Compressed Air Best Practices, May 2014, by Hank Van Ormer.
http://www.airbestpractices.com/article/four-action-items-save-money-and-energy-refinery

"This case study shows just how a large facility, which grows over time, is the right situation for a compressed air system assessment. Most optimization opportunities are present and the potential for quick wins and very attractive project ROI’s is very high. Piping systems, upgrading air compressors and air dryers, leak surveys, end uses, are all areas which were improved in the compressed air system at this refinery."