wwwMINEPORTALin CALLWHATSAPP8804777500 wwwfbcommineportalin Heat source of underground mine Unusual high heat flow from earth Need for development of new sources of minerals calls for an expansion of underground mining deeper therefore hotter levels of the earth crust ID: 637613
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Slide1
Heat stress in mining
MINE PORTAL TEAM
www.MINEPORTAL.in
CALL/WHATSAPP-8804777500
www.fb.com/mineportal.inSlide2
Heat source of underground mine
Unusual high heat flow from earth
.
Need for development of new sources of minerals calls for an expansion of underground mining deeper therefore, hotter levels of the earth crust.
Use of electricity and other mechanical processes adds to the heat load of underground mines.
Estimated 90-95% of the energy released in blasting find its way into the underground environment as heat.
By
Autocompression
Slide3
Source
--
www.smenet.org/docs/meetings/2008/030.pdf
underground heat contributorsSlide4
HUMAN BODY AND ENVIRONMENT
Human body metabolism provides heat and energy for our physiological functions.
When environment and our body has temperature difference ,part of difference become less through convection and radiation from body to surrounding environment.
An active person loses part of his body heat through sweat evaporation .
The body core can dissipate its heat only through the shell. Blood serves as a vehicle for heat transfer.Slide5
Assessing the heat risk
Several factors can influence the heat load on the body. These include:
air temperature (Wet Bulb and Dry Bulb);
radiant heat;
humidity;
air movement;
the level of physical work; and
the amount and type of clothing being worn.
It is not possible to estimate the strain placed on the body by examining any one of these factors in isolation. In the mining situation, where radiant heat is not a major factor, it has been found that the best index is the Effective Temperature (ET), because it takes air velocity into account. Slide6
Concern
The steady stage of thermal equilibrium is represented by the following heat balance equation
M - E +/- K +/- C +/- R=0
where,M
=Metabolic heat generated
E=Evaporative heat loss
K=Conductive heat exchange
C=Convective heat exchange
R=
Radiative
heat exchange
For normal body
function,heat
exchange between the body and it’s environment need to be balanced and practically relies on
convection,conduction
and evaporation.Slide7
Continued…
In hot
environment,where
ambient temperature reaches core body temperature ,conduction and convection as a mean of thermoregulation.
Hyperthermia is caused by accumulation of heat .
Humidity decreases sweat evaporation.
Clothing impedes convective heat loss and interferes with the evaporation of sweat from the skin.
Heat stress overall affects the worker efficiency and thereby affects the production.Slide8
Variation of mean skin temp. with ambient wet bulb temp. for clothed(light and heavy),unclothed
Source
--
www.he.gov.uk/pubns/mines07.pdfSlide9
HOW HUMAN BODY COPES WITH HEAT STRESS
Warm-blooded animals can function regularly in almost all types of weather and climate.
At best, only some percent of the energy generated by the body's metabolism is converted into mechanical work.
Too much heat will interfere with the metabolism and cause health problems.Slide10
Heat Illness
Heat fainting-
It may occur as a result of
vasolidation,pooling
of blood in dependent
extremeties,reduced
.
Reduced blood volume (from dehydration ) result in reduced cardiac output.
It is not associated with an elevated body temperature.Slide11
Heat exhaustion-
There is a complex symptoms of
fatigue,headache,nausea
and giddiness.
Heat exhaustion occurs as a result of either dehydration and/or electrolyte depletions.Slide12
Heat cramp-
If the electrolytic balance of body fluids is sufficiently perturbed then painful muscular contraction occur in the
arms,legs
and abdomen.
This may occur by salt deficiency or drinking
lar
amounts of water following dehydration.Slide13
Heat rash-
Heat rash is caused by sweat duct obstruction and results in sweat retention within the gland.
This may result in infection or more commonly rupture within the skin with an inflammatory
respponse
result.
Sunburned skin and
occulsive
clothing interfering with free evaporation of sweat
increse
the risk of this condition.Slide14
Heat stroke-
This is a life threatening medical
condition.Symptoms
include altered mental status and core body temperatures above 40 degree
celcius
.
It occurs when the body’s thermoregulatory mechanism is overwhelmed by internal or external heat load and results in increasing core temperature.
Multiple organ failure or
distruption
of function is common and
shoul
be expected.Slide15
Improving the environment
The first step must be to reduce the impact of the environment,
ie
reducing effective temperature by engineering controls.
Provision of good quality air
Careful attention should be paid to the position and timing of ventilation connections, and the
minimising
of leakages between intake and return
outbye
, to
maximise
the quantity of air reaching the
inbye
workings.Slide16
Siting
of equipment that generates heat
Static equipment that generates heat should be kept sited either in the return airstream or in cross cuts.
Such equipment includes conveyors, as detailed above, compressors, pumps, and electrical switchgear, particularly transformers. Slide17
Use of equipment
A common source of excess heat is equipment that has been left running when not required.
Equipment should also be selected for the duty to be performed .
The selection of fire resistant hydraulic fluids can also have an effect on machine running temperature. Slide18
Control of water to
minimise
humidity
This can be achieved by eliminating standing water and by
minimising
the amount of water that is introduced underground .
Slide19
Artificial cooling
Air coolers remove heat from the passing air, but then dump that heat elsewhere. The plant is an additional heat source, but its use must be considered as part of the control measures.
Chilling the water supply underground is also worth considering. Slide20
CASE STUDY
:
The Granites Callie Mine - Australia
INTRODUCTION
-
Mineral : Granite
Production-2.1
Mtpa
Depth- 1000 m
Final Expected depth-1800 m
Mining Method:
Longhole
open
stoping
Slide21
Severe heat condition in mine
The mine heat load includes auto-compression, heat flow from rock and fissure water, heat released by the operation of electrical and diesel powered equipment.
The mine geothermal gradient is approximately 2°C/100 m resulting in 50°C rock temperature at the base of the mine.Slide22
FUTURE INFRASTRUCTURE
source--
www.deep
mining
2012.com/data/page/6998/5_howes.pdf
Slide23
COOLING REQUIREMENT-
Assuming an overall cooling requirement of 12500
kWR
, for an average mine airflow of 675 m3/s, the amount of cooling required is 18.5
kWR
/m3/s. The average mine cooling required is expected to average 10000 kW or 14.8
kWR
/m3/s.
.Slide24
WET AND DRY CONDENSING METHOD
Firstly condensers of a refrigeration plant remove heat from the refrigerant.
The refrigerant gas discharged from the compressor is superheated
Condenser cools it initially to the condensing temperature and then to a fully condensed liquid refrigerant in the condenser.Slide25
CONCLUSION
Heat Stress affects the mental condition of workers , hence affects the production.
The best solution to control heat is to use available technologies.
Better heat conditions in mine reduces mine accidents.Slide26
REFERENCES
Dresosti
A.O.,Problems
arising out of temperature and humidity in deep mines of the
Witwaterstand.Mine
society of
S.Africa
,vol.36:pp 102-129 retrieved from
http://www.minetech.com/technology/miningheat/
visited on 29 august 2011
Polton,E.C.,Environment
and human efficiency.vol 1:pp 204
McPherson M.J.,
Subsurface Ventilation and Environmental
Engineering,chapter
17-18:pp 680-749
http://www.geoexpro.com/technology/miningheat/
Date:1 sep 2011
www.hse.gov.uk/pubns/
mines
07.pdf
Date:30
aug
2011
http://www.sciencedirect.com/science/article/pii/037663497790013X
Date:30
aug
2011
www.deep
mining
2012.com/__data/page/6998/5_howes.pdf
Date:1 sep 2011