PEM Fuel Cell for Electricity
Generation using Hydrogen from a
Chlorine Plant
Integrated ACM Model in Aspen plus
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Contents
1
Background .......................................................................................... 2
2
PEM Fuel cell in ACM............................................................................... 2
2.1
Mass and energy balances in the Anode: .............................................. 2
2.2
Mass and energy balances in the Cathode: ........................................... 2
2.3
Energy balance in the solid layer:........................................................ 3
2.4
Current density and power:................................................................ 3
3
Flowsheet ............................................................................................. 3
4
Simulation Results ................................................................................. 5
5
Conclusion ............................................................................................ 6
1
1 Background
Chemical industry accounts for approximately 10 % of global energy demand and
about 7% of the global GHG emissions [1]. Among different sectors, chlorine and
sodium hydroxide production capacity is poised to see moderate growth over the next
five years, potentially increasing from 87.69 million tons per annum (Mtpa) in 2019
to 92.13Mtpa in 2024, registering total growth of 5%. In Europe, chlor-alkali industry
productions are of more than 11.5 million metric tons while the US produced around
of 10.9 million metric tons by 2019 and China being the largest producer with around
25 million metric tons per year [2]. Chlorine and sodium hydroxide can be produced
by means of chlor-alkali electrolysis, which is an energy-intensive process, therefore
the increase in production will also lead to increasing the energy requirements for
this process. During the chlorine and sodium hydroxide production, hydrogen is
produced as byproduct and in most of the cases cannot be recovered. The former can
overcome the energy requirements by means of the Fuel cell technology [3–8].
Among the different types of fuel cells, proton exchange membrane fuel cells
(PEMFCs) have gained attention in recent years.
2 PEM Fuel cell in ACM
Aspen custom Modeler (ACM) already provides a model for the PEM process. The
existing model has been modified to be exported to Aspen Plus. The model consists
of mass and energy balance equations in steady state as reported in the literature by
Yi and Nguyen [9].
2.1 Mass and energy balances in the Anode:
2
( )
( )
2
( )
2
2
= −β
=
=
( )
(1)
2
( ( )
( )
2
( )+
2
c
)
.
( )
( )+
2
( )
( )−
( )
( )
( )
(2)
( )
= ℎ
(3)
( )−
( )
(4)
2.2 Mass and energy balances in the Cathode:
2
( )
2
2
2
= −β
( )
( )
=
=−
( )+
( )
2
( ( )
(5)
( )
2
2
c
.
)
( )+
( )+
2
( )−
( )
( )
(6)
( )
( )
( )
= βℎ
(7)
( )−
( )
(8)
2
2.3 Energy balance in the solid layer:
( )
3.6
−
2
2 ( ) − 1E3 ( )
3600
−
2
( )
( )+
( )
2
( )
2
− 1E3 ( )
2
( )
( )
= −3600 βℎ
( )
+ 3.6ℎ1 4
−
( )+
( )−
( )I( ) −
(9)
2.4 Current density and power:
( )
= ∑
(10)
( )
( )=
=
=
( )−
( )−
(11)
( )
(12)
(13)
ℎ
Where the membrane conductivity and the net water flux per proton flux are given
by:
( ) = (0.005139 ∗
( ) ( )=
( )
( )
( ) ( )−
( .
( ) − 0.00326)
( )
2
)
( )
( )
( )
2
( )
.
−
( )
(14)
(15)
3 Flowsheet
The model built in Aspen Plus was taken from literature [10–11] and it has as main
goal the production of energy based on hydrogen consumption. It considers as feed
the hydrogen produced in the chlorine plant (H2DRY). The hydrogen is humidified
and feed to the PEM by the anode side (AIN). While compressed air is also humidified
and used as feed to the cathode side of the PEM (CIN). The humidifiers were
represented by radfrac blocks. Excess hydrogen was recirculated and mixed with the
fresh feed (H2REC) while exhaust air is cooled down to recover demineralized water.
A schematic representation of the flowsheet can be seen in Figure 1.
3
Figure 1: Aspen Plus flowsheet of the PEM system for energy generation.
The PEM was built taking advantage of ACM capabilities. The set of equations that
were presented in Section 2 can be built and exported as an atmlz file to be read
inside aspen plus. All the information regarding the PEM model that was created in
ACM can be displayed in Aspen Plus UI as shown in Figure 2.
Figure 2: Screenshot of PEM block information.
4
4 Simulation Results
The previous flowsheet was used to validate the applicability of the PEM Fuel Cell
model created in ACM, specially at industrial scale for generation of electricity based
on hydrogen consumption. The works of Verhage et al. [10] and Guandalinia et al.
[11] were used as a reference since they simulated a pilot and industrial scale
cogeneration plants for chlorine industry. In the industrial cogeneration unit, the
intention is to generate a unit capable of generate around 1MW of energy, while the
pilot plant generates around 70kW. For the industrial unit, the authors provided the
following operating conditions:
Table 1: Operating parameters for validation.
T (°C)
Hydrogen to stacks (dry)
Recirculated
hydrogen
(dry)
Air to stacks (dry)
50
65
Flow rate
(Nm3/hr)
1200
600
63
3450
Under these conditions, the authors reported an electric generation of 1040kW.
Nevertheless, there is not sufficient information regarding the cell’s geometry or the
actual number of them in the stack. For the simulation presented in this investigation,
2500 cells were assumed in the ACM model given an electric generation of 942kW as
shown in the variables table of the PEM (Figure 3).
Figure 3: Screenshot of PEM power generation.
5
5 Conclusion
This exercise showed that it is possible to simulate a PEM fuel cell in Aspen Plus for
an industrial scale cogeneration plant. The results are quite representative according
to literature reports. Given that this flowsheet only requires the hydrogen feed, it
may be easy to connect it with a full flowsheet for a chlorine plant or other type of
chemical process that generates H2 as byproduct, making it attractive for scale up of
cogeneration projects.
6
References
[1] IEA (International Energy Agency), “Technology Roadmap - Energy and GHG Reductions in the Chemical
Industry via Catalytic Processes,” OECD/IEA, Paris, France, 2013.
[2]
Production-capacity-chlorine-europe-by-country.
[Online].
Available:
https://www.statista.com/statistics
[3] T. Brinkmann, G. G. Santonja, F. Schorcht, et al., “Best Available Techniques (BAT) - Reference
Document for the Production of Chlor-alkali,” JRC (Joint Research Center EU), JRC91156, 2014.
[4] EuroChlor, “Chlorine industry review 2014-2015,” Brussels, 2014.
[5] ResearchInChina, “Global and China Chlor-alkali Industry Report,” 2013.
[6] “DEMCOPEM-2MW Project official website.” [Online]. Available: http://www.demcopem-2mw.eu/.
[7] U.S. DOE (Department of Energy), Fuel cell handbook, 7th ed. EG&G Services, Inc., 2004.
[8] M. Smit, “Towards 40 000 hours of operation for Nedstack’s FCS XXL PEM fuel cell stacks,” Fuel cells
Bull., vol. 8, pp. 12–15, Aug. 2014.
[9] J. S. Yi and T. V. Nguyen, “An Along‐the‐Channel Model for Proton Exchange Membrane Fuel Cells”, J.
Electrochem. Soc., vol. 145, No. 4, April 1998
[10] A. J. L. Verhage, J. F. Coolegem, M. J. J. Mulder, et al., “30,000 h operation of a 70 kW stationary PEM
fuel cell system using hydrogen from a chlorine factory,” Int. J. Hydrogen Energy, vol. 38, no. 11, pp.
4714–4724, Apr. 2013.
[11] G. Guandalinia, S. Forestia, S. Campanaria, et al., “Simulation of a 2 MW PEM Fuel Cell Plant for
Hydrogen Recovery from Chlor-Alkali Industry”, The 8th International Conference on Applied Energy
– ICAE2016, Energy Procedia, vol. 105 pp. 1839 – 1846, 2017.
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