Method for treating household garbage incineration fly ash and preparing modified mineral powder and modified mineral powder

Abstract

The invention discloses a method for treating household garbage incineration fly ash and preparing modified mineral powder and the modified mineral powder. The method comprises the following steps that S1, the household garbage incineration fly ash is subjected to low-temperature detoxification treatment, secondary countercurrent washing treatment and mechanochemical method treatment, and detoxified fly ash is obtained; and S2, drying the detoxified fly ash, and stirring and mixing the dried detoxified fly ash with the superfine slag powder to obtain the fly ash modified mineral powder. The method can solve the problems of degradation of dioxin in the fly ash and unqualified leaching of heavy metals, then the detoxified fly ash is compounded with the superfine slag powder, the excitation effect of fly ash minerals is fully played, the performance of mineral powder products is improved, meanwhile, the household garbage incineration fly ash is fully utilized, waste is turned into wealth, and the method is suitable for industrial production. The method has important significance for realizing'zero landfill of fly ash 'and promoting'waste-free city' construction.

Description

Technical Field

[0001] The present invention relates to the field of hazardous waste treatment and resource utilization, and in particular to a method for treating fly ash from the incineration of domestic waste and preparing modified mineral powder, and the modified mineral powder. Background Art

[0002] Fly ash from the incineration of municipal solid waste (hereinafter referred to as "fly ash") is a by-product of the incineration of urban municipal solid waste. It contains soluble salts (mainly chlorides), heavy metals (such as Cd, Zn, Pb, Cu, and Hg), and dioxins, and is listed as Class HW18 hazardous waste in the "National List of Hazardous Wastes".

[0003] With the improvement of living standards, the amount of fly ash produced in my country is also increasing year by year; the current treatment method of fly ash is mainly "stabilization solidification + landfill". In recent years, due to the limited capacity of landfill areas, fly ash faces the problem of shortage of land resources, and the heavy metals and dioxins and other highly toxic organic pollutants in fly ash pose a threat to human health and the ecological environment, and the risk of landfill is prominent. At present, the harmless disposal technology of fly ash is diverse, and can be generally divided into thermal disposal technology and non-thermal disposal technology. Some of these methods are relatively mature and widely used, such as cement or chelating agent solidification, cement kiln co-disposal, high-temperature melting technology, sintering disposal technology, hydrothermal treatment technology, low-temperature pyrolysis technology, water washing technology, etc. Fly ash has usable components such as CaO, SiO2, Al2O3, NaCl, KCl, etc., and has the potential for resource utilization. Detoxifying fly ash and then utilizing it as a resource is the inevitable trend and the best way to dispose and utilize fly ash in the future.

[0004] At present, the resource utilization of fly ash from the incineration of domestic waste at home and abroad is mainly concentrated in the field of civil engineering, mainly based on high-temperature melting and high-temperature sintering technologies, producing high-temperature products such as glass particles, cement products, and sintered ceramsite. High-temperature disposal can effectively dispose of heavy metals and dioxins in fly ash, but it is energy-intensive, high-emission, high-investment, and high-production cost. Low-temperature detoxification and building material utilization technologies are also gradually gaining attention. The existing low-temperature detoxification technology for fly ash cannot effectively solve the problem of excessive heavy metal leaching. The detoxified fly ash has low activity and a narrow application scenario. Summary of the invention

[0005] In view of the industry difficulties in the disposal and utilization of fly ash from the incineration of domestic waste in the prior art, the purpose of the present invention is to provide a method for treating fly ash from the incineration of domestic waste and preparing modified mineral powder, and the modified mineral powder, which can solve the problems of dioxin degradation and unqualified heavy metal leaching in fly ash, and then compound the detoxified fly ash with slag micropowder to give full play to the stimulating effect of fly ash minerals, so as to achieve the goal of improving the performance of the mineral powder product while making full use of the fly ash from the incineration of domestic waste, turning waste into treasure, which is of great significance for achieving "zero landfill of fly ash" and promoting the construction of "waste-free city".

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a method for treating fly ash from the incineration of domestic waste and preparing modified mineral powder, comprising the following steps:

[0008] S1, subjecting the fly ash from the incineration of domestic waste to low-temperature detoxification treatment, secondary countercurrent water washing treatment and mechanochemical treatment to obtain detoxified fly ash;

[0009] S2, drying the detoxified fly ash, and then mixing the dried detoxified fly ash with slag powder to obtain fly ash modified mineral powder.

[0010] Preferably, in the step S1, in the low-temperature detoxification treatment, the raw fly ash from the incineration of domestic waste is subjected to pyrolysis treatment at 340 to 460° C. under anaerobic conditions in an electrically heated tubular furnace for 30 to 60 minutes.

[0011] Preferably, after the low-temperature detoxification treatment, the residual dioxin toxicity equivalent in the fly ash is less than 50 ng-TEQ / kg.

[0012] Preferably, in the step S1, in the secondary countercurrent water washing treatment, the fly ash after the low-temperature detoxification treatment is cooled, enters the primary water washing tank, is washed with water at a water-ash ratio of 2 to 4:1, and after 30 to 60 minutes, is filtered through a diaphragm filter press, and then is transported to the secondary water washing tank by screw conveyor, is washed with water at a water-ash ratio of 2 to 4:1, and after 30 to 60 minutes, is filtered through a diaphragm filter press to obtain a fly ash water-washed filter cake.

[0013] Preferably, in step S1, in the mechanochemical treatment, the fly ash washed filter cake after the secondary countercurrent water washing treatment enters a ball mill, an inorganic salt admixture is added, and wet ball milling is performed at a water-cement ratio of 2 to 4:1. After ball milling for 0.5 to 3 hours, it is filtered through a diaphragm filter press to obtain detoxified fly ash.

[0014] Preferably, the inorganic salt additive is selected from one or more of sodium hydroxide, calcium hydroxide, and sodium phosphate;

[0015] The addition amount of the inorganic salt admixture is 0.5-5% of the mass of the fly ash water-washed filter cake.

[0016] Preferably, in step S2, the moisture content of the dried detoxified fly ash is ≤3wt%, the average particle size is 3-30μm, and the chloride ion content is ≤1wt%.

[0017] Preferably, in the step S2, in the fly ash modified mineral powder, the content of the dried detoxified fly ash is 1-10wt%, and the content of the slag powder is 90-99wt%.

[0018] The second aspect of the present invention provides a fly ash modified mineral powder, which is prepared by the method for treating fly ash from incineration of domestic waste and preparing modified mineral powder as described in the first aspect of the present invention, and the properties of the fly ash modified mineral powder are as follows: 7-day activity index>80%, 28-day activity index>100%, specific surface area≥400m 2 / kg, sulfur trioxide content ≤4.0%, chloride ion content ≤0.06%, fluidity ratio ≥95%.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention adopts a low-temperature detoxification-water washing dechlorination-mechanical chemical treatment method to treat fly ash from the incineration of domestic waste, thereby achieving the purpose of low-cost degradation of dioxins and stabilization of heavy metals;

[0021] 2. The detoxified fly ash treated by the present invention has high activity, and can be compounded with slag powder to obtain modified ore powder with high early strength, which meets the technical indicators of S95 grade ore powder in GB / T18046 "Granulated blast furnace slag powder for cement and concrete";

[0022] 3. The present invention can solve the problem of fly ash dioxin degradation and unqualified heavy metal leaching, and effectively meet the pollution control requirements of fly ash resource utilization in HJ1134;

[0023] 4. The present invention compounds the detoxified fly ash after drying with slag powder, gives full play to the stimulating effect of fly ash minerals, promotes the increase of CSH content in the early stage of hydration of modified mineral powder, and has a significant early strength promoting effect; while improving the performance of mineral powder products, it fully utilizes the fly ash from the incineration of domestic waste, turning waste into treasure, making it a high value-added resource, which is of great significance for achieving "zero landfill of fly ash" and promoting the construction of "waste-free city". DETAILED DESCRIPTION

[0024] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form.

[0025] The present invention discloses a method for treating fly ash from incineration of domestic waste and preparing modified mineral powder, comprising the following steps:

[0026] S1, subjecting the fly ash from the incineration of domestic waste to low-temperature detoxification treatment, secondary countercurrent water washing treatment and mechanochemical treatment to obtain detoxified fly ash;

[0027] This step is mainly to treat the fly ash from the incineration of domestic waste, which specifically includes three parts, namely, low-temperature detoxification treatment, secondary countercurrent water washing treatment and mechanochemical treatment;

[0028] During the low-temperature detoxification treatment process, the raw ash from the incineration of domestic waste is pyrolyzed in an electric heating tubular furnace at 350-450°C and anaerobic (the oxygen content in the furnace is controlled below 1%) for 30-60 minutes. The dioxin toxicity equivalent of the residual fly ash is <50ng-TEQ / kg, which meets the technical requirements of HJ 1134-2020 "Technical Specifications for Pollution Control of Fly Ash from Incineration of Domestic Waste (Trial)".

[0029] During the secondary countercurrent water washing process, the fly ash after low-temperature detoxification treatment is cooled and then enters the primary water washing tank, where it is washed with water at a water-ash ratio of 2 to 4:1. After 30 to 60 minutes, it is filtered through a diaphragm filter press; it is then transported to the secondary water washing tank by screw conveyor, where it is washed with water at a water-ash ratio of 2 to 4:1. After 30 to 60 minutes, it is filtered through a diaphragm filter press to obtain a fly ash water-washed filter cake.

[0030] In the mechanochemical treatment process, the fly ash water-washed filter cake after the secondary countercurrent water washing treatment enters the ball mill, and an inorganic salt admixture is added, and wet ball milling is performed according to a water-cement ratio of 2 to 4:1. After ball milling for 0.5 to 3 hours, it is filtered through a diaphragm filter press to obtain detoxified fly ash. In the mechanochemical treatment process, the inorganic salt admixture can be selected from one or more of sodium hydroxide, calcium hydroxide, and sodium phosphate, and the addition amount is 0.5 to 5% of the mass of the fly ash water-washed filter cake.

[0031] In this step, the detoxified fly ash is prepared into a leaching solution according to the method of HJ557 "Horizontal Oscillation Method for Toxicity Leaching of Solid Waste", in which the leaching concentration of heavy metals does not exceed the maximum allowable emission concentration limit specified in GB8978, complies with the provisions of HJ1134 "Technical Specifications for Pollution Control of Fly Ash from Incineration of Municipal Waste (Trial)", and can be used as a raw material for building materials.

[0032] S2, drying the detoxified fly ash, and then mixing the dried detoxified fly ash with slag powder to obtain fly ash modified mineral powder.

[0033] In this step, fly ash modified mineral powder is prepared by compounding detoxified fly ash and slag powder. Specifically, the detoxified fly ash is dried to ensure that the moisture content of the dried detoxified fly ash is ≤3%, the average particle size is 3-30 μm, and the chloride ion content is ≤1%. The dried detoxified fly ash and slag powder are weighed and stirred to obtain fly ash modified mineral powder; wherein the content of the dried detoxified fly ash is 1-10wt%, and the content of the slag powder is 90-99wt%.

[0034] In this step, the detoxified fly ash after drying is compounded with slag powder to give full play to the stimulating effect of fly ash minerals, promote the increase of CSH content in the early stage of hydration of modified mineral powder, and have a significant early strength promoting effect. While improving the performance of mineral powder products, the fly ash from the incineration of domestic waste is fully utilized to turn waste into treasure, and finally obtain highly active fly ash modified mineral powder.

[0035] The fly ash modified ore powder prepared above has a 7-day activity index of >80%, a 28-day activity index of >100%, and a specific surface area of ​​≥400m 2 / kg, sulfur trioxide content ≤4.0%, chloride ion content ≤0.06%, fluidity ratio ≥95%. The fly ash modified mineral powder of the present invention has a significantly improved 7-day and 28-day activity index compared with ordinary mineral powder, and when it can be used in ready-mixed concrete, it is better in durability indicators such as carbonization resistance, frost resistance, and chloride ion penetration resistance, and can improve the early shrinkage crack performance of hardened concrete.

[0036] The oily wastewater treatment sludge sintered brick and its preparation method of the present invention are further introduced in conjunction with specific examples below;

[0037] Example 1

[0038] This embodiment is a low-temperature detoxification treatment, secondary countercurrent water washing treatment and mechanochemical treatment process of fly ash from the incineration of domestic waste, which is specifically as follows:

[0039] The fly ash raw ash from the incineration of domestic waste is pyrolyzed in an electric heating tubular furnace at 350°C ± 10°C under anaerobic conditions (the oxygen content in the furnace is controlled below 0.5%) for 30 minutes, and then subjected to secondary countercurrent water washing (water-ash ratio of 2.5:1, water washing for 35 minutes) to obtain a fly ash water-washed filter cake; the fly ash water-washed filter cake after the secondary water washing is wet ball milled, wherein the amount of inorganic salt admixture added is 1.0% of the mass of the fly ash water-washed filter cake (sodium phosphate is selected as the inorganic salt admixture), the water-ash ratio is 2.5:1, and the ball milling is performed for 45 minutes to obtain the detoxified fly ash;

[0040] The detoxified fly ash after the above treatment was sampled and tested. The results are shown in Tables 1, 2 and 3. The chloride ion content of the detoxified fly ash is 0.71%, the average particle size is 14.5 μm, the dioxin toxicity equivalent is 5.0 ng-TEQ / kg, the heavy metal leaching is qualified, and it meets the pollution control requirements of HJ 1134.

[0041] Example 2

[0042] This embodiment is a low-temperature detoxification treatment, secondary countercurrent water washing treatment and mechanochemical treatment process of fly ash from the incineration of domestic waste, which is specifically as follows:

[0043] The fly ash raw ash from the incineration of domestic waste is pyrolyzed in an electric heating tubular furnace at 400°C ± 10°C under anaerobic conditions (the oxygen content in the furnace is controlled below 0.7%) for 45 minutes, and then subjected to secondary countercurrent water washing (water-ash ratio 3:1, water washing 45 minutes) to obtain a fly ash water-washed filter cake; the fly ash water-washed filter cake after the secondary water washing is wet ball milled, wherein the amount of inorganic salt admixture added is 2.5% of the mass of the fly ash water-washed filter cake (sodium phosphate and sodium hydroxide are selected as inorganic salt admixtures), the water-ash ratio is 3:1, and the detoxified fly ash is obtained after ball milling for 90 minutes;

[0044] The detoxified fly ash after the above treatment was sampled and tested. The results are shown in Table 1, Table 2, and Table 3. The chloride ion content of the detoxified fly ash was 0.65%, the average particle size was 7.4 μm, the dioxin toxicity equivalent was 7.0 ng-TEQ / kg, and the heavy metal leaching was qualified, meeting the pollution control requirements of HJ 1134.

[0045] Example 3

[0046] This embodiment is a low-temperature detoxification treatment, secondary countercurrent water washing treatment and mechanochemical treatment process of fly ash from the incineration of domestic waste, which is specifically as follows:

[0047] The fly ash raw ash from the incineration of domestic waste is pyrolyzed in an electrically heated tubular furnace at 450°C ± 10°C under anaerobic conditions (the oxygen content in the furnace is controlled below 1%) for 60 minutes, and then subjected to secondary countercurrent water washing (water-ash ratio of 3.5:1, water washing for 45 minutes) to obtain a fly ash water-washed filter cake; the fly ash water-washed filter cake after the secondary water washing is wet ball milled, wherein the amount of inorganic salt admixture added is 4.5% of the mass of the fly ash water-washed filter cake (the inorganic salt admixture is one or more of calcium hydroxide and sodium phosphate), the water-ash ratio is 3.5:1, and the ball milling is performed for 120 minutes to obtain the detoxified fly ash;

[0048] The detoxified fly ash after the above treatment was sampled and tested. The results are shown in Tables 1, 2 and 3. The chloride ion content of the detoxified fly ash is 0.55%, the average particle size is 6.5 μm, the dioxin toxicity equivalent is 10.0 ng-TEQ / kg, the heavy metal leaching is qualified, and it meets the pollution control requirements of HJ 1134.

[0049] Table 1

[0050]

[0051] Table 2

[0052]

[0053] Table 3

[0054] Chloride ion content / % Average particle size / μm Domestic waste incineration fly ash 17.5 28.5 Example 1 0.71 14.5 Example 2 0.65 7.4 Example 3 0.55 6.5

[0055] Example 4

[0056] The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder in this embodiment is as follows:

[0057] The detoxified fly ash is obtained by the treatment in Example 1, and the detoxified fly ash is dried. The moisture content of the dried detoxified fly ash is less than 3%. 99wt% of slag powder and 1wt% of detoxified fly ash are weighed separately, and the fly ash modified mineral powder is prepared by mechanical stirring and mixing. The performance of the fly ash modified mineral powder in various aspects is tested with reference to GB18046-2017 "Granulated blast furnace slag powder for cement and concrete". The benchmark cement adopts 42.5 grade silicate cement. The results are shown in Table 4.

[0058] Example 5

[0059] The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder in this embodiment is as follows:

[0060] The detoxified fly ash obtained by the treatment in Example 2 is dried, and the moisture content of the dried detoxified fly ash is less than 3%; 95wt% of slag powder and 5wt% of detoxified fly ash are weighed respectively, and the fly ash modified mineral powder is prepared by mechanical stirring and mixing. The performance of the fly ash modified mineral powder in various aspects is tested with reference to GB18046-2017 "Granulated blast furnace slag powder for cement and concrete". The benchmark cement adopts 42.5 grade silicate cement. The results are shown in Table 4.

[0061] Example 6

[0062] The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder in this embodiment is as follows:

[0063] The detoxified fly ash obtained by the treatment in Example 2 is dried, and the moisture content of the dried detoxified fly ash is less than 3%; 90wt% of slag powder and 10wt% of detoxified fly ash are weighed respectively, and the fly ash modified mineral powder is prepared by mechanical stirring and mixing. The performance of the fly ash modified mineral powder in various aspects is tested with reference to GB18046-2017 "Granulated blast furnace slag powder for cement and concrete". The benchmark cement adopts 42.5 grade silicate cement. The results are shown in Table 4.

[0064] Table 4

[0065]

[0066] Combined with Table 4, it can be seen that the fly ash modified mineral powder prepared in the embodiment of the present invention has a 7-day activity index of 80% to 88%, a 28-day activity index of 107% to 110%, and a density of 2.8 to 3.0 g / cm 3 , with a specific surface area of ​​422 to 426 m 2 / kg, fluidity ratio of 98-101%, sulfur trioxide content of 0.3-1.8%, chloride ion content of 0.01-0.055%, and loss on ignition of 0.8-0.9%; compared with S95 mineral powder, the fly ash modified mineral powder prepared by the present invention has greatly improved 7-day and 28-day activity indexes, and when it can be used in ready-mixed concrete, it is better in durability indicators such as carbonization resistance, frost resistance, and chloride ion penetration resistance, and can improve the early shrinkage crack performance of hardened concrete.

[0067] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for treating fly ash from incineration of domestic waste and preparing modified mineral powder, characterized in that: The following steps are involved: S1, subjecting the fly ash from the incineration of domestic waste to low-temperature detoxification treatment, secondary countercurrent water washing treatment and mechanochemical treatment to obtain detoxified fly ash; S2, drying the detoxified fly ash, and then mixing the dried detoxified fly ash with slag powder to obtain fly ash modified mineral powder.

2. The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder according to claim 1, characterized in that: In the step S1, in the low-temperature detoxification treatment, the fly ash from the incineration of domestic waste is subjected to pyrolysis treatment at 340 to 460° C. under anaerobic conditions for 30 to 60 minutes in an electrically heated tubular furnace.

3. The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder according to claim 2, characterized in that: After the low-temperature detoxification treatment, the residual dioxin toxicity equivalent in the fly ash is less than 50ng-TEQ / kg.

4. The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder according to claim 1, characterized in that: In the step S1, in the secondary countercurrent water washing treatment, the fly ash after the low-temperature detoxification treatment is cooled and then enters the primary water washing tank, where it is washed with water at a water-ash ratio of 2 to 4:

1. After 30 to 60 minutes, it is filtered through a membrane filter press, and then it is spirally conveyed to the secondary water washing tank, where it is washed with water at a water-ash ratio of 2 to 4:

1. After 30 to 60 minutes, it is filtered through a membrane filter press to obtain a fly ash water-washed filter cake.

5. The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder according to claim 1, characterized in that: In the step S1, in the mechanochemical treatment, the fly ash washed filter cake after the secondary countercurrent water washing treatment enters a ball mill, an inorganic salt admixture is added, and wet ball milling is performed at a water-cement ratio of 2 to 4:

1. After ball milling for 0.5 to 3 hours, it is filtered through a membrane filter press to obtain detoxified fly ash.

6. The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder according to claim 5, characterized in that: The inorganic salt additive is selected from one or more of sodium hydroxide, calcium hydroxide, and sodium phosphate; The addition amount of the inorganic salt admixture is 0.5-5% of the mass of the fly ash water-washed filter cake.

7. The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder according to claim 1, characterized in that: In the step S2, the moisture content of the dried detoxified fly ash is ≤3wt%, the average particle size is 3-30μm, and the chloride ion content is ≤1wt%.

8. The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder according to claim 1, characterized in that: In the step S2, in the fly ash modified ore powder, the content of the dried detoxified fly ash is 1-10wt%, and the content of the slag powder is 90-99wt%.

9. A fly ash modified mineral powder, characterized in that: The method for treating fly ash from incineration of domestic waste and preparing modified mineral powder as claimed in any one of claims 1 to 8 is adopted, and the properties of the fly ash modified mineral powder are as follows: 7-day activity index>80%, 28-day activity index>100%, specific surface area≥400m 2 / kg, sulfur trioxide content ≤4.0%, chloride ion content ≤0.06%, fluidity ratio ≥95%.

Images