A method for comprehensive resource utilization of municipal sludge incineration ash graded treatment

Abstract

The present invention discloses a method for the graded treatment and comprehensive resource utilization of municipal sludge incineration ash. The method includes drying the municipal sludge, crushing it into lumps with a diameter of 4 to 6 mm, and then incinerating it in an incinerator. The residue, fly ash, and flue gas are discharged and processed separately. The residue is screened, and residue with a particle size ≥1 mm is recycled as building materials. Residue with a particle size <1 mm and >0.1 mm is vitrified and microcrystallized to produce microcrystalline glass. Residue with a particle size ≤0.1 mm is uniformly mixed with fly ash and slag with a particle size ≤0.1 mm to obtain a mixed powder. The powder is then plasma treated, subjected to a first reduction using ethanol, and then to a second reduction using a mixture of ammonia and nitrogen to obtain an alloy material. The flue gas enters a combustion chamber containing a catalyst for further combustion, discharging the residue and purified flue gas. The residue is returned to the screening step, and the purified flue gas is cooled and directly discharged. The present invention achieves the comprehensive resource utilization of municipal sludge incineration ash by graded treatment, particularly obtaining an alloy material that can be further separated and purified for metal recovery.

Description

Technical Field

[0001] The present invention relates to a sludge resource treatment method, in particular to a method for comprehensive resource utilization of municipal sludge incineration ash graded treatment. Background Art

[0002] With economic development and improved living standards, urban sewage discharge is increasing in staggering quantities, and sewage treatment generates significant amounts of municipal sludge. Municipal sludge is high in organic matter, has a strong odor, and is prone to spoilage and stinking. Currently, landfill and incineration are the primary methods used to treat municipal sludge. However, landfilling wastes land resources and further pollutes the surrounding environment. In comparison, incineration achieves a greater degree of harmlessness.

[0003] However, municipal sewage sludge incineration produces a large amount of ash. Besides silicon oxide, silicates, and sulfates, this ash also contains organic pollutants such as dioxins, as well as heavy metals such as zinc, lead, copper, and chromium, making it a highly hazardous waste. Therefore, it is crucial to improve the existing municipal sewage sludge incineration process.

[0004] Patent CN103256608B discloses a sludge incineration method. A sludge distributor evenly distributes sludge into the incinerator, facilitating efficient combustion. This method also prevents uneven combustion air supply caused by uneven material layers and uneven combustion resistance within the incinerator. The incinerator uses bottom ash discharge, and the rate of discharge controls the residence time of sludge blocks within the incinerator, ensuring that the sludge blocks remain within the incinerator for more than one hour and that the organic matter content of the ash output is less than 0.2%. Primary air from an air preheater is blown from the bottom of the incinerator, creating a positive pressure at the bottom and a slightly negative pressure at the top. This sludge incineration method uses high-temperature, multiple-pass incineration to completely burn the sludge, killing bacteria and pathogens within it. The incineration ash produced during the incineration process can be used to make bricks, cement, and other building materials. The waste heat generated by the incineration is also fully utilized, and the overall incineration method is cost-effective. However, the patent does not address the recovery of metals from the fly ash.

[0005] Patent CN1195879C discloses a method for recovering copper from metal sludge. The method uses precipitated sludge containing high concentrations of metals as the treatment target. High-temperature treatment is used to convert metal hydroxides into metal oxides. Coke then reacts with the metal oxides to deoxidize the metal oxides, yielding the metals. Finally, metal refining is performed. This patent treats metal sludge obtained from treating metal-ion-containing wastewater, such as those produced by circuit board production. This method differs from municipal sludge in composition, and applying this method to municipal sludge treatment still presents challenges such as high dioxin and metal content in fly ash. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide a method for the comprehensive utilization of municipal sludge incineration ash by graded treatment.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for the comprehensive resource utilization of graded treatment of municipal sewage sludge incineration ash, comprising the following specific steps:

[0009] (1) First, the municipal sludge is dried and crushed into mud blocks with a diameter of 4 to 6 mm, and then placed in an incinerator for incineration, and the residue, fly ash and flue gas are discharged and then placed in steps (2), (3) and (4) respectively;

[0010] (2) The residue is screened, and the residue with a particle size of ≥1 mm is recycled as a building material; the residue with a particle size of <1 mm and >0.1 mm is vitrified and microcrystallized to produce microcrystalline glass; the residue with a particle size of ≤0.1 mm enters step (3);

[0011] (3) fly ash and slag with a particle size of ≤0.1 mm are uniformly mixed to obtain a mixed powder, which is then subjected to plasma treatment, first reduced using ethanol, and then second reduced using a mixed gas of ammonia and nitrogen to obtain an alloy material;

[0012] (4) The flue gas enters a combustion chamber containing a catalyst for re-combustion, and the residue and purified flue gas are discharged. The residue returns to step (2), and the purified flue gas is directly discharged after cooling.

[0013] Preferably, in step (1), the drying is performed until the moisture content by mass is below 35%.

[0014] Preferably, in step (1), the incineration temperature is 850-950° C., and the incineration time is 60-90 minutes.

[0015] Preferably, in step (2), the vitrification process conditions are: vitrification at 1300-1400° C. for 40-50 minutes.

[0016] Preferably, in step (2), the process conditions for microcrystallization are: first cooling to 900-1000°C at 10-15°C / min, keeping warm for 35-45 minutes, then cooling to 500-600°C at 5-8°C / min, keeping warm for 40-50 minutes, and naturally cooling to room temperature.

[0017] Preferably, in step (3), the process conditions of the plasma treatment are: air as the working gas, the air input pressure is 0.1-0.2 MPa, the power is 300-400 W, and the treatment time is 8-10 s.

[0018] Preferably, in step (3), the first reduction is carried out in a fixed bed reactor, and the process conditions are as follows: temperature 200-300°C, pressure 2-4 MPa, nitrogen as carrier gas carrying ethanol into the fixed bed reactor, and the liquid space velocity of ethanol is 2-3 mL / (h·g cat ), the volume ratio of nitrogen to ethanol is 300-400:1.

[0019] Preferably, in step (3), a plasma reaction is used for the second reduction, the volume ratio of ammonia to nitrogen is 10-15:85-90, the input pressure of the mixed gas is 0.4-0.5 MPa, the power is 400-500 W, and the processing time is 40-50 s.

[0020] Preferably, in step (4), the catalyst is prepared by the following method in parts by weight:

[0021] (A) First, 2-3 parts of ammonium metavanadate, 2-3 parts of ammonium molybdate, and 0.8-1 part of indium nitrate are stirred and dissolved in 50-60 parts of a 6-8% monoethanolamine aqueous solution, and then 20-30 parts of titanium dioxide are added and stirred to obtain a premixed solution;

[0022] (B) Then, 4 to 5 parts of concentrated ammonia water with a mass concentration of 25 to 28% are slowly added to the premixed solution, stirred at room temperature for 6 to 7 hours, dried, calcined, and granulated to form granules.

[0023] Further preferably, in step (B), the concentrated ammonia solution is added for 30 minutes.

[0024] More preferably, in step (B), the drying process conditions are: drying at 80-90° C. for 10-12 hours.

[0025] More preferably, in step (B), the calcination process conditions are: calcination at 600-650° C. for 6-7 hours.

[0026] More preferably, in step (B), the particle size is 40 to 50 meshes.

[0027] Preferably, in step (4), the process conditions for re-combustion are: combustion at 150-200° C. for 20-30 minutes.

[0028] Beneficial effects of the present invention:

[0029] The present invention first dries municipal sludge, crushes it into lumps with a diameter of 4 to 6 mm, and then incinerates it in an incinerator, discharging residue, fly ash, and flue gas for separate treatment. The residue is screened, and residue with a particle size ≥1 mm is recycled as building materials; residue with a particle size <1 mm and >0.1 mm is vitrified and microcrystallized to produce microcrystalline glass; residue with a particle size ≤0.1 mm is uniformly mixed with fly ash and slag with a particle size ≤0.1 mm to obtain a mixed powder, which is then plasma-treated, subjected to a first reduction using ethanol, and then to a second reduction using a mixture of ammonia and nitrogen to obtain an alloy material; the flue gas enters a combustion chamber containing a catalyst for further combustion, discharging residue and purified flue gas, returning the residue to the screening step, and the purified flue gas is cooled and directly discharged. The present invention achieves comprehensive resource utilization through graded treatment of municipal sludge incineration ash, particularly obtaining alloy materials that can be further separated and purified for metal recovery.

[0030] The residue, fly ash and flue gas discharged from the incineration of municipal sewage sludge are treated separately. After the residue is screened, the large particles can be used directly as building materials, the medium particles can be vitrified and microcrystallized to make microcrystalline glass, and the small particles can be combined with fly ash for metal recovery.

[0031] Since the flue gas contains pollutants such as dioxins, the present invention introduces a catalyst for re-combustion. The active ingredients of the catalyst are oxides of vanadium, molybdenum and indium, which can catalyze the decomposition of pollutants such as dioxins. Therefore, the flue gas can be directly discharged after cooling to avoid air pollution. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the embodiments. It should be noted that the following description is only for explaining the present invention and does not limit the content thereof.

[0033] Example 1:

[0034] A method for the comprehensive resource utilization of graded treatment of municipal sewage sludge incineration ash, comprising the following specific steps:

[0035] (1) First, the municipal sludge is dried to a moisture content of less than 35% by mass, crushed into mud blocks with a diameter of 4 mm, and placed in an incinerator for incineration at a temperature of 850°C for 60 minutes. The residue, fly ash and flue gas are discharged and then enter steps (2), (3) and (4) respectively;

[0036] (2) The residue is screened, and the residue with a particle size of ≥1 mm is recycled as a building material; the residue with a particle size of <1 mm and >0.1 mm is vitrified and microcrystallized to produce microcrystalline glass; the residue with a particle size of ≤0.1 mm enters step (3);

[0037] The process conditions for vitrification were as follows: vitrification at 1300 °C for 40 min;

[0038] Preferably, in step (2), the process conditions for microcrystallization are: first cooling to 900°C at 10°C / min, keeping warm for 35 minutes, then cooling to 500°C at 5°C / min, keeping warm for 40 minutes, and naturally cooling to room temperature;

[0039] (3) fly ash and slag with a particle size of ≤0.1 mm are uniformly mixed to obtain a mixed powder, which is then subjected to plasma treatment, first reduced using ethanol, and then second reduced using a mixed gas of ammonia and nitrogen to obtain an alloy material;

[0040] The process conditions of plasma treatment were: air as the working gas, air input pressure of 0.1 MPa, power of 300 W, and treatment time of 8 s;

[0041] The first reduction was carried out in a fixed-bed reactor under the following process conditions: temperature 200°C, pressure 2 MPa, nitrogen as carrier gas carrying ethanol into the fixed-bed reactor, and the liquid space velocity of ethanol was 2 mL / (h·g cat ), the volume ratio of nitrogen to ethanol is 300:1;

[0042] The second reduction was carried out by plasma reaction, with a volume ratio of ammonia to nitrogen of 10:90, an input pressure of the mixed gas of 0.4 MPa, a power of 400 W, and a processing time of 40 s.

[0043] (4) The flue gas enters a combustion chamber containing a catalyst and is burned again (burned at 150°C for 20 minutes), and the residue and purified flue gas are discharged. The residue returns to step (2), and the purified flue gas is directly discharged after cooling;

[0044] The catalyst is prepared by the following method:

[0045] (A) First, 2 kg of ammonium metavanadate, 2 kg of ammonium molybdate, and 0.8 kg of indium nitrate were stirred and dissolved in 50 kg of a 6% monoethanolamine aqueous solution, and then 20 kg of titanium dioxide was added and stirred to obtain a premixed solution;

[0046] (B) Then, 4 kg of 25% concentrated ammonia water was slowly added to the premixed solution, stirred at room temperature for 6 hours, dried, calcined, and granulated into particles with a particle size of 40 mesh;

[0047] In step (B), the concentrated ammonia solution is added for 30 minutes;

[0048] The drying process conditions were: drying at 80 °C for 10 hours;

[0049] The calcination process conditions are: calcination at 600°C for 6 hours.

[0050] Example 2:

[0051] A method for the comprehensive resource utilization of graded treatment of municipal sewage sludge incineration ash, comprising the following specific steps:

[0052] (1) First, the municipal sludge is dried to a moisture content of less than 35% by mass, crushed into mud blocks with a diameter of 6 mm, and placed in an incinerator for incineration at a temperature of 950°C for 90 minutes. The residue, fly ash, and flue gas are discharged and then enter steps (2), (3), and (4) respectively;

[0053] (2) The residue is screened, and the residue with a particle size of ≥1 mm is recycled as a building material; the residue with a particle size of <1 mm and >0.1 mm is vitrified and microcrystallized to produce microcrystalline glass; the residue with a particle size of ≤0.1 mm enters step (3);

[0054] The process conditions for vitrification were as follows: vitrification at 1400 °C for 50 min;

[0055] Preferably, in step (2), the process conditions for microcrystallization are: first cooling to 1000°C at 15°C / min, keeping warm for 45 minutes, then cooling to 600°C at 8°C / min, keeping warm for 50 minutes, and naturally cooling to room temperature;

[0056] (3) fly ash and slag with a particle size of ≤0.1 mm are uniformly mixed to obtain a mixed powder, which is then subjected to plasma treatment, first reduced using ethanol, and then second reduced using a mixed gas of ammonia and nitrogen to obtain an alloy material;

[0057] The process conditions of plasma treatment were: air as the working gas, air input pressure of 0.2 MPa, power of 400 W, and treatment time of 10 s;

[0058] The first reduction was carried out in a fixed-bed reactor under the following process conditions: temperature 300°C, pressure 4 MPa, nitrogen as carrier gas carrying ethanol into the fixed-bed reactor, and the liquid space velocity of ethanol was 3 mL / (h·g cat ), the volume ratio of nitrogen to ethanol is 400:1;

[0059] The second reduction was carried out by plasma reaction, with a volume ratio of ammonia to nitrogen of 15:85, an input pressure of the mixed gas of 0.5 MPa, a power of 500 W, and a processing time of 50 s.

[0060] (4) The flue gas enters a combustion chamber containing a catalyst for further combustion (burning at 200°C for 30 minutes), and the residue and purified flue gas are discharged. The residue returns to step (2), and the purified flue gas is directly discharged after cooling;

[0061] The catalyst is prepared by the following method:

[0062] (A) First, 3 kg of ammonium metavanadate, 3 kg of ammonium molybdate, and 1 kg of indium nitrate were stirred and dissolved in 60 kg of an 8% monoethanolamine aqueous solution, and then 30 kg of titanium dioxide was added and stirred to obtain a premixed solution;

[0063] (B) then slowly adding 5 kg of 28% concentrated ammonia water to the premixed solution, stirring at room temperature for 7 hours, drying, calcining, and granulating to produce particles with a particle size of 50 mesh;

[0064] In step (B), the concentrated ammonia solution is added for 30 minutes;

[0065] The drying process conditions were as follows: drying at 90 °C for 12 hours;

[0066] The calcination process conditions are: calcination at 650°C for 7 hours.

[0067] Example 3:

[0068] A method for the comprehensive resource utilization of graded treatment of municipal sewage sludge incineration ash, comprising the following specific steps:

[0069] (1) First, the municipal sludge is dried to a moisture content of less than 35% by mass, crushed into mud blocks with a diameter of 4 mm, and placed in an incinerator for incineration at a temperature of 950°C for 60 minutes. The residue, fly ash and flue gas are discharged and then enter steps (2), (3) and (4) respectively;

[0070] (2) The residue is screened, and the residue with a particle size of ≥1 mm is recycled as a building material; the residue with a particle size of <1 mm and >0.1 mm is vitrified and microcrystallized to produce microcrystalline glass; the residue with a particle size of ≤0.1 mm enters step (3);

[0071] The process conditions for vitrification were as follows: vitrification at 1400 °C for 40 min;

[0072] Preferably, in step (2), the process conditions for microcrystallization are: first cooling to 900°C at 15°C / min, keeping warm for 45 minutes, then cooling to 600°C at 5°C / min, keeping warm for 40 minutes, and naturally cooling to room temperature;

[0073] (3) fly ash and slag with a particle size of ≤0.1 mm are uniformly mixed to obtain a mixed powder, which is then subjected to plasma treatment, first reduced using ethanol, and then second reduced using a mixed gas of ammonia and nitrogen to obtain an alloy material;

[0074] The process conditions of plasma treatment were as follows: air as the working gas, air input pressure of 0.2 MPa, power of 300 W, and treatment time of 10 s;

[0075] The first reduction was carried out in a fixed bed reactor under the following process conditions: temperature 200°C, pressure 4 MPa, nitrogen as carrier gas carrying ethanol into the fixed bed reactor, and the liquid space velocity of ethanol was 2 mL / (h·g cat ), the volume ratio of nitrogen to ethanol is 400:1;

[0076] The second reduction was carried out by plasma reaction, with a volume ratio of ammonia to nitrogen of 10:90, an input pressure of the mixed gas of 0.4 MPa, a power of 500 W, and a processing time of 40 s.

[0077] (4) The flue gas enters a combustion chamber containing a catalyst for further combustion (burning at 200°C for 20 minutes), and the residue and purified flue gas are discharged. The residue returns to step (2), and the purified flue gas is directly discharged after cooling;

[0078] The catalyst is prepared by the following method:

[0079] (A) First, 3 kg of ammonium metavanadate, 2 kg of ammonium molybdate, and 1 kg of indium nitrate were stirred and dissolved in 50 kg of an 8% monoethanolamine aqueous solution, and then 20 kg of titanium dioxide was added and stirred to obtain a premixed solution;

[0080] (B) then slowly adding 5 kg of 25% concentrated ammonia water to the premixed solution, stirring at room temperature for 7 hours, drying, calcining, and granulating to produce particles with a particle size of 40 mesh;

[0081] In step (B), the concentrated ammonia solution is added for 30 minutes;

[0082] The drying process conditions were as follows: drying at 90 °C for 10 hours;

[0083] The calcination process conditions are: calcination at 650°C for 6 hours.

[0084] Example 4:

[0085] A method for the comprehensive resource utilization of graded treatment of municipal sewage sludge incineration ash, comprising the following specific steps:

[0086] (1) First, the municipal sludge is dried to a moisture content of less than 35% by mass, crushed into mud blocks with a diameter of 5 mm, and placed in an incinerator for incineration at a temperature of 900°C for 80 minutes. The residue, fly ash and flue gas are discharged and then enter steps (2), (3) and (4) respectively;

[0087] (2) The residue is screened, and the residue with a particle size of ≥1 mm is recycled as a building material; the residue with a particle size of <1 mm and >0.1 mm is vitrified and microcrystallized to produce microcrystalline glass; the residue with a particle size of ≤0.1 mm enters step (3);

[0088] The process conditions for vitrification are: vitrification at 1350°C for 45 minutes;

[0089] Preferably, in step (2), the process conditions for microcrystallization are: first cooling to 950°C at 12°C / min, keeping warm for 40 minutes, then cooling to 550°C at 6°C / min, keeping warm for 45 minutes, and naturally cooling to room temperature;

[0090] (3) fly ash and slag with a particle size of ≤0.1 mm are uniformly mixed to obtain a mixed powder, which is then subjected to plasma treatment, first reduced using ethanol, and then second reduced using a mixed gas of ammonia and nitrogen to obtain an alloy material;

[0091] The process conditions of plasma treatment were: air as the working gas, air input pressure of 0.1 MPa, power of 400 W, and treatment time of 9 s;

[0092] The first reduction was carried out in a fixed bed reactor under the following process conditions: temperature 250°C, pressure 3 MPa, nitrogen as carrier gas carrying ethanol into the fixed bed reactor, and the liquid space velocity of ethanol was 2 mL / (h·g cat ), the volume ratio of nitrogen to ethanol is 350:1;

[0093] The second reduction was carried out by plasma reaction, with a volume ratio of ammonia to nitrogen of 12:88, an input pressure of the mixed gas of 0.5 MPa, a power of 500 W, and a processing time of 45 s.

[0094] (4) The flue gas enters a combustion chamber containing a catalyst and is burned again (burned at 180°C for 25 minutes), and the residue and purified flue gas are discharged. The residue returns to step (2), and the purified flue gas is directly discharged after cooling;

[0095] The catalyst is prepared by the following method:

[0096] (A) First, 2.5 kg of ammonium metavanadate, 2.5 kg of ammonium molybdate, and 0.9 kg of indium nitrate were stirred and dissolved in 55 kg of a 7% monoethanolamine aqueous solution, and then 25 kg of titanium dioxide was added and stirred to obtain a premixed solution;

[0097] (B) then slowly adding 4.5 kg of 26% concentrated ammonia water to the premixed solution, stirring at room temperature for 6 hours, drying, calcining, and granulating to form particles with a particle size of 50 mesh;

[0098] In step (B), the concentrated ammonia solution is added for 30 minutes;

[0099] The drying process conditions were as follows: drying at 85 °C for 11 hours;

[0100] The calcination process conditions are: calcination at 620°C for 6 hours.

[0101] Comparative Example 1

[0102] A method for the comprehensive resource utilization of graded treatment of municipal sewage sludge incineration ash, comprising the following specific steps:

[0103] (1) First, the municipal sludge is dried to a moisture content of less than 35% by mass, crushed into mud blocks with a diameter of 4 mm, and placed in an incinerator for incineration at a temperature of 850°C for 60 minutes. The residue, fly ash and flue gas are discharged and then enter steps (2), (3) and (4) respectively;

[0104] (2) The residue is screened, and the residue with a particle size of ≥1 mm is recycled as a building material; the residue with a particle size of <1 mm and >0.1 mm is vitrified and microcrystallized to produce microcrystalline glass; the residue with a particle size of ≤0.1 mm enters step (3);

[0105] The process conditions for vitrification were as follows: vitrification at 1300 °C for 40 min;

[0106] Preferably, in step (2), the process conditions for microcrystallization are: first cooling to 900°C at 10°C / min, keeping warm for 35 minutes, then cooling to 500°C at 5°C / min, keeping warm for 40 minutes, and naturally cooling to room temperature;

[0107] (3) uniformly mixing fly ash and slag with a particle size of ≤0.1 mm to obtain a mixed powder, plasma-treating the mixed powder, and reducing the mixed powder with ethanol to obtain an alloy material;

[0108] The process conditions of plasma treatment were: air as the working gas, air input pressure of 0.1 MPa, power of 300 W, and treatment time of 8 s;

[0109] The reduction was carried out in a fixed bed reactor under the following process conditions: temperature 200°C, pressure 2 MPa, nitrogen as carrier gas carrying ethanol into the fixed bed reactor, and the liquid space velocity of ethanol was 2 mL / (h·g cat ), the volume ratio of nitrogen to ethanol is 300:1;

[0110] (4) The flue gas enters a combustion chamber containing a catalyst and is burned again (burned at 150°C for 20 minutes), and the residue and purified flue gas are discharged. The residue returns to step (2), and the purified flue gas is directly discharged after cooling;

[0111] The catalyst is prepared by the following method:

[0112] (A) First, 2 kg of ammonium metavanadate, 2 kg of ammonium molybdate, and 0.8 kg of indium nitrate were stirred and dissolved in 50 kg of a 6% monoethanolamine aqueous solution, and then 20 kg of titanium dioxide was added and stirred to obtain a premixed solution;

[0113] (B) Then, 4 kg of 25% concentrated ammonia water was slowly added to the premixed solution, stirred at room temperature for 6 hours, dried, calcined, and granulated into particles with a particle size of 40 mesh;

[0114] In step (B), the concentrated ammonia solution is added for 30 minutes;

[0115] The drying process conditions were: drying at 80 °C for 10 hours;

[0116] The calcination process conditions are: calcination at 600°C for 6 hours.

[0117] Comparative Example 2

[0118] A method for the comprehensive resource utilization of graded treatment of municipal sewage sludge incineration ash, comprising the following specific steps:

[0119] (1) First, the municipal sludge is dried to a moisture content of less than 35% by mass, crushed into mud blocks with a diameter of 4 mm, and placed in an incinerator for incineration at a temperature of 850°C for 60 minutes. The residue, fly ash and flue gas are discharged and then enter steps (2), (3) and (4) respectively;

[0120] (2) The residue is screened, and the residue with a particle size of ≥1 mm is recycled as a building material; the residue with a particle size of <1 mm and >0.1 mm is vitrified and microcrystallized to produce microcrystalline glass; the residue with a particle size of ≤0.1 mm enters step (3);

[0121] The process conditions for vitrification were as follows: vitrification at 1300 °C for 40 min;

[0122] Preferably, in step (2), the process conditions for microcrystallization are: first cooling to 900°C at 10°C / min, keeping warm for 35 minutes, then cooling to 500°C at 5°C / min, keeping warm for 40 minutes, and naturally cooling to room temperature;

[0123] (3) fly ash and slag with a particle size of ≤0.1 mm are uniformly mixed to obtain a mixed powder, which is then subjected to plasma treatment, first reduced using ethanol, and then second reduced using a mixed gas of ammonia and nitrogen to obtain an alloy material;

[0124] The process conditions of plasma treatment were: air as the working gas, air input pressure of 0.1 MPa, power of 300 W, and treatment time of 8 s;

[0125] The first reduction was carried out in a fixed-bed reactor under the following process conditions: temperature 200°C, pressure 2 MPa, nitrogen as carrier gas carrying ethanol into the fixed-bed reactor, and the liquid space velocity of ethanol was 2 mL / (h·g cat ), the volume ratio of nitrogen to ethanol is 300:1;

[0126] The second reduction was carried out by plasma reaction, with a volume ratio of ammonia to nitrogen of 10:90, an input pressure of the mixed gas of 0.4 MPa, a power of 400 W, and a processing time of 40 s.

[0127] (4) The flue gas enters a combustion chamber containing a catalyst and is burned again (burned at 150°C for 20 minutes), and the residue and purified flue gas are discharged. The residue returns to step (2), and the purified flue gas is directly discharged after cooling;

[0128] The catalyst is prepared by the following method:

[0129] (A) First, 2 kg of ammonium metavanadate and 2 kg of ammonium molybdate were stirred and dissolved in 50 kg of a 6% monoethanolamine aqueous solution, and then 20 kg of titanium dioxide was added and stirred to obtain a premixed solution;

[0130] (B) Then, 4 kg of 25% concentrated ammonia water was slowly added to the premixed solution, stirred at room temperature for 6 hours, dried, calcined, and granulated into particles with a particle size of 40 mesh;

[0131] In step (B), the concentrated ammonia solution is added for 30 minutes;

[0132] The drying process conditions were: drying at 80 °C for 10 hours;

[0133] The calcination process conditions are: calcination at 600°C for 6 hours.

[0134] Test example

[0135] For ease of comparison, municipal sludge from the same source was treated using the methods of Examples 1 to 4 and Comparative Examples 1 and 2, respectively. The sludge contained metal components such as copper and nickel, which existed in an oxidized state in fly ash and slag. The reduced copper and nickel contents in the alloy materials obtained in Examples 1 to 4 and Comparative Example 1 were tested, and the reduction rates of copper oxide and nickel oxide (by mass) were calculated. The results are shown in Table 1.

[0136] The components of the purified flue gases emitted by Examples 1 to 4 and Comparative Example 2 were tested, and the dioxin content was tested with reference to GB / T18485-2014 "Standard for Pollution Control of Municipal Waste Incineration". The results are shown in Table 2.

[0137] Table 1. Comparison of reduction rates of copper oxide and nickel oxide

[0138] Copper oxide reduction rate (%) Nickel oxide reduction rate (%) Example 1 95.4 95.3 Example 2 95.6 95.6 Example 3 95.9 95.8 Example 4 96.4 96.1 Comparative Example 1 88.3 87.4

[0139] Table 2. Comparison of dioxin content in purified flue gas

[0140]

[0141]

[0142] As can be seen from Tables 1 and 2, the alloy materials obtained in Examples 1 to 4 fully reduce the metal oxides in the small-particle slag and fly ash after sludge incineration, obtaining alloy materials with a high content of reduced metals, thereby achieving metal recovery, and reducing the content of dioxins in the purified flue gas, which can be directly discharged without pollution. Therefore, the graded treatment and comprehensive resource utilization of urban sludge incineration ash are realized.

[0143] In Comparative Example 1, the second reduction was omitted, and the reduction rate of the metal oxide was low, indicating that the reduction was not sufficient and the metal resource utilization was affected. In Comparative Example 2, indium nitrate was omitted when preparing the catalyst, and the dioxin content in the flue gas increased, indicating that the specific catalyst of the present invention has a better removal effect on dioxins in the flue gas.

[0144] Although the above describes the specific implementation methods of the present invention, it does not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A method for the comprehensive utilization of municipal sludge incineration ash by graded treatment, characterized in that: The specific steps are as follows: (1) First, the municipal sludge is dried and crushed into mud blocks with a diameter of 4 to 6 mm, and then sent to the incinerator for incineration. The residue, fly ash and flue gas are discharged and enter steps (2), (3) and (4) respectively; (2) Screening the residues, and recycling the residues with a particle size ≥1 mm as building materials; The residue with a particle size of less than 1 mm and greater than 0.1 mm is vitrified and microcrystallized to produce microcrystalline glass; the residue with a particle size of ≤ 0.1 mm enters step (3); (3) Fly ash and slag with a particle size of ≤0.1 mm are uniformly mixed to obtain a mixed powder, which is then subjected to plasma treatment, first reduced using ethanol, and then second reduced using a mixed gas of ammonia and nitrogen to obtain an alloy material; (4) The flue gas enters a combustion chamber containing a catalyst for re-combustion, and the residue and purified flue gas are discharged. The residue returns to step (2), and the purified flue gas is cooled and directly discharged; In step (3), the process conditions of plasma treatment are: air as the working gas, air input pressure of 0.1-0.2 MPa, power of 300-400 W, and treatment time of 8-10 s; The first reduction was carried out in a fixed-bed reactor under the following process conditions: temperature 200-300°C, pressure 2-4 MPa, nitrogen as carrier gas carrying ethanol into the fixed-bed reactor, and the liquid space velocity of ethanol was 2-3 mL / (h·g cat ), the volume ratio of nitrogen to ethanol is 300-400:1; The second reduction is carried out by plasma reaction, with a volume ratio of ammonia to nitrogen of 10-15:85-90, an input pressure of the mixed gas of 0.4-0.5 MPa, a power of 400-500 W, and a processing time of 40-50 s; In step (4), the catalyst is prepared by the following method in parts by weight: (A) First, 2-3 parts of ammonium metavanadate, 2-3 parts of ammonium molybdate and 0.8-1 part of indium nitrate are stirred and dissolved in 50-60 parts of a 6-8% monoethanolamine aqueous solution, and then 20-30 parts of titanium dioxide are added and stirred to obtain a premixed solution; (B) then slowly adding 4 to 5 parts of concentrated ammonia water with a mass concentration of 25 to 28% to the premixed solution, stirring at room temperature for 6 to 7 hours, drying, calcining, and granulating to form granules; The process conditions for re-combustion are: burning at 150-200°C for 20-30 minutes.

2. The method according to claim 1, characterized in that In step (1), the product is dried until the moisture content is less than 35%.

3. The method according to claim 1, characterized in that In step (1), the incineration temperature is 850-950°C, and the incineration time is 60-90 minutes.

4. The method according to claim 1, wherein In step (2), the process conditions for vitrification are: vitrification at 1300-1400° C. for 40-50 minutes.

5. The method according to claim 1, wherein In step (2), the process conditions for microcrystallization are: first, cool down to 900-1000°C at 10-15°C / min, keep warm for 35-45 minutes, then cool down to 500-600°C at 5-8°C / min, keep warm for 40-50 minutes, and cool naturally to room temperature.

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