Energy Integration of IRCC

I NTRODUCTION M ETHODS AND T OOLS I NTEGRATION C ASE S TUDY S UMMARY

E NERGY I NTEGRATION OF C OMBINED
H YDROGEN & E LECTRICITY P RODUCTION -
M ETHODOLOGY & T OOLS I NTEGRATION

Rahul Anantharaman, Olav Bolland & Truls Gundersen

Department of Energy & Process Engineering
Norwegian University of Science and Technology

PRES 08
Prague, 27.08.2008


O UTLINE

1 I NTRODUCTION
Motivation
The Process

2 M ETHODS AND T OOLS
Methods
Tools

3 I NTEGRATION C ASE S TUDY
Utilities and cost information
ELCC
Heat Exchanger Network Synthesis

4 S UMMARY


BACKGROUND


CO2 CAPTURE PROCESSES AND SYSTEMS


H YDROGEN AS AN ENERGY VECTOR

H2 is predicted to be key player in future energy scenarios.
Significant steps are being taken, specifically within
Norway and the EU, to develop H2 infrastructure.
H2 is increasingly needed in oil refineries to make more
environmentally friendly fuels.

Power generation with pre-combustion process provides H2 as
a product that can be supplied to a H2 network.


M OTIVATION

T HE PLANT
400 MW power plant with 50 MW (LHV) of H2 with 90% CO2
capture using Natural Gas as the fuel.

Most capture plants are associated with large energy
penalty (~10%) - decreasing their economic viability.
Efﬁciency is the most important factor when selecting and
designing plants with CO2 capture.

A IM
Develop an engineer-driven procedure for improving the
efﬁciency of CO2 capture plants using an integration of tools
and methodologies.


C OMBINED H2 AND E LECTRICITY PRODUCTION


K EY PROCESS PARAMETERS

R EFORMING S ECTION
Reforming system pressure: 30 bar
S/C Ratio: 1.4
Pre-reformer/Reformer feed temperature: 500 °C
Reformer temperature: 950 °C
HTS/LTS inlet temperature: 325/250 °C

H2 P RODUCT S ECTION
H2 pressure: 70 bar
H2 purity: 99.9 %


K EY PROCESS PARAMETERS

CO2 C APTURE S ECTION
Type: aMDEA (with piperazine)
CO2 capture rate: 95 %
Reboiler temperature: 120 °C(max)
Speciﬁc reboiler duty: 0.9 MJ/kg CO2
Total energy consumption: 1.02 MJ/kg CO2
CO2 pressure: 110 bar

P OWER I SLAND
Turbine: GE 9FA
Derating: 30 °C
Steam system: 3 pressure levels - no reheat


E NERGY L EVEL C OMPOSITE C URVES (ELCC)
I NTRODUCING E NERGY L EVEL

E NERGY L EVEL
Energy levels at target & supply conditions are evaluated as:

(H−H0 )−T0 (S−S0 )
Ω= H−H0

Streams with increasing energy levels are energy sinks
Streams with decreasing energy levels are energy sources
Energy sources at higher energy levels can be potentially
integrated with energy sinks at lower energy levels

N OTE
It may not be possible to transfer energy from a stream at a higher
energy level to that at a lower energy level as Ω is not an explicit
driving force.


E NERGY L EVEL C OMPOSITE C URVES

ELCC are energy level –enthalpy curves constructed by plotting
energy level intervals of process streams against cumulative values
of enthalpy differences.

ELCC merges Pinch Analysis and Exergy Analysis into a
methodology utilizing the graphical approach of Pinch Analysis.
It functions as a screening tool or idea generator, giving physical
insight for energy integration between streams on energy source
curve and energy sink curve


E XAMPLE - M ETHANOL PLANT


E NERGY TARGETING

Energy targeting is performed by identifying optimal path
for each stream from supply to target conditions.
Optimal path implies maximizing shaft work produced and
minimizing shaft work consumed.
Optimal path heuristics were developed for 4 possible
temperature and pressure combinations above
atmospheric conditions.


S EQUENTIAL F RAMEWORK FOR HENS
M OTIVATION

Pinch based methods for Network Design
Improper trade-off handling
Cannot handle constrained matches
Time consuming
Several topological traps
MINLP Methods for Network Design
Severe numerical problems
Difﬁcult user interaction
Fail to solve large scale problems
Stochastic Optimization Methods for Network Design
Non-rigorous algorithms
Quality of solution depends on time spent on search


M OTIVATION

HENS TECHNIQUES DECOMPOSE THE MAIN PROBLEM
Pinch Design Method is sequential and evolutionary
Simultaneous MINLP methods let math considerations
deﬁne the decomposition
The Sequential Framework decomposes the problem into
subproblems based on knowledge of the HENS problem

Engineer acts as optimizer at the top level
Quantitative and qualitative considerations included


U LTIMATE G OAL

Solve Industrial Size Problems
Defined to involve 30 or more streams
Include Industrial Realism
Multiple and ``Complex´Útilities
Constraints in Heat Utilization (Forbidden matches)
Heat exchanger models beyond pure countercurrent
Avoid Heuristics and Simplifications
No global or fixed ∆ Tmin
No Pinch Decomposition
Develop a Semi-Automatic Design Tool
EXCEL/VBA (preprocessing and front end)
MATLAB (mathematical processing)
GAMS (core optimization engine)
Allow significant user interaction and control
Identify near optimal and practical networks


T HE E NGINE

C OMPROMISE BETWEEN P INCH D ESIGN AND MINLP METHODS


M ODELING T OOLS

HYSYS
The steady-state simulation tool ASPEN HYSYS is used to
model the reforming section, the CO2 capture section and the
H2 purification section.

GTP RO
GTPro from Thermoflow Inc. is used to model the power island.
GTPro is particularly effective for creating new designs and
finding their optimal configurations. To this end, it has a library
of gas turbine models that replicates real performance.
Initial HRSG design and marginal costs for HP, IP & LP steam
are derived from GTPro.


T OOLS I NTEGRATION
HYSYS-GTP RO XL A DD - IN


U TILITIES

S TEAM L EVELS
HP/IP/LP steam: 118/32/3.5 bar

U TILITIES COST
Electricty: 63 ¤/MWh
HP steam: 0.79 MW for 1 kg/s of sat steam raised
IP Steam: 0.68 MW for 1 kg/s of sat steam raised
LP Steam: 0.42 MW for 1 kg/s of sat steam raised

H EAT E XCHANGER C OST L AW
10,000 ¤+ (800 ¤)*(Area)0.8



P RELIMINARY E NERGY TARGETS
Shaft work required: 28 MW
Hot utility requirement: 0 MW
Cooling Water requirement: 34 MW


H EAT E XCHANGER N ETWORK S YNTHESIS
I NTEGRATION O PTIONS

1 Integrate Amine reboiler directly to the process
2 Extract LP steam from utility system to feed the reboiler
3 Generate required LP steam for reboiler from LTS exit


H EAT E XCHANGER N ETWORK S YNTHESIS
I NTEGRATION R ESULTS

O PTION HP STEAM IP STEAM LP STEAM E FFICIENCY U NITS C AP. C OST
KG / S KG / S KG / S % ¤
1 126.3 81 36 44.2 21 12107600
2 128.9 81.31 51 44.45 23 12434000
3 122.2 79 42 43.7 24 12420100


S UMMARY

Combined hydrogen and power generation with carbon
capture is expected to play a significant role in the near
future energy portfolio.
An integration of methodologies and tools for the energy
integration of a combined hydrogen and electricity is
presented.
The methodologies presented lead to designs with slightly
higher efficiency than those presented in literature.

The methodology provides multiple designs with same
efficiency and similar costs but with varying degrees of
complexity to enable the engineer to select an integration
scheme based on qualitative parameters such as operability
etc.

Energy Integration of IRCC

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