Hi:
I need to measure the viscosity on-line of a ore slurry with gold, silver, cyanide, lime. I don't know if there is some viscometer that can do this. Every equipment i look at the internet always speak abut fuel, oil, or something like that. Can anyone help me?
I've seen some that use a vibrating technology... how it works?

thanks in advance

PD I'm Electronics Engineer with specialty on Automation

 

Slurries can be non-newtonian (viscosity changes with shear rate changes)which means that the conventional approach is to use an instrument which has a constant shear rate such as a rotational viscometer. For slurries and drilling muds it has been usual to use a Fann rotational viscometer ("www.fann.com":http://www.fann.com )

However, in recent years a number of new technologies have becaome available based on vibration. These have many advantages, not least that they have no moving parts so they are reliable and do not usually require frequent re-calibration. Changes in viscosity cause changes in the damping of the fluid on the oscilator. Not all vibrational instruments are the same. Nametre ("www.nametre.com":http://www.nametre.com ) use the energy required to maintain constant amplitude as a measure of viscosity. Others operate at the resonant frequency and use the change in amplitude at the resonant frequency as a measure of viscosity. (see "www.Hydramotion.com":http://www.Hydramotion.com , "www.sofraser.com":http://www.sofraser.com ,"www.viscositymeter.com":http://www.viscositymeter.com ). The VAF viscosense uses bandwidth measurement; the bandwidth about the resonant frequency ("www.VAF.nl":http://www.VAF.nl ) as does Solartron Mobreys tuning fork design ("www.solartron.com":http://www.solartron.com ). With the exception of the solartron viscometer which measures the dynamic viscosity and the density and so calculates the kinematic viscosity, base density,degrees baume and %solids etc, most only measure the dynamic viscosity.

Several can indicate the viscosity at a reference temperature using a variety of algorythms. This is important as in some applications it is necessary to discriminate between a change in viscosity due to a temperature change and a change in visco due to a change in quality e.g. solids content.

Some sensors are more robust than others and some do not respond well in slurries. Vibrational sensors do not have a constant shear rate and many may consider this a disadvantage with a non-newtonian fluid however in practise this need not be a problem and many non-newtonian fluids are routinely measured using vibrational sensors).

I would suggest that any of the above manufacturers would be happy to advise you on their success with slurry measurement. You should be prepared to advise on floculent or viscosity modifier addittion. In shina clays, chalk slurries etc various additives which affect viscosity are commonly encountered. In chalk slurries, for example, sodium ligno sulphonate is
added to reduce the viscosity and hence allow higher solids content (reducing the energy at the cement plant to remove the water)and additives therefore represent an important consideration. Importantly, vibrational technologies do perform well in some slurry applications and are certainly worth investigating.

 

A very good method for determining online viscosities if you have a operating flow of the slurry is to utilize a pipeline viscometer. in other words a fixed length of know diameter pipe or tubing. Depending on the type of fluid characteristics you can fit the pressure drop versus flow data to a rheological model and extract the viscosity numbers. This becomes a useful tool then for on-line measurement of the
slurry viscosity and allows process control issues to come into play.
Good luck

 

We are manufacturers of in-line torsional oscillation (vibrating) viscometers, which measure viscosity based on the power required to maintain a constant amplitude. Such viscometers (ours as well as our competitors) actually measure the viscosity times the density. Our website "www.marimex.cc":http://www.marimex.cc is currently undergoing a conversion and will likely be back up in about two months.

We have successfully applied such viscometers to slurries - mainly clay. The advantage of a torsional ocillation viscometers especially in clay is the extremely small enery input into the slurry. This ensures that unlike with a rotational viscometer molecular bonds, which are forming, are not being disturbed by the viscometer. Applications have included porcellain manufacturing automation and lost form control.

 

Hello,
Did you already consider to measure the density of the slurry ultrasonically?
Advantage of this method is the lack of moving parts, and there are no objects that protrude into the pipe. Rhosonics is supplier of this equipment using ultrasound waves. It is suitable for the concentration or density of lime-stone slurries, at very high density levels.
You might want to check their website: "www.rhosonics.nl":http://www.rhosonics.nl .

Best regards,
Willem van Ballegoijen

 

>From the website, it appears that the sensors for Rhosonics do go into the process. Also, no mention is made of applications on mineral slurries. For those applications, any probe into the pipe will not survive.

There are sonic density meters that do not have penetrations into pipes. Those systems do have limitations on %solids concentrations which are
dependent on pipe size. The proven method of measuring mineral slurry densities is a gamma gauge. These devices do not intrude into the process, they clamp on to the process pipe. They survive harsh environments and are very reliable.

For both sonic and gamma density system information, you may want to view:

"www.thermomeasuretech.com":http://www.thermomeasuretech.com

L.Kolbert

 

Dear Sir,

We do not have any experience measuring this type of slurry, but we are interested. However, we would like to know a little more. Can you please advise:

Temp and % Cyanide in solution.

Thanking you in anticipation

B Rgds

Nick Pope
Area Sales Executive
VAF Instruments b.v.