A system for treating nitrogen oxides in exhaust gas

Abstract

This invention provides a system for treating nitrogen oxides in exhaust gas, including a denitrification reactor and a denitrification reaction bed. The inlet of the denitrification reactor is connected to a first branch and a second branch; the inlet of the denitrification reaction bed is connected to a third branch and a fourth branch. Each of the first, second, third, and fourth branches is equipped with a regulating valve for adjusting the intake air volume. The first and third branches are respectively connected to an ammonia gas source, and the second and fourth branches are respectively connected to an air gas source. The denitrification reactor is connected to a first process gas source, and the denitrification reaction bed is connected to a second process gas source. In this invention, the intake air of the denitrification reactor and the denitrification reaction bed is controlled independently, thus preventing interference and airflow fluctuations when adjusting the intake air volume. The ammonia intake volume can be precisely controlled separately, reducing ammonia escape. The denitrification reactor and the denitrification reaction bed can be used simultaneously, thereby improving efficiency.

Description

Technical Field

[0001] This utility model relates to the field of exhaust gas treatment technology, and in particular to a system for treating nitrogen oxides in exhaust gas. Background Technology

[0002] In the petroleum refining process, to control nitrogen oxide emissions in the tail gas, two denitrification catalyst beds are installed in the waste acid regeneration unit, located in the denitrification reactor and the secondary converter, respectively. Both denitrification catalyst beds require the introduction of ammonia and air. Currently, the ammonia and air are mixed in the two denitrification catalyst beds and then introduced separately through two pipelines. When the required ammonia and / or air content of one denitrification catalyst bed changes, it affects the air intake of the other denitrification catalyst bed. This mutual interference between the two denitrification catalyst beds leads to large airflow fluctuations. If the ammonia cannot be precisely controlled, ammonia escape may occur, and it may even prevent both denitrification catalyst beds from being used simultaneously, resulting in low tail gas treatment efficiency. Summary of the Invention

[0003] This invention provides a system for treating nitrogen oxides in exhaust gas to solve the technical problem of low exhaust gas treatment efficiency when two denitrification catalyst beds are used simultaneously and the intake of ammonia and / or air needs to be adjusted, resulting in large airflow fluctuations and the inability to use the two denitrification catalyst beds at the same time.

[0004] This utility model provides a tail gas nitrogen oxide treatment system, including a denitrification reactor and a denitrification reaction bed. The inlet of the denitrification reactor is connected to a first branch and a second branch; the inlet of the denitrification reaction bed is connected to a third branch and a fourth branch; the first branch is equipped with a first regulating valve for adjusting the intake air volume, the second branch is equipped with a second regulating valve for adjusting the intake air volume, the third branch is equipped with a third regulating valve for adjusting the intake air volume, and the fourth branch is equipped with a fourth regulating valve for adjusting the intake air volume; the first branch and the third branch are respectively connected to an ammonia gas source, and the second branch and the fourth branch are respectively connected to an air gas source; the inlet of the denitrification reactor is connected to a first process gas source through a fifth branch, and the inlet of the denitrification reaction bed is connected to a second process gas source through a sixth branch; the outlet of the denitrification reactor is connected to a seventh branch, and the outlet of the denitrification reaction bed is connected to an eighth branch.

[0005] In one embodiment of the present invention, the first branch and the second branch are both connected to one end of the first mixing air inlet pipe, and the other end of the first mixing air inlet pipe is connected to the air inlet of the denitrification reactor; the third branch and the fourth branch are both connected to one end of the second mixing air inlet pipe, and the other end of the second mixing air inlet pipe is connected to the air inlet of the denitrification reaction bed.

[0006] In one embodiment of the present invention, the exhaust gas nitrogen oxide treatment system further includes a mixer, the first mixing inlet pipe is connected to the first inlet of the mixer, the fifth branch is connected to the second inlet of the mixer, and the outlet of the mixer is connected to the inlet of the denitrification reactor through a ninth branch.

[0007] In one embodiment of the present invention, a first instrument for detecting the nitrogen oxide content in the gas discharged from the denitrification reactor is connected to the seventh branch, and a first flow detection controller is provided on the first branch. The first flow detection controller is used to control the first regulating valve according to the data of the first instrument.

[0008] In one embodiment of the present invention, a second instrument for detecting the oxygen content in the gas discharged from the denitrification reactor is connected to the seventh branch, and a second flow detection controller is provided on the second branch. The second flow detection controller is used to control the second regulating valve according to the data of the second instrument.

[0009] In one embodiment of this utility model, a third instrument for detecting the nitrogen oxide content in the gas discharged from the denitrification reaction bed is connected to the eighth branch. A third flow detection controller is provided on the third branch. The third flow detection controller is used to control the third regulating valve based on the data from the third instrument.

[0010] In one embodiment of the present invention, a fourth flow detection controller for controlling the opening degree of the fourth regulating valve is provided on the fourth branch.

[0011] In one embodiment of this utility model, a shut-off valve is provided on the third branch.

[0012] In one embodiment of the present invention, heating structures for heating are provided on the pipes of the first branch and the third branch.

[0013] In one embodiment of this utility model, the heating structure is a steam tracing pipe, and the heating structure is used to heat the pipes of the first branch and the third branch respectively.

[0014] The beneficial effects of this utility model are as follows: The exhaust gas nitrogen oxide treatment system proposed in this utility model has a first branch and a second branch connected to a denitrification reactor, and a third branch and a fourth branch connected to a denitrification reaction bed. This allows the air intake of the denitrification reactor and the denitrification reaction bed to be controlled separately, so that the air intake of the denitrification reactor and the denitrification reaction bed can be adjusted without interference and without airflow fluctuations. The ammonia intake can be precisely controlled separately, reducing ammonia escape. The denitrification reactor and the denitrification reaction bed can be used simultaneously, thereby improving efficiency. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0016] In the attached diagram: Figure 1 A schematic diagram of the structure of the exhaust gas nitrogen oxide treatment system provided by this utility model.

[0017] The attached figures are labeled as follows: 1-First branch, 2-Second branch, 3-Third branch, 4-Fourth branch, 5-Fifth branch, 6-Sixth branch, 7-Seventh branch, 8-Eighth branch, 9-Ninth branch, 10-First regulating valve, 11-Second regulating valve, 12-Third regulating valve, 13-Fourth regulating valve, 14-Stop valve, 15-First instrument, 16-First flow detection controller, 17-Second instrument, 18-Second flow detection controller, 19-Third instrument, 20-Third flow detection controller, 21-Fourth flow detection controller, 22-First mixing inlet pipeline, 23-Second mixing inlet pipeline, 24-Mixer, R1-Denitrification reactor, R2-Denitrification reaction bed. Detailed Implementation

[0018] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0019] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0020] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the present invention.

[0021] Please see Figure 1 , Figure 1 This is a schematic diagram of a tail gas nitrogen oxide treatment system according to an embodiment of the present invention. The tail gas nitrogen oxide treatment system includes a denitrification reactor R1 and a denitrification reaction bed R2. The inlet of the denitrification reactor R1 is connected to a first branch 1 and a second branch 2; the inlet of the denitrification reaction bed R2 is connected to a third branch 3 and a fourth branch 4. The first branch 1 and the third branch 3 are respectively connected to an ammonia gas source, and the second branch 2 and the fourth branch 4 are respectively connected to an air gas source. The air intake into the denitrification reactor R1 and the denitrification reaction bed R2 is controlled separately. The air intake includes ammonia and / or air. When the air intake of the denitrification reactor R1 is adjusted, it has no effect on the denitrification reaction bed R2; correspondingly, when the air intake of the denitrification reaction bed R2 is adjusted, it has no effect on the denitrification reactor R1.

[0022] In some embodiments, to precisely control the ratio of ammonia and oxygen entering the denitrification reactor R1 and the denitrification reaction bed R2, a first regulating valve 10 for adjusting the intake air volume is provided on the first branch 1, a second regulating valve 11 for adjusting the intake air volume is provided on the second branch 2, a third regulating valve 12 for adjusting the intake air volume is provided on the third branch 3, and a fourth regulating valve 13 for adjusting the intake air volume is provided on the fourth branch 4. This is equivalent to each intake branch having a regulating valve for control. The first regulating valve 10, the second regulating valve 11, the third regulating valve 12, and the fourth regulating valve 13 can be manual valves or electric valves, preferably electric valves for ease of control.

[0023] The inlet of the denitrification reactor R1 is connected to the first process gas source via the fifth branch 5. The process gas in the first process gas source reacts chemically with ammonia and oxygen in the denitrification reactor R1 to treat the process gas. The inlet of the denitrification reaction bed R2 is connected to the second process gas source via the sixth branch 6. The process gas in the second process gas source reacts chemically with ammonia and oxygen in the denitrification reactor R1 to treat the process gas.

[0024] The outlet of the denitrification reactor R1 is connected to a seventh branch 7, and the outlet of the denitrification reaction bed R2 is connected to an eighth branch 8. Since the denitrification reaction bed R2 is a two-stage converter, the seventh branch 7 is connected to the sixth branch 6. Isolation valves are installed on the seventh branch 7 and / or the sixth branch 6. When the gas discharged from the seventh branch 7 fails to meet emission standards, the isolation valve is opened, and the gas in the seventh branch 7 enters the sixth branch 6. This allows the gas discharged from the denitrification reactor R1 to re-enter the denitrification reaction bed R2 for secondary treatment, ensuring that it meets emission standards before being released into the atmosphere.

[0025] In some embodiments, if the nitrogen oxide content in the tail gas after treatment by the denitrification reactor R1 meets the standard, the denitrification reaction bed R2 is not needed, and ammonia does not need to enter the denitrification reaction bed R2. Therefore, a shut-off valve 14 is installed on the third branch 3 to cut off the ammonia in the third branch 3 and prevent ammonia escape. To better prevent ammonia escape, two shut-off valves 14 are installed on the third branch 3 in series to prevent ammonia leakage caused by leakage from one of them. One of the shut-off valves 14 can be installed in a position closer to the ammonia source. The two shut-off valves 14 serve as backups for each other. If one shut-off valve 14 jams or its actuator malfunctions, the other shut-off valve 14 can still safely shut off the gas.

[0026] In some embodiments, if the pipeline temperature of the first branch 1 and the third branch 3 is lower than the dew point of ammonia, the ammonia will condense into liquid ammonia, causing flow meter distortion, fluctuations in ammonia injection, and a sharp drop in denitrification efficiency. If liquid ammonia combines with trace amounts of moisture, it will form crystals that clog valves. Liquid ammonia will also corrode the pipelines of the first branch 1 and the third branch 3. Therefore, heating structures are generally installed on the pipelines of the first branch 1 and the third branch 3 to heat the pipelines of the first branch 1 and the third branch 3, so that the pipeline temperature of the first branch 1 and the third branch 3 is always higher than the dew point temperature, thus preventing ammonia from turning into liquid ammonia.

[0027] In some embodiments, the heating structure is generally a steam tracing pipe, which heats the pipes of the first branch 1 and the third branch 3 by means of steam tracing. The first branch 1 and the third branch 3 are made of 316L stainless steel pipes. Multiple tracing pipes can be wrapped around the outside of the pipes of the first branch 1 and the third branch 3, and steam flows in the tracing pipes to heat the first branch 1 and the third branch 3.

[0028] In some embodiments, ammonia is a polar small molecule that diffuses extremely rapidly. Therefore, to prevent excessively high local ammonia concentrations and ammonia escape, a first mixing inlet pipe 22 is provided in the tail gas nitrogen oxide treatment system. Ammonia from the first branch 1 and air from the second branch 2 are mixed in the first mixing inlet pipe 22 to form a first mixed gas. The first mixing inlet pipe 22 is connected to the inlet of the denitrification reactor R1. Similarly, a second mixing inlet pipe 23 is provided in the tail gas nitrogen oxide treatment system. Ammonia from the third branch 3 and air from the fourth branch 4 are mixed in the second mixing inlet pipe 23 to form a second mixed gas. The second mixing inlet pipe 23 is connected to the inlet of the denitrification reaction bed R2. Before entering the denitrification reactor R1 and the denitrification reaction bed R2, ammonia gas is first mixed with air to form a mixed gas. This mixed gas reduces ammonia escape and ensures a uniform molar ratio of ammonia to process gas. This is particularly important for the denitrification reactor R1, which is highly sensitive to the molar ratio of ammonia to process gas. If ammonia and air enter R1 separately, concentration stratification will occur at the catalyst inlet, with some areas having a high molar ratio of ammonia to process gas and others having a low ratio. This could potentially lead to a decrease in overall denitrification efficiency or a surge in the probability of ammonia escape. Therefore, by diluting the ammonia gas with air before it enters the denitrification reactor R1, the diluted ammonia gas mixes better with the process gas.

[0029] In some embodiments, a mixer 24 is provided to further mix the ammonia and process gas, ensuring thorough mixing before they enter the denitrification reactor R1. A first mixing inlet pipe 22 is connected to the first inlet of the mixer 24, a fifth branch 5 is connected to the second inlet of the mixer 24, and the outlet of the mixer 24 is connected to the inlet of the denitrification reactor R1 via a ninth branch 9. Ammonia and oxygen are initially mixed in the first mixing inlet pipe 22 before entering the mixer 24, where the mixed gas and process gas are thoroughly mixed. The gas mixed in the mixer 24 then enters the denitrification reactor R1, further ensuring a uniform molar ratio of ammonia to process gas and improving denitrification efficiency.

[0030] To analyze the exhaust gas from the denitrification reactor R1, a first instrument 15 for detecting the nitrogen oxide content in the gas discharged from the denitrification reactor R1 is connected to the seventh branch 7. A first flow detection controller 16 is installed on the first branch 1, which controls the first regulating valve 10 based on the data from the first instrument 15. A second instrument 17 for detecting the oxygen content in the gas discharged from the denitrification reactor R1 is connected to the seventh branch 7, and a second flow detection controller 18 is installed on the second branch 2, which controls the second regulating valve 11 based on the data from the second instrument 17. By detecting the nitrogen oxide content in the gas discharged from the denitrification reactor R1 using the first instrument 15 and the oxygen content using the second instrument 17, the opening degrees of the first regulating valve 10 and the second regulating valve 11 can be precisely controlled, allowing for precise control of the ammonia-to-air ratio, preventing ammonia escape, and reducing the nitrogen oxide content in the gas discharged into the atmosphere.

[0031] In some embodiments, a third instrument 19 for detecting the nitrogen oxide content in the gas discharged from the denitrification reaction bed R2 is connected to the eighth branch 8. A third flow detection controller 20 is provided on the third branch 3, and the third flow detection controller 20 controls the third regulating valve 12 based on the data from the third instrument 19. A fourth flow detection controller 21 is provided on the fourth branch 4, and the detection result of the fourth flow detection controller 21 can be used to control the opening degree of the fourth regulating valve 13. The first flow detection controller 16, the second flow detection controller 18, the third flow detection controller 20, and the fourth flow detection controller 21 can detect the flow rate on each branch, and the opening degree of the regulating valve on each branch can be remotely controlled based on the detection result.

[0032] The exhaust gas nitrogen oxide treatment system provided by this invention allows for precise and individual control of the ammonia regulating valves in both circuits when the denitrification reactor R1 and the denitrification reaction bed R2 are used simultaneously, effectively reducing the possibility of ammonia escape due to excessive ammonia injection. Simultaneously, it minimizes nitrogen oxide emissions in the exhaust gas, better protecting the environment.

[0033] The denitrification reactor R1 is located at the inlet of the primary process gas blower, and the denitrification reaction bed R2 is located at the outlet of the secondary process gas blower. The ammonia entering the denitrification reactor R1 and the denitrification reaction bed R2 are controlled separately, thus adjusting the amount of ammonia entering the denitrification reaction bed R2 will not cause airflow fluctuations in the denitrification reactor R1. The fourth regulating valve 13 of the denitrification reaction bed R2 allows air to enter the denitrification reaction bed R2. The air in the denitrification reaction bed R2 is used as the carrier gas; therefore, the fourth regulating valve 13 can be independently controlled to a small opening to prevent cross-contamination of process gas between the denitrification reactor R1 and the denitrification reaction bed R2.

[0034] The air entering the denitrification reactor R1 and the denitrification reaction bed R2 is also controlled separately, which can effectively control the amount of air injected into the reactor, thereby reducing the generation of nitrogen oxides, saving energy and increasing efficiency, and being more environmentally friendly.

[0035] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A system for treating nitrogen oxides in exhaust gas, characterized in that: The system includes a denitrification reactor and a denitrification reaction bed. The inlet of the denitrification reactor is connected to a first branch and a second branch; the inlet of the denitrification reaction bed is connected to a third branch and a fourth branch; the first branch is equipped with a first regulating valve for adjusting the inlet air volume, the second branch with a second regulating valve for adjusting the inlet air volume, the third branch with a third regulating valve for adjusting the inlet air volume, and the fourth branch with a fourth regulating valve for adjusting the inlet air volume; the first and third branches are respectively connected to an ammonia gas source, and the second and fourth branches are respectively connected to an air gas source; the inlet of the denitrification reactor is connected to a first process gas source via a fifth branch, and the inlet of the denitrification reaction bed is connected to a second process gas source via a sixth branch; the outlet of the denitrification reactor is connected to a seventh branch, and the outlet of the denitrification reaction bed is connected to an eighth branch.

2. The exhaust gas nitrogen oxide treatment system according to claim 1, characterized in that: The first branch and the second branch are both connected to one end of the first mixing air inlet pipe, and the other end of the first mixing air inlet pipe is connected to the air inlet of the denitrification reactor; the third branch and the fourth branch are both connected to one end of the second mixing air inlet pipe, and the other end of the second mixing air inlet pipe is connected to the air inlet of the denitrification reaction bed.

3. The exhaust gas nitrogen oxide treatment system according to claim 2, characterized in that: The exhaust gas nitrogen oxide treatment system also includes a mixer, the first mixing inlet pipe is connected to the first inlet of the mixer, the fifth branch is connected to the second inlet of the mixer, and the outlet of the mixer is connected to the inlet of the denitrification reactor through a ninth branch.

4. The exhaust gas nitrogen oxide treatment system according to any one of claims 1-3, characterized in that: The seventh branch is connected to a first instrument for detecting the nitrogen oxide content in the gas discharged from the denitrification reactor. The first branch is equipped with a first flow detection controller, which is used to control the first regulating valve based on the data from the first instrument.

5. The exhaust gas nitrogen oxide treatment system according to claim 4, characterized in that: The seventh branch is connected to a second instrument for detecting the oxygen content in the gas discharged from the denitrification reactor. The second branch is equipped with a second flow detection controller, which is used to control the second regulating valve based on the data from the second instrument.

6. The exhaust gas nitrogen oxide treatment system according to claim 1, characterized in that: The eighth branch is connected to a third instrument for detecting the nitrogen oxide content in the gas discharged from the denitrification reaction bed. The third branch is equipped with a third flow detection controller, which is used to control the third regulating valve based on the data from the third instrument.

7. The exhaust gas nitrogen oxide treatment system according to claim 1, characterized in that: A fourth flow detection controller for controlling the opening degree of the fourth regulating valve is provided on the fourth branch.

8. The exhaust gas nitrogen oxide treatment system according to claim 1 or 7, characterized in that: A shut-off valve is installed on the third branch.

9. The exhaust gas nitrogen oxide treatment system according to claim 1, characterized in that: Both the first and third branch pipes are equipped with heating structures for heating.

10. The exhaust gas nitrogen oxide treatment system according to claim 9, characterized in that: The heating structure is a steam-heated pipeline, which is used to heat the pipelines of the first branch and the third branch respectively.

Images