Fuels and Coal: Characteristics and Classifications

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What are the two phases of the coalification process?

The two phases are biochemical and geochemical.

Besides carbon and hydrogen, what are three common impurities found in coal?

Sulfur, nitrogen, and ash.

List one advantage and one disadvantage of using coal as a fuel source.

Advantage: High energy output. Disadvantage: Production of greenhouse gases/pollutants.

Approximately how many years ago was hard coal formed?

300-200 million years ago. Signup and view all the answers

Name the three main constituents of coal.

Organic matter, mineral matter, and moisture. Signup and view all the answers

What is the most probable origin of crude oil and natural gas?

Organic. Signup and view all the answers

In what four mediums can natural gas be found?

Separately, diluted in oil, diluted in water, diluted in rocks (in coal). Signup and view all the answers

Define 'self ignition temperature'.

The lowest temperature at which a substance spontaneously ignites without an external ignition source. Signup and view all the answers

List the three primary (natural) forms of chemical fuels.

Solid, liquid, and gaseous. Signup and view all the answers

Provide two examples of renewable alternative motor fuels.

Biogas, syngas, vegetable oil, spirits, or methyl esters of vegetable oils. Signup and view all the answers

Name three different classifications of oils.

Compressor oils, gear oils, and turbine oils (other correct answers possible). Signup and view all the answers

What is the primary origin of crude oil?

Organic matter. Signup and view all the answers

What are the three classifications of crude oil based on sulphur content, density and paraffins?

Low sulphur oils (<=2%), light (< 0.87 kg/m3), medium (0.87–0.91 kg/m3), and heavy (> 0.91 kg/m3), low paraffin oils (<=10%). Signup and view all the answers

Name two classifications of gaseous fuels based on their origin.

Natural and artificial. Signup and view all the answers

Give two examples of liquid petroleum fuels considered as gasoline.

Aviation gasoline, unleaded gasoline 98, or unleaded gasoline 95. Signup and view all the answers

Name three transport classifications of gaseous fuels.

LPG (liquefied petroleum gas), CNG (compressed natural gas), LNG (liquefied natural gas). Signup and view all the answers

Besides carbon and hydrogen, what other three elements are commonly found in crude oil?

Oxygen (O), sulfur (S), and nitrogen (N). Signup and view all the answers

What effect do normal paraffins have on diesel engine operation?

Normal paraffins cause soft engine opporation in diesel engines. Signup and view all the answers

Why are aromatic hydrocarbons undesirable in diesel fuel?

They cause auto-ignition delay and hard engine operation. Signup and view all the answers

Why are olefinic hydrocarbons generally considered harmful in fuels?

They oxidize easily, forming oxides and organic acids that promote corrosion. Signup and view all the answers

How does the presence of sulfur in fuel affect engine corrosion, and what is another environmental concern?

The corrosive effect of sulfur increases when the engine is cold, and the presence of sulfur in fuel contributes to air pollution. Signup and view all the answers

Briefly explain how 'cracking' is used in oil processing.

Cracking breaks heavier, higher-boiling point petroleum fractions into more valuable, lighter products. Signup and view all the answers

What role does 'vacuum distillation' play in oil processing?

Vacuum distillation separates crude oil into boiling fractions at different temperature ranges, under reduced pressure. Signup and view all the answers

Explain why nickel, vanadium, and copper are removed during oil refining.

These compounds can severely affect the activities of catalysts and result in lower quality products. Signup and view all the answers

What is the primary purpose of the octane number?

The octane number determines the resistance of engine fuel to uncontrolled, spontaneous ignition in spark-ignition engines. Signup and view all the answers

How is the octane number of a fuel determined?

It is determined by comparing the fuel's knocking characteristics to those of a mixture of iso-octane (ON 100) and n-heptane (ON 0) in a test engine. Signup and view all the answers

What does the cetane number indicate about a diesel fuel?

The cetane number evaluates the ignition properties of fuels used in diesel engines. Signup and view all the answers

What is the significance of a short ignition delay in diesel engines?

A short ignition delay means that the fuel self-ignites more quickly after injection, leading to better combustion. Signup and view all the answers

For what type of fuel is the CCAI (Calculated Carbon Aromaticity Index) used, and why?

CCAI is used for residual fuels because the cetane number cannot be used due to different combustion conditions in marine engines. Signup and view all the answers

List three fractions obtained from distilling crude oil, ordered by increasing boiling point.

Light gasoline, kerosene, diesel oil. Signup and view all the answers

Why is a high content of light fractions desirable in motor fuels?

A high content of light fractions makes it easier to start the engine at low temperatures. Signup and view all the answers

Name three of the main types of hydrocarbons found in crude oil.

Alkanes, cycloalkanes, and aromatic hydrocarbons. Signup and view all the answers

What is the clouding point of a liquid, and what visual change indicates that it has been reached?

The clouding point is the temperature at which dissolved waxes in a liquid start to precipitate as solid particles. This is indicated by the liquid appearing hazy or cloudy. Signup and view all the answers

Define solidification temperature and provide the approximate solidification temperatures for heavy oils and light diesel.

Solidification temperature is the temperature at which a fuel stagnates. For heavy oils, it is about +5°C, and for light diesel, it is about -20°C. Signup and view all the answers

Explain the difference between absolute density and relative density (specific gravity). Include the common units and scales used for each.

Absolute density is the ratio of mass to volume (e.g., g/cm3, kg/m3). Relative density (specific gravity) is the ratio of the density of a substance to the density of a reference substance and is unitless. API degrees are used as a relative scale. Signup and view all the answers

What is absolute viscosity, and how is it defined?

Absolute viscosity is the amount of resistance that occurs when two adjacent layers of a liquid are moved relative to each other. Signup and view all the answers

What is relative viscosity, and what is used as a reference to calculate it. What scale is used?

Relative viscosity is the ratio of the viscosity of a fluid to the viscosity of a reference fluid. Engler degrees [°E] are used as a scale. Signup and view all the answers

Distinguish between heat of combustion and calorific value. What units are used for each term?

Heat of combustion includes cooling the combustion products to the initial temperature and complete condensation of water vapor, while calorific value assumes water remains as steam. Both are measured in [kJ/kg] or [kJ/m3]. Signup and view all the answers

What is incomplete combustion, in terms of the resulting products?

Incomplete combustion is when there are solid combustibles in the products, such as coke or soot. Signup and view all the answers

What is 'no-total' combustion, in terms of the resulting products?

No-total combustion is when there are flammable gases in the products, like CO, CH4, or H2. Signup and view all the answers

Chemical Fuels

Fuels classified into primary (natural) and secondary (derived) categories.

Primary Fuels

Natural fuels that include solid (wood, coal), liquid (crude oil), and gaseous (natural gas).

Secondary Fuels

Derived fuels that include solid (coke), liquid (kerosene), and gaseous types (biogas).

Motor Fuels

Fuels used in vehicles classified into conventional (petrol, diesel) and alternative (renewable/non-renewable).