Inherently safe chemicals

Hurme, M. Heikkila, A-M. 1998. Synthesis of Inherently Safe Chemical Processes by Using Genetic Optimization and Case-Based Reasoning. In Koikkalainen, P. Puuronen, S. (Eds.). Human and Artificial Information Processing. Finnish Artificial Intelligence Society. Espoo. Pp. 134—143. 

It has become popular in the past few years to talk about the inherently safe chemical plant. Using the dictionary definition of inherent, such a plant would be safe regardless of other forces, including the actions of humans. 

The remaining chapter is in the macroscale, where Englund addresses Opportunities in the Design of Inherently Safer Chemical Plants. He carefully points out that there is no such thing as an inherently safe chemical plant, since there is always risk, but we can make chemical plants inherently safer. The major and minor chemical plant accidents in the past years are constant reminders of the importance of this topic. The day will come when this topic will move from industrial good practice to university research,... 

A chemical substance is safe for a certain use if it is demonstrated that it poses no risk when taking into consideration risk reduction measures that reduce exposure of man or environment [86-88]. However, this is not enough to indicate that it is also a sustainable chemical. A sustainability target consists of the development of inherently safe chemicals (ISCs), for example, without risks for human health and the environment, even without specific exposure control. 

The best-known measure for safety is risk. Risk is defined as the potential for loss or the probability of a specified undesired event s occurring in a particular period of time and its consequences. An inherently safe chemical process is one that avoids hazards instead of controlling them. Heikkila (1999) developed a method for... 

In the words of Trevor Kletz, a pioneer of inherently safe chemical engineering, what you don t have, can t leak. Likewise, what you don t have can t be made the target of a terrorist attack. 

Toxicology examines the dose and time-dependence of interactions between external agents (chemicals and elements) and normal metabolic agents. The first and most important principle of toxicology is that of dose-response, which states that there is a toxic dose and a safe dose for every external agent. Just as there are no inherently safe chemicals (safe under all conditions of exposure), there are also no agents that cannot be used safely by simply reducing the exposure. 

Benson and Ponton (1993) and Ponton (1996) have speculated on the ultimate results of continuing efforts for process minimization. They envision a twenty-first century chemical industry totally revolutionized by technological innovation, automation, and miniaturization. Small, distributed manufacturing facilities would produce materials on demand, at the location where they are needed. Raw materials would be nonhazardous, and the manufacturing processes would be waste free and inherently safe. While their vision of future technology is speculative, we are beginning to see progress in this direction. 

Pilz, V. (1995). Bayer s Procedure for the Design and Qperation of Safe Chemical Plants. Inherently Safer Process Design, 4.54-4.65. Rugby, England The Institution of Chemical Engineers. 

Snyder, P. G. (1996). Inherently Safe(r) Plant Design. Process Plant Safety Symposium, Volume 1, April 1-2,1996, Houston, TX, ed. H. Cullingford, 203-215. Houston, TX South Texas Section of the American Institute of Chemical Engineers. 

Clearly, the designer should always select a process that is inherently safe whenever it is practical, and economic, to do so. However, most chemical manufacturing processes are, to a greater or lesser extent, inherently unsafe, and dangerous situations can develop if the process conditions deviate from the design values. 

The design of inherently safe process plant is discussed by Kletz in a booklet published by the Institution of Chemical Engineers, Kletz (1984) and Keltz and Cheaper (1998). He makes the telling point that what you do not have cannot leak out so cannot catch fire, explode or poison anyone. Which is a plea to keep the inventory of dangerous material to the absolute minimum required for the operation of the process. 

The global rates of heat generation and gas evolution must be known quite accurately for inherently safe design.. These rates depend on reaction kinetics, which are functions of variables such as temperature, reactant concentrations, reaction order, addition rates, catalyst concentrations, and mass transfer. The kinetics are often determined at different scales, e.g., during product development in laboratory tests in combination with chemical analysis or during pilot plant trials. These tests provide relevant information regarding requirements... 

Most factors affecting inherent safety are quite straightforward to estimate since they are e.g. based on the physical and chemical properties of the compounds present. An inherently safe process structure is not possible to define by explicit rules, but one has to rely on standards, recommendations and accident reports. This information is based on the experience gained in the operation practice of different processes (Lees, 1996). For example accident reports, which are made after accidents, give valuable information of the possible weaknesses in the different process solutions. Also extensive databases have been collected from accident reports (Anon, 1996). From this data a database of good and bad designs can be collected. 

The aim of the reasoning is to determine the inherently safe process configuration for this process by using the Inherent Safety Index as an objective function in the genetic optimization. The index can be once again simplified, since the compounds present are fixed by the product produced. Therefore also the physical and chemical properties are fixed and the related subindices are... 

Hendershot, D. C. 1991. Design of inherently safer process facilities. Texas Chemical Council Safety Seminar, Session D, Inherently Safe Plant Design, pp. 2-22. 

Designing and Operating Safe Chemical Reaction Processes (HSE 2000). Published by the U.K. Health and Safety Executive and directed to small to medium-sized chemical manufacturing companies using batch and semi-batch processes. It addresses chemical reaction hazards and inherently safer processes, hazards assessment, preventive and protective measures, and management practices. 

Keller, A., E. Heinxle, and K. Hungerbuhler (1996). "Development and Assessment of Inherently Safe Processes in the Fine Chemical Industry. " International Conference and Workshop on Process Safety Management and Inherently Safer Processes, October 8-11, 1996, Orlando, FL, 213-223. New York American Institute of Chemical Engineers. 

Inadequate information about the potential for catastrophic accidents, the significant costs of secondary prevention and mitigation and the costs of chemical accidents, and the existence of inherently safe[r] alternatives. 

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