LIQUID BIO-FUEL PRODUCTION FROM NON-FOOD BIOMASS VIA HIGH TEMPERATURE STEAM ELECTROLYSIS Page: 4 of 11
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This process is similar to the GTI process described in Ref .
GTI does not disclose the material or nature of the catalysts
The process heat demands include a steam generator, a
high temperature steam electrolysis unit, a power conversion
unit (PCU), a hydropyrolysis reactor, and a biomass dryer. The
steam generator produces steam for feed to the high
temperature steam electrolysis unit. For highest efficiency
operation, the HTSE unit operates in a net endothermic mode,
requiring a net high temperature process heat input. A more
complete description of the high temperature electrolysis
process is given below. Nuclear process heat is also required
for power generation via the power conversion unit (e.g.,
Rankine cycle). Depending on the plant configuration, the
SMR and the PCU could be sized for dedicated biomass-to-
liquids (BTL) operation. Alternately, the reactor and PCU
could be sized for excess power generation, beyond what is
required for liquids fuels production. Power supplied to BTL
or to the grid could be varied daily and seasonally to maximize
profit. The reactor also supplies process heat to the
hydropyrolysis unit, which operates endothermically. The
range of operating pressures and temperatures for the
hydropyrolysis unit is indicated in Fig. 1. Finally, reactor
process heat is supplied to the biomass dryer to remove excess
moisture from the carbon feedstock. This heating could
possibly be supplied at lower temperature, using heat rejection
from the power cycle. It should be noted that a fully developed
process would include as much heat recuperation from the
various processes as is feasible to minimize the overall net high
temperature heat requirement.
High Temperature Electrolysis. The biomass-to-liquids
synthetic fuels production processes described in this paper
require supplemental hydrogen for efficient conversion of
biomass to liquid hydrocarbon fuels. Supplementary hydrogen
is used in conventional refining processes for hydrocracking
and hydrogenation of increasingly low quality petroleum
resources. The supplementary hydrogen used in conventional
refineries is produced almost exclusively from steam reforming
of methane, a process that increases the already high demand
for natural gas while emitting significant quantities of carbon
dioxide into the atmosphere. High temperature electrolysis
offers an efficient carbon-free alternate route to hydrogen
production. In fact, HTSE has the highest conversion
efficiency of any water splitting process that is driven by
electricity. HTSE is based on electrochemical splitting of steam
into hydrogen and oxygen. High temperature electrolysis
makes use of solid-oxide cells, similar to solid oxide fuel cells,
but operating in reverse with a per-cell operating voltage
greater than the open-cell voltage. High-temperature
electrolytic water-splitting supported by nuclear process heat
and electricity has the potential to produce hydrogen with
overall thermal-to-hydrogen efficiencies of 50% or higher,
based on high heating value. From 2003 - 2009, development
and demonstration of advanced nuclear hydrogen technologies
were supported by the US Department of Energy under the
Nuclear Hydrogen Initiative  during 2009, which sponsored
a technology down-selection activity in which an independent
review team recommended high temperature electrolysis (HTE)
as the most appropriate advanced nuclear hydrogen production
technology for near-term deployment .
The INL HTE program also includes an investigation of
the feasibility of direct syngas production by simultaneous
electrolytic reduction of steam and carbon dioxide
(coelectrolysis) at high temperature using solid-oxide cells.
Syngas, a mixture of hydrogen and carbon monoxide, can be
used for the production of synthetic liquid fuels via Fischer-
Tropsch or other synthesis processes. This concept, coupled
with nuclear energy, provides a possible path to reduced
greenhouse gas emissions and increased energy independence,
without the major infrastructure shift that would be required for
a purely hydrogen-based transportation system .
Furthermore, if the carbon dioxide feedstock is obtained from
biomass, the entire concept would be climate-neutral.
As an alternative to centralized large-scale systems with
direct coupling to high-temperature reactors, distributed
hydrogen production could be accomplished using modular
HTE units powered from grid electricity and an alternate high-
temperature heat source such as concentrated solar energy 
or a biomass gasifier . This approach could be quite
economical if off-peak electricity is used .
To demonstrate the performance potential of advanced
nuclear hydrogen systems, detailed process analyses have been
performed . Summary results are presented in Fig. 2. This
figure shows overall hydrogen production efficiencies, based on
high heating value, plotted as a function of reactor outlet
temperature. The figure includes a curve that represents 65%
of the thermodynamic maximum efficiency , assuming
TL = 200C (Tow). Three different advanced-reactor/power-
conversion combinations were considered: a helium-cooled
reactor coupled to a direct recuperative Brayton cycle, a
supercritical CO2-cooled reactor coupled to a direct
recompression cycle, and a sodium-cooled fast reactor coupled
300 400 500 600 700 800 900 1000
T ( C)
Figure 2. Overall thermal-to-hydrogen production
efficiencies based on HHV for several reactor/process
concepts, as a function of reactor outlet temperature.
-65/ of max possible
fU INL, HTE I He Recup Brayton
f INL LTE He Recup Brayton
-0- INL, HTE Na -cooled Rankine
-*- INL, LTE I Na-cooled Rankine
+4-INL, HTEI/Sprcrt C02
-INL LTEISprcrt C2 ---- -'----------
SI Process (GA)
MIT AGR -SCQ2/HTE
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Hawkes, G. L.; O'Brien, J. E. & McKellar, M. G. LIQUID BIO-FUEL PRODUCTION FROM NON-FOOD BIOMASS VIA HIGH TEMPERATURE STEAM ELECTROLYSIS, article, November 1, 2011; Idaho Falls, Idaho. (digital.library.unt.edu/ark:/67531/metadc845769/m1/4/: accessed November 12, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.