Medium-temperature heat treatment method for dioxin in household garbage incineration fly ash

Abstract

The invention discloses a medium-temperature heat treatment method for dioxin in household garbage incineration fly ash, and belongs to the technical field of environmental engineering. The medium-temperature heat treatment method for the dioxin in the household garbage incineration fly ash comprises the following steps that (1) fly ash to be treated is subjected to ammonium leaching treatment, and ammonium washing ash is obtained; (2) putting the ammonium washing ash into a heat treatment device, heating at 400-600 DEG C, and carrying out medium-temperature heat treatment; and (3) conveying the fly ash subjected to medium-temperature heat treatment obtained in the step (2) and a gas mixture to a catalytic oxidation reactor, and further oxidizing under the action of a composite catalyst to remove dioxin. According to the method, ammonium washing, medium-temperature heat treatment and composite catalyst catalytic oxidation are combined, dioxin in fly ash is efficiently removed, the method is simple, and the removal efficiency is high.

Description

Technical Field

[0001] The present application relates to a medium-temperature thermal treatment method for dioxins in fly ash from the incineration of domestic waste, and belongs to the field of environmental engineering. Background Art

[0002] Waste incineration technology has become an effective method for reducing urban waste and has been widely used. However, fly ash after waste incineration will cause environmental pollution. The pollution properties of fly ash mainly come from dioxin organic pollutants and heavy metal elements. Dioxin compounds are one of the most toxic compounds known. They are poisons of the century and have teratogenicity, carcinogenicity, mutagenicity, and the ability to damage the human reproductive system and immune system. Studies have shown that dioxins in fly ash account for about 70% of dioxin emissions during the incineration process. Therefore, fly ash is the main carrier of dioxin emissions during waste incineration and must be removed.

[0003] At present, the treatment methods of dioxins in fly ash can be mainly divided into: physical and chemical methods, solidification methods and thermal treatment methods. Physical and chemical methods usually include water washing, chemical precipitation and chemical extraction methods; among them, chemical precipitation and chemical extraction methods are not widely used due to high costs and other reasons. Solidification methods mainly include cement solidification and chemical agent solidification; cement solidification is simple to operate, but the soluble salts in fly ash can easily cause the solidified body to break; and the use of chemical agents for solidification has the problem of high cost. Thermal treatment methods mainly include hydrothermal methods and high-temperature sintering methods, but this method has high energy consumption and is prone to produce secondary fly ash during the sintering process.

[0004] Therefore, there is an urgent need to develop a method for treating dioxins in fly ash with low cost and good treatment effect. Summary of the invention

[0005] In order to solve the above problems, a medium-temperature thermal treatment of dioxins in fly ash from incineration of domestic waste is provided. The present application combines ammonium washing, medium-temperature thermal treatment and catalytic oxidation with a composite catalyst to efficiently remove dioxins in fly ash. The method is simple and has high removal efficiency.

[0006] According to one aspect of the present application, the present application provides a medium-temperature thermal treatment method for dioxins in fly ash from the incineration of domestic waste, comprising the following steps:

[0007] (1) subjecting the ash to be treated to ammonium leaching to obtain ammonium washed ash;

[0008] (2) placing the ammonium washed ash in a heat treatment device and heating it at 400-600° C. for medium temperature heat treatment;

[0009] (3) The fly ash and gas mixture obtained after the medium temperature heat treatment in step (2) is transported to a catalytic oxidation reactor for further oxidation under the action of a composite catalyst to remove dioxins.

[0010] Optionally, the time of the warm heat treatment in step (2) is 45 min to 100 min.

[0011] Optionally, in step (3), the temperature of catalytic oxidation is 300-400° C., and the oxidation time is 20-40 min.

[0012] Optionally, the ammonium leaching treatment in step (1) specifically comprises the following steps:

[0013] S1 will treat the fly ash and NH 4 Cl solution was mixed evenly and stirred at room temperature;

[0014] S2 is filtered, washed with deionized water, filtered again and dried to obtain ammonium washed ash.

[0015] Optionally, the fly ash and NH 4 The mass ratio of the Cl solution is 1:(3-5); the NH 4 The concentration of Cl solution is 2-3 mol / L.

[0016] Optionally, the composite catalyst comprises 30 to 60 parts of active components, 15 to 25 parts of catalyst promoters and 80 to 100 parts of carriers; the active components comprise a main active component and a secondary active component; the main active component comprises MnO 2 and / or Co 3 O 4 , the secondary active components include MoO 3 and / or Fe 2 O 3 ; The catalytic promoter includes one or more of Mg, Ca, La, and Ce; and the carrier is a porous carbon material.

[0017] Specifically, in the composite catalyst, the weight ratio of the main active component to the secondary active component is (2-5):1.

[0018] Specifically, the main active component is MnO 2 and Co 3 O 4 The weight ratio of the two is 1:(1-2); the secondary active component is MoO 3 and Fe 2 O 3 When the weight ratio of the two is 1: (2-3).

[0019] Optionally, the preparation method of the composite catalyst comprises the following steps:

[0020] Step 1: dissolving a manganese precursor and / or a cobalt precursor in deionized water, adding a carrier, removing moisture after ultrasonic immersion, drying, and calcining;

[0021] Step 2: dissolving a molybdenum precursor and / or an iron precursor in deionized water, adding the product obtained in step 1, immersing in ultrasound, removing moisture, drying, and calcining;

[0022] Step 3: placing the product obtained in step 2 in a catalyst promoter solution, immersing it in ultrasound, removing moisture, drying, and calcining to obtain a composite catalyst.

[0023] Optionally, the manganese precursor is manganese nitrate, the cobalt precursor is cobalt nitrate, the molybdenum precursor is ammonium molybdate, and the iron precursor is iron nitrate; the catalyst promoter solution includes Ce(NO 3 ) 3 6H 2 O、La(NO 3 ) 3 6H 2 O, Ca(NO 3 ) 2 ·4H 2 O、Mg(NO 3 ) 2 6H 2 O is an aqueous solution of one or more of the following.

[0024] Optionally, in step 1, step 2 and step 3, the ultrasonic power is 200-300W, the immersion time is 3-6h, the drying temperature is 100-120°C, the roasting temperature is 400-500°C, and the roasting time is 3-5h.

[0025] According to another aspect of the present application, the present application also provides the application of the above-mentioned medium-temperature thermal treatment method for dioxins in fly ash from the incineration of domestic waste in terms of removing dioxins from fly ash.

[0026] The beneficial effects of this application include but are not limited to:

[0027] 1. According to the medium-temperature heat treatment method for dioxins in fly ash from incineration of domestic waste of the present application, ammonium washing, medium-temperature heat treatment and composite catalyst catalytic oxidation are combined to efficiently remove dioxins in fly ash. The method is simple, the energy consumption is greatly reduced, and the removal efficiency is high. On the one hand, in the ammonium washing step, NH 4 The Cl solution reacts with the metal chlorides in the fly ash to generate chlorides that are more soluble in water, thereby replacing heavy metal ions such as copper and iron in the fly ash, reducing the precursors of dioxin formation, and facilitating the subsequent medium-temperature heat treatment and catalytic oxidation process; on the other hand, the medium-temperature heat treatment is combined with catalytic oxidation to completely decompose dioxins and improve the dioxin removal rate and efficiency.

[0028] 2. According to the medium-temperature thermal treatment method for dioxins in fly ash from incineration of domestic waste of the present application, a catalytic oxidation process is added after the medium-temperature pyrolysis process to remove dioxins remaining in the flue gas and fly ash after pyrolysis treatment by medium-temperature pyrolysis, thereby greatly improving the removal effect.

[0029] 3. According to the medium-temperature thermal treatment method for dioxins in fly ash from the incineration of domestic waste of this application, this application makes specific restrictions on the reaction time and reaction temperature of the medium-temperature thermal treatment and catalytic oxidation. Under specific reaction conditions, combined with a composite catalyst, the removal efficiency is greatly improved.

[0030] 4. According to the medium-temperature thermal treatment method for dioxins in fly ash from the incineration of domestic waste of the present application, the present application achieves better catalytic degradation of dioxins through the coordinated action of the main active components and the secondary active components. By adding specific catalytic aids, on the one hand, it is possible to effectively inhibit the agglomeration of active components on the catalyst surface, weaken the interaction between active components and the carrier, and increase the dispersion of active phases on the catalyst surface; on the other hand, the addition of catalytic aids is beneficial to improving the structural stability of the composite catalyst and extending the service life of the composite catalyst. DETAILED DESCRIPTION

[0031] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0032] Unless otherwise specified, the raw materials in the examples and comparative examples of the present application were purchased through commercial channels.

[0033] Unless otherwise specified, the methods used in the examples and comparative examples of the present application are conventional methods in the prior art.

[0034] Example 1

[0035] Preparation method of composite catalyst:

[0036] Step 1: dissolve 20 parts of manganese nitrate in deionized water, add 80 parts of porous carbon material carrier, immerse in ultrasound for 3 hours, remove moisture, dry, and calcine. The ultrasonic power is 200W, the drying temperature is 100°C, the calcination temperature is 400°C, and the calcination time is 3 hours;

[0037] Step 2: dissolve 10 parts of ammonium molybdate in deionized water, add the product obtained in step 1, immerse in ultrasound for 3 hours, remove moisture, dry, and roast. The ultrasonic power is 200 W, the drying temperature is 100° C., the roasting temperature is 400° C., and the roasting time is 3 hours;

[0038] Step 3: Place the product obtained in step 2 in 15 parts of Ce(NO 3 ) 3 6H 2O solution, immersed in ultrasound for 3 hours, then removed moisture, dried, and calcined. The ultrasonic power was 200 W, the drying temperature was 100° C., the calcination temperature was 400° C., and the calcination time was 3 hours to obtain a composite catalyst.

[0039] A medium-temperature thermal treatment method for dioxins in fly ash from domestic waste incineration:

[0040] (1) The fly ash to be treated is subjected to ammonium leaching treatment, and the fly ash and NH 4 The mass ratio of the Cl solution is 1:3; the NH 4 The concentration of Cl solution is 2 mol / L, and ammonium washed ash is obtained;

[0041] (2) placing the ammonium washed ash in a heat treatment device and heating it at 400° C. for medium temperature heat treatment, wherein the medium temperature heat treatment time is 45 minutes;

[0042] (3) The fly ash and gas mixture obtained after the medium temperature heat treatment in step (2) is transported to a catalytic oxidation reactor for further oxidation under the action of a composite catalyst at a catalytic oxidation temperature of 300° C. and an oxidation time of 20 min to remove dioxins.

[0043] Example 2

[0044] Preparation method of composite catalyst:

[0045] Step 1: Dissolve 50 parts of manganese nitrate in deionized water, add 100 parts of porous carbon material carrier, immerse in ultrasound for 6 hours, remove moisture, dry, and calcine. The ultrasonic power is 300W, the drying temperature is 120°C, the calcination temperature is 500°C, and the calcination time is 5 hours;

[0046] Step 2: dissolve 10 parts of ammonium molybdate in deionized water, add the product obtained in step 1, immerse in ultrasound for 6 hours, remove moisture, dry, and roast. The ultrasonic power is 300 W, the drying temperature is 120° C., the roasting temperature is 500° C., and the roasting time is 5 hours;

[0047] Step 3: Place the product obtained in step 2 in 25 parts of Mg(NO 3 ) 2 6H 2 O solution, immersed in ultrasound for 6 hours, then removed moisture, dried, and calcined. The ultrasonic power was 300 W, the drying temperature was 120° C., the calcination temperature was 500° C., and the calcination time was 5 hours to obtain a composite catalyst.

[0048] A medium-temperature thermal treatment method for dioxins in fly ash from domestic waste incineration:

[0049] (1) The fly ash to be treated is subjected to ammonium leaching treatment, and the fly ash and NH 4 The mass ratio of the Cl solution is 1:5; the NH4 The concentration of Cl solution is 3 mol / L, and ammonium washed ash is obtained;

[0050] (2) placing the ammonium washed ash in a heat treatment device and heating it at 600° C. for medium-temperature heat treatment, wherein the medium-temperature heat treatment time is 100 min;

[0051] (3) The fly ash and gas mixture obtained after the medium temperature heat treatment in step (2) is transported to a catalytic oxidation reactor for further oxidation under the action of a composite catalyst at a catalytic oxidation temperature of 400° C. and an oxidation time of 40 minutes to remove dioxins.

[0052] Example 3

[0053] Preparation method of composite catalyst:

[0054] Step 1: dissolve 40 parts of manganese nitrate in deionized water, add 90 parts of porous carbon material carrier, immerse in ultrasound for 5 hours, remove moisture, dry, and roast. The ultrasonic power is 200W, the drying temperature is 100°C, the roasting temperature is 450°C, and the roasting time is 4 hours;

[0055] Step 2: dissolve 10 parts of ammonium molybdate in deionized water, add the product obtained in step 1, immerse in ultrasound for 5 hours, remove moisture, dry, and roast. The ultrasonic power is 200 W, the drying temperature is 100° C., the roasting temperature is 450° C., and the roasting time is 4 hours;

[0056] Step 3: Place the product obtained in step 2 in 20 parts of La(NO 3 ) 3 6H 2 O solution, immersed in ultrasound for 5 hours, then removed moisture, dried, and calcined. The ultrasonic power was 200 W, the drying temperature was 100° C., the calcination temperature was 450° C., and the calcination time was 4 hours to obtain a composite catalyst.

[0057] A medium-temperature thermal treatment method for dioxins in fly ash from domestic waste incineration:

[0058] (1) The fly ash to be treated is subjected to ammonium leaching treatment, and the fly ash and NH 4 The mass ratio of the Cl solution is 1:4; the NH 4 The concentration of Cl solution is 3 mol / L, and ammonium washed ash is obtained;

[0059] (2) placing the ammonium washed ash in a heat treatment device and heating it at 500° C. for medium temperature heat treatment, wherein the medium temperature heat treatment time is 80 minutes;

[0060] (3) The fly ash and gas mixture obtained after the medium temperature heat treatment in step (2) is transported to a catalytic oxidation reactor for further oxidation under the action of a composite catalyst at a catalytic oxidation temperature of 350° C. for an oxidation time of 30 min to remove dioxins.

[0061] Example 4

[0062] The difference between Example 4 and Example 3 is that in the preparation method of the composite catalyst, in step 1, 20 parts of manganese nitrate and 20 parts of cobalt nitrate are used to replace 40 parts of manganese nitrate; in step 2, 3.3 parts of ammonium molybdate and 6.7 parts of ferric nitrate are used to replace 10 parts of ammonium molybdate, and the rest are the same.

[0063] Example 5

[0064] The difference between Example 5 and Example 3 is that in the preparation method of the composite catalyst, in step 1, 14 parts of manganese nitrate and 26 parts of cobalt nitrate are used to replace 40 parts of manganese nitrate; in step 2, 2.5 parts of ammonium molybdate and 7.5 parts of ferric nitrate are used to replace 10 parts of ammonium molybdate, and the rest are the same.

[0065] Example 6

[0066] The difference between Example 6 and Example 3 is that in step (2), the heat treatment time is 40 minutes, and the rest are the same.

[0067] Example 7

[0068] The difference between Example 7 and Example 3 is that in step (2), the heat treatment time is 120 min, and the rest are the same.

[0069] Example 8

[0070] The difference between Example 8 and Example 3 is that in step (3), the temperature of catalytic oxidation is 500° C., and the rest are the same.

[0071] Example 9

[0072] The difference between Example 9 and Example 3 is that the ammonium leaching treatment NH 4 The concentration of Cl solution is 1 mol / L, and the rest are the same.

[0073] Example 10

[0074] The difference between Example 10 and Example 3 is that the composite catalyst does not include a secondary active component, and the rest is the same.

[0075] Embodiment 11

[0076] The difference between Example 11 and Example 3 is that the composite catalyst does not include a catalyst promoter, and the rest is the same.

[0077] Comparative Example 1

[0078] The difference between Comparative Example 1 and Example 3 is that water is used instead of NH 4 Cl solution, and the rest were the same.

[0079] Comparative Example 2

[0080] The difference between Comparative Example 2 and Example 3 is that step (3) of catalytic oxidation is not included, and the rest are the same.

[0081] Comparative Example 3

[0082] The difference between Comparative Example 3 and Example 3 is that the heat treatment temperature in step (2) is 700° C., and the rest are the same.

[0083] Comparative Example 4

[0084] The difference between Comparative Example 4 and Example 3 is that the heat treatment temperature in step (2) is 300° C., and the rest are the same.

[0085] Experimental Example 1

[0086] The above treatment was carried out on fly ash from a landfill, and the dioxin toxic equivalent concentration in the fly ash before and after the treatment was measured. The sampling and analysis methods of dioxins refer to the "Determination of Dioxins in Solid Waste by Isotope Dilution High Resolution Gas Chromatography-High Resolution Mass Spectrometry" (HJ 77.3-2008). The test results are shown in Table 1.

[0087] Table 1 Determination results of dioxin toxicity equivalent concentration in fly ash

[0088]

[0089]

[0090] As shown in Table 1, the medium-temperature heat treatment method for dioxins in fly ash from incineration of domestic waste provided by the present application has a high dioxin removal rate. The dioxin removal rates of Examples 1 to 5 can all reach more than 98.6%, among which Example 4 is the best example. The present application combines ammonium washing, medium-temperature heat treatment and composite catalyst catalytic oxidation to efficiently remove dioxins from fly ash. The method is simple and has high removal efficiency.

[0091] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A medium-temperature thermal treatment method for dioxins in fly ash from incineration of domestic waste, characterized in that: The following steps are involved: (1) subjecting the ash to be treated to ammonium leaching to obtain ammonium washed ash; (2) placing the ammonium washed ash in a heat treatment device and heating it at 400-600° C. for medium temperature heat treatment; (3) The fly ash and gas mixture obtained after the medium temperature heat treatment in step (2) is transported to a catalytic oxidation reactor for further oxidation under the action of a composite catalyst to remove dioxins.

2. The medium-temperature thermal treatment method for dioxins in fly ash from domestic waste incineration according to claim 1, characterized in that: The time of the warm heat treatment in step (2) is 45 min to 100 min.

3. The medium-temperature thermal treatment method for dioxins in fly ash from household waste incineration according to claim 1, characterized in that: In step (3), the temperature of catalytic oxidation is 300-400° C., and the oxidation time is 20-40 min.

4. The medium-temperature thermal treatment method for dioxins in fly ash from household waste incineration according to claim 1, characterized in that: The ammonium leaching treatment in step (1) specifically comprises the following steps: S1. Mix the fly ash to be treated and the NH4Cl solution evenly and stir at room temperature; S2 is filtered, washed with deionized water, filtered again and dried to obtain ammonium washed ash.

5. The medium-temperature thermal treatment method for dioxins in fly ash from household waste incineration according to claim 4, characterized in that: The mass ratio of the fly ash to the NH4Cl solution is 1:(3-5); the concentration of the NH4Cl solution is 2-3 mol / L.

6. The medium-temperature thermal treatment method for dioxins in fly ash from household waste incineration according to claim 1, characterized in that: The composite catalyst comprises 30 to 60 parts of active components, 15 to 25 parts of catalytic promoters and 80 to 100 parts of carriers; the active components comprise a main active component and a secondary active component; the main active component comprises MnO2 and / or Co3O4, and the secondary active component comprises MoO3 and / or Fe2O3; the catalytic promoter comprises one or more of Mg, Ca, La, and Ce; and the carrier is a porous carbon material.

7. The medium-temperature thermal treatment method for dioxins in fly ash from household waste incineration according to claim 6, characterized in that: The preparation method of the composite catalyst comprises the following steps: Step 1: dissolving a manganese precursor and / or a cobalt precursor in deionized water, adding a carrier, removing moisture after ultrasonic immersion, drying, and calcining; Step 2: dissolving a molybdenum precursor and / or an iron precursor in deionized water, adding the product obtained in step 1, immersing in ultrasound, removing moisture, drying, and calcining; Step 3: placing the product obtained in step 2 in a catalyst promoter solution, immersing it in ultrasound, removing moisture, drying, and calcining to obtain a composite catalyst.

8. The medium-temperature thermal treatment method for dioxins in fly ash from household waste incineration according to claim 7, characterized in that: The manganese precursor is manganese nitrate, the cobalt precursor is cobalt nitrate, the molybdenum precursor is ammonium molybdate, and the iron precursor is ferric nitrate; the catalytic additive solution includes an aqueous solution of one or more of Ce(NO3)3·6H2O, La(NO3)3·6H2O, Ca(NO3)2·4H2O, and Mg(NO3)2·6H2O.

9. The medium-temperature thermal treatment method for dioxins in fly ash from household waste incineration according to claim 7, characterized in that: In the steps 1, 2 and 3, the ultrasonic power is 200-300W, the immersion time is 3-6h, the drying temperature is 100-120°C, the calcination temperature is 400-500°C, and the calcination time is 3-5h.

10. Use of the medium-temperature thermal treatment method for dioxins in fly ash from incineration of domestic waste as claimed in any one of claims 1 to 9 in removing dioxins from fly ash.

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