Types and Properties of Coal

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Questions and Answers

What is the primary characteristic of peat in the formation of coal?

It has a low moisture content.

It is the first stage in the formation of coal. (correct)

It contains a high percentage of ash.

It is the last stage in coal formation.

Which type of coal burns with long yellow and smoky flames?

Bituminous Coal (correct)

Anthracite

Semi-anthracite

Lignite

What is the primary method through which coal is converted into gaseous or liquid fuels?

Mining

Combustion

Carbonization

Conversion (correct)

What is the calorific value of anthracite coal?

35500 kJ/kg Signup and view all the answers

Which type of coke is produced at temperatures between 1200-1400°C and is known to burn with smoke?

Hard Coke Signup and view all the answers

How is moisture content in coal primarily determined?

By heating a sample at 104-110°C until constant weight is reached. Signup and view all the answers

What happens to the volatile combustible material (VCM) when coal is heated?

It is driven off when heated in the absence of air. Signup and view all the answers

What is the calorific value of charcoal approximately?

6050 cal/kg Signup and view all the answers

What is the advantage of using liquid fuels compared to solid fuels?

Higher calorific value per unit mass Signup and view all the answers

Which coal type is most suitable for local use due to its low heat content and high ash?

Lignite Signup and view all the answers

Which property of coal can significantly affect the design of ash-handling systems?

Mineral (ash) content Signup and view all the answers

Subbituminous B coal has a heating range of approximately how many BTUs?

9500 - 10500 Signup and view all the answers

What is a distinguishing feature of semi-bituminous coal compared to anthracite?

More volatile matter Signup and view all the answers

Which process involves cleaning and crushing coal preparing it for use?

Processing Signup and view all the answers

Which type of manufactured solid fuel is created by compressing small-size waste materials, possibly with binders?

Briquettes Signup and view all the answers

What is a significant disadvantage of using liquid fuels compared to solid fuels?

Greater risk of fire hazards Signup and view all the answers

What primarily composes paraffinic base type crude petroleum?

Saturated hydrocarbons and a small amount of naphthenes Signup and view all the answers

Which petroleum product is primarily used as jet fuel?

Kerosene Signup and view all the answers

Which type of crude petroleum is characterized as having both paraffinic and asphaltic hydrocarbons?

Mixed Base Type Signup and view all the answers

At what temperature range is diesel fuel produced during fractional distillation?

392° to 662° Fahrenheit Signup and view all the answers

What is the main purpose of asphalt in construction?

Road surfacing and waterproofing Signup and view all the answers

Which product is identified as the heaviest commercial fuel produced from crude oil?

Fuel Oil Signup and view all the answers

How is gasoline primarily characterized in terms of its composition?

Mixture of paraffins, naphthenes, and olefins Signup and view all the answers

What is the primary use of lubricating oil among petroleum products?

Reducing friction in engines Signup and view all the answers

What gases primarily make up Liquefied Petroleum Gas (LPG)?

Propane and butane Signup and view all the answers

Which of the following is NOT a method used in the manufacture of lubricating oil?

Fractional distillation Signup and view all the answers

At what temperature range does paraffin wax typically melt?

117° to 147° Fahrenheit Signup and view all the answers

What is the primary use of bitumen?

Paving roads and waterproofing Signup and view all the answers

Which of the following is NOT a characteristic property of petroleum?

Boiling point Signup and view all the answers

What is the primary purpose of lubricating oil in machinery?

To reduce friction and wear Signup and view all the answers

What is the typical range of carbon numbers for kerosene-type jet fuel?

8-16 Signup and view all the answers

What property measures the lowest temperature at which fuel can ignite?

Flash point Signup and view all the answers

What does the Cetane Number indicate about fuels?

The ignition delay of fuels during testing Signup and view all the answers

Which property is measured by the Smoke Point of a liquid fuel?

The tendency to form soot Signup and view all the answers

What is a significant disadvantage of gaseous fuels?

Need for large storage tanks Signup and view all the answers

Which type of gas is produced by heating coal in the absence of air at high temperatures?

Coal gas Signup and view all the answers

What is indicated by the Fire Point of a fuel?

The lowest temperature for vapor ignition and combustion Signup and view all the answers

Which of the following is a property of gaseous fuels that compares density with air?

Relative Density Signup and view all the answers

What does the term ‘Heating Value’ refer to in the context of fuels?

The heat released during complete combustion Signup and view all the answers

Which gaseous fuel is a byproduct of iron ore reduction using coke?

Blast furnace gas Signup and view all the answers

Study Notes

Coal Types

Peat: Initial stage of coal formation, high moisture content, used in Europe and Russia.
Lignite/Brown Coal: Intermediate stage, high moisture & ash, low heat content, difficult to transport.
Bituminous Coal: High volatile matter, burns with smoky flames, average calorific value of 31,350 kJ/kg.
Semi-bituminous Coal: Softer than anthracite, less smoke, contains 15-20% volatile matter.
Semi-anthracite: Less fixed carbon and luster than anthracite, longer, luminous flames.
Anthracite: Hardest coal, high fixed carbon, burns with blue flames or no flames, high calorific value (~35,500 kJ/kg).

Coal Properties

As-mined: Freshly extracted from the mine.
As-fired: Resided in a coal pile for months, analyzed before burning.
As-received: Examined immediately after mine transport.

Moisture Content

Ranges from 5% to 70%, undesirable as it reduces heating value and increases transport costs.
Determined by heating an air-dried sample at 104-110°C until a constant weight is reached.
Increases with decreasing coal rank, ranging from 1% to 40%.

Volatile Combustible Material (VCM)

Measured by heating a dried sample in airless conditions to remove moisture.
Ranges from 2% to 50%.
Material driven off when coal is heated to 900°C in airless condition for 7 minutes.

Mineral (Ash) Content

Consists of varying proportions of minerals.
Transformed into ash when burned, affects ash-handling system design.

Coal Classifications based on Rank

Anthracite: Fixed Carbon > 86%, Volatile Matter <14%, HHV > 14,000 BTU/lb.
Bituminous: Fixed Carbon 69-86%, Volatile Matter 14%-31%, HHV 10,500-14,000 BTU/lb.
Subbituminous: Fixed Carbon 31-69%, Volatile Matter > 31%, HHV 8,300-11,500 BTU/lb.
Lignite: Fixed Carbon < 31%, Volatile Matter > 31%, HHV < 8,300 BTU/lb.

Coal Utilization Pathways

Mining: Extracting coal from the earth.
Processing: Preparing coal for use (cleaning, crushing).
Transport: Moving coal to its destination.
Combustion: Burning for heat or electricity generation.
Carbonization: Heating coal in the absence of air to produce coke.
Conversion: Transforming coal into gaseous or liquid fuels.

Manufactured Solid Fuels

Charcoal: Solid residue from destructive distillation of wood, burns rapidly with clear flame and no smoke.
Coke: Solid residue from destructive distillation of coal, used in metallurgical processes.
- Soft Coke: Produced at 600-650°C, contains 5-10% volatile matter, burns without smoke.
- Hard Coke: Produced at 1200-1400°C, burns with smoke, used in metallurgy.
Briquettes: Compressed waste materials from lignite, peat, coke, etc., into regular shapes.

Liquid Fuels

Advantages: High calorific value per unit mass, burn without dust, easy to transport through pipes.
Disadvantages: Higher cost, require special storage tanks, fire hazards.

Petroleum

Viscous mineral oil found deep in the Earth's crust, primarily composed of hydrocarbons.
Types: Paraffinic, asphaltic, mixed base type.

Classification of Petroleum

Paraffinic Base Type: Saturated hydrocarbons with small amounts of napthenes and aromatics.
Asphaltic Base Type: Mainly cycloparaffins or napthenes with smaller amounts of paraffins and aromatics.
Mixed Base Type: Contains both paraffinic and asphaltic hydrocarbons.

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.

Ten Main Product Categories

Asphalt: Colloid of asphaltenes and maltenes, used for roads, waterproofing, soundproofing.
Diesel: Fuel for diesel engines, produced by fractional distillation.
Fuel Oil: Liquid petroleum product burned in furnaces, heaviest commercial fuel.
Gasoline: Used as fuel in internal combustion engines, mixture of paraffins, naphthenes, and olefins.
Kerosene: Collected by fractional distillation, used as jet fuel, heating fuel, and in lanterns.
Liquefied Petroleum Gas (LPG): Mixture of gases used for heating appliances, aerosol propellants, and refrigerants.
Lubricating Oil: Protects moving parts in engines, classified as paraffinic, naphthenic, or aromatic.
Paraffin Wax: Odorless, tasteless, waxy solid at room temperature, used in drywall, building insulation, and candle making.
Bitumen: Thick, black, sticky material used for paving roads, waterproofing, and soundproofing.
Petrochemicals: Chemical products made from petroleum, used in wide variety of applications.

Jet Fuel

Aviation fuel for turbine engines, common types: Jet A and Jet A-1.
Mixture of hydrocarbons, types: kerosene-type, wide-cut/naphtha-type, Jet B.

Properties of Petroleum

Elemental composition: 83-87% carbon, 11-16% hydrogen, 0-4% oxygen, 0-4% sulfur, small amount of nitrogen.
Contains more hydrogen than coals.

Basic Properties

Density: Ratio of mass to volume at 15°C, measured by a hydrometer.
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: Internal resistance to flow, decreases with increasing temperature.
Flash Point: Lowest temperature for fuel vapor to flash when exposed to an open flame.
Pour Point: Lowest temperature for fuel to pour or flow when cooled.
Specific Heat: Heat required to raise the temperature of 1 kg of oil by 1°C.
Calorific Value: 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: Indication of the tendency of oil to deposit carbon on a hot surface.
Water Content: Normally low but can cause damage to furnace surfaces.
Octane Number: Tendency of gasoline to knock in spark ignition engines.
Cetane Number: Ranks fuels based on ignition delay in diesel engines.
Smoke Point: Measures tendency of liquid fuel to form soot.
Ignition Temperature: Minimum temperature for self-ignition without a spark or flame.
Flammability Limits in Air: Lower and upper limits of flammability in air.
Fire Point: Lowest temperature for sustained burning of fuel vapor.
Reid Vapor Pressure: Pressure exerted by a vapor at a given temperature.

Gaseous Fuels

Occur naturally and are manufactured from solid and liquid fuels.
Advantages: Conveyance through pipelines, ease of lighting, free from impurities.
Disadvantages: Large storage tanks required, high flammability.

Types of Gaseous Fuels

Coal Gas: Produced by heating coal without air at 1300°C.
Blast Furnace Gas: Byproduct of iron ore reduction with coke.
Water Gas: Mixture of CO and H₂, produced by passing steam and air through hot coal/coke.
Producer Gas: Mixture of CO and hydrogen with non-combustible gases, produced by passing air and steam over red-hot coal/coke.
Biogas: Produced by decomposition of organic matter by bacteria.
Town Gas: Low to mid-temperature coal gasification.
Coke Gas: High-temperature coal gasification.
Hydrogen: Produced by reforming natural gas with water steam and a catalyst.

Properties of Gaseous Fuels

Heating Value: Heat released per unit mass during combustion.
- Higher Heating Value (HHV): Includes latent heat of water vapor condensation.
- Lower Heating Value (LHV): Does not include latent heat of water vapor condensation.
Relative Density: Density of gas relative to air.

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Description

This quiz explores the different types of coal, including peat, lignite, bituminous, and anthracite, along with their unique properties and moisture content. Test your knowledge on how these variations impact their use and heating value in practical applications.