CEA’s assessment of the sulfur-iodine cycle for hydrogen production Fourth OECD-NEA Information Exchange Meeting on the Nuclear Production of Hydrogen CEA’s assessment of the sulfur-iodine cycle for hydrogen production P. Carles, X. Vitart, P. Yvon philippe.carles@cea.fr

The sulfur-iodine cycle H2SO4 ↓ H2O + SO2 + ½ O2 [850 °C] 2 HI → H2 + I2 [330 °C] I2 + SO2 + 2 H2O → H2SO4 + 2 HI [120 °C] Sum of the reactions H2O → H2 + ½ O2

alkaline electrolysis Project objectives Objective : assess the technical and economic viability of massive hydrogen production processes using water as raw material Reference process: alkaline electrolysis Cost components

Hydrogen production cost estimation Technico- economical assumptions Components Plant design Other cost components Investment cost Flowsheet Thermodynamic data Materials Hydrogen Production cost Energy consumption

Bunsen section optimization for improved efficiency (x+1)I2 + SO2 + (n+2)H2O → [H2SO4 + (n-m)H2O] + [2HI + xI2 + mH2O] H2SO4 phase HIx phase Reference: x = 8 / n = 14 120°C Studies of H2SO4/HI/I2/H2O mixtures: Reduction of iodine and water overstoichiometry seems possible Counter-current reactor Better yield Better purity of the phases Lower level of side reactions

S-I cycle efficiency Assumptions Energy consumption: 39.3 % efficiency Optimized Bunsen reaction Reactive distillation for iodine section Modified Neumann model for HIx description Energy consumption: 7 I2 + SO2 + 15 H2O → [H2SO4 + 4 H2O] + [2 HI + 6 I2 + 9 H2O] 39.3 % efficiency Allows 2 kg/s hydrogen production with a 600 MWth V/HTR

Iodine section flowsheet 3 EAU BUNSEN 1 100°C – 50 bars 13 L2 9 L23 3b HIx BUNSEN 130°C – 3 bars 2 EAU 9b 8 L12 L1 L10 L13 1b 7 12 7b 7c L24 IODE BUNSEN 130°C – 50 bars 5c HYDROGENE 120 bars 4 4b L14 L200 L210 L201 L211 L21 L20 L22 5 5b 6 10 10b 11 11b P301 50 bars E302 E304 E301 He E307 C302 E305 E303 E306 234,2 kJth 4,4 kJélec 2,7 kJélec E308 E309 E310 D301 D302 PAC 2/0,3 bar 52,5/102,7 bar C301 / T301 Total: 353,8 kJ th (He: 234,2 kJ Elec: 59,8 kJ) 52,7 kJélec 261°C 313°C 312,3°C 270°C 244,6°C 108,3°C 1 Reactive distillation column: 10 x (23 trays, F4m x H26 m) Heat exchanges: 1950 kJ/mol

Materials for iodine section Nb-1%Zr

S-I plant investment cost 1 shop (0.2 kg/s) 2.5 G€ for a 1st of a kind plant

Main assumptions for hydrogen production cost General assumptions Discount rate: 8% Construction period: 3 yrs Operating life: 30 yrs without replacing any equipment (cf. maintenance) Start-up / stopping phases: none Load factor: 80% Investment cost Process unit investment cost: assessed according to the flowsheet Contingency: 30% of the principal equipment General facilities: 15% of the installed base price Engineering fees: 12% of the installed base price Contractor fees: 5% of the installed base price Initial loads include the initial stock of sulphuric acid and iodine O&M costs Energy: Electricity: 40 €/MWh Heat: 20 €/MWh Labor: Number of operators: 30 Labor cost: 0.4 M€/op./year Maintenance: 7%/year of the installed real equipment cost Taxes and insurance: 2%/year of the installed real equipment cost Plant overhead costs: 1%/year of the installed base equipment cost

Hydrogen production cost ~10 €/kg of H2 for a Nth of a kind plant

Discussion Uncertainties remain large Costing methods accuracy 30%+ €-$ conversion rate and material prices fluctuations

Steel prices and $ exchange rate do fluctuate a lot! Material prices Steel prices and $ exchange rate do fluctuate a lot! $ / tonne Jan 2006 Jan 2008 Jul 2008 Ordinary steel price: 0,86 $ / kg Exchange rate: 1 $ = 0,63 €

Discussion Uncertainties remain large Costing methods accuracy 30% €-$ conversion rate and material prices fluctuations Catalyst cost and efficiency poorly known Iodine section remains poorly known and understood

Iodine section: some LVE measurement results LT : less iodine more HI HT : more iodine less HI than reference model Total pressure measurements around 130°C for various mixtures with 39 % I2 Experimental evidence of hydrogen formation: liquid phase decomposition? Results to be included in new thermodynamic model

Discussion Uncertainties remain large Costing methods accuracy 30% €-$ conversion rate and material prices fluctuations Catalyst cost and efficiency poorly known Iodine section remains poorly known and understood Are assumptions made pessimistic? Simplified chemistry Effect of a 45% efficiency? Chemical flows are high Corrosion resistant materials are expensive New technologies? Low temperatures?

Conclusion S-I cycle Efficiency 39-40%, likely to be revised to a lower value Hydrogen production cost around 10 €/kg Competitiveness seems difficult to achieve with today’s state of the art knowledge and technology Uncertainties remain, but breakthroughs are required! New material technologies Low temperature distillation Liquid phase HI decomposition Bunsen reaction optimization … CEA’s strategy: Continue ongoing international collaborations (GIF, HYCYCLES, BARC, I-NERI…) Publish results and discuss them with international partners Update the assessment with results from international research