Are intensified processes safer and more reliable than traditional processes? an emblematic case study

One of the best ways of preventing accidents is to avoid hazards by inherently safer design. As many processes, particularly those in the chemicals, nuclear and oil industries, involve the production, handling and use of hazardous substances, process intensification (PI) apparently offers to the plant managers many benefits such as safer, cleaner, smaller, and cheaper equipments. Process Intensification could lead to a higher process flexibility, increased inherent safety and energy efficiency, distributed manufacturing capability, and ability to use reactants at higher concentrations. These goals are achieved by multifunctional reactors, e.g. reactive distillation or membrane reactors, and miniaturization that can be done by employing micro reactors and/or improving heat and mass transfer. Within the benefits of process intensification with reference to process safety the following can be considered: The use of process intensification can reduce the number of process operations, which leads to fewer transfer operations and less pipework, preventing source of leakages; It can be easier to design a smaller vessel to contain the maximum pressure of any probable explosion; For exothermic reactions, the enhanced specific surface area of intensified plants makes heat transfer, and thus heat removal, easier, minimising the triggering potential of a runaway reaction. Process intensification has thus the potential to be a significant factor in the implementation of inherent safety practices Although safety can benefit from process intensification, it should be ensured that new hazards are not created. This can be obtained applying at a early design stage the reliability and safety analysis that are traditionally used in process risk assessment. In this paper in particular the above techniques are applied to a VOC (Volatile organic compound) treatment plant, comparing the traditional plant (a fixed bed reactor) to the intensified reverse flow reactor. From the results of the application of a recursive operability analysis and the successive fault trees fully quantified, some conclusions are drawn from the point of view of the reliability of intensified processes and from the adequateness of risk assessment methodologies.