Electrical Power Generation Using Coffin Butte Landfill Biogas And Solid Oxide Fuel Cell Technology

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Electrical Power Generation Using Coffin Butte
Landfill BiogasAnd Solid Oxide Fuel Cell
Technology
PNGC
Power
Oregon State
OSU
Smart, Local, Connected
UNIVERSITY
Coffin Butte Resource Project
Chemical Engineering
A Community Investment In A Green Future
A Green Opportunity at Coffin Butte
Solid Oxide Fuel Cells (SOFCs)
Crescent Valley High School
The Coffin Butte Landfill, located approximately
eight miles north of Corvallis, provides sanitary
services for Corvallis and many surrounding
communities. Biogas (around 60 methane) is
produced as organic material deposited within the
landfill decomposes. Pipes buried within the
landfill currently collect this gas and feed it
to three Caterpillar Series-3516 16-cylinder
engines operated by PNGC Power a non-profit
power cooperative that manages the Coffin Butte
Resource Project on behalf of 12 Northwest
electric utility cooperatives. At present, these
three engines produce approximately 2.4 MW of
electrical power. This power is currently placed
upon the grid and used locally in nearly 1,800
households.
These are completely solid-state devices that use
an oxide ion-conducting ceramic material as the
electrolyte. As a result, it is simpler than
other fuel cells because only two phases are
required solid and gas. Electrolyte management
issues that are present with Molten Carbonate
Fuel Cells (MCFCs) are absent with SOFCs. The
high operating temperatures of SOFCs make
precious metal electro catalysts unnecessary,
allow for higher efficiencies, and provide for
internal fuel reformation so that both methane
(hydrogen) and carbon monoxide can serve as fuels.
Science Department
Until recently, SOFCs have been based on an
electrolyte of zirconia (ZrO2) stabilized with
the addition of a small percentage of yttria
(Y2O3). Above a temperature of about 800oC,
zirconia becomes a conductor of oxygen ions
(O2-), and typically the state-of-the-art
zironcia based SOFC operates between 800 and
1100oC. This is the highest temperature of any
operating fuel cell. The anode of the SOFC is
usually a zirconia cermet (an intimate mixture of
ceramic and metal). The metallic component is
typically nickel chosen because of its high
electronic conductivity and stability under
chemically reducing and part-reducing conditions.
In addition, the nickel serves as a catalyst for
internal reforming right at the anode. Most
cathodes are made from electronically conducting
oxides or mixed electronically conducting and
ion-conducting ceramics. Strontium-doped
lanthanum manganite is commonly used as an
electrolyte. The Zr4 ions in the lattice
associate themselves with 4 oxygen ions while the
Y3 ions (that have been added to the zirconia)
are associated with three oxygen ions.
Therefore, the occasional vacancy of oxygen ions
allows for the migration of oxygen ions through
the electrolyte. Thin electrolyte structures of
about 40 ?m in thickness can be fabricated.
Product water as steam available for steam
reformation of fuel
Hydrogen Fuel
Working Together
Anode 2H2 2O2- ? 2H2O 4e-
2H2 2O2- ? 2H2O 4e-
O2- ions through electrolyte
LOAD (i.e. electric motor)
Cathode
During the Spring of the 2003-2004 academic year,
chemistry and physics students from Crescent
Valley High School joined forces with four senior
OSU chemical engineering students to produce
preliminary feasibility studies looking at the
suitability of using a high temperature fuel cell
to convert existing excess landfill gas to
electricity. Used in this fashion, a fuel cell
will increase the power produced at Coffin Butte,
realize higher efficiencies than the existing gas
engines, and will reduce environmental impact.

O2 4e- ? 2O2-
Unfortunately, the existing facility cannot
convert all of the gas presently produced by the
landfill. Excess gas is currently flared --
burned, with no recovery of its energy value.
The amount of gas that is flared is anticipated
to increase. Coffin Butte is a regional landfill
that takes in garbage from a 75-mile radius. Use
of the Coffin Butte landfill has increased
significantly since 1995 and is projected to
Oxygen, usually from the air
Carbon Monoxide Fuel
Anode 2CO O2- ? 2CO2 4e-
2CO O2- ? 2CO2 4e-
O2- ions through electrolyte
LOAD (i.e. electric motor)
Cathode
The three community partners believe
students realize deeper understanding when given
real contexts, real reasons, and actual
opportunities to apply material and concepts
learned in the
O2 4e- ? 2O2-
Picture obtained _at_ http//www.pngcpower.com/PNGC/I
nnovation_HowItWorksDiagram.aspx
continue growing. In 1995, garbage flows were
175,000 tons per year. Currently they are now
approximately 550,000 tons per year. This upward
trend is expected to increase biogas volume from
the landfill, suggesting the need to expand the
facility at Coffin Butte. While expansion will
likely occur, questions have arisen. Should
additional gas engines be utilized to capture
this green energy? Or, instead, should a fuel
cell, with its higher efficiency, be employed?
And if fuel cell technology is to be utilized,
which type of fuel cell should be used, and can
this new technology, so heavily dependent upon a
clean hydrogen source, be made reliable and
economically practical in a landfill application?
This has been, and continues to be, the focus of
on-going research by three community partners
the OSU Chemical Engineering Department, the
Crescent Valley High School Science Department,
and PNGC Power.
Oxygen, usually from the air
Unlike the MCFC, the SOFC requires no CO2
recycling which tends to simplify the overall
system design. However, the higher operating
temperature means that the Gibbs free energy of
formation of water is less negative. As a
result, the open circuit voltage of the SOFC at
1000oC is about 100mV lower than the MCFC at
650oC. This disadvantage is offset by lower
internal resistance of the SOFC and the use of
thinner electrolytes.
This seal or joint is quite straightforward to
maintain
Air
Fuel
Exhaust
Combustion
Deliberately imperfect seals around the tube
In tubular designs, air is placed on the
inside, the cathode forms the base level of the
tube, the electrolyte is deposited upon this
first layer, and the anode material is plasma
sprayed over the top. Fuel is fed in around the
tubes. The cell interconnects allow electrons to
travel from the anode of the first cell to the
cathode of the second cell. A primary advantage
of tubular designs is the elimination of high
temperature gas-tight seals since each tube is
manufactured like a large test tube. As you can
see, the tubular SOFC has a built in air preheat
and anode exhaust gas combustor. Also, by
allowing imperfect sealing around the tubes, some
recirculation of anode product gas occurs
allowing internal reforming (the anode product
contains steam and CO2) of fuel gas on the SOFC
anode.
classroom. This year, student groups will build
on last years findings and move closer to an
installed unit at the landfill. Students will
work within small groups on issues supporting a
final installation. As groups, students will
adhere to scientific procedures and apply newly
learned class content when seeking solutions to
specific, but critical problems. CVHS
AIR
SOFCs At Coffin Butte Issues
Fuel Internally reformed using product steam
Tubular fuel cell

• Despite last years efforts, much preliminary
  work remains. Last years student teams
  identified the following issues to target for the
  2004-2005 endeavor.
• Landfill gas must be characterized in order to
  identify sulfur contaminants (that will poison
  any fuel cell) and the energy content of the gas.
  Additionally, temporal variation in gas flow
  must be determined.
• Gas reformer trials should be carried out to
  determine the viability of silica gel as a
  portion of a gas reformation system. Sampling
  methodology should be redesigned and improved
  over last years attempts.
• The use of sulfur-eating bacterium should be
  investigated as a viable reformation step.
• An analysis of the existing electrical
  installation is required before additional
  capacity is added.
• A complete balance of plant should be produced,
  verified, and checked.
• A commercially available SOFC needs to be
  identified.

biology, chemistry, and physics students will
collaborate with, OSU chemical and civil
engineering students, PNGC represent-atives, and
various
Tubular SOFC Design
vendors of equipment and services. Together,
these multi-disciplined, heterogeneous teams of
individuals from our community will move toward a
viable design. Such cooperation underscores the
true nature of science and engineering. Both
disciplines require teams of individuals working
together in creative ways while seeking solutions
to both a significant environmental and community
issue.
Preliminary SOFC Process Design
Revision Date 11/6/04 File 11-13-04 OSU
Engineering Fair Coffin Butte Poster