The invention relates to a device and a method for loading a chamber with a divided solid, particularly for loading a chemical reactor with a catalyst, and serving in particular, thanks to the hollow configuration of a rotating shaft, for the introduction and/or withdrawal of a functional device in the chamber during loading.
The invention relates more particularly to the loading of chemical or electrochemical, petroleum or petrochemical fixed bed reactors, with solid particles in the divided state, which may have the form of beads, grains, cylinders, pellets, rods, or any other shape, but which generally have relatively small dimensions. The particles may in particular be molecular sieves or solid catalyst grains, generally extruded, prepared either in irregular shape, or in the form of single- or multilobe rods, whereof the dimensions vary according to each individual case, from a few tenths of millimeters to a few centimeters.
This is the application to which reference is made more particularly in the rest of the specification, but the inventive device and method apply to the loading of a chamber with any other type of solid particles.
A number of methods and devices are known for increasing the density of a fixed bed of catalyst particles in a chemical reactor. These methods have the common feature of the introduction of the particles to be loaded via the top of the reactor and the collision of the individual particles during their fall with fixed or mobile mechanical deflectors, causing a random deviation of the particles. Ideally, the particles thus deviated from their vertical falling path fall individually and freely by a shower effect on the overall surface of the filling front where they form a dense and uniform deposit.
The Applicant, as part of its efforts to optimize these reactor loading systems, has developed an improved feeding device which, thanks to a particular dispersal system with flexible deflectors hinged on a rotating shaft, has succeeded in considerably reducing the steric hindrance of the system of deflectors and facilitating its installation in the reactors. This basic system is described in patent application EP 0 007 854 and the improvements to this filling device are disclosed for example in applications EP 0 116 246 and EP 0 769 462.
Despite the use of efficient deflector systems, the real behavior of the catalyst particles during the filling of the reactor may be different from the ideal behavior described above. The “filling front”, also called the “loading profile”, that is, the interface between the catalyst bed and the still unfilled part of the reactor, may sometimes deviate substantially from the horizontal. The catalyst particles, particularly when they have an anisotropic shape, then take position in preferential directions, thereby creating preferential paths for the liquid feed and the reagent gas through the catalyst bed, giving rise to unsatisfactory reactor operation for the operator.
The Applicant has currently succeeded in guaranteeing to its clients filling front slopes not exceeding 10%, but it continues to try to reduce this value in order to ensure optimal operation of the reactors filled with the dense loading device.
It is consequently important to be able to check the horizontality of the filling front during the loading, continuously or at certain intervals, in order, if necessary, to modify the operating parameters of the loading device to correct any drift of the slope of this filling front.
One solution currently consists in interrupting the loading to check the horizontality of the filling front by appropriate means, with regard to the quality criteria of the company responsible for the loading and also those of the operator. While this verification serves to correct the operating parameters of the filling device, particularly the speed of rotation of the particle dispersal system, the interruption of the loading operation that it entails is penalizing for the operator because it increases the reactor down time. Moreover, this solution is relatively complex because it requires the dismantling of the filling device for the installation of an appropriate measuring system.
Other solutions have been proposed in the prior art, for example, Japanese patent application JP 7-242337, which discloses a method and a device for monitoring the filling of a chamber (reactor) with a granular catalyst. The device described in this application comprises filling means, located in the upper central part of the chamber, spreading a shower of catalyst grains, and a device emitting a laser beam sweeping the surface of the filling front and means detecting the laser beam emitted by the emitting device and reflected by the surface of the loading front. The emitting and detecting devices are fixed to the chamber wall, at the level of the filling means. The system described in this application has the drawback of being rather difficult and time-consuming to install on the chamber to be filled, thereby undesirably lengthening the down time of the reactor. Furthermore, this system, comprising telemetry measurement means at the height of the filling means, cannot operate with the dense loading device described in EP 0 769 462, because the presence of the rotating deflectors between the filling front and the telemetry measuring system would disturb the laser telemetry measurements.
The Applicant has recently developed a system which, while essentially operating according to the same principle as the dense loading system (Densicat®) disclosed in EP 0 769 462, with the same ease of installation and operation, serves, among other possibilities, to introduce a device for measuring the progress and quality of filling and, in particular, the slope of the filling front. According to the present invention, the introduction of a measuring instrument is made feasible by supplanting the solid rotating shaft of the prior art by a hollow shaft having appropriate internal dimensions, that is, dimensions permitting either the passage of means for suspending said instrument, or the passage of said instrument itself after installation of the loading device on the reactor, or also permitting the performance of a precise operation in the zone to be loaded, or even a combination thereof.
The subject of the present invention is therefore a device for uniformly loading solid particles in a chamber comprising, in its upper part, particle feed means and, at its base located in the chamber to be loaded, a dispersal system integral with a central shaft rotated about a substantially vertical axis by drive means, and a feed line at least partially surrounding said central shaft, this device being characterized in that the central shaft is a tube having a sufficient inside diameter for carrying out, in the zone to be loaded, via this tube and during the loading period, a number of operations ancillary or complementary to said loading operation.
A further subject of the present invention is a method for loading a chamber with solid particles, from the top downward over the whole cross section of said chamber, using such a device.
A final object of the invention is the use of such a device for loading petroleum, chemical or petrochemical reactors.
In the loading device of the present invention, the catalyst particles issuing from the feed means fall by gravity into the feed line, between the inside wall of said feed line and the outer wall of the rotating central shaft. The feed line comprises, at its base, at least one discharge opening, located above the dispersal system, through which the particles fall on the dispersal system rotated by the central shaft.
The motor which rotates the tubular central shaft of the inventive device is preferably off-centered to said shaft and may be supplied with any compressed gas, for example air or nitrogen. The rotary motion can be transmitted from the drive means to the tubular shaft by any appropriate known means, for example by a belt, a chain or a set of gears, or a combination thereof.
As stated above, the inside dimensions of the central shaft must be sufficient for carrying out, in the zone to be loaded, and during the loading period, a number of operations ancillary or complementary to said loading operation.
Such operations may or may not involve the passage of a functional device. When the passage of a functional device is unnecessary for the operation to be performed, that is, for example, for a simple suction of dust through the rotating tube, or when a functional device is suspended, before the activation of the rotating system, from suspension means passing through the opening of said tube, the diameter of this tube may be relatively small. In contrast, to introduce and/or withdraw a functional device through the opening defined by the hollow shaft, the inside diameter thereof is generally larger and must in any case be sufficient for the passage of said functional device.
In concrete terms, the tube forming the central shaft of the inventive device preferably has an inside diameter larger than 2 cm, and more particularly larger than 10 cm.
Upon the introduction of the functional device during loading, via the opening in the central shaft, this functional device is liable to strike the rotating tube and be damaged. Furthermore, the operator who guides the functional device through the vertical channel of the shaft runs the risk of touching the rotating tube and being injured. To remedy this dual drawback, an additional fixed tube has been provided, isolating the rotating tube from the functional device and from the operator. In consequence, the loading device of the invention preferably further comprises a fixed protective tube having a smaller outside diameter than the inside diameter of the rotating tube. This fixed protective tube is placed inside the opening of the rotating tube so that the two tubes are substantially coaxial. This fixed tube is integral with the feed line. The fixed tube can be joined to the feed line, for example at their upper end.
The replacement of a solid shaft by a hollow shaft with a relatively large inside diameter is liable to create a central shadow in the central zone of the loading front, located immediately below the opening of the shaft or of the fixed tube, resulting in a hollow on the filling front due to insufficient input of particles. To make up for this possible shortage of particles and to avoid the formation of a hollow in the central zone of the chamber, the applicant has developed a device for aiming particles toward the center of the loading front. This device is a central deflector fixed to the bottom end of the fixed tube or of the rotating tube and located below the dispersal system. It has been designed to permit for distributing a controlled quantity of particles into the zone located immediately under the opening of the rotating tube.
It is in principle possible to use any type of deflector capable of diverting the particles toward the center of the chamber. In a preferred embodiment of the inventive device, this deflector has the shape of a funnel, preferably an openwork funnel, that is, a funnel comprising a number of openings that are sufficiently large to allow the passage of the particles to be loaded. These openings may be provided with a mechanism for adjusting their size, for example adjustable flaps, which may be remote-controlled, particularly from outside the reactor. This allows very fine adjustment of the distribution of the particles collected by the deflector in the central zone of the loading front.
In a particularly preferred embodiment of the inventive device, the funnel forming the central deflector integral with the bottom end of the fixed tube is supplied by a second funnel, referred to below as the “central deflector feed funnel”.
This central deflector feed funnel takes up a limited stream of solid particles from the base of the feed line and sends this particle stream directly toward the central deflector by short-circuiting the dispersal system. The central deflector feed funnel is integral with the rotating tube. It traverses the particle dispersal system and terminates above the central deflector. Obviously, the bottom part of said feed funnel must have a sufficient diameter for the free flow of the solid particles toward the central deflector.
The central deflector feed funnel receives particles from at least one orifice provided in the base of the feed line. These orifice(s) is/are located above the circular trajectory formed by the upper end of the feed funnel, integral with the rotating tube. The base of the feed line preferably comprises several orifices located equidistant from one another, above the trajectory of the central deflector feed funnel.
As explained in the introduction, the inventive device preferably comprises a functional device suspended below the bottom end of the rotating tube, of the fixed tube or of the central deflector. This functional device is held by suspension means, for example a wire, a rod, a tube, a cable or a chain, passing through the opening of the rotating tube or of the fixed tube. It may be controlled by external control means and serves to perform operations ancillary or complementary to the loading operation.
Although the problem which led to the present invention was the difficulty of introducing an instrument into the chamber to be filled, in order to monitor the filling quality, the channel defined by the hollow shaft can obviously serve for the passage of a wide variety of functional devices serving for very different purposes.
In a preferred embodiment of the invention, the functional device introduced via the opening in the hollow shaft is a telemetry device operating with mechanical waves (for example, a sonar or an ultrasonic telemeter) or with electromagnetic waves (for example, a laser telemeter). The data gathered by such a telemetry device are preferably transmitted immediately, recorded and processed by an appropriate data processing system and may serve, if necessary, to modify the operating parameters of the dense loading device of the invention, in order to correct an insufficient horizontality of the loading front.
Such a telemetry device can also be replaced by a camera or a photographic apparatus, preferably digital, for visually evaluating the loading quality. The use of a photographic apparatus or camera generally implies the introduction of a lighting source which is preferably fixed to the photographic apparatus or camera but may be introduced separately.
During the loading of the chamber, it may also be advantageous to monitor physical or physicochemical parameters other than the horizontality of the loading front, such as the temperature, relative humidity, quantity of fine dust in suspension in the air, oxygen or chlorine content in the chamber, etc. Appropriate sensors for measuring these parameters are known in the prior art and can be selected and adapted by a person skilled in the art to the particular conditions of use of the device of the present invention.
In one alternative of the device of the present invention, the functional device introduced via the opening in the hollow shaft does not serve for measuring the physicochemical parameters in the chamber, but for introducing or withdrawing material. For example, one possibility is a sampling device for taking samples of divided solid or dust in suspension in the air above the deposit, or a suction device for continuously sucking out this fine dust. Finally, the hollow shaft of the device of the present invention could serve for introducing a second divided solid and a device for uniformly distributing or dispersing said second divided solid. Such an introduction and dispersal device is described in greater detail below with reference to the drawings appended hereto.
It goes without saying that the various functional devices can be introduced simultaneously or successively, or that a device may combine several functions.
In another embodiment of the loading device of the present invention, a functional device can be fixed, not via suspension means passing through the opening of the hollow tube, but directly to the fixed tube, at the end thereof, projecting beyond the rotating tube.
The hollow shaft of the loading device of the invention could also allow the passage of means for controlling a large functional device installed prior to the loading below the dispersal system.
As mentioned above, the hollow shaft of the dense loading device of the present invention allows the passage of a suction device for continuously, or at regular intervals, sucking out the dust or fines, in suspension in the air above the deposit of divided solids. In the context of the filling of reactors with catalysts, the existence of these fines in the catalyst or their formation by attrition during the chamber filling operation, raises a problem of fouling of the effluent treatment and separation systems, located downstream of the reactor. It is therefore advisable to remove these fines before starting up the reactor. The solution mentioned above, whereby a suction device is introduced via the channel of the hollow shaft into the zone located below the rotating deflectors, is not ideal in this case because of the risk of disturbing the air flow in this zone and modifying the trajectory of fall of the catalyst particles, with the consequence of a nonuniform deposit.
The Applicant has found means for effectively sucking out the catalyst fines by exploiting the hollow feature of the rotating shaft and of the fixed tube, without necessarily disturbing the air flow in the zone below the deflectors. This suction can be obtained thanks to a system for sucking out the dust via the rotating tube or via the fixed tube. The walls of the rotating tube and of the fixed tube, optionally present, comprise one or more suction openings for this purpose, preferably located in the zone of the onset of the free fall of the solid particles issuing from the orifice of the feed line and/or in the zone of formation of the dust fines due to impact against the surface of the rotating deflectors, in other words, in the zone of the dispersal system.
The loading device of the present invention can operate with any type of dispersal system designed to deviate in a perfectly random manner the solid particles issuing from the discharge opening in the base of the feed line, and making them fall individually in a shower of particles (“shower” dispersal system).
In a preferred embodiment, the distribution system comprises deflecting elements integral with the central shaft. These deflectors are generally made from a semirigid material, preferably rubber, and are capable of diverging angularly from the central shaft under the effect of the centrifugal force when said central shaft is rotating. Such a set of deflectors is described for example in application EP 0 769 462. The deflectors are preferably arranged in several levels and the same number of deflector elements is provided at each level, having substantially identical shapes, arranged vertically above one another.
The dispersal system may also be a dispersal head consisting of a series of substantially horizontal plates, parallel to one another and coaxial, arranged above one another and whereof the area swept during the rotation decreases from the top plate to the bottom plate, each plate, with the exception of the bottom plate, comprising a substantially circular opening at its center for the flow of at least part of the solid particles, by gravity, toward the plate located immediately below. Such a dispersal system is described in detail in application FR 2 721 900 and is used under the trade name CATAPAC by Petroval.
Another feasible embodiment for the dispersal system capable of operating with the loading device of the invention is the one described in international application WO 00/43304. This dispersal system comprises two lines, each having a particle flow opening, one opposite the other and curved about the same axis perpendicular to the axis of rotation of said dispersal system, so that their flow openings are each located on one side of the axis of rotation of said dispersal system, substantially in the same diametral plane. Each of these lines further comprises at least one longitudinal partition extending over all or a large part of its length, this partition being capable of dividing the particle stream and of spreading the flow thereof, against the centrifugal force, over all or a large part of the flow opening.
A method for loading a chamber with a catalyst according to the invention using a device as described above generally comprises the adjustment of the speed of rotation of the central shaft according to the diameter of the chamber to be loaded, the continuous introduction, via the feed means, of the solid particles into the feed line of the device, and the carrying out of an operation complementary or ancillary to the loading operation through the opening of the rotating tube or of the fixed tube.
The loading method of the invention using the device described in detail below preferably comprises the following steps:
during the loading of the chamber, at least one record is made of the profile of the loading front of the catalyst bed using a functional measuring device, introduced via the opening of the rotating tube or of the fixed tube,
the deviations of the loading profile from an ideal substantially horizontal profile are determined quantitatively by mathematical processing of said record,
and, according to the result thus obtained, electrical signals are sent to order the adjustment of certain functional parameters of the loading device.
The functional parameters of the loading device which can be adjusted according to the filling profile recorded are, for example, the speed of rotation of the central shaft, the opening of the discharge opening(s) placed at the base of the feed line and the orientation of the dispersal system with regard to the vertical axis of the chamber.
The speed of rotation of the central shaft is comprised within the range generally used for known devices, and preferably between 25 and 250 revolutions per minute, and particularly between 40 and 150 revolutions per minute.
The invention is now described with reference to the drawings appended hereto, which are nonlimiting, in which:
a and 6b show profiles of the loading front, recorded by a sonar type of telemetry device, obtained with a device according to the invention respectively without and with a central deflector as shown in
The filling device in
The feed line 2 is axially traversed, along its whole length, by a hollow shaft 3, securely held by at least two bearings, and rotated by drive means 4, preferably a compressed air motor, placed on the feed line side. The transmission between the motor 4 and the drive shaft 3 takes place by any appropriate means, for example by a belt. The overall filling device is securely held and fixed in the manhole of the reactor by support tubes 16. In the zone below the bottom end of the discharge line 2, rubber deflectors 8 are fixed to the outer wall of the hollow shaft via deflector-holding elements 17.
During the filling of a reactor using the device in
According to the present invention, after installation of the filling device, before, during or after the filling process, it is possible to introduce a functional device 9 into the chamber, having sufficiently small dimensions for its passage via the opening in the hollow shaft. The functional device is suspended from appropriate suspension means 20 which may, for example, be a wire, a rod, a tube, a cable or a chain.
Demonstration of the Effectiveness of the Central Deflector
A chamber having a diameter of about 3 meters was loaded using a device according to the present invention, comprising, as a dispersal system, rubber strips arranged in three series of distinct heights at the end of the rotating tube. The rotating tube was hollow and had an inside diameter of 14 cm. It was duplicated by a fixed tube having an inside diameter of 13 cm. This fixed tube projected beyond the rotating tube by about 5 cm. Fixed to the end of the fixed tube was a Puls68 model sonar detector sold by VEGA, of which the detection head can pivot through an angle of 360° in order to take measurements over the entire filling front. The sonar detector was remote-controlled via cable, by a data processing system. This system allows the recording, in a very short time, about 30 seconds, of the profile of the loading front, at any time during the filling operation.
A first loading operation was first carried out with such a device rotating at a speed of about 70 revolutions per minute, in the absence of a central deflector.
The loading operation was repeated under identical conditions with the difference that an openwork frustoconical deflector was fixed to the end of the fixed tube, as shown in
Number | Date | Country | Kind |
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0407355 | Jul 2004 | FR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FR05/01486 | 6/15/2005 | WO | 7/30/2007 |