A QUANTITATIVE RISK MANAGEMENT FRAMEWORK FOR DUST AND HYBRID MIXTURE EXPLOSIONS
Dust and hybrid mixture explosions continue to occur in industrial processes that handle fine powders and flammable gases. Considerable research is therefore conducted throughout the world with the objective of both preventing the occurrence and mitigating the consequences of such events. In the current work, research has been undertaken to help advance the field of dust explosion prevention and mitigation from an emphasis on hazards to a focus on risk. Employing the principles of quantitative risk assessment (QRA) of dust and hybrid mixture explosions, a methodological framework for the management of these risks has been developed. The Quantitative Risk Management Framework (QRMF) is based on hazard identification via credible accident scenarios for dust explosions, followed by probabilistic Fault Tree Analysis (using Relex – Reliability Excellence – software) and consequence severity analysis, represented by maximum explosion pressure, (using DESC – Dust Explosion Simulation Code – software). Identification of risk reduction measures in the framework is accomplished in a hierarchical manner by considering inherent safety measures, passive and active engineered devices, and procedural measures. Dust explosion tests to determine icing and granulated sugar dust explosibility characteristics have been achieved in a 20-L Siwek chamber, and, accordingly, DESC fuel files were built and DESC has validated. Three industrial case studies are presented to show how the QRMF could has been helpful in reducing dust and hybrid mixture explosion risk at the Imperial Sugar refinery, the Semabla grain storage silo, and a hypothetical 400-m3 polyethylene storage silo. DESC simulations and Probit equation for structural damage provide the destructive percentage of each pressure zone in the simulations, followed by probabilistic FTA that were achieved for the first two case studies, before and after applying the framework. Detailed individual and societal risks calculations were made and F-N curves plotted for the two processes. The polyethylene silo case study is presented to show how inherent safety measures can be helpful in reducing dust and hybrid mixture explosion risk. The framework showed significant risk reduction to the point where the residual risks are acceptable for both processes. Finally, assessment results are compared and improvements measured.