Improved preparation device and method of polypropylene

Abstract

The invention discloses an improved preparation device and method of polypropylene. The device comprises a polymerization unit, a steaming unit and a drying unit, the polymerization unit comprises a pre-polymerization kettle, a first reactor, a first reaction condenser, a first propylene condensate tank and a second reactor; the first reactor is communicated with the prepolymerization kettle; the first reaction condenser is communicated with the top of the first reactor; the top of the first propylene condensate tank is respectively communicated with the first reaction condenser and the first reactor, and the bottom of the first propylene condensate tank is communicated with the first reactor; the top of the second reactor is communicated with the bottom of the first reactor. According to the preparation device and method of polypropylene, the production cost can be reduced, and the cleanliness of the obtained product is high.

Description

Technical Field

[0001] The invention relates to the technical field of a polypropylene production device and process, and in particular to an improved polypropylene preparation device and method. Background Art

[0002] At present, there are two mainstream polypropylene production process technologies in the world: bulk-gas phase combined process and gas phase process. Among them, the reactor form of the bulk-gas phase combined process is loop reactor + fluidized bed reactor; the gas phase process has various forms of reactors, including: fluidized bed reactor + fluidized bed reactor, vertical kettle reactor + vertical kettle reactor, horizontal kettle reactor + horizontal kettle reactor and multi-zone circulation reactor + fluidized bed reactor. Local hot spots are easily formed in the gas phase reactor, causing polymer agglomeration, thereby causing device agglomeration. To solve this problem, most of the gas phase reactors are equipped with mechanical stirring. The forced mechanical stirring makes the wet material evenly distributed, thereby reducing the probability of hot spots appearing during the reaction. However, the reactor and its agitator and the mechanical seal between the two are difficult to design, difficult to process and manufacture, and require high processing precision, that is, the design, processing and later maintenance costs are very high. The bulk-gas phase combined process avoids the "hot spot" problem, and the device can operate reliably for a long time. Compared with the gas phase method, the combined process of bulk method and gas phase method has many advantages, but it also has the following problems: 1. No co-polymers can be evaporated from slurry polymerization at 70°C; 2. The steam consumption is large; 3. The co-polymers and other heavy components and high molecular weight powders obtained by washing in the high-pressure propylene washing tower are all returned to the finished product. If they are not returned, it will greatly affect the unit consumption.

[0003] The applicant has previously filed an invention patent with application number CN202211075974.7 and invention name "A device and method for preparing SPGⅡ polypropylene". The present invention is an improvement on the invention. In the invention of CN202211075974.7, the applicant found that if the second reactor and the third reactor simultaneously produce the same brand of products, the production method in the invention will cause complexity in the control process; secondly, in the temperature control of CN202211075974.7, due to the setting error of the sensor, there are some problems of increased error and fluctuation; in addition, there is also a problem of low efficiency in the subsequent processing of the product such as material connection; finally, in the treatment of propylene tail gas, there is still room for improving environmental protection and recovery efficiency. Summary of the invention

[0004] To solve the above problems existing in the bulk method-gas phase combination process, especially the above problems existing in the invention of CN202211075974.7.

[0005] In order to achieve the above object, the present invention provides the following technical scheme: an improved preparation device for polypropylene, comprising a polymerization unit, a steaming unit and a drying unit; the polymerization unit comprises a prepolymerization kettle, a first reactor, a first reaction condenser, a first propylene condensate tank and a second reactor; the first reactor is connected to the prepolymerization kettle; the first reaction condenser is connected to the top of the first reactor; the top of the first propylene condensate tank is connected to the first reaction condenser and the first reactor respectively, and the bottom of the first propylene condensate tank is connected to the first reactor; the top of the second reactor is connected to the bottom of the first reactor; the polymerization unit also includes a third reactor, a third reaction cyclone separator, a third reaction condenser and a third propylene condensate tank, the third reaction cyclone separator is connected to the top of the third reactor, the third reaction condenser is connected to the top of the third reaction cyclone separator, the third propylene condensate tank is connected to the third reaction condenser, and the third propylene condensate tank is also connected to the third reactor; the second reactor and the third reactor are connected in series or in parallel; it is characterized in that when the second reactor and the third reactor simultaneously produce products of the same brand, the same process control parameters are adopted.

[0006] As a preferred technical solution of the present invention, the first reactor is provided with a first controller, which stores initial control process parameters and can execute the initial control process parameters; the second reactor is provided with a second controller, which stores second reactor control process parameters and can execute the second reactor control process parameters; the third reactor is provided with a third controller, which stores third reactor control process parameters and can execute the third reactor control process parameters; the second reactor control process parameters follow the second reactor control model, and the third reactor control process parameters follow the third reactor control model, wherein a device data collector and a device controller are provided in the polypropylene preparation device, the device data collector collects signals transmitted by various sensors, the device controller processes various sensor signals collected by the device data collector through a preprocessor, and classifies these sensor signals, and transmits the classified signals to the first controller, the second controller and the third controller respectively. wherein the signals transmitted to the second controller and the third controller are respectively calculated by using the preset control models of each reactor to calculate the corresponding signal data, and the calculated signal data are compared with the signal data of the last execution. If the signal data of the two comparisons are within the prescribed threshold range, the preset weight of the control model is adjusted until the calculated signal data and the target value are minimized, and then the execution is performed; if the signal data of the two comparisons exceed the prescribed threshold range, the signal transmitted to the second controller and the signal transmitted to the third controller are exchanged, that is, the signal transmitted to the second controller is transmitted to the signal of the third controller, and the signal transmitted to the third controller is transmitted to the signal of the second controller, and then the comparison is performed again. If the compared signal data are within the prescribed threshold range, the preset weight of the control model is adjusted until the calculated signal data and the target value are minimized, and then the execution is performed; if the compared signal data still exceeds the prescribed threshold range, the signal data of the last time is executed, and the above process is repeated during the next execution.

[0007] As a preferred technical solution of the present invention, the polymerization unit further includes a second reaction cyclone separator, a second reaction condenser, and a second propylene condensate tank, wherein the second reaction cyclone separator is connected to the top of the second reactor, the second reaction condenser is connected to the top of the second reaction cyclone separator, the second propylene condensate tank is connected to the second reaction condenser, and the second propylene condensate tank is also connected to the second reactor; an air lock and a reversing valve are also provided between the second reactor and the third reactor, and the reversing valve is a 30° reversing valve, a 60° reversing valve or a 120° reversing valve; the second reactor and the third reactor are single air bag type or double air bag type; the products output by the second reactor and the third reactor are controlled by a product output controller; the product output controller reads the output predetermined signals of the second reactor and the third reactor respectively, and makes corresponding material receiving preparations according to the output predetermined signals of the second reactor and the third reactor, and when the output predetermined signal is sent to the product output controller, the corresponding material receiving equipment receives the material.

[0008] As a preferred technical solution of the present invention, the steaming unit comprises: a bag filter, a propylene cooler, a propylene gas buffer tank, a steamer, a steamer cyclone separator, a steamer washing tower and a hydrocarbon-water separation tank; the top of the bag filter is connected to the propylene cooler and the propylene gas buffer tank in sequence, and the bottom of the bag filter is connected to the steamer; the top of the steamer is connected to the steamer cyclone separator; the bottom of the steamer cyclone separator is connected to the steamer; the top of the steamer cyclone separator is connected to the steamer washing tower; the middle and upper parts of the steamer washing tower are connected to the hydrocarbon-water separation tank; the steamer washing tower is an integrated or split condenser and washing tower.

[0009] As a preferred technical solution of the present invention, the drying unit includes: a dryer, a dryer cyclone separator, a first powder hopper, a second powder hopper, a dry gas scrubber, a plate heat exchanger, a wire mesh demister, a dry gas circulation fan and a dry gas heater; the bottom of the dryer is connected to the second powder hopper, the top of the dryer is connected to the middle and upper part of the dryer cyclone separator, the bottom of the dryer cyclone separator is connected to the first powder hopper, the top of the dryer cyclone separator is connected to the middle and lower part of the dry gas scrubber, the top of the dry gas scrubber is connected to the wire mesh demister, and the wire mesh demister is connected to the dry gas circulation fan, the dry gas heater and the dryer in sequence. The bottom is connected; an overflow plate and a plurality of distribution plates are arranged in the dryer, and the plurality of distribution plates are evenly distributed; a rotary discharge valve is arranged at the bottom of the dryer cyclone separator, the first powder hopper and the second powder hopper; the rotary discharge valve is a pneumatic plug valve, or two valves are combined into a Y-type reversing valve; the plate heat exchanger is a shell and tube heat exchanger; the drying gas heater is a shell and tube heat exchanger or a fin heat exchanger or an electric heater; the polypropylene preparation device also includes a propylene tail gas treatment device, which is arranged on a base and includes a nitrogen charging device, a gas mixing chamber, a tail gas adsorption chamber and a tail gas outlet chamber, and the nitrogen charging device, the gas mixing chamber, the tail gas adsorption chamber and the tail gas outlet chamber are connected to each other.

[0010] As a preferred technical solution of the present invention, a method for preparing polypropylene comprises the steps of (1): inputting a reaction raw material containing propylene into a prepolymerization kettle for prepolymerization reaction, inputting a product of the prepolymerization reaction into a first reactor for a first polymerization reaction, and removing reaction heat by vaporizing propylene during the first polymerization reaction;

[0011] Step (2): introducing the product of the first polymerization reaction in step (1) into a second reactor for a first gas phase reaction, wherein the reaction heat is removed by vaporizing propylene during the first gas phase reaction;

[0012] Step (3): subjecting the product of the first gas phase reaction in step (2) to a first gas-solid separation, recycling the separated gas, and steaming the separated solid to remove organic matter and oligomers in the product; and drying the wet material after steaming to obtain polypropylene.

[0013] As a preferred technical solution of the present invention, in step (1), the reaction raw materials include propylene, a main catalyst, a co-catalyst, an electron donor and mineral oil, the main catalyst is a titanium magnesium catalyst TiCl4 / MgCl2; the co-catalyst is a trialkyl aluminum compound, the trialkyl aluminum compound is at least one of triethyl aluminum and tri-n-butyl aluminum; the electron donor is at least one of dicyclopentyldimethoxysilane, cyclohexyldimethoxysilane and triethoxysilane; the pressure of the prepolymerization reaction is 2.0~6.0MPaG, the temperature is -5~70°C, and the reaction time is 8~30 minutes; the pressure of the first polymerization reaction is 2.0~4.0MPaG, the temperature is 30~95°C, and the reaction time is 0.5~2 hours; in the reaction raw materials, propylene gas formed by partial propylene vaporization due to the heat release of the first polymerization reaction is condensed and then subjected to gas-liquid separation, the gas obtained by the gas-liquid separation is returned to the first reactor as a reaction raw material for recycling, and the liquid obtained by the gas-liquid separation is used for heat removal of the first polymerization reaction in the first reactor.

[0014] As a preferred technical solution of the present invention, in step (2), the pressure of the first gas phase reaction is 1.5-2.7 MPaG, the temperature is 70-150°C, and the time is 3-4 hours. In step (2), during the first gas phase reaction, gas carrying solid particles is discharged from the top of the second reactor, the gas carrying solid particles is subjected to a second gas-solid separation, the gas obtained by the second gas-solid separation is condensed and returned to the second reactor as a reaction raw material for recycling or for removing heat from the first gas phase reaction in the second reactor, and the solid obtained by the second gas-solid separation is mixed with ethylene and hydrogen and returned to the second reactor to repeat the first gas phase reaction.

[0015] As a preferred technical solution of the present invention, step (2-1) is further included between step (2) and step (3); step (2-1) is: the product of the first gas phase reaction in step (2) is input into a third reactor for a second gas phase reaction, and the reaction heat is removed by vaporizing propylene during the second gas phase reaction; the gas phase product obtained in the second gas phase reaction is subjected to a third gas-solid separation, the gas obtained by the third gas-solid separation is condensed and returned to the third reactor as a reaction raw material for recycling or for removing heat from the second gas phase reaction in the third reactor, and the solid obtained by the third gas-solid separation is mixed with ethylene and hydrogen and returned to the third reactor for the second gas phase reaction again; the pressure of the second gas phase reaction is 1.0-2.0 MPaG, the temperature is 70-150°C, and the time is 2-3 hours.

[0016] As a preferred technical solution of the present invention, the drying adopts a vertical fluidized bed and uses circulating nitrogen to remove moisture.

[0017] Compared with the prior art, the present invention provides a method having the following beneficial effects: the present invention provides an improved device and method for preparing polypropylene, the device for preparing polypropylene of the present invention can reduce production costs, and the product brand switching is flexible, and the obtained product has high cleanliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A process flow chart of a polymerization unit of an embodiment of a polypropylene preparation device of the present invention;

[0019] Figure 2 A process flow chart of a steaming unit of an embodiment of a polypropylene preparation device of the present invention;

[0020] Figure 3 A process flow chart of a drying unit of an embodiment of a polypropylene preparation device of the present invention;

[0021] Figure 4 The dimension N×M created for all temperature-time curves of the present invention is a data set;

[0022] Figure 5 The propylene tail gas treatment device of the present invention;

[0023] Figure 6 A diagram of a portion of the area not actually equipped with the present invention;

[0024] In the figure: 101-propylene feed tank, 102-propylene feed pump, 103-feed pump cooler, 104-prepolymerization kettle, 105-first reactor, 106-first reaction condenser, 107-first propylene condensate tank, 108-first reaction circulation fan, 109-second reactor, 110-second reaction cyclone separator, 111-second reaction condenser, 112-second propylene condensate tank, 113-first propylene condensate pump, 114-second reaction circulation fan, 115-reversing valve, 116-air lock, 117-third reactor, 118-third reaction cyclone separator, 119-third reaction condenser, 120-third propylene condensate tank, 121-second propylene condensate pump, 122-third reaction circulation fan, 123-first rotary discharge valve, 124-first ejector, 125-second rotary discharge valve, 126-second ejector, 20 1-bag filter, 202-steamer, 203-propylene cooler, 204-propylene gas buffer tank, 205-propylene gas booster fan, 206-steamer cyclone separator, 207-third rotary discharge valve, 208-steamer washing tower, 209-drain valve, 210-washing tower circulation pump, 211-hydrocarbon water separation tank, 301-dryer, 302-dryer cyclone separator, 303-fourth rotary discharge valve, 304- The first powder hopper, 305-the fifth rotary unloading valve, 306-the dry gas washing tower, 307-the washing liquid circulation pump, 308-the plate heat exchanger, 309-the wire mesh demister, 310-the dry gas circulation fan, 311-the dry gas heater, 312-the second powder hopper, 313-the sixth rotary unloading valve, 314-the seventh rotary unloading valve, 315-the third ejector, 316-the fourth ejector, 317-the fifth ejector. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] The polypropylene preparation device of the present invention comprises: a polymerization unit, a steaming unit and a drying unit.

[0029] Please refer to Figure 1 , Figure 1 The process flow chart of the polymerization unit of one embodiment of the polypropylene preparation device of the present invention. In this embodiment, the polymerization unit includes: a prepolymerization kettle 104, a first reactor 105, a first reaction condenser 106, a first propylene condensate tank 107 and a second reactor 109; the first reactor 105 is connected to the prepolymerization kettle 104; the first reaction condenser 106 is connected to the top of the first reactor 105; the top of the first propylene condensate tank 107 is connected to the first reaction condenser 106 and the first reactor 105 respectively, and the bottom of the first propylene condensate tank 107 is connected to the first reactor 105; the top of the second reactor 109 is connected to the bottom of the first reactor 105.

[0030] Propylene is input into a propylene feed tank 101, and the propylene is transported to a feed pump cooler 103 through a propylene feed pump 102, and then cooled and mixed with a main catalyst, a co-catalyst, an electron donor and mineral oil to form a reaction raw material containing propylene, and then input into a prepolymerization reactor 104, wherein the main catalyst of the present invention includes but is not limited to a titanium magnesium catalyst TiCl4 / MgCl2, the co-catalyst includes but is not limited to a trialkyl aluminum compound, the trialkyl aluminum compound includes but is not limited to at least one of triethyl aluminum and tri-n-butyl aluminum, the electron donor includes but is not limited to at least one of dicyclopentyldimethoxysilane, cyclohexyldimethoxysilane and triethoxysilane, the mass ratio of the main catalyst of the present invention to the electron donor includes but is not limited to 1:0.01-1:100, the mass ratio of the main catalyst of the present invention to propylene includes but is not limited to 1:20000-1:100000, the mass ratio of the main catalyst of the present invention to the co-catalyst includes but is not limited to 1:0.01-1:50, and the mass ratio of the main catalyst of the present invention to mineral oil includes but is not limited to 1:1-1:1000. The reaction raw materials are prepolymerized in the prepolymerization kettle 104. The pressure of the prepolymerization reaction is 2.0-6.0 MPaG, the reaction temperature is -5-70°C, and the reaction time is 8-30 minutes. During the prepolymerization reaction, the reaction heat can be withdrawn through the jacket and the inner cooling pipe of the prepolymerization kettle 104 through circulating water, so as to ensure the temperature stability during the reaction.

[0031] After the prepolymerization reaction is completed, the reaction slurry in the prepolymerization kettle 104 is pressed to the first reactor 105 by its own pressure, and then the first polymerization reaction is carried out in the first reactor 105. The pressure of the first polymerization reaction is 2.0~4.0MPaG, the reaction temperature is 30~95°C, and the reaction time is 0.5~2 hours. The temperature during the first polymerization reaction can be controlled by the following method: at the initial stage of the reaction, hot water is introduced into the jacket of the first reactor 105, the temperature of the reaction slurry in the first reactor 105 increases, and then the first polymerization reaction occurs. As the first polymerization reaction occurs, the temperature in the first reactor 105 increases. The hot water in the jacket of the first reactor 105 can be withdrawn and circulating cooling water can be introduced to ensure temperature stability during the reaction. Since the first polymerization reaction is an exothermic reaction, the heat released during the first polymerization reaction vaporizes part of the propylene in the reaction slurry to form propylene gas. The propylene gas is discharged from the top of the first reactor 105 and enters the first reaction condenser 106. The propylene gas is condensed into liquid propylene by the first reaction condenser 106 and flows into the first propylene condensate tank 107 for gas-liquid separation. The liquid obtained by the gas-liquid separation flows back to the first reactor 105 for recycling and is used for removing heat from the first polymerization reaction in the first reactor 105. The gas obtained by the gas-liquid separation is propylene gas, which is pressurized by the first reaction circulation fan 108 and returned to the first reactor 105 for recycling as a reaction raw material.

[0032] When the reaction in the first reactor 105 is complete, the reaction product in the first reactor 105 is pressed by its own pressure to the second reactor 109 for a first gas phase reaction. The pressure of the first gas phase reaction is 1.5-2.7 MPaG, the reaction temperature is 70-150°C, and the reaction time is 3-4 hours. Part of the propylene gas in the second reactor 109 carries a small amount of powder and is discharged from the gas bag of the second reactor 109 and enters the second reaction cyclone separator 110 for second gas-solid separation. The propylene gas obtained by the second gas-solid separation is condensed by the second reaction condenser 111 and enters the second propylene condensate tank 112. The liquid propylene collected in the second propylene condensate tank 112 and the newly added fresh propylene are transported to the second reactor 109 through the first propylene condensate pump 113. The fresh propylene is used as the reaction raw material for the first gas phase reaction; the liquid propylene condensed by the second reaction condenser 111 is used for heat removal of the first gas phase reaction in the second reactor 109; the gas in the second propylene condensate tank 112 is pressurized by the second reaction circulation fan 114 and then returned to the second reactor 109 in two ways, one part of which transports the solid powder separated by the second reaction cyclone separator 110 to the second reactor 109 for further polymerization, and the other part directly enters the second reactor 109 to participate in the polymerization reaction. Ethylene and hydrogen are introduced into the second propylene condensate tank 112 to adjust different product grades. Some grades of products are produced in the second reactor 109 and transported to the steaming unit through the reversing valve 115. Some grades of products need to continue to react in the third reactor 117, so the materials in the second reactor 109 enter the third reactor 117 through the reversing valve 115 for the second gas phase reaction. The reversing valve 115 can be a 30° reversing valve, a 60° reversing valve, and a 120° reversing valve.

[0033] When the first gas phase reaction in the second reactor 109 is completed, the reaction product in the second reactor 109 is pressed into the gas lock 116 by its own pressure. The gas lock 116 is used to isolate the second reactor 109 and the third reactor 117 production lines. Part of the gas enters the propylene recovery system through the gas lock 116 to adjust the reaction pressure in the third reactor 117; part of the gas and all the solids enter the third reactor 117 for a second gas phase reaction. The pressure of the second gas phase reaction is 1.0-2.0 MPaG, the reaction temperature is 70-150°C, and the reaction time is 2-3 hours. Part of the propylene gas in the third reactor 117 carries a small amount of powder and is discharged from the gas bag of the third reactor 117 and enters the third reaction cyclone separator 118 for the third gas-solid separation. The separated propylene gas is condensed by the third reaction condenser 119 and enters the third propylene condensate tank 120. The liquid propylene collected in the third propylene condensate tank 120 and the newly added fresh propylene are transported to the third reactor 117 through the second propylene condensate pump 121. The fresh propylene is used as the raw material for the second gas phase reaction; the liquid propylene condensed by the third reaction condenser 119 is used for heat removal of the polymerization reaction in the third reactor 117; the gas in the third propylene condensate tank 120 is pressurized by the third reaction circulation fan 122 and then returned to the third reactor 117 in two ways, one part of which transports the solid powder separated by the third reaction cyclone separator 118 to the third reactor 117 for further polymerization, and the other part directly enters the third reactor 117 to participate in the polymerization reaction. Ethylene and hydrogen are introduced into the third propylene condensate tank 120 to adjust different product grades. After the reaction is completed, the materials in the reactor enter the steaming process.

[0034] A first rotary discharge valve 123 and a first ejector 124 are provided at the bottom of the second reaction cyclone separator 110, and a second rotary discharge valve 125 and a second ejector 126 are provided at the bottom of the third reaction cyclone separator 118. The first rotary discharge valve 123, the first ejector 124, the second rotary discharge valve 125 and the second ejector 126 are used for discharging materials from the second reaction cyclone separator 110 and the third reaction cyclone separator 118. The first rotary discharge valve 123 and the second rotary discharge valve 125 can be pneumatic gate valves or hand valves.

[0035] The second reactor 109 and the third reactor 117 can be connected in series or in parallel; the second reactor 109 and the third reactor 117 are of single air bag type or double air bag type.

[0036] Please refer to Figure 2 , Figure 2The process flow chart of the steaming unit of one embodiment of the polypropylene preparation device of the present invention is as follows. The propylene gas and solid polypropylene mixture from the polymerization unit enters the bag filter 201 for the first gas-solid separation, and the separated propylene gas is output through the pipe port above the bag filter 201 and enters the propylene cooler 203 to exchange heat with the circulating cooling water, and then enters the propylene gas buffer tank 204, and then after being pressurized by the propylene gas booster fan 205, a small part enters the bag filter 201 for backblowing of the cloth bag inside, and most of it enters the propylene recovery process. The polypropylene solid powder separated by the bag filter 201 flows into the steamer 202 by gravity to further remove the propylene gas in the material; the polypropylene solid powder entering the steamer 202 is fully mixed and contacted with the low-pressure steam introduced from the bottom and middle of the steamer 202 under the mechanical stirring of the steamer stirrer, and the propylene gas in the polypropylene solid powder is taken out by the low-pressure steam; the low-pressure steam, propylene gas and a small amount of solid particles leave the top of the steamer 202 and enter the steamer cyclone separator 206 for gas-solid separation, and the solid material separated by the steamer cyclone separator 206 is discharged through the third rotary discharge valve 207. The steam in the process gas is condensed, and the uncondensed part of the gas is further condensed through the condenser at the top of the steamer washing tower 208, and the condensate is refluxed to the steamer washing tower 208. The non-condensable gas is propylene gas, and the part of the propylene gas enters the propylene recovery process for recovery.

[0037] The mineral oil added to the polymerization unit to dissolve the main catalyst, co-catalyst and electron donor is discharged from the middle and upper part of the steamer washing tower 208 to the hydrocarbon water separation tank 211. Most of the hot water in the hydrocarbon water separation tank 211 is sucked in by the washing tower circulation pump 210, and a small amount of oil, hydrocarbon and hot water are discharged from the system through the upper part of the hydrocarbon water separation tank 211. The steam condensate condensed by the steamer washing tower 208 is transported to the steam system for recycling. When the steamer 202 has an abnormal operating condition and condensate is generated therein, the condensate can be discharged through the steam trap 209 installed at the bottom of the steamer 202, thereby ensuring the stability of the system. The steaming process removes organic matter, mineral oil and oligomers in the product.

[0038] A third rotary discharge valve 207 is provided at the bottom of the steamer cyclone separator 206 for discharging, and the third rotary discharge valve 207 can be a pneumatic gate valve or a hand valve. The steamer washing tower 208 can be an integrated condenser and washing tower, or a split type.

[0039] Please refer to Figure 3 , Figure 3The process flow chart of the drying unit of one embodiment of the polypropylene preparation device of the present invention. The drying unit adopts a vertical fluidized bed and uses circulating nitrogen to remove moisture from propylene so that the moisture content of the product meets the standard. The drying unit includes a dryer 301, a dryer cyclone separator 302, a first powder hopper 304, a second powder hopper 312, a dry gas washing tower 306, a plate heat exchanger 308, a wire mesh demister 309, a dry gas circulation fan 310 and a dry gas heater 311; the bottom of the dryer 301 is connected to the second powder hopper 312, the top of the dryer 301 is connected to the middle and upper part of the dryer cyclone separator 302, and the dryer cyclone separator 302 is connected to the middle and upper part of the dryer cyclone separator 302. The bottom is connected to the first powder hopper 304, the top of the dryer cyclone separator 302 is connected to the middle and lower part of the dry gas washing tower 306, the top of the dry gas washing tower 306 is connected to the wire mesh demister 309, the wire mesh demister 309 is connected to the dry gas circulation fan 310, the dry gas heater 311 and the bottom of the dryer 301 in sequence, and the bottoms of the dryer cyclone separator 302, the first powder hopper 304 and the second powder hopper 312 are all provided with rotary discharge valves.

[0040] After the solid polypropylene particles from the steaming unit flow into the middle of the dryer 301 from the feed pipe of the dryer 301, they are evenly distributed by the distribution plate in the dryer 301. The solid polypropylene particles from the steaming unit are carried and dried by the drying gas (such as but not limited to nitrogen) at 110-150°C. After reaching a certain residence time, the dried polypropylene particles overflow the overflow plate in the dryer 301 and flow into the second powder hopper 312 by gravity; then they are transported to the third ejector 315 (or the fourth ejector 316) through the sixth rotary discharge valve 313 (or the seventh rotary discharge valve 314), and are transported to the silo by the nitrogen from the air delivery system; the wet nitrogen after the material is dried by the dryer 301 leaves the top pipe port of the dryer 301 and enters the dryer cyclone separator 302 for gas-solid separation. 2 is provided with a fourth rotary discharge valve 303 at the bottom, and the separated solid powder enters the first powder hopper 304, and then is transported to the fifth ejector 317 through the fifth rotary discharge valve 305, and then is transported to the silo by the nitrogen from the fourth ejector 316; the gas separated by the dryer cyclone separator 302 enters from the middle and lower part of the dry gas washing tower 306, and is reversely contacted and washed with the washing liquid pressurized by the washing liquid circulation pump 307 and cooled by the plate heat exchanger 308. The washed dry gas is defogged by the baffle demister at the top of the dry gas washing tower 306 and then enters the wire mesh demister 309 to further remove the moisture carried in the dry gas; the nitrogen after thorough defogging is successively pressurized by the dry gas circulation fan 310 and heated to 110°C by the dry gas heater 311, and then enters from the bottom of the dryer 301 to dry the wet material therein.

[0041] The dryer 301 can be a vertical fluidized bed, and the distribution plate can be a single layer or a double layer. The fourth rotary discharge valve 303 and the fifth rotary discharge valve 305 can be pneumatic gate valves or hand valves. The sixth rotary discharge valve 313 and the seventh rotary discharge valve 314 can be pneumatic gate valves, or two valves can be combined into a Y-type reversing valve. The plate heat exchanger 308 can be a shell and tube heat exchanger. The drying gas heater 311 can be a shell and tube heat exchanger, a fin heat exchanger, or an electric heater.

[0042] Furthermore, when the second reactor and the third reactor simultaneously produce the same brand of product, the same process control parameters are adopted; the first reactor is provided with a first controller, the first controller stores initial control process parameters and can execute the initial control process parameters; the second reactor is provided with a second controller, the second controller stores second reactor control process parameters and can execute the second reactor control process parameters; the third reactor is provided with a third controller, the third controller stores third reactor control process parameters and can execute the third reactor control process parameters; the second reactor control process parameters follow the second reactor control model, and the third reactor control process parameters follow the third reactor control model, wherein a device data collector and a device controller are provided in the polypropylene preparation device, the device data collector collects signals transmitted by various sensors, the device controller processes various sensor signals collected by the device data collector through a preprocessor, and classifies these sensor signals, and transmits the classified signals to the first controller, The second controller and the third controller; wherein the signals transmitted to the second controller and the third controller are respectively calculated by using the preset control models of each reactor to calculate the corresponding signal data, and the calculated signal data are compared with the signal data of the last execution. If the signal data of the two comparisons are within the prescribed threshold range, the preset weight of the control model is adjusted until the calculated signal data and the target value are minimized, and then execution is performed; if the signal data of the two comparisons exceed the prescribed threshold range, the signal transmitted to the second controller and the signal transmitted to the third controller are exchanged, that is, the signal transmitted to the second controller is transmitted to the signal of the third controller, and the signal transmitted to the third controller is transmitted to the signal of the second controller, and then comparison is performed again. If the compared signal data are within the prescribed threshold range, the preset weight of the control model is adjusted until the calculated signal data and the target value are minimized, and then execution is performed; if the compared signal data still exceeds the prescribed threshold range, the previous signal data is executed, and the above process is repeated during the next execution.

[0043] Reference Figure 4In the above signal acquisition process, all the collected temperature-time curves are used to create a dataset with a dimension of N×M. All samples in the dataset can be expressed as , , where N represents the total number of samples of the temperature curve, M represents the total number of sampling points contained in each temperature curve, and x represents the sample subset. represents the i-th sample subset, Represents the set of real numbers.

[0044] In the construction of the data control model, the input layer, hidden layer and output layer are used, that is, the data signal of the input layer is reconstructed in the output layer, and the output data signal of the output layer can be expressed as:

[0045]

[0046] Where f(·) represents the activation function of the hidden layer unit; W (1) represents the weight between the input layer and the hidden layer unit, b (1) Represents the corresponding bias term between the input layer and the hidden layer units; W (2) represents the weight between the hidden layer and the output layer, b (2) Represents the corresponding bias term between the hidden layer and the output layer; Represents the input value of the i-th sample subset; represents the output data signal of the output layer of the i-th sample subset; T represents transposition; the cost function of the above reconstruction process is:

[0047]

[0048] The second term on the right side of the equation is the weight decay term, which aims to limit the amplitude of the weights in the network structure to reduce the risk of overfitting. λ represents the parameter of the weight decay term. represents the weight cost correction term between the input layer and hidden layer units of the i-th subset, and Si represents the number of i-th hidden layers; Represents the cost function of the reconstruction process.

[0049] In the actual network training process, if the activation output of a hidden layer unit is close to 1, the unit is considered to be in an "activated" state, otherwise it is in an "inactivated" state. Therefore, the sparsity of the network means that most of the hidden layer units need to be kept in an "inactivated" state. To this end, let a = f(WX + b) represent the activation value of the hidden layer unit, which is used to measure its activation degree, where WX represents the weight between the hidden layer and the output layer of the x-th sample subset, and b represents the weight between the hidden layer and the output layer of the x-th sample subset. represents the corresponding bias term between the hidden layer and the output layer, and a represents the activation value of the hidden layer unit; then the average activation degree of the hidden layer unit j can be expressed as:

[0050]

[0051] in, represents the activation value of hidden layer unit j; represents the input value of the i-th sample subset, Represents the average activation level of hidden layer unit j.

[0052] In order to ensure that the average activation degree of the hidden layer units is close to zero during the training process, that is, to keep most of the hidden layer units in an "inactive" state, set the sparsity parameter ρ. j If the reconstruction cost function deviates significantly from ρ, it will be constrained by the sparse penalty term, where the sparse penalty term is expressed as:

[0053]

[0054] Where S2 is the number of hidden layer units; KL(·) is the penalty function divergence, expressed as:

[0055]

[0056] If j = ρ, then the penalty function KL(ρ||ρ j ) = 0; otherwise, as ρ j increases with the deviation from ρ.

[0057] The expression of the reconstruction cost function after adding the sparse penalty is:

[0058] Among them, β represents the weight of the sparsity penalty.

[0059] In the data training process, it is essentially the process of determining the two parameters W and b. Given a training sample, the values ​​of the parameters W and b directly determine the result of the reconstruction cost function.

[0060] In this way, when the second reactor and the third reactor simultaneously produce the same brand of product, the same process control parameters are used, and the quality of the obtained products is basically the same, ensuring the consistency of the products. In the processing calculation of the model, in particular, the present invention creatively exchanges the signal transmitted to the second controller and the signal transmitted to the third controller if the signal data of the two comparisons exceeds the specified threshold range, which greatly improves the efficiency of sample training, especially for the same brand of products, improves the control accuracy and improves the training efficiency. However, there is no such exchange strategy in the current control process.

[0061] The preparation method of polypropylene of the present invention comprises the following steps:

[0062] Step (1): feeding a reaction raw material containing propylene into a prepolymerization kettle for prepolymerization reaction, feeding a product of the prepolymerization reaction into a first reactor for a first polymerization reaction, and removing reaction heat by vaporizing propylene during the first polymerization reaction;

[0063] Step (2): introducing the product of the first polymerization reaction in step (1) into a second reactor for a first gas phase reaction, wherein the reaction heat is removed by vaporizing propylene during the first gas phase reaction;

[0064] Step (3): subjecting the product of the first gas phase reaction in step (2) to a first gas-solid separation, recycling the separated gas, and steaming the separated solid to remove organic matter and oligomers in the product; and drying the wet material after steaming to obtain polypropylene.

[0065] In one embodiment, step (2-1) is further included between step (2) and step (3); step (2-1) is: inputting the product of the first gas phase reaction in step (2) into the third reactor for a second gas phase reaction.

[0066] The products produced by the second reactor and the third reactor are controlled by a product output controller. The product output controller reads the output predetermined signals of the second reactor and the third reactor respectively, and makes corresponding material receiving preparations according to the output predetermined signals of the second reactor and the third reactor. When the output predetermined signal is sent to the product output controller, the corresponding material receiving equipment receives the materials. The specific method includes the following steps: (1) When the output predetermined signal detects that each reactor outputs a product, a reservation signal is sent to the corresponding material receiving equipment to reserve the material receiving equipment to receive the material; (2) When the product continues to be transported on each material receiving equipment, a ready signal is triggered, and the processing equipment of the subsequent process performs subsequent operations on the product (such as packaging, etc.); (3) The processing equipment of the subsequent process gives priority to the subsequent operation processing of the product produced by its corresponding reactor. Taking the material receiving equipment and subsequent processing equipment of the second reactor as an example, when the second reactor and the third reactor produce products at the same time, the material receiving equipment of the second reactor receives the material, and then the subsequent processing equipment of the second reactor performs subsequent operations, and the third reactor receives the material. The receiving device of the second reactor receives the material, and then the subsequent processing equipment of the third reactor performs subsequent operations; when one of the second reactor and the third reactor is producing products and the other is in a shutdown or maintenance state, the first receiving device receives the material, and then the second receiving device receives the material, the first receiving device transfers the product to the first subsequent processing equipment, and the second receiving device transfers the product to the second subsequent processing equipment; (4) when the second reactor and the third reactor simultaneously produce the same brand of products, the receiving device of the second reactor and the subsequent processing of the second reactor and the receiving device of the third reactor and the subsequent processing equipment of the third reactor can be cross-operated to improve efficiency;

[0067] The invention greatly improves the production efficiency of the product.

[0068] like Figure 5 The figure shows the propylene tail gas treatment device of the present invention. At present, the methods for recovering propylene from exhaust gas containing propylene include cryogenic method, absorption method, solvent extraction method, adsorption method and membrane method. Among them, the adsorption method has potential in reducing energy consumption and investment costs. The core of the adsorption method is the selection of adsorbent. There have been many reports on the recovery of propylene from industrial tail gas at home and abroad. For example, commercial activated carbon and silver-loaded silica gel adsorbents are used to separate propylene, and 5A molecular sieves are used to perform four-tower vacuum pressure swing adsorption on a mixture of propylene and propane. In the present invention, NJ type copper-loaded adsorbent is used. Related devices such as Figure 5As shown. The propylene tail gas treatment device D uses the propylene tail gas G0 as the treated gas and converts it into tail gas G1 through an adsorption method. The propylene tail gas treatment device is arranged on a base B, and includes a nitrogen charging device 1, a gas mixing chamber 2, a tail gas adsorption chamber 3 and a tail gas outlet chamber 4, and the nitrogen charging device 1, the gas mixing chamber 2, the tail gas adsorption chamber 3 and the tail gas outlet chamber 4 are interconnected. The adsorbent unit 35 is arranged in the tail gas adsorption chamber 3, and a backflush cleaning device 5 is arranged on the upper part of the tail gas adsorption chamber 3. A charging pump 11 is arranged in the nitrogen charging device 1, and the charging pump 11 is used to pump nitrogen into the gas mixing chamber 2. The connecting pipe 22 is connected to the connecting hole 21 on the upper part of the gas mixing chamber 2, and the tail gas delivery pump 23 pumps the propylene tail gas into the gas mixing chamber 2 through the connecting pipe 22. The tail gas adsorption chamber is provided with a sealable opening and closing port 31, and the adsorbent unit 35 is installed and removed through the opening and closing port, so that the adsorbent unit can be replaced when the adsorbent unit fails or ends its life. The adsorbent unit 35 is arranged on a mobile bearing device 34, and the mobile bearing device 34 includes an end plate 32 and a bearing tray 33, and a plurality of adsorbent units 351-353 are arranged on the bearing tray 33 (three are exemplarily shown in the present invention, and those skilled in the art can understand that it is one or more), the mobile bearing device 34 moves, and the bearing tray 33 and the adsorbent unit 35 enter the tail gas adsorption chamber 3, and the opening and closing port 31 is closed by the end plate 32. Those skilled in the art can understand that a sealing gasket and a fastening mechanism are provided on the end plate 32, so as to ensure the sealing of the tail gas adsorption chamber 3. Those skilled in the art can understand that the NJ type copper-loaded adsorbent is arranged in the adsorbent unit 35. The backflush cleaning device 5 includes a plurality of driving cylinders 56 (561-563). A plurality of purge sections 511-513 are arranged at the front end of the driving cylinder rod 56a. The upper ends of the purge sections 511-513 are connected to purge pipes respectively, and each purge pipe is connected to each air supply pipe through a three-way branch pipe. A control valve 57a is installed on the air supply pipe respectively, and each air supply pipe is connected to the main air pipe 57 through the control valve, and the main air pipe 57 is connected to the air supply pump 58. Each air supply pipe can be a bellows or a hose, so that it moves vertically under the movement of the driving cylinder. A wind shield 59 can be optionally arranged on the purge section 511-513. An air outlet 41 is arranged on the upper part of the tail air outlet cavity 4 to discharge the ethylene tail gas after adsorption treatment into the subsequent process. When shutting down, check the adsorbent unit 35. If the adsorbent unit 35 is attached with too much dust or impurities, turn on the back-blowing cleaning device 5 for cleaning.

[0069] In summary, the introduction of the catalyst in the reaction of the polypropylene preparation device and method of the present invention adopts solvent-free feeding technology, which reduces the catalyst solvent recovery process, thereby reducing equipment investment and refining the production process. The prepolymerization reaction of the present invention adopts low-temperature prepolymerization reaction, and the product particle size distribution is better. The prepolymerization reaction and the first polymerization reaction occur in liquid propylene, and no inert solvent is used. The monomer concentration in the reaction system is high and the polymerization rate is fast, which greatly improves the production capacity of the device. The polypropylene slurry of the present invention has low viscosity and simple mechanical stirring, which reduces the design and manufacturing costs of the reactor in the device, and also reduces the energy consumption in the device and the reaction process. The reaction of the present invention adopts propylene flash evaporation to remove heat, and does not require a large liquid pump to remove heat, saving electricity consumption. The product obtained by the preparation method and device of the present invention has high cleanliness, can obtain high-quality products and has a wide brand coverage. The preparation method of the present invention has low precision requirements for the raw material monomer propylene, and the raw material propylene has abundant sources, thereby reducing production costs. The preparation method and device of the present invention adopt a new horizontal gas phase plug flow reactor, which is close to a plug flow reactor, can avoid catalyst short circuit, improve reaction efficiency, thereby reducing the reactor volume and reducing fixed asset investment. The volume of this reactor is much smaller than that of other process gas phase reactors, thereby improving the safety of the process system. The preparation method of the present invention has a simple process, low investment, quick results, simple operation, flexible production and flexible product brand conversion. The second reactor and the third reactor can produce products of the same brand at the same time; the second reactor and the third reactor can also produce products of different brands at the same time, and the two production lines are separated independently by an air lock. The device of the present invention has high safety and high operability. The preparation method and device of the present invention do not produce block materials, which overcomes the disadvantage that the horizontal kettle process is easy to produce block materials. The device of the present invention has a short construction period and a compact layout, and can be constructed in a modular manner. The investment cost of the device of the present invention is low, which is about one-third of the mainstream device.

[0070] The bag filter back-blowing gas of the steaming unit of the present invention adopts propylene gas at the bag filter outlet, which simplifies the process; the steamer washing tower adopts hot water washing, and the hot water extracted after washing is transported to the steam system for recycling, which saves energy consumption; a steam trap is arranged at the bottom of the steamer, and the steam trap can discharge the steam condensate in the steamer under abnormal working conditions, while ensuring the stability of the steaming system, reducing the water content of the material inlet of the subsequent drying system, thereby saving the energy consumption of the drying system and ensuring the stable operation of the subsequent process; a steam purge pipeline is added at the bottom of the third rotary unloading valve to prevent material blockage.

[0071] The bottom of the dryer feed pipe of the drying unit of the present invention is equipped with a solid material distribution plate, which effectively solves the problem of easy accumulation of materials directly below the feed pipe; the overflow plate inside the steamer is height-adjustable, and the residence time of the material can be adjusted by adjusting the height of the overflow plate, thereby increasing the operational flexibility of the drying system.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An improved preparation device for polypropylene, characterized in that: include: Polymerization unit, steaming unit and drying unit; The polymerization unit comprises a prepolymerization kettle, a first reactor, a first reaction condenser, a first propylene condensate tank and a second reactor; the first reactor is connected to the prepolymerization kettle; the first reaction condenser is connected to the top of the first reactor; the top of the first propylene condensate tank is connected to the first reaction condenser and the first reactor respectively, and the bottom of the first propylene condensate tank is connected to the first reactor; the top of the second reactor is connected to the bottom of the first reactor; the polymerization unit also comprises a third reactor, a third reaction cyclone separator, a third reaction condenser, and a third propylene condensate tank, the third reaction cyclone separator is connected to the top of the third reactor, the third reaction condenser is connected to the top of the third reaction cyclone separator, the third propylene condensate tank is connected to the third reaction condenser, and the third propylene condensate tank is also connected to the third reactor; the second reactor and the third reactor are connected in series or in parallel; it is characterized in that when the second reactor and the third reactor simultaneously produce products of the same brand, the same process control parameters are adopted.

2. The improved preparation device of polypropylene according to claim 1, characterized in that: The first reactor is provided with a first controller, which stores initial control process parameters and can execute the initial control process parameters; the second reactor is provided with a second controller, which stores second reactor control process parameters and can execute the second reactor control process parameters; the third reactor is provided with a third controller, which stores third reactor control process parameters and can execute the third reactor control process parameters; the second reactor control process parameters follow the second reactor control model, and the third reactor control process parameters follow the third reactor control model, wherein a device data collector and a device controller are provided in the polypropylene preparation device, the device data collector collects signals transmitted by various sensors, the device controller processes various sensor signals collected by the device data collector through a preprocessor, and classifies these sensor signals, and transmits the classified signals to the first controller, the second controller and the third controller respectively; wherein the signals transmitted to the The signals of the second controller and the third controller are respectively calculated by using the preset control models of each reactor to calculate the corresponding signal data, and the calculated signal data are compared with the signal data of the last execution. If the signal data of the two comparisons are within the specified threshold range, the preset weight of the control model is adjusted until the calculated signal data and the target value are minimized, and then execution is performed; if the signal data of the two comparisons exceed the specified threshold range, the signal transmitted to the second controller and the signal transmitted to the third controller are exchanged, that is, the signal transmitted to the second controller is transmitted to the signal of the third controller, and the signal transmitted to the third controller is transmitted to the signal of the second controller, and then comparison is performed again. If the compared signal data is within the specified threshold range, the preset weight of the control model is adjusted until the calculated signal data and the target value are minimized, and then execution is performed; if the compared signal data still exceeds the specified threshold range, the signal data of the last time is executed, and the above process is repeated during the next execution.

3. An improved polypropylene production device according to claim 1 or 2, characterized in that: The polymerization unit further includes a second reaction cyclone separator, a second reaction condenser, and a second propylene condensate tank. The second reaction cyclone separator is communicated with the top of the second reactor, the second reaction condenser is communicated with the top of the second reaction cyclone separator, the second propylene condensate tank is communicated with the second reaction condenser, and the second propylene condensate tank is also communicated with the second reactor. An air lock and a reversing valve are also provided between the second reactor and the third reactor. The reversing valve is a 30° reversing valve, a 60° reversing valve or a 120° reversing valve. The second reactor and the third reactor are single air bag type or double air bag type. The products produced by the second reactor and the third reactor are controlled by a product output controller. The product output controller reads the output predetermined signals of the second reactor and the third reactor respectively, and makes corresponding material receiving preparations according to the output predetermined signals of the second reactor and the third reactor. When the output predetermined signal is sent to the product output controller, the corresponding material receiving equipment receives the material.

4. The improved preparation device of polypropylene according to claim 1, characterized in that: The steaming unit comprises: a bag filter, a propylene cooler, a propylene gas buffer tank, a steamer, a steamer cyclone separator, a steamer scrubber and a hydrocarbon-water separation tank; the top of the bag filter is connected with the propylene cooler and the propylene gas buffer tank in sequence, and the bottom of the bag filter is connected with the steamer; the top of the steamer is connected with the steamer cyclone separator; the bottom of the steamer cyclone separator is connected with the steamer; the top of the steamer cyclone separator is connected with the steamer scrubber; the middle and upper parts of the steamer scrubber are connected with the hydrocarbon-water separation tank; the steamer scrubber is an integrated or split condenser and scrubber.

5. The improved preparation device of polypropylene according to claim 1, characterized in that: The drying unit comprises: a dryer, a dryer cyclone separator, a first powder hopper, a second powder hopper, a dry gas scrubber, a plate heat exchanger, a wire mesh demister, a dry gas circulation fan and a dry gas heater; the bottom of the dryer is connected to the second powder hopper, the top of the dryer is connected to the middle and upper part of the dryer cyclone separator, the bottom of the dryer cyclone separator is connected to the first powder hopper, the top of the dryer cyclone separator is connected to the middle and lower part of the dry gas scrubber, the top of the dry gas scrubber is connected to the wire mesh demister, and the wire mesh demister is connected to the dry gas circulation fan, the dry gas heater and the bottom of the dryer in sequence; An overflow plate and a plurality of distribution plates are arranged in the dryer, and the plurality of distribution plates are evenly distributed; a rotary discharge valve is arranged at the bottom of the dryer cyclone separator, the first powder hopper and the second powder hopper; the rotary discharge valve is a pneumatic plug valve, or two valves are combined into a Y-type reversing valve; the plate heat exchanger is a shell-and-tube heat exchanger; the drying gas heater is a shell-and-tube heat exchanger or a fin heat exchanger or an electric heater; the polypropylene preparation device also includes a propylene tail gas treatment device, which is arranged on a base and includes a nitrogen charging device, a gas mixing chamber, a tail gas adsorption chamber and a tail gas outlet chamber, and the nitrogen charging device, the gas mixing chamber, the tail gas adsorption chamber and the tail gas outlet chamber are interconnected.

6. A method for preparing polypropylene, characterized in that: Using the polypropylene preparation device according to any one of claims 1 to 5, the preparation method comprises the following steps: Step (1): feeding a reaction raw material containing propylene into a prepolymerization kettle for prepolymerization reaction, and feeding a product of the prepolymerization reaction into a first reactor for a first polymerization reaction, wherein the reaction heat is removed by vaporizing propylene during the first polymerization reaction; Step (2): introducing the product of the first polymerization reaction in step (1) into a second reactor for a first gas phase reaction, wherein the reaction heat is removed by vaporizing propylene during the first gas phase reaction; Step (3): subjecting the product of the first gas phase reaction in step (2) to a first gas-solid separation, recycling the separated gas, and steaming the separated solid to remove organic matter and oligomers in the product; and drying the wet material after steaming to obtain polypropylene.

7. The method for preparing polypropylene according to claim 6, characterized in that: In step (1), the reaction raw materials include propylene, a main catalyst, a co-catalyst, an electron donor and mineral oil, the main catalyst is a titanium magnesium catalyst TiCl4 / MgCl2; the co-catalyst is a trialkyl aluminum compound, the trialkyl aluminum compound is at least one of triethyl aluminum and tri-n-butyl aluminum; the electron donor is at least one of dicyclopentyldimethoxysilane, cyclohexyldimethoxysilane and triethoxysilane; the pressure of the prepolymerization reaction is 2.0~6.0MPaG, the temperature is -5~70°C, and the reaction time is 8~30 minutes; the pressure of the first polymerization reaction is 2.0~4.0MPaG, the temperature is 30~95°C, and the reaction time is 0.5~2 hours; in the reaction raw materials, propylene gas formed by vaporization of part of propylene due to the heat release of the first polymerization reaction is condensed and then subjected to gas-liquid separation, the gas obtained by the gas-liquid separation is returned to the first reactor as a reaction raw material for recycling, and the liquid obtained by the gas-liquid separation is used for heat removal of the first polymerization reaction in the first reactor.

8. The method for preparing polypropylene according to claim 6, characterized in that: In step (2), the pressure of the first gas phase reaction is 1.5-2.7 MPaG, the temperature is 70-150°C, and the time is 3-4 hours. In step (2), during the first gas phase reaction, gas carrying solid particles is discharged from the top of the second reactor, the gas carrying solid particles is subjected to a second gas-solid separation, the gas obtained by the second gas-solid separation is condensed and returned to the second reactor as a reaction raw material for recycling or for removing heat from the first gas phase reaction in the second reactor, and the solid obtained by the second gas-solid separation is mixed with ethylene and hydrogen and returned to the second reactor to repeat the first gas phase reaction.

9. The method for preparing polypropylene according to claim 6, characterized in that: The step (2-1) is further included between step (2) and step (3); the step (2-1) comprises: inputting the product of the first gas phase reaction in step (2) into a third reactor for a second gas phase reaction, wherein propylene is vaporized during the second gas phase reaction to remove reaction heat; the gas phase product obtained in the second gas phase reaction is subjected to a third gas-solid separation, the gas obtained by the third gas-solid separation is condensed and returned to the third reactor for recycling as a reaction raw material or for removing heat from the second gas phase reaction in the third reactor, and the solid obtained by the third gas-solid separation is mixed with ethylene and hydrogen and returned to the third reactor for the second gas phase reaction again; the pressure of the second gas phase reaction is 1.0-2.0 MPaG, the temperature is 70-150°C, and the time is 2-3 hours.

10. The method for preparing polypropylene according to claim 6, characterized in that: The drying adopts a vertical fluidized bed and utilizes circulating nitrogen to remove moisture.

Images