POSSIBILITY OF A CHEMICAL HYDROGEN CARRIER SYSTEM BASED ON NUCLEAR POWER

Transcription

1 POSSIBILITY OF A CHEMICAL HYDROGEN CARRIER SYSTEM BASED ON NUCLEAR POWER Yukitaka Kato Research Laboratory for Nuclear Reactors Tokyo Institute of Technology 6 th October, 2005, Oarai, Japan 3rd Information Exchange Meeting on the Nuclear Production of Hydrogen 2nd HTTR Workshop on Hydrogen Production Technology OECD NUCLEAR ENERGY AGENCY(OECD-NEA) & Japan Atomic Energy Agency(JAEA) 1

2 Contents Introduction Need for chemical energy conversion technology Need for efficient carrier system for fuel cell Chemical equilibrium for energy utilization Non-equilibrium Technologies for hydrogen productions Zero CO 2 emission hydrogen carrier system Experiment Evaluation for the carrier system with HTGR Conclusions. 2

3 Fuel reforming for Hydrogen Production 3

4 Hydrogen for FC -A fuel cell is environmental friendly?- Problems of supply to a conventional fuel cell vehicle Compressed fuel : high-energy consumptions for production and pressurization, and explosiveness Need for efficient carrier system 1 st Energy input 2 nd Energy input Explosiveness of Hydrogen source Compressed cylinder Fuel cell O Fig. Conventional hydrogen supply process for a fuel cell vehicle 4

5 Fuel reforming for hydrogen supply to a fuel cell vehicle Problems of supply to a conventional fuel cell vehicle Fuel Reforming: complex structure, and CO 2 emission Heat input Heat output Cat. Cat. O Reformer Shift Converter CO 2, Fuel cell CO 2, O Fig. Conventional reforming system for a FC vehicle 5

6 Separation process for hydrogen production Fuel reforming +2 O 4 +CO 2 Separation processes enhance production by Le Chatelier s principle. Separation processes Separating from system using a membrane Separating CO 2 from system using chemical absorption 6

7 Shifting strategy map Reforming processes (a) Conventional, non-treatment Reforming, CO 2, CO, others C n H m O k +b O hydrogen source (b) separation Reforming+ separation Non-equilibrium Equilibrium mixture Pure Exhaust CO 2 Fuel cell (c) CO 2 separation Reforming+CO 2 separation Pure Non-equilibrium CO 2 fixation 7

8 Zero CO 2 emission hydrogen carrier system 8

9 Regenerative Reforming -Use of chemical absorption- Fuel reforming for methane + O 3 +CO, ΔH 1 = kj/mol CO+ O +CO 2, ΔH 2 = 41.1kJ/mol CaO carbonation CaO(s)+CO 2 (g) CaCO 3 (s), ΔH 3 = kj/mol Regenerative reforming (CO 2 absorption reforming, self-heating) CaO(s)+ (g)+2 O(g) 4 (g)+caco 3 (s), ΔH 4 = 13.3 kj/mol 9

10 CO 2 zero-emission FC vehicle Regenerative reforming CO 2 recoverable, self heating, and simple reforming system thermally regenerative CO 2 zero-emission FC vehicle Safety carrier system under low-pressure and (1) CO 2 absorption reforming O CaO, Cat. CO 2 absorption reforming Fuel cell O (2) CaO regeneration/co 2 recovery Surplus heat/electricity high-density CaCO 3, Cat. CO 2 CO 2 recovery process 10

11 Zero CO 2 emission carrier system Hydrogen system driven by off-peak power from nuclear power plant & high temperature processes. Safe and compact hydrogen transportation CO 2 zero emission energy system Fuel cell vehicles Recycle Renewable energy system Electricity/ Heat CO 2 Electrolysis of water Hydrogenation CaO CO 2 regenerator storage regenerator Regeneration Station Nuclear power plants (HTGR), high temperature. Industrial process 11

12 CO 2 absorption reforming During the initial 60 min, hydrogen production was higher than the equilibrium concentration of conventional reforming. Charged CaO absorbed well CO 2 by carbonation. CO 2 <1% CO was removed, <1% Low-temperature reforming (conventional reform. temp. > 700 o C) c [mol%] Equilibrium concentration of the conventional reforming t [min] Equilibrium concentration of the regenerative reforming T=550 o C CO 2 CO Al 2 O 3 Ni cat+cao (a) regenerative reformer (RGR) Fig. Temporal change of effluent composition of the regenerative reformer at 550 C 12

13 Comparison between systems Table: Scale of energy storage facilities for 100 km mileage, 14.7 kwh, 500 mol- (= Petroleum of 4 L, 2.8 kg) Hydrogen cylinder, 70 MPa 25.6 L mass [kg] volume [liter] Metal hydride, 1.5 wt% 67 kg Advanced Li-ion battery Advanced lead-acid battery Regenerative reformer* 20.1 kg 13.5 L 100 kg 400 kg volume [liter], mass [kg] (*total reactant amount including CaO, O and liquefied assuming under 3.86 MPa and at -88 o C). 13

14 Merits of regenerative reforming CaO(s)+ (g)+2 O(g) 4 (g)+caco 3 (s), ΔH 4 = 13.3 kj/mol CO 2 removing induces the reforming state into nonequilibrium Self heating Reaction enhancement by non-equilibrium Enhancement of production yield Reduction of reforming temperature Improvement of hydrogen purity Good for power generation in FC CO 2 recoverable 14

15 The hydrogen carrier system with HTGR 15

16 Combination of the carrier system and HTGR HTGR CaO regenerator Regenerated CaO package CaCO CaO 3 CO 2 compressor precooler recuperator turbine 4 O 4 Electricity 2O 2 Water electrolyser Methanator Regenerated 2 O 16

17 The carrier vs. O electrolysis (1) Enthalpy balance per 1 mol- Conventional hydrogen production, Water electrolysis Total 311 kj/ -mol O electrolysis Compression* cylinder FC * isenthalpic & 5 stages Compression to 700 bar Zero CO 2 emission hydrogen carrier system Total 331 kj/h O electrolysis 2 -mol CaO Re-generation CO Methanation Comp** 4.9 LHV, Enthalpy per 1 mol of ** isenthalpic & 5 stages Compression to 175 bar 17

18 The carrier vs. O electrolysis (2) HTGR system (GTHTR300) HTGR thermal power 1 Outlet coolant temperature from HTGR Proposed carrier system Conventional water electrolysis system HTGR operation duration for hydrogen processes 8h/day Inlet/outlet coolant temperature for CaO 850 / 835 o C - Inlet/outlet coolant temperature for gas-turbine 835 / 587 o C 850 / 587 o C Power input for CaO regeneration 34.8 MWt - Plant power input for gas-turbine power MWt MWt Gas-turbine power efficiency % 45.0 % Water electrolysis efficiency ( H base) 3 Compression pressure 175 bar- 90 % 700 bar- Power for H2 electrolysis MWe MWe Power for compression 3.8 MWe MWe- H2 production/equivalent 2.26E+07 -mol equ 2.27E+07 -mol Number of FC vehicles for 100 km mileage each E E+04 - Based on GTHTR 300, (Kunitomi et al, JAESJ, 1(4), 352(2002)) MWt o C 18

19 Enthalpy balance of the carrier & O electrolysis systems based on HTGR Conventional hydrogen production, Water electrolysis 3.82% compres. Zero CO 2 emission hydrogen carrier system 41.2% O electrolysis 4.54x10 4 cars 789 mol/s 5.8% CaO regeneration 0.63% compres. 41.0% O electrolysis 4.52x10 4 cars 784 mol/s Fig. Enthalpy consumption ratio of HTGR output (600 MWt, 8h/day) for both systems The carrier system : Reduction of compression pressure & work and transportation risk with consisting the same efficiency of conventional system > Safe and compact carrier system 19

20 Enthalpy balance CO 2 open cycle: Reduction of reformer complexity and CO 2 emission with high efficiency Zero CO 2 emission hydrogen carrier system: CO 2 open cycle On-board fuel reforming Total 44.6 kj/ -mol reforming 44.6 CO mol/ -mol CaO Re-generation Total 41.1 kj/ -mol CO mol/ -mol LHV, Enthalpy per 1 mol of 20

21 Conclusions Zero CO 2 emission carrier system has possibility to realize efficient transportation by reduction of storage compression work, storage volume and transportation risk. Total energy consumption is the same with conventional O electrolysis system. The carrier system can utilize the top temperature part in the primary loop of HTGR, and have good compatibility with HTGR 21

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