Self-detoxification process in household garbage incineration fly ash incineration power plant

Abstract

The invention discloses a self-detoxification process in a household garbage incineration fly ash incineration power plant, which comprises the following steps of: removing chlorine salt and water-soluble and acid-extracted heavy metals in fly ash in a multi-stage countercurrent mode of combining two-stage water washing, acid pickling and water washing to obtain dechlorinated and heavy metal-removed fly ash wet slag; the fly ash is compatible with high-calorific-value general industrial solid waste or aged low-water-content high-calorific-value household garbage, and a fly ash derived fuel rod is pressed; and secondary incineration is carried out through cooperation of an incineration system in the household garbage incineration power plant, so that dioxin detoxification of the fly ash is completed. According to the technology, existing equipment and resources of a waste incineration plant are fully utilized for carrying out in-site fly ash disposal, the fly ash resource utilization cost is saved, the problem of fly ash resource utilization product disposal is solved, and great social benefits are achieved.

Description

Technical Field

[0001] The invention relates to the field of engineering technology, and in particular to a self-detoxification process in a domestic waste incineration fly ash incineration power plant. Background Art

[0002] Domestic waste incineration fly ash (referred to as "fly ash") comes from fine particles obtained from the flue gas collection system of waste incineration power plants. Taking mechanical grate furnace fly ash as an example, the main components of fly ash are calcium silicon sodium potassium iron aluminum magnesium salts, among which CaO has the highest mass fraction, which is 20.4-37.9%; the chlorine content of fly ash is also as high as 25%, of which soluble chlorine accounts for 40.6-83.9% of the total chlorine. Different from the incineration slag of general industrial solid waste, fly ash is a hazardous waste (HW18), and its main harmful substances are heavy metals (Zn, Pb, Cu, Cr, Cd, Ni and Hg, etc.) and dioxin-like organic compounds.

[0003] The resource utilization of fly ash is the general trend, and its application methods mainly include water washing-cement kiln co-treatment, high-temperature melting, sintering and low-temperature thermal decomposition. Among them, only water washing-cement kiln co-treatment has relatively complete standards and technical specifications, but the application and promotion of this technology is still limited by cement production capacity and regional cement kiln construction conditions. For areas without cement production lines in the surrounding areas, it is impossible to rely on cement kilns for fly ash treatment at low cost; low-temperature thermal decomposition technology can effectively remove dioxins, but it does not reduce the total amount of heavy metals in fly ash, and its building materials products still have heavy metal risks, which affects the enthusiasm of downstream market applications; in addition, the introduction of large-scale new equipment such as high-temperature melting furnaces and sintering furnaces for fly ash resource treatment has high investment costs and high energy consumption, coupled with the cost of transporting and disposing of fly ash, resulting in excessively high comprehensive treatment costs. In summary, the resource utilization methods of fly ash and the destination of resource utilization products are still the pain points and bottlenecks of the environmental protection industry.

[0004] It can be seen that the existing technology still needs to be improved and enhanced. Summary of the invention

[0005] In view of the shortcomings of the above-mentioned prior art, such as the need to rely on external disposal facilities, the high risk of product chlorine and heavy metals, and the high disposal cost, the purpose of the present invention is to provide a self-detoxification process in a domestic waste incineration fly ash incineration power plant, which is used to solve the problems of high fly ash treatment cost and difficult fly ash disposal in the prior art.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a self-detoxification process for incineration power plants of fly ash from incineration of domestic waste, comprising the following steps: S1. After the fly ash from incineration of domestic waste enters the site, it is ground to less than 100 mesh, transported and delivered to a water washing unit after metering, and the mud-water mixture is subjected to solid-liquid separation after the first and second level water washing of the water washing unit to obtain wet residue of water-washed dechlorinated fly ash and first and second level water washing filtrate; S2. The wet residue of water-washed dechlorinated fly ash is transported to a pickling tank, and after pickling with a pickling extract, the mud-water mixture is subjected to solid-liquid separation to obtain wet residue of pickled fly ash and pickling filtrate; S3. The wet residue of pickled fly ash is washed again, and the pre-treated residue is obtained after solid-liquid separation. The dechlorinated and heavy metal-free fly ash wet slag and the tertiary washing filtrate; S4. The pretreated dechlorinated and heavy metal-free fly ash wet slag is evenly mixed with general industrial solid waste with high calorific value or aged domestic waste with low moisture content and high calorific value, crushed, humidified and pressed to form fly ash-derived fuel rods; S5. The fly ash-derived fuel rods are evenly mixed with the garbage raw materials in the domestic garbage pit, and the existing incineration system of the garbage incineration plant is used for coordinated secondary incineration to complete the dioxin detoxification of the fly ash; S6. The slag obtained from the secondary incineration is subjected to solid waste identification and hazardous waste identification. After meeting the general industrial solid waste detection requirements, it enters the supporting incineration slag resource utilization center for resource utilization.

[0007] In one embodiment of the present invention, in step S1, the liquid-to-solid ratio of the domestic waste incineration fly ash water washing is 2-5:1, the water washing stirring time is 15-30min, the water washing liquid of the secondary water washing is derived from the tertiary water washing filtrate in step S3, and the secondary water washing filtrate is recovered and used as the primary water washing liquid.

[0008] In one embodiment of the present invention, in steps S1-S3, a three-stage countercurrent water washing-acid washing method is used to dechlorinate and remove heavy metals from fly ash; the first-stage water washing filtrate is evaporated and crystallized to obtain mixed salt, or after removing heavy metals and hardness ions such as calcium and magnesium, salt is evaporated and separated using the MVR method, and the condensed water is used as a water washing replenisher to continue washing the next batch of fly ash; the acid washing waste liquid is treated with a coagulation and precipitation agent, and the precipitate is dehydrated to obtain a heavy metal residue, which is further evaporated and dried and then incorporated into a hazardous waste disposal terminal for treatment, and the remaining liquid is discharged into the leachate treatment system of the municipal solid waste incineration power plant for coordinated treatment.

[0009] In one embodiment of the present invention, in step S2, the pickling leaching solution is one or more of acetic acid, citric acid, nitric acid, sulfuric acid and phosphoric acid, the acid concentration is 1-5 mol / L, the liquid-to-solid ratio is 2-5:1, and the pickling stirring time is 30-60 min.

[0010] In one embodiment of the present invention, in step S3, the soluble chlorine content of the pretreated fly ash wet residue is less than 1%, the moisture content is 40%-60%, and the concentrations of heavy metals lead, zinc, copper, cadmium, chromium, nickel, arsenic, and manganese in the leachate are lower than the limit requirements of HJ 1134-2020.

[0011] In one embodiment of the present invention, in step S4, the fly ash derived fuel rod is made of pre-treated dechlorinated and heavy metal-free fly ash wet residue as the main material, supplemented by one or more other solid wastes with low chlorine and low heavy metal content such as waste textiles, waste paper, waste wood chips, etc., and is pressed by a pulverizer, a mixer and a molding machine.

[0012] In one embodiment of the present invention, in step S4, the fly ash derived fuel rods are pressed at a pressure of 10-20 MPa and are in the shape of rods, cakes or spheres, with an average particle size of 1-5 cm, a moisture content of 15-30%, and a calorific value of 7.5-12 MJ / Kg.

[0013] In one embodiment of the present invention, in steps S5-S6, the fly ash derived fuel rods and domestic waste put into the waste incinerator are controlled to be uniformly mixed and co-combusted, and the blending ratio of the fly ash derived fuel rods is not higher than 5%.

[0014] The self-detoxification process of the domestic waste incineration fly ash incineration power plant of the present invention has the following beneficial effects:

[0015] 1. Make full use of the existing equipment (incineration system, leachate treatment system, flue gas treatment system, etc.) and various resources (combustible domestic waste, general industrial solid waste, hot steam, etc.) of the waste incineration plant to dispose of fly ash on site, saving the investment cost of large new equipment and the transportation cost of external disposal;

[0016] 2. Through "water washing-acid washing", the chloride salts and water-soluble and acid-extractable heavy metals in the fly ash are removed, which effectively avoids the continuous accumulation and enrichment of chloride ions and heavy metals in the system to cause a "dead cycle". The chlorine content of the fly ash after pretreatment is extremely low, which cuts off the possibility of dioxin regeneration during the incineration of fly ash. At the same time, under the high temperature environment of the furnace, the dioxins in the fly ash can be fully decomposed. Even in the most unfavorable conditions, the flue gas treatment system in the original incineration site can effectively provide a bottom line, and the chemical state of the remaining heavy metals is further solidified and stabilized;

[0017] 3. Two-stage water washing removes most of the soluble chlorine, and effectively washes out lead and zinc, reducing acid loss in the pickling stage; pickling strengthens heavy metal removal and further removes insoluble chlorides; water washing after pickling prevents soluble salts and heavy metal impurities in the pickling filter cake from entering the thermal decomposition process, improves thermal treatment stability, and further reduces the amount of heavy metal leaching from fly ash after pretreatment;

[0018] 4. Fly ash derived fuel rod RDF is easy to press, flexible in proportion, and has low molding strength requirements. The moisture content of molded fly ash derived fuel rods is about 20%. They are made by mixing and pressing metal fly ash wet residue with a moisture content of 40-50% and general industrial solid waste with a low moisture content. Membrane concentrate can be used for synergistic humidity adjustment to reduce the pressure of the nanofiltration concentrate reduction system;

[0019] 5. This process has little impact on the existing waste incineration system and flue gas treatment system, and there is no need to modify the production line. It can be compatible with the waste incineration power plant by adding a fly ash pretreatment process at the front end, realizing a closed-loop treatment of pollutants on site. It is suitable for in-plant construction of incineration power plants with a fly ash output of 20-50t / d;

[0020] 6. Some fly ash resource utilization products have hidden risks when used as building materials (there is a risk of re-dissolution without dechlorination and heavy metal reduction), and downstream companies are less willing to accept them. The chlorine content and total amount of heavy metals in the terminal product (slag) of this process are reduced, and the environmental risk is lower; this process solves the problem of high cost of fly ash resource utilization in waste incineration power plants and poor sales of terminal products. It is a fly ash resource utilization technology with great development potential and significant social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 The schematic diagram of the process of self-detoxification in a power plant for incinerating fly ash from domestic waste provided by the present invention is as follows:

[0023] Figure 2 Another schematic flow diagram of the self-detoxification process in a domestic waste incineration fly ash incineration power plant provided by the present invention;

[0024] Figure 3 A schematic diagram of the multi-stage water washing-acid washing countercurrent process provided by the present invention.

[0025] Technical term explanation:

[0026] MVR: Mechanical vapor recompression technology;

[0027] RDF: fly ash derived fuel rods. DETAILED DESCRIPTION

[0028] The present invention provides a self-detoxification process in a domestic waste incineration fly ash incineration power plant. In order to make the purpose, technical scheme and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples.

[0029] In the description of the present invention, it should be understood that the terms "up, down, left, right, etc." indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and should not be understood as limiting the present invention; in addition, the terms "installation" and "connection" should be understood in a broad sense, and those skilled in the art can understand the specific meanings of the above terms in the present invention according to specific circumstances.

[0030] Embodiment 1

[0031] See also Figures 1 to 3 The present invention provides a self-detoxification process for incineration power plants of fly ash from incineration of domestic waste, comprising the following steps: S1. After the fly ash from incineration of domestic waste enters the site, it is ground to less than 100 meshes, transported and delivered to a water washing unit after metering, and the mud-water mixture is subjected to solid-liquid separation after the primary and secondary water washing of the water washing unit to obtain water-washed dechlorinated fly ash wet residue and primary and secondary water washing filtrates; S2. The water-washed dechlorinated fly ash wet residue is transported to a pickling tank, and after pickling with a pickling leaching solution, the mud-water mixture is subjected to solid-liquid separation to obtain pickled fly ash wet residue and pickling filtrate; S3. The pickled fly ash wet residue is washed again, and the pre-treated dechlorinated and heavy metal-free residue is obtained after solid-liquid separation. Fly ash wet slag and tertiary water washing filtrate; S4. The pre-treated dechlorinated and heavy metal-free fly ash wet slag is evenly mixed with general industrial solid waste with high calorific value or aged low-moisture content and high-calorific value domestic waste to form fly ash-derived fuel rods; S5. The fly ash-derived fuel rods are evenly mixed with the garbage raw materials in the domestic garbage pit, and the existing incineration system of the garbage incineration plant is used to coordinate the secondary incineration to complete the dioxin detoxification of the fly ash; S6. The slag obtained from the secondary incineration is subjected to solid waste identification and hazardous waste identification. After meeting the general industrial solid waste detection requirements, it enters the supporting incineration slag resource utilization center for resource utilization.

[0032] In steps S1-S3, the liquid-to-solid ratio of the domestic waste incineration fly ash washing is 2-5:1, the washing stirring time is 15-30min, the two-stage washing liquid is derived from the three-stage washing filtrate in step S3, and the two-stage washing filtrate is recycled as the first-stage washing liquid. For details, please refer to Figure 3, the fly ash is pretreated by a three-stage countercurrent water washing-acid washing method, including the following steps: the fly ash is washed with water for 15 minutes at a liquid-to-solid ratio of 2:1, and the fly ash is acid washed with sulfuric acid at a concentration of 1 mol / L at a liquid-to-solid ratio of 2:1 for 30 minutes. After water washing / acid washing, solid-liquid separation is performed. At the start-up, the first batch of water washing stages are all washed with water. In addition to the third-stage water washing, the collected water washing filtrate is used for water washing again. The acid washing liquid is reused 3-5 times depending on the situation.

[0033] In steps S1-S3, a three-stage countercurrent water washing-acid washing method is used to dechlorinate and remove heavy metals from fly ash; the first-stage water washing liquid is evaporated and crystallized to obtain mixed salt, or after removing heavy metals and hardness ions such as calcium and magnesium, salt is evaporated and separated using the MVR method, and the condensed water is used as a water washing replenisher to continue washing the next batch of fly ash; the acid washing waste liquid is treated with a coagulation and precipitation agent, and the precipitate is dehydrated to obtain a heavy metal residue, which is further evaporated and dried and then incorporated into a hazardous waste disposal terminal for treatment, and the remaining liquid is discharged into the leachate treatment system of the municipal solid waste incineration power plant for coordinated treatment.

[0034] In step S4, the fly ash derived fuel rod is made of pretreated dechlorinated and deheavy metal-free fly ash wet residue as a main material, and is pressed by a pulverizer, a mixer and a molding machine. The fly ash derived fuel rod has a pressing pressure of 10-20 MPa and is in the shape of a rod, a cake or a sphere, with an average particle size of 1-5 cm, a moisture content of 15-30%, and a calorific value of 7.5-12 MJ / Kg.

[0035] In steps S5-S6, the fly ash derived fuel rods and domestic waste put into the waste incinerator are controlled to be uniformly mixed and co-combusted, and the blending ratio of the fly ash derived fuel rods is not higher than 5%.

[0036] In this embodiment, the moisture content of the pre-treated fly ash wet residue after solid-liquid separation is about 40%. The soluble chlorine content of the ash leachate after the original ash, primary water washing, secondary water washing, acid washing and tertiary water washing (pre-treatment) is 23959mg / L, 7255mg / L, 3779mg / L, 405mg / L and 156mg / L respectively, that is, after pre-treatment by a combination of three-stage countercurrent water washing and acid washing, the soluble chlorine of 23.959% of the original ash is reduced to 0.156%. The heavy metal leaching concentration is shown in Table 1 below.

[0037] Table 1 Heavy metal leaching concentration (unit: mg / L)

[0038]

[0039] Embodiment 2

[0040] The fly ash was washed with water for 15 minutes at a liquid-to-solid ratio of 2:1. After two-stage water washing, three different concentrations of acid wash solutions were used to extract heavy metals from the fly ash. The acid wash liquid-to-solid ratio was 2:1 and the acid wash time was 30 minutes. The heavy metal content in the solid phase was analyzed. The removal rate (η) was calculated as follows:

[0041] η=(m1×c1-m2×c2) / (m1×c1)

[0042] Among them, m1 and m2 are the fly ash masses before and after pickling, kg;

[0043] c1 and c2 are the heavy metal concentrations in fly ash before and after pickling, mg / kg.

[0044] The pickling heavy metal removal rate (%) is shown in Table 2 below:

[0045] Table 2 Acid washing enhanced heavy metal removal effect (removal rate unit: %)

[0046]

[0047]

[0048] Embodiment 3

[0049] like Figure 2 The figure shows a self-detoxification process flow chart of fly ash from incineration of domestic waste in an incineration power plant. After the fly ash from incineration of domestic waste is collected, it is transported to the water washing-acid washing system for dechlorination and heavy metal removal to obtain pre-treated dechlorinated and heavy metal-free fly ash wet slag. The pre-treated dechlorinated and heavy metal-free fly ash wet slag is used as the main material and mixed with general industrial solid waste, auxiliary materials, etc., and then pressed into fly ash derived fuel rods RDF, and sent to the material pit to mix with domestic waste, and then co-combusted using the existing incineration system of the waste incineration plant.

[0050] Among them, after the pickling waste liquid is treated by the pickling liquid treatment system, the remaining liquid is introduced into the existing leachate treatment system in the domestic waste incineration power plant, and the heavy metal residue is further dried; the water washing liquid enters the salt evaporation system for treatment to obtain mixed salt, which can be further selected through MVR salt separation to obtain industrial sodium salt and potassium salt. The hot steam used in this process comes from the waste heat of steam generated by the incineration system.

[0051] Embodiment 4

[0052] The fly ash was dechlorinated and de-heavy metalized by a three-stage water-acid washing method. The wet slag was mixed with waste fabrics and wood chips at a mass ratio of 4:1:1 to prepare 2cm round cake-shaped fly ash-derived fuel rods RDF at 15MPa. The slag was fully incinerated at 1000℃. The incineration slag was identified as solid waste and hazardous waste, and the dioxin content and heavy metal leaching concentration were determined.

[0053] In this embodiment, water washing is carried out for 15 minutes in a liquid-solid ratio of 2:1, and the pickling solution is pickled for 30 minutes with 2mol / L mixed acid. The mass loss of fly ash after water washing-pickling is 40.24%. After dechlorination and heavy metal removal, the soluble chlorine content of the ash is 0.157%, and the heavy metals lead, zinc, copper, cadmium, chromium, nickel, arsenic and manganese in the leaching solution meet the requirements of HJ 1134-2020 standard. After secondary incineration, the RDF thermal loss rate is 56.46%, and the dioxins in the ash are far less than 50ng-TEQ / kg. After solid waste identification (GB34330-2017) and hazardous waste identification (GB 5085-2007), it meets the general industrial solid waste requirements.

[0054] In summary, the self-detoxification process of the incineration power plant of fly ash from the incineration of domestic waste of the present invention makes full use of the existing equipment and resources of the waste incineration power plant to dispose of fly ash on site, saving the cost of fly ash resource utilization; the chloride salts and water-soluble and acid-extractable heavy metals in the fly ash are removed by "water washing-acid washing", effectively avoiding the continuous accumulation and enrichment of chloride ions and heavy metals in the system, and at the same time, under the high temperature environment of the furnace temperature, the dioxins in the fly ash can be fully decomposed, and the chemical state of the remaining heavy metals is further solidified and stabilized; the environmental risk of the fly ash product after treatment is low, and the slag enters the supporting slag yard for resource utilization, which solves the problem of fly ash disposal and has significant social benefits.

[0055] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0056] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the protection scope of the present invention.

Claims

1. A self-detoxification process for incineration of fly ash from domestic waste incineration power plant, characterized in that: The steps include: S1. After the fly ash from the incineration of domestic waste enters the site, it is ground into smaller than 100 meshes, transported to the water washing unit after metering, and the mud-water mixture is subjected to solid-liquid separation after the primary and secondary water washing of the water washing unit to obtain the wet residue of the washed dechlorinated fly ash and the primary and secondary water washing filtrate; S2. The wet residue of the dechlorinated fly ash is transported to a pickling tank, and after being pickled with a pickling extract, the mud-water mixture is subjected to solid-liquid separation to obtain the pickled fly ash wet residue and the pickling filtrate; S3. The pickled fly ash wet residue is washed again, and the pre-treated dechlorinated and heavy metal-free fly ash wet residue and the tertiary washing filtrate are obtained after solid-liquid separation; S4. uniformly mixing, crushing, adjusting humidity and pressing the pretreated dechlorinated and deheavy metal-free fly ash wet residue with high calorific value general industrial solid waste or aged low moisture content high calorific value domestic waste to produce fly ash derived fuel rods; S5. Evenly blend the fly ash-derived fuel rods with the garbage raw materials in the domestic garbage pit, and use the existing incineration system of the garbage incineration plant to carry out secondary incineration to complete the dioxin detoxification of the fly ash; S6. The slag obtained from the secondary incineration is identified as solid waste and hazardous waste. Once it meets the general industrial solid waste detection requirements, it enters the supporting incineration slag resource utilization center for resource utilization.

2. The self-detoxification process in a domestic waste incineration fly ash incineration power plant according to claim 1 is characterized in that: In step S1, the liquid-to-solid ratio of the domestic waste incineration fly ash washing is 2-5:1, the washing stirring time is 15-30min, the washing liquid of the secondary washing is derived from the tertiary washing filtrate in step S3, and the secondary washing filtrate is recovered and used as the primary washing liquid.

3. The self-detoxification process in a domestic waste incineration fly ash incineration power plant according to claim 2 is characterized in that: In steps S1-S3, a three-stage countercurrent water washing-acid washing method is used to dechlorinate and remove heavy metals from fly ash; the first-stage water washing filtrate is evaporated and crystallized to obtain mixed salt, or after removing heavy metals and hardness ions such as calcium and magnesium, salt is evaporated and separated using the MVR method, and the condensed water is used as a water washing replenisher to continue washing the next batch of fly ash; the acid washing waste liquid is treated with a coagulation and precipitation agent, and the precipitate is dehydrated to obtain a heavy metal residue, which is further evaporated and dried and then incorporated into a hazardous waste disposal terminal for treatment, and the remaining liquid is discharged into the leachate treatment system of the municipal solid waste incineration power plant for coordinated treatment.

4. The self-detoxification process in a domestic waste incineration fly ash incineration power plant according to claim 1 is characterized in that: In step S2, the pickling leaching solution is one or more of acetic acid, citric acid, nitric acid, sulfuric acid and phosphoric acid, the acid concentration is 1-5 mol / L, the liquid-to-solid ratio is 2-5:1, and the pickling stirring time is 30-60 min.

5. The self-detoxification process in a domestic waste incineration fly ash incineration power plant according to claim 1 is characterized in that: In step S3, the soluble chlorine content of the pretreated fly ash wet residue is less than 1%, the moisture content is 40%-60%, and the concentrations of heavy metals lead, zinc, copper, cadmium, chromium, nickel, arsenic, and manganese in the leachate are lower than the limit requirements of HJ 1134-2020.

6. The self-detoxification process in a domestic waste incineration fly ash incineration power plant according to claim 1 is characterized in that: In step S4, the fly ash derived fuel rod is made of pretreated fly ash wet residue as the main material, supplemented by one or more other solid wastes with low chlorine and low heavy metal content such as waste textiles, waste paper, waste wood chips, etc., and is pressed by a pulverizer, a mixer and a molding machine.

7. The self-detoxification process in a domestic waste incineration fly ash incineration power plant according to claim 1 is characterized in that: The fly ash derived fuel rod has a pressing pressure of 10-20 MPa and is in the shape of a rod, a cake or a sphere, with an average particle size of 1-5 cm, a moisture content of 15-30%, and a calorific value of 7.5-12 MJ / Kg.

8. The self-detoxification process in a domestic waste incineration fly ash incineration power plant according to claim 1 is characterized in that: In steps S5-S6, the fly ash derived fuel rods and domestic waste put into the waste incinerator are controlled to be uniformly mixed and co-combusted, and the blending ratio of the fly ash derived fuel rods is not higher than 5%.

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