Comparison of methods for assessing environmental, health and safety (EHS) hazards in early phases of chemical process design

This paper compares, qualitatively and quantitatively, some simple environmental, health and safety (EHS) assessment methods that are used in the early phases of chemical process design. The qualitative work summarises the methods into a set of categories, the parameters needed within each category and how each method uses the different parameters to calculate the assessment score. The quantitative part involves the comparison of the methods based on the original process mass calculations, applied to six alternative routes of methyl methacrylate (MMA) production. The results demonstrate that generally, the higher the number of reaction steps, the higher the probability of the process being more hazardous. The more toxic substances a process has, the higher its environmental impact. The use of the reaction mass in the original form defined in each method significantly affected the evaluation results. The use of a unit mass instead gave the same rank pattern of the routes to all the health and safety methods. These unit-mass-based results were further analysed into the level of categories, e.g. fire/explosion, within each EHS aspect, where methods use either different parameters and/or different mathematical formulations or the same parameters and formulations. Surprisingly, in many cases even the results for methods with different parameters and/or formulations agreed rather well. In summary, there is no unique merit of one method over the other in any of the environmental, health and safety aspects. The appropriate simplicity of a method according to early design phase where it can be applied is the only merit that separates the methods. (C) 2007 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.