Sam Mannan

Evaluation of the Thermal Runaway Decomposition of Cumene Hydroperoxide by Adiabatic Calorimetry

Many industrial accidents in the recent past showed that the thermal decomposition of Cumene Hydroperoxide (CHP) can lead to runaway reactions and subsequent fires and explosions. Still this organic peroxide is extensively used in the petrochemical industry. This paper is aimed at a better understanding of the possible consequences of CHP decomposition by analyzing its thermal behavior when dissolved in a high boiling point solvent using two different adiabatic calorimeters. The experimental data obtained allowed us to assess the general trends on the main runaway parameters and to characterized the thermal decomposition of the mixture with respect to the peroxide concentration, as well as the influence of the thermal inertia of the equipment. The gas generation rate for each of experiment was calculated and then corrected to adiabatic conditions. The data generated can assist as a guidance for designing processes where CHP is involved, along with their safeguards.

An Episode as a Trace of Resilient Performance in Large-Scale Incident Management Systems

Disasters have revealed persistent challenges for incident management systems in preparing for, responding to, and recovering from disruptive events. Such challenges have been reflected in recent catastrophic events such as natural disasters, industrial accidents, and terrorist attacks. To address the challenges, a need for resilience of incident management systems has been increasingly recognized (Comfort, Boin, & Demchak, 2010). Resilience is defined as a system’s capacity to adjust its performance before, during and after a disturbance (Hollnagel, Woods, & Leveson, 2007). From the theory of Joint Cognitive System (JCS), resilient performance is rendered through an interplay among the JCS triad: human operators, technological artifacts, and demands from the world (Hollnagel & Woods, 2005; Woods & Hollnagel, 2006). Hence, this study aims to identify resilient performance of an incident management system (e.g., Incident Management Team (IMT)) by investigating interac-tions among the JCS triad. The research team conducted two naturalistic observations at a high-fidelity emergency exercise facility and collected audio and video recordings from participants. These recordings were then weaved together to facilitate the analysis of interactions. To represent the interactions among humans and technological tools that cope with demands from an incident, an Interactive Episode Analysis (IEA) was developed and applied to the collected data. The IEA was designed to capture three C’s of an interaction: Context, Content and Characteristics. Context refers to an initiator, a receiver of the interaction, and a technology used. Content indicates actions and communications that occur between human operators and technical tools. Characteristics refer to frequency and time duration of the interaction. To identify the IMT’s performance to cope with incident demands, an episode was constructed after an inject (a piece of simulated information input) was given to the IMT. Using the IEA, two episodes were extracted as preliminary results. Both similar and different patterns of information management were observed. First, both episodes suggest that the IMT follows a common information flow: collecting incident data (e.g., field report), documenting the data, and disseminating the data to other members of the IMT. In both episodes, participants tended to use similar technologies for a certain information management task. For example, a telephone was used for collection of incident data, a photocopying machine (i.e., printer and photocopier) for documentation, and a paper form for dissemination. On the other hand, dissimilar patterns were captured. As members of I/I Unit in the second episode struggled to find out a preferred method of communication (e.g., paper vs. email), the members interacted with instructors that were not seen in the first episode. As such, the second episode took almost twice the duration of the first episode. The findings from the current study, albeit preliminary, suggest non-linear and dynamic interactions among emergency operators, technical tools, and demands from an incident. As Woods (2006) noted, resilience of a system may not be visible until the system faces disruptive events. In such regards, the IEA would serve as a tool to represent the system’s resilient performance after a work demand. In addition, the IEA showed promise as a diagnostic tool that examines the interactions among the JCT triad. To gather more evidence to support findings in the preliminary analysis, future research will focus on extracting more episodes from the collected data and identifying emerging patterns of resilient performance of the IMT.

Effect of Backup Detection Levels in P-Median Formulations for Optimal Placement of Detectors in Mitigation Systems

Abstract This work considers optimization formulations for optimal placement of detectors in mitigation systems. Considering independent detector failure probability leads to a mixed-integer stochastic programming formulation with nonlinear terms. Our problem formulation differs from others in that it explicitly considers different backup detection levels, allowing an approximation where the maximum degree of the nonlinear products considered can be determined by the modeller. Since these are products of probabilities, it is possible to select a level of redundancy that gives a reasonable accuracy while reducing the complexity of the MINLP. In this paper we analyse the effect of reducing the number of detection levels using real data for the gas detector placement problem. For the problem, our results show that there is minimal deterioration of the optimal objective as a result of this reduction.

Modelling of LNG Pool Spreading on Land with Included Vapour-Liquid Equilibrium and Different Boiling Regimes

This paper presents a source term model for estimating the rate of unconfined LNG pool spreading on land. The model takes into account the composition changes of a boiling mixture, the variation of thermodynamic properties due to preferential boiling in the liquid mixture and the effect of boiling regime on conductive heat transfer. The heat, mass and momentum balance equations were solved for continuous and instantaneous spills. A sensitivity analysis was conducted to determine the relative effect of each of these phenomena on pool spreading. The model was compared to a commonly used gravityinertia integral pool-spreading model with one-dimensional conductive heat transfer. 1. Introduction Although some pool spreading models have been developed as outlined by Webber et al. (2010), most of them are integral models and based on work carried out in the early 1970’s on non-volatile liquid spills. These early models tend to overlook the complexity associated with cryogenic pool spreading. Cryogens (e.g. LNG: boiling point = -162 °C) exhibit vigorous boiling upon being released on land or water at ambient temperature. In the case of an LNG release, some of the LNG will flash while rest will spread very quickly. The conditions of heat transfer from the surroundings and the composition of the LNG mixture may affect the spread rate and the vaporization rate. Most of the current modelling work on LNG spillage estimates the LNG properties either using fixed thermo-physical properties of a mixture or using those of pure methane as an analogue. This is questionable since the vaporization behaviour of a mixture is different from that of a pure fluid due to preferential boil-off of the lighter hydrocarbons, which in turn results to time varying properties of the spilled mixture. The complex phenomena governing the spread and vaporization of a LNG pool have to be accounted for and their relative importance must be understood to develop a comprehensive model that is both adaptable and applicable to a variety of scenarios. In this paper, a pool-spreading model that takes into account the composition changes of a boiling LNG mixture, the effect of different boiling modes on conductive heat transfer as well as the varying mixture thermodynamics and vapour liquid equilibrium effects is proposed. A sensitivity analysis is conducted to identify the relative importance of each of the governing parameters on the pool spreading process. The model incorporates the multicomponent nature of LNG and its effect on the behaviour of the spill with the aim of developing the most accurate and comprehensive representation of the pool spreading process.

Qatar, LNG, Spill Experiments and Process Safety

Publisher Summary The Liquefied Natural Gas (LNG) industry is developing rapidly throughout the world. The need for internationally accepted design standards and risk assessment procedures for land based LNG facilities is stressed. Risk assessments necessitate modeling worst credible scenarios using the best available techniques. The Health and Safety Laboratory (HSL) and National Fire Protection Association (NFPA) have summarized LNG field trial data that can be used for validation of models and software. The LNG industry has an enviable safety record: this includes offshore exploration and production, onshore processing, storage, tanker loading, transportation and offloading, and storage and re-gasification. But because of the international aspect of LNG trading a single major incident would probably have worldwide ramifications. Operations in all parts of the LNG industry must be subjected to the most rigorous risk assessments and facilities designed so that they remain adequately safe for both operators and the public even during worst credible maloperations.