2.10 Energy system
The fuel required for the production of steam and power or for the firing of the furnaces originates either from fuels that are produced by the refinery itself (refinery fuels) or from natural gas that is bought outside, or a combination of both. Normally, most or all of the gaseous and liquid refinery fuels used are by-products of refinery processes. The composition and quality of these fuels vary with the crude oils processed. Generally speaking, the refinery fuel pool is a careful balance between energy required, type of crude processed, emission limits and economics.
The majority of the fuel used in a refinery is gas (methane, ethane and ethylene in combination with excess hydrogen) which is internally generated in the different refinery processes and collected in the refinery gas system, but has to be used quickly and cannot normally be sold as a valuable product. RFG, if properly treated, is a low-polluting fuel. Most of the refinery fuel gas systems have two or three alternative sources of supply: refinery gas, imported gas (normally natural gas) and liquified petroleum gas (LPG).[…]