UFC 3-240-13FN
25 May 2005
c) Carbonate CO2 contribution (2 x 2) x 0.35 = 1.4
d) Carbon dioxide estimate CO2 = 44.2 + 1.4 = 45.6 ppm CO2 in the steam
NOTE: This is a significant amount of CO2 in steam due to the amounts of P and M
alkalinity in the feedwater. There is some requirement to reduce alkalinity in this quality
of feedwater.
3-2.7.3
Control of Carbon Dioxide by Neutralizing Amines. Amines are organic
compounds containing a nitrogen group similar to ammonia. They are referred to as
"neutralizing amines" in boiler applications because they neutralize acidic (carbonic
acid) conditions by raising the pH of the condensate. These amine compounds are
volatile and escape the boiler with the steam and eventually dissolve in the steam
condensate.
3-2.7.3.1
Control Limits. Amines are added to maintain the pH between 7.5 to 9.0,
ideally 7.5 to 8.5, in all parts of the condensate return system. The condensate pH level
should not be allowed to fall below 7.5 anywhere within the entire condensate return
system or corrosion will occur. For shore-to-ship steam, the Navy requires 8.0 to 9.5 pH
(see Table 3-17). These amines are fed separately from other chemicals and are fed
directly into the boiler steam drum where they vaporize and travel with the steam into
the steam lines. Use continuous amine feed to maintain a constant, effective pH in the
steam condensate.
3-2.7.3.2
Vapor-Liquid Distribution Ratios. Morpholine, diethylamino-ethanol
(DEAE), and cyclohexylamine are the three neutralizing amines approved for use in
military boilers. Limitations of their use are described in paragraph 3-2.7.6. Physical and
chemical properties of these amines are shown in Table 3-4. When steam condenses in
a condensate return system that services multiple heat exchangers in different locations
along the steam distribution system, some amines tend to "fall out" into condensate in
legs close to the boiler while some amines tend to stay in the steam and come out in
condensate toward the end of the steam distribution system. The degree to which this
occurs is called the "vapor-liquid distribution ratio" and is expressed:
Vapor-Liquid Distribution Ratio
=
Amine in steam phase
Amine in condensate phase
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