Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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.
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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
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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.
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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.
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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.
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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.
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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
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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
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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.
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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
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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.
