China
Africa
Explore chapters and articles related to this topic
Terms and Definitions
Published in Rick Houghton, William Bennett, Emergency Characterization of Unknown Materials, 2020
Rick Houghton, William Bennett
All organic peroxides slowly decompose because they are inherently unstable. The rate of decomposition is dependent on the temperature and is unique to each organic peroxide. A characteristic of the decomposition reaction is the release of heat, which hastens further decomposition. Self-accelerating decomposition temperature (SADT) is the temperature at which the organic peroxide will produce heat faster than it can dissipate. This is defined as ≥ 6°C in one week. Most organic peroxide SADTs range from –10 to 200°C. Smaller containers have a larger surface area to the mass within and are therefore more sensitive to heating because they cannot dissipate the heat as well as a larger mass.
Identify and Assess Process Hazards
Published in James A. Klein, Bruce K. Vaughen, Process Safety, 2017
James A. Klein, Bruce K. Vaughen
Some additional key chemical reactivity parameters include [55–57]: Reaction type – The type of reaction, such as oxidation, nitration, hydrogenation, polymerization, condensation, esterification, and many others, provides high level, basic information on reaction mechanisms, thermodynamics, and kinetics. Nitration, for example, is typically a highly exothermic reaction that proceeds at high rates, and esterification, in contrast, is typically less exothermic and proceeds at slower rates. Although all reactions should be evaluated in more detail, the overall reaction type can quickly provide insight into basic chemical reactivity hazards.Onset temperature (Tonset) – the lowest temperature where decomposition or reaction increases the temperature due to higher heat of reaction than heat loss. Above the onset temperature, the rate of reaction may accelerate due to the increasing temperature until a maximum self-heat rate (dT/dt)max is obtained. Onset temperatures near ambient or possible process conditions indicate that reaction is possible and must be carefully evaluated.Self-accelerating decomposition temperature (SADT) – the lowest temperature at which self-accelerating thermal decomposition may occur for a peroxide or other self-reactive substance in its largest size shipping container. Above the SADT, thermal decomposition of the substance occurs raising the temperature and leading to increasingly faster decomposition rates. The SADT therefore determines the safe handling and storage requirements for the substance, such as ambient or refrigerated storage.Adiabatic temperature rise (ΔTr) – the maximum temperature increase resulting from reaction under adiabatic conditions. Because no heat is lost to the environment, all heat generated by the reaction is used to increase the temperature.Maximum attainable temperature (Tmax) – the maximum temperature resulting from reaction under adiabatic conditions (Tmax = Tonset + ΔTr).
Thermal equilibrium safety assessment of storage and transportation for 2,2’-Azobis(2,4-dimethylvaleronitrile) initiator required for polymer resin in construction industries
Published in Cogent Engineering, 2021
The self-exothermic phenomenon in the storage process is caused by the energy-consuming material being consumed due to its own transformation. The mass storage of substances under specific packaging conditions hinders the heat transfer of a bulk material to the surrounding environment. The heat accumulation caused by a long residence time causes the temperature to rise above the reaction threshold and triggers the substance to form a decomposition reaction. Temperature is the key factor for ensuring that large amounts of a material can maintain thermal stability. If the temperature is properly controlled, the subsequent heat accumulation can be eliminated, even if self-heating occurs. If the temperature can be controlled below the value of the self-accelerating decomposition temperature (SADT), the effect of self-heating can be reduced. This value is defined for a substance being stored under ambient temperature conditions during commercial packaging, and the temperature of the packaging center increases within seven days by no more than 6 degrees (Kossoy et al., 2015). Simulations were performed for the use of ABVN in intense commercial activities under different industry conditions. The reaction of the upper heating rate is expressed in Eq. (9):