Inherent Safety Research

Development of a Hierarchical Fuzzy Model for the Evaluation of Inherent Safety

Inherent safety has been recognized as a design approach useful to remove or reduce hazards at the source instead of controlling them with add-on protective barriers. It is widely accepted as a good engineering practice. However, inherent safety is based on qualitative principles that cannot easily be evaluated and analyzed, and this is one of the major difficulties for the systematic application and quantification of inherent safety in plant design. During the last few years, several measurement techniques and analysis tools have been developed to estimate the degree of inherent safety of a plant or a process unit. To address this problem, here we propose the use of fuzzy logic for the measurement of inherent safety by proposing a hierarchical fuzzy model (Gentile, 2004). This project has the objective to bring inherent safety to systematic quantification and analysis by proposing a mathematical tool to work with subjective, uncertain, and imprecise data and to incorporate information from experience and heuristic knowledge. It can be applied to process design, process synthesis, evaluation of inherent safety, process simulation, and transportation of hazardous substances. A more ambitious goal of this research is to break the traditional boundaries of safety ideology associated with the idea that safety is subjective and hence non-quantifiable. The only aspect of safety that is subjective is associated with human factors.

Integrating Process Safety into Process Design and Optimization

The principle of inherent safer design is cheapest if applied at the early stage of process development and design. And, the integration of safety into process design and optimization is highly desired. This research proposes a procedure for integrating safety into design and optimization framework by using safety parameters as an optimization constraint (Suardin, 2005).

As a preliminary attempt, this research employs Dow’s Fire and Explosion Index as a safety parameter to be integrated into process optimization. The proposed procedure of integrating F&EI into process design and optimization framework is verified by applying it into process design and optimization of reactor-distillation column system. As mentioned earlier, this research is focused on integrating safety, not the Dow’s fire and explosion index, into process design and optimization framework. Developing or improving existing evaluation index to generate the safety expression gives better safety parameter representation, which couples this research with the inherent safety index research at the Center.

Practical risk reduction for refining processes

Process safety has been emphasized in the petroleum refining and petrochemical industry over the decades. This is especially true in the refinery unit processes, where reactive and hazardous materials are handled at elevated temperatures and pressures. The guiding principles of inherent safety have been clearly illustrated by Trevor Kletz. While there is no argument against the concepts of inherent safety principles, the application of these principles often gives rise to a discussion of overall risk. The current research includes a literature review of the fundamental concepts and evaluation systems that have been applied to the petroleum industries for previously implemented risk reduction projects.

This project is an attempt to identify practical risk reduction options for the petroleum industry to make its operations inherently safer in a pro-active manner. Future directions of this research include an in-depth review of the hazards existing in the major processes in the petroleum industry and a comprehensive synthesis of the technology and equipment that have been used or proposed to enhance safety and reduce risk. General guidelines to evaluate a process in terms of the holistic impact to the greater system can be developed from this study.

Inherently Safer Design of Ethanol Plants

The proposed systematic approach is based on the fact that Inherently Safer Design is best implemented in the early stages of a plant. Ethanol can be made by a dry mill process or a wet mill process. Most of the ethanol in the U.S. is made using the dry mill method. In the dry mill process, the starch portion of the corn is fermented into sugar then distilled into alcohol. The first stage of the technical approach will be to determine which portion of the ethanol production process has the largest area of opportunity. Early literature review is showing that dust explosions and transportation may be the most significant areas of opportunity. After the area of opportunity is identified the next step is to determine which inherent safety principle (intensification, substitution, attenuation, simplification, limitation) will best minimize or eliminate hazards from the ethanol production process. Because safety must be balanced with profitability, the last step in this approach is to determine the financial impact of proposed changes.

Task 1: Identify specific areas of opportunity (dust explosions, transportation)
Task 2: Develop inherently safer recommendations for each area of opportunity
Task 3: Evaluate financial impact of proposed changes

Integrating Safety Issues in the Process of Optimizing Solvent Selection
Facility Siting
Natural Gas Emissions