HF Acid Alkylation Processes: Pump and Mechanical Seal Application and Design Considerations for Increased Reliability

Abstract

Hydrofluoric (HF) acid is an extremely corrosive solution commonly found in many oil refineries where it is used as a catalyst in the production of high octane gasoline blending stock. HF acid is almost synonymous with the alkylation unit, which is where the processing takes place within the refinery process flow. There are two main alkylation processes available, HF and Sulfuric acid; this tutorial will focus on HF alkylation and the challenges associated with handling this solution and the process streams that come in contact with HF acid. The HF alkylation process uses hydrofluoric acid which is dangerous and requires special treatment, particularly in the area of shaft sealing along with pump design and construction. While each individual facility may have its safety and reliability guidelines in place to manage HF acid and exposure to it, it is universally accepted in industry that minimizing personnel exposure to this fluid is a prime concern. This tutorial will attempt to address several topics centered on reliable operation of pumps in an HF alky unit, including pump and mechanical seal design and construction, along with mechanical seal support system considerations. In covering these topics, the tutorial will draw upon the combined previous experience of the authors in addressing these applications along with accepted good practices from relevant industry standards. The reader should review the content and consult as a reference, keeping in mind that not all of the content is applicable to every application and that each application should always undergo a thorough engineering review.