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What is an oil refinery?

An oil refinery is an industrial process facility built specifically to transform and refine crude oil into more useful products such as gasoline, diesel fuel, heating oil, kerosene, liquefied petroleum gas, jet fuel, asphalt base, heating oil, etc.

It also consists of other structures such as storage facilities where refineries store crude oil and refined petroleum products. The oil refinery, a complex structure built on several acres of land, operates 24 hours a day and 365 days a year.

Crude oil in its raw form has little or no value until it is processed through refining processes into various usable products.

How many types of oil refineries are there?

Refineries consist of many different processing units. The combination of these processing units in an oil refinery is called a configuration. The more units an oil refinery has, the better its ability to process heavier crude grades and produce higher rates of higher-value oil products such as diesel and gasoline, and the more complex the refinery.


1. Topping Oil Refinery - Topping Refinery without Conversion

2. Hydroskimming Oil Refinery - Hydroskimming with product processing

3. Conversion or Cracking Oil Refinery - Fracking of oil refinery, transformation of heavier oil

4. Deep Conversion, Coking or Full Conversion or Complex Oil Refineries - Full conversion or deep conversion, maximum conversion.

5. Mineral Oil Refinery

6. Petrochemical Oil Refinery

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1. Topping Oil Refinery

Topping refinery is the simplest refinery configuration designed to produce feedstocks for petrochemical production facilities or industrial fuel production. It is a simple Crude oil distillation unit that produces large quantities of crude oil and is highly dependent on local markets. The raw filling unit consists of tanks, raw distillation unit, gases and light hydrocarbon recovery units and necessary auxiliary systems (steam, electricity and water treatment plants). The Topping refinery produces naphtha but not gasoline. But because they do not have the processing units necessary to reduce sulfur levels, they produce large quantities of weakly refined oil. Additionally, their production is generally limited to the domestic market.


2. Hydroskimming Oil Refinery

The next level of refining is the hydroskimming refinery, which is more complex than the peak refinery. Hydroskimming refinery consists of atmospheric distillation unit, naphtha reforming and necessary purification units. This type of refinery is more complex than the hill refinery and produces gasoline.


Hydro-stripping facilities, a refining facility with greater capacity, can produce refined products from small amounts of raw materials as well as high-octane gasoline. It can also produce naphtha and hydrogen as byproducts. The addition of hydrotreating, hydrocracking, and several other functional units to hydrostripping refineries makes them more efficient than refineries.


3. Conversion or Cracking Oil Refinery - Fracking of oil refinery, transformation of heavier oil

The cracking or hydrocracking refinery is equipped with vacuum distillation and catalytic cracking in addition to the hydroskimming refinery. A conversion refinery includes all the basic units found in both topping and hydroskimming refineries. In addition, the conversion refinery includes residual oil conversion facilities such as catalytic cracking and hydrocracking units and olefin conversion facilities such as alkylation or polymerization units.

The cracking oil refinery configuration uses catalysts, high temperature and high pressure to reduce crude oil, vacuum residue or residual oil into more valuable gasoline and distillate components. Compared to hydroskimming, a cracking refinery adds a vacuum distillation unit and a liquid catalytic cracking (FCC) unit, as well as an alkylation unit or a hydrocracker, to convert vacuum gas oil. Additional feeding or product processing is needed to meet the most stringent specifications.

A refinery with a high gasoline market will prefer FCC (Fluid Catalytic Cracking). Residues can also be converted by Residual Liquid Catalytic Cracking (RFCC). In the diesel market, the cracking refinery will prefer hydrocracking over FCC.

The advantages of cracking refinery are that the elasticity of crude oil is greatly increased and higher value products are produced per barrel of crude. This type of facility can produce greater variation in margins than topping or hydroskimming. However, to achieve operational flexibility, the conversion or cracking refinery needs higher capital and operating costs. It is worth noting that light products are more profitable and environmentally friendly.


4. Deep Conversion, Coking or Full Conversion or Complex Oil Refineries

Deep Conversion refinery is the final level of refining that consists of a combination of all components of a conversion refinery and an additional unit known as a coking unit. The coking refinery is equipped to convert vacuum residue into high-value products using the delayed coking process. The cooking unit makes it possible to process extremely heavy crude oil fractions and convert them into lighter products.

Additionally, deep conversion refinery also converts gases or other hydrocarbon feedstocks into petrochemicals.


Installation of additional conversion capacity increases clean product yield and reduces heavy fuel oil yield. However, increased conversion capacity generally results in higher energy use and therefore higher operating costs. These higher operating and capital costs must be offset by the lower cost of heavier crude oil and profits from selling the products.


• The deep conversion refinery configuration provides refineries with the flexibility to process cheaper, heavier crude and lower quality synthetic crude oil and provide flexibility in crude oil purchasing decisions.

• Modern catalytic cracking and coke refineries produce large amounts of gasoline, with the balance distributed among liquefied petroleum gas, jet fuel, diesel fuel and small amounts of coke. Many such refineries also include solvent extraction processes to produce lubricants and petrochemicals to recover propylene, benzene, toluene and xylenes for further processing into polymers.

• You can see that the potential margin increases significantly as conversion increases. These margins do not include operating costs or shipping costs, which reduce the actual realized margin for each type; but the trend towards greater profitability for a more complex plant still remains even after costs are taken into account.


5. Mineral Oil Refinery

The processes used in the Lube Oil Refinery include extraction and dewaxing of conventional oil stocks. Only about 8 to 10 base lubricating oil stocks are produced from refinery streams. Hundreds of commercial grade lubricating oils used in industry and transportation are blends of these base stocks with some small amounts of specialty additives (mostly organic acid derivatives) included to meet the required specifications.

Mineral oil also has two very important by-products. These are bitumen and waxes. Most refineries include bitumen blending in their configuration, but only a few of the older refineries process waxes.


6. Petrochemical Oil Refinery

The raw materials used for the production of petrochemicals come from refineries that have processes similar to those described previously to produce fuel. In fact, there are only a few refineries worldwide catering exclusively to petrochemical requirements. Most petrochemical feedstocks are produced by varying the operating parameters of normal fuel refinery processes. To meet petrochemical needs, most refinery product flows are adapted as follows:

• Aromatic streams – high in benzene, toluene and xylene, produced a naphtha stream from the naphtha catalytic reforming or Hydrocracking unit.

• Olefin streams – contain high amounts of ethylene, propylene and C4 and originate from the FCCU, thermal cracker or steam cracker unit.

Understanding Crude Oil Refining


A refinery is a well-organized processing facility where crude oil is converted into various useful products. Crude oil refining, on the other hand, is the process of breaking down all organic matter in crude oil and separating it for further reforming.


Crude oil refining includes stages and processes such as distillation, cracking and refining.


Distillation Stage


The distillation step involves boiling the crude oil at two boiling points known as Atmosphere and Vacuum distillation.


Atmospheric distillation, also known as overhead refining, involves heating crude oil at the bottom of a column. The column is usually 60 meters high and the standard heating temperature at this stage is between 350 and 400°C. The essence of heating is to allow evaporation as the temperature drops, while residues remain at the bottom. At this stage of distillation, refineries can obtain methane, light gas, propane, kerosene, gas and fuel oil.


Vacuum distillation, on the other hand, involves heating the bases, which refineries transfer from atmospheric distillation units (ADUs) to vacuum distillation units for further processing. Removing more petroleum products from the residues of the heated oil requires less heating of the bottoms in the VDU. A typical vacuum distillation can produce gas oils, lubricating oil, and heavy oil for deasphalting propane.


Transformation Stage


This process involves using catalysts to speed up chemical reactions while breaking heavy molecules into smaller molecules. It requires converting large hydrocarbons into lighter products such as petroleum and light fuel oil.


At a boiling point of 500°C, the catalyst cracking or conversion process can convert 75% of the heavy products into gas, gasoline and diesel.


Treatment Phase


The processing stage involves removing environmentally unfriendly ingredients from finished products. They ensure that air pollutants such as sulfur are removed from final products as part of refineries' efforts to improve air quality.


Importance of Storage Tanks in Crude Oil Refinery


Storage tanks are crucial to crude oil refining and we cannot emphasize their usefulness enough. Their usefulness is immeasurable because without them there would be no place to store crude oil or finished products. They differ not only in shape but also in size.


Additionally, each refinery has multiple storage tanks to prevent product contamination. So, they provide a separate storage tank for each product to prevent product contamination.

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