What factor affects a coal dust explosion happen in mines?
The smaller size of particle, low moisture in coal and high coal dust dispersion can increase the possibility or risk of dust explosion. Also, the shorter time of dust dispersion exposed to ignition source can enhance relatively low the possibility of coal dust explosion.
Why is coal dust an explosion risk?
Coal dust suspended in air is explosive—coal dust has far more surface area per unit weight than lumps of coal, and is more susceptible to spontaneous combustion. As a result, a nearly empty coal store is a greater explosion risk than a full one.
How does a coal dust explosion work?
Dust explosions are the result of high concentrations of combustible dust particles rapidly combusting inside an enclosed space. When mixed with oxygen, these fine particles can be ignited when coming into contact with a spark, metal ember, cigarette butt, or other ignition source.
What is coal dust made of?
Chemical and Mineral Compositions of Coal Dust. The proximate analysis results (Table 1) show that the dust in each mine is mainly composed of organic matter, along with different amounts of minerals. The ash content varies greatly among the mines within the range of 12.59–77.08% (avg. 28.85%).
What is the LEL of coal dust?
LEL is the maximum concentration of dust allowed in environment not to cause explosion. Explosion can be prevented by controlling the coal-dust concentration below LEL, which, furthermore, can be used to estimate the dangerous threshold of coal-dust layer thickness and accumulation.
How is coal dust measured?
The coal dust explosibility meter (CDEM) is a portable optical device that determines whether or not a coal and rock dust mixture is explosible (figure 1). It consists of an optical probe connected to a small electronics box with a digital display.
What factors control the phenomenon of a dust explosion?
The mechanism of a dust explosion is dependent on a number of variables including the chemical make-up of the dust, the activation energy, the heat of combustion, the particle separation, the particle size and shape, the specific surface area, the moisture content, the amount of available oxygen, etc.
What is minimum explosive concentration?
The lowest concentration of a combustible dust in air, expressed in grams per cubic meter that will propagate a flame.
What is the size of coal dust?
between 50 and 200 microns
Coal dust generally comprises a small component of total dust present in air near coal mines, railways and coal export terminals. Nevertheless, coal dust emissions can affect amenity, and predominantly comprises coarse dust particles (dustfall) of particle size generally between 50 and 200 microns in diameter.
What is coal meter?
The coal dust explosibility meter (CDEM) is a portable optical device that determines whether or not a coal and rock dust mixture is explosible (figure 1).
Is coal dust hazardous?
Exposure to coal mine dust causes various pulmonary diseases, including coal workers’ pneumoconiosis (CWP) and chronic obstructive pulmonary disease (COPD). 2. Coal miners are also exposed to crystalline silica dust, which causes silicosis, COPD, and other diseases. 3.
What are the effects of dust?
Health and safety effects of dust
| Health effect | Dust particle content |
|---|---|
| Lung scarring and fibrosis | Asbestos, quartz (crystalline silica) |
| Cancer | Chromates, asbestos, quartz (crystalline silica) |
| Irritation of the mucous membranes of the nose and throat | Acid, alkali, other irritating particles |
What can cause an explosion?
Many explosions occur when gases are exposed to a source of heat- such as fire, sparks, even static elec- tricity-or an increase in pressure. Explosions can also be caused by chemical reactions. For instance, when two or more incompatible substances are combined, they may explode.
How is Lel tested?
A test series is undertaken with a systematic decrease of the dust concentration until no ignition of the dust / air mixture is observed. The test is repeated to ensure no ignition is found in three consecutive tests. An ignition is deemed to have occurred if the maximum explosion pressure is at or above 0.5 bar.
What is dust concentration?
Dust concentration. Devices used for the continuous dust measurement register in the wider sense the physical changes caused by the particles in the measuring system converting them into electrical signals.
What are the effects of coal dust?
Exposure to coal mine dust causes various pulmonary diseases, including coal workers’ pneumoconiosis (CWP) and chronic obstructive pulmonary disease (COPD). 2. Coal miners are also exposed to crystalline silica dust, which causes silicosis, COPD, and other diseases.
What is the effect of dust on the environment?
Impacts on the environment and society But dust also has many negative impacts on agriculture, including reducing crop yields by burying seedlings, causing loss of plant tissue, reducing photosynthetic activity and increasing soil erosion.