ANS:D - Furnace oil

The °API (American Petroleum Institute) gravity scale is used to measure the density or specific gravity of petroleum liquids relative to water. Higher °API gravity values indicate lighter and less dense liquids, while lower values indicate heavier and more dense liquids. Among the options provided:

• Diesel: Typically has a °API gravity in the range of 30-40.
• Kerosene: Generally has a °API gravity in the range of 40-50.
• Petrol (Gasoline): Usually has a °API gravity in the range of 50-70.
• Furnace oil (Heavy Fuel Oil): Has a °API gravity generally less than 30, often in the range of 10-25.

Based on this information, furnace oil (heavy fuel oil) has the minimum °API gravity of all the options listed. It is denser and heavier compared to diesel, kerosene, and petrol. Therefore, furnace oil would have the lowest °API gravity among diesel, kerosene, petrol, and itself. Furnace oil, also known as heavy fuel oil (HFO) or residual fuel oil (RFO), is a type of petroleum fuel that is a byproduct of crude oil refining processes. Here are some key characteristics and uses of furnace oil:

1. Composition: Furnace oil is typically composed of heavier hydrocarbons that remain after the distillation of crude oil to produce lighter products like gasoline, diesel, and kerosene. It contains a mixture of long-chain hydrocarbons, including some aromatic compounds.
2. Properties:
   • Density: Furnace oil is denser and heavier than diesel, kerosene, and gasoline. It has a high viscosity and tends to flow less readily at ambient temperatures compared to lighter fuels.
   • °API Gravity: Furnace oil typically has a low °API gravity, often ranging from 10 to 25 °API. This indicates its high density and heaviness compared to lighter petroleum products.
3. Uses:
   • Industrial Heating: Furnace oil is commonly used as a fuel in industrial boilers, furnaces, and heating systems where high temperatures are required for processes such as steam generation, heating buildings, and powering industrial equipment.
   • Marine Fuel: It is also used as a fuel for large ships and vessels, particularly in marine diesel engines that are designed to burn heavy fuel oils.
4. Storage and Handling: Due to its high viscosity and density, furnace oil requires specific handling and storage conditions to maintain its fluidity and prevent issues such as solidification or clogging of fuel systems.
5. Environmental Considerations: Furnace oil combustion can produce emissions of sulfur oxides (SOx) and particulate matter, contributing to air pollution. Efforts are often made to reduce sulfur content in furnace oil to comply with environmental regulations.

In summary, furnace oil is a heavy, dense petroleum fuel derived from crude oil refining processes. It is primarily used in industrial applications and marine transportation where its high energy content and ability to sustain high temperatures are advantageous.