CN115166137A - Method for detecting various calcium-containing compounds in absorption liquid after smoke absorption - Google Patents

Method for detecting various calcium-containing compounds in absorption liquid after smoke absorption Download PDF

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CN115166137A
CN115166137A CN202210762399.1A CN202210762399A CN115166137A CN 115166137 A CN115166137 A CN 115166137A CN 202210762399 A CN202210762399 A CN 202210762399A CN 115166137 A CN115166137 A CN 115166137A
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calcium
absorption liquid
content
filter residue
absorbing
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邵宗强
李祖君
吴峰
蓝云燕
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Shenzhen Koala Ecological Technology Co ltd
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    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
    • G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
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Abstract

The invention discloses a method for detecting various calcium-containing compounds in absorption liquid after absorbing smoke, which comprises the following steps: s1, detecting the content of soluble calcium: filtering the absorption liquid I after absorbing the smoke, and measuring the content of calcium ions in the filtrate I; s2, detecting the content of the residual effective calcium: adding an organic weak acid solution into the filter residue I obtained in the step S1, filtering II, and measuring the content of calcium ions in the filtrate II; s3, detecting the content of sulfur-containing insoluble calcium: adding a carbonation reagent into the filter residue II obtained in the step S2, filtering III, adding an organic weak acid solution into the filter residue III, filtering IV, and measuring the content of calcium ions in the filtrate IV; s4, detecting the content of fluorine-containing insoluble calcium: adding hydrochloric acid into the filter residue IV, filtering V, and measuring the content of calcium ions in the filtrate V; and when the content of calcium ions in the filtrate II is less than 80g/L, replacing the absorption liquid. This application can short-term test analysis, changes the absorption liquid according to the testing result, has reduced the flue gas treatment cost and to the influence of environment.

Description

Method for detecting various calcium-containing compounds in absorption liquid after smoke absorption
Technical Field
The invention relates to the technical field of calcium treatment of smoke dust and smoke, in particular to a method for detecting various calcium-containing compounds in absorption liquid after smoke is absorbed.
Background
A large amount of smoke can be generated in the production of smelting, chemical industry and other industries, and the smoke contains toxic and harmful gases such as NO and NO 2 、Cl 2 、HF、F 2 、SO 2 And SO 3 And the like. The smoke is directly discharged to the outside, pollutes the environment, does not accord with the environmental protection requirement, is harmful to the human health and is smokeThe gas is treated before being discharged. At present, the method for treating the flue gas generated in the production of smelting, chemical industry and other industries is mainly a calcium treatment method, and in order to reduce the production cost, limestone (CaCO) is often adopted 3 ) Or slaked lime Ca (OH) 2 The dispersion liquid is used as absorption liquid of the flue gas, the flue gas generated in the production is directly and continuously introduced into the absorption liquid or the absorption liquid is directly sprayed into the flue gas, so that the NO and the NO in the limestone or hydrated lime and the flue gas 2 、Cl 2 、HF、F 2 、SO 2 And SO 3 The toxic and harmful gases are chemically reacted to generate Ca (NO) 2 ) 2 、Ca(NO 3 ) 2 、CaCl 2 、CaF 2 、CaSO 3 And CaSO 4 And the like, so as to achieve the purpose of removing toxic and harmful gases in the smoke.
Along with NO and NO in limestone or slaked lime and flue gas 2 、Cl 2 、HF、F 2 、SO 2 And SO 3 And the content of limestone or hydrated lime is reduced when the reaction of toxic and harmful gases is carried out. Many domestic enterprises worry that when the absorption liquid used once is reused, the content of the residual limestone or hydrated lime is not enough to completely convert the toxic and harmful gases in the flue gas, so that the absorption liquid is replaced by new absorption liquid after being used once. Although the complete conversion of toxic and harmful gases in the flue gas can be ensured, the treatment cost of the flue gas is increased, and the method is not suitable for industrial large-scale treatment. In order to reduce the cost, some enterprises fix the cycle treatment times of the absorption liquid according to experience, but due to the difference of raw materials and production processes in smelting and chemical production, the types and contents of various toxic and harmful gases in the generated flue gas are different, so that the toxic and harmful gases possibly exist according to the set cycle times and are not completely converted into calcium-containing compounds, and the toxic and harmful gases are thrown outside without meeting the environmental protection requirements and are punished by the environmental protection bureau; and the possibility of high calcium fluoride content in the absorption liquid is harmful to human bodies and environment, and the calcium fluoride in the waste absorption liquid can be sold and discharged only after being treated again, so that the treatment cost is increased.
Therefore, how to find out in time that the content of limestone or hydrated lime in the absorption liquid is insufficient in the circulating treatment process and timely replace the absorption liquid with new one, the using amount of the absorption liquid is reduced to the maximum extent, the toxic and harmful gas is completely converted, and the calcium fluoride with high content in the absorption liquid is found and treated in time, so that the method has an important effect.
Disclosure of Invention
In order to reduce the cost of treating the flue gas and the influence on the environment, the application provides a method for detecting various calcium-containing compounds in the absorption liquid after absorbing the flue gas, and the content of various calcium-containing compounds converted from the limestone or the hydrated lime in the absorption liquid after absorbing the flue gas and the limestone or the hydrated lime after reacting with the toxic and harmful flue gas is quickly detected and analyzed, so that new absorption liquid is added or replaced at proper time according to the detection result, the using amount of the absorption liquid is reduced to the maximum extent, the complete conversion of the toxic and harmful gas is ensured, and the content of calcium fluoride is reduced.
In a first aspect, the application provides a method for detecting various calcium-containing compounds in absorption liquid after absorbing smoke, which adopts the following technical scheme:
a method for detecting various calcium-containing compounds in absorption liquid after smoke absorption comprises the following steps:
s1, detecting the content of soluble calcium: adding a soluble oxidant into the absorption liquid after absorbing the smoke, mixing, filtering I to obtain filter residue I and filtrate I, and detecting the content of calcium ions in the soluble calcium by using an EDTA titration method;
s2, determining the content of the residual effective calcium: adding an organic weak acid solution into the filter residue I obtained in the step S1 until the pH value is 2.3-2.5, filtering II to obtain a filter residue II and a filtrate II, and detecting the content of calcium ions in the residual effective calcium by using an EDTA titration method;
s3, measuring the content of sulfur-containing insoluble calcium: adding a carbonation reagent and deionized water into the filter residue II obtained in the step S2, reacting, adding deionized water, and filtering III to obtain filter residue III and filtrate III; adding organic weak acid solution into the filter residue III until the pH value is 2.3-2.5, filtering IV to obtain filter residue IV and filtrate IV, and detecting the content of calcium ions in sulfur-containing insoluble calcium by using an EDTA titration method;
s4, measuring the content of fluorine-containing insoluble calcium: adding hydrochloric acid into the filter residue IV in the step S3, heating to dissolve fluorine-containing insoluble calcium, filtering V to obtain filter residue V and filtrate V, and detecting the content of calcium ions in the fluorine-containing insoluble calcium by using an EDTA titration method;
when the content of calcium ions corresponding to the residual effective calcium in the absorption liquid after the smoke is absorbed is less than 80g/L, readjusting the content of the effective calcium in the absorption liquid to ensure that the content of the calcium ions corresponding to the effective calcium in the adjusted absorption liquid is not less than 80g/L; the available calcium comprises limestone and/or hydrated lime.
The specific method for adjusting the content of the effective calcium in the absorption liquid comprises the following steps: adding new absorption liquid into the absorption liquid after absorbing the flue gas to obtain adjusted absorption liquid; or directly replacing the absorption liquid after absorbing the flue gas with new absorption liquid to prepare adjusted absorption liquid;
the total mass of the calcium-containing compounds (limestone and hydrated lime) in the adjusted absorption liquid is not less than 50wt%.
The deionized water in the application meets the three-level water standard (GBT 6682-2008, conductivity is less than or equal to 0.50 ms/m) of detection water in an analysis laboratory.
The limestone or hydrated lime in the absorption liquid can absorb NO and NO in the flue gas 2 、Cl 2 、HF、F 2 、SO 2 And SO 3 The toxic and harmful gases are converted into corresponding Ca (NO) compounds containing calcium 2 ) 2 、Ca(NO 3 ) 2 、CaCl 2 、CaF 2 、CaSO 3 And CaSO 4 And so on.
Wherein, the NO and NO in the limestone, hydrated lime and flue gas 2 The chemical reaction equation of (1):
2NO+O 2 =2NO 2 ↑
3NO 2 +H 2 O=2HNO 3 +NO↑
NO+NO 2 +CaCO 3 =Ca(NO 2 ) 2 +CO 2 ↑
2HNO 3 +CaCO 3 =Ca(NO 3 ) 2 +H 2 O+CO 2 ↑
NO+NO 2 +Ca(OH) 2 =Ca(NO 2 ) 2 +H 2 O
2HNO 3 +Ca(OH) 2 = Ca(NO 3 ) 2 +2H 2 O
NO and NO in limestone, slaked lime and flue gas 2 Ca (NO) is mainly generated after the reaction 3 ) 2 And also a small amount of Ca (NO) 2 ) 2 ，Ca(NO 3 ) 2 And Ca (NO) 2 ) 2 All are soluble calcifications, ca (NO) 2 ) 2 Is oxidized to Ca (NO) by soluble oxidant 3 ) 2 That is, the N-containing easily soluble calcium compound present in the filtrate I is Ca (NO) 3 ) 2 。
Limestone or hydrated lime and Cl in flue gas 2 The chemical reaction equation of (1):
2Cl 2 +H 2 O+CaCO 3 =CaCl 2 +2HClO+CO 2 ↑
2Cl 2 +2Ca(OH) 2 =CaCl 2 +2H 2 O+Ca(ClO) 2
Ca(ClO) 2 +2CO 2 +2H 2 O=Ca(HCO 3 ) 2 +2HClO (pH
Figure 377145DEST_PATH_IMAGE001
8)
Ca(HCO 3 ) 2 =CaCO 3 ↓+CO 2 ↑+H 2 O
HClO+SO 2 +H 2 O=HCl+H 2 SO 4
2HCl+CaCO 3 =CaCl 2 +CO 2 ↑+H 2 O
2HCl+Ca(OH) 2 =CaCl 2 +2H 2 O
H 2 SO 4 +CaCO 3 =CaSO 4 ↓+CO 2 ↑+H 2 O
H 2 SO 4 + Ca(OH) 2 =CaSO 4 ↓+2H 2 O
cl in limestone and flue gas 2 After the reaction, caCl is mainly generated 2 Hydrated lime and Cl in flue gas 2 After the reaction, caCl is mainly generated 2 And small amounts of Ca (HCO) 3 ) 2 ；CaCl 2 ，Ca(HCO 3 ) 2 Is made a purpose ofSoluble calcification, i.e. presence of CaCl in filtrate I 2 And a small amount of Ca (HCO) 3 ) 2 。
Therefore, the soluble calcium Ca (NO) in the absorption liquid after absorbing the smoke 3 ) 2 、Ca(NO 2 ) 2 And CaCl 2 、Ca(HCO 3 ) 2 Corresponding calcium ions exist in the filtrate I, and the calcium ion concentration in the filtrate I represents soluble calcium Ca (NO) in the absorption liquid after the smoke is absorbed 3 ) 2 、Ca(NO 2 ) 2 And CaCl 2 、Ca(HCO 3 ) 2 The total content of calcium ions in the smoke is measured by S1, namely the total content of calcium ions of soluble calcium in the absorption liquid after the smoke is absorbed.
HF and F in limestone or hydrated lime and flue gas 2 The chemical reaction equation of (2):
2F 2 +2H 2 O=4HF+O 2 ↑
2HF+CaCO 3 =CaF 2 ↓+H 2 O+CO 2 ↑
2HF+ Ca(OH) 2 = CaF 2 ↓+2H 2 O
HF, F in limestone or hydrated lime and flue gas 2 After the reaction, caF is mainly generated 2 ，CaF 2 Is fluorine-containing insoluble calcium, is insoluble in water, is not easily dissolved by the weak organic acid solution in the step S2, and is not easily dissolved by the carbonation reagent and the weak organic acid solution in the step S3, so that CaF 2 In residue IV. CaF in filter residue IV 2 Is dissolved by hydrochloric acid and converted into CaCl 2 ，CaCl 2 Is a soluble calcic, present in filtrate V. Therefore, the fluorine-containing insoluble calcium CaF in the absorption liquid after absorbing the flue gas 2 The calcium ion in the filtrate V is converted into CaCl in the filtrate V 2 Calcium ion in the filtrate V, and the concentration of calcium ion in the filtrate V shows that fluorine-containing insoluble calcium CaF in the absorption liquid after absorbing the smoke 2 The content of medium calcium ion, namely, S4 is measured by the fluorine-containing insoluble calcium CaF in the absorption liquid after absorbing smoke 2 Calcium ion content of (a).
The CaF 2 The chemical equation for the reaction with hydrochloric acid is:
2HCl+CaF 2 =CaCl 2 +2HF↑
SO in limestone or hydrated lime and flue gas 2 And SO 3 The chemical reaction equation of (1):
2SO 2 +O 2 =2SO 3 ↑
SO 2 +H 2 O=H 2 SO 3
H 2 SO 3 +CaCO 3 =CaSO 3 ↓+H 2 O+CO 2 ↑
H 2 SO 3 +Ca(OH) 2 =CaSO 3 ↓+2H 2 O
SO 3 +H 2 O=H 2 SO 4
H 2 SO 4 + CaCO 3 =CaSO 4 ↓+H 2 O+CO 2 ↑
H 2 SO 4 + Ca(OH) 2 =CaSO 4 ↓+2H 2 O
SO in limestone or hydrated lime and flue gas 2 、SO 3 After the reaction, caSO is mainly generated 4 And also a small amount of CaSO 3 ，CaSO 4 And CaSO 3 All contain sulfur insoluble calcium, caSO in step S1 3 Oxidized to CaSO by soluble oxidant 4 That is, caSO is the sulfur-containing insoluble calcium in the residue I 4 。CaSO 4 Is not easy to be dissolved by the organic weak acid solution in the step S2, and the CaSO is filtered after the II is filtered 4 In residue II. CaSO 4 Conversion to CaCO by reaction with a carbonating agent in the S3 stage 3 Due to CaCO 3 Insoluble in water, adding a small amount of deionized water to dissolve part of ammonium carbonate solid, filtering to obtain filtrate III, caCO 3 Is present in residue III. CaSO in filter residue II 4 Converted CaCO 3 Dissolved by organic weak acid solution to generate corresponding soluble calcium salt, and the corresponding soluble calcium salt is filtered and exists in filtrate IV. Therefore, the sulfur-containing insoluble calcium CaSO in the absorption liquid after absorbing the flue gas 4 And CaSO 3 The calcium ion in the filtrate IV is converted into calcium ion in soluble calcium salt, and the calcium ion concentration in the filtrate IV represents sulfur-containing insoluble calcium CaSO in the absorption liquid after absorbing the flue gas 4 And CaSO 3 Total content of calcium ions ofThat is, S3 is a measure of CaSO in the absorbent after absorption of flue gas 4 And CaSO 3 Total calcium ion content of (b).
The CaSO 3 The chemical equation for the reaction with the soluble oxidizing agent (hydrogen peroxide) is: caSO 3 +H 2 O 2 =CaSO 4 +H 2 O。
The CaSO 4 The chemical equation for the reaction with the carbonation agent (ammonium carbonate) is: caSO 4 +(NH 4 ) 2 CO 3 =CaCO 3 ↓+(NH 4 ) 2 SO 4 。
The above CaCO 3 The chemical equation for the reaction with weak organic acid solution (acetic acid) is: 2CH 3 COOH+CaCO 3 =Ca(CH 3 COO) 2 +H 2 O+CO 2 ↑
In the step S2, the content of calcium ions in the residual limestone or hydrated lime in the absorption liquid after the flue gas is absorbed is measured, the content of limestone or hydrated lime is calculated according to the content of calcium ions in the filtrate II in the step S2, and when the content of calcium ions corresponding to the residual limestone or hydrated lime in the absorption liquid after the flue gas is absorbed is less than 80g/L, the absorption liquid is replaced. The absorption liquid after absorbing the flue gas can be sampled at any time and then the calcium ion content in the residual limestone or hydrated lime in the absorption liquid after absorbing the flue gas is rapidly detected, when the content is less than 80g/L, the absorption liquid is replaced in time, the limestone or hydrated lime can completely convert toxic and harmful gases into corresponding calcium compounds, the influence on the environment and the human body is reduced or eliminated, otherwise, when the content is not less than 80g/L, the absorption liquid can be put into a flue gas treatment process again, and the cost for treating the flue gas is reduced.
In the step S1, the absorption liquid after absorbing the flue gas is derived from a liquid in the flue gas treatment process.
Herein, in the S1 step, the soluble oxidant includes, but is not limited to, hydrogen peroxide solution. From the perspective of detection cost and environment, the hydrogen peroxide is low in cost, and not only can remove Ca (NO) 2 ) 2 、CaSO 3 Are respectively oxidized into Ca (NO) 3 ) 2 、CaSO 4 And no other impurities or toxic and harmful substances are added, so that the oxidant is a green and environment-friendly strong oxidant.
In the present application, H in hydrogen peroxide solution 2 O 2 The concentration of (B) is 50wt%.
In the application, in the step S1, the volume ratio of the absorption liquid after absorbing the flue gas to the hydrogen peroxide solution is 10.
Ca (NO) mentioned above 2 ) 2 、CaSO 3 The chemical equation for the reaction with hydrogen peroxide is:
Ca(NO 2 ) 2 +2H 2 O 2 =Ca(NO 3 ) 2 +2H 2 O
CaSO 3 +H 2 O2=CaSO 4 +H 2 O
the application, filter I, with deionized water washing filter residue I, wash 5-7 times, the volume that deionized water washed at every turn is the same with the volume of the absorption liquid after absorbing the flue gas, collect the washing liquid, move washing liquid and filtrating I into the volumetric flask, detect calcium ion content in the easy soluble calcium with EDTA titration method.
In the application, the EDTA titration method for detecting the content of calcium ions in the soluble calcium, the EDTA titration method for detecting the content of calcium ions in the residual limestone, the EDTA titration method for detecting the content of calcium ions in the sulfur-containing insoluble calcium and the EDTA titration method for detecting the content of calcium ions in the fluorine-containing insoluble calcium are the same.
The method for detecting calcium by EDTA titration in the application adopts GB/T5762-2012 limestone chemical analysis method for building materials, but has the following two differences: (1) Diluents in the indicator are different in selection, a glycerol-triethanolamine mixed solution is adopted in the indicator, and potassium nitrate solid is adopted in GB/T5762-2012 limestone chemical analysis method for building materials; (2) The concentration of the standard EDTA-2Na solution and the concentration and the addition of the reagent solution are different (as known by those skilled in the art, in one detection method, the concentration of the standard solution and the concentration and the addition of the reagent solution are appropriately changed according to the concentration or the content of the detection object, the method which is allowed in the field and is commonly used by those skilled in the field (in the detection process) has no influence on the accuracy of the detection result, and in some national detection standards or industrial detection standards, two or more than two standard solution concentrations and additions of the reagent solution exist, and the volume of the detection object to be detected is removed).
Preferably, the specific steps of EDTA titration detection include:
a. preparing a liquid;
b. adding hydrochloric acid, stirring, adding triethanolamine solution, stirring, and standing;
c. adding potassium hydroxide solution to make pH be greater than 13, dripping calcium indicator, and titrating with EDTA-2Na standard solution until yellow green fluorescence disappears.
The EDTA titration method for testing the content of calcium ions adopts hydrochloric acid, so that the hydrochloric acid is low in cost, the interference of the hydrochloric acid on yellow green fluorescence is minimum, and the hydrochloric acid does not chemically react with the calcium ions to generate Ca 3 (PO 4 ) 2 、CaSO 4 And (3) precipitation can ensure that calcium ions can be completely complexed with EDTA-2Na, so that the detection accuracy is improved. Adding triethanolamine solution as masking agent to mask Fe 3+ 、Al 3+ Interfering with plasma, and adjusting the pH value of the system to be more than 13 by using a potassium hydroxide solution subsequently, wherein Mg is generated 2+ 、Mn 2+ 、Fe 3+ 、Al 3+ The plasma forms a precipitate, so when EDTA-2Na standard solution titrates calcium ions, other metal ions do not interfere with the titration process, and the detection accuracy is improved.
Preferably, in the step b, the concentration of the hydrochloric acid is 3.5-4.5mol/L; more preferably, the concentration of the hydrochloric acid is 4mol/L.
In the application, the triethanolamine masks the interference of Fe & lt 3+ & gt, al & lt 3+ & gt and other ions, and can effectively mask under an acidic condition, and the triethanolamine is an alkaline substance and is added in a large amount, so that a large amount of hydrochloric acid needs to be added in advance in a solution to be detected containing calcium to ensure that the solution to be detected containing calcium after the triethanolamine is added is acidic.
Preferably, in the step b, the triethanolamine solution is prepared by mixing triethanolamine and deionized water according to a volume ratio of 1.
Preferably, in the step c, the potassium hydroxide solution is prepared by mixing potassium hydroxide and deionized water according to a mass ratio of 1.
In the application, in the step c, the concentration of the standard EDTA-2Na solution (before calibration) is about 0.025mol/L, calibration is required, the calibration method adopts a calibration method for the standard EDTA-2Na solution in GB/T5762-2012 limestone chemical analysis method for building materials, and the accurate concentration of the standard EDTA-2Na solution after calibration is 0.02506mol/L.
Preferably, in the step c, the calcium indicator is a glycerol-triethanolamine mixed solution of calcein, phenolphthalein and methyl thymol blue; in 100mL of glycerol-triethanolamine mixed solution of calcein, phenolphthalein and methyl thymol blue, the mass of the calcein, the mass of the phenolphthalein and the mass of the methyl thymol blue are respectively 1g, 0.2g and 1g, and the volume of the glycerol-triethanolamine mixed solution is 100mL.
The application adopts the glycerol-triethanolamine mixed solution of calcein, phenolphthalein and methyl thymol blue as the calcium indicator, can effectively ensure that the color change of the titration end point of the calcium-containing liquid to be detected is sharp, the color chromaticity of the calcium-containing liquid to be detected is kept consistent, the color change of the titration end point can be quickly and simply judged, and the operation is simple. The method can effectively avoid that the color change of the calcium indicator in the calcium-containing liquid to be detected is not sharp at the titration end point; or when an operator adds a calcium indicator into the calcium-containing liquid to be detected, the added quality cannot be kept equal due to manual uncontrollable reasons, so that the color and chroma in the calcium-containing liquid to be detected are different, the titration end point is difficult to accurately judge, and the titration error (end point error) is increased, thereby improving the detection accuracy. Compare with the calcium indicator who uses the potassium nitrate solid as the diluent, the method in this application, at normal atmospheric temperature than the calcium indicator who uses the potassium nitrate solid as the diluent is more difficult for rotting, and effective live time is longer moreover, and it is more convenient to use, operates simpler, and the color change of the calcium-containing liquid that awaits measuring when facing the titration end point is more acute, changes the accurate judgement titration end point, and the precision and the degree of accuracy of detection are higher.
Preferably, in the step c, the calcium indicator is added in an amount of 4-8 drops (each drop has a volume of 0.05 mL); preferably, the adding amount of the calcium indicator is 6 drops, that is, when the adding amount volume of the calcium indicator is 0.3mL, the color chromaticity of each calcium-containing liquid to be detected, the calcium content of which needs to be detected, can be kept consistent, the simple and accurate judgment of the color change of the titration end point is facilitated, and the problem that when an operator adds the calcium indicator into the calcium-containing liquid to be detected, the adding quality cannot be kept equal due to the fact that the calcium indicator is uncontrollable manually, the judgment of the inconsistency of the color change of the titration end point is caused, and the titration error (end point error) is increased can be solved, so that the precision and the accuracy of detection are improved.
In the application, from the viewpoint of reducing the production cost, the weak organic acid solution is an acetic acid solution or a citric acid solution, the acetic acid solution or the citric acid solution has strong acidity in the weak organic acid and can dissolve calcium carbonate, but the acidity of the acetic acid solution or the citric acid solution does not easily dissolve calcium sulfate and calcium fluoride, so that the residual limestone or hydrated lime can be dissolved from the filter residue I by selective acid.
Preferably, the weak organic acid solution is an acetic acid solution.
Preferably, the concentration of the acetic acid solution is 1.7-1.8mol/L; more preferably, the concentration of the acetic acid solution is 1.75mol/L, and by adopting the acetic acid solution with the above concentration, calcium sulfate and calcium fluoride are not dissolved by the acetic acid solution on the premise of ensuring that calcium carbonate is quickly and completely dissolved, so that the reduction of the detection accuracy is avoided.
In the application, as acetic acid is liquid, the speed of preparing the acetic acid solution by adopting the acetic acid is higher, and when the concentration of the acetic acid solution is controlled to be 1.70-1.80mol/L, the reaction speed of the acetic acid and limestone or hydrated lime is higher, the solubility of calcium sulfate and calcium fluoride is less, and the content of calcium ions corresponding to the limestone or hydrated lime in the absorption liquid after the absorption of flue gas can be more accurately detected. In particular, 1.75mol/L acetic acid solution is added and CaCO is added 3 (Or Ca (OH) 2 ) When the pH of the reaction system with acetic acid is maintained at 2.3-2.5, the acetic acid and the generated calcium acetate form a buffer system, the concentration of the acetic acid in the buffer system is 0.5-1.5mol/L, and the carbon content isThe calcium sulfate and the hydrated lime are alkaline substances, so that a buffer system solution (with the pH value of 2.3-2.5) formed by acetic acid and calcium acetate can quickly and completely dissolve the calcium carbonate or the hydrated lime, the concentration of the easily soluble calcium acetate generated in a reaction system can be high in a short time, and the calcium sulfate and the calcium fluoride can not be dissolved by the acetic acid solution due to the existence of a homoionic effect and in the buffer system with the pH value of 2.3-2.5 in the reaction system, so that the reduction of the detection accuracy is avoided. The test proves that; under the conditions that the reaction time is 12min and the reaction temperature is 40 ℃, the concentration of acetic acid for dissolving calcium carbonate is 1.70-1.80mol/L, and when a buffer system consisting of calcium acetate and acetic acid and having the pH value of 2.3-2.5 is adopted, the dissolution rates of calcium sulfate and calcium fluoride in filter residue I dissolved by acetic acid are 0.10% and 0.06%, namely the calcium sulfate and the calcium fluoride are basically not dissolved.
The above CaCO 3 And Ca (OH) 2 The chemical equation for the reaction with acetic acid is:
2CH 3 COOH+CaCO 3 =Ca(CH 3 COO) 2 +H 2 O+CO 2 ↑
2CH 3 COOH+Ca(OH) 2 =Ca(CH 3 COO) 2 +2H 2 O
in the application, in the step S2, the reaction time of adding the weak organic acid solution and the filter residue I is 8-12min; preferably, the reaction time of adding the organic weak acid solution and the filter residue I is 10min.
In the application, in the step S2, the reaction temperature of adding the organic weak acid solution and the filter residue I is 10-40 ℃; preferably, the reaction temperature of the added weak organic acid solution and the filter residue I is 25 ℃.
Preferably, in the step S3, the carbonation agent is a carbonate or bicarbonate compound containing ammonium, potassium and sodium; more preferably, the carbonating agent is ammonium carbonate.
In the application, ammonium carbonate is used as the carbonation agent because ammonium carbonate and ammonium bicarbonate are both carbonate and ammonium salt, while calcium sulfate is partially soluble in various salt compound solutions, but the solubility in the ammonium salt solution is the greatest, so the reaction speed and conversion rate with calcium sulfate are higher than those of carbonic acidThe reaction speed and the conversion rate of (potassium, sodium) and bicarbonate (potassium, sodium) with calcium sulfate are higher, the price is lower, the use amount of ammonium carbonate required by the reaction with calcium sulfate with equal mass is less than that of ammonium bicarbonate, the conversion rate of calcium sulfate into calcium carbonate is higher, the calcium sulfate content in the filter residue II is reduced, the calcium carbonate content in the filter residue III is improved, and the content of sulfur-containing insoluble calcium CaSO in the absorption liquid after absorbing the smoke is improved 4 And CaSO 3 And fluorine-containing insoluble calcium CaF 2 Corresponding to the accuracy of the calcium content.
The ammonium carbonate and the calcium sulfate generate chemical reaction to generate calcium carbonate and ammonium sulfate, and the chemical equation of the reaction is as follows: caSO 4 +(NH 4 ) 2 CO 3
Figure 654542DEST_PATH_IMAGE002
CaCO 3 ↓+(NH 4 ) 2 SO 4 。
Preferably, in the step S3, the mass ratio of the filter residue II, the ammonium carbonate and the deionized water is 1 (3-4) to 0.8-1.2; more preferably, the mass ratio of the filter residue II, ammonium carbonate and deionized water is 1.
The reaction of ammonium carbonate and calcium sulfate to produce calcium carbonate and ammonium sulfate is reversible, and tests prove that; under the conditions that the reaction time is 35min and the reaction temperature is 40 ℃, when the mass ratio of the filter residue II to the ammonium carbonate to the deionized water is 1) Therefore, the mass of the added ammonium carbonate is far larger than that of the filter residue II and far larger than that of the deionized water, and the concentration of the ammonium carbonate in the reaction system and the filter residue III washing operation in the previous second time is always kept in a saturated state (namely when ammonium carbonate solid exists). So that the reaction can be carried out rightwards, calcium sulfate is converted into calcium carbonate to the maximum extent, and the content of sulfur-containing insoluble calcium CaSO in absorption liquid after absorbing smoke is improved 4 And CaSO 3 Corresponding to the detection accuracy of calcium content. And when the mass ratio of the filter residue II to the ammonium carbonate to the deionized water is 1.
In the application, in the step S3, the reaction time of the filter residue II, ammonium carbonate and deionized water is 25-35min; preferably, the reaction time of the filter residue II, ammonium carbonate and deionized water is 30min.
And the reaction time of the filter residue II, the ammonium carbonate and the deionized water is controlled to be 30min, so that the conversion degree of converting calcium sulfate into calcium carbonate can be improved, the content of calcium sulfate in the filter residue III can be reduced, and the content of calcium carbonate in the filter residue III can be improved.
In the application, in the step S3, the reaction temperature of the filter residue II, ammonium carbonate and deionized water is 10-40 ℃; preferably, the reaction temperature of the filter residue II, ammonium carbonate and deionized water is 25 ℃.
In this application, in the step S3, the solid content of the added ammonium carbonate is too much, so that an equal amount of deionized water needs to be added into the reaction system before filtering III to dilute the concentration of the reaction system, so that the mass ratio of the filter residue II, the ammonium carbonate and the deionized water in the reaction system is changed from 1 to 1.
In the application, in the step S3, 1.75mol/L acetic acid solution is added into the filter residue III to ensure that the pH of the system is 2.3-2.5, and the effect is to use CaCO 3 Converting into water-soluble calcium acetate without dissolving fluorine-containing insoluble calcium, and dissolving sulfur-containing insoluble calciumCalcium CaSO 4 And CaSO 3 CaCO obtained by reaction with a carbonating agent 3 And also to calcium acetate which is readily soluble in water.
In the application, in the step S3, the reaction time of the filter residue III and 1.75mol/L acetic acid solution is 10min, and the reaction temperature is 10-40 ℃.
In the step S4, the concentration of the hydrochloric acid is 3.5-4.5mol/L; preferably, the concentration of the hydrochloric acid is 4mol/L.
In the step S4, the filter residue IV contains fluorine-containing insoluble calcium CaF 2 The hydrochloric acid used can be reacted with CaF at 4mol/L 2 Reaction to form soluble CaCl 2 The chemical formula is as follows: 2HCl + CaF 2 =CaCl 2 +2HF↑
In the step S4, the heating and dissolving temperature is 85-95 ℃; more preferably, the temperature for dissolving by heating is 90 ℃.
Control of CaF 2 The reaction temperature of the hydrochloric acid and 4mol/L is 85-95 ℃, and the reaction temperature of the hydrochloric acid and CaF can be improved 2 While reducing hydrogen chloride volatilization to make CaF 2 The dissolution is complete.
In the application, the volume dosage of hydrochloric acid (4 mol/L) required for dissolving fluorine-containing insoluble calcium is determined; when the dissolving temperature is 85-95 ℃ and the time is 30min, 0.2513g of fluorine-containing insoluble calcium can be dissolved in 50ml of hydrochloric acid (4 mol/L), and when the content of the fluorine-containing insoluble calcium is high, the mass of filter residue IV (fluorine-containing insoluble calcium) needs to be taken, so that the fluorine-containing insoluble calcium can be completely dissolved, and the detection accuracy of the content of the fluorine-containing insoluble calcium is ensured.
In summary, the present application has the following beneficial effects:
1. the method for detecting various calcium-containing compounds in the absorption liquid after absorbing the flue gas can quickly detect and analyze the content of the residual limestone or hydrated lime and various converted calcium-containing compounds in the absorption liquid after absorbing the flue gas, and meanwhile, new absorption liquid is added or replaced in due time according to the content of the residual limestone or hydrated lime, so that the using amount of the absorption liquid is reduced to the maximum extent, and the toxic and harmful gases are ensured to be exhaustedFull conversion, reduced calcium fluoride content, timely discovery and treatment of calcium fluoride with high content in the absorption liquid, reduced treatment cost of flue gas generated in smelting, chemical industry and other industries, and reduced toxic and harmful gas such as NO and NO contained in the flue gas 2 、Cl 2 、HF、F 2 、SO 2 And SO 3 The impact on the environment. Moreover, according to the detection results of the content of soluble calcium, the content of sulfur-containing insoluble calcium and the content of fluorine-containing insoluble calcium in the absorption liquid after absorbing the flue gas, corresponding calcium-containing compounds can be purposefully collected and recovered, the effective treatment of industrial solid hazardous/solid wastes is realized, the comprehensive utilization rate is improved, the solid hazardous/solid wastes are completely converted into products with economic value as far as possible, the solid hazardous/solid wastes are changed into valuables, the danger is changed into safety, and huge social value and economic value can be created.
2. The reaction of ammonium carbonate and calcium sulfate to generate calcium carbonate and ammonium sulfate is reversible reaction, when the mass ratio of filter residue II, ammonium carbonate and deionized water is 1 (3-4) to 0.8-1.2, the concentration of ammonium carbonate in the reaction system and the filter residue III in the previous secondary washing is saturated (solid ammonium carbonate exists), the reversible reaction is favorably carried out rightwards, the calcium sulfate is converted into calcium carbonate to the maximum extent, and therefore, the content of sulfur-containing indissolvable calcium CaSO in absorption liquid after smoke absorption is improved 4 And CaSO 3 And fluorine-containing poorly soluble calcium CaF 2 Corresponding to the detection accuracy of calcium content.
3. In acetic acid with CaCO 3 During the reaction, acetic acid reacts with calcium sulfate and calcium fluoride until a small amount of calcium sulfate and calcium fluoride are dissolved by the acetic acid solution, but the low-concentration acetic acid solution (the concentration is 1.70-1.80 mol/L) is adopted, and in the method of forming the buffer system with the pH value of 2.3-2.5 by the acetic acid solution and the calcium acetate in the reaction system, calcium carbonate can be quickly and completely dissolved, and simultaneously, calcium sulfate and calcium fluoride can not be dissolved by the acetic acid solution because the same ion effect exists in the buffer system with the pH value of 2.3-2.5 formed by the acetic acid solution and the calcium acetate, thereby avoiding the reduction of the detection accuracy.
Detailed Description
The present application will be described in further detail with reference to examples.
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application, but the technical solutions are not limited to the scope of the present application. It should be apparent that the described embodiments are only a few embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, other embodiments obtained by persons of ordinary skill in the art with the understanding of the inventive concepts in the present application are within the scope of the present application.
In addition, in order to reduce detection errors, the purity of the chemical reagent used in the method for detecting various calcium-containing compounds in the absorption liquid after the absorption of the flue gas is analytical purity.
Example 1, a method for detecting various calcium-containing compounds in an absorption liquid after absorbing flue gas, comprising the steps of:
s0, sampling of absorption liquid after absorption of flue gas:
s01, mixing limestone and water according to a mass ratio of 1 2 、Cl 2 、HF、F 2 、SO 2 And SO 3 Carrying out chemical reaction on toxic and harmful gases to generate various calcium-containing compounds, then settling and gathering the calcium-containing compounds together, spraying the calcium-containing compounds into a chimney in an atomized state by using a chemical pump again, and circulating for three times to obtain absorption liquid after absorbing smoke;
s02, uniformly stirring the absorption liquid after absorbing the smoke, and then transferring 50.00mL of the absorption liquid into a container.
S1, measuring the content of soluble calcium:
s11, adding 5mL of 50wt% hydrogen peroxide solution into a container filled with 50.00mL of absorption liquid after absorbing the smoke, stirring for 10min, and then carrying out filtration I operation to obtain filter residue I and filtrate I; washing the filter residue I with deionized water for 6 times (the volume of the deionized water used for each time is 50 mL), collecting washing liquid for each time, moving the washing liquid and the filtrate I into a 1000mL volumetric flask, diluting the washing liquid with the deionized water to a marked line, and shaking the volumetric flask to ensure that the solution in the volumetric flask is uniform to obtain a calcium-containing solution I to be detected;
s12, transferring 20.00mL of the calcium-containing liquid I to be detected into a beaker, adding 50mL of deionized water, adding 10mL of hydrochloric acid with the concentration of 4mol/L, uniformly stirring, and adding 5mL of triethanolamine solution (prepared from commercial concentrated triethanolamine (with the concentration)
Figure 602776DEST_PATH_IMAGE003
98 percent) and deionized water according to the volume ratio of 1; adding deionized water until the total volume of the liquid is about 200mL, adding 25mL of potassium hydroxide solution (prepared by mixing potassium hydroxide solid and deionized water according to the mass ratio of 1 to 5) while stirring, and dropwise adding 6 drops (0.3 mL) of a calcium indicator (prepared by mixing 1g of calcein, 0.2g of phenolphthalein, 1g of methyl thymol blue and 100mL of glycerol-triethanolamine); then, the EDTA-2Na standard solution (EDTA-2 Na is disodium ethylene diamine tetraacetate, the concentration is 0.02506 mol/L) with known accurate concentration after calibration is poured into a 100mL burette until the burette reaches 0.00mL marked line, the burette is titrated under the stirring condition until the yellow-green fluorescence of the solution in the beaker is just disappeared, the volume number of the consumed EDTA-2Na standard solution is recorded to be 50.55mL, and the calculation formula is as follows:
Figure 991032DEST_PATH_IMAGE004
wherein, W 1 Indicates that 1L of absorption liquid after absorbing smoke is easy to dissolve calcium [ Ca (HCO) 3 ) 2 、Ca(NO 2 ) 2 、Ca(NO 3 ) 2 、CaCl 2 ]The mass of the corresponding calcium ions, unit g/L;
C sign The concentration of the standard EDTA-2Na solution after calibration is expressed, namely, 0.02506mol/L;
V sign board Represents the volume number of EDTA-2Na standard solution consumed, i.e., 0.05055L;
40.08 refers to the molar mass of calcium ions, in g/mol;
Figure 91843DEST_PATH_IMAGE005
represents a conversion factor corresponding to 20.00mL of the total volume of the calcium-containing solution I to be measured (1000.00 mL)
Figure 274562DEST_PATH_IMAGE005
Is 50;
V suction device The volume of the absorption liquid after the absorbed smoke was removed, i.e., 0.05000L.
Calculating W from the above formula 1 The value of (A) is 50.77g/L, which indicates that calcium [ Ca (NO) is easily dissolved in the absorption liquid after the absorption of the smoke 2 ) 2 、Ca(NO 3 ) 2 、CaCl 2 、Ca(HCO 3 ) 2 ]The corresponding calcium ion content was 50.77g/L.
S2, measuring the content of the residual limestone or hydrated lime:
s21, dropwise adding 1.75mol/L acetic acid solution into the filter residue I under stirring till the pH of a reaction system is 2.4, stirring for 10min, and immediately filtering II to obtain filter residue II and filtrate II; washing the filter residue II with deionized water for 6 times (the volume of the deionized water used for each time is 50 mL), collecting washing liquid for each time, transferring the washing liquid and the filtrate II into a 1000mL volumetric flask together, diluting the washing liquid to a marked line with the deionized water, and shaking to make the solution in the volumetric flask uniform to obtain a calcium-containing liquid II to be detected;
s22, transferring 20.00mL of the calcium-containing liquid II to be detected into a beaker, adding 50mL of deionized water, adding 10mL of hydrochloric acid with the concentration of 4mol/L, uniformly stirring, and adding 5mL of triethanolamine solution (prepared from commercial concentrated triethanolamine (with the concentration)
Figure 975671DEST_PATH_IMAGE003
98 percent) and deionized water are mixed according to the volume ratio of 1; adding deionized water until the total volume of the liquid is about 200mL, adding 25mL of potassium hydroxide solution (prepared by mixing potassium hydroxide solid and deionized water according to the mass ratio of 1 to 5) while stirring, and dropwise adding 6 drops (0.3 mL) of a calcium indicator (prepared by mixing 1g of calcein, 0.2g of phenolphthalein, 1g of methyl thymol blue and 100mL of glycerol-triethanolamine); then pouring the calibrated EDTA-2Na standard solution (the concentration is 0.02506 mol/L) into a 100ml burette,until the 0.00mL mark line of the burette is titrated under the stirring condition until the yellow-green fluorescence of the solution in the beaker is just disappeared, the volume number of the consumed EDTA-2Na standard solution is recorded to be 65.28mL, according to the following calculation formula:
Figure 902039DEST_PATH_IMAGE006
wherein, W 2 The mass of calcium ions corresponding to residual limestone in 1L of absorption liquid after the absorption of the flue gas is expressed in unit g/L;
C sign board Represents the concentration of the EDTA-2Na standard solution after calibration, namely 0.02506mol/L;
V sign board Represents the volume of EDTA-2Na standard solution consumed, i.e., 0.06528L;
40.08 refers to the molar mass of calcium ions, in g/mol;
Figure 857356DEST_PATH_IMAGE005
represents that a conversion coefficient corresponding to the volume of 20.00mL is divided from the total volume of the calcium-containing liquid II1000.00mL to be measured, namely
Figure 476557DEST_PATH_IMAGE005
Is 50;
V suction device The volume of the absorption liquid after the absorbed smoke is removed, i.e., 0.05000L.
From the above formula, W is calculated 2 The value of (A) is 65.57g/L, which indicates that the calcium ion content corresponding to the residual limestone in the absorption liquid after absorbing the flue gas is 65.57g/L, and 65.57g/L is less than 80g/L, which indicates that the absorption liquid after absorbing the flue gas can not be reused, and the absorption liquid with the limestone mass of not less than 50wt% needs to be supplemented into the absorption liquid after absorbing the flue gas in time to form new absorption liquid, so that the calcium ion content corresponding to the limestone in the new absorption liquid is more than 80g/L, or the new absorption liquid with the limestone mass of not less than 50wt% is replaced, and the new absorption liquid is sprayed into a chimney in an atomized manner by a chemical pump to absorb NO and NO in the flue gas 2 、Cl 2 、HF、F 2 、SO 2 And SO 3 Etc. are toxic and harmfulA gas.
S3, measuring the content of sulfur-containing insoluble calcium
S31, adding ammonium carbonate solid (the mass of the ammonium carbonate solid is 4 times that of the filter residue II) and deionized water (the mass of the deionized water is equal to that of the filter residue II) into the filter residue II under stirring, stirring for 30min at 25 ℃, immediately adding 50mL of deionized water to dissolve a part of the remaining ammonium carbonate solid, immediately filtering to obtain filter residue III and filtrate III, and washing the filter residue III with deionized water for 6 times (the volume of the deionized water used each time is 50 mL);
s32, dropwise adding 1.75mol/L acetic acid solution into the washed filter residue III until the pH value of a reaction system is 2.4, stirring for 10min, and immediately filtering IV to obtain filter residue IV and filtrate IV; washing the filter residue IV with deionized water for 6 times (the volume of the deionized water used for each time is 50 mL), collecting washing liquid for each time, transferring the washing liquid and the filtrate IV into a 1000mL volumetric flask together, diluting the solution to a marked line with the deionized water, and shaking the volumetric flask to ensure that the solution in the volumetric flask is uniform to obtain calcium-containing liquid III to be detected;
s33, transferring 25.00mL of the calcium-containing liquid III to be detected into a beaker, adding 50mL of deionized water, adding 10mL of 4mol/L hydrochloric acid, stirring uniformly, and adding 5mL of triethanolamine solution (prepared from commercial concentrated triethanolamine (concentration)
Figure 399382DEST_PATH_IMAGE003
98 percent) and deionized water are mixed according to the volume ratio of 1; then adding deionized water until the total volume of the liquid is about 200mL, adding 25mL of potassium hydroxide solution (prepared by mixing potassium hydroxide solid and deionized water according to a mass ratio of 1 to 5) while stirring, and dropwise adding 6 drops (0.3 mL) of a calcium indicator (prepared by mixing 1g of calcein, 0.2g of phenolphthalein, 1g of methyl thymol blue and 100mL of glycerol-triethanolamine); then pouring the calibrated EDTA-2Na standard solution (with the concentration of 0.02506 mol/L) into a 100mL burette to the position of 0.00mL marking line of the burette, titrating under the stirring condition until the yellow-green fluorescence of the solution in the beaker is just disappeared, recording the volume number of the consumed EDTA-2Na standard solution as 64.78mL, and calculating according to the following formula:
Figure 332703DEST_PATH_IMAGE007
wherein, W 3 Shows that 1L of sulfur-containing insoluble calcium (CaSO) in the absorption liquid after absorbing the flue gas 3 And CaSO 4 ) The mass of the corresponding calcium ions, in g/L;
C sign board Represents the concentration of the EDTA-2Na standard solution after calibration, namely 0.02506mol/L;
V sign board Represents the volume of EDTA-2Na standard solution consumed, i.e., 0.06478L;
40.08 refers to the molar mass of calcium ions, in g/mol;
Figure 267161DEST_PATH_IMAGE005
shows that a conversion coefficient corresponding to the volume of 25.00mL is divided from the total volume of the calcium-containing liquid III1000.00mL to be detected, namely
Figure 932629DEST_PATH_IMAGE005
Is 40;
V suction device The volume of the absorption liquid after the absorbed smoke is removed, i.e., 0.05000L.
From the above formula, W is calculated 3 The value of (A) is 52.05g/L, which indicates that sulfur-containing hardly soluble calcium (CaSO) is contained in the absorption liquid after absorption of flue gas 3 And CaSO 4 ) The corresponding calcium ion content was 52.05g/L.
S4, measuring content of fluorine-containing insoluble calcium
S41, placing the washed filter residue IV into a polytetrafluoroethylene beaker, adding 200mL 4mol/L hydrochloric acid, covering a polytetrafluoroethylene watch glass on an opening of the polytetrafluoroethylene beaker, heating to 90 ℃, keeping at 90 ℃ for 30min, and filtering V after the reaction is finished to obtain filter residue V and filtrate V; washing the filter residue V with deionized water for 6 times (the volume of the deionized water used for each time is 50 mL), collecting washing liquid for each time, transferring the washing liquid and the filtrate V into a 1000mL volumetric flask together, diluting the washing liquid to a marked line with the deionized water, and shaking to make the solution in the volumetric flask uniform to obtain a calcium-containing solution IV to be detected;
s42, transferring 25.00mL of the calcium-containing liquid IV to be detected into a beaker, adding 50mL of deionized water, adding 10mL of 4mol/L hydrochloric acid, stirring uniformly, and adding 5mL of triethanolamine solution (prepared from commercial concentrated triethanolamine (concentration)
Figure 218117DEST_PATH_IMAGE003
98 percent) and deionized water are mixed according to the volume ratio of 1; adding deionized water until the total volume of the liquid is 200mL, adding 25mL of potassium hydroxide solution (prepared by mixing potassium hydroxide solid and deionized water according to a mass ratio of 1 to 5) while stirring, and dropwise adding 6 drops (0.3 mL) of a calcium indicator (prepared by mixing 1g of calcein, 0.2g of phenolphthalein, 1g of methyl thymol blue and 100mL of glycerol-triethanolamine); then pouring the calibrated EDTA-2Na standard solution (with the concentration of 0.02506 mol/L) into a 100mL burette to the position of 0.00mL marked line of the burette, titrating under the stirring condition until the yellow-green fluorescence of the solution in the beaker is just disappeared, recording the volume number of the consumed EDTA-2Na standard solution as 34.71mL, and calculating according to the following formula:
Figure 610921DEST_PATH_IMAGE008
wherein, W 4 Shows that 1L of fluorine-containing insoluble calcium (CaF) in the absorption liquid after absorbing the flue gas 2 ) The mass of the corresponding calcium ions, in g/L;
C sign board Represents the concentration of the EDTA-2Na standard solution after calibration, namely 0.02506mol/L;
V sign Represents the volume number of the EDTA-2Na standard solution consumed, namely, 0.03471L;
40.08 refers to the molar mass of calcium ions, in g/mol;
Figure 665464DEST_PATH_IMAGE005
represents that a conversion coefficient corresponding to a volume of 25.00mL is extracted from a total volume of 1000mL of the calcium-containing solution to be measured IV
Figure 501833DEST_PATH_IMAGE005
Is 40;
V suction device The volume of the absorption liquid after the absorbed smoke was removed, i.e., 0.05000L.
From the above formula, W is calculated 4 The value (D) of (D) is 27.89g/L, which represents that the absorption liquid after absorbing the flue gas contains fluorine-containing poorly soluble calcium (CaF) 2 ) The corresponding calcium ion content was 27.89g/L.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims (10)

1. A detection method for various calcium-containing compounds in absorption liquid after absorbing smoke is characterized by comprising the following steps;
s1, detecting the content of soluble calcium: adding a soluble oxidant into the absorption liquid after absorbing the smoke, mixing, filtering I to obtain filter residue I and filter liquor I, and detecting the content of calcium ions in the soluble calcium by using an EDTA titration method;
s2, determining the content of the residual effective calcium: adding an organic weak acid solution into the filter residue I obtained in the step S1 until the pH value is 2.3-2.5, filtering II to obtain a filter residue II and a filtrate II, and detecting the content of calcium ions in the residual effective calcium by using an EDTA titration method;
s3, measuring the content of sulfur-containing insoluble calcium: adding a carbonation reagent and deionized water into the filter residue II obtained in the step S2, reacting, adding deionized water, and filtering III to obtain filter residue III and filtrate III; adding organic weak acid solution into the filter residue III until the pH value is 2.3-2.5, filtering IV to obtain filter residue IV and filtrate IV, and detecting the content of calcium ions in the sulfur-containing insoluble calcium by using an EDTA titration method;
s4, measuring the content of fluorine-containing insoluble calcium: adding hydrochloric acid into the filter residue IV obtained in the step S3, heating to dissolve fluorine-containing insoluble calcium, filtering V to obtain filter residue V and filtrate V, and detecting the content of calcium ions in the fluorine-containing insoluble calcium by using an EDTA titration method;
when the content of calcium ions corresponding to the residual effective calcium in the absorption liquid after the absorption of the flue gas is less than 80g/L, the content of the effective calcium in the absorption liquid is readjusted, and the content of the calcium ions corresponding to the effective calcium in the adjusted absorption liquid is ensured to be not less than 80g/L.
2. The method for detecting various types of calcium-containing compounds in the absorption liquid after absorbing the smoke according to claim 1, wherein in the step S3, the carbonation reagent is a carbonate or bicarbonate compound containing ammonium, potassium and sodium.
3. The method for detecting various calcium-containing compounds in the absorption liquid after absorbing the smoke according to claim 2, wherein in the step S3, the mass ratio of the filter residue II, the ammonium carbonate and the deionized water is 1 (3-4) to (0.8-1.2).
4. The method for detecting various calcium-containing compounds in the absorption liquid after absorbing the flue gas according to claim 3, wherein in the step S3, the mass ratio of the filter residue II, the ammonium carbonate and the deionized water is 1.
5. The method for detecting various calcium-containing compounds in the absorption liquid after absorbing the smoke according to claim 2, wherein in the step S3, the reaction time of the filter residue II, ammonium carbonate and deionized water is 25-35min.
6. The method for detecting various calcium-containing compounds in the absorption liquid after absorbing the flue gas as claimed in claim 1, wherein the organic weak acid solution is an acetic acid solution.
7. The method for detecting various types of calcium-containing compounds in absorption liquid after absorbing smoke according to claim 6, wherein the concentration of the acetic acid solution is 1.7-1.8mol/L.
8. The method for detecting various calcium-containing compounds in the absorption liquid after absorbing the smoke according to claim 1, wherein the EDTA titration method comprises the following specific steps:
a. preparing a liquid;
b. adding hydrochloric acid, stirring, adding triethanolamine solution, stirring, and standing;
c. adding potassium hydroxide solution to make pH be greater than 13, dripping calcium indicator, and titrating with EDTA-2Na standard solution until yellow-green fluorescence disappears.
9. The method for detecting various types of calcium-containing compounds in absorption liquid after absorbing smoke according to claim 8, wherein the concentration of hydrochloric acid in the step b is 3.5-4.5mol/L.
10. The method for detecting various calcium-containing compounds in the absorption liquid after absorbing smoke according to claim 8, wherein in the step c, the calcium indicator is a glycerol-triethanolamine mixed solution of calcein, phenolphthalein, and methyl thymol blue.
CN202210762399.1A 2022-06-30 2022-06-30 Method for detecting various calcium-containing compounds in absorption liquid after smoke absorption Pending CN115166137A (en)

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