CN116944221A - Fly ash online decalcification method capable of reducing sodium carbonate consumption - Google Patents
Fly ash online decalcification method capable of reducing sodium carbonate consumption Download PDFInfo
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- CN116944221A CN116944221A CN202310840708.7A CN202310840708A CN116944221A CN 116944221 A CN116944221 A CN 116944221A CN 202310840708 A CN202310840708 A CN 202310840708A CN 116944221 A CN116944221 A CN 116944221A
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- fly ash
- sodium carbonate
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- decalcification
- carbon dioxide
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- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 title claims abstract description 114
- 239000010881 fly ash Substances 0.000 title claims abstract description 82
- 229910000029 sodium carbonate Inorganic materials 0.000 title claims abstract description 57
- 238000000034 method Methods 0.000 title claims abstract description 40
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 100
- 239000007788 liquid Substances 0.000 claims abstract description 81
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 48
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 48
- 239000007787 solid Substances 0.000 claims abstract description 43
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 43
- 238000006243 chemical reaction Methods 0.000 claims abstract description 37
- 238000005406 washing Methods 0.000 claims abstract description 30
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims abstract description 27
- 229910052938 sodium sulfate Inorganic materials 0.000 claims abstract description 26
- 235000011152 sodium sulphate Nutrition 0.000 claims abstract description 26
- 238000000926 separation method Methods 0.000 claims abstract description 25
- 238000002156 mixing Methods 0.000 claims abstract description 16
- 238000012544 monitoring process Methods 0.000 claims abstract description 12
- 239000011790 ferrous sulphate Substances 0.000 claims abstract description 10
- 235000003891 ferrous sulphate Nutrition 0.000 claims abstract description 10
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims abstract description 10
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims abstract description 10
- 238000001914 filtration Methods 0.000 claims abstract description 8
- 229910052979 sodium sulfide Inorganic materials 0.000 claims abstract description 8
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims abstract description 8
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 8
- 230000003247 decreasing effect Effects 0.000 claims description 7
- 239000000706 filtrate Substances 0.000 claims description 6
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 4
- 239000006228 supernatant Substances 0.000 claims description 4
- 238000009287 sand filtration Methods 0.000 claims description 3
- 238000007873 sieving Methods 0.000 claims description 3
- 238000009736 wetting Methods 0.000 claims description 3
- 230000001419 dependent effect Effects 0.000 claims description 2
- 238000002203 pretreatment Methods 0.000 claims description 2
- 238000010298 pulverizing process Methods 0.000 claims description 2
- 238000005261 decarburization Methods 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 40
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 12
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 12
- 239000011575 calcium Substances 0.000 description 12
- 229910052791 calcium Inorganic materials 0.000 description 12
- 229910000019 calcium carbonate Inorganic materials 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 229910001385 heavy metal Inorganic materials 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 3
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 3
- NKWPZUCBCARRDP-UHFFFAOYSA-L calcium bicarbonate Chemical compound [Ca+2].OC([O-])=O.OC([O-])=O NKWPZUCBCARRDP-UHFFFAOYSA-L 0.000 description 3
- 229910000020 calcium bicarbonate Inorganic materials 0.000 description 3
- 235000011089 carbon dioxide Nutrition 0.000 description 3
- 150000001768 cations Chemical class 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- HGUFODBRKLSHSI-UHFFFAOYSA-N 2,3,7,8-tetrachloro-dibenzo-p-dioxin Chemical compound O1C2=CC(Cl)=C(Cl)C=C2OC2=C1C=C(Cl)C(Cl)=C2 HGUFODBRKLSHSI-UHFFFAOYSA-N 0.000 description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 238000005273 aeration Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 2
- 230000000875 corresponding effect Effects 0.000 description 2
- 229910001448 ferrous ion Inorganic materials 0.000 description 2
- 238000002386 leaching Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000001376 precipitating effect Effects 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 238000010936 aqueous wash Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000008364 bulk solution Substances 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000005262 decarbonization Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003546 flue gas Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- -1 lead Chemical class 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 238000007781 pre-processing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 210000002966 serum Anatomy 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000000859 sublimation Methods 0.000 description 1
- 230000008022 sublimation Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
- 238000004056 waste incineration Methods 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
- B09B3/80—Destroying solid waste or transforming solid waste into something useful or harmless involving an extraction step
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
- B09B2101/00—Type of solid waste
- B09B2101/30—Incineration ashes
Landscapes
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
The application relates to a fly ash online decalcification method for reducing the consumption of sodium carbonate, belonging to the field of fly ash treatment. The method comprises the following steps: mixing the fly ash water washing liquid without solid-liquid separation with ferrous sulfate and sodium sulfide for reaction, and then carrying out solid-liquid separation to obtain a first clear liquid; mixing the first clear liquid and solid carbon dioxide in a closed reaction vessel for reaction, and then filtering to obtain a second clear liquid; adding sodium sulfate solution into the second clear liquid, monitoring the hardness of the clear liquid, and filtering to obtain a third clear liquid when the hardness reaches a preset value; mixing the third clear solution with sodium carbonate solution, and performing solid-liquid separation after reaction. The method can realize decarburization of the fly ash with lower consumption of sodium carbonate.
Description
Technical Field
The application belongs to the technical field of fly ash treatment, and particularly relates to a system and a method for collaborative treatment and resource comprehensive utilization of a fly ash water-washing cement kiln.
Background
The household garbage is incinerated to form a product called fly ash. Fly ash is collected in a flue gas cleaning system of a waste incineration plant. The fly ash from garbage incineration is rich in a great amount of heavy metals, dioxin, potassium, sodium, calcium, magnesium and the like. The fly ash cannot be discharged directly and needs to be treated. The calcium content in fly ash is a significant proportion, and therefore, fly ash decalcification is an important consideration. Currently, sodium carbonate is generally used as a decarbonization agent for fly ash decalcification. However, sodium carbonate is used in a large amount, and this means a large cost for use as an important chemical raw material. Therefore, it is desirable to reduce the sodium carbonate consumption during fly ash decalcification.
Disclosure of Invention
Aiming at the defects of the prior art, the application aims to provide a fly ash online decalcification method for reducing the consumption of sodium carbonate, which aims to improve and even overcome the problem of larger consumption of sodium carbonate in the process of decalcification by using the fly ash in the prior art.
The application provides a fly ash online decalcification method for reducing the dosage of sodium carbonate, which comprises the following steps:
mixing water washing liquid obtained from fly ash through water washing with ferrous sulfate and sodium sulfide for reaction under the condition of not carrying out solid-liquid separation, and carrying out solid-liquid separation to obtain a first clear liquid;
mixing the first clear liquid and solid carbon dioxide in a closed reaction vessel for reaction, and then filtering to obtain a second clear liquid, wherein the addition amount of the solid carbon dioxide depends on the hardness of the clear liquid and the pressure in the vessel;
adding sodium sulfate solution into the second clear liquid, monitoring the hardness of the clear liquid, and filtering to obtain a third clear liquid when the hardness reaches a preset value;
and mixing the third clear solution with sodium carbonate solution, and performing solid-liquid separation after reaction, wherein the adding amount of the sodium carbonate solution is dynamically related to the adding amount of the sodium sulfate solution.
Preferably, the hardness of the filtrate obtained by mixing the third clear liquid with the sodium carbonate solution and performing solid-liquid separation after the reaction is 50mg/L or less.
Preferably, the carbonate concentration in the filtrate of the solid-liquid separation after the reaction of the third clear solution with the sodium carbonate solution is higher than 1500mg/L.
Preferably, the method of dynamically correlating the addition amount of the sodium carbonate solution with the addition amount of the sodium sulfate solution is as follows:
when the addition of the sodium sulfate solution was stopped, the addition amount of the sodium carbonate solution was increased, and when the sodium sulfate solution was added, the sodium carbonate solution was gradually decreased.
Preferably, the method of adding solid carbon dioxide in an amount depending on the hardness of the clear liquid and the pressure in the container includes: the target application amount of solid carbon dioxide is calculated from the hardness of the first clear liquid, and the addition amount of solid carbon dioxide is adjusted correspondingly to the target application amount while monitoring the pressure in the container.
Preferably, the method of correspondingly adjusting the addition amount of solid carbon dioxide to the target application amount while monitoring the pressure in the container includes: adding a first preset amount of solid carbon dioxide less than the target applied amount, stopping adding and monitoring the pressure in the container, continuing to add solid carbon dioxide when the pressure is changed from increasing to decreasing and gradually reducing the added amount until the total added amount reaches the target applied amount.
Preferably, the temperature in the reaction vessel is monitored during the reaction of the supernatant and solid carbon dioxide, and as the temperature continues to drop, the reaction vessel is warmed and a portion of the gas is released to reduce the pressure.
Preferably, in the step of washing the fly ash with water to obtain a water wash solution, the liquid-solid ratio is 15:1 to 18:1.
Preferably, the method for online decalcification of fly ash further comprises a pretreatment step of fly ash before subjecting the fly ash to water washing; the pretreatment method comprises the following steps: crushing the fly ash, sieving and extracting oversize materials; the fly ash is washed by washing the oversize material with water.
Preferably, a wetting amount of sodium hydroxide is added to the step of comminuting the fly ash.
Preferably, the third clear liquid is mixed with sodium carbonate solution for reaction, and then the solid-liquid separation method is sand filtration.
The beneficial effects are that:
in the prior art, sodium carbonate (Na 2 CO 3 ) As decalcifying agent. However, the cost of decalcifying fly ash is high due to the large amount of the catalyst. Calcium carbonate is produced in large quantities by decalcification and its industrial value is relatively low. In the application, the sodium sulfate and the sodium carbonate are combined for decalcification, so that the less consumption of the sodium carbonate can be realized.
In addition, the application also combines ferrous sulfate and sodium sulfide, so that heavy metals which are difficult to wash and remove can be used, and sulfate radical can be provided by utilizing ferrous sulfate to serve as a precipitation function, thereby reducing the use amount of sodium sulfate to a certain extent.
In addition, the carbon dioxide used can produce carbonation, thereby also serving as a precipitate. Carbon dioxide has a relatively low solubility in water, so that the use of solid carbon dioxide in a closed vessel increases the pressure in the vessel by its vaporization, allowing it to dissolve more and also precipitating more salts.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a process flow diagram of the present application for treating fly ash.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail below. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments, based on the examples herein, which are within the scope of the application as defined by the claims, will be within the scope of the application as defined by the claims.
The main components of the fly ash formed by the incineration treatment of the municipal refuse comprise various metal and nonmetal oxides and refractory organic matters, such as benzene organic matters, dioxin and the like. Directly discharging it presents significant environmental problems. And therefore need to be treated; one of the important tasks is the removal of calcium from fly ash, which can also be described simply as decalcification.
Among the numerous fly ash treatment modes, water washing treatment is one of the more mainstream. During the water washing of the fly ash, calcium is largely introduced into the water washing liquid. Therefore, the water wash needs to be subjected to a de-hardening treatment, i.e. decalcification, before further treatment.
Currently, sodium carbonate is generally selected for use as a precipitant to precipitate calcium for removal from the fly ash. However, the use of sodium carbonate is also caused by the fact that the calcium content in fly ash is large. How to reduce the use amount of sodium carbonate and realize good decalcification effect is a problem to be solved.
In general, in the present application, decalcification is performed using sodium sulfate in combination with sodium carbonate. Sodium carbonate is partially replaced by using calcium sulfate as a decalcifying agent. In addition, such operations consume large amounts of sodium sulfate and they only serve the decalcification function without the positive use value otherwise exhibited in the process of treating fly ash. Thus, in the present application, the inventors have chosen to use the finished sodium sulfate not entirely. But rather, in view of other desirable materials in fly ash to be removed, in combination with the need for decalcification, a more overall beneficial decalcification scheme has been developed.
Specifically, the application provides a fly ash online decalcification method capable of reducing the dosage of sodium carbonate. It relates to the treatment of a composition essentially consisting of (in mass percent): siO (SiO) 2 About 20% -24%, caO about 26% -29%, al 2 O 3 About 18% -23%, fe 2 O 3 About 2 to 8 percent of MgO and 16 to 18 percent of Na in total 2 O and K 2 O, wherein a small amount of Zn, cu, pb, cr, cd and other heavy metals and organic matters are also contained.
Referring to fig. 1, the method for decalcifying fly ash mainly comprises the following steps:
and step 1, mixing water washing liquid obtained by washing fly ash with ferrous sulfate and sodium sulfide for reaction under the condition of not carrying out solid-liquid separation, and carrying out solid-liquid separation to obtain a first clear liquid.
As described above, fly ash contains a large amount of insoluble substances and insoluble substances (for water). Thus, it can be separated from other substances which are readily soluble with respect to water by washing with water. Therefore, by washing fly ash with water and then performing solid-liquid separation, a solution and a solid/slurry can be obtained.
Wherein the water washing mode is to soak the fly ash into water in one scheme and stir the fly ash sufficiently to form water washing liquid.
Alternatively, fly ash may be added to a continuously flowing water stream to form a water wash.
Alternatively, the fly ash may be first mixed with water in small amount to form one mixture flow, and then mixed with water flow in opposite direction to separate insoluble matter from soluble matter.
Wherein the liquid-solid ratio (mL: g) in the step of washing the fly ash with water to obtain a washing liquid is 15:1 to 18:1; but may also be 16:1, 17:1, etc. Controlling the solids to liquid ratio allows the concentration of various solutes in the aqueous wash to be adjusted and thus also has an effect on subsequent reactions.
Or further, the mixture flow passing through the water and the fly ash is continuously dissolved in the aeration tank. The gas used for aeration may be air or ozone is preferably used because ozone can perform an oxidation function so that organic matters and the like in fly ash are oxidized and thus can be removed better.
After washing with water, fly ash can form a slurry containing insoluble or insoluble substances, and a solution composed of various soluble salts and the like dissolved in water. Unlike the conventional method of separating slurry from solution, the present application treats water washing liquid with medicine without solid-liquid separation.
In the concrete implementation, the water washing liquid is mixed with ferrous sulfate and sodium sulfide for reaction, and then solid-liquid separation is carried out to obtain a first clear liquid. The solid part is dried, dehydrated or other harmless operation, and can be further buried and the like.
Wherein the ferrous sulfate is capable of providing sulfate radicals to react with the calcium plasma to precipitate to complete decalcification. The strong reducibility of ferrous ions can reduce some heavy metal ions into water-insoluble simple substances. On the other hand, ferrous ions can also be oxidized to trivalent ions and hydrolyzed to various complexes which react with heavy metals in water to flocculate and precipitate, thereby forming hydroxides and precipitating. While part of the heavy metal ions, such as lead, can also be reacted with sulfur to form water-insoluble solids. In addition, sulfur and ferrous iron can react and precipitate from the water.
In the application, ferrous sulfate and sodium sulfide are added into the water washing liquid in different procedures. Specifically, ferrous sulfate is added first to react, and then sodium sulfide is added.
In this step, after the treatment, solid-liquid separation produces first clear liquid, respectively, which is subjected to subsequent treatment.
In particular, the method of online decalcification of fly ash preferably further comprises a step of pretreatment of the fly ash, before subjecting the fly ash to water washing. And in particular, the method of preprocessing comprises: crushing the fly ash, sieving and extracting oversize materials; the fly ash is washed by washing the oversize material with water. Wherein the crushing operation can remove the components limited or embedded in the fly ash, and is convenient for subsequent reaction with other substances and removal from the fly ash.
Furthermore, when wastewater treatment was performed, the inventors found that: if the fly ash is ground to a particle size that is too small, this may result in a decrease in the leaching rate of the calcium, making the leaching rate less desirable. Analysis found that this was probably because grinding to too fine increased its void fraction, while having strong adsorption, making calcium difficult to fall out. The oversize is selected to avoid too uniform and too small fly ash particles. Further, a wetting amount of sodium hydroxide is added in the step of pulverizing the fly ash, which can react with the surface of the fly ash, thereby facilitating the removal of calcium.
Step 2, mixing the first clear liquid and solid carbon dioxide in a closed reaction vessel for reaction, and then filtering to obtain a second clear liquid, wherein the addition amount of the solid carbon dioxide depends on the hardness of the first clear liquid and the pressure in the vessel.
In this step, calcium is precipitated mainly by the formation of calcium carbonate. At the same time, other non-removed portions of the metal ions in step 1 may also be removed from the bulk solution in a precipitation manner. Wherein the carbonate ions are derived mainly from carbon dioxide provided in the process.
The introduction of carbonic acid is achieved by injecting carbon dioxide into the solution. In practice, carbon dioxide is added as a solid. This is considered to be that the solubility of carbon dioxide in water is not large and the dissolution rate is slow under normal pressure. Therefore, in order to obtain the desired precipitation effect, it is taken to introduce an excess of carbon dioxide into the liquid. However, since such carbon is consumed with a large amount, the addition of solid carbon dioxide to the container is selected and may be referred to as dry ice. The dry ice is gradually converted into gas, so that the pressure in the closed container is increased, thereby promoting the dissolution of carbon dioxide and further facilitating the conversion into calcium carbonate for precipitation.
The amount of solid carbon dioxide added depends on the hardness of the first clear liquid and the pressure in the container.
For example, solid carbon dioxide is theoretically added in an amount consistent with or corresponding to hardness so that all cations can be precipitated. However, in a practical process, the addition of solid carbon dioxide is not ideally dependent on the hardness of the first serum. And carbon dioxide is also difficult to dissolve completely to convert to calcium carbonate, but is partially converted to calcium bicarbonate material (soluble). Therefore, the amount of solid carbon dioxide added is partially increased to the above-described level corresponding to the hardness.
On the other hand, the process of converting solid carbon dioxide into gas and dissolving in water and reacting with various cations is analyzed, and the phenomenon of temperature drop (temperature reduction makes carbon dioxide more soluble) exists when the solid carbon dioxide is converted into gas. Short term carbon dioxide excess may result in less calcium carbonate production, forming calcium bicarbonate. The continuous decrease in temperature indicates that sublimation of dry ice (which is also increasing in pressure within the closed container) is continuous. Then, as described above, it is necessary to control the dissolution of carbon dioxide. Thus, during the reaction of the first clear liquid and the solid carbon dioxide, the temperature within the reaction vessel is monitored, and as the temperature continues to drop, the reaction vessel is warmed and a portion of the gas is released to reduce the pressure.
For example, the method of adding solid carbon dioxide in an amount depending on the hardness of the clear liquid and the pressure in the container includes: the target application amount of solid carbon dioxide is calculated according to the hardness of the clear liquid, and the addition amount of solid carbon dioxide is adjusted correspondingly to the target application amount while monitoring the pressure in the container. For example, a first predetermined amount (e.g., 30 to 60w% of the target amount) of solid carbon dioxide, which is less than the target applied amount, is added first. The addition was then stopped and the pressure in the vessel monitored. During monitoring, when the pressure is changed from increasing to decreasing, the solid carbon dioxide is continuously added and the addition amount is gradually reduced until the total addition amount reaches the target application amount.
And 3, adding sodium sulfate solution into the second clear liquid, monitoring the hardness of the clear liquid, and filtering to obtain a third clear liquid when the hardness reaches a preset value.
The effect of the addition of carbon dioxide in step 2 is such that most of the calcium is transferred to calcium carbonate and a portion is transferred to calcium bicarbonate. The remaining part of the calcium ions can then be precipitated by the sodium sulphate added in this step. This step is selected to control the hardness of the liquid. Therefore, during the addition of sodium sulfate, the hardness of the liquid is monitored, and the amount and time of sodium sulfate addition are selected accordingly.
And 4, mixing the third clear solution with a sodium carbonate solution, and performing solid-liquid separation after reaction, wherein the adding amount of the sodium carbonate solution is dynamically related to the adding amount of the sodium sulfate solution.
After the reaction in the step 3, solid-liquid separation is carried out, and the obtained third clear liquid is mixed with sodium carbonate solution for reaction. At this time, most of the cations have been precipitated, and thus, the amount of sodium carbonate used in this step has been greatly reduced. And the amount of sodium carbonate in this step is dynamically related to the amount of sodium sulfate in step 3. This is based on-line decalcification considerations for fly ash. Due to the large amount of fly ash that needs to be treated. The second supernatant in step 3 may be present in large quantities, in unstable quantities, and requires long-term continuous treatment of the fly ash.
Step 4 is the final stage of the decalcification process.
In view of this, the addition amount of the sodium carbonate solution was dynamically correlated with the addition amount of the sodium sulfate solution. For example, the method of dynamically correlating the addition amount of sodium carbonate solution with the addition amount of sodium sulfate solution is as follows: when the addition of the sodium sulfate solution was stopped, the addition amount of the sodium carbonate solution was increased, and when the sodium sulfate solution was added, the sodium carbonate solution was gradually decreased.
By the treatment in this step, for example, the hardness of the filtrate obtained by mixing the third clear liquid with a sodium carbonate solution and then subjecting the mixture to a solid-liquid separation such as sand filtration after the reaction is reduced to 50mg/L or less. Alternatively, the carbonate concentration in the filtrate obtained by mixing the third clear solution with the sodium carbonate solution and performing solid-liquid separation after reaction can be higher than 1500mg/L.
The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (10)
1. The online decalcification method for the fly ash for reducing the consumption of sodium carbonate is characterized by comprising the following steps of:
mixing water washing liquid obtained from fly ash through water washing with ferrous sulfate and sodium sulfide for reaction under the condition of not carrying out solid-liquid separation, and carrying out solid-liquid separation to obtain a first clear liquid;
mixing the first clear liquid and solid carbon dioxide in a closed reaction vessel to react, and then filtering to obtain a second clear liquid, wherein the addition amount of the solid carbon dioxide depends on the hardness of the first clear liquid and the pressure in the vessel;
adding sodium sulfate solution into the second clear liquid, monitoring the hardness of the clear liquid, and filtering to obtain a third clear liquid when the hardness reaches a preset value;
and mixing the third clear solution with sodium carbonate solution, and performing solid-liquid separation after reaction, wherein the adding amount of the sodium carbonate solution is dynamically related to the adding amount of the sodium sulfate solution.
2. The method for online decalcification of fly ash with reduced sodium carbonate consumption according to claim 1, wherein the hardness of the filtrate obtained by mixing the third clear liquid with sodium carbonate solution and performing solid-liquid separation after reaction is below 50 mg/L;
alternatively, the third clear solution is mixed with sodium carbonate solution, and the concentration of carbonate in the filtrate subjected to solid-liquid separation after reaction is higher than 1500mg/L.
3. The method for online decalcification of fly ash with reduced sodium carbonate content according to claim 1, wherein the method for dynamically correlating the addition amount of sodium carbonate solution with the addition amount of sodium sulfate solution comprises the following steps:
when the addition of the sodium sulfate solution was stopped, the addition amount of the sodium carbonate solution was increased, and when the sodium sulfate solution was added, the sodium carbonate solution was gradually decreased.
4. A method of online decalcification of fly ash with reduced sodium carbonate dosage according to claim 3, wherein the method of adding solid carbon dioxide in an amount dependent on the hardness of the supernatant and the pressure in the vessel comprises:
calculating a target application amount of solid carbon dioxide according to the hardness of the first clear liquid, and correspondingly adjusting the addition amount of the solid carbon dioxide to the target application amount while monitoring the pressure in the container.
5. The method of on-line decalcification of fly ash with reduced sodium carbonate usage according to claim 4, wherein the method of correspondingly adjusting the addition amount of solid carbon dioxide to the target application amount while monitoring the pressure in the vessel comprises:
adding a first preset amount of solid carbon dioxide less than the target applied amount, stopping adding and monitoring the pressure in the container, continuing to add solid carbon dioxide when the pressure is changed from increasing to decreasing and gradually reducing the added amount until the total added amount reaches the target applied amount.
6. The method for online decalcification of fly ash with reduced sodium carbonate according to claim 5, wherein the temperature in the reaction vessel is monitored during the reaction of the first supernatant and solid carbon dioxide, and when the temperature is continuously decreased, the reaction vessel is warmed and part of the gas is released to decrease the pressure.
7. The method for online decalcification of fly ash with reduced sodium carbonate content according to claim 5, wherein in the step of washing the fly ash with water to obtain a water washing liquid, the liquid-solid ratio is 15:1 to 18:1.
8. The method for online decalcification of fly ash with reduced sodium carbonate consumption according to any one of claims 3 to 7, wherein said method for online decalcification of fly ash further comprises, prior to subjecting the fly ash to water washing: a step of pretreatment of fly ash; the pretreatment method comprises the following steps: crushing the fly ash, sieving and extracting oversize materials; the fly ash is washed by washing the oversize material with water.
9. The method for online decalcification of fly ash with reduced sodium carbonate content according to claim 8, wherein said step of pulverizing said fly ash comprises adding a wetting amount of sodium hydroxide.
10. The method for online decalcification of fly ash with reduced sodium carbonate content according to claim 1, wherein the solid-liquid separation method is sand filtration after the third clear solution is mixed with sodium carbonate solution and reacted.
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| JPH08155417A (en) * | 1994-12-06 | 1996-06-18 | Kurita Water Ind Ltd | Method for treatment of alkali fly ash |
| US20150307400A1 (en) * | 2014-04-23 | 2015-10-29 | Calera Corporation | Methods and systems for utilizing carbide lime or slag |
| CN109604312A (en) * | 2019-01-09 | 2019-04-12 | 北京金隅琉水环保科技有限公司 | A kind of method of trap heavy metals during flying dust water-washing pre-treatment |
| CN114804439A (en) * | 2022-05-23 | 2022-07-29 | 安徽海螺环保集团有限公司 | Pretreatment system for fly ash washing liquid |
| CN115448349A (en) * | 2022-08-31 | 2022-12-09 | 江西盖亚环保科技有限公司 | Method for recovering calcium salt from waste incineration fly ash |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH08155417A (en) * | 1994-12-06 | 1996-06-18 | Kurita Water Ind Ltd | Method for treatment of alkali fly ash |
| US20150307400A1 (en) * | 2014-04-23 | 2015-10-29 | Calera Corporation | Methods and systems for utilizing carbide lime or slag |
| CN109604312A (en) * | 2019-01-09 | 2019-04-12 | 北京金隅琉水环保科技有限公司 | A kind of method of trap heavy metals during flying dust water-washing pre-treatment |
| CN114804439A (en) * | 2022-05-23 | 2022-07-29 | 安徽海螺环保集团有限公司 | Pretreatment system for fly ash washing liquid |
| CN115448349A (en) * | 2022-08-31 | 2022-12-09 | 江西盖亚环保科技有限公司 | Method for recovering calcium salt from waste incineration fly ash |
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