Hydrocarbon Compression

Archive for the ‘Process Cooling’ tag

Process Cooling Insuffient Air Flow

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If the air flow existing from the tube bundle is hotter than the effluent gas, the chances are there is insufficient air flow to properly cool the gas. In particular, if the air temperature blowing out of the effluent end of the tube bundle is only 10°-15° cooler than the effluent gas, lack of air flow is almost certainly the culprit.

Written by Jack

October 25th, 2009 at 12:04 pm

Gas Cooling Process

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Underground gas transmission pipelines are externally wrapped in a protective plastic type coating. Gas temperatures in excess of 130°F to 140″F can cause embrittlement and eventual failure of this coating. For this reason, the usual industry practice is to specify that natural gas discharging into a transmission pipeline be cooled to less than 120°F. Also gas entering a pipeline is cooled to promote efficient glycol dehydration. For example, with an ordinary triethylene glycol dehydration unit, operating at a 900 PSIG contactor temperature, an inlet gas temperature of not more than 125°F is necessary to meet pipeline moisture specifications.

 Gas Cooling Process

Natural gas effluent from a compressor is typically 150°F to 200°F. Wellhead gas from high pressure wells is also in this temperature range. Most often, gas is cooled in a fin-fan air cooler as shown in figure 5-1. The fan is rotated by a belt drive powered by a compressor’s engine. Alternately, the fan may be powered by circulating high pressure oil.

WHAT CAN GO WRONG

  • Air cooling is deceptively simple. For instance, I have encountered
  • the following problems while troubleshooting air coolers:
  • Air leakage around the tube bundle.
  • Fan speed too low.
  • Belts loose.
  • Fan blade pitch wrong.
  • External tube fouling.
  • Internal tube fouling.
  • Maldistribution of gas in parallel tube passes.
  • Excessive number of tubes plugged.
  • Pass-partition baffle leaking.
  • Excessive gas inlet temperature.

Written by Jack

October 23rd, 2009 at 2:44 pm