DEVICE AND METHOD FOR SIMULATED WANDERBED SEPARATION

Abstract

The present invention relates to a simulated moving bed separation device and method, comprising a plurality of in-series adsorbers (1, 2) arranged alternately with upflow and downflow configuration, wherein each adsorber (1, 2) is divided into n adsorption chambers, each comprising an adsorbent bed, the n adsorbent beds being separated by n plates for injecting at least a feedstock and a desorbent and withdrawing at least an extract and a raffinate.

Description

[0001] Device and method for simulated moving bed separation with high height / diameter ratio

[0002] Technical field

[0003] The present invention relates to a device and a method for simulated moving bed separation, in particular for the separation of paraxylene from a mixture of aromatic compounds comprising 8 carbon atoms (orthoxylene, metaxylene and ethylbenzene).

[0004] Prior art

[0005] Current technologies for simulated moving bed separation (sometimes abbreviated in the rest of the text as LMS or SMB for "Simulated Moving Bed" according to English terminology) use units which have a certain number of common points: one or two adsorbers (or separation column) each comprising a plurality of adsorption chambers arranged between a distribution channel and a collection channel, said adsorption chambers comprising an adsorbent bed within which a fluid flows, injection systems, in particular for the feedstock and desorbent, and withdrawal systems, in particular for the effluents produced called extract and raffinate, collection and redistribution systems, called inter-bed zones, to pass from one bed to the next bed.

[0006] A problem with current LMS separation technology is that adsorbers have a large number of beds (typically 12 or more beds) with a low height H to diameter D ratio (ratio typically much less than 1), so that the adsorber is not too tall and thus difficult to erect, operate and maintain.

[0007] Another problem with current LMS separation technology is that the flow of fluids in the adsorber beds is from top to bottom, with fluids from the bottom of the adsorber being pumped up to the top of the adsorber or the next adsorber, which requires a significant investment in energy and equipment (valves, pumps, etc.) to push thousands of m 3 / h of fluid over a height of more than ten meters.

[0008] Another problem with current LMS separation technology is that adsorbers have large volumes of so-called inter-bed zones, which limit separation capacity and increase the need for heavy equipment.

[0009] Another problem with current LMS separation technology is that all beds (eg 12 beds) of the same adsorber need to be stopped in order to maintain or repair a predetermined section of the adsorber.

[0010] Summary of the invention

[0011] In the context described above, a first object of the present description is to overcome the problems of the prior art and to provide an LMS separation device and method which is simpler to erect, use and maintain.

[0012] A second object of the present description is to provide a device and a method for separation in LMS allowing savings in energy and equipment.

[0013] A third object of the present description is to provide a device and a method for separation in LMS making it possible to isolate only part of the beds (e.g. a bed or a pair of beds), without stopping the rest of the device, which can operate in a fallback mode, with sufficient performance.

[0014] According to a first aspect of the invention, the aforementioned objects, as well as other advantages, are obtained by a simulated moving bed separation device comprising a plurality of adsorbers arranged in series arranged alternately in ascending and descending flow, each adsorber being divided into n adsorption chambers each comprising an adsorbent bed, the n adsorbent beds being separated by n trays for injecting a feedstock and a desorbent and withdrawing an extract and a raffinate. According to one or more embodiments, the number of adsorbers m is between 3 and 15, preferably between 4 and 12, very preferably between 5 and 10.

[0015] According to one or more embodiments, the number of adsorbers m is an even number.

[0016] According to one or more embodiments, the number n of adsorbent beds per adsorber is between 1 and 4, preferably between 1 and 3, very preferably between 1 and 2.

[0017] According to one or more embodiments, the total number t of adsorbent beds is between 6 and 24, preferably between 8 and 19, very preferably between 12 and 15.

[0018] According to one or more embodiments, the adsorbent beds have a height H / D ratio to diameter D equal to or greater than 1, preferably equal to or greater than 1.5, very preferably equal to or greater than 2.

[0019] According to one or more embodiments, the adsorbent beds have a height H / D ratio to diameter D of between 1 and 12, preferably between 1.5 and 10, very preferably between 2 and 8.

[0020] According to one or more embodiments, the device further comprises at least one short-circuit line adapted to short-circuit at least one adsorber.

[0021] According to one or more embodiments, the short-circuit line is adapted to short-circuit two adjacent adsorbers.

[0022] According to one or more embodiments, the shorting line connects a downflow adsorber to an upflow adsorber.

[0023] According to one or more embodiments, the adsorbers are arranged in a vertical arrangement for a substantially vertical distribution of the fluid circulating in the adsorbers. According to one or more embodiments, the adsorbers are arranged in a horizontal arrangement for a substantially horizontal distribution of the fluid circulating in the adsorbers. Advantageously, the circulation (ascending / descending) in the adsorbers can take place in a horizontal plane and in two opposite directions.

[0024] According to a second aspect of the invention, the aforementioned objects, as well as other advantages, are obtained by a simulated moving bed separation method using the simulated moving bed separation device according to the first aspect, the method comprising the following steps: the adsorbers are fed with at least one feedstock and one desorbent, and at least one extract and at least one raffinate are withdrawn from said adsorbers, the adsorbent beds being interconnected in a closed loop, the feed and withdrawal points in the adsorbers being offset over time by a value corresponding to an adsorbent bed with a permutation period and determining a plurality of operating zones of the simulated moving bed separation device, and in particular the following main zones: zone I for desorption of a product (of interest) to be separated (egparaxylene) is included between the injection of desorbent D and the withdrawal of extract E; zone II of desorption of the isomers of the product to be separated is included between the withdrawal of extract E and the injection of feed F; zone III of adsorption of the product to be separated is included between the injection of feed F and the withdrawal of raffinate R; and zone IV is included between the withdrawal of raffinate R and the injection of desorbent D.

[0025] According to one or more embodiments, the adsorbent beds are distributed in zones I to IV according to the following configurations known as type a / b / c / d: a is the number of beds in zone I; b is the number of beds in zone II; c is the number of beds in zone III; and d is the number of beds in zone IV, and

[0026] - a = (t * 0.2) * (1 ± 0.2);

[0027] - b = (t * 0.4) * (1 ± 0.2);

[0028] - c = (t * 0.27) *(1 ± 0.2); and

[0029] - d = (t * 0.13) * (1 ± 0.2), and in which t is a natural integer between 6 and 24, preferably between 8 and 15.

[0030] According to one or more embodiments, the adsorbent beds are distributed in zones I to IV according to the following configurations known as type a / b / c / d: a is the number of beds in zone I; b is the number of beds in zone II; c is the number of beds in zone III; and d is the number of beds in zone IV, and

[0031] - a = (t * 0.17) * (1 ± 0.2);

[0032] - b = (t * 0.42) * (1 ± 0.2);

[0033] - c = (t * 0.25) * (1 ± 0.2); and

[0034] - d = (t * 0.17) * (1 ± 0.2), and in which t is a natural integer between 6 and 24, preferably between 8 and 15.

[0035] According to one or more embodiments, the method comprises at least one of the following operating conditions: the desorbent is selected from the group consisting of one or more isomers of diethylbenzene and toluene; the adsorbent used comprises / consists of a Faujasite selected from the group consisting of BaX, BaKX, and BaLSX; the feedstock is selected from the group consisting of a mixture of essentially C8 aromatic compounds; the temperature in the adsorbent beds is between 140°C and 189°C; the pressure is controlled to remain in the liquid phase at all points of the device; the permutation period ST is between 20 seconds and 90 seconds; and the average circulation flow rate between the beds is between 1000 and 5000 m 3 / h.

[0036] Other characteristics and advantages of the invention according to the aforementioned aspects will appear on reading the description below and non-limiting examples of embodiments, with reference to the figures appended and described below.

[0037] List of figures

[0038] Figure 1 schematically shows a reference LMS separation device in which the adsorbers are downflow.

[0039] Figure 2 schematically shows an LMS separation device according to one or more embodiments of the invention in which the adsorbers are alternately downflow and upflow.

[0040] Description of the embodiments

[0041] The invention relates to a device and a method for simulated moving bed separation, in particular for the separation of paraxylene.

[0042] Embodiments of the device and method according to the foregoing aspects will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the method. However, it will be apparent to those skilled in the art that the method can be carried out without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. In the present application, the term "comprise" is synonymous with (means the same as) "include" and "contain", and is inclusive or open and does not exclude other elements not recited. It is understood that the term "comprise" includes the exclusive and closed term "consist". Furthermore, in the present description, the terms "essentially" or "substantially" correspond to an approximation of ± 5%, preferably ± 1%, most preferably ± 0.5%.For example, an effluent essentially comprising or consisting of compounds A corresponds to an effluent comprising at least 95% by weight of compounds A.

[0043] The present invention may be defined as a device or unit comprising a plurality of adsorbers (or separation columns) arranged in series for the simulated moving bed separation of compounds (e.g. xylenes), each adsorber being divided into n adsorption chambers each comprising an adsorbent bed, the n adsorbent beds being separated by n inter-bed trays or zones (i.e., n distribution zones and n collection zones), in which the adsorbers are arranged alternately in ascending and descending flow. The distribution and collection zones comprise collection and redistribution systems for transmitting the fluid passing through the adsorber from one bed to the next bed.

[0044] In the present application, it is considered that the first distribution zone of the first adsorbent bed and the last collection zone of the last adsorbent bed together form a single inter-bed zone.

[0045] The device

[0046] A simulated moving bed separation device according to the invention is, for example, a chromatographic column or adsorption column, operating in a simulated moving bed. Simulated moving bed separation is a well-known technique. As a general rule, the column operating in a simulated moving bed comprises at least three zones, generally four, and possibly five, each of these zones comprising a certain number of successive adsorbent beds (e.g. fixed beds), and each zone being defined by its position between a feed point and a withdrawal point. Typically, a simulated moving bed column is fed with at least one feed F (mixture of xylenes) to be fractionated and a desorbent D (sometimes called eluent), and at least one raffinate R (mixture of xylenes depleted in paraxylene) and an extract E (desorbent and paraxylene) are withdrawn from said column.The feed and draw points are modified over time, typically shifted in the same direction by an amount corresponding to an adsorbent bed.

[0047] Advantageously, the alternating upflow / downflow arrangement of the adsorbers of the device and method according to the present invention makes it possible to improve the construction of the unit, to simplify and limit the necessary equipment, to improve the separation of fluids, and to reduce the operating energy costs by reducing the volume of the so-called inter-bed zones. In addition, the present invention allows the maintainability of the unit with the possibility of completely isolating only one pair of beds, without stopping the rest of the unit, which can operate in a fallback mode, with acceptable, although sometimes reduced, performance.

[0048] The state of the art describes in detail various devices for carrying out charge separation in a simulated moving bed. Mention may be made in particular of patents US 2,985,589, US 3,214,247, US 3,268,605, US 3,592,612, US 4,614,204, US 4,378,292, US 5,200,075, US 5,316,821.

[0049] According to one or more embodiments, the distribution and collection zones comprise injection systems, in particular for a feedstock (e.g. mixture of xylenes) and a desorbent (e.g. toluene or paradiethylbenzene), and for withdrawal, in particular for the effluents produced called extract (e.g. mixture of paraxylene and desorbent) and raffinate (e.g. mixture of orthoxylene, metaxylene, desorbent and optionally ethylbenzene).

[0050] The controlled means / devices for supplying and withdrawing fluids from a simulated moving bed separation device are, for example, one of two main types of technology:

[0051] - either, for each tray, a plurality of on-off controlled valves (optionally with flow control elements) for supplying or withdrawing fluids, these valves typically being located in the immediate vicinity of the corresponding tray. Each tray typically comprises at least four two-way valves, controlled on-off, to respectively supply the feedstock and the desorbent and withdraw the extract and the raffinate;

[0052] - either a multi-way rotary valve for supplying or withdrawing fluids from all the trays.

[0053] The present invention is particularly within the framework of columns operating in a simulated moving bed using a plurality of valves to ensure the supply and withdrawal of the different fluids.

[0054] Preferably, the number m of adsorbers is between 3 and 15, preferably between 4 and 12, very preferably between 5 and 10. Preferably, the number m of adsorbers is an even number.

[0055] Preferably, the number n of adsorbent beds per adsorber is between 1 and 4, and preferably between 1 and 3, very preferably between 1 and 2.

[0056] Preferably, the total number t of adsorbent beds is between 6 and 24, preferably between 8 and 19, very preferably between 12 and 15.

[0057] According to one or more embodiments of the present invention, the adsorbent beds have a height H / D ratio to diameter D of at least 1 (preferably greater than 1), preferably at least 1.5, very preferably at least 2, such as at least 3 or 4. According to one or more embodiments of the present invention, the adsorbent beds have a height H / D ratio to diameter D of between 1 and 12, preferably between 1.5 and 10, very preferably between 2 and 8.

[0058] An additional advantage of the device and method according to the invention is the possibility of using adsorbent beds having a larger H / D ratio (height H to diameter D) than the prior art and gives access to the use of radial beds which allow improved separation. According to one or more embodiments, the device according to the invention further comprises a short-circuit line adapted to short-circuit at least one adsorber, for example two adsorbers of the device. Advantageously, it is possible to isolate only a portion of the adsorbent beds for maintenance, for example by isolating one or two successive adsorbers, and to continue the separation process with acceptable and improved performance compared to, for example, the shutdown of a 12-bed adsorber.

[0059] According to one or more embodiments, the short-circuit line connects an upstream adsorber i (i being between 1 and m) to a downstream adsorber i+2 or a downstream adsorber i+3. According to one or more embodiments, the short-circuit line is adapted to short-circuit, for example by means of a bypass valve, adsorber i+1 and / or adsorber i+2 by sending the flows exiting adsorber i to adsorber i+2 or adsorber i+3. According to one or more embodiments, the short-circuit line connects a downflow adsorber i to an upflow adsorber i+3.

[0060] According to one or more embodiments, the adsorbers are arranged in a vertical arrangement. The invention also applies in the case of a horizontal arrangement of the adsorbers. Then the circulation takes place in the horizontal plane and in two opposite directions. The concept remains identical to the ascending / descending flow and the associated gain is the same.

[0061] Referring to Figure 1, a reference LMS separation device comprises a plurality of downflow adsorbers 1, each adsorber comprising a shell disposed between an upper dome and a lower dome. The downflow arrangement of the reference device corresponds to the overall downward circulation of fluids in all the adsorbers by means of a line connecting the bottom of an adsorber i to the head of the next adsorber i+1. Generally, the reference devices are 24-bed units comprising two downflow adsorbers each containing 12 beds. Referring to Figure 2, an LMS separation device according to one or more embodiments of the invention comprises a plurality of adsorbers arranged alternately in upflow and downflow, each adsorber comprising a shell disposed between an upper dome and a lower dome.

[0062] The alternative arrangement of the downflow adsorbers 1 and the upflow adsorbers 2 of the device according to the invention corresponds to a generally upward circulation of the fluids in adsorbers i, i+2, i+4, etc. and a generally downward circulation of the fluids in adsorbers i+1, i+3, i+5, etc., the head of an adsorber i being connected to the head of the following adsorber i+1 and the bottom of the adsorber i+1 being connected to the head of the following adsorber i+2. The LMS separation device according to one or more embodiments of the invention further comprises a plurality of short-circuit lines 3, each short-circuit line 3 connecting (in the flow direction) each an upstream downflow adsorber 1 to a downstream upflow adsorber 2, thus short-circuiting 2 adsorbers.

[0063] The process

[0064] In the rest of the text, we speak of a step to designate an operation or a group of similar operations carried out on a given flow at a certain point in the process. The process is described in its different steps taken in the order of flow of the flows or products.

[0065] The LMS separation process comprises the following steps: the adsorbers are fed with at least one feed F and one desorbent D, and at least one extract E and at least one raffinate R are withdrawn from said adsorbers, said adsorbers comprising one or more beds of an adsorbent solid interconnected in a closed loop (i.e., the last bed of the last adsorber being adapted to send the circulating flow into the first bed of the first adsorber), the feed and withdrawal points in the adsorbers being offset over time by a value corresponding to an adsorbent bed with a permutation period (denoted ST) and determining a plurality of operating zones of the LMS device, and in particular the following main zones:

[0066] By definition, each of the operating zones is designated by a number: zone I of paraxylene desorption is included between the injection of desorbent D and the withdrawal of extract E; zone II of isomer desorption is included between the withdrawal of extract E and the injection of feed F; zone III of paraxylene adsorption is included between the injection of feed F and the withdrawal of raffinate R; and zone IV is included between the withdrawal of raffinate R and the injection of desorbent D.

[0067] According to one or more embodiments, the adsorbent beds are distributed in zones I to IV according to configurations known as a / b / c / d type, that is to say that the distribution of the beds is as follows: a is the number of beds in zone I; b is the number of beds in zone II; c is the number of beds in zone III; and d is the number of beds in zone IV.

[0068] According to one or more embodiments:

[0069] - a = (t * 0.2) * (1 ± 0.2);

[0070] - b = (t * 0.4) * (1 ± 0.2);

[0071] - c = (t * 0.27) * (1 ± 0.2); and

[0072] - d = (t * 0.13) * (1 ± 0.2), and in which t is a natural integer between 6 and 24, preferably between 8 and 15 (eg 12). According to one or more embodiments:

[0073] - a = (t * 0.17) * (1 ± 0.2);

[0074] - b = (t * 0.42) * (1 ± 0.2);

[0075] - c = (t * 0.25) * (1 ± 0.2); and

[0076] - d = (t * 0.17) * (1 ± 0.2), and in which t is a natural integer between 6 and 24, preferably between 8 and 15 (eg 12).

[0077] In normal operation (e.g., without bypassing an adsorber), the feed and draw are carried out with a predetermined proportion of the number of adsorbent beds in operation in zones I to IV. For example, the proportion of adsorbent beds in zone I in normal operation is equal to a / t, t being the total number of adsorbent beds. According to one or more embodiments, when a number x of adsorbers is bypassed, the controlled feed and draw devices (e.g., multiple on-off valve system, multi-way rotary valve) are adapted to modify the position of the feed points and draw points so that the predetermined proportion of the average number of adsorbent beds in operation in zones I to IV is maintained within an approximation of ± 20%, preferably ± 10%, very preferably ± 5%. For example, the proportion of adsorbent beds in zone I in short-circuiting operation is equal to a / (tx).

[0078] In the present description, a zone comprising "an average number" of adsorbent beds corresponds to a zone which may punctually comprise a first number X (natural integer) of adsorbent beds, and punctually a second number X-1 or X+1 (natural integer) of adsorbent beds. For example, a zone I comprising 2.5 beds, punctually comprises 2 adsorbent beds and punctually comprises 3 adsorbent beds.

[0079] According to one or more embodiments, during a first part of the permutation period ST (eg when permutations of the injection and withdrawal points are out of phase), at least one zone comprises a first number X of adsorbent beds; and during a second part of the permutation period ST, the at least one zone comprises a second number X+1 or X-1 of adsorbent beds.

[0080] According to one or more embodiments, during a first cycle time, or a first part of a cycle time, at least one zone comprises a first number X of adsorbent beds; and during a second cycle time, or a second part of the cycle time, the at least one zone comprises a second number X+1 or X-1 of adsorbent beds. In the present description, the cycle time corresponds to the time during which the injection and withdrawal points of the unit evolve until they return to their initial position.

[0081] According to one or more embodiments, when a number x of adsorbers is short-circuited, the feeding and the withdrawal are carried out in short-circuiting operation according to the following configuration a / b / c / d:

[0082] - a = ((tx) * 0.2) * (1 ± 0.2);

[0083] - b = ((tx) * 0.4) * (1 ± 0.2);

[0084] - c = ((tx) * 0.27)* (1 ± 0.2); and

[0085] - d = ((tx) * 0.13) * (1 ± 0.2), and in which t is a natural integer between 6 and 24, preferably between 8 and 15 (eg 12).

[0086] According to one or more embodiments, when a number x of adsorbers is short-circuited, the feeding and the withdrawal are carried out in short-circuiting operation according to the following configuration a / b / c / d:

[0087] - a = ((tx) * 0.17) * (1 ± 0.2);

[0088] - b = ((tx) * 0.42) * (1 ± 0.2);

[0089] - c = ((tx) * 0.25) * (1 ± 0.2); and

[0090] - d = ((tx) * 0.17) *(1 ± 0.2), and in which t is a natural integer between 6 and 24, preferably between 8 and 15 (eg 12). Preferably, the number x of short-circuited adsorbers is equal to 1 or 2, very preferably, x is equal to 2.

[0091] Consider, for example, a reference simulated moving bed separation device, such as a tower comprising 12 beds stacked in a single shell for the separation of xylenes. In the event of a bed malfunction (leak, breakage, etc.) in a 12-bed tower, the entire tower must be shut down, unloaded, and reloaded before restarting. This involves long periods during which the device is shut down and there is no production.

[0092] Let us now consider a device of the invention, comprising for example 12 adsorbers for the separation of xylenes in which one bed is defective. The bed can be isolated using the short-circuit line, preferably with an adjacent bed. The bypass is preferably carried out from the bottom of the adsorbers, thus allowing the heads of the isolated shells to be opened for unloading and repair. During the maintenance operation the simulated moving bed can continue to operate with the remaining 10 beds.

[0093] Advantageously, it is possible to adjust the sequence so as to maintain the same distribution of adsorbent beds or sieves by zones. For example, for a normal operation in configuration 3 / 6 / 4 / 2. Maintenance can be carried out during a short-circuiting operation in configuration 2,6 / 5,2 / 3,5 / 1,7. Advantageously, the method according to the present invention can implement a synchronous movement of the inlet / outlet pipes, but can also implement a non-synchronous movement of the inlet / outlet valves in the device according to the present invention, a non-synchronous movement also being known as VARICOL. Advantageously, the production can be maintained at the desired purity. The efficiency of the operation may be slightly affected by a smaller volume of sieves available.

[0094] According to one or more embodiments, the desorbent is selected from the group consisting of one or more isomers of diethylbenzene and toluene. According to one or more embodiments, the desorbent is paradiethylbenzene or toluene. According to one or more embodiments, the desorbent is toluene.

[0095] According to one or more embodiments, the adsorbent used comprises / consists of a Faujasite selected from the group consisting of BaX, BaKX, and BaLSX.

[0096] According to one or more embodiments, the filler is selected from the group consisting of a mixture of essentially C8 aromatic compounds (e.g. xylenes and ethylbenzene). According to one or more embodiments, the mixture comprises at least 95%, preferably at least 97% (e.g. at least 99%) of essentially C8 aromatic compounds. According to one or more embodiments, the filler comprises at least 15% by weight of paraxylene and / or 30% by weight of metaxylene relative to the total weight of the filler.

[0097] An example of an industrially important LMS separation process concerns the separation of aromatic C8 cuts to produce paraxylene of commercial purity, typically at least 99.7% by weight, and a raffinate rich in ethylbenzene, orthoxylene and metaxylene.

[0098] The extract produced contains desorbent, paraxylene and possibly traces of isomers (paraxylene purity greater than 95%, preferably greater than 98%). This extract can be treated to separate the desorbent (e.g. by distillation) and then purified either by crystallization or by simulated moving bed adsorption to increase the paraxylene purity.

[0099] According to one or more embodiments, the temperature in the adsorbent beds is between 140°C and 189°C and preferably between 155°C and 185°C, particularly preferably between 170°C and 180°C.

[0100] The pressure is adjusted so that the liquid phase remains at all points in the process according to the invention. According to one or more embodiments, the pressure in the adsorbent beds is between 1 MPa and 10 MPa, preferably between 2 MPa and 4 MPa, preferably between 2 MPa and 3 MPa. According to one or more embodiments, the ST permutation period (period between two successive permutations of the feeds / extractions) used is between 20 seconds and 90 seconds. Preferably, the ST permutation period used is between 30 seconds and 70 seconds (eg 50 ± 10 seconds).

[0101] According to one or more embodiments, the average circulation flow rate between the beds is between 1000 m 3 / h and 5000 m 3 / h, preferably between 2000 m 3 / h or 2500 m 3 / h and 4000 m 3 / h, very preferably between 3000 m 3 / h and 4000 m 3 / h.

[0102] Examples Reference device

[0103] Consider a reference LMS separation device consisting of 12 adsorbers, each containing 1 adsorbent bed with a volume of 45.9 m 3 and a height H / D ratio of 4.

[0104] The flow is downward in each adsorber. The diameter of each adsorber is 3 m, the height 4 between the tangency lines of the domes is 12 m.

[0105] The average circulation flow between the beds is 3850 m 3 / h.

[0106] The inter-bed volume of the unit is estimated at 177.7 m 3 .

[0107] Device according to the invention Let us consider an LMS separation device according to the invention consisting of 12 adsorbers, each containing 1 adsorbent bed with a volume of 45.9 m 3 and a height H / D ratio of 4.

[0108] The flow is alternately ascending and descending in the successive adsorbers. The diameter of each adsorber is 3 m, the height 4 between the tangency lines of the domes is 12 m.

[0109] The average traffic flow between the beds of 3500 m 3 / h.

[0110] The inter-bed volume of the unit is estimated at 125.2 m 3 This example illustrates in particular the gain in inter-bed volume, which leads to a gain in the circulation flow in the unit, therefore an operational gain in the operating cost, as well as in the cost of construction of the unit (reduced mass of metal).

Claims

Demands 1. Simulated moving bed separation device comprising a plurality of adsorbers (1, 2) arranged in series alternately in upward and downward flow, each adsorber (1, 2) being divided into n adsorption chambers each comprising an adsorbent bed, the n adsorbent beds being separated by n trays for injecting a charge and a desorbent and withdrawing an extract and a raffinate.

2. Device according to claim 1, wherein the number of adsorbers m is between 3 and 15.

3. Device according to claim 1 or claim 2, wherein the number of adsorbers m is an even number.

4. Device according to any one of the preceding claims, wherein the number n of adsorbent beds per adsorber (1, 2) is between 1 and 4, preferably between 1 and 3, most preferably between 1 and 2.

5. Device according to any one of the preceding claims, wherein the total number t of adsorbent beds is between 6 and 24, preferably between 8 and 19, most preferably between 12 and 15.

6. Device according to any one of the preceding claims, wherein the adsorbent beds have an H / D ratio (height H to diameter D) equal to or greater than 1, preferably equal to or greater than 1.5, most preferably equal to or greater than 2.

7. A device according to any one of the preceding claims, wherein the adsorbent beds have a height H / D ratio (height H to diameter D) between 1 and 12, preferably between 1.5 and 10, most preferably between 2 and 8.

8. Device according to any one of the preceding claims, further comprising at least one short-circuit line (3) adapted to short-circuit at least one adsorber (1, 2).

9. Device according to claim 8, wherein the short-circuit line (3) is adapted to short-circuit two adjacent adsorbers (1, 2).

10. Device according to claim 8 or claim 9, wherein the short-circuit line (3) connects a down-current adsorber (1) to an up-current adsorber (2).

11. Device according to any one of the preceding claims, wherein the adsorbers (1, 2) are arranged in a vertical arrangement for a substantially vertical distribution of the fluid circulating in the adsorbers (1, 2).

12. Device according to any one of claims 1 to 10, wherein the adsorbers (1, 2) are arranged in a horizontal arrangement for a substantially horizontal distribution of the fluid circulating in the adsorbers (1, 2), the circulation in the adsorbers (1, 2) taking place in a horizontal plane and along two opposite directions.

13. A simulated moving bed separation method using the simulated moving bed separation device according to any one of the preceding claims, the method comprising the following steps: - feeding the adsorbers (1, 2) with at least one feed and one desorbent, and withdrawing at least one extract and at least one raffinate from said adsorbers (1, 2), the adsorbent beds being interconnected in a closed loop, the feeding and withdrawal points in the adsorbers (1, 2) being shifted over time by a value corresponding to an adsorbent bed with a permutation period and determining a plurality of operating zones of the simulated moving bed separation device, of which the following main zones are: - the desorption zone I of a product to be separated is located between the injection of the desorbent D and the withdrawal of the extract E; - zone II of desorption of the isomers of the product to be separated is located between the withdrawal of extract E and the injection of charge F; - Zone III, the adsorption zone for the product to be separated, is located between the injection of charge F and the withdrawal of raffinate R; and - Zone IV is located between the withdrawal of raffinate R and the injection of desorbent D.

14. A method according to claim 13, wherein the adsorbent beds are distributed in zones I to IV according to the following so-called type a / b / c / d configurations: - a is the number of beds in zone I; - b is the number of beds in zone II; - This is the number of beds in zone III; and - d is the number of beds in zone IV, and - a = (t * 0.2) * (1 ± 0.2); - b = (t * 0.4) * (1 ± 0.2); - c = (t * 0.27) * (1 ± 0.2); and - d = (t *0.13) * (1 ± 0.2), and in which t is a natural integer between 6 and 24, preferably between 8 and 15.

15. A method according to claim 13, wherein the adsorbent beds are distributed in zones I to IV according to the following so-called type a / b / c / d configurations: - a is the number of beds in zone I; - b is the number of beds in zone II; - This is the number of beds in zone III; and - d is the number of beds in zone IV, and - a = (t * 0.17) * (1 ± 0.2); - b = (t * 0.42) * (1 ± 0.2); - c = (t * 0.25) * (1 ± 0.2); and -d = (t * 0.17) * (1 ± 0.2), and in which t is a natural integer between 6 and 24, preferably between 8 and 15.