EP2419186A1

EP2419186A1 - Petroleum distillation method and facility reusing low-thermal-level energy

Info

Publication number: EP2419186A1
Application number: EP10718237A
Authority: EP
Inventors: Tahar Benali
Original assignee: Centre National de la Recherche Scientifique CNRS
Current assignee: TAHAR, BENALI
Priority date: 2009-04-16
Filing date: 2010-04-15
Publication date: 2012-02-22
Also published as: FR2944452A1; FR2944452B1; WO2010119189A1

Abstract

The invention relates to a method for distilling a multicompound liquid mixture, such as crude oil, including: (a) a step of preheating said mixture; (b) a step of evaporating said preheated mixture; and (c) a step of distilling said evaporated mixture, a method in which heat from step (c), the temperature of which is greater than 100°C, is used during the preheating step (a), and in which at least one step for separating said preheated mixture into a liquid portion and an evaporated portion is carried out, the latter portion corresponding to at least one component of the mixture and being directly treated during the distillation step (c), and the mixture treated during the evaporation step (b) being depleted of said evaporated portion, characterized in that it includes a complementary heating step, in which residual power having low heat level is used, the temperature of which is less than 100°C.

Description

METHOD AND INSTALLATION FOR DISTILLING PETROLE REUSE OF LOW LEVEL HEAT ENERGY

The present invention relates to a method and an installation for the distillation of a multicomponent mixture.

It is particularly suitable for the distillation of oil. It is known that the conventional processes for the distillation of petroleum can use a simple distillation column with a preheating furnace and, at several levels of this column, lateral underdrawing means for finished products having specific characteristics. like naphtha, kerosene and diesel. They can also implement a distillation column with strippers and heat conditioners of the finished products, as well as lateral recirculations for the stabilization of the thermal profile of this column.

The thermal energy required for the separation of petroleum constituents is mainly introduced by preheating the mixture to be distilled. This preheating is partly carried out with the heat that can be recovered from the thermal conditioners of the finished products and from the distillation column, thanks to lateral recirculations. At the exit of

Distillation column, the fluid passing through the lateral recirculation is at a temperature above 100 ⁰ C, and up to 350 ⁰ C or 400 ⁰ C.

After this preheating, the mixture, partly vaporized, is then superheated in a vaporization oven to finally be brought to the distillation column.

The detailed thermodynamic analysis of such a process shows

That within the distillation column and in the vaporization furnace, a significant degradation of the useful or "noble" energy takes place.

In the distillation column, most of this energy degradation is due to mixing and non-equilibrium phenomena throughout the column, and to large fluxes of the many components of the mixture that pass through a large part of the column. . These energy degradations are increasing, from the head to the bottom of the distillation column, as the number of components of the mixture that must be separated. The object of the invention is therefore to reduce the quantity of fossil fuel required for the implementation of distillation processes of multicomponent mixtures, for example oil, by recovering and recovering low-level energy available elsewhere, either in the distillation process itself, either in the near environment of this process, in the plant or refinery.

High energy means here fossil fuel

(natural gas) burned to heat the oven. Low-level energy is understood to mean "low temperature" calories, typically less than 100 ^° C., which are otherwise released into the environment with cooling water or condensates of heating vapor.

It should be noted that the fossil fuel economy also results in a proportional decrease in CO ₂ emissions.

Processes have already been proposed to achieve this objective, by attempting to limit the energy consumed by the steam oven, through prior separations of the mixture.

However, these processes use complementary installations, such as distillation columns, which correspond to costly investments and important modifications of the existing processes.

In addition, some of these processes are essentially adapted to light oils.

The document FR-2,703,600 describes a process for the distillation of complex mixtures in which, during the preheating step, at least one separation step of the mixture is provided, the vaporized part of the mixture being directly supplied to the column of distillation.

This prior separation has the effect of reducing the energy consumed in the preheater by irradiation which ensures the vaporization of the mixture. However, in the context of the invention, it has been demonstrated that the organic vapor inputs from the separators to the distillation column are at a lower temperature than those trays where these inputs are injected. This causes internal cooling of the distillation column.

If no changes are made to the side recirculation flows, the temperature profile of the distillation column and the amount of heat extracted from its overhead condenser will not be maintained. The quantity and quality of finished products obtained at the outlet of the distillation column may not be ensured.

If the profile is well maintained, the flows of lateral recirculations must be reduced. The energy provided during the preheating step is then lower. Thus, under these conditions, the prior separations do not significantly reduce the energy consumption during the implementation of the distillation process.

The object of the invention is therefore to reduce the energy consumption induced by the distillation processes of multicomponent mixtures, without requiring major modifications of the process and without causing significant material investments, while ensuring the quantity and quality of the finished products. .

For this purpose, the invention relates to a process for the distillation of a multicomponent liquid mixture such as crude oil comprising: (a) a step of preheating said mixture

(b) a step of vaporizing said preheated mixture

(c) a step of distilling said vaporized mixture, in which process, during step (a) of preheating, is used heat from step (c) whose temperature is greater than 100 ^° C. and at least one separation step of said preheated mixture is carried out in a liquid part and a vaporized part, the latter part corresponding to at least one component of the mixture and being directly treated during the distillation stage (c), and the treated mixture during the vaporization step (b) being depleted of said vaporized part, characterized in that it comprises a complementary heating step, in which low thermal level residual energies whose temperature is below 100 ° C. are used. . It is understood that this prior separation step reduces the number of constituents present in the mixture which is treated during the vaporization step and therefore, in the lower part of the column.

This prior separation step therefore has the direct result of reducing the charge supplied to the steam oven and thus saving the energy necessary for the operation of this oven.

However, it creates an internal cooling of the distillation column. In order to maintain the temperature profile of the distillation column and the amount of heat extracted from its overhead condenser and thus its efficiency, it is necessary to reduce the flow rate of the lateral recirculations. This has the direct consequence of reducing the energy input during the preheating of the mixture.

Indeed, during the preheating step, is used the heat from the lateral recirculations. The introduction of this additional heating step makes it possible to compensate for the reduction of the energy input during the preheating step (a), due to the prior separations.

It implements energies that are not usually recovered such as those resulting from the completion of the conditioning of the finished products to their storage temperatures, the heating steam condensates and the cooling waters of the finished or intermediate internal products. or external to the process.

This supplementary preheating stage may concern all or part of the mixture to be distilled. It can be performed in series with the step (a) preheating and upstream thereof or in parallel with a portion of step (a).

This separation step is preferably carried out adiabatically and it advantageously intervenes after a possible preliminary treatment step of the mixture. This treatment step consists, for example, in a desalination when the mixture is oil.

In a preferred embodiment of this method, the preheating step (a) comprises at least two successive substeps, each of which is followed by a liquid / vapor separation step. The at least two substeps are performed in series or in parallel.

Moreover, a separation step may be common to at least two substeps, whether they are performed in series or in parallel. The invention also relates to an installation for the distillation of a multicomponent liquid mixture such as crude oil comprising: at least one means for preheating the vaporization means and a distillation column at least one liquid / vapor separation means, located after preheating means and, at the outlet of said separation means, means for directly bringing the part of said vaporized mixture and corresponding to at least one constituent, into said distillation column, characterized in that it also comprises, upstream of said at least one preheating means, a heating means using residual energies of low thermal level, the temperature of which is less than 100 ^° C.

Preferably, the distillation column comprising different trays each corresponding to a given temperature and at least one component, said supply means open at the plateau of the distillation column corresponding to a temperature and at a concentration of at least a constituent close to those of the vaporized part.

This feature makes it possible to make the best use of the beneficial effects of the prior separation of a constituent.

The liquid / vapor separation means is located, preferably, downstream of a possible pre-treatment means of the mixture.

It can in particular be a desalination tank, when the installation is intended for the distillation of oil. Furthermore, the installation preferably comprises as many liquid / vapor separation means as preheating means.

The liquid / vapor separation means preferably operate adiabatically. The invention will be better understood, and other objects, advantages and characteristics thereof will appear more clearly on reading the description which follows and which is carried out with regard to: FIG. 1 which illustrates a conventional distillation system of 2, which illustrates an installation according to the invention, corresponding to the installation of FIG. 1, in which new means have been introduced, FIG. 3 which illustrates a variant embodiment of a preheating train of FIG. a conventional oil distillation plant, and Figure 4 which illustrates a preheating train according to the invention, corresponding to that of Figure 3, wherein new means have been introduced. The purpose of this description is to describe the characteristic means of the invention, their operation and their advantages.

The elements common to the different figures will be designated by the same references.

The conventional installation illustrated in FIG. 1 comprises a preheating train 2 with preheating means 21 to 26, through which the mixture is heated, before being brought to the steaming oven 3, the vaporized mixture then serving to supply the distillation column 4.

In practice, the preheating of the mixture takes place in two stages, separated by a desalination step carried out in the desalination tank 5.

Thus, a flow of crude oil is first brought into the first heating means 21 by means symbolized by the arrow 1 and heated therein. The latter is conventionally a heat exchanger that heats the oil through the flow of kerosene produced in the stripper 62 and transmitted to the exchanger by the means symbolized by the arrow 621. The recovery of kerosene at the outlet of the exchanger 21 is symbolized by the arrow 622. The mixture available at the outlet of exchanger 21 is supplied to heating means 22 which is also conventionally a heat exchanger. This exchanger uses the flow that flows in the means 71, located between the heating means 22 and the column 4. These means allow the circulation of fluid extracted from a tray of the column 4, from the upper part 41 of the column to the heating means 22, then the return of the cooled fluid to the upper part 41. These means 71 are conventionally referred to as first lateral recirculation. They contribute to the control of the thermal profile of the distillation column. The mixture at the outlet of the heating means 22 is supplied to the desalination tank 5.

This reservoir 5 is conventionally a magnetic field desalination tank, in which the oil is freed from dissolved salts which are eliminated in the aqueous phase and incondensable gases which are separated in a small cutting tower which is not illustrated on FIG. 1. The water brought into the inlet of the tank 5 is symbolized by the arrow 50, while the water recovered at the outlet of the tank 5 is symbolized by the arrow 51.

The mixture obtained at the outlet of the tank 5 is fed to a third heating means 23 which is an exchanger using the energy of the product coming from the stripper 61 (of the diesel) and which is transmitted to the exchanger by the means symbolized by the arrow 611. The diesel recovery at the outlet of the exchanger 23 is symbolized by the arrow 612.

The mixture available at the outlet of the third heating means 23 is sent to the fourth heating means 24 which is still a heat exchanger. This exchanger uses the flow that circulates in the means 72, located between the heating means 24 and the column 4. These means allow the circulation of fluid extracted from the central or intermediate portion 42 of the column, to the heating means 24, then the return of the cooled fluid to the intermediate portion 42. These means 72 are conventionally referred to as second lateral recirculation.

The mixture at the outlet of the heating means 24 is supplied to the fifth heating means 25. This is again an exchanger which allows the mixture to be heated by the diesel fuel from the stripper 60 and transmitted to the exchanger by the means symbolized by the arrow 601. The recovery of the diesel fuel at the outlet of the exchanger 24 is symbolized by the arrow 602.

The mixture obtained at the outlet of the fifth heating means 25 is supplied to the sixth heating means 26, which is also a heat exchanger. This exchanger uses the flow that circulates in the means 73, located between the heating means 26 and the column 4. These means 73 allow the circulation of fluid extracted from the lower part 43 of the column to the heating means 26, then the return of the cooled fluid to the lower part 43. These third means 73 are conventionally referred to as third lateral recirculation.

The preheating train 2 which has just been described represents only one embodiment example. However, such a preheating train conventionally comprises a plurality of exchangers making it possible to preheat the mixture by heat exchange with, in particular, the condenser of the top products of the column, the conditioning exchangers downstream of the strippers of the finished products, such as naphtha, kerosene, turbosene, light gas oil and heavy diesel fuel and lateral recirculations for controlling the thermal profile of the distillation column. In general, the lateral recirculation and the exchangers make it possible to evacuate an excess of heat within the distillation column, thanks to a cooling of the fluids passing through the lateral recirculations. This cooling is carried out outside the distillation column while according to the invention, this cooling is partly ensured by the organic vapors within the column itself.

The mixture supplied at the outlet of the sixth heating means 26 and therefore at the outlet of the preheating train 2 is supplied to the vaporization oven 3.

This direct fire oven is powered by natural gas and air, the supply of which is shown schematically by the arrow 30.

This oven comprises two parts 31 and 32. The combustion chamber constitutes the lower part 31 which is intended for heating the mixture or the load, while the upper part 32, called fabric, is used to produce water vapor which will serve as entrainment steam in column 4 and its three strippers 60, 61 and 62.

The arrow 33 symbolizes the exit of the furnace combustion gases.

At the outlet of the vaporization oven 3, the vaporized charge is fed (arrow 34) to the distillation column 4, in the zone 44 located at the lower end of the column, called the zone of the overflash or washing zone (wash zone), from which the vaporized charge is conveyed to the rectification zone 45, using a steam flow. The latter flows from the bottom to the top of the column. It is symbolized by the arrow 48. This column 4 comprises a number of trays and / or packings. The number of trays is typically between 20 and 40. It is also provided with complementary elements. There may be mentioned in particular a head condenser 46 and a flash 47 where the light gases and the liquid naphtha water, the kerosene stripper 60, the turbosene stripper 61 and the diesel stripper 62 are separated.

The flow from the distillation column 4 and entering the condenser 46 is symbolized by the arrow 460. The condensate outlet from the condenser 46 is symbolized by the arrow 461.

The outlets of water, naphtha and light gas from the flash 47 are respectively symbolized by the arrows 470, 471 and 472.

The steam supply of the strippers from the furnace is symbolized by the arrows 600, 610 and 620 respectively.

The residue that can be recovered at the bottom of the distillation column can either feed a vacuum distillation column or be returned before the vaporization oven 3, for use in the preheating train 2. The recovery of the residue is symbolized by the arrow 49.

The description will now be continued with reference to FIG. 2 which illustrates an example of an installation according to the invention, made from the conventional installation illustrated in FIG. 1. The means which have already been described in detail, in reference to Figure 1, will not be described again. Only the differences between the two figures will be highlighted. Firstly, upstream of the preheating train 2, there is provided a complementary heating means 8 which uses the residual energy of low thermal level coming from the installation or the rest of the refinery. It is preferably a heat exchanger. Residual energies come, for example, from steam condensates, in the case of an oil refinery.

Conventionally, heat for preheating can be recovered from the distillation column, for example from the top condenser 46 of the column and the lateral recirculation 71 to 73, but also from the coolers of the finished products. At the outlet of the distillation column, this heat is available at various temperatures, ranging from 100 ^° C. to about 350 ° -400 ° C., depending on the level at which it is extracted from the distillation column.

Of course, a stream withdrawn from the distillation column at a temperature above 100 ° C, can then be used in successive heat exchangers of the preheating process at temperatures that have become less than 100 ⁰ C.

It should be noted, however, that when the preheat train reaches a temperature that is too high, it can no longer be used to cool the finished products. These are then cooled with cold water.

Thus, in refineries, there is always available an excess of low quality heat whose temperature is below 100 ⁰ C, from condensates of heating steam or hot water from chillers. In a conventional refinery, this excess heat is evacuated by the cooling towers planned in the refinery, so lost. Thus, some of the heat contained in the finished products is lost.

In the embodiment illustrated in FIG. 2, the crude oil is generally fed at the temperature of the storage tank. On the other hand, thanks to the heat exchange achieved in the means 8, the oil flow is reheated before the flow of oil is introduced into the preheating train 2. This means 8 may consist of one or more exchangers arranged in series and / or in parallel.

Thus, this means 8, added to the conventional preheating train, makes it possible to use low-level heat recovered, moreover, in the installation and more specifically in the refinery. Part of the total energy consumed during the implementation of the process according to the invention then comes from heat of low level of recovery, heat which is normally lost in a conventional refinery.

As illustrated in FIG. 2, an installation according to the invention is distinguished from a conventional installation by the presence of several liquid / vapor separators inside the preheating train 2.

Typically, a vapor and liquid separator consists of a simple empty container and is conventionally referred to as "flash".

FIG. 2 illustrates here three separators 91, 92 and 93 which are here all located downstream of the desalination tank 5. It could also be provided at least one separator upstream of the tank 5.

The first separator 91 is located downstream of the third heating means 23.

Thus, the mixture available downstream of this heating means 23 is supplied to the first separator 91. In this mixture, the lightest products have already been vaporized thanks to the heat input of the heating means 21, 22 and 23 and also complementary heating means 8.

Thus, the vaporized portion of the mixture is transmitted by the means 91a directly into the upper part 41 of the column 4. Furthermore, the liquid portion is returned to the inlet of the fourth preheating means 24 to be preheated by the second lateral recirculation 72.

FIG. 2 illustrates a second separator 92 which is situated downstream of the fifth heating means 25. The feedstock which is fed to the inlet of the second separator 92 has already been depleted of the vaporized part of the mixture, supplied by the means 91a in the column distillation. This charge is partly vaporized by the heat input of the heating means 24 and 25.

The second separator will make it possible to extract the vaporized part of the charge to bring it, thanks to the means 92a, to the central part 42 of the column 4. The liquid part of the charge, already depleted twice, is then brought sixth heating means 26.

A third separator 93 is provided downstream of the sixth heating means 26.

Each separation is preceded by preheating so that separation can occur. The temperature of the mixture at a separator is substantially the temperature of the mixture at the outlet of the preceding heating means.

This third separator 93 receives the charge, partly vaporized, from this sixth heating means and separates the vaporized portion which is transmitted in the lower part 43 of the column, by means 93a and the liquid part which is supplied at the entrance of the vaporization oven 3.

It can thus be seen that at the outlet of each separator, the steam flow is sent directly to the distillation column, at the level of the column tray having a temperature and composition similar to or close to those of the flow in question.

Thus, thanks to the separations made upstream of the vaporization furnace 3, the latter consumes less energy to vaporize the part of the mixture that it receives from the separator 93 than to vaporize the entire mixture, as in the installation illustrated in FIG. Figure 1. Now, it is a fossil source energy.

Moreover, the flow of steam from the separators 91 to 93 to the column 4 causes internal cooling of the latter. To maintain the temperature profile of the column, a decrease in the flow of lateral recirculation is therefore necessary.

However, much of the heat supplied to crude oil in the preheating train comes from heat exchange with the flow of lateral recirculation. This amount of heat is reduced by the installation of the separators.

It is understood that the supplementary means of preheating 8 makes it possible to fill this deficit. Or ₁ this supplementary means 8 uses residual low level thermal energy which are generally lost in a conventional refinery. It is therefore understood that the invention makes it possible to compensate for a reduction in the high level of energy consumption by the use of residual energies which are conventionally lost. It should be noted that the vaporized part of the mixture which is introduced into the column 4 at the outlet of the separator may comprise several constituents. This is the case during the distillation of oil in particular.

The example illustrated in FIG. 2 is absolutely not limiting.

For example, a separator or flash may be provided after each heating means of the preheating train 2. This would correspond to providing an additional separator between the fourth and fifth heating means illustrated in FIG. 2.

This is possible, especially for oil, because it is in continuous vaporization. For processes specifically designed to distill a specific type of oil, the number of separators can be reduced.

Thus, when the process is only intended to distil a light oil, more separators can be provided in the upstream part of the preheating train and reduce them in the downstream part of this preheating train. Of course, reverse measures could be taken for the distillation of a heavy oil.

Preferably, the separators used operate adiabatically.

Preferably, the energy required to operate each separator comes from heating means in front, and it is therefore not necessary ^{^} to bring energy to the separator. Reference is now made to FIG. 3 which represents a variant of the preheating train illustrated in FIG. 1. This preheating train 20 comprises preheating means 210 to 290, 300 and 310.

In this embodiment, the preheating train comprises two sub-trains of parallel preheating means that meet.

The first sub-train comprises preheating means 210, 230, 250, 260, 270 and 290. The second preheating sub-train comprises preheating means 220, 240, 260 and 280. These two sub-trains meet in output of the preheating means 290 and 280, the preheating train ending with the preheating means 300 and 310 arranged in series.

In the example illustrated in FIG. 3, the two sub-trains have the desalination tank 5 in common. In other embodiments, each preheating sub-train could have its own desalination tank.

Thus, the flow of crude oil, symbolized by the arrow 1 is divided to be brought into each pre-heating sub-train. An arrow 11 symbolizes the flow brought into the input of the first preheating train, while the arrow 12 symbolizes the flow of oil brought into the input of the second preheating sub-train.

At the level of the first preheating sub-train, the exchangers 210 and 230 are arranged in series. The exchanger 210 receives the naphtha stream from the flash 47 (arrow 471). The recovery of the naphtha at the outlet of the exchanger 210 is symbolized by the arrow 473.

The mixture available at the outlet of exchanger 210 is supplied to exchanger 230. This uses kerosene from stripper 62 (arrow 621). The recovery of kerosene at the outlet of the exchanger 230 is symbolized by the arrow 622. The mixture at the outlet of the exchanger 230 is supplied to the desalination tank 5.

Before the desalination tank, the second preheating sub-train comprises an exchanger 220 corresponding to the condenser of head 46 shown in Figures 1 and 2. It receives the flow of oil symbolized by the arrow 12 and the heating through the vapors from the distillation column 4 (arrow 460). The condensate recovery at the outlet of the exchanger 220 is symbolized by the arrow 461. The mixture at the outlet of the exchanger 220 is also supplied to the desalination tank 5.

Tank 5 will not be described again. The mixture obtained at the outlet of the tank 5 is divided to be fed into each preheating sub-train. Thus, the part of the mixture symbolized by the arrow 13 is brought into the inlet of the continuation of the first preheating sub-train, while the other part of the flow, symbolized by the arrow 14, is brought into the input of the continuation of the second preheating sub-train.

The first preheating sub-train therefore still includes exchangers 250, 270 and 290 arranged in series. These three exchangers are arranged in parallel with the other three exchangers of the second preheating sub-train, the exchangers 240, 260 and 280, also arranged in series.

The exchanger 250 receives as input the mixture symbolized by the arrow 13 and the heating by means of diesel from the stripper 61 (arrow 611). The diesel recovery at the outlet of the exchanger 250 is symbolized by the arrow 612.

The mixture available at the outlet of the exchanger 250 is sent to the exchanger 270 which heats it by means of the gas oil recovered at the outlet of the exchanger 300. The supply of the diesel fuel to the exchanger 270 is symbolized by the arrow 602. The diesel fuel recovered at the outlet of the exchanger 270 is symbolized by the arrow 603.

Finally, the mixture at the outlet of the exchanger 270 is supplied to the exchanger 290 which heats it by means of the flow of residue coming from the exchanger 310 and symbolized by the arrow 490. The recovery of the residue at the outlet of the exchanger 290 is symbolized by the arrow 491.

The exchanger 240 of the second preheating sub-train receives as input the mixture symbolized by the arrow 14 and the heater by the flow flowing in the means 71. The mixture obtained at the outlet of exchanger 240 is supplied to exchanger 260 which uses the flow flowing in means 72 to heat it.

Finally, the mixture available at the outlet of the exchanger 260 is supplied to the exchanger 280 which heats it by means of the flow flowing in the means 73.

The means 71 to 73 are the first, second and third lateral recirculations described with reference to FIGS. 1 and 2.

The mixtures available at the outlet of exchangers 290 and 280 are supplied to exchanger 300. Thus, the two preheating sub-trains first arranged in parallel, meet at this exchanger 300.

It heats the mixture it receives input through diesel fuel from the stripper 60 (arrow 601).

The diesel recovery at the outlet of the exchanger 300 is symbolized by the arrow 602.

As explained above, the gas oil recovered at the outlet of exchanger 300 is supplied at the inlet of exchanger 270.

The mixture available at the outlet of exchanger 300 is supplied to the last exchanger 310 of the preheating train. This heats the mixture with the residue from the bottom of the distillation column (arrow 49).

The recovery of the residue at the outlet of the exchanger 310 is symbolized by the arrow 490.

As explained above, this residue is then added to the exchanger 290. Finally, the mixture available at the outlet of the exchanger 310 is supplied to the vaporization oven 3.

Figure 3 shows that the preheating train can be made to use all the products from the distillation of oil. It can, moreover, be realized in a rather complex manner.

It will be noted that the exchangers of the preheating train are arranged in parallel, as in FIG. 3, when the flows used by the exchangers are at substantially identical temperatures. The description will now be continued with reference to FIG. 4 which illustrates a preheating train of an installation according to the invention, this preheating train being produced from that illustrated in FIG.

The means which have already been described in detail, with reference to FIG. 3, will not be described again. Only the differences between the two figures will be highlighted.

First of all, upstream of the second preheating sub-train, a complementary heating means 80 is advantageously provided. Thus, this additional heating means 80 receives as input the portion of the crude oil stream, symbolized by the arrow 12. The oil flow heated by this means 80 is then fed to the inlet of the preheating means 220 of the second preheating sub-train.

In this variant embodiment, this additional heating means 80 thus only heats a portion of the oil flow fed to the preheating train inlet. Remember that in the embodiment illustrated in Figure 2, the additional heating means 8 is intended to heat the entire flow of oil that feeds the preheating train.

Thus, this means 80 is located upstream of the second preheating sub-train and in parallel with the first preheating sub-train.

As already described for the complementary means 8, this complementary heating means 80 preferably consists of a heat exchanger or of several exchangers arranged in series and / or in parallel, these exchangers using the low-level residual energies. thermal energy from the facility or the rest of the refinery, whose temperature is less than 100 ⁰ C. It is therefore understood that this means 80 is necessarily placed upstream exchangers that use higher temperature energies.

This means 80 has the advantages that have been described for the means 8.

As illustrated in FIG. 4, the preheating train according to the invention differs from that illustrated in FIG. 3 by the presence of several liquid / vapor separators referenced 910 to 970. The first separator 910 is located downstream of the heating means 250 located in the first preheating sub-train.

Thus, the vaporized portion of the mixture, available downstream of the heating means 250, is transmitted by the means 910a directly to the column 4. Furthermore, the liquid portion of the mixture is returned to the inlet of the preheating means 270.

Another separator is located downstream of this preheating means 270, whereby the already depleted charge of the vaporized portion of the mixture has also been partially vaporized. The separator 920 extracts this vaporized portion of the charge to bring it, through the means 920a, to the column 4. The liquid portion of the load, depleted by two times, is then fed to the heating means 290.

Another separator 930 is provided downstream of the heating means 290. It will be described later.

The two separators 940 and 950 present in the second preheating sub-train will be described more succinctly.

The separator 940 is placed between the outlet of the heating means 240 and the inlet of the heating means 260. The vaporized portion of the mixture from the heating means 240 is extracted by the separator 940 and fed, by the means 940a, to the column 4.

The separator 950 is placed between the heating means 260 and 280. It makes it possible to extract the vaporized part of the mixture delivered by the heating means 260 to bring it, by means 950a, to the column 4.

The mixtures available at the outlet of the exchangers 290 and 280 are supplied to the separator 930. Here again, this separator extracts the vaporized part of the mixture resulting from these two heating means to bring it, by means 930a, to the column 4. The liquid portion of the mixture, at the outlet of the separator 930, is returned to the inlet of the exchanger 300.

Another separator 960 is provided between the exchangers 300 and 310. Thus, the separator 960 extracts the vaporized portion of the feedstock from the exchanger 300 and feeds it through the means 960a to the column.

Finally, a last separator 970 is provided at the outlet of the exchanger 310. This separator extracts the vaporized part of the mixture delivered by the exchanger 310 to bring it, through means 970a, to the column.

The liquid part of the mixture is fed to the inlet of the vaporization oven 3.

Thus, in the variant embodiment illustrated in FIG. 4, a separator is provided after each exchanger located downstream of the desalination tank 5. FIG. 4 also shows that certain separators may be common to exchangers located in parallel in the train of preheating. This is the separator 930 which is common to the exchangers 290 and 280. In the example illustrated in FIG. 4, the fossil fuel economy can exceed 40 kJ / kg of distilled petroleum at the level of the vaporization furnace. compared to the installation according to FIG.

This is due to the fact that the oil has been partly heated by residual energies and that only a part of the mixture is vaporized in the furnace 3, since vaporized constituents have been previously brought to the column, at the outlet of a separator.

In practice, the quantity of energy consumed in each installation, all other things being equal, is slightly less for the use according to FIG. 4. However, the fossil fuel burn is reduced by about 20%, the rest of the energy being the energy of recovery, therefore of low level, which is normally lost.

In the plant illustrated in Figure 4, the separators 910 to 930 return vapors to the distillation column and cause internal cooling of the column. As a result, the flow rate of the lateral recirculations is reduced, for example in comparison with the flows generated in the installation illustrated in FIG. 3. The part of the mixture preheated in the second preheating sub-train therefore receives a reduced energy input. . It is then understood that the complementary preheating means 80 makes it possible to fill this deficit, by using residual energies which are usually lost, therefore without additional cost.

In addition, this makes it possible to prevent these energies from being dissipated in the environment and thus contributes to reducing the impact of the refining process on the environment.

It should be noted that the method described in document FR-2,703,600 makes it possible to achieve a fossil fuel energy saving of between 6 and 20 kJ / kg of refined oil. This difference is essentially due to the use of residual energies during the preheating of the mixture. Thus, the separation step causes internal cooling of the distillation column and the heat deficit generated in step a) by reducing the flow of the lateral recirculation is compensated by the supply of residual energy during preheating. The addition of liquid / vapor separators in the preheating train makes it possible to separate some of its lighter components from the mixture before it is supplied to the steamer. As a result, the number of components of the filler fed to the vaporization furnace is reduced. This results in a reduction in the energy consumed by the steamer to vaporize the charge as well as a reduction in CO ₂ emissions.

In addition, the cost of installing, maintaining and controlling a flash type separator is relatively low. Thus, the process according to the invention does not involve significant additional cost at the distillation plant.

This method can be easily implemented with already existing installations, since the hardware modifications are reduced and easy to achieve. Indeed, this adaptation does not involve any major modification of equipment, the operation and control of conventional processes being maintained.

Finally, the process according to the invention is very flexible since it can be adapted to any type of multicomponent mixture and in particular to any type of oil, according to its more or less heavy nature. The process according to the invention also makes it possible to reduce the amount of driving water vapor which is injected at the bottom of the distillation column.

Calculations indicate that the process according to the invention would allow a fuel saving exceeding 20% and up to 30% and a concomitant reduction of CO ₂ emissions, compared to a conventional distillation process, all things being equal otherwise.

Furthermore, it is understood that when a new installation is designed according to the invention, the cost of the equipment can be considerably reduced.

Indeed, because of successive liquid / vapor separations, the size of the heating means can be reduced. Indeed, in a heat exchanger, for example, the necessary exchange area is less important. It will be the same for the vaporization furnace and possibly the distillation column.

Thus, a new installation made according to the invention will be of reduced cost, despite the introduction of the separators.

It can also be seen that apart from the reduction of the flow rate, upstream of the distillation column, this operates by causing a reduced degradation of the internal energy. This is related to a better standardization of the number of compounds per plate, along the column, and therefore also to a more uniform distribution of energy degradations, which is known to be generally favorable to the performance of the processes. The reference signs inserted after the technical characteristics appearing in the claims are only intended to facilitate understanding of the latter and can not limit its scope.

Claims

A method of distilling a multicomponent liquid mixture, such as crude oil, comprising: (a) a step of preheating said mixture

(b) a step of vaporizing said preheated mixture

(c) a step of distillation of said vaporized mixture in which, during step (a) preheating is used heat from step (c) whose temperature is greater than 100 ⁰ C and is carried out at least one step of separating said preheated mixture into a liquid part and a vaporized part, the latter part corresponding to at least one constituent of the mixture and being directly treated during the distillation stage (c), and the mixture treated during the vaporization step (b) being depleted of said vaporized part, characterized in that it comprises a complementary heating step, in which low thermal level residual energies whose temperature is below 100 ^° C. are used.

2. Method according to claim 1, characterized in that said complementary heating step is carried out in series with the step (a) of preheating and upstream thereof.

3. Method according to claim 1, characterized in that said complementary heating step is performed in parallel with a portion of the step (a) of preheating.

4. Method according to one of claims 1 to 3, characterized in that said at least one separation step is performed after a possible prior treatment step of said mixture, such as a desalination step.

5. Method according to claim 4, characterized in that said at least one separation step is carried out adiabatically.

6. Method according to one of claims 1 to 5, characterized in that the step (a) of preheating comprises at least two successive substeps, each of which is followed by a liquid / vapor separation step.

7. Method according to claim 6, characterized in that said at least two substeps are carried out in series or in parallel.

8. Method according to claim 6 or 7, characterized in that a separation step is common to two substeps.

9. Installation for the distillation of a multicomponent liquid mixture such as crude oil, comprising: at least one preheating means (21 to 26) of the vaporization means (3) and a distillation column (4), - at least one liquid / vapor separation means (91 to 93;

910 to 970), located after a preheating means (23, 25, 26; 250 to 310) and, at the outlet of said separation means, means (91a to 93a; 910a to 970a) for directly feeding the portion of said vaporized mixture and corresponding to at least one constituent in said distillation column (4), characterized in that it also comprises upstream of said at least one preheating means (21; 220), a complementary heating means (8, 80 ) using residual energies of low thermal level, whose temperature is below 100 ⁰ C.

10. Installation according to claim 9 wherein the distillation column comprises different trays each corresponding to a temperature and at least one component, characterized in that said supply means (91a to 93a, 910a to 970a) open at the the distillation column tray corresponding to a temperature and the concentration of at least one constituent close to those of the vaporized portion.

11. Installation according to one of claims 9 or 10, characterized in that said at least one liquid / vapor separation means is located downstream of any pre-treatment means of the mixture (5).

12. Installation according to one of claims 9 to 11, characterized in that said at least one liquid / vapor separation means operates adiabatically.

13. Installation according to one of claims 9 to 12, characterized in that it comprises as many liquid / vapor separation means as preheating means.