Types of Coal PDF

# Types of Coal - **Peat:** First stage in the formation of coal from wood. Contains a large amount of moisture, dried for 1-2 months before use. Used domestically in Europe and for power generation in Russia. It is not considered a good fuel in India. - **Lignite and Brown Coal:** Intermediate sta...

# Types of Coal - **Peat:** First stage in the formation of coal from wood. Contains a large amount of moisture, dried for 1-2 months before use. Used domestically in Europe and for power generation in Russia. It is not considered a good fuel in India. - **Lignite and Brown Coal:** Intermediate stages between peat and coal. Characterized by a woody or clay-like appearance, high moisture, high ash, and low heat content. Usually amorphous in character, making transport difficult due to their ease of breaking. Burn with a smoky flame and are only suitable for local use. - **Bituminous Coal:** Burns with long yellow and smoky flames and has a high percentage of volatile matter. Average calorific value is 31350 kJ/kg. Can be caking or non-caking. - **Semi-bituminous Coal:** Softer than anthracite, burns with a small amount of smoke. Contains 15-20% volatile matter and tends to break into small sizes during storage or transport. - **Semi-anthracite:** Has less fixed carbon and luster compared to anthracite, burns with longer and more luminous flames. - **Anthracite:** Very hard coal with a shining black luster. Ignites slowly unless the furnace temperature is high. Non-caking and has a high percentage of fixed carbon. Burns with short blue flames or no flames. Calorific value is high at ~35500 kJ/kg, making it suitable for steam generation. ## Coal Properties The basis of coal analysis helps to specify the conditions under which it is tested. Coal samples can be: - **As-mined:** Freshly taken from the mine. - **As-fired:** Resided in a coal pile for months, analyzed just before burning. - **As-received:** Examined immediately after transport from the mine. ### Moisture Content - Ranges from about 5% to 70%. - Moisture is undesirable as it reduces heating value and increases transport costs. - Determined by heating an air-dried coal sample at 104-110°C for one hour or until a constant weight is obtained. - Increases with decreasing rank, ranging from 1% to 40% for different coal ranks. ### Volatile Combustible Material (VCM) - Measured by heating a dried coal sample in the absence of air to remove its moisture. - Ranges from 2% to 50%. - Material driven off when coal is heated to 900°C in the absence of air for 7 minutes in a closed crucible. ### Mineral (Ash) Content - Consists of minerals in varying proportions. - Transformed into ash when the coal is burned. - Affects ash-handling system design based on its amount and nature. - Determined by heating a weighed coal sample in an open crucible for 2 hours at 500-815°C. ### Fixed Carbon Content (FC) - Solid combustible residue remaining after a coal particle is heated. - Determined by subtracting moisture, volatile matter, and ash percentages from a sample. - Higher fixed carbon content indicates a long combustion time. - Ranges from 50% to 98%. - Anthracites have high fixed carbon content, making them suitable for domestic heating fuel. ### Calorific Value - Amount of chemical energy stored in a coal that is released as thermal energy upon combustion. - Measured in British thermal units or megajoules per kilogram. - Only volatile matter and fixed carbon actually burn and liberate thermal energy. - Corrected for moisture and ash content, as they do not contribute to heating value. - Lowered by the presence of non-combustible moisture and ash. ### Formula - **FC = 100 - N - VCM - Ash** ## Testing Analyses of Solid Fuels ### Proximate Analysis - Determines moisture, volatile combustible matter, fixed carbon, and ash content. - Provides a general indication of coal's heating and burning properties. ### Ultimate Analysis - More precise way to find the chemical composition of coal, with respect to elements like carbon, hydrogen, oxygen, nitrogen, sulfur, and ash. - **Carbon and Hydrogen:** Principal combustible elements, with carbon typically constituting 60% to 95% of the total weight. - **Nitrogen:** Ranges from 1% to 2% in most coal. - **Oxygen:** Inversely related to carbon content. - **Sulfur:** Variable. ## Classification of Coal by Ranks | Class and Group | Fixed Carbon (%) | Volatile Matter (%) | Heating Value (BTU/lb) | |------------------------------|-----------------|---------------------|------------------------| | **Anthracite** | | | | | 1. Meta-anthracite | >98 | <2 | | | 2. Anthracite | 92-98 | 2-8 | | | 3. Semi-anthracite | 86-92 | 8-14 | | | **Bituminous** | | | | | 1. Low Volatile | 78-86 | 14-22 | | | 2. Medium Volatile | 69-78 | 22-31 | | | 3. High Volatile A | <69 | >31 | >14,000 | | 4. High Volatile B | | | 13,000 - 14,000 | | 5. High Volatile C | | | 10,500 - 13,000 | | **Subbituminous** | | | | | 1. Subbituminous A | | | 10,500 - 11,500 | | 2. Subbituminous B | | | 9500 - 10,500 | | 3. Subbituminous C | | | 8300 - 9500 | | **Lignite** | | | | | 1. Lignite A | | | 6300 - 8300 | | 2. Lignite B | | | <6300 | ## Coal Utilization ### Pathways to Coal Utilization - **Mining:** Extracting coal from the earth. - **Processing:** Preparing coal for use, including cleaning and crushing. - **Transport:** Moving coal to its destination. - **Combustion:** Burning coal to generate heat or electricity. - **Carbonization:** Heating coal in the absence of air to produce coke. - **Conversion:** Transforming coal into gaseous or liquid fuels. ## Manufactured Solid Fuels ### Charcoal - Derived from the destructive distillation of wood. - Solid residue. - Burns rapidly with a clear flame, producing no smoke. - Heat of about 6050 cal/kg. ### Coke - Obtained from destructive distillation of coal. - Solid residue. - Soft Coke: Produced at 600-650°C, contains 5-10% volatile matter and burns without smoke. - Hard Coke: Produced at 1200-1400°C, burns with smoke and is a useful fuel for metallurgical processes. ### Briquettes - Compressed small-size waste materials from lignite, peat, coke, etc., into regular shapes with or without binders. ## Liquid Fuels ### Advantages - Higher calorific value per unit mass than solid fuels. - Burn without dust, ash, or clinkers. - Easy to transport through pipes. ### Disadvantages - Higher cost compared to solid fuel. - Require special storage tanks. - Greater risk of fire hazards, especially for volatile fuels. ### Petroleum - Dark greenish brown viscous mineral oil, found deep in the earth's crust. - Primarily composed of hydrocarbons like paraffins, cycloparaffins, olefins, and aromatics, with small amounts of organic compounds containing oxygen, nitrogen, and sulfur. - Composition varies depending on its type: paraffinic, naphthenic, or asphaltic. ### Classification of Petroleum - **Paraffinic Base Type Crude Petroleum:** Mainly composed of saturated hydrocarbons from methane to C₃₅H₇₂, with a small amount of napthenes and aromatics. - **Asphaltic Base Type Crude Petroleum:** Contains mainly cycloparaffins or napthenes with smaller amounts of paraffins and aromatic hydrocarbons. - **Mixed Base Type Crude Petroleum:** Contains both paraffinic and asphaltic hydrocarbons and is generally rich in semisolid waxes. ### Petroleum Products - Separated by fractional distillation in a column. - Heavier fractions condense at higher temperatures in the lower part of the column. - Lighter fractions condense at lower temperatures in the upper part of the column. - Common fuels produced: gasoline, kerosene, jet engine fuel, diesel fuel, and fuel oil. ## Ten Main Product Categories - Asphalt - Diesel - Fuel Oil - Gasoline - Kerosene - Liquefied Petroleum Gas - Lubricating Oil - Paraffin Wax - Bitumen - Petrochemicals ### Asphalt - Colloid of asphaltenes and maltenes. - Separated from other petroleum components by fractional distillation. - Processed in a de-asphalting unit and "blown" with oxygen to harden it. - Used for roads, waterproofing roofs and boats, and soundproofing dishwashers and hard drives. ### Diesel - Fuel used in diesel engines. - Produced by fractional distillation between 392° and 662° Fahrenheit. - Higher density than gasoline. - Simpler to refine from crude oil. ### Fuel Oil - Liquid petroleum product burned in furnaces to generate heat. - Heaviest commercial fuel produced from crude oil. - Six classes: distillate fuel oil, diesel fuel oil, light fuel oil, gasoil, residual fuel oil, and heavy fuel oil. ### Gasoline - Almost half of crude oil is refined into gasoline. - Used as fuel in internal combustion engines like car engines. - Mixture of paraffins, naphthenes, and olefins. - Specific ratios depend on the refinery. ### Kerosene - Collected by fractional distillation between 302° and 527° Fahrenheit. - Thin and clear combustible liquid. - Used as jet fuel and heating fuel. - Replaced whale oil in lanterns in the early days. - Now used in portable stoves, kerosene space heaters, and liquid pesticides. ### Liquefied Petroleum Gas (LPG) - Mixture of gases used for heating appliances, aerosol propellants, and refrigerants. - Primarily propane and butane. - Evaporates at normal atmospheric pressure, requiring pressurized steel bottles. ### Lubricating Oil - Manufactured by special processes like solvent extraction, catalytic dewaxing, hydrocracking, and isohydromerization. - Classified as paraffinic, naphthenic, or aromatic. - Used between surfaces to reduce friction and wear. - Most common is motor oil, which protects moving parts in internal combustion engines. ### Paraffin Wax - Odorless, tasteless, waxy solid at room temperature. - Melting point between 117° and 147° Fahrenheit. - Excellent electrical insulator. - Used in drywall, building insulation, and candle making. ### Bitumen - Thick, black, sticky material, commonly known as tar. - Produced by distillation in crude oil. - Used for paving roads, waterproofing roofs and boats, and soundproofing. ### Petrochemicals - Chemical products made from the raw materials of petroleum. - Examples: ethylene, propylene, benzene, toluene, and xylene. - Used in a wide variety of applications, including anesthetics, antifreeze, detergents, explosives, solvents, and cleaning agents. ### Jet Fuel - Aviation fuel for turbine engines. - Common types: Jet A and Jet A-1. - Mixture of a large number of different hydrocarbons. - Types: kerosene-type (carbon numbers 8-16), wide-cut/naphtha-type (carbon numbers 5-15), and Jet B (carbon numbers 5-15). ## Properties of Petroleum - Elemental composition is less variable than coal: 83-87% carbon, 11-16% hydrogen, 0-4% oxygen, 0-4% sulfur, and a small amount of nitrogen. - Crude oils contain substantially more hydrogen than coals. ### Basic Properties - **Density:** Ratio of mass to volume at 15°C. Measured by a hydrometer, used for ignition quality assessment. - **Specific Gravity:** Ratio of the weight of a given volume of oil to the weight of the same volume of water at a given temperature. - **Viscosity:** Measure of internal resistance to flow. Decreases with increasing temperature. - **Flash Point:** Lowest temperature at which the fuel can be heated so that vapor will flash when an open flame is passed over it. - **Pour Point:** Lowest temperature at which fuel will pour or flow when cooled under prescribed conditions. - **Specific Heat:** Amount of heat required to raise the temperature of 1 kg of oil by 1°C. - **Calorific Value:** Measurement of heat or energy produced. Measured as gross or net calorific value. - **Sulfur:** Varies depending on crude oil source and refining process. - **Ash Content:** Related to inorganic material in fuel oil. - **Carbon Residue:** Indicates the tendency of oil to deposit a carbonaceous solid residue on a hot surface. - **Water Content:** Normally low in furnace oil when supplied, but can cause damage to furnace surfaces if present. - **Octane Number:** Indicates tendency of gasoline to knock when the compression ratio in a spark ignition engine is raised. - **Cetane Number:** Ranks fuels based on ignition delay when undergoing standard test. - **Smoke Point:** Measures tendency of liquid fuel to form soot. - **Ignition Temperature:** Minimum temperature at which the material will ignite without a spark or flame. - **Flammability Limits in Air:** Percentage concentration in air for the lower and upper limits of flammability. - **Fire Point:** Lowest temperature at which application of a test flame to the oil sample surface causes the vapor to ignite and burn for at least five seconds. - **Reid Vapor Pressure:** Measure of pressure exerted by a vapor at a given temperature. ## Gaseous Fuels - Occur in nature and are also manufactured from solid and liquid fuels. - Advantages: conveyance through pipelines, ease of lighting, and freedom from impurities. - Disadvantages: large storage tanks required, high flammability. ### Types of Gaseous Fuels - **Coal Gas:** Produced by heating coal in the absence of air at 1300°C. - **Blast Furnace Gas:** Byproduct of iron ore reduction using coke. - **Water Gas:** Mixture of CO and H₂ with a small amount of other gases, produced by passing steam and air through a bed of hot coal or coke. - **Producer Gas:** Mixture of CO and hydrogen with non-combustible gases, produced by passing air and steam over a red-hot coal or coke bed. - **Biogas:** Produced from decomposition of organic matter by bacteria in enclosed digesters. - **Town Gas:** Low to mid-temperature coal gasification. - **Coke Gas:** High-temperature coal gasification. - **Hydrogen:** Produced by reforming natural gas in the presence of a nickel catalyst and water steam at 800°C. ## Properties of Gaseous Fuels - **Heating Value:** Heat released per unit mass when fuel reacts completely with oxygen. Higher Heating Value (HHV) includes latent heat of water vapor condensation, Lower Heating Value (LHV) does not. - **Relative Density:** Density of gas relative to air. - **Wobbe Index:** Used for assessment of gas exchange, takes into account both heating value and density. - **Flammability Limits:** Percentage of combustible gas in a mixture, between which limits this mixture is flammable. ## Renewable Fuels - Formed in a year or a few years. - Gaseous: biogas, gasogen gas from pyrolysis of biomass. - Liquid: alcohols, ethers (biopetrol), esters (biodiesel). - Solid: wood, charcoal, fuel pellets, agricultural residues, cattle manure, urban waste. ## Biofuels - General term for fuels obtained from renewable sources. - May include both unprocessed biomass and derived fuels. - Biomass: unprocessed organic matter, such as forest waste, crop waste, animal waste, etc. ### Advantages of Biofuels - Renewable source of energy. - Can reduce reliance on fossil fuels. - Can help to reduce greenhouse gas emissions. ### Disadvantages of Biofuels - Less energy-dense than fossil fuels. - Requires significant land area for cultivation. - Can be more expensive than fossil fuels. - May require significant processing. - May have environmental impacts. ### Types of Biofuels - **Bioethanol:** Ethanol (C₂H₅OH) produced from feedstock and other biomass. - **Biodiesel:** Fatty Acid Methyl Ester (FAME) or mono-alkyl esters derived from vegetable oils or animal fats and other biomass derived oils. - **Biofuel:** General term for bioethanol and biodiesel. ### Biofuel Production Methods - **Fermentation:** Ethanol is produced by fermenting biomass sugars, starch, or cellulose with yeast or bacteria. - **Anaerobic Digestion:** Methane is produced by anaerobic digestion of biomass waste like manure, straw, and sewage. - **Reforming:** Biodiesel is produced by reforming oleaginous plant seeds like colza, sunflower, and soya. - **Wood-Waste Distillation:** Methanol can be produced by distilling wood waste. - **Hydrogen Reform:** Hydrogen can be produced by reforming other biofuels like ethanol or methane, or by electrolysis of water using solar or wind energy. ## Biofuels Act in the Philippines - Republic Act 9367 (2007) made the Philippines the first country in Southeast Asia to have biofuels legislation in place. - Mandates 10% ethanol and 2% biodiesel blends. - Sugarcane and molasses are used for ethanol production. - Coconut oil is the preferred feedstock for biodiesel.