Treatment method for recycling waste incineration fly ash

Abstract

The invention discloses a treatment method for recycling waste incineration fly ash, and relates to the technical field of solid waste treatment.According to the treatment method, a process of firstly washing and then cracking is adopted, and a drying technology is added before the cracking process, so that the cracking temperature can be reduced to 300-400 DEG C while energy consumption can be saved, toxic and harmful substances such as dioxin can be effectively removed, and environmental protection is achieved. Therefore, the problem of unstable curing after a long time can be solved. Meanwhile, tail gas can be effectively purified through a flue gas purification system, so that environmental pollution can be effectively reduced, fly ash building material utilization is carried out on a finally obtained solid sample product, income can be created, fly ash solidification and landfill can be avoided, the industrial problem of land waste is solved, and cyclic utilization of resources is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of solid waste treatment, and particularly to a treatment method for resource utilization of municipal solid waste incineration fly ash. Background Art

[0002] At present, the disposal of municipal solid waste incineration fly ash in China mainly relies on solidification followed by landfill. Although the fly ash solidification landfill technology is mature and the cost is relatively low, there are still many drawbacks. First, it is difficult to select a landfill site, and the landfill capacity of the national landfill sites is close to saturation. The landfill process requires a large amount of land resources to be occupied permanently. Second, fly ash solidification landfill poses a high risk to the environment. Salts and heavy metals are easily leached out, and dioxins are not eliminated. After a long time, the solidification becomes unstable. At the same time, there are also problems such as the long distance between the waste treatment facilities and the urban area, and high transportation and treatment costs.

[0003] In 2020, China issued the "Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash (HJ1134-2020)", confirming that after the municipal solid waste incineration fly ash is treated, dioxins, heavy metals, and soluble chlorine meet the relevant standards and can be used for other utilization methods other than the production of washed clinker. This standard provides a new direction for the resource utilization of fly ash. In 2021, the "Work Plan for the Construction of a 'Zero-Waste City'" pointed out that about 100 prefecture-level and above cities should be promoted to carry out the construction of a 'Zero-Waste City'. By 2025, the generation intensity of solid waste in the 'Zero-Waste City' will decrease rapidly, the comprehensive utilization level will be significantly improved, the harmless treatment capacity will be effectively guaranteed, and the solid waste treatment system and treatment capacity will be significantly improved. In 2023, the "Three-Year Action Plan for the 'Nearly Zero Landfill' of Hazardous Wastes in Zhejiang Province" pointed out that by 2025, the proportion of hazardous waste landfill in each region of the province should be controlled within 5%. As a national pilot city for the construction of a 'Zero-Waste City', Shaoxing should take the lead in achieving the 'nearly zero landfill' of hazardous waste. Thus, it can be seen that the resource utilization of municipal solid waste incineration fly ash is the only way to solve the environmental pollution pressure in China and an inevitable trend of the industry development.

[0004] In the related art, most of the patented technologies are first pyrolyzed and then washed with water, or pyrolyzed at 300-800°C in an oxygen-free atmosphere after being washed with water or pickled with acid. However, such treatment methods not only require a large amount of energy consumption, but also fail to eliminate toxic and harmful substances such as dioxins, and the solidification will become unstable after a long time. Summary of the Invention

[0005] The purpose of the present application is to provide a treatment method for resource utilization of municipal solid waste incineration fly ash to solve the problem that in the related art, most of the patented technologies are first pyrolyzed and then washed with water, or pyrolyzed at 300-800°C in an oxygen-free atmosphere after being washed with water or pickled with acid. However, such treatment methods not only require a large amount of energy consumption, but also fail to eliminate toxic and harmful substances such as dioxins, and the solidification will become unstable after a long time.

[0006] A treatment method for resource utilization of municipal solid waste incineration fly ash provided by this application adopts the following technical solutions:

[0007] A treatment method for resource utilization of municipal solid waste incineration fly ash includes the following steps:

[0008] S1. Transport the municipal solid waste incineration fly ash in the original ash bin to the water washing system to wash the municipal solid waste incineration fly ash. After washing, the municipal solid waste incineration fly ash is transported to the water-washed fly ash buffer bin, and the washing liquid generated during the water washing process is transported to the wastewater treatment system for cyclic purification treatment;

[0009] S2. Then transport the water-washed fly ash in the water-washed fly ash buffer bin to the horizontal paddle dryer, and dry the water-washed fly ash by means of indirect steam heating. The hot steam dries the water-washed fly ash through the rotation and stirring of the paddle;

[0010] S3. Then transport the dried material to the low-temperature thermal decomposition furnace through a screw, and heat the temperature in the furnace to 335-380 °C to thermally decompose the material;

[0011] S4. After 25-60 minutes of thermal decomposition, discharge the thermally decomposed material and perform cooling treatment. Finally, the solid sample product obtained after cooling is used for fly ash building material utilization.

[0012] Further, in step S1, the water washing system is a three-stage water washing system to perform three-stage water washing and pressure filtration treatment on the municipal solid waste incineration fly ash, so that the fly ash can remove the soluble chlorides therein through three-stage water washing and reduce the chlorine content in the fly ash.

[0013] Further, in step S1, the wastewater treatment system performs three-stage countercurrent recycling on the washing liquid obtained after pressure filtration treatment and then performs salt separation and purification treatment to generate income from the industrial salt by-product generated.

[0014] Further, simultaneously, during the process of performing three-stage water washing treatment on the municipal solid waste incineration fly ash, a heavy metal stabilizer in a set proportion is added to the water washing system to treat the heavy metals contained in the municipal solid waste incineration fly ash.

[0015] Further, in step S2, when using the horizontal paddle dryer to dry the water-washed fly ash, tail gas will be generated; meanwhile, in step S3, when using the low-temperature thermal decomposition furnace to thermally decompose the dried material, tail gas will also be generated; the tail gas generated in steps S2 and S3 is extracted by an induced draft fan and transported to the flue gas treatment system to treat the tail gas.

[0016] Further, the flue gas treatment system successively includes a bag filter, a spray tower, and an activated carbon adsorber. The induced draft fan is used to successively extract the tail gas into the bag filter, the spray tower, and the activated carbon adsorber for dust removal and purification treatment, and finally the purified tail gas is transported to the incinerator for co-treatment.

[0017] Further, after the particulate matter is removed from the tail gas by the bag filter to obtain secondary tail gas, the induced draft fan is used to re-extract the secondary tail gas into the water-washed fly ash buffer bin.

[0018] Further, in step S3, a set proportion of dioxin detoxification chelating agent is added to the low-temperature pyrolysis furnace to degrade the dioxin content in the fly ash.

[0019] Compared with the prior art, the beneficial effects of the present application are as follows:

[0020] The technology of the present application adopts the process of washing first and then pyrolyzing. A drying technology is added before the pyrolysis process, which can save energy consumption and reduce the pyrolysis temperature to 300 - 400 °C. It can effectively remove toxic and harmful substances such as dioxin, thus solving the problem of unstable solidification after a long time. At the same time, it has a flue gas purification system that can effectively purify the tail gas, thus effectively reducing environmental pollution. Moreover, the final solid sample product is used for fly ash building material utilization, which can not only generate income but also avoid fly ash solidification landfill, thus solving the industry problem of land waste and forming a circular utilization of resources. Description of the Drawings

[0021] Figure 1 is a flow chart of the treatment method for the resource utilization of waste incineration fly ash in the embodiment of the present application.

[0022] Figure 2 is a flow chart of the fly ash water washing process in the embodiment of the present application. Detailed Description of the Embodiment

[0023] The following is a further detailed description of the present application in conjunction with the attached Figure 1-2 drawings.

[0024] The embodiment of the present application discloses a treatment method for the resource utilization of waste incineration fly ash. Referring to Figure 1 and Figure 2 , the treatment method includes the following steps:

[0025] S1. Transport the waste incineration fly ash in the raw ash bin to the water washing system to wash the waste incineration fly ash. The washed waste incineration fly ash is transported to the water-washed fly ash buffer bin, and the washing liquid generated during the washing process is transported to the wastewater treatment system for cyclic purification treatment.

[0026] Specifically, in step S1, the water washing system is divided into two stages. First, in the first stage, fly ash is metered and discharged from the original ash bin into the interior of water washing tank A. At the same time, the filtrate collected after water washing is added according to a suitable liquid / solid ratio. This filtrate is stored in the temporary storage tank and stirred for the first water washing.

[0027] After the fly ash slurry is fully stirred and washed in water washing tank A, the fly ash water washing slurry is transported into plate and frame filter press 1 or plate and frame filter press 2 for pressure filtration and dehydration. Plate and frame filter press 1 and plate and frame filter press 2 work in a staggered manner. The first filtrate obtained from dehydration enters the sewage treatment system and the salt extraction section.

[0028] According to empirical data, the plate and frame filter press can filter the fly ash slurry to a water content of less than 35%. The filter cake after pressure filtration is subjected to a second water washing in plate and frame filter press 1 or plate and frame filter press 2, and the secondary filtrate after the secondary water washing enters water washing tank A for recycling; when the filter cake is dehydrated to a water content of about 35%, it is then transported to water washing tank B by the action of the water washing ash conveyor belt and the slurry pump for the second-stage water washing.

[0029] Then, in the second stage, the filter cake produced by the first-stage water washing enters water washing tank B for the second-stage water washing. The fly ash is subjected to three water washings in water washing tank B. The slurry after the three water washings enters plate and frame filter press 3 or plate and frame filter press 4 for secondary pressure filtration. Plate and frame filter press 3 and plate and frame filter press 4 work in a staggered manner. The filtrate after pressure filtration enters the temporary storage tank and is supplied to water washing tank A for the first-stage use.

[0030] The filter cake after pressure filtration is subjected to a fourth water washing in plate and frame filter press 3 or plate and frame filter press 4, and the filtrate after water washing enters the temporary storage tank for recycling. The mud cake after the discharge of plate and frame filter press 3 and plate and frame filter press 4 has a water content of about 35%, enters the conical silo for temporary storage, and then enters the low-temperature catalytic cracking system for further treatment in the low-temperature degradation section. Finally, the fly ash mud cake after low-temperature degradation treatment is transported into the water washing fly ash buffer bin. In addition, the secondary filtrate generated by pressure filtration is re-transported into water washing tank B for recycling.

[0031] Therefore, after the above elution of fly ash, the soluble chlorides therein can be effectively removed, and the chlorine content in the fly ash can be reduced, so that the re-synthesis of dioxins in the subsequent process can be effectively avoided in this link; more specifically, the chloride ion removal rate in the fly ash can reach more than 90%, and the alkali metal removal rate can reach more than 80%, meeting the requirements of the "Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash" (HJ1134-2020).

[0032] Meanwhile, during the three-stage water washing treatment of municipal solid waste incineration fly ash, a heavy metal stabilizer is added to the water washing system in a set proportion, which can treat the heavy metals contained in the fly ash to reduce the leaching risk of heavy metals in the fly ash building material products.

[0033] The following table shows the data on the treatment of heavy metals in municipal solid waste incineration fly ash:

[0034]

[0035] In addition, preferably, in step S1, the wastewater treatment system performs three-stage countercurrent recycling on the water washing liquid obtained after pressure filtration and dehydration by the plate and frame filter press 1 or the plate and frame filter press 2, and then performs salt separation and purification treatment to generate income from the industrial salt by-products. Then, the treated water washing liquid is recycled and transported back to the water washing system to effectively recycle the water washing liquid.

[0036] S2. Then, the washed fly ash in the water washing fly ash buffer bin is transported to a horizontal paddle dryer, and the water washing fly ash is dried by indirect steam heating. The hot steam dries the water washing fly ash through the rotation and stirring of the paddles; specifically, after the paddle dryer indirectly dries the incoming fly ash at a low temperature, the materials can be mixed evenly and dried to a moisture content of less than 5%.

[0037] Meanwhile, the step of drying by using the paddle dryer first can effectively save the energy consumption in the subsequent thermal decomposition process. Condensate is generated during the drying process, and a condensate pipe is installed on the outer side of the bottom of the horizontal paddle dryer to drain the condensate away uniformly.

[0038] S3. Then, the dried material is transported to a low-temperature thermal decomposition furnace by a screw conveyor, and the temperature in the furnace is heated to 335-380 °C to thermally decompose the material; meanwhile, in step S3, a set proportion of dioxin detoxification chelating agent is added to the low-temperature thermal decomposition furnace to degrade the dioxin content in the fly ash, and at the same time, different heavy metal ions in the fly ash can be chelated to stabilize the heavy metal ions, thus providing good support for the resource utilization of fly ash.

[0039] In this way, the low-temperature thermal decomposition treatment step in this link can effectively degrade and remove the dioxin content in the fly ash, and can also stabilize the heavy metal ions in the fly ash.

[0040] Specifically, when the horizontal paddle dryer is used to dry the washed fly ash in step S2, tail gas will be generated. At the same time, when the low-temperature pyrolysis furnace is used to pyrolyze the dried material in step S3, tail gas will also be generated. Therefore, the tail gas generated in steps S2 and S3 is extracted by an induced draft fan and transported into the flue gas treatment system to treat the tail gas.

[0041] More specifically, the flue gas treatment system sequentially includes a bag filter, a spray tower, and an activated carbon adsorber. Among them, the bag filter is used to remove particulate matter in the tail gas; the spray tower is connected to the bag filter and is used to remove residual powder in the tail gas; and the activated carbon adsorber is used to remove dioxin pollutants in the tail gas.

[0042] In this way, by using the induced draft fan to sequentially extract the tail gas into the bag filter, the spray tower, and the activated carbon adsorber for dust removal and purification treatment, and finally transporting the purified tail gas to the incinerator for co-treatment, environmental pollution can be effectively reduced.

[0043] Preferably, after the particulate matter in the tail gas is removed by the bag filter to obtain secondary tail gas, the induced draft fan is used to re-extract the secondary tail gas into the washed fly ash buffer bin to perform cyclic drying and low-temperature pyrolysis treatment on the secondary tail gas.

[0044] S4. After pyrolysis for 25 - 60 minutes, the pyrolyzed material is discharged and cooled. Finally, the solid sample product obtained after cooling is used for fly ash building material utilization. In this way, both income can be generated and fly ash solidification and landfill can be avoided, thus solving the industry problem of land waste and forming a circular utilization of resources.

[0045] In this way, through the treatment method for resource utilization of municipal solid waste incineration fly ash of the present application, the municipal solid waste incineration fly ash is treated by "washing + drying + low-temperature pyrolysis", effectively realizing the preliminary treatment of resource utilization of municipal solid waste incineration fly ash, so that its dioxin, heavy metals, and soluble chlorine can all meet the requirements of the "Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash" (HJ1134 - 2020). The flue gas pollutants detection all meets the requirements of the "Pollution Control Standard for Hazardous Waste Incineration" (GB18484 - 2020). The wastewater generated by washing can be recycled and salt-separated and purified, and no intermediate pollutants are generated. And the fly ash by-product can be used for building material utilization, which not only increases income but also avoids the solidification and landfill of fly ash, forming a circular utilization of resources, thus completing the "last mile" of fly ash treatment and disposal.

[0046] The following table shows the data situation of treating dioxin in municipal solid waste incineration fly ash:

[0047]

[0048]

[0049] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A method for recycling fly ash from waste incineration, characterized in that: The following steps are involved: S1. The waste incineration fly ash in the original ash bin is transported to the water washing system to wash the waste incineration fly ash. The washed waste incineration fly ash is transported to the water washing fly ash buffer bin, and the washing liquid generated during the washing process is transported to the wastewater treatment system for circulation and purification treatment; S2, transporting the washed fly ash in the washed fly ash buffer bin to a horizontal paddle dryer, and drying the washed fly ash by indirect steam heating, wherein the hot steam dries the washed fly ash through the rotating stirring of the paddles; S3, the dried material is then conveyed to a low-temperature thermal decomposition furnace via a spiral, and the temperature in the furnace is heated to 335-380°C to thermally decompose the material; S4. After 25-60 minutes of thermal decomposition, the thermally decomposed material is discharged and cooled, and the solid sample product obtained after cooling is used as fly ash building material.

2. A method for recycling fly ash from waste incineration according to claim 1, characterized in that: In step S1, the water washing system is a three-stage water washing system, which performs three-stage water washing and filter pressing treatment on the waste incineration fly ash, so that the fly ash can be washed with three-stage water to remove soluble chloride salts and reduce the chlorine content in the fly ash.

3. A method for recycling fly ash from waste incineration according to claim 2, characterized in that: In step S1, the wastewater treatment system uses the washing liquid obtained after the filter press treatment in a three-stage countercurrent cycle and then performs salt separation and purification treatment to generate income for the generated industrial salt by-product.

4. A method for recycling fly ash from waste incineration according to claim 2, characterized in that: At the same time, during the three-stage water washing process of the waste incineration fly ash, a set proportion of heavy metal stabilizer is added to the water washing system to treat the heavy metals contained in the waste incineration fly ash.

5. A method for recycling fly ash from waste incineration according to claim 1, characterized in that: In step S2, when the washed fly ash is dried by the horizontal paddle dryer, exhaust gas is generated; at the same time, in step S3, when the dried material is thermally decomposed by the low-temperature thermal decomposition furnace, exhaust gas is also generated; the exhaust gas generated in steps S2 and S3 is extracted by the induced draft fan and transported to the flue gas treatment system to treat the exhaust gas.

6. A method for recycling fly ash from waste incineration according to claim 5, characterized in that: The flue gas treatment system includes a bag dust collector, a spray tower and an activated carbon adsorber in sequence. The exhaust gas is drawn into the bag dust collector, the spray tower and the activated carbon adsorber in sequence by the induced draft fan for dust removal and purification. Finally, the purified exhaust gas is transported to the incinerator for coordinated treatment.

7. A method for recycling fly ash from waste incineration according to claim 6, characterized in that: After the particulate matter is removed from the tail gas by the bag filter, secondary tail gas is obtained, and then the secondary tail gas is re-extracted into the water-washed fly ash buffer bin by using an induced draft fan.

8. A method for recycling fly ash from waste incineration according to claim 1, characterized in that: In step S3, a set proportion of dioxin detoxification chelating agent is added into the low-temperature thermal decomposition furnace to degrade the dioxin content in the fly ash.

Images