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3-Stage Vent Condenser Troubleshooting Assistance

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#1 EnvironChemePerson


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Posted 19 September 2021 - 03:59 PM

Our process utilizes a low pressure header to inert VOCs that may spontaneously combust in the presence of oxygen.  This header has 4 conservation vents that release for overpressure scenarios and a control valve that releases the gaseous solvent+nitrogen+water mixture to a finned vent condenser for inbreathing/outbreathing.


This vent condenser contains 3 stages.  2 stages utilize glycol refrigerant chilled water and the middle stage uses cooling water.  My understanding is that one chilled water stage is active at a time, while cooling water is continuously on to assist in defrosting the other chilled water stage.  Solvent and water condenses on the fins and falls via gravity into a recovered solvent tank.


What actions can I take for optimization of this heat exchanger without complete replacement?  PI trends show temperature to atmosphere cycles based off the chilled water stage that is on.  Outlet temperature doesn't match the design, and I want to validate if condensate entrainment in the exchanger could be occurring - I only really have temperature transmitters so I don't have a good way to model the system.


Really I just want to see if there are any resources on this specific type of vent condenser because the mode-of-operation seems really weird.  I can get flow transmitters or pressure transmitters installed on the inlet/outlet but the fact that our efficiency is so poor has me believing condensate is either getting entrained in the vent condenser or non-condensables aren't being removed through the line to atmosphere.


Also any input on appropriate next steps for capital investment are appreciated.  Would assume since flares aren't feasible for smaller plants like ours that the most effective solution would be a stripping unit.

#2 breizh


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Posted 19 September 2021 - 07:20 PM


It seems that your system has been in operation for some time with relative success. What was the performance at the start up ? within the specification? 

When was the last shut down when these equipment were opened and cleaned ? what about auxiliary equipment like pumps , chiller are they in good conditions ? What about the fluid in the chiller , still ok? 

Do you have way to monitor flowrates , temperatures and pressure on your system ? You may use an external flow meter clamped on pipe (ultrasonic) or ask a third party to perform the measurement for you . 

A good start will be to compare the performance today based on mass and heat balance Vs at the start up of the unit . 

You also need to check whether the materials  are still the same (composition ))


I've been using this set up with a main condenser on Cooling water and the secondary condenser on Chiller prior to release gas to atmosphere. 


Regarding Capex , you should consult your local EPA about the technology suitable for your area; Regulations are becoming tougher and tougher these days. 


I cannot offer more.

Note : Can you draw a simple sketch of the unit or share a P&I D?


Good luck


#3 horatorres


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Posted 23 September 2021 - 08:21 PM



please attach a  P&ID, Temperatures, Flows and Pressure along the condensers step to get an idea of what is your trouble and how to make it optimus.. Data is essential.



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