Patent Application
20060236598
The National Biodiesel Board and others attribute significant benefits to blending of biodiesel into diesel fuel for use in diesel engines. This practice is subject to a significant problem that has not been reported in the public or patent literature. The problem can occur when warm biodiesel is blended into cold diesel fuel. The solubility of water in biodiesel is substantially higher than the solubility of water in diesel fuel. Also the solubility of water in biodiesel is expected to be reduced by the addition of diesel fuel to biodiesel. This phenomenon creates problems when biodiesel is blended into cold diesel fuel. In the most problematic embodiment of this phenomenon, when biodiesel that contains dissolved water is added to diesel fuel the resulting system will have total water content that exceeds the water saturation of the mixture of biodiesel and diesel fuel. In this situation a water rich phase can form as a separate phase from the mixture of diesel fuel and biodiesel. This free water phase can be corrosive relative to diesel fuel.
Furthermore, if the system temperature is below the freezing point of the water rich phase, the water rich phase can freeze and form a suspended solid phase. The suspended solid phase will then settle and plug system valves or lines, or it can be removed by filters that are typically used in the handling of diesel fuel in the distribution and diesel engine user system. The removal on filters tends to plug these filters and can result in premature shut down of systems because of excessive pressure drop. This problem is exacerbated when the biodiesel is blended into very cold diesel fuel as is done in the winter months in more northern locations. As the temperature of the diesel fuel decreases, the water solubility in the mixture of diesel fuel and biodiesel decreases proportionately, and the probability that the water rich phase will precipitate, freeze, and form a problematic solid phase in the diesel fuel-biodiesel mixture proportionately increases. Thus the disclosure primarily addresses compositions and methods for blending biodiesel blends in cold climates during winter months.
The present disclosure can be described as compositions and methods for improving cold weather performance of biodiesel fuels in cold climates, or at low temperatures. The disclosure arises from a surprising discovery by the present inventors that biodiesel blends that contain a significant water content can form precipitates that clog filters at low temperatures. The disclosure thus provides compositions and methods that inhibit such precipitation from a water rich phase of biodiesel fuels at low temperature and avoid clogged filters.
In certain embodiments, the disclosure provides biodiesel blends with low water content, such as a water content of less than 400 ppm, for example, or from 400-5 ppm. Alternatively, certain embodiments include a biodiesel fuel comprising from 2 to 20% biodiesel relative to petroleum diesel and with a water content no greater than about 20 ppm.
Such low water biodiesel can be used in low temperature without forming a precipitate and thus providing good filterability. Certain embodiments include the addition of chemical agents that prevent or inhibit precipitation of a water rich phase at low temperatures. Such agents include, but are not limited to glycol ethers such as methylene glycol ethers such as the mono methyl ether of diethylene glycol, or ethylene glycol ethers, and also can include alcohols, preferably lower alcohols such as methanol, ethanol or propanol. It is also understood that other chemical agents known to those of skill in the art can be used to accomplish the same effect and that such agents also fall within the scope of the invention as described and claimed.
The disclosure includes, therefore, biodiesel fuel compositions that include biodiesel, diesel and a chemical additive such as a glycol ether. The glycol ether can be a methylene glycol ether or an ethylene glycol ether and is added to a concentration effective to inhibit filter clogging at low temperature, and preferably to a temperature near or at the cloud point of the biodiesel fuel blend. In certain embodiments the agent is added to a final concentration of at least 50 ppm, to a final concentration of from about 50 ppm to about 1500 ppm, to a final concentration of from about 50 ppm to about 1000 ppm, to a final concentration of from about 50 ppm to about 800 ppm, or to a final concentration of from about 50 ppm to about 500 ppm. The present disclosure can also be described in certain embodiments as a biodiesel blend fuel including from 2-20% biodiesel relative to petroleum diesel and from 50 ppm to 1500 ppm mono methyl ether of diethylene glycol.
The improved biodiesel blends may be provided by first blending the additive into the bulk biodiesel, which can then be added to the diesel fuel at a fuel terminal for example. Alternatively, a terminal may include a separate tank and piping to mix the additive into the diesel prior to addition of the biodiesel, or the additive can be added simultaneously with the biodiesel to produce the final biodiesel blend. The biodiesel may be blended to any appropriate level such as B20, B10, B5 or B2, or any blend from B2 to B20, for example. Certain embodiments of the disclosure also include a biodiesel composition formulated to blend with petroleum diesel, wherein the biodiesel contains from 0.25% to 10% mono methyl ether of diethylene glycol. The concentration of chemical agent can depend on the blend to be made with petroleum diesel. For example, a biodiesel stock to be blended at B20 can contain less agent than a stock for blending B2. It is contemplated, however, that a biodiesel blend stock is formulated to provide from 50 ppm to 1500 ppm in the final biodiesel/diesel blend.
In certain aspects, the disclosure can be described as a biodiesel fuel blend including biodiesel, diesel, and a chemical agent effective to inhibit precipitation and problematic effects of water from the fuel at temperatures that are below the freezing point of water, i.e. 32° F., or below 20° F., below 10° F., below 0° F., below −10° F., below −20° F., below −30° F., or from 20° F. to −40° F. As used herein biodiesel blend or biodiesel fuel is meant to have its ordinary meaning as used in the art, and is meant to include a blend of bulk biodiesel and petroleum diesel fuel. The diesel fuel is typically #1 or #2 diesel fuel. The term biodiesel is well known in the art and is defined as mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats which conform to ASTM D6751 specifications for use in diesel engines. Biodiesel refers to the pure fuel before blending with diesel fuel. Biodiesel blends are denoted as, “BXX” with “XX” representing the percentage of biodiesel contained in the blend (ie: B20 is 20% biodiesel, 80% petroleum diesel, B2 is 2% biodiesel, 98% petroleum diesel and B5 is 5% biodiesel, 95% petroleum diesel.
The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.
The present disclosure provides an improvement in conventional methods of blending biodiesel in cold temperatures in part by providing compositions and methods for overcoming at least some of the problems related to water content in cold weather biodiesel blends. For example, the present disclosure provides production of biodiesel with minimized water content such that there is less water available for precipitation from the biodiesel, preferably the water content of the biodiesel is controlled to such a low level that it does not form a separate and potentially solid water rich phase when blended with cold diesel fuel. For example, a biodiesel may be provided with a water content of less than 400 ppm, less than 300 ppm, less than 200 ppm, less than 100 ppm, less than 50 ppm, less than 25 ppm, less than 15 ppm, less than 10 ppm or even less than 5 ppm.
The disclosure further provides methods and compositions in which chemical agents are added to the diesel, to the biodiesel, or to the mixture of diesel and biodiesel that prevent or inhibit formation of a separate phase when the biodiesel is blended into cold diesel fuel. In preferred embodiments, a chemical agent is utilized to increase the solubility of water in the blend of biodiesel and diesel fuel. Alternatively a chemical agent is added that affects the melting point of a water rich phase should it be formed such that it does not form a solid phase at the temperatures that are encountered in blending of the biodiesel and diesel fuel. In certain preferred embodiments, mono methyl ether of diethylene glycol or mono methyl ether of ethylene glycol is added to the diesel fuel, to the biodiesel, or to a blend of diesel fuel and biodiesel in an amount effective to prevent or inhibit the formation of a solid precipitate of a water rich phase at cold temperatures. Other chemical agents that perform the same or a similar function are known to those of skill in the art and are included within the scope of the present disclosure.
In the practice of the disclosure, the chemical additive can be provided at the blending location, such that the appropriate amount of biodiesel and additive is added to a tank of diesel at a diesel terminal, the additive can be added to the diesel prior to addition of biodiesel into the blend, or the additive can be added to the blended diesel/biodiesel product. A favorable location to add the glycol ether chemistry for the diesel, biodiesel, water, and glycol ether system would be into the supplied biodiesel. This would save an additive system at the blending locations. Biodiesel that is supplied for application in cold locations can be changed to include biodiesel and glycol ether or other appropriate additive for inhibiting the formation of a solid precipitate of a water rich phase at cold temperature. For example if the biodiesel were being blended to a B2 level, a popular level, at least in Minnesota, the glycol ether could be added to the biodiesel at a level of about 2% of the blend with biodiesel. This would then give about a 400 ppm level of glycol ether in the diesel fuel that contains 2% biodiesel. The amount of additive can be adjusted to address various situations such as treatment of a biodiesel with higher water content, or to provide biodiesel that is used in different final blends, such as B2 (2% biodiesel blend) versus B5 (5% biodiesel blend) for example. To supply biodiesel for a B5 blend, one of skill can take into account the possible higher water content, the water solubility in a B5 blend, and the dilution factor of the biodiesel and additive into the diesel product to produce the final blend. As such, a biodiesel composition according to the present disclosure can contain from about 0.1 to about 10% glycol ether additive, from about 0.5 to about 10%, from about 1% to about 10%, or about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9% or about 10% glycol ether additive, which are useful for the purpose of providing a less problematic cold weather blend stock for biodiesel blends.
An aspect of the present disclosure is the effect of glycol ether concentration on the filterability of mixtures that contain diesel fuel, biodiesel, water and glycol ether at low temperatures. Disclosed herein is significant improvement in low temperature filterability even down to 100 ppm of glycol ether, the lowest level reported in the disclosed tests. It is contemplated that levels even below 100 ppm also provide benefit, and that levels higher than 100 ppm glycol ether generally give even greater benefit than 100 ppm glycol ether. Based on these tests, the benefits of the additive continue to 500 ppm concentration and higher. As such, an aspect of the present disclosure is a biodiesel/diesel blend composition for providing improved performance in cold weather, wherein the composition includes from about 50 ppm to about 1500 ppm glycol ether, from about 100 ppm to about 1000 ppm glycol ether, about 50 ppm glycol ether, about 100 ppm glycol ether, about 200 ppm glycol ether, about 300 ppm glycol ether, about 400 ppm glycol ether, about 500 ppm glycol ether, about 600 ppm glycol ether, about 700 ppm glycol ether, about 800 ppm glycol ether, about 900 ppm glycol ether, about 1000 ppm glycol ether, about 1100 ppm glycol ether, about 1200 ppm glycol ether, about 1300 ppm glycol ether, about 1400 ppm glycol ether, or about 1500 ppm glycol ether. Of course these ranges depend on the circumstances and levels below 50 ppm can have a beneficial effect in some circumstances and levels above 1500 ppm can also be used within the scope of the disclosure. The lower limit is determined only by that amount necessary to achieve some benefit, and the higher limit only by a determination of whether a higher level of additive would be cost effective for a user.
Cold Filter Plugging Point Test
The CFPP test is widely used to predict the low temperature performance of diesel fuel and biodiesel blends. In the CFPP test protocol a diesel fuel sample is cooled in a bath to a low temperature. At the test temperature, suction, via small vacuum is pulled on the sample and it is sucked through a filter at the test temperature. The sample achieves a CFPP test pass if 60 ml are sucked through the filter in 60 seconds. The fill time is an indication of flow rate through the filter. Alternatively, a pressure difference across the filter is used to indicate filter plugging.
The National Biodiesel Board website includes data on the CFPP performance of biodiesel blends with diesel fuel and for blends that contain well known cold flow improvers. As stated in a report by the Cold Flow Blending Consortium entitled Biodiesel, Cold Flow Blending Study “Increased use of biodiesel has created some handling challenges for bringing blended fuels to the consumer. The most immediate handling concern for blenders is assurance that diesel fuels and biodiesel can be blended uniformly and in a single phase. More specifically, blenders need guidelines and parameters for blending diesel fuel and biodiesel in colder climates. Neat biodiesel has a much higher cloud point than conventional diesel fuels and this can impact handling procedures. This concern became a priority following the passage of a bill in Minnesota that required all on-highway diesel fuels to contain at least 2% biodiesel as early as Jul. 1, 2005.” The study, using unadditized diesel and blended with biodiesel to produce 2% biodiesel (B2), concluded “Results from the testing showed that the biodiesel must be kept at least 10° F. above its cloud point to successfully blend with diesel fuels in cold climates.”
In other work referenced on the NBB web site studies conclude that low blends of biodiesel have only a minimal effect on the CFPP of the base diesel fuel. It is common knowledge that the standard filter size on the CFPP device is 45 microns and problems with smaller filter sized would not be detected.
An experimental system based on the CFPP apparatus was used to generate the data herein. The present inventor, however, observed a substantial difference between the filterability of the mixtures of diesel fuel, biodiesel, and water when the filter was changed from a 45 micron filter to the 20 micron filter used in the test apparatus for the examples described below. The tests on the 45 micron filter show a small effect of the biodiesel and water upon the filterability of No. 1 diesel fuel; whereas the tests with a 20 micron filter show a dramatic difference in filterability for samples with the same diesel fuel, biodiesel, and water content. This is important because the 45 micron filter is that used in the CFPP test, and thus the problem addressed by the present disclosure has not been previously recognized based on the standard testing procedure.
The initial data presented herein supports the principle disclosed herein that the water content of biodiesel has an effect on the performance characteristics of the fuel at low temperature. A summary of filterability data is shown in the graph of
The data in
The data shown in
The data in
The examples disclosed herein with the 20 micron filter demonstrate that biodiesel that meets the ASTM biodiesel specification can have a significant effect on the filterability or flow rate through a 20 micron filter in cold temperature, as both of the biodiesel samples used in the examples, (i.e. 471 ppm and 1266 ppm water content) meet the ASTM biodiesel specification. The problem with filtration for biodiesel blends when using a 20 micron filter or smaller that are made from biodiesel that complies with ASTM biodiesel specifications is a previously unrecognized problem for biodiesel users of either B2 or B5 biodiesel. The No. 1 diesel used in these studies does not have an unusually high water content and is believed to be lower in water content than the majority of the No. 1 or No. 2 diesel fuel that is currently in commerce. Therefore the problems that can be encountered in commercial use of diesel will not likely be less than simulated in these tests.
These data show that both B2 and B5 “split” from the No. 1 in filter flowability as the temperature is lowered. The splitting is also a function of the water content of the biodiesel used for the blend, the greater water content leading to greater splitting at a higher temperature. The data also show the effect of the addition of a glycol ether to the biodiesel compositions. This new composition containing diesel fuel, biodiesel, water, and glycol ether behaves in a greatly improved manner from the behavior of the compositions tested without additive. With the addition of glycol ether the biodiesel blend compositions perform in a very acceptable manner and exhibit filterability that is not significantly different from that of No. 1 diesel fuel to temperatures well below −30 F.
In practical terms, the user of the tested B2 and B5 compositions or the equivalent could expect to have considerable problems during cold winters with diesel fuel filterability. These data indicate that these compositions will impede filter performance at temperatures even higher than −20 F. It can be expected that as finer filter sizes are used, the problems will be encountered at even higher temperatures than indicated in the figures. It is probable that users of such mixtures will encounter the effects of smaller filter sizes as it is common for diesel engine fuel systems to be protected by filters of 10 micron size and smaller. In contrast to the problems that can be expected for the user with the conventional biodiesel blends, the user who has the compositions including additive can expect unimpeded filter performance for his composition of diesel fuel, biodiesel, water and glycol ether to very low temperatures of −35 F and even lower. In fact, the B5 with Glycol Ether exhibits good performance at temperatures approaching −41° F. which is the Cloud Point for this B5 sample. B2 would be expected to operate to an even lower temperature when fortified with the glycol ether composition.
The following examples are provided to demonstrate the effect of precipitation of solids from a water rich phase of biodiesel when the biodiesel is added to diesel at low temperatures, and to demonstrate the prevention or inhibition of such precipitation. The Cold Filter Plugging Point (CFPP) test is used in the following examples. At the test temperature, suction, via a small vacuum is pulled on the sample and it is sucked through a filter at the test temperature. The sample achieves a CFPP test pass if 60 ml are sucked through the filter in 60 seconds. The fill time is an indication of flow rate through the filter. The fill time is used as the pertinent measure of filterability in the examples.
A Cold Filter Plugging Point Test was conducted with the apparatus set up according to the ASTM method with a 45 micron filter. The test samples included low sulfur #1 diesel and West Central soybean biodiesel. The biodiesel was used both as received and near water saturation, in a 5% biodiesel blend in order to determine if differences in flow rates or plugging temperatures could be observed. With these samples the fill times were all about 15 seconds at 0° C. and −10° C., with changes beginning to show up in the sample with saturated biodiesel at about −28° C. The run was stopped before the #1 diesel by itself failed, as the ability of the cooler was nearing its limit and it still took only 26 seconds to fill the chamber.
When using the ASTM method screen size as shown in this example, the No. 1 diesel and the 5% biodiesel blend with No. 1 diesel were similar, although there was some indication of “splitting” away of the biodiesel blends at the lowest temperatures.
The water content for the samples of #1 diesel and biodiesel shown above were also used for the following examples 2-4.
In a subsequent test, the 45 micron screen was replaced with a 5 micron screen. The samples used in the test were portions of the same mixtures that had been used in the previous example with the 45 micron screens. In this example all three of the fuel samples failed at 0° C. which is the regular starting temperature used to run the CFFP test. It appears that with the very small amount of vacuum applied in the test even the #1 diesel could not fill the chamber in the prescribed 60 seconds. Actually the chamber on the #1 diesel sample did fill about ⅔ full in the 60 seconds, the chamber with 5% (as rec'd biodiesel) filled about ½ full, and the chamber with 5% (saturated biodiesel filter filled less than 10% full. The difference in water content, therefore, has a significant effect in plugging at 0° C. using the 5 micron screen. The samples were removed from the unit and allowed to warm to a temperature above 20° C. and the test was repeated with the starting temperature being set to 20° C. Again, none of the samples were pulled into the chamber within the sixty seconds allotted, even at 20° C. In this instance, however, all three of the samples did fill the chambers to about the 70% level. It appears that the way this test is set up, the vacuum generated is simply too low to pull the fuel through 5 micron filters at a fast enough rate to fill the chamber in 60 seconds, at any normal temperature. The inventors were thus able to generate limited fail temperature data, but were able to confirm an effect of water content using the 5 micron filters.
In a third series of tests, screening material with 20 micron openings was obtained and used to replace the 5 micron filters in the holders. Runs were made with the same mixtures as previously used. A separate series of tests included the biodiesel and saturated biodiesel in a 2% blend with the #1 diesel. This test again confirmed that the amount of water in the biodiesel fuel does make a difference although it is small at these levels. Although an increase is seen in the fill time for #1 diesel at lower temperatures. It is contemplated that the increasing fill time for #1 diesel is due to viscosity changes and that not enough waxes are present to cause blockage of the filter. These tests also show that both B2 and B5 “split” from the No. 1 diesel in filter flowability as the temperature is lowered. The splitting is also a function of the water content of the biodiesel used for the blend, the greater water content leading to greater splitting at a higher temperature.
In a further series of tests, 500 ppm of diethylene glycol monomethyl ether was added to the 5% biodiesel mix samples and subjected to CFFP testing with a 20 micron screen as described in Example 3. In this example, the water no longer had any apparent effect on the filter plugging, unless it was to serve as a slight diluent. Since the filter plugging temperatures of the mixtures are effectively the same as they were when using the 45 micron screen, it is suggested that the ice crystals, when present, might serve as nucleation sites and cause the growth of wax crystals to occur at a lower temperature than would otherwise be the case.
The data shown in Table 4 show the effect of the addition of a glycol ether to the test blends. This new composition that includes diesel fuel, biodiesel, water, and glycol ether behaves in a greatly improved manner from the behavior of the composition tested in example 3, and gives filterability that is not significantly different from that of No. 1 diesel fuel to temperatures well below −30 F.
All of the compositions and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions and/or methods and in the steps or in the sequence of steps of the methods described herein without departing from the concept, spirit and scope of the invention. More specifically, it will be apparent that certain agents which are chemically or functionally related may be substituted for the agents described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.
| Number | Date | Country | |
|---|---|---|---|
| 60674799 | Apr 2005 | US |
