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Abstract  

Investigations of nitrogen content and thermal decomposition activation energy (E a) of two different kinds of nitrocellulose (NC) products, NMNC and MNC from the non-fat and original processes of linters, respectively, were discussed. In this study, differential scanning calorimetry (DSC) and element analyzer (EA) are used, for the above two chemicals, along with the same nitration condition in use of sulfuric acid (H2SO4) and nitric acid (HNO3) mixing acid. E a was calculated by our induced model. According to our experimental results, the nitrogen content of NMNC/MNC was 11.71 and 11.55 mass%, in a low nitrogen content condition of mixing acid. The E a parameters were 319.91 (NMNC) and 347.27 (MNC) kJ mol−1, individually. They indicated that the non-fat process of a linter made a higher degree of stability than the others. This research also presents an efficient and accurate model of the thermal decomposition property evaluation for non-fat process of linters. The outcome is believed to be very useful for helping to understand, and be applied as, an inherently safer design during relevant NC manufacturing processes.

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Abstract  

Diphenylcarbonate (DPC) has been regarded as a potential substitute material for highly toxic phosgene, reacting with bisphenol A (BPA) in a phosgene-free process to produce polycarbonate (PC). For synthesizing DPC, methylphenylcarbonate (MPC) was the critical intermediate with potential flammability in a transesterification reaction from dimethylcarbonate (DMC) and phenol. Under the National Fire Protection Association (NFPA) criterion, MPC is viewed as one sort of combustible liquid (Class IIIB). Once it fires or burns during storage, operation or transportation, it can cause a serious fire and explosion. However, researches are still scanty in mentioning the basic but crucial fire and explosion features of MPC to date. A sound background of material safety properties is essential for safe handling; in particular, flammability information is extremely crucial for a specific chemical during a unit operation to prevent any fire and explosion hazards. In this study, we investigated the explosion limits (LEL, UEL), maximum explosion pressure (P max), maximum rate of explosion pressure rise ((dP/dt)max), and gas or vapor explosion constant (K g) of MPC, according to its practical operating conditions (1 atm, 250°C, 21 vol.% O2) and by means of a 20 L vessel (20-L-Apparatus). By surveying and defining the experimental data through flammability tests, these basic but crucial safety-related parameters on flammability characteristics of MPC were proposed, so as to advance understanding and to avoid fire and explosion accidents for such relevant processes.

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Abstract  

Information about the kinetics and thermal decomposition of hydrogen peroxide (H2O2) has been required for safety reasons, due to its broad applications in many chemical industries. To determine the inherent hazards during H2O2 manufacturing, transportation, disposal, usage, and so on, this study deliberately selected various H2O2 concentrations and analyzed them by differential scanning calorimetry (DSC). In addition, thermokinetic parameters were not only established for each of these reactions, but also aimed at comprehensive, kinetic models with various tests conducted at different heating rates. To build up a comprehensive kinetic model, various tests were conducted by heating rates of 1, 2, 4, 10C min–1, respectively. According to dynamic DSC tests, the experimental curves show that H2O2 decomposition has one exothermic peak and may start to decompose under 47–81C. The total heat of decomposition is about 192–1079 J g–1. Not only can these results prevent accidents caused by H2O2 during storage and transportation, but also assess its inherent hazards and thereby design procedures for emergency response while runaway reactions occurring.

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Abstract  

Thermal runaway reactions associated with exothermic behaviors of tert-butyl hydroperoxide (TBHP) solutions and TBHP reacting with alkaline contaminants were studied. A differential scanning calorimetry (DSC) was used to characterize these inherent behaviors of TBHP solutions with KOH, NaOH, LiOH and NH4OH. The exothermic peak in thermal curves of TBHP solutions with different alkali were detected by DSC thermal analysis. By thermal analysis, we compared various heats of decomposition of TBHP solutions with alkaline impurities, and determined the incompatible hazards of various TBHP solutions with alkaline contaminants. Comparing with TBHP in various diluents, the adiabatic runaway reaction via vent sizing package 2 (VSP2) indicated that aqueous TBHP intrinsically possesses the phenomena of thermal explosion with dramatic self-reactive rate and pressure rise under adiabatic conditions. Many commercial organic peroxides may have different hazard behaviors. Therefore, using thermal method to classify the hazards is an important subject.

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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  

Information about the kinetics and thermal decomposition of dicumyl peroxide (DCPO) is required for safety concerns, due to its wide applications and accident cases. To understand the inherent hazards during DCPO manufacturing, we selected various concentrations in different stages and analyzed them by differential scanning calorimetry (DSC). We evaluated thermokinetic parameters to set up a simple, but comprehensive kinetic model, with various tests conducted at heating rates of 2, 4, 6 and 10C min-1 . Subsequently, we established a more efficient, resource-effective, and cost-effective model of safety evaluation for DCPO with different concentrations, according to thermokinetic parameters, such as activation energy E a is 125.35 kJ mol-1 , frequency factor k 0 is 3.12410 12 s-1 , reaction order n is 0.9 and heat of decomposition ΔH is 750.52 J g-1 for DCPO 99 mass%.

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Abstract  

Analytical equations related adiabatic runaway reactions to programmed scanning thermal curves from differential scanning calorimetry (DSC) were proposed. Thermal or pressure hazards can be assessed from the adiabatic trajectories expressed in the analytical equations. These industrially energetic materials include polymerizable monomers, unstable organic peroxides and nitro-compounds. Various emergency relief behaviors, such as tempered vapor, gassy, and hybrid were re-evaluated for calculating vent sizing or mass flow rates from DSC thermal curves and the related physical properties.

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Abstract  

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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Abstract  

Flammable chemicals are frequently encountered in industrial processes. Under the safe operation basis and for fire/explosion danger prevention, it is imperative to recognize the flammability characteristics of these processes, especially under the working scenarios for elevated pressure and temperature. This study was conducted to investigate fire and explosion properties, including the explosion limits (LEL and UEL), maximum explosion overpressure (P max), maximum rate of explosion pressure rise (dP/dt)max, gas or vapor deflagration index (K g) and explosion class (St) of various acetone/water solutions (100, 75, 50 and 25 vol.%) at higher initial pressure/temperature up to 2 atm and 200°C via a 20-L-Apparatus. We further discussed the safety-related parameters and fire/explosion damage degree variations in the above aqueous acetone within 1 atm and 150°C. The results offered a successful solution for evaluating the flammability hazard effect in such a relevant crucial process with elevated pressure and temperature.

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