Low Cost, Off-board Regeneration of Sodium Borohydride€¦ · Millenium Cell sodium borohydride...
Transcript of Low Cost, Off-board Regeneration of Sodium Borohydride€¦ · Millenium Cell sodium borohydride...
Low Cost, Off-board Regeneration of
Sodium Borohydride
Ying Wu
Millennium Cell Incorporated
26 May 2004
2004 DOE Hydrogen, Fuel Cells & Infrastructure
Technologies Program Review
This presentation does not contain any proprietary or confidential information This presentation does not contain any proprietary or confidential information
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ObjectivesObjectives
Development of a Reliable Regeneration Process of Sodium Borohydride(NaBH4) that meets DOE Cost Targets
New Contract
Signed Feb 19, 2004
Technical Approach is to Identify Electrolytic Processes which Reduce Cost
Direct Borate Reduction
High Efficiency Sodium Reduction
A Key Tool is to use Hydrogen Gas To Reduce Cell Voltage and ImproveRegeneration Efficiency.
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BudgetBudget
$1,097,326
$1,500,000
FY’04 Funding As of End of
March’04:
FY’04 –’06
$ 900,000
$3,600,000
$4,500,000
$70,846MCEL&APCI
$ 283,381DOE funds
$ 354,227Total Project
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Technical Barriers and TargetsTechnical Barriers and Targets
Barriers
C. Efficiency
G. Life Cycle and Efficiency Analyses
Q. Regeneration Processes for IrreversibleSystems
R. By-Product Removal
Applicable to Delivery and Off-Board Storage
Targets
Will Meet Long Term Cost Target!
2010– $1.5 / gallon of gasoline equivalent
Energy Efficiency and Fuel Cost areIntimately Related
Regenerate By-Products into NewHydrogen Gas Carrier
100%
38%
21% 4% 2% 1%
$40.00
$71.00
$200.00
$4.60$7.10$1.40
0%
20%
40%
60%
80%
100%
120%
$/k
g S
BH
-20
0
20
40
60
80
100
120
140
160
180
200
$/k
g H
2
Proj'd SBH cost ($/kg)
Current SBH cost ($/kg)
Eq/ H2 Cost ($/kg)
Est. Prdctn.
Cost SBH
($3.5/kgNa)
Retail SBH
($3.5/kgNa)
Schl.
Process
($1.0/kg Na)
Direct
H-assist SBH
($0.5/kg NaBO2)
Direct H-assist
SBH (recyc'd
NaBO2)
Minimum Cost
($0.05/kWh,
$0.80/kg H2)
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System Storage Density : Gravimetric Projections
Hydrogen on DemandTM System (50-75 kW, 7.5 kg stored H2 )
System Storage Density : Gravimetric Projections
Hydrogen on DemandTM System (50-75 kW, 7.5 kg stored H2 )
2.5% 3.0%
4.3%
6.9%7.8%
0
10
20
30
40
50
60
70
80
90
100
1998 2000 2002 2004 2006 2008 2010 2012 2014 2016
Year
NaB
H 4 S
tore
d C
on
cen
trati
on
(wt%
)
0
2
4
6
8
10
12
14
16
18
20
Syste
m H
2 S
tora
ge (
wt%
)
Stored Conc System wt% DOE Targets
Pre-Natrium
Natrium
Need FC Water!
Next Generation
Prototypes
Note: Projected System H2 Storage is based on an average weight.
NaBH4 Has an Exceptional Combination of Volumetric and Gravimetric EnergyDensities, and More Room for Upward Growth than Most Other Storage Technology!
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4 NaH
(+B(OCH3)3)
4 Na
(+2 H2)
4 NaCl
NaBH4
365 kJ4 NaOH
(+2 H2)
500 kJ
100 kJ
1880 kJ
NaBH4 Regeneration is Keys To Cost ReductionNaBH4 Regeneration is Keys To Cost Reduction
• Direct reaction route toNaBH4 is highly desirable.
• Only one step!
• More efficient Naprocess will significantlyimpact NaBH4
regeneration efficiency
Reaction Steps
CO2
CO2Cl2 or HCl
CH4
Steam
Reforming
NaClElectrolysis
BoraxRefining
Na Metal
H2
CH3OH
NaH
H3BO3 B(OCH3)3
NaBH4
3 CH3OH + 3 NaOH
3 NaOCH3
H2SO4 Na2SO4
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Reduce # of Process StepsReduce # of Process Steps Eliminate Inefficiency in Critical StepsEliminate Inefficiency in Critical Steps
3200 kJ
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Technical ApproachTechnical Approach
Identify a one-pot electrolytic synthesis of the borohydride anion
Improve efficiency/cost of the present synthesis at most costlystep: Identify a reduced energy electrolysis to sodium metal
Integrated intoSchlesinger Process
Separator material
B2O3 removal from cell
E0rev = 2.16 V
H-assisted NaBO2
Electrolysis
Integrated intoSchlesinger Process
Separator material
Efficiency
E0rev = 1.07 V
H-assisted molten
NaOH electrolysis
Replacement technology
Separator materialNaBH4 stability
Cathode “catalyst”
E0rev = 0.89 V
Direct H-assisted
Electrolysis
Issues
How toImplement
Std CellPotential
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Project SafetyProject Safety
General Safety Procedures
Fume Hood
Removable PlexiglassShielding
Distant Operator Interface
Standard and RegularSafety Inspections
Specific Safety Procedures
Double Bubbler
All Stainless SteelManifolding
“Pop-Top” Pressure Relief
Aluminum Housed Mantles
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Task 1 – Study of the NaBH4 synthesis alternatives
Deliverable - Summary report Interim report on experimental work
Task 2 – Evaluate 3 methods for lower cost electrolytic synthesis
Deliverable - Detailed experimental report
Select Best Pathway to Proceed
Task 3 – Preliminary Engineering and Economics Study
Deliverable - Preliminary report on engineering on economic assessment
Select Best Pathway to Proceed
Task 4 – Laboratory Prototype Demonstration Unit
Deliverable - Recommendation for future development
Task 5 – Ongoing Project Management and Reporting
Deliverable - Final project report
Timeline of Proposed TasksTimeline of Proposed Tasks
Q1 Q3Q2 Q4 Q8Q7Q6Q5 Q9 Q10 Q11 Q12
Nov 1, 2005 – Oct 31, 2006Nov 1, 2003 – Oct 31, 2004 Nov 1, 2004 – Oct 31, 2005
Task 1 Task 3Task 2 Task 4
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Progress and Technical AccomplishmentsProgress and Technical Accomplishments
New Project Start-Up ItemsAlternate Pathway Analysis Completed
Installation of New NMR CapabilitiesCompleted
Air Products Duplicate Set Up In Progress
Electrolysis ResultsSodium Metal Generated at Cell Potentialof 1.2 V
Apparent Electrolytic Activity of SodiumMetaborate in Hydroxide Melt Observed
Hydride Transfer Catalyst Study Completed
Anode
Tube madefrom ”-
alumina
Na+
Cathode
NaOHAnolyte
NaOHCatholyte
Na+
Na+
H2
Frit
Reference ElectrodeNa/Na+ couple in ”-
alumina tube
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Electrolytic Reduction of NaOH to Na MetalElectrolytic Reduction of NaOH to Na Metal
Current Industrial Processes Require 9.7 kWh/kg Na Produced
H2 Assisted Electrolysis Shown Below Required only 1.8 kWh/kg Na!
Target is 1.5 kWh/kg Na, or 85% Efficiency
Reduced cell voltage and improved efficiency is directly applicable toelectrosynthesis of NaBH4.
Results
Theoretical Cell Voltage at 360°C Is 1.07 V
Steady State Operating Voltage: 1.2 V
Voltage Efficiency: 89%
Current Efficiency: 78%
Total Electrolytic Efficiency Is 69%
Results
Switching from Nitrogen to Hydrogen at theCounter Electrode Shows:
No Change in Cell Performance
Big Change in Cell Voltage
-500
-400
-300
-200
-100
0
0 3000 6000 9000 12000 15000 18000
Time (seconds)
Cu
rren
t (m
A)
-1.5
-1.2
-0.9
-0.6
-0.3
0
Cell P
ote
nti
al
(vo
lts)
Current Cell Potential
0
0.5
1
1.5
2
2.5
0 20 40 60 80 100 120 140
Time (seconds)
Po
ten
tial
(vo
lts)
-250
-200
-150
-100
-50
0
50
100
150
200C
urr
en
t (m
illiam
ps)
H2 Counter Electrode Potential N2 Counter Electrode Potential
H2 Current N2 Current
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Apparent Electrolytic Activity of Sodium
Metaborate in Hydroxide Melt
Apparent Electrolytic Activity of Sodium
Metaborate in Hydroxide Melt
Direct Electrolysis of Borates Lowers Number of Process Steps
AND Requires Less Voltage than Current Methods of Sodium Production
AND May Allow Direct Reprocessing of the Chemical Hydride
-8
-6
-4
-2
0
2
4
6
8
-3 -2 -1 0 1 2
Potential (volts)
Cu
rren
t (m
A,
No
Bo
rate
)
-80
-60
-40
-20
0
20
40
60
80
Cu
rren
t (m
A,
Bo
rate
)
No Borate Borate
Results
Addition of NaBO2 to aHydroxide Melt CausesRadical Change in the CyclicVoltammogram
Reduction Wave RemainsUnidentified
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Air Products and Chemicals IncorporatedSubcontractor
Engineering Expertise, Process Development, Scale-Up
Monthly In-person Project Team Meetings
Air Products Equipment on Loan to Millennium Cell
Princeton UniversityConsultant
Electrochemistry Expertise
INEELPreliminary discussion with Bruce Wilding on NaBH4 generation byradiation chemistry.
Ionotec LtdKey Supplier of Membranes
Technical Support, Custom Electrode Designs
Interactions and CollaborationsInteractions and Collaborations
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Future Work(Year 1 of Project)
Future Work(Year 1 of Project)
Ascertain NaBO2 Electrolysis Results; Rule Out False Positives;Demonstrate Feasibility of Direct Electro-Reduction of NaBO2. (One-stepRegeneration)
Improve Sodium Electrolysis Efficiency Through Cell Design; Progressfrom Batch Synthesis to Flow Through System. (Efficiency Improvement)
Transfer Successes in Sodium Electrolysis to an Aqueous NaBO2/NaOHSystem, and Demonstrate Sodium Electrolysis Concurrent with Sodium andBoron Separation (Efficiency Improvement)
From the Different Methods, Select the Most Promising One for Economicand Engineering Study
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Response to FreedomCAR Tech Team CommentsResponse to FreedomCAR Tech Team Comments
System storage efficiency – gravimetric and volumetric
Revised gravimetric storage efficiency by taking the average system weight ofthe fully charged state and the fully depleted state. New results included onpage 5 of this presentation.
Roadmap to improving volumetric storage efficiency pending furtherdevelopment work.
Confirm storage system cost
Initial estimates based on material cost (mostly off-the-shelf parts) forconstructing the fuel system and the first tank of fuel.
Further analysis of system cost is needed to update initial estimates.
Regeneration process energy efficiency
Experiments underway to optimize electrolysis process efficiency.