EPA/AA/CTAB-87-08
Technical Report
Evaluation of Coloroll Methanol Dissociator
For Cold Start Assist Application
by
Gregory K. Piotrowski
December 1987
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 RADIATION
December 22, 1987
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 Technology Division
The attached report entitled, "Evaluation of Coloroll
Methanol Dissociator For Cold Start Assist Application,"
(EPA-AA-CTAB-87-08) describes the evaluation of a methanol
dissociator supplied by Coloroll, pic., with regard to its
ability to start and idle a light-duty engine. Dissociator
product gas was piped to a warm engine and a start attempted.
This dissociator was unable to start and idle the test engine
due to its low product flowrate.
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.
Approved: (__
/
Date:
Charles L. Gray, J/c. /Dir., ECTD
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Table of Contents
Page
Number
I. Summary "' 1
II. Introduction 1
III. Dissociator Operation 2
A. Boiler Unit and Feedback Tank 2
B. Superheater 4
C. Catalytic Dissociator 4
D. Ancillary Dissociator Components 4
IV. Supporting Eguipment 5
V. Program Design 5
VI. Discussion of Test Results 5
VII. Conclusions 8
VIII.Acknowledgments 8
IX. References 10
APPENDIX A - Hydrogen Content Determination A-l
APPENDIX B - Test Engine Specifications A-2
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I. Summary
A low flow methanol dissociator was procured from
Coloroll, pic., U,K. , for use as a cold start assist for a
methanol engine. This dissociator made use of resistively
heated ceramic and carbon fiber filters in the boiler,
superheater, and catalytic dissociator elements.
The objective of this experimentation was to start and
idle a 4-cylinder engine on the dissociated methanol product
from the Coloroll-supplied dissociator.
H2 and CO product gas mixture from the dissociator was
piped to the exhaust gas recirculation ports of the test
engine. This product gas mixture served as the fuel supply
during the start experiments; the main methanol injectors on
the test engine were disabled prior to the start testing.
Prior to attempting this start, the engine was operated at idle
for 30 minutes to ensure a warmed engine, and thus very
favorable starting conditions.
The engine was allowed to receive product gas for various
periods, of 15 seconds to 4 minutes in duration, before
cranking was attempted. The engine received product gas
continuously during each cranking period. On each attempt, the
engine failed to start. The most probable cause of this
failure to start was the low flowrate of product gas generated,
approximately .013 grams per second. An air/fuel ratio during
the attempted start was calculated; this calculated value
exceeded 40, too lean to have allowed a cold start.
II. Introduction
Light-duty ML.OO neat methanol-fueled engines are difficult
to start and run in cold weather because of the single boiling
point characteristic of this fuel. 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 may be vaporized before the cylinder at
relatively low temperatures.
Some state-of-the-art methanol engines require the
addition of gasoline to the fuel to improve their
startability.[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 a
combination of mechanical approaches may produce reliable cold
starts of a neat methanol-fueled engine at relatively low
ambient conditions.[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 fuel for cold start.
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The goal of this project was to evaluate a methanol
dissociator supplied by Coloroll, pic, for use as a cold start
assist to a methanol engine. Ideally, the dissociator should
have provided enough fuel to start and idle a 2.0-liter,
4-cylinder methanol engine. The design of the program and a
discussion of the results obtained is given below.
Ill. Dissociator Operation
Methanol may be dissociated to hydrogen and carbon
monoxide via the reaction:
CH3OH(1) 2H2(g) + C0(g)
The Coloroll-supplied dissociator accomplishes this
reaction by a three-step process. First, methanol is vaporized
in a boiler and moved by an inert carrier gas to a
superheater. The methanol/carrier gas mixture is then
superheated to approximately 500°C and the superheated mixture
is passed to a catalyzed and heated dissociator. The hot
methanol vapor is dissociated in this final stage and passes
out of a product tube and into an engine manifold. A detailed
description of each part of the process is given below.
A. Boiler Unit and Feedback Tank
The methanol feed is provided from a sealed glass pipe
section fitted with stainless steel end plates. The capacity
of this fuel reservoir is approximately 3 liters. A connection
to the top of the tank is made to a bottle of compressed
nitrogen gas. The inert gas serves three functions.
1. The N2 acts as a carrier gas to assist product
flow throughout the system;
2. The inert N2 provides an atmosphere safe against
rapid oxidation and fires in the dissociator; and
3. The absence of air in the dissociator hinders
undesirable, competing chemical reactions such as complete
oxidation of the methanol feed.
A schematic drawing indicating the locations of ties to
the N2 gas supply made to egualize pressure over the entire
system is provided as Figure 1. The bottom of the reservoir
contains a drain and a feed line to the level control tank.
A level control tank was installed between the fuel
reservoir and the boiler. This tank controls the level of
methanol in the boiler. A level switch ballcock in the tank
switches off power to all electrically heated elements if fuel
level in the controller falls below a certain level. An outlet
in the bottom of the controller feeds the boiler.
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Figure 1
Schematic Drawing of Coloroll Methanol . Dissociator
RESERVOIR
NITROGEN
LEVEL
CHAMBER
CATALYTIC HEATER
HEATER 3
HEATER 2
.BOILER/SUPERHEATER
HEATER 1
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The boiler used for the evaporative stage is a ceramic
element with a resistance of approximately 40 ohms. This
element was powered by 220-volt alternating current, and is
isolated electrically from the rest of the dissociator by a
base plate constructed from "Tufnol" brand insulation. The
amount of current supplied to the boiler element determines the
vaporization rate of the liquid methanol. A drain is also
fitted to the boiler to facilitate maintenance of the unit.
B. Superheater
The superheater is an electrically heated carbon element
with a resistance of approximately one ohm. This element is
powered from a 12-volt tapping of a transformer. A perforated
metal plate surrounds this element, and this surround absorbs
radiation from the heating element and transfers it to the
gases passing through it. The outlet temperature of the
superheater is measured by a thermocouple in the tube above the
cover plate.
The vessel housing the boiler and superheater consists of
two glass tube sections held together by end and middle
flanges. Gaskets throughout form gas-tight seals. Tie rods
from the base plate to the top plate hold the unit firmly in
place. A 'Perspex" tube surrounds the glass tube for extra
safety.
C. Catalytic Dissociator
The hot methanol vapor and N2 carrier gas pass upward
through a further porous element heater which has been coated
with platinum. This catalyzed heater acts as a dissociator.
Gas flows radially through the porous heater walls and out of
the unit through a 1-inch nominal bore tube. A thermocouple in
the gas stream measures temperature out of the dissociator.
D. Ancillary Dissociator Components
Several ancillary components were also installed in order
to make the dissociator safer to operate. First, a safety
device consisting of a rotameter and an electrical control unit
was installed between the compressed N2 source and the
dissociator. This device shuts off electrical power to the
dissociator unless a specified minimum flowrate of N2 was
exceeded, approximately 5.0 standard liters per minute. A
pressure relief valve constructed of stainless steel and having
an opening pressure of 35 psig was installed in the product
tube out of the dissociator, to prevent an unsafe buildup of
pressure in the unit. A flame arrestor constructed of
stainless steel and filled with stainless steel wool, was also
installed after the product tube. Finally, a 7.5 kilovolt-amp
isolation transformer of 240-volt input/output capacity was
purchased and installed between the 220-volt AC supply (line,
line, neutral and ground) and the dissociator, which was wired
for 240-volt AC Mains Electricity (line, neutral and ground).
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Power to each of the porous element heaters was controlled
by a remote control box, which may be operated up to 20 feet
away from the dissociator. This remote panel contained three
potentiometers which were adjusted to limit the current to each
element.
IV. Supporting Equipment
The flow of methanol feed to the boiler was determined by
an indirect method, which involved a procedure for weighing the
fuel supply before and after dissociator operations and
accounting for hang-up in the level controller, reservoir and
boiler. H2 composition in the product gas, however, was
determined by gas chromatography. A GOW-MAC Model 69-550 gas
chromatograph was used, and its operation is detailed in
Appendix A.
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.
V. Program Design
The goal of this program was to start and idle a methanol
engine using the product gases from the Coloroll-supplied
methanol dissociator as a fuel supply. The program was
conducted in two phases:
1. Installation, checkout and flow measurement; and
2. Engine testing of the dissociator.
The first phase of the program involved setting up the
dissociator and measuring the methanol feed rate from the
reservoir. Product composition was also determined, and
reactor efficiency thereby established. 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 that supplied by the dissociator product.
VI. Discussion of Test Results
Initial testing involved the determination of feed
methanol flowrate from the reservoir and H2 composition of
the product gas. From these measurements the dissociator
capacity and efficiency could be determined.
During this initial testing, the boiler element was
exposed to a current of 2.55 amps over a voltage of 220 volts
for 561 watts applied. The superheater element experienced a
current of 55 amps over a voltage of 12 volts (limited by a
transformer) for a power output of 660 watts. Gas temperature
out of the superheater was in the range of 500-515°C during
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sampling. The dissqciator operated at 57 amps over 12 volts
for a power output of 680 watts. Product gas temperature out
of the dissociator was measured at 490°C during sampling.
Methanol feed rate was measured indirectly by a careful
sequence of controlled weighings of the fuel introduced into
the reservoir. These weighings accounted for methanol hangup
in the reservoir, flow level controller and boiler. A flowrate
of 160-170 grams per hour of vaporized methanol from the boiler
was determined by this process.
H2 content of the product gas was measured at 9.5 volume
percent. Inert N£ carrier gas flowed into the dissociator at
a rate of 6 liters/minute. The dissociated product yield
calculated from these conditions was 29 percent, equating to a
dissociation of roughly .013 grams per second of feed
methanol. Dissociated product yield is defined here as grams
of methanol dissociated to H2 and CO per minute over grams of
methanol per minute into the dissociator.
The next phase of this program involved piping the product
gas into a warm engine and attempting a start and idle. The
engine described in Appendix B was utilized. Product gas was
piped into the intake manifold runners via ports for exhaust
gas recirculation. The engine was warmed for 30 minutes prior
to beginning the start test. The engine fuel injectors were
disabled prior to the test, allowing a fuel supply exclusively
composed of the dissociator product. The engine was cranked at
240 revolutions per minute.
This testing consisted of successively longer fills of the
intake manifold runners, each fill followed by 2-3 second
cranking periods. The fill periods allowed were of 15, 20, 25,
30, 35, and 40-second lengths. Extended fills of 2, 3, and
4-minute lengths were also tried, followed each time by the
cranking sequence referred to above.
During this phase, the boiler element operated at 2.6 amps
over 220 volts for 570 watts applied. The superheater operated
at 57 amps over 12 volts for a power output of 680 watts. The
gas mixture exited the superheater at 450°C. The dissociator
element received 55 amps at 12 volts for a power output of 660
watts. Product gas temperature out of the dissociator measured
493°C during cranking.
The methanol vaporization rate in the boiler was measured
at 237.4 grams per hour during this testing. H2 product gas
concentration was measured at 7.5 volume percent. A 20 percent
yield was determined, equating to a dissociated product flow of
.013 grams per second.
The engine failed to start on each attempt. After one
fill attempt, that of 30 seconds duration, the engine did fire,
but even then on only one revolution. During successively
longer fill periods, the engine gave no indication of an
ability to start.
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The low flowrate provided by the boiler may substantially
contribute to this dissociator's inability to start and idle
the warmed engine. The dissociated product flowrate to start
an engine of similar size has been calculated [5,6] as .3 to .6
grams per second or .45 grams per second. The .013 grams per
second achieved here may simply be too J.ow to allow a start and
idle. Extended fill periods did not seem to aid the start
either. Temperatures into and out of the dissociator appeared
adequate to promote the desired reaction. The choice of a
platinum catalyst appeared appropriate, and no attempts at
scientific determination of the dissociator element's ability
to promote the desired reaction were made after this testing.
An air/fuel ratio was calculated at start conditions in
order to determine if an appropriate mixture was present to
permit cold starting. A summary of this determination is given
below.
Air flow through the engine air induction system was
measured at 4.7 cfm during cranking with the dissociator
feeding product gas into the exhaust gas recirculation ports.
Methanol was vaporized in the boiler section at a rate of 3.96
grams per minute, and 6 liters per minute of N2 carrier gas
flowed into the engine during cranking. The dissociation
reaction occurred with a yield of 20 percent, which amounted to
a total fuel feed stream into the engine from the dissociator
of:
a. .10 grams per minute H2;
b. .69 grams per minute CO; and
c. 3.17 grams per minute vaporized methanol.
An equimolar amount of oxygen is required to oxidize
either 1 mole of methanol or its dissociated product; this fact
aids the calculation of an air/fuel ratio where the fuel is a
mixture of H2, CO, and vaporized methanol. It may be
instructive to view the weight of fuel in terms of "equivalent
methanol grams." This term is defined here as grams of
specific fuels adjusted by their combustion energies relative
to methanol to arrive at methanol equivalent weights. Using
the information given in reference 6:
Feed Rate From
Dissociator to Engine Methanol Equivalent Feedrate
3.17 gpm methanol 3.17 gpm methanol equivalents
.69 gpm CO .33 gpm methanol equivalents
.10 gpm H2 •57 gpm methanol equivalents
4.07 grams per minute methanol equivalents is the fuel source
during cranking for the test engine.
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Using the ideal gas law, the rate of air supplied through
the engine's air induction system at cranking is 160 gpm air.
N2 carrier gas is supplied to the engine at a rate of 7 gpm
N2- If air/fuel ratio is then defined as:
Weight of air + weight of carrier gas
Weight of fuel in methanol equivalents
then air/fuel ratio at cranking would be calculated as (160 +
7)/4.07, or 41, much too lean to start. If the concept of
methanol equivalents is neglected and weight of fuel is defined
as total fuel weight, regardless of chemical composition,
air/fuel ratio is calculated as (160 + 7)/3.96 or 42, much too
lean to start.
Further experiments with this technology may make use of
the superheater and catalytic dissociator elements. The rate
of vaporization prior to superheating will have to be
substantially improved before satisfactory results using this
technology as a cold start assist for a methanol engine can be
achieved.
VII. Conclusions
A low flow methanol dissociator was tested as a cold start
assist for a methanol engine. The engine was operated prior to
the cold start testing to ensure a most favorable case scenario
(fully warmed engine). Dissociated product gas flowing
directly from the dissociator comprised the fuel supply; the
methanol engine fuel injectors were disabled during the start
testing.
The engine was allowed to receive dissociated product gas
for various periods of 15 seconds to 4 minutes in duration
before cranking was attempted. On each occasion the engine
failed to start. The most probable cause of the failure to
start was the low flowrate of product gas generated,
approximately .013 grams per second. Air/fuel ratio during the
attempted start was calculated; this calculated value exceeded
40, too lean to permit a cold start.
Future cold start efforts with this technology may limit
the use of the resistively heated ceramic fiber elements to the
catalytic dissociator and superheater sections.
VIII.Acknowledgments
The methanol dissociator used in this experimentation was
provided by Coloroll, pic., a United Kingdom corporation. The
test engine was provided by Nissan Research and Development,
Inc., Ann Arbor, MI.
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The author appreciates the efforts of James Martin,
technician, Standards Development and Support Branch, Emission
Control Technology Division, who greatly assisted the author
with this project. Jim was also largely responsible for the
setup of the engine used for this testing. The efforts of
Michael Murphy, electrical engineer, also of SDSB, with several
electrical problems that developed during setup and testing are
also greatly appreciated.
In addition, the author appreciates the efforts of
Jennifer Criss and Marilyn Alff of the Control Technology and
Applications Branch, ECTD, who typed this manuscript.
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IX. 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. "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.
6. Dissociated Methanol Fuel Requirements to Start A
Four-Cylinder Engine, Memo from Gregory K. Piotrowski,
OAR/OMS/ECTD/CTAB, Ann Arbor, MI, 1986.
7. • Fundamentals o_f Gas Analysis By Gas Chromatography,
Thompson, B., Varian Associates, Inc., Palo Alto, CA, 1977.
8. Basic Gas Chromatography, McNair, H., Bonelli, E.,
Consolidated Printers, Berkeley, CA, 1968.
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A-l
APPENDIX A
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.[7,8]
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A-2
APPENDIX A (cont'd)
Specifications:
Chromatograph model
Detector:
Operating principle
Temperature control
Carrier gas
Detector elements
Noise
Drift
Injection:
Number of ports
Control
Operating temperature
Column Oven:
Temperature range
Control
Column:
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
Dual-column with dual-injection
ports and exits
Continuous current adjust 50-300
mA. Bridge zero adjust.
Attenuator for bridge output, 10
positions 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
Soltech model 3318
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B-l
APPENDIX B
Test Engine Specifications
Manufacturer
Basic engine designator
Displacement
Cylinder arrangement
Valvetrain
Combustion chamber
Bore x stroke
Compression ratio
Compression pressure
Fuel control system
EGR
Valve clearance
Idle speed
Engine oil
Fuel
Engine cranking speed
Nissan Motor Co., LTD.
CA18E
1809 cc
4-cylinder, in-line
Single-overhead camshaft
Semi-spherical, 2-spark plugs
per cylinder
83 mm x 83.6 mm
11.0
17.0 kg/square cm (350 rpm, 80°C)
Electronically controlled fuel
injection
EGR not used
0.30 mm HOT, intake and exhaust
700 rpm
Special formulation supplied by
Nissan for methanol engine
operation.
M100 neat methanol
240 rpm
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