How does an oil refinery work?

What is an oil refinery?

An oil refinery, also known as a petroleum refinery, is an industrial process plant that converts and refines crude oil into useful products such as gasoline (petrol), Diesel, Asphalt base, Fuel oils, Kerosene, LPG, and Naphtha.

What does an oil refinery do?

An oil refinery breaks crude oil into various components and then reconfigure it into new products such as Petrol, Diesel, LPG, Naphtha, etc.

How does an oil refinery work?

Every oil refinery is based on three following basic steps. They are

  • Separation (Distillation)
  • Conversion
  • Reforming
  • Blending and treatment


Separation is considered the primary step of processing crude oil. Separation involves distillation at atmospheric pressure or under a vacuum. Separation makes the separation or breaking of crude oil into various products.

Separation is also known as the distillation process.

The liquids and vapors inside the towers separate into components or fractions based on weight and boiling point. The lightest fractions, such as Gasoline and Liquid Petroleum Gas (LPG) vaporize and rise to the tower’s top, where they condense back into liquids. Medium-weight liquids, such as Kerosene and Diesel oil distillates, remain in the center. (Heavier liquids, known as gas oils, separate lower down, while the heaviest fractions with the highest boiling points sink to the bottom.)


This process involves a number of processes that alter the size and structure of hydrocarbon molecules. These hydrocarbon molecules are divided and decomposed using hydro, thermal, and catalytic cracking, or coking. The molecule arrangements are combined and rearranged during the unification and alteration processes. These hydrocarbon molecule manipulations result in the various grades of crude oil that must be treated.

Some of the conversion processes are

  • Visbreaking
  • Fluid Catalytic Cracking
  • Hydrocracking
  • Delayed Coking


A mild form of thermal cracking reduces the viscosity of heavy crude-oil residue while maintaining the boiling point range.

Fluid Catalytic Cracking

The crude oil is separated or cracked in the presence of a catalyst that is kept aerated or fluidized by the oil.


Hydrocracking is a two-stage process that combines catalytic cracking and hydrogenation to produce more desirable products by cracking heavier feedstocks in the presence of hydrogen.

Delayed Coking

The heated charge (typically residuum from atmospheric distillation towers) is transferred to large coke drums, which provide the necessary residence time for the cracking reactions to complete.


Another process designed to increase the amount of gasoline that can be produced from a barrel of crude oil is reforming. Hydrocarbons in the Naphtha (another petroleum byproduct) stream, for example, have roughly the same number of carbon atoms as those in gasoline, but their structure is generally more complex. Naphtha hydrocarbons are rearranged into gasoline molecules during the reforming process.

Blending and treatment

Hydrocarbon fractions, additives, and other components are formulated and blended to create finished products with specific performance characteristics.

There are numerous other operations and facilities within the plant that have an indirect impact on the refinery process, such as all water treatment processes, cooling, hydrogen production, and so on. There are also non-process related facilities such as utilities, power generation, product movement, tank storage, flares, alarms and sensors, control rooms, and many others that contribute to the efficiency and safety of refineries.

Some useful questions and answers

1. What does an operator do at a refinery?

A refinery operator monitors and controls specialized equipment that processes raw material into products.

2. What temperature does crude oil become petroleum Oni?

402.85 °C