Re: [PipingDesign] Compressed Natural Gas Cooler

From: <elie>
Date: Thu Jul 21 2005 - 15:06:00 EDT

Thanks for your reply,

I am working for a consultant and I don't know why the coolers are undersized. During hot summer days when ambient temperature reaches 105+ deg, the temperature of the gas exiting the coolers is 115+ deg. The dehy is about 150 feet from the compressor. Relative humidity is ~18% and the station is 7000 ft above sea level (asl), P(atm) 11.4 psia.

The produced water is from coal bed methane and is not clean. Fouling the exchanger is a big concern. We will have to install filtration (two - 60" dia vessels. w/ 5 micron filter elements), and analyze & treat the water. The water transfer line passes through the station. We will install a block valve in the line, and divert the water from the pipeline, through the heat exchanger, and back to the downstream side of the block valve of the pipeline.

The question I have: did nyone implemented this approach successfully?

George McKinney <gmckinney@augustaeng.com> wrote: Elie:
Some comments on your question about natural gas cooling: If I understand what you are saying, you would like to add a gas to water aftercooler downstream of the existing fin-fan compressor coolers, using your available produced water as the cooling medium. If so, there should be a good number of available manufacturers for this type of exchanger. GEA is one company that comes to mind, but if you search the web for "shell and tube heat exchangers" you will get a number of sources. Or, check Compressor Tech2 - Compression Technology Sourcing Supplement - would probably give you a number of sources.

Comments:
First of all, why are your aftercoolers undersized - were they properly sized, what is your ambient air temperature, has compressor suction/discharge changed increasing discharge temperature, are coolers needing cleaning? Generally, determine if you really need the new cooler. Second, what is the BTU/hr load of the gas that you are rejecting - it is going to go to your water, and then what? What will be the temperature of the effluent water? Do you have a discharge that will not be affected by the increased temperature of the water?
And, what is the content of your produced water? Is it really just water, or does it have salt and pipeline liquids? Will it foul the cooler when you go circulating?

It sounds like you have a reasonable approach, but a number of details need resolved.

George McKinney

   The Problem:

   This plant has 4 recip compressor units and 4 TEG dehydration units. The finfan coolers on the compressors are undersized and the gas outlet temperature from the finfans exceeds the dehy unit design inlet gas temperature of 100 deg F, resulting in gas to the pipeline with >7 lb/mmscf water content. On site we have available >2500 bbl/day of produced water at 70 deg F. Plant normal output is 60 MM @ 400 psig.

   We are looking at several option, one of which is installing a gas cooler with water pumps instead of fans, all what we need .

   The Request

  1. Anyone implemented this approach successfully?
  2. We are looking at decreasing the gas temp from 120 deg F to 95 deg. F?
  3. I am looking for a ASME Certified design/fabricator in the USA only?

   Thank a lot. ET.



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[Non-text portions of this message have been removed] Received on Thu Jul 21 15:06:00 2005

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