For example, oxidation of cyclohexane into cyclohexanol and cyclohexanone and ortho-xylene into phthalic anhydride have led to catastrophic explosions when reaction control failed. Such a scenario may arise in stars containing degenerate matterin which electron degeneracy pressure rather than normal thermal pressure does most Runaway reactions the work of supporting the star against gravity, and in stars undergoing implosion.
The white dwarf and companion remain intact, however, so the process can repeat. Helium flashes in red giant stars[ Runaway reactions ] When stars in the 0. Serious incidents can result in death, injury, capital loss, and business interruptions.
Quantification of adverse reactions: Runaway reactions 13, at 2: Many incidents involve materials that have NFPA hazard ratings of 0 and 1. Devices with an intrinsic positive temperature coefficient PTC of electrical resistance are less prone to current hogging, but thermal runaway can still occur because of poor heat sinking or other problems.
Novae[ edit ] A nova results from runaway hydrogen fusion via the CNO cycle in the outer layer of a carbon-oxygen white dwarf star. It is important to remember to update the process safety information, as a process undergoes changes during its lifecycle.
One way to gain the additional mass would be by accreting gas from a giant star or even main sequence companion. Remember to include reactor agitation as a source of energy, Consider the impact of possible deviations from the intended reactant charges and operating conditions, Identify all heat sources connected to a reaction vessel and assume the maximum possible worst-case scenario, Determine the effect of the lowest possible temperature to which the reactor heat-transfer fluid could cool the reaction mixture, i.
Consequently, reactions that easily cool fast enough in the laboratory can dangerously self-heat at ton scale. See also Thermal Design Power. Almost such reports are available to view as of January Microwave heating[ edit ] Microwaves are used for heating of various materials in cooking and various industrial processes.
Failure of the mixer can result in localized heating, which initiates thermal runaway. Depending on the design of the circuit, this increase in leakage current can increase the current flowing through a transistor and thus the power dissipationcausing a further increase in collector-to-emitter leakage current.
This causes a drop in the pressure within the core, leading it to contract and heat further, causing more pair production, a further pressure drop, and so on. To handle larger currents, circuit designers may connect multiple lower-capacity devices e. Identify any adverse or thermal runaway reactions and characterize them using adiabatic calorimetrysuch as ARC accelerating rate calorimetryor ARSST.
When thermal pressure is in equilibrium with overlying pressure, a star will respond to the increase in temperature and thermal pressure due to initiation of a new exothermic reaction by expanding and cooling. Comparison to nonrunaway supernovae[ edit ] Not all supernovae are triggered by runaway nuclear fusion.
If connected directly across an AC or DC power bus a common usage for protection against electrical transientsa MOV which has developed a lowered trigger voltage can slide into catastrophic thermal runaway, possibly culminating in a small explosion or fire.
A comprehensive hazard evaluation should be conducted using appropriate estimation and experimental techniques to identify potential reaction hazards in materials, as well as the desired and adverse reactions. The reader is encouraged to add plant-specific items or issues to the guidelines in this article, as needed for their particular situation.
Typically, one device may have a slightly lower resistance, and thus draws more current, heating it more than its sibling devices, causing its resistance to drop further. If circuit conditions cause markedly increased current flow in these situations, increased power dissipation may raise the temperature further by Joule heating.
If multiple BJT transistors are connected in parallel which is typical in high current applicationsa current hogging problem can occur. The tantalum sponge then comes into direct contact with the manganese dioxide, and increased leakage current causes localized heating; usually, this drives an endothermic chemical reaction that produces manganese III oxide and regenerates self-heals the tantalum oxide dielectric layer.
Batteries[ edit ] When handled improperly, or if manufactured defectively, some rechargeable batteries can experience thermal runaway resulting in overheating.
Thermal runaway may result from unwanted exothermic side reaction s that begin at higher temperatures, following an initial accidental overheating of the reaction mixture. Regardless, an inadequate heat sink with a thermal resistance of over 0.
Thus, an array of devices may end up no more robust than its weakest component. Conduct a basic energy balance to consider the heats during various additions, heat generated during the chemical reaction, and the heat removal capability of the plant reactor system. Prior to scale-up, it is critical to have a clear understanding of the reactivity of all process chemicals as well as the energetics of both desired reaction sdefining a worst-case scenario, characterizing the resulting adverse reaction, and understanding how to mitigate the process safety impact.
The core starts to undergo gravitational collapse.Before you can handle chemical reactions safetly, you must first understand them. In this course, you'll identify potential runaway reactions and tools for sizing relief systems to safely control and contain them.
A runaway reaction is frequently going to the worst case contingency when sizing the relief devices for your reactor systems.
The problem is, these are extremely involved calculations that require specialized data, and chemical engineering and modeling expertise.
Runaway Reactions (Published as IChemE Symposium series no. 68) A General Approach to the Prediction and Control of Potential Runaway Reaction. Runaway Reactions Reactive chemical hazards can lead to runaway reactions with a catastrophic consequence.
The hazards in such system are seldom the characteristics of the chemical by itself but are highly dependent on the process conditions and modes of operations.
How to Prevent Runaway Reactions August Phenol-formaldehyde reactions are common industrial processes. The reaction of phenol or substituted phenol with an aldehyde, such as formaldehyde, in the presence of an acidic or basic catalyst is used to prepare phenolic resins.
A General Strategy for the Safer Scale-Up of Batch and Semi-Batch Reactions -with Richard Kwasny, Ph.D., Senior Consulting Engineer, Fauske & Associates, LLC.
Thermal runaway incidents continue to occur in batch production facilities in the chemical and pharmaceutical industries. Serious incidents can result in death, injury, capital loss, and business interruptions.Download