Preliminary Process Analysis and Simulation of Thermochemical

Hydrogen Generation Using Copper-Chloride Cycle

Mohammad Arif Khan and Yitung Chen

Department of Mechanical EngineeringUniversity of Nevada Las Vegas

3rd Information Exchange Workshop on Hydrogen Production TechnologyOctober 5-7, 2005

Oarai, Japan

2

Outline

IntroductionAdvantages of Nuclear EnergyAdvantages of Using HydrogenU.S. Nuclear Hydrogen InitiativeGenIV Outlet Temperature RequirementNuclear Hydrogen R&D AreasSulfur-based CyclesThermochemical ProcessesSulfur-iodine (S-I) Thermochemical Cycle

Low Temperature (550°C) Cu-ClThermochemical Cycle

3

Outline (Cont.)

Advantages of Cu-Cl Thermochemical CycleThermodynamic Feasibility of the ReactionsSchematic Diagram of Cu-Cl ThermochemicalCycleAnalysis of Simulation Flowsheet of Cu-ClThermochemical CycleEfficiency Estimation of Cu-Cl ThermochmicalCycleSummary of Cu-Cl Thermochemical CycleAcknowledgement

4

Advantages of Nuclear Energy

Does not produce greenhouse gasesUses domestically available resourcesProduces hydrogen equally efficient to gasolineAvoids use of carbon or fossil fuels

5

Advantages of Using Hydrogen

Clean and secureAbundant fuel sourceCan be stored for future useReduce Green house effectTransforms via an electrochemical reaction efficiently into electrical energy with the use of fuel cells

6

Nuclear Hydrogen R & D Plan

March 2004

Final Draft

Sequ

estr

atio

n

Coal

Natural Gas

Oil

Biomass

HydroWindSolar

Nuclear

U.S. Nuclear Hydrogen InitiativeHydrogen production options for Generation IV reactors

• Production and interface technologies for Gen IV reactors (NGNP)

• NHI R&D

•Thermochemical cycles

•High temperature electrolysis

•High temperature heat exchangers and materials

• NHI 10 Year Program Plan

Source: DOE Review Meeting

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 2015Domestic hydrogen production in a large-scale, emission free and cost effective mannerTo fuel the future hydrogen economy

8

Gen IV Reactor Outlet Temperatures Electrical / Hydrogen Requirements

300 400 500 600 700 800 900 1000 1100Temp C

VHTRGFR

Pb FRSFR

SCWR

S-I

High Temp Elect

He BraytonSupercrit CO2

MSR

Ca-Br

Temperature Ranges

300 400 500 600 700 800 900 1000 1100Temp C

VHTRGFR

Pb FRSFR

SCWR

S-I

He BraytonSupercrit CO2

MSR

Ca-Br Hydrogen Production Temperature RangesHydrogen Production Temperature Ranges

Electrical Conversion TechnologiesRankine (SC,SH)

Gen IV Reactor Output

Source: DOE Review Meeting

9

Nuclear Hydrogen R&D Areas

1/2O2+SO2 + H2O SO2+2H2O+I2 I2 + H2

2HIH2SO4

SO2

H2O2H2O

I2

H2SO4H2SO4 + 2HI 2HI

900-C

Thermochemical Cycles

Interface Technologies (HX, Materials)

• Thermochemical cycles

• High temperature electrolysis

• System interface (high temp materials and HX design

High Temperature Electrolysis

10

• Identified as a baseline process

• High overall efficiencies

• Most extensively demonstrated thermochemical process

• Least complex system• Increased viability

based on number of process options

Sulfur-based Cycles

Source: DOE Review Meeting

11

Thermochemical Processes

Source: DOE Review Meeting

12

Sulfur-iodine (S-I) Thermochemical Cycle

Developed by General Atomics (GA) in 1970sAdvantages - 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

13

Sulfur-iodine (S-I) Thermochemical Cycle (Cont.)

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 1981.Designated by H-6 Cycle Consisted of four reactions

Three thermal processOne electrochemical process

H-6 Cycle was defined as workable even though the electrochemical step had not been proven experimentallyChemical 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

15

Advantages and Disadvantages of Cu-Cl Thermochemical Cycle

Advantages:Maximum cycle temperature (<550°C) allows the use of multiple and proven heat sourcesThe intermediate chemicals are relatively safe, inexpensive and abundantMinimal solids handling is neededAll 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.

16

Reactions Involve in Cu-Cl Thermochemical Cycle

ReactionNo.

Reactions Temp. ° C

ΔGkcal/mol

ΔHkcal/mol

1. 2Cu(s)+2HCl(g) = 2CuCl(l)+H2(g) 450 3.85 -13.50

2. 4CuCl(s)+4Cl-=4CuCl2-

Electrochemical Step

30 8.27 0.06

3. 4CuCl2-= 2CuCl2(aq)+2Cu(s)+4Cl-Electrochemical Step

30 14.54 2.93

4. 2CuCl2(aq) = 2CuCl2(s) 100 6.00 19.92

5. 2CuCl2(s)+H2O(g) = CuO(s) +CuCl2(s)+ 2HCl(g)

400 9.50 28.00

6. CuO(s)+CuCl2(s) = 2CuCl(l)+1/2O2(g) 550 -2.75 31.00

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 process1.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 H2 Production, GRI-80-0023 (June, 1981)

18

Schematic Diagram of Cu-Cl Thermochemical Cycle

Source: Chemical Engineering Division, ANLProcess heat

19

Simulation Flowsheet of Cu-Cl Thermochemical Cycle

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 O2-REACT does the oxygen production reaction, and Block H2-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

21

Efficiency Estimation of Cu-ClThermochmical Cycle

The efficiency of the Cu-Cl cycle can be calculated by using the following equation:

where ε = Thermal efficiencyΔH = Hydrogen heating value (Low)Qi = External Heat DemandWi = External Power Demand

η = Efficiency of External Electrical Power Generation

All energy values are based on the generation of one mole ofhydrogen by the process.

η

εi

iWQ

H∑+∑

Δ=

Source: Dr. Michele Lewis, Chemical Engineering Division, ANL

22

Efficiency Estimation of Cu-ClThermochmical Cycle (Cont.)

The efficiency calculated is referred to as the low heating value efficiency.Low heating value of hydrogen is taken as 241.83 kJ/mole.Total heat input = 26851.81 kJTotal heat recovery = -23842.20 kJTotal power recovery = 1093.6 kJAn 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 )

23

Summary of Cu-Cl ThermochemicalCycle

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 energyProcess flowsheet for Cu-Cl cycle has been developed for hydrogen generationThough the simulation results converged, operating conditions for heat exchanger and reactors should be modified for better efficiencyThe 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 definedProcess heat for generating hydrogen will be supplied from the nuclear power plant

24

Acknowledgement

This project is funded by the U.S. Department of Energy (DOE) DE-FG36-03GO13062Dr. Michele Lewis (ANL) and Dr. Joe Masin (ANL) for their suggestions

25

Questions ?