Method for regulating and controlling polyolefin molecular weight distribution based on hydrogen consumption in olefin polymerization

Abstract

The invention provides a method for regulating and controlling polyolefin molecular weight distribution based on hydrogen dosage in olefin polymerization. The method comprises the following steps: measuring in real time to obtain actually measured pressure in a slurry polymerization reactor, actually measured molecular weight distribution of a discharged material at an outlet of the slurry polymerization reactor and actually measured circulating hydrogen flow at the outlet of a circulating hydrogen compressor; calculating to obtain a slurry polymerization cycle hydrogen flow rate required by the slurry polymerization reactor and a gas phase polymerization cycle hydrogen flow rate required by the gas phase polymerization reactor; during normal regulation and control, the second control valve is kept closed, and the first control valve is regulated; during first abnormal regulation and control, an exhaust port in the top of the slurry polymerization reactor is opened to discharge light components; and in the second abnormal regulation and control process, the second control valve is opened, and the second control valve is regulated. According to the invention, the molecular weight distribution of the polyolefin product in the olefin polymerization production process is accurately regulated and controlled.

Description

Technical Field

[0001] The invention relates to a method for regulating olefin polymerization, in particular to a method for regulating polyolefin molecular weight distribution based on hydrogen dosage in olefin polymerization, and belongs to the technical field of olefin polymerization. Background Art

[0002] Polyolefins are important polymer materials widely used in modern industry, and their performance depends largely on molecular weight and its distribution. In the production process of polyolefins, especially in the production of polypropylene, hydrogen, as a key chain transfer agent, plays a vital role in regulating the molecular weight of polymer products. And the appropriate molecular weight distribution has an important influence on the processing properties and final product properties of polyolefins. Hydrogen plays the following main roles in polyolefin production: molecular weight regulation and molecular weight distribution regulation. Hydrogen can effectively terminate the growing polymer chain, thereby controlling the molecular weight of polyolefins. By adjusting the hydrogen concentration, the termination rate of the polymer chain is affected, thereby regulating the molecular weight distribution (PDI).

[0003] In traditional polyolefin production processes, the use of hydrogen mainly relies on experience and batch adjustments, which makes it difficult to achieve precise control. This not only affects the stability of product quality, but may also lead to excessive use of hydrogen and increase production costs.

[0004] In the prior art, there is a method for regulating the molecular weight distribution of polymers by controlling the partial pressure ratio of hydrogen to olefin monomers and the change of reaction time in a single polymerization reaction device, but it only involves a single polymerization reaction device, and there are often multiple reactions that need to be controlled in the industrial production of polyolefins, and the temperature and pressure ranges are relatively narrow. Although this method can adjust the molecular weight distribution, it may not be as accurate as the method based on real-time monitoring and feedback mechanism in terms of control.

[0005] On the other hand, in a multi-stage reactor system, the conventional practice is to measure the PDI at the outlet of the last reactor to feedback and adjust the polymer molecular weight. However, this method has obvious hysteresis. Since each reactor has a long residence time, regulation based on the measurement results of the last reactor is often not timely enough to meet the needs of modern polyolefin production for rapid response and precise control.

[0006] In summary, although the industry generally recognizes the importance of achieving precise control of polyolefin product quality, improving hydrogen utilization efficiency and reducing production costs, the existing technology still has deficiencies in the following aspects: lack of accurate PDI prediction and control methods based on real-time data, especially in multi-stage reactor systems; lack of rapid and effective response mechanism to reactor pressure fluctuations caused by changes in hydrogen dosage; the efficiency of hydrogen recovery and recycling systems needs to be improved, especially to achieve precise control while ensuring the purity of recovered hydrogen; lack of comprehensive solutions that organically combine hydrogen dosage control, product quality regulation and cost optimization. Summary of the invention

[0007] Based on the above background, the purpose of the present invention is to provide a method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization, and to accurately control the amount of hydrogen used through real-time monitoring, calculation analysis and regulation steps to achieve accurate regulation of the molecular weight distribution of polyolefin products.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] A method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization, which is used in a dual-reactor olefin polymerization system, wherein the dual-reactor olefin polymerization system comprises a slurry polymerization reactor, a gas phase polymerization reactor, a gas-solid separator, a distillation tower, a hydrogen separator, a circulating hydrogen compressor, a first control valve and a second control valve, wherein the first control valve is used to control the hydrogen flow from the circulating hydrogen compressor to the slurry polymerization reactor, and the second control valve is used to control the hydrogen flow from the circulating hydrogen compressor to the gas phase polymerization reactor;

[0010] The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization comprises the following steps:

[0011] Real-time measurement to obtain the measured pressure in the slurry polymerization reactor, the measured molecular weight distribution of the outlet of the slurry polymerization reactor, and the measured outlet circulating hydrogen flow rate of the circulating hydrogen compressor;

[0012] Determine whether the actual pressure in the slurry polymerization reactor is within a first preset range. If it exceeds the first preset range, trigger the first abnormal regulation. If it is within the first preset range, calculate the theoretical pressure through the first relationship according to the measured outlet circulating hydrogen flow rate. If the absolute value of the difference between the theoretical pressure and the measured pressure exceeds 0.005Mpa, trigger the first abnormal regulation. Calculate the theoretical molecular weight distribution of the outlet discharge of the slurry polymerization reactor through the second relationship according to the measured outlet circulating hydrogen flow rate. If the absolute value of the difference between the theoretical molecular weight distribution and the measured molecular weight distribution exceeds 0.001, trigger the second abnormal regulation. If neither the first abnormal regulation nor the second abnormal regulation is triggered, enter normal regulation.

[0013] According to the preset target molecular weight distribution of the outlet discharge of the slurry polymerization reactor and the preset target molecular weight distribution of the outlet discharge of the gas phase polymerization reactor, the slurry polymerization circulating hydrogen flow rate required for the slurry polymerization reactor and the gas phase polymerization circulating hydrogen flow rate required for the gas phase polymerization reactor are reversely calculated through the second relationship;

[0014] During normal regulation, the second control valve is kept closed, and the valve opening of the first control valve is calculated through the third relationship according to the slurry polymerization circulating hydrogen flow required by the slurry polymerization reactor, and the first control valve is adjusted accordingly; during the first abnormal regulation, the exhaust port at the top of the slurry polymerization reactor is opened to discharge the light component until the measured pressure in the slurry polymerization reactor is within the first preset range, and the absolute value of the difference between the theoretical pressure and the measured pressure is less than or equal to 0.005Mpa; during the second abnormal regulation, the second control valve is opened, and the valve opening of the second control valve is calculated through the fourth relationship according to the slurry polymerization circulating hydrogen flow required by the slurry polymerization reactor and the gas phase polymerization circulating hydrogen flow required by the gas phase polymerization reactor, and the second control valve is adjusted accordingly, until the absolute value of the difference between the theoretical molecular weight distribution and the measured molecular weight distribution is less than or equal to 0.001, and the second control valve is gradually closed.

[0015] Preferably, the first preset range is 2.7 MPa to 3.1 MPa.

[0016] Preferably, the first relational expression is:

[0017] P = 2.91332942 + 0.00336149x;

[0018] Wherein, P represents the theoretical pressure in the slurry polymerization reactor, and x represents the measured outlet circulating hydrogen flow rate of the circulating hydrogen compressor.

[0019] Preferably, the second relational expression is:

[0020] y m =-0.4282exp(-x m / 1.546)-1.2232exp(-x m / 30.9614)+4.51648;

[0021] y n =-0.3793exp(-x n / 1.827)-1.2939exp(-x n / 40.1797)+4.42756;

[0022] In the formula, y m represents the target molecular weight distribution of the outlet material of the slurry polymerization reactor, yn represents the target molecular weight distribution of the outlet material of the gas phase polymerization reactor, x m represents the amount of circulating hydrogen required for the slurry polymerization reactor, x n Indicates the amount of circulating hydrogen added to the phase polymerization reactor.

[0023] Preferably, the third relational expression is:

[0024] Z1=(HC-HF) / HN*100%;

[0025] Wherein, Z1 represents the valve opening of the first control valve, HC represents the required total circulating hydrogen flow rate, HF represents the flow rate of recycled hydrogen separated by the membrane, and HN is the flow rate of fresh hydrogen that can pass when the valve is fully opened.

[0026] Preferably, the fourth relational expression is:

[0027] Z2=(HC-HC1) / HC2*100%;

[0028] Wherein, Z2 represents the valve opening of the second control valve, HC represents the required total circulating hydrogen flow rate, HC1 represents the slurry polymerization circulating hydrogen flow rate required by the slurry polymerization reactor, and HC2 represents the maximum hydrogen flow rate that can pass when the second control valve is fully opened.

[0029] Preferably, the reaction temperature range of the slurry polymerization reactor is 68°C to 70°C.

[0030] Preferably, a gradient reaction temperature interval is set in the gas phase polymerization reactor, and during the second abnormal regulation, the circulating hydrogen to the gas phase polymerization reactor is added to each reaction temperature interval in the gas phase polymerization reactor according to different proportions.

[0031] Preferably, in the dual-reactor olefin polymerization system, the feed stream enters the slurry polymerization reactor for slurry polymerization reaction with hydrogen, and then enters the gas phase polymerization reactor for gas phase polymerization reaction and is divided into two discharges. The first gas-solid two-phase discharge is separated into a polyolefin product and a gas phase stream by a gas-solid separator. The gas phase stream is combined with the second gas phase discharge from the gas phase polymerization reactor and enters a distillation tower to separate hydrogen. The hydrogen separated and purified by the hydrogen separator is returned to the slurry polymerization reactor through a circulating hydrogen compressor to participate in the slurry polymerization reaction.

[0032] Preferably, the hydrogen sources of the circulating hydrogen compressor include two streams, one of which is the hydrogen separated and purified by a hydrogen separator, and the other is fresh hydrogen introduced from an external device.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen in olefin polymerization of the present invention can accurately control the amount of hydrogen through real-time monitoring, calculation analysis and regulation steps, thereby realizing accurate regulation of the molecular weight distribution of polyolefin products in the olefin polymerization production process, while taking into account the potential harm caused by the change of reactor pressure caused by the molecular weight regulator, reducing excessive use of hydrogen, reducing energy consumption and raw material costs, quickly responding to customer needs for different PDI products, helping polymers to obtain more detailed quality grading, improving the stability and controllability of the production process, and providing effective technical support for the production of high-quality polyolefins. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0036] Figure 1 is a schematic diagram of a dual-reactor olefin polymerization system of the present invention;

[0037] Figure 2 It is a fitting curve diagram of the pressure of the slurry polymerization reactor and the measured values ​​of PDI of the polypropylene when the hydrogen flow rate is adjusted to change from 0 to 5 kg / hr in the present invention, and the calculated values ​​obtained by the various relationship formulas of the present invention at this flow rate. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any form of modification and / or change made to the present invention will fall within the protection scope of the present invention.

[0039] In the present invention, unless otherwise specified, all parts and percentages are weight units, and the equipment and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following embodiments, unless otherwise specified, are conventional methods in the art. The components or equipment in the following embodiments, unless otherwise specified, are universal standard parts or components known to those skilled in the art, and their structures and principles are known to those skilled in the art through technical manuals or conventional experimental methods.

[0040] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, one or more embodiments may also be implemented by those skilled in the art without these specific details.

[0041] The embodiment of the present invention discloses a method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization, which is used in a dual-reactor olefin polymerization system. Figure 1 As shown, the dual-reactor olefin polymerization system includes a slurry polymerization reactor R1, a gas-phase polymerization reactor R2, a gas-solid separator SPLIT, a distillation tower T, a hydrogen separator M, a circulating hydrogen compressor C, a first control valve V1 and a second control valve V2. The first control valve is used to control the hydrogen flow from the circulating hydrogen compressor to the slurry polymerization reactor, and the second control valve is used to control the hydrogen flow from the circulating hydrogen compressor to the gas-phase polymerization reactor. Specifically, in the dual-reactor olefin polymerization system, after the feed stream enters the slurry polymerization reactor to undergo a slurry polymerization reaction with hydrogen, it then enters the gas-phase polymerization reactor to undergo a gas-phase polymerization reaction and is divided into two discharges, the first gas-solid two-phase discharge is separated into a polyolefin product and a gas-phase stream through a gas-solid separator, the gas-phase stream is combined with the second gas-phase discharge of the gas-phase polymerization reactor and then enters a distillation tower to separate hydrogen, and the hydrogen separated and purified by the hydrogen separator is returned to the slurry polymerization reactor through a circulating hydrogen compressor to participate in the slurry polymerization reaction. Among them, the hydrogen sources of the circulating hydrogen compressor include two streams, one of which is the hydrogen separated and purified by the hydrogen separator, and the other is the fresh hydrogen introduced by an external device.

[0042] The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization comprises the following steps:

[0043] The measured pressure in the slurry polymerization reactor, the measured molecular weight distribution of the outlet of the slurry polymerization reactor, and the measured outlet circulating hydrogen flow rate of the circulating hydrogen compressor are measured in real time; wherein, the measured pressure is measured by the pressure detection device P, the measured molecular weight distribution is measured by the online molecular weight distribution detection device G, and the measured outlet circulating hydrogen flow rate is measured by the flow meter F; the calculation analysis and control described later are performed by the calculation analysis device H and control instructions are given to the first control valve V1 and the second control valve V2;

[0044] Determine whether the actual pressure in the slurry polymerization reactor is within a first preset range. If it exceeds the first preset range, trigger the first abnormal regulation. If it is within the first preset range, calculate the theoretical pressure through the first relationship according to the measured outlet circulating hydrogen flow rate. If the absolute value of the difference between the theoretical pressure and the measured pressure exceeds 0.005Mpa, trigger the first abnormal regulation. Calculate the theoretical molecular weight distribution of the outlet discharge of the slurry polymerization reactor through the second relationship according to the measured outlet circulating hydrogen flow rate. If the absolute value of the difference between the theoretical molecular weight distribution and the measured molecular weight distribution exceeds 0.001, trigger the second abnormal regulation. If neither the first abnormal regulation nor the second abnormal regulation is triggered, enter normal regulation.

[0045] According to the preset target molecular weight distribution of the outlet discharge of the slurry polymerization reactor and the preset target molecular weight distribution of the outlet discharge of the gas phase polymerization reactor, the slurry polymerization circulating hydrogen flow rate required for the slurry polymerization reactor and the gas phase polymerization circulating hydrogen flow rate required for the gas phase polymerization reactor are reversely calculated through the second relationship;

[0046] During normal regulation, the second control valve is kept closed, and the valve opening of the first control valve is calculated through the third relationship according to the slurry polymerization circulating hydrogen flow required by the slurry polymerization reactor, and the first control valve is adjusted accordingly; during the first abnormal regulation, the exhaust port at the top of the slurry polymerization reactor is opened to discharge the light component until the measured pressure in the slurry polymerization reactor is within the first preset range, and the absolute value of the difference between the theoretical pressure and the measured pressure is less than or equal to 0.005Mpa; during the second abnormal regulation, the second control valve is opened, and the valve opening of the second control valve is calculated through the fourth relationship according to the slurry polymerization circulating hydrogen flow required by the slurry polymerization reactor and the gas phase polymerization circulating hydrogen flow required by the gas phase polymerization reactor, and the second control valve is adjusted accordingly, until the absolute value of the difference between the theoretical molecular weight distribution and the measured molecular weight distribution is less than or equal to 0.001, and the second control valve is gradually closed.

[0047] Specifically, the first preset range is 2.7 MPa to 3.1 MPa.

[0048] Specifically, the first relation is:

[0049] P = 2.91332942 + 0.00336149x;

[0050] Wherein, P represents the theoretical pressure in the slurry polymerization reactor, and x represents the measured outlet circulating hydrogen flow rate of the circulating hydrogen compressor.

[0051] Specifically, the second relation is:

[0052] y m =-0.4282exp(-x m / 1.546)-1.2232exp(-x m / 30.9614)+4.51648;

[0053] y n =-0.3793exp(-x n / 1.827)-1.2939exp(-x n / 40.1797)+4.42756;

[0054] In the formula, y m represents the target molecular weight distribution of the outlet material of the slurry polymerization reactor, y nrepresents the target molecular weight distribution of the outlet material of the gas phase polymerization reactor, x m represents the amount of circulating hydrogen required for the slurry polymerization reactor, x n Indicates the amount of circulating hydrogen added to the phase polymerization reactor.

[0055] Specifically, the third relation is:

[0056] Z1=(HC-HF) / HN*100%;

[0057] Wherein, Z1 represents the valve opening of the first control valve, HC represents the required total circulating hydrogen flow rate, HF represents the flow rate of recycled hydrogen separated by the membrane, and HN is the flow rate of fresh hydrogen that can pass when the valve is fully opened.

[0058] Specifically, the fourth relation is:

[0059] Z2=(HC-HC1) / HC2*100%;

[0060] Wherein, Z2 represents the valve opening of the second control valve, HC represents the required total circulating hydrogen flow rate, HC1 represents the slurry polymerization circulating hydrogen flow rate required by the slurry polymerization reactor, and HC2 represents the maximum hydrogen flow rate that can pass when the second control valve is fully opened.

[0061] Specifically, the reaction temperature range of the slurry polymerization reactor is 68°C to 70°C.

[0062] Specifically, a gradient reaction temperature interval is set in the gas phase polymerization reactor. During the second abnormal regulation, the circulating hydrogen to the gas phase polymerization reactor is added to each reaction temperature interval in the gas phase polymerization reactor according to different proportions. For example, liquid propylene with a flow rate of 3000 kg / hr, a temperature of 70° C. and a pressure of 2.9 MPa enters reactor R1 for slurry polymerization. The polymerization temperature of reactor R1 is between 68 and 70° C., and then enters reactor R2 for gas phase polymerization. R2 is divided into 4 temperature intervals, with temperatures of 65° C., 75° C., 80° C. and 85° C., respectively, and the polymerization reaction pressure is between 2.9 and 3.1 MPa. After the discharge from reactor R2, it is treated by gas-solid separator SPLIT, merged with gas phase discharge, and sent to distillation tower T to separate hydrogen. The mass fractions of the components in the impure hydrogen gas stream coming out from the top of the tower are approximately: C3H6—0.865, C3H8—0.082, H2—0.003, C2H6—0.050. After further purification by membrane hydrogen separator M, the purity of hydrogen is stably greater than 99.998%wt. The maximum fresh hydrogen flow rate that can pass through the first control valve V1 is 4.7 kg / hr.

[0063] In the method of this embodiment, the PDI of the produced polypropylene is usually between 2.5 and 4.5. The 51 points in this interval are used as the set target PDI. The circulating hydrogen flow rate is calculated according to various relationship equations to control the valve opening. Finally, the PDI and pressure detected in this interval are as follows: Figure 2 shown.

[0064] Figure 2 The fitting effect of the PDI actually measured under the circulating hydrogen flow rate calculated by each target PDI and the PDI relationship curve of the two reactors is also demonstrated. It can be seen that the molecular weight distribution of the polypropylene obtained by regulation according to the method of this embodiment is very ideal. Within this interval, all regulated PDIs and pressures do not exceed the prescribed range, so the second control valve V2 is in a normally closed state.

[0065] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization, which is used in a dual-reactor olefin polymerization system, characterized in that: The dual-reactor olefin polymerization system comprises a slurry polymerization reactor, a gas phase polymerization reactor, a gas-solid separator, a distillation tower, a hydrogen separator, a circulating hydrogen compressor, a first control valve and a second control valve, wherein the first control valve is used to control the hydrogen flow from the circulating hydrogen compressor to the slurry polymerization reactor, and the second control valve is used to control the hydrogen flow from the circulating hydrogen compressor to the gas phase polymerization reactor; The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization comprises the following steps: Real-time measurement to obtain the measured pressure in the slurry polymerization reactor, the measured molecular weight distribution of the outlet of the slurry polymerization reactor, and the measured outlet circulating hydrogen flow rate of the circulating hydrogen compressor; Determine whether the actual pressure in the slurry polymerization reactor is within a first preset range. If it exceeds the first preset range, trigger the first abnormal regulation. If it is within the first preset range, calculate the theoretical pressure through the first relationship according to the measured outlet circulating hydrogen flow rate. If the absolute value of the difference between the theoretical pressure and the measured pressure exceeds 0.005Mpa, trigger the first abnormal regulation. The theoretical molecular weight distribution of the outlet material of the slurry polymerization reactor is calculated by the second relationship according to the measured outlet circulating hydrogen flow rate. If the absolute value of the difference between the theoretical molecular weight distribution and the measured molecular weight distribution exceeds 0.001, the second abnormal regulation is triggered; if the first abnormal regulation and the second abnormal regulation are not triggered, normal regulation is entered; According to the preset target molecular weight distribution of the outlet discharge of the slurry polymerization reactor and the preset target molecular weight distribution of the outlet discharge of the gas phase polymerization reactor, the slurry polymerization circulating hydrogen flow rate required for the slurry polymerization reactor and the gas phase polymerization circulating hydrogen flow rate required for the gas phase polymerization reactor are reversely calculated through the second relationship; During normal regulation, the second control valve is kept closed, and the valve opening of the first control valve is calculated through the third relationship according to the slurry polymerization circulating hydrogen flow required by the slurry polymerization reactor, and the first control valve is adjusted accordingly; during the first abnormal regulation, the exhaust port at the top of the slurry polymerization reactor is opened to discharge the light component until the measured pressure in the slurry polymerization reactor is within the first preset range, and the absolute value of the difference between the theoretical pressure and the measured pressure is less than or equal to 0.005Mpa; during the second abnormal regulation, the second control valve is opened, and the valve opening of the second control valve is calculated through the fourth relationship according to the slurry polymerization circulating hydrogen flow required by the slurry polymerization reactor and the gas phase polymerization circulating hydrogen flow required by the gas phase polymerization reactor, and the second control valve is adjusted accordingly, until the absolute value of the difference between the theoretical molecular weight distribution and the measured molecular weight distribution is less than or equal to 0.001, and the second control valve is gradually closed.

2. The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization according to claim 1, characterized in that: The first preset range is 2.7Mpa to 3.1Mpa.

3. The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization according to claim 1, characterized in that: The first relation is: P = 2.91332942 + 0.00336149x; Wherein, P represents the theoretical pressure in the slurry polymerization reactor, and x represents the measured outlet circulating hydrogen flow rate of the circulating hydrogen compressor.

4. The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization according to claim 1, characterized in that: The second relation is: y m =-0.4282exp(-x m / 1.546)-1.2232exp(-x m / 30.9614)+4.51648; y n =-0.3793exp(-x n / 1.827)-1.2939exp(-x n / 40.1797)+4.42756; In the formula, y m represents the target molecular weight distribution of the outlet material of the slurry polymerization reactor, y n represents the target molecular weight distribution of the outlet material of the gas phase polymerization reactor, x m represents the amount of circulating hydrogen required for the slurry polymerization reactor, x n Indicates the amount of circulating hydrogen added to the phase polymerization reactor.

5. The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization according to claim 1, characterized in that: The third relational expression is: Z1=(HC-HF) / HN*100%; Wherein, Z1 represents the valve opening of the first control valve, HC represents the required total circulating hydrogen flow rate, HF represents the flow rate of recycled hydrogen separated by the membrane, and HN is the flow rate of fresh hydrogen that can pass when the valve is fully opened.

6. The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization according to claim 1, characterized in that: The fourth relational expression is: Z2=(HC-HC1) / HC2*100%; Wherein, Z2 represents the valve opening of the second control valve, HC represents the required total circulating hydrogen flow rate, HC1 represents the slurry polymerization circulating hydrogen flow rate required by the slurry polymerization reactor, and HC2 represents the maximum hydrogen flow rate that can pass when the second control valve is fully opened.

7. The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization according to claim 1, characterized in that: The reaction temperature range of the slurry polymerization reactor is 68°C to 70°C.

8. The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization according to claim 1, characterized in that: A gradient reaction temperature interval is set in the gas phase polymerization reactor. During the second abnormal regulation, the circulating hydrogen to the gas phase polymerization reactor is added into each reaction temperature interval in the gas phase polymerization reactor according to different proportions.

9. The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization according to claim 1, characterized in that: In the dual-reactor olefin polymerization system, the feed stream enters the slurry polymerization reactor to undergo slurry polymerization reaction with hydrogen, then enters the gas phase polymerization reactor to undergo gas phase polymerization reaction and is divided into two discharge streams. The first gas-solid two-phase discharge is separated into a polyolefin product and a gas phase stream by a gas-solid separator. The gas phase stream is combined with the second gas phase discharge from the gas phase polymerization reactor and then enters a distillation tower to separate hydrogen. The hydrogen separated and purified by the hydrogen separator is returned to the slurry polymerization reactor through a circulating hydrogen compressor to participate in the slurry polymerization reaction.

10. The method for regulating the molecular weight distribution of polyolefins based on the amount of hydrogen used in olefin polymerization according to claim 9, characterized in that: The hydrogen sources of the circulating hydrogen compressor include two streams, one of which is the hydrogen separated and purified by a hydrogen separator, and the other is fresh hydrogen introduced from an external device.

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