Liquid purification or separation – Processes – Chromatography
Reexamination Certificate
1999-07-29
2001-07-17
Yildirim, Bekir L. (Department: 1764)
Liquid purification or separation
Processes
Chromatography
C210S661000, C210S123000, C208S31000R, C208S345000, C585S825000
Reexamination Certificate
active
06261458
ABSTRACT:
The invention relates to a device that is used for alternately merging several streams of fluid, that enters a zone for bringing it into contact or that exits the zone, with at least one trunnion-mounted ball valve.
The invention is applied particularly within the framework of a process for separating a feedstock that uses several adsorbent beds to circulate the stream or flow of the feedstock, the stream of the extract, the stream of the raffinate, the stream of the desorbent and various flows that circulate between two beds. In this case, the trunnion-mounted ball comprises, for example, at least three fluid connections.
It pertains more particularly to an improved process for separation in a simulated moving bed, such as the one that is described in the patent application of the applicant (FR-97/16,273), where the purity of a product is improved by using a synchronous by-pass. The technical teaching of this application is incorporated with reference.
It also finds its application in all sorts of processes where several streams of fluid circulate from the outside toward a zone of a device where a reaction is carried out or else from a zone toward the outside, or else between several zones of the device.
The invention thus can be used in various processes of chemistry, petrochemistry or else in other areas.
It pertains more particularly to the separation of paraxylene from aromatic hydrocarbon feedstocks with eight carbon atoms.
The invention relates to a DME that can be used in a process for separating paraxylene in a simulated moving bed into a mixture of xylenes and ethylbenzene that contains, with respect to the terephthalic acid synthesis, an intermediate petrochemical in the production of textiles.
The technological background that illustrates the use of an adsorption device with simulated countercurrent is described in, for example, U.S. Pat. No. 2,985,589. In this device, a main fluid that is introduced by a pump circulates along the central axis of a column that contains a solid mass of adsorbent. The flow of this fluid is of piston type (plug flow), so that its composition and its front flow are approximately uniform at all points of a given section of the column.
To attain this type of flow, it is possible to use a device for distributing and mixing fluids as described in U.S. Pat. Nos. 3,214,247 or 4,378,292, whose teachings are incorporated with reference.
In a brief and diagrammatic manner, the device generally comprises a number of adsorbent beds that are fed by a number of distributor plates, whereby each bed is supported by an upper lattice that is placed approximately perpendicular to the axis of the reactor and makes possible the flow of the fluid. Each plate is divided into sectors and each distributor plate segment comprises two non-perforated deflectors that are flat or have a variable thickness and that are placed on the same horizontal plane, between which is placed a space for circulation of the fluid. A lower lattice that is positioned under the deflectors makes it possible to distribute the fluid uniformly into the lower adsorbent bed.
At each distribution plate, at least four transfer lines of secondary fluids (a feedstock injection line, a desorbent injection line, a line for draw-off of an extract or a line for draw-off of a raffinate) that comprise a set of valves are connected to means for swapping out this set of valves.
The injections and the draw-offs of these secondary fluids are carried out among certain beds, and with a regular space of time called period T, introduction and draw-off points that delimit the zones of the interval are moved between beds (Ck) and (Ck+1) in the interval between beds (Ck+1) and (Ck+2).
If n is the number of beds, n*T defines the cycle time.
A pump ensures the recycling of the fluid of the low end of the column toward its upper end.
The secondary fluids, for example the feedstock or the desorbent, are introduced or drawn off for the extract or the raffinate, in or from the circulation space by an introduction or draw-off chamber that is pierced with orifices.
The distribution of fluids over each of the beds requires a collection of the main flow that originates from the previous bed (main flow), the possibility of injecting a supplementary fluid there while mixing these two streams as well as possible, the possibility of sampling a fluid portion that is collected to send it toward the outside and a redistribution over the next bed. To do this, it is possible either to send the entire main flow through the inside of the adsorber according to the diagram that is described in U.S. Pat. No. 2,985,589, or to bring out this entire flow toward the outside to make it enter the adsorber toward the next stage as in U.S. Pat. No. 5,200,075.
According to the teaching of the patent application of the applicant FR-97/16,273, the majority of the main flow is sent toward the inside, and a small minority of this flow is sent toward the outside, typically 2 to 20%, so that the secondary fluids that circulate in the circuits for injecting and for sampling fluids continuously have approximately the same composition as the main fluid. For this purpose, the device is provided with an outside circuit that is known under the name of synchronous by-pass. In this circuit, all-or-nothing valves for sampling secondary fluids, a nonreturn valve and optionally an all-or-nothing valve are branched so that the injections and draw-offs are made on a single plate at the same time.
Although effective, such a circuit exhibits several drawbacks, however. It actually generates dead volumes in a T shape on the synchronous by-pass. It requires the use of several mechanical devices, for example a nonreturn valve, a valve for segregating injections and draw-offs between one plate and the next or the previous plate, all-or-nothing valves that are used for merging the secondary flows and the portion of the main flow that circulates in the synchronous by-pass. All of these devices increase the cost of the installation, its volume and the cost of its maintenance, whereby the by-pass valves and the nonreturn valve are particularly stressed mechanically.
U.S. Pat. No. 4,434,051 describes the use of valves that comprise at least three paths that are arranged in three groups to minimize the number of valves that are usually used to rinse the lines that are effective for a separation device where the entire main flow is sent into the adsorber and the secondary fluids are distributed with a single distribution basket via an adsorbent bed.
The object of this invention consists in using trunnion-mounted valves, whereby the number and the arrangement of these valves is based on the sequence that makes it possible to carry out the separation in a simulated moving bed.
The object of this invention relates to a system that makes it possible to merge at least four fluids with a column for separating a feedstock, whereby said column comprises several hoses for introducing or drawing off one or more fluids.
It is characterized in that it comprises at least one trunnion-mounted valve, whereby said valve comprises at least one means that makes it possible to circulate one or more fluids, whereby said means is placed inside said valve to ensure communication between two zones of said column or between at least one of said zones and at least one point that is outside of said column and several openings (O
A
, O
B
) are placed to ensure the circulation of the fluids according to the stages that are necessary to the process for separation that is carried out in said column.
Said circulation means and said openings are found, for example, in the same plane of the valve.
The valve can comprise at least three communication paths and at least two active positions.
The valve comprises, for example, at least four communication paths and at least three active positions.
The circulation means between two zones comprise at least one channel that is placed in a first plane (meridian) of said valve to ensure the connection between two zones of the column and at least one
Callebert Olivier
Hotier Gerard
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Yildirim Bekir L.
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