The differential reaction calorimeter: examples of use

A new kind of calorimeter, commercialized by SETARAM SA and operating in isoperibolic mode, appeared 2 years ago: the differential calorimeter DRC^®. This DRC was developed by Aventis Pharma in their own laboratories and has been used as standard tool for 10 years. The Swiss Institute for the promotion of safety and security (Organic Process Research and Development (2002) to be published) has also studied this calorimeter. In order to show the accuracy of this apparatus, we can compare the DRC with the RC1 from Mettler Toledo which is the reference for safety studies. We can demonstrate the exactitude of results in a wide range of reactions: with one step (neutralization) or two steps (aldolisation–crotonisation), semi-batch reactions with addition of one reagent or simultaneous additions of two reagents, slightly or very exothermic reactions. In each situation, DRC will obtain the same data and results in less time with a smaller amount of raw materials.     

Thermal performance assessment of heat resistant fabrics based on a new thermal wave model of skin heat transfer.

A thermal wave skin model incorporating surface heat flux from a skin simulant sensor is developed to characterize the thermal performance of heat resistant fabrics covering the skin simulant sensor. Comparisons of time to 2nd-degree skin burn and temperature elevation of skin beneath a layer of fabric between the Pennes' equation and the newly developed thermal wave skin model are performed in this research. Results of tolerance time from the Stoll criterion method are also compared with those from 2 skin models in a thermal protective performance calorimeter. It is concluded that the thermal properties of heat resistant fabrics can be characterized more precisely than previously.     

旅客行李对高速客车车厢火源热释放速率的影响研究

为了得到考虑旅客行李影响情况下的高速客车车厢火源热释放速率的合理取值范围,以CRH1型动车组二等座车厢为例,以锥型量热仪和大型量热仪测定的高速客车车体内材料和行李的燃烧性能为输入参数,运用FDS软件模拟9种火灾场景下车厢的火源热释放速率随时间的变化规律,分析行李重量对车厢火源热释放速率的影响。研究结果表明:旅客行李对高速客车车厢火源热释放速率的影响是与通风条件协同作用的结果;在车门与车窗关闭条件下,旅客行李对于火源热释放速率的贡献值基本可忽略;在车门开启与车窗关闭条件下,旅客人均携带10kg和20kg行李时,行李对车厢火源热释放速率的贡献值为0.24MW和0.6MW,贡献率为5%和11%;在车门与逃生车窗开启条件下,旅客人均携带10kg和20kg行李时,行李对车厢火源热释放速率的贡献值分别为1.3MW和3.8MW,贡献率分别为7%和21%。     

CRH_1型动车组一等座车厢火源热释放速率研究

为了得到不同通风条件和旅客行李条件下CRH1动车组一等座车厢的火源热释放速率的合理取值范围,以CRH1型动车组一等座车厢为研究对象,以锥形量热仪和大型量热仪测定的高速客车车体内材料和行李的燃烧性能为输入参数,运用FDS软件模拟6种火灾场景下车厢的火源热释放速率随时间的变化规律,分析了通风条件、火灾荷载密度、可燃物间距和行李重量对车厢火源热释放速率的影响。研究结果表明:在不考虑旅客行李时,各种通风条件下车厢最大火灾热释放速率在1.86-4.34MW之间;在车门与车窗开启条件下,与不考虑旅客行李的情况比较,人均携带10、20kg行李时,火源热释放速率分别增加了12.84、15.38MW,增加的幅度分别为570%和684%。     

Numerical simulation of the thermal inertia of an adiabatic reaction calorimeter in reaction thermal safety process

Obtaining accurate thermal risk assessment parameters of chemical processes and substance properties is essential for improving the safety of chemical production and substance use and storage, and the adiabatic reaction calorimeter (ARC) has been employed by many researchers for this purpose. However, with the improvement and upgrading of the instrument, an examination of the factors that affect its detection accuracy is warranted. A simplified reaction model of the adiabatic thermal decomposition of tert-butyl peroxyacetate was constructed using computational fluid dynamics in which the adiabatic thermal decomposition kinetic model and fluid-solid coupling model were combined to simulate heat transfer. To verify the reliability of the parameters of the numerical calculation model, the effects of the sample cell's material, wall thickness, and mass were investigated in relation to the thermal inertia of the ARC. The results indicated that the thermal inertia of the system was lowest when the sample cell was composed of titanium. When the sample pool's composition is determined, the thermal inertia of the system can be reduced to a certain extent through an approximate increase in the sample mass. Finally, an analysis of the heat flow cloud diagram of the wall of sample pools made from different materials revealed that the thermal conductivity of titanium was high; this information can assist in controlling the adiabatic process.     

Investigation of the decomposition reaction and dust explosion characteristics of crystalline dicumyl peroxide

The dicumyl peroxide (DCP) is widely used as a polymerization initiator, catalyst and vulcanizing agent in the chemical industry. A number of accidents have been caused by its thermal instability in storage or manufacturing process. Thus, its hazard characteristics have to be clearly identified. First of all, the differential scanning calorimeter (DSC) is used to measure the heat of decomposition reaction, which can contribute to understanding the reaction characteristics of DCP. The accelerating rate calorimeter (ARC) is used to measure the rates of temperature and pressure rises of decomposition reaction, and then the kinetics parameters are estimated. Furthermore, the MIKE 3 apparatus and the 20-l-Apparatus are used to measure and analyze the dust explosion characteristics of DCP at room temperature and atmospheric pressure. Finally, Semenov's thermal explosion theory is applied to investigate the critical runaway condition and the stability criterion of decomposition reaction, and to build the relationship of critical temperature, convective heat transfer coefficient, heat transfer surface area and ambient temperature. These results contribute to improving the safety in the reaction, transportation and storage processes of DCP.     

辐射热流条件下多层电缆着火的数值模拟

通过CFD计算软件对锥形量热燃烧实验条件下的多层电缆着火性能进行数值模拟计算,对比相应CONE电缆燃烧实验结果,其计算结果表明所建立的电缆模型所得计算结果能够较好预测电缆着火时间。在此基础上,对护套层、绝缘层厚度、线芯层直径等参数对着火时间的影响进行了分析,发现护套层厚度对着火时间影响最大,线芯层对着火时间影响较小;当护套层及绝缘层厚度达到一定数值之后,电缆着火时间将不再发生变化。另外,因为电缆由多层热特性各异的材料组成,不能简单的划分为热薄材料或者热厚材料,但就所模拟电缆而言,其着火时间在不同的热辐射强度下分别表现出与热薄材料或者热厚材料相似的变化规律。     

玻璃纤维增强聚对苯二甲酸乙二醇酯/次磷酸铈复合材料的制备及其阻燃性能研究

首先合成并表征了一种新的阻燃剂-次磷酸铈（CHP）;然后采用熔融共混的方法制备了玻璃纤维（GF）增强聚对苯二甲酸乙二醇酯（PET）/CHP（PET/GF/CHP）复合材料;探讨了CHP对PET/GF复合材料热稳定性和燃烧性能的影响。材料的热稳定性是由热失重分析（TGA）进行表征的,燃烧性能是通过氧指数（LOI）、垂直燃烧（UL-94）以及锥形量热仪进行测试的,炭渣形貌由扫描电子显微镜（SEM）进行表征。结果表明：CHP的引入保持了PET/GF的热稳定性。含有15wt%CHP的PET/GF材料（PET/GF/CHP15）,其LOI为30%,且能达到UL-94V-0级别。此外,与PET/GF相比,PET/GF/CHP15热释放速率峰值和热释放总量分别下降了67%和27%。SEM分析表明CHP的加入使得材料在燃烧后有大量致密的炭渣覆盖在玻璃纤维的表面,这些炭渣不仅降低了玻璃纤维的导热性,而且切断了可燃物质的传送通道,从而提高了材料的阻燃性能。     

二叔丁基过氧化物的热失控动力学研究

为研究二叔丁基过氧化物(DTBP)热失控危险性,利用C600微量量热仪对DTBP热分解动力学进行试验研究,测定DTBP在不同升温速率下的起始放热温度和分解热,分别用非等转化率法和等转化率法得到DTBP热分解反应的动力学参数。用非等转化率法确定反应的最佳反应级数为1,相应的活化能分别为137.75、132.60、128.61和122.93 kJ/mol,指前因子分别为8.82×1012、6.69×1012、2.06×1012和3.89×10111/s。用等转化率法确定的活化能范围为102～138 kJ/mol,并拟合出活化能与转化率的关系曲线。结合计算出的动力学参数,通过对DTBP分解机理的分析,可以推断其具有热失控危险性。     

采用锥形量热仪(CONE)研究和评价新型可膨胀石墨防火涂料

利用锥形量热仪(CONE)实验获得的热失重速率(MLR)、热释放速率(HRR)、有效燃烧热(EHC)、比消光面积(SEA)、CO2、CO和点燃时间(TTI)等参数对可膨胀石墨防火涂料与传统的膨胀型防火涂料的阻燃性能、烟毒释放、阻燃机理进行了对比研究。结果表明,与传统的膨胀型防火涂料相比,可膨胀石墨防火涂料由于在热降解过程中成炭量较高,炭层具有更好的热稳定性,因而其阻燃和隔热性能更为优良,具有更长的耐燃时间,且烟毒释放少,安全性能更高。     

辐射热流作用下树叶样品的燃烧特征研究

研究植物叶样在外部热辐射和值班火源作用下的燃烧现象特征并探索其成因和物理及化学本质。采用锥形量热仪开展实验,热辐射强度分别设定为35kW m-2、55kW m-2、70kW m-2和85kW m-2。实验样品为针阔叶树种共13种,其含水率在45%至79%间变化。实验表明,样品表现出不同的着火模式,有的为明火,有的则为阴燃,取决于树种和设定的辐射强度。样品出现有焰燃烧现象的最低热释放速率峰值(PHRR)在22.3kW m-2至35.6kW m-2之间,反映了形成气相火焰所需最低挥发分质量流率。气相产物CO2产生速率的峰值与PHRR呈高度线性性,表明了不同样品间气相燃烧或固相表面氧化(阴燃燃烧)反应的相似性。进一步分析表明,出现的独特热释放速率尖锐峰形是样品分层特性以及树叶的物理属性和热物性共同作用的结果。具有热薄特性的样品表层,在实验初期是接受外部辐射热的主体,其热解的产物是形成气相火焰的物质来源;在其转变为焦炭层后,对辐射热流向内层的渗透具有阻挡作用。建立起来的认识对于评估分层样品的燃烧性有一定的指导意义。     

基于人体皮肤热模型的热防护服评价方法研究

在热防护服热防护性能测试装置基础上,用自行研制的新型耐高温模拟皮肤传感器代替铜片热流计测量通过应急热防护服装面料的热流量,将热流量作为热波皮肤模型边界条件,得到人体皮肤表层下80μm处的温度值,从而得到一定条件下人体真实皮肤达到二级烧伤所需时间,用其评价热防护服用织物的热防护性能,并将热波皮肤模型(TWMBT)的测试值与Pennes模型以及铜片热流计的测试结果进行分析比较。采用热波皮肤模型分析织物层下的"皮肤"防热时间更接近实际皮肤达到二级烧伤时间值,可较为精确的量化织物热防护性能,为应急救援热防护服装的热设计提供理论依据。     

基于锥形量热仪的计算机显示器燃烧特性分析

利用锥形量热仪对计算机显示器材料进行小尺寸燃烧性能试验研究,通过改变锥形量热仪的热辐射强度模拟中、小规模火灾。分析火灾中显示器样品的热释放速率(HRR)、质量损失速率、CO产生率和比消光系数。试验发现当热辐射强度为35 kW/m2时,计算机显示器的热释放速率比其在热辐射强度为75 kW/m2时多一个加速增长阶段,主要原因是在此热辐射强度下,材料热解速度缓慢,表面炭层厚度逐渐增厚,热量积聚后,材料热解速度增大,热释放速率加速达到第二个峰值;显示器材料在2种热辐射强度下的质量损失速率分3个阶段,炭层的包覆作用对其质量燃烧速率影响较小;显示器材料在燃烧过程中CO产生率、比消光系数和质量燃烧速率成线性递增关系。试验结果可反映显示器在真实火灾中的燃烧特性。     

ZR-KVV电缆排布数量对燃烧特性影响的实验研究

电缆在实际布置情况下通常是多根成束装配,而电缆的排布数量对运行安全性有很大影响,研究电缆的排布数量对燃烧特性的影响具有重要意义。使用锥形量热仪,对ZR-KVV电缆以不同数量排布,研究分析其质量损失速率、热释放速率等主要燃烧性能参数。实验结果表明,当电缆受到固定火源的辐射热流影响时,质量损失速率峰值和热释放速率峰值随着水平布置电缆数量的增加呈指数递增;随着外部辐射热流强度的增强,质量损失速率峰值和热释放速率峰值增加,总热释放速率则减小。     

过氧化苯甲酸叔丁酯热危险性实验研究

为了研究TBPB的热危险性,采用液体自燃点测试仪研究TBPB自燃点随浓度的变化规律,应用快速筛选量热仪研究不同升温速率下TBPB的热分解,同时利用差示扫描量热仪研究TBPB热流-温度变化规律。研究结果表明:当TBPB浓度为0.83 g/L时,自燃温度达到最低值125.1 ℃,浓度是影响其自燃温度的重要指标;随升温速率升高,初始分解温度逐渐升高,可见升温速率越高,TBPB分解的初始温度越高,当环境温度未达到初始分解温度时,相对较安全;TBPB最低起始反应温度为95.4 ℃,平均放热量为893.28 J/g,运用Kissinger,Ozawa 这2种方法得出E1=84 063.2 J/mol,E2=86 442.3 J/mol,指前因子为1.69×109,反应级数为0.92。其放热量较大,起始反应温度较低,热量无法及时移出时,极易发生燃烧爆炸事故。     

Effect of transient heat transfer on ignition of solid particles

Ignition and combustion of solid particles are the issues of interest for many industrial applications. When simulating ignition and combustion of solid particles using available standard (ST) models, a number of simplifying assumptions are usually adopted, which are not always justified. For example, for calculating heat flux to particle surface, the Newton law is often applied with the heat flux proportional to the difference between the gas temperature and the mean particle temperature. However, Newton law is known to be valid only for steady-state heat transfer. Moreover, the actual heat flux is determined by the particle surface temperature rather than its mean temperature. The objective of this work is to develop a new particle-heating model with the correction factors to the Newton law taking into account transient heat transfer to a particle and nonuniform temperature distribution inside the particle. It was shown that the new particle-heating model correlates much better with detailed numerical calculations than the ST model. The transient heating effects were shown to be important for the problem of solid particle ignition in the oxidizer gas.     

Experimental Study of the Interation Between the Water Mists and PVC Fire

Effect of water mist on the small-scale solid fuel polyvinyl chloride (PVC) fire in the confined space has been studied experimentally with the heat release rate measured by a cone calorimeter in this paper.The water mist is generated by a single pressure nozzle and the diffusion flame is produced from PVC samples respectively. The LDV/APV system is employed to determine the water mist characteristics. The Cone Calorimeter is used to measure the heat release rate, oxygen and carbon monoxide concentrations and other important parameters of the interaction under various conditions.The results of the test showed that heat extraction cooling (flame cooling and fuel surface cooling) plays a dominating role to suppress the PVC fire, when the water mist with enough volume flux are applied to the diffusion flame in the confined space. The higher the operation pressure, the easier the suppression. The faster the PVC fire suppressed by water mist with large enough water flux, the less the total amount of toxic gases (CO, CO₂) produced.     

交联剂TAIC反应风险评估分析

利用全自动反应量热仪和绝热加速量热仪等相关实验仪器检测出TAIC(三烯丙基异氰尿酸酯)合成反应的反应热、比热容及热稳定性等数据,依据绝热温升、工艺温度、技术最高温度、最大反应速率到达时间及失控体系可能达到的最高温度这5个温度参数按照评估标准从分解热、严重度、可能性、矩阵、工艺危险度这5个方面分别进行评估。通过对热参数及实验过程进行分析提出降低工艺危险等级的工艺优化方法。根据最终评估结果对TAIC生产装置的安全性进行评价,提出相应的整改措施及建议。