A de-asphalter is a unit in a crude

oil refinery An oil refinery or petroleum refinery is an industrial processes, industrial process Factory, plant where petroleum (crude oil) is transformed and refining, refined into products such as gasoline (petrol), diesel fuel, Bitumen, asphalt base, ...

or bitumen upgrader that separates

asphalt Asphalt most often refers to: * Bitumen, also known as "liquid asphalt cement" or simply "asphalt", a viscous form of petroleum mainly used as a binder in asphalt concrete * Asphalt concrete, a mixture of bitumen with coarse and fine aggregates, u ...

from the residuum fraction of

crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...

bitumen Bitumen ( , ) is an immensely viscosity, viscous constituent of petroleum. Depending on its exact composition, it can be a sticky, black liquid or an apparently solid mass that behaves as a liquid over very large time scales. In American Engl ...

. The primary purpose of the separation is to remove contaminants (asphaltenes, metals) from the feed that would cause rapid deactivation of catalysts in downstream processing units. In doing so, the de-asphalter is the first step in a series of processes that upgrade a low-value

feedstock A raw material, also known as a feedstock, unprocessed material, or primary commodity, is a basic material that is used to produce goods, finished goods, energy, or intermediate materials/Intermediate goods that are feedstock for future finishe ...

to high-value refined products. The de-asphalter unit is usually placed after the vacuum distillation tower and receives feed from the bottom (residuum) stream. It is usually a solvent de-asphalter unit, SDA. The SDA separates the asphalt from the feedstock because light hydrocarbons will dissolve

aliphatic In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated (in which all ...

compounds but not

asphaltene Asphaltenes are molecular substances that are found in crude oil, along with resins, aromatic hydrocarbons, and saturates (i.e. saturated hydrocarbons such as alkanes). The word "asphaltene" was coined by Jean-Baptiste Boussingault in 1837 whe ...

s. The output from the de-asphalter unit is de-asphalted oil ("DAO") and

. DAO from

propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...

de-asphalting has the highest quality but lowest yield, whereas using

pentane Pentane is an organic compound with the chemical formula, formula C5H12—that is, an alkane with five carbon atoms. The term may refer to any of three structural isomerism, structural isomers, or to a mixture of them: in the IUPAC nomenclature, h ...

may double or triple the yield from a heavy feed, but at the expense of contamination by metals and carbon residues that shorten the life of downstream cracking catalysts. If the

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

butane Butane () is an alkane with the formula C4H10. Butane exists as two isomers, ''n''-butane with connectivity and iso-butane with the formula . Both isomers are highly flammable, colorless, easily liquefied gases that quickly vaporize at ro ...

the unit will be referred to as a butane de-asphalter ("BDA") and if the solvent is

, it will be called a propane de-asphalter ("PDA") unit.

References

Study of selected petroleum refining residuals by US EPALubricants and Lubrication (Second Edition)

External links

Solvent de-asphalting

Solvent de-asphalting of vacuum residuumAsphalt used for gasification
{{Petroleum refining Chemical equipment Distillation Petroleum technology