Differential pressure stabilization apparatus and control method for gas-phase polyethylene solid catalyst feeder

Abstract

A differential pressure stabilization apparatus and control method for a gas-phase polyethylene solid catalyst feeder. The differential pressure stabilization apparatus comprises: a differential pressure measurement unit, a high-pressure side of which is connected to a solid catalyst feeding storage tank (14), a low-pressure side of which is connected to a reactor, and which is configured to measure a differential pressure between the solid catalyst feeding storage tank (14) and the reactor; a regulation unit, which is configured to regulate the flow rate of nitrogen that is input into or output from the solid catalyst feeding storage tank (14); a control unit, which is configured to receive a differential pressure signal collected by the differential pressure measurement unit, and control, when the differential pressure between the solid catalyst feeding storage tank (14) and the reactor deviates from a set value range, the regulation unit to regulate the flow rate of nitrogen; and a discharge treatment unit, which is connected to the solid catalyst feeding storage tank (14) by means of a nitrogen outlet channel, wherein a dust removal filter element (8) is provided on an outlet side of the discharge treatment unit, and is configured to purify nitrogen that contains catalyst particles and is discharged from the outlet side of the discharge treatment unit.

Description

Differential pressure stabilization device and control method for gas-phase polyethylene solid catalyst feeder

[0001] This application claims priority to Chinese Patent Application No. 2024119714859, filed on December 30, 2024, entitled "Differential Pressure Stabilizing Device and Control Method for Gas-Phase Polyethylene Solid Catalyst Feeder", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the technical field of polyethylene production, and in particular to a differential pressure stabilization device and control method for a solid catalyst feeder in the gas-phase polyethylene process. Background Technology

[0003] The solid catalyst feeder is a core piece of equipment in the gas-phase polyethylene process. The feed rate is a crucial parameter for reactor output, and precise solid catalyst feeding is essential for product quality and production efficiency. In gas-phase polyethylene production, the stability of the pressure difference between the feed tank and the reactor has a vital impact on catalyst feeding accuracy and production continuity. However, due to various factors, pressure difference fluctuations are prone to occur, leading to uneven feeding and affecting product quality and production efficiency. Summary of the Invention

[0004] This invention provides a pressure differential stabilization device and control method for a gas-phase polyethylene solid catalyst feeder, aiming to achieve stable control of the pressure differential between the feeder and the reactor, thereby improving production stability and product quality.

[0005] In a first aspect, a differential pressure stabilization device for a gas-phase polyethylene solid catalyst feeder is provided, comprising:

[0006] The differential pressure detection unit is connected to the solid catalyst feeding tank on its high-pressure side and to the reactor on its low-pressure side, and is used to detect the differential pressure between the solid catalyst feeding tank and the reactor.

[0007] The regulating unit includes two pneumatic regulating valves, which are respectively installed at the inlet and outlet of the solid catalyst feeding tank; the regulating unit is used to regulate the nitrogen flow rate input or output in the solid catalyst feeding tank;

[0008] The control unit receives the differential pressure signal collected by the differential pressure detection unit. When the differential pressure signal indicates that the differential pressure between the solid catalyst feeding tank and the reactor deviates from the set value range, the control unit adjusts the nitrogen flow rate to achieve stable control of the differential pressure.

[0009] In conjunction with the first aspect, in some implementations of the first aspect, when the pressure difference between the solid catalyst feeding tank and the reactor is detected to be 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 tank is increased to pressurize the solid catalyst feeding tank;

[0010] When the pressure difference between the solid catalyst feeding tank and the reactor is detected to be 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 tank is increased to depressurize the solid catalyst feeding tank.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the inlet pneumatic regulating valve is installed in the nitrogen inlet channel of the solid catalyst feeding tank, and a high-pressure nitrogen inlet supply valve and an inlet feeder shut-off valve are respectively installed before and after the inlet pneumatic regulating valve in the nitrogen inlet channel.

[0012] In conjunction with the first aspect, in some implementations of the first aspect, the outlet pneumatic regulating valve is installed in the nitrogen outlet channel of the solid catalyst feeding tank, and an outlet feeder shut-off valve and an outlet discharge shut-off valve are respectively installed before and after the outlet pneumatic regulating valve in the nitrogen outlet channel.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the differential pressure stabilizing device further includes an emission treatment unit; the emission treatment unit is connected to the solid catalyst feeding tank through a nitrogen outlet channel, and a dust removal filter element is provided on the outlet side of the emission treatment unit for purifying the nitrogen containing catalyst particles emitted from the outlet side of the emission treatment unit.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the emission treatment unit includes a catalyst collection tank; a dust removal filter element is installed on the top of the catalyst collection tank; the catalyst collection tank includes four ports, namely an injection port, a nitrogen emission port, a filter element backflush port, and a dust emission port; the injection port corresponds to the inlet of the collection tank, a filtered gas emission valve is provided at the nitrogen emission port; a filter element backflush valve is provided at the filter element backflush port; and the dust emission port corresponds to the catalyst waste emission port.

[0015] In conjunction with the first aspect, in some implementations of the first aspect, after the catalyst collection tank has been running 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 after deactivation, it is discharged through the discharge port.

[0016] In conjunction with the first aspect, in some implementations of the first aspect, the differential pressure detection unit is a differential pressure transmitter, and a backflush valve assembly is installed at the pressure port of the differential pressure transmitter.

[0017] In conjunction with the first aspect, in some implementations of the first aspect, the control unit adopts a PLC control unit or a DCS control unit.

[0018] In a second aspect, a method for stabilizing and controlling the differential pressure of a gas-phase polyethylene solid catalyst feeder is provided, wherein the control method is applied to a differential pressure stabilization device as described in any of the implementations of the first aspect above; the control method includes:

[0019] The differential pressure detection unit is responsible for real-time monitoring of the differential pressure between the solid catalyst feeding tank and the reactor, and converting the pressure signal into an electrical signal to transmit it to the control unit.

[0020] After receiving the signal from the differential pressure detection unit, the control unit compares it with the set value range. If the differential pressure deviates from the set value range, the control unit sends a control signal to the regulating unit.

[0021] The regulating unit adjusts the valve opening according to the control signal; when the pressure difference between the solid catalyst feeding tank and the reactor is too high, the outlet pneumatic regulating valve increases its opening to release excess pressure; when the pressure difference between the solid catalyst feeding tank and the reactor is too low, the inlet pneumatic regulating valve increases its opening to pressurize the tank, thereby stabilizing the pressure difference within the set value range.

[0022] Nitrogen containing the catalyst is discharged from the solid catalyst feeding tank and then enters the catalyst collection tank. After being filtered by the dust removal filter element, it is discharged. After each certain operating cycle, the backflush valve is opened and the filter element is cleaned with high-pressure nitrogen. The cleaned catalyst falls into the collection tank and is discharged through the discharge port after deactivation.

[0023] Compared with the prior art, the solution provided by the present invention has at least the following beneficial technical effects:

[0024] 1. Significantly improves feeding accuracy: Through stable differential pressure control, the amount of solid catalyst fed can be precisely controlled, thereby greatly improving the consistency and stability of product quality.

[0025] For example, in a large polyethylene production plant A, before using the device and control method of this invention, unstable pressure differentials led to poor catalyst feeder accuracy, resulting in unstable reactions within the reactor and inconsistent physical properties of the products. After introducing this invention, the consistency and pass rate of product performance indicators were significantly improved.

[0026] 2. Enhance the continuity and stability of production: A stable pressure differential helps reduce abnormal situations in the production process, lower the equipment failure rate, and ensure the continuous and stable operation of production.

[0027] For example, in a large polyethylene production plant A, before using the device and control method of this invention, accidents causing differential pressure alarms and interlocking shutdowns in the conveyor belt section occurred frequently due to unstable differential pressure. After introducing this invention, the equipment failure rate was reduced, ensuring continuous and stable production operation.

[0028] 3. High adaptability: The device and control method of the present invention can be applied to various solid catalysts of different specifications, and have wide applicability. Attached Figure Description

[0029] Figure 1 is a structural diagram of a differential pressure stabilization device for a gas-phase polyethylene solid catalyst feeder according to the present invention.

[0030] Figure 2 is a schematic diagram of the feeder discharge curves before and after the differential pressure stabilization device is put into use.

[0031] Attached reference numerals: 1. High-pressure nitrogen inlet supply valve; 2. Inlet pneumatic regulating valve; 3. Inlet feeder shut-off valve; 4. Differential pressure transmitter; 5. Outlet feeder shut-off valve; 6. Outlet pneumatic regulating valve; 7. Outlet discharge shut-off valve; 8. Dust collector 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 Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0033] This invention provides a differential pressure stabilization device for a gas-phase polyethylene solid catalyst feeder, comprising a differential pressure detection unit, an adjustment unit, and a control unit.

[0034] In the embodiment shown in Figure 1, the differential pressure detection unit is a high-precision differential pressure transmitter 4. The high-pressure side of the differential pressure detection unit is connected to the solid catalyst feeding tank 14, and the low-pressure side is connected to the reactor. In some embodiments, to avoid catalyst particles clogging the pressure measurement pipeline, a backflush pressure measurement method is required, i.e., a backflush valve assembly is installed at the pressure input port of the differential pressure transmitter 4.

[0035] The regulating unit includes two pneumatic regulating valves, respectively located at the inlet and outlet of the solid catalyst feeding tank 14. These valves can rapidly and accurately adjust the nitrogen flow rate according to control signals, thereby achieving stable pressure differential control. In the embodiment shown in Figure 1, the regulating unit includes an inlet pneumatic regulating valve 2 and an outlet pneumatic regulating valve 6. When a high pressure differential is detected between the solid catalyst feeding tank 14 and the reactor, the inlet pneumatic regulating valve 2 pressurizes the solid catalyst feeding tank 14; conversely, the outlet pneumatic regulating valve 6 depressurizes the tank to ensure pressure differential stability.

[0036] In the embodiment shown in Figure 1, a high-pressure nitrogen inlet supply valve 1 and an inlet feeder shut-off valve 3 can be respectively installed before and after the inlet pneumatic regulating valve 2. An outlet feeder shut-off valve 5 and an outlet discharge shut-off valve 7 can be respectively installed before and after the outlet pneumatic regulating valve 6.

[0037] The control unit can be a PLC control unit or a DCS control unit, which has fast data processing capabilities and precise control algorithms. It can effectively analyze and process the detected data and generate accurate control signals.

[0038] The differential pressure stabilization device may also include an emission treatment unit. The emission treatment unit includes a catalyst collection tank 10. A dust filter element 8 is installed on the top of the catalyst collection tank 10, which is used to purify the nitrogen gas containing catalyst particles emitted from the outlet side. The catalyst collection tank 10 may include four ports: an injection port, a nitrogen emission port, a filter element backflush port, and a dust emission port. In the embodiment shown in Figure 1, the injection port may correspond to the collection tank inlet 9, and a filtered gas emission valve 13 may be installed at the nitrogen emission port. A filter element backflush valve 12 may be installed at the filter element backflush port. The dust emission port may correspond to the catalyst waste emission port 11.

[0039] As shown in Figure 1, the present invention provides a differential pressure stabilization 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 shut-off valve 3, a differential pressure transmitter 4, an outlet feeder shut-off valve 5, an outlet pneumatic regulating valve 6, an outlet discharge shut-off 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.

[0040] The solid catalyst feeding storage tank 14 has a nitrogen inlet channel and a nitrogen outlet channel. The nitrogen inlet channel is equipped with a high-pressure nitrogen inlet supply valve 1, an inlet pneumatic regulating valve 2, and an inlet feeder shut-off valve 3. The nitrogen outlet channel is equipped with an outlet feeder shut-off valve 5, an outlet pneumatic regulating valve 6, and an outlet discharge shut-off valve 7. The nitrogen outlet channel of the solid catalyst feeding storage tank 14 is connected to the catalyst collection tank 10 through the collection tank inlet 9.

[0041] After the solid catalyst feeding tank 14 is put into operation, the inlet high-pressure nitrogen supply valve 1, the inlet feeder shut-off valve 3, the outlet feeder shut-off valve 5, and the outlet discharge shut-off valve 7 are opened to activate the differential pressure stabilization device. The control unit receives the signal from the differential pressure transmitter 4 and compares it with the set differential pressure value. If the actual differential pressure deviates from the set value range, the control unit sends 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 their opening according to the control signal. Specifically, when the differential pressure between the solid catalyst feeding tank 14 and the reactor is too high, the outlet pneumatic regulating valve 6 will increase its opening to release excess pressure; when the differential pressure between the solid catalyst feeding tank 14 and the reactor is too low, the inlet pneumatic regulating valve 2 will increase its opening to pressurize the tank, thereby maintaining the differential pressure within a stable set value range.

[0042] Because the catalyst has certain polluting and toxic properties, the nitrogen gas containing the catalyst emitted during operation first enters the catalyst collection tank 10 through the collection tank inlet 9, is filtered by the dust removal filter element 8, and is then discharged through the discharge valve 13. After each certain operating cycle, the filter element backflush valve 12 is opened, and the filter element 8 is cleaned with high-pressure nitrogen gas. The cleaned catalyst falls into the catalyst collection tank 10, and after deactivation, is discharged through the discharge port 11.

[0043] Referring to Figure 2, in practical applications, this differential pressure stabilization device successfully controls the differential pressure fluctuation between the feeding tank and the reactor within ±0.05MPa, significantly improving the feeding accuracy of the catalyst and the stability of production.

[0044] The following describes a method for stabilizing the differential pressure of a gas-phase polyethylene solid catalyst feeder, provided by this invention. This method can be applied to the differential pressure stabilization device shown in Figure 1. The specific steps of this control method are as follows.

[0045] Step 1: The differential pressure detection unit is responsible for real-time monitoring of the pressure difference between the solid catalyst feeding tank 14 and the reactor, and converting the pressure signal into an electrical signal to be transmitted to the control unit. This allows the regulating unit to control the pressure of the solid catalyst feeding tank.

[0046] Step 2: After receiving the signal from the differential pressure detection unit, the control unit compares it with the set pressure value. If the differential pressure deviates from the set value range, the control unit will send a control signal to the regulating unit.

[0047] Step 3: The regulating unit adjusts the valve opening according to the control signal.

[0048] 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 pressurize the tank, thereby keeping the pressure difference within a stable set range.

[0049] Step 4: Nitrogen gas containing the catalyst, after being discharged from the solid catalyst feeding tank, first enters the catalyst collection tank, and is then filtered through a dust removal filter before being discharged. After each certain operating cycle, the backflush valve is opened, and the filter element is cleaned with high-pressure nitrogen gas. The cleaned catalyst falls into the collection tank, and after deactivation, it is discharged through the exhaust port.

[0050] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can 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 should be determined by the scope defined in the claims of the present invention.

Claims

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

2. The differential pressure stabilizing device according to claim 1, characterized in that, When the pressure difference between the solid catalyst feeding tank (14) and the reactor is detected to be 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 tank (14) is increased to pressurize the solid catalyst feeding tank (14); When the pressure difference between the solid catalyst feeding tank (14) and the reactor is detected to be lower than the lower limit of the set value range, the opening degree of the outlet pneumatic regulating valve (6) on the outlet side of the solid catalyst feeding tank (14) is increased to depressurize the solid catalyst feeding tank (14).

3. The differential pressure stabilizing device according to claim 2, characterized in that, The inlet pneumatic regulating valve (2) is installed in the nitrogen inlet channel of the solid catalyst feeding tank (14). In the nitrogen inlet channel, a high-pressure nitrogen inlet supply valve (1) and an inlet feeder shut-off valve (3) are respectively installed before and after the inlet pneumatic regulating valve (2).

4. The differential pressure stabilizing device according to claim 2, characterized in that, The outlet pneumatic regulating valve (6) is installed in the nitrogen outlet channel of the solid catalyst feeding storage tank (14). On the nitrogen outlet channel, the outlet pneumatic regulating valve (6) is installed before and after the outlet feeder shut-off valve (5) and the outlet discharge shut-off valve (7).

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

6. The differential pressure stabilizing device according to claim 5, characterized in that, 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); the catalyst collection tank (10) includes four ports, namely an injection port, a nitrogen emission port, a filter element backflush port, and a dust emission port; the injection port corresponds to the inlet of the collection tank (9), a filtered gas emission valve (13) is provided at the nitrogen emission port; a filter element backflush valve (12) is provided at the filter element backflush port; and the dust emission port corresponds to the catalyst waste emission port (11).

7. The differential pressure stabilizing device according to claim 6, characterized in that, After each certain cycle of operation, the catalyst collection tank (10) opens the filter backflush valve (12) and uses high-pressure nitrogen to clean the filter element (8). The cleaned catalyst falls into the catalyst collection tank (10) and is discharged through the discharge port (11) after deactivation.

8. The differential pressure stabilizing device according to claim 1, characterized in that, The differential pressure detection unit is a differential pressure transmitter (4), and a backflush valve assembly is installed at the pressure port of the differential pressure transmitter (4).

9. The differential pressure stabilizing device according to claim 1, characterized in that, The control unit is either a PLC control unit or a DCS control unit.

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

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