CN114751429A - Treatment process for preparing baking soda from desulfurized ash - Google Patents

Treatment process for preparing baking soda from desulfurized ash Download PDF

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CN114751429A
CN114751429A CN202210338340.XA CN202210338340A CN114751429A CN 114751429 A CN114751429 A CN 114751429A CN 202210338340 A CN202210338340 A CN 202210338340A CN 114751429 A CN114751429 A CN 114751429A
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salt
baking soda
sodium bicarbonate
filtrate
crystallization
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CN114751429B (en
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李保震
李雅
王美娇
赵宇靖
韦凤密
王天慧
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Beijing Saike Kanglun Environmental Science & Technology Co ltd
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Beijing Saike Kanglun Environmental Science & Technology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D7/00—Carbonates of sodium, potassium or alkali metals in general
    • C01D7/02—Preparation by double decomposition
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C1/00—Ammonia; Compounds thereof
    • C01C1/24—Sulfates of ammonium
    • C01C1/244—Preparation by double decomposition of ammonium salts with sulfates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
    • C01D5/04—Preparation of sulfates with the aid of sulfurous acid or sulfites, e.g. Hargreaves process
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
    • C01D5/16—Purification
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D7/00—Carbonates of sodium, potassium or alkali metals in general
    • C01D7/10—Preparation of bicarbonates from carbonates
    • C—CHEMISTRY; METALLURGY
    • C05—FERTILISERS; MANUFACTURE THEREOF
    • C05C—NITROGENOUS FERTILISERS
    • C05C3/00—Fertilisers containing other salts of ammonia or ammonia itself, e.g. gas liquor
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity

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  • Inorganic Chemistry (AREA)
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Abstract

A treatment process for preparing baking soda from desulfurized fly ash, belonging to the technical field of desulfurized fly ash treatment. One technical scheme comprises the following steps: (1) dissolving and filtering; (2) removing organic matters; (3) aeration and impurity removal; (4) removing fluorine; (5) salt separation; (6) sodium sulfate is used for preparing baking soda; (7) and (5) treating crystallization mother liquor. The other technical proposal replaces the step (1) with saturated Na2SO4And (5) leaching and filtering the solution. The invention firstly transfers a large amount of sodium bicarbonate out of the system and then transfers the systemThe sodium sulfate in the desulfurization ash is converted into the baking soda, so that the use amount of a conversion reagent for converting the sodium sulfate into the baking soda is reduced, and the resource recycling of the desulfurization ash is fully realized.

Description

Treatment process for preparing baking soda from desulfurized ash
Technical Field
The invention belongs to the technical field of desulfurized fly ash treatment, and relates to a treatment process for preparing baking soda from desulfurized fly ash.
Background
The flue gas desulfurization ash is first-level dangerous solid waste generated in the flue gas desulfurization process of a coke oven by using sodium carbonate and sodium bicarbonate as desulfurizing agents, wherein the main components of the flue gas desulfurization ash are sodium carbonate, sodium bicarbonate, sodium sulfate and the like, and the flue gas desulfurization ash contains impurity ions in a certain proportion. In general, Na is contained in the desulfurized fly ash 2SO310-20 percent of (A), 0.5-1 percent of NaF and Na2CO35-15 percent of the total weight of the composition, a small amount of insoluble solid impurities, and the balance of sodium bicarbonate and sodium sulfate. The desulfurized fly ash is easily dissolved in water, and can infiltrate into soil through dripping of rainwater during stacking or landfill treatment, thereby causing serious pollution to the soil and underground water.
CN11207363A proposes a resource utilization method of sodium bicarbonate desulfurized ash, which comprises the steps of dissolving the desulfurized ash by using pure water, clarifying, carrying out solid-liquid separation, adding sodium bicarbonate crystals into the clarified liquid, and carrying out evaporation concentration to obtain a sodium bicarbonate product.
CN109850922A proposes a method and a device for recycling desulfurized ash of baking soda, which, on the basis of the dissolution and filtration of desulfurized ash, proposes that the carbonate in the solution is converted into bicarbonate by the combined action of lime milk and carbon dioxide and oxygen, the purity of baking soda is improved, and calcium sulfate as a byproduct is recovered, but the added value of the calcium sulfate is lower than that of the baking soda. And because of the existence of organic matters and fluorine ions in the desulfurized fly ash, the purity of the recovered calcium sulfate cannot be ensured.
CN111701419A proposes a recycling method of sodium-alkali dry desulfurized ash, which comprises mixing and dissolving desulfurized ash and evaporated condensed water, introducing compressed air to oxidize sodium sulfite into sodium sulfate, adding sulfuric acid solution to convert sodium bicarbonate and sodium carbonate into sodium sulfate, filtering out impurities, and adding ammonium bicarbonate to convert sodium sulfate into sodium bicarbonate and ammonium sulfate through double decomposition reaction.
CN110697738A proposes a method for recycling desulfurized ash from baking soda by dry method, which recovers desulfurized ash as solid sodium sulfate, but the added value of sodium sulfate is lower for enterprises than baking soda, and cannot be reused inside enterprises.
The treatment process of the desulfurized fly ash is urgently needed, so that the desulfurized fly ash is recycled, and the environmental pollution is avoided.
Disclosure of Invention
The invention aims to provide a treatment process for preparing baking soda from desulfurized fly ash, which optimizes and perfects an impurity removal process in the process of recovering baking soda from desulfurized fly ash.
The invention provides two technical schemes for preparing baking soda by using desulfurized ash, wherein one technical scheme comprises the following steps:
(1) dissolving and filtering: dissolving desulfurized fly ash with water, filtering, and removing insoluble substances to obtain filtrate;
(2) removing organic matters: removing organic matters in the filtrate obtained in the step (1) by adopting an adsorption method or an oxidation method;
(3) aeration and impurity removal: introducing air or oxygen into the filtrate obtained after the organic matters are removed in the step (2) to ensure that Na is contained 2SO3All oxidized to Na2SO4Then introducing CO into the solution2Making the pH of the solution less than or equal to 8.3, adding CO3 2-All turn toTo HCO3 -At the moment, by utilizing the principle that the solubility of the sodium bicarbonate is obviously reduced compared with that of the sodium carbonate at the same temperature, the sodium bicarbonate in the solution is saturated and separated out, and filtrate and solid are obtained after filtration;
(4) and (3) fluorine removal: removing fluoride ions from the filtrate obtained in the step (3);
(5) salt separation: separating salt from the filtrate obtained in the step (4) after removing the fluorine ions by adopting one or more of evaporative crystallization, freezing crystallization and nanofiltration processes to obtain crystal salt and crystallization mother liquor;
(6) sodium sulfate baking soda: adding water to dissolve the crystalline salt obtained in the step (5), adding ammonium bicarbonate to convert sodium sulfate into sodium bicarbonate and ammonium sulfate, and supersaturating and separating out sodium bicarbonate; mixing the separated sodium bicarbonate and the sodium bicarbonate separated in the step (3) and then putting the mixture into a drying system to prepare a baking soda product, wherein the purity of the baking soda is more than 95 percent, and ammonium sulfate can be used as a nitrogenous fertilizer;
(7) and (3) crystallization mother liquor treatment: and (4) continuously concentrating the crystallization mother liquor obtained in the step (5) until the crystallization is completed, and drying to obtain a small amount of mixed salt, wherein the mixed salt comprises sodium chloride, sodium nitrate, sodium fluoride and other small components.
The other technical scheme is different from the previous technical scheme in that saturated sodium sulfate solution is used for leaching desulfurized ash and then filtering, the purity of sodium sulfate in a filter cake reaches more than 99 percent, and the sodium sulfate can be directly used for preparing baking soda; the subsequent treatment mode of the leached filtrate is the same as the subsequent treatment mode of the filtrate obtained by dissolution and filtration in the previous technical scheme, and the specific technical scheme comprises the following steps:
(1) leaching and filtering: with saturated Na2SO4The solution is used for leaching desulfurized fly ash, because saturated sodium sulfate is used for leaching, a large amount of sodium sulfate solid is separated out, and Na is formed after the solid is dried2SO4The content of the sodium sulfate is more than 99 percent, and the sodium sulfate is mixed with the sodium sulfate and the sodium bicarbonate after the salt separation of the subsequent crystallization to prepare the baking soda; filtering the washed desulfurized ash to remove insoluble substances to obtain filtrate;
(2) removing organic matters: removing organic matters in the filtrate obtained in the step (1) by adopting an adsorption method or an oxidation method;
(3) aeration and impurity removal: introducing air or oxygen into the filtrate obtained after the organic matters are removed in the step (2) to ensure that Na is contained2SO3All oxidized to Na2SO4Then introducing CO into the solution2So that the pH of the solution is less than or equal to 8.3, adding CO3 2-All conversion to HCO3 -At the moment, by utilizing the principle that the solubility of the sodium bicarbonate is obviously reduced compared with that of the sodium carbonate at the same temperature, the sodium bicarbonate in the solution is saturated and separated out, and filtrate and solid are obtained after filtration;
(4) And (3) fluorine removal: removing fluoride ions from the filtrate obtained in the step (3);
(5) salt separation: separating salt from the filtrate obtained after the fluoride ions are removed in the step (4) by adopting one or more of evaporative crystallization, freezing crystallization and nanofiltration processes to obtain crystallized salt and crystallized mother liquor;
(6) sodium sulfate baking soda: adding water to dissolve the crystalline salt obtained in the step (5), adding ammonium bicarbonate to convert sodium sulfate into sodium bicarbonate and ammonium sulfate, and supersaturating and separating out sodium bicarbonate; mixing the separated sodium bicarbonate and the sodium bicarbonate separated in the step (3) and then putting the mixture into a drying system to prepare a baking soda product, wherein the purity of the baking soda is more than 95 percent, and ammonium sulfate can be used as a nitrogenous fertilizer;
(7) and (3) crystallization mother liquor treatment: and (4) continuously concentrating the crystallization mother liquor obtained in the step (5) until the crystallization is completed, and drying to obtain a small amount of mixed salt, wherein the mixed salt comprises sodium chloride, sodium nitrate, sodium fluoride and other small components.
Further, in the first technical scheme, the dissolving temperature in the step (1) is 20-40 ℃, and the mass ratio of the desulfurized fly ash to the water is 1: 1-1: 5.
Further, in the second technical scheme, the leaching temperature in the step (1) is 20-40 ℃, and the mass ratio of leaching solid to liquid is 1: 1-1: 5.
Further, in the step (2), organic matters in the filtrate obtained in the step (1) are removed by adopting an adsorption method, wherein the adsorption material is selected from one or more of carbon-based materials (such as walnut shells, fruit shells, sawdust, anthracite, fly ash and activated carbon), inorganic materials (such as diatomite, kaolin, bentonite, expanded shale, alumina and natural zeolite), fibrous materials (such as fiber balls and sponge) and adsorption resin; when static adsorption is adopted, the addition amount of the adsorbent is 0.01-20 g/L, and the adsorption time is 0.5-1.5 h; when dynamic adsorption is adopted, the height-diameter ratio of the adsorption bed is 1: 1-3: 1, and the water inflow speed is 1-12 BV/h. The removal rate of organic matters in the filtrate after adsorption is over 90 percent.
Further, in the step (2), organic matters in the filtrate obtained in the step (1) are removed by adopting an oxidation method, and the oxidation process comprises one or a combination of more of medicament oxidation, wet oxidation, Fenton oxidation, ozone catalytic oxidation, photocatalytic oxidation and electrochemical oxidation.
Further, the method for removing fluorine in the step (4) is one or more of calcium method fluorine removal, aluminum salt fluorine removal and resin adsorption fluorine removal, and the calcium method fluorine removal specifically comprises the following steps: according to the molar ratio of Ca2+：F-Adding CaSO in a ratio of 1: 1-6: 14Reacting for 0.5-4 h, precipitating and filtering to obtain filtered liquid and CaF2Precipitating; the aluminum salt defluorination method specifically comprises the following steps: adding aluminum sulfate according to the molar ratio of Al to F =1: 1-9: 1, reacting for 0.5-4 h, precipitating, and filtering to obtain filtrate and AlF3Precipitating; the resin adsorption defluorination method specifically comprises the following steps: adsorbing the filtrate by using defluorination resin for 0.5-4 h. After defluorination, Na in solute of filtrate2SO4And NaHCO3The total proportion is more than 93 percent.
Further, the evaporation crystallization process in the step (5) specifically comprises the following steps: evaporating the filtrate obtained in the step (4) at a negative pressure of 60-90 ℃, and concentrating to Na2SO4Stopping evaporation when the temperature is close to saturation, precipitating crystal salt, and centrifuging the crystal salt at a temperature above 50 deg.C to obtain crystal salt and crystal mother liquor; the nanofiltration process specifically comprises the following steps: and (4) the filtrate obtained in the step (4) enters a nanofiltration membrane component, salt separation is carried out to obtain nanofiltration concentrated water and nanofiltration fresh water, the nanofiltration concentrated water is evaporated and crystallized to obtain crystal salt and crystal mother liquor, and the nanofiltration fresh water and the crystal mother liquor are mixed.
Further, in the step (6), ammonium bicarbonate is added according to the molar ratio of 1: 1-1: 10 of ammonium bicarbonate to sodium sulfate.
The invention has the following beneficial technical effects:
1) the invention adopts an effective process to prepare the industrial desulfurized fly ash into the baking soda with high added value, and the baking soda is reused in the desulfurization process, thereby realizing the resource recycling of the industrial desulfurized fly ash. And for impurities in the desulphurised ash: COD, sulfite, carbonate, fluoride ions, chloride ions, nitrate and the like are comprehensively removed, and the purity of the recovered baking soda is higher than that of the recovered baking soda by a combined process, and the recovery rate is also higher than that of the recovered baking soda by a traditional process.
2) Utilizing the solubility difference of sodium carbonate and sodium bicarbonate at the same temperature, converting sodium sulfite into sodium carbonate by air aeration or introduced oxygen in the process of impurity removal, and introducing CO2The sodium carbonate is completely converted into the sodium bicarbonate and is saturated and separated out, so that the sodium bicarbonate is primarily purified and recovered, and the influence of carbonate on the subsequent defluorination effect is effectively avoided. Various impurity removal agents are added, are the same ions of the valuable ions in the solution, and no other impurity ions are introduced, so that the purity of the subsequent product is ensured.
3) In the course of separating salt by evaporative crystallization, according to Na 2SO4-NaCl-H2An O ternary phase diagram, the temperature is reasonably controlled, and the separated Na is ensured2SO4Is in solution Na2SO4The total content is more than 85 percent, and the mixture of anhydrous sodium sulfate and baking soda with the purity of more than 98 percent is obtained.
4) By using Na2SO4Reacting with NaHCO at a certain temperature3Difference in solubility, when adding ammonium bicarbonate to react with Na2SO4All conversion to NaHCO3Then, NaHCO3Precipitation begins and the conversion reaches 90%, and two industrial products of baking soda solid and ammonium sulfate are obtained.
5) The desulfurized ash is leached by adopting saturated sodium sulfate, so that sodium sulfate solid with the purity of more than 99 percent can be obtained, and the purity can be directly used for preparing baking soda.
Drawings
Fig. 1 is a schematic flow chart of a first technical scheme.
Fig. 2 is a schematic flow chart of a second technical scheme.
Detailed Description
The technical scheme of the invention is clearly and completely described by embodiments in the following with reference to the attached drawings of the specification. It is to be understood that the described embodiments are merely exemplary of some, and not necessarily all, embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without making creative efforts based on the embodiments of the present invention, belong to the protection scope of the present invention. "first" and "second" are used herein for descriptive purposes only and are not to be construed as indicating or implying a relative importance or quantity or location.
Example 1
The analysis of the desulfurized fly ash content of a coal-coking plant is shown in Table 1.
TABLE 1 analysis of desulfurized fly ash content by mass percentage
Composition (A) Ratio of the ingredients
NaCl 7.618%
Na2SO3 0.512%
Na2SO4 61.419%
Na2CO3、NaHCO3 24.66~31.11%
NaF 0.612%
Nitric acidSodium salt 0.809%
COD（TOC） 1.042%（0.137%）
Water-insoluble substances and other substances 0~3.82%
Step 1: at the constant temperature of 30 ℃, desulfurizing ash according to the mass: water =1:4, and then filtered to remove insoluble solid impurities, to obtain a filtrate.
Step 2: adding 10g/L powdered activated carbon into the filtrate, adsorbing for 1h, precipitating for 30min, and filtering to obtain light yellow transparent filtrate.
And step 3: according to the molar ratio of O2:SO3 2-=3:1 bubbling O into the filtered solution after adsorption2Detecting SO in the water3 2-Introducing sufficient CO after the catalyst has been completely oxidized2Until the pH is less than or equal to 8.3, a large amount of NaHCO exists at the moment3And (4) precipitating.
And 4, step 4: adding Ca with a molar ratio into the solution separated in the step 32+：F-CaSO of =6:14Reacting for 3h, precipitating for 30min, and detecting F in the filtrate-The removal rate is reduced from 702.24mg/L to 104.15mg/L and reaches 85.17 percent.
And 5: evaporating and concentrating the filtered solution obtained in the step 4 to 5.56% of the volume of the original solution by adopting negative pressure at 80 ℃, separating and drying the precipitated crystals at 60 ℃, and obtaining powder with an analysis component of Na2SO486% of NaHCO3The proportion is 13 percent.
Step 6: na obtained in step 5 2SO4And NaHCO3The mixture is dissolved in water to Na2SO4The concentration is 20%, ammonium bicarbonate solid is added according to the mol ratio of ammonium bicarbonate to sodium sulfate of 1:1, and sodium bicarbonate is supersaturated and separated out; the precipitated sodium bicarbonate and the carbon precipitated in the step 3Sodium bicarbonate is mixed and enters a drying system to prepare the baking soda product, and the total recovery rate of the sodium bicarbonate is 89%.
And 7: and continuously evaporating the mother liquor in the step 5 until all the mother liquor is crystallized to obtain the mixed salt.
Example 2
The analysis of the desulfurized fly ash content of a coal coking plant is shown in Table 1.
Step 1: at the constant temperature of 30 ℃, desulfurizing ash according to the mass: water =1:3, and then filtered to remove insoluble solid impurities, to obtain a filtrate having a dark yellow color.
And 2, step: and (3) passing the filtrate through resin adsorbing organic matters at the flow rate of 3BV/h, wherein the effluent is colorless and transparent.
And step 3: according to the molar ratio of O2:SO3 2-Blowing O into the adsorbed filtered solution in a ratio of =2:12Detecting SO in the water3 2-Introducing sufficient CO after the catalyst has been completely oxidized2Until the pH is less than or equal to 8.3, a large amount of NaHCO exists at the moment3And (4) precipitating.
And 4, step 4: adding Al in a molar ratio: f-Reacting aluminum sulfate in a ratio of =3:1 for 1h, precipitating for 30min, and detecting F in the filtered liquid-The removal rate is reduced from 702.24mg/L to 70.22 mg/L, and the removal rate reaches 90 percent.
And 5: concentrating the filtered solution obtained in step 4 by evaporation at 80 deg.C under negative pressure to 5.56% of the original solution volume, separating and drying the precipitated crystals at 50 deg.C to obtain powder with Na as analytical component2SO485% of NaHCO3The proportion is 14 percent.
And 6: na obtained in step 52SO4And NaHCO3The mixture is dissolved in water to Na2SO4Adding ammonium bicarbonate solid with the concentration of 20 percent and the mol ratio of ammonium bicarbonate to sodium sulfate of 1:2, and supersaturating and separating out sodium bicarbonate; and (3) mixing the separated sodium bicarbonate with the sodium bicarbonate separated in the step (3) and feeding the mixture into a drying system to prepare the baking soda product, wherein the total recovery rate of the sodium bicarbonate is 91%.
And 7: and (5) continuously evaporating the mother liquor in the step 5 until all the mother liquor is crystallized to obtain the mixed salt.
Example 3:
the desulfurization ash content of a coal-electric-aluminum enterprise is shown in Table 2
TABLE 2 analysis of the desulfurized fly ash content in terms of percentage by mass
Composition (I) Ratio of occupation of
NaCl 2.31%
Na2SO3 13.52%
Na2SO4 70.74%
NaF 0.4639%
Sodium carbonate 13.1452%
Sodium nitrate 0.4232%
Ca 0.1093%
K、Fe、Al、Pb、Zn、 Mo Trace amount of
COD 0.2483%
Oil 0.03%
Water insoluble substance 0.005%
Step 1: at the constant temperature of 30 ℃, desulfurizing ash according to the mass: leaching and filtering saturated sodium sulfate solution at the ratio of =1:3, drying filter cake and then adding Na2SO4The content of 99.18%, and the analysis of the filtrate after washing are shown in Table 3.
TABLE 3 analysis results of the composition of the elution filtrate
Item Index (I)
SO4 2-（mg/L） 172660
SO3 2-（mg/L） 38452
Cl-（mg/L） 16213
F-（mg/L） 525
CO3 2-（mg/L） 22701
NO3 -（mg/L） 890
COD（mg/L） 2709
Oil (mg/L) 7.62
And 2, step: adding 10g/L powdered activated carbon into the filtrate, adsorbing for 1h, precipitating for 30min, and filtering.
And step 3: according to the molar ratio of O2:SO3 2-Blowing O into the filtrate after adsorption by a ratio of =3:12Detecting SO in the water3 2-Introducing sufficient CO after the catalyst has been completely oxidized2Until the pH is less than or equal to 8.3, a large amount of NaHCO exists at the moment3And (4) precipitating.
And 4, step 4: adding Ca with a molar ratio into the solution separated in the step 32+：F-CaSO of =6:14Reacting for 3h, precipitating for 30min, and detecting F in the filtrate-The removal rate is reduced from 525mg/L to 94.56mg/L, the removal rate reaches 81.99 percent, and the water F is adsorbed by aluminum-based resin at the rate of 4BV/h-The concentration is reduced to below 20 mg/L.
And 5: evaporating and concentrating the solution treated in the step 4 to 4.54% of the original solution volume by adopting negative pressure at 80 ℃, separating and drying the precipitated crystals at 60 ℃, and obtaining powder with an analysis component of Na2SO488% of NaHCO3The ratio is 11%.
Step 6: na obtained in step 52SO4And NaHCO3The mixture is dissolved in water to Na2SO4Adding ammonium bicarbonate solid with the concentration of 20 percent and the mol ratio of ammonium bicarbonate to sodium sulfate of 1:1, and supersaturating and separating out sodium bicarbonate; mixing the separated sodium bicarbonate and the sodium bicarbonate separated in the step 3, and feeding the mixture into a drying systemThe sodium bicarbonate product was obtained with a recovery of 85%.
And 7: and (5) continuously evaporating the mother liquor in the step 5 until all the mother liquor is crystallized to obtain the mixed salt.
Example 4
The desulfurized fly ash content of a coke plant is shown in Table 4.
TABLE 4 analysis of desulfurized fly ash content by mass percentage
Composition (I) Ratio of occupation of
NaCl 4.69%
Na2SO3 11.36%
Na2SO4 75.32%
NaF 0.3855%
Sodium carbonate 7.8498%
Sodium nitrate 0.3378%
Ca 0.0992%
K、Fe、Al、Pb、Zn、 Mo Trace amount of
COD 0.1808%
Oil 0.01%
Water insoluble substance 0.004%
Step 1: at the constant temperature of 30 ℃, desulfurizing ash according to the mass: water =1:5 to remove insoluble matter, and the filtrate was obtained.
Step 2: according to the ozone: the ozone catalytic oxidation is carried out on the added amount of COD =2:1, and the oxidized effluent is light yellow and transparent.
And step 3: detecting the content of residual sulfite and according to the molar ratio O2:SO3 2-Blowing O into oxidized effluent water in a ratio of =2:12Detecting SO in the water3 2-Introducing sufficient CO after the catalyst has been completely oxidized2Until the pH is less than or equal to 8.3, a large amount of NaHCO exists at the moment3And (4) precipitating.
And 4, step 4: adding Al in a molar ratio: f-Reacting aluminum sulfate in a ratio of =3:1 for 1h, precipitating for 30min, and detecting F in the filtered liquid-The removal rate is reduced from 546.11mg/L to 65.22 mg/L, and the removal rate reaches 88.06 percent.
And 5: and 4, allowing the solution treated in the step 4 to enter a nanofiltration membrane component, separating salt to obtain sodium sulfate concentrated water and nanofiltration fresh water, and evaporating and crystallizing the nanofiltration concentrated water to obtain a mixture of anhydrous sodium sulfate and baking soda with the purity of more than 98%.
And 6: na obtained in step 52SO4And NaHCO3The mixture is dissolved in water to Na2SO4Adding ammonium bicarbonate solid with the concentration of 20% and the molar ratio of ammonium bicarbonate to sodium sulfate of 1:3, and supersaturating and separating out sodium bicarbonate; separating out hydrogen carbonateAnd (3) mixing sodium with the sodium bicarbonate separated out in the step (3) and feeding the mixture into a drying system to prepare a baking soda product, wherein the recovery rate of the obtained sodium bicarbonate is 90%.
And 7: and (5) evaporating the nanofiltration fresh water in the step (5) until all crystals are crystallized to obtain the mixed salt.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.

Claims (9)

1. The treatment process for preparing baking soda from desulfurized ash is characterized by comprising the following steps:
(1) dissolving and filtering: dissolving desulfurized fly ash with water, filtering, and removing insoluble substances to obtain filtrate;
(2) removing organic matters: removing organic matters in the filtrate obtained in the step (1) by adopting an adsorption method or an oxidation method;
(3) Aeration impurity removal: introducing air or oxygen into the filtrate obtained after the organic matters are removed in the step (2) to ensure that Na is contained2SO3All oxidized to Na2SO4Then introducing CO into the solution2So that the pH of the solution is less than or equal to 8.3, adding CO3 2-All conversion to HCO3 -Saturating and separating out sodium bicarbonate in the solution, and filtering to obtain filtrate and solid;
(4) and (3) fluorine removal: removing fluoride ions from the filtrate obtained in the step (3);
(5) salt separation: separating salt from the filtrate obtained in the step (4) after removing the fluorine ions by adopting one or more of evaporative crystallization, freezing crystallization and nanofiltration processes to obtain crystal salt and crystallization mother liquor;
(6) sodium sulfate baking soda: adding water to dissolve the crystalline salt obtained in the step (5), adding ammonium bicarbonate to convert sodium sulfate into sodium bicarbonate and ammonium sulfate, and supersaturating and separating out sodium bicarbonate; mixing the separated sodium bicarbonate and the sodium bicarbonate separated in the step (3) and adding the mixture into a drying system to prepare a baking soda product;
(7) and (3) crystallization mother liquor treatment: and (4) continuously concentrating the crystallization mother liquor obtained in the step (5) until the crystallization is completed, and drying to obtain a small amount of mixed salt.
2. The treatment process according to claim 1, wherein the dissolving temperature in the step (1) is 20-40 ℃, and the mass ratio of the desulfurized fly ash to the water is 1: 1-1: 5.
3. The treatment process for preparing baking soda from desulfurized ash is characterized by comprising the following steps of:
(1) leaching and filtering: with saturated Na2SO4Leaching desulfurized fly ash by using the solution to separate out a large amount of sodium sulfate solid, and mixing the sodium sulfate with sodium sulfate and sodium bicarbonate after subsequent crystallization and salt separation to prepare baking soda; filtering the washed desulfurized ash to remove insoluble substances to obtain filtrate;
(2) removing organic matters: removing organic matters in the filtrate obtained in the step (1) by adopting an adsorption method or an oxidation method;
(3) aeration impurity removal: introducing air or oxygen into the filtrate obtained after the organic matters are removed in the step (2) to ensure that Na is contained2SO3All oxidized to Na2SO4Then introducing CO into the solution2So that the pH of the solution is less than or equal to 8.3, adding CO3 2-All conversion to HCO3 -Saturating and separating out sodium bicarbonate in the solution, and filtering to obtain filtrate and solid;
(4) and (3) fluorine removal: removing fluoride ions from the filtrate obtained in the step (3);
(5) salt separation: separating salt from the filtrate obtained in the step (4) after removing the fluorine ions by adopting one or more of evaporative crystallization, freezing crystallization and nanofiltration processes to obtain crystal salt and crystallization mother liquor;
(6) sodium sulfate baking soda: adding water to dissolve the crystalline salt obtained in the step (5), adding ammonium bicarbonate to convert sodium sulfate into sodium bicarbonate and ammonium sulfate, and supersaturating and separating out sodium bicarbonate; mixing the separated sodium bicarbonate and the sodium bicarbonate separated in the step (3) and adding the mixture into a drying system to prepare a baking soda product;
(7) Crystallization mother liquor treatment: and (4) continuously concentrating the crystallization mother liquor obtained in the step (5) until the crystallization is completed, and drying to obtain a small amount of mixed salt.
4. The treatment process according to claim 3, wherein the leaching temperature in the step (1) is 20-40 ℃, and the leaching solid-liquid mass ratio is 1: 1-1: 5.
5. The treatment process according to claim 1 or 3, wherein in the step (2), organic matters in the filtrate obtained in the step (1) are removed by adopting an adsorption method, wherein the adsorption material is selected from one or more of carbon-based materials, inorganic materials, fiber materials and adsorption resins; when static adsorption is adopted, the addition amount of the adsorbent is 0.01-20 g/L, and the adsorption time is 0.5-1.5 h; when dynamic adsorption is adopted, the height-diameter ratio of the adsorption bed is 1: 1-3: 1, and the water inflow speed is 1-12 BV/h.
6. The treatment process according to claim 1 or 3, wherein the step (2) adopts an oxidation method to remove organic matters in the filtrate obtained in the step (1), and the oxidation process comprises one or more of chemical oxidation, wet oxidation, Fenton oxidation, ozone catalytic oxidation, photocatalytic oxidation and electrochemical oxidation.
7. The treatment process according to claim 1 or 3, wherein the fluorine removal method in the step (4) is one or more of calcium method fluorine removal, aluminum salt fluorine removal and resin adsorption fluorine removal, and the calcium method fluorine removal specifically comprises: according to the molar ratio of Ca 2+：F-Adding CaSO in a ratio of 1: 1-6: 14Reacting for 0.5-4 h, precipitating and filtering to obtain filtered liquid and CaF2Precipitating; the aluminum salt defluorination method specifically comprises the following steps: adding aluminum sulfate according to the molar ratio of Al to F =1: 1-9: 1, reacting for 0.5-4 h, precipitating, and filtering to obtain filtrate and AlF3Precipitating; the resin adsorption defluorination method specifically comprises the following steps: adsorbing the filtrate by using defluorination resin for 0.5-4 h.
8. The treatment process according to claim 1 or 3, wherein the evaporative crystallization process in the step (5) is specifically: evaporating the filtrate obtained in the step (4) at a negative pressure of 60-90 ℃, and concentrating to Na2SO4Stopping evaporation when the temperature is close to saturation, precipitating crystal salt, and centrifuging the crystal salt at a temperature above 50 deg.C to obtain crystal salt and crystal mother liquor; the nanofiltration process specifically comprises the following steps: and (5) the filtrate obtained in the step (4) enters a nanofiltration membrane component, salt separation is carried out to obtain nanofiltration concentrated water and nanofiltration fresh water, the nanofiltration concentrated water is evaporated and crystallized to obtain crystallized salt and crystallized mother liquor, and the nanofiltration fresh water and the crystallized mother liquor are mixed.
9. The treatment process according to claim 1 or 3, wherein the ammonium bicarbonate is added in the step (6) according to the molar ratio of the ammonium bicarbonate to the sodium sulfate of 1: 1-1: 10.
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