Pumps for Slurry © 2012 Dr. B. C. Paul Note – These slide illustrate a solution approach using Sysel, a program developed by GIW and contain screen shots from the operation of the program Credit for the program is given to its developers.

Slysel Can Be Used for Plain Water or Water Containing Solids Water containing solids is called a slurry Solid particles usually increase the over-all density (since most solids are more dense than water) This increases the energy required to move the flow Solid particles can make the water thicker and gooier (also called raising the viscosity) This can also increase energy required.

Slurries Can Misbehave Usually the solids are not a part of the water and can separate out of the water Settling out can plug pipes rather nicely Some slurries are fine enough and develop enough charge on the particle surfaces to keep them stable almost indefinitely This is not typical of something a mining engineer would mix up to pump.

Lets Consider a Coal Prep Plant We will use a pump to feed a coal water slurry to a bank of cyclones. We will go for 15% solids We will assume our cyclones need about 15 psi feed pressure We will assume each of our cyclones need about 600 gpm and we have a bank of 6 such cyclones (ie 3600 gpm) Our coal is between -20 mesh and 100 mesh

My Layout Slurry Cyclone Feed Point Pump

I Begin with My Normal Project Naming and Unit Selection Use the first Tab.

I Start With My Suction Side Note this time I had a Positive Pressure on The intake side Note also that This time my Outlet is Required to Provide the Needed feed Pressure to The cyclones. Note I am on 2 nd Tab

I Proceed to Enter My Pipe System

I Then Complete the Pipe System

My 3 rd Panel Starts Out Normally I specify my flow Rate and tell the Program to Compute my Head Requirements.

We Need to Fill In Slurry Properties We put the curser on the S.G. solids and the right Click to get a list of typical specific gravities. Obviously I’m going to pick coal

When I Type in 15% Solids By Weight the Program Fills in the Other Mixture Properties

Now I Need to Deal With Particle Sizes My Slurry is 20 X 100 mesh I assume my top size is controlled by screening I screen for the bottom size to but there will always be some slimes that hold on to other particles The program wants dimensions in microns

Conversions 20 mesh = 0.85 mm 100 mesh = 0.15 mm We will assume our D50 (50% passing size) is about 40 mesh = mm mm to microns 1mm= 1000 microns Top size is 850 microns 100 mesh is 150 microns D50 is 425 microns

Put in My Sizes I had to uncheck the boxes Because otherwise the Program tries to estimate All the other sizes from my D50 which makes either An unrealistic top size or A D50 finer than 100 mesh. (My D50 needs to be right Because it influences how Easy things settle out. My Largest size needs to be Right because it controls Impeller clearances needed)

Now I Need to Deal With the Miller Number (which is a measure of abrasiveness and wear) I use the right click for suggestions trick again and pick coal.

The Next Page Looks at Energy Requirements for Pumping Slurry as Slurry Density Changes It’s really a side Check routine And not part of The main Program. If you are doing Long range Solids transport In a horizontal Line its helpful In our case our Slurry density is Pretty well fixed By our cyclones

Slysel Has Us Look at a Range of Flows in Our Pipes (This is a critical punch-line section) My target flow is 3600 GPM so I decided to try 3,000 to 4,900 in increments of 100 GPM

The Top of the Report is an Echo of My Input Obviously This is a good Place to check That you are Studying what You believe You are. One defect I Find is it always Call S.G Even when a 1.1 density Slurry has 15% solids

We Are Told the Flow Rates to Minimize Friction and Avoid Settling Flow rates for minimal friction are all lower than our 3600 GPM – on the other hand We had not better try those flow rates or our solids will settle. It recommends 2400 GPM to avoid settling – at 3600 GPM I should be OK.

Bottom of Table Shows Head Losses at Different Flow Rates I’m not Seeing Anything that Makes we Want to Change right Away.

Configurator Allows Us to Specify Things About Pump Construction I’m sticking with The defaults here For now.

Now I Go to Pump Selections They are in order of Efficiency – My top choice is 81% efficient and needs an Impeller speed of 930 RPM. 196 HP will be required. I could scroll down looking for a lower RPM but my efficiency would be declining To select this pump click on it and it highlights blue.

It Then Offers Me Some Additional Details We will not be delving into the details of pump construction but you can see the bearing Assembly is what is changing. I will click on the first choice to move on.

A Bunch of Pump Details Appear

Slysel Does Not Draw Us the Pump Curve But It Does Give Us the Points on It This is the point where our pipe curve intersects the pump curve.

If We Plotted Things We Would See This Flow Rate Head Pump Curve Pipe Curve Operating Point

A Critical Detail to Check Net Positive Suction Head (ie can the pump Suck fluid into itself) We need 10.6 ft We Have 33.5 We are OK

For Motor Sizing It is suggesting a 250 HP motor to meet our 196 HP Need (Motors come in standard sizes)

Under System Results it Shows Our Pipe System and Pump System at Different Flows We could use these point to Plot the pump pipe curve I Showed a few slides back.

Under Sheave Duty It Shows We could use a constant speed sheave with a 250 HP motor turning 1780 rpm and Driving the pump between 925 and 957 rpm.

Now Its Your Turn Feed a similar cyclone bank with a 15% phosphate rock slurry (will be apatite on the solids density selection). Draw Out the Pump Pipe Curve Identify your motor size and speed and your pump speed. Turn in your Slysel File.