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[Neelakantan]

dear sirs

 

A 42" high pressure natural gas line, 2.2 km long section is to be evacuated by depressurizing  and then burning the gas (there is app 300-400 ppm of H2s) in a burning chamber. The burning chamber capacity is 5000 Nm3/hr; the current operating pressure of the line is 60-80 kg/cm2-g. Thus the total evacuation and disposal time is ~36-48 hours to dispose ~175000 Nm3.

 

An engineering company was asked to provide the system. (see the scheme below);

 dep pid.pdf   88.48KB   19 downloads

The engineering company suggested a tap-off followed by a pressure reduction system (with two pressure reduction valves in series - the first one reducing the tap-off to 25 barg and the second one to 2 barg). To Overcome the J/T effect a line heater is provided before the pressure reduction and an FCV is provided at the end to limit the flow to 5000 Nm3/hr.

 

The client's operation team reviewed the scheme and suggested moving the FCV to the section between the heater and the feed separator. The client's project team has contacted our company to vet the scheme; since the operation is manual and also some condensate is expected to flow into the tap-off, i have suggested a slightly different scheme (hand drawn, below).

 modified prds.pdf   315.61KB   19 downloads

kindly go through them and give your suggestions on the same; and one more question is that since the line is expected to have some condensate, the condensate may remain in the line section as it may not evaporate fully from the line.

 

regards

neelakantan

 

 

Edited by Neelakantan, 14 February 2015 - 11:13 AM.

[Bobby Strain]

You should be having this discussion with your engineering company.

 

Bobby