Dust explosions–Cases, causes, consequences, and control

In spite of extensive research and development for more than 100 years to prevent and mitigate dust explosions in the process industries, this hazard continues to threaten industries that manufacture, use and/or handle powders and dusts of combustible materials. Lack of methods for predicting real dust cloud structures and flame propagation processes has been a major obstacle to prediction of course and consequences of dust explosions in practice. However, work at developing comprehensive numerical simulation models for solving these problems is now on its way. This requires detailed experimental and theoretical studies of the physics and chemistry of dust cloud generation and combustion. The present paper discusses how this kind of work will promote the development of means for prevention and mitigation of dust explosions in practice. However, progress in other areas will also be discussed, e.g. ignition prevention. The importance of using inherently safe process design, building on knowledge in powder science and technology, and of systematic education/training of personnel, is also emphasized.

Current status and expected future trends in dust explosion research

Right from the early days of the process industries, continuous efforts have been made to develop and improve measures for prevention and mitigation of dust explosions in these industries. Nevertheless this hazard continues to threaten industries that manufacture, use and/or handle powders and dusts of a wide range of combustible materials. To improve methods for predicting explosion development in real industrial plant has been one major challenge. Hence, during the last years comprehensive numerical simulation codes, for addressing this problem, have been developed. Progress has also been made in other areas, for example, ignition source prevention. The importance of adopting inherently safer process design, by building on firm knowledge in powder science and technology, and of systematic education/training of personnel, is also emphasized.

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Dust Explosion Prevention and Mitigation, Status and Developments in Basic Knowledge and in Practical Application

An experimental apparatus was built to study the external pressure caused by vented explosions of methane and air mixtures. In some circumstances, two peak points of external pressure induced by vented explosion appear. One of the peaks is caused by the vented flow from the vessel while the other one is due to the vented flow from the vessel or external explosion. Both the maximum external pressure and pressure rising rate increase with initial pressure, explosion venting pressure and vent diameter of the vented vessel. The maximum external pressure and pressure rising rate decrease with the volume of the vessel. The maximum pressure and the maximum pressure increase rate occur when the methane concentration is 9.5%. Compared with explosion outside one single big vessel, explosion outside the connected vessels is more severe. The external pressure caused by ignition in the center of the small vessel is higher than that in the center of the big vessel while the external pressure rising rate caused by ignition in the center of the small vessel is lower than that in the center of the big vessel. © 2014 American Institute of Chemical Engineers Process Saf Prog 33: 385–391, 2014

Effects on external pressures caused by vented explosion of methane‐air mixtures in single and connected vessels

An investigation of the consequences of primary dust explosions in interconnected vessels.

Much industrial dust-handling plant consists of vessels connected by pipelines. If a dust explosion propagates through such a system, the overall explosion event can be more violent than if a single vessel only is involved, due to a combination of increased turbulence, pressure piling and a jet flame ignition source in the second vessel. This paper gives guidance, based on an extensive experimental programme reported previously, on two aspects of the protection of interconnected vessels: containment and venting.

Dust explosion protection in linked vessels: guidance for containment and venting

This paper is a report of an experimental programme on the explosion protection of bucket elevators by venting. The project was a collaborative effort with funding by the Health and Safety Executive and manufacturers and users of bucket elevators through the British Materials Handling Board. Two bucket elevators were used in the project—a single leg elevator and a twin-leg elevator. Four dusts were used with KSt values up to 211 bar m s−1 and dust clouds were produced by dust injection and by normal operation. Reduced explosion pressures were measured and guidance has been derived from the results. This guidance is in terms of vent spacing as a function of the KSt value of the dust.

G.A. Lunn

Papers

Dust explosion protection in linked vessels: guidance for containment and venting

Explosion venting of bucket elevators