The solution consits of an online microwave based moisture measurement, completed by a bulk density compensation by gamma rays if necessary.

Please contact

Berthold Technologies, Bad Wildbad, Germany

http://www.bertholdtech.com

The product manager for this branch is

Ulrich Klute

ulrich.klute@bertholdtech.com

Regards,

J.-M. Weber ■

There is also a solution with a non density independent Microwave method. These microwave systems are able to compensate density variations without an additional gamma ray. Simple to install and use with high accuracy. Please contact www.doescher.com or j.doescher@doescher.com ■

Arizona Instrument (AZI) manufactures the Computrac line of moisture analyzers.

AZI has worked closely with the Gypsum industry further developing the Computrac that has become the industry standard. Specific features for the Gypsum industry include:

Link test options for quickly identifying free and combined moistures in one test sequence

Identifies Free/Combined and purity in Mined and synthetic gypsum

Weight gain feature for identifying soluble anhydrate

Time out feature allows for completion if no weight loss is present

Purity calculation for Hemihydrates as well as Dihydrated states

Purge capabilities for even heat distribution and drying

For more information, please contact AZI @: ■

Microwaves are definitely the best solution. Scantech has a commercial unit to provide real time data from the material on the conveyor, without collecting samples, and which does not require gamma ray compensation.

Please visit www.scantech.com.au, or email info@scantech.com.au for more information. ■

Yes, we have some experience with moisture analysis of

gypsum powder. Please send me your detailed adress including

email and I will send some data sheets to you.

First information you could find:

www.water-content-measurement.com

www. liebherr.com ■

I wouldn't restrict your research to microwave and RF!

We have developed many sucessful solutions for non contact moisture measurement in chemicals and minerals and we would be pleased to discuss the merits of our technology for the measurement of moisture in DSG.

Visit http://www.ndcinfrared.com/IndustryView.aspx?id=71 to see solutions in the chemicals and minerals industries. ■

Near infra-red units are a non contact method to do on-line moisture analyses of Gypsum Powder.

This method is relatively inexpensive, but the placement of these units is critical for optimum performance. ■

Hydronix Ltd specialises in the research, development and design of online microwave moisture measuring systems. Although our systems are used primarily in the concrete industry for measuring the moisture in aggregates, we are also involved with other applications including cement, animal feed, asphalt, grain, clay and sugar.

Although at present we have no practical application experience with moisture measurement in Gypsum Powder, we are always happy to check feasibility by performing laboratory experiments, and would ask for sample of the material.

For more information please look at out website: http://www.hydronix.com

or e-mail us at info@hydronix.com ■

I have done a few years ago several moisture analysis in gypsum. Although the gypsum I had experience with was gypsum as a waste product at a production of phosphoric acid. The origin of the gypsum is not the same, but I think that problems with the moisture analysis should be the same.

The most important is what type of gypsum has to be analysed for moisture and what type of moisture.

I have experience with 5 types of gypsum:

- anhydrite gypsum (CaSO4 . 0aq)

- hemihydrate gypsum (CaSO4 . 0,5aq or plaster of paris) in alfa and beta form

- dihydrate gypsum (CaSO4 . 2 aq) in alfa and beta form

It is also important if you want to analyse for total water content, free water content or (crystal)bonded water content.

Total water content:

To get an accurate total water content is easy via the loss on weight/loss on ignition method: put a few grams of gypsum filtercake in an oven at 200°C and dry the gypsum some time untill the weight of the gypsum is constant (>2 hrs?) The reduction in weight is the Total water content (free and crystal bonded).

Free water content:

To measure the free water content is somewhat more difficult because it has to be avoided that crystal bonded water will be analysed as free water.

My experience is that the temperature is important for the free water content analysis via the loss on weight method:

Dihydrate gypsum should be dried at 60°C for 24 hrs (longer time because water will not evaporate quickly at this temperature). In this case only free water will evaporate and crystal bonded water will remain in the gypsum.

Hemihydrate and anhydrite gypsum can be dried at 100°C for 24 hrs to analyse for free water content.

Total water content - free water content = crystal bonded water content.

Sorry for all the others, but my experience with IR- or halogene moisture analysers are not very positive if the water content has to be analysed in dihydrate and hemihydrate gypsum. With these devices it was never sure that none of the crystal bonded water was evaporated (in case of free water analysis) or if all crystal bonded water was evaporated (in case of total water content)

Ok, this was approx 5 years ago and I am not surprised if the technology for these type of moisture analysers are improved.

Regards,

Wouter Hijmans

Holland Novochem BV ■

Great information Mr Hijmans! Your response to this question explains why the Computrac Moisture analyzers have been accepted as the standard for moisture in Gypsum.

It was our desire to meet these exact requirements for the industry. The features and capabilities of the Computrac instruments were born out of experiences just like these and the need for a better solution to this problem. Our customers drove the development of this product line. Their requirements for an accurate and stable heat control lead us away from IR, halogen and microwave heat sources and to a much better solution. The Computrac provides even heating controlled to +/-1° C of the setpoint and it is maintained by a ten-point NIST calibration standard.

In reference to Mr. Hijmans concern about the free and crystal (bound) moisture, the Computrac can determine both free and bound moistures as well as perform automatic calculations to determine purity all in one test.

If you have specific questions about the methods and programs in the Computrac, would like a sample test report for gypsum analysis or any number of referrals, please call or email!

Thank you,

Scott Percy

spercy@azic.com

800-290-1414

www.azic.com ■

I feel that from comment to comment, it has been forgotten that the request was fro an on line measurement after the flue gas/calcium reactor.

In this case, the free water measurement is more important. The ratio of bound (crystalized) water is more important for the enduser who produces plaster boards.

If really both free and bound water have to be determined, then we come back to the 1st suggestion:

Berthold Technologies is able to determine both online:

- free water by microwaves,

- total water by neutrons,

- the difference being the bound water.

They also have solutions for dosing the chalk milk or limestone for the reactor.

See Ya! ■

We have experience in moisture measurement of free moisture in gypsum powder on DSG applications moisture range 6-12% after a centrifuge, NIR offers the most simplistic installation as it is non contact and can be sited some 20-30 cm from the product, the important part of the installation and calibration is the moisture varies from the start of the discharge to the end of the discharge of the cyclone.

The lab method for the moisture measurement of free moisture and bound water is very different.



If you are interested please send me an email it may be possible to offer a test installation having discussed in more detail the measurement point.

Please see www.processsensors.com, for contact please use the Uk office. ■

We can offer you widest ranges in Moisture Meters for food grains, rice, wheat, tea, wood, timber, etc and ask for your current and all future demands

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We can offer you widest ranges in Moisture Meters for food grains, rice, wheat, tea, wood, timber, etc and ask for your current and all future demands

SurajParkash

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