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 mill’s 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 ■

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. ■

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 ■

Dear Mr. V.P. Kamath,

I would like to answer your three questions you posted.

1Vertical 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 today’s 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. Today’s 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.

2Disc 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

3The 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 ■

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 ■

DEAR SIR,

CAN SOME ONE SUGGEST SUITABLE EQUIPMENT FOR THE FOLLOWING:

MICA FLAKES - GRINDING IN WATER MEDIUM BY A SLOW FRICTIONAL DELAMINATING PROCESS USING LINED MILLS.

REGARDS

MOHIDDIN

DUBAI

PH:+971507846745

EMAIL: ghouse8@yhaoo.com ■

New TOSOH YTZ Grinding Media is available at vastly reduced prices on eBay.

http://search.ebay.co.uk/ytz-grindin...fltZ9QQfromZR8 ■