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Polymerization Reactions Inhibitor Modeling - Styrene and Butyl Acrylate Incidents Case Studies

High levels of inhibitor can improve long term storage stability but may be detrimental to operational safety in the case of a fire, loss of cooling, or an external heating induced runaway reaction. Read more

Predicting Dust Deflagration Behavior Using A Burn Rate Model

NFPA 68 (2013) provides simple calculation methods for sizing vents for combustible dust deflagrations. These methods have limited applicability to process operations. For systems outside of the applicability limits of NFPA 68, Murphy and Melhem presented in 2016 a methodology using a burn rate model for deflagration vent sizing. It involved estimating a reference laminar burning velocity and then using this velocity to simulate behavior at different operating conditions. The paper introduced the methodology and derived a laminar burning velocity for Niacin from measurements in an explosion severity test in a 20-liter sphere. Read more

Pressure Relief Design for Reactive Systems

Pressure relief design for reactive systems requires a different way of thinking than standard non-reactive designs. Reactive systems are in a constant state of flux: compositions, mixture properties, temperatures, and pressures are all changing throughout the relief event. Being able to safely vent a reactive system requires careful consideration of the mixture properties before reaction, the pressure and temperature rates during the reaction, and the mixture properties after reaction. To understand how these system properties effect the sizing of pressure relief systems requires careful experimentation, analysis and scale-up application. This presentation will explain a model-based approach to reactive pressure relief system design. Read more

Quantify Explosion Venting Dynamics in Vessels, Enclosures, and Energy Storage Systems

Explosions can occur in vessels or enclosures containing flammable gases and/or dusts. Explosion venting, often referred to as deflagration venting (because we cannot practically vent detonations), is used to protect from catastrophic vessel/enclosure failure. Simplified equations are often used to determine the deflagration relief requirements. Simplified equations can be found in standards such as NFPA-68. While easy to use, simplified equations tend to overestimate the relief requirements and have several practical limitations. Simplified equations provided in NFPA-68 [1] require the use of an explosion severity index, usually obtained from actual testing in a 20 liter sphere or a 1 m3 vessel. Published severity index data for flammable gases or dusts are also used. Typically, simplified equations for deflagration venting apply to ideal geometries and for short vent lines. They are not readily applicable to complex geometries, systems with elevated initial temperatures or pressures, hybrid systems containing flammable gases and dusts, systems with diluents and/or chemical oxidizers, systems with reduced venting set pressures, geometries with long L/D ratios or geometries with long vent piping where flame acceleration becomes significant. We have developed detailed deflagration and explosion dynamics methods and computer codes that address many of the shortcomings of simplified sizing methods. These dynamic methods rely on a detailed representation of all possible independent combustion reaction(s) using direct Gibbs free energy minimization [2, 3, 4] coupled with a detailed burning rate model developed from measured explosion data using a 20 liter sphere or a 1 m3 vessel. We describe these methods in what follows and provide examples of how they are applied and how the burning rate models are developed from measured data. Read more

Quickly Develop Chemical Interaction Matrices with SuperChems™

The development of accurate chemical interaction matrices can provide valuable information for the management of potential chemical reactivity hazards. SuperChems™, a component of Process Safety Office®, provides intuitive and easy to use utilities for the rapid development of chemical interaction matrices. These utilities were developed based on known heuristics and rules for the interaction of certain chemical groupings. SuperChems™ also provides additional utilities for the calculation of energy release and stoichiometry of one or more chemical reactions using detailed multiphase chemical equilibrium algorithms and reacting flow dynamics. In addition to thermo-physical and transport properties databanks, SuperChems™ provides hazards databanks where chemical groupings and other reactivity and toxicity data are available for approximately three thousand chemicals. Of particular interest is version 8.5 of the hazards databanks, released in March of 2018. Read more

Reactive Chemical Storage

It is a common practice to insulate storage tanks containing reactive chemicals to protect against fire exposure. While this mitigation technique is appropriate for vessels handling non-reactive chemicals, reactive chemicals storage represents a special challenge and must be examined on a case-by-case basis. Read more