Compressed Air Best Practices - February 2009 - (Page 16)

| 02/09 | POWER PLANTS COMPRESSED AIR AUDIT OF THE MONTH Boiler Soot Blowing in Power Plants Required compressor pressures are normally conservatively picked to account for large pressure drops through the piping system and control valves of the soot blowers. The overall pressure drop may be as high as 100 psig from the compressor discharge to the soot blower nozzle. Approximately 50 psig maybe lost in the control valve at the entrance to the lance. This is often recoverable. Wall Blowers or IR Blowers Wall blowers are used to clean the furnace walls and will probably use approximately 2,200 to 2,300 scfm. Wall blowers normally operate in one or more pairs depending on the overall cycle. Their basic job is to reduce slag that has accumulated on the pipes in the upper levels of the boiler and superheated region. When the slag builds up on the pipes, the rate of heat transfer decreases. This will lower the temperature of the steam going to the superheated portion of the system therefore decreasing overall efficiency of the system. A normal cycle for a wall blower starts when it energizes and moves out into the furnace to its outermost position where the control valve opens and air starts flowing. It takes three seconds to go from zero to full flow. The wall blower rotates one or more times depending on the amount of cleaning required and then the control valve closes in three seconds and the blower retracts into the wall. The time for a wall blower cycle is approximately three to six minutes and the period of zero flow between wall blower flow to no-flow to flow can be as high as 1.5 minutes in a normal sequence. This may be reduced if cycle time needs to be reduced by overlapping. Long Retractable Lances or IR Blowers Long retractable blowers are used to clean pendant-type radiant surfaces and convection surfaces in high-temperature zones as well as convection passes to reduce slag buildup on the walls of the boiler and for temperature control. These areas are normally in the superheater, reheater and the economizer section. The long retractable lance cycle starts when the lance energizes and extends into the boiler and air starts flowing with the three-second delay from the control valve. The lance travels outward and rotates at the same time. The linear speed varies from 65 to 150 inches per minute depending on the cleaning and temperature zone requirements. One or more revolutions for cleaning 16 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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