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HF Alkylation Units

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Hydrofluoric Acid (HF) Alkylation Units, often referred to as HF Alky units, are process units used in petroleum refining to convert isobutane and alkenes (primarily propylene or butylene) into alkylate, which is used to make gasoline.

Before being transferred to the alkylation unit, the alkenes are generated in a fluidized catalytic cracking unit (FCCU). Once in the alkylation unit, the alkenes react to the isobutane while in the presence of a catalyst, causing the two substances to combine, creating the alkylates. In HF Alkylation units, hydroflouric acid is used as the catalyst.

The alkylation process itself generates a significant amount of heat. Because of this, regular cooling is required. HF Alkylation units are particularly vulnerable to hydrofluoric acid corrosion.

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Articles about HF Alkylation Units
Blog

There are some significant changes coming in the fifth edition of API RP 751 on Safe Operation of Hydrofluoric Acid Alkylation Units in the section on Mechanical Integrity, Damage Mechanisms and Maintenance Work Practices.

Authors: John Reynolds
March/April 2015 Inspectioneering Journal

This article provides a discussion of a recent inspection performed at a U.S. refinery. Industry HF lines are experiencing piping failures in increasing numbers due to the presence of residual elements entrained within their carbon steel components.

January/February 2005 Inspectioneering Journal

Hydrogen stress cracking occurs when corrosion from acids like wet hydrogen sulfide or hydrofluoric acid (HF) cause atomic hydrogen to penetrate hardened or higher strength steels and cause stress cracking.

Authors: John Reynolds
July/August 2004 Inspectioneering Journal

The following is the final part of a 2-part series outlining the relationship between key operating parameters and corrosion that has been used to develop a set of guidelines to define an operating envelope.

May/June 2004 Inspectioneering Journal

Corrosion and fouling in HF Alkylation Units are closely linked to feed quality and operating conditions. This article outlines the relationship between key operating parameters and corrosion that has been used to develop a set of guidelines to...

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FFS assessment techniques are applicable to a wide range of damage types: LTA's, cracks, creep damage, dents, and more. These are very powerful analytical tools that often allow operators to not only keep the plant running, but to keep it running...

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