FUELS AND ENERGY

FUELS AND ENERGY

FUELS

What are fuels?

Fuels are substances which when burnt release energy. This energy in can be in the form of heat, light, electricity or sound. Combustion is a chemical process, so fuels are also known as chemical fuels.

Examples of fuels are petroleum, coal, charcoal, wood etc.

CATEGORIES OF FUELS

Fuels can be classified on the basis of either occurrence or physical state.

(a)    The following is the classification of fuels on the basis of their occurrence.

(i)     Natural fuels

The fuels that occur in nature, it includes the fossils fuels which are formed from the remains of dead living organisms such as plants and tiny marine animals lived millions years ago. The remains became buried under layers of sediment. Immense pressure and heat resulted in the formation of coal, natural gas and petroleum.

Example of natural fuels including wood, coal, peat, petroleum and natural gas

·         The energy that released from natural fuels is originated from the sun. it was captured by the plants through photosynthesis.

(ii)   Artificial fuels

Artificial fuels are either manufactured in industries or derived from natural fuels by refining. They including coke, kerosene, petrol, coal gas and producer gas

(b)   Classification of fuels based on their physical states.

(i)     Solid fuels

The fuels that occurs in solid physical state, includes wood, coal, charcoal, coke, ignite, and peat. Wood and wood charcoal are obtained from plants while different types of coal are fossil remains of plants and organisms that lived in past geologic ages. The solid fuels produces ashes when burnt, they cannot regulated by automatic devices, and they are less convenient to handle than the liquid fuels.

(ii)   Liquid fuels

The type fuel that occurs in liquid state, which includes crude petroleum, petrol, diesel, kerosene, biodiesel. Liquid fuels have no ashes when burnt, they can be regulated by automatic devices and they are more convenient to handle than solid fuels.

(iii) Gaseous fuels

The fuel which occurs in gaseous state; example of gaseous fuel includes natural gas, liquefied petroleum gas (LPG), coal gas, water gas and hydrogen gas. It is used for domestic heating in cooking stoves, and gas heater.

CHARACTERISTICS OF GOOD FUEL

The following are characteristics that are considered when choosing a good fuel:

·         Should have high heat content i.e. it must burn easily and produce a lot of energy.

·         It must be cheap

·         It should have little or no waste products like ash, and smoke.

·         It must not give off dangerous by-products, e.g., poisonous fumes.

·         It should be easily controlled

·         It should be easily stored and transported

COAL

Coal is the fossil fuel formed from plants lived in past geological ages. The chemical energy available in coal originated from the sun through photosynthesis and this energy remains in compounds left after decaying process during the formation of coal.

Composition of coal

The four major components of coal are;

·         Moisture

·         Volatile matter is a material that is driven off when coal is heated to about 950˚C in absence of air. It consists of gases and low-boiling point organic compounds that condense into oils when cooled, and tar.

·         Ash is the non-combustible residue material left after coal is burnt.

·         Coke (fixed carbon) I s the material left after the volatile matter driven off.

Types of coal

The different types of coal vary in compositions and properties depending on coal’s age and conditions under which it was formed. The most important types of coal are;

·         Peat

·         Lignite

·         Bituminous (soft) coal

·         Anthracite (hard) coal

Destructive distillation

Destructive distillation is a process through which organic fuels are decomposed by heating them in absence of air to obtain useful products such as coke, charcoal, oils and gases.

Destructive distillation of coal

This is the process of heating the coal in absence of air to form coke, coal gas, coal tar, and ammoniacal liquor.

CHARCOAL

Charcoal is a solid residue left when a certain organic matter are heated in absence of air. The organic matter can be obtained from plants and animal sources such as wood and animal bones.

Types of charcoal

(a)    Wood charcoal is a substance formed by destructive distillation of wood. A good charcoal is porous, brittle, and retains the form of wood. It burns with non-luminous flame and ignite easily.

Uses of wood charcoal

·         Used in absorption of gases in purification of water, and in gas-masks because it absorbs poisonous gases.

·         Used as a source of heat for domestic purposes

What is destructive distillation of wood?

The destructive distillation of wood  heating wood in absence of air to produce wood charcoal, wood tar, acid liquor and wood gas.

(b)   Anima charcoal is a type of charcoal formed by heating animal bones under limited supply of air. Anima charcoal absorbs colour from solutions hence employed in removing brown colour from crude sugar.

Important gaseous fuels used in industry

The most important gaseous fuels used in industries are water gas and producer gas.

Producer gas

Producer gas is a mixture of carbon dioxide and nitrogen. Producer gas is made by reacting air with hot coke (carbon).

How does it produced?

·         Air is blown through hot coke. Carbon dioxide is first formed, and is reduced to the carbon monoxide in the middle of the coke where there is no oxygen.

·         The reaction is exothermic, and the coke becomes very hot:

Representing air as

·         As a fuel produce gas burns to give out carbon dioxide

·         Producer gas is therefore one-third carbon monoxide and two-thirds nitrogen by volume, i.e. only one-third of the gas can burn. It has low calorific value compared to water gas.

Uses of producer gas

1.       Producer gas provides a reducing atmosphere in certain metal-extraction operations.

2.       Producer gas is used as a fuel for heating open-hearth furnaces (used in steel and glass manufacturing), muffle furnaces and retorts (used in the production of coke and coal gas).

Water gas

The gas is a mixture of hydrogen and carbon monoxide. It is produced by passing steam over white hot coke. The reaction is endothermic, causing the coke to cool.

·         Steam is blown through white hot coke

·         Water gas consists of equal volumes of hydrogen and carbon monoxide, i.e. all the gas can burn. Usually producer gas and water gas are made alternately; the coke becomes hot in the air stream and the steam cools it again.

·         Water gas burns as a fuel to give out carbon dioxide and steam.

Properties of water gas

·         Water gas burns with a non-luminous blue flame and hence it is also called blue water gas.

·         It has energy value of about.

·         It burns with a high temperature flame of about

Uses of water gas

1.       Water gas has a high energy value and is therefore widely used as an industrial fuel especially in the making of steel.

2.       It is also used in the preparation of hydrogen.

ENERGY

Energy is the ability of a body to do work. The SI unit of energy is Joule (J)

Types of Energy

Energy exists in two major forms, namely potential and kinetic energy.

Potential Energy

Potential energy is the energy in matter due to its position or state. Example of potential energy includes chemical energy, elastic energy, nuclear energy, and gravitational energy.

Kinetic energy

Kinetic energy is the energy possessed by a body due to motion. The motion could be of waves, electrons, atoms or the object itself. The examples of kinetic energy are electric energy, radiant energy, and thermal energy.

Mechanical energy is the sum of kinetic energy and potential energy.

Conservation of energy

The law of conservation of energy states that “energy can neither be created nor destroyed, but it can be transformed from one form to another”.

Transformation of energy

Below are five examples of how energy can be transformed from one form to another.

(a)    Changing of mechanical energy to electrical energy

Hydroelectric power plant converts mechanical energy into electrical energy.

(b)   Changing of electrical energy to heat energy

Appliance that produces heat when connected to a source of electricity includes electric cooker, electric iron, electric heater and electric bulb

(c)    Change of electrical energy into mechanical energy

When an electric current is passed through an electric motor, the rotation motion is produced in the motor. In this way electrical energy is converted to mechanical energy.

(d)   Change of light energy into chemical energy

Green parts of the plant convert light energy into chemical through the process of photosynthesis.

(e)   Change of electrical energy to sound energy.

In an electric bell, electrical energy is converted into sound energy.

Energy value fuel

The energy value fuel is the amount of energy released when one mole of a substance burns in air.

The unit of energy value is J/g or KJ/kg.

A good fuel burns easily to produce large amount of energy.

Environmental effects on using charcoal and firewoods

Burning of charcoal and firewood causes various effects on the environment. The following are some of the environmental impacts based on the use of charcoal and firewood as the main source of energy for domestic activities.

·         Deforestation; the cutting down of trees it may results into disappearance of trees in various places that form up a forest.

·         Drought; due to cutting down of tree may resulted into change in climatically such as absence of rain and rapid evaporation of soil water. This may leads into drought.

·         Floods and erosion

Since the soil is bared, so it is easy for soil to be eroded by moving agents like wind and water. But the presence huge amount of running water on bared land floods tends to occurs.

·         Diseases; under the conditions of drought caused by cutting down of trees, then famine occurs which leads into malnutrition.

·         Global warming; generally plants helps to buffer the atmosphere by removing excess carbon dioxide from the atmosphere. Deforestation leads into accumulation of carbon dioxide above the level required in the atmosphere. Since carbon dioxide is greenhouse gas so it results into global warming

Alternative sources of energy

The sources of energy can be divided into renewable and non-renewable sources.

Renewable sources of energy are those which are self replenished sources of energy. They are continually being replaced within short period of time. They are non-exhaustible, since they are available all the time.

They include solar energy and wind.

Non-renewable sources of energy are sources that cannot be replenished within short period of time. They include fossil fuels such as petroleum, natural gas and coal, and nuclear energy.

Most of the energy being used in the world today comes from non-renewable sources of energy, mainly fossils fuels. The rate of consumption is higher than the rate at which is being replaced hence could get exhausted.

The following are alternative sources of energy that can be used.

Solar energy

Refers to the energy coming from the sunlight; solar energy cannot be exhausted, it is self replenished all over the time. This energy can be trapped in various ways.

·         Generating electricity using photovoltaic solar cells.

·         Generating electricity using concentrated solar power.

·         Heating and cooking using parabolic mirrors that focus the sun’s rays to central position.

·         Heating and cooking using solar chimneys.

Biomass

Biomass is an organic matter in living plant material. It is the solar energy stored in organic matter, such as carbohydrates. When plants die, the process of decay releases energy stored in the carbohydrates.

·         Biomass is a renewable energy source because the growth of new plants and trees replenishes the supply.

·         Biomass can be used directly as a fuel and indirectly to produce liquid biofuel. Example biodiesel and ethanol which is by-product of sugarcane processing can be used in combustion engines and boilers.

·         They contribute to a very little to global warming.

Biogas

Biogas is a fuel gas derived from decomposition of organic wastes. Biogas can be easily produced from both industrial and domestic wastes such as paper, sugar production wastes, sewage and animal wastes. The wastes fermented naturally to produce biogas. The rains wastes after all the gas have been extracted can be used as fertilizers.

Wind energy

Wind is a moving air. The wind energy be harnessed using the windmills, which in turn run turbines and produce energy. It is clean and friendly to the environment.

Water power

Water possesses energy in the form of kinetic energy due to motion or thermal energy resulting from temperature differences. The energy can be harnessed and put into use.

Forms of water energy;

·         Hydroelectric energy, the energy produced in the hydroelectric power plant

·         Tidal stream energy; the energy resulting from the flow of tides.

·         Wave energy, from the movement of waves

·         Ocean thermal energy; the energy resulting from the temperature difference between the warmer surface of the ocean and the cooler deep part of the ocean.