Thermal Runaway Reactions Essay

1902 WordsMar 31, 20138 Pages
Thermal runaway An exothermic reaction can lead to thermal runaway, which begins when the heat produced by the reaction exceeds the heat removed. The surplus heat raises the temperature of the reaction mass, which causes the rate of reaction to increase. This in turn accelerates the rate of heat production. An approximate rule of thumb suggests that reaction rate - and hence the rate of heat generation - doubles with every 10°C rise in temperature. Thermal runaway can occur because, as the temperature increases, the rate at which heat is removed increases linearly but the rate at which heat is produced increases exponentially. Once control of the reaction is lost, temperature can rise rapidly leaving little time for correction. The reaction vessel may be at risk from over-pressurisation due to violent boiling or rapid gas generation. The elevated temperatures may initiate secondary, more hazardous runaways or decompositions. Causes of incidents An analysis1 of thermal runaways in the UK has indicated that incidents occur because of: inadequate understanding of the process chemistry and thermochemistry; inadequate design for heat removal; inadequate control systems and safety systems; and inadequate operational procedures, including training. These are some of the key factors you will want to consider in defining a safe process. Effects of thermal runaway A runaway exothermic reaction can have a range of results from the boiling over of the reaction mass, to large increases in temperature and pressure that lead to an explosion. Such violence can cause blast and missile damage. If flammable materials are released, fire or a secondary explosion may result. Hot liquors and toxic materials may contaminate the workplace or generate a toxic cloud that may spread off-site. There can be serious risk of injuries, even death, to plant operators, and the general

More about Thermal Runaway Reactions Essay

Open Document