Engineering Application of Exergy Analysis - circe - Universidad de ...

2
EXTERNAL AIR
103
M
101
DRUM
HRSG
3
1
M
104
P
102
COND.
1
COND.
2
ACC.
1
Gas leaving the converter (flow 1) reacts with
external air entering through the hole between the
converter and the heat recovery generator (flow 2)
to form flow 3, which is cooled in the heat
recovery steam generator (HRSG) down to point
4. It should be noted that part of the burning
reactions take place inside the HRSG, but here
reaction and heat transfer have been separated for
simplicity. Besides, the operator has two ways of
controlling the amount of external air (under
certain limits). First, the hood that directs gases
towards the heat recovery steam generator can be
moved upwards and downwards (and thus the gap
between the converter and the hood can be
modified). Second, position of venturi located
downstream can also be modified.
Gas leaving the HRSG (flow 4) is washed and
cooled in two washing venturi. Afterwards, a third
venturi is present to measure the gas flow, and a
blower establishes the draft needed to impulse the
gases. Finally, a three-way valve is located in
ACC.
2
4 5 6 7 8 10
WASHING WASHING VENTURI
BLOWER GASHOLDER
VENTURI 1 VENTURI 2
GAS
T X
T T
M
T
GAS FROM
CONVERTER
TO STEEL
TREATMENT
131
105
106
109 110
M M
111 112
107
108 114
113
121
131
117
122
M
VENT
132
133 134
115 116
118 119
123 124
ACC.
3
120
125
126
129
ACC.
4
128
130
FLARE
Fig. 1. Flow scheme of the gas recovery system.
127
9
136
DEAERATOR
138
STEAM TO NET
135
137
order to choose whether the gas is flared (flow 9)
or stored in the gasholder (flow 10). In this choice,
quality requirements to store gas are considered.
Heat released during gas cooling within the HRSG
is used to transform saturated water from the drum
(flow 101) into a mixture of liquid and steam
going back to that component (flow 102). Part of
the steam produced in the drum (flow 103) is used
for steel treatments (flow 104). Another part flows
through a pressure regulator and then can flow
towards the general steam network of the
steelworks (flow 135) or be used by the deaerator
(flow 136). It should be noted that it is possible to
import medium pressure from the steam network;
accordingly, flow 135 can have two senses.
Steam generated in the drum can also be stored in
four accumulators for later use (flows 114 to 120).
Besides, if there is excess of steam, it is possible to
condense part of it in two condensers (flows 109
and 110). For safety reasons, if pressure increases,
http://www.ecos2010.ch 2 14-17th june 2010, Lausanne, Switzerland
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