Final Presentation-Water Splitting

Final Presentation-Water Splitting - Evaluation and Design...

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Unformatted text preview: Evaluation and Design of WaterDesign Splitting Cycles Scott Mullin, Jacob Tarver, Uchenna Odi Scott Uchenna University of Oklahoma May 2006 Overview Overview Need for hydrogen Need Water-splitting cycles as solution Water Current evaluation methods Current Efficiency defined Efficiency Our methodology as improvement Our Results of our analysis Results Economics Economics Conclusions Conclusions Accomplishments Accomplishments Novel methodology Novel Rapidly screen cycles without detailed Rapidly process flowsheets Optimize T, P and excess reactants for nonOptimize spontaneous reactions Scoping algorithm Scoping Calculations refined for best cycles Calculations Found better cycles than currently favored Found Sulfur-Iodine and UT-3 Hydrogen Economy Hydrogen Currently 11 million tons/year Currently In H2 economy†: In 200 million tons/year for transportation 200 450 million tons/year for all non-electric 450 H2 is not a natural resource Must be produced Must Steam reformation of methane Steam CO2 output CO Rising fuel prices Rising † K. R. Schultz 2003, General Atomics, DOE grant Alternative H2 Production Alternative Petroleum CO2, expensive CO Electrolysis, high T electrolysis Premature, inefficient Premature, Photocatalytic reactors Premature Premature Thermochemical cycles Efficient, established processing techniques Efficient, Abundant heat, electricity 2 2 2 Water-Splitting Cycles Water “New” technology, chosen by DOE through Nuclear Hydrogen Initiative Efficient hydrogen production Efficient 50-60% currently, 80-90%+ possible 50 Use 950ºC or cooler process heat Use 202 cycles known, but few researched 202 Others can be found, as described by Others Holiastos and Manousiouthakis 1998 Economics Economics $1 billion for water-splitting facility $1 $100 million range annual energy costs $100 Which cycle is best? Which Few cycles researched in detail Few Process design too complex Process Efficient cycles desirable Efficient Justify increased equipment costs Justify Bottom line: saving few % efficiency has huge Bottom savings over plant lifetime savings Cycles Cycles Most are thermochemical, some hybrid electric Most Any number of reactions, species Any Named after institutions or chemicals Named Steady-state operation Steady T1 O2 T2 H2 A Sample 2-step cycle T1 A ⎯⎯ B + C + O 2 → T2 B + C + H 2 O ⎯⎯ A + H 2 → B, C H2O Efficiency Efficiency Theoretical, 1 mol basis for cycle comparison Theoretical, Minimum reversible energy (heating and work) Minimum requirement Performance limit Performance Thermodynamics: JANAF tables for state Thermodynamics: functions, pure component averages ΔH f (H 2 O) η= Q+W †Shaft Q is total heat requirement W is separation, electric and shaft work† work (pumping, compression) small compared to other terms Previous Surveys Previous Brown et al 2000 scored cycles based on Brown known characteristics Good starting point, but not reproducible Good Arbitrary criteria, no emphasis on efficiency Arbitrary Elemental abundance, “corrosivity”, # elements Elemental Rejects cycles with “too positive” free energies Rejects Favors well-researched cycles Favors Score† Score 0 1 2 3 # reactions 6 - - 5 # separations 10 9 8 7 # elements 7 - 6 - Least abundant element Ir Rh, Tc, Os, Ru, Re, Au Pt, Bi, Pd, Hg, Se Ag, In, Cd, Sb, Tm, Tl, Lu Brown’s method is good at identifying cycles based on estimated process complexities, but is not quantitative or reproducible. What happens if you change the weights, or add further scoring criteria? †Adapted from Brown et al 2000 Previous Surveys cont’d Previous Cycles are complex, so Lewis et al 2005 Cycles developed systematic approach Scoping method based on efficiency Scoping Quantitative, standard basis Quantitative, Oversimplifications Oversimplifications Requires detailed flowsheets Requires Not truly scoping Not Assumes 50% loss of all work energy Assumes Does not estimate real separation energy Does Our method is truly scoping, based on Our theoretical requirements theoretical General Methodology General Cyclic nature couples all calculations Cyclic Decouple the problem Decouple Find realistic estimates for Q, W Find Refine calculations for best cycles Refine Account for additional energy requirements Account Economic analysis of best cycles Economic Apply methodology to all cycles Apply Evaluate the 202 from literature Evaluate Find unknown cycles Find Equilibrium Equilibrium Excess reactants added to shift reactions to Excess the right How do we handle excess after the How reaction? Requires optimization, coupled equations Requires vi ⎛ ni ⎞ ∏ ⎜∑n ⎟ ⎜ ⎟ products ⎝ ν ν i⎠ K eq = K x P ∑ = P∑ vi ⎛ ni ⎞ ∏⎜ n⎟ ⎜ ⎟ reactants ⎝ ∑ i ⎠ Excess Reactant Handling Excess Immediate recycle: full separation energy costs T1 A ⎯⎯ B + C + O 2 → T2 B + C + H 2 O ⎯⎯ A + H 2 → No recycle: saves separation energy, but negatively shifts equilibrium in most cases and increases heat cascade requirement We optimize T, P, # excess mols and their handling Cycles cont’d Cycles B Methodology Methodology accounts for arbitrarily complex cycles D + H 2 O ⎯⎯ E + F + H 2 → T2 H2 A + B ⎯⎯ C + O 2 → T2 O2 A D, H2O T1 T1 T3 C + H 2 O ⎯⎯ B + F → T4 H2O T3 C E + F ⎯⎯ A + D + H 2 O → T4 Conditions optimized for each reactor E, F Heat Requirements Heat Maximize heat recovery from exothermic reactions and cooling Maximize streams Pinch occurs when there is not enough heat to power reactions or Pinch heat streams, requiring input from the hot utility Generic Heat Integration Generic Hhot is total enthalpy of cooling streams Hcold is total enthalpy of heating streams Pinch Point and Approach Temp. Pinch Heat is added above the pinch. Heat transfer over the pinch (greater than the minimum heat requirement) goes to cold utility and is wasted. ΔTmin is closest feasible temperature, since complete heat transfer requires infinite exchanger area. Heat Integration Method† Heat Zonal analysis Zonal Approach temperature Approach Simplifying algorithm Simplifying Keep track of total Keep heat usage, advancing to successive zones and reactors Cold utility ignored Cold Leftover heat Leftover sometimes useful for electricity generation † PT&W Plant Design and Economics for Chemical Engineers Electrical Work Electrical Nernst equation for electrolytic cells Nernst Assume steady-state operation of electrolytic cells Assume New electrolysis methods efficient compared to batch process† New Hybrid cycles treated same in heat integration Hybrid Welec = −nFE d(E (T)) E = E (298) + ∫ 298 dT T †Motupally et al 1998 Separation Work Separation Minimum separation estimate Minimum Wsep = −ΔG = −Δ ∑ ni μi = − RT Δ ∑ ni ln xi i =0 i =0 Assuming isothermal separation ⎡⎛ ⎞ Wsep = RT ⎢⎜ ∑ ni ln xi ⎟ ⎠out ⎣⎝ i = 0 ⎛ ⎞⎤ − ⎜ ∑ ni ln xi ⎟ ⎥ ⎝ i =0 ⎠in ⎦ Phases self-separate Phases We don’t pay for it We Estimate separation efficiencies Estimate W= Wsep ,ideal η separation This provides us with a minimum requirement. Chemical mixing and individual processes will increase W. Assign efficiencies to each process: e.g. assume distillation columns 50% efficient Solution Procedure Solution Most reactions go to completion Most No excess reactants to handle No Optimize reactors individually Optimize For other reactions For Find equilibrium concentrations Find Newton method to solve for conversion Newton Know how much product we need from Know connectivity Solution Procedure cont’d Solution Computer algorithm finds optimum Computer efficiency for each T P easy to find easy Finds Q and W for each # mols excess Finds Optimize these for each recycle scheme Optimize Computer crawls through solutions, and Computer maximizes efficiency Example Optimization Example Wmin and Excess Cl2 Required for varying excess H2O 1.2 Wmin Separation (kJ/mol) 39 Wmin 1 CL2 38.5 38 0.8 37.5 0.6 37 36.5 0.4 36 0.2 Excess Cl2 Required (moles) 39.5 35.5 35 0 0.2 0.3 0.4 0.48227768 0.6 0.7 0.8 Excess H2O (moles) Cl2 (g) + H2O (g) -> 2HCl (g) + ½O2 (g), ∆Grxn= -17 kJ / cycle mol Sample Thermochemical Cycles Thermochemical Julich Julich T = 1073 K Fe3O 4(s) + 3FeSO 4(s) ⎯⎯⎯⎯ 3Fe 2 O3(s) + 3SO 2(g) + → 1 2 O 2(g) T = 973 K 3FeO(s) + H 2 O(g) ⎯⎯⎯⎯ Fe3O4(s) + H 2(g) → T = 473 K 3Fe 2 O3(s) + 3SO 2(g) ⎯⎯⎯⎯ 3FeO (s) + 3FeSO 4(s) → Ispra Mark 9 Ispra 3FeCl2(s) + 4H 2O (g) ⎯T = 923 K → Fe3O 4(s) + 6HCl(g) + H 2(g) ⎯⎯⎯ 3 2 T = 693 K Cl2(g) + Fe3O 4(s) + 6HCl(g) ⎯⎯⎯⎯ 3FeCl3(l) + 3H 2 O(g) + → T = 423 K 3FeCl3(s) ⎯⎯⎯⎯ → 3 2 Cl 2(g) + 3FeCl2(s) 1 2 O 2(g) Sample Thermochemical Cycles Thermochemical Sulfur Iodine Sulfur T = 1123 K H 2SO 4(g) ⎯⎯⎯⎯ SO 2(g) + H 2 O(g) + → T = 573 K 2HI(g) ⎯⎯⎯⎯ I 2(g) + H 2(g) → T = 473 K I 2(g) + SO 2(g) + 2H 2 O(l) ⎯⎯⎯⎯ 2HI(g) + 1H 2SO 4(g) → US-Chlorine US T = 1123 K Cl2(g) + H 2 O(g) ⎯⎯⎯⎯ HCl(g) + → 1 2 O 2(g) T = 773 K 2CuCl2(s) ⎯⎯⎯⎯ 2CuCl(l) + Cl2(g) → T = 473 K 2CuCl(s) + 2HCl(g) ⎯⎯⎯⎯ 2CuCl 2(s) + H 2(g) → 1 2 O 2(g) Sample Thermochemical Cycles Thermochemical Gaz de France Gaz T = 1098 K 2K 2 O(s) ⎯⎯⎯⎯ K (g) + K 2 O 2(s) → T = 998 K 2K (l) + 2KOH (l) ⎯⎯⎯⎯ 2K 2 O(s) + H 2(g) → T = 398 K K 2 O 2(s) + H 2 O(l) ⎯⎯⎯⎯ KOH (s) + → 1 2 O 2(g) UT-3 Tokyo UT T = 1023 K CaBr2(l) + H 2 O(g) ⎯⎯⎯⎯ CaO(s) + HBr(g) → T = 873 K 4H 2O (g) + 3FeBr2(s) + Br2(g) + CaO(s) ⎯⎯⎯⎯ → CaBr2(s) + 1 2 O 2(g) + Fe3O 4(s) + HBr(g) + H 2(g) T = 573 K Fe3O 4(s) + 8HBr(g) ⎯⎯⎯⎯ Br2(g) + 3FeBr2(s) + 4H 2 O(g) → Sample Thermochemical Cycles Thermochemical Ispra Mark 4 Ispra T = 1123 K Cl2(g) + H 2 O(g) ⎯⎯⎯⎯ 2HCl(g) + → 1 2 O 2(s) T = 1073 K H 2S(g) ⎯⎯⎯⎯ S(g) + H 2(g) → T = 693 K 2FeCl3(l) ⎯⎯⎯⎯ Cl2(g) + 2FeCl2(s) → T = 473 K → 2FeCl2(s) + 2HCl(g) + S(l) ⎯⎯⎯⎯ 2FeCl3(s) + H 2S(g) Ispra Mark 7A Ispra 3 2 Cl2(g) + 1 2 T = 1273 K Fe 2 O3(s) ⎯⎯⎯⎯ FeCl3(l) + → 3 4 O 2(g) T = 923 K 3FeCl2(s) + 4H 2 O(g) ⎯⎯⎯⎯ Fe3O 4(s) + 6HCl(g) + H 2(g) → T = 693 K 3FeCl3(l) ⎯⎯⎯⎯ → 3 2 Cl 2(g) + 3FeCl2(s) T = 623 K → O 2(g) ⎯⎯⎯⎯ 3 2 Fe 2 O3(s) Fe3O 4(s) + 1 4 T = 393 K Fe 2 O3(s) + HCl(g) ⎯⎯⎯⎯ 2FeCl3(l) + 3H 2 O (l) → Sample Thermochemical Cycles Thermochemical Ispra Mark 7B Ispra 9 2 Cl 2(g) + 3 2 T = 1273 K → Fe 2 O3(s) ⎯⎯⎯⎯ 3FeCl3(l) + 9 4 O 2(g) T = 923 K → 3FeCl2(s) + 4H 2 O(g) ⎯⎯⎯⎯ Fe3O4(s) + 6HCl(g) + H 2(g) T = 693 K → 3FeCl3(l) ⎯⎯⎯⎯ 3 2 Cl2(g) + 3FeCl2(s) 6HCl(g) + 3 2 T = 673 K O 2(g) ⎯⎯⎯⎯ 3Cl 2(g) + 3H 2O (g) → Fe3O 4(s) + 1 4 T = 623 K O 2(g) ⎯⎯⎯⎯ → 3 2 Fe 2 O3(s) Sample Hybrid Cycles Sample Westinghouse Westinghouse T = 1123 K H 2SO 4(g) ⎯⎯⎯⎯ SO 2(g) + H 2 O(g) + → 1 2 O2(g) T = 350 K SO 2(g) + 2H 2 O(l) ⎯⎯⎯⎯ H 2SO 4(g) + H 2(g) → Ispra Mark 13 Ispra T = 1123 K → H 2SO 4(g) ⎯⎯⎯⎯ SO 2(g) + H 2 O (g) + T = 350 K → 2HBr(aq) ⎯⎯⎯⎯ Br2(aq) + H 2(g) T = 350 K → Br2(l) + SO 2(g) + 2H 2 O(l) ⎯⎯⎯⎯ HBr(g) + H 2SO 4(g) Hallett Air Products Hallett T = 1073 K Cl2(g) + H 2 O(g) ⎯⎯⎯⎯ 2HCl(g) + 1 O 2(g) → 2 T = 298 K 2HCl(g) ⎯⎯⎯⎯ Cl2(g) + H 2(g) → 1 2 O 2(g) Results Results Cycle rankings based on QH analysis with Cycle analysis ΔTmin=0 1. 1. 1. 1. 1. 2. 3. 4. 5. 6. 7. 8. Hallett Air Products US-Chlorine Sulfur Iodine Ispra Mark 13 Westinghouse Ispra Mark 9 Ispra Mark 4 Gaz de France UT-3 Tokyo Julich Ispra Mark 7B Ispra Mark 7A QH analysis with ΔTmin=0 analysis Cycle Efficiencies using Qh for ΔTmin=0 100.0% US-Chlorine 100.0% Sulfur Iodine 100.0% Ispra Mark 13 Cycle Hallett Air Products 100.0% Westinghouse 100.0% Ispra Mark 9 85.7% Ispra Mark 4 78.2% Gaz de France 75.0% UT3 Tokyo 54.9% Julich 54.8% Ispra Mark 7B 52.4% Ispra Mark 7A 52.3% 0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% Efficiency 70.0% 80.0% 90.0% 100.0% Results cont. Results Now we consider Wsep, stoich and Welec as well Now stoich and QH only 1. 1. 1. 1. 1. 2. 3. 4. 5. 6. 7. 8. Hallett Air Products US-Chlorine Sulfur Iodine Ispra Mark 13 Westinghouse Ispra Mark 9 Ispra Mark 4 Gaz de France UT-3 Tokyo Julich Ispra Mark 7B Ispra Mark 7A QH, Wsep, stoich, and Welec 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. US-Chlorine Sulfur Iodine Westinghouse Ispra Mark 9 Gaz de France Ispra Mark 4 Ispra Mark 13 Julich Hallett Air Products UT-3 Tokyo Ispra Mark 7A Ispra Mark 7B Note: arrows indicate only cycles that change 3+ positions QH, Welec, and stoichiometric and stoichiometric separation analysis with ΔTmin=0 separation Cycle Efficiencies using Qh, W elec, and W sep, stoich for ΔTmin=0 US-Chlorine 96.1% Sulfur Iodine 88.1% Westinghouse 85.1% Ispra Mark 9 78.6% Gaz de France 75.0% Ispra Mark 4 73.4% Ispra Mark 13 55.7% Julich 51.9% Hallett Air Products 51.1% UT3 Tokyo 49.6% Ispra Mark 7A 49.4% Ispra Mark 7B 0.0% 47.9% 10.0% 20.0% 30.0% 40.0% 50.0% Efficiency 60.0% 70.0% 80.0% 90.0% 100.0% Results cont’d Results Now we substitute Wsep, stoich with Wsep, excess Now stoich with QH, Wsep, stoich, and Welec 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. US-Chlorine Sulfur Iodine Westinghouse Ispra Mark 9 Gaz de France Ispra Mark 4 Ispra Mark 13 Julich Hallett Air Products UT-3 Tokyo Ispra Mark 7A Ispra Mark 7B QH, Wsep, excess, and Welec 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Westinghouse Gaz de France US-Chlorine Sulfur Iodine Ispra Mark 13 Ispra Mark 9 Julich Hallett Air Products Ispra Mark 7A Ispra Mark 4 Ispra Mark 7B UT-3 Tokyo QH, Welec, and excess separation and analysis with ΔTmin=0 Cycle Efficiencies using Qh, W elec, and W sep, excess for ΔTmin=0 Westinghouse 85.1% Gaz de France 75.0% US-Chlorine 60.9% Sulfur Iodine 55.2% Ispra Mark 13 53.0% Ispra Mark 9 52.1% Julich 49.4% Hallett Air Products 48.9% Ispra Mark 7A 39.8% Ispra Mark 4 38.9% Ispra Mark 7B 34.0% UT3 Tokyo 0.0% 33.3% 10.0% 20.0% 30.0% 40.0% 50.0% Efficiency 60.0% 70.0% 80.0% 90.0% 100.0% Top 6 Thermochemical Thermochemical Cycles Based upon full analysis at ΔTmin=0 Based 1. 2. 3. 4. 5. 6. Westinghouse Gaz de France US-Chlorine Sulfur Iodine Ispra Mark 13 Ispra Mark 9 What about ΔTmin > 0? What Some cycles more sensitive Some Effect of ΔTmin on QH Ispra Mark 9 Ispra Mark 13 Sulfur Iodine US-Chlorine Gaz de France Westinghouse Qh v s ΔTmin for Top 6 Cycles 405 Qh (kJ / cycle mol) 385 365 345 325 305 285 0 5 10 15 ΔTmin (K) 20 25 Corresponding Efficiency Corresponding Cycle Efficiencies using Qh v s ΔTmin for Top 6 Cycles Ispra Mark 9 Ispra Mark 13 Sulfur Iodine US-Chlorine Gaz de France Westinghouse 100.0% Cycle Efficiency 95.0% 90.0% 85.0% 80.0% 75.0% 0 5 10 15 ΔTmin (K) 20 25 Effect of ΔTmin on QH+Welec+Wsep, stoich on stoich Qh + W elec + W sep, stoich v s ΔTmin for Top 6 Cycles Ispra Mark 9 Ispra Mark 13 Sulfur Iodine US-Chlorine Gaz de France Westinghouse Qh + W sep, stoich (kJ / cycle mol) 535.0 485.0 435.0 385.0 335.0 285.0 0 5 10 15 ΔTmin (K) 20 25 Corresponding Efficiency Corresponding Cycle Efficiencies using Qh + W elec + W sep, stoich v s ΔTmin for Top 6 Cycles Julich US-Chlorine Ispra Mark 4 Sulfur Iodine Ispra Mark 7a Gaz de France 100.0% 95.0% Cycle Efficiency 90.0% 85.0% 80.0% 75.0% 70.0% 65.0% 60.0% 55.0% 50.0% 0 5 10 15 ΔTmin (K) 20 25 Wsep, stoich vs. Wsep, excess stoich vs. Comparison of W sep, stoich and W sep, excess for Top 6 Cycles 250.0 232.0 W sep ( kJ / cycle mol) 215.2 200.0 183.7 150.0 Wsep (excess) Wsep (stoich) 100.0 50.0 43.3 38.7 30.3 17.2 11.7 11.7 11.7 0.0 0.0 Ispra Mark 9 Ispra Mark 13 Sulfur Iodine 0.0 US-Chlorine Gaz de France Westinghouse Effect of ΔTmin on QH+Welec+Wsep, excess on Qh + W sep, excess (kJ / cycle mol) Qh + W elec + W sep, excess v s ΔTmin for Top 6 Cycles Ispra Mark 9 Ispra Mark 13 Sulfur Iodine US-Chlorine Gaz de France Westinghouse 585.0 535.0 485.0 435.0 385.0 335.0 285.0 0 5 10 15 ΔTmin (K) 20 25 Corresponding Efficiency Corresponding Cycle Efficiencies using Qh + W elec + W sep, excess v s ΔTmin for Top 6 Ispra Mark 9 Ispra Mark 13 Cycles Sulfur Iodine US-Chlorine Gaz de France Westinghouse Qh + Wsep, excess (kJ / cycle mol) 100.0% 95.0% 90.0% 85.0% 80.0% 75.0% 70.0% 65.0% 60.0% 55.0% 50.0% 0 5 10 15 ΔTmin (K) 20 25 Efficiency: Literature Comparison† Comparison Sulfur-Iodine Reported Theoretical Theoretical Reported Theoretical Theoretical (thermal) (thermal) (heat/work) (thermal) (thermal) (heat/work) 52%‡ 100% 55% Tokyo UT-3 49%‡ 55% 33% Westinghouse 50% 100% 85% †Brown ‡10% et al 2000 additional efficiency projected with electricity co-generation Good Cycle Characteristics Good Hottest reaction exothermic, cascades Hottest heat to power rest of the cycle Minimizes Q Minimizes Products phase separate from each other, Products and from reactants Minimizes W Minimizes No high T, P, corrosivity, etc. as described No by Brown et al 2000 Economic Methodology Economic 500 ton/day production target 500 Enough for 0.95 million cars, according to Schultz Enough Heat Integration Heat Temperature intervals Temperature Cascades Cascades Heat exchanger network Heat Process Flow Diagrams Process Assumptions Assumptions Solids handling Solids Capital cost Capital Westinghouse Cycle - Heat Profile Westinghouse Cycle - Heat Profile Westinghouse - Heat Cascade QH -288.0 kJ H2O + SO2 -110.3 kJ -103.2 kJ -184.8 kJ ∆Hrxn 1 184.8 kJ -26.3 kJ O2 -13.5 kJ -84.0 kJ ∆Hrxn 2 129.5 kJ -10.3 kJ H2SO4 94.3 kJ 7 exchangers H2 -1.5 kJ -3.2 kJ -1.5 kJ H2O 4.7 kJ Westinghouse - Heat Exchanger Heat Network Network 1073 K ∆Hrxn 1 = 184.8 kJ -184.8 kJ QH H2SO4(g) HX-6 SO2(g) + H2O(g) + 0.5 O2(g) -84.0 kJ 1173 1173 455 HX-4 500 HX-4 H2SO4 = 94.3 kJ SO2, H2O = -110.3 kJ Zone 1 = -28.8 kJ -10.3 kJ 455 350 HX-3 350 K O2 QH -103.2 kJ 1173 -26.3 kJ SO2(g) + 2 H2O(l) H2SO4(g)+H2(g) HX-7 350 Zone 2 = 2.4 kJ 298 K H2O -3.2 kJ 318 HX-2 318 298 HX-1 -1.5 kJ P-51 508 HX-3 ∆Hrxn 2 = 129.5 kJ 500 350 HX-5 508 298 HX-2 350 298 HX-1 H2 Westinghouse - Heat Exchanger Heat Network Network H2O + SO2 O2 1173 K 1173 K H2 350 K 1173 K 455 K 350 K HX-3 HX-2 508 K 500 K 350 K 318 K HX-2 298 K 298 K H2O HX-1 298 K 350 K HX-6 H2SO4 ∆Hrxn 2 HX-5 350 K 1173 K HX-7 ∆Hrxn 1 Westinghouse - Process Flow Process Diagram Diagram Reactor Heat H2O(l) Reactor 1 1173 K O2(g) O2(g) HX-2 H2(g) SO2(g), H2O(g), O2(g) H2O(l) HX-7 H2SO4(g) HX-1 Reactor Heat Electrolyzer Heat Separator H2O(l) H2(g) Electrolyzer 350 K H2SO4(l) SO2(g), H2O(g) SO2(g), H2O(l) HX-5 HX-4 O2(g) HX-6 Electrolyzer Heat HX-3 Handling Solids Handling Physical transport of solids difficult Physical Grinders necessary Grinders Slow heat transfer between solids Slow Use sweep gas as intermediate heat carrier Use Solid separations Solid Usually oxides and halide salts – solvent separation Usually UT-3 University of Tokyo† UT CaBr2 + H2O → CaO + 2HBr 3FeBr2 + 4H2O → Fe3O4 + 6HBr + H2 Membrane H2 H2O O2 Membrane P-15 CaO + Br2 → CaBr2 + 0.5O2 Fe3O4 + 8HBr → 3FeBr2 + 4H2O + Br2 •Solids do not move – reactors run in parallel batch •Preserves efficiency, but increases capital costs and instability •Reported thermal efficiency 49%, compared to 55% theoretical †Adapted from Brown et al 2000 US Chlorine – Heat Cascade Cl2(v) + H2O(v) 2HCl(v) + 1/2O2(v) 1123 K 773 K Cl2 2CuCl2(s) CuCl2 473 K 298 K H2O 2CuCl(l) + Cl2(v) 2CuCl(s) + 2HCl(aq) 2CuCl2(s) + H2(v) HCl O2 CuCl H2 US Chlorine – Process Flow Process Diagram Diagram Gaz de France - Heat Exchange Gaz de Heat Network Network O2 ∆Hrxn 3 398 K 398 K H2 K2O2 998 K K 1098 K 1098 K 1098 K 998 K HX-1 1040 K 998 K HX-2 998 K 621 K HX-4 398 K HX-8 HX-7 398 K K2O ∆Hrxn 2 1030 K 398 K KOH HX-3 998 K 298 K H2O HX-5 298 K 298 K 1098 K ∆Hrxn 1 HX-6 Gaz de France Gaz H2O(l) 298K H2O O2(g) O2 (g) 298K HX-8 HX-5 KOH(s) 398K Reactor 3 HX-3 K(g) K(g) KOH 621K HX-6 K2O2(s) HX-4 K2O2(s) 1098K Reactor 1 Nuclear Reactor K2O(s) K2O(S) 998K HX-1 K(g) HX-2 K(l) H2(g) H2 (g) 298K HX-7 KOH(l) 998K Reactor 2 Capital Cost Capital New technology New Processes involve highly corrosive Processes materials and high temperatures† Resistance to degradation involved within the Resistance cycles High temperature quality material required High Research involved for design Research Some kinetics are currently unknown Some Contract work involved Contract †Perret et al 2004 Capital Cost cont’d Capital 500 tons/day hydrogen production 500 Equilibrium (complete reaction) Equilibrium Maximum heat exchange area possible Maximum Highly corrosive materials Highly Scale up has never been done Scale Capital Cost Results Capital Westinghouse Efficiency FCI Energy Cost Process Cost, $/lb H2 produced Gaz de France US-Chlorine 85% 75% 60% $3,100,000,000 $6,200,000,000 $3,100,000,000 $27,000,000 $39,000,000 $38,000,000 $0.07 $0.11 $0.11 Conclusions Conclusions Scoping methodology can screen large Scoping number of cycles with reasonable accuracy Sulfur-Iodine and other popular cycles are Sulfur Iodine not necessarily best not Find cycles with phase separations and Find good heat cascade Questions? Questions? References References Brown, L.C.; Showalter, S.K.; Funk, J.F.; Nuclear Production of Hydrogen Using Brown, Thermochemical Water-Splitting Cycles. 2000. US DOE project under NERI grant Thermochemical 2000. DE-FG03-99SF21888 DE 99SF21888 Holiastos, K.; Manousiouthakis, V.; Automatic Synthesis of Thermodynamically Feasible Holiastos K.; Manousiouthakis V.; Automatic Thermodynamically Reaction Clusters AIChE Journal, Vol. 44, No. 1, January 1998 pp. 164-173 Reaction 173 Lewis, M. A.; High-Temperature Thermochemical Processes. DOE Hydrogen Program, High Temperature Thermochemical DOE FY 2005 Progress Report. September 2005. Argonne National Laboratory FY ratory Motupally, S.; Mah, D.T; Freire, F.J.; Weidner, J.W.; Recycling Chlorine from Hydrogen Motupally S.; Mah D.T; Freire F.J.; Chloride - A new and economical electrolytic process. The Electrochemical Society The Interface, 1998 Peters, M.; Timmerhaus, K. D.; West, R. E.; Optimization Application: Pinch Technology Timmerhaus K. Analysis Plant Design and Economics for Chemical Engineers. pp. 414-433. 433. Analysis McGraw-Hill, NYC, 2003 McGraw Schultz, K. R. Use of the Modular Helium Reactor for Hydrogen Production. General Schultz, Use General Atomics Report. September 2003 US DOE Grant No. DE-FG03-99SF21888 Atomics 99SF21888 ...
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