liquid circulation vacuum pump

[byl]

We are using liquid ring vacuum pump to create vacuum in few reactor. In order to reduce the water consumption, we recycle the water. The problem we have is that solvent, beiong soluble in water, accumulate in the water. This can build up to 40%.
I was wondering if there was any way of replacing water by another liquid for which the solubilty of solvent will be very low.
I heard about using H2SO4 (no corrrosion if concentrate) but we will have water coming from the reactors, therefor it will turn into a very corrosive solution.

Does any one got a solution? We don't want to change to dry vacuum pump (cost).

Thanks

 

[gelpino]

I think are necessary some more info...about solvent and reactor you use....
Regards

 

[Torricelli]

which kind of solvents are you using? the easiest would be to use the solvent as recirculated seal liquid? H2SO4 is definitively not a good idea if you condense water in the pump. Glycol or thermal oils are sometime used as seal liquid.

Torricelli

http://www.vacuum-guide.com

 

[byl]

Our problem rely on the fact we use lot of different solvents:
IPA, MeOH, IMS, Hexane, Toluene, Heptane, Dichloromethane, Xylene, Acetone, Butanol, Ethyl acetate, THF.
That's only to name the most commonly used.

I read about using oil, but i am afraid of the mixture with water (bad memories of blowing a head gasket on my car!)

 

[moltenmetal]

Why not trap the solvents on their way into the liquid ring compressor? A refrigerant trap will probably help a lot.

 

[byl]

it is not trap because at very low pressure (30mmbar), the boiling point of the solvent are very low. We only have cooling capacity to go down to -10degC. As well as this there is some air entry in the system and nitrogen is often blow in the reactor for safety reason which create some kind of a blanket in the heat exchanger reducing dramaticaly is efficiency

 

[Torricelli]

it sounds like a good application for a T4 dry running vacuum pump with a discharge condenser. What are vacuum and suction capacity?

Torricelli

http://www.vacuum-guide.com

 

[byl]

We have 8 reactors on the system, with capacity between 2500L and 5000L. The vacuum required is 30mbar.

I was tempting by the solution with the oil, but I am a bit afraid that it might be decompose by some solvent (THF in particular).

 

[pmureiko]

I agree with Toricelli that a dry vacuum pump is worthwhile to look at for this application. I've had good experience with Busch and Edwards among the suppliers out there.

 

[pmureiko]

I reread your initial question and missed the part about not picking the dry vacuum pump because of cost. I recommend you take a look at the life time cost of the vacuum pump. It sounds like the cost of a modified liquid ring system may approach that of using the dry pump in the first place. Also the cost of handling solvent contaminated fluid may quickly overwhelm the initial capital savings.

 

[byl]

I totally agree with you all, the dry vacuum pump is the solution. After a rough estimate, I get a pay back time of 3 1/2 year. The only problemn is that the actual economical situation only allows us to make saving but no real investment.
Does anyone know second hand dealer with good prices on dry vacuum pump??
Thanks all of you anyway!

 

[Torricelli]

Where are you (geographical area)? and tell us if you like the suction capacity (or the electrical power installed for the existing liquid ring vacuum pump).

 

[byl]

I am in Ireland.
At the moment we are operating two liquid ring vacuum pump of 5.5kw each

 

[rmw]

Graham now has a good hook and claw dry vacuum pump that is designed so that it can start up completely flooded. Give them a call.

 

[Torricelli]

A 80-100 m³/h dry vacuum pump will do the job. A second-hand pump - or a new set (pump, condenser, flame arrestors, frequency converter) from Korea, would be very unexpensive but the ATEX certification could be a real challenge. I would prefer a screw- than a claw-pump but important for your solvent is the T4-certification.
hope it helps, regards
Torricelli

http://www.vacuum-guide.com

 

[unclesyd]

Here is an excellent site for Liquid Ring pumps and others. The first link is an excellent pamphlet and the second is Sterling’s home page. You need to check their downloads, truly outstanding.

http://www.sterlingfluidsystems.com/art/

procam/pdf/FundamentalsRev1.pdf

http://www.sterlingfluidsystems.com/

 

[seanatkinson]

Dry running vacuum pumps bought new for installation into an ATEX regulated plant will be complex as the manufacturers response to ATEX has included the installation of many new temperature switches & pressure switches. These will need to be incorporated into a shutdown system meeting IEC 61508, althought the SIL might be as low as 1, depending on your risk profile.
Overall I would suggest to go for a dry system as the lifetime cost will be less.

 

[brite750]

If you wanted to stay with liquid ring and water seal fluid, would you be interested in recovering the solvent to reuse the water and even reuse the solvent. This way nothing is wasted. We have designed many types of evaporative recovery systems, using falling film, columns, or wiped film technology.