Sizing Of Key Components; Sizing Of 4-Draught Steam Boiler - Bosch CHP CE 240 NE Technical Manual

3.3

Sizing of key components

With the customer-specific requirements concerning
steam, LT heat and current demand, the optimum
system combination is selected. The occurring
temperatures, pressures and mass flow rates of the
individual components must be optimally matched.
3.3.1

Sizing of 4-draught steam boiler

For sizing the steam boiler, it is important in a first step,
to determine together with the user the most important
design criteria:
• Fuel
• Vapour pressure
• Vapour demand
The amount of steam required by the customer, results
from the total of the steam amounts that are used for the
respective processes. To which extent different
concurrences have to be considered here, has to be
determined together with the user.
To determine the amount of steam that the boiler has to
provide, simply the customer steam amount and the
internal consumption (for feed water heating, heat
losses etc.) have to be added.
As an estimate, this internal steam amount can be
assumed as a value between 5 % ... 15 % of the
customer steam amount, depending on portion and
temperature of the reusable condensate. For optimum
waste heat use of the CHP flue gases by the steam
boiler, a base load requirement as continuous as
possible is decisive.
IMPORTANT: If the maximum steam amount must be
available at any time, e.g. also if the CHP module is idle
due to missing LT heat utilisation or maintenance, the
output of the fourth draught must not be considered for
sizing.
Systemlösung – 6 720 885 509 (2018/03)
Engineering information and sizing
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[%]
120
100
80
60
40
20
0
3
Fig. 13 Ratio boiler output/required steam amount for
system
[1] Required steam amount for system
[2] Required boiler output with consideration of waste
heat part
[3] Required boiler output without consideration of
waste heat part
Performance of fourth draught
(waste heat, CHP module)
Performance first ... third draught
The higher the waste hear performance, i.e. the flue gas
mass flow rate of the CHP module, the more flue pipes
are required in the steam boiler for the fourth draught.
Because these flue pipes "miss" in the third draught, the
maximum steam output in the boiler is reduced. Possibly
a larger boiler, with correspondingly higher costs, is
required.
Therefor it makes sense to set the output of the fourth
draught in relation to the total output with 20 % of the
total output.
Higher performance of the fourth draught is
possible, but must be checked precisely by
Bosch Industriekessel GmbH.
In this case please contact the responsible
sales person.
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6 720 819 535-15.1T
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