Petroleum refineries are responsible for turning crude oil into petroleum products. These products can be used as fuel for transportation, paving roads, heating, electricity generation, as well as feedstock for making chemicals. The refining process essentially breaks down crude oil into its distinctive components, which are subsequently reconfigured selectively into new productions. Petroleum refineries are quite complex industrial facilities. Paul Favret mentions that all such refineries have processes for three important stages, which include separation, conversion, and treatment. Paul has been associated with numerous energy, oil, and gas companies, and his years in the industry have offered a good insight into its varying aspects.
The contemporary crude oil separation process involves piping crude oil through hot surfaces. The resulting vapors and liquids are discharged into distillation units. Atmospheric distillation units are present in most refineries, while more complex ones may have vacuum distillation units. The vapors and liquids separate into components known as fractions inside the distillation units, on the basis of their boiling points. Light fractions are on the top and heavy fractions are at the bottom. The lightest fractions, which include liquefied refinery gases and gasoline, vaporize and rise to the top of the distillation tower where they might condense back to liquids. On the other hand, medium-weight liquids like distillates and kerosene stay in the middle of the distillation tower. Liquids that are heavier, like gas oil, essentially, separate lower down in the distillation tower, and the heaviest fractions having the highest boiling points end up settling at the bottom of the tower.
Paul Favret mentions that after the distillation process, the lower-value and heavier distillation fractions can be processed further into lighter and high-value products like gasoline. This is the stage where fractions from the distillation units are transformed into streams that ultimately become finished products. Cracking is the most extensively used conversion method as it makes use of catalysts; pressure, heat, and at times even hydrogen in order to crack heavy hydrocarbon molecules into lighter ones. A cracking unit typically features one or more tick-walled and tall rocket-shaped reactors, along with a network of heat exchangers, furnaces, and other vessels. Complex refineries might have one or more types of crackers, which includes hydro-cracking/hydrocracker units and fluid catalytic cracking units.
Cracking, however, is not the only form of crude oil conversion. Other refinery processes rearrange molecules for the purpose of adding value instead of splitting molecules. For instance, alkylation makes gasoline components by combining a few of the gaseous byproducts of cracking. The process takes place in a series of tall, skinny towers and large, horizontal vessels. The reforming process turns naphtha, a light, and relatively low-value fraction, into high-octane gasoline components with the use of heat, moderate pressure, and catalysts.
The finishing touches take place in the final treatment process. Refinery technicians basically combine a variety of streams from the processing units to make gasoline. The gasoline blend is determined by octane level, vapor pressure ratings, and certain other special considerations.