Propylene polymerization plant and propylene polymerization process

Abstract

Loop-loop-gas phase reactor polypropylene plant and process for producing polypropylene and polypropylene copolymers.

Description

[Technical field]

[0001] The present invention relates to a polymerization plant suitable for very large scale propylene polymerization. The present invention further relates to a process for the polymerization of propylene using such a plant. [Background technology]

[0002] The combination of loop reactors and gas-phase reactors has been known for more than 20 years under the trademark Borstar® and can be found in virtually every textbook in the field of polyolefins. The basic process layout is described, for example, in WO 9858975 A1, which deals with the preparation of homopolymers and copolymers of propylene, which comprises the polymerization of propylene, optionally with comonomers, in the presence of a catalyst at high temperature and pressure in at least one slurry reactor and at least one gas-phase reactor, the polymerization product of the at least one slurry reactor containing unreacted monomer being sent directly to the first gas-phase reactor, with substantially no recycling of this unreacted monomer to the slurry reactor.

[0003] One important aspect of the loop-gas-phase reactor configuration is the once-through conversion. For example, the earlier WO 9925741 describes a method of introducing the polymer slurry obtained from a slurry reactor into a gas-phase reactor containing a fluidized bed (C, D) with a first fluidization zone (C) on top of a second fluidization zone (D), the fluidization zones having different flow patterns in order to optimize the once-through conversion of the process.

[0004] Unfortunately, medium-sized polypropylene production plants have significantly higher operating and fixed costs per ton of product produced when compared to very large polypropylene plants. However, increasing the scale of production can lead to quality and operational issues. Increasing the capacity of the loop reactor can be done by adding additional legs to the reactor. In industry, loop reactors have been scaled up from two legs to six legs, and even eight-leg loop reactors are not uncommon. However, the cycle time for one run using an eight-leg loop reactor is roughly doubled when compared to a four-leg loop reactor. Unfortunately, such modifications can lead to drawbacks. For example, large concentration gradients can occur. For example, in polypropylene homopolymerization, the ratio of hydrogen to propylene can vary over the length of the loop reactor, and especially in random propylene ethylene copolymerization, the ratio of ethylene to propylene can cause large gradients in the loop reactor. Needless to say, the randomness will be affected if the C2 / C3 ratio decreases over the length of the loop reactor. Therefore, when producing, for example, random propylene ethylene copolymers, workarounds such as localized feeding of ethylene or multiple feed points to the reactor are mandatory. In summary, the scale-up of loop reactors is very cumbersome.

[0005] Another challenge for polymerization processes at very high throughput, especially for very large gas-phase reactors, is to control the temperature within a wide operating window, e.g., even at a turndown ratio of 50%, to establish a wide operating window, e.g., a wide temperature range. The turndown ratio characterizes the ability to operate a plant at reduced throughput. The turndown ratio is usually defined as [1-(minimum capacity / design capacity)]. In the case of turndown, the cooling water return (CWR) stream temperature can rise to high temperatures outside the normal operating window of the cooling water system. Losses in efficiency and corrosion cracking problems can be expected in relation to stainless steel equipment. Avoiding unnecessary high temperatures in the cooling water return stream is particularly important since chlorine is added to the cooling water circuit and / or cooling water tower to prevent biological growth.

[0006] Thus, there remains a need for ultra-scalable processes and plants that at least partially avoid these and related problems. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 9858975A1 Brochure [Patent Document 2] International Publication No. 9925741 Brochure Summary of the Invention [Means for solving the problem]

[0008] The present invention relates to a plant for preparing a propylene homopolymer or a propylene copolymer, comprising: (i) supply vessels for the catalyst (1), optional cocatalyst (2), optional activator and / or optional external donor (3); (ii) an optional precontacting unit (4) for mixing catalysts, connected to said supply tank by supply lines (5, 5', 5"); (iii) a prepolymerization reactor (6) connected to the feed vessels (1, 2, 3) or to a precontacting unit (4); (iv) a propylene supply tank (7); and (v) a first loop reactor (8) connected to the prepolymerization reactor; (vi) a second loop reactor (9) connected to the first loop reactor via a loop reactor connecting line (10); (vii) means for feeding monomer and optional comonomer (11) and hydrogen (12) to one or more of the first loop reactor (8), the second loop reactor (9) and / or the loop reactor connecting lines (10) between said loop reactors; (viii) a gas-phase reactor (13) comprising a gas circulation line (14), a circulation gas compressor (15) and a circulation gas cooler (16), said gas-phase reactor (13) being connected to at least said second loop reactor by a direct feed line (17); (ix) means for feeding monomer (44) and / or comonomer (18) and / or hydrogen (19) to the gas phase reactor (13), preferably the means for feeding monomer and / or comonomer being suitable for feeding the monomer and / or comonomer in condensed form; (x) optionally, a product discharge vessel (20) connected to the gas phase reactor; (xi) optionally, a product outlet heater (21); (xii) an optional product discharge vessel (20) or product receiving vessel (22) connected to the gas-phase reactor (13); (xiii) at least one purge bin (23); (xiv) at least one propylene nitrogen recovery unit (24); and (xv) a tower feed line (241) for supplying a hydrocarbon stream to the tower (28); (xvi) a nitrogen resupply line (243) for resupplying the nitrogen-rich stream to the purge bin (23); (xvii) optionally a thermal oxidizer unit (43); and (xviii) optionally, an exhaust line (242) for discharging the exhaust stream to an optional thermal oxidizer (43); (xix) means (25) for recovery of the propylene homopolymer or propylene copolymer, which may include means for homogenization, additization and pelletization; (xx) a stripping gas treatment unit (26) comprising at least one compressor (27), the column (28) and a reflux supply vessel (28a), the reflux supply vessel (28a) being connected to the gas circulation line (14) of the gas-phase reactor (13) via a stripping line (29); (xxi) a cooling circuit (30) for the circulating gas cooler (16); (xxii) a blowdown unit (31) including a high-pressure blowdown bin (blowdown vessel) (32) and a low-pressure blowdown bin (33), which may be connected to a product receiving vessel (22) via a connecting line (34); (xxiii) a recovery feed line (35) connecting the recovery gas treatment unit (26) to the propylene feed tank (7); Including, The circulating gas cooler (16) provides a plant that is a heat exchanger in a closed loop cooling water system (300) that includes a cooling water pump (301), a secondary heat exchanger (302), an expansion vessel (303), and a secondary heat exchanger bypass (304).

[0009] The present invention further comprises: A process for preparing propylene homopolymers and copolymers comprising the steps of: a) providing a catalyst, an optional cocatalyst, an optional activator and / or an optional external donor to a feed vessel (1, 2, 3); b) feeding said catalyst, said optional cocatalyst, said optional activator and / or said optional external donor to a precontacting unit (4) to provide a mixed catalyst system and feeding said mixed catalyst system to a prepolymerization reactor (6); or feeding said catalyst, said optional cocatalyst, said optional activator and / or said optional external donor directly into a prepolymerization reactor (6); c) initiating prepolymerization by introducing propylene monomer and, optionally, a comonomer, thereby providing a prepolymer; d) feeding said prepolymer into a first loop reactor (8) to polymerize propylene, optionally together with a comonomer, to obtain a first intermediate; e) feeding said first intermediate to a second loop reactor (9) via a loop reactor connecting line (10) and further polymerizing propylene, optionally together with a comonomer, to obtain a second intermediate, propylene being fed from a propylene feed tank (7) via a propylene re-feed line (41) to the first loop reactor (8) and to the second loop reactor (9); f) introducing optional comonomer and / or hydrogen into the loop reactor at further feed points (11, 12); g) feeding the second intermediate containing unreacted monomer(s) directly into the gas phase reactor (13) via a direct feed line (17); h) further polymerization of propylene and optional comonomer in the gas phase reactor (13) by supplying and circulating propylene monomer and / or comonomer and / or hydrogen upwardly through said gas phase reactor (13) via a gas circulation line (14), the circulation gas being cooled in a circulation gas cooler (16); i) discharging the gas phase reactor product to an optional product discharge vessel (20) and subsequently through an optional product outlet heater (21) to a product receiving vessel (22) to provide a feed mixture; or discharging the gas-phase reactor product directly into a product receiving vessel (22) to provide a feed mixture; j) feeding the raw material mixture to a purge bin (23); k) purging the feed mixture with nitrogen and a catalyst deactivator, the catalyst deactivator being preferably steam (water vapor); l) separating the nitrogen, quencher and hydrocarbons from the purge bin (23) to a propylene nitrogen recovery unit (24), thereby providing an essentially pure nitrogen stream which is fed to a purge bin (23) via a nitrogen resupply line (243); providing a hydrocarbon-lean waste stream that is fed via exhaust line (242) to an optional thermal oxidizer unit (43); providing a dry hydrocarbon-rich stream which is fed to a column (28) via a column make-up line (241), said column (28) being operated at a pressure higher than the pressure of the gas phase reactor (13) to remove oligomers, wax and oil; m) redirecting a portion of the non-condensed propylene back to the gas phase reactor via a first recovery line (29) and / or redirecting the condensed propylene back to the propylene feed tank (7) via a second recovery line (35) and / or feeding a portion of the condensed propylene to a propylene propane splitter, preferably inert light components can be purged from the portion of the non-condensed propylene and can be directed to a furnace or stream production unit. Including, The circulating gas cooler (16) is a heat exchanger in a closed-loop cooling water system (300) that includes a cooling water pump (301), a secondary heat exchanger (302), an expansion vessel (303), and a bypass (304) for the secondary heat exchanger. A method is provided.

[0010] The plant according to the invention, in contrast to conventional Borstar plants, includes a recovery feed line (29) that allows the non-condensed propylene to be redirected back to the gas-phase reactor (13). This setup has surprisingly proven to be beneficial in terms of overall conversion and also in terms of the monomer factor. For example, huge savings are observed when producing random polypropylene copolymers.

[0011] In the process according to the invention, the column (28) is operated at a pressure higher than that of the gas phase reactor (13). This makes it possible to recycle part of the hydrocarbons back to the gas phase reactor via the recovery lines (29, 29'). Surprisingly, it was found that high hydrogen concentrations are possible in the presence of ethylene and the process is characterized by high once-through conversions. As another surprising aspect, a large hydrogen recovery was observed, which is particularly beneficial in the case of high melt flow rate grades. Less fresh hydrogen can be required for the gas phase reactor.

[0012] In a further aspect, the nitrogen, steam and the resulting propylene are a dry hydrocarbon-rich stream (N2 lean <0.5 mol %) which is returned to column (28); a pure nitrogen (>99 mol %) stream returned to the purge bin (23) via nitrogen resupply line (243), and a wastewater stream and a hydrocarbon-lean nitrogen stream fed to a thermal oxidizer unit (43); is separated into

[0013] The plant according to the invention is configured such that the circulating gas cooler (16) is a heat exchanger in a closed loop cooling water system (300) including a cooling water pump (301), a secondary heat exchanger (302), an expansion vessel (303) and a bypass of the secondary heat exchanger (304). In the plant and process according to the invention, the gas circulating stream is cooled by a heat exchanger in order to achieve a very efficient temperature control in the gas phase reactor, usually and preferably a fluidized bed reactor. The polymerization heat is preferably transferred to the closed loop cooling water system (300) including a cooling water pump (301), a secondary heat exchanger (302), an expansion vessel (303) and a bypass of the secondary heat exchanger (304). The polymerization heat is further transferred via this closed loop cooling water system heat exchanger to a common on-site cooling water system, which may be, for example, a cooling water tower. The main advantage is that the cooling water stream through the primary heat exchanger can be kept constant at a temperature higher than the dew point of the circulating gas, providing a wide operating window for the production rate in the gas phase reactor. A turndown ratio of 50% or more is possible. Turndown ratio characterizes the ability of a plant to operate at reduced throughput. Turndown ratio is defined as [1-(minimum capacity / design capacity)]. If a direct cooling water system is used, the cooling water return temperature will rise to values ​​above the typical designed operating temperatures of common on-site cooling water systems, i.e., the operating window will have to be limited.

[0014] The plant according to the present invention preferably comprises: (i) knockout drum (38), (ii) Gas-phase reactor zone decompression cyclone (39) (iii) Gas phase reactor flare knockout drum (40) Contains one or more of the following: Such a unit increases the safety of the plant according to the invention.

[0015] In the process according to the invention, the cycle gas cooler (16) is a heat exchanger and the heat is transferred to a closed loop cooling water system including a cooling water pump, a secondary heat exchanger, an expansion vessel, and a bypass of the secondary heat exchanger. More preferably, the polymerization heat is transferred to a common on-site cooling water system, such as a cooling water tower, via the closed loop cooling water system to allow a constant flow of cooling water through the heat exchangers in the gas cycle at a temperature above the dew point of the cycle gas. In a further embodiment, the method according to the invention is characterized in that a turndown ratio of more than 50% is possible, this high turndown allowing a really high flexibility with regard to different products and demands.

[0016] The split, i.e. the ratio of the amounts of materials produced in the loop reactor and the gas phase reactor, respectively, is in the range of 40-60-60-40.

[0017] In a still further embodiment the polymerization temperature in the first and / or second loop reactor, preferably both loop reactors, is below 72°C, more preferably below 70°C. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 shows a plant according to the invention which can be used to carry out the process according to the invention. [Diagram 2] FIG. 2 shows the cooling setup of the present invention. [Diagram 3] FIG. 3 shows a comparative cooling water setup. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] In the following, the invention will be explained with reference to the drawings. Reference numbering in Figure 1 1. Supply tank for catalyst 2. Optional Feed Tank for Cocatalyst 3 Optional supply tank for activator and / or optional external donor 4 Optional pre-contacting unit for catalyst mixing 5, 5', 5" Feed lines connecting the feed tank with the catalyst feed vessel or the feed tank connecting the prepolymerization reactor 6 Prepolymerization Reactor 7 Propylene supply tank 8 First Loop Reactor 9 Second Loop Reactor 10 Loop reactor connection line 11 Means for feeding monomer and optional comonomer 12 Means for supplying hydrogen 13 Gas Phase Reactor 14 Gas circulation line 15 Circulation gas compressor 16 Circulating gas cooler 17 Direct Supply Line 18 Means for supplying comonomer 19 Means for supplying hydrogen 20 Optional product discharge vessel 21 Product outlet heater 22 Product receiving tank 23 Purge Bin 24 Propylene Nitrogen Recovery Unit 25 Exit line (for polymer powder) with means for recovery of propylene homopolymer or propylene copolymer (may include means for homogenization, additive and pelletization) 26 Gas recovery processing unit 27 Gas recovery compressor 28 tower 28a Return recovery supply vessel 29, 29' Recovery Supply Line 30 Cooling circuit for circulating gas cooler 31 Blowdown unit 32 High Pressure Blowdown Bin 33 Low Pressure Blowdown Bin 34 Connection Lines 35 Recovery Supply Line 36 Further supply lines which may include dryer(s) 38 Knockout Drum 39 Gas Phase Reactor Zone Pressure Reducing Cyclone 40 Gas Phase Reactor Flare Knockout Drum 41, 41', 41" Propylene Supply Line 42 Means for catalyst deactivation (e.g. means for introducing low pressure steam) 43 Thermal Oxidizer Unit 44 Means for supplying liquid propylene monomer 48 Purge Bin Supply Line 49 Line connecting the product receiving tank (22) and the gas recovery compressor (27) 51 Supply line from purge bin (23) to propylene nitrogen recovery unit (24) 241 Tower Supply Line 242 Exhaust Line 243 Nitrogen resupply line 244 External nitrogen supply line 245 Supply line for catalyst deactivator (usually low pressure steam) 246 Additional Nitrogen Supply Line 247 Line for transporting nitrogen Exit line for 249 oligomers

[0020] FIG. 1 shows a plant according to the invention which can be used to carry out the process according to the invention.

[0021] FIG. 2 shows the cooling setup of the present invention. Reference numbering in Figure 2 300 Gas phase reactor circulation gas cooler 301 Cooling Water Pump for Closed Loop Cooling Water System 302 Secondary heat exchanger 303 Expansion vessel for closed loop cooling water system 304 Secondary Heat Exchanger Bypass 305 On-site cooling water pump(s) 306 On-site cooling water tower(s) 310 Gas recycle flow to gas phase reactor 311 Gas recycle stream after compression stage from gas phase reactor 312 Cooling water flow after closed loop cooling 313 Total Closed Loop Cooling Water Flow into Gas Phase Reactor Circulating Cooler 314 Closed-loop cooling water flow from a gas-phase reactor circulation cooler 315 On-site cooling water make-up flow 316 On-site cooling water return flow

[0022] FIG. 3 shows a comparative cooling water setup. Reference numbering in Figure 3 400 Gas Phase Reactor Circulation Gas Cooler 401 Cooling water pump for gas phase reactor cooling system 402 Cooling water return control line 403 Cooling Water Bypass 404 Cooling water supply control line 405 On-site cooling water pump(s) 406 On-site cooling water tower(s) 410 Gas recycle flow to gas phase reactor 411 Gas recycle stream after compression stage from gas phase reactor 412 Fresh cold water make-up stream 413 Total cooling water flow to gas phase reactor recycle gas cooler

[0023] The plant according to the invention is further explained with reference to FIG.

[0024] The plant according to the invention for preparing propylene homo- and copolymers comprises a feed tank for the catalyst (1), an optional cocatalyst (2), an optional activator and / or an optional external donor (3). Optionally, there is a precontacting unit (4) for catalyst mixing, connected to the feed tank by a feed line (5, 5', 5"); in various embodiments and for various catalyst systems, a precontacting tank is not necessary. The plant according to the invention also comprises a prepolymerization reactor (6) connected to the feed tanks (1, 2, 3) or precontacting unit (4). Such prepolymerization (prepolymerization) is known in the art. The plant also comprises a propylene feed tank (7), a first loop reactor (8) connected to the prepolymerization reactor, a second loop reactor (9) connected to the first loop reactor via a loop reactor connection line (10), and means for feeding comonomer (11) and hydrogen (12) to one or more of the first loop reactor (8), the second loop reactor (9) and / or the loop reactor connection line (10) between said loop reactors.

[0025] Such setups are frequently found in existing plants.

[0026] The plant according to the invention also comprises, apart from the loop reactor, a gas-phase reactor (13) with a gas circulation line (14), a circulation gas compressor (15) and a circulation gas cooler (16), connected to said at least second loop reactor by a direct feed line (17), as well as means for feeding monomer (44) and / or comonomer (18) and / or hydrogen (19) to the gas-phase reactor (13). In addition, the plant optionally comprises a product discharge vessel (20) connected to the gas-phase reactor. Such a product discharge vessel contributes to the operational stability. Optionally, a product outlet heater (21) is present. Usually, the product outlet heater is several units. The plant according to the invention also comprises a product receiver vessel (22) connected to the optional product discharge vessel (20) or to the gas-phase reactor (13), and at least one purge bin (23). In addition, the plant also includes at least one propylene nitrogen recovery unit (24) having a column make-up line (241) for feeding the hydrocarbon stream to the column (28), a nitrogen re-feed line (243) for re-feeding the nitrogen-rich stream to the purge bin (23), an optional thermal oxidizer unit (43), and optionally a vent line (242) for discharging a vent stream to the optional thermal oxidizer (43). Optionally, there may be further feed lines such as a nitrogen re-feed line (243), an external nitrogen feed line (245), a feed line for the catalyst deactivator, i.e., typically low pressure steam. Preferably, there is also an outlet (249) for oligomers.

[0027] The plant according to the invention comprises means (25) for the recovery of propylene homopolymers or propylene copolymers, which means (25) may also comprise means for homogenization, additive and pelletization, and a stripping gas treatment unit (26) comprising at least one compressor (27), said column (28) and a reflux supply vessel (28a), said reflux supply vessel (28a) being connected to the gas circulation line (14) of the gas-phase reactor (13) via a stripping line (29); Also includes. In addition to this there is a cooling circuit 30 for the circulating gas cooler 16. Such a circulating gas cooler contributes to a wide operating window. Separately, there is also a blowdown unit (31) including a high pressure blowdown bin (32) and a low pressure blowdown bin (33), which may be connected to the product receiving vessel (22) via a connecting line (34). The plant according to the invention further comprises a recovery feed line (35) connecting the recovery gas treatment unit (26) to the propylene feed tank (7). This essential recovery feed line (35) also allows for the re-feed of propylene to the loop reactor, i.e. resulting in an integrated recovery system.

[0028] With reference to Figure 2, a cooling setup according to the present invention is described. A cooling medium, typically water, is circulated by a chilled water pump (301) in a closed loop chilled water system. This water enters a secondary heat exchanger (302) where heat is transferred to an on-site chilled water circuit. This on-site chilled water circuit includes on-site chilled water tower(s) (306), on-site chilled water pump(s) (305) but may also include recycling of heat for heat consumers, i.e. residential heating, etc. The secondary heat exchanger may be of any type, such as plate, shell and tube, etc. To properly regulate the temperature and keep the flow through the primary heat exchanger (300) constant, there is also a secondary heat exchanger bypass (304) in the closed loop cooling water system where heat is transferred from the gas to the water in the gas phase reactor cycle gas cooler (300). There is also a closed loop cooling water system expansion vessel (303) as is known in the art.

[0029] A direct heat exchanger for an on-site cooling water system with a recirculation pump is shown in Figure 3. Such a configuration is used for comparison purposes and is not preferred. It can be seen that the on-site cooling water circuit is directly connected to the gas phase reactor cycle gas cooler (400). EXAMPLES

[0030] Plants and processes according to the present invention are illustrated in the following examples, which are included for illustrative purposes and are not intended to be limiting of the invention.

[0031] Examples 1 and 2 In REF1 and REF2, no gas circulation cooler was used and there was only one loop reactor. In example IE1, a gas phase reactor and a gas circulation cooler were used. In example IE2, the recycle was reduced.

[0032] [Table 1]

[0033] It can be seen that the plant according to the invention and the process according to the invention make it possible to simultaneously achieve high production rates and high once-through conversions in the gas-phase reactor.

[0034] Example 3 The second experimental evaluation evaluated catalyst mileage (IE1 vs. REF2).

[0035] [Table 2]

[0036] Surprisingly, high catalyst fuel consumption was obtained for the process of the present invention.

[0037] Example 4 In yet further experimental evaluations using the inventive plant and inventive process, cooling water temperature was monitored when producing random ethylene propylene copolymers. The inventive examples used a closed loop cooling water system as shown in Figure 2, while the comparative examples used a configuration as shown in Figure 3.

[0038] The results are shown in Table 3 below.

[0039] [Table 3(1)] [Table 3(2)]

[0040] As can be seen from Table 3 above, the temperature of the cooling water return (TCWR) remained below 36°C for all inventive examples. Thus, a surprisingly wide operating window was found. For the comparative examples, the temperature of the exiting cooling water, abbreviated as TCW exit, rose to values ​​above 50°C, and even to values ​​above 60°C. Thus, many constraints are imposed on the operation. Needless to say, temperatures above 50°C or even above 60°C are not acceptable due to the constraints of the large amount of piping and heat exchangers.

Claims

1. A plant for preparing a propylene homopolymer or a propylene copolymer, comprising: (i) supply vessels for the catalyst (1), optional cocatalyst (2), optional activator and / or optional external donor (3); (ii) an optional precontacting unit (4) for mixing catalysts, connected to said supply tank by supply lines (5, 5', 5"); (iii) a prepolymerization reactor (6) connected to said feed tank (1, 2, 3) or to said precontacting unit (4); (iv) a propylene supply tank (7); and (v) a first loop reactor (8) connected to said prepolymerization reactor; (vi) a second loop reactor (9) connected to the first loop reactor via a loop reactor connecting line (10); (vii) means for feeding monomer and optional comonomer (11) and hydrogen (12) to one or more of the first loop reactor (8), the second loop reactor (9) and / or the loop reactor connecting lines (10) between said loop reactors; (viii) a gas-phase reactor (13) comprising a gas circulation line (14), a circulation gas compressor (15) and a circulation gas cooler (16), said gas-phase reactor (13) being connected to at least said second loop reactor by a direct feed line (17); (ix) means for feeding monomer (44) and / or comonomer (18) and / or hydrogen (19) to said gas phase reactor (13); (x) optionally a product discharge vessel (20) connected to said gas phase reactor; (xi) optionally a product outlet heater (21); (xii) an optional product discharge vessel (20) or a product receiving vessel (22) connected to the gas-phase reactor (13); (xiii) at least one purge bin (23); and (xiv) at least one propylene nitrogen recovery unit (24); and (xv) a column feed line (241) for feeding a hydrocarbon stream to the column (28); (xvi) a nitrogen resupply line (243) for resupplying the nitrogen rich stream to said purge bin (23); (xvii) optionally a thermal oxidizer unit (43); and (xviii) optionally, an exhaust line (242) for discharging the exhaust stream to said optional thermal oxidizer (43); (xix) means for recovery of the propylene homopolymer or propylene copolymer (25), which may include means for homogenization, additization and pelletization; (xx) a stripping gas treatment unit (26) comprising at least one compressor (27), the column (28) and a reflux supply vessel (28a), the reflux supply vessel (28a) being connected to the gas circulation line (14) of the gas-phase reactor (13) via a stripping line (29); (xxi) a cooling circuit (30) for said circulation gas cooler (16); (xxii) a blowdown unit (31) including a high pressure blowdown bin (32) and a low pressure blowdown bin (33), which may be connected to the product receiving tank (22) via a connecting line (34); (xxiii) a recovery supply line (35) connecting the recovery gas treatment unit (26) to the propylene supply tank (7); Including, The circulating gas cooler (16) is a heat exchanger in a closed loop cooling water system (300) that includes a cooling water pump (301), a secondary heat exchanger (302), an expansion vessel (303) and a secondary heat exchanger bypass (304).

2. below (xxiv) knockout drum (38) (xxv) Gas Phase Reactor Zone Decompression Cyclone (39) (xxvi) Gas Phase Reactor Flare Knockout Drum (40) The plant of claim 1 further comprising one or more of:

3. 1. A process for preparing a propylene homopolymer or a propylene copolymer, comprising the steps of: a) providing a catalyst, an optional cocatalyst, an optional activator and / or an optional external donor to a feed vessel (1, 2, 3); b) feeding said catalyst, said optional cocatalyst, said optional activator and / or said optional external donor to a precontacting unit (4) to provide a mixed catalyst system and feeding said mixed catalyst system to a prepolymerization reactor. or feeding said catalyst, said optional cocatalyst, said optional activator and / or said optional external donor to a prepolymerization reactor (6); c) initiating prepolymerization by introducing propylene monomer and, optionally, comonomer, thereby providing a prepolymer; d) feeding said prepolymer into a first loop reactor (8) to polymerize propylene, optionally together with a comonomer, to obtain a first intermediate; e) feeding said first intermediate through a loop reactor connecting line (10) to a second loop reactor (9) for further polymerizing propylene, optionally with a comonomer, to obtain a second intermediate, propylene being fed from a propylene feed tank (7) to said second loop reactor through a propylene re-feed line (41); f) introducing comonomer and / or hydrogen into the loop reactor at a further feed point; g) feeding said second intermediate containing unreacted monomer directly into a gas phase reactor (13) via a direct feed line (17); h) further polymerization of propylene and optional comonomers in said gas phase reactor (13) by supplying and circulating propylene and / or comonomers and / or hydrogen via a gas circulation line (14), the circulation gases being cooled in a circulation gas cooler (16); i) optionally discharging the gas phase reactor product to an optional product discharge vessel (20) and then via a connecting line (34) to a product receiving vessel (22) to provide a feed mixture; or discharging the gas-phase reactor product directly into a product receiving vessel (22) to provide a feed mixture; j) feeding the raw material mixture to a purge bin 23; k) purging the feed mixture with nitrogen and a catalyst deactivator; l) separating nitrogen, quenching agent and hydrocarbons from said purge bin (23) to a propylene nitrogen recovery unit (24), thereby providing a nitrogen-rich stream fed to a purge bin (23) via a nitrogen resupply line (243); providing a hydrocarbon-lean waste stream fed to a thermal oxidizer unit (43) via an exhaust line (242); providing a dry hydrocarbon-rich stream which is fed to a column (28) via a column make-up line (241), said column (28) being operated at a pressure higher than the pressure of said gas phase reactor (13) to remove oligomers, wax and oil; m) The condensed propylene and propane are mixed with the propylene supply tank (7) via a recovery supply line (35); Optional Propane / Propylene Splitter and feeding at least a portion of the non-condensables via line 29 to said gas phase reactor. wherein the circulating gas cooler (16) is a heat exchanger and heat is transferred via a closed loop cooling water system (300) including a cooling water pump (301), a secondary heat exchanger (302), an expansion vessel (303) and a bypass (304) of the secondary heat exchanger.

4. 4. The method of claim 3, wherein heat of polymerization is transferred via said closed loop cooling water system to a common on-site cooling water system, such as a cooling water tower, to enable a constant flow of cooling water through said heat exchangers in said gas cycle at a temperature above the dew point of said cycle gas.

5. 5. The process according to claim 3 or claim 4, wherein the possible turndown ratio in terms of production rate in the gas phase reactor is 50% or more.

6. 5. The process according to claim 3 or claim 4, wherein the first loop reactor and / or the second loop reactor.

7. 5. The process according to claim 3 or 4, wherein the homopolymer is produced in a split of 40% to 60% produced in the gas phase reactor.

8. 5. The process of claim 3 or claim 4, wherein the random ethylene propylene copolymer is produced in a split of 40% to 60% produced in the gas phase reactor.

9. A process according to claim 3 or claim 4, wherein the polymerization temperature in the gas phase reactor is from 80°C to 90°C and the pressure is from 19 to 25 barg.

10. 5. A process according to claim 3 or claim 4, wherein the operating pressure of the column is 26 barg.

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