Call 2 UKCCSRC Industrial CCS: Novel Materials and Reforming Process Route for the
Production of Ready-Separated CO2/N2/H2 from Natural Gas Feedstocks
Modelling of Packed bed Sorption Enhanced Steam Reforming (SE-SMR)
Z.S. Abbas, V. Dupont, T. Mahmud School of Chemical and Process Engineering,
The University of Leeds
Concept of SE-SMR process
• Carbon dioxide emission
• Hybrid reactor
• No water gas shift (WGS) reactor
• Energy efficient
• Reduced temperature
OPEN VALVE
CLOSED VALVE
Circulating Bed
Model Description
The flow pattern is assumed to be plug flow in nature and Ideal gas
behaviour is applicable
The heat and mass flow patterns are only studied in axial direction.
The operation is considered to be adiabatic in nature.
Uniform size of catalyst and sorbent throughout the modelling work.
Porosity of the bed is constant.
Reaction Scheme Reaction Rate Equation CH4 g + H2O g ↔CO g + 3H2 g R1 = k1
pH22.5 pCH4pH2O −
pH23 pCOKI
1Ω2
Froment GF et al. (1989)
CO g + H2O g ↔CO2 g + H2 g
R2 = k2pH2
pCOpH2O −pH2pCO2
KIII
1Ω2
Froment GF et al. (1989)
CH4 g + 2H2O g ↔CO2 g + 4H2 g R3 = k3
pH23.5 pCH4pH2O
2 −pH24 pCO2KII
1Ω2
Froment GF et al. (1989)
CaO(s) + CO2(g)↔CaCO3(s)
R4 = ƞMCaO
dqCO2dt
Bhatia S et al. (1983)
dqCO2dt
= kcarb Xmax − X ʋCO2 − ʋCO2,eq
ʋCO2,eq = 4.137 × 107 exp−20474
T
Experimental Setup
Experimental set-up for Sorption Enhanced Steam Reforming Process available at SCAPE (School of Chemical
and Process Engineering) ,University of Leeds
Operating conditions used in Modelling Reactor characteristics and operating conditions
Gas feed temperature, [Tin] 873-973 K Initial solid temperature, [To] 873-973 K
Total pressure, [P] 20-35 bar Steam to carbon ratio, [S/C] 3.0-5.0
Apparent density of reforming catalyst, [ρcat] 550 kg m-3
Apparent density of CaO based sorbent, [ρCaO] 1125 kg m-3
Diameter of particles, [dp] 0.01 m
Reactor bed length, [L] 7 m
Bed porosity, [ɛb] 0.5
Intel gas mass velocity, [Gs] 2.0-3.5 kg m-2 s-1
Reference used for Validation of the
Model
Fernandez J et al. (2012)
Model validation Pre-Breakthrough Period
Dry Mole composition of product gases [%] CH4 CO H2 CO2
N/E: 4.8 E: 3.9
N/E: 0.32 E: 0.09
N/E: 93.6 E: 95.81
N/E: 1.3 E: 0.15
CH4 Conversion [%] H2 Purity [%] N/E: 86 E: 86 N/E: 93.5 E: 95.8
Post-breakthrough Period Dry Mole composition of product gases [%]
CH4 CO H2 CO2
N/E: 30.8 E: 20.8
N/E: 1.2 E: 2.72
N/E: 55.1 E: 62.8
N/E: 12.7 E: 13.6
CH4 Conversion [%] N/E: 31.2 E: 44
N/E : Non Equilibrium E : Equilibrium
Temperature profile validation
The adsorption of CO2 is highly exothermic reaction
Steam methane reforming
process is endothermic in nature
The maximum temperature 953.70 K i.e. increase of 30.70 K
Effect of Inlet Temperature
Effect of Pressure and S/C ratio
S/C ratio
CH4 Conversion
[%]
H2 yield [wt% of
CH4 feed]
H2 purity [vol %]
CO2 capture
[%]
1 N/E : 32.4 N/E : 12.5 N/E : 58.2 N/E : 28.8
E : 34.4 E : 17.4 E : 67.6 E : 34.0
2 N/E : 51.7 N/E : 20.1 N/E : 74.7 N/E : 46.1
E : 56.2 E : 28.3 E : 83.5 E : 55.8
3 N/E : 67.5 N/E : 26.2 N/E : 84.1 N/E : 60.7
E : 71.4 E : 36.1 E : 90.8 E : 71.0
Effect of Gas Mass Velocity
The lower mass velocity results in longer pre-breakthrough period and higher conversion of CH4
At mass velocity of 2 kg m-2 s-1, the conversion of methane is 71%. As the space velocity increases, the CH4 conversion goes down
At 3.5 kg m-2 s-1 CH4 conversion is 67.47%
Comparison of SMR and SE-SMR process
Conclusion
The optimum temperature under 30 bar pressure conditions is 923K.
At optimum temperature, max 67.47% CH4 conversion and 84.12% purity of H2 at S/C of 3.0 and 30 bar
Pressures higher than 5 bar have negative effect on the conversion of CH4 and H2 purity.
The selection of optimum pressure for industrial scale is a trade-off between H2 purity and downstream pressure requirements. 30 bar is considered as optimum in this study as it fulfil the requirement of industrial pressure of H2 and gives a considerable purity of H2 (84.12%).
S/C ratio of 3.0 is selected to meet the requirements of H2 purity at minimum operational cost.
The gas mass velocity of 3.5 kg m-2 s-1 is picked as optimum value
The CH4 conversion enhancement is around 180% due to the presence of the sorbent in the system.
Future work
The developed model of SE-SMR is further modified for sorption enhanced
chemical looping steam reforming (SE-CLSR) process to feature nickel oxide
reduction by methane and nickel oxidation under air and O2-enriched air flow.
Acknowledgment
We would like to thank the UK’s EPSRC for a UKCCSRC Call 2 grant in
Industrial CCS for consumables as well as University of Engineering and
technology (UET) Lahore, Pakistan and University of Leeds, UK for financial
support (Mr Z. S. Abbas scholarship). In addition we are grateful for the use of
gPROMS model builder 4.1.0® license through Prof. Mojtaba Gadhiri.
