Preliminary Process Analysis and Simulation of Thermochemical Hydrogen Generation Using Copper-Chloride Cycle

Transcription

1 Preliminary Process Analysis and Simulation of Thermochemical Hydrogen Generation Using Copper-Chloride Cycle Mohammad Arif Khan and Yitung Chen Department of Mechanical Engineering University of Nevada Las Vegas 3rd Information Exchange Workshop on Hydrogen Production Technology October 5-7, 2005 Oarai, Japan

2 Outline Introduction Advantages of Nuclear Energy Advantages of Using Hydrogen U.S. Nuclear Hydrogen Initiative GenIV Outlet Temperature Requirement Nuclear Hydrogen R&D Areas Sulfur-based Cycles Thermochemical Processes Sulfur-iodine (S-I) Thermochemical Cycle Low Temperature (550 C) Cu-Cl Thermochemical Cycle 2

3 Outline (Cont.) Advantages of Cu-Cl Thermochemical Cycle Thermodynamic Feasibility of the Reactions Schematic Diagram of Cu-Cl Thermochemical Cycle Analysis of Simulation Flowsheet of Cu-Cl Thermochemical Cycle Efficiency Estimation of Cu-Cl Thermochmical Cycle Summary of Cu-Cl Thermochemical Cycle Acknowledgement 3

4 Advantages of Nuclear Energy Does not produce greenhouse gases Uses domestically available resources Produces hydrogen equally efficient to gasoline Avoids use of carbon or fossil fuels 4

5 Advantages of Using Hydrogen Clean and secure Abundant fuel source Can be stored for future use Reduce Green house effect Transforms via an electrochemical reaction efficiently into electrical energy with the use of fuel cells 5

6 U.S. Nuclear Hydrogen Initiative Hydrogen production options for Generation IV reactors Biomass Hydro Wind Solar Production and interface technologies for Gen IV reactors (NGNP) NHI R&D Thermochemical cycles Nuclear Hydrogen R & D Plan Nuclear High temperature electrolysis March 2004 Oil Coal Natural Gas Sequestration High temperature heat exchangers and materials NHI 10 Year Program Plan Source: DOE Review Meeting Final Draft 6

7 U.S. Nuclear Hydrogen Initiative (Cont.) The goal of the Nuclear Hydrogen Initiative (NHI) is to demonstrate economic commercial-scale of hydrogen production by 2015 Domestic hydrogen production in a largescale, emission free and cost effective manner To fuel the future hydrogen economy 7

8 Gen IV Reactor Outlet Temperatures Electrical / Hydrogen Requirements Temp C VHTR GFR MSR Pb FR SFR SCWR Gen IV Reactor Output Temperature Ranges S-I Ca-Br High Temp Elect He Brayton Supercrit CO2 Rankine (SC,SH) Hydrogen Production Temperature Ranges Electrical Conversion Technologies Source: DOE Review Meeting 8

9 Nuclear Hydrogen R&D Areas High Temperature Electrolysis Thermochemical cycles High temperature electrolysis System interface (high temp materials and HX design Interface Technologies (HX, Materials) 900-C O 2 H 2 O H 2 I 2 SO 2 1/2O 2 +SO 2 + H 2 O SO 2 +2H 2 O+I 2 I 2 + H 2 H 2 SO 4 H 2 SO 4 + 2HI 2HI H 2 SO 4 2HI Thermochemical Cycles 9

10 Sulfur-based Cycles Identified as a baseline process High overall efficiencies Most extensively demonstrated thermochemical process Least complex system Increased viability based on number of process options Source: DOE Review Meeting 10

11 Thermochemical Processes Source: DOE Review Meeting 11

12 Sulfur-iodine (S-I) Thermochemical Cycle Developed by General Atomics (GA) in 1970s Advantages - All fluid process - Side reactions are minimal - Fully flowsheeted cycle - Highest efficiency among the STCWS cycle 47% Challenges -High temperature 850 C - Integrated cycle not yet demonstrated - Process economic not yet verified 12

13 Sulfur-iodine (S-I) Thermochemical Cycle (Cont.) 13 Source: Final Report, GA, Sep, 2003

14 Low Temperature (550 C) Cu-Cl Thermochemical Cycle First proposed by R. H.Carty in a GRI Report in Designated by H-6 Cycle Consisted of four reactions Three thermal process One electrochemical process H-6 Cycle was defined as workable even though the electrochemical step had not been proven experimentally Chemical Engineering Division of ANL is currently working on this cycle which is designated as ALTC-1. ANL adds two additional reactions with the H-6 cycle 14

15 Advantages: Advantages and Disadvantages of Cu-Cl Thermochemical Cycle Maximum cycle temperature (<550 C) allows the use of multiple and proven heat sources The intermediate chemicals are relatively safe, inexpensive and abundant Minimal solids handling is needed All reactions have been proven in the laboratory and no significant side reactions have been observed. Disadvantages: This process involves six reactions. Two of the reaction are electrochemical, which imposes significant energy cost. 15

16 Reactions Involve in Cu-Cl Thermochemical Cycle Reaction Reactions Temp. ΔG ΔH No. C kcal/mol kcal/mol 1. 2Cu(s)+2HCl(g) = 2CuCl(l)+H 2 (g) CuCl(s)+4Cl - =4CuCl 2 - Electrochemical Step 3. 4CuCl 2- = 2CuCl 2 (aq)+2cu(s)+4cl - Electrochemical Step CuCl 2 (aq) = 2CuCl 2 (s) CuCl 2 (s)+h 2 O(g) = CuO(s) +CuCl 2 (s) + 2HCl(g) CuO(s)+CuCl 2 (s) = 2CuCl(l)+1/2O 2 (g)

17 Thermodynamic Feasibility of the Reactions ΔG and ΔH for the reactions obtained from HSC Chemistry 5.11 software. ΔG of each reaction step is ±10 kcal/mole, except for the electrochemical step. ΔG lies within ±10 kcal/mole for a given temperature are considered candidates for a cyclic process 1. Small positive ΔG are acceptable if non-equilibrium reactor can be utilized (continuous product removal) 1. Reactions with positive ΔG of 10 to 25 kcal/mole can generally be accomplished electrochemically. 1. Carty, R.H.; Mazumder, M.; Schreiber, J., Thermochemical H 2 Production, GRI (June, 1981) 17

18 Schematic Diagram of Cu-Cl Thermochemical Cycle Process heat Source: Chemical Engineering Division, ANL 18

19 Simulation Flowsheet of Cu-Cl Thermochemical Cycle 19

20 Analysis of Simulation Flowsheet of Cu-Cl Thermochemical Cycle Simulation flowsheet has been developed and modified from the actual flowsheet developed by ANL. Two ASPEN PLUS process blocks (one reactor and one separator) combined together to model an electrolyzer. Block ELCTRLYZ does the electrolysis reactions and Block SEP-1 separates the reaction products into anode and cathode streams. Reactions have been defined in the individual reactor blocks instead of globally. Block O 2 -REACT does the oxygen production reaction, and Block H 2 -REACT contains the hydrogen production reaction. In the simulation model, a filter has been used to remove the Cu slurry from the rest of the aqueous solution 20

21 Efficiency Estimation of Cu-Cl Thermochmical Cycle The efficiency of the Cu-Cl cycle can be calculated by using the following equation: ε = Δ H W + η where ε = Thermal efficiency ΔH = Hydrogen heating value (Low) Q i = External Heat Demand W i = External Power Demand η = Efficiency of External Electrical Power Generation All energy values are based on the generation of one mole of hydrogen by the process. Q i i Source: Dr. Michele Lewis, Chemical Engineering Division, ANL 21

22 Efficiency Estimation of Cu-Cl Thermochmical Cycle (Cont.) The efficiency calculated is referred to as the low heating value efficiency. Low heating value of hydrogen is taken as kj/mole. Total heat input = kj Total heat recovery = kj Total power recovery = kj An efficiency of 50% is assumed for any electrical generation not supplied by the process. Based on the above heat input and power recovery, the preliminary study of LHV efficiency is about 29% which is less than that of ANL (41% based on thermodynamic analysis ) 22

23 Summary of Cu-Cl Thermochemical Cycle The thermodynamic feasibility of the reactions involved in Cu-Cl cycle has been studied. It can concluded that all reactions are thermodynamically viable based on the values of the free energy Process flowsheet for Cu-Cl cycle has been developed for hydrogen generation Though the simulation results converged, operating conditions for heat exchanger and reactors should be modified for better efficiency The efficiency of Cu-Cl is about 29% which is less than the efficiency calculated by the Chemical Engineering Division of ANL (41%) More reliable efficiency values can be obtained after the chemistry model of the cycle is well defined Process heat for generating hydrogen will be supplied from the nuclear power plant 23

24 Acknowledgement This project is funded by the U.S. Department of Energy (DOE) DE-FG36-03GO13062 Dr. Michele Lewis (ANL) and Dr. Joe Masin (ANL) for their suggestions 24

25 Questions? 25