Polyethylene slurry density on-line monitoring device

Abstract

The invention discloses a polyethylene slurry density on-line monitoring device, which belongs to the technical field of polyethylene production, comprises a polymerization reactor, and a first pressure gauge and a first thermometer which are arranged on the polymerization reactor, and is characterized in that a first pipeline and a second pipeline are connected to the middle of the polymerization reactor, the first pipeline is communicated with a flash tank, and the second pipeline is communicated with a second pipeline; the second pipeline converges with the first pipeline, the first pipeline is connected with a third pipeline to be communicated with the top of the polymerization reactor for backflow, the second pipeline is connected with a fourth pipeline to be communicated with the top of the polymerization reactor for backflow, and the first pipeline and the second pipeline are arranged in the same way; the electric valve, the radioactive source density sensor, the first ball valve, the first centrifugal pump, the second pressure gauge, the second ball valve and the third ball valve are sequentially arranged on the first pipeline, the technical problems of long consumed time for detecting the slurry density through a density gradient method and radiation leakage of a split density sensor are solved, and the device is mainly applied to the aspect of polyethylene density detection.

Description

Technical Field

[0001] The invention belongs to the technical field of polyethylene production, and in particular relates to an online monitoring device for polyethylene slurry density. Background Art

[0002] The Hostal en ACP process is a low-pressure slurry process. Three reactors can achieve the production of multi-modal HDPE products and have the advantage of rapid grade switching. The Hostal en ACP patent is provided by LyondeBase II, the company's patent licensor. In 2023, the total polyolefin production capacity of the company accounted for 26% of the global total polyolefin production capacity, ranking first;

[0003] The Hostal en ACP process is equipped with three reactors, and each reactor needs to be quality inspected, which is a huge workload. In terms of quality control of polyethylene products, density is a key control parameter, which directly affects various performance indicators of polyethylene products, including tensile yield stress, tensile fracture stress, tensile fracture nominal strain, dart impact, haze, hardness, feel and other properties. The density of polyethylene in the reactor directly affects the density of the finished product, so accurate and timely measurement of the density of polyethylene in the reactor is crucial for product quality control;

[0004] In all Hostalen ACP processes for producing HDPE, the reactor density is monitored by the operator taking samples through the reactor sampler and then sending the samples to the laboratory for analysis and testing. Because the reactor slurry is a mixture of hexane and polyethylene powder, the laboratory also needs to dry the samples and then analyze them using the density gradient method;

[0005] The above test operation cycle is relatively long, which takes about 4 hours, causing a certain time delay, resulting in a certain deviation between the test results and the actual production conditions; the operator or the advanced control system can only predict the polymer density in the reactor through the curve, and then make corresponding adjustments, resulting in fluctuations in product quality. At the same time, the frequent sampling frequency causes the loss of hexane and increases the unit consumption of hexane. The hexane in the sample will evaporate into the air, which has a certain impact on environmental protection. The sampling operation and the test analysis also occupy a certain manpower cost. In normal production, this problem is a technical problem that needs to be solved urgently.

[0006] On the other hand, since the radioactive density sensor is easy to disassemble, the disassembled part is prone to radiation leakage. Based on this, how to solve the leakage problem at the disassembled part is still a technical problem to be solved. Summary of the invention

[0007] Purpose of the invention: The purpose of the present invention is to provide an online monitoring device for polyethylene slurry density to solve the technical problems of long time consumption for detecting slurry density by density gradient method and radiation leakage of split density sensor.

[0008] The above technical objectives of the present invention are achieved through the following technical solutions: an online monitoring device for polyethylene slurry density, comprising a polymerization reactor and a first pressure gauge and a first thermometer installed on the polymerization reactor, characterized in that: a first pipeline and a second pipeline are connected from the middle of the polymerization reactor, the first pipeline is connected to a flash tank, the second pipeline merges with the first pipeline, the first pipeline is connected to a third pipeline connected to the top of the polymerization reactor for reflux, the second pipeline is connected to a fourth pipeline connected to the top of the polymerization reactor for reflux, the first pipeline and the second pipeline are arranged in the same manner, wherein;

[0009] An electric valve, a radiation source density sensor, a first ball valve, a first centrifugal pump, a second pressure gauge, a second ball valve and a third ball valve are arranged in sequence on the first pipeline.

[0010] Further: the first pipeline is connected to the third pipeline and connected to the top of the polymerization reactor for reflux, the second pipeline is connected to the fourth pipeline and connected to the top of the polymerization reactor for reflux, and the third pipeline and the fourth pipeline are arranged in the same manner, wherein;

[0011] The fourth ball valve, the third flow meter, the second thermometer and the heat exchanger are arranged in sequence on the third pipeline.

[0012] Furthermore: the radiation source density sensor is installed on the first pipeline and the second pipeline through a protective device.

[0013] Further: the protective device comprises an upper column and a lower column, the lower column is fixedly connected to the first pipeline, and the lower column has a lower lead cover and a receiver;

[0014] A lead cover and a radiation source density sensor are arranged in the upper column, and the lower end surface of the upper column is fitted with the upper end surface of the lower column.

[0015] Further: a continuous first inner groove is provided on the upper end surface of the lower cylinder, a plurality of annular teeth extend in the first inner groove, a pressure ring is fixedly installed on the closed surface of the first inner groove, and a second inner groove extends on the closed surface of the pressure ring;

[0016] The lower end of the upper column faces the card and the plate extending outward, a locking ring is installed on the card and the plate, and the locking ring is inserted into the first inner groove with the card and the plate to achieve sealing;

[0017] Furthermore: the locking ring includes a soft connection ring connected to the abutment plate, the soft connection ring has a locking toe, a first sealing gasket and a second sealing gasket are installed between the locking toe and the abutment plate, wherein the first sealing gasket is slidably installed on the locking ring, and the second sealing gasket is fixedly connected to the abutment plate.

[0018] Compared with the prior art, the present invention has the following advantages: a radioactive source density sensor is installed on the first pipeline and the second pipeline at one side close to the polymerization reactor to detect the slurry density in real time, thereby avoiding the influence of temperature changes on the slurry density. By monitoring the slurry density in real time, the density can be adjusted in time, the stability can be improved, and the product quality fluctuation can be avoided. On the other hand, the radioactive source density sensor is fixed on the first pipeline and the second pipeline by adopting a combination of a protective upper column and a lower column, the lower column is fixedly connected to the first pipeline, the upper column is vertically inserted into the lower column to achieve sealing, and the sealing is maintained by its own weight. On the other hand, it can be dismantled by vertically pulling upwards. Since the structure of the present application is more reasonable, the production cost is low, and it is suitable for comprehensive promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow chart of the present invention;

[0020] Figure 2 is a cross-sectional view of the present invention;

[0021] Figure 3 It is a structural diagram of the cleaning drum of the present invention;

[0022] Figure 4 It is a structural diagram of the fixing member of the present invention;

[0023] Figure 5 It is a structural diagram of a filter plate according to the second embodiment of the present invention.

[0024] In the figure: 1, polymerization reactor; 2, first pressure gauge; 3, first thermometer; 4, first pipeline; 5, second pipeline; 6, flash tank; 7, third pipeline; 8, fourth pipeline; 9, electric valve; 10, radiation source density sensor; 11, first ball valve; 12, first centrifugal pump; 13, second pressure gauge; 14, second ball valve; 15, third ball valve; 16, fourth ball valve; 17, third flowmeter; 18, second thermometer; 19, heat exchanger; 21, upper cylinder; 22, lower cylinder; 23, lead sheet bottom; 24, receiver; 25, lead sheet cover; 28, first inner groove; 29, pressure ring; 30, annular gear; 31, second inner groove; 32, card and plate; 33, locking ring; 34, butt plate; 35, locking toe; 36, first sealing gasket; 37, second sealing gasket; 38, soft ring. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] In the description of the invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0027] Embodiment 1:

[0028] In the first embodiment of the present invention, Figure 1 As shown, an online monitoring device for polyethylene slurry density comprises a polymerization reactor 1 and a first pressure gauge 2 and a first thermometer 3 installed on the polymerization reactor 1, characterized in that: a first pipeline 4 and a second pipeline 5 are connected to the middle of the polymerization reactor 1, the first pipeline 4 is connected to a flash tank 6, the second pipeline 5 merges with the first pipeline 4, the first pipeline 4 is connected to a third pipeline 7 connected to the top of the polymerization reactor 1 for reflux, the second pipeline 5 is connected to a fourth pipeline 8 connected to the top of the polymerization reactor 1 for reflux, and the first pipeline 4 and the second pipeline 5 are arranged in the same manner, wherein;

[0029] The first pipeline 4 is sequentially provided with an electric valve 9, a radiation source density sensor 10, a first ball valve 11, a first centrifugal pump 12, a second pressure gauge 13, a second ball valve 14 and a third ball valve 15;

[0030] The first pipeline 4 is connected to the third pipeline 7 and connected to the top of the polymerization reactor 1 for reflux, the second pipeline 5 is connected to the fourth pipeline 8 and connected to the top of the polymerization reactor 1 for reflux, and the third pipeline 7 and the fourth pipeline 8 are arranged in the same manner, wherein;

[0031] The third pipeline 7 is sequentially arranged with a fourth ball valve 16 , a third flow meter 17 , a second thermometer 18 and a heat exchanger 19 .

[0032] By adopting the above technical scheme, one embodiment of the present invention is that the slurry (84°C) in the polymerization reactor 1 flows out from the outlet of the polymerization reactor 1 by its own gravity, enters the first pipeline 4 and the second pipeline 5, passes through the electric valve 9, the radiation source density sensor 10 and the first ball valve 11, and then enters the centrifugal pump 12. The centrifugal pump 12 uses centrifugal force to throw out the slurry, and a part of it enters the flash tank 6 after passing through the second pressure gauge 13, the second ball valve 14 and the third ball valve 15. The flash tank 6 is used to flash out excess hydrogen, and then it is sent to the next system through the flash tank. The other part of the slurry flows back to the heat exchanger 19 through the third pipeline 7 and the fourth pipeline 8 for heat exchange, and then returns to the polymerization reactor 1 through the second thermometer 18, the third flowmeter 17 and the fourth ball valve 16. The slurry returned to the top of the polymerization reactor 1 through the heat exchanger 19 has completed heat removal, and the temperature drops from 84°C to about 76°C;

[0033] In the above operation cycle, the radioactive source density sensor 10 is used to detect and calculate the density of the polyethylene powder in the polymerization reactor 1. The radioactive source density sensor 10 is installed between the electric valve 9 and the first centrifugal pump 12, where the temperature is the same as the reactor temperature, to avoid the influence of temperature changes on the slurry density and interference with the measurement of the radioactive source density sensor 10;

[0034] The radiation source density sensor 10 will detect the slurry density at the outlet of the polymerization reactor 1 in real time, thereby calculating the real-time density of the polymer powder, which is the same as the density of the polymer in the polymerization reactor. The operator can detect the polymer density in the polymerization reactor 1 based on the real-time data, reducing the delay caused by the analysis and testing process, and facilitating better adjustment of product quality to ensure the stability of product quality.

[0035] Embodiment 2:

[0036] In a second embodiment of the present invention, Figure 2-Figure 5 As shown, a polyethylene slurry density online monitoring device is characterized in that: the radioactive source density sensor 10 is installed on the first pipeline 4 and the second pipeline 5 through a protective device;

[0037] The protection device comprises an upper column 21 and a lower column 22, wherein the lower column 22 is fixedly connected to the first pipeline 4, and a lower lead cover 23 and a receiver 24 are arranged in the lower column 4;

[0038] The upper cylinder 21 has a lead cover 25 and a radiation source density sensor 10, and the lower end surface of the upper cylinder 21 is in contact with the upper end surface of the lower cylinder 22;

[0039] A continuous first inner groove 28 is provided on the upper end surface of the lower cylinder 22, a plurality of annular teeth 30 extend in the first inner groove 28, a pressing ring 29 is fixedly mounted on the closed surface of the first inner groove 28, and a second inner groove 31 extends on the closed surface of the pressing ring 29;

[0040] The lower end of the upper cylinder 21 faces the card and plate 32 extending outward, and a locking ring 33 is installed on the card and plate 32. The locking ring 33 is inserted into the first inner groove 28 along with the card and plate 32 to achieve sealing;

[0041] The locking ring 33 includes a soft ring 38 connected to the abutment plate 34 , and the soft ring 38 has a locking toe 35 , and a first sealing gasket 36 and a second sealing gasket 37 are installed between the locking toe 35 and the abutment plate 34 , wherein the first sealing gasket 36 is slidably installed on the locking ring 33 , and the second sealing gasket 37 is fixedly connected to the abutment plate 34 .

[0042] By adopting the above technical solution, an embodiment of the present invention is as follows: a circular hole is provided on the lower column 22, and the lower column 22 is sleeved on the first pipeline 4 and the second pipeline 5 through the circular hole and fixedly connected;

[0043] During installation, the staff holds the upper column 21, aligns the upper column 21 with the lower column 22, and then presses vertically downward, so that the locking ring 33 gradually approaches the first inner groove 28, and the locking ring 33 slides on the card and plate 32 as it is squeezed until the locking ring 33 fits the lower surface of the upper column 21. At this time, the soft ring 38 is continued to be inserted into the first inner groove 28, and the card and plate 32 are continued to be inserted into the second inner groove 31. At the same time, as the card and plate 32 are penetrated into the upper surface of the lower column 22, the first sealing gasket 36 is pushed until it abuts against the second sealing gasket 37 and then continues to be squeezed. The first sealing gasket 36 and the second sealing gasket 37 are lead sheets, thereby completing the assembly of the upper column 21 and the lower column 22. After assembly, it is maintained under the dead weight of the upper column 21. When disassembling, the worker holds the upper column 21 and moves it vertically upward to disassemble;

[0044] It should be noted that the first sealing gasket 36 and the second sealing gasket 37 are made of lead sheets, and the first sealing gasket 36 is replaced every time it is disassembled.

[0045] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements without departing from the principle of the present invention. These improvements should also be regarded as within the scope of protection of the present invention.

Claims

1. A polyethylene slurry density online monitoring device, comprising a polymerization reactor (1) and a first pressure gauge (2) and a first thermometer (3) installed on the polymerization reactor (1), characterized in that: The first pipeline (4) and the second pipeline (5) are connected to the middle of the polymerization reactor (1), the first pipeline (4) is connected to the flash tank (6), the second pipeline (5) and the first pipeline (4) are connected, the first pipeline (4) is connected to the third pipeline (7) and is connected to the top of the polymerization reactor (1) for reflux, the second pipeline (5) is connected to the fourth pipeline (8) and is connected to the top of the polymerization reactor (1) for reflux, the first pipeline (4) and the second pipeline (5) are arranged in the same manner, wherein; An electric valve (9), a radiation source density sensor (10), a first ball valve (11), a first centrifugal pump (12), a second pressure gauge (13), a second ball valve (14) and a third ball valve (15) are sequentially arranged on the first pipeline (4).

2. The polyethylene slurry density online monitoring device according to claim 1, characterized in that: The first pipeline (4) is connected to the third pipeline (7) and is connected to the top of the polymerization reactor (1) for reflux, the second pipeline (5) is connected to the fourth pipeline (8) and is connected to the top of the polymerization reactor (1) for reflux, and the third pipeline (7) and the fourth pipeline (8) are arranged in the same manner, wherein; A fourth ball valve (16), a third flow meter (17), a second thermometer (18) and a heat exchanger (19) are arranged in sequence on the third pipeline (7).

3. The polyethylene slurry density online monitoring device according to claim 2, characterized in that: The radiation source density sensor (10) is installed on the first pipeline (4) and the second pipeline (5) via a protective device.

4. The online monitoring device for polyethylene slurry density according to claim 3, characterized in that: The protective device comprises an upper column (21) and a lower column (22), wherein the lower column (22) is fixedly connected to the first pipeline (4), and a lead bottom (23) and a receiver (24) are provided in the lower column (4). The upper column (21) has a lead cover (25) and a radiation source density sensor (10) in it, and the lower end surface of the upper column (21) is in contact with the upper end surface of the lower column (22).

5. The online monitoring device for polyethylene slurry density according to claim 3, characterized in that: A continuous first inner groove (28) is provided on the upper end surface of the lower cylinder (22), a plurality of annular teeth (30) extend in the first inner groove (28), a pressure ring (29) is fixedly mounted on the closed surface of the first inner groove (28), and a second inner groove (31) extends on the closed surface of the pressure ring (29); The lower end of the upper column (21) faces a card and a plate (32) extending outwards, a locking ring (33) is installed on the card and the plate (32), and the locking ring (33) is inserted into the first inner groove (28) along with the card and the plate (32) to achieve sealing.

6. The online monitoring device for polyethylene slurry density according to claim 5, characterized in that: The locking ring (33) comprises a flexible ring (38) connected to the abutment plate (34), the flexible ring (38) having a locking toe (35), a first sealing gasket (36) and a second sealing gasket (37) being installed between the locking toe (35) and the abutment plate (34), wherein the first sealing gasket (36) is slidably installed on the locking ring (33), and the second sealing gasket (37) is fixedly connected to the abutment plate (34).

Images