An oil refinery in Wisconsin, USA will continue to use hydrogen fluoride (HF) in its petroleum alkylation operations once rebuilding efforts have been completed. The Superior Refinery, run by Canada-based Husky Energy, was badly damaged in 2018 after an explosion caused an asphalt tank to rupture, resulting in a major fire. No HF was released during the incident, but local residents were evacuated as a precaution. Husky has decided that the rebuilt facility will continue to use HF, indicating that a review found alternative options would not be commercially viable. Partial operations at the 38,000 BPD refinery are expected to resume in late 2020. Meanwhile, it has been reported that in Los Angeles, USA a County public health official has called on the region’s air quality watchdog to work towards the phase-out of HF use at facilities run by Torrance Refining Company and Valero—the only two HF-consuming refineries in the state. Concerns again centre on the risk posed to nearby residents in the event of an accidental release of the acid.
Petroleum alkylation is the process of converting low molecular weight olefins to more valuable, higher octane fuel products. Strong acid catalysts are required, and the global industry is split between the use of HF and sulphuric acid (H2SO4) although new investments have been dominated by the latter since 1990. Refineries using H2SO4 are considered to pose less of a safety risk as the substance does not readily form a vapour cloud on release. It is, however, more costly than the use of HF, which can be more easily recycled on site meaning much smaller overall volumes are required. Additionally, converting an existing HF facility for the use of H2SO4 is technically challenging and cost prohibitive. An alternative technology, using non-volatile ionic liquids, has been developed by UOP but has yet to be proven on a commercial scale. A 5,000 BPD HF-based alkylation unit operated by Chevron in Utah, USA is being retrofitted with the new technology and is expected to begin operations in 2020.
Given the tendency for new facilities to opt for H2SO4, petroleum alkylation is one of the few end-uses of HF which is not expected to exhibit appreciable growth in demand over the next 3 years. The actual acid-grade fluorspar (acidspar) requirement generated by petroleum alkylation is low, however, probably only representing around 1% of world acidspar consumption in 2018.