In-situ regeneration method for low-temperature sulfur-poisoned denitrification catalyst

Abstract

The present invention relates to an in-situ regeneration method for a low-temperature sulfur-poisoned denitration catalyst, and belongs to the technical field of catalyst regeneration. The method comprises: firstly, after lowering the inlet temperature of the denitration tower, spraying an ash regulator solution to change the properties of the ash, and blowing away the accumulated ash on the catalyst surface and in the pores; then, restoring the temperature of the denitration tower to the normal operating temperature, and then spraying dry ice or liquid nitrogen on the surface of the catalyst to be treated to deeply remove the pollutants in the catalyst; finally, evenly spraying the active slurry on the surface of the catalyst to achieve in-situ regeneration of the catalyst. The process of the present invention is convenient, does not require the removal of the catalyst, has a short construction period, and the regeneration process does not damage the physical properties of the catalyst. Moreover, the regenerated catalyst has good resistance to sulfur poisoning, which extends the service life of the catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection and catalyst regeneration, and particularly relates to an in-situ regeneration method for a low-temperature sulfur-poisoned denitration catalyst. Background Art

[0002] Nitrogen oxides (NOx) are currently one of the most significant atmospheric pollutants. In recent years, an increasing number of industries have established NOx emission standards. Selective catalytic reduction (SCR) denitrification technology is currently the most widely used industrial flue gas denitrification technology worldwide. However, conventional SCR denitrification catalysts are primarily used in coal-fired power plant flue gas environments at 300-420°C. When flue gas temperatures fall below 300°C, the catalyst activity decreases significantly due to sulfur poisoning or inappropriate temperature conditions. With the increasing adoption of NOx emission standards across various industries, flue gas denitrification is becoming increasingly common. For example, in waste incineration, cement, steel, and biomass boilers, flue gas denitrification temperatures typically range from 150-250°C. However, the primary challenge facing catalysts operating at low temperatures is sulfur poisoning and deactivation. When catalyst activity falls below the required level, annual catalyst replacement not only increases the operating costs of the denitrification system but also places a significant burden on the environment. Therefore, the regeneration of spent catalysts is crucial.

[0003] Chinese patent CN113058588A discloses a process for regenerating a deactivated SCR flue gas denitration catalyst: the deactivated denitration catalyst is subjected to ash removal, cleaning with a cleaning solution, drying, impregnation with an active solution, and drying and calcining to obtain a regenerated catalyst. This method requires the catalyst to be removed from the denitration tower and transferred to a regeneration and cleaning line for offline regeneration. The construction period is long, and the cleaning process will cause the mechanical properties of the catalyst to deteriorate. Chinese patent CN113663515A discloses a device and method for online regeneration of SCR catalysts in coal-fired power plants. First, high-pressure air is used to remove the accumulated dust on the catalyst surface and in the pores. Then, the catalyst is cleaned with dry ice / liquid nitrogen to remove pollutants on the catalyst surface, thereby achieving rapid and efficient cleaning of pollutants on the surface of the deactivated catalyst. This patent only provides a method for removing surface pollutants. The activity of the cleaned catalyst is still low and its life is short. Therefore, it is urgent to develop a convenient method that can deeply clean ammonium sulfate salts and the regenerated catalyst has sulfur poisoning resistance. Summary of the Invention

[0004] The present invention addresses the problems of existing catalyst regeneration methods, such as high energy consumption, low ammonium sulfate removal efficiency, low regenerated catalyst activity, and a lack of sulfur poisoning resistance. The present invention provides a method for in-situ regeneration of a low-temperature, sulfur-poisoned denitrification catalyst. This method enables online, in-situ regeneration of the sulfur-poisoned catalyst. The regeneration process is gentle and does not affect the mechanical properties of the catalyst. Furthermore, the regenerated catalyst exhibits high activity, improved sulfur poisoning resistance, and extended catalyst service life.

[0005] The present invention adopts the following technical solution: A method for in-situ regeneration of a low-temperature sulfur-poisoned denitrification catalyst, comprising the following steps:

[0006] (1) Control the denitrification tower inlet temperature at 110~130℃;

[0007] (2) The ash regulator solution is evenly sprayed into the flue gas through the ammonia spray system so that the ash regulator solution is evenly sprayed on the surface of the catalyst to be treated. The spraying time is 5-10 minutes;

[0008] (3) Clean the dust accumulated in the pores on the surface of the catalyst to be treated by high pressure blowing;

[0009] (4) Raise the temperature of the denitrification tower to 150-220°C, spray dry ice or liquid nitrogen on the surface of the catalyst to be treated for 5-10 minutes to crush the pollutants on the surface of the catalyst to be treated; then perform high-pressure cleaning on the catalyst to be treated to remove the pollutants on the catalyst surface;

[0010] (5) Use an atomizing spray device to evenly spray the active slurry on the surface of the catalyst to be treated. The spraying amount of the active slurry is 10~80kg / m 3 The spraying rate of the active slurry is 0.5~1.5kg / min.

[0011] Furthermore, the operating temperature of the catalyst to be treated is 150°C to 220°C.

[0012] Furthermore, in step (1), the flue gas temperature is controlled at 110°C to 130°C by adding cold air or stopping heating.

[0013] Furthermore, the ash regulator in step (2) consists of polyacrylamide and ammonium carbonate.

[0014] Furthermore, in the ash regulator solution in step (2), the mass concentration of polyacrylamide is 0.1-0.4%, and the mass concentration of ammonium carbonate is 10-45%.

[0015] Furthermore, in step (3) and step (4), an air pressurizing device is used for high-pressure blowing, and the air flow rate at the outlet of the air pressurizing device is 400m~500m / s.

[0016] Furthermore, the spraying speed of dry ice or liquid nitrogen in step (4) is 150-180 m / s.

[0017] Furthermore, the components of the active slurry in step (5) include, by mass percentage, 10-12% vanadium pentoxide, 40-60% molybdenum trioxide, 10-30% antimony trioxide, 5-15% kaolin, 5-10% glass fiber, 1-3% carboxymethyl cellulose, and 1-3% polyethylene oxide.

[0018] Furthermore, the preparation method of the active slurry in step (5) is as follows: vanadium pentoxide, molybdenum trioxide, antimony trioxide powder and water are placed in a nano sand mill and ground for 4 to 6 hours; kaolin and glass fiber are then added to the nano sand mill and ground for 2 to 3 hours; finally, carboxymethyl cellulose and polyethylene oxide are ground for another 4 to 8 hours to obtain an active slurry.

[0019] Furthermore, in step (5), the active slurry has a water content of 65-80%, a viscosity of 10-15 mPa.s, and a particle size of 10-20 nm.

[0020] The advantages of the present invention are as follows: (1) After the ash regulator solution is sprayed onto the surface of the sulfur-poisoned catalyst, ammonium carbonate reacts with ammonium bisulfate in the ash to produce ammonium sulfate, carbon dioxide, etc. By spraying ammonium carbonate, the ammonium bisulfate, which is sticky at low temperatures and causes catalyst clogging and poisoning, is converted into ammonium sulfate, which is non-sticky and powdery at low temperatures, thereby converting the sticky agglomerated ash into powdery ash, which is easier to remove. In addition, the reaction between ammonium carbonate and ammonium bisulfate releases carbon dioxide, making the ash more fluffy; and the addition of polyacrylamide can also change the properties of the ash, making the ash easier to separate from the catalyst, further improving the efficiency of ash removal.

[0021] (2) After the dust on the surface of the catalyst is removed, high-speed dry ice or liquid nitrogen is sprayed, and the dry ice particles or liquid nitrogen gas collides with the catalyst at high speed, forming a temperature difference between the ammonium sulfate salt and the catalyst on the catalyst surface and shrinking, which can produce cracks between the ammonium sulfate salt and the catalyst; at the same time, the dry ice or liquid nitrogen can penetrate into the pores of the catalyst, and the dry ice or liquid nitrogen sublimates or evaporates in the pores and cracks, and the volume expands significantly, thereby separating toxic substances such as ammonium sulfate salt from the catalyst, and then effectively removing toxic substances such as ammonium sulfate salt.

[0022] (3) Compared with conventional low-temperature sulfur-poisoned catalyst regeneration technology, the regenerated catalyst activity is still lower than that of the fresh catalyst and has a shorter service life. The present invention significantly improves the catalyst activity by continuing to spray the active component slurry after effectively removing toxic substances such as ammonium sulfate, and can restore or even exceed the activity of the fresh catalyst. In addition, antimony trioxide is added to the active slurry to improve the catalyst's resistance to sulfur poisoning, further extending the catalyst's service life.

[0023] (4) Kaolin, glass fiber and other materials are added to the active slurry to enhance the adhesion strength of the coating on the catalyst surface and ensure the life of the catalyst.

[0024] (5) The maximum temperature of the entire regeneration process is the normal design operating temperature of the catalyst, and the energy consumption is much lower than the existing regeneration process; and the entire process is simple and easy to perform in-situ regeneration on site, which greatly saves the disassembly time in conventional methods, shortens the construction period, and reduces the overall operation and maintenance costs. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are further described below in conjunction with specific embodiments. Example 1:

[0026] (1) Preparation of active slurry:

[0027] 12 kg of vanadium pentoxide, 45 kg of molybdenum trioxide, 27 kg of antimony trioxide powder and 233 kg of water were placed in a nano sand mill and ground for 4 to 6 hours; 8 kg of kaolin and 6 kg of glass fiber were then added to the nano sand mill and ground for 2 to 3 hours; finally, 1 kg of carboxymethyl cellulose and 1 kg of polyethylene oxide were ground for another 4 to 8 hours to obtain a slurry, wherein the active slurry had a water content of 70%, a viscosity of 12 mPa.s and a particle size of 10 nm to 20 nm;

[0028] (2) Catalyst in situ regeneration

[0029] A steel sintering machine uses activated carbon desulfurization combined with low-temperature SCR denitrification. The flue gas temperature after desulfurization is below 130°C, and the denitrification inlet flue gas temperature is 180-200°C. The catalyst is a 30-cell honeycomb catalyst. After eight months of operation, the system experienced severe clogging. First, the denitrification tower inlet temperature was controlled below 130°C. An ash conditioning solution containing 0.1wt% polyacrylamide and 15wt% ammonium carbonate was evenly sprayed into the flue gas, ensuring a uniform spray distribution over the catalyst surface for 5 minutes. An air pressurizer was then used to purge any accumulated ash from the catalyst pores. The denitrification tower temperature was raised to 180-200°C, and dry ice was evenly sprayed over the catalyst surface for 10 minutes to pulverize contaminants. The air pressurizer was then used to perform a high-pressure purge of the catalyst to remove contaminants. Finally, an atomizing sprayer positioned above the catalyst evenly sprayed the activated slurry over the catalyst surface at a rate of 0.5 kg / min.

[0030] The performance of the catalyst before and after regeneration is shown in Table 1.

[0031] Table 1 Changes in operating parameters before and after catalyst regeneration

[0032]

[0033] It can be seen from Table 1 that after the catalyst is regenerated, the catalyst activity and sulfur content can basically be restored to the level of fresh catalyst.

[0034] Example 2:

[0035] (1) Preparation of active slurry

[0036] 10 kg of vanadium pentoxide, 55 kg of molybdenum trioxide, 18 kg of antimony trioxide powder and 257 kg of water were placed in a nano sand mill and ground for 4 to 6 hours; 5 kg of kaolin and 7 kg of glass fiber were then added to the nano sand mill and ground for 2 to 3 hours; finally, 3 kg of carboxymethyl cellulose and 2 kg of polyethylene oxide were ground for another 4 to 8 hours to obtain a slurry, wherein the active slurry had a water content of 72%, a viscosity of 14 mPa.s and a particle size of 10 nm to 20 nm;

[0037] (2) Catalyst in situ regeneration

[0038] A waste incineration power plant uses activated carbon desulfurization combined with low-temperature SCR denitrification. The flue gas temperature after desulfurization is below 120°C, and the flue gas temperature at the denitrification inlet is 160-180°C. The catalyst is a corrugated plate catalyst, and after six months of operation, the system experienced severe clogging. First, the denitrification tower inlet temperature was controlled below 120°C. An ash conditioning solution containing 0.2wt% polyacrylamide and 22wt% ammonium carbonate was evenly sprayed into the flue gas, ensuring a uniform spray distribution over the catalyst surface for approximately 5 minutes. An air pressurizer was then used to purge any accumulated ash from the catalyst pores. The denitrification tower temperature was raised to 160-180°C, and liquid nitrogen was evenly sprayed over the catalyst surface for 10 minutes to pulverize contaminants. The air pressurizer was then used to perform a high-pressure purge of the catalyst to remove contaminants. Finally, an atomizer positioned above the catalyst sprayed the activated slurry evenly over the catalyst surface at a rate of 1 kg / min.

[0039] The performance of the catalyst before and after regeneration is shown in Table 2.

[0040] Table 2 Changes in operating parameters before and after catalyst regeneration

[0041]

[0042] It can be seen from Table 2 that after the catalyst is regenerated, the catalyst activity and sulfur content can basically be restored to the level of fresh catalyst.

[0043] Example 3:

[0044] (1) Preparation of active slurry

[0045] 12 kg of vanadium pentoxide, 42 kg of molybdenum trioxide, 25 kg of antimony trioxide powder and 212 kg of water are placed in a nano sand mill and ground for 4 to 6 hours; then 12 kg of kaolin and 6 kg of glass fiber are added to the nano sand mill and ground for 2 to 3 hours; finally, 2 kg of carboxymethyl cellulose and 1 kg of polyethylene oxide are ground for another 4 to 8 hours to obtain a slurry, wherein the active slurry has a water content of 68%, a viscosity of 14 mPa.s, and a particle size of 10 nm to 20 nm.

[0046] (2) Catalyst in situ regeneration

[0047] A waste incineration power plant uses activated carbon desulfurization combined with low-temperature SCR denitrification. The flue gas temperature after desulfurization is below 130°C, and the flue gas temperature at the denitrification inlet is 170-190°C. The catalyst is a flat-plate catalyst, and after 14 months of operation, it has become severely clogged. First, the denitrification tower inlet temperature is controlled below 130°C. Then, an ash conditioning solution containing 0.1wt% polyacrylamide and 40wt% ammonium carbonate is evenly sprayed into the flue gas, ensuring a uniform spray distribution over the catalyst surface for approximately 5 minutes. An air pressurizer is then used to purge any accumulated ash from the catalyst pores. The denitrification tower temperature is raised to 170-190°C, and dry ice is evenly sprayed over the catalyst surface for 10 minutes to pulverize contaminants. The air pressurizer then performs high-pressure cleaning on the catalyst to remove contaminants. Finally, an atomizing sprayer positioned above the catalyst evenly sprays the activated slurry over the catalyst surface at a rate of 1.5 kg / min.

[0048] The performance of the catalyst before and after regeneration is shown in Table 3.

[0049] Table 3 Changes in operating parameters before and after catalyst regeneration

[0050]

[0051] As shown in Table 3, after the catalyst is regenerated, the catalyst activity and sulfur content can basically be restored to the level of fresh catalyst.

Claims

1. A method for in-situ regeneration of a low-temperature sulfur-poisoned denitrification catalyst, characterized in that: include: (1) Control the denitrification tower inlet temperature at 110~130℃; (2) The ash regulator solution is evenly sprayed into the flue gas through the ammonia spray system so that the ash regulator solution is evenly sprayed on the surface of the catalyst to be treated. The spraying time is 5-10 minutes. The ash regulator is composed of polyacrylamide and ammonium carbonate; (3) Clean the dust accumulated in the pores on the surface of the catalyst to be treated by high pressure blowing; (4) Raise the temperature of the denitrification tower to 150-220°C, spray dry ice or liquid nitrogen evenly on the surface of the catalyst to be treated for 5-10 min to crush the pollutants on the surface of the catalyst to be treated; then perform high-pressure purge on the catalyst to be treated again to remove the pollutants on the catalyst surface; (5) Use an atomizing spray device to evenly spray the active slurry on the surface of the catalyst to be treated. The spraying amount of the active slurry is 10~80kg / m 3 The spraying rate of the active slurry is 0.5~1.5kg / min, and the components of the active slurry include, by mass percentage, 10~12% vanadium pentoxide, 40~60% molybdenum trioxide, 10~30% antimony trioxide, 5~15% kaolin, 5~10% glass fiber, 1~3% carboxymethyl cellulose, and 1~3% polyethylene oxide.

2. The in-situ regeneration method for a low-temperature sulfur-poisoned denitration catalyst according to claim 1, characterized in that: The operating temperature of the catalyst to be treated is 150°C to 220°C.

3. The in-situ regeneration method for a low-temperature sulfur-poisoned denitration catalyst according to claim 1, characterized in that: In the step (1), the denitrification tower inlet temperature is controlled at 110° C. to 130° C. by adding cold air or stopping heating.

4. The in-situ regeneration method for a low-temperature sulfur-poisoned denitration catalyst according to claim 1, characterized in that: In the ash regulator solution in step (2), the mass concentration of polyacrylamide is 0.1-0.4%, and the mass concentration of ammonium carbonate is 10-45%.

5. The in-situ regeneration method for a low-temperature sulfur-poisoned denitration catalyst according to claim 1, characterized in that: In the steps (3) and (4), an air pressurizing device is used for high-pressure blowing, and the air flow rate at the outlet of the air pressurizing device is 400-500 m / s.

6. The in-situ regeneration method for a low-temperature sulfur-poisoned denitration catalyst according to claim 1, characterized in that: The spraying speed of dry ice or liquid nitrogen in step (4) is 150-180 m / s.

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