Understanding Coal Analysis

by Michael Hutagalung on 02/06/08 at 1:30 am | 78 Comments | |

“How to understand a coal sample analysis? What is the difference between proximate and ultimate analysis? What is AR (as-received) basis? Is is the same with DAF (dry, ash free) basis? How about AD (air-dried) basis? And what coal ash analysis is all about?”

Well, it is indeed a long list of questions to answer but the explanation is actually not as twisted as it seems. The main purpose of coal sample analysis is to determine the rank of the coal along with its intrinsic characteristics. Furthermore, these data will be used as the fundamental consideration for future concerns, for instance: coal trading and its utilizations.

Coal Properties

Coal comes in four main types or ranks: lignite or brown coal, bituminous coal or black coal, anthracite and graphite. Each type of coal has a certain set of physical parameters which are mostly controlled by moisture, volatile content (in terms of aliphatic or aromatic hydrocarbons) and carbon content.

1. MoistureMoisture is an important property of coal, as all coals are mined wet. Groundwater and other extraneous moisture is known as adventitious moisture and is readily evaporated. Moisture held within the coal itself is known as inherent moisture and is analyzed. Moisture may occur in four possible forms within coal:

o Surface moisture: water held on the surface of coal particles or maceralso Hydroscopic moisture: water held by capillary action within the microfractures

of the coalo Decomposition moisture: water held within the coal’s decomposed organic

compoundso Mineral moisture: water which comprises part of the crystal structure of

hydrous silicates such as clays.2. Volatile matter

Volatile matter in coal refers to the components of coal, except for moisture, which are liberated at high temperature in the absence of air. This is usually a mixture of short and long chain hydrocarbons, aromatic hydrocarbons and some sulfur. The volatile matter of coal is determined under rigidly controlled standards. In Australian and British laboratories this involves heating the coal sample to 900 ± 5 °C (1650 ±10 °F) for 7 minutes in a cylindrical silica crucible in a muffle furnace. American Standard procedures involve heating to 950 ± 25 °C (1740 ± 45 °F) in a vertical platinum crucible.

3. AshAsh content of coal is the non-combustible residue left after coal is burnt. It represents the bulk mineral matter after carbon, oxygen, sulfur and water (including from clays) has been driven off during combustion. Analysis is fairly straightforward, with the coal thoroughly burnt and the ash material expressed as a percentage of the original weight.

4. Fixed carbonThe fixed carbon content of the coal is the carbon found in the material which is left after volatile materials are driven off. This differs from the ultimate carbon content of the coal because some carbon is lost in hydrocarbons with the volatiles. Fixed carbon is used as an estimate of the amount of coke that will be yielded from a sample of coal. Fixed carbon is determined by removing the mass of volatiles determined by the volatility test, above, from the original mass of the coal sample.

Coal Proximate Analysis

The objective of coal ultimate analysis is to determine the amount of fixed carbon (FC), volatile matters (VM), moisture, and ash within the coal sample. The variables are measured in weight percent (wt. %) and are calculated in several different bases. AR (as-received) basis is the most widely used basis in industrial applications. AR basis puts all variables into consideration and uses the total weight as the basis of measurement. AD (air-dried) basis neglect the presence of moistures other than inherent moisture while DB (dry-basis) leaves out all moistures, including surface moisture, inherent moisture, and other moistures. DAF (dry, ash free) basis neglect all moisture and ash constituent in coal while DMMF (dry, mineral-matter-free) basis leaves out the presence of moisture and mineral matters in coal, for example: quartz, pyrite, calcite, etc. Mineral matter is not directly measured but may be obtained by one of a number of empirical formula based on the ultimate and proximate analysis.

Proximate Analysis unit (ar) (ad) (db) (daf)Moisture (wt. %) 3.3 2.7Ash (wt. %) 22.1 22.2 22.8Volatile Matter (wt. %) 27.3 27.5 28.3 36.6Fixed Carbon (wt. %) 47.3 47.6 48.9 63.4Gross Calorific Value (MJ/kg) 24.73 24.88 25.57 33.13

A table is shown above containing an example of proximate analysis data of coal. Conversion from one basis to another can be performed using mass balance equations. The standard practice for proximate analysis of coal may be referred to ASTM D3172-07a or ISO 17246:2005.

Coal Ultimate Analysis

Similar to coal proximate analysis, the objective of coal ultimate analysis is to determine the constituent of coal, but rather in a form of its basic chemical elements. The ultimate analysis determines the amount of carbon (C), hydrogen (H), oxygen (O), sulfur (S), and other elements within the coal sample. These variables are also measured in weight percent (wt. %) and are calculated in the bases explained above.

Ultimate Analysis unit (ar) (ad) (db) (daf)Carbon (C) (wt. %) 61.1 61.5 63.2 81.9Hydrogen (H) (wt. %) 3.00 3.02 3.10 4.02Nitrogen (N) (wt. %) 1.35 1.36 1.40 1.81Total Sulfur (S) (wt. %) 0.4 0.39 0.39Oxygen (O) (wt. %) 8.8 8.8 9.1

A table is shown above containing an example of coal ultimate analysis data and showing significant elements only. Conversion from one basis to another can be performed using mass balance equations. The standard practice for ultimate analysis of coal may be referred to ASTM D3176-89(2002) or ISO 17247:2005.

Ash Analysis

Oxides wt.% of ash(Calculated)

Elements wt.% of ash(Measured)

Na2O 0.35 Na 0.26MgO 0.48 Mg 0.29Al2O3 20.0 Al 10.6SiO 74.1 Si 34.6P2O5 0.05 P 0.05K2O 1.1 K 0.92CaO 0.68 Ca 0.49TiO2 0.80 Ti 0.48Mn3O4 0.06 Mn 0.05Fe2O3 3.25 Fe 2.28

An analysis of coal ash may also be carried out to determine not only the composition of coal ash, but also to determine the levels at which trace elements occur in ash. These data are useful for environmental impact modelling, and may be obtained by spectroscopic methods such as ICP-OES or AAS. An example of coal ash composition is shown on the right.

Beside composition of coal ash, ash fusion point is also one significant parameter in ash analysis. The optimum operating temperature of coal processing will depend on the gas temperature and also the ash fusion point. Melting of the ashes may cause them to stick to the walls of the reactor and result in a build-up.

You might be interested to read an article of coal characterization equipments here, illustrated with photos, including coal proximate analysis, ultimate analysis, and ash fusion point analysis equipments.

METHODS FOR SAMPLING AND INORGANIC ANALYSIS OF COALU.S. Geological Survey Bulletin 1823

Edited by D.W. Golightly and F.O. Simon

Preparation of Coal for Analysis

By F.G. Walthall and S.L. Fleming, II

Abstract

Bulk quantities of coal weighing 3 to 15 kg are individually reduced to approximately 150 m m (100 mesh) by comminution procedures that minimize contamination by grinding surfaces or by other samples. Seventy grams of each pulverized coal sample is oxidized at 525° C for 36 h to determine the percent ash and to provide ash required for chemical and instrumental analyses.

INTRODUCTION

All procedures described in subsequent sections of this bulletin on the chemical and instrumental analysis of coals depend upon the comminution step. The pulverization of bulk coal samples from the field serves both to homogenize the coal, which typically is quite heterogeneous, and to reduce the material to small particles needed for rapid ashing and dissolution. The comminution of a field sample and the splitting of the resulting pulverized sample into portions to be distributed to various laboratories, while minimizing contamination from grinding surfaces, sieves, and other coals, are essential to the success of all subsequent chemical measurements. Thus, the comminution process is of critical importance, and all aspects of the laboratory arrangement and of procedures for grinding coals must be carefully planned (Swaine, 1985).

Coals submitted for chemical analysis are first received and prepared by the sample preparation (grinding) laboratory. The typical sizes of individual field samples vary from 3 to 15 kg. The normal preparation procedure requires that each air-dried coal sample pass through a jaw crusher; one subsample (split) of the crushed material (2 to 4 mm, or 5 to 10 mesh) is then taken for the ultimate and proximate analyses, and another split is reduced to approximately 150 m m (100 mesh) by a vertical grinder for chemical analysis. An additional split is kept for archival storage, and the excess sample is returned to the submitter.

EQUIPMENT AND PROCEDURES

Sample Preparation (Grinding) Laboratory-- Equipment

The instrumentation, equipment, and related items required for the safe operation and maintenance of a grinding laboratory for coal are listed here. The kiln and balance are included because this laboratory both determines the ash from coal and supplies coal ash to other laboratories for chemical analysis.

1. Jaw crusher, partially corrugated manganese steel jaw plates, model 2X6, Sturtevant Mill Company, Boston, MA.

2. Vertical grinder, alumina ceramic plates with aluminum ring, aluminum ore pan, model 6R (catalog no. 242-72A), Bico Braun, Inc., Burbank, CA.

3. Rolls crusher, 8X5, Sturtevant Mill Company, Boston, MA.4. Mixer-mill, model 8000, Spex Industries, Edison, NJ.5. Kiln, 6 kW.6. Laboratory balance, 0.005 to 500 g.7. Riffle splitter, with pans, Wards Natural Science Establishment, Inc., Rochester, NY.8. Plastic bag sealmaster, Packaging Aids Corporation, San Francisco, CA.9. Sieves, nylon screen in methacrylate rings, 100 mesh, Spex Industries, Edison, NJ.10. Exhaust hoods, size and location shown in figure 8.11. Aluminum pans (23 cm circular "pie" pans).12. Plastic drying pans, sides less than 38 mm high, sample spread less than 25 mm deep.13. Porcelain crucibles, 65 to 70 g.14. Wire brush, stainless steel.15. Spatula, stainless steel.16. Polystyrene jars, 120 mL, 5.8-cm diameter, with lids.17. 17. Polystyrene vials (26 mL) with caps.18. 18. Polyethylene vials (polyvials, 3.7 mL) with snap caps.19. 19. Paper cartons, 0.55 L, 8.5-cm diameter.20. 20. Plastic bags, 15 ´ 30 cm, sealed by plastic bag sealmaster (item 8).21. 21. Wax paper, 30 ´ 46 cm.22. 22. Lint-free paper towels.23. Cleaning sand (clean quartz sand).24. Compressed-air supply, filtered, with hose and nozzle. (For safety, the pressure at

which the compressed air is supplied should be kept below 0.2 kPa (30 psi).)

Safety Equipment and Provisions

1. Safety goggles for protection of eyes from small projectiles and dust from grinding machines, Macalaster Bicknell Company, Millville, NJ.

2. Ear covers (muff type) or inserts for protection from loud noises emitted by grinding machinery.

3. Laboratory coats or coveralls.4. Plastic gloves, disposable.5. Safety shoes with protective steel toes.6. Fire extinguishers (ABC tri-class dry chemical, 5.25 kg).7. Explosion-proof switches and light fixtures in grinding laboratory.

8. Respirator masks with interchangeable paper filters.

Safety Procedures

As in all procedures for the comminution of geologic materials, precautions must be taken to protect the operator of grinding equipment from dust inhalation, the noise of the machinery, small projectiles emanating from the grinding process for a sample, and injury (especially to the hands) that can be inflicted by the powerful machinery required for grinding of samples. Moreover, high concentrations of coal dust in air can constitute an explosion hazard. Thus, an adequate ventilation system and the complete absence of high-temperature sources (cigarettes, sparks from electrical switches, electrostatic sparks, flames, etc.) are essential for a safe grinding facility for coal.

Safety goggles, ear protection, a laboratory coat, and an air-filter mask should be used at all times while operating the crushing and grinding equipment. A rapid stream of compressed air, used in cleaning grinder surfaces, should always be directed away from the operator. Electrical power to grinding equipment should be switched off before hands or tools are inserted into the machinery. Periodic medical examinations, which may include chest X-ray examinations to reveal developing respiratory disorders such as silicosis, are generally considered to be a good preventive measure.

Maintenance of Equipment

Adequate maintenance of equipment basically consists of regular lubrication and replacement of worn components. The following procedure is suggested for the grinding laboratory.

1. Identify all grease fittings and keep the fittings capped.2. Lubricate each piece of equipment in accordance with an established schedule that is

posted near the device.3. Replace worn parts on jaw crusher.4. Resurface worn ceramic plates that are used on the vertical grinder.5. Replace worn drive belts.6. Keep drawings and brochures related to equipment on file for lists of proper

replacement parts and for instructions on proper lubrication.

Sample Preparation (Grinding) Laboratory--Facilities

The grinding laboratory, which contains heavy machinery that is capable of producing significant floor vibrations, should be located on the ground floor of a building. The laboratory should have no overhead water plumbing, including fire-sprinkler systems, because the failure, or breakup, of such plumbing presents a serious hazard to both the equipment and the operator. Fire extinguishers that use carbon dioxide or halon TM are suggested.

The arrangement of the laboratory currently used by the U.S. Geological Survey for all grinding procedures on coal is shown in figure 8. This laboratory occupies an area of 51 m2

and has four specially constructed exhaust hoods that are ducted to a "rotocone" dust collector. Electrical power for equipment is made available through eight duplex outlets (single phase, 110-V alternating current, 20 A) and four outlets providing three-phase, 220-V alternating current, 30 A. Compressed air is provided at five outlets, and hot and cold tapwater are available at the sink. A water drain is located in the center of the floor.

Adjacent to the laboratory is an office area (31 m2), in which field samples are received and information concerning each sample is recorded. A sample-drying room (20 m2) is used both for short-term storage and for drying of samples. Archives of samples are stored in a separate area of the facility.

Crushing and Grinding

The coal sample, as received from the field, consists of 3 to 15 kg of material that first is reduced to a particle size of 2 to 4 mm (5 to 10 mesh) in a jaw crusher. This crushed material is then divided into three splits. The first split is forwarded to a laboratory for standard ultimate and proximate analyses. The second split, which is intended for chemical analysis and archiving within the U.S. Geological Survey, is pulverized to 150 m m (100 mesh) in a vertical grinder. The remaining split is returned to the submitter. These and subsequent steps are outlined in figure 9, which is a flowchart that shows the treatment and routing of each sample.

Description of Procedure

1. Generally, samples are received in plastic bags that are tightly packed into a cubic box that has a 30-cm edge. The individual plastic bags, which have been labeled in the field, are removed from the box and necessary recordkeeping is first completed. Special grinding and routing instructions that accompany the sample are noted on a form that also has descriptive information pertaining to the coal.

2. Samples that need air drying are identified. Typically, moisture is readily apparent on these samples, or the coal powder commonly present in the samples does not move about freely as the container is agitated. Each of these samples is poured into a plastic or aluminum pan, and each of the sample numbers is written on a strip of masking tape attached to the pan. The empty plastic bag is placed under the pan for later use. Wet samples typically are air dried for one week; however, longer drying times may be required for samples that tend to stick to surfaces during grinding.

3. Containers needed for sample splits from the crushing process are cleaned with a stream of air and labeled prior to the crushing procedure.

4. Samples are taken into the grinding laboratory to be crushed one at a time, while the remainder of the samples are stored on a cart outside the door of the grinding laboratory. This practice reduces the possibility of cross contamination.

5. Just prior to crushing the first sample, the gap between the jaws of the jaw crusher is adjusted to approximately 4 mm.

6. After crushing the entire sample, the sample is homogenized by rolling it on a sheet of waxed paper. Then, the homogeneous, crushed sample is fed into a riffle splitter (fig. 10) to produce splits A and B. A minimum of 100 g of sample from the first split is poured into the container for samples that are intended for ultimate and proximate analyses (fig. 10, split A). The second split (fig. 10, split B) is fed again into the riffle splitter (fig. 10, splits C and D), and a 15-cm-long plastic bag is filled from split D for return to the submitter. Split C (fig. 10) is distributed into a paper carton (550 mL), a polystyrene vial (26 mL), and a snap-cap polyvial (3.7 mL); the paper carton and the polystyrene vial are filled approximately two-thirds full, and the polyvial is filled to within 3 mm of the top. These individual portions are to be used for ashing and for subsequent chemical and instrumental analyses. All remaining sample is placed in the original plastic bag, which is then resealed and returned to the submitter.

7. The simultaneous use of two vertical grinders is recommended. This arrangement enables a machine operator to pulverize one sample while the previously pulverized sample is being split and the other grinder is being cleaned. Each sample is split by a riffle splitter inside a hood (46 ´ 61 ´ 61 cm).

8. Splits must be prepared for five laboratories: a 20-g split for analysis by neutron activation is packaged in a paper carton; a separate 3.5-g sample for delayed-neutron determinations of uranium and thorium is placed in a polyvial; a 140-g split for the ultimate and proximate analyses is placed in a metal can; 70 g of coal is split for high-temperature (525° C) ashing; and the submitter receives a 140-g portion in plastic bags.

A similar method for preparing coal samples is described in the ASTM (1984a) book of standards.

Ashing Procedure

Pulverized coal samples are ashed in an electrically heated kiln that can ash 40 samples simultaneously. The steps followed in the ashing process are listed here.

1. Forty sequentially numbered porcelain crucibles (or evaporating dishes) are cleaned and dried prior to ashing the coal samples. The weight of each crucible, approximately 70 g, is sufficiently constant to make repeated weighings unnecessary for each ashing cycle.

2. Approximately 70 g of sample is weighed into each crucible. Appropriate records are maintained for the weights of the sample and the crucible and for the sample number or name used by the laboratory.

3. The crucibles are placed in the kiln. The electrical power to the kiln is switched on, and the kiln is slowly heated to 200° C. After the kiln is operated at 200° C for 1.5 h, the temperature is increased to 350° C and is maintained at that temperature for 2 h.

Finally, the temperature is increased to 525° C and the ashing is completed at that temperature; generally, a period of 36 h is required.

4. After 36 h, the electrical power is switched off and the kiln and samples are allowed to cool (1 to 2 h). After the crucibles have cooled to room temperature, the "crucible-plus-ash" weight is measured for each sample. These data are recorded, and the percent ash is calculated.

5. Forty 118 mL polystyrene jars are labeled, and three 6-mm-diameter glass beads are placed in each jar.

6. Ash from each crucible is then transferred into an individual polystyrene jar, and the jar is closed. Each jar subsequently is placed into a mixer-mill and agitated for 30 s. These homogenized samples are provided to the chemical laboratories for analysis.

Another method for determining ash in coal and coke is described by the ASTM (1984a) book of standards.

Cleaning of Work Area and Equipment

1. Make certain that the vents on the hoods are open; switch on electrical power to the exhaust system.

2. For the jaw crusher,a. Remove loose dust on the plates and surrounding area with a fast stream of air

from the compressed-air line.b. Remove buildup of sample on the crusher plates with a wire brush, and again

blow away loose material with a fast stream of air from the compressed-air line.

c. Wipe off the plates with a water-dampened sponge, and dry the plates with a stream of air from the compressed-air line.

d. Finally, wipe off the plates with a KimwipeTM tissue soaked with acetone.e. Blow away loose dust from the pan with a stream of air; then, clean the pan

with a water-dampened sponge.3. For the vertical grinder,

a. Blow away loose dust from the plates and pan with a stream of air.b. Pass clean sand through the grinder, as you would in grinding a coal sample,

and repeat step 3.a.4. In the work area and hood,

a. Wipe the inside of the hood and the counter space with a water-dampened sponge.

b. Dry the cleaned surfaces with a stream of air.

c. Once each week, thoroughly clean the entire floor with a broom and dust pan. Vacuum cleaning with a cleaner that does not generate sparks is quite appropriate.

REFERENCES

American Society for Testing and Materials (ASTM), 1984a, D2013-72(1978) Standard method of preparing coal samples for analysis: 1984 annual book of ASTM standards, Petroleum products, lubricants, and fossil fuels, sect. 5, v. 05.05: Gaseous fuels, coal, and coke: Philadelphia, ASTM, p. 298-312.

_______ 1984b, D3174-82 Standard test method for ash in the analysis sample of coal and coke from coal: 1984 Annual Book of ASTM Standards, Petroleum products, lubricants, and fossil fuels, sect. 5, v. 05.05: Gaseous fuels, coal, and coke: Philadelphia, ASTM, p. 401-404.

Swaine, D.J., 1985, Modern methods in bituminous coal analysis: trace elements: CRC Critical Reviews in Analytical Chemistry, v. 15, no. 4, p. 323.

COAL BASICSCoal is a term used to describe a wide range of organic compounds composed of macerals (as opposed to minerals). A maceral is a component of coal or oil shale. The term 'maceral' in

reference to coal is analogous to the use of the term 'mineral' in reference to igneous or metamorphic rocks. Examples of macerals are inertinite, vitrinite and liptinite.

Coal maceral groups, names and hydrocarbon potential. Coals are often described by their common names instead of maceral type, as shown below.

Bituminous coal is an organic sedimentary rock formed by diagenetic and submetamorphic compression of peat bog material. Il has been compressed and heated so that its primary constituents are macerals. The carbon content of bituminous coal is around 60 to 80%; the rest is composed of water, air, hydrogen, and sulfur, which have not been driven off from the macerals. Bituminous coal or black coal is relatively soft, containing a tarlike substance called bitumen. It is of higher quality than lignite coal but of poorer quality than anthracite coal.

Lignite, often referred to as brown coal, is a soft brown fuel with characteristics that put it somewhere between coal and peat. It is considered the lowest rank of coal, used almost exclusively as a fuel for steam-electric power generation. Lignite has a carbon content of around 25 to 35%, a high inherent moisture content sometimes as high as 66%, and an ash content ranging from 6% to 19% compared with 6% to 12% for bituminous coal.

Anthracite is a hard, compact variety of mineral coal that has a high luster. It has the highest carbon content, between 92% and 98%, and contains the fewest impurities of all

coals, despite its lower calorific content. Anthracite is the most metamorphosed type of coal. The term is applied to coals which do not give off tarry or other hydrocarbon vapours when heated below their point of ignition.

Coal rank depends on thermal maturity

PROXIMATE ANALYSISProximate analysis of coal is a simple laboratory method for determining the components of coal, obtained when the coal sample is heated (pyrolysis) under specified conditions. The coal sample is extracted from a core and placed quickly in a canister to preserve as much gas as possible.

As defined by ASTM D 121, proximate analysis separates the coal into four groups: 1. moisture, 2. volatile matter, consisting of gases and vapors driven off during pyrolysis, 3. fixed carbon, the nonvolatile fraction of coal 4. ash, the inorganic residue remaining after combustion.

Fixed carbon is also called carbon, dry coal, pure coal, or dry ash-free coal. The latter term is the most descriptive - dry ash-free is often abbreviated as "daf" or "DAF".

Moisture is an important property of coal, as all coals are mined wet. Groundwater and other extraneous moisture is known as adventitious moisture and is readily evaporated. Moisture held within the coal itself is known as inherent moisture and is analyzed quantitatively. Adventitious moisture is removed in the lab by evaporation in air.

Moisture may occur in four possible forms within coal: 1. surface moisture: water held on the surface of coal particles or macerals 2. hydroscopic moisture: water held by capillary action within the micro-fractures of the coal 3. decomposition moisture: water held within the coal's decomposed organic compounds

4. mineral moisture: water which comprises part of the crystal structure of hydrous silicates such as clays

Total moisture is analyzed by loss of mass between an air-dried sample and the sample after driving off the inherent moisture with heat. This is achieved by any of the following methods; 1. heating the coal with toluene 2. drying in a minimum free-space oven at 150 °C (302 °F) within a nitrogen atmosphere 3. drying in air at 100 to 105 °C (212 to 221 °F)

Methods 1 and 2 are suitable with low-rank coals but method 3 is only suitable for high-rank coals as free air drying low-rank coals may promote oxidation.

Volatile matter in coal refers to the components of coal, except for moisture, which are liberated at high temperature in the absence of air. This is usually a mixture of short and long chain hydrocarbons, aromatic hydrocarbons, and some sulfur. In Australian and British laboratories, this involves heating the coal sample to 900 ± 5 °C (1650 ±10 °F) for 7 minutes in a cylindrical silica crucible in a muffle furnace. American procedures involve heating to 950 ± 25 °C (1740 ± 45 °F) in a vertical platinum crucible. These two methods give different results and thus the method used must be stated.

Fixed carbon content of the coal is the carbon found in the material which is left after volatile materials are driven off. This differs from the ultimate carbon content of the coal because some carbon is lost in hydrocarbons with the volatiles. Fixed carbon is used as an estimate of the coke yield from a sample of coal. Fixed carbon is determined by subtracting the mass of volatiles, determined above, from the original mass of the coal sample.

Ash content of coal is the non-combustible residue left after coal is burnt. It represents the bulk mineral matter after carbon, oxygen, sulfur and water (including from clays) has been driven off during combustion. Analysis is fairly straightforward, with the coal thoroughly burnt and the ash material expressed as a percentage of the original weight.

Example of Proximate Analysis of several coal seams - data is in Weight %

Well log showing location of coal layers analyzed by proximate analysis. Log curves are GR, CAL, PE, neutron, density, density correction.

Float Sink Analysis is used to separate non-coal cavings from cuttings samples. The crushed material is placed in a liquid with a density of 1.75 g/cc. The coal fraction is floated off and the non-coal sinks and is removed. Some mineral (ash) in the coal may sink, reducing the apparent ash content. By comparing the ash analysis to the float sink analysis with that from core analysis, the gas contents can be normalised to reflect true ash contents of the coal cuttings.

Vitrinite is the most common component of coal. It is also abundant in kerogen, derived from the same biogenic precursors as coals, namely land plants and humic peats. Vitrinite forms diagenetically by the thermal alteration of lignin and cellulose in plant cell walls. It is therefore common in sedimentary rocks that are rich in organic matter, such as shales and marls with a terrigenous origin. Conversely, carbonates, evaporites, and well-sorted sandstones have very low vitrinite content. Vitrinite is absent in pre-Silurian rocks because land plants had not yet evolved.

Vitrinite reflectance was first studied by coal geologists attempting to determine the thermal maturity, or rank, of coal beds. More recently, it is used to study sedimentary organic matter from kerogen. It is sensitive to temperature ranges that correspond to hydrocarbon generation (60 to 120°C). This means that, with a suitable calibration, vitrinite reflectance can be used as an indicator of maturity in hydrocarbon source rocks. Generally, the onset of oil generation is correlated with a reflectance of 0.5 to 0.6% and the termination of oil generation with reflectance of 0.85 to 1.1%

VISUAL ANALYSIS OF COALThe use of well logs for analyzing coal deposits dates back many years. Most methods are based on a multi-mineral model which solves for moisture, volatile components, fixed carbon, and ash. These are the same components determined from coal cores or sample chips by proximate analysis.

Visual analysis of logs for coal is relatively unambiguous. High neutron porosity, high density porosity (low density), high sonic, high resistivity, and clean gamma ray mean coal.

Thresholds on each curve are used to trigger a coal flag. Three or more flags is a pretty good indication of the presence of coal. Some coals are very dirty (shaly) so the gamma ray and resistivity may not trigger.

COAL ANALYSIS FROM LOGSThe use of well logs for analyzing coal deposits dates back many years. Most methods are based on a multi-mineral model which solves for moisture, volatile components, fixed carbon, and ash. These are the same components determined from coal cores or sample chips by proximate analysis.

One log analysis model calculates a 3-mineral model from PE, density, neutron, sonic crossplot methods and solves for the fraction of lignite, bituminous coal, and anthracite. With this breakdown, the coal matrix density can be determined, and the other parameters follow from this value: 1: DENSMAcoal = Vlignite * 1.19 + Vbituminous * 1.34 + Vanthracite * 1.47

An alternative method is a 3-mineral model using ash, fixed carbon, and moisture. The GR is used to obtain Vclay, making a 4-mineral model relatively easy. Both models can be solved by crossplots or the math shown elsewhere in this Handbook. MATRIX PARAMETERS FOR 3-MINERAL MODEL - COAL TYPE DENSMA PHIN DTC DTCMA PE g/cc frac us/ft us/m us/ft us/m Anthracite 1.47 0.41 105 345 48 157 0.16 Bituminous 1.24 0.60+ 120 394 44 144 0.17 Lignite 1.19 0.54 160 525 50 164 0.20 Peat 1.14 0.26 0.25 MATRIX PARAMETERS FOR 3-MINERAL MODEL - COAL COMPOSITION DENSMA PHIN DTCMA PE g/cc frac us/ft us/m cu Ash (Quartz) 2.65 0.00 55 182 1.8 Could vary if other minerals (eg calcite) are also present Ash (Clay) 2.18 - 2.65 0.25 80 250 3.5 Includes clay bound water, varies with clay mineral Carbon 1.19 - 1.47 0.60 120 394 0.2 Varies with coal type (dry, ash-free value) Water 1.00 1.00 200 656 0.1 Free water or "moisture", excludes clay bound water

Density neutron crossplot for coal analysis (bottom left), density sonic crossplot (top right). Data points show that the ash in this coal is mostly clay (log data falls to the right of the quartz point).

The mineral end points are not firm, so some experimentation and sample descriptions are needed. If a 3-mineral model is not possible, the analyst must decide on the correct coal type.

A dry clay model can also be used, but the water term will include the clay bound water, not just the free water. It can be removed by subtracting clay bound water from the tptal to get the free water answer.

The ash data points may vary with clay type and other noncombustible mineral content, so crossplots of lab ash content (by volume) versus log readings can help pin down these values.

CALCULATING COAL PROPERTIESThe following equations are found in the coal assay literature and are based on correlations between core analysis values and log data. Parameters can be tuned by making your own crossplots. Standard 3- and 4- mineral models using simultaneous equations, DENSma-Uma crossplots, or Mlith-Nlith crossplots (or equivalent math) are probably more practical when the core data correlations are not available.

Initial results are in volume fractions and are converted to weight fractions by using the density of each component.

Ash Content: 2: Vash = (DENS - DENSMAcoal) / (2.5 – DENSMAcoal)OR 2a: Vash = 0.65 * (DENS - 1.00)

Equations specific to a project area can be obtained by plotting coal assay data versus density log data, as shown in the examples at the right.

Fixed Carbon (dry coal): 3: Vfcarb = 0.512 * (1.0 – Vash)

Moisture (free water): 4: Vwtr = 0.461 – Vash

Volatile Matter: 5: Vvolatile = 1.0 – Vash - Vfcarb – Vwtr

Numerical Example:Given: DENSMAcoal = 1.24 DENS = 1.36 g/cc Vash = 0.10 OR Vash = 0.23 Vfcarb = 0.36 0.39 Vwtr = 0.47 0.23 Vvolatile = 0.07 0.15

All proximate analysis results are reported in weight fraction or percent. To convert log analysis volume fractions to weight fractions, use the following: 6: WTash = Vash * DENSash 7: WTfcarb = Vfcarb * DENSfcarb

8: WTwtr = Vwtr * DENSwtr 9 : WTvolatile = Vvolatile * DENSvolatile 10: WTcoal = WTash + WTfcarb + WTwtr + WTvolatile

Mass fractions are as follows (multiply by 100 to get weight percent): 11: Wash = WTash / WTcoal 12: Wfcarb = WTfcarb / WTcoal 13: Wwtr = WTwtr / WTcoal 14: Wvolatile = WTvolatile / WTcoal

Weight percent is often used in reports: 15: WT%ash = 100 * Wash 16: WT%fcarb = 100 * WTfcarb 17: WT%wtr = 100 * WTwtr 18: WT%volatile = 100 * WTvolatile

Where: DENS = density log reading in a coal (g/cc) DENSMAcoal = matrix density of a coal (g/cc) DENSxxx = density of a component (g/cc) Vxxx = volume fraction of a component (fractional) WTxxx = weight of a component (grams) Wxxx = mass fraction of a component (fractional) WT%xxx = weight percent of a component (percent)

Numerical Example:Given: DENSMAcoal = 1.24 DENS = 1.36 g/cc Volume Density Weight Mass Fraction Ash 0.10 2.65 0.25 0.21 Fcarb 0.36 1.24 0.57 0.48 Wtr 0.47 1.00 0.37 0.31 Volatile 0.07 0.00 0.00 0.00 Rock 1.00 1.19

COAL ANALYSIS EXAMPLE LOG

Log analysis of an Alberta Foothills coal using a model for coal composition (fixed carbon, volatiles, moisture, and ash (2nd track from the right). These results can be ca;ibrated to the proximate analysis from lab measurements.

Example of coal log analysis results using a 3-mineral model for coal type (lignite, bituminous, anthracite) in right hand track. Zones outside the coal are analyzed with conventional oil and gas models.

COAL: Ancient Gift Serving Modern Manby the American Coal Foundation [http://www.teachcoal.org]

Types of Coal

We use the term "coal" 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.

Coal is classified into four general categories, or "ranks." They range from lignite through sub-bituminous and bituminous to anthracite, reflecting the progressive response of individual deposits of coal to increasing heat and pressure. The carbon content of coal supplies most of its heating value, but other factors also influence the amount of energy it contains per unit of weight. (The amount of energy in coal is expressed in British thermal units per pound. A BTU is the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.)

About 90 percent of the coal in this country falls in the bituminous and sub-bituminous categories, which rank below anthracite and, for the most part, contain less energy per unit of weight. Bituminous coal predominates in the Eastern and Mid-continent coal fields, while sub-bituminous coal is generally found in the Western states and Alaska.

Lignite ranks the lowest and is the youngest of the coals. Most lignite is mined in Texas, but large deposits also are found in Montana, North Dakota, and some Gulf Coast states.

Anthracite

Anthracite is coal with the highest carbon content, between 86 and 98 percent, and a heat value of nearly 15,000 BTUs-per-pound. Most frequently associated with home heating, anthracite is a very small segment of the U.S. coal market. There are 7.3 billion tons of anthracite reserves in the United States, found mostly in 11 northeastern counties in Pennsylvania.

Bituminous

The most plentiful form of coal in the United States, bituminous coal is used primarily to generate electricity and make coke for the steel industry. The fastest growing market for coal, though still a small one, is supplying heat for industrial processes. Bituminous coal has a carbon content ranging from 45 to 86 percent carbon and a heat value of 10,500 to 15,500 BTUs-per-pound.

Sub-bituminous

Ranking below bituminous is sub-bituminous coal with 35-45 percent carbon content and a heat value between 8,300 and 13,000 BTUs-per-pound. Reserves are located mainly in a half-dozen Western states and Alaska. Although its heat value is lower, this coal generally has a lower sulfur content than other types, which makes it attractive for use because it is cleaner burning.

Lignite

Lignite is a geologically young coal which has the lowest carbon content, 25-35 percent, and a heat value ranging between 4,000 and 8,300 BTUs-per-pound. Sometimes called brown coal, it is mainly used for electric power generation.

___________________________________________________________________________

CoalFrom Wikipedia, the free encyclopedia

Coal

— Sedimentary Rock —

Anthracite coal

Composition

Primary carbon

Secondary

sulfur,

hydrogen,

oxygen,

nitrogen

Example chemical structure of coal

Coal is a combustible black or brownish-black sedimentary rock normally occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon along with variable quantities of other elements, chiefly hydrogen, with smaller quantities of sulfur, oxygen and nitrogen.[citation needed]

Contents

[hide]

1 Formation 2 Types

o 2.1 Hilt's Law 3 Early uses as fuel 4 Uses today

o 4.1 Coal as fuel o 4.2 Coking and use of coke o 4.3 Ethanol production o 4.4 Gasification o 4.5 Liquefaction o 4.6 Refined coal o 4.7 Industrial processes

5 Cultural usage 6 Coal as a traded commodity 7 Environmental effects 8 Economic aspects 9 Energy density 10 Carbon intensity 11 Underground fires 12 Production trends

o 12.1 World coal reserves o 12.2 Major coal producers o 12.3 Major coal exporters o 12.4 Major coal importers

13 See also 14 References 15 Further reading 16 External links

[edit] Formation

Coal begins as layers of plant matter accumulate at the bottom of a body of water. For the process to continue the plant matter must be protected from biodegradation and oxidization, usually by mud or acidic water. This trapped atmospheric carbon in the ground in immense peat bogs that eventually were covered over and deeply buried by sediments under which they metamorphosed into coal. Over time, the chemical and physical properties of the plant remains were changed by geological action to create a solid material.[1]

The wide shallow seas of the Carboniferous period provided ideal conditions for coal formation, although coal is known from most geological periods. The exception is the Coal gap in the Lower Triassic, where coal is incredibly rare: presumably a result of the mass extinction which prefaced this era. Coal is even known from Precambrian strata, which predate land plants: this coal is presumed to have originated from algal residues.[2][3]

Coal, a fossil fuel, is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide anthropogenic sources of carbon dioxide releases. Gross carbon dioxide emissions from coal usage are slightly more than those from petroleum and about double the amount from natural gas.[4] Coal is extracted from the ground by mining, either underground by shaft mining through the seams or in open pits.

[edit] Types

Coastal exposure of the Point Aconi Seam (bituminous coal; Pennsylvanian).

Believed approximate position of the proto-continents toward the end of the Carboniferous period; the light blue represents shallow seas where many of today's coal deposits are found, as opposed to deeper waters which gave rise to oil-bearing rocks derived from marine species. The ice caps were known to be very large, lowering sea levels extensively by locking up oceanic waters into solid ice, though how large the ice caps became is a matter of debate.

As geological processes apply pressure to dead biotic material over time, under suitable conditions it is transformed successively into

Peat , 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 , 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 Upper Palaeolithic

Sub-bituminous coal , whose properties range from those of lignite to those of bituminous coal are used primarily as fuel for steam-electric power generation. Additionally, it is an important source of light aromatic hydrocarbons for the chemical synthesis industry.

Bituminous coal , dense sedimentary rock, 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

Steam coal is a grade between bituminous coal and anthracite, once widely used as a fuel for steam locomotives. In this specialized use it is sometimes known as sea-coal in the U.S.[5] Small steam coal (dry small steam nuts or DSSN) was used as a fuel for domestic water heating

Anthracite , 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

Graphite , technically the highest rank, but difficult to ignite and is not so commonly used as fuel: it is mostly used in pencils and, when powdered, as a lubricant.

The classification of coal is generally based on the content of volatiles. However, the exact classification varies between countries. According to the German classification, coal is classified as follows:[6]

Name Volatiles % C H O S Heat content

Carbon % Hydrogen % Oxygen % Sulfur % kJ/kg

Braunkohle (Lignite) 45-65 60-75 6.0-5.8 34-17 0.5-3 <28470

Flammkohle (Flame coal) 40-45 75-82 6.0-5.8 >9.8 ~1 <32870

Gasflammkohle (Gas flame coal)

35-40 82-85 5.8-5.6 9.8-7.3 ~1 <33910

Gaskohle (Gas coal) 28-35 85-87.5 5.6-5.0 7.3-4.5 ~1 <34960

Fettkohle (Fat coal) 19-28 87.5-89.5 5.0-4.5 4.5-3.2 ~1 <35380

Esskohle (Forge coal) 14-19 89.5-90.5 4.5-4.0 3.2-2.8 ~1 <35380

Magerkohle (Non baking coal)

10-14 90.5-91.5 4.0-3.75 2.8-3.5 ~1 35380

Anthrazit (Anthracite) 7-12 >91.5 <3.75 <2.5 ~1 <35300

Percent by weight

The middle six grades in the table represent a progressive transition from the English-language sub-bituminous to bituminous coal, while the last class is an approximate equivalent to anthracite, but more inclusive (the U.S. anthracite has < 6% volatiles).

Cannel coal (sometimes called "candle coal"), is a variety of fine-grained, high-rank coal with significant hydrogen content. It consists primarily of "exinite" macerals, now termed "liptinite".

[edit] Hilt's Law

This section does not cite any references or sources.Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2011)

Hilt's Law is a geological term that states the deeper the coal, the deeper its rank (grade). The law holds true if the thermal gradient is entirely vertical, but metamorphism may cause lateral changes of rank, irrespective of depth.

[edit] Early uses as fuel

Further information: History of coal mining

Chinese coal miners in an illustration of the Tiangong Kaiwu encyclopedia, published in 1637

The earliest reference to the use of coal as fuel is from the geological treatise On stones (Lap. 16) by the Greek scientist Theophrastus (c. 371–287 BC):

Among the materials that are dug because they are useful, those known as coals are made of earth, and, once set on fire, they burn like charcoal. They are found in Liguria… and in Elis as one approaches Olympia by the mountain road; and they are used by those who work in metals.[7]

Outcrop coal was used in Britain during the Bronze Age (3000–2000 BC), where it has been detected as forming part of the composition of funeral pyres.[8][9] In Roman Britain, with the exception of two modern fields, "the Romans were exploiting coals in all the major coalfields in England and Wales by the end of the second century AD".[10] Evidence of trade in coal (dated to about AD 200) has been found at the inland port of Heronbridge, near Chester, and in the Fenlands of East Anglia, where coal from the Midlands was transported via the Car Dyke for use in drying grain.[11] Coal cinders have been found in the hearths of villas and military forts, particularly in Northumberland, dated to around AD 400. In the west of England contemporary writers described the wonder of a permanent brazier of coal on the altar of Minerva at Aquae Sulis (modern day Bath) although in fact easily accessible surface coal from what became the Somerset coalfield was in common use in quite lowly dwellings locally.[12] Evidence of coal's use for iron-working in the city during the Roman period has been found.[13] In Eschweiler, Rhineland, deposits of bituminous coal were used by the Romans for the smelting of iron ore.[10]

There is no evidence that the product was of great importance in Britain before the High Middle Ages, after about AD 1000.[14] Mineral coal came to be referred to as "seacoal" in the 13th century; the wharf where the material arrived in London was known as Seacoal Lane, so identified in a charter of King Henry III granted in 1253.[15] Initially the name was given because much coal was found on the shore, having fallen from the exposed coal seams on cliffs above or washed out of underwater coal outcrops,[14] but by the time of Henry VIII it was understood to derive from the way it was carried to London by sea.[16] In 1257–59, coal from Newcastle was shipped to London for the smiths and lime-burners building Westminster Abbey.[14] Seacoal Lane

and Newcastle Lane where coal was unloaded at wharves along the River Fleet, are still in existence.[17] (See Industrial processes below for modern uses of the term.)

These easily accessible sources had largely become exhausted (or could not meet the growing demand) by the 13th century, when underground mining from shafts or adits was developed.[8] The alternative name was "pitcoal," because it came from mines. It was, however, the development of the Industrial Revolution that led to the large-scale use of coal, as the steam engine took over from the water wheel. In 1700, 5/6 of the world's coal was mined in Britain. Without coal, Britain would have run out of suitable sites for watermills by the 1830s.[18] In 1947, there were some 750,000 miners,[19] but by 2004 this had shrunk to some 5,000 miners working in around 20 collieries.[20]

In ancient China, coal was used as fuel by the 4th century AD, but there was little extensive use until the 11th century.[21]

[edit] Uses today

Coal fired power plants provide 49% of consumed electricity in the United States. This is the Castle Gate Plant near Helper, Utah.

Coal rail cars

[edit] Coal as fuel

Further information: Electricity generation, Clean coal technology, Coal electricity, and Global warming

Coal is primarily used as a solid fuel to produce electricity and heat through combustion. World coal consumption was about 6,743,786,000 short tons in 2006[22] and is expected to increase 48% to 9.98 billion short tons by 2030.[23] China produced 2.38 billion tons in 2006. India produced about 447.3 million tons in 2006. 68.7% of China's electricity comes from coal. The USA consumes about 14% of the world total, using 90% of it for generation of electricity.[24]

When coal is used for electricity generation, it is usually pulverized and then combusted (burned) in a furnace with a boiler. The furnace heat converts boiler water to steam, which is then used to spin turbines which turn generators and create electricity. The thermodynamic efficiency of this process has been improved over time. Simple cycle steam turbines have topped out with some of the most advanced reaching about 35% thermodynamic efficiency for the entire process. Increasing the combustion temperature can boost this efficiency even further.[25] Old coal power plants, especially "grandfathered" plants, are significantly less efficient and produce higher levels of waste heat. At least 40% of the world's electricity comes from coal,[26] and in 2008 approximately 49% of the United States' electricity came from coal.[27] The emergence of the supercritical turbine concept envisions running a boiler at extremely high temperatures and pressures with projected efficiencies of 46%, with further theorized increases in temperature and pressure perhaps resulting in even higher efficiencies.[28]

Other efficient ways to use coal are combined heat and power cogeneration and an MHD topping cycle.

More than 40% of the world electricity production uses coal.[29] The total known deposits recoverable by current technologies, including highly polluting, low energy content types of coal (i.e., lignite, bituminous), is sufficient for many years. However, consumption is increasing and maximal production could be reached within decades (see World Coal Reserves, below).

A more energy-efficient way of using coal for electricity production would be via solid-oxide fuel cells or molten-carbonate fuel cells (or any oxygen ion transport based fuel cells that do not discriminate between fuels, as long as they consume oxygen), which would be able to get 60%–85% combined efficiency (direct electricity + waste heat steam turbine).[citation needed] Currently these fuel cell technologies can only process gaseous fuels, and they are also sensitive to sulfur poisoning, issues which would first have to be worked out before large-scale commercial success is possible with coal. As far as gaseous fuels go, one idea is pulverized coal in a gas carrier, such as nitrogen. Another option is coal gasification with water, which may lower fuel cell voltage by introducing oxygen to the fuel side of the electrolyte, but may also greatly simplify carbon sequestration. However, this technology has been criticised as being inefficient, slow, risky and costly, while doing nothing about total emissions from mining, processing and combustion.[30] Another efficient and clean way of coal combustion in a form of coal-water slurry fuel (CWS) was well-developed in Russia (since the Soviet Union time). CWS significantly reduces emissions saving the heating value of coal.

[edit] Coking and use of coke

Main article: Coke (fuel)

Coke oven at a smokeless fuel plant in Wales, United Kingdom

Coke is a solid carbonaceous residue derived from low-ash, low-sulfur bituminous coal from which the volatile constituents are driven off by baking in an oven without oxygen at temperatures as high as 1,000 °C (1,832 °F) so that the fixed carbon and residual ash are fused together. Metallurgical coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. The product is cast iron and is too rich in dissolved carbon, and so must be treated further to make steel.

The coke must be strong enough to resist the weight of overburden in the blast furnace, which is why coking coal is so important in making steel by the conventional route. However, the alternative route to is direct reduced iron, where any carbonaceous fuel can be used to make sponge or pelletised iron. Coke from coal is grey, hard, and porous and has a heating value of 24.8 million Btu/ton (29.6 MJ/kg). Some cokemaking processes produce valuable by-products that include coal tar, ammonia, light oils, and "coal gas".

Petroleum coke is the solid residue obtained in oil refining, which resembles coke but contains too many impurities to be useful in metallurgical applications.

[edit] Ethanol production

The reaction of coal and natural gas was used by a German manufacturer for Buna rubber: Chemische Werke Huls, at Marl, Germany, and AVCO Corp in the US. Consequently several references had described both Huls Arc Process and AVCO rotating arc reactor.[31][32] Both reactors are of cylindrical shape and have a rotating electric arc. The cathode is at the cylinder axis, while the anode is on the circumference. As methane gas provided the highest yield, then it is forced with coal powder into a vortex passing through the electric arc for few milliseconds.

Huls Arc Process[33] produced a mixture of acetylene and ethylene gases. The reaction conditions can be varied to determine the needed product. Increasing the Specific Energy Requirement (SER) favors acetylene production, and lower SER is for ethylene:

Enthalpy Change for Ethylene:[34] = 127.34 kJ/mol, while for acetylene: = 301.4 kJ/mol. As a consequence, recent production processes are using conventional heating instead of electric arc.

Hydration of ethylene gas producing ethanol is the most important process for ethanol production. Vapor phase process is the preferred one[35] in which ethylene and steam pass over a catalyst. One of the most accepted catalysts is diatomite impregnated with phosphoric acid.

[edit] Gasification

Main articles: Coal gasification and Underground coal gasification

Coal gasification can be used to produce syngas, a mixture of carbon monoxide (CO) and hydrogen (H2) gas. This syngas can then be converted into transportation fuels like gasoline and diesel through the Fischer-Tropsch process. This technology is currently used by the Sasol chemical company of South Africa to make gasoline from coal and natural gas. Alternatively, the hydrogen obtained from gasification can be used for various purposes such as powering a hydrogen economy, making ammonia, or upgrading fossil fuels.

During gasification, the coal is mixed with oxygen and steam (water vapor) while also being heated and pressurized. During the reaction, oxygen and water molecules oxidize the coal into carbon monoxide (CO) while also releasing hydrogen (H2) gas. This process has been conducted in both underground coal mines and in coal refineries.

(Coal) + O2 + H2O → H2 + CO

If the refiner wants to produce gasoline, the syngas is collected at this state and routed into a Fischer-Tropsch reaction. If hydrogen is the desired end-product, however, the syngas is fed into the water gas shift reaction where more hydrogen is liberated.

CO + H2O → CO2 + H2

High prices of oil and natural gas are leading to increased interest in "BTU Conversion" technologies such as gasification, methanation and liquefaction. The Synthetic Fuels Corporation was a U.S. government-funded corporation established in 1980 to create a market for alternatives to imported fossil fuels (such as coal gasification). The corporation was discontinued in 1985.

In the past, coal was converted to make coal gas, which was piped to customers to burn for illumination, heating, and cooking. At present, the safer natural gas is used instead.

[edit] Liquefaction

Main article: Coal liquefaction

Coal can also be converted into liquid fuels such as gasoline or diesel by several different processes. In the direct liquefaction processes, the coal is either hydrogenated or carbonized. Hydrogenation processes are the Bergius process,[36] the SRC-I and SRC-II (Solvent Refined

Coal) processes and the NUS Corporation hydrogenation process.[37][38] In the process of low-temperature carbonization, coal is coked at temperatures between 360 °C (680 °F) and 750 °C (1,380 °F). These temperatures optimize the production of coal tars richer in lighter hydrocarbons than normal coal tar. The coal tar is then further processed into fuels. Alternatively, coal can be converted into a gas first, and then into a liquid, by using the Fischer-Tropsch process. An overview of coal liquefaction and its future potential is available.[39]

Coal liquefaction methods involve carbon dioxide (CO2) emissions in the conversion process. If coal liquefaction is done without employing either carbon capture and storage technologies or biomass blending, the result is lifecycle greenhouse gas footprints that are generally greater than those released in the extraction and refinement of liquid fuel production from crude oil. If CCS technologies are employed, reductions of 5-12% can be achieved in CTL plants and up to a 75% reduction is achievable when co-gasifying coal with commercially demonstrated levels of biomass (30% biomass by weight) in CBTL plants.[40] For most future synthetic fuel projects, Carbon dioxide sequestration is proposed to avoid releasing it into the atmosphere. Sequestration will, however, add to the cost of production. Currently all US and at least one Chinese synthetic fuel projects,[41] include sequestration in their process designs.

Coal liquefaction features intense research work, particularly in China, Germany, South Africa and the USA. Every year, the World CTL Award rewards an individual who has contributed substantially in the understanding and development of Coal and Biomass Conversion. In 2011, the World CTL Award was granted to Rudi Heydenrich, executive manager of Sasol Technology.

[edit] Refined coal

Main article: Refined coal

Refined coal is the product of a coal-upgrading technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals. It is one form of several pre-combustion treatments and processes for coal that alter coal's characteristics before it is burned. The goals of pre-combustion coal technologies are to increase efficiency and reduce emissions when the coal is burned. Depending on the situation, pre-combustion technology can be used in place of or as a supplement to post-combustion technologies to control emissions from coal-fueled boilers.

[edit] Industrial processes

Finely ground bituminous coal, known in this application as sea coal, is a constituent of foundry sand. While the molten metal is in the mould the coal burns slowly, releasing reducing gases at pressure and so preventing the metal from penetrating the pores of the sand. It is also contained in mould wash, a paste or liquid with the same function applied to the mould before casting.[42] Sea coal can be mixed with the clay lining (the "bod") used for the bottom of a cupola furnace. When heated the coal decomposes and the bod becomes slightly friable, easing the process of breaking open holes for tapping the molten metal.[43]

[edit] Cultural usage

Coal is the official state mineral of Kentucky (even though coal is not a mineral) and the official state rock of Utah. Both U.S. states have a historic link to coal mining.

Some cultures uphold that children who misbehave will receive only a lump of coal from Santa Claus for Christmas in their stockings instead of presents.

It is also customary and lucky in Scotland and the North of England to give coal as a gift on New Year's Day. It happens as part of First-Footing and represents warmth for the year to come.

[edit] Coal as a traded commodity

In North America, Central Appalachian coal futures contracts are currently traded on the New York Mercantile Exchange (trading symbol QL). The trading unit is 1,550 short tons (1,410 t) per contract, and is quoted in U.S. dollars and cents per ton. Since coal is the principal fuel for generating electricity in the United States, coal futures contracts provide coal producers and the electric power industry an important tool for hedging and risk management.[44]

In addition to the NYMEX contract, the IntercontinentalExchange (ICE) has European (Rotterdam) and South African (Richards Bay) coal futures available for trading. The trading unit for these contracts is 5,000 tonnes (5,500 short tons), and are also quoted in U.S. dollars and cents per ton.[45]

The price of coal increased from around $30.00 per short ton in 2000 to around $150.00 per short ton as of September 2008. As of October 2008, the price per short ton had declined to $111.50. Prices further declined to $71.25 as of October 2010.[46]

[edit] Environmental effects

Main article: Environmental effects of coal

Aerial photograph of Kingston Fossil Plant coal fly ash slurry spill site taken the day after the event

There are a number of adverse health[47] and environmental effects of coal burning[48] especially in power stations, and of coal mining. These effects include:

Coal-fired power plants shorten nearly 24,000 lives a year in the United States, including 2,800 from lung cancer [49]

Generation of hundreds of millions of tons of waste products, including fly ash, bottom ash, flue gas desulfurization sludge, that contain mercury, uranium, thorium, arsenic, and other heavy metals

Acid rain from high sulfur coal Interference with groundwater and water table levels Contamination of land and waterways and destruction of homes from fly ash spills such as

Kingston Fossil Plant coal fly ash slurry spill Impact of water use on flows of rivers and consequential impact on other land-uses Dust nuisance Subsidence above tunnels, sometimes damaging infrastructure Coal-fired power plants without effective fly ash capture are one of the largest sources of

human-caused background radiation exposure Coal-fired power plants emit mercury, selenium, and arsenic which are harmful to human health

and the environment[50]

Release of carbon dioxide, a greenhouse gas, which causes climate change and global warming according to the IPCC and the EPA. Coal is the largest contributor to the human-made increase of CO2 in the air[51]

[edit] Economic aspects

Coal liquefaction is one of the backstop technologies that could potentially limit escalation of oil prices and mitigate the effects of transportation energy shortage that will occur under peak oil. This is contingent on liquefaction production capacity becoming large enough to satiate the very large and growing demand for petroleum. Estimates of the cost of producing liquid fuels from coal suggest that domestic U.S. production of fuel from coal becomes cost-competitive with oil priced at around $35 per barrel,[52] with the $35 being the break-even cost. With oil prices as low as around $40 per barrel in the U.S. as of December 2008, liquid coal lost some of its economic allure in the U.S., but will probably be re-vitalized, similar to oil sand projects, with an oil price around $70 per barrel.

In China, due to an increasing need for liquid energy in the transportation sector, coal liquefaction projects were given high priority even during periods of oil prices below $40 per barrel.[53] This is probably because China prefers not to be dependent on foreign oil, instead utilizing its enormous domestic coal reserves. As oil prices were increasing during the first half of 2009, the coal liquefaction projects in China were again boosted, and these projects are profitable with an oil barrel price of $40.[54]

China is by far the largest producer of coal in the world.[55] It has now become the world's largest energy consumer[56] but relies on coal to supply about 70% of its energy needs.[57] An estimated 5 million people work in China's coal-mining industry.[58]

Among commercially mature technologies, advantages for indirect coal liquefaction over direct coal liquefaction are reported by Williams and Larson (2003).

[edit] Energy density

Main article: Energy value of coal

The energy density of coal, i.e. its heating value, is roughly 24 megajoules per kilogram.[59]

The energy density of coal can also be expressed in kilowatt-hours, the units that electricity is most commonly sold in, per units of mass to estimate how much coal is required to power electrical appliances. One kilowatt-hour is 3.6 MJ, so the energy density of coal is 6.67 kW·h/kg. The typical thermodynamic efficiency of coal power plants is about 30%, so of the 6.67 kW·h of energy per kilogram of coal, 30% of that—2.0 kW·h/kg—can successfully be turned into electricity; the rest is waste heat. So coal power plants obtain approximately 2.0 kW·h per kilogram of burned coal.

As an example, running one 100-watt lightbulb for one year requires 876 kW·h (100 W × 24 h/day × 365 day/year = 876000 W·h = 876 kW·h). Converting this power usage into physical coal consumption:

It takes 325 kg (714 lb) of coal to power a 100 W lightbulb for one year.[60] One should also take into account transmission and distribution losses caused by resistance and heating in the power lines, which is in the order of 5–10%, depending on distance from the power station and other factors.

[edit] Carbon intensity

Commercial coal has a carbon content of at least 70%. Coal with a heating value of 6.67 kWh per kilogram as quoted above has a carbon content of roughly 80%, which is

, where 1 mol equals to NA (Avogadro Number) atoms.

Carbon combines with oxygen in the atmosphere during combustion, producing carbon dioxide, with an atomic weight of (12 + 16 × 2 = 44 kg/kmol). The CO2 released to air for each kilogram of incinerated coal is therefore

.

This can be used to calculate an emission factor for CO2 from the use of coal power. Since the useful energy output of coal is about 30% of the 6.67 kWh/kg(coal), the burning of 1 kg of coal produces about 2 kWh of electrical energy. Since 1 kg coal emits 2.93 kg CO2, the direct CO2 emissions from coal power are 1.47 kg/kWh, or about 0.407 kg/MJ.

The U.S. Energy Information Agency's 1999 report on CO2 emissions for energy generation,[61] quotes a lower emission factor of 0.963 kg CO2/kWh for coal power. The same source gives a factor for oil power in the U.S. of 0.881 kg CO2/kWh, while natural gas has 0.569 kg CO2/kWh. Estimates for specific emission from nuclear power, hydro, and wind energy vary, but are about 100 times lower.

[edit] Underground fires

Main article: Coal seam fire

There are hundreds of coal fires burning around the world.[62] Those burning underground can be difficult to locate and many cannot be extinguished. Fires can cause the ground above to subside, their combustion gases are dangerous to life, and breaking out to the surface can initiate surface wildfires. Coal seams can be set on fire by spontaneous combustion or contact with a mine fire or surface fire. Lightning strikes are an important source of ignition, the coal continues to burn slowly back into the seam until oxygen (air) can no longer reach the flame front. A grass fire in a coal area can set dozens of coal seams on fire.[63][64] Coal fires in China burn 109 million tons of coal a year, emitting 360 million metric tons of CO2. This contradicts the ratio of 1:1.83 given earlier,[clarification needed] but it amounts to 2-3% of the annual worldwide production of CO2 from fossil fuels, or as much as emitted from all of the cars and light trucks in the United States.[65][66] In Centralia, Pennsylvania (a borough located in the Coal Region of the United States), an exposed vein of coal ignited in 1962 due to a trash fire in the borough landfill, located in an abandoned anthracite strip mine pit. Attempts to extinguish the fire were unsuccessful, and it continues to burn underground to this day. The Australian Burning Mountain was originally believed to be a volcano, but the smoke and ash comes from a coal fire which may have been burning for over 5,500 years.[67]

At Kuh i Malik in Yagnob Valley, Tajikistan, coal deposits have been burning for thousands of years, creating vast underground labyrinths full of unique minerals, some of them very beautiful. Local people once used this method to mine ammoniac. This place has been well-known since the time of Herodotus, but European geographers misinterpreted the Ancient Greek descriptions as the evidence of active volcanism in Turkestan (up to the 19th century, when the Russian army invaded the area).

The reddish siltstone rock that caps many ridges and buttes in the Powder River Basin (Wyoming), and in western North Dakota is called porcelanite, which also may resemble the coal burning waste "clinker" or volcanic "scoria".[68] Clinker is rock that has been fused by the natural burning of coal. In the Powder River Basin approximately 27 to 54 billion tons of coal burned within the past three million years.[69] Wild coal fires in the area were reported by the Lewis and Clark Expedition as well as explorers and settlers in the area.[70]

[edit] Production trends

Coal output in 2005

A coal mine in Wyoming, United States. The United States has the world's largest coal reserves.

In 2006, China was the top producer of coal with 38% share followed by the USA and India, according to the British Geological Survey.

[edit] World coal reserves

The 930 billion short tons of recoverable coal reserves estimated by the Energy Information Administration are equal to about 4,116 BBOE (billion barrels of oil equivalent).[citation needed] The amount of coal burned during 2007 was estimated at 7.075 billion short tons, or 133.179 quadrillion BTU's.[71] This is an average of 18.8 million BTU per short ton. In terms of heat content, this is about 57,000,000 barrels (9,100,000 m3) of oil equivalent per day. By comparison in 2007, natural gas provided 51,000,000 barrels (8,100,000 m3) of oil equivalent per day, while oil provided 85,800,000 barrels per day.

BP, in its 2007 report, estimated at 2006 end that there were 909,064 million tons of proven coal reserves worldwide, or 147 years reserves-to-production ratio. This figure only includes reserves classified as "proven"; exploration drilling programs by mining companies, particularly in under-explored areas, are continually providing new reserves. In many cases, companies are aware of coal deposits that have not been sufficiently drilled to qualify as "proven". However, some nations haven't updated their information and assume reserves remain at the same levels even with withdrawals. Collective projections generally predict that global peak coal production may occur sometime around 2025 at 30 percent above current production in the best case scenario, depending on future coal production rates.[72]

Continental United States coal regions

Of the three fossil fuels, coal has the most widely distributed reserves; coal is mined in over 100 countries, and on all continents except Antarctica. The largest reserves are found in the USA, Russia, China, India and Australia. Note the table below.

Proved recoverable coal reserves at end-2008 (million tons (teragrams))[73]

CountryBituminous & Anthracite

SubBituminousLignite TOTAL

Percentage of World Total

United States 108,501 98,618 30,176 237,295 22.6

Russia 49,088 97,472 10,450 157,010 14.4

China 62,200 33,700 18,600 114,500 12.6

Australia 37,100 2,100 37,200 76,500 8.9

India 56,100 0 4,500 60,600 7.0

Germany 99 0 40,600 40,699 4.7

Ukraine 15,351 16,577 1,945 33,873 3.9

Kazakhstan 21,500 0 12,100 33,600 3.9

South Africa 30,156 0 0 30,156 3.5

Serbia 9 361 13,400 13,770 1.6

Colombia 6,366 380 0 6,746 0.8

Canada 3,474 872 2,236 6,528 0.8

Poland 4,338 0 1,371 5,709 0.7

Indonesia 1,520 2,904 1,105 5,529 0.6

Brazil 0 4,559 0 4,559 0.5

Greece 0 0 3,020 3,020 0.4

Bosnia and Herzegovina

484 0 2,369 2,853 0.3

Mongolia 1,170 0 1,350 2,520 0.3

Bulgaria 2 190 2,174 2,366 0.3

Pakistan 0 166 1,904 2,070 0.3

Turkey 529 0 1,814 2,343 0.3

Uzbekistan 47 0 1,853 1,900 0.2

Hungary 13 439 1,208 1,660 0.2

Thailand 0 0 1,239 1,239 0.1

Mexico 860 300 51 1,211 0.1

Iran 1,203 0 0 1,203 0.1

Czech Republic 192 0 908 1,100 0.1

Kyrgyzstan 0 0 812 812 0.1

Albania 0 0 794 794 0.1

North Korea 300 300 0 600 0.1

New Zealand 33 205333-

7,000571-

15,000[74] 0.1

Spain 200 300 30 530 0.1

Laos 4 0 499 503 0.1

Zimbabwe 502 0 0 502 0.1

Argentina 0 0 500 500 0.1

All others 3,421 1,346 846 5,613 0.7

Total world 404,762 260,789 195,387 860,938 100

[edit] Major coal producers

See also: List of countries by coal production

The reserve life is an estimate based only on current production levels and proved reserves level for the countries shown, and makes no assumptions of future production or even current production trends. Countries with annual production higher than 100 million tonnes are shown. For comparison, data for the European Union is also shown.

Production of Coal by Country and year (million tonnes)[75][76][77]

Country 2003 2004 2005 2006 2007 2008 2009 ShareReserve Life (years)

China 1722.0 1992.3 2204.7 2380.0 2526.0 2782.0 3050.0 45.6 % 38

USA 972.3 1008.9 1026.5 1053.6 1040.2 1062.8 973.2 15.8 % 245

India 375.4 407.7 428.4 447.3 478.4 521.7 557.6 6.2 % 105

EU 638.0 628.4 608.0 595.5 593.4 587.7 536.8 4.6 % 55

Australia 351.5 366.1 378.8 385.3 399.0 401.5 409.2 6.7 % 186

Russia 276.7 281.7 298.5 309.2 314.2 326.5 298.1 4.3 % 150+

Indonesia 114.3 132.4 146.9 195.0 217.4 229.5 252.5 3.6 % 17

South Africa 237.9 243.4 244.4 244.8 247.7 250.4 250.0 3.6 % 122

Germany 204.9 207.8 202.8 197.2 201.9 192.4 183.7 2.6 % 37

Poland 163.8 162.4 159.5 156.1 145.9 143.9 135.1 1.7 % 56

Kazakhstan 84.9 86.9 86.6 96.2 97.8 111.1 101.5 1.5 % 308

Total World 5,187.6 5,585.3 5,886.7 6,195.1 6,421.2 6,781.2 6,940.6 100 % 119

[edit] Major coal exporters

Countries with annual export higher than 10 million tonnes are shown.

Exports of Coal by Country and year (million short tons)[78][79][80]

Country 2003 2004 2005 2006 2007 2008 2009 Share

Australia 238.1 247.6 255.0 255.0 268.5 278.0 288.5 26.5%

Indonesia 107.8 131.4 142.0 192.2 221.9 228.2 261.4 24.0%

Russia 41.0 55.7 98.6 103.4 112.2 115.4 130.9 12.0%

Colombia 50.4 56.4 59.2 68.3 74.5 74.7 75.7 6.9%

South Africa 78.7 74.9 78.8 75.8 72.6 68.2 73.8 6.8%

USA 43.0 48.0 51.7 51.2 60.6 83.5 60.4 5.5%

China 103.4 95.5 93.1 85.6 75.4 68.8 38.4 3.5%

Canada 27.7 28.8 31.2 31.2 33.4 36.5 31.9 2.9%

Vietnam 6.9 11.7 19.8 23.5 35.1 21.3 28.2 2.6%

Kazakhstan 30.3 27.4 28.3 30.5 32.8 47.6 25.7 2.4%

Poland 28.0 27.5 26.5 25.4 20.1 16.1 14.6 1.3%

Total 713.9 764.0 936.0 1,000.6 1,073.4 1,087.3 1,090.8 100%

[edit] Major coal importers

Countries with annual import higher than 30 million tonnes are shown.

Imports of Coal by Country and year (million short tons)[81]

Country 2006 2007 2008 2009 Share

Japan 199.7 209.0 206.0 182.1 17.5%

China 42.0 56.2 44.5 151.9 14.5%

South Korea 84.1 94.1 107.1 109.9 10.6%

India 52.7 29.6 70.9 76.7 7.4%

Taiwan 69.1 72.5 70.9 64.6 6.2%

Germany 50.6 56.2 55.7 45.9 4.4%

United Kingdom 56.8 48.9 49.2 42.2 4.1%

Total 991.8 1,056.5 1,063.2 1,039.8 100%

Stove Help & Advice Home

The rank of coal is based on the degree to which the orginal plant material has been transformed into carbon and can be seen as a rough indication of how old the coal is: the older the coal the higher the carbon content (generally). The ranks of coal (from most to least carbon content) are as follows: anthracite, bituminous coal, sub bituminous coal, and lignite. The coal with the highest carbon content is the best and cleanest type of coal to use. As you move down the coal rank the heat given out decreases and the dirtyness of the fuel and moisture content increases.

Lignite coal

Used almost exclusively for electric power generation lignite is a young type of coal. Lignite is brownish black, has a high moisture content (up to 45 %), and a high suphur content. Lignite is more like soil than a rock and tends to disintegrate when exposed to the weather. Lignite is also called brown coal. Lignite has a colorific value of less than 5 kw/kg approximately.

Sub bituminous coal

Sub bituminous coal is also called black lignite. Sub bituminous coal black and contains 20-30 % moisture. Sub bituminous coal is used for generating electricity and space heating.Subbitumnious coal has calorific values ranging from 5 - 6.8 kW/kG approximately.

Bituminous coal

Bituminous coal is a soft, dense, black coal. Bituminous coal often has bands of bright and dull material in it. Bituminous coal is the most common coal and has moisture content less than 20 %. Bituminous coal is used for generating electricity, making coke, and space heating.Bituminous coal has calorific values ranging from 6.8 - 9 kW/kG approximately.

Anthracite coal

Often referred to as hard coal, anthracite is hard, black and lustrous. Anthracite is low in suplhur and high in carbon. It is the highest rank of coal. moisture content generally is less than 15 %. Anthracite has a calorfific values of around 9 kW/kG or above.

Pages about coal:Coal is a fossil fuelMakes of coalTypes / ranks of coalHow coal is formedCO2 comparison of fuelsWhat to do with coal ash

Power Production From The Coal Reserves in Pakistan That not Only Fulfill our country Demand But Also Surplus Energy

As we all knows that Pakistan has great Geological aspects and God bless our country with strong nation, esteemed nation with four weathers and four provinces and every province has importance. Punjab and Sindh fulfill the demand of foods with blessing of fertility in the Land. This province is land of Five Rivers on the other end toward the South this province has deserts keeping the buried treasures of nature like Different Ores and minerals. Similarly if we see NWFP our North Province, it is diversified with Mountain Ranges and Fata Fana Forests. The Beauty of the Valleys with great importance for Tourism as well. The Ice that froze on its Hills in the winters on after melting fills the rivers of the Country. Baluchistan is the province with resources of Energy like Natural Gas. and others Ores like Chromium, Gypsum and Coal.

Coal is one of major energy source which is contributing in world’s energy systems with the share of 23.80% and 23.75% of production and consumption respectively. In order to obtain clean fuels, the liquefaction and gasification of the world’s most abundant fuel i.e., coal, have gained increasing attention. The energy sector requires efficient and clean energy supplies. In case of coal, we would have to ensure higher efficiencies, environmental acceptance, prolonging its availability and proper replacement for oil and natural gas. This is only possible through sustainable development of new coal conversion technologies.

Coal – the black gold is found in all the four provinces of Pakistan. Country has huge coal resources, about 185 billion tons, out of which 3.3 billion tons are in proven/measured category and about 11 billion are indicated reserves, the bulk of it is found in Sindh province.

Pakistan’s Thar Desert contains the largest coal reserves discovered to date, covering an area of 10,000 square kilometers. The Thar Coal Field, should it be developed, will yield over 200 billion ton of coal used to produce electricity, it will yield sufficient power to make Pakistan self-sufficient in Electrical power. Pakistan has reserves of natural gas, but these will start to diminish by 2010.

Thar Coal Composition

The rank of Thar coal ranges from lignite-B to sub-bituminous-A with high moisture and low sulfur content. The average chemical analyses of the coal samples from the entire Thar coalfield are:

Moisture (AR) 46.77%VolatileMatter (AR) 23.42%Fixed Carbon (AR) 6.66%

Ash (AR) 6.24%Sulfur (AR) 1.16%

Heating 10,898 Btu/lbValue (Dry)

It is also another myth that this project will alleviate the need for hydel electricity. The fact is that any electricity eventually produced from Thar coal would be at least twice as expensive as that generated from large dams. The main problem in electricity sector is not how to generate electricity, but how to generate electricity at an affordable price. If the issue had only been power generation than we also have abundant wind and solar resources, but these cannot be fully utilized because electricity produced from these sources would be prohibitively expensive. The average power generation cost given the current generation mix of Pakistan is about 6.5 cents/kwh. Electricity from Thar coal would provide relief to consumers if it can be generated at a cost lower than this average.

Zain Ahmed Siddiqee

COAL

Untapped potential

By SHABBIR H. KAZMIJuly 09 - 15, 2001

Pakistan spends billions of dollars annually to meet its primary energy requirements. Oil and POL import bill is expected to further increase due to inadequate gas supply and price of crude oil remaining high. The fact that higher crude oil price is rendering local industries uncompetitive needs no analytical elucidation. While the GoP is making efforts to make it obligatory, for the industries, to switchover from oil and gas to coal, the objective cannot be achieved without announcing a comprehensive Coal Policy and investing heavily in infrastructure development.

Historically, coal has been used as a major source of energy for hundred of years. The industrial revolution and enhanced use of electricity was also due to coal. Until sixties, coal was the single largest source of primary energy. Large discoveries of oil and gas resulted in massive switchover from coal to furnace oil and gas. However, once again there is a shift back to use of coal as a major source of energy. Many developed and developing countries have already reverted back to coal. The transition is being facilitated by Clean Coal Technologies and availability of coal at competitive price.

While efforts are being made to shift back to coal for power generation and cement manufacturing, use of coal in other processing industries is also on a constant increase. It is estimated that the share of coal in global electricity generation now exceeds 37 per cent. Therefore, Pakistan, having some of the largest and superior quality coal reserves of the world, must also initiate the transition. Cement industry, being energy intensive, can be the largest beneficiary of this transition. Similarly, power generation sector can also become a major user of coal and optimize cost per kwh.

Theoretically, while the switchover offers many advantages, the transition should not be difficult. However, the real issue is availability of coal in large quantities at point of consumption. Production of coal has remained stagnant in Pakistan mainly due to its low demand/consumption. At present, coal is mainly consumed by the brick-kiln sector. Out of around 3 million tonnes of coal produced annually,

nearly 80 per cent is consumed by kilns. Other than this, only Lakhra power plant of WAPDA is based on indigenous coal. According to sector experts production of coal can be increased to 8 million tonnes per annum with the existing resources and infrastructure.

Indigenous coal

The discovery of coal in Balochistan during the late 18th century led to its commercial utilization mainly by North-Western Railways during the colonial regime. During fifties coal constituted 50 per cent of total energy consumption. Up to mid sixties the major consumers of coal were railways, cement, fertilizer and power plants. The availability of furnace oil and discovery of Sui gas field became instrumental in switching over to these fuels. It is unfortunate that instead of capitalizing on usage of coal and constant improvement in coal technology, policy makers chose to encourage use of imported furnace oil. Therefore, production of coal has remained stagnant mainly due to poor demand for the commodity.

At present total coal reserves of Pakistan are estimated around 185 billion tonnes. These include lately discovered huge deposits of low sulphur coal at Thar. The indigenous coal reserves vary in moisture, carbon, sulphur and ash contents. The local coal fall in the lignite and sub-bituminous categories. Coal from Lakhra and Sonda fields of Sindh has relatively higher moisture, sulphur and ash contents. As oppose to this, Thar coal having an estimated reserves of 184.6 billion tonnes is much superior in quality due to low sulphur content and higher heating value.

Coal mining

Coal mining is one of the oldest industries of Pakistan. It assumed new heights in fifties when cement, fertilizer and other process industries became major users of coal. This led to an increase in production from 0.7 million tonnes/annum in 1959 to 1.4 million tonnes/annum in 1968. Until discovery of natural gas, coal was meeting 50 per cent of country's total energy requirement. The boom in construction activities in eighties provided new impetus and coal production touched 3.14 million tonnes in 1989-90. Since then annual coal production has remained stagnant between 3.2 to 3.5 million tonnes per annum.

COAL PRODUCTION

(000 tonnes)

. 1994-95

1995-96

1996-97

1997-98

1998-99

1999-00

Balochistan 1,565 1,798 1,828 1,574 1,671 1,681

Punjab 413 515 425 366 479 454

Sindh 1,023 1,278 1,238 1,165 1,250 985

NWFP 42 47 62 54 61 46

Total 3,043 3,638 3,553 3,159 3,461 3,166

Though coal mining is undertaken at all the four provinces, Pakistan has not been able to exploit the real benefit of huge reserves of the commodity. One of the reasons for this is poor demand for coal. The mining sector in each province is faced with peculiar set of issues ranging from higher cost of production to lack of infrastructure. The cost of mining per tonne not only varies from province to province but also varies within each province. Main reasons being different mining methods, level of application of technology and variations in working depths of mines. Despite the fact that coal found in Balochistan is superior in quality, it is expensive due to mines being deeper and steeper. The overall mining cost can be reduced by upgrading the present technology used in coal mining. This requires heavy capital investment. The payback of this investment can be reduced by achieving higher production. Demand for coal can be increased by making its use obligatory for various industries.

Another important area which needs massive investment is the infrastructure for coal transportation. At present, coal from mines is transported mostly by road. While railway lines passes through or near the coal fields, slow and outdated system coupled with limited availability of railway wagons are the key issues faced by the miners and the ultimate coal using industries. Therefore, transportation infrastructure requires urgent development to facilitate the coal mining industry to cope with increased demand for coal in future.

Shift back to coal

As stated earlier importance of shift back to coal needs no elucidation. The question is how quickly and efficiently coal can be utilized by the process industries. The switchover, to coal, is largely dependent on uninterrupted supply of processed quality coal. However, the situation is, 'chicken or egg first'. Miners are not willing to increase coal production unless there is a demand and processors are not willing to undertake switchover unless there is adequate supply of coal. According to sector experts, demand for coal can be increased by making its use obligatory for cement manufacturing and power generation. This has to be done according to a programme whereby cement plants are given three years and power plants are given five years to make the complete transition. This also requires incentives for the mining sector to ensure higher coal production. Both, the coal miners and the coal users, should be allowed duty free import of requisite plant and machinery to avoid front loading of the projects.

According to a report prepared by Experts Advisory Cell of Ministry of Industries and Production cement industry could be the first and the largest beneficiary of this transition. In the past, Wah, Rohri, Dandot and Daud Khel cement plants were using coal. Therefore, these units have past experience of using coal and switch back does not pose too problems. One of cement plants in Sindh, Dadabhoy Cement, is in the process of transition and experience has been satisfactory to a large extent.

The utilization of indigenous coal by cement industry seems attractive simply on the basis of cost per tonne of clinker produced. To produce one tonne of clinker a cement plant uses 850,000 kcal, using any type of fuel. Since the heating value of furnace oil is almost double than that of local coal — a cement plant uses 88 kgs of furnace oil whereas it will use 170 kgs of coal. According to the Report, use of coal will translate to a net saving of Rs 491 and Rs 415 per tonne of clinker for the cement plants located in the North and South respectively.

At present, there are 23 cement plants with an installed capacity of 16.5 million tonnes per annum operating in the country. However, capacity utilization is around 63 per cent due to a number of factors — higher cost and low offtake being the two main reasons. Cement industry is highly energy intensive and fuel cost constitute about 30 per cent of the total cost of cement manufacturing. Based on the total installed capacity, furnace oil requirement comes to 1.5 million tonnes per annum. However, based on the actual capacity utilization, furnace oil requirement is estimated at slightly less than one million tonnes per annum. If all the cement plants switcheover to coal and capacity utilization remains the same, the industry will be able to save over Rs 5 billion annually. Not only this there will be huge saving of foreign exchange currently being spent on import of furnace oil.

Saying this much, it is also important to take into account two factors: 1) investment required to by the cement industry to switchover from furnace oil to coal and 2) uninterrupted supply of quality coal at cement plants. According to the Report this investment has 12 to 18 months payback period and should be a valid reason to undertake the switchover. However, the second factor is very crucial. Not only that coal production is low, the existing infrastructure is highly inadequate to ensure uninterrupted supply of processed coal to ultimate users.

Cement plants can either buy coal in raw form and then process it to suit their demand or buy processed coal from a coal processing and distribution company (on the pattern of existing gas transmission and distribution companies). The first option is not economically viable. Therefore, establishment of coal processing and distribution companies seems to be a better option — also offering economy of scale and cost optimization.

Sindh coal

The province of Sindh posses around 99 per cent of the total coal reserves of Pakistan. These are located at Lakhra, Sonda, Badin, Metting and Thar. The Lakhra field in District Dadu, covers an area of over 1,309 sq. kms. However, exploration activities are confined to an area around 500 sq. kms. The coal seams have been developed at the depth of 50 to 150 meters. Annual production from this field is estimated at about 2 million tonnes per annum.

The Sonda field covers 1,822 sq. kms. and coal seams are at a depth of 16 to 240 meters. The field comprises of four blocks: 1) Sonda-Thatta Block, 2) Jherruck Block, 3) Ongar Block and 4) Indus East Block.

Badin field has been discovered recently. Geological features indicate that Badin coal field may extend towards Indus East block of Sonda field.

Metting is the smallest field covering only 90 sq. kms. in District Thatta.

The Thar field, one of the largest coal field in the world, is spread over an area of about 10,000 sq. kms. in District Tharparkar.

Thar coal

Incentives

According to some sector experts, to ensure greater use of coal by various industries, the GoP should follow 'carrot and stick policy'. Cost optimization is the carrot and obligatory use is the stick. In the past, cement industry had switched over from natural gas to furnace oil, only because the government refused to supply gas to cement plants. The same policy can now be followed to switchover from furnace oil to coal. However, this time the transition is difficult. Handling and using furnace oil is much convenient than coal. Since this switchover is the need of cement industry, the willingness is there but the only apprehension is uninterrupted supply of quality coal at cement plants.

Since the GoP will be the largest beneficiary of this switchover, it should provide incentives to the coal miners as well as the cement industry. To avoid front-loading of the projects, the GoP should abolish import duty on coal mining and related handling (transport and storage) equipment and requisite plant and machinery to be installed at cement plants.

The Sindh government should also convince the federal government to allow establishment of at least two coal-based power plants of 500MW each at/around Karachi. This is the need of the hour because KESC has a dependable capacity of 1300MW only as against a peak demand of over 2000MW. This can be done by following a bidding process based on price per kwh and by following an amended Power Policy.

Environmental impact

The presence of impurities and mineral matters in coal leads to the formation of various pollutants during combustion having adverse environmental impacts when emitted into the atmosphere. The major environmental aspects that are associated with use of coal are: the formation of pollutants such as fly ash, sulphur oxides, nitrogen oxides, carbon monoxide and other mineral matters. However, the Clean Coal Technologies have been designed to enhance the thermal efficiency of coal, reduce emissions and waste and make coal environmentally acceptable. Therefore, use of coal by utilizing modern technologies does not create the havoc as it used to create in the past.

According to sector experts, most of the equipment required to facilitate use of coal can be manufactured locally. As far as the existing oil-fired burners are concerned, these can be modified or the new multichannel burners can be manufactured by HMC and KSEW under licence agreement with the leading manufacturers. If HMC/KSEW acquire the engineering design, they can supply the same to entire cement industry at competitive prices.

Global scenario

World coal consumption, despite decline in some regions, has been on a constant increase. The countries that have witnessed increase in coal consumption include the United States, Japan and many developing countries in Asia. Coal is mostly used for power generation, steel production, cement manufacturing and other process industries. However, half of global coal production is used for power generation.

Conclusion

Crude oil price is expected to remain high due to the policy followed by OPEC. Since Pakistan has no other alternative except to make use of coal obligatory by process industries, the GoP must announce a comprehensive Coal Policy immediately on the basis of report prepared by the Experts Advisory Cell. The policy should address the following points:

* Duty free import of required plant and machinery* Establishment of coal processing and distribution companies* Allocation of funds for upgrading infrastructure* Allocation of special funds for exploitation of Thar coal* Establishment of coal-based power generation plants

WORLD COAL CONSUMPTION

* World coal consumption is projected to increase to 7.6 billion tonnes in 2020* Coal use in developing countries of Asia alone is projected to increase by 2.4 billion tonnes* China is projected to add an estimated 180 gigawatts of new coal fired power generating capacity (600 plants of 300 megawatts each) by 2020 and India approximately 50 gigawatts (167 plants of 300 megawatts each)* The coal share as a percentage of total energy consumed worldwide for electricity generation is projected to decline from 36 per cent in 1997 to 34 per cent in 2020.

Source: International Energy Book 2000

COAL BENEFICATION

Coal preparation, commonly known as coal benefication, is the process of cleaning, gradation and preparation of uniform coal suitable for commercial consumption. Effective preparation of coal, prior to use, improves homogeneity of coal, reduces transport cost, improves utilization efficiency, results in less ash production and more importantly reduces emission of toxic gases.

There are various technologies globally used for preparation of coal. While Pulverized Fuel technology is in use in cement industry, other technologies, though having significant application in power plants and other industries are more expensive. The various technologies is used for the preparation of coal are:-

* Pulverized Fuel (PF) technology

In this process, coal is reduced to fine powder form, stored and then transported by air to the burner as coal air mixture for combustion.

* Fluidized Bed Combustion (FBC) technology

In this method coal is added to the bed of heated particles and continuous mixing encourages complete combustion at a lower temperature then pulverized fuel technology.

* Coal Gasification (CG) technology

In this process coal is brought into contact with steam and oxygen and thermo-chemical reactions produce fuel gas. This process is mainly used in power generation and is a costlier method of fuel preparation.

* Coal-Liquid-Mixtures (CLMs) technology

These include the coal-oil-mixture and coal-water-mixture. These are costly technologies. The disadvantage of coal-oil-mixture is that 60 per cent of the total energy is derived from oil.

* Coal-Briquetting (CB) technology

In this process coal is compacted for use, transportation or further processing. The main purpose of briquetting is to convert low grade coal into compact mass having higher calorific value.

CONSUMPTION OF VARIOUS FUELS

(Per tonne of clinker)

Fuel Heating Value Fuel quantity

Furnace oil 9,700 kcal/kg 88kg

Natural gas 7,700 kcal/M3 110M3

Local coal 5,000 kcal/kg 170kg

COST PER TONNE OF CLINKER

Fuel Fuel quantity Rate Cost

Furnace oil 88kg Rs 11,370/tonne Rs 1,001

Natural gas 110M3 Rs 490/M3 Rs 539

Local coal (South) 170kg Rs 3,000/tonne Rs 510

Local coal (North) 170kg Rs 3,450/tonne Rs 586

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      Title | [Info] Coal Reserves in Pakistan

      Date | 2007-11-15

Coal Reserves in Pakistan

Coal Reserves in Pakistan

The presence of coal deposits in Pakistan was known before independence, but its economic value was highlighted in 1980. Pakistan is now included as 6th richest nation of the world in respect of estimated coal resources. Coal resources available in Pakistan exist in all four provinces and in AJK.

Association

The following is the information of Coal reserves in Pakistan.

1. Please visit ‘Geological Survey of Pakistan’ www.gsp.gov.pk , all information of mineral & energy resources in

Pakistan including the following can be found.- Location Map showing the Coal Fields and Coal Occurrences- Major Economic Mineral Deposits of Pakistan - Energy resources map of Pakistan- Mineral maps & precious stones

2. Petroleum & Natural Resources Division, Ministry of Petrol & Natural Resource:

3. Mines & Minerals, Government of Sindh: www.sindh.gov.pk 4.** Sindh Coal Authority: www.sca.com.pk

5. Investment opportunities in Mineral sector: www.pakistan.gov.pk6. Presentation from ‘Oil & Gas Conference’ on Feb. 18~20, 2007 organized by Government of Sindh:

gas.com