Which factor explains why coal dust in an enclosed space is more explosive than coal dust blown outdoors into an open space Brainly?
Confinement means the dust is in an enclosed or limited space. This restriction allows pressure to build up, increasing the likelihood of an explosion.
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.
Does coal dust burn?
If not properly controlled, coal and coal dust can cause fires, explosions, and implosions at power plants.
What is the LEL of coal dust?
Explosibility of coal dust has been studied in laboratories, in explosion galleries and in an experimental coal mine. The data and results obtained from the tests showed that finely pulverized coal dust has a lower explosive limit of 0.035 to 0.08 ounces per cubic foot.
How do dust explosions occur?
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.
Why is there a danger of explosions in coal mines where there are large quantities of powdered combustible materials?
The danger of a violent explosion is enhanced by dust is not sufficiently inerted by rock dust. In most coal mines, the methane flammable limit and render the s processes within the coal itself may reduce the atmospheric oxygen, thereby further reducing the flammability in the sealed atmosphere.
What is coal dust made of?
Coal dust is a fine powdered form of which is created by the crushing, grinding, or pulverizing of coal. Because of the brittle nature of coal, coal dust can be created during mining, transportation, or by mechanically handling coal. It is a form of fugitive dust.
How do mines explode?
Explosions in underground mines and surface processing facilities are caused by accumulations of flammable gas and/or combustible dust mixed with air in the presence of an ignition source.
Does coal dust explode?
Fine bituminous coal dust is highly explosive when suspended in air. In a typical coal dust explosion, the dust is scoured by a small methane gas explosion, which also provides the initiating flame.
Why is dust explosive?
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.
Why is coal dust a fire hazard?
Coal dust only needs to accumulate to a footprint size and already it is a fire hazard. As the conveyor moves, any friction that occurs can be enough of a heat source to cause an explosion. Any machine that is not running impeccably can cause friction and, as a result, a heat source.
Why is dust so flammable?
Dust has a high surface area that can be heated much quicker and when it is suspended in the air, it has a large amount of oxygen to fuel ratio. These two things are the primary reasons dust behaves so differently and can even explode. Also read: Is Flour Flammable?
Why is grain dust so explosive?
Grain Dust Explosion Elements fuel – very small particles of dry grain dust from wheat, milo, oats, barley, wheat or oat flour, corn starch, etc. Grain dust must be suspended in the air to create an explosion. Layers of dust in a confined space provide explosive potential.
Why do coal mines explode?
Coal mine explosions are generally caused by either methane or coal dust. Methane gas is a byproduct of coal. It can build up over time in coal mines when there are not enough other types of gases to dilute it to prevent an explosion. Air can explode when it contains 5 to 15 percent methane.
Why is coal dust harmful?
1. 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.
How do you stop coal dust explosion?
Coal dust explosions in underground coal mines are prevented by generous application of rock dust (usually limestone). If an explosion should occur, the rock dust disperses, mixes with the coal dust and prevents flame propagation by acting as a thermal inhibitor or heat sink.
How is coal combustible?
Coal is a readily combustible rock consisting more than 70% by volume and 50% by weight of carbonaceous material (20). The inorganic non-combustible compounds which produce sulphur compounds and ash is the non-carbonaceous matter and mineral matter in coal.
What is explosive in mining?
What explosives are used for blasting? Dynamite, a nitroglycerin-based explosive, is rarely used today for blasting at surface mines in Illinois. Blasting agents account for almost 99% of the explosive materials used. ANFO, ammonium nitrate and fuel oil, is the most common explosive.
What causes explosions in mines?
Explosions in underground mines and surface processing facilities are caused by accumulations of flammable gas and/or combustible dust mixed with air in the presence of an ignition source.
Is any dust explosive?
If such a dust is suspended in air in the right concentration, under certain conditions, it can become explosible. Even materials that do not burn in larger pieces (such as aluminum or iron), given the proper conditions, can be explosible in dust form.
Why are gases and explosion risk in coal mines?
Most coal deposits release significant amounts of methane gas which is flammable when mixed with air in concentrations between 5 and 16%. Coal mine operators need to carefully ventilate underground mine openings to dilute and render harmless concentrations of methane to prevent ignitions and explosions. Krog et al.
Why is grain dust explosive?
Grain handling creates an environment that can result in combustion and explosion of dust. The three elements needed for a fire — grain dust as a fuel source, oxygen, and an ignition source — can create a flash fire that is dispersed within a confined space, resulting in the deadly ingredients for an explosion.
Why is dust flammable?
Dusts have a very large surface area compared to their mass. Since burning can only occur at the surface of a solid or liquid, where it can react with oxygen, this causes dusts to be much more flammable than bulk materials.
Why is corn dust explosive?
Grain dust is the main source of fuel for explosions in grain handling. Grain dust is highly combustible and can burn or explode if enough becomes airborne or accumulates on a surface and finds an ignition source (such as hot bearing, overheated motor, misaligned conveyor belt, welding, cutting, and brazing).
What are the factors that are the bases for an explosion?
In general, an explosive has four basic characteristics: (1) It is a chemical compound or mixture ignited by heat, shock, impact, friction, or a combination of these conditions; (2) Upon ignition, it decom- poses rapidly in a detonation; (3) There is a rapid release of heat and large quantities of high-pressure gases …
Which condition is caused by coal and dust in the lungs?
Pneumoconioses (meaning dusty lung) can cause impairment, disability and premature death. The two main types of pneumoconioses that affect miners are coal workers' pneumoconiosis (CWP) and silicosis. CWP, commonly called black lung, affects workers in coal mining.
Is coal dust corrosive?
In addition to mine waters, coal itself has been shown to be corrosive. This is not surprising since graphite is one of the most noble components of the galvanic series. Thus, galvanic corrosion should be expected.
What gas is responsible for most of the explosion in coal mines?
Methane (CH4) Methane (CH4) is the principle combustible gas found in coal mines. What is the explosive range of methane-air mixtures? 5 to 15 percent of methane in air is explosive.
Why is coal flammable?
Coal, and particularly brown coal, is very reactive to oxygen, and will generate CO2 and that creates heat. As the coal gets hotter it will eventually get to flame temperature and that coal will burn."
What causes spontaneous combustion in coal?
Spontaneous combustion in the coal or coal refuse is related to the oxidation of the coal to form CO2, CO, and H2O. The oxidation of pyrite and the adsorption of water on the coal surface also are exothermic or heat-generating reactions that increase the probability of spontaneous combustion (Kim, 1977).