Integrating Safety Issues in Solvent Selection and Process Design

Integration of safety aspects in process design has become of utmost significance in light of many chemical process incidents that occur frequently. Solvents are commonly applied in various processes and operations but at the same time they are extremely hazardous materials. Many incidents involving fire/explosion events and toxic exposure events have been escalated because of large amounts of flammable solvents being used in the process. Safety can be integrated into the design of solvent processes by considering inherently safer design concepts. The concept of 'Substitution' can be achieved by making use of Computer Aided Molecular Design (CAMD). Guidance for desired values of hazardous properties can be obtained from previously developed inherent safety indices. The concepts of 'Attenuation' and 'Intensification' can be incorporated by developing safety constraints based on consequence modeling guidelines. Constraints can be placed on several safety requirements such as maximum permissible release amount, maximum concentration levels reached upon release of material and risk associated with fire/explosion/toxic events, while concurrently satisfying constraints on product quality requirements. Suitable limits on effects of hazardous events can be judged from regulatory requirements such as EPA RMP. Employing such techniques in early phases of design can lead to better risk management and application of better risk reduction techniques. In this work, a simple case study on liquid -liquid extraction has been evaluated and the effects of applying such safety constraints on the different process variables have been assessed.