Oil refining and distribution

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Content – Energy distribution

 


 
Refining – An oil refinery is a chemical plant that process and refine crude oil into useful products such as petroleum naphtha, gasoline, diesel fuel, asphalt base, heating oil, kerosene and liquefied petroleum gas. The crude oil feedstock has normally has been processed or stabilized by an oil production plant.

Petroleum products are grouped into three categories:

  • Light distillates (LPG, gasoline, naphtha)
  • Middle distillates (kerosene, diesel)
  • Heavy distillates and residuum (heavy fuel oil, lubricating oils, wax, asphalt).

This classification is based on the way crude oil is distilled and separated into fractions.

Main products:

  • Liquified petroleum gas (LPG)
  • Gasoline (also known as petrol)
  • Gasoline (also known as petrol)
  • Naphtha
  • Kerosene and related jet aircraft fuels
  • Diesel fuel
  • Fuel oils
  • Lubricating oils
  • Paraffin wax
  • Asphalt and tar
  • Petroleum coke
  • Sulfur

Other products:

  • Hydrogen,
  • Light hydrocarbons,
  • Reformate and pyrolysis gasoline.

These products are normally blended or processed further in petrochemical plants.

Main componets of an oil refinery:

Desalter unit – Washes out salt from the crude oil before it enters the atmospheric distillation unit.

Fractinonal distillation unit (crude oil distillation tower) – Distills crude oil into fractions.

Vacuum distillation unit – Further distills residual bottoms after atmospheric distillation.

Naphtha hydrotreater unit – Use hydrogen to desulfurize naphtha from atmospheric distillation.

Catalytic reformer unit – Used to convert the naphtha-boiling range molecules into higher octane reformate (reformer product). 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 – 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 – Uses sulfuric acid or hydrofluoric acid to produce high-octane components 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.

Isomerization unit – Converts linear molecules to higher-octane branched molecules for blending into gasoline or feed to alkylation units.

Steam reforming unit – Produces hydrogen for the hydrotreaters or hydrocracker.

Liquified gas storage vessels – Store propane and similar gaseous fuels at pressure sufficient to maintain them in liquid form.

Storage tanks – store crude oil and finished products,.

Amine gas treater, Claus unit, and tail gas treatment – Convert hydrogen sulfide from hydrodesulfurization into elemental sulfur.

Utility units – Such as cooling towers circulate cooling water, boiler plants generates steam, and instrument air systems include pneumatically operated control valves and an electrical substation.

Wastewater collection and treating systems – Consist of API separators, dissolved air flotation (DAF) units and further treatment units such as an activated sludge biotreater to make water suitable for reuse or for disposal.

Solvent refining units – Use solvent such as cresol or furfural to remove unwanted, mainly aromatics from lubricating oil stock or diesel stock.

Solvent dewaxing units – Remove the heavy waxy constituents petrolatum from vacuum distillation products.

The fractional distillation process is one of the most basic and common processes within an oil refinery.

The incoming crude is heated to its boiling point before it enters the distillation column, which separates the different fractions. This is a reflux column where condensed fluids running downward are reheated by rising vapours that in turn condense. Thermal zones are created and different products may be drained.

Distribution – Products (fractions) resulting from the refining are blended into markeable products according to standard or client specific specifications. Distribution from the refineries to terminals, other industry or gas stations is by pipeline, ship, rail or truck.