Dust explosion

Dust explosions can occur where any dispersed powdered combustible material is present in high-enough concentrations in the atmosphere or other oxidizing gaseous medium, such as pure oxygen.

Finely divided wood dust can undergo explosive combustion and produce a blast wave.

Dust explosions are a frequent hazard in coal mines, grain elevators, and other industrial environments.

In the past, grain elevators sometimes experienced silo explosions.

Dust is defined as powders with particles less than about 500 micrometres in diameter, but finer dust will present a much greater hazard than coarse particles by virtue of the larger total surface area of all the particles.

In addition, if enough coal dust is dispersed within the air in a given area, in very rare circumstances, it can create an explosion hazard under certain circumstances.

Primary dust explosions may occur inside process equipment or similar enclosures, and are generally controlled by pressure relief through purpose-built ducting to the external atmosphere.

In addition, many otherwise mundane organic materials can also be dispersed into a dangerous dust cloud, such as grain, flour, starch, sugar, powdered milk, cocoa, coffee, and pollen.

Because sugars burn easily when exposed to flame, the handling of sugars risks dust explosion.

In special effects pyrotechnics, lycopodium powder and non-dairy creamer are two common means of producing safe, controlled fire effects.

Both these uses rely on the same principle as a dust explosion, as the spores have a large surface area per unit of volume, (a single spore's diameter is about 33 micrometers (μm)), and a high fat content.

Mining of coal leads to coal dust, and flour mills likewise have large amounts of flour dust as a result of milling.

The worst mining accidents in history have been caused by coal dust explosions, such as the disaster at Senghenydd in South Wales in 1913 in which 439 miners died, the Courrières mine disaster in Northern France which killed 1,099 miners in 1906, the Luisenthal Mine disaster in Germany, which claimed 299 lives in 1962, and the worst: the explosion at Benxihu Colliery, China, which killed 1,549 in 1942.

A dust explosion is the rapid combustion of fine particles suspended in the air within an enclosed location.

In addition, many otherwise mundane organic materials can also be dispersed into a dangerous dust cloud, such as grain, flour, starch, sugar, powdered milk, cocoa, coffee, and pollen.

Risks include grain entrapment, where workers are submerged in the grain and unable to remove themselves; explosions caused by fine particles of grain dust, and falls.

In addition, many otherwise mundane organic materials can also be dispersed into a dangerous dust cloud, such as grain, flour, starch, sugar, powdered milk, cocoa, coffee, and pollen.

Flour dust suspended in air is explosive—as is any mixture of a finely powdered flammable substance with air (see dust explosion).

Since the advent of industrial production–scale metal powder–based additive manufacturing (AM) in the 2010s, there is growing need for more information and experience with preventing dust explosions and fires from the traces of excess metal powder sometimes left over after laser sintering or other fusion methods.

Carbon nanoparticle emissions and processes using powder metals are highly combustible and raise the risk of dust explosions.

Powdered metals (such as aluminum, magnesium, and titanium) can form explosive suspensions in air, if finely divided.

The high surface-area-to-volume ratio of the powders can increase their chemical reactivity in biological exposures (for example, inhalation or ingestion), and increases the risk of dust explosions.

Fourteen people were killed and forty injured when a dust explosion occurred at a sugar refinery owned by Imperial Sugar.

The explosion is believed to have been caused by the ignition of grain dust.

In special effects pyrotechnics, lycopodium powder and non-dairy creamer are two common means of producing safe, controlled fire effects.

As with many other powders, large amounts of powdered non-dairy creamer powder are susceptible to dust explosion when suspended in air.

The dust explosion, which occurred on a music stage during a "Color Play Asia" party, has been called the "worst incident of mass injury [ever] in New Taipei".

The 2014 Kunshan explosion was a dust explosion that occurred at Zhongrong Metal Production Company, an automotive parts factory located in Kunshan, Jiangsu, China, on 2 August 2014.

Thermobaric weapons utilize this principle by rapidly saturating an area with an easily combustible material and then igniting it to produce explosive force.

Previously, such explosions were most often encountered in flour mills and their storage containers, and later in coal mines; but, now, most commonly in partially or fully empty oil tankers and refinery tanks and vessels, including an incident at Buncefield in the UK in 2005 where the blast wave woke people 150 km from its centre.

To support rapid combustion, the dust must consist of very small particles with a high surface area to volume ratio, thereby making the collective or combined surface area of all the particles very large in comparison to a dust of larger particles.

When a source cannot be found, ignition will often be attributed to static electricity.

Aerosol of flammable dust can be ignited as well, resulting in a dust explosion; the lower explosive limit usually lies between 50 and 1000 g/m 3 ; finer dusts tend to be more explosive and requiring less spark energy to set off.

Similarly, if the fuel to air ratio increases above the upper explosive limit (UEL), there is insufficient oxidant to permit combustion to continue at the necessary rate.

The combustion may take place in a controlled manner such as in an internal combustion engine or industrial furnace, or may result in an explosion (e.g., a dust explosion, gas or vapour explosion or in a thermobaric weapon).

The investigation initially focused on two separate possibilities: a failure of a newly installed gas line, and a large dust explosion.

Like many other powders, cornstarch is susceptible to dust explosions.

On April 26, 1942, a gas and coal-dust explosion in the mine sent flames bursting out of the mine shaft entrance.

According to Williamson, flammable powder or dust suspended in air in high concentrations is explosive.