Note: Descriptions are shown in the official language in which they were submitted.
CA 02683295 2009-10-22
METHOD OF MONITORING AND OPTIMIZING
DENATURANT CONCENTRATION IN FUEL ETHANOL
TECHNICAL FIELD
[001] This invention relates generally to methods of monitoring and/or
controlling denaturant composition dosages in fuel ethanol. More specifically,
the
invention relates to monitoring and optimizing dosages of denaturant
compositions and
mixtures of corrosion inhibitor(s) and denaturants in fuel ethanol. The
invention has
particular relevance to monitoring such dosages using spectroscopic absorbance
or
transmittance signals from one or more components in the denaturant
composition.
BACKGROUND
[002] Fuel ethanol production in the U.S. increased by about 440% during the
period from 1996 to 2007 (from 1.1 to 6.5 billion gallons per year) and world
ethanol
production reached about 13.1 billion gallons per year in 2007. Fuel ethanol
plants under
construction/expansion are expected to double current U.S. production
capacity, and
legislation has been passed that could increase fuel ethanol demand by more
than 600%
by 2022.
[003] Two most commonly used types of additives in fuel ethanol include
denaturants and corrosion inhibitors, the use of which is growing
concomitantly with the
growth in fuel ethanol production. Inaccurate dosing of such additives can
create a
multitude of problems, including noncompliance with ASTM D-4806. Inaccurate
dosing
of denaturant causes significant government regulatory and legal problems.
Releasing
inaccurately dosed batches of fuel ethanol would likewise violate ASTM D-4806.
Both
underdosing and overdosing of denaturant leads to out-of-specification results
that in turn
lead to higher production/shipping costs and delays due to rework of batches.
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[004] The maximum specification range currently allowed in the U.S. for
denaturant is typically about 1.96 to 4.76% by volume. Due to the cost
differential
between ethanol and denaturant, it is valuable for a fuel ethanol plant to
have the ability
to be as close as possible to the upper or lower edge of denaturant dosage
specification
range. When ethanol costs exceed denaturant costs, for instance, it is
desirable for the
fuel ethanol plant to be at the high dosage edge of denaturant specification
range to keep
production costs to a minimum. On the other hand, when denaturant costs more
than
ethanol, it is desirable for the fuel ethanol plant to be at the low dosage
edge of
denaturant specification range.
[005] To operate near either edge of the denaturant (and/or denaturant plus
corrosion inhibitor mixture) dosage specification range requires highly
accurate and
precise measuring/dosing of denaturant concentration. Presently, fuel ethanol
plants tend
to dose denaturants via "splash blending" and/or based on how "long" a
chemical feed
pump is "on" with a "constant flowrate assumed" or sometimes based on
flowmeters or
depth gauges. Even when such flowmeters are regularly and properly calibrated,
proper
dosage rates are not always achieved. Very rarely (if ever) is dosage of fuel
ethanol
denaturants directly measured. Also, batch-to-batch variations and the complex
chemical
nature of denaturants increase difficulty of precisely and accurately
measuring dosages
with currently used methods.
[006] There thus exists an ongoing need to develop methods of accurately and
efficiently monitoring and controlling denaturant concentrations in fuel
ethanol
production plants. Such methods would allow the fuel ethanol producer to
easily
minimize costs of production by adjusting formulations based upon raw material
costs
and to maximize the quality and value of the fuel ethanol product.
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CA 02683295 2009-10-22
SUMMARY
[007] This invention accordingly includes methods of monitoring and
optimizing dosage of one or more fuel ethanol denaturants and/or denaturant
plus
corrosion inhibitor(s) mixtures (collectively sometimes referred to as
"denaturant(s)") by
measuring a spectroscopic absorbance or transmittance signal. Such
measurements are
taken, for example, from one or more components of a denaturant composition or
a
derivative of a component in the denaturant to provide an indication of dosage
concentration. It is contemplated that the described method may be applied to
any
denaturant or denaturant/corrosion inhibitor mixture for fuel ethanol.
[008] In a preferred embodiment, the method is applied to measuring and
controlling dosages of denaturant(s) and/or mixtures of denaturant(s) and
corrosion
inhibitor(s). Such monitoring and control may be directed to additives present
in or
added to the fuel ethanol. Alternative methods of measuring concentrations
include, for
example, a denaturant having one or more components intrinsically capable of
providing
a spectroscopic absorbance or transmittance signal or adding a reagent that
reacts with
one of the components of the denaturant formulation (grab sample). Certain
limitations
and extensions of these alternatives are explained in more detail below.
[009] In a preferred aspect, the invention includes a method of monitoring and
optionally optimizing the concentration of a denaturant composition in a fuel
ethanol.
The method comprises adding a known amount of the denaturant composition to
the fuel
ethanol to create a treated fuel ethanol. The known amount is calculated or
calibrated
based upon mathematical derivative treatment and/or multivariate analysis of
spectroscopic signals to provide an optimum concentration range for the
denaturant
composition in the treated fuel ethanol. Preferably, the denaturant
composition includes
at least one component that is either inherently capable of providing a
spectroscopic
absorbance or transmittance signal or capable of being chemically derivatized
to provide
the spectroscopic absorbance or transmittance signal.
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[0010] In an embodiment, the method includes measuring the spectroscopic
absorbance or transmittance signal for the component in the treated fuel
ethanol at a point
subsequent to adding the known amount of the denaturant composition.
[0011] In another embodiment, the method includes determining the
concentration of the denaturant composition in the treated fuel ethanol based
upon the
measured spectroscopic absorbance or transmittance signal of the component at
the point
subsequent.
[0012] In a preferred embodiment, if the determined concentration of the
denaturant composition is above the optimum concentration range, the method
includes
optionally diluting the treated fuel ethanol by adding a known additional
volume of the
fuel ethanol. Such an additional volume is preferably calculated to bring the
concentration of the denaturant composition in the treated fuel ethanol into
the optimum
concentration range. Conversely, if the determined concentration of the
denaturant
composition is below the optimum concentration range, the method includes
optionally
adding an additional known amount of the denaturant composition. Such known
amount
is preferably calculated to bring the concentration of the denaturant
composition in the
treated fuel ethanol into the optimum concentration range.
[0013] In a further embodiment, the method includes optionally repeating the
described method until the determined concentration of the denaturant
composition is
within the optimum concentration range.
[0014] It is an advantage of the invention to provide an easy, accurate, and
precise method to measure denaturant dosages in fuel ethanol and to
definitively adjust
the dosage setpoint as needed.
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[0015] It is another advantage of the invention to provide methods of
controlling denaturant dosages at fuel ethanol manufacturing plants thereby
significantly
reducing operating costs by preventing inaccurate dosing of treatment
chemicals.
[0016] An additional advantage of the invention is to enable fuel ethanol
producers to include certificates of analysis with respect to denaturant
dosage for each
fuel ethanol shipment.
[0017] It is also an advantage of the invention to provide accurate
measurements of additive dosages in fuel ethanol for compliance with
government
regulations.
[0018] A further advantage of the invention is to provide a versatile method
of
monitoring and controlling denaturant dosages in fuel ethanol that could be
used in both a
grab sample analysis scheme and/or adapted to online dosage control with
datalogging
capabilities.
[0019] Another advantage of the invention is to provide a method of
compensating for changes in fuel ethanol system characteristics by adjusting
denaturant
dosage.
[0020] Yet another advantage of the invention is to provide methods of
controlling denaturant dosages at fuel ethanol manufacturing plants to
eliminate the
possibility of out-of-specification product batches and prevent costly
reworking of
batches to achieve specification and/or government compliance.
[0021] Additional features and advantages are described herein, and will be
apparent from, the following Detailed Description, Examples, and Figures.
CA 02683295 2009-10-22
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 shows the second derivative spectrum of denaturant-fuel
ethanol, where the portions of the spectrum with significant readings above
and below the
line are favorable for measuring denaturant. R2 refers to the linear
correlation and
RMSEC refers to the root mean square error of calculation. Circled regions 1
to 4
indicate spectral areas where characteristics of the denaturant are embedded
and the NIR
spectrum of the denaturant may be detected in the fuel ethanol mixture.
[0023] Figure 2 illustrates the linearity and predictability of near infrared
in a
preferred embodiment to measure the dosage of denaturant in fuel ethanol, as
explained
in Example 4.
DETAILED DESCRIPTION
[0024] In preferred embodiments, the invention includes methods of
monitoring, regulating, and/or optimizing the concentration of a denaturant
composition
in a fuel ethanol using a spectroscopic absorbance or transmittance signal
generated from
a component in the denaturant composition. Throughout this disclosure, the
term
"denaturant" refers to either one or more denaturants and/or to
denaturant/corrosion
inhibitor(s) combinations. The disclosed method of this invention is suitable
for all
manner of fuel ethanol production and is compatible with essentially all
grades of fuel
ethanol mixtures. The method is particularly well suited for use in
conjunction with a
variety of fuel ethanol denaturants. The addition of one or more corrosion
inhibitors into
the denaturant composition does not adversely affect the spectroscopic
absorbance or
transmittance signal of the composition.
[0025] Application of the method begins in the production process where
denaturants and/or denaturant plus corrosion inhibitor(s) are typically added,
and may
also be implemented at any stage of the packaging and shipping process. The
described
method is equally applicable to various sampling techniques including grab
samples,
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sidestream and inline measurements, and measurements taken from a bulk
container or
vessel.
[0026] It should be appreciated that the method, in certain embodiments, may
be combined with other utilities known in the ethanol industry. Representative
utilities
include sensors for measuring alcohol content in, for example, gasoline;
sensors for
determining fuel composition; individual alcohol concentration sensors (e.g.,
methanol,
ethanol); alcohol/gasoline ratio sensors; dissolved or particulate contaminant
sensors;
other sensors based upon resistance, capacitance, spectroscopic absorbance or
transmittance, colorimetric measurements, and fluorescence; and mathematical
tools for
analyzing sensor/controller results (e.g., multivariate analysis,
chemometrics, on/off
dosage control, PID dosage control, the like, and combinations thereof).
[0027] In addition to solvents, stabilizers, and other components, the
denaturant
composition may have a corrosion inhibitor, other denaturant(s), or a mixture
of both.
The denaturant may also be a neat product or a mixture of one or more
denaturants and
one or more corrosion inhibitors. It should be appreciated that the denaturant
composition may include any number of compounds or components. Executing the
method involves adding a known amount of the denaturant composition to the
fuel
ethanol to create a treated fuel ethanol. The added amount is calculated to
provide an
optimum concentration range for the denaturant composition in the treated fuel
ethanol.
[0028] Though other wavelengths may be used, the preferred wavelength range
for implementing the invention is the near infrared ("NIR") range. NIR
measurements
may be used to determine dosage and concentration of denaturant, combinations
of one or
more denaturants, or combinations of one or more denaturants and one or more
corrosion
inhibitors.
[0029] In an embodiment, the denaturant composition includes a corrosion
inhibitor. It is contemplated that the described method is operable with any
such
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composition used for fuel ethanol. For example, a corrosion inhibitors
containing
compounds such as organic acid anhydrides; monomer, dimer, and/or trimer
organic fatty
acid mixtures; and tertiary organic amines may be used. Corrosion inhibitors
also
typically include a mixture of one or more of the following: organic
(cyclohexyl-
containing) amine; monomer, dimer, and/or trimer organic fatty acids including
synthetics; organic acid anhydride; and organic solvents such as alcohol,
xylenes, or other
hydrocarbon-based solvent. The optimum concentration range for corrosion
inhibitor
products is typically in the ppm range (see Examples), although this range may
be above
or below the optimum target dosage for certain applications. It should be
appreciated that
the described method is applicable for use with any denaturant/corrosion
inhibitor
composition.
[0030] In another embodiment, the additive composition includes a denaturant.
Typical denaturants include condensates from natural gas condensate, which may
include
gasoline, methanol, straight-chain hydrocarbons, naphthenes, aromatics, and
others. It
should be appreciated that any denaturant known in the art may be used with
the method
of the invention.
[0031] FIG I illustrates an example of an NIR spectrum of denaturant in fuel
ethanol. These areas are shown circled and marked as "1," "2," "3," and "4" on
FIG 1.
The second derivative spectrum of denaturant-fuel ethanol is shown, where the
portions
of the spectrum with significant readings above and below the line are
favorable for
measuring denaturant. R 2 refers to the linear correlation and RMSEC refers to
the root
mean square error of calculation. Values closer to the value of 1 are
preferred for the
linear correlation, and values closer to 0 are preferred for the root mean
square error of
calculation.
[0032] In alternative embodiments, the spectroscopic absorbance or
transmittance signal is acquired at one, two, or more points. In a preferred
embodiment,
the spectroscopic absorbance or transmittance signal is acquired online,
either
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continuously or intermittently. Such online measurements may be analyzed in
real-time
or with a user-defined or other delay. For example, online measurements may
take place
by using a side-stream, inline, or other suitable flow-through device.
[0033] In another embodiment, a sample of treated fuel ethanol is removed,
either automatically or manually, and the spectroscopic absorbance or
transmittance
signal is acquired from the removed sample.
[0034] Based upon the spectroscopic absorbance or transmittance signal, the
total or component concentration of the denaturant composition may be
determined.
Three possible scenarios exist for the outcome of this determination. The
first is that the
concentration of the denaturant composition is within the optimum
concentration range.
In this instance, no further action would be taken. In the event the
determined
concentration of the denaturant composition is higher than the optimum
concentration
range, the treated fuel ethanol would optionally be diluted with a known
additional
volume of untreated fuel ethanol. The additional volume would be calculated to
bring the
concentration of the denaturant composition into the optimum concentration
range. If the
determined concentration of the denaturant composition is below the optimum
concentration range, an additional amount of the denaturant composition would
optionally be introduced into the treated fuel ethanol in an amount calculated
to bring the
concentration of the denaturant composition into the optimum concentration
range. The
method of the invention may optionally be repeated (e.g., in an iterative
fashion) until the
determined concentration of the denaturant composition is within the optimum
concentration range (or another chosen concentration range, such as a user-
selected
concentration range).
[0035] Fuel ethanol (usually approximately E95) is typically mixed with
gasoline to form ethanol-containing gasolines, such as E10 and E85. For
example, an
E10 formulation generally includes about 9.5 to 9.8% vol/vol ethanol, about
0.2% to
0.5% vol/vol denaturant, and about 90% vol/vol gasoline. The described method
is
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equally applicable in such fuel ethanol compositions, including determining
the total
ethanol content in an alternative embodiment.
[0036] A manual operator or an electronic device having components such as a
processor, memory device, digital storage medium, cathode ray tube, liquid
crystal
display, plasma display, touch screen, or other monitor, and/or other
components may be
used to execute all or parts of the described method. In certain instances,
the controller
may be operable for integration with one or more application-specific
integrated circuits,
programs, computer-executable instructions, or algorithms, one or more hard-
wired
devices, wireless devices, and/or one or more mechanical devices. Some or all
of the
controller system functions may be at a central location, such as a network
server, for
communication over a local area network, wide area network, wireless network,
Internet
connection, microwave link, infrared link, and the like. In addition, other
components
such as a signal conditioner or system monitor may be included to facilitate
signal-
processing algorithms. It is also contemplated that any needed sensors,
couplers,
connectors, or other data measuring/transmitting/communicating equipment may
be used
to capture and transmit data.
[0037] The foregoing description may be better understood by reference to the
following examples, which are intended for illustrative purposes and are not
intended to
limit the scope of the invention.
Examples 1 to 3
[0038] Examples 1 to 3 illustrate the differences between current methods of
adjusting denaturant dosages; direct manual measurement of denaturant, either
with or
without providing a measurement for added denaturant (by NIR); and automatic
control
of corrosion inhibitor dosage, either with or without providing a measurement
for added
denaturant, based on NIR measurements, being added to fuel ethanol. In each of
these
examples, it can be seen that NIR measurement of denaturant dosage could
significantly
CA 02683295 2009-10-22
improve accuracy and reduce variability. Manual adjustment of product dosage
after
measuring of denaturant (and/or denaturant + corrosion inhibitor mixture)
concentration
would provide for improved dosage accuracy and reduced variability in the
final treated
fuel ethanol. Online monitoring/control of the denaturant dosage would result
in further
improved accuracy and reduced variability in concentration levels. The
predicted
variability is shown as 3 SIGMA and based on assumption that a statistically
normal
distribution would occur.
Example 1
[0039] To illustrate denaturant dosage monitoring and/or control by NIR of one
or more components in an additive formulation, a denaturant may initially be
added by
the plant to series of batches of fuel ethanol using a "splash addition"
method (standard
industry practice). The estimated volume of denaturant (and/or denaturant +
corrosion
inhibitor mixture) to be added is typically based on the estimated volume of
fuel ethanol
in the storage tank.
[0040] The prophetic results in Table 1 shows dosage of denaturant during
three
phases of denaturant dosage monitoring and/or control. Under current legal
standards,
denaturant can typically be added from about 1.96% up to about 4.76%
volume/volume
(or about 1.63% to about 3.98% weight/weight) into fuel ethanol, depending on
the
locality of fuel ethanol manufacture. Batch numbers 1 to 5 illustrate dosage
prior to any
changes in denaturant mixture dosing procedure (i.e., manual addition with no
measurement during addition of denaturant mixture); 6 to 10 show improved
results with
direct measurement of denaturant and manual addition/adjustment of denaturant
mixture
based on NIR measurement; and 11 to 15 exemplify further improvement in
results
(average closer to target dosage and lower 3 SIGMA value) due to automatic
measurement and dosage control of denaturant dosage being added to fuel
ethanol. The
target dosage of denaturant is 4.6 % vol/vol in fuel ethanol mixture for this
Example.
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Predicted variability is shown as 3 SIGMA and based on assumption that a
statistically
normal distribution occurs.
Table 1- Denaturant Addition to Fuel Ethanol
Manual addition w/out Manual addition/adjustment and Automatic measurement
adjustment during addition measurement durin addition and dosage control
Batch # Dosage (% Batch # Dosage (% Batch # Dosage (%
vol/vol) vol/vol vol/vol)
1 4.51 6 4.38 11 4.50
2 5.52 7 4.56 12 4.59
3 2.51 8 4.27 13 4.56
4 3.07 9 4.50 14 4.62
4.94 10 4.43 15 4.45
Avg. f 3 4.11 t 3.82 Avg. t 3 4.43 f 0.34 Avg. f 3 4.54 f 0.21
SIGMA SIGMA SIGMA
[0041] Results listed in Table 1(Batch # 1-5 for manual addition of denaturant
without adjustment of dosage during addition) indicate that average denaturant
dosage of
4.11 % vol/vol is well-below target dosage of 4.6% vol/vol. High variability
also exists in
the readings with the 3 SIGMA value being 3.82% vol/vol, almost as high as
the
average denaturant dosage. These results indicate poor control of denaturant
dosage and
Batches # 2 and # 5 (5.52% vol/vol and 4.94 % vol/vol, respectively) were also
outside of
allowable denaturant specification range of 1.96 to 4.76 % vol./vol.
[0042] Batches # 6 to 10 were all within specification range for denaturant
dosage, demonstrating a much improved denaturant dosage with average
denaturant
dosage of 4.43% vol/vol much closer to target dosage of 4.6% vol/vol and
variability of
3 SIGMA = 0.34% much lower as compared to denaturant dosage was not adjusted
during addition.
[0043] Batches # 11 to 15 demonstrated the best results with average dosage of
4.54% vol/vol being closest to the target dosage of 4.6% vol/vol and having
the lowest
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level of variability ( 3 SIGMA 0.21% vol/vol). These batches were likewise
all
within the specification range for denaturant dosage.
Example 2
[0044] Denaturant may be mixed with corrosion inhibitor at a prescribed ratio
to provide monitoring and/or control of denaturant and corrosion inhibitor
dosage by NIR
measurement of denaturant. Under current legal standards, denaturant can
typically be
added from about 1.96% up to about 4.76% volume/volume (or about 1.63% to
about
3.98% weight/weight) into fuel ethanol, depending on the locality of fuel
ethanol
manufacture. If the target dosage for corrosion inhibitor was 72 ppm (or
0.0072%
weight/weight) and denaturant was 2.20% volume/volume (1.83% weight/weight),
the
corrosion inhibitor may be added to denaturant in a ratio of 1 part corrosion
inhibitor to
254 parts (by weight/weight) of denaturant. The mixture of denaturant and
corrosion
inhibitor may then be added to the fuel ethanol and the dosages of denaturant
and
corrosion inhibitor can both be monitored and/or controlled based on NIR
measurement
of denaturant dosage.
[0045] Results in Table 2A to 2C show possible dosages of corrosion inhibitor
and denaturant during three phases of dosage monitoring and/or control: (A)
prior to any
changes in corrosion inhibitor and denaturant dosing procedure with manual
dosage
control, (B) with direct measurement of traced corrosion inhibitor and
denaturant by NIR
measurement of denaturant dosage and with manual corrosion inhibitor addition,
and (C)
automatic control of corrosion inhibitor and denaturant dosages based on NIR
measurements of the denaturant mixture being added to fuel ethanol. Target
dosage of
corrosion inhibitor is typically 72 ppm and 2.20% volume/volume (or 1.84%
weight/weight) denaturant to produce treated fuel ethanol (the low end of the
%
denaturant specification range).
Table 2A - Manual Addition w/out Adjustment and w/ Measurement During Addition
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Batch # Corr. Inh. (ppm) Denat. (% vol/vol)
1 61 1.86
2 101 3.09
3 116 3.53
4 77 2.35
140 4.27
Avg. 99 94 3.02 2.85
f 3 SIGMA
Table 2B -Manual Addition/Adjustment During Measurement
Batch # Corr. Inh. (ppm) Denat. (% vol/vol)
6 71 2.17
7 70 2.14
8 77 2.35
9 79 2.41
75 2.29
Avg. 74 12 2.27 0.35
3 SIGMA
Table 2C - Automated Measurement and Dosage Control
Batch # Corr. Inh. (ppm) Denat. (% vol/vol)
11 70 2.14
12 72 2.20
13 74 2.26
14 70 2.14
73 2.23
Avg. 72 5 2.19 0.16
f 3 SIGMA
[0046] The results above demonstrate that using NIR measurement of
denaturant with a denaturant plus corrosion inhibitor mixture to measure
denaturant an
corrosion inhibitor dosages can significantly improve accuracy and reduce
variability in
concentration of both additives. For example, it can be seen that Batch #1 in
Table 2A
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has a denaturant vol% that is less than specification range of 1.96% to 4.76%
(vol/vol),
with a concomitantly low inhibitor dosage and overall high average dosage of
denaturant
and corrosion inhibitor and high variability in dosage of those two additions.
That batch
of treated ethanol would require additional denaturant plus corrosion
inhibitor mixture to
meet specifications and regulatory/legal requirements.
[0047] Results listed in Table 2A (Batch # 1 to 5 for manual addition of
denaturant and corrosion inhibitor mixture to fuel ethanol without adjustment
of dosage)
show an average dosage of denaturant (3.02% vol/vol) much higher than the
target
dosage (2.2% vol/vol), with variability in denaturant dosage ( 3 SIGMA =
2.85 %
vol/vol) in fuel ethanol almost as high as average denaturant dosage (3.0%
vol/vol).
These results indicate a high level of denaturant dosage variability. The
average dosage
of corrosion inhibitor (based on ratio of corrosion inhibitor to denaturant in
the mixture)
in fuel ethanol follows a similar trend as denaturant dosage. The average
corrosion
inhibitor dosage (99 ppm) in fuel ethanol is much higher than the target
dosage ( 3
SIGMA = 94 ppm) and variability is almost as high as dosage of corrosion
inhibitor (99
ppm) in fuel ethanol.
[0048] Table 2B (Batch # 6 to 10 for manual addition of denaturant and
corrosion inhibitor mixture with dosage adjustment during mixture addition to
fuel
ethanol) shows an average dosage of denaturant (2.27% vol/vol) close to the
target
dosage (2.2% vol/vol) and variability in denaturant dosage ( 3 SIGMA = 0.35
vol/vol)
much lower than when denaturant and corrosion inhibitor mixture dosage was not
adjusted during addition to fuel ethanol. Batch # 6 to 10 were all within
specification
range for denaturant dosage. The corrosion inhibitor average dosage (74 ppm)
was also
close to target dosage (72 ppm) and the corrosion inhibitor dosage variability
( 3
SIGMA = 12 ppm) in fuel ethanol was much lower than previous results.
[0049] Results shown in Table 2C (Batch # 11 to 15 for automated addition of
denaturant and corrosion inhibitor mixture with dosage measurement and
adjustment
CA 02683295 2009-10-22
during mixture addition to fuel ethanol) display an average dosage of
denaturant (2.19%
vol/vol) in fuel ethanol closest to target range dosage (2.2% vol/vol) and the
lowest
dosage variability was ( 3 SIGMA 0.16% vol/vol) as compared to other
methods.
Batch # 11 to 15 were all within specification range for denaturant dosage in
fuel ethanol.
The corrosion inhibitor average dosage (72 ppm) was also right at the target
dosage (72
ppm) in fuel ethanol and the corrosion inhibitor dosage variability ( 3 SIGMA
= 5
ppm) was the lowest when automatic dosage control of denaturant and corrosion
inhibitor
mixture was used in combination with measurement of denaturant dosage by NIR
and
adjustment of dosage during addition of denaturant and corrosion inhibitor
mixture to
fuel ethanol.
Example 3
[0050] In order to measure and/or control higher dosages of denaturant, the
target dosage for corrosion inhibitor can be increased, the level of corrosion
inhibitor can
be increased in its mixture with denaturant, or the level of corrosion
inhibitor can be
adjusted. In this scenario, the corrosion inhibitor would be mixed into
denaturant at a
prescribed dosage to provide monitoring and/or control of higher dosages of
denaturant
and corrosion inhibitor dosage. Current legal guidelines allow for a
denaturant range
from 1.96% up to 4.76% on a volume/volume basis (or 1.63% to 3.98%
weight/weight)
into fuel ethanol, depending on the locality of fuel ethanol manufacture. If
the target
dosage for corrosion inhibitor was 72 ppm (or 0.0072% weight/weight) and
denaturant
was 4.50% volume/volume (3.74% weight/weight), corrosion inhibitor would be
added to
denaturant in a ratio of 1 part corrosion inhibitor to 519 parts (by
weight/weight) of
denaturant. The mixture of denaturant and corrosion inhibitor would be added
to the fuel
ethanol and the dosages of denaturant and corrosion inhibitor would both be
monitored
and/or controlled based on the NIR signal of denaturant.
[0051] Results in Tables 3A to 3C show dosage of the denaturant and corrosion
inhibitor mixture during three phases of dosage monitoring and/or control of
addition of
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that mixture: (A) prior to any changes in corrosion inhibitor and denaturant
dosing
procedure with manual addition of corrosion inhibitor, (B) with measurement of
denaturant in the mixture and with manual addition of the mixture, and (C)
automatic
control of corrosion inhibitor and denaturant mixture dosages based on NIR
measurements of the corrosion inhibitor plus denaturant mixture being added to
fuel
ethanol.
Table 3A - Manual Addition w/o Adjustment and w/ Measurement During Addition
Batch # Corr. Inh. (ppm) Denat. (% vol/vol)
1 78 4.88
2 112 7.02
3 57 3.58
4 70 4.40
81 5.09
Avg. 80 t 61 4.99 3.82
3 SIGMA
Table 3B -Manual Addition/Adjustment During Measurement
Batch # Corr. Inh. (ppm) Denat. (% vol/vol)
6 65 4.06
7 71 4.44
8 73 4.56
9 72 4.50
73 4.56
Avg. 71 10 4.42 0.63
~ 3 SIGMA
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.r ,
Table 3C - Automatic Measurement and Dosage Control
Batch # Corr. Inh. (ppm) Denat. (% vol/vol)
11 70 4.38
12 74 4.63
13 73 4.56
14 73 4.56
15 72 4.50
Avg. 72 5 4.53 0.28
3 SIGMA
[0052] It can be seen that the dosage for Batch #1, #2, and #5 of Table 3A was
outside of the 1.96% to 4.76% (volume/volume) specification and legal limit
range for
denaturant in fuel ethanol, as well as having a high corrosion inhibitor
dosage. That
batch of treated ethanol would require dilution with an additional volume of
untreated
fuel ethanol to meet specifications and regulatory/legal requirements.
[0053] The trends in Tables 3A to 3C are comparable to those in Tables 2A to
2C. The poorest results (average dosage vs. target dosage, 3 SIGMA
variability and
number of batches in specification for denaturant dosage) are observed in
Table 3A with
manual addition of denaturant and corrosion inhibitor dosage mixture to fuel
ethanol
without adjustment of dosage during addition and with measurement of
denaturant
dosage by NIR. The best results are observed in Table 3C with automatic
addition of
denaturant and corrosion inhibitor mixture to fuel ethanol with adjustment of
mixture
dosage during addition and with measurement of denaturant dosage by NIR.
Example 4
[0054] FIG 2 illustrates the linearity and predictability of NIR measurement
of
denaturant dosage when added to fuel ethanol. The test was conducted with a
range of
the corrosion inhibitor concentration from 0 to 5 % (vol/vol) of denaturant.
Excellent
linearity of response was observed (R2 = 0.99932, where 1.00 = perfect
linearity), as well
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CA 02683295 2009-10-22
as excellent reproducibility (RMSEC = 0.0055, where 0.00 = perfect
reproducibility).
Excitation wavelength was 540 nm and emission wavelength was 560 nm.
[0055] It should be understood that various changes and modifications to the
presently preferred embodiments described herein will be apparent to those
skilled in the
art. Such changes and modifications can be made without departing from the
spirit and
scope of the invention and without diminishing its intended advantages. It is
therefore
intended that such changes and modifications be covered by the appended
claims.
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