Fuel Properties, Coal Analysis, and Corrosion Science
Fuel Definition and Types
A fuel is defined as any substance that can provide heat and produce energy when it is burned. The energy released is generally in the form of chemical energy or heat energy.
Examples of fuel:
- Methanol
- Gasoline
- Diesel
- Natural gas
Types of fuel:
- Solid fuel
- Liquid fuel
- Biofuel
- Fossil fuel
Characteristics of a Good Fuel
A good fuel has the following characteristics:
- Availability: It should be readily available.
- Cost: It should be inexpensive.
- Combustion: It should burn easily in air at a moderate rate, producing a large amount of heat.
- Pollution: It should not produce smoke or cause pollution.
- Controllability: Its burning should be controllable.
- Moisture: It should be dry and have low moisture content.
- Ash: It should produce little ash after combustion.
Coal Analysis Methods
Coal analysis is a process that measures various properties of coal, including its composition, heating potential, and how it behaves when heated. Two primary methods are used:
Proximate Analysis
Determines the chemical composition of a material in terms of its moisture content, fixed carbon, volatile matter, and ash content. Proximate analysis can be performed using standard laboratory equipment and is suitable for competent scientists or engineers.
Ultimate Analysis
Determines the elemental composition of a material in terms of its carbon, hydrogen, nitrogen, sulfur, and oxygen content. Ultimate analysis requires expensive equipment and highly trained analysts.
High and Low Calorific Value
Calorific value is the amount of heat energy released during the complete combustion of a unit amount of fuel.
Higher Calorific Value (HCV)
Also known as gross calorific value (GCV), this is the amount of heat released when a fuel is completely combusted and the products are cooled to room temperature. It includes the energy from water vapor during condensation.
Lower Calorific Value (LCV)
Also known as net calorific value (NCV), this is the amount of heat released when a fuel is completely burned and the products are not cooled. It does not include the energy from water vapor during condensation.
Corrosion Definition and Types
Corrosion is a natural process in which a refined metal is converted to a more chemically stable form, such as oxide, hydroxide, or sulfide. It is the gradual decomposition of materials (usually metals) as a result of chemical and/or electrochemical reactions with their surroundings.
Types of corrosion:
- Crevice Corrosion: Occurs whenever there is a difference in ionic concentration between any two local areas of a metal, leading to a localized form of corrosion.
- Stress Corrosion Cracking (SCC): Refers to the cracking of the metal as a result of the corrosive environment and the tensile stress placed on the metal. It often occurs at high temperatures.
- Galvanic Corrosion: Can arise when there is electric contact between two electrochemically dissimilar metals in an electrolytic environment. It refers to the degradation of one of these metals at a joint or junction.
Why Gold Resists Oxidation Corrosion
Gold does not corrode due to oxidation because it is a very unreactive metal with a highly stable electron configuration. Its outer electrons are not easily available to bond with oxygen, preventing the oxidation process that leads to corrosion in other metals. Essentially, gold is considered a “noble metal” and does not readily react with air or moisture.
Oxidation Corrosion and Noble Metals
Noble metals resist oxidation and corrosion because of their electron configuration, which makes it difficult for them to lose electrons and form oxides. This resistance allows noble metals to maintain their strength and shine over time.
Explanation
Corrosion is the gradual degradation of a metal’s surface when it comes into contact with air and moisture. Noble metals are less reactive than other metals and are the only metals that are found in nature in their purest form. They are unaffected by oxygen and acids, and are more stable than their compounds, like oxides and sulfides.