1. Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

2. Introduction
A fuel is defined as any substance used to produce heat or power by combustion. Any chemical process accompanied by the evolution of light and heat is called combustion. It is simply the reaction of substances with oxygen and converts chemical energy into heat and light.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

3. Classifications of Fuels
Based on Physical State
Solid fuel (e.g., wood, coal)
Liquid fuel (e.g., crude petroleum, natural gasoline)
Gaseous fuel (e.g., natural gas)
Based on occurrence
Primary or natural fuels (e.g., wood, crude petroleum oil, coal)
Secondary or prepared fuels (e.g., charcoal, gasoline, water gas).
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

4. Characteristics of a Good Fuel
It should ignite easily. The temperature of the fuel at which ignition starts and continues to burn without further addition of heat is called ignition temperature. It should be moderate for a good fuel. Very low ignition temperature leads to fi re hazard and very high ignition temperature disfavors the starting of fi re.
It should give out a lot of heat, that is, its specific heat should be high.
It should have low smoke and combustible matter such as ash. It should not give out harmful combustion products. This property depends on the nature of elements present in the fuel.
It should be inexpensive and readily available.
It should be easy to store and transport.
It should have low ash content. Ash reduces the calorific value of the fuel, causes hindrance to the flow of air and heat, reduces the specific heat and leads to unwanted disposable problems.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

5. Calorific Value Units Gross and Net Calorific Values
Mean British Thermal Unit (BTU)
Calorie (cal)
Gross and Net Calorific Values
Higher calorific value (HCV) or gross calorific value
Lower calorific value (LCV) or net calorific value
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

6. Experimentally Determination of calorific value
Bomb calorimeter
For calorific values of solid and liquid fuels
Known amount of fuel is burnt at constant volume
Temperature of surrounding water increases as heat is produced.
Quantity of heat and calorific values are calculated.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

7. Solid Fuels – Coal
Formed from dead plants buried for several million years.
Types of Coal
Peat
The lowest carbon content
Lignite
Brown variety containing 25-30% carbon and 60% moisture content.
Sub-bituminous coal
Black variety, 35-45% carbon
Bituminous coal
Hard black variety, 45-86% carbon.
Anthracite coal
The highest ranking coal, carbon content 86-97%.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

8. Pulverized Coal
Pulverized coal generally refers to coal in powdered form obtained by crushing, grinding or pulverizing coal. As the surface area of pulverized coal is large, the volatile matter present in it comes quickly in contact with air and is released, enabling the combustion of fixed carbon. This increases the calorific value of the coal and enhances its quality.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

9. Semi-Solid Fuels – Some Recent Advances
The term semi-solid fuel in modern context refers to non-volatile substances that are environmentally safe and produce no hazardous waste on burning. These have long shelf-life and their ignition can be easily started and stopped. The conventional solid and liquid fuels are now being used as formulations in semi-solid form to circumvent the problems associated with their use in the regular form.
The use of coal is associated with many environmental problems, starting from its excavation from mines to gaseous and fly ash emissions. To overcome these problems, developing countries are transforming coal into gaseous or liquid fuel formulations or converting it into low ash and low sulphur varieties. For example, a solvent-refined, semi-solid form of coal has been prepared by suspending pulverized coal in a solvent and treating it with hydrogen gas at high temperature and pressure. The product compares well with high grade anthracite in combustion properties, is free from ash and has high calorific value of BTU per pound.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

10. Liquid fuels – Petroleum
Petroleum is made from the remains of plants and animals buried millions of years ago.
It is a non-renewable resource.
It contains straight or cycloparaffins.
Olefins
Aromatics
Other organic compounds containing N, O, S.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

11. Composition
Petroleum is a dark, greenish brown, viscous liquid that is found underground. It comprises hydrocarbons such as:
Straight paraffins such as methane, ethane, propane, butane, isobutane, pentane, hexane c or cycloparaffins cyclohexane, methyl cyclopentane
Olefins such as ethylene, butene, isobutene and acetylene, butadienes.
Aromatics such as benzene, naphthalene
Some organic compounds containing nitrogen, oxygen and sulphur.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

12. Production from Refining of Crude Oil
The petroleum obtained by mining is viscous and dark colored liquid. Due to the presence of sulphur, it has an unpleasant smell. It also contains impurities of sand, brine or sea water. Hence it is called crude oil.
The important steps involved are:
Fractional distillation to give various fractions.
Conversion of less desirable fractions to valuable products by processes like cracking.
Treatment of fractions to remove undesirable substances.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

13. Fractional Distillation
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

14. Fractions of petroleum
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

15. Cracking
Cracking is decomposition of high molecular weight compounds (with high boiling points) to low molecular weigh compounds (with low boiling points).
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

16. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2
Methods of Cracking
Thermal Cracking
Catalytic Cracking
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

17. Knocking Knocking in Spark Ignition Engines and Octane Number
Petrol is used in spark ignition engines. The rapid compression of the fuel-air mixture heats the engine, and it detonates without the spark being passed. This causes a violent jerk to the piston giving a metallic sound called knocking.
Octane number is the percentage volume of isooctane in the isooctane-heptane
mixture that matches the knocking characteristics of the fuel being tested is called the octane number.
Molecular structure affects the octane number.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

18. Knocking in Compression Ignition Engines and Cetane Number
Diesel is used in compression ignition engines.
Cetane number represents the spontaneous ignition temperature of a particular diesel fuel. It is the percentage of cetane present in a mixture of cetane and alpha-methylnaphthalene which matches the fuel under test in ignition property.
Engineering Chemistry (revised edition)
ISBN:
Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

19. Lubricants and lubrication
Lubricant is a substance which when introduced between two moving parts reduces friction by forming a slippery film between the two surfaces and thus improving efficiency and decreasing wear
So, lubrication is the process of reducing friction and wear between two moving surfaces by applying lubricating substances between the parts.

20. Purpose of lubrication
To keep moving parts apart: by forming thin layer between the surfaces
To reduce friction: lubricant to surface friction is lesser than surface to surface friction
To protect against wear: lubricant prevent wear by keeping moving part apart
To transfer heat: liquid lubricants are effective in heat circulation due to high specific capacity
To prevent corrosion: as surface of metal do not come in contact with air (Oxygen)
To seal gapes: lubricant seal the space between moving parts through capillary force
To carry away contaminants and debris