Patent Application
20100101140
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
It is also an advantage of the invention to provide accurate measurements of additive dosages in fuel ethanol for compliance with government regulations.
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.
Another advantage of the invention is to provide a method of compensating for changes in fuel ethanol system characteristics by adjusting denaturant dosage.
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.
Additional features and advantages are described herein, and will be apparent from, the following Detailed Description, Examples, and Figures.
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.
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, sidestream and inline measurements, and measurements taken from a bulk container or vessel.
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, calorimetric 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).
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.
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.
In an embodiment, the denaturant composition includes a corrosion inhibitor. It is contemplated that the described method is operable with any such 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.
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.
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 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.
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.
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).
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 equally applicable in such fuel ethanol compositions, including determining the total ethanol content in an alternative embodiment.
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.
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 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 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.
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.
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. Predicted variability is shown as ±3 SIGMA and based on assumption that a statistically normal distribution occurs.
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.
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.
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 level of variability (±3 SIGMA=±0.21% vol/vol). These batches were likewise all within the specification range for denaturant dosage.
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.
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).
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 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.
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.
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 volt/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.
Results shown in Table 2C (Batch #11 to 15 for automated addition of denaturant and corrosion inhibitor mixture with dosage measurement and adjustment 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.
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.
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 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.
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.
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.
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.
