Improve Gas Processing by Controlling Condensation

 The best part of Emerson Exchange is getting to hear how customers have solved problems and saved money by using our products. Read on for a particularly interesting example resulting in seven figures savings.

The application here fits the primary purpose for this product to a “T” and Chris Diaz, the end user, was even willing to turn it into an article so you can read about it in the February 2020 issue of Gas Processing & LNG: Improve Gas Processing by Controlling Condensation. Chris provides much more detail, but long story short, the inability for operators to measure and control incoming gas temperature at a pipeline collection site was causing a huge problem with their H2S removal process. Due to temperature fluctuations causing condensation, changing the carbon pellets in the H2S removal towers suddenly became a miserable task.

One day, workers doing the carbon replacement made an unwelcome discovery. The normally granular carbon had turned into a porous solid mass, glued together due to liquids in the gas stream. A task that should have been simple turned into an ordeal stretching into weeks, requiring workers to blast the carbon out of the tower with high-pressure water jets. Worse, it happened to more than one tower, racking up costs of $800,000 and drastically reducing processing capacity at the site as multiple towers went offline while waiting for clean out.

Investigations concluded that the incoming gas temperature had fallen below the dew point, allowing liquid to wet the carbon adsorbent pellets, causing them to form a mass. It was possible to heat the gas at the compressor station just upstream to avoid condensation, but there was no mechanism to measure the temperature when it reached the towers.

It became clear that solving the problem would require adding more temperature measurement points at strategic locations throughout the facility. This in itself presented its own set of problems. Welding thermowells into the existing piping would be a major undertaking:

  • The facility would need to be shut down, and the affected lines purged with nitrogen
  • All the welds would need to be X-ray inspected
  • During the shutdown, production would have to be stopped at roughly 100 wells feeding the facility
  • A shutdown would cost the facility about $1 MM/d.

So, the question became how to add temperature measurements while avoiding these issues. Answer: Rosemount X-well technology. It delivers accurate process temperature data without thermowells or process penetrations. Using a thermal conductivity algorithm combined with an understanding of the conductive properties of the temperature measurement assembly and piping, Non-intrusive process temperature solution accurately measures internal process temperature without the need for welding or cutting. It also measures the ambient temperature so it can compensate for changing local conditions. These factors work together in the instrument to deliver a more accurate process temperature reading than conventional surface measurements. In addition, this solution simplifies measurement point specification, installation, and maintenance, while eliminating new possible leak points.

Occidental installed four X-well transmitters in critical locations. Result: Problem solved. Controlling the gas temperature avoided condensation with liquid formation.

This option avoided adding to the already-stretched capital expense budget. It was also the fastest option to implement, with no operating shutdowns required, so the site did not experience a loss of income. All the wells continued to produce with no interruption, with no special work permits required and no safety concerns created with hot taps.

Where could you use this solution in your plant?

  • Are there places where you could really use additional temperature monitoring points, but don’t have the option of installing conventional instruments with process penetrations?
  • Are your temperature measurement points located where they need to be, or would you like to reposition some of them?
  • Are there existing conventional installations that are maintenance headaches (thermowell failures, leaking, etc.), that you’d like to replace?

Tell us about your situation and what’s on your wish list. You can share with others about your implementations and experiences at the Emerson Exchange 365 community forum, a place where you can exchange ideas and experiences with others in the same situation. It’s a site where you can communicate with experts and peers in all sorts of industries around the world. Look for the Temperature and Oil & Gas Communities, plus other specialty areas for opportunities to provide input, suggestions, and answers.