DEFINITION OF COAL Many geologists, scientists and technologists have defined coal in different ways. More 1 9. iM. than dozen of definitions are available in literature. Some of them are as under: . Coal is a chemically and physically hetero; saat is an extremely complex heterogeneous solid material af@ plant origin. It developed under elevated temperature and Pressure of earth crust after a long period of geological time. blame coal is a combustible rock of érigin composed mainly of C, H, O, N and Ss well as trace amount*of other elements, ” Coal is a carbonaceous solid fitel or fossil fu el of plant origin carrying the heterogeneous solid phases of organic and inorganic materials : Coal is organic rock composed of carbon and it is compleS’and also containg and mineral matter. Coal is sedimentary rock and is also organic mineral called fuel mineral Coal is unique rock because it has organic origin Coal is a solid, brittle, combustible, carbonaceous and sedimentary rock formed by the decomposition and aeration of vegetation by compaction, temperature and pressure. It varies in colour from brown to black and is usually stratified. Coal is a rock, sedimentary, conglomerates and biological fossil and a complete colloidal system ygeneous combustible sedimentary rock consisting of both organic and inogganic materials. It consists primarily of C, H, O and with lesser of § and N, a feanically coal consists of wide range of ash forming complex mineral matter distributed throughout the coal. Coal is heterogeneous combustible sedimentary rock of plant origin which has formed under elevated temperature and pressure of the earth crust over a long period of geological time. Its formation brought about a lot of changes in its physical and chemical character. Coal may be considered as a solid rock having both organic and inorganic ‘components. The organic part is composed of elements like C, H, O, N, $ which are released on combustion oF cal alo contains mineral matter and many trace metallic elements like Hg, Pb, Zn, $i, $Cr, As, Sb, Cu, Fe, etc. We peftniions at Noland 12 are more comprehensive if both of them are combined to Definit define coal. See a fossil fuel. By definition fossil is a product eh © : jentists do not consider coal as a fossil fuel. By def i Penied om organic material and ultimately is converted into inom product, But ae | retain’ its organic matter right from the beginning to the en pe coal s)ny COAL & MINERAL Sone iy Coal is a combustible sedimentary Tock of plant origin which has developed under elevated temperature and pressure of the earth crust over a long period of time. Its formation brought about a lot of changes into its physical and chemical characters. The coal may also be carrying heterogeneous solid phases of organic maties, MINERALS = ane organic matters “7 ‘The mineral is defined as a naturally occurring inorganic element or compound which has definite’ chemical formula and specific crystalline structure. Coal as a mineral ids The coal has definite formula (c) but has not specific crystalline structure. So the coal does not qualigf for the definition of mineral However, the coal has the following characteristics similar to the mineral - 1. Coal and minergl deposits exist in nature in similar pattern. 2. Mining method'used for coal and minerals are similar. 3. Mining equipment is similar for both mineral and coal. 4. Prospecting techniques and reserves estimation methods are similar. 5. Coal processing and mineral processing method are similar. Processing equipments are also simil : ‘The trade regulations and eal aspects used for minerals are also applicable for AA puelty coal. Keeping in view the above considerations,the coal has also been included in IX a the category of minerals and is called fuel miner Define coal and mineral. Justify that coal is also considered to be a mineral.COAL CHEMISTRY General Comments ‘The coal chemistry relates to two major parts: 1) Organic Matter (F%tx CAy5 ow ) 2) Inorganic Mineral M rN In addition three more components i.e, volatile matter also important constituents of coal. 1) Organic Matter The organic matter consists of fatter Ys} igetal matier and moisture ar Carbon containing materials'present in major quantity (20-90%) ii Volatile matter (1-40%) ili, Vegetal matter (0,1-0.2%) Mattei ers 10 (i) inorganic compounds present in coal, ‘They are present relatively in TROP prepertion-byt # an appreciable amount (5-40 %) and (ii) moisture (2-40%) The mineral matter also contains suc h, compounds which release trace elements of heavy metals like Cu, Pb, Zn, Hg, As, Sb, Bi’ete, Among them Pb, Hg and As are dangerous for heath and are enviror mentally hazardous, The coal chemistry is actually the chemistry of Components of coal in eis Juve Uses of Coal The coal has a great industrial significance. as under 1) As a solid fuel, it is used for production of steam in boilers for running power gf plants asf@ cement, sugar, fertilizer plants and many industrial uatts, « 2) Itis dsed as reduci nt in metallurgical processes largely as a coke in iron making 3) It is used for domestic heating and cooking, 4) It serves as raw material for production of chemicals and dyes, Mf There are vast reserves of coal, about ta lion (Os, in the world, which vary in types and grades, above referred fivefnajor and minor Vila ile mailer fined Carbon mibveral weattry d vegetal matey ) {ts major uses and industrial applications are Baton mmatae firvack wipers 5 The high grade coal is directly used in the industrial sector, whereas the low-grade Coal requires cleaning to achieve an acceptable grade, suited for the industry. It is up to the coal scientists, engineers and technologists to work on deposits to make them efficiently useful to achieve the above mentioned applications, The study of the coal chemistry therefore, is the fundamental necessity to understand coal and coal components, Study Areas for Coal The following study areas are essential for complete understanding of physical and chemical aspects of coal. 1) Physical characteristics of coal 2) Petrographic study of coal through thin and polished sections 3) Chemical composition and properties of organic and inorganic constituents of coal and their significance 4) Coal ranks and their specifications 5) Chemicals from coal and coal tar ‘Coal Chemistry6) Sophisticated instrumental methods of analysis for coal and coal products 7) Coal conversion technologies 8) Coal cleaning processes Coal Composition As mentioned above the coal consists of mainly sb¢ organic and mineral matters, which are briefly described below: (A) Organic Matter in Coal The broad categories of organic matter are as follows: = 1) Carbon (Macerals): major component (20-90 %). 2) Volatile Matter: The volatile matter varies in different ranks of coal. It is least in sexi jous and lignite coals anthracite (0.5-1.5%) and maximum in semi bituminous, bitomin (upto 40%) 3) Vegetal Matter: cellulose, wood fragments, fossil moths, plant’s pollens, spores, leaves and seeds, ete (0.1-0.2 %). Organic Compounds in coal: resins, gums, waxes, (CisHas to CisHss), humic acids and humates (mostly present in lignite), paraffins (CucltasO2s) mostly present in peat and lignite (1-2 %), sulphur and nitrogen containing compounds like sulphides and poly sulphides, proteins, mecaptans and lignin, ete (0.1 to 0.5 essential oils, fatty acid and their salts % or more). (B) Inorganic Matter in Coal The inorganic matter in coal is mainly composed of mineral matter which is also called ash forming mineral matter. It exists in coal in the following forms: Inherent or Intrinsic Mineral Matter Extraneous or Extrinsic Mineral Matter Complex Metallic Cations and Anions iff present in coal in an unacceptable limit, is harmful and must be is and is deposited i iii The mineral matter, removed by coal cleaning processes. The mineral matter, in the form of sediments, enters into coal seam: there. The major part of it j6 found in coal ih easily separable form but when it enters into coal matrix and deposits there in finely disseminated form, is not separable without chemical treatment. The mineral sediments, deposited in coal beds contain pure and largely altered <4y minerals, The major part of inorganic mineral matter is composed of altered silicate groups" rinerals called clay minerals. In small proportions, pure minerals in the form of oxides, carbonates, sulphates, phosphates, sulphides are also deposited. “The mineral matter. jn coal is generally found in the form of shale, slate, sandstone, limestone, claystoh®'@e pyrite or marcasite. Trace elements of various metals are also present in a vary small proportions. In Pakistani coals, the major components of mineral matter exist in the form of shale, sandstone, limestone, claystones and pyrite. Minor minerals inthe form of oxides, sulphates, Surface or Free Moisture: 54. Air dry moistur 7 Moisture due to water of ery Types of Moisture 1. Inherent Moisture: (also called bed or seam moisture, e moisture) It refers-to the water which Pores and capillaries during th quilibrium moisture and capacity H entered in matrix or total structure of c he process of coalification, * (also called adsorbed or free moisture) algo includes surface this refers to water conter al through and adsorbed moisture) nt held on surface of coal when it is yx mixed and taken for transportation, .9¢ can Le removed by ait, drying A. Total Moisture: It 'sthe sum of inherent ard surface Yee moisture md AEVHiSLL mesiture Ttis the moisture which has lost during air drying of coal « S+ Residual moisture: Is the moisture which remained in coal afer itis air dved Heis-aso called air dry Yost maisttire (or moisture remained after air drying) 6. As Received Moisture: referred as total moisture Present at the time of analysis in the laboratoy ry. 7. Decomposition moisture: the moisture which is released 3 thermal decomposition of Organic constituents of coal ie. decomposition of OH, CHO groups, ete ‘tallization or water of dehydration of mineral matter: © It refers to water of crystallization Le, gypsum CaSO, 2420, limonite Fe,03.xH0 etc Determination of Total Moisture Be ees It is in as received copl sample which includes inberentape surfatete’ moisture ze" (wheatear air dried or not, and is immediately determined in laboratory). The sample should not be left in open atmosphere to avoid the effect of humidity. The total moisture is determined by following the ASTM standard method referred as ASTM D-3302. The method is based on the loss of weight in coal sample at rigidity controlled conditions of temperature, en ebal Weis fore Ip oheber mri med by placred Ip of do mesh (250 And time and air flow. bos for ot kau, Vr Waeaghs Lott i ona grn seople Hak mais fare Souple. ever Importance of Moisture in coal in ee i. Specific quantity of total moisture has been assigned, for each Commercial explotauen provesttet coal and is important for controlling the process with respect to amount of moisture present in coal. ii, For coking process, the desired moisture contents is needed, the excess quantity of moisture if prentwill need more heat for vaporization of moisture and it be cost effective , ii, Inherent or equilibrium moisture is often used for calculating ¢winerat-metir free) calorific value forthe rank classification of high volatile bituminous coals. ane Due to physical limitation, inherent moisture is determined at ia Surface moisture is determined by subtracting inherent moisture from moisture. 2 $73 fo meesh ov 250 wr = Sz ) termination = _¢4e=se##4)- ; a of powdered coalin preheated and dried crucible and put remove and cool it in dessicator, loss in weight is the Method for moisture,d 1. Thermal Method: Fike 1 las it in an oven at 110°C for two hours, total moisture. This method is more popular and reliable. Coal Chemistry dict ind visite (it is the sum of inherent, and Surface eae) moisture yAvhicl isme/s bereDistillation method: Heat the weighed sample in boiling water-immiscible organic qui, filter, dry. The loss in weight is total moisture By Solvent extraction with reagent which takes water away. Electrical method: find the dielectric constant of coal from which water can be determined. Note: ‘4 Larger the surface area, greater will be the amount of surface moisture asorbed, if exposed for longer time in open atmosphere. Moisture is driven off during crushing and grinding of coal but it does not largely reduce the calorific valye of coal entering the boiler/combustiony a» er « Completely driven ‘Coal is difficult to ignite. The OH group of moisture promotes the ignition of carbon. Thus in pulverized coal 1-1.5% moisture will promote combustion - The moisture evaporation is an endothermic reaction and there is heat loss from coal. But- the addition eraondensation of water-vapaurs-in the-coakadds heateontent tort Sev = Gress eabowific Vibew = Henk im Gorrg oP babes keab/ky ~ BTW Crebnsthbe teats + Late ola moithene erapevete ov kabent Aone op op eee BTU 2 18% keal ky Net her fe vnher 2 Teta heat on berg wnat aaa renabte mimses teat lene & EYEE ae Table 1.3 Predominant Coal-Genérating Geologie Periods and the Various Coal Types Mean age of coals Era Period (years x 1H) Quaternary Holocene Principal coal formations Moorland pea's in Europe, Siberia, N. and S America, Spitzbergen Peat swamps in Bast Indies, Africa; forest peats in Florida, Wisconsin, Alaska, British Columbia: lignites in New Zealand and Tasman Tertiary, Pliocene 212 Lignitesin $. E. Europe, Alaska, S. Nig New Zealand Lignites in Spitabergen, Germany, France, Grevn- lund, W. Indies, Venezuela, Mexico, New Zea. lund, B. and S. B. Australi, Tasmania Lignites in England (Bovey Tracey), Europe, Spitebergen, British Columbia Lignites and subbituminous pals in ‘Tyrol, Sax- ony, Spain, N. America (Rocky Mountain states, Pacific Coast areas, Alaska, and Arctic Islands), Bomeo, Japan, $. Nigeria, New Zea. a land (S. Island), Pakistan-Punjab, Salt Range / Kashmir, Rajasthan Mesozoie Lignites and subbituminous and bituminous coals in N. America (western and Rocky Mountain areas of U.S. and Canada), Mexico, Chile, | ; Japan, Assam, S. Nigeria, Queensland, Now Zealand Coals in Russia, China (Chungking), Queensland (Ipswich and Walloon Series), ‘New South Wales (Clarence and Richmond), S. Australis (Leigh Creek), S. Victoria, Tasmania, New Zealand Coals in Poland (Dombrova Basin), Upper Silesia the Vosges, S. Mexico, Queensland {Ipswich and Bundamba), N. Carolina, and Virginia Coals in France (Central Plateau), Saxony. Russia (Urals), United States (astern states), N E. and B. China, India, Africa’ (Rhodesi, Transvaal, Natal), W. Australia. (Collie) Queensland (Dawson and Bowen Rivers), New i South Wales (General), Tasmania, Argentina, Carboniferous Coals in France (St. Etienne, Brittany. and Nor Upper randy), Saar, Boherhia (Pilsen, Kladno), Rus sia (Donetz Basin), N. America, Interior and Gulf Provinces andthe Appalachian Region ot ULS., New South Wales (Stronga and Bullsh Delish) ope , 2 Coals in Great Britain (Middle and Lower Coal Laos : Measures), Germany (Westphalia), Saar, Sile- sia, Poland, Moravia, France (Northen Dis tects) and Belgium, Russia (Moscow Basi) Spain Santander and Granada), S, America (S Brazil) eee : Edge Coal Series of Scotland. Spitebergen: a Tower thractes of Pennsylvania; coals in Nova Seotia sd New a ny cel a in Bea [sland (south of Spitehergen}; eanne pena ee olin ae ens Pleistocene 1 and Miocene 20 Oligocene 40 Eocene ar) Cretaceous 100 Jurassic 150 “Triassic 180 Upper Paleozoic Permian, 210 Permo- carbonifer- ous Source: Lewis (19: —a ee