Thermal runaway reaction, hazard

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. 

Controlling legionella m nursing and residential care homes Chemical reaction hazards and the risk of thermal runaway... 

Barton, J. A. and Nolan, P. F. Incidents in the Chemical Industry due to Thermal-runaway Chemical Reactions, Hazards X Process... 

As mentioned before, the vast majority of accidents in batch processing arise when the control of the temperature of the reaction mixture is lost. This situation often leads to a temperature thermal) runaway, i.e. a temperature overshoot that can result in undesired reactions (decompositions), evaporation, or gas formation. As a consequence, pressure is built up inside a reactor and this can cau.se an explosion. The explosion is usually accompanied by damage to the equipment and release of hazardous (toxic, explosive, or flammable) species to the. surroundings. 

Safety. The MR is much safer than the MASR. (1) The reaction zone contains a much smaller amount of the reaction mixture (hazardous material), which always enhances process safety. (2) In case of pump failure, the reaction automatically stops since the liquid falls down from the reaction zone. (3) There is no need to filter the monolithic catalyst after the reaction has been completed. Filtration of the fine catalysts particles used in slurry reactors is a troublesome and time-consuming operation. Moreover, metallic catalysts used in fine chemicals manufacture are pyrophoric, which makes this operation risky. In a slurry reactor there is a risk of thermal runaways. (4) If the cooling capacity is insufficient (e.g. by a mechanical failure) a temperature increase can lead to an increase in reaction, and thus heat generation rate. 

After a thermal runaway reaction dining chlorination in DMF solution, investigation revealed that saturated solutions of chlorine in DMF are hazardous, and will self-heat and erupt under either adiabatic or non-adiabatic conditions. Principal products are tetramethylformamidinium chloride and carbon dioxide, with dimethylammonium chloride and carbon monoxide in small amounts. A detailed account of the mechanism is to be published. 

Precautions should be taken, especially in a scale-up approach, when dealing with exothermic reactions in the microwave field. Due to the rapid energy transfer of microwaves, any uncontrolled exothermic reaction is potentially hazardous (thermal runaway). Temperature increase and pressure rise may occur too rapidly for the instrument s safety measures and cause vessel rupture. 

Mix, K. K., "The Use of Advanced DTA Methods for the Evaluation of Thermal Instability, Hazard Evaluation, and Process Design," in Proceedings Runaway Chemical Reaction Hazards Symposium, IBC, London, England (1987). 

Gustin, J. L., "Thermal Stability Screening and Reaction Calorimetry—Application to Runaway Hazard Assessment and Process Safety Management," /. Loss Prev. Proc. Ind., 6,275 (1993). 

Historical perspective An analysis of thermal runaways in the United Kingdom (Barton and Nolan, Incidents in the Chemical Industry due to Thermal Bunaway Chemical Reactions, Hazards X Process Safety in Fine and Specialty Chemical Plants, IChem 115 3-18) indicated that such incidents occur because of the following general causes ... 

The process is dependent upon temperature, pH and hypochlorite concentration, and must be carefully controlled to avoid thermal runaway reactions. The reaction itself, combined with settling times for the catalyst slurry, can take three to four days, and the end-product - heavy metal salts - must be handled as hazardous waste. 

Chemical Reaction Hazards and the Risk of Thermal Runaway HSE Reviewed only... 

Heat removal Removal of reaction heat from a highly viscous polymeric fluid or a heterogeneous reaction mixture is often a critical reactor design and operational problem. In many industrial exothermic polymerization processes, reactor thermal runaway is the most serious potential hazard. 

An investigation of potential thermal runaway reactions is a significant part of a thorough hazard evaluation. Important parameters of the exothermic reaction as well as of the large-scale system are discussed. Their relationship is explained through the Semenov Theory. 

In reviewing the hazard associated with a chemical process, one of the hazards which should be considered is that of a potential runaway reaction. If either the desired chemical reaction or an undesired reaction (e.g., a side reaction or the unintended decomposition of a product) produces more heat than can be dissipated, the heat will accumulate in the system. This can lead to the thermal runaway. If the exothermic reaction(s) is accompanied by significant pressure generation, the runaway reaction can lead to rupture of the reaction vessel. 

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