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Thread: Fluidization in Cement Silos

  1. #1
    vikas Guest

    Fluidization in cement silos

    Dear Sirs,

    I would like to know how to determine the optimum fluidization rate in the cement silos, especially in the regions of cold weather like Canada.

    Thank you

    Regards

    vikas,,,

    ****************************************************

  2. FLUIDIZATION

    DEAR SIR.

    BY FILLING THE POWDER, WHEN FALLING TROUGH THE AIR, FLUIDIZES. THE QUESTION IS HOW QUICK IT CAN DE-AERATE. AIR TEMPERATURE CAN HAVE A SIGNIFICANT INFLUENCE.

    IN OUR PROGRAM WE HAVE AN FLUIDIZATION AND DE-AERATION TESTER – AERO-100. WITH THIS TESTER YOU WOULD BE ABLE TO GET ANSWER ON YOUR QUESTION. PLEASE CONSULT OUR WEBSITE -

    WWW.IPT-ONLINE.COM

    OR CONTACT US.

    REGARDS

    R. WOHLWEND

  3. #3
    vikas Guest
    Dear Mr. Wohlwend,

    Thank you for your reply.

    Its true that while feeling silo, the powder gets fluidized, but to maintain in in fluidized state, it is normally needed to inject air or use vibration pads at the bottom of the silo, so as to avoid the problems in discharging the silo.

    So I was interested in knowing are there some specific curves or literature which will furnish information about the quantity of air to be passed per unit cross section of the silo, for different materials, to keep them fluidized. (in my case I specially wanted the data for material such as cement, clinker, fly ash, coal and sand). This data is needed to design the aeration system used at the bottom of silos.

    Can AERO-100 be used to determine such rate ?

    Thank you

    vikas,,,

    ****************************************************

  4. silo aeration

    We are pleased to introduce ourself as one of leading engineering company having expertise in Fly ash silos, Cement silos and blending systems. We supply complete aeration and extraction systems for silos.We also supply blenders for mixing fine fly ash/ground slag with cement.Please forward your enquiry for cement silo aeration and extraction system.
    thanking you,
    SANDEEP SANGHAVI
    SANGHAVI ENGINEERING,
    121, C.I.E, BALANAGAR EXPN,
    GANDHINAGAR,
    HYDERABAD-500037,
    ANDHRA PRADESH,
    INDIA.
    SANDEEP SANGHAVI

  5. Dear Vikas,

    please have a look to our homepage
    www.vsr-industrietechnik.de

    We are the manufacturer of air cannons for activating bulk materials.
    we have more than 27 years experiences in the
    problems of cement industries worldwide.

    We are working worldwide.

    Please sent an detailed inquiry to our address
    or to me directly
    VSR Industrietechnik GmbH
    Export Manager
    Wolfgang Schlabach

  6. #6
    The key to the fluidisation of cement silos depends on just how long you expect to store the cement in the silo. If it is a long time, than you can have agglomeration, bridging and a number of other problems impeding the cement flow. For shorter periods of storage the problems diminish. Flow pads at the base of the silo, acoustic horns or mechanical devices (or indeed, silo rash) are sufficient to get the cement flowing, However, for a system to solve many of the problems with long-term or short-term storage the systems devised for the bakery industry are the best. That system includes the use of a sintered polyethylene base on the silo which allows pumped air to pass through the sintered sheet to the superadjacent cement. This induces a flow and, being smooth and 'slippery' a reduced friction surface along which the flow can slide. The system can be operated with a dessicator to remove or control humidiy within the silo and, since the flow is induced from the base, the dry air percolates to the top of the cement stored, keeping the entire contents dry and slightly aerated. There are no moving parts and the sintered polyethylene (one can also use sintered stainless steel or copper) from companies like Sintair, is cheap and effective. The induced air can also be heated for cold climates, keeping a constant temperature and humidity in the silo

  7. #7
    Neal Biege - FLSmidth, Canada Guest

    Smile Fluidization velocity in Cement Silos

    Dear Mr. Vikas,
    Our company FFEMinerals Canada is the ex Fuller Company and the FLSmidth Company here in Canada. We have supplied most of the silo aereation systems in Canada.
    Please do not hesitate to call or e-mail us for help on any of these application.
    A rule of thumb for most cement fluidization is about 10CFM per Square foot. This is adjusted depending on slope and other special consideration.
    Tell us more about the application and we can give you a more specific answer.

  8. Cement fluidization

    Dear Vikas

    the correct material discharge from a silo depends not only on the air rate but on silo bottom form, aerating medium quality, the aerating air pressure, richness of active aerating area, storage period and others, too. So nobody can tell you only one optimal value of air rate.

    Send us all data like: size and form of silo and silo bottom, layout and dimension of discharge outlet, cement data (temperature, granulometry, bulk density...) and our company will make an offer for technical design of aerating system or for delivery of it, both with specification of the air consumption and parametres.

    When is a cold weather amount of water vapours in the air decreases. It causes that water comming into cement with the aerating air does not affect cement quality comparing with operation in warm year period. Generaly an aerating system must be operated only in time of discharge and not constantly.

    With best regards

    Petr Rayman
    technical director
    RAYMAN spol. s r. o. Kladno
    Czech Republic
    E-mail: petr.rayman@rayman.cz

  9. #9

    SILO EXTRACTION SYSTEMS

    WE HAVE DESIGNED SILO FEEDING AND EXTRACTION SYSTEMS
    FOR MORE THEN 50 SILO OF VARIOUS SIZES AND SHAPE.WE CAN PROVIDE YOU THE G.A AND FABICATION DWGS. FOR THE ENTIRE
    SYSTEMS AT A VERY COPMETITIVE RATES.

    REGARDS,
    ANIL
    Last edited by libranengineering; 1st March 2004 at 14:29.

  10. #10
    Teus Tuinenburg

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    Found another cold thread.

    Aeration and fluidization of bulk materials in relation to silo flow are different phenomena.

    Aeration:
    The void volume between the particles is pressurized, whereby the particles are still touching each other.
    The material stress and silo wall stress are in principle unaffected, as long there is no pressure gradient in the material column.
    In principle, the silo material flow does not change, as the inter particle friction does not change..

    Fluidization:
    Here, the particles are subject to a vertical airflow, lifting the particles until the particles are separated and become in suspension.
    The inter particle becomes zero and the bulk material starts flowing like water.
    This is the fluidized state.
    A declined air slide functions according this principle

    Emptying a full cement silo (or a cement hold in a cement carrier) starts with aerating the lower part of the cement silo volume. The aeration situation.

    At the outlet opening of the silo, the following theory applies:

    - At the silo outlet valve. the entrapped gas expands between the silo injection point and the outlet.
    - The expanding gas shares the acquired gas impulse with the related amount of material, resulting in a mixture velocity
    - The outlet area determines the discharge rate of the outlet valve. (IBAU control gate)
    - The required injection airflow equals the expanded entrapped gas flow of the discharged cement mass flow.

    The required cement aeration mass flow can easily be calculated from the designed silo discharge rate.
    Normally, aeration starts approx. 0.5 hrs before the actual silo discharge starts, to create the required inter particle void gas pressure. (approx. 0.5 barg)


    When the silo is emptied to approx. 1-2 m above the bottom, the cement column cannot maintain the interstitial gas pressure and the particles are separated by the upwards gas flow into a fluidized state.
    Under these conditions, the gas mass flow to maintain the fluidized state is much higher than required for aeration only.

    For cement, a fluidization velocity of 0.05 m/sec is normally chosen.
    The fluidization area is based on the operating area in the silo.

    If the fluidization blower(s) are sized for fluidization, they are certainly enough for aeration.

    Merry Christmas and a happy new year 2018
    Teus

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