Inherently safe processes

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. 

This section discusses how a runaway reaction occurs and lists some of the process deviations that can lead to such a runaway. Equipment for identifying potentially hazardous process steps is reviewed, and general principles for inherently safe process design are given. 

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... 

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. 

The rates of reaction (energy release in the form of heat or pressure) which depend on the temperature, pressure, and concentrations. In any hazard evaluation process, the rates of reaction during normal and abnormal operations (including the worst credible case) must be considered in order to design an inherently safe process. 

Because there is always risk when equipment, instrumentation, and human activity are involved, there is no method of making a plant completely safe. However, facilities can be made inherently safer by careful examination of all aspects of design and management, using modem techniques that are now available. If we are to improve our process safety performance and our public image, inherently safe process design coupled with inherently safe process management is imperative. 

Is risk management an issue or can the material be created by an inherently safe process ... 

The synthetic processes of traditional chemical industry vill be strongly affected by new opportunities offered by biotechnology and process intensification (such as micro-reaction technology). The fiexible integration of inherently safe process technologies w ith small holding volumes w ill be a key to success for future products. 

A reduction in size means also a better controlled process and the managing of lower amounts of chemicals per reactor. In addition, microreactors often offer intrinsically safer operations [3]. In fact, with respect to conventional reactors, they offer a much better control of heat transfer (e.g., reduced possibility of runaway reactions) and a higher wall to volume ratio, which minimize the possibility of side radical reactions (e.g., of explosion). PI concepts are thus essential to develop inherently safe processes as well as energy efficient operations. 

In most situations, safety is best achieved by an inherently safe process design whenever practicable, combined, if necessary, with a number of protective systems which rely on different technologies (for example, chemical, mechanical, hydraulic, pneumatic, electrical, electronic, thermodynamic (for example, flame arrestors), programmable electronic) which manage any residual identified risk. Any safety strategy considers each individual safety instrumented system in the context of the other protective systems. To facilitate this approach, this standard... 

It is estimated that 43% of today s high-production-volume chemicals do not have complete toxicity data—and 7% of these chemicals have no data at all. Inherent safety implies that the process is inherently safe and that it is not kept safe with the help of several safety checks and alarms. Several available hazard analysis techniques can be used at various stages of the process development. Developing inherently safe process is more advantageous than... 

All plant/facility owners at present are looking for SIS manufacturers/suppliers that are capable of offering a set of products and services to provide complete support of their installed systems for the entire life cycle. On account of steep competition, no plant/facility owner can afford to accept downtime because of system failure/property loss/penalty caused by violation of regulations/deterioration of their product quality at the same time the products shall be competitively priced also. The best way to reduce risks in a plant/facility is to design inherently safe processes. However, this is neither possible nor can it ensure that the system will be completely safe, especially in cases where there are inherent risks (say) because of handling of hazardous or toxic materials. Industry culture is very much responsible and related to safety of the system. Apart from the safety culture of the company there are a few other issues responsible for increased risks that at any cost should be avoided as far as possible. The major reasons for increased risks are ... 

Process safety must be of paramount consideration in the design of any facility. There are many routes to a safe instaliation such as the use of control and interlock systems as well as other technology to achieve the necessary level of safety. The most effective route is through the use of inherently safe process design concepts. These utilize the ppncept that if the ingredients for a hazard are not present, then the process is much safer that if add-on protection is used to control the hazard. 

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