Gas phase method polyethylene solid catalyst feeder pressure difference stabilizing device and control method

Abstract

The invention discloses a gas phase method polyethylene solid catalyst feeder pressure difference stabilizing device and a control method. The pressure difference stabilizing device comprises: a pressure difference detection unit, the high-pressure side of which is connected to the solid catalyst feeding storage tank and the low-pressure side of which is connected to the reactor, for detecting the pressure difference between the solid catalyst feeding storage tank and the reactor; the adjusting unit is used for adjusting the flow of nitrogen input or output from the solid catalyst feeding storage tank; the control unit is used for receiving the pressure difference signal acquired by the pressure difference detection unit and controlling the adjusting unit to adjust the nitrogen flow when the pressure difference between the solid catalyst feeding storage tank and the reactor deviates from a set value range; the discharge treatment unit is connected with the solid catalyst feeding storage tank through a nitrogen outlet channel, and a dust removal filter element is arranged on the outlet side of the discharge treatment unit and used for purifying nitrogen which is discharged from the outlet side of the discharge treatment unit and contains catalyst particles. Therefore, the pressure difference between the feeder and the reactor is stably controlled, and the production stability and the product quality are improved.

Description

Technical Field

[0001] The invention relates to the technical field of polyethylene production, in particular to a pressure difference stabilizing device and a control method for a gas phase polyethylene solid catalyst feeder. Background Art

[0002] The solid catalyst feeder is the core equipment of the gas phase polyethylene process. The feeder feeding speed is an important parameter of the reactor output. The accurate feeding of solid catalyst is crucial to product quality and production efficiency. In the gas phase polyethylene production process, the pressure difference stability between the feed tank and the reactor has a crucial influence on the catalyst feeding accuracy and production continuity. However, due to the interference of various factors, the pressure difference is prone to fluctuations, resulting in uneven feeding, affecting product quality and production efficiency. Summary of the invention

[0003] The invention provides a pressure difference stabilizing device and a control method for a gas phase polyethylene solid catalyst feeder, aiming to achieve stable control of the pressure difference between the feeder and the reactor and improve production stability and product quality.

[0004] In a first aspect, a pressure difference stabilizing device for a solid catalyst feeder for a gas phase polyethylene is provided, comprising:

[0005] A pressure difference detection unit, wherein the high-pressure side of the pressure difference detection unit is connected to the solid catalyst feeding storage tank, and the low-pressure side of the pressure difference detection unit is connected to the reactor, and is used to detect the pressure difference between the solid catalyst feeding storage tank and the reactor;

[0006] The regulating unit includes two pneumatic regulating valves, which are respectively arranged at the inlet and outlet of the solid catalyst feeding storage tank; the regulating unit is used to regulate the nitrogen flow input or output in the solid catalyst feeding storage tank;

[0007] The control unit is used to receive the pressure difference signal collected by the pressure difference detection unit. When the pressure difference signal indicates that the pressure difference between the solid catalyst feeding storage tank and the reactor deviates from the set value range, the control regulating unit adjusts the nitrogen flow rate to achieve stable control of the pressure difference.

[0008] In combination with the first aspect, in certain implementations of the first aspect, when it is detected that the pressure difference between the solid catalyst feeding storage tank and the reactor is higher than the upper limit of the set value range, the opening of the inlet pneumatic regulating valve on the inlet side of the solid catalyst feeding storage tank is increased to pressurize the solid catalyst feeding storage tank;

[0009] When it is detected that the pressure difference between the solid catalyst feeding storage tank and the reactor is lower than the lower limit of the set value range, the opening of the outlet pneumatic regulating valve on the outlet side of the solid catalyst feeding storage tank is increased to relieve the pressure of the solid catalyst feeding storage tank.

[0010] In combination with the first aspect, in certain implementations of the first aspect, an inlet pneumatic regulating valve is arranged at the nitrogen inlet channel of the solid catalyst feeding storage tank, and on the nitrogen inlet channel, a high-pressure nitrogen inlet supply valve and an inlet feeder stop valve are respectively arranged before and after the inlet pneumatic regulating valve.

[0011] In combination with the first aspect, in certain implementations of the first aspect, the outlet pneumatic regulating valve is arranged in the nitrogen outlet channel of the solid catalyst feeding storage tank, and on the nitrogen outlet channel, an outlet feeder stop valve and an outlet discharge stop valve are respectively arranged before and after the outlet pneumatic regulating valve.

[0012] In combination with the first aspect, in certain implementations of the first aspect, the pressure difference stabilization device also includes an emission treatment unit; the emission treatment unit is connected to the solid catalyst feeding storage tank through a nitrogen outlet channel, and a dust removal filter is provided on the outlet side of the emission treatment unit, and the dust removal filter is used to purify the nitrogen containing catalyst particles discharged from the outlet side of the emission treatment unit.

[0013] In combination with the first aspect, in certain implementations of the first aspect, the emission treatment unit includes a catalyst collecting tank; a dust removal filter element is installed on the top of the catalyst collecting tank; the catalyst collecting tank includes four interfaces, namely an injection port, a nitrogen discharge port, a filter element backflush port, and a dust discharge port; the injection port corresponds to the collection tank inlet, a filtered gas discharge valve is provided at the nitrogen discharge port; a filter element backflush valve is provided at the filter element backflush port; the dust discharge port corresponds to the catalyst waste discharge port.

[0014] In combination with the first aspect, in certain implementations of the first aspect, after the catalyst collection tank has run for a certain period of time, the filter element backflush valve is opened and the filter element is cleaned with high-pressure nitrogen. The cleaned catalyst falls into the catalyst collection tank and is discharged through the discharge port after deactivation.

[0015] In combination with the first aspect, in certain implementations of the first aspect, the differential pressure detection unit is a differential pressure transmitter, and a back-blowing valve group is installed at the pressure inlet of the differential pressure transmitter.

[0016] In combination with the first aspect, in certain implementations of the first aspect, the control unit is a PLC control unit or a DCS control unit.

[0017] In a second aspect, a pressure difference stabilization control method for a gas phase polyethylene solid catalyst feeder is provided, wherein the control method is applied to a pressure difference stabilization device as described in any one of the implementations of the first aspect above; the control method comprises:

[0018] The pressure difference detection unit is responsible for real-time monitoring of the pressure difference between the solid catalyst feeding tank and the reactor, and converting the pressure signal into an electrical signal and transmitting it to the control unit;

[0019] After receiving the signal from the pressure difference detection unit, the control unit compares it with the set value range. If the pressure difference deviates from the set value range, the control unit sends a control signal to the regulating unit;

[0020] The regulating unit adjusts the valve opening according to the control signal; when the pressure difference between the solid catalyst feeding storage tank and the reactor is too high, the pneumatic regulating valve on the outlet side increases the opening to release the excess pressure; when the pressure difference between the solid catalyst feeding storage tank and the reactor is too low, the pneumatic regulating valve on the inlet side increases the opening to increase the pressure in the storage tank, so that the pressure difference is stabilized within the set value range;

[0021] The nitrogen containing the catalyst is discharged from the solid catalyst feeding storage tank and enters the catalyst collecting tank, and is discharged after being filtered by the dust removal filter element; after each certain operation cycle, the backflush valve is opened and the filter element is cleaned with high-pressure nitrogen. The cleaned catalyst falls into the collecting tank and is discharged through the discharge port after being deactivated.

[0022] Compared with the prior art, the solution provided by the present invention includes at least the following beneficial technical effects:

[0023] 1. Significantly improve the accuracy of feeding: Through stable pressure difference control, the feeding amount of solid catalyst can be accurately controlled, thereby greatly improving the consistency and stability of product quality.

[0024] For example, in a large polyethylene production plant A, before using the device and control method of the present invention, the unstable pressure difference caused poor catalyst feeder feeding accuracy, resulting in unstable reaction in the reactor and uneven physical properties of the product. After the introduction of the present invention, the consistency and qualified rate of product performance indicators were greatly improved.

[0025] 2. Enhance the continuity and stability of production: Stable pressure difference helps to reduce abnormal situations in the production process, reduce the occurrence rate of equipment failures, and ensure continuous and stable operation of production.

[0026] For example, in a large polyethylene production plant A, before the device and control method of the present invention were used, accidents of carrying section pressure difference alarm chain shutdown due to unstable pressure difference often occurred. After the introduction of the present invention, the occurrence rate of equipment failure was reduced, ensuring continuous and stable operation of production.

[0027] 3. Strong adaptability: The device and control method of the present invention can be applied to solid catalysts of various specifications and have wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a structural diagram of a pressure difference stabilizing device for a gas phase polyethylene solid catalyst feeder according to the present invention.

[0029] Figure 2This is a schematic diagram of the feeder discharge curve before and after the pressure difference stabilization device is put into use.

[0030] Figure numerals: 1. High-pressure nitrogen inlet supply valve; 2. Inlet pneumatic regulating valve; 3. Inlet feeder stop valve; 4. Differential pressure transmitter; 5. Outlet feeder stop valve; 6. Outlet pneumatic regulating valve; 7. Outlet discharge stop valve; 8. Dust removal filter element; 9. Collection tank inlet; 10. Catalyst collection tank; 11. Catalyst waste discharge port; 12. Filter element backflush valve; 13. Filtered gas discharge valve; 14. Solid catalyst feeding storage tank. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The invention provides a pressure difference stabilizing device for a gas phase polyethylene solid catalyst feeder, comprising a pressure difference detecting unit, a regulating unit and a control unit.

[0033] exist Figure 1 In the illustrated embodiment, the pressure difference detection unit is a high-precision pressure difference transmitter 4. The high-pressure side of the pressure difference detection unit is connected to the solid catalyst feeding storage tank 14, and the low-pressure side of the pressure difference detection unit is connected to the reactor. In some embodiments, in order to avoid catalyst particles blocking the pressure measuring pipeline, it is necessary to use a back-blowing method for pressure measurement, that is, to install a back-blowing valve group at the pressure inlet of the differential pressure transmitter 4.

[0034] The regulating unit includes two pneumatic regulating valves, which are respectively arranged at the inlet and outlet of the solid catalyst feeding storage tank 14. The pneumatic regulating valve can quickly and accurately adjust the nitrogen flow rate according to the control signal, thereby achieving stable control of the pressure difference. Figure 1 In the embodiment shown, the regulating unit includes an inlet pneumatic regulating valve 2 and an outlet pneumatic regulating valve 6. When it is detected that the pressure difference between the solid catalyst feeding storage tank 14 and the reactor is too high, the solid catalyst feeding storage tank 14 is pressurized through the inlet pneumatic regulating valve 2; otherwise, the pressure is released through the outlet pneumatic regulating valve 6 to ensure the stability of the pressure difference.

[0035] exist Figure 1 In the embodiment shown, a high-pressure nitrogen inlet supply valve 1 and an inlet feeder stop valve 3 may be respectively arranged before and after the inlet pneumatic regulating valve 2. An outlet feeder stop valve 5 and an outlet discharge stop valve 7 may also be respectively arranged before and after the outlet pneumatic regulating valve 6.

[0036] The control unit can adopt a PLC control unit or a DCS control unit, which has fast data processing capabilities and accurate control algorithms, can effectively analyze and process the detected data, and generate accurate control signals.

[0037] The pressure difference stabilization device may also include an emission treatment unit. The emission treatment unit includes a catalyst collection tank 10. A dust removal filter element 8 is installed on the top of the catalyst collection tank 10, and the dust removal filter element 8 is used to purify the nitrogen containing catalyst particles discharged from the outlet side. The catalyst collection tank 10 may include four interfaces, namely an injection port, a nitrogen discharge port, a filter element backflush port, and a dust discharge port. Figure 1 In the embodiment shown, the injection port may correspond to the collection tank inlet 9, and the nitrogen discharge port may be provided with a filtered gas discharge valve 13. The filter element backflush port may be provided with a filter element backflush valve 12. The dust discharge port may correspond to the catalyst waste discharge port 11.

[0038] like Figure 1 As shown, the present invention provides a pressure difference stabilizing device for a gas phase polyethylene solid catalyst feeder, comprising a high-pressure nitrogen inlet supply valve 1, an inlet pneumatic regulating valve 2, an inlet feeder stop valve 3, a differential pressure transmitter 4, an outlet feeder stop valve 5, an outlet pneumatic regulating valve 6, an outlet discharge stop valve 7, a dust removal filter element 8, a collection tank inlet 9, a catalyst collection tank 10, a catalyst waste discharge port 11, a filter element backflush valve 12, a filtered gas discharge valve 13, and a solid catalyst feeding storage tank 14.

[0039] The solid catalyst feeding storage tank 14 has a nitrogen inlet channel and a nitrogen outlet channel. The nitrogen inlet channel is provided with a high-pressure nitrogen inlet supply valve 1, an inlet pneumatic regulating valve 2, and an inlet feeder stop valve 3. The nitrogen outlet channel is provided with an outlet feeder stop valve 5, an outlet pneumatic regulating valve 6, and an outlet discharge stop valve 7. The nitrogen outlet channel of the solid catalyst feeding storage tank 14 is connected to the catalyst collecting tank 10 through the collecting tank inlet 9.

[0040] When the solid catalyst feeding storage tank 14 is put into operation, the inlet high-pressure nitrogen supply valve 1, the inlet feeder stop valve 3, the outlet feeder stop valve 5, and the outlet discharge stop valve 7 are opened to put the pressure difference stabilization device into use. After receiving the signal from the pressure difference transmitter 4, the control unit compares it with the set pressure difference value. If the actual pressure difference deviates from the set value range, the control unit will send a control signal to the inlet pneumatic regulating valve 2 and / or the outlet pneumatic regulating valve 6. The inlet pneumatic regulating valve 2 and / or the outlet pneumatic regulating valve 6 adjust the valve opening according to the control signal. Among them, when the pressure difference between the solid catalyst feeding storage tank 14 and the reactor is too high, the outlet pneumatic regulating valve 6 will increase the opening to release the excess pressure; when the pressure difference between the solid catalyst feeding storage tank 14 and the reactor is too low, the inlet pneumatic regulating valve 2 will increase the opening and pressurize the tank, so that the pressure difference is kept within a stable set value range.

[0041] Since the catalyst is polluting and toxic, the nitrogen containing the catalyst discharged during operation first enters the catalyst collection tank 10 through the collection tank inlet 9, and is discharged through the discharge valve 13 after being filtered by the dust removal filter element 8. After each certain operation cycle, the filter element backflush valve 12 is opened to clean the filter element 8 with high-pressure nitrogen. The cleaned catalyst falls into the catalyst collection tank 10 and is discharged through the discharge port 11 after being deactivated.

[0042] refer to Figure 2 In practical applications, the pressure difference stabilization device successfully controlled the pressure difference fluctuation between the feeding tank and the reactor within ±0.05MPa, significantly improving the catalyst feeding accuracy and production stability.

[0043] The following describes a method for stabilizing the pressure difference control of a solid catalyst feeder for gas phase polyethylene, which can be applied to Figure 1 The pressure difference stabilizing device shown in the figure. The specific steps of the control method are as follows.

[0044] Step 1: The pressure difference detection unit is responsible for real-time monitoring of the pressure difference between the solid catalyst feeding storage tank 14 and the reactor, and converts the pressure signal into an electrical signal and transmits it to the control unit, so that the pressure of the solid catalyst feeding storage tank can be controlled by the regulating unit.

[0045] Step 2: After receiving the signal from the pressure difference detection unit, the control unit compares it with the set pressure value. If the pressure difference deviates from the set value range, the control unit sends a control signal to the regulating unit.

[0046] Step 3: The regulating unit adjusts the opening of the valve according to the control signal.

[0047] When the pressure difference between the solid catalyst feeding tank and the reactor is too high, the pneumatic regulating valve on the outlet side will increase its opening to release excess pressure; when the pressure difference between the solid catalyst feeding tank and the reactor is too low, the pneumatic regulating valve on the inlet side will increase its opening to increase the pressure in the tank, thereby keeping the pressure difference within a stable set value range.

[0048] Step 4: After the nitrogen containing the catalyst is discharged from the solid catalyst feeding storage tank, it first enters the catalyst collection tank and is discharged after being filtered by the dust removal filter element. After each certain period of operation, the backflush valve is opened to clean the filter element with high-pressure nitrogen. The cleaned catalyst falls into the collection tank and is discharged through the discharge port after being deactivated.

[0049] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A pressure difference stabilizing device for a solid catalyst feeder for gas phase polyethylene, characterized in that: include: A pressure difference detection unit, wherein the high-pressure side of the pressure difference detection unit is connected to the solid catalyst feeding storage tank (14), and the low-pressure side of the pressure difference detection unit is connected to the reactor, and is used to detect the pressure difference between the solid catalyst feeding storage tank (14) and the reactor; A regulating unit, comprising two pneumatic regulating valves, respectively arranged at the inlet and outlet of the solid catalyst feeding storage tank (14); The regulating unit is used to regulate the nitrogen flow rate input or output from the solid catalyst feeding storage tank (14); The control unit is used to receive the pressure difference signal collected by the pressure difference detection unit, and when the pressure difference signal indicates that the pressure difference between the solid catalyst feeding storage tank (14) and the reactor deviates from the set value range, the control regulating unit regulates the nitrogen flow rate to achieve stable control of the pressure difference.

2. The pressure difference stabilizing device according to claim 1, characterized in that: When it is detected that the pressure difference between the solid catalyst feeding storage tank (14) and the reactor is higher than the upper limit of the set value range, the opening of the inlet pneumatic regulating valve (2) on the inlet side of the solid catalyst feeding storage tank (14) is increased to increase the pressure of the solid catalyst feeding storage tank (14); When it is detected that the pressure difference between the solid catalyst feeding storage tank (14) and the reactor is lower than the lower limit of the set value range, the opening of the outlet pneumatic regulating valve (6) on the outlet side of the solid catalyst feeding storage tank (14) is increased to relieve the pressure of the solid catalyst feeding storage tank (14).

3. The pressure difference stabilizing device according to claim 2, characterized in that: The inlet pneumatic regulating valve (2) is arranged at the nitrogen inlet passage of the solid catalyst feeding storage tank (14). On the nitrogen inlet passage, a high-pressure nitrogen inlet supply valve (1) and an inlet feeder stop valve (3) are arranged before and after the inlet pneumatic regulating valve (2).

4. The pressure difference stabilizing device according to claim 2, characterized in that: The outlet pneumatic regulating valve (6) is arranged on the nitrogen outlet channel of the solid catalyst feeding storage tank (14), and an outlet feeder stop valve (5) and an outlet discharge stop valve (7) are respectively arranged before and after the outlet pneumatic regulating valve (6) on the nitrogen outlet channel.

5. The pressure difference stabilizing device according to claim 4, characterized in that: The pressure difference stabilization device also includes an emission treatment unit; the emission treatment unit is connected to the solid catalyst feeding storage tank (14) through a nitrogen outlet channel, and a dust removal filter (8) is provided on the outlet side of the emission treatment unit. The dust removal filter (8) is used to purify the nitrogen containing catalyst particles discharged from the outlet side of the emission treatment unit.

6. The pressure difference stabilizing device according to claim 5, characterized in that: The emission treatment unit comprises a catalyst collection tank (10); a dust removal filter element (8) is installed on the top of the catalyst collection tank (10); the catalyst collection tank (10) comprises four interfaces, namely an injection port, a nitrogen discharge port, a filter element backflush port, and a dust discharge port; the injection port corresponds to the collection tank inlet (9); a filtered gas discharge valve (13) is arranged at the nitrogen discharge port; a filter element backflush valve (12) is arranged at the filter element backflush port; and the dust discharge port corresponds to the catalyst waste discharge port (11).

7. The pressure difference stabilizing device according to claim 6, characterized in that: After the catalyst collection tank (10) runs for a certain period of time, the filter element backflush valve (12) is opened to clean the filter element (8) with high-pressure nitrogen. The cleaned catalyst falls into the catalyst collection tank (10) and is discharged through the discharge port (11) after being deactivated.

8. The pressure difference stabilizing device according to claim 1, characterized in that: The differential pressure detection unit is a differential pressure transmitter (4), and a back-blowing valve group is installed at the pressure inlet of the differential pressure transmitter (4).

9. The pressure difference stabilizing device according to claim 1, characterized in that: The control unit adopts a PLC control unit or a DCS control unit.

10. A method for stabilizing the differential pressure control of a solid catalyst feeder for gas phase polyethylene, characterized in that: The control method is applied to the pressure difference stabilization device according to any one of claims 1 to 9; the control method comprises: The pressure difference detection unit is responsible for real-time monitoring of the pressure difference between the solid catalyst feeding storage tank (14) and the reactor, and converting the pressure signal into an electrical signal and transmitting it to the control unit; After receiving the signal from the pressure difference detection unit, the control unit compares it with the set value range. If the pressure difference deviates from the set value range, the control unit sends a control signal to the regulating unit; The regulating unit adjusts the opening of the valve according to the control signal; when the pressure difference between the solid catalyst feeding storage tank (14) and the reactor is too high, the pneumatic regulating valve on the outlet side increases the opening to release the excess pressure; when the pressure difference between the solid catalyst feeding storage tank (14) and the reactor is too low, the pneumatic regulating valve on the inlet side increases the opening to increase the pressure in the storage tank, thereby stabilizing the pressure difference within the set value range; Nitrogen containing the catalyst is discharged from the solid catalyst feeding storage tank (14) and enters the catalyst collecting tank, and is discharged after being filtered by a dust removal filter element; after each certain operation cycle, the backflush valve is opened, and the filter element is cleaned with high-pressure nitrogen, and the cleaned catalyst falls into the collecting tank and is discharged through the discharge port after being deactivated.

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