Coupling effect on the thermal hazard assessment of hazardous chemical materials via calorimetric technologies and simulation approaches

The coupling effect of heat absorption and release exists in the thermal decomposition of a few chemical materials.However,the impact of the above coupling on thermal hazard assessment is not considered in the literature studies.In this work,nitroguanidine(NQ)and 1,3,5-trinitro-1,3,5-triazine(RDX)are selected as representative materials to explore the influence of the coupling effect on the thermal hazard assessment of chemical materials.The linear heating experiments of NQ and RDX are carried out by a microcalorimeter and synchronous thermal analyser.The thermal decomposition curves are decoupled by advanced thermokinetics software.The thermal decomposition and kinetic parameters before and after decoupling are calculated.The results of TG experiment show that both NQ and RDX began to lose mass during the endothermic stage.The endothermic melting and exothermic decomposition of NQ and RDX are coupled within this stage.The coupling effect has different degrees of influence on its initial decomposition temperature and safety parameters.Compared with the parameters in the coupling state,the initial decomposition temperature and adiabatic induction period after decoupling decrease.The self-accelerating decomposition temperature increases,and internal thermal runaway time decreases.In the thermal hazard assessment of chemical materials with coupling effects,the calculated parameters after decoupling should be taken as an important safety index。

Study on thermal decomposition kinetics of azobenzene-4,4′-dicarboxylic acid by using compensation parameter method and nonlinear fitting evaluation

Recently,azobenzene-4,4'-dicarboxylic acid(ADCA)has been produced gradually for use as an organic synthesis or pharmaceutical intermediate due to its eminent performance.With large quantities put into application in the future,the thermal stability of this substance during storage,transportation,and use will become quite important.Thus,in this work,the thermal decomposition behavior,thermal decomposition kinetics,and thermal hazard of ADCA were investigated.Experiments were conducted by using a SENSYS evo DSC device.A combination of differential iso-conversion method,compensation parameter method,and nonlinear fitting evaluation were also used to analyze thermal kinetics and mechanism of ADCA decomposition.The results show that when conversion rate α increases,the activation energies of ADCA's first and main decomposition peaks fall.The amount of heat released during decomposition varies between 182.46 and 231.16 J·g^(-1).The proposed kinetic equation is based on the Avrami-Erofeev model,which is consistent with the decomposition progress.Applying the Frank-Kamenetskii model,a calculated self-accelerating decomposition temperature of 287.0℃is obtained.

Effect of safety valve types on the gas venting behavior and thermal runaway hazard severity of large-format prismatic lithium iron phosphate batteries

The safety valve is an important component to ensure the safe operation of lithium-ion batteries(LIBs).However,the effect of safety valve type on the thermal runaway(TR)and gas venting behavior of LIBs,as well as the TR hazard severity of LIBs,are not known.In this paper,the TR and gas venting behavior of three 100 A h lithium iron phosphate(LFP)batteries with different safety valves are investigated under overheating.Compared to previous studies,the main contribution of this work is in studying and evaluating the effect of gas venting behavior and TR hazard severity of LFP batteries with three safety valve types.Two significant results are obtained:(Ⅰ)the safety valve type dominates over gas venting pressure of battery during safety venting,the maximum gas venting pressure of LFP batteries with a round safety valve is 3320 Pa,which is one order of magnitude higher than other batteries with oval or cavity safety valve;(Ⅱ)the LFP battery with oval safety valve has the lowest TR hazard as shown by the TR hazard assessment model based on gray-fuzzy analytic hierarchy process.This study reveals the effect of safety valve type on TR and gas venting,providing a clear direction for the safety valve design.

Evaluation on the Thermal Stability and Hazards Behaviors of ADVN Using Green Thermal Analysis Approach

ADVN （2,2＇-Azobis （2,4-dimethyl） valeronitrile）, a free radical initiator, is widely applied for the polymerization reaction of polymers in the chemical industries. When ADVN releases free radical during the decomposition process, it can accompany abundant heat and huge pressure to increase the possibility of thermal runaway and hazard, causing unacceptable thermal explosion or fire accidents. To develop an inherently safer process for ADVN, the thermal stability parameters of ADVN were obtained to investigate thermal decomposition characteristics using a DSC （differential scanning calorimetry） and TG （thermogravimetry）. We used various kinetic models to completely depict the kinetic behavior and determine the thermal safety parameters for ADVN. The green thermal analysis approach could be used to substitute for complicated procedures and large-scale experiments of traditional thermal analysis methods, avoiding environmental pollution and energy depletion.

Studies on the flame propagation characteristic and thermal hazard of the premixed N2O/fuel mixtures

An experimental study was carried out to investigate the flame propagation and thermal hazard of the premixed N2O/fuel mixtures,including NH3,C3H8 and C2H4.The study provided the high speed video images and data about the flame locations,propagation patterns,overpressures and the quenching diameters during the course of combustion in different channels to elucidate the dynamics of various combustion processes.The onset decomposition temperature was determined using high-performance adiabatic calorimetry.It was shown that the order of the flame acceleration rate and thermal hazard was N2O/C2H4>N2O/C3H8>N2O/NH3.

Mechanistic understanding of the role separators playing in advanced lithium-sulfur batteries

The lithium-sulfur battery is considered one of the most promising candidates for portable energy storage devices due to its low cost and high energy density.However,many critical issues,including polysulfide shuttling,self-discharge,lithium dendritic growth,and thermal hazards need to be addressed before the commercialization of lithium-sulfur batteries.To this end,tremendous efforts have been made to explore battery configurations and components,such as electrodes,electrolytes,and separators,among which the separator plays an especially critical role in addressing aforementioned issues.Thus,this review analyzes the mechanisms and interactions of these critical issues and summarizes both the function of separators and recent progress made towards remedying such issues.Additionally,promising directions for the development of separators in lithium-sulfur batteries are proposed.

Permafrost Thaw and Associated Settlement Hazard Onset Timing over the Qinghai-Tibet Engineering Corridor

In permafrost areas, the timing of thermal surface settlement hazard onset is of great importance for the construction and maintenance of engineering facilities.Future permafrost thaw and the associated thermal settlement hazard onset timing in the Qinghai-Tibet engineering corridor(QTEC) were analyzed using high-resolution soil temperature data from the Community Land Model version4 in combination with multiple model and scenario soil temperature data from the fifth phase of the Coupled Model Intercomparison Project(CMIP5). Compared to the standard frozen ground map for the Tibetan Plateau and ERAInterim data, a multimodel ensemble reproduces the extent of permafrost and soil temperature change in the QTEC at a 1 m depth from 1986–2005. Soil temperature and active layer thickness increase markedly during 2006–2099 using CMIP5 scenarios. By 2099, the ensemble mean soil temperature at 15 m depth will increase between 1.0 and 3.6 ℃ in the QTEC. Using crushed-rock revetments can delay the onset of thermal settlement hazard for colder permafrost areas by approximately 17 years in the worst case scenario of RCP8.5. Nearly one-third of the area of the QTEC exhibits settlement hazard as early as 2050, and half of this one-third of the area is traversed by the QinghaiTibet highway/railway, a situation that requires more planning and remedial attention. Simulated onsets of thermal settlement hazard correspond well to the observed soil temperature at 15 m depth for seven grid areas in the QETC, which to some extent indicates that these timingestimates are reasonable. This study suggests that climate model-based timing estimation of thermal settlement hazard onset is a valuable method, and that the results are worthy of consideration in engineering design and evaluation.