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Posted by Francisco Gil on March 30, 2009 at 12:26:07:
I am working on a Cleaver Brooks fire tube boiler 600 BHP, 250 PSIG in order to tune the combustion. This boiler was originally designed to burn fuel oil but about 10 years ago it was converted to burn natural gas as well. The gas train was designed to have 42 "H2O after the gas regulator (this is stated by Cleaver Brooks for this type of boilers) but when working at this pressure the CO measurement is very high (mor than 1000 ppm). Because of this, I tried decreasing the natural gas pressure and found out that adjusting it to 25 "H2O works fine. To do this I had to increase the opening of the automatic gas control valve in order to keep the gas flow to about 20,000 cfh. With this adjustment the O2 stays between 2% and 6% from high fire to low fire, and CO is always less than 400 ppms but the flame looks always too yellow. Why did I have to change the design pressure to get good combustion parameters? Why does the flame don't look good?
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