Fuelso Fuel is a substance containing major ingredient as carbon which

gives large amount of heat when combusted.

o During the process of combustion of a fuel, carbon, hydrogen etc. will combine with oxygen to liberate heat at a rapid rate.

Fuel + O2 Products + heat

o Fuels are divided as

a) Primary fuels (or) Natural fuels

b) Secondary fuels (or) artificial fuels

o Further these are classified as solid, liquid and gaseous fuels.

Fuels

Chemical Fuels

Primary fuelsOr

Natural fuels

Secondary fuelsOr

Artificial fuels

Solid fuelsWood, coal

Liquid fuelsPetroleum

Gaseous fuelsNatural gas

Solid fuelsCoke

Liquid fuelsPetrol, diesel,

kerosene

Gaseous fuelsBio gas,

Water gas,Producer gas

Characteristics of a good fuelA good fuel should have the following characteristics:A good fuel should have the following characteristics:

oo High calorific valueHigh calorific value

oo Moderate ignition temperatureModerate ignition temperature

oo Low moisture contentLow moisture content

oo Low nonLow non--combustible mattercombustible matter

oo Moderate velocity of combustionModerate velocity of combustion

oo Pollution free combustion products Pollution free combustion products

oo Low costLow cost

oo Easy to transportEasy to transport

oo Controllable combustionControllable combustion

oo Should not undergo spontaneous combustionShould not undergo spontaneous combustion

oo Storage should be cheap and easyStorage should be cheap and easy

oo Should burn in air easily without much smokeShould burn in air easily without much smoke

No ash and no smoke are produced

No ash is produced but some flue gases are produced

Ash and smoke are produced during the process of combustion

6

Can be used in IC engines but to a lesser extent

Can be used in IC engines

Cannot be used in IC engines

5

Calorific value is higher that liquid fuels

Calorific value is relatively high

Calorific value is relatively low

4

High risk involved in storage

Risk involved in storageStorage is safe3

Transportation is easy through pipelines and containers

Transportation is easy through pipelines and containers

Transportation is difficult

2

Combustion is rapid and burning can be controlled

Quick combustion and it can be controlled

Slow combustion and not easy to control it

1

Gaseous fuelsLiquid fuelsSolid fuels

Calorific value of a fuelCalorific value of a fuelHigher or Gross Calorific Value (HCV or GCV):Higher or Gross Calorific Value (HCV or GCV):

“ The amount of heat liberated when one unit weight or volume of a fuel is completely burnt and the products of combustion are cooled to room temperature”

Net or Lower Calorific Value (LCV or NCV):Net or Lower Calorific Value (LCV or NCV):

““ The amount of heat liberated when one unit weight or The amount of heat liberated when one unit weight or volume of a fuel is completely burnt and the products volume of a fuel is completely burnt and the products of combustion are allowed to escape into the of combustion are allowed to escape into the atmosphereatmosphere””

o Units of heat are Calories, k.calories and B.Th.U (British thermal unit) or C.H.U (Centrigrade heat unit)

1 B.Th.U = 252 cal = 0.252 k.Cal

1 k.Cal = 3.968 B.Th.U = 2.2 C.H.U

Determination of Calorific ValueDetermination of Calorific Value

Bomb calorimeterBomb calorimeter

CalculationCalculation

m = mass of fuel pellet (g)m = mass of fuel pellet (g)W = mass of water in the calorimeter (g)W = mass of water in the calorimeter (g)w = water equivalent of calorimeter (g)w = water equivalent of calorimeter (g)tt11 = initial temperature of calorimeter.= initial temperature of calorimeter.tt22 = final temperature of calorimeter.= final temperature of calorimeter.HCV = gross calorific value of fuel.HCV = gross calorific value of fuel.

CorrectionsCorrections►► Fuse wire correctionFuse wire correction. Heat liberated during sparking should be . Heat liberated during sparking should be

subtracted from heat liberated.subtracted from heat liberated.

►► Acid correctionAcid correction. Fuels containing Sulphur and Nitrogen if oxidized, . Fuels containing Sulphur and Nitrogen if oxidized, the heats of formation of Hthe heats of formation of H22SOSO44 and HNOand HNO33 should be subtracted (as should be subtracted (as the acid formations are exothermic reactions).the acid formations are exothermic reactions).

►► Cooling correctionCooling correction. The rate of cooling of the calorimeter from. The rate of cooling of the calorimeter frommaximum temperature to room temperature is noted. From this ratemaximum temperature to room temperature is noted. From this rate of of cooling (i.e., cooling (i.e., dtdt°°/min) and the actual time taken for cooling (t min) then/min) and the actual time taken for cooling (t min) thencorrection (correction (dtdt ×× t) is called cooling correction and is added to the (t2 . t) is called cooling correction and is added to the (t2 . t1) term.t1) term.

CorrectionsCorrections

DulongDulong’’s Formulas FormulaThe approximate calorific value of a fuel can be determined by knowing the amount of constituents present:

Gross or higher calorific value (HCV) from elemental constituents of a fuel.

H = 34500 kcal/kg; C = 8080 kcal/kg; S = 2240 kcal/kg

Oxygen present in the fuel is assumed to be present as water (fixed hydrogen). Available Hydrogen = Total hydrogen - Fixed hydrogen

= Total hydrogen - 1/8 mass of oxygen in fuel.

Dulongs formula for calorific value from the chemical composition of fuel is,

KnockingKnocking

►► Knocking characteristics of a fuel depends on the chemical Knocking characteristics of a fuel depends on the chemical structurestructure

►► Maximum power Maximum power –– Gasoline when burnt uniformly, silently in Gasoline when burnt uniformly, silently in an ICEan ICE

►► Presence of certain constituents in gasoline, rate of oxidation Presence of certain constituents in gasoline, rate of oxidation becomes so great that the unburnt fuel may rapidly react with becomes so great that the unburnt fuel may rapidly react with the formation of explosive violence. This is called the formation of explosive violence. This is called KnockingKnocking

►► Knocking results in loss of efficiency of the engine Knocking results in loss of efficiency of the engine ►► Knocking tendency:Knocking tendency:►► Straight chain paraffins > Branched chain paraffins > Straight chain paraffins > Branched chain paraffins >

Cycloparaffins > Olefins > AromaticsCycloparaffins > Olefins > Aromatics

►► Knocking characteristics of a combustion engine fuel Knocking characteristics of a combustion engine fuel –– octane octane numbernumber

Octane numberOctane number

►► Antiknock quality of a fuel is expressed as its octane numberAntiknock quality of a fuel is expressed as its octane number

►► Percentage of Percentage of isoiso--octane (2,2,4octane (2,2,4--trimethyl pentane). in ntrimethyl pentane). in n--heptaneheptane--isoiso--octane octane blend blend –– octane numberoctane number

►► Isooctane Isooctane –– best antiknocking properties and assigned O.N of 100best antiknocking properties and assigned O.N of 100

►► nn--heptane heptane –– poor antiknocking property and assigned O.N. of 0poor antiknocking property and assigned O.N. of 0

►► Most effective antiknock agent is tetraethyl lead (TEL) along wiMost effective antiknock agent is tetraethyl lead (TEL) along with ethylene th ethylene dibromide which prevents deposition of lead by forming volatile dibromide which prevents deposition of lead by forming volatile lead lead halideshalides

►► Others are tetramethyl lead, tertiary butyl acetate, diethyl telOthers are tetramethyl lead, tertiary butyl acetate, diethyl tellurideluride

►► Greater the octane number, greater is the resistance of Greater the octane number, greater is the resistance of knockingknocking

Diesel knockDiesel knock

►► Long ignition delays lead to accumulation of more Long ignition delays lead to accumulation of more vapoursvapours in in the engine and when ignited an explosion results as the the engine and when ignited an explosion results as the combined effect of temperature and pressure. This is combined effect of temperature and pressure. This is responsible for diesel knock. responsible for diesel knock.

►► Diesel Index: Specific gravity (API) X Aniline point (Diesel Index: Specific gravity (API) X Aniline point (ooF)/100F)/100►► API API –– American Petroleum InstitutionAmerican Petroleum Institution

Cetane numberCetane number

►► Long ignition delays lead to accumulation of more vapours in Long ignition delays lead to accumulation of more vapours in the engine and when ignited an explosion results as the the engine and when ignited an explosion results as the combined effect of temperature and pressure. This is combined effect of temperature and pressure. This is responsible for diesel knock. responsible for diesel knock.

►► There is a delay period between injection of diesel fuel There is a delay period between injection of diesel fuel

Cetane numberCetane number

►► There is a delay period between the injection of diesel fuel andThere is a delay period between the injection of diesel fuel and its ignition. its ignition. If this delay period is large, too much fuel accumulates in the If this delay period is large, too much fuel accumulates in the cylinder and cylinder and burn very rapidly and causes diesel knock. burn very rapidly and causes diesel knock.

►► Increasing delay period occurs in the series : nIncreasing delay period occurs in the series : n--paraffin < Olefins < paraffin < Olefins < naphthenes < isoparaffins < aromatics.naphthenes < isoparaffins < aromatics.

►► Order is the reverse for gasoline antiknock quality.Order is the reverse for gasoline antiknock quality.►► nn--hexadecane ; Cetane number 100hexadecane ; Cetane number 100►► αα –– methyl naphthalene ; cetane number 0methyl naphthalene ; cetane number 0

►► A given fuel matches in quality with the blend having 40/60 bleA given fuel matches in quality with the blend having 40/60 blend of nd of cetane and methyl naphthalene, it is assigned a cetane number 40cetane and methyl naphthalene, it is assigned a cetane number 40

►► Cetane number of diesel can be improved by adding amyl/butyl nitCetane number of diesel can be improved by adding amyl/butyl nitrite, rite, carbamates, ditertiary butyl peroxide and metal organic compoundcarbamates, ditertiary butyl peroxide and metal organic compounds.s.

Gaseous FuelsGaseous Fuels

►► Natural gas:Natural gas:

►► Found in oil wells.Found in oil wells.►► Can be liquified by compression and coolingCan be liquified by compression and cooling►► Methane : 70Methane : 70--90%; Ethane :590%; Ethane :5--10% and other gases like CO10% and other gases like CO2 2 -- NN2 2

etc are found in tracesetc are found in traces►► Calorific value : 12,000Calorific value : 12,000--14,000Kcal/m14,000Kcal/m33

►► Dry gas Dry gas –– Natural gas + crude oilNatural gas + crude oil►► Wet gas Wet gas –– Natural gas + petroleumNatural gas + petroleum

ApplicationsApplications►► Domestic fuelDomestic fuel

►► Raw material for the manufacture of carbon black (filler for Raw material for the manufacture of carbon black (filler for rubber) and hydrogen (used in ammonia synthesis)rubber) and hydrogen (used in ammonia synthesis)

►► Microbiological fermentation of methane yields synthetic Microbiological fermentation of methane yields synthetic protein used as animal feed.protein used as animal feed.

Compressed Natural Gas (CNG)Compressed Natural Gas (CNG)

►► Natural gas compressed to high pressure of 1000 atm. Natural gas compressed to high pressure of 1000 atm. –– substitute for petrol substitute for petrol and dieseland diesel

►► Less polluting as during combustion as it doesnLess polluting as during combustion as it doesn’’t evolve nitrogen, carbon t evolve nitrogen, carbon and sulphurand sulphur

►► Initial cost of engine designing Initial cost of engine designing -- highhigh

Advantages over LPG:Advantages over LPG:Ignites at higher temperatureIgnites at higher temperatureCheaper Cheaper Lesser CO emission than gasolineLesser CO emission than gasolineMixes well with air than liquid fuelsMixes well with air than liquid fuelsNo emission of smoke, SONo emission of smoke, SO2, 2, SOSO3, 3, etc.,etc.,

LPGLPG►► Obtained as a byproduct during cracking process or from Obtained as a byproduct during cracking process or from

natural gasnatural gas►► Consists of hydrocarbons of such volatility that they can exist Consists of hydrocarbons of such volatility that they can exist

as gas at atmospheric pressure but can be liquified under as gas at atmospheric pressure but can be liquified under pressure.pressure.

►► Dehydrated, desulphurised and traces of organic sulphides Dehydrated, desulphurised and traces of organic sulphides mercaptans are added mercaptans are added –– warning of leak and compressed under warning of leak and compressed under pressurepressure

►► Calorific value 27,800Kcal/mCalorific value 27,800Kcal/m33

►► Constituents are nConstituents are n--butane, isobutane, iso--butane, butylene and butane, butylene and propane with trace amounts of propylene and ethane propane with trace amounts of propylene and ethane

►► Domestic, industrial and automobile fuel.Domestic, industrial and automobile fuel.

Advantages/DisadvantagesAdvantages/Disadvantages

►► Advantages:Advantages:►► Cheaper than gasolineCheaper than gasoline►► High efficiency and heating rateHigh efficiency and heating rate►► Complete combustion with no smokeComplete combustion with no smoke►► Can easily mix with airCan easily mix with air►► High knockHigh knock--resistantresistant

►► DisadvantagesDisadvantages►► Difficult to handle as fuelDifficult to handle as fuel►► Limited to only to certain classes of vehiclesLimited to only to certain classes of vehicles►► Poor blending characteristicsPoor blending characteristics

BioBio--gasgas

Raw materials : Animal dung, poultry wastes, vegetable wastes,waste paper and cotton clothes, plant wastes, human excreta, bird’s excreta etc.,

Forms of biogasForms of biogas

►► Natural gas Natural gas –– biogas obtained long period decay of animal and vegetable biogas obtained long period decay of animal and vegetable matters inside the earthmatters inside the earth

►► Gobar gas Gobar gas –– anaerobic fermentation of cattle dunganaerobic fermentation of cattle dung►► Can also be produced by sewage wastes and organic wastesCan also be produced by sewage wastes and organic wastes

►► Constituents of biogasConstituents of biogas::Methane = 50Methane = 50--60% 60% -- makes it an excellent fuelmakes it an excellent fuelCOCO2 2 = 30= 30--40%40%HH22S = tracesS = tracesHH22 = 5= 5--10%10%NN22 = 2= 2--6%6%

Calorific value : 1200Kcal/mCalorific value : 1200Kcal/m33

Gobar gasGobar gas►► Dung + water slurry Dung + water slurry –– fed in to digester tank fed in to digester tank –– undergoes undergoes

fermentation fermentation –– anaerobic bacteria anaerobic bacteria –– evolution of bio gas evolution of bio gas –– fresh fresh feed to let inside the well feed to let inside the well (Refer book for figure)(Refer book for figure)Uses / Advantages:Uses / Advantages:

►► As a domestic fuel, run engines, illuminant in villagesAs a domestic fuel, run engines, illuminant in villages►► Burns without smoke and harmful gasesBurns without smoke and harmful gases►► Waste from biogas plant Waste from biogas plant –– manuremanure►► EconomicalEconomical

Limitation:Limitation:►► Need to have gas lamp or burner within 10metres of the plant.Need to have gas lamp or burner within 10metres of the plant.

BiodieselBiodiesel

►►Diesel equivalent biofuel from renewable Diesel equivalent biofuel from renewable biological materials such as vegetable oils or biological materials such as vegetable oils or animal fats animal fats –– usually a transesterified oilusually a transesterified oil

►►Used alone or can be blended with petrodieselUsed alone or can be blended with petrodiesel

►►B factor to state the amount of biodiesel in any B factor to state the amount of biodiesel in any fuel mix. Pure biodiesel B100; Fuel containing fuel mix. Pure biodiesel B100; Fuel containing 30% biodiesel is labelled B3030% biodiesel is labelled B30

►►Also derived from triglycerides of plant Also derived from triglycerides of plant (BOTADIESEL) or animals (ZOODIESEL)(BOTADIESEL) or animals (ZOODIESEL)

Biodiesel from plant and animal sourcesBiodiesel from plant and animal sources

►► Plant oils are from sunflower, soyabeans, jatropha, corn, canolaPlant oils are from sunflower, soyabeans, jatropha, corn, canola, , safflower and rapeseed oilsafflower and rapeseed oil

►► From animal source, it is less prevalent From animal source, it is less prevalent –– though the process is though the process is comparatively cheaper than extraction from plant sourcecomparatively cheaper than extraction from plant source

►► PROCESSPROCESSMade by transesterification where organically derived oils Made by transesterification where organically derived oils (vegetable oils, animal fats) are combined with alcohol (vegetable oils, animal fats) are combined with alcohol (methanol) and chemically altered to form fatty esters such as (methanol) and chemically altered to form fatty esters such as methyl ester. The process results in two products methyl ester. The process results in two products -- methylesters methylesters –– chemical name for biodieselchemical name for biodiesel-- Glycerine Glycerine –– valuable byvaluable by--product sold for use in production of product sold for use in production of

soapsoap

Bomb calorimeter

Bomb calorimeter