Lessons in Process Safety Management Learned in an Explosion Accident in Taiwan

PresentationA substantial explosion attributed to thermal decomposition of o,o-dimethyl phosphoramidothioate (DMPAT) resulted in 1 fatalities and 1 injury in Taichung, Taiwan, in 2016. An analysis of this explosion indicated that such an accident could have been prevented, or the consequences might not have been as severe if certain elements of process safety management (PSM) had been applied. Proper execution of process safety management, including process safety information, operating procedures, pre-startup safety review, and process hazard analysis, can prevent the occurrence of such explosion accidents. The impact of this explosion could have been reduced had these process safety management elements, particularly management of change, been executed

A Method to Identify the Chemical Hazards of Tasks Derived from Abnormal Conditions of Processes

PresentationHazards, which were resulted from operation of improper tasks derived from process abnormal conditions, cannot be identified effectively by the traditional hazard identification methods, such as HAZOP and JSA. A method based on the hazardous information of chemicals to identify the hazards of tasks derived from abnormal conditions of processes was proposed. A checklist for the intrinsic chemical hazard identification and a worksheet for the process/task hazard identification were included in the proposed method. The intrinsic hazards of chemicals can be identified based on the hazardous information of chemicals, such as those provided on SDS. Combining with the enabling condition of the chemical hazards and the possible tasks derived from process abnormal conditions, the tasks derived from process abnormal conditions, which will supply the condition of initiating the chemical hazards, were identified. Based on the identified tasks, the potential hazards of the tasks can be identified by a pre-designed worksheet, and the safeguards and the suggestions can be identified. An example of using the proposed method to identify the hazards of tasks derived from process abnormal conditions was included in this manuscript

Deficiencies Frequently Encountered in the Promotion of Process Safety Information

PresentationProcess Safety Information (PSI) is one of the fourteen elements of Process Safety Management (PSM). The findings of the PSI element in the PSM audit for more than 50 plants in Taiwan were reported in this manuscript, and such findings were not limited to the requirements of OSHA. The information pertaining to the hazards of the highly hazardous chemicals in process should not be limited to the Safety Data Sheet (SDS), although the information provided by the SDS satisfied the requirements of OSHA. The necessary information for the hazards of the highly hazardous process chemicals should considered the characteristics of the process. The unexpected process chemistry is more important than the expected one for the information pertaining to the technology of the process, from the safety viewpoint. The frequently encountered problem for the information pertaining to the equipment in the process is the inconsistence between the piping and instrument diagram and the real process

Flash Point Measurements and Modeling for Ternary Partially Miscible Aqueous­Organic Mixtures

Flash point is the most important variable used to characterize the fire and explosion hazard of liquids. This paper presents the first partially miscible aqueousorganic mixtures flash point measurements and modeling for the ternary type-I mixtures, water + ethanol + 1-butanol, water + ethanol + 2-butanol, and the type-II mixture, water + 1-butanol + 2-butanol. Results reveal that the flash points are constant in each tie line. Handling the non-ideality of the liquid phase through the use of activity coefficient models, the general flash-point model of Liaw et al. extended to partially miscible mixtures predicts the experimental data well when using literature LLE and the VLE activity coefficient model binary parameters to estimate sequentially the span and flash point in each tie line and the flash point in the mutual solubility region, respectively. The constant flash-point behavior in a tie line is also observed and predicted, in agreement with the VLLE tie line property that a single vapor is in equilibrium with all liquid composition on a tie line. For the aqueousorganic mixtures here studied, a deviation between prediction and measurements is observed, arising from the failure of the constant lower flammable limit assumption in the mutual solubility inert-rich region. Potential application for the model concerns the assessment of fire and explosion hazards and the development of inherently safer designs for chemical processes containing partially miscible aqueousorganic mixtures

Flash-Point prediction for binary partially miscible aqueous-organic mixtures

Flash point is the most important variable used to characterize fire and explosion hazard of liquids. Herein, partially miscible mixtures are presented within the context of liquid-liquid extraction processes and heterogeneous distillation processes. This paper describes development of a model for predicting the flash point of binary partially miscible mixtures of aqueous-organic system. To confirm the predictive efficiency of the derived flash points, the model was verified by comparing the predicted values with the experimental data for the studied mixtures: water + 1-butanol; water + 2-butanol; water + isobutanol; water + 1-pentanol; and, water + octane. Results reveal that immiscibility in the two liquid phases should not be ignored in the prediction of flash point. Overall, the predictive results of this proposed model describe the experimental data well when using the LLE and VLE parameters to estimate sequentially the span of two liquid phases and the flash point, respectively. Potential application for the model concerns the assessment of fire and explosion hazards, and the development of inherently safer designs for chemical processes containing binary partially miscible mixtures of aqueous-organic system

Prediction of Miscible Mixtures Flash-point from UNIFAC group contribution methods

Flash point is one of the most important variables used to characterize fire and explosion hazard of liquids. This paper predicts the flash point of miscible mixtures by using the flash point prediction model of Liaw and Chiu (J. Hazard. Mater. 137 (2006) 38-46) handling non-ideal behavior through liquid phase activity coefficients evaluated with UNIFAC-type models, which do not need experimentally regressed binary parameters. Validation of this entirely predictive model is conclusive with the experimental data over the entire flammable composition range for twenty four flammable solvents and aqueousorganic binary and ternary mixtures, ideal mixtures as well as Raoult’s law negative or positive deviation mixtures. All the binary-mixture types, which are known to date, have been included in the validated samples. It is also noticed that the greater the deviation from Raoult’s law, the higher the probability for a mixture to exhibit extreme (minimum or maximum) flash point behavior, provided that the pure compound flash point difference is not too large. Overall, the modified UNIFAC-Dortmund 93 is recommended, due to its good predictive capability and more completed database of binary interaction parameters. Potential application for this approach concerns the classification of flammable liquid mixtures in the implementation of GHS

Effect of stirring on the safety of flammable liquid mixtures

Flash point is the most important variable employed to characterize fire and explosion hazard of liquids. The models developed for predicting the flash point of partially miscible mixtures in the literature to date are all based on the assumption of liquid-liquid equilibrium. In real-world environments, however, the liquid-liquid equilibrium assumption does not always hold, such as the collection or accumulation of waste solvents without stirring, where complete stirring for a period of time is usually used to ensure the liquid phases being in equilibrium. This study investigated the effect of stirring on the flash point behavior of binary partially miscible mixtures. Two series of partially miscible binary mixtures were employed to elucidate the effect of stirring. The first series was aqueous-organic mixtures, including water + 1-butanol, water + 2-butanol, water + isobutanol, water + 1-pentanol, and water + octane ; the second series was the mixtures of two flammable solvents, which included methanol + decane, methanol + 2,2,4-trimethylpentane, and methanol + octane. Results reveal that for binary aqueous-organic solutions the flash-point values of unstirred mixtures were located between those of the completely stirred mixtures and those of the flammable component. Therefore, risk assessment could be done based on the flammable component flash point value. However, for the assurance of safety, it is suggested to completely stir those mixtures before handling to reduce the risk

Flash-point prediction for binary partially miscible mixtures of flammable solvents

Flash point is the most important variable used to characterize fire and explosion hazard of liquids. Herein, partially miscible mixtures are presented within the context of liquid-liquid extraction processes. This paper describes development of a model for predicting the flash point of binary partially miscible mixtures of flammable solvents. To confirm the predictive efficacy of the derived flash points, the model was verified by comparing the predicted values with the experimental data for the studied mixtures: methanol + octane; methanol + decane; acetone + decane; methanol + 2,2,4-trimethylpentane; and, ethanol + tetradecane. Our results reveal that immiscibility in the two liquid phases should not be ignored in the prediction of flash point. Overall, the predictive results of this proposed model describe the experimental data well. Based on this evidence, therefore, it appears reasonable to suggest potential application for our model in assessment of fire and explosion hazards, and development of inherently safer designs for chemical processes containing binary partially miscible mixtures of flammable solvents

On the relation between azeotropic behavior and minimum / maximum flash point occurrences in binary mixtures of flammable compounds

The flash point temperature and the boiling temperature of a mixture are related by the fact that both can be modeled based on vapor-liquid equilibrium (VLE) of each component. It has been suggested in the literature that there might exist a concomitance between azeotropic behavior and minimum/maximum flash point temperature for binary mixtures. In order to verify this statement, we derive new temperature dependent functions that relate the conditions valid for azeotropic behavior and those valid for minimum/maximum flash point behavior. Analysis of experimental data and predicted results allowed us to propose a heuristic to forecast extremum flash point based on the sole knowledge of azeotropic data and boiling and flash point temperatures differences. Extremum flash point might occur when both components are flammable and when the gap between the flash point temperatures of individual components (ΔT_fp) is of the same order or smaller than the boiling temperature gap (ΔT_b). Hence, we contribute to the assessment of the fire and explosion hazards in binary mixtures eventually presenting a minimum flash point behavio

Classification for ternary flash point mixtures diagrams regarding miscible flammable compounds

Flash point is a major indicator on the study of fire and explosion hazards of liquid mixtures. Mixtures presenting a minimum flash point behavior are particularly dangerous. It has been shown before that minimum/maximum flash point mixtures could be related with azeotropic behavior under some conditions. Since the 70's a classification of ternary azeotropic mixtures has been developed based on the topological properties of residue curve maps arising from the simple evaporation equilibrium model. In this paper we show that such a general classification also exists for flash point diagram of miscible flammable compound ternary mixtures and that it could help anticipate fire and explosion hazard in ternary mixtures. The demonstration is based on the construction of an auxiliary theoretical system under equilibrium equivalent to a non-equilibrium flash point system