What is spontaneous heating in coal?
A
Heating coal using electricity
B
Heat generated due to microbial activity
C
Self-heating of coal due to slow oxidation
D
Burning coal with external fire
Analysis & Theory
Spontaneous heating occurs due to slow oxidation of coal in the presence of air, generating heat over time.
Which factor increases the risk of spontaneous heating in coal?
A
High humidity and good ventilation
C
Poor ventilation and accumulation of heat
D
Low temperature storage
Analysis & Theory
Poor ventilation causes heat build-up, leading to spontaneous combustion.
Which type of coal is most susceptible to spontaneous heating?
C
Sub-bituminous and lignite
Analysis & Theory
Lower-rank coals like lignite and sub-bituminous are more reactive and prone to spontaneous heating.
Which of the following is a preventive measure for spontaneous heating?
A
Store coal in closed, airtight spaces
B
Allow coal to remain undisturbed for long periods
C
Proper ventilation and regular coal turnover
D
Use oil to coat the coal surface
Analysis & Theory
Proper air flow and regular coal movement prevent localized heating.
What happens during the initial phase of spontaneous heating?
C
Oxidation produces heat slowly
D
Water evaporates instantly
Analysis & Theory
Initially, coal oxidizes slowly, generating small amounts of heat.
What temperature range can lead to thermal runaway in spontaneous heating?
Analysis & Theory
Temperatures around 70–80°C can accelerate oxidation, leading to thermal runaway and combustion.
What is the role of moisture in spontaneous heating?
B
It increases oxidation rate initially
Analysis & Theory
Moisture initially accelerates oxidation, increasing heating rate, but excessive moisture may reduce oxygen contact.
Which of the following methods is used to detect early stages of spontaneous heating?
B
Gas monitoring (CO, CH4 levels)
Analysis & Theory
CO levels rise during oxidation, making gas monitoring an effective early detection method.
Which of the following is NOT a preventive method for spontaneous heating?
A
Isolation of old workings
D
Increasing oxygen flow to the area
Analysis & Theory
Increasing oxygen flow accelerates oxidation and should be avoided.
In mines, where is spontaneous heating most likely to occur?
A
At fully ventilated conveyor belts
C
In old, poorly ventilated goaf areas
Analysis & Theory
Old goaf areas with poor ventilation and coal remnants are common zones for spontaneous heating.