EPA/AA/CTAB-88-02
Technical Report
Resistively Heated Methanol Dissociator for
Engine Cold Start Assist -
Interim Report
by
Gregory K. Piotrowski
March 1988
NOTICE
Technical Reports do not necessarily represent final EPA
decisions or positions. They are intended to present technical
analysis of issues using data which are currently available.
The purpose in the release of such reports is to facilitate the
exchange of technical information and to inform the public of
technical developments which may form the basis for a final EPA
decision, position or regulatory action.
U. S. Environmental Protection Agency
Office of Air and Radiation
Office of Mobile Sources
Emission Control Technology Division
Control Technology and Applications Branch
2565 Plymouth Road
Ann Arbor, Michigan 48105
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
ANN ARBOR. MICHIGAN 48105
OFFICE OF
AIR AND F1ADIATION
May 18, 1988
MEMORANDUM
SUBJECT: Exemption From Peer and Administrative Review
FROM
TO:
Karl H. Hellman, Chief
Control Technology and Applications Branch
Charles L. Gray, Jr., Director
Emission Control Technoloav Division
The attached report entitled, "Resistively Heated Methanol
Dissociator for Engine Cold Start Assist - Interim Report,"
(EPA/AA/CTAB/88-02) describes a methanol dissociation system
that provides a cold start assist for a light-duty methanol
engine. Methanol was boiled in a steam-heated vessel,
superheated and passed to a dissociator which made use of
resistively heated porous silicon carbide technology. The
product gas from this system was used to start and idle a test
engine which had been cooled to 43°F.
Since this report is concerned only with the presentation
of data and its analysis and does not involve matters of policy
or regulations, your concurrence is requested to waive
administrative review according to the policy outlined in your
directive of April 22, 1982.
Concurrence: / -•-"'
Date
Charles L. Gray ,/J/-, Dir., ECTD
Nonconcurrence:
Date
Charles L. Gray, Jr., Dir., ECTD
cc: E. Burger, ECTD
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Table of Contents
Page
Number
I . Summary 1
II. Introduction 1
III. Dissociator Operation 2
A. Boi ler Unit 2
B. Superheater 4
C. Catalytic Dissociator 4
IV. Supporting Equipment 4
V. Program Design 5
VI. Discussion 5
A. Boiler Flow Rate 5
B. Superheater Operation 6
C. Cold Start Experiments 7
D. Reactor Power Requirements 8
E. Emission Levels 12
VII. Conclusions 12
VI11.Future Effort 13
IX. Acknowledgments 13
X. References 14
APPENDIX A - Dissociator Element Specifications A-1
APPENDIX B - Hydrogen Content Determination B-1
APPENDIX C - Test Engine Specifications C-1
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I. Summary
A methanol dissociation system was constructed to provide
a cold start assist for a methanol-fueled light-duty engine.
The system consisted of a steam-heated methanol boiler, a gas
superheater, and a platinum-catalyzed dissociation element.
The dissociation element substrate was resistively heated and
constructed primarily from fibrous silicon carbide.
The objective of this experimentation was to start and
idle a 4-cylinder engine on the product gas from this methanol
dissociator.
H2, CO, non-dissociated methanol, and possibly other
reactor products from the dissociator were piped to the exhaust
gas recirculat ion port of the test engine. This product gas
mixture served as the fuel supply during the start experiments;
the stock methanol injectors on the test engine were disabled
prior to the start testing.
The engine was allowed to receive product gas for 5
seconds before cranking was attempted. At an engine
temperature of 73°F the product gas mixture was sufficient to
start and idle the engine. The engine was then cooled to 43°F;
the product gas mixture was sufficient to start the engine on
the second crank attempt and idle without laboring.
11. Introduct ion
Light-duty M100 neat methanol-fueled engines are difficult
to start and run in cold weather because of the high boiling
point of methanol, methanol's high heat of vaporization (5.5
percent of the heat of combustion compared to less than 1
percent for gasoline), and the increased fuel flow needed for
methanol (about double that of gasoline). Gasoline-fueled
engines start with less difficulty under the same conditions
partly because of the easily ignitable light ends of this fuel
such as butanes, which are vaporized at relatively low
temperatures.
Some state-of-the-art methanol engines require the
addition of gasoline to the fuel to improve their
startabiIity. [1] Other methanol engines utilize separate cold
start systems relying on gasoline or propane for cold start
assist.[2,3] Finally, some researchers have suggested that
stratified-charge combustion will produce reliable cold starts
of a neat methanol-fueled engine at relatively low ambient
condi t ions.[4]
Methanol may be catalytically decomposed to hydrogen and
carbon monoxide gases. Hydrogens' higher flame speed and lower
boiling point may make it an ideal cold start fuel.
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The goal of this project was to construct a methanol
dissociator that could provide H2 and CO fuels in quantities
that could be used as a cold start assist for a methanol
engine. This dissociator would utilize resistively heated
ceramic technology to provide the energy necessary to bring the
catalyst to operating temperature quickly. A methanol
dissociator using this technology has been tested by EPA for
its cold start assist potential.[5] Though that particular
dissociator was unable to provide enough dissociated product
gas to start a 4-cyUnder engine, the resistively heated
ceramic was able to quickly heat methanol vapor to temperatures
necessary for the dissociation reaction to occur. EPA used
this resistively heated ceramic together with equipment that
would increase the flow of methanol vapor feed in order to
improve the reactor's output and efficiency.
III. Dissoeiator Operation
Methanol may be dissociated to hydrogen and carbon
monoxide via the reaction:
CH3OH< , , * 2H2 (g , + CO, 9 ,
The dissociator described below accomplished this reaction
by a three-step process (Figure 1). First, methanol was
vaporized in a boiler and moved by an inert carrier gas to a
superheater. The methanol/carrier gas mixture was then
superheated to approximately 600°F and the superheated mixture
passed to a catalyzed and heated dissociator. The hot methanol
vapor was dissociated in this final stage and passed into an
engine intake manifold. A detailed description of each part of
the process is given below.
A. BoiIer Unit
The boiler was a 5-gallon capacity, type 316 stainless
steel pressure vessel. The vessel was fitted with a steam
heating coil, pressure relief valve, liquid temperature monitor
and pressure gauge. The boiler was filled with approximately
three gallons of methanol prior to each test and sealed; no
provision was made for adding fuel to the vessel following the
commencement of a test.
Liquid temperature and pressure inside the boiler were
maintained at approximately 190-195°F and 30 psig respectively
during testing. Fuel feed rate was determined indirectly; the
filled vessel was carefully weighed prior to and at the end of
testing, and the test process timed.
The flow of vaporized methanol was assisted by the passage
of a pressurized carrier gas through the boiler. Nitrogen at 6
standard cubic feet per hour was added to the boiler during
testing and the vessel was purged at the same flow rate for 10
minutes prior to the start of heating. This inert gas flow
served three functions.
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Figure 1
Methanol Dissociation System
Nitrogen
Boiler
Dissociator
Superheater
Flame
Arrestor
To Engine
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1. The N2 acted as a carrier gas to assist product
flow throughout the system;
2. The inert N2 provided an atmosphere safe against
rapid oxidation and fires in the dissociator; and
3. The absence of air in the dissociator hindered
undesirable, competing chemical reactions such as complete
oxidation of the methanol feed.
B. Superheater
The superheater was constructed from a 3-foot-long section
of 1-inch diameter 304 stainless steel pipe. This pipe section
was heated by wrapping it with a ceramic-bead-insulated
nichrome wire heater that utilized 120-volt alternating
current. Power to the heater was controlled by a thyristor.
C. Catalytic Dissociator
The hot methanol vapor and N2 carrier gas passed through
a porous silicon carbide filter which had been coated with
platinum. This filter was resistively heated by passing
120-volt alternating current through it. This catalyzed heater
acted as the methanol dissociator.
The filter was shaped in the form of a hollow cylinder.
Methanol vapor flowed radially through the porous heater walls;
the dissociation reaction occurred as the vapor contacted the
hot catalyzed walls. Element specifications are given in
Appendix A.
IV. Supporting Equipment
H2 composition in the product gas mixture was determined
by gas chromatography. A GOW-MAC Model 69-550 gas chromatograph
was used, and its operation is detailed in Appendix B.
The test engine used for this experimentation was a Nissan
CA18E, single-overhead camshaft, 1.8-liter displacement
engine. Details and engine specifications are provided in
Appendix B.
Exhaust unburned fuel (UBF) emissions were measured with a
Beckman Model 400 flame ionization detector. A FID response
factor of 76 percent was used.[6]
Exhaust formaldehyde was measured using a dinitrophenyI-
hydrazine (DNPH) technique.[7] Exhaust carbonyls including
formaldehyde are drawn through DNPH-coated cartridges forming
hydrazone derivatives. These derivatives are separated from
the remaining unreacted DNPH by high performance liquid
chromatography (HPLC). A spectrophotometer in the
chromatograph effluent stream drives an integrator which
determines formaldehyde derivative concentration.
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V. Program Design
The goal of this program was to start and idle a
light-duty vehicle engine using the product gases from the
methanol dissociator as a fuel supply. The program was
conducted in two phases:
1. Construction of the dissociator and flow
measurement; and
2. Engine testing of the dissociator.
The first phase of the program involved building the
dissociator and measuring the methanol feed rate from the
reservoir. We also attempted to determine product composition
and thereby establish reactor efficiency. The second phase
involved piping the product to a warmed engine and attempting a
start. Immediately prior to the attempted start the methanol
engine main injectors were disabled, in order to limit the fuel
to the product gas supplied from the dissociator.
VI. Discussion
A. Boiler Flow Rate
The low flow rate provided by the boiler in the
dissociator previously tested [5] may have substantially
contributed to that dissociator's inability to start the test
engine. The dissociated product flow rate to start an engine
similar in displacement to our test engine has been calculated
[8,9] as .3 to .6 grams per second or .45 grams per second.
The product generated by the lower flow dissociator,[5] .013
grams per second H2/CO and .053 grams per second
non-dissociated methanol, was low when compared to these
calculated requirements.
A steam-heated boiler was used in the system presented in
this report to increase the feed rate to the dissociator. The
temperature of the liquid in the boiler is a function of the
pressure above the liquid charge in the boiler, the amount of
fuel charge present, and the condition of the steam flowing
through the heating coils. The flow of vaporized methanol out
of the boiler is a function of boiler pressure, temperature,
and the flow rate of carrier gas through the boiler. These
variables were difficult to simultaneously control.
Measurement of vaporized methanol flow rate was accomplished by
weighing the boiler prior to testing, obtaining steady-state
conditions and operating over a period of time, then reweighing
the boiler after the cessation of testing. The difference in
weight was divided by the time of operation to determine a
rough flow rate.
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At the conditions of 30 psig in the vapor dome above the
liquid methanol, 195-200°F liquid temperature and 6 SCFH N2
into the boiler, approximately 1900 grams per hour of methanol
feed was delivered to the superheater. This was a significant
improvement over the methanol feed rate of the lower flow
dissociator mentioned previously, and within the guidelines of
the rates necessary to ensure .3 to .6 grams per second of
dissociated product gas to the engine.
A higher methanol flow rate could be obtained by
increasing the flow of N2 carrier gas to the boiler.
Although this technique increases the amount of inert N2 fed
to the engine, a vaporized methanol flow rate in excess of 2500
grams per hour was made possible by increasing N2 flow to 20
SCFH. The use of helium at 6 SCFH, rather than N2 , also had
the effect of raising the vaporized methanol flow rate over
2500 grams per hour. The use of these higher flow rates was
not necessary, however, as a rate of 1900 grams per hour proved
sufficient to start and idle the test engine.
B. Superheater Operation
The superheater was capable of heating the methanol vapor
(1900 g/hr) and N2 carrier gas (6 SCFH) stream to 600°F.
Higher gas temperatures were made possible by lengthening the
pipe and adding additional nichrome wire heaters (gas
temperatures out of the superheater in excess of 1200°F were
recorded).
A problem with coking of the methanol fuel was observed at
elevated superheater temperatures. This coking led to plugging
of the superheater and coating of the catalyst with coke. The
coking, or decomposition of the methanol to elemental carbon,
appeared to occur mainly on the inner wall surfaces of the
superheater. Coking on the catalyst substrate surface also
appeared to have occurred, although some of the carbon in the
catalyst can may have flowed through from the superheater.
Coke formation appeared to positively correlate with
operating temperature in the superheater and dissociator.
Temperatures in excess of 900°F and a vaporized methanol/N2
gas mixture invariably led to sooting of the superheater.
However, some carbon formation was noted at a gas mixture
temperature of 525°F and an outside wall temperature of the
superheater of 700°F.
Other researchers working with methanol dissociation have
noted this coking problem.[10,11] The optimum solution to this
problem appears to be the use of a catalyst that promotes the
dissociation reaction at very low temperatures (less than or
equal to 570°F). For the present effort, we attempted to hold
the gas mixture temperature below 600°F at all points in the
system.
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C. Cold Start Experiments
A cold start of the 73°F overnight-soaked engine was
attempted using only the product gas from the dissociator as
the fuel source. (Prior to testing the engine main fuel
injectors were disconnected.) Test conditions are given in
Table 1.
Table 1
Test Conditions For 73°F Cold Start Test
Variable Condition
Engine temperature 73°F (overnight soak)
Boiler liquid temperature 192°F
Boiler pressure 30 psig
Methanol flow rate from boiler 1900 grams per hour
Gas temperature out of superheater 532°F
Gas temperature out of dissociator 300°F
Gas temperature into EGR port 149°F
N2 carrier gas flow into boiler 6 SCFH
Product gas from the dissociator was fed to the EGR port
for 5 seconds prior to a crank attempt. The engine started on
the first 3-second crank attempt. It idled without laboring;
at no time was there any indication of stalling. We allowed
the engine to idle for 1 minute, then shut it off.
Approximately 12 feet of plastic tubing connected the
dissociator to the EGR port. A valve to allow emissions
sampling and a flame arrester were also located in this line.
These restrictions, however, did not combine to reduce fuel
flow to the point that engine performance at idle was
noticeably affected. Although the fuel entry passageway to the
combustion chambers was not standard (via EGR chamber to
cylinders) it proved sufficient to allow a start and idle at
the conditions in Table 1.
It was very difficult to calculate a dissociator yield for
this experiment. The Tedlar sample bags used to determine H2
content of the product gas also collected a substantial
quantity of liquid which could not be passed through the gas
chrooatograph. The product that remained in the gas phase
however was analyzed; the H2 content of the gas was 7
percent. This indicates a yield of less than 10 percent. This
experiment was repeated with essentially the same conditions as
described in Table 1. A 6 percent H2 concentration in the
sample bag was obtained, and the engine started and idled with
no observable difficulty.
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The experiment was then repeated at a lower engine
temperature. The test cell was chilled and the engine soaked
to a temperature of 43°F. Lower temperatures were impractical
because of the possibility of freezing water lines in the test
cell. The higher flow rate of methanol was probably due to an
improved quality of steam (less water) allowing for a more
efficient heat transfer to the methanol. Attempts to control
the boiler and superheater to the same operating conditions as
in the previous experiment were made, but the quality of the
steam in the lines is a function of demand on the building
steam system on a particular day. The conditions for this test
are given in Table 2.
Table 2
Test Conditions For 43°F Cold Start Test
Variable Condition
Engine temperature 43°F
Boiler liquid temperature 193°F
Boiler pressure 30 psig
Methanol flow rate from boiler 2600 grams per hour
Gas temperature out of superheater 600°F
Gas temperature out of dissociator 300°F
Gas temperature into EGR port 139°F
N2 carrier gas flow into boiler 6 SCFH
Product gas was fed from the dissociator to the EGR port
for 10 seconds prior to the first crank attempt. The engine
fired but did not start on the first 3-second crank. On the
second crank attempt, the engine started and idled smoothly.
We allowed the engine to idle for 30 seconds; it did not
exhibit any tendency to stall. We then shut the engine off.
During this experiment a considerable quantity of liquid
again accumulated in the sampling bag. The gaseous portion of
the sample was tested by gas chromatograph, and a H2
concentration of 12 percent was obtained. This indicates a
dissociator efficiency yield of less than 15 percent.
D. Reactor Power Requirements
The gas temperatures in the superheater and dissociator
were kept below 600°F during the cold start testing in order to
prevent the coking mentioned previously. However, it is
necessary to provide a significant amount of energy to the
methanol at the catalyst surface in order to further the
dissociation reaction.
Karpuk[12] in a private communication to EPA, calculated a
power requirement of 2256 watts necessary to dissociate 2000
g/hr of methanol at 25°C. Our calculations of this requirement
show it to be 2230 watts, essentially the same. Therefore,
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increasing amounts of power were applied to a catalyzed filter
while flowing 1900 g/hr vaporized methanol through it. The
objective of this test was to determine how power level
affected both gas temperature out of the dissociator and
product yield.
Gas temperatures into and out of the dissociator at
various power levels were recorded after the reaction had
reached steady state. Voltage drop was measured across the
dissociator while current was measured with an ammeter in
series. H2 concentration in the product gas stream was
determined at higher power levels.
The power supply used for this experiment was a Power Mate
AC to DC converter allowing a maximum DC output of 1000 watts.
Resistance across the ceramic filter was measured at .65 ohms.
Details from this experimentation are given in Table 3.
Table 3
Dissociator Power/Gas Temperature Characterization
Gas Temperature Gas Temperature
Volts Amps Watts Into Dissociator Out of Dissociator
7 5 35 550°F 195°F
9 8 72 550°F 225°F
11 10 110 550°F 256°F
13 11 143 540°F 304°F
14 13 182 540°F 340°F
15 14 210 540°F 355°F
16 15 240 540°F 385°F
17 16 272 546°F 410°F
18 18 324 547°F 430°F
20 20 400 547°F 470°F
22 23 506 570°F 571°F
23 23 529 570°F 571°F
Total power dissipated was limited to 529 watts. Attempts
were made, but failed to increase the current above 23 amps at
23 volts with this equipment. H2 concentrations in the
product gas of 6 and 10 percent were determined for power
levels of 400 and 529 watts, respectively. Again, significant
amounts of liquid collected in the sample bags; this indicates
that the conversion rate of methanol was less than 10 percent
even at the higher power level.
The 5KVA power supply that Coloroll provided to EPA was
next utilized to increase the power to the dissociator. Gas
temperature into the dissociator was also increased over
previous levels in order to determine whether this would aid
the dissociation reaction. The results of this experimentation
are presented in Table 4.
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Table 4
Dissociator Power/Gas Temperature Characterization
Gas Temperature Gas Temperature
Vol ts Amps Watts Into Dissociator Out of Dissociator
138°F
150°F
265°F
363 °F
401 °F
428°F
440 °F
460°F
28.40 35.5 1008.2** 755°F 448°F
* This power level maintained only 60 seconds.
** This power level maintained less than 10 seconds; unit
failed during this test.
The highest power levels attained here were not sustained;
the information presented in Table 4 was obtained from several
experiments. At gas temperatures out of the dissociator in
excess of 450°F numerous leaks were experienced in the
dissociator housing. Several methods of improving the seams
were tried; the concentrated methanol vapor attacks most gasket
materials at temperatures in excess of 450°F, however.
Overheating of the electrical connections was also a problem:
several measurement attempts at higher power were halted due to
melted instrument connections.
Typically 5 to 10 minutes was necessary for the reaction
to achieve steady-state status (constant gas temperature out of
the dissociator) as the level of power applied changed in
increments of 20 watts. This is due to heat loss through the
insulated dissociator housing as well as from gas passing
through the dissociator. At the last data point presented in
Table 4, 1008 watts, only a 448°F gas temperature out of the
dissociator was measured. The dissociator failed after
operating for less than 10 seconds at this power level. The
unit therefore never achieved steady-state operating conditions
at this power level.
The dissociator failed shortly after the application of
1008 watts. The stainless steel wool gaskets and stainless
steel contacts were unaffected; instead the nichrome
flaae-sprayed ceramic ends physically separated from the rest
of the hollow ceramic cylinder. This indicates that failure
was due to a difference in thermal expansion coefficients
between the silicon carbide and the nichrome flame spray.
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H2 concentration in the product gas was measured at
approximately 40 percent at a power input of 611 watts. Again,
a substantial portion of liquid was present in the sample bag,
making it difficult to calculate a H2 yield. The higher gas
temperature into the dissociator, because of greater
superheating during this testing, may have substantially
contributed to the higher H2 bag concentrations. A thin film
of carbon due to coking of the fuel was evident, however, on
the surface of the catalyst when the unit was dismantled after
testing.
A sample of the liquid which collected in the Tedlar bag
at 611 watts was taken and analyzed for its distillation
curve. The equipment used for this analysis was a Model
TS-74645 AR-2 Automatic Distillation Apparatus (ADA Ml), made
by the Precision Group, GCA Corporation. This analysis
indicated that the liquid in the sample bag was 99 volume
percent methanol and I percent water.
The data presented here suggests that the dissociation
reaction may be more limited by the amount of energy supplied
to the feed gas and catalyst surface than by the amount of
catalyst present on the substrate. H2 concentrations in the
product gas increased slightly, from 6 to approximately 10
percent, as the product gas temperature increased from 300°F to
571°F respectively. According to an unpublished memorandum
from Nissan,[13] a fresh Pt catalyst could have generated a
H2 concentration of approximately 30 percent in the 571°F
product gas, a substantial increase over the level we
experimentally obtained. Increasing the power output to 611
watts and the feed gas temperature to 755°F increased the H2
concentration to 40 percent (cooling of the feed gas in the
reactor from 755°F to 571°F would make available an additional
140 watts for the dissociation reaction). However, even at
this increased power level a substantial amount of methanol
condensed in the sample bag, indicating a much lower H2
concentration, had the bag contents been entirely vaporized
prior to chromatographic analysis.
Compounding the problem of an insufficient amount of
energy necessary to completely dissociate 2000 grams per hour
of feed gas is the energy loss from the dissociator due to heat
transfer to its environment. Heat losses occur convectively to
the air from the ceramic-wool insulation blanketing the
dissociator housing and conductive Iy to the metal fittings and
polymer tubing which carry the product gas to the engine.
These losses, though unquantified here, would lessen the amount
of energy available to initiate the endothermic dissociation
reaction.
The product yield, therefore, increases as the rate of
energy supplied to the dissociator is increased, at conditions
of approximately 600 watts and a 2000 grams per hour methanol
feed rate to the dissociator. This indicates that at these
conditions the rate of energy supplied to the dissociator
limits the product yield.
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E. Emission Levels
Levels of emissions characterized as unburned fuel (UBF)
and formaldehyde were measured in order to determine whether
the choice of fuel systems influenced pollutant emission
levels. The test cycle was a cold start followed by a 5-minute
idle. UBF and formaldehyde emissions are expressed in average
rates of g/min and mg/min respectively; this information is
presented in Table 5. NOx and CO emissions were not measured
due to problems with the analyzers. Each test was conducted
following an overnight soak of the engine at 73°F.
UBF emissions for the dissociator fuel are reported as if
they are all methanol. While this neglects the effect that the
CO and H2 have on the result, the nature of the exhaust
emission measurement capability in the test cell at the time of
the tests make this an appropriate approach.
UBF emissions increased slightly when the test engine was
operated on fuel supplied from the dissociator. This increase
in emissions, (.56 g/min), while noted, is not definitive; the
engine was emissions-tested only once using the dissociator as
the fuel supply system. Formaldehyde levels appear to vary
considerably, from an average 1 mg/min using fuel injector-
supplied methanol versus no detectable concentration when the
dissociator supplied fuel. Again, however, only limited
testing was conducted. Additional testing must be conducted to
properly define the difference in emission levels.
Table 5
Emission Levels Over Cold Start and Idle (73°F)
Forma I-
UBF dehyde
Engine Fuel System Configuration No. of Tests g/min mg/min
Methanol injectors functioning 2 2.76 1.0
Oissociator fuel system 1 3.32
VII. Conclusions
1. The test engine started and idled at 43°F using
dissociator product gas as the fuel, under the conditions
described in Table 2. It is not possible to state to what
extent the limited amount of H2 produced under these
conditions would assist a cold start at temperatures below 43°F.
2. Coking of the fuel and subsequent catalyst poisoning
was a problem with the system at gas temperatures greater than
600°. Some coking was noticed, however, at lower gas
temperatures into the dissociator.
3. At the conditions of 529 watts applied, gas
temperature into the dissociator of 570°F and a methanol flow
rate through the system of 1900 g/hr, a H2 concentration of
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4. UBF emission rates from the test engine
'
were
"
a. Methanol from the engine fuel injectors; and
b. Dissociator product gas with the engine fuel
injectors disabled.
n/minro?-°n, levels measur^ "»re 2.76 g/m i n and 3.32
g/mn respectively. Formaldehyde emission levels over this
rnn^n/r°arti«neeSe fuel systems «wre 1.0 mg/m i n and no detectable
«r!m}««?™ fme«.aSUred' resPect j ve > Y • Only a limited number
of emission tests were conducted, however; two tests were
conducted using the engine fuel injection system and one test
to I Ing "system. 9 *** dlssocjator Produc* 9as only as the
VI 1 1. Future Effort
*.that wi" more favorably promote the
on reaction at temperatures below 500°F is currently
being sought. A lower temperature reaction would have the dual
advantages of requiring less activation energy and not
promoting undesirable reactions such as the tendency to coke.
A lower operating temperature would also make possible a more
compact heat exchanger/dissociator design.
irim.*?f7!ri. ca!;dldate cata'yst configurations have been
identified, permission is being sought to try these new
catalysts on the resistively heated ceramic elements described
here. The evaluation of these new catalysts will be the
subject of a separate technical report.
IX. Acknowledgments
The methanol dissociator used in this experimentation was
l ColoroM'. P'c" a u"ited Kingdom corporation. The
a"d Development,
c*^ afPn:ciates the efforts of James Martin,
Standards Development and Support Branch, Emission
u- °'°?y Division. who greatly assisted the author
with this project. Jim was also largely responsible for the
5®!? ,°t. u engine used for this testing. The efforts of
Michael Murphy, electrical engineer, also of SDSB, with several
t"tln« are
In addition, the author appreciates the efforts of
Jennifer Cnss and Marilyn Alff of the Control Technology and
ftfirH yn™,,ranC,h> E5T5; Wh° typed thls nianuscript, Ind J.
Oil lard Murrell, also of CTAB, who drew Figure 1.
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X. References
1. "Development of Methanol Lean Burn System," Katoh,
K. Y. Imamura, and T. Inoue, SAE Paper 860247, February 1986.
2. "Interim Report On Durability Testing of Low Cost
Catalysts for Methanol-Fueled Vehicles," Wagner, R. and L.
Landman, EPA/AA/CTAB/TA/84-4, August 1984.
3. "Using Methanol Fuels In Light-Duty Vehicles,"
Brown, D., F. Golden, E. Gons, R. Potter, SAE Paper 872071,
November 1987.
4. "Unassisted Cold Starts to -29°C and Steady-State
Tests of a Direct-Injection Stratified-Charge (DISC) Engine
Operated On Neat Alcohols," Siewert, R. and E. Groff, SAE Paper
872066, November 1987.
5. "Evaluation of ColorolI Methanol Dissociator For
Cold Start Assist Application," Piotrowski, G., EPA/AA/CTAB/
87-08, December 1987.
6. FID Methanol Response, Memo, Edward A. Barth,
OAR/OMS/ECTD/TEB, Ann Arbor, Ml, August 1987.
7. Formaldehyde Measurement In Vehicle Exhaust At MVEL,
Memo, Gilkey, R. L., OAR/OMS/EOD, Ann Arbor, Ml, 1981.
8. "Engine Cold Start With Dissociated Methanol,"
Greiner, L. and E. Likos, Proceedings of the Third
International Symposium on Alcohol Fuels Technology, May 29-31,
1979.
9. Dissociated Methanol Fuel Requirements to Start A
Four-Cylinder Engine, Memo from Gregory K. Piotrowski,
OAR/OMS/ECTD/CTAB, Ann Arbor, Ml, 1986.
10. "Study of the Methanol Reformed Gas Engine," Hirota,
T., Japan Society of Automotive Engineers Review, March 1981.
11. "Dissociated Methanol Citation: Final Report,"
Finegold, J., G. Glinsky, and G. Voecks, SERI/TR-235-2083,
DE85000505, August 1984.
12. Private Communication, Karpuk, M. E., to U.S. EPA,
1987.
13. Briefing to C. Gray, Jr., by Nissan Motor Company,
March 1987.
14. Fundamentals of Gas Analysis by Gas Chromatoqraphy,
Thoopson, B., Varian Associates, Inc., Palo Alto, CA, 1977.
15. Basic Gas Chromatography, McNair, H., Bonelli, E.,
Consolidated Printers, Berkeley, CA, 1968.
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APPENDIX A
DISSOCIATOR ELEMENT SPECIFICATIONS
The dissociator substrate consists of a highly porous
ceramic to which electric current is applied. The fluid to be
heated is passed through the void spaces in the material. Heat
transfer is encouraged by the very large surface area of the
ceramic (the material contains greater than 80 percent void
space).
Specification ranges for certain properties of the
material used in the dissociator are given below. The exact
specifications for the dissociator material are proprietary to
the manufacturers of the elements, Coloroll, pic., Havenside,
Boston, Lincolnshire, U.K.
Property Range of Values
Power density: 10-1600 W/cm3
Normal range: 10-300 W/cm3
Power dissipation: 0.01-0.75 W/cm2
Heatup/response time: Milliseconds
Heat transfer surface/volume: 400-750 cm2/cm3
Operating temperature: Up to 1000°C
Material density: 0.1-0.5 gm/cm3
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APPENDIX B
HYDROGEN CONTENT DETERMINATION
Background
The basis for gas chromatographic separation is the
distribution of a sample between two phases. One of these
phases is a stationary bed, and the other is a gas which
percolates through the stationary bed. An inert carrier gas
carries the components to be separated through a column
containing the stationary phase. The active component of the
stationary phase selectively retards the sample components
according to their distribution coefficients, until they form
separate bands in the carrier gas. These component bands leave
the column in the gas stream and are recorded as a function of
time by a detector.
If the stationary phase is a solid, this particular gas
chromatographic technique is referred to as gas-solid
chromatography. Common packings used are silica gel, molecular
sieve and charcoal. Gas-solid chromatography was used in this
experimentation, and the details of the procedure are given
below. More complete explanations of gas chromatographic
technique are provided by Thompson and McNair.[14,15]
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APPENDIX B (cont'd)
Spec!fI cat ions:
Chromatograph model
Detector:
Operating principle
Temperature control
Carrier gas
Detector elements
Noise
Drift
Inject ion:
Number of ports
Control
Operating temperature
Column Oven:
Temperature range
Control
Co Iumn:
Gas flow system;
Thermal conductivity
bridge control:
Electrical :
Power requirements
Circuit breaker
Physical :
Compressed Gas Auxiliaries:
Zero gas
Span gas
Output:
Stripchart recorder
GOW-MAC Model 69-550
Thermal conductivity type
Ambient to 300°C
N2
Four (4) rhenium tungsten elements
10-micro volts maximum
40-micro volts/hour maximum
Two
Solid-state, variable-voltage
phase control
Ambient to 300°C
Ambient to 300°C
Solid state time apportioning
5' x 1/4" molecular sieve
Qua I-co Iumn with dual-inject ion
ports and exits
Continuous current adjust 50-300
mA. Bridge zero adjust.
Attenuator for bridge output, 10
posi t ions to 512.
105-125 volts, 50/60 H2
7 amps
Two-section construction. Upper
section houses column oven,
detector and vaporizers. Lower
section contains power supply,
bridge control circuit and
temperature controllers.
N2
40 percent H2/60 percent N2
So I tech model 3318
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APPENDIX C
TEST
Manufacturer
Basic engine designator
Displacement
Cylinder arrangement
Valvetrain
Combusti on chamber
Bore x stroke
Compression ratio
Compression pressure
Fuel control system
EGR
Valve clearance
Idle speed
Eng i ne oil
Fuel
Engine cranking speed
ENGINE SPECIFICATIONS
Nissan Motor CO., LTD.
CA18E
1809 cc
4-cyIinder, in-Iine
Single-overhead camshaft
Semi-spherical, 2-spark plugs
per cyIinder
83 mm x 83.6 mm
11.0
17.0 kg/square cm (350 rpm, 80°C)
Electronically controlled fuel
inject ion
EGR not used
0.30 mm HOT, intake and exhaust
700 rpm
Special formulation supplied by
Nissan for methanol engine
operat ion.
M100 neat methanol
240 rpm
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