Since the 1960s, hydrocracking units have been developed as a core unit in a complex refinery. In the early decades, the reactor and REAC coolers were made from carbon steel. Multiple studies in the 1970s, 80s and 90s showed that corrosive attacks were a major problem for these units.
Several failures and loss of containment have been observed, NH4 and H2S form corrosive ammonium bisulfide NH4HS and ammonium chloride NH4Cl salts. These salts deposit in the top row of tubes and cause corrosion. Wash water is applied with mixed success to dissolve these salts. The MOC of these REACs has changed over the years from the aforementioned CS to SS316 and Duplex. The latter has, however, posed significant problems in header box welds, often due to manufacturing problems related to the two-phase duplex. Alloy 825 is currently the most commonly used construction material and has been advised by several licensors.
In the latest version of API 932-b, numerous improvements have been proposed for a safe and reliable REAC. Bronswerk Heat Transfer understands the issues and can design and produce a customized REAC for both greenfield and brownfield applications.