FR2878763A1 - Process for improving hydrogen rich gas effluent in refineries comprises adjusting low hydrogen gas effluent to specific pressure, treating gas effluent, reinjecting part of enriched flow into catalytic reforming unit and removing hydrogen - Google Patents

Abstract

The low effluent gases (3) are treated in a pressure swing adsorption unit of gases (4), which is supplied by the hydrogen rich effluent gas (1) results from the catalytic reforming unit (2) having two exits, an enriched flow (5) having a hydrogen concentration higher than the hydrogen rich effluent gas and a residual flow (6). The hydrogen from the circuit is removed and reinjected into another unit of the refinery.

Description

The present invention relates to a method of upgrading the effluent

  hydrogenated gas from a catalytic reforming unit.

  Each refinery has at least one catalytic reforming unit in its crude oil processing part. This catalytic reforming unit makes it possible to produce automotive fuels with a high octane number (RON of 95 to 105). The charge of a catalytic reforming is obtained by direct distillation of the crude oil; it is generally a C6-C10 gasoline cut, with cutting points between 85 and 175 ° C, and having a bad octane number between 30 and 50. The reactions implemented during the catalytic reforming (dehydrogenation of naphthenes to aromatics, dehydrocyclization of paraffins to aromatics, isomerization of linear paraffins to isoparaffins) are highly hydrogen producing. The hydrogen produced is upgraded within the refinery and until recently, this hydrogen was sufficient to supply all the hydrogen demand of the refinery, and in particular that of the hydrotreating units.

  Today, the evolution of the new specifications on petrol and diesel fuels requires the use of a hydrogenated gas of high hydrogen concentration, generally greater than 92% by volume to increase the desulfurization reactions. Now a catalytic reforming unit produces a hydrogenated gas comprising only 70 to 90% by volume of hydrogen, the balance being a mixture of light hydrocarbons, mainly C1-C2, and some traces of aromatics. The hydrogenated gas produced by the catalytic reforming unit can therefore no longer be directly recovered in certain hydrotreating units of the refinery.

  It has been proposed to purify the hydrogenated gas resulting from catalytic reforming by pressure swing adsorption methods, or PSA ("pressure swing adsorption" in English). These processes make it possible to produce a hydrogen of very high purity (> 99% by volume), but the yield of hydrogen does not exceed 85 to 90% by volume; this loss of hydrogen is a limitation to the implementation of these methods at the output of catalytic reforming.

  An object of the present invention is to provide a method for upgrading a portion of the hydrogenated gas from a catalytic reforming unit in all the hydrogen consuming units of the refinery, including units requiring hydrogenated gas of high concentration. in hydrogen.

  An object of the present invention is to provide a method for upgrading a portion of the hydrogenated gas from a catalytic reforming unit in all the hydrogen consuming units of the refinery, including units requiring hydrogenated gas of high concentration. in hydrogen without loss of yield.

  For this purpose, the invention relates to a process for the recovery of the gaseous effluent rich in hydrogen produced by a catalytic reforming unit of a refinery and having a pressure P, in which the following steps are carried out: during step a), at least one gaseous effluent that is poor in hydrogen from the refinery is recovered and adjusted to the pressure P, - during step b), the gaseous effluent that is poor in hydrogen resulting from of the refinery and adjusted to the pressure P during step a) in a pressure-modulated gas adsorption unit fed by a portion of the hydrogen-rich off-gas from the catalytic reforming unit so as to to provide, at a first outlet, an enriched flow having a hydrogen concentration higher than that of the hydrogen-rich gaseous effluent from the catalytic reforming unit and, at a second outlet, a residual flow, during the 'Etap ec), at least a portion of the enriched stream from the first outlet of the adsorption unit is reinjected into the catalytic reforming unit, so as to form a hydrogen recycling circuit, during the step d), at least a portion of the hydrogen is withdrawn from the recycling circuit so as to reinject it into another unit of the refinery.

  Other characteristics and advantages of the invention will appear on reading the description which follows. Embodiments and embodiments of the invention are given by way of nonlimiting examples, illustrated by the accompanying drawings, in which: FIG. 1 is a diagrammatic representation of a first embodiment of the process according to FIG. invention, - Figure 2 is a schematic representation of a second embodiment of the method according to the invention.

  The invention therefore relates to a method of upgrading the gaseous effluent rich in hydrogen produced by a catalytic reforming unit of a refinery and having a pressure P, in which the following steps are carried out: step a), at least one hydrogen-poor gaseous effluent from the refinery is recovered and adjusted to the pressure P, during step b) the hydrogen-poor gaseous effluent from the refinery is treated. and adjusted to the pressure P during step a) in a pressure modulated gas adsorption unit fed by a portion of the hydrogen-rich off-gas from the catalytic reforming unit so as to supply, at a first outlet, an enriched stream having a hydrogen concentration greater than that of the hydrogen-rich gaseous effluent from the catalytic reforming unit and, at a second outlet, a residual stream, during step c ), we reinjects at least a portion of the enriched stream from the first outlet of the adsorption unit into the catalytic reforming unit, so as to form a hydrogen recycling circuit, during step d) at least a portion of the hydrogen is withdrawn from the recycling circuit so as to reinject it into another unit of the refinery.

  The invention consists in the installation of a pressure-modulated gas adsorption unit between the hydrogenated gas networks of several reaction units producing or using hydrogen units of the refinery. The adsorption unit particularly treats the hydrogenated gas produced by the catalytic reforming unit to produce a hydrogenated gas of higher hydrogen concentration without loss of yield and to supply refinery units with a hydrogenated gas of high purity. The invention makes it possible to achieve the objectives set by using the different hydrogenated effluents of the refinery. These effluents must be chosen so as to have certain characteristics, it being understood that according to the process of the invention, it is possible to treat only a part of each of these effluents. The process according to the invention operates from at least two hydrogenated effluents having different hydrogen concentrations. The catalytic reforming unit produces a hydrogenated effluent having a higher hydrogen concentration than all the other hydrogenated effluents from the other units of the refinery treated by the adsorption unit. Thus, the term "hydrogen-rich effluent" denotes the effluent from the catalytic reforming unit which has the highest hydrogen purity. Generally, this hydrogen-rich effluent has a hydrogen concentration of at least 70% by volume, preferably between 70 and 90% by volume. This hydrogen-rich effluent from the catalytic reforming unit may have a pressure P of at least 10 bar, preferably at least 15 bar. The hydrogen-rich off-gas produced by the catalytic reforming unit can be compressed before supplying the pressurized gas adsorption unit with said effluent, for example using the compressor of the recycling loop. hydrogenated effluent from the catalytic reforming unit. According to the process of the invention, in general, a portion of the gaseous effluent rich in hydrogen is not treated by the adsorption unit and is mixed with the enriched stream. The other gaseous effluents from the refinery are said to be "low in hydrogen" which means that, for each, the value of their hydrogen concentration is at least 10% lower than the value of the hydrogen concentration of the effluent rich in hydrogen, preferably less than 15% and more preferably less than 15 to 50%. According to the invention, the refinery produces at least one gaseous effluent that is poor in hydrogen. Preferably, this gaseous effluent that is poor in hydrogen has a pressure close to the pressure P. It is also possible to use different effluents that are poor in hydrogen from the refinery. then mixed. The hydrogen-poor gaseous effluent from the refinery can come from different refining units (hydrodesulphurization units and / or distillate hydrotreatment units, hydrodesulfurization and / or residue hydrotreating units, hydrocracking unit, FCC unit, Cocker Span, Visor Reducer, Amine Wash Unit, Steam Cracker, Isomerization Unit or any other unit consuming and / or producing hydrogen) or refinery fuel gas network. According to the invention, the pressure of the hydrogen-poor effluent or of the hydrogen-poor effluent mixture is adjusted so that it is close to P. The pressure can be adjusted by compression or pressure drop. To reach the pressure P, it may be necessary to compress a part of the effluents poor in hydrogen and pressure lower than the pressure P. However, this compression may be optional if at least one of the hydrogen-poor effluent has a pressure greater than P In addition, if the pressure of a low hydrogen effluent is greater than p, it is possible to reduce its pressure, for example by means of pressure drop. The invention also covers the process where the hydrogen-poor effluent or the hydrogen-poor effluent mixture already have a pressure close to P; in these cases, no pressure adjustment is necessary. By treatment of these different effluents, the invention makes it possible to enrich the hydrogen-rich effluent from the catalytic reforming unit so as to be able to use it in a reaction unit that consumes hydrogen. This enrichment is obtained by depletion of effluents poor in high purity hydrogen. The unit thus produces a hydrogen-enriched stream generally having a hydrogen purity of greater than 99% by volume, and the unit also produces a low purity hydrogen and low pressure waste stream that can be fed into a gas network. combustible. The pressure and the hydrogen concentration of the waste stream are respectively lower than the pressure and hydrogen concentration values of all the effluents entering the adsorption unit.

  The enriched stream from the first outlet of the adsorption unit is reinjected at least partially into the catalytic reforming unit so as to form a circuit for recycling the hydrogen. This recycling circuit generally comprises a compressor making it possible to obtain the correct hydrogen pressure in the catalytic reforming section. According to a first variant, the hydrogen recycling circuit comprises a compressor and the adsorption unit is placed in the hydrogen recycling loop after the compressor of said loop (according to the hydrogen displacement ses) ). This variant makes it possible to use the compressor of the recycling loop to bring the gaseous effluent rich in hydrogen to the pressure P. According to a second variant, the circuit for recycling the hydrogen comprises a compressor and the adsorption unit. is placed in the hydrogen recycle loop before the compressor of said loop (according to the hydrogen displacement ses).

  According to a last essential characteristic of the invention, part of the hydrogen of the recycling circuit is withdrawn so as to be reinjected into another unit of the refinery, which consumes hydrogen. If the first variant mentioned above is implemented, it is preferable to take at least a portion of the hydrogen from the recycling circuit at a point in the circuit located before the adsorption unit. If the second variant mentioned above, it is possible to reinject hydrogen of different concentrations into the refinery; thus according to this variant, at least part of the hydrogen of the recycling circuit can be withdrawn: at a point in the circuit situated between the adsorption unit and the mixing point of the enriched stream and the part of the gaseous effluent rich in hydrogen not treated by the adsorption unit, so as to form a highly enriched hydrogen effluent, and - at a point in the circuit situated between the reforming unit and the mixing point of the enriched stream and of the part of the gaseous effluent rich in hydrogen not treated by the adsorption unit, so as to form an effluent less enriched in hydrogen.

  Preferably, the pressure swing gas adsorption unit (PSA) is associated with an integrated compressor, and in that, for each adsorber of the unit, a pressure modulation cycle comprises a pressure modulation cycle. sequence of phases which define adsorption, decompression, purge and pressure rise phases, such that: during the adsorption phase: during a first stage, the gaseous effluent rich in hydrogen from the reforming unit and having a pressure P is brought into contact with the bed of the adsorber, and during a second step, is introduced, in contact with the bed of the adsorber, the pressure mixture P consisting of: on the one hand, the mixture of all the hydrogen-poor off-gases from the refinery adjusted to the pressure P during step a), and. on the other hand, PSA recycle gas, so as to adsorb the different compounds of the hydrogen and to produce at the head of the adsorber bed the enriched stream having a hydrogen concentration higher than that of the gaseous effluent rich in hydrogen from the reforming unit, during the decompression phase, the residual stream of the PSA is produced, during the purge phase, a purge gas is produced, and where the recycle gas the PSA is either the residual stream compressed at the pressure P or the purge gas compressed at the pressure P. According to this PSA process, in a first adsorption phase, the gaseous effluent rich in hydrogen from the catalytic reforming is in contact with a first PSA adsorbent bed and in a second phase, it is the hydrogen-poor effluent from the refinery and the PSA recycle gas which are brought into contact with this first set of adsorbent. The recycle gas may consist of two gases, alone or in mixture: the waste gas from the PSA that has been compressed, and the purge gas from the PSA that has been compressed. Preferably, it is the purge gas and not the waste gas. The waste gas comes from the final step of the decompression phase of the PSA and is partly compressed by the compressor integrated in the PSA PSA processing device while the purge gas is from the purge phase of the PSA and is partly compressed by the same compressor integrated PSA before being used as recycle gas. Both of these gases both comprise hydrogen and essentially impurities. Once compressed, they are mixed with effluents low in hydrogen. This mixing can be done in different ways depending on the pressure values of the low hydrogen effluents from the refinery. The hydrogen-poor effluent or effluents having very low pressures can be mixed with the waste gas or the purge gas, and this mixture can be compressed by the PSA integrated compressor to the pressure P. If a hydrogen-poor effluent has a pressure greater than p, the compression of other effluents low in hydrogen can be avoided; in this case, only the waste gas or purge gas is compressed to form the recycle gas. The introduction into the bed of the adsorbent of all these gases mixed with the pressure P allows their reprocessing. During the adsorption phase, the gaseous effluents are introduced in the lower part of the bed in the direction said co-current. During this contacting step, the most adsorbable compounds other than H 2 are adsorbed on the adsorbent and a gas comprising essentially hydrogen is produced at the pressure P reduced by about one bar of loss. charge. During this step, the hydrogen produced is generally of a purity greater than at least 99% by volume, preferably greater than at least 99.5%. This hydrogen is used in a unit of the refinery.

  In order to obtain an efficient purification, the adsorbent of the PSA beds must in particular allow adsorption and desorption of the impurities. The adsorbent bed is generally composed of a mixture of several adsorbents, said mixture comprising for example at least two adsorbents chosen from: activated carbons, silica gels, aluminas or molecular sieves. Preferably, the silica gels must have a pore volume of between 0.4 and 0.8 cm 3 / g and a mass area greater than 600 m 2 / g. Preferably, the aluminas have a pore volume greater than 0.2 cm 3 / g and a mass area greater than 220 m 2 / g. The zeolites preferably have a pore size of less than 4.2 Å, an Si / Al molar ratio of less than 5 and contain Na and K. The activated carbons preferably have a mass area greater than 800 m 2 / g and a micropores of between 8 and 20 A. According to a preferred embodiment, each PSA adsorbent bed is composed of at least three layers of adsorbents of different natures. Each PSA adsorbent bed may comprise: at the bottom, a protective layer composed of alumina and / or silica gel surmounted by a layer of activated carbon and / or carbon molecular sieve and optionally at the top of a layer of molecular sieve. The proportions vary according to the nature of the gaseous mixture to be treated (in particular according to its percentages of CH4 and C3 + hydrocarbons). For example, a water-free gaseous mixture comprising 75 mol% H2, 5% C3 + and 20% light hydrocarbons (C1-C2), CO and N2 can be treated by an adsorption unit. whose beds comprise at least 10% by volume of alumina and 15% by volume of silica gel in low bed, the balance being obtained by activated carbon.

  During the decompression phase of the PSA, the waste gas is produced. This waste gas production can be obtained by countercurrent decompression initiated at a pressure lower than P. This residual gas comprises the impurities and has a hydrogen concentration lower than all the effluents from the refinery. This waste gas can be removed from the process and burned or reused as recycle gas in the PSA as previously indicated.

  The low pressure of the cycle being reached, a purge phase is carried out to finalize the regeneration of the adsorber. During the purge phase, a gas is introduced countercurrently into the adsorber and a purge gas is produced. The gas introduced countercurrent into the adsorber during the purge phase is a gas stream from one of the stages of the decompression phase. The purge gas is generally used as a recycle gas after recompression.

  During the pressure rise phase, the pressure of the adsorber is increased by countercurrent introduction of gaseous flow comprising hydrogen such as the gas produced during different stages of the decompression phase.

  The use of the pressure-swing adsorption unit associated with an integrated compressor (CPSA) has the advantage of allowing the simultaneous treatment of all the effluents comprising hydrogen and to achieve better recovery efficiencies. only if each stream was to be treated separately by a pressure swing adsorption unit. In addition, because of the feeding of the CPSA by two different effluents, it is possible to maintain a constant production of hydrogen for another unit of the refinery.

  FIG. 1 illustrates a first implementation of the method according to the invention. In the illustrated refinery, a naphtha-type hydrocarbon feed 8 is treated by a catalytic reforming unit 2. The catalytic reforming unit comprises the catalytic reaction section where the feedstock is treated under hydrogen pressure (hydrogen from recycling hydrogenated gas of this unit) and a liquid / vapor separation section producing a liquid stream and a gaseous effluent rich in hydrogen 1. This gaseous effluent rich in hydrogen 1 is compressed at the pressure P by the compressor 10 of the recycling loop of the reforming unit. In the usual operation of the refinery, this effluent rich in hydrogen 1 is compressed by the compressor 10 before being recycled directly into the reaction section of the catalytic reforming unit. According to the invention, a part 11 of this compressed effluent can be recycled directly to the catalytic section of the reforming unit, while the other part of this compressed hydrogen-rich effluent 1 is introduced into a adsorption unit of pressure-modulated gas 4 in which a gaseous effluent low in hydrogen 3 is simultaneously treated. The effluent rich in hydrogen 1 is introduced at the top of the adsorption unit 4, the impurities it contains are eliminated therefrom. The adsorption unit 4 produces a hydrogen enriched stream which has a higher hydrogen concentration than the effluent 1 and a pressure close to P. The hydrogen-rich stream produced by the adsorption unit 4 is used. in the reforming unit 2. The PSA also produces a waste stream 6 containing the impurities of the various hydrogenated effluents introduced into the adsorption unit 4. According to a first variant, the purge gas 7 produced by the unit of adsorption 4 can be mixed with the low hydrogen effluent 3. The mixture of these two effluents 3 and 7 is optionally compressed by the compressor (not shown) of the adsorption unit 4 to the pressure P and the mixture The tablet is processed by the adsorption unit 4 during one of the stages of the adsorption phase. According to a second variant of the process, it is the waste gas 6 produced by the adsorption unit 4, which is mixed with the effluent that is poor in hydrogen 3. The mixture of these two effluents 3 and 6 is optionally compressed by the compressor (not shown) of the adsorption unit 4 to the pressure P and the compressed mixture is treated by the adsorption unit 4 during one of the steps of the adsorption phase. Due to the combination of the purification of the hydrogen-rich effluent 1 and its recycling, the reforming unit 2 produces a hydrogen-rich effluent 1 of increased purity and which can be recovered in other units of the refinery. consuming hydrogen (effluent 9).

  Figure 2 illustrates a second implementation of the method of the invention. This second implementation is distinguished by the fact that the adsorption unit makes it possible to treat the hydrogen-rich effluent from the catalytic reforming unit before it is recompressed by the compressor 10 of the recycling loop. Part 12 of the hydrogen-rich effluent may not be treated by the adsorption unit 4 as in the prior art. The remainder of this hydrogen-rich effluent 1 is introduced at the pressure P into the pressure-modulated gas adsorption unit 4 in which a gaseous effluent low in hydrogen 3 is simultaneously treated. The adsorption unit 4 produces a hydrogen-enriched stream which has a higher hydrogen concentration than the effluent 1 and a pressure close to P. The operation of the adsorption unit 4 is identical to that described for FIG. 1. Part 51 of the rich stream the hydrogen produced by the adsorption unit 4 is used in the reforming unit 2. The other part 52 of the hydrogen-rich stream produced by the adsorption unit 4 may be upgraded to other units of the refinery consuming hydrogen. Part of the hydrogen-rich effluent 12 not treated by the adsorption unit 4 is combined with the part of the stream enriched with hydrogen 51 recycled in the reforming unit 2 after compression in the compressor 10. This second implementation The work allows great operational flexibility. It makes it possible to generate hydrogenated gases of different purities either for recycling to the reforming unit, or to the various units of the refinery (effluents 52 and 53).

  The invention has several advantages. Firstly, it makes it possible to purify the hydrogen-rich effluent from the catalytic reforming unit and to recycle it without loss of yield. In addition, the recycling of this hydrogen enriched effluent allows a better operation of the reforming unit leading to: - better products, that is to say having a better octane number, - the output production of the reforming unit of a hydrogen-rich effluent of increased purity compared to the prior art, recoverable in the refinery's hydrotreating units - to the reduction of the power and consumption of the recycling compressor of the refinery; the catalytic reforming unit; - the increase of the cycle time between two regenerations of catalyst of the reforming unit.

  Finally, compared to a pressure swing adsorption unit (PSA) according to the prior art, the hydrogen yield reaches 100% or even exceeds 100% because of the hydrogen supply of the gaseous effluent that is poor in hydrogen. .

EXAMPLES

  Example 1 Installation of the adsorption unit in the recycling loop of the catalytic reforming unit The process illustrated in FIG. 1 is used to demonstrate the impact of the adsorption unit in the loop recycling unit of the catalytic reforming unit. Table 1 gives the characteristics of the process carried out according to the prior art and of the process implemented according to the invention in two distinct configurations: - case 1 allows a comparison while keeping the pressure values at the inlet of a catalytic reactor, of molar ratio H2 / hydrocarbons at the inlet of catalytic reactor and of octane number, - case 2 illustrates the implementation making it possible to increase the quality of the reformate (that is to say its octane number) while maintaining the same cycle time between two catalyst regenerations.

Table 1

  PRIOR ART Process according to the process according to the invention the invention case 1 case 2 H 2 / hydrocarbon molar ratio 5 5 at the inlet of a catalytic reactor Temperature at the inlet of the reactor TTT + 10 C catalyticGasflow of recycled gas at the outlet of the 63 840 46 922 55 414 of the liquid / vapor separation section of the reforming unit (Nm3 / h) (effluent 1) Pressure difference within 6 3.2 3.7 the recycling loop (bar) H2 flow rate evacuated to the network 11 966 11 770 12 043 (Nm / h) (effluent 9) Volume concentration in 79.2 93 91.2 hydrogen of the effluent 1 RON octane number of 96 96 100.2 liquid hydrocarbons obtained at the outlet of the liquid / vapor separation section of the reforming unit 83.9% 83.7% hydrocarbon yield 79.4 C5 + obtained at the outlet of the liquid / vapor separation section of the reforming unit Cycle time between two 9,2 13,7 9.2 catalyst regenerations Recompression (kW) 1348 695 721 For two embodiments of the invention (case 1 and case 2), the operating characteristics of the adsorption unit are collated in table 2.

12 Table 2

  Rich effluent Poor effluent Enriched stream 5 Residual stream of hydrogen 1 to hydrogen 3 6 Case 1 Flow 43 637 9697 43 637 9697 Hydrogen (Nm3 / h) 0/0 Volume 93 50 99.9 43 Hydrogen P (bar) 20 4 19 4 Case 2 Flow 55 414 11 230 55 414 11 230 hydrogen (Nm3 / h) 0/0 volume 91.2 50 99.9 41 hydrogen P (bar) 20 4 19 4 It can be seen that the implementation of case 1 of the first mode of the process according to the invention: - the purification of the effluent rich in hydrogen 1 makes it possible to increase the cycle time between two regenerations of the catalyst by nearly 49%, - makes it possible to generate a very pure hydrogen (99.9 mol%) for the refinery network and in particular hydrotreating applications requiring a high purity of hydrogen, - the decrease in the molar mass of the hydrogenated effluent 1 of the unit of catalytic reforming (due to the increase of its hydrogen purity) and the reduction of the total recycling flow rate makes it possible to reduce the power of the compress 48% recycling.

  It can be observed that by using case 2 of the first mode of the process according to the invention: recycling a hydrogenated flow of high purity makes it possible to work at a higher temperature than in the prior art while retaining the the same cycle time, the octane number increasing from 96 to 100.2, the purity of the hydrogen-rich effluent 1 remains much greater than that of the prior art (91.2%), the power The compression process in the recycle loop is greatly reduced from 1395 to 721 W. EXAMPLE 2 Treatment of a Part of the Effluent of the Recycling Loop of the Catalytic Reforming Unit The process illustrated in FIG. in order to demonstrate the impact of the adsorption unit in the recycling loop of the catalytic reforming unit.

  FIGS. 3 and 4 illustrate the impacts of the quantity of effluent rich in hydrogen (expressed in Nm3 / h) sent to the adsorption unit over the cycle time, expressed in months (curve a), the cost of compression expressed in kW (curve b), and the purity of the hydrogenated stream directed to other units of the refinery (effluent 52), expressed in% mol of H2 (curve c). It is observed, for example, that for point B where the adsorption unit 4 processes a hydrogen-rich gas flow 1 of 30 000 Nm 3 / h: the percentage of hydrogen of the gas directed towards the refinery is increased, the pressure drop is reduced from 6 to 4.2 bar, the cycle time is extended from 9.2 to 12.5 months, the compression power is reduced from 1348 to 772 kW, the With adsorption 4 treating only a part of the effluent rich in hydrogen 1, it is possible to generate two hydrogenated gases of improved hydrogen purity: one of high purity corresponding to the hydrogenated stream leaving the adsorption unit 52 and the other of lower purity corresponding to the mixture of this flow of high purity 52 and the portion of the effluent rich in untreated hydrogen 12.

  Table 3 gives the characteristics of the process implemented according to the prior art and of the method implemented according to the invention in point B of FIGS. 4 and 5.

Table 3

  PRIOR ART Process according to the invention, point B H 2 / hydrocarbon molar ratio 5 at the catalytic reactor inlet Flow rate of recycled gas at the outlet of the liquid / vapor separation section of the reforming unit (Nm3 / h) (effluent 1) Difference of pressure within 6 4.2 the effluent effluent effluent loop 52 53 Flow rate of H2 discharged to the system 11 966 2500 9340 Volume concentration in 79.2 99.9 89 , 9 hydrogen of the effluent discharged to the network RON octane number of the 96 96 liquid hydrocarbons obtained recycled at the outlet of the liquid / vapor separation section of the reforming unit Cycle time between two 9.2 12, Catalyst regeneration Recompression (kW) 1348 772 The operating characteristics of the case 3 adsorption unit are collated in Table 4.

Table 4

  Rich effluent Poor effluent Enriched stream 5 Residual stream of hydrogen 1 to hydrogen 3 6 Flow 28157 5719 28157 5719 hydrogen (Nm3 / h)% volume 91.4 50 99.9 541 hydrogen P (bar) 20 4 19 4

Claims (14)

  1. Process for the recovery of the gaseous effluent rich in hydrogen (1) produced by a catalytic reforming unit (2) of a refinery and having a pressure P, in which the following steps are carried out: from step a), at least one hydrogen-poor gaseous effluent (3) from the refinery is recovered and adjusted to the pressure P, during step b) the low-grade gaseous effluent is treated with hydrogen (3) from the refinery and adjusted to the pressure P during step a) in a pressure-modulated gas adsorption unit (4) fed by a portion of the hydrogen-rich off-gas (1 ) from the catalytic reforming unit (2) so as to provide, in a first outlet, an enriched stream (5) having a hydrogen concentration higher than that of the gaseous hydrogen rock effluent (1) derived from the catalytic reforming unit (2) and, in a second outlet, a waste stream (6), - in the middle s of step c), at least a portion of the enriched stream (5, 51) from the first outlet of the adsorption unit (4) is reinjected into the catalytic reforming unit (2), in such a way that to form a circuit for recycling hydrogen, - during step d), at least a portion (9, 52, 53) of hydrogen is withdrawn from the recycling circuit so as to reinject it into another unit of the refinery. 20 2. Method according to claim 1, characterized in that the gaseous effluent rich in hydrogen (1) produced by the catalytic reforming unit (2) has a pressure of at least 10 bar.   3. Process according to claim 1 or 2, characterized in that the hydrogen-rich gaseous effluent (1) produced by the catalytic reforming unit (2) is compressed before supplying the gas adsorption unit. pressure modulated (4) with said effluent.   4. Method according to one of the preceding claims, characterized in that the effluent rich in hydrogen (1) from the catalytic reforming unit (2) has a hydrogen concentration of at least 70% by volume, preferably between 70 and 90% by volume.   5. Method according to one of the preceding claims, characterized in that the gaseous effluent low in hydrogen (3) from the refinery has a hydrogen concentration of at least 10% lower than the value of the concentration of hydrogen. hydrogen from the gaseous effluent gas (1) produced by the catalytic reforming unit (2).   6. Method according to one of the preceding claims, characterized in that the gaseous effluent liquefied with hydrogen (3) from the refinery comes from a purge of a reaction unit of the refinery.   7. Method according to one of the preceding claims, characterized in that the gaseous effluent low in hydrogen (3) from the refinery comes from the fuel gas network of the refinery.   8. Method according to one of the preceding claims, characterized in that part of the gaseous effluent rich in hydrogen (11, 12) is not treated by the adsorption unit (4) and is mixed with enriched stream (5, 51).   9. Method according to one of the preceding claims, characterized in that the hydrogen recycling circuit comprises a compressor (10) and that the adsorption unit (4) is placed in the recycling loop of the hydrogen after the compressor (10) of said loop.   10. The method of claim 9, characterized in that takes away at least a portion (9) of the hydrogen recycle circuit at a point of the circuit located before the adsorption unit (4).   11. Method according to one of claims 1 to 8, characterized in that the hydrogen recycling circuit comprises a compressor (10) and that the adsorption unit (4) is placed in the recycling loop hydrogen before the compressor (10) of said loop.   12. The method of claim 11, characterized in that takes away at least a portion (52, 53) of the hydrogen recycle circuit at a point of the circuit located after the adsorption unit (4).   13. Process according to claim 11, characterized in that at least a portion of the hydrogen is removed from the recycling circuit: at a point in the circuit situated between the adsorption unit (4) and the mixing the enriched stream (51) and the portion of the hydrogen-rich off-gas (12) not treated with the adsorption unit (4) to form a highly enriched hydrogen effluent (52), and at a point in the circuit situated between the reforming unit (2) and the mixing point of the enriched stream (51) and the part of the hydrogen-rich off-gas (12) not treated by the unit of adsorption (4), so as to form an effluent less enriched in hydrogen (53).   14. Method according to one of the preceding claims, characterized in that the pressure-modulated gas adsorption unit (4) is associated with an integrated compressor, and in that it uses, for each adsorber of the unit, a pressure modulation cycle comprising a succession of phases which define adsorption, decompression, purge and pressure rise phases, such that: during the adsorption phase: during the a first step, the gaseous effluent rich in hydrogen (1) from the reforming unit (2) and having a pressure P is brought into contact with the bed of the adsorber, and in a second step the pressure mixture P is introduced into contact with the bed of the adsorber and comprises: on the one hand, or the gaseous effluents with low hydrogen content (3) coming from the refinery adjusted to the pressure P during of step a), and secondly, recycle gas PSA, so as to adsorb the diff compounds hydrogen at the top of the bed of the adsorber the enriched stream (5) having a hydrogen concentration higher than that of the gaseous effluent rich in hydrogen (1) from the reforming unit (2). ), during the decompression phase, the waste stream (6) of the PSA is produced, - during the purge phase, a purge gas (7) is produced, and the PSA recycle gas is either the residual stream (6) compressed at the pressure P, or the purge gas (7) compressed at the pressure P.