AD ALTA
JOURNAL OF INTERDISCIPLINARY RESEARCH
=
4.23×10
15
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−240
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=2.00×10
6
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−67.1
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(8)
,
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−26830
+30.114
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,
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4400
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38.28
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2
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−88.68
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82.90
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× (
70.65
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(14)
3 Process description
3.1 Hydrogen production process
Generally, hydrogen production includes two major processes:
steam methane reforming (SMR) and pressure swing adsorption
(PSA). SMR and PSA processes can be categorized into six
stages which are shown in Fig1.
Figure 1: Overall scheme of hydrogen production system
Figure 2: Steam methane reforming coupled with pressure swing
adsorption process
In Figure 2, the hydrogen production system, which includes
SMR and PSA processes, is shown. After the temperature and
pressure of S1 and S13 increased to 700°C and 1010 Kpa, the
feed mixture enters the reformer which the reaction 1 takes
place. Then, in order to have a higher hydrogen production rate,
the syngas (S6) is transferred to water gas shift process (WGS).
It includes the high and low temperature reactors (1010 Kpa,
350°C and 200°C). In water removal stage, the S11 is cooled
down to condensate the water. The water is separated from
syngas in three stages.
In the next step, syngas (S35) is transferred to the PSA process
for purification which the reaction 3 takes place. In the PSA
process, Calcium Oxide (CaO) sorbent is utilized to adsorb
CO2. Therefore, pure hydrogen is separated in the flash tank.
Finally, CO2- enriched sorbent is sent to desorption column.
Heat exchangers 09 and 10 are used to calculate the heat of
adsorption and desorption reactions.
3.2 Simulation model
The SMR process is simulated using the commercial simulator
software PRO/II v9.4. In this simulation, Peng-Robinson
equation of state is used as the thermodynamic method for fluid
properties computations. Reformer and WGS reactors are
assumed as conversion reactors in which the rate of conversion
is determined via Equations 4 to 6. Heat exchangers are counter-
current type, and formulated using the pinch analysis and
specified minimum temperature approach. It is also assumed
that there is no heat loss within the heat exchangers. Minimum
temperature difference in all heat exchangers is set at 10° C. The
isentropic efficiency of the pump and compressor are set at
85%.
In addition, pressure drop in the adsorption and desorption
columns is neglected. Since PSA columns operate at near-
adiabatic conditions, they are assumed as a single column for
simplification. In this section, conversion reactors are used
instead of adsorption columns; hence, additional heater and
cooler are used for computing the adsorption and desorption
heats during the process.
Steam
Methane
Reforming
High
Temperature
WGS
Low
Temperature
WGS
Water
Removal
Adsorption
Desorption
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