CN106830428B - Method for recycling waste liquid generated by combining steel slag as absorbent with desulfurization and denitrification processes - Google Patents

Method for recycling waste liquid generated by combining steel slag as absorbent with desulfurization and denitrification processes Download PDF

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CN106830428B
CN106830428B CN201710124358.9A CN201710124358A CN106830428B CN 106830428 B CN106830428 B CN 106830428B CN 201710124358 A CN201710124358 A CN 201710124358A CN 106830428 B CN106830428 B CN 106830428B
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filtrate
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nano bubble
liquid
waste liquid
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CN106830428A (en
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王晨晔
陈艳
李会泉
王兴瑞
孟子衡
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Institute of Process Engineering of CAS
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/36—Nitrates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/36—Nitrates
    • C01F11/44—Concentrating; Crystallisating; Dehydrating; Preventing the absorption of moisture or caking
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/048—Purification of waste water by evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/727—Treatment of water, waste water, or sewage by oxidation using pure oxygen or oxygen rich gas
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/74—Treatment of water, waste water, or sewage by oxidation with air
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/18—Nature of the water, waste water, sewage or sludge to be treated from the purification of gaseous effluents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions

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  • Chemical & Material Sciences (AREA)
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  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Treating Waste Gases (AREA)
  • Treatment Of Water By Oxidation Or Reduction (AREA)

Abstract

The invention provides a method for recycling waste liquid generated by combining steel slag as an absorbent with a desulfurization and denitrification process2And NOxAnd then performing solid-liquid separation on the waste liquid reaching a certain total salt concentration, adding quicklime and/or slaked lime into the liquid phase obtained after separation to adjust the pH value of the filtrate to 5-7 after filtration, introducing the filtrate into a micro-nano bubble generating device, completely oxidizing nitrite in the filtrate into nitrate, and performing subsequent evaporation, concentration, crystallization, filtration, drying and other operations to obtain a calcium nitrate product. The method is used as a subsequent process of a metallurgical waste residue combined desulfurization and denitrification method, solves the problem of secondary pollution caused by waste liquid generated in the production process of the process, completely converts nitrite into nitrate, realizes the complete utilization of N element in the waste liquid, obtains a pure calcium nitrate product, simultaneously reaches the national standards of industrial calcium nitrate and agricultural calcium nitrate, and has good application prospect.

Description

Method for recycling waste liquid generated by combining steel slag as absorbent with desulfurization and denitrification processes
Technical Field
The invention relates to the fields of environmental protection and wastewater recovery, in particular to a method for recovering and treating waste liquid generated by combining steel slag as an absorbent with a desulfurization and denitrification process.
Background
In recent years, with the improvement of the industrialization level of China, the economy is rapidly increased, the atmospheric pollution condition is increasingly serious, and SO is2And NOxIs increasing. For containing SO at home2And NOxThe gas is treated and then discharged after reaching the standard.
In the desulfurization and denitrification method disclosed in the prior art, the process related to the ammonia method has the problems of long flow, ammonia leakage, catalyst requirement and the like; the dry desulfurization and denitration method has high cost and low removal rate; the adoption of nano-scale materials for desulfurization and denitrification has the problems of high preparation cost, difficult industrial amplification and the like. Meanwhile, the discharge amount of metallurgical waste residues in China is very large, the utilization rate is very low, a large amount of land is occupied by long-term accumulation and stacking, the ecological environment is polluted, and the resources are greatly wasted. The metallurgical waste slag contains a large amount of alkaline f-CaO, and great economic benefit can be generated if the metallurgical waste slag can be applied to desulfurization and denitrification.
CN10482648A discloses a method for combined desulfurization and denitrification by using metallurgical waste residues, which adopts absorbent slurry prepared by using the metallurgical waste residues to replace quicklime or ammonia as raw materials to absorb SO in flue gas2And NOx. The invention takes the metallurgical waste residue as the raw material, which can effectively relieve the pollution to the environment and the waste of resources; simultaneously, the desulfurization and the denitrification are integrated to absorb SO2And NOxThe absorbent slurry can be recycled, the cost is saved, the low-cost flue gas combined desulfurization and denitrification is realized, and the method has good economic benefits and wide industrial application prospects.
However, the treatment process can generate a large amount of desulfurization and denitrification waste liquid, and the metallurgical slag has complex components, so that the anion and cation in the combined desulfurization and denitrification waste liquid have various types and simultaneously contain NO3 -、NO2 -、SO4 2-、SO3 2-、HSO4 -、HSO3 -Plasma anion and Mg2+、Ca2+、Mn2+Or Fe3+And the like, making it difficult to handle. And NO therein3 -And NO2 -Are mixed together and NO2 -And the nitrate is difficult to be completely oxidized, so that a pure nitrate product is difficult to obtain when the waste liquid is subjected to subsequent recovery treatment.
Disclosure of Invention
In view of the problems in the prior art, the invention aims to recover and treat the waste liquid generated in the process of combining steel slag as an absorbent with a desulfurization and denitrification process to prepare a pure calcium nitrate product.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a method for recycling waste liquid generated by combining steel slag as an absorbent with a desulfurization and denitrification process, which comprises the following steps:
(1) carrying out solid-liquid separation on waste liquid generated by combining steel slag as an absorbent with a desulfurization and denitrification process;
(2) adding quicklime and/or slaked lime into the liquid obtained after the solid-liquid separation in the step (1) to adjust the pH value for removing impurities, and filtering after complete precipitation;
(3) adjusting the pH value of the filtrate obtained in the step (2) to 5-7, and oxidizing by a micro-nano bubble generating device;
(4) and (4) evaporating and concentrating the liquid obtained after oxidation in the step (3), crystallizing, filtering and drying to obtain a calcium nitrate product.
The invention discloses a subsequent process of 'a method for combining desulfurization and denitrification by using metallurgical waste residues' disclosed in patent CN10482648A, which mainly recycles waste liquid generated in the process of combining desulfurization and denitrification by using steel slag as an absorbent to prepare a pure calcium nitrate product, thereby realizing resource recycling of the waste liquid. The anions and cations in the waste liquid of the combined desulfurization and denitrification of the steel slag are various and mainly comprise NO3 -、NO2 -、SO4 2-、SO3 2-、HSO4 -、HSO3 -Plasma and Mg2+、Ca2+、Mn2+、Fe3+Etc., and the pH is weakly acidic. The invention firstly absorbs SO2And NOxThen the steel slag slurry (waste liquor) which reaches a certain total salt concentration is subjected to solid-liquid separation to remove solid impurities in the steel slag slurry, and then quicklime and/or hydrated lime are added into the liquid phase obtained after separation for regulating pH value so as to remove NO by precipitation3 -、NO2 -、Ca2+Other impurity ions bring in sufficient Ca2+Adjusting the pH value of the filtrate to 5-7 after filtration to provide a weakly acidic environment for nitrite ion oxidation, introducing the filtrate into a micro-nano bubble generation device, controlling conditions to completely oxidize nitrite in the filtrate into nitrate, and performing subsequent evaporation, concentration, crystallization, filtration, drying and other operations to obtain pure calcium nitrate productAnd (5) preparing the product. And the recovery of all N elements in the waste liquid is realized.
The waste liquid of the invention refers to absorbing SO2And NOxThen the total salt concentration of the steel slag slurry is 10-60 wt%.
According to the invention, the steel slag content in the waste liquid of step (1) is 1-30 wt%, for example 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt% or 30 wt%, and the specific values between the above values, limited to space and for the sake of brevity, are not exhaustive and do not list the specific values included in the range.
According to the invention, the waste liquid obtained in step (1) contains NO3 -And NO2 -。
According to the invention, the waste liquid obtained in step (1) contains SO4 2-、SO3 2-、HSO4 -Or HSO3 -At least one of them, for example, may contain SO4 2-、SO3 2-、HSO4 -Or HSO3 -A typical but non-limiting combination of any of: SO (SO)4 2-And SO3 2-；HSO4 -And HSO3 -；SO4 2-、SO3 2-And HSO4 -；SO4 2-And HSO4 -；SO3 2-、HSO4 -And HSO3 -；SO4 2-、SO3 2-、HSO4 -And HSO3 -Etc., are not exhaustive for the invention, but are for brevity and clarity.
According to the invention, the waste liquid in the step (1) contains Mg2+、Ca2+、Mn2+Or Fe3+At least two of (B) may contain, for example, Mg at the same time2+And Ca2+；Mn2+And Fe3+；Mg2+And Mn2+；Mg2+And Fe3+；Ca2+And Mn2+；Ca2+And Fe3+；Mg2+、Ca2+And Mn2+；Mg2+、Ca2+And Fe3+；Ca2+、Mn2+And Fe3+；Mg2+、Ca2+、Mn2+And Fe3+。
According to the invention, the pH of the effluent from step (1) is between 4 and 7, and may be, for example, 4, 4.5, 5, 5.5, 6, 6.5 or 7, and the values between these values are specific, for reasons of space and brevity, and are not exhaustive.
According to the invention, the waste liquor of step (1) contains salts in a total concentration of 10-60 wt.%, for example 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.% or 60 wt.%, and the particular values between the above values, are not intended to be exhaustive for reasons of brevity and clarity, and the invention is not intended to be exhaustive of the particular values included in the recited ranges.
The present invention selects the method known in the art to perform solid-liquid separation on the waste liquid, and is not limited in particular, and the solid-liquid separation mode may be, for example, filtration, sedimentation, suspension, or the like, but is not limited thereto.
According to the invention, the quicklime and/or hydrated lime in the step (2) is added in a dry feeding mode and/or a wet feeding mode.
According to the invention, the pH is adjusted to 9-13, for example 9, 9.5, 10, 10.5, 11, 12, 12.5 or 13, after the addition of quicklime and/or slaked lime in step (2), and the values between these values, which are not exhaustive for reasons of space and simplicity, are included in the range.
The filtrate obtained by filtering after complete precipitation contains calcium nitrate and calcium nitrite, the calcium nitrate and the calcium nitrite are not easy to separate, and the calcium nitrite is difficult to be completely oxidized, the mixed crystal of the calcium nitrate and the calcium nitrite can be used as a concrete additive within the range of 1:1, but the dosage is not high, and the pure calcium nitrate has wider application range, more dosage and higher value in industry and agriculture.
According to the invention, nitric acid is added in step (3) to adjust the pH of the filtrate. The pH of the solution is adjusted by using nitric acid, so that other impurity anions can be prevented from being brought in.
According to the invention, before the micro-nano bubble generation device is introduced, the pH of the filtrate obtained in the step (2) is adjusted to 5-7, for example, 5, 5.5, 6, 6.5 or 7, and specific values between the above values are limited to space and for the sake of brevity, and the invention is not exhaustive list of specific values included in the range.
According to the invention, the specific operation after the pH value of the filtrate is adjusted to 5-7 in the step (3) is as follows: introducing the filtrate in the filtrate tank from the water inlet of the micro-nano bubble generating device, simultaneously introducing oxygen-enriched gas from the air inlet, introducing the filtrate into the filtrate tank from the water outlet after the filtrate is aerated in the micro-nano bubble generating device, and repeating the operation until the NO in the filtrate2 -Is completely oxidized to NO3 -Until now.
According to the invention, the volume-mass ratio of the air input to the liquid input of the micro-nano bubble generation device is 20-100, for example, 20, 30, 40, 50, 60, 70, 80, 90 or 100, and the specific values between the above values are limited by space and for the sake of brevity, and the invention is not exhaustive list of the specific values included in the range.
The volume-mass ratio refers to the ratio of the air inflow (volume) and the liquid inflow (mass) of the micro-nano bubble generating device, and the unit is L/t.
According to the invention, the volume ratio of the filtrate per hour to the total amount of the filtrate is 1 (1-2), and may be, for example, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, and specific values between the above values are limited to space and for simplicity, and the invention does not exhaustive list the specific values included in the range.
The aeration in the invention refers to a process of forcibly transferring oxygen in the air into the filtrate.
According to the invention, the aeration time is 0.5-5h, for example 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, and the specific values between the above values, limited to space and for the sake of brevity, are not exhaustive and do not list the specific values included in the range.
According to the invention, the oxygen content of the oxygen-enriched gas is between 20% and 100%, and may be, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%, and the specific values between the above values are limited to space and for the sake of brevity, and the invention is not intended to be exhaustive to include the specific values included in the range.
The present invention is not limited to the specific composition of the oxygen-enriched gas, as long as the oxygen content is controlled within the above range, and the oxygen-enriched gas may be, for example, air, oxygen, or a mixture of air and other gases, but is not limited thereto.
According to the invention, 0-10 wt% of hydrogen peroxide is added into the micro-nano bubble generation device to help nitrite to be oxidized into nitrate more quickly and fully. The 0-10 wt% refers to 0-10 wt% of the total amount of the filtrate. The adding mode can be directly adding into the micro-nano bubble generating device through a water inlet, and can also be directly adding into the filtrate.
According to the invention, the concentration of the liquid after evaporative concentration in step (4) is 30-60 wt%, for example 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt% or 60 wt%, and the specific values between the above values, which are limited by space and for the sake of brevity, are not exhaustive and do not list the specific values included in the range.
According to the invention, the crystallization temperature in step (4) is between 0 ℃ and 30 ℃, and may be, for example, 0 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃ or 30 ℃, and the specific values between the above values are not exhaustive for the invention, and for the sake of brevity.
According to the invention, the temperature of the drying in step (4) is 10-30 ℃, for example 10 ℃, 15 ℃, 20 ℃, 25 ℃ or 30 ℃, and the specific values between the above values are not exhaustive for the invention and for the sake of brevity.
As a preferred technical scheme, the method for recycling the waste liquid generated by the process of combining the steel slag as the absorbent with the desulfurization and denitrification comprises the following steps:
(1) carrying out solid-liquid separation on waste liquid generated after desulfurization and denitrification are combined by using steel slag as an absorbent; the pH value of the waste liquid is 4-7, the total concentration of the contained salt is 10-60 wt%, and the content of the steel slag is 1-30 wt%;
(2) adding quicklime and/or slaked lime into the liquid obtained after the solid-liquid separation in the step (1) to adjust the pH value to 9-13, and filtering after complete precipitation;
(3) adding nitric acid into the filtrate obtained in the step (2) to adjust the pH value to 5-7, introducing the filtrate in the filtrate tank from a water inlet of the micro-nano bubble generating device, simultaneously introducing oxygen-enriched gas with the oxygen content of 20-100% from an air inlet, aerating the filtrate in the micro-nano bubble generating device for 0.5-5h, then introducing the filtrate into the filtrate tank from a water outlet, and repeating the operation until NO in the filtrate2 -Is completely oxidized to NO3 -Until the end; the volume-mass ratio of the air input of the micro-nano bubble generating device to the liquid input is 20-100, the volume ratio of the amount of the filtrate introduced into the micro-nano bubble generating device per hour to the total amount of the filtrate is 1 (1-2), and 0-10 wt% of hydrogen peroxide is added into the micro-nano bubble generating device;
(4) evaporating and concentrating the liquid obtained after oxidation in the step (3) to 30-60 wt%, crystallizing at 0-30 ℃, filtering, and drying the crystal obtained by filtering at 10-30 ℃ to obtain a calcium nitrate product.
Compared with the prior art, the invention at least has the following beneficial effects:
the invention solves the problem that the waste liquid generated in the process of combining steel slag as an absorbent with desulfurization and denitrification is easy to cause secondary pollution, completely converts nitrite into nitrate, realizes the complete utilization of N element in the waste liquid, obtains a pure calcium nitrate product, simultaneously achieves the national standards of industrial calcium nitrate and agricultural calcium nitrate, and has good economic benefit and wide industrial application prospect.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
The specific embodiment of the invention partially provides a method for recycling and treating waste liquid generated by combining steel slag as an absorbent with a desulfurization and denitrification process, and the preparation method comprises the following steps:
(1) carrying out solid-liquid separation on waste liquid generated by combining steel slag as an absorbent with a desulfurization and denitrification process;
(2) adding quicklime and/or slaked lime into the liquid obtained after the solid-liquid separation in the step (1) to adjust the pH value for removing impurities, and filtering after complete precipitation;
(3) adjusting the pH value of the filtrate obtained in the step (2) to 5-7, and oxidizing by a micro-nano bubble generating device;
(4) and (4) evaporating and concentrating the liquid obtained after oxidation in the step (3), crystallizing, filtering and drying to obtain a calcium nitrate product.
Wherein the specific operation after the pH of the filtrate is adjusted to 5-7 in the step (3) is as follows: introducing the filtrate in the filtrate tank from the water inlet of the micro-nano bubble generating device, simultaneously introducing oxygen-enriched gas from the air inlet, introducing the filtrate into the filtrate tank from the water outlet after the filtrate is aerated in the micro-nano bubble generating device, and repeating the operation until the NO in the filtrate2 -Is completely oxidized to NO3 -Until now.
The following are typical but non-limiting examples of the invention:
example 1
In this example, the steel slag slurry absorbs SO2And NOxThe steel slag content in the waste liquid generated later was 15 wt%, the pH was 6, and the total salt concentration was 30 wt%.
(1) Filtering the waste liquid to remove solid impurities;
(2) adjusting the pH of the filtrate obtained in the step (1) to 9 by using quicklime, and removing NO by precipitation3 -、NO2 -And Ca2+Filtering the foreign impurity ions to obtain filtrate;
(3) adding nitric acid into the filtrate obtained in the step (2) to adjust the pH value to 6, then introducing the filtrate in a filtrate tank from a water inlet of a micro-nano bubble generation device, controlling the introduction amount per hour to be 1/2 of the total amount of the filtrate, simultaneously adding hydrogen peroxide with the total mass of 10% of the filtrate from the water inlet, introducing air (the oxygen content is 21%) from an air inlet, enabling the volume mass ratio of the air input to the liquid inlet to be 50L/t, aerating the filtrate in the micro-nano bubble generation device for 3 hours, then, allowing the filtrate to enter the filtrate tank from a water outlet, and repeating the operation until NO in the filtrate2 -Is completely oxidized to NO3 -Until the end;
(4) and (4) evaporating and concentrating the liquid obtained after oxidation in the step (3), wherein the concentration of calcium nitrate in the concentrated solution is 30 wt%, crystallizing the concentrated solution at 5 ℃, filtering, and drying at 10 ℃ to obtain a pure calcium nitrate product. The calcium nitrate product reaches the national standard of industrial calcium nitrate and agricultural calcium nitrate.
Example 2
In this example, the steel slag slurry absorbs SO2And NOxThe steel slag content in the waste liquid generated later was 10 wt%, the pH was 5.5, and the total salt concentration was 40 wt%.
(1) Filtering the waste liquid to remove solid impurities;
(2) regulating the pH of the filtrate obtained in the step (1) to 10.8 by using a CaO saturated solution, and removing NO by precipitation3 -、NO2 -And Ca2+Filtering the foreign impurity ions to obtain filtrate;
(3) adding nitric acid into the filtrate obtained in the step (2) to adjust the pH value to be 6.5, then introducing the filtrate in a filtrate tank from a water inlet of a micro-nano bubble generating device, controlling the introduction amount per hour to be 0.8 of the total amount of the filtrate, simultaneously adding hydrogen peroxide with 5% of the total mass of the filtrate from the water inlet, introducing air and oxygen mixed gas (the oxygen content is 30%) from an air inlet, controlling the volume-mass ratio of the air input to the liquid inlet to be 30L/t, aerating the filtrate in the micro-nano bubble generating device for 2h, then introducing the filtrate into the filtrate tank from a water outlet, and repeating the operation until NO in the filtrate is reduced to 6.2 -Is completely oxidized to NO3 -Until the end;
(4) and (4) evaporating and concentrating the liquid obtained after oxidation in the step (3), wherein the concentration of calcium nitrate in the concentrated solution is 60 wt%, crystallizing the concentrated solution at 30 ℃, filtering, and drying at 15 ℃ to obtain a pure calcium nitrate product. The calcium nitrate product reaches the national standard of industrial calcium nitrate and agricultural calcium nitrate.
Example 3
In this example, the steel slag slurry absorbs SO2And NOxThe steel slag content in the waste liquid generated later was 20 wt%, the pH was 6.5, and the total salt concentration was 35 wt%.
(1) Filtering the waste liquid to remove solid impurities;
(2) adjusting the pH value of the filtrate obtained in the step (1) to 10 by using hydrated lime, and removing NO by precipitation3 -、NO2 -And Ca2+Filtering the foreign impurity ions to obtain filtrate;
(3) adding nitric acid into the filtrate obtained in the step (2) to adjust the pH value to be 6.7, then introducing the filtrate in a filtrate tank from a water inlet of a micro-nano bubble generating device, controlling the introduction amount per hour to be 0.8 of the total amount of the filtrate, simultaneously adding hydrogen peroxide with 4% of the total mass of the filtrate from the water inlet, introducing air and oxygen mixed gas (oxygen content is 40%) from an air inlet, controlling the volume-mass ratio of air inflow to liquid inflow to be 40L/t, aerating the filtrate in the micro-nano bubble generating device for 2.5h, then introducing the filtrate into the filtrate tank from a water outlet, and repeating the operation until NO in the filtrate is reduced to 6.72 -Is completely oxidized to NO3 -Until the end;
(4) and (4) evaporating and concentrating the liquid obtained after oxidation in the step (3), wherein the concentration of calcium nitrate in the concentrated solution is 50 wt%, crystallizing the concentrated solution at 15 ℃, filtering, and drying at 30 ℃ to obtain a pure calcium nitrate product. The calcium nitrate product reaches the national standard of industrial calcium nitrate and agricultural calcium nitrate.
Example 4
In this example, the steel slag slurry absorbs SO2And NOxThe steel slag content in the waste liquid generated later was 25 wt%, the pH was 6.8, and the total salt concentration was 25 wt%.
(1) Filtering the waste liquid to remove solid impurities;
(2) using Ca (OH) to filtrate obtained in the step (1)2Regulating pH to 12 with saturated solution, precipitating to remove NO3 -、NO2 -And Ca2+Filtering the foreign impurity ions to obtain filtrate;
(3) adding nitric acid into the filtrate obtained in the step (2) to adjust the pH value to 7, then introducing the filtrate in a filtrate tank from a water inlet of a micro-nano bubble generating device, controlling the introduction amount per hour to be 0.9 of the total amount of the filtrate, simultaneously adding hydrogen peroxide with 2% of the total mass of the filtrate from the water inlet, introducing air and oxygen mixed gas (oxygen content is 60%) from an air inlet, controlling the volume-mass ratio of air inflow to liquid inflow to be 60L/t, aerating the filtrate in the micro-nano bubble generating device for 3.5 hours, then introducing the filtrate into the filtrate tank from a water outlet, and repeating the operation until NO in the filtrate2 -Is completely oxidized to NO3 -Until the end;
(4) and (4) evaporating and concentrating the liquid obtained after oxidation in the step (3), wherein the concentration of calcium nitrate in the concentrated solution is 40 wt%, crystallizing the concentrated solution at 10 ℃, filtering, and drying at 15 ℃ to obtain a pure calcium nitrate product. The calcium nitrate product reaches the national standard of industrial calcium nitrate and agricultural calcium nitrate.
Example 5
In this example, the steel slag slurry absorbs SO2And NOxThe steel slag content in the waste liquid generated later was 30 wt%, the pH was 5.5, and the total salt concentration was 50 wt%.
(1) Filtering the waste liquid to remove solid impurities;
(2) adjusting the pH of the filtrate obtained in the step (1) to 13 by using quicklime, and removing NO by precipitation3 -、NO2 -And Ca2+Filtering the foreign impurity ions to obtain filtrate;
(3) adding nitric acid into the filtrate obtained in the step (2) to adjust the pH value to be 5.8, then introducing the filtrate in a filtrate tank from a water inlet of a micro-nano bubble generating device, controlling the introduction amount per hour to be 0.6 of the total amount of the filtrate, simultaneously adding hydrogen peroxide with the total mass of the filtrate being 6% of the total mass of the filtrate from the water inlet, and introducing oxygen from an air inletGas (oxygen content 100%), the volume-mass ratio of air inflow to liquid inflow is 80L/t, filtrate enters a filtrate tank from a water outlet after being aerated for 1h in the micro-nano bubble generating device, and then the operation is repeated until NO in the filtrate2 -Is completely oxidized to NO3 -Until the end;
(4) and (4) evaporating and concentrating the liquid obtained after oxidation in the step (3), wherein the concentration of calcium nitrate in the concentrated solution is 55 wt%, crystallizing the concentrated solution at 25 ℃, filtering, and drying at 14 ℃ to obtain a pure calcium nitrate product. The calcium nitrate product reaches the national standard of industrial calcium nitrate and agricultural calcium nitrate.
Comparative example 1
Compared with example 1, the conditions were the same as example 1 except that the quicklime in step (2) was replaced with NaOH solution.
The results show that: introduction of Na as an impurity+Ionic, a large amount of sodium nitrate impurity was present in the prepared product.
Comparative example 2
The conditions were the same as in example 1 except that the pH in step (3) was adjusted to 4 as compared with example 1.
The results show that: NO2 -Unstable, and generate nitrate radical and NO to generate harmful gas.
Comparative example 3
The conditions were the same as in example 1 except that the pH in step (3) was adjusted to 8 as compared with example 1.
The results show that: as in comparative example 2, NO could not be completely reduced2 -Oxidation to NO3 -Calcium nitrite impurities appear in the prepared product.
Comparative example 4
Compared with example 1, the conditions were the same as example 1 except that step (3) was replaced by "heating the filtrate obtained in step (2) to 40 ℃ and treating for 3 hours under an oxygen atmosphere".
The results show that: part of the calcium nitrite impurity was still present in the prepared product, indicating that NO was present under the above conditions2 -Is not completeOxidation to NO3 -。
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims (17)

1. A method for recycling waste liquid generated by combining steel slag as an absorbent with a desulfurization and denitrification process is characterized by comprising the following steps:
(1) carrying out solid-liquid separation on waste liquid generated by combining steel slag as an absorbent with a desulfurization and denitrification process;
(2) adding quicklime and/or slaked lime into the liquid obtained after the solid-liquid separation in the step (1) to adjust the pH value to 9-13 for impurity removal, and filtering after complete precipitation;
(3) adjusting the pH value of the filtrate obtained in the step (2) to 5-6.7, introducing the filtrate in a filtrate tank from a water inlet of a micro-nano bubble generating device, introducing oxygen-enriched gas from an air inlet, introducing the filtrate into the filtrate tank from a water outlet after the filtrate is aerated in the micro-nano bubble generating device, and repeating the operation until NO in the filtrate2 -Is completely oxidized to NO3 -Until the end; adding 2-10 wt% of hydrogen peroxide into the micro-nano bubble generating device;
(4) and (4) evaporating and concentrating the liquid obtained after oxidation in the step (3), crystallizing, filtering and drying to obtain a calcium nitrate product.
2. The method of claim 1, wherein the steel slag content in the waste liquid of step (1) is 1-30 wt%.
3. The method of claim 1, wherein the waste stream of step (1) contains NO3 -And NO2 -。
4. The method of claim 1, wherein the waste stream of step (1) contains SO4 2-、SO3 2-、HSO4 -Or HSO3 -At least one of (1).
5. The method of claim 4, wherein the waste stream of step (1) contains Mg2+、Ca2+、Mn2+Or Fe3+At least two of them.
6. The method of claim 1, wherein the pH of the waste stream of step (1) is from 4 to 7.
7. The method of claim 1, wherein the waste stream of step (1) contains a total concentration of salt of 10 to 60 wt%.
8. The method of claim 1, wherein the quicklime and/or hydrated lime of step (2) is added in a dry and/or wet manner.
9. The method of claim 1, wherein nitric acid is added to adjust the pH of the filtrate in step (3).
10. The method as claimed in claim 1, wherein the volume-mass ratio of the air input and the liquid input of the micro-nano bubble generating device is 20-100.
11. The method according to claim 1, wherein the volume ratio of the filtrate per hour to the total amount of the filtrate in the micro-nano bubble generation device is 1 (1-2).
12. The method according to claim 1, wherein the aeration time is 0.5 to 5 hours.
13. The method of claim 1, wherein the oxygen-enriched gas has an oxygen content of 20-100%.
14. The method of claim 1, wherein the concentration of the liquid after evaporative concentration in step (4) is from 30 to 60 wt%.
15. The method of claim 1, wherein the temperature of the crystallization in step (4) is 0-30 ℃.
16. The method of claim 1, wherein the drying temperature of step (4) is 10-30 ℃.
17. The method of claim 1, wherein the method comprises the steps of:
(1) carrying out solid-liquid separation on waste liquid generated after desulfurization and denitrification are combined by using steel slag as an absorbent; the pH value of the waste liquid is 4-7, the total concentration of the contained salt is 10-60 wt%, and the content of the steel slag is 1-30 wt%;
(2) adding quicklime and/or slaked lime into the liquid obtained after the solid-liquid separation in the step (1) to adjust the pH value to 9-13, and filtering after complete precipitation;
(3) adding nitric acid into the filtrate obtained in the step (2) to adjust the pH value to 5-6.7, introducing the filtrate in the filtrate tank from a water inlet of the micro-nano bubble generation device, simultaneously introducing oxygen-enriched gas with the oxygen content of 20-100% from an air inlet, aerating the filtrate in the micro-nano bubble generation device for 0.5-5h, then, introducing the filtrate into the filtrate tank from a water outlet, and repeating the operation until NO in the filtrate2 -Is completely oxidized to NO3 -Until the end; the volume-mass ratio of the air input of the micro-nano bubble generating device to the liquid input is 20-100, the volume ratio of the amount of the filtrate introduced into the micro-nano bubble generating device per hour to the total amount of the filtrate is 1 (1-2), and 2-10 wt% of hydrogen peroxide is added into the micro-nano bubble generating device;
(4) evaporating and concentrating the liquid obtained after oxidation in the step (3) to 30-60 wt%, crystallizing at 0-30 ℃, filtering, and drying the crystal obtained by filtering at 10-30 ℃ to obtain a calcium nitrate product.
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CN107857310B (en) * 2017-11-02 2021-03-23 东南大学 Desulfurization and denitrification waste liquid degradation treatment equipment
CN107973323A (en) * 2017-12-06 2018-05-01 中国科学院过程工程研究所 A kind of method for oxidation of desulphurization denitration waste liquid Nitrite ion
CN110127641B (en) * 2018-02-02 2021-02-05 中国科学院过程工程研究所 Method for recovering nitrite from desulfurization and denitrification waste liquid
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