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Letter to the Editor

Response to comments for thermal explosion and runaway reaction simulation of lauroyl peroxide by DSC tests

Journal of Thermal Analysis and Calorimetry
Authors: M.-L. You and C.-M. Shu
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Abstract  

Many concerns over unsafe or unknown properties of multi-walled carbon nanotubes (MWNTs) have been raised. The thermal characteristics regarding stability would represent potential hazards during the production or utilization stage and could be determined by calorimetric tests for various thermokinetic parameters. Differential scanning calorimetry (DSC) was employed to evaluate the thermokinetic parameters for MWNTs at various compositions. Thermoanalytical curves showed that the average heat of decomposition (ΔH d) of the MWNTs samples in a manufacturing process was about 31,723 J g−1, by identifying them as an inherently hazardous material. In this study, significant thermal analysis appeared in the presence of sulfuric acid (H2SO4). From the DSC experiments, the purification process of MWNTs could induce an unexpected reaction in the condition of batch addition with reactants of H2SO4. The results can be applied for designing emergency relief system and emergency rescue strategies during a perturbed situation or accident.

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Styrene is an important commodity chemical that is globally applied in various polymerization processes. The aim of this study was to obtain integrated thermokinetics and safety parameters for polymerization of styrene. We mainly used differential scanning calorimetry (DSC), thermal activity monitor (TAM), and simulative methods to investigate thermal polymerization of styrene and styrene containing various levels of 4-tertiary-butylcatechol (TBC). The results obtained included the rate constant (k), reaction order (n), apparent activation energy (E a), frequency factor (A), and so on, from various DSC curves and simulative methods. From DSC curves, the exothermic onset temperature (T 0) was about 105 and 132C for styrene and styrene containing 10 ppm TBC. On the other hand, the test results from TAM indicated that styrene polymerization displays an autocatalytic phenomenon from 50–85C. By means of this study, the intrinsic safety of a system for styrene during transportation and storage could be established.

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Explosion limits are crucial information for people who handle/operate flammable vapors or gases. It was reported in our previous studies that there is a theoretical linear relation between the reciprocal of the explosion limits and the reciprocal of the molar fraction of hydrocarbons diluted with inert carbon dioxide or nitrogen. In this work, oxygenated hydrocarbons were inertized by inert steam, and the relation of the upper explosion limit and the extent of the inertization was explored. With the assumption that the adiabatic flame temperatures are the same for all limit mixtures, it was found that the aforementioned linear relation still holds in case the inert gas is of steam and the flammable material is of oxygenated hydrocarbons. Experimental work was carried out in a 20-L-Apparatus at 101 kPa and 423 K to measure the upper explosion limit of methyl alcohol, acetone, and methyl formate diluted with steam, respectively. It was found that experimental results fit the theoretical model very well.

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Knowledge of material safety properties is critical for safe handing in the chemical process industries, especially for flammable chemicals that might result in serious fires and explosions. This study investigated the flammability characteristics of methanol under working conditions during the process. The targeted fire and explosion properties, like explosion limits (UEL and LEL), vapor deflagration index (K g), maximum explosion pressure (P max), and maximum explosion pressure rise [(dP dt −1)max], were deliberately obtained via a 20-L-Apparatus in 101 kPa (i.e., 760 mmHg/1 atm), 150 and 200 °C, along with various experimental arrangements containing nitrogen (N2) or carbon dioxide (CO2) as inert component. Particularly, this study discussed and elucidated the inert influence on the above safety-related parameters by two different inerting gases of N2 and CO2. The results indicated that adding an inert component to fuel–inert gas mixtures determined the decrease of explosion range and flammability hazard degree. The results also demonstrated that CO2 possessed higher inerting capability than N2 in this study.

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Abstract  

The minimum oxygen concentration (MOC) is an important safety parameter of safety for fire/explosion prevention of practical processes with fuel-air-inert mixtures. In this study, the critical fire and explosion properties stand for the explosion sensitivity (lower explosion limit (LEL), upper explosion limit (UEL)), explosion maximum indices (maximum explosion pressure (P max), maximum rate of explosion pressure rise (dP dt −1)max) and explosion damage degree (gas or vapor deflagration index (K g)/St Class). These imperative parameters of various toluene/methanol mixing solvents (100/0, 75/25, 50/50, 25/75 and 0/100 vol.%) were experimentally determined within a closed spherical vessel of 20 L (20-L-Apparatus) at 101 kPa and 150 °C. Particularly, we discussed the variations both on the above characteristics and implied flammability hazard degree within different initial oxygen circumstances; the specific effects on toluene/methanol mixing solvents were to be clarified accompanied with reducing loading oxygen concentrations, gradually approaching up to the MOC in this present work. Finally, a triangle flammability diagram with the five toluene/methanol components in our testing arrangements and conditions was established for graphically indicating the dangerous fire/explosion hazard region. It has been confirmed that this study would be very useful in relevant industrial processes for a proactive loss prevention program. The experimentally derived outcomes are recommended for the inherently safer design (ISD) for forestalling any accidents from fires and explosions.

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Abstract

Vent sizing package 2 (VSP2) was used to measure the thermal hazard and runaway characteristics of 18650 lithium-ion batteries, which were manufactured by Sanyo Electric Co., Ltd. Runaway reaction behaviors of these batteries were obtained: 50% state of charge (SOC), and 100% SOC. The tests evaluated the thermal hazard characteristics, such as initial exothermic temperature (T 0), self-heating rate (dT dt −1), pressure-rise rate (dP dt −1), pressure temperature profiles, maximum temperature, and pressure which were observed by adiabatic calorimetric methodology via VSP2 using customized test cells. The safety assessment of lithium-ion cells proved to be an important subject. The maximum self-heating rate (dT dt −1)max and the largest pressure-rise rate (dP dt −1)max of Sanyo 18650 lithium-ion battery of 100% SOC were measured to be 37,468.8 °C min−1 and 10,845.6 psi min−1, respectively, and the maximum temperature was 733.1 °C. Therefore, a runaway reaction is extremely serious when a lithium-ion battery is exothermic at 100% SOC. This result also demonstrated that the thermal VSP2 is an alternative method of thermal hazard assessment for battery safety research. Finally, self-reactive ratings on thermal hazards of 18650 lithium-ion batteries were studied and elucidated to a deeper extent.

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Abstract  

Styrene is an important chemical in the petrochemical industry. In recent years, there have been sporadic releases, runaway reactions, fires, and thermal explosion accidents incurred by styrene and its derivatives worldwide. The purpose of this study was to estimate the impact of styrene and its derivatives of α-methylstyrene (AMS) and trans-β-methylstyrene (TBMS) contacting with benzaldehyde. Experiments were carried out to evaluate the thermokinetic parameters estimated by differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III). TAM III was used to determine the fundamental thermokinetics under various isothermal temperatures, 80, 90 and 100°C. This autocatalytic reaction was demonstrated in thermal curves. After styrene was contacted with benzaldehyde, the exothermic onset temperature (T 0) and the total heat of reaction (Q total) were altered by DSC tests. When benzaldehyde is mixed with AMS and TBMS, the reaction time will be shorter but the enthalpy reduced, as revealed by TAM III tests. As AMS and TBMS, respectively, were contacted with benzaldehyde, both exothermic phenomena were changed during the reaction excursion. According to the results of this research, an operator should dictate the oxygen concentration in order to avoid any potential hazards during handling and transportation.

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Abstract  

Methyl ethyl ketone peroxide (MEKPO) possesses complex structures which have caused many incidents involving fires or explosions by mixing with incompatible substances, external fires, and others. In this study, reactivities or incompatibilities of MEKPO with inorganic acids (HCl, HNO3, H3PO4 and H2SO4) were assessed by differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2). Parameters obtained by the above-mentioned devices could be readily employed to discuss the runaway reaction, such as onset temperature (T 0), heat of reaction (ΔH d), time to maximum rate (TMR), maximum self heat rate (dT/dt)max, adiabatic temperature rise (ΔT ad), maximum pressure of decomposition (P max) and so on. Mixing MEKPO with hydrochloric acid resulted in the lowest T 0 among inorganic acids. Nitric acid not only lowered the T 0 but also delivered the highest heat releasing rate or self heat rate (dT/dt), which was concluded to be the worst case in terms of contamination hazards during storage or transportation of MEKPO.

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