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Introduction to Petroleum Refinery Processing. Gennaro J. (Jerry) Maffia ; Professor of Chemical Engineering and Process Engineering Manager, Petrochemicals Industry. Introduction.
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Introduction to Petroleum Refinery Processing Gennaro J. (Jerry) Maffia; Professor of Chemical Engineering and Process Engineering Manager, Petrochemicals Industry
Introduction Introduction
“The ground begins to rumble, then shake. The hero of the film – a lean excowboy with a square jaw under his hat and a gorgeous brunette on his arm – reaches out to brace himself against his horse. A smile creases his face as the rumbling grows louder. Suddenly, a gush of black goo spurts into the air and splashes down on him, his side-kick and his best gal. They dance with ecstasy until the music swells and the credits start to roll. Why is our hero so happy? Because he’s rich! After years of drilling dry holes in every county between the Red River and the Rio Grande, he finally struck oil.” Paul R. Robinson Introduction
What is petroleum ? • Petroleum is a thick, flammable, yellow-to-black combustible mixture of gaseous, liquid, and solid hydrocarbons that occur naturally beneath the earth’s surface. • After processing it is usually separated to fractions, which can be used as fuel, or as raw material for chemical or petrochemical plants. Introduction- What is petroleum ?
What is petroleum ? • Petroleum produced from a well is not pure hydrocarbons, it has some impurities including water, brine, inert gasses, mercaptants, carbon dioxide, H2S, drilling sands and others. • It can be classified as light, intermediate or heavy according to its specific gravity. And as sweet or sour according to the amount of sulfur compounds present in it. Introduction- What is petroleum ?
Importance of Petroleum • Petroleum can be refined (fractionated)and split to it’s components each of which can be either used directly or processed to give a wide range of products. • These products include: fuels, lubricating oils, solvents, ink, polymers, adhesives, soap, waxes, alcohols, fertilizers, and a lot others. Introduction- Importance of petroleum
Steps of production in nature Introduction- Production of petroleum- Generation, Migration, Accumelation
Generation In oceans: • Dead animals and plants sank to the bottom of the ocean. • Buried under sediments of sand and mud. • Layers increase in thickness with time. • Temperature and pressure increase. • Causing the change to sedimentary rocks. Introduction- Production of petroleum- Generation, Migration, Accumulation
Generation • In absence of oxygen conditions deposits are changed to kerogen. • At high temperature (greater than 110oC) and pressure kerogen is thermally degraded to oil and gas. • This process takes hundreds millions of years to occur. Introduction- Production of petroleum- Generation, Migration, Accumelation
Generation On land: • dead plants and animals undergo similar processes to become coal, which is if deeply buried under high temperature conditions is transformed to gas and petroleum. • The factor that determined the transformations is to gas or oil is the severity of the conditions of which the organisms are buried the more severer the conditions, the smaller is the hydrocarbon produced, in extreme cases methane (natural gas). Introduction- Production of petroleum- Generation, Migration, Accumelation
Migration • Once the deposits are converted to oil it must move from the source rock to the reservoir to accumulate there to form reserves that can be exploited by human. • Migration is controlled by the physical properties of the sedimentary strata the oil is moving through (permeability, porosity, etc). • The driving force is mainly pressure. • There are two types of migration; primary and secondary. Introduction- Production of petroleum- Generation, Migration, Accumelation
Migration Primary migration • where the oil is moved from the center of the source rock to the contact with the reservoir strata. • The main driving force for primary migration is sediment compaction due to overburden load. • Saturated hydrocarbons are preferentially expelled, while NSO compounds remain preferentially within the pore space of the source rock. • Migration of gas is by dissolving in oil or at great depths where high pressures causes both natural gas and oil to be a single phase. Introduction- Production of petroleum- Generation, Migration, Accumelation
Migration Secondary Migration • After the oil has crossed the source/reservoir contact and entered the reservoir rock. • The main driving force is buoyancy which is due to the density difference between oil, gas and water. • The reservoir rock has much higher porosity and permeability. • Since the driving force is buoyancy, the diffusion is in the upward direction where gas is at the top and oil is below it. Introduction- Production of petroleum- Generation, Migration, Accumulation
Migration Introduction- Production of petroleum- Generation, Migration, Accumulation
Migration Introduction- Production of petroleum- Generation, Migration, Accumulation
Accumulation • Oil and gas continue to move upwards through permeable rock until they encounter an impermeable layer of rock. • The most common traps are anticlines which are culminations of folds. • Since the gas is lightest it is at the top of the formation forming the gas cap, followed by oil then water. • The trap is formed if impermeable cap rock at the top mainly clay or salts where there is a very small number of pores or very small pore diameter that it cannot be entered by the oil or gas. Introduction- Production of petroleum- Generation, Migration, Accumelation
Accumulation • Very special cases of gas accumulations occur in the form of so-called gas hydrates. • These are solid, ice-like compounds whereby water molecules are arranged in crystal lattices forming cages (called clathrate compounds). • Methane molecules are arranged inside these cages. Per unit volume of reservoir pore space, more methane can be stored in hydrate condition as compared to free gas. Introduction- Production of petroleum- Generation, Migration, Accumelation
Accumulation Introduction- Production of petroleum- Generation, Migration, Accumelation
Summary of Crude generation & migration The following is needed for crude to be produced in commercially attractive amounts: 1- A source rock (sedimentary type) should be present to be the source of the oil. (generation step) 2- Sediment compaction or other factor that leads to the expulsion of petroleum from the source rock to the reservoir. 3- Presence of a reservoir rock that has sufficient porosity and permeability to allow for the flow of the formed petroleum. (migration step) Introduction- Production of petroleum- Generation, Migration, Accumelation
Summary of crude generation & migration 4- Structural configurations whereby reservoir rocks form traps to allow for the accumulation of the oil and gas. 5- Traps should be sealed from the top by impermeable layers (cap rocks) to prevent petroleum and gas from leaving the trap. (4, 5 for the accumulation step) 6- The absence of factors that can lead to the destruction of the geological trap which can cause the release of the accumulated gas and oil. Introduction- Production of petroleum- Generation, Migration, Accumelation
Summary Introduction- Production of petroleum- Generation, Migration, Accumulation
History • First the crude oil was obtained by collecting the oil that seeped out cracks in the ground or was mined. • It’s uses were limited to waterproofing ships, as adhesives in construction and for flaming projectiles. • Over time the uses of petroleum increased slowly till the year 1859. • The invention of countless applications at that date, that used the fractions of petroleum in their operation caused a huge increase in the demand for petroleum products. Introduction- History
History • An example is the kerosene lamp and the depletion of other sources of fuel for lighting such as whale oil. • Since then the uses of petroleum products have increased greatly the demand for the production of larger amounts of petroleum products increased. • Nowadays it is used to provide fuel, lubricants for all vehicles and provides raw materials for petrochemical industry, reaching a point that the stoppage of the steady flow of petroleum products will lead to a halt in most of the human activities. Introduction- History
Discussion Discussion
Characterization of crude oil • The ultimate goal of oil processing is turning it into useful products such as fuel, lubricants and polymers. • It is important to know the properties of crude oil to be able to determine the processes needed to give the desired product. • Crude assays include two types of information, bulk properties, and fractional properties. Discussion- Characterization of crude oil
1- Bulk properties • Bulk properties are properties for the crude as a whole such as specific gravity, sulfur content, nitrogen content, pour point, flash point, freeze point, smoke point, aniline point, cloud point, carbon residue, boiling point curve, and others. Discussion- Characterization of crude oil- Bulk properties
Important Bulk properties Discussion- Characterization of crude oil- Bulk properties
1- Specific gravity • The specific gravity is expressed using the API gravity (American Petroleum Institute), API= (141.5/SG)-131.5. • It is the ratio between the density of the crude and that of water both at 15.6oC. • It should be noted that the API gravity decreases with increase in specific gravity. Discussion- Characterization of crude oil- Bulk properties
Specific gravity Discussion- Characterization of crude oil- Bulk properties
Specific gravity Discussion- Characterization of crude oil- Bulk properties
2- Viscosity • The viscosity is the ability of the fluid to resist shearing forces mainly during flow, and is due to the frictional forces between liquid layers. • It is measures in centistokes or saybolt seconds or redwood seconds usually at 100oF and 210oF and is the time taken by a specific volume of liquid to flow through a standardized weir. Viscosity specifications are different from summer to winter due to difference in temperature. Discussion- Characterization of crude oil- Bulk properties
3- Viscosity index • The viscosity index which is the rate of change of viscosity with temperature. It is high if the rate of change of viscosity with temperature is high. This property can be improved by adding specific polymers which act as viscosity index improvers. Discussion- Characterization of crude oil- Bulk properties
4- Sulfur content • The sulfur content is expressed as the weight percentage of sulfur in the crude. • Crude oils with less than 1% sulfur are called low sulfur (sweet) crudes, and those with more sulfur than 1% are called high sulfur (sour) crudes. • Sulfur containing compounds are mainly mercaptants, sulfides and polycyclic acids. Discussion- Characterization of crude oil- Bulk properties
5- Pour point & Dew point • The pour point is a measure of how easy it is to pump the crude; it becomes of importance in cold weather. It is the lowest temperature at which crude oil will behave as liquid. • The dew point is the temperature at which the hydrocarbons in the gas phase will start to condense out of the gaseous phase. Discussion- Characterization of crude oil- Bulk properties
6- Bubble point & Flash point • The bubble point is the temperature at which the liquid hydrocarbon begins to boil and form vapor bubbles. It should be the same as the dew point for pure components but for mixtures it is different as boiling occurs on a range of temperatures. • The flash point is the lowest temperature at which there is sufficient vapor is produced above the liquid to form an explosive mixture with air, which can cause ignition if a spark is present.
7- Fire point & Freeze point • The fire point is a temperature well above the flash point where the products can catch fire easily. • The freeze point is the temperature at which the hydrocarbons solidify at atmospheric pressure. It should be noted that it is different from the pour point as reaching the pour point will make the oil very viscous that it will not flow under the effect of gravity but is still a liquid. Discussion- Characterization of crude oil- Bulk properties
8- Smoke point & Cloud point • The smoke point is the maximum height of a smokeless flame from burning a fuel measured in meters. • The cloud point it the temperature at which waxes start to crystallize and separate from the solution when cooling. Discussion- Characterization of crude oil- Bulk properties
9- Aniline point & TBP curve • The aniline point represents the minimum temperature for complete miscibility of equal volumes of aniline and crude oil, it is an important property of diesel fuels and a low aniline point indicates the presence of a larger amount of aromatics. • The true boiling point curve is the boiling point of the oil fraction versus the fraction of oil vaporized. Discussion- Characterization of crude oil- Bulk properties
10- C residue 7 Heating value • The Conradson carbon residue is a measure of the coke forming tendency of oil. It is determined by destructive distillation of oil to elemental carbon in absence of air, expressed as a weight percentage of the original sample. • The heating value is the amount of heat released from burning a unit mass of the oil. It can be higher heating value or lower heating value depending on whether the heat of vaporization of the produced water from combustion is subtracted. Discussion- Characterization of crude oil- Bulk properties
Properties of crude from different locations Discussion- Characterization of crude oil- Bulk properties
2- Fractional properties • Bulk properties provide a quick understanding of the type of crude as a whole. • Fractional properties provides the properties of a specific boiling point range. • Fractional properties usually include properties for paraffins, naphthenes, and aromatics contents, sulfur, and nitrogen contents for each boiling point range. • And other properties each specific for a product such as octane number for gasoline and smoke point for kerosene and diesel.
Important fractional properties Discussion- Characterization of crude oil- Fractional properties
1- Octane number • The octane number is a measure of the knocking properties of a fuel (gasoline). In other words it is a measure of how difficult is it for the fuel (gasoline) to self ignite before the spark plug fires. • A high octane number indicates a higher self ignition temperature meaning that this fuel will withstand higher compression ratios before self-igniting. Discussion- Characterization of crude oil- Fractional properties
Octane number • It is determined by measuring the knocking value of the fuel compared to that of a mixture of n-heptane and isooctane. • It is between 0 and 100 where the octane number 90 is for the same knocking properties as 90% iso octane and 10% n-heptane mixture. Discussion- Characterization of crude oil- Fractional properties
Octane number • There are two types of octane number, the motor octane number which is at 900 rpm at severe conditions. • While the research octane number is at normal conditions (600 rpm) the second is usually higher due to higher efficiency of engine at lower rpm. Discussion- Characterization of crude oil- Fractional properties
Octane number • The pump octane number is the one used by consumers and is the average between the two. The octane number can be improved by using additives to gasoline such as tetra ethyl lead (TEL), lead chlorides, and oxygentates (MTBE methyl tertiary butyl ether) which will be discussed later. • If the use of additives improved the ignition properties beyond pure iso octane the octane number will be higher than 100. Discussion- Characterization of crude oil- Fractional properties
Octane number • It can be measured by comparison of the ignition property of the fuel with that of pure iso-octane with different TEL additions. • Or using the performance number which is the ratio of the knock limited power of the fuel to that of pure iso octane then this ratio converted to octane number by a simple equation. Discussion- Characterization of crude oil- Fractional properties
2- Cetane number • The cetane number is the ease of self ignition of a diesel fuel, and can be considered s the opposite of the octane number where high cetane number means easier self ignition at lower temperatures. This is desired in diesel engines as these do not have spark plugs so self ignition is desired. Discussion- Characterization of crude oil- Fractional properties
Cetane number • It is represented by the percentage of pure cetane in a mixture of cetane and alpha methyl-naphthalene that has the same knocking properties (ignition quality) of the fuel. The knocking properties in both the cetane and octane number are measured in a special test engine which has a single cylinder, a multi bowl carburetor for different mixtures of fuel, and a pressure gauge to measure the intensity of the knock. Discussion- Characterization of crude oil- Fractional properties
Composition of Crude Oil Discussion- Composition of crude oil