Conditions
Like fuel, lube oil and engine cooling water, water
for exhaust gas boiler plants is a consumable,
which has carefully to be chosen, treated and
supervised. In the case of improper water mainte-
nance, corrosion and deposits may form up in the
water. Deposits will on their part again result in cor-
rosion and have an adverse effect on heat transfer.
Any additional requirements for water quality speci-
fied in the boiler manufacturer's manual have to be
taken into consideration.
Applications
Two different systems are used:
• Exhaust gas boiler plants generate steam, which
is used as heat transfer agent in other systems.
• With regard to steam turbines, steam generated
by means of the exhaust gas temperature is used
for energy production.
Separate demands made on feed and circulating
water are valid for both application cases.
Exhaust gas boiler without steam turbine
The quality requirements for feed and circulating
water comply with TRD 611 (Technische Regeln für
Dampfkessel = technical rules for steam boilers).
Low-salt and salt-laden feed water can be used if
the specifications in
Table 1
, are kept. The utilisa-
tion of the salt-free feed water is possible, but not
necessary. When using saltless feed water, corre-
sponding limit values are valid for circulating water.
Saltless
feed water
Low-salt or
salt-laden
feed water
pH value at 25
o
C > 9 > 9
Hardness
< 0.06 ûdH
resp.
< 0.01 mmol/l
Conductivity at
25
o
C
< 0.2 µS/cm
1)
Oxygen content < 0.1 mg/l < 0.02 mg/l
Table 1: Requirements for feed water in exhaust gas boilers
1) After strongly acid sample drawing cation
exchanger
Saltless
circulating water
Low-salt or
salt-laden
circulating water
pH value at 25
o
C 9.5 - 10.5 10.5 - 12
Conductivity at
25
o
C
< 50 µS/cm < 5000 µS/cm
Acid capacity up
to pH 8.2
1 - 12 mmol/l
Table 2: Requirements for circulating water in exhaust gas boiler
Exhaust gas boiler with steam turbine
Only saltless feed water, which complies with the
requirements
according to Table 3
, may be used for
steam turbines.
Saltfree feed water
pH value at 25
o
C > 9
Conductivity at 25
o
C < 0.2 µS/cm
1)
Oxygen content < 0.1 mg/l
Iron, total Fe < 0.03 mg/l
Copper, total Cu < 0.005 mg/l
Silicic acid, SiO
2
< 0.02 mg/l
Table 3: Requirements for feed water in steam turbines
1)
After strongly acid drawing cation exchanger
Saltfree circulating water
pH value at 25
o
C 9.5 - 10.5
Conductivity at 25
o
C < 3 µS/cm
Silicic acid, SiO
2
< 4 mg/l
Table 4: Requirements for circulating water in steam turbines
Treatment
The feed water has to be treated with suitable
chemicals. If an exhaust gas boiler without turbine is
used, the conditioning agent must contain the fol-
lowing products:
• Residue softener
• Oxygen binder
• Alkalising medium
• Steam-volatile alkalising medium for corrosion
protection in the condensate system (not compul-
sorily required in the case of saltless feed water)
MAN Diesel & Turbo
1699251-7.0
Page 1 (2)
Quality of water used in exhaust gas boiler plants
B 13 00 0
L28/32S, L27/38S, L23/30S, L21/31S, L16/24S, V28/32S, L16/24, L21/31,
L23/30H, L27/38, L28/32H
2008.10.27
To Next Page
Loading...
Need help?
General
