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Thread: Transfer Rate Prediction Dense Phase System

  1. #11

    Pneumatic Conveying Calculations

    My article "Theory and Design of Pneumatic Conveying Systems" was published in Powder Handling and Processing magazine in its April 2005 issue. This article gives all of the equations that are needed to run calculations for pneumatic conveying systems and to understand what and why every thing is happening. Only a basic knowledge of Excel is needed. A PDF copy is available from me.

    Regards,

    Amrit T. Agarwal
    Consulting Engineer
    Pneumatic Conveying Consulting Services
    Email: polypcc@aol.com
    Ph and Fax: 304 346 5125

  2. #12
    Teus Tuinenburg

    Professional Experience 53 Years / 11 Month Teus Tuinenburg has 53 Years and 11 Month professional experience

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    Another “cold case”,

    Mr. Ken T asks:

    Material : Cement, Barite or Bentonite
    Transfer dry bulk from blow tank to process plant.
    Blow tank is with top discharge pipe.
    Compressed air is fed into blow tank through 6 to 10 nozzles for fluidizing effect and conveying of powder.
    Distance of blow tank to process plant : about 100ft to 150ft
    Conveying pipe size : 5 inch
    Pipe elbows along conveying pipe line : about 5 to 10
    Compressed air pressure (to blow tank) : 40 to 70 psi
    Compressed air flow rate (to blow tank) : 300 to 700 cu.ft / min
    Compressed air pipe size : 3 inch
    Dense phase system
    Expected transfer rate : about 80ton to 120ton per hour

    Other conditions, vent air from process plant will pass through a cyclone separator before being piped to atmosphere (5 inch with 50ft, 3 elbows).
    The description indicates a pneumatic conveying system for a drilling platform.
    The given parameters are varying quite a lot, which makes a precise answer difficult.

    Could someone recommend a good software suitable for following system performance prediction, or provide some guidance so that I can do the prediction effectively with a spread sheet.
    “good software” is as good as the accuracy of the used algorithms and there representation of all the involved physics.
    Then, the user has to understand and be familiar with the physics, the mathematical approach of the algorithms and the practical technology of pneumatic conveying.
    (Knowledge and behavior of built installations)
    This is not an overnight study and a spreadsheet program will not be useful if accuracy is required. Copying built installations will give better results.

    Case 1, would like to predict the bulk transfer rate by fixing the compressed air pressure and flow rate.
    To answer this question, the compressor flow rate has to be fixed and for a selection of compressor air pressures, calculate the transfer rate.
    This must be executed for a selection of compressor air flows.
    The result is a 3 dimensional table.
    Too much work.



    Case 2, would like to determine the compressed air pressure by fixing the transfer rate. Hence, determine the compressor size.
    I calculated:

    horizontal length = 7m
    vertical length = 30m
    bends = 8
    Diameter 5”(128 mm)
    Compressor: 25 m3/min at 4.5 bar

    Conveying rate cement = 105 tph at 4.5 bar (bends start to fill up)
    Conveying rate barite = 101 tph at 4.5 bar (bends start to fill up)
    Conveying rate bentonite = 101 tph at 4.5 bar (bends start to fill up)

    These operating points are at the lowest point of the Zenz diagram and therefore the maximum capacity with this airflow.

    Would like to have more feedback from forum members.

    Have a nice day
    Teus

  3. Dear Teus,

    on the basis of my general state diagram, developed with the aid of operating data from industrial conveying systems, I have to offer for example the following results for your "case 2", whereby the vertical pipe length is increased by a factor of 2, and each pipe arc has been taken into account with an additional length of 1 m.

    1. Operating point at the boundary of the dense phase area to the unstable area

    Click image for larger version. 

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    2. Operating point in the dense phase at a distance to the edge which is often to be found

    Click image for larger version. 

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    What do you think?

    Regards
    Manfred Heyde

  4. #14
    Teus Tuinenburg

    Professional Experience 53 Years / 11 Month Teus Tuinenburg has 53 Years and 11 Month professional experience

    Discussions 1940 Teus Tuinenburg acceded to 1940 discussions, Articles 0 Teus Tuinenburg wrote 0 articles, Publications 0 Teus Tuinenburg Tuinenburg released 0 publications

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    Know-How Conveying (1469) Teus Tuinenburg used this tag 1469 times, Pneumatic Conveying (1267) Teus Tuinenburg used this tag 1267 times, Pneumatic (562) Teus Tuinenburg used this tag 562 times

    Dear Manfred,

    I understand that case 2 is remodeled by you, according to:

    horizontal length = 7m becomes 7 m
    vertical length = 30 m becomes 60 m
    bends = 8 becomes 8 m
    Giving a total equivalent length of 75 m

    Then you calculate the system for 2 gas flows:
    1) nitrogen 25 m3/min = 1780 kg/hr
    2) nitrogen 39 m3/min = 2808 kg/hr

    For a capacity of 101 tons/hr (cement, barite or bentonite), the calculated pressure drop is:
    1) 3.44 barg (I calculated 4.5 barg, conveying gas air)
    2) 2.43 barg

    It is difficult to interpret the calculation results as the used algorithms are not really comparable.

    What we actually need is a measured installation.

    Have a nice day
    Teus

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