Material balance in steam boiler
A simplified flow sheet of water in boiler circuit is
presented at the above sketch.
The boiler is producing steam (S) which is driven to the
consumption. There its heat is recovered, and the steam is condensed. During
this process a part of water is lost as losses (L) and the remaining returns to
the condensate collection tank as condensate (C). From the condensate collection
tank is driven to the feed water tank (hotwell), maybe through deaerator.
At the hotwell is added also fresh water (Make-up, MU) as
to cover the losses, and the mixture is fed to the boiler as feed water (FW).
Feed water contains dissolved solids from make-up. As the
produced steam is pure distilled water, these dissolved solids are left behind
and its concentration into the boiler is increased.
As to avoid the overconcentration we deconcentrate the
boiler by removing a quantity of concentrated boiler water, replacing by fresh
water. This is called blow down (BD).
From the drawing we can obtain the relationships:
a. FW = MU +
C
b. FW = S +
BD
c. MU = L +
BD
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