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Topic: Propane refrigerant contaminated by Ethane  (Read 8318 times)

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Offline gas_treater

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Propane refrigerant contaminated by Ethane
« on: July 28, 2008, 08:54:19 PM »
Hi, all.

Our LPG recovery plant operate a refrigeration unit which utilizes propane as the refrigerant. The propane refrigerant is used as cooling media in two HE, one of them is a Deethanizer Overhead Condenser where the deethanizer overhead vapor (consist of H2, C1, C2, C3, and a little iC4) is condensed to form liquid reflux, and the other HE is a feed gas chiller where the feed gas (consist of H2 and C1-C6+) is chilled and condensed.

Some month later we found that the propane in the refrigeration system was contaminated by lighter hydrocarbon such as C1 and C2, and we suspected that there is a leak within the Deethanizer Ovhd Condenser since the process side in the condenser has a higher pressure than the refrigerant side and also because of we didn't find any hydrocarbon heavier than C4 in the contaminated propane.

In almost the same time, we saw that the condensing presure is higher than normal and there was a decrease in the HE's chilling capability. I thought that the increase in condensing pressure is a possible consequence for the existence of some non condensable gas in the system. But I haven't had any idea whether the second phenomenon is caused by the same cause or not. Does anybody have any idea about this?

Thank you in advance.

Offline eugenedakin

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Re: Propane refrigerant contaminated by Ethane
« Reply #1 on: July 29, 2008, 08:12:34 PM »
Hello gas_treater,

You are probably righ with a leak from the deethanizer leaking into the propane refrigeration unit.

A higher condensing pressure in the propane chiller exists because the ethane is not converting from a gas to a liquid .. making the process inefficient.

You are correct in your assumptions. Fix the leak between the deethanizer unit and safetly flash off the ethane in the propane unit.  Your system should return to normal.

You have followed this process in a logical way, and it makes sense, based on the many deethanizing units that I have been troubleshooting in the field.

Well done.


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Offline gas_treater

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Re: Propane refrigerant contaminated by Ethane
« Reply #2 on: July 30, 2008, 08:13:40 PM »
Dear Eugenedakin,

Thank you very much for your helpful answer.

Best regards.

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