Bulk Viscosity Prediction of Slurry 1

[Mech85]

Hi,

Can anyone help with a viscosity prediction for a slurry if the solids concentration is known and the viscosity of the carrying liquid is known.

I have seen the equation by Einstein

Visc slurry = Visc Liq*(1 + 2.5*(1-e))

where e is ratio of Volume liquid/Volume of mixture. However this is only valid for very dilute slurries/suspensions - that is where e = 0.98 to 0.99

I am looking for a correlation for slurries up to where e = 0.90

 

[stanier]

There is no such algorithm.

The properties of a particular slurry are affected by twelve or more parameters not just the solids concentration.

Other matters include solids density, flow regime, shear rate,, temperature, solid particle shape, density distribution across bands of solid sizing, carrier fluid, dissolved salts in carrier fluid, entrained gas, velocity of fluid.

There are some approximations in the work by Wilson, Addie and Thomas for some hetereogenous slurries. For homogenous slurries correlation with other slurry pipeline characteristics may be possible however these will only define the book ends to your problem. You really needs to test the fluid.

Depending upon the slurry the type of viscometer to use will vary. If the slurry has an initial shear stress that will affect starting of the pipeline a series of tests at very low shear rates is required. You cannot extrapolate low shear rates and determine the inital shear stress. A Weissenberg regionometer or Bofer apddle type instrument is required.

Prof David Boger at the University of Melbourne is a world leader in this research. he has been involve don many pipelines of alumina red mud, caol, waxy crude oils etc.

Work by Dr Allan Thomas is considered to be at the forefront of this technology.

The book Slurry Transport Using Centrifugal Pumps is the latest and greatest in this field.

Pilot plant testing can be carried out for youn at GIW in Canada.

Good Luck.

 

[jmw]

Don't forget the effect of viscosity modifiers.
For cement production sodium lignosulphonate is added to the chalk slurries which reduces the viscosity significantly. This allows the solid content to be significantly increased. This is important as the higher the solids content the less energy required for drying.
So a relatively small amount of additive can produce a significant change in viscosity. Additives can be designed to increase or decrease the viscosity as required.
In the phosphorescent coating of TV tubes PVA is used to increase the viscosity.

JMW

http://www.viscoanalyser.com

 

[m777182]

In the Chemical Engineering January 1997 p 123 there is an article "Pumping slurries" that deals with the minimum viscosity of a slurry as a function of particle size distribution. There are three more references cited there that might help you.
m777182

 

[Mech85]

I have found the algorithm which I needed. Section 1.5.3 of Slurry Systems Handbook (McGraw-Hill) by Baha Abulnaga gives an approximation of the "absolute viscosity of mixtures with high concentration of solids" as follows

Visc slurry = Visc Liq*(1 + 2.5*Cv + 10.05*(Cv)^2 + 0.00273*exp(16.6Cv)

Where Cv = Volumetric concentration of solids

 

[MikeHydroPhys]

You may also have to consider boundary problems where the highly viscous, yet particulate state can cause a layer to adhere in the low velocity, low energy zone along the pipe, or channel (G.Tchobanoglous: Wastewater Engineering Transport Metcalfe and Eddy)
mdshydroplane

mdshydroplane

 

[MikeHydroPhys]

PS:
the adherence of slurry and its dry, dewatered state will of course reduce the cross section and sections may drop into the flow as blocks forming a very definitely non-Newtonian state !! at a later date. This is a mass transport problem with chemical and soil mechanics factors and a look through sedimentary geology books and soils and erosion texts might give some principles that could be adopted. Obviously most slurry is usually transported by addition of extra water, storm water in sewers, but that is becoming increasingly unpopular. You might try CEGB England on pulverized fuel ash transportation prior to dumping to see if any experiments were condutcted 1960s 1970s, or look at kaolin clay mining. Somebody might be able to model; John Lewin UCW Aberystwyth is a close limestone (chalk) and sediments expert : recent Institute Earth Sciences mdshydroplane

mdshydroplane