Lime Slurry Viscosity

[bradyle]

Hi,

I'm currently doing research on pumping a lime slurry with a 1:1 of lime to water by weight. I will have roughly 3 tonne of lime an hour.

I am trying to find the viscosity of such a slurry but am getting conflicting answers, ranging from 10PaS to 10mPaS. I was wondering if anyone knew where I could get this data?

Also while doing this research I've found very few places that use such a high ratio, and am finding it very difficult to get any slaker capable of mixing this. Do you think it would be best to increase the amount of water?

Also do you know if a Sg of 1.65 seems about reasonable?

 

[BigInch]

If I'm not sure, but isn't this one of those nonNewtonian fluids. If you keep it moving it's easy and the viscosity remains low, but if it slows down, it turns to toothpaste ?? Might explain all the different viscosity data you're finding.

What would you be doing, if you knew that you could not fail?

 

[bradyle]

Yea it's newtonian up until like 38% mixture, sadly since I'm going for 50% mixture it fit's into the non-newtonian phase.

I've never had to source a pump for a non newtonian mixture so I don't really know what viscosity to use when sizing the pump. Like it will obviously have to get the fluid to start flowing so it will need to be capable of that, but how to get that figure is where I'm stuck.

 

[BigInch]

The largest value you've seen x 2, or 3???
Best to do your own testing.

SG 1.65 sounds close for a reasonably thick soup.

What would you be doing, if you knew that you could not fail?

 

[Artisi]

I would google "lime slurry pumping" - there is a lot of info' there - but bear in mind lime slurry of any consistancy is a very difficult product to handle, the actual "pumping" is only one of the problems.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[bimr]

The slaking process is normally done with considerable excess water ranging from 2½ parts water to 1 part CaO to 6 parts water to 1 part CaO.

What is your process? A slaker must mix the correct amount of quick lime (CaO) and water, hydrate the quicklime, and separate the impurities and grit from resultant calcium hydroxide slurry.

If you have a paste, there is no way to separate the impurities and grit. How are you planning to remove the impurities and grit?

How far are you planning to pump? Have you considered a screw conveyor?

I would expect that you would have problems with the slaking process. I am not sure any firms make a slaker to do what you are asking.

Contact a slaker supplier for information on the process.

http://agtgroup.cl/mining/doc/OverviewLimeSlakingProcess.pdf

 

[rutherford703]

For non-Newtonian flow, the viscosity is not constant because the viscosity will be related to shear rate. Your system is most likely the Bingham Plastic behavior. To find the pressure drop through the system, you need two parameters, plastic viscosity and yield stress. As BigInch said, the best way to find the plastic viscosity and yield stress is to do the real test. However, if you want a real number, I can give you a estimation. The plastic viscosity for 50% lime slurry is about 50 mPa.s. The yield stress is about 10Pa. In Canada, SRC model is used for engineering design.

 

[bradyle]

Hi thanks everyone!

We are a cement factory and are hoping to use the cement kiln dust in the lime slurry, this will then be washed and filtered to remove the salts, leaving a water high in chlorides, which can be used to reduce the HCl admissions.

The company that 1st suggested the washing system said a 1:1 slurry would be best for this

I have just startd to run into the issues with the slakers, best I can see is a 2:1 paste slaker, which obviously wont do so think we are going to have to look at increasing the water content.

Our pump suppliers have offered to do the test for us as our lab hasn't the equipment so hopefuly i'll get that answer soon.
But I've a feeling as long as we stick with 1:1 the problems wil just keep going

 

[bimr]

The lime slaking process depends on three primary factors: quicklime properties, water properties, and water to lime ratio. The presence of certain chemicals in the slaking water will accelerate or hinder the slaking process. Water with high dissolved solids generally causes excessive foaming, which results in operational problems.

It is typical with waste products that the volume and consistency will vary. Since your water quality is unknown and the CKD content is variable, there is no method to predict the viscosity.

 

[stanier]

The properties of the lime slurry will vary considerably dependent upon the quality of the lime. One pof the challenges is scale formation inside the piping which reduces the diameter and that impacts on the head loss in a piping system.

Generally lime slurry is pumped with slow running progressive cavity pumps and thus the changes in head are less consequantial compared to centrifugal pumps.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[stanier]

This free book may help

http://www.pumpfundamentals.com/pump_book.htm

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[bimr]

Stanier,

Open impeller centrifugal pump are commonly used for pumping lime slurry with concentration of 5-6% and maintain pipe velocities of 5 ft/sec to keep the solids moving.

 

[stanier]

bimr,

The fluid to which you refer is often called "milk of lime" as it is so dilute. Yes easily pumped with a centrifugal pump. The OP was for a fluid with Cw=50% not 5-6%.

When you are pumping lime slurry it will be like a paste. You need to establish the non-Newtonian properties based on the concentration, temperature, velocity (ie shear rate) contamination from other solids etc etc.



"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/