Pool Fire Scenarios Research Articles

Research on the dangerous scenarios of propylene oxide leakage from tank in a chemical plant in an industrial park of Tongling City, China

ABSTRACT Propylene oxide (PO) is toxic, flammable and explosive. Accidents from the release of PO from large-scale storage tanks can have disastrous consequences associated with meteorological conditions. Therefore, this study explores the dangerous scenarios of PO leakage from a 1000 m3 spherical tank in a chemical plant located in an industrial park during various seasons using the Aerial Location of Hazardous Atmospheres software. Our results show that the maximum hazard distance of poisoning, flash fire and vapour cloud explosion caused by leakage and diffusion from the PO storage tank occur in the summer season and the affected distances were 2900, 372, and 374 m, respectively. In regard the thermal radiation resulting from a pool fire scenario, the longest threat distance was 110 m in the summer. For the boiling liquid expanding vapour explosion (BLEVE), the maximum thermal effect was 2100 m in winter. The BLEVE scenario has the largest impact area and its toxic vapour cloud is the primary accident. Adequate safety management and technical measures should be put in place for the prevention and emergency response of accidental PO release in the factory.

Detailed modeling of the radiative feedback in the large eddy simulation of a lab-scale heptane pool fire

This article proposes a detailed modeling of gas/soot radiation for large eddy simulation (LES) of sooting pool fires with a focus on the radiative heat feedback through the fuel vapor dome. The numerical model combines a non-adiabatic steady laminar flamelet (SLF) model, a two-equation acetylene/benzene-based soot production model, the Rank-Correlated Full-Spectrum K (RCFSK) and a presumed filtered density function (FDF) approach to model the subgrid-scale (SGS) interactions between turbulence, chemistry, soot production and radiation. This LES model is applied to simulate 15 cm heptane pool fire. The reliability of the RCSFK and the acetylene/benzene soot model for heptane pool fire scenarios is investigated through a priori analysis. First, decoupled radiative heat transfer calculations along lines of sight, representative of heptane pool fires and covering a wide range of optical thicknesses, demonstrate that the RCFSK computes the absorption of the fuel vapor dome with a similar accuracy as the narrow-band correlated-k (NBCK) model. Second, simulations of laminar coflow diffusion flame are used to extend the acetylene/benzene-based soot production model, previously validated for C1-C3 hydrocarbons, to n-heptane flames. LES of the 15 cm heptane pool fire reproduces with fidelity the flame structure in terms of mean and fluctuating temperatures and mean soot volume fraction (SVF). Simulations with and without considering heptane vapor radiation evidences its effects on the radiative outputs and the heat feedback. The radiative contribution of heptane vapor noticeably enhances the radiative loss to the surroundings and the peak of axial radiative flux. On the hand, the heat feedback to the pool surface is predicted within the experimental uncertainty when this contribution is taken into account with the radiative component being reduced by more than 10 %.

Numerical analysis of liquid sodium spreading on sloped floor surface under pool fire scenario in SFR systems

The accidental leaks of coolant from the heat transport circuit of Sodium-cooled Fast Reactor (SFR) can create fire events due to the reactivity of sodium with atmospheric oxygen, which can pose threat to safe operation of the reactor. The leaked sodium eventually reaches the cell floor, spreads gradually, and forms a burning pool. The thermal consequences of pool fire depend on its surface area, which is determined by the spreading process of sodium on the floor surface. In this context, numerical investigation has been carried out on the spreading behavior of burning sodium pool on the plane/sloped cell floor by developing a 3-D numerical model based on the viscous-gravity current equation of the shallow layer model. The governing equations of the model have been solved numerically by implementing the Finite Volume Method. The model developed has been validated using the experimental results published on liquid pool spreading under burning and non-burning conditions on plane and sloped floors for different leak rates. Using this model, numerical simulations have been carried out on sodium pool spreading under various leak scenarios envisaged in SFR cells based on the specific burning characteristics of sodium pool fire. The time-varying pool size and shape, pool height profile, and maximum pool area have been estimated for a wide range of sodium leak rates and typical floor slopes of interest to nuclear power plants. These predictions contribute towards the numerical evaluation of sodium pool fire scenarios pertaining to the safety of SFR.

Experimental and numerical study of an elevated pool fire scenario in a confined and mechanically ventilated compartment

The present work deals with an experimental and numerical investigation of an elevated pool fire scenario in a confined and forced ventilated compartment. Although often encountered in industrial installations or in common buildings, this type of configuration is rarely studied in the literature. This study is supported by a set of two large-scale fire experiments performed in the framework of the OECD-PRISME3 project and numerical simulations (RANS and LES methods) carried out with the CALIF3S-Isis software. The objective is to improve the physical understanding of the phenomena that are experimentally highlighted and to assess the capabilities of Computational Fluid Dynamics (CFD) on this type of configuration. First, the comparison between the two large-scale fire tests (one elevated and its equivalent on the ground) exhibits a strong modification of the fuel mass loss rate associated with a change in the thermal and species stratifications. Then, a preliminary simulation using a predictive approach commonly used and efficient for the case of a ground fire scenario shows by contrast its limitations when applied to the case of the elevated fire. Therefore, in addition to the essential step consisting in the validation of the code with a prescribed approach on this type of elevated fire, the simulations also reveal a specific phenomenology (smoke filling, strong vitiation, oxygen-pumping, …). Finally, taking into account these particularities allows in fine, for the studied case, the improvement of the prediction of the mass loss rate of the fire.

Improved pool fire-initiated domino effect assessment in atmospheric tank farms using structural response

Domino effects are severe accident scenarios affecting storage tanks and are often initiated by pool fires. Flame engulfment and heat radiation are the two major sources triggering domino effect. Threshold-based and probit-based methods are widely used to assess the possibility and probability of a secondary accident. These methods are also a part of advanced methods devoted to examining synergic or coupling effects. The current work examines (i) how effective the threshold-based methods are and (ii) how accurate the current time to failure (TTF) estimation models are, which are the basis of probit-based methods. The results suggest that threshold-based methods are not pertinent for the quantitative assessment of domino effect and that significant improvement can be made in the existing TTF prediction models using site-specific structural response data. A new set of equations for TTF estimation using data analytics is proposed. Application to 4,080 pool fire scenarios demonstrates that the newly developed model can improve the TTF prediction performance compared to the existing models (around 22% in terms of R2). In addition, a method has been proposed and validated to correlate time with the failure probability for time-dependent domino effect assessment, which is a limitation of probit-based methods.

Oil Onshore Pipeline Quantitative Risk Assessment under Fire and Explosion Scenarios

Pipeline is one of the safest and most cost-effective means of transportation for hydrocarbons. However, hydrocarbon releases and the subsequent fires and explosions, are presented as persistent events. Quantitative Risk Assessment (QRA) enables one to address the risk and to prevent these events. In this regard, different approaches have been proposed for pipelines, but few studies are focused on oil transportation. This paper presents a methodology for performing QRA for onshore oil pipelines, which is based on the calculation of individual and societal risk indicators. This methodology is illustrated using an authentic case study of a segment of 17.53 km of the length of an onshore oil pipeline located in the southwest of Colombia, considering jet and pool fire scenarios. The results show that the Individual Risk Per Annum (IRPA) for operation (and maintenance) and administrative workers are 6.14 × 10−4 and 8.52 × 10−5 yr−1, respectively. The IRPA for people close to the pipeline is between 2.31 × 10−4 and 2.60 × 10−4 yr−1. The IRPA for workers is tolerable, while for people may be classified as unacceptable. The societal risk was represented using the F–N curve, indicating that risk is unacceptable and nearby populations could be relocated.

A new approach to chemicals warehouse risk analysis using computational fluid dynamics simulation and fuzzy Bayesian network

This study aims to assess the risk of chemicals warehouse using a Bayesian networks (BNs) and computational fluid dynamics (CFD). A methodology combining Bow-Tie (BT), fuzzy set theory (FST), and Bayesian network was employed, in which the BT was drawn for chemical spill scenarios. FST was utilized for the estimation of the basic events (BEs) occurrence probability, and the probability of interaction among a set of variables was obtained using BNs. Pool fire scenario radiation heat flux was evaluated using CFD code, fire dynamic simulator (FDS), and the solid flame model (SFM). Fail in forklift brake system (BE1), was the most significant cause for a chemical spill. Based on the CFD model, the heat flux is 31 kW/m2 at a distance of 3.5 m from the fire, decreasing to 6.5 m gradually. The maximum safety distance of 4 m is predicted by the CFD for heat flux that exceeds 12.5 kW/m2; however, SFM predicts approximately 4.5 m. According to the results, the amount of posterior risk is higher than the prior value. The framework presented in the chemicals warehouse for consequence analysis and dynamic risk assessment (DRA) of pool fire could be used for preventing the accidents and domino effects in the chemicals warehouse.

Probabilistic fire risk analysis of process pipelines

Pool fires are considered catastrophic events in hydrocarbon liquid process pipelines. There is much research performed on fire risk analysis of liquid pipelines; however, probabilistic-quantitative methods that are based on the leak size are yet to be further developed. This paper develops a framework for quantitative fire risk analysis in liquid process pipelines based on probabilistic analysis and computational fluid dynamics. The significance of leaked volume and its dependency on the leak size, here the pipeline failure frequency is distributed into the frequencies of different leak sizes using historical data and the Bayesian network. The frequency of fire occurrence is then determined by combining the ignition probability of each leakage rate, the flammability specification of released materials, and the frequency of each leak size. In the vulnerability assessment, the thermal dose received by individuals is modified to account for the possibility of escape. The developed framework is next employed in a gasoline pipeline with a 1 km length. Results show that the pool fire scenario resulting from the rupture of the pipeline, with a frequency of 1.18 × 10−7 (km−1. y−1) and an area of exposure of 5498.4 m2, is the maximum-credible scenario. Two separate escape routes with different distances to the fire center are defined. As well, two escape speeds of 4 and 6 m/s are considered. The results show that the initial radiation and the escape speed can significantly affect the sustained damage to individuals. This study is a step forward in dynamic-quantitative individual risk analysis in pool fires of hydrocarbon liquid pipelines.

Numerical Simulations of a Postulated Methanol Pool Fire Scenario in a Ventilated Enclosure Using a Coupled FVM-FEM Approach

Numerical investigations have been carried out for a postulated enclosure fire scenario instigated due to methanol pool ignition in a chemical cleaning facility. The pool fire under consideration is radiation-dominated and poses a risk to the nearby objects if appropriate safety requirements are not met. The objective of the current study was to numerically evaluate the postulated fire scenario and provide safety recommendations to prevent/minimize the hazard. To do this, the fire scenario was first modeled using the finite volume method (FVM) based solver to predict the fire characteristics and the resulting changes inside the enclosure. The FDS predicted temperatures were then used as input boundary conditions to conduct a three-dimensional heat transfer analysis using the finite element method (FEM). The coupled FVM–FEM simulation approach enabled detailed three-dimensional conjugate heat transfer analysis. The proposed FVM–FEM coupled approach to analyze the fire dynamics and heat transfer will be helpful to safety engineers in carrying out a more robust and reliable fire risk assessment.

A REVIEW OF NEW COMPOSITE MATERIALS FOR THERMAL PROTECTION IN AN AERO-ENGINE APPLICATION

The paper is aimed at exploring new composite materials for thermal protection in an aero-engine application. Aluminium hybrid composites have been widely used to substitute materials in the aerospace industry because of their high thermal resistance, wear resistance and strength-to-weight ratio. This review article covers standard fire test results of different types of burners and burn-through times of the composites and polymeric materials. The paper evaluates the performance of different structural composite materials including synthetic fibres, natural fibres and some type of coating on the materials in a pool-fire scenario. It also deals with the practical use of flame retardancy and performance factors including safety in an aircraft related to polymer composites. It was found that most of the materials used could only be categorized as fire resistance materials except GLARE materials and synthetic/natural fibre composites and aerogel composites which showed the characteristic of fireproof materials.

Three dimensional CFD simulation of LPG tanks exposed to partially engulfing pool fires

The availability of accurate and robust models for the prediction of the behavior of pressurized tanks under fire exposure is a key requirement to improve the design of fire protection systems. Most of the models present in the literature take into consideration fully engulfing pool fire scenarios only. In the present study, a CFD modelling approach previously validated against full engulfing pool fire tests is used to simulate partial engulfment conditions. The model allowed analyzing local flow field promoting thermal stratification, which in turn drives internal pressurization of the tank. Comparison with fire test results shows good agreement with experimental measurements both in terms of temperature and pressurization curves. The results obtained represent a valuable source of information to support risk management, planning of emergency response and improve fire protection systems design.

Simulation of Pool and Compartment Fire Using Flamelet Generated Manifold With/Without Radiation Coupling

One of the critical issues in fire dynamic simulation is the selection of suitable combustion model. Typically, combustion models based on infinite fast chemistry are used in fires. In this paper, the flamelet generated manifold (FGM) has been used as a combustion model and the fireFoam solver of OpenFOAM has been used. Two distinct FGMs, with and without radiation coupling, have been investigated to illustrate the role of radiation in simulations. The energy equation with discrete ordinates radiation model is used for coupling of FGM with radiation. These models will be examined in two scenarios of the pool and compartment fire. The FGM with the heat equation is in a good agreement with the experiments. In addition, the basic FGM has a deviation from the experimental results, in a pool fire scenario. The mean of vertical velocity of basic FGM and FGM with energy equation has 40 and 15 percent relative error, respectively, in the pool fire scenario. In the compartment fire, FGM model, with and without radiation coupling shows the same behavior and the velocity results have 9% relative error in the doorway. In general, the radiation coupling in pool fire is more important than compartment scenario.

Multicomponent pool fires: Trends in burning rate, flame height, and flame temperature

The composition of a multicomponent pool fire will vary over the course of burning due to preferential distillation of more volatile compounds. As a result, key fire properties like the burning rate, flame temperature, flame height, and soot emissions will change as the properties of the fuel change. This adds uncertainty about the combustion properties of the fire, especially for fuel blends with widely varying boiling points (e.g., gasoline-ethanol). The heat release rate, which is proportional to the burning rate, is essential for estimating the radiative flux to nearby structures or personnel, so understanding how fire dynamics are impacted by the composition of a fuel mixture is a pre-requisite for dealing with hazard assessments of fire scenarios involving multicomponent fuels. Continuously fed pool fire experiments were conducted in a 0.30 m diameter pan with binary mixtures of ethanol-water, ethanol-isopropanol, and ethanol-hexane. The relationship between burning rate and fuel composition was strongly dependent on vapour-liquid equilibria and relative volatility of the mixture. It was found that burning rate models dependent on fuel properties gave better predictions of the relationship between burning rate and fuel composition. Heskestad’s flame height and flame temperature correlations were found to be suitable for use in multicomponent pool fire scenarios.

An overview of test standards and regulations relevant to the fire testing of pressure vessels

Fire exposure of storage and transportation vessels of hazardous materials (including pressure liquefied gases) can result in BLEVEs and other high-consequence incidents with large societal and economic impacts. To reduce risk most countries have numerous regulations, codes of practice and guidance notes covering the design, operation and maintenance of vessels and thermal protection systems. Yet despite such regulations there remains no internationally accepted fire test procedure for pressure vessel and accompanying thermal protection systems that is capable of meeting a range of regulatory requirements. This paper considers some of the regulations in place in the western world and considers the origin of these based on large and medium-scale testing conducted to date. It examines conditions found in these tests to propose a set of recommendations on which to base a standard method of test. These recommendations are proposed as being representative of a credible large pool fire scenario that may occur.

Development of full spectrum correlated k-model for spectral radiation penetration within liquid fuels

In this paper, full spectrum correlated k-distribution (FSCK) models are developed for several liquid fuels including decane, ethanol, ethylene glycol, heptane, and toluene. The models were built using high-resolution absorption spectra, collected from the literature. To validate the novel FSCK models, they were used to solve radiative heat transfer within liquid pools assuming three temperature profiles (i.e. constant temperature, linear and nonlinear temperature profiles) and the calculated transmissivity and radiative heat source of FSCK were compared with those of using high resolution absorption spectra and the gray models implementing Planck mean absorption coefficient. The sensitivity analysis was performed for the accuracy of the FSCK results with number of quadrature points for different fuels. Using seven quadrature points for FSCK model has been found to be sufficient for providing good accuracy of spectral radiative heat transfer within the liquid fuels with a reasonable computational cost. Moreover, we studied the effect of the reference temperature used in FSCK model and found out that for the pool fire scenario, the FSCK provides its best accuracy if an equivalent temperature representing the radiation feedback from the flame is used as the reference temperature. Comparison of computational costs of high-resolution spectral radiation calculations and FSCK method revealed a significant computational gain by use of FSCK model.

Analysis of liquid sodium spills spreading on floor surface pertaining to sodium pool fire events in SFR cells

Analysis of postulated sodium leak events and resultant pool fire scenarios is essential in the safety evaluation of Sodium-cooled Fast Reactors (SFR). In this connection, numerical studies have been carried out to analyze the spreading characteristics of accidental liquid sodium spills on the cell floor surface under pool fire conditions in SFR systems. The dynamics of sodium pool spreading has been investigated by implementing the integral model, which is commonly employed for liquefied hydrocarbon fuel spills spreading on land or water surface by using the specific characteristics of sodium pool fire. The governing equations have been solved numerically, and the model predictions have been validated with the liquid sodium and water spreading experimental results available in the literature. The present analysis results have shown that the 1-D integral model could fairly predict the overall behaviour of sodium pool spreading, under burning conditions. The validated model has been used to evaluate liquid sodium spreading and pool formation for different leak scenarios under postulated accidental conditions in SFR. The model is useful to simulate the spreading behaviour of sodium spills with the numerical codes developed to evaluate the sodium fire safety.

On the use of dynamic turbulence modelling in fire applications

In an attempt to make a step forward towards predictive fire modelling, the application of turbulence modelling approaches, calculating the sub-grid scale viscosity, kinetic energy, turbulent Prandtl and Schmidt numbers based on a dynamic procedure, has been tested on a wide range of pool fire scenarios (i.e., MaCFP workshop test cases). Through the use of Large Eddy Simulations, it is investigated whether the applied modelling approaches can accurately predict the pool fire dynamics on different grid sizes and result in improved predictions compared to models using constant parameters. Additionally, it is evaluated whether the theoretical constants related to turbulence modelling, derived from isotropic decaying turbulence scenarios, are justified in turbulent buoyant flows.

Numerical simulation of small-scale pool fires of LNG

Liquefied natural gas (LNG) has been largely indicated as a promising alternative solution for the transportation and storage of natural gas. In the case of accidental release on the ground, a pool fire scenario may occur. Despite the relevance of this accident, due to its likelihood and potential to trigger domino effects, accurate analyses addressing the characterization of pool fires of LNG are still missing.In this work, the fire dynamic simulator (FDS) has been adopted for the evaluation of the effects of the released amount of fuel and its composition (methane, ethane, and propane), on the thermal and chemical properties of small-scale LNG pool fire. More specifically, the heat release rate, the burning rate, the flame height, and thermal radiation, at different initial conditions, have been evaluated for pool having diameter smaller than 10 m. Safety distances have been calculated for all the investigated conditions, as well.Results have also been compared with data and correlations retrieved from the current literature. The equation of Thomas seems to work properly for the definition of the height over diameter ratio of the LNG pool fire for all the mixture and the investigated diameters.The addition of ethane and propane significantly affects the obtained results, especially in terms of radiative thermal radiation peaks, thus indicating the inadequacy of the commonly adopted assumption of pure methane as single, surrogate species for the LNG mixture.

Numerical study on thermal buckling of empty thin-walled steel tanks under multiple pool-fire scenarios

Fire incidents at fuel storage tank farms are high risk incidents due to the fact that can result in severe socio-economic losses, injuries, deaths and have a serious environmental impact. In the case of a tank fire, there is a serious possibility that the fire will spread to adjacent tanks. The research activity in this area is mainly focused on the prediction of the heat transfer characteristics of pool fires, the thermal response of neighbouring tanks (or target tanks) and the potential of fire spreading. On the contrary, the research for the structural integrity of tanks involved in pool fire scenarios is limited. This paper aims to study the thermal buckling behaviour of fixed-roof tanks in the case of pool fire scenarios, considering one or more burning tanks. To this end, different scenarios are examined, aiming to study the key factors (the burning fuel, the wind, the separation distance between tanks and the size of the burning tanks) that may affect the thermal buckling response of the target tanks. Semi-empirical models, available in the literature, are used for the calculation of the characteristics of flames that arise from burning tanks. Then, the problem is solved numerically, through the Finite Element Method. The heat transfer from the burning tanks to the target tank is treated through the open cavity option, and the response of the target tank is predicted in the same thermo-mechanical analysis. The basic objective is the investigation of the inherent fire resistance of thin-walled tanks and to predict their failure.

Security risk analysis of a hydrogen fueling station with an on-site hydrogen production system involving methylcyclohexane

Although many studies have looked at safety issues relating to hydrogen fueling stations, few studies have analyzed the security risks, such as deliberate attack of the station by threats such as terrorists and disgruntled employees. The purpose of this study is to analyze security risks for a hydrogen fueling station with an on-site production of hydrogen from methylcyclohexane. We qualitatively conducted a security risk analysis using American Petroleum Institute Standard 780 as a reference for the analysis. The analysis identified 93 scenarios, including pool fires. We quantitatively simulated a pool fire scenario unique to the station to analyze attack consequences. Based on the analysis and the simulation, we recommend countermeasures to prevent and mitigate deliberate attacks.