Oil refinery or petroleum refinery is an industrial process plant where crude oil is transformed and refined into more useful products such as petroleum naphtha, gasoline, diesel fuel, asphalt base, heating oil, kerosene, liquefied petroleum gas, jet fuel and fuel oils.
There are five processes to refine the crude oil and those are :
1. Desalting and dewatering :
Desalting process removes salt and other contaminants because they can be corrosive to the refining pipes. Then, water is removed before it is sent to distillation stage
2. Atmospheric distillation :
Molecules of crude oil are separated using distillation based on their molecular weights. The crude oil is heated in a tank with different temperatures at different heights. First, the oil is heated at the bottom of the tank with temperature of 350-400 C, causing lighter molecules to vaporize. The vapors rise up and condense into liquids at different levels according to their weight. Each level yields different petroleum fraction. The molecules at the bottom usually go through second distillation.
3. Conversion :
Gasoline and the group of products called middle distillates are the finished products with the highest demands. However, separation process still yields heavy distillates. Therefore, the heavy molecules need to go through conversion, which is divided into 3 types: cracking, combining, and modifying. Cracking is the most common type, which involves breaking large molecules into smaller ones. It may use heat (thermalcracking) or fluid (such as hydrogen) and also catalyst to speed up the process.
4. Treating :
Treating is the process of removing substances that are corrosive or air polluting, especially sulfur and nitrogen. The most common method is hydroprocessing, where these substances are reacted with hydrogen at high pressure and temperature.
5. Blending :
Market demands on low cost, high octane fuel led to a process called blending. In this process, high octane components are blended with lower octane to produce various blendstocks with different selling prices.
Downey, M. (2009) Oil 101. Wooden Table Press.