EP0246956B1 - Process for the elimination of asphaltenes from a hydrocarbon feedstock - Google Patents

Description

The present invention relates to a process for deasphalting a heavy hydrocarbon feed.

By heavy hydrocarbon filler is meant, within the meaning of the present invention, a filler having a density at 15 _° C greater than about 930 kg / m ³ , composed essentially of hydrocarbons, but also containing other chemical compounds which, in addition to carbon and hydrogen atoms, have heteroatoms such as oxygen, nitrogen, sulfur and metals such as vanadium or nickel.

This charge can be constituted, in particular, by a crude oil or a heavy oil having the density indicated above.

The feedstock can also come from the fractionation or processing of crude oil, heavy oil, oil shale or even coal. It may thus be the residue from the distillation under reduced pressure or the residue from the distillation at atmospheric pressure of the starting materials mentioned above or, for example, the products obtained by the heat treatment of these starting materials or their distillation residues.

A trend has appeared in recent years, to seek to develop more and more hydrocarbon products with a high density, which was not the case before. This quest for the valuation of heavy products has become more pressing, since it is expected that the demand for light products such as fuels should increase relatively faster than that of heavier products, such as fuel oils.

The heaviest part of the heavy hydrocarbon charges consists of a mixture of an oily phase and an asphaltic phase. One way to obtain light products from the oily phase is to subject it to catalytic cracking. The catalytic cracking charge must not, however, be excessively polluted by metals and must not have an excessively high "Conradson" residue. It may be recalled that the "Conradson" residue, which gives indications on the tendency of a product to form coke, is determined according to the AFNOR NFT 60-116 standard.

As stated above, heavy hydrocarbon feedstocks contain compounds having, in addition to hydrogen and carbon atoms, heteroatoms such as oxygen, nitrogen, sulfur and metals. Some of these compounds, especially those having metals, are contained in particular in the asphalt phase.

We are used to distinguishing two families in the compounds constituting the asphalt phase: resins and asphaltenes. Asphaltenes like resins have polycyclic aromatic structures. Next to the aromatic rings are thiophenic and pyridine rings. But resins have less condensed structures than asphaltenes and lower molecular weights.

The compounds which precipitate by addition to the charge of a saturated aliphatic hydrocarbon having from 5 to 7 carbon atoms are generally designated under the name of asphaltenes: pentane, hexane, heptane. Thus, according to AFNOR standard NFT 60-115, the asphaltene content of a product is determined by precipitation using normal heptane at boiling point.

Resins precipitate at the same time as asphaltenes, when using a hydrocarbon with a lower boiling point, for example propane. In fact, this distinction is conventional and it is obvious that, if a given solvent is used at a given temperature to treat a charge, it will be possible, if the solvent and the temperature are suitable, to obtain the precipitation of asphaltene-type compounds . If the charge freed from asphaltenes is then treated with the same solvent at a higher temperature, precipitation of the resins can be obtained.

• - les hydrocarbures aliphatiques, saturés ou non saturés, ayant de 2 à 8 atomes de carbone, seuls ou en mélange,
• - les mélanges d'hydrocarbures, appelés distillats, ayant des poids moléculaires voisins de ceux des hydrocarbures ayant de 2 à 8 atomes de carbone,
• - les mélanges de tous les hydrocarbures précédemment cités.

In the well-known deasphalting process, the oily phase and the asphaltic phase are separated by the operation which consists in extracting the oily phase from the residue using a solvent. This solvent can be chosen from the group consisting of:

• - aliphatic hydrocarbons, saturated or unsaturated, having 2 to 8 carbon atoms, alone or as a mixture,
• - mixtures of hydrocarbons, called distillates, having molecular weights close to those of hydrocarbons having from 2 to 8 carbon atoms,
• - mixtures of all the previously mentioned hydrocarbons.

The deasphalting can be carried out in a single step, obtaining, in this case, an oily phase and an asphaltic phase, the latter containing both the asphaltenes and the resins. It can also be carried out in two stages, with the use of two different solvents and / or different operating conditions in the two stages (see, for example, US Pat _. Nos _. 3,830,732 and 2,940,920). The oily phase, the resins and the asphaltenes are obtained separately, in this two-step process.

US Patent No. 3,830,732 thus describes a process using two solvents, propane and pentane, which requires two completely separate solvent recovery units and, therefore, a significant investment.

In the process with a single solvent (see US Patent No. 2,940,920, for example), it is necessary and difficult to very precisely adjust the operating conditions of the two stages in order to obtain the products of desired qualities. It is even sometimes impossible, with this process, to obtain both an oily phase suitable as a catalytic cracking charge and a very hard pitch which can be ground and used as solid fuel.

Also known from FR-A 2 007 587 is a process for deasphalting a heavy hydrocarbon feed, which uses two solvents in two stages. In the first stage, the residual oil is separated into asphaltenes and into deasphaltenized oil using as solvent a hydrocarbon comprising from 5 to 10 carbon atoms. In the second step, the deasphalted oil is separated into resins and into deasphaltened oil and freed from the resins using as solvent one or more hydrocarbons, comprising less than 5 carbon atoms, for example propane, and mixtures thereof with aliphatic hydrocarbons comprising from 5 to 10 carbon atoms.

• - relativement peu différents, ce qui permet de n'employer, au moins dans une forme de mise en oeuvre, qu'une seule installation de séparation de solvant,
• - suffisamment différents, pour obtenir à la fois: une phase huileuse "propre" d'une qualité parfaitement convenable pour être utilisée comme charge de craquage catalytique, sans traitement complémentaire à l'hydrogène,
• - et une fraction asphaltènes, qui, à température ambiante, est suffisamment solide pour être broyée et utilisée comme combustible solide.

The Applicant has designed a two-step deasphalting process, using, during the two steps, solvents at the same time:

• - relatively little different, which makes it possible to use, at least in one form of implementation, only one solvent separation installation,
• - sufficiently different, to obtain both: a "clean" oily phase of a quality perfectly suitable for use as a catalytic cracking charge, without additional treatment with hydrogen,
• - And an asphaltenes fraction, which, at room temperature, is sufficiently solid to be ground and used as solid fuel.

Therefore, the asphaltenes fraction does not require an additional expense of flux to be used liquid.

The object of the present invention is therefore the preparation, in particular from a heavy hydrocarbon feedstock, of a product suitable as feedstock for a catalytic cracking.

• - d'une phase huileuse désasphaltée ayant un indice "Conradson" égal ou inférieur à 10,
• - d'une fraction "résines",
• - d'une fraction "asphaltènes" ayant son point de ramollissement égal ou supérieur à 150_°C, ledit procédé comportant deux étapes de précipitation, à partir de la charge, d'une part, de la fraction "asphaltènes" seule, d'autre part, de la fraction "résines", éventuellement en compagnie de la fraction "asphaltènes", à l'aide, respectivement, d'un solvant lourd et d'un solvant léger, ledit procédé étant caractérisé en ce que le solvant lourd contient de 5 à 40% en volume d'un hydrocarbure à 3 atomes de carbone et 60 à 95% d'au moins un hydrocarbure à 5 atomes de carbone et le solvant léger contient de 20 à 80% en volume d'un hydrocarbure à 3 atomes de carbone et de 20 à 80% en volume d'au moins un hydrocarbure à au moins 5 atomes de carbone, la proportion de l'hydrocarbure comprenant 3 atomes de carbone étant plus élevée dans le solvant léger que dans le solvant lourd.

To this end, the subject of the invention is a process for deasphalting a heavy hydrocarbon feed, said process leading to the obtaining:

• - a deasphalted oily phase having a "Conradson" index equal to or less than 10,
• - a "resin" fraction,
• - an "asphaltenes" fraction having its softening point equal to or greater than 150 _° C., said process comprising two stages of precipitation, starting from the charge, on the one hand, of the "asphaltenes" fraction alone, on the other hand, from the "resins" fraction, optionally in the company of the "asphaltenes" fraction, using respectively a heavy solvent and a light solvent, said process being characterized in that the heavy solvent contains from 5 to 40% by volume of a hydrocarbon with 3 carbon atoms and 60 to 95% of at least one hydrocarbon with 5 carbon atoms and the light solvent contains from 20 to 80% by volume of a hydrocarbon with 3 carbon atoms and from 20 to 80% by volume of at least one hydrocarbon with at least 5 carbon atoms, the proportion of the hydrocarbon comprising 3 carbon atoms being higher in the light solvent than in the heavy solvent.

• 1. phase huileuse, une phase de. laquelle a été éliminée pratiquement toute la phase asphaltique, c'est-à-dire la phase qui précipite par addition d'un solvant léger tel que défini dans l'objet de l'invention; cette phase huileuse a un résidu "Conradson" inférieur ou égal à 10 (mesuré selon la norme AFNOR NFT 60-116);
• 2. fraction "résines" et fraction "asphaltènes": les fractions respectivement la plus légère et la plus lourde de la phase asphaltique, la frontière entre ces deux fractions, au sens de l'invention, étant définie par le fait que la fraction "asphaltènes" doit avoir un point de ramollissement égal ou supérieur à 150_°C (mesuré selon la norme AFNOR NFT 66-008).

In this object of the invention and in the remainder of this description, taking into account the fact that the separation from the chemical point of view between the oily phase, the "resins" and the "asphaltenes", cannot be precisely defined , we hear by:

• 1. oily phase, a phase of. which has been eliminated practically all of the asphaltic phase, that is to say the phase which precipitates by adding a light solvent as defined in the subject of the invention; this oily phase has a "Conradson" residue less than or equal to 10 (measured according to standard AFNOR NFT 60-116);
• 2. "resins" fraction and "asphaltenes" fraction: the lightest and heaviest fractions respectively of the asphaltic phase, the border between these two fractions, within the meaning of the invention, being defined by the fact that the fraction " asphaltenes "must have a softening point equal to or greater than 150 _° C (measured according to standard AFNOR NFT 66-008).

• - le solvant lourd est apte à faire précipiter la fraction "asphaltènes", mais solubilise la fraction "résines" et, a fortiori, la phase huileuse,
• - le solvant léger est apte à faire précipiter la fraction "résines" et donc, bien sûr, la fraction "asphaltènes", mais solubilise la fraction huileuse.

In the process according to the invention, two solvents are used, a light solvent and a heavy solvent, which contain the same chemical compounds, but in different proportions, which explains their different functions:

• the heavy solvent is capable of causing the "asphaltenes" fraction to precipitate, but dissolves the "resins" fraction and, a fortiori, the oily phase,
• - The light solvent is able to precipitate the "resins" fraction and therefore, of course, the "asphaltenes" fraction, but dissolves the oily fraction.

• - au moins un hydrocarbure comprenant 3 atomes de carbone : propane et/ou propène,
• - au moins un hydrocarbure comprenant au moins 5 atomes de carbone, aliphatique saturé ou oléfinique (dont, notamment, le pentane, le pentène, l'hexane, l'hexène, l'heptane, l'heptène).

The two solvents contain:

• - at least one hydrocarbon comprising 3 carbon atoms: propane and / or propene,
• - at least one hydrocarbon comprising at least 5 carbon atoms, saturated aliphatic or olefinic (including, in particular, pentane, pentene, hexane, hexene, heptane, heptene).

The process is therefore characterized by a search for selectivity, which leads to the combination of two solvents containing little or no hydrocarbons with 4 carbon atoms, so as to vary the selectivity according to the stage at which one takes place. .

Solvents can consist of a single hydrocarbon, or a mixture of hydrocarbons; thus, the heavy solvent can consist of a mixture of pentane and hexane for example.

It is understood that, in this definition and in the rest of the present description, when a hydrocarbon, pentane for example, is cited, it may be either a well-defined hydrocarbon, such as normal pentane, or also, and this is practically always the case industrially, of a mixture of isomers of this hydrocarbon, such as, in the case of pentane, normal pentane and isopentane, essentially.

The light solvent contains a higher proportion than the heavy hydrocarbon solvent comprising 3 carbon atoms.

The method according to the invention can be implemented in two different ways.

In the first embodiment of the method according to the invention, the first step is the step of separation of the "asphaltenes" fraction using the heavy solvent.

• - d'une part, la fraction "asphaltènes" contenant un peu de solvant qui est éliminé ultérieurement,
• - d'autre part, en solution dans le solvant lourd, la fraction "résines" et la phase huileuse.

At the end of this step, we collect:

• on the one hand, the "asphaltenes" fraction containing a little solvent which is subsequently removed,
• - on the other hand, in solution in the heavy solvent, the fraction "resins" and the oily phase.

The "resins" fraction is then precipitated using a light solvent.

• - d'une part, la fraction résines contenant un peu de solvant, qui est éliminé ultérieurement,
• - d'autre part, la phase huileuse en solution dans le solvant léger.

To obtain this light solvent, in a particular embodiment, a heavy solvent is added to the mixture of the heavy solvent, the resin fraction and the oily phase, in a second stage which is the stage of separation of the resins. as the light solvent, the latter thus resulting from the combination of the heavy solvent and said third solvent. At the end of this step, we collect:

• on the one hand, the resin fraction containing a little solvent, which is subsequently removed,
• - on the other hand, the oily phase in solution in the light solvent.

• - ledit troisième solvant, qui est recyclé à la deuxième étape,
• - une solution de la phase huileuse dans le solvant lourd, dont elle est séparée de façon classique, le solvant lourd étant recyclé à la première étape.

This solution is then subjected to a treatment, which makes it possible to obtain:

• - said third solvent, which is recycled in the second step,
• - A solution of the oily phase in the heavy solvent, from which it is separated in a conventional manner, the heavy solvent being recycled in the first step.

The treatment of the solution of the oily phase in the light solvent can in particular consist of heating said solution, preferably vaporizing the hydrocarbon comprising 3 carbon atoms.

The heating can be replaced by an expansion under reduced pressure of said solution.

In the first step of this first embodiment of the method according to the invention, the heavy solvent may preferably contain from 10 to 40% by volume of hydrocarbon with 3 carbon atoms and from 60 to 90% by volume d '' at least one hydrocarbon with at least 5 carbon atoms, and, better still, from 15 to 35% by volume of hydrocarbon with 3 carbon atoms and from 65 to 85% by volume of at least one hydrocarbon with at least 5 carbon atoms.

In the second step of this first embodiment of the process according to the invention, the light solvent may preferably contain from 20 to 80% by volume of hydrocarbon with 3 carbon atoms and from 20 to 80% by volume. volume of at least one hydrocarbon with at least 5 carbon atoms and, better still, from 25 to 75% by volume of hydrocarbon with 3 carbon atoms and from 25 to 75% by volume of at least one hydrocarbon with at minus 5 carbon atoms.

• - d'un part, un mélange des fractions "résines" et "asphaltènes",
• - d'autre part, la phase huileuse en solution dans le solvant léger, dont elle est séparée ultérieurement.

In the second embodiment of the method according to the invention, the first step is a step of simultaneous precipitation of the "resin" and "asphaltene" fractions using the light solvent obtained by combining, during this step, the heavy solvent and a third solvent lighter than the desired light solvent. At the end of this first step, we obtain:

• - on the one hand, a mixture of the "resins" and "asphaltenes" fractions,
• - on the other hand, the oily phase in solution in the light solvent, from which it is separated later.

• - d'une part, la fraction "asphaltènes" contenant un peu de solvant, qui est éliminé ultérieurement,
• - d'autre part, la fraction "résines" en solution dans le solvant lourd, dont elle est séparée ultérieurement.

In a second step, "solvent" and "asphaltene" fractions are added to the mixture of heavy solvent which dissolves the "resin" fraction. At the end of this second step, we obtain:

• - on the one hand, the "asphaltenes" fraction containing a little solvent, which is subsequently removed,
• - on the other hand, the fraction "resins" in solution in the heavy solvent, from which it is separated later.

In the first step of this second embodiment of the process according to the invention, the light solvent may preferably contain from 20 to 80% by volume of hydrocarbon with 3 carbon atoms and from 20 to 80% by volume. volume of at least one hydrocarbon with at least 5 carbon atoms and, better still, from 30 to 70% by volume of at least one hydrocarbon with 3 carbon atoms and from 30 to 70% by volume of at least one hydrocarbon with at least 5 carbon atoms.

In the second step of this second embodiment of the method according to the invention, the heavy solvent may preferably contain from 5 to 30% by volume of hydrocarbon with 3 carbon atoms and from 70 to 95% by volume d '' at least one hydrocarbon with at least 5 carbon atoms and, better still, from 10 to 25% by volume of hydrocarbon with 3 carbon atoms and 75 to 90% by volume of at least one hydrocarbon with at least 5 atoms of carbon.

• - pression comprise entre 20.10⁵ et 1.10⁷ pascals absolus,
• - température comprise entre 100 et 300_°C,
  
  entre 1 et 10.

The operating conditions, in the deasphalting stages, can be as follows:

• - pressure between 20.10 ⁵ and 1.10 ⁷ absolute pascals,
• - temperature between 100 and 300 _° C,
  
  between 1 and 10.

• - la nature de la charge,
• - la nature des solvants utilisés.

These conditions vary, of course, in particular according to:

• - the nature of the load,
• - the nature of the solvents used.

The invention will be better understood on reading the detailed description which follows, with reference to the accompanying drawings, which are not limiting.

• Les figures 1 et 2 sont des schémas de deux unités mettant en oeuvre, respectivement, le premier mode et le second mode de réalisation du procédé selon l'invention.
• La figure 3 illustre une variante de mise en oeuvre du procédé de la figure 1.

In these drawings:

• Figures 1 and 2 are diagrams of two units implementing, respectively, the first mode and the second embodiment of the method according to the invention.
• FIG. 3 illustrates an alternative implementation of the method of FIG. 1.

With reference to FIG. 1, which represents a unit implementing the first embodiment of the method according to the invention, the hydrocarbon charge is introduced via line 1, into the upper part of a first extraction tower 2 heavy to deasphalt. A heavy solvent, the source of which will be explained later, is also introduced into the bottom of tower 2, via line 3.

The same heavy solvent can also be added to the feed in line 1, by a line not shown.

The heavy solvent of line 3 and the operating conditions of tower 2 are chosen so that only the "asphaltenes" fraction of feed 1 whose softening point is greater than or equal to 150 _° C. precipitates in said tower.

peut être compris entre 1 et 10, sans que ces valeurs puissent être considérées comme des limites.The pressure inside tower 2 can be between 20.105 and 1.10 ⁷ absolute pascals, the temperature between 100 and 200 ° C, and the mass rate

can be between 1 and 10, without these values being considered as limits.

By way of example, for a heavy solvent C ₃ -20 / C ₅ -80, that is to say containing 20% by volume of propane and 80% by volume of pentane, the pressure may be approximately 40.10 ⁵ absolute pascals, the temperatures at the bottom and at the top of tower 2 being respectively approximately 100 and 140 _° C., the mass ratio of heavy solvent on charge being approximately 2/1.

The "asphaltenes" fraction containing a little heavy solvent is collected at the bottom of tower 2, by line 4.

The charge is collected at the top of tower 2, via line 5, freed from the "asphaltenes" fraction, in solution in most of the heavy solvent introduced into tower 2.

The fraction collected by line 4 is conducted, after passing through at least one heater 6, in an expansion tower 7 operating, in the case of a heavy solvent C ₃ -20 / C ₅ -80, at a temperature of approximately 300 _° C and a pressure of approximately 5.105 absolute pascals. Heavy solvent is collected at the top of the tower 7, by the line 8, which, after passage through a coolant 9, is led into a flask 10.

The balloon 10 serves as storage for the heavy solvent. In the case of a heavy solvent C ₃ -20 / C ₅ -80, the temperature in the flask 10 is approximately 60 ° C and the pressure approximately 5.10 ⁵ absolute pascals.

The “asphaltenes” fraction is collected in the bottom of tower 7, by line 11, which is conducted in a tower 12, operating, in the case of a heavy solvent C ₃ -20 / C ₅ -80, at a temperature of about 300 ° C and a pressure of about 0.5.10 ⁵ pascals absolute.

The “asphaltenes” fraction, freed from the heavy solvent, is collected at the bottom of tower 12, via line 13. This fraction can be used as solid fuel after grinding.

Solvent is collected at the top of tower 12, via line 19, which is led into a condenser 14.

• - par la ligne 15, de l'eau qui est évacuée (la provenance de cette eau est expliquée plus loin),
• - et, dans le cas d'un solvant lourd C₃-20/C₅-80, par la ligne 16, le ou les hydrocarbures à au moins 5 atomes de carbone, qui est (ou sont) conduit(s) au ballon 10 et, par la ligne 17, l'hydrocarbure à 3 atomes de carbone qui, après passage dans un compresseur 18, est conduit dans la ligne 8 et donc au ballon 10.

We collect, at the outlet of the condenser 14:

• - by line 15, water which is discharged (the source of this water is explained below),
• - and, in the case of a heavy solvent C ₃ -20 / C ₅ -80, via line 16, the hydrocarbon (s) with at least 5 carbon atoms, which is (or are) conducted (s) in the balloon 10 and, via line 17, the hydrocarbon with 3 carbon atoms which, after passing through a compressor 18, is led into line 8 and therefore to balloon 10.

The mixture of heavy solvent and filler freed from the "asphaltenes" fraction collected by line 5 is carried out in a second extraction tower 20. A third solvent is introduced into this tower, via line 21, so that , in tower 20, the extraction is carried out in fact using a light solvent, resulting from the combination of the heavy solvent and the third solvent and whose proportion of hydrocarbon with 3 carbon atoms is higher than that of the heavy solvent.

Thus, in the case of a heavy solvent C ₃ -20 / C ₅ -80, the third solvent can be a solvent C ₃ -40 / C ₅ -60, that is to say containing 40% by volume of propane and 60% by volume of pentane, the light solvent then being a solvent C ₃ -30 / C ₅ -70, containing 30% by volume of propane and 70% by volume of pentane.

The operating conditions inside tower 20 are such that the "resin" fraction precipitates.

étant compris entre 1 et 10, sans que ces valeurs puissent être considérées comme limites.The pressure inside tower 20 can be between 20.10 ⁵ and 1.107 absolute pascals, the temperature between 100 and 300 _° C, the mass rate

being between 1 and 10, without these values being considered as limits.

étant environ de 4/1.For example, for a light solvent Ca-30 / Cs-70, the pressure can be approximately 40 × 10 ⁵ absolute pascals, the temperatures at the bottom and at the top of tower 20 being approximately, respectively, 110 and 150 ° C, the mass rate

being about 4/1.

Is collected at the top of tower 20, through line 22, a mixture of deasphalted oily phase and light solvent.

The "resins" fraction containing a little light solvent is collected at the bottom of tower 20, through line 28.

The mixture of deasphalted oily phase and of light solvent collected by line 22 is led, after passage through a heater 23, in an expansion tower 24 operating, in the case of a light solvent C ₃ -30 / C ₅ -70 , at a pressure of about 25.105 absolute pascals and a temperature of about 150 _° C. As a result of the passage through the heater 23, part of the solvent is vaporized. The hydrocarbon with 3 carbon atoms is preferably so. A third solvent enriched in hydrocarbon with 3 carbon atoms is therefore collected at the top of tower 24, via line 25. In the case of a light solvent C ₃ -30 / C ₅ -70, a third solvent C ₃ -40 / C ₅ -60 is thus obtained.

The installation of trays inside this tower improves, if necessary, the separation.

The third solvent collected by line 25 is led, after passage through a cooler 26, into a storage flask 27. In the case of a third solvent C ₃ -40 / C ₅ -60, the temperature inside the tank 27 is around 110 _° C and the pressure around 25 bar.

The third solvent is then recycled via line 21 to tower 20.

Is collected at the bottom of the tower 24, through line 29, a mixture of deasphalted oil and heavy solvent, which, after passing through an expansion valve 30, where its pressure and temperature are lowered (in the case of a heavy solvent C ₃ -20 / C _s -80 at, respectively, about 5 × 10 5 absolute pascals and 100 ° C.), and passage through a heater 31, is led into an expansion tower 32, operating, in the case of a heavy solvent C ₃ -20 / C ₅ -80, at a pressure of approximately 5.10 ⁵ absolute pascals and a temperature of approximately 130 _° C.

The major part of the heavy solvent is collected at the top of the tower 32, via the line 33, which, after passing through a condenser 34, is led to the flask 10.

The flask 10 is connected by line 35 to line 3 and the heavy solvent can therefore be recycled to tower 2.

The deasphalted oily phase containing a small amount of solvent is collected at the bottom of the tower 32, via line 36, which, after passing through a heater 37, is conducted in a steam tower 38, where water vapor is introduced via line 39.

In the case of a heavy solvent C ₃ -20 / C ₅ -80, this tower operates at a pressure of approximately 1.5 × 10 ⁵ absolute pascals and a temperature of approximately 250 _° C.

The deasphalted oil is collected at the bottom of the tower 38, by the line 41, and, at the top of the said tower, by the line 40, water and solvent, which are led to the condenser 14.

The "resins" fraction containing a little light solvent, collected by line 28 at the bottom of tower 20, is conducted, after passing through a heater 50, in an expansion tower 51 operating, in the case of a light solvent C ₃ -30 / C ₅ -70, at a pressure of approximately 5,105 absolute pascals and at a temperature of approximately 280 _° C.

A little light solvent is collected at the top of tower 51, via line 52, which is taken to line 8.

Is collected at the bottom of tower 51, through line 53, the fraction "resins" still containing a little solvent, which is conducted in a steam tower 54, where steam water is introduced via line 55.

Is collected at the bottom of tower 54, through line 57, the fraction "resins" which can be used as an oil base, be incorporated into bitumens, or even constitute an excellent load of visbreaker.

Water and solvent are collected at the top of the tower 54, via line 56, which are led to the condenser 14.

It can be noted that, if heavy solvent is introduced into the flask 10 via line 33, light solvent is also introduced from lines 52 and 56. However, it is the whole which is recycled as heavy solvent. In fact, the quantity of light solvent relative to the heavy solvent is very small and it suffices to add a little hydrocarbon having at least 5 carbon atoms to the flask 10 to obtain a heavy solvent of correct composition.

Of course, in the units shown in FIG. 1, as well as in FIGS. 2 and 3 which will be described below, additions of solvents, not shown, are provided to compensate for the losses of solvent.

With reference to FIG. 2, which represents a unit implementing the second embodiment of the method according to the invention, the hydrocarbon charge is introduced via line 101, into the upper part of a first extraction tower 102 heavy to deasphalt. A light solvent is also introduced into the bottom of tower 102, via line 103, the source of which will be explained below. The "resins" and "asphaltenes" fractions precipitate.

The light solvent can be, for example, a solvent C ₃ -60 / C _s -40, containing 60% by volume of propane and 40% by volume of pentane.

peut être compris entre 1 et 10, sans que ces valeurs puissent être considérées comme des limites.The pressure inside tower 102 can be between 20.105 and 1.107 absolute pascals, the temperature between 100 and 300 _° C, the mass rate

can be between 1 and 10, without these values being considered as limits.

For example, for a light solvent C ₃ -60 / C ₅ -40, the pressure may be approximately 40 × 10 ⁵ absolute pascals, the temperatures at the bottom and at the top of the tower 102 being approximately, respectively, of 100 and 130 _° C, the mass rate

being about 2/1.

The entire asphalt phase containing the "asphaltenes" and "resins" fractions and a little light solvent are collected at the bottom of tower 102, via line 105. To this mixture is added via line 106, a solvent whose source will be explained later. This solvent contains few hydrocarbons with 3 carbon atoms. This new mixture is conducted by line 107, after passing through a heater 108, in a second extraction tower 109, where the extraction is carried out in the presence of a heavy solvent, by mixing the solvents of lines 105 and 106 .

The solvent and the operating conditions of tower 109 are chosen so that only the "asphaltenes" fraction of line 105 whose softening point is greater than or equal to 150 ° C. precipitates in said tower.

If the light solvent is a solvent C ₃ -60 / C ₅ -40, the heavy solvent can be a solvent C ₃ -20 / C ₅ -80, the solvent of line 106 being a solvent C ₃ -10 / C ₅ -90.

peut être compris entre 1 et 10, sans que ces valeurs puissent être considérées comme des limites.The pressure inside tower 109 can be between 20.105 and 1.105 absolute pascals, the temperature between 100 and 200 _° C, the mass rate

can be between 1 and 10, without these values being considered as limits.

For example, for a heavy solvent C ₃ -20 / C ₅ -80, the pressure can be around 40 × 10 5 absolute pascals, the temperatures at the bottom and at the top of the tower 109 being respectively about 100 and 140 _° C, the heavy solvent mass ratio on charge of tower 102 being approximately 2/1.

The "asphaltenes" fraction containing a little heavy solvent is collected at the bottom of tower 109, via line 110.

The processing of this fraction is identical to that of the unit in FIG. 1. It will not be described, for the purpose of simplification. This part of the unit, identical to that of FIG. 1, has been represented in the same way, the reference numbers of the equipment being assigned the index '.

Is collected at the top of tower 109, by line 111, a mixture of fraction "resins" and heavy solvent.

The mixture of "resins" fraction and of heavy solvent collected by line 111 is led, after passage through a heater 112, in an expansion tower 113 operating, in the case of a heavy solvent C ₃ -20 / Cs-80 , at a pressure of approximately 25.10 ⁵ absolute pascals and at a temperature of approximately 150 ° C. Following the passage through the heater 112, part of the solvent is vaporized. The hydrocarbon with 3 carbon atoms is preferably so. Therefore, at the top of tower 113, by line 114, light solvent C ₃ -60 / C ₅ -40 is collected, which is recycled to line 103, after passage through a condenser 115, to reconstitute the solvent. slight drag in line 105.

The establishment of trays inside this tower 113 improves, if necessary, the separation.

Is collected at the bottom of tower 113, by line 116, a mixture of "resins" and a heavier solvent than the heavy solvent, which, after passing through an expansion valve 117, where its pressure and temperature are lowered, in the case of a solvent C ₃ -10 / Cs-90, to respectively approximately 5,105 pascals absolute and 120 _° C, and passage through a heater 118, is conducted in a flash tower 119, operating, in the case of a solvent Cs-10 / Cs-90, at a pressure of approximately 5.105 absolute pascals and a temperature of approximately 140 _° C.

The major part of the solvent is collected at the top of the tower 119, via the line 120, which, after passing through a condenser 121, is led to the flask 122.

The flask 122 is connected by line 123 to line 106 and the solvent can therefore be recycled.

Is collected at the bottom of tower 119, through line 124, the phase "resins" still containing a little solvent, which, after passing through a heater 125, is conducted in a steam tower 126 , where water vapor is introduced via line 127.

In the case of a solvent C ₃ -10 / C ₅ -90, this tower operates at a pressure of approximately 1.5 × 10 5 absolute pascals and a temperature of approximately 280 _° C.

The "resins" are collected at the bottom of the tower 126, by the line 128, and at the top of the said tower, by the line 129, water and solvent, which are led to the condenser 14 '.

A mixture of deasphalted oil and light solvent is collected at the top of the tower 102, via the line 129, which, after passing through a heater 131, is led into an expansion tower 132 operating, in the case of a light solvent C ₃ -60 / C ₅ -40, at a pressure of about 25,105 absolute pascals and a temperature of about 140 ° C.

The major part of the light solvent is collected at the top of tower 132, via line 133, which is recycled to line 103 through line 114 and the refrigerant 115.

The deasphalted oily phase containing a little solvent is collected at the bottom of tower 132, via line 134, which, after passing through a heater 135, is carried out in a tower 136 for driving with steam, where water vapor is introduced via line 137.

In the case of a light solvent C ₃ -60 / C ₅ -40, this tower operates at a pressure of approximately 1.5 × 10 ⁵ absolute pascals and a temperature of approximately 250 _° C.

The deasphalted oil is collected at the bottom of the tower 136, by the line 138, and, at the top of the said tower, by the line 139, water and solvent, which are led to the condenser 14 '.

FIG. 3 represents a variant of FIG. 1, in which the separation of the light solvent from the deasphalted oil is carried out in such a way that the light solvent contains even more hydrocarbon with 3 carbon atoms. The separation of the resins from the oil is better and allows an even "cleaner" deasphalted oil to be obtained, that is to say having an even lower "Conradson" residue.

For the description of this figure, we will take as an example a heavy solvent C ₃ -20 / C ₅ -80 and a light solvent C ₃ -35 / C ₅ -65, but, of course, this example of a couple of solvents n ' is not limiting.

Only the part of Figure 3 different from Figure 1 will be described and only the equipment containing different or different products themselves from the equipment of Figure 1 have been renumbered, the other bodies keep the same reference numbers.

étant d'environ de 4/1.The mixture of heavy solvent C ₃ 20 / C ₅ -80 and of filler no longer containing "asphaltenes" collected by line 5 is led into a second extraction tower 200. In this tower, line 210 is introduced. , a third solvent C ₃ -50 / C ₅ -50, the extraction being carried out in fact using a light solvent C ₃ -35 / C ₅ -65. The pressure in the tower can be approximately 40.10 ^s absolute pascals, the temperatures at the bottom and at the top of the tower 200 being approximately, respectively, 115 and 145 _° C., the mass rate

being about 4/1.

The mixture of deasphalted oily phase and of light solvent C ₅ -35 / C ₅ -65 is collected at the top of the tower 200, via line 220.

The “resins” fraction containing a little light solvent is collected at the bottom of tower 200, by line 28, which is treated in the same way as for FIG. 1. The mixture of deasphalted oily phase and light solvent C ₃ -35 / C ₅ -65 is led, after passage through a heater 230, in an expansion tower 240, operating, in the case of the light solvent C ₃ -35 / C ₅ -65, at a pressure of 25.10 ^s pascals absolute and a temperature of 145 _° C.

• - au fond de la tour, par la ligne 290, un mélange d'huile désasphaltée et de solvant C₃-20/C₅-80, qui, après passage dans une vanne de détente 300, où sa pression et sa température sont abaissées, respectivement, à 5.105 pascals absolus et 95_°C, et passage dans un réchauffeur 310, est conduit dans une tour de détente 320 fonctionnant à une pression de 5.10^s pascals absolus et une température d'environ 120_°C,
• - par un soutirage latéral 500, un solvant C₃-30/C₅-70, dont une partie est conduite à la ligne 33, l'autre partie étant recyclée à la tour 240 par la ligne 510, après passage dans un réfrigérant 520;
• - au sommet de la tour 240, par la ligne 250, un solvant C₃-50/C₅50, qui, après passage dans un réfrigérant 260, est conduit dans un ballon de stockage 270, ce solvant étant ensuite recyclé à la tour 200 par la ligne 210.

Tower 240 is equipped with three rackings. As a result of the partial vaporization of the hydrocarbon with 3 carbon atoms, we collect:

• - at the bottom of the tower, via line 290, a mixture of deasphalted oil and solvent C ₃ -20 / C ₅ -80, which, after passing through an expansion valve 300, where its pressure and temperature are lowered , respectively, at 5.105 absolute pascals and 95 _° C, and passage through a heater 310, is conducted in an expansion tower 320 operating at a pressure of 5.10 ^s absolute pascals and a temperature of approximately 120 _° C,
• - by a lateral racking 500, a solvent C ₃ -30 / C ₅ -70, part of which is taken to line 33, the other part being recycled to tower 240 by line 510, after passing through a refrigerant 520 ;
• - at the top of tower 240, via line 250, a solvent C ₃ -50 / C ₅ 50, which, after passing through a refrigerant 260, is led into a storage flask 270, this solvent then being recycled to the tower 200 by line 210.

• - au sommet de cette tour, on recueille, par la ligne 528, du solvant C₃-50/C₅-50, qui est recyclé à la ligne 250;
• - on recueille, par un soutirage latéral 530, un solvant C₃-15/C₅-85 dont une partie est conduite à la ligne 33, tandis que l'autre partie est recyclée dans la tour 320, par la ligne 550, après passage dans un réfrigérant 540;
• - on recueille, au fond de la tour 320, par la ligne 360, la phase huileuse désasphaltée contenant un peu de solvant.

Tower 320 is equipped with three withdrawals:

• - At the top of this tower, there is collected, via line 528, solvent C ₃ -50 / C ₅ -50, which is recycled to line 250;
• - A solvent C ₃ -15 / C ₅ -85 is collected by a lateral withdrawal 530, part of which is taken to line 33, while the other part is recycled in tower 320, by line 550, after passage through a refrigerant 540;
• - The deasphalted oily phase containing a little solvent is collected at the bottom of tower 320, via line 360.

As in the case of FIG. 1, with a view to removing the solvent from the oily phase, from line 360, this phase, after passing through a heater 370, is carried out in a water vapor drive tower 380, where water vapor is introduced via line 390.

At the bottom of tower 380, deasphalted oil is collected by line 410 and, at the top of said tower, by line 400, water and solvent, which are led to condenser 14.

The combination of the solvents of lines 500 and 530 makes it possible to obtain a heavy solvent C ₃ -20 / C ₅ -80, which is recycled from the flask 10 to line 3.

It can be seen from this description of FIG. 3 that, thanks to the two lateral withdrawals from towers 240 and 320, it is possible to enrich the light solvent with a hydrocarbon with 3 carbon atoms.

The process according to the invention is particularly useful, as the following examples show, for the simultaneous preparation of a deasphalted oil, suitable as a catalytic cracking charge, having a "Conradson" residue less than or equal to 10, preferably less than or equal to 9 and, better still, less than or equal to 8, and of an "asphaltenes" fraction, having a softening point equal to or greater than 150 _° C, preferably equal to or greater than 160 _° C and, better still, 170 _° C or higher.

These examples are intended to illustrate the invention without limitation.

EXAMPLE 1

This example relates to the treatment of a hydrocarbon feedstock constituted by the residue from the distillation under reduced pressure of the residue from the distillation under atmospheric pressure of a crude oil of Safaniya origin.

• - masse volumique à 15_°C (measurée selon la norme AFNOR NFT 60-101): 1035 kg/m³,
• - viscosité à 100_°C (mesurée selon la norme AFNOR NFT 60-100) : 0,56.10-2 m2/s,
• - résidu "Conradson" (mesuré selon la norme AFNOR NFT 60-116) : 23 % en poids,
• - teneur en :

• ^* asphaltènes (mesurée selon la norme AFNOR NFT 60-115) : 16 % en poids,
• ^* soufre (mesurée par fluorescence -X) : 5,5% en poids,
• ^* nickel (mesurée par fluorescence X) : 43 p.p.m.,
• ^* vanadium (mesurée par fluorescence X): 138 p.p.m.

The characteristics of this charge are as follows:

• - density at 15 _° C (measured according to AFNOR NFT 60-101 standard): 1035 kg / m ³ ,
• - viscosity at 100 _° C (measured according to AFNOR NFT 60-100 standard): 0.56.10-2 m2 / s,
• - "Conradson" residue (measured according to AFNOR NFT 60-116 standard): 23% by weight,
• - content of:

• ^* asphaltenes (measured according to standard AFNOR NFT 60-115): 16% by weight,
• ^* sulfur (measured by fluorescence -X): 5.5% by weight,
• ^* nickel (measured by X-ray fluorescence): 43 ppm,
• ^* vanadium (measured by X-ray fluorescence): 138 ppm

This charge is treated in a unit implementing the method according to the invention of the type presented in FIG. 1.

Solvents C ₃ -C ₅ are used in the unit, the compositions of which are given in Table 1 below.

The operating conditions are given in Table II below.

After separation of the solvent from the various products, the final balance obtained is given in Table III below.

The characteristics of the products obtained are given in Table IV below.

This table clearly shows the advantage of the process according to the invention, which makes it possible to obtain very hard asphaltenes and an oil which can be used as catalytic cracking charge, since having a residue, "Conradson" less than 8.

EXAMPLE 2

This example relates to the treatment of a hydrocarbon feedstock constituted by the residue from the distillation under atmospheric pressure of the visbreaking effluent from a residue from the distillation under reduced pressure of a SAFANIYA crude oil.

• - masse volumique à 15_°C (mesurée selon la norme AFNOR NFT 60-101) : 1 060 kg/m3,
• - viscosité à 100_°C (mesurée selon la norme AFNOR NFT 60-100) : 0,17.10-2 m2/s,
• - résidu "Conradson" (measurée selon la norme AFNOR NFT 60-116) : 27 % en poids,
• - teneur en :

• ^* asphaltènes (mesurée selon la norme AFNOR NFT 60-115) : 22 % en poids,
• ^* soufre (mesurée par fluorescence X) : 6,2 % en poids,
• ^* nickel (mesurée par fluorescence X) : 53 p.p.m.,
• ^* vanadium (mesurée par fluorescence X) : 175 p.p.m.

The characteristics of this charge are as follows:

• - density at 15 _° C (measured according to AFNOR NFT 60-101 standard): 1,060 kg / m3,
• - viscosity at 100 _° C (measured according to AFNOR NFT 60-100 standard): 0.17.10-2 m2 / s,
• - "Conradson" residue (measured according to AFNOR NFT 60-116 standard): 27% by weight,
• - content of:

• ^* asphaltenes (measured according to AFNOR NFT 60-115 standard): 22% by weight,
• ^* sulfur (measured by X-ray fluorescence): 6.2% by weight,
• ^* nickel (measured by X-ray fluorescence): 53 ppm,
• ^* vanadium (measured by X-ray fluorescence): 175 ppm

This load is treated in a unit implementing the method according to the invention of the type shown in FIG. 1.

Solvents C ₃ -C _{5 are} used in the unit with compositions identical to those of the solvents of Example 1.

The operating conditions are given in Table V below.

After separation of the solvent from the different products, the final balance obtained is given in Table VI below:

The characteristics of the products obtained are given in Table VII below:

This table clearly shows the advantage of the process according to the invention, which makes it possible to obtain very hard asphaltenes and an oil which can be used as catalytic cracking charge, since it has a "Conradson" residue of less than 8.

EXAMPLE 3

This example relates to the treatment of a hydrocarbon feedstock constituted by the residue of the distillation under reduced pressure of the residue of the distillation under atmospheric pressure of a crude oil of Iraq origin.

• - masse volumique à 15_°C (mesurée selon la norme AFNOR NFT 60-101) : 1 016 kg/ m³,
• - viscosité à 100_°C (mesurée selon la norme AFNOR NFT 60-100) : 900 10-e m2/s
• - résidu "Conradson" (mesurée selon la norme AFNOR NFT 60-116) : 17 % en poids,
• - teneur en :

• ^* asphaltènes (mesurée selon la norme AFNOR NFT 60-115) : 6 % en poids,
• ^* soufre (mesurée par fluorescence X) : 4,9 % en poids,
• ^* nickel (mesurée par fluorescence X) : 43 p.p.m.,
• ^* vanadium (mesurée par fluorescence X) : 102 p.p.m.

The characteristics of this charge are as follows:

• - density at 15 _° C (measured according to AFNOR NFT 60-101 standard): 1016 kg / m ³ ,
• - viscosity at 100 _° C (measured according to AFNOR NFT 60-100): 900 10-e m2 / s
• - "Conradson" residue (measured according to AFNOR NFT 60-116): 17% by weight,
• - content of:

• ^* asphaltenes (measured according to AFNOR NFT 60-115 standard): 6% by weight,
• ^* sulfur (measured by X-ray fluorescence): 4.9% by weight,
• ^* nickel (measured by X-ray fluorescence): 43 ppm,
• ^* vanadium (measured by X-ray fluorescence): 102 ppm

This load is treated in a unit implementing the method according to the invention of the type shown in FIG. 1.

Les conditions opératoires sont données dans le tableau IX ci-après.

Solvents C ₃ -C ₆ are used in the unit, the compositions of which are given in Table VIII below.

The operating conditions are given in Table IX below.

After separation of the solvent from the various products, the final balance obtained is given in Table X below.

The characteristics of the products obtained are given in Table XI below.

This table clearly shows the advantage of the process according to the invention, which makes it possible to obtain very hard asphaltenes and an oil which can be used as catalytic cracking charge, since it has a "Conradson" residue of less than 8.

EXAMPLE 4

This example concerns the treatment of a hydrocarbon feedstock constituted by the residue from the distillation under reduced pressure of the residue from the distillation under atmospheric pressure of a crude oil of SAFANIYA origin.

• - masse volumique à 15_°C (mesurée selon la norme AFNOR NFT 60-101) : 1 035 kg/m³,
• - viscosité à 100_°C (mesurée selon la norme AFNOR NFT 60-100) : 5 600 10^-6 m²/s
• - résidu "Conradson" (mesurée selon la norme AFNOR NFT 60-116) : 23 % en poids,
• - teneur en :

• ^* asphaltènes (mesurée selon la norme AFNOR NFT 60-115) : 16 % en poids,
• ^* soufre (mesurée par fluorescence X) : 5,5 % en poids,
• *nickel (mesurée par fluorescence X) : 43 p.p.m.,
• *vanadium (mesurée par fluorescence X) : 138 p.p.m.

The characteristics of this load are as follows:

• - density at 15 _° C (measured according to AFNOR NFT 60-101 standard): 1035 kg / m ³ ,
• - viscosity at 100 _° C (measured according to AFNOR NFT 60-100 standard): 5,600 10 ^-6 m ² / s
• - "Conradson" residue (measured according to AFNOR NFT 60-116 standard): 23% by weight,
• - content of:

• ^* asphaltenes (measured according to AFNOR NFT 60-115 standard): 16% by weight,
• ^* sulfur (measured by X-ray fluorescence): 5.5% by weight,
• * nickel (measured by X-ray fluorescence): 43 ppm,
• * vanadium (measured by X-ray fluorescence): 138 ppm

This charge is treated in a unit implementing the method according to the invention of the type presented in FIG. 2.

Les conditions opératoires sont données dans le tableau XIII ci-après.

Solvents C ₃ -C ₅ are used in the unit, the compositions of which are given in Table XII below.

The operating conditions are given in Table XIII below.

After separation of the solvent from the various products, the final balance obtained is given in Table XIV below.

The characteristics of the products obtained are given in Table XV below.

This table clearly shows the advantage of the process according to the invention, which makes it possible to obtain very hard asphaltenes and an oil which can be used as catalytic cracking charge, since it has a "Conradson" residue of less than 8.

Claims (10)

1. Process for the elimination of asphaltenes from a heavy hydrocarbon feedstock, said process leading to the obtaining:

- of a de-asphalted oily phase with a "Conradson" index equal to or less than 10,

- of a "resins" fraction,

- of an "asphaltenes" fraction whose softening point is equal to or higher than 150_°C, said process comprising two stages of precipitation from the feedstock, firstly of the "asphaltenes" fraction alone, and secondly of the "resins" fraction, in certain cases accompanied by the "asphaltenes" fraction, by means, respectively, of a heavy solvent and a light solvent, said process being characterised in that the heavy solvent contains from 5 to 40% by volume of a hydrocarbon with 3 carbon atoms and 60 to 95% of at least one hydrocarbon with 5 carbon atoms and the light solvent contains from 20 to 80% by volume of a hydrocarbon with 3 carbon atoms and from 20 to 80% by volume of at least one hydrocarbon with at least 5 carbon atoms, the proportion of the hydrocarbon containing 3 carbon atoms being higher in the light solvent than in the heavy solvent.

2. Process according to claim 1, characterized in that it comprises two stages:

a) a first stage of precipitation from the feedstock, by means of a heavy solvent, of the "asphaltenes" fraction, said first stage leading to the obtaining:

- on the one hand, of the "asphaltenes" fraction, after separation of the solvent which it contains,

- on the other, of a solution in the heavy solvent of the "resins" fraction and the oily phase;

b) a second stage of precipitation from the solution obtained in stage a), by means of a light solvent, of the "resins" fraction, said second stage leading to the obtaining:

- on the one hand, of the "resins" fraction, after separation of the solvent which it contains,

- on the other, of the de-asphalted oily phase, after separation of the light solvent in which it is in solution.

3. Process according to claim 2, characterized in that the light solvent used for the precipitation of the "resins" fraction is obtained by combining the heavy solvent contained in the solution obtained at the conclusion of stage a) with a third solvent lighter than the light solvent, said third solvent being obtained during the separation of the light solvent from the oily phase by preferential vaporization of the hydrocarbon with 3 carbon atoms, said vaporization leading to the obtaining of said third solvent and a heavy solvent recycled to the first stage of precipitation of the "asphaltenes" fraction.

4. Process according to claim 3, characterized in that the content in the hydrocarbon with 3 carbon atoms of the third light solvent is augmented by refluxes used during the separation of the de-asphalted oil and the light solvent.

5. Process according to any one of claims 2 to 4, characterized in that:

a) the heavy solvent used in the first stage contains from 10 to 40% by volume of hydrocarbon with 3 carbon atoms and from 60 to 90% by volume of at least one hydrocarbon with at least 5 carbon atoms and, preferably, from 15 to 35% by volume of hydrocarbon with 3 carbon atoms and from 65 to 85% by volume of at least one hydrocarbon with at least 5 carbon atoms,

b) the light solvent used in the second stage contains from 20 to 80% by volume of hydrocarbon with 3 carbon atoms and from 20 to 80% by volume of at least one hydrocarbon with at least 5 carbon atoms and, preferably, from 25 to 75% by volume of hydrocarbon with 3 carbon atoms and from 25 to 75% by volume of at least one hydrocarbon with at least 5 carbon atoms.

6. Process according to claim 1, characterized in that it comprises two stages:

a') a first stage of precipitation from the feedstock, by means of a iight solvent, of the "resins" and "asphaltenes" fractions, said first stage leading to the obtaining:

- on the one hand, of a mixture of the "resins" and "asphaltenes" fractions containing some light solvent,

- on the other, of the de-asphalted oily phase, after separation of the light solvent in which it is in solution and which is reused in the first stage;

b') a second stage of treatment of the mixture of the "resins" and "asphaltenes" fractions by means of the heavy solvent, leading to the obtaining after dissolution of the "resins" fraction in the heavy solvent:

- on the one hand, of the "resins" fraction, after separation of the heavy solvent in which it is in solution;

- on the other, of the "asphaltenes" fraction, after separation of the solvent which it contains.

7. Process according to claim 6, characterized in that the light solvent used for the precipitation of the "resins" and "asphaltenes" fractions is obtained by combining the light solvent recycled at the conclusion of stage a') with the light solvent obtained during the separation of the heavy solvent from the "resins" fraction by preferential vaporization of the hydrocarbon with 3 carbon atoms, said vaporization leading to the obtaining of said light solvent and a solvent heavier than the heavy solvent, which is used to reconstitute the heavy solvent used in the second stage in combination with the light solvent contained in the mixture of the "resins" and "asphaltenes" fractions obtained at the conclusion of stage a').

8. Process according to any one of claims 6 and 7, characterized in that:

a) the light solvent used in the first stage contains from 20 to 80% by volume of hydrocarbon with 3 carbon atoms and from 20 to 80% by volume of at least one hydrocarbon with at least 5 carbon atoms and, preferably, from 30 to 70% by volume of at least one hydrocarbon with 3 carbon atoms and from 30 to 70% of at least one hydrocarbon with at least 5 carbon atoms,

b) the heavy solvent used in the second stage contains from 5 to 30% by volume of hydrocarbon with 3 carbon atoms and from 70 to 95% by volume of at least one hyrocarbon with at least 5 carbon atoms and, preferably, from 10 to 25% by volume of hydrocarbon with 3 carbon atoms and from 75 to 90% of at least one hydrocarbon with at least 5 carbon atoms.

9. Process according to any one of claims 1 to 8, characterized in that the hydrocarbons with 3 carbon atoms and with at least 5 carbon atoms are respectively propane and pentane.

10. Process according to any one of claims 1 to 8, characterized in that the hydrocarbons with 3 carbon atoms and with at least 5 carbon atoms are respectively propane and hexane.

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