Low-energy-consumption high-efficiency decomposition treatment method for dioxin in fly ash

Abstract

The invention discloses a low-energy-consumption high-efficiency decomposition treatment method for dioxin in fly ash, which comprises the following steps: firstly, crushing the fly ash to be treated until the particle size is 2-100mu m, and drying to obtain fly ash powder with uniform components and water content of less than 1%; the method comprises the following steps: mixing a transition metal catalyst or a synthetic inhibitor which accounts for 5-10wt% of the weight of the fly ash into the fly ash powder, and carrying out low-temperature thermal decomposition on dioxin in the dry fly ash at 250-350 DEG C in an anaerobic environment with the oxygen content of less than 0.5 vol%. The incineration fly ash or the chelated fly ash is treated through the method, dioxin can be lower than 50 ng-TEQ / kg, the requirement of HJ 1134-2020 Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash (Trial) is met, the treated fly ash can be used for recycling of building materials and the like, the efficiency is high, the operation is simple, and high economical efficiency is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of dioxin treatment in fly ash from garbage incineration, and in particular relates to a low-energy-consumption and high-efficiency decomposition treatment method for dioxins in fly ash. Background Art

[0002] Fly ash is solid waste generated during the combustion process of coal-fired power plants, which has a high risk of environmental pollution. Because it contains a large amount of harmful metal ions and heavy metals, the treatment and disposal of fly ash has always been a difficult problem in the field of environmental protection. Traditional fly ash treatment methods include landfill, solidification, stacking, etc., but these methods have problems such as large footprint, high treatment cost, secondary pollution, etc., and cannot effectively recover the valuable components in fly ash. The main treatment methods at present are organic chelating agent chelation or cement solidification.

[0003] In order to reduce environmental pollution, researchers have proposed a variety of fly ash resource treatment technologies in recent years. Among them, thermal decomposition technology has become a research hotspot in the field of fly ash treatment due to its advantages such as high efficiency, controllability, and high energy utilization. The Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration (Trial) (HJ 1134-2020) stipulates that the total amount of dioxin residues in fly ash treatment products should be controlled to not exceed 50 ng-TEQ / kg (based on fly ash dry weight); the heavy metal leaching concentration should not exceed the maximum allowable emission concentration value specified in GB 8978; the soluble chlorine content should not exceed 2%, preferably not more than 1%.

[0004] However, the existing fly ash thermal decomposition technology generally has two major problems: first, the temperature required for the thermal decomposition process is high, which consumes a lot of energy; second, the removal effect of harmful heavy metals and toxic substances in fly ash is limited, making it difficult to meet environmental protection requirements. Therefore, how to achieve efficient decomposition of fly ash at a lower temperature and effectively remove harmful substances in it is still a technical problem that needs to be solved in the field of fly ash resource treatment.

[0005] Therefore, it is very necessary to develop a method that can significantly reduce energy consumption, effectively remove harmful substances in fly ash, and achieve green treatment and resource utilization of fly ash. Summary of the invention

[0006] In order to solve at least one of the above problems, the present invention provides a low-energy consumption and high-efficiency decomposition treatment method for dioxins in fly ash.

[0007] In order to achieve the above object, the present invention adopts the following technical means: a low-energy consumption and high-efficiency decomposition and treatment method for dioxins in fly ash, comprising the following steps: S1. Crushing the fly ash to be treated into a particle size of 2-100 μm, drying, and obtaining fly ash powder with uniform components and a moisture content of less than 1%; S2. After 5-10 wt% of the fly ash weight of the transition metal catalyst or synthesis inhibitor is mixed into the fly ash powder, the dioxins in the dry fly ash are subjected to low-temperature thermal decomposition at 250°C-350°C in an anaerobic environment with an oxygen content of less than 0.5 vol%.

[0008] In some embodiments of the present invention, further, the step of passing fly ash particles in the mixed gas discharged during the fly ash crushing, drying and low-temperature thermal decomposition steps into a low-temperature thermal decomposition system for circulation treatment after flue gas purification is included.

[0009] In some embodiments of the present invention, the transition metal catalyst is a Fe / C catalyst.

[0010] In some embodiments of the present invention, the transition metal catalyst is prepared by using a nitrate hydrate of the corresponding metal, dissolved in deionized water and used as a precursor, and is added to activated carbon for impregnation at a mass ratio of 1:10, and the metal element is loaded on the activated carbon to obtain a transition metal catalyst.

[0011] In some embodiments of the present invention, preferably, the amount of the transition metal catalyst used is 5 wt % of the weight of the fly ash.

[0012] In some embodiments of the invention, the synthesis inhibitor is diammonium phosphate.

[0013] In some embodiments of the present invention, preferably, the amount of the synthesis inhibitor is 5 wt % of the fly ash weight.

[0014] In some embodiments of the present invention, the transition metal catalyst is dried in a tube furnace at 100-105°C for 22-24 hours before mixing with fly ash, activated at 120-150°C for 15-20 minutes under a nitrogen flow of 1,000 sccm, and further activated at 450-500°C for 1.5-2 hours.

[0015] In some embodiments of the present invention, in step S2, the thermal decomposition time is 10 min to 60 min. Preferably, the thermal decomposition temperature is 300°C.

[0016] In some embodiments of the present invention, in step S2, the anaerobic environment is a nitrogen atmosphere in which an inert gas is introduced so that the oxygen content in the nitrogen atmosphere is less than 0.5 vol%.

[0017] In some embodiments of the present invention, in step S1, the fly ash to be treated includes grate furnace incineration fly ash, fluidized bed incineration fly ash and chelated fly ash, the initial moisture content of the fly ash to be treated is less than 20%, and the initial dioxin concentration is 50-5000ng-TEQ / kg.

[0018] In some embodiments of the present invention, the chelated fly ash includes organic chelated fly ash, inorganic chelated fly ash and cement-solidified fly ash.

[0019] In some embodiments of the present invention, in step S1, the drying temperature is 120-130°C, and the drying heat source comes from the hot flue gas after low-temperature thermal decomposition and combustion.

[0020] The present invention also provides a fly ash dioxin low temperature thermal decomposition treatment system, which uses the fly ash dioxin low temperature thermal decomposition treatment method as described above, and the fly ash dioxin low temperature thermal decomposition treatment system comprises: Fly ash storage silo, using a screw device to transport the fly ash to be disposed to the crushing device; A crushing device, used for crushing the fly ash to be processed to obtain powdered fly ash; A drying device, connected to the crushing device, for drying the powdered fly ash to obtain dry fly ash; The thermal decomposition furnace is connected to the drying device and is used to perform low-temperature thermal decomposition of dioxins in the dry fly ash in an anaerobic environment to obtain pyrolyzed fly ash.

[0021] The fly ash dioxin low-temperature thermal decomposition treatment system also includes a flue gas purification device connected to the crushing device, the drying device and the thermal decomposition furnace to purify the discharged tail gas.

[0022] Beneficial Effects of the Invention Compared with the prior art, the present invention has the following beneficial effects: the present invention improves the thermal decomposition efficiency of dioxins by adding a transition metal catalyst or a resynthesis inhibitor, reduces the temperature required for the reaction, saves fuel costs, has low energy consumption, and degrades the dioxins in the fly ash. The dioxin concentration after decomposition is lower than 50 ngI-TEQ / kg, which is better than the "Pollution Control Specification for Fly Ash from Incineration of Municipal Waste (HJ 1134-2020)". It can be used as a raw material for subsequent green building materials, etc., and the fly ash can be utilized as a resource, which has high economic efficiency. At the same time, in the treatment process, the hot flue gas from the thermal decomposition furnace is used as the heat source of the drying device, and the energy is utilized in a cascade manner, with high energy utilization rate, good economy, and a flue gas purification system with low pollutant emissions. DETAILED DESCRIPTION

[0023] The following examples are used to demonstrate preferred embodiments of the present invention. It will be appreciated by those skilled in the art that the techniques disclosed in the following examples represent techniques discovered by the inventors that can be used to implement the present invention and therefore can be considered as preferred embodiments of the present invention. However, it will be appreciated by those skilled in the art based on this specification that many modifications may be made to the specific embodiments disclosed herein and still achieve the same or similar results without departing from the spirit or scope of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs, and the materials cited herein and those cited by them are incorporated by reference. Those skilled in the art will recognize or will learn through routine experimentation that there are many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the claims.

[0025] The technical solution of the present application is further described in detail below in conjunction with specific implementation methods.

[0026] Example 1 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 250℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0027] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 576.45 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 26.12%, and the natural gas consumption for fly ash disposal was 24.1Nm 3 / t.

[0028] Example 2 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was tested to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The moisture content of the fly ash is 0.8%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0029] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 298.45 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 61.75%, and the natural gas consumption for fly ash disposal was 30.1Nm 3 / t.

[0030] Example 3 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0031] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 13.81 ng-TEQ / kg, which met the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 98.23%. The natural gas consumption for fly ash disposal was 34.5 Nm 3 / t.

[0032] Example 4 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 400℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0033] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 9.13 ng-TEQ / kg, which met the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 98.83%. The natural gas consumption for fly ash disposal was 24.1 Nm 3 / t, the natural gas consumption for fly ash treatment is 42.4Nm 3 / t.

[0034] Example 5 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 0.1%, the residence time is 10min, and the air flow velocity is 8m 3 / h.

[0035] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 41.04 ng-TEQ / kg, which met the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 94.74%, and the natural gas consumption for fly ash disposal was 31.5 Nm 3 / t.

[0036] Example 6 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 0.1%, the residence time is 40min, and the air flow velocity is 8m 3 / h.

[0037] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 13.58 ng-TEQ / kg, which met the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 98.26%. The natural gas consumption for fly ash disposal was 36.8Nm 3 / t.

[0038] Example 7 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 0.1%, the residence time is 60min, and the air flow velocity is 8m 3 / h.

[0039] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 16.31 ng-TEQ / kg, which met the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 97.91%, and the natural gas consumption for fly ash disposal was 39.1Nm 3 / t.

[0040] Example 8 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 0.5%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0041] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 25.59 ng-TEQ / kg, which met the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 96.72%, and the natural gas consumption for fly ash disposal was 34.1Nm 3 / t.

[0042] Example 9 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 2.0%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0043] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 76.15 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 90.24%, and the natural gas consumption for fly ash disposal was 34.7 Nm 3 / t.

[0044] Example 10 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 4.0%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0045] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 292.67 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 62.49%, and the natural gas consumption for fly ash disposal was 35.3Nm 3 / t.

[0046] Embodiment 11 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 6.0%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0047] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 569.89 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 26.96%, and the natural gas consumption for fly ash disposal was 34.4Nm 3 / t.

[0048] Example 12 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 4 m 3 / h.

[0049] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 32.54 ng-TEQ / kg, which met the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 95.83%. The natural gas consumption for fly ash disposal was 31.8Nm 3 / t.

[0050] Embodiment 13 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 6 m 3 / h.

[0051] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 17.48 ng-TEQ / kg, which met the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 97.76%, and the natural gas consumption for fly ash disposal was 32.8Nm 3 / t.

[0052] Embodiment 14 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by an impact crusher, its average particle size was found to be 54μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.8%. It then enters a pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 350℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 10 m 3 / h.

[0053] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 12.87 ng-TEQ / kg, which met the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 98.35%, and the natural gas consumption for fly ash disposal was 36.2Nm 3 / t.

[0054] Embodiment 15 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 1wt% Fe / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0055] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 44.08 ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 94.35%, and the natural gas consumption for fly ash disposal was 27.1Nm 3 / t.

[0056] Example 16 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 2.5wt% Fe / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0057] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 26.29 ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 96.63%, and the natural gas consumption for fly ash disposal was 26.9Nm 3 / t.

[0058] Embodiment 17 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% Fe / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0059] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 10.30 ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 98.68%, and the natural gas consumption for fly ash disposal was 27.0Nm 3 / t.

[0060] Embodiment 18 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 7.5wt% of Fe / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0061] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 9.83 ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 98.74%, and the natural gas consumption for fly ash disposal was 26.6Nm 3 / t.

[0062] Embodiment 19 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 10wt% Fe / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0063] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 11.63 ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 98.51%, and the natural gas consumption for fly ash disposal was 26.7Nm 3 / t.

[0064] Embodiment 20 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% Mn / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m3 / h.

[0065] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 20.68 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 97.35%, and the amount of natural gas used for fly ash disposal was 26.2Nm 3 / t.

[0066] Embodiment 21 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% Ce / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0067] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 201.46 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Incineration of Domestic Waste. The dioxin degradation rate was 74.18%, and the natural gas consumption for fly ash disposal was 26.9 Nm 3 / t.

[0068] Embodiment 22 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was tested to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% Cu / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0069] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 133.11 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 82.94%, and the natural gas consumption for fly ash disposal was 26.0 Nm 3 / t.

[0070] Embodiment 23 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% Ni / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0071] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 47.05 ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 93.97%, and the natural gas consumption for fly ash disposal was 27.3Nm 3 / t.

[0072] Embodiment 24 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% Pd / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0073] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 39.32 ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 94.96%, and the natural gas consumption for fly ash disposal was 27.1Nm 3 / t.

[0074] Embodiment 25 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% of the resynthesis inhibitor ADP is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m3 / h.

[0075] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 3.28ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Incineration of Domestic Waste. The dioxin degradation rate was 99.58%, and the natural gas consumption for fly ash disposal was 24.1Nm 3 / t.

[0076] Embodiment 26 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% of the resynthesis inhibitor THI is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0077] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 25.67 ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 96.71%, and the natural gas consumption for fly ash disposal was 25.2 Nm 3 / t.

[0078] Embodiment 27 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% of the resynthesis inhibitor PDP is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0079] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 61.09 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 92.17%, and the natural gas consumption for fly ash disposal was 25.6 Nm 3 / t.

[0080] Embodiment 28 The fly ash from a waste incineration plant has a dioxin toxic equivalent concentration of 780.25ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 54μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% of the resynthesis inhibitor SDP is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0081] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 170.72 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 78.12%, and the amount of natural gas used for fly ash disposal was 25.2Nm 3 / t.

[0082] Embodiment 29 The organic chelated fly ash from a landfill has a dioxin toxic equivalent concentration of 914.82ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was tested to be 74μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from natural gas combustion. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the pyrolysis furnace comes from natural gas combustion, the temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0083] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 342.05 ng-TEQ / kg, which did not meet the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 62.61%, and the natural gas consumption for fly ash disposal was 30.1Nm 3 / t.

[0084] Embodiment 30 The organic chelated fly ash from a landfill has a dioxin toxic equivalent concentration of 914.82ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 74μm. After being dried at 130℃ in a drum dryer, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% Fe / C catalyst is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0085] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 8.05 ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 99.12%, and the natural gas consumption for fly ash disposal was 27.1Nm 3 / t.

[0086] Embodiment 31 The organic chelated fly ash from a landfill has a dioxin toxic equivalent concentration of 914.82ng-TEQ / kg. After being crushed by a roller crusher, its average particle size was found to be 74μm. After being dried in a drum dryer at 130℃, the heat source of the drum dryer comes from the hot flue gas of the thermal decomposition furnace. During the thermal decomposition process, 5wt% of the resynthesis inhibitor ADP is mixed in. The fly ash has a moisture content of 0.9%. Then it enters the pyrolysis furnace for low-temperature thermal decomposition of dioxins. The heat source of the thermal decomposition furnace comes from natural gas combustion. The temperature is 300℃, the oxygen content is 0.1%, the residence time is 20min, and the air flow velocity is 8m 3 / h.

[0087] After disposal, samples were collected for testing. The toxic equivalent concentration of dioxins in the fly ash was 5.76 ng-TEQ / kg, which was in line with the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. The dioxin degradation rate was 99.37%, and the natural gas consumption for fly ash disposal was 25.5 Nm 3 / t.

[0088] The comparison of reaction conditions and dioxin removal efficiency in the above examples is shown in Tables 1 and 2 below.

[0089] Table 1 Reaction conditions and dioxin removal efficiency in Examples 1-14

[0090] Table 2 Reaction conditions and dioxin removal efficiency of Examples 2, 15-31

[0091] As can be seen from the table above, after screening the treatment temperature, residence time, oxygen concentration, airflow velocity, etc., in Examples 1-14, combined with the degradation rate and gas consumption, the optimal working conditions for low-temperature thermal decomposition without adding a catalyst were determined: temperature 350°C, residence time 20min, oxygen concentration less than 0.5%, preferably less than 0.1%, airflow velocity 8m 3 / h is the best. Different fly ashes have very different degradation characteristics. Under this condition, the low-temperature thermal decomposition degradation rate of dioxins in fly ash can stably reach more than 98%, and the toxic equivalent concentration is less than 20 ng-TEQ / kg, which is better than the "Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration".

[0092] Compared with Example 2, Examples 15-19 differ only in the amount of Fe / C added and the low-temperature thermal decomposition residence time, and the degradation rates of Examples 15-19 increase, indicating that the Fe / C catalyst can effectively improve the low-temperature thermal decomposition degradation efficiency and reduce the natural gas consumption of the dioxin thermal decomposition system. When the Fe / C addition exceeds 5%, the degradation rate temperature reaches 98%, and the dioxin toxic equivalent concentration is less than 12 ng-TEQ / kg, which is better than the requirements of the Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration. Compared with the low-temperature thermal decomposition effect without adding a catalyst, adding a catalyst further reduces the temperature to 300°C.

[0093] Compared with Example 17, Examples 20-24 differ only in the types of transition metal catalysts, namely Fe / C, Mn / C, Ce / C, Cu / C, Ni / C, and Pd / C catalysts. The degradation effects are shown in Table 2. Various transition metals have improved the degradation effect of dioxins, and their performance is ranked as follows: Fe / C>Mn / C>Pd / C>Ni / C>Cu / C>Ce / C. By adding transition metal catalysts, the natural gas consumption of the dioxin pyrolysis system is reduced at the same time.

[0094] Compared with Example 2, the only difference between Examples 25-28 is the addition of different types of resynthesis inhibitors, namely ADP, THI, PDP, and SDP, among which ADP has the best effect with a decomposition efficiency of 99.58%. The performance ranking is: ADP>THI>PDP>SDP.

[0095] Examples 29-31 demonstrate that Fe / C transition metal catalysts and ADP resynthesis inhibitors are also applicable to the low-temperature thermal decomposition process of chelated fly ash dioxins. After the addition of Fe / C and ADP, the degradation rate increased from 62.61% to 99.12% and 99.37%, and the toxic equivalent concentration of dioxins after degradation decreased from 342.05 ng-TEQ / kg to 8.05 ng-TEQ / kg and 5.76 ng-TEQ / kg; at the same time, the temperature required for the reaction was reduced, thereby reducing energy consumption.

[0096] In view of the numerous embodiments of the scheme of the present invention, the raw materials and dosage involved can be selected according to actual needs within the limited range, and the experimental data of each embodiment is huge and numerous, which is not suitable for listing and explaining one by one here, but the content required to be verified and the final conclusion obtained in each embodiment are similar. Therefore, the verification content of each embodiment will not be explained one by one here.

[0097] All documents mentioned in the present invention are cited as references in this application, just as each document is cited as references separately. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined in the present application.

Claims

1. A low-energy and high-efficiency decomposition method for dioxins in fly ash, characterized in that: The following steps are involved: S1. Crushing the fly ash to be treated into a particle size of 2-100 μm, drying, and obtaining fly ash powder with uniform components and a moisture content of less than 1%; S2. After 5-10 wt% of the fly ash weight of the transition metal catalyst or synthesis inhibitor is mixed into the fly ash powder, the dioxins in the dry fly ash are subjected to low-temperature thermal decomposition at 250°C-350°C in an anaerobic environment with an oxygen content of less than 0.5 vol%.

2. The method according to claim 1, characterized in that: The method also includes the step of passing fly ash particles in the mixed gas discharged during the fly ash crushing, drying and low-temperature thermal decomposition steps into a low-temperature thermal decomposition system for cyclic treatment after flue gas purification.

3. The method according to claim 1, characterized in that: The transition metal catalyst is a Fe / C catalyst.

4. The method according to claim 1, characterized in that: The synthesis inhibitor is diammonium phosphate.

5. The method according to claim 3, characterized in that: The preparation method of the transition metal catalyst is as follows: ferric nitrate nonahydrate is dissolved in deionized water as a precursor, activated carbon is added for impregnation, the mixture is uniformly mixed with magnetic stirring at 80°C until dry, dried in a tube furnace at 100-105°C for 22-24 hours, activated at 120-150°C for 15-20 minutes under a nitrogen flow of 1,000 sccm, and continued to be activated at 450-500°C for 1.5-2 hours.

6. The method according to claim 1, characterized in that: In step S2, the thermal decomposition time is 10 min-60 min.

7. The method according to claim 1, characterized in that: In step S2, the anaerobic environment is provided by introducing inert gas nitrogen.

8. The method according to claim 1, characterized in that: In step S1, the fly ash to be treated includes grate furnace incineration fly ash, fluidized bed incineration fly ash and chelated fly ash, the initial moisture content of the fly ash to be treated is less than 20%, and the initial dioxin concentration is 50-5000ng-TEQ / kg.

9. The method according to claim 8, characterized in that: The chelated fly ash includes organic chelated fly ash, inorganic chelated fly ash and cement solidified fly ash.

10. The method according to claim 1, characterized in that: In step S1, the drying temperature is 120-130°C, and the drying heat source comes from the hot flue gas after low-temperature thermal decomposition and combustion.

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