CA2538499A1 - Slurry catalyst delivery system for polymerization reactors - Google Patents
Slurry catalyst delivery system for polymerization reactors Download PDFInfo
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- CA2538499A1 CA2538499A1 CA 2538499 CA2538499A CA2538499A1 CA 2538499 A1 CA2538499 A1 CA 2538499A1 CA 2538499 CA2538499 CA 2538499 CA 2538499 A CA2538499 A CA 2538499A CA 2538499 A1 CA2538499 A1 CA 2538499A1
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- catalyst
- catalyst slurry
- syringe pump
- cylinder
- delivery system
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J4/00—Feed or outlet devices; Feed or outlet control devices
- B01J4/02—Feed or outlet devices; Feed or outlet control devices for feeding measured, i.e. prescribed quantities of reagents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/0015—Feeding of the particles in the reactor; Evacuation of the particles out of the reactor
- B01J8/002—Feeding of the particles in the reactor; Evacuation of the particles out of the reactor with a moving instrument
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/20—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/20—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium
- B01J8/22—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
- B01J2208/00743—Feeding or discharging of solids
- B01J2208/00752—Feeding
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Polymerisation Methods In General (AREA)
Abstract
A catalyst delivery system useful for the delivery of a catalyst slurry to a polymerization reactor is provided. The catalyst delivery system overcomes the plugging and reliability issues commonly associated with delivery of a catalyst slurry to a polymerization reactor. The catalyst slurry delivery system comprises a syringe pump with an internal agitator. The modified syringe pump maintains a substantially homogeneous suspension of catalyst or catalyst component particles for delivery to a polymerization reactor.
Description
FIELD OF THE INVENTION
The present invention relates to a catalyst slurry delivery system and method of operation in which catalyst slurry is pumped from a holding tank to a polymerization reactor. The delivery system comprises a syringe pump with an internal agitator. The modified syringe pump provides continuous agitation of a catalyst slurry within the syringe pump cylinder during catalyst delivery to a polymerization reactor. The delivery system provides a means of pumping a catalyst slurry reliably to a polymerization reactor.
BACKGROUND TO THE INVENTION
Several processes for the polymerization of olefins are run in a continuous manner. For such processes the required catalysts are often fed to a polymerization reactor as components in an inert hydrocarbon carrier fluid. For catalysts that are soluble in the carrier fluid, catalyst delivery is relatively straightforward. However, many useful polymerization catalysts are insoluble in the carrier fluid. Catalysts that are insoluble in the carrier fluid are often fed to a polymerization reactor as slurried catalysts or suspended catalysts. However, one of the problems associated with delivering these slurried (suspended) catalysts to a polymerization reactor is system plugging. Plugging can occur when inhomogenities (e.g. chunks) arise in the catalyst slurry.
Combination of continuous carrier fluid flow and agitation is the most common method in which catalyst slurry can be reliably fed to a polymerization reaction zone.
U:\Trevor\TTSpec\2006009can.doc 2 United States Patent 6,908,971 issued June 21, 2005 to Chevron Phillips Chemical Company discloses an apparatus and process for feeding catalyst slurry from a storage tank to a continuous loop reactor. In the Chevron Phillips system, positive displacement pumps are used to push catalyst slurry in a continuous manner from a single mixing tank to the polymerization reaction zone.
United States Patent 5,098,677 issued March 24, 1992 to Phillips Petroleum Company discloses an apparatus and process for continuously feeding catalyst slurry from a storage tank to a stirred polymerization reactor. A key feature of the apparatus is a ball check feeder valve for adding measured amounts of catalyst slurry. Operation of the valve involves rotation of a metering chamber with reciprocating motion of a ball piston, which communicates with an inlet and outlet.
United States Patent 4,610,574 issued September 9, 1986 to Amoco Corporation discloses an apparatus for feeding catalyst slurry, which contains as an essential feature a rotating metering ball valve for adding catalyst slurry to a polymerization reactor. Other similar methods and apparatus of feeding catalyst slurry have been developed and are described in United States Patents 3,846,394 and 3,726,845.
United States Patent 6,319,995 issued November 20, 2001 to Equistar Chemicals discloses an apparatus for adding dry catalyst to a liquid filled polymerization reactor. In the Equistar patent a quantity of dry catalyst is loaded to a metering chamber, which can be flushed with an inert fluid to carry the catalyst to a polymerization reaction zone.
U:\Trevor\TTSpec\2006009can.doc 3 In United States Patent 4,123,601 an apparatus for feeding catalyst slurry includes a bypass loop, which can be loaded with catalyst slurry and flushed with inert hydrocarbon, thereby carrying slurried catalyst to the polymerization reactor.
The catalyst feeding systems discussed above rely on conventional mixing tanks and metering valves connected in various arrangements with a polymerization reactor through fluid carrying conduits. None of the above references contemplates the use of a syringe pump comprising an internal agitator to maintain a homogeneous catalyst suspension for delivery to a polymerization reactor. It is also the purpose of this invention to provide a system and process for reliably and efficiently delivering more than one type of catalyst slurry to a polymerization reactor in an alternating, a sequential or a concomitant manner.
SUMMARY OF THE INVENTION
The present invention provides a catalyst slurry delivery system comprising: one or more holding tanks each equipped with an agitator, said one or more holding tanks fluidly connected to one or more syringe pumps for delivering catalyst slurry from a holding tank to a polymerization reactor wherein each syringe pump comprises in cooperating arrangement: a piston; a cylinder with an open end and a closed end, wherein the closed end has one or more inputs and outputs connected to a fluid carrying conduit; one or more glands; a drive means to extend or displace the piston; and an agitator such that, the impeller of the agitator is contained within the free volume of the cylinder that is housed between the U:\Trevor\TTSpec\2006009can.doc 4 piston and the closed end of the cylinder at maximum piston extension, provided that the piston does not touch the impeller.
The invention further provides a process by which catalyst slurry is delivered to a polymerization reactor which comprises: loading a catalyst slurry into a pressurized holding tank equipped with an agitator to maintain a substantially homogeneous suspension of solids; pumping solvent into the syringe pump cylinder free volume prior to loading the cylinder with catalyst slurry from the holding tank; transferring a catalyst slurry from a holding tank to a syringe pump wherein the syringe pump comprises an internal agitator to maintain a substantially homogeneous suspension of solids within the free volume of the cylinder between the piston and cylinder end; and pumping a catalyst slurry from the syringe pump cylinder to a polymerization reactor.
Additionally, the present invention provides a process wherein catalyst slurry is continuously delivered to a polymerization reactor using at least two catalyst slurry delivery systems each comprising: a holding tank equipped with an agitator, fluidly connected to a syringe pump for delivering catalyst slurry from the holding tank to a polymerization reactor wherein the syringe pump comprises in cooperating arrangement: a piston; a cylinder with an open end and a closed end, wherein the closed end has one or more inputs and outputs connected to a fluid carrying conduit; one or more glands; a drive means to extend or displace the piston; and an agitator such that, the impeller of the agitator is contained within the free volume of the cylinder that is housed between the piston U:\Trevor\TTSpec\2006009can.doc 5 and cylinder end at maximum piston extension, provided that, the piston does not touch the impeller.
It is also the purpose of the invention to provide a system and process for reliably and efficiently delivering more than one type of catalyst slurry to a polymerization reactor in an alternating, a sequential or a concomitant manner.
DESCRIPTION OF THE DRAWINGS
Figure 1 schematically illustrates a catalyst slurry delivery system of the present invention.
Figure 2 schematically illustrates two cooperating catalyst slurry delivery systems of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst slurry delivery system of the current invention is applicable to a gas phase, slurry phase or a solution phase polymerization reactor.
A catalyst slurry includes any catalysts or catalyst components that form suspensions in an inert liquid carrier such as but not limited to a hydrocarbon. Catalysts and catalyst components that form a slurry in hydrocarbon are well known in the art. Ziegler-Natta catalysts, vanadium containing catalysts, Phillips type catalysts (e.g. Cr based catalysts) or components thereof are particularly useful. Supported single site catalysts or components thereof are also contemplated for use in the present invention. Single site catalysts may be supported on an inert solid carrier.
Inert supports include but are not limited to silica, alumina and MgC12.
Single site catalysts are well known in the art and include but are not U:\Trevor\TTSpec\2006009can.doc 6 limited to metallocenes and constrained geometry type catalysts. Co-catalysts, or other catalyst additives may also be used with the current invention and are well known to those practiced in the art. Some representative co-catalysts include but are not limited to aluminum alkyls, alkylaluminoxanes, perfluoroboranes and anilinium or trityl perfluoroborates. Suitable liquid carriers for such catalysts are also well known in the art. These include but are not limited to toluene, xylene, propane, isobutene, n-butane, pentane, isopentane, n-hexane, cyclohexane, methylcylcohexane, isohexane and n-heptane.
The terms "diluent", "carrier fluid", "liquid carrier" and "solvent" can be used interchangeably and are meant to encompass any liquid in which catalysts or catalyst component particles can be suspended or dissolved.
A "homogeneous" suspension of solids, or a "homogeneous" slurry is a mixture in which solid particles are evenly distributed within a liquid carrier. A catalyst slurry is homogeneous when the distribution of catalyst or catalyst component particles within the liquid carrier provides an essentially constant solids to liquids weight ratio.
The term "free volume" is defined as that volume within the syringe pump cylinder that is between the syringe pump piston and the closed end of the cylinder.
The "head" of the syringe pump piston is that end of the piston that is most near the closed end of the syringe pump cylinder.
The piston may be extended into or be displaced out of the syringe pump cylinder by a distance Y. Extension of the piston is a movement in which the piston head moves toward the closed end of the cylinder.
U:\Trevor\TTSpec\2006009can.doc 7 Displacement of the piston is a movement of the piston head in a direction that is away from the closed end of the cylinder. The terms "piston extension" and "piston displacement" have the piston moving in opposite directions.
The term "free volume at maximum piston extension" is meant to describe that volume within the syringe pump cylinder that is housed between the piston and the closed end of the cylinder when the piston is maximally extended. "Maximum piston extension" is that limit to which the piston can be extended into the syringe pump cylinder provided that it does not make physical contact with an impeller housed within the closed end of the cylinder.
By the term "internal agitator" it is meant that the impeller of the agitator is contained within the free volume of the syringe pump cylinder that is housed between the piston and the closed end of the cylinder at maximum piston extension provided that the piston does not touch the impeller.
The catalyst delivery system of the current invention is illustrated in Figure 1. Figure 1 is not drawn to scale. In Figure 1, the catalyst delivery system includes a closed holding tank, 1 which is fitted with at least one agitator, 2 and a catalyst loading port, 3. The closed holding tank may be pressurized. The holding tank has inlets connected to conduits for inert gas, 4, and inert solvent, 5 and is fluidly connected to a syringe pump cylinder, 6 through a conduit, 7. Optionally, conduits 4 and 5 may be part of the same conduit network. In a preferred embodiment, conduit 7 has solenoid valves, 8a, 8b, and 8c, to control the passage of catalyst slurry U:\Trevor\TTSpec\2006009can.doc 8 and solvent to the syringe pump cylinder, 6, a polymerization reactor, 9, or a drainage container, 10. The solenoid valves may be pneumatically or electrically operated. Additional valves, not shown in Figure 1 may also be present. By way of an example, flow of inert gas and inert solvent into conduits 4 and 5 is controlled by valves.
The syringe pump cylinder, 6 which receives catalyst slurry from the holding tank, 1 is fitted with a piston, 11 and an agitator, 12a, such that impeller 12b of the agitator is contained within the free volume of the cylinder that is housed between the piston and the closed end of the cylinder at maximum piston extension, provided that the piston does not touch the impeller.
The syringe pump piston, 11 is fitted with one of more glands, 13a, which can be washed by pumping solvent through a recirculation conduit, 14, which connects the gland to a vessel holding wash solvent, 15. The gland, 13a is composed of the space contained in the radial direction between the wall of the cylinder, 6 and the piston, 11 and in the vertical direction between two pressure seals that circle the piston. The two pressure seals circumferentially contact both the piston, 11 and the wall of the cylinder, 6 and are preferably placed near the head of the piston. A
low-pressure seal, 13b prevents leakage of wash solvent. A high-pressure seal, 13c prevents loss of pressure or leakage of catalyst slurry from the syringe pump cylinder. A diaphragm pump, 16, can be used for pushing solvent through the recirculation conduit, 14. Other types of pump well known in the art are also contemplated for use with recirculation conduit U:\Trevor\TTSpec\2006009can.doc 9 14. Optionally, conduit 14 may be connected to a drainage vessel, 10 or 17 through a valve.
The closed end of the syringe pump cylinder has one or more inputs and outputs connected to a fluid carrying conduits 7 and 18, which facilitate movement of catalyst slurry, solvent and inert gas into and out of the syringe pump cylinder. Conduit 18 has inlet valves for inert gas, 19 and inert solvent, 20. The syringe pump piston is compressed using a drive means, 21. The drive means may be a motor, which rotates a combination of gear, screw and threaded piston shaft in either a clockwise or a counter-clockwise direction for the purposes of extending or displacing the piston. Alternatively, the drives means may be but is not limited to a pneumatic, electrical or mechanical device, or a combination thereof. Some non-limiting examples include a cam shaft or a crank shaft.
A pressure gauge or transducer, 22 may be connected to the catalyst slurry holding tank, 1 and other gauges or transducers may be connected to the closed end of the catalyst cylinder or to any point along fluid carrying conduits, 7 and 18. Conduits 4, 5 and 18 and optionally 7 conduct pressurized inert carrier fluid or pressurized inert gas from pressurized cylinders and fluidly connect said cylinders to the catalyst slurry delivery system of the current invention.
Types of agitator impellers are those used in the art and some non-limiting examples include turbine, helical ribbon, flat blade, pitched blade and magnetic bar. The impeller may be part of a magnetic drive or a direct drive agitation system.
U:\Trevor\TTSpec\2006009can.d0c 10 Conduits 7 and 18 may be the part of same or different conduit networks. Additional conduit networks not shown in Figure 1 may also be used with the current invention. Additional valves of any type such as needle valve, ball valve, globe valves, check valves not shown in Figure 1 may also be used with the current invention.
The holding tank, 1, the syringe pump cylinder, 6, and the polymerization reactor, 9, may be in any vertical position with respect to each other. In a preferred embodiment the syringe pump cylinder, 6, is in a higher vertical position than the polymerization reactor, 9.
In a preferred embodiment of the current invention the syringe pump of the catalyst slurry delivery system is in an inverted configuration.
By the term "inverted" it is meant that, when the cylinder is held approximately parallel to the direction of gravity, the open end of the cylinder is directed upward and the closed end of the cylinder is directed downward as shown schematically in Figure 1. When gravity induces catalyst slurry particles to settle, such an arrangement ensures that the particles seffle toward the end of the cylinder housing the impeller of the internal agitator. This arrangement ensures that the catalyst or catalyst component particles are continuously agitated by the internal agitator and that the catalyst slurry remains homogeneous. In a most preferred embodiment, the syringe pump cylinder is in a vertical or upright position approximately perpendicular to the ground.
The catalyst slurry and optionally a diluent hydrocarbon solvent are loaded into holding tank 1 via catalyst loading port, 3. Inert gas or inert hydrocarbon solvent may be added through conduit 4 or 5 respectively.
U:\Trevor\TTSpec\2006009can.doc 11 The catalyst slurry is agitated within the holding tank, with agitator, 2 to maintain a homogeneous suspension of catalyst or catalyst component particles. Catalyst can be added to the holding tank through loading port, 3 by cannula, syringe, or any other means well know in the art for transferring catalyst including but not limited to piping associated with pumps, differential pressures or gravity pressure. Optionally, a dry catalyst can be added to holding tank 1 and suspended in a diluent hydrocarbon added through conduit 5. Pressure within the holding tank may be adjusted by controlling supply of pressurized inert gas through conduit 4 and optionally by release of inert gas through a vent, 23. In a preferred embodiment the pressure in the holding tank is maintained between 5 and 50 psig. Preferably, the catalyst holding tank, 1 has a larger storage volume than the syringe pump cylinder, 6.
Displacement of a piston, 11 away from the closed end of the cylinder creates a positive pressure differential between the holding tank, 1 and the syringe pump cylinder, 6, provided that valve 8a is open while valves 8b and 8c are closed and inlet valves for inert gas, 19 and inert solvent, 20 are also closed. This positive pressure differential between the holding tank, 1 and the syringe pump cylinder, 6, causes the catalyst slurry to flow from the holding tank to the cylinder. The piston, 11 may be displaced using a drive means, 21. While charging the syringe pump cylinder, the pressure in the holding tank is maintained at or above atmospheric pressure, preferably between 5 and 50 psig. Catalyst slurry housed in the closed end of the cylinder is continuously agitated by impeller 12b which is controlled by agitator 12a, providing a homogeneous U:\Trevor\TTSpec\2006009can.doc 12 suspension of catalyst or catalyst component particles. Flow of catalyst slurry from the holding tank, 1 to the syringe pump cylinder, 6 is additionally controlled by solenoid valves 8a, 8b and 8c.
Inert solvent is added through conduit 18 to the free volume of the cylinder, 6 prior to loading with catalyst slurry. Accordingly, a dilution factor is applied on charging the catalyst slurry to the cylinder. The minimum dilution term must be equal to the free volume housing the impeller between the closed end to the cylinder and the piston at maximum piston extension. By way of example, at maximum piston extension, the free volume may be 86.3 mL, which is applied as a dilution term on charging the cylinder with catalyst slurry. Further dilution of the catalyst slurry may be accomplished by adding inert diluent solvent in amounts larger than 86.3 mL. The theoretical limit of the dilution term is determined by the overall volume of the cylinder at maximum piston displacement. By way of example, to a 1000 mL syringe pump cylinder having at maximum piston extension a free volume of 86.3 mL, can be added catalyst slurry in amounts, x ranging from 913.7 - 0 mL.
Corresponding diluent solvent may be added in amounts from 1000 - x mL. It will be readily apparent to one skilled in the art, that a syringe pump of any size or volume wherein the piston, 11 does not touch the impeller, 12b at maximum piston extension can be used in the current invention.
Flow of diluent solvent into the cylinder through conduit 18 is controlled by solenoid valves 8a, 8b and 8c and inlet valves, 19 and 20 for inert gas and inert solvent. To add diluent solvent in volumes greater than the free volume available at maximum piston extension, the piston, 11 is displaced U:\Trevor\TTSpec\2006009can.doc 13 by drive means, 21. For purposes of this invention the syringe pump cylinder always contains residual solvent or residual catalyst slurry prior to charging the cylinder with catalyst slurry or after discharging catalyst slurry from the cylinder.
Flow of catalyst slurry either to the polymerization reactor, 9 or to a drainage vessel, 10 is accomplished by extension of the displaced piston.
Solenoid valves 8b and 8c control the direction of catalyst slurry flow toward the polymerization reactor or toward a drainage vessel. Extension of piston, 11, with solenoid valves 8a and 8c in a closed position while solenoid valve 8b is in an open position, pumps catalyst slurry to the polymerization reactor. Extension of piston, 11 with solenoid valves 8a and 8b in a closed position while solenoid valve 8c is open, pumps catalyst slurry to the drainage vessel.
The drainage vessel, 10 is useful for collecting unwanted catalyst slurry, which can be rinsed out of the catalyst syringe pump cylinder with wash solvent. Rinsing the syringe pump cylinder, 6 is carried out when catalyst is not being delivered to the polymerization reactor, 9. Rinsing involves feeding a wash solvent, which is typically an inert hydrocarbon, from conduit 18 (and inlet valve 20) into the syringe pump cylinder, optionally with concomitant displacement of the syringe pump piston, 11.
The syringe pump piston may lie somewhere between minimum and maximum displacement during flushing. Pressure applied through conduit 18 or extension of the syringe pump piston, 11 forces the wash solvent from the cylinder, 6 toward a drainage vessel, 10 through open solenoid valve, 8c while 8a and 8b are closed. To ensure that the syringe cylinder U:\Trevor\TTSpec\2006009can.doc 14 is thoroughly cleaned, this process may be repeated. In a preferred embodiment, the wash solvent is an inert hydrocarbon. Other solvents are also contemplated for use as wash solvents. Wash solvents are well known in the art.
During normal operation, the gland, 13a may be continuously washed by circulation of wash solvent through conduit 14. The gland, 13a has an inlet and outlet for conduit 14 through which wash solvent is circulated. Conduit 14 is connected to the gland, 13a in any manner that allows the flow of wash solvent into and out of the gland while allowing the piston to move freely within the syringe pump cylinder. In a preferred embodiment conduit 14 may be fluidly connected to the gland through the open end of the syringe pump cylinder. In another preferred embodiment, the conduit 14 may be fluidly connected to the gland through channels within the piston. In a preferred embodiment, the wash solvent is an inert hydrocarbon. Other solvents are also contemplated for use as wash solvents. Wash solvents are well known in the art.
Flow meters may be incorporated with conduits 7 and 18. The flow of the catalyst slurry delivered to a polymerization reactor is based on the rate of piston extension, but any means capable of measuring flow of the catalyst slurry may be used. By way of example, information such as the volume and diameter of the syringe pump cylinder is saved in the controller. After entering the desired flowrate into the controller the rate of piston extension is calculated in the controller, which is electronically connected to and operates the drive means, 21 for piston, 11. The controller may control the rate of flow of catalyst slurry from the syringe U:\Trevor\TTSpec\2006009can.doc 15 pump cylinder to the polymerization reactor. The controller may increase, reduce or stop the flow of catalyst slurry to the reactor. The controller may control the flow of catalyst slurry to a polymerization reactor in response to feedback received from a pressure transducer on conduit 7. If the pressure in the syringe pump cylinder, 6 exceeds a pre-determined value, a non-limiting example of which is 2000 psig, the controller may stop the flow of catalyst slurry to the polymerization reactor. In addition, a second pressure transducer on the same conduit, 7 may be connected to a second controller to prevent the opening of solenoid valve, 8a if the pressure in the syringe pump cylinder, 6 is higher than a pre-determined value, a non-limiting example of which is 20 psig. A pressure safety valve (PSV) may also be connected to conduit, 7. The PSV can open if the if the pressure in the syringe pump cylinder, 6 exceeds a pre-determined value, a non-limiting example of which is 1800 psig. Opening of the PSV valve allows drainage of the syringe pump contents to container, 10 via conduit 7. The controllers may be electronically connected to and operate additional valves not shown in Figure 1.
It is also contemplated that two or more catalyst slurry delivery systems of the current invention may be used cooperatively in a process to feed catalyst slurry to a polymerization reactor. The two or more catalyst slurry delivery systems, may feed catalyst through the same or different fluid carrying conduits to the same of different feeding points in the reactor.
This embodiment of the current invention is illustrated in Figure 2, in which analogous component parts are numbered as in Figure 1. Catalyst slurry may be delivered from said two or more catalyst delivery systems in an U:\Trevor\TTSpec\2006009can.doc 16 alternating, sequential or concomitant manner. The two or more catalyst delivery systems may be used to deliver the same or different type of catalyst slurry to the polymerization reactor.
The invention as contemplated allows catalyst slurry to be fed in a continuous manner and without interruption to the polymerization reactor by a) charging a first syringe pump cylinder with catalyst slurry while concomitantly pumping catalyst slurry from a second syringe pump cylinder; b) reversing the charging and pumping steps for the syringe pump cylinders; and c) repeating steps a and b. The invention as contemplated allows the operator to feed the same type of catalyst to a polymerization reactor in an uninterrupted and continuous manner. In another embodiment, the invention allows transition from one type of slurried catalyst to another type of slurried catalyst without interruption of the polymerization reactor. In yet another embodiment of the invention, two or more different types of catalyst slurry may be fed simultaneously to the polymerization reactor.
For each embodiment of the current invention using said two or more catalyst slurry delivery systems, the same or different types of catalyst slurry may be fed to the polymerization reactor at different flow rates.
The present invention is illustrated by the following examples.
EXAMPLES
The holding tank, syringe pump cylinder free volume and the fluid carrying conduits were first flushed with an inert hydrocarbon or diluent.
After the system has been adequately cleaned, 86.3 mL of inert U:\Trevor\TTSpec\2006009can.doc 17 hydrocarbon diluent was added to the syringe pump cylinder. 86.3 mL is equal to the free volume within the cylinder at maximum piston extension.
Charging the syringe pump cylinder was controlled by a syringe pump controller, which displaced the piston by a desired amount thereby allowing catalyst slurry to flow from the holding tank to the cylinder.
Catalyst slurry was stirred in the holding tank for more than 15 minutes prior to loading the syringe pump cylinder. To deliver catalyst to the polymerization reactor, the syringe pump piston was extended into the cylinder to achieve the desired flow rates and pressures. Valve 8b was open and valves 8a and 8c were closed to feed the catalyst slurry into the polymerization reactor. Flow rates and pressures were maintained as desired by the syringe pump controller. The agitator that drives the impeller within the syringe pump cylinder was kept in constant operation throughout the cylinder charging and discharging process.
Catalyst slurry comprising Ziegler-Natta type catalysts and containing 0.05 to 0.15 wt% solids were pumped at different rates without affecting the catalyst performance in a solution polymerization reactor.
Optionally, catalyst slurry comprising Ziegler-Natta type catalysts and containing > 0.15 wt% solids in the holding tank were diluted within the syringe pump cylinder to a give a solids wt% of <_ 0.15. The syringe pump delivery system ran without interruption and without a seal change for more than two weeks. The time period between seal changes could be extended when the concentration of solids in the catalyst slurry was less than 0.10 wt%. The catalyst delivery system showed no signs of pluggage during polymerization operation.
U:\Trevor\TTSpec\2006009can.doc 18 Run No. 1 2 Wt % solids in catalyst holding 0.075 0.15 tank Flow Rate to Reactor mUmin 2.0 1.0 Q% 90.6 90.6 Note: Mg/Ti = 5; Mg / Ali = 15; AI2 / Ti = 2.0 Run No. 1 2 3 4 5 wt % Solids In 0.075 0.15 0.30 0.30 0.30 Catalyst Holding Tank Flow Rate to 4.0 2.0 1.0 1.0 1.0 Reactor mUmin 0 % 94.1 93.3 93.5 94.8 92.2 Note: Mg/Ti = 10; Mg / AI, = 30; AI2 / Ti = 2.0 Run No. 1 2 3 4 Wt % Solids In Catalyst 0.15 0.30 0.30 0.30 Holding Tank Flow Rate to Reactor 4.0 2.0 2.0 2.0 mUmin Q% 85.4 74.7 75 74.3 Note: MgITi = 20; Mg / AI1 = 60; AI2 / Ti = 2.0 Q(%), ethylene conversion, is defined as:
Q% _ Ethylene Flowing to Reactor - Ethylene Flowing Out From Reactor x 100 Ethylene Flowing to Reactor Mg = magnesium chloride Ti = titanium compound A,= trialkyl aluminum compound A2 = alkoxydialkyaluminum compound U:\TrevoATTSpec\2006009can.doc 19
The present invention relates to a catalyst slurry delivery system and method of operation in which catalyst slurry is pumped from a holding tank to a polymerization reactor. The delivery system comprises a syringe pump with an internal agitator. The modified syringe pump provides continuous agitation of a catalyst slurry within the syringe pump cylinder during catalyst delivery to a polymerization reactor. The delivery system provides a means of pumping a catalyst slurry reliably to a polymerization reactor.
BACKGROUND TO THE INVENTION
Several processes for the polymerization of olefins are run in a continuous manner. For such processes the required catalysts are often fed to a polymerization reactor as components in an inert hydrocarbon carrier fluid. For catalysts that are soluble in the carrier fluid, catalyst delivery is relatively straightforward. However, many useful polymerization catalysts are insoluble in the carrier fluid. Catalysts that are insoluble in the carrier fluid are often fed to a polymerization reactor as slurried catalysts or suspended catalysts. However, one of the problems associated with delivering these slurried (suspended) catalysts to a polymerization reactor is system plugging. Plugging can occur when inhomogenities (e.g. chunks) arise in the catalyst slurry.
Combination of continuous carrier fluid flow and agitation is the most common method in which catalyst slurry can be reliably fed to a polymerization reaction zone.
U:\Trevor\TTSpec\2006009can.doc 2 United States Patent 6,908,971 issued June 21, 2005 to Chevron Phillips Chemical Company discloses an apparatus and process for feeding catalyst slurry from a storage tank to a continuous loop reactor. In the Chevron Phillips system, positive displacement pumps are used to push catalyst slurry in a continuous manner from a single mixing tank to the polymerization reaction zone.
United States Patent 5,098,677 issued March 24, 1992 to Phillips Petroleum Company discloses an apparatus and process for continuously feeding catalyst slurry from a storage tank to a stirred polymerization reactor. A key feature of the apparatus is a ball check feeder valve for adding measured amounts of catalyst slurry. Operation of the valve involves rotation of a metering chamber with reciprocating motion of a ball piston, which communicates with an inlet and outlet.
United States Patent 4,610,574 issued September 9, 1986 to Amoco Corporation discloses an apparatus for feeding catalyst slurry, which contains as an essential feature a rotating metering ball valve for adding catalyst slurry to a polymerization reactor. Other similar methods and apparatus of feeding catalyst slurry have been developed and are described in United States Patents 3,846,394 and 3,726,845.
United States Patent 6,319,995 issued November 20, 2001 to Equistar Chemicals discloses an apparatus for adding dry catalyst to a liquid filled polymerization reactor. In the Equistar patent a quantity of dry catalyst is loaded to a metering chamber, which can be flushed with an inert fluid to carry the catalyst to a polymerization reaction zone.
U:\Trevor\TTSpec\2006009can.doc 3 In United States Patent 4,123,601 an apparatus for feeding catalyst slurry includes a bypass loop, which can be loaded with catalyst slurry and flushed with inert hydrocarbon, thereby carrying slurried catalyst to the polymerization reactor.
The catalyst feeding systems discussed above rely on conventional mixing tanks and metering valves connected in various arrangements with a polymerization reactor through fluid carrying conduits. None of the above references contemplates the use of a syringe pump comprising an internal agitator to maintain a homogeneous catalyst suspension for delivery to a polymerization reactor. It is also the purpose of this invention to provide a system and process for reliably and efficiently delivering more than one type of catalyst slurry to a polymerization reactor in an alternating, a sequential or a concomitant manner.
SUMMARY OF THE INVENTION
The present invention provides a catalyst slurry delivery system comprising: one or more holding tanks each equipped with an agitator, said one or more holding tanks fluidly connected to one or more syringe pumps for delivering catalyst slurry from a holding tank to a polymerization reactor wherein each syringe pump comprises in cooperating arrangement: a piston; a cylinder with an open end and a closed end, wherein the closed end has one or more inputs and outputs connected to a fluid carrying conduit; one or more glands; a drive means to extend or displace the piston; and an agitator such that, the impeller of the agitator is contained within the free volume of the cylinder that is housed between the U:\Trevor\TTSpec\2006009can.doc 4 piston and the closed end of the cylinder at maximum piston extension, provided that the piston does not touch the impeller.
The invention further provides a process by which catalyst slurry is delivered to a polymerization reactor which comprises: loading a catalyst slurry into a pressurized holding tank equipped with an agitator to maintain a substantially homogeneous suspension of solids; pumping solvent into the syringe pump cylinder free volume prior to loading the cylinder with catalyst slurry from the holding tank; transferring a catalyst slurry from a holding tank to a syringe pump wherein the syringe pump comprises an internal agitator to maintain a substantially homogeneous suspension of solids within the free volume of the cylinder between the piston and cylinder end; and pumping a catalyst slurry from the syringe pump cylinder to a polymerization reactor.
Additionally, the present invention provides a process wherein catalyst slurry is continuously delivered to a polymerization reactor using at least two catalyst slurry delivery systems each comprising: a holding tank equipped with an agitator, fluidly connected to a syringe pump for delivering catalyst slurry from the holding tank to a polymerization reactor wherein the syringe pump comprises in cooperating arrangement: a piston; a cylinder with an open end and a closed end, wherein the closed end has one or more inputs and outputs connected to a fluid carrying conduit; one or more glands; a drive means to extend or displace the piston; and an agitator such that, the impeller of the agitator is contained within the free volume of the cylinder that is housed between the piston U:\Trevor\TTSpec\2006009can.doc 5 and cylinder end at maximum piston extension, provided that, the piston does not touch the impeller.
It is also the purpose of the invention to provide a system and process for reliably and efficiently delivering more than one type of catalyst slurry to a polymerization reactor in an alternating, a sequential or a concomitant manner.
DESCRIPTION OF THE DRAWINGS
Figure 1 schematically illustrates a catalyst slurry delivery system of the present invention.
Figure 2 schematically illustrates two cooperating catalyst slurry delivery systems of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst slurry delivery system of the current invention is applicable to a gas phase, slurry phase or a solution phase polymerization reactor.
A catalyst slurry includes any catalysts or catalyst components that form suspensions in an inert liquid carrier such as but not limited to a hydrocarbon. Catalysts and catalyst components that form a slurry in hydrocarbon are well known in the art. Ziegler-Natta catalysts, vanadium containing catalysts, Phillips type catalysts (e.g. Cr based catalysts) or components thereof are particularly useful. Supported single site catalysts or components thereof are also contemplated for use in the present invention. Single site catalysts may be supported on an inert solid carrier.
Inert supports include but are not limited to silica, alumina and MgC12.
Single site catalysts are well known in the art and include but are not U:\Trevor\TTSpec\2006009can.doc 6 limited to metallocenes and constrained geometry type catalysts. Co-catalysts, or other catalyst additives may also be used with the current invention and are well known to those practiced in the art. Some representative co-catalysts include but are not limited to aluminum alkyls, alkylaluminoxanes, perfluoroboranes and anilinium or trityl perfluoroborates. Suitable liquid carriers for such catalysts are also well known in the art. These include but are not limited to toluene, xylene, propane, isobutene, n-butane, pentane, isopentane, n-hexane, cyclohexane, methylcylcohexane, isohexane and n-heptane.
The terms "diluent", "carrier fluid", "liquid carrier" and "solvent" can be used interchangeably and are meant to encompass any liquid in which catalysts or catalyst component particles can be suspended or dissolved.
A "homogeneous" suspension of solids, or a "homogeneous" slurry is a mixture in which solid particles are evenly distributed within a liquid carrier. A catalyst slurry is homogeneous when the distribution of catalyst or catalyst component particles within the liquid carrier provides an essentially constant solids to liquids weight ratio.
The term "free volume" is defined as that volume within the syringe pump cylinder that is between the syringe pump piston and the closed end of the cylinder.
The "head" of the syringe pump piston is that end of the piston that is most near the closed end of the syringe pump cylinder.
The piston may be extended into or be displaced out of the syringe pump cylinder by a distance Y. Extension of the piston is a movement in which the piston head moves toward the closed end of the cylinder.
U:\Trevor\TTSpec\2006009can.doc 7 Displacement of the piston is a movement of the piston head in a direction that is away from the closed end of the cylinder. The terms "piston extension" and "piston displacement" have the piston moving in opposite directions.
The term "free volume at maximum piston extension" is meant to describe that volume within the syringe pump cylinder that is housed between the piston and the closed end of the cylinder when the piston is maximally extended. "Maximum piston extension" is that limit to which the piston can be extended into the syringe pump cylinder provided that it does not make physical contact with an impeller housed within the closed end of the cylinder.
By the term "internal agitator" it is meant that the impeller of the agitator is contained within the free volume of the syringe pump cylinder that is housed between the piston and the closed end of the cylinder at maximum piston extension provided that the piston does not touch the impeller.
The catalyst delivery system of the current invention is illustrated in Figure 1. Figure 1 is not drawn to scale. In Figure 1, the catalyst delivery system includes a closed holding tank, 1 which is fitted with at least one agitator, 2 and a catalyst loading port, 3. The closed holding tank may be pressurized. The holding tank has inlets connected to conduits for inert gas, 4, and inert solvent, 5 and is fluidly connected to a syringe pump cylinder, 6 through a conduit, 7. Optionally, conduits 4 and 5 may be part of the same conduit network. In a preferred embodiment, conduit 7 has solenoid valves, 8a, 8b, and 8c, to control the passage of catalyst slurry U:\Trevor\TTSpec\2006009can.doc 8 and solvent to the syringe pump cylinder, 6, a polymerization reactor, 9, or a drainage container, 10. The solenoid valves may be pneumatically or electrically operated. Additional valves, not shown in Figure 1 may also be present. By way of an example, flow of inert gas and inert solvent into conduits 4 and 5 is controlled by valves.
The syringe pump cylinder, 6 which receives catalyst slurry from the holding tank, 1 is fitted with a piston, 11 and an agitator, 12a, such that impeller 12b of the agitator is contained within the free volume of the cylinder that is housed between the piston and the closed end of the cylinder at maximum piston extension, provided that the piston does not touch the impeller.
The syringe pump piston, 11 is fitted with one of more glands, 13a, which can be washed by pumping solvent through a recirculation conduit, 14, which connects the gland to a vessel holding wash solvent, 15. The gland, 13a is composed of the space contained in the radial direction between the wall of the cylinder, 6 and the piston, 11 and in the vertical direction between two pressure seals that circle the piston. The two pressure seals circumferentially contact both the piston, 11 and the wall of the cylinder, 6 and are preferably placed near the head of the piston. A
low-pressure seal, 13b prevents leakage of wash solvent. A high-pressure seal, 13c prevents loss of pressure or leakage of catalyst slurry from the syringe pump cylinder. A diaphragm pump, 16, can be used for pushing solvent through the recirculation conduit, 14. Other types of pump well known in the art are also contemplated for use with recirculation conduit U:\Trevor\TTSpec\2006009can.doc 9 14. Optionally, conduit 14 may be connected to a drainage vessel, 10 or 17 through a valve.
The closed end of the syringe pump cylinder has one or more inputs and outputs connected to a fluid carrying conduits 7 and 18, which facilitate movement of catalyst slurry, solvent and inert gas into and out of the syringe pump cylinder. Conduit 18 has inlet valves for inert gas, 19 and inert solvent, 20. The syringe pump piston is compressed using a drive means, 21. The drive means may be a motor, which rotates a combination of gear, screw and threaded piston shaft in either a clockwise or a counter-clockwise direction for the purposes of extending or displacing the piston. Alternatively, the drives means may be but is not limited to a pneumatic, electrical or mechanical device, or a combination thereof. Some non-limiting examples include a cam shaft or a crank shaft.
A pressure gauge or transducer, 22 may be connected to the catalyst slurry holding tank, 1 and other gauges or transducers may be connected to the closed end of the catalyst cylinder or to any point along fluid carrying conduits, 7 and 18. Conduits 4, 5 and 18 and optionally 7 conduct pressurized inert carrier fluid or pressurized inert gas from pressurized cylinders and fluidly connect said cylinders to the catalyst slurry delivery system of the current invention.
Types of agitator impellers are those used in the art and some non-limiting examples include turbine, helical ribbon, flat blade, pitched blade and magnetic bar. The impeller may be part of a magnetic drive or a direct drive agitation system.
U:\Trevor\TTSpec\2006009can.d0c 10 Conduits 7 and 18 may be the part of same or different conduit networks. Additional conduit networks not shown in Figure 1 may also be used with the current invention. Additional valves of any type such as needle valve, ball valve, globe valves, check valves not shown in Figure 1 may also be used with the current invention.
The holding tank, 1, the syringe pump cylinder, 6, and the polymerization reactor, 9, may be in any vertical position with respect to each other. In a preferred embodiment the syringe pump cylinder, 6, is in a higher vertical position than the polymerization reactor, 9.
In a preferred embodiment of the current invention the syringe pump of the catalyst slurry delivery system is in an inverted configuration.
By the term "inverted" it is meant that, when the cylinder is held approximately parallel to the direction of gravity, the open end of the cylinder is directed upward and the closed end of the cylinder is directed downward as shown schematically in Figure 1. When gravity induces catalyst slurry particles to settle, such an arrangement ensures that the particles seffle toward the end of the cylinder housing the impeller of the internal agitator. This arrangement ensures that the catalyst or catalyst component particles are continuously agitated by the internal agitator and that the catalyst slurry remains homogeneous. In a most preferred embodiment, the syringe pump cylinder is in a vertical or upright position approximately perpendicular to the ground.
The catalyst slurry and optionally a diluent hydrocarbon solvent are loaded into holding tank 1 via catalyst loading port, 3. Inert gas or inert hydrocarbon solvent may be added through conduit 4 or 5 respectively.
U:\Trevor\TTSpec\2006009can.doc 11 The catalyst slurry is agitated within the holding tank, with agitator, 2 to maintain a homogeneous suspension of catalyst or catalyst component particles. Catalyst can be added to the holding tank through loading port, 3 by cannula, syringe, or any other means well know in the art for transferring catalyst including but not limited to piping associated with pumps, differential pressures or gravity pressure. Optionally, a dry catalyst can be added to holding tank 1 and suspended in a diluent hydrocarbon added through conduit 5. Pressure within the holding tank may be adjusted by controlling supply of pressurized inert gas through conduit 4 and optionally by release of inert gas through a vent, 23. In a preferred embodiment the pressure in the holding tank is maintained between 5 and 50 psig. Preferably, the catalyst holding tank, 1 has a larger storage volume than the syringe pump cylinder, 6.
Displacement of a piston, 11 away from the closed end of the cylinder creates a positive pressure differential between the holding tank, 1 and the syringe pump cylinder, 6, provided that valve 8a is open while valves 8b and 8c are closed and inlet valves for inert gas, 19 and inert solvent, 20 are also closed. This positive pressure differential between the holding tank, 1 and the syringe pump cylinder, 6, causes the catalyst slurry to flow from the holding tank to the cylinder. The piston, 11 may be displaced using a drive means, 21. While charging the syringe pump cylinder, the pressure in the holding tank is maintained at or above atmospheric pressure, preferably between 5 and 50 psig. Catalyst slurry housed in the closed end of the cylinder is continuously agitated by impeller 12b which is controlled by agitator 12a, providing a homogeneous U:\Trevor\TTSpec\2006009can.doc 12 suspension of catalyst or catalyst component particles. Flow of catalyst slurry from the holding tank, 1 to the syringe pump cylinder, 6 is additionally controlled by solenoid valves 8a, 8b and 8c.
Inert solvent is added through conduit 18 to the free volume of the cylinder, 6 prior to loading with catalyst slurry. Accordingly, a dilution factor is applied on charging the catalyst slurry to the cylinder. The minimum dilution term must be equal to the free volume housing the impeller between the closed end to the cylinder and the piston at maximum piston extension. By way of example, at maximum piston extension, the free volume may be 86.3 mL, which is applied as a dilution term on charging the cylinder with catalyst slurry. Further dilution of the catalyst slurry may be accomplished by adding inert diluent solvent in amounts larger than 86.3 mL. The theoretical limit of the dilution term is determined by the overall volume of the cylinder at maximum piston displacement. By way of example, to a 1000 mL syringe pump cylinder having at maximum piston extension a free volume of 86.3 mL, can be added catalyst slurry in amounts, x ranging from 913.7 - 0 mL.
Corresponding diluent solvent may be added in amounts from 1000 - x mL. It will be readily apparent to one skilled in the art, that a syringe pump of any size or volume wherein the piston, 11 does not touch the impeller, 12b at maximum piston extension can be used in the current invention.
Flow of diluent solvent into the cylinder through conduit 18 is controlled by solenoid valves 8a, 8b and 8c and inlet valves, 19 and 20 for inert gas and inert solvent. To add diluent solvent in volumes greater than the free volume available at maximum piston extension, the piston, 11 is displaced U:\Trevor\TTSpec\2006009can.doc 13 by drive means, 21. For purposes of this invention the syringe pump cylinder always contains residual solvent or residual catalyst slurry prior to charging the cylinder with catalyst slurry or after discharging catalyst slurry from the cylinder.
Flow of catalyst slurry either to the polymerization reactor, 9 or to a drainage vessel, 10 is accomplished by extension of the displaced piston.
Solenoid valves 8b and 8c control the direction of catalyst slurry flow toward the polymerization reactor or toward a drainage vessel. Extension of piston, 11, with solenoid valves 8a and 8c in a closed position while solenoid valve 8b is in an open position, pumps catalyst slurry to the polymerization reactor. Extension of piston, 11 with solenoid valves 8a and 8b in a closed position while solenoid valve 8c is open, pumps catalyst slurry to the drainage vessel.
The drainage vessel, 10 is useful for collecting unwanted catalyst slurry, which can be rinsed out of the catalyst syringe pump cylinder with wash solvent. Rinsing the syringe pump cylinder, 6 is carried out when catalyst is not being delivered to the polymerization reactor, 9. Rinsing involves feeding a wash solvent, which is typically an inert hydrocarbon, from conduit 18 (and inlet valve 20) into the syringe pump cylinder, optionally with concomitant displacement of the syringe pump piston, 11.
The syringe pump piston may lie somewhere between minimum and maximum displacement during flushing. Pressure applied through conduit 18 or extension of the syringe pump piston, 11 forces the wash solvent from the cylinder, 6 toward a drainage vessel, 10 through open solenoid valve, 8c while 8a and 8b are closed. To ensure that the syringe cylinder U:\Trevor\TTSpec\2006009can.doc 14 is thoroughly cleaned, this process may be repeated. In a preferred embodiment, the wash solvent is an inert hydrocarbon. Other solvents are also contemplated for use as wash solvents. Wash solvents are well known in the art.
During normal operation, the gland, 13a may be continuously washed by circulation of wash solvent through conduit 14. The gland, 13a has an inlet and outlet for conduit 14 through which wash solvent is circulated. Conduit 14 is connected to the gland, 13a in any manner that allows the flow of wash solvent into and out of the gland while allowing the piston to move freely within the syringe pump cylinder. In a preferred embodiment conduit 14 may be fluidly connected to the gland through the open end of the syringe pump cylinder. In another preferred embodiment, the conduit 14 may be fluidly connected to the gland through channels within the piston. In a preferred embodiment, the wash solvent is an inert hydrocarbon. Other solvents are also contemplated for use as wash solvents. Wash solvents are well known in the art.
Flow meters may be incorporated with conduits 7 and 18. The flow of the catalyst slurry delivered to a polymerization reactor is based on the rate of piston extension, but any means capable of measuring flow of the catalyst slurry may be used. By way of example, information such as the volume and diameter of the syringe pump cylinder is saved in the controller. After entering the desired flowrate into the controller the rate of piston extension is calculated in the controller, which is electronically connected to and operates the drive means, 21 for piston, 11. The controller may control the rate of flow of catalyst slurry from the syringe U:\Trevor\TTSpec\2006009can.doc 15 pump cylinder to the polymerization reactor. The controller may increase, reduce or stop the flow of catalyst slurry to the reactor. The controller may control the flow of catalyst slurry to a polymerization reactor in response to feedback received from a pressure transducer on conduit 7. If the pressure in the syringe pump cylinder, 6 exceeds a pre-determined value, a non-limiting example of which is 2000 psig, the controller may stop the flow of catalyst slurry to the polymerization reactor. In addition, a second pressure transducer on the same conduit, 7 may be connected to a second controller to prevent the opening of solenoid valve, 8a if the pressure in the syringe pump cylinder, 6 is higher than a pre-determined value, a non-limiting example of which is 20 psig. A pressure safety valve (PSV) may also be connected to conduit, 7. The PSV can open if the if the pressure in the syringe pump cylinder, 6 exceeds a pre-determined value, a non-limiting example of which is 1800 psig. Opening of the PSV valve allows drainage of the syringe pump contents to container, 10 via conduit 7. The controllers may be electronically connected to and operate additional valves not shown in Figure 1.
It is also contemplated that two or more catalyst slurry delivery systems of the current invention may be used cooperatively in a process to feed catalyst slurry to a polymerization reactor. The two or more catalyst slurry delivery systems, may feed catalyst through the same or different fluid carrying conduits to the same of different feeding points in the reactor.
This embodiment of the current invention is illustrated in Figure 2, in which analogous component parts are numbered as in Figure 1. Catalyst slurry may be delivered from said two or more catalyst delivery systems in an U:\Trevor\TTSpec\2006009can.doc 16 alternating, sequential or concomitant manner. The two or more catalyst delivery systems may be used to deliver the same or different type of catalyst slurry to the polymerization reactor.
The invention as contemplated allows catalyst slurry to be fed in a continuous manner and without interruption to the polymerization reactor by a) charging a first syringe pump cylinder with catalyst slurry while concomitantly pumping catalyst slurry from a second syringe pump cylinder; b) reversing the charging and pumping steps for the syringe pump cylinders; and c) repeating steps a and b. The invention as contemplated allows the operator to feed the same type of catalyst to a polymerization reactor in an uninterrupted and continuous manner. In another embodiment, the invention allows transition from one type of slurried catalyst to another type of slurried catalyst without interruption of the polymerization reactor. In yet another embodiment of the invention, two or more different types of catalyst slurry may be fed simultaneously to the polymerization reactor.
For each embodiment of the current invention using said two or more catalyst slurry delivery systems, the same or different types of catalyst slurry may be fed to the polymerization reactor at different flow rates.
The present invention is illustrated by the following examples.
EXAMPLES
The holding tank, syringe pump cylinder free volume and the fluid carrying conduits were first flushed with an inert hydrocarbon or diluent.
After the system has been adequately cleaned, 86.3 mL of inert U:\Trevor\TTSpec\2006009can.doc 17 hydrocarbon diluent was added to the syringe pump cylinder. 86.3 mL is equal to the free volume within the cylinder at maximum piston extension.
Charging the syringe pump cylinder was controlled by a syringe pump controller, which displaced the piston by a desired amount thereby allowing catalyst slurry to flow from the holding tank to the cylinder.
Catalyst slurry was stirred in the holding tank for more than 15 minutes prior to loading the syringe pump cylinder. To deliver catalyst to the polymerization reactor, the syringe pump piston was extended into the cylinder to achieve the desired flow rates and pressures. Valve 8b was open and valves 8a and 8c were closed to feed the catalyst slurry into the polymerization reactor. Flow rates and pressures were maintained as desired by the syringe pump controller. The agitator that drives the impeller within the syringe pump cylinder was kept in constant operation throughout the cylinder charging and discharging process.
Catalyst slurry comprising Ziegler-Natta type catalysts and containing 0.05 to 0.15 wt% solids were pumped at different rates without affecting the catalyst performance in a solution polymerization reactor.
Optionally, catalyst slurry comprising Ziegler-Natta type catalysts and containing > 0.15 wt% solids in the holding tank were diluted within the syringe pump cylinder to a give a solids wt% of <_ 0.15. The syringe pump delivery system ran without interruption and without a seal change for more than two weeks. The time period between seal changes could be extended when the concentration of solids in the catalyst slurry was less than 0.10 wt%. The catalyst delivery system showed no signs of pluggage during polymerization operation.
U:\Trevor\TTSpec\2006009can.doc 18 Run No. 1 2 Wt % solids in catalyst holding 0.075 0.15 tank Flow Rate to Reactor mUmin 2.0 1.0 Q% 90.6 90.6 Note: Mg/Ti = 5; Mg / Ali = 15; AI2 / Ti = 2.0 Run No. 1 2 3 4 5 wt % Solids In 0.075 0.15 0.30 0.30 0.30 Catalyst Holding Tank Flow Rate to 4.0 2.0 1.0 1.0 1.0 Reactor mUmin 0 % 94.1 93.3 93.5 94.8 92.2 Note: Mg/Ti = 10; Mg / AI, = 30; AI2 / Ti = 2.0 Run No. 1 2 3 4 Wt % Solids In Catalyst 0.15 0.30 0.30 0.30 Holding Tank Flow Rate to Reactor 4.0 2.0 2.0 2.0 mUmin Q% 85.4 74.7 75 74.3 Note: MgITi = 20; Mg / AI1 = 60; AI2 / Ti = 2.0 Q(%), ethylene conversion, is defined as:
Q% _ Ethylene Flowing to Reactor - Ethylene Flowing Out From Reactor x 100 Ethylene Flowing to Reactor Mg = magnesium chloride Ti = titanium compound A,= trialkyl aluminum compound A2 = alkoxydialkyaluminum compound U:\TrevoATTSpec\2006009can.doc 19
Claims (32)
1. A catalyst slurry delivery system comprising:
one or more holding tanks each equipped with an agitator, said one or more holding tanks fluidly connected to one or more syringe pumps for delivering catalyst slurry from a holding tank to a polymerization reactor wherein each syringe pump comprises in cooperating arrangement:
a) a piston;
b) a cylinder with an open end and a closed end, wherein the closed end has one or more inputs and outputs connected to a fluid carrying conduit;
c) one or more glands;
d) a drive means to extend or displace the piston; and e) an agitator, such that the impeller of the agitator is contained within the free volume of the cylinder that is housed between the piston and the closed end of the cylinder at maximum piston extension, provided that the piston does not touch the impeller.
one or more holding tanks each equipped with an agitator, said one or more holding tanks fluidly connected to one or more syringe pumps for delivering catalyst slurry from a holding tank to a polymerization reactor wherein each syringe pump comprises in cooperating arrangement:
a) a piston;
b) a cylinder with an open end and a closed end, wherein the closed end has one or more inputs and outputs connected to a fluid carrying conduit;
c) one or more glands;
d) a drive means to extend or displace the piston; and e) an agitator, such that the impeller of the agitator is contained within the free volume of the cylinder that is housed between the piston and the closed end of the cylinder at maximum piston extension, provided that the piston does not touch the impeller.
2. A catalyst delivery system according to claim 1 wherein the syringe pump cylinder is fluidly connected to both a holding tank and a polymerization reactor by one or more fluid carrying conduit(s).
3. A catalyst delivery system according to claim 1, wherein the syringe pump cylinder is connected to a fluid carrying conduit for adding diluent or wash solvent to the free volume between the piston and the closed end of the cylinder.
4. A catalyst delivery system according to claim 1, wherein each syringe pump gland is washed by pumping solvent through a recirculation conduit that connects the gland to a vessel holding wash solvent.
5. A catalyst delivery system according to claim 1, wherein the catalyst slurry flows from a holding tank to a syringe pump when a positive pressure differential is applied between a holding tank and a syringe pump, thereby charging the cylinder with catalyst.
6. A catalyst delivery system according to claim 1, wherein the catalyst slurry is continuously agitated within the free volume between the piston and the closed end of the cylinder, to maintain a substantially homogeneous suspension of solids.
7. A catalyst delivery system according to claim 1, wherein the catalyst slurry is fed to a polymerization reactor by controlled extension of the syringe pump piston.
8. A catalyst delivery system according to claim 1, wherein the syringe pump of the catalyst slurry delivery system has an inverted configuration.
9. A catalyst slurry delivery system according to claim 1, further comprising:
a) a flow meter adapted to measure the flow of catalyst slurry through a conduit; and b) a controller that receives input from the flow meter and which controls the rate of flow of catalyst slurry from the syringe pump to the polymerization reactor.
a) a flow meter adapted to measure the flow of catalyst slurry through a conduit; and b) a controller that receives input from the flow meter and which controls the rate of flow of catalyst slurry from the syringe pump to the polymerization reactor.
10. A catalyst slurry delivery system comprising at least two of:
a holding tank equipped with an agitator, fluidly connected to a syringe pump for delivering catalyst slurry from the holding tank to a polymerization reactor wherein each syringe pump comprises in cooperating arrangement:
a) a piston;
b) a cylinder with an open end and a closed end, wherein the closed end has one or more inputs and outputs connected to a fluid carrying conduit;
c) one or more glands;
d) a drive means to extend or displace the piston; and e) an agitator, such that the impeller of the agitator is contained within the free volume of the cylinder that is housed between the piston and the closed end of the cylinder at maximum piston extension, provided that the piston does not touch the impeller.
a holding tank equipped with an agitator, fluidly connected to a syringe pump for delivering catalyst slurry from the holding tank to a polymerization reactor wherein each syringe pump comprises in cooperating arrangement:
a) a piston;
b) a cylinder with an open end and a closed end, wherein the closed end has one or more inputs and outputs connected to a fluid carrying conduit;
c) one or more glands;
d) a drive means to extend or displace the piston; and e) an agitator, such that the impeller of the agitator is contained within the free volume of the cylinder that is housed between the piston and the closed end of the cylinder at maximum piston extension, provided that the piston does not touch the impeller.
11. A catalyst delivery system according to claim 10, wherein the syringe pump cylinder is fluidly connected to both a holding tank and a polymerization reactor by one or more fluid carrying conduit(s).
12. A catalyst delivery system according to claim 10, wherein the syringe pump cylinder is connected to a fluid carrying conduit for adding diluent or wash solvent to the free volume between the piston and the closed end of the cylinder.
13. A catalyst delivery system according to claim 10, wherein each syringe pump gland is washed by pumping solvent through a recirculation conduit that connects the gland to a vessel holding wash solvent.
14. A catalyst delivery system according to claim 10, wherein the catalyst slurry flows from the holding tank to the syringe pump when a positive pressure differential is applied between the holding tank and the syringe pump, thereby charging the cylinder with catalyst.
15. A catalyst delivery system according to claim 10, wherein the catalyst slurry is continuously agitated within the free volume between the piston and the closed end of the cylinder, to maintain a substantially homogeneous suspension of solids.
16. A catalyst delivery system according to claim 10, wherein the catalyst slurry is fed to a polymerization reactor by controlled extension of the syringe pump piston.
17. A catalyst delivery system according to claim 10, wherein the syringe pump of the catalyst slurry delivery system has an inverted configuration.
18. A catalyst slurry delivery system according to claim 10, further comprising:
a) a flow meter adapted to measure the flow of catalyst slurry through a conduit; and b) a controller that receives input from the flow meter and which controls the rate of flow of catalyst slurry from the syringe pump to the polymerization reactor.
a) a flow meter adapted to measure the flow of catalyst slurry through a conduit; and b) a controller that receives input from the flow meter and which controls the rate of flow of catalyst slurry from the syringe pump to the polymerization reactor.
19. A process by which catalyst slurry is delivered to a polymerization reactor which comprises:
a) loading a catalyst slurry into a pressurized holding tank equipped with an agitator to maintain a substantially homogeneous suspension of solids;
b) pumping solvent into a syringe pump cylinder free volume, prior to loading the cylinder with catalyst slurry from the holding tank;
c) transferring a catalyst slurry from said holding tank to said syringe pump wherein the syringe pump comprises an internal agitator to maintain a substantially homogeneous suspension of solids within the free volume of the cylinder between the piston and the closed end of the cylinder; and d) pumping a catalyst slurry from said syringe pump cylinder to a polymerization reactor.
a) loading a catalyst slurry into a pressurized holding tank equipped with an agitator to maintain a substantially homogeneous suspension of solids;
b) pumping solvent into a syringe pump cylinder free volume, prior to loading the cylinder with catalyst slurry from the holding tank;
c) transferring a catalyst slurry from said holding tank to said syringe pump wherein the syringe pump comprises an internal agitator to maintain a substantially homogeneous suspension of solids within the free volume of the cylinder between the piston and the closed end of the cylinder; and d) pumping a catalyst slurry from said syringe pump cylinder to a polymerization reactor.
20. A process according to claim 19, wherein the catalyst slurry can be pumped to the polymerization reactor at different rates.
21. A process wherein catalyst slurry is continuously delivered to a polymerization reactor which comprises:
the alternating, sequential or concomitant use of the at least two catalyst slurry delivery systems as described in claim 10.
the alternating, sequential or concomitant use of the at least two catalyst slurry delivery systems as described in claim 10.
22. A process according to claim 21 comprising:
a) charging a first syringe pump cylinder with catalyst slurry while concomitantly pumping catalyst slurry from a second syringe pump cylinder to a polymerization reactor;
b) reversing the charging and pumping steps for the syringe pump cylinders; and c) repeating steps a and b.
a) charging a first syringe pump cylinder with catalyst slurry while concomitantly pumping catalyst slurry from a second syringe pump cylinder to a polymerization reactor;
b) reversing the charging and pumping steps for the syringe pump cylinders; and c) repeating steps a and b.
23. A process according to claim 21, wherein the at least two catalyst slurry delivery systems feed catalyst to the polymerization reactor at one or more feeding points or feed catalyst slurry to two or more polymerization reactors at one or more feeding points as in claim 27.
24. A process according to claim 23, wherein each catalyst slurry delivery system delivers the same slurried catalyst type.
25. A process according to claim 23, wherein each catalyst slurry delivery system delivers a different slurried catalyst type.
26. A process according to claim 23, wherein one slurried catalyst type is changed to another slurried catalyst type without interrupting operation of the polymerization reactor.
27. A process according to claim 22, wherein the at least two catalyst slurry delivery systems feed catalyst slurry to the polymerization reactor at one or more feeding points or feed catalyst slurry to two or more polymerization reactors at one or more feeding points.
28. A process according to claim 27, wherein each catalyst slurry delivery system delivers the same slurried catalyst type.
29. A process according to claim 27, wherein each catalyst slurry delivery system delivers a different slurried catalyst type.
30. A process according to claim 27, wherein one slurried catalyst type is changed to another slurried catalyst type without interrupting operation of the polymerization reactor.
31. A process according to claims 19-30, wherein the catalyst slurry comprises:
a hydrocarbon, and one or more catalysts selected from the group consisting of a Ziegler-Natta catalyst, a vanadium containing catalyst and a Phillips catalyst.
a hydrocarbon, and one or more catalysts selected from the group consisting of a Ziegler-Natta catalyst, a vanadium containing catalyst and a Phillips catalyst.
32. A process according to claim 31, wherein the catalyst slurry comprises one or more single site catalysts.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2538499 CA2538499A1 (en) | 2006-03-06 | 2006-03-06 | Slurry catalyst delivery system for polymerization reactors |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2538499 CA2538499A1 (en) | 2006-03-06 | 2006-03-06 | Slurry catalyst delivery system for polymerization reactors |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2538499A1 true CA2538499A1 (en) | 2007-09-06 |
Family
ID=38468958
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2538499 Abandoned CA2538499A1 (en) | 2006-03-06 | 2006-03-06 | Slurry catalyst delivery system for polymerization reactors |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2538499A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2516700A (en) * | 2013-07-31 | 2015-02-04 | Anaero Technology Ltd | Reactor system |
| CN112324727A (en) * | 2020-11-09 | 2021-02-05 | 菲立化学工程(遂昌)有限公司 | Multi-pump full-automatic injection pump |
-
2006
- 2006-03-06 CA CA 2538499 patent/CA2538499A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2516700A (en) * | 2013-07-31 | 2015-02-04 | Anaero Technology Ltd | Reactor system |
| US9850460B2 (en) | 2013-07-31 | 2017-12-26 | Anaero Technology Ltd. | Reactor system |
| CN112324727A (en) * | 2020-11-09 | 2021-02-05 | 菲立化学工程(遂昌)有限公司 | Multi-pump full-automatic injection pump |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |
Effective date: 20130306 |