Petroleum Products & Classification

Petroleum Products

• Specifications exist for over 2000 individual refinery products.
• Few products are made inside the refinery because most go through petrochemical processing.
• Intermediate feed stocks can be routed to various units for blending, based on market demand.
• Refinery design is dictated by a small number of products.
• Items are sometimes sold for less than the cost of fuel oil to avoid storage and waste disposal costs.
• Further processing of some fractions may be more economical for producing more valued products.

Classification of petroleum products

• Refinery products are classified based on their specific gravity which denotes volatility:
  • Low boiling point products
  • Gasoline
  • Distillate fuels
  • Residue fuel oil

Petroleum Products: Low Boiling Point Products

• Gases in this category include C1, C2, C3 and their olefins.
• Methane is commonly flared or utilized as refinery fuel within boilers and heaters.
• Methane is essential for producing H₂ through pyrolysis cracking and in the reforming reaction with steam.
• Ethane serves as fuel or feedstock in the production of ethylene or hydrogen.
• Propane is primarily used as LPG (liquefied petroleum gas).
• Propylene and ethylene have uses in polymers.

Low Boiling Point Products: n-C₄

• Butanes are used as LPG.
• C₄ is used as an additive to gasoline.
• C₄ is cheaper than gasoline with a high Octane Number(ON) (90s).
• n-C₄ has a lower Reid Vapor Pressure(RVP) than i-C₄.
• Normal butane has RVP of 52 psi (358 kPa), compared to the 71 psi (490 kPa) RVP of isobutane.
• The amount of added gasoline is limited by the RVP of gasoline due to environmental and mechanical concerns.

Low Boiling Point Products: i-C₄

• Isobutane (i-C4) is mainly produced via Fluid Catalytic Cracking (FCC) and hydrocracking(HC).
• i-C4 is used for the alkylation process.
• i-C4 is converted for the production of Oxygenates via reaction with alcohol, like MTBE and ETBE.

Refinery Products: Liquefied Petroleum Gases, LPG

• LPG primarily consists of propane and butane (60-40) and is intended to be used for use as fuel, and as an intermediate material in petrochemicals manufacturing.
• Key specifications for optimal performance are vapor pressure and the level of contaminants.
• When butanes are sold as LPG, the vapor pressure is 70 psig (483 kPa) or less at 100°F (37.7°C).
• Components like C3 (BP=-43.7°F), n-C4 (BP=31.1°F), and i-C4 (BP=10.9°F) can be stored once liquefied through pressure and cooling.

2-Refinery Products: Gasoline

• Gasoline is the most important refinery product.
• The boiling point(BP) range in hydrocarbons found in Gasoline is between 38 to 205°C.
• The different market grades are influenced by antiknock performance, know as Octane Number(ON).
• 90% of gasoline produced goes towards automobiles.
• Additives like identifying color dye, anti-icing, and anti-corrosion compounds are included.
• Gasoline uses blends from different units inside of the refinery.

2.3 Characteristics of Gasoline

• It must possess Antiknock quality.
• There must be ease of starting for the engine.
• There should be low tendency to vapor lock.
• There must be low engine deposits.
• Vapor lock is a problem when liquid fuel changes to gas inside the fuel delivery system of gasoline-fueled internal combustion engines.

2.3 Gasoline Specifications

• Essential gasoline qualities are octane number (antiknock), volatility (for starting and preventing vapor lock), and vapor pressure.
• Gasoline quality is determined by its resistance to knocking. The higher the antiknock rating leads to a more powerful and efficient engine.
• Tetraethyllead (TEL) was effective as an antiknock material but now banned.
• Methanol, ethanol, MTBE, and ETBE are now commonly used.

Characteristics of Gasoline: Antiknock Characteristics

• Engine knocking happens when the air-fuel mixture ignites prematurely or uncontrollably inside the engine cylinders.
• Octane Number (ON) measures gasoline's resistance to self-ignition (knocking).
• It shows the percentage by volume of isooctane in an isooctane & n-heptane mixture that produces a knock with the fuel’s intensity being tested.
• Knocking causes mechanical damage through erosion of the cylinder head, the piston and deterioration of the spark ignition and valves.
• Gasoline's antiknocking qualities are shown through its Octane number (ON).

Octane Number

• ON indicates that isooctane is 100 (minimal knock) and heptane is 0 (bad knock).
• A fuel with an ON of 90 resists knocking similar to a mixture of 90% isooctane and 10% n-heptane.
• Research octane number (RON) is the octane number measured at 600 rpm during city driving (mild conditions).
• Motor octane number (MON) is measured at 900 rpm during highway driving (tough conditions)..
• PON, Posted (pump) octane number, is the average of Research Octane Number(RON) and Motor Octane Number(MON).
• PON is acquired using: (RON + MON)/2.
• The difference between MON and RON highlights how sensitive the fuel is to altering engine conditions.

Characteristics of Gasoline: 2-RVP

• RVP (Reid Vapor Pressure) measures the pressure built by gasoline vapors inside a standardized bomb at 37.8 °C, characterizing the fuel's vaporization capacity.
• VP (Vapor Pressure) is a function relating to temperature.
• RVP level is an indicator of how easy the car is to start because vapor-lock tendency, explosion, and evaporation hazards are correlated.
• The Reid Vapor Pressure level should not exceed the maximum allowable limit to avoid vapor lock.
• Summer gasoline have lower RVP level (around 7.2 psi or 49.6 kPa) to minimize evaporation losses and prevent vapor-lock during hot wheather.
• Winter gasoline has a higher RVP level (around 13.5 psi or 93.1 kPa) to ensure simpler engine starting and improve performance under cold weather.

Light Straight Run Gasoline

• It is a fraction of naphtha with a boiling point betwee C5 - 88° C, containing mainly C5 and C6
• Cannot be upgraded by reforming but can by isomerization.
• The fuel can also be added directly to the gasoline pool.
• It has a low octane number (70-80), as well as high vapor pressure.

Reformate Gasoline

• Gasoline can also be produced through catalytic reforming.
• Typical octane number for the type of gasoline is ~ 90-104.
• Contains a high ratio of aromatics
• Aromatics lead to a higher ON compared to paraffins which in turn may form pollutants in the air and cause carcenogenic effects.

Non-gasoline components

• Include n-butane, which is blended with gasoline to adjust vapor pressure.
• Oxygenates have methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE), tertiary Amyl methyl ether (TAME), Methanol, and Ethanol.
• Oxygenates are blended with gasoline to increase the fuel’s Octane Rating.

Properties of Oxygenates

• RON and MON vary based on the compound; Methanol (125-135 and 100-105), Ethanol (120-130 and 98-103), MTBE (113-117 and 95-101), ETBE (118-122 and 100-102), TBA (105-110 and 95-100), TAME (110-114 and 96-100)

Alcohol

• High concentrations can damage engines, hoses, gaskets, and cause metals to corrode.

MTBE and ETBE

• They cause water contaminations due to high water solubility.
• It is harder to break them down and lead to potential carcinogenics.

Kerosene

• It is used as fuel for heating and in jet engines.
• It is a starting material from which to make other products.
• It is liquid with a mix of alkanes that comprise 10 to 15 carbon atoms, and aromatics.
• The two basic types of jet fuels are naphtha and kerosene.
• Naphtha jet fuel used to be primarily used for military purposes.
• It covered a wide boiling-range stock by extending through the gasoline and kerosene boiling ranges.
• Naphtha-type jet fuel is more volatile but creates more safety problems when handled.

Jet, Turbine Fuel Characteristics

• Must have a freeze point of between -40 to -50°C.
• Must have a boiling point range of between 177-288°C.
• Must have a flashpoint range of between 38-60°C.
• Total aromatic concentration must be 20%.
• Naphthalene content must be at 3.0%.

Smoke Point

• A smoke point is used to measure the quality of combustion.
• It characterizes the content of aromatics and naphthalenes
• The higher the smoke point, the less smoke will be generated
• It is measured by burning fuel in a special wick lamp until the flame height increases and produces smoke.
• The maximum height (millimeters) of a smokeless flame before it starts emitting smoke is called a smoke point.
• A high smoke point indicates a low smoke-producing tendency in fuel.

Flash Point

• Flash point testing finds out whether a vapor and air mix is flammable.
• To ignite, enough vapor must be formed to start combustion.

Gas Oil or Diesel Distillate

• Useful for using as fuel for diesel engines and for heating oil.
• Also used as a starting material to create other products.
• Alkanes are containing around 13-18 carbon atoms
• Boils between 182 to 316°C.
• Diesel is a mixture of LGO and HGO
• (LGO is light gas oil, and HGO is heavy gas oil.)
• Part of a light product must be added to heavy product in order to improve it's specifications.

Automotive Diesel Fuels

• The ignition properties of diesel fuels are shown using cetane number and cetane index.
• Properties are similar when compared to octane number. Important specifications for diesel:
  • viscosity
  • sulfur content
  • percent aromatics
  • cloud point
• The flash point limit has to be at 52°C.
• Cetane Number (CN) is synonymous to Octane Number for gasoline.
• Cetane Number shows the how high the % of n-cetane (high quality ignition) is in its mixture with α- methyl naphthalene (low quality ignition).
• Measures the fuel’s ignition delay.
• Diesel fuel have a CN between 40-55.
• Stringent restrictions have been posed on sulfur and aromatic content in diesel fuels so air quality can be improved.

Trends of CN and ON

• In the aromatic + iso-Paraffin (to increase high ON) trends are opposite compared to smooth kompustion
• When taking environmental sunsideration into account it helps to remove olefin from the enviroment.

Heavy Gas Oil

• Heavy gas oil is generally sent for industrial fuel, also can be used as a startin material to make other products.
• Consist of liquid long chains of alkanes between 16 to 40 carbon atoms.
• Boiling range is 321-566 C
• Composed of naphthene, aromatics
• Viscosity and Sulfur Content are importatnt properties of the material.
• Is either blended or sent for use at the cracking unit.

Residuals

• Includes coke, asphalt, tar and waxes, generally found within the vaccum
• Used commonly as a starting material for products.
• Only for solid compounds
• Composed of mutiple ringed compounds that consist of 40 carbon atoms
• Has boiling range that is greater than 565 C.

Heating Oils

• There has been reduced fuel production due to the increase in transportation as well as the use of natural gasses.
• Environmental regulations has lead to the replacment with oils and natural gasses.

No. 1 Fuel Oil

• The number 1 type of fuel is used in furnaces with pot-type burners to vaporize it when it comes in contact

No. 2 Fuel Oil

• The number 2 type is a blend of kerosene, naphtha, diesel, and cracked gas oil from coker or FCC units.
• Used for furnaces with atomizing-type burners
• There are limiting specifications for sulfur content, pore point, distillation, flashpoint.

No. 4 Fuel Oil

• The number 4 type is usually a light residual oil and is used for furnaces with burners that can atomize oils.
• It requires a higher viscosity compared with other types.
• It may require preheating to vaoprize in a spray-nozzle burner, specifically when stored at low temperatures.

No. 6 Fuel Oil

• the number 6 type is a residual oil with higher viscosities than No. 4.
• It needs the process of preheating for storage, handeling, and artomizing.

Bunker C Oil

• A heavy residual oil that is typically used for oil tankers
• Specifications are deterimined by contractual aggreements

Heavy Residual Fuel Oil

• The heavy fuel is from fractionating towers and the bottoms for crude.
• it sells at about 70% relative to the price of Crude oil.
• it is considered as a byproduct of crude production
• The critical specs are viscosity and sulfur control.