Risk-based chemical process route selection considering inherent environmental friendliness

Abstract

Chemical process route selection is one of the key decisions taken during the preliminary design stage of process plant development. A chemical process route is defined as the raw material(s) and the sequence of reaction step(s) that convert them to the desired product. In the past, the 'best' process route was selected solely considering economic factors. However, with the disastrous chemical plant accidents experienced in the past, attention has been drawn to select process routes considering other factors such as inherent environmental friendliness. Therefore, methodologies that assess chemical process routes considering environmental aspects are needed for the development of inherently environmentally friendly chemical process plants. The work presented in this thesis proposes a risk-based methodology to assess and rank chemical process routes considering inherent environmental friendliness using the data available during preliminary design stage of chemical process plant design and development. The environmental impacts that could occur due to chemical plant accidents such as accidental chemical releases, fires and explosions are considered when developing the methodology. In the proposed methodology, the chemical process routes are assessed in three approaches. They are fires and explosions, accidental chemical releases and all these three accidents in combination. Therefore, three risk indices are proposed namely, the Inherent Environmental Risk Index for Fires and Explosions (F&E-IERI), the Inherent Environmental Risk Index for accidental Chemical Releases (Chem-IERI), and the Inherent Environment Risk Index (Chem F&E-IERI). A lower risk index of a process route indicates a lower environmental risk and, thus the most inherently environmentally friendly route among the alternate process routes. The proposed methodology is applied in four potential process routes in acetone production. The results obtained show that the process route that has the lowest environmental risk due to fires and explosions in the chemical plant is the p-diisopropyl benzene oxidation process. The dehydrogenation of 2-propanol process route shows the lowest environmental risk due to accidental chemical release. The chemical route that has the lowest environmental risk due to all three major chemical plant accidents, fires, explosions, and chemical releases is the dehydrogenation of 2-propanol process. Keywords: Environmental risk assessment, chemical process route selection, accidental chemical releases, fires and explosions, inherent safety