Process for loading ceramic spheres into a vertical reactor
The present invent ion relates to a process for loading ceramic
spherical part icles into a vert ical reactor.
The process of the present invent ion is particularly suitable fo5 r
loading fragile ceramic part icles that are likely to break into the
bottom of a high container. In part icular, the process of the invent ion
allows loading ceramic balls into a vert ically orientated reactor, such
as for example those found in refinery and petrochemical processes.
10 The process of the invent ion will be hereafter described and
illustrated with regard to its use in the refinery and petrochemica l
fields. However it will be clear for those skilled in the art that it can
be direct ly implemented in any other technical field where ceramic
particles that are likely to be broken need to be loaded into a high
15 vertical reactor.
Several refinery and petrochemical processes require that
particulate material such as inert support particles be loaded into
reactors, which are large vert ical containers in which the hydrocarbon
feeds are treated. The part icles shall generally be loaded onto a grid or
20 other mechanical support structure at the bottom of the reactor.
Representat ive examples of such processes are hydrotreating
processes, which correspond to reactions carried out in the presence of
hydrogen and which are generally int ended to treat or remove
undes irable compounds which are present in the hydrocarbon
25 fract ions, such as unsaturated hydrocarbons, sulphur-comprising,
nitrogen-compris ing, aromat ic or metal compounds. Ment ion may be
made, as non-limit ing examples, of hydrogenat ion,
hydrodesulphurizat ion, hydrodenitrogenation, hydrodearomat izat ion
and hydrodemetallizat ion of various types of hydrocarbon feeds ( for
30 example kerosene, gasoil, gasoline, atmospheric residue…), which are
used extensively in both the refining and petrochemical industries.
Such hydrotreating processes are performed in large reactors
that contain a large quant ity of granulat e catalyst loaded as a single
3
bed or as mult iple beds. The reactors that are concerned by the present
invent ion are those having an int ernal diameter of a least 0.5 m, such
as an internal diameter ranging typically from 0.5 m to 5 m, more
preferably from 2 to 5m, and a height typically ranging from 2 m to
more than 40 m5 .
Before loading the granulate catalyst used in these reactors, a
first layer of part iculate support material is generally loaded at the
bottom of each catalyst bed, on a support grid or structure.
The support material is typically made of ceramic spherica l
10 particles (hereafter called ceramic spheres or ceramic balls), with
typical diameters ranging from 6 mm to 25 mm.
When loading the support particles into an empty reactor, there
are important considerat ions as regards the quality and the efficacy of
the loading process, of which the three main ones are:
15 - The loading process must avoid breakage of the part icles.
Such breakage will in part icular result in increased pressure drop
during the reactor operation, which affe cts the performances of the
process.
- The loading process must be as fast as pract ical. Extended
20 downt ime for catalyst changeout can result in very considerable
financial penalt ies due to lost production.
- The loading process must ensure the safety of the personne l
loading the material so that no part icles or element s of the loading
device may fall on the person operat ing the loading device inside the
25 vessel.
Achieving all these object ives poses a severe pract ical problem
when performing a loading operat ion. Simply pouring the part icles
from the top of the reactor will result in each part icle accelerat ing
under the force of gravity and gaining in vertical falling velocit y over
30 the height of the reactor. Taking into account the high height of the
reactors, this will result in an unacceptably high impact velocity in the
bottom of the reactor, either onto the bottom support structure in the
case of an empty reactor, or onto the surface of the bed of part ic les in
the case of a part ially loaded reactor.
4
This problem is especia lly important for the loading of the
support material. Indeed, the support materia l part icles have a
particularly large size, and need to be loaded at the very bottom of the
reactor, which means that they are submit ted to a part icularly high fall
height. Should such large and heavy partic les simply be poured int5 o
vessel from the top opening, their very high impact velocity when
reaching the bottom will result in signific ant breakage.
The init ia l concept for avoiding the high velocity impact from
free fa lling was to lower down into the reactor, by means of a rope or
10 a cable, discreet small quant it ies of particulate material enclosed
within a container such as a bag or a bucket. The material is only
discharged once the container has reached the bottom.
While these methods achieved the objective of avoiding free
fall of the part icles, they were st ill inefficient with respect to duration
15 of loading and safety of operating people ins ide the vessel.
The next concept for the loading of part iculate material into a
vessel involved using a sock connected to a hopper for feeding the
particulate material from the top of the vessel. This sock can be used
in two different ways: either by twist ing the sock to slow down the
20 particles by frict ion all along the sock wall. The support material can
then be loaded at a low rate. Or the sock can be twisted t ight before
opening the hopper and untwisted slowly with the hopper valve open.
In this way, the sock is filled slowly from the top to the bottom. The
loading rate is then controlled manually by the operator. The major
25 drawback of the first method is to control the opening of the sock and
the hopper simultaneously to avoid breakage. The drawback of the
second method is the safety of the operator who is located inside the
vessel. A sock filled with part iculate mat erial can become very heavy
and the structural integrity of the sock becomes constrained. Severe
30 injuries are reported every year due to the rupture or collapse of a
filled loading sock.
Further innovat ion in part iculate material loading techniques
introduced mechanical means into the container to reduce the fall
velocity.
5
Under this concept, a flexible tube formed into large S shaped
bends is used and bended all a long the height of the container. With
this arrangement, the part icles no longer fall freely down the sock, but
slide along the inc lined parts of the S shapes, thus experiencing some
decelerat ing resistance. Such a technique is for example disclosed i5 n
FR 2 829 107.
EP1939115 describes a series of helicoidal devices inserted
ins ide a sock and attached to the top hopper over substant ially it s
ent ire length. These devices create a phys ical obstruct ion to the
10 falling part icles. The part iculate material is poured into the top hopper
and the flow of part icles is manually regulated through a valve
opening, but before the part icles can reach a too high fa lling velocity,
they encounter and impact on these phys ical obstructions. In this
fashion, the falling velocity is reduced, in a stage-wise fashion, over
15 the ent ire length.
These methods represent a significant improvement over the
previous ly used processes, notable with respect to loading quality,
speed and safety, but they st ill have some drawbacks.
A main drawback is that the particles phys ically impact onto
20 the obstructions of the decelerat ing device, with a substant ial risk of
breakage of both the device and the part icles.
The latest innovat ion is described in EP 2 029 463 which
discloses a rigid pipe fixed on the top flange of the container. This
pipe is equipped with a piston which is controlled by an air driven
25 winch. This piston, starting from the top of the pipe is slowly lowered
down inside the pipe while the top hopper valve is open. The pipe is
filled from the top to the bottom in a secured manner. By virtue of
being constructed from steel or stainless steel, this device is capable
of supporting the very considerable weight of the filled pipe without
30 rupturing or collapsing as is the case for flexible loading socks.
However, this concept requires heavy hoist ing equipment to lift the
pipe and some special arrangements must be made on the top plat form
to install all the needed equipment (hopper, winches, safety
equipment).
6
The present invent ion aims at providing an improved process,
which allows the loading of ceramic spheres into a large vert ical
reactor, and overcomes the drawbacks of the processes of the prior art.
The present invent ion therefore concerns a process for loading
ceramic spheres having a diameter ranging from 6 mm to 25 mm into 5 a
vertical reactor having a diameter of at least 0.5 m, which comprises:
- introducing into the reactor along a substant ial height thereof
a feeding pipe that is opened at it s bottom part, said feeding pipe
being vert ical or having an angle of inc linat ion with regard to vert ical
10 of at most 15 degrees,
- inducing an upflow of air and/or nitrogen into said pipe from
the bottom opening to the top thereof by sucking air from the top of
the feeding pipe (4) using a vacuum system, and
- pouring said ceramic spheres into the pipe from the upper
15 part thereof in such a way that said spheres fa lls down ins ide the said
pipe, counter current ly to said upflow of air and/or nitrogen,
characterized in that no phys ical device or air-supplying conduit is
present inside the inner sect ion of the feeding pipe.
According to the invent ion, the part icle s are loaded into the
20 bottom of the reactor via a substant ially vertical feeding pipe that is
inserted into the reactor. Preferably, said feeding pipe is vert ical or
has an angle of inclinat ion with regard to vert ical of at most 10
degrees. According to the invent ion, the feeding pipe is
advantageously rigid or semi-rigid. Rigid means a metallic pipe and
25 semi-rigid means a rubber or plast ic tube with steel re inforcing.
According to a preferred embodiment, the feeding pipe is
straight over its whole length.
An ascendant flow of air is created inside the pipe from the
bottom to the top thereof, which slows down the fa lling part icles to a
30 velocity that is low enough to avoid any breakage thereof at the
moment of impact at the bottom of the reactor or at the surface of the
bed of particles for a partially loaded reactor.
By regulat ing the velocity of the upflow of air and/or nitrogen
into the pipe, the drag force on the part icles falling ins ide the pipe can
7
be controlled over the ent ire length of the pipe and up to the exit
thereof.
According to the present invent ion, no phys ical device or airsupplying
conduit is present inside the inner sect ion of the feeding
pipe during the loading operations, neither for phys ically slowin5 g
down the falling part icles nor for supplying air into the pipe nor for
any other purpose such as controlling the loading level or rate. The
present invent ion thus allows overcoming other drawbacks of some
processes disclosed in the prior art.
10 In part icular, the absence of any phys ical device inside the
feeding pipe avoids the risk of blockage during loading, which can
exist due to the reduced cross-sect ional diameter of the feeding pipe.
Thus, the present invent ion allows for a significant ly increased
loading rate, with a corresponding reduction in the overall loading
15 durat ion.
The feeding pipe should be inserted into the reactor deeply
enough, so that the distance between the exit of the pipe and the
bottom of the reactor or the top of the particles bed is low enough to
avoid any substant ial breakage of the particles. In other terms, when
20 the particles exit the pipe, the remaining height along which the
particles fa ll freely should be as low as possible. Lowering as much as
possible such remaining height allows one to eliminate almost all risks
of breakage of the part icles.
Of course, the maximum rema ining height that should be
25 allowed depends largely on the amount of free space required to
perform the other act ivit ies associated with the loading support
materials, such as spreading out and levelling off the layer of support
material.
In a general manner, according to a preferred embodiment the
30 feeding pipe is introduced into the reactor so that the distance between
the lower exit of the pipe and the bottom of the reactor or the top of
the bed of ceramic spheres in the case of a part ially loaded reactor is
at most 2 m, more preferably at most 1 m.
8
A main benefit of the process of the invent ion is that it allows
to control and to reduce as much as desired the net downwards
velocity of the falling part icles relat ive to the container. It therefore
allows to substant ially reduce the impact velocity of the part icles
when they reach the bottom of the reactor, which reduces the risk o5 f
breakage.
Furthermore, the process is simple and allows a fast and
efficient loading of ceramic balls into very high reactors.
A substant ial advantage of the process of the invent ion is it s
10 very good safety for the personnel performing the loading operat ions.
ins ide the reactor. In some instances, it may even be possible to
perform the loading of the ceramic balls without anybody ins ide the
reactor, and only send personnel inside at the end of the operat ion to
perform the fina l act ions such as levelling off the layer.
15 Another advantage of the process over those used in the prior
art is that the air flowing up into the feeding pipe will remove any
dust or small pieces, typically referred to as chips, that are present in
the ceramic balls as delivered. The air/nit rogen that is sucked into the
feeding pipe at its bottom end will also remove some of the dust that
20 is generated as the balls are loaded into the reactor. The combinat ion
of these two effects will result in a substant ial reduct ion of dust inside
the reactor during the loading process, which is benefic ial from a
safety and comfort viewpoint for the person or persons working inside
the reactor during the loading process.
25 According to the invent ion, the impact velocity of the ceramic
spheres is advantageously controlled at a value that reduces breakage
thereof, and more preferably that totally avoids breakage.
According to a preferred embodiment, the impact velocity of
the spheres is controlled so that it remains at a mean value below 10
30 m/s, and preferably below 6m/s.
The value of the impact velocit y of a falling part icle is the
value of the falling velocity achieved by said part icle when it reaches
either the bottom of the reactor or the top of the bed of part icles
9
already loaded. The velocity hereabove is expressed relat ive to the
reactor.
The mean impact velocit y of the balls is controlled by
controlling the mean net velocity of the balls with regard to the
reactor at the exit of the feeding pipe5 .
To obtain the required mean net ve locity of the ceramic
spheres at the exit of the feeding pipe, one must control the upflow
rate of air (and/or nitrogen). The rate of upflowing air required to
obtain a part icular net ve locity can be calculated. It depends in
10 particular on the dimensions of the feeding pipe, specifically it s ins ide
diameter and its length; the aerodynamic characterist ics of the
particles; and the condit ions of the upflowing air/nitrogen,
spec ifically the pressure and temperature. Typically, the velocity of
the upflowing air and/or nitrogen shall be at least 20 m. s-1.
15 According to the invent ion, the upflow of air and/or nitrogen is
induced by sucking air from the top of the feeding pipe using a
vacuum system. This requires that a vacuuming system be connected
to the upper part of the feeding pipe.
In this case, the rate of upflowing air/nitrogen is controlled by
20 controlling the amount of air that is allowed to flow to the vacuum
system.
The system used for pouring the ceramic spheres at the top of
the feeding pipe can be any convent iona l one, provided that it allows
controlling the flow rate of part icles supplied to the pipe. This control
25 of the part icle flow rate does not need to be precise, as long as it is
able to limit the flow rate to a value where the system does not
become overloaded. For example, a slide valve such as typically used
in this service will be sufficient.
According to the invent ion, the reactor advantageously remains
30 opened at its top part during the loading process. It means that the top
exit of the reactor is not sealed.
Furthermore, in the present invent ion no addit ional pipe or
conduit is introduced into the reactor to introduce air and/or nitrogen
into the reactor. The air that is being sucked out of the reactor is being
10
replenished by air being drawn in through the open top exit of the
reactor.
The process of the present invent ion can be used in all
technical fie lds, in all cases in which at least one vert ical reactor of
significant height needs to be filled with ceramic balls that are likel5 y
to be broken due to impact on a hard surface under condit ions of
gravitat ional free fall.
By “significant height”, it is meant a reactor having an int ernal
height ranging from 5 to 40 m, or even higher (such as for example up
10 to 60 m).
The process is part icularly suit able for loading ceramic balls
used as support material into the bottom of a reactor in the fields of
(petro) chemistry and petroleum refining.
Hence, according to a preferred embodiment, said reactor is a
15 vertical reactor used in a chemical, petrochemical or petroleum
refining process.
The invent ion will now be further illustrated in a non
limit at ive embodiment, with reference to the accompanying Figure
which illustrates a preferred example of implementat ion of the process
20 of the invent ion, in the case of loading ceramic balls into the bottom
of a large vert ical reactor such as a hydrotreat ing reactor.
Figure 1 shows a vert ical large reactor 1 that is opened on it s
top part, into which a support material made of ceramic balls 2 needs
to be loaded, onto support grid 3 in the bottom of the reactor.
25 According to the invent ion, a vert ical feeding pipe 4 that is
open at its bottom has been introduced into reactor 1, along a
substant ial height thereof, so that the distance (d) between the lower
exit of pipe 4 and grid 3 is less than 2 m.
A suitably powered vacuum system not shown sucks air from
30 the top of feeding pipe 4 via chamber 7 and conduit 8, thereby
creat ing an ascendant flow of air and/or nitrogen from the bottom to
the top of pipe 4, which is shown by the bold dotted arrows.
The air/nitrogen is sucked from the interior of reactor 1, enters
at the bottom of the pipe 4, and flow from the bottom to the top of
11
pipe 4. The air that is sucked from the interior is replenished by air
flowing in through the open top exit.
Prior to introducing the ceramic balls, an upflow of air is
established ins ide pipe 4 and set to an appropriate value, as
determined from experience, taking into account the diameter of th5 e
pipe 4 and the size and weight of the ceramic balls. The air flow rate
is set by adjust ing the manual control valve 9 to obtain the required
upflow air velocit y ins ide pipe 4.
This upflow air/nitrogen velocity will typically be measured by
10 measuring the velocity of the air/nitrogen entering the bottom open
end of pipe 4, by means of a device such as a handheld anemometer.
Once a sat isfactory air flow rate is achieved, as determined by the
anemometer reading, the reading on the vacuum gauge 10 is noted for
future reference during the loading operation.
15 Once the air flow rate is established, the ceramic balls 2 to be
loaded onto grid 3 are poured into pipe 4 at the upper part thereof.
They are fed from the part icles supply hopper 5, through a particles
flow control device 6 and then via chamber 7 which is attached to pipe
4 via sealing clamp 13.
20 The part icles flow control device 6 is manually set to give the
appropriate supply rate of balls 2.
As shown on the Figure, the ceramic balls 2 are loaded onto
grid 3 via feeding pipe 4, in which they fall downwardly counter
current ly to the upflow of air and/or nitrogen.
25 The upflow of air/nitrogen s lows down the falling ceramic
balls 2 to a velocity that is low enough to avoid any breakage thereof
when they reach the bottom of reactor 1.
It is possible that, once the ceramic balls are introduced into
pipe 4, the previously established air flow rate may be affected. In this
30 case, the manual flow control valve 9 can be adjusted by making
reference to the previously noted reading on vacuum gauge 10.
In addit ion, visual observat ion of the ceramic balls as they exit
pipe 4 and impact in the bottom of the vessel may dictate further
minor adjustments to the manual flow control valve 9.
12
During the loading operat ion, the supply hopper 5 should be
properly sealed at the top to avoid excessive ingress of air. Such
sealing does not need to be perfect ly a ir-tight, and can for instance be
done with a lid 12a. An alt ernat ive is to cover the top surface of the
ceramic balls ins ide the hopper with a tarpaulin or fire blanket 125 b
which extends up to the side walls of said hopper.
Using the device disclosed in Figure 1, the support material
made of ceramic balls 2 is loaded into reactor 1 in a safe and effic ient
manner, without breakage thereof.
10 Of course, the process of the present invent ion can be
implemented in vertical reactors of all types and configurat ions, and
one skilled in the art can easily accommodate the part icular device
arrangement to match all types of part icular configurat ions.

CLAIMS
1. A process for loading ceramic spheres having a diameter
ranging from 6 mm to 25 mm (2) into a vertical reactor (1) having an
int ernal diameter of at least 0.5 m, which comprises:
- introducing into the reactor (1) along a substant ial heigh5 t
thereof a feeding pipe (4) that is opened at its bottom part, said
feeding pipe (4) being vert ical or having an angle of inclinat ion with
regard to vert ical of at most 15 degrees,
- induc ing an upflow of air and/or nitrogen into said pipe (4)
10 from the bottom opening to the top thereof by sucking air from the top
of the feeding pipe (4) using a vacuum system, and
- pouring said ceramic spheres into the pipe (4) at the upper
part thereof in such a way that said spheres (2) falls downwardly
counter current ly to said upflow of air and/or nitrogen,
15 characterized in that no phys ical device or air-supplying conduit is
present inside the inner sect ion of the feeding pipe (4).
2. The process of the preceding cla im, wherein the rate o f
upflowing air and/or nitrogen is controlled by adjust ing the amount of
air and/or nitrogen that is allowed to flow to the vacuum syst em.
20 3. The process of anyone of the preceding claims, wherein
said feeding pipe (4) is vert ical or has an angle of inclinat ion with
regard to vert ical of at most 10 degrees.
4. The process of anyone of the preceding claims, wherein
said feeding pipe (4) is straight over its whole length.
25 5. The process of anyone of the preceding claims, wherein the
impact velocity of the spheres (2) is monitored so that it remains at a
mean value that is less than 10 m/s, and preferably less than 6 m/s.
6. The process of anyone of the preceding claims, wherein the
mean net velocity of the spheres at the exit of the feeding pipe (4) is
30 controlled by controlling the rate of upflowing air and/or nitrogen.
7. The process of anyone of the preceding claims, wherein the
feeding pipe (4) is introduced into the reactor (1) so that the distance
(d) between the lower exit of the pipe (4) and the bottom (3) of the
14
reactor or the top of the bed of ceramic spheres in the case of a
partially loaded container is at most 2 m, more preferably at most 1 m.
8. The process of anyone of the preceding claims, wherein the
reactor (1) has an int ernal height ranging from 5 to 40 m or higher.
9. The process of anyone of the preceding claims, wherein th5 e
feeding pipe (4) is rigid or semi-rigid.
10. The process of anyone of the preceding claims, wherein the
reactor (1) has an int ernal diameter ranging from 0.5 m to 5 m,
preferably from 2 to 5m.
10 11. The process of any preceding cla im, wherein , the reactor
used in a petrochemical or petroleum refining process.