Explosion, runaway

Fire/explosion Runaway reaction Fatality, Install temperature... 

Here we consider the case of a viscous or even solid reactive material contained in a vessel of known geometry. In this case, heat transfer takes place by pure conduction there is no flow within the reactive material. The situation is stable, when the heat losses by conduction compensate for the heat release in the material. Thus, the following questions must be answered Under which conditions may a thermal explosion (runaway) be triggered Under which conditions is the heat transfer by conduction sufficient to compensate for the heat release ... 

Throughout history, the chemical and pharmaceutical industries have gained mind-boggling unexpected experience in the hazards of working with chemicals. The safety literature provides a sobering and dark commentary with regard to explosions, runaway reactions, fires, toxic emissions, asphyxiations, spills, and so on, and their consequences. Consequences are seen in the injuries and deaths of people and in physical, social, and environmental damage around the world. 

If is not small, this will be a low steady-state concentration, but as tends to zero so [A"]ss increases. For < = 0, d[A"]/dr = = constant and so [AT] would grow linearly until the assumption that the reactant concentration is constant becomes invalid. With < > > 0, [A ] grows exponentially with time again until the consumption of A must be taken into account. The condition for an acceptable steady-state then is clearly (/> < 0, with the condition (/> = 0 being the critical case separating steady-state from explosive runaway. The critical concentration of the reactant obtained from the condition (f> = 0 is then... 

While a number of synthetic routes are available to various sulfoxides, the primary methods for commercial production of DMSO involve oxidation of dimethyl sulfide by oxides of nitrogen or by air in the presence of NO cat-alyst.f Dimethyl sulfoxide is both the product and the reaction solvent. To alleviate the potential for exothermic, and potentially explosive, runaway reactions in these oxidations, the feed rate for dimethyl sulfide is adjusted to ensure complete conversion and, thus, low instantaneous concentrations at any time. Alternate oxidants for the conversion of sulfides to sulfoxides include nitric acid, H202/acetic acid, peracids, and halogen/water. ... 

When storing and handling CHP at medium or even elevated temperatures, the heat release from the thermal decomposition must be efficiently removed in order to avoid any hazards from thermal explosion (runaway). Especially, in large reactors for cumene oxidation, the exothermic decomposition of CHP has to be taken into account during a shutdown process when there is no more mixing by aeration, so only limited heat removal to ambient takes place. The heat evolved from thermal decomposition is 270 kj/mol [8,9]. From process safety point of view, and also to understand the auto-catalyzed mechanism in the cumene oxidation, it is necessary to describe and quantify the thermal decomposition characteristics of CHP. 

The results shown in Figs. 3.1 and 3.2 were obtained with the scheme of Eq. (3.24) with At = 0.01 s and a Runge-Kutta integration of second order with variable step size (cf. [9]). The difference between the two procedures may be neglected in this case. It is obvious that the thermal explosion (runaway) leaves but little time for emergency interventions. 

Explosion—possible presence of an explosible atmosphere at or near workplaces, possibility of a confined explosion inside equipment or apparatuses, thermal explosion (runaway reaction), decomposition of unstable substances, physical explosion (contact of water with hot melts or other hot liquid media). 

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. 

Explosions can be caused by nuclear reactions, loss of containment in high pressure vessels, high explosives, runaway reactions, or a combination of dust, mist or gas in air or other oxidisers. This chapter concentrates on the latter examples. 

Apart form the pioneering works by Bilous and Amundson (1956) and Barkelew (1959), the criteria for parametric sensitivity mostly used in practice have been developed by Thomas and Bowes (1961) and Adler and Enig (19 ) in the context of thermal explosions. Runaway was defined to occur when the temperature profile exibits a region with positive second-order derivative somewhere before the hot-spot, in the temperature-time or temperature-conversion... 

Some vessels may be exposed to a runaway chemical reaction or even an explosion. This requires relief valves, rupture disks, or, in extreme cases, a barricade (the vessel is expendable). A vessel with a large rupture disk needs anchors designed For the jet thrust when the disk blows. 

Some vent streams, such as light hydrocarbons, can be discharged directly to the atmosphere even though they are flammable and explosive. This can be done because the high-velocity discharge entrains sufficient air to lower the hydrocarbon concentration below the lower explosive limit (API RP 521, 1997). Toxic vapors must be sent to a flare or scrubber to render them harmless. Multiphase streams, such as those discharged as a result of a runaway reaction, for example, must first be routed to separation or containment equipment before final discharge to a flare or scrubber. 

Have formal process hazard analyses (PHAs) been completed for highly hazardous processes (for example, those processes involving toxic or volatile substances, highly toxic materials, severe lachrymators, flammables, explosive compounds or potential runaway reactions) If yes, please summarize status of each. 

Consequence Phase 3 Develop Detailed Quantitative Estimate of the impacts of the Accident Scenarios. Sometimes an accident scenario is not understood enough to make risk-based decisions without having a more quantitative estimation of the effects. Quantitative consequence analysis will vary according to the hazards of interest (e.g., toxic, flammable, or reactive materials), specific accident scenarios (e.g., releases, runaway reactions, fires, or explosions), and consequence type of interest (e.g., onsite impacts, offsite impacts, environmental releases). The general technique is to model release rates/quantities, dispersion of released materials, fires, and explosions, and then estimate the effects of these events on employees, the public, the facility, neighboring facilities, and the environment. 

Common reaction rate v. temperature characteristics for reactions are illustrated in Figure 7.5. To avoid runaway conditions (Fig. 7.5a) or an explosion (Figure 7.5c), control may involve ... 

The released energy might result from the wanted reaction or from the reaction mass if the materials involved are thermodynamically unstable. The accumulation of the starting materials or intermediate products is an initial stage of a runaway reaction. Figure 12-6 illustrates the common causes of reactant accumulation. The energy release with the reactant accumulation can cause the batch temperature to rise to a critical level thereby triggering the secondary (unwanted) reactions. Thermal runaway starts slowly and then accelerates until finally it may lead to an explosion. 

Runaway A thermally unstable reaction system, which shows an accelerating increase of temperature and reaction rate. The runaway can finally result in an explosion. 

Temperature of no-return Temperature of a system at which the rate of heat generation of a reactant or decomposition slightly exceeds the rate of heat loss and possibly results in a runaway reaction or thermal explosion. 

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. 

SpotHaneoiis Reactions Polymerization, Runaway rcMction, Internal explosion, IXvomposition h. nvehpt hailures Pipes, tanks, vessels, gaskets, - .cals... 

We would never knowingly tolerate a situation in which accidental operation of a valve resulted in the overpressuring of a vessel. We would install a relief valve. In the same way, accidental operation of a valve should not be allowed to result in explosion or runaway reaction. 

This volume does not address subjects such as toxic effects, explosions in buildings and vessels, runaway reactions, condensed-phase explosions, pool fires, jet flames, or structural responses of buildings. Furthermore, no attempt is made to cover the frequency or likelihood that a related accident scenario will occur. References to other works are provided for readers interested in these phenomena. 

Accidents can occur in many ways. Tliere may be a chemical spill, an explosion, or a runaway reaction in a nuclear plant. Tliere are often accidents in transport trucks overturning, trains derailing, or ships capsizing. Tliere are acts of God such as eartliquakes and storms. It is painfully clear that accidents are a fact of life. Tlie one common tlnead tlirougli all of tliese situations is tliat accidents are rarely expected and, unfortunately, they are frequently mismanaged. 

Failure followed by inunediate combustion Runaw ay chemical reaction before failure Runaway nuclear reaction before failure BLEVEs (boiling liquidexpanding vapor explosion pressure vessel containing a flash-evaporating liquid) External Heating Immediate combustion after release No combustion after release... 

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