A low nitrogen ground flare system for LNG receiving station

Abstract

A low-nitrogen ground flare system for an LNG receiving station includes a cylinder, a windbreak wall, multiple sets of LNG-specific low-nitrogen burner equipment, and a burner grading system. Among them, the LNG-specific low-nitrogen burner includes a gas inlet pipe, a burner branch, a gas spray hole, a flame stabilizing hole, a ring pipe, an air / steam inlet pipe, an air / steam spray hole, and a connecting plate. The LNG-specific low-nitrogen burner achieves graded combustion of the flare exhaust gas and reduces the high-temperature combustion area through differentiated and reasonable arrangement of the gas spray hole aperture, opening angle, and opening position. The burner of the ground flare system of the present invention is arranged in the hollow annular space inside the cylinder, which effectively increases the air distribution at the center and edge of the cylinder, reduces the overall combustion temperature, further reduces NOx emissions, and prolongs the life of the system. The system is suitable for the characteristics of low temperature, high pressure, and light components of the LNG industry flare gas, and can also be used to treat other light-component ground flare exhaust gases that are not easy to smoke.

Description

Technical Field

[0001] The invention relates to a waste gas treatment technology, in particular to a natural gas flare waste gas combustion technology, specifically to a low-nitrogen ground flare system for an LNG receiving station. Technical Background

[0002] With the country's increasing attention to environmental protection, the LNG industry has developed rapidly in recent years. In the daily operation of LNG receiving stations, LNG ship unloading, gasification, transportation, tank emptying and other operations will produce a large amount of flammable gases. These gases have the characteristics of low temperature, high pressure and light components.

[0003] For the natural gas produced by LNG gasification, the main pollutant in its combustion products is NOx. As the country's restrictions on pollutant emissions become increasingly stringent, the ground flare system suitable for the LNG industry must not only meet the requirements of stable combustion, but also meet the requirements of low nitrogen emissions.

[0004] The present invention proposes a low-nitrogen ground flare system for LNG receiving stations based on the characteristics of low temperature, high pressure and light components of combustible gas in LNG receiving stations and taking low nitrogen emissions into consideration. Summary of the invention

[0005] The purpose of the present invention is to design a low-nitrogen ground flare system for LNG receiving stations in view of the problems that the fuel gas produced by LNG gasification has low temperature, higher pressure than other flare gases, lighter components, great combustion difficulty and serious pollution, while considering the demand for low-nitrogen combustion.

[0006] The technical solution of the present invention is:

[0007] A low-nitrogen ground flare system for an LNG receiving station is characterized in that it includes a cylinder 1, a windbreak wall 2 and an LNG low-nitrogen burner 3. The cylinder 1 is located in the windbreak wall 2 and is raised to a certain height as an air inlet channel, that is, a natural wind inlet channel is provided at the lower part of the cylinder 1, and the LNG low-nitrogen burner 3 is arranged in a hollow annular space at the bottom of the cylinder 1. The LNG low-nitrogen burner 3 is controlled by a burner hierarchical control system.

[0008] The top of the gas inlet pipe 4 of the LNG low-nitrogen burner 3 is provided with 3 to 8 burner branches 5, and the burner branches 5 are provided with gas spray holes 6, and the gas spray holes are divided into 2 to 3 rows, and the size and direction of each row of holes are different. The air / steam inlet pipe 8 is connected to the ring pipe 9, and the ring pipe 9 is provided with air / steam spray holes 10. The ring pipe 9 and the gas inlet pipe 4 are fixed by a connecting plate 11; the ring pipe 9 is located at the lower part of the burner branch 5.

[0009] The gas spray holes 6 are divided into a first row of gas spray holes 6a and a second row of gas spray holes 6b, which are arranged on each burner branch 5. The first row of gas spray holes 6a have larger holes with a diameter ranging from 4 to 9 mm, and the axial direction of the holes forms an angle of 0° to 20° with the vertical direction. The second row of gas spray holes 6b have smaller holes with a diameter ranging from 2.5 to 5 mm, and the axial direction of the holes forms an angle of 10° to 30° with the vertical direction.

[0010] Some burner branches 5 are provided with the first row of gas spray holes 6a and the second row of gas spray holes 6b, and the root thereof is also provided with flame stabilizing holes 7. When the gas pressure is ≥15kPa, the flame stabilizing holes 7 play a role in stabilizing the flame, so that the flame does not flame out, thereby ensuring the burnout rate of the flare gas.

[0011] In addition, compressed air or steam is added to enhance the internal combustion air supply of the LNG low-nitrogen burner 3. The compressed air or steam enters the annular pipe 9 through the air / steam inlet pipe 8. A plurality of groups of air / steam spray holes 10 are arranged on the annular pipe 9. The diameter of the air / steam spray holes 10 ranges from 2 to 4 mm. The air / steam spray holes 10 are arranged close to the gas spray holes 6, and the horizontal distance does not exceed 60 mm.

[0012] The LNG low-nitrogen burner 3 is opened in stages by a burner hierarchical control system, wherein the first stage is provided with 2 to 8 sets of burners, the second stage is provided with 4 to 16 sets of burners, the third stage is provided with 8 to 24 sets of burners, and the remaining stages are arranged accordingly according to the ground flare processing volume, wherein the adjacent burners within the second to third stages and between the stages are directly opposite and the ends of the adjacent burner branches 5 are provided with 1 to 3 flame transfer holes 12, to ensure that the ground flare exhaust gas can be ignited in time and be promptly and fully processed; thereby making the overall nitrogen oxide emission of the ground flare system ≤25ppm.

[0013] The beneficial effects of the present invention are:

[0014] The burner of the ground flare system of the present invention is arranged in the hollow annular space inside the cylinder, which effectively increases the air distribution at the center and edge of the cylinder, reduces the overall combustion temperature, further reduces NOx emissions, and prolongs the life of the system.

[0015] The invention is suitable for the LNG industry flare gas with low temperature, high pressure and light components, and can also be used to treat other light component ground flare waste gases that are not easy to smoke. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic structural diagram of a low-nitrogen ground flare system for an LNG receiving station according to the present invention;

[0017] Figure 2 A schematic structural diagram of the LNG-specific low-nitrogen burner of the present invention;

[0018] Figure 3The working principle diagram of the low nitrogen ground flare system for LNG receiving station of the present invention;

[0019] Figure 4 Arrangement diagram of flame transfer holes between adjacent burners of the present invention.

[0020] Among them: 1-cylinder; 2-windbreak wall; 3-LNG low-nitrogen burner; 4-gas inlet pipe; 5-burner branch; 6-gas spray hole; 7-flame stabilizing hole; 8-air / steam inlet pipe; 9-ring pipe; 10-air / steam spray hole; 11-connecting plate; 12-flame transfer hole.

[0021] Each burner branch 5 has two rows of gas spray holes, 6a is the first row of gas spray holes, 6b is the second row of gas spray holes, and the hole diameters of 6a and 6b are different. DETAILED DESCRIPTION

[0022] The present invention is further described with reference to the following structural drawings and embodiments.

[0023] Example 1.

[0024] The burner of the ground flare system is arranged at the bottom of the cylinder, so a large amount of NOx is often produced during the combustion process due to insufficient air supply to the burner in the central area. At the same time, insufficient air supply inside the cylinder will cause the temperature inside the cylinder to be too high, affecting the service life of the system.

[0025] In order to solve the above problems, the present invention proposes the following implementation scheme. Figure 1 A low-nitrogen ground flare system for an LNG receiving station includes a cylinder 1, a windbreak 2 and an LNG low-nitrogen burner 3. The cylinder 1 is located in the windbreak 2 and is raised to a certain height as an air inlet channel, that is, a natural wind inlet channel is provided at the bottom of the cylinder 1. The LNG low-nitrogen burner 3 is arranged in the hollow annular space at the bottom of the cylinder 1. The LNG low-nitrogen burner 3 is controlled by a burner hierarchical control system. The burner in the cylinder 1 is arranged in the hollow annular space in the cylinder, that is, no burner is arranged in the central area of ​​1 to 5m, and no burner is arranged within 1 to 3m near the wall). This method can increase the air distribution in the central area of ​​the cylinder 1, solve the problem of oxygen deficiency in the center of the traditional ground flare system, make the combustion more complete, and reduce NOx emissions. At the same time, no burner is arranged near the wall, and sufficient air cools the combustion temperature in the cylinder 1, extending the life of the system.

[0026] In addition to the hollow burner arrangement, the present invention also uses an LNG low-nitrogen burner 3. Figure 2The outer diameter of the LNG low nitrogen burner 3 is 320mm to 550mm. The gas enters each burner branch 5 through the gas inlet pipe 4. The burner branches 5 are evenly distributed along the circumference, with 3 to 8 branches. Two rows of gas spray holes 6 are radially opened on the burner branches 5. The gas spray holes 6 are divided into gas spray holes 6a and gas spray holes 6b. The first row of gas spray holes 6a have larger holes, with a diameter range of 4 to 9mm, and the axial direction of the holes is at an angle of 0° to 20° with the vertical direction. The second row of gas spray holes 6b have smaller holes, with a diameter range of 2.5 to 5mm, and the axial direction of the holes is at an angle of 10° to 30° with the vertical direction. Most of the gas is sprayed out from the gas spray holes 6a, and a small part of the gas is sprayed out from the gas spray holes 6b with smaller apertures, so that the flare gas presents obvious graded combustion, thereby reducing the local high temperature area. In addition, the LNG exhaust gas sprayed from the spray holes 6 can draw a large amount of surrounding air to participate in the combustion, reduce the combustion temperature, and thus reduce the emission of nitrogen oxides. Some burner branches 5 are provided with gas spray holes 6a, 6b and flame stabilizing holes 7. When the gas pressure is high (≥15kPa), the flame stabilizing holes 7 can stabilize the flame so that the flame does not flame out, thereby ensuring the burnout rate of the flare gas.

[0027] The present invention further provides compressed air or steam to enhance the internal combustion air supply of the burner. Compressed air or steam enters the annular tube 9 through the air / steam inlet pipe 8, and a plurality of groups of air / steam spray holes 10 are arranged on the annular tube 9. The compressed air or steam is sprayed into the flame at high speed through the spray holes 10 to alleviate the problem of insufficient internal air, significantly increase turbulent disturbance to make the air and gas mix more evenly, further reduce the flame temperature and the size of the high-temperature zone, reduce the residence time of nitrogen oxides in the high-temperature zone, and further significantly reduce the generation and emission of nitrogen oxides. The diameter of the air / steam spray hole 10 ranges from 2 to 4 mm, and is arranged close to the gas spray hole 6, with a horizontal distance of no more than 60 mm. The annular tube 9 and the gas inlet pipe 4 are fixed by a connecting plate 11.

[0028] Furthermore, the dedicated burners 3 are opened in stages by the burner hierarchical control system, wherein the first stage is provided with 2 to 8 sets of burners, the second stage is provided with 4 to 16 sets of burners, the third stage is provided with 8 to 24 sets of burners, and the remaining stages are arranged accordingly according to the ground flare processing volume, wherein 1 to 3 flame transfer holes are arranged on the branches 5 facing the adjacent burners within the 2nd and 3rd stages and between the stages, to ensure that the exhaust gas from the ground flare can be ignited in time and be promptly and fully processed.

[0029] The above technical solution ensures that the overall nitrogen oxide emission of the low-nitrogen ground flare system for the LNG receiving station of the present invention is ≤25ppm.

[0030] Example 2

[0031] like Figure 3As shown, a low-nitrogen ground flare system for a certain LNG receiving station is equipped with 20 sets of LNG low-nitrogen burners 3 in the cylinder, numbered 1 to 20, of which 1 to 4 are the first stage, 5 to 8 are the second stage, and 9 to 20 are the third stage (when the processing volume is large, more burners and more stages can be set). Except for the first stage (the first stage is normally open), each branch pipe upstream is respectively provided with a switch valve, which is controlled by a hierarchical control system. After the gas discharged from the upstream enters the main pipe, it first enters the first stage for combustion. At the same time, the hierarchical control system detects the pressure of the first-stage branch pipe in real time. If the pressure is large, the hierarchical control system determines that the gas exceeds the processing capacity of the first stage, and then the hierarchical control system automatically opens the second-stage switch valve. At this time, the gas is processed by the first and second stages at the same time. If the hierarchical control system detects that the pressure is still large at this time, the third-stage switch valve is opened. At the same time, if the hierarchical control system detects that the pressure in the branch pipe suddenly decreases during the operation of the flare system, the hierarchical control system will sequentially close (from the third stage to the second stage) the switch valve. When arranging adjacent burners within and between stages, the branches with flame transfer holes 12 are as opposite as possible, such as Figure 4 As shown, the advantage of such an arrangement is that when one of the burners is ignited, its flame can ignite the adjacent burners through the flame transfer holes, thereby improving the reliability of ignition of the entire system. Generally speaking, an LNG low-nitrogen burner 3 should have two burner branches 5 arranged with flame transfer holes 12 to satisfy the ignition between adjacent burner branches 5 within a stage, as well as the ignition between adjacent burner branches 5 between stages.

[0032] The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. A person skilled in the art may make various changes and modifications. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

[0033] The present invention does not involve parts that are the same as the prior art or can be implemented by using the same technology.

Claims

1. A low nitrogen ground flare system for an LNG receiving station, characterized in that: The invention comprises a cylinder (1), a windbreak wall (2) and an LNG low-nitrogen burner (3). The cylinder (1) is located in the windbreak wall (2) and is raised to a certain height as an air inlet passage, that is, a natural wind inlet passage is provided at the lower part of the cylinder (1). The LNG low-nitrogen burner (3) is arranged in a hollow annular space at the bottom of the cylinder (1). The LNG low-nitrogen burner (3) is controlled by a burner hierarchical control system. 3 to 8 burner branches (5) are arranged at the top of a gas inlet pipe (4) of the LNG low-nitrogen burner (3). Gas spray holes (6) are opened on the burner branches (5). The gas spray holes are divided into two rows, and the size and direction of each row of holes are different. The gas spray holes (6) are divided into a first row of gas spray holes (6a) and a second row of gas spray holes (6b), and are arranged on each burner branch (5). The first row of gas spray holes (6a) have relatively large holes, and the diameter ranges from 4 to 9 mm. The second row of gas spray holes (6b) have relatively large holes, and the diameter of the second row of gas spray holes (6b) is relatively large. The diameter of the first row of gas spray holes (6a) is small, and the diameter ranges from 2.5 to 5 mm; the axial direction of the first row of gas spray holes (6a) forms an angle of 0° to 20° with the vertical direction, and the axial direction of the second row of gas spray holes (6b) forms an angle of 10° to 30° with the vertical direction; the air / steam inlet pipe (8) is connected to a ring pipe (9), and the ring pipe (9) is provided with air / steam spray holes (10), and the ring pipe (9) and the gas inlet pipe (4) are fixed by a connecting plate (11); the ring pipe (9) is located at the lower part of the burner branch (5); some burner branches (5) are provided with both the first row of gas spray holes (6a) and the second row of gas spray holes (6b), and the root thereof is also provided with a flame stabilizing hole (7), and when the gas pressure is ≥15 kPa, the flame stabilizing hole (7) plays a role in stabilizing the flame, so that the flame does not fall out, thereby ensuring the burnout rate of the flare gas.

2. The low nitrogen ground flare system for LNG receiving station according to claim 1 is characterized in that In addition, compressed air or steam is added to intensify the internal combustion air supply of the LNG low-nitrogen burner (3). The compressed air or steam enters the annular pipe (9) through the air / steam inlet pipe (8). A plurality of groups of air / steam spray holes (10) are arranged on the annular pipe (9). The diameter of the air / steam spray holes (10) ranges from 2 to 4 mm. The air / steam spray holes (10) are arranged close to the gas spray holes (6) and the horizontal distance does not exceed 60 mm.

3. The low nitrogen ground flare system for LNG receiving station according to claim 1, characterized in that The LNG low nitrogen burners (3) are opened in stages by a burner stage control system, wherein the first stage is provided with 2 to 8 sets of burners, the second stage is provided with 4 to 16 sets of burners, the third stage is provided with 8 to 24 sets of burners, and the remaining stages are provided accordingly according to the ground flare treatment volume, wherein 1 to 3 flame transfer holes (12) are provided at the ends of adjacent burner branches (5) facing each other within the second to third stages and between the stages, to ensure that the ground flare exhaust gas can be ignited in time and be promptly and fully treated; thereby making the overall nitrogen oxide emission of the ground flare system ≤25ppm.

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