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Thread: Fine Coal Flow Problem

  1. Solutions that introduce air into the coal storage or processing chamber can cause combustion issues.

    We have an alternative and safe solution that is simple to install. The mounting plate simply welds to the bunker wall. The BH vibrator is then bolted to the mounting plate. Cutting or drilling of the bunker wall is not required. Air blasters require complex and expensive installation. The bunker wall must be drilled or cut to accommodate the blaster nozzle. Additional access holes must be cut to attach the nozzle inside the bunker. The bunker must be emptied and cleaned prior to installation of air blasters and cannons – **adding to the cost and down-time.**

    NAVCO BH vibrators produce energy that is transmitted efficiently through the bunker wall and into the coal. Through the principles of conservation of momentum and energy, energy produced by NAVCO BH vibrators propagate through the hopper structure affecting material over a large area of influence. NAVCO BH vibrators effectively reduce sliding wall friction and material strength. On the other hand, Air Blasters direct a high pressure burst of air into the bunker. The burst dissipates quickly and is not transmitted efficiently throughout the bunker. Air Blasters have a limited area of influence, **especially with difficult wet or frozen coal.**

    NAVCO BH vibrators have excellent clean-out characteristics, effectively removing stagnant pockets of coal and reducing potential for spontaneous combustion. Additionally, the external installation and activation of the BH vibrator does not introduce additional air into the bunker. Air Blasters principle of operation is to introduce a blast of high pressure air into the bunker. In a bunker full of combustible material (fine coal), blasting air into the bunker by air cannon type devices can increase the potential for spontaneous combustion.

    NAVCO
    The Vibration Experts

    www.navco.us
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by navco; 7th August 2008 at 15:14.
    Tiffany Moore
    Two companies under one roof:
    http://www.navco.us
    Experts in Applied Vibration - Industrial Vibrator Mfg.
    and
    JVI Vibratory Equipment
    http://www.JVIVibratoryEquipment.com
    Vibratory Feeder and Screen Mfg.
    Call toll free for info:
    1 (800)231-0164

  2. Fine coal flow problem

    I would take issue that installing a vibrator is anything like as effective as installing an acoustic cleaner. I personally have come accross many instances where the vibrator has caused stress cracks in the hopper as, unlike acoustic cleaners, all the vibrational 'energy' first has to pass through the vessel before it can have any effect on the fine coal. I have also seen applications where indeed the vibrator has simply compacted the material further. Acoustic energy is 100% absorbed by the fine coal, causing maximum debonding and Acoustic Cleaners do not cause any damage to the vessel or structure.

  3. If the vibrator is causing stress cracks it is not being run properly as is usually the case when suppliers sell off the shelf vibrators, not flow solutions, and they do not provide any experience or support for installation and operation techniques. Several things can cause this: - air pressure too high, poor installation (probably the biggest), operating the vibrator too long, vibrator too large for the application.

    It is true that vibrators can cause compaction with certain materials - and also if not installed and operated correctly.
    Running too long instead of intermittently, running when the discharge opening is closed/blocked off.

    I recommend the proprietary Bin Map Solution to virtually guarantee material flow for any material in any vessel.

    The unique NAVCO® Bin Mapping methodology involves a detailed evaluation of the storage vessel and its intended bulk material. Recommendations are made based on a variety of factors including bulk density, particle size, moisture content, temperature, vessel size and shape as well as material of construction. NAVCO® pneumatic piston vibrators are sized for the application and their area of influence is determined. As shown in the Diagram on this page
    http://www.navco.us/industrial-bin-v...s/bhbinmap.htm
    the vibrators are located on the hopper so that the areas of influence overlap; vibrations are controlled through a sequence that provides optimal flow pattern and minimal utility consumption which is also provided in detail on a complete Bin Map Solution Drawing by NAVCO®.

    This solution is provided for free upon request when applicable.
    Last edited by navco; 7th August 2008 at 14:47.
    Tiffany Moore
    Two companies under one roof:
    http://www.navco.us
    Experts in Applied Vibration - Industrial Vibrator Mfg.
    and
    JVI Vibratory Equipment
    http://www.JVIVibratoryEquipment.com
    Vibratory Feeder and Screen Mfg.
    Call toll free for info:
    1 (800)231-0164

  4. #14

    Pfister Pulverise weight feeder

    Hello,

    I just give you a tip: instead use air purging to deblock the sticky coal, you should study to apply Agigator:
    - You put system to fire risk because of increasing Oxygen inside fine coal bin by compressed air.
    - If the compressed air is not a dry one, you get more sticky on the bin wall.
    Regards
    Last edited by dbthai; 20th October 2008 at 15:36.

  5. dbthai said: You increase "...fire risk because of increasing Oxygen inside fine coal bin by compressed air ."
    AND
    "If the compressed air is not a dry one, you get more sticky on the bin wall."

    THAT IS CORRECT!
    Here is our Bulletin detailing these drawbacks of air surge type vibratory devices which require penetration of the bin wall and also introduce air into the coal bunker, which NAVCO vibrators do not do. NAVCO Piston vibrators are very safe for use on coal bunkers.
    lWhite Paper: Air Cannons VS Piston Vibrators on Coal Bunkers
    Tiffany Moore
    Two companies under one roof:
    http://www.navco.us
    Experts in Applied Vibration - Industrial Vibrator Mfg.
    and
    JVI Vibratory Equipment
    http://www.JVIVibratoryEquipment.com
    Vibratory Feeder and Screen Mfg.
    Call toll free for info:
    1 (800)231-0164

  6. Air Cannons have just taken a good blasting haven't they? I was never tempted to use them on anything, something about Newtons words on action and reaction. Hoppers are tricky things. You can't put a dither on the wall and expect vibration to all go away from the wall and into the material. Otherwise you wouldn't need to bolt the ditherer to the wall so well! Assume that a modern hopper has been designed to a Standard and then examine what safety factors are available before you start shaking it to bits. Ultrasonics might have come of age if the hopper is a bit on the delicate side..like a powder tub would be.

  7. louispanjang said: "You can't put a dither on the wall and expect vibration to all go away from the wall and into the material. Otherwise you wouldn't need to bolt the ditherer to the wall so well! Assume that a modern hopper has been designed to a Standard and then examine what safety factors are available before you start shaking it to bits. "

    I am assuming by 'dither' you meant piston vibrator?

    If so let me point out how a vibrator works, so you understand how it can vibrate material to cause flow, with out 'shaking the bunker to bits'.

    It sometimes helps to view this animation attached:

    You can also read this White Paper to learn how vibration works:
    Vibration Comparison

    And read this for a White Paper on Energy Assisted Gravity Flow Theory as it relates to storage vessels.


    To learn about NAVCO Vibrators for Power Plants read this:Industrial Vibrators for Power
    Tiffany Moore
    Two companies under one roof:
    http://www.navco.us
    Experts in Applied Vibration - Industrial Vibrator Mfg.
    and
    JVI Vibratory Equipment
    http://www.JVIVibratoryEquipment.com
    Vibratory Feeder and Screen Mfg.
    Call toll free for info:
    1 (800)231-0164

  8. Here is a video showing why blasters are not a very good solution for coal bunkers. They way they shoot compressed air quickly into the bunker is very dangerous and can cause spontaneous combustion in coal fines:

    Air Blaster Video
    Tiffany Moore
    Two companies under one roof:
    http://www.navco.us
    Experts in Applied Vibration - Industrial Vibrator Mfg.
    and
    JVI Vibratory Equipment
    http://www.JVIVibratoryEquipment.com
    Vibratory Feeder and Screen Mfg.
    Call toll free for info:
    1 (800)231-0164

  9. #19
    Join Date
    Nov 14
    Posts
    13

    sonic horn

    Quote Originally Posted by Yogesh View Post
    Dear John,

    Thank you very much for your reply, Actualy we are not facing any problem with the pfister pump. We are using the Pfister pump to transport the fine coal from silo to the calciner

    Fine coal flows from the silo to the Pfister pump (gravitational flow) which is placed below the silo. We are giving compressed air to the silo bottom area for a smoother flow

    If this flow is normal, then the load on the Pfister pump will be normal and required amount of coal will be transported

    Our problem is the coal is not flowing in sufficient amount from silo to the Pfister pump. This problem is not a continues problem
    Intermediately the coal will fail to flow from silo..
    Hi dear,
    please don't give compressed air directly.
    a sonic horn by compressed air could work better. obviously you have problem with smooth flow of fine coal out of silo.
    if the particles are fine enough, bridging or ratholing occurs quite common.


    regards.
    charlie
    Last edited by Gary Blenkhorn; 8th August 2019 at 16:30. Reason: removed advertising link

  10. Flow problem with fine coal

    This problem was reported in 2008 so I would think it has been resolved. Discussion on the relative merits of vibrators, air cannons, air injection and sonic horns omitted to include sledge hammers, but do not address the basic reason for flow problems, that of hopper design. A design based on measured bulk property values will provide reliable performance, whereas brute force has unpredictable consequences. This first step in a failure analysis is to examine the shortfall of the basic design and establish if that can be rectified.

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