Method for sorting spent catalyst as a function of the metals of the catalyst

Abstract

A method and device for separating at least one catalyst from a mixture of homogeneously shaped catalysts, the catalysts comprising at least one metal selected from the group formed by Ni, Co, Mo, W, the catalyst to be separated comprising a characteristic metal selected from the group formed by Ni, Co, Mo, W and the other catalysts of the mixture not containing said characteristic metal, in which method: the grains of the catalyst of said mixture pass in front of the LIBS detection system, the presence of said characteristic metal in the catalysts is detected by the LIBS technique, the wavelength being selected so as to detect said characteristic metal, the LIBS detection system sends a signal to a means for evacuating grains of catalyst to be separated in a manner such as to separate said grains from the other catalysts of said mixture.

Claims

1. A method for separating at least one catalyst from a mixture of homogeneously shaped catalysts, the catalysts being in the form of grains and comprising at least one metal selected from Ni, Co, Mo, and W, the catalyst to be separated comprising W as a characteristic metal and the other catalysts of the mixture containing at least one metal selected from Ni, Co and Mo but not containing said characteristic metal W, said method comprising: passing the grains of the catalyst of said mixture in front of a Laser Induced Breakdown Spectroscopy (LIBS) detection system, detecting the presence of said characteristic metal in the catalysts by the LIBS, the wavelength of the LIBS being selected so as to detect said characteristic metal, and sending a signal from the LIBS detection system to a means for evacuating the grains of catalyst comprising said characteristic metal W in a manner such as to separate said grains comprising said characteristic metal W from the grains of the other catalysts of said mixture containing at least one metal selected from Ni, Co and Mo, but not containing W.

2. The method according to claim 1, in which the other catalysts of the mixture not containing said characteristic metal W include at least one catalyst containing molybdenum.

3. The method according to claim 1, in which the catalyst to be separated comprising W as the characteristic metal also contains Ni, and the other catalysts of the mixture not containing said characteristic metal W include at least one catalyst containing NiMo or CoMo or NiCoMo.

4. The method according to claim 1, in which the catalysts of the mixture are hydrotreatment and/or hydrocracking catalysts.

5. The method according to claim 1, in which the catalysts are spent hydrotreatment and/or hydrocracking catalysts the support of which is constituted by alumina or silica-alumina, with zeolite optionally being present.

6. The method according to claim 1, in which the catalysts are homogeneously shaped.

7. The method according to claim 1, in which the catalysts of the mixture are in the form of cylindrical extrudates.

8. The method according to claim 1, in which the catalysts of the mixture are spent catalysts.

9. The method according to claim 1, in which the time period for one grain to pass in front of the LIBS detection system is less than 50 ms.

10. The method according to claim 1, in which the maximum spacing between the grains, when passing in front of the LIBS, is equal to their largest characteristic dimension.

11. The method according to claim 1, in which the grains, when passing in front of the LIBS, flow in a manner such that they are spaced apart by a distance in the range from zero to their largest characteristic dimension, the measurement frequency being in the range 1/t to 1/2t, t being the period of time for a grain to pass in front of the LIBS detection system.

12. The method according to claim 1, in which the grains are passed in front of the LIBS via a transport means and the LIBS is positioned in a manner such that the depth of the analysis field above the surface of the transport means is in the range 1/3 to 3 times the smallest characteristic dimension of the grain.

13. A device for separating at least one catalyst from a mixture of homogeneously shaped catalysts, the catalysts being in the form of grains, the catalyst to be separated comprising W as a characteristic metal and the other catalysts of the mixture containing at least one metal selected from Ni, Co and Mo but not containing said characteristic metal W, said device comprising: a Laser Induced Breakdown Spectroscopy (LIBS) detection system comprising at least one laser in front of which the catalyst grains pass, the detection time for the LIBS being less than 50 ms, and the detecting wavelength of the LIBS being that of the characteristic metal W, at least one analyser (8) and at least one control means (10), a line for transporting the grains of the mixture of catalysts in front of the LIBS, the line being provided with a transport means, means for controlling the rate of flow of the grains onto said transport means and means for controlling the speed of said transport means, said transport means being regulated in a manner such that the maximum distance between the grains of catalyst when being transported in front of the LIBS is equal to the largest characteristic dimension of a grain and in that the period of time for a grain to pass in front of the LIBS detection means is less than 50 ms, and at least one means for evacuating grains of the catalyst to be separated comprising said characteristic metal W and at least one means for evacuating grains of the other catalysts containing at least one metal selected from Ni, Co and Mo but not containing said characteristic metal W, said means for evacuating grains of catalyst to be separated being actuated from said control means when the characteristic metal is detected by the LIBS.

14. The device according to claim 13, in which the transport means is a ribbed belt, the depth of the ribs being in the range 0.7 to 1.3 times the largest characteristic dimension of the grains.

15. The device according to claim 13, in which the transport means is provided so that the grains flow in a manner such that their spacing is in the range from zero to their largest characteristic dimension, the measurement frequency being in the range 1/t to 1/2t, t being the period of time for a grain to pass in front of the LIBS detection system.

16. The method according to claim 6, in which the catalysts are in the form of cylindrical extrudates, beads, trilobes or multilobes.

17. The method according to claim 1, in which the time period for one grain to pass in front of the LIBS detection system is less than 10 ms.

18. The device according to claim 13, wherein the detection time for the LIBS is less than 10 ms, and the period of time for a catalyst grain to pass in front of the LIBS detection means is less than 10 ms.

19. The device according to claim 13, wherein the device allows for separating at least one catalyst from a mixture of homogeneously shaped catalysts wherein the catalyst are in the form of cylindrical extrudates.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows, as an illustration, a preferred but non-limiting embodiment of a method and device of the present invention having a plate, 2, which vibrates in two orthogonal directions.

(2) FIG. 2 shows a non-limiting embodiment of a method and device of the present invention wherein the grains of catalyst fall onto a band conveyor which is a ribbed conveyor belt.

DETAILED DESCRIPTION OF THE METHOD AND THE SEPARATION DEVICE

(3) The mixture of catalyst initially stored in silos or in sacks is supplied to a transport line which advantageously comprises a band conveyor such as a conveyor belt and which comprises means for controlling the flow rate of the grains onto the band conveyor.

(4) The transport means may also be other means such as, for example, a die in which an endless screw with a hollow axle is rotated to cause the grains of catalysts to advance, with openings being provided in the die to allow detection on the one hand and separation of the grains of catalyst on the other hand.

(5) The grains of catalyst are transported in front of the LIBS system for qualitative analysis of the chemical composition in order to determine whether the grains of catalyst contain the characteristic metal. A qualitative analysis is carried out in order to detect the presence of one or more unwanted elements. As an example, the presence or absence of tungsten could be investigated in order to separate grains containing this metal.

(6) FIG. 1 shows, as an illustration, a preferred but non-limiting embodiment of the method and device of the present invention.

(7) The mixture of unsorted catalyst 1 is supplied to a means 2 for controlling the rate of flow of the grains onto the band conveyor 5. The means for supplying the mixture 3 may be manual (emptying bags, for example) or automatic (for example, controlled dispensing from a silo).

(8) The invention is described with a band conveyor as the transport means, but the description is entirely applicable to another transport means such as the screw and die described above, for example.

(9) The means for controlling the flow rate are means which are well known to the person skilled in the art such as, for example, inclined vibrating plates, which can distribute the grains of catalyst in a uniform manner and can allow the rate of flow of catalyst on the plate towards the band conveyor to be adjusted. In this manner, the person skilled in the art will be able to adjust the distance between two grains on the transport line and adjust the frequency of detection as a consequence or, conversely, will be able to adjust the distance as a function of the detection frequencies.

(10) By way of example, in FIG. 1, we have represented at 2 a plate which vibrates in two orthogonal directions. With this type of equipment, it is possible to adjust the vibration frequencies in order to modulate the flow rate of solid 4 towards the band conveyor 5, to adjust the distribution between the grains on the cross section of passage and thus to control the spacing between the grains as a function of the rate of displacement of the conveyor.

(11) As an optimum, the device will be adjusted so that the maximum distance between the grains is equal to the largest characteristic dimension of a grain, as defined above.

(12) At the outlet from the flow rate control means 2, the grains of catalyst fall onto the band conveyor which may be a simple flat conveyor belt or a ribbed conveyor belt, as can be seen in FIG. 2.

(13) The ribbed belt of FIG. 2 is of distinct interest when sorting extrudates (as is the case with catalysts containing tungsten), because it can advantageously be used to orientate the grains of catalyst in the direction of flow. The flow of the catalysts is thus more regular and spaced, which favours detection, and separation and improves the productivity of the facility.

(14) In the case of a ribbed belt 20, a crenellated shape 21 with an equilateral triangular shape as can be seen in FIG. 2 is advantageous; the depth of the ribs on the belt is thus ideally in the range 0.7 times to 1.3 times the largest characteristic dimension of the grains (which is the diameter of the grains of catalyst in the case of extrudates or beads). In the case of trilobes or multilobes, the depth of the ribs on a belt is thus ideally in the range 0.7 times to 1.3 times the largest characteristic dimension of the grains. In this context, the diameter and said dimension refer to fresh catalysts. In general, the depth is close to said largest dimension (i.e. approximately single-fold).

(15) The grains 22 are positioned on the belt 20. The rate of advance of the belt is adjusted in order to optimize the production capacity on the one hand and on the other hand the capacity of the system to detect the desired characteristic metal in the grains of catalyst.

(16) Preferably, the period of time for one grain to pass is selected so as to be less than 50 ms, and is preferably less than 10 ms. More generally, the period for passage is as short as possible, in alignment with the response time of the detection system.

(17) Under these conditions, for example, for a cylindrical extrudate with a length of 10 mm, the speed of transport of the grains on the band conveyor is more than 0.2 m/s and preferably in the range 0.2 to 10 m/s, the period of time for passing in front of the detection system thus varying between 1 and less than 50 ms.

(18) In the case of a 5 mm extrudate, the speed is preferably in the range 0.1 to 5 m/s.

(19) Since the maximum mean spacing of the grains is their largest characteristic dimension, it is then possible to make these measurements every 1 to less than 50 ms, in alignment with the capacities of the measurement instruments, and thus to carry out the detection on all of the grains of catalyst.

(20) The detection system comprises at least one laser 6, at least one spectrometer (or analyser) 8 and at least one means 10 for controlling the opening or otherwise of at least one evacuation means.

(21) A laser 6 emits a beam which is focussed on the surface of the sample 7. Following a pulse of the order of a femtosecond to a nanosecond between the laser and the sample, a plasma which is a reflection of the composition of the sample is generated and after a few milliseconds, emits at wavelengths which reflect the composition of the sample 9.

(22) The emissions from the sample 9 are analysed by a spectrometer 8 at the wavelengths which are specific to the characteristic metal which is to be detected.

(23) As an example, in order to detect the presence or absence of tungsten in the hydrocracking or hydrotreatment catalysts, the line at a wavelength of 400.875 nm is used because of its high intensity. The line at 297.971 nm may also be used. These two lines can be used to detect the presence of tungsten while minimizing the interference from Ni, Co, Mo, Al or Si.

(24) Depending on requirements, it is possible to analyse all of the grains passing in front of the detection system 6-7-8-9 on the band conveyor 5, overall or individually, by using several laser systems 6 in parallel so as to cover the width of the band conveyor and also by adapting or decoupling the laser and the spectrometer 8 analysing the emissions 9.

(25) It is also possible to elect to operate statistically by analysing only a fraction of the flow or to consider displacing the lasers 6 and the spectrometer(s) 8 across the width.

(26) The detection system, and more precisely the spectrometer 8, is connected to control means 10 which can be used to convert the results of the analysis into an action in order to actuate said evacuation means (in this case the valve 12).

(27) These means are, for example, constituted by a computer which can be used to trigger opening of a valve 12.

(28) As an example, when the analyser 8 detects the presence of the desired element in a grain of catalyst, it sends a signal to the control means 10 which actuates opening of the valve 12.

(29) This is located on a line of inert fluid (for example air) under a pressure, if possible, of more than 5 bars (preferably with air) in order to favour the generation of a jet of gas (air) which is sufficient to evacuate the grain.

(30) The valve 12 opens for a predetermined period DT1, then closes automatically. Opening of the valve means that a jet can be generated at the lower end of the line 11. It acts with the line as a nozzle for ejecting gas (air).

(31) Advantageously, the line 11 is positioned at the end of the conveyor belt at a distance of at most 10 cm from the end of the belt (depending on the speed of advance of the belt; the lower the speed of advance of the belt, the closer the line 11 can be from the end of the belt) at a height above the belt 5 which is preferably in the range 2 to 10 times that of the largest characteristic dimension of the grain of catalyst (its length in the case of an extrudate).

(32) It is possible to position one or more lines 11 in parallel, depending on the width of the transport band and the shape of the line end.

(33) In the case of a spherical line nozzle, the diameter of the nozzle of the line is preferably less than or equal to the largest characteristic dimension of the grain of catalyst.

(34) If the belt allows the simultaneous passage of N particles simultaneously across the width, up to N tubes 11 can be positioned in parallel, each with a valve, the valves being controlled simultaneously or separately by the control means 10 as a function of the number of analysers used in parallel.

(35) It is also possible to operate with a single line 11, but where the end has a rectangular cross section which can generate a blade jet of gas, the thickness of the jet then being preferably less than or equal to the largest characteristic dimension of the grain of catalyst.

(36) In order to take into account the distance between the detection means and the evacuation means, the control system triggers opening-closing cycles with a delay which is a function of the distance to travel between these two points. As an example, if the length of the belt between the focal position of the analyser on the belt 9 and the evacuation means (valve, air injection nozzle 12) is 3 m and the speed of travel on the conveyor belt is 3 m/s, a delay of one second is used, optionally corrected to account for the response time of the analyser 8, the control means 10 or the valve 12.

(37) For the requirements of the invention and in order to be selective, the opening-closing cycle of the valve has to be rapid and consistent with the period of time for the grains to pass in front of the detector. Preferably, the opening-closing cycle time will not exceed 1 to 5 times the time for the grains to pass in front of the detector, preferably less than 3 times this mean passage time.

(38) Thus, the valve and actuator technologies will be selected so as to have an opening-closing cycle in the range 5 to 250 ms depending on the speed of travel of the transport means 5.

(39) The jet of gas (for example air) generated during this period has a speed which is at least equal to 5 times the terminal velocity of fall of the grain of catalyst, preferably 10 times the terminal velocity of fall (in the case of a hydrotreatment extrudate, the terminal velocity of fall is generally close to 5 m/s and in the range 2 to 7 m/s).

(40) When the actuator triggers opening of the valve, the jet of gas deflects the trajectory of the grain of catalyst towards a receptacle 14 which harvests all of the grains to be eliminated containing the unwanted element.

(41) If the actuator is not triggered, then the trajectory of the grain leaving the belt describes a normal parabola which is a function of the speed of travel of the conveyor belt and the terminal velocity of fall of the particles. The grain of catalyst then falls into a receptacle 13 which harvests all of the grains to be eliminated not containing the unwanted element.

(42) Thus, the catalyst collected at 13 will constitute a new batch not containing the unwanted chemical element.

(43) Compared with the prior art, the invention can be used for rapid sorting of at least 20 to 100 objects (grains of catalyst)/second, in general at least 50 or even 100 objects/second, and its use means that up to 1000 objects/second can be processed.