Title of Invention

OLEFIN POLYMERIZATION PROCESS WITH OPTIMIZED PRODUCT DISCHARGE

Abstract The present invention relates to a polymerization process for producing olefin polymers in a loop reactor comprising the steps of: introducing into the loop reactor one or more olefin reactants, polymerization catalysts and diluents, and while circulating said reactants, catalysts and diluents, polymerizing said one or more olefin reactants to produce a polymer slurry comprising essentially liquid diluent and solid olefin polymer particles, said process further comprising one or more cycles of: (a) allowing said polymer slurry to settle in one or more settling legs connected to said reactor, and(b) discharging from a settling leg a predetermined volume of polymer slurry substantially equal to the volume of polymer slurry settled in said settling leg since its previous discharge. The invention is also for a loop reactor for said process.
Full Text Olefin polymerization process with optimized product discharge
Field of the invention
The present invention relates to improvements in the removal of polymer slurry from a
reactor for olefin slurry polymerization. The present invention further relates to a
polymerization process occurring in a loop reactor wherein discharge of the settled
polymer slurry is optimized.
Background of the invention
Olefin polymerizations such as ethylene polymerization are frequently carried out using
monomer, diluent and catalyst and optionally co-monomers in a loop reactor. The
polymerization is usually performed under slurry" conditions, wherein the product consists
usually of solid particles and is in suspension in a diluent The slurry contents of the
reactor are circulated continuously with a pump to maintain efficient suspension of the
polymer solid particles in the liquid diluent, the product being often taken off by means of
settling legs which operate on a batch principle to recover the product. Settling legs are
used to increase the solids concentration of the slurry finally recovered as product slurry.
The product is further either transferred to another reactor or discharged to a flash tank,
through flash lines, where most of the diluent and unreacted monomers are flashed off
and recycled. This recycling may be done either through recompression and reinjection to
the reactor with or without intermediate purification. An important operational cost is linked
to this fluid effluent recycling. The polymer particles are dried, additives can be added and
finally the polymer is extruded and pelletized. This technique has enjoyed.international
success with millions of tons of ethylene polymers being so produced annually.
Optimal behavior of the settling legs is reached when the quantity of recovered polymer is
maximized with respect to the amount of fluid effluent that must be recycled, so that the
recycling cost may be minimized for a given production rate. Classically, operation of the
plant is based on attempting to discharge the same amount of slurry from all settling legs
in order to afford equivalent pressure drops when discharging each leg, however this
operation may be far from optimal.
Various alternatives to conventional settling legs are known. For example, WO 01/05842
describes an apparatus for removing concentrated slurry from a flowing stream of slurry in
a conduit characterized by a channel in an outlet area of the conduit, the outlet being
adapted to continuously remove slurry.


EP 0891990 describes an olefin polymerization process wherein the product slurry is
recovered by means of a continuous product take off, more in particular by means of an
elongated hollow appendage provided on the reactor. Said hollow appendage being in
direct fluid communication with a heated flash line and thus being adapted for continuous
removal of product slurry.
However the above-described apparatus and processes have the disadvantage that the
suspension withdrawn from the reactor still contains a large amount of diluent and of other
reactants, such as the monomer, which it is then necessary to subsequently separate
from the polymer particles and to treat for the purpose of reusing it in the reactor.
It is therefore an object of the present invention to provide a polymerization process
occurring in a loop reactor wherein discharge of the settled polymer slurry is optimized.
Another object of the invention is to provide processes wherein the settling efficiencies of
the polymer slurry and its further discharge is optimized. A yet further object of the present
invention is to decrease the fluid effluent throughput at a given polymer production rate by
the use of optimized discharge. It is another object to provide a loop reactor having
optimized settling legs.
Summary of the invention
The present objects are achieved by the processes and devices according to the present
invention.
The present invention therefore relates to a polymerization process for producing olefin
polymers in a loop reactor comprising the steps of: introducing into the loop reactor one or
more olefin reactants, polymerization catalysts and diluents, and while circulating said
reactants, catalysts and diluents, polymerizing said one or more olefin reactants to
produce a polymer slurry comprising essentially liquid diluent and solid olefin polymer
i particles, said process further comprising one or more cycles of:
(a) allowing said polymer slurry to settle in one or more settling legs connected to said
reactor,
(b) monitoring the volume of polymer slurry settled in a settling leg since its previous
discharge,

(c) discharging from said settling leg, a predetermined volume of polymer slurry
substantially equal to the volume of polymer slurry settled in said settling leg since its
previous discharge.
The present invention also relates to a loop reactor suitable for olefin polymerization
process comprising: a plurality of interconnected pipes defining a flow path for a polymer
slurry, said slurry consisting essentially of an olefin reactant, a polymerization catalyst,
liquid diluent and solid olefin polymer particles, means for introducing olefin reactant,
polymerization catalyst and diluent into said reactor, a pump suitable for maintaining the
polymer slurry in circulation in said reactor, one or more settling legs connected to the
pipes of said reactor,
at least one measurement means suitable for inferring the volume of settled slurry inside
the settling legs such as for example by mathematical or statistical modeling techniques,
including neural networks, and
at least one valve control means operatively connected to said measurement means and
to the valve of said settling legs.
The process and reactor according to the present invention present several advantages
over the prior art such as allowing for an optimized discharge of settled slurry from settling
legs to a product recovery zone. The volume of polymer slurry that settles in a settling leg
may be different from one settling leg to another according to the position of said settling
leg on the loop reactor and its geometrical characteristics. The present process allows the
settling legs to be completely emptied of settled material at each discharge without
substantially discharging further unsettled slurry that would impose a severe overload to
the fluid recycling section for a minimal additional polymer production. The present
process also allows that no settled polymer remains in the settling leg at the time it closes.
This further significantly decreases the risk of plugging- of the settling leg. Indeed such
plugging is often due to mass polymerization of the settled slurry remaining under active
polymerization conditions in the settling leg, which has poor heat removal characteristics.
The present invention will be further disclosed in detail hereunder. The description is only
given by way of example and does not limit the Invention. The reference numbers relate to
the hereto-annexed figures.
Brief description of the drawings


Figure 1 represents a schematic representation of a single loop polymerization reactor
according to an embodiment of the present invention.
Figure 2 represents a schematic cross-sectional side view of a section of the loop reactor
of Figure 1, showing two settling legs positioned on said section with their connection to
said section having different angles alpha from a horizontal line.
Figure 3 is a schematic representation of a double loop polymerization reactor according
to an embodiment of the present invention.
Detailed description of the invention
The polymerization processes according to the present invention are suitable for any
process producing an effluent comprising a slurry of particulate solids suspended in a
liquid medium. Such reaction processes include but are not limited to those that have
come to be known in the art as particle form polymerizations.
This invention is particularly suitable for polymerization processes occurring in loop
reactors for the production of polymer, more particularly polyethylene, wherein a
polymerization effluent is formed which is a slurry of particulate polymer solids suspended
in a liquid medium, ordinarily the reaction diluent and unreacted reactants.
The present invention is suitable for polymerization process for the manufacture of
particulate olefin polymers consisting of the catalytic polymerization or copolymerization of
one or several olefins such as C2 to C8 olefins iri a diluent containing the monomer to be
polymerized, the polymerization slurry being circulated in a loop reactor to which the
starting material is fed and from which the polymer formed is removed. Examples of
suitable monomers include but are not limited to those having 2 to 8 carbon atoms per
molecule, such as ethylene, propylene, butylene, pentene, butadiene, isoprene, 1-hexene
and the like.
The polymerization reaction can be carried out at a temperature of from 50 to 120 oC,
preferably at a temperature of from 70 to 115oC, more preferably at a temperature of from
80 to 110 oC, and at a pressure of from 20 to 100 bars, preferably at a pressure of from 30
to 50 bars, more preferably at a pressure of 37 to 45 bars.
In a preferred embodiment, the present invention is particularly suitable for the
polymerization of ethylene in isobutane diluent. Suitable ethylene polymerization includes
but is not limited to homopolymerization of ethylene, copolymerization of ethylene and a

higher 1-olefin co-monomer such as 1-butene, 1-pentene, 1-hexene, 1-octene or 1-
decene. In an embodiment of the present invention, said co-monomer is 1-hexene.
Ethylene polymerizes in a liquid diluent in the presence of a catalyst, optionally a co-
catalyst, optionally a co-monomer, optionally hydrogen and optionally other additives,
thereby producing a polymerization slurry.
As used herein, the term "polymerization sluny or "polymer slurry" or "slurry" means
substantially a multi-phase composition including at least polymer solid particles and a
liquid phase and allowing for a third phase (gas) to be at least locally present in the
process, the liquid phase being the continuous phase. The solids include catalyst and
polymerized olefin, such as polyethylene. The liquids include an inert diluent, such as
isobutane, with dissolved monomer such as ethylene and optionally one or more co-
monomers, molecular weight control agents, such as hydrogen, antistatic agents,
antifouling agents, scavengers, and other process additives.
Suitable diluents are well known in the art and include hydrocarbons which are inert or at
least essentially inert and liquid under reaction conditions. Suitable hydrocarbons include
isobutane, n-butane, propane, n-pentane, isopentane, neopentane, isohexane and n-
hexane, with isobutane being preferred.
Suitable catalysts are well known in the art. Examples of suitable catalysts include but are
not limited to chromium oxide such as those supported on silica, organometal catalysts
including those known in the art as "Ziegier" or "Ziegler-Natta" catalysts, metallocene
catalysts and the like. The term "co-catalyst" as used herein refers to materials that can be
used in conjunction with a catalyst in order to improve the activity of the catalyst during the
polymerization reaction.
The polymerization slurry is maintained in circulation in a loop reactor comprising a
plurality of interconnected pipes such as vertical jacketed pipe sections connected through
elbows. The polymerization heat can be extracted by means of cooling water circulating in
the jacket of the reactor. Said polymerization may be performed in a single or in two or
more loop reactors according to the present invention, which can be used in parallel or in
series. Said reactors are aimed to operate in a liquid full mode. When used in series they
can be connected through means such as for example through one or more settling legs
of the first reactor. The produced polymer may be withdrawn from the loop reactor along
with some diluent through at least one settling leg in which the solid content is increased
with respect to its concentration in the body of the reactor.

Settling legs may be in continuous fluid connection with the "product recovery zone". As
used herein "product recovery zone" includes but is not limited to heated or not heated
flash lines, flash tank, cyclones, filters and the associated vapor recovery and solids
recovery systems or transfer lines to another reactor or said other reactor when several
reactors are connected in series.
When no reactor is present downstream of the settling legs, the extracted slurry may be
depressurized and transferred through for example heated or not heated flash lines to a
flash tank where the polymer and the unreacted monomer and/or co-monomers and
diluent are separated. The degassing of the polymer may be further completed in a purge
column.
When at least one reactor is present downstream of the settling legs, the extracted slurry
is transferred through transfer lines to the next reactor. Transfer is made possible by
injecting the slurry in the downstream reactor in a point where the pressure is lower than
the pressure at the outlet of the settling legs.
The present invention more particularly relates to a polymerization process for producing
olefin polymers in a loop reactor as described above, said process comprising one or
more cycles of:
(a) allowing said polymer slurry to settle in one or more settling legs connected to said
reactor,
(b) monitoring the volume of polymer slurry settled in a settling leg since its previous
discharge,
(c) discharging from said settling leg, a predetermined volume of polymer slurry
substantially equal to the volume of polymer slurry settled in said settling leg since its
previous discharge.
As used herein the term "substantially equal" refers to a volume ± 20 % equal to the
volume of slurry settled in a given settling leg.
As used herein the term "equal" refers to a volume ± 5 % equal to the volume of slurry
settled in a given settling leg.
In an embodiment of the present invention, a predetermined volume of polymer slurry can
be discharged which is equal to the volume of polymer slurry settled in a given settling leg

since its previous discharge, in another embodiment, a predetermined volume of polymer
slurry can be discharged which is superior to the volume of polymer slurry settled in said
settling leg since its previous discharge.
The process according to the present invention presents several advantages over the
prior art such as allowing for an optimized discharge of settled slurry from settling legs to a
product recovery zone. The present process allows the settling legs to be completely
emptied from settled materials at each discharge without substantially discharging further
unsettled slurry that would impose a severe overload to the fluid recycling section for a
minimal additional polymer production.
In one embodiment, the present process is further characterized in that it comprises one
or more cycles of: (a) allowing said polymer slurry to settle in one or more settling legs
connected to said reactor, (b) assessing the time T required for the settling of a
predetermined volume of polymer slurry in a given settling leg after the previous closing of
that given settling leg, (c) triggering the discharge of said predetermined volume of settled
polymer slurry from said given settling leg into a product recovery zone at said time T after
the previous closing of said leg, and (d) discharging during a predetermined period At,
said predetermined volume of settled polymer slurry from said settling leg, wherein said
predetermined volume is substantially equal to the volume of polymer slurry settled in said
settling leg since its previous discharge.
In another embodiment, the present process is further characterized in that it comprises
one or more cycles of: (a) allowing said polymer slurry to settle in one or more settling
legs connected to said reactor, (b) evaluating the volume of polymer settled in a leg since
its previous discharge, (c) adjusting the opening speed of the valve and/or the aperture of
a flow adjusting device so that the volume discharged from the leg is substantially equal to
the evaluated settled volume.
According to an embodiment of the present invention, said process comprises the step of
adjusting the opening time of a settling leg such that the volume of polymer slurry to be
discharged from said settling leg is substantially equal to the volume of polymer slurry
settled in said settling leg since its previous discharge.
I According to another embodiment of the present invention, said process comprises the
step of adjusting the time between two discharges far a settling leg such that the volume
of polymer slurry to be discharged from said settling leg is substantially equal to the
volume of polymer slurry settled in said settling leg since its previous discharge.

According to yet another embodiment of the present invention, said process comprises
the step of adjusting the discharge aperture of a settling leg such that the volume of
polymer slurry to be discharged from said settling leg is substantially equal to the volume
of polymer slurry settled in said settling leg since its previous discharge.
The present processes can be suitably performed in conventional single and double loop
reactor. In the case of a single loop reactor the present invention facilitates the treatment
of the recycle stream. In the case of a double loop reactor the present invention minimizes
the transfer of comonomer into the second reactor. The present invention further
encompasses single and double loop reactors comprising adequate measurement means
suitable for inferring the settling characteristics in each settling leg and the volume of
settled slurry inside said legs and valve control means in operative connection with the
settlings legs of said reactor.
Referring now to the drawings, Figure 1 schematically illustrates an example of a loop
reactor 1 for use in the invention. Said loop reactor 1 comprises a plurality of
interconnected pipes 9. It will be understood that while the loop reactor 1 is illustrated with
six vertical pipes, said loop reactor 1 may be equipped with less or more pipes, such as 4
or more pipes, for example between 4 and 20 vertical pipes. The vertical sections of the
pipe segments 9 are preferably provided with heat jackets 10. Polymerization heat can be
extracted by means of cooling water circulating in these jackets of the reactor. Reactants
are introduced into the reactor 1 by line 3. Catalyst, optionally in conjunction with a co-
catalyst or activation agent, is injected in the reactor 1 by means of the conduct 17. It is to
be understood that Figure 1 is a simplified illustration of a loop reactor and that said
diluent, co-monomers, monomers, catalysts and other additives may enter the reactor
separately. In a preferred embodiment as illustrated herein, catalysts are introduced just
upstream from the circulation pump 2, diluent, monomer, potential co-monomers and
reaction additives just downstream of the circulation pump 2.
The polymerization slurry is directionally circulated throughout the loop reactor 1 as
illustrated by the arrows 6 by one or more pumps, such as axial flow pump 2. The pump
may be powered by an electric motor 5. As used herein the term "pump" includes any
device from compressing driving, raising the pressure of a fluid, by means for example of
a piston or set of rotating impellers 4.
The reactor 1 is further provided with one or more settling legs 7 connected to the pipes 9
of the reactor 1. Although only five settling legs 7A to 7E are illustrated in Figure 1, the

present process encompasses a loop reactor comprising one or more settling legs. In an
embodiment of the present invention, said loop reactor comprises 1 to 20 settling legs,
preferably 4 to 12 settling legs, more preferably 6 to 10 settling legs.
The settling legs 7 are preferably provided with an isolation valve 19. These valves 19
may be ball valves for example. These valves 19 are open under normal conditions and
can be closed for example to isolate a settling leg from operation. Said valves can be
closed when the reactor pressure falls below a chosen value.
Furthermore, the settling legs can be provided with product take off or discharge valves
15. The discharge valve 15 may be any type of valve, which can permit continuous or
periodical discharge of polymer slurry, when it is fully open. Polymer slurry settled in the
settling legs 7 may be removed by means of one or more product recovery lines 8, e.g. to
a product recovery zone.
The discharge valve 15 that can be used in this invention may be any type of valve which
can permit continuous or periodical discharge of a polymer slurry, when it is fully open. An
angle valve, or ball valves may be suitably used. For example, the valve may have such a
structure that solid matter is prevented from accumulating or precipitating at the main
body portion of the valve. However, the type and structure of the discharge valve can be
selected by those skilled in the art as required.
Said loop reactor 1 further comprises measuring means 21, one or more, located on the
leg and/or on the reactor, that allow inferring the settling characteristics in each settling leg
and valve control means 22 in operative communication with said measuring means 21
and with the valves 15 of the settling legs 7. Any conventional measuring device may be
used to infer the volume of polymer slurry settled in the settling legs 7, which may then
transmit a signal to the valve control means 22 to for example discharge the settled
volume, when a predetermined volume is reached- in a given settling leg. Examples of
suitable devices include but are not limited to gamma ray density gauge, or level
radiography devices or sonometric measuring devices. Those measures may be either
directly transmitted to the valve control means or be input to a mathematical or statistical
model whose output is transmitted to the valve control means.
Figure 2 illustrates a section of the loop reactor 1 of Figure 1. Two settling legs 7A and 7B
are connected to a section of said reactor, the settling leg 7A with area of contact 13A and
settling leg 73 with the area of contact 13B. Said settling legs 7A and 7B are also
illustrated respectively with arbitrary volume V1 and V2. The settling leg 7A located on

the curved section 11 of the reactor may have a diameter D1 identical to the diameter D2
of the settling leg 7B located on a straight section of said reactor. However, due to its
position characterized by the angle alpha 16, delimited from a horizontal line 12 by the line
18, the settling leg 7A has different settling characteristics compared to settling leg 7B. Its
location in the curved portion of the pipe 9 modifies the amount of polymer slurry settling
in settling leg 7A compared to settling leg 7B, for a given time T. Due to the positioning of
the leg 7A in the elbow section of the reactor, said settling leg is not equivalent in term of
settling rate with the other settling legs. More precisely, the rate at which the slurry settles
in the bottom part of a settling leg is not equal for all the legs.
When setting the parameters of the present process the volume of settled slurry in each
settling leg can be inferred using measurements means 21. The measurements means 21
can indicate, directly or through the use of a mathematical or statistical model when the
settled polymer slurry depth is outside the desired range arbitrarily represented by line 14.
At this time, a signal is transmitted to the valve control means 22 The valve control means
will then actuate the discharge valve 15 of said settling legs and thereby control the
discharge of the settled polymer slurry from said settling legs.
In said settling legs 7 the polymerization slurry decants so that the slurry exiting the
reactor is more concentrated in solid than the circulating slurry. Its concentration is
actually as high as it can be because in the settled phase the polymer solid particles are in
close contact to each other. The liquid phase occupies only the solids internal and inter-
granular porosity. The present process and reactor allow the optimized discharge of
settled slurry from said settling leg, and therefore permit to limit the quantity of diluent that
has to be treated and re-fed to the reactor. Typically settled polymer slurry comprises from
60 to 65 % of polymer particles, whereas the unsettled slurry in said leg comprises from
30 to 45 % of polymer particles.
According to an embodiment of the present invention, when a predetermined volume of
settled polymer slurry is reached in a given settling leg at time T, the discharge of that
particular leg is triggered. The settling leg is actuated during a time At required to allow the
complete discharge of said predetermined volume.
Said volume V can be efficiently discharged by adjusting the opening time of said given
settling leg. In another embodiment, said volume V can be efficiently discharged by
adjusting the discharge aperture of said given settling leg so as to limit the volume
discharged from said leg to the volume V. In an embodiment of the present invention, the

discharge of said settled polymer slurry from said settling legs is triggered when said
settled slurry has reached an optimum predetermined volume in said settling legs.
Adjusting the discharge aperture of a given settling leg includes but is not limited to
reducing or enlarging the size of the opening of a discharge valve, or adding downstream
of said discharge valve another flow regulating device of adjustable smaller aperture or an
adjustable reduction of smaller aperture.
The present process encompasses any measuring means able to determine the volume
of settled slurry at a time T in a settling leg. The monitoring step can be performed using
measuring means selected from the group comprising level radiography means and
gamma ray probes or using models.
Discharging said settled polymer slurry from said settling legs through discharge valves
into a product recovery zone, is performed in such a way that the volume discharged from
a settling leg is substantially equal to the volume of polymer slurry settled In said settling
leg since its previous discharge.
According to the present invention, the actuation of the discharge valve is controlled by
valve control means 22 which can be also operatively connected with said volume control
means 21 for example. The valve control means 22 allow the adjustment and the control
of the periodical gpening at predetermined frequencies and sequence of the settling legs
to permit the continuous or periodical discharge of said polymer slurry. Other control
means such as pressure controllers and flow controllers, flow transducers and flow
sensors may be used to further fine-tune the discharging process.
The process and reactor according to the invention, provides the advantage of optimizing
the discharge of settled polymer slurry from a given settling leg without discharging further
unsettled slurry thereby reducing the amount of diluent to be recycled, and further
reducing the operation costs.
In another embodiment, the loop reactor according to the present invention comprises
settling legs wherein the area of contact between said settling leg and said reactor pipe is
at an angle alpha within the range of 0° to 60° from a horizontal line.
The present invention also encompasses a loop reactor suitable for an olefin
polymerization process comprising two or more settling legs connected to the pipes of
said reactor, wherein the effective volume or the settling rate of at least one settling leg is

substantially different from the effective volume or the settling rate of at least another
settling leg.
As used herein the term "effective volume" refers to the volume of polymer slurry which
may settle into a settling leg if the settling is continuously under the same circulation
conditions in the reactor. This effective volume may be smaller than the total settling leg
volume because turbulence created on the top of the leg will prevent settling up to the top
of the leg.
As used herein, the term settling rate refers to the volume of the currently produced
polymer that may settle in a given settling leg per unit of time when the settled volume is
50% of the previously defined effective volume.
As used herein the term "substantially different" refers to a difference larger than 2%.
The present invention also encompasses a loop reactor as described above wherein the
settling legs are modified and/or designed such as to obtain a substantially different
settling rate and/or settling volume in each settling leg.
In an embodiment of the present invention, the loop reactor comprises settling legs having
an internal diameter within the range of 0.2 to 0.5 times the internal diameter D3 of the
pipes of said reactor.
In another embodiment of the present invention, the settling legs connected to a section of
said loop reactor may have an internal diameter within the range of 0.3 to 0.5 times the
internal diameter of said reactor pipe section.
The present invention is particularly suited for the discharge of multiple loop reactors
connected in series.
Figure 3 represents a double loop reactor 100/116, comprising two single loop reactors
100,116, which are interconnected in series. Both reactors 100,116 consist of a plurality
of interconnected pipes 104. The vertical sections of the pipe segments 104 are preferably
provided with heat jackets 105. Reactants are introduced into the reactors 100 by line
107. Catalyst, optionally in conjunction with a co-catalyst or activation agent, may be
injected in one or both of the reactors 100 and 116 by means of conduct 106. The
polymerization slurry is directionally circulated throughout the loop reactors 100, 116 as
illustrated by the arrows 108 by one or more pumps, such as axial flow pump 101. The
pumps may be powered by an electric motor 102. The pumps may be provided with a set

of rotating impellers 103, The reactors 100, 116 are further provided with one or more
settling legs 109 connected to the pipes 104 of the reactors 100, 116. The settling legs
109 are preferably provided with an isolation valve 110. Further the settling legs can be
provided with product take off or discharge valves 111 or can be in direct communication
with the downstream section. Downstream the exit of the settling leg 109 of reactor 100, a
transfer line 112 is provided which allows to transfer polymer slurry settled in the settling
legs 109 to the other reactor 116, preferably through a piston valve 115 . Along the
transfer line 112, a three-way valve 114 may divert the flow to a product recovery zone if
the multiple loop reactor has to be used in a parallel configuration. Polymer slurry settled
in the settling legs 109 of reactor 116 can be removed by means of one or more product
recovery lines 113, e.g. to a product recovery zone.
Both reactors 100 and 106 and/or their respective settling legs are furthermore operatively
connected to measurements means 210, which are farther directly or through
mathematical or statistical models in operative communication with valve control means
220.
The present invention encompasses different types of measurements means and valve
control means, which can accomplish the purpose of the invention. The invention is also
applicable to mechanical, hydraulic or other signal means for transmitting information. In
almost all control systems some combination of electrical, pneumatic, mechanical or
hydraulic signals will be used. However, use of any other type of signal transmission,
compatible with the process and equipment in use, is within the scope of the invention.
The actuation and the control of a periodical discharging process can be implemented
using electrical analog, digital electronic, pneumatic, hydraulic, mechanical or other similar
types of equipment or combinations of one or more such equipment types. A
computational means is used in the preferred embodiment of this invention to operate and
control the process parameters. Computers or other types of computing devices can be
used in the invention.
The present invention also relates to computational means comprising a process
controller operatively connected to the discharge valves of said settling legs.
The present processes and reactors allow the discharge of each settling leg at a different
time and for a different time period, thereby controlling the volume of polymer slurry to be
discharged from said leg such that said discharged volume is substantially equal to the

volume of polymer slurry settled in said settling leg since the previous discharge of said
leg without substantially discharging further unsettled slurry.
Adjusting the opening duration of the discharge valve of each settling leg can be a
function of (a) the position of each settling leg on the loop reactor, and/or (b) the
geometrical characteristic of each settling leg, and/or (c) the volume of settled polymer
slurry in each settling leg.
This provides the advantage of optimizing the discharge of settled polymer slurry from a
given settling leg without discharging further unsettled slurry thereby reducing the amount
of diluent to be recycled, and further reducing the operation costs.
Although the present invention has been described with considerable detail with reference
to certain preferred variations thereof, other variations are possible. Therefore, the spirit
and scope of the appended claims should not be limited to the preferred variations
described herein.

We claim:
1. Loop reactor suitable for olefin polymerization process comprising:
- a plurality of interconnected pipes defining a flow path for a polymer slurry, said
slurry consisting essentially of an olefin reactant, a polymerization catalyst, liquid
diluent and solid olefin polymer particles,
- means for introducing olefin reactant, polymerization catalyst and diluent into said
reactor,
- a pump suitable for maintaining the polymer slurry in circulation in said reactor,
- one or more settling legs connected to the pipes of said reactor,
the improvement of which consists in providing
- at least one measuring means suitable for inferring the volume of slurry settled
inside the settling legs and
- at least one valve control means operatively connected to said measurement
means and to the valve of said settling legs.

2. Loop reactor as claimed in claim 1, wherein the control means acts on the interval
between two openings of the valve.
3. Loop reactor as claimed in claim 1, wherein the control means acts on the duration of
the opening of the valve.
4. Loop reactor as claimed in claim 1, wherein the control means acts on the discharge
aperture of the valve.
5. Loop reactor as claimed in claims 1-4, wherein the slurry exiting the settling leg is
directly injected into a second loop reactor.
6. Polymerization process for producing olefin polymers in a loop reactor comprising the
steps of:
introducing into the loop reactor one or more olefin reactants, polymerization catalysts
and diluents, and while circulating said reactants, catalysts and diluents,

polymerizing said one or more olefin reactants to produce a polymer slurry comprising
essentially liquid diluent and solid olefin polymer particles,
said process further comprising one or more cycles of:
(a) allowing said polymer slurry to settle in one or more settling legs connected to said
reactor, and
(b) discharging from a settling leg a predetermined volume of polymer slurry
corresponding to the volume of polymer slurry settled in said settling leg since its
previous discharge, said predetermined volume differing by ± 20 %, preferably by ± 15
%, more preferably by ± 10 %, most preferably by ± 5 % from the volume of polymer
slurry settled in said settling legs since its previous discharge
7. Process as claimed in claim 6, comprising one or more cycles of:
(a) allowing said polymer slurry to settle in one or more settling legs connected to said
reactor,
(b) monitoring the volume of polymer slurry settled in a settling leg since its previous
discharge,
(c) discharging from said settling leg, a predetermined volume of polymer slurry
substantially equal to the volume of polymer slurry settled in said settling leg since its
previous discharge.
8. Process as claimed in claim 6, comprising one or more cycles of:
(a) allowing said polymer slurry to settle in one or more settling legs connected to said
reactor,
(b) assessing the time T required for the settling of a predetermined volume of polymer
slurry in a given settling leg after the closing of that given settling leg,
(c) triggering the discharge of said predetermined volume of settled polymer slurry
from said given settling leg into a product recovery zone, and
(d) discharging during a predetermined period At, said predetermined volume of
settled polymer slurry from said settling leg, wherein said predetermined volume is

substantially equal to the volume of polymer slurry settled in said settling leg since its
previous discharge.
9. Process as claimed in any of claims 6 to 8, comprising the step of adjusting the
opening time of a settling leg such that the volume of polymer slurry to be discharged
from said settling leg is substantially equal to the volume of polymer slurry settled in
said settling leg since its previous discharge.
10. Process as claimed in any of claims 6 to 9, comprising the step of adjusting the time
between two discharges for a settling leg such that the volume of polymer slurry to be
discharged from said settling leg is substantially equal to the volume of polymer slurry
settled in said settling leg since its previous discharge.
11. Process as claimed in any of claims 6 to 10, comprising the step of adjusting the
discharge aperture of a settling leg such that the volume of polymer slurry to be
discharged from said settling leg is substantially equal to the volume of polymer slurry
settled in said settling leg since its previous discharge.
12. Process as claimed in any of claims 6 to 11, comprising the step of evaluating the
volume of polymer settled in a leg since its previous discharge, and adjusting the
opening speed of the valve and/or the aperture of a flow adjusting device so that the
volume discharged from the leg is substantially equal to the evaluated settled volume.
13. Process as claimed in any of claims 6 to 12, comprising the step of discharging from a
settling leg a predetermined volume of polymer slurry equal to the volume of polymer
slurry settled in said settling leg since its previous discharge.
14. Process as claimed in any of claims 6 to 12, comprising the step of discharging from a
settling leg a predetermined volume of polymer slurry superior to the volume of
polymer slurry settled in said settling leg since its previous discharge.


The present invention relates to a polymerization process for producing olefin
polymers in a loop reactor comprising the steps of: introducing into the loop
reactor one or more olefin reactants, polymerization catalysts and diluents, and
while circulating said reactants, catalysts and diluents, polymerizing said one or
more olefin reactants to produce a polymer slurry comprising essentially liquid
diluent and solid olefin polymer particles, said process further comprising one or
more cycles of: (a) allowing said polymer slurry to settle in one or more settling
legs connected to said reactor, and(b) discharging from a settling leg a
predetermined volume of polymer slurry substantially equal to the volume of
polymer slurry settled in said settling leg since its previous discharge.
The invention is also for a loop reactor for said process.

Documents:

02058-kolnp-2006-abstract.pdf

02058-kolnp-2006-asignment.pdf

02058-kolnp-2006-claims.pdf

02058-kolnp-2006-correspondence other.pdf

02058-kolnp-2006-description (complete).pdf

02058-kolnp-2006-drawings.pdf

02058-kolnp-2006-form-1.pdf

02058-kolnp-2006-form-3.pdf

02058-kolnp-2006-form-5.pdf

02058-kolnp-2006-international publication.pdf

02058-kolnp-2006-international search report.pdf

02058-kolnp-2006-pct form.pdf

02058-kolnp-2006-priority document.pdf

2058-KOLNP-2006-ABSTRACT 1.1.pdf

2058-KOLNP-2006-AMANDED PAGES OF SPECIFICATION.pdf

2058-kolnp-2006-assignment.pdf

2058-KOLNP-2006-CLAIMS.pdf

2058-KOLNP-2006-CORRESPONDENCE.pdf

2058-kolnp-2006-correspondence1.1.pdf

2058-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

2058-KOLNP-2006-DRAWINGS 1.1.pdf

2058-KOLNP-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

2058-kolnp-2006-examination report.pdf

2058-KOLNP-2006-FORM 1.1.pdf

2058-kolnp-2006-form 18.1.pdf

2058-kolnp-2006-form 18.pdf

2058-KOLNP-2006-FORM 2.pdf

2058-KOLNP-2006-FORM 3-1.1.pdf

2058-KOLNP-2006-FORM 3.1.pdf

2058-kolnp-2006-form 3.pdf

2058-kolnp-2006-form 5.pdf

2058-KOLNP-2006-FORM-27.pdf

2058-kolnp-2006-gpa.pdf

2058-kolnp-2006-granted-abstract.pdf

2058-kolnp-2006-granted-claims.pdf

2058-kolnp-2006-granted-description (complete).pdf

2058-kolnp-2006-granted-drawings.pdf

2058-kolnp-2006-granted-form 1.pdf

2058-kolnp-2006-granted-form 2.pdf

2058-kolnp-2006-granted-specification.pdf

2058-KOLNP-2006-OTHERS DOCUMENTS.pdf

2058-kolnp-2006-others.pdf

2058-KOLNP-2006-PETITION UNDER RULE 137.pdf

2058-kolnp-2006-reply to examination report.pdf


Patent Number 249629
Indian Patent Application Number 2058/KOLNP/2006
PG Journal Number 44/2011
Publication Date 04-Nov-2011
Grant Date 31-Oct-2011
Date of Filing 21-Jul-2006
Name of Patentee TOTAL PETROCHEMICALS RESEARCH FELUY
Applicant Address ZONE INDUSTRIELLE C, B-7181 SENEFFE (FELUY)
Inventors:
# Inventor's Name Inventor's Address
1 LEWALLE, ANDRÉ AVENUE JEANNE, 19, BTE 17 B-1050 BRUXELLES
PCT International Classification Number B01J 4/00
PCT International Application Number PCT/EP2005/050541
PCT International Filing date 2005-02-08
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 04100578.6 2004-02-13 EUROPEAN UNION