A low-nitrogen incomplete regeneration flue gas incineration system

Abstract

The present invention discloses a low-nitrogen incomplete regeneration flue gas incineration system, which aims to solve the problem of low NOx generation during the incineration process of incomplete regeneration flue gas in an incinerator. To this end, the low-nitrogen incomplete regeneration flue gas incineration system provided by an embodiment of the present invention includes an incinerator, a regeneration flue gas cyclone and an isolation tube, wherein the air outlet of the regeneration flue gas cyclone is connected to the smoke inlet of the incinerator, the regeneration flue gas cyclone is arranged around the isolation tube, a burner is provided at the tail end of the isolation tube, and a secondary combustion air inlet pipe is provided between the regeneration flue gas cyclone and the isolation tube.

Description

Technical Field

[0001] The invention belongs to the technical field of flue gas incineration, and in particular relates to a low-nitrogen incomplete regeneration flue gas incineration system. Background Art

[0002] In petroleum refining, the catalytic cracking unit is a core component in the conversion of heavy oil to lighter fuels. With increasing environmental protection requirements, clear NOx levels in its exhaust flue gas have been set, and local governments have also issued specific emission targets. Currently, the flue gas from the incomplete regeneration process of catalytic cracking contains a high level of CO (3.5%-6.8% by volume). To recover energy, a CO incinerator is typically installed. The flue gas from the incomplete regeneration process is then recycled through a boiler to recover heat. Compared to the complete regeneration of the catalyst, the flue gas from the incomplete regeneration process generally does not contain NOx, but rather contains small amounts of NH3 and HCN. These substances, when incinerated with the CO in the flue gas, generate significant amounts of NOx. In engineering, this process is treated with a denitrification unit to achieve NOx emission standards in the exhaust flue gas. However, implementing this denitrification technology requires significant investment, specialized catalysts, and the introduction of ammonia, resulting in varying degrees of secondary pollution. Furthermore, this type of retrofit is subject to site constraints. Summary of the Invention

[0003] The main purpose of the present invention is to provide a low-nitrogen incompletely regenerated flue gas incineration system, aiming to solve the problem of low NOx generation during the incineration process of incompletely regenerated flue gas in an incinerator.

[0004] To this end, an embodiment of the present invention provides a low-nitrogen incomplete regenerated flue gas incineration system, which includes an incinerator, a regenerated flue gas cyclone and an isolation tube. The air outlet of the regenerated flue gas cyclone is connected to the smoke inlet of the incinerator. The regenerated flue gas cyclone is arranged around the isolation tube. A burner is provided at the tail end of the isolation tube. A secondary combustion air inlet pipe is provided between the regenerated flue gas cyclone and the isolation tube.

[0005] Specifically, a support tube is provided on the periphery of the isolation tube, an annular gap is formed between the support tube and the isolation tube, and an air inlet hole connecting the annular gap and the regenerated flue gas cyclone is provided on the support tube.

[0006] Specifically, a plurality of secondary combustion air inlet pipes are evenly arranged around the circumference of the isolation tube.

[0007] Specifically, it also includes a secondary combustion-supporting air distribution chamber, and the plurality of secondary combustion-supporting air inlet pipes are all connected to the secondary combustion-supporting air distribution chamber.

[0008] Specifically, it also includes a combustion-supporting air fan, the air outlet pipe of which is divided into two branches respectively connected to the primary combustion-supporting air inlet and the secondary combustion-supporting air distribution chamber of the burner, and a combustion-supporting air regulating valve is provided on each branch.

[0009] Specifically, the incinerator is provided with an explosion-proof door.

[0010] Specifically, the smoke exhaust port of the incinerator is connected to the tail flue, and the tail end of the tail flue is provided with an expansion joint.

[0011] Specifically, the air inlet of the regeneration flue gas cyclone is connected to the incomplete regeneration flue gas pipe including the expansion joint.

[0012] Specifically, the incinerator is provided with a temperature sensor and an oxygen content analyzer, and the oxygen content analyzer is arranged away from the burner.

[0013] Specifically, the cross section of the secondary combustion-supporting air inlet pipe gradually decreases along the airflow direction, and a straight pipe of equal diameter is provided on the air outlet end of the secondary combustion-supporting air inlet pipe.

[0014] Specifically, the incinerator includes a cylindrical horizontal furnace, and the axes of the isolation tube and the regenerated flue gas cyclone coincide with the axis of the horizontal furnace.

[0015] Compared with the prior art, at least one embodiment of the present invention has the following beneficial effects: the incompletely regenerated flue gas does not directly contact the flame center and flame column of the burner, and under the action of the regenerated flue gas cyclone, the secondary combustion area in the incinerator furnace is increased, and the high-temperature combustion area is reduced, so that a small amount of NH3 in the flue gas to be burned at low temperature is first burned and oxidized to generate NOx, and the remaining large amount of CO that has not been converted in time is reduced to generate N2, thereby reducing the generation of NOx. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 Schematic diagram of the structure of a low-nitrogen incomplete regeneration flue gas incineration system provided by an embodiment of the present invention;

[0018] Figure 2 yes Figure 1 Cross-sectional view in the AA direction;

[0019] Among them: 1. Incinerator; 2. Regeneration flue gas cyclone; 3. Isolation tube; 4. Burner; 5. Secondary combustion air inlet pipe; 6. Support tube; 7. Annular gap; 8. Secondary combustion air distribution chamber; 9. Air outlet pipe; 10. Combustion air regulating valve; 11. Explosion-proof door; 12. Tail flue; 13. Incomplete regeneration flue gas connection pipe. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0023] To recover the chemical energy of CO in incompletely regenerated flue gas, existing technologies employ a burner positioned at the axially forward end of the incinerator. This burns externally introduced fuel to ignite the incoming incompletely regenerated flue gas, recovering the chemical energy of CO in the flue gas. This combustion method directly contacts the center and column of the burner's flame, resulting in temperatures exceeding 1000°C. This not only generates thermal NOx, but also significantly generates NOx from the combustion of NH3 contained in the incompletely regenerated flue gas.

[0024] The inventors have discovered that when flue gas containing CO and NH3 is burned at a lower temperature, such as around 700°C, which is higher than their auto-ignition points, the competitive oxidation reactions between the two are exactly the opposite compared to when burned at high temperatures. That is, the reaction of NH3 burning and oxidizing to produce NOx is easier than the reaction of CO oxidizing to produce CO2, and the remaining CO that has not yet been converted reacts with NOx to produce N2, thereby significantly reducing the NOx content in the flue gas after combustion. Therefore, if an incineration system can be designed in the incinerator so that the incompletely regenerated flue gas to be burned does not directly contact the high-temperature ignition flame zone, and can be evenly mixed with the high-temperature flue gas generated by the burner and a strictly controlled amount of combustion-supporting air, the above-mentioned problem can be solved. This application proposes a solution based on this concept.

[0025] See also Figure 1 and Figure 2 A low-nitrogen incomplete regenerated flue gas incineration system includes an incinerator 1, a regenerated flue gas cyclone 2 and an isolation tube 3. The air outlet of the regenerated flue gas cyclone 2 is connected to the smoke inlet of the incinerator 1. The regenerated flue gas cyclone 2 is arranged around the isolation tube 3. A burner 4 is provided at the tail end of the isolation tube 3. A secondary combustion-supporting air inlet pipe 5 is provided between the regenerated flue gas cyclone 2 and the isolation tube 3. The outlets of the secondary combustion-supporting air inlet pipe 5 and the isolation tube 3 are both facing the furnace body of the incinerator 1.

[0026] In this embodiment, the fuel sprayed from the gas gun of the burner 4 is mixed and burned once in the isolation tube 3. The regenerated flue gas to be burned does not directly contact the flame center and flame column of the burner 4. In addition, under the action of the regenerated flue gas cyclone 2, the secondary combustion area in the furnace of the incinerator 1 is increased, and the high-temperature combustion area is reduced, so that a small amount of NH3 in the flue gas to be burned at low temperature is first burned and oxidized to generate NOx, and the remaining large amount of CO that has not been converted in time reduces NOx to generate N2, thereby reducing the generation of NOx.

[0027] In some embodiments, a support tube 6 is provided on the periphery of the isolation tube 3, and an annular gap 7 is formed between the support tube 6 and the isolation tube 3. The support tube 6 is provided with an air inlet hole (not shown in the figure) connecting the annular gap 7 and the regeneration flue gas cyclone. The advantage of such a design is that the incompletely regenerated flue gas from the catalytic regeneration device enters the furnace of the incinerator 1 through the regeneration flue gas cyclone 2 and mixes with the secondary combustion-supporting air. At the same time, part of the regenerated flue gas enters the annular gap 7 between the isolation tube 3 and the support tube 6 through the air inlet hole on the support tube 6. On the one hand, it cools the isolation tube 3 in the primary combustion area, and on the other hand, it isolates the hot flue gas after the primary combustion within a certain range near the outlet of the annular gap 7 so that it does not mix with the secondary air, thereby delaying the ignition time of the secondary combustion and expanding the combustion area to reduce the generation of NOx.

[0028] In some embodiments, to ensure uniformity of secondary combustion air intake, multiple secondary combustion air inlet pipes 5 are evenly arranged circumferentially around the isolation tube 3. Furthermore, it is understood that, in actual design, the secondary combustion air inlet pipe 5 can be designed as a trumpet-shaped pipe whose cross-section gradually decreases along the airflow direction. A straight pipe of equal diameter is provided at the outlet end of the secondary combustion air inlet pipe 5. Reinforced ribs are welded between the secondary combustion air inlet pipe 5 and the incinerator 1 to reduce vibrations generated by the flow of regenerated flue gas and air, minimizing resonance. To prevent internal cyclone backfire during production fluctuations, the end of the secondary combustion air inlet pipe 5 should be at least 50 mm higher than the radial cross-section of the flue gas cyclone.

[0029] In some embodiments, the incineration system also includes a combustion-supporting air fan (not shown in the figure) and a secondary combustion-supporting air distribution chamber 8. Multiple secondary combustion-supporting air inlet pipes 5 are connected to the secondary combustion-supporting air distribution chamber 8. The outlet pipe 9 of the combustion-supporting air fan is divided into two branches that are respectively connected to the primary combustion-supporting air inlet of the burner 4 and the secondary combustion-supporting air distribution chamber 8. A combustion-supporting air regulating valve 10 is provided on each branch.

[0030] In the incineration system of the above structure, the primary combustion air from the outside is adjusted in flow rate by the corresponding combustion air regulating valve 10, and then mixed with the fuel sprayed from the gas gun of the burner 4, and burned in the space of the sufficiently long isolation tube 3. By controlling the fuel gas pressure and combustion air volume of the burner 4, the length of the burning flame is maintained to ensure that the open flame does not enter the furnace area of ​​the incinerator 1, and to avoid direct contact between the flue gas to be burned and the flame, forming an environment where the incompletely regenerated flue gas to be burned and the high-temperature flue gas generated by the combustion of the burner 4 are burned. The secondary combustion air, which is adjusted by another combustion air regulating valve 10, is evenly distributed to each secondary combustion air inlet pipe 5 through the secondary combustion air distribution chamber 8, and then enters the furnace area of ​​the incinerator 1.

[0031] In this embodiment, the combustion air regulating valve 10 provided at the primary combustion air inlet of the burner 4 ensures that the primary combustion flame is maintained at an optimal state when fuel consumption changes. The combustion air regulating valve 10 provided at the secondary combustion air inlet of the secondary combustion air distribution chamber 8 adjusts the secondary combustion air volume based on the amount of incompletely regenerated flue gas and the concentration of CO, thereby achieving complete combustion of CO. Furthermore, under normal circumstances, the valve core of the combustion air regulating valve 10 is generally positioned at a distance of no less than 2000 mm from the incinerator 1.

[0032] In some embodiments, an explosion-proof door 11 may be further provided on the incinerator 1. By providing the explosion-proof door 11, pressure relief can be achieved in the event of an abnormality in the incinerator 1, effectively ensuring the safety of incineration. The explosion-proof door 11 is provided at a position not less than 1000 mm downstream of the regeneration flue gas cyclone 2 along the direction of flue gas flow, and at least two doors are provided. In addition, the exhaust port of the incinerator 1 may be connected to a tail flue 12, the tail end of which is provided with an expansion joint. The air inlet of the regeneration flue gas cyclone 2 is connected to an incomplete regeneration flue gas pipe 13 containing an expansion joint. The provision of the expansion joint effectively ensures the safety of the docking equipment, so that the docking equipment will not be damaged due to the expansion of the pipe due to heat.

[0033] In this embodiment, when the hot flue gas generated by the primary combustion passes through the regenerated flue gas cyclone 2, it is fully mixed with the incompletely regenerated flue gas to be burned and the secondary combustion-supporting air due to the swirl effect, and diffuses to the entire subsequent tail flue 12 to cause secondary combustion, forming a very large secondary combustion area, greatly reducing the high-temperature area, and effectively reducing the generation of NOx.

[0034] In some embodiments, the incinerator 1 includes a cylindrical horizontal furnace, the axes of the isolation tube 3 and the regenerated flue gas cyclone 2 coincide with the axis of the horizontal furnace, the smoke inlet and exhaust port of the incinerator 1 are respectively arranged on the left and right sides of the furnace body, and the incinerator 1 is provided with a temperature sensor and an oxygen content analyzer (not shown in the figure), and the oxygen content analyzer is arranged away from the burner 4. In this embodiment, a temperature measuring point is provided in the furnace body of the incinerator 1, and a temperature sensor is provided to measure the furnace temperature. An oxygen content analyzer is provided at the rear end of the furnace body to guide the adjustment of the ratio of fuel gas and combustion-supporting air.

[0035] In specific applications, an annular gap 7 of no less than 50 mm is reserved between the support tube 6 and the isolation tube 3. The deviation of the annular gap 7 between the support tube 6 and the isolation tube 3 is controlled within ±3 mm, so that the incompletely regenerated flue gas evenly surrounds the high-temperature area of ​​the burner 4 when it flows out. When the incompletely regenerated flue gas flows out of the annular gap, it has a certain effect of isolating the secondary combustion air and the flue gas after primary combustion, delaying the ignition time of the incompletely regenerated flue gas secondary combustion, expanding the combustion area, and reducing NOx generation. In addition, a number of air inlet holes with a size of no less than 50×100 mm are uniformly distributed in the contact area between the support tube and the incompletely regenerated flue gas, and the total flow area of ​​the air inlet holes is no less than 20% of the total flue gas flow.

[0036] It should be explained that in the actual design, the swirl blades of the regenerated flue gas cyclone 2 are bent in the same direction to a certain arc. After being deformed by heat, the swirl blades expand in the same direction, and the spacing between adjacent swirl blades remains basically unchanged, achieving uniform mixing of the incompletely regenerated flue gas and the secondary combustion air under different temperature conditions. In addition, the burner 4 uses a single multi-hole air gun nozzle. The air gun nozzle is located at a distance from the main combustion outlet that is greater than the length of the combustion flame and is not less than 3000mm. The open flame combustion area is located within the space of the isolation tube 3 with a diameter of 600-800mm. The combustion area is equipped with high-temperature resistant lining bricks. The length of the secondary combustion area formed by the high-temperature flue gas after the primary combustion and the flue gas to be burned is not less than 5000mm, so that the incompletely regenerated flue gas to be burned is distributed in a gradient in the furnace of the incinerator 1, which greatly reduces the temperature of the secondary combustion center area. The tail flue 12 including the expansion joint has a total length of not less than 15000mm, and the gradient secondary combustion flue gas is fully mixed internally to avoid the flue gas with too high a temperature locally entering the rear waste heat recovery device and causing high temperature impact on the equipment.

[0037] Unless otherwise stated, for any of the technical solutions disclosed in the present invention, if a numerical range is disclosed, the disclosed numerical range is a preferred numerical range. Any person skilled in the art should understand that the preferred numerical range is merely a numerical range that is representative or has a more obvious technical effect among many feasible numerical values. Due to the large number of numerical values, it is impossible to enumerate them exhaustively. Therefore, the present invention discloses some numerical values ​​to illustrate the technical solutions of the present invention. Moreover, the numerical values ​​listed above should not be construed as limiting the scope of protection of the present invention.

[0038] At the same time, if the above-mentioned invention discloses or involves components or structural parts that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, using bolts or screws to connect), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by a casting process) (except where it is obviously impossible to use an integrated forming process).

[0039] In addition, unless otherwise stated, terms used in any of the technical solutions disclosed herein to represent positional relationships or shapes include states or shapes that are similar, analogous, or approximate. Any component provided by the present invention may be assembled from multiple separate components or may be a single component manufactured using an integral molding process.

Claims

1. A low-nitrogen incomplete regeneration flue gas incineration system, comprising an incinerator (1), a regeneration flue gas cyclone (2) and an isolation tube (3), characterized in that: The air outlet of the regenerated smoke cyclone (2) is connected to the smoke inlet of the incinerator (1), the regenerated smoke cyclone (2) is arranged around the isolation cylinder (3), a burner (4) is provided at the tail end of the isolation cylinder (3), and a secondary combustion air inlet pipe (5) is provided between the regenerated smoke cyclone (2) and the isolation cylinder (3); A support cylinder (6) is provided on the periphery of the isolation cylinder (3), an annular gap (7) is formed between the support cylinder (6) and the isolation cylinder (3), and an air inlet hole is provided on the support cylinder (6) for connecting the annular gap (7) and the regenerated smoke cyclone (2); The air inlet of the regeneration flue gas cyclone (2) is connected to the incomplete regeneration flue gas pipe (13) containing an expansion joint; The cross section of the secondary combustion-supporting air inlet pipe (5) gradually decreases along the airflow direction, and a straight pipe of equal diameter is provided on the air outlet end of the secondary combustion-supporting air inlet pipe (5).

2. The low-nitrogen incomplete regeneration flue gas incineration system according to claim 1 is characterized in that: A plurality of secondary combustion-supporting air inlet pipes (5) are evenly arranged circumferentially around the isolation cylinder (3).

3. The low-nitrogen incomplete regeneration flue gas incineration system according to claim 2, characterized in that: It also includes a secondary combustion-supporting air distribution chamber (8), and a plurality of secondary combustion-supporting air inlet pipes (5) are all connected to the secondary combustion-supporting air distribution chamber (8).

4. The low-nitrogen incomplete regeneration flue gas incineration system according to claim 3, characterized in that: It also includes a combustion-supporting air fan, the air outlet pipe (9) of the combustion-supporting air fan is divided into two branches respectively connected to the primary combustion-supporting air inlet and the secondary combustion-supporting air distribution chamber (8) of the burner (4), and a combustion-supporting air regulating valve (10) is provided on each branch.

5. The low-nitrogen incomplete regeneration flue gas incineration system according to any one of claims 1 to 4, characterized in that: The smoke exhaust port of the incinerator (1) is communicated with a tail flue (12), and an expansion joint is provided at the tail end of the tail flue (12).

6. The low-nitrogen incomplete regeneration flue gas incineration system according to any one of claims 1 to 4, characterized in that: The incinerator (1) is provided with a temperature sensor and an oxygen content analyzer, and the oxygen content analyzer is arranged away from the burner (4).

7. The low-nitrogen incomplete regeneration flue gas incineration system according to any one of claims 1 to 4, characterized in that: The incinerator (1) comprises a cylindrical horizontal furnace, and the axes of the isolation tube (3) and the regenerated flue gas cyclone (2) coincide with the axis of the horizontal furnace.

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