CN1068336C - Process for polymerizing monomers in fluidized beds - Google Patents

Abstract

The invention relates to a method for determining a stable operating region of gas phase fluidized bed polymerization and a gas phase polymerization method. More specifically, methods for determining the stable operating region of gas-phase fluidized-bed polymerization reactors operating in condensing mode include observing changes in FBD in the reactor in relation to changes in the composition of the fluidizing medium and increasing the cooling capacity of the recycle stream by changing the composition , without causing it to exceed a level where FBD decline becomes irreversible.

Description

Monomer Polymerization Process in Fluidized Bed

The present invention relates to a stable operating region determination method for gas fluidized bed polymerization and a gas phase polymerization method, where "gas fluidized bed polymerization" means that polymer particles are cooled by a gas flow containing monomers, fluidized and stirred with or without additional Polymerization method with mechanical stirring.

The gas fluidized bed polymerization equipment adopts a continuous cycle, in which the heat of polymerization is used to heat the circulating gas flow in a part of the reactor, and another part of the heat is removed in another part of the cycle by a cooling system outside the reactor, in which continuous or discontinuous The catalyst is added and additional monomer is added to replace the consumed monomer, and the removal of the polymer particles is completed.

Large-scale equipment is expensive and has high productivity, loss of downtime, and the dangers of experimenting in it, so it is difficult to determine the boundaries of design and operation in terms of cost and risk.

The invention proposes a method for determining the stable operation area of the gas fluidized bed polymerization and the required process conditions in the given equipment design, which can promote the optimal design of the equipment.

The gas fluidized bed reactor can be controlled to achieve the required melt index and polymer density at optimum yield, where care should be taken to avoid the formation of unstable streams that could form lumps or bands or worse, which would collapse The fluidized bed or the conditions that cause the polymer particles to fuse together, so the fluidized bed must be controlled to reduce the formation of lumps and bands and prevent the bed from collapsing or avoiding the operation of terminating the reaction and shutting down the reactor, which is why industrial reactors Reasons for good operation in areas of proven stability and applied in a carefully designed manner.

Even under the conventional safe operation constraints, if one wants to seek new and improved operating conditions, the control is too complicated, which will further increase the difficulty and uncertainty of the experiment.

The operating temperature, the ratio of comonomer to monomer and the ratio of hydrogen to monomer can be determined by the polymer and catalyst, and then the reactor and cooling system are set in the compression device, and the materials in it are monitored and not removed. Unnecessarily disturbing fluidization, where (1) head pressure, (2) pressure difference at different heights in the bed, (3) temperature upstream of the bed, (4) temperature in the fluidized bed and downstream of the bed, and (5) gas composition are determined and (6) gas flow rate, and then use these measured values to control the catalyst feed amount, monomer partial pressure and cycle gas flow rate, and in some cases use the deposited bulk density (unfluidized) or fluidized bulk density according to the equipment design scheme (This must also be monitored) and the ash content in the polymer limits the amount of polymer withdrawn. The equipment is a closed system, and changes in one or more measured values in operation will cause changes in other places, and the optimization of capacity in equipment design depends on the most limiting factor in the overall design.

There is generally no consensus as to what causes the formation of lumps or bands, which apparently involves partial fusion of the polymer particles, which may be caused by insufficient heat transfer due to improper fluidization in the fluidized bed , but so far no clear relationship has been found between individual components and measurements and the formation of chunks and bands, so all measurements and controls are often kept at known safe levels for a given equipment design within the operating range.

This requires the development of a gas fluidized bed polymerization process in which the reactor achieves maximum productivity.

Jenkins et al in US4588780 and 4543399 illustrate the difficulty and complexity of the overall control and try to expand the stable operating region that can improve the space-time yield.

Jenkins et al cooled the circulating gas and added it to the reactor. The temperature was lower than the dew point, so that the condensate evaporated in the reactor, and the cooling capacity of the circulating gas was further increased. Of course, at a given temperature of the cooling heat transfer medium, the scheme mentioned One is the addition of a non-polymeric material (isopentane) to raise the dew point, but higher space-time yields are said to be achievable due to more heat removal with greater cooling. Jenkins et al recommend no more than 20 wt%, preferably 2-12 wt%, of condensate in the recycle gas, the potential hazards mentioned therein include the formation of "slurry" (US4588790, col.5, lines 35-39), so keep Sufficiently high circulating gas velocity (col. 6, lines 12-20) or avoid liquid accumulation on the distribution plate (col. 6, lines 28-32). The use of more than 20% condensate is only possible if the condensate is fed directly into the fluidized bed (col. 8, lines 16-20).

Particularly advantageous from the point of view of the invention are Examples 6, 7 and 10a, in which 14.2, 10.5 and 12.9 mol% isopentane are used in the recycle gas, which are cooled to 65.9, 34.0 and 53.5°C, respectively, so that Condensate levels of 11.5, 10.5 and 14.3 wt% and time yields of 7.0, 10.7 and 6.2 lb/hr- ^ft3 (111.6, 170.5 and 98.8 kg/hr- ^m3 ) were achieved.

Jenkins et al. What is the upper limit of the non-polymerizable or polymerizable condensable material is not mentioned, nor how to optimize the space-time yield by condensation. Jenkins et al. Nor does it assign any particular role to the fluidized bulk density, let alone any suggestion that the composition of the recycle stream is related to the determination of the stable operating region for high space-time yields.

Therefore the object of the invention is to propose measures that help to determine the stable operating area and equipment design scheme of the fluidized bed process, seek the safe operating process with low risk of abnormal operation and the high criterion of the reactor productivity and/or avoid reaction due to Any limitation that may be placed on the total capacity of the equipment due to the production rate of the equipment.

The present invention can utilize varying fluidized bulk density (FBD) for a given grade of polymer and/or catalyst composition to optimize process conditions and equipment design. Jenkins et al. It is believed that the percentage of condensate helps to define the upper limit of the amount of cooling that can be performed and thus determine how high the space-time yield can be achieved, while the present invention uses the FBD limit to possibly include more than Jenkins et al. Safe operating area for larger quantities of condensate than stated.

The present invention thus relates in a first aspect to a fluidized bed polymerization process comprising passing a gaseous stream comprising monomer under reaction conditions through a fluidized bed reactor in the presence of a catalyst to produce a polymerized product and a stream comprising unreacted monomer gas , the stream is compressed and cooled, mixed with the feed components and returned to the reactor in both the gas and liquid phases, wherein methods for determining stable operating conditions include (a) observation of the fluidized bed in the reactor in relation to changes in the composition of the fluidized medium A change in bulk density or its indicative parameter and (b) increasing the cooling capacity of the recirculating stream by compositional changes not exceeding a level at which the reduction in fluidized bulk density or its indicative parameter becomes irreversible. The fluidized bulk density is referred to as FBD, and the deposited bulk density is referred to as SBD. Generally speaking, if the ratio of FBD to SBD falls below 0.59, there will be a danger of fluidized bed collapse, which should be avoided.

FBD is the ratio of the measured pressure drop up through the central fixed section of the reactor to the height of that section. It should be appreciated that, under certain conditions known to those skilled in the art, greater or less than the average actual bed bulk density can be measured.

Applicants have discovered that as the concentration of condensable components increases in the gaseous phase stream passing through the bed, an identifiable point is reached beyond which the concentration may become catastrophic to failure of the process Dangerous, this point is characterized by an irreversible change in the density of the fluidized bed at any higher concentration of condensable fluid in the gas. The amount of liquid in the recycle stream entering the reactor may not be directly relevant, and a decrease in FBD generally does not result in a corresponding change in the SBD of the final product particles, so changes in the fluidization effect reflected by a decrease in FBD will not significantly change the properties of the polymer particles permanent change.

The concentration of condensable fluid in the gas which reduces FBD depends on the type of polymer produced and other process conditions, which can be identified by monitoring the FBD at increasing concentrations of condensable fluid in the gas for a given polymer type and other process conditions.

In addition to the concentration of condensable fluids in the gas, the FBD depends on other changes including, for example, the superficial velocity of the gas flowing through the reactor, the height of the fluidized bed and the product SBD as well as the gas and particle density, temperature and pressure, so in the gas condensable In experiments where changes in fluid concentration lead to changes in FBD, significant changes in other conditions should be avoided.

While a certain decrease in FBD will not be uncontrolled, further changes in gas composition or other variables that simultaneously increase the dew point may cause a significant irreversible decrease in FBD, resulting in "hot spots" and/or formation of frits in the reactor bed, which The reactor can be shut down if necessary.

Other practical consequences directly related to FBD reduction include reduced polymer capacity for fixed volume reactor discharge systems and reduced polymer/catalyst reactor residence time at a constant polymer production rate, which, for a given catalyst, reduces catalyst productivity and increase the level of catalyst residue in the product polymer. In the practice of applying this invention, for a given target reactor production rate and associated cooling requirements, it is desirable to minimize the concentration of condensable fluids in the gas.

Applying this FBD change, a region of stable operation can be identified, and once identified as a stable composition, that composition can be applied to achieve higher cooling capacity in the recycle stream (without causing bed instability), where at Cool the composition to a greater extent. A high reactor yield is achieved by adding condensable non-polymerizable materials in appropriate amounts at specific stages, while maintaining good conditions in the fluidized bed in which it is maintained in the stable operating region thus defined. Higher reactor productivity can be achieved in the process, or equipment with larger production capacity can be designed with a relatively small reactor diameter during equipment design, or existing equipment can be improved to increase without changing the reactor size production capacity.

At higher reactor yields it has been found that condensate levels well above 15%, 20% or even 25% can be achieved within the boundaries defined by the FBD variation, while avoiding significant losses from fluidized bed collapse. Blocks or strips form levels.

The FBD is preferably observed using the differential pressure value measured in the part of the fluidized bed above the distribution plate that is not susceptible to disturbance, and in general the change in FBD in the lower part of the bed often indicates the collapse of the bed above the distribution plate, where the pressure measured away from the distribution plate The resulting upper FBD was used as a stability parameter, but it has been surprisingly seen that upper FBD changes correlate with stream composition changes and can be used to seek and define stable operating regions.

The cooling capacity is increased in different ways, preferably by increasing the proportion of components that increase the dew point, including increasing the proportion of non-polymerizable higher hydrocarbon components or on the other hand increasing the proportion of comonomers including 3-12 carbons. The proportion of polymerizable monomers, where the proportion of non-condensable inert components is reduced. In certain processes, the cooling capacity of the recycle stream can be further increased if necessary by lowering the temperature of the fluidizing medium, for example by refrigeration. Improved process conditions can be obtained after a safe operating area has been identified.

A second aspect of the present invention is therefore to provide a process for the gas-phase fluidized bed polymerization of polymers in which a gaseous stream comprising monomers is passed under reaction conditions through a fluidized bed reactor in the presence of a catalyst to produce a polymerized product and comprising unreacted monomers The stream, which is compressed and cooled, mixed with the feed components and returned to the reactor in both the gas and liquid phases, the improvement comprises cooling the stream so that the liquid phase reaches 15, preferably more than 20 wt% of the total weight of the returned stream and allowing The stream composition is such that the ratio of FBD to SBD exceeds 17.8:30.2, preferably 18.1:30.2.

A third aspect of the present invention is a process for the gas phase fluidized bed polymerization of polymers, wherein a gaseous stream comprising monomers is passed under reaction conditions through a fluidized bed reactor in the presence of a catalyst to produce a polymerized product and a gaseous stream comprising unreacted monomers A stream, which is compressed and cooled, mixed with the feed components and returned to the reactor in both the gaseous and liquid phases, modified to include polymerizable or non-polymerizable components containing at least 3 carbons such that the amount of these components increases by 1 mol % FBD decreases reversibly.

It is advantageous to allow the stream to cool and pass through the reactor at such a rate that its cooling capacity is sufficient to allow the reactor production rate (lbs polymer/hr-ft reactor cross ^- sectional area) to exceed 500 lb/hr- ^ft (2441 kg/hr- m ² ), especially 600 lb/hr-ft ² (2929 kg/hr-m ² ), including an enthalpy change of at least 40 Btu/lb (21.9 cal/g ), preferably 50Btu/lb (27.4cal/g). Preferably, the liquid and gaseous components of the stream are fed in admixture below the reactor distributor plate. The reactor productivity is equal to the space-time yield multiplied by the height of the fluidized bed.

In another aspect of the invention, the recycle stream may be split into two or more separate streams, one or more of which may be introduced directly into the fluidized bed, provided that the gas velocity below and through the fluidized bed is sufficient to suspend the bed , eg the recycle stream can be divided into liquid and gaseous streams which can then be introduced into the reactor separately.

When the improved method of the present invention is implemented, the recycle stream comprising a mixture of gaseous and liquid phases in the portion below the reactor distributor plate can be formed by injecting liquid and recycle gas respectively under conditions that will generate a stream comprising two phases.

Increased cooling capacity through careful control of the composition of the gas phase stream can significantly increase reactor productivity, reduce the risk of fluid bed collapse, and allow even greater condensation where the percentage of liquid in the recycle stream is increased. For any given liquid percentage in the recycle stream, the reactor gas composition, temperature, pressure and superficial velocity should be controlled according to product particle composition and physical properties to maintain a variable fluidized bed.

In the process according to the invention, the cooling capacity of the recycle stream can be significantly increased by evaporating entrained condensate in the recycle stream and due to the greater temperature difference between the incoming recycle stream and the temperature of the fluidized bed. Suitable polymers of manufacture may be selected from film grade materials having a MI value of 0.01-5.0, preferably 0.5-5.0 and a density of 0.900-0.930 or molding grade materials having a MI value of 0.10-150.0, preferably 4.0-150.0 and Density 0.920-0.939 or high-density material, its MI value is 0.01-70.0, preferably 2.0-70.0 and density 0.940-0.970, all density units g/Cm ³ , melt index unit g/10min, all measured according to ASTM-1238 condition E .

The features and advantages of the above objects of the present invention can be seen in detail in the following and with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of a preferred reactor for the improved gas-phase fluidized-bed polymerization process of the polymer of the present invention.

Figure 2 is a line diagram of isopentane mol% and FBD in Table 1.

FIG. 3 is a line diagram of the relationship between isopentane mol% and FBD in Table 2. FIG.

FIG. 4 is a line diagram including FIGS. 2 and 3 .

The same reference numerals are used to designate the same parts in the text and drawings, and the drawings are not drawn to scale, some parts of which have been exaggerated in order to better illustrate the present invention.

The present invention is not limited to any particular polymerization reaction, but is particularly suitable for one or more monomers, such as olefin monomers, such as ethylene, propylene, butene-1, pentene-1, 4-methylpentene-1 , the polymerization of hexene-1, octene-1 and styrene, other monomers may include polar vinyl, conjugated and non-conjugated dienes, acetylene and aldehyde monomers.

The catalysts used in the improved process can include coordination anion catalysts, cationic catalysts, free radical catalysts, anionic catalysts and include transition metal components or metallocenes, wherein the single catalyst reacted with a metal alkyl or alkoxy component or an ionic compound component or polycyclopentadiene components. These catalysts include partially and fully activated precursor compositions as well as prepolymerized or encapsulated. In practicing the invention, the amount of gas in the recycle stream and the velocity of the recycle stream should be maintained at a level sufficient to suspend the liquid phase in the mixture in the gaseous phase. , until the recycle stream enters the fluidized bed so that liquid does not collect at the bottom of the reactor below the distribution plate. The velocity of the recycle stream should be high enough to support and mix the fluidized bed in the reactor, and it is also required that the liquid entering the fluidized bed is rapidly dispersed and evaporated.

Controlling the gas composition, temperature, pressure and superficial velocity based on the composition and physical properties of the polymer is important to maintain a viable fluidized bed, which is defined as being suspended in a steady state under the reaction conditions and well mixed without at the same time A fluidized bed of particles can form in large numbers of agglomerates (lumps or bands) that can disable reactor or downstream process operations.

15 wt% of the recycle stream can be condensed or in the liquid phase without failing the fluidization process, where the safe operating boundaries of the stable operating region determined by FBD are not exceeded or breached.

In the polymerization process, a small amount (generally less than about 10%) of the gas stream flowing upward through the fluidized bed is reacted, while the unreacted large amount of stream enters the region above the fluidized bed called the free zone, which may also be the velocity reduction zone, where Large solid polymer particles carried above the bed by air bubbles across the surface or entrained in the gas flow can fall back into the fluidized bed. Small solid polymer particles known in the industry as "fines" are withdrawn with the recycle stream because their final settling velocity is lower than that of the recycle stream in the free zone.

In a preferred solution of the present invention, the inlet point of the recycle stream is preferably below the fluidized bed to obtain a uniform recycle stream, thereby maintaining the fluidized bed in a suspended state and ensuring the uniformity of the recycle stream passing upward through the fluidized bed.

In another aspect of the invention, the recycle stream can be divided into liquid and gas phase components which are introduced into the reactor separately.

The advantages of the present invention are not limited to the production of polyolefins, therefore the present invention can be practiced with any exothermic reaction carried out in a gas fluidized bed, the process operating in the condensed state is superior to other processes in that it generally follows directly the dew point of the recycle stream The degree of reaction temperature in the fluidized bed increases. For a given dew point, the benefits of this process increase directly with the percentage of liquid phase in the recycle stream fed back into the reactor, and high percentages of liquid can be used in the process of the present invention.

The gas fluidized bed reactor that is especially suitable for producing polymer with the inventive method is clearly shown in the accompanying drawings, generally referred to as 10 in Fig. 1, it should be noted that the reaction system shown in Fig. 1 is only schematic, and the actual It is also suitable for any conventional fluidized bed reaction system.

The reactor 10 in Figure 1 comprises a reaction zone 12 and a free zone, which in the present case is actually also a velocity reduction zone 14, the height/diameter ratio of the reaction zone 12 can vary with the required throughput and residence time, This in turn comprises a fluidized bed containing forming polymer particles, existing formed polymer particles and a small amount of catalyst, the fluidized bed in the reaction zone 12 is supported by a recycle stream 16 typically consisting of a feed fluid and a recycle fluid , the recycle enters the reactor through a distribution plate 18 in the bottom section of the reactor, which helps to achieve uniform fluidization in the fluidized bed in the reaction zone 12 and supports the fluidized bed. In order to keep the reaction zone fluidized bed 12 in a suspended and reliable state, the superficial gas velocity (SGV) of the gas flow through the reactor generally exceeds the minimum flow velocity required for fluidization, generally about 0.2 ft/sec (0.061 m/ s) to 0.5 ft/sec (0.153 m/s), preferably not less than about 0.7 ft/sec (0.214 m/s), more preferably not less than 1.0 ft/sec (0.305 m/s), but preferably should not More than 5.0ft/sec (1.5m/s), especially 3.5ft/sec (1.07m/s).

The polymer particles in the reaction zone 12 help prevent the formation of localized "hot spots" and maintain and distribute the catalyst particles throughout the fluidized bed. At the beginning of the operation, a matrix of polymer particles is added to the reactor 10 prior to the introduction of the recycle stream 16. The polymer particles are preferably the same as the new polymer particles to be produced, but if not at the same time. At the beginning of the cycle, the catalyst flows in and the reaction is established. It is then removed with the newly formed first batch, generally separating this mixture from the subsequent substantially new production process. Catalysts used in the improved process of the present invention are generally sensitive to oxygen and are therefore preferably stored in catalyst tank 20, which is protected by a gas inert to the stored catalyst, such as, but not limited to, argon or nitrogen.

The recycle stream 16 flowing through the reactor 10 reaches a high velocity to fluidize the fluidized bed in the reaction zone 12. The speed of the recycle stream 16 during operation is generally about 10-15 times the speed at which the feed is introduced into the recycle stream 16 , the velocity of the recycle stream is so high that the superficial gas velocity is sufficient to suspend and mix the fluidized bed in the reaction zone 12 to become fluidized.

The appearance of the fluidized bed is similar to that of a fully boiling liquid, in which dense particles are moved independently by the percolation and bubbling of gas through the fluidized bed. The recycle stream 16 will produce a pressure drop after passing through the fluidized bed in the reaction zone 12, and its value is equal to or slightly greater than the fluidized bed weight in the reaction zone 12 divided by the cross-sectional area of the reaction zone 12, so this is related to the geometry of the reactor Size matters.

The combined feed enters recycle stream 16 in Figure 1 at point 22, but is not limited thereto. Gas analyzer 24 receives a gas sample on recycle stream 16 and monitors the composition of recycle stream 16 flowing therethrough. The analyzer may also adjust the composition of recycle stream 16 and the feed to maintain steady state conditions in reaction zone 12. The analyzer typically analyzes a sample taken from recycle stream 16 at a point between free zone 14 and heat exchanger 26 , preferably between compressor 28 and heat exchanger 26 , over the composition range of recycle stream 16 .

The recycle stream 16 flows upward through the reaction zone 12 to absorb the heat generated by the polymerization reaction, and this part of the recycle stream 16 that does not participate in the reaction in the reaction zone 12 is discharged from the reaction zone 12 and passes through the free zone 14 . As previously stated, this zone is the velocity reduction zone where most of the entrained polymer falls back into the fluidized bed reaction zone 12, thereby reducing the load on solid polymer particles entering the recycle stream 16. Recycle stream 16 is in the modified catalyst once withdrawn from the reactor in free zone 14 .

While the present invention is not, as previously stated, limited to any particular polymerization reaction, the following discussion of the operation of the improved process refers primarily to the polymerization of olefinic monomers, such as polyethylene, in which the present invention may be found to be particularly advantageous.

The process operating temperature is set or adjusted below the melting or melting temperature of the polymer pellets produced. It is important to maintain this temperature to prevent the reactor from being blocked by the rapid formation of polymer clumps when the temperature is increased. Chunks may be too large to be withdrawn from the reactor as a polymer product and may render the process and reactor ineffective, and large chunks entering downstream processing of the polymer may damage eg conveying systems, drying equipment or extruders.

The improvement of the fluidized bed polymerization process by the present invention can significantly increase the productivity of the reactor without causing significant changes in product quality or performance. In this preferred embodiment, the entire polymerization process of the present invention is carried out continuously.

To achieve higher cooling capacity and thus higher reactor productivity, it may be required to increase the dew point of the recycle stream to allow greater heat removal from the fluidized bed, where the operating pressure of the reaction/recycle stream and/or Or increasing the percentage of condensable fluid and decreasing the percentage of non-condensable gas in the recycle stream, methods have been seen in Jenkins et al., US4588790 and 4543399. Condensable fluids may be inert to catalysts, reactants and polymer products and may also include comonomers which may be introduced into the reaction/recycle system at any point in the process system, see Figure 1 for details, a suitable example is Volatile liquid hydrocarbons, which can be selected from 2-8 carbon saturated hydrocarbons, such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, n-hexane, isohexane and other saturated _C6 hydrocarbons, n- Heptane, n-octane and other _C7 and _C8 hydrocarbons or mixtures thereof, preferably _C5 and _C6 saturated hydrocarbons, which may also include polymerizable condensable comonomers, such as olefins, dienes or mixtures thereof, containing Some of the above-mentioned monomers of the above-mentioned products may be added partially or completely. Compression in compressor 28 then passes through heat exchanger 26 in which heat from the polymerization reaction and gas compression is removed from recycle stream 16 and returned to reaction zone 12 in reactor 10. The heat exchanger 26 is of conventional type and may be placed in the recycle stream line 16 in a vertical or horizontal manner, and in another aspect of the invention more than one heat exchange or compression zone is provided in the recycle stream line 16 .

In Fig. 1, once the recycle stream 16 comes out of the heat exchanger 26, it enters the bottom of the reactor 10. Preferably, a fluid baffle 30 is arranged below the gas distribution plate 18 to prevent the polymer from settling out and entering the solid part and distributing Entrainment of liquid and polymer particles is maintained in recirculating stream 16 below plate 18, preferably baffles in the form of ring discs, as described in US4933149, to achieve center up and outer edge flow, center up flow aids entrainment at the bottom Droplets, while outward edge flow helps minimize polymer particle buildup at the bottom end. The distributor plate 18 spreads the recycle stream 16 to avoid that stream entering the reaction zone 12 in a centrally located upflowing stream or jet, which could cause the fluidized bed in the reaction zone 12 to fail to fluidize.

The temperature of the fluidized bed can be determined according to the stickiness point of the particles, but basically depends on three factors: (1) catalyst activity and catalyst injection rate, which controls the rate of polymerization and heat generation, (2) Recycle and mixture stream temperature, pressure and composition and (3) volume of recycle stream flowing through the fluidized bed. The amount of liquid introduced into the bed either with the recycle stream or separately as mentioned above affects the temperature in particular, as the liquid evaporates in the reactor to lower the temperature of the fluidized bed, and the rate of catalyst addition is usually used to control the rate of polymer formation.

In the preferred version, the temperature of the fluidized bed in the reaction zone 12 is kept constant in a steady state, wherein the heat of reaction is continuously taken out, and the steady state of the reaction zone 12 will occur when the heat generated in the process is balanced by the heat taken out, wherein it is required to enter the polymerization The overall throughput of the process is balanced by the amount of polymer and other materials withdrawn. Thus, at any given point in the process temperature, pressure and composition are constant over time, with no significant temperature gradients in the fluidized bed for the majority of reaction zone 12, but in the region above gas distribution plate 18 in reaction zone 12 There is a temperature gradient at the bottom of the fluidized bed because there is a difference between the temperature of the recycle stream 16 entering through the distribution plate 18 at the bottom of the reactor 10 and the temperature of the fluidized bed in the reaction zone 12.

Efficient operation of the reactor 10 requires good distribution of the recycle stream 16. If the forming or formed polymer and catalyst particles can settle from the fluidized bed, the polymer may melt, which in extreme cases can lead to form a solid substance. Commercially sized reactors contain thousands of pounds or kilograms of polymer particles at any given time, and removal of such large quantities of polymer solids can present great difficulty requiring great effort and Park for a long time. With the help of FBD measurements to determine a stable region of operation, an improved polymerization process can be carried out in which the fluidized bed is kept fluidized and supported in the reaction zone 12 of the reactor 10 .

In a preferred embodiment of the invention, the liquid introduced into the reactor 10 is vaporized to achieve the advantage of increased reactor cooling capacity for the polymerization process. Large amounts of liquid in the bed can promote the formation of large particles that cannot be broken by mechanical forces in the bed, potentially leading to fluidization failure, bed collapse and reactor shutdown. In addition, the presence of liquid may affect the local bed temperature and the ability of the process to produce polymers with constant properties, as this requires the attainment of a substantially constant temperature in the bed, for which reason the amount of liquid introduced into the fluidized bed under given conditions should be No greater than the amount that will evaporate in the lower part of the fluidized bed where the mechanical force of the recycle stream entering and passing through the distribution plate is sufficient to break up the clumps formed by the liquid-particle interaction.

It has been found in the present invention that, for a given composition and physical properties of the product particles in a fluidized bed, and other given or relevant reactor and cycle conditions, by defining boundary conditions related to the composition of the gas flowing through the bed, it is possible to Maintain a reliable fluidized bed at high cooling levels.

The observed decrease in FBD may reflect the expansion of the dense phase of particles in the fluidized bed and changes in the bubbling operation, but the reasons are not fully understood.

As shown in Figure 1, the catalyst activator is generally added downstream of the heat exchanger 26, and if necessary, it is added according to the catalyst used, and the catalyst activator can be introduced into the recycle stream 16 from the feeder 32, but the improved method of the present invention is not limited to the catalyst This is the point of addition for activators or any other desired ingredients, such as co-catalysts.

Catalyst can be injected intermittently or continuously from its storage tank into the fluidized bed reaction zone 12 at a preferred rate at a point 34 above the gas distribution plate 18 . In the above-mentioned preferred scheme, the mixing of the catalyst and the polymer particles in the fluidized bed 12 can be injected at the most complete point, wherein because some catalysts are very active, the injection point to the reactor 10 should preferably be at the gas distributor 18 above, not below. Injection of the catalyst in the area below the gas distribution plate 18 will cause the product to polymerize in this area, which in turn may cause the gas distribution plate 18 to become clogged. Furthermore, injecting the catalyst above the gas distribution plate 18 helps to distribute the catalyst evenly in the fluidized bed 12, thereby avoiding the formation of "hot spots" due to excessive localized catalyst concentrations. The catalyst is preferably injected into the lower part of the fluidized bed in the reaction zone 12 to achieve uniform distribution and minimize the possibility of catalyst being carried into the circulation pipe, because polymerization in the circulation pipe may cause the circulation pipe and heat exchanger to be blocked.

A number of catalyst injection techniques can be used in the improved process of the present invention, such as that described in US 3,779,712, the disclosure of which is incorporated herein by reference. Preferably, an inert gas such as nitrogen or an inert liquid that is volatile under reactor conditions is used to bring the catalyst into the fluidized bed reaction zone 12. The catalyst injection rate and the monomer concentration in the recycle stream 16 determine the polymer concentration in the fluidized bed reaction zone 12. The production speed can simply adjust the catalyst injection speed to control the production speed of the polymer.

In the preferred method of operation of reactor 10 utilizing the improved method of the present invention, the fluidized bed height in reaction zone 12 can be maintained by withdrawing a portion of the polymer product at a rate consistent with polymer product formation. Changes in the conditions of the fluidized bed in reaction zone 12 are monitored with instrumentation capable of measuring any temperature or pressure changes in reactor 10 and recycle stream 16 . Furthermore, the instrument can also manually or automatically adjust the catalyst injection rate or the temperature of the recycle stream.

During operation of the reactor 10, product is discharged from the reactor via the discharge system 36, after which the fluid is preferably separated from the polymer material, and the fluid can be returned to the recycle line 16 at the point 38 as a gas and/or at the point 40 as a condensate , the polymer is sent to the point 42 for subsequent processing, but the discharge method of the polymer product is not limited to that shown in Figure 1, in fact Figure 1 only shows a special discharge method, of course other discharge systems can be used , as seen in US4543399 and US4588790 (Jenkins et al.).

The present invention also proposes a method for increasing the polymer yield of the reactor in a fluidized bed reactor for exothermic polymerization, wherein the recycle stream is cooled below its dew point and the thus obtained recycle stream is fed back into the reactor, which can A recycle stream containing more than 15% by weight liquid was recycled to the reactor to maintain the fluidized bed at the desired temperature.

Reactor throughput levels that were not possible before can be achieved using different cycle conditions depending on the material of interest.

Firstly, it can be produced, for example, film grade material, wherein the butene/ethylene mol ratio in the recycle stream is 0.00-0.60, preferably 0.30-0.50 or 4-methylpentene-1/ethylene mol ratio 0.00-0.50, preferably 0.08-0.33 or hexa ene/ethylene mol ratio 0.00-0.30, preferably 0.05-0.20; or octene-1/ethylene mol ratio 0.00-0.10, preferably 0.02-0.07; hydrogen/ethylene mol ratio 0.00-0.4, preferably 0.1-0.3; and isopentane Amount of 3-20mol% or isohexane amount of 1.5-10mol% and the cooling capacity of the recycle stream is at least 40Btu/lb (21.9cal/g), preferably at least 50Btu/lb (27.4cal/g) or condensed wt% at least 15.

Secondly, this method can be used to make molding grade materials, wherein the recycle stream butene-1/ethylene mol ratio is 0.00-0.60, preferably 0.10-0.50 or 4-methyl-pentene-1/ethylene mol ratio is 0.00-0.50, preferably 0.08- 0.20 or hexene/ethylene mol ratio 0.00-0.30, preferably 0.05-0.12 or octene-1/ethylene mol ratio 0.00-0.10, preferably 0.02-0.04; hydrogen/ethylene mol ratio 0.00-1.6, preferably 0.3-1.4; and iso 3-30 mol% pentane or 1.5-15 mol% isohexane and a recycle stream cooling capacity of at least 40 Btu/lb (21.9 cal/g), preferably at least 50 Btu/lb (27.4 cal/g) or condensed wt% of at least 15.

And it can be made into high-density grade materials, the recycle stream butene/ethylene mol ratio is 0.00-0.30 in its manufacturing method, preferably 0.00-0.15 or 4-methyl-pentene-1/ethylene mol ratio is 0.00-0.25, preferably 0.00- 0.12 or hexene/ethylene mol ratio 0.00-0.15, preferably 0.00-0.07 or octene-1/ethylene mol ratio 0.00-0.05, preferably 0.00-0.02; hydrogen/ethylene mol ratio 0.00-1.5, preferably 0.3-1.0; and iso The amount of pentane is 10-40mol% or the amount of isohexane is 5-20mol% and the recycle stream cooling capacity is at least 60Btu/lb (32.9cal/g), preferably at least 73Btu/lb (40.0cal/g), more preferably at least 75Btu/lb ( 41.1 cal/g) or a condensed wt% of at least 12.

Example 1

Copolymers containing ethylene and butene are prepared by operating a fluidized gas phase reactor using tetrahydrofuran as a catalyst, diethylaluminum chloride for magnesium chloride and titanium chloride (diethylaluminum chloride/tetrahydrofuran molar ratio 0.50) and three Composite of n-hexylaluminum (tri-n-hexylaluminum/tetrahydrofuran molar ratio 0.30) reduced and triethylaluminum-treated silica-impregnated, the activator being triethylaluminum (TEAL).

The data presented in Table 1 and Figure 2 demonstrate the reactor parameters for increased cooling capacity necessary to achieve high reactor yields with increasing isopentane levels. This example shows that excess isopentane causes fluidized bed changes and extreme In case of collapse due to formation of hot spots and agglomerates, the reactor must be shut down. As the concentration of isopentane increases, FBD decreases, indicating a change in the fluidization state of the bed, which increases the bed height. Bed level can be lowered by lowering the catalyst velocity, and the isopentane concentration can also be lowered to reverse the fluidized bed, but at this point, while the bed height returns to normal, the bed collapse from hot spots and agglomerates is irreversible , so the reactor needs to be shut down.

Also, in the second experiment, Table 2 and Figure 3 show that with increasing isopentane concentration, FBD decreases as shown in Table 1, but this time due to decreasing isopentane concentration, FBD is gradually increased, so In this case the change in fluidization state in the bed is recoverable and reversible.

Therefore, Figure 4 shows the results of Figures 1 and 2, where it is clearly shown that the bed fluidization change point is irreversible due to excess use of condensable fluid, defined as the ratio of reactor bed FBD to SBD Points less than 0.59. Example 1 clearly shows that there is a limit to the condensable materials that can be used to optimize the space-time yield or reactor productivity of a reactor operated in condensing mode.

Example 2

The following examples were carried out essentially as in Example 1, using the same catalyst and activator to produce homopolymers and ethylene/butene copolymers in various densities and melt index ranges.

These tests show that higher reactor yields are achieved at condensed liquid levels in excess of 20 wt%, while maintaining the superiority of the FBD to SBD ratio of at least 0.59.

Due to downstream processing, such as product discharge systems and extruders, certain reactor conditions had to be adjusted so as not to exceed the overall plant capacity, so the full advantages of the present invention could not be shown by the examples shown in Table 3.

For example, in Test 1 listed in Table 3, the superficial gas velocity was kept very low, about 1.69 ft/sec (0.52 m/sec), thus reflecting a much lower space-time yield than in other cases. If the speed is maintained at about 2.4 ft/sec (0.73 m/sec), it is estimated that the space-time yield of more than 15.3 lb/hr-ft ³ (243.8 kg/hr-m ³ ) can be achieved. Table 3, Runs 2 and 3. Effect of operating the reactor at high tower gas velocities and wt% condensation well in excess of 20%. The achieved space-time yields were approximately 14.3 lb/hr-ft ³ (227.9 kg/hr-m ³ ) and 13.0 lb/hr-ft ³ (207.2 kg/hr-m ³ ), indicating a significant increase in production rate, such a high STY or production velocity is not disclosed or mentioned at all in the Jenkins et al paper. Similar to Test 1, Test 4 of Table 3 shows that the superficial gas velocity is 1.74 ft/sec (0.53 m/sec) under the condition of 21.8 wt% condensed liquid, but if the velocity in Test 4 is increased to 3.0 ft/sec (0.91 m/sec sec), the achievable STY (space-time yield) can rise from 7.7lb/hr-ft ³ (122.7kg/hr-m ³ ) to 13.3lb/hr-ft ³ (212.0kg/hr-m ³ ), And if the speed in test 5 rises to 3.0ft/sec (0.91m/sec), the achievable space-time yield can rise from 9.8lb/hr-ft ³ (156.2kg/hr-m ³ ) to 17.0lb/hr -ft ³ (270.9kg/hr-m ³ ). For all trials 1-4, the ratio of FBD to SBD remained at least above 0.59.

Example 3

The data listed in each case in Table 4 of Example 3 are obtained by extrapolating the actual operating conditions to the specified target conditions using the thermodynamic equation known in the art. The data in Table 4 demonstrate the superiority of removing the constraints of the ancillary reaction equipment.

In Test 1, the superficial gas velocity increased from 1.69 ft/sec (0.52m/sec) to 2.40 ft/sec (0.73m/sec), compared to the initial 10.8lb/hr-ft ³ (172.1kg/hr-m ³ ) Comparatively, this achieves a higher STY of 15.3 lb/hr-ft ³ (243.8 kg/hr-m ³ ). Further, the inlet recycle stream is cooled from 46.2°C to 40.6°C. This cooling increases the recycle condensate to 34.4 wt%, and can further increase the STY to 18.1 lb/hr- ^ft3 (288.5 kg/hr- ^m3 ). In the final step, the gas composition is changed by increasing the concentration of condensable inert isopentane, thereby increasing the cooling capacity. With this measure, the recycle condensate was further increased to 44.2 wt%, resulting in an STY of 23.3 lb/hr-ft ³ (371.3 kg/hr-m ³ ). Overall, the increasing number of steps in the reactor system resulted in a 116% increase in production capacity.

In Trial 2, the cycle inlet temperature dropped from 42.1°C to 37.8°C, this cooling increased cycle condensate from 25.4 wt% to 27.1 wt% and STY from 14.3 lb/hr-ft ³ (227.9 kg/hr-m ³ ) to 15.6 lb/hr-ft ³ (248.6 kg/hr-m ³ ). Further, the concentration of 6-carbon hydrocarbons increases from 7mol% to 10mol%, and this increase in cooling capacity can increase the STY to 17.8lb/hr-ft ³ (283.7kg/hr-m ³ ). As a final step to show this improvement, the recycle inlet temperature was lowered to 29.4°C. This further cooling achieved an STY of 19.8 lb/hr-ft ³ (315.6 kg/hr-m ³ ), where the recycle stream condensed to 38.6 wt%. Overall, the increasing number of steps in the reactor system resulted in a 39% increase in throughput.

Table 1 time (h) 1 7 10 13 15 17 18 Resin MI(dg/10min) 1.01 1.04 1.03 1.12 1.09 1.11 1.11 Resin density (g/cc) 0.9176 0.9183 0.9190 0.9190 0.9183 0.9193 0.9193 Circular logistics composition: Vinyl 47.4 46.0 44.7 44.1 44.0 45.9 46.3 Butene-1 19.0 18.1 17.3 17.0 16.9 18.5 19.5 Hexene-1 hydrogen 9.5 9.4 9.3 9.3 8.9 8.7 8.9 Isopentane 8.0 10.8 13.7 15.1 15.4 14.3 13.2 6 carbon saturated hydrocarbons nitrogen 14.3 13.9 13.3 12.8 13.2 11.2 10.7 ethane 1.8 1.8 1.7 1.7 1.6 1.4 1.4 methane 8 carbon saturated hydrocarbons Recycle Air Dew Point (°F) 142.9 153.5 163.8 168.3 170.1 168.8 165.0 Circulating gas dew point (℃) 61.6 67.5 73.2 75.7 76.7 76.0 73.9 Reactor inlet temperature (°F) 126.2 135.6 143.5 144.0 149.0 150.2 146.3 Reactor inlet temperature (°C) 52.3 57.6 61.9 62.2 65.0 65.7 63.5 Liquid in circulating gas (wt%) 11.4 12.1 14.3 17.4 14.5 11.6 12.3 Reverse pressure temperature (°F) 182.4 182.1 182.7 182.8 183.1 184.8 185.2 Reactor temperature (°C) 83.6 83.4 83.7 83.8 83.9 84.9 85.1 Reactor pressure (psig) 311.9 311.5 314.2 313.4 314.7 313.5 312.6 Counter pressure (kPag) 2150.5 2147.7 2166.3 2160.8 2169.8 2161.5 2155.3 Reactor superficial gas velocity (Ft/sec) 2.29 2.30 2.16 2.10 1.92 2.00 2.11 Reactor superficial gas velocity (m/sec) 0.70 0.70 0.66 0.64 0.59 0.61 0.64 Reactor bed height (ft) 43.4 43.3 43.5 49.3 51.3 45.8 45.4 Reactor bed height (m) 13.2 13.2 13.3 15.0 15.6 14.0 13.8 Resin SBD(lb/ft ³ ) 30.1 30.2 30.2 30.2 30.0 29.9 29.9 Resin SBD(kg/m ³ ) 482.2 483.8 483.8 483.8 480.6 479.0 479.0 Reactor bed FBD(lb/ft ³ ) 18.9 19.6 18.1 17.8 17.2 16.4 15.8 Reactor bed FBD(kg/m ³ ) 302.8 314.0 290.0 285.2 275.5 262.7 253.1 FBD/SBD ratio 0.63 0.65 0.60 0.59 0.57 0.55 0.53 Space-Time Yield (lb/hr-ft ³ ) 9.6 9.5 9.3 8.5 6.6 7.1 7.3 Space-time yield (kg/hr-m ³ ) 153.0 151.8 149.3 136.0 106.0 113.8 117.2 Production speed(klb/hr) 68.5 67.8 67.0 69.2 56.1 53.8 54.9 Production speed (Tohs/hr) 31.1 30.7 30.4 31.4 25.4 24.4 24.9 Reactor productivity (lb/hr-ft ² ) 415 411 406 419 340 326 332 Production rate of counter pressure (kg/hr-m ² ) 2026 2006 1982 2045 1660 1591 1621 Enthalpy Change of Recycle Stream (Btu/lb) 42 40 40 42 37 34 33 Enthalpy change of recycle stream (Cal/g) twenty three twenty two twenty two twenty three twenty one 19 18

Table 2 time (h) 1 3 5 7 9 11 14 16 18 Resin MI(dg/10min) 0.92 0.99 1.08 1.02 1.05 1.09 1.11 1.05 0.98 Resin density (g/cc) 0.9187 0.9184 0.9183 0.9181 0.9178 0.9177 0.9186 0.9184 0.9183 I Circular logistics composition: Vinyl 52.6 53.2 52.6 52.0 52.1 51.6 52.9 52.8 52.8 Tene-1 20.0 19.8 19.7 20.4 19.7 19.8 19.1 20.1 20.1 Hexene-1 hydrogen 9.7 10.2 10.3 9.9 9.9 9.9 10.4 10.0 9.6 Isopentane 9.9 9.5 10.7 11.2 12.2 12.8 11.5 10.4 9.6 6 carbon saturated hydrocarbons nitrogen 8.7 8.0 7.3 6.7 6.3 6.0 6.5 7.3 8.1 ethane 1.2 1.2 1.1 1.1 1.1 1.1 1.2 1.2 1.3 methane 8 carbon saturated hydrocarbons Recycle Air Dew Point (°F) 154.1 152.5 156.9 160.0 161.9 165.0 159.4 155.9 153.3 Circulating gas dew point (℃) 67.8 66.9 69.4 71.1 72.2 73.9 70.8 68.8 67.4 Reactor inlet temperature (°F) 124.2 118.3 119.7 125.3 127.3 13.2 128.0 126.2 123.0 Reactor inlet temperature (°C) 51.2 47.9 48.7 51.8 52.9 56.2 53.3 52.3 50.6 Liquid in circulating gas (wt%) 22.2 24.9 27.4 26.4 27.0 24.3 23.2 22.1 22.2 Reactor temperature (°F) 184.6 185.2 184.1 183.4 183.5 183.3 182.8 181.9 181.8 Reactor temperature (°C) 84.8 85.1 84.5 84.1 84.2 84.0 83.8 83.3 83.2 Reactor pressure (psig) 314.7 315.2 315.2 315.1 315.3 314.8 312.9 312.9 313.4 Reactor pressure (kPag) 2170.0 2173.3 2173.3 2172.5 2174.2 2170.7 2157.6 2157.7 2160.6 Reactor superficial gas velocity (Ft/see) 1.73 1.74 1.75 1.76 1.77 1.76 1.75 1.74 1.74 Reactor superficial gas velocity (m/see) 0.53 0.53 0.53 0.54 0.54 0.54 0.53 0.53 0.53 Reactor bed height (ft) 44.7 45.0 44.6 44.9 46.0 47.0 45.5 45.6 45.2 Reactor excrement layer height (m) 13.6 13.7 13.6 13.7 14.0 14.3 13.9 13.9 13.8 Resin SBD(l/ft ³ ) 29.9 29.9 29.7 28.8 29.O 29.1 29.3 29.4 29.4 Resin SBD(kg/m ³ ) 479.0 479.0 475.8 461.4 464.6 465.4 468.6 471.3 471.8 Reactor bed FBD (Ib/ft ³ ) 20.2 20.7 19.6 19.3 18.2 17.1 18.5 19.2 20.0 Reactor bed FBD(kg/m ³ ) 323.9 330.9 314.4 309.9 291.1 274.3 296.2 308.1 321.1 FBD/SBD ratio 68 69 66 67 63 59 63 65 68 Space-Time Yield (lb/hr-ft ³ ) 9.7 10.3 11.1 11.1 11.1 9.9 9.3 9.1 9.2 Space-time yield (kg/hr-m ³ ) 154.9 165.1 178.1 178.0 177.0 158.4 149.1 144.9 147.3 Production speed(klb/hr) 71.3 76.6 82.2 82.3 84.0 76.8 69.9 68.0 68.5 Production speed(Tons/hr) 32.3 34.7 37.3 37.3 38.1 34.8 31.7 30.8 31.1 Reactor productivity (lb/hr-ft ² ) 432 464 498 498 509 465 423 412 415 Reactor productivity (kg/hr-m ² ) 2109 2265 2413 2413 2485 2270 2065 2011 2026 Enthalpy Change of Recycle Stream (Btu/lb) 54 59 61 60 61 55 52 51 52 Enthalpy change of recycle stream (Cal/g) 30 33 34 33 34 31 29 28 29

table 3 test 1 2 3 4 5 Resin MI(dg/10min) 0.86 6.74 7.89 22.22 1.91 Resin density (g/cc) 0.9177 0.9532 0.9664 0.9240 0.9186 Circular logistics composition: Vinyl 53.1 40.5 49.7 34.1 44.0 Butene-1 20.2 14.9 18.2 Hexene-1 0.6 hydrogen 8.9 17.7 26.5 25.0 11.9 Isopentane 9.7 3.7 0.7 14.1 9.6 6 carbon saturated hydrocarbons 7.0 10.2 nitrogen 8.7 19.2 8.8 9.4 14.9 ethane 1.7 9.4 4.0 2.5 3.3 methane 1.1 0.3 8 carbon saturated hydrocarbons 0.4 0.5 Recycle Air Dew Point (°F) 154.0 172.6 181.6 162.1 148.5 Circulating gas dew point (℃) 67.8 78.1 83.1 72.3 64.7 Reactor inlet temperature (°F) 115.2 107.8 117.7 135.0 114.2 Reactor inlet temperature (°C) 46.2 42.1 47.6 57.2 45.7 Liquid in circulating gas (wt%) 28.6 25.4 27.6 21.8 24.4 Reactor temperature (°F) 183.3 208.4 209.3 178.0 183.7 Reactor temperature (°C) 84.1 98.0 98.5 81.1 84.3 Counter pressure (psig) 315.7 300.2 299.8 314.7 314.3 Reactor pressure (kPag) 2176.7 2069.7 2066.8 2169.8 2167.2 Reactor superficial gas velocity (Ft/sec) 1.69 2.76 2.36 1.74 1.73 Reactor superficial gas velocity (m/sec) 0.52 0.84 0.72 0.53 0.53 Reactor bed height (ft) 47.2 43.0 42.0 44.3 45.6 Reactor bed height (m) 14.4 13.1 12.8 13.5 13.9 Resin SBD(lb/ft ³ ) 28.3 23.2 29.0 24.5 29.3 Resin wax SBD(kg/m ³ ) 453.4 371.0 464.0 392.5 468.6 Reactor bed FBD(lb/ft ³ ) 19.6 16.7 21.7 15.7 19.1 Reactor bed FBD(kg/m ³ ) 314.0 267.9 347.4 251.5 305.7 FBD/SBD ratio 0.69 0.72 0.75 0.64 0.65 Space-Time Yield (lb/hr-ft ³ ) 10.8 14.3 13.0 7.7 9.8 Space-time yield (kg/hr-m ³ ) 172.8 228.8 208.0 123.2 157.2 Production speed(klb/hr) 83.7 101.2 90.2 56.6 73.7 Production speed(Tons/hr) 38.0 45.9 40.9 25.7 33.4 Reactor productivity (lb/hr-ft ² ) 507 613 546 343 446 Reactor productivity (kg/hr-m ² ) 2475 2992 2665 1674 2177 Enthalpy Change of Recycle Stream (Btu/lb) 65 67 75 49 60 Enthalpy change of recycle stream (Cal/g) 36 37 42 27 33

Table 4 test 1 test 2 love 1 2 3 4 1 2 3 4 Resin MI(dg/10min) 0.86 6.74 Resin (g/cc) 0.9177 0.9532 Circular logistics composition: Vinyl 53.1 53.1 53.1 53.1 40.5 40.5 40.5 40.5 Butene-1 20.2 20.2 20.2 20.2 Hexene-1 0.6 0.6 0.6 0.6 hydrogen 8.9 8.9 8.9 8.9 17.7 17.7 17.7 17.7 Isopentane 9.7 9.7 9.7 9.7 3.7 3.7 3.7 3.7 6 carbon saturated hydrocarbons 7.0 7.0 10.0 10.0 nitrogen 8.7 8.7 8.7 5.9 19.2 19.2 17.2 17.2 ethane 1.7 1.7 1.7 1.2 9.4 9.4 8.5 8.5 methane 1.1 1.1 1.0 1.0 8 carbon saturated hydrocarbons 0.4 0.4 0.4 0.4 Recycle Air Dew Point (°F) 154.0 154.0 154.0 167.9 172.6 172.6 188.3 188.3 Circulating gas dew point (℃) 67.8 67.8 67.8 75.5 78.1 78.1 86.8 86.8 Reactor inlet temperature (°F) 115.2 115.2 105.0 105.0 107.8 100.0 100.0 85.0 Reactor inlet temperature (°C) 46.2 46.2 40.6 40.6 42.1 37.8 37.8 29.4 Liquid in circulating gas (wt%) 28.6 28.6 34.4 44.2 25.4 27.1 35.9 38.6 Reactor temperature (°F) 183.3 183.3 183.3 183.3 208.4 208.4 208.4 208.4 Reactor temperature (°C) 84.1 84.1 84.1 84.1 98.0 98.0 98.0 98.0 Reactor pressure (psig) 315.7 315.7 315.7 315.7 300.2 300.2 300.2 300.2 Reactor pressure (kPag) 2176.7 2176.7 2176.7 2176.7 2069.7 2069.7 2069.7 2069.7 Reactor superficial gas velocity (Ft/sec) 1.69 2.40 2.40 2.40 2.76 2.76 2.76 2.76 Reactor superficial gas velocity (m/sec) 0.52 0.73 0.73 0.73 0.84 0.84 0.84 0.84 Reactor bed height (ft) ) 47.2 47.2 47.2 47.2 43.0 43.0 43.0 43.0 Reactor bed height (m) 1) 14.4 14.4 14.4 14.4 13.1 13.1 13.1 13.1 Space-Time Yield (lb/hr-ft ² ) 10.8 15.3 18.1 23.3 14.3 15.6 17.8 19.8 Space-time yield (kg/hr-m ² ) 172.8 245.4 290.3 372.2 228.8 249.9 284.4 317.6 Production speed(klb/hr) 83.7 118.9 140.6 180.3 101.2 110.5 125.8 140.5 Production speed(Tons/hr) 38.0 53.9 53.8 81.7 45.9 50.1 57.0 63.7 Reactor productivity (lb/hr-ft ² ) 507 720 851 1092 613 669 762 851 Reactor productivity (kg/hr-m ² ) 2475 3515 4154 5331 2992 3266 3720 4154 Enthalpy Change of Recycle Stream (Btu/lb) 67 67 77 95 69 76 81 90 Enthalpy change of recycle stream (Cal/g) 37 37 43 53 38 42 45 50

Claims (27)

1. A fluidized bed polymerization process comprising passing a gaseous stream containing monomer under reaction conditions through a fluidized bed reactor in the presence of a catalyst to produce a polymerized product and a stream containing unreacted monomer gas, said stream being compressed and mixed with the feed components after cooling and returning the gas and liquid phases to said reactor, the modification comprising cooling said stream such that the liquid phase reaches greater than 20 wt% to 44.2 wt% of the total weight of the returned stream and stable as determined by Operating conditions: (a) observing changes in the fluidized bulk density or its indicator parameters in relation to changes in the composition of the fluidized medium in the reactor; and (b) Improve the cooling capacity of the circulating stream by changing the composition of the stream, wherein the decrease in the fluidized bulk density cannot make the ratio of the fluidized bulk density to the deposited bulk density lower than 0.59. 2. The method according to claim 1, wherein the liquid phase is 22.1-44.2 wt% of the total weight of the return stream. 3. The method according to claim 2, wherein the liquid phase is 25-44.2 wt% of the total weight of the return stream. 4. The method according to claim 3, wherein the liquid phase is 28.6-44.2wt% of the total weight of the return stream. 5. 4. A method according to any one of claims 1-4, wherein the composition of the stream is such that the ratio of fluidized bulk density to deposited bulk density exceeds 17.8:30.2. 6. The method according to claim 5, wherein the composition of the stream is such that the ratio of the fluidized bulk density to the deposited bulk density exceeds 18.1:30.2. 7. A method according to any one of claims 1-4, comprising detecting when the reactor is approaching a condition related to an irreversible change in fluidized bed density or an indicative parameter thereof and adjusting the reactor conditions with compositional changes if necessary to maintain the reactor under stable operating conditions. 8. 2. The method of claim 1, wherein the bulk density of the fluidized bed is observed using a pressure measurement in a portion of the fluidized bed above the distribution plate which is not susceptible to disturbance. 9. The method according to claim 1, wherein the cooling capacity is increased by increasing the proportion of the composition which increases the dew point. 10. The method according to claim 9, wherein the proportion of non-polymerizable higher hydrocarbon components is increased. 11. The method according to claim 10, wherein the non-polymerizable component is a saturated hydrocarbon having 2 to 8 carbon atoms or a mixture thereof. 12. The method according to claim 11, wherein said saturated hydrocarbon is selected from the group consisting of propane, n-butane, isobutane, n-pentane, isopentane, neopentane, n-hexane, isohexane and other saturated 6-carbon hydrocarbons, n-heptane alkanes, n-octane and other saturated 7 or 8 carbon hydrocarbons or mixtures thereof. 13. The method according to claim 12, wherein said saturated hydrocarbon is a 5 or 6 carbon saturated hydrocarbon or a mixture thereof. 14. The method according to claim 9, wherein the proportion of polymerizable monomers including 3-12 carbon comonomers is increased by reducing the proportion of non-condensable inert components. 15. A process according to claim 1, wherein the stream is cooled and passed through the reactor at a rate such that the achievable reactor yield exceeds 2441 kg/hr- ^m2 . 16. The method according to claim 15, wherein the reactor production rate exceeds 2929 kg/hr- ^m2 . 17. A process according to claim 1, wherein the liquid and gaseous components of the stream are fed as a mixture below the reactor distributor plate. 18. The method according to claim 1, wherein the butene/ethylene mol ratio in the recycle stream is 0.00-0.60, or the 4-methylpentene-1/ethylene mol ratio is 0.00-0.50, or the hexene/ethylene mol ratio is 0.00-0.00- 0.30, or an octene-1/ethylene mol ratio of 0.00-0.10, a hydrogen/ethylene mol ratio of 0.00-0.4, and based on the stream containing 3-20 mol% isopentane or 1.5-10 mol% isohexane as condensable inert fluid. 19. The method according to claim 18, wherein the condensable inert fluid is isopentane. 20. The method according to claim 1, wherein the butene/ethylene mol ratio in the recycle stream is 0.00-0.60, or the 4-methylpentene-1/ethylene mol ratio is 0.00-0.50, or the hexene/ethylene mol ratio is 0.00-0.00- 0.30, or an octene-1/ethylene mol ratio of 0.00-0.10, a hydrogen/ethylene mol ratio of 0.00-1.6, and based on this stream containing 3-30 mol% isopentane or 1.5-15 mol% isohexane as condensable inert fluid. twenty one. The method according to claim 20, wherein the condensable inert fluid is isopentane. twenty two. A method according to claim 18 or 20, wherein the recycle stream has a cooling capacity of at least 21.9 cal/g. twenty three. The method according to claim 22, wherein the cooling capacity of the recycle stream is at least 27.4 cal/g. twenty four. The method according to claim 1, wherein the butene/ethylene mol ratio in the recycle stream is 0.00-0.30, or the 4-methylpentene-1/ethylene mol ratio is 0.00-0.25, or the hexene/ethylene mol ratio is 0.00-0.00- 0.15, or an octene-1/ethylene mol ratio of 0.00-0.05, a hydrogen/ethylene mol ratio of 0.00-1.50, and based on the stream containing 10-40 mol% isopentane or 5-20 mol% isohexane as condensable inert fluid. 25． The method according to claim 24, wherein the condensable inert fluid is isopentane. 26． The method according to claim 24, wherein the cooling capacity of the recycle stream is at least 41.1 cal/g. 27． The method according to claim 26, wherein the cooling capacity of the recycle stream is at least 43.8 cal/g.

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