Safety and environmental impact reduction. a case-study applied to coal dry distillation industry

As reported by Trevor Kletz, changes made to improve the environment have sometimes produced unforeseen and hazardous side-effects. Before changing designs, or methods of operation we should try to foresee their effects and we should balance the risks to people against the risks to environment. Notwithstanding technological development, enforcement of ATEX Directives and safety management system application, explosions in the process sector still claim lives and severe economic losses. Experience shows that in the process industry high severity events frequently occur in auxiliary areas, such as transport and storage of raw materials and products. Even a consolidated process like coke dry distillation allows the opportunity of preventing environmental impact, reducing as well explosion risk connected to fugitive emissions. In this activity, two intervention lines were identified: the former deals with accident risk, i.e. the occurrence of hazardous factors that may cause the ignition of coke oven gas during work activities on pressurized gas pipelines. The latter concerns environmental risk reduction referred to the transport of raw material from the harbour temporary storage site to the final plant. Considering explosion risk in confined environment and possible evolving scenarios, a short-cut mathematical approach to the maximum allowed hazardous substance build-up is developed based on the intrinsic hazards of the released material. This framework from one side will help identifying and assessing small hazardous releases consequences in closed areas and set-up appropriate control measures. From the other side, it is adopted in connection with the design of an underground conveyor belt for coal, so as to limit fugitive emissions. In this context, the study involves an in-depth quantitative risk assessment and the planning of severe control and prevention measures suitable to mitigate explosion/fire risk, both reducing the probability and the severity of adverse consequences. The methodology successfully tested at the real-scale can be applied to more complex situations, allowing, as well, the attainment of a more generalized approach for the design, once given the release parameters, the building and plant layout.