HF Alkylation Units

Overview of HF Alkylation Units

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
  • March/April 2015 Inspectioneering Journal
    By Ana Benz at IRISNDT, Michael O. Nichols at Marathon Petroleum Company, and Bradley Baudier at Marathon Petroleum Company LP

    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 (such as Cr, Ni, and Cu among others) entrained within their carbon steel components.

  • July/August 2004 Inspectioneering Journal
    By Jonathan D. Dobis at The Equity Engineering Group, Inc., Dana G. Williams at Marathon Ashland Petroleum LLC, and David L. Bryan, Jr. at Marathon Ashland Petroleum LLC

    The following is the final part of a 2 part series. Part 1 covered the following considerations that are critical in establishing effective reliability and inspection programs for these complex units: - HF Alkylation Process Description - An extensive explanation of how HF alky unit process conditions affect corrosion for the various sections of these types of units. The abstract, introduction, explanation of terms, references, figures and a typical unit PFD are reiterated in part 2 as reference materials.

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