Chapter 18 - Fuels (Courtesy of Biscuit Notes)

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@biscuitnotes on carousell Chapter18-FuelsandCrudeOil Sourcesoffuel:- Fossil fuelsintheformofcrudeoil,natural gasandcoal (carbon)- Biofuels Fossil fuelsareburnedinoxygentoformCO2 andH2 O.Thisexothermicreactioniscombustionandthethermal energygeneratedfromthecombustionoffossil fuelscanbeconvertedtootherformsofenergy Combustion:Fuel burnsinthepresenceofexcess/sufficientoxygentoproduceCO2 andH2 OIncompletecombustion:FuelsburninthepresenceofinsufficientoxygentoproduceCOand/orC(s)andH2 O CharacteristicsofNatural gas1. Itiscolourless2. Itisamixtureoflighthydrocarbons,mainlyconsistingofmethane3. Itcanbeeasilyliquefied(duetolowboilingpoint)andstoredintanks.Itcanflow4. Itproducesalmostnopollutant5. Combustion: - CompletecombustionCH4 burnsinexcessoxygentoformCO2 andH2 Otoproduceenergy𝐶𝐻4 (𝑔) + 2𝑂2 (𝑔)→𝐶𝑂2 (𝑔) + 2𝐻2 𝑂(𝑙) - IncompletecombustionCH4 burnsininsufficientoxygentoformCOand/orC(s)andH2 Otoproduceenergy𝐶𝐻4 (𝑔) +𝑂2 (𝑔)→𝐶𝑂(𝑔) + 𝐶(𝑠) +𝐻2 𝑂(𝑙) - Comparingcompleteandincompletecombustion,for1moleofCH4 ,2molesofO2 isrequiredforcompletecombustionwhereasonly1moleofO2 isrequiredforincompletecombustion.Hence,whenthereisinsufficientoxygensupply,completecombustionismorelikelytooccuraslessmoleofO2 isrequiredforthesamemoleofCH4 - However,formethane,mostofthetimes,completecombustionoccurs99%ofthetime,asinmostcases,therewill besufficientoxygensuppliedforcompletecombustiontotheitslowpercentagemassofcarbon(ithasonly1carbonatomineachmolecule)- Lowpercentagemassofcarbon: -[1]𝐶𝐻4 (𝑔) + 2𝑂2 (𝑔)→𝐶𝑂2 (𝑔) + 2𝐻2 𝑂(𝑙)- Higherpercentageofcarbon: -[2]𝐶3 𝐻8 (𝑔) + 5𝑂2 (𝑔)→3𝐶𝑂2 (𝑔) + 4𝐻2 𝑂(𝑙) Whichequation[1]or[2]will giveoutsootierproducts/havemoreincompletecombustion? 71

@biscuitnotes on carousell - ForthesamemoleofCH4 andC3 H8 ,C3 H8 requiresmoreoxygenthanCH4 forcompletecombustion.Hence,thismeansthatC3 H8 will undergomoreincompletecombustionascomparedto ,henceproducingmoresoot.𝐶𝐻4 - Ruleofthumb:Forthesamemoleoffuel,thefuel thatrequiresthegreaternumberofmolesofoxygenforcompletecombustionwill undergomoreincompletecombustionandhencemoresoot/COwill beproduced Characteristicsofcrudeoil1. Itisadarkbrownliquid2. Itisamixtureofhydrocarbons(compoundswithhydrogenandcarbononly)3. Itcanbestoredandtransportedeasilybytankers.Itcanflowthroughapipeeasily.4. Itismoderatelypollutingassomesootisproducedduetoincompletecombustion(duetoslightlyhigherpercentagemassofcarboncomparedtonatural gas)5. Italsoundergoescombustionintheformsofcompleteandincompletecombustion. Characteristicsofcoal:1. Itisablacksolid2. Itismainlyjustcarbon3. Itisnoteasilystoredandtransported.4. Itisextremelypollutingaslargeamountofsootisproducedduetoincompletecombustion(dueto100%percentagemassofcarbo)5. Itundergoescombustionintheformsofcompleteandincompletecombustion. Completecombustion:- Coal burnsinexcessoxygentoformCO2 toproduce- 𝐶(𝑠) +𝑂2 (𝑔)→𝐶𝑂2 (𝑔) Incompletecombustion:- Coal burnsininsufficientoxygentoformCOtoproduceenergy- 2𝐶(𝑠) +𝑂2 (𝑔)→2𝐶𝑂(𝑔) 72

@biscuitnotes on carousell Separationofcrudeo