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Questions and Answers
What is defined as the amount of heat liberated when unit mass of fuel is burnt completely?
What is defined as the amount of heat liberated when unit mass of fuel is burnt completely?
- Energy Yield
- Combustion Rate
- Heat Efficiency
- Calorific Value (correct)
Which of the following fuels is classified as a solid fuel?
Which of the following fuels is classified as a solid fuel?
- Natural gas
- Charcoal (correct)
- Crude oil
- Kerosene
What type of calorific value includes the heat of condensation of combustion products?
What type of calorific value includes the heat of condensation of combustion products?
- Net Energy Value
- Higher Calorific Value (correct)
- Lower Calorific Value
- Specific Heat Capacity
Which of the following is considered an artificial or secondary fuel?
Which of the following is considered an artificial or secondary fuel?
Which classification of fuel occurs naturally in the environment?
Which classification of fuel occurs naturally in the environment?
Which of the following fuels is classified as a liquid fuel?
Which of the following fuels is classified as a liquid fuel?
What is the main difference between Higher Calorific Value and Lower Calorific Value?
What is the main difference between Higher Calorific Value and Lower Calorific Value?
Which of the following describes gaseous fuels?
Which of the following describes gaseous fuels?
What is the cetane number of a fuel that has the same ignition delay as a mixture of 40% cetane and 60% methyl naphthalene?
What is the cetane number of a fuel that has the same ignition delay as a mixture of 40% cetane and 60% methyl naphthalene?
Which of the following statements about cetane number is true?
Which of the following statements about cetane number is true?
What cetane number is generally required for high-speed diesel engines?
What cetane number is generally required for high-speed diesel engines?
Which of the following is NOT an additive used to improve cetane number?
Which of the following is NOT an additive used to improve cetane number?
In cetane number testing, what component is compared with cetane to assess ignition delay?
In cetane number testing, what component is compared with cetane to assess ignition delay?
What causes knocking in an internal combustion engine?
What causes knocking in an internal combustion engine?
Which order represents the knocking tendency based on gasoline constituents?
Which order represents the knocking tendency based on gasoline constituents?
What is the purpose of an antiknocking agent added to fuels?
What is the purpose of an antiknocking agent added to fuels?
What is the octane number of iso-octane?
What is the octane number of iso-octane?
What characteristic is associated with a high cetane number in diesel fuel?
What characteristic is associated with a high cetane number in diesel fuel?
Which compound is used to improve the octane number by reducing knocking?
Which compound is used to improve the octane number by reducing knocking?
What happens if the combustion of diesel fuel does not start quickly enough in a compression ignition engine?
What happens if the combustion of diesel fuel does not start quickly enough in a compression ignition engine?
What does the compression ratio in an engine indicate?
What does the compression ratio in an engine indicate?
Which of the following is true about straight chain paraffins?
Which of the following is true about straight chain paraffins?
What is the primary factor that influences the knocking tendency of a fuel?
What is the primary factor that influences the knocking tendency of a fuel?
Which characteristic does NOT belong to a good quality fuel?
Which characteristic does NOT belong to a good quality fuel?
What is the primary purpose of cracking in petroleum processing?
What is the primary purpose of cracking in petroleum processing?
Which type of thermal cracking is conducted at a higher temperature?
Which type of thermal cracking is conducted at a higher temperature?
What is a significant advantage of catalytic cracking over thermal cracking?
What is a significant advantage of catalytic cracking over thermal cracking?
What does 'knocking' refer to in internal combustion engines?
What does 'knocking' refer to in internal combustion engines?
Which process requires a catalyst to improve gasoline production?
Which process requires a catalyst to improve gasoline production?
In which internal combustion engine does petrol serve as the fuel?
In which internal combustion engine does petrol serve as the fuel?
Which characteristic of a good fuel relates to its usability and transport?
Which characteristic of a good fuel relates to its usability and transport?
What type of catalyst is commonly used in catalytic cracking?
What type of catalyst is commonly used in catalytic cracking?
What is a key disadvantage of straight run gasoline?
What is a key disadvantage of straight run gasoline?
What is the formula for calculating the Lower Calorific Value (LCV) of a fuel?
What is the formula for calculating the Lower Calorific Value (LCV) of a fuel?
Which of the following is a method used to determine the moisture content in coal?
Which of the following is a method used to determine the moisture content in coal?
What is the significance of determining the volatile matter in coal?
What is the significance of determining the volatile matter in coal?
Which statement correctly describes fixed carbon in coal?
Which statement correctly describes fixed carbon in coal?
How is the percentage of nitrogen in coal determined?
How is the percentage of nitrogen in coal determined?
What effect does high oxygen content have on coal's calorific value?
What effect does high oxygen content have on coal's calorific value?
Which testing method is employed for ultimate analysis of coal?
Which testing method is employed for ultimate analysis of coal?
Why is the presence of sulfur in coal considered undesirable?
Why is the presence of sulfur in coal considered undesirable?
What is the main purpose of proximate analysis of coal?
What is the main purpose of proximate analysis of coal?
How is the percentage of ash in coal determined?
How is the percentage of ash in coal determined?
Which type of fuel is characterized as being in solid state?
Which type of fuel is characterized as being in solid state?
What term is used for fuels that are manufactured from primary fuels?
What term is used for fuels that are manufactured from primary fuels?
Which type of calorific value accounts for the heat of condensation of combustion products?
Which type of calorific value accounts for the heat of condensation of combustion products?
What describes a fuel primarily found in the gaseous state?
What describes a fuel primarily found in the gaseous state?
What is the definition of calorific value?
What is the definition of calorific value?
Which of the following is a primary fuel?
Which of the following is a primary fuel?
What characterizes the Lower Calorific Value (LCV) of a fuel?
What characterizes the Lower Calorific Value (LCV) of a fuel?
Which of these fuels can be classified as a liquid fuel?
Which of these fuels can be classified as a liquid fuel?
What is the effect of knocking in an internal combustion engine?
What is the effect of knocking in an internal combustion engine?
Which fuel structure has the highest knocking tendency?
Which fuel structure has the highest knocking tendency?
What is the octane number of iso-octane used as a standard of comparison?
What is the octane number of iso-octane used as a standard of comparison?
What primary factor contributes to the increase in knocking tendency?
What primary factor contributes to the increase in knocking tendency?
What is the primary role of antiknocking agents in fuels?
What is the primary role of antiknocking agents in fuels?
Which compound is commonly used to improve octane number in fuels?
Which compound is commonly used to improve octane number in fuels?
Which characteristic is described by a higher cetane number in diesel fuel?
Which characteristic is described by a higher cetane number in diesel fuel?
What happens when the entire quantity of diesel is injected before combustion starts in a diesel engine?
What happens when the entire quantity of diesel is injected before combustion starts in a diesel engine?
Which type of hydrocarbons are known to produce less knocking in internal combustion engines?
Which type of hydrocarbons are known to produce less knocking in internal combustion engines?
What effect does temperature have on the rate of oxidation of hydrocarbon molecules?
What effect does temperature have on the rate of oxidation of hydrocarbon molecules?
What does a cetane number of 40 indicate about a diesel fuel's ignition delay?
What does a cetane number of 40 indicate about a diesel fuel's ignition delay?
Which of the following is necessary to improve the cetane number of diesel oil?
Which of the following is necessary to improve the cetane number of diesel oil?
Which type of engine requires diesel fuel with a cetane number of 25?
Which type of engine requires diesel fuel with a cetane number of 25?
What is the cetane number assigned to methyl naphthalene?
What is the cetane number assigned to methyl naphthalene?
Which statement correctly describes why cetane number is important?
Which statement correctly describes why cetane number is important?
What effect does moisture have on the effective calorific value of coal?
What effect does moisture have on the effective calorific value of coal?
Which analysis method involves determining the percentage of carbon in coal?
Which analysis method involves determining the percentage of carbon in coal?
How is ash content in coal generally viewed in terms of fuel quality?
How is ash content in coal generally viewed in terms of fuel quality?
What happens to the calorific value with an increase in oxygen content in coal?
What happens to the calorific value with an increase in oxygen content in coal?
Which of the following statements is true regarding the significance of volatile matter in coal?
Which of the following statements is true regarding the significance of volatile matter in coal?
What method is used to determine the nitrogen content in coal?
What method is used to determine the nitrogen content in coal?
How is the percentage of fixed carbon in coal calculated?
How is the percentage of fixed carbon in coal calculated?
In ultimate analysis, how is the percentage of sulfur determined?
In ultimate analysis, how is the percentage of sulfur determined?
Why is the presence of nitrogen in coal considered undesirable?
Why is the presence of nitrogen in coal considered undesirable?
What is the key significance of determining the hydrogen content in coal?
What is the key significance of determining the hydrogen content in coal?
What characteristic helps improve the calorific value of a fuel?
What characteristic helps improve the calorific value of a fuel?
What is an important aspect of a good fuel regarding its combustion?
What is an important aspect of a good fuel regarding its combustion?
Which method of cracking operates at higher temperatures?
Which method of cracking operates at higher temperatures?
What type of internal combustion engine uses petrol as fuel?
What type of internal combustion engine uses petrol as fuel?
What is a key benefit of catalytic cracking compared to thermal cracking?
What is a key benefit of catalytic cracking compared to thermal cracking?
What factor can improve the antiknocking properties of petrol?
What factor can improve the antiknocking properties of petrol?
What undesirable effect can be caused by high sulfur content in fuel?
What undesirable effect can be caused by high sulfur content in fuel?
What happens to the catalyst during fixed bed catalytic cracking?
What happens to the catalyst during fixed bed catalytic cracking?
What does 'knocking' in an internal combustion engine refer to?
What does 'knocking' in an internal combustion engine refer to?
What is one characteristic of a good quality fuel related to its handling?
What is one characteristic of a good quality fuel related to its handling?
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Study Notes
Introduction to Chemical Fuels
- Fuel is an essential material for industrial, domestic, and vehicular applications.
- Limited natural fuel sources have prompted the rise of synthetic fuel manufacturing.
- Fuel combustion involves the rapid combination of carbon and hydrogen with oxygen, releasing significant heat.
Classification of Fuels
-
By Physical State:
- Solid Fuels: Examples include wood, coal, and dung.
- Liquid Fuels: Examples include petrol, kerosene, and diesel.
- Gaseous Fuels: Examples include natural gas and LPG.
-
By Occurrence:
- Natural Fuels: Fuels found in nature without human intervention.
- Artificial Fuels: Manufactured from natural fuels.
Calorific Value
-
Defined as the heat released when a unit mass of fuel completely burns.
-
Types of Calorific Value:
- Higher Calorific Value (HCV): Total heat produced, including condensation of combustion products.
- Lower Calorific Value (LCV): Heat produced when combustion products can escape, excluding heat of condensation.
-
Relation Between GCV and LCV:
- LCV = GCV - Heat of condensation
-
Units of Measurement:
- Solid and liquid fuels: calories per gram (cal/g), kilocalories per kilogram (kcal/kg).
- Gaseous fuels: kilocalories per cubic meter (kcal/m³).
Analysis of Coal
-
Proximate Analysis: Assesses coal quality by evaluating:
- Moisture: Affects heat liberation; high moisture reduces calorific value.
- Volatile Matter: Determines the burning characteristics; lower values indicate better coal quality.
- Ash: Non-combustible matter that lowers calorific value.
- Fixed Carbon: Calculated by 100 - (% moisture + % volatile matter + % ash).
-
Ultimate Analysis: Determines specific elements in coal:
- Carbon and Hydrogen: High percentages indicate better quality.
- Nitrogen: Undesirable as it contributes no calorific value.
- Sulphur: Reduces quality and causes pollution.
- Oxygen: High levels decrease calorific value.
Characteristics of Good Fuel
- Availability and economic cost.
- Low moisture content to enhance calorific value.
- Moderate ignition temperature and low ash residue.
- Safe handling, non-explosive combustion, and no toxic emissions.
Cracking of Petroleum Fractions
-
Decomposes high molecular weight hydrocarbons into lighter ones.
-
Essential due to high gasoline demand exceeding direct distillation yields.
-
Methods of Cracking:
- Thermal Cracking: Uses heat and pressure to produce gasoline.
- Liquid Phase: Cracks oil at 475-530°C.
- Vapour Phase: Cracks vaporized oil at 600-650°C.
- Catalytic Cracking: Improves yield/quality using catalysts such as alumina.
- Processes include fixed bed and moving bed catalytic cracking with varying pressures.
- Thermal Cracking: Uses heat and pressure to produce gasoline.
Internal Combustion (IC) Engine
-
Combustion of fuel-air mixture occurs internally.
-
Types of engines:
- SI Engine: Utilizes petrol with spark ignition.
- CI Engine: Uses diesel with compression ignition.
-
Knocking:
- Uncontrolled combustion causing metallic noise and loss of efficiency.
- Influenced by fuel type, engine design, and operational conditions.
Octane and Cetane Numbers
-
Octane Number: Measures fuel's knocking resistance in SI engines.
- Iso-octane = 100, n-heptane = 0; octane number defines a fuel's quality.
-
Cetane Number: Indicates knocking characteristics of diesel fuel.
- Higher cetane numbers signify easier ignition and combustion efficiency.
Antiknocking Agents
- Substances added to increase octane ratings and reduce knocking, e.g., TEL and MTBE.
- TEL forms harmful lead oxide; safer alternatives are sought to minimize environmental impacts.
Diesel Knocking
- Abnormal combustion in CI engines can lead to excessive pressure and sound.
- Knocking depends on the properties of diesel and engine design.
Summary
- Understanding fuel types, properties, and analysis methods is crucial for efficient energy use and development of cleaner alternatives.### Fuel Ignition in Compression Ignition Engines
- Quick ignition of fuel is crucial upon injection into a compression ignition engine cylinder.
- The time from fuel injection start to combustion onset is known as the ignition delay period.
Cetane and Ignition Quality
- Cetane (C16H34) is a saturated hydrocarbon that ignites rapidly, assigned a cetane number of 100.
- Methyl naphthalene, being an aromatic hydrocarbon, has a long ignition delay and a cetane number of zero.
- Cetane number indicates a fuel's ignition quality, defined as the volume percentage of cetane in a mixture with methyl naphthalene that matches the ignition delay of the fuel being tested.
Comparison and Examples
- A diesel fuel with a cetane number of 40 has an ignition delay equal to a mixture of 40% cetane and 60% methyl naphthalene.
- Different diesel engines necessitate fuels with varying cetane numbers:
- High-speed engines require cetane number of 50.
- Medium-speed engines require cetane number of 45.
- Low-speed engines require cetane number of 25.
Improving Cetane Number
- Cetane number of diesel can be enhanced by using additives such as:
- Acetylene
- Ethyl nitrile
- Ethyl nitrate
- Acetone
Introduction to Chemical Fuels
- Fuel is an essential material for industrial, domestic, and vehicular applications.
- Limited natural fuel sources have prompted the rise of synthetic fuel manufacturing.
- Fuel combustion involves the rapid combination of carbon and hydrogen with oxygen, releasing significant heat.
Classification of Fuels
-
By Physical State:
- Solid Fuels: Examples include wood, coal, and dung.
- Liquid Fuels: Examples include petrol, kerosene, and diesel.
- Gaseous Fuels: Examples include natural gas and LPG.
-
By Occurrence:
- Natural Fuels: Fuels found in nature without human intervention.
- Artificial Fuels: Manufactured from natural fuels.
Calorific Value
-
Defined as the heat released when a unit mass of fuel completely burns.
-
Types of Calorific Value:
- Higher Calorific Value (HCV): Total heat produced, including condensation of combustion products.
- Lower Calorific Value (LCV): Heat produced when combustion products can escape, excluding heat of condensation.
-
Relation Between GCV and LCV:
- LCV = GCV - Heat of condensation
-
Units of Measurement:
- Solid and liquid fuels: calories per gram (cal/g), kilocalories per kilogram (kcal/kg).
- Gaseous fuels: kilocalories per cubic meter (kcal/m³).
Analysis of Coal
-
Proximate Analysis: Assesses coal quality by evaluating:
- Moisture: Affects heat liberation; high moisture reduces calorific value.
- Volatile Matter: Determines the burning characteristics; lower values indicate better coal quality.
- Ash: Non-combustible matter that lowers calorific value.
- Fixed Carbon: Calculated by 100 - (% moisture + % volatile matter + % ash).
-
Ultimate Analysis: Determines specific elements in coal:
- Carbon and Hydrogen: High percentages indicate better quality.
- Nitrogen: Undesirable as it contributes no calorific value.
- Sulphur: Reduces quality and causes pollution.
- Oxygen: High levels decrease calorific value.
Characteristics of Good Fuel
- Availability and economic cost.
- Low moisture content to enhance calorific value.
- Moderate ignition temperature and low ash residue.
- Safe handling, non-explosive combustion, and no toxic emissions.
Cracking of Petroleum Fractions
-
Decomposes high molecular weight hydrocarbons into lighter ones.
-
Essential due to high gasoline demand exceeding direct distillation yields.
-
Methods of Cracking:
- Thermal Cracking: Uses heat and pressure to produce gasoline.
- Liquid Phase: Cracks oil at 475-530°C.
- Vapour Phase: Cracks vaporized oil at 600-650°C.
- Catalytic Cracking: Improves yield/quality using catalysts such as alumina.
- Processes include fixed bed and moving bed catalytic cracking with varying pressures.
- Thermal Cracking: Uses heat and pressure to produce gasoline.
Internal Combustion (IC) Engine
-
Combustion of fuel-air mixture occurs internally.
-
Types of engines:
- SI Engine: Utilizes petrol with spark ignition.
- CI Engine: Uses diesel with compression ignition.
-
Knocking:
- Uncontrolled combustion causing metallic noise and loss of efficiency.
- Influenced by fuel type, engine design, and operational conditions.
Octane and Cetane Numbers
-
Octane Number: Measures fuel's knocking resistance in SI engines.
- Iso-octane = 100, n-heptane = 0; octane number defines a fuel's quality.
-
Cetane Number: Indicates knocking characteristics of diesel fuel.
- Higher cetane numbers signify easier ignition and combustion efficiency.
Antiknocking Agents
- Substances added to increase octane ratings and reduce knocking, e.g., TEL and MTBE.
- TEL forms harmful lead oxide; safer alternatives are sought to minimize environmental impacts.
Diesel Knocking
- Abnormal combustion in CI engines can lead to excessive pressure and sound.
- Knocking depends on the properties of diesel and engine design.
Summary
- Understanding fuel types, properties, and analysis methods is crucial for efficient energy use and development of cleaner alternatives.### Fuel Ignition in Compression Ignition Engines
- Quick ignition of fuel is crucial upon injection into a compression ignition engine cylinder.
- The time from fuel injection start to combustion onset is known as the ignition delay period.
Cetane and Ignition Quality
- Cetane (C16H34) is a saturated hydrocarbon that ignites rapidly, assigned a cetane number of 100.
- Methyl naphthalene, being an aromatic hydrocarbon, has a long ignition delay and a cetane number of zero.
- Cetane number indicates a fuel's ignition quality, defined as the volume percentage of cetane in a mixture with methyl naphthalene that matches the ignition delay of the fuel being tested.
Comparison and Examples
- A diesel fuel with a cetane number of 40 has an ignition delay equal to a mixture of 40% cetane and 60% methyl naphthalene.
- Different diesel engines necessitate fuels with varying cetane numbers:
- High-speed engines require cetane number of 50.
- Medium-speed engines require cetane number of 45.
- Low-speed engines require cetane number of 25.
Improving Cetane Number
- Cetane number of diesel can be enhanced by using additives such as:
- Acetylene
- Ethyl nitrile
- Ethyl nitrate
- Acetone
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