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March 18-20 2013Goteborg, Sweden
Steam Power Plant Optimization & Retrofit
in An Industrial Park at
Chih-Yao Lin · Jui-Yuan Lee
Cheng-Liang Chen
PSELABORATORY
Department of Chemical EngineeringNational TAIWAN University
Chen CL 1
Steam Power Plant Optimization & RetrofitAn Industrial Park at Taiwan
An Industrial Park at Taiwan – Original design
and recent trend to total site integration
Superstructure-based MINLP Formulationfor total site heat and power integration
Steam Power Plant Optimization & Retrofit
A steel mill
A petroleum refinery
Concluding Remarks
Chen CL 2
Steam Power Plant Optimization & Retrofit
in An Industrial Park at
A Steel Mill and A Petroleum Plant
Chen CL 7
Steam Power Plant Optimization & RetrofitAn Industrial Park at Taiwan
Original design (∼1975): independent operation
Chen CL 8
Steam Power Plant Optimization & RetrofitAn Industrial Park at Taiwan
Original design (∼1975): independent operation
Chen CL 8
Steam Power Plant Optimization & RetrofitAn Industrial Park at Taiwan
Original design (∼1975): independent operation
95→11 Elec
Europe ×1.5USAsia ×1.0
Chen CL 8
Steam Power Plant Optimization & RetrofitAn Industrial Park at Taiwan
Original design (∼1975): independent operation
95→11 Elec
Europe ×1.5USAsia ×1.0
95→11 Elec Fuel
Europe ×1.5 ×4USAsia ×1.0
Chen CL 9
Steam Power Plant Optimization & RetrofitAn Industrial Park at Taiwan
Recent trend: enhanced total site M/E integration
?
?
Steam Power Plant Optimization & Retrofit?
Chen CL 10
Steam Power Plant Optimization & Retrofit
in An Industrial Park at
Superstructure-based MINLP Formulation
Chen CL 12
Steam Power Plant Optimization & RetrofitSuperstructures for Steam Distribution System
Unit
Models
Chen CL 13
Steam Power Plant Optimization & RetrofitModeling the Superstructures
Ω1 =
x
∣∣∣∣∣∣∣∣∣∣∣∣∣∣
fbfwb =
∑i∈I
fbi +∑i∈I
fbdbi ∀b ∈ B
fbfwb Hdeaer + qb =
∑i∈I
fbihbi +∑i∈I
fbdbi H
sat,li ∀b ∈ B
fbdbi = ϕfbi ∀b ∈ B, i ∈ I
fbu =Zbuqb
ηbHLHVu
∀b ∈ B, u ∈ U
Ωbzbi ≤ fbi ≤ Ωbzbi ∀b ∈ B, i ∈ I
zb =∑i∈I
zbi ∀b ∈ B
Boiler
Chen CL 13
Steam Power Plant Optimization & RetrofitModeling the Superstructures
Ω1 =
x
∣∣∣∣∣∣∣∣∣∣∣∣∣∣
fbfwb =
∑i∈I
fbi +∑i∈I
fbdbi ∀b ∈ B
fbfwb Hdeaer + qb =
∑i∈I
fbihbi +∑i∈I
fbdbi H
sat,li ∀b ∈ B
fbdbi = ϕfbi ∀b ∈ B, i ∈ I
fbu =Zbuqb
ηbHLHVu
∀b ∈ B, u ∈ U
Ωbzbi ≤ fbi ≤ Ωbzbi ∀b ∈ B, i ∈ I
zb =∑i∈I
zbi ∀b ∈ B
Boiler
material andenergy balances
blowdown ratio
fuel type/rate
upper/lowercapacitis ↑
one boiler connected toone single steam header
Chen CL 14
Steam Power Plant Optimization & RetrofitModeling the Superstructures
header i
↓turbine t
↓header i′
Ω2 =
x
∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣
wii′t = 4hisii′t
Lii′+1
Bii′fii′t − Lii′W
dii′t − (Lii′ + 1)
Aii′Bii′
∀i, i′ ∈ I, t ∈ C
fii′thii′t = fii′t(hi − 0.8384 hisii′t) + 809.721 ∀i, i′ ∈ I, t ∈ C
Lii′ = aL + bL 4 T satii′ ∀i, i′ ∈ I
Aii′ = a0 + a1 4 T satii′ ∀i, i′ ∈ I
Bii′ = a2 + a3 4 T satii′ ∀i, i′ ∈ I
qcwii′t = fii′t(hii′t − hi′t) ∀i, i′ ∈ I, t ∈ CT
zii′t ≤ zt ≤∑
i, i′ ∈ Ii < i′
zii′t ∀i, i′ ∈ I, i < i
′, t ∈ T
Ωtzii′t ≤ fii′t ≤ Ωtzii′t ∀i, i′ ∈ I, i < i′, t ∈ T
Γtzii′t ≤ wii′t ≤ Γtzii′t ∀i, i′ ∈ I, i < i′, t ∈ T
SteamTurbine
Chen CL 14
Steam Power Plant Optimization & RetrofitModeling the Superstructures
header i
↓turbine t
↓header i′
Ω2 =
x
∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣
wii′t = 4hisii′t
Lii′+1
Bii′fii′t − Lii′W
dii′t − (Lii′ + 1)
Aii′Bii′
∀i, i′ ∈ I, t ∈ C
fii′thii′t = fii′t(hi − 0.8384 hisii′t) + 809.721 ∀i, i′ ∈ I, t ∈ C
Lii′ = aL + bL 4 T satii′ ∀i, i′ ∈ I
Aii′ = a0 + a1 4 T satii′ ∀i, i′ ∈ I
Bii′ = a2 + a3 4 T satii′ ∀i, i′ ∈ I
qcwii′t = fii′t(hii′t − hi′t) ∀i, i′ ∈ I, t ∈ CT
zii′t ≤ zt ≤∑
i, i′ ∈ Ii < i′
zii′t ∀i, i′ ∈ I, i < i
′, t ∈ T
Ωtzii′t ≤ fii′t ≤ Ωtzii′t ∀i, i′ ∈ I, i < i′, t ∈ T
Γtzii′t ≤ wii′t ≤ Γtzii′t ∀i, i′ ∈ I, i < i′, t ∈ T
SteamTurbine
linear unit model
regressioncoefficients −→CW for CT −→
turbine t exists if steam from i
passes it to i′
steam turbine tdoes not existif no steam
passes itfrom any i
to any i′
Chen CL 15
Steam Power Plant Optimization & RetrofitModeling the Superstructures
Ω3 =
x
∣∣∣∣∣∣∣∣∣∣
∑i∈I
fi + fc+ f
w=
∑b∈B
fbfwb +
∑i∈I
fldi
∑i∈I
fihi + fcH
c+ f
wH
w=
( ∑b∈B
fbfwb +
∑i∈I
fldi
)H
deaer
ΩD ≤∑i∈I
fi + fc+ f
w ≤ ΩD
Deaerator
Chen CL 16
Steam Power Plant Optimization & RetrofitModeling the Superstructures
Ω4 =
x
∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣
∑b∈B
fbi +∑
i′ ∈ Ii′ < i
∑t∈T
fi′it +∑
i′ ∈ Ii′ < i
fi′i + fldi + F
psi + f
imp,si
=∑
i′ ∈ Ii′ > i
∑t∈T
fii′t +∑
i′ ∈ Ii′ > i
fii′ + Fpdi + fi + f
venti + f
exp,si ∀i ∈ I
∑b∈B
fbihbi +∑
i′ ∈ Ii′ < i
∑t∈T
fi′ithi′it +∑
i′ ∈ Ii′ < i
fi′ihi′ + fldi H
deaer+ F
psi H
psi + f
imp,si H
imp,si
=( ∑
i′ ∈ Ii′ > i
∑t∈T
fii′t +∑
i′ ∈ Ii′ > i
fii′ + Fpdi + fi + f
venti + f
exp,si
)hi ∀i ∈ I
SteamHeader
Chen CL 17
Steam Power Plant Optimization & RetrofitModeling the Superstructures
Ω5 =
x
∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣
∑i, i′ ∈ Ii < i′
wii′t =∑j∈J
wtj ∀t ∈ T S
zt =∑j∈J
ztj ∀t ∈ T S
Γtztj ≤ wtj ≤ Γtztj ∀j ∈ J , t ∈ T S
∑t∈T S
wtj +∑
m∈Mwmj = W
dem,sj ∀j ∈ J
∑i, i′ ∈ Ii < i′
∑t∈T E
wii′t + wimp,e
= Wdem,e
+∑
m∈M
∑j∈J
wmj
ηm+ w
exp,e
zimp,e + zexp,e ≤ 1
wimp,e ≤ Ω zimp,e
wexp,e ≤ Ω zexp,e
PowerBalance
Chen CL 17
Steam Power Plant Optimization & RetrofitModeling the Superstructures
Ω5 =
x
∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣∣
∑i, i′ ∈ Ii < i′
wii′t =∑j∈J
wtj ∀t ∈ T S
zt =∑j∈J
ztj ∀t ∈ T S
Γtztj ≤ wtj ≤ Γtztj ∀j ∈ J , t ∈ T S
∑t∈T S
wtj +∑
m∈Mwmj = W
dem,sj ∀j ∈ J
∑i, i′ ∈ Ii < i′
∑t∈T E
wii′t + wimp,e
= Wdem,e
+∑
m∈M
∑j∈J
wmj
ηm+ w
exp,e
zimp,e + zexp,e ≤ 1
wimp,e ≤ Ω zimp,e
wexp,e ≤ Ω zexp,e
PowerBalance
shaft demand W dem,sj
andelectricity de. W dem,e
are givenshaft balance −→
shaft demandprovided byturbine or motor
electricity balance
to prevent coexistenceof powerimport/export
Chen CL 18
Steam Power Plant Optimization & RetrofitMINLP Formulation
minx∈Ω
J =[
Cwfw + C imp,ewimp,e − Cexp,ewexp,e (water; electricity imp/exp)
+∑b∈B
∑u∈U
Cufbu +∑
i,i′∈I
∑t∈T C
Ccwqcwii′t (fuels; cooling)
+∑i∈I
(C imp,s
i f imp,si − Cexp,s
i f exp,si
) ]thrs (steam import/export)
− JAOCbase + JAIC
retrofit (base AOC; retrofit cost)
Ω = Ω1 ∩ · · · ∩ Ω5 (searching space)
x ≡
zb, zt, zm; zbi, zii′t, ztj; zimp,e, zexp,e;
fbfwb , fbu, fbi, f
bdbi ; fi, f
ldi , f imp,s
i , f exp,si , f vent
i ;
fii′, fii′t; f c, fw; hi, hbi, hii′t;
qb, qcwii′t; wii′t, wtj, wmj; wimp,e, wexp,e
∀b ∈ B, u ∈ U , t ∈ T ,m ∈M, i ∈ I, j ∈ J
(variables)
Minimizing AOC
or
Max Retrofit Benefit
Chen CL 21
Steam Power Plant Optimization & RetrofitA Steel Mill: Current Status
B3: coal, B1, B2, B4: SG; ΩB′is= 375, 750, 600, 800
Chen CL 22
Steam Power Plant Optimization & RetrofitA Steel Mill: Current Status
B3: coal, B1, B2, B4: SG; ΩB′is= 375, 750, 600, 800
Total working hours 8,600 hr/yr
Coal LHV 28,000 kJ/kg
Synthesis gas LHV 52,000 kJ/kg
Electricity price (export) 0.0833 USD/kWh
Steam price (for export) 33.333 USD/ton
Coal price 120 USD/ton
Synthesis gas price 192 USD/ton
Synthesis gas flow rate 75.5 ton/hr
Steam demand (17.6 kg/cm2) 300 ton/hr
Steam demand ( 2.0 kg/cm2) 278 ton/hr
Power demands 300 MW
Shaft power demand 1 25 MW
Shaft power demand 2 30 MW
Chen CL 23
Steam Power Plant Optimization & RetrofitA Steel Mill: Current Status
B3: coal, B1, B2, B4: SG; ΩB′is= 375, 750, 600, 800
Power self-sufficient Power import allow
Optimization Scenario 1 Scenario 3
Retrofit Scenario 2 Scenario 4
Chen CL 24
Steam Power Plant Optimization & RetrofitA Steel Mill: Current Status
AOC 164.53∆AOC -
T I C -PB (y) -
mUSD/y
Chen CL 25
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 1 – Power Self-sufficient?
AOC 164.53∆AOC -
T I C -PB (y) -
Chen CL 25
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 1 – Power Self-sufficient?
AOC 164.53∆AOC -
T I C -PB (y) -
zb=1 =1 zexp,e=0zbi=11=1 zimp,e=0
i = 1zt=4 zb=3 zb=4
zbi=32 zbi=42
i = 2zb=2zbi=23 zt=5 zt=6 zt=7
i = 3 ztj=72
zt=1 zt=2 zt=3i = 4 ztj=31 i = 4
zii′t=342 zii′t=144 zii′t=246
i = 5zii′t=255
zii′t=361 zii′t=362 zii′t=363 zii′t=164 zii′t=265 zii′t=266 zii′t=267i = 6 i = 6
Chen CL 26
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 1 – Power Self-sufficient
AOC 164.53 133.31∆AOC - -33.22
T I C - -PB (y) - -
Chen CL 26
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 1 – Power Self-sufficient
AOC 164.53 133.31∆AOC - -33.22
T I C - -PB (y) - -
reduceMHP steam
turn off ST1(condensing)
Chen CL 26
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 1 – Power Self-sufficient
AOC 164.53 133.31∆AOC - -33.22
T I C - -PB (y) - -
reduceMHP steam
turn off ST1(condensing)
increaseHP steam
increase←−VHP steam
Chen CL 26
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 1 – Power Self-sufficient
AOC 164.53 133.31∆AOC - -33.22
T I C - -PB (y) - -
reduceMHP steam
turn off ST1(condensing)
increaseHP steam
increase←−VHP steam
increase MP steam extraction
inc. exportMP steam
Chen CL 26
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 1 – Power Self-sufficient
AOC 164.53 133.31∆AOC - -33.22
T I C - -PB (y) - -
reduceMHP steam
turn off ST1(condensing)
increaseHP steam
increase←−VHP steam
increase MP steam extraction
inc. exportMP steam
increaseelectricitygeneration
stop exportelectricity
↓ 20%
Chen CL 27
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 2 – Power Self-sufficient
AOC 164.53 133.31∆AOC - -33.22
T I C - -PB (y) - -
reduceMHP steam
turn off ST1(condensing)
increaseHP steam
increase←−VHP steam
increase MP steam extraction
inc. exportMP steam
increaseelectricitygeneration
stop exportelectricity
zt=8=1zii′t=248zii′t=258zii′t=268
reach maxcapacity
−→ ←−space forexpansion
Chen CL 28
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 2 – Power Self-sufficient
AOC 164.53 133.31 123.92∆AOC - -33.22 -9.39
T I C - - 5.00PB (y) - - 0.53
reduceMHP steam
turn off ST1, ST2(condensing)
increaseHP steam
increase←−VHP steam
increase MP steam extraction
inc. exportMP steam
stop exportelectricity
inc.electricity
newST8
zt=8=1zii′t=248=1zii′t=258=0zii′t=268=0
↓ 7%
Chen CL 29
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 3 – Power Import Allow
AOC 164.53 133.31 123.92 72.24∆AOC - -33.22 -9.39 -92.26
T I C - - 5.00 -PB (y) - - 0.53 -
reduceMHP steam
turn off ST1(condensing)
increaseHP steam
increase←−VHP steam
increase MP steam extraction
inc. exportMP steam
decreaseelectricitygeneration
importelectricity
Chen CL 30
Steam Power Plant Optimization & RetrofitA Steel Mill: Scenario 4 – Power Import Allow
AOC 164.53 133.31 123.92 72.24 53.46∆AOC - -33.22 -9.39 -92.26 -18.78
T I C - - 5.00 - 5.00PB (y) - - 0.53 - 0.27
reduceMHP steam
turn off ST1, ST2(condensing)
increaseHP steam
increase←−VHP steam
increase MP steam extraction
max exportMP steam
importelectricity
dec.electricity
newST8
Chen CL 31
Steam Power Plant Optimization & RetrofitA Steel Mill: Summaries
Power Self-sufficient Power Import Allow
Current Optimization Retrofit Optimization RetrofitAOC 164.53 133.31 123.92 72.24 53.46
∆AOC - -33.22 -9.39 -92.26 -18.78
T I C - - 5.00 - 5.00
PB (y) - - 0.53 - 0.27
Decrease condensing rate Reduce power generation
Increase MP steam(17.6 kg
cm2
) More MP steam export
Operational Optimization ⇒ Annual operating cost reduced by 20%
Chen CL 34
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Current Status
Existing layout and current operating conditions
Chen CL 34
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Current Status
Existing layout and current operating conditions
Total working hours 8,000 hr/yr
Fuel oil LHV 28,000 kJ/kg
Synthesis gas LHV 42,800 kJ/kg
Electricity price (import) 0.1267 USD/kWh
Steam price (import) 33.333 USD/ton
Fuel price (oil) 824.33 USD/ton
Steam demand (101.0 bar) 13.0 ton/hr
Steam demand (20.6 bar) 146.3 ton/hr
Steam demand (4.5 bar) 196.5 ton/hr
Power demand 81.3 MW
Shaft power demand 1 15.2 MW
Shaft power demand 2 7.7 MW
Shaft power demand 3 5.3 MW
65% of self-production←− cost
Chen CL 35
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Current Status
Existent layout and current operating conditionsAOC 299.28
∆AOC -T I C -
PB (y) -
mUSD/y
Chen CL 36
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 1
Best operating conditions without modifying layout and units?AOC 299.28
∆AOC -T I C -
PB (y) -
Chen CL 36
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 1
Best operating conditions without modifying layout and units?AOC 299.28
∆AOC -T I C -
PB (y) -
zb=1 zexp,e, zimp,e zb=2zbi=11 zbi=22
i = 1 i = 2
zb=3 zb=4 zt=1 zt=2zbi=33 zbi=43 ztj=21
i = 3
zt=3 zt=4ztj=32 ztj=43
i = 4zii′t=344
zii′t=353 zii′t=151 zii′t=252
i = 5
zii′t=131
Chen CL 37
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 1
Best operating conditions without modifying layout and unitsAOC 299.28 297.19
∆AOC - -2.09T I C - -
PB (y) - -
increaseVHP steam
decrease MP steam
increaseMP steamextraction &electricity
Chen CL 38
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 2
Retrofit of steam system without installing new equipment?AOC 299.28 297.19
∆AOC - -2.09T I C - -
PB (y) - -
Chen CL 38
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 2
Retrofit of steam system without installing new equipment?AOC 299.28 297.19
∆AOC - -2.09T I C - -
PB (y) - -
excess MPlarge let-down
less LP
Chen CL 39
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 2
Retrofit of steam system without installing new equipment?AOC 299.28 297.19
∆AOC - -2.09T I C - -
PB (y) - -
zb=1 zexp,e, zimp,e zb=2zbi=11 zbi=22
i = 1 i = 2
zb=3 zb=4 zt=1 zt=2zbi=33 zbi=43 ztj=21
i = 3
zt=3 zt=4ztj=32 ztj=43
i = 4zii′t=344
zii′t=353 zii′t=151 zii′t=252
i = 5
zii′t=131
zii′t=141
Chen CL 40
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 2
Retrofit of steam system without installing new equipmentAOC 299.28 297.19 261.85
∆AOC - -2.09 -35.35T I C - - 10.00
PB (y) - - 0.28
increaseVHP steam
turn off B3, B4
increaseMP steamextraction &electricity
condensingturbine
⇒ extractionturbine
reducelet-down
MP→LP
↓ 12%
Chen CL 41
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 3
Retrofit of steam system with installing new equipmentAOC 299.28 297.19 261.85 257.84
∆AOC - -2.09 -35.35 -4.00T I C - - 10.00 5.00
PB (y) - - 0.28 1.25
increaseVHP steam
turn off B3, B4
increaseMP steamextraction &electricity
condensingturbine
⇒ extractionturbine
reducelet-downHP→MP→LP
new ST5
zt=5=1zii′t=235=1zii′t=245=0zii′t=255=0
Chen CL 42
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 4
Integration of steam import in a steam systemAOC 299.28 297.19 261.85 257.84 253.95
∆AOC - -2.09 -35.35 -4.00 -3.89T I C - - 10.00 5.00 2.50
PB (y) - - 0.28 1.25 0.64
turn off B3, B4
increaseMP steamextraction &electricity
condensingturbine
⇒ extractionturbine
reducelet-downHP→MP→LP
new ST5
steamejector
↑import steamfrom steel mill
Chen CL 43
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 4
Integration of steam import in a steam system
Chen CL 43
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Scenario 4
Integration of steam import in a steam system
Chen CL 44
Steam Power Plant Optimization & RetrofitA Petroleum Plant: Summaries
Optimization Retrofit
Current Current Without With Steam(106 USD/yr) Condition Layout New Unit New Unit Ejector
AOC 299.28 297.19 261.85 257.84 253.95
∆AOC - -2.09 -35.35 -4.00 -3.89
T I C - - 10.00 5.00 2.50
PB (y) - - 0.28 1.25 0.64
Condensing → Extraction turbine Decrease power generation
Increase HP steam (101 bar) Import more MP & enhanced by HP
Installed cost ≈ 10 mUSD ⇒ AOC reduced by 12.5%
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