Targetted Production( ) 50.4 Million tonnes Actual Production( ) Million tonnes Output per manshift ) 2.72 Tonnes Major consumers Power,Cement and others 8

9 1.3.1 Performance of SCCL New benchmarks in production have been created. New heights of productivity have been scaled. New technologies are being deployed. With innovative management practices and eco-friendly measures aimed at the welfare of the workmen, there is a new buzz at Singareni. Tablet.6 Overall Performance of SCCL (2005 to 2010) Coal Production (MilLTons) Coal despatches (MilLTons) j ' Productivity(OMS) OB j Removal(Mill.Cu.Mtr) 75,573 70,586 : Manpower 86,025 82,224 69,043 Table 1.7 Production Performances NO. OF MINIES PRODUCTION (Lakh Tonnes) YEAR Under Open Underjground Opencast Total Total ground Cast Target Actual Target Actual Target Actual

10 1.3.2 Technology in SCCL The SCCL had put up a pioneering effort in the introduction of mechanization in coal mining industry in India. Continuous efforts have been made to replace progressively the conventional technology and to introduce modem machinery. Technology occupies the top position among the priorities of perspective plan and it certainly holds the key to the objectives and targets of the plan. The coal cutting machine -Gathering arm loader-shuttle car is a system of mechanisation along with belt conveyors for development of seams was successfully used by SCCL from the late 40s to the early 80s. This system of mechanisation was not adaptable for depillaring operations and therefore found only limited application in development of flat seams. Subsequently side dump loaders (SDL) and load-haul-dumpers (LHD) which combine the operation of loading of coal at the face and transport by belt conveyors became available.sccl introduced these machines in the years 197 SDLs and LHDs need gradients flatter than about one in six for efficient operation and in view of the limited deposits with such gradients, application of these machines are not extended to all the underground mines 8 and 1979 respectively. LHDs are in use for mechanized depillaring operations since Coal Reserves in A.P Table 1.8 District-Wise, Grade-Wise and Depth-Wise Proved Geological Reserves of Godavari Valley Coalfield (A.P) District ADILABAD Total Depth (m) Reserve (m.t.) > TOTAL

11 KARIMNAGAR WARANGAL KHAMMAM TOTAL >600 - TOTAL > TOTAL >600 - TOTAL > TOTAL Fig 1.5 OB Dumping-In-pit Crusher & Conveyor Technology 1.4 Coal Mining Geology Coal is a sedimentary rock formed from plants that flourished millions of years ago. Coal formation began during the Carboniferous Period (known as the first coal age), which spanned 360 million to 290 million years before present. Coal formation continued throughout the Permian, Triassic, Jurassic, Cretaceous, and Tertiary Periods (known collectively as the second coal age), 11

12 which spanned 290 million to 1.6 million years before present. Coals formed during the first coal age are older, so they are generally located deeper in the earth's crust. The greater heat and pressures at these depths produces highergrade coals such as anthracite and bituminous coals. Conversely, coals formed during the second coal age under less intense heat and pressure is generally located at shallower depths. Consequently, these coals tend to be lower-grade sub bituminous and lignite coals. We see that with the starting of the theorized coal formation periods large portions of Asia, Europe and North America were located in the tropics area of the globe and with Africa and South America starting out located in the southern region of the globe and slowly over time moving up into their present positions. Australia which has significant coal deposits, starts off in the tropics, moves down and then back up. Therefore, theoretically during the start of the coal formation ages the continents with the concentrations of coal resources had been located for extended times in the tropics regions especially during the Carboniferous Period. I I I I I I I I I Million years ago ZoomSchoo I.coni Figl.6 Continental Drift (Million years ago) 1.5 Methods of Coal Mining The most economical method of coal extraction from coal seams depends on the depth and quality of the seams, and the geology and environmental factors. Coal mining processes are differentiated by whether they operate on the 12

13 surface or underground. Surface mining or Open Cast (OC) and Underground (UG) mining are the two basic methods of mining Modern surface mining When coal seams are near the surface, it may be economical to extract the coal using open cut (also referred to as open cast, open pit, or strip) mining methods [1071. Open cast coal mining recovers a greater proportion of the coal deposit than underground methods, as more of the coal seams in the strata may be exploited. Large Open Cast mines can cover an area of many square kilometres and use very large pieces of equipment. This equipment can include the following: Draglines which operate by removing the overburden, power shovels, large trucks in which transport overburden and coal, bucket wheel excavators, and conveyors In this mining method, explosives are first use in order to break through the surface of the mining area. The coal is then removed by draglines or by shovel and truck. Once the coal seam is exposed, it is drilled, fractured and thoroughly mined in strips. The coal is then loaded on to large trucks or conveyors for transport to either the coal preparation plant or direct to where it will be used. Figl.7 Open Cast Mine 13

14 mw trw> softs are rt!0ac<chl m U*i»r prop«f secfcuooce, inty are ftpped to compsetiori arid ilwt cairivatod. HrtHXl asxt fartiufiad Figl.8 Process of extraction of coal in OC mines Area mining Strip mining exposes the coal by removing the overburden (the earth above the coal seam(s)) in long cuts or strips. The spoil from the first strip is deposited in an area outside the planned mining area. Spoil from subsequent cuts is deposited as fill in the previous cut after coal has been removed. Usually, the process is to drill the strip of overburden next to the previously mined strip. The drill holes are filled with explosives and blasted. The overburden is then removed using large earthmoving equipment such as draglines, shovel and trucks, excavator and trucks, or bucket-wheels and conveyors. This overburden is put into the previously mined (and now empty) strip. The underlying coal seam will be exposed (a 'block' of coal) after all the overburden is removed. This block of coal may be drilled and blasted (if hard) or otherwise loaded onto trucks or conveyors for transport to the coal 14

15 preparation (or wash) plant. Once this strip is empty of coal, the process is repeated with a new strip being created next to it. This method is most suitable for areas with flat terrain Contour mining The contour mining method consists of removing overburden from the seam in a pattern following the contours along a ridge or around a hillside. This method is most commonly used in areas with rolling to steep terrain. It was once common to deposit the spoil on the down slope side of the bench thus created, but this method of spoil disposal consumed much additional land and created severe landslide and erosion problems. To alleviate these problems, a variety of methods were devised to use freshly cut overburden to refill minedout areas. These haul-back or lateral movement methods generally consist of an initial cut with the spoil deposited down slope or at some other site and spoil from the second cut refilling the first. A ridge of undisturbed natural material 15 to 20 feet (6.1 m) wide is often intentionally left at the outer edge of the mined area Mountaintop removal mining Mountaintop coal mining is a surface mining practice involving removal of mountaintops to expose coal seams, and disposing of associated mining overburden in adjacent "valley fills." Valley fills occur in steep terrain where there are limited disposal alternatives. Mountaintop removal combines area and contour strip mining methods. In areas with rolling or steep terrain with a coal seam occurring near the top of a ridge or hill, the entire top is removed in a series of parallel cuts. Overburden is deposited in nearby valleys and hollows. This method usually leaves ridge and hill tops as flattened plateaus Room and pillar mining Room and pillar mining consists of coal deposits that are mined by cutting a network of rooms into the coal seam. Pillars of coal are left behind in order to 15

16 keep up the roof. The pillars can make up to forty percent of the total coal in the seam. Though, this can be extracted at a later stage Underground mining Figl.9 Process of extraction of coal in UG mines Most coal seams are too deep underground for opencast mining and require underground mining, which method currently accounts for about 60% of world coal production. In deep mining, the room and pillar or bord and pillar method progresses along the seam, while pillars and timber are left standing to support the mine roof. Once room and pillar mines have been developed to a stopping point (limited by geology, ventilation, or economics), a supplementary version of room and pillar mining, termed second mining or retreat mining, is commonly started. Miners remove the coal in the pillars, thereby recovering as much coal from the coal seam as possible. There are five principal methods of underground mining: Longwall mining: It accounts for about 50% of underground production. The longwall shearer has a face of 1,000 feet (300 m) or more. It is a sophisticated machine with a rotating drum that moves mechanically back 16

17 and forth across a wide coal seam. The loosened coal falls on to a pan line that takes the coal to the conveyor belt for removal from the work area. Longwall systems have their own hydraulic roof supports which advance with the machine progress. Figl.10 Under Ground Mine Continuous Mining: It utilizes a machine with a large rotating steel drum equipped with tungsten carbide teeth that scrape coal from the seam. Operating in a room and pillar (also known as bord and pillar ) system where the mine is divided into a series of 20-to-30 foot rooms or work areas cut into the coalbed. Conveyors transport the removed coal from the seam Blast Mining or Conventional Mining: It is an older practice that uses explosives such as dynamite to break up the coal seam, after which the coal is gathered and loaded on to shuttle cars or conveyors for removal to a central loading area. 17

18 Shortwall mining: It is a method currently accounting for less than 1% of deep coal production, involves the use of a continuous mining machine with movable roof supports, similar to longwall Retreat mining : It is a method in which the pillars or coal ribs used to hold up the mine roof are extracted; allowing the mine roof to collapse as the mining works back towards the entrance. This is one of the most dangerous forms of mining owing to imperfect predictability of when the ceiling will collapse and possibly crush or trap workers in the mine. 1.6 Coal Mining Machinery Gold-bearing gravels are shoveled into a trommel at the Blue Ribbon placer mine, Alaska.Heavy machinery is needed in mining for exploration and development, to remove and stockpile overburden, to break and remove rocks of various hardness and toughness, to process the ore and for reclamation efforts after the mine is closed. Bulldozers, drills, explosives and trucks are all necessary for excavating the land. In the case of placer mining, unconsolidated gravel, or alluvium, is fed into machinery consisting of a hopper and a shaking screen or trommel which frees the desired minerals from the waste gravel. The minerals are then concentrated using sluices or jigs. Large drills are used to sink shafts, excavate stopes and obtain samples for analysis. Trams are used to transport miners, minerals and waste. Lifts carry miners into and out of mines, as well as moving rock and ore out, and machinery in and out of underground mines. Huge trucks, shovels and cranes are employed in surface mining to move large quantities of overburden and ore. Processing plants can utilize large crushers, mills, reactors, roasters and other equipment to consolidate the mineral-rich material and extract the desired compounds and metals from the ore. 18

19 Figl.ll Moving machinery (driller) 1.7 Various Types of Coals We use the term "coal" [1091 to describe a variety of fossilized plant materials, but no two coals are exactly alike. Heating value, ash melting temperature, sulfur and other impurities, mechanical strength, and many other chemical and physical properties must be considered when matching specific coals to a particular application Peat: It is considered to be a precursor of coal, has industrial importance as a fuel in some regions, for example, Ireland and Finland. In its dehydrated form, peat is a highly effective absorbent for fuel and oil spills on land and water Lignite: It is also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation. Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Iron Age. 19

20 1.7.3 Bituminous coal: It is dense mineral, black but sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke Anthracite: It is the highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating. It may be divided further into metamorphically altered bituminous coal and petrified oil, as from the deposits in Pennsylvania Tablel.9 Carbon percentage of various types of coals Type of Coal Carbon content Commonly known as Peat 111% Lignite 38% Soft coal / brown coal Bituminous 65% Household coal Anthracite 96% Hard coal t Anthracite coal Composition Primary carbon Secondary sulphur, oxygen, hydrogen, nitrogen Figl.12 Coal Composition 20