5
charges would have been decreased in the presence of the
ions in these fluids. Water quality obviously plays a role
in surfactant effectiveness, showing the importance of any
surfactant testing with site water.
TECHNOLOGIES FOR SURFACTANT
APPLICATION
Water spray systems designed for dust control use two
modes of dust suppression: 1) water sprays wet the mate-
rial to prevent dust particles from becoming airborne dur-
ing the mining or mineral beneficiation process or 2) water
sprays are used to knockdown dust particles after they have
become airborne. (31). These systems use water as the
medium for dust control and may include the use of surfac-
tants added to enhance dust control efficiency.
Surfactants are added to water at a low dosage and are
then applied to the bulk material surface to prevent air-
borne dust generation or to the area above the bulk material
to knockdown airborne particles by particle agglomeration
to return the dust particles back to the material bed. The
application devices are typically sprays, though the appli-
cation of foam or fog has been successful as well (32). As
mentioned previously, the addition of surfactants to water
can reduce the water requirement by ~50%, while the use
of a foam system with surfactants can reduce water con-
sumption to less than 1/20th of that of water alone (32).
Dry fog systems use considerably less water.
Spray velocity, nozzle orifice size, and spray location are
all considered when setting up a spray system. For dust par-
ticle knockdown, droplet-particle collision efficiency is key,
so reducing droplet size, increasing droplet frequency and
velocity, and decreasing droplet surface tension are all key
parameters for system set up (32, 33). Water sprays are used
in many locations to mitigate the production of respirable
and fugitive dust. For example, Caterpillar has developed a
new spray water truck that uses a unique water spray design
with a water delivery system specially designed to deliver
appropriate water flow onto the haul road based upon truck
speed (34).
Foam applications are directly applied to material
or sources in order to prevent the generation of airborne
dust particles because foam is generally not effective once
dust particles are airborne (35), create even finer droplets
to maximize the probability of droplet-particle collisions/
attachment (32, 33).
Fog applications can be used without surfactants but
use droplet atomization to produce droplets of sizes that
can match the ultrafine respirable dust size of even 5
microns to improve collision efficiency. These units often
use special ultrasonic nozzles (32). A benefit of the fogging
system is the creation of a widely dispersed mist. However,
one drawback is that the fine mist can be dispersed by air or
wind movement (36).
GUIDANCE FOR DEVELOPING A SILICA
DUST SUPPRESSION PLAN INCLUDING
APPLICATION OF SURFACTANTS
Combining guidance for the use of surfactants from sev-
eral resources (37, 38, 39, 40), the following steps should
be considered when developing a respirable silica dust sup-
pression plan or any dust suppression plan for that matter.
1. Determine the location(s) and timing for dust sup-
pression applications through a site survey—dur-
ing mining, processing, and stockpiling, on paved/
unpaved roadways, at transfer points, during trans-
portation, etc.
2. Anticipate potential changes in equipment and the
need to relocate any dust suppression system.
3. Address any material handling system issues repair
any dust handling enclosures like curtains and
skirting.
4. Evaluate mechanical dust collectors as part of the
overall dust control strategy, reviewing costs.
5. Address continued housekeeping and equipment
maintenance, including work force load.
6. Work with multiple surfactant suppliers to test
your material with your water. Note that dust
samples should always be collected and sealed to
prevent any changes in surface properties prior to
testing.
7. Test multiple additives in the lab before any field
testing
8. Conduct field tests to ensure the surfactant works
under operating conditions. Consider the location
of sprays or fog and, perhaps test different applica-
tion points—directly on the dust source or bulk
material or in the air above the source, for example.
9. Select a supplier, evaluating whether they will also
provide the dust suppressant application equip-
ment in addition to the surfactant and if they will
service the equipment. Evaluate the costs.
10. Install and commission the dust suppression sys-
tem using reputable companies or site personnel
if available.
11. Inspect and maintain the dust suppression system.
The most important part of this guidance is the need for
housekeeping and maintenance.
charges would have been decreased in the presence of the
ions in these fluids. Water quality obviously plays a role
in surfactant effectiveness, showing the importance of any
surfactant testing with site water.
TECHNOLOGIES FOR SURFACTANT
APPLICATION
Water spray systems designed for dust control use two
modes of dust suppression: 1) water sprays wet the mate-
rial to prevent dust particles from becoming airborne dur-
ing the mining or mineral beneficiation process or 2) water
sprays are used to knockdown dust particles after they have
become airborne. (31). These systems use water as the
medium for dust control and may include the use of surfac-
tants added to enhance dust control efficiency.
Surfactants are added to water at a low dosage and are
then applied to the bulk material surface to prevent air-
borne dust generation or to the area above the bulk material
to knockdown airborne particles by particle agglomeration
to return the dust particles back to the material bed. The
application devices are typically sprays, though the appli-
cation of foam or fog has been successful as well (32). As
mentioned previously, the addition of surfactants to water
can reduce the water requirement by ~50%, while the use
of a foam system with surfactants can reduce water con-
sumption to less than 1/20th of that of water alone (32).
Dry fog systems use considerably less water.
Spray velocity, nozzle orifice size, and spray location are
all considered when setting up a spray system. For dust par-
ticle knockdown, droplet-particle collision efficiency is key,
so reducing droplet size, increasing droplet frequency and
velocity, and decreasing droplet surface tension are all key
parameters for system set up (32, 33). Water sprays are used
in many locations to mitigate the production of respirable
and fugitive dust. For example, Caterpillar has developed a
new spray water truck that uses a unique water spray design
with a water delivery system specially designed to deliver
appropriate water flow onto the haul road based upon truck
speed (34).
Foam applications are directly applied to material
or sources in order to prevent the generation of airborne
dust particles because foam is generally not effective once
dust particles are airborne (35), create even finer droplets
to maximize the probability of droplet-particle collisions/
attachment (32, 33).
Fog applications can be used without surfactants but
use droplet atomization to produce droplets of sizes that
can match the ultrafine respirable dust size of even 5
microns to improve collision efficiency. These units often
use special ultrasonic nozzles (32). A benefit of the fogging
system is the creation of a widely dispersed mist. However,
one drawback is that the fine mist can be dispersed by air or
wind movement (36).
GUIDANCE FOR DEVELOPING A SILICA
DUST SUPPRESSION PLAN INCLUDING
APPLICATION OF SURFACTANTS
Combining guidance for the use of surfactants from sev-
eral resources (37, 38, 39, 40), the following steps should
be considered when developing a respirable silica dust sup-
pression plan or any dust suppression plan for that matter.
1. Determine the location(s) and timing for dust sup-
pression applications through a site survey—dur-
ing mining, processing, and stockpiling, on paved/
unpaved roadways, at transfer points, during trans-
portation, etc.
2. Anticipate potential changes in equipment and the
need to relocate any dust suppression system.
3. Address any material handling system issues repair
any dust handling enclosures like curtains and
skirting.
4. Evaluate mechanical dust collectors as part of the
overall dust control strategy, reviewing costs.
5. Address continued housekeeping and equipment
maintenance, including work force load.
6. Work with multiple surfactant suppliers to test
your material with your water. Note that dust
samples should always be collected and sealed to
prevent any changes in surface properties prior to
testing.
7. Test multiple additives in the lab before any field
testing
8. Conduct field tests to ensure the surfactant works
under operating conditions. Consider the location
of sprays or fog and, perhaps test different applica-
tion points—directly on the dust source or bulk
material or in the air above the source, for example.
9. Select a supplier, evaluating whether they will also
provide the dust suppressant application equip-
ment in addition to the surfactant and if they will
service the equipment. Evaluate the costs.
10. Install and commission the dust suppression sys-
tem using reputable companies or site personnel
if available.
11. Inspect and maintain the dust suppression system.
The most important part of this guidance is the need for
housekeeping and maintenance.