Pressure relief system and pulverized coal conveying device

Abstract

The utility model relates to the technical field of pulverized coal conveying, in particular to a pressure relief system and a pulverized coal conveying device.The pressure relief system comprises a main pipeline communicated with a pulverized coal storage tank and a pulverized coal lock hopper, and the two ends of the main pipeline are communicated through a plurality of branch pipelines connected in parallel; at least one branch pipeline is provided with a first valve and a flow limiting pore plate, and the other branch pipelines are provided with second valves; flow limiting holes are formed in the flow limiting hole plate; the pressure relief speed of the pulverized coal lock hopper can be improved, and downstream equipment damage caused by too fast pressure relief is avoided.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of coal powder conveying, in particular to a pressure relief system and coal powder conveying device. BACKGROUND

[0002] The coal powder gasification technology is to intermittently convey the qualified coal powder prepared by grinding to the coal powder storage tank through the coal powder lock hopper system, and then convey to the gasification furnace for reaction through the airflow.

[0003] The coal powder lock hopper needs to be depressurized to normal pressure to start receiving material in the next cycle after unloading is completed. When depressurizing, a proper rate needs to be maintained. If the lock hopper is depressurized too fast, a large amount of gas will enter the filter of the coal powder storage tank in a short time, and the coal powder particles are mixed in the gas, which can easily cause impact damage to the filter bag and cage, and finally lead to filter failure. On the contrary, if the depressurization rate is too slow, the coal powder lock hopper depressurization time will be prolonged, which will lead to the extension of the single cycle period of the coal powder lock hopper, and will not meet the demand for coal powder supply when the gasification furnace is running at full load. SUMMARY

[0004] In view of the above shortcomings of the prior art, the purpose of the utility model is to provide a pressure relief system and coal powder conveying device to improve the depressurization rate of the coal powder lock hopper, which can not only avoid damage to the downstream equipment, but also ensure the demand for coal powder supply when the gasification furnace is running at full load.

[0005] To achieve the above-mentioned purpose and other related purposes, the utility model provides a pressure relief system, which comprises a main pipeline connected with a coal powder storage tank and a coal powder lock hopper, and the two ends of the main pipeline are connected through a plurality of parallel branch pipelines.

[0006] At least one of the branch pipelines is provided with a first valve and a flow limiting orifice plate, and the rest of the branch pipelines are provided with a second valve.

[0007] In an embodiment of the utility model, the material strength of the side of the flow limiting orifice plate facing the coal powder lock hopper is greater than or equal to the material strength of the side of the flow limiting orifice plate away from the coal powder lock hopper.

[0008] In an embodiment of the utility model, at least the side of the flow limiting orifice plate facing the coal powder lock hopper is provided with a tungsten carbide layer.

[0009] In an embodiment of the utility model, the first valve and / or the second valve is a pressure relief cut-off valve.

[0010] In an embodiment of the utility model, among the branch pipelines provided with the flow limiting orifice plate, the flow limiting orifice plate in the branch pipeline is only provided with a single stage, and a plurality of flow limiting orifices are arranged on the flow limiting orifice plate of the single stage.

[0011] In an embodiment of the utility model, the thickness of the flow limiting orifice plate is greater than the preset thickness.

[0012] In an embodiment of the utility model, the at least three branch pipes are provided with two second valves on one branch pipe and first valves and flow limiting orifice plates on the rest of the branch pipes.

[0013] In an embodiment of the utility model, the surface of the flow limiting orifice plate is recessed from the side of the coal powder lock hopper to the side of the coal powder storage tank, and the area of the flow limiting orifice plate close to the flow limiting orifice is arc-shaped.

[0014] In an embodiment of the utility model, the diameters of at least part of the branch pipes are greater than the diameters of the rest of the branch pipes.

[0015] To achieve the above object and other related objects, the utility model provides a coal powder conveying device, which comprises a coal powder storage tank, a coal powder lock hopper and the pressure relief system.

[0016] In summary, the utility model can effectively control the pressure change rate in the pressure relief process by providing multiple pressure relief pipelines, can reduce the pressure relief impact force through the branch pipes with flow limiting orifice plates, thereby avoiding or reducing the impact damage to part of the equipment caused by the excessive impact force during pressure relief, and can improve the pressure relief amount per unit time through the branch pipes with second valves, thereby shortening the single cycle period of the coal powder lock hopper, and maximizing the demand for the coal powder supply amount when the gasification furnace is in full load operation, and improving the overall production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0017] To make the technical scheme of the embodiments of the utility model or the prior art clearer, the drawings needed in the embodiment or prior art description will be briefly introduced below, and obviously, the drawings in the following description can only be some embodiments of the utility model, and other drawings can be obtained by those skilled in the art without creative labor.

[0018] Figure 1 It is a connection schematic view of the pressure relief system, the coal powder storage tank and the coal powder lock hopper in an embodiment of the utility model.

[0019] Figure 2 It is a connection schematic view of the pressure relief system, the coal powder storage tank and the coal powder lock hopper in another embodiment of the utility model.

[0020] Figure 3 It is a structure schematic view of the flow limiting orifice plate in an embodiment of the utility model.

[0021] Figure 4 is a sectional view of the flow-limiting orifice plate structure in an embodiment of the present application;

[0022] Figure 5 is a model relationship diagram of each component in the pressure relief system in an embodiment of the present application;

[0023] Element number explanation: coal powder storage tank 10, coal powder lock hopper 20, main pipeline 31, branch pipeline 32, first branch pipeline 321, second branch pipeline 322, third branch pipeline 323, first valve 33, flow-limiting orifice plate 34, flow-limiting orifice 341, arc surface 342, second valve 35. DETAILED DESCRIPTION

[0024] The embodiments of the present application will be described in detail with specific examples. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the specification. The present application can also be implemented or applied in different specific embodiments, and each detail in the specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. It should also be understood that the terms used in the embodiments of the present application are for describing specific specific embodiments, not for limiting the protection scope of the present application. The test methods not specified in the following embodiments are usually performed under conventional conditions or under conditions recommended by the manufacturers.

[0025] Please refer to Figures 1 to 5 It should be noted that the structures, proportions, sizes, etc. shown in the drawings of the specification are only used to cooperate with the content disclosed in the specification, to be understood and read by those skilled in the art, and do not have technical significance to limit the conditions under which the present application can be implemented. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application. At the same time, the terms such as "up", "down", "left", "right", "middle" and "one" in the specification are only for the convenience of clear description, not for limiting the scope of the present application, and the change or adjustment of the relative relationship without substantially changing the technical content is also considered as the scope of the present application.

[0026] When the embodiments give a numerical range, it should be understood that, unless otherwise stated by the utility model, both ends of each numerical range and any one numerical between both ends can be selected. Unless otherwise defined, all technical and scientific terms used in the utility model are used by the skilled in the art and the description of the utility model, and any method, equipment and material of the prior art similar or equivalent to the method, equipment and material described in the embodiments of the utility model can be used to realize the utility model.

[0027] In the utility model, the coal powder lock hopper 20 is a key equipment in the coal powder conveying device, which is mainly used for conveying coal powder from the low-pressure coal powder bin to the coal powder storage tank 10. Its working principle is to pressurize the coal powder through a high-pressure gas source, and then control the inlet and outlet of the coal powder through a program-controlled valve to ensure the stable conveying of the coal powder. The structure of the coal powder lock hopper 20 usually includes a lock hopper body, a material receiving pipeline, a material unloading pipeline, a pressure increasing pipeline and a pressure relief system, and these components work together to ensure the smooth conveying of the coal powder and the safe operation of the system. The coal powder storage tank 10 is used for storing coal powder to ensure that enough coal powder can be supplied when needed.

[0028] Please refer to Figure 1 Or 2, the utility model provides a kind of pressure relief system, including the main pipeline 31 being communicated with coal powder storage tank 10 and coal powder lock hopper 20, and the both ends of the main pipeline 31 are communicated by multiple parallel branch pipelines 32;

[0029] At least one branch pipeline 32 is provided with first valve 33 and flow limiting orifice plate 34, and the rest branch pipelines 32 are provided with second valve 35;Flow limiting orifice plate 34 is provided with flow limiting orifice 341.

[0030] It should be understood that the first valve 33 and the second valve 35 can be the same or different; the first branch pipe 32 with the first valve 33 and the flow limiting orifice plate 34 is the first branch pipe 32, the branch pipe 32 with the second valve 35 is the last opened branch pipe 32, in addition to the first branch pipe 32, the second branch pipe 32 or more branch pipes 32 can be provided, and the last branch pipe 32 or several branch pipes 32 are provided with the second valve 35. When pressure relief, the first branch pipe 32 is relieved first, then the second branch pipe 32, the third branch pipe 32 and the subsequent branch pipe 32, it should be understood that within the pressure bearing range of the subsequent equipment of the pressure relief system, the first branch pipe 32 and the second branch pipe 32 or more branch pipes 32 can be relieved at the same time; until the pressure of the pulverized coal lock hopper 20 is reduced to the preset pressure value, the branch pipe 32 with the second valve 35 is opened, and the pressure is released once and quickly, and the preset pressure value is set according to the pressure bearing range of the subsequent equipment of the pressure relief system. Generally, when the first valve 33 and the second valve 35 are fully opened, the total amount of pressure relief of the branch pipe 32 with the second valve 35 per unit time is generally greater than that of the branch pipe 32 with the flow limiting orifice plate 34 per unit time, because there is no blockage of the flow limiting orifice plate 34, thereby increasing the total amount of pressure relief per unit time of the last branch pipe 32 or several branch pipes 32, ensuring the pressure relief rate and saving the pressure relief time. When pressure relief, the branch pipe 32 with the flow limiting orifice plate 34 is the first branch pipe 32, that is, the first branch pipe 32 is relieved first, so that the airflow rate of the branch pipe 32 with the flow limiting orifice plate 34 is greater than that of the branch pipe 32 with the second valve 35 when pressure relief, at this time, although the airflow rate is high, the total amount of pressure relief per unit time is low, and the impact force is limited, which is within the pressure bearing range of the subsequent equipment. After the first branch pipe 32 is relieved, the second branch pipe 32 can be automatically switched to relieve pressure by automatic control, or the pressure relief process can be manually controlled, the pressure relief process is controlled by automatic pressure, for example, a related pressure sensor and a controller can be provided, the pressure sensor can be provided in the pulverized coal lock hopper 20 or the pipe, the pressure sensor is electrically connected with the controller, and the controller controls the opening and closing of the first valve 33 and the second valve 35; when the branch pipe 32 with the second valve 35 is relieved, although the pressure relief rate is reduced, the total amount of airflow per unit time is large due to the absence of the flow limiting orifice plate 34, thereby saving the pressure relief time and shortening the single cycle period of the pulverized coal lock hopper, thereby maximizing the demand for coal supply amount when the gasifier is running at full load, and improving the overall production efficiency.

[0031] It should be noted that in terms of improving the safety of the device, the present case can effectively control the pressure change rate during the pressure relief process by setting multiple pressure relief pipelines, avoiding impact damage to the filter bag and cage due to rapid pressure change. At the same time, the blocking of the flow limiting orifice plate 34 makes the airflow impact force and pressure after the flow limiting orifice plate 34 release and decrease, protecting the downstream equipment from damage. It should be understood that the size and number of the pressure relief holes 341 of the pressure relief orifice plate 34 should be controlled to ensure that the pressure relief speed or impact force will not be too large to impact and damage the downstream equipment. In terms of ensuring production efficiency, the present case can shorten the single cycle period time of the coal powder lock hopper 20 by reasonably designing the pressure relief system, thereby meeting the demand for full-load coal powder supply of the gasification furnace and improving the overall production efficiency. Because only the sub-pipeline 32 with the first valve 33 and the flow limiting orifice plate 34 is used for pressure relief, the pressure relief time is longer, and when only the sub-pipeline 32 with the second valve 35 is used for pressure relief, the initial pressure relief pressure may be too large to cause damage to the downstream equipment. In terms of use, the present case allows the use of pipelines and valve combinations of different diameters at different pressure stages, providing more operation options and adjustment space. In terms of reliability, the present case is provided with multiple parallel sub-pipelines 32, so even if one of them fails or needs maintenance, the others can still work normally, ensuring the continuous operation of the entire system. Since each sub-pipeline 32 is in a parallel relationship and is provided with an independent valve, the corresponding valve can be closed individually during maintenance or component replacement, without affecting the normal operation of other pipelines, thereby reducing maintenance difficulty and cost.

[0032] At the beginning of the improvement of the present case, the sub-pipelines 32 used multi-stage flow limiting orifice plates 34, that is, the same sub-pipeline 32 was provided with multiple flow limiting orifice plates 34. During the gasification furnace shutdown and maintenance period in the early stage of the gasification device trial operation, it was found that the first stage flow limiting orifice plate 34 of each sub-pipeline 32 appeared different degrees of damage and fell into the coal powder storage tank 10, causing coal line fluctuation or flow interruption. The first stage flow limiting orifice plate 34 in one of the sub-pipelines 32 appeared cracks, and the connection weld between the flow limiting orifice plate 34 and the outer cylinder of the sub-pipeline 32 also appeared cracks. The rupture of the flow limiting orifice plate 34 affected the long-period stable operation of the system. Therefore, in the design of the present case, the material strength of the side of the flow limiting orifice plate 34 facing the coal powder lock hopper 20 is greater than or equal to the material strength of the side of the flow limiting orifice plate 34 away from the coal powder lock hopper 20. In the present case, by making the material strength of the side of the flow limiting orifice plate 34 facing the coal powder lock hopper 20 greater than or equal to the material strength of the side of the flow limiting orifice plate 34 away from the coal powder lock hopper 20, such design helps to better withstand the pressure impact from the direction of the coal powder lock hopper 20, prolongs the service life of the flow limiting orifice plate 34, and further ensures that the pressure relief system itself will not be damaged during the pressure relief process.

[0033] As an optional embodiment of the present case, the flow limiting orifice plate 34 comprises a tungsten carbide layer, which is at least located on the side of the flow limiting orifice plate 34 facing the coal powder lock hopper 20. It should be understood that the flow limiting orifice plate 34 can also be entirely coated with a tungsten carbide layer. Tungsten carbide (WC) is a compound composed of carbon and tungsten atoms in a 1:1 ratio, with the chemical formula WC. According to Mohs hardness, the hardness of tungsten carbide is between 8.5 and 9.5, second only to a few materials such as diamond, and tungsten carbide can maintain its chemical stability at high temperatures without decomposition or phase change. Due to its high hardness, the tungsten carbide coating can effectively resist wear when contacting other hard materials; at the same time, the tungsten carbide layer remains stable in various corrosive media and is not prone to chemical reactions. In the present case, high-velocity oxy-fuel spraying (HVOF) is used, which produces a high-temperature, high-velocity combustion flame that can heat the sprayed particles to a molten or semi-molten state and accelerate them to speeds of 300-500 m / s or even higher, thereby forming a high-quality tungsten carbide coating with high bonding strength and density on the surface of the flow limiting orifice plate 34.

[0034] Due to the presence of a large number of coal powder particles in the pipeline, the valve core is subjected to erosion and corrosion, and the material requirements for the valve core are higher. If a flow-adjustable regulating valve is used, if the control fails, it may cause excessive release, causing damage to the normal pressure equipment. Therefore, as an optional embodiment of the present case, the first valve 33 and / or the second valve 35 is a pressure relief cut-off valve.

[0035] It should be noted that the pressure relief cut-off valve automatically cuts off the fluid flow when the pressure in the pipeline or equipment exceeds the preset value to prevent equipment damage or safety accidents caused by overpressure. When the pressure in the equipment or pipeline exceeds the set pressure of the pressure relief valve, the valve will automatically open to release some pressure, thereby ensuring that the medium pressure in the equipment and pipeline returns to the set safe range. The design of such a valve can effectively prevent explosions or other dangerous situations caused by excessive pressure, ensuring the safety of industrial production. For example, after the coal powder lock hopper 20 finishes unloading, it needs to be depressurized to start the next cycle of receiving material. At this time, if the pressure relief rate is too fast, a large amount of gas will enter the coal powder storage tank 10 filter in a short period of time, causing damage to the filter bag and cage. If the pressure relief rate is slow, it will result in a long single cycle period of the coal powder lock hopper 20, which cannot meet the demand for full-load coal powder supply of the gasifier. Therefore, by designing multiple pressure relief pipelines and setting flow limiting orifice plates 34, the single-layer orifice plate structure limits the maximum gas release amount under the design pressure of the pipeline to be no higher than the allowable value of the normal pressure equipment, which can effectively control the pressure relief rate and avoid the above problems.

[0036] Please refer to Figure 1Or 2, as an optional embodiment of the case, the said branch pipeline 32 is provided with the said flow limiting orifice plate 34, the said flow limiting orifice plate 34 in the said branch pipeline 32 is provided with only a single stage, and the said flow limiting orifice plate 34 of the single stage is provided with a plurality of flow limiting orifices 341.

[0037] It should be noted that the flow limiting orifice plate 34 of the multi-stage point flow is generally insufficient in strength before the tungsten carbide layer is not used, and frequent rupture occurs, which causes damage to the downstream equipment, causes coal line fluctuation, even causes the gasification furnace to stop, the multi-stage point flow orifice plate structure is complex, the manufacturing and repair difficulty is large, the cost is relatively high; the maintenance difficulty is large, the construction procedure is complicated, and the maintenance amount is large; the structure of the single-stage flow limiting orifice plate 34 provided with a plurality of flow limiting orifices 341 is simple, the cost is low, the maintenance cost is low combined with the tungsten carbide layer, and the use reliability is high.

[0038] In order to prevent the flow limiting orifice plate 34 from being damaged under the action of strong pressure difference and impact force, the thickness of the flow limiting orifice plate 34 is a theoretical thickness calculation value, therefore, as an optional embodiment of the case, the thickness of the said flow limiting orifice plate 34 is greater than the preset thickness; the said preset thickness is the theoretical thickness calculation value of the flow limiting orifice plate 34, and the case is thickened on the basis of the theoretical thickness calculation value, from the original theoretical thickness calculation value 24mm to 30mm or thicker size, so as to avoid that the single-stage flow limiting orifice plate 34 is subjected to a larger impact force, the flow limiting orifice plate 34 is designed to be a single-stage multi-hole form, which is beneficial to disperse the impact of fluid when pressure relief.

[0039] Please refer to Figure 2 and 5 , as an optional embodiment of the case, the branch pipeline 32 with the said first valve 33 and the flow limiting orifice plate 24 is the first branch pipeline 32; the branch pipeline 32 with the second valve 25 is the second branch pipeline 32; the minimum flow path of the first branch pipeline 32 is smaller than the minimum flow path of the second branch pipeline 32;

[0040] The first branch pipe 32 is configured to release the pressure of the coal bunker 20 from the first pressure to the second pressure, and the second branch pipe 32 is configured to release the pressure of the coal bunker 20 from the second pressure to the third pressure or the normal pressure, wherein the minimum flow path of the first branch pipe 32 is greater than the minimum flow path of the second branch pipe 32, the first pressure is greater than the second pressure, the second pressure is greater than the third pressure, and the third pressure is greater than the normal pressure, and the maximum impact force of the first branch pipe 321 is less than the predetermined impact force; wherein the predetermined impact force is the impact force that the equipment in the entire pressure release system can withstand, the minimum flow path of the first branch pipe 32 refers to the sum of the hole diameters of all the flow limiting holes 241 of the flow limiting orifice plate 24 when the first branch pipe 32 is fully opened for pressure release, and the minimum flow path of the second branch pipe 32 refers to the minimum flow path of the second branch pipe 32 when the second valve 25 is fully opened, and the second branch pipe 32 increases the minimum flow path to compensate for the gas flow per unit time, so that the pressure release system can ensure the pressure release efficiency and avoid damage to other equipment during the pressure release process.

[0041] Please refer to Figure 2 and 5 As an optional embodiment of the present application, the branch pipe 32 is provided with at least three branch pipes, one of which is provided with two second valves 35, and the remaining branch pipes are provided with first valves 33 and flow limiting orifice plates 34, and the flow limiting orifice plate 34 is located on the side of the first valve 33 close to the coal bunker 10.

[0042] It should be noted that one of the said branch pipes 32 is provided with two second valves 35, which are more secure and can prevent the sudden opening of only one valve, which can cause the pressure relief system to suddenly release pressure, the high pressure to become low pressure, and the downstream equipment to be unable to withstand the consequences and be damaged. Among the two valves, there is a standby valve after the damage of one of the valves, and the entire system can still operate normally. For example, three branch pipes 32 for pressure relief are designed on the coal powder lock hopper 20, among which the first branch pipe 321 is a DN200 pressure relief pipe line, provided with a pressure relief cut-off valve XV122 and a flow limiting orifice plate 34, which can reduce the pressure of the coal powder lock hopper 20 from 4.8 MPa to 2.0 MPa; the second branch pipe 322 is a DN300 pressure relief pipe line, provided with a pressure relief cut-off valve XV118 and a flow limiting orifice plate 34, which can reduce the pressure of the coal powder lock hopper 20 from 2.0 MPa to 0.15 MPa; the third branch pipe 323 is a DN200 pipe line, provided with a pressure relief valve XV120 and a pressure relief valve XV121, which can reduce the pressure of the coal powder lock hopper 20 from 0.15 MPa to normal pressure. Among them, the XV120 pressure relief valve is suitable for low to medium pressure range, and the specific pressure grade needs to be selected according to actual demand. The XV121 pressure relief valve is used in high pressure environment and can withstand the highest pressure inside the system to ensure that it is not damaged or deformed in abnormal conditions of the equipment. The nominal diameter of DN200 is 200 mm, and since the inner diameter is relatively small, the amount of fluid passing through is relatively small; the nominal diameter of DN300 is 300 mm, and the larger inner diameter allows higher flow.

[0043] Please refer to Figure 4 As an optional embodiment of the present case, the surface of the flow limiting orifice plate 34 is recessed from one side of the coal powder lock hopper 20 to one side of the coal powder storage tank 10, and the area near the flow limiting orifice 341 on the flow limiting orifice plate 34 is an arc surface 342.

[0044] It should be noted that by recessing the surface of the flow limiting orifice plate 34 from one side of the coal powder lock hopper 20 to one side of the coal powder storage tank 10, the airflow on the flow limiting orifice plate 34 can be collected into the flow limiting orifice 341, reducing the frontal impact force on the flow limiting orifice plate 34; at the same time, the area near the flow limiting orifice 341 on the flow limiting orifice plate 34 is an arc surface 342, which reduces stress concentration and improves the strength and stability of the overall structure.

[0045] Please refer to Figure 5As an optional embodiment of the present application, in the plurality of parallelly arranged branch pipes 32, the diameters of at least some of the branch pipes 32 are greater than those of the other branch pipes 32. For example, the diameters of at least some of the branch pipes 32 located in the middle are greater than those of the branch pipes 32 located at the sides. Since the flow pressure in the branch pipes 32 located in the middle is reduced and the flow rate is slow, in order to ensure that the single cycle time of the coal powder lock hopper 20 is long, at least the diameters of at least some of the branch pipes 32 located in the middle are increased, so as to increase the pressure relief speed and meet the demand of the coal powder supply amount of the gasifier under full load.

[0046] The utility model also provides a coal powder conveying device, including coal powder storage jar 10, coal powder lock hopper 20 and the pressure relief system of the pressure relief system intercommunication coal powder storage jar 10 and coal powder lock hopper 20.

[0047] In conclusion, the utility model effectively overcomes some practical problems in the prior art and has high utilization value and use significance.

[0048] The above-mentioned embodiments only exemplarily illustrate the principle and effect of the utility model, and are not used to limit the utility model. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the utility model. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the utility model should be covered by the claims of the utility model.

Claims

1. A pressure relief system characterized by, The main pipeline comprises a coal powder storage tank and a coal powder lock hopper, and the two ends of the main pipeline are connected by a plurality of parallel branch pipelines; At least one of the branch pipelines is provided with a first valve and a flow limiting orifice plate, and the rest of the branch pipelines are provided with a second valve; the flow limiting orifice plate is provided with a flow limiting orifice.

2. The pressure relief system of claim 1, wherein, The material strength of the side of the flow limiting orifice plate facing the coal powder lock hopper is greater than or equal to the material strength of the side of the flow limiting orifice plate away from the coal powder lock hopper.

3. The pressure relief system of claim 1, wherein, At least the side of the flow limiting orifice plate facing the coal powder lock hopper is provided with a tungsten carbide layer.

4. The pressure relief system of claim 1, wherein, The first valve and / or the second valve is a pressure relief cut-off valve.

5. The pressure relief system of claim 1, wherein, The flow limiting orifice plate provided in the branch pipeline is provided with only one stage, and the flow limiting orifice plate of the stage is provided with a plurality of flow limiting orifices.

6. The pressure relief system of claim 1, wherein, The thickness of the flow limiting orifice plate is greater than a preset thickness.

7. The pressure relief system of claim 1, wherein, The branch pipeline is provided with at least three, and one of the branch pipelines is provided with two second valves, and the rest of the branch pipelines are provided with a first valve and a flow limiting orifice plate.

8. The pressure relief system of claim 1, wherein, The surface of the flow limiting orifice plate is recessed from the side of the coal powder lock hopper to the side of the coal powder storage tank, and the area of the flow limiting orifice plate close to the flow limiting orifice is an arc surface.

9. The pressure relief system of claim 7, wherein, In the plurality of parallel branch pipelines, at least part of the branch pipelines has a diameter greater than the diameter of another part of the branch pipelines.

10. A pulverized coal delivery device characterized by comprising: The pressure relief system comprises a coal powder storage tank, a coal powder lock hopper, and the pressure relief system of any one of claims 1-9, and the pressure relief system connects the coal powder storage tank and the coal powder lock hopper.

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