CN106215850B - Method for improving microstructure and demercuration performance of magnetic beads in fly ash and product - Google Patents
Method for improving microstructure and demercuration performance of magnetic beads in fly ash and product Download PDFInfo
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
- B01J20/08—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04 comprising aluminium oxide or hydroxide; comprising bauxite
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
- B01J20/28002—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
- B01J20/28009—Magnetic properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/12—Silica and alumina
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/005—Spinels
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/74—Iron group metals
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0201—Impregnation
Abstract
The invention discloses a method for improving the microstructure and demercuration performance of magnetic beads in fly ash, which comprises the following steps: selecting magnetic bead particles from the fly ash by using a magnetic separator; testing chemical components of the magnetic beads by adopting X-ray fluorescence spectrum analysis (XRF), and determining the content m (Si, Al) of silicon and aluminum in the magnetic beads; placing the magnetic bead particles in a polytetrafluoroethylene container, adding an HF solution, and mechanically stirring; filtering out the magnetic bead particles impregnated by the HF solution, and washing the magnetic bead particles with deionized water for several times until the magnetic bead particles are neutral; and drying the magnetic bead particles to obtain the magnetic beads with improved microstructures. The invention also discloses a corresponding magnetic bead. The method adopts HF solution to carry out surface treatment on the magnetic beads, peels off aluminosilicate covered on the surfaces of the magnetic beads, fully exposes the wrapped spinel phase substances, improves the microstructure of the magnetic beads, increases the specific surface area, develops the pore structure and greatly improves the catalysis and adsorption performances of the magnetic beads.
Description
Technical Field
The invention belongs to the field of fine utilization of magnetic beads in fly ash of coal-fired solid waste and mercury removal of a coal-fired power plant, and particularly relates to a method and a product for improving the microstructure and the mercury removal performance of the magnetic beads of the fly ash.
Background
the fly ash magnetic beads have stronger magnetism and a special spinel structure, thereby having higher resource utilization value. According to the prediction, the annual output of fly ash in China at the end of 'twelve five hundred thousand' can reach 5.7 hundred million tons, and the magnetic bead yield in fly ash of a typical coal-fired power plant in China is 1.5 to 11.5 percent, so that the annual output of the magnetic beads reaches at least 2850 million tons (the magnetic bead yield is 5 percent), and the fly ash has good resource utilization prospect.
the magnetic beads are mainly derived from iron-containing minerals (pyrite, siderite and the like) in coal, and comprise 70-90% of iron spinel, 5-20% of hematite, a small amount of mullite, quartz and iron-containing silicate. In addition to the iron-rich component, the magnetic beads usually contain higher proportion of silicon and aluminum and small amount of manganese, calcium, magnesium, titanium, sodium and other elements. During the coal combustion process, iron-containing minerals evolve into magnetic beads of different morphologies: smooth magnetic beads, flaky magnetic beads, dendritic magnetic beads, granular magnetic beads, primary and secondary magnetic beads and the like. The magnetic beads can be divided into 4 types according to different iron content and crystallization states: an iron oxide phase, an aluminum-silicon containing iron oxide phase, an iron-rich aluminosilicate phase, and an iron-containing aluminosilicate phase. Because of its good catalytic and magnetic separation properties, magnetic beads have been widely used in the fields of catalysis, metallurgy, special concrete materials, etc.
The fly ash magnetic beads have a certain catalytic oxidation effect on elemental mercury in the flue gas, and the good catalytic performance of the magnetic beads is mainly derived from the special hercynite structure. However, the surface of the magnetic beads is usually covered by dense aluminosilicate, so that spinel phase substances with catalytic action in the magnetic beads are wrapped in the spinel phase substances and cannot really play a role, and the catalytic performance of the spinel phase substances is usually low. In addition, different magnetic beads have different microstructures such as specific surface area and pore structure, which greatly affect the catalytic performance.
in order to improve the catalytic performance of magnetic beads, the prior art has developed a scheme for optimizing and improving magnetic beads, such as the papers "A regenerated cobalt oxide loaded magnetic Catalyst from flash space for polymerization Removal in cobalt synthesis flow gas" (Environ. Sci. Technol, YangJ.; Zoy.; Zhang J.; ZongC, 2014,48, 14837. 14843.) and "Removal of elastic flow gas by regenerative Cu. Cl2 modified magnetic catalysts, catalysis and catalysis from flash space" (catalytic conversion and impregnation scheme) in which a novel catalytic solution with high catalytic activity is used as a Catalyst loaded on the surface of a carrier 428.
However, in this scheme, the adsorption performance of the magnetic beads is optimized only by loading a substance with catalytic activity on the surfaces of the magnetic beads, and since the specific surface area of the magnetic beads is small, the loading amount of the active substance on the surfaces of the magnetic beads is limited, and meanwhile, the active substance loaded on the surfaces of the magnetic beads is easy to agglomerate, resulting in low catalytic activity. In addition, when the magnetic beads loaded with the active substances are sprayed into flue gas for mercury removal, the magnetic beads and fly ash particles in the flue gas can rub and collide with each other, so that the active substances loaded on the surfaces of the magnetic beads are peeled off, and the catalytic activity of the magnetic beads is greatly reduced.
Disclosure of Invention
aiming at the defects or improvement requirements of the prior art, the invention provides a method and a product for improving the microstructure and the demercuration performance of a magnetic bead in fly ash, wherein the microstructure of the magnetic bead is optimized and improved, namely, HF solution is adopted to carry out surface treatment on the magnetic bead, and aluminosilicate covered on the surface of the magnetic bead is peeled off, so that the wrapped spinel phase substance is fully exposed, the catalytic performance of the wrapped spinel phase substance is improved, meanwhile, the microstructure of the magnetic bead can be improved, the specific surface area of the magnetic bead is increased, the pore structure of the wrapped spinel phase substance is developed, and the catalytic and adsorption performances of the magnetic bead can be further improved.
in order to achieve the above object, the present invention provides a method for improving the microstructure and demercuration performance of magnetic beads in fly ash, which comprises the following steps:
(1) selecting magnetic bead particles from the fly ash, and grinding and screening the magnetic beads;
(2) Placing the magnetic bead particles obtained in the step (1) in a polytetrafluoroethylene container, adding an HF solution, and mechanically stirring;
(3) filtering the magnetic bead particles soaked by the HF solution in the step (2), and washing the magnetic bead particles with deionized water for several times until the magnetic bead particles are neutral;
(4) And (4) drying the magnetic bead particles washed to be neutral in the step (3) to obtain the magnetic bead with the improved microstructure.
through the scheme, the magnetic beads are subjected to surface treatment by adopting the HF solution, and the aluminosilicate covered on the surfaces of the magnetic beads is peeled off, so that the coated hercynite phase substances are fully exposed, and the catalytic performance of the hercynite phase substances is improved. In addition, the method can also improve the microstructure of the magnetic beads, increase the specific surface area of the magnetic beads and develop the pore structure of the magnetic beads, thereby further improving the catalytic and adsorption performances of the magnetic beads.
As a further preferred of the invention, the method for improving the microstructure and the mercury removal performance of the magnetic beads in the fly ash further comprises the step of determining the content m (Si, Al) of silicon and aluminum in the magnetic beads by adding an HF solution to test the chemical composition of the magnetic beads.
as a further preferred aspect of the present invention, the addition amount of the HF solution is preferably determined by the content m (Si, Al) of silicon and aluminum in the magnetic beads, and specifically as follows:
m(Si,Al)＝12.27-0.029R+4.10C+0.51t-(5.0×10)RC+(1.6×10)Rt-
0.058Ct-(7.7×10)R-0.23C+(8.8×10)t
wherein m (Si, Al) is the content of silicon and aluminum in the magnetic beads; r is the ratio of the volume of the HF solution to the mass of the magnetic beads; c is the concentration of HF solution; t is the stirring time.
As a further preferred embodiment of the present invention, the content m (Si, Al) of silicon and aluminum in the magnetic bead is determined by testing the chemical composition of the magnetic bead using X-ray fluorescence spectroscopy (XRF).
In a further preferred embodiment of the present invention, the magnetic bead particle size is 100-400 mesh, preferably 200 mesh.
As a further preferred aspect of the present invention, the content of silicon in the magnetic beads is 25% to 35%; the content of aluminum is 15-25%.
In a further preferred embodiment of the present invention, the HF solution/magnetic bead ratio is 10 to 20ml/g, preferably 15 ml/g.
as a further preference of the invention, the concentration of the HF solution is from 1% to 10%, preferably 5%.
In a further preferred embodiment of the present invention, the stirring time is 5 to 30min, preferably 20 min.
In a further preferred embodiment of the present invention, the drying temperature is 105 ℃ and the drying time is 12 hours.
as another aspect of the invention, the microstructure modified magnetic beads prepared by the method for improving the microstructure and the demercuration performance of the magnetic beads in the fly ash are provided.
In general, compared with the prior art, the technical scheme of the invention can provide a method for improving the microstructure and the demercuration performance of the magnetic beads in the fly ash, thereby achieving the following beneficial effects:
(1) The invention adopts HF solution to process the surface of the magnetic bead, peels off aluminosilicate covered on the surface of the magnetic bead, fully exposes the wrapped hercynite phase substance, and greatly improves the catalytic oxidation performance of elemental mercury.
(2) in the technical scheme of the invention, the HF solution is adopted to carry out surface treatment on the magnetic beads, so that the microstructure of the magnetic beads is improved, the specific surface area of the magnetic beads is increased, and the pore structure of the magnetic beads is developed, thereby further improving the catalytic and adsorption performances of the magnetic beads.
(3) Concentration C and mechanical stirring's time t of R, HF solution of content decision HF solution/magnetic bead proportion through silicon and aluminium in the magnetic bead, can realize the concentration C of R, HF solution of corresponding HF solution/magnetic bead proportion of content rational configuration according to silicon and aluminium in the magnetic bead, and stirring time t, thereby make the aluminosilicate on magnetic bead surface peel off more thoroughly, and then make the spinel looks material that is wrapped up fully expose, improve the magnetic bead microstructure greatly, the adsorption efficiency is improved, furthermore, the concentration C of R, HF solution of reasonable configuration HF solution/magnetic bead proportion, and stirring time t, not only practiced thrift the quantity of HF solution greatly, avoid the waste of HF solution, and simple process.
Drawings
FIG. 1(a) is a structural diagram of a magnetic bead microstructure involved in a method for improving the microstructure and mercury removal performance of magnetic beads in fly ash according to example 1 of the present invention;
FIG. 1(b) is a view showing the microstructure of modified magnetic beads involved in a method for improving the microstructure and mercury removal performance of magnetic beads in fly ash according to example 1 of the present invention;
FIG. 1(c) is a schematic view of a magnetic bead microstructure and a mercury removal performance of fly ash according to example 2 of the present invention;
FIG. 1(d) is a view showing the microstructure of modified magnetic beads involved in a method for improving the microstructure and mercury removal performance of magnetic beads in fly ash according to example 2 of the present invention;
FIG. 1(e) is a structural diagram of the microscopic structure of primary magnetic beads involved in a method for improving the microscopic structure and mercury removal performance of magnetic beads in fly ash according to example 3 of the present invention;
FIG. 1(f) is a view showing the microstructure of modified magnetic beads involved in a method for improving the microstructure and mercury removal performance of magnetic beads in fly ash according to example 3 of the present invention;
FIG. 2(a) is a comparison graph of the mercury removal efficiency before and after modification of the microstructure of the magnetic beads by the method for improving the microstructure and mercury removal performance of the magnetic beads in fly ash in example 1 of the present invention;
FIG. 2(b) is a comparison graph of the mercury removal efficiency before and after modification of the microstructure of the magnetic beads by the method for improving the microstructure and mercury removal performance of the magnetic beads in fly ash in example 2 of the present invention;
fig. 2(c) is a comparison graph of the mercury removal efficiency before and after the modification of the microstructure of the magnetic beads by the method for improving the microstructure and the mercury removal performance of the magnetic beads in the fly ash in example 3 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1
the method for improving the microstructure and the demercuration performance of the magnetic beads in the fly ash comprises the following specific steps:
(1) Separating magnetic beads from fly ash by using a magnetic separator, grinding, and screening magnetic bead particles with proper particle size by using a 200-mesh standard to serve as a carrier;
(2) XRF is adopted to test the chemical components of the magnetic beads, and the silicon content in the magnetic beads is 27.8 percent, and the aluminum content in the magnetic beads is 20.4 percent. Weighing 2g of magnetic bead particles and placing the magnetic bead particles in a polytetrafluoroethylene container;
(3) Adding 30ml of 5% HF solution according to the proportion of the HF solution to the magnetic beads being 15 ml/g;
(4) mechanically stirring for 20 min;
(5) Filtering out the magnetic bead particles impregnated by the HF solution, and washing the magnetic bead particles with deionized water for several times;
(6) Drying at 105 deg.c for 12 hr to obtain the magnetic bead with improved microstructure.
observing the microscopic morphology of the magnetic beads before and after the dipping of the HF solution by adopting an environmental Scanning Electron Microscope (SEM); testing the specific surface area of the magnetic beads before and after the HF solution is soaked by adopting a specific surface area tester; and respectively using the magnetic beads before and after the impregnation of the HF solution in a catalytic oxidation experiment of elemental mercury in the flue gas.
As shown in fig. 1(a), before the HF solution is dipped, the surface of the magnetic beads is coated with dense aluminosilicate; after being immersed in 5% HF solution for 20min, the aluminosilicate on the surface is corroded and peeled off, and the hercynite phase material wrapped in the magnetic beads is exposed, as shown in FIG. 1 (b). The specific surface area of the magnetic beads before the impregnation with the HF solution was 0.28m2/g, and the specific surface area of the magnetic beads after the impregnation with the HF solution with the concentration of 5% for 20min was increased to 10.8m 2/g. As shown in fig. 2(a), the catalytic oxidation efficiency of the magnetic beads to the elemental mercury before the impregnation with the HF solution is only 19.2%, and the catalytic oxidation efficiency to the elemental mercury after the impregnation with the 5% HF solution for 20min is increased to 56.7%. In general, the microscopic morphology and the specific surface area of the magnetic beads are improved to a great extent after the magnetic beads are dipped in the HF solution, and the catalytic performance of the magnetic beads is correspondingly and greatly improved.
example 2
the method for improving the microstructure and the demercuration performance of the magnetic beads in the fly ash comprises the following specific steps:
(1) separating magnetic beads from fly ash by using a magnetic separator, grinding, and screening magnetic bead particles with proper particle size by using a 200-mesh standard to serve as a carrier;
(2) XRF is adopted to test the chemical components of the magnetic beads, and the silicon content in the magnetic beads is 31.3 percent, and the aluminum content in the magnetic beads is 24.1 percent. Weighing 2g of magnetic bead particles and placing the magnetic bead particles in a polytetrafluoroethylene container;
(3) adding 30ml of HF solution with the concentration of 8% according to the proportion of the HF solution to the magnetic beads being 15 ml/g;
(4) mechanically stirring for 25 min;
(5) Filtering out the magnetic bead particles impregnated by the HF solution, and washing the magnetic bead particles with deionized water for several times;
(6) drying at 105 deg.c for 12 hr to obtain the magnetic bead with improved microstructure.
observing the microscopic morphology of the magnetic beads before and after the dipping of the HF solution by adopting an environmental Scanning Electron Microscope (SEM); testing the specific surface area of the magnetic beads before and after the HF solution is soaked by adopting a specific surface area tester; and respectively using the magnetic beads before and after the impregnation of the HF solution in a catalytic oxidation experiment of elemental mercury in the flue gas.
As shown in fig. 1(c), before the HF solution is dipped, the surface of the magnetic beads is coated with dense aluminosilicate; after being immersed in 8% HF solution for 25min, the aluminosilicate on the surface of the magnetic beads is corroded and peeled off, and the hercynite phase substances coated inside the magnetic beads are exposed as shown in FIG. 1 (d). The specific surface area of the magnetic beads before the impregnation with the HF solution was 0.42m2/g, and the specific surface area of the magnetic beads after the impregnation with the HF solution having a concentration of 8% for 25min was increased to 13.1m 2/g. As shown in fig. 2(b), the catalytic oxidation efficiency of the magnetic beads to the elemental mercury before the HF solution immersion is only 21.5%, and after the HF solution with the concentration of 8% is immersed for 25min, the catalytic oxidation efficiency to the elemental mercury is increased to 66.3%. In general, the microscopic morphology and the specific surface area of the magnetic beads are improved to a great extent after the magnetic beads are dipped in the HF solution, and the catalytic performance of the magnetic beads is correspondingly and greatly improved.
example 3
The method for improving the microstructure and the demercuration performance of the magnetic beads in the fly ash comprises the following specific steps:
(1) Separating magnetic beads from fly ash by using a magnetic separator, grinding, and screening magnetic bead particles with proper particle size by using a 200-mesh standard to serve as a carrier;
(2) XRF is adopted to test the chemical components of the magnetic beads, and the silicon content in the magnetic beads is 28.2 percent, and the aluminum content in the magnetic beads is 19.7 percent. Weighing 2g of magnetic bead particles and placing the magnetic bead particles in a polytetrafluoroethylene container;
(3) Adding 40ml of 1% HF solution according to the proportion of the HF solution to the magnetic beads being 20 ml/g;
(4) mechanically stirring for 5 min;
(5) filtering out the magnetic bead particles impregnated by the HF solution, and washing the magnetic bead particles with deionized water for several times;
(6) drying at 105 deg.c for 12 hr to obtain the magnetic bead with improved microstructure.
observing the microscopic morphology of the magnetic beads before and after the dipping of the HF solution by adopting an environmental Scanning Electron Microscope (SEM); testing the specific surface area of the magnetic beads before and after the HF solution is soaked by adopting a specific surface area tester; and respectively using the magnetic beads before and after the impregnation of the HF solution in a catalytic oxidation experiment of elemental mercury in the flue gas.
as shown in fig. 1(e), before the HF solution is dipped, the surface of the magnetic beads is coated with dense aluminosilicate; in FIG. 1(f), after being immersed in 1% HF solution for 5min, the aluminosilicate on the surface is corroded and peeled off, and the spinel phase material coated inside the magnetic beads is exposed. The specific surface area of the magnetic beads before the impregnation with the HF solution was 0.32m2/g, and after the impregnation with the HF solution having a concentration of 1% for 5min, the specific surface area increased to 4.83m 2/g. As shown in fig. 2(c), the catalytic oxidation efficiency of the magnetic beads to the elemental mercury before the HF solution immersion is only 20.5%, and after the HF solution with the concentration of 1% is immersed for 5min, the catalytic oxidation efficiency to the elemental mercury is increased to 44.8%. In general, the microscopic morphology and the specific surface area of the magnetic beads are improved to a great extent after the magnetic beads are dipped in the HF solution, and the catalytic performance of the magnetic beads is correspondingly and greatly improved.
in the technical solution of the present invention, a value with a better content effect of silicon and aluminum in a magnetic bead is given in the examples, but the present invention is not limited to the value in the examples, wherein the content of silicon in the magnetic bead is 25% to 35%, 27.8%, 31.3%, 28.2% in the examples can be selected, and 25.2%, 26.1%, 29.3%, 30.1%, 32.3%, 33.2%, 34.1% and the like can also be selected; the content of aluminum is 15% to 25%, which may be 20.4%, 24.1%, 19.7% in the embodiments, and may also be 15.3%, 16.4%, 17.2%, 18.6%, 21.5%, 22.4%, 23.3%, etc., and the content of silicon and aluminum in the magnetic beads may be arbitrarily matched within the above range, and is not limited to the content values given in the above embodiments, and the specific content of silicon and aluminum may be determined according to the specific situation of the actual magnetic beads.
In addition, in the technical scheme of the invention, the concentration C of the HF solution/magnetic bead ratio R, HF solution and the mechanical stirring time t are determined by the content m (Si, Al) of silicon and aluminum in magnetic beads, and the concentration C and the mechanical stirring time t are obtained by optimizing a response surface method, which comprises the following specific steps:
1) Taking three key factors of the HF solution/magnetic bead ratio R, HF solution concentration C and the stirring time t as independent variables, and taking the contents m (Si, Al) of silicon and aluminum in the magnetic beads as dependent variables, designing an experimental scheme;
2) carrying out experiments on the experimental scheme designed in the step (1) to obtain experimental data of the incidence relation between m (Si, Al) and R, C, t;
3) Establishing a mathematical model which takes the contents m (Si, Al) of silicon and aluminum in the magnetic beads as dependent variables and factors influencing the contents of the silicon and the aluminum in the magnetic beads, namely the concentration C of the HF solution/magnetic beads ratio R, HF solution and the stirring time t as independent variables:
m(Si,Al)＝β+βR+βC+βt+βRC+βRt+βCt+βR+βC+βt
4) Performing regression analysis on the experimental data obtained in the step (2) to obtain a fitting equation of the mathematical model:
m(Si,Al)＝12.27-0.029R+4.10C+0.51t-(5.0×10)RC+(1.6×10)Rt-
0.058Ct-(7.7×10)R-0.23C+(8.8×10)t
5) Obtaining the optimal proportion R of the HF solution/magnetic beads, the optimal HF solution concentration C and the optimal stirring time t according to the mathematical model in the step (4);
Wherein m (Si, Al) refers to the total content of silicon and aluminum in the magnetic beads, corresponds to most magnetic beads, has the silicon content of 25-35 percent and the aluminum content of 15-25 percent, and is analyzed by a response surface method in an optimization way, and the proportion of the added HF solution to the magnetic beads is 10-20 ml/g; the concentration of the HF solution is 1-10%; the stirring time is 5-30min, the solution concentration C of the HF solution/magnetic bead ratio R, HF and the value range of the stirring time t are value ranges with optimal effects obtained through response surface method optimization analysis, and are not limited to the value ranges given in the above embodiments, and the value ranges of the solution concentration C of the HF solution/magnetic bead ratio R, HF and the stirring time t can be determined according to actual conditions.
In addition, the size of the magnetic bead particles in the present invention is not limited to the value in the above embodiment, for example, the size of the magnetic bead particles is 100-400 mesh, preferably 200 mesh, 200 mesh in the embodiment, 100, 150, 250, 300, 400, and the like.
The invention provides a method for improving the microstructure and the demercuration performance of magnetic beads in fly ash, which adopts HF solution to carry out surface treatment on the magnetic beads, so that HF reacts with silicon-aluminum components on the surfaces of the magnetic beads as follows:
SiO+4HF＝SiF+4HO
AlO+6HF＝2AlF
AlO+12HF＝HAlF
SiF4 and H6AlF6 are soluble in water, so that the silicon-aluminum component covered on the surface of the magnetic bead can be removed by HF, the hercynite phase substance wrapped by aluminosilicate in the magnetic bead is fully exposed, and Fe3+ and lattice oxygen in the hercynite phase substance have catalytic performance on the oxidation of elemental mercury, so that the method can improve the catalytic performance. In addition, the HF removes a compact aluminosilicate coating film on the surface of the magnetic bead, and has a certain corrosion effect on the surface of the magnetic bead, so that pores can be increased, and the specific surface area of the magnetic bead is increased. The large specific surface area and the developed pore structure are beneficial to physical adsorption and chemical adsorption of mercury on the surfaces of the magnetic beads, so that the demercuration performance of the magnetic beads can be improved.
it will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (3)
1. a method for improving the microstructure and demercuration performance of magnetic beads in fly ash comprises the following steps:
(1) Selecting magnetic bead particles from the fly ash, and grinding and screening the magnetic beads;
(2) Placing the magnetic bead particles obtained in the step (1) in a polytetrafluoroethylene container, adding an HF solution, and mechanically stirring; the ratio of the HF solution to the magnetic beads is 10-20 ml/g; the concentration of the HF solution is 1% -10%; the stirring time is 5-30 min;
(3) Filtering the magnetic bead particles soaked by the HF solution in the step (2), and washing the magnetic bead particles with deionized water for several times until the magnetic bead particles are neutral;
(4) drying the magnetic bead particles washed to be neutral in the step (3) to obtain magnetic beads with improved microstructures;
In addition, the method also comprises the step of determining the content m (Si, Al) of silicon and aluminum in the magnetic beads by adding an HF solution to test the chemical composition of the magnetic beads; in the step (2), the addition amount of the HF solution is determined by the content m (Si, Al) of silicon and aluminum in the magnetic beads, and specifically is as follows:
m(Si,Al)＝12.27-0.029R+4.10C+0.51t-(5.0×10)RC+(1.6×10)Rt-0.058Ct-(7.7
×10)R-0.23C+(8.8×10)t
wherein m (Si, Al) is the content of silicon and aluminum in the magnetic beads; r is the ratio of the volume of the HF solution to the mass of the magnetic beads; c is the concentration of HF solution; t is the stirring time.
2. The method as claimed in claim 1, wherein the size of the magnetic beads is 100-400 mesh.
3. The method for improving the microstructure of magnetic beads in fly ash and the mercury removal performance of claim 1, wherein the drying temperature is 105 ℃ and the drying time is 12 hours.
Priority Applications (1)
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| JP2009268690A (en) * | 2008-05-07 | 2009-11-19 | Tokyo Metropolitan Univ | Heavy metal removing apparatus |
| CN102698598A (en) * | 2012-05-21 | 2012-10-03 | 华中科技大学 | Method and apparatus for catalyzing and oxidizing elemental mercury in flue gas by magnetic balls in fly ash |
| CN104307539A (en) * | 2014-07-24 | 2015-01-28 | 华中科技大学 | A catalyst used for oxidation of elementary substance mercury in coal-fired flue gas, and a preparation method and a regeneration method of the catalyst |
| CN105214601A (en) * | 2015-09-24 | 2016-01-06 | 华中科技大学 | Elemental Mercury mineral adsorbent and preparation method thereof |
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| JP2009268690A (en) * | 2008-05-07 | 2009-11-19 | Tokyo Metropolitan Univ | Heavy metal removing apparatus |
| CN102698598A (en) * | 2012-05-21 | 2012-10-03 | 华中科技大学 | Method and apparatus for catalyzing and oxidizing elemental mercury in flue gas by magnetic balls in fly ash |
| CN104307539A (en) * | 2014-07-24 | 2015-01-28 | 华中科技大学 | A catalyst used for oxidation of elementary substance mercury in coal-fired flue gas, and a preparation method and a regeneration method of the catalyst |
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