Heat load due to use of explosive in coal mine

1. ASSIGNMENT
ON
HEAT PRODUCES DUE TO USE OF EXPLOSIVE
SUBMITTED BY-
NITESH KUMAR SHAH
23152021
SUBMITTED TO -
Dr. TARUN VERMA
DEPARTMENT OF MINING ENGINEERING
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2. Heat Load Due to Explosive
“When a high order explosion is initiated, a very rapid exothermic chemical reaction
occurs. As the reaction progresses, the solid or liquid explosive material is converted
to very hot, dense, high-pressure gas.”
 The heat that is produced during blasting varies with the type and amount of
explosives used (charge density).
 The amount of heat released by most explosives employed in mining falls within the
range of 3700 kJ/kg for ANFO to 5800 kJ/kg for nitro-glycerine.
 This heat is dispersed in two ways. First, a fraction of it will appear in the blasting
fumes and cause a peak heat load on the ventilation system following blasting. In
mines where a re-entry period is enforced this peak load should have cleared prior to
personnel being readmitted to the area.
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3. Cont…….
Blasting causes combustion
of explosive created heat
Exothermic reaction
Heat produced mostly depends
on calorific value of fuel used
Secondly, the remainder of the heat will be stored in the broken rock. The magnitude of this
will depend upon the mining method. If the rock is blasted into a free space through which the
ventilating airstream passes, such as an open stope or on a longwall face, and the fragmentation
is high, then as much as 40-50% of the heat produced by the explosive may be removed rapidly
as a peak load with the blasting fumes.
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4. Heat Load Due to Explosive
 if the blast occurs within a region through which there is little or no ventilation such as
in sublevel or forced caving techniques, or if the fragmentation is poor, then a much
larger proportion of the heat will be retained in the rock.
Fuel Oxidizer Combustion product Heat
Sensitizer
Ignite
Heat by blasting
Sensible heat
Latent heat(negligible)
Mine
Atmosphere Rock
After some time 04

5.  Example.
In a 2000 tonne blast, the charge density of ANFO is 0.8 kg/t. It is estimated that 20% of the
blast heat will be removed within 1 h with the blasting fumes.
(1) Calculate the mean value of the rate of heat removed by the airflow during this hour.
(2) If the specific heat of the rock is 950 J/kg °C determine the average increase in
temperature of the rock due to blasting.
 Solution:
1. Mass of explosive used = 2000 x 0.8 =1600kg ANFO
Heat produced by ANFO = 3700 x 1600 =5 920 000 kJ
Twenty per cent of this heat is removed in the blasting fumes over 1 hour.
Average rate of heat removal with blasting fumes
(5920 000 /3600 ) × 0.2kJ/s = 329 kW
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6. Cont…….
2. Heat retained in rock = 5 920 000 x 0.8 = 4 736 000 kJ
Rise in rock temperature = Heat retained / (Mass x Specific heat)
= 4736000/(2000x1000x0.950)kJ kg °C/kg kJ
= 2.49 °C
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7. References:-
 Subsurface Ventilation Engineering by Malcolm J. McPherson.
 Mine environment book by GB mishra.
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8. THANK YOU