Petroleum Refinery Basics• Crude Oil components• Refinery Flowchart• Other refinery units• Unit Opns & Unit Proces in refining• Physical and process Hazards
Thanks to• John Kulluk Ph.D.• Torrance Fire Department• &• Robert Distaso PE – 714/573-6253• Orange County Fire Authority
Petroleum is extracted from underground reserves;then it is cracked or “refined” into end products forvarious uses. The petroleum industry thus has twoparts: an oil exploration and production industryupstream and a refinery industry downstream.Most oil producers also own refineries. But thereverse is not true; a high proportion of oil is soldto refinery companies that do not produce crudeoil.
Refining Means. . .1. To reduce to a pure state, to remove impurities2. To improve or perfect Salable products are made from crude.
What is Crude Oil?• Mixture of organic carbon chain molecules• Impurities include sulfur and nitrogen compounds• Some metals and salts too
Heat & Mass Transfer OpnsThe reactor effluent is then cooled via heatexchange with unit feedstocks, fractionated intothe desired product streams via distillation,which are then further cooled via heat exchangewith unit feedstocks. Individual refineryprocesses are described subsequently,simplified process flow diagrams will beprovided to illustrate the specific process flowsequence for the applicable process.
In fractionation or distillation the feedstock isdistilled into various cuts of target boiling ranges oreven separated into individual hydrocarboncompounds. Distillation is accomplished byimposing a temperature profile across the towerenabling differences in the equilibriumcompositions of the vapor and liquid phases tochange the compositions throughout the distillationtower.
Heat is added to the hydrocarbons at the bottomof the tower through heat exchange in a reboilerwhich vaporizes a portion of the tower bottomsliquid for recirculation to the bottom of the tower.Heat is removed from the top of the tower throughheat exchange in an overhead condenser andthen returning a portion of the condensedhydrocarbons back to the tower as .reflux..
This heat addition at the bottom and heatremoval from the top of the tower establishes thetemperature profile across the tower. In someapplications, additional heat is removed by heatexchange with circulating liquid „pump-around‟streams which are withdrawn and returned atintermediate levels of the tower. Perforated traydecks or packed bed sections allow intimatecontacting of the liquid and vapor phasesfollowed by separation.
Composition of crude oil• Petroleum crude oils are : numerous hydrocarbons.• Hydrocarbons are chemical compounds made up of predominantly carbon and hydrogen.• Hydrocarbons found in crude oils generally also contain the elements sulfur and nitrogen. Many crude oils also contain absorbed levels of the toxic gas hydrogen sulfide (H2S).
Components_ To be removed• Crude oils may contain trace amounts of metals such as nickel and vanadium, as well as salts.• Most of the nonhydrogen, non-carbon elements found in crude oils are undesirable and are removed from the hydrocarbons in total or in part during refinery processing.
Refinery Process Flow Chart Sulfur Gas Plant Fuel Gas Splitter Isom Gasoline Reformer Distilling Jet Fuel Hydrotreating Distillate Fuel Hydrotreating Alky CCU Flasher Residual Visbreaker FuelLeffler, 1985
The principal products, with theirapproximate boiling points, are petroleumgas (20ºC), naphtha (40ºC), petrol (70ºC),kerosene and jet fuel (120ºC), diesel (200ºC),lubricant (300ºC), and furnace oil (370ºC);solid petroleum coke collects at the bottomafter the liquid fractions are removed.
Many fuels products are treated as a finishingstep prior to being shipped as .finished. products.Treating removes impurities which causeobjectionable odors, unwanted colors orcorrosion of the product. Hydrogen sulfide (H2S)and other sulfur compounds such as mercaptansare examples of such impurities.
Amine contacting using aqueous amine solutions such asmonoethanolamine (MEA), diethanolamine (DEA), ormethyldiethanol amine (MDEA) are commonly used toremove H2S from light ends streams prior todisposition as fuel gas or propane (i.e., LiquefiedPetroleum Gas or .LPG.) product. The amine solution isthen regenerated in a still in which the applicationof heat drives off the H2S. The H2S-rich stream producedfrom the still (called acid gas.) is then routed to the SulfurConversion process.
Other Refinery Units• Steam Generation• Wastewater Treatment• Hydrogen Generation• Power Generation (e.g., cogen)• Air Separation Plant• Loading/Unloading - Railcar, Trucks, etc.• Storage (high pressure hydrocarbon, crude oil, intermediates) Floating-Roof Tanks - 150„ diameter is common Spherical Tanks - 50„ are common Horton Spheroid (refrigerated) Steam-Heated Tanks for “Heavier” Products• Self-Contained Firewater Supply• Firewater Pumps
What Goes on at a Refinery. . .?• Separation of components by distillation, e.g.: Atmospheric Vacuum Hydrotreating (uses excess hydrogen)• Breaking apart molecules to make smaller ones, e.g.: catalytic cracking hydrocracking• Joining molecules to make bigger ones, e.g.: Reforming - alkylation that lengthens the hydrocarbon chain Reforming - cyclic that generates hydrogen
Physical Hazards• High Pressure/Temperature Steam• Oil/Gas-Fired Furnaces• Acoustic• High Voltage (4160V, 480V, 13.2 kV)• Falling Hazards• Confined Space Hazards• Cranes/Lifting Hazards• Hot Work Hazards• Acid Exposure• Toxic Vapors• Radiation• Flammability Hazards
Common PPE Requirements• Hardhat• Hardsoled / Hardtoe Shoes• Safety Glasses with Side Protection• Safety Goggles or Faceshield• Fire-Resistant Clothing
Process Hazards• Emergency Flare• Atmospheric Pressure Relief• High Temperature (up to 2000oF)• Low Temperature (e.g., Brittle Fracture)• High Pressure (up to 3000 psig)• Low Pressure (e.g., vacuum)
Some petrochemicals are produced in large enough bulk totake a significant proportion of refinery products: theworld consumed 345 million tons of hydrocarbons in 2004to make 310 million tons of petrochemicals.Most of the hydrocarbons are first turned into one of threeintermediates - ethylene, propylene and aromatics – beforebeing converted to other products. Of the latter, plasticsaccounted for 225 million tons, and fibres for 38 milliontons; solvents, detergents and synthetic rubber accountedfor most of the rest.