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General Introduction

Refining is the manufacture of petroleum products from crude oil. Refining involves two major branches; separation processes and conversion processes.

There are many processes available to the refiner and the final processes chosen is determined by the products required (both quantity and quality) and the crude oil available. Over time changes to either product requirements or available crude oil can result in changes to the refining processes necessary in the refinery.

Refinery Products

Shell Refining Company (SRC) produces the following petroleum products:

  • Liquefied Petroleum Gas, or "LPG"
  • Propylene
  • Gasoline, or Petrol
  • Jet Fuel, or Avtur
  • Gasoil, or Diesel
  • Sulphur

SRC also produces a number of petroleum components which can either be sold or processed in the refinery.

Crude Oil

Petroleum products are made from Crude Oil. There are many types of crude oil which come from many different sources around the world.

Selection of the right crude oil is a key part of the refining process. The decision as to what crude oil, or combination of crude oil, to process depends on many factors including; quality, availability, volume, and price.

Shipping costs (or "Freight") are another important element in crude oil selection and are determined by the size of the cargo and the distance from the supplier to the refinery.


The first stage of crude processing is known as distillation, or fractionation, and occurs in a column known as a Distillation Column.

In this process, the crude oil, which is a mixture of many types of hydrocarbons, is boiled and recondensed to separate the crude oil into components based on ranges of boiling points.

Components which are heavier are harder to boil and will collect in the lower part of the column. Lighter components are easier to boil and will be collected in the upper part of the column.

Very heavy components which are unable to boil will leave from the bottom of the column, in a stream known as residue, while very light components will leave from the top of the column. This stream is known as Liquefied Petroleum Gas, or LPG.


To meet environmental specifications or to assist is further processing, some components then undergo a process known as hydroprocessing. The objective of this process is to remove sulphur from the component stream.

This process will consume hydrogen to assist in the sulphur removal. The sulphur removed from this process is converted into pure liquid sulphur and is sold to local industry for the production or acid and fertiliser.


This process converts a low value component called 'naphtha' into a product known as reformate or platformate. This reformate has a much higher octane number and is used for gasoline blending.

This is achieved using a catalyst that contains platinum.

Catalytic Cracking

This conversion process involves the breaking up of large hydrocarbon molecules into smaller molecules using a combination of heat and catalytic action.

The unit at SRC is a Long Residue Catalytic Cracking (LRCC) unit and takes a heavy hydrocarbon stream called Long Residue and converts it into a number of more valuable components and products, including LPG, Propylene and some Fuel Oil components. However, the main product form the SRC LRCC is a gasoline blending component known as Cat Cracked Gasoline (CCG).

A by-product of this process is Coke (or carbon), which is burnt to generate steam and electricity.

Secondary Treating

The refinery also has a number of smaller, so-called "secondary" processes. These are mainly involved with further polishing of components and products to remove sulphur and other impurities.


The final stage of the refining process is called blending. This is a crucial step where the various hydrocarbon components manufactured in the refinery are mixed together to make the final products sold by the refinery. The final blend recipes will depend on the quality of the available components and on the customer's requirements, called specifications.

All blended products are tested before they are sold to ensure that they meet the customer's specifications.

Product Distribution

Once the petroleum products are blended and tested they can then be delivered to our customers.

In the case of SRC, the main distribution channels are ship, pipeline, road tanker, and rail car.

Refining Process Animation

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