Compressor Issues Get New Airing

Plants increasingly re-evaluate economic and technical factors

By Seán Ottewell, Editor at Large

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Speaking at the International Oil Summit in Paris on May 3rd, Royal Dutch Shell downstream director Mark Williams described last year's opening of the Pearl gas-to-liquid (GTL) plant in Qatar as a significant landmark. "With a total investment of $18–19 billion, it illustrates the scale of infrastructure needed to meet rising demand," he said.

Jointly developed by Shell and Qatar Petroleum, the Pearl GTL plant (Figure 1) is the largest of its kind in the world and takes gas from two unmanned platforms 60 km offshore. It's targeted to produce 1.6 billion ft3/d of gas. Post processing, this will generate 120,000 bbl/d of condensate and natural gas liquids, plus 140,000 bbl/d of products such as chemical feedstocks and lubricants.

The plant also is breaking records when it comes to the demands it made on Atlas Copco Rental, Abu Dhabi.

"Atlas Copco Services Middle East has been mainly involved in the provision of equipment used in the massive pre-commissioning program of the Pearl facility," says Akram Tamari, regional rental manager. "As an example, our oil-free compressors and desiccant air dryers were employed in activities that included air blowing for cleaning, generating instrument air and the pneumatic testing of the fuel gas processing and air separation units. In total, our compressors generated more than 300 million m³ of dry 100%-oil-free air for the project, making it one of the biggest compressor rental projects ever."

"You can imagine that during projects of this size they need compressed air on multiple locations... If they need more flow than expected, the compressors are just a phone call away. That's one of the advantages versus owning equipment," notes Kris Herremans, business development manager, Atlas Copco Rental, Rumst, Belgium.

Regardless of whether a plant requires compressed air for commissioning, a turnaround or to maintain production, reliability is crucial, he adds. "The last thing they want is a breakdown of a rental compressor. That's part of our daily challenges — offering state-of-the-art equipment on a 24/7 basis."

RENT VERSUS BUY
However, air systems auditor Chris Beals, president of Air System Management, Centennial, Colo., says one of the major reasons plants call him in is because they want to eliminate the need for rental equipment.

"Saving energy is a key driver for audits, but clients really want to improve the system reliability and eliminate the need to rent air compressors, especially if they're running on diesel. The fuel cost associated with operating diesel-engine-driven rental compressors is enormous. Audits are often carried out, too, for clients who are faced with adding another air compressor because they don't have enough backup capacity," he explains.

He cites the case of a Texas refinery, where he recommended replacing old heatless dryers with internally heated or blower purge units. This, combined with a couple of demand-side opportunities, would cut demand by 8,000 cfm and allow the company to relegate an existing compressor to backup. "It completely did away with the need to install a new compressor. Yes, you do have to spend a fair amount on the new dryers, but you save both in energy use and rental charges and also improve system reliability. The simple payback was less than 24 months. Bear in mind that the typical rental for a single oil-free compressor (1,600–2,200 cfm) is about $8,000/month and that adding a dryer brings this up to about $12,000/month. And that's without even turning it on."

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