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4 Case Study
4.1 System Model of a CFB Boiler
Consider a 150 t/h power plant circulating fluidized bed boiler system in Sichuan,
China, whose structure is shown in Fig. 3. It can be seen from Fig. 3. that there
are three entrances as coal feeding, two entrances at bottom of the CFB tank
as primary air, and two entrances of secondary air from different height of bed
tank. Manipulated variables of the CFB boiled are bed temperature (
◦
C), main
steam pressure (MPa), the main steam temperature (
◦
C) and flue gas oxygen
content (%).
Fig. 3.
The circulating fluidized bed boiler system of a power plant
The parameters of the considered 150 t/h circulating fluidized bed boiler are
Bed temperature: 850
◦
C; Steam pressure: 9.8MPa; Steam temperature: 540
◦
C; Flue gas oxygen content: 3% to 5%. The allowed range of zone control of
temperature is 800 to 900
◦
C, the range of steam pressure is 0.01Mpa, the range
of steam temperature is 5
◦
C, and the range of flue gas oxygen-containing is
1%. According to identification method given in [16], equation (4) is identified
to shows the linear model of the CFB boiler. The corresponding step response
is shown in Fig. 4. Choose sampling period
T
=10
s
, the model length
N
= 500.
Then, the dynamic matrix can be constructed.
⎡
⎣
⎤
⎦
T
P
0
T
Y
O
2
=
⎡
⎣
⎤
⎦
44
.
1(1
−
39
.
6
s
)
(117
.
43
s
+1)(878
.
33
s
+1)
e
−
150
s
0
.
00041(623
.
26
s−
1)
(625
s
+1)
2
(13
.
3
s
+1)
e
−
30
s
0
.
0024(425
.
11
s−
1)
(323
.
56
s
+1)
2
e
−
5
.
14
s
(4)
⎡
⎣
⎤
⎦
e
−
40
s
0
.
00015(20
.
19s+1)
(173
.
67
s
+1)(154
.
27
s
+1)
e
−
80
s
B
Q
Q
2
0
.
05
(397
.
24
s
+1)
2
0
.
0011
(93
.
774
s
+1)
2
e
−
37
s
0
.
00051(864
.
8
s
+1)
(296
.
77
s
+1)
2
e
−
100
s
e
−
39
.
43
s
20
.
158
(1701
.
6
s
+1)(1
.
475
s
+1)
0
.
00115
(1270
s
+1)(250
s
+1)
−
0
.
511(211
.
01
s
+1)
(252
.
8
s
+1)
2
(1000
s
+1)
0
.
00008(138
.
6
s
+1)
(673
.
14
s
+1)
2
0
.
00045
(74
.
32
s
+1)(9
.
93
s
+1)
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