Common process units found in a refinery
• Desalter unit washes out salt from the crude oil before it enters the atmospheric distillation unit. • Atmospheric distillation unit distills crude oil into fractions. See Continuous distillation. • Vacuum distillation unit further distills residual bottoms after atmospheric distillation. • Naphtha hydrotreater unit uses hydrogen to desulfurize naphtha from atmospheric distillation. Must hydrotreat the naphtha before sending to a Catalytic Reformer unit. • Catalytic reformer unit is used to convert the naphtha-boiling range molecules into higher octane reformate (reformer product). The reformate has higher content of aromatics and cyclic hydrocarbons). An important byproduct of a reformer is hydrogen released during the catalyst reaction. The hydrogen is used either in the hydrotreaters or the hydrocracker. • Distillate hydrotreater unit desulfurizes distillates (such as diesel) after atmospheric distillation. • Fluid catalytic cracker (FCC) unit upgrades heavier fractions into lighter, more valuable products. • Hydrocracker unit uses hydrogen to upgrade heavier fractions into lighter, more valuable products. • Visbreaking unit upgrades heavy residual oils by thermally cracking them into lighter, more valuable reduced viscosity products. • Merox unit treats LPG, kerosene or jet fuel by oxidizing mercaptans to organic disulfides. • Coking units (delayed coking, fluid coker, and flexicoker) process very heavy residual oils into gasoline and diesel fuel, leaving petroleum coke as a residual product. • Alkylation unit produces high-octane component for gasoline blending. • Dimerization unit converts olefins into higher-octane gasoline blending components. For example, butenes can be dimerized into isooctene which may subsequently be hydrogenated to form isooctane. There are also other uses for dimerization. • Isomerization unit converts linear molecules to...
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