CA1135647A

CA1135647A - Catalytic reactor

Info

Publication number: CA1135647A
Application number: CA000320468A
Authority: CA
Inventors: Robert R. Edison; Martin P. Grosboll; Lloyd A. Baillie
Original assignee: Atlantic Richfield Co
Current assignee: Atlantic Richfield Co
Priority date: 1978-02-24
Filing date: 1979-01-30
Publication date: 1982-11-16
Also published as: GB2015369B; BE874170A; GB2015369A; JPS54123103A

Abstract

ABSTRACT OF THE DISCLOSURE
A catalytic reactor for hydroconverting hydrocarbon material comprising: a closed vessel; a fixed bed of hydrocarbon conversion catalyst particles within the vessel; inlet means in the upper portion of the vessel; outlet means in the lower portion of the vessel; at least one gas distributor in the bed of catalyst particles for providing temperature control, said gas distributor comprising:a gas supply means; a plurality of conduits extending from the gas supply means having orifices spaced along the conduit; and a screen structure spaced from and surrounding the conduit to hold catalyst particles away from the conduit.

Description

113~4t~

CATALYTIC REACTOR
BACICGROUND OF THE INVENTION
1. Field of the Invention The field of this invention relates to catalytic reactors for converting hydrocarbon material having means for introducing temperature controlling amounts of gas directly into a bed of catalyst particles in the reactor vessel.

2. Description of the Prior Art Catalytic reactors for converting, e.g., hydrotreating hydrocarbon material are often process vessels in which one or more fluids flow through a bed of catalyst particles at high temperature to hydrotreat the hydrocarbon material. ~ known method for providing temperature control of the hydrocarbon conversion process is to introduce a temperature controlling amount of gas into the process vessel to provide such heating or cooling as the process might require. In exothermic hydro-treating processes such as hydrodesulfurization and hydro-cracking,for example, it is a common practice to introduce cool hydrogen to the reaction vessel to quench the reaction.
Effective quenching can be quite critical in exothermic hydrotreating processes. If the reactor temperature is not kept within a proper range by quenching, the reactor temperature can "run away" presenting a dangerous situation. In addition, excessive temperatures can damage the reactor, deactivate catalyst and adversely affect the process.
~ eretofore, hydroconversion reactor designs have included large zones devoted exclusively to providing mixing space for the temperature controlling gas and the reactants.

~13S647 Fbr example, many hydrotreater reactordesigns commonly include open spaces in the cataLyst bed (plenum chambers) into which the ~mperature controlling gas is introduced. The number of plenum chambers for introducing temperature controlling gas into the packed bed can vary widely. Depending upon the process (and the amount of temperature control required) the number of plenum chambers can vary from one, several or to many more. These plenum chambers can often occupy a considerable portion of the volume of the reactor.
While reactor designs employing plenum chambers are quite common, such designs can be difficult to execute since the catalyst must be supported within the reactor vessel. If the reactor requires several plenum chambers such that a series of catalyst beds within the reactor vessel are required, the difficulties involved are multiplied. Rather than open spaces, quench zones filled with aluminum balls are suggested in U.S.
Patent 3,563,886 to Carlson et al, issued February 16, 1971, which discloses a reactor with multiple quench zones for a hydrodesulfurization process. While this reactor design may have merit, a problem remains in that a significant portion of the reactor volume does not contain catalyst particles.
Elimination of plenum chambers or other spaces in à
reaction vessel not containing catalyst would be very desirable since elimination of such spaces would allow a given reactor to be smaller in size.
Minimizing reactor size would be very desirable, of course, since reaction vessels can be very expensive.
This is particularly the case in hydrocarbon conversion processes where high temperatures and high pressures often necessitate the use of reactor vessels employing special steel alloys and ~13564q other materials such that their costs can be quite high. In the case of existing reactors, elimination of such spaces would allow filling the reactor with more catalyst. Charging more catalyst to the reactor would allow for increased throughput of reactants at the same space velocity. The desirable result is that the efficiency of the catalytic reactor is increased.
SUM~RY OF THE INVENTION
In summary, this invention provides a catalytic reactor for converting, e.g., hydroconverting hydrocarbon materials comprising a closed vessel, a fixed bed of catalyst particles effective to promote such conversion within the vessel, inlet means in the upper portion of the vessel, outlet means in the lower portion of the vessel, at least one gas distributor in the bed of catalyst particles for providing temperature control, said gas distributor comprising a gas supply means, a plurality of conduits extending from the gas supply means having orifices spaced along the conduit, and a screen structure spaced from and surrounding the conduit to hold catalyst particles away from the conduit. In a preferred aspect of the invention, an impervious deflector plate is located a distance D from each orifice.
An advantage of the catalytic reactors of this invention is that the percentage of reactor vessel volume filled with catalyst is increased since large mixing zones e.g., plenum `
chambers, are not required.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagramatic sectional plan view of a catalytic reactor in accordance with this invention.
Figure 2 is a top plan sectional view along line 2-2 of Fig. 1 showing a gas distributor of a reactor in accordance with the invention.

113S~4q Figure 3 is a partially broken side view of a section of conduit of a preferred gas distributor employed in a catalytic reactor in accordance with the invention.
Figure 4 is an end sectional view along line 4-4 of Fig. 3 of a preferred conduit of the gas distributor employed in a catalytic reactor in accordance with the invention.
Figure 5 is a sectional end view showing an alternative configuration of a conduit suitable for use in a gas distributor in accordance with the invention.

113564q DETAILED DESCRIPTION OF THE INVENTION
AND ITS PREFERRED EMBODI~NTS
The catalytic reactors for converting, e.g., hydro-converting hydrocarbon material of this invention have means for introducing temperature controlling amounts of gas directly into the fixed catalyst bed without the necessity for plenum chambers or other mixing zones not occupied by catalyst. It has now Deen found that temperature controlling amounts of gas can be intro-duced directly into the catalyst bed employing a gas distributor which provides good mixing of the gas with the reactants, attenuates the velocity of the gas such that catalyst attrition is avoided, and does no~ cause significant maldistribution of fluid flow in the reactor.
Referring now to the drawings, in Fig. 1 there is illustrated a conventional catalytic reactor vessel 10 having an inlet 11 and outlet 12. The reactor vessel contains a pac~ed bed comprising hydroconversion catalyst particles 13. Within the packed bed 13 is a gas distributor 14 for supplying temperature controlling amounts of gas to the catalytic reactor.
Referring to Fig. 2 it can be seen that gas distributor 14 comprises a gas inlet means, for example, header pipe 15 and extending from the headex pipe a plurality of conduits, conduit 16 being representative of the conduits. The conduits are pre--ferably evenly spaced from each other along the length of the header pipe. Preferably the conduits extend horizontally and at right angles from header pipe 15. The conduit length should be such that it approaches the interior wall of the reactor vessel.
Conduit 16 is sealed at the end away from header pipe 15 and, spaced along the length of the conduit are orifices 17 for emitting temperature controlling amounts of gas into catalyst bed 13.

The orientation of the orifices can vary. The orifices are pre-ferably spaced from about 1 to 5 inches from each other, more preferably from about 2 to 3 inches from each other, along the conduit. Preferably the orifices are equidistant from each other and have the same orientation. The conduits are generally spaced from about one-sixth foot to two feet from each other, and most preferably are spaced from about one-third foot to one foot from each other. Close spacing of the orifices and conduits is desirable in order to provide fast, unirorm mixing of the temperature controlling gas and the reactants. This is important if good heat transfer is to be obtained. If the conduits and/or orifices are spaced too far apart the undesirable result will be a series of alternately "hot" and "cold" regions persisting an unacceptable distance into the catalyst bed.
In hydroconversion, the temperature controlling gas will genera~ly be hydrogen. Depending upon the partieular hydro-conversion proeess the temperature of the temperature controlling gas will be either higher or lower than the temperatures desirably eontrolled within the reaetor. High temperature gas is employed to supply heat to those reaetions requiring heat. Lower temperature gas is employed to quench exothermie reaetions.
Referring to Fig. 3 and Fig. 5 spaeed from and surrounding eonduit 16 is sereen strueture 18 for holding eatalyst partieles away from eonduit 16. This sereen strueture ean - suitably be a wire mesh material. The screen strueture has openings of a size that does not permit passage of the eatalyst partieles.
The serèen strueture ean be spaeed from the eonduit in a variety of ways. For example, a variety of supports ean be affixed to the eonduit and the sereen strueture attaehed to the supports.
30 In Fig. 3, a length of wire 19 is shown wound about conduit 16.

3S~;47 The wire _ can be tack-welded to the conduit 16 to provide a support for screen structure 18. A suitable screen 18 can then be wrapped about conduit 16 and tack-welded to wire 19. For example, wire having a diameter of about 1/4 inch to 1/2 irch can very suitably be employed in this manner as support for holding screen structure 18 in spaced relationship to conduit 16 such that screen structure 18 is spaced from about 1/4 inch to 1/2 inch from conduit 16. Chain with links of suitable dimension can also be wound about the conduit and employed in an equivalent manner as wire 19 as a support. In using a continuous length of chain or wire wound about the conduit as a support, the pitch should be such that the orifices are not obstructed, The screen structure is useful not only because it holds catalyst particles away from the conduit, but also because the screen attenuates the velocity of the gas emitted from the orifices. It is important that the velocity of gas impinging on the catalyst bed in the reactor not be such that the catalyst is fluidized. (For any given reactor the velocity of gas from the gas distributor must be such that the gas impinging on the catalyst not provide a pressure exceeding the solids pressure of the bed of catalyst).
In a preferred aspect of this invention, an impervious deflector plate is located a distance D above orifice 17. Distance D is at least equal to the diameter of orifice 17, and is preferably greater. In Fig. 3 and Fig. 4, a preferred embodiment of the invention is shown wherein the deflector plate 20 is located above orifice 17. When the conduit 16 and screen 18 have a cylindrical configuration as illustrated in the drawings, deflector plate 20 can very suitably be a continuous strip of sheet metal 113S~i4t7 having an arc of from about 70 to 180, and is very suitably fitted over screen structure 18. Alternatively, deflector plate 20 and screen structure 18 can be joined together to form a contiguous surface. In such a design the screen structure need surround only that portion of the conduit not surrounded by the deflector plate as the deflector plate itself will hold catalyst particles away from the conduit.
Gas distributor _ wherein the conduits include deflector plate 20 represents a highly preferred aspect of the invention in that temperature controlling gas from orifice 17 is highly reduced in velocity on impinging against deflector plate 20 such that its pressure on entering the catalyst bed is very much attenuated. The desirable result is that the possibility of catalyst fluidization is reduced. The deflector plate also acts to spread the temperature controlling gas providing better mixing of the gas and the reactants such that the duration of "hot" and "cold" zones is reduced. In addition, it has been found that the deflection plate when oriented in a preferred manner to deflect down-flowing fluid, e.g., liquid, away from the conduits desirably prevents heat exchange between the conduits and the down-flowing fluid. Such exchange is undesirable because it is non-uniform across the catalyst bed.
The pressure of the temperature controlling gas entering header pipe 15 is preferably such that the velocity of the temperature controlling gas emitted from the orifices is substantially uniform.
The gas distributor design of the present invention is, as heretofore mentioned,employed within the context of a catalytic reactor for chemically converting hydrocarbon material, e.g., hydroconversion. For example, the gas distributor can be 1~3S6~7 employed in any conventional hydrotreating reactor having one or more æones for introducing temperature controlling amounts of gas. Such reactors, typically circular, have diameters ranging from about 3 feet to about 20 feet or more, preferably from about 5 feet to about 15 feet, and from about 5 feet to about 125 feet or more, preferably from about 10 feet to about 70 feet, in length. The catalyst particles used to form the fixed catalyst bed within such a reactor may have any suitable geometry, e.g., spheres, cylinders, pills, tablets, irregularly shaped particles, etc. Preferably, the maximum linear dimension of the particles does not exceed about 3~ of the reactor diameter.
Typically, such catalyst particles have a minimum dimension of at least about 0.01 inch and a maximum dimension of from about 1/2 inch or 1 inch.
As used herein, fixed catalyst bed means a non-moving packed bed of catalyst particles. Th~ reactors of the invention are employed in carrying out the catalytic chemical conversion ; of hydrocarbons such as that involved in petroleum refining and petrochemical processing and the like. Included among the conventional and well known hydrocarbon chemical conversion reactions which may be promoted by such catalyst and in which the catalytic reactor of the invention can be useful are hydrodesulfurization, hydrocracking, reforming, hydrogenation and the like. Typical operating conditions and catalyst compositions employed in each of these catalytic reaction processes are well known to those skilled in the art and may be varied to meet the requirements of the individual nydrocarbon process. For this reason, an extensive list of reaction conditions and catalyst compositions is not included herein.

_g_ 113564~

However, to illustrate, typical examples of hydrocarbon hydro-desulfurization catalysts comprise a support and any one or more of the transition metals, metal oxides, metal sulfides, or other metal salts which are known to catalyze hydrodesulfurization.
Hydrocarbon reforming catalysts typically comprise at least one platinum group metal on a support. Typical examples of hydrocracking catalyst include crystalline metallic alumino-silicate zeolites, having a platinum group metal, e.g., platinum or palladium, deposited thereon or composited therewith.
Hydrogenation catalysts may comprise at least one Group VIII
metal of the Periodic Table, such as nickel, cobalt, iron, the platinum group metals such as palladium, platinum, iridium or ruthenium and mixtures thereof on a suitable support.
Suitable carriers or supports for these catalyst may comprise materials such as silica, alumina, zirconia, titania, magnesia, boria, silica-alumina, silica-magnesia, acidic clays, halidea alumina and the like. Mixtures of more than one of such materials may be used in these catalysts.
A highly preferred aspect of the invention involved a catalytic reactor of the invention wherein the bed of hydroconversion catalyst particles has been loaded according to a process such that a bulk density approaching the maximum bulk density is obtained. Such a process involves charging catalyst to the reactor at a rate of fill of the reactor of up to about 17 verticle inches per minute, more pre-ferably from about 1 to about 6 and still more preferably from about 2 to about 4 inches per minute. The rate of fill of the reactor can be non-uniform, that is, the rate of fill can vary within the above range. It is preferred, however, that the rate of fill be uniform and that after a given rate of fill ~13564q is established, that this rate of fill be maintained while preparing the catalyst bed. The catalyst particles are introduced into the reactor at a point such that the distance to the catalyst surface formed as the catalyst particles are introduced through a gaseous medium provides an average free fall distance of catalyst particles of at least about 1 foot, more preferably an average free fall distance of from about 5 to about 125 feet and still more preferably from about 10 to about 70 feet. The gaseous medium in general is air, or depending on the catalyst, an inert medium such as nitrogen.
In general the minimum fr~e fall distance provides for a downward velocity sufficient to orient the catalyst particle along the major axis of the catalyst particle, that is the free fall distance should be sufficient to provide for the catalyst particle to move a slight vertical distance upwardly after contact with the catalyst surface in order to accomplish the orientation. Thus, in general, the catalyst particles fall individually to the catalyst surface as the catalyst bed is formed. A dense, uniformly packed bed such as provided by this catalyst loading process is highly desirable because any liquid maldistribution caused by liquid flowing about and around the gas distributor is quickly re-distributed in a substantially uniform manner in the dense, uniformly packed bed.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A catalytic reactor for hydroconverting hydrocarbon materials comprising a closed vessel;
a fixed bed of hydrocarbon conversion catalyst particles within the vessel;
inlet means in the upper portion of the vessel;
outlet means in the lower portion of the vessel;
at least one gas distributor in the bed of catalyst particles for providing temperature control, said gas distributor comprising a gas supply means;
a plurality of conduits extending from the gas supply means having orifices spaced along the conduit;
a screen structure spaced from and surrounding the conduit to hold catalyst particles away from the conduit.

2. The catalytic reactor of claim 1 wherein the conduits extend horizontally from the header pipe.

3. The catalytic reactor of claim 2 wherein the conduits extend at right angles from the header pipe.

4. The catalytic reactor of claim 2 wherein the conduits extending from the header pipe are evenly spaced from each other along the header pipe.

5. The catalytic reactor of claim 4 wherein the conduits are spaced from about one-sixth foot to two feet from each other.

6. The catalytic reactor of claim 5 wherein the conduits are spaced from about one-third foot to one foot from each other.

7. The catalytic reactor of claim 6 wherein the orifices are equidistant from each other.

8. The catalytic reactor of claim 1 wherein an impervious deflector plate is located a distance D, at least equal to the diameter of the orifice, from the orifices spaced along the conduit to deflect gas emitted from the orifices.

9. The catalytic reactor of claim 2 wherein an impervious deflector plate is located a distance D, at least equal to the diameter of the orifice, from the orifices spaced along the conduit to deflect gas emitted from the orifices.

10. The catalytic reactor of claim 3 wherein an impervious deflector plate is located a distance D, at least equal to the diameter of the orifice, from the orifices spaced along the conduit to deflect gas emitted from the orifices.

11. The catalytic reactor of claim 4 wherein an impervious deflector plate is located a distance D, at least equal to the diameter of the orifice, from the orifices spaced along the conduit to deflect gas emitted from the orifices.

12. The catalytic reactor of claim 5 wherein an impervious deflector plate is located a distance D, at least equal to the diameter of the orifice, from the orifices spaced along the conduit to deflect gas emitted from the orifices.

13. The catalytic reactor of claim 6 wherein an impervious deflector plate is located a distance D, at least equal to the diameter of the orifice, from the orifices spaced along the conduit to deflect gas emitted from the orifices.

14. The catalytic reactor of claim 7 wherein an impervious deflector plate is located a distance D, at least equal to the diameter of the orifice, from the orifices spaced along the conduit to deflect gas emitted from the orifices.

15. The catalytic reactor of claim 1 wherein the fixed catalyst bed is formed by charging to the reactor in down-flow relationship to the reactor catalyst particles at a rate of fill of the reactor of up to about 17 vertical inches per minute, and at an average free fall distance through a gaseous medium to catalyst surface of at least about one foot.

16. The catalytic reactor of claim 8 wherein the fixed catalyst bed is formed by charging to the reactor in down-flow relationship to the reactor catalyst particles at a rate of fill of the reactor of up to about 17 vertical inches per minute, and at an average free fall distance through a gaseous medium to catalyst surface of at least about one foot.