Compressed Air Best Practices - February 2009 - (Page 12)

| 02/09 Focus Industry POWER PLANTS | COMPRESSED AIR AUDIT OF THE MONTH Boiler Soot Blowing in Power Plants Looking at air vs. steam on an economic basis: STEAM VS. AIR ECONOMICS Operating Cost AIR STEAM Approximately equal but depends on quality of steam used and quality of H2O make-up. Steam capacity can be built in at a moderate cost or may be already available. Steam system is very expensive with piping insulation, steam traps, drip legs, etc. Initial Cost Purchase of a compressor is a large negative. Piping Cost Air piping is generally less expensive than steam. Reliability Obtaining adequate reliability for constant sustained use requires a redundant compressor. Steam available as long as boiler is in operation. Maintenance of Piping and System Air piping is usually low maintenance. Steam piping system requires higher maintenance. Equipment Maintenance New compressors add to the maintenance-required effort. Larger horsepower centrifugal compressors do not readily shut down for short duration and often must stay on running inefficiently. The boiler is already being maintained. Off-Load Capability When Not Needed Steam can easily be turned off and on. Deploy a Dedicated Low-Pressure Air Compressor Often because the large horsepower, high-pressure compressors cannot easily be shut off and also have to run the low-pressure (100 psig) plant, service and instrument air is taken from the high-pressure receiver that is regulated down to the low pressure. This is very inefficient compared to running a dedicated, low-pressure compressor. On a recent compressed air audit at a Midwestern power plant, we developed the following data profile. All costs are based on the power plants selling price of electricity, $0.06/kWh at 8760 hours per year. The progressive thinking here is, “If you don’t use the energy to produce electric power — you can sell it.” All the compressed air, high pressure and low pressure, was supplied by the High-Pressure, “Soot-Blowing Compressors,” 12,500 scfm at an annual electrical energy cost of $195.99 scfm per year or $2,449,876 per year. The low-pressure system has been supplied since the mid 1990s by the high-pressure centrifugals and regulated down to the 100 psig class level. Initially, the low-pressure air demand was relatively small, and it made more sense to use regulated low pressure rather than start up another low-pressure compressor and still not being able to shut off any of the three, 2000 hp, 12 www.airbestpractices.com http://www.airbestpractices.com

Table of Contents Feed for the Digital Edition of Compressed Air Best Practices - February 2009

Compressed Air Best Practices - February 2009 Contents From the Editor Utility-Air News Compressed Air Audit of the Month Air Standards Instrument Air in Nuclear Power Plants Seven Sustainability Projects for Industrial Energy Savings The Pneumatic Advantage Personal Productivity Resources for Energy Engineers Wall Street Watch Advertiser Index Classifieds

Compressed Air Best Practices - February 2009

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