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Thread: Wet Grinding

  1. #1
    vpkamath Guest

    Wet Grinding

    We are in the process of upgrading our wet grinding mills which are used to grind aqueous slurries containing 25-45% solids from an initial particle size of 35-50 microns to < 1 micron (99%).

    The questions confronting us are -

    1. How does one choose between a vertical and a horizontal mill ? The existing mills are all vertical.
    2. How does the disc profile and/or the presence/absence and profile of the slots in the disc affect the performance of the mill.
    3. Is there any guideline for the size of the media to be used ?

  2. #2
    Mr. Kamath

    If you will go to www.unionprocess.com and fill out the wet grinding datasheet, we will be glad to help with your application.

    Bob Schilling

  3. #3
    GLEN MILLS INC. Guest

    WET BEAD MILLING

    Dear Mr. Kamath:

    1. Vertical mills are an older design and lower cost. Vertical are better for thinner systems so that the media is not lifted out of the grinding chamber. My suspicion is the horizontal mills will produce a finer material for they are often loaded with a higher percent of bead fill than the vertical mills. Examples are the DYNO-MILL or ECM MILL (www.wab.ch).

    2. The disc design is to both accelerate the media and, when there are reverse cut holes, to promote some back mixing which allows for more even temperature and wear (prevents bead packing at exit end).

    3. Media selections are a consideration of the following points:
    - Chemical interaction (e.g. do not use metal beads when Fe could cause electrical interference.)
    - Density (e.g. light beads as glass for thin suspensions. Otherwise a dense bead would just smash through the suspension and wear the mills inner liner.)
    - Size (generally, smaller beads for smaller final particles. More beads, more impact contacts. However, if too small for a larger starting material, they would not break the subject materials.)
    - Cost and life. E.g. for ceramics we carry the US$ 9.00/lbs. ZrO/SiO2 (sp. gr. 3.8) that last ~1,000 to ~3,000 hours as well as the US$ 100.00/lbs. ZrO/yttria (sp. gr. 6.0) that can last ~10,000 hours and longer. Cost/benefit consideration. Also, wear of the mill parts and ease to separate are to be evaluated.

    May I suggest you take a peek at www.glenmills.com for more suggestions and to contact us.

    S. Goldberg - Director
    GLEN MILLS INC.
    January 2, 2003

  4. #4
    Lawrence K. Nordell

    Lawrence K. Nordell

    President and CEO

    Conveyor Dynamics Inc. [eDir]

    Conveyor Dynamics Inc.

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    Dear Kamath

    Some helpfull websites on choice of milling:

    http://www.itdg.org/html/technical_e...ng_milling.pdf

    http://www.min-eng.com/commin_refs2.html

    http://www.micronized.com/

    http://www.metsominerals.com/

    http://www.jktech.com.au/Books/mincom.htm

    By disc profile do you mean exit grate in horizontal milling?

    In general, the gringing media should be at least 20 times the largest particle size to obtain a grip by the grinding media on the largest particle size. The input size distribution and product size may vary this selection. The feed and product size P80 or D50 are not stated and will also have a influence on the selection.

    Lawrence Nordell
    Conveyor Dynamics, Inc.
    www.conveyor-dynamics.com

  5. #5
    Srissley Guest

    Wet Grinding

    Dear Mr. Kamath:

    For ultra fine dispersions and grinds, please consider a Zinger Horizontal Media Mill. For a complete report on the advantages of the Zinger compared to disk mills email me at srissley@mfics.com You can also view our equipment at www.morehousecowles.com

    We have a full service lab to process a sample for you from 1 liter to 15 gallons. We also have demo and rental equipment available. Give me a call today at 800-566-9021 (269-637-2128) and let me explain how our equipment can help your process.

  6. #6
    vpkamath Guest

    Wet Grinding

    Dear Mr. Nordell,

    By disc profile I mean the profile of the multiple discs which by their rotation agitate/propel the slurry and the media and thereby grind the slurry particles.

    V. P. Kamath
    Last edited by vpkamath; 6th January 2003 at 7:02.

  7. #7

    Re: Wet Grinding

    Originally posted by vpkamath
    We are in the process of upgrading our wet grinding mills which are used to grind aqueous slurries containing 25-45% solids from an initial particle size of 35-50 microns to < 1 micron (99%).

    The questions confronting us are -

    1. How does one choose between a vertical and a horizontal mill ? The existing mills are all vertical.
    2. How does the disc profile and/or the presence/absence and profile of the slots in the disc affect the performance of the mill.
    3. Is there any guideline for the size of the media to be used ?
    Dear Mr. Kamath,

    we got the information about this inquiry from our English collegue.

    1) A vertical mill is normally used for mass productions (i.e. limestone) and has often a simpler design than a high tec horizontal mill. The advantage of a vertical mill is that it produces a steeper particle size distribution than a horizontal mill whenboth systems are run as a single passage grinding. For circuit processes our horizontal mill is easier to handle and therefore used.
    Normally one chooses between a vertical and horizontal system by checking all parameters, such as: throughput rate, viscosity of the end product, psd's, etc. Our horizontal mills are cheaper for products with smaller through put rates, so that is an important figure as well.

    2)There are many theories in tha market about the advantages of disk profiles. We think that a cheap solution that can be easily lined with ceramic or polyurethan is the best solution.

    3)There is a guideline for the size of the grinding media: the media should be at least 5 times bigger than the feed product. This has to be optimised for the process (type of mill, volume flow, etc.)

    I attach some information about our horizontal wet milling system. We can also offer a vertical ones.We would be happy to send you some more broshures, as soon as we get your Email and company address.

    If you have any further questions, please do not hesitate to contact us direcly.

    Best regards
    Gabriele Adam

  8. #8
    Join Date
    Jul 02
    Posts
    28

    surplus equipment

    We can assist you with surplus equipment, in many cases UNUSED, enabling you to cut your capital expenditure by as much as 65%.

    In addition our engineering department can do a study to select the correct solution. You will be charged for this study.

    Our engineering division is headed by qualified people, formerly working for Hosokawa, but are obviously are now working independent from Hosokawa.

    An independent will enable you to select the best option.

    Sincerely
    Hans Kwist
    Management@allsurplusworld.com

  9. #9
    Rene Eisenring Guest
    Dear Mr. V.P. Kamath,

    I would like to answer your three questions you posted.

    1 Vertical mills are an older design, but are still used quiet frequently for the News Ink Offset market. Most lower cost vertical bead mills had a poor separation of the grinding media and were used only for thinner products. The Buhler Vertical mill is called the Cobra mill and has separating rings, that holds the media in the chamber. In addition all Buhler bead mills can handle product pressures up to 90psi. The Vertical bead mills use larger beads. But with the todays quality requirement the media has to be smaller and the bead fill percentage has to be higher. That is why today more horizontal bead mills are on the market.

    Horizontal Bead mills are also an old design, but in the last few years all
    the manufactures have spent much of their time to improve the designs
    and to overcome the problems of the Horizontal Bead mill.
    One problem was the separation of the media and the product. If the mill
    used separating screens, they had the tendency to clog up fast and needed
    lots of attention of the operator. The mills that used separating rings had
    by far less problems with the operation. Today we even use mills that
    separate the media with centrifugal force.
    The second problem was to prevent the mechanical compression of the
    beads, towards the outlet. Many different approaches where taken, but
    the one approach that has proven over and over to be successful is the
    conical chamber and rotor design by Buhler in the K Mill. The media is
    pulled away from the product outlet with the dynamic pressure relief of the
    conical design. Todays horizontal bead mills from Buhler are capable of
    operating with 90 % bead fill, with media from 0.2 mm to 2.5 mm and with
    product pressures of 90 psi.

    For your water based slurry with a high solid content I would recommend
    only a Conical bead mill.

    2 Disc or Pins are designed to accelerate the media. The Disc design has little or no cooling possibility, where pins can accelerate the media but are also cooled and close to the rotor where cooling is available. I would recommend a mill with stator and rotor cooling

    3 The grinding media needs to be about 20 times larger then the particles you are trying to mill. We use today steel and ceramic grinding media over glass. Generally the smaller the media the finer the final particles. But if your premix is too coarse the small beads will not get the job done. Best grinding media today is YTZ by Tosoh, 2nd best media are the Mill Mates by Zircoa.

    I hope I was able to help you with your questions if not give me a call or visit our web page ( buhlergroup.com )

    Rene Eisenring
    Sales Manager
    Buhler Inc. USA

    Ph: (763) 847 0381
    rene.eisenring@buhlergroup.com

  10. #10
    vpkamath Guest

    Smile

    Gentlemen,

    I appreciate all your replies that has given me some additional insight into this aspect of wet grinding which I have not been able to get from the literature available to me.

    My colleagues and I have already been / are in touch with most of the respondents' organisations.

    Thanks and regards,
    V. P. Kamath

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