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Solid Oxide Fuel Cells for Waste to Materials & Energy
MSW to Materials & Energy Processes Workshop (ARPA-E)
Newark, NJ
11/8/2019
Bryan Blackburn, Ph.D.
Redox Power Systems
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Interesting WTE Opportunities with SOFCs
• SOFCs: 50-60% (LHV) electric conversion efficiency (>80% in CHP)– steam turbine @ 18-25%; large gas turbine (single cycle) @ ~35-40%– high efficiency even @ partial loads (unlike, e.g., gas turbines)
– MSW: variable energy content (1.2-2.5 MWh/ton)→ syngas compression/storage for certain tech
• Typical fuel is natural gas (other: liquid fuel & bio-fuel)
• Redox’s SOFC technology– higher power densities + lower temperatures = smaller, lower cost
(>1.5 W/cm2 vs ~0.3 W/cm2) (450-650°C * vs 800-900°C)11/8/19 2REDOX POWER SYSTEMS LLC
x N = Stack
RepeatUnit
ceramic/metal (cermet), ex. Ni-YSZ
ceramic
SOFC
YSZ: Yttria Stabilized ZirconiaCHP: Combined Heat & Power
ceramic
SOFC: chemical energy → electrical energy
H2O + CO2+
Heat
Air+
Heat
*ARPA-E REBELS Program
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Natural gas
SOFCStack
reac
tor
bu
rner
Air
Typical SOFC Power System
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System CostBreakdown
Reformer: ~25%SOFC: ~50%Other: ~25%
WTE can replacereformer, reduce cost!
Manufacturing Cost Analysis ofStationary Fuel Cell Systems, B. James et. al., Strategic Analysis, Sept. 2012
Steam Reforming CH4 + H2O (g) <--> CO + 3H2
Water Gas Shift (WGS) CO+H2O (g) <--> CO2+ H2
Reformer Output CO, CO2, H2 (75% dry), H2O
SYNGAS RequirementsDon’t want: Halides, particulates,
chlorides, sulfur, tars
Want: CO, H2, CH4, (too lesser degree) lower HCs
Tolerate: H2O, N2, CO2 (diluent)
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SOFC System Examples
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~230 sq ft for 200 kW
Bloom Energy Redox Power Systems
~100 sq ft for 200 kW
Nissan: SOFCs for Automotive
Microsoft: SOFCs for Data Centers
(25 kW to 300 kW building blocks)
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SOFCs/WTE: FB Gasifier + plasma clean-up
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Possible outputs: fuel production (e.g., bio-methane) and efficient electricitySee: Tetronics/APP
Conventional Fluidized Bed Gasifier
Opt
.#2
RDF or MSW
Plasma Cleanup
*Tunable H2 / CO
ratio
Compressor
Opt
.#1
Raw syngas
Remove remaining (minimal) HCl, S, particulate
Water Gas Shift
Methanation
Opt
.#4 Opt
.#3
Syngas Storage
vitrified solids
• Different options for SOFC fuel feed
1. Clean syngas2. Compressed syngas3. H2-rich syngas4. Bio-methane
• Native DC electricity (SOFC) feeds DC plasma
• Cold gas efficiency >75%
• Vitrified solids pozzolanic for cement
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SOFCs in WTE: Combustion Steam Reforming
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Pulsed combustion steam reforming
(gasification)
•Primary Stage: Indirect heating of MSW in medium temperature, low pressure (indirect bubbling) fluidized bed gasifier/steam reformer
• 2nd Stage: higher temperature, low-pressure fluidized bed gasifier → partial oxidation of stage 1 char (tune H2/CO)
SOFC electricityTail gas (heat)
MSW
Steam Steam, Oxygen
Ash
Syngas
Boiler
Stage 1
Stage 2
cleanup
See: Thermochem Recovery International
*Tunable H2 / CO
ratio
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Syngas from Traditional WTE (incineration)?
• Create syngas from incinerator ash– Assumes some remaining carbon (e.g., perhaps to reduce NOx without SCR)– Divert toxic material from landfill → clean, efficient electricity (SOFC)– Mass and volume reduction– Pozzolanic material to use in, e.g., cement production
• Plasma/Ash + SOFC → add to incineration power11/8/19 REDOX POWER SYSTEMS LLC 7
Modified from Čarnogurská et. Al. (10.1016/j.measurement.2014.11.014)
INCINERATION
MSW
Thermalenergy
SOFC
Thermalenergy
DC or ACPower
DC Current Clean Syngas
Raw Syngas
N2
Vitrified Solids
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Syngas or H2 from Traditional WTE (incineration)?
Solid Oxide Fuel Cell• Incineration heats boiler → steam
drives (NG or landfill gas) steam reforming → syngas to SOFC
• Combined cycle with SOFC & steam turbine producing electricity for higher efficiency?
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SOEC
incinerator boiler
Turbine
H2
SOFCs (stationary
power)
SOFC/PEMFC (electric vehicles)
MSW
Solids
Storage
Heat
Heat
electricity
SOFC
incinerator boiler
Turbine MSW
Solids
Heat
Heat
Electricity
Electricity
Natural gas
or
landfill gas
Solid Oxide Electrolyzer Cell (SOEC) + Fuel Cells• SOEC is like SOFC running in reverse (electrolytic operating mode)
• Use heat from incineration to make steam for turbine and SOEC
• Turbine electricity + steam feed SOEC → H2 *
*Also make O2→ use to improve incinerator combustion?
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SOFC-Related WTE Challenges
• Impurities can poison SOFC– Potential minor impact: Hg, Si, Zn, NH3, Cd, Se
(e.g., some evidence, tolerate Hg < 10ppm)
– Potential major impact: Cl, As, Sb, H2S, P (react with Ni in anode)
– Potential tar tolerance: Napthalene < 100 ppm; Benzene < 150 ppm
• Possible Solutions– WTE Process• Front-end recycling (most Cl-based plastics)• Syngas cleanup, may be cost & efficiency sensitive
– SOFC: use non-Ni catalysts at anode
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Triple Play Increases the Odds of Success
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• Find ways to further optimize waste-to-energy– Better recycling (plastics)– Minimize final waste stream (quantity)– Expand uses for solids, improve economics with complete cycle
• Find synergistic technologies to maximize benefit– Advanced energy conversion technology (e.g., SOFC / SOEC)– Syngas: gasification or pyrolysis tech– Novel integrations of SOFC/SOEC into incineration while simultaneously
improving solids– Boost energy efficiency, coupling electrical/thermal
Waste/Landfill Problem
Cleaner Electricity Product
Cleaner Solid product
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Challenges, Risks, Strategies
• Overcome “New Technology” barrier– Unavoidable, unless solutions can fit into status quo (at least at early
stages of implementation)– Find early adopters (e.g., USVI: ~$0.50/kWh)
• Cost– Find ways to boost economic output on multiple fronts (e.g., syngas
for SOFC while simultaneously improving solids for sale, or vice versa)
• Scalability– Modular approach for WTE that can match SOFC modularity– Find ways to fit SOFC/SOEC, gasification into incineration at smaller
scale for real world experience with less financial risk
• Flexibility– Integrations that allow for flexibility in revenue stream– Use technology that is less sensitive to changes in variable ”fuel”
content (e.g., SOFC)– Designs that allow for variable MSW (e.g., syngas/H2
production/compression)11/8/19 REDOX POWER SYSTEMS LLC 11