Dust Control Handbook for Industrial Minerals Mining and Processing

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Electrostatic precipitators normally have a higher initial cost than local exhaust ventilationsystems, but a number of advantages that make them worth considering. Once installed, ESPsrequire very little maintenance because there are no moving parts. The installation time and theoperating costs are also lower than for a local exhaust ventilation system. One last advantage isthat the product is easily recovered and recycled right back into the process.There are four basic types of ESPs: plate and wire (dry), flat plate (dry), wet, and two-stage.ESPs provide a large air volume, operate favorably in various temperatures, and require littlemaintenance. Their limitations include their physical size, operation expenses, and inconsistentcollection efficiencies. A more thorough discussion of electrostatic precipitators, includingdistinctions between single-stage and two-stage types, is available in the ACGIH handbook,Industrial Ventilation: A Manual of Recommended Practice for Design [ACGIH 2010].COLLECTOR DISCHARGE DEVICESThe dust collected in a baghouse falls into a hopper below the bags. This hopper must have adischarge device that not only releases the accumulated dust, but ensures a seal between thebaghouse and outside air to maintain negative pressure within the unit. Common hopper wastedischarge devices available for baghouses are the rotary airlock valve, double dump valve (flapvalve), tilt valve, and vacuum valve (dribble valve). Each of these is readily available in variousdesigns from several manufacturers.Rotary Airlock ValvesRotary airlock valves are normally used in applications where both an active airlock and materialmetering are required. Although they are used in many baghouse installations, such common usemay not be the best application for this valve. The initial cost is high, and maintenance costsmay also be high in abrasive applications.Double Dump ValvesDouble dump valves are dual flapper valves mounted in tandem off the discharge of thebaghouse and can be either automated or weight-based. For automated double dump valves, anautomated rotating cam briefly opens the normally closed spring-loaded door to each valve. Thedual valves are opened individually in a sequence that allows the top door to open, dump, andclose before the lower door follows the same sequence. This allows a negative pressure to bemaintained in the discharge hopper. The weight-based valve is very similar except that the valveopens based upon the weight of the product and not on an automated basis (Figure 1.24). Bothtypes of double dump valves require sufficient vertical room below the baghouse hopper. Somewear can be expected at the actuator cam lever of each door.Fundamentals of Dust Collection Systems 43
Figure 1.24. Double dump weight-based valves.Tilt ValvesTilt valves are similar to double dump valves and are normally used in pairs. These valvescommonly have a near horizontal and counterweighted flap door that is adjustable for closedtension. The function of the valve is to allow material to build up on the near horizontal flap gateuntil it overcomes the pull of the negative pressure in the baghouse. The material then dumps tothe next valve as the gate shuts behind it. Typically a divider chute 24–30 inches long is usedbetween the two valves to allow one valve to close completely before the other opens.Tilt valves are less expensive than double dump and rotary valves, but can be hard to adjust.They have been known to stick open after being in service for a period of time, and they require4'0" clearance below the baghouse for installation.Vacuum or Dribble ValvesA vacuum valve basically consists of a soft gum rubber tube mounted in a steel housing, whichattaches to the bottom of a baghouse hopper discharge. Manufacturers have various designsavailable for purchase, some using a "fishtail" dribble bladder mounted inside a flanged pipe.The valve works using the negative pressure of the hopper to collapse the rubber tube and sealthe discharge until sufficient material builds up and "dribbles" through. This valve normally haslow initial cost, high reliability, and low maintenance, and can fit in a short discharge space.FILTER FABRICSThe majority of development work that has been done in the industry over the last ten years hasnot been in the area of the collector itself but in filter fabrics. Some of these fabrics have beendesigned to handle the more challenging applications. Problems that particular fabrics address44 Fundamentals of Dust Collection Systems
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Report of Investigations 9689Dust C
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FUNDAMENTALS OF DUSTCOLLECTION SYST
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Minimizing Field Fits and Welds ...
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Recommendations for Proper Wet Dril
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CONTROL TECHNOLOGIES FOR FILLING 50
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Effective Filtration ..............
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ILLUSTRATIONSFigure 1.1. Relationsh
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Figure 3.2. The air and water flow
Page 22: Figure 9.5. Problem created by heat
Page 25 and 26: UNIT OF MEASURE ABBREVIATIONSUSED I
Page 28: Robert J. Franta, Quotation Enginee
Page 32 and 33: silica. Quartz is the most common s
Page 34 and 35: DUST CONTROL HANDBOOK FOR INDUSTRIA
Page 36 and 37: CHAPTER 1: FUNDAMENTALS OFDUST COLL
Page 38 and 39: The shape of particles affects how
Page 40 and 41: EXHAUST SYSTEMS DESIGNAll exhaust s
Page 42 and 43: stripping, which allows workers to
Page 44 and 45: When using the air quantities in Ta
Page 46 and 47: X = distance in feet from the face
Page 48 and 49: Checklist for Hood EffectivenessThe
Page 50 and 51: A major disadvantage of the high-ve
Page 52 and 53: A common misconception when designi
Page 54 and 55: Avoiding Mitered Elbows Greater Tha
Page 56 and 57: Figure 1.13. Depiction of the horiz
Page 58 and 59: Figure 1.14. Typical design of grav
Page 60 and 61: Baghouse CollectorsBaghouse dust co
Page 62 and 63: Table 1.2. Emission factors for cru
Page 64 and 65: Figure 1.17. Typical design of a me
Page 66 and 67: Reverse Jet (Pulse Jet) CollectorsR
Page 68 and 69: Figure 1.20. Cartridge collector wi
Page 70 and 71: Wet scrubbers are particularly adva
Page 74 and 75: may be related to specific applicat
Page 76 and 77: times. When considering the depth o
Page 78 and 79: Figure 1.25. Demonstration of how a
Page 80 and 81: Figure 1.26. A typical fan performa
Page 82 and 83: Fan TypesThere are two basic types
Page 84 and 85: Figure 1.30. Typical centrifugal fa
Page 86 and 87: Figure 1.32. Typical roof ventilato
Page 89 and 90: DUST CONTROL HANDBOOK FOR INDUSTRIA
Page 91 and 92: The vast majority of dust particles
Page 93 and 94: Table 2.1. Particle/droplet size in
Page 95 and 96: Air Atomizing NozzlesAir atomizing
Page 97 and 98: Hydraulic Flat Fan NozzlesFigure 2.
Page 99 and 100: for dust knockdown or suppression,
Page 101 and 102: Nozzle MaintenanceFigure 2.14. Typi
Page 103 and 104: Accidental DamageInadvertent harm t
Page 105 and 106: NDT Educational Resource Center, Io
Page 107 and 108: 78 Wet Spray SystemsDUST CONTROL HA
Page 109 and 110: contains a piston which delivers ha
Page 111 and 112: produce an increase in the penetrat
Page 113 and 114: Dry DrillingDry drilling is accompl
Page 115 and 116: Circular ShroudIn contrast to the u
Page 117 and 118: The collector airflow has a more su
Page 119 and 120: Air-Blocking ShelfThe air-blocking
Page 121 and 122: dust emissions from mast lowering,
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This simple procedure of creating a
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Figure 3.15. Air ring seal used to
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Figure 3.17. Illustrations showing
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unsubstantiated due to the inconsis
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safety considerations may preclude
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Figure 3.22. A filtration unit, loc
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Miller S, Emerick JC, Vogely WA [19
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USBM [1995]. The reduction of airbo
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110 Drilling and BlastingDUST CONTR
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Wet Control MethodsPREVENTION AND S
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Figure 4.2. Examples of compressive
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Figure 4.5. Illustration of a dry (
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Figure 4.6. Illustration of a dry (
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Wet dust control methods for crushi
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Work Practices to Minimize Dust Exp
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Some specialty grinding operations
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should be frequently inspected for
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Open screen decks slowly to allow i
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DUST CONTROL HANDBOOK FOR INDUSTRIA
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CHAPTER 5: CONVEYING AND TRANSPORTT
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Figure 5.3. Basic depiction of mate
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that the material falls before land
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Figure 5.10. Skirtboard used within
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CarrybackMaterial that sticks or cl
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CONVEYOR DESIGN AND MAINTENANCE ISS
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Figure 5.15. Conveyor transfer encl
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High-volume, high-pressure sprays s
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Figure 5.19. Depiction of a bucket
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Figure 5.21. Depiction of two types
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Figure 5.25. Venturi eductor utiliz
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CHAPTER 6: BAGGINGThis chapter disc
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caused during manufacturing, includ
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Overall PerforationsThe use of over
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Figure 6.5. Open-top bag being load
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Bagging operators should be aware t
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Figure 6.8. Exhaust hood to capture
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In the original design, a single no
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The OASIS is a relatively simple de
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Figure 6.13. Bag storage shelves sh
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Figure 6.14. Bag and belt cleaner d
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other industrial application using
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The robotic arm automatic palletize
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For many years, this plastic wrappi
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warehouse location until a later ti
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used successfully to perform this c
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CHAPTER 7: BULK LOADINGDuring the b
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Figure 7.2. Loading spout discharge
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Cascading Loading SpoutFigure 7.5 i
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a seal at the entry and exit points
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REFERENCESBiere G, Swinderman RT, M
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200 Bulk LoadingDUST CONTROL HANDBO
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many years, as well as some new and
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Figure 8.2. Air spray manifold desi
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Figure 8.3. Test subject wearing po
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Spills of product material are a co
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epetitive dust leaks should not sim
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Effective Upward Airflow PatternThe
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Figure 8.8. Open-structure design c
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manually removing the bags and plac
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Figure 8.12. Increase in worker’s
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In other cases, an operation may wa
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Cecala AB, O'Brien AD, Pollock DE,
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224 Controls for Secondary SourcesD
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where C o = outside respirable dust
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minimal improvement in the cab's ai
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RECOMMENDATIONS FOR FILTRATION/PRES
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Effective FiltrationFigure 9.4. Res
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average decay times were between 16
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Figure 9.6. Filtration unit showing
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This table highlights a number of c
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NIOSH [2001b]. Technology news 486:
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upon the wind velocity (or disturba
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Maximum size is the largest particl
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Figure 10.4. Use of end-dumping wit
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conditions. Performance of each of
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A water truck, used to apply water
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Surfactants work by reducing the su
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which differed for the various site
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Figure 10.9. Self-tarping dump truc
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percent [Fryrear and Skidmore 1985]
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Figure 10.12. The armoring process
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A current method of stockpile forma
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Figure 10.15. Demonstration of how
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Chekan GJ, Cecala AB, Colinet JF [2
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Midwest Research Institute [1981].
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GLOSSARYAbrader. An implement used
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Carryback. Material that sticks or
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End-dumping. A process of spreading
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Open structure building design. A p
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Table bushing. A bushing used to se
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Delivering on the Nation’s promis
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