CN114620961B

CN114620961B - Harmless filler for household garbage incineration fly ash and preparation method and application thereof

Info

Publication number: CN114620961B
Application number: CN202210079310.1A
Authority: CN
Inventors: 刘建磊; 叶珍; 佟强; 陈菲菲
Original assignee: Hangzhou Huihong Environmental Protection Technology Co ltd
Current assignee: Hangzhou Huihong Environmental Protection Technology Co ltd
Priority date: 2022-01-24
Filing date: 2022-01-24
Publication date: 2022-11-18
Anticipated expiration: 2042-01-24
Also published as: CN114620961A

Abstract

The invention belongs to the technical field of harmless treatment of waste incineration fly ash, and particularly relates to a harmless filler of household waste incineration fly ash as well as a preparation method and an application thereof. The preparation method mainly comprises two parts, namely reinforced pretreatment and harmless disposal, provides an excellent additive for large-scale application of a mechanochemical degradation technology by proportioning the proportion of the fly ash and the ferrous sulfate, and obtains the harmless filler of the fly ash generated by burning the household garbage by combining a mechanochemical method, and the harmless filler is applied to concrete or geopolymer raw materials. The method has the advantages of simple process flow, mild operation conditions, high effective energy conversion rate and good safety, and effectively realizes the reduction, harmlessness and reclamation of the fly ash; the curing rate of heavy metal in the treated fly ash is more than 97%, and the degradation rate of dioxin is more than 98.5%.

Description

Harmless filler for household garbage incineration fly ash and preparation method and application thereof

Technical Field

The invention belongs to the technical field of harmless treatment of waste incineration fly ash, and particularly relates to a harmless filler of household waste incineration fly ash, and a preparation method and application thereof.

Background

In the process of waste incineration, the combustion flue gas is kept for 2 seconds above 850 ℃ or 1 second above 1000 ℃, so that dioxin in the flue gas can be effectively degraded. However, due to chlorine, organic carbon, and catalytic metalloids (Cu, fe, cr, ni, etc.) enriched in the fly ash, dioxin is regenerated on the surface of the fly ash through heterogeneous catalytic reaction of de novo synthesis (de novo) when the temperature of flue gas is lowered to 300-400 ℃. In a flue gas treatment system of a household garbage incineration power plant, the currently and widely used control technology for the treatment of dioxin is an activated carbon injection technology and a cloth bag dust removal technology. Incineration fly ash is defined in the standard for pollution control of incineration of household waste (GB 18485-2014): the flue gas purification system captures objects and bottom ash settled at the bottom of a flue and a chimney. So that the activated carbon particles containing dioxin collected by the bag-type dust collector are collected as part of the waste incineration fly ash. Therefore, the removal of dioxin in the treatment and utilization technology of fly ash is very important.

Aluminum ash is a hazardous solid waste generated in the production process of metal aluminum. China is a large aluminum producing country, and it is reported that 15 to 25kg of aluminum ash is produced on average per 1t of metallic aluminum produced. The aluminum ash is divided into primary aluminum ash (the main components are metallic aluminum simple substance and aluminum oxide, and are generated in the processes of electrolyzing primary aluminum, casting and the like) and secondary aluminum ash (waste generated after the primary aluminum ash extracts metallic aluminum), the content of the metallic aluminum in the primary aluminum ash accounts for 30% -80%, and the aluminum ash has extremely high utilization value. At present, the main measures for treating the aluminum ash are landfill and stockpiling, which not only causes environmental pollution, but also causes waste of resources. The comprehensive utilization of the aluminum ash is realized, the aluminum ash stockpiling is reduced, and the method has important significance for the development of the aluminum industry.

The invention adopts a mechanochemical method to cooperatively treat the waste incineration fly ash and the aluminum ash, modifies the solid reactant through a plurality of action modes of mechanical force, such as collision, compression, shearing, friction and the like, induces the physical and chemical properties of the solid reactant to change, and increases the reaction activity of the solid reactant, thereby activating or accelerating the chemical reaction between solids and degrading dioxin in the fly ash. The mechanochemical degradation technology is expected to be applied in large scale, and an excellent additive cannot be obtained, and the additive has the characteristics of strong practicability, high degradation efficiency, low price and the like.

Publication No. CN112266188A discloses a method for preparing phosphorus modified calcium aluminate cement by using municipal solid waste incineration fly ash and aluminum ash, which comprises the following steps: (1) Mixing water and phosphoric acid, and stirring uniformly to prepare a phosphoric acid aqueous solution; (2) Mixing phosphoric acid aqueous solution and municipal solid waste incineration fly ash, and stirring to obtain phosphorus-carrying fly ash; (3) Introducing the phosphorus-loaded fly ash slurry into an electrolytic cell sample area, then switching on a power supply to remove the phosphorus-loaded fly ash electrically, pouring out the slurry from the electrolytic cell sample area to obtain dechlorinated fly ash, and discharging electrolyte from an electrolytic cell cathode chamber to obtain catholyte; (4) Mixing the catholyte obtained in the step (3) with aluminum ash, and stirring to obtain aluminum alkali slurry; (5) And (4) mixing the aluminum alkali slurry with the dechlorinated fly ash obtained in the step (3), sequentially stirring, drying, firing, cooling to normal temperature, and grinding to obtain the phosphorus modified calcium aluminate cement. The electrolytic tank is used, has great difference with the scheme in principle, and can not achieve the effect of the scheme.

Publication No. CN112645615A discloses a system and a method for preparing sulphoaluminate cement from whole solid waste of garbage fly ash heat treatment, comprising the following steps: mixing the garbage fly ash and the aluminum ash in proportion, and then carrying out high-temperature heating pretreatment; and drying the desulfurized gypsum, mixing the desulfurized gypsum with the pretreated garbage fly ash and the aluminum ash in proportion, ball-milling, homogenizing, and adding into a calcining furnace for calcining to obtain the sulphoaluminate cement clinker. The method uses dry ball milling, has a mechanochemical reaction principle different from that of the scheme, does not provide a high-efficiency additive, and cannot achieve the effect of the scheme.

Disclosure of Invention

In order to solve the problems, the invention provides the harmless filler of the fly ash generated by burning the household garbage as well as the preparation method and the application thereof, and the harmless filler has the advantages of simple process flow, mild operation conditions, high effective energy conversion rate and good safety, and effectively realizes the reduction, the harmlessness and the resource utilization of the fly ash; the curing rate of heavy metals in the treated fly ash is more than 97%, the degradation rate of dioxin is more than 98.5%, an excellent additive is provided for the large-scale application of the mechanochemical degradation technology, and the problem that the commercial pure aluminum is used as a high-efficiency additive in the mechanical ball-milling degradation of dioxin due to the high price limit value is solved by using aluminum ash rich in metal aluminum and aluminum oxide as the additive.

The specific technical scheme of the invention discloses a method for preparing harmless filler of household garbage incineration fly ash, which comprises the following steps:

(1) Strengthening pretreatment: mixing the raw ash with water, and carrying out primary washing to obtain a primary washing filter cake; decalcifying the primary water washing filter cake to obtain a decalcified filter cake; carrying out secondary washing treatment on the decalcified filter cake to obtain an enhanced pretreated filter cake;

(2) And (3) harmless treatment: 2a, preparing an additive: putting the aluminum ash into a ferrous sulfate solution to separate out ferrous sulfate, filtering and drying to obtain a mixture of 65-80 wt% of aluminum ash and 20-35 wt% of ferrous sulfate, and ball-milling the mixture to obtain an additive;

2b, mechanochemical treatment: and (2) mixing a solvent, the strengthened pretreatment filter cake obtained in the step (1) and the additive obtained in the step 2a according to the ratio of (1-3): (1-2): 1, and mixing and ball-milling, wherein the mass ratio of the grinding balls to the slurry is (2-20): 1, ball milling time is 3-15 h, ball milling rotating speed is 100-650 rpm, and ball grinding materials are obtained;

and 2c, performing solid-liquid separation on the ball milled material, and cleaning and drying to obtain the fly ash harmless filler.

The preparation method of the invention is mainly divided into two parts, namely strengthening pretreatment and harmless disposal;

the reinforced pretreatment comprises three processes of primary washing, calcium elution and secondary washing in sequence, the fly ash subjected to reinforced pretreatment enters harmless treatment after being dried, the reinforced pretreatment ensures that the fly ash is extremely decalcified under the condition of ensuring that the leaching amount of heavy metal is very small, the amount of the original fly ash can be reduced by 70-80% by reinforced pretreatment, the treatment amount of mechanical and chemical degradation of the fly ash is greatly reduced by the process, dioxin and heavy metal in the fly ash are enriched, and the energy utilization in the mechanical and chemical treatment process is facilitated. The fly ash treated by hydrochloric acid in the pretreatment process is strengthened, and original spherical structures of the fly ash are broken, so that the contact area between dioxin wrapped in micropores of fly ash spherulites and a ball-milling medium is increased, and the degradation efficiency of the dioxin is greatly improved; the method removes soluble chloride in the fly ash and elutes most of calcium, so that the fly ash is reduced greatly, and the subsequent harmless treatment of the fly ash is facilitated. Meanwhile, evaporating and crystallizing the primary washing filtrate to separate salt to obtain industrial potassium salt and sodium salt, and evaporating and crystallizing the decalcified high calcium-containing filtrate to obtain industrial calcium chloride salt.

The harmless treatment comprises three processes of material preparation, efficient mechanical ball milling and solid-liquid separation, so that the heavy metals are stabilized while the dioxin in the fly ash is degraded. Firstly, placing the aluminum ash in a ferrous sulfate solution to separate out ferrous sulfate, filtering and drying to obtain a mixture of 65-80 wt% of aluminum ash and 20-35 wt% of ferrous sulfate, and ball-milling the mixture to obtain the additive. The fly ash is put into the solution according to the proportion, a small amount of iron powder is added into the solution to prevent ferrous ion oxidation, and then the ferrous sulfate is separated out by recrystallization or evaporation of a solvent, ferrous sulfate crystals are separated out on the surface of the fly ash or in the inside of a pore channel, so that two components of the additive are more uniformly distributed, the two components are dried after separation, the iron powder is sucked out by a magnet, and then the additive is further ball-milled, so that the two components in the additive are further compounded, the particle size of the fly ash is reduced, the specific surface is increased, and the surface performance of the additive is improved.

And (2) adding the secondary water-washed filter cake in the step (1) and the additive in the step 2a into a ball milling tank, and then adding a solvent, wherein the addition ratio of the fly ash to the additive to the solvent is (1-3): (1-2): 1, forming mixed slurry, strengthening the pre-treated fly ash and additives to form CaO-SiO ₂ -Al-Al ₂ O ₃ -FeSO ₄ A system in which the aluminium ash dominates the degradation process of fly ash dioxin, ferrous sulfate (FeSO) ₄ ) Leading the stabilization process of heavy metal in fly ash. In the preparation process of the additive, ferrous sulfate is deposited in the fly ash pore channel, the subsequent ball milling increases the specific surface area of the additive, simultaneously changes the chemical activity of the fly ash and the ferrous sulfate, and during the subsequent mechanochemical ball milling, dioxin can be brought into the pore channel by the existence of ethanol, so that the decomposition of the dioxin is further promoted. The solvent can be used as a grinding medium to extract the dioxin in the fly ash, so that the dioxin is desorbed from micropores of the fly ash and enters a liquid phase environment, the contact area of the reaction is increased, and the generation of flying dust during grinding is avoided in the grinding process in the liquid phase. Adding grinding balls into a reaction chamber of a roller ball mill to perform batch reaction operation, wherein the mass ratio of the grinding balls to the slurry is 3:1 to 20:1, the ball milling time is 3-15 h, the ball milling rotating speed is 100-650 rpm, the filling rate of a cavity is 45-60 percent, and the effective transfer of energy is ensured. During the mechanochemical treatment, fly ash particles are repeatedly crushed and polymerized continuously to form a plurality of new surfaces, the surface energy is greatly increased, and meanwhile, cavities and dislocation in the crystals are accumulated continuously to amorphize the crystals. The fly ash after the strengthening pretreatment contains about 15% of SiO ₂ And 40% of CaO and SiO in the CaO, fly ash system ₂ The effect of (A) is to release O which reacts with dioxin molecules ₂ ^－ Promoting dechlorination reaction, charge transfer occurring in O in reducing agent CaO ₂ ^－ In situ, al in the additive system acts as an electron donor for CaO, promoting O in the CaO crystals ₂ ^－ Releasing while SiO ₂ As a catalyst to promote the reaction, siO ₂ During the ball milling process, the crystal can generate various charged particles to attack C-Cl bonds of dioxin, so that the degradation reaction rate is accelerated. Fly awayThe ash lattice defects are accumulated continuously in the ball milling process, and heavy metals are gradually and irreversibly adsorbed to a crystal network structure on the newborn surface of fly ash particles, so that the fly ash particles are solidified and stabilized. The addition of the ferrous sulfate effectively realizes the stabilization of various heavy metals in the fly ash, which is probably due to the fact that in the mechanochemical treatment process, ferrous ions form iron oxyhydroxide (FeOOH) under the action of oxygen and water, the iron oxyhydroxide has a large specific surface area, heavy metals can enter iron oxide crystal lattices to be adsorbed, the FeOOH and soluble or unstable heavy metal compound crystals in the fly ash are activated under the continuous action of mechanical force, the reaction activity of the activated crystals is greatly increased, further, chemical reaction is carried out under the action of grinding balls, insoluble or stable heavy metal mineral salts are generated, the distribution form of the heavy metals is changed, and the stabilization of the heavy metals is realized.

After the ball milling process is finished, solid-liquid separation is carried out on the slurry, the liquid phase can be returned to the step 2.2 for recycling, the solid phase is completely detoxified, the solid phase can be used as a raw material of geopolymer to replace common portland cement materials, the consumption of clayey mineral raw materials can be reduced, the material requirements in the fields of buildings and roads are met, and the resource utilization of fly ash is promoted.

Preferably, in the step (1), the ratio of raw ash to water in the primary water washing is 1: (1-3); the decalcification condition is to adjust the pH value to 8-9; the solid-to-liquid ratio of the second-stage water washing is 1: (5-10).

The ratio of raw ash to water is 1: (1-3) carrying out primary washing, carrying out evaporation crystallization on primary washing filtrate to separate salt to obtain industrial potassium salt and sodium salt, and carrying out calcium elution treatment on a primary washing filter cake; calcium elution is carried out by adding hydrochloric acid to adjust the most suitable pH value for calcium extraction, the pH value is adjusted to 8-9, the maximum decalcification is carried out on the premise of ensuring the extremely low dissolution rate of heavy metals, the obtained high calcium-containing filtrate is evaporated and crystallized to obtain industrial calcium chloride salt, and the decalcification filter cake is subjected to secondary washing treatment; the solid-to-liquid ratio of the second-stage water washing is 1:5 to 1:10, evaporating and crystallizing the secondary washing filtrate and the high calcium-containing filtrate obtained in the step 1.2 together to prepare calcium chloride salt, and directly performing harmless treatment on the secondary washing filter cake without drying, so that the energy consumption in the drying process is saved, and the generation of flying dust in the drying process is avoided.

Preferably, in the step 2a, the mass fraction of the ferrous sulfate solution is 20wt% to 28wt%, and the method for separating out the ferrous sulfate is a recrystallization method or an evaporation solvent method; the ball milling conditions of the mixture are as follows: the mass ratio of the grinding ball to the mixture is (2-20): 1, ball milling time is 2-5h, and ball milling rotating speed is 200-800 rpm; the grain diameter of the additive is 50-100 mu m.

Preferably, in step 2b, the solvent is ethanol; the grain diameter of the ball grinding material is 20-50 mu m; the filling rate of the cavity is 45-60%, and the diameter of the grinding ball is 10-150 mm.

The solvent in the scheme is preferably ethanol, ethanol is firstly used as a hydrogen donor (from two types of hydrogen atoms on hydroxyl and methyl), provides sufficient hydrogen source for the hydrodechlorination process of dioxin, caO is used as a reducing agent and a proton scavenger in liquid-phase dechlorination reaction, alcohol is used as a hydrogen donor, and the alcohol reacts with electrons generated in a system to generate hydrogen atoms (MeOH +2 e) ^- →2MeO ^- + 2H), the generated hydrogen atom attacks the C-Cl bond on the dioxin molecule (H. + R-Cl → HCl + R., H. + R. → R-H), and the hydrodechlorination reaction occurs, so that the dioxin is degraded. The ethanol is used as an organic solvent with weaker chemical polarity, the mutual dissolution of solid and liquid phases is effectively prevented in the grinding process, the stabilization process of heavy metals in the fly ash is enhanced, meanwhile, the dioxin in the fly ash can be extracted by the alcohol solution, so that the dioxin enters the liquid phase from the solid phase, the reaction contact area for the degradation of dioxin molecules is greatly increased, and the degradation rate of the dioxin is accelerated. Meanwhile, the ferrous sulfate is insoluble in ethanol, so that the stability of the ferrous sulfate can be ensured, the ethanol can avoid the generation of flying dust in the ball milling process, and the ethanol has the characteristic of strong volatility and saves the energy consumption in the drying process; the particle size of the ball grinding material is 20-50 mu m, so that better performance can be provided for products, for example, the product can be used as a cement filler, and the comprehensive performance of the cement can be improved due to the small particle size of the filler. The filling rate of the cavity is 45-60%, the diameter of the grinding ball is 10-150 mm, and the ball milling efficiency and the product quality are mainly considered.

The mechanism of stabilizing dioxin and heavy metal degradation by a wet mechanochemical method comprises the following steps:

the scheme also providesThe harmless filler of the fly ash from incineration of the household garbage prepared by the method comprises the chemical compositions of 20-25% of CaO and 20-30% of SiO ₂ 35 to 50 percent of Al ₂ O ₃ And 10wt% to 25wt% of an iron-containing compound.

The harmless filler of the household garbage incineration fly ash provided by the scheme is applied to concrete or geopolymer raw materials.

The harmless filler of the municipal solid waste incineration fly ash is applied to concrete and can replace powder in the concrete, such as sand material and the like, the replacement and addition proportion can reach 50 percent, the recycling of wastes is realized, and the sand material resource is saved.

The invention has the beneficial effects that:

1. the scheme synergistically disposes the waste incineration fly ash and the industrial aluminum ash, realizes 'waste treatment by waste', has simple treatment process flow, mild operation conditions, high effective energy conversion rate and good safety, and effectively realizes the reduction, harmlessness and recycling of the fly ash; 2. the reinforced pretreatment process can reduce the fly ash by about 65-80 percent, reduce the subsequent fly ash wet-method mechanical chemical treatment amount, simultaneously, the drying process is not needed, and the treatment cost is greatly reduced;

3. the wet ball milling is adopted, so that the generation of flying dust in the ball milling process is avoided, the alcoholic solution is used as a solvent, the dissolution of a solid phase and heavy metals of the fly ash is avoided, the nonpolar dioxin is transferred from the solid phase to the liquid phase, the reaction activity is enhanced, and the reaction rate is accelerated;

4. the additive has good material fluidity in the ball milling process of the mixed fly ash, so that the grinding balls can uniformly act on all slurry, the additive is ensured to be fully contacted and reacted with pollutants in the fly ash, the volatile property of an alcohol solution is good, the solid-liquid separation effect is good, the drying energy consumption of the dehydrated fly ash is low, the heavy metal curing rate of the treated fly ash is more than 97%, and the dioxin degradation rate is more than 98%.

Detailed Description

The present invention will be further described with reference to the following examples. The devices and reagents used in the present invention are all known in the art, unless otherwise specified.

General examples

A preparation method of harmless filler of household garbage incineration fly ash comprises the following steps:

(1) Strengthening pretreatment: mixing the raw ash with water, and carrying out primary washing to obtain a primary washing filter cake; decalcifying the primary water washing filter cake to obtain a decalcified filter cake; carrying out secondary washing treatment on the decalcified filter cake to obtain an enhanced pretreated filter cake; and the ratio of the raw ash to the water in the primary water washing is 1: (1-3); the decalcification condition is to adjust the pH value to 8-9; the second-stage water washing solid-liquid ratio is 1: (5-10);

(2) And (3) harmless treatment: 2a, preparing an additive: putting the aluminum ash into a ferrous sulfate solution to separate out ferrous sulfate, filtering and drying to obtain a mixture of 65-80 wt% of aluminum ash and 20-35 wt% of ferrous sulfate, and ball-milling the mixture to obtain an additive; the mass fraction of the ferrous sulfate solution is 20-28 wt%, and the ferrous sulfate precipitation method is a recrystallization method or an evaporation solvent method; the mass ratio of the grinding balls to the mixture is (2-20): 1, ball milling time is 2-5h, and ball milling rotating speed is 200-800 rpm; the grain diameter of the additive is 50-100 mu m;

2b, mechanochemical treatment: and (2) mixing ethanol, the strengthened pretreatment filter cake obtained in the step (1) and the additive obtained in the step 2a according to the ratio of (1-3): (1-2): 1, and mixing and ball-milling, wherein the mass ratio of the grinding balls to the slurry is (2-20): 1, ball milling time is 3-15 h, and ball milling rotating speed is 100-650 rpm, so as to obtain a ball grinding material; the grain diameter of the ball grinding material is 20-50 mu m; the filling rate is 45-60%, and the diameter of the grinding ball is 10-150 mm;

Example 1

(1) Strengthening pretreatment: mixing the raw ash with water for primary washing to obtain a primary washing filter cake; decalcifying the primary water washing filter cake to obtain a decalcified filter cake; carrying out secondary washing treatment on the decalcified filter cake to obtain an enhanced pretreated filter cake; and the ratio of the raw ash to the water in the primary water washing is 1:2; the decalcification condition is to adjust the pH value to 8; the solid-to-liquid ratio of the second-stage water washing is 1:6;

(2) Innocent treatment: 2a, preparing an additive: putting the aluminum ash into a ferrous sulfate solution to separate out ferrous sulfate, filtering and drying to obtain a mixture of 65wt% of aluminum ash and 35wt% of ferrous sulfate, and ball-milling the mixture to obtain an additive; the mass fraction of the ferrous sulfate solution is 25wt%, and the method for separating out the ferrous sulfate is a recrystallization method; the mass ratio of the grinding balls to the mixture is 10:1, ball milling time is 3h, and ball milling rotating speed is 500rpm; the particle size of the additive is 75 μm;

2b, mechanochemical treatment: and (2) mixing ethanol, the strengthened pretreated filter cake obtained in the step (1) and the additive obtained in the step 2a according to the weight ratio of 2:1:1, mixing and ball-milling, wherein the mass ratio of the grinding balls to the slurry is 10:1, ball milling time is 3h (stopping for 20min every 30 min), ball milling rotating speed is 100rpm, and ball grinding materials are obtained; the grain diameter of the ball grinding material is 50 mu m; the filling rate is 60 percent, and the diameter of the grinding ball is 10 mm-150 mm;

and 2c, performing solid-liquid separation on the ball milling material, and cleaning and drying to obtain the fly ash harmless filler.

Example 2

The difference from example 1 is that in step (1), decalcification was carried out to set a pH of 9.

Example 3

The difference from example 1 is that in step 2a, a mixture of 75wt% aluminum ash and 25wt% ferrous sulfate is obtained after filtration and drying.

Example 4

The difference from example 1 is that in step 2a, a mixture of 85wt% aluminum ash and 15wt% ferrous sulfate is obtained after filtration and drying.

Example 5

The difference from the example 1 is that in the step 2b, the adding ratio of the ethanol, the enhanced pretreatment filter cake and the additive is 3:1:1.

example 6

The difference from the example 1 is that in the step 2b, the adding ratio of the ethanol, the enhanced pretreatment filter cake and the additive is 3:2:1.

example 7

The difference from example 1 is that in step 2b, the ball milling time is 10h (20 min for each 30min run) and the ball milling speed is 100rpm.

Example 8

The difference from example 1 is that in step 2b, the ball milling time is 15h (20 min for each 30min run) and the ball milling speed is 100rpm.

Example 9

The difference from example 1 is that in step 2b, the ball milling time is 3 hours (20 min for each 30min run) and the ball milling speed is 300rpm.

Example 10

The difference from example 1 is that in step 2b, the ball milling time is 3h (20 min for each 30min run) and the ball milling speed is 500rpm.

Example 11

The difference from example 1 is that in step 2b, the ball milling time is 3h (20 min for each 30min run) and the ball milling speed is 600rpm.

Comparative example 1

The difference from the embodiment 1 lies in that the water washing pretreatment process comprises the following specific steps:

mixing raw ash and water in a ratio of 1:2, mixing the materials according to the mass ratio, performing primary washing, performing solid-liquid separation, and performing secondary washing treatment; the primary water-washed cake was mixed with water at a ratio of 1:2, performing secondary washing, performing solid-liquid separation, and performing tertiary washing treatment; mixing the secondary water-washed filter cake with water in a ratio of 1:2, and carrying out three-stage water washing to obtain pretreated dry ash.

Comparative example 2

The difference from example 1 is that the mixture of the additive 95wt% aluminium ash and 5wt% ferrous sulphate is a simple mechanical mixture.

Comparative example 3

The difference from example 1 is that the mixture of 55wt% aluminium ash and 45wt% ferrous sulphate additive is a simple mechanical mixture.

Comparative example 4

The difference from example 1 is that in step (1), decalcification was carried out to set a pH of 7.

Comparative example 5

The difference from example 1 is that the pH value was set to 10 in the decalcification in step (1).

Comparative example 6

The difference from the example 1 is that in the step 2b, the adding ratio of the ethanol, the enhanced pretreatment filter cake and the additive is 1:1:2.

comparative example 7

The difference from the example 1 is that in the step 2b, the adding ratio of the ethanol, the strengthened pretreatment filter cake and the additive is 5:1:1.

comparative example 8

The difference from example 1 is that in step 2b, the ball milling time is 3 hours (20 min for each 30min run) and the ball milling speed is 50rpm.

Comparative example 9

The difference from example 1 is that in step 2b, the ball milling time is 18h (20 min for each 30min run) and the ball milling speed is 50rpm.

Comparative example 10

The difference from example 1 is that in step 2b, the solvent is water.

The results of comparative tests of examples and comparative examples are shown in tables 1 to 5.

The fly ash reduction and calcium elution efficiency in the strengthening pretreatment process are shown in table 1, the calcium elution efficiency in the strengthening pretreatment process of example 1 is 15.5 times that in the water washing pretreatment process of comparative example 1, and the fly ash reduction is 2.6 times that in the water washing pretreatment process of comparative example 1; example 2 the calcium elution efficiency of the enhanced pretreatment process was 15.4 times that of the comparative example water washing pretreatment process, and the fly ash reduction was 2.5 times that of the comparative example 1 water washing pretreatment process. Table 2 shows the change of the fly ash component content before and after the water washing pretreatment and the strengthening pretreatment, the fly ash after the water washing in comparative example 1 has a CaO content of 65.50%, while the fly ash after the strengthening pretreatment in example 1 has a CaO content of 40.47%, and the fly ash after the strengthening pretreatment in example 2 has a CaO content of 42.19%, thereby greatly realizing the decalcification of the fly ash. At the same time, greatly improves SiO ₂ Example 1 SiO in fly ash after enhanced pretreatment ₂ The content of (B) is about 2.44 times that of comparative example 1, and example 2 is strongSiO in fly ash after chemical pretreatment ₂ The content of (b) was about 2.41 times as much as that of the water washing treatment of comparative example 1. The content of heavy metal ions in the strengthening pretreatment filtrate is shown in table 3, and in the strengthening pretreatment process by adding hydrochloric acid to adjust the pH, the dissolving-out content of Pb and Cd exceeds the specified value (the concentration limit of Pb is 5mg/L and the concentration limit of Cd is 1 mg/L) in the hazardous waste identification standard leaching toxicity identification (GB 5085.3-2007), and the dissolving-out amount of the other heavy metals is extremely small and reaches the standard, which indicates that the strengthening pretreatment method can realize the maximum decalcification under the condition of extremely low dissolving-out rate of the heavy metals.

TABLE 1 fly ash reduction by Water washing pretreatment and enhanced pretreatment

	Calcium elution Rate (%)	Fly ash reduction (%)
			Comparative example 1	5.55	29.57
Example 1	86.32	77.45
			Example 2	85.68	75.01

Table 2 fly ash composition (%)

	Cl	CaO	SiO ₂	Al ₂ O ₃	Fe ₂ O ₃	MgO
							Raw ash	17.85	45.80	4.53	1.25	1.24	1.23
Comparative example 1	2.04	65.50	6.52	1.56	0.85	1.76
							Example 1	0.92	40.47	15.97	3.37	2.46	2.34
Example 2	0.96	42.19	15.75	2.35	2.35	3.11

TABLE 3 content (mg/L) of heavy metal ions dissolved out in the calcium elution step in the intensified pretreatment process

	Pb	Zn	Cr	Cd	Cu	Mn	Ni
								Example 1	5.65	2.36	0.006	8.65	8.95	0.216	0.005
Example 2	1.39	0.01	0.004	5.94	7.80	0.037	0.008

Taking the fly ash samples treated by the harmless treatment units in quantitative examples 1 to 11 and comparative examples 2 to 10, carrying out dioxin detection according to isotope dilution high resolution gas chromatography-high resolution mass spectrometry for determination of dioxins in solid waste (HJ 77.3-2008), as shown in Table 4, the degradation rates of dioxins in the fly ash samples of examples 1 to 11 after wet grinding treatment reach more than 98%, the degradation rate of the fly ash samples of examples 1 to 11 is improved by about 15% compared with that of the fly ash samples of comparative example 10 by adding water as a grinding medium by using an alcohol solution as the grinding medium, and the content of the dioxin in the treated fly ash is far lower than that in the total content of dioxin residues in the treated products regulated in technical Specification for controlling pollution of fly ash from incineration of domestic waste (HJ 1134-2020), and the total content of dioxin residues in the treated products is not more than 50ng TEQ/kg.

TABLE 4 efficiency of dioxin degradation

Heavy metal leaching toxicity tests were carried out on the dried raw ash and fly ash samples treated by the innocent treatment units in examples 1 to 11 and comparative examples 2 to 10 by the sulfuric acid-nitric acid method (HJ/T299-2007). The leaching contents of heavy metals in raw ash and treated fly ash are shown in table 5, and it is known that the leaching concentrations of Pb, zn, cr, cd, cu, mn and Ni in the treated fly ash are extremely low, the leaching concentrations all meet the concentration limit value of heavy metals in hazardous waste identification Standard Leaching toxicity identification (GB 5085.3-2007), the solidification rate of the heavy metals reaches more than 97%, and the treated sample has been detoxified by dioxin and heavy metals, belongs to general solid waste, and can be used as a resource utilization raw material.

TABLE 5 heavy metal leaching content in fly ash before and after treatment

Application example 1

The fly ash harmless filler obtained in the example 1 replaces the filler of common concrete, and the doping proportion is 30-45%.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modifications, alterations and equivalent changes made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of harmless filler of household garbage incineration fly ash is characterized by comprising the following steps:

(1) Strengthening pretreatment:

mixing the raw ash with water for primary washing to obtain a primary washing filter cake; decalcifying the primary water washing filter cake to obtain a decalcified filter cake; carrying out secondary washing treatment on the decalcified filter cake to obtain an enhanced pretreated filter cake; in the step (1), the ratio of raw ash to water in the primary washing is 1: (1 to 3); the decalcification condition is to adjust the pH value to 8 to 9; the second-stage water washing solid-liquid ratio is 1: (5 to 10);

(2) Innocent treatment:

2a, preparing an additive: placing the aluminum ash in a ferrous sulfate solution to precipitate ferrous sulfate, filtering and drying to obtain a mixture of 65-80 wt% of aluminum ash and 20-35 wt% of ferrous sulfate, and ball-milling the mixture to obtain an additive;

2b, mechanochemical treatment: and (3) mixing a solvent, the reinforced pretreatment filter cake obtained in the step (1) and the additive obtained in the step 2a according to the ratio of (1-3): (1 to 2): 1, mixing and ball-milling, wherein the solvent is ethanol, and the mass ratio of the grinding balls to the slurry is (2 to 20): 1, ball milling for 3 to 15 hours at a ball milling speed of 100 to 650rpm to obtain a ball grinding material;

2. The method for preparing harmless filler of fly ash from incineration of domestic garbage according to claim 1, wherein in step 2a, the mass fraction of the ferrous sulfate solution is 20wt% to 28wt%, and the method for separating out ferrous sulfate is recrystallization or solvent evaporation.

3. The method for preparing the harmless filler of the fly ash from incineration of household garbage according to claim 1, wherein in the step 2a, the ball milling conditions of the mixture are as follows: the mass ratio of the grinding ball to the mixture is (2 to 20): 1, ball milling time is 2-5h, and ball milling rotating speed is 200 to 800rpm; the particle size of the additive is 50-100 um.

4. The method for preparing the harmless filler of the fly ash generated by incinerating the household garbage according to claim 1, wherein in the step 2b, the particle size of the ball grinding material is 20 to 50 um.

5. The method for preparing the harmless filler of the fly ash from the incineration of household garbage according to claim 1, wherein in the step 2b, the filling rate of the cavity is 45% -60%, and the diameter of the grinding ball is 10 mm-150 mm.

6. A harmless filler of fly ash from incineration of household garbage is prepared by the method as claimed in any one of claims 1-5.

7. The harmless filler for the fly ash from incineration of household garbage according to claim 6, wherein the harmless filler for the fly ash from incineration of household garbage comprises 30-45% of CaO and 10-25% of SiO in terms of chemical composition ₂ 35% -40% of Al ₂ O ₃ And 10wt% to 25wt% of an iron-containing compound.

8. Use of a harmless filler of fly ash from incineration of household waste as defined in claim 6 or 7 in concrete or geopolymer raw materials.