Dynamic modelling of a supercritical coal fired po er plant integrated coal fired power plant integrated with post-combustion CO 2 capture 3 rd Post Comb stion Capt re Conference (PCCC3) 3 rd Post Combustion Capture Conference (PCCC3) 8-11 th September 2015 Stefanía Ósk Garðarsdóttir Chalmers University of Technology Division of Energy Technology
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Dynamic modelling of a supercritical coal fired po er plant integrated coal fired power plant integrated
with post-combustion CO2 capture
3rd Post Comb stion Capt re Conference (PCCC3)3rd Post Combustion Capture Conference (PCCC3)8-11th September 2015
Stefanía Ósk GarðarsdóttirChalmers University of Technologyy gy
Division of Energy Technology
Background• There is a need for dynamic modeling of power plants with CO2
capture– Dynamic models are useful for improving design operation– Dynamic models are useful for improving design, operation
and control of new and existing plants– Dynamic power plant modelling has been done to some
extent but often some important characteristics are left out (e.g. feedwater heaters, steam drum level…)
Aim
• Develop a simplified representation of a supercritical coal-fired l tpower plant
• Construct a dynamic model of a coal fired power plant according to y p p gthe simplified design
• Link the power plant model with a model of a post combustion CO• Link the power plant model with a model of a post-combustion CO2capture (PCC) system from previous work– Identify effects of PCC on the power plant dynamics
Steam cycle simplification• Starting point: Existing detailed steady-state model of
Nordjyllandsvaerket power plant constructed in Ebsilon Professional‒ Detailed model validated against plant data‒ Detailed model validated against plant data
Power plant model overview
FGD Stack
Water
Steam
Air
Flue gas
Fuel
Econ.
Superh2
Reheat2VHP HP IP LP1 LP2
W.Wall
Reheat1
Superh1
Comb.Load set point
To VHP and HP spray
FWH
Boiler
Dynamic process modeling
• Dynamic power plant model constructed in Dymola accordingconstructed in Dymola according to simplified design– Based on Modelica language
(aca sal eq ation based(acausal equation based modeling)
– Components from Modelon’sThermalPower library, the Modelica standard library and custom made componentscustom made components
Dynamic model evaluation• Steady-state results in Dymola compared with plant data• Main input to the model is the load curve
ar]
t [M
W]
Pres
sure
[ba
ener
ator
out
puG
e
Power plant model – example of results
• Boiler dynamics – Transition from full load to 70% part load m
ber [
kg/s
]
kg/s
]
from full load to 70% part load
• Load change implemented by mbu
stio
n ch
am
wat
er w
alls
[k
Load change implemented by ramping down fuel feed rate
flow
from
com
am fl
ow fr
om
• Dynamics on gas side very fast compared with the water side Fl
ue g
as f
Stea
CO2 absorption model
• Rate-based model originally developed by Åkesson et al.developed by Åkesson et al. (collaboration with ModelonAB)– 30 wt% MEA assumed non30 wt% MEA, assumed non-
volatile and degradation not accounted for
• Chemical reactions atChemical reactions at equilibrium, influence of reaction rates on mass transfer accounted for by using anaccounted for by using an enhancement factor
System model overviewTo stack Pure CO2
FGD
Water
Steam
Air
Flue gas
Fuel
Solvent
Econ.
Reheat2
Control signal
Superh2
Reheat2
Reheat1
Superh1
VHP HP IP LP1 LP2LP_CCS
W.Wall
Comb.Load set point
FWH
Boiler
To VHP and HP spray
Integration of PCC unit• Steam extracted from an
additional extraction point in the LP turbine section
• Extraction pressure maintained at ~3bars in the
To stack Pure CO2
maintained at 3bars in the load range tested by throttling steam between LP turbine stages
turbine stages• Steam extraction to PCC
system affects e.g. mass From reheat
To feedwater heaters
flows in FWH system– Effective control of water levels
in tanks and heat exchangers of
VHP HP LP_CCS LP1
To reheat
LP2IP
importance
Preliminary resultsTransition from full load to 70% part load- load change implemented by ramping down fuel feed rate
[kg/
s]
w [k
g/s]
[kg/
s]
te [%
]
Fuel
inpu
t
Flue
gas
flow
Fuel
inpu
t
Cap
ture
rat
Preliminary results
°C]
W]
l inp
ut [k
g/s]
tem
pera
ture
[°
tor o
utpu
t [M
W
Fuel
Reb
oile
r
Gen
erat
Similar trends, small effects of PCC system?
Preliminary results
kg/s
]
S bi li i i
l inp
ut [k
g/s]
e st
eam
flow
[kSteam turbine limitations –minimum flow and changes in steam quality
Fuel
LP tu
rbin
e
Next steps
• Continue with model and scenario development– Some adjustments are feasible e g updating mass transfer andSome adjustments are feasible, e.g. updating mass transfer and
liquid hold-up correlations, possible improvements in heat transfer calculations in boiler components
• Collaboration study with Norwegian University of Science and Technology (NTNU)
Ai i t i ti ti ff t f i t ti PCC it ith l d– Aiming at investigating effects of integrating PCC unit with coal and gas fired power plants on the power plant dynamics
– How will the power plants ability to operate flexibly be affected?
Summary
• A simplified steam cycle was designed using the existing Nordjyllandsvaerket coal fired power plant as basisNordjyllandsvaerket coal fired power plant as basis– The steady-state performance of the dynamic power plant model is
reasonable, compared with plant data• Data for dynamic validation is scarce dynamic behavior• Data for dynamic validation is scarce, dynamic behavior
reasonable?– PCC system does not have a large influence on the power plant
load ramp rate• The coupling between the power plant steam cycle and the
post-combustion system needs to be carefully designedp y y g– Flow conditions in LP turbine might prove problematic at low loads
Dynamic modelling of a supercritical coal fired power plant integrated with coal fired power plant integrated with
post-combustion CO2 capture
3rd Post Comb stion Capt re Conference (PCCC3)3rd Post Combustion Capture Conference (PCCC3)8-11th September 2015
Stefanía Ósk GarðarsdóttirChalmers University of Technologyy gy