Each oil refining plant is uniquely configured to process a specific raw material into a desired slate of products. In order to determine which configuration is most economical, engineers and planners survey the local market for petroleum products and assess the available raw materials. Since about half the product of fractional distillation is residual fuel oil, the local market for it is of utmost interest. In parts of Africa, South America, and Southeast Asia, heavy fuel oil is easily marketed, so that refineries of simple configuration may be sufficient to meet demand. However, in the United States, Canada, and Europe, large quantities of gasoline arein demand, and the market for fuel oil is constrained by environmental regulations and the availability of natural gas. In these places, more complex refineries are necessary.
Topping and hydroskimming refineries
The simplest refinery configuration, called a topping refinery, is designed to prepare feedstocks for petrochemical manufacture or for production of industrial fuels in remote oil-production areas. It consists of tankage, a distillation unit, recovery facilities for gases and light hydrocarbons, and the necessary utility systems (steam, power, and water-treatment plants).
Topping refineries produce large quantities of unfinished oils and are highly dependent on local markets, but the addition of hydrotreating and reforming units to this basic configuration results in a more flexible hydro skimming refinery, which can also produce desulfurized distillate fuels and high-octane gasoline.