WO2009004206A2

WO2009004206A2 - Device and method for removing a compound from bio-diesel, method for purifying bio-diesel from a transesterification step, and equipment for producing bio-diesel including same

Info

Publication number: WO2009004206A2
Application number: PCT/FR2008/051003
Authority: WO
Inventors: Ivan Sanchez-Molinero; Ximena Rodriguez; Sudhir Brahmbhatt; Vincent Boisdon
Original assignee: L'air Liquide Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude
Priority date: 2007-06-14
Filing date: 2008-06-05
Publication date: 2009-01-08
Also published as: WO2009004206A3; FR2917420A1; EP2158017A2; FR2917420B1

Abstract

The invention relates to a device and a method for removing a compound related to the production of bio-diesel resulting from a transesterification step, said compound being ethanol or methanol or water, that comprises a stripping column at a pressure higher than or equal to the atmospheric pressure using a gas that mainly contains nitrogen or CO2 or mixtures thereof, the column being preferably connected to an exchanger of the cryogenic type. The invention also relates to a method for purifying bio-diesel resulting from a transesterification step, and to equipment for producing bio-diesel that comprises said device and implements said methods.

Description

DEVICE AND METHOD FOR REMOVING A COMPOUND FROM

BIODIESEL, PROCESS FOR PURIFYING BIODIESEL FROM A

TRANSESTERIFICATION STAGE, AS WELL AS AN INSTALLATION OF

PRODUCTION OF BIODIESEL INCLUDING

The present invention relates to a device and a process for the removal of a by-product or compound related to the manufacture of biodiesel, to a process for purifying biodiesel from a transesterification step, and to a plant for production of biodiesel including said device and allowing the implementation of said methods.

Transesterification is the classic technique for producing biodiesel. It is a process in which oils, which may be vegetable oils, cooking oils, animal fats and / or microalgae oils, are mixed with an alcohol (usually ethanol). or methanol) in the presence of a catalyst (usually sodium or potassium hydroxide) to form fatty esters

(ethyl or methyl ester). This conversion of triglyceride oils to ethyl or methyl esters by transesterification reduces the molecular weight to about one. third of that of the oil, reduce the viscosity by about eight times and increase the volatility of these esters, thus making them attractive as a clean and renewable fuel.

Following the transesterification reaction, the products resulting from this reaction can be separated into two liquid phases: a first phase comprising an aqueous solution of glycerol and a second phase comprising predominantly the desired ester, that is to say biodiesel. However, this separation in liquid phases facilitates the removal of glycerol, a sub-component. industrial product used in the chemical, cosmetic and pharmaceutical industry, then allows the removal of traces of unreacted alcohol, catalyst and soaps produced by saponification of fatty acids in the residual liquid alcohol / ester phase during the transesterification step. Finally, cleaning or purification of the esters is carried out by washing with water, drying under vacuum and filtration.

Currently, some standards define specifications for biodiesel fuel, such as EN 12124, which defines a maximum methanol content of 0.2% by weight and 500 ppm for water. Consequently, to meet these requirements, the main transesterification processes on the market today (for example, "basic-batch", "CD", "Esterfip") use a vacuum stripping column (ignition) and a pump associated with this column to remove the alcohol (ie ethanol or methanol) from the product (ie biodiesel). This vacuum stripping column system with associated pump allows recovery of the methanol / ethanol reagent. This same vacuum stripping column system is also found in the context of the drying step (in order to remove from the product the remaining water) which generally follows the purification step.

Vacuum in these stripping columns is achieved through vacuum pumps. This rotating part equipment results in considerable power consumption and inherent operational and reliability problems, which result in high maintenance costs and possibly failures that can cause the unit to shut down.

There is therefore a real need for a device which is both reliable and at the same time of low consumption of electrical energy, enabling efficiency of elimination of equivalent vacuum stripping products currently implemented.

The applicant Company has found that it is possible to satisfy these requirements by substituting or adapting the vacuum stripping column, and eliminating the associated pump, by a device comprising: a stripping column at atmospheric pressure or greater than atmospheric pressure, advantageously supplemented by a "cryogenic trap" type exchanger. The main advantage of the invention is therefore the removal of the vacuum pump equipment. Other advantages of the present invention are a sharp reduction in electricity consumption in the stripping columns and a large reduction in the size of the compressors used in the columns.

In the context of the present invention, the term "stripping" refers to a separation of a light component of biodiesel in a column in which the biodiesel and the stripping gas flow countercurrently.

In the context of the present invention, the term "cryogenic trap" designates a device that allows the condensation of the vapors contained in the product by passing through a bath of cryogenic fluid and the expression "co-current hydro-ejector" designates a liquid jet gas compressor for drawing a gas into a pressurized liquid. In what precedes and what follows we speak indifferently of "by-product" of the biodiesel or "compound" of the biodiesel, as one will have understood it is about compounds related to the manufacture of the biodiesel in such a reaction of transesterification, in this case methanol or ethanol or water: in the case of methanol or ethanol these are reagents in excess or unreacted, in the case of water these are the remains of the reaction medium which have not been separated from the oil phase (ie the biodiesel to be purified).

The subject of the present invention is therefore a device for removing a by-product or a biodiesel compound resulting from a transesterification stage, comprising a stripper column at a higher pressure or also at the atmospheric pressure in which the biodiesel circulates. and a stripping gas, the column being connected to a means for recovering said by-product from the stripping step, characterized in that the compound is methanol or ethanol or water, and that the device comprises at least one source of stripping gas composed mainly of nitrogen, CO ₂ or their mixtures.

It will be preferably at atmospheric pressure or a few hundred millibars above atmospheric pressure, for example because of the intervention of a booster upstream.

According to the invention, preference will be given to a gas consisting of nitrogen, CO ₂ or their mixture, but it is possible to envisage having to work with non-pure gases such as resulting, for example, from recycling operations, in any case. The term "majority" should be understood to include at least 80% of the target gas or mixture, and even more preferably at least 90% or even 99% of the target gas or mixture.

The column is advantageously connected to a "cryogenic trap" type exchanger (as will be seen below, other means of capture or recovery are possible according to the invention, even if the cryogenic coin type exchanger is the means preferred here). In a complete plant for producing biodiesel, several devices according to the invention can be implemented successively. In particular, a device can be implemented for the removal of alcohol and will be followed by a second device for the removal of water, that is to say, drying.

According to the invention, the "cryogenic trap" type exchanger is fed with a cryogenic fluid selected from the group comprising liquid nitrogen and / or carbon dioxide.

As indicated above, it is also possible, without departing from the scope of the present invention, to consider instead of a cryogenic trapping solution, another technical solution of capture, such as an adsorption solution on activated carbon fabric. or even a combination of several techniques, for example a coupling of a cryogenic trapping solution with an absorption solution on activated carbon fabric.

It is interesting to note that nitrogen is already a required component in the production of biodiesel, so it is advantageous. In fact, the nitrogen can be used in particular: for the inerting of the vegetable oils before treatment, to prevent their oxidation in contact with air and its degradation by contact with moisture, for the inerting of the biodiesel, to avoid degradation by oxidation and moisture, for the inerting of storage and methanol or transesterification ethanol lines for reasons of flammability, and

as an instrument nitrogen ("instrument gas" for supplying, for example, pneumatically controlled valves). Therefore, it is advantageous to use nitrogen in the biodiesel by-product removal process.

It should be noted that if it is possible to use nitrogen as stripping gas, it is also possible to envisage according to the invention the use of CO ₂ as a stripping gas for the transesterification processes using basic catalysis. Indeed, the choice of this CO ₂ is then doubly justified, firstly for the benefits it brings to the stripping step compared to the vacuum drying solution, but also to the required gains in strong acids. for the neutralization of glycerine, a by-product of the transesterification step.

Mixtures of nitrogen-C0 ₂ may also be used according to the invention as stripping gas.

According to a particular embodiment, the device according to the invention also comprises means for heating at least a portion of the cryogenic fluid and to bring it to the stripping column to be used as a stripping gas. Thus, in the stripping column, the biodiesel is circulated countercurrently with the stripping gas which may be a part of the cryogenic fluid having been reheated.

The heating means of a portion of the cryogenic fluid may be constituted by at least one heat exchanger allowing a heat exchange between the biodiesel by-product from the stripping going to the cryogenic trap and the cryogenic fluid.

According to a particular embodiment, the device according to the invention may also comprise a capacitor receiving said biodiesel byproduct from the stripping column before it passes into the cryogenic trap. This capacitor allows a first separation between the by-product which appears in the liquid phase and the stripping gas. This first separation thus makes it possible to limit the amount of by-product passing through the cryogenic trap. Subsequently, a second separation will take place, for example in a cryogenic trap, to remove residual residual impurities of the byproduct that occurs in the gas phase of the stripping gas.

According to a particular embodiment, the device according to the invention further comprises a recycling fan or a co-current hydro-ejector which will be used for the stripping gas, freed from residual impurities after passing through the cryogenic trap. , either recycled and returned to the stripping column. This recirculating fan or hydro-ejector co-current may be used including, but not exclusively, in the so-called "closed-loop" unit defined below.

The subject of the invention is also a process for the removal of a biodiesel compound resulting from a transesterification step, the compound being methanol or ethanol or water, characterized in that it comprises: the stripping at a pressure greater than or equal to the atmospheric pressure of the biodiesel in a stripping column using a stripping gas mainly comprising nitrogen, or CO ₂ or mixtures thereof, and

recovering said compound resulting from the stripping step by means of a recovery means.

Advantageously, the recovery step is performed using a "cryogenic trap" type exchanger. According to an advantageous embodiment, the recovery of said by-product is conducted by condensation and cryogenic trapping of the gas phase resulting from this condensation.

According to a particular embodiment of the elimination process according to the invention, the cryogenic fluid and the stripping gas are of the same nature. They are for example selected from the group consisting of carbon dioxide or nitrogen and mixtures thereof.

It is also possible, without departing from the scope of the present invention, to consider instead of a cryogenic trapping solution, another technical solution of capture, such as an adsorption solution on activated carbon fabric, or even a combination of several techniques, for example a coupling of a cryogenic trapping solution with an absorption solution on activated carbon fabric.

According to a particular embodiment, called "closed loop", the process for removing a by-product according to the invention further comprises the recycling of the stripping gas (for example nitrogen , CO ₂ or a mixture) via a recirculation fan or a co-current hydro-ejector.

The method according to the invention is called a "closed loop" when it comprises the subsequent step of recycling the stripping gas via a recycling fan or a co-current hydro-ejector, while it says to " open loop "when he does not understand this subsequent recycling step.

The elimination process according to the invention may further comprise heating at least a portion of the cryogenic fluid prior to its use in the column of stripping (open loop) or heating the stripping gas free of residual impurities at the outlet of the cryogenic trap (closed loop).

It is understood that when it is desired to remove both alcohol and water, the steps of the process should be repeated. Thus, the invention also relates to a process for purifying biodiesel resulting from a transesterification which comprises: the stripping at a pressure greater than or equal to atmospheric pressure of the biodiesel in the stripping column using a gas of stripping,

the recovery of the alcohol resulting from the stripping step by means of a capture means (preferentially a "cryogenic trap" type exchanger),

the washing with water of biodiesel freed from alcohol, and

the elimination of water, that is to say drying.

Drying can be carried out by stripping at higher pressure or also at atmospheric pressure of the biodiesel obtained from the washing step and then recovering the water from the stripping using the cryogenic trap, that is to say at using the disposal method according to the invention.

All embodiments of the by-product removal process described above can be implemented for both alcohol recovery and water removal.

According to a particular embodiment, the biodiesel purification process according to the invention comprises the recovery of said by-product resulting from the stripping step as well as the elimination of the water by means of the elimination process and of the device described above. Advantageously, in the biodiesel purification process, the alcohol removal step is conducted with a closed loop using a recirculation fan and the drying step is carried out with a closed loop at the end of the cycle. using a co-current hydro-ejector.

It is of course possible that the biodiesel purification process includes the closed loop alcohol removal step and the open loop drying step and either the open loop elimination step and the closed loop drying step.

The invention also further relates to a biodiesel production plant, comprising a biodiesel transesterification unit, an alcohol elimination unit comprising an elimination device according to the invention and a washing unit and a elimination of water (drying) comprising an elimination device according to the invention.

The operating principle of the method of the invention will be described in more detail below with reference to the drawings, in which: FIG. 1 is a schematic view of a biodiesel production installation according to the prior art; FIG. 2 is a diagrammatic view of a biodiesel production facility according to the invention; FIG. 3 is a schematic view of an open-loop elimination unit of biodiesel by-products according to the invention; Figure 4 is a schematic view of a closed-loop elimination unit of biodiesel by-products according to the invention.

In order to facilitate the description and the link to the elements of the figures, the methanol will be used in what follows, although other alcohols and water may be eliminated in the same way. Likewise, liquid nitrogen will be used in the following description, while other cryogenic fluids may be used.

In Figure 1, there is shown a biodiesel production facility according to the prior art. This facility includes a transesterification unit (IA), an alcohol removal unit (IB) and a water washing and removal (drying) unit (IC) from biodiesel. In particular, the alcohol elimination unit (IB) allows the recovery of the reagent having been used for transesterification by means of a vacuum stripping column (1) with associated pump (2). The water washing and removal unit (IC) also comprises a vacuum stripping column (3) with associated pump (4).

In Figure 2, there is shown a plant for producing biodiesel according to the invention. This facility includes a transesterification unit

(2A), an alcohol removal unit (2B) and a water washing and removal (drying) unit (2C) from biodiesel. The alcohol elimination unit

(2B) comprises an atmospheric pressure stripping column (7) connected to a "cryogenic trap" type exchanger (12) and may include a recirculation fan (17) as part of the "closed loop" process. The unit for washing and removing water (2C) (ie drying) also comprises an atmospheric pressure stripping column connected to a "cryogenic trap" type exchanger and may comprise a co-current hydro-ejector as part of the "closed loop" process.

Figure 3 shows a unit (2B) for open-loop removal of methanol from biodiesel. Unit (2B) is adapted to remove methanol from biodiesel from a transesterification step (2A). Biodiesel, coming from the reactor (5) after trans-esterification, is preheated to between 120 and 150 ^° C. in a heat exchanger (6) before being introduced into the stripping column (7). At the outlet of this column, the stripping nitrogen is loaded with the excess methanol removed from the biodiesel. This stripping nitrogen charged with methanol is subsequently cooled in a second heat exchanger (8) and placed in a condenser (9). From this condenser, a liquid phase (ie most of the methanol by-product) (10) is recovered on the one hand and a gaseous phase (ie stripping nitrogen containing trace amounts of methanol) on the other hand. will be directed to the cryogenic trap. The remaining traces of methanol (11) from the gas phase from the condenser are then trapped in a liquid nitrogen-supplied (13) cryogenic trap (12) which is used for the proper nitrogen requirements. at the factory. The stripping nitrogen thus recovered without a trace of methanol can then be returned to the other zones of the plant in order to be used in particular as an inerting gas (14). This unit is called "open loop" since the stripping nitrogen thus recovered without trace of methanol is returned to the plant (ie inerting), while the liquid nitrogen having fed the cryogenic trap, will be used to feed again the stripping column.

FIG. 4 shows a unit (2B ') for closed-loop elimination of methanol from biodiesel.

This unit (2B ') is adapted to remove methanol, from biodiesel resulting from a transesterification step (2A). Biodiesel, coming from the reactor

(5) after trans-esterification, is preheated to between 120 and 150 ° C in a heat exchanger (6) before being introduced into the stripping column (7). At the outlet of this column, the stripping nitrogen is loaded with the excess methanol removed from the biodiesel. This stripping nitrogen charged with methanol is subsequently cooled in a second heat exchanger (8) and placed in a condenser (9). From this condenser, a liquid phase (ie most of the methanol by-product) (10) is recovered on the one hand and a gaseous phase (ie stripping nitrogen containing trace amounts of methanol) on the other hand. will be directed to the cryogenic trap. The remaining traces of methanol (11) from the gas phase from the condenser are then trapped in a liquid nitrogen-supplied (13) cryogenic trap (12) which is used for the proper nitrogen requirements. at the factory. The stripping nitrogen thus recovered without a trace of methanol can then be returned to the stripping column to supply said stripping column again via a recycling fan (17). The liquid nitrogen fed to the cryogenic trap will be directed to the plant (16). An additional nitrogen supply can be made to fill the losses (18).

Other aspects, objects, advantages and features of the invention will be presented on reading the following examples given by way of illustration only.

EXAMPLES

EXAMPLE 1 Open Loop Removal of Methanol

This example will be described in connection with FIG. 3. In this figure are identified steps "a" to

"I". At these stages, the flow composition is analyzed during the process and the results are presented in Table 1.

The biodiesel coming from the reactor after transesterification (a) is preheated to between 120 and 150 ^° C. before being introduced (b) into the nitrogen stripping column. At the outlet of the column, the biodiesel is cooled (c) and directed to the water washing and removal unit (d). As for the stripping nitrogen charged with excess methanol, it is directed (f) to the alcohol removal unit. After a first temperature condensation of the cooling water, most of the methanol is recovered in liquid form (10). The remaining traces of methanol in the stripping nitrogen are then directed (g) and trapped in a "cryogenic trap" type exchanger fed with liquid nitrogen. This liquid nitrogen having fed the cryogenic trap, returns to the stripping column (h), while the stripping nitrogen thus recovered without trace of methanol is returned to the factory (i).

The material, energy (nitrogen and heat) and cost savings for this aspect of the invention are as follows:

1 / Material balance:

This material balance comes from simulations using the Hysys software of the relevant stage of the disposal process for an average biodiesel purification plant, producing 100,000 tons / year. TABLE 1: Elimination of methanol [month]

Components a b C d e f g h i

Biodiesel 43. 1 43.1 4 3.1 4 3.1 0 0 0 0 0

Water

Methanol 26. 4 26.4 0 .73 0 .73 25.7 1.75 0 0.007

Nitrogen 0 0 0 .13 0 .13 8.75 8.6 8.6 8.75 8.6

Pressure (bar) 1 1 1 1 1 1 1 1 1

Temperature ( ⁰ C) 69. 6 153 1 97 87.8 153 151 25 10 -40

The outlet temperature of the cryogenic trap (i) has been adjusted according to the material balance, and it could further fall according to the methanol content criteria of the inerting nitrogen.

2 / Energy balance:

Nitrogen balance

An example of overall nitrogen consumption for a biodiesel purification plant is 26 tonnes / day of nitrogen for a production of 250,000 tonnes / year of biodiesel.

The amount of nitrogen used for carrying out the process of the invention is given in Table 2 below.

TABLE 2

Required quantity of liquid nitrogen in the cryogenic trap kg / hr 220

Nitrogen required for plant needs kg / hr 433

It can thus be appreciated that the quantity of nitrogen to be vaporized in the cryogenic trap is less than the quantity of nitrogen that is already vaporized for the consumption of the plant (inerting and others). Heat balance consumed: TABLE 3

This assessment in Table 3 shows that the reboiler heat consumption (15) for the methanol stripping column according to the invention is slightly less than that for the vacuum methanol stripping column used in the prior art.

3 / Economic balance sheet

With previous assumptions of:

TABLE 4

An economic balance sheet (Table 5) can be established for electricity consumption, maintenance costs and water vapor costs.

The method according to the invention "open loop" thus allows a gain of 8498 C / year compared to the method of the prior art.

TABLE 5

Example 2 Closed-loop elimination of methanol and water.

This example will be described in connection with FIG. 4. In this figure are identified steps "j" to "r" for methanol. At these stages, the composition of the flow is analyzed during the process and the results are presented in Table 6 (note that in the table we find the steps "j" to "r" representing the same steps as for methanol, but this time for water, although these steps' j '' to 'r' have not been shown in the figure).

The biodiesel coming from the reactor after transesterification (j), is preheated to between 120 and 150 ^° C. before being introduced (k) into the column of stripping with nitrogen. At the outlet of the column, the biodiesel is cooled (1) and directed to the water washing and removal unit (m). As for the stripping nitrogen charged with excess methanol, it is directed (o) to the alcohol removal unit. After a first temperature condensation of the cooling water, most of the methanol is recovered in liquid form (10). The remaining traces of methanol in the stripping nitrogen are then directed (p) and trapped in a heat exchanger.

10 type "cryogenic trap" powered by liquid nitrogen. The stripping nitrogen thus recovered without trace of methanol is recovered via a recirculation fan (17) and returned (q) to the stripping column, while the liquid nitrogen having fed the cryogenic trap, will return

15 to the factory (16). An additional nitrogen supply (18) can be made to fill the losses (r).

The material, energy (nitrogen and heat) and subsequent savings show that the invention saves 0.32 € / ton of biodiesel.

1 / Material balance:

These material balances are derived from simulations using the Hysys software of the relevant stage of the disposal process for an average biodiesel production plant, producing 100,000 tons / year.

2 / Energy balance:

Nitrogen balance

An example of overall nitrogen consumption for a biodiesel facility is 26 tonnes / day of nitrogen for a production of 250,000 tonnes / year of biodiesel.

The amount of nitrogen used for carrying out the process of the invention is given in Table 7 below.

TABLE 7

It can thus be appreciated that the amount of nitrogen to be vaporized in the cryogenic trap corresponds to the amount of nitrogen already vaporized for the consumption of the plant (inerting).

20 Heat balance consumed:

The balance sheet of Table 8 shows a variation of heat consumption in the opposite direction in the two units with the method according to the invention: positive in the case of the elimination of methanol and negative in the case of drying. This increase in heat consumption in the case of water removal or drying is the consequence of the need for heat for the preheating of nitrogen. Overall, in the purification process according to the invention, the steam consumption is lower than that of the conventional method.

3 / Economic balance sheet

With previous assumptions of:

TABLE 9

An economic balance sheet (Table 10) can be established for electricity consumption, maintenance costs and water vapor costs. TABLE 10

The method according to the invention "closed loop" thus allows a gain of 16547 € / year compared to the method of the prior art.

The operating cost balance is therefore advantageous for the proposed nitrogen stripping column solution when compared to the existing vacuum column solution.

This increase in operating costs comes mainly from the elimination of the vacuum pump (and therefore the power consumption and maintenance cost associated with the rotating equipment) and the gain in steam consumption.

Although the present invention has been described above by way of examples of its preferred embodiments, it is understood that it may be modified without divert from the spirit and nature of the invention as defined in the appended claims.

Claims

A process for removing a compound bound to the biodiesel production by transesterification, the compound being methanol or ethanol or water, characterized in that it comprises:

the stripping at a pressure greater than or equal to the atmospheric pressure of the biodiesel in a stripping column using a stripping gas composed mainly of nitrogen, CO ₂ or their mixtures, and

2. Disposal method according to claim 1, characterized in that the recovery of said compound is conducted using a "cryogenic trap" type exchanger.

3. Disposal method according to claim 1, characterized in that the recovery of said compound is conducted by condensation and cryogenic trapping of the gas phase resulting from this condensation.

4. Disposal method according to one of claims 2 or 3, characterized in that the cryogenic fluid supplying the cryogenic trap and the stripping gas are of the same kind and are selected from gases comprising predominantly nitrogen or nitrogen. carbon dioxide or their mixtures.

5. Disposal method according to any one of claims 2 or 3, characterized in that it comprises heating at least a portion of the cryogenic fluid before use in the stripping column.

6. Disposal method according to any one of claims 1 to 5, characterized in that it further comprises the recycling of the stripping gas via a recirculation fan or a co-current hydro-ejector.

7. A process for purifying biodiesel from a transesterification step, characterized in that it comprises:

the stripping at a pressure greater than or equal to the atmospheric pressure of the biodiesel in a stripping column using a stripping gas composed mainly of nitrogen, or of CO ₂ and their mixtures, stripping resulting in recovery one of methanol or ethanol; recovering said compound resulting from the stripping step by means of a recovery means,

washing the biodiesel with alcohol, and removing the water, that is to say, drying, with water.

8. A process for purifying biodiesel from a transesterification step according to claim 7, characterized in that said recovery means is a "cryogenic trap" type exchanger.

9. A method for purifying biodiesel from a transesterification step according to claim 7 or 8, characterized in that the recovery of said compound from the stripping step and the removal of water are conducted according to the method. of any one of claims 1 to 6.

10. A device for removing a compound related to the production of biodiesel from a transesterification stage, comprising a stripping column at a pressure greater than or equal to the atmospheric pressure in which the biodiesel circulates and a stripping gas, the column being connected to a means of recovery of said compound resulting from the stripping step, characterized in that the compound is methanol or ethanol or water, and in that the device comprises at least one stripping gas source composed mainly of nitrogen , or CO ₂ or their mixtures.

11. Elimination device according to claim 10 characterized in that the column is connected to a type of exchanger "cryogenic trap".

12. Disposal device according to claim 10 characterized in that the column is connected to a means of adsorption on activated carbon fabric.

13. Elimination device according to claim 10 characterized in that the column is connected to a recovery means employing a combination of several techniques, for example a coupling of a cryogenic trapping solution with a solution of absorption on activated carbon cloth.

14. Elimination device according to claim 11, characterized in that the type of "cryogenic trap" is fed by a cryogenic fluid selected from the group comprising liquid nitrogen or carbon dioxide or mixtures thereof.

15. Disposal device according to claim 14, characterized in that it further comprises means able to heat at least a portion of the cryogenic fluid and to bring it to the stripping column to be used as stripping gas.

16. Disposal device according to one of claims 10 to 15, characterized in that it further comprises a capacitor receiving said compound from the stripping column before its passage in the recovery means.

17. Disposal device according to one of claims 10 to 16, characterized in that it further comprises a recycling fan or a co-current hydro-ejector.

18. A biodiesel production plant, comprising a biodiesel transesterification unit, a methanol or ethanol removal unit comprising an elimination device according to any one of claims 10 to 17 and a washing unit and water removal (drying) apparatus comprising an elimination device according to any one of claims 10 to 17.

22

divert from the spirit and nature of the invention as defined in the appended claims.