Chemistry runaway reaction

Inherent An atmospheric pressure reaction using nonvolatile solvents which is incapable of generating any pressure in the event of a runaway reaction. There is no potential for overpressure of the reactor because of the chemistry and physical properties of the materials. 

The first major objective for the inherent safety review is the development of a good understanding of the hazards involved in the process. Early understanding of these hazards provides time for the development team to implement recommendations of the inherent safety effort. Hazards associated with flammability, pressure, and temperature are relatively easy to identify. Reactive chemistry hazards are not. They are frequently difficult to identify and understand in the lab and pilot plant. Special calorimetry equipment and expertise are often necessary to fully characterize the hazards of runaway reactions and decompositions. Similarly, industrial hygiene and toxicology expertise is desirable to help define and understand health hazards associated with the chemicals employed. 

The information to be compiled about the chemicals, including process intermediates, needs to be comprehensive enough for an accurate assessment of the fire and explosion characteristics, reactivity hazards, the safety and health hazards to workers, and the corrosion and erosion effects on the process equipment and monitoring tools. Current material safety data sheet (MSDS) information can be used to help meet this requirement but must be supplemented with process chemistry information, including runaway reaction and over-pressure hazards, if applicable. 

The other root causes were (1) the poor understanding of the chemistry, (2) an inadequate risk analysis, and (3) no safeguard controls to prevent runaway reactions. This EPA case history also summarized seven similar accidents with phenol-formaldehyde reactions during a 10-year period (1988-1997). 

Leggett, D. J. (2000). "Runaway Reactions Ignore the Chemistry at Your Peril." Chemical Engineering 107, 8 (August), 78-85. 

Good processes are safe for the operators, the environment, and the consumer. OSHA has proposed exposure limits for many compounds, and worker safety considerations will only become more stringent with time. An out-of-control, runaway reaction can lead to fatal consequences and to spills and emissions that are injurious to the environment. Environmental emissions standards are posed and regulated by agencies at the federal (EPA), state, and local levels. Green chemistry is becoming more important. The consumer is protected by the effective process controls filed with the FDA, so that the purity and impurity levels of the API are held within specified ranges. 

In order to study the potential for a runaway reaction, the investigator must be aware of the characteristics of the chemical reaction (s) as well as the characteristics of the actual large-scale system. In other words, a review of the hazards of an exothermic reaction requires a knowledge of both the "chemistry" of the reaction and the "engineering" of the large-scale system. 

So numerous, pervasive, and important are safety considerations in process research and chemical development that fipcos employ specialists to deal properly with them. To appreciate this importance, let us consider only one topic in any detail, namely runaway reactions. Carried out on a large scale, such reactions can destroy property and injure or loll people they thus threaten the plant, surrounding homes, employees, and community residents. Runaways arise fi om two causes, poor understanding of kinetics or chemistry and inadequate operators training or procedures (Etchells,... 

This process makes use of a catalytic reaction using an environmentally friendly oxidant and fits nicely into the context of green chemistry. The main problems of this type of reaction are, however, the danger of an explosion due to oxygen-rich gas phase, the danger of runaway reactions due to the exothermic nature of the reaction, and overoxidation of the product, especially at high conversions. 

As an advanced undergraduate in chemistry you are likely to be involved in one or more research projects with one of your professors. It is also likely that you have heard about explosions in a laboratory as well as explosions in facilities that handle chemicals. While it is unlikely that you will be involved in any project where this could happen, you should have at least some understanding of one of the major causes of many explosions—runaway reactions. 

Grignard reagents are exceptionally useful tools in synthetic organic chemistry. Victor Grignard won a Nobel Prize in 1912 for the discovery of this reaction. These reagents are not only useful on the laboratory scale but they are also used in the chemical industry at pilot and plant scales. As Incident 5.3.10.2 illustrates, this reaction can present a safety hazard that can potentially lead to a runaway reaction if not carried out under optimal conditions. 

Process safety involves many of the topics that we have covered in this book - flammability, explosions, toxicology, reactive chemicals, and runaway reactions (see Section 5.3.10 on runaway reactions). It also involves many of the basic concepts in chemistry, including kinetics and thermodynamics. 

The CSB investigation determined that BP Amoco was unaware of the hazardous reaction chemistry of the polymer because of inadequate hazard identification during process development. This lack of awareness is a commonly cited cause of reactive incidents within the CSB data. The BP Amoco incident also involved an endothermic (or heat consuming) reaction rather than the more commonly recognized exothermic (or heat producing) runaway chemical reaction. 

This sort of analysis could be extended to any metal-catalyzed chemistry in which a large runaway chiral excess is induced in the product by way of a small chiral excess of the molecules that serve as ligands to the metal. It is only necessary that the D,L-metal center be kinetically slower and thermodynamically more stable than the d,d- or L,L-complexes in order that any small e.e. of a chiral ligand be translated into chiral dominance of the reaction product. That the initial e.e. resulting in chiral takeover within a reacting system can be induced by asymmetric mineral surfaces indicates that a general chemical route to the asymmetry of life may exist. 

For the thermal runaway hazard evaluation, the "chemistry" of the exothermic reaction can be defined in terms of three sets of parameters the thermodynamic, kinetic, and physical parameters. (1) A list of some of the parameters of interest is given in Table I. 

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