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Runaway Reaction (runaway + reaction)

Distribution by Scientific Domains
Chemistry90%

Selected Abstracts

Runaway Reaction Kinetics for Emulsion Polymerization and its Consequences

MACROMOLECULAR REACTION ENGINEERING, Issue 5-6 2009
Lambertus G. Manders
Abstract For industrial semi-batch emulsion polymerization, it is difficult to predict the composition of the reactor contents during a runaway reaction since many recipes are involved and it actually may be a fault in the feeds to the reactor that leads to the runaway reaction, as a distributed control system cannot safely prevent wrong feeds. Therefore, in order to safeguard the reactor, very high kinetics need to be taken into account, as discussed theoretically as well as based on an example. Corresponding maximum temperature increase rates may be above 100 K,·,min,1. This needs to be taken into account when designing safety measures for emulsion polymerization reactions. As a result, large safety relief valves or rupture discs may need to be installed. [source]

A heuristic approach of calculating spray water flux needed to avert fire-induced runaway reactions,,

PROCESS SAFETY PROGRESS, Issue 3 2006
BChE (Honors), Dilip K. Das BSc (Honors), MSChE
In general all reactions have some heat effects. When the ability of the equipment to remove the heat is exceeded by the heat generated by a reaction, a hazardous situation called a runaway reaction may take place. Sometimes the exothermicity of runaway reactions is so high that the size of an emergency vent becomes impractical to install. A water spray system can sometimes be used to avert a fire-induced runaway reaction. Because the water spray system has a finite activation time, insulation helps to prolong the time required to reach the decomposition temperature. This article concludes that the required water flux to avert the fire-induced runaway reaction may be conservatively estimated by adding the water flux necessary to maintain an unbroken water film on the external surface of the equipment and the water flux necessary to absorb the fire heat after allowing for the splash loss and the in-flight loss. When adequate spray water is used, the metal temperature of the insulation jacket cannot theoretically exceed the boiling point of water thereby ensuring the avoidance of fire-induced runaway reactions whose adjusted onset decomposition temperature exceeds 100 ° C. Fire-induced runaway reactions with lower onset temperature can also be avoided depending on the initial temperature of the contents, mass of the contents and equipment, insulation thickness, and fire duration, for example, but a detailed calculation including dynamic simulation is necessary and the burden of proof lies with the designer. The reliability of the spray water system must be maintained high to include its credit as an environmental factor defined according to NFPA 30 to avoid the fire-induced runaway reaction as a scenario. Although API RP 521 does not allow any credit for sprinkler water, it allows credit, unlike NFPA 30, for insulation thickness and thus a runaway reaction can be avoided by using insulation alone according to API RP 521. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006 [source]

Toxic gas release caused by the thermal decomposition of a bulk powder blend containing sodium dichloroisocyanurate

PROCESS SAFETY PROGRESS, Issue 2 2003
Andrew R. Carpenter P.E.
A thermal runaway reaction occurred during the mixing of a batch of a bulk powder that resulted in the production and release of toxic gases. The mixture consisted of an oxidizer (sodium dichloroisocyanurate), some organic compounds, and inert compounds. This toxic release led to the evacuation of the building and resulted in extensive damage to the facility. This was only the fourth time an 1,100-pound batch of this material had been mixed in this equipment. Prior to this production run, the material had been prepared in small batches of 2 to 50 kilograms. Accelerated Rate Calorimetry (ARC) testing had been performed prior to the scale-up to production batches. This paper looks into the root causes of this particular accident and demonstrates how proper analysis of the testing data and other warning signs observed during the bench testing could have revealed the likelihood of this accident. Further, this paper will consider how simple design changes to the manufacturing process resulted in an inherently safer design. [source]

Detection of hazardous reaction products during a thermal runaway

PROCESS SAFETY PROGRESS, Issue 2 2003
Ronald J. A. Kersten
The control of major accident hazards linked with the storage and processing of dangerous substances in chemical and petrochemical installations is regulated in the European Union by the so-called "Seveso II Directive." One of the requirements in this Directive is the declaration of not only the hazardous substances as present onsite, but also any hazardous products that could form during a loss of control situation. This study focused on the development of an experimental technique to determine the substances that might be formed during an uncontrolled chemical reaction or runaway reaction. The decomposition reaction of a diazo compound was studied with the technique to assess its applicability. The results show that, apart from its applicability in relation to the Seveso II Directive, the same technique can be used to obtain data for the design of gas treatment systems or to study the mechanism behind runway reactions. Understanding this mechanism, in turn, helps to identify conditions that might favor the occurrence of, or might temper the course of, the runaway reaction. [source]

Guidance on Safety/Health for Process Intensification including MS Design; Part I: Reaction Hazards

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2009
O. Klais
Abstract The implementation of process intensification by multiscale equipment will have a profound impact on the way chemicals are produced. The shift to higher space-time yields, higher temperatures, and a confined reaction volume comprises new risks, such as runaway reactions, decomposition, and incomplete conversion of reactants. Simplified spreadsheet calculations enable an estimation of the expected temperature profiles, conversion rates, and consequences of potential malfunction based on the reaction kinetics. The analysis illustrates that the range of optimal reaction conditions is almost congruent with the danger of an uncontrolled reaction. The risk of a spontaneous reaction with hot spots can be presumed if strong exothermic reactions are carried out in micro-designed reactors. At worst, decomposition follows the runaway reaction with the release of noncondensable gases. Calculations prove that a microreactor is not at risk in terms of overpressure as long as at least one end of the reactor is not blocked. [source]

A heuristic approach of calculating spray water flux needed to avert fire-induced runaway reactions,,

PROCESS SAFETY PROGRESS, Issue 3 2006
BChE (Honors), Dilip K. Das BSc (Honors), MSChE
In general all reactions have some heat effects. When the ability of the equipment to remove the heat is exceeded by the heat generated by a reaction, a hazardous situation called a runaway reaction may take place. Sometimes the exothermicity of runaway reactions is so high that the size of an emergency vent becomes impractical to install. A water spray system can sometimes be used to avert a fire-induced runaway reaction. Because the water spray system has a finite activation time, insulation helps to prolong the time required to reach the decomposition temperature. This article concludes that the required water flux to avert the fire-induced runaway reaction may be conservatively estimated by adding the water flux necessary to maintain an unbroken water film on the external surface of the equipment and the water flux necessary to absorb the fire heat after allowing for the splash loss and the in-flight loss. When adequate spray water is used, the metal temperature of the insulation jacket cannot theoretically exceed the boiling point of water thereby ensuring the avoidance of fire-induced runaway reactions whose adjusted onset decomposition temperature exceeds 100 ° C. Fire-induced runaway reactions with lower onset temperature can also be avoided depending on the initial temperature of the contents, mass of the contents and equipment, insulation thickness, and fire duration, for example, but a detailed calculation including dynamic simulation is necessary and the burden of proof lies with the designer. The reliability of the spray water system must be maintained high to include its credit as an environmental factor defined according to NFPA 30 to avoid the fire-induced runaway reaction as a scenario. Although API RP 521 does not allow any credit for sprinkler water, it allows credit, unlike NFPA 30, for insulation thickness and thus a runaway reaction can be avoided by using insulation alone according to API RP 521. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006 [source]

Guidance on Safety/Health for Process Intensification Including MS Design.

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2010
III: Risk Analysis
Abstract The new technology of process intensification by multiscale equipment can significantly contribute to achieve a safer design by going from batch/semi-batch to continuous operation combined with a reduction of inventory of hazardous substances in critical stages. On the other hand, the shift to higher space-time-yields comprises new risks such as runaway reactions with hot spot formation, described in Part,I, and handling an explosive atmosphere in the presence of potential permanent ignition sources, described in Part,II. A tool was developed for preliminary risk assessments, called HAZOP-LIKE study, to cover the characteristic features of micro-designed equipment that are relatively unimportant when handling conventional equipment. Two generic cases concerning liquid/liquid and gas/gas reactions were studied to demonstrate the method. [source]

Guidance on Safety/Health for Process Intensification including MS Design; Part I: Reaction Hazards

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2009
O. Klais
Abstract The implementation of process intensification by multiscale equipment will have a profound impact on the way chemicals are produced. The shift to higher space-time yields, higher temperatures, and a confined reaction volume comprises new risks, such as runaway reactions, decomposition, and incomplete conversion of reactants. Simplified spreadsheet calculations enable an estimation of the expected temperature profiles, conversion rates, and consequences of potential malfunction based on the reaction kinetics. The analysis illustrates that the range of optimal reaction conditions is almost congruent with the danger of an uncontrolled reaction. The risk of a spontaneous reaction with hot spots can be presumed if strong exothermic reactions are carried out in micro-designed reactors. At worst, decomposition follows the runaway reaction with the release of noncondensable gases. Calculations prove that a microreactor is not at risk in terms of overpressure as long as at least one end of the reactor is not blocked. [source]