A system suitable for online regeneration of medium and low temperature SCR denitrification catalysts

Abstract

The present invention discloses a system suitable for online regeneration of medium- and low-temperature SCR denitration catalysts. The system comprises an ammonia station, an ammonia evaporator, a mixer, an upper ammonia grid inlet valve, a lower ammonia grid inlet valve, an air inlet valve, and a dilution fan. The system evaporates the ammonia water into ammonia gas, which is supplied to the two-layer ammonia grids of the denitration reactor. The present invention aims to provide a system suitable for online regeneration of medium- and low-temperature SCR denitration catalysts, addressing the problem of ammonium bisulfate accumulating within the catalyst's micropores in existing medium- and low-temperature SCR denitration catalysts, isolating the catalyst from contact with flue gas and leading to decreased catalyst activity.

Description

Technical Field

[0001] The present invention relates to the technical field of SCR denitration catalyst cleaning and regeneration, and in particular to a system suitable for online regeneration of medium and low temperature SCR denitration catalysts. Background Art

[0002] Selective catalytic reduction (SCR) is currently the most widely used and reliable flue gas denitrification technology, having been widely adopted in flue gas treatment applications such as boilers and cement kilns. SCR, or selective catalytic reduction, works by using a suitable catalyst and ammonia as a reducing agent to catalyze a reaction under certain temperature conditions, converting nitrogen oxides into harmless nitrogen and water vapor. Currently, the reducing agents used for SCR flue gas denitrification are primarily aqueous ammonia, urea, and liquid ammonia (which is now less commonly used in China). Regardless of the reducing agent, the active component is NH3. The most widely used catalysts use TiO2 as a carrier and V2O5, V2O5-WO3, or V2O5-MnO3 as the active ingredients.

[0003] The reaction equation is as follows:

[0004] 4NO+4NH3+O2=4N2+6H2O

[0005] 2NO2+4NH3+O2=3N2+6H2O

[0006] Because this method has a high denitrification efficiency, which can reach over 95%, it is currently the most important technical means for denitrification of boiler flue gas in the power industry. Traditional SCR technology requires that the flue gas temperature be controlled between 300℃ and 450℃ to complete the catalytic reduction reaction. In recent years, with the continuous updating and development of low-temperature catalyst products at home and abroad, the lower limit of the temperature window of low-temperature SCR technology has been expanded to around 150℃. Under certain conditions, efficient low-temperature or even ultra-low-temperature denitrification can be achieved. The lower the temperature, the wider the application range of the SCR catalyst. For some flue gas conditions that require heating for normal denitrification, the use of low-temperature catalysts can greatly save fuel and energy consumption. However, not all types of flue gas conditions are suitable for SCR low-temperature denitrification, and this method also has several constraints.

[0007] Among various influencing factors, SO3 has the greatest and most common impact. SO2 in flue gas will be oxidized to SO3 under the action of a catalyst. SO3 reacts with H20 and NH3 in the flue gas to produce ammonium bisulfate (molecular formula: NH4HSO4, dew point temperature 147℃, boiling point temperature 350℃). Denitrification catalysts are conducive to this reaction. The reaction equation is as follows:

[0008] NH3+SO3+H2O→NH4HSO4

[0009] This reaction is a reversible reaction. When the temperature is higher than 350℃, the reaction proceeds in the reverse direction.

[0010] Ammonium bisulfate is a white, crystalline substance with high viscosity. The operating temperature of medium- and low-temperature catalysts is determined by the fact that when the flue gas temperature falls below the dew point of ammonium bisulfate, it condenses within the catalyst's micropores, isolating the catalyst from the flue gas and causing a decrease in catalyst activity. The extent of the denitrification catalyst's activity reduction depends on the degree of catalyst surface isolation. Excessive decreases in catalyst activity can lead to excessive flue gas nitrogen oxide levels, increased flue gas resistance, and increased fan power consumption. Therefore, developing a method and system suitable for the online regeneration of medium- and low-temperature SCR denitrification catalysts is of great significance.

[0011] The present invention is a technology for inhibiting the generation of ammonium bisulfate or decomposing ammonium bisulfate, which can keep the catalyst in a high-efficiency state and increase the life of the catalyst. Summary of the Invention

[0012] The purpose of the present invention is to provide a system suitable for online regeneration of medium- and low-temperature SCR denitration catalysts to solve the problem that ammonium bisulfate in existing medium- and low-temperature SCR denitration catalysts condenses in the micropores of the catalyst, isolating the area of ​​contact between the catalyst and the flue gas, resulting in a decrease in catalyst activity.

[0013] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0014] The present invention provides a system suitable for online regeneration of a medium- and low-temperature SCR denitration catalyst, comprising a denitration reactor and a mixer;

[0015] The denitration reactor comprises an upper part and a lower part which are connected. The top of the upper part is provided with a denitration reactor inlet flue, an upper catalyst bypass flue is provided in the upper part, and the other side is provided with an upper catalyst main flue inlet baffle, an upper ammonia injection grid, an upper catalyst and an upper catalyst main flue outlet baffle in sequence from top to bottom. The lower part is provided with a lower catalyst bypass flue, and the other side is provided with a lower catalyst main flue inlet baffle, a lower ammonia injection grid and a lower catalyst in sequence from top to bottom. The lower end of the lower part is also connected to the denitration reactor outlet flue.

[0016] The inlet of the mixer is connected to the ammonia evaporator and the air inlet valve respectively, and the ammonia evaporator is connected to the ammonia station; the outlet of the mixer is connected to the upper ammonia injection grid inlet valve and the lower ammonia injection grid inlet valve of the denitration reactor respectively;

[0017] The bypass of the flue gas outlet of the denitrification reactor is also connected to a clean flue gas inlet valve, which is connected to a clean flue gas heater via a clean flue gas delivery fan. The clean flue gas heater is respectively connected to an upper catalyst regeneration valve and a lower catalyst regeneration valve. The upper catalyst regeneration valve and the lower catalyst regeneration valve are respectively connected to a pipeline of the upper ammonia injection grid inlet valve and a pipeline of the lower ammonia injection grid inlet valve;

[0018] The upper end of the upper catalyst bypass flue is provided with an upper catalyst bypass flue inlet baffle, and the upper and lower ends of the lower catalyst bypass flue are respectively provided with a lower catalyst bypass flue inlet baffle and a lower catalyst main flue outlet baffle.

[0019] Furthermore, the air inlet valve is connected to the mixer via a dilution fan.

[0020] Furthermore, an upper catalyst soot blower, an upper catalyst inlet pressure measuring point, an upper catalyst outlet pressure measuring point, and an upper catalyst inlet temperature measuring point are also provided in the upper part of the denitration reactor.

[0021] Furthermore, a lower catalyst soot blower, a lower catalyst inlet pressure measuring point, and a lower catalyst outlet pressure measuring point are also provided in the lower part of the denitration reactor.

[0022] Furthermore, the denitration reactor is also provided with a lower catalyst inlet temperature measuring point.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] When the pressure difference between the inlet and outlet of the catalyst layer increases to 1.2-1.3 times of the original value, the catalyst layer is regenerated. After regeneration, the ammonium bisulfate and other impurities such as particulate matter condensed in the micropores of the catalyst are removed, the pressure difference between the inlet and outlet of the catalyst layer is reduced, the activity of the catalyst layer is restored, the service life of the catalyst layer is increased, and the denitration efficiency of the denitration reactor is guaranteed.

[0025] The service life of medium and low temperature SCR catalysts is generally designed to be 3 years. After using the present invention, the service life can be extended to more than 5 years, thereby reducing the cost of catalyst use.

[0026] After the regeneration system restores the catalyst activity, the denitrification efficiency of the catalyst is improved, the consumption of ammonia or urea is reduced, and the cost of using materials is reduced. In addition, improving the denitrification efficiency of the catalyst can reduce the ammonia content in the flue gas, reducing the amount of ammonia escape is beneficial to protecting the ecological environment;

[0027] After the catalyst layer is regenerated, the flue resistance is reduced. The smaller resistance can reduce the power consumption of the booster fan, which is beneficial to reducing electricity costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the accompanying drawings.

[0029] Figure 1 This is a process flow chart of a system for online regeneration of a medium- and low-temperature SCR denitration catalyst according to the present invention;

[0030] Explanation of the reference numerals: 1. ammonia station; 2. ammonia evaporator; 3. mixer; 4. inlet valve of the upper ammonia injection grid; 5. inlet valve of the lower ammonia injection grid; 6. upper ammonia injection grid; 7. upper catalyst; 8. lower ammonia injection grid; 9. lower catalyst; 10. denitration reactor; 11. inlet flue of the denitration reactor; 12. inlet baffle of the main flue of the upper catalyst; 13. outlet baffle of the main flue of the upper catalyst; 14. inlet baffle of the main flue of the lower catalyst; 15. outlet baffle of the main flue of the lower catalyst; 16. outlet flue of the denitration reactor; 17. inlet baffle of the bypass flue of the upper catalyst; 18. bypass flue of the upper catalyst; 1 9. Lower layer catalyst bypass flue inlet baffle; 20. Lower layer catalyst bypass flue; 21. Clean flue gas conveying fan; 22. Clean flue gas heater; 23. Upper layer catalyst regeneration valve; 24. Lower layer catalyst regeneration valve; 25. Clean flue gas inlet valve; 26. Air inlet valve; 27. Dilution fan; 28. Upper layer catalyst soot blower; 29. ​​Upper layer catalyst inlet pressure measuring point; 30. Upper layer catalyst outlet pressure measuring point; 31. Lower layer catalyst soot blower; 32. Lower layer catalyst inlet pressure measuring point; 33. Lower layer catalyst outlet pressure measuring point; 34. Upper layer catalyst inlet temperature measuring point; 35. Lower layer catalyst inlet temperature measuring point. DETAILED DESCRIPTION

[0031] like Figure 1 As shown, a system suitable for online regeneration of a medium- and low-temperature SCR denitration catalyst comprises a denitration reactor 10 and a mixer 3;

[0032] The denitration reactor 10 includes an upper part and a lower part that are connected. The top of the upper part is provided with a denitration reactor inlet flue 11, and an upper catalyst bypass flue 18 is provided in the upper part. The other side is provided with an upper catalyst main flue inlet baffle 12, an upper ammonia injection grid 6, an upper catalyst 7 and an upper catalyst main flue outlet baffle in sequence from top to bottom. The lower part is provided with a lower catalyst bypass flue 20, and the other side is provided with a lower catalyst main flue inlet baffle 14, a lower ammonia injection grid 8 and a lower catalyst 9 in sequence from top to bottom. The lower end of the lower part is also connected to the denitration reactor outlet flue 16.

[0033] The inlet of the mixer 3 is connected to the ammonia evaporator 2 and the air inlet valve 26 respectively, and the ammonia evaporator 2 is connected to the ammonia station 1; the outlet of the mixer 3 is connected to the upper ammonia injection grid inlet valve 4 and the lower ammonia injection grid inlet valve 5 of the denitration reactor 10 respectively;

[0034] The bypass of the denitration reactor outlet flue 16 is also connected to a clean flue gas inlet valve 25, which is connected to a clean flue gas heater 22 via a clean flue gas delivery fan 21. The clean flue gas heater 22 is respectively connected to an upper catalyst regeneration valve 23 and a lower catalyst regeneration valve 24. The upper catalyst regeneration valve 23 and the lower catalyst regeneration valve 24 are respectively connected to a pipeline of the upper ammonia injection grid inlet valve 4 and a pipeline of the lower ammonia injection grid inlet valve 5;

[0035] The upper end of the upper catalyst bypass flue 18 is provided with an upper catalyst bypass flue inlet baffle 17, and the upper and lower ends of the lower catalyst bypass flue 20 are respectively provided with a lower catalyst bypass flue inlet baffle 19 and a lower catalyst main flue outlet baffle 15.

[0036] The air inlet valve 26 is connected to the mixer 3 via a dilution fan 27 .

[0037] An upper catalyst soot blower 28 , an upper catalyst inlet pressure measuring point 29 , an upper catalyst outlet pressure measuring point 30 , and an upper catalyst inlet temperature measuring point 34 are also provided in the upper portion of the denitration reactor 10 .

[0038] The lower portion of the denitration reactor 10 is further provided with a lower catalyst soot blower 31 , a lower catalyst inlet pressure measuring point 32 , a lower catalyst outlet pressure measuring point 33 , and a lower catalyst inlet temperature measuring point 35 .

[0039] The above-mentioned baffles are all movable baffles that can be closed and opened, and can be controlled by manual pulling or electric pulling.

[0040] The action process of the present invention is as follows: The working principle and use process of the present invention are as follows:

[0041] 1. When the flue gas treatment system operates normally;

[0042] The ammonia water in the ammonia station 1 evaporates into ammonia gas in the ammonia water evaporator 2. The ammonia gas is diluted in the mixer 3 and then fed into the upper ammonia spray grid 6 and the lower ammonia spray grid 8 through the upper ammonia spray grid inlet valve 4 and the lower ammonia spray grid inlet valve 5 respectively.

[0043] When the denitration reactor 10 is operating normally, the raw flue gas passes through the denitration reactor inlet flue 11, the upper catalyst main flue inlet baffle 12, the upper ammonia injection grid 6, the upper catalyst 7, the upper catalyst main flue outlet baffle 13, the lower catalyst main flue inlet baffle 14, the lower ammonia injection grid 8, the lower catalyst 9, the lower catalyst main flue outlet baffle 15, and the denitration reactor outlet flue 6 in sequence, and is processed into clean flue gas;

[0044] The nitrogen oxides in the raw flue gas are reduced to nitrogen and water under the action of the catalyst and ammonia, thereby processing the raw flue gas into clean flue gas to achieve the purpose of flue gas denitrification.

[0045] 2. When the upper catalyst layer is regenerated;

[0046] In the denitration reactor 10, the upper catalyst main flue inlet baffle 12 and the upper catalyst main flue outlet baffle 13 are closed, and the upper catalyst bypass flue inlet baffle 17 is opened. The raw flue gas passes through the denitration reactor inlet flue 11, the upper catalyst layer catalyst bypass flue inlet baffle 17, the upper catalyst bypass flue 18, the lower catalyst main flue inlet baffle 14, the lower ammonia injection grid 8, the lower catalyst 9, the lower catalyst main flue outlet baffle 15, and the denitration reactor outlet flue 6 in sequence.

[0047] The upper catalyst main flue inlet baffle 12 and the upper catalyst main flue outlet baffle 13 are in a closed state, the upper catalyst 7 is out of operation and meets the regeneration conditions;

[0048] The clean flue gas inlet valve 25 is opened, and the clean flue gas delivery fan 21 delivers the clean flue gas processed by the denitrification reactor 10 to the clean flue gas heater 22, where the flue gas is heated to approximately 350°C to 400°C. The upper ammonia injection grid inlet valve 4 is closed, the lower catalyst regeneration valve 5 is opened, the upper catalyst regeneration valve 23 is opened, the lower catalyst regeneration valve 24 is closed, and the heated clean flue gas is delivered to the upper ammonia injection grid 6. The high-temperature clean flue gas passes through the upper ammonia injection grid 6 to evenly heat the upper catalyst 7, removing ammonium bisulfate condensed in the catalyst's micropores.

[0049] The upper catalyst soot blower 28 blows soot when the upper catalyst 7 is regenerated to remove impurities such as particulate matter condensed in the pores of the catalyst.

[0050] 3. When the lower catalyst layer is regenerated;

[0051] In the denitration reactor 10, the lower catalyst main flue inlet baffle 14 and the lower catalyst main flue outlet baffle 15 are closed, and the lower catalyst bypass flue inlet baffle 19 is opened. The raw flue gas passes through the denitration reactor inlet flue 11, the upper catalyst main flue inlet baffle 12, the upper ammonia injection grid 6, the upper catalyst 7, the upper catalyst main flue outlet baffle 13, the lower catalyst bypass flue inlet baffle 19, the lower catalyst bypass flue 20, and the denitration reactor outlet flue 16 in sequence.

[0052] The lower catalyst main flue inlet baffle 14 and the lower catalyst main flue outlet baffle 15 are in a closed state, the lower catalyst 9 is out of operation and has the conditions for regeneration;

[0053] The clean flue gas inlet valve 25 is opened, and the clean flue gas delivery fan 21 delivers the clean flue gas processed by the denitrification reactor 10 to the clean flue gas heater 22, where the flue gas is heated to approximately 350°C to 400°C. The upper ammonia injection grid inlet valve 4 is opened, the lower catalyst regeneration valve 5 is closed, the upper catalyst regeneration valve 23 is closed, and the lower catalyst regeneration valve 24 is opened, delivering the heated clean flue gas to the lower ammonia injection grid 8. The high-temperature clean flue gas passes through the lower ammonia injection grid 8, uniformly heating the lower catalyst 9 and removing ammonium bisulfate condensed in the catalyst's micropores.

[0054] The lower catalyst soot blower 31 blows soot when the lower catalyst 9 is regenerated to remove impurities such as particulate matter condensed in the pores of the catalyst.

[0055] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A system suitable for online regeneration of medium and low temperature SCR denitration catalyst, characterized in that: It includes a denitrification reactor (10) and a mixer (3); The denitration reactor (10) comprises an upper portion and a lower portion that are connected to each other, wherein a denitration reactor inlet flue (11) is provided at the top of the upper portion, an upper catalyst bypass flue (18) is provided in the upper portion, and an upper catalyst main flue inlet baffle (12), an upper ammonia injection grid (6), an upper catalyst (7) and an upper catalyst main flue outlet baffle are provided on the other side in order from top to bottom, a lower catalyst bypass flue (20) is provided in the lower portion, and a lower catalyst main flue inlet baffle (14), a lower ammonia injection grid (8) and a lower catalyst (9) are provided on the other side in order from top to bottom, and the lower end of the lower portion is also connected to the denitration reactor outlet flue (16); The inlet of the mixer (3) is connected to the ammonia evaporator (2) and the air inlet valve (26), respectively. The ammonia evaporator (2) is connected to the ammonia station (1). The outlet of the mixer (3) is connected to the upper ammonia injection grid inlet valve (4) and the lower ammonia injection grid inlet valve (5) of the denitration reactor (10). The bypass of the flue gas outlet (16) of the denitrification reactor is also connected to a clean flue gas inlet valve (25), and the clean flue gas inlet valve (25) is connected to a clean flue gas heater (22) via a clean flue gas delivery fan (21). The clean flue gas heater (22) is respectively connected to an upper catalyst regeneration valve (23) and a lower catalyst regeneration valve (24). The upper catalyst regeneration valve (23) and the lower catalyst regeneration valve (24) are respectively connected to a pipeline of the upper ammonia injection grid inlet valve (4) and a pipeline of the lower ammonia injection grid inlet valve (5); The upper end of the upper catalyst bypass flue (18) is provided with an upper catalyst bypass flue inlet baffle (17), and the upper end and lower end of the lower catalyst bypass flue (20) are respectively provided with a lower catalyst bypass flue inlet baffle (19) and a lower catalyst main flue outlet baffle (15); The air inlet valve (26) is connected to the mixer (3) via a dilution fan (27); the denitration reactor (10) is also provided with a lower catalyst inlet temperature measuring point (35).

2. The system for online regeneration of medium and low temperature SCR denitration catalyst according to claim 1, characterized in that: An upper catalyst soot blower (28), an upper catalyst inlet pressure measuring point (29), an upper catalyst outlet pressure measuring point (30), and an upper catalyst inlet temperature measuring point (34) are also provided in the upper portion of the denitration reactor (10).

3. The system for online regeneration of medium and low temperature SCR denitration catalyst according to claim 1, characterized in that: A lower catalyst soot blower (31), a lower catalyst inlet pressure measuring point (32), and a lower catalyst outlet pressure measuring point (33) are also provided in the lower portion of the denitration reactor (10).

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