CN114470979A - Purging device and polyethylene production equipment - Google Patents
Purging device and polyethylene production equipment Download PDFInfo
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- CN114470979A CN114470979A CN202011271614.5A CN202011271614A CN114470979A CN 114470979 A CN114470979 A CN 114470979A CN 202011271614 A CN202011271614 A CN 202011271614A CN 114470979 A CN114470979 A CN 114470979A
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- 238000010926 purge Methods 0.000 title claims abstract description 133
- 239000004698 Polyethylene Substances 0.000 title claims abstract description 37
- -1 polyethylene Polymers 0.000 title claims abstract description 37
- 229920000573 polyethylene Polymers 0.000 title claims abstract description 37
- 238000004519 manufacturing process Methods 0.000 title claims description 34
- 238000006243 chemical reaction Methods 0.000 claims abstract description 46
- 230000007704 transition Effects 0.000 claims description 35
- 238000011144 upstream manufacturing Methods 0.000 claims description 11
- 230000005484 gravity Effects 0.000 claims description 4
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical class C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 claims description 3
- 239000000843 powder Substances 0.000 abstract description 5
- 238000009825 accumulation Methods 0.000 abstract 1
- 238000006116 polymerization reaction Methods 0.000 description 14
- 239000003054 catalyst Substances 0.000 description 10
- 239000007787 solid Substances 0.000 description 10
- 238000000034 method Methods 0.000 description 7
- 239000002245 particle Substances 0.000 description 7
- 229920013716 polyethylene resin Polymers 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 230000004048 modification Effects 0.000 description 6
- 238000012986 modification Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 238000007664 blowing Methods 0.000 description 2
- 230000008602 contraction Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000010408 sweeping Methods 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D45/00—Separating dispersed particles from gases or vapours by gravity, inertia, or centrifugal forces
- B01D45/18—Cleaning-out devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
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- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Organic Chemistry (AREA)
- Cyclones (AREA)
- Polymerisation Methods In General (AREA)
Abstract
The invention provides a purging device, which is used for producing polyethylene and comprises a purging pipeline, a purging pipe and a purging pipe, wherein the purging pipeline comprises a return air pipe and a purging pipe; the return air pipe is used for connecting a return air inlet of the reaction kettle and an air outlet of the cyclone separator and is provided with a shunting port; the purging pipe is used for connecting the shunting port and a feed back port of the reaction kettle, and the purging pipe is used for purging the cyclone separator; the Venturi tube is arranged on the return air pipe; the venturi tube is positioned between the flow dividing port and the air outlet of the air return pipe, and the small-diameter end of the venturi tube faces the air outlet of the air return pipe; the compressor is arranged on the air return pipe; the air compressor is positioned between the flow dividing port and the air inlet of the air return pipe. The invention provides power by the compressor and simultaneously cooperates with the venturi tube and the purging pipeline to increase the flow of the purging gas of the cyclone separator, solves the problem of accumulation and blockage of fine powder in the cyclone separator caused by over-small flow of the purging gas without adding an additional fan, and reduces the cost.
Description
Technical Field
The invention relates to the technical field of polyethylene production, in particular to a purging device and polyethylene production equipment.
Background
The technology for producing polyethylene by using a low-pressure gas phase method developed by British oil company is called Innovene process, and the process comprises the steps of preparing a prepolymer by using a catalyst in a prepolymerization kettle, and then injecting the prepolymer into a gas phase reactor for reaction to produce a polyethylene product. With the continuous progress of polyethylene production process and catalyst technology, the catalyst preparation and control requirements of an Innovene process device are fine and strict, and the failure of catalyst preparation can be caused by the problem of any link, so that the unplanned shutdown of the whole device is caused, and the long-period operation of the device is difficult to ensure.
If use novel catalyst then need carry out the direct injection transformation of catalyst to the device, promptly: the catalyst is directly injected into the fluidized bed reactor for polymerization reaction. The direct injection of catalyst into the gas phase reactor produces a polyethylene resin with a reduced particle size compared to the prepolymer feed, resulting in a large amount of finely powdered product entrained in the fluidizing gas. The circulating gas comes out from the top of the polymerization reactor and then enters the cyclone separator, the content of fine powder in the cyclone separator is increased at the moment, and the flow rate of the sweeping gas at the bottom of the cyclone separator is not increased, so that the cyclone separator is frequently blocked, and the long-period operation of the device cannot be ensured.
In order to solve the problem of blockage of the cyclone separator, the related technology adopts a mode of additionally arranging a fan on a blowing gas pipeline of the cyclone separator to increase the blowing gas quantity of the cyclone separator, so that polyethylene fine powder enters the polymerization reaction kettle again for continuous reaction. However, the method has large modification engineering amount and high modification cost.
Disclosure of Invention
The invention provides a purging device and polyethylene production equipment, which are used for solving the problem of blockage of a cyclone separator in the prior art.
According to an embodiment of the present invention, in one aspect, there is provided a purging device for the production of polyethylene, comprising: the purging pipeline comprises a return air pipe and a purging pipe; the air return pipe is used for connecting an air return inlet of the reaction kettle and an air outlet of the cyclone separator and is provided with a flow dividing port; the purging pipe is used for connecting the flow dividing port and the gas outlet of the reaction kettle and purging the cyclone separator; the Venturi tube is arranged on the air return pipe; the venturi tube is positioned between the flow dividing port and the air outlet of the air return pipe, and the small-diameter end of the venturi tube faces the air outlet of the air return pipe; the compressor is arranged on the air return pipe; the compressor is positioned between the flow dividing port and the air inlet of the air return pipe.
In one possible implementation, the venturi is vertically mounted to the return duct in the direction of gravity.
In one possible implementation, the large-diameter end of the venturi tube is connected to the return air pipe through a first transition pipe, and the small-diameter end of the venturi tube is connected to the return air pipe through a second transition pipe.
In one possible implementation, the ratio of the length of the first transition pipe to the diameter of the large diameter end of the venturi is greater than 20; the ratio of the length of the second transition pipe to the diameter of the small diameter end of the venturi pipe is greater than or equal to 10.
In one possible implementation, the purge tube is a plurality of purge tubes, each purge tube being for purging one of the cyclones.
In one possible implementation, the venturi is a classical venturi or a double-tube venturi.
In one possible implementation, the return air duct is further provided with a first heat exchanger, which is arranged upstream of the air compressor.
In one possible implementation, the purge tube is provided with a second heat exchanger, which is located downstream of the venturi.
In one possible implementation, the distance between the small-diameter end of the venturi tube and the air inlet of the second heat exchanger is equal to the distance between the small-diameter end of the venturi tube and the flow dividing port.
According to an embodiment of the present invention, in another aspect, there is provided a polyethylene production apparatus including: the reaction kettle, the cyclone separator and the purging device are adopted, and the air inlet of the cyclone separator is connected with the air outlet of the reaction kettle.
The purging device provided by the invention is used for producing polyethylene, the Venturi tube is arranged between the flow dividing port and the air outlet of the air return pipe, and due to the existence of the necking in the Venturi tube, air blown by the air compressor forms less gas inflow at the inlet of the Venturi tube, so that more gas flows into the purging pipe, namely, the purging flow of the cyclone separator is increased, the frequent blockage of the cyclone separator is solved without adding an additional fan at the purging section of the cyclone separator, and the modification cost is reduced.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure.
Fig. 1 is a schematic structural diagram of a purging device according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of another purging device provided in an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of another purging device according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of another purging device according to an embodiment of the present disclosure;
FIG. 5 is a schematic structural diagram of a polyethylene production apparatus according to an embodiment of the present invention;
fig. 6 is a block flow diagram of another polyethylene production facility according to an embodiment of the present invention.
Reference numerals:
100-a purge line;
101-an air return pipe; 102-a purge tube; 103-a shunt port;
200-a venturi tube;
201-small diameter end; 202-large diameter end;
300-a compressor;
400-a first transition duct;
500-a second transition duct;
600-a reaction kettle;
700-a cyclone separator;
800-a first heat exchanger;
900-second heat exchanger.
With the foregoing drawings in mind, certain embodiments of the disclosure have been shown and described in more detail below. These drawings and written description are not intended to limit the scope of the disclosed concepts in any way, but rather to illustrate the concepts of the disclosure to those skilled in the art by reference to specific embodiments.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the exemplary embodiments below are not intended to represent all implementations consistent with the present disclosure. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the disclosure, as detailed in the appended claims.
It should be noted that, in the present disclosure, terms indicating orientations such as "upper", "lower", "left", "right", "inner", "outer", etc., are used with reference to the orientation shown in the drawings without specific description, but it should be understood that the terms are used for convenience of description and are not intended to specifically limit the orientation of the product.
In addition, in the present disclosure, unless otherwise specified, "connected" may mean that two objects are directly connected to each other or that two objects are indirectly connected to each other through an intermediate object.
Finally, "first" and "second" are used in this disclosure only to distinguish one structure from another, and do not denote any order or quantity of such structures.
The prior polyethylene production has the problem that the catalyst is directly injected into a gas phase reactor to produce polyethylene resin with reduced particle size, so that a large amount of fine powder products are carried in fluidized gas. Circulating gas enters the cyclone separator after coming out of the top of the reaction kettle, the content of fine powder in the cyclone separator is increased at the moment, and the flow rate of a sweeping gas at the bottom of the cyclone separator is not increased, so that the cyclone separator is frequently blocked. However, the method has large modification engineering amount and high modification cost.
In view of the above, in the polyethylene polymerization reaction, the polymerized gas is pushed to flow in the reaction kettle and the cyclone separator by the gas compressor and the venturi tube, and an additional purge fan is not required to be added. Specifically, venturi pipe is installed between the flow splitting port of the return air pipe and the air outlet, the small-diameter end of the venturi pipe faces the air outlet of the return air pipe, air pushed by the compressor is split at the flow splitting port, the gas flow passing through the venturi pipe is limited due to the existence of the necking of the venturi pipe, most gas enters the purging pipe, then flows into the reaction kettle after the cyclone separator is purged, the amount of the purging device of the cyclone separator is favorably increased, solid at the bottom of the cyclone separator is timely purged, and blockage at the bottom of the cyclone separator is relieved.
It should be noted that the gas passing through the return air pipe and the purge pipe is mainly the gas after the polymerization reaction in the reaction kettle, and the compressor pushes the gas to flow in the circulating pipeline formed by the reaction kettle, the cyclone separator, the return air pipe and the purge pipe.
Exemplary implementations of the present invention are described below in conjunction with the appended drawings so that those skilled in the art will more clearly understand the aspects of the present disclosure. It should be noted that, some or all of the structures in the different implementations described below may be replaced with each other, and the implementations of the present disclosure are not limited to the following examples, and under the above conception, a person skilled in the art may also obtain other possible implementations according to the following examples, and these implementations should also be regarded as the content of the present disclosure.
Fig. 1 shows a purging device. As shown in fig. 1, there is provided a purge apparatus for the production of polyethylene comprising: a purge line 100 comprising a return air pipe 101 and a purge pipe 102; wherein, the air inlet of the return air pipe 101 is communicated with the air outlet of the cyclone separator 700, the air outlet of the return air pipe 101 is communicated with the air return inlet of the reaction kettle 600, and the return air pipe 101 is provided with a shunt port 103; the purging pipe 102 is arranged between the branch opening 103 and the feed back opening of the reaction kettle 600, and the middle part of the purging pipe 102 is communicated with the solid outlet at the bottom of the cyclone separator 700; a venturi tube 200 is arranged between the diversion port 103 of the return air duct 101 and the air outlet 104 of the return air duct 101, and the small-diameter end 201 of the venturi tube 200 faces the air outlet 104 of the return air duct 101; a compressor 300 is arranged between the branch opening 103 of the return air pipe 101 and the air inlet 105, and the compressor 300 provides power for air.
Specifically, the venturi tube 200 may be vertically installed in the return air duct 101 along the gravity direction, and the vertical installation along the gravity direction may prevent entrained polymer from being retained at the diameter-variable portion of the venturi tube 200.
In some alternatives, the large-diameter end 202 of the venturi 200 may be connected to the return air duct 101 through a first transition duct 400, and the small-diameter end 201 of the venturi 200 may be connected to the return air duct 101 through a second transition duct 500. The first transition pipe 400 is connected with the large-diameter end 202 of the venturi 200 and the adjacent return air pipe 101 through the first transition pipe 400, so that the flow rate at the inlet of the large-diameter end 202 of the venturi 200 can be kept in a more relatively stable state, while the small-diameter end 201 of the venturi 200 and the second transition pipe 500 are connected with the adjacent return air pipe 101, so that the flow rate at the outlet of the small-diameter end 201 of the venturi 200 is kept more relatively stable.
Wherein, in order to make the gas flow rate of the large-diameter end 202 and the small-diameter end 201 of the venturi 200 pass stably and make more gas flow into the purge pipe 102 due to the arrangement of the venturi 200, the ratio of the length of the first transition pipe 400 to the diameter of the large-diameter end 202 of the venturi 200 is more than 20; the ratio of the length of the second transition tube 500 to the diameter of the small-diameter end 201 of the venturi 200 is equal to or greater than 10.
In some alternative implementations, the venturi 200 may be a classical venturi or a double-pipe venturi, taking into account the larger caliber of the venturi 200 in the polymerization reaction. Classical venturis are used to measure the volumetric flow of a single phase steady fluid (liquid, gas or vapor) in a closed conduit. The straight pipe sections of the upstream and the downstream required by all standard throttling devices are shortest, the pressure loss is minimum, the performance is stable, and the maintenance is convenient. The classical venturi tube comprises an inlet cylindrical section, a conical contraction section, a cylindrical throat and a conical diffusion section. The sleeve type Venturi tube comprises a sleeve on the outer side, and an inlet cylindrical section, a conical contraction section, a cylindrical throat part and a conical diffusion section which are sleeved in the sleeve, and the structural strength of the sleeve type Venturi tube is higher than that of a classical Venturi tube.
It should be noted that the number of purge tubes 102 shown in fig. 1 is merely illustrative, and in other examples, a plurality of purge tubes 102 may be provided according to specific conditions, and each purge tube 102 may purge the cyclone 700 interfacing the purge tube 102.
Figure 2 shows another purging device. As shown in fig. 2, there is provided a purge apparatus for the production of polyethylene comprising: the purging pipeline 100 comprises a return air pipe 101 and two purging pipes 102, and each purging pipe 102 independently purges the cyclone separator 700 matched with the purging pipe 102; wherein, the air inlet of the return air duct 101 is communicated with the total air outlet formed by connecting the air outlets of the two cyclone separators 700 in parallel, the air outlet of the return air duct 101 is communicated with the return air inlet of the reaction kettle 600, and the return air duct 101 is provided with a shunt opening 103.
Wherein, two purge tube 102 are established between the feed back of reposition of redundant personnel mouth 103 and reation kettle 600 respectively in parallel, the reposition of redundant personnel mouth 103 of return air pipe 101 and the income wind gap of two purge tube 102 pass through the tee junction, the three-way entry end and reposition of redundant personnel mouth 103 intercommunication, the three-way first export and one purge tube 102 intercommunication, the three-way second export and another purge tube 102 intercommunication, and in the same way, reation kettle 600's feed back mouth and two purge tube 102's air outlet also through tee junction and three-way export and reation kettle 600's feed back intercommunication, the three-way first entry communicates with a purge tube 102's air outlet, the three-way second entry communicates with another purge tube 102's air outlet.
With continued reference to fig. 2, a venturi tube 200 is installed between the diversion port 103 of the return duct 101 and the air outlet of the return duct 101, the venturi tube 200 includes a small diameter end 201 and a large diameter end 202, the small diameter end 201 of the venturi tube 200 faces the air outlet of the return duct 101, the large diameter end 202 of the venturi tube 200 faces the diversion port 103 of the return duct 101, the large diameter end 202 of the venturi tube 200 is connected to the return duct 101 through a first transition pipe 400, and the small diameter end 201 of the venturi tube 200 is connected to the return duct 101 through a second transition pipe 500; a compressor 300 is arranged between the branch opening 103 and the air inlet of the return air pipe 101, and the compressor 300 provides power for air.
It should be noted that the other purging device shown in fig. 2 is different from the one shown in fig. 1 in that one purging pipe 102 and the cyclone 700 used in cooperation with the purging pipe 102 are added, and the rest of the structure is the same as that of the purging device shown in fig. 1. The number of the purge pipes 102 can be appropriately adjusted according to actual production requirements, when the production capacity is increased and a single cyclone separator 700 cannot meet the production requirements, the number of the cyclone separators 700 needs to be increased according to actual working conditions, and certainly, a purge device for purging the cyclone separator 700 needs to be modified in a matching manner, that is, the purge pipes 102 need to be correspondingly increased, and the power of the compressor 300 needs to be correspondingly adjusted.
Fig. 3 shows yet another purging device. As shown in fig. 3, there is provided a purge apparatus for the production of polyethylene comprising: a purge line 100 comprising a return air pipe 101 and a purge pipe 102; wherein, the air inlet of the return air pipe 101 is communicated with the air outlet of the cyclone separator 700, the air outlet of the return air pipe 101 is communicated with the air return inlet of the reaction kettle 600, and the return air pipe 101 is provided with a shunt port 103; the purging pipe 102 is arranged between the branch opening 103 and the feed back opening of the reaction kettle 600, and the middle part of the purging pipe 102 is communicated with the discharge opening at the bottom of the cyclone 700.
The venturi tube 200 is installed between the diversion port 103 of the return air duct 101 and the air outlet 104 of the return air duct 101, the small-diameter end 201 of the venturi tube 200 faces the air outlet 104 of the return air duct 101, the large-diameter end 202 of the venturi tube 200 can be connected with the return air duct 101 through the first transition pipe 400, and the small-diameter end 201 of the venturi tube 200 can be connected with the return air duct 101 through the second transition pipe 500; the compressor 300 is installed between the diversion port 103 of the air return pipe 101 and the air inlet 105, the compressor 300 provides power for air, the first heat exchanger 800 is arranged on the air return pipe 101 at the upstream of the compressor 300, and the first heat exchanger 800 cools the air with higher temperature generated after polymerization reaction, so that the air with lower temperature passes through the compressor 300.
It should be noted that the other purging device shown in fig. 3 is different from the one shown in fig. 1 in that a first heat exchanger 800 is added, and the rest of the structure is the same as that of the purging device shown in fig. 1. The polymerization reaction is an exothermic reaction, in the polyethylene polymerization process, the temperature of gas exhausted from the reaction kettle 600 rises, the return air pipe 101 can have a gas circulation with a higher temperature, the high-temperature gas directly passes through the compressor 300 and can damage the compressor 300, the service life of the compressor 300 is shortened, and therefore the first heat exchanger 800 is added at the upstream of the compressor 300, and the first heat exchanger 800 cools the air passing through the compressor 300.
Fig. 4 shows yet another purging device. As shown in fig. 4, there is provided a purging device for the production of polyethylene comprising: a purge line 100 comprising a return air pipe 101 and a purge pipe 102; wherein, the air inlet of the return air pipe 101 is communicated with the air outlet of the cyclone separator 700, the air outlet of the return air pipe 101 is communicated with the air return inlet of the reaction kettle 600, and the return air pipe 101 is provided with a shunt port 103; the purging pipe 102 is arranged between the branch opening 103 and the feed back opening of the reaction kettle 600, and the middle part of the purging pipe 102 is communicated with the discharge opening at the bottom of the cyclone 700.
The venturi tube 200 is installed between the diversion port 103 of the return air duct 101 and the air outlet 104 of the return air duct 101, the small-diameter end 201 of the venturi tube 200 faces the air outlet 104 of the return air duct 101, the large-diameter end 202 of the venturi tube 200 can be connected with the return air duct 101 through the first transition pipe 400, and the small-diameter end 201 of the venturi tube 200 can be connected with the return air duct 101 through the second transition pipe 500. A compressor 300 is arranged between the branch opening 103 of the return air pipe 101 and the air inlet 105, and the compressor 300 provides power for air. A first heat exchanger 800 is provided in the return duct 101 upstream of the compressor 300, and a second heat exchanger 900 is provided in the return duct 101 downstream of the venturi tube 200.
It should be noted that the other purging device shown in fig. 4 is different from the one shown in fig. 3 in that a second heat exchanger 900 is added, and the rest of the structure is the same as that of the purging device shown in fig. 3. It should be noted that, in the polyethylene polymerization process, the temperature of the gas discharged from the reaction kettle 600 increases, and the gas with higher temperature directly passes through the compressor 300 to damage the compressor 300. Thus, in some implementations, a first heat exchanger 800 may be added upstream of the compressor 300, the first heat exchanger 800 cooling the air passing through the compressor 300.
It should be appreciated that when the production capacity is small, the higher temperature gas is reduced by the single first heat exchanger 800 to pass through the compressor 300, whereas when the production capacity is large, the single first heat exchanger 800 can only reduce the higher temperature gas to the temperature of the gas that just can pass through the compressor 300 with a strong working intensity, so that the temperature is still high for the whole gas in the return air duct 101. Therefore, in other implementations, a second heat exchanger 900 located downstream of the venturi 200 may be further configured on the return air duct 101, and the second heat exchanger 900 can effectively relieve the working pressure of the first heat exchanger 800, so that the overall temperature of the gas in the return air duct 101 is in a reasonable temperature range.
Figure 5 shows a polyethylene production plant. As shown in fig. 5, there is provided a polyethylene production apparatus comprising: reation kettle 600, reation kettle 600's upper end is equipped with the air outlet, reation kettle 600's middle part is equipped with the feed back mouth and reation kettle 600's lower extreme is equipped with the return air inlet, reation kettle 600's air outlet outer end is equipped with cyclone 700, cyclone 700's top is equipped with gas outlet, cyclone 700's middle part is equipped with gas inlet, cyclone 700's bottom is equipped with the solid export, reation kettle 600's air outlet passes through the gas inlet intercommunication of connecting pipe with cyclone 700.
Specifically, a polymerization reaction is performed in the reaction kettle 600 to generate polyethylene particles, the gas discharged from the reaction kettle 600 carries polyethylene resin with small particle size, the gas carrying the polyethylene resin particles firstly enters the cyclone 700 along with the circulating gas to perform gas-solid separation, the separated circulating gas enters the purging pipeline 100, and the solid outlet at the bottom of the cyclone 700 takes the circulating gas as power to re-enter the reaction kettle 600 through the material return port of the reaction kettle 600 to perform the polymerization reaction again. The gas discharged from the reaction kettle 600 firstly enters the cyclone separator 700, and the gas-solid separation of the cyclone separator 700 avoids the problem that the purging pipeline 100 is blocked when the small-particle polyethylene resin enters the compressor 300.
With continued reference to fig. 5, a polyethylene production plant is provided that further comprises a purge arrangement comprising a purge line 100, the purge line 100 comprising a return air duct 101 and a purge duct 102; wherein, the air inlet of the return air pipe 101 is communicated with the air outlet of the cyclone separator 700, the air outlet of the return air pipe 101 is communicated with the air return inlet of the reaction kettle 600, and the return air pipe 101 is provided with a shunt port 103; the purge pipe 102 is arranged between the branch port 103 and the feed back port of the reaction kettle 600, and the middle part of the purge pipe 102 is communicated with the solid outlet at the bottom of the cyclone 700.
Wherein, install venturi 200 between the diverging port 103 of return air duct 101 and the air outlet 104 of return air duct 101, venturi 200 includes path end 201 and path end 202, and venturi 200's path end 201 is towards return air duct 101's air outlet 104 simultaneously, and venturi 200's path end 202 is towards the diverging port 103 of return air duct 101. The large-diameter end 202 of the venturi tube 200 is connected to the return air duct 101 through the first transition pipe 400, and the small-diameter end 201 of the venturi tube 200 is connected to the return air duct 101 through the second transition pipe 500.
Specifically, the gas flow passing through the venturi tube 200 is small due to the variable diameter of the venturi tube 200, and the gas flow in the purge pipe 102 passing through the diversion port 103 of the return air pipe 101 is increased, so that the small-particle-size polyethylene resin discharged from the bottom solid outlet of the corresponding cyclone separator 700 in the purge pipe 102 can be discharged under the condition that the compressor 300 for circulating gas provides power, and the small-particle-size polyethylene resin gas-solid separated by the cyclone separator 700 is blown back to the reaction kettle 600.
Illustratively, the gas passes through the venturi 200, the pressure of the gas at the inlet end and the outlet end of the venturi 200 is different due to the design of the reducing diameter of the venturi 200, and in order to allow a more stable flow of the gas at the two ends, a first transition pipe 400 is added at the large diameter end 202 of the venturi 200, and the diameter of the first transition pipe 400 is equal to the diameter of the large diameter end 202 of the venturi 200, and the ratio of the length of the first transition pipe 400 to the diameter of the large diameter end 202 of the venturi 200 is greater than 20; a second transition pipe 500 is added to the small-diameter end 201 of the Venturi pipe 200, the diameter of the second transition pipe 500 is equal to that of the small-diameter end 201 of the Venturi pipe 200, and the ratio of the length of the second transition pipe 500 to the diameter of the small-diameter end 201 of the Venturi pipe 200 is greater than or equal to 10.
With continued reference to fig. 5, a compressor 300 is installed between the diversion port 103 of the return air duct 101 and the air inlet 105, and the compressor 300 provides power for the air; a first heat exchanger 800 is provided upstream of the compressor 300 on the return air duct 101, the first heat exchanger 800 being used to reduce the temperature of the gas entering the compressor 300.
Specifically, in the polymerization process of polyethylene, the temperature of the gas discharged from the reaction kettle 600 increases, and the gas with a higher temperature directly passes through the compressor 300 to damage the compressor 300, so that the first heat exchanger 800 is added upstream of the compressor 300, and the first heat exchanger 800 cools the air passing through the compressor 300.
It should be noted that, besides the air outlet, the air return inlet, and the material return port, the reaction kettle 600 may further have a fluidized bed, an air supply port, a catalyst feeding port, a polyethylene particle discharging port, and the like which are conventionally arranged. The reaction kettle 600, the cyclone 700, the compressor 300, the venturi 200, the first transition pipe 400 and the second transition pipe 500 are connected with each other through connecting pipes and a purge line 100 to form a circulating gas loop.
Figure 6 shows another polyethylene production plant. As shown in fig. 6, there is provided a polyethylene production apparatus comprising: the reaction kettle 600 is characterized in that an air outlet is formed in the upper end of the reaction kettle 600, a material return port is formed in the middle of the reaction kettle 600, and an air return port is formed in the lower end of the reaction kettle 600; cyclone 700, cyclone 700 have two, and two cyclone 700 are established in parallel in the air outlet outer end of reation kettle 600, and the air outlet of reation kettle 600 passes through the connecting pipe and communicates with the gas inlet of two cyclone 700 in proper order.
With continued reference to fig. 6, the polyethylene production facility further comprises a purging device, wherein the purging device comprises a purging line 100, the purging line 100 comprises a return air pipe 101 and two purging pipes 102, and each purging pipe 102 independently purges the cyclone 700 used in cooperation with the purging pipe 102; wherein, the air inlet of the return air duct 101 is communicated with the total air outlet formed by connecting the air outlets of the two cyclone separators 700 in parallel, the air outlet of the return air duct 101 is communicated with the return air inlet of the reaction kettle 600, and the return air duct 101 is provided with a shunt opening 103.
Wherein, two purge tube 102 connect in parallel respectively and establish between the sprue spreader 103 and reation kettle 600's feed back mouth, and the sprue spreader 103 of return-air hose 101 and the income wind gap of two purge tube 102 pass through the tee junction, and in a similar way, reation kettle 600's feed back mouth also communicates with reation kettle 600's feed back mouth with the air outlet of two purge tube 102 through tee junction and the export of tee junction.
With continued reference to fig. 6, a venturi tube 200 is installed between the diversion port 103 of the return duct 101 and the air outlet of the return duct 101, the venturi tube 200 includes a small diameter end 201 and a large diameter end 202, the small diameter end 201 of the venturi tube 200 faces the air outlet of the return duct 101, the large diameter end 202 of the venturi tube 200 faces the diversion port 103 of the return duct 101, the large diameter end 202 of the venturi tube 200 is connected to the return duct 101 through a first transition pipe 400, and the small diameter end 201 of the venturi tube 200 is connected to the return duct 101 through a second transition pipe 500.
With continued reference to fig. 6, a compressor 300 is installed between the diversion opening 103 and the air inlet of the return air duct 101, and the compressor 300 provides power for the air. A first heat exchanger 800 is provided in the return duct 101 upstream of the compressor 300, and a second heat exchanger 900 is provided in the return duct 101 downstream of the venturi tube 200.
It should be noted that the other polyethylene production facility shown in fig. 6 is different from the one shown in fig. 5 in that a cyclone 700, a purge pipe 102 used in cooperation with the cyclone 700, and a second heat exchanger 900 are added, and the rest of the structure is the same as that of the polyethylene production facility shown in fig. 5. The number of cyclones 700 is determined according to a specific production condition, and the specific number is determined according to the production condition. The two cyclone separators 700 mainly increase the gas-solid separation amount of the gas and reduce the resistance of the circulating gas discharged from the reaction kettle 600.
It is noted that, in the polyethylene polymerization process, the gas discharged from the reaction kettle 600 is heated, and the gas with higher temperature directly passes through the compressor 300 to damage the compressor 300. Thus, in some implementations, a first heat exchanger 800 may be added upstream of the compressor 300, the first heat exchanger 800 cooling the air passing through the compressor 300.
It should be appreciated that when the production capacity is small, the higher temperature gas is reduced by the single first heat exchanger 800 to pass through the compressor 300, whereas when the production capacity is large, the single first heat exchanger 800 can only reduce the higher temperature gas to the temperature of the gas that just can pass through the compressor 300 with a strong working intensity, so that the temperature is still high for the whole gas in the return air duct 101. Therefore, in some implementations, a second heat exchanger 900 located downstream of the venturi 200 may be further configured on the return air duct 101, and the second heat exchanger 900 may effectively relieve the working pressure of the first heat exchanger 800, so that the overall temperature of the gas in the return air duct 101 is in a reasonable temperature range.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
It will be understood that the present disclosure is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.
Claims (10)
1. A purge device for the production of polyethylene, comprising:
the purging pipeline comprises a return air pipe and a purging pipe; the air return pipe is used for connecting an air return inlet of the reaction kettle and an air outlet of the cyclone separator and is provided with a flow dividing port; the purging pipe is used for connecting the shunting port and a feed back port of the reaction kettle and purging the cyclone separator;
the Venturi tube is arranged on the air return pipe; the venturi tube is positioned between the flow dividing port and the air outlet of the air return pipe, and the small-diameter end of the venturi tube faces the air outlet of the air return pipe;
the compressor is arranged on the air return pipe; the compressor is positioned between the flow dividing port and the air inlet of the air return pipe.
2. A purge device as claimed in claim 1, wherein the venturi is vertically mounted to the return air conduit in the direction of gravity.
3. A purging device as claimed in claim 1, wherein the large diameter end of the venturi tube is connected to the return air duct via a first transition duct and the small diameter end of the venturi tube is connected to the return air duct via a second transition duct.
4. A purge device according to claim 3,
the ratio of the length of the first transition tube to the diameter of the large diameter end of the venturi is greater than 20;
the ratio of the length of the second transition pipe to the diameter of the small diameter end of the venturi pipe is greater than or equal to 10.
5. A purge device as claimed in claim 1, wherein the purge tube is plural in number, each purge tube being for purging one of the cyclones.
6. The purge device of claim 1, wherein the venturi is a classical venturi or a double-barreled venturi.
7. A purge device as claimed in claim 1, wherein the return air conduit is further provided with a first heat exchanger, the first heat exchanger being provided upstream of the air compressor.
8. A purge device as claimed in claim 7, wherein the purge tube is provided with a second heat exchanger downstream of the venturi.
9. The purge device of claim 8, wherein the venturi tube small diameter end is equidistant from the second heat exchanger inlet as the venturi tube large diameter end is equidistant from the flow split.
10. A polyethylene production plant, comprising: a reaction kettle, a cyclone separator and the purging device as claimed in any one of claims 1 to 9, wherein the gas inlet of the cyclone separator is connected with the gas outlet of the reaction kettle.
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Cited By (1)
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| CN114470979B (en) | 2024-06-25 |
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