Measures to control pollution in Mineral processing plant

1. Air Pollution control in
mineral processing plant

2. Sources of pollution
• Essentially all mining and mineral processing operations are potential
sources of particulate emissions . Emission may be categorized as fugitive
emissions and fugitive dust. Fugitive emissions include those sources for
which emissions are amenable to capture and subsequent control. Fugitive
dusts are not amenable to control using conventional system and and
generally involve the reentertainment of settled dust by wind or machine
movement.

3. Emission sources at non metallic mineral
facilities
Fugitive emissions Fugitive dust sources
Drilling Blasting
Crushing Hauling
Screening Haul road
Grinding Stock Piles
ConveyorTransfer point PlantYard
Loading Conveying

4. Particle size data for mineral processing plant

5. Pollution control
• For conveyers:Fugitive dust emissions are generated by the wind blowing
across the material being transferred from one process operation to another
on unclosed conveyor systems.~The two methods available for the control
of fugitive dust emissions from conveyor systems are coverings or wet dust
suppression.Coverings can consist of enclosing the entire conveyor system
with sheet metal or the use of plastic or canvas sheets which block the
action of the wind across the conveyor system.The use of wet dust
suppression would require the installation of spray bars at various intervals
along the conveyor systems.

6. • At Stockpiles:Fugitive dust emissions, as judged by visible emissions, may
result during the formation of new aggregate piles and the erosion of
previously formed piles. During the formation of stockpiles by stacking
conveyors, particulate emissions are generated by wind blowing across the
streams of falling stone and segregating fine particles from coarse particles.
Control methods include wet dust suppression and devices designed to
minimize the free-fall distance to which the material is subjected, thus
lessening its exposure to wind and reducing emissions generated upon
impact.

7. CONTROL OF FUGITIVE PROCESS SOURCES
• Methods utilized to reduce fugitive process emissions include wet dust
suppression, dry collection systems, and a combination of the two.

8. Wet dust supression
• In a wet dust suppression system, dust emissions are controlled by applying
moisture in the form of water or water plus a surfactant sprayed at critical
dust producing points in the process flow.This causes dust particles to
adhere to larger mineral pieces or to form agglomerates too heavy to
become or remain airborne.The objective of wet dust suppression is not to
fog an emission source with a fine mist to capture and remove particulates
emissions, but rather to keep the material moist at all process stages

9. Wet dust supression

10. Dry collection system
• Particulate emissions generated at plant process operations (crushers, screens,
grinders, conveyor transfer points, product loading operations, and bagging
operations) may be controlled by capturing and exhausting potential emissions to
a control device. Depending on the physical layout of the plant, emission sources
may be either manifolded to a single centrally located control device or ducted to a
number of individual control devices. Control systems consist of an exhaust system
utilizing hoods and enclosures to capture and confine emissions, ducting and fans
to convey the captured emissions to a control device, and the control device for
particulate removal prior to exhausting the air stream to the atmosphere.

11. Fig.A.Dust suppression application at crusher discharge

12. Fig.B. Hood configuration used to control a cone crusher

13. Fig.C.Hood configuration for vibrating screen.
Fig.D.Hood configuration for conveyor transfer
less than 0.91 meter (3 feet) fall.

14. Product Loading and Bagging
• Particulate emissions from truck and railcar loading of coarse material can
be minimized by reducing the open height that the material must fall from
the silo or bin to the shipping vehicle. Shrouds, telescoping feed tubes, and
windbreaks can further reduce the fugitive process emissions from this
intermittent source. Particulate emissions from loading of fine material into
either trucks or railcar can be controlled by an exhaust system vented to a
baghouse.

15. Fig.E.Typical baghouse operation Fig.F. Baghouse cleaning methods

16. Combination System
• Wet dust suppression and dry collection systems are often used in combination to
control particulate emissions from crushing plant facilities. As illustrated in Figure,
wet dust suppression techniques are generally used to prevent emissions at the
primary crushing stage and at subsequent screens, transfer points, and crusher
inlets. Dry collection systems are generally used to control emissions at the
discharge of the secondary and tertiary crushers where new dry surfaces and fine
particulates are formed. In addition to controlling ~missions, dry collection systems
result in the removal of a large portion of the fine particulates generated with the
resultant effect of making subsequent dust suppression applications more effective
with a minimum of added moisture.

17. Fig. F.Typical combination dust control system.