WO2012101361A1

WO2012101361A1 - Process and device for extracting molecules

Info

Publication number: WO2012101361A1
Application number: PCT/FR2012/050121
Authority: WO
Inventors: Alain VALLAGEAS
Original assignee: Celsius
Priority date: 2011-01-25
Filing date: 2012-01-20
Publication date: 2012-08-02
Also published as: FR2970659B1; FR2970659A1

Abstract

The present invention relates to a process for extracting molecules from a solid matrix, carried out using a solvent having a boiling point at atmospheric pressure of between -35°C and +90°C, comprising the following steps: - a contacting step between the solvent in liquid form and the matrix, in an extractor (1); - a separation step between the solvent in gas form and the molecules extracted (solute), in a separator (2); - a step of recovering the solvent in liquid form by condensation, in a condenser (3); - a step of reintroducing the solvent into the extractor (1), via passage in a receiving/storage system (4), according to which the solvent is recycled in a closed loop, the circulation in a loop of the solvent not involving mechanical pumping of the gaseous solvent, but being advantageously provided by at least one of the following mechanisms: • pressure difference; • temperature difference; • gravity; and • thrust by a gas. Also targeted by the invention are a device suitable for the implementation of this process and the use thereof for extracting molecules of interest of plant or animal matter, or for purifying a synthetic product.

Description

METHOD AND DEVICE FOR EXTRACTING MOLECULES

TECHNICAL FIELD The invention relates to the extraction of molecules using a solvent characterized by a boiling point at room temperature of between -35 ° C. and + 90 ° C., such as an alkane or a refrigerant. .

In the context of the present invention, there is provided a method and a device for optimizing solvent recycling through a closed loop. In this loop, the circulation of the solvent is ensured in the absence of a gas compressor, solely by gravity, by changes in temperature or pressure, and / or by the use of a gas ensuring the growth of the solvent under liquid form. PRIOR STATE OF THE TECHNIQUE

Many natural molecules are extracted from plant or animal substances to be incorporated in pharmaceutical or cosmetic preparations, to be used as a component of a perfume or aroma, or to be introduced into a circuit of the food industry.

Several processes have been implemented to extract these molecules from a substrate called "matrix", some of all time, others more recently. A conventional method is mechanical pressing. The present invention, however, is part of solvent extraction processes.

In general, any solvent extraction process consists of dissolving the desired molecule adsorbed on the matrix in a solvent and then separating the molecule from the solvent. These processes can be classified by type of solvent used, depending on whether it is solid, gaseous, liquid or supercritical.

A first technique is called cold enfleurage. In perfumery, the flowers are arranged manually on fat that dissolves the desired odorous molecules. At the end of the solid solution, the molecule is generally transferred into alcohol and the alcoholic solution is called absolute. This method cited as an example of a solid solvent is of a non-transposable implementation on an industrial scale. Another example is steam extraction or hydrodistillation. In this case, the molecule is driven by water vapor in the gas phase. Two methods can be used: either the matrix is immersed in boiling water, or the water vapor passes through the matrix arranged in a bed. The extracted molecules are then separated from the vapor solvent by condensation on a cold wall and then decantation. These methods can be implemented only for immiscible molecules with water and are thus commonly used to extract essential oils.

There is also extraction by liquid solvent. An organic solvent is chosen according to the molecule to be extracted, which must in particular be soluble in the liquid solvent. Various equipment can be implemented to obtain a solution. The molecule is then extracted from the liquid solution by distillation.

Supercritical fluid extraction relies on the property of a solvent brought to the supercritical state to dissolve organic molecules. After driving the desired molecule, it is separated from the supercritical solution by phase transformation: the solvent goes into the gaseous state, while the molecule is condensed in the liquid state. The extraction equipment recycles the solvent in a closed loop during successive stages where it is supercritical to extract the molecules from the matrix in the extractor, then gaseous to condense the molecules extracted in the condenser. The supercritical fluid used is generally carbon dioxide (C0 ₂ ).

However, the processes described have a number of disadvantages which reduce their interest:

The high temperature of steam during steam extraction can degrade the desired molecules;

The liquid organic solvent is not always able to cross the cytoplasmic membrane and thus dissolve the molecules present inside the cells. In addition, the subsequent separation by distillation between solvent and solute is governed by the phase diagram of the solution: there are always at least traces of solute in the solvent, just as there are always at least traces of solvent in the solvent. final product.

In fact, supercritical fluid extraction is an improvement over vapor phase extraction and liquid phase extraction:

The extraction temperature is entirely compatible with the safeguarding of the molecules to be extracted, for example of the order of 30 ° C for the supercritical C0 ₂ ; The supercritical CO ₂ molecules cross the cytoplasmic membranes and can thus dissolve the desired molecules in the core of the matrix; Even if the separation between the solute and the C0 ₂ is not complete, there remain molecules of C0 ₂ in solution in the finished product according to the thermodynamic equilibrium with the surrounding atmosphere and these residual molecules are not harmful and do not risk of degrading the product.

However, the major disadvantage of the supercritical fluid extraction process lies in the implementation of the corresponding device. In order for the carbon dioxide to become supercritical at the temperature of 30 ° C, a pressure of 300bar must be reached. Due to the very high pressure of the supercritical state, the investment costs of the devices are very important and all the more prohibitive as the size of the batch is large. This is why extraction by supercritical fluid is still poorly developed. It remains limited to multi-purpose pilot plants treating batches of a few liters for pharmaceutical or cosmetic applications. Large capacity extraction units dedicated to a single product are also used, whose operation in 3/8 ensures profitability: decaffeination units, ....

Another family of extraction processes uses as solvent a liquefied gas. A gaseous compound is commonly called "liquefied gas" under normal (ambient) pressure and temperature conditions, which can be liquefied by acting on its temperature, pressure, or both.

Processes and extraction devices using liquefied gases have been described for example in WO 03/057342 and WO 2004/034801. WO 2004/034801 focuses on a method and a liquefied gas extraction device, in this case a saturated hydrocarbon, of butter and cocoa powder respectively. It does not contemplate the use of this method and this apparatus for treating other substances for the purpose of extracting other molecules. Furthermore, this document describes a continuous process of suspending the matrix with a static mixer, and then extraction and separation between solvent and solute. This continuous process can be implemented only for a raw material in large quantities and constant characteristics. Moreover, it is certainly envisaged the recycling of the washing fluid, but it is a local recycling and not a global recycling: the solvent is reused several times against the current of the direction of the process, with a continuous refill new solvent and continuous evacuation of used solvent. The document WO 03/057342 describes a process for extracting essential oils in which:

The solvent is distributed on the matrix in the form of a "fog";

The extraction is carried out under adiabatic conditions;

The recycled solvent is pumped in gaseous form using a compressor.

The process described in this document has a certain number of drawbacks which limit its use:

The use of a mist assumes that the liquid solvent does not wet the entire matrix and thus the desired molecules remain trapped in the matrix, which limits the extraction efficiency;

The solvent is introduced into the extractor during adiabatic expansion: the extraction temperature is imposed by the liquid-vapor equilibrium of the solvent at the pressure prevailing in the extractor;

The solvent in the extractor is at the limit of the gas / liquid phase equilibrium. The portion of gaseous solvent present in the extractor does not have the same solvation capacities as the liquid solvent. The gaseous solvent is extracted by suction of the extractor, pure, without causing molecules, which limits the efficiency of the extraction;

Depression is created by a gaseous solvent compressor, which limits the level of vacuum obtained and induces additional risks of ignition; The extraction device described has no heating element which limits its use to an adiabatic process;

The device relies on the use of a mechanical compressor to ensure the circulation of the solvent via its physical pumping. Such a compressor is therefore a central unit for managing all flows. It is an expensive apparatus, of delicate use, which, if it breaks down, endangers the whole system.

Overall, the method and the device described in WO 03/057342 are based on the principle of the mechanical compression of a refrigerant used in refrigeration production units and in heat pumps. The principle is based on the establishment of a so-called Carnot cycle, during which heat is transferred by mechanical action from an evaporator to a condenser. Equipment built on the basis of this principle is optimized so that with a minimum of mechanical energy, a maximum of energy is transferred. In particular, the refrigerant is evaporated at low pressure and condensed at high pressure. It appears that there is a clear need to develop new methods and devices for extracting molecules from any matrix, in particular based on the use of liquefied gases as a solvent. SUMMARY OF THE INVENTION

The present invention relates to a method for extracting molecules from a solid matrix, carried out using a solvent whose boiling temperature at atmospheric pressure is between -35 ° C and + 90 ° C, advantageously a liquefied gas, according to which the solvent is recycled in a closed loop. Typically, the loop circulation of the solvent is in the absence of the mechanical pumping of the gaseous solvent, in particular by means of a gas compressor. Advantageously, it is only ensured by pressure variations, by temperature variations, by gravity and / or by means of a gas capable of "pushing" the solvent in liquid form (gas) and / or possibly by mechanical pumping of the liquid solvent.

Even more advantageously, the method and the device according to the invention do not involve any mechanical pumping of the solvent, whether in gaseous form or in liquid form.

Note that during operation with gas compressor, the fluid travels a Carnot cycle, its evaporation and condensation being performed at two different pressures. According to the invention and in the absence of a gas compressor, the fluid travels only back and forth on the same isobar. Thus, the invention proposes for the first time an isobaric separation process in a solvent, advantageously a liquefied gas.

A method according to the invention can be used both for extracting molecules of a so-called natural raw material, in particular animal or plant, as for purifying a chemical synthesis product. Advantageously, the matrix is in solid form.

In the process described, the solvent consisting of a pure substance or a mixture is characterized by its boiling point at atmospheric pressure, between -35 ° C and + 90 ° C. Said solvent can also incorporate additives, provided that its boiling point at atmospheric pressure is always between -35 ° C and + 90 ° C.

It is advantageously a liquefied gas, in particular an alkane and even more preferably butane. Among liquefied gases, in addition to alkanes and mixtures of alkanes, the solvent used may be a fluid called refrigerant because likely to be used in cold-producing plants: these are halogenated fluids synthesized from alkanes or alkenes in which hydrogen atoms are substituted with chlorine and / or fluorine atoms. Thus, the solvent used may be a Freon ™.

More generally, the processes and devices described in the context of the present application can be applied to any solvent whose boiling temperature at atmospheric pressure is between -35 ° C and + 90 ° C. Thus and by way of example are also concerned certain alcohols such as methanol or ethanol, acetone or other organic solvents.

It should be noted that certain solvents are advantageously excluded, for example:

short-chain alkanes (methane, ethane or propane) whose boiling point at atmospheric pressure is too low;

carbon dioxide (C0 ₂ ) whose boiling point is -78 ° C at atmospheric pressure and which is also used as a solvent in another process in the supercritical state;

ammonia (NH ₃ , boiling temperature = -33 ° C) and sulfur dioxide (S0 ₂ , boiling temperature = -10 ° C) could be retained because of their physical properties but are excluded because of their of their great potential chemical reactivity with respect to the matrix and the molecules to be extracted.

The solvents targeted by the invention have the following physical and chemical properties particularly suitable for the claimed process:

The liquid-vapor phase changes, namely the evaporation and the condensation of the solvent, are carried out for temperature and pressure conditions that are easily reached industrially and compatible with the stability of the molecules to be extracted. Thus, the temperature and pressure conditions prevailing in the extraction device correspond to conditions of thermodynamic equilibrium with the liquid solvent. Moreover, the temperature and pressure conditions prevailing in the separation device correspond to thermodynamic equilibrium conditions with the gaseous solvent. For example, for butane, the boiling temperature is -0.5 ° C at atmospheric pressure, and 64 ° C at 6 bar relative. Another example is Freon ™ RI 34a:

the boiling point at atmospheric pressure (0 bar) is -26 ° C;

an evaporation / condensation is obtained at -17 ° C. for a pressure of 0.5 bar; the equilibrium vaporization temperature is 39 ° C. for a pressure of 9 bars. In addition, the molecules of this type of solvent are relatively small, particularly for short hydrocarbon chains such as butane. These molecules can easily cross the cytoplasmic membranes of cells and thus have a strong power of solvation. In the case of solvent mixtures, various chain lengths may be used to broaden the range of application.

In addition, alkanes and refrigerants are chemically inert. These molecules react neither with the components of the matrix nor with the finished product. In addition, with regard to saturated hydrocarbons, there may remain traces of solvent in the finished product, whether it is liquid or solid since these traces of solvent are inert and can be safely ingested by any organism. This advantage is clear compared to other organic solvents commonly used for extraction and whose traces can reduce the range of application of the product extracted in pharmacy, cosmetic, perfume, aroma, or various food applications.

Finally, as part of the process, the solvent used must be recyclable. Since the alkane or refrigerant type solvents are chemically inert, they can be recycled indefinitely. The only limit is the saturation of the solvent into molecules that it is required to extract. But once the saturation reached, the first use, all the extracted molecules remain in the finished product. Advantageously, it is advisable not to reuse this recycled solvent to extract molecules of a different nature from another matrix.

In a conventional manner, the targeted process comprises a step of contacting the solvent in liquid form with the (solid) matrix, resulting in the extraction of the molecules of interest from the matrix.

This step advantageously takes place in an enclosure called extractor. At this stage, the solvent is introduced into the extractor in liquid form. When it comes into contact with the matrix, the solvent must also remain permanently in the liquid state. In other words, the temperature and pressure conditions prevailing in the extractor are maintained such that the solvent remains in the liquid state. Suitably, the extractor is provided with a device for regulating the pressure. Thanks to a pressure probe, it is possible to maintain the pressure in the extractor and in particular to regulate the escape of gaseous solvent to avoid excessive overpressure which could prevent the arrival of the solvent from the storage tank (via a valve exhaust). Advantageously, the extractor is also provided with a pressurizing device. Indeed, prior to the introduction of the liquid solvent, it may be necessary to ensure that the pressure in the chamber, associated with the temperature of the matrix, are such that the injected solvent will remain liquid.

In practice, it is possible to initially pressurize the extractor, before any injection of solvent, by one of the following devices:

Either by the injection of an inert gas such as nitrogen at controlled pressure. This is particularly advantageous when the solvent used is a fuel such as an alkane or a mixture of alkanes. Inerting the enclosure, possibly associated with a sweep or even successive phases of vacuum (via the use of an at least partial evacuation device) and pressurization with inert gas, allows evacuate the oxygen present in the chamber and avoid a combustible-oxidant mixture that could cause an explosion;

Or by the injection of a steam from the solvent itself, at controlled pressure. In practice, a fraction of the stored liquid solvent is boiled in an evaporator heated with a hot fluid or with electricity, and the gas obtained is injected into the extractor. The advantage of this solution is to avoid introducing into the solvent loop a substance foreign to the solvent itself, including an inert gas, to be removed later in the process;

Either by a combination of the above two methods during successive operations. It may indeed be useful depending on the nature of the matrix, the solvent and the molecules to be extracted, to evacuate as much as possible the air present in the extractor after introduction of the matrix and closure of the enclosure, or to avoid the presence of oxidizing oxygen, either to avoid the presence of water likely to be entrained with the molecules extracted or likely to cause icing situations on the cold points of the installation.

If the extractor is not pressurized before the introduction of the solvent, whether it is under atmospheric pressure or under partial vacuum, the liquid introduced solvent will undergo an adiabatic expansion which will cool it to the equilibrium pressure evaporation temperature. reigning in the enclosure. The introduction of solvent will then cause the cooling of the matrix which can be harmful depending on the nature of the matrix and the temperature obtained. In particular, if the temperature obtained is negative, the cells of the matrix may possibly be destroyed, resulting in the release of molecules that are not to be extracted. In this case, the extraction will be less selective. During this extraction step, the two phases, liquid for the solvent and solid for the matrix, are as intimately as possible mixed, either by spraying the liquid, or by flooding, or using any other device used to contact a liquid and a solid. Thus, the extractor is advantageously provided with a device for introducing the solvent in liquid form (for example an injection valve) and possibly a mixing device.

Advantageously, the extractor may also be provided with a heating device such as a double jacket enclosure or a coil, allowing in a subsequent step the drying of the matrix.

During the extraction phase, the desired molecules present in the matrix are dissolved in the liquid solvent and the solution obtained is extracted from the apparatus by filtration or by any device making it possible to prevent the matrix from leaving the extractor . Only the solution composed of the liquid solvent and the solute is extracted from the extractor.

The next stage of the process is the separation step between the solvent and the extracted molecules (solute), by distillation in the case where the solute is produced in liquid form or by crystallization in the case where the solute is produced in solid form. .

This step advantageously takes place in a separate enclosure, called separator. However, and as described below, the extractor and the separator may be two separate chambers in a common enclosure.

During the separation step, the solvent passes in gaseous form by boiling and optionally by expansion.

In the case where there is a pressure difference between extractor and separator (extractor> separator), the separation is advantageously in three successive phases:

an adiabatic expansion phase: the solution is extracted from the extractor by pressure difference. As soon as outside the extractor, at a lower pressure, the solvent is at a pressure and a temperature corresponding to its evaporative equilibrium. A fraction of the solvent vaporizes, the residual fraction of liquid solvent remains more concentrated in solute. The communication between the extractor and the separator is advantageously done by means of an expansion valve. a boiling phase: the solution is boiled by heating. This operation aims to provide the necessary energy for phase transformation. The solvent gradually evaporates and two cases can occur depending on the nature of the solute molecules:

· Either the solute is a liquid under the conditions of temperature and pressure prevailing in the device. The device is then called a boiler. The separation process is then a distillation process governed by the phase diagram of the two solvent-solute components. At the end of this distillation process, there always remains a fraction of solute entrained in the gas phase, just as there is always a fraction of solvent in the solute.

Or the solute is a solid under the conditions of temperature and pressure prevailing in the apparatus. The device is then called a crystallizer. The separation process is then a crystallization process governed by the solubility properties of the solute in the solvent. As the solvent evaporates, the residual solvent is concentrated in solute until the solubility limit of the solute in the solvent is reached. From this threshold, the solute crystallizes in parallel with the evaporation of the solvent. Since solubility is generally an increasing function of temperature, it may be useful to lower the temperature of the solution to decrease the solubility. At the end of this crystallization process, there always remains a solvent fraction adsorbed on the powder.

a possible phase of evacuation: the molecules extracted from the matrix, whether they are liquid after the distillation phase, or solids in powder form after the crystallization phase, are brought under vacuum more or less pushed, thanks to an at least partial evacuation device, for example a vacuum pump which discharges into the condenser. This last phase aims to extract from these the maximum residual solvent in liquid solution or adsorbed in liquid solution. By evacuation, the pressure is lowered below the vapor pressure of the solvent to the temperature thereof. The higher the vacuum is pushed, and the higher the temperature, the more the residual solvent molecules evaporate.

If the desired molecules are collected in the liquid state, the vacuum phase can be conducted in the same boiler of the previous phase. This is evacuated at least partially and even advantageously heated within the accounting limit with the product. If the desired molecules are collected in the solid state, the evacuation phase can be conducted in the same crystallizer or advantageously in a dryer, or even after a filtration phase in a filter or mechanical spin in a wringer. The methods used are then the known methods of separating a liquid and a solid, mechanical separation and / or drying.

Suitably, the separator is thus provided with a heating device such as a double jacket enclosure or a coil. Advantageously, it is also equipped with an at least partial evacuation device, for example a vacuum pump.

Furthermore, and to promote heat exchange, the separator may be provided with a mixing device.

The complete process referred to may be discontinuous or semi-continuous. With respect to the matrix, the process is always discontinuous: it involves treating a batch or batch of raw material. With respect to the solvent and the extracted molecules, extraction, adiabatic expansion, boiling and evacuation are performed in successive or simultaneous steps.

The process is discontinuous when the extraction is carried out in a closed extractor. When the extraction time is considered sufficient, the solution is introduced into the separator for separation. The boiling and evacuation phases follow one another.

The process is semi-continuous when the extraction is carried out in an extractor in permanent communication with the separator which follows through an expansion member. The solvent passes successively and continuously in the extractor where it is liquid and then in the separator where it is evaporated. The next phase of evacuation can be conducted either semi-continuously after a new expansion in a third device, or discontinuously in the separator. If the flow of the solvent in the production unit can be semi-continuous or discontinuous, the matrix remains trapped in the extractor. The method consists in extracting the maximum of molecules contained in a batch of matrix spread in a bed contained in the extractor. From the point of view of the matrix, the process is discontinuous. After batch treatment, it is necessary to drain the extractor and recharge it with a new batch.

Moreover and as already said, the extractor and the separator are advantageously equipped with an at least partial evacuation system, for example a vacuum pump. This system has two advantages: it improves the separation between solvent and solute at the separator;

it allows the recovery of the solvent in gaseous form for the purpose of its condensation, both at the extractor and the separator.

As already explained above for the extractor, the separator can also be connected to an inerting system or device for putting under inert gas, that is to say supply and circulation in an inert gas such as nitrogen. The inerting is advantageously carried out on the entire device and at the beginning of the process, after having loaded the matrix, and necessarily before introducing the solvent into the extractor.

After separation, the solvent is condensed in liquid form in an enclosure called a condenser. In this chamber, the temperature and pressure conditions must be such that the solvent leaving the separator in gaseous form becomes liquid again.

Insofar as the pressure in the condenser is generally substantially equivalent to that prevailing in the extractor, this chamber is advantageously provided with a cooling device, such as a refrigeration unit. It is thanks to this lowering of the temperature or cooling that the solvent circulates between the separator and the condenser, and returns in liquid form.

Optionally, the condenser is also provided with a pressurizing or pressurizing device for less stress on the cooling device.

In contrast to the solvent extraction processes using a gaseous solvent compressor as described in WO 03/057342 and WO 2004/034801, the innovation provided by the present process is that the pressures in the separator and in the condenser are substantially equal, the only pressure difference between the two speakers being due to the pressure drop generated by the steam flow. It is therefore an isobaric process.

In a particular mode of operation, the extraction can also be conducted not at a higher pressure but at an identical pressure (with the pressure drops close) to that of the separation and the condensation. The process is then completely isobaric, without expansion valve between extractor and separator, the action of the only temperature being the engine of the solvent flow. This is feasible, for example, with RI 34a as a solvent, at a positive pressure of 9 bar (with a vaporization equilibrium temperature of 39 ° C.). In this case, the evaporation of the solvent in the separator is provided by heating, the relaxation and the evacuation being optional. At the condenser, the cooling device is not necessarily a refrigeration unit, the cooling of the condenser can be provided with water or air. In this case where the two enclosures (extractor and separator) are at the same pressure and in a discontinuous mode of operation (in which the extraction and the separation are successive), the process can be carried out in a single enclosure comprising a extraction chamber in the upper part and a separation chamber in the lower part, the two being separated by a grid or a filter cloth retaining the matrix and both being subjected simultaneously to the same conditions of pressure and temperature during the successive steps of the method. In particular in such an apparatus, the drying of the matrix by heating is simultaneous with the evaporation of the solvent by heating in the separator, then, subsequently, the evacuation simultaneously completes the drying of the matrix and the evaporation of the residual solvent. in the separator.

At the end of the extraction process and before its reuse for a new extraction, the solvent is advantageously stored in liquid form in a receiving / storage system. The passage between the condenser and the receiving / storage system is advantageously at constant pressure due to gravity.

However, the circulation of the solvent between the receiving / storage system and the extractor requires pressurization or pressurization, for example according to one of the following three devices:

- thanks to a pump. The advantage of a mechanical pump is its reduced investment cost. The disadvantage is to introduce into the installation a mechanical member likely to fail and leaks, but this is a liquid solvent pump, more reliable than gas solvent compressors implemented in the art prior. However, and according to a preferred embodiment, the use of this pump is not implemented.

thanks to a flow of nitrogen or air if the solvent is not combustible. The reception / storage system is then advantageously provided with a device for pressurized gas.

thanks to a device for pressurizing the solvent by partial evaporation in a hot source. Concretely, the solvent storage is in charge over a heat exchanger used as an evaporator because fed by a hot fluid or electrically heated. The liquid solvent is brought into communication with the evaporator where it enters by gravity, then is heated to boiling and even until the desired pressure is obtained in the gas phase, advantageously measured using a probe. The gaseous solvent pipe is placed in communication with the sky of the liquid solvent storage, which is sufficient to raise the storage pressure to the pressure necessary for the introduction of the liquid solvent into the extractor. The pressurization by the solvent itself is advantageous with respect to the pressurization with an inert gas described above, in that it avoids introducing into the installation a foreign body that will have to be evacuated elsewhere. .

Whatever the nature of the gas used (nitrogen, air or solvent), it acts as a "growth gas" facilitating the circulation of solvent in liquid form in the device according to the invention.

In addition to this role, an evaporator disposed between the receiving / storage system and the extractor, advantageously in parallel with the liquid solvent introduction line, enables:

to ensure pinertage of the extractor as explained above; and

to improve the recovery rate of the solvent. Indeed, the solvent stored in liquid form in the receiving / storage system is converted into superheated gaseous solvent which is sent to the matrix present in the extractor and vaporizes the traces of solvent still present on this matrix. The corresponding step is advantageously carried out at the end of the extraction process described, before changing the matrix. It is important to recover almost all the solvent used to treat the matrix. Not only can the cost of the solvent be high, but it can also contribute to the destruction of the ozone layer and / or the greenhouse effect.

It may be the same evaporator device as used to pressurize the solvent storage, as described above, or a parallel device.

The present invention also relates to a device specially designed for the work of the described method, in particular without any gas compressor. DETAILED DESCRIPTION OF THE INVENTION

The invention and the advantages that result therefrom will emerge more clearly from the detailed description below, in support of the appended figure, which however has no limiting scope.

FIG. 1 represents a diagram of the principle at the origin of the present invention, involving at least one extractor, a separator, a condenser and a reception / storage system (tanks). The bold lines represent the principal closed-loop flow of the solvent. The solid and dashed lines represent secondary solvent flows, by drying or under vacuum, respectively.

According to the principle of the invention, a batch of matrix to be treated is introduced into an extraction device (1). The liquid solvent is introduced through a pipe into this extractor. It emerges from another pipe, still in liquid form but loaded with extracted solute. It is then introduced into a separation device (2). During or following the various separation phases, the extracted molecules are separated from the solvent and leave the separator by a pipe, in liquid or crystallized form. During this same operation, the gaseous solvent, pure or almost pure, is extracted from the separation device (2) by a pipe, condensed in a condenser (3) and stored liquid in a receiving / storage system (4), in a occurrence a first tank. Then, the liquid solvent is transferred to a second tank to be brought to a pressure sufficient to allow the solvent to be recycled through the return line for further introduction into the extraction device (1). Thus, as shown in bold in FIG. 1, the solvent, sometimes liquid and sometimes gaseous, circulates in a closed loop in the device according to the invention. The closed-circuit loop of the solvent advantageously does not include any mechanical pumping device, in particular of the gas compressor type. The solvent circulates in this loop only by the game of gravity, temperature differences, pressure differences and / or a shoot with a gas that can be the solvent itself or another gas.

The solvent used in the context of the invention may be a flammable product. The device according to the invention is therefore advantageously equipped with an inerting system (putting under inert gas), that is to say a system for circulating throughout the device, in particular tanks and conduits, a gas inert such as nitrogen (N ₂ ) for hunting in particular oxygen or any oxidizing gas, or even remnants of the solvent or water vapor. This is particularly useful in the extractor which will be described below. A device according to the invention for implementing the claimed method is as follows:

The raw material which can be of animal as well as plant origin, in solid form, is loaded into the extractor (1). The extractor is defined as a closed chamber in which the extraction of the molecules of interest takes place.

Advantageously, the material to be extracted is placed in the form of a layer resting on a grid, or a filter cloth, or more generally on any device intended to retain the solid matrix while permitting the flow (by gravity) of the solute. that is to say the solvent loaded with molecules extracted from the matrix.

It is in the extractor (1) that contact and extraction between solvent and material to be extracted. The contact between the solvent and the matrix may be carried out by spraying the solvent onto the matrix or by flooding the matrix in the solvent. In practice, the solvent is introduced into the liquid extractor, for example by means of an introduction pipe, a spray boom or any means for distributing the solvent on the matrix bed. Said extractor is under pressure, for example at a pressure of 3 bar, so that the gas (stored in a recovery / storage system 4, described below) which is injected into the reactor, advantageously butane, is under liquid form. The extractor is therefore advantageously equipped with a device for regulating the pressure. To promote extraction, it is possible to heat the enclosure, in particular by using a double-walled enclosure in which circulates a thermal fluid whose temperature is regulated by a device external to the extractor, or via a coil. Thus, the conditions of pressure and temperature in the extractor are perfectly controlled, and this to ensure the equilibrium state of the solvent: liquid, gas, or the limit of the liquid-gas equilibrium.

It is also possible to envisage active mixing between matrix and solvent, for example by stirring the matrix or mechanical mixing. In practice, the extractor can be completed by an agitator for stirring the bed of the matrix, or a stirrer with a device for raising and lowering. The solvent, passing through the matrix bed, charges solute, passes through the grid or the filter that holds the bed and is collected in the bottom of the device, and then discharged through a tubular bottom. For a semi-continuous operation, the solute is removed from the extractor as it flows. For discontinuous operation, the extraction pipe is for example closed by an isolation valve, closed during the extraction phase, opened after a residence time of the solvent in the extractor considered sufficient, when the solvent is sufficiently concentrated in solute and / or when the matrix has released enough molecules.

More generally, the extractor (1) is thus provided with a valve for recovering the solution, namely the liquid solvent loaded with solute. The solution in liquid form then flows to the separator (2) due to the difference in pressure or level. The separator (2) is advantageously at atmospheric pressure or at a positive pressure, less than or equal to the pressure of the extractor.

It should be noted that after complete gravity draining of the solution of the extractor (1), residual liquid solvent remains on the matrix, which can be dangerous during the subsequent opening of the extractor and what represents a loss of solvent that one seeks to recycle. It is then necessary to apply temperature and pressure conditions to evaporate the residual solvent, and desorb as much as possible the solvent adsorbed on the matrix. As will be detailed below, this can be achieved by means of a set of means such as a double envelope, a stirring device of the matrix, a temperature control device used in heating, a feed system. nitrogen, a hot gaseous solvent supply system, and an evaporation solvent system.

In the separator (2), the solvent and the extracted molecules are separated. This separation is carried out by distillation in the case where the recovered concentrated fraction (solute) is in liquid form, or by crystallization in the case where the latter is in solid form.

In practice, evaporation of the solvent takes place in the separator (2). This evaporation can be obtained by two mechanisms:

- by expansion, ie by reducing the pressure. As already said, this chamber is preferably at atmospheric pressure, namely about 0 bar, or at a positive pressure. Note, as explained below, that this pressure can, however, be reduced (for example up to about -0.5 bar) by drawing vacuum; and or

- by supply of energy. As for the extractor (1), the separator (2) can be heated, in particular thanks to the use of a double-walled enclosure in which circulates a thermal fluid whose temperature is regulated by a device external to the extractor , or via a coil.

Advantageously, the separator is also equipped with an agitator, in particular making it possible to homogenize the temperature of the solution and thus to improve the heat transfer.

Thus, the pressure and the temperature of the separator are controlled and regulated to ensure the different stages of the separation between solvent and solute. In practice, the solution (solvent + solute) is introduced into the separator via a pipe, located after a possible expansion valve. In this case, the relaxation of the solution when it enters the separator has the effect of vaporizing a part.

More generally, the pressure can be measured and regulated using different devices:

placing the separator in communication with a vent line for working at a pressure close to atmospheric pressure, or at a positive pressure;

- The communication of the separator with a vacuum group (5) to work under vacuum.

Commonly, the separator is called a boiler when the finished product is a liquid.

Thus, when the solute is recovered in liquid form, the three stages of the batch process for the separation solvent / solute occur as follows: l ^st step (optional): The solution enters the boiler through a pipe after expansion using a progressive valve. The liquid phase flows into the bottom of the boiler, while the solvent evaporated by the expansion is found in the boiler sky, possibly mixed with residual nitrogen inerting. The boiler sky is put in communication with a vent by the opening of a valve, through a condenser (3) for the recovery of the evaporated solvent. The condenser (3) is fed by a circulation of cold thermal fluid in order to condense the largest possible amount of gaseous solvent that escapes from the boiler. ^2nd step: When all of the solvent has passed from the extractor to the boiler, the communication valve between the two chambers is closed. The solvent is then brought to boiling by action of the heating group the thermal fluid of the double jacket of the separator and by the possible action of stirring. During this phase at a pressure close to atmospheric pressure, the boiler sky is in communication with the vents, the valve open, always through the condenser (3) to cut down the gaseous solvent.

^Step 3 (optional): At the end of evaporation of the solvent at atmospheric pressure or under slight pressure, the separation was carried out under at least partial vacuum, with an appropriate device such as a vacuum pump (5).

Of course, it is possible to stop evaporation during the second or third step above. However, the most thorough separation is obtained at the end of the third step, when the enclosure is under vacuum, at the minimum absolute pressure that allows the device and when the temperature in the boiler is equal to the maximum temperature tolerable by the product.

In the context of the invention, the maximum separation efficiency corresponds to a minimum content of residual solvent in the product obtained, and vice versa to a minimum content of solvent in solute.

At the end of the passage in the separator (2), the solvent freed of the solute is recovered and can be used for new extractions.

In practice, at the end of the separation phase, the solute in liquid form is removed from the boiler (2) by the opening of a bottom valve.

Alternatively, the extracted end product is a solid obtained by crystallization. In practice, the separating device between the solvent and the solute is a dryer filter or equivalent apparatus grouping the three stages of the separation phase.

The dryer filter is used in a similar way and in the same steps as the boiler described above:

- A first possible phase of relaxation of the solution in a valve, with injection into the dryer filter by a pipe;

a second phase at atmospheric pressure or at positive pressure by supplying either the frigories necessary for lowering the solubility of the solute in the solvent and thus for the crystallization of the solute, or the calories necessary for Evaporation of the solvent to increase the solute concentration to the solubility threshold. The working temperature is regulated by a temperature sensor of the fluid of the jacket operating by the group of thermal fluid. The sky of the dryer filter is connected to a vent after the condenser (3);

- A possible third phase under vacuum, always controlled temperature through the double envelope, the sky is gradually subjected to a depression increasingly high by action of a vacuum group (5). From the thermodynamic point of view, the successive phenomena implemented are a reduction of the solvent partial pressure in the sky of the apparatus, followed by the evaporation of the solvent in an attempt to regain equilibrium between phases, resulting in the concentration of the solute in the residual solvent. From the moment when the solubility threshold of the solute in the solvent is reached, the evaporation of the solvent is accompanied by a parallel crystallization of the solute, the concentration of the solute in the solvent being maintained at the limit of solubility.

The drying phase begins at the moment when the liquid phase has disappeared and only solvent molecules adsorbed on the powder remain. The solvent molecules are then progressively desorbed from the powder to tend to equilibrium sorption laws between the solid and the gas phase.

All these phases can be implemented in a single device, namely a dryer filter or an equivalent device. The temperature of the process is regulated by the circulation of thermal fluid in the double envelope of the separator, or even in a stirring machine. The pressure or the vacuum in this chamber is for example regulated by an absolute pressure sensor driving the solvent introduction valve, the vent valve or the vacuum valve. The agitation mobile responds to the need for homogenization of the solution and the powder in terms of concentration, temperature and dryness, then removal of the powder at the end of operation by pushing it to a drain hatch.

Alternatively, the separation device between the solvent and the solute is a crystallizer followed by a dryer. For some operations, it may be useful to interpose, between the two devices, a centrifuge. In the crystallizer, heated or cooled by its jacket connected to a group of thermal fluid are conducted the phases of solvent evaporation, solute concentration and crystallization. Then the powder obtained, more or less wet adsorbed solvent, is, through the opening of the drain valve, loaded into a dryer itself equipped with a double jacket supplied with fluid thermostatically controlled by a device. The technology chosen for the dryer depends on the quantities to be treated and the characteristics of the product. It can be a tray dryer, a bicone dryer, a fluid bed dryer or any other technology. The dryer is equipped with its own temperature control device to reach the temperature conducive to the desorption of the solvent.

Since the process is discontinuous, the product passes successively in the crystallizer and then in the dryer, possibly with an intermediate stage in a wringer. Then, the vapors from the crystallizer and the dryer are condensed in the condenser (3) before being rejected by the vent or aspirated by the vacuum pump (5). Only one of the two devices being used at a time, the condenser (3) can be common to both devices. For this purpose, the steam lines are equipped with isolation valves to select the line in operation. The next step of the process according to the invention is to put in liquid form, the solvent that leaves the separator in gaseous form. In practice, this step takes place in a chamber called condenser (3). This phase change of the solvent is essentially ensured thanks to a supply of constant temperature frigories. The device implemented at this stage contributes to the recycling of the solvent. As already mentioned, typically according to the invention, the solvent is recycled to be used in liquid form for the treatment of a next batch, and this advantageously without a mechanical device to set it in motion, in any case without compressor gas.

The condenser (3) is used downstream of one of the separation devices described above (2) and prepares the solvent for it to be introduced again into the extractor (1).

In practice, the solvent vapors from the boiler, the dryer filter, the crystallizer or the dryer are condensed in the condenser (3) fed by a circulation of cold thermal fluid.

The temperature of the thermal fluid in the condenser (3) is advantageously less than the boiling temperature of the solvent in the presence. It is therefore a question of controlling the temperature in the condenser, possibly using a refrigerating unit.

In a preferred manner, the condenser (3) is at atmospheric pressure or positive pressure, close to that of the separator (2). In practice, during the three successive stages of the separation phase, the solvent is condensed in the condenser (3) by the action of the circulation of a cold fluid, and then collected gravitarily liquid in a tank. At the outlet of the condenser (3), the purpose is to be able to store the reusable solvent in liquid form, advantageously in a receiving / storage system (4) or tank. In a preferred manner, the transfer of the liquid solvent from the condenser (3) to the receiving / storage system (4) is done by gravity. More specifically, the condensates from the condenser (3) are collected in the receiving / storage system (4). The condensed solvent flows directly from the condenser to the tank, these being at the same pressure, namely the atmospheric pressure or a positive pressure. Advantageously and as already mentioned, prior to the extraction and separation cycle, the entire installation is inerted with nitrogen or with an equivalent gas from upstream of the unit. This operation is intended to remove any oxidizer or water vapor in the installation, and to establish the necessary operating pressure. For this purpose, the line of vents from the condenser is advantageously equipped with a discharge valve providing this pressure upstream.

Advantageously, the receiving / storage system (4) consists of two tanks arranged in series or in parallel. The flow of the solvent is advantageously ensured by gravity. Generally speaking, in a device in series, the first tank is in the same conditions as the condenser, advantageously at atmospheric pressure. On the other hand, the second tank is advantageously placed at a higher pressure, in particular under pressure. This overpressure causes the flow of the liquid solvent to the extractor (1).

In a particular embodiment, the first tank corresponds to the tank described above and the second to a storage tank. The mass of liquid solvent is then transferred gravitarily from the tank to the storage tank, preferably by the opening of a valve and optionally the opening of another valve on a balancing line.

After the solvent has completely drained into the storage tank, the valves are closed and the installation is ready for a new batch. Indeed, this second tank allows the storage of the recycled solvent, suitable for use as a raw material to treat a new batch of matrix introduced into the extractor (1), or the same batch if it is not exhausted.

At the end of the previous batch, and only in the case where the evaporation and the condensation were operated at low temperature at a pressure relaxed with respect to the extraction, the solvent contained in the tank is stored liquid, at low temperature, at a pressure close to atmospheric pressure. If the interval between two batches is sufficiently long, the solvent has time to increase in temperature to ambient temperature, and the pressure in the tank is consequently raised to a pressure which may be sufficient for the solvent to be injected. in the extractor by passing through a flow control valve.

Alternatively and in the case where the pressure in the tank is insufficient to compensate for the pressure drops of the pipe, the valve and the injection device, the tank is pressurized with an inert gas such as nitrogen at a pressure controlled by a valve, or with the aid of a solvent evaporator (6 ') whose energy supplied to the primary is controlled by a pressure sensor.

Note that in this type of operation, it is necessary that the capacity of the tank at atmospheric pressure, and the tank both at atmospheric pressure and under pressure, are greater than the volume of liquid solvent needed to treat a batch.

In a variant of the device, the two tanks are mounted in parallel and used alternately, one at atmospheric pressure collecting the condensed solvent downstream of the process, the other under pressure supplying the extractor solvent. The control of the liquid levels in these tanks makes it possible to invert the role of the tanks when the upstream tank is exhausted. The mode of operation of this variant allows a continuous recycling of the solvent and reduces the capacity of the solvent tanks.

In the next step where the liquid solvent is rerouted to the extractor (1), this routing is provided again by pressurization with a carrier gas such as nitrogen, or with the aid of a solvent evaporator. (6 '). The described operation implies that the receiving / storage system (4), and in particular the two tanks, are equipped with a system for regulating the pressure or even the temperature. According to another variant of the device, with a single solvent storage tank (4), it is a mechanical pump which ensures the liquid solvent supply of the extractor (1).

Note that the solvent supply of the extractor (1) and the separator (2) can be carried out continuously, in which case the extraction and separation proceed in parallel. Alternatively, the extraction and separation steps are carried out successively.

It appears from the above that the proposed method is a sequential process for treating the raw material batch or batch.

The proposed method and the adapted device thus provide a closed-loop system, where the majority of the solvent (with losses) is reused. There is therefore no need to refill fresh solvent, unlike the prior art.

To further improve the recycling efficiency of the solvent, a particular embodiment can be envisaged:

Indeed, at the extractor (1) and at the end of the extraction, there remains the extracted matrix, wetted residual solvent to desorb. This has drawbacks, in particular solvent losses and a possible risk of explosion depending on the nature of the solvent used, or even a contribution to the destruction of the ozone layer and / or the greenhouse effect. The original idea according to the invention is to dry the extracted matrix, thanks to the solvent in the form of superheated steam. For this, the solvent present in liquid form in the receiving / storage system (4) is sent to an evaporator (6) where it is brought, thanks to a source of energy such as hot water, to a higher temperature. at its boiling point. The solvent in the form of superheated gas is then sent into the extractor (1) in contact with the matrix. Thanks to the energy supplied to the core of the matrix by the superheated gas, the "prisoner" solvent of the matrix is then evaporated and recovered in liquid form in the condenser (3). As previously described, the solvent thus recovered, which is in liquid form, can then be conveyed to the receiving / storage system (4) as described above.

Advantageously, the step of drying the matrix can be carried out simultaneously with one of the separation steps between solvent and solute. In particular, if necessary, the at least partial evacuation of the extractor (1) may be concomitant or simultaneous with the evacuation of the separator (2). In fact, the gaseous solvents emitted by the extractor and the separator are of the same nature and can be condensed in the same apparatus.

Moreover, and as already described, with regard to the traces of residual solvent present in the extractor (1) and / or the separator (2), it is possible to evacuate the corresponding enclosures by means of a vacuum pump ( 5) and / or a nitrogen sweep. The traces of solvent are again recovered at the condenser (3). As mentioned above, the evacuation at the extractor has another beneficial effect of further purifying the solute by eliminating contamination by the solvent.

Of course, the installation described can be completed by all sensors, actuators, safety and automation, necessary for the user to be informed of the process flow, control and be assured of perfect safety in all circumstances .

As it appears from the present description, the method and the device described are based solely on simple physical laws (pressure, temperature, gravity or gas) allowing the circulation of the solvent without the need for expensive or sophisticated equipment and constraining such as a gaseous solvent compressor, a potential source of pollution, leakage and breakdowns. The only mechanical devices that may be used are:

• a liquid solvent pump that can be an alternative solution to the double tank solvent system with gas pressurization or heating;

· A vacuum pump, the purpose of which is to perfect extraction and avoid solvent losses. Note that this organ carries only a small portion of the solvent involved for the extraction.

The markets are vast and numerous, as well in the pharmaceutical, cosmetic or food field. The method can thus be implemented on the so-called natural raw material, in particular plant or animal, to extract molecules of animal or plant origin of interest. This process can also be implemented to extract or dissolve a molecule obtained by synthesis. Indeed, in certain purification operations of a crystallized solid obtained by chemical synthesis, selective solvents are used. The pure liquefied gases or constituted by a mixture of alkanes, or even with additives, or a so-called refrigerant fluid can be used as a solvent to selectively resolubilize a particular molecule leaving a solid foreign body, the dissolved molecule being subsequently separated from its solvent by crystallization as described above. Solvents that can be used in the context of the present application must have a boiling point of advantageously between -35 ° C. and + 90 ° C. at atmospheric pressure (0 bar). The lower limit corresponding to the temperature that can be achieved with conventional refrigeration equipment type. The upper limit corresponds to the limit temperatures for the degradation of molecules of interest.

Among the liquefied gases of particular interest are alkanes or mixtures of alkanes and more specifically, butane. The use of Freon ™ or ethanol is also possible.

Claims

A method for extracting molecules from a solid matrix, carried out using a solvent having a boiling point at atmospheric pressure of between -35 ° C. and + 90 ° C., comprising the following steps: :

a step of bringing the solvent in liquid form into contact with the matrix in an extractor (1);

a separation step between the solvent in gaseous form and the extracted molecules (solute), in a separator (2);

a step of recovering the solvent in liquid form by condensation, in a condenser (3);

a step of reintroduction of the solvent into the extractor (1), via the passage in a reception / storage system (4),

wherein the solvent is recycled in a closed loop, the loop circulation of the solvent does not involve mechanical pumping of the gaseous solvent, for example by means of a gas compressor.

2. Extraction process according to claim 1 characterized in that the loop circulation of the solvent is only provided by at least one of the following mechanisms:

• pressure difference;

• temperature difference ;

• gravity; and

• pushed by a gas.

3. Extraction process according to claim 1 or 2 characterized in that the solvent is an alkane, preferably butane, optionally enriched with additives.

4. Extraction process according to claim 1 or 2 characterized in that the solvent is a refrigerant.

5. Extraction process according to one of the preceding claims characterized in that the circulation of the solvent between the extractor (1) and the separator (2) is essentially provided by pressure difference.

6. Extraction process according to one of the preceding claims, characterized in that the separation between the solvent and the extracted molecules (solute) is carried out by distillation or crystallization.

7. Extraction process according to one of the preceding claims characterized in that in the separation step, the solvent passes gaseous form by boiling, and optionally by expansion.

8. Extraction process according to one of the preceding claims characterized in that the circulation of the solvent between the separator (2) and the condenser (3) is ensured by lowering temperature, without the aid of a mechanical member such than a gas compressor.

9. Extraction process according to one of the preceding claims characterized in that in the condensation step, the solvent passes in liquid form by cooling.

10. Extraction process according to one of the preceding claims characterized in that the circulation of the solvent between the condenser (3) and the receiving / storage system (4) is provided by gravity at constant pressure.

11. Extraction process according to one of the preceding claims characterized in that the circulation of the solvent between the receiving / storage system (4) and the extractor (1) is provided by thrust by a gas.

12. Extraction process according to claim 11 characterized in that the gas used for the thrust is solvent of the same kind as the solvent used for extraction, pressurized by passage through an evaporator (6 ').

13. Device adapted to the implementation of a method according to one of claims 1 to 12 comprising at least:

an extractor (1);

- a separator (2);

a condenser (3);

- a reception / storage system (4);

a closed loop allowing the circulation of the solvent in liquid or gaseous form in the absence of a pumping member for the gaseous solvent.

14. Device according to claim 13 characterized in that the closed mouth allows the circulation of the solvent in liquid or gaseous form only by at least one of the following mechanisms:

• pressure difference;

• temperature difference ;

• gravity; and

• pushed by a gas.

15. Device according to claim 13 or 14 characterized in that:

the extractor (1) is equipped at least with a device for regulating the pressure; and or

the separator (2) is equipped at least with a heating device; and or

the condenser (3) is equipped at least with a cooling device; and or

- The receiving / storage system (4) is equipped with at least one pressurizing device.

16. Device according to one of claims 13 to 15 characterized in that the extractor (1) and the separator (2) are located in the same enclosure.

17. Device according to one of claims 13 to 16 characterized in that an at least partial evacuation system (5) is disposed between the extractor (1) and / or the separator (2) on the one hand , and the condenser (3) on the other hand.

18. Device according to one of claims 13 to 17 characterized in that an evaporator (6 ', 6) is disposed at the receiving / storage system (4) or between the latter and the extractor (1) .

19. Device according to one of claims 13 to 18 characterized in that it is connected to a device for putting under inert gas, such as nitrogen.

20. Use of the method according to one of claims 1 to 12 or the device according to one of claims 13 to 19 for extracting molecules of an animal or plant material or for purifying a chemical synthesis product.