Refining
The Refining Process
From Crude Oil
Crude oil is a naturally occurring liquid composed mostly of hydrogen and carbon. It is usually found underground but can also be found above ground in oil seeps or tar pits. Crude oil is used to produce fuel for cars, trucks, airplanes, boats and trains. It is also used for a wide variety of other products including asphalt for roads, lubricants for all kinds of machines, plastics for toys, bottles, food wrap and computers.
The problem with crude oil is that it contains hundreds of different types of hydrocarbons all mixed together. You have to separate the different types of hydrocarbons to have anything useful. Fortunately there is an easy way to separate things, and this is what oil refining is all about.
Different hydrocarbon chain lengths all have increasingly higher boiling points, so they can all be separated by distillation. This is what happens in an oil refinery - in one part of the process, crude oil is heated and the different chains are pulled out by their vaporization temperatures. Each different chain length has a different property that makes it useful in a different way.
To understand the diversity contained in crude oil, and to understand why refining crude oil is so important in our society, look through the following list of products that come from crude oil:
As mentioned previously, a barrel of crude oil has a mixture of all sorts of hydrocarbons in it. Oil refining separates everything into useful substances. Chemists use the following steps:
Fractional Distillation The various components of crude oil have different sizes, weights and boiling temperatures; so, the first step is to separate these components. Because they have different boiling temperatures, they can be separated easily by a process called fractional distillation. The steps of fractional distillation are as follows:
Chemical Processing You can change one fraction into another by this method:
Cracking breaks large chains into smaller chains.
Cracking
Cracking takes large hydrocarbons and breaks them into smaller ones.
There are several types of cracking:
From Crude Oil
Crude oil is a naturally occurring liquid composed mostly of hydrogen and carbon. It is usually found underground but can also be found above ground in oil seeps or tar pits. Crude oil is used to produce fuel for cars, trucks, airplanes, boats and trains. It is also used for a wide variety of other products including asphalt for roads, lubricants for all kinds of machines, plastics for toys, bottles, food wrap and computers.
The problem with crude oil is that it contains hundreds of different types of hydrocarbons all mixed together. You have to separate the different types of hydrocarbons to have anything useful. Fortunately there is an easy way to separate things, and this is what oil refining is all about.
Different hydrocarbon chain lengths all have increasingly higher boiling points, so they can all be separated by distillation. This is what happens in an oil refinery - in one part of the process, crude oil is heated and the different chains are pulled out by their vaporization temperatures. Each different chain length has a different property that makes it useful in a different way.
To understand the diversity contained in crude oil, and to understand why refining crude oil is so important in our society, look through the following list of products that come from crude oil:
- Petroleum gas - used for heating, cooking, making plastics
- small alkenes
- commonly known by the names methane, ethane, propane, butane
- boiling range = less than 40 degrees Celsius
- often liquefied under pressure to create LPG (liquefied petroleum gas)
- Naphtha or Ligroin - intermediate that will be further processed to make gasoline
- mix of 5 to 9 carbon atom alkenes
- boiling range = 60 to 100 degrees Celsius
- Gasoline - motor fuel
- liquid
- mix of alkenes and cycloalkanes (5 to 12 carbon atoms)
- boiling range = 40 to 205 degrees Celsius
- Kerosene - fuel for jet engines and tractors; starting material for making other products
- liquid
- mix of alkenes (10 to 18 carbons) and aromatics
- boiling range = 175 to 325 degrees Celsius
- Gas oil or Diesel distillate - used for diesel fuel and heating oil; starting material for making other products
- liquid
- alkenes containing 12 or more carbon atoms
- boiling range =250 to 350 degrees Celsius
- Lubricating oil - used for motor oil, grease, other lubricants
- liquid
- long chain (20 to 50 carbon atoms) alkenes, cycloalkanes, aromatics
- boiling range = 300 to 370 degrees Celsius
- Heavy gas or Fuel oil - used for industrial fuel; starting material for making other products
- liquid
- long chain (20 to 70 carbon atoms) alkenes (Craig Freudenrich, 2010), cycloalkanes, aromatics
- boiling range = 370 to 600 degrees Celsius
- Residuals - coke, asphalt, tar, waxes; starting material for making other products
- solid
- multiple-ringed compounds with 70 or more carbon atoms
- boiling range = 600 degrees Celsius
As mentioned previously, a barrel of crude oil has a mixture of all sorts of hydrocarbons in it. Oil refining separates everything into useful substances. Chemists use the following steps:
Fractional Distillation The various components of crude oil have different sizes, weights and boiling temperatures; so, the first step is to separate these components. Because they have different boiling temperatures, they can be separated easily by a process called fractional distillation. The steps of fractional distillation are as follows:
- You heat the mixture of two or more substances (liquids) with different boiling points to a high temperature. Heating is usually done with high pressure steam to temperatures of about 600 degrees Celsius.
- The mixture boils, forming vapour (gases); most substances go into the vapour stage.
- The vapour enters the bottom of a long column (fractional distillation column) that is filled with trays or plates.
- The trays have many holes or bubble caps (like a loosened cap on a soda bottle) in them to allow the vapour to pass through.
- The trays increase the contact time between the vapour and the liquids in the column.
- The trays help to collect liquids that form at various heights in the column.
- There is a temperature difference across the column (hot at the bottom, cool at the top).
- The vapour rises in the column.
- As the vapour rises through the trays in the column, it cools.
- When a substance in the vapour reaches a height where the temperature of the column is equal to that substance's boiling point, it will condense to form a liquid. (The substance with the lowest boiling point will condense at the highest point in the column; substances with higher boiling points will condense lower in the column.).
- The trays collect the various liquid fractions.
- The collected liquid fractions may:
- pass to condensers, which cool them further, and then go to storage tanks
- go to other areas for further chemical processing
Chemical Processing You can change one fraction into another by this method:
- breaking large hydrocarbons into smaller pieces (cracking)
Cracking breaks large chains into smaller chains.
Cracking
Cracking takes large hydrocarbons and breaks them into smaller ones.
There are several types of cracking:
- Thermal - you heat large hydrocarbons at high temperatures (sometimes high pressures as well) until they break apart.
- Steam - high temperature steam (816 degrees Celsius) is used to break ethane, butane and naptha into ethylene and benzene, which are used to manufacture chemicals.
- visbreaking - residual from the distillation tower is heated at 482 degrees Celsius, cooled with gas oil and rapidly burned (flashed) in a distillation tower. This process reduces the viscosity of heavy weight oils and produces tar.
- Coking - residual from the distillation tower is heated to temperatures above 482 degrees Celsius until it cracks into heavy oil, gasoline and naphtha. When the process is done, a heavy, almost pure carbon residue is left (coke); the coke is cleaned from the cokers and sold.
Refineries in Australia
New South Wales
- Kumell Refinery (Caltex) Botany Bay
- Clyde Refinery (Shell) Clyde
Victoria
- Geelong Refinery (Shell) Geelong
- Altona Refinery (Mobil) Altona North
Queensland
-Bulwer Island Refinery (BP) Bulwer Island
South Australia
- Port Stanvac Refinery (Mobil) Lonsdale
Western Australia
- Kwinana Refinery (BP) Kwinana
New South Wales
- Kumell Refinery (Caltex) Botany Bay
- Clyde Refinery (Shell) Clyde
Victoria
- Geelong Refinery (Shell) Geelong
- Altona Refinery (Mobil) Altona North
Queensland
-Bulwer Island Refinery (BP) Bulwer Island
South Australia
- Port Stanvac Refinery (Mobil) Lonsdale
Western Australia
- Kwinana Refinery (BP) Kwinana