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[morvenlight]

hi,

i want to know about reflux ratio in gas sweetning unit utilizing MDEA..

its moles of water per mole of acid gases

i only have the amount of acid gases that are being flared from reflux drum...its about 12000 scf/h

anyone please tell me how to calculate moles of these acid gases and water in order to know the current reflux ratio of my plant

[paulhorth]

Morvenlight,
No-one's answered this yet, so I'll give it a try, though I am not an amine system expert.

I guess what you are asking is how much water is in the overhead stream and is being condensed and returned, related to the acid gas flow. I suggest the following approach.

Read the temperature and pressure at the column overhead. The water vapour partial pressure is dependent on the temperature and can be found from steam tables. The mol fraction water is equal to this partial pressure divided by the total pressure.
Do the same at the condenser outlet, and determine the water vapour mol fraction in the acid gas stream.
You know the flow of the total acid gas stream, 12000 SCFH, equal to 31.6 lbmol/h. Now you can calculate the water content of this stream, so you can calculate the dry acid gas molar flow.

This acid gas molar flow is in the overhead stream, and you know its mol fraction, so you can calculate the total molar flow of overheads and thus the water flow in the overheads.

Water flow in overheads minus water in the acid gas equals water condensed and returned to the column.

Paul