CN114956620B - Method for preparing modified magnesium oxychloride cement by using bischofite and waste incineration fly ash - Google Patents

Method for preparing modified magnesium oxychloride cement by using bischofite and waste incineration fly ash Download PDF

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CN114956620B
CN114956620B CN202210597153.3A CN202210597153A CN114956620B CN 114956620 B CN114956620 B CN 114956620B CN 202210597153 A CN202210597153 A CN 202210597153A CN 114956620 B CN114956620 B CN 114956620B
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fly ash
bischofite
activated
oxychloride cement
modified magnesium
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CN114956620A (en
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黄涛
宋东平
周璐璐
杨春海
徐娇娇
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Changshu Institute of Technology
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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
    • C04B9/00—Magnesium cements or similar cements
    • C04B9/20—Manufacture, e.g. preparing the batches
    • 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
    • C04B9/00—Magnesium cements or similar cements
    • C04B9/02—Magnesium cements containing chlorides, e.g. Sorel cement
    • 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
    • C04B9/00—Magnesium cements or similar cements
    • C04B9/06—Cements containing metal compounds other than magnesium compounds, e.g. compounds of zinc or lead
    • 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
    • C04B9/00—Magnesium cements or similar cements
    • C04B9/11—Mixtures thereof with other inorganic cementitious materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Abstract

The invention discloses a method for preparing modified magnesium oxychloride cement by using bischofite and waste incineration fly ash. The preparation process is simple, the prepared modified magnesium oxychloride cement has high activity, the highest compressive strength can reach 53.45MPa, the dioxin content in the prepared modified magnesium oxychloride cement is lower than 10ng-TEQ/kg, and the leachable heavy metal content is far lower than the limit value specified in GB 30760.

Description

Method for preparing modified magnesium oxychloride cement by using bischofite and waste incineration fly ash
Technical Field
The invention relates to a method for preparing modified magnesium oxychloride cement by using bischofite and waste incineration fly ash, belonging to the field of harmless treatment and resource utilization of hazardous wastes.
Background
The domestic garbage incineration fly ash is fine powdery particles obtained by quenching high-temperature flue gas generated in the domestic garbage incineration process, and capturing the high-temperature flue gas by a dry reactor (an activated carbon system and a slaked lime system) and a bag-type dust collector. The fly ash from incineration of household garbage is listed in national records of dangerous waste (2021 edition) because of the dioxin and heavy metal pollutants, and is strictly managed according to the dangerous waste. Meanwhile, the fly ash from incineration of the household garbage contains a large amount of calcium-based materials, so that the fly ash can be used as cement raw meal to replace part of limestone for production of portland cement. However, the content of salt in the fly ash from incineration of household garbage is usually as high as 25% -45% (sodium chloride and potassium chloride). The high salt content of the fly ash from the incineration of the household garbage and the known harmfulness of salt to cement production and the limit control (less than 0.06%) of the chlorine content of portland cement strictly limit the usage amount of the fly ash from the incineration of the household garbage in the cement kiln process. In order to avoid the influence of salt introduced by the household garbage incineration fly ash on the production of the cement kiln as much as possible, the garbage incineration fly ash is subjected to multi-stage water washing before entering the kiln besides controlling the doping amount so as to separate the salt from the garbage incineration fly ash as much as possible. However, the waste incineration fly ash washing process cannot completely remove the salt in the waste incineration fly ash, and simultaneously, the waste incineration fly ash washing process can also generate a large amount of washing waste liquid. The prior treatment process of the waste incineration fly ash washing waste liquid has various technical problems in the links of impurity removal, detoxification, scale inhibition, crystal dispersion, separation of different salts and the like.
Therefore, based on the above analysis, it is necessary to develop a new technology for avoiding the generation of waste liquid as much as possible while overcoming the environmental hazards of heavy metals and dioxin in the waste incineration fly ash and separately utilizing various components in the waste incineration fly ash to realize the full resource utilization of the waste incineration fly ash.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a method for preparing modified magnesium oxychloride cement by using bischofite and waste incineration fly ash.
The technical scheme is as follows: the invention relates to a method for preparing modified magnesium oxychloride cement by using bischofite and waste incineration fly ash, which comprises the following steps:
(1) Mixing the waste incineration fly ash with bischofite, and uniformly stirring to obtain a fly ash bischofite-doped mixture;
(2) Mixing the fly ash doped brucite mixture with water, and uniformly stirring to obtain fly ash doped brucite mixed slurry;
(3) Adding the flyash-doped bischofite mixed slurry into a cathode chamber of an electrolytic cell, mixing, and connecting a direct-current power supply to electrolyze to obtain electrolytically-activated flyash-doped bischofite mixed slurry;
(4) Mixing the electrolytic activated fly ash doped bischofite mixed slurry with the printing and dyeing sludge, and uniformly stirring to obtain activated printing and dyeing sludge ash;
(5) And drying and activating the activated printing and dyeing sludge ash to obtain a high-temperature activated mixture, and grinding the high-temperature activated mixture to obtain the modified magnesium oxychloride cement.
Preferably, in the step (1), the mass ratio of the waste incineration fly ash to the bischofite is 15-45.
Preferably, in the step (2), the liquid-solid ratio of the water to the fly ash doped bischofite mixture is 1-3.
Preferably, in the step (3), the dc power supply voltage threshold range is 20 to 200V, and the dc power supply threshold range is 100 to 1000A.
Preferably, in the step (3), the electrolysis time is 1-6 h.
Preferably, in the step (4), the mass ratio of the printing and dyeing sludge to the electrolytically activated fly ash doped bischofite mixed pulp is 5-15.
Preferably, in the step (5), the activation temperature is 800-1200 ℃, and the activation time is 0.5-2.5 h.
The reaction mechanism is as follows: adding the fly ash doped bischofite mixed slurry into a cathode chamber of an electrolytic cell, and after a power supply is switched on, part of chloride ions ionized from magnesium chloride and sodium chloride in the fly ash doped bischofite mixed slurry are transferred to an anode and converted into chlorine and hypochlorite. Under the action of electron balance, water obtains electrons on the surface of the cathode to generate hydroxyl and hydrogen. The hydroxide radical combines with magnesium ion, calcium ion and sodium ion in the fly ash doped bischofite mixed slurry to generate magnesium hydroxide precipitate, calcium hydroxide precipitate and sodium hydroxide. Under the conditions of high-temperature activation and alkali excitation, the magnesium hydroxide precipitate is decomposed into high-activity magnesium oxide, the calcium hydroxide is decomposed into calcium oxide, organic matters in the printing and dyeing sludge are thermally decomposed and converted into carbon dioxide and water, and chlorine and hypochlorite are decomposed into hydrogen chloride gas and oxygen. Inducing the silicon-based material in the printing and dyeing sludge to react with calcium oxide and magnesium oxide by using hydrogen chloride gas, oxygen and water vapor to generate a calcium chloride magnesium-based cementing material; the carbon dioxide gas and oxygen make the cement fluffy and porous. The magnesium-based gelled material of high-activity magnesium oxide, calcium oxide, magnesium chloride and calcium silicate chloride generated by the reaction forms the main active component of the modified magnesium oxychloride cement.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:
based on the component characteristics of bischofite and waste incineration fly ash, the invention realizes the purpose of changing waste into valuable by a method combining electrolysis activation and high-temperature activation, and realizes the preparation of the modified magnesium oxychloride cement. The preparation process is simple, the modified magnesium oxychloride cement prepared by using bischofite and waste incineration fly ash has high activity, the highest compressive strength can reach 53.45MPa, the dioxin content in the prepared modified magnesium oxychloride cement is lower than 10ng-TEQ/kg, and the content of leachable heavy metals is far lower than the limit value specified in GB 30760.
Drawings
FIG. 1 is a flow chart of the preparation method of the present invention.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
Incineration fly ash of household garbage: the household garbage incineration fly ash is taken from a certain normally-cooked garbage incineration power plant and collected by a bag-type dust collector. CaO content in the refuse incineration fly ash sample of 61.37% and SO content of 3.62% 3 、4.68％SiO 2 、1.64％Al 2 O 3 、6.32％Na 2 O、3.46％K 2 O、15.37％Cl、1.12％MgO、1.17％ZnO、0.76％PbO、0.49％CdO。
Printing and dyeing sludge: the printing and dyeing sludge is taken from a well-done printing and dyeing mill and collected in a wastewater treatment sedimentation tank. The printing sludge contains 20.48% C, 3.75% H, 1.94% N, 2.06% S, 31.77% organic matter, 2.98% Al, 31.44% Fe, 2.12% Ca, 5.58% others.
Bischofite: bischofite is provided by gelmu Bimeida chemical Limited liability company.
Example 1 influence of the quality ratio of fly ash from waste incineration to bischofite on the Properties of the modified magnesium oxychloride cement
The method comprises the following steps of (1) weighing the waste incineration fly ash and bischofite according to the mass ratio of 12.5. And respectively weighing the water and fly ash doped brucite mixture according to the liquid-solid ratio of 1. And respectively adding 9 groups of the fly ash and brucite blended slurry into a cathode chamber of an electrolytic cell, mixing, connecting a direct current power supply to electrolyze for 1h to obtain 9 groups of the electrolyzed and activated fly ash and brucite blended slurry, wherein the voltage threshold range of the direct current power supply is 20V, and the threshold range of the direct current power supply is 100A. Respectively weighing the printing and dyeing sludge and the electrolyzed and activated fly ash doped bischofite mixed slurry according to the mass ratio of 5. And drying the 9 groups of activated printing and dyeing sludge ash, activating for 0.5h at 800 ℃ to obtain 9 groups of high-temperature activated mixture, and grinding into powder to obtain 9 groups of modified magnesium oxychloride cement.
And (4) performance testing: the 9 groups of modified magnesium oxychloride cement materials are respectively prepared into the sand to be detected, wherein the doped sand is selected from ISO standard sand specified in Cement mortar Strength test method (ISO method) GB/T17671-1999, and the water is selected from tap water. The preparation of the mortar, the preparation of the test piece, the maintenance of the test piece and the measurement of the compression strength of the 28d test piece are all carried out according to the Standard in the test methods for the strength of Cement mortar (ISO method) GB/T17671-1999.
Heavy metal leaching test in the modified magnesium oxychloride cement: the leachate is prepared from the modified magnesium oxychloride cement according to the method of horizontal oscillation method of solid waste leaching toxicity (HJ 557), and the concentration of heavy metals in the leachate is measured by using an inductively coupled plasma mass spectrometer (Thermo Scientific) TM ELEMENT TM ) And (6) detecting.
A detection test of dioxin content in modified magnesium oxychloride cement comprises the following steps: the detection of the dioxin content in the modified magnesium oxychloride cement is carried out according to the technical specification for controlling the pollution of the fly ash from the incineration of household garbage (HJ 1134).
The test results of this example are shown in Table 1.
TABLE 1 influence of the quality ratio of fly ash from incineration of refuse and bischofite on the properties of the modified magnesium oxychloride cement prepared
Figure BDA0003668564370000031
Figure BDA0003668564370000041
As can be seen from Table 1, the total amount of dioxin residues in the prepared modified magnesium oxychloride cement is not more than 50ng-TEQ/kg, and the leaching concentration of the heavy metal in the prepared modified magnesium oxychloride cement is far lower than the maximum allowable emission concentration limit specified in GB 8978. When the mass ratio of the waste incineration fly ash to the bischofite is less than 15, the mixing amount of the waste incineration fly ash is less, the chlorine and hypochlorite generated in the electrolysis process are less, and simultaneously the calcium oxide generated under the conditions of high-temperature activation and alkali excitation is reduced, so that the generated calcium-magnesium-calcium-chloride-based cementing material is reduced, and the uniaxial compressive strength of the prepared modified magnesium-oxy-chloride cement is obviously reduced along with the reduction of the mass ratio of the waste incineration fly ash to the bischofite. When the mass ratio of the waste incineration fly ash to the bischofite is equal to 15-45, adding the fly ash doped bischofite mixed slurry into a cathode chamber of an electrolytic cell, and transferring partial chloride ions ionized from magnesium chloride and sodium chloride in the fly ash doped bischofite mixed slurry into an anode and converting the chloride ions into chlorine and hypochlorite after a direct current power supply is switched on. Under the action of electron balance, water obtains electrons on the surface of the cathode to generate hydroxyl and hydrogen. The hydroxide radical combines with magnesium ion, calcium ion and sodium ion in the fly ash doped brucite mixed slurry to generate magnesium hydroxide precipitate, calcium hydroxide precipitate and sodium hydroxide. Under the conditions of high-temperature activation and alkali excitation, the magnesium hydroxide is precipitated and decomposed into high-activity magnesium oxide, the calcium hydroxide is decomposed into calcium oxide, organic matters in the printing and dyeing sludge are decomposed into carbon dioxide and water through heat and are converted into chlorine gas and hypochlorite gas through heat, and the chlorine gas and hypochlorite are decomposed into hydrogen chloride gas and oxygen. The hydrogen chloride gas, the oxygen gas and the water vapor induce the reaction of the silicon-based material in the printing and dyeing sludge with the calcium oxide and the magnesium oxide to generate calcium chloride and magnesium chloride-based gelled material; the carbon dioxide gas and oxygen make the cement fluffy and porous. Finally, the uniaxial compressive strength of the prepared modified magnesium oxychloride cement is more than 43MPa. When the mass ratio of the waste incineration fly ash to the bischofite is more than 45 and 100, the domestic waste incineration fly ash is excessively added, excessive chlorine and hypochlorite are introduced in the electrolysis process, and excessive calcium oxide is generated under the conditions of high-temperature activation and alkali excitation, so that the magnesium chloride content of the generated calcium magnesium chloride silicate-based cementing material is excessive, and the uniaxial compressive strength of the prepared modified magnesium oxychloride cement is obviously reduced along with the further increase of the mass ratio of the waste incineration fly ash to the bischofite. Therefore, in summary, the combination of efficiency and cost is most beneficial to improving the uniaxial compressive strength of the prepared modified magnesium oxychloride cement when the mass ratio of the waste incineration fly ash to the bischofite is 15-45.
Example 2 influence of the energizing time of the DC power supply on the properties of the modified magnesium oxychloride cement
Respectively weighing the waste incineration fly ash and the bischofite according to the mass ratio of 45. And respectively weighing the water and fly ash doped bischofite mixture according to the liquid-solid ratio of 2. Adding the fly ash doped brucite mixed slurry into a cathode chamber of an electrolytic cell, mixing, connecting a direct current power supply to electrolyze for 0.25h, 0.5h, 0.75h, 1h, 3.5h, 6h, 7h, 8h and 9h respectively to obtain 9 groups of electrolyzed activated fly ash doped brucite mixed slurry, wherein the voltage threshold range of the direct current power supply is 110V, and the threshold range of the direct current power supply is 550A. Respectively weighing the printing and dyeing sludge and the electrolyzed and activated fly ash doped bischofite mixed slurry according to the mass ratio of 10. And drying the 9 groups of activated printing and dyeing sludge ash, activating for 1.5 hours at the temperature of 1000 ℃ to obtain 9 groups of high-temperature activated mixture, and grinding into powder to obtain 9 groups of modified magnesium oxychloride cement.
The performance test of the modified magnesium oxychloride cement, the leaching test of heavy metals in the modified magnesium oxychloride cement and the detection test of the dioxin content in the modified magnesium oxychloride cement are the same as those in the example 1. The test results of this example are shown in Table 2.
TABLE 2 influence of DC power supply on the properties of modified magnesium oxychloride cement
Figure BDA0003668564370000051
As can be seen from the table 2, the total amount of dioxin residues in the prepared modified magnesium oxychloride cement is not more than 50ng-TEQ/kg, and the leaching concentration of the heavy metal in the prepared modified magnesium oxychloride cement is far lower than the maximum allowable emission concentration limit specified in GB 8978. When the direct-current power supply is electrified for less than 1 hour, the fly ash doped brucite mixed slurry is added into a cathode chamber of the electrolytic cell, and chlorine, hypochlorite and magnesium hydroxide generated after the power supply is switched on are precipitated, and calcium hydroxide precipitate and sodium hydroxide are less, so that the generated calcium-magnesium-calcium-chloride-based cementing material is reduced, and the cement uniaxial compressive strength of the prepared modified magnesium oxychloride is obviously reduced along with the reduction of the electrified electrolysis time of the direct-current power supply. When the direct current power supply is electrified and the electrolysis time is equal to 1-6 h, the fly ash doped brucite mixed slurry is added into the cathode chamber of the electrolytic cell, and after the power supply is switched on, part of chloride ions ionized from magnesium chloride and sodium chloride in the fly ash doped brucite mixed slurry is transferred to the anode and converted into chlorine and hypochlorite. Under the action of electron balance, water obtains electrons on the surface of the cathode to generate hydroxyl and hydrogen. The hydroxide radical combines with magnesium ion, calcium ion and sodium ion in the fly ash doped brucite mixed slurry to generate magnesium hydroxide precipitate, calcium hydroxide precipitate and sodium hydroxide. Finally, the uniaxial compressive strength of the prepared modified magnesium oxychloride cement is more than 46MPa. When the direct-current power supply is electrified and electrolyzed for more than 6 hours, the electrolysis time is too long, the chlorine gas escapes more, and the generation amount of the high-activity calcium magnesium silicate chloride-based cementing material is reduced under the conditions of high-temperature activation and alkali excitation, so that the uniaxial compressive strength of the prepared modified magnesium oxychloride cement is obviously reduced along with the further increase of the electrolysis time. Therefore, comprehensively, the efficiency and the cost are combined, and when the direct current power supply is electrified and the electrolysis time is 1-6 h, the uniaxial compressive strength of the prepared modified magnesium oxychloride cement is improved.
Example 3 Effect of quality ratio of printing and dyeing sludge and electrolytic activated fly ash blended with bischofite paste on Property of modified magnesium oxychloride Cement
Respectively weighing the waste incineration fly ash and the bischofite according to the mass ratio of 45. And respectively weighing the water and fly ash doped bischofite mixture according to the liquid-solid ratio of 3. Adding the flyash-doped bischofite mixed slurry into a cathode chamber of an electrolytic cell, mixing, connecting a direct-current power supply to electrolyze for 6 hours to obtain the electrolytically-activated flyash-doped bischofite mixed slurry, wherein the voltage threshold range of the direct-current power supply is 200V, and the voltage threshold range of the direct-current power supply is 1000A. The method comprises the following steps of (1) weighing the printing and dyeing sludge and the electrolytically activated fly ash doped bischofite mixed slurry according to the mass ratio of 2.5. And drying the 9 groups of activated printing and dyeing sludge ash, activating for 2.5 hours at 1200 ℃ to obtain 9 groups of high-temperature activated mixture, and grinding into powder to obtain 9 groups of modified magnesium oxychloride cement.
The performance test of the modified magnesium oxychloride cement, the leaching test of heavy metals in the modified magnesium oxychloride cement, and the detection test of dioxin content in the modified magnesium oxychloride cement are the same as those in example 1. The test results of this example are shown in Table 3.
TABLE 3 influence of quality ratio of mixed slurry of printing and dyeing sludge and electrolytic activated fly ash doped with brucite on properties of the prepared modified magnesium oxychloride cement
Figure BDA0003668564370000061
As can be seen from Table 3, the total amount of dioxin residues in the prepared modified magnesium oxychloride cement is not more than 50ng-TEQ/kg, and the leaching concentration of the heavy metal in the prepared modified magnesium oxychloride cement is far lower than the maximum allowable emission concentration limit specified in GB 8978. When the mass ratio of the printing and dyeing sludge to the electrolyzed and activated fly ash doped bischofite mixed slurry is less than 5, the mixing amount of the printing and dyeing sludge is less, and the generation amount of the high-activity calcium silicate magnesium base chloride cementing material under the conditions of high-temperature activation and alkali excitation is reduced, so that the uniaxial compressive strength of the prepared modified magnesium oxychloride cement is obviously reduced along with the reduction of the mass ratio of the printing and dyeing sludge to the electrolyzed and activated fly ash doped bischofite mixed slurry. When the mass ratio of the printing and dyeing sludge to the electrolyzed and activated fly ash doped bischofite mixed slurry is 5-15, under the conditions of high-temperature activation and alkali excitation, magnesium hydroxide is precipitated and decomposed into high-activity magnesium oxide, calcium hydroxide is decomposed into calcium oxide, organic matters in the printing and dyeing sludge are thermally decomposed and converted into carbon dioxide and water, and chlorine and hypochlorite are decomposed into hydrogen chloride gas and oxygen. Inducing the silicon-based material in the printing and dyeing sludge to react with calcium oxide and magnesium oxide by using hydrogen chloride gas, oxygen and water vapor to generate a calcium chloride magnesium-based cementing material; the carbon dioxide gas and oxygen make the cement fluffy and porous. Finally, the uniaxial compressive strength of the prepared modified magnesium oxychloride cement is more than 49MPa. When the mass ratio of the printing and dyeing sludge to the electrolyzed and activated fly ash doped bischofite mixed slurry is more than 15, the mixing amount of the printing and dyeing sludge is too high, and the generation amount of the high-activity calcium silicate magnesium-based cementing material under the conditions of high-temperature activation and alkali excitation is reduced, so that the uniaxial compressive strength of the prepared modified magnesium oxychloride cement is obviously reduced along with the further increase of the mass ratio of the printing and dyeing sludge to the electrolyzed and activated fly ash doped bischofite mixed slurry. Therefore, in summary, the efficiency and the cost are combined, and when the mass ratio of the printing and dyeing sludge to the electrolytically activated fly ash doped brucite mixed slurry is 5-15.
Comparative example 1 comparison of properties of modified magnesium oxychloride cement prepared by different processes
The process of the invention comprises the following steps: respectively weighing the waste incineration fly ash and the bischofite according to the mass ratio of 45. And respectively weighing the water and fly ash doped bischofite mixture according to the liquid-solid ratio of 3. Adding the flyash-doped bischofite mixed slurry into a cathode chamber of an electrolytic cell, mixing, connecting a direct-current power supply to electrolyze for 6 hours to obtain the electrolytically-activated flyash-doped bischofite mixed slurry, wherein the voltage threshold range of the direct-current power supply is 200V, and the voltage threshold range of the direct-current power supply is 1000A. Respectively weighing the printing and dyeing sludge and the electrolyzed and activated fly ash doped bischofite mixed slurry according to the mass ratio of 15. And drying the activated printing and dyeing sludge ash, activating for 2.5 hours at 1200 ℃ to obtain a high-temperature activated mixture, and grinding into powder to obtain the modified magnesium oxychloride cement.
Comparative process 1: respectively weighing the waste incineration fly ash and the bischofite according to the mass ratio of 45. And respectively weighing the water and fly ash doped brucite mixture according to the liquid-solid ratio of 3. And respectively weighing the printing and dyeing sludge and the fly ash doped brucite mixed slurry according to the mass ratio of 15 to 100, and uniformly stirring to obtain the printing and dyeing sludge ash. Drying the printing and dyeing sludge ash, activating for 2.5 hours at 1200 ℃ to obtain a high-temperature activated mixture, and grinding into powder to obtain the modified magnesium oxychloride cement.
Comparative process 2: respectively weighing the waste incineration fly ash and the bischofite according to the mass ratio of 45. And respectively weighing the water and fly ash doped brucite mixture according to the liquid-solid ratio of 3. Adding the flyash-doped bischofite mixed slurry into a cathode chamber of an electrolytic cell, mixing, connecting a direct-current power supply to electrolyze for 6 hours to obtain the electrolytically-activated flyash-doped bischofite mixed slurry, wherein the voltage threshold range of the direct-current power supply is 200V, and the voltage threshold range of the direct-current power supply is 1000A. Respectively weighing the printing and dyeing sludge and the electrolyzed and activated fly ash doped bischofite mixed slurry according to the mass ratio of 15. And drying the activated printing and dyeing sludge ash, and grinding into powder to obtain the modified magnesium oxychloride cement.
Comparative process 3: respectively weighing the waste incineration fly ash and the bischofite according to the mass ratio of 45. And respectively weighing the water and fly ash doped brucite mixture according to the liquid-solid ratio of 3. Respectively weighing the printing and dyeing sludge and the fly ash doped bischofite mixed slurry according to the mass ratio of 15. Drying the printing and dyeing sludge ash, and grinding into powder to obtain the modified magnesium oxychloride cement.
The performance test of the modified magnesium oxychloride cement, the leaching test of heavy metals in the modified magnesium oxychloride cement, and the detection test of dioxin content in the modified magnesium oxychloride cement are the same as those in example 1. The test results of this example are shown in Table 3.
TABLE 4 comparison of properties of modified magnesium oxychloride cement prepared by using fly ash from waste incineration in different processes
Figure BDA0003668564370000081
As can be seen from table 4, the leaching toxicity and dioxin content of heavy metals in the modified magnesium oxychloride cement prepared by the comparative process 1, the comparative process 2 and the comparative process 3 are much higher than those in the process of the present invention, while the uniaxial compressive strength of the modified magnesium oxychloride cement prepared by the comparative process 1, the comparative process 2 and the comparative process 3 is much lower than that in the process of the present invention.

Claims (1)

1. A method for preparing modified magnesium oxychloride cement by using bischofite and waste incineration fly ash is characterized by comprising the following steps:
(1) Mixing waste incineration fly ash and bischofite, and uniformly stirring to obtain a fly ash bischofite mixture, wherein the mass ratio of the waste incineration fly ash to the bischofite is (15) - (45);
(2) Mixing the fly ash doped brucite mixture with water, and uniformly stirring to obtain fly ash doped brucite mixed slurry, wherein the liquid-solid ratio of the water to the fly ash doped brucite mixture is 1 to 3;
(3) Adding the flyash-doped brucite mixed slurry into a cathode chamber of an electrolytic cell, mixing, connecting a direct-current power supply to electrolyze to obtain the electrolytically-activated flyash-doped brucite mixed slurry, wherein the electrolyzing time is 1-6 h, the voltage threshold range of the direct-current power supply is 20-200V, and the direct-current power supply direct-current threshold range is 100-1000A;
(4) Mixing the electrolysis activated fly ash doped brucite mixed slurry with printing and dyeing sludge, and uniformly stirring to obtain activated printing and dyeing sludge ash, wherein the mass ratio of the printing and dyeing sludge to the electrolysis activated fly ash doped brucite mixed slurry is 5-15;
(5) Drying and activating the activated printing and dyeing mud ash to obtain a high-temperature activated mixture, and grinding the high-temperature activated mixture to obtain the modified magnesium oxychloride cement, wherein the activation temperature is 800-1200 ℃, and the activation time is 0.5-2.5 h.
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CN115893883A (en) * 2022-09-09 2023-04-04 中国科学院青海盐湖研究所 Method for preparing magnesium oxide for magnesium cement from bischofite-calcium-based solid waste
CN115572085B (en) * 2022-11-03 2023-05-23 常熟理工学院 Preparation method of magnesium aluminum sulfate cement and product thereof
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