Q.1 what is the role of Chemical Engineers in Petroleum refineries?

Ans.1 The imaginative and pioneering efforts of chemical engineers have been responsible for the development of a complex array of chemical conversion processes. These processes are used to create physical changes in crude oil and natural gas, which yield the many end products we rely on today. These products run the gamut from gasoline and diesel fuel, to kerosene, lubricating oils, waxes, and asphalt, as well as many intermediate petrochemical products. Chemical conversion processes

Some of the important chemical process operations instrumental in modern-day refining include

Thermal cracking,

Distillation,

Fluid catalytic cracking,

Hydrocracking, and

Powerforming.

This list is merely representative, as the total number of petroleum-refining operations to which chemical engineers have made significant contributions is very large.The chemical-engineering community is constantly working to modify and improve the petroleum-refining processes. Their objectives are to

Achieve higher conversion rates and greater yields,

Improve overall energy efficiency,

Produce cleaner fuels,

2 Reduce refinery emissions, and

Reduce operating costs.

Q.2 what is Octane number and Cetane number?

Ans.2 Octane rating or octane number is a standard measure of the anti-knock properties (i.e. the performance) of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating. In broad terms, fuels with a higher octane rating are used in high-compression engines that generally have higher performance.Cetane number or CN is actually a measure of a fuel's ignition delay; the time period between the start of injection and the first identifiable pressure increase during combustion of the fuel. In a particular diesel engine, higher cetane fuels will have shorter ignition delay periods than lower cetane fuels. Cetane numbers are only used for the relatively light distillate diesel oils. The higher the Cetane number the more easily the fuel will combust in a compression setting (such as a diesel engine). The characteristic diesel "knock" occurs when fuel that has been injected into the cylinder ignites after a delay causing a late shock wave. Minimizing this delay results in less unburned fuel in the cylinder and less intense knock. Therefore higher-cetane fuel usually causes an engine to run more smoothly and quietly. This does not necessarily translate into greater efficiency, although it may in certain engines.

Q.3 write short note on Petrol, Diesel, Aviation fuels and Propellants.

Ans.3 Petrol: - Petrolalso known asGasoline, is a transparent,petroleum-derived liquid that is used primarily as a fuel ininternal combustion engines. It consists mostly oforganic compoundsobtained by thefractional distillationof petroleum, enhanced with a variety of additives; a 42-gallon barrel of crude oil yields about 19 gallons of gasoline, when processed in arefinery. The characteristic of a particular gasoline blend to resist igniting too early (which causes knocking and reduces efficiency in reciprocating engines) is measured by itsoctane rating. Gasoline is produced in several grades of octane rating.Tetraethylleadand other lead compounds are no longer used in most areas to regulate and increase octane-rating, but many other additives are put into gasoline to improve its chemical stability, control corrosiveness and provide fuel system 'cleaning,' and determine performance characteristics under intended use. Sometimes, gasoline also containsethanolas analternative fuel, for economic or environmental reasons.

Diesel: - Diesel in general is any liquidfuelused indiesel engines, whose fuel ignition takes place, without spark, as a result of compression of the inlet air mixture and then injection of fuel. (Glow plugshelp achieve high temperatures for combustion during engine start up in cold weather.) Diesel engines have found broad use as a result of higher thermodynamic and thus fuel efficiencies. This is particularly noted where diesel engines are run at part-load; as their air supply is not throttled as in apetrol engine, their efficiency still remains high. The most common type of diesel fuel is a specificfractional distillateof petroleumfuel oil, but alternatives that are not derived from petroleum, such asbiodiesel,biomass to liquid(BTL) orgas to liquid(GTL) diesel, are increasingly being developed and adopted. To distinguish these types, petroleum-derived diesel is increasingly calledpetro diesel. Ultra-low-sulfur diesel(ULSD) is a standard for defining diesel fuel with substantially loweredsulfurcontents. Most diesel fuels freeze at common winter temperatures, while the temperatures greatly vary. Petro diesel typically freezes around temperatures of 8.1C (17.5F), whereas biodiesel freezes between temperatures of 2 to 15C (35 to 60F). The viscosity of diesel noticeably increases as the temperature decreases, changing it into a gel at temperatures of 19C (2.2F) to 15C (5F), that cannot flow in fuel systems. Conventional diesel fuels vaporise at temperatures between 149C and 371C. Conventional dieselflash pointsvary between 52 and 96C, which makes it safer than petrol and unsuitable for spark-ignition engines. Unlike petrol, the flash point of a diesel fuel has no relation to its performance in an engine nor to its auto ignition qualities.

Aviation fuels: - Aviation fuelis a specialized type ofpetroleum-basedfuelused to poweraircraft. It is generally of a higher quality than fuels used in less critical applications, such asheatingorroad transport, and often contains additives to reduce the risk of icing or explosion due to high temperature, among other properties. Most aviation fuels available for aircraft are kinds ofpetroleum spiritused in engines with spark plugs (i.e.pistonandrotary engines), or fuel for jet turbine engines, which is also used in diesel aircraft engines. Aviation fuels consist of blends of over a thousand chemicals, primarilyhydrocarbons(paraffins,olefins,naphthenes, andaromatics), additives such asantioxidantsand metal deactivators, and impurities. Principal components includen-heptaneandisooctane. Like other fuels, aviation fuel for spark-ignited piston engines are described by theiroctane rating. Alcohol, alcohol mixtures, and other alternative fuels may be used experimentally, but alcohol is not permitted in any certified aviation fuel specification.

Propellants: - Apropellantis a chemical used in the production of energy or pressurized gas that is subsequently used to create movement of a fluid or to generatepropulsionof avehicle, projectile, or other object. Common propellants areenergetic materialsand consist of afuellikegasoline,jet fuel,rocket fuel, and anoxidizer. Propellants are burned or otherwise decomposed to produce the propellant gas. Other propellants are simply liquids that can readily be vaporized. In rockets and aircraft, propellants are used to produce a gas that can be directed through a nozzle, thereby producing thrust. In rockets,rocket propellantproduces an exhaust, and the exhausted material is usually expelled under pressure through anozzle. The pressure may be from a compressed gas, or a gas produced by a chemical reaction. The exhaust material may be agas,liquid,plasma, or, before the chemical reaction, asolid, liquid, orgel. In aircraft, the propellant is usually a fuel and is combusted with the air. In firearm ballistics, propellants fill the interior of anammunition cartridgeor the chamber of a gun or cannon, leading to the expulsion of a bullet or shell (gunpowder,smokeless powder, and large gun propellants). Explosives can be placed in a sealed tube and act as a deflagrant low explosive charge in mining and demolition, to produce a low velocity heave effect (gas pressure blasting). Cold gas propellants may be used to fill an expansible bag or membrane, such as an automotive airbag (gas generator propellants) or in pressurised dispensing systems, such as aerosol sprays, to force a material through a nozzle. Examples of can propellants includenitrous oxidethat is dissolved in cannedwhipped cream, and thedimethyl etheror low-boilingalkaneused inhair spray. Rocket propellant may also be expelled through an expansion nozzle as a cold gas, that is, without energetic mixing and combustion, to provide smallchanges in velocityto spacecraft by the use ofcold gas thrusters.

Q.4 Explain Petroleum refining processes & light, medium and heavy distillates?

Ans.4 Anoil refineryorpetroleum refineryis anindustrial processplantwherecrude oilis processed and refined into more useful products such aspetroleum naphtha,gasoline,diesel fuel,asphalt base,heating oil,keroseneandgas. Oil refineries are typically large, sprawlingindustrialcomplexes with extensivepipingrunning throughout, carrying streams offluidsbetween largechemical processingunits. In many ways, oil refineries use much of the technology of, and can be thought of, as types ofchemical plants. The crude oil feedstock has typically been processed by anoil production plant. There is usually anoil depot(tank farm) at or near an oilrefineryfor the storage of incoming crude oil feedstock as well as bulk liquid products. An oil refinery is considered an essential part of thedownstreamside of thepetroleum industry.

Refining processes:-

Desalterunit washes out salt from the crude oil before it enters the atmospheric distillation unit.

Atmospheric distillation unit distills crude oil into fractions. Seecontinuous distillation.

Vacuum distillationunit further distills residual bottoms after atmospheric distillation.

Naphthahydrotreaterunit useshydrogento desulfurize naphtha from atmospheric distillation. Must hydrotreat the naphtha before sending to a catalytic reformer unit.

Catalytic reformerunit is used to convert the naphtha-boiling range molecules into higher octanereformate(reformer product). The reformate has higher content of aromatics and cyclic hydrocarbons). An important by-product of a reformer is hydrogen released during the catalyst reaction. The hydrogen is used either in the hydrotreaters or the hydrocracker.

Distillate hydrotreaterdesulfurizes distillates (such as diesel) after atmospheric distillation.

Fluid Catalytic Cracker(FCC) unit upgrades heavier fractions into lighter, more valuable products.

Hydrocrackerunit uses hydrogen to upgrade heavier fractions into lighter, more valuable products.

Visbreakingunit upgrades heavy residual oils by thermally cracking them into lighter, more valuable reduced viscosity products.

Meroxunit treats LPG, kerosene or jet fuel by oxidizingmercaptansto organicdisulfides.

Alternative processes for removing mercaptans are known, e.g.doctor sweetening processand caustic washing.

Coking units(delayed coking, fluid coker, and flexicoker) process very heavy residual oils into gasoline and diesel fuel, leaving petroleum coke as a residual product.

Alkylationunit usessulfuric acidorhydrofluoric acidto produce high-octane components for gasoline blending.

Dimerizationunit convertsolefinsinto higher-octane gasoline blending components. For example,butenescan be dimerized into isooctene which may subsequently be hydrogenated to formisooctane. There are also other uses for dimerization. Gasoline produced through dimerization is highly unsaturated and very reactive. It tends spontaneously to form gums. For this reason the effluent from the dimerization need to be blended into the finished gasoline pool immediately or hydrogenated.

Isomerizationunit converts linear molecules to higher-octane branched molecules for blending into gasoline or feed to alkylation units.

Steam reformingunit produces hydrogen for the hydrotreaters or hydrocracker.

Liquified gas storage vessels store propane and similar gaseous fuels at pressure sufficient to maintain them in liquid form. These are usually spherical vessels or "bullets" (i.e., horizontal vessels with rounded ends).

Storage tanks store crude oil and finished products, usually cylindrical, with some sort of vapor emission control and surrounded by an earthenbermto contain spills.

Amine gas treater,Claus unit, and tail gas treatment converthydrogen sulfidefromhydrodesulfurizationinto elemental sulfur.

Utility units such ascooling towerscirculate cooling water,boiler plantsgeneratessteam, and instrument air systems include pneumatically operatedcontrol valvesand anelectrical substation.

Wastewatercollection and treating systems consist ofAPI separators,dissolved air flotation (DAF) unitsand further treatment units such as anactivated sludgebiotreater to make water suitable for reuse or for disposal.

Solvent refining units use solvent such ascresolorfurfuralto remove unwanted, mainly aromatics from lubricating oil stock or diesel stock.

Solvent dewaxing units remove the heavy waxy constituentspetrolatumfrom vacuum distillation products.

Major refining products:-

Petroleum products are usually grouped into three categories: light distillates (LPG, gasoline, and naphtha), middle distillates (kerosene, diesel), heavy distillates and residuum (heavy fuel oil, lubricating oils, wax, and asphalt). This classification is based on the way crude oil is distilled and separated into fractions (calleddistillatesandresiduum) as in the above drawing.

Liquefied petroleum gas(LPG)

Gasoline(also known as petrol)

Naphtha

Keroseneand relatedjet aircraft fuels

Diesel fuel

Fuel oils

Lubricating oils

Paraffin wax

Asphaltandtar

Petroleum coke

Sulfur

Oil refineries also produce various intermediate products such ashydrogen, light hydrocarbons,reformateandpyrolysis gasoline. These are not usually transported but instead are blended or processed further on-site. Chemical plants are thus often adjacent to oil refineries. For example, light hydrocarbons are steam-cracked in anethyleneplant, and the produced ethylene is polymerized to producepolyethene.

The primary end-products produced in petroleum refining may be grouped into four categories: light distillates, middle distillates, heavy distillates and others.

Light distillates

Liquid petroleum gas (LPG)

Gasoline (also known as petrol)

Heavy Naphtha

Light Naphtha

Middle distillates

Kerosene

Automotive and rail-road diesel fuels

Residential heating fuel

Other light fuel oils

Heavy distillates

Heavy fuel oils

Bunker fuel oil and other residual fuel oils

Q.5 Explain types of Diesel.

Ans.5 Diesel fuel is produced from various sources, the most common beingpetroleum. Other sources include biomass, animal fats, biogas, natural gas, and coal.

Petroleum diesel

Petroleum diesel, also calledpetro diesel,or fossil diesel is the most common type of diesel fuel. It is produced from thefractional distillationofcrude oilbetween 200C (392F) and 350C (662F) atatmospheric pressure, resulting in a mixture of carbon chains that typically contain between 8 and 21carbonatomspermolecule.

Synthetic diesel

Synthetic diesel can be produced from any carbonaceous material, including biomass, biogas, natural gas, coal and many others. The raw material is gasified into synthesis gas, which after purification is converted by theFischerTropsch processto a synthetic diesel. The process is typically referred to asbiomass-to-liquid(BTL),gas-to-liquid(GTL) orcoal-to-liquid(CTL), depending on the raw material used. Paraffinic synthetic diesel generally has a near-zero content of sulfur and very low aromatics content, reducing unregulated emissions of toxic hydrocarbons, nitrous oxides and particulate matter (PM).

Biodiesel

Fatty-acid methyl ester (FAME), more widely known asbiodiesel, is obtained fromvegetable oilor animal fats (biolipids) which have been transesterifiedwithmethanol. It can be produced from many types of oils, the most common being rapeseed oil (rapeseed methyl ester, RME) in Europe and soybean oil (soy methyl ester, SME) in the USA. Methanol can also be replaced with ethanol for the transesterification process, which results in the production of ethyl esters. The transesterification processes use catalysts, such as sodium or potassium hydroxide, to convert vegetable oil and methanol into FAME and the undesirable byproducts glycerine and water, which will need to be removed from the fuel along with methanol traces. FAME can be used pure (B100) in engines where the manufacturer approves such use, but it is more often used as a mix with diesel, BXX where XX is the biodiesel content in percent. FAME as a fuel is regulated underDIN EN 14214andASTM D6751. FAME has a lower energy content than diesel due to its oxygen content, and as a result, performance and fuel consumption can be affected. It also can have higher levels of NOx emissions, possibly even exceeding the legal limit. FAME also has lower oxidation stability than diesel, and it offers favorable conditions for bacterial growth, so applications which have a low fuel turnover should not use FAME.The loss in power when using pure biodiesel is 5 to 7%. Fuel equipment manufacturers (FIE) have raised several concerns regarding FAME fuels: free methanol, dissolved and free water, free glycerine,monoanddiglycerides, freefatty acids, total solid impurity levels, alkaline metal compounds in solution and oxidation and thermal stability. They have also identified FAME as being the cause of the following problems: corrosion of fuel injection components, low-pressure fuel system blockage, increased dilution andpolymerizationof engine sump oil, pump seizures due to high fuel viscosity at low temperature, increased injection pressure, elastomeric seal failures and fuel injector spray blockage.

Unsaturated fatty acidsare the source for the lower oxidation stability; they react with oxygen and form peroxides and result in degradation byproducts, which can cause sludge and lacquer in the fuel system. As FAME contains low levels of sulfur, the emissions ofsulfur oxidesandsulfates, major components ofacid rain, are low. Use of biodiesel also results in reductions of unburned hydrocarbons,carbon monoxide(CO), and particulate matter. CO emissions using biodiesel are substantially reduced, on the order of 50% compared to most petrodiesel fuels. The exhaust emissions of particulate matter from biodiesel have been found to be 30 percent lower than overall particulate matter emissions from petrodiesel. The exhaust emissions of total hydrocarbons (a contributing factor in the localized formation of smog and ozone) are up to 93 percent lower for biodiesel than diesel fuel. Biodiesel also may reduce health risks associated with petroleum diesel. Biodiesel emissions showed decreased levels ofpolycyclic aromatic hydrocarbon(PAH) and nitrited PAH compounds, which have been identified as potential cancer-causing compounds. In recent testing, PAH compounds were reduced by 75 to 85 percent, except forbenz(a)anthracene, which was reduced by roughly 50 percent. Targeted nPAH compounds were also reduced dramatically with biodiesel fuel, with 2-nitrofluoreneand1-nitropyrenereduced by 90 percent, and the rest of the nPAH compounds reduced to only trace levels.

Hydrogenated oils and fats

This category of diesel fuels involves converting thetriglyceridesin vegetable oil and animal fats into alkanes byrefiningandhydrogenation, such asH-Bio. The produced fuel has many properties that are similar to synthetic diesel, and are free from the many disadvantages of FAME.

DME

Dimethyl ether, DME, is a synthetic, gaseous diesel fuel that results in clean combustion with very little soot and reduced NOx emissions.

Q.6 what are the uses of Petroleum products and Diesel?

Ans.6 Uses of Petroleum products:-

Bunker fuelBunker fuel, which is alsoknownas heavy oil, is used to power ships. It typically contains a high number of pollutants and contaminants. Use is increasing with the shipping associated with global commerce.

DetergentAllsoaplessdetergents used to wash clothes and dishes are derived from the petrochemical glycerin.

PlasticsAll plastic, unless it is bioplastic, is made from petrochemicals. Every product made from or containing plastic is a product that exists only through the distillation of petroleum.

Jet fuelthe standard type of jet fuel, Jet A, is a petroleum product with a number of additives to prevent sparking, gumming, corrosion, and icing.

Diesel fuelDiesel, unless it is biodiesel, is made from refining crude oil. It is generally used in medium- and heavy-duty vehicles requiring a great deal of power and torque, like garbage trucks, road equipment, buses, and trains.

Heating OilHeating oil is a petroleum product used to fuel furnaces or boilers. In the U.S., most heating oil is consumed in the northeast.

Synthetic Rubber-Synthetic rubber is used for car tires and rubber soles on shoes. The demand for synthetic rubber is four times greater than that for natural rubber.

Synthetic Fibbers-Polyester, nylon, and acrylic are all derived from petrochemicals. They are used for curtains, carpets, rope and even our everyday clothing.

Fertilizers &Pesticides-All major commercial fertilizers are ammonia based, made from natural gas, and most commercial pesticides come from oil.

Paint-Plastic and oil based paints, as well as paint additives, are manufactured from petrochemicals.

Gasoline-Gasoline is the most commonly used product by Americans for their day to day transportation needs.45% of all oil used in the U.S. goes to gasoline, which means we consume in excess of 180 million gallons of gasoline a day.

Photographic film -Pertochemicalethylene is what is used inphotographic film.

Food additives- The shelf life of canned foods can be increased byfood additives, derived frompetrochemicals.

Makeup -Make-ups that containoils, perfumes, waxes and color, are derived from petrochemicals.

Medicine-Acetylsalicylic acid (ASA), the active ingredient in many pain reliever medicines, is manufactured from petrochemicals.

Candles-Wax is a raw petroleum product.

Uses of Diesel:-

Diesel fuel is widely used in most types oftransportation. Thegasoline-powered passengerautomobileis the major exception. Unlikegasolineandliquefied petroleum gasengines, diesel engines do not use high-voltage spark ignition (spark plugs). An engine running on diesel compresses the air inside the cylinder to high pressures and temperatures (compression ratiosfrom 14:1 to 18:1 are common in current diesel engines); the engine generally injects the diesel fuel directly into the cylinder, starting a few degrees beforetop dead center(TDC) and continuing during the combustion event. The high temperatures inside the cylinder cause the diesel fuel to react with the oxygen in the mix (burn oroxidize), heating and expanding the burning mixture to convert the thermal/pressure difference into mechanical work, i.e., to move the piston. Engines haveglow plugsto help start the engine by preheating the cylinders to a minimumoperating temperature. Diesel engines arelean burnengines,burning the fuel in more air than is required for the chemical reaction. They thus use less fuel thanrich burnspark ignition engines which use astoichiometricair-fuel ratio (just enough air to react with the fuel). As Professor Harvey of the University of Toronto notes, "due to the absence of throttling [constant amount of air admitted, per unit fuel, with no user-determined variation], the high compression ratio and lean fuel mixture, diesel engines are substantially more efficient than spark-ignited engines", generally; Harvey cites the side-by-side comparisons of Schipper et al. and the estimates of >20% lower fuel use and (given difference in differences in energy content between fuel types) >15% lower energy use.Gas turbineand some other types of internal combustion engines, andexternal combustion engine, both can also be designed to take diesel fuel. Theviscosityrequirement of diesel fuel is usually specified at 40C.A disadvantage of diesel as a vehicle fuel in cold climates, is that its viscosity increases as the temperature decreases, changing it into agel(seeCompression Ignition Gelling) that cannot flow in fuel systems. Speciallow-temperature dieselcontains additives to keep it liquid at lower temperatures, but starting a diesel engine in very cold weather may still pose considerable difficulties. Another disadvantage of diesel engines compared to petrol/gasoline engines is the possibility ofrunawayfailure. Since diesel engines do not need spark ignition, they can run as long as diesel fuel is supplied. Fuel is typically supplied via a fuel pump. If the pump breaks down in an "open" position, the supply of fuel will be unrestricted, and the engine will run away and risk terminal failure. Withturbochargedengines, the oil seals on the turbocharger may fail, allowing lubricating oil into the combustion chamber, where it is burned like regular diesel fuel. In vehicles or installations that use diesel engines and alsobottled gas, a gas leak into the engine room could also provide fuel for a runaway, via the engine air intake.

RailroadDiesel displaced coal and fuel oil for steam-powered vehicles in the latter half of the 20th century, and is now used almost exclusively for the combustion engines of self-powered rail vehicles (locomotives and railcars).Military vehicles

Armored fighting vehiclesuse diesel because of its lower flammability risks and the engines' higher provision of torque and lower likelihood ofstalling.

Cars

Diesel-poweredcars generally have a betterfuel economythan equivalent gasoline engines and produce lessgreenhouse gasemission.Their greater economy is due to the higher energy per-litre content of diesel fuel and the intrinsic efficiency of the diesel engine.While petro diesels higher density results in higher greenhouse gas emissions per litre compared to gasoline,]the 2040% better fuel economy achieved by modern diesel-engine automobiles offsets the higher per-litre emissions of greenhouse gases, and a diesel-powered vehicle emits 1020 percent less greenhouse gas than comparable gasoline vehicles.Biodiesel-powered diesel engines offer substantially improved emission reductions compared to petro diesel or gasoline-powered engines, while retaining most of the fuel economy advantages over conventional gasoline-powered automobiles. However, the increased compression ratios mean there are increased emissions of oxides of nitrogen (NOx) from diesel engines.This is compounded by biological nitrogen in biodiesel to make NOxemissions the main drawback of diesel versus gasoline engines.

Other uses

Poor quality (highsulfur) diesel fuel has been used as an extraction agent forliquidliquid extractionofpalladiumfromnitric acidmixtures. Such use has been proposed as a means of separating thefission productpalladium fromPUREXraffinatewhich comes from usednuclear fuel.In this system of solvent extraction, thehydrocarbonsof the diesel act as thediluentwhile the dialkylsulfidesact as the extractant. This extraction operates by asolvationmechanism. So far, neither apilot plantnor full scale plant has been constructed to recover palladium,rhodiumorrutheniumfromnuclear wastescreated by the use ofnuclear fuel. Diesel fuel is also often used as the main ingredient in oil-base mud drilling fluid. The advantage of using diesel is its low cost and that it delivers excellent results when drilling a wide variety of difficult strata including shale, salt and gypsum formations. Diesel-oil mud is typically mixed with up to 40% brine water. Due to health, safety and environmental concerns, Diesel-oil mud is often replaced with vegetable, mineral, or synthetic food-grade oil-base drilling fluids, although diesel-oil mud is still in widespread use in certain regions.

Q.7 List & uses of aviation fuels.

Ans.7 Avgas(aviationgasoline) is used in spark-ignited internal-combustion engines inaircraft. Its formulation is distinct frommogas(motor gasoline) used incars. Avgas is formulated for stability, safety, and predictable performance under a wide range of environments, and is typically used in aircraft that usereciprocatingorWankel engines.

Jet fuelis a clear to straw-colored fuel, based on either anunleadedkerosene(Jet A-1), or anaphtha-keroseneblend (Jet B). It is similar todiesel fuel, and can be used in eithercompression ignition enginesorturbine engines. Jet-A powers modern commercial airliners and is a mix of pure kerosene and anti-freeze and burns at temperatures at or above 49 degrees Celsius (120 degrees Fahrenheit). Kerosene-based fuel has a much higher flash point than gasoline-based fuel, meaning that it requires significantly higher temperature to ignite. It is a high-quality fuel; if it fails the purity and other quality tests for use on jet aircraft, it is sold to other ground-based users with less demanding requirements, like railroad engines.

Uses

Aviation fuel is often dispensed from a tanker orbowser, which is driven up to parkedaircraftandhelicopters. Some airports have pumps similar tofilling stationsto which aircraft must taxi. Some airports have permanent piping to parking areas for large aircraft.

Aviation fuels consist of blends of over a thousand chemicals, primarilyhydrocarbons(paraffins,olefins,naphthenes, andaromatics), additives such asantioxidantsand metal deactivators, and impurities. Principal components includenheptaneandisooctane. Like other fuels, aviation fuel for spark-ignited piston engines are described by theiroctane rating. Alcohol, alcohol mixtures, and other alternative fuels may be used experimentally, but alcohol is not permitted in any certified aviation fuel specification.

Q.8 Write short note on kerosene & Gasoline.

Ans.8 Kerosene:-

Keroseneis acombustiblehydrocarbonliquid widely used as a fuel, in industry, and in households. Its name is derived fromGreek:(keros) meaningwax, and was registered as a trademark byAbraham Gesnerin 1854 before evolving into agenericized trademark. Kerosene is widely used to powerjet enginesof aircraft (jet fuel) and somerocket engines, but is also commonly used as a cooking and lighting fuel and for fire toys such aspoi. In parts of Asia, where the price of kerosene is subsidized, it fuels outboard motors on small fishing boats. Kerosene lampsare widely used for lighting in rural areas of Asia and Africa where electrical distribution is not available or too costly for widespread use. Kerosene is a thin, clear liquid formed from hydrocarbons obtained from thefractional distillationofpetroleumbetween 150Cand 275C, resulting in a mixture with adensityof 0.780.81 g/cm3composed of carbon chains that typically contain between 6 and 16carbonatomspermolecule. It is miscible in petroleum solvents butimmisciblein water. Regardless of crude oil source or processing history, kerosene's major components are branched and straight chainalkanesandnaphthenes(cycloalkanes), which normally account for at least 70% by volume.Aromatic hydrocarbonsin this boiling range, such asalkylbenzenes(single ring) and alkylnaphthalenes (double ring), do not normally exceed 25% by volume of kerosene streams.Olefinsare usually not present at more than 5% by volume. Theflash pointof kerosene is between 37 and 65C (100 and 150F), and itsauto ignition temperatureis 220C (428F).Thepour pointof kerosene depends on grade, with commercial aviation fuel standardized at 47C (53F).

Gasoline:-

Gasolinealso known aspetrol, is a transparent,petroleum-derived liquid that is used primarily as a fuel ininternal combustion engines. It consists mostly oforganic compoundsobtained by thefractional distillationof petroleum, enhanced with a variety of additives; a 42-gallon barrel of crude oil yields about 19 gallons of gasoline, when processed in anoil refinery. The characteristic of a particular gasoline blend to resist igniting too early (which causes knocking and reduces efficiency in reciprocating engines) is measured by itsoctane rating. Gasoline is produced in several grades of octane rating.Tetraethylleadand other lead compounds are no longer used in most areas to regulate and increase octane-rating, but many other additives are put into gasoline to improve its chemical stability, control corrosiveness and provide fuel system 'cleaning,' and determine performance characteristics under intended use. Sometimes, gasoline also containsethanolas analternative fuel, for economic or environmental reasons. Gasoline, as used worldwide in the vast number of internal combustion engines used in transport and industry, has a significant impact on the environment, both in local effects (e.g., smog) and in global effects (e.g.,effect on the climate). Gasoline may also enter the environment uncombusted, as liquid and as vapours, from leakage and handling during production, transport and delivery, from storage tanks, from spills, etc. As an example of efforts to control such leakage, many (underground) storage tanks are required to have extensive measures in place to detect and prevent such leaks. Thematerial safety data sheetfor unleaded gasoline shows at least 15 hazardous chemicals occurring in various amounts. Benzene and many anti-knocking additives arecarcinogenic.

Q.9 what is Knocking and Anti-Knocking?

Ans.9 Knocking:-

Knocking(also calledknock,detonation,spark knock,pingingorpinking) in spark-ignitioninternal combustion enginesoccurs when combustion of theair/fuel mixturein the cylinder does not start off correctly in response to ignition by thespark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. The fuel-air charge is meant to be ignited by the spark plug only, and at a precise point in the piston's stroke. Knock occurs when the peak of the combustion process no longer occurs at the optimum moment for thefour-stroke cycle. The shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically. Effects of engine knocking range from inconsequential to completely destructive. Knocking should not be confused withpre-ignition they are two separate events. However, pre-ignition is usually followed by knocking.

Anti-Knocking:-

In antiknocking,gasoline additiveused to reduceengine knockingand increase the fuel'soctane ratingby raising the temperature and pressure at which auto-ignition occurs. The mixture known as gasoline, when used in highcompressioninternal combustion engines, has a tendency toknock(also called "pinging" or "pinking") and/or to ignite early before the correctly timed spark occurs.