Design of a stirrer
Design of a stirrer
(OP)
I would like to know the recommendations of which design amongst the attached would be the best for :
** Creating a VORTEX and highest downward thrust (for pushing the fluid down towards a drain plug) when used as a stirrer...
I would like to know if there are any better designs than the ones I have thought of for achieving my purpose. Thanks in advance
** Creating a VORTEX and highest downward thrust (for pushing the fluid down towards a drain plug) when used as a stirrer...
I would like to know if there are any better designs than the ones I have thought of for achieving my purpose. Thanks in advance





RE: Design of a stirrer
RE: Design of a stirrer
RE: Design of a stirrer
RE: Design of a stirrer
Would it be able to provide more homogenous mixing & probably thrust too???
RE: Design of a stirrer
Please also refrain from double posting: thread378-274808: Stirrer Design Query as it tends to result in duplication of answers
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RE: Design of a stirrer
you may consider shaping the bottom of the container, which might help the flow circulate.
are you trying to mix the fluids ? maybe work it from both sides ... one propeller pushing the lighter fluid down, another pushing the heavier fluid up ??
RE: Design of a stirrer
Am just worried though that the bottom propeller might push the melt upwards or a single propeller @ bottom might not be sufficient to create the thrust we need in a large chamber...
Shaping the bottom of the chamber might work out great....have to though probably consider re-designing the whole chamber which would be costly....
RE: Design of a stirrer
RE: Design of a stirrer
it'd be easy to separate them.
random thought d'jour ... could you heat the mixture slightly ?? (to encourage them to get along with each other)
RE: Design of a stirrer
Skimming is not possible as the chamber is a pressure vessel which is closed....Mixture is heated till 150 C so that the polymer is melted...
Aim is to get the melt out of the chamber to room pressure via the valve @ the chamber bottom so that the polymer will expand due to pressure differential....Water is essential though so that the material is not overheated......
Due to density difference though water gushes out first from the valve rather than the polymer so we need to make sure it is being thrusted down and forced out...
RE: Design of a stirrer
B.E.
RE: Design of a stirrer
RE: Design of a stirrer
Remember this screw is pushing your material down.
The screw will pull a column of polymer water mix towards your outlet, some of your material will escape the sides of the screw and recirculate in the tank. A sleeve around part of the screw at the bottom will minimise that. Remember this screw would have to be centered over your outlet to work
What stops your water from draining out and leaving your polymer high and dry? do you open a valve in the bottom of the tank and let the water flash to wet steam? are you re-filling as you drain?
Is this a continuous flow, or a batch production system ?
If this is a batch production system then a tapered bottom to the tank will give you a better discharge. However I feel that if the flow rate is too slow your polymer will agglomerate in your tank.
B.E.
RE: Design of a stirrer
This is batch production system. Polymer tends to agglomerate but we are using surfactants to prevent that issue. I am giving the propellers a shot today as other coveted members have recommended.
Would also try to get the archimedes screw and give it a try if needed - any recommended companies to buy/customize the archimedes screw?
I need to somehow add resistance to the water flow to slow it down because it escapes far more easily than the polymer melt.
Info that all of you have provided though has been a big help and am in a much more better position than before for sure. Big thanks and please continue to assist with your recommendations if possible.
RE: Design of a stirrer
RE: Design of a stirrer
RE: Design of a stirrer
RE: Design of a stirrer
An archimedes screw is simply the working part of a screw conveyor, there are many companies that can make what you want. Here is a link to just one of them.
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B.E.
RE: Design of a stirrer
it sounds like you're using the water as a heat sink ... could you use something else ? maybe the water is also a transport agent ?
it sounds ike you want to do the opposite of mixing ... you want to separate the polymer from the water. is the polymer still fluid at say 90C and 1atm ? reduce the temp, reduce the pressure, get a more controlled release ??
RE: Design of a stirrer
Water is both heat sink & transport agent - favoured for use because of cost and no chemical reactions.
No i cannot lower the temp. as the polymer melts @ 150 C...once it melts it absorbs the gas and becomes unstable...once vented to the atmosphere the pressure differential causes it to expand. Polymer achieves "fluidity" @ 150 so it helps in coming out easily with water.
Would metering valves or say a spiral tube @ the bottom port enable me to add more resistance to control the release and also help me provide more resistance to water flow?
RE: Design of a stirrer
If the way I explained it didn't make any sense, open a toilet tank and have a look at the overflow tube.
And now that I think about it, at that pressure and temperature, you can simply put a valve on the bottom and let it flow on its own without having to pump anything into it.
Engineering is not the science behind building. It is the science behind not building.
RE: Design of a stirrer
i don't think he's trying to push the ploymer through the water, but rather trying to separate the water (drive it to the bottom of the receiving tank) and the polymer (drive it to the top of the tank).
it sounds like the water and the polymer mix (at 600psi and 150C). but i'm confused by "the polymer melts @ 150 C...once it melts it absorbs the gas and becomes unstable".
i also have difficulty with venting to atmoshpere a vessel at 150C and 600psi containing a water mixture. this isn't my speciality but isn't the water superheated ? won't it (does it ?) flash to steam ?? won't the 600psi drive the mixture out the vent (something like an enema) ?
is the polymer mixed in with the water ? evenly distributed or globby ??
RE: Design of a stirrer
RE: Design of a stirrer
Polymer is evenly distributed in water (agglomeration is prevented by use of talc / surfactant).
Water is used as a transport agent "to" the valve where it is discharged...after discharge water is not important but is critical before that to help drive the polymer to the exit (besides also helping as a dispersing agent during saturation which generates heat due to exothermic polymerization process).
Polymer & Water are "Immisscible" - polymer does not dissolve in water....just floats around and based on water table @ higher temp. evenly "moves" with water (not @ top as densities become same)...
Maybe just my communication is bad as probably I am not being able to explain it properly .....this process is termed "Pre-expansion Of Polypropylene beads (EPP)" in an autoclave.
RE: Design of a stirrer
RE: Design of a stirrer
RE: Design of a stirrer
RE: Design of a stirrer
If you let it sit, the oil will float on the vinegar.
When you shake it up well, the two will mix temporarily.
ajxxx wants to get the mixture out of the vessel while it is still mixed up.
B.E.
RE: Design of a stirrer
At least that was my read.
And thus my suggestion to pull the pellets off the top of the kettle, where they are floating...
RE: Design of a stirrer
I must be missing something here. I will admit that I had trouble with the file that he uploaded (100% a problem on my end) but either way, I must be failing to grasp what the problem is if he can't have a standpipe in the vessel, where he pumps more water into the bottom to force the polymer out through the tube. Or perhaps trying the floating tube as rb1957 suggested.
What I had said before is that you would have the end of the tube a few inches below the top of the vessel, but this would be wrong. My thinking is that if you are making this in batches, you determine where the height of the water-polymer interface will be and set the end of the tube to be at exactly this height. Each batch, you add (ECACTLY) enough water to cover - JUST BARELY - the end of the pipe, then you add however much polymer you need for the batch and the space above the polymer will be filled with steam.
When you open your valve at the bottom of the tank, the polymer is pushed out until you get steam throttling through the valve. To maximize the amount of polymer coming out, you might try having a funnel shape on the upper end of the inner standpipe, up to almost the full diameter of the inside of the tank.
If that wouldn't work, then I have to say that I have no idea what's going on.
Engineering is not the science behind building. It is the science behind not building.
RE: Design of a stirrer
A single hole in the top of the tank seems to be the way to go. Or else I have no idea what's going on either.
RE: Design of a stirrer
but like i said, people have examined this problem in detail and arrived at workable solutions, after investing way more effort and thought than we're likely to put in. And i'd expect that all the ideas we're "pop-corning" have been considered already and incorporated or rejected.
just my 2c ...
RE: Design of a stirrer
RE: Design of a stirrer
Mike Halloran
Pembroke Pines, FL, USA