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American Society for Testing and Materials

Pulse detonation propulsion : challenges, current status, and future perspective

Dust explosions–Cases, causes, consequences, and control

This paper is an overview of and introduction to the subject of dust explosions. The purpose is to provide information on the explosibility and ignitability properties of dust clouds that can be used to improve safety in industries that generate, process, use, or transport combustible dusts. The requirements for a dust explosion are: a combustible dust, dispersed in air, a concentration above the flammable limit, the presence of a sufficiently energetic ignition source, and some confinement. An explosion of a fuel in air involves the rapid oxidation of combustible material, leading to a rapid increase in temperature and pressure. The violence of an explosion is related to the rate of energy release due to chemical reactions relative to the degree of confinement and heat losses. The combustion properties of a dust depend on its chemical and physical characteristics, especially its particle size distribution. In this paper, the explosion characteristics of combustible dusts will be compared and contrasted with those of flammable gases, using methane as an example. These characteristics include minimum explosible concentration, maximum explosion pressure, maximum rate of pressure rise, limiting oxygen concentration, ignition temperature, and amount of inert dust necessary to prevent flame propagation. The parameters considered include the effects of dust volatility, dust particle size, turbulence, initial pressure, initial temperature, and oxygen concentration. Both carbonaceous and metal dusts will be used as examples. The goal of this research is to better understand the fundamental aspects of dust explosions.

https://stacks.cdc.gov/view/cdc/9139/cdc_9139_DS1.pdf

Overview of dust explosibility characteristics

The impacts of combustion emissions on air quality and climate - From coal to biofuels and beyond

This work is a comprehensive account of the existing practical and theoretical knowledge of the origin, development, prevention and mitigation of dust explosions in the process industries. It offers an up-to-date evaluation of prevalent activities, testing methods, design measures and safe operating techniques in a detailed and comprehensive critique of all the significant phases relating to the hazard and control of a dust explosion. This should be a useful reference work for design, production, maintenance and safety engineers in the process industries, safety consultants and students.

Dust Explosions in the Process Industries

Dust explosion causation, prevention and mitigation: An overview

Dust explosions in the process industries practically always start inside process equipment such as mills, dryers, mixers, classifiers, conveyors, and storage silos and hoppers. For any given dust type the ease with which dust clouds ignite and the rates with which they burn, vary considerably with factors well known in powder science and technology. The key factors include the primary particle size distribution of the dust, the degree of de-agglomeration of the dust particles in the cloud, the dust concentration distribution in the cloud, and the cloud turbulence. The last three factors are entirely dependent on the actual process situation in which the dust cloud is generated and sustained. The paper first discusses influences of these factors on the ignition sensitivity and explosion violence of dust clouds. Secondly, the concept of inherently safer process design to prevent accidental dust explosions is discussed, using design of hoppers and silos as an example. Then some consequences of the mentioned factors in design of mitigatory measures such as explosion isolation, explosion venting, and automatic explosion suppression, are discussed. The role of powder science and technology in understanding development and propagation of secondary dust explosions is also considered.

Understanding dust explosions. The role of powder science and technology

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

On August 2, 2014 a catastrophic dust explosion occurred in a large industrial plant for polishing various aluminium-alloy parts in Kunshan, China. The explosion occurred during manual polishing of the surfaces of aluminium-alloy wheel hubs for the car industry. 75 people lost their lives immediately and another 185 were injured. Subsequently, 71 of the seriously injured also died, which increased the total loss of lives to 146. The direct economic loss of was 351 million yuan. This is probably one of the most serious dust explosion catastrophes known apart from some very major coal dust explosion disasters in coal mines. Based on measurements of explosion parameters of dust samples collected on the explosion site and on-site investigations and interviews, it was concluded that a series of consecutive explosions was initiated in one of the external dust filters. Then it propagated into the main building via the dust extraction ducting and further onto the second floor. At the same time the propagating in-house dust flame was sucked into the ducts leading to seven other external dust filters, which also exploded. On the basis of investigations on site after the explosion and subsequent laboratory experiments and data analyses it was concluded that the explosion was most probably initiated by self-ignition of contaminated aluminium-alloy dust in the dust collecting barrel below the external bag filter unit in which the initial primary explosion took place. General ignorance of the potential risk of dust explosions in industries producing fine metal dusts as a low-mass waste by-product is the most probable basic root cause of this catastrophic accident. Therefore, avoiding accumulation of deposits of such dusts indoors by good regular housekeeping and other means is regarded the most effective and practical way of loss prevention due to metal dust explosions in such plants. In addition, explosion isolation between dust collecting systems and workshops appears to be another important measure towards minimizing the consequences of such explosions.

Rolf K. Eckhoff

Papers

Dust Explosions in the Process Industries

Dust explosion causation, prevention and mitigation: An overview

Understanding dust explosions. The role of powder science and technology

Current status and expected future trends in dust explosion research

A catastrophic aluminium-alloy dust explosion in China