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A Detailed Reaction Study of Phosphorus Trichloride and Water

This paper reports on a comprehensive literature search and small scale experimental work on the reaction characteristics of phosphorous trichloride and water. More than 30 tests were conducted, including both closed and open test cells. The water to phosphorus trichloride molar ratio was varied form 1 to 25. When in contact, water and phosphorus trichloride will form two liquid layers with a reaction starting at the interface. The impact of variables on reaction rates (including the interface surface area, layer depth, and stirring were investigated experimentally. A reaction rate model that fits all the measured data is presented. Case studies illustrating the use of this data for emergency relief systems and vent containment design are presented in reference [1]. Read more

A Kinetic Model for the Polymerization and Decomposition of Acrylonitrile

Conclusions that can be drawn from this presentation include: The presence of sodium hydroxide and ammonia will greatly accelerate the reaction of AN with HCN, AN Polymerization, and HCN polymerization. Small amounts of sodium hydroxide and ammonia present a significant safety hazard. We have developed a working model based on 21 calorimetry data sets that can be used to assess the effectiveness of existing relief systems in case of contamination and/or fire exposure to vessels containing mixtures of AN/HCN. Read more

A Systematic Approach to Chemical Reactivity Evaluation

Reactive chemicals are materials capable of giving rise to an uncontrolled chemical reaction (a.k.a., a runaway reaction). Reactions with a significant release of heat, gas and/or toxic materials have the potential to cause harm to people, property or the environment. Despite OSHA’s Process Safety Management Standard (PSM) and EPA’s Risk Management Plan (RMP) regulations, accidents with reactive chemicals continue to happen. In their 2002 report, the U.S. Chemical Safety and Hazard Investigation Board (CSB) identified failure of management systems for reactive chemistry as a key root cause of reactive chemical accidents. Managing reactive chemistry involves a systematic approach. The approach presented here incorporates both screening and experimental steps. As seen in Table 1, it begins with computational assessment, followed by experimental screening and finally, experimental testing. Read more

Addressing Combustible Dust Hazards

Many industries — from chemicals, plastics, and pharmaceuticals to food processing and mineral recovery — face combustible dust hazards in their facilities. Incidents such as the explosions and fires at the Imperial Sugar refinery in Port Wentworth, GA in February 2008 demonstrate the need to effectively manage these risks. Follow this approach to understand and mitigate your combustible dusts. Read more

An Advanced Method for the Estimation of Reaction Stoichiometry and Rates from ARC Data

Effect design of emergency relief systems requires accurate modeling. In particular, the PVT relation of such systems is fundamental and unique. This relation must be accurately represented during direct scale-up or computerized simulation. Variables which can significantly alter the PVT behavior of a system should be quantified, and included in the design. The pressure/temperature (PT) relation is a function of thermal inertia, liquid fill level (vessel void fraction), composition and chemical identity (vapor-liquid equilibrium, liquid/vapor density, heat of formation, etc). For a specified relief device set pressure, there is a unique corresponding system temperature. For reactive systems, this temperature corresponds to a reaction state. Small errors in estimating this temperature can lead to inadequate sizing and potential catastrophic vessel failure. Estimation of fluid flow rates and their associated energy depletion rates is a strong function of chemical identity. Often, simple reaction models are used which ignore this fact. If the reaction model only fits the observed constant PVT relation nd PT time histories, it will yield inaccurate predictions. The model may assume, for example, that the reaction products are made of a heavy and a light component. It may also specify a heat of reaction independently. However, these assumptions are often thermodynamically inconsistent and do not guarantee a unique solution, i.e., the chemical identities of the products are not unique. As a result, the estimated flow rates are often in error. This paper presents a method that guarantees a thermodynamically consistent and unique solution. Read more

Butadiene Thermal DimerizationTrimerization, Free-Radical Polymerization, and Polymer Decomposition Reactions

1,3-butadiene monomer undergoes thermally initiated, reversible dimerization/trimerization reactions with essentially the same kinetics in both the gaseous and liquid phases. Kinetics for formation of the dimer and the trimer are available from the open literature. The rate of reaction becomes significant (0.02°C/min = 29°C/day) at temperatures above 70-80°C. Inhibitors (t-butylcatechol, et al.) are used to prevent/minimize free-radical polymerization reactions in the liquid phase and to maintain product quality at ambient or subambient temperatures. These inhibitors do not prevent dimerization/trimerization reactions. Unless adequate emergency relief is provided, emergency relief is provided, the adiabatic temperature rise from the dimerization/trimerization reactions can lead to both a free-radical polymerization, initiated by adventitious peroxides, and a thermal decomposition of the resultant polymer to produce residues, volatiles, and not condensable gases. Temperatures of 600°C and pressures of over 2,000 psig are possible. Heat rates of 10,000°C/min pressure rise rates of 10,000 psig/min are also possible in unvented/undervented vessels. Emergency relief devices protecting vessels containing high concentrations of 1,3-butadiene should be reviewed to identify potentially reactive cases. This review is recommended to ensure that current that current emergency relief system designs are adequate and that equipment is being operated with an adequate margin safety. Read more

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