We suspect that the exchanger is over-surfaced, which results in very low steam chest pressure inside the exchanger. Because of the low pressure, the condensate pressure is not sufficient to push the condensate to the LP condensate header. Due to this, the exchanger starts getting flooded with condensate until enough pressure builds up to push the condensate out. In our case the condensate needs about 1.5 kg/cm²(g) pressure to move to the header, while the condensate temperature is around 70°C. This intermittent discharge of condensate is creating severe hammering issues in the system.

There was no equalization line between the exchanger and the condensate pot in the original system. We tried installing a temporary equalization connection, but this did not resolve the problem. As a trial, we injected nitrogen (a non-condensable gas) into the exchanger and pressurized the condensate pot to around 1.5 kg/cm²(g). After doing this the system started working smoothly, condensate was flowing continuously to the header, the exchanger did not flood, and the hammering problem disappeared.

Based on this observation there is now a proposal to install a permanent nitrogen connection with a PCV to maintain around 1.5 kg/cm²(g) pressure in the condensate system. However, I am not very confident about implementing this as a long-term solution because I could not find much literature or industry references supporting the practice of injecting nitrogen into a steam condensate system. I am concerned about potential issues such as accumulation of non-condensable gases, possible impact on heat transfer in the exchanger, steam trap performance, two-phase flow instability, or other operational risks over the long term.

Has anyone experienced a similar situation or used nitrogen injection to maintain pressure in a condensate return system? Is this something that is practiced in industry, or would it generally be considered only a temporary workaround? Any insights, experience, or references would be greatly appreciated.

I would appreciate some input regarding best practice for setting MDMT in gas systems.

In a dry high-pressure nitrogen storage system (around 60 barg), gas is let down through a control valve into a downstream header lower pressure. One scenario considered is a control valve fail-open case (not a formal emergency blowdown).

Should a control valve fail-open case normally be treated as a governing basis for MDMT selection of downstream piping and vessels?

Or is it more common practice to:

• Treat low temperatures as local to the restriction/PSV tie-in region

Assume:

• Dry gas (no liquid flashing)

• No cryogenic service

• Downstream overpressure protected by PSV

• Normal restart controls in place.

I’m interested in typical industry practice rather than specific simulation results.

Thanks in advance.

Do you know any method allowing neutralization of off-spec ethylene oxide in other way than reprocessing in EO plant?
Maybe there are any related regulations or standards.

Regards

Background:

- We distill an organic peroxide using 2 columns under vacuum.  

- The first column separates the peroxide from alcohols and is running fine.

- The organic stream is then mixed with 50%NaOH & DI Water before entering the second column  (7 trays)

- The top is condensed and sent to a plain horizontal decanter.  The top layer splits into majority organic material in water (70/30) while the bottom is around 82/18 organic/water.  This bottom layer is refluxed. while the top goes further into the process.

Before shutting down, we were able to run maximum rates without issue.

When trying to restart, our vacuum pump seized and was replaced.  This has been the only major change to the process.

When restarting, we're unable to get past very minimum rates.  When we increase raw material flow, we end up with a small, white layer at the interface in the decanter and the top product is hazy when it is typically crystal clear.

The only major difference I can see is the column dP.  While it was ~30 mbar with the old pump, it's now ~18-22 mbar.  This column is typically at 140 mbar as well (decanter is under same vacuum) 

I can only assume it's potentially weeping and we need to increase vapor flow (more steam to reboiler), but any experience with this type of probably that could be shared would be welcome.  If there's other information that could be vital, please ask.  We increased the raw material feed to try to load the trays more, giving the vapor resistance, but this caused the entire decanter to turn white, due to mixing I assume.