WO2008052308A1

WO2008052308A1 - Continuous counter-current bio-diesel refining method

Info

Publication number: WO2008052308A1
Application number: PCT/CA2007/001756
Authority: WO
Inventors: Harvey Haugen
Original assignee: Harvey Haugen
Priority date: 2006-10-02
Filing date: 2007-10-02
Publication date: 2008-05-08
Also published as: CA2561797A1

Abstract

Embodiments of a system that provides continuous production of methyl esters and glycerin from triglycerides are described. Transesterification of triglycerides with methanol, and catalyzed by hydroxide, produces glycerol and methyl esters. The methyl esters are useful as a biodiesel fuel. In some embodiments, the method takes advantage of the differences in density of triglycerides, glycerol and methyl esters, using a countercurrent mechanism to provide a method of dealing with the unfavorable density of methanol, while achieving separation of the desired products. In some embodiments, reactants are injected into a zone in a biodiesel reactor. Lighter methyl esters rise to the top of the reactor, while higher density glycerol settles to the bottom of the reactor. Ports at the top and bottom facilitate continuous collection of products. The reactor is continually charged with fresh reactant as products are removed, providing for continuous production of biodiesel.

Description

CONTINUOUS COUNTER-CURRENT BIO-DIESEL REFINING METHOD

Background

With the ever- increasing demand for petroleum-based fuels, combined with the decrease in proven reserves of petroleum, and the current concern over the environmental impacts of using petroleum-based fuels, there has been a growing interest in the use of alternative sources of energy. It had been previously discovered that traditional diesel engines are able to use plant-based oils as fuel. As triglycerides can be obtained from plant and animal sources, there has thus been great interest in the production of fuel from biological rather than from traditional mineral-based sources.

Summary of the Invention

In some embodiments, methods and apparatus are provided for the production of biodiesel fuel in a continuous flow manner. In some embodiments, an apparatus comprises a reactor with a single vertical column with a cone-shaped bottom. Reagents such as potassium methoxide and oil feedstock comprising triglyceride can be continuously added in predetermined proportions ,and at a predetermined location, in the reactor, such that substantially complete conversion of feedstock to methyl ester and glycerol results.

In some embodiments, mixing of the reactants and feedstock, optimization of the reaction conditions and separation of the products are achieved by a countercurrent mechanism. Methyl esters rise to the top of the reactor column, while glycerol sinks to the bottom. By providing a predetermined input flow, essentially pure glycerol and methyl ester (biodiesel) can be extracted from the reactor column in a continuous manner.

In some embodiments, an apparatus comprises a plurality of reactors, with reactors arranged such that crude methyl ester produced in an upstream reactor is used as a feedstock in a downstream reactor. In multi-reactor embodiments, the glycerol/methoxide can be recycled from a downstream, reactor and used as a reagent in an upstream reactor. Embodiments of multi-reactor systems can be configured to require lower headroom and to provide easier control visibility. In some embodiments of a multi-reactor system, methyl ester of higher purity is obtained, as compared to a single reactor system.

Some embodiments further comprise a collector system, effective to trap excess unreacted methoxide, for recycling back to the reactor.

Some embodiments can include systems for regulating flow of reactants into the reactor, and for removing products produced by the transesterification reaction. Some embodiments include systems for agitation of reactants in order to enhance the rate of the transesterification of the triglyceride.

Conveniently, apparatus and controls for regulating temperature, can be included to maintain the system at an temperature for the refining process. In some embodiments, refining will be performed at a temperature between 60-70°C, and in particular at about 65°C.

Thus, in contrast to prior art batch methods of biodiesel production, embodiments of the present disclosure provide for the continual and efficient conversion of triglyceride to methyl ester and glycerol, and the separation of these two products. Embodiments as disclosed herein further provide that synthesis and separation can be achieved using smaller vessels than are typically used when employing prior art methods of producing biodiesel.

Accordingly, in some embodiments, there is provided a system, for use in continuous production of an alcohol ester from an oil feedstock, by a transesterification reaction, the system comprising: a reactor chamber, having a volume; a least one circulation leg, comprising: at least one input line configured to introduce reactants, and at least one catalyst, into the reactor chamber; output lines configured to remove by- products of the transesterification reaction from the reaction chamber; wherein the reactor chamber is configured such that, during the transesterification reaction, a counter-current flow of the reactants and the at least one catalyst within the reaction chamber results in mixing of the contents of the reactor chamber; and wherein the system is further configured such that input of reactants and the at least one catalyst into the reactor chamber, and output of by-products from the reactor chamber, occurs substantially continuously, for a volume of reactants greater than at least the reactor chamber volume.

In some embodiments, the by-products comprise at least one alcohol ester and a by-product alcohol. In some embodiments, the alcohol ester comprises a methyl ester, and the by-product alcohol comprises glycerol.

In some embodiments, the reactor chamber has an aspect ratio in a range from about 2:1 to about 10:1. In some embodiments, the aspect ratio is about 5:1.

In some embodiments, the system further comprises the reactants and the at least one catalyst. In some embodiments, the reactants comprise the oil feedstock and a reactant alcohol. In some embodiments, the at least one catalyst is effective to promote transesterification of the oil feedstock to an alcohol ester. In some embodiments, the at least one catalyst comprises hydroxide.

In some embodiments, the reactants and the at least one catalyst are introduced via a single input line. In some embodiments, the reactants and the at least one catalyst are introduced via separate input lines. In some embodiments, output lines for said byproducts comprise an alcohol ester output line, and a by-product alcohol output line.

In some embodiments, the system further comprises a heat exchange module, the one heat exchange module operative to maintain the contents of the reactor chamber in a range from about 6O⁰C to about 70°C.

In some embodiments, the system further comprises an agitator, said agitator effective to enhance at least one of mixing of reactants in the reactor chamber and coalescence of the by-product alcohol.

In some embodiments, the system comprises a plurality of reactor chambers arranged in parallel. In some embodiments, the system comprises a plurality of reactor chambers arranged in series.

In some embodiments, a first reactor chamber is configured to receive as an input at least one by-product from a subsequent reactor chamber in the series.

In some embodiments, the system further comprises at least one meter effective to monitor at least one of an input of a reactant, an input of a catalyst, and an output of a byproduct. In some embodiments, the system further comprises at least one valve configured to regulate flow of the reactants and the at least one catalyst into the reactor chamber. In some embodiments, the system further comprises at least one valve configured to regulate the flow of at least one by-product out of the reactor chamber.

In some embodiments, the system further comprises a control module, wherein the control module is effective to control at least one of the input of reactants, output of byproducts, and temperature of the contents of the reaction chamber. In some embodiments, the control module comprises a computerized control module, effective to automatically control operation of the reactor chamber in response to instructions from a computer program. In some embodiments, the system further comprises the computer program.

In some embodiments, there is provided a method, for production and purification of an alcohol ester by transesterification of an oil feedstock, the method comprising the steps of: providing a reactor chamber; providing at least one circulation leg, wherein the at least one circulation leg comprises: at least one input line for introducing reactants, and at least one catalyst, into the reactor chamber; output lines for removing by-products of the transesterification reaction from the reaction chamber; inputting reactants, and at least one catalyst, into the reactor chamber; contacting the reactants and the at least one catalyst, such that an alcohol ester and a byproduct alcohol are produced; outputting the alcohol ester and the by-product alcohol; wherein the input of the reactants and the at least one catalyst, and the output of the alcohol ester and the by-product alcohol occur continuously.

In some embodiments, the method comprises providing a reactor chamber having an aspect ratio in a range from about 2: 1 to about 10: 1. In some embodiments, the method comprises providing a reactor chamber having an aspect ratio of about 5:1. O

In some embodiments, the reactants comprise an oil feedstock and a reactant alcohol. In some embodiments, the at least one catalyst comprises a hydroxide.

In some embodiments, he alcohol ester and the by-product alcohol separate in the reaction chamber according to their density. In some embodiments, the method further comprises agitating the reactor contents, wherein the agitating is effective to result in at least one of, an increase in the rate of the transesterification reaction, an increase in the purity of the outputted alcohol ester, and coalescence of the by-product alcohol.

In some embodiments, the temperature of the reaction is maintained substantially within a range from about 6O⁰C to about 70°C. In some embodiments, the temperature of the reaction is maintained at about 65⁰C.

In some embodiments, the method further comprises providing a methoxide collector to collect methoxide from the reaction chamber.

In some embodiments, at least a portion of the oil feedstock is contacted with methoxide collected by the methoxide collector.

In some embodiments, the method further comprises providing a plurality of reactor chambers arranged in parallel. In some embodiments, the method further comprises providing a plurality of reactor chambers arranged in series.

In some embodiments, the method comprises inputting oil feedstock to a first reactor chamber, and at least one catalyst to each subsequent reactor chamber in the series. In some embodiments, a crude methyl ester and an unreacted oil feedstock, from a first reactor chamber, are provided as an input in a subsequent reactor chamber in the series.

In some embodiments, at least one catalyst and a by-product alcohol from a subsequent reactor in the series, are provided as an input to the first reactor in the series.

In some embodiments, the method further comprises separating the by-product alcohol from the alcohol ester. In some embodiments, the separating comprises at least one of distillation and centrifugation.

In some embodiments, the by-product alcohol comprises glycerol, and the alcohol ester comprises a methyl ester. In some embodiments, the oil feedstock is obtained from an oilseed processing plant. In some embodiments, the method further comprises providing an oilseed processing plant.

Brief Description of the Figures

Fig. 1 is a diagram representing a single reactor continuous flow biodiesel production system; and

Fig. 2 is a diagram representing a multiple reactor continuous flow biodiesel production system. o

Detailed Description

As used herein, the terms "biodiesel" or "biofuels" are meant to include any and all alcohols esters derived by transesterification of a vegetable oil or animal derived oil or fat including, for example, transesterification of monoglycerides, diglycerides, and triglycerides.

As used herein, the term "oil feedstock" is meant to include, without being limiting, any vegetable or animal derived oil or fat comprising triglycerides that can be used in a transesterification reaction system to produce an alcohol ester.

As used herein, the term "reactant alcohol" refers to an alkyl alcohol used in the transesterification reaction.

As used herein, the term "byproduct alcohol" refers to an alcohol produced as a result of transesterification of a vegetable or animal derived oil or fat, including, for example, transesterification of monoglycerides, diglycerides, and triglycerides.

While in principle plant-based oils can be used as fuel in diesel engines, a number of factors make their use desirable than petroleum-based diesel. For example, plant oils are of higher viscosity and density than diesel making it difficult to form a combustible aerosol within an engine's combustion chamber. Plant oils also have a lower cetane number (a measure of ignitability) and thus are less potent as fuels when compared to traditional petroleum-derived diesel products. In addition, the use of high levels of unmodified triglycerides is known to result in the accumulation of undesirable deposits in the engine combustion chamber. It has been discovered, however, that methyl or ethyl esters derived from triglycerides solve many of the problems associated with unrefined plant oils, and can be used as an effective and practical substitute for petroleum-based diesel fuels. These methyl ester derivatives are collectively termed "biodiesel fuels." They are characterized as low emissions, and are essentially sulfur-free. Sulfur is a problem related to the use of petroleum fuels. In engines, sulfur is converted to sulfuric acid, which is an environmental contaminant, as well as being corrosive to the engine. Thus, biofuels provide a number of advantages over petroleum products. One of the present disadvantages of using biodiesel is cost, due to the cost of raw materials, as well as the cost of refining.

Thus, methods of producing biodiesel that reduce either the cost of raw materials, or their refining, will be expected to increase the acceptance of biodiesel as a viable alternative to traditional diesel fuels. In some methods, the production of biodiesel is accomplished by treating triglycerides obtained from plant or animal sources, or waste oils and the like, with sodium or potassium hydroxide and methanol (which produces methoxide). Methoxide promotes the transesterification of triglycerides in oils to methyl or ethyl esters and glycerol. The esters are useful as fuel, while glycerol is useful in the manufacture of pharmaceuticals, and in the food and beverage industries.

The conversion reaction is difficult due to the relative immiscibility of oil, triglycerides and methanol. When reacted in a batch process, the esterification reaction occurs relatively slowly, until such time as some mono- and di-glycerides are formed. At this point the reaction rate increases, and the reaction proceeds more rapidly to completion. While agitation can sometimes be used to increase the rate of the reaction, high rates of agitation can be problematic due to emulsification due to the unavoidable presence of water and finely divided glycerol droplets.

Thus, to drive the reaction to completion, some methods use extra methanol and catalyst, with the crude ester being reacted a second time with fresh methoxide in order to obtain an ester product of higher purity. While these methods generally work, they are expensive and wasteful of reagents, unless methanol recovery systems are included, which also add to the cost and complexity of the production system.

Once the reaction is complete, the products will typically be transferred to a settling tank, where the glycerol and methyl ester separate based on their differential density. Glycerol being of a higher density than the esters settles to the bottom of the settling tank, while the esters rise to the top. After a sufficient time, the glycerol is drained from the settling tank. The ester is subsequently drained following the removal of the glycerol. Typically each product fraction is withdrawn from the reactor through appropriately located outlet ports (Normally a single bottom discharge point).

The primary drawback in this method is that large tanks are required, and reaction rates are generally slow. In addition, as these methods of production are discontinuous, the reactor tank and settling tanks have to be repeatedly filled and emptied, increasing the time and effort and thus the cost of producing biodiesel. Discrete methods of production also necessitate a significant downtime when reactors are not producing the desired fuel product. Batch methods also increase the chance of batch-to-batch variability in product quality, making production of a consistent and reliable product more difficult. Thus, it would be desirable in the field of biodiesel production to have a system that operates in a continuous flow arrangement with relatively rapid reaction rates to improve the throughput of the biodiesel production process.

Prior art methods of continuous flow production of methyl esters from triglyceride have been described. U.S. Patent Application 2006/0069274 (Dias de

Morales e Silva et al.) discloses a method of continual production of methyl esters from biological oils. Columns of calcium and magnesium oxide catalyst in the form of "stones" are provided. Oil passing over the "stones" is converted to methyl ester and glycerol.

Likewise, U.S. Patent Application 2005/0081435 (Lastella) discloses a method of continual production of methyl ester from triglyceride. However, the separation of products and reactants occurs in a separate "settler" tank and so the method is a discontinuous, batch-type one.

Thus, there is a need to provide an efficient method of converting triglyceride to methyl ester (biodiesel), and separating the biodiesel from the glycerol produced in the reaction in a continuous flow manner.

The detailed description below is intended as a description of exemplary embodiments. It is therefore not intended to be limiting to either the scope or spirit of the invention as claimed. It will be understood by those skilled in the art that equivalent functions and products may be accomplished by variations in the described embodiments. Such variation will be readily apparent to one skilled in the art of biodiesel production and are intended to fall within the scope of the present disclosure. In some embodiments, an example of which is shown in Fig. 1, a single reactor system 10 provides for the continuous conversion of triglycerides to methyl esters and glycerol, using methoxide and triglycerides as reactants. The system 10 further provides for the continuous separation of methyl esters and glycerol, the products of the conversion reaction, and their continual withdrawal from the reactor vessel as these products are produced (indicated as methyl ester byproduct and glycerine byproduct).

In some embodiments, the reactor is provided in the form of a column. In some embodiments the column has an aspect ratio in a range from about 2: 1 to about 10: 1. In some embodiments, the aspect ratio is about 5:1. As used herein, the term "aspect ratio" refers to the ratio of the height to width of the reactor chamber. In an exemplary embodiment of a reactor chamber, the reactor chamber is 150 cm in height, and 75 cm in width, and has an aspect ratio of 2: 1.

In some embodiments, the two primary reactants are triglycerides and methoxide. Triglycerides can be obtained, without limitations, from oilseed, animal sources, or from waste oils used in cooking and the like. The use of used oils from sources such as restaurant may require various pre-treatment before the material is suitable for use as an oil feedstock in the present invention, but such treatments and methods are well known in the prior art. The choice of oils feedstock is not considered to be limiting, and one skilled in the art will readily recognize that triglyceride from a variety of sources can be successfully used.

In some embodiments, methoxide will be used to drive the conversion reaction. It can be obtained commercially and mixed with methanol, or synthesized on site from methanol and sodium (or potassium) hydroxide. In some embodiments, methoxide will be provided from a methoxide supply means. Conveniently, a methoxide tank 20 provides sufficient methoxide to supply a reactor, or reactors, for a desired period of time.

The oil feedstock has a average density of about 0.91, while methoxide has a density of about 0.8. The products of the reaction, glycerol and methyl esters have significantly different densities (1.26 and 0.86 respectively), and thus will naturally tend to separate. Accordingly, as triglyceride is converted to methyl ester and glycerol, the methyl ester will tend to rise to the top of the reactor column while glycerol well tend to sink to the bottom. The movement of the byproducts in the reactor column will be effective to generate a countercurrent within the reactor as the reaction proceeds. The counter-current is effective to overcome the tendency of methanol (part of the catalyst mixture) to rise in the column which reduces the effectiveness of the transesterification reaction, and which can also lead to contamination of the product ester with methanol.

In embodiments of the present disclosure, efficiency of the conversion reaction, and separation of the byproducts, is aided by the countercurrent mechanism established by virtue of the differential density of the triglyceride feedstock and products of the triglyceride conversion process. Under ideal conditions, the countercurrent mechanism provides that the most depleted methoxide comes into contact with fresh oil, and fresh methoxide comes into contact with the most reacted oil. As methoxide has a relatively low density compared to the other reactants, in some embodiments it is added in a lower region of the reactor column, or in two or more separate stages, via at least one methoxide inlet port 22. In some embodiments, the reactor chamber is configured to provide a reaction center, a region within the reactor chamber where the most effective conversion of the oil feedstock to alcohol ester takes places. In some embodiments, the reactor chamber can be configured such that multiple reaction centers exist within a single reactor column, thus improving the overall efficiency of the conversion process.

In some embodiments, triglyceride from plant or animal oil sources can be introduced from an oil feedstock supply 12 into a vertically oriented reactor chamber 15 to a first stage reaction zone 29. Conveniently, the oil feedstock can be fed into the reactor chamber through an oil inlet 30. The system can further comprise a circulating pump 34 that provides the force to move oil from the oil feedstock supply into the reactor chamber. In some embodiments, the oil inlet 30 can be located toward the bottom of the reactor chamber. In some embodiments, the oil inlet 30 can also serve as an inlet for the introduction of other materials into the reactor chamber. The reactor chamber can further comprise an upper methoxide inlet 36, through which fresh methoxide can be introduced into the reactor.

In some embodiments, the rate at which oil and methoxide are added to the reactor can be regulated by metering pumps 38A and 38B. In some cases, introducing materials into the reactor chamber is accomplished using pumps specifically suited for each particular component. Conveniently, the rate of flow of any or all products or byproducts of the refining process can be monitored or controlled by flow meters and flow control valves. In some cases, gravity feed methods can be used, for example in smaller scale operations where high throughput is not required. For optimal reaction control, the flow of reactants into the reactor, and withdrawal of products from the reactor can be best achieved through the use of metering pumps, flow meters and flow control valves. Control systems can conveniently be used to monitor reaction conditions and thus restrict the input of reactants to a desired rate in order to maximize throughput and purity of the products. Control systems can be monitored manually, or in some cases, an automated system can monitor the process according to predetermined design parameters. In some embodiments, the automated control system further comprises a computer and a control program to regulate the refining process. The program can be executed from either software or firmware.

The desired conversion rate will depend on a number of factors including the actual rate of the conversion reaction, volume and geometry of the reactor chamber, other attachments to the reactor, and the desired degree of purity of the glycerol and methyl ester produced. One skilled in the art will appreciate that by adding the reactants in certain proportions, and to a certain location in the reactor chamber, the reaction will approach stoichiometric conversion wherein all input materials are substantially converted to products.

In some embodiments, the location of the methoxide inlet, through which the methoxide is introduced into the reactor, can be varied in order to optimize the geometry of the triglyceride conversion reaction. For example, a position high in the column will contact the most reacted ester with the freshest methoxide; a lower position will provide a higher density glycerol/methoxide byproduct in the second stage reaction zone 31, which will separate easier from the methyl ester. In some embodiments, the most desirable situation is where essentially all the triglyceride is converted to methyl ester and glycerol, o

and the products of the conversion reaction can be collected essentially free of unreacted triglyceride and methoxide. Thus, the methoxide inlet can be located somewhere near the midpoint of the reactor chamber, with the precise location being determined empirically or by any other suitable method.

As introduced above, the basic mechanism of the refining process is the mixing of triglyceride and methoxide, which converts triglyceride to esters and glycerol, and the separation of these products by a countercurrent mechanism. Conceptually, the reactor chamber comprises four functional zones. In some embodiments, these comprise first and second reactions zones, 29 and 31 respectively, a by-product alcohol zone 50 and an alcohol ester separation zone 51. In some embodiments, the by-product alcohol is glycerol, and the alcohol ester is a methyl ester.

In some embodiments, oil feedstock introduced in the lower portion of the reactor chamber is mixed with a small amount of recovered methoxide from a methoxide collector 60, as well as partially reacted methyl ester from the top of the glycerol-settling zone 50. A circulating pump 34 discharges through near, or slightly below, the midpoint of the reactor chamber. Here the mix of fresh triglyceride and partially reacted material comes in contact with a mix of methoxide and glycerol as it settles down the column from the second stage reaction zone as described below. In the countercurrent system an advantage is provided in that the reaction occurs quickly and continuously, avoiding the delayed reaction observed when using batch systems.

In some embodiments, methoxide can introduced into the reactor between the first and second stage reaction zones. This can provide for sufficient contact with the most reacted material present in the second stage reaction zone, thus completing the conversion reaction. The methoxide rises through the second stage reaction zone, coming in contact with the relatively pure ester as it also rises in the column from the first stage reaction, and also converting any remaining triglyceride. The result is relatively pure ester. The glycerol formed by the reaction will mix with the excess methoxide and settle in the column, providing the bulk of the fresh reagent to the first stage reaction zone.

Unreacted methoxide, which is lower in density than the unreacted oil and the glycerol produced by the conversion reaction, will rise in the reactor chamber. In some embodiments, unreacted methoxide can be collected by a methoxide collector 60, located in the upper portion of the reactor chamber. In some embodiments the methoxide collector is a simple inverted cone. The collected methoxide can be returned to the reactor for reuse, via a connection to a recirculation pump circuit that draws material from near the top of the reactor chamber and reintroduces it into the bottom of the reactor chamber.

In some embodiments, heat can be applied to the reactor maintain the reactor chamber at a desired temperature. In some cases, the conversion of triglyceride to methyl ester is most effective at a temperature in the range of 60-70⁰C, and in particular at about 65⁰C. Thus, in another embodiment at least one heat exchanger 70 is provided to heat the oil and/or other reactants to the desired temperature, prior to introduction into the reaction chamber. A variety of heat exchange techniques area available and one skilled in the art would readily appreciate the best particular form of heat exchange system that would be most advantageous for use in the reactor chamber of the present invention. The reactor can further comprises internal heater exchangers in order to better maintain a desired reaction temperature. Depending on the volume of the reactor chamber, a o

plurality of internal and/or external heat exchanger can be used to maintain reaction temperatures within a pre-determined range, for example between about 60⁰C and about 7O⁰C. The number of heat exchangers, and the precise temperature of the contents of the reactor chamber are not considered to be limiting.

As discussed above, as the conversion reaction progresses, relatively lighter methyl ester will rise through the reactor, while denser glycerol will settle to the bottom of the reactor. The movement of these products therefore provides at least some of the impetus resulting in development of the countercurrent flow present in the reactor chamber. In some embodiments, the enhance the countercurrent and mixing of reactants, agitators 80 and the like, can be included. Mixing will improve the efficiency of the conversion reaction and enhance the countercurrent flow.

Providing agitation means also serves to facilitate the conversion reaction by providing increased contact surface area for the oil and methoxide to react with each other. In some embodiments, agitators can comprise perforated plates mounted on a vertically oriented shaft that are either rotated or moved up and down to provide mild agitation. Agitator plates can also serve to enhance the removal of the more dense glycerol by providing a surface upon which glycerol will coalesce into larger droplets, improving the rate of settling of glycerol in the reactor.

As products are removed, the reactor contents can be replenished with triglyceride and methoxide as described earlier. Conveniently, methyl ester will overflow from a methyl ester outlet port 90 located at or near the top of the reactor as it is produced, while glycerol can be removed from a glycerol outlet port 91 at or near the bottom of the reactor. In this way, a continuous flow system is established that both converts triglyceride to methyl ester and glycerol, as well as providing for the separation of these two products in a single reaction vessel.

In practice a small amount of oil and other reactants might be expected to settle along with the glycerol collected. Removal of contaminants of the glycerol, which will include methyl ester and methoxide may be removed by a variety of means including, but not limited to density centrifugation or by transfer of the glycerol to a separate settling tank. Lighter density components may be returned if desired to the reactor chamber. Alternatively increasing the height or diameter of the reactor chamber might also be used to provide more effective separation of the glycerol and methyl ester products. Advantages provided by variations to reactor chamber geometry will be apparent to those skilled in the art of density separation. Thus, in some embodiments, there is further provided a optional density separation system for further purification of byproducts. In some embodiments, the density separation system comprises a centrifuge, in some embodiments the centrifuge is a decanter centrifuge.

In some embodiments, one of which is shown in Fig. 2, the system comprises a multi-reactor system 100 comprising two or more reactors. In some embodiments, the reactor chambers are arranged in parallel to increase output. In some embodiments, reactor chambers are arranged in series, and are effective to improve both the output and efficiency of the conversion reaction, as well as to increase the purity of the methyl ester and glycerol products obtained. In a multiple reactor system, oil can be added to a first reactor 101 and methoxide is continuously added to each of a second 102, or final, stage reactor chamber. In some embodiments, adjustable metering pumps or by supply pumps regulated by flow meters or flow control valves control the flow of reactants and reagents.

Oil can be added to the intake of the circulating pump 34 of the first reactor 101 along with glycerol and methoxide collected from the bottom portion of the second reactor 102. Thus, in some embodiments, the conversion reaction can occur in the pump, the circulation leg 35, and finally in the reactor chamber. In some embodiments, the system includes a plurality of circulation legs configured to provide for more than one reaction center within the reactor chamber. In some embodiments, there are two circulation legs configured to establish two reaction centers within the reaction chamber.

Crude methyl ester produced in the first reactor chamber 101 can be collected from the top of the first reactor chamber 101 and passed to the input of a second line pump 36 and to a second reactor 102. As with the first reactor 101 a recirculation pump can circulate material from the upper portion to the bottom portion of the second reactor 102, which will include unreacted oil and methoxide as well as methyl ester and glycerol. In addition, unreacted oil and the crude methyl ester obtained from the first reactor 101 can be fed into the bottom of the second reactor 102 via the recirculation pump.

An advantage provided by using multiple reactors is that the conversion reaction can be more effectively carried out as compared to a single reactor chamber 102 type system. In some embodiments, the glycerol/methoxide collected from the second stage 102 is carefully controlled to ensure no interruption in flow, since it provides the reagent to the first stage reactor 101. The net result is that in the second 102 and any subsequent reactors (if more than two reactor chambers are used in-line), progressively higher purity methyl ester is produced. As before, the products methyl ester and glycerol can be collected from the top of the second stage reactor 102 (or final stage reactor, if more than two) with the glycerol withdrawn from the bottom of the first stage reactor 101, the second stage reactor 102 and subsequent reactors.

Exemplary embodiments as described herein can provide an additional advantage that the system can be adapted for use in conjunction with an oilseed processing plant. Oil suitable for use in a biodiesel production process can be produced from seeds using techniques well known in the prior art. For example, oil can extracted by crushing seeds at 6O⁰C. Crude oil can then filtered to remove pulp, gum and fine particulates. Oil can be transferred to a holding tank large enough to provide a continuous supply of oil to the reactor system. In some embodiments, the oil will be pre-heated to 60-70°C in the holding tanks so that the oil is at an optimum temperature for the conversion reaction to proceed once the oil is introduced into the reactor chamber.

Combining the oil production and biodiesel production provides several advantages. The biodiesel produced by the plant can be used to drive diesel equipment used in the cultivation and harvesting of oilseed. For example, one acre of palm trees is capable of producing 650 gallons of oil feedstock, while algal sources may produce up to 10,000 gallons of oil feedstock per acre. In some cases, canola seed can be processed and converted to yield up to 8 - 10 litres per bushel. Embodiments of the present disclosure can also be provided to produce biofuels on a range of scales. In some embodiments, from 1,000,000 to 20,000,000 litres per year of biodiesel can be produced. Excess biodiesel can be marketed providing profitability to the production setup. Thus is provided a method and apparatus for the continuous production of biodiesel that solves many of the problems and limitation inherent in prior art methods of biodiesel production.

While specific embodiments of the invention have been described, the foregoing is considered as illustrative of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. Accordingly, all such suitable changes or modifications in structure or operation that may be resorted to are intended to fall within the scope of the claimed invention.

Claims

1. A system, for use in continuous production of an alcohol ester from an oil feedstock, by a transesterification reaction, the system comprising:

a reactor chamber, having a volume;

a least one circulation leg, comprising:

at least one input path for introducing at least one of a reactant and a catalyst into the reactor chamber;

output paths through which by-products of a transesterification reaction are extracted from the reaction chamber;

wherein the reactor chamber is configured such that, during the transesterification reaction, a counter-current flow of reactants within the reaction chamber results in mixing of the contents of the reactor chamber; and

wherein the system is further configured such that input of the reactants into the reactor chamber, and output of by-products from the reactor chamber, occur substantially continuously.

2. The system of Claim 1, wherein the by-products comprise at least one alcohol ester and a by-product alcohol.

3. The system of Claim 1, wherein the alcohol ester comprises a methyl ester, and the by-product alcohol comprises glycerol.

4. The system of Claim 1, wherein the reactor chamber has an aspect ratio in a range from about 2:1 to about 10: 1.

5. The system of Claim 1, wherein the aspect ratio is about 5: 1.

6. The system of Claim 1, further comprising the reactants and the at least one catalyst.

7. The system of Claim 1, wherein the reactants comprise the oil feedstock and a reactant alcohol.

8. The system of Claim 1, wherein the at least one catalyst is effective to promote transesterification of the oil feedstock to an alcohol ester.

9. The system of Claim 8, wherein the at least one catalyst comprises hydroxide.

10. The system of Claim 1, wherein the reactants and the at least one catalyst are introduced via a single input line.

11. The system of Claim 1, wherein the reactants and the at least one catalyst are introduced via separate input lines.

12. The system of Claim 1, wherein output lines for said by-products comprise an alcohol ester output line, and a by-product alcohol output line.

13. The system of Claim 1, further comprising a heat exchange module, the one heat exchange module operative to maintain the contents of the reactor chamber in a range from about 60⁰C to about 70⁰C.

14. The system of Claim 1, further comprising an agitator, said agitator effective to enhance at least one of mixing of reactants in the reactor chamber and coalescence of the by-product alcohol.

15. The system of Claim 1, comprising a plurality of reactor chambers arranged in parallel.

16. The system of Claim 1, comprising a plurality of reactor chambers arranged in series.

17. The system of Claim 16, wherein a first reactor chamber is configured to receive as an input at least one by-product from a subsequent reactor chamber in the series.

18. The system of Claim 1, further comprising at least one meter effective to monitor at least one of an input of a reactant, an input of a catalyst, and an output of a byproduct.

19. The system of Claim 1, further comprising at least one valve configured to regulate flow of the reactants and the at least one catalyst into the reactor chamber.

20. The system of Claim 1, further comprising at least one valve configured to regulate the flow of at least one by-product out of the reactor chamber.

21. The system of Claim 1, further comprising a control module, wherein the control module is effective to control at least one of the input of reactants, output of byproducts, and temperature of the contents of the reaction chamber.

22. The system of Claim 21, wherein the control module comprises a computerized control module, effective to automatically control operation of the reactor chamber in response to instructions from a computer program.

23. The system of Claim 22, further comprising the computer program.

24. A system, for use in continuous production of by-products from an oil feedstock, by a transesterification reaction, the system comprising:

a reactor chamber, having a volume;

a least one circulation leg, comprising:

output paths along which by-products of a transesterification reaction from the reaction chamber are extracted;

wherein the system is further configured such that, if an input of the reactants into the reactor chamber is substantially continuous, then an extraction, of by-products of the transesterification reaction, from the reactor chamber is also substantially continuous.

25. A method, for production and purification of an alcohol ester by transesterification of an oil feedstock, the method comprising the steps of: providing a reactor chamber;

providing at least one circulation leg, wherein the at least one circulation leg comprises: at least one input path for introducing at least one of a reactant and a catalyst into the reactor chamber;

output paths for removing by-products of a transesterification reaction from the reaction chamber;

inputting reactants, and at least one catalyst, into the reactor chamber;

contacting the reactants and the at least one catalyst, such that an alcohol ester and a byproduct alcohol are produced;

outputting the alcohol ester and the by-product alcohol;

wherein an input of the reactants, and an output of the alcohol ester and the by-product alcohol occur substantially continuously.

26. The method of Claim 25, comprising providing a reactor chamber having an aspect ratio in a range from about 2: 1 to about 10: 1.

27. The method of Claim 25, comprising providing a reactor chamber having an aspect ratio of about 5: 1.

28. The method of Claim 25, wherein, the reactants comprise an oil feedstock and a reactant alcohol.

29. The method of Claim 25, wherein the at least one catalyst comprises a hydroxide.

30. The method of Claim 25, wherein the alcohol ester and the by-product alcohol separate in the reaction chamber according to their density. o

31. The method of Claims 25, further including agitating the reactor contents, wherein the agitating is effective to result in at least one of, an increase in the rate of the transesterification reaction, an increase in the purity of the outputted alcohol ester, and coalescence of the by-product alcohol.

32. The method of Claim 25, wherein the temperature of the reaction is maintained substantially within a range from about 60°C to about 7O⁰C.

33. The method of Claim 32, wherein the temperature of the reaction is maintained at about 65⁰C.

34. The method of Claim 25, further comprising providing a methoxide collector to collect methoxide from the reaction chamber.

35. The method of Claim 34, wherein at least a portion of the oil feedstock is contacted with methoxide collected by the methoxide collector.

36. The method of Claim 25, comprising providing a plurality of reactor chambers arranged in parallel.

37. The method of Claim 25, comprising providing a plurality of reactor chambers arranged in series.

38. The method of Claim 37, comprising inputting oil feedstock to a first reactor chamber, and at least one catalyst to each subsequent reactor chamber in the series.

39. The method of Claim 37, wherein a crude methyl ester and an unreacted oil feedstock, from a first reactor chamber, are provided as an input in a subsequent reactor chamber in the series.

40. The method of Claim 37, wherein at least one catalyst and a by-product alcohol from a subsequent reactor in the series, are provided as an input to the first reactor in the series.

41. The method of Claim 25, further comprising separating the by-product alcohol from the alcohol ester.

42. The method of Claim 41, wherein the separating comprises at least one of distillation and centrifugation.

43. The method of Claim 24, wherein the by-product alcohol comprises glycerol, and the alcohol ester comprises a methyl ester.

44. The method of Claim 24, wherein the oil feedstock is obtained from an oilseed processing plant.

45. The method of Claim 24, further comprising providing an oilseed processing plant.

46. A method, for production and purification of an alcohol ester by transesterification of an oil feedstock, the method comprising the steps of:

providing a reactor chamber;

providing at least one circulation leg, wherein the at least one circulation leg comprises:

at least one input path for introducing at least one of a reactant and a catalyst into the reactor chamber; output paths for removing by-products of a transesterification reaction from the reaction chamber;

inputting reactants, and at least one catalyst, into the reactor chamber, via the input path;

contacting the reactants and the at least one catalyst, such that an alcohol ester and a by-product alcohol are produced;

outputting the alcohol ester and the by-product alcohol, via the output paths;

wherein if an input of the reactants into the reactor chamber is substantially continuous, then an output of the alcohol ester and the by-product alcohol, from the transesterification reaction in the reactor chamber, is substantially continuous.