Thermal decomposition study of hydroxylamine nitrate during storage and handling

Hydroxylamine nitrate (HAN), an important agent for the nuclear industry and the U.S. Army, has been involved in several costly incidents. To prevent similar incidents, the study of HAN safe storage and handling boundary has become extremely important for industries. However, HAN decomposition involves complicated reaction pathways due to its autocatalytic behavior and therefore presents a challenge for definition of safe boundaries of HAN storage and handling. This research focused on HAN decomposition behavior under various conditions and proposed isothermal aging testing and kinetic-based simulation to determine safety boundaries for HAN storage and handling. Specifically, HAN decomposition in the presence of glass, titanium, stainless steel with titanium, or stainless steel was examined in an Automatic Pressure Tracking Adiabatic Calorimeter (APTAC). n-th order kinetics was used for initial reaction rate estimation. Because stainless steel is a commonly used material for HAN containers, isothermal aging tests were conducted in a stainless steel cell to determine the maximum safe storage time of HAN. Moreover, by changing thermal inertia, data for HAN decomposition in the stainless steel cell were examined and the experimental results were simulated by the Thermal Safety Software package. This work offers useful guidance for industries that manufacture, handle, and store HAN. The experimental data acquired not only can help with aspects of process safety design, including emergency relief systems, process control, and process equipment selection, but also is a useful reference for the associated theoretical study of autocatalytic decomposition behavior

Computational study of self-heating ignition of Lithium-ion batteries during storage: effects of heat transfer and multi-step kinetics

Fire safety is a serious concern when storing a large number of Lithium-ion batteries (LIBs) stacked as an ensemble. Many such fires reported in recent years have caused severe damage to industrial facilities, public property, and even loss of life. It is crucial to understand the mechanisms and causes of these storage fires to provide insights for prevention. While previous studies mostly focused on the chemistry of LIBs and ignition while charging or discharging, this thesis explores the possibility of another fundamental cause of such fires driven by heat transfer, self-heating ignition. Three major challenges are identified for the modelling of self-heating ignition of LIB ensembles: large sizes, multi-dimensional heat transfer, and multiple chemical reactions. In this thesis, a typical LiCoO2 (LCO) battery with four-step reaction kinetics is chosen for analysis and modelling the fundamentals of self-heating ignition. Four numerical models based on COMSOL Multiphysics are developed to deal with these challenges. The numerical results show that the critical ambient temperature triggering self-heating ignition decreases significantly with the size of the battery ensemble, from 155℃ for a single cell to 45℃ for a rack of cells. The spacing and packaging materials used to separate LIBs in storage can promote self-heating ignition further decreasing the critical temperature. The increase in size and the presence of packaging materials result in slower internal heat transfer, which allows the cells to self-ignite at lower ambient temperatures. The heat from self-discharge, which is often neglected in the literature, is predicted to have minor effects on small LIB ensembles but to be dominating for a shelf of LIBs, indicating a substantial change in important chemical mechanism for different sizes. The differences resulting from different numerical models are investigated by a benchmarking analysis using two simulation tools: COMSOL and Gpyro. This thesis provides insights on the fundamental mechanism of self-heating ignition of LIBs during open-circuit storage and scientifically proves that self-heating ignition can be a cause of fires when LIBs are stacked to large sizes.Open Acces

Reaction mechanism of cumene hydroperoxide decomposition in cumene and evaluation of its reactivity hazards

Cumene hydroperoxide (CHP), a type of organic peroxide, is widely used in the chemical industry for diverse applications. However, it decomposes and undergoes highly exothermic runaway reactions under high temperature because of its unstable peroxide functional group. The risk of runaway reaction is intensified by the fact that operation temperature of CHP is close to its onset temperature in many cases. To ensure safe handling of CHP in the chemical industry, a lot of research has been done on it including theoretical research at the microscopic level and experimental research at the macroscopic level. However, the unstable radicals in the CHP decomposition reactions make it difficult to study its reaction pathway, and therefore lead to incomplete understanding of the reaction mechanism. The slow progress in theoretical research hinders the application of the theoretical prediction in experimental research. For experimental research, the lack of integration of operational parameters into the reactivity evaluation limits its application in industrial process. In this thesis, a systematic methodology is proposed to evaluate the reactivity hazards of CHP. This methodology is a combination of theoretical research using computational quantum chemistry method and experimental research using RSSTTM. The theoretical research determined the dominant reaction pathway of CHP decomposition reaction through the study of thermodynamic and kinetic stability, which was applied to the analysis of experimental results. The experimental research investigated the effect of CHP concentration on runaway reactions by analyzing the important parameters including temperature, pressure, self-heat rate and pressure rate. This methodology could also be applied to other organic peroxides or other reactive chemicals. The results of theoretical research on reaction mechanism show that there is a dominant reaction pathway, which consumes most of the CHP in decomposition reaction. This conclusion agrees with the experimental results that 40 wt% is a critical point for almost all important parameters of runaway reactions. In the high concentration range above 40 wt%, some unknown reaction pathways are involved in decomposition of CHP because of lack of cumene. The shift of reaction mechanism causes the change of the effect of concentration on runaway reactions

Development and validation of the HarsMeth NP methodology for the assessment of chemical reaction hazards.

L'objectiu d'aquest treball es centra en el desenvolupament, comprovació i millora d'una metodologia per l'assessorament del perill tèrmic de les reaccions químiques, orientada especialment a les petites i mitjanes empreses. La metodologia està basada en un sistema de llistes de comprovació per identificar els perills, així com en altres eines senzilles d'entendre per a personal no expert en seguretat. Els orígens del desenvolupament de la metodologia es basen en dos eines existents, HarsMeth i Check Cards for Runaway. S'han pres diferents enfocaments per tal d'aconseguir una metodologia d'assessorament fiable. En primer lloc s'ha verificat l'eficàcia d'ambdues metodologies en diferents empreses dedicades al desenvolupament de productes de química fina, per determinar els punts forts i els punts febles de cada una de elles, i per aprofitar els avantatges identificats per tal de crear una unica metodologia anomenada HarsMeth version 2. A continuació, s'ha provat aquesta versió exhaustivament en dos empreses químiques per tal de millorarla, detectant fallades i allargant les llistes de comprovació amb la finalitat de cobrir el màxim número possible de qüestions per l'assessorament. Altres activitats s'han centrat en el desenvolupament d'eines per a la determinació teòrica de entalpies de reacció i per la identificació de perills tèrmics en equips de procés. La versió final de la metodologia que s'ha desenvolupat, anomenada HarsMeth New Process, està estructurada per tal de realitzar l'assessorament seguint els passos lògics en el desenvolupament d'un procés químic, començant per el disseny de la reacció química en el laboratori, seguit per l'anàlisi de la estabilitat i compatibilitat dels reactius, l'anàlisi de la perillositat de la reacció, l'escalat del procés, i la determinació de les mesures de seguretat necessàries per implementar el procés a escala industrial en funció dels perills identificats anteriorment. Un altre estratègia seguida per millorar la metodologia ha estat analitzar els accidents químics inclosos en la base de dades MARS amb la finalitat de determinar lliçons per aprendre dels accidents, així com per identificar quins aspectes de la metodologia haurien ajudat a prevenir els accidents, i a posar de relleu quins aspectes de la seguretat quimica s'han de tenir especialment en compte a les indústries de procés.El objetivo de este trabajo se centra en el desarrollo, comprobación y mejora de una metodología para el asesoramiento del peligro térmico de las reacciones químicas, orientada especialmente a las pequeñas y medianas empresas. La metodología está basada en un sistema de listas de comprobación para identificar los peligros, así como en otras herramientas fáciles de entender para personal no experto en seguridad. Los orígenes del desarrollo de la metodología se basan en dos herramientas existentes, HarsMeth y Check Cards for Runaway. Se han seguido diferentes enfoques para llegar a una metodología de asesoramiento fiable. En primer lugar se ha verificado la eficacia de ambas metodologías en diferentes empresas dedicadas al desarrollo de productos de química fina, para determinar las fuerzas y debilidades de cada una de ellas, y para aprovechar las ventajas identificadas para crear una única metodología llamada HarsMeth version 2. A continuación, se ha probado esta versión exhaustivamente en dos empresas químicas para mejorarla, detectando fallos y expandiendo las listas de comprobación con el fin de cubrir el máximo número de cuestiones posibles en el asesoramiento. Otras actividades se han centrado en el desarrollo de herramientas para la determinación teórica de entalpías de reacción y para la identificación de peligros térmicos en equipos de proceso. La versión final de la metodología que se ha desarrollado, llamada HarsMeth New Process, está estructurada para realizar el asesoramiento siguiendo los pasos lógicos del desarrollo de un proceso químico, empezando por el diseño de la reacción química en el laboratorio, siguiendo con el análisis de la estabilidad y compatibilidad de los reactivos, el análisis de la peligrosidad de la reacción, el escalado del proceso y la determinación de medidas de seguridad necesarias para implementar el proceso a escala industrial en función de los peligros identificados anteriormente. Otra estrategia seguida para mejorar la metodología ha sido analizar los accidentes químicos incluidos en la base de datos MARS con el fin de determinar lecciones a aprender de los accidentes, así como identificar qué aspectos cubiertos por la metodología podrían haber ayudado a prevenir los accidentes, y a enfatizar qué aspectos de la seguridad química deben tener especialmente presentes las industrias de proceso.The aim of this work is focused on the development, testing and improvement of a methodology for the assessment of thermal hazards of chemical reactions, mainly oriented to be used at small and medium enterprises. The methodology consists on a checklist based system to identify thermal hazards, including tools easy to be followed by non experts in the field of safety. The origins of the development are two already existing tools known as HarsMeth and Check Cards for Runaway. Different approaches have been followed in order to come up with a reliable assessment tool. In the first place, the two mentioned methodologies were tested at different companies working on fine chemical production, which gave the possibility to determine strengths and weaknesses for both methodologies, and to profit from the identified strengths to combine them to create one single tool called HarsMeth version 2. Later, this version was thoroughly tested at two different companies to improve it, by detecting flaws and expanding the checklists in order to cover as many issues as possible in the assessment. Further work performed aimed at the development of tools for the theoretical estimation of reaction enthalpies and for the identification of thermal hazards in process equipment. A final version of the methodology was produced, called HarsMeth New Process, structured to perform the hazard assessment at every step followed in the development of a chemical process, starting from the design of the chemical reaction at the laboratory, followed by the study of stability and compatibility of the reactants involved, the bench scale analysis of the synthesis path chosen, the scale up of the process and the determination of the necessary safety measures for the implementation of the process at industrial scale in accordance with the hazards identified. Another strategy followed in order to improve the methodology has been to analyse the chemical accidents reported to the MARS database in order to establish lessons learned from such accidents, and to identify what topics of the methodology could have helped to prevent the accidents and to emphasize what aspects of chemical safety need to be taken into account by the process industries

Thermal stability and explosive hazard assessment of diazo compounds and diazo transfer reagents

Despite their wide use in academia as metal-carbene precursors, diazo compounds are often avoided in industry owing to concerns over their instability, exothermic decomposition and potential explosive behaviour. The stability of sulfonyl azides and other diazo-transfer reagents is relatively well understood, but there is little reliable data available for diazo compounds. This work firstly collates available sensitivity and thermal analysis data for diazo-transfer reagents and diazo compounds to act as an accessible reference resource. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC) data for the model donor/acceptor diazo compound ethyl (phenyl)diazoacetate is presented. We also present a rigorous DSC dataset with 43 other diazo compounds, enabling direct comparison to other energetic materials to provide a clear reference work to the academic and industrial chemistry communities. Interestingly, there is a wide range of onset temperatures (Tonset) for this series of compounds which varied between 75 and 160 °C. The thermal stability variation depends on the electronic effect of substituents and the amount of charge delocalisation. A statistical model is demonstrated to predict the thermal stability of differently substituted phenyl diazoacetates. A maximum recommended process temperature (TD24) to avoid decomposition is estimated for selected diazo compounds. Average enthalpy of decomposition (∆HD) for diazo compounds without other energetic functional groups is −102 kJ mol−1. Several diazo transfer reagents are analyzed using the same DSC protocol and found to have higher thermal stability, which is in general agreement with reported values. For sulfonyl azide reagents an average ∆HD of −201 kJ mol−1 is observed. High quality thermal data from ARC experiments shows the initiation of decomposition for ethyl (phenyl)diazoacetate to be 60 °C , compared to 100 °C for the common diazo transfer reagent p ABSA. The Yoshida correlation is applied to DSC data for each diazo compound in order to provide an indication of both their impact sensitivity (IS) and explosivity. As a neat substance, none of the diazo compounds tested are predicted to be explosive but many (particularly donor/acceptor diazo compounds) are predicted to be impact sensitive. It is therefore recommended that manipulation, agitation, and other processing of neat diazo compounds is conducted with due care to avoid impacts, particularly with large quantities. The full dataset is presented to inform chemists of the nature and magnitude of hazards when using diazo compounds and diazo transfer reagents. Given the demonstrated potential for rapid heat generation and gas evolution, adequate temperature control and cautious addition of reagents which begin the reaction is strongly recommended when conducting reactions with diazo compounds

Experimental and computational study of self-heating ignition and calorimetry of Lithium-ion batteries during storage

Fire accidents involving Lithium-ion batteries (LIBs) threaten the safety of their storage facilities, where there are thousands of open-circuit cells stacked together forming ensembles. Ignition of ensembles could be triggered by self-heating but this important ignition phenomenon has received little attention in the literature. A few studies have investigated the self-heating of a single cell, but do not account for the effect of heat transfer. However, a large-size open-circuit LIB ensemble during storage can develop temperature gradients and therefore ignition is affected by both heat transfer and chemistry. In this thesis, I conducted ignition and calorimetry experiments using a commercial type of prismatic LiCoO2 cell to quantify self-heating conditions and find the chemical kinetics and thermal properties. Results show that self-heating ignition is possible when cells are stacked together and that the critical ambient temperature decreases with the number of cells. A computational model, based on open-source code Gpyro, is used to understand and predict ignition in different ensemble sizes and storage conditions. I used both ignition experiments and model predictions to quantify and compare two critical temperatures: the cell thermal runaway temperature defined in standard SAE-J2464, and the critical ambient temperature triggering ignition. I find that the cell thermal runaway temperature is insensitive to size, but the critical ambient temperature decreases with size. This shows that the critical ambient temperature should be used to design safe storage rather than the SAE standard. I further use the experiments and computational model to predict LIB ignition during storage with different states of charge and cathode materials. In order to understand whether the accelerating rate calorimetry (ARC) can properly quantify self-heating ignition, for the first time, I quantify the uncertainty caused by ignoring heat transfer in experiments. ARC can generally measure the onset of self-heating, but underestimate the heat of reaction, the maximum temperature and cannot measure critical ignition temperature. The results in this thesis help improve the safety of the open-circuit LIB storage and provide a scientific understanding of self-heating hazards and guidance for better standards.Open Acces

Thermal Hazard Assessment of the Styrene Polymerization System

Polymerization reactions are prone to runaway risks due to the unstable nature of monomers and the complex interactions between reactants. The major direct cause of polymerization runaway incidents is the deviation from the standard recipe or designed operation conditions. These unintended reactions may lead to auto-accelerated temperature and pressure rise, followed by rupture of reaction vessels, fire, and explosion. To minimalize the risk, the polymerization reaction runaway behavior under various hazardous scenarios should be fully identified and carefully quantified. The understanding of the thermal/pressure behaviors and mechanisms during thermal runaway is essential to facilitate safer handling and storage of the reactive styrene system. In this work, three most credible hazardous scenarios have been identified regarding the styrene system during polymerization and storage, including the deviation in monomer mass fraction, the deviation in initiator type and concentration, and the contact between monomer and a variety of impurities. Runaway hazards of these scenarios were calorimetrically investigated. Lumped kinetic models have been developed to predict reaction hazards. Calorimetric results showed that the onset of the runaway reaction was strongly affected by the co-existing chemicals in the polymerization recipe. Polymerization inhibitor retarded the initial stage of the runaway reaction. The mischarging of the solvent had a complex effect on the runaway hazards of the polymerization reaction, as the addition of solvent monotonically reduced temperature-related thermal hazards and increased the pressure hazards. Experiment and thermodynamic calculations indicated that volatile diluent increased system vapor pressure even at a lower adiabatic temperature rise. The mischarging effect of two different radical initiators, including benzoyl peroxide (BPO) and azobisisobutyronitrile (AIBN), was investigated at a series of elevated concentrations in both screening and adiabatic calorimeters. The onset temperature shifted to lower values with higher initiator dosage in the system. The overall heat generation, pressure building-up rate monotonically increased with initiator concentration. Finally, screening calorimeters were employed to quantify the contamination effects of styrene in contact with impurities, including water, alkaline, and acid. The exothermic characteristics of styrene mixed with contaminating substances were significantly related to the impurity concentrations and mixing conditions, especially for strong acids

Application of calorimetric testing and dynamic simulation to predict and control violently reactive chemical reactions

The purpose of this thesis is to demonstrate the use of calorimetric testing and dynamic simulation to predict and prevent the runaway reactions in a chemical process. A simple distillation process involving a complex runaway reaction is used to demonstrate this concept. An Accelerated Rate Calorimeter (ARC) is used to obtain reaction data (i.e. heats of reaction, reaction rates, reaction by products, etc.). The reaction data is then used to develop a dynamic simulation of the distillation process for the purpose of evaluating failure scenarios that may trigger a runaway reaction. Finally, the simulator is used to assess the performance of different emergency safety systems (such as emergency shutdown systems, quench systems, dump systems, etc.) to prevent a potential runaway reaction. Three failures scenarios (loss of cooling, loss of vacuum, and excess heat) are simulated in the refining process. The simulation results indicate that a typical emergency shutdown strategy (ESD) will prevent vessel over-pressurization in two of the three cases. For loss of vacuum, however, the emergency shutdown system, by itself, is ineffective for preventing vessel over-pressure. The simulation indicates that a reduction of the ESD initiation temperature and the addition of an emergency dump system can significantly reduce the potential for vessel over-pressurization

Integrating Chemical Hazard Assessment into the Design of Inherently Safer Processes

Reactive hazard associated with chemicals is a major safety issue in process industries. This kind of hazard has caused the occurrence of many accidents, leading to fatalities, injuries, property damage and environment pollution. Reactive hazards can be eliminated or minimized by applying Inherently Safer Design (ISD) principles such as "substitute" or "moderate" strategies. However, ISD would not be a feasible option for industry without an efficient methodology for chemical hazard assessment, which provides the technical basis for applying ISD during process design. In this research, a systematic chemical hazard assessment methodology was developed for assisting the implementation of ISD in the design of inherently safer process. This methodology incorporates the selection of safer chemicals and determination of safer process conditions, which correspond to "substitute" and "moderate" strategies in ISD. The application of this methodology in conjunction with ISD technique can effectively save the time and investment spent on the process design. As part of selecting safer chemicals, prediction models were developed for predicting hazardous properties of reactive chemicals. Also, a hazard index was adopted to rate chemicals according to reactive hazards. By combining the prediction models with the hazard index, this research can provide important information on how to select safer chemicals for the processes, which makes the process chemistry inherently safer. As part of determining safer process conditions, the incompatibility of Methyl Ethyl Ketone Peroxide (MEKPO) with iron oxide was investigated. It was found that iron oxide at low levels has no impact on the reactive hazards of MEKPO as well as the operational safety. However, when iron oxide is beyond 0.3 wt%, it starts to change the kinetics of MEKPO runaway reaction and even the reaction mechanism. As a result, with the presence of a certain level of iron oxide (> 0.3 wt%), iron oxide can intensify the reactive hazards of MEKPO and impose higher risk to process operations. The investigation results can help to determine appropriate materials for fabricating process equipment and safer process conditions

Thermal decomposition study of hydroxylamine nitrate during storage and handling

Hydroxylamine nitrate (HAN), an important agent for the nuclear industry and the U.S. Army, has been involved in several costly incidents. To prevent similar incidents, the study of HAN safe storage and handling boundary has become extremely important for industries. However, HAN decomposition involves complicated reaction pathways due to its autocatalytic behavior and therefore presents a challenge for definition of safe boundaries of HAN storage and handling. This research focused on HAN decomposition behavior under various conditions and proposed isothermal aging testing and kinetic-based simulation to determine safety boundaries for HAN storage and handling. Specifically, HAN decomposition in the presence of glass, titanium, stainless steel with titanium, or stainless steel was examined in an Automatic Pressure Tracking Adiabatic Calorimeter (APTAC). n-th order kinetics was used for initial reaction rate estimation. Because stainless steel is a commonly used material for HAN containers, isothermal aging tests were conducted in a stainless steel cell to determine the maximum safe storage time of HAN. Moreover, by changing thermal inertia, data for HAN decomposition in the stainless steel cell were examined and the experimental results were simulated by the Thermal Safety Software package. This work offers useful guidance for industries that manufacture, handle, and store HAN. The experimental data acquired not only can help with aspects of process safety design, including emergency relief systems, process control, and process equipment selection, but also is a useful reference for the associated theoretical study of autocatalytic decomposition behavior