Fuel Types - Characteristics of Ideal Fuel
Any substance that when undergoing chemical or nuclear change to produce energy and which can be converted into useful work is known as fuel.
The calorific value of a fuel is defined as the amount of energy released when the unit mass of the substance(fuel) undergoes complete combustion.
The SI Unit to Measure Calorific Value is J/kg.
Fuels can be Generally Classified Into
Renewable Sources of Energy
The sources of energy that when once consumed can be obtained back by various biogeochemical cycles occurring in nature are known as renewable sources of energy. Energy from running water is an example of a renewable source of energy because once consumed we can get it back through rain. Another example is solar energy. For sustainable development, we should try to make maximum use of renewable energy resources.
Non-Renewable Sources of Energy
The sources of energy that once consumed cannot be obtained back by any biogeochemical cycle is known as a non-renewable energy resource. For example, fossil fuels take millions of years to come into existence, once finished cannot be generated back for our use, hence termed non-renewable energy resources. Non-renewable resources must be used judiciously, before their use all other alternative sources of energy must be taken into consideration.
Some Properties of Ideal Fuel are
Ignition Temperature: The temperature at which a substance catches fire is known as its ignition temperature. An ideal fuel must have an easily attainable ignition temperature. For example, the chemical present on the head of the matchstick catches fire easily using the heat produced by friction generated by rubbing it with the side of the matchbox.
Calorific Value: The purpose of the fuel is to convert its chemical energy into heat and other forms of energy on burning. An ideal fuel must have a high calorific value to serve the purpose better.
Impact on Environment: An ideal fuel must leave less residue (harmful) on burning. It should undergo complete combustion so as not to add particulate matter to the atmosphere. For example, Compressed natural gas leaves almost no residue on burning.
Rate of Combustion: An ideal fuel must burn at a constant/moderate rate. Rapid and explosive combustion is not the characteristic feature of an ideal fuel.
Availability: An ideal fuel should be easily and ever available. It should be available at a low cost.
Handling: Easy storage and transportation prevent the loss of fuel and also protects the environment. It improves the accessibility of the fuel.
Types of Fuels
On Basis of Their State
Solid Fuels: The fuels which exist in a solid state only in their primary stage are termed solid fuels.
Liquid Fuels: The fuels which exist in a liquid state only in their primary stage are termed liquid fuels.
Fuel Gases: The fuels which exist in a gaseous state only in their primary stage are termed fuel gases.
On Basis of their Occurrence
Natural Fuels: The fuels which are present naturally are known as natural fuels.
BioFuels: The fuels obtained from the living matter on earth are termed biofuels.
Fossil Fuels: Dead and decaying plants and animals buried deep under the earth, under high pressure and temperature gets converted into extremely high-quality fuel termed fossil fuels. Coal and petroleum are two important types of fossil fuels. Coal is mainly obtained from dead and decaying plants, whereas petroleum (crude oil) is obtained from dead and decaying animals (especially aquatic animals). Since fossil fuels are generated from organic matter, they are a rich source of energy but are non-renewable as it takes millions of years for the conversion of organic matter into fossil fuels.
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Artificial Fuels: The fuels which are obtained through different chemical processes are termed artificial fuels. For example, water gas and producer gas are fuels obtained in a laboratory under required conditions.
Examples of Fuels
Solid Fuels:
Liquid Fuels:
Gaseous Fuels
Types of Gaseous Fuels
Naturally Occurring Gaseous Fuels: Natural gas is found over petroleum deposits and around coal deposits (Firedamp). The composition of natural gas obtained from different sources vary with the main component being methane gas. Other than methane some higher hydrocarbons are also found in natural gas. Traces of H2S gas are also present in Natural gas.
Characteristics-
High calorific value
Proper ignition temperature
Extraction of natural gas from Petroleum deposits is comparatively easier than extracting from coal deposits.
Natural gas can be easily liquified for distribution by tanker. It is termed liquified natural gas (LNG)
Gaseous Fuels Derived From Solid Fuels: Methane gas found around coal deposits, Gaseous fuels obtained from waste and biomass, Fuels obtained from industrial processes such as gases produced in blast furnaces.
Gaseous Fuels Obtained From Petroleum: Liquified petroleum gas, Gases obtained from various refining processes, Gaseous fuel obtained from oil gasification.
Gaseous Fuels Obtained From Fermentation Processes: For example, ethyl alcohol is obtained from the fermentation of sugarcane.
Nuclear Fuels
The energy obtained during nuclear reactions (Nuclear fusion or nuclear fission reactions) is known as nuclear energy and the reactants are termed nuclear fuels. Uranium-235 is a widely used nuclear fuel because - energy released from a single pellet of uranium = energy released from one ton of coal = energy released from 149 gallons of oil = energy released from 17000 cu ft of Natural gas
Apart from Uranium-235, plutonium-239 is also used extensively in nuclear reactions.
Advantages of Nuclear Energy
Sustainable Development: The world population living without electricity is more than one billion. Nuclear energy is the low-cost and ever-available source of energy for developing nations. It is an affordable source of energy.
Climate: Almost all sources of energy emit some or other kind of harmful gases, but nuclear fuel is emissions-free. Nuclear energy prevents more than 52b million metric tons of CO2 from entering our atmosphere.
National Security: Nuclear fuel empowers nations by building weapons for their own security purposes.
Disadvantages of Nuclear Energy
High Upfront Costs: Nuclear thermal plants that are needed to harness the nuclear energy of a substance are though cheaper to run, but require an enormous amount of money to establish.
Radioactive Waste: The use of nuclear energy produces Radioactive Waste, which can be dangerous to the environment. And it is also very troublesome to get rid of this waste.
FAQs on Fuel Types
1. What is a fuel, and how are fuels generally classified?
A fuel is any substance that can be made to react with other substances to release energy, typically in the form of heat, which can then be used for work. Fuels are broadly classified based on two main criteria:
- By Physical State: This classifies fuels as Solid Fuels (e.g., coal, wood), Liquid Fuels (e.g., petrol, kerosene), and Gaseous Fuels (e.g., CNG, LPG).
- By Occurrence: This classifies them as Natural Fuels (found in nature, like wood and crude oil) and Artificial Fuels (processed by humans, like coke and producer gas).
2. What are the key characteristics of an ideal fuel?
An ideal fuel is one that is efficient, safe, and economical. Its main characteristics, as per the CBSE syllabus, are:
- High Calorific Value: It should produce a large amount of heat per unit mass.
- Proper Ignition Temperature: It should have a moderately low ignition temperature, making it easy to start burning but not so low that it's a fire hazard.
- Low Environmental Impact: It should burn without producing harmful gases or leaving behind much residue like ash.
- Moderate Rate of Combustion: It should burn at a steady and controllable rate.
- Easy Availability and Low Cost: It should be readily available and affordable.
- Safe to Handle and Transport: It should be easy and safe to store and move from one place to another.
3. Can you provide examples of solid, liquid, and gaseous fuels and their common uses?
Fuels are used across various sectors based on their physical state. Here are some common examples and their uses:
- Solid Fuels: Coal is used in thermal power plants to generate electricity, while wood and cow dung cakes are used for cooking in rural households.
- Liquid Fuels: Petrol and diesel are primarily used in vehicles for transportation. Kerosene is used as a cooking fuel and for lighting in lamps.
- Gaseous Fuels: Liquefied Petroleum Gas (LPG) is the main cooking fuel in urban homes, while Compressed Natural Gas (CNG) is a cleaner fuel used in automobiles.
4. What are fossil fuels, and why are they considered non-renewable?
Fossil fuels are energy-rich substances formed from the decomposed remains of ancient plants and animals buried deep under the Earth's surface for millions of years. Examples include coal, petroleum, and natural gas. They are considered non-renewable because the rate at which we are consuming them is vastly faster than the millions of years it takes for them to form. Once the current reserves are depleted, they cannot be replenished within a human lifespan.
5. Why is a fuel's ignition temperature just as important as its calorific value?
While calorific value tells us how much energy a fuel can release, the ignition temperature determines how practical and safe it is to use that fuel. A fuel with a very high ignition temperature would be difficult to light, requiring a lot of energy just to start the combustion. Conversely, a fuel with an extremely low ignition temperature, like white phosphorus, can catch fire at room temperature, making it incredibly dangerous to store and handle. Therefore, an ideal fuel has an ignition temperature that is low enough for convenience but high enough for safety.
6. What does the 'calorific value' of a fuel indicate, and why is a higher value desirable?
The calorific value of a fuel indicates the total quantity of heat energy produced when a unit mass or volume of the fuel is completely burned. It is typically measured in kilojoules per kilogram (kJ/kg). A higher calorific value is desirable because it signifies greater fuel efficiency. This means you get more energy from a smaller amount of fuel, making it more cost-effective and reducing the amount of fuel needed for storage and transportation.
7. How do renewable and non-renewable fuels differ in their long-term environmental impact?
The primary difference lies in their sustainability and by-products. Non-renewable fuels, like coal and petroleum, release significant amounts of greenhouse gases (like CO2) and pollutants (like sulphur dioxide) when burned, contributing to global warming and acid rain. Renewable fuels, such as biofuels or energy from solar and wind, are considered more environmentally friendly. Biofuels are often carbon-neutral because the carbon dioxide they release during combustion is roughly equivalent to the amount the plants absorbed during their growth.
8. How is nuclear fuel different from conventional chemical fuels like coal or petroleum?
The fundamental difference is the source of energy. Chemical fuels like coal and petroleum release energy through combustion, a chemical reaction where atomic bonds are broken and reformed. Nuclear fuels, such as Uranium-235, release energy through nuclear fission, a process where the nucleus of an atom is split. This nuclear reaction releases millions of times more energy per unit mass than a chemical reaction, but it also produces radioactive waste that requires careful disposal.
