Patent Grant
7754905
The present invention relates generally to biodiesel production and more particularly to biodiesel production using a controlled flow cavitation apparatus.
Biodiesel is a non-petroleum-based diesel fuel. Production of fatty acid alkyl esters for use as biodiesel comprises the transesterification of fatty acids of a feedstock into fatty acid alkyl esters. Natural fats and oils that make up the feedstocks for biodiesel production generally contain free fatty acids as either a naturally occurring component or as a result of an enzymatic decomposition process.
Generally, the transesterification reaction is carried out in the presence of an alcohol and a catalyst. Conventional methods of biodiesel production utilize either a batch reactor or a continuous process. These methods do not yield a conversion of fatty acids to fatty acid alkyl esters at a rate above 99%. The reaction times can also vary from several minutes to several hours. Batch process reactions are easy to control but are often cost ineffective due to ineffective mixing methods and long reaction times. Continuous transesterification processes can reduce the reaction times but have been unable to provide efficient mixing necessary to reduce the time and cost to produce biodiesel.
Accordingly, there is a need in the art for an apparatus and method of converting fatty acids to fatty acid alkyl esters that is cost effective and reduces reaction time. The apparatus and method can be easily retrofitted into an existing biodiesel production process. The apparatus and method can provide effective mixing such that the conversion rate of fatty acid into fatty acid alkyl esters is sufficiently high, and preferable above 90%.
A method for preparing a fatty acid alkyl ester from a feedstock comprising providing a feedstock comprising at least one source of fatty acids. The feedstock is mixed with a treatment composition comprising alcohol and a catalyst to form a reaction mixture. The reaction mixture is preferably in the range of 40° to 200° C. The reaction mixture is forced through at least two controlled flow cavitation apparatuses at a processing pressure capable of generating a hydrodynamic cavitation zone in each apparatus. A pressure differential across each controlled flow cavitation apparatus is preferably maintained in the range of 30 to 500 psi. At least one of the fatty acids from the source of fatty acid is converted into a fatty acid alkyl ester.
A method of increasing the conversion rate of fatty acid to fatty acid alkyl ester comprising combining a feedstock comprising fatty acids with an alcohol and a catalyst to form a reaction mixture. The reaction mixture is preferably in the range of 40° to 200° C. The reaction mixture is passed through at least two controlled flow cavitation apparatuses to convert the fatty acids in the feedstock to fatty acid alkyl esters through a transesterification reaction. The conversion rate of fatty acids in the feedstock to fatty acid alkyl esters is preferably greater than 90%.
Aspects of the invention will be appreciated by a person having ordinary skill in the art based on the following description with reference to the following drawings, which are provided by way of illustration and not limitation.
Herein, when a range such as 5-25 (or 5 to 25) is given, this means preferably at least 5 and, separately and independently, preferably not more than 25.
The use of a controlled flow cavitation apparatus in a biodiesel production process can both reduce the transesterification reaction time and increase the conversion rate of fatty acids to fatty acid alkyl esters, otherwise known as biodiesel fuel. Apparatuses 12 capable of generating a controlled flow cavitation, as applied during the reaction phase of biodiesel production, can impart a high level of energy into the reaction mixture, which acts to increase the transesterification rate of fatty acids to fatty acid alkyl esters. The energy generated from controlled flow cavitation acts to effectively mix and introduce alcohol to the reaction sites on the fatty acid chains at a quicker rate than conventional methods. Application of a controlled flow cavitation apparatus to the biodiesel production process has multiple benefits, such as an increase in the mixing efficiency, a decrease in reaction time, increase in the conversion rate, and a reduction in production costs and time.
The fatty acids used in the transesterification reaction can be supplied from feedstocks containing at least one source of fatty acids, such as oils and animal fats. The at least one source of fatty acids can be, for example, soybean, corn, sunflower, palm, jatropha, nut, safflower, olives, cotton, linseed, mustard seed, rapeseed, canola, peanuts, coconut, castor beans, tall oil, algae, raw or rendered animal fats, brown grease, white grease, yellow grease, lard or tallow from pork, chicken, mutton, beef, horse, or combinations thereof. The at least one source of fatty acids can also be wastes, effluents and/or residues from the processing oils or animal fats. The feedstock 1 can comprise multiple sources of fatty acids, such as a blend of oils and/or animal fats.
A process for preparing biodiesel using a controlled flow cavitation apparatus is shown in
The reaction mixture 10 can comprise varying amounts of a fatty acid source 1, alcohol 2 and catalyst 3. For example, the ratio of fatty acid source/alcohol/catalyst can be 0.1-5/1-10/0.01-1. As shown in the Examples below, the ratio can be 1/6/0.22.
The reaction mixture 10 of
The process of
Turning to
The invention can be practiced by using any of the known controlled flow cavitation apparatuses, such as those described in U.S. Pat. Nos. 5,810,052; 5,931,771; 5,937, 906; 5,971,601; 6,012,492; 6,502,979; 6,802,639; and 6,857,774, the entire contents of which are incorporated herein by reference.
As the reaction mixture 10 comprising feedstock 1, alcohol 2, and catalyst 3 passes through the cavitation apparatus 12, the feedstock 1 and alcohol 2 are reacted in the presence of the catalyst 3. The reaction takes place in the local hydrodynamic cavitation zone. The product of the reaction is a reaction product stream 30 that comprises fatty acid alkyl esters, unreacted fatty acid, catalyst, unreacted alcohol and optionally glycerol. In a preferred embodiment, the reaction mixture 10 passes through four controlled flow cavitation apparatuses 12. Feedstock 1 and the alcohol 2 are reacted in each of the hydrodynamic cavitation zones. After passing through each of the first, second, and third apparatuses, an intermediate reaction product stream is formed that comprises fatty acid esters, unreacted fatty acid, catalyst, unreacted alcohol and optionally glycerol.
The hydrodynamic cavitation zone is produced as a function of one or more of the temperature of the reaction, the pressure drop across the constriction 21, 22, and the residence time across the restriction orifice 22. A pressure differential is created by the flow of the reaction mixture 10 as it passes over and through the local restriction orifice 22 or orifices (not shown) of each cavitation apparatus 12. The magnitude of the pressure differential is controlled by the size of the orifice 22, the flow rate of the reaction mixture 10, and a localized hydraulic resistance 26 downstream of the apparatus 12.
The restriction of flow in the controlled flow cavitation apparatus 12 can be provided by localized flow constriction 21, such as an orifice 22, baffle, nozzle or the like. As shown in
As shown in
The processing pressure is reduced as the reaction mixture 10 passes through the flow-through channel 20 and orifice 22. Maintaining a pressure differential across the localized flow constriction 21 or orifice 22 allows control of the cavitation intensity in the flow through channel 20. The pressure differential across the localized flow constriction 21 or orifice 22 is at least 100, 120, 140, 150, 170, 200, 250, or 300 psi. Preferably, a pressure differential across a controlled flow cavitation apparatus 12 can be maintained in the range of 30-500, preferably 30-250, more preferably 30-200 or about at least 40, 60, 100, 120, 140, 150, 170, 200, 250, or 300 psi. In the embodiment illustrated in
Flow of the reaction mixture 10 across the orifice 22 or orifices (not shown) create a hydrodynamic cavitation zone that promotes a high density of cavitation power dissipation locally inside the flow-through channel 20, and more preferably in the orifice 22 chamber (l) and downstream of the orifice 22 in the second chamber 24. The high energy dissipation in the hydrodynamic cavitation zone causes the formation, growth, and eventual implosive collapse of vapor bubbles within the liquid. This collapse then releases a tremendous amount of energy which acts to break apart the fatty acids and facilitate an increased number in reaction sites for the alcohol to attack.
Hydrodynamic cavitation zone in the orifice chamber (l) and second chamber 24 arises in the fluid jets of the reaction mixture 10 flowing from the orifice 22 in the form of intermingling cavitation bubbles and separate cavitation cavities. The length (l) in orifice 22 in localized flow constriction 21 is selected in such a manner in order that the residence time of the cavitation bubble in the orifice 22 and/or the second chamber 24 does not exceed 1 second or preferably 0.1 second. Thus, the hydrodynamic cavitation zone comprises the orifice 22 and second chamber 24. The reaction mixture 10 is maintained in the hydrodynamic cavitation zone of at least one apparatus 12 for preferably less than 1 second, preferably less than 0.1 second, preferably less than 0.01 second, preferably less than 0.001 second, preferably less than 0.0001 second, preferably less than 0.000001 second, and preferably less than 0.0000005 second. In one preferred embodiment as shown in
The given dynamic pressure and residence time of the bubble in the localized flow constriction 21 and orifice 22 allows for production of cavitation bubbles and cavities in the reaction mixture 10 flow. The cavity sizes are dependent on the magnitude of the dynamic pressure jet as well as the sizes of orifice 22 in the localized flow constriction 21. Increase of the dynamic pressure jet as well as size of orifice 22 leads to the increase in the sizes of cavitation bubbles. Increase of the dynamic pressure of the cavitation fluid jet also promotes increase of the concentration of cavitation bubbles. Therefore, given the dynamic pressure of the cavitation fluid jet, its shape, and the number of fluid jets, it is possible to produce a cavitation zone of cavitation bubbles and their required concentration and sizes. Cavitation bubbles and cavities together with the liquid jets enter into the second chamber 24, where they collapse under the influence of static pressure P2. The energy emitted during collapse of cavitation bubbles is directly proportional to the magnitude of the static pressure in the surrounding liquid bubbles. Therefore, the greater the magnitude of P2 the greater the energy emitted during collapse of cavitation bubbles and the better the dispersion and/or size reduction effect. In other words, the level of energy dissipation in the reaction mixture 10 increases as the magnitude of P2 increases and thus the severity or hardness of collapse of each cavitation bubble separately increases, as well as the level of energy dissipation due to the decrease of the volume in which these bubbles collapse.
As discussed above, the magnitude of static pressure P2 in second chamber 24 is maintained due to the location of the additional localized restriction 26 at the outlet from this chamber. The additional localized restriction may be adjustable or non-adjustable. By utilizing the adjustable additional localized resistance 26 it is possible to control the severity or hardness of cavitation influence and in the same process, the cavitation dispersion and conversion rate of fatty acids to fatty acid alkyl esters formed by the transesterification reaction.
In another embodiment,
A controlled flow cavitation apparatus can be integrated or retrofitted into a biodiesel production process, such as shown in
After the reaction mixture 10 passes through the cavitation apparatuses(s) 12, the final reaction product 30 is collected. The reaction product 30 can be placed in a centrifuge for the purpose of separating glycerol, unreacted fatty acid, catalyst, and/or unreacted alcohol from the fatty acid alkyl esters. The separated or isolated fatty acid alkyl esters can be subsequently washed and/or dried. Chromatography can be used to determine the quantity and purity of the fatty acid alkyl esters. One preferred fatty acid ester is a fatty acid methyl ester (FAME).
Using the cavitation apparatus 12 as described herein, fatty acids are consistently converted to fatty acid alkyl esters at a conversion rate above 90% and often above 98%. With each additional cavitation apparatus 12 that the reaction mixture 10 and/or reaction product 30 passes through, the conversion rate can be further increased. Consistent conversion rates over 99% are obtainable with the use of two or more cavitation apparatuses 12, preferably in series.
In order to promote a further understanding of the invention, the following examples are provided. These examples are shown by way of illustration and not limitation.
A reaction mixture was prepared by combining the reactants from the two holding tanks to comprise a molar ratio of 1 part oil, 6 parts methanol, and 0.219 parts NaOH. Four separate runs were conducted using the reaction mixture. The results of the runs are shown in Table 1 below. In a first run, the reaction mixture was passed through one cavitation apparatus at a temperature of 100° C., a residence of time of 0.12 microseconds in the hydrodynamic cavitation zone and a pressure differential across the orifice of 250 psi. In a second run using the same molar ratio, the reaction mixture was passed through two cavitation apparatus in series with each other at a temperature of 100° C. A residence time of 0.12 microseconds and a pressure differential of 250 psi were obtained for the first cavitation apparatus and a residence time of 0.17 microseconds and a pressure differential of 120 psi were obtained for the second cavitation apparatus. In a third run using the same molar ratio, the reaction mixture was fed through three cavitation apparatuses in series with each other at a temperature of 100° C. A residence time of 0.12 microseconds and a pressure differential of 250 psi was obtained for the first cavitation apparatus; a residence time of 0.17 microseconds and a pressure differential of 120 psi was obtained for the second cavitation apparatus; and a residence time of 0.12 microseconds and a pressure differential of 250 psi were obtained for the third cavitation apparatus. In a fourth run using the same molar ration, the reaction mixture was fed through four cavitation apparatuses in series with each other at a temperature of 100° C. A residence time of 0.12 microseconds and a pressure differential of 250 psi were obtained for the first cavitation apparatus; a residence time of 0.17 microseconds and a pressure differential of 120 psi were obtained for the second cavitation apparatus; a residence time of 0.12 microseconds and a pressure differential of 250 psi were obtained for the third cavitation apparatus; and a residence time of 0.25 microseconds in the hydrodynamic cavitation zone and a pressure differential of 60 psi were obtained for the fourth cavitation apparatus.
As can be seen in Table 1, the conversion rate of fatty acids to fatty acid methyl esters was greater than 98% after passing the reaction mixture in a single pass through a single cavitation apparatus. In the single pass, single apparatus run #1, the processing pressure was greater than 250 psi and the pressure differential across the apparatus was 250 psi. The conversion rate was greater than 99% after passing the reaction mixture through at least 2 cavitation apparatuses in series. The conversion rate increased after each successive pass through an additional cavitation apparatus with a 99.8% conversion rate after passing through four cavitation apparatuses in series.
Further experimentation was done with reaction mixtures at different temperatures. Six runs were completed using four cavitation apparatuses in series. Residence times in the hydrodynamic cavitation zones of each apparatus was held constant at 0.12, 0.17, 0.17, and 0.25 microseconds for the first, second, third, and fourth cavitation apparatuses, respectively. Pressure drops of 250, 150, 120, and 60 psi were also maintained for the first, second, third, and fourth cavitation apparatuses, respectively. A molar ratio for oil/methanol/NaOH was held at 1:6:0.219 for runs one, four, five, and six and a molar ratio of 1:6:0.217 was held for runs two and three. The temperature of the reaction mixture started at 60° C. for the first run and increased to 80° C. for the second, 90° C. for the third, 100° C. for the fourth, 120° C. for the fifth, and finally 150° C. for the sixth run.
As can be seen in Table 2, the conversion rate of fatty acids to fatty acid alkyl esters was about 99% or greater in each of the six runs after passing through four cavitation apparatuses in series. The greatest conversion rate, 99.9%, occurred at a temperature of 100° C. and an oil/methanol/NaOH molar ratio of 1:6:0.219. As temperatures increased from 60 to 100° C., the conversion rate increased from 99% to 99.9%. Temperature intervals above 100° C. showed a decrease in the conversion rate: 99.8% at 120° C. and 99.4% at 150° C. The conversion rate was the highest at 100° C. and in the temperature range of 80 to 120° C., the conversion rate was at least 99.8%. A rate of 98% for the conversion of fatty acids to fatty acid alkyl esters was consistently obtained by passing the reaction mixture through at a controlled cavitation apparatus.
A controlled cavitation apparatus 12 allows a user to control the conversion rate by varying the temperature of the reaction mixture, which can be done by passing the reaction mixture 10 through a heat exchanger. Another parameter under the control of the user is the pressure drop pressure across the local constriction 2. For example, a user can vary the processing pressure in the apparatus 12 by varying the outlet pressure of the pump used pass the reaction mixture 10 through the controlled flow cavitation apparatus 12. A user can also vary the diameter of the orifice. A user can further adjust the number and/or arrangement of cavitation apparatuses 12 that the reaction mixture 10 will flow through.
It should now be apparent that there has been provided, in accordance with the present invention, a novel process for increase the rate of conversion fatty acids to fatty acid alkyl esters, otherwise known as biodiesel fuel. Moreover, it will be apparent to those skilled in the art that many modifications, variations, substitutions, and equivalents for the features described above may be effected without departing from the spirit and scope of the invention as defined in the claims to be embraced thereby.
The preferred embodiments have been described, herein. It will be apparent to those skilled in the art that the above methods may incorporate changes and modifications without departing from the general scope of this invention. It is intended to include all such modifications and alterations in so far as they come within the scope of the appended claims or the equivalents thereof.
This application claims the benefit of U.S. provisional application Ser. Nos. 60/954,659 filed Aug. 8, 2007 and 60/973,332 filed Sep. 18, 2007, the contents of which are incorporated herein in their entirety by reference.
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