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What is meant by spontaneous heating?
[spän′tā·nē·əs ′hēd·iŋ] (chemistry) The slow reaction of material with atmospheric oxygen at ambient temperatures; liberated heat, if undissipated, accumulates so that in the presence of combustible substances a fire will result.
Which is a cause for spontaneous heating of coal?
Coal can ignite spontaneously when exposed to oxygen, which causes it to react and heat up when there is insufficient ventilation for cooling. Pyrite oxidation is often the cause of coal’s spontaneous ignition in old mine tailings. … Once ignition temperature is reached, combustion occurs with oxidizers present (oxygen).
Which is one of the stage of spontaneous heating of coal?
After the dehydration of coal, its spontaneous combustion passes to the active stage; during this stage, the temperature of the coal and its related gaseous products increase dramatically. When the oxygen content drops down to 5%, the process enters the final, hypoxic stage.
Is coal dust spontaneous combustion?
4.2.
The spontaneous combustion of coal is caused by low-temperature oxidation [4]. While mining, crushing, or transporting coal, unexpected explosions like dust explosion sometimes occur. … It is well known that the low-temperature oxidation of coal causes spontaneous combustion.
How do you prevent spontaneous combustion?
Preventing spontaneous combustion from occurring is as simple as practicing a little routine housekeeping. Anytime you have an oily rag left over after some wood-finishing or another project, hang it up to dry, preferably outdoors. You can use a clothesline or a fence, but just be sure to isolate each rag individually.
What materials can spontaneously combust?
Materials that may catch fire by spontaneous ignition are:
- Rags and waste with oil and paint residues.
- Towels and linen, during laundering and drying.
- Paint overspray or material from a paint spray booth.
- Coal.
- Haystacks.
- Green waste piles and compost.
- A number of chemical substances, such as cellulose nitrate.
What is the ignition temperature of coal?
Ignition Temperature
| Fuel | Ignition Temperature (°C) | Source |
|---|---|---|
| Ethanol | 425 | |
| High-volatile coal | 670 | Mühlen and Sowa, 1995 |
| Medium-volatile coal | 795 | Mühlen and Sowa, 1995 |
| Anthracite | 930 | Mühlen and Sowa, 1995 |
What is the chemical reaction of burning coal?
Gasification reactions
| equilibrium conditions | ||
|---|---|---|
| reaction | effect of increase in temperature | heat of reaction |
| carbon + oxygen = carbon dioxide (combustion) | — | exothermic |
| carbon + carbon dioxide = carbon monoxide (Boudward) | to right | endothermic |
| carbon + water = carbon monoxide + hydrogen (water-gas) | to right | endothermic |
What are the chances of spontaneous combustion of coal can decrease?
An increase or a decrease in heat transfer affects the oxidation rate and moisture content. Panigrahi and Sahu (2004) and Onifade and Genc (2018b, e) indicated that as ash content increases, the spontaneous combustion liability of coal decreases.
At what temperature does coal spontaneously combust?
The ignition temperature for coal, which depends on several factors such as coal rank, volatile matter content and particle size, varies between 160 and 685 °C for most coals. Under adiabatic conditions, the minimum temperature at which a coal will self-heat is 35–140°C (Smith and Lazarra, 1987).