Dr. SURENDRAN PARAMBADATH (M.Sc, M.Phil, M.Tech) Formerly: Post Doctoral Research Associate,Nano-Information Materials Research Laboratory, Pusan National University, Busan-South Korea Currently: Assistant Professor Govt. Polytechnic College, Perinthalmanna
Any substance which on proper burning in air gives amountof heat, that can be used economically for domestic andindustrial purposes.Classification of fuels:A. Based upon their occurrence or preparation (i) Natural or primary fuels-which occur in nature ie available in nature and can be used directly.Eg: Wood, charcoal, Peat, Lignite, bituminous coal, anthracite coal, petroleum and natural gas. (ii) Artificial or secondary fuels which are manufactured artificially, generally from primary fuels.Eg: Coke, kerosene oil, Petrol, Diesel oil, Coal gas, water gas,etc…B. Based upon their physical state, there are (i) Solid fuels (ii) Liquid fuels and (III) Gaseous fuels.
Classification of fuelsType of Fuel Primary (Natural) Secondary (Artificial)1) Solid Wood, Wood, Charcoal, Coke, charcoal, Peat, Charred Lignite, bituminous peat, Coal coal etc. briquette.2) Liquid Crude Petroleum Various fractions of petroleum.3) Gaseous Natural gas Coal gas, Oil gas, Water gas, Producer gas, Gobar gas etc.
The calorific value of a fuel is defined as thequantity of heat liberated by the completecombustion of a unit mass of the fuel in air oroxygen with the subsequent cooling of the productsof combustion to the initial temperature of the fuel.The presence of moisture in the fuel will reduce itscalorific value.
Characteristics of a good fuel1 High calorific value which determines the amount of heat produced and temperature attained.2 Moderate ignition temperature.3 Moderate velocity of combustion for continuous supply of heat.4 Low moisture content. Velocity of combustion in presence of moisture leads to low temperature.5 Low non-combustible matter content, as their presence lead to formation of ash, decreases in calorific value of fuel, additional cost of storage handling of disposal of waste products etc.
Liquid FuelsThe main source of liquid fuel is petroleum, whichon distillation gives important liquid fuels petrol,diesel and kerosene oil.Petra = rock, oleum = oil.
Treatment of PetroleumRemove dirt, water sulphur etc.Fractional distillation Heating up to 400oC in an ironretort, whereby all volatileconstituents except the residue areevaporated, and fractionallyseparated during condensation.
3. Diesel oilIt is a mixture of hydrocarbons with boilingrange (250-320oC).
KnockingThe metallic sound produced during irregularburning of the fuel is termed as knocking.Straight chain alkane> branched chain alkane>Olefines> Cycloalkane> Aromatic hydrocarbons
Octane NumberThe octane number of a fuel is ameasure of its tendency to knock;when burnt in a spark-ignition engine. n-hptane ----------Maximum knocking Octane number 0 Iso-octane -----------Minimum knocking Octane number 100 Tetraethy lead or Diethyl telluride: Anti knocking agents.
Cetane NumberIt a measure of the ignition quality ie theantikonocking character of a diesel oil.
CrackingIt is the process of breaking up of lessvolatile bigger molecule of hydrocarbonsfrom petroleum into more volatile lowermolecules of hydrocarbons.
1. Thermal crackingFuel oil and lubricant oil are subjected to hightemperature pyrolysis at about 770K and highpressure, when random cleavage of carbon-carbon bonds takes place and lower alkanesresult. A-A-A-A-A-A-A- A-A-A A-A-A + A-A-A-A + A-A-A-A-A-A-A
2. Catalytic crackingIn this process heating is done at a lowertemperature in presence of catalysts silicaand alumina mixture to produce gasoline.
1. Natural GasIt is formed by the decomposition of organic matter under theearth and is almost always present in petroleum wells.Composition:CH4 = 71%, C2H6 = 5-10% , H2 = 3%, CO + CO2 = restIt is a cheap convenient fuel and burns with ahot blue flame.
Uses:1.It is an excellent fuel for domestic and industrial purpose.2.Manufacture of a number of chemicals by synthetic process.3.As a raw material for the manufacture of carbon black.4.In preparation of synthetic proteins by microbiological fermentation of methane (CH4)
2. Water GasIt is a mixture of combustible gases CO and H2with small amounts of non-combustible CO2 andN2.Water gas can be made by passing steam and alittle air alternatively through a bed of red hotcoal or coke maintained at a temperature ofabout 900-1000oC in a reactor. C + O2 CO2 2C + O2 2CO
Uses:1.As a fuel gas2.As an illuminating gas3.As a source of hydrogen gas4.In manufacture of ammonia gas.Combination of water gas:CO = 41%, H2 = 51%, CO2 = 4.2%, N2 = 3%, CH4 = 0.8%
3. Producer GasIt is a mixture of CO and N2 and isprepared by blowing controlled amountof air through a deep bed of red hot cokeor coal, maintained at about 1100oC in aspecial reactor.Composition:CO = 30%, N2 = 52%, H2 = 13%, CH4 = 3% and CO2 = 2%
Uses:1.For running gas engines.2.For heating open-hearth furnace muffle furnace, retorts etc.3.As a reducing agent in metallurgical operations.
4. Gobar Gas (Dung Gas)Degradation of biological matter by the bacterialaction in the absence of free oxygen produces,biogas.Combination of water gas:CH4 = 50-60%, H2 = 5-10%, CO2 = 30-40%, N2 = 2%
Uses:1.It is mainly used as domestic cooking gas.2.As an illuminant in villages3.As a fuel to run engines.
5. LPG (Liquefied Petroleum Gas)It is obtained as a by product, during the crackingof heavy oils and from natural gas.The main constituents of LPG are n-butane, iso-butane, propane and butene with little or nopropene and ethane.
Uses:1.Mainly as a domestic fuel for burning gas stove in houses.2.As a fuel in some of the industries.3.As motor fuel.4.In laboratories in gas burners for heating purpose.
Advantages of LPG1.Easy to operate, to control and easy to store.2.Higher efficiency and heating rate.3.No smoke and hence neat, clean and no pollution.4.Easy to transport, undergoes complete combustion.5.Cheaper than gasoline, as a motor fuel.
6. CNG (Compressed Natural Gas)It is highly compressed form of natural gas. Itconsists of methane and may contain smallamounts of ethane and propane.Uses:1. In commercial vehicles such as taxis, truck, buses.Disadvantage:1. Mainly maintaining at high pressure.2. The release of methane gas through pipe line during transport and from vehicles due to its incomplete combustion.
1. Wood2. Charcoal Charcoal is a black porous brittle solid which can burn in air to give CO2 and traces of CO. It is the most active form of carbon and a good adsorbent.3. Peat The progressive transformation of wood to anthracite under the earth, due to excessive pressure, high temperature, absence of oxygen, presence of bacteria and time. Wood Peat Lignite Anthracite Coal Bituminous Coal
4. Lignite It is soft, dark brown colored variety,representing second stage in the conversion ofvegetable matter into coal.C= 67%, H = 6%, O = 35% and Ash = 2.5%Uses: i) Lignites are usually dried, powderedand pressed into small briquettes and burnt ashouse hold fuels and for steam raising boilerfuel,ii) Most important use is in manufacture ofproducer gas.
5. Bituminous CoalIt is the third stage of conversion of vegetablematter into coal.C= 75-88%, H = 5%, O = 2 % and Ash = 10%Uses:1.Widely used as a domestic fuel.’2.In several industries for making metallurgical coke, coal gas and for steam raising.
6. Anthracite CoalIt is a class of highest rank coal, the last one in theformation of coal from vegetable matter. It is thehardest of all kind of coal.It is dense, black and brittle.C= 90%, H = 3%, O = 2 % and Ash = 5%Uses:1. As a fuel for house hold purposes2. For steam raising3. In metallurgical purposes, where high local heat and no smoke are desirable.
Otto Han discovered the fissionof Uranium opened theprospects of using the vastenergy stored in the atomicnucleus for the production ofelectric power.1 Kg of Uranium = 3x106 Kg of high grade coal.
Mass Defect and Nuclear Energy A B + C High Mass Low massDifference is called Mass defect. Thatdifference is the loss of mass during theformation of the nucleus of the isotope or theactual loss of mass equivalent to the energyreleased during the formation of the givennucleus from individual nucleons.
Main Parts of a Typical Nuclear Reactor1. Reactor core: Consists of an assemblage of fuel elements, control rods, coolant and moderator. The fission chain reaction takes place in this part of the reactor and heat energy is liberates.2. Reflector: To reflect back some of the leaking neutrons.3. Pressure Vessel: Which encloses the core and reflector.4. Shielding: To weaken the Y-rays and radiations coming out from the reactor.5. Heat Exchanger: To transfer the heat liberated from the reactor core to boil water and get steam.6. Turbine: To operate utilizing the steam from the heat exchanger, and to drive a generator to produce electricity.7. Moderators: Used are graphite or beryllium or heavy water. Reduce the KE of fast fission neutrons.8. Control roads: Boron, steel or cadmium to absorb some neutrons.9. Coolants: Used ordinary water, heavy water, liquid metal like sodium, organic liquids and gases. They remove heat from the reactor.
Nuclear FusionNuclear fusion is the process of combination of lightweight nuclei to form heavier nucleus, with thesimultaneous release of energy.
Advantageous Over Fission Reaction1.Much greater amount of energy.2.Products of fusion are non radioactive while fission products are unstable and radioactive and hence fission products pose a waste-disposal problem.
Rocket PropellantFuels used in rockets for their propulsion are calledpropellant.1.Solid Propellant2.Liquid Propellant3.Hybrid propellant
Solid PropellantThe first mankind Propellant.Modern Solid Propellants are divided in to two classes.A. Composite propellant Consists of a blend of polyurethane or polybutadiene as fuel and ammonium perchlorate as oxidizer. Along with some finely divided Al or Mg.B. Double base propellant Consists of nitroglycerine and nitrocellulose, both containing the oxidizer and fuel element in the same molecule.
Liquid PropellantA. Monoliquid propellant: Consists of a single of asingle liquid chemical compound, which ondecomposition or ignition gives out a large volume ofhot gases.Eg: Hydrazine, Methyl nitrate, nitro methane andhydrogen peroxide.B. Biliquid propellant: Consists of a combination ofliquid fuels like kerosene, alcohol, liquid H2 orhydrazine and liquid oxidizer like liquid oxygen,dinitrogen tetroxide or nitric acid.
Hybrid PropellantIt consists of a solid fuel and a liquidoxidizer.Eg: A mixture of acrylic rubber andliquid N2O4