CN114621027A - Method for preparing modified geopolymer perforated brick from waste incineration fly ash - Google Patents
Method for preparing modified geopolymer perforated brick from waste incineration fly ash Download PDFInfo
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- CN114621027A CN114621027A CN202210246752.0A CN202210246752A CN114621027A CN 114621027 A CN114621027 A CN 114621027A CN 202210246752 A CN202210246752 A CN 202210246752A CN 114621027 A CN114621027 A CN 114621027A
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- 239000010881 fly ash Substances 0.000 title claims abstract description 147
- 238000000034 method Methods 0.000 title claims abstract description 68
- 229920000876 geopolymer Polymers 0.000 title claims abstract description 42
- 238000004056 waste incineration Methods 0.000 title claims abstract description 21
- 239000011470 perforated brick Substances 0.000 title claims abstract description 6
- 238000005406 washing Methods 0.000 claims abstract description 67
- 239000000203 mixture Substances 0.000 claims abstract description 42
- 239000011449 brick Substances 0.000 claims abstract description 39
- 239000002002 slurry Substances 0.000 claims abstract description 32
- 238000005336 cracking Methods 0.000 claims abstract description 27
- 239000011398 Portland cement Substances 0.000 claims abstract description 22
- 238000002156 mixing Methods 0.000 claims abstract description 20
- 239000004088 foaming agent Substances 0.000 claims abstract description 18
- 239000005995 Aluminium silicate Substances 0.000 claims abstract description 17
- 235000012211 aluminium silicate Nutrition 0.000 claims abstract description 17
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000012190 activator Substances 0.000 claims abstract description 15
- HGUFODBRKLSHSI-UHFFFAOYSA-N 2,3,7,8-tetrachloro-dibenzo-p-dioxin Chemical compound O1C2=CC(Cl)=C(Cl)C=C2OC2=C1C=C(Cl)C(Cl)=C2 HGUFODBRKLSHSI-UHFFFAOYSA-N 0.000 claims abstract 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 59
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- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 20
- 230000018044 dehydration Effects 0.000 claims description 13
- 238000006297 dehydration reaction Methods 0.000 claims description 13
- 239000000243 solution Substances 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 11
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- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 10
- 239000000460 chlorine Substances 0.000 claims description 8
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 7
- 229910052801 chlorine Inorganic materials 0.000 claims description 7
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 6
- 239000011259 mixed solution Substances 0.000 claims description 6
- 241000537371 Fraxinus caroliniana Species 0.000 claims description 5
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- RCEAADKTGXTDOA-UHFFFAOYSA-N OS(O)(=O)=O.CCCCCCCCCCCC[Na] Chemical compound OS(O)(=O)=O.CCCCCCCCCCCC[Na] RCEAADKTGXTDOA-UHFFFAOYSA-N 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 239000000706 filtrate Substances 0.000 description 4
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- 230000004048 modification Effects 0.000 description 4
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- 230000001988 toxicity Effects 0.000 description 4
- 239000002351 wastewater Substances 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- 241000196324 Embryophyta Species 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- -1 aluminum ions Chemical class 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 3
- 239000002585 base Substances 0.000 description 3
- 229910052793 cadmium Inorganic materials 0.000 description 3
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 3
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N Furan Chemical compound C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 239000002956 ash Substances 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
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- 150000001875 compounds Chemical class 0.000 description 2
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- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000001413 cellular effect Effects 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
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- 150000004827 dibenzo-1,4-dioxins Chemical class 0.000 description 1
- 230000000185 dioxinlike effect Effects 0.000 description 1
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- 238000010169 landfilling Methods 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 239000011268 mixed slurry Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
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- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
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- 239000010703 silicon Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/006—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing mineral polymers, e.g. geopolymers of the Davidovits type
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/40—Porous or lightweight materials
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/20—Mortars, concrete or artificial stone characterised by specific physical values for the density
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Engineering & Computer Science (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
The invention provides a method for preparing a modified geopolymer perforated brick by using waste incineration fly ash, which comprises the following steps: carrying out washing on the fly ash after dioxin cracking to obtain a washing product; carrying out first mixing on the washing product, the fly ash, the kaolin and the portland cement to obtain a first mixture; carrying out second mixing on the first mixture and an alkaline activator to obtain a second mixture; thirdly mixing the second mixture and a foaming agent to obtain slurry; and curing the slurry after forming to obtain the geopolymer porous brick. The method provided by the invention can realize harmless and recycling of the waste incineration fly ash, and the porous brick has excellent performance and higher compressive strength and rupture strength and can be used as a non-structural light-weight fireproof heat-insulating material.
Description
Technical Field
The invention belongs to the technical field of waste incineration, and particularly relates to a method for preparing a modified geopolymer perforated brick from waste incineration fly ash.
Background
The fly ash is a necessary product of waste incineration, is rich in heavy metals with high leaching concentration, soluble salts, dioxin, furan and other organic pollutants, belongs to hazardous waste (national hazardous waste record (number HW 18)), and has the yield accounting for 3% -5% of the amount of the incinerated waste.
According to the content of the technical specification for controlling the fly ash pollution caused by burning the household garbage (HJ1134-2020), the fly ash utilization and disposal are divided into two modes of landfill and resource utilization; landfilling is the traditional method of fly ash disposal, and reclamation is a new treatment modality that has been developed in recent years. Before the fly ash is buried or recycled, the fly ash needs to be properly pretreated, and the prior treatment technology of the fly ash mainly comprises solidification/stabilization, water washing cement kiln cooperation, high-temperature sintering, high-temperature melting, low-temperature building material formation and the like.
The co-processing technology of the water washing cement kiln is that the fly ash is used as a cement raw material after water washing treatment (chloride removal), dioxin is thoroughly decomposed by high-temperature sintering in the cement kiln, heavy metals are solidified and stabilized in cement clinker, and water washing wastewater is completely recycled after treatment. The main chemical components of the fly ash are calcium, silicon, aluminum, iron and the like, the requirements of producing raw materials of ordinary portland cement are met, the fly ash can be used as a part of cement raw materials, and the fly ash is recycled by a cement kiln to produce cement clinker. The cement kiln co-disposal is to calcine the waste incineration fly ash in the kiln instead of part of the cement clinker, so as to solidify harmful heavy metals in the cement clinker. The method can thoroughly eliminate organic pollutants such as dioxin and the like, has no pollution problem caused by secondary ash treatment, and realizes reduction, harmlessness and resource treatment of the fly ash. However, the content of chloride ions in the fly ash is too high, which affects the production of cement enterprises, so that fly ash water is required to be pretreated by eluting chloride salt, and volatile heavy metals and compounds enter flue gas in the process of cooperatively treating waste incineration fly ash in a cement kiln, and the volatile heavy metals and compounds need to be detected and controlled to prevent pollution to the atmosphere. After the fly ash is treated by the cooperation of the cement kiln, the leaching toxicity of heavy metals in cement clinker meets the standard requirement of technical Specification for treating solid waste by the cooperation of the cement kiln (GB30760-2014), the concentration of pollutants in discharged flue gas is lower than the middle limit value of the pollution control Standard for treating solid waste by the cooperation of the cement kiln (GB30485-2013), and the quality of cement meets the standard of general Portland cement (GB 175-2008). According to the requirement that the chlorine content of the raw materials of the cement rotary kiln is not more than 0.015 percent, considering that other raw materials are possible to bring in chloride ions, the addition amount of the fly ash after washing is determined to be 5 percent, so the consumption proportion is limited, and some cities around a waste incineration plant are not provided with cement kilns, and the transportation cost is increased.
The high-temperature sintering ceramic grain preparation technology is characterized in that additives such as fluxing agents and binding agents are added into a mixture of fly ash or industrial solid waste or clay, the mixture is heated to 900-1100 ℃ to be partially melted, and a sintered product is formed after cooling. The sintered product is a light compact solid, can coat and stabilize heavy metals, and can be used as ceramsite, thereby reducing the demand of the ceramsite industry on natural raw materials. The technology is characterized in that dioxin in the fly ash is thoroughly decomposed at a high-temperature section, but the technology has the advantages of more complex process route, higher energy consumption, narrower sintering temperature range, difficult control, high tail gas treatment difficulty and more secondary fly ash.
The plasma melting technology is a process of mixing the fly ash or the treated product thereof with other silicon-aluminum components and a fluxing agent, heating the fly ash to 1300-1500 ℃ by using a heat source generated by a plasma torch until the fly ash is completely melted, and then carrying out quenching treatment such as water quenching to form a compact vitreous body product. The technology can completely decompose dioxin and other organic pollutants in the fly ash, and finally generates non-toxic and harmless vitreous slag which can be directly used as building materials, but the technology is only in a small-scale disposal stage at present due to the problems of complex process route, high energy consumption, high difficulty in tail gas treatment, secondary fly ash and the like, and the application and popularization of the technology have a long way.
The technology of low-temperature building materials is a new technology, and currently, in research, according to technical specifications (trial) of pollution control of fly ash from incineration of household garbage (HJ1134-2020), a treatment method applied to cement kiln cooperation needs to meet the following conditions: firstly, the dioxin decomposition technologies such as low-temperature cracking, high-temperature sintering, high-temperature melting and the like are adopted to control the content of dioxin in a fly ash treatment product; secondly, controlling the leaching concentration of heavy metals in the fly ash treatment product; thirdly, the soluble chlorine content in the fly ash treatment product is removed by adopting the technologies of water washing and the like. The low-temperature cracking technology is used for removing dioxins in the fly ash at low temperature and then using the fly ash as a substitute raw material for producing building material products.
Generally, the cement kiln cooperative treatment is a fly ash resource utilization technology successfully developed in recent years, but according to the requirement that the chlorine content of raw materials of a rotary cement kiln is not more than 0.015%, the possibility that other raw materials carry chloride ions is considered, the addition amount of fly ash after water washing is determined to be 5%, so the consumption ratio is limited, and some cities around a waste incineration plant are provided with no cement kiln, and the transportation cost is increased; the ceramsite prepared by high-temperature sintering is currently applied to fly ash treatment in Tianjin, but the sintering temperature is as high as 900-1100 ℃, the process energy consumption is large, the process route is complex, the tail gas treatment difficulty is high, and more secondary fly ash is generated; plasma melting is used as an important way for high-temperature melting of fly ash, and in recent years, medium-scale tests have been carried out, but the melting temperature is as high as 1300-1500 ℃, the process energy consumption is high, the process route is complex, the tail gas treatment difficulty is high, and more secondary fly ash is generated; other treatment methods have the defects of no pretreatment measures on dioxin and chlorine salt, no modification on the strength of a final product and the like.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for preparing a modified geopolymer porous brick from fly ash from waste incineration, and the geopolymer porous brick prepared by the method provided by the present invention has good performance.
The invention provides a method for preparing a modified geopolymer porous brick from waste incineration fly ash, which comprises the following steps:
carrying out dioxin cracking on the fly ash, and then washing to obtain a washing product;
carrying out first mixing on the washing product, the fly ash, the kaolin and the portland cement to obtain a first mixture;
carrying out second mixing on the first mixture and an alkaline activator to obtain a second mixture;
thirdly mixing the second mixture and a foaming agent to obtain slurry;
and curing the slurry after forming to obtain the geopolymer porous brick.
Preferably, the temperature for cracking the dioxin is 350-400 ℃; the cracking time of the dioxin is 0.5-1 hour.
Preferably, the water washing comprises:
primary water washing and secondary water washing;
the mass ratio of water ash in the first-stage water washing and the second-stage water washing is independently selected from (2-3): 1.
preferably, after the first stage of washing, the method further comprises:
carrying out mechanical dehydration; the water content of the solid fly ash after mechanical dehydration is 40-50%;
after the second-stage water washing, the method also comprises the following steps:
carrying out mechanical dehydration; the water content of the solid fly ash after mechanical dehydration is 30-40%, and the content of soluble chlorine is less than 2%.
Preferably, the mass content of the water-washed product in the first mixture is not more than 50%;
the mass content of the fly ash in the first mixture is 20-40%;
the mass content of the kaolin in the first mixture is 10-30%;
the mass content of the Portland cement in the first mixture is 6-10%.
Preferably, the alkali-activator includes:
sodium hydroxide solution and water glass;
the concentration of the sodium hydroxide solution is 8-16 mol/L;
the mass ratio of the sodium hydroxide solution to the water glass is (0.8-1.2): 1.
preferably, the mass of the alkali-activator is 5 to 10% of the mass of the first mixture.
Preferably, the foaming agent comprises:
a mixed solution of hydrogen peroxide and sodium dodecyl sulfate;
the mass of the foaming agent is 0.5-2% of that of the second mixture.
Preferably, the curing time is 12-24 hours; the curing temperature is 50-60 ℃.
Preferably, after the curing, the method further comprises:
curing under natural conditions after demolding to obtain the modified geopolymer porous brick;
and the curing time under the natural condition is 25-35 days.
The method provided by the invention mixes fly ash after two steps of pretreatment of cracking low-temperature dioxin and removing chloride by washing with water with fly ash, portland cement clinker, calcined kaolin and alkaline excitation solution to prepare geopolymer slurry, adds foaming agent aqueous solution into the slurry, and then cures and releases the mold to prepare the modified geopolymer porous brick. The method provided by the invention can realize harmless and recycling of the waste incineration fly ash, and the porous brick has excellent performance and higher compressive strength and rupture strength and can be used as a non-structural light-weight fireproof heat-insulating material.
Drawings
FIG. 1 is a flow chart of a process for preparing a modified geopolymer cellular brick according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a method for preparing a modified geopolymer porous brick from waste incineration fly ash, which comprises the following steps:
carrying out washing on the fly ash after dioxin cracking to obtain a washing product;
carrying out first mixing on the washing product, the fly ash, the kaolin and the portland cement to obtain a first mixture;
carrying out second mixing on the first mixture and an alkaline activator to obtain a second mixture;
thirdly mixing the second mixture and a foaming agent to obtain slurry;
and curing the slurry after forming to obtain the geopolymer porous brick.
In the present invention, the dioxin cracking is preferably carried out in a dioxin cracking apparatus; the dioxin cracking is preferably carried out in a nitrogen anoxic environment; the temperature for cracking the dioxin is preferably 350-400 ℃, more preferably 360-390 ℃, and most preferably 370-380 ℃; the dioxin cracking time is preferably 0.5-1 hour, more preferably 0.6-0.9 hour, and most preferably 0.7-0.8 hour; after the dioxin cracking is completed, the heated fly ash is preferably quenched to 50-70 ℃, preferably 55-65 ℃, and more preferably 60 ℃ to prevent the dioxin from being resynthesized.
In the present invention, the decomposition rate of dioxin after cracking of dioxin is preferably > 99.5%, and the total amount of dioxin-like substance remaining in the product after cracking is preferably not more than 50ngTEQ/kg (based on dry weight of fly ash).
In the present invention, dioxins are persistent organic pollutants including polychlorinated dibenzo-p-dioxins and polychlorinated benzofurans; in recent years, with the increase of household garbage and the annual increase of the garbage incineration power generation industry, the amount of fly ash is rapidly increased; fly ash is one of the main carriers of dioxin pollution; the low-temperature pyrolysis technology generally refers to that fly ash is subjected to heat treatment under the anoxic reduction condition, the decomposition temperature of dioxin is lower than the standard decomposition temperature (350 ℃ -400 ℃), the decomposition rate is more than 99.5%, and heated fly ash is quenched to reduce the resynthesis of the dioxin; in the low-temperature pyrolysis process, dioxin is subjected to a series of physicochemical changes such as adsorption and desorption, dechlorination degradation, oxidation open-loop degradation and the like on the surface of fly ash.
In the present invention, the water washing preferably includes primary water washing and secondary water washing; the water washing is preferably carried out in a stirred tank reactor; the washing water of the first-stage water washing preferably adopts reflux filtrate mechanically removed after the second-stage water washing and supplements part of process water; the mass ratio of the water ash in the first-stage water washing is preferably (2-3): 1, more preferably 3: 1; preferably, mechanically dewatering the fly ash slurry after the primary water washing; the mechanical dehydration preferably adopts a centrifugal dehydrator; the water content of the solid fly ash after mechanical dehydration is preferably 40-50%, more preferably 43-47%, and most preferably 45%.
In the invention, the washing water of the secondary washing is preferably fresh process water, and the water-ash mass ratio of the secondary washing is preferably (2-3): 1, more preferably 3: 1; after the secondary washing, the obtained fly ash slurry is preferably subjected to mechanical dehydration, the obtained filtrate is preferably refluxed to the primary washing process to be used as washing water, the water content in the obtained solid fly ash is preferably 30-40%, more preferably 33-37%, most preferably 35%, and the soluble chlorine content in the fly ash is preferably less than 2%; the mechanical dewatering device is preferably a centrifugal dewatering machine.
In the invention, the waste incineration fly ash contains up to 20 percent of soluble inorganic chlorine salt, and the chlorine salt in the fly ash is mostly NaCl, KCl and CaCl2The chlorine salt in the fly ash can greatly reduce the product quality of the fly ash building material resource utilization; taking the example of preparing the building heat-insulation filling building block by the waste fly ash, the joint of the main body component and the filling wall is connected by the steel wire mesh to limit the generation of wall cracks in a certain range during construction, but Cl in the heat-insulation filling building block prepared by the fly ash-The steel wire can be corroded to lose strength, so that the steel wire mesh has no limiting effect, and the engineering quality is reduced; therefore, before the fly ash building material is recycled, a water washing process is firstly adoptedAnd removing soluble chloride salt in the fly ash to ensure the quality of subsequent products.
In the present invention, the kaolin is preferably calcined kaolin; the portland cement is preferably portland cement clinker.
In the invention, the mass content of the water-washed product in the first mixture is preferably not more than 50%, more preferably 39-45%, and most preferably 42%; the mass content of the fly ash in the first mixture is preferably 20-40%, more preferably 25-35%, and most preferably 30%; the mass content of the kaolin in the first mixture is preferably 10-30%, more preferably 15-25%, and most preferably 20%; the mass content of the portland cement in the first mixture is preferably 6-10%, more preferably 7-9%, and most preferably 8%.
In the invention, the compression strength and the flexural strength of the prepared brick are greatly reduced due to the doping of the fly ash and the use of the foaming agent, the matrix raw material is optimized, the proportion of the fly ash is not more than 40 percent (the fly ash after washing and dehydration is referred to herein), a small amount of ordinary portland cement is added for modification to improve the compression strength and the flexural strength of the brick, and the limitation of the addition amount of the fly ash is equivalent to the dilution of the heavy metal content of the brick.
In the present invention, the first mixing is preferably performed under stirring; preferably, a small amount of process water is added in the first mixing process and is continuously and uniformly stirred into a slurry shape.
In the present invention, the alkali-activator preferably comprises a sodium hydroxide solution and water glass; the concentration of the sodium hydroxide solution is preferably 8-16 mol/L, more preferably 10-14 mol/L, and most preferably 12 mol/L; the mass ratio of the sodium hydroxide solution to the water glass is preferably (0.8-1.2): 1, more preferably (0.9 to 1.1): 1, most preferably 1: 1.
in the present invention, the amount of the alkali-activator is preferably 5 to 10% by mass, more preferably 6 to 9% by mass, and most preferably 7 to 8% by mass of the first mixture.
In the present invention, the second mixing is preferably uniformly stirred to a slurry state; the stirring time is preferably 20-30 min, more preferably 23-27 min, and most preferably 25 min.
In the present invention, the blowing agent preferably includes:
a mixed solution of hydrogen peroxide and sodium lauryl sulfate.
In the invention, the mass ratio of the hydrogen peroxide to the sodium dodecyl sulfate is preferably (3-2): (2-1), more preferably (2.3-2.7): (1.3 to 1.7), most preferably 2.5: 1.5.
in the present invention, the mass of the blowing agent is preferably 0.5 to 2%, more preferably 1 to 1.5% of the mass of the second mixture.
In the invention, the mixed solution of hydrogen peroxide and lauryl sodium sulfate is used as a foaming agent, the foaming effect is obvious, the addition amount is about 1 percent, and the porosity can reach the porosity (namely 40 percent) required by the common porous brick for building heat preservation.
In the present invention, the third mixing is preferably rapid stirring.
In the present invention, the molding is preferably performed in a brick mold.
In the present invention, the curing is preferably performed in an oven; the curing time is preferably 12-24 hours, more preferably 15-20 hours, and most preferably 16-18 hours; the curing temperature is preferably 50-60 ℃, more preferably 53-57 ℃, and most preferably 55 ℃.
In the present invention, it is preferable that the curing process further includes:
and (4) curing under natural conditions after demolding to obtain the modified geopolymer porous brick.
In the present invention, the curing time under the natural condition is preferably 25 to 35 days, and more preferably 28 to 32 days.
In the embodiment of the present invention, the process flow for preparing modified geopolymer porous brick from fly ash from waste incineration is shown in fig. 1, and preferably comprises:
the fly ash enters a dioxin cracking device, nitrogen is introduced into the device to maintain an anoxic reduction environment, the device heats the fly ash to 350-400 ℃ and stays for 0.5-1 h, wherein the decomposition rate of the dioxin is more than 99.5%, the total amount of dioxin residues in a treated product is not more than 50ngTEQ/kg (dry weight of the fly ash), and the heated fly ash is quenched to 60 ℃ to prevent the dioxin from being resynthesized and then discharged.
The fly ash after dioxin cracking enters a primary washing stirring tank reactor, washing water uses backflow filtrate which is mechanically separated from the fly ash after secondary washing and supplements part of process water, and the proportion of water and ash is (2-3): 1 is preferred; the water content of the solid fly ash after the fly ash slurry after the first-stage water washing is mechanically dewatered is about 40-50 percent, and a centrifugal dehydrator is preferably selected as mechanical dewatering equipment; and (3) feeding the solid fly ash subjected to primary washing into a secondary washing stirring tank reactor, wherein the washing water is fresh process water, and the water-ash ratio is (2-3): 1 is preferred; the water content of solid fly ash after the fly ash slurry after the secondary washing is mechanically dewatered is about 30-40%, filtrate flows back to a primary washing stirring tank reactor to be used as washing water, and a centrifugal dehydrator is preferably selected as mechanical dewatering equipment; the content of soluble chlorine in the fly ash after the secondary washing is less than 2 percent.
Adding fly ash, calcined kaolin and portland cement clinker into the washed solid fly ash, and stirring, wherein the doping proportion of the fly ash is not more than 50% of the mass ratio of the matrix raw material, and the adding proportion of the portland cement clinker is preferably 6% -10% of the mass ratio of the matrix raw material; a small amount of process water can be added into the mixture in a proper amount and the mixture is continuously stirred uniformly to be in a slurry shape.
Adding an alkaline activator into the uniformly mixed slurry, and uniformly stirring to form a slurry, wherein the alkaline activator adopts 8-16 mol/L sodium hydroxide solution and water glass according to the weight ratio of 1: 1 proportion, the addition amount of the alkaline activator is 5-10% of the mass ratio of the base raw material, and the stirring time is 20-30 min.
And pouring a foaming agent into the slurry, quickly stirring, and then injecting the slurry into a brick mold, wherein the foaming agent is a mixed solution of hydrogen peroxide and lauryl sodium sulfate, and the addition amount of the foaming agent is preferably 0.5-2% of the mass ratio of the matrix raw material.
Curing the grouted mould in a constant temperature box for 12-24 h at 50-60 ℃; demolding after curing is finished, and curing for 28 days under natural conditions to prepare the modified geopolymer perforated brick; testing the heavy metal leaching concentration of the brick at the 7 th day of natural maintenance, wherein the heavy metal leaching concentration of the brick does not exceed the maximum allowable emission concentration limit value specified in GB 8978; the compression and breaking strengths of the blocks were tested on day 28 of natural curing.
In the present invention, the concept of geopolymer was proposed in 1978 by the French nation Davidovits, a type of geopolymer produced by AlO4And SiO4The tetrahedral structural unit forms an inorganic polymer with a three-dimensional network structure, and the chemical formula is Mn { - (SiO)2)zAlO2}n〃wH2O, amorphous to semi-crystalline, belonging to non-metallic materials; the most widely accepted geopolymer reaction mechanism is the theory of depolymerization and polycondensation, i.e. the coagulation hardening process of geopolymer material is the reaction process of forming three-dimensional macromolecular structure by recombination and polycondensation after silicon-oxygen bond and aluminum-oxygen bond in raw material (oligomer) are broken under the action of alkaline catalyst; the oligomer can be prepared by taking mineral waste, construction waste and the like as raw materials, has excellent mechanical properties and acid and alkali resistance, fire resistance and high temperature resistance, and is very useful in building materials; in addition, the structure of the geopolymer is a crystal-like structure formed by cyclic molecular chains, the cyclic molecules are combined to form a closed cavity (cage shape), metal ions and other toxic substances can be divided and enclosed in the cavity, and meanwhile, the aluminum ions in the framework can also adsorb the metal ions, so that the metal ions in the system can be more effectively fixed; researches show that the fixing rate of the geopolymer matrix to Hg, As, Fe, Mn, Ar, Co and Pb is greater than or equal to 90 percent, so that the geopolymer matrix can also be used in the field of recycling of fly ash buildings.
The modified geopolymer porous brick prepared by the method provided by the invention has excellent performance and higher compressive strength and flexural strength, can be used as a non-structural light-weight fireproof heat-insulating material, meets the requirements of technical specification (trial) for controlling pollution of the fly ash from incineration of household garbage (HJ 1134) 2020, and is a method for efficiently recycling the fly ash from incineration of garbage at low temperature.
The method carries out low-temperature building material utilization on the waste incineration fly ash, and compared with the prior art, the method does not occupy land resource disposal (compared with solidification/stabilization-landfill); the consumption ratio is higher and other large-scale cooperative facilities (compared with a water washing cooperative cement kiln) are not needed to be relied on; in the treatment process, only the dioxin cracking process needs to heat the fly ash to 350-400 ℃, and high-temperature treatment is not needed, so that the energy consumption is large (compared with water washing cement kiln cooperation 1300 ℃, high-temperature sintering for preparing ceramic particles is 1000 ℃, and plasma melting is 1300 ℃). Pollutants such as most of dioxin, chlorine salt and a small part of heavy metal in the fly ash are removed by adopting a pretreatment process of low-temperature cracking of dioxin and secondary washing for removing chlorine salt, so that a subsequent treatment product meets the requirements of technical specifications (trial) for controlling pollution of fly ash from incineration of household garbage (HJ 1134-; the compression strength and the bending strength of the prepared brick are greatly reduced due to the doping of the fly ash and the use of the foaming agent, the matrix raw material is optimized, the proportion of the fly ash is not more than 50 percent (the fly ash after washing and dehydration is referred to herein), a small amount of ordinary portland cement is added for modification to improve the compression strength and the bending strength of the brick, and the limitation on the addition amount of the fly ash is equivalent to the dilution of the heavy metal content of the brick; the foaming effect is obvious by using the mixed solution of hydrogen peroxide and lauryl sodium sulfate as a foaming agent, the addition amount is about 1 percent, and the porosity can reach the porosity (namely 40 percent) required by the common porous brick for building heat preservation.
The invention prepares the geopolymer by using fly ash as a matrix raw material through an alkali excitation method, wherein the geopolymer is prepared from AlO4And SiO4The inorganic polymer with a three-dimensional net structure formed by tetrahedral structural units can be prepared by taking mineral waste, construction waste and the like as raw materials, has excellent mechanical properties and acid-base-resistant, fire-resistant and high-temperature-resistant properties, is a 'crystal-like' structure formed by cyclic molecular chains, and is combined with the cyclic molecules to form a closed cavity (cage shape), so that metal ions and other toxic substances can be divided and enclosed in the cavity, and meanwhile, aluminum ions in the framework can also adsorb the metal ions, thereby more effectively fixing the metal ions in the system. Researches show that the fixing rate of the geopolymer matrix to Hg, As, Fe, Mn, Ar, Co and Pb is greater than or equal to 90 percent, so that the geopolymer matrix can also be used in the field of recycling of fly ash buildings.
The fly ash used in the following examples of the invention is from a refuse incineration project in Zhejiang, the yield of the fly ash in the plant is 3.12%, and the main chemical components are CaO and SiO2And Al2O3The contents are 32.7%, 23.2% and 6.8% respectively.
Example 1
The fly ash enters a dioxin cracking device, the heating temperature is 350 ℃, the fly ash stays for 1 hour, the water content of the fly ash is 36 percent after chlorine salt is eluted by primary and secondary water, the fly ash, calcined kaolin and portland cement clinker are added into the fly ash, wherein the fly ash accounts for 40 percent by weight, the fly ash accounts for 30 percent by weight, the calcined kaolin accounts for 23.5 percent by weight and the portland cement clinker accounts for 6.5 percent by weight, and a small amount of process water is added to uniformly stir the mixture into a slurry shape; and then adding 8 wt% of alkaline activator (prepared by 16mol/L sodium hydroxide and industrial water glass in a mass ratio of 1: 1) into the slurry, continuously stirring for 30min, pouring 1 wt% of foaming agent (prepared by mixing hydrogen peroxide and sodium dodecyl sulfate in a mass ratio of 3: 2) into the slurry, quickly stirring, then injecting the slurry into a 190 mm-115 mm-90 mm brick mold, curing the mold in a thermostat for 24h at the curing temperature of 50 ℃, demolding after the curing is finished, and curing for 28d under natural conditions to obtain the modified geopolymer porous brick.
In the embodiment 1 of the invention, leachate is prepared from the natural maintenance day 7 according to HJ557-2010 horizontal oscillation method for leaching toxicity from solid waste, wherein the leaching concentrations of total lead, total cadmium, total chromium, total mercury and total arsenic are respectively 0.36mg/L, 0.06mg/L, 0.43mg/L, 0.02mg/L and 0.39mg/L, and the maximum allowable discharge concentration limit value specified in GB 8978 Integrated wastewater discharge Standard is met.
The tests of compression strength and rupture strength are carried out on the 28 th day of natural curing, the average compression strength of the brick reaches 11.4MPa, the rupture strength reaches 3.6MPa, the porosity is 43 percent, and the volume density is 1.09kg/m3(test method for concrete small hollow building blocks GBT 4111-.
Example 2
The fly ash enters a dioxin cracking device, the heating temperature is 380 ℃, the fly ash stays for 0.5h, the water content of the fly ash is 30 percent after chlorine salt is eluted by primary and secondary water, the fly ash, calcined kaolin and portland cement clinker are added into the fly ash, wherein the proportion of the fly ash is 42 percent by weight, the proportion of the fly ash is 40 percent by weight, the proportion of the calcined kaolin is 10 percent by weight and the proportion of the portland cement clinker is 8 percent by weight, and a small amount of process water is added to uniformly stir the mixture into a slurry shape; and then adding 5 wt% of alkaline activator (prepared by 12mol/L of sodium hydroxide and industrial water glass in a mass ratio of 1: 1) into the slurry, continuously stirring for 30min, pouring 0.5 wt% of foaming agent (prepared by mixing hydrogen peroxide and sodium dodecyl sulfate in a mass ratio of 2: 1) into the slurry, quickly stirring, then injecting the slurry into a 190mm 115mm 90mm brick mould, curing the grouted mould in a constant temperature box for 24h at the curing temperature of 50 ℃, demoulding after the curing is finished, and curing for 28d under natural conditions to obtain the modified geopolymer porous brick.
In the embodiment 2 of the invention, leachate is prepared from the natural maintenance day 7 according to HJ557-2010 horizontal oscillation method for leaching toxicity of solid waste, wherein the leaching concentrations of total lead, total cadmium, total chromium, total mercury and total arsenic are respectively 0.53mg/L, 0.09mg/L, 1.21mg/L, 0.05mg/L and 0.46mg/L, and the maximum allowable discharge concentration limit value specified in GB 8978 Integrated wastewater discharge Standard is met.
The tests of compression strength and rupture strength are carried out on the 28 th day of natural curing, the average compression strength of the brick reaches 9.6MPa, the rupture strength reaches 3.1MPa, the porosity is 39 percent, and the volume density is 1.07kg/m3(test method for concrete small hollow building blocks GBT 4111-.
Example 3
The fly ash enters a dioxin cracking device, the heating temperature is 400 ℃, the fly ash stays for 0.8h, the fly ash is subjected to chlorine salt elution by primary and secondary water, the moisture content of the fly ash is 40 percent after passing through a centrifugal dehydrator, the fly ash, calcined kaolin and portland cement clinker are added into the fly ash, wherein the fly ash accounts for 45 percent by weight, the fly ash accounts for 20 percent by weight, the calcined kaolin accounts for 28 percent by weight and the portland cement clinker accounts for 7 percent by weight, and a small amount of process water is added to uniformly stir the mixture into a slurry shape; and then adding 10 wt% of alkaline activator (prepared by 8mol/L of sodium hydroxide and industrial water glass in a mass ratio of 1: 1) into the slurry, continuously stirring for 30min, pouring 2 wt% of foaming agent (prepared by mixing hydrogen peroxide and lauryl sodium sulfate in a mass ratio of 1: 1) into the slurry, quickly stirring, then injecting the slurry into a 190 mm-115 mm-90 mm brick mold, curing the mold in a thermostat for 24h at a curing temperature of 60 ℃, demolding after curing is finished, and curing for 28d under natural conditions to obtain the modified geopolymer porous brick.
In the embodiment 3 of the invention, leachate is prepared from the natural maintenance day 7 according to HJ557-2010 horizontal oscillation method for leaching toxicity of solid waste, wherein the leaching concentrations of total lead, total cadmium, total chromium, total mercury and total arsenic are respectively 0.32mg/L, 0.05mg/L, 0.41mg/L, 0.03mg/L and 0.36mg/L, and the maximum allowable discharge concentration limit value specified in GB 8978 Integrated wastewater discharge Standard is met.
The tests of the compressive strength and the flexural strength are carried out on the 28 th day of natural curing, the average compressive strength of the brick reaches 9.4MPa, the flexural strength reaches 3.0MPa, the porosity is 46 percent, and the volume density is 1.02kg/m3(test method for concrete small hollow blocks GBT 4111-1997) meets the requirements of non-bearing heat-insulating light wall.
The invention prepares the geopolymer by using fly ash as a matrix raw material through an alkali excitation method, wherein the geopolymer is prepared from AlO4And SiO4The inorganic polymer with a three-dimensional net structure formed by tetrahedral structural units can be prepared by taking mineral waste, construction waste and the like as raw materials, has excellent mechanical properties and acid-base-resistant, fire-resistant and high-temperature-resistant properties, is a 'crystal-like' structure formed by cyclic molecular chains, and is combined with the cyclic molecules to form a closed cavity (cage shape), so that metal ions and other toxic substances can be divided and enclosed in the cavity, and meanwhile, aluminum ions in the framework can also adsorb the metal ions, thereby more effectively fixing the metal ions in the system. Researches show that the fixing rate of the geopolymer matrix to Hg, As, Fe, Mn, Ar, Co and Pb is greater than or equal to 90 percent, so that the geopolymer matrix can also be used in the field of recycling of fly ash buildingsA domain. Pollutants such as most of dioxin, chlorine salt and a small part of heavy metal in fly ash are removed by adopting a pretreatment process of low-temperature cracking of dioxin and secondary washing for removing chlorine salt, so that subsequent treatment products meet the requirements of technical specifications (trial) for controlling pollution of fly ash from incineration of household garbage (HJ 1134) 2020.
The modified geopolymer porous brick prepared by the invention has a good pore structure, is quick to form, low in shrinkage, light in weight, good in heat preservation, fireproof and corrosion-resistant, and has potential in the market of non-structural light fireproof heat preservation building materials. The fixation/stabilization-landfill of the waste incineration fly ash occupies land resources, the cooperative consumption proportion of the water washing-cement kiln is low (5%), the dependence on large-scale cement kiln enterprises is high, the high-temperature building material utilization (sintering for preparing ceramsite and melting for vitrification) can be effectively and harmlessly recycled, but the construction, operation and maintenance costs are high, and a large amount of heat energy is consumed, so that the low-temperature green building material transformation of the waste incineration fly ash is a currently explored route, the special structure of the geopolymer can fix heavy metals, and the material strength is improved, thereby being one of the future development directions.
While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be clearly understood by those skilled in the art that various changes may be made to adapt a particular situation, material, composition of matter, substance, method or process to the objective, spirit and scope of this application without departing from the true spirit and scope of the invention as defined by the appended claims. All such modifications are intended to be within the scope of the claims appended hereto. Although the methods disclosed herein have been described with reference to particular operations being performed in a particular order, it should be understood that these operations may be combined, sub-divided, or reordered to form equivalent methods without departing from the teachings of the present disclosure. Accordingly, unless specifically indicated herein, the order and grouping of the operations is not a limitation of the present application.
Claims (10)
1. A method for preparing modified geopolymer perforated bricks by using waste incineration fly ash comprises the following steps:
carrying out washing on the fly ash after dioxin cracking to obtain a washing product;
performing first mixing on the washing product, the fly ash, the kaolin and the portland cement to obtain a first mixture;
carrying out second mixing on the first mixture and an alkaline activator to obtain a second mixture;
thirdly mixing the second mixture and a foaming agent to obtain slurry;
and curing the slurry after forming to obtain the geopolymer porous brick.
2. The method according to claim 1, wherein the temperature for cracking dioxin is 350 to 400 ℃; the cracking time of the dioxin is 0.5-1 hour.
3. The method of claim 1, wherein the water washing comprises:
primary washing and secondary washing;
the mass ratio of water ash of the first-stage washing and the second-stage washing is independently selected from (2-3): 1.
4. the method of claim 1, wherein the primary washing step further comprises:
carrying out mechanical dehydration; the water content of the solid fly ash subjected to mechanical dehydration is 40-50%;
after the second-stage water washing, the method also comprises the following steps:
carrying out mechanical dehydration; the water content of the solid fly ash after mechanical dehydration is 30-40%, and the content of soluble chlorine is less than 2%.
5. The method of claim 1, wherein the water-washed product comprises no more than 50% by mass of the first mixture;
the mass content of the fly ash in the first mixture is 20-40%;
the mass content of the kaolin in the first mixture is 10-30%;
the mass content of the Portland cement in the first mixture is 6-10%.
6. The method according to claim 1, wherein the alkaline stimulant comprises:
sodium hydroxide solution and water glass;
the concentration of the sodium hydroxide solution is 8-16 mol/L;
the mass ratio of the sodium hydroxide solution to the water glass is (0.8-1.2): 1.
7. the method according to claim 1, wherein the mass of the alkali-activator is 5 to 10% of the mass of the first mixture.
8. The method of claim 1, wherein the blowing agent comprises:
a mixed solution of hydrogen peroxide and sodium dodecyl sulfate;
the mass of the foaming agent is 0.5-2% of that of the second mixture.
9. The method according to claim 1, wherein the curing time is 12 to 24 hours; the curing temperature is 50-60 ℃.
10. The method of claim 1, further comprising, after said maintaining:
curing under natural conditions after demolding to obtain the modified geopolymer porous brick;
and the curing time under the natural condition is 25-35 days.
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| CN115466096A (en) * | 2022-07-25 | 2022-12-13 | 河海大学 | Alkali-activated garbage incineration fly ash light prefabricated insulating brick and preparation method thereof |
| CN115624961A (en) * | 2022-10-24 | 2023-01-20 | 苏州市吴中区固体废弃物处理有限公司 | Recycling treatment method for utilizing household garbage incineration fly ash |
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