Chemical inherently safer design

Trevor A KletZ/ D Sc / Senior Visiting Research Fellow, Depatiment of Chemical Engineering, Loughborough, University U.K. Fellow, American Institute of Chemical Engineers, Royal Academy of Engineers (U.K.), In stitution of Chemical Engineers (U.K.), and Royal Society of Chemlstiy (U.K.). (Inherently Safer Design)... 

Inherently safer design is a fundamentally different way of thinking about the design of chemical processes and plants. It focuses on the elimination or reduction of the hazards, rather than on management and control. This approach should result in safer and more robust processes, and it is likely that these inherently safer processes will also be more economical in the long run (Kletz, 1984, 1991b). 

These inherently safer design strategies are discussed in more detail in Chapter 3, and examples can also be found in Chapter 4, which discusses inherently safer design opportunities through the life cycle of a chemical process. 

Many of the inherently safer design aspects discussed here appear in Guidelines for Safe Automation of Chemical Processes (CCPS, 1993b). It makes excellent reading for greater depth and treatment of inherently safer/process control concepts. 

Dow (Sheffler, 1996 Gowland, 1996a,b) describes the use of the Dow Fire and Explosion Index (Dow, 1994b) and the Dow Chemical Exposure Index (Dow, 1994a) as measures of inherent safety, along with the use of inherently safer design principles to reduce hazards. 

McCarthy, A. J., J. M. Ditz, and P. M. Geren (1996). "Inherently Safer Design Review of a New Alkylation Process." 5th World Congress of Chemical Engineering, July 14-18, 1996, San Diego, CA, Paper 52b. New York American Institute of Chemical Engineers. 

The concept of inherently safer plant has been with us now for many years. But in spite of its clear potential benefits related to safety, health and the environment (SHE), as well as the costs, there has been few applications in chemical plant design. But as Kletz (1996) has written there are hurdles to be overcome. Inherently safer design requires a basic change in approach. Instead of assuming e.g. that we can keep large quantities of hazardous materials under control we have to try and remove them. Changes in belief and the corresponding actions do not come easily. 

While the basic principle of inherently safer design is generally accepted, it is not always easy to put it into practice. Inherently safer design has been advocated since the explosion at Flixborough in 1974. Progress has been real but nevertheless the concept has not been adopted nearly as rapidly as quantitative risk assessment, introduced into the chemical industry only a few years earlier (Kletz, 1996). 

Intensification is the preferred route to inherently safer design as the plants, being smaller, are also cheaper (Bell, Loss Prevention in the Process Industries, Institution of Chemical Engineers Symposium Series no. 34, 1971 p. 50). 

There, are a number of means of achieving safe operation of chemical, reactors. Usually, the best option is to avoid the hazards completely, or at least minimise them, by inherently safer design. However, this may not be reasonably practicable and,.to maintain a viable process, other safety measures will. be required, either alorie or in combination.. , ... 

Hendershot, D. Berger, S., 2006, Inherently safer design and chemical plant security and safety, American Institute of Chemical Engineering,... 

Inherently safer design of chemical processes involves the use of smaller quantities of hazardous materials, the use of less hazardous materials, the use of alternative reaction routes or process conditions to reduce the risk of runaway exothermic reactions, fires, explosions and/or the generation or release of toxic materials. 

Substitution of an hazardous chemical is often an even more complex problem, in particular regarding the trade-off between inherently safer design and sustainable chemistry. Several examples are discussed in subsequent chapters. We thus limit our discussion here to a few aspects. Up until around the 1960s the Reppe process was employed for of synthesis of acrylic esters ... 

The concept of inherently safer design was first proposed by Kletz, who developed a set of specific design principles for the chemical industry [92] (see also [50]), but it has been publicized and promoted later by many technologists from petrochemical and chemical companies such as Dow, Rohm and Haas, ExxonMobil, and many others. A relevant source of information is the book Inherently Safer Chemical Processes A Life Cycle Approach [49]. 

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