What Is Deasphalting?

Mary McMahon

Deasphalting is part of the oil refining process.
Deasphalting is part of the oil refining process.

Deasphalting is a chemical process that separates asphalt and other compounds from petroleum products. It is part of the refining process used to break crude oil down into various components of commercial value. Each barrel of oil can yield a variety of useful products which can be sold after separation. The most common deasphalting tactic uses solvents to extract the asphalt, supervised by a refinery technician who tests the oil and determines how it should be processed.

Deasphalting occurs after the fractional distillation of crude oil.
Deasphalting occurs after the fractional distillation of crude oil.

In refining, crude oil moves through a series of steps to pull out various compounds. Commonly, it is heated in a vacuum for fractional distillation, where the heated components move up a column, dropping out at different temperatures to yield a set of separated compounds. After fractional distillation, individual materials may need further processing. Some products, for example, contain valuable oils and gases that are locked up with asphalt and rendered inaccessible without deasphalting.

The solvent extraction process subjects a sample of mixed materials to solvents that force the asphalt out. This leaves clean, usable oil behind. Refineries can sell the oil or add it to blends, and may subject it to cracking to break down the hydrocarbon chains and use it for other purposes. The asphalt left behind is also salable for use in paving and composition shingle for roofs.

At the deasphalting unit where this process takes place, a refinery worker needs to consider the kind of materials being processed to determine which solvents should be used. The worker can run some chemical tests to find out what compounds are present in a sample, and which solvents would be most appropriate to extract them. Depending on the source and what kinds of refining activities have already occurred, the composition of the sample can be quite variable. Inappropriate solvents may fail to lift the asphalt and other impurities, which would make the resulting oil less usable.

Refineries and chemical companies may experiment with new deasphalting technology to determine if it is possible to get cleaner, more usable materials with greater efficiency. Refining can eat up considerable energy, and firms have to consider how to process the solvents they use. They may be recyclable, in which case a recovery unit can recapture them for use in another treatment, or they may need to be disposed of in a secure area. In either case, time and energy are necessary to handle the solvents and keep the refinery operational. Cutting down on costs associated with refining can keep prices within a reasonable range.

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