A regeneration method for improving synergistic mercury oxidation performance of a vanadium-poisoned catalyst

Abstract

The present application belongs to the field of environmental protection, and particularly relates to a regeneration method for improving the synergistic mercury oxidation performance of a vanadium-poisoned catalyst. The present application provides a method for removing the vanadium-poisoned catalyst in two steps in the regeneration process. Vanadium crystallization is extracted by oxalic acid, and the catalyst is activated by a process in combination with sulfuric acid. On this basis, the loading of molybdenum and cerium is realized by a one-step method, which increases the mercury oxidation performance. Moreover, the oxalic acid extract can be reused, and the vanadium element is recycled in the whole process through the action of sulfuric acid, which has the characteristics of green chemistry.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection, and in particular relates to a regeneration method for synergistically improving the mercury oxidation performance of vanadium-poisoned catalysts. Background Technology

[0002] SCR catalyst regeneration is an economical and effective technical solution in catalyst lifetime management. The loading of active components is crucial for restoring the catalyst's denitrification performance and controlling SO2 / SO3 conversion. The SCR denitrification reaction mainly occurs within the first 0.1 mm of the catalyst surface, while SO2 oxidation is a slow reaction that occurs across the entire catalyst wall thickness. Restoring the vanadium content of the cleaned sample is an extremely important process technology.

[0003] In deep regeneration processes, the main cost component is the loading of active components, with the cost of the loading raw materials being tens of times that of the cleaning raw materials. Therefore, researching staged and controllable loading processes can help reduce unnecessary losses and lower the cost of deep regeneration. Introducing active components into the catalyst can effectively enhance its denitrification performance, but it also leads to an increase in the oxidation rate of side reactions. Therefore, quantitative control of staged loading can achieve optimal performance.

[0004] Commercially available vanadium-based regenerated catalysts typically use vanadium oxysulfate, ammonium metavanadate, or vanadium oxalate, while ammonium metatungstate or ammonium metamolybdate are primarily used as loading solutions for co-active components. Current regeneration processes generally involve acidic cleaning, which does not cause the loss of co-active components such as tungsten or molybdenum; only the vanadium content on the SCR catalyst needs to be replenished. The loading of vanadium as an active component is crucial for restoring the catalyst's denitrification performance and controlling the SO2 / SO3 conversion rate.

[0005] Catalyst regeneration and cleaning processes inevitably result in the loss of active components. Therefore, key processes in catalyst regeneration include the recovery of active components. Increasing the amount of active components can significantly improve catalyst performance, but it also leads to an increase in the oxidation rate of byproducts. Therefore, the loading process needs to carefully control the amount of active components added to achieve a balance between high activity and low oxidation rate. Summary of the Invention

[0006] To address the problems existing in current technologies, this invention provides a regeneration method for synergistically improving the mercury oxidation performance of vanadium-poisoned catalysts. The method involves targeted regeneration and cleaning of the vanadium-poisoned catalyst to remove excessive agglomerated vanadium crystals. By adjusting the regeneration process, the mercury oxidation performance is simultaneously improved.

[0007] A regeneration method for synergistically enhancing the mercury oxidation performance of a vanadium-poisoned catalyst includes the following steps: (1) The catalyst poisoned by vanadium is subjected to the front-end steps of the conventional regeneration process; the catalyst obtained after removing common silicon, aluminum, alkali metals and other poisonings is then regenerated in a targeted manner after vanadium poisoning. (2) The catalyst after the regeneration process in step (1) is added to an oxalic acid solution and then extracted by ultrasound to obtain a preliminarily cleaned vanadium-poisoned catalyst and a leachate. (3) After the vanadium-poisoned catalyst was initially cleaned, it was placed in clean water and soaked for 15 minutes. The solution that was drained was collected in the leachate from step (2). (4) Slowly add sulfuric acid solution to the leachate obtained in step (3) and stir gently to control the temperature to obtain vanadium oxysulfate solution, thereby realizing the recycling of vanadium element; (5) Place the preliminarily cleaned vanadium-poisoned catalyst in a sulfuric acid solution and sonicate it; this step is a surface site activation process for the catalyst, which can help the active components to be better loaded. (6) After the activation process is completed, remove the catalyst to drain the water and shake it slightly; (7) The catalyst loading solution is a vanadium salt solution, preferably the vanadium oxysulfate solution obtained in step (4); it needs to be prepared to 1 wt% for loading and allowed to stand for soaking; (8) Remove and drain the vanadium-loaded catalyst from step (7); (9) The drained catalyst is immersed in a solution containing molybdenum salt and cerium salt for loading and allowed to stand for soaking; (10) Remove the catalyst from the loading process in step (9) and drain it. The drained solution is then returned to the soaking loading tank. (11) Dry the drained catalyst. The catalyst is placed in the drying equipment with the channels vertically up and down. Heat to 80°C, then heat to 100°C for 60 min; heat to 120°C for 300 min; and cool to room temperature naturally to obtain a regenerated catalyst with mercury oxidation performance.

[0008] Preferably, the front-end steps of the conventional regeneration process described in step (1) specifically include water rinsing, chemical soaking, and ultrasonic vibration assistance.

[0009] Preferably, the concentration of oxalic acid solution in step (2) is 2-5 wt%.

[0010] Preferably, the liquid-solid ratio of oxalic acid solution to catalyst in step (2) is 3:1-5:1.

[0011] Preferably, the ultrasonic temperature in step (2) is 55°C and the ultrasonic time is 20 min.

[0012] Preferably, the ultrasonic frequency in step (2) is 40 Hz.

[0013] Preferably, the concentration of sulfuric acid solution in steps (4) and (5) is 0.02-0.08 wt%.

[0014] Preferably, in step (5), the ultrasonic temperature is 25°C, the ultrasonic frequency is 40Hz, and the ultrasonic time is 5min.

[0015] Preferably, the soaking time in step (7) is 25-35 min.

[0016] Preferably, in step (9), the concentration of molybdenum salt is 1-5 wt%, the concentration of cerium salt is 0.5-2 wt%, and the standing soaking time is 25-35 min.

[0017] The beneficial effects of this invention are as follows: This invention pioneered a two-step cleaning method for removing vanadium-poisoned catalysts in the regeneration process. Vanadium crystals are extracted using oxalic acid, and the catalyst is activated using a sulfuric acid-based process. Furthermore, a one-step loading method for molybdenum and cerium enhances mercury oxidation performance. The oxalic acid extract can be reused, and the vanadium is recovered throughout the entire process using sulfuric acid, demonstrating green chemistry characteristics. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Example 1 A regeneration method for synergistically enhancing the mercury oxidation performance of a vanadium-poisoned catalyst includes the following steps: (1) The catalyst poisoned by vanadium is subjected to conventional regeneration process, including rinsing with clean water, soaking in reagents, and ultrasonic vibration assistance; the catalyst is obtained after removing common poisonings such as silicon, aluminum, and alkali metals, and then the vanadium poisoned catalyst is regenerated in a targeted manner. (2) The catalyst after the regeneration process in step (1) is added to a 2% oxalic acid solution and then extracted by ultrasound to obtain a preliminarily cleaned vanadium-poisoned catalyst and a leachate; the liquid-solid ratio of oxalic acid solution to catalyst is 4:1. (3) After the vanadium-poisoned catalyst was initially cleaned, it was placed in clean water and soaked for 15 minutes. The solution that was drained was collected in the leachate from step (2). (4) Slowly add 1 wt% sulfuric acid solution to the leachate obtained in step (3) and stir gently to control the temperature to obtain vanadium oxysulfate solution, thereby realizing the recycling of vanadium. (5) The vanadium-poisoned catalyst that has been initially cleaned was placed in a 0.04 wt% sulfuric acid solution and sonicated; the sonication temperature was 25 ℃, the sonication frequency was 40 Hz, and the sonication time was 5 min. (6) After the activation process is completed, remove the catalyst to drain the water and shake it slightly; (7) The catalyst loading solution is the vanadium oxysulfate solution obtained in step (4); it is prepared to a concentration of 1 wt% for loading and allowed to stand for 30 min. (8) Remove and drain the vanadium-loaded catalyst from step (7); (9) The drained catalyst is immersed in a solution containing molybdenum nitrate and cerium nitrate for loading and allowed to stand for soaking; the concentration of molybdenum nitrate is 2 wt% and the concentration of cerium nitrate is 1 wt%. (10) Remove the catalyst from the loading process in step (9) and drain it. The drained solution is then returned to the soaking loading tank. (11) Dry the drained catalyst. The catalyst is placed in the drying equipment with the channels vertically up and down. Heat to 80°C, then heat to 100°C for 60 min; heat to 120°C for 300 min; and cool to room temperature naturally to obtain a regenerated catalyst with mercury oxidation performance.

[0020] Experimental Example 1 Pilot-scale evaluation of the field performance of mercury oxidation modified catalyst Full-size (150mm×150mm×1000mm) regenerated samples were prepared, and pilot-scale denitrification activity and conversion rate tests were conducted on the full-size samples.

[0021] (1) The “acid-base cleaning + surface loading” regeneration process was applied to the full-size catalyst regeneration pilot project.

[0022] (2) In the pilot-scale regeneration of full-size catalyst, it was found that drying before loading can improve the content gradient of active components in the catalyst. When the loading time is 5s, the CeO2 content on the catalyst surface / matrix is ​​1.60% / 0.57%. When Mo is used as the active formulation, although the conversion rate is well controlled, the denitrification activity is poor. Therefore, the combination of Ce+V should be used as the oxidation formulation for better results. When the surface CeO2 loading is 1.60%, the SO2 / SO3 conversion rate of the dual-root sample is 0.74%, and the single-root activity is 41.2m / h, which meets the requirements.

[0023] (3) Complete the modification of the pilot-scale testing system at Tongchuan Power Plant, load the optimal catalyst sample into the reactor of the testing system, and measure the Hg of the two samples. 0 The oxidation efficiency was 83.9%, and the test results are shown in Table 2.

[0024] Table 1 Hg 0Oxidation rate test results

[0025] The table shows two tests, each measuring the concentration of mercury in the flue gas at the inlet (before catalyst) and outlet (after catalyst) (unit: μg / m³). 3 HgT: Total mercury (sum of all forms); Hg 2+ Mercury oxide (soluble in water and easily removed); Hg 0 Zero-valent mercury (poorly soluble in water and difficult to remove directly); HgP: particulate mercury (attached to particulate matter).

[0026] The table shows that: 1. Mercury oxidation rate: Test 1 showed 86.5%; Test 2 showed an oxidation rate of 81.2%; indicating that the catalyst effectively oxidized most of the mercury in both tests. 0 Oxidized to Hg 2+ (Oxidized mercury is easily captured by subsequent desulfurization equipment).

[0027] 2. Trends in the speciation of mercury: Hg 0 Significant decline: Exports of Hg 0 The significant decrease in Hg confirms that an oxidation reaction has occurred. 2+ Significant increase: Exports of Hg 2+ The concentration was much higher than at the inlet, further proving that Hg 0 Converted to Hg 2+ Hg T A slight decrease: This could be due to some mercury being adsorbed by the catalyst or particulate matter, or measurement error. (Hg) P Slight fluctuations: This may be related to particulate matter adsorption / desorption, but the changes are relatively small.

[0028] 3. Consistency Verification: The oxidation rate in both tests was above 80%, indicating that the catalyst performance is relatively stable. (Inlet Hg) 0 Different concentrations (18.35 vs 20.38 μg / m³) 3 However, the oxidation rates are close, indicating that the catalyst still maintains good performance under different loads.

Claims

1. A regeneration method for synergistically enhancing the mercury oxidation performance of a vanadium-poisoned catalyst, characterized in that, The regeneration method includes the following steps: (1) Perform the front-end steps of conventional regeneration process on the catalyst after vanadium poisoning; (2) The catalyst after the regeneration process in step (1) is added to an oxalic acid solution and then extracted by ultrasound to obtain a preliminarily cleaned vanadium-poisoned catalyst and a leachate. (3) After the vanadium-poisoned catalyst was initially cleaned, it was placed in clean water and soaked for 15 minutes. The solution that was drained was collected in the leachate from step (2). (4) Slowly add sulfuric acid solution to the leachate obtained in step (3) and stir gently to control the temperature to obtain vanadium oxysulfate solution; (5) Place the initially cleaned vanadium-poisoned catalyst in a sulfuric acid solution and sonicate; (6) After the activation process is completed, remove the catalyst to drain the water and shake it slightly; (7) The catalyst loading solution is a vanadium salt solution; after preparation, it is loaded and allowed to stand for soaking; (8) Remove and drain the vanadium-loaded catalyst from step (7); (9) The drained catalyst is immersed in a solution containing molybdenum salt and cerium salt for loading and allowed to stand for soaking; (10) Remove the catalyst from the loading process in step (9) and drain it. The drained solution is then returned to the soaking loading tank. (11) Dry the drained catalyst. The catalyst is placed in the drying equipment with the channels vertically up and down. Heat to 80°C, then heat to 100°C for 60 min; heat to 120°C for 300 min; and cool to room temperature naturally to obtain a regenerated catalyst with mercury oxidation performance.

2. The regeneration method according to claim 1, characterized in that, The front-end steps of the conventional regeneration process in step (1) specifically include water rinsing, chemical soaking, and ultrasonic vibration assistance.

3. The regeneration method according to claim 1, characterized in that, In step (2), the concentration of oxalic acid solution is 2-5 wt%; the liquid-solid ratio of oxalic acid solution to catalyst is 3:1-5:

1.

4. The regeneration method according to claim 1, characterized in that, In step (2), the ultrasonic temperature is 55℃ and the ultrasonic time is 20min.

5. The regeneration method according to claim 1, characterized in that, The ultrasonic frequency in step (2) is 40 Hz.

6. The regeneration method according to claim 1, characterized in that, The concentration of sulfuric acid solution in steps (4) and (5) is 0.02-0.08 wt%.

7. The regeneration method according to claim 1, characterized in that, In step (5), the ultrasonic temperature is 25℃, the ultrasonic frequency is 40HZ, and the ultrasonic time is 5min.

8. The regeneration method according to claim 1, characterized in that, The catalyst loading solution in step (7) is the vanadium oxysulfate solution obtained in step (4) with a concentration of 1 wt%; the standing soaking time is 25-35 min.

9. The regeneration method according to claim 1, characterized in that, In step (9), the concentration of molybdenum salt is 1-5 wt%, and the concentration of cerium salt is 0.5-2 wt%; the standing soaking time is 25-35 min.

10. The regenerated catalyst with mercury oxidation properties obtained by the regeneration method according to any one of claims 1-9.

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