Arsenic removal and cleaning method for arsenic poisoning denitrification catalyst

Abstract

The invention discloses a method for cleaning arsenic removal from an arsenic-poisoned denitration catalyst, comprising: pretreatment: preliminary physical dust removal of the collected deactivated denitration catalyst; configuration of a cleaning solution: dissolving an oxidant, a strong base and a calcium salt in 40-60°C water in a certain proportion to obtain a mixed solution; cleaning reaction: placing the deactivated denitration catalyst obtained by physical dust removal into the above-mentioned mixed solution, washing it with water for 20min-60min in a room temperature environment, and then acid-washing it for 20min-60min in an environment with a water temperature of 30-60°C; after completing the cleaning process, rinsing it with pure water for 20min-60min in a room temperature environment to neutrality and drying to obtain an arsenic removal denitration catalyst. Through the above-mentioned method, the arsenic removal cleaning method for the arsenic-poisoned denitration catalyst of the present invention has a simple cleaning process and a wide source of raw materials, and the arsenic content of the catalyst after cleaning can meet the requirements of the national standard.

Description

Technical Field

[0001] The invention relates to the technical field of regeneration of deactivated denitration catalysts, and in particular to a method for removing arsenic from arsenic-poisoned denitration catalysts. Background Art

[0002] With the economic growth of my country, atmospheric environmental problems have become increasingly prominent. The country has successively issued the "Three-Year Action Plan to Win the Blue Sky Defense War" and the "Integrated Control Plan for Atmospheric Pollution from Industrial Furnaces", which clearly require the implementation of total atmospheric pollutant control and the reduction of pollutant emissions, and promote the continuous improvement of environmental air quality and high-quality development of the industry. Atmospheric pollution mainly comes from fixed source emissions in thermal power, steel, cement and other industries. At present, denitrification catalysts (SCR) are mainly used to treat NOx emitted from fixed sources. Waste flue gas denitrification catalysts are included in the management of hazardous wastes. If the replaced waste catalysts are randomly stored or improperly disposed of, it will cause environmental pollution and waste of resources. The regeneration and harmless treatment of waste catalysts is the best way to solve these problems, with significant social and economic benefits.

[0003] However, the differences in production processes in different industries and the complexity of fuels have multiple negative impacts on the normal operation of deNOx catalysts, including physical and chemical factors. Physical factors are mainly wear and dust clogging. Compared with physical factors, chemical factors are more complex, such as alkali (earth) metal poisoning (Na, K, Mg, Ca, etc.), heavy metal poisoning (Pb, Cr, Hg, etc.), SO3 poisoning, arsenic poisoning, etc.

[0004] The arsenic content in my country's coal is not high overall, but the main component of arsenic-containing coal after high-temperature combustion and oxidation is gaseous As2O3. As the flue gas temperature drops, it gradually enriches on the surface of the denitrification catalyst and continues to be oxidized into dense As2O5, which blocks the micropores of the denitrification catalyst or occupies the acidic sites of the catalyst, hindering the adsorption of NOX / NH3, thereby reducing the denitrification efficiency of the catalyst. As the service life of the denitrification catalyst increases, the enrichment of arsenic is inevitable, and the regeneration of arsenic-poisoned catalysts has become an urgent problem to be solved in the actual production and application of waste denitrification catalyst regeneration. Summary of the invention

[0005] In order to solve the above technical problems, a technical solution adopted by the present invention is: a method for removing arsenic from an arsenic-poisoned denitrification catalyst, the steps of which include: (1) Pretreatment: preliminary physical cleaning of the collected deactivated denitrification catalyst; (2) Prepare cleaning solution: dissolve the oxidant, strong alkali and calcium salt in 40-60°C water in a certain proportion to obtain a mixed solution; (3) Cleaning reaction: the deactivated denitration catalyst obtained by physical cleaning is placed in the above-mentioned mixed solution, washed with water at room temperature for 20 minutes to 60 minutes, and then acid-washed in a water temperature environment of 30-60°C for 20 minutes to 60 minutes; (4) After completing the cleaning process of step (3), rinse with pure water at room temperature for 20 minutes to 60 minutes until it becomes neutral and dry to obtain the arsenic removal and denitrification catalyst.

[0006] In an embodiment of the present invention, the drying temperature in step (4) is 120° C. and the drying time is 80 min-140 min.

[0007] In an embodiment of the present invention, in step (1), the deactivated denitration catalyst is initially physically cleaned by blowing with compressed air.

[0008] In an embodiment of the present invention, the deactivated denitration catalyst is a honeycomb type, a plate type, a corrugated plate type, and a VW / Mo-Ti based denitration catalyst.

[0009] In an embodiment of the present invention, the ratio of the oxidant, the strong base, the calcium salt and the water is (1-4): (1-2): (0.1-1): 93.

[0010] In an embodiment of the present invention, the oxidant is one or more of hydrogen peroxide, peracetic acid, sodium hypochlorite, potassium chlorate, etc.

[0011] In an embodiment of the present invention, the strong base is one or more of sodium hydroxide, potassium hydroxide, quaternary ammonium hydroxide, etc.

[0012] In an embodiment of the present invention, the calcium salt is one or more of calcium chloride, calcium gluconate, calcium nitrate, calcium dihydrogen phosphate, etc.

[0013] In an embodiment of the present invention, the deactivated denitration catalyst is washed with water for 40 minutes at room temperature, acid washed for 40 minutes at a water temperature of 50° C., and rinsed with pure water for 50 minutes at room temperature.

[0014] In another embodiment of the present invention: a catalyst for arsenic removal and denitrification is provided, which is prepared by the above-mentioned preparation method.

[0015] The beneficial effects of the present invention are as follows: the present invention adopts an oxidation-dissolution-precipitation method to clean the denitration catalyst to achieve the purpose of arsenic removal, the method has a good cleaning and arsenic removal effect, and can control the arsenic content in the catalyst to be below 0.05%; the raw materials of the cleaning agent are low in price, and the arsenic dissolved from the catalyst is fixed by calcium ions and directly precipitated into the sludge, which is convenient for the recovery and treatment of arsenic-containing secondary hazardous wastes; the oxidants hydrogen peroxide and peracetic acid selected by the present invention will not introduce other elements that cause catalyst poisoning, and even if sodium hypochlorite and potassium chlorate are selected, they can be easily removed in the subsequent pickling process, which is safe and reliable. 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 describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which: Figure 1 is the XRD spectra of the deactivated denitration catalyst before and after cleaning in Example 1 of the present invention; Figure 2 It is a comparison of elemental composition of the deactivated denitration catalyst before and after arsenic removal in the present invention. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] See also Figure 1-2 The embodiment of the present invention includes: a method for removing arsenic from an arsenic-poisoned denitration catalyst, the steps of which include: (1) Pretreatment: preliminary physical cleaning of the collected deactivated denitrification catalyst; (2) Prepare cleaning solution: dissolve the oxidant, strong alkali and calcium salt in 40-60°C water in a certain proportion to obtain a mixed solution; (3) Cleaning reaction: the deactivated denitration catalyst obtained by physical cleaning is placed in the above-mentioned mixed solution, washed with water at room temperature for 20 minutes to 60 minutes, and then acid-washed in a water temperature environment of 30-60°C for 20 minutes to 60 minutes; (4) After completing the cleaning process of step (3), rinse with pure water at room temperature for 20 minutes to 60 minutes until it becomes neutral and dry to obtain the arsenic removal and denitrification catalyst.

[0019] Further preferably, in step (1), the deactivated denitration catalyst is preliminarily physically cleaned by blowing with compressed air.

[0020] Further preferably, the deactivated denitration catalyst is of honeycomb type, plate type and corrugated plate type, and is a VW / Mo-Ti based denitration catalyst.

[0021] Further preferably, the ratio of the oxidant, the strong base, the calcium salt and the water is (1-4):(1-2):(0.1-1):93.

[0022] Further preferably, the oxidant is one or more of hydrogen peroxide, peracetic acid, sodium hypochlorite, potassium chlorate, etc.

[0023] More preferably, the strong base is one or more of sodium hydroxide, potassium hydroxide, quaternary ammonium hydroxide and the like.

[0024] More preferably, the calcium salt is one or more of calcium chloride, calcium gluconate, calcium nitrate, calcium dihydrogen phosphate, etc.

[0025] In another embodiment of the present invention: a catalyst for arsenic removal and denitrification is provided, which is prepared by the above-mentioned preparation method. Example

[0026] The method for removing arsenic from an arsenic-poisoned denitrification catalyst comprises the following steps: (1) Pretreatment: The collected 5*5*5cm deactivated denitrification catalyst is preliminarily physically cleaned, and then blown or washed with compressed air to remove floating dust on the surface; (2) Prepare a cleaning solution for cleaning reaction: Mix 1g of calcium chloride (CaCl2) and 10g of hydrogen peroxide (H2O2) with 10g of sodium hydroxide, dissolve in 1L of deionized water, heat to 40°C, put the washed deactivated denitration catalyst module into the cleaning solution, bubble for 1h, take it out and rinse it again with pure water until it is close to neutral, put the module into 1% acidic cleaning solution, and bubble for 1h; (3) After the above cleaning process is completed, the product is taken out and rinsed again with pure water at room temperature for 40 minutes until it becomes neutral, and then dried at 120°C to obtain the arsenic removal and denitrification catalyst. The product is ground and sieved, and the powder with a particle size of less than 120 mesh is pressed into a tablet for XRD and XRF testing. Figure 1 This is the XRD spectrum of Example 1. The crystal structure of the catalyst does not change before and after cleaning. Figure 2 The test results of catalyst components in this group of experiments are listed in the figure. Example

[0027] The method for removing arsenic from an arsenic-poisoned denitrification catalyst comprises the following steps: (1) Pretreatment: The collected 5*5*5cm deactivated denitrification catalyst is preliminarily physically cleaned, and then blown or washed with compressed air to remove floating dust on the surface; (2) Prepare a cleaning solution for cleaning reaction: Mix 1.5g of calcium chloride (CaCl2) and 10g of hydrogen peroxide (H2O2) with 15g of sodium hydroxide, dissolve in 1L of deionized water, heat to 60°C, put the washed deactivated denitration catalyst module into the cleaning solution, bubble for 1h, take it out and rinse it again with pure water until it is close to neutral, put the module into 1% acidic cleaning solution, and bubble for 1h; (3) After the above cleaning process is completed, the catalyst is taken out and rinsed again with pure water at room temperature for 50 minutes until it becomes neutral, and then dried at 120°C to obtain the arsenic removal and denitrification catalyst. The catalyst is ground and sieved, and the powder with a particle size of less than 120 mesh is pressed into a tablet for XRD and XRF testing. The crystal structure of the catalyst does not change before and after cleaning. Figure 2 The test results of catalyst components in this group of experiments are listed in the figure. Example

[0028] The method for removing arsenic from an arsenic-poisoned denitrification catalyst comprises the following steps: (1) Pretreatment: The collected 5*5*5cm deactivated denitrification catalyst is preliminarily physically cleaned, and then blown or washed with compressed air to remove floating dust on the surface; (2) Prepare a cleaning solution for cleaning reaction: Mix 1.7g of calcium chloride (CaCl2) and 20g of hydrogen peroxide (H2O2) with 7g of sodium hydroxide, dissolve in 1L of deionized water, heat to 60°C, put the washed deactivated denitration catalyst module into the cleaning solution, bubble for 1h, take it out and rinse it again with pure water until it is close to neutral, put the module into 1% acidic cleaning solution, and bubble for 1h; (3) After the above cleaning process is completed, the catalyst is taken out and rinsed again with pure water at room temperature for 50 minutes until it becomes neutral, and then dried at 120°C to obtain the arsenic removal and denitrification catalyst. The catalyst is ground and sieved, and the powder with a particle size of less than 120 mesh is pressed into a tablet for XRD and XRF testing. The crystal structure of the catalyst does not change before and after cleaning. Figure 2 The test results of catalyst components in this group of experiments are listed in the figure.

[0029] The beneficial effects of the arsenic removal and cleaning method of the arsenic poisoning denitration catalyst of the present invention are: 1. This method has good cleaning and arsenic removal effects and can control the arsenic content in the catalyst to below 0.05%. The raw materials of the cleaning agent are cheap, and the arsenic dissolved from the catalyst is fixed by calcium ions and directly precipitated into the sludge, which is convenient for the recovery and treatment of arsenic-containing secondary hazardous wastes. 2. The oxidizing agents hydrogen peroxide and peracetic acid selected in the present invention will not introduce other elements that cause catalyst poisoning. Even if sodium hypochlorite and potassium chlorate are selected, they can be easily removed in the subsequent pickling process, which is safe and reliable.

[0030] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for removing arsenic from an arsenic-poisoned denitration catalyst, characterized in that: The following steps are involved: (1) Pretreatment: preliminary physical cleaning of the collected deactivated denitrification catalyst; (2) Prepare cleaning solution: dissolve the oxidant, strong alkali and calcium salt in 40-60°C water in a certain proportion to obtain a mixed solution; (3) Cleaning reaction: the deactivated denitration catalyst obtained by physical cleaning is placed in the above-mentioned mixed solution, washed with water at room temperature for 20 min to 60 min, and then acid washed for 20 min to 60 min in a water temperature environment of 30-60 °C; (4) After completing the cleaning process of step (3), rinse with pure water at room temperature for 20 minutes to 60 minutes until it becomes neutral and dry to obtain the arsenic removal and denitrification catalyst.

2. The arsenic removal and cleaning method for arsenic-poisoned denitration catalyst according to claim 1, characterized in that: The drying temperature in step (4) is 120°C and the drying time is 80 min-140 min.

3. The arsenic removal and cleaning method for arsenic-poisoned denitration catalyst according to claim 1, characterized in that: In step (1), the deactivated denitration catalyst is initially physically cleaned by blowing with compressed air.

4. The arsenic removal and cleaning method for arsenic-poisoned denitration catalyst according to claim 1, characterized in that: The deactivated denitration catalyst is a honeycomb type, a plate type, a corrugated plate type or a VW / Mo-Ti series denitration catalyst.

5. The arsenic removal and cleaning method for arsenic-poisoned denitration catalyst according to claim 1, characterized in that: The ratio of the oxidant, strong base, calcium salt and water is (1-4): (1-2): (0.1-1):

93.

6. The arsenic removal and cleaning method for arsenic-poisoned denitration catalyst according to claim 1, characterized in that: The oxidant is one or more of hydrogen peroxide, peracetic acid, sodium hypochlorite, potassium chlorate and the like.

7. The arsenic removal and cleaning method for arsenic-poisoned denitration catalyst according to claim 1, characterized in that: The strong base is one or more of sodium hydroxide, potassium hydroxide, quaternary ammonium hydroxide and the like.

8. The arsenic removal and cleaning method for arsenic-poisoned denitration catalyst according to claim 1, characterized in that: The calcium salt is one or more of calcium chloride, calcium gluconate, calcium nitrate, calcium dihydrogen phosphate and the like.

9. The method for removing arsenic from an arsenic-poisoned denitration catalyst according to claim 1, characterized in that: The deactivated denitration catalyst has a water washing time of 40 minutes at room temperature, an acid washing time of 40 minutes at a water temperature of 50° C., and a pure water rinsing time of 50 minutes at room temperature.

10. A catalyst for arsenic removal and denitrification, characterized in that: Prepared by the preparation method described in any one of claims 1 to 9.

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