Dust control measures
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Dec 29, 2019
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About This Presentation
Dust control measures
Slide Content
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DUST CONTROL
Generally there are four rules regarding dust control
•(1)Keep the, dust production to a minimum and prevent it
from becoming airborne at its source
•(2) Dilute it as rapidly as possible by ventilation
•(3) where appropriate, separate the dust by filtration
•(4) remove persons from areas of high dust
concentrations and use personal protective devices.
DUST CONTROL
Generally there are four rules regarding dust control
•(1)Keep the, dust production to a minimum and prevent it
from becoming airborne at its source
•(2) Dilute it as rapidly as possible by ventilation
•(3) where appropriate, separate the dust by filtration
•(4) remove persons from areas of high dust
concentrations and use personal protective devices.
3
•to prevent the formation of dust use of sharp
picks, taking a deep cut and using a low
operating speed is to be practiced in operation
of shearer loaders.
•Production of fine dust during can be minimized
by using sharp bits in drilling so that there is
more of chipping than of grinding action.
•Water sprays are mainly used not only for
preventing the dusts from becoming airborne but
also for capture of airborne dust.
•to prevent the formation of dust use of sharp
picks, taking a deep cut and using a low
operating speed is to be practiced in operation
of shearer loaders.
•Production of fine dust during can be minimized
by using sharp bits in drilling so that there is
more of chipping than of grinding action.
•Water sprays are mainly used not only for
preventing the dusts from becoming airborne but
also for capture of airborne dust.
4
•Exhaust ventilation coupled with dust filtration has
become a common practice in development headings
•Suction hoods with dust filtration devices are used in
some mines to control dust at highly vulnerable locations
such as crushers, screens ,bunkers, and loading and
transfer points
•Exhaust ventilation coupled with dust filtration has
become a common practice in development headings
•Suction hoods with dust filtration devices are used in
some mines to control dust at highly vulnerable locations
such as crushers, screens ,bunkers, and loading and
transfer points
5
Mines Regulations require that dust emitted by
any machinery or operation be diluted by
ventilation current to a concentration below the
permissible limit but at the same time enjoins
that the air velocity should not be too high to
raise dust in the atmosphere.
•Also require that dust respirators be provided to
workers who have to work in places where it is
technically not feasible to reduce the respirable
dust concentration below permissible limit.
Mines Regulations require that dust emitted by
any machinery or operation be diluted by
ventilation current to a concentration below the
permissible limit but at the same time enjoins
that the air velocity should not be too high to
raise dust in the atmosphere.
•Also require that dust respirators be provided to
workers who have to work in places where it is
technically not feasible to reduce the respirable
dust concentration below permissible limit.
6
Shearer loader machine for
long wall
•a most effective means of dust suppression is pick face flushing
•directing jets of water on, or close to the leading faces of the cutter
picks.
•The water passes through ducts in the body of the drum
and is generally phased to allow flow only to the cutting side of the
drum.
Besides suppressing dust, the pick-face flushing cools the picks and
reduces the risk of frictional sparks.
•In addition to water applied through the shearer drums, water sprays
are mounted on the inside of cowls also
Shearer loader machine for
long wall
•a most effective means of dust suppression is pick face flushing
•directing jets of water on, or close to the leading faces of the cutter
picks.
•The water passes through ducts in the body of the drum
and is generally phased to allow flow only to the cutting side of the
drum.
Besides suppressing dust, the pick-face flushing cools the picks and
reduces the risk of frictional sparks.
•In addition to water applied through the shearer drums, water sprays
are mounted on the inside of cowls also
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•a ventilated shearer drum with (nine 100
mm diameter) venturi tubes incorporated
in the body of the shearer to capture the
dust from the face sideof the drum
•High pressure sprays (at '10 M Pa
pressure) are fitted in the tubes
•Induces a total airflow of 1.5 m3/s from the
face side of the drum and deposits the
dust in slurry form at the bottom.
•a ventilated shearer drum with (nine 100
mm diameter) venturi tubes incorporated
in the body of the shearer to capture the
dust from the face sideof the drum
•High pressure sprays (at '10 M Pa
pressure) are fitted in the tubes
•Induces a total airflow of 1.5 m3/s from the
face side of the drum and deposits the
dust in slurry form at the bottom.
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•flushing by using extra-high pressure
water of 200 to 400 bar in an attempt to
improve the process of cutting.
•The technique, known as jet-assisted
cutting, is claimed to use the same water
flow rate as employed in conventional pick
face flushing
•but permits application of a shearer loader
to cut much harder material and reduces
the dust formation
•flushing by using extra-high pressure
water of 200 to 400 bar in an attempt to
improve the process of cutting.
•The technique, known as jet-assisted
cutting, is claimed to use the same water
flow rate as employed in conventional pick
face flushing
•but permits application of a shearer loader
to cut much harder material and reduces
the dust formation
11
Continuous miner
•Continuous miners are equipped with water spray systems designed
to suppress dust, cool motors and cutting bits, and serve as
emergency fire-suppression systems.
•A number of external spray nozzles mounted on the machine body
delivers water to strategic areas for dust control.
The purpose of these sprays is to wet the coal as it is cut and to
direct the dust-laden air away from the operator and other face
personnel.
•The spray nozzles are typically located on top of the boom directed
at the top of the drum ,beneath the boom directed at the bottom of
the drum and the gathering arms, and in the conveyor throat
Continuous miner
•Continuous miners are equipped with water spray systems designed
to suppress dust, cool motors and cutting bits, and serve as
emergency fire-suppression systems.
•A number of external spray nozzles mounted on the machine body
delivers water to strategic areas for dust control.
The purpose of these sprays is to wet the coal as it is cut and to
direct the dust-laden air away from the operator and other face
personnel.
•The spray nozzles are typically located on top of the boom directed
at the top of the drum ,beneath the boom directed at the bottom of
the drum and the gathering arms, and in the conveyor throat
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•When face entry air velocity is low,
an improper spray system can cause face dust
roll back to the machine operator's position.
Some of the remedial measures are reduction of
spray pressure, change of orientation of nozzles
and increase of face airflow.
•When face entry air velocity is low,
an improper spray system can cause face dust
roll back to the machine operator's position.
Some of the remedial measures are reduction of
spray pressure, change of orientation of nozzles
and increase of face airflow.
13
Road header machines
•Dust control in a road header
drivage is of great importance as the
machine works entirely in rock drivage
or in mixed coal and rock drivage, thus
producing dust rich in free silica.
•The first precaution is to use water sprays
directed at the cutting point and
at the material being loaded by the
gathering arms.
Road header machines
•Dust control in a road header
drivage is of great importance as the
machine works entirely in rock drivage
or in mixed coal and rock drivage, thus
producing dust rich in free silica.
•The first precaution is to use water sprays
directed at the cutting point and
at the material being loaded by the
gathering arms.
14
Ventilation
•Still a lot of dust is generated and becomes airborne
which is tackled by having a good ventilation system,
specially an exhaust duct close to the face to suck the
dust-laden air .
•The dust produced at the cutting head tends to flow
backwards and is known variously as 'back-up' or 'boil-
back' dust.
•The "amount of 'boil-back' dust reaching the operator's
position is related to the ventilation quantity reaching the
heading, the positioning of the exhaust inlet and the
forward induced air velocity over the RH machine.
Ventilation
•Still a lot of dust is generated and becomes airborne
which is tackled by having a good ventilation system,
specially an exhaust duct close to the face to suck the
dust-laden air .
•The dust produced at the cutting head tends to flow
backwards and is known variously as 'back-up' or 'boil-
back' dust.
•The "amount of 'boil-back' dust reaching the operator's
position is related to the ventilation quantity reaching the
heading, the positioning of the exhaust inlet and the
forward induced air velocity over the RH machine.
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•a minimum forward air velocity of 0.4 m/s is desirable to reduce the
dust concentration level at the RH operator's position.
•In an exhaust overlap system, the exhaust duct end has to be
advanced frequently to 2 to 4.5 m of the face to achieve such
a forward velocity as can be seen from the arrangement practiced in
Moonidih RH faces
•In modern road header machines, however, a duct system is fitted
on the machine itself so that the duct entry is fixed at about
2 m from the cutting head. A short flexible duct connects the
mounted duct to the exhaust fan cum scrubber system sited out bye
of the face
•a minimum forward air velocity of 0.4 m/s is desirable to reduce the
dust concentration level at the RH operator's position.
•In an exhaust overlap system, the exhaust duct end has to be
advanced frequently to 2 to 4.5 m of the face to achieve such
a forward velocity as can be seen from the arrangement practiced in
Moonidih RH faces
•In modern road header machines, however, a duct system is fitted
on the machine itself so that the duct entry is fixed at about
2 m from the cutting head. A short flexible duct connects the
mounted duct to the exhaust fan cum scrubber system sited out bye
of the face
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C C M
•In operation, a CCM produces a significant
amount of fine coal and dust at the sides
of the cutter bar.
•Wet bar cutting technique with spray
nozzles mounted at the front and rear side
of the bar helps to control the dust
by keeping the chain wet.
C C M
•In operation, a CCM produces a significant
amount of fine coal and dust at the sides
of the cutter bar.
•Wet bar cutting technique with spray
nozzles mounted at the front and rear side
of the bar helps to control the dust
by keeping the chain wet.
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Roof support in long wall faces
•In mechanized long wall faces significant amount of dust
is produced due to crushing of roof and floor strata
by repeated raising and lowering of supports and their
movement.
•The two common precautions adopted are use of wide-
web roof beams to distribute pressure over a large area
and fitting of water sprays on the goaf side of top
edge of the supports to wet the broken down roof
material.
•Another precaution sometimes taken is to seal the gaps
between adjacent canopies of roof support units with
flexible plastic sheets to prevent dust falling into the face
zone.
Roof support in long wall faces
•In mechanized long wall faces significant amount of dust
is produced due to crushing of roof and floor strata
by repeated raising and lowering of supports and their
movement.
•The two common precautions adopted are use of wide-
web roof beams to distribute pressure over a large area
and fitting of water sprays on the goaf side of top
edge of the supports to wet the broken down roof
material.
•Another precaution sometimes taken is to seal the gaps
between adjacent canopies of roof support units with
flexible plastic sheets to prevent dust falling into the face
zone.
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Drilling
•In rotary-percussive drilling a large quantity of
rock is pulverized to form dust.
•Supply of water to drill bits through hollow drill
steels keeps the rock surface wet all the time, so
that the rock is actually broken under a film of
water.
•Only sharp bits should be used and suitable
pressure should be applied on the bits.
•For wet drilling to be effective, sufficient
pressure of water should available.
Drilling
•In rotary-percussive drilling a large quantity of
rock is pulverized to form dust.
•Supply of water to drill bits through hollow drill
steels keeps the rock surface wet all the time, so
that the rock is actually broken under a film of
water.
•Only sharp bits should be used and suitable
pressure should be applied on the bits.
•For wet drilling to be effective, sufficient
pressure of water should available.
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•Pneumatic drills generally have internal
water feed arrangement by means of a
water tube passing through the piston and
delivering water to the hollow drill rod at
the shank end.
•In an alternative less commonly used
system of feeding water into the drill steel,
an external flush head is provided at the
shank end of the drill steel.
•Pneumatic drills generally have internal
water feed arrangement by means of a
water tube passing through the piston and
delivering water to the hollow drill rod at
the shank end.
•In an alternative less commonly used
system of feeding water into the drill steel,
an external flush head is provided at the
shank end of the drill steel.
20
•In hot and deep mines where wet drilling
causes unacceptable increase of humidity
or where water has a deleterious effect on
the strata, dry dust extractors are to be
used while drilling.
•In a dry dust extractor, the dust-laden air is
sucked through the central hole in the drill
steel and taken to a system of cyclones
and filters for separating the dust.
•In hot and deep mines where wet drilling
causes unacceptable increase of humidity
or where water has a deleterious effect on
the strata, dry dust extractors are to be
used while drilling.
•In a dry dust extractor, the dust-laden air is
sucked through the central hole in the drill
steel and taken to a system of cyclones
and filters for separating the dust.
21
•Hand-held electric rotary drills, commonly used
with solid diamond or turbine section rods, have
no provision for sending a jet of water to the bit.
However, the eccentric type drilling bit, when
used with proper thrust produces large chips of
coal and only a small amount of dust comes out
of the hole, which is diluted by the air current.
Where auger type rods with a central hole is
used for rotary drilling, the external flush-head
system can be used to send a jet of water to the
cutting bit and the drill cuttings come out
in such a case in the form of a slurry along the
auger paths in the rod.
•Hand-held electric rotary drills, commonly used
with solid diamond or turbine section rods, have
no provision for sending a jet of water to the bit.
However, the eccentric type drilling bit, when
used with proper thrust produces large chips of
coal and only a small amount of dust comes out
of the hole, which is diluted by the air current.
Where auger type rods with a central hole is
used for rotary drilling, the external flush-head
system can be used to send a jet of water to the
cutting bit and the drill cuttings come out
in such a case in the form of a slurry along the
auger paths in the rod.
22
ROOF BOLTS
•Dust from drilling roof bolt holes is a major problem in
most of the
Indian coal mines where the holes are drilled manually
using the rotary electric coal drills, only replacing the
coal bit with rock bit.
•The process is slow and the dust falls directly on the
heads of the drillers.
•Dust can be suppressed by supplying water under
pressure to the bits,
•or alternatively a dry dust collection system using cloth
bag or pleated-paper-cartridge type filter can be used.
ROOF BOLTS
•Dust from drilling roof bolt holes is a major problem in
most of the
Indian coal mines where the holes are drilled manually
using the rotary electric coal drills, only replacing the
coal bit with rock bit.
•The process is slow and the dust falls directly on the
heads of the drillers.
•Dust can be suppressed by supplying water under
pressure to the bits,
•or alternatively a dry dust collection system using cloth
bag or pleated-paper-cartridge type filter can be used.
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DRILLING AND BLASTING
•Dust production in drilling and blasting can be
reduced by use of water filled plastic ampoules
as stemming material in place of the usual clay
stemming.
•The common type of water ampoule is made of
0.15 mm thick PVC, is 38 cms long and 5 cm
wide and has a self sealing valve
•Water is filled underground at a convenient point
near to place of blasting.
DRILLING AND BLASTING
•Dust production in drilling and blasting can be
reduced by use of water filled plastic ampoules
as stemming material in place of the usual clay
stemming.
•The common type of water ampoule is made of
0.15 mm thick PVC, is 38 cms long and 5 cm
wide and has a self sealing valve
•Water is filled underground at a convenient point
near to place of blasting.
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•For shot holes of up to 1.5 m depth, only one water
ampoule is inserted after the explosive charge. In holes
longer than 1.5 m, an additional water ampoule is
introduced at the back of the hole before inserting the
explosive cartridges
•Alternate methods to shot firing, which utilize
compressed air or water pressure to fracture the coal
such as Airdox; Hydrox etc., produce
a larger sized product with less fines (and hence less
respirable dust) than
chemical explosives.
•For shot holes of up to 1.5 m depth, only one water
ampoule is inserted after the explosive charge. In holes
longer than 1.5 m, an additional water ampoule is
introduced at the back of the hole before inserting the
explosive cartridges
•Alternate methods to shot firing, which utilize
compressed air or water pressure to fracture the coal
such as Airdox; Hydrox etc., produce
a larger sized product with less fines (and hence less
respirable dust) than
chemical explosives.
25
LOADING
•After blasting, the coal or rock pile is .generally
wetted with water sprays prior to loading.
•In some metalliferous mines, fog producing
machines of either the spinning disc or
compressed air type are positioned upstream of
the blast area to remove airborne dust by
impingement and to moisten the broken rock.
•Such machines are switched on shortly before
blasting and allowed to during the re-entry
period.
LOADING
•After blasting, the coal or rock pile is .generally
wetted with water sprays prior to loading.
•In some metalliferous mines, fog producing
machines of either the spinning disc or
compressed air type are positioned upstream of
the blast area to remove airborne dust by
impingement and to moisten the broken rock.
•Such machines are switched on shortly before
blasting and allowed to during the re-entry
period.
26
BELT FCONVEYORS
•On belt conveyor systems, the goal is to keep the
mineral damp enough to reduce the likelihood of dust
becoming airborne
•Hence, rewetting of the mineral at intervals along the belt
may be necessary
•Flat-fan type spray nozzles operating at 300 to 350 k Pa
pressure are preferred for this purpose.
•However, over-liberal use of water can cause slippage at
the driving drums and damage to the -belt and also give
rise to the problem of in handling the mineral
BELT FCONVEYORS
•On belt conveyor systems, the goal is to keep the
mineral damp enough to reduce the likelihood of dust
becoming airborne
•Hence, rewetting of the mineral at intervals along the belt
may be necessary
•Flat-fan type spray nozzles operating at 300 to 350 k Pa
pressure are preferred for this purpose.
•However, over-liberal use of water can cause slippage at
the driving drums and damage to the -belt and also give
rise to the problem of in handling the mineral
27
TRANSFER POINTS
•At transfer points, displaced air causes adhering
dust to rise and at the same time ventilating air
gets an opportunity to make the dust airborne.
•Moreover, fresh quantities of dust may be
produced from fall of minerals over a height.
•It is important to keep mineral damp when it
reaches the transfer point. In addition to a water
spray directed onto the falling stream of mineral,
TRANSFER POINTS
•At transfer points, displaced air causes adhering
dust to rise and at the same time ventilating air
gets an opportunity to make the dust airborne.
•Moreover, fresh quantities of dust may be
produced from fall of minerals over a height.
•It is important to keep mineral damp when it
reaches the transfer point. In addition to a water
spray directed onto the falling stream of mineral,
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•It is preferable to install a dribbler bar across the belt some 10 m
before the transfer points
•It would permit the mineral and water to mix before reaching the
transfer point.
•As boil back of dust is a common phenomenon at transfer points the
spray nozzles should be inside an enclosure with fogger type mist
producing jets suitable for dust capture
•The accumulation of coal and dust particles on the top and bottom
sides of the return belt is scraped by placing wipers near ·the belt
drive or by spraying the belt with a low quantity flat-fan type nozzle.
•It is preferable to install a dribbler bar across the belt some 10 m
before the transfer points
•It would permit the mineral and water to mix before reaching the
transfer point.
•As boil back of dust is a common phenomenon at transfer points the
spray nozzles should be inside an enclosure with fogger type mist
producing jets suitable for dust capture
•The accumulation of coal and dust particles on the top and bottom
sides of the return belt is scraped by placing wipers near ·the belt
drive or by spraying the belt with a low quantity flat-fan type nozzle.
29
SPRAY PARAMETERS
The type and placement of the spray nozzles should be selected on
the basis of the requirement of the particular application,
The various spray parameters to be selected are the ,nozzle type,
water flow and pressure, the size and velocity of the water drops In
the spray, the distance. of placement of the nozzles and their
orientation.
For moistening of a surface by an impinging water spray, the
optimum size of water drops is approximately 500 microns.
On the other hand, the optimum size of drops for capture of airborne
respirable coal dust is approximately 200 microns.
For the latter, the nozzles should be placed at a greater distance
and need a higher line pressure of 7 to 10 atmosphere.
SPRAY PARAMETERS
The type and placement of the spray nozzles should be selected on
the basis of the requirement of the particular application,
The various spray parameters to be selected are the ,nozzle type,
water flow and pressure, the size and velocity of the water drops In
the spray, the distance. of placement of the nozzles and their
orientation.
For moistening of a surface by an impinging water spray, the
optimum size of water drops is approximately 500 microns.
On the other hand, the optimum size of drops for capture of airborne
respirable coal dust is approximately 200 microns.
For the latter, the nozzles should be placed at a greater distance
and need a higher line pressure of 7 to 10 atmosphere.
30
Spray types used for dust
control in mining.
Spray types used for dust
control in mining.
31
Types of spray nozzles
•Full cone, hollow cone, flat spray, (or flat fan), solid
stream; fine spray and atomizing type
The full and hollow cone spray nozzles can give
tapering-edge or even-edge spray patterns.
The solid stream nozzle is a special case of a flat spray
nozzle with a spray angle of zero degrees.
The nozzles are made of various materials such as
brass, steel, stainless steel, nylon, PVC etc.
Types of spray nozzles
•Full cone, hollow cone, flat spray, (or flat fan), solid
stream; fine spray and atomizing type
The full and hollow cone spray nozzles can give
tapering-edge or even-edge spray patterns.
The solid stream nozzle is a special case of a flat spray
nozzle with a spray angle of zero degrees.
The nozzles are made of various materials such as
brass, steel, stainless steel, nylon, PVC etc.
32
•Spray nozzle type, location, pattern, flow, and
pressure are all factors to consider when
designing a spray system.
•The type of spray used at a particular location
depends on the desired application
•for suppression of dust, high flow at low
pressure close to the source is most effective.
•For airborne dust capture, smaller high-velocity
droplets are required to impact with dust and
remove it from the air
•For redirection, higher pressure is required
•Spray nozzle type, location, pattern, flow, and
pressure are all factors to consider when
designing a spray system.
•The type of spray used at a particular location
depends on the desired application
•for suppression of dust, high flow at low
pressure close to the source is most effective.
•For airborne dust capture, smaller high-velocity
droplets are required to impact with dust and
remove it from the air
•For redirection, higher pressure is required
33
For the same nozzle size, the capacity in
l/mn increases with the square root of the
applied water pressure.
The manufacturers' catalogues provide the
capacity and spray angle for various orifice
sizes and types of nozzles when subjected
to different line pressures.
For the same nozzle size, the capacity in
l/mn increases with the square root of the
applied water pressure.
The manufacturers' catalogues provide the
capacity and spray angle for various orifice
sizes and types of nozzles when subjected
to different line pressures.
34
•A major problem associated with water spray systems is
the frequent clogging of spray nozzles caused mainly by
particulate matter in the water line including pipe scale
and mineral particles.
•Experience has shown the necessity of incorporating
efficient water filters to avoid jet blockage and the
need to maintain adequate water pressure
•Interlocking switches are generally fitted in coal and rock
cutting and drilling machine to ensure that the cutting
machine or the drill cannot be operated unless water is
flowing.
•A major problem associated with water spray systems is
the frequent clogging of spray nozzles caused mainly by
particulate matter in the water line including pipe scale
and mineral particles.
•Experience has shown the necessity of incorporating
efficient water filters to avoid jet blockage and the
need to maintain adequate water pressure
•Interlocking switches are generally fitted in coal and rock
cutting and drilling machine to ensure that the cutting
machine or the drill cannot be operated unless water is
flowing.
35
continuous miners
•Most continuous miners use a combination of
spray types to achieve the best control. Although
higher water pressure will raise the effectiveness
of water sprays,
•a marked disadvantage is that it entrains large
volumes of air and subsequently dust.
•This can result in dust rollback.
•The earliest water sprays on a continuous miner
were used for bit lubrication, bit cooling, and
dust control.
continuous miners
•Most continuous miners use a combination of
spray types to achieve the best control. Although
higher water pressure will raise the effectiveness
of water sprays,
•a marked disadvantage is that it entrains large
volumes of air and subsequently dust.
•This can result in dust rollback.
•The earliest water sprays on a continuous miner
were used for bit lubrication, bit cooling, and
dust control.
36
37
VENTILATION
•The velocity and quantity of face ventilating air
are important factors for controlling respirable
dust exposure of the continuous miner operator.
•A good ventilation plan consists of sufficient
mean entry air velocity to confine dust near the
face and/or direct it toward the return entry with
high enough quantity for diluting generated
respirable dust.
•The two ventilation schemes most widely used
for underground coal mining are blowing and
exhausting.
VENTILATION
•The velocity and quantity of face ventilating air
are important factors for controlling respirable
dust exposure of the continuous miner operator.
•A good ventilation plan consists of sufficient
mean entry air velocity to confine dust near the
face and/or direct it toward the return entry with
high enough quantity for diluting generated
respirable dust.
•The two ventilation schemes most widely used
for underground coal mining are blowing and
exhausting.
38
•When blowing ventilation is used, intake air is delivered
to the face of the working entry by blowing it from behind
line brattice or tubing. The clean air is blown toward the
face and sweeps the dust-laden air toward the return
entries.
•This system allows the continuous miner operator to be
positioned in the clean discharge air at the end of the
blowing curtain or tubing.
•Although this method effectively sweeps dust and
methane from the face, it also positions mobile
equipment operators (e.g., shuttle car operators) and
roof bolter operators working downwind in return air.
•When blowing ventilation is used, intake air is delivered
to the face of the working entry by blowing it from behind
line brattice or tubing. The clean air is blown toward the
face and sweeps the dust-laden air toward the return
entries.
•This system allows the continuous miner operator to be
positioned in the clean discharge air at the end of the
blowing curtain or tubing.
•Although this method effectively sweeps dust and
methane from the face, it also positions mobile
equipment operators (e.g., shuttle car operators) and
roof bolter operators working downwind in return air.
39
•When exhausting ventilation is used, intake air is
delivered to the face in the working entry.
•The clean air sweeps the face, and the dust-laden air is
then drawn behind the return curtain or through the
exhaust tubing to the return entries.
•This system will keep mobile equipment in fresh air and
affords the continuous miner operator more freedom of
movement than a blowing ventilation system.
•In addition, exhausting ventilation allows more visibility
around the loading area so that shuttle car operators can
easily determine where the continuous miner operator is
located when entering the face area.
•When exhausting ventilation is used, intake air is
delivered to the face in the working entry.
•The clean air sweeps the face, and the dust-laden air is
then drawn behind the return curtain or through the
exhaust tubing to the return entries.
•This system will keep mobile equipment in fresh air and
affords the continuous miner operator more freedom of
movement than a blowing ventilation system.
•In addition, exhausting ventilation allows more visibility
around the loading area so that shuttle car operators can
easily determine where the continuous miner operator is
located when entering the face area.
40
WETTING AGENTS
•Rocks vary considerably in their wet ability
characteristics and coal dust in particular
is hydrophobic in nature.
•The relatively high surface tension of
water. (72 dynes per centimeter) prevents
wetting of coal and many mineral dusts
and results in low penetration of water
through rock or coal layers
WETTING AGENTS
•Rocks vary considerably in their wet ability
characteristics and coal dust in particular
is hydrophobic in nature.
•The relatively high surface tension of
water. (72 dynes per centimeter) prevents
wetting of coal and many mineral dusts
and results in low penetration of water
through rock or coal layers
41
•Addition of wetting agents (normally anionic or nonionic surfactants
or surface active reagents) into the water reduces its surface tension
to the range of 28 to 36 dynes per centimeter and improves
penetration into the dust layer.
•In practice the wetting agent is either added in the water tank
feeding the mine or is injected into the water line leading to the
sprays at a given rate by a dosing pump
•DGMS Circular mentions of four wetting agents -calsolene oil, shell
non-ionic detergent P-47-C, coal set, and coal set x 5 -as approved
wetting agents for coal dust in mines
•Although a few mines continue to use wetting agents in water spray
lines the method is not widely practiced and the cost effectiveness of
the technique has not been proved beyond doubt.
•Addition of wetting agents (normally anionic or nonionic surfactants
or surface active reagents) into the water reduces its surface tension
to the range of 28 to 36 dynes per centimeter and improves
penetration into the dust layer.
•In practice the wetting agent is either added in the water tank
feeding the mine or is injected into the water line leading to the
sprays at a given rate by a dosing pump
•DGMS Circular mentions of four wetting agents -calsolene oil, shell
non-ionic detergent P-47-C, coal set, and coal set x 5 -as approved
wetting agents for coal dust in mines
•Although a few mines continue to use wetting agents in water spray
lines the method is not widely practiced and the cost effectiveness of
the technique has not been proved beyond doubt.
42
•The dust layer is leveled and sprayed with water such that the dust
is wetted to a depth of at least 25 mm.
•Addition of a wetting agent (e.g. Teepol or Lissapol) at this stage is
helpful, After about an hour of the wetting operation, flakes of
calcium .chloride are spread evenly on the road at a rate dependent
on the relative humidity of air in the roadway.
•The rate varies from 3.8 kg/m2 (for 40% R.H.) down to 0.1 kg/m2
(for 90% R.H.). Three quarters of the salt is distributed at the first
application and the remainder about a week later.
•Calcium chloride, being hygroscopic, absorbs moisture from . the air
and keeps the dust layer moist.
•Subsequent trampling by men further helps in consolidation of the
dust.
•Re-spraying with water may be necessary after three months and
re-treatment with the salt may become necessary after six months
depending upon deposition of fresh dust and spillage of coal.
•The dust layer is leveled and sprayed with water such that the dust
is wetted to a depth of at least 25 mm.
•Addition of a wetting agent (e.g. Teepol or Lissapol) at this stage is
helpful, After about an hour of the wetting operation, flakes of
calcium .chloride are spread evenly on the road at a rate dependent
on the relative humidity of air in the roadway.
•The rate varies from 3.8 kg/m2 (for 40% R.H.) down to 0.1 kg/m2
(for 90% R.H.). Three quarters of the salt is distributed at the first
application and the remainder about a week later.
•Calcium chloride, being hygroscopic, absorbs moisture from . the air
and keeps the dust layer moist.
•Subsequent trampling by men further helps in consolidation of the
dust.
•Re-spraying with water may be necessary after three months and
re-treatment with the salt may become necessary after six months
depending upon deposition of fresh dust and spillage of coal.
43
•In an alternative salt crust process (Linacrej") the dust is bound up
on a hard crust of sodium chloride.
•The method consists of sprinkling common salt on the dust and then
spraying it with water. The salt dissolves and penetrates into the
dust, hut as water gradually evaporates, the salt recrystallizes and
forms a hard crust on the surface.
•Particles of dust are trapped in the growing salt crystals and thus
consolidated. Light spraying of water at intervals becomes
necessary so that the salt can dissolve and re-crystallize entrapping
the freshly deposited dust.
•The salt crust method is suitable only for the relative humidity
ranges of 55 and 75%. Both sodium chloride and calcium chloride
are corrosive substances and rails, ropes, electrical apparatus etc.
should be kept out of contact with the salt.
•The method of roadway dust consolidation by application of salt is
rarely practiced these days due to high cost of the process and the
corrosive nature of the salts.
•In an alternative salt crust process (Linacrej") the dust is bound up
on a hard crust of sodium chloride.
•The method consists of sprinkling common salt on the dust and then
spraying it with water. The salt dissolves and penetrates into the
dust, hut as water gradually evaporates, the salt recrystallizes and
forms a hard crust on the surface.
•Particles of dust are trapped in the growing salt crystals and thus
consolidated. Light spraying of water at intervals becomes
necessary so that the salt can dissolve and re-crystallize entrapping
the freshly deposited dust.
•The salt crust method is suitable only for the relative humidity
ranges of 55 and 75%. Both sodium chloride and calcium chloride
are corrosive substances and rails, ropes, electrical apparatus etc.
should be kept out of contact with the salt.
•The method of roadway dust consolidation by application of salt is
rarely practiced these days due to high cost of the process and the
corrosive nature of the salts.
44
SURFACE HAUL ROADS
•Various chemical products are available for consolidation of dust on
surface mine haul roads. These are generally mixtures of
surfactants (e.g. detergents), humectants (e.g. hygroscopic salts)
and adhesives (e.g. various lignin sulphonates or petroleum resins).
•The efficacy of the chemical dust suppressants for haul road dust
depends upon a number of factors such as application parameters
(concentration of chemical, frequency and procedure of application),
characteristics of vehicles plying on the road, property of the
surface to be treated and climatic factors.
•the efficacy of application of four dust control chemicals -emulsified.
petroleum resin, acrylic cement, generic petroleum resin,
SURFACE HAUL ROADS
•Various chemical products are available for consolidation of dust on
surface mine haul roads. These are generally mixtures of
surfactants (e.g. detergents), humectants (e.g. hygroscopic salts)
and adhesives (e.g. various lignin sulphonates or petroleum resins).
•The efficacy of the chemical dust suppressants for haul road dust
depends upon a number of factors such as application parameters
(concentration of chemical, frequency and procedure of application),
characteristics of vehicles plying on the road, property of the
surface to be treated and climatic factors.
•the efficacy of application of four dust control chemicals -emulsified.
petroleum resin, acrylic cement, generic petroleum resin,
45
•Spraying of salt on unpaved roads in the
iron and steel industry has shown an
efficiency greater than 50 percent
•Filset-1-50 has surfactant as well as
adhesive properties
•Jalshakti ', a starch based absorbent
powder for roadway dust consolidation is
tried
•Spraying of salt on unpaved roads in the
iron and steel industry has shown an
efficiency greater than 50 percent
•Filset-1-50 has surfactant as well as
adhesive properties
•Jalshakti ', a starch based absorbent
powder for roadway dust consolidation is
tried
46
Water infusion
•Water infusion is a dust control technique involving the injection of
water under pressure into the coal seam-ahead of the face
•One or more boreholes of 75 mm diameter are drilled into the seam
in advance of the coal face, the holes sealed either with inflatable
packers or by grouting a pipe into the hole, and then water under
pressure is injected into the borehole.
•Water circulates in the coal through a network of cracks
and fissures, and, under pressure, penetrates a considerable
distance-from the hole radially, wetting the fine dust present in the
cracks and cleavages in the coal.
Water infusion
•Water infusion is a dust control technique involving the injection of
water under pressure into the coal seam-ahead of the face
•One or more boreholes of 75 mm diameter are drilled into the seam
in advance of the coal face, the holes sealed either with inflatable
packers or by grouting a pipe into the hole, and then water under
pressure is injected into the borehole.
•Water circulates in the coal through a network of cracks
and fissures, and, under pressure, penetrates a considerable
distance-from the hole radially, wetting the fine dust present in the
cracks and cleavages in the coal.
47
•Many studies have shown the efficacy of the system as 50 to 75%
reductions in dust levels has not been practiced in India.
•The water quantity infused is generally in the range of 7 to 20 lit and
the pressure employed ranges from 2 to 34 MPa depending on
fracture permeability of the coal seam.
•Water infusion in a coal seam may be done at the development
faces with say 4 holes of 30 m length for a 6 heading panel of 150 m
width. A flooded zone develops ahead of the face that is maintained
by repeating the infusion process every 30 m advance of the faces
For long wall blocks, three alternative methods of water infusion are
practiced in European mines,
•(a) in-seam infusion from the working face
•(b) long-hole in-seam infusion from advance roads, and
•(c) cross-measure remote infusion from outside the seam
•Many studies have shown the efficacy of the system as 50 to 75%
reductions in dust levels has not been practiced in India.
•The water quantity infused is generally in the range of 7 to 20 lit and
the pressure employed ranges from 2 to 34 MPa depending on
fracture permeability of the coal seam.
•Water infusion in a coal seam may be done at the development
faces with say 4 holes of 30 m length for a 6 heading panel of 150 m
width. A flooded zone develops ahead of the face that is maintained
by repeating the infusion process every 30 m advance of the faces
For long wall blocks, three alternative methods of water infusion are
practiced in European mines,
•(a) in-seam infusion from the working face
•(b) long-hole in-seam infusion from advance roads, and
•(c) cross-measure remote infusion from outside the seam
48
FACE INFUSION
•Face infusion, in which horizontal holes are drilled into the face,
consists of two variations.
•Shallow infusion, the holes are drilled to a depth of approximately
the daily advance of the panel.
In the second variation fewer but longer holes are drilled to a depth
equivalent to one week's advance.
•The second variation permits drilling to be carried out on weekends
and is less disruptive of the mining cycles.
•In the second method of infusion from advanced gate roads, holes
are drilled at an angle of 70°relative to the centre-line of the road.
•In retreat long wall faces, long holes parallel to the face can be
easily drilled from the gate roads without causing any interference
with the mining cycle.
FACE INFUSION
•Face infusion, in which horizontal holes are drilled into the face,
consists of two variations.
•Shallow infusion, the holes are drilled to a depth of approximately
the daily advance of the panel.
In the second variation fewer but longer holes are drilled to a depth
equivalent to one week's advance.
•The second variation permits drilling to be carried out on weekends
and is less disruptive of the mining cycles.
•In the second method of infusion from advanced gate roads, holes
are drilled at an angle of 70°relative to the centre-line of the road.
•In retreat long wall faces, long holes parallel to the face can be
easily drilled from the gate roads without causing any interference
with the mining cycle.
49
•The third method of remote infusion, popular in
Germany and known as 'hyper-tele water
infusion' is possible' if a roadway is available in
an upper or lower seam or the roof or floor strata
from where an infusion hole can be drilled into
the coal block.
The infusion is completely independent of face
operations and may be carried out at low
pressure over a long period. Besides the primary
benefit of reduction in dust production,
•water infusion has a secondary benefit of
reduced gas migration to the working face.
•The third method of remote infusion, popular in
Germany and known as 'hyper-tele water
infusion' is possible' if a roadway is available in
an upper or lower seam or the roof or floor strata
from where an infusion hole can be drilled into
the coal block.
The infusion is completely independent of face
operations and may be carried out at low
pressure over a long period. Besides the primary
benefit of reduction in dust production,
•water infusion has a secondary benefit of
reduced gas migration to the working face.
50
VENTILATION
•Measures to suppress dust, is never hundred
percent effective, and whatever respirable dust
gets emitted by any machinery or operation
be so diluted by air current that the dust
concentration falls below the permissible limit.
•For a given quantity of dust production at a face
or a roadway, the higher the airflow, the greater
is the degree of dilution and lower is the dust
concentration.
VENTILATION
•Measures to suppress dust, is never hundred
percent effective, and whatever respirable dust
gets emitted by any machinery or operation
be so diluted by air current that the dust
concentration falls below the permissible limit.
•For a given quantity of dust production at a face
or a roadway, the higher the airflow, the greater
is the degree of dilution and lower is the dust
concentration.
51
,
•There is an optimum velocity iri a long wall from dust
control point of view. The dust pick-up velocity increases
with moisture content and density of the dust.
Optimum air velocity in a long wall coal face goes up
from 2.4 m/s for dust with low moisture content (3 to 4%)
to 4.5 m/s for wetted dust with 5 to 8% moisture content
•What is true of long wall faces is also true for mine
airways. However, ventilation economics may justify a
higher velocity in fan drifts and main airways, specially,
where personnel are likely to be exposed to the airflow
,
•There is an optimum velocity iri a long wall from dust
control point of view. The dust pick-up velocity increases
with moisture content and density of the dust.
Optimum air velocity in a long wall coal face goes up
from 2.4 m/s for dust with low moisture content (3 to 4%)
to 4.5 m/s for wetted dust with 5 to 8% moisture content
•What is true of long wall faces is also true for mine
airways. However, ventilation economics may justify a
higher velocity in fan drifts and main airways, specially,
where personnel are likely to be exposed to the airflow
52
RECOMMENDED MAXIMUM AIR
VELOCITIES
(DGMS CIRCULAR 42/1974)
» Max velocity
•Ventilation shafts not provided 15m/s
with winding equipment, fan drifts
•Ventilation shafts where man winding
is not carried out, or hoisting shafts only 12m/s
•Shafts used for man-winding
or man-hoisting 8m/s
•Shafts and haulage roads
(other than conveyor roads) 6m/s
Other roadways
Conveyor roads, loading points
and transfer points 4m/s
Working, faces in developing or depillaring /
stoping areas including longwall faces. 4m/s
RECOMMENDED MAXIMUM AIR
VELOCITIES
(DGMS CIRCULAR 42/1974)
» Max velocity
•Ventilation shafts not provided 15m/s
with winding equipment, fan drifts
•Ventilation shafts where man winding
is not carried out, or hoisting shafts only 12m/s
•Shafts used for man-winding
or man-hoisting 8m/s
•Shafts and haulage roads
(other than conveyor roads) 6m/s
Other roadways
Conveyor roads, loading points
and transfer points 4m/s
Working, faces in developing or depillaring /
stoping areas including longwall faces. 4m/s
53
•It might be noted that only 4 m/s
maximum air velocity has been
recommended for conveyor roads.
•This is because in most mines an
antitropal system of ventilation is practiced
so that even with 4 m/s air velocity,
a relative velocity between the coal and air
stream would be higher and dust
may be picked up from the conveyor bed.
•It might be noted that only 4 m/s
maximum air velocity has been
recommended for conveyor roads.
•This is because in most mines an
antitropal system of ventilation is practiced
so that even with 4 m/s air velocity,
a relative velocity between the coal and air
stream would be higher and dust
may be picked up from the conveyor bed.
54
DUST EXTRACTION
Where excessive concentrations of dust become airborne, the dusty
air can be exhausted and the dust can be separated from the air by
filtration, inertial separation, wet scrubbing or electrical precipitation
and the cleaned air can be re circulated.
. In some conveyor transfer points, a hood is placed almost wholly
enclosing the installation, and connected to an exhaust system
The main consideration in designing an exhaust hood is to produce
a good capture velocity, which is generally taken as a minimum of 1
m/s for conveyor loading
The volume of air to be exhausted from an enclosed belt conveyor
transfer point is generally taken as 0.5 to 0.8 m3/s per metre width
of belt.
The air velocity in the exhaust duct should be sufficient to prevent
settlement of the dust and at the same time the pressure
requirement should not be too high
Hence a velocity of 15 to 20 m/s is usually maintained in' the duct.
DUST EXTRACTION
Where excessive concentrations of dust become airborne, the dusty
air can be exhausted and the dust can be separated from the air by
filtration, inertial separation, wet scrubbing or electrical precipitation
and the cleaned air can be re circulated.
. In some conveyor transfer points, a hood is placed almost wholly
enclosing the installation, and connected to an exhaust system
The main consideration in designing an exhaust hood is to produce
a good capture velocity, which is generally taken as a minimum of 1
m/s for conveyor loading
The volume of air to be exhausted from an enclosed belt conveyor
transfer point is generally taken as 0.5 to 0.8 m3/s per metre width
of belt.
The air velocity in the exhaust duct should be sufficient to prevent
settlement of the dust and at the same time the pressure
requirement should not be too high
Hence a velocity of 15 to 20 m/s is usually maintained in' the duct.
55
ORE BINS
•The amount of dust generated in an ore bin or
receiving pit depends upon a number of factors
such as the height of fall, quantity of material
falling, size, shape and type of material falling,
cross section of the ore bin etc.
•However, in all cases, certain volume of air is
displaced and airflow is induced. In addition,
when the falling stream of material comes to
rest, it gets compacted and the air entrained in it
is violently expelled carrying with it a lot of dust.
ORE BINS
•The amount of dust generated in an ore bin or
receiving pit depends upon a number of factors
such as the height of fall, quantity of material
falling, size, shape and type of material falling,
cross section of the ore bin etc.
•However, in all cases, certain volume of air is
displaced and airflow is induced. In addition,
when the falling stream of material comes to
rest, it gets compacted and the air entrained in it
is violently expelled carrying with it a lot of dust.
56
•The bin-top should be as much enclosed
as possible and the dusty air should be
drawn into an exhausting system.
•In case of crushers, the crusher-top should
be enclosed and connected to the exhaust
system, and the discharge point of the
crusher should be separately enclosed
and exhausted.
•The bin-top should be as much enclosed
as possible and the dusty air should be
drawn into an exhausting system.
•In case of crushers, the crusher-top should
be enclosed and connected to the exhaust
system, and the discharge point of the
crusher should be separately enclosed
and exhausted.
57
•The dusty air has to be cleaned of dust before
discharge to the surface atmosphere in case of a
surface installation or to the mine airway in case
of an underground mine
The methods commonly used are
•(a) wet scrubbing
•(b) inertial cleaning
•(c) filtration and
•(d) electrical precipitation.
•The dusty air has to be cleaned of dust before
discharge to the surface atmosphere in case of a
surface installation or to the mine airway in case
of an underground mine
The methods commonly used are
•(a) wet scrubbing
•(b) inertial cleaning
•(c) filtration and
•(d) electrical precipitation.
58
Wet scrubbers
•In wet scrubbers, the dust particles are brought
into intimate contact with wetted surfaces within
a highly turbulent air stream and the dust
removed with the water run off
•There are various kinds of wet scrubbers in use,
some having fans, others using a venturi and still
others use a wetted fibrous bed to bring the dust
particles in intimate contact with water droplets.
Wet scrubbers
•In wet scrubbers, the dust particles are brought
into intimate contact with wetted surfaces within
a highly turbulent air stream and the dust
removed with the water run off
•There are various kinds of wet scrubbers in use,
some having fans, others using a venturi and still
others use a wetted fibrous bed to bring the dust
particles in intimate contact with water droplets.
59
•In the simplest type of wet scrubbers a
high pressure water spray is operated
inside a tube .
•If the tube is open ended, the momentum
of the water jet induces airflow and some
of the dust particles in the air stream are
captured
•The outlet air, however, will have fine
water droplets in it
•In the simplest type of wet scrubbers a
high pressure water spray is operated
inside a tube .
•If the tube is open ended, the momentum
of the water jet induces airflow and some
of the dust particles in the air stream are
captured
•The outlet air, however, will have fine
water droplets in it
60
61
62
•In a venturi type wet scrubber water is
sprayed perpendicularly into the throat or
slightly upstream of a venturi where the
high velocity leads to turbulent mixing of
dust and water.
•In a venturi type wet scrubber water is
sprayed perpendicularly into the throat or
slightly upstream of a venturi where the
high velocity leads to turbulent mixing of
dust and water.
63
64
•The wet scrubbers are highly efficient for coarse
size dust and some manufacturers claim up to
96% efficiency of removal even for respirable
size of dust.
•The equipment is compact and can be installed
in a roadway.
•One disadvantage however, is the increased
moisture content of the outlet air, a matter of
importance in hot and deep mines.
•The wet scrubbers are highly efficient for coarse
size dust and some manufacturers claim up to
96% efficiency of removal even for respirable
size of dust.
•The equipment is compact and can be installed
in a roadway.
•One disadvantage however, is the increased
moisture content of the outlet air, a matter of
importance in hot and deep mines.
65
INERTIAL COLLECTOR
•A vertically oriented conical cyclone is the most common
type of inertial collector used in the mines, particularly
on surface of mines
•The dust laden air is imparted a rotating motion by virtue
of its tangential entry into the cyclone. The dust particles
are subject to two opposing forces, the centrifugal force
that tends to throw the particles outward toward the wall
of the cyclone, and the drag of the air stream opposing
the centrifugal force.
•The greater the mass of a dust particle and the, higher
the rotational speed of the air stream the better is the
separation of the dust particle from the air stream.
INERTIAL COLLECTOR
•A vertically oriented conical cyclone is the most common
type of inertial collector used in the mines, particularly
on surface of mines
•The dust laden air is imparted a rotating motion by virtue
of its tangential entry into the cyclone. The dust particles
are subject to two opposing forces, the centrifugal force
that tends to throw the particles outward toward the wall
of the cyclone, and the drag of the air stream opposing
the centrifugal force.
•The greater the mass of a dust particle and the, higher
the rotational speed of the air stream the better is the
separation of the dust particle from the air stream.
66
INERTIAL TYPE
INERTIAL TYPE
67
•Cyclones are found to be very efficient for coarser size airborne particulates
but not so efficient for the respirable fraction of dust
.
•Efficiency of removal of small particles can be improved by injecting water
into the cyclone. Resulting agglomeration increases the mass of the dust
particles improving the separation from the air stream and also reduces the
probability of re-entrainment of the dust,
•The dust particles are collected at the bottom of the conical part of the
cyclone from where these are removed at frequent intervals.
•Capital cost of an inertial collector is low, and there being no moving
parts, the maintenance is also easy.
The main disadvantage is the poor efficiency of separation of small size
dust.
Rotary blast hole drills employed in surface mines are commonly equipped
with cyclone type dry dust extractors.
•Cyclones are found to be very efficient for coarser size airborne particulates
but not so efficient for the respirable fraction of dust
.
•Efficiency of removal of small particles can be improved by injecting water
into the cyclone. Resulting agglomeration increases the mass of the dust
particles improving the separation from the air stream and also reduces the
probability of re-entrainment of the dust,
•The dust particles are collected at the bottom of the conical part of the
cyclone from where these are removed at frequent intervals.
•Capital cost of an inertial collector is low, and there being no moving
parts, the maintenance is also easy.
The main disadvantage is the poor efficiency of separation of small size
dust.
Rotary blast hole drills employed in surface mines are commonly equipped
with cyclone type dry dust extractors.
68
DUST FILTRATION
•The most widely used wet scrubber in mines uses a fan as well as
an extractor panel made of fibrous material for causing intimate
mixing of dust and water.
•To prevent clogging of the fibrous bed, the extractor panel is
continually wetted from the top and hence the type is sometimes
called as 'flooded bed' or irrigated bed dust extractor.
•In a typical model dust laden air is drawn into the fan where it is
mixed with finely atomized water discharged from a water spray
located upstream of the fan.
•The dust is wetted at the fan impeller, along the internal surfaces of
the fan case and then in the wetted extractor panel containing the
fibrous bed. The water and dust mixture falls down to a sump
located below and any remaining water and dust
mixture in the air stream is collected in a panel having catchments
vanes and trickle down to the sump.
•The dust collects as sludge at the bottom of the sump and water
from the top of the sump is re-circulated by a pump.
DUST FILTRATION
•The most widely used wet scrubber in mines uses a fan as well as
an extractor panel made of fibrous material for causing intimate
mixing of dust and water.
•To prevent clogging of the fibrous bed, the extractor panel is
continually wetted from the top and hence the type is sometimes
called as 'flooded bed' or irrigated bed dust extractor.
•In a typical model dust laden air is drawn into the fan where it is
mixed with finely atomized water discharged from a water spray
located upstream of the fan.
•The dust is wetted at the fan impeller, along the internal surfaces of
the fan case and then in the wetted extractor panel containing the
fibrous bed. The water and dust mixture falls down to a sump
located below and any remaining water and dust
mixture in the air stream is collected in a panel having catchments
vanes and trickle down to the sump.
•The dust collects as sludge at the bottom of the sump and water
from the top of the sump is re-circulated by a pump.
69
Dry Filtration through Fabric
Filter
•Cotton or felt bags are used as filters
through which the dusty air is
pushed out so that the dust is collected on
the walls of the bags.
•Usually, a number of bags are connected
in parallel and hung vertically, and the
composite is known as a 'Bag House' .
Dry Filtration through Fabric
Filter
•Cotton or felt bags are used as filters
through which the dusty air is
pushed out so that the dust is collected on
the walls of the bags.
•Usually, a number of bags are connected
in parallel and hung vertically, and the
composite is known as a 'Bag House' .
70
Bag house-type dust collector
•The bags may remain inflated by the air
pressure only or may be placed on an internal
wire frame (similar to that of a reinforced
ventilation duct), in which case the airflow may
also be from outside to inside of the filter bag.
•The usual woven filters have apertures of about
100 microns size but as the 'dust from the air
gets deposited on the filter material, the pore
sizes available for air passage gets reduced and
fine size dust particles down to approximately
0.5 urn also get collected on the filter
Bag house-type dust collector
•The bags may remain inflated by the air
pressure only or may be placed on an internal
wire frame (similar to that of a reinforced
ventilation duct), in which case the airflow may
also be from outside to inside of the filter bag.
•The usual woven filters have apertures of about
100 microns size but as the 'dust from the air
gets deposited on the filter material, the pore
sizes available for air passage gets reduced and
fine size dust particles down to approximately
0.5 urn also get collected on the filter
71
Bag house· type dust collector
Bag house· type dust collector
72
•The felt type filters can also collect fine particles of such .low
size and because of its smaller interstitial pores does not depend
upon the formation of a filter cake to arrest the small size particles.
With the gradual choking of air passages, the resistance to airflow
progressively increases and the airflow through the bag house
progressively reduces.
Hence the filters need to be cleaned of the dust cakes formed on it
periodically.
In case of small installations connected to some intermittent
processes that permit stoppage of the fan at intervals, the filtration
bags maybe cleaned manually or agitated by an electro-mechanical
device but it is more common to have an automatic arrangement of
cleaning the bags
•The felt type filters can also collect fine particles of such .low
size and because of its smaller interstitial pores does not depend
upon the formation of a filter cake to arrest the small size particles.
With the gradual choking of air passages, the resistance to airflow
progressively increases and the airflow through the bag house
progressively reduces.
Hence the filters need to be cleaned of the dust cakes formed on it
periodically.
In case of small installations connected to some intermittent
processes that permit stoppage of the fan at intervals, the filtration
bags maybe cleaned manually or agitated by an electro-mechanical
device but it is more common to have an automatic arrangement of
cleaning the bags
73
.
The automatic method may be based on periodical mechanical
shaking and twisting of the bags, reverse-jet flushing or application
of ultra sound technique.
The initial pressure drop across the filter bags is typically 150 to 200
Pa but goes up to 600 to 750 Pa when the bags are ready for
cleaning.
The dust adhering to a filter surface falls down to a hopper from
where it is removed manually or automatically by water flushing.
Bag house filters have been popular in South African gold mines
and are common in surface installations in mines and factories.
.
The automatic method may be based on periodical mechanical
shaking and twisting of the bags, reverse-jet flushing or application
of ultra sound technique.
The initial pressure drop across the filter bags is typically 150 to 200
Pa but goes up to 600 to 750 Pa when the bags are ready for
cleaning.
The dust adhering to a filter surface falls down to a hopper from
where it is removed manually or automatically by water flushing.
Bag house filters have been popular in South African gold mines
and are common in surface installations in mines and factories.
74
ELECTRO STATIC PRECIPITATORS
•The principle of dust collection by an ESP is the
ionization of the air around a discharge electrode
maintained at a high negative DC voltage (20 to 60 kV)
and subsequent charging of the dust particles passing by
the electrode.
•The charged dust particles travel to the earthed positive
electrode (commonly kept in the form of parallel plates
on both sides of the discharge electrode) and get
precipitated
•The ground electrode has to be cleaned periodically and
the collected dust in a hopper located below is removed
hydraulically or mechanically.
ELECTRO STATIC PRECIPITATORS
•The principle of dust collection by an ESP is the
ionization of the air around a discharge electrode
maintained at a high negative DC voltage (20 to 60 kV)
and subsequent charging of the dust particles passing by
the electrode.
•The charged dust particles travel to the earthed positive
electrode (commonly kept in the form of parallel plates
on both sides of the discharge electrode) and get
precipitated
•The ground electrode has to be cleaned periodically and
the collected dust in a hopper located below is removed
hydraulically or mechanically.
75
•ESPs are commonly applied to clean flue gases
from boilers in a power station, but are rarely
applied in moist underground condition in
mines.
•In coalmines, the risk of fire and explosion of
coal dust precludes their use. In a few
metalliferous mines in South Africa,
•ESPs have been used to
clean mine air of airborne dust particles.
•ESPs are commonly applied to clean flue gases
from boilers in a power station, but are rarely
applied in moist underground condition in
mines.
•In coalmines, the risk of fire and explosion of
coal dust precludes their use. In a few
metalliferous mines in South Africa,
•ESPs have been used to
clean mine air of airborne dust particles.
76
Additional dust control measures in
opencast workings and surface
plants
•Regulation 123(1) of Coal Mines
Regulations1957 the management of all
mines including an opencast mine has to
ensure \ that the respirable dust
concentration at all workplaces is less than
3 mg/m
3
Or as stipulated .
Additional dust control measures in
opencast workings and surface
plants
•Regulation 123(1) of Coal Mines
Regulations1957 the management of all
mines including an opencast mine has to
ensure \ that the respirable dust
concentration at all workplaces is less than
3 mg/m
3
Or as stipulated .
77
•If the dust contains high values of free silica.
The manager of an opencast mine has to ensure
that the ambient air quality in areas nearby the
mine is not affected by the activities going on in
the mine to such an extent that the National
Ambient Air Quality Standards prescribed under
the Environment Protection Rules 1986 are
violated.
•If the dust contains high values of free silica.
The manager of an opencast mine has to ensure
that the ambient air quality in areas nearby the
mine is not affected by the activities going on in
the mine to such an extent that the National
Ambient Air Quality Standards prescribed under
the Environment Protection Rules 1986 are
violated.
78
EP RULES
•The air quality standards prescribed under the EP Rules
for coalmines coming up after December 1998 and for
other non-coal mines are 500 mg/m3 and 250 mg/m3 for
24 hourly samples for suspended particulate matter and
respirable particulate matter respectively,
•These values should not be exceeded at 500 m
downstream from the various dust generating sources.
•For older mines the Central Pollution Control Board has
allowed certain relaxations.
EP RULES
•The air quality standards prescribed under the EP Rules
for coalmines coming up after December 1998 and for
other non-coal mines are 500 mg/m3 and 250 mg/m3 for
24 hourly samples for suspended particulate matter and
respirable particulate matter respectively,
•These values should not be exceeded at 500 m
downstream from the various dust generating sources.
•For older mines the Central Pollution Control Board has
allowed certain relaxations.
79
•Haul roads are the most prolific dust
sources in a mine.
•The common methods of dust control on a
haul road are
•(a) water spraying with mobile sprinklers
•(b) water , spraying with fixed sprinklers
•(c) use of road dust control chemical and
•(d) proper maintenance of haul roads and
cleaning of spilled material.
•Haul roads are the most prolific dust
sources in a mine.
•The common methods of dust control on a
haul road are
•(a) water spraying with mobile sprinklers
•(b) water , spraying with fixed sprinklers
•(c) use of road dust control chemical and
•(d) proper maintenance of haul roads and
cleaning of spilled material.
80
•Water spraying on haul roads with mobile sprinklers with
arrangement for pressurized water spraying from a
manifold fitted with multiple sprays at the back and
capable of spraying the roadsides as well.
•These water sprinklers can double up as fire tenders in
case of emergency.
•The manager should decide on the frequency of water
spraying on a road depending upon the climatic
condition, shift timing, material used in road construction
and traffic density on the road.
•Water spraying on haul roads with mobile sprinklers with
arrangement for pressurized water spraying from a
manifold fitted with multiple sprays at the back and
capable of spraying the roadsides as well.
•These water sprinklers can double up as fire tenders in
case of emergency.
•The manager should decide on the frequency of water
spraying on a road depending upon the climatic
condition, shift timing, material used in road construction
and traffic density on the road.
81
82
Water spraying on haul roads with
fixed sprinklers
•On permanent haul roads with heavy traffic, fixed water
sprays may be fitted on posts on roadsides located at
intervals. Many variations of the fixed water spray
systems have been adopted, some with sprinklers with
moving heads located on the central divider of the road,
others located on one or both sides of the road working
continuously or with the moving nozzles working over
180
0
only.
•In still other variations, the sprays work intermittently in
batches.
Water spraying on haul roads with
fixed sprinklers
•On permanent haul roads with heavy traffic, fixed water
sprays may be fitted on posts on roadsides located at
intervals. Many variations of the fixed water spray
systems have been adopted, some with sprinklers with
moving heads located on the central divider of the road,
others located on one or both sides of the road working
continuously or with the moving nozzles working over
180
0
only.
•In still other variations, the sprays work intermittently in
batches.
83
•For success of a fixed spraying system
attention has to be paid on the pressure
and quality of water and the type of
nozzles used in the system.
•Heavy watering with thick water jets,
instead of mist spray, may damage the
road requiring frequent application of road
grader.
•For success of a fixed spraying system
attention has to be paid on the pressure
and quality of water and the type of
nozzles used in the system.
•Heavy watering with thick water jets,
instead of mist spray, may damage the
road requiring frequent application of road
grader.
84
Maintenance of haul roads and
cleaning of spilled material
Bad road condition leads to spillage, increased
dust production, increased maintenance and
slower speed of vehicles Overloading and poor
body condition of trucks also leads to increased
spillage.
All spilled material, unless removed promptly,
ultimately becomes dust
Maintenance of haul roads and
cleaning of spilled material
Bad road condition leads to spillage, increased
dust production, increased maintenance and
slower speed of vehicles Overloading and poor
body condition of trucks also leads to increased
spillage.
All spilled material, unless removed promptly,
ultimately becomes dust
85
•Spillage material on blacktopped
roads can be cleaned. manually or by truck
mounted vacuum cleaners.
•For unpaved roads, frequent application of road
grader, use of 'morrum', provision
of drains on sides and periodical removal of
heaped materials from the sides are also
measures leading to improvement of road
condition and
•reduction in dust generation from the road
surface.
•Spillage material on blacktopped
roads can be cleaned. manually or by truck
mounted vacuum cleaners.
•For unpaved roads, frequent application of road
grader, use of 'morrum', provision
of drains on sides and periodical removal of
heaped materials from the sides are also
measures leading to improvement of road
condition and
•reduction in dust generation from the road
surface.
86
In mechanized opencast mines, rotary blast hole
drills are commonly used these days. In such
drills, compressed air is sent down through a
hole in the drilling rod, released at the bit and
the drill cuttings are brought up by the return air
current coming up through the annular space
between the rod and the hole.
In mechanized opencast mines, rotary blast hole
drills are commonly used these days. In such
drills, compressed air is sent down through a
hole in the drilling rod, released at the bit and
the drill cuttings are brought up by the return air
current coming up through the annular space
between the rod and the hole.
87
DUST EXTRACTOR
Normally the drill collar zone is enclosed by flaps
suspended from the underside of the drill body
and an exhaust fan sucks the dusty air from this
enclosure including the air coming out of the
hole and routes it through a cyclone for
separation of the dust and subsequent release
into the atmosphere.
DUST EXTRACTOR
Normally the drill collar zone is enclosed by flaps
suspended from the underside of the drill body
and an exhaust fan sucks the dusty air from this
enclosure including the air coming out of the
hole and routes it through a cyclone for
separation of the dust and subsequent release
into the atmosphere.
88
Typical dry dust collection
system used on surface drills
Typical dry dust collection
system used on surface drills
89
Cyclones are efficient for separating the coarse
fraction of the dust but some fine dust inevitably
escapes into the atmosphere.
If bag filters are introduced in the system after
the cyclone fine dust is arrested but the cost of
the dust suppression system greatly increases
and
hence such drills are rarely used.
.
Cyclones are efficient for separating the coarse
fraction of the dust but some fine dust inevitably
escapes into the atmosphere.
If bag filters are introduced in the system after
the cyclone fine dust is arrested but the cost of
the dust suppression system greatly increases
and
hence such drills are rarely used.
.
90
•In an alternative system adopted in many
Indian opencast mines, the drilling dust is
suppressed at the source by injecting
water spray into the air stream going down
the drill rod which gets released at the bit
and in turn wets the fine dust and forms
small pellets which are brought up by the
ascending air current, which then gets
deposited near the drill collar instead of
getting airborne
•In an alternative system adopted in many
Indian opencast mines, the drilling dust is
suppressed at the source by injecting
water spray into the air stream going down
the drill rod which gets released at the bit
and in turn wets the fine dust and forms
small pellets which are brought up by the
ascending air current, which then gets
deposited near the drill collar instead of
getting airborne
91
92
Dust control through tree
plantation
•Trees act as windbreaks and the leaves work as dust filter
•Much of the dust produced in permanent roads in surface mines can
be trapped by having trees with dense foliage planted on both sides
of the road.
•Major dust producing areas such as coal handling plants, mineral-
processing plants, sidings and mineral stockyards should be
surrounded by a wide expanse of green belt created for the purpose.
•Normally mining colonies and nearby villages are protected from
dust by creation of 20 to 30 m wide green belts at the initial stage of
the mine.
•Early biological reclamation Of overburden dumps, grassing of soil
dumps and limiting the area bared of vegetation to the minimum
extent possible are measures helpful in erosion control and
reduction in generation of wind borne dust from the dumps and
bared areas.
Dust control through tree
plantation
•Trees act as windbreaks and the leaves work as dust filter
•Much of the dust produced in permanent roads in surface mines can
be trapped by having trees with dense foliage planted on both sides
of the road.
•Major dust producing areas such as coal handling plants, mineral-
processing plants, sidings and mineral stockyards should be
surrounded by a wide expanse of green belt created for the purpose.
•Normally mining colonies and nearby villages are protected from
dust by creation of 20 to 30 m wide green belts at the initial stage of
the mine.
•Early biological reclamation Of overburden dumps, grassing of soil
dumps and limiting the area bared of vegetation to the minimum
extent possible are measures helpful in erosion control and
reduction in generation of wind borne dust from the dumps and
bared areas.
93
94
95
Personal protection devices
•Dust respirator
Even with good engineering control, the workers
engaged in certain mining operations such as
dozing, drilling chute loading etc., are often
exposed to high levels of dust concentration.
When other methods of dust control fail the
Mines Regulations prescribe the use of suitable
dust respirator as a secondary means of
protection of worker's health.
Personal protection devices
•Dust respirator
Even with good engineering control, the workers
engaged in certain mining operations such as
dozing, drilling chute loading etc., are often
exposed to high levels of dust concentration.
When other methods of dust control fail the
Mines Regulations prescribe the use of suitable
dust respirator as a secondary means of
protection of worker's health.
96
A wide variety of dust respirators are available in the
market.
They are usually made of filter grade fabrics shaped like
a cup to cover the nose and mouth of the wearer
With long use and dust loading on the filter material, the
resistance to breathing increases.
Models suitable for long duration use are fitted with an
exhalation valve In still other heavier models,
replaceable filter cartridges are fitted in the mask.
•
A wide variety of dust respirators are available in the
market.
They are usually made of filter grade fabrics shaped like
a cup to cover the nose and mouth of the wearer
With long use and dust loading on the filter material, the
resistance to breathing increases.
Models suitable for long duration use are fitted with an
exhalation valve In still other heavier models,
replaceable filter cartridges are fitted in the mask.
•
97
Dust respirators are relatively inexpensive,
Highly effective when used properly and easy to maintain by the wearer
But besides causing increased resistance to breathing, the respirators
cause interference with voice communication
Often cause facial irritation, does not permit spitting and needs care in use
so that leakage does not take place due to poor fitting of the cup on the
face.
The throwaway type respirators weigh only 17 to 20 g and those with
replaceable filter cartridge may weigh in the range of 165 to 235 g.
All dust respirators for use in mines must satisfy the
requirement of BIS specification No. 9473 of 1980, which requires a
minimum of 98% filtration efficiency for dust sizes down to 0.6 micron.
Dust respirators are relatively inexpensive,
Highly effective when used properly and easy to maintain by the wearer
But besides causing increased resistance to breathing, the respirators
cause interference with voice communication
Often cause facial irritation, does not permit spitting and needs care in use
so that leakage does not take place due to poor fitting of the cup on the
face.
The throwaway type respirators weigh only 17 to 20 g and those with
replaceable filter cartridge may weigh in the range of 165 to 235 g.
All dust respirators for use in mines must satisfy the
requirement of BIS specification No. 9473 of 1980, which requires a
minimum of 98% filtration efficiency for dust sizes down to 0.6 micron.
98
99
DUST HELMET
•Dust helmets provide protection against dust
without some of the voice communication,
spitting and fit problems associated with the
typical dust respirators.
•In a dust helmet, a small fan is placed in the rear
side of the helmet with a pre-filter on the inlet
side and the main filter on the outlet side of the
fan . The fan is powered by a rechargeable belt
mounted battery suitable for full shift operation.
•Filtered air flows downward between a
transparent plastic visor and the face of the
wearer.
DUST HELMET
•Dust helmets provide protection against dust
without some of the voice communication,
spitting and fit problems associated with the
typical dust respirators.
•In a dust helmet, a small fan is placed in the rear
side of the helmet with a pre-filter on the inlet
side and the main filter on the outlet side of the
fan . The fan is powered by a rechargeable belt
mounted battery suitable for full shift operation.
•Filtered air flows downward between a
transparent plastic visor and the face of the
wearer.
100
101
Environmentally Friendly Dust
Control Solution Introduced to
Harsh Gobi Desert
•The Gobi desert is a rain shadow desert formed by the Himalaya
mountains, which blocks rain carrying clouds from entering the
desert and causes massive amounts of dust to be generated in the
Gobi on an annual basis.
•A solution was desperately needed for dust control and soil
stabilization on a coal mine haul road that stretches over 100km-
long, which hauls coal from Southern Mongolia into Northern China.
•In May of 2009, tests were carried out using two of Cypher
Environmental's 100% environmentally friendly soil stabilization and
dust control products, Earth Zyme and Dust Stop, both of which had
overwhelming success.
•
Environmentally Friendly Dust
Control Solution Introduced to
Harsh Gobi Desert
•The Gobi desert is a rain shadow desert formed by the Himalaya
mountains, which blocks rain carrying clouds from entering the
desert and causes massive amounts of dust to be generated in the
Gobi on an annual basis.
•A solution was desperately needed for dust control and soil
stabilization on a coal mine haul road that stretches over 100km-
long, which hauls coal from Southern Mongolia into Northern China.
•In May of 2009, tests were carried out using two of Cypher
Environmental's 100% environmentally friendly soil stabilization and
dust control products, Earth Zyme and Dust Stop, both of which had
overwhelming success.
•
102
•On average, 300 trucks weighing 100t each
travel back and forth from Mongolia to China on
a daily basis using the haul road, which is why
dust control and soil stabilization were of such a
major concern. A demonstration was carried out
on 500m of the mine haul road using Earth
Zyme to help stabilize the soil and reduce the
dust.
•On average, 300 trucks weighing 100t each
travel back and forth from Mongolia to China on
a daily basis using the haul road, which is why
dust control and soil stabilization were of such a
major concern. A demonstration was carried out
on 500m of the mine haul road using Earth
Zyme to help stabilize the soil and reduce the
dust.
103
•EarthZyme significantly increases the strength of a
treated soil, and reduces the maintenance requirements
and costs, as well as providing some dust control
benefits. The results of the demonstration were so good
that the mine followed up the demonstration by
completing another 10km of EarthZyme roads last year
and has several more kilometers slated to be built this
year using EarthZyme.
•Due to the poor soil conditions in the Gobi, it has proven
to be extremely difficult to build a satisfactory road,
which is why EarthZyme has been meticulously chosen
as the preferred aid in environmental soil stabilization
methods in the region due to the great results it provides.
•EarthZyme significantly increases the strength of a
treated soil, and reduces the maintenance requirements
and costs, as well as providing some dust control
benefits. The results of the demonstration were so good
that the mine followed up the demonstration by
completing another 10km of EarthZyme roads last year
and has several more kilometers slated to be built this
year using EarthZyme.
•Due to the poor soil conditions in the Gobi, it has proven
to be extremely difficult to build a satisfactory road,
which is why EarthZyme has been meticulously chosen
as the preferred aid in environmental soil stabilization
methods in the region due to the great results it provides.
104
•A demonstration with Dust Stop was also carried out at
the mine camp for dust control around all the housing
units where the mine staff live while working at the mine
site.
•Due to the high winds prevalent in the Gobi, large
amounts of dust are constantly blowing around the mine
camp, which is a risk to the health and safety of the
workers.
•Dust Stop was used as a dust suppressant solution to
control this dust and keep it from circulating in
dangerous levels around the camp.
•Both products proved highly valuable for dust control and
soil stabilization results, and were more than capable of
handling the harsh Gobi conditions.
•A demonstration with Dust Stop was also carried out at
the mine camp for dust control around all the housing
units where the mine staff live while working at the mine
site.
•Due to the high winds prevalent in the Gobi, large
amounts of dust are constantly blowing around the mine
camp, which is a risk to the health and safety of the
workers.
•Dust Stop was used as a dust suppressant solution to
control this dust and keep it from circulating in
dangerous levels around the camp.
•Both products proved highly valuable for dust control and
soil stabilization results, and were more than capable of
handling the harsh Gobi conditions.
105
106
107
108
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