CN107262021B - Method for preparing halogen modified fly ash adsorbent - Google Patents
Method for preparing halogen modified fly ash adsorbent Download PDFInfo
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- CN107262021B CN107262021B CN201710569714.8A CN201710569714A CN107262021B CN 107262021 B CN107262021 B CN 107262021B CN 201710569714 A CN201710569714 A CN 201710569714A CN 107262021 B CN107262021 B CN 107262021B
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- 239000010881 fly ash Substances 0.000 title claims abstract description 42
- 229910052736 halogen Inorganic materials 0.000 title claims abstract description 31
- 150000002367 halogens Chemical class 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title claims abstract description 26
- 239000003463 adsorbent Substances 0.000 title abstract description 26
- 239000002994 raw material Substances 0.000 claims abstract description 25
- 239000007864 aqueous solution Substances 0.000 claims abstract description 17
- 239000000126 substance Substances 0.000 claims abstract description 13
- 238000001035 drying Methods 0.000 claims abstract description 12
- 239000002245 particle Substances 0.000 claims abstract description 10
- 238000005406 washing Methods 0.000 claims abstract description 10
- -1 firstly Substances 0.000 claims abstract description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 30
- 239000000203 mixture Substances 0.000 claims description 13
- 238000003756 stirring Methods 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 6
- 229910001622 calcium bromide Inorganic materials 0.000 claims description 6
- WGEFECGEFUFIQW-UHFFFAOYSA-L calcium dibromide Chemical compound [Ca+2].[Br-].[Br-] WGEFECGEFUFIQW-UHFFFAOYSA-L 0.000 claims description 6
- 239000001110 calcium chloride Substances 0.000 claims description 4
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 4
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical group [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 3
- 239000002594 sorbent Substances 0.000 claims description 3
- 238000007598 dipping method Methods 0.000 claims description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 abstract description 28
- 229910052753 mercury Inorganic materials 0.000 abstract description 28
- 229910001385 heavy metal Inorganic materials 0.000 abstract description 5
- 239000003245 coal Substances 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 238000002360 preparation method Methods 0.000 description 31
- 238000001179 sorption measurement Methods 0.000 description 24
- 238000012360 testing method Methods 0.000 description 11
- 239000000243 solution Substances 0.000 description 7
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 5
- 239000003546 flue gas Substances 0.000 description 5
- 238000011068 loading method Methods 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 238000002485 combustion reaction Methods 0.000 description 3
- 239000000428 dust Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000007935 neutral effect Effects 0.000 description 3
- 238000010998 test method Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical class [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical class [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical class [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 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
- 150000003842 bromide salts Chemical class 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- XMBWDFGMSWQBCA-UHFFFAOYSA-M iodide Chemical compound [I-] XMBWDFGMSWQBCA-UHFFFAOYSA-M 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 238000011160 research Methods 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
- 239000011734 sodium Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
- 239000011701 zinc Chemical class 0.000 description 1
- 229910052725 zinc Chemical class 0.000 description 1
Classifications
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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
- 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
- B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
- B01J20/103—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate comprising silica
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
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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
- 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
- B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
- B01J20/0225—Compounds of Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt
- B01J20/0229—Compounds of Fe
-
- 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
- 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
- B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
- B01J20/024—Compounds of Zn, Cd, Hg
- B01J20/0244—Compounds of Zn
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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
- 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
- B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
- B01J20/0274—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04 characterised by the type of anion
- B01J20/0288—Halides of compounds other than those provided for in B01J20/046
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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
- 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
- B01J20/04—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium
- B01J20/046—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium containing halogens, e.g. halides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/60—Heavy metals or heavy metal compounds
- B01D2257/602—Mercury or mercury compounds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/02—Other waste gases
- B01D2258/0283—Flue gases
- B01D2258/0291—Flue gases from waste incineration plants
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- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Treating Waste Gases (AREA)
Abstract
The invention relates to the field of fire coal, and discloses a method for preparing a halogen modified fly ash adsorbent, which comprises the following steps: under the condition of aqueous solution, firstly, raw material fly ash is contacted with alkaline substances; then washing and drying a product obtained after the contact to obtain a first intermediate; (ii) subjecting the first intermediate to impregnating contact with a halogen source; wherein the specific surface area of the raw material fly ash is 0.5-2.5 m2(iv) a specific particle size of 80 to 200 mesh. The adsorbent obtained by the method has excellent removal efficiency on heavy metal mercury in emissions of coal-fired power plants, and has the advantage of low production cost.
Description
Technical Field
The invention relates to the field of fire coal, in particular to a method for preparing a halogen modified fly ash adsorbent.
Background
In recent years, the control of coal-fired pollutants has become a focus of attention in various countries of the world due to the large amount of coal used. The metallic element mercury contained in the coal is discharged into the atmosphere together with the flue gas in the combustion process, and can stay in the atmosphere for a long time, so that a water source is polluted, and the human health is seriously harmed.
Coal-fired power plants are one of the main emission sources of heavy metal mercury pollution, have attracted the attention of scholars at home and abroad aiming at the emission and control of mercury, and have conducted extensive research. At present, a common way for realizing mercury emission control is to use the existing pollutant control devices for desulfurization, denitration, dust removal and the like to carry out cooperative control.
The cooperative control technology is not specially developed for mercury pollution, and the mercury pollution removal effect is difficult to ensure stability. In the technology specially aiming at mercury pollution removal, the most industrialized application at present is to spray a solid-phase adsorbent before a dust removal device and capture the solid-phase adsorbent by the dust removal device.
The activated carbon material is a kind of adsorbent which is tested in many stages at present, has higher capture efficiency on mercury in flue gas, but has higher production cost. Therefore, the development of a novel high-efficiency low-cost adsorbent material is urgently needed to remove heavy metal mercury pollution in coal-fired flue gas.
Disclosure of Invention
The invention aims to overcome the problem of low adsorption efficiency of a mercury removal adsorbent in the prior art, and provides a novel method for preparing a halogen modified fly ash adsorbent.
In order to achieve the above object, the present invention provides, in one aspect, a method for preparing a halogen-modified fly ash adsorbent, comprising: under the condition of aqueous solution, firstly, raw material fly ash is contacted with alkaline substances; then washing and drying a product obtained after the contact to obtain a first intermediate; (ii) subjecting the first intermediate to impregnating contact with a halogen source; wherein the specific surface area of the raw material fly ash is 0.5-2.5 m2(iv) a specific particle size of 80 to 200 mesh.
The inventor of the invention finds that the specific surface area is 0.5-2.5 m2The raw material fly ash with the average particle size of 80-200 meshes is subjected to alkali treatment firstly and then is contacted with a halogen source, so that the obtained adsorbent has excellent removal efficiency on heavy metal mercury in emissions of a coal-fired power plant, and has the advantage of low costThis completes the technical solution of the present invention.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
As previously mentioned, the present invention provides a method of preparing a halogen-modified fly ash sorbent comprising: under the condition of aqueous solution, firstly, raw material fly ash is contacted with alkaline substances; then washing and drying a product obtained after the contact to obtain a first intermediate; (ii) subjecting the first intermediate to impregnating contact with a halogen source; wherein the specific surface area of the raw material fly ash is 0.5-2.5 m2(iv) a specific particle size of 80 to 200 mesh.
The specific surface area of the raw material fly ash was measured by a specific surface area analyzer.
The aqueous solution conditions of the present invention refer to a system containing water, which may be a suspension, a suspension or a clear transparent system.
The conditions for drying to obtain drying in the first intermediate may be, for example: the temperature is 70-200 ℃, and the time is 4-48 h.
Preferably, the specific surface area of the raw material fly ash is 0.8-2.0 m2(iv) a specific particle size of 100 to 150 mesh.
According to a first preferred embodiment, the step of contacting the raw material fly ash with an alkaline material comprises:
1) firstly, contacting raw material fly ash with an alkaline substance at a first temperature of 25-45 ℃ for 18-24 h;
2) contacting the mixture obtained in the step 1) for 6-18 h at a second temperature which is 5-20 ℃ lower than the first temperature.
The adsorbent obtained by adopting the first preferred embodiment of the invention has obviously more excellent removal efficiency on heavy metal mercury in emissions of coal-fired power plants.
More preferably, the second temperature is 5 to 10 ℃ lower than the first temperature.
Preferably, the alkaline substance is sodium hydroxide and/or potassium hydroxide.
Preferably, the alkaline substance is used in an amount such that the concentration of the alkaline substance in the aqueous solution condition is 0.05 to 5% by weight.
Preferably, the halogen source is at least one selected from the group consisting of halide salts of calcium, iron, and zinc.
The halide salt of the present invention may be, for example, any one or more of a chloride salt, a bromide salt and an iodide salt.
Preferably, the halogen source of the present invention is calcium chloride and/or calcium bromide.
Preferably, the conditions for the impregnation contact of the first intermediate with the halogen source are controlled so that the loading amount of the halogen source in the adsorbent obtained by the method of the present invention is 0.5 to 50 wt%. The concentration of the solution can be controlled by one skilled in the art to control the loading of the halogen source, for example.
According to a second preferred embodiment, the step of bringing said first intermediate into impregnating contact with a halogen source comprises:
1) standing the first intermediate and a halogen source at 10-30 ℃ for 2-8 h;
2) stirring the mixture obtained in the step 1) for 4-48 h at 10-30 ℃, wherein the stirring speed is 100-500 rpm.
Preferably, the halogen source is used in an amount such that the concentration of the halogen source in the system for impregnating and contacting the first intermediate with the halogen source is 0.1 to 20 wt%.
Preferably, the method of the present invention further comprises: and drying the product obtained after the first intermediate and a halogen source are subjected to dipping contact for 4-24 h at 70-200 ℃.
Preferably, the conditions for washing the product obtained after the contacting with water include: washing with water until the pH value of the obtained product is 7-8; more preferably, the water is washed until the resulting product is neutral.
Preferably, the raw material fly ash is fly ash obtained after combustion in a circulating fluidized bed boiler. In order to enable the fly ash obtained after the combustion of the circulating fluidized bed boiler to meet the requirements in the technical scheme of the invention, the fly ash can be screened to obtain raw material fly ash with the average particle size of 80-200 meshes.
The composition of the raw material fly ash of the present invention may be, for example: CaO content of 10.2 to 11.2 wt%, SiO250.3 to 54.7 wt.% of Al2O321.0 to 21.9 wt.% of Fe2O3Content of 4.2-4.9 wt.%, K23.5 to 4.2 wt% of O, 0.6 to 0.8 wt% of MgO, 0.04 to 0.08 wt% of MnO, and Na20.7 to 0.95 wt% of O and other inevitable impurities.
The adsorbent obtained by the method has high mercury adsorption and removal efficiency, and can realize secondary utilization of fly ash in a power plant.
The present invention will be described in detail below by way of preparation examples and test examples.
In the following preparation examples and test examples, various raw materials used were commercially available without specific description.
Preparation example 1
(1) Under the condition of aqueous solution, firstly, the raw material fly ash (the average specific surface area is 1.2 m)2(ii)/g, average particle size 95 microns) with sodium hydroxide (in an amount such that the concentration of sodium hydroxide in the aqueous solution conditions is 3.5 wt%) at a first temperature of 25 ℃ for 24 h;
(2) contacting the resulting mixture at a second temperature 5 ℃ lower than the first temperature for 10 h;
(3) washing the product obtained after the contact to be neutral and drying the product at 150 ℃ for 8 hours to obtain a first intermediate;
(4) standing the first intermediate and calcium chloride aqueous solutions (0-20 wt%) with different concentrations for 5h at 20 ℃;
(5) stirring the mixture obtained in the step (4) at 25 ℃ for 24 hours, wherein the stirring speed is 400 rpm;
(6) and (5) drying the product obtained in the step (5) at 150 ℃ for 10 hours to obtain a finished product.
Respectively according to CaCl2Sorbent samples were prepared at 0 wt% loading (unloaded, for comparison), 10 wt%, 20 wt%, and 40 wt% loading on fly ash. Samples of unloaded fly ash and loaded amounts of 10 wt%, 20 wt% and 40 wt%, respectively, were labeled FYCA0, FYCA1, FYCA2 and FYCA4, respectively. The inorganic composition contents of the obtained samples are shown in Table 1.
TABLE 1
Test example 1
Preparing coal-fired flue gas by using a dropping tube furnace, sampling by using a 30B method and adopting Lumex RA915+The results of measuring the mercury content of the sample obtained in preparation example 1 by an atomic absorption spectrometer are shown in table 2, and experiments show that the modified fly ash adsorbent obtained by the method of the present invention has high adsorption capacity.
TABLE 2
| Sample (I) | Mercury adsorption capacity (ng/g) |
| FYCA0 | 36571 |
| FYCA1 | 523055 |
| FYCA2 | 647811 |
| FYCA4 | 605871 |
Test example 2
Hg is matched by adopting a continuous mercury analyzer of PSA company0Source of generation, mercury continuous adsorption breakthrough test of the adsorbent sample obtained in preparation example 1 was performed. Specifically, the method comprises the following steps:
the temperature of the fixed bed reactor was set at a constant temperature of 120 ℃ and 1g of the adsorbent sample was charged per time. Fixed bed inlet Hg0The concentration is 40g/m2。
From the experimental results it appears that: the unmodified FYCA0 sample had the worst mercury adsorption capacity and essentially no adsorption occurred. The adsorption efficiency of the FYCA1 sample in the initial adsorption stage can reach 38%, and the adsorption saturation is basically reached after 40 h. The FYCA2 and FYCA4 samples performed close to and both better, with initial adsorption efficiency close to 60% and breakthrough time around 80 h.
Preparation example 2
(1) Under the condition of aqueous solution, firstly, the raw material fly ash (the average specific surface area is 1.3 m)2(ii)/g, average particle size 82 microns) with sodium hydroxide (in an amount such that the concentration of sodium hydroxide in the aqueous solution conditions is 2.5 wt%) at a first temperature of 35 ℃ for 22 h;
(2) contacting the resulting mixture at a second temperature 7 ℃ lower than the first temperature for 14 h;
(3) washing the product obtained after the contact to be neutral and drying the product for 6 hours at 180 ℃ to obtain a first intermediate;
(4) standing the first intermediate with different concentrations of aqueous calcium bromide solutions (0 wt%, 5 wt%, 10 wt% and 20 wt%) at 25 ℃ for 4 h;
(5) stirring the mixture obtained in the step (4) at 20 ℃ for 30 hours, wherein the stirring speed is 300 rpm;
(6) and (5) drying the product obtained in the step (5) at 180 ℃ for 8 hours to obtain a finished product.
Samples obtained without fly ash loading and using 5 wt.%, 10 wt.% and 20 wt.% impregnation solutions (calcium bromide aqueous solution) were labeled FYCB0, FYCB1, FYCB2 and FYCB3, respectively. The inorganic composition contents of the obtained samples are shown in Table 3.
TABLE 3
Test example 3
Preparing coal-fired flue gas by using a dropping tube furnace, sampling by using a 30B method and adopting Lumex RA915+The results of measuring the mercury content of the sample obtained in preparation example 2 by an atomic absorption spectrometer are shown in table 4, and experiments show that the modified fly ash adsorbent obtained by the method of the present invention has high adsorption capacity.
TABLE 4
| Sample (I) | Mercury adsorption capacity (ng/g) |
| FYCB0 | 38309 |
| FYCB1 | 1023055 |
| FYCB2 | 1247811 |
| FYCB3 | 1805871 |
Test example 4
Hg is matched by adopting a continuous mercury analyzer of PSA company0Source of generation, mercury continuous adsorption breakthrough test of the adsorbent sample obtained in preparation example 2 was performed. In particular to：
The temperature of the fixed bed reactor was set at a constant temperature of 120 ℃ and 1g of the adsorbent sample was charged per time. Fixed bed inlet Hg0The concentration is 40g/m2。
From the experimental results it appears that: the unmodified FYCB0 sample had the worst mercury adsorption capacity and essentially no adsorption occurred. The adsorption efficiency of the FYCB1 sample in the initial adsorption stage can reach 45%, and the adsorption saturation is basically reached after 35 h. The FYCB2 and FYCB3 samples performed close to and both better, with initial adsorption efficiency close to 75% and breakthrough time around 65 h.
Preparation example 3
This preparation was carried out in a similar manner to preparation 2, except that: the step (1) and the step (2) of the present preparation example were respectively:
(1) under the condition of aqueous solution, the raw material fly ash which is the same as that in the preparation example 2 is firstly contacted with sodium hydroxide (the dosage is that the concentration of the sodium hydroxide in the aqueous solution is 2.5 weight percent) at a first temperature of 35 ℃ for 22 hours;
(2) contacting the resulting mixture at a second temperature 2 ℃ lower than the first temperature for 14 h;
the rest was the same as in preparation example 2, and the concentration of the aqueous calcium bromide solution in this preparation example was 5% by weight.
The adsorbent samples obtained in this preparation example were tested for mercury adsorption capacity by the same test method as in test example 3, and the results were: 801268 ng/g.
Preparation example 4
This preparation was carried out in a similar manner to preparation 3, except that:
the step (1) and the step (2) of the present preparation example were respectively:
(1) under the condition of aqueous solution, the raw material fly ash which is the same as that in the preparation example 2 is firstly contacted with sodium hydroxide (the dosage is that the concentration of the sodium hydroxide in the aqueous solution is 2.5 weight percent) at a first temperature of 35 ℃ for 22 hours;
(2) the obtained mixture is continuously contacted for 14h at a second temperature of 25 ℃;
the rest was the same as in preparation example 3, and the concentration of the aqueous calcium bromide solution in this preparation example was 5% by weight.
The adsorbent samples obtained in this preparation example were tested for mercury adsorption capacity by the same test method as in test example 3, and the results were: 755641 ng/g.
Comparative preparation example 1
This comparative preparation was carried out in a similar manner to preparation 1, except that:
the average specific surface area of the raw material fly ash in this comparative preparation example was 1.5m2(ii)/g, average particle diameter 51 μm.
The rest is the same as in preparation example 1.
The adsorbent samples obtained in this comparative preparation example were tested for mercury adsorption capacity by the same test method as in test example 1, and the results were: 482530 ng/g.
From the results, the adsorbent obtained by the method has high mercury adsorption and removal efficiency, and the preparation method is simple and low in cost.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (8)
1. A method of preparing a halogen-modified fly ash sorbent comprising: under the condition of aqueous solution, firstly, raw material fly ash is contacted with alkaline substances; then washing and drying a product obtained after the contact to obtain a first intermediate; (ii) subjecting the first intermediate to impregnating contact with a halogen source; wherein the specific surface area of the raw material fly ash is 0.5-2.5 m2(ii)/g, and the average particle diameter is 80 to 200 mesh;
wherein the step of contacting the raw material fly ash with an alkaline substance comprises:
1) firstly, contacting raw material fly ash with an alkaline substance at a first temperature of 25-45 ℃ for 18-24 h;
2) contacting the mixture obtained in the step 1) for 6-18 h at a second temperature which is 5-20 ℃ lower than the first temperature; and the number of the first and second groups,
the halogen source is calcium chloride and/or calcium bromide;
the alkaline substance is sodium hydroxide and/or potassium hydroxide;
the raw material fly ash is fly ash obtained after the circulating fluidized bed boiler burns.
2. The method of claim 1, wherein the second temperature is 5-10 ℃ lower than the first temperature.
3. The method according to claim 1, wherein the alkaline substance is used in an amount such that the concentration of the alkaline substance in the aqueous solution condition is 0.05 to 5% by weight.
4. The method of any one of claims 1-3, wherein the step of bringing the first intermediate into impregnating contact with a halogen source comprises:
1) standing the first intermediate and a halogen source at 10-30 ℃ for 2-8 h;
2) stirring the mixture obtained in the step 1) for 4-48 h at 10-30 ℃, wherein the stirring speed is 100-500 rpm.
5. The method according to claim 1, wherein the halogen source is used in an amount such that the concentration of the halogen source in the system for impregnating and contacting the first intermediate with the halogen source is 0.1 to 20% by weight.
6. The method according to claim 5, wherein the halogen source is used in an amount such that the concentration of the halogen source in the system for impregnating and contacting the first intermediate with the halogen source is 1 to 10% by weight.
7. The method of claim 1, wherein the method further comprises: and drying the product obtained after the first intermediate and a halogen source are subjected to dipping contact for 4-24 h at 70-200 ℃.
8. The process of claim 1, wherein the conditions under which the product obtained after the contacting is subjected to water washing comprise: and washing with water until the pH value of the obtained product is 7-8.
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