In addition to the units that directly process hydrocarbons, a refinery will have a number of supporting units providing utilities and other services. These typically include:

• Gas processing - Separation of light ends (propane, butane) from fuel gas coming from distillation and all of the conversion units

• Acid gas recovery - Separation of H2S and CO2 from refinery gas

• Sulfur recovery - Conversion of H2S to elemental sulfur

• Hydrogen production - Generation of hydrogen from natural gas or other hydrocarbons for use in hydrotreaters and hydrocracker

• Hydrogen capture - Extraction of hydrogen from conversion unit gas

• Steam production - Generation of steam for process units

• Cooling water - Cooling water used in process units

• Waste water treating - Removal of contaminants from process and runoff water