United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-97/153 January 1998
&EPA Project Summary
Hynol Process Evaluation
Robert H. Borgwardt
Fuel-cell vehicles (FCVs) have the po-
tential to offer a major improvement in
efficiency relative to current motor ve-
hicles. The potential of FCVs to nearly
eliminate pollutant emissions and re-
duce the economic pressures of petro-
leum imports will be a major factor
contributing to the sustainability of the
current system of highway transport.
Greenhouse gas emissions, of which
the transportation sector is a major con-
tributor, are another part of the
sustainability issue. FCVs and the fu-
els used in them also offer the poten-
tial for an economical and effective
technological option for mitigation of
anthropogenic carbon dioxide (CO2)
emissions. The hydrogen that is re-
quired for fuel cells can be produced
from natural gas (which contributes to
greenhouse gas emissions) and from
biomass (which does not). This report
examines process alternatives for the
optimal use of these resources for pro-
duction of FCV fuel, emphasizing maxi-
mum displacement of petroleum and
maximum reduction of overall fuel-cycle
CO2 emissions at least cost. Three
routes are evaluated: (i) production of
methanol from biomass and from natu-
ral gas by independent processes, (ii)
production of methanol or hydrogen
by hydrogasification of biomass using
natural gas as co-feedstock supple-
mented with, and without, the use of
carbonaceous municipal wastes as co-
feedstocks, and (iii) production of
methanol or hydrogen by addition of
natural gas to a biomass-to-methanol
process originally designed for biom-
ass only. The results show that the
combined use of natural gas and biom-
ass in a single process can reduce net
fuel-cycle CO2 emissions by 20% rela-
tive to separate systems and reduce
the cost of fuel production to a range
competitive with the current cost of
gasoline. A plant optimized for effi-
ciency and size, with 25% of the feed-
stock energy consisting of biomass,
should be able to produce methanol at
a cost of $0.42/gal ($6.09/GJ), or hydro-
gen at $5.98/GJ. This technology rep-
resents a "no regrets" approach to CO2
mitigation and a cost-effective use of
biomass as a source of fuel energy.
This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
The economic, environmental, and
health impacts of an ever increasing popu-
lation of vehicles, and the dependence on
foreign sources for the petroleum needed
for the U.S. system of road transport, add
up to an unsustainable situation. National
goals have been established by the Na-
tional Energy Strategy of 1991, the En-
ergy Policy Act of 1992, and the Clean Air
Act Amendments of 1990 for the develop-
ment of alternative fuels that could reduce
the environmental and economic impacts
of petroleum fuels. New technologies that
can effectively deal with many of the prob-
lems of road transport are nearing com-
mercialization. Among the new technolo-
gies, fuel-cell vehicles (FCVs) offer an at-
tractive solution to these problems for the
foreseeable future. An alternative to pe-
troleum fuel should be compatible with
the existing refueling infrastructure, pro-
vide a driving range comparable to gaso-
line used in current vehicles, and be com-
patible with FCVs when they enter the
commercial market. FCVs require hydro-
gen—either as compressed gas or as a
liquid hydrogen-carrier that can be re-
formed on board to produce hydrogen.
Hydrogen or methanol (the preferred liq-
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uid hydrogen-carrier that is most easily
reformed or used directly in special fuel
cells) can be produced from biomass. A
fuel produced entirely from renewable bio-
mass, such as short-rotation woody crops
or perennial grasses, would have the im-
portant advantage that it would not con-
tribute to greenhouse gas emissions. From
that standpoint, as well as the renewable
standpoint, it could reduce the sustainability
problem of transportation fuels. There are
two major barriers to this approach: (i) the
amount of biomass that could be pro-
duced as energy crops on land that is
suitable for that purpose (<5.8 quads)3
could not displace a major fraction of the
U.S. transportation fuel needs even if there
were no competing uses, and (ii) cost: an
alternative to gasoline must be competi-
tive in selling price if it is to gain accep-
tance in the marketplace. The production
cost of fuels produced from biomass alone
is much higher than the production cost of
gasoline. By use of natural gas as a co-
feedstock, the yield of methanol or hydro-
gen can be greatly increased and the cost
reduced to a competitive market price.
The object of this report is to evaluate
thermochemical processes by which bio-
mass and natural gas could be utilized
most effectively to displace petroleum and
reduce greenhouse gas emissions at least
cost.
Procedure
Two basic approaches are considered
in detail for the production of transporta-
tion fuel from biomass and natural gas: (i)
biomass alone is converted to liquid trans-
portation fuel (methanol) by the best cur-
rently available technology and natural gas
is used in a separate conventional pro-
cess to produce methanol, and (ii) it is
assumed that the same two feedstocks
are utilized in a single thermochemical
process to produce methanol. The pri-
mary objective is to compare the metha-
nol yield, production cost, and net overall
CO2 emission for the two approaches and,
by that comparison, assess the relative
merits of the latter technology, called
Hynol. These evaluations were conducted
by computer simulations using the Aspen
Plus process simulation software which
enables calculation of material and en-
ergy balances, thermal efficiency, and CO2
emissions for any variety of input assump-
tions, including alternative configurations
of the components, and design details of
those components. A critical factor in com-
parisons of this type is the uniformity of
the assumptions on which they are based.
Equal values of input variables, including
biomass composition, plant size, reactor
performance, mechanical efficiencies,
heat-recovery efficiencies, and cost bases,
were used everywhere possible.
Using this procedure, a process con-
sisting of a biomass gasifier developed by
Battelle Columbus Laboratory (BCL) and
modified by Princeton University to pro-
duce methanol was examined in detail to
establish a basis for methanol yield when
biomass is used as the sole feedstock.
This gasifier utilizes an external combus-
tor to provide the energy for biomass gas-
ification and operates at atmospheric pres-
sure. The gases produced are reformed
at 14 atmb pressure and 847°C, after which
a shift reactor and Selexol unit prepare a
synthesis gas which is fed to a methanol
converter. All components are conventional
commercial design or, in the case of the
gasifier, have been demonstrated on a
large scale. Similar calculations were per-
formed for the Hynol process which con-
sists of a biomass hydrogasifier, a steam
reformer, and a methanol converter oper-
ating at higher pressure (30 atm) than the
other system. The reformer also operates
at higher temperature (950-1000°C). The
Hynol system (Figure 1) consists of two
process loops: a gasification loop con-
tains the gasifier, desulfurizer, reformer,
heat recovery steam generators (HRSGs),
distillation unit, and compressor. The sec-
ond Hynol loop contains a methanol con-
verter, a recycle compressor, and a con-
denser. A recycle stream, predominantly
hydrogen, is returned from the methanol
converter to the gasifer, thus connecting
the two process loops. This hydrogen re-
cycle, which is passed through a heat
exchanger to recover high temperature
heat from the reformer, is a unique fea-
ture that distinguishes Hynol from other
systems: the recycle stream entering the
gasifier provides sufficient enthalpy for gas-
ification so that no external combustor, or
internal partial oxidation of the biomass, is
necessary. Thus, a higher overall conver-
sion efficiency is expected for Hynol as
well as a leveraging of methanol yield due
to the natural gas added. Another impor-
tant distinction of this gasifier is that no
tars are expected to be produced, allow-
ing heat recovery before desulfurization.
A base-case Hynol system was set up
and analyzed, consisting of a biomass
preparation block, a gasification block, a
steam reforming block, a distillation block,
and a methanol synthesis block. Material
a1 quad = 1015Btu = 1.055x1018J
b1 atm= 101 kPa
and energy balances on each block and
the overall electric power were determined
for operation of the integrated system.
Adjustments were then made in operating
conditions to bring the overall power re-
quirements in balance with the power that
can be recovered within the system. The
basis for comparison of process configu-
rations and operating performance with
regard to CO2 emissions, methanol yield,
and cost was that no electric power im-
port be required. A sensitivity analysis of
the base case established the effects of
the operating variables for which assumed
values were required, including biomass
carbon conversion, steam/carbon ratio,
reformer and methanol converter ap-
proach-to-equilibrium, reformer tempera-
ture, and natural-gas-to-biomass feed ra-
tio. Guided by the relative effects of these
variables, process optimization was car-
ried out using reactor pressures and heat
exchanger pressure drops as inputs.
Results and Discussion
Table 1 gives the composition and con-
ditions of the principal streams identified
in Figurel, assuming 100 kg of dry biom-
ass feed containing 10 wt% moisture.
These compositions correspond to a natu-
ral gas feed rate of 3.79 kg-mols as pro-
cess feed and 2.60 kg-mols as reformer
fuel. This ratio of total natural-gas-to-bio-
mass is optimum for overall fuel-cycle CO2
emission reduction as indicated by Figure
2. Fuel-cycle CO2 emissions include those
from biomass cultivation, harvest, and de-
livery to the plant; natural gas extraction,
purification, and transport to the plant; pro-
duction of methanol from the feedstocks;
transport of the methanol to vehicle refu-
eling stations; and use of that fuel in FCVs.
The net overall CO2 emission reduction is
determined by comparison with gasoline
where the fuel cycle emissions include
those from oil extraction, transport, and
refining; and the distribution and use of
gasoline in conventional vehicles.
Methanol can be produced also from
biomass or natural gas separately, and it
is, therefore, pertinent to compare the effi-
ciency of the Hynol process with the per-
formance of the best options for using the
same biomass and natural gas feedstocks
for production of methanol by separate
routes. For this purpose, the Princeton
system that utilizes the Battelle gasifer
was taken as the most efficient method
for biomass, and the conventional steam
reforming route used for commercial
methanol production was taken for natural
gas conversion. This comparison shows
that the Hynol route would achieve 20 %
greater combined net CO2 emission re-
duction than the other options for use of
-------
Biomass
51.06 kg C
7.49 kg H
51.53 kg O
0.15kg N
0.08 kg S
0.792 kg ash
Natural gas
3.79 mols
Steam 19.79 mols
Air
31.5 mols
Natural gas (fuel)
2.60 mols
H2O condensate
14.9 mols
Purge 1.2 mols
(to reformer fuel)
CH3OH 7.293 mols
H2O 1.85 mols
Figure 1. The Hynol process.
Table 1. Composition of Hynol Process Principal Streams Identified in Figure 1
Stream composition, kg-mols
H20
H,
CO
C02
CH4
C2H6
N
CH3OH
Sum
DegC
Atm
Stream
1
2.997
6.10
1.698
0.9006
2.713
0
0.847
0
15.26
800
29
Stream
2
0.168
26.23
6.540
2.335
0.247
0
0.935
0
36.45
51
22.3
Stream
3
0.163
193.93
17.63
10.77
4.92
0
18.74
2.44
248.6
40
30.0
Stream
4
0.265
220.16
24.17
13.10
5.165
0
19.68
2.44
285
51
36.0
Stream
5
0.0008
0.9361
0.0851
0.0520
0.0237
0
0.0905
0.0118
1.20
40
30
Stream
6
1.407
8.714
0.7923
0.4838
0.2210
0
0.8421
0.1096
12.57
950
29.5
Stream
7
0
0
0
0.00758
3.589
0.1061
0.08717
0
3.79
90
28.0
Stream
8
0
0
0
0.0052
2.462
0.0728
0.0589
0
2.60
90
1.5
those resources. Given the fact that biom-
ass supply will be the limiting factor that
determines the extent to which petroleum
can be displaced by that resource, it is
important that the use of natural gas as
co-feedstock greatly leverages the yield
of transportation fuel (by a factor of 4.8).
As a result of this leveraging and increased
gasoline displacement, the CO2 emission
reduction from the overall vehicle popula-
tion is twice as great as that which could
be expected if biomass alone were used
as a source of alternative fuel for FCVs.
A thermochemical process such as
Hynol that utilizes natural gas as co-feed-
stock with biomass has the additional ad-
vantage that it can be configured to pro-
duce either methanol or hydrogen. Hydro-
gen, although not compatible with the ex-
isting vehicle refueling infrastructure, is
the ideal fuel for FCVs and the most fa-
vorable in terms of environmental benefits
and petroleum displacement potential.
Simulations of the Hynol process for pro-
duction of hydrogen were, therefore, also
examined. Figure 3 and Table 2 show this
re-configuration which replaces the metha-
nol converter and condenser with shift re-
actors and pressure swing adsorbers
(PSAs). The results show that 21.74 kg-
mols of hydrogen can be produced (and
compressed to 5000 psi) from the same
feedstocks used for methanol production
with a thermal efficiency of 68.1 % and a
total fuel-cycle CO2 emission reduction of
1091 kg when utilized in FCVs and com-
pared to gasoline used currently. This com-
pares to 68.4 % thermal efficiency and
724 kg CO2 emission reduction for the
methanol production case.
Cost estimates were carried out for both
methanol and hydrogen production. A plant
size of 7870 tonnes (biomass) per day
was assumed in accordance with
Princeton's evaluation of the optimal bal-
ance between economy of scale for the
plant and the cost of biomass delivered
from remote sources. The delivered cost
of woody biomass for that plant, produced
in North Central region of the U.S., was
$61/tonne and a price of S2.37/GJ was
assumed for natural gas. Other cost as-
sumptions included a capital recovery fac-
tor of 15.45%; 13% after-tax rate of re-
turn, including 2.7% inflation rate; and 26%
corporate income tax rate. The cost esti-
mate for the production of methanol on
this basis is $0.416/gal ($6.09/GJ) and
S5.98/GJ for hydrogen. Compared to the
production cost of gasoline and the fuel
economy of gasoline in current vehicles,
methanol used in dedicated conventional
vehicles would cost about 2.4 cents per
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70
60
£•
T3
-------
Natural gas
3.79 mols .
Biomass (10% moisture)
51.06 kg C
7.49 kg H
51.52 kg O
0.151 kgN
Unreacted
carbon
0.549 mol
Steam 0.57 mol
Desulfurizer
HRSG-1
U'
Steam
*
Reformer
Furnace
Nat
\j\ 2'6
Natural gas (fuel,
.633 mols
Air
32.5 mols
Purge 1.2 mols
(to former fuel)
H2 21.74 mols
75 atm
CO2 7.42 mols
H20 0.156 mol
Condensate
7.48 mols
Figure 3. Hynol process configured for hydrogen production (BFW = boiler feed water).
Methanol can be produced from bio-
mass and natural gas at a cost that
will be competitive with current gaso-
line costs and provide major reduc-
tion of net CO2 emissions as well as
elimination of particulates and criteria
pollutant (carbon monoxide, volatile
organic compound, and nitrogen ox-
ide) emissions when used in fuel cell
vehicles. Using natural gas as the
primary energy source, and biomass
providing 25% of the energy input for
methanol production, the amount of
petroleum displaced would be lever-
aged by a factor of 4.8 relative to the
use of biomass alone, and the pro-
duction cost would be reduced by
40%. Overall CO2 emission reduction
would be twice as great as the poten-
tial for CO2 reduction using bio-fuels
alone.
Thermochemical processes can pro-
duce either methanol or hydrogen for
FCVs, leveraging the yield of either
fuel and reducing its cost by using
natural gas as co-feedstock. Munici-
pal carbonaceous wastes such as
sewage sludge, landfill gas, digester
gas, and solid wastes normally flared
or sent to landfills should be accept-
able co-feedstocks with energy crops
for production of methanol or hydro-
gen. Landfill gas or digester gas can
displace part of the natural gas used
by the process, limited only by the
amount of such waste gas available
at a given location.
The BCL process, using only biom-
ass and no natural gas, will yield 14.77
kg-mols of methanol per tonne of bio-
mass at a cost of S12.4/GJ. Used in
FCVs, that methanol will displace 134
gallons0 of gasoline with a net overall
fuel-cycle CO2 emission reduction of
2.04 tonnes. The thermal efficiency
Table 2. Composition of Streams Identified in Figure 3 for Hydrogen Production
Stream composition, mols
H20
H,
CO
CH2
C H
N2 6
Sum
DegC
Atm
Stream
1
2.240
6.214
1.042
0.4055
3.127
0
0.8535
13.88
800
30.5
Stream
2
13.057
26.593
5.761
1.995
0.6284
0
0.9407
48.98
407
22.9
Stream
3
10.062
29.588
2.766
4.990
0.6283
0
0.9407
48.98
167
21.9
Stream
4
7.632
32.018
0.3361
7.420
0.6284
0
0.9407
48.98
227
22.3
Stream
5
0.1562
32.45
0.350
7.420
0.655
0
0.9806
42.02
40
20.8
Stream
6
0
1.0122
0.0331
0
0.0619
0
0.0927
1.20
40
1.5
Stream
7
0
9.697
0.3173
0
0.5930
0
0.8878
11.50
40
20.8
Stream
8
0
0.453
0.0142
0
0.0266
0
0.0398
0.515
40
20.8
Stream
9
0.570
9.262
0.0303
0
0.5665
0
0.848
11.55
900
31.0
Stream
10
0
0
0
0.00758
3.589
0.1061
0.08717
3.79
150
30.3
Stream
11
0
0
0
0.00526
2.493
0.0737
0.0606
2.633
150
1.5
-------
-------
Natural
gas */DesulfurizerJ—£^~
CH3OH
BFW
6 7
I
Methanol
converter
L^VJ
Crude
methanol
Figure 5. Configuration of biomass-to-methanol process for addition of natural gas.
Table 3. Compositions of Streams Identified in Figure 5
Stream composition, mols
Stream Stream Stream
1 2 3
Stream Stream Stream Stream Stream Stream
45678 SeSe 9
H20
CO
C02
CH4
C H
C2H6
N2
CH3OH
Sum
DegK
Atm
1.645 2.922 19.85 12.24 0.2193 0.0552 0.0736 2.330
0.776 0.776 0.776 18.36 18.36 18.356 56.94 41.09
1.726 1.726 1.726 4.637 4.637 4.637 6.131 1.591
0.416 0.416 0.4255 2.774 2.774 2.774 7.337 5.081
0.588 0.588 5.086 0.535 0.535 0.535 8.247 8.249
0.194 0.194 0.194 00000
0.027 0.027 0.160 0 0 0 0 0
0.016 0.016 0.1253 0.1253 0.1253 0.1253 2.005 2.005
00 0000 0.2192 7.015
5.388 6.665 28.34 38.67 26.65 26.48 80.95 67.36
1200 355 858 1140 313 313 319 533
1.0 1.0 16.89 14.11 9.13 104.5 104.5 104
Natural gas used as process co-feedstock, mols 4.75
Natural gas used as reformer fuel, mols 1 .526
Steam fed toeformer, mols 19.8
Steam/carbon ratio in reformer 2.50
Reformer duty, cal/sec 95379
Methanol product, mols 6.781
0.0012
2.493
0.0965
0.2949
0.4984
0
0
0.1215
0.0141
3.52
313
96
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Robert H. Borgwardt is the EPA Project Officer (see below).
The complete report, entitled "Hynol Process Evaluation," (Order No. PB98-
127319; Cost: $41.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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