Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
(OP)
We have a tank where one or more different chemicals are charged, mixed, and then fed to the reactors. After the last addition and before mixing, we currently flush the line to the tank with water to get all the active ingredients into the tank.
We want to stop using flush water and use nitrogen to blow the ingredients into the tank.
All the two phase flow information I have found so far deals with continuous flows of liquid and a continuous flow of gas, L/G is fixed. What we will have is a dynamic situation where the quantity of liquid decreases (full pipe to empty pipe) over time. I suspect the resistance to flow of the nitrogen will vary also, from liquid to two phase to gas flow.
I've done a little thinking on how to design this, but I figured someone else has probably done this before, maybe many times before, so . . . does anyone have a good reference, guidelines, or advice on this?
Thanking you in advance for any help you can give me!
We want to stop using flush water and use nitrogen to blow the ingredients into the tank.
All the two phase flow information I have found so far deals with continuous flows of liquid and a continuous flow of gas, L/G is fixed. What we will have is a dynamic situation where the quantity of liquid decreases (full pipe to empty pipe) over time. I suspect the resistance to flow of the nitrogen will vary also, from liquid to two phase to gas flow.
I've done a little thinking on how to design this, but I figured someone else has probably done this before, maybe many times before, so . . . does anyone have a good reference, guidelines, or advice on this?
Thanking you in advance for any help you can give me!
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.





RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
For the most part, if you have enough nitrogen to initiate flow of the liquid column, and sustain it enough to evacuate it in one go, you quickly run out of liquid and on into mist flow, however quickly depends heavily on length and profile.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
A larger diameter pipeline when blown may allow the gas to pass over the liquid, particularly if there is a change in elevation.
Have you considered having looped piping systems for the chemicals? If you have a looped system, you can takeoff the chemicals at the point of application using a valve and a short length of discharge pipe.
Are any of these chemicals air pollutants? You may need an air pollution control to collect the blown material.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
You must know the score here, details.....
Does the pipe go up, down, level, top of tank, can you blue at high velocity?, what is your venting rater?
Size, flowrate, viscosity, velocity sill make a huge difference as to whether this is feasible or not.
Give us something to work with here.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
I'm sure I forgot something important.
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
We do have a few dedicated, high volume monomer loop systems, but we can't afford one of those for every monomer. Thus, it's a common drum add station that charges about a dozen different monomers.
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
I am also dimly aware that ice pigging technology (really slush pigging) exists, and might be adaptable to your smal lines and elbows.
Mike Halloran
Pembroke Pines, FL, USA
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
Seems to me that you're not likely to simply push the fluid; a lot of it will evaporate, so the vapor will likely go wherever the nitrogen goes after the tank.
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RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
If you got 70' closer, maybe.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
I think this depends on what you're really trying to achieve. Is it simply to get ~90% of the liquid in the line into the tank before mixing OR strip the line of nearly 100% of the liquid to avoid contamination of the system the next time?
If the former the key velocity will be the one that maintains a virtually solid interface between gas and liquid in the vertical section. My estimate is that would need to be in 10 m/sec range, but that might generate some significant pressure drop and if the control is such that you would just stop injecting nitrogen after you hear it enter the tank, then you could generate a lot of vapour.
Much slower than the range I gave above and you risk getting a significant blow by of the gas on the vertical up and horizontal legs. Suspect given your piping layout this will be a matter of trial and error to see how much of the pipe contents make it into the pipe.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
Zdas04 and MikeHalloran – I agree, if we could "swine the line", that would be an excellent solution. But, winter is on the way! I don’t think we have time to help develop the 1” pigging technology at this time. Plus, it would be relatively expensive IF blowing with nitrogen works good enough. If I see it will not work good enough, I may have to revisit pigging.
Racookepe1978 – those dang elbows ruined your brilliant idea! Thanks though!
LittleInch - We don’t have to get 100% of the liquid out of the line. I’d like to see the line 95% empty. These monomers are not incompatible from a safety stand point. We just want to keep the contamination low enough that quality is not affected. We may have to pay some attention to which product follows which product though. 90% empty would be about the minimum we could stand. I did a little Googling yesterday on this line clearing subject and came up completely empty. Today, I’m going to search some more and see what I can find. Then, I’m going to take what I find and your advice and run some numbers.
More later!
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
What you need is something that will go through the bends while not twisting or rolling over: The axial length of the total effective "plug" needs to be longer than the ID of the pipe (minus the maximum expected tolerances and any weld inclusions obviously)
Freeze two shorter plugs with a compatible cord between them.
Get fancy and make a two-part wooden mold for the plug like a pair of bar bells (two spheres on a central smaller diameter section supporting both ends)
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
Have you considered pneumatic transport of the chemicals? You can be completely water free.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
or inject a bit of this stuff and then blow. http://aubingroup.com/products/pipelines/pipeline-...
Or use these things! http://www.ricoservices.co.uk/products/?by=cat&...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
I've used the pipeline gels for cleaning pipe, and they do that very very well. The first time I tried it, I took the manufacturer's name (gel pig) literally and just poured the goop into the launcher chem injection port and opened the gas. What a mess that turned out to be. It really needs a pig in front of it to keep it pushed to the top of the pipe and one behind it to keep it moving (the video omits the leading pig, but I found that it was hard to get much gel to the top of the pipe without it). With two poly pigs (not spheres, spheres made a horrible mess because they could roll over the gel) it is fantastic, but I don't think it really applies here.
The pellets look interesting if there is a way to get them into and out of the line.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
Page 3 on http://www3.epa.gov/gasstar/documents/ll_options.p...
Several references in http://www.netl.doe.gov/File%20Library/Research/Oi...
Those would be for continuous "unloading" through a vertical pipe/tube using 5-10 ft/sec for HCs and 10-20 ft/sec for water. I wouldn't want to wait long (i.e. continuously) to clear my line, so 10 m/sec is sounding like a good starting point to look at.
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
I was thinking because it is only a 1" pipe 25m long, it would survive long enough to prevent too much blow by and you could use slightly lower velocity.
Inserting the "pellet" - You can get 3 port valves? like this http://www.nero.co.uk/Catalogue/Ball-Valves/Three-...
With anything inserted, I wouldn't want to go much more than 5 m/sec
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
It was absolutely a CFC. Probably illegal now...
Mike Halloran
Pembroke Pines, FL, USA
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
There are a number of potential solutions. Pigging with proper design is one, but I've never found this to be practical. The usual approach is to always keep the line full, or let it drain back after every use.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
I don't believe that blowing out with compressed gas would clear the line of solids or other deposits in 10 sec, but it will produce fumes or particulates.
RE: Guidelines/References for Clearing/Blowing Liquid out of a Line with Nitrogen
So, where are these projectiles going to come from and how are they going to hurt someone outside the tank? I don't see it.
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.