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Refining process

Crude oil refining is about converting the raw material into the oil products that consumers demand.

Crude oil refining is about converting the raw material into the oil products that consumers demand. Crude oil is pumped ashore from large tankers and into crude oil tanks. From there it is pumped through a heating system (heat exchangers and furnace) to the main distillation tower for a "primary sorting" of the various main components.

The refining processes are monitored and controlled from a control center by means of advanced electronics and computer based control programs.

The loading and discharge of raw material and oil products are handled from a separate control room located by the pier. The control room also monitors the tank farm, the water treatment plant, and various pump operations. The refinery is operated around the clock all around the year, with highly qualified technicians keeping a vigilant eye on operations at all times. Temperatures, pressure and through-put in all parts of the plant may be monitored from the two control rooms. The operation is optimized to get an optimum value added in the form of oil products using the lowest amount of energy possible.

Crude oil

Crude oil is a mixture of hundreds of different types of chemical substances (made up of carbon and hydrogen) called hydrocarbons. No other natural raw material has to the same extent impacted the evolution of contemporary industrial society. Crude oil is fractionated and processed into the products that the market demands. Crude oil comes in all varieties, from very light (e.g. North Sea crudes) to very heavy crudes.

Examples of the composition of three North Sea crudes and one Arabic are provided below, with highly qualified technicians keeping a vigilant eye on operations at all times. Temperatures, pressure and through-put in all parts of the plant may be monitored from the two control rooms. The operation is optimized to get an optimum value added in the form of oil products using the lowest amount of energy possible.

Fuel gas sulfur recovery plant

The sulfur recovery plant is required for the control of the refinery emissions of SO2 and the contribution to acid rain. Sulfur removed from the products in the desulfurization processes, has to be removed from the refinery gas before it is fired in the process furnaces. Thus one achieves that neither the products nor the refinery’s own energy consumption contribute to acidification of the environment. The hydrogen sulphide gas is converted to liquid sulphur which is sold to the paper and pulp processing industry.


These processes remove sulfur from the petrol production feedstock, diesel oil and gas oil.

This happens at high temperature and high pressure in the presence of hydrogen gas and a catalyst (enhances the speed of reactivity). Sulfur is removed as hydrogen sulfide gas which is fed to the sulfur treatment plant.

Visbreaking of heavy oil

The visbreaker converts 25-35% of the heavy bottoms from crude oil distillation into lighter and more valuable products (gas, naphtha and diesel). This is carried out through thermal cracking where heavy oil molecules are exposed to such high temperatures (460ยบC) in the visbreaker furnace that they crack into smaller and lighter molecules.

The converted product is separated through distillation and further processing in desulfurization plants before they can be sold or processed further. The plant provides an important adjustment by bringing the refinery's product yield more in line with market demand. The bulk of the heavy fuel oil production is exported to power plants and as bunker fuel for ships.

Clean fuel gas

After sulfur removal the refinery produced gas is fired in process furnaces to heat up feed to the different plants. The gas consists of hydrogen and light hydrocarbons, mainly methane and ethane.

Petrol plant

Naphtha, which is a lighter fraction of the crude oil, is the raw material for gasoline production. The octane number of the naphtha is too low, and has to be increased before it may be used as motor fuel.

First, sulfur is removed in a desulfurization plant, and next the octane number is increased from around 50 to 100 in a catalytic reformer. It is this product, the reformate, which is the main component in the gasoline marketed at the petrol stations.

The naphtha is mixed with suitable components to make the end product gasoline. By conversion of naphtha to reformate, hydrogen is split from the naphtha molecules, and this hydrogen gas is used in all desulfurization plants.

In 1998, a separate benzene extraction plant was installed to comply with new petrol specifications.


Sulfur components removed in desulfurization processes are converted into pure sulfur (yellow solid at ambient temperature). This non-hazardous material is used by the paper and pulp processing industry.


Naphtha is a light hydrocarbon fraction. Distinction is made between light naphtha with a boiling range from 30-70°C, and heavy naphtha with a boiling range from 60-170°C. Small volumes of light naphtha are mixed into the gasoline, but the bulk of the production goes to the petrochemical industry. The heavy naphtha is feed stock for the petrol production.


LPG, Light Petroleum Gas, is a generic term for propane and butane. LPG is used for heating, transportation fuel, and in the petrochemical industry.

Kerosine / jet fuel

ESSO FYRINGSPARAFIN is a kerosene ideally suited for heating purposes. Until 2000, the product was clear as water and without color. ESSO FYRINGSPARAFIN may be used for all types of wick burners and burner pots. It does not provide a high enough flame before sooting, so for lighting purposes, illuminating kerosene is recommended. As from 20 February 2000 ESSO FYRINGSPARAFIN has a green color. The dye has no effect on  the combustion.

Aviation fuel has the same properties as kerosene, but has to meet much more stringent quality requirements. Slagen produces and supplies two types of aviation fuel – one for the Norwegian defense and one for civil aircraft. The fuel produced for the defense contains additives which makes it better suited for storage.

Unlike kerosene aviation fuel is not colored green.

Diesel/ light fuel oil

For cars and boats, a large number of diesel types, as well as different types of fuels, may be employed.

1. Diesel

Advanced fuel for you and your engine

At Esso we pride ourselves on developing fuels to help your engine run more smoothly. That’s why our advanced fuels have been developed with you and your engine in mind:

  • Diesel 2000. Our regular diesel grade that helps improve your fuel economy

Our fuels are developed to help your car’s engine deliver better performance. They also work at a molecular level to help remove deposits that have formed in your fuel system. This helps your engine’s fuel economy wherever you are driving towards.

Esso diesel has been engineered to help*:

  • Clean diesel fuel injectors
  • Improve fuel economy
  • Improve engine responsiveness
  • Reduce emissions
  • Protect engines from corrosion

We Fuel Progress.

2. Esso Offroad Diesel/ Diesel for plants and factories

Esso Offroad Diesel OLJE (diesel oil) is a standard diesel exempted from tax which is employed for special purposes such as construction machines, tractors etc. As from 20.02.2000 the product is colored green.

3. Esso Light Diesel

Esso Lettdiesel  (light diesel) is a kerosene based diesel, which gives the product excellent cold resisting properties, with an operational limit touching -50°C. To avoid increased wear of the diesel pump, lubricant is added to the product. Esso Lettdiesel has a slightly lower cetane rating and density than conventional ADO. When switching to this type of fuel this can be noticed through reduced traction force. If the conditions demand it (low outdoor temperature, tunneling etc.) Esso Lettdiesel may be employed for high-speed diesel engines.

4. Esso Low Sulfur Gas Oil (LSGO)

Esso Lavsvovel Gassolje (LSGO) (Low sulfur gas oil) is a gas oil with good ignition and combustion properties, and with cold resisting properties adapted to summer and winter climates in Norway. The product has a low sulfur contents to meet stricter environmental standards, and good lubrication properties. LSGO is suited for use in marine high-speed and medium speed diesel engines.

5. Esso Fuel Oil No.1

Esso Fyringsolje NR.1 (fuel oil no. 1) is a light fuel oil, with good combustion properties and suited for plants designed for light fuel oil.

6. Esso Marine Gas Oil (MGO)

Esso Marine Gassolje (marine gas oil) is a gas oil with good ignition properties suitable for use in marine high-speed and medium speed diesel engines.

7. Esso Marine Spesial (EMS)

Esso Marine Spesial is a heavy marine distillate quality suitable for use in all marine medium speed diesel engines.

8. Esso Special Fuel Oil (EFS)

Esso Fyringsolje Spesial (special fuel oil) is suitable for use in oil-heating plants with medium large oil burners where the fuel oil may be preheated to meet the proper atomization for viscosity.

Heavy distillates

Heavy distillate (Heavy Atmospheric Gas Oil) is a heavy hydrocarbon fraction with a density of 0.92 kg/l. It contains approx. 0.5 % sulfur and has a dark, brandy-colored hue. HAGO is shipped from Slagentangen to other refineries/chemical industry for further processing.

Heavy fuel oil

The heaviest of our products. It is black in color and contains around 1% sulfur. Heavy oil is used as bunker fuel on tankers, and as fuel oil in heavy industries.

*Emissions refers to CO, HC and NOx. Claims based on one or more of the following: (1) internal or third party vehicle engine testing; (2) government publications; and/or (3) industry or other scientific literature. Basis for comparison for all claims is versus unadditised standard fuel. Available at participating Esso service stations only. Engine type, driving behaviour and other factors may also determine fuel and vehicle performance, including emissions and fuel economy. Digital simulation of product and artistic rendition of engine have been used. Esso, Esso. We Fuel Progress are trademarks of Exxon Mobil Corporation.