Abstract Booklet 2006 - Swanson School of Engineering - University ...

high selectivity (theoretically producing a 100% purity H 2 product). Unlike the ceramic
membranes developed to date (which could only achieve up to 90% H 2 selectivity in a single
pass and requires cascades of membrane modules to provide higher purities), Pd alloy
membranes can achieve high selectivity in a single module. Pd alloy membranes also
achieve very high hydrogen flux, with at least an order of magnitude higher flux than the
high temperature dense ceramic membranes. The operating temperature of the Pd alloy
membranes (300-600°C) is also well matched to that of the WGS process (200-600°C),
where the reaction kinetics and the thermodynamic equilibrium both favor formation of
hydrogen. The operating temperature for PSA systems (40-80°C) are too low for good WGS
reaction kinetics and the equilibrium is unfavorable at the high operating temperature of the
dense ceramic membranes (600-800°C). However, in spite of these potential benefits,
several hurdles inhibit commercial implementation of this membrane technology. To be
commercially viable: 1) the robustness of these membranes must be improved, 2) the cost of
the membrane must be reduced, and 3) the sealing problems encountered when integrating
the membrane into the process equipment must be eliminated; a key problem for any
membrane system.
TDA Research Inc., in collaboration with Colorado School of Mines (CSM) is developing a
sulfur and CO-tolerant membrane to produce the clean hydrogen from syngas using Pd
membrane films prepared on a variety of supports (e.g., symmetric ceramic supports and
porous stainless steel supports). This paper summarizes the results of the membrane
development and testing efforts. Membranes that showed superior properties in screening
tests using hydrogen/nitrogen mixtures were further evaluated under representative
conditions (the baseline gas composition used in these evaluations were 51% H 2 , 26% CO 2 ,
21% H 2 O and 2% CO vol.). In general, membranes showed very good stability in water gas
shift environment and were tested for several days with stable permeance and selectivity. We
examined the effect of operating parameters including temperature, pressure and H 2 recovery
on membrane performance. We also investigated the impact of CO, CO 2 and H 2 S
concentration in the reformate gas on the H 2 permeation and selectivity of the membrane.
17-4
High-Pressure Operation of Dense Hydrogen Transport Membranes for
Pure Hydrogen Production and Simultaneous CO 2 Capture
Xiaobing Xie, Carl R. Everson IV, Michael V. Mundschau, Harold A. Wright, Paul J.
Grimmer, Eltron Research Inc., USA
Eltron has developed a family of dense inorganic membranes that enable high H 2 separation
rates with essentially 100% selectivity to H 2 . The membranes are designed to operate at the
same conditions as high-temperature water-gas shift (WGS) reactors (320−440°C) and can
be operated with up to 1,000 psi pressure differential across the membrane. In synthesis gas
systems that incorporate WGS, the membranes facilitate efficient, low cost separation of H 2
and CO 2 at high pressure, enabling efficient capture of CO 2 . The membranes are being
developed to work with refinery waste streams as well as synthesis gas derived from natural
gas, liquid hydrocarbons, coal, petroleum coke and biomass. The membranes may be ideal
for natural gas or coal-based IGCC applications with or without hydrogen export. Compared
to palladium-based membranes, the Eltron membrane exhibits 20 times the flux for a given
set of conditions and costs about 10 times less. The high hydrogen permeability and low cost
of the membrane materials allows the use of relatively thick membranes, which is crucial for
their operation under high pressure differential. This technology has many advantages over
competing hydrogen separation technologies. Advantages are listed as follows: (1) the
membranes allow the capture of CO 2 at high pressure. The CO 2 is essentially captured at
gasification or reforming pressure; (2) the membrane is low cost with long membrane life.
Stability tests have been conducted for over eleven months on line with high flux retained;
(3) the membranes, in principle, will work with synthesis gas generated from any source
including coal, petroleum coke, natural gas, or biomass; (4) essentially 100% pure hydrogen
is separated since the membrane works by transporting dissociated hydrogen across the
membrane material; (5) hydrogen recoveries of 90% or higher are possible; (6) the
membranes can be operated under high permeate pressures of pure hydrogen, and thus the
costs associated with hydrogen compression can be substantially reduced; (7) the
membranes can be integrated with commercial high temperature water-gas shift catalysts.
The integrated membrane/WGS reactor has been demonstrated capable of achieving
significantly higher CO conversion over the thermodynamic equilibrium limitation.
Eltron was recently awarded a program from the United States Department of Energy aimed
at scaling up these membranes for possible use in the FutureGen coal-based power and
hydrogen plant. This paper discusses recent advances in the development of these
membranes including experimental demonstrations of the above mentioned advantages, and
membrane performance.
17-5
Effect of Nanocrystalline Catalysts on the Desorption Temperature of
MgH 2 for Hydrogen Storage Applications
M.S. Seehra, P. Dutta, S. Pal, J. Fortune, West Virginia University, USA
MgH 2 is an attractive hydrogen storage material with 7.6 wt% hydrogen capacity and with a
safe endothermic desorption of hydrogen at Td ≈ 4320°C [1]. However for practical
applications, this Td is too high. In this work, we will report recent results of our experiments
to lower Td. Our approach is based on the use of nanocrystalline Ni to reduce Td. Our recent
experiments using 20 nm Ni nanoparticles mixed ultrasonically in the amount of 1 mol %
with a commercial β-MgH 2 followed by ball milling of the mixture for 15 minutes, have
yielded Td ≈ 2700°C as revealed by thermogravimetric analysis (TGA) and differential
15
scanning calorimetry (DSC). X-ray diffraction (XRD) of the sample at different stages of the
reaction shows that sonicating alone shifts Td to 3400°C, without any chemical changes in
Ni or β-MgH 2 . However, milling converts a part of β-MgH 2 to γ-MgH 2 . Additional
experiments are underway to determine whether the lower Td ≈ 2700°C corresponds to γ-
MgH 2 . From our experiments, it is also evident that lowering the crystalline size of both
MgH 2 and the Ni catalyst and thorough mixing is likely to further reduce Td. An additional
motivation to lower Td is to avoid the formation of Mg 2 Ni which in our experiments forms
at 2700°C. This may be possible if the amount and crystallite size of the Ni catalyst are
further reduced. Results of these experiments, now in progress, will be reported.
* Work supported by U.S Department of Energy, Contract # DE-FC26-05NT42456.
[1] See the review by J. Huot in Nanoclusters and Nanocrystals edited by H.S.Nalwa (Amer.
Sci.Publishers, 2003) pages 53-85.
SESSION 18
GLOBAL CLIMATE CHANGE:
GREENHOUSE GAS UTILIZATION AND NOVEL CONCEPTS
18-1
Use of Coal Mine Methane in a Microturbine at CONSOL Energy’s Bailey Mine
Deborah Kosmack, Richard A. Winschel, CONSOL Energy Inc., USA
Patrick Rienks, Jay Johnson, Ingersoll-Rand Energy Systems, USA
CONSOL Energy Inc Research & Development and Ingersoll Rand Energy Systems, with
partial funding by the Clean Air Fund provided by the Pennsylvania Department of
Environmental Protection, are installing a low-emission 70 kW microturbine generator on a
large underground coal mine in Pennsylvania to reduce emissions of methane by capturing
them and converting them into usable electricity. The generator will be fueled with coal
mine methane that is currently being vented as part of the mine’s ventilation system. Coal
mine methane is one of several major sources of anthropogenic methane, accounting for
about 10% of anthropogenic methane emissions in the United States. Methane is the second
most important non-water greenhouse gas, with a global warming potential 21 times as great
as that of carbon dioxide (CO 2 ) on a mass basis. Thus, any coal mine methane that is emitted
rather than utilized simultaneously represents a lost potential resource and the emission of a
powerful greenhouse gas. The project objectives are to: 1) convert the low and variable
concentrations of methane contained in coal mine methane gas that would otherwise be
vented to the atmosphere to electricity; 2) provide the generated electric power to an existing
electric power grid; 3) donate the value of the electricity generated during the project period
to a local school district; and 4) determine the quantity of useful energy that can be
economically produced when processing coal mine methane from a working coal mine and
perform a techno-economic evaluation of the system. When operating at 95% capacity factor
and a heat rate of 13,550 Btu/kWh HHV (higher heating value), the 70 kW generator will
produce 583 MWh of electricity as it consumes 7,954,000 cubic feet of methane, with a
global warming potential equivalent to 3,522 short tons of carbon dioxide, each year. Startup
and commissioning of the system will be followed by 12 months of operations.
18-2
Green Power Technologies for High Ash Indian Coals-Evaluation of
CO 2 Mitigation Options,
D.N. Reddy, Centre for Energy Technology, INDIA; V.K. Sethi, Rajiv Gandhi
Technological University, INDIA
The Global concern for reduction in emission of green house gases (GHG) especially CO 2
emissions are likely to put pressure on Indian Power System for adoption of improved
generation technologies. Although India does not have GHG reduction targets, it has actively
taken steps to address the climate change issues. Mitigation options for CO 2 reduction which
have been taken up vigorously include GHG emission reduction in power sector through
adoption of Co-generation, Combined cycle, Clean Coal Technologies and Coal
Beneficiation. CO 2 emissions per unit of electricity generated are significantly high in India
as large proportion of power generated comes from low sized, old and relatively inefficient
generating units which constitute over 50% of our total installed capacity of about 103,000
MW. The technology up gradation through life extension of old polluting units is expected to
increase the generating efficiency of these units thereby reducing CO 2 emissions. Presently
about 32 power stations with 106 units of various capacities ranging from 30MW to 200MW
totaling to about 10,400 MW dated capacities are taken-up for Life extension (LE) during
10 th five year plan (2002-07). In addition to above about 60 Thermal Power plants units
(13,900 MW) have been taken up for Renovation and Modernization (R&M) in the country,
which is expected to contribute significantly in terms of CO 2 reduction.
A major thrust on CO 2 reduction on long term and sustainable basis would however come
through adoption of advanced technologies of power generation like Supercritical/Ultrasupercritical
power cycles, Integrated Gasification Combined Cycles (IGCC), Fluidized Bed
Combustion/Gasification Technologies and so on. A beginning towards adoption of super
critical units has already been made in the country and it is foreseen that super critical
technology would almost universally be adopted for all large sized pithead units in the
country. The attained efficiency gains of these technologies are likely to reduce the
environmental emissions especially CO 2 significantly. Adoption of higher parameters for
super critical units after sufficient feedback and operational experience would further reduce
these emissions to a great extent. A total additional efficiency of about 1.5-2% is normally