MX2008003904A - Hydrotreating and hydrocracking process and apparatus - Google Patents

Abstract

Partial conversion hydrocracking process comprising the steps of (a) hydrotreating a hydrocarbon feedstock with a hydrogenrich gas to produce a hydrotreated effluent stream comprising a liquid/vapour mixture and separating the liquid/vapour mixture into a liquid phase and a vapour phase, and (b) separating the liquid phase into a controlled liquid portion and an excess liquid portion, and (c) combining the vapour phase with the excess liquid portion to form a vapour plus liquid portion, and (d) separating an FCC feed-containing fraction from the controlled liquid portion and simultaneously hydrocracking the vapour plus liquid portion to produce a dieselcontaining fraction, or hydrocracking the controlled liquid portion to produce a diesel-containing fraction and simultaneously separating a FCC feed-containing fraction from the vapour plus liquid portion. The invention also includes an apparatus for carrying out the partial conversion hydrocracking process.

Description

HYDROCHRAPHY PROCESS AND APPARATUS FOR PARTIAL CONVERSION FIELD OF THE INVENTION The invention relates to a process and a hydrocracking apparatus for partial conversion by means of which a heavy oil feed is hydrotreated and partially converted to produce a feed for a fluidized bed catalytic cracking unit (FCC, for its acronym in English) . The invention is particularly useful in the production of ultra-low sulfur content diesel (ULSD) and a high quality FCC feed, which can be used to produce ultra-low sulfur content gasoline. (USLG, for its acronym in English) in the FCC unit without further treatment of FCC gasoline to meet the sulfur specifications.

BACKGROUND OF THE INVENTION The partial conversion or "mild" hydrocracking has been used by refineries for many years to produce increased yields of middle distillate while improving the raw material for fluidized bed catalytic cracking (FCC). Initially, specialized catalysts were adapted for conditions at low or moderate pressures in FCC feed desulfurizers to achieve 20 to 30 percent conversion of heavy diesel to lighter diesel. The combination of low pressure and high temperatures used to achieve hydro-conversion conditions typically resulted in high, heavy aromatic products with low cetane quality. The promulgation of new specifications for both gasoline and diesel products has put pressure on these processes to make lighter products with lower sulfur contents that can fit into the refinery reserves of diesel and gasoline with ultra-low sulfur content ( ULSD and ULSG). The continued growth in the demand for middle distillate fuel compared to gasoline has once again focused attention on hydrocracking and particularly on hydrocracking for partial conversion as a key process option for the adaptation to the modern clean fuel environment. The new specifications in both E.U.A. as in the U.E. they have demanded dramatic reductions in the sulfur levels of both diesel and gasoline. It is now clear that the lower sulfur levels in these products provide substantial benefits in terms of reduced emissions from automobile and truck exhaust pipes. Transportation by oil pipelines Degrees of both low sulfur content and high sulfur content of distillates are still a work in progress. Recent studies in E.U.A. they indicate that as much as 10% of ultra-low sulfur content diesel (ULSD) will be degraded by transportation by common pipelines and some carriers are requiring that the ULSD have no more than 5 wppm of sulfur at the refinery boundary. The environmental benefits and transport logistics of products ensure that there will be continuous pressure to force all fuels into the ultra-low sulfur content category. The conventional partial conversion units used in many refineries around the world have been designed for pressure levels in the range of 50 to 100 barg depending on the quality of the feed and the objectives in the cycle. They have been designed to achieve 20% to 30% net conversion of heavy vacuum gas oil and total sulfur removal of approximately 95% to produce an adequate FCC feed to make low sulfur gasoline. The process configuration has evolved to include hot high pressure separators to improve the heat integration and amine absorbers to mitigate the effects of a very high content of hydrogen sulfide gas from the recycle.

A significant drawback of this technology has been the inability to have an independent control of the stringency of the hydro-conversion and hydro-desulfurization reaction. While the sulfur in the diesel product can be greatly reduced by applying more hydrotreating catalyst and by achieving a deeper HDS stringency, the only real option to improve the density and quality of cetane is to increase the operating pressure of the reactor or increase the rigor of hydrocracking. Large increases in reactor pressure can result in a chemical hydrogen consumption of 70% to 100%. The high cost of capital and operation associated with these large increases in hydrogen consumption is a significant disadvantage for using high pressure designs to achieve product lift. Patent application WO 99/47626 discloses an integrated hydroconversion process comprising the hydrocracking of a combined stream of refinery and hydrogen to form liquid and gaseous components. The unreacted hydrogen from the hydrocracking step is combined with a second refinery stream and is hydrotreated. The product is separated in a stream of hydrogen and a portion of this stream is recycled to the hydrocracking step. Yields were obtained Higher naphtha and diesel and lower fuel oil yields. However, this process has the disadvantage of requiring a raw material with a relatively low content of nitrogen, sulfur and aromatic elements. This implies, in many cases, that the raw material needs to be pre-treated before the process disclosed. US Patent No. 6294079 discloses an integrated low conversion process comprising separating the effluent from a hydrotreating step into three fractions: a light fraction, an intermediate fraction and a heavy fraction. The light fraction and a portion of the intermediate and heavy fractions avoid the hydrocracking zone and are sent to a separator. A series of high pressure separators is used. The remaining intermediate and heavy fractions are hydrocracked. A raw material of FCC is produced. An increased separator and other separators are used to separate the hydrotreated effluent into a vapor stream and two liquid streams. The parts of each liquid stream are controlled with respect to the flow and mixed again with the stream of compressed, cooled vapor, they are reheated and hydrocracked at a high stringency to generate the highest quality intermediate distillate products. The complex ordering of multiple separators and the cooling of the current of steam lead to the use of additional equipment and an added cost. Sometimes, increasing the stringency of total hydrocracking is not a viable option. When the objective of the process is to make a required amount of FCC feed, a high conversion leads to the formation of good quality diesel. However, the high conversion also results in the production of an insufficient FCC feed since more diesel is produced. The aim of this invention is to provide a process and apparatus in which the FCC feed is treated to produce an FCC feed of ultra-low sulfur content suitable for the production of ultra-low sulfur content gasoline (USLG) that does not require a post-treatment of gasoline. Another objective of this invention is to provide a process and apparatus for producing diesel with an ultra-low sulfur content and a substantially improved ignition quality as measured by the cetane number, cetane number, aromatic content and density. A further objective of this invention is to provide a simple apparatus for carrying out the process of the invention.

SUMMARY OF THE INVENTION The process of the invention comprises hydrotreating and partially converting a heavy oil feed stream which boils above 260 ° C while having a low asphaltene content (<0.1 wt%). By simultaneously producing a high quality FCC feed, the process creates the possibility of producing ultra-low sulfur content gasoline (USLG) from the FCC unit. Diesel and naphtha are also produced. The process of the invention comprises a hydrocracking process for partial conversion comprising the steps consisting of: (a) hydrotreating a hydrocarbon feedstock with a hydrogen-rich gas to produce a hydrotreated effluent stream comprising a liquid / vapor mixture and separating the liquid / vapor mixture into a liquid phase and a vapor phase, (b) separating the liquid phase into a portion of liquid controlled and a portion of excess liquid, (c) combining the vapor phase with the portion of excess liquid to form a portion of vapor and liquid, and (d) separating a fraction containing FCC feed from the liquid portion controlled and simultaneously hydrocracking the vapor and liquid portion to produce a fraction containing diesel or hydrocracking the controlled liquid portion to produce a fraction containing diesel and simultaneously separating a fraction containing FCC feed from the vapor and liquid portion. The apparatus of the invention comprises an apparatus for the hydrocracking process for partial conversion comprising a hydrotreating reactor having one or more catalytic beds and in series with a hydrocracking reactor and having a downstream liquid / vapor separation system. of one or more of the catalytic beds of the hydrotreating reactor, the liquid / vapor separation system comprises an outlet device and an outlet pipe in a separator vessel, the outlet device comprises a pipe extension on the bottom of the separation vessel, the pipe extension is provided with a baffle anti-swirl at the upper open end of the pipe extension, the separator vessel is provided with an outlet pipe at the bottom of the separator vessel, the outlet pipe is provided with an anti-swirl baffle.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows a hydrocracking process for partial conversion of the invention. Figure 2 shows a hydrocracking process for alternative partial conversion of the invention. Figure 3 shows a section through the bottom of the hydrotreating reactor. Figure 4 shows the process of the invention where the liquid / gas separation system is located between the hydrotreating reactor and the hydrocracking reactor.

DETAILED DESCRIPTION OF THE INVENTION The process of the invention is a hydrocracking process for partial conversion at intermediate pressure comprising a hydrotreating step and a hydrocracking step. The process and apparatus of the invention provide a solution that meets current and expected product specifications for both gasoline and diesel fuel without the need for further processing or combination with other lighter components of higher quality. An advantage of the process is that both the hydrogen partial pressure and the hydrocracking conversion can be used for the improvement of diesel quality, while the relatively low total conversion and HDS (hydrodesulphurisation) requirements that are dictated are maintained. for the FCC pre-treatment applications.

By the term "hydrotreat" (HDT) is proposed a process carried out in the presence of hydrogen by means of which the heteroatoms such as sulfur and nitrogen are removed from the hydrocarbon feedstock and the aromatic content of the hydrocarbon feedstock is reduces. The hydrotreatment covers hydrodesulfurization and hydrodesnitrogenation. By the term "hydrodesulfurization" (HDS) the process is proposed, by means of which the sulfur is removed from the hydrocarbon raw material. By the term "hydrodesnitrogenation" (HDN) the process by which nitrogen is removed from the hydrocarbon feedstock is proposed. By the term "hydrocracking" (HC) a process is proposed by means of which a hydrocarbon-containing raw material is catalytically decomposed into a smaller molecular weight chemical species in the presence of hydrogen. In the process of the invention, the main reactor circuit of the process has two reactors in series, a hydrotreating reactor for the pretreatment of the raw material and a hydrocracking reactor for hydrocracking a part of the hydrotreatment reactor effluent. By the term "in series" it is proposed that the hydrocracking reactor be located downstream of the hydrotreating reactor. There is a liquid / vapor separation system integrated in the bottom of the hydrotreating reactor or contained in a separator vessel located between the two reactors to separate the effluent, a mixture of liquid and vapor, that emerges from the catalytic beds of the hydrotreating reactor . In the liquid / vapor separation system a separation is carried out using an outlet device and an outlet pipe. The liquid / vapor mixture is separated into a liquid phase and a vapor phase in the separator vessel. The output device is an internal drain riser pipe to divide the liquid phase into a portion of controlled liquid and a portion of excess liquid. The vapor phase is combined with the excess liquid portion and this portion of steam and liquid can be fed to the hydrocracking reactor. In this case, the controlled liquid portion is removed, bypassing the hydrocracking reactor and is piped to a scrubber to produce the feed of FCC and naphtha and lighter products. It is also possible to send the controlled liquid portion to the hydrocracking reactor and simultaneously separate a fraction containing FCC feed from the vapor and liquid portion. The term "separation" proposes a individual stage distillation in which the hydrotreated effluent stream comprising a liquid / vapor mixture is separated into a liquid portion and a vapor and liquid portion. No change in pressure is required. An advantage of the process of the invention is that a simple separation step is used instead of an increased scheme and multiple separators, complex for dividing the effluent of the catalytic beds of the hydrotreating reactor into two portions. The vapor and liquid portion is sent to the hydrocracking reactor without substantially cooling the vapor, other than the cooling required to control the temperature for the hydrocracking reactor inlet. Part of the liquid phase in the effluent of the hydrotreater is channeled to the FCC feed scrubber. A low pressure separation drum can optionally be added. Only naphtha and lighter hydrocarbons are recovered. The diesel contained in this portion is of lower quality since it has a higher density, a higher content of aromatic elements and a lower cetane value than the diesel produced in the hydrocracking reactor, so that it is more suitable as an FCC feed. The entire diesel produced by the inventive process occurs in the step of hydrocracking and has a much improved quality. An unconverted oil having a boiling range higher than the diesel product (> 370 ° C +) is recovered from the hydrocracked effluent in a fractionating column. This is not converted and can be used as an FCC feed or as a raw material for an ethylene plant or a lubricant plant because it has a higher hydrogen content and a lower aromatic content than the FCC feed produced in the FCC power debugger. Suitable raw material for the process of the invention is vacuum gas oil (VGO), heavy coker gas oil (HCGO), thermally cracked or broken viscosity gas oil (TCGO or VBGO, by its acronym in English) and deasphalted oil (DAO, for its acronym in English) derived from crude oil or other oil produced synthetically hydrocarbon. The boiling range of these feeds is in the range of 300 ° C to 700 ° C with a sulfur content of 0.5 to 4% by weight and a nitrogen content of 500 to 10,000 wppm. The objective of the hydrotreating reactor is mainly to desulfurize the feed below a level of 200 to 1000 wtppm of sulfur, which will result in an FCC gasoline with an ultra-low sulfur content which is suitable for the combination to meet both European and E.U.A. (10 and 30 wtppm, respectively), eliminating the need for post-hydrotreatment of gasoline. Low sulfur content in the feed also has the benefit of dramatically reducing sulfur oxides (SOx) emissions from the FCC regenerator. Secondly, the hydrotreating reactor reduces the nitrogen content in the feed to the hydrocracking reactor. Third, the aromatic content of the FCC feed is also reduced, which will result in higher conversion and higher gasoline yields. The hydrotreating reactor comprises a hydrotreating zone followed by a separation zone. The hydrotreatment zone contains one or more catalyst beds for hydrodesulfurization (HDS) and hydrodesitrogenation (HDN) of the raw material. The products of the hydrotreating zone comprise a mixture of liquid and vapor. In a conventional hydrotreating reactor, the catalyst beds are supported by bed support arms and the vacuum in the header of the bottom reactor is filled with inert beads supporting the last catalyst bed. The mixture of steam and liquid leaves the reactor via an outlet collector which sits on the head of bottom reactor. In one embodiment of the inventive process, the last catalyst bed in the hydrotreating reactor is supported by bed support arms as well as the upper beds. However, instead of retaining a large volume of inert balls, the vacuum in the bottom reactor header is used to separate the liquid / vapor mixture. The liquid / vapor separation system is used in the bottom header to divide the liquid and vapor mixture from the catalytic beds of the hydrotreating reactor into a liquid portion and a vapor portion containing a liquid fraction, ie a portion of vapor and liquid. The vapor and liquid portion can be directed to the hydrocracking reactor and can be converted under suitable conditions to produce the ULSD. The feed for the FCC is composed mainly of the liquid portion. The liquid / vapor separation system is integrated in the hydrotreating reactor and is located in the vacuum at the bottom of this reactor. It comprises an output device for the transfer of the vapor and liquid portion to the hydrocracking reactor. The liquid portion is contained in the bottom of the reactor outside the output device and leaves the reactor hydrotreating separately through the outlet pipe for transfer to, for example, a scrubber. The level of the liquid portion at the bottom of the reactor and therefore the amount of liquid transferred to the scrubber is controlled by conventional flow control valves. Excess liquid not required for transfer to the scrubber enters with the outgoing device with all steam and leaves the reactor as the vapor and liquid portion. The quantity of liquid, ie the portion of liquid controlled, removed by the outlet pipe is established by the desired HVGO conversion. The controlled liquid portion comprises from 30 to 100% by weight of the liquid phase and the excess liquid portion comprises from 0 to 70% by weight of the liquid phase. Preferably, the controlled liquid portion comprises from 60 to 95% by weight of the liquid phase and the excess liquid portion comprises from 5 to 40% by weight of the liquid phase. The integration of the liquid / vapor separation system in the hydrotreating reactor has the advantage of reducing the amount of processing equipment compared with the conventional separation outside the reactor. Conventional separation outside the reactor would require the addition of a high pressure separator vessel with the additional disadvantage of a capital cost increased. The controlled liquid portion is sent to a scrubber in which a vapor stream removes the light hydrocarbons in the naphtha boiling range and dissolves hydrogen sulphide (HS) and ammonia (NH3) in the liquid. The purified product is used as a feed for the FCC unit. The light premium products of the scrubber are predominantly comprised of light hydrocarbons of the boiling range of naphtha together with ammonia and hydrogen sulfide. The entire vapor and liquid portion leaves the separation zone of the hydrotreating reactor and is transferred to the hydrocracking reactor. The hydrocracking reactor also contains one or more catalytic beds. This reactor may contain some hydrotreating catalyst to further decrease the nitrogen to an optimum level (<100 wppm) and a number of hydrocracking catalyst beds. The products of the hydrocracking reactor are cooled and transferred to an external high-pressure separator vessel. A gaseous hydrogen-rich product stream is separated from the cracked product and recycled to the hydrotreating reactor. The liquid stream from the separator is sent to a distillation column where the naphtha, the diesel and the products of Unconverted oil is fractionated. Alternatively, in another embodiment of the invention, after leaving the separation zone where the products of the hydrotreating zone are divided into a liquid portion and a vapor and liquid portion, the vapor and liquid portion is directed to a separator for the removal of a hydrogen-rich stream. The hydrogen-rich stream can be further purified from hydrogen sulphide and ammonia by means of amine scouring and washing with water. The liquid product of the separators (a high pressure hot separator in series with a cold high pressure separator) is mainly an FCC feed and is sent to the scrubber for the removal of the light hydrocarbons, H2S and NH3 dissolved in the liquid . The purified product is used as a feed for the FCC unit. The liquid portion of the separation zone is sent to the hydrocracking reactor which operates with a rigorous cracking sufficient to produce a diesel fraction with product properties in accordance with EN 590 ULSD specifications. The operating conditions in the hydrocracking reactor can be adjusted to provide a product that meets the market requirements of E.U.A. This mode provides an environment of ammonia and hydrogen sulfide lower in the hydrocracking reactor which increases the activity of the hydrocracking catalyst. In another embodiment of the invention, a second feed may be added as feed to the hydrocracking reactor. In this embodiment, the second feed can be hydrotreated and hydrocracked in the hydrocracking reactor and avoids the hydrotreating reactor. An example of a second feed is a light cycle oil (LCO, for its acronym in English) of the FCC, which needs hydrotreatment and additional hydrocracking to convert it into diesel, jet and high quality naphtha. Figure 1 illustrates an embodiment of the invention in which the vapor and liquid portion of the separation zone is cracked in the hydrocracking reactor and the controlled liquid portion is sent to a scrubber. A feed 1 is combined with hydrogen, for example a hydrogen-rich recycle gas 2, and sent to a hydrotreating reactor 3 for hydrodesulfurization and hydrodesitrogenation in one or more catalytic beds. The effluent from one or more of the catalytic beds is a mixture of vapor and liquid which is separated into a liquid phase and a vapor phase. In separation zone 4 downstream of the last catalytic bed takes place the separation in a portion of steam and liquid 5 and a portion of liquid 6 using a system of integrated liquid / vapor separation in the hydrotreating reactor. The liquid / vapor separation system comprises the outlet device and the outlet pipe (shown in Figure 3). The liquid portion 6 consists solely of liquid and the vapor and liquid portion 5 includes all the vapor. The flow rate of the liquid portion 6 is controlled by the conventional flow control valve 7 and the excess liquid not required comes out of the separation zone 4 as a drain through the outlet device together with all the steam and water. this way forms the vapor and liquid portion 5. The controlled liquid portion 6 is comprised of heavy liquid hydrocarbons with a substantially reduced content of sulfur and nitrogen relative to the feed 1. This leaves the hydrotreatment reactor 3 and avoids the reactor of hydrocracking 8 to enter a scrubbing column 9. The light hydrocarbons together with ammonia and hydrogen sulfide are separated in the upper stream 10 of the scrubbing column 9 and the liquid stream resulting from the bottom of the scrubbing column 9 is suitable as an FCC feed of low sulfur content 11. The steam and liquid portion 5 leaves the reactor of hydrotreatment 3. It may optionally be combined with a second hydrocarbon feedstock 22. It then enters the hydrocracking reactor 8 where it is catalytically cracked to form a hydrocracked effluent 12 having suitable properties for the preparation of diesel fuel. One or more catalyst beds are present in this reactor. The hydrocracked effluent 12 is sent to a separator vessel 13 and a stream of hydrogen-rich gas 14 is recycled from the separator 13 to the hydrotreatment reactor 3 via a recycle gas compressor 15. The supplemental hydrogen 16 can be added to the hydrogen-rich stream 14 either upstream or downstream of the compressor 15 to maintain the required pressure. The liquid product 17 of the separator vessel 13 comprising light and heavy hydrocarbons together with dissolved ammonia and hydrogen sulfide is then sent to the fractionating column 18, where a stream of naphtha 19 with ammonia and hydrogen sulfide is removed from above. The heavy hydrocarbon components comprising a diesel stream 20 and an unconverted oil stream 21 are separated and recovered further down in the fractionating column 18. The naphtha stream 19 can be subjected to further separation steps. The diesel stream 20 can also be further separated by the points of boiling in other valuable products such as jet fuel. The streams 11 (low sulfur content FCC feed) and 21 (non-converted oil stream) are typically combined as an individual feed for the FCC unit. However, stream 21 can also be kept segregated for use as a valuable intermediate to make lubricating oils or as a feed to make ethylene. The separation of the liquid phase in a controlled liquid portion and a portion of excess liquid makes it possible to avoid the controlled liquid portion around the hydrocracking reactor. This allows a high conversion in the hydrocracking reactor and this improves the quality of the diesel while maintaining a low total conversion so that the desired amount of FCC feed is produced. Figure 2 illustrates an embodiment of the invention in which the liquid portion of the separation zone is cracked in the hydrocracking reactor and the vapor and liquid portion is sent to the scrubber column. A feed 1 is combined with hydrogen, for example hydrogen-rich recycle gas 2, and is sent to a hydrotreatment reactor 3 for hydrodesulfurization and hydrodesitrogenation in one or more of the catalytic beds. The hydrotreated effluent stream comprising a liquid / vapor mixture enters the separation zone 4 downstream of the last catalytic bed and is separated into a portion of vapor and liquid 5 and a portion of controlled liquid 6 using the outlet device as shown in FIG. described in Figure 1. The flow rate of the controlled liquid portion 6 is controlled by the conventional flow control valve 7 and the excess liquid is not required to leave the separation zone 4 as a drain through the device outlet (shown in Figure 3) along with all the vapor and thus forms the vapor and liquid portion 5. The vapor and liquid portion 5 leaves the hydrotreatment reactor 3 and flows to a separator vessel 8. A stream hydrogen-rich steam 9 is produced from the upper separator and a hydrocarbon liquid stream 10 is produced from the bottom of the separator vessel 8. The hydrocarbon liquid stream uro 10 also contains dissolved ammonia and hydrogen sulfide and flows to the scrubber column 11. A stream of light hydrocarbons 12 together with ammonia and hydrogen sulfide is separated from the scrubber column 11 and the resulting liquid stream from the bottom of the scrubber column 11 is suitable as a low-sulfur content FCC feed 13.

The controlled liquid portion 6 is comprised of heavy liquid hydrocarbons with a substantially reduced content of sulfur and nitrogen relative to feed 1. It leaves the hydrotreating reactor through the flow control valve 7 and combines with the feed stream. hydrogen-rich steam 9 from the separator vessel 8 to make the mixed vapor-liquid stream 14. A second hydrocarbon raw material 26 can optionally be added to the mixed vapor-liquid stream 14 if required. The mixed vapor-liquid stream 14, optionally combined with the second feed, enters the hydrocracking reactor 8, where it is catalytically cracked into the components of the stream 16 having the properties suitable for the preparation of diesel fuel. One or more catalyst beds are present in the reactor 15. The stream 16 flows to the separator vessel 17 where a vapor stream rich in hydrogen 18 is separated from above and recycled to the hydrotreating reactor via a recycle compressor 19. The supplemental hydrogen 20 can be added to the hydrogen-rich stream 18 either upstream or downstream of the compressor 19 to maintain the required pressure. The liquid product 21 of the separator 17 which comprises light and heavy hydrocarbons together with dissolved ammonia and hydrogen sulfide is then sent to the fractionating column 22, where the naphtha with ammonia and hydrogen sulfide is removed from above in the stream of naphtha 23. The heavy hydrocarbon components comprising a The diesel stream 24 and an unconverted oil stream 25 are separated and recovered further down in the fractionating column 22. The naphtha stream 23 can be subjected to additional separation steps. The diesel stream 24 can also be further separated by the boiling points in other valuable products such as jet fuel. Figure 3 shows an embodiment of the invention in which the bottom section of the hydrotreating reactor is adapted to include the liquid / vapor separation system. Therefore, the separating vessel is integrated into the bottom section of the hydrotreating reactor. The output device is located below the support of the last catalyst bed 1 and the support can typically be provided by arms and grids 2. A decoupling space 3 is created in the bottom of the reactor vessel to allow separation of the vapor phases and liquid. In this embodiment of the invention, the output device is in the form of an ascending pipe 4 provided with an anti-swirl baffle 5 at the upper open end of the riser pipe 4. A liquid interface level 6 is created at the height of the baffle 5 which allows all of the reactor steam and a portion of the liquid phase overflow as a portion of steam and liquid and leave the reactor through the transfer line 7 to the downstream hydrocracking reactor (not shown). An outlet pipe 8 is provided to remove a controlled portion of the liquid phase from the central low point of the bottom header of the reactor also covered by an anti-swirl baffle 5. The flow of the liquid portion through the pipeline outlet 8 is regulated by the flow control element 9 through a standard flow control valve 10 through the transfer line 11 to a downstream scrubber (not shown). Figure 4 illustrates another embodiment of the invention where a separator vessel 13 containing the outlet device and the outlet pipe is added downstream of the hydrotreating reactor. The separator vessel 13 is connected via the pipe 12 by transferring all the vapor and liquid contents of the bottom catalyst bed 1 of the hydrotreating reactor to the separator vessel 13. In this In the embodiment, the outlet device is in the form of an ascending pipe 4 provided with an antireflux baffle 5 at the upper open end of the pipe. A liquid interface level 6 is created at the height of the baffle 5 which allows all the reactor steam and a portion of the liquid phase, i.e. the vapor and liquid portion, to overflow and leave the hydrotreating reactor at through the transfer pipe 7 to the downstream hydrocracking reactor (not shown). An outlet pipe 8 is provided to remove a portion of the liquid phase, i.e. the controlled liquid portion, from the central low point of the reactor bottom header also covered by an anti-swirl baffle 5. The flow through this pipe is regulated by the flow control element 9 through a standard flow control valve 10 through the transfer pipe 11 to a downstream scrubber (not shown). This embodiment of the invention is especially advantageous when there are plants that have to be modernized. In these cases, it may not be possible to install the liquid / vapor separation system in the existing hydrotreating reactor. The installation of the liquid / vapor separation system outside the hydrotreating reactor in the form of a separating vessel that contains the outlet device and the outlet pipe directly downstream of the hydrotreating reactor allows a separation of the mixture of steam and liquid effluent from the hydrotreating reactor in a liquid stream and a vapor and liquid stream suitable for further processing . The effluent from one or more of the catalytic beds in the hydrotreating reactor is a mixture of vapor and liquid which is separated into a liquid phase and a vapor phase. The boiling range of the liquid phase is slightly lower than the boiling range of the feed entering the hydrotreating reactor. The liquid phase has a boiling range of 200-580 ° C. The hydrocracking catalysts for partial conversion useful in the process of the invention need to satisfy the following key functional requirements: Size and activity gradation to minimize fouling and pressure drop - Demetallization and reduction of carbon residues Hydrodesulphurisation for the pretreatment of FCC feed at sulfur levels of typically 100 to 1000 wppm Hydrodesitrogenation for pre-treatment of hydrocracker feed at nitrogen levels of typically 50 to 100 wppm - Hydrocracking with high conversion activity and high selectivity towards diesel. In order to maximize performance in each of these functional categories, stacked (multiple) catalyst systems are useful and provide better overall performance and lower cost compared to individual multi-functional catalyst systems. The process described in this document is useful to facilitate independent control of the stringency of the reaction for multiple catalysts which leads to optimized performance and a longer life. The hydrotreating catalysts are individually specified to optimize sulfur removal for the pre-treatment of FCC feed and for the removal of nitrogen for the pre-treatment of hydrocracking feed. The zeolitic and amorphous silica-alumina hydrocracking catalysts are also useful in the process of the invention for converting a heavy feed to lighter products with a high diesel yield. The hydrotreating catalysts can be based, for example, on combinations of cobalt, molybdenum, nickel and tungsten such as CoMo, NiMo, NiCoMo and NiW and can be supported on suitable carriers. Examples of these catalysts are TK-558, TK-559 and TK-565 of Haldor Topsoe A / S. Suitable carrier materials are silica, alumina, silica-alumina, titanium oxide and other support materials known in the art. Other components can be included in the catalyst for example phosphorus. The hydrocracking catalysts may include an amorphous cracking component and / or a zeolite such as zeolite Y, ultra-stable zeolite Y, dealuminated zeolites and so on. Combinations of nickel and / or cobalt and molybdenum and / or tungsten may also be included. Examples are TK-931, TK-941 and TK-951 of Haldor Topsoe A / S. Hydrocracking catalysts are also supported by suitable carriers such as silica, alumina, silica-alumina, titanium oxide and other conventional carriers known in the art. Other components such as phosphorus may be included, may be included as promoters of the reactivity. The reaction conditions in the hydrotreating reactor include a reactor temperature between 325 ° C-425 ° C, an hourly space velocity of the liquid (LHSV) in the range of 0.3 hr "1 to 3.0 hr. "1, a gas / oil ratio of 500-1,000 Nm3 / m3 and a reactor pressure of 80-140 bar.

The reaction conditions in the hydrocracking reactor include a reactor temperature between 325 ° C-425 ° C, an hourly space velocity of the liquid (LHSV) in the range of 0.3 hr "1 to 3.0 hr" 1, a gas / oil ratio of 500-1,500 Nm3m3 and a reactor pressure of 80-140 bar. The controlled liquid portion can comprise 30-100% by weight of the liquid phase and the excess liquid portion can comprise 0-70% by weight of the liquid phase. Preferably, the controlled liquid portion comprises 60-95% of the liquid phase and the excess liquid portion comprises 5-40% of the liquid phase. The specifications of the current European standard EN 590 EU ULSD for diesel are: Sulfur: 10 - 50 wppm Density: <845 kg / m3 T95 (D-86): < 360 ° C Cetane No. D-630: > 51 Cetane Index D-4737: > 46 Poly-Aromatic Elements: < 11% by weight. The current standard specifications of E.U.A. They are less restrictive than the specifications of the European standard menti above. The terms of performance are defined with respect to the cuts of the true boiling point (TBP, for its acronym in English) and the following definitions are used in the examples: Component: cut of TBP Naphtha: < 150 ° C Kerosene: 150-260 ° C Heavy Diesel: 260-390 ° C Full range diesel: 150-390 ° C Unconverted: > 390 ° C The conversion terms are defined below, the power and product values are in%: 390 ° C + net conversion = Power39o0c + - Product390oc + 390 ° C + true conversion = (Feeding39o0c + Product39o ° c +) / Food39o ° c + 390 ° C + crude conversion = 100 - Product390 ° c + EXAMPLES Example 1: In this example, the liquid / vapor separation system is integrated in the hydrotreating reactor. This example shows how the different boiling ranges of the hydrotreating reactor effluent are divided into the separation in the outlet device and the outlet pipe in the liquid / vapor separation system.

The temperature and pressure of the hydrotreating reactor are shown under the conditions of start of operation in Table 1 and the end-of-operation conditions in Table 2.

Table 1 Table 2 The results show that the liquid phase contains mainly material from the boiling range of diesel with some diesel material, but only a small portion of jet and naphtha. He Diesel boiling range material of the hydrotreating reactor has a relatively high sulfur content and a high density and has a high content of mono-aromatic elements so that it is more suitable as an FCC feed preferably than as a high ULSD. quality. The process of the invention leads to substantial economic benefits as illustrated in Table 2.

Example 2: (Comparative) This example shows how diesel quality a 260-390 ° C improves with the additional hydrocracking compared to only hydrotreating an HVGO.

The results are shown in Table 3. The diesel at 260-390 ° C is produced at a hydrogen pressure of 80 bar.

Table 3 The results in Table 3 show that the qualities of an HVGO improve with the conversion, as the specific weight decreases and the cetane index increases.

Example 3 (Comparative): This example illustrates a simplified comparison of both a conventional intermediate pressure hydrocracking process and a high pressure hydrocracking process using a conventional hydrocracker as compared to the process of the invention, ie a hydrocracking process for partial convention of intermediate pressure. The same level of pressure was used in both the MHC and the process of the invention. Sufficient catalyst was used to achieve the sulfur level of ULSD (10 wppm). Table 4 shows the performance that can be achieved through the process of the invention.

Table 4 (1) 100 percent by volume less of the FCC feed from the bottom of the fractionator (2) Cut of full-range diesel, TBP of 150-360 ° C (true boiling point) (3) Relative cost with respect to the intermediate pressure HC unit (which does not include the generation of hydrogen). The results shown in Table 4 indicate that it is not possible for an MHC process to make the diesel density and cetane quality equivalent in comparison with the process of the invention. Increasing the hydrogen pressure to achieve sufficient aromatic saturation to equal the diesel density achieved with the invention requires an operating pressure about 60% higher for the conventional hydrocracker unit as shown by the results in Table 4. For a unit that processes 5000 tons per day of total load, it is calculated that the process of the invention can save a cost of capital of 10 to 20 million euros compared to a hydrocracker for conversion partial high-pressure conventional open circuit that provides the same product quality. Hydrogen is also used more efficiently using the apparatus of the invention resulting in savings of 250, 000 normal cubic meters of hydrogen per day. The annual savings in operating costs based on the demand for hydrogen would be from 2 to 3 million euros. Utility costs are decreased in relation to the high pressure hydrocracker option, mainly as a result of the reduced requirements of hydrogen supplementation and recycling compression.

Claims (9)

1. CLAIMS 1. A hydrocracking process for partially converting a hydrocarbon feedstock, characterized in that it comprises the steps consisting of (a) hydrotreating a hydrocarbon feedstock with a hydrogen-rich gas to produce a hydrotreated effluent stream comprising a mixture of liquid / vapor that separates into a liquid phase and a vapor phase and (b) in a separation step, separating the liquid phase into a controlled liquid portion established by the conversion and a portion of excess liquid by means of the regulating the controlled liquid flow of the separation step with a flow control element and combining the vapor phase with the excess liquid portion to form a vapor and liquid portion and (c) subsequently separating a fraction containing feed for the fluidized bed catalytic cracking of the liquid portion controlled and simultaneously hydrocrack the portion of steam and liquid to produce a diesel-containing fraction or hydrocrack the controlled liquid portion to produce a diesel-containing fraction and simultaneously remove a fraction containing a feed for the fluidized bed catalytic cracking of the vapor and liquid portion.
2. 2. A process in accordance with the claim 1, characterized in that either the vapor and liquid portion or the controlled liquid portion is combined with a second hydrocarbon feedstock to provide a feed for the hydrocracking step.
3. 3. A process according to claim 1, characterized in that the controlled liquid portion is hydrocracked to produce a fraction containing diesel and the fraction containing a feed for fluidized bed catalytic cracking is separated from the vapor and liquid portion. by cooling, washing and phase separation in a hydrogen-rich vapor stream with low content of ammonia and hydrogen sulfide and a hydrocarbon liquid stream comprising the fraction containing an FCC feed.
4. 4. A process according to claim 3, characterized in that the hydrogen-rich vapor stream with a low content of ammonia and hydrogen sulfide is combined with the controlled liquid portion and hydrocracked to produce a diesel-containing fraction.
5. 5. A process according to claim 1, characterized in that the fraction containing a feed for fluidized bed catalytic cracking is separated from the liquid portion. 4 controlled by means of debugging.
6. 6. A process according to claim 3, characterized in that the fraction containing a feed for the fluidized bed catalytic cracking is separated from the hydrocarbon liquid stream comprising the fraction containing a feed for the fluidized bed catalytic cracking. by means of debugging.
7. An apparatus for carrying out a hydrocracking process, characterized in that it comprises a hydrotreating reactor having one or more catalytic beds and in series with a hydrocracking reactor and having a liquid / vapor separation system downstream of one or more of the catalytic beds of the hydrotreating reactor, the liquid / vapor separation system comprises an outlet device and an outlet pipe in a separator vessel, the outlet device comprises a pipe extension on the bottom of the separation vessel , the pipe extension is provided with an anti-vortex baffle at the upper open end of the pipe extension, the separator vessel is provided with an outlet pipe at the bottom of the separator vessel, the outlet pipe is provided with a baffle anti-swirl and with a flow control element through a control valve flow.
8. 8. An apparatus according to claim 7, characterized in that the separator vessel is integrated in the hydrotreating reactor downstream of the last catalytic bed of one or more of the catalytic beds.
9. 9. An apparatus according to claim 7, characterized in that the separator vessel is located downstream of the hydrotreating reactor.