Abstract1. Establishing the rate kinetics and mass transfer resistance effects in

a gas-solid heterogeneous sulfur trioxide decomposition conducted in a packed bed continuous reactor.

2. Evaluation of effectiveness factor in terms of catalyst composition, bulk fluid temperature, shape and size for catalytic decomposition of SO3 to SO2.

3. Estimation of reaction kinetic parameter.4. Development of 2-D model for the most effective catalyst shape.5. Model validation with experimental results.

Introduction

Materials and Methods

References1. Mocciaro, C.; Mariani, N. J.; Martínez, O. M.; Barreto, G. F. Ind. Eng. Chem. Res. 2011, 50 (5), 2746–2754.2. Norman, J. H., Mysels, K. J., Sharp, R. & Williamson, D. Studies of the sulfur-iodine thermochemical water-splitting cycle. Int. J. Hydrogen Energy 7, 545–556 (1982).3. Vitart X., Duigou A. Le, and Carles P. Energy Conversion and Management, 2006, Vol. 47, Issue 17, 2740-7.

AcknowledgementThe authors are thankful to ONGC Energy Centre Trust (OECT), India for funding support.

Conclusions1. Gas phase packed bed continuous flow reactor was used to conduct the sulfuric acid to sulfur dioxide

two step decomposition in both homogeneous gas phase and heterogeneous gas-solid phases.2. Kinetics of the step two, sulfur trioxide decomposition to sulfur dioxide, were investigated and a check

for mass transfer resistances in the packed bed which affect the rate kinetics of the reaction were modeled for various shapes of catalyst pellets along the packed bed length.

3. A model was developed to establish relationship for the effectiveness factor of the catalyst with regard to composition, size, heat and concentration profiles and this matched well with the experimental results.

4. Effectiveness factor was calculated for different shapes and sizes of pellets at different temperature and 7

5. hole cylindrical shapes were found to have highest effectiveness factor.

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Industrial Significance Clean hydrogen energy by the most efficient thermo-chemical process of iodine-sulfur

cycle using waste heat from nuclear reactor. It will be necessary in the future to develop alternatives to conventional petroleum when

world demand outstrips supply, and this technology could be used as petroleum alternatives.

Hydrogen being ultra-clean fuel for both transportation and stationary applications enhances energy security for India and reduces the dependency on hydrocarbon fuel.

Technology Readiness Level: In house continuous closed loop Iodine-Sulfur cycle pilot plant developed and running successfully.

Kinetic Modelling and 2-D Simulations of Catalyst Pellets for Sulfuric Acid Decomposition

Shailesh Pathak, Anshuman Goswami, Kishore Kondamudi, D. Parvatalu, Sreedevi Upadhyayula*

Result

Industry Day Theme # 4: Sustainable Habitat

Results from theoretical modeling

Simulation results

Simulation results

Concentration distribution sulfur tri-oxide across the catalyst surface for Fe2O3

Temperature distribution across the catalyst surface for Fe2O3

Catalyst k [W/m/K] A [1/s] Ea[kJ/mol]

Cr2O3 10.99 2.223 × 109 170.0

Pt 11.7 2.209 × 106 40.18

CuO 18.0 7.739 × 106 122.73

Fe2O3 4.0 2.934 × 107 187.00

Parameter Value / Emperical Relationship

C0i 𝐶𝑆𝑂30= 0.86 mol/m3

𝐶𝑆𝑂20= 0 = 𝐶𝑂20

ΔH 97.584 kJ/mol

T 1073-1173K

a 0.75-12mm

Simulation parameter

Catalyst composition

ƞ =observed rate

rate without internal gradients

= 0Arate C, T dA

rate Cs, Ts ∗ A

Single pellet modeling

Reaction Rate kinetics

1. Hydrogen is an alternative source of energy.2. Due to highest efficiency (>56%), water

splitting in Iodine-Sulfur (I-S) cycle is themost reliable and propitious for hydrogenproduction.

3. Catalytic decomposition of H2SO4 showslarge kinetic barrier and takes place at hightemperatures (>1123 K).

4. The catalyst’s size and shapes affects theheat and mass transport resistancesultimately affects the catalyst performance.

5. Due to the these transport resistance, 1-Dmodel is not enough to predict the behaviorof pellet.

Iodine-Sulfur cycle for water splittingVitart X., Duigou A. Le, and Carles P. Energy Conversion and Management, 2006, Vol. 47, Issue 17, 2740-7.

Catalysts: CuO /Al2O3 , Fe2O3/ Al2O3, Pt/ Al2O3, Cr2O3/Al2O3

Pellet size : 0.75-12 mm. Bed length : 50 mm

Parameter Values

keff 0.2 W/m-K

Deff 1.8E-6 m2/s

P 1 bar

ySO3 0.3

R 1.5 mm-9 mm

Density 0970 kg/m3

i. Catalyst compositionii. Bulk fluid temperatureiii. Catalyst shapeiv. Catalyst size

1. Only the catalytic decomposition of SO3 to SO2

was modelled.2. SO3 to SO2 decomposition was modelled as first order irreversible reaction.3. Rate of reaction depends on the concentration of species and temperature.

Main reactions as follows.

𝑆𝑂3 𝑔 → 𝑆𝑂2 𝑔 +1

2𝑂2(𝑔)

In terms of activation energy,

(𝑅𝑆𝑂3) = 𝑘𝑜" exp −

𝐸𝑎𝑅𝑇

𝐴𝑐𝑎𝑡𝐶𝑆𝑂3

Catalyst shapes

Assumptions

Simulation varying parametersParameter Values

Reaction kinetics

Arrhenius plot for the decomposition of sulfuric acid over Fe2O3/Al2O3

Effectiveness factor