ESTIMATION OF THE CRITICAL RATE OF TEMPERATURE INCREASE OF THERMAL EXPLOSION OF NITROCELLULOSE USING NON-ISOTHERMAL DSC

A method of estimating the critical rate of temperature increase of thermal explosion for the first orderautocatalytic decomposition reaction system using non-isothermal DSC is presented. Information is obtained on theincreasing rate of temperature in nitrocellulose containing 13.54% of nitrogen when the first order autocatalytic decomposition converts into thermal explosion.     

用非等温DSC估算3,4-双(4’-硝基呋咱-3’-基)-2-氧化呋咱(BNFOF)放热自催化分解反应的热爆炸临界温升速率和动力学参数

A method of estimating the kinetic parameters and the critical rate of temperature rise in the thermal explosion for the autocatalytic decomposition of 3,4-bis（4＇-nitrofurazan-3＇-yl）-2-oxofurazan （BNFOF） with non-isothermal differential scanning calorimetry （DSC） was presented. The rate equation for the decomposition of BNFOF was cstablished, and information was obtained on the rate of temperature increase in BNFOF when the empiric-order autocatalytic decomposition was converted into thermal explosion.     

Utilization of microcalorimetry for an assessment of the potential for a runaway decomposition of cumene hydroperoxide at low temperatures

The exothermic decomposition of cumene hydroperoxide (CHP) in cumene liquid was characterized by isothermal microcalorimetry, involving the thermal activity monitor (TAM). Unlike the exothermic behaviors previously determined from an adiabatic calorimeter, such as the vent sizing package 2 (VSP2), or differential scanning calorimetry (DSC), thermal curves revealed that CHP undergoes an autocatalytic decomposition detectable between 75 and 90°C. Previous studies have shown that the CHP in a temperature range higher than 100°C conformed to an n ^th order reaction rate model. CHP heat of decomposition and autocatalytic kinetics behavior were measured and compared with previous reports, and the methodology and the advantages of using the TAM to obtain an autocatalytic model by curve fitting are reported. With various autocatalytic models, such as the Prout-Tompkins equation and the Avrami-Erofeev rate law, the best curve fit among models was also investigated and proposed.     

Estimation of the critical rate of temperature rise for thermal explosion of nitrocellulose using non-isothermal DSC

The expressions to calculate the critical rate of temperature rise of thermal explosion $ ({\text{d}}T / {\text{d}}t)_{{\text{T}_{\text{b}} }} $ for energetic materials (EMs) were derived from the Semenov’s thermal explosion theory and autocatalytic reaction rate equation of nth order, C_nB, B_na, first-order, apparent empiric-order, simple first-order, A_u, apparent empiric-order of m = 0, n = 0, p = 1 and m = 0, n = 1, p = 1, using reasonable hypotheses. A method to determine the kinetic parameters in the autocatalytic-decomposing reaction rate equations and the $ ({\text{d}}T / {\text{d}}t)_{{\text{T}_{\text{b}} }} $ in EMs when autocatalytic decomposition converts into thermal explosion from data of DSC curves at different heating rate was presented. Results show that (1) under non-isothermal DSC conditions, the autocatalytic-decomposing reaction of NC (12.97 % N) can be described by the first-order autocatalytic reaction rate equation dα/dt = 10^16.00exp(?174520/RT)(1 ? α) + 10^16.00exp(?163510/RT)α(1 ? α); (2) the value of $ ({\text{d}}T / {\text{d}}t)_{{\text{T}_{\text{b}} }} $ for NC (12.97 % N) when autocatalytic decomposition converts into thermal explosion is 0.354 K s^?1.     

N-脒基脲二硝酰胺放热分解反应的动力学行为

用DSC和微热量仪研究了N-脒基脲二硝酰胺(GUDN)的放热分解反应动力学行为和比热容, 计算得到程序升温下GUDN主放热分解反应的动力学参数(活化能Ea和指前因子A)、自加速分解温度(TSADT)、绝热条件下达到最大分解反应速率的时间(tTMRad)和至爆时间(tTIad). 结果表明, 在非等温DSC条件下, GUDN的热分解过程可用经验级数自催化动力学方程dα/dt=10^18.49exp(-195500/RT)(1-α)^0.81+10^18.00exp(-177000/RT)α^1.29(1-α)^0.71描述. 热分解转热爆炸的临界温升速率为0.1236 K·h-1. 所得的TSADT、tTMRad和tTIad值分别为473.95 K、2.24 s和3.51 s.     

从DSC曲线数据计算/确定含能材料自催化分解反应动力学参数和热爆炸临界温升速率的方法

为应用热爆炸临界温升速率(dT/dt)_Tb评价含能材料(EMs)的热安全性, 得到计算(dT/dt)_Tb值的基本数据, 用合理的假设, 由Semenov的热爆炸理论和9 个自催化反应速率方程[dα/dt=Aexp(-E/RT)α(1-α) (I), dα/dt=Aexp(-E/RT)(1-α)ⁿ(1+K_catα) (II), dα/dt=Aexp(-E/RT)[α^a-(1-α)ⁿ)] (III), dα/dt=A₁exp(-E_a1/RT)(1-α)+A₂exp(-E_a2/RT)α(1-α) (IV), dα/dt=A₁exp(-E_a1/RT)(1-α)^m+A₂exp(-E_a2/RT)αⁿ(1-α)^p (V), dα/dt=Aexp(-E/RT)(1-α) (VI), dα/dt=Aexp(-E/RT)(1-α)ⁿ (VII), dα/dt=A₁exp(-E_a1/RT)+A₂exp(-E_a2/RT)(1-α) (VII), dα/dt=A₁exp(-E_a1/RT)+A₂exp(-E_a2/RT)α(1-α) (IX)]导出了计算(dT/dt)_Tb值的9 个表达式. 提出了从不同恒速升温速率(β)条件下的差示扫描量热(DSC)曲线数据计算/确定EMs自催化分解反应的动力学参数和自催化分解转向热爆炸时的(dT/dt)_Tb的方法. 由DSC曲线数据的分析得到了用于计算(dT/dt)_Tb值的β→0 时的onset 温度(T_e0),热爆炸临界温度(T_b)和相应于T_b时的转化率(α_b). 分别用线性最小二乘法和信赖域方法得到方程(I)和(VI)及方程(II)-(V)和方程(VII)-(IX)中的自催化分解反应动力学参数. 用上述基础数据得到了EMs的(dT/dt)_Tb值. 结果表明: (1) 在非等温DSC条件下硝化棉(NC, 13.54% N)分解反应可用表观经验级数自催化反应速率方程dα/dt=10^15.82exp(-170020/RT)(1-α)^1.11+10^15.82exp(-157140/RT)α^1.51(1-α)^2.51描述; (2) NC (13.54% N)自催化分解转向热爆炸时的(dT/dt)_Tb值为0.103 K·s^-1.     

Thermal decomposition behaviors and dust explosion characteristics of nano-polystyrene

With the development of nano-powder technology, polymeric nano-materials are widely used in various industries, while not much research on their thermal decomposition and dust explosion characteristics has been conducted. The thermal behaviors and explosion characteristic parameters of the nano-polystyrene (nano-PS) with a typical particle size of 90 nm were studied by employing thermogravimetric analysis (TG), MIE-D 1.2 minimum ignition energy (MIE) test device, and 20-L spherical dust explosion test equipment. The results showed that the thermal decomposition of the nano-PS occurred in a two-step process which was different from the single process for conventional PS. Meanwhile, the reaction rate of the thermal decomposition for nano-PS increased with the heating rate. The TG and DTG curves shifted to the higher-temperature zone when the heating rate increased, and the initial temperature, final temperature, temperature at the maximum rate, and the maximum rate also increased. The sensitivity parameter of the minimum ignition energy of nano-PS varied as the dust concentration altered, and the most sensitive explosive concentration was about 200 g m⁻³. Also, nano-PS was proved to be quite sensitive to the electrostatic spark, as its calculated MIE value was as low as 11 mJ. For the severity parameters, the explosion pressure and its rising rate of nano-PS tended to increase at first and then decrease with the increase in dust concentrations. According to the risk classification standard, the explosion risk class of nano-PS was St2. The results were further extensively compared to other previous works. The results demonstrated both the higher explosion possibility and severity of nano-PS. This study could provide guidance for the safety management of nano-PS in its manufacture, storage, and handling process.

     

An LX-10 kinetic model calibrated using simulations of multiple small-scale thermal safety tests

A new chemical kinetic model for the beta-delta transition and decomposition of LX-10 (95% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, 5% Viton A binder) is presented here. This model implements aspects of previous kinetic models but calibrates the model parameters to data sets of three experiments: differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and one-dimensional time to explosion (ODTX). The calibration procedure contains three stages: one stage uses open-pan DSC and TGA to develop a base reaction for formation of heavy gases, a second stage features closed-pan DSC to ascertain the autocatalytic behavior of reactant gases attacking the solid explosive, and a final stage adjusts the rate for the breakdown of heavy reactant gases using ODTX experimental data. The resultant model presents a large improvement in the agreement between simulated DSC and TGA results and their respective experiments while maintaining the same level of agreement with ODTX, scaled thermal explosion, and laser heating explosion times when compared to previous models.     

Synthesis and thermal decomposition of ditetrazol-5-ylamine

Ditetrazol-5-ylamine (DTA) was synthesized from cyanuric chloride in four steps. The thermal decomposition of DTA in the solid state was studied by thermogravimetry, volumetry, mass spectrometry, IR spectroscopy, and calorimetry. Under isothermal conditions at 200–242 °C, thermal decomposition obeys the first order autocatalytic kinetics. The kinetic and activation parameters of DTA decomposition were determined. The composition of gaseous reaction products and the structure of condensed residue were studied. The thermal effect of thermal DTA decomposition is 281.4 kJ mol⁻¹. The nitrogen content in a mixture of gaseous products formed by the reaction in a temperature interval of 200–242 °C exceeds 97 vol.%. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1660–1664, July, 2005.     

2,4-二硝基甲苯热解自催化特性鉴别及其热解动力学

为研究2,4-二硝基甲苯(2,4-DNT)的热危险性及其分解反应的特征, 利用差示扫描量热仪(DSC)对该物质进行了动态扫描测试, 得到其起始分解温度T₀范围为272.4-303.5℃, 分解热ΔH_d约为2.22 kJ·g^-1. 在此基础上, 采用瑞士安全技术与保障研究所提出的快速鉴别法(瑞士方法)及数值模拟技术, 对其分解反应的特性参数进行了推算, 结果表明其分解具有自催化性. 采用Malek法分析了该物质分解反应的最概然机理函数并得出了相关动力学参数, 表明其分解具有自催化性且符合Sestak-Berggren 双参数自催化模型(SB模型), 这与瑞士方法所得结论一致. 采用等温DSC测试获得了该物质的‘钟形’热解曲线, 从而验证了两种方法的结论.     

Thermal properties of hydrazine in nitric acid solution

Since some combustible, oxidative and reductive chemicals are used in the extracting process in the nuclear reprocessing plant the process has potential hazards of a fire and explosion due to the undesired reaction. In this study to obtain a better understanding of the thermal properties of hydrazine in nitric acid solution which is used for preventing the oxidation of extracted plutonium, thermal analysis was carried out for the mixtures in various conditions. From the results of DSC it was revealed that the vessel material has an influence on the thermal decomposition of hydrazine. It was also found that hydrazine reacted with nitric acid in an autocatalytic manner, and concentration of nitric acid has a strong influence on the thermal hazard of hydrazine and nitric acid mixtures.     

Modeling liquid thermal explosion reactor containing <Emphasis Type="Italic">tert</Emphasis>-butyl peroxybenzoate

This study investigated the role played by green thermal analysis technology in promoting the use of resources, preventing pollution, reducing energy consumption and protecting the environment. The chemical tert-butyl peroxybenzoate (TBPB) has been widely employed in the petrifaction industries as an initiator of polymerization formation agent. This study established the thermokinetic parameters and thermal explosion hazard for a reactor containing TBPB via differential scanning calorimetry (DSC). To simulate thermokinetic parameters, a 5-ton barrel reactor of liquid thermal explosion model was created in this study. The approach was to develop a precise and effective procedure on thermal decomposition, runaway, and thermal hazard properties, such as activation energy (E _a), control temperature (CT), critical temperature (TCR), emergency temperature (ET), heat of decomposition (∆H _d), self-accelerating decomposition temperature (SADT), time to conversion limit (TCL), total energy release (TER), time to maximum rate under isothermal condition (TMR _iso), etc. for a reactor containing TBPB. Experimental results established the features of thermal decomposition and huge size explosion hazard of TBPB that could be executed as a reduction of energy potential and storage conditions in view of loss prevention.     

Kinetic analysis of isothermal decomposition of 2,4-dinitrophenylhydrazine using differential scanning calorimetry

Differential scanning calorimetry was used to study the thermal decomposition of 2,4-dinitrophenylhydrazine (DNPH) in isothermal regime. The DSC curves were carried out at several constant temperatures lower than the melting temperature. The standard isoconversional analysis of the obtained curves suggests an autocatalytic decomposition mechanism. This mechanism is also supported by the temperature dependence of the observed induction periods.     

Influence of DSC Measurement Conditions on Kinetic Parameters of Thermal Decomposition of 2,4,6-trinitrotoluene

An autocatalytic model involving the limited solubility of volatile catalytic products was applied to the thermal decomposition of 2,4,6-trinitrotoluene. The critical supersaturation of the thermal decomposition products with the catalytic properties was higher at a low heating rate. Decrease of the sample mass led to an increased critical supersaturation of the decomposition products. This is probably a result of the greater contribution of products adsorption on the aluminium pan surface. It is presumed that the differences observed in the rate constant are connected with the uncontrolled critical supersaturation of the volatile thermal decomposition products. This revised version was published online in August 2006 with corrections to the Cover Date.     

乙酰氧肟酸的热稳定性分析

为预防化工生产、储运和使用中由乙酰氧肟酸(Acetohydroxamic acid, AHA)引发的火灾和爆炸事故, 采用绝热量热法对其热稳定性进行实验研究, 并将加速量热仪(Accelerating Rate Calorimeter, ARC)的测试结果与差示扫描量热仪(Differential Scanning Calorimetry, DSC)的结果进行了比较. ARC绝热测试结果表明, AHA的初始放热温度为352.68 K, 最高放热温度为465.82 K, 最大温升速率和最大温升速率时间分别为8.748 K•min^－1和382.65 min, 单位质量AHA生成气体的最大压力为2.22 MPa•g^－1. 根据ARC绝热测试结果, 采用速率常数法计算了AHA的动力学参数表观活化能和指前因子, 并求出了AHA的某种典型包装的不可逆温度和自加速反应温度. 研究结果表明, AHA的热稳定性较差, 爆炸性较强.     

Evaluating the Thermal Hazard of Double-Base Propellant SQ-2 by Using Microcalorimetry Method

The thermal decomposition behavior of double‐base rocket propellant SQ‐2 was studied by a Calvet microcalorimeter at four different heating rates. The kinetic and thermodynamic parameters were obtained from the analysis of the heat flow curves. The critical temperature of thermal explosion (T_b), the self acceleration decomposition temperature (T_SADT), the adiabatic decomposition temperature rise (ΔT_ad), the time‐to‐explosion of adiabatic system (t), critical temperature of hot‐spot initiation (T_cr), critical thermal explosion ambient temperature (T_acr), safety degree (SD) and thermal explosive probability (P_TE) were presented to evaluate the thermal hazard of SQ‐2.     

Simulation approach to decomposition kinetics and thermal hazards of hexamethylenetetramine

The thermal stability of HMT under dynamic, isothermal and adiabatic conditions was investigated using differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC), respectively. It is found from the dynamic DSC results that the exothermic decomposition reaction appears immediately after endothermic peak, a coupling phenomenon of heat absorption and generation, and the endothermic peak and exothermic peak were indentified at about 277–289 and 279–296 °C (T_peak) with the heating rates 1, 2, 4 and 8 °C min⁻¹. The ARC results reveal that the initial decomposition temperature of HMT is about 236.55 °C, and the total gas production in decomposition process is 6.9 mol kg⁻¹. Based on the isothermal DSC and ARC data, some kinetic parameters have been determined using thermal safety software. The simulation results show that the exothermic decomposition process of HMT can be expressed by an autocatalytic reaction mechanism. There is also a good agreement between the kinetic model and kinetic parameters simulated based on the isothermal DSC and ARC data. Thermal hazards of HMT can be evaluated by carrying out thermal explosion simulations, which were based on kinetic models (Isothermal DSC and ARC) to predict several thermal hazard indicators, such as T_D24, T_D8, TCL, SADT, ET and CT so that we can optimize the conditions of transportation and storage for chemical, also minimizing industrial disasters.

     

The effect of crystal structure on the thermal reactivity of CL-20 and its C4-bonded explosives

The critical temperature and mechanism functions for thermal decomposition of ε-CL-20, RS-ε-CL-20, α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4 were evaluated based on non-isothermal TG data. A two-step mechanism has been found for thermal decomposition of α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4, where the initial step is partly controlled by crystal structure of CL-20. The more reasonable mean activation energies could be obtained after peak separation for each individual steps. In fact, the activation energy for the post integrated process is almost equivalent with that of the second step, indicating that the total activation energy at the main decomposition process is dominated by thermolysis of CL-20 molecular. Besides, it has been found that the decomposition of C4 matrix does not affect the decomposition of normal ε-CL-20, resulting in identical activation energy and reaction model. However, the interaction between the C4 matrix and RS-ε-CL-20 is significant especially at the initial stage, where the activation energy of RS-ε-CL-20/C4 was overestimated before peak separation, while the activation energy for the second step due to thermolysis of CL-20 molecular is underestimated. The first decomposition step for α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4 could be considered as autocatalytic process (AC model), whereas the second as JMA model, which is also applicable to that of pure ε-CL-20 and RS-ε-CL-20. Moreover, The critical temperatures of thermal explosion (T _b) are obtained as 205.6, 205.5, 209.4, 214.4, and 227.5 °C for α-CL-20, ε-CL-20, RS-ε-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4, respectively. It proves that the C4 matrix could stabilize ε-CL-20 while the crystal form of CL-20 has little effect on its thermal stability.     

Non-isothermal Decomposition Kinetics of K(AHDNE)

The thermal behavior and non-isothermal decomposition kinetics of 1-amino-1-hydrazino-2,2-dinitro- ethylene potassium salt[K(AHDNE)] were studied under the non-isothermal conditions by different scanning calorimeter(DSC) method. The thermal behavior of K(AHDNE) presents three exothermic decomposition processes. The kinetic equation of the first thermal decomposition reaction obtained is dα/dT=(10^19.63/β)3(1-α)[-ln(1-α)]^2/3exp(-1.862× 10⁵/RT). The self-accelerating decomposition temperature(T_SADT) and critical temperature of thermal explosion(T_b) of K(AHDNE) are 162.5 and 171.4 ℃, respectively. K(AHDNE) has higher thermal stability than AHDNE.