FR3040311A1 - PROCESS FOR VACUUM DISTILLATION OF A HYDROCARBON FILLER AND ASSOCIATED INSTALLATION - Google Patents

Abstract

The method comprises the following steps: introducing a charge (12) into a flash zone (N1) of a vacuum distillation column (16); withdrawing a distillate stream (58, 64, 70) at an intermediate level (N3, N4, N5) from the vacuum distillation column (16); drawing of a column top stream (80); partially condensing the overhead stream (80) to recover a liquid stream (84) and a gas stream (82); - Passing the gas stream (82) in a vacuum generating unit (34). The method comprises introducing into the vacuum distillation column (16) a stream (52) of a charge-depleting fluid (12) consisting of a mixture of hydrocarbons having an average weighted boiling point (Tmav) between 150 ° C and 250 ° C ..

Description

Process for the vacuum distillation of a hydrocarbon feedstock and associated plant

The present invention relates to a process for the vacuum distillation of a hydrocarbon feedstock, comprising the following steps: - heating the feedstock; introduction of the charge into a flash zone of a vacuum distillation column; withdrawing at least one distillate stream at an intermediate level from the vacuum distillation column; drawing, at the top of the vacuum distillation column, a column top stream; partial condensation of the overhead stream to recover a liquid flow and a gas flow; - Passing the gas stream into a vacuum generating unit and recovering at least one condensate and a gas fraction of incondensable gas.

Such a process is intended in particular for the distillation of a hydrocarbon feedstock comprising heavy compounds having high boiling points. In particular, the process is intended for the distillation of a feed resulting from the atmospheric distillation of crude oil.

Crude oil refining generally includes atmospheric distillation in which temperatures are maintained below 370 ° C - 380 ° C to prevent high molecular weight components from thermal cracking and form petroleum coke.

The formation of coke is particularly undesirable and results in particular in a fouling of the tubes in the furnace for heating the charge of the distillation column.

Due to the limitation of the heating temperature, the atmospheric distillation produces a residual oil which is collected at the bottom of the atmospheric distillation column. This oil contains hydrocarbons which generally have boiling points above 350 ° C.

This oil is then distilled under vacuum to recover recoverable distillates. For this purpose, the vacuum distillation is operated at very low pressures generally between 13 mbar and 133 mbar (10 mmHg to 100 mmHg), to limit the exit temperature of the oven and consequently limit the risk of cracking and coke formation by lowering the required exit temperatures.

To achieve this level of vacuum, it is known to use a vacuum generation unit comprising several stages of steam jet ejectors installed in series. These ejectors require a significant consumption of driving steam.

Moreover, at this level of vacuum, the condensation of light hydrocarbons and water vapor recovered at the column head requires a very high consumption of cooling water.

To facilitate the distillation, a steam-based exhaust stream is introduced into the distillation column under the feed at the bottom of the distillation column. This exhaustion flow is recovered at the top of the column in the form of steam, mixed with the residual hydrocarbons, and then condensed before being treated in a downstream unit.

Finally, the highest withdrawal in the column where the light vacuum distillation oils are taken has a not inconsiderable viscosity at room temperature, which is penalizing for the design of the air exchangers.

An object of the invention is to obtain a vacuum distillation process which has a decreased utility consumption and a reduction in the size of certain equipment, while maintaining at least as good separation performance. For this purpose, the subject of the invention is a process of the abovementioned type, characterized in that it comprises the introduction into the vacuum distillation column of a flow of a fluid for the depletion of the charge, the fluid exhaust system consisting of a mixture of hydrocarbons having a weighted average boiling temperature of between 150 ° C and 250 ° C, preferably between 190 ° C and 210 ° C.

According to particular embodiments, the method according to the invention comprises one or more of the following characteristics, taken alone or in any technically possible combination: the depletion fluid consists of kerosene; it comprises a step of forming a recycle stream of the depletion fluid from the liquid flow; it comprises the sampling, in the recycle stream of the depletion fluid, of a purge stream of a part of the depletion fluid, and the introduction, downstream of the withdrawal of the purge stream, of a exhaust fluid backup stream, the depletion fluid recycle stream forming at least a portion of the depletion fluid stream; the depletion fluid consists entirely of a make-up stream, no stream coming from the liquid stream being recycled into the flow of depletion fluid introduced into the vacuum distillation column; it comprises the introduction of the heated exhaust fluid stream into the vacuum distillation column at a level below the feed introduction level; it comprises the derivation of a part of the flow of exhaustion fluid, before its introduction into the vacuum distillation column, and its introduction into the charge; the condensation step of the overhead stream is carried out in a first downstream heat exchanger, advantageously a plate heat exchanger, in particular with a small pressure drop, the first downstream heat exchanger being arranged in the distillation column; under vacuum or outside the vacuum distillation column; the condensation step of the overhead stream is carried out in a first downstream heat exchanger, advantageously a plate heat exchanger, in particular with a low pressure drop, the process comprising a step of passing the gas stream from the first downstream heat exchanger in a second downstream heat exchanger, to obtain an additional condensate; the step of passing the gas stream through the second downstream heat exchanger comprises spraying a liquid hydrocarbon stream into the gas stream; it comprises a step of recovering the or each condensate in a capacity and recovering in the capacity of a stream of water to be treated and a stream of recovered hydrocarbons; the step of passing the gas stream into a vacuum generating unit comprises introducing the gas stream into at least one steam ejector, to form an ejected stream, and partially condensing the ejected stream produced by each steam ejector in a condenser. The invention also relates to a vacuum distillation plant, comprising: - a charge heating assembly; a vacuum distillation column and a charge introduction assembly in a flash zone of the vacuum distillation column; a collection assembly of at least one distillate stream at an intermediate level of the vacuum distillation column; a drawing assembly, at the top of the vacuum distillation column, of a column top stream; a partial condensing unit of the column top stream for recovering a liquid stream and a gas stream; a vacuum generation unit, a gas flow passage assembly in the vacuum generation unit and a recovery assembly of at least one condensate and a gaseous fraction of combustible gas produced in the generation unit. vacuum from the gas stream; characterized by an introduction into the vacuum distillation column of a charge-depleting fluid stream, the depletion fluid having a weighted average boiling temperature of from 150 ° C to 250 ° C.

According to particular embodiments, the installation according to the invention comprises one or more of the following characteristics, taken separately or in any technically possible combination: it comprises a depletion fluid recycling element, plant comprising a formation assembly of the depletion fluid stream at least partly from the depletion fluid recycle element; the condensing unit of the column top stream comprises a first downstream heat exchanger, advantageously a plate exchanger, preferably with low losses, placed in the vacuum distillation column or installed outside the column; vacuum distillation; the condensing unit of the column top stream comprises a first downstream heat exchanger, advantageously a plate heat exchanger, preferably with a low pressure drop, and a second downstream heat exchanger, the plant comprising a flow passage assembly; gas in the second downstream heat exchanger, to obtain additional condensate. The invention will be better understood on reading the description which follows, given solely by way of example, and with reference to the appended drawings, in which: FIG. 1 is a block diagram of a first installation of vacuum distillation, intended for the implementation of a first method according to the invention; FIG. 2 is a view similar to FIG. 1, of a second vacuum distillation installation intended for the implementation of a second method according to the invention; FIG. 3 is a view similar to FIG. 1, of a third vacuum distillation installation intended for the implementation of a third method according to the invention.

In all that follows, we will designate by the same references a current flowing in a pipe and the pipe that carries it.

In addition, unless indicated otherwise, the flow rates quoted are mass flow rates, the pressures are given in absolute millibars.

A first installation 10 according to the invention is illustrated in FIG. 1. This installation 10 is intended for the implementation of a first method according to the invention, for the vacuum distillation of a charge 12. The installation 10 comprises an oven 14 for heating the charge 12 and a depletion fluid, a vacuum distillation column 16, and bottom heat exchangers 18. The installation 10 further comprises lateral withdrawals 20, 22, 24 and, associated respectively with each lateral withdrawal 20, 22, 24, respective heat exchangers 26, 28 and 30. In variants, the plant 10 comprises other types of vacuum distillation arrangements (withdrawal number 20 , 22, 24 variables, number of packing beds 43 variables, number of packing beds 41 variables). The installation 10 comprises a downstream heat exchanger 32, a vacuum generating unit 34, and a condensate recovery capacity 36. In this example, the installation 10 comprises an optional downstream separator 38 for recovering the depletion fluid and a pump 40 for recycling the depletion fluid.

In this example, the vacuum distillation column 16 has a first packing bed 43 whose role is to ensure a heat exchange over each rack 20, 22, 24, and whose liquid feed is provided by a first diffuser 44. The vacuum distillation column 16 has, below each withdrawal 20, 22, 24, a second bed 41 of packing, whose role is to ensure a fractionation and whose feeding is provided by a second liquid diffuser 42.

In the example shown in FIG. 1, the heat exchangers 26 and 28 are heat exchangers making it possible to cool part of the withdrawals 58 and 64. The downstream heat exchanger 32 is a water exchanger, fed by a stream of water. at room temperature. The heat exchangers 30 are heat exchangers with air. The vacuum generation unit 34 comprises a plurality of steam jet ejectors 45, connected in series with each other, and for each ejector 45, a downstream water condenser 46. Depending on the desired vacuum level, the number of ejector stages in series may vary.

In the example shown in FIG. 1, the unit 34 comprises three ejectors 45 in series and three condensers 46 interposed between the ejectors 45.

A first method of vacuum distillation of the feed 12 in the plant 10 will now be described.

Initially, the charge 12 is provided. This charge 12 is for example a charge of liquid hydrocarbons, such as a residual oil charge from an atmospheric distillation.

The mass flow rate of the feed 12 is generally between 100 t / h and 1000 t / h.

The feedstock 12 originates either directly from the bottom of an atmospheric crude distillation column (generally of the order of 350.degree. C.) or from a storage tank (at a temperature for example of the order of 80.degree. C) after reheating to a temperature of the order of 300 ° C. The charge 12 is first introduced into the furnace 14 to be heated and advantageously vaporized.

The temperature of the heated charge 50 at the outlet of the furnace 14 is generally between 380 ° C. and 420 ° C. as a function of the desired distillation performances and the TBP cut point between the vacuum residue 79 and the vacuum distillate 20 (FIG. The acronym TBP comes from "True Boiling Point", the English term meaning "true boiling point." The cutting points quoted represent the distilled fraction of crude at the indicated temperatures.

The partially vaporized charge 50 is then introduced into the vacuum distillation column 16 at a level N1 located in the flash zone above the bottom of the vacuum distillation column 16.

Simultaneously, and according to the invention, a depletion fluid stream 52, consisting of hydrocarbons having a mean average boiling point (in English or Tmav) temperature between 150 ° C and 250 ° C ( typically of the order of 200 ° C), is introduced into the furnace 14 to be heated and advantageously vaporized. This temperature Tmav is defined in the "Databook on hydrocarbons" written by J. B. Maxwell under the English expression "mean average boiling point".

A kerosene obtained from an atmospheric distillation of crude oil having an initial TBP cut point of between 145 ° C. and 180 ° C. and a final TBP cut poirb of between 220 ° C. and 250 ° C. advantageously constitutes the exhaust fluid.

The depletion fluid 52 is completely vaporized and superheated before being introduced at the bottom of column 16. Part of this depletion fluid is injected in liquid form into the vacuum oven radiation beam as an accelerating fluid in order to limit the film temperatures in the tubes.

The superheated depletion fluid stream 54 is introduced into the vacuum distillation column 16 at a level N2 located below the last plateau of a depletion zone 56 of the vacuum distillation column 16.

The heated exhaust fluid stream 54 flows up through the trays of the depletion zone 56 between the N1 and N2 levels and vaporizes the lighter fractions of the vacuum residue.

In the vacuum distillation column 16, the vacuum level at the top of the column is advantageously between 13 mbar and 40 mbar (10 mmHg and 30 mmHg), here substantially around 27 mbar (20 mmHg).

A first stream 58 of heavy vacuum distillate ("HVGO" or "Heavy Vacuum Gas Oil") is taken laterally at a first withdrawal 20 at a lower level N3 located above the level N1.

A first fraction 60 of the vacuum heavy distillate stream 58 is reintroduced into the column 16 through the second diffuser 42 associated with the withdrawal 20. The remainder of the vacuum heavy distillate stream 58 passes into a heat exchanger 26 and a second fraction 62 the heavy distillate stream 58 from the heat exchanger 26 is reintroduced into the vacuum distillation column 16, through the first diffuser 44 associated with the withdrawal 20. The remainder of the stream is the production of 180 heavy vacuum distillate from unit.

A second stream 64 of optional mean vacuum distillate ("MVGO" or "Medium Vacuum Gas Oil" in English) is taken at a second rack 22 at an average level N4 above the level N3.

A first fraction 66 of the optional vacuum middle distillate stream 64 is reintroduced into the vacuum distillation column 16 through the second diffuser 42 associated with the second withdrawal 22. The remainder of the average vacuum distillate stream 64 passes through a heat exchanger 28. A second optional fraction 64 of the vacuum middle distillate stream 64 from the heat exchanger 28 is reintroduced into the vacuum distillation column 16, through the first diffuser 44 of the second withdrawal 22. The remainder of the stream constitutes the production of middle vacuum distillate from the unit.

A third stream 70 of light vacuum distillate ("LVGO" or "Light Vacuum Gas Oil" in English) is taken at a third withdrawal 24 at a high level N5 located above the level N4, in the vicinity of the head of the vacuum distillation column 16.

A first fraction 72 of the light vacuum distillate stream 70 is reintroduced into the vacuum distillation column 16 through the second diffuser 42 associated with the third withdrawal 24. The remainder of the stream 70 passes into an air exchanger 30. A second fraction 74 of the light vacuum distillate stream 70 from the heat exchanger 30 is reintroduced into the distillation column 16, through the first diffuser 44 of the third withdrawal 24. The remainder of the stream is the production 160 of light distillate under vacuum from the unit.

A bottom stream 79 is recovered at the bottom of the vacuum distillation column 16 and passes through bottom heat exchangers.

A top stream 80 is drawn at the top of the column, under the effect of the suction produced by the vacuum generating unit 34.

The overhead stream 80 has a pressure equal to the overhead operating pressure 16 and has a temperature generally between 60 ° C and 100 ° C.

The overhead stream 80 is then introduced into the downstream heat exchanger 32, to be partially condensed by heat exchange with the water circulating in the downstream heat exchanger 32. The overhead stream 80 is thus separated into a gaseous flow of head 82 and a liquid foot flow 84.

The head gas stream 82 is fed to the vacuum generation unit 34. It is introduced into a first ejector 45 where it is driven by a driving steam flow 150. The mixture thus formed is introduced into the first condenser 46, to form a first condensate 86 and a first gas stream 88.

The first gas stream 88 is introduced successively into a second ejector 45, then into a second condenser 46, to form a second condensate 90 and a second gas stream 92.

The second gas stream 92 is then introduced into a third ejector 45, then into a third condenser 46, to form a third gas stream 94 of incondensable fuel gas and a third condensate 96 available at a pressure slightly above atmospheric pressure.

The condensates 86, 90, 96 are recovered in a capacity 36 and are separated into a stream of condensed hydrocarbons 98 and a stream of water to be treated 100.

The liquid foot stream 84 contains the majority of the depletion fluid introduced into the depletion fluid stream 52 at the bottom of the vacuum distillation column 16. In fact, the boiling point of the depletion fluid 52 is less than that of the vacuum light distillate stream 70 and is greater than that of water vapor.

The depletion fluid is however more easily condensable than water vapor. This makes it possible to operate the column at a low pressure, as described above.

The liquid foot flow 84 is introduced into the optional downstream separator 38 in equilibrium with the gas flow 82.

The bottom fraction 112 contains the majority of the depletion fluid. It is pumped into the pump 40 to form a stream 114 for recycling the depletion fluid.

A purge stream 116 is withdrawn from the recycle stream 114 to decrease the amount of impurities and maintain a constant recycle stream quality 114 that will be as close as possible to the auxiliary exhaustion stream 118. purge stream 116 generally represents between 5% by weight and 20% by weight of the bottom fraction 112 introduced into the pump 40. In a variant, the process is carried out without total purge recycling (the absence of a recycle flow being compensated by an additional extra flow 118).

Referring to Figure 1, the remainder of the recycle stream 114 is returned to the furnace 14 to form, with a supply stream 118 of depletion fluid, the stream 52 of depletion fluid.

The withdrawal of the purge stream 116 and the supply provided by the feed stream 118 make it possible to renew the exhaust fluid circulating in the process according to the invention. This ensures the maintenance of a good quality of distillation, and a good ability to condense the depletion fluid, eliminating the slightest fractions possibly accumulated.

Furthermore, the flow rate of the depletion fluid stream 52 introduced into the distillation column 16 can be controlled by adjusting the respective flow rates of the purge stream 116 and the supply stream 118.

Table 1 below illustrates the results obtained by numerical simulation for the first process according to the invention, in the context of the treatment of a hydrocarbon feedstock 12 with a mass flow rate of 666.7 t / h resulting from the distillation. atmospheric of a rough type "OURAL". The depletion fluid is kerosene from an atmospheric distillation having a TBP cut point 145 ° C-230 ° C, a molecular weight of 152 g / mol and a density at 15 ° C of Q781.

The results obtained are compared with those of a method of the state of the art, in which the exhaust fluid is water vapor, the installation being devoid of a downstream separator 38 and a recycling pump 40.

Table 1

The presence of a readily condensable depletion fluid provides a flow to the vacuum group 34 much less consumer driving steam 150, which greatly limits the overall consumption of water vapor.

Similarly, the temperatures are higher at the top of column 16, which allows a higher flow temperature 74 than in a conventional scheme. The viscosity of the stream 74 is then reduced, reducing the size of the first air heat exchanger 30.

Similarly, the size of the downstream heat exchanger 32 is reduced because there is no more water vapor to condense.

Moreover, the use of a depletion fluid other than water vapor limits the amount of water to be treated 100 recovered in the capacity 36.

A portion 119 of the flow of fluid 52 is derived in the feed 12 before it passes into the furnace 14 or during this passage.

A second installation 130 according to the invention is illustrated in FIG. 2. The second installation 130 is intended for the implementation of a second vacuum distillation method according to the invention. Unlike the first installation 10, the downstream heat exchanger 32 of the second installation 130 is disposed directly in the distillation column 16, at the head of the column, above the upper bed 43 associated with the upper racking 30. The downstream heat exchanger 32 is here a plate heat exchanger with low pressure drop (typically less than 7 mbar (5 mmHg), in particular of the order of 1.3 mbar (1 mmHg)). Unlike the process shown in FIG. 1, the overhead vapors forming the overhead stream 80 from the distillation in the vacuum distillation column 16 enter the heat exchanger 32 within the vacuum distillation column 16. , by the top. The overhead stream 80 condenses in the heat exchanger 32.

As before, a gas stream 82 is extracted from the heat exchanger 32, to be fed to the vacuum generation unit 34 and a liquid foot stream 84 is recovered at the bottom of the heat exchanger 32, to be brought into the downstream separator 38.

The table below illustrates the results obtained for the second process according to the invention, in the context of the treatment of a hydrocarbon feedstock 12 of mass flow rate equal to 666.7 t / h, resulting from the atmospheric distillation of a rough type "OURAL". The depletion fluid is kerosene from an atmospheric distillation having a TBP cut point 145 ° C - 230 ° C, a molecular weight of 152 g / mol and a density at 15 ° C of 0.781.

The results obtained are compared with a method of the state of the art, in which the exhaust fluid is steam, the installation being devoid of a downstream separator 38 and a recycling pump 40. TABLE 2

Unlike the process shown in FIG. 1, the process illustrated in FIG. 2 has an even lower pressure at the head of the column, for example less than 27 mbar (20 mmHg), and especially between 13 mbar (10 mmHg). and 20 mbar (15 mmHg). At performance identical to the performance of FIG. 10 (recovery rate of the identical heavy vacuum distillate), this diagram reduces the flow of depletion fluid 52 necessary, while maintaining a reduced heat exchange area in the downstream heat exchanger. 32, and in the exchangers 30.

As the quantity of depletion fluid injected into the vacuum distillation column 16 is reduced, the consumption of fuel gas intended for the vaporization of the depletion fluid is thus reduced, which significantly reduces the overall consumption of fuel gas.

The consumption of cooling water is furthermore further reduced, taking into account the lower amount of exhaustion fluid to be condensed in the heat exchanger 32.

In a variant (not shown), the exchanger 32 is located outside the distillation column 16. The performance of this variant is between the performance obtained with the installation shown in FIG. 1 and the performances obtained with the installation shown in FIG.

A third installation 140 according to the invention is illustrated in FIG. 3. Unlike the second installation 130 shown in FIG. 2, the installation 140 comprises a second downstream heat exchanger 142 disposed downstream of the first downstream heat exchanger 32 situated in the vacuum distillation column 16. The second downstream heat exchanger 142 is disposed outside the vacuum distillation column 16, and receives the gas stream 82 from the first downstream heat exchanger 32.

The second downstream heat exchanger 142 is a plate heat exchanger with a low pressure drop (typically less than 7 mbar (5 mmHg), in particular of the order of 1.3 mbar (1 mmHg)). It is here provided with a ramp 143 for spraying a stream of liquid hydrocarbons 144, typically a stream coming from the atmospheric distillation plant. The liquid hydrocarbon stream 144 is for example an atmospheric heavy distillate stream ("HAGO" or "Heavy Atmospheric Gas Oil").

The third vacuum distillation method according to the invention differs from the second method in that the head stream 82 produced in the first downstream heat exchanger 32 is introduced into the second heat exchanger 142. The head stream 82 is at least partially condensed. on the one hand, thanks to the absorption generated by the introduction of the fluid 144, and on the other hand, by heat exchange with the water.

An additional condensate 146 is produced at the foot of the second downstream heat exchanger 142, the remainder of the gas stream 82 being introduced into the vacuum generation unit 34, as previously described. The additional condensate is collected in the capacity 36.

The table below illustrates the results obtained for the third method according to the invention, in the context of the treatment of a hydrocarbon load of mass flow rate equal to 666.7 t / h resulting from the atmospheric distillation of a crude type "OURAL". the exhaustion fluid is kerosene.

The results obtained are compared with a method of the state of the art, in which the exhaust fluid is steam, the installation being devoid of a downstream separator 38 and a recycling pump 40. TABLE 3

The third method according to the invention further reduces the steam consumption of the vacuum generation unit 34. Thus, the overall fuel consumption in the process is further reduced, as well as the amount of water to be treated 100 produced.

As indicated above, the processes according to the invention considerably reduce the consumption of utilities, in particular cooling water and water vapor, which reduces the operating costs of the installation, while maintaining a method for Achieve ambitious performance of vacuum distillate recovery rate.

Claims (16)

1. -Procédé vacuum distillation of a charge (12) of hydrocarbons comprising the steps of: - heating the load (12); introducing the charge (12) into a flash zone (N1) of a vacuum distillation column (16); withdrawing at least one distillate stream (58, 64, 70) at an intermediate level (N3, N4, N5) from the vacuum distillation column (16); drawing, at the top of the vacuum distillation column (16), a column top stream (80); partially condensing the overhead stream (80) to recover a liquid stream (84) and a gas stream (82); - Passing the gas stream (82) in a vacuum generating unit (34) and recovering at least one condensate (86, 90, 96) and a gas fraction of incondensable gas (94); characterized in that the method comprises introducing into the vacuum distillation column (16) a stream (52) of a charge-depleting fluid (12), the depletion fluid being comprised of a hydrocarbon mixture having a weighted average boiling temperature (Tmav) of between 150 ° C and 250 ° C, preferably between 190 ° C and 210 ° C. 2. - The method of claim 1, wherein the depletion fluid is made of kerosene. 3. - Process according to any one of claims 1 or 2, comprising a step of forming a stream (114) for recycling the depletion fluid, from the liquid stream (84). 4. - The method of claim 3, comprising removing, in the recycle stream of the depletion fluid (114), a stream (116) for purging a portion of the depletion fluid, and the introduction , downstream of bleed-off (116), a make-up stream (118) of exhaust fluid, the depletion fluid recycle stream (114) forming at least a portion of the fluid stream of exhaustion (52). 5. - Process according to claim 1 or 2 wherein the depletion fluid consists entirely of a makeup stream (118), no stream from the liquid stream (84) being recycled into the stream (52). ) of depletion fluid introduced into the vacuum distillation column (16). The method of any of the preceding claims comprising introducing the heated exhaust fluid stream (54) into the vacuum distillation column (16) at a level (N2) below the level. (N1) for introducing the charge (12). 7. - The method of claim 6, comprising the derivation of a portion (119) of the depletion fluid stream (52), before its introduction into the vacuum distillation column (16), and its introduction into the load (12). 8. - Process according to any one of the preceding claims, wherein the step of condensing the overhead stream (80) is carried out in a first downstream heat exchanger (32), preferably a plate heat exchanger, in particular at low pressure drop, the first downstream heat exchanger (32) being arranged in the vacuum distillation column (16) or outside the vacuum distillation column (16). 9. - Process according to any one of the preceding claims, wherein the step of condensing the overhead stream (80) is carried out in a first downstream heat exchanger (32), preferably a plate heat exchanger, in particular at low pressure drop, the method comprising a step of passing the gas stream (82) from the first downstream heat exchanger (32) in a second downstream heat exchanger (142) to obtain an additional condensate (146). The method of claim 9, wherein the step of passing the gas stream (82) into the second downstream heat exchanger (142) comprises spraying a liquid hydrocarbon stream (144) into the gas stream ( 82). 11. - Method according to any one of the preceding claims, comprising a step of recovering the or each condensate (86, 90, 96) in a capacitor (36) and recovering in the capacitor (36) a current of water to be treated (100) and a recovered hydrocarbon stream (98). 12 - Process according to any one of the preceding claims, wherein the step of passing the gas stream (82) in a vacuum generating unit (34) comprises introducing the gas stream into at least one steam ejector ( 45) to form an ejected current, and partially condensing the ejected stream produced by each steam ejector (45) in a condenser (46). 13. - Vacuum distillation plant (10; 130; 140) comprising: - a heating assembly of the load (12); - a vacuum distillation column (16) and a charge introduction assembly (12) in a flash zone (N1) of the vacuum distillation column (16); a collection assembly of at least one distillate stream (58, 64, 70) at an intermediate level (N3, N4, N5) of the vacuum distillation column (16); - a drawing assembly, at the top of the vacuum distillation column (16), a column top stream (80); a partial condensing unit of the column top stream (80) for recovering a liquid stream (84) and a gas stream (82); a vacuum generating unit (34), a gas flow passage assembly (82) in the vacuum generating unit (34) and a recovery assembly of at least one condensate (86, 90, 96). and a gaseous fraction of fuel gas (94) produced in the vacuum generation unit (34) from the gas stream (82); characterized by an introduction into the vacuum distillation column (16) of a flow (52) of the charge-depleting fluid (12), the depletion fluid having a weighted average boiling temperature ( Tmav) between 150 ° C and 250 ° C. The apparatus (10; 130; 140) of claim 13 including a depletion fluid recycle element (114), the plant (10; 130; 140) comprising a fluid flow formation assembly (114); depletion (52) at least partially from the depletion fluid recycle element (114). 15. - Installation (130; 140) according to any one of claims 13 or 14, wherein the condensing assembly of the column top stream (80) comprises a first downstream heat exchanger (32), preferably a heat exchanger. plates, preferably with low pressure drops, arranged in the vacuum distillation column (16) or installed outside the vacuum distillation column (16). 16. - Installation (140) according to any one of claims 13 to 15, wherein the condensing assembly of the column top stream (80) comprises a first downstream heat exchanger (32), preferably a plate heat exchanger, preferably at low pressure drop, and a second downstream heat exchanger (142), the plant (140) comprising a gas flow passage assembly (82) in the second downstream heat exchanger (142), to obtain additional condensate (146).