AU2007308739A1

AU2007308739A1 - Process and apparatus for biofuel production

Info

Publication number: AU2007308739A1
Application number: AU2007308739A
Authority: AU
Inventors: Andrew Aleksander Warton
Original assignee: BLUE DIESEL Pty Ltd
Current assignee: BLUE DIESEL Pty Ltd
Priority date: 2006-10-23
Filing date: 2007-10-23
Publication date: 2008-05-02
Also published as: WO2008049154A1

Description

WO 2008/049154 PCT/AU2007/001607 TITLE "PROCESS AND APPARATUS FOR BIOFUEL PRODUCTION" FIELD OF THE INVENTION The present invention relates to a process and apparatus for the production of biofuel, particularly biodiesel. BACKGROUND TO THE INVENTION There are several processes known for the production of biodiesel. Most common of these is known as base catalyzed transesterification. In the base catalyzed transesterification process vegetable oil and an alcohol are mixed in the presence of a catalyst such as potassium hydroxide to produce biodiesel and glycerine. Typically the temperature at which this process operates is less than 1 00 0 C because of the vapour pressure of the alcohol. This process is a relatively time consuming one. Firstly, a significant residence time is required for the esterification reaction to take place. Secondly, following esterification a long settling time is required to separate biodiesel from glycerine The present invention attempts to overcome at least in part the aforementioned disadvantages of previous processes for the production of biodiesel. SUMMARY OF THE PRESENT INVENTION In accordance with one aspect of the present invention there is provided a process for the production of biodiesel characterized in that it comprises the steps of combining oil or fat 1 WO 2008/049154 PCT/AU2007/001607 with an alcohol in the presence of a catalyst to form a reaction mixture, heating the reaction mixture to above 100 C and raising the pressure of the mixture to above 100 psi, passing the heated and pressurised reaction mixture along a fluid flow path in which turbulent flow is induced to promote a chemical esterification reaction to provide a reacted mixture of biodiesel and glycerine, reducing the pressure of the reacted mixture to about atmospheric pressure and the temperature of the reacted mixture to a temperature lower than the boiling point of the alcohol at atmospheric pressure and separating the biodiesel and glycerine into separate phases. Preferably, the alcohol in methanol and in this case the temperature of the heated mixture is reduced to below 65'C the boiling point of methanol, at atmospheric pressure. In accordance with a further aspect of the present invention there is provided an apparatus for the production of biodiesel characterized in that the apparatus comprises means for admixing oil or fat with an alcohol and a catalyst to produce a reaction mixture, means for increasing the temperature of the reaction mixture to above 1 00 0 C, means for increasing the pressure of the reaction mixture to above 100 psi, an elongated fluid flow path, means for feeding the heated and pressurised reaction mixture along the elongated fluid flow path, the fluid flow path being provided with means to induce turbulent flow in the reaction mixture so as to promote an esterification reaction to produce a reacted mixture of biodiesel and glycerine, and means for separating the reacted mixture into glycerine and biodiesel. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 2 WO 2008/049154 PCT/AU2007/001607 Figure 1 is a schematic representation of a flow diagram for operation of the process of the present invention; Figure 2 is a sectional elevation of a section of a tube used in a reactor of the flow diagram of Figure 1; Figure 3 is a view similar to Figure 2 showing an alternative embodiment of the present invention; and Figure 4 is a front elevation of turbulator used in the tube of Figure 2. DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the Figure 1, there is shown a flow diagram 10 of the process of the present invention. The flow diagram 10 shows the primary inputs into the process being vegetable or animal oil or fat 12 and methanol 14, with an alkali metal methylate catalyst 16. It will be appreciated that other oils, alcohols or catalysts may be used within the process of the present invention. As shown, the methanol 14 is first combined with the catalyst 16. The resulting solution is then combined with the oil or fat 12 to form a reaction mixture with or without a separate mixing step. The reaction mixture then passes through a heat exchanger 20. The heat exchanger 20typically raises the temperature of the mixture to about 120*C. The mixture undergoes a final heating stage at 21 before entering a reactor 22 at about 160*C. The reactor 22 comprises a continuous small bore tube 24 which winds through an insulated housing 26. Typically, the housing 26 is filled with absorbent and heat insulating material such as diatomaceous earth for heat insulation and fire protection. 3 WO 2008/049154 PCT/AU2007/001607 The tube 24 may complete as many as 100 turns within the housing 26, thus resulting in an elongated flow path for the reaction mixture. The tube 24 preferably has a bore in the range from 3/8" to 4" With a small bore, it is possible for pressure within the tube to reach as much as 3000psi such as from 300 to 500psi. This high pressure enables the various reagents and products of the reaction to remain liquid despite the high temperature. As a result, an esterification reaction proceeds at a significantly increased rate when compared to the prior art. The low viscosity of reagents at high temperature promotes mixing and further increases the rate of reaction. Preferably, the tube 24 contains means 25 to promote turbulent flow of reagents and products, in order to prevent flow stratification. The means 25 are hereinafter referred to as turbulators 25. By the time the mixture exits the housing 26, esterification to biodiesel and glycerine, in a two phase reacted mixture is substantially complete. The two phases, however, are at a very high temperature and pressure such as close to 150*C and 300psi. The phases are first passed through the heat exchanger 20 to reduce the temperature to about 80*C. They may also be passed through an additional cooler, reducing temperature further to about 60*C. The reacted mixture is then passed through a pressure reducing means 30. In a preferred embodiment of the invention, the pressure reducing means comprises an elongated, spiral flow path of relatively small cross-sectional size. The biodiesel and glycerine phases travel along this flow path at a high speed. This means that the more dense phase, glycerine, is pushed to the outside of the flow path due to the operation of centrifugal forces. This enhanced separation of the phases during pressure reduction substantially 4 WO 2008/049154 PCT/AU2007/001607 prevents emulsification of the two phases. A particularly preferred form of pressure reducing means is described in pending Australian Provisional Patent Application Number 200690611 in the name of the present applicants. The entire disclosure of Australian Provisional Patent Application Number 200690611 is incorporated herein by reference. Settling, separation, and cleaning of the biodiesel and glycerine can then take place by known means. It will be appreciated that only minimal separation is required. The biodiesel component is removed through an outlet 32 after passing through a dry wash apparatus 34. The glycerine component is removed via an outlet 36. The components from the separation are passed through respective methanol flash apparatuses 38 (for biodiesel) and 40 (glycerine). The methanol which is recovered is returned to the methanol supply 14. Typically, the turbulators 25 are located at the joints between sections of tube used to construct the reactor 22. The joints may be formed by means of butt welding, socket welding, flanging, swaging or any other means of connecting the tube sections. In Figure 2 of the accompanying drawings there is shown a portion of a tube 24 having an outer wall which is formed in multiple parts 52. Each part 52 has an end 54. Sandwiched between adjacent ends 54 is a turbulator 25. The turbulator 25 has an outer circumferential flange 58 and a central aperture 60. Extending inwardly from the flange 58 into the aperture 60 are a plurality of radially extending projections 62. The projections 62 extend inwardly a part of the way towards a centre of the aperture 60 as can be seen in Figure 4. The projections 62 are disposed at an angle to the perpendicular relative to the length of the tube 24 so as to induce a spiralling effect in the flowing liquid. The parts 52 are joined together by means of a circumferential bridging member 5 WO 2008/049154 PCT/AU2007/001607 64 which has an inwardly directed projection 66 disposed between the ends 54. Further, the bridging member is attached to the parts 52 by means of welds 68. The welds 68 attach the parts 52 to the bridging member 64 so that the parts 52 are each secured to the bridging member 64. In operation, liquid reactants are fed into the tube 24 in the direction of an arrow 64 as shown in Figure 2. The reactants pass through a plurality of turbulators 25 as they pass through the tube 24. The presence of the projections 62 induces the flow of liquid to move towards a centre of the aperture 60 and away from the walls of the parts 52. This leads to increased turbulence in the flowing stream of reactants in the process of the present invention. In this way the mixing of the reactants is enhanced so that the chemical reaction proceeds more efficiently compared to a system where no turbulators 25 are used. An alternative embodiment to the embodiment of Figure 2 is shown in Figure 3. In the embodiment of Figure 3 like reference numerals denote like parts to those found in Figure 2. In this embodiment, the bridging member 64 is secured in place between the parts 52 by means of circumferential compression members 70. Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. 6

Claims

1. A process for the production of biodiesel characterized in that it comprises the steps of combining oil or fat with an alcohol in the presence of a catalyst to form a reaction mixture, heating the reaction mixture to above 1 00"C and raising the pressure of the mixture to above 100 psi, passing the heated and pressurised reaction mixture along a fluid flow path in which turbulent flow is induced to promote a chemical esterification reaction to provide a mixture of biodiesel and glycerine, reducing the pressure of the reacted mixture to about atmospheric pressure and the temperature of the reacted mixture to a temperature lower than the boiling point of the alcohol at atmospheric pressure, and separating the biodiesel and glycerine into separate phases.

2. A process according to claim 1, characterized in that the biodiesel and glycerine are separated by subjecting the reacted mixture to centrifugal force.

3. A process according to claim 1 or 2, characterized in that the alcohol is methanol.

4. A process according to any one of the preceding claims, characterized in that the reaction mixture is passed through a heat exchanger to raise the temperature of the reaction mixture to above 1 00C.

5. A process according to claim 4, characterized in that the reaction mixture is subjected to a further heating stage to further increase the temperature thereof.

6. A process according to any one of the preceding claims, characterized in that the reaction mixture is passed through a reactor having a continuous small bore tube in which the pressure of the mixture is increased above ambient pressure.

7. A process according to claim 6, wherein the small bore tube is provided with a plurality of turns so as to provide an elongated flow path within the reactor. 7 WO 2008/049154 PCT/AU2007/001607

8. A process according to claim 6 or 7, characterized in that the small bore tube contains means to promote turbulent flow of reagents.

9. A process according to any one of the preceding claims, characterized in that the reacted mixture is passed through a heat exchanger to reduce the temperature of the reacted mixture.

10. A process according to claim 9, characterized in that the reacted mixture is subsequently passed through an additional cooler so as to further reduce the temperature of the reacted mixture.

11. A process according to any one of the preceding claims, characterized in that the reacted mixture is passed through a pressure reducing means having an elongated spiral flow path so passing the reacted mixture through the pressure reducing means causes the reacted mixture to separate into glycerine on an outside of the flow path and biodiesel on an inside of the flow path.

12. An apparatus for the production of biodiesel characterized in that the apparatus comprises means for admixing oil or fat with an alcohol and a catalyst to produce a reaction mixture, means for increasing the temperature of the reaction mixture to above 100 0 C, means for increasing the pressure of the reaction mixture to above 100 psi, an elongated fluid flow path, means for feeding the heated and pressurised reaction mixture along the elongated fluid flow path, the fluid flow path being provided with means to induce turbulent flow in the reaction mixture, so as to promote an esterification reaction to produce a reacted mixture of biodiesel and glycerine, and means for separating the reacted mixture into glycerine and biodiesel.

13. An apparatus according to claim 12, characterized in that the apparatus further .8 WO 2008/049154 PCT/AU2007/001607 comprises a pressure reducing means having an elongated spiral flow path so that the reacted mixture is separated into glycerine and biodiesel by centrifugal force upon passing through the pressure reducing means.

14. An apparatus according to claim 12 or 13, characterized in that the fluid flow path comprises a continuous small bore tube.

15. An apparatus according to any one of claims 12 to 14, characterized in that the means for inducing fluid flow comprises a plurality of radially extending turbulators which extend into the fluid flow path from a periphery thereof so as to induce the reaction mixture to a central aperture defined by the turbulators.

16. An apparatus according to claim 15, characterized in that a plurality ofturbulators are arranged at spaced intervals along the tube.

17. An apparatus according to claim 16, characterized in that the tube is formed in a plurality of joined sections and the turbulators are disposed in joints between adjacent sections.

18. An apparatus according to claim 17, characterized in that the turbulators are disposed at an angle relative to a direction perpendicular of the length of the tube so as to induce a spiraling effect on liquid flowing in the tube. 9