Are you keen to know about Gaseous Fuels?
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Gaseous fuels are considered to be better fuels in comparison to solid and liquid fuels. The main elements of gaseous fuels are carbon and hydrogen. Apart from this, there are traces of oxygen and nitrogen.
Gas fuels have the special property of being cold and clean. Their calorific value at normal temperature and pressure (N.T.P.) varies from 4 MI/m to 63 MJ/m3.
Gas fuels are mainly used in IC Engines, boiler furnaces, domestic and industrial uses etc. They are carried to the place of use through pipelines.
They are also carried from one place to another place, filled in cylinders. The use of gaseous fuels is costlier than the other fuels for the same heat energy.
Components of Gaseous fuels-
Gaseous fuels have two components:
- Combustible Gaseous Fuels: Combustible fuels are composed of gases like Carbon Monoxide (CO), Hydrogen (H). Methane(CH), Ethane (C, H). Propane (C, H), Butane (C, H) etc.
- Non-combustible Gaseous Fuels: Non-combustible gaseous fuel materials are Carbon-dioxide (CO) and Nitrogen (N).
Classification of Gaseous Fuels-
Gaseous fuels can be classified on the basis of their Availability and Calorific Value and they are-
On the basis of Availability-
On the basis of availability, gaseous fuels are of the following two types:
- Natural gaseous fuels
- Artificial gaseous fuels
1. Natural Gaseous Fuel-
Natural gaseous fuels are gaseous fuels which are found in nature freely and used in their original form in which they exist in nature. Such natural gases are propene and butene etc. Which are found with petroleum and coal underneath the earth’s surface.
2. Artificial Gaseous Fuel-
Artificial gaseous fuels are gaseous fuels which are produced in the artificial form in industrial establishments under various processes in their original form or as by-products.
For example- Water-gas, blast furnaces, gas coke-oven gas etc.
On the basis of calorific value-
On the basis of calorific value, the gaseous fuels are of the following two types-
- High calorific value gaseous fuels
- Low calorific value gaseous fuels
1. High calorific value gaseous fuels–
Among the high calorific value gaseous fuels, coke gas, coke oven gas and natural gas are prominent fuel gases which emit high heat during combustion.
2. Low calorific value gaseous fuels–
Among the low calorific value gaseous fuels, blast furnace gas, producer gas etc, are prominent fuel gases which emit comparatively low heat during combustion.
Examples of Gaseous Fuels-
Details of main gaseous fuels or Types of gaseous fuels or gaseous fuels examples are given below:
- Natural Gas
- Liquified Petroleum Gas Fuel
- Coke-oven gas and coal gas
- Water gas or Blue gas
- Blast furnace gas
- Producer gas
- Acetylene gas
- Sewer gas
- Oil gas
Let’s deal with types or examples of these gaseous fuels one by one-
1. Natural Gas-
Natural gas is obtained in its natural form beneath the earth’s surface at a high pressure of 30 to 200 atmospheric pressure where it is available in abundance.
Natural gas is taken out by digging deep wells (about 3 to 4 km) by means of pipelines. It is then treated to reduce moisture in it and sent to the place of use through pipes.
Natural gas is also obtained during the extraction of petroleum from beneath the earth. The gas thus obtained is purified and filled in cylinders for use.
Natural gas is also obtained from coal mines but it is not used in commercial form.
Natural gas is colourless and odourless. Normally it is free from sulphur, clean and pure. It is non-toxic too. It is lighter than air and its specific gravity is 0.57 to 0.7. Its thermal value is 26 to 35 MJ/m.
Natural gas which is obtained along with petroleum is also known as oil gas. Natural gas having heavy hydrocarbon splits up at high temperature and produce soot.
To avoid the production of soot, a large amount of blast furnace gas is mixed with natural gas so that free carbon produced by heating at natural gas reacts with the carbon dioxide of blast furnace gas and soot will not form.
2. Liquified Petroleum Gas Fuel-
It is a liquified mixture of hydro-carbon stored under pressure. The composition of this gas consists of ethylene, propane, propylene, butane, Isobutane and butylene.
From the commercial point of view, it is classified as propane, propane-butane mixture and butane. Its transportation, storage and uses are very simple.
It is colourless, odourless and non-toxic in nature. It is obtained by refining the gas available with petroleum. These gases are used for domestic purposes, industrial purposes and commercially for making artificial gas.
It is also being used in I.C. Engines. Its storage is done in tankers or cylinders (over the earth or below the earth).
3. Coke-oven gas and coal gas-
When coke coal is heated in a coke oven, coke is obtained as the basic product and coke-oven gas is obtained as a by-product. When coal is heated in horizontal or vertical retorts, coal gas is produced as a basic product. Coal gas is also called illuminating gas.
Both these gases are similar. They are obtained by fractional distillation of bituminous coal at a high temperature (about 990°C). These gases are mostly used in steel furnaces, power production and heating purpose in industries.
The main elements of these gases are methane and hydrogen. Their percentage depends upon the type of coal, method of coke making, temperature and time, the quantity of oil used on coal, air infiltrations and some other reasons.
So before using any gas its sample should be tested to know its composition. In India mostly, coke-oven gas is used. About 290 m³ of coke oven gas can be produced per 1000 kg of coal.
Its specific density is 0.45 to 0.49 kg/m and its calorific value is 14 to 22 MJ/m. Coal gas has a higher calorific value than coke-oven gas.
4. Water gas or Blue gas-
This gas is produced by passing steam over a contest fuel having a high percentage of carbon. Basically, it is a mixture of 40% CO, 40% of H2 and remaining CO2, and N2.
Its calorific value is 10 to 11.3 MJ/ m3. This gas has a low calorific value, so it is not useful from an industrial point of view. To improve its calorific value, it is mixed with oil gas.
The mixture of water gas and oil gas is called carburated water gas. It contains about 35% CO, and 35% H2. 20% CH4(Methane), C2H4(Athelyno) etc. and 10% CO2, and N2.
Then its calorific value increases up to 19 MJ/m³. These gases are used in the manufacture of chemical products like ammonia methanol and in forge welding. It is a good gas fuel for domestic purposes.
5. Blast furnace gas-
It is a byproduct of a blast furnace. It has dust and toxic materials mixed with it which must be removed before using the gas.
The composition of this gas contains about 28% carbon monoxide (CO), 11% carbon dioxide (CO2), 58% nitrogen (N2), 2.9% Hydrogen (H2) and 0.2% Methane (CH4).
This gas contains non-combustible gases like CO2 and N2 in excess. So its calorific value is low (about 2.5 to 3.5 MJ/m³).
It is used within the plant itself for various purposes like heating air for the blast furnace, heating coke ovens, heating boiler tubes, and gas engine power plants. It is also used in an industrial furnace.
6. Producer gas-
It is produced by the partial oxidation of coal, coke or peat when they are burnt with an insufficient quantity of air. The process is carried out in specially designed retorts.
It has a low heating value and in general, is suitable for large installations. This gas is mostly used in ceramic kilns, glass-making furnaces, coke furnaces etc. It is also used in steel plants and stationary I.C. engines.
7. Acetylene gas-
This gas is obtained by the action of calcium carbide with water. It is a hydrocarbon. 0It can also be prepared by carbon electric arc.
In this method, acetylene is produced in an atmosphere of hydrogen by igniting an electric area between carbon electrodes. In low-pressure generators, it is produced at up to 10 kPa pressure and in medium-pressure generators, it is produced at up to 150 kPa pressure.
Acetylene gas generators have a production capacity of 0.8 to 8 m³/hour.
This gas is colourless and has a pleasing smell. When burnt in the air it gives a sharp flame at 300°C. This gas prepares an explosive mixture with air and produces numerous amounts of heat.
This gas can be prepared at the place of use or it may be produced at a production place at high pressure of about 1500 kPa and then filled in cylinders.
It is then carried to the place of use in cylinders. This gas is not stable at high pressure so it is dissolved in acetone and kept in cylinders.
This gas is mostly used in oxy-acetylene welding and cutting processes. During welding, its flame burns at about 3100°C, which is not possible to obtain by any other gas.
When liquifying at 0°C temperature and 48 atmospheric pressure liquid acetylene produces which is an explosive. This gas is also used for lumination.
It is also used in other Industrial jobs like the production of vegetable oil, benzene, acetic acid, oxalic acid etc. It is also used in the manufacturing of highly poisonous “Hydro cynic acid”.
8. Sewer Gas-
It is obtained from sewage disposal waste in which fermentation and decay occur. It consists mainly marsh gas and is collected at large disposal plants.
It works as a fuel for gas engines which in turn drive the plant pumps and agitators.
It is produced by animal dung stored in biogas plants by mixing with water in a ratio of 4: 5. Due to the fermentation process the gas is formed.
It contains 55% methane and 45% carbon dioxide and Its calorific value is 19 MJ/m.
10. Oil gas-
This gas is produced by cracking of kerosene oil in hot iron retorts. It can also be produced by the gasification of oils. It is obtained by flowing steam-oil mixture over the hot coal.
The calorific value of this gas depends upon the calorific value of cracked oil. This gas is mostly used in laboratories as fuel.
Now, Let’s discuss gaseous fuels advantages and disadvantages one by one-
Advantages of Gaseous Fuel-
The advantages or benefits of gaseous fuels over solid and liquid fuels are given below:
- Transportation and storage of gaseous fuels are easy to be carried out. Within the plant, these can be carried from one place to other through pipelines. Outside the plant, they are carried in large tankers or cylinders.
- High heat energy is obtained. Their quantity and temperature are easy to control.
- The combustion process of gaseous fuels can be carried out with a minimum of pieces of equipment. It can be made fully automatic.
- During the combustion process and after, deposition of ash, soot, smoke, dust etc does not take place. Thus atmospheric pollution is prevented.
- The types of equipment used for combustion remain neat and clean. Dust, soot etc are not deposited, so maintenance cost remains low.
- Gaseous fuels need not be heated before use.
- For the combustion of gaseous fuels, excess air is not required.
- They are completely free from solid and liquid impurities.
- They can be used directly in I.C. Engines.
- The flue gases emitted from the furnaces can be utilised to pre-heat air for obtaining higher temperatures.
Disadvantages of Gaseous Fuel-
Here are some of the limitations of gaseous fuel-
- They are highly inflammable and prone to explosion.
- High storage capacity is required.
Application of gaseous fuels-
Here are some of the uses of gaseous fuel–
- IC Engines
- Boiler Furnace
- Industrial applications
- Domestic Applications
- Gas engine power plants
- Welding Process
- Must Read: Liquid Fuels: A Detailed Guide All you Need
- Related Article: Types of Solid Fuels: A Detailed Overview Guide
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Abhishek Tiwary is a blogger by passion and a Quality Engineer by profession. He completed his B.Tech degree in the year 2017. Now working in a reputed firm. He loves to share his knowledge with others.