Dust Explosion Suppression System and Method for Linear Low-Density Polyethylene Plants

Abstract

This disclosure relates to a dust explosion suppression system for a linear low-density polyethylene (LLDPE) plant, comprising: a first pressure sensing element configured to detect the internal pressure of a first subsystem within a plurality of subsystems of a solid additive delivery system; and a first explosion isolation valve disposed in a first delivery line connected to the first subsystem and normally open under normal operating conditions. The first pressure sensing element sends a first closing signal to the first explosion isolation valve upon detecting that the internal pressure of the first subsystem exceeds a first threshold pressure, and the first explosion isolation valve closes at a first closing speed in response to receiving the first closing signal, thereby isolating the first subsystem from the other subsystems within the plurality of subsystems. This disclosure also relates to a dust explosion suppression method for a LLDPE plant.

Description

Technical Field

[0001] This disclosure relates to a dust explosion suppression system for linear low-density polyethylene (LLDPE) plants. Additionally, this disclosure also relates to a dust explosion suppression method for linear low-density polyethylene plants. Background Technology

[0002] In existing vapor-phase linear low-density polyethylene (LLDPE) plants, combustible solid additives are required. To reduce losses caused by accidental explosions of combustible dust in these solid additives, currently applied technologies include, but are not limited to: increasing the particle size of the additives to improve the minimum ignition energy; designing and installing electrostatic grounding facilities to prevent static electricity buildup from forming an ignition source; regularly cleaning additive dust accumulated in the solid additive delivery system within the plant; and using vacuum delivery systems to reduce solid additive leakage.

[0003] However, the aforementioned technical measures can only reduce the probability of dust explosions from solid additives. Once a dust explosion does occur, it can still lead to serious consequences, such as threatening the lives of workers and causing significant property damage. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this disclosure provides a dust explosion suppression system and method for linear low-density polyethylene (LLDPE) plants.

[0005] According to one aspect of this disclosure, a dust explosion suppression system for a linear low-density polyethylene (LLDPE) plant is provided, the LLDPE plant including a solid additive delivery system, the solid additive delivery system including a plurality of subsystems, the plurality of subsystems including a first subsystem, the dust explosion suppression system including:

[0006] A first pressure sensing element, configured to detect the internal pressure of the first subsystem; and

[0007] A first explosion isolation valve is installed in a first delivery pipeline connected to the first subsystem and remains normally open under normal operating conditions.

[0008] When the first pressure sensing element detects that the internal pressure of the first subsystem is greater than a first threshold pressure, it sends a first shut-off signal to the first explosion isolation valve, and the first explosion isolation valve closes at a first shut-off speed in response to receiving the first shut-off signal, thereby isolating the first subsystem from other subsystems in the plurality of subsystems.

[0009] In some embodiments, the length of the first delivery pipeline between the installation location of the first explosion isolation valve and the first subsystem is a first installation distance, and the first installation distance is greater than or equal to a first minimum distance, wherein the first minimum distance is determined based on the first closing speed, the diameter of the first delivery pipeline, and the maximum flame propagation rate of the solid additive contained in the first subsystem during a dust explosion.

[0010] In some embodiments, the first subsystem further includes a first pressure relief safety valve, and the first threshold pressure is set to be greater than or equal to twice the opening pressure of the first pressure relief safety valve.

[0011] In some embodiments, the first closing speed of the first explosion isolation valve is less than or equal to 5 milliseconds per inch of pipe diameter.

[0012] In some embodiments, the first subsystem is a first storage tank, and the first pressure sensing element is a first pressure sensor.

[0013] In some embodiments, the plurality of subsystems further includes a second subsystem, and the dust explosion suppression system further includes: a second pressure sensing element configured to detect the internal pressure of the second subsystem; and a second explosion isolation valve disposed in a second delivery line connected to the second subsystem and normally open under normal operating conditions, wherein the second pressure sensing element sends a second closing signal to the second explosion isolation valve when it detects that the internal pressure of the second subsystem is greater than a second threshold pressure, and the second explosion isolation valve closes at a second closing speed in response to receiving the second closing signal, thereby isolating the second subsystem from the other subsystems in the plurality of subsystems.

[0014] In some embodiments, the length of the second delivery pipeline between the installation location of the second explosion isolation valve and the second subsystem is a second installation distance, and the second installation distance is greater than or equal to a second minimum distance, wherein the second minimum distance is determined based on the second closing speed, the diameter of the second delivery pipeline, and the maximum flame propagation rate of the solid additives contained in the second subsystem during a dust explosion.

[0015] In some embodiments, the second subsystem further includes a second pressure relief safety valve, and the second threshold pressure is set to be greater than or equal to twice the opening pressure of the second pressure relief safety valve.

[0016] In some embodiments, the second closing speed of the second explosion isolation valve is less than or equal to 5 milliseconds per inch of pipe diameter.

[0017] In some embodiments, the second subsystem is a second storage tank or unloading station, and the second pressure sensing element is a second pressure sensor.

[0018] In some embodiments, the solid additives in the solid additive delivery system include one or more of antioxidant 168, zinc stearate, and mesoamide.

[0019] According to another aspect of this disclosure, a dust explosion suppression method for a linear low-density polyethylene (LLDPE) plant is provided. The LLDPE plant includes a solid additive delivery system comprising a plurality of subsystems, including a first subsystem. The dust explosion suppression method includes: detecting the internal pressure of the first subsystem by a first pressure sensing element; and, upon detecting that the internal pressure of the first subsystem is greater than a first threshold pressure, sending a first closing signal to a first explosion isolation valve disposed in a first delivery pipeline connected to the first subsystem and normally open under normal operating conditions, and the first explosion isolation valve closing at a first closing speed in response to receiving the first closing signal, thereby isolating the first subsystem from the other subsystems in the plurality of subsystems.

[0020] In some embodiments, the first subsystem is a first storage tank, and the first pressure sensing element is a first pressure sensor.

[0021] In some embodiments, the plurality of subsystems further includes a second subsystem, and the dust explosion suppression method further includes: detecting the internal pressure of the second subsystem by a second pressure sensing element; and when the internal pressure of the second subsystem is detected to be greater than a second threshold pressure, the second pressure sensing element sends a second closing signal to a second explosion isolation valve disposed in a second delivery pipeline connected to the second subsystem and kept open under normal operating conditions, and the second explosion isolation valve closes at a second closing speed in response to receiving the second closing signal, thereby isolating the second subsystem from the other subsystems in the plurality of subsystems.

[0022] In some embodiments, the second subsystem is a second storage tank or unloading station, and the second pressure sensing element is a second pressure sensor. Attached Figure Description

[0023] The various objectives, features, and advantages of this disclosure will become more apparent from the following description of preferred embodiments in conjunction with the accompanying drawings. The drawings are merely illustrative illustrations of this disclosure and are not necessarily drawn to scale. In the drawings, the same reference numerals always denote the same or similar parts. It should be understood that the given drawings are merely exemplary illustrations of this disclosure. Modifications and variations can be made based on these drawings to obtain other feasible embodiments.

[0024] Figure 1 This is a schematic diagram of a conventional solid additive delivery system used in linear low-density polyethylene plants.

[0025] Figure 2 This is a schematic diagram of a solid additive delivery system for a linear low-density polyethylene plant according to an embodiment of the present disclosure, wherein a dust explosion suppression system according to the present disclosure is provided.

[0026] Figure 3 This is a schematic diagram of the dust explosion suppression system according to this disclosure.

[0027] List of reference numerals in the attached diagram:

[0028] 1-First storage tank; 2-Second storage tank; 3-Unloading station; 4-Exhaust fan; 5-Rotating valve; 6-First conveying pipeline; 7-First pressure sensing element; 8-First pressure relief safety valve; 10-First explosion isolation valve; 20-Second explosion isolation valve Detailed Implementation

[0029] The present disclosure will now be described with reference to the accompanying drawings, which illustrate preferred embodiments of the present disclosure. However, it should be understood that the present disclosure can be presented in many different ways and is not limited to the embodiments described below; in fact, the embodiments described below are intended to make the disclosure more complete and to fully illustrate the scope of protection of the present disclosure to those skilled in the art. It should also be understood that the technical features in the embodiments disclosed herein can be combined in various ways to provide more additional embodiments. Those skilled in the art can appropriately modify the details without departing from the spirit of the present disclosure.

[0030] Unless otherwise stated, the terminology used herein (including technical and scientific terms) should have the meaning that would be normally understood by one of ordinary skill in the art to which this disclosure pertains. Unless otherwise stated, the terms “comprising” and “including” as used in the specification and claims should be interpreted in an open-ended sense, that is, “comprising” and “including” should be interpreted as synonymous with the terms “at least comprising” or “at least comprising”.

[0031] It should be understood that the terminology used in this specification is for describing specific embodiments only and is not intended to limit this disclosure. For the sake of brevity and / or clarity, well-known functions or structures may not be described in detail.

[0032] Figure 1 This is a schematic diagram of a conventional solid additive delivery system used in linear low-density polyethylene (LLDPE) plants. Figure 1 As shown, the solid additive conveying system of the linear low-density polyethylene plant includes multiple subsystems such as a first storage tank 1, a second storage tank 2, a discharge station 3, and an exhaust fan 4. The various subsystems of the solid additive conveying system are connected by pipes and valves (e.g., rotary valve 5). Figure 1 The solid additive delivery system shown is such that if a dust explosion occurs inside a subsystem, the shock wave and energy from the explosion will rapidly spread to other subsystems because ordinary valves cannot be closed quickly, thereby damaging other equipment and potentially causing other equipment to explode.

[0033] Embodiments of this disclosure provide a dust explosion suppression system for linear low-density polyethylene (LLDPE) plants.

[0034] Figure 2 This is a schematic diagram of a solid additive delivery system for a linear low-density polyethylene plant according to an embodiment of the present disclosure, wherein a dust explosion suppression system according to the present disclosure is provided. Figure 3 This is a schematic diagram of the dust explosion suppression system according to this disclosure.

[0035] like Figure 2 As shown, the solid additive conveying system of the linear low-density polyethylene plant includes multiple subsystems such as a first storage tank 1, a second storage tank 2, a unloading station 3, and an exhaust fan 4. Dust explosion suppression systems can be installed for one or more subsystems where there is a risk of dust explosion. For example, Figure 2 An example of a dust explosion suppression system is shown for a first storage tank 1, which is a first subsystem, and a second storage tank 2, which is a second subsystem. Alternatively, similar dust explosion suppression systems can be installed for other subsystems (such as unloading station 3) depending on the specific circumstances.

[0036] like Figure 2 and Figure 3 As shown, the dust explosion suppression system according to this disclosure includes a first pressure sensing element 7 and a first explosion isolation valve 10. The first pressure sensing element 7 is configured to detect the internal pressure of the first storage tank 1 (i.e., the first subsystem). For example, the first pressure sensing element 7 may be a first pressure sensor. The first explosion isolation valve 10 is disposed in a first delivery line 6 connected to the first storage tank 1 and remains normally open under normal operating conditions. The first explosion isolation valve 10 is a fast-response valve, with a closing speed on the order of milliseconds per inch of pipe diameter.

[0037] If a dust explosion occurs in the first storage tank 1, the internal pressure of the first storage tank 1 will rise sharply due to the explosion. Therefore, when the first pressure sensing element 7 detects that the internal pressure of the first storage tank 1 is greater than a first threshold pressure, it can determine that a dust explosion has occurred in the first storage tank 1 and send a first closing signal to the first explosion isolation valve 10. The first explosion isolation valve 10 closes at a first closing speed in response to receiving the first closing signal, thereby isolating the first storage tank 1 from other subsystems in the multiple subsystems of the solid additive delivery system. Thus, the closed first explosion isolation valve 10 can isolate the dust explosion flame inside the first storage tank 1, thereby preventing the dust explosion from spreading to the entire solid additive delivery system. In other words, even if a dust explosion occurs inside the first storage tank 1, which is the first subsystem, it will not trigger secondary or multiple dust explosions in other subsystems of the solid additive delivery system, thereby mitigating the consequences of the accident.

[0038] like Figure 3 As shown, the length of the first delivery pipeline 6 between the installation position of the first explosion isolation valve 10 and the first storage tank 1 is a first installation distance X. Preferably, the first installation distance X should be greater than or equal to a first minimum distance. This first minimum distance can be determined based on the first closing speed of the first explosion isolation valve 10, the diameter of the first delivery pipeline 6, and the maximum flame propagation rate of the solid additives contained in the first storage tank 1 in the event of a dust explosion.

[0039] For example, the first closing speed of the first explosion isolation valve 10 can be set to be less than or equal to 5 milliseconds per inch of pipe diameter. Commonly used solid additives in solid additive delivery systems include one or more of antioxidant 168, zinc stearate, and mesoamide. The solid additive in the first storage tank 1 can be any of the aforementioned commonly used solid additives. Experimental tests show that the flame propagation rates of antioxidant 168, zinc stearate, and mesoamide, as commonly used solid additives, are all lower than those of corn starch during a dust explosion. Therefore, corn starch can be chosen as a reference, and the highest flame propagation rate of corn starch under turbulent conditions (inside the pipe or equipment), 100 m / s (i.e., 0.1 m / ms), can be used as the maximum flame propagation rate of the solid additive during a dust explosion. In this case, when the diameter of the first delivery pipeline 6 is 4 inches, the first minimum distance can be calculated as: maximum flame propagation rate (0.1 m / ms) × diameter of the first delivery pipeline 6 (4 inches) × first closing speed of the first explosion isolation valve 10 (5 milliseconds per inch of pipe diameter) = 2 meters. In other words, as long as the first installation distance X of the first explosion isolation valve 10 can be ensured to be greater than or equal to the first minimum distance (2 meters), the first explosion isolation valve 10 can be ensured to close in time when an additive dust explosion occurs in the first storage tank 1, thereby effectively isolating the explosion flame inside the first storage tank 1 and avoiding affecting other subsystems.

[0040] Furthermore, such as Figure 3 As shown, the first storage tank 1 may include a first pressure relief safety valve 8. In this case, the first threshold pressure can preferably be set to be greater than or equal to twice the opening pressure of the first pressure relief safety valve 8. This ensures that the first explosion isolation valve will not be falsely triggered due to normal increases in internal pressure of the first storage tank 1 caused by fluctuations in the production process. Moreover, once an additive dust explosion occurs inside the first storage tank 1, the rate of pressure rise inside the first storage tank 1 will be significantly higher than the release rate of the first pressure relief safety valve 8, thus ensuring that the first explosion isolation valve 10 is triggered and closed in time to achieve emergency isolation.

[0041] Figure 3 A dust explosion suppression system is shown for a first storage tank 1, which is a first subsystem. Similarly, a dust explosion suppression system can also be provided for a second subsystem (different from the first subsystem) among the multiple subsystems included in the solid additive conveying system. The second subsystem can be a second storage tank 2, an unloading station 3, or other subsystems where there is a risk of dust explosion.

[0042] In this configuration, the dust explosion suppression system also includes a second pressure sensing element and a second explosion isolation valve. The second pressure sensing element is configured to detect the internal pressure of the second subsystem. For example, the second pressure sensing element could be a second pressure sensor. The second explosion isolation valve is located in a second delivery line connected to the second subsystem and remains normally open under normal operating conditions. The second explosion isolation valve is a fast-response valve, with a closing speed on the order of milliseconds per inch of pipe diameter. For example, the second closing speed of the second explosion isolation valve could be set to less than or equal to 5 milliseconds per inch of pipe diameter.

[0043] If a dust explosion occurs in the second subsystem, the internal pressure of the second subsystem will rise sharply due to the explosion. Therefore, when the second pressure sensing element detects that the internal pressure of the second subsystem exceeds a second threshold pressure, it determines that a dust explosion has occurred in the second subsystem and sends a second closing signal to the second explosion isolation valve. The second explosion isolation valve closes at a second closing speed in response to the second closing signal, thereby isolating the second subsystem from other subsystems in the solid additive delivery system. The second closing speed of the second explosion isolation valve can be set to be the same as or different from the first closing speed of the first explosion isolation valve, as needed. Thus, the closed second explosion isolation valve can isolate the dust explosion flame within the second subsystem, preventing the dust explosion from spreading to the entire solid additive delivery system.

[0044] The length of the second delivery pipeline between the installation location of the second explosion isolation valve and the second subsystem is the second installation distance. Preferably, the second installation distance should be greater than or equal to a second minimum distance. This second minimum distance can be determined based on the second closing speed of the second explosion isolation valve, the diameter of the second delivery pipeline, and the maximum flame propagation rate of the solid additives contained in the second subsystem in the event of a dust explosion.

[0045] Furthermore, the second subsystem may also include a second pressure relief safety valve. In this case, the second threshold pressure can preferably be set to be greater than or equal to twice the tripping pressure of the second pressure relief safety valve. This ensures that the second explosion isolation valve will not be falsely triggered due to normal pressure increases within the second subsystem caused by fluctuations in the production process. Moreover, if an additive dust explosion occurs within the second subsystem, the rate of pressure increase within the second subsystem will be significantly higher than the release rate of the second pressure relief safety valve, thus ensuring that the second explosion isolation valve is triggered to close promptly for emergency isolation.

[0046] Furthermore, a second embodiment of this disclosure provides a dust explosion suppression method for a linear low-density polyethylene (LLDPE) plant. The LLDPE plant includes a solid additive delivery system, which comprises multiple subsystems, including a first subsystem. The dust explosion suppression method includes: detecting the internal pressure of the first subsystem using a first pressure sensing element; and, when the detected internal pressure of the first subsystem exceeds a first threshold pressure, sending a first closing signal to a first explosion isolation valve located in a first delivery pipeline connected to the first subsystem and normally open under normal operating conditions, and the first explosion isolation valve closing at a first closing speed in response to receiving the first closing signal, thereby isolating the first subsystem from other subsystems within the multiple subsystems. The first subsystem may be a first storage tank, and the first pressure sensing element may be a first pressure sensor.

[0047] Furthermore, the plurality of subsystems of the solid additive conveying system also includes a second subsystem, and the dust explosion suppression method further includes: detecting the internal pressure of the second subsystem by a second pressure sensing element; and, when the detected internal pressure of the second subsystem is greater than a second threshold pressure, sending a second closing signal to a second explosion isolation valve located in a second conveying pipeline connected to the second subsystem and normally open under normal operating conditions, and the second explosion isolation valve closing at a second closing speed in response to receiving the second closing signal, thereby isolating the second subsystem from the other subsystems in the plurality of subsystems. The second subsystem may be a second storage tank or unloading station or other subsystems with a dust explosion risk, and the second pressure sensing element may be a second pressure sensor.

[0048] The beneficial effects of the dust explosion suppression system and method for linear low-density polyethylene plants according to this disclosure are as follows: A dust explosion suppression system is set up for one or more subsystems with a risk of dust explosion, so that once a dust explosion occurs in a subsystem, the corresponding explosion isolation valve can quickly close in response to a closing signal sent by a pressure sensing element to isolate the dust explosion flame within that subsystem, thereby preventing the dust explosion from spreading to the entire solid additive delivery system, mitigating the consequences of the accident, and improving the overall safety performance of the system.

[0049] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to cover all such variations and equivalent structures and functions.

Claims

1. A dust explosion suppression system for a linear low-density polyethylene (LLDPE) plant, the LLDPE plant comprising a solid additive delivery system, the solid additive delivery system comprising a plurality of subsystems, the plurality of subsystems comprising a first subsystem, the dust explosion suppression system comprising: A first pressure sensing element is configured to detect the internal pressure of the first subsystem; as well as A first explosion isolation valve is installed in a first delivery pipeline connected to the first subsystem and remains normally open under normal operating conditions. The first pressure sensing element sends a first closing signal to the first explosion isolation valve when it detects that the internal pressure of the first subsystem is greater than a first threshold pressure, and the first explosion isolation valve closes at a first closing speed in response to receiving the first closing signal, thereby isolating the first subsystem from other subsystems in the plurality of subsystems. The first subsystem further includes a first pressure relief safety valve, and the first threshold pressure is set to be greater than or equal to twice the opening pressure of the first pressure relief safety valve.

2. The dust explosion suppression system according to claim 1, characterized in that, The length of the first delivery pipeline between the installation location of the first explosion isolation valve and the first subsystem is a first installation distance, and the first installation distance is greater than or equal to a first minimum distance, wherein the first minimum distance is determined based on the first closing speed, the diameter of the first delivery pipeline, and the maximum flame propagation rate of the solid additive contained in the first subsystem during a dust explosion.

3. The dust explosion suppression system according to claim 1, characterized in that, The first closing speed of the first explosion isolation valve is less than or equal to 5 milliseconds per inch of pipe diameter.

4. The dust explosion suppression system according to claim 1, characterized in that, The first subsystem is the first storage tank, and the first pressure sensing element is the first pressure sensor.

5. The dust explosion suppression system according to claim 1, characterized in that, The plurality of subsystems further includes a second subsystem, and the dust explosion suppression system further includes: A second pressure sensing element, configured to detect the internal pressure of the second subsystem; and A second explosion isolation valve is installed in a second delivery pipeline connected to the second subsystem and remains normally open under normal operating conditions. When the second pressure sensing element detects that the internal pressure of the second subsystem is greater than the second threshold pressure, it sends a second shut-off signal to the second explosion isolation valve, and the second explosion isolation valve closes at a second shut-off speed in response to receiving the second shut-off signal, thereby isolating the second subsystem from other subsystems in the plurality of subsystems.

6. The dust explosion suppression system according to claim 5, characterized in that, The length of the second delivery pipeline between the installation location of the second explosion isolation valve and the second subsystem is a second installation distance, and the second installation distance is greater than or equal to a second minimum distance, wherein the second minimum distance is determined based on the second closing speed, the diameter of the second delivery pipeline, and the maximum flame propagation rate of the solid additives contained in the second subsystem during a dust explosion.

7. The dust explosion suppression system according to claim 5, characterized in that, The second subsystem also includes a second pressure relief safety valve, and the second threshold pressure is set to be greater than or equal to twice the opening pressure of the second pressure relief safety valve.

8. The dust explosion suppression system according to claim 5, characterized in that, The second closing speed of the second explosion isolation valve is less than or equal to 5 milliseconds per inch of pipe diameter.

9. The dust explosion suppression system according to claim 5, characterized in that, The second subsystem is a second storage tank or unloading station, and the second pressure sensing element is a second pressure sensor.

10. The dust explosion suppression system according to any one of claims 1 to 9, characterized in that, The solid additives in the solid additive delivery system include one or more of antioxidant 168, zinc stearate, and mesoamide.

11. A method for dust explosion suppression in a linear low-density polyethylene (LLDPE) plant, the LLDPE plant comprising a solid additive conveying system, the solid additive conveying system comprising multiple subsystems, the multiple subsystems comprising a first subsystem, characterized in that, The dust explosion suppression method includes: The internal pressure of the first subsystem is detected by the first pressure sensing element; and If the internal pressure of the first subsystem is detected to be greater than a first threshold pressure, the first pressure sensing element sends a first closing signal to a first explosion isolation valve located in a first delivery pipeline connected to the first subsystem and which remains open under normal operating conditions. The first explosion isolation valve then closes at a first closing speed in response to receiving the first closing signal, thereby isolating the first subsystem from the other subsystems within the plurality of subsystems. The first subsystem further includes a first pressure relief safety valve, and the first threshold pressure is set to be greater than or equal to twice the opening pressure of the first pressure relief safety valve.

12. The dust explosion suppression method according to claim 11, characterized in that, The first subsystem is the first storage tank, and the first pressure sensing element is the first pressure sensor.

13. The dust explosion suppression method according to claim 11 or 12, characterized in that, The plurality of subsystems further includes a second subsystem, and the dust explosion suppression method further includes: The internal pressure of the second subsystem is detected by the second pressure sensing element; and If the internal pressure of the second subsystem is detected to be greater than the second threshold pressure, the second pressure sensing element sends a second closing signal to a second explosion isolation valve located in the second delivery pipeline connected to the second subsystem and which is normally open under normal operating conditions. The second explosion isolation valve closes at a second closing speed in response to receiving the second closing signal, thereby isolating the second subsystem from the other subsystems in the plurality of subsystems.

14. The dust explosion suppression method according to claim 13, characterized in that, The second subsystem is a second storage tank or unloading station, and the second pressure sensing element is a second pressure sensor.

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