Thermal hazard in a batch process involving hydrogen peroxide

Hydrogen peroxide is a versatile and interesting reagent for many industrial processes; nevertheless, it is very sensitive to impurities that can catalyze its decomposition, so that the desired reaction could be accompanied by undesired parallel and consecutive reactions. As an example, the butadiene free radical polymerization with hydrogen peroxide in the presence of an organic solvent was studied. Batch polymerization occurs in the liquid phase at about 120 °C. Because of the involved reactive compounds and the relatively high temperature, this is an intrinsically dangerous reaction. Therefore calorimetric data can give important information about safety and process optimization during the scale-up. The aim of this research project was to study the influence of impurities on the overall heat of reaction. The experiments were made in a high-pressure reaction calorimeter. The study has revealed that impurities do indeed affect the reaction course. Most importantly, the presence of carboxylic acids and/or ionic iron must be avoided and the recycle of unreacted reagents must be carefully controlled to minimize the build-up of these impurities.     

过氧化氢热爆炸研究进展

过氧化氢作为绿色环保的氧化剂,广泛应用于工业的各个领域,同时也因其热分解爆炸危险性导致了一系列严重的火灾爆炸事故。过氧化氢在高温或与一些不兼容化学物质作用下,将会激发其热危险性,进而引发热失控反应,最终导致爆炸事故的发生。结合近年来国内发生的过氧化氢热爆炸事故,简要概述了其热爆炸事故历程,并从理论研究和实验研究两个方面综述了过氧化氢热爆炸的研究进展。理论研究方面,主要介绍了化学反应失控模型和基于热动力学的研究方法,尤其对基于热失控模型的热风险评估进行了详细的阐述。实验研究方面,分析了高温条件下与杂质催化作用下过氧化氢的热危险性,包括无机杂质和有机杂质。最后就过氧化氢热爆炸的研究提出了进一步的研究方向。     

过氧丙酸分解反应的失控泄放特性研究

为研究过氧丙酸分解反应的失控泄放特性,利用泄放模式实验装置对过氧丙酸在不同泄放口径和泄放压力下的顶部和底部的泄放过程进行了试验模拟,得到了过氧丙酸的失控特性参数和不同条件下的泄放特征。结果表明:过氧丙酸失控反应泄放易出现二次峰值现象,初次峰值为气相泄放,二次峰值为气液两相泄放;二次峰值的出现取决于泄放口径及泄放时的物料温度,与泄放压力无关;恒压泄放容易出现非平衡泄放,导致较高最大累积压力和较高的釜内物料温度;底部泄放能够使釜内物料快速排空。     

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。     

Parametric sensitivity analysis for thermal runaway in semi-batch reactors: Application to cyclohexanone peroxide reactions

The semi-batch reactors (SBRs) system, which is widely used in industrial processes, possesses an intrinsic parametric sensitivity, in which infinitesimal disturbances of input parameters can result in large variations in output variables. In this work, local parametric sensitivity analysis (PSA) was used to understand parameter variations and global PSA was conducted to examine the interaction of input parameters. The effects of these parameters on the output of the system model were analyzed based on the Monte Carlo method with Latin hypercube sampling and the extended Fourier amplitude sensitivity test model. The results showed that the evolution of thermal behaviors in SBRs were observed: marginal ignition; thermal runaway; and the quick onset, fair conversion, and smooth temperature profile. The threshold point of transition from marginal ignition to thermal runaway was at the maximal value of local sensitivity, for which the slope with respect to cooling temperature equaled zero. Moreover, the sequence of the global sensitivity of six common input parameters was computed and evaluated. The reliability of the numerical models was verified by using our previous experimental results of cyclohexanone peroxide reaction. This comprehensive sensitivity analysis could provide valuable operating information to improve chemical process safety.     

Calorimetric studies on the thermal stability of methyl ethyl ketone peroxide (MEKP) formulations

The energetic decomposition of methyl ethyl ketone peroxide (MEKP) and its formulations have long been known to present a significant risk. Indeed, MEKP has the highest number of reported decomposition incidents of all organic peroxides, many of which have led to significant numbers of fatalities, injuries and damage. It is noteworthy that incidents have been reported at all stages of the product lifecycle.This paper is derived from incident-investigation work and provides a summary of serious incidents involving MEKP, followed by details of calorimetric experiments performed to investigate thermal stability of representative MEKP formulations containing varying amounts of MEKP monomer. In particular we report the wide degree of variation that exists between commercial MEKP formulations, even between materials that are of the same nominal formulation. Such variations are detectable using differential scanning calorimetry (DSC).Follow-up studies performed on a representative MEKP formulation containing MEKP monomer indicate that a risk of decomposition exists at temperatures well below the reported self-accelerating decomposition temperature (SADT) of the products. As such, the experimental results reported here suggest that lower storage temperatures (commonly recommended by manufacturers to maximise shelf life) should be considered as being essential throughout the product lifecycle to reduce the risk of accidents in storage and transportation.     

金属离子对双氧水热稳定性的影响研究

为了研究金属离子对双氧水在绝热条件下分解特性的影响,利用泄放尺寸设计装置VSP2模拟双氧水及分别掺杂0.01%质量分数Fe~(2+)、Fe~(3+)、Gu~(2+)的双氧水在绝热条件下的反应失控过程,得到绝热分解过程的热力学和动力学参数,依此推算出该4种试样25 kg包装下的自加速分解温度SADT,以及绝热条件下到达最大反应速率的时间TMRad。结果表明,Fe~(2+)、Fe~(3+)、Gu~(2+)使双氧水的起始分解温度T0、SADT、TMRad均降低,提高了双氧水的热危险性。在Fe~(3+)的作用下,双氧水在常温下就发生缓慢分解,发生失控的可能性最大;掺杂了Gu~(2+)的双氧水分解反应最剧烈,热失控严重度最高。     

Refinery wastewater degradation with titanium dioxide,zinc oxide,and hydrogen peroxide in a photocatalytic reactor

This paper presents the photo-catalytic degradation of real refinery wastewater from National Refinery Limited (NRL) in Karachi, Pakistan, using TiO₂, ZnO, and H₂O₂. The pretreatment of the refinery effluent was carried out on site and pretreated samples were tested at 32–37 °C in a stirrer bath reactor by using ultra-violet photo oxidation process. The degradation of wastewater was measured as a change in initial chemical oxygen demand (COD) and with time. Optimal conditions were obtained for catalyst type, and pH. The titanium dioxide proved to be very effective catalysts in photo-catalytic degradation of real refinery wastewater. The maximum degradation achieved was 40.68% by using TiO₂ at 37 °C and pH of 4, within 120 min of irradiations. When TiO₂ was combined with H₂O₂ the degradation decreased to 25.35%. A higher reaction rate was found for titanium dioxide. The results indicate that for real refinery wastewater, TiO₂ is comparatively more effective than ZnO and H₂O₂. The experiments indicated that first-order kinetics can successfully describe the photo-catalytic reaction. The ANOVA results for the model showed satisfactory and reasonable adjustment of the second-order regression model with the experimental data. The ANOVA results also showed that pH is significant than reaction time and catalyst dosage of TiO₂; and in case of ZnO, reaction time is significant than pH and catalyst dosage. This study proves that real refinery wastewater reacts differently than synthetic refinery wastewater, oil field produced water or oil water industrial effluent.     

Thermal decomposition kinetic of liquid organic peroxides

This study demonstrates the application of isothermal calorimeter for investigating the thermal decomposition of several liquid organic peroxides, such as t-Butyl peroxy acetate (TBPA), Di-tert butyl peroxide (DTBP), and Cumene hydroperoxide (CHP). The decomposition mechanism and kinetic can be identified from case to case. TBPA and DTBP undergo first order reaction, whereas CHP occurs autocatalysis. Accurate kinetic can be assessed on the basis of discerning these various schemes of given samples. Consequently, the thermal runaway or reactive hazards potential of organic peroxides can be determined, for instance as a self accelerating decomposition temperature (SADT).     

过氧化氢除藻及相关环境条件优化

采用室内培养的方式,通过正交试验研究了H_2O_2质量浓度、光照、pH值和温度4个因素复合作用对铜绿微囊藻去除的影响。结果表明,在所设置的各因素梯度范围内,对去除铜绿微囊藻影响最大的因素是H_2O_2质量浓度;光照和pH值对藻细胞数和叶绿素a的去除,以及H_2O_2残留量的影响各不相同;温度对藻细胞数的影响最小,对H_2O_2残留量的影响较小,对叶绿素a质量浓度的影响较大。除藻的最佳组合为A_1B_2C_3D_2,即光照为1 500 lx,H_2O_2质量浓度为50mg/L,pH值为8.5,温度为25℃。     

过氧化苯甲酰合成工艺热危险性分析

采用RC1e反应量热仪对过氧化苯甲酰(BPO)合成工艺危险性进行研究,测试不同Na OH溶液初始浓度(1.96 mol/L、3.93 mol/L、7.14 mol/L)下反应的放热历程,获得BPO合成反应过程中的热危险性参数,并采用PHI-TECⅡ绝热加速量热仪对产物进行热稳定性分析,最后评估该反应热风险。结果表明,Na OH浓度为7.14 mol/L时,反应初期放热速率慢,热累积度大,后期反应剧烈,绝热温升(ΔTad)及热失控时工艺反应达到的最高温度(MTSR)最大。热稳定性试验表明,合成的粗产物BPO初始分解温度、活化能、指前因子、最大放热速率到达时间为24 h时的对应温度(TD24)均低于纯BPO。利用合成粗产物BPO的TD24对反应进行危险度评估,该工艺热危险性等级均为5级,工艺危险性大。     

Thermal hazard accident investigation of hydrogen peroxide mixing with propanone employing calorimetric approaches

Hydrogen peroxide (H₂O₂), historically, due to its broad applications in the chemical industries, has caused many serious fires and explosions around the world. Its thermal hazards may also be incurred by an incompatible reaction with other chemicals, and a runaway reaction may be induced in the last stage. This study applied thermal analytical methods to explore the H₂O₂ leading to these accidents by incompatibility and to discuss what might be formed by the upset situations. Thermal hazard analysis contained a solvent, propanone (CH₃COCH₃, so-called acetone), which was deliberately selected to mix with H₂O₂ for investigating the degree of thermal hazard. Differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2) were employed to evaluate the thermal hazard of H₂O₂. The results indicated that H₂O₂ is highly hazardous while mixed with propanone, as a potential contaminant. The time to maximum rate (TMR) was used as emergency response time in the chemical industries. Therefore, TMR of H₂O₂ was calculated to be 70 min for runaway reaction (after T₀) and TMR of H₂O₂/propanone was discovered to be 27 min only. Fire and explosion hazards could be successfully lessened if the safety-related data are properly imbedded into manufacturing processes.     

BIPB的热分解动力学和失控反应模拟

为了评估双(叔丁过氧基)二异丙苯(BIPB)的热危害,对其热分解过程进行多速率的动态扫描C80热分析,用几种简单的热危害评估方法分析其热危害。然后应用模式法、无模式法(Friedman微分等转化率法)分别对试验结果进行处理,得到分解动力学数据,并用ASTM E 698法得到活化能数据,同时用C80、ARC和DSC的试验数据验证分解动力学数据的可靠性。最后利用无模式法的分解动力学数据进行BIPB绝热条件下和非绝热的2m3球形容器中的失控反应模拟,得到类似工艺条件下BIPB的安全控制温度。     

CFD modelling of hydrogen release, dispersion and combustion for automotive scenarios

The paper describes the analysis of the potential effects of releases from compressed gaseous hydrogen systems on commercial vehicles in urban and tunnel environments using computational fluid dynamics (CFD). Comparative releases from compressed natural gas systems are also included in the analysis.

This study is restricted to typical non-articulated single deck city buses. Hydrogen releases are considered from storage systems with nominal working pressures of 20, 35 and 70 MPa, and a comparative natural gas release (20 MPa). The cases investigated are based on the assumptions that either fire causes a release via a thermally activated pressure relief device(s) (PRD) and that the released gas vents without immediately igniting, or that a PRD fails. Various release strategies were taken into account. For each configuration some worst-case scenarios are considered.

By far the most critical case investigated in the urban environment, is a rapid release of the entire hydrogen or natural gas storage system such as the simultaneous opening of all PRDs. If ignition occurs, the effects could be expected to be similar to the 1983 Stockholm hydrogen accident [Venetsanos, A. G., Huld, T., Adams, P., & Bartzis, J. G. (2003). Source, dispersion and combustion modelling of an accidental release of hydrogen in an urban environment. Journal of Hazardous Materials, A105, 1–25]. In the cases where the hydrogen release is restricted, for example, by venting through a single PRD, the effects are relatively minor and localised close to the area of the flammable cloud. With increasing hydrogen storage pressure, the maximum energy available in a flammable cloud after a release increases, as do the predicted overpressures resulting from combustion. Even in the relatively confined environment considered, the effects on the combustion regime are closer to what would be expected in a more open environment, i.e. a slow deflagration should be expected.

Among the cases studied the most severe one was a rapid release of the entire hydrogen (40 kg) or natural gas (168 kg) storage system within the confines of a tunnel. In this case there was minimal difference between a release from a 20 MPa natural gas system or a 20 MPa hydrogen system, however, a similar release from a 35 MPa hydrogen system was significantly more severe and particularly in terms of predicted overpressures. The present study has also highlighted that the ignition point significantly affects the combustion regime in confined environments. The results have indicated that critical cases in tunnels may tend towards a fast deflagration, or where there are turbulence generating features, e.g. multiple obstacles, there is the possibility that the combustion regime could progress to a detonation.

When comparing the urban and tunnel environments, a similar release of hydrogen is significantly more severe in a tunnel, and the energy available in the flammable cloud is greater and remains for a longer period in tunnels. When comparing hydrogen and natural gas releases, for the cases and environments investigated and within the limits of the assumptions, it appears that hydrogen requires different mitigation measures in order that the potential effects are similar to those of natural gas in case of an accident. With respect to a PRD opening strategy, hydrogen storage systems should be designed to avoid simultaneous opening of all PRD, and that for the consequences of the released energy to be mitigated, either the number of PRDs opening should be limited or their vents to atmosphere should be restricted (the latter point would require validation by a comprehensive risk assessment).     

双氧水爆炸事故机理分析及预防措施研究

为了对双氧水引起的爆炸事故的机理进行分析,用加速量热仪对双氧水进行了热危险性测试.通过对数据校正和分析,得到了浓度为30%的双氧水初始热分解温度为34.5 ℃,热分解可达到的最高温度为246 ℃,最大温升速率时间为100 min.结果表明,双氧水极易发生爆炸,并且爆炸威力很大.针对双氧水的爆炸危险,提出采取适当的预防措施,如冷却水法,以避免爆炸事故的发生.     

某恒温间歇反应的热失控研究

为得到某恒温间歇反应冷却系统临界温度Tc并评估该反应体系的热危险性,基于间歇反应体系热参数的敏感性,探讨数值计算方法和选用4种反应热失控临界判据得到的不同Tc值。结果表明,数值计算方法得到了反应体系的Tc为31.7℃,Semenov判据、Sliding判据、Da/St判据得到的Tc值分别为10℃,17℃和27℃;无量纲绝热温升B给出的结论是,在允许的工艺温度范围内,该反应对任意的冷却系统温度都处于难以控制状态。数值计算方法及各判据得到的Tc的较大差异性说明各方法均有一定的局限性。在运用参数敏感性分析的基础上,结合风险矩阵图方法对系统冷却失效的热危险性进行评估,得到不同Tc下风险可接受、有条件接受及不可接受对应的参数范围的物料累积度Xac与最大反应速率到达时间θ间的关系。     

锂离子电池组热失控蔓延热传递机制的影响研究

分析通风和电池组数量对电池组热失控发展蔓延热传递机制的影响.选择荷电状态(SOC)为100％的镍钴锰(NCM523)三元锂离子动力电池组作为研究对象,改变电池组底部外加热源的热流量和加热时间,利用多物理场仿真软件COMSOL,进行热滥用导致不同风速通风环境和不同电池数量电池组热失控过程的模拟.结果表明:随着风速不断增大...     

Comparison of criteria for prediction of runaway reactions in the sulphuric acid catalyzed esterification of acetic anhydride and methanol

Loss of temperature control is one of the major reasons that can lead to runaway reaction. This occurrence is commonly named thermal runway. The aim of this paper is the application of thermal runaway criteria in order to predict the onset of runaway phenomena and define the range of stability related to operating conditions in the reactor, with specific reference to the esterification of acetic anhydride and methanol catalysed by sulphuric acid tested in isoperibolic conditions. The isoperibolic calorimeter has also been used to obtain thermodynamic, kinetic and physical chemistry data necessary to develop a model for the reaction. Some runaway criteria applied in this work require a model for the process, so a model for the analyzed system been developed.Because of the modest reaction enthalpy and low activation energy this reacting system provide a severe test to the runaway criteria.In this work, various runaway criteria have been applied to the experimental and simulated data and the results obtained have been compared.     

Kinetic parameter estimation for decomposition of organic peroxides by means of DSC measurements

The thermal stability of organic peroxides (cumene hydroperoxide 80 wt% and dicumyl peroxide) was studied by means of calorimetric measurement (DSC, TA Q1000) in an isotherm mode and a dynamic mode. Analysis of power profiles released in the isothermal mode was combined with the analysis of the decomposed compounds by a gas chromatograph/mass spectrometer (GC/MS) to determine the reaction mechanisms corresponding to each of the two reactions. In this work, a methodology for estimating kinetic parameters was based on the comparison of the power profile (dynamic mode) given by the model to that obtained experimentally by changing the parameters values. Parameter estimation is achieved using the mixed estimation method where a genetic algorithm is combined with a locally convergent method.     

亚硝酸乙酯分解危险性研究

为了了解亚硝酸乙酯的分解危险性,通过微量热仪研究并确定了亚硝酸乙酯的分解热、起始分解温度、峰值温度等基础数据;通过爆轰管研究并确定了不同温度下亚硝酸乙酯的分解临界压力,对比了氮气和一氧化碳的稀释效果。研究表明:亚硝酸乙酯分解临界压力较低易发生分解,亚硝酸乙酯的分解会降低偶联反应的选择性,甚至造成装置的非计划停车。因此,为避免亚硝酸乙酯发生分解爆炸,建议严格按照亚硝酸乙酯分解物性操作。