Topics: I want to design a slurry system.
on General Discussion
I want to design a slurry system.
I want to design a slurry system. What are the factors that I should take into consideration and how should I proceed for it?
03-25-2014 10:59 AM
What is the end goal/product being produced? Your question is very open ended. Without knowing additional informaiton such as what type of reaction or atleast the components going in and out of the process, your question can not be answered.
03-25-2014 01:40 PM
Okay. Thanks for the suggestion. My system has 29.8% solid (particle size of 74 microns) and rest is water. I need to decide the agitator and reactor geometry followed by pipeline design and pump selection and design. I can't disclose the actual product composition as it has to be kept secret. Although I am trying to design the system but I would really appreciate , if someone can suggest me something based on his/her experience.
03-25-2014 03:49 PM
(1) abrasive property ,corrosive property , contamination risk and end use of material to be transported,
(2) relative density of solid and fluid. particle density and geometry
Determine terminal velocity at various concentration by laboratory trials, ensure slurry velocity exceeds terminal velocity and avoid laminar flow specially if having considerable length of horizontal runs
03-25-2014 06:39 PM
Is this a continuous system or batch? If batch, you may want to consider a tickler blade below the main agitator.
How much agitation? You have basically two choices: Off bottom suspension or uniform suspension. The later takes 2.5 to 3 x the horsepower.
Is this metal or glass-lined construction? If metal, you can easily include a vortex breaker to assure more emptying.
Do you know the do's and don't for pump selection? Example: Closed end impellors are more efficient but may plug for slurries. 1750 RPM pumps likely preferred to prevent breakage.
How delicate are the particles? There are lower shear pumps, such as a hose pump, if it is really important.
03-25-2014 09:06 PM
The big thing is "settling" velocity. It is easy to determine. Take a sample, shake it up and see how long it takes to settle or clear. This is your minimum velocity for your agitator and flow in the pipes.
What are you feeding the slurry to? Is keeping the crystals large important? Are the solids hard, soft, or sticky? If you are worried about not breaking the crystals then pump and agitator speed and design becomes extremely important. You might want to concidered either a recessed impeller pump or a disc pump. Disc pumps have very very low efficencies but are gentle on the crystal. Recessed impeller pumps are also gentle on the crystals and have higher efficencies. If you don't care about the solids, then any open face pump will work.
Also consider long radius elbows and keep pipe distances short.
Soft and sticky materials will not filter well.
Another thing is to flush all of lines after the slurry has transferred. When you stop the slurry flow, it is hard to get it restarted.
Lined pipe has limited life.
03-25-2014 11:36 PM
I am using a Glass-Lined Reactor and since the dimensions of a GL-R are fixed, I am not able to find the values of Zwietering constant,S (for the corresponding values of T/D, T/Z and T/C). What should I do? Is there any correlation, using which I can find the value of S. And if I am conducting a pilot trial, how to ensure that minimum suspension condition has reached?
T- Tank Diameter
Z-Clearance (Distance from Impeller bottom to the dished bottom)
C-Distance from Impeller center line to the dished bottom
03-26-2014 02:32 AM
Thank you all for responding to my question and enlightening me with such a good anaysis and knowledge.
Thank you so much for such a nice response.
My system is batch only, but I am using GL-R because of corrosion problems.
As far as pump selection is concerned I was thinking to go for lobe pumps (because of minimum shearing and abrasion and also the space constraint). Is it advisable?
Very useful information was provided by you. Thank you for that.
No, I don't have any sticky particles. But I was thinking to go for Lobe pumps since my solid concentration is quite high (29.8%). Moreover, My slurry contains both fines as well as coarse particles, So I am not able to decide what kind of behaviour it will show ( Newtonian or non- Newtonian). Could you help me out?
Also, my slurry finally will enter into an exchanger.
Thank you for your wonderful answer.
Yeah my system is corrosive. Particle are spherical only and solid density is coming around 1170 Kg/m3. But problem is that since it contains both fines as well as coarse particles, so on what basis I decide whether it will show Newtonain or non-newtonain behaviour. Could you suggest something.
03-26-2014 05:03 AM
Need to better specify particle size distribution -e g. D25, D50, D75, D90; what is your top-size (largest particle)?
It is likely to be Non-Newtonian - possible Bingham plastic (essentially Newtonian with a yield stress); recommend you look up literature to understand the rheograms of similar slurries, whilst keeping in mind that the actual viscosity could be (and likely is) dependent on the shear rate applied to it, both in the reactor and in the pipeline.
Also, doing some viscometer and/or basic pipe-loop work will give you a feel for the rheogram (the slurry type, and profile vs shear rate).
03-26-2014 07:05 AM
Larger particle are of 74 microns (6.78%) and smaller are in the range of 1-1.2 microns (25.79%) in size. Yeah, it is showing Non- Newtonian behaviour only but yield stress is not very significant.