KR102324603B1 - Rapid depressurization of a reactor system - Google Patents

Abstract

Systems and methods for rapidly depressurizing a reactor system are disclosed. The systems and methods are particularly useful for high pressure polymerization of ethylene.

Description

RAPID DEPRESSURIZATION OF A REACTOR SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of USSN 62/234,348, filed September 29, 2015, and EP application 15201299.3, filed December 18, 2015, the disclosures of which are incorporated herein by reference in their entirety. .

field of invention

The present invention relates to a system and method for rapidly depressurizing a reactor system. The disclosed systems and methods are particularly useful for high pressure polymerization of ethylene.

background of the invention

The high pressure polymerization reactor converts relatively inexpensive olefinic monomers, such as ethylene, optionally combined with one or more comonomers, into expensive polyolefin products. Such methods using oxygen or organic free radical initiators are known and have been used in industry for a long time. Polymerization occurs at relatively high temperatures and pressures and is highly exothermic.

High pressure polymerization processes generally use two main compressors to compress the monomer feed, each having a plurality of stages arranged in series, followed by a reactor in which polymerization takes place. The high pressure polymerization reactor system may include a tubular reactor or an autoclave reactor. Such reactors typically operate at very high pressures in excess of 2000 bar and sometimes as high as 3100 bar. Other large-scale industrial processes are unlikely to operate at higher pressures.

The high pressure polymerization of ethylene is a very exothermic process. In order for the reaction to proceed under favorable conditions, it is necessary to constantly remove heat from the polymerization zone. During polymerization, the polymer can adhere to the inner wall of the reactor, substantially reducing its ability to remove heat. These deposits can separate from the walls and travel through the reactor. They can cause clogging that results in severe and rapid pressure build-up in the reactor, which leads to monomer decomposition or thermal runaway in the reaction mixture.

The high pressure reactor is protected from overpressure, overheating and decomposition by rapid depressurization. Rapid depressurization in commercial reactors will generally be initiated in response to decomposition. Decomposition occurs most often downstream of the initiator injection point, causing the temperature and pressure in the reactor to rise rapidly. Immediate action must be taken to prevent runaway reactions and more complex problems.

Commercial reactors generally have strict design criteria for reactor depressurization capability. For example, a high pressure polymerization system can be designed such that the reactor can be depressurized below 1000 bar within 12 seconds. These design criteria may require the use of multiple pressure relief valves, particularly in large capacity reactors. However, multiple pressure relief valves can cause stagnant flow areas between the valves due to flow reversal during depressurization. The stagnant zone is hotter than the other zones, and cracking can cause overheating and failure of the reactor over time. This can also make disintegration control more difficult. Additionally, it is also common to arrange a pressure relief valve at the inlet of the preheater or between the inlet of the preheater and the reactor. The relief valve in this position can also cause a flow reversal and stagnation zone in the first reaction zone of the reactor, which is usually already the highest temperature and the zone where decomposition is most likely to occur. Background references include US Pat. Nos. 4,804,725, 4,115,638, and US Patent Application Publication No. 2015/080533.

There is a need for improved processes and systems for rapidly depressurizing high pressure polymerization systems, particularly large reactor systems, in accordance with often required stringent design criteria.

Summary of the invention

The present invention provides a compressor comprising: a compressor in fluid communication with a reactor comprising at least one reaction zone and at least one cooling zone; a first pressure relief valve located downstream of the reactor; and a second pressure relief valve positioned along the reactor within the cooling zone.

The present invention also provides a compressor system for compression in fluid communication with a reactor, the compressor system comprising at least one reaction zone and at least one cooling zone, wherein the total internal volume of the reactor is less than about 6 m 3 ; and a first pressure relief valve located downstream of the reactor.

The present invention also relates to a method of rapidly depressurizing a reactor comprising opening a first relief valve located downstream of the reactor. The method may also optionally include opening a second pressure relief valve located along the reactor in the cooling zone.

The systems and methods of the present invention are particularly useful for high pressure polymerization of ethylene.

Brief description of the drawing
1 schematically shows a typical high pressure ethylene polymerization system.
2 schematically depicts a reactor system according to embodiments of the present invention.
3 is a mass flux distribution within a reactor for a polymerization reactor system similar to that of FIG. 2 having a capacity of about 450 KTA.
FIG. 4 is a graph of pressure drop over time at various points in the reactor system for the polymerization reactor system of FIG. 3 ;
5 is a mass flux distribution within a reactor for a polymerization reactor system similar to that of FIG. 2 having a slightly smaller capacity of about 420 KTA.
FIG. 6 is an enlarged version of the mass flux distribution of FIG. 5 , enlarged at the location of the stagnant flow zone about 2000 m from the preheater inlet.

details

As used herein, a pressure dump event refers to the process of rapidly depressurizing a polymerization reactor system. Typically, rapid depressurization reduces the pressure at one or more points in the reactor system from at least about 2000 bar to no more than about 1000 bar in a relatively short time. A pressure dump event may be initiated in response to any condition or event in which rapid depressurization is necessary or useful. In high pressure ethylene polymerization reactors, for example, rapid depressurization is typically initiated in response to decomposition detected within the reactor.

A pressure dump event typically begins when one or more relief valves or high pressure drop valves open to relieve pressure from the reactor and ends when the reactor system reaches the desired pressure. For example, a pressure dump event may be considered to end when the pressure at the inlet of a preheater or another location within the reactor system drops below about 1000, 500, or 250 bar.

As used herein, a stagnation zone is a location within a reactor where, during a pressure dump event, the mass flux is 0 and there is no extraction from the system. During a pressure dump event, the mass flux near the relief valve may be zero, but this is because the flow is directed outward in the system. Thus, it is an extraction point and not a stagnant zone as defined herein. The location of the stagnation zone can be determined by measuring or simulating the mass flux distribution along the reactor during a pressure dump event, which will be described in more detail in the examples below.

High pressure ethylene polymerization reactor systems typically include at least one preheater upstream of the reactor. A preheater is used to heat one or more monomer streams, such as ethylene monomer, prior to entry into the reactor. Such systems also typically include a high pressure drop valve downstream of the reactor. Under normal operating conditions, the reactor product mix exits the reactor through a high pressure drop valve and is then cooled and sent through one or more separation systems.

It is common to place a pressure relief valve at the inlet of the preheater or between the inlet of the preheater and the reactor. This has been identified as an undesirable location for the pressure relief valve, as it can lead to flow reversal and stagnation zones within the reactor's first reaction zone, which is usually already the highest temperature and most susceptible to decomposition. . The stagnant zone is hotter than the other zones and can cause overheating and failure of the reactor over time due to cracking.

Smaller capacity polymerization reactor systems, such as those having reactors with a total internal volume of about 6 m or less, may require the use of only one relief valve in addition to the high pressure drop valve to achieve the desired rapid pressure reduction capability. As mentioned above, pressure relief valves have typically been placed upstream of the preheater inlet or between the preheater and the reactor in prior art processes. However, in embodiments of the present invention, when the total internal volume of the reactor is less than or equal to about 6 m 3 , a single relief valve is located downstream of the reactor. This is upstream of the high pressure drop valve. Having the pressure relief valve in this position instead of upstream of the preheater inlet or between the preheater and the reactor, the direction of flow in the reactor is not reversed in the first reaction zone during a pressure dump event. Thus, such a reactor system can rapidly depressurize a smaller capacity reactor during a pressure dump event without creating a stagnant zone within the reactor.

Larger capacity polymerization reactor systems may require the use of multiple pressure relief valves in addition to the high pressure drop valve. However, the use of multiple pressure relief valves can be particularly problematic in that they cause flow reversal and stagnant zones during pressure dump events. The stagnation zone is typically located somewhere between the valves. If these stagnant zones cannot be eliminated, which is generally not possible when multiple valves are used, it is advantageous to control the position of the stagnant zones and ensure that during a pressure dump event they are in the cooling zone of the reactor rather than in the hotter reaction zone. Further, the stagnant zone is likely to shift location during the pressure dump event. Although they migrate, it is also advantageous to allow them to remain completely within the cooling zone of the reactor.

The location of the stagnant zone is affected by the design, number and location of the relief valve used. The present invention allows a stagnation zone to be located within the cooling zone of the reactor during a pressure dump event and eliminates the possibility for flow reversal and stagnation zones within the first reaction zone. Additionally, although the location of the stagnant zone may shift over time, the present invention allows the stagnant zone to remain entirely within the cooling zone during a pressure dump event.

One or more rupture disks may be present in the secondary compressor of the reactor system as backup pressure relief means and may be used in case either the main relief valve or the high pressure drop valve fails. The reactor itself may also comprise one or more rupture disks. For example, any reaction zone may include one or more rupture disks, or each reaction zone may include one or more rupture disks. A rupture disk, if used, is provided in addition to the pressure relief valve(s) and the high pressure drop valve.

A pressure dump event can be initiated and conducted in a variety of ways. This may be initiated by opening one or more relief valves in any order or simultaneously. For example, in a system comprising a relief valve downstream of the reactor and a relief valve along the reactor in a cooling zone, these two valves may be opened in any order or simultaneously. The high pressure drop valve may also be opened before or after opening the pressure relief valve or at the same time. The high pressure drop valve may be partially or fully open, and may be partially or fully closed if one or more relief valves are found to be open. This may be ascertained in any suitable manner, for example by using a limit or position switch indicating the position of the valve or other measuring device.

In a preferred embodiment of the invention, the pressure dump event is initiated by simultaneously opening the high pressure drop valve and at least two relief valves. When it is confirmed that at least two relief valves are open, the high pressure drop valve is partially or fully closed and the pressure dump continues through the pressure relief valve.

At any point during the pressure dump event or concurrently with the initiation of the pressure dump event, the secondary compressor may also be stopped. One or more or all of the suction valve(s) to the secondary compressor may be closed. To reduce monomer loss and release of material to the atmosphere, one or more feed valves to the reactor may be closed after the initiation of a pressure dump event. This helps retain the monomers in the secondary compressor interstage. In a preferred embodiment of the present invention, one or more or both of the feed valves to the reactor are closed when the pressure in the preheater inlet or one or more zones of the reactor is below about 1500 bar.

Polyethylene process

1 is a general schematic diagram of a polymerization plant 1 comprising an ethylene feed line 2 which feeds fresh ethylene to a primary compressor 3 . The function of the primary compressor (3) is to pressurize fresh ethylene to the pressure of the ethylene recycling system for supply to the secondary compressor (5). Primary compressor 3 may be a single compressor that alone pressurizes ethylene to the pressure of the recycle stream, or in combination may be two or more compressors in series or parallel that pressurize fresh ethylene to the pressure of the ethylene recycle system. In some existing ethylene reactor plants, the ethylene discharged from the primary compressor (3) is split into two streams (not shown), one stream is combined with recycled ethylene and fed to the suction section of the secondary compressor (5), The remaining stream is injected into the ethylene/polymer mixture downstream of the high pressure drop valve to provide rapid cooling of the ethylene/polymer mixture prior to entry into the product separation unit.

Ethylene discharged from the primary compressor 3 flows via a conduit 4 having a valve 4a to the conduit 6a and then to the secondary compressor 5 . Recycled ethylene is also fed from the high pressure recycling system 16 to the secondary compressor 5 via conduit 6b. The secondary compressor (5) compresses ethylene to a pressure of at least 1000 bar for supply to the reactor (9). The secondary compressor 5 is typically a unit driven by a single motor, but may include two or more compressors in series or parallel driven by separate motors (not shown). Any configuration of the compressor is intended to be within the scope of the present disclosure as long as it is suitable for compressing ethylene from a pressure of ethylene when the primary compressor 3 is brought to a desired reactor pressure of at least 1000 bar.

The secondary compressor 5 discharges the compressed ethylene in four streams 8a, 8b, 8c, and 8d. Stream 8a may be heated by a steam jacket (not shown) prior to entry into the front end of reactor 9 . Each of the three remaining ethylene streams 8b, 8c, and 8d enters the reactor as a side stream and may be cooled prior to entry into the reactor.

The reactor 9 has an initiator pumping station 11 for injecting the initiator into the reactor. The initiator may be injected through one initiator inlet 10 or through a plurality of initiator inlets (not shown). The reactor system may include a plurality of reaction zones and/or a plurality of cooling zones. A cooling zone may be followed directly downstream of each reaction zone. In a reactor having a plurality of initiator inlets, each initiator inlet may be considered to define the beginning of a reaction zone. Each side stream inlet of cold monomer can be considered to define the end of the reaction zone and the beginning of the cooling zone. Injection of the initiator causes an exothermic temperature rise downstream of the inlet which is removed by cooling. Cooling may be carried out through the reactor wall via a cooling jacket (not shown) mounted on the reactor 9 and assisted by cooling liquid and/or by a downstream supply of cold monomer.

Reactor 9 may also have a modifier pumping station (not shown) for injection of modifier into the reactor via one or more forward and/or side streams. The modifier may be fed through a flow controller (not shown) to set the amount of modifier fed through each stream. In addition, the initiator and modifier may be premixed (not shown) and fed together through the initiator pumping station 11 , thereby obviating the need for a separate modifier pumping station.

The polymerization is initiated immediately after the start of the first reaction zone, thereby raising the temperature of the reaction mixture. As the temperature rises, the rate of initiator decomposition and polymerization increases, promoting heat generation and further raising the temperature. As the initiator is consumed, initiation and polymerization slows, and the temperature peaks and then begins to drop, at which point the exotherm equals the heat conducted from the reaction mixture.

The reactor system typically has a high pressure drop valve 12 downstream of the reactor. The high pressure drop valve 12 controls the pressure in the reactor 9 . Opening the valve reduces the pressure in the reactor and closing the valve increases the pressure. A pressure drop exists along the length of the reactor, pushing the reaction mixture along the reactor at the desired rate. Immediately downstream of the high pressure drop valve 12 is a product cooler 13 . The reaction mixture is cooled and then discharged from the product cooler (13) to the high-pressure separator (14). Overhead gas from high pressure separator 14 flows into high pressure recycling system 16 where unreacted ethylene is cooled and returned to secondary compressor 5 .

The polymer product mixture flows from the bottom of the high pressure separator 14 into a low pressure separator 15 where it separates almost all of the remaining ethylene from the polymer. The ethylene is sent to a flare (not shown) or a purification unit (not shown) or recycled via the primary compressor (3). The molten polymer flows from the bottom of the low pressure separator 15 to an extruder (not shown) for downstream processing, such as extrusion, cooling and pelletization.

The proportion of the total ethylene entering the reactor 9, whether in the main feed stream 8a or as a side stream 8b, 8c or 8d, that is converted to polymer before exiting the reactor 9 is referred to as the conversion. In embodiments of the invention, the conversion may be between 30% and 40%, alternatively at least 35%. Conversions higher than 40% are possible but generally undesirable, in part because the rate of the reaction mixture increases with polymer content, which in turn results in an increase in the pressure drop required to maintain the required flow rate. am.

The reactor system of the present invention includes at least one pressure relief valve. At least one relief valve may be located downstream of the reactor. The at least one pressure relief valve may be located immediately downstream of the reactor and upstream of the high pressure drop valve. In smaller reactors, where the total internal volume of the reactor is less than about 6 m 3 , one relief valve located immediately downstream of the reactor may be sufficient to achieve the rapid pressure reduction capability required for commercial scale reactors. However, these smaller reactors may further comprise at least one relief valve along the reactor in the cooling zone.

The reactor system of the present invention, particularly for large reactors with a total internal volume of the reactor greater than or equal to about 6 m 3 , may include at least two pressure relief valves, at least one located downstream of the reactor and at least one located along the reactor in the cooling zone. do. For example, the reactor may include at least three cooling zones spaced apart longitudinally along the reactor, with pressure relief valves located along the reactor in cooling zone 3 or further downstream cooling zone. The reactor may also include at least four cooling zones spaced apart longitudinally along the reactor, with pressure relief valves located along the reactor in cooling zone 4 or further downstream cooling zone. At least one pressure relief valve may be located in any cooling zone. The pressure relief valve may be a dump valve, a vent valve, a blowdown valve, or any other suitable valve for rapid pressure relief.

The reactor system of the present invention may further comprise one or more preheaters upstream of the reactor. The system may or may not include a pressure relief valve at the inlet of the preheater or between the preheater and the reactor. In a preferred embodiment of the present invention, the system does not comprise a pressure relief valve at the inlet of the preheater or between the preheater and the reactor. The systems and methods of the present invention increase the operating pressure at the inlet of the preheater from at least about 2000, 2500, or 3000 bar to about 1000 bar or less in about 12 seconds, 10 seconds, 8 seconds, 6 seconds, 4 seconds, or even 2 seconds. can be reduced within

The ethylene polymer product prepared according to the present invention may have a density of 0.910 to 0.940 g/cm 3 (as measured by ASTM D1505) and a melt index of 0.1 to 40 dg/min (as measured by ASTM D1238). For example, the ethylene polymer obtained from the process according to the invention may have a density of 0.915 to 0.920 g/cm 3 and a melt index of 2 to 6 dg/min. The processes herein may be used to prepare ethylene homopolymers and copolymers, such as ethylene-vinyl acetate copolymers. Other possible comonomers include propylene, 1-butene, iso-butene, 1-hexene, 1-octene, other lower alpha-olefins, methacrylic acid, methyl acrylate, acrylic acid, ethyl acrylate and n-butyl acrylate do. As used herein, "ethylene" should be understood to include mixtures of ethylene and comonomers, except where the other meaning is implied by the context.

modifier

The term "modifier" or "chain transfer agent" as used herein refers to a compound added to a process to control the molecular weight and/or melt index of the resulting polymer. Examples thereof include tetramethylsilane, cyclopropane, sulfur hexafluoride, methane, t-butanol, perfluoropropane, deuterobenzene, ethane, ethylene oxide, 2,2-dimethylpropane, benzene, dimethyl sulfoxide, vinyl Methyl ether, methanol, propane, 2-methyl-3-buten-2-ol, methyl acetate, t-butyl acetate, methyl formate, ethyl acetate, butane, triphenylphosphine, methylamine, methyl benzoate, ethyl benzoate ate, N,N-diisopropylacetamide, 2,2,4-trimethylpentane, n-hexane, isobutane, dimethoxymethane, ethanol, n-heptane, n-butyl acetate, cyclohexane, methylcyclohexane, 1,2-dichloroethane, acetonitrile, N-ethylacetamide, propylene, n-decane, N,N-diethylacetamide, cyclopentane, acetic anhydride, n-tridecane, n-butyl benzoate, isopropanol, Toluene, hydrogen, acetone, 4,4-dimethylpentene-1, trimethylamine, N,N-dimethylacetamide, isobutylene, n-butyl isocyanate, methyl butyrate, n-butylamine, N,N-dimethylformamide , diethylsulfide, diisobutylene, tetrahydrofuran, 4-methylpentene-1, p-xylene, p-dioxane, trimethylamine, butene-2, 1-bromo-2-chloroethane, octene-1 ,2-methylbutene-2, cumene, butene-1, methyl vinyl sulfide, n-butyronitrile, 2-methylbutene-1, ethylbenzene, n-hexadecene, 2-butanone, n-butyl isothiocia nate, methyl 3-cyanopropionate, tri-n-butylamine, 3-methyl-2-butanone, isobutyronitrile, di-n-butylamine, methyl chloroacetate, 3-methylbutene-1, 1,2-dibromoethane, dimethylamine, benzaldehyde, chloroform, 2-ethylhexene-1, propionaldehyde, 1,4 dichlorobutene-2, tri-n-butylphosphine, dimethylphosphine, methyl cyanoacetate , carbon tetrachloride, bromotrichloromethane, di-n-butylphosphine, acetaldehyde, and phosphine.

The modifier may comprise a C ₂ to C ₂₀ or C ₂ to C ₁₂ aldehyde. The modifier may also include a C ₂ to C ₂₀ or C ₂ to C ₁₂ saturated modifier. Additionally, the modifier may include a C ₂ to C ₂₀ or C ₂ to C ₁₂ unsaturated modifier. For further details on modifiers, see Advances In Polymer Science, Vol. 7, pp. 386-448, (1970)]. Here, Table 7 ranks several shuttling agents in the order of the chain transfer constants determined under the set conditions. Aldehydes, including propionaldehyde and acetaldehyde, are known to have preferentially higher chain transfer constants compared to other chain transfer agents such as propane, butane, isobutane, propene, isobutene, and 1-butene.

The modifier may be added to the reaction mixture in any suitable manner. For example, the modifier can be injected into the reactor along with the initiator, which can result in financial savings by reducing the amount of initiator required for the process as the initiator is generally expensive. The modifier may also be injected into the discharge or suction of the secondary compressor. The modifier may also be injected directly into the reactor and premixed with the initiator.

initiator

The term “initiator” as used herein refers to a compound that initiates a free radical ethylene polymerization process. Initiators suitable for use in the present invention include, but are not limited to, organic peroxide initiators and mixtures thereof. Further examples of suitable initiators are bis(2 ethylhexyl)peroxydicarbonate, tert-butyl per(2-ethyl)hexanoate, tert-butyl perpivalate, tert-butyl perneodecanoate, tert-butyl periso Peresters, including but not limited to butyrate, tert-butyl per-3,5,5,-trimethylhexanoate, tert-butyl perbenzoate, and di-tert-butyl peroxide dialkyl peroxides including, and mixtures thereof. The initiator(s), typically in a hydrocarbon solvent, may be mixed and then injected into the reactor at a suitable location. Any suitable pump may be used, for example a hydraulically driven piston pump.

Example

2 is a schematic design diagram of a high pressure polyethylene reactor system 17 similar to the reactor system used in the following examples. In this reactor system (17), compressed ethylene flows from the secondary compressor (18) to the preheater (19). The compressed ethylene leaves the preheater (19) and enters the reactor (20). Unlike other high pressure ethylene polymerization systems, reactor system 17 does not have a pressure relief valve upstream of preheater 19 or between preheater 19 and the inlet to reactor 20 .

Reactor 20 comprises five reaction zones 21a-e, and five cooling zones 22a-e, in the arrangement shown in FIG. 2 . The reaction zones may be numbered sequentially, with reaction zone 1 (eg, 21a) closest to the inlet of reactor 20 and reaction zone 5 (eg, 21e) closest to the outlet of reactor 20 . Cooling zones may also be numbered in a similar manner. A pressure relief valve 25 is located along the reactor in cooling zone 4 (eg, 22d). Another pressure relief valve 26 is located immediately downstream of cooling zone 5 (eg, immediately downstream of 22e ) and immediately upstream of high pressure drop valve 27 . In this system, both pressure relief valves 25 and 26 are dump valves. The product mixture exits the high pressure drop valve 27 via conduit 28 .

Examples 1-450 KTA reactor system (simulated)

In a reactor system similar to that of Figure 2, with a design capacity of about 450 KTA, computational fluid dynamics (“CFD”) modeling software was used to simulate a pressure dump event. ^{The software used for this simulation was EcosimPro TM} modeling and simulation software developed by Empresarios Agrupados AIE, Madrid, Spain. In the reactor system of the simulation, a distance of 0 m was designated as the inlet location of the preheater. Table 1 below provides the distance in meters from the inlet of the preheater to the beginning of the reaction zone for each of the five reaction zones.

Location of the reaction zone for the 450 KTA reactor system location Distance from the preheater inlet, m preheater 0 reaction zone 1 351 reaction zone 2 501 reaction zone 3 660 reaction zone 4 955 reaction zone 5 2009

The operating pressure of the simulated reactor was about 3000 bar. The pressure dump event was initiated by opening both pressure relief valves 25 and 26 simultaneously. 3 is a plot of mass flux distribution at various locations and time points within the reactor after the onset of a pressure dump event. 3 , the mass flow rate (kg/s) is plotted on the Y axis. A positive mass flow represents a flow shift from the preheater towards the high pressure drop valve. A negative mass flow indicates a flow shift from the high pressure drop valve towards the preheater. The position (in meters) is plotted on the X axis, and the position of 0 m corresponds to the inlet of the preheater as previously mentioned.

In Figure 3, the time of 0 seconds was the start of the pressure dump event. As shown, the mass flow rate at each location varies with time as the decompression progresses. Figure 3 shows that after both pressure relief valves 25 and 26 have been opened, there are two positions in the reactor where the mass flow rate is zero. The first location is near the pressure relief valve located along the reactor in cooling zone 4, at a location of about 1250 m from the inlet of the preheater. Here, the mass flow is directed outward from the system, so it is an extraction point and therefore not a stagnant zone. The second location is in the cooling zone 5 in both cases at a location varying between about 2250 m and about 2340 m. It is initially at about 2340 m and then moves to about 2250 m in the direction of the preheater. Because there is no mass flow and no extraction, this location is a stagnant zone.

4 shows the pressure drop over time at the inlet of each of the reaction zone and preheater during a pressure dump event. Figure 4 shows that in this system the pressure at the preheater inlet decreases at the slowest rate but falls below 1000 bar within 6 seconds, with the pressure in each reaction zone dropping below 1000 bar more rapidly.

Examples 2-420 KTA reactor system (simulated)

Similar to Example 1, a pressure dump event was simulated in a reactor system similar to that of FIG. 2 except with a slightly smaller design capacity of about 420 KTA. The operating pressure of this simulated reactor was also about 3000 bar. In a manner similar to Example 1, a pressure dump event was initiated by opening both pressure relief valves 25 and 26 simultaneously.

5 is a plot of mass flux distribution at various locations and time points within the reactor after the onset of a pressure dump event. A positive mass flow represents a flow shift from the preheater towards the high pressure drop valve. A negative mass flow indicates a flow shift from the high pressure drop valve towards the preheater. The 0 m position also corresponds to the inlet of the preheater.

Figure 5 shows that after both pressure relief valves 25 and 26 have been opened, there are two positions in the reactor where the mass flow rate is zero. The first location is near the pressure relief valve located along the reactor in cooling zone 4 at a location of about 1000 m from the inlet of the preheater. This is an extraction point and therefore not a stagnant zone. The second position varies between about 1960 m and about 2020 m within cooling zone 5 in both cases. Because there is no mass flow and no extraction, this location is a stagnant zone.

FIG. 6 is an enlarged view of FIG. 5 around the location of 2000 m where the congestion zone is located; 6 shows that the stagnant zone is initially at about 2020 m and then moves in the direction of the preheater and remains almost continuously at about 1960 m. In this system, the pressure at the inlet of the preheater and at all reaction zones also drops below 1000 bar within 6 seconds.

The systems and processes in these examples illustrate only possible embodiments of the invention. Those of ordinary skill in the art will appreciate that specific systems and/or processes may vary from these embodiments and still fall within the scope of the present invention, as defined by the following claims.

Claims (24)

a. a compressor in fluid communication with the reactor comprising at least one reaction zone and at least one cooling zone;
b. a first pressure relief valve located downstream of the reactor;
c. a second pressure relief valve positioned along the reactor within the cooling zone; and
d. Preheater upstream of the reactor
A reactor system comprising: a reactor system having no pressure relief valve upstream of the preheater or between the preheater and the reactor. The reactor system of claim 1 , wherein the total internal volume of the reactor is less than 6 m 3 . 3. The reactor system of claim 1 or 2, wherein the reactor comprises at least three cooling zones and a second pressure relief valve is located along the reactor in cooling zone 3 or further downstream of the cooling zone. 3. The reactor system of claim 1 or 2, wherein the reactor comprises at least four cooling zones and a second pressure relief valve is located along the reactor in cooling zone 4 or further downstream of the cooling zone. The reactor system according to claim 1 or 2, wherein the operating pressure at the inlet of the preheater can be reduced from above 2000 bar to below 1000 bar in less than 10 seconds. 3. The reactor system of claim 1 or 2, further comprising a stagnation zone within the reactor during a pressure dump event, wherein the stagnation zone is located entirely within the at least one cooling zone. 7. The reactor system of claim 6, wherein the position of the stagnant zone moves during the pressure dump event, but remains entirely within the cooling zone. A process for rapidly depressurizing a polymerization reactor comprising at least one reaction zone and at least one cooling zone, the process comprising:
(i) opening a first pressure relief valve located downstream of the reactor; and
(ii) opening a second relief valve located along the reactor in the at least one cooling zone, optionally opening the second relief valve simultaneously with the opening of the first relief valve;
wherein the preheater is located upstream of the reactor and the pressure relief valve is not located upstream of the preheater or between the preheater and the reactor. 9. The method according to claim 8, further comprising the step of opening the high pressure drop valve located downstream of the first pressure relief valve, optionally further comprising the step of opening the high pressure drop valve simultaneously with the opening of the first pressure relief valve and/or the second pressure relief valve. How to include. 10. The method of claim 9, further comprising partially or fully closing the high pressure drop valve after confirming that at least one of the first relief valve or the second relief valve is open. The process according to claim 8 or 9, wherein the process reduces the operating pressure at the inlet of the preheater upstream of the reactor from greater than 2000 bar to less than 1000 bar in less than 10 seconds. 10. The method of claim 8 or 9, wherein the primary and secondary compressors are located upstream of the reactor and further comprising the step of shutting down the secondary compressors. 13. The method of claim 12, wherein the secondary compressor includes at least one suction valve and includes closing the at least one suction valve. 10. The method of claim 8 or 9, wherein the reactor comprises at least one feed valve and further comprising closing the at least one feed valve. 15. The method of claim 14, further comprising closing the at least one feed valve when the pressure at any point in the reactor is below 1500 bar. 10. The method of claim 8 or 9, further comprising initiating the method when decomposition is detected in the reactor. delete delete delete delete delete delete delete delete

Images