Mine Air Conditioning MINE PORTAL TEAM www.MINEPORTAL.in CALL/WHATSAPP-8804777500 www.fb.com/mineportal.in

Why are we here? To understand the Need for Air-Conditioning in mines. Methods of Air-conditioning and their underlying principle. Design of Mine Air-conditioning system Case Study Conclusion

What necessitates Air-Conditioning? Cooling : Heat increases with depth ->due to geothermal gradient. Auto-compression. Extensive mechanization. Ground water->from hot fissures and natural rock reservoirs. Oxidation->spontaneous combustion of coal, oxidation of timber and sulphur Blasting->90% of energy released in the blasting is in the form of heat. Human metabolism. Heating : Relatively shallow mines in cold climates for comfort reasons and as well as prevention of freezing of air at the intake end.

As per the regulation:- According to sub-section 2(iii) of section 155 : “the wet bulb temperature in any working place does not exceed 33.5 degrees centigrade;and where the wet bulb temperature exceeds 30.5 degrees centigrade arrangements are made to ventilate the same with a current of air moving at a speed of not less than onemetre per second”

Types of Cooling Evaporative Cooling Refrigerative Cooling Spot Cooling

1.Evaporative cooling (Cooling effect is produced by evaporation)

Basic principle of the cooling effect Courtesy: http://library.thinkquest.org/C006669/data/Chem/colligative/phase.html Accessed on 13/9/2011 Note: Graph not to Scale

Disadvantage->cannot give cooling effect beyond the Wet Bulb Temperature Courtesy:www.retscreen.net/fichier.php/898/Chapter-Cooling%20Towers.pdf Accessed on 13/9/2011

2.Refrigeration cycle ( vapour compression cycle)

Courtesy: http://library. thinkquest Note: Graph not to Scale

Note: the refrigeration cycle does not create “cold” it merely transfers heat from one place to another Courtesy: www.ior.org.uk/ior_/images/pdf/fundamentals1Cycle.pdf Accessed on 17/9/2011

3.Spot Cooling Advantages Cooling effect produced is utilised immediately No loss of efficiency. Disadvantages Increases Humidity of the Mine air. More heat would be added as the Air returns the condenser. Spot cooler Courtesy: Surface Ventilation By MJ McPherson

Design of Mine Cooling Systems

When a large amount of cooling is not required Courtesy: Mine Ventilation and Air Conditioning by Hartman Et al.

Use of bypass valve Courtesy: Mine Ventilation and Air Conditioning by Hartman Et al.

Case Study Homestake Mine (South Dakota) The Homestake Mine was a deep underground gold mine located in Lead, South Dakota. Until it closed in 2002 it was the largest and deepest gold mine in North America. The Homestake Mine is famous in scientific circles for being the site at which the Solar neutrino problem On July 10, 2007, the mine was selected by the National Science Foundation as the location for the Deep Underground science and Engineering Laboratory(DUSEL) http://scienceblogs.com/startswithabang/2011/09/faster_than _light_neutrinos.php Accessed[22/10/11]

The re-openeing operations are carried out in two phases Phase-1 ->no air-conditioning required Phase-2->air-conditioning required Courtesy: SME Mining Engineering handbook

condensor used- water. Ambient air temperature->53degrees Celsius. Wet bulb temperature->ranges from 15-20 degrees Celsius. METHODOLOGY USED Cooling water is processed in water chillers on the 5000- ft (1.5-km) level for service in the deepest parts of the mine. The chilled water is utilized in spray-chamber type coolers. Water from the spray chambers is rejected to the dewatering system. Some direct-expansion coil air chillers are also used; the condensers serving these units are cooled by service water that is rejected to the dewatering system.

Conclusions:- Cooling is required in deep mines to provide workable environments. Evaporative cooling is used to produce cooling effect upto wet bulb temperatures. Refrigerative cooling is used to produce cooling effect beyond wet bulb temperatures. Cooling tower can be eliminated if cold source of water is available near the mine and much cooling effect is not required. Energy can be conserved by the use of bye-pass valve in winters (it depends on wet bulb temperature and efficiency)

References:- Hartman, H.L.,Mutmansky J.M. and Wang Y.J. (1982), Mine Ventilation and Air Conditioning, (2nd. Ed.), John Wiley & Sons, New York. pp. 595–652. McPherson, M.J.(1997) ,Subsurface Ventilation and Environmental Engineering,(3rd Ed.) ,Chapman and Hall, London.pp.740-752. MISRA,G.B.(1986),Mine Environment And Ventilation,Oxford University Press, New Delhi, pp. 225-249. http://library.thinkquest.org/C006669/data/Chem/colligative/phase.html[ Accessed on 13/9/2011] www.ior.org.uk/ior_/images/pdf/fundamentals1Cycle.pdf [Accessed on 17/9/2011] www.dusel.org/.../A15_Reentry%20Ventilation%20Plan_05-01-07_version_SDSTA8.pdf[Accessed on 22/10/2011]