Fundamental of PetroleumDiah Agustina Puspitasari, ST., MTChemical Engineering DepartmentEngineering FacultyBrawijaya University

Indonesians Energy

Composition of Crude OilOil and gas are made of a mixture of different hydrocarbons (C : 85-90%; H : 10-14%) Non hydrocarbon element : 0.2-3 %Nitrogen : < 0.1-2 %Oxygen : 1-1.5 % As the name suggests these are large molecules made up of hydrogen atoms attached to a backbone of carbon.

Hydrocarbon GroupParaffin is a compound where all four bonds of a carbon atom are linked to four separate atoms.They carry out substitution reactions slowly with chlorine in sunlight and with bromine in the presence of a catalyst.Paraffins are available both as normal and iso-paraffin. Normal paraffins are straight chain compounds and iso-paraffins are branched compounds.Iso-paraffins are more reactive than normal paraffins and are desirable in motor spirit.

Olefins are unsaturated hydrocarbons, the double bond is present between the two carbon atoms in the formula. Olefins are not present in crude oil, but they are produced by thermal and catalytic decomposition or dehydrogenation of normal paraffins.

Naphthenes are cyclic saturated hydrocarbons with the general formula (CnH2n) also known as cyclo-alkanes. They are relatively inactive, like paraffins. Naphthenes are desirable compounds for the production of aromatics and good quality lube oil base stocks.

Crude oil also contains a large number of hydrocarbons that do not fall into the category of paraffins, olefins, naphthenes, or aromatics, but may be the combined group of any two or more groups of paraffins, naphthenes, or aromatic hydrocarbons.

Non Hydrocarbon or Hetero Atomic CompoundHydrogen sulfide (H2S) gas is associated with crude oil in dissolved form and is released when heated. H2S is corrosive at high temperatures and in the presence of moisture.

Crude oil that contains large amounts of H2S is called sour crude. H2S can be removed from gases by absorption in an amine solution

Sulfur present in petroleum fuel products also forms various oxides of sulfur (SOx) during combustion, which are strong environmental pollutants.

Nitrogen compounds in hydrocarbons are usually found in the heavier parts of the crude oil.

These are responsible for colour and colour instability and poisoning of certain catalysts.

Nitrogen in petroleum fuels causes the generation of oxides of nitrogen (NOx).

Nitrogen can be eliminated from petroleum products by catalytic hydrogenation.

Oxygen compounds: crude oil may contain oxygen containing compounds, such as naphthenic acids, phenols, and cresols, which are responsible for corrosive activities.

Oxygen also acts as a poison for many catalysts. This can be removed by catalytic hydrogenation.

Excess oxygen compounds may even lead to explosion.

Physical Properties of Crude OilAPI gravity is expressed as the relation developed by the American Petroleum Institute, as

where s is the specific gravity of oil measured with respect to water, both at 60F (15.5C).Oil is lighter than water, API gravity is always greater than 10. The lighter the oil, the larger the API gravity.

Petroleum Components are Needed to Make Many Products

Petroleum Components are Needed to Make Many ProductsChemistry; An Environmental Perspective; Buelll, Phyllis and Girard, James; Prentice Hall 1994, p443

Distillation Separates the Components of Crude Oil MixtureAs the number of carbons in petroleum substance increase; boiling point increasesDistillation separates petroleum mixture by different boiling points

Fig.04.15

Petroleum Components

Fraction# Cs in MoleculeBoiling Pt,CUseGas1-4-160 to 30Gaseous FuelGasoline5-1230 to 200Motor fuelKerosene12-18180 to 400Diesel fuel, furnace fuelLubricants >17350 and upLubricantsParaffins>20Low melting solidscandlesAsphalt>36Gummy residueSurfacing roads

Petroleoum ProductLiquefied petroleum gas, commonly called LPG, is also known by the names of its principal generic components, propane and butane.LPG as a liquid is colorless, and in vapor form it cannot be seen.The calorific value of LPG on a volume basis is significantly higher (propane, 95 MJ/m3; butane, 121 MJ/m3) compared with that of natural gas (38 MJ/m3).

Pure LPG has no smell, but for safety reasons an odoring agent (mercaptant).LPG is a mixture of propane and butane in liquified format a pressure of about 1015 atm.LPG is the most versatile fuel used in domestic applications. It is used like natural gas and can do everything that natural gas can do.

LPG is tested for its quality as required by its use as a domestic cooking gas. One of the simplest tests of LPG quality is the weathering test

If the temperature < 0 C, then the proportion of propane in the mixture is more. if it is temperature 0-2C, then the proportion of butane will be more. For domestic use, the maximum : 2C

Petroleum FuelGasolineGasoline may be defined as the fuel derived from crude oil, in the boiling range of 100 to 400F.It is estimated that production of gasoline world wide in 2007 was approximately 1150 million tons.Composition : Hydrocarbon

Gasoline EngineThe gasoline engine (spark ignition engine) is used widely as the power source of automobiles.In the SI engines, fuel is burnt directly by introducing an electrical spark into the mixture of air and vapour of MS through the carburettor (a mixing device of air and vapour of fuel) of the engine. Power is developed due to the volumetric expansion of burnt gases (flue gas) in the engine cylinder during the expansion stroke (forward stroke) and exhausted to the atmosphere in the compression stroke (return stroke) in a repeated cycle.

1. Octane NumberThe octane number is a relative measure of knocking, or the tendency to self-ignition of a fuel in a spark-ignited internal combustion engine.If fuel has too low an octane number, it caused Preignition and will damage the engine.The antiknock quality of motor gasoline is expressed in terms of octane numbers.

If an engine runs with 100% pure iso-octane, the power rating is 100% (knock free).If the engine is run with n-heptane, the octane number is taken as zero.The octane number falls with the increase in speed Aircrafts using gasoline require very high RON fuel as necessary with the cruising speed.

Items that Increase Octane RatingBranches in MoleculeCracking and Catalytic Combination increase branching

Oxygen in MoleculeOctane EnhancersLead before 1975Fuels with OR>100 (methanol, ethanol, MTBE)

Increasing the Amount of Gasoline from Petroleum MixtureCracking Reactions : Cracking Kerosene Molecules to Form Gasoline- sized Molecules

C16H34C8H18C8H16

Catalytic reaction : combination joins smaller molecules to form a gasoline sized molecule

C2H4 + C2H4 + C2H4 + C2H4 C8H16

Octane Rating Describe the Amount of Knocking a Fuel Undergoes When it is Burned

Gasoline Blend Component

A. MTBE (Methyl tertiary-butyl ether)MTBE is most suited as a gasoline blend component, and it being used in gasoline blending to partly replace aromatics.MTBE can be used up to 11 vol % in the blend, and it gives an oxygen content of 2 wt % (percentage by weight) to gasoline blend.A negative effect of MTBE use in gasoline is ground and surface water pollution, which can occur through leaking underground storage tanks, pipeline, spills, and emissions from marine engines.

C. Tetraethyl Lead (TEL)Tetraethyl is an organometallic compound with the formula (C2H5)4 Pb.Lead is a poisonous metal that has neurotoxic effects on humans even at very low levels.Lead in automotive engine exhaust can be deposited on the catalyst in the converter and thus permanently deactivate the catalyst.

2. Reid Vapor PressureA gasoline engine needs a fuel that is sufficiently volatile to allow easy formation of the fuel vapor-air mixture required for combustion.If fuel vaporizes too much, it will not flow to the engine due to vapor lock. If fuel is less volatile, it will not evaporate and will remain in liquid form.The Reid Vapor Pressure (RVP) is vapor pressure of gasoline at 100F.The RVP of various gasoline grades varies between 35 and 84 kPa.

DistillationGasolines tendency to vaporize is also characterized by determining a series of temperatures at which various percentages (10, 50, 90 %) of the fuel have evaporated as described in ASTM D 86.The 10 % evaporated temperature : 70 0C (easy cold starting)The 50 % evaporated temperature : 125 0C (low enough to provide good warm up and cool weather)The 90 % (FBP) : 180 0C (low enough to minimize crankcase and combustion chamber deposits, spark plug fouling, and dilution of engine oil.)

Distillation Analysis

Gasoline Specification

Diesel FuelPure air is drawn into the cylinderThe air is compressed to high temperature and pressureAround TDC fuel is injected, which self-ignites and burns, further increasing pressure and therby forcing the piston down.The hot gas is released to the surrounding.

Diesel Fuels SpecificationsDiesel fuels

Pour pointFlash pointSulphurViscosity

1. ViscosityViscosity is a measure of resistance to flow, and it decreases as the temperature increases.The viscosity of the fuel must be low enough toballow free flow at its lowest operating temperature but high enough to provide lubrication to the moving parts of finely machined injectors.Diesel fuel viscosity typically lies between 1.5 and 6 cSt at 100F. A viscosity of 4 cSt at 100 F is considered optimum for atomization, lubrication, and good penetration into the combustion chamber.

2. Flash PointFlash Point (ASTM D 93).The flash point is defined as the temperature of the oil at which it momentarily flashes in the presence of air and the igniting source.

3. Pour PointThe pour point is the temperature at which there is no movement of a chilled sample in a test jar. However, the fuel may still flow under static head at pour point (e.g., from storage tank to pump suction). In a temperate climate, the diesel pour point generally varies between 6 and -6 0C.

4. SulphurSulfur has a definite effect on the wear of compression-ignited engine components such as piston rings.Fuel sulfur contributes to deposits in the combustion chamber and in the injection system.Sulfur specification was reduced from 1 wt % (percent by weight) a decade ago to 500 to 15 ppm in 2007, in most developed countries of the world.

5. DistillationThis test measures at what maximum temperature would the B-100 product completely be vaporized under a reduced pressure .Data is collected of the initial and final boiling temperature point as well as the boiling curve (the volume per cent distilled over different temperature increments).

6. Cetana NumberThe cetane number of diesel fuel is a rating to indicate how quickly a fuel will ignite in a diesel engine.A diesel engine if run on a fuel with a lower cetane number than what it was designed for will be harder to start and noisier, and it will have higher exhaust emissions.Ignition quality is compared with a mixture of cetane or n-hexadecane (C16H34) and alpha methyl naphthalene or 1-methyl naphthalene (C11H10).Cetane ignites quickly and is arbitrarily given a cetane number of 100.

Diesel Fuels Spesification

Gasoline is Available in 87, 89, and 92 Octane

Octane Rating Scale is Based on Heptane (OR-0) and Iso-octane (OR=100)

Angka Oktan Angka oktan suatu bahan bakar dinyatakan dengan besar prosen volume iso-oktana dalam campuran yang terdiri dari iso-oktana dan n hepatana.Angka oktan yang merupakan salah satu faktor utama untuk mengetahui kualitas bensin adalah nilai ketahanan suatu bahan bakar bersama dengan udara terhadap terjadinya penyalaan disaat langkah kompresi atau disebut dengan kemampuan anti-ketukan.

Uji angka oktan digunakan motor khusus yang bersilinder tunggal dimana perbandingan kompresinya dappat diubahubah, yang disebut dengan motor CFR

(Cooperative Fuel Research). Research Octane Number (RON) (CFR F-1) Motor Octane Number (MON) (CFR F-2)

Cooperative Fuel Research (CFR)

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Pengaruh MTBE Terhadap Angka Oktan

Konsentrasi MTBE 20% menghasilkan daya optimum pada putaran 2500 Rpm.Konsentrasi MTBE 25% menghasilkan daya optimum yang lebih kecil.

Pengaruh Putaran Motor Terhadap Daya Motor

Aviation fuelHigh performance aviation engines were made possible because of the concurrent development of high performance aviation fuelsAviation fuels are specifically designed forIncreased engine performanceIncreased reliabilityThis is true for both piston and turbine aviation engines and fuels

Increased Performance, Reliability & SafetyKeroseneJet Fuel(Jet-A, JP-8)GasolineAvgas(100 LL)

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