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[CH3CH2OH]

Hello,

 

At my plant, I am having issues with a molten liquid (Polyethylene Glycol [PEG], 500-8000 Molecular Weight) getting into vent lines and causing plugging on a particular reactor.

 

Downstream from the reactor where PEG is contained, is 2" and 4" vent piping, an overhead condenser, and a conservation vent which vents to a scrubber.  The PEG has been found in the piping between the conservation vent and the scrubber and has lead to plugging in this line and pressure accumulation in the reactor.

 

I am trying to do some root cause analysis and troubleshooting and I am quite baffled by this problem.  I am amazed that the PEG is able to transfer this far into the vent piping then freeze.

 

My top two theories are:

 

• The PEG has some vapor pressure at the 100-150°C temperature and 0.5 psig pressure we maintain on the reactor -- I'm looking into this one
• The PEG is being swept or entrained by nitrogen in the vessel and it is being carried downstream.  

The second theory is very baffling, but I'm trying to wrap my head around it using an equation.  I'm familiar with the Souders-Brown equation for maximum allowable vapor velocity in a liquid-vapor separator:

 

V = k * SQRT( (r_L - r_v) / r_v )         https://en.wikipedia...–Brown_equation

 

Will this equation work for my analysis?  If so, what do I use for the value "k"?  The given k value is for a mesh demister pad.

 

My intention is to determine the maximum allowable vapor velocity, then ensure I stay below that in the vapor head space to prevent entrainment of the PEG liquid.

 

If not, is there another equation I'm not familiar with (or forgetting)?  Any other theories or thoughts?

 

Thank you!

Edited by CH3CH2OH, 15 November 2017 - 08:28 AM.