Mitigation of HF releases

Abstract

Abstract The hazards of hydrogen fluoride (HF) have long been recognized and industry performance reflects sound operating practices. However, full-scale industry-sponsored HF release tests conducted at the US Department of Energy Test Site in 1986 caused concern in view of the toxicity of HF. Ambient impacts were greater than anticipated, and diking, a primary mitigation technique, proved ineffective for releases of pressurized superheated HF. In partial response to these new technical data, an ad-hoc three-component industry cooperative hydrogen fluoride (HF) mitigation and assessment programme (ICHMAP) was begun in late-1987 to study and test techniques for mitigating accidental releases of HF and alkylation unit acid (AUA), and to enhance capabilities to estimate ambient impacts from such releases. The programme's mitigation components have recently been completed while work on the impact assessment component is nearing completion. The purpose of this article is to describe the programme and to summarize the objective, scope of work, structure, and conclusions from the two mitigation components. The objectives and scope of work of the impact assessment component are also briefly described. Detailed and summary reports for each programme component will shortly be available through the US Department of Commerce, National Technical Information Service (NTIS) of Springfield, Virginia, ICHMAP member companies, collaboratively and individually, screened numerous potential mitigation techniques for accidental HF releases including techniques such as total enclosures with exhaust scrubbers, liquid containment dikes, foam application, water sprays, vapour barriers, and surface tension modifying agents. Water sprays and vapour barriers were judged to be the most promising techniques. Accordingly, the ICHMAP mitigation components consisted of both water spray and vapour barrier programmes. The water spray programme investigated the effectiveness of water or augmented water application systems in mitigating accidental releases of both HF and AUA. The vapour barrier programme assessed the effectiveness of vapour barriers in delaying and diluting accidental releases of heavier-than-air HF vapour clouds in an industrial setting and determined what impact such barriers might have on the consequences of an unconfined vapour cloud explosion.