Precise detection method of calcium hydroxide in waste incineration fly ash

Abstract

The present application relates to waste incineration flue gas treatment technical field, specifically discloses a kind of precision detection method of calcium hydroxide in waste incineration fly ash, comprising:1) sample vacuum drying is carried out and is washed gradually;2) the pretreated sample is carried out and is analyzed by TGA-DSC-FTIR combined with double atmosphere: first in pure N2 atmosphere, with 5 ℃ / min slow speed to 600 ℃, utilize pure N2 cut off carbonation reverse path, while using FTIR real-time monitoring confirmation that the interval escaping gas only contains H2O;Again switch to the O2 atmosphere heating to 850 ℃;3) the content of Ca (OH) 2 is calculated by combining TGA weight loss and DSC peak area double method mutual school;4) the mass of Ca 2+ Approximately represent the dissolution loss amount of Ca (OH) 2, establish mathematical model decoupling CaCl2 and the dissolution contribution of Ca (OH) 2, calculate correction coefficient K to compensate water washing loss, finally converted into original ash reference content.

Description

Technical Field

[0001] This invention relates to the field of waste incineration flue gas treatment technology, specifically to a precise detection method for calcium hydroxide in waste incineration fly ash. Background Technology

[0002] Waste-to-energy plants commonly employ a combined process of "semi-dry acid removal + bag filter + SCR" to treat flue gas. The utilization rate of the acid removal agent Ca(OH)2 is typically only 40%–60%, and a large amount of Ca(OH)2 remaining in the raw ash can be recycled back into the acid removal system. To achieve efficient recovery and utilization of Ca(OH)2, its content must be accurately measured to guide the setting and optimization of recovery process parameters.

[0003] Currently, the existing detection methods mainly include: (1) Sucrose method (HG / T 4120-2009): It is not suitable for industrial calcium hydroxide with high purity, but it cannot distinguish CaO and is severely interfered with by water-soluble calcium salts such as CaCl2. It is also not suitable for fly ash. (2) Single atmosphere thermogravimetric analysis (TGA): The temperature is raised in a single atmosphere (N2 or air), and Ca(OH)2 is calculated based on the weight loss at 400-520℃. However, there are problems such as overlapping decomposition temperatures of CaCO3, offsetting weight gain due to CaSO3 oxidation, and superposition of carbon combustion. (3) EDTA titration method: The difference is calculated after determining the total calcium content. The operation is cumbersome, the cumulative error is large, and the indicator is easily blocked by heavy metals. (4) XRD quantitative analysis method: The detection sensitivity is low, and it is greatly affected by preferred orientation and amorphous state. The quantitative accuracy is only ±10%-20%. (5) Carbonation method (CN104155203A): For concrete design, fly ash has a high background CaCO3 and soluble salts hinder carbonation, resulting in large errors.

[0004] In summary, the existing detection methods still have some shortcomings, including: (1) the technical bias of "no water washing": it is generally believed in the traditional thermal analysis field that water washing will lead to the loss of Ca(OH)2, so the raw ash is inclined to be directly dry thermogravimetric analysis. However, the research team of this invention found that the interference of CaClOH generation and organic matter volatilization caused by direct dry analysis has an error that is much greater than the trace dissolution loss caused by water washing. The traditional technology abandons water washing because of the fear of loss, which is actually a technical bias, resulting in a larger systematic error that cannot be eliminated. (2) the carbonation transformation blind zone of single atmosphere TGA: under single atmosphere, the decomposition temperature of Ca(OH)2 and CaCO3 partially overlaps, and there are secondary reactions between decomposition products. It is impossible to achieve thermodynamic isolation by simply relying on the heating rate. (3) lack of qualitative means: simple TGA can only provide mass change, and it cannot trace the source of multiple reactions (such as dehydration, decarboxylation, dechlorination) that may occur in the same temperature zone in complex fly ash matrix.

[0005] Therefore, accurately and reliably detecting the calcium hydroxide content in waste incineration fly ash (raw ash) has become one of the challenges facing this field. Specifically, this includes the following aspects: (1) Identification and elimination of hidden interference sources: Existing technologies only focus on the weight loss interference of CaCl2 itself, and have not discovered the hidden mechanism of the in-situ reaction of CaCl2 and Ca(OH)2 to form CaClOH at high temperature. The decomposition temperature range of CaClOH highly overlaps with that of Ca(OH)2, resulting in a systematic overestimation of the single-atmosphere TGA results. Therefore, it is necessary to consider how to block this reaction pathway from the root.

[0006] (2) Suppression of dynamic carbonation transformation: In a single atmosphere heating process, the H2O and trace amounts of CO2 produced by the decomposition of Ca(OH)2 will cause the undecomposed Ca(OH)2 to undergo dynamic carbonation, producing a false weight loss phenomenon of "one increasing while the other decreases". Therefore, it is necessary to consider how to completely cut off this transformation from the thermodynamic and kinetic perspectives.

[0007] (3) Precise decoupling and source tracing of multi-source weight loss signals: In complex matrices, it is necessary to consider how to prove that the weight loss in a specific temperature range is indeed due to the dehydroxylation of Ca(OH)2, rather than other unknown components. (4) Precise kinetic compensation for associated losses during pretreatment: Although water washing can remove impurities, it inevitably leads to the dissolution of trace amounts of Ca(OH)2. Traditional macroscopic mass weighing methods cannot distinguish whether the dissolved calcium comes from CaCl2 or Ca(OH)2, so it is necessary to consider how to establish an accurate chemical speciation source correction model. Summary of the Invention

[0008] The purpose of this invention is to provide a precise detection method for calcium hydroxide in waste incineration fly ash. This method is an original detection method based on "source blocking - atmosphere isolation - multi-mode verification - kinetic compensation" to achieve precise quantification of Ca(OH)2 in fly ash.

[0009] Specifically, the technical solution of the present invention is as follows: A precise detection method for calcium hydroxide in waste incineration fly ash includes the following steps: The sample was vacuum dried at 60℃ and then washed in stages: first, it was washed with water at 25℃ and a liquid-to-solid ratio of 20:1 to remove CaCl2 in order to block the CaClOH generation pathway, and then ultrasonically washed with anhydrous ethanol to break the organic matter encapsulation. The pretreated samples were analyzed using a dual-atmosphere TGA-DSC-FTIR system: First, the temperature was slowly increased to 600℃ at 5℃ / min under a pure N2 atmosphere to cut off the carbonation reversal path and construct a Ca(OH)2-specific decomposition window. At the same time, FTIR was used to monitor and confirm that the escaping gas in this range contained only H2O. Then, the temperature was switched to an O2 atmosphere and increased to 850℃ to force the decomposition of CaCO3. The Ca(OH)2 content was calculated by combining the TGA weight loss and DSC peak area methods for cross-calibration. Based on Ca in multi-stage washing solution 2+ The kinetics of concentration decrease were analyzed, and the Ca concentration in the subsequent washing solution was calculated. 2+ The mass of Ca(OH)2 is used to approximate the dissolution loss of Ca(OH)2. A mathematical model is established to decouple the dissolution contributions of CaCl2 and Ca(OH)2. The correction coefficient K is calculated to compensate for the washing loss, and finally converted into the original ash baseline content.

[0010] Furthermore, the specific steps include: (1) Low-temperature vacuum drying and mechanochemical depolymerization Take the mixed raw ash and place it in a vacuum drying oven and dry it at 60℃ and -0.09MPa for 4 hours; after taking it out, grind it with an agate mortar and pass it through a 75μm standard sieve.

[0011] (2) Multi-stage countercurrent washing under kinetic control to block the CaClOH formation pathway Accurately weigh 5.00 g of dried fly ash and add it to 100 mL of deionized water at a liquid-to-solid ratio of 20:1. Stir magnetically in a constant temperature water bath at 25±2℃ for 10 min at a speed of 400-600 r / min. Vacuum filter (0.45 μm microporous membrane), and wash the filter cake with 10 mL of cold water (5℃). Repeat the washing process three times, collecting the filtrate from each wash and labeling it L1, L2, and L3, and then dilute to volume separately for later use.

[0012] (3) Low surface tension solvent deep desorption breaks the lattice blockage of organic matter. Transfer the washed filter cake and add 50 mL of anhydrous ethanol at a liquid-to-solid ratio of 10:1. Sonicate at 25°C for 10 min (200 W, 40 kHz), filter, and repeat once; vacuum dry the filter cake at 60°C for 4 h.

[0013] (4) Thermodynamic window reconstruction of dual-atmosphere TGA-DSC-FTIR coupled analysis Weigh the pretreated sample and place it in a TGA-DSC-FTIR instrument; The first stage uses a N2 atmosphere (dedicated dehydroxylation window): high-purity N2, 50 mL / min, 25℃→10℃ / min heating up→350℃, hold temperature for 5 min→5℃ / min heating up→600℃, hold temperature for 5 min; The second stage uses an O2 atmosphere (forced decarbonation window): switch to O2, 50 mL / min, switch <30 s, 600 ℃ → 10 ℃ / min temperature increase → 850 ℃, hold temperature for 10 min; (5) ICP-OES compensation calculation based on dissolution kinetics decoupling ①TGA-DSC Dual-Mode Cross-Calibration Quantitative Analysis W1 was calculated using the TGA weight loss method; W2 was calculated using the DSC peak area method, and the average value was taken as the content after washing. ② ICP-OES Washing Loss Kinetics Source Tracing and Compensation Determination: The Ca in the three washing solutions L1, L2, and L3 was determined by ICP-OES. 2+ Concentrations C1, C2, C3; Kinetic decoupling and full compensation: Based on the kinetic differences between the rapid dissolution of CaCl2 and the slightly soluble and linearly slow dissolution of Ca(OH)2, the Ca in L1 is set... 2+ The main contributor is CaCl2; simultaneously, the concentration difference ΔC = C2 - C3 between L2 and L3 is considered as the dissolution gradient of Ca(OH)2, and the contribution of Ca(OH)2 to L1 is calculated by linear extrapolation. 2+ Concentration C 1a =C2+ΔC; Loss Calculation: Let the volumes of L1, L2, and L3 after constant volume be V1, V2, and V3, respectively. Then the total mass of calcium ions contributed by the dissolution of Ca(OH)2 is m. Ca =(C2+ΔC)×V1+C2×V2+C3×V3; The amount of Ca(OH)2 lost through dissolution is n. Ca(OH)2 =m Ca / M Ca ; and then calculate the mass of Ca(OH)2 lost through dissolution as m. loss = n Ca(OH)2 ×M Ca(OH)2 ; Precise correction: Calculate the actual loss rate η = m loss / (total mass of sample after washing × preliminary calculated Ca(OH)2 content), derive correction coefficient K=1+η; combined with total weight loss η from washing. m Convert the original ash content to the standard content: W original = [(W1+W2) / 2]× K × (1 - η m ).

[0014] Where, m Ca : Total mass of calcium ions contributed by Ca(OH)2 dissolution in L2 and L3 washing solutions, unit: mg; C2: Ca in the second washing solution L2 2+ Concentration, unit: mg / L; V2: Volume of the second washing solution L2 after final volume adjustment, unit: L; C3: Ca in the third washing solution L3 2+ Concentration, unit: mg / L; V3: Volume of the third washing solution L3 after final volume adjustment, unit: L; nCa(OH)2 : Amount of Ca(OH)2 lost through dissolution, unit: mmol; m Ca Total mass of calcium ions contributed by the dissolution of Ca(OH)2, unit: mg; M Ca Molar mass of calcium, unit: mg / mmol; mloss: Mass of Ca(OH)2 lost through dissolution, in mg; M Ca(OH)2 Molar mass of calcium hydroxide Ca(OH)2, unit: mg / mmol; η: Actual water washing loss rate, unit: % W original : The final actual content of Ca(OH)2 in the raw ash, in % %. W1: Ca(OH)2 content after washing, calculated by TGA weight loss method, in % W2: Ca(OH)2 content after water washing, calculated by DSC peak area method, unit: % K: Washing loss correction coefficient, unit: dimensionless; η m Total weight loss after water washing and ethanol washing, unit: dimensionless, calculation formula: 1 - (total mass of sample after washing / mass of original ash sample).

[0015] In step (2), methanol or dilute methanol solution can be used to replace deionized water and cold water for washing.

[0016] In step (4), the second stage can use N2 / O2 mixed gas or air instead of pure O2.

[0017] In step (4), TGA-MS (mass spectrometry) can also be used instead of FTIR to monitor H2O (m / z=18) and CO2 (m / z=44). If the DSC module is missing, calculations can be performed using only the TGA weightlessness method combined with FTIR qualitative analysis.

[0018] The technical principle of the detection method of this invention is as follows: (1) Washing strategy: Water washing is introduced to thoroughly wash away CaCl2 and cut off the precursor of CaClOH from the source; ethanol washing breaks the organic matter encapsulation and releases the sealed Ca(OH)2.

[0019] (2) Reconstruction of the thermodynamic window: The dual atmosphere switching from N2 to O2 aims to completely cut off the secondary reaction path between CaO and CO2 using a pure N2 atmosphere, avoiding interference from dynamic carbonation; to create a "Ca(OH)2 exclusive decomposition window" free from carbonation interference before 600℃, and then switch to O2 to promote the rapid and complete decomposition of CaCO3 in the high-temperature region, thus achieving time-atmosphere isolation of the two-step reaction.

[0020] (3) Multi-source signal closed-loop verification: FTIR is not only used to "look at the gas", but also to confirm whether there is absolutely no CO2 leakage in the N2 section (to verify whether carbonation is completely suppressed) and whether there is HCl leakage (to verify whether water washing is thorough).

[0021] (4) Filtrate Ca 2+ Kinetic origin: Based on the differences in dissolution kinetics, a mathematical model is established to separate the cross-contribution of CaCl2 and Ca(OH)2 to the calcium concentration of the washing solution, so as to achieve accurate compensation for the loss.

[0022] The key innovation of this invention's method for accurate detection of calcium hydroxide in waste incineration fly ash lies mainly in: (1) Washing strategy that breaks through technical bias: Actively adopt water washing-ethanol washing combination with specific parameters, in exchange for the complete elimination of hidden interference of CaClOH and blockage of organic matter with small dissolution loss that can be accurately corrected. The thermodynamic proof of CaClOH formation and interference mechanism is shown in the table below.

[0023] (2) Dual atmosphere switching of thermodynamic window reconstruction: switch N2 / O2 at the critical point of 600℃, use N2 atmosphere to cut off the secondary carbonation path, and achieve time-atmosphere absolute isolation of Ca(OH)2 and CaCO3 decomposition through atmosphere switching to overcome carbonation transformation.

[0024] The decomposition reaction of CaCO3 under pure N2. Due to the purging effect of N2, the generated CO2 is rapidly removed, resulting in an extremely low CO2 partial pressure within the system. According to Le Chatelier's principle, this actually shifts the equilibrium to the right (forward decomposition), meaning the initial decomposition temperature of CaCO3 under N2 is neither "pushed up" nor "delayed." However, the core value of a pure N2 atmosphere lies in its complete elimination of the pathway for the secondary combination of CaO generated during dehydration with CO2 in the atmosphere (dynamic carbonation reversal), avoiding the illusion that the weight loss of Ca(OH)2 is masked. Simultaneously, choosing 600℃ as the switching point ensures that Ca(OH)2 decomposes completely within a temperature range free from carbonation interference. Subsequently, the introduction of O2 utilizes a high-temperature oxidizing atmosphere to promote the complete decomposition of CaCO3. This synergy based on "reaction path blocking" and "time-atmosphere isolation" is easily deduced by non-specialists using conventional logic.

[0025] Fly ash often contains small amounts of CaSO3 and CaSO4. Since CaSO4 is extremely thermally stable below 850℃, and CaSO3 does not decompose in an inert atmosphere, neither undergoes mass change in the first stage under a pure N2 atmosphere (350~600℃), and therefore does not interfere with the weight loss of Ca(OH)2 due to dehydroxylation. Although CaSO3 oxidizes and gains weight in the second stage under an O2 atmosphere, this only affects the quantification of CaCO3. Furthermore, because this invention employs a dual-atmosphere switching method, the determination of Ca(OH)2 is completely isolated from the oxidation of CaSO3 in the time-atmosphere dimension, thus ensuring the absolute accuracy of Ca(OH)2 detection.

[0026] (3) Multi-mode closed-loop verification: FTIR is not only a qualitative method, but also a criterion for the validity of the experiment (the absence of CO2 / HCl in the N2 segment indicates validity).

[0027] (4) Source correction model based on dynamic decoupling: using multi-stage water washing liquid Ca 2+ By analyzing the decreasing concentration pattern, the contributions of CaCl2 and Ca(OH)2 are eliminated, enabling precise compensation for the losses.

[0028] (5) The effect of CaClOH in raw ash on this technology ① The CaClOH naturally present in the raw ash and the CaClOH generated in situ during the TGA heating process cannot be distinguished on the thermogravimetric curve. The decomposition temperature range of CaClOH (450~500℃) highly overlaps with that of Ca(OH)2. If the existing single-atmosphere TGA is used to directly detect the raw ash, the weight loss caused by the decomposition of the CaClOH naturally present in the raw ash will be 100% misinterpreted by the instrument software as the dehydration weight loss of Ca(OH)2. The higher the CaClOH content in the raw ash, the more artificially high the measured Ca(OH)2 content will be.

[0029] ② The multi-stage countercurrent washing step of this invention not only washes away free CaCl2, but also removes and hydrolyzes a large amount of CaClOH originally present in the original ash. After washing, the originally complex "Ca(OH)2 + CaCl2 + CaClOH" symbiotic system is purified into a pure "Ca(OH)2" system, completely eliminating this biggest hidden source of interference from the source.

[0030] ③ The compensation model of this invention (step five) sets a premise: "Ca in L1" 2+ The vast majority of the Ca comes from CaCl2 (fast-dissolving), and the Ca in L2 and L3... 2+"Approximately entirely contributed by Ca(OH)2 (slightly soluble and continuously soluble)." Since the dissolution kinetics of CaClOH is "rapidly soluble," its calcium contribution is naturally "incorporated" into the rapidly soluble calcium pool of L1, and is not mixed into the slowly soluble calcium pools of L2 and L3.

[0031] ④ If the water washing is incomplete (e.g., only one wash), the residual CaClOH will decompose and produce HCl gas when the temperature in the N2 section of the TGA is raised to 450-500℃. The present invention uses FTIR to monitor the escaping gas in the 350-600℃ range in real time. If the CaClOH present in the original ash is not completely washed away, the FTIR will immediately capture the characteristic peak of HCl, directly invalidating the experiment.

[0032] Compared with the prior art, the method for accurate detection of calcium hydroxide in waste incineration fly ash of the present invention has at least the following beneficial effects: (1) The method of the present invention overcomes the CaClOH overlap interference that cannot be overcome by single atmosphere TGA: the existing technology is helpless against CaClOH interference. The present invention blocks the generation of the substance from the source by the non-obvious path of "washing away the precursor with water", which solves the false positive problem that has existed in the field for a long time.

[0033] (2) The method of the present invention overcomes the problem of "dynamic carbonation" in thermal analysis: existing technology cannot prevent Ca(OH)2 from partially transforming into CaCO3 during heating. The present invention blocks the secondary reaction path of CaO and CO2 by purging with N2 gas flow, and achieves absolute isolation of the phase change path.

[0034] (3) The method of this invention transforms “extensive” water washing into “precise” quantitative washing: Traditional thinking holds that water washing is uncontrollable, but the method of this invention uniquely uses Ca in the filtrate. 2+ The dynamic source tracing model transforms unknown washing losses into mathematically compensable losses, eliminating obstacles caused by technological bias.

[0035] (4) The method of the present invention realizes the leap from "blind test" to "white box verification": the FTIR closed-loop verification mechanism ensures that each thermogravimetric loss has a clear gas source attribution, eliminating the interference of unknown reactions in complex matrices. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0037] A precise detection method for calcium hydroxide in waste incineration fly ash includes the following steps: (1) Low-temperature vacuum drying and mechanochemical depolymerization Take the mixed raw ash and place it in a vacuum drying oven and dry it at 60℃ and -0.09MPa for 4 hours; after taking it out, grind it with an agate mortar and pass it through a 75μm standard sieve.

[0038] Mechanism: Traditional sample preparation often uses 105℃ forced-air drying. This conventional operation leads to accelerated carbonation of Ca(OH)2 adsorbed on the surface of fly ash with residual CO2 in the flue gas, and easily causes partial dehydration of Ca(OH)2 to form CaO, resulting in changes in the target analyte before detection. This invention forces vacuum drying at 60℃, using low pressure to lower the boiling point of water, removing physically adsorbed water while freezing chemical changes. Passing through a 75μm sieve is not only for uniformity but also to break up the agglomeration of fly ash particles and release the encapsulated inner layer of Ca(OH)2.

[0039] (2) Multi-stage countercurrent washing under kinetic control to block the CaClOH formation pathway Accurately weigh 5.00 g of dried fly ash and add it to 100 mL of deionized water at a liquid-to-solid ratio of 20:1. Stir magnetically in a constant temperature water bath at 25±2℃ for 10 min at a speed of 400-600 r / min. Vacuum filter (0.45 μm microporous membrane), and wash the filter cake with 10 mL of cold water (5℃). Repeat the washing process three times, collecting the filtrate from each wash and labeling it L1, L2, and L3, and then dilute to volume separately for later use.

[0040] Mechanism (Overcoming the "No-Wash" Bias): Traditional thermal analysis suggests that washing leads to the loss of Ca(OH)2, thus avoiding its use. However, this invention reveals that the CaClOH generated from the in-situ reaction of CaCl2 and Ca(OH)2 in the raw ash during TGA heating has a decomposition temperature range (450-500℃) that completely overlaps with that of Ca(OH)2, inevitably leading to inflated single-atmosphere TGA results. This invention proactively introduces washing, sacrificing precisely correctable minor dissolution losses to completely eliminate the hidden source of interference from CaClOH.

[0041] The combination of 25℃ and 10 min is the culmination of creative effort. Above 30℃, the solubility of Ca(OH)2 increases exponentially; below 20℃, the dissolution kinetics of CaCl2 are hindered. Rinsing with cold water at 5℃ utilizes the negative temperature coefficient of Ca(OH)2 solubility, displacing residual CaCl2 from the gaps in the filter cake without damaging the Ca(OH)2 crystal lattice.

[0042] (3) Low surface tension solvent deep desorption breaks the lattice blockage of organic matter. Transfer the washed filter cake and add 50 mL of anhydrous ethanol at a liquid-to-solid ratio of 10:1. Sonicate at 25°C for 10 min (200 W, 40 kHz), filter, and repeat once; vacuum dry the filter cake at 60°C for 4 h.

[0043] Mechanism: Organic compounds such as dioxins in fly ash not only volatilize and interfere with weight loss at 300-500℃, but more seriously, they form a hydrophobic and dense film (lattice blockage) on the surface of Ca(OH)2, hindering the escape of internal water of crystallization during thermal analysis, resulting in delayed or incomplete dehydration. Ethanol's extremely low surface tension, under ultrasonic cavitation, allows it to penetrate into the mesopores, peeling away the organic film and completely exposing the internal Ca(OH)2, while remaining almost undissolved.

[0044] (4) Thermodynamic window reconstruction of dual-atmosphere TGA-DSC-FTIR coupled analysis Weigh the pretreated sample and place it in a TGA-DSC-FTIR instrument; The first stage uses a N2 atmosphere (dedicated dehydroxylation window): high-purity N2, 50 mL / min, 25℃→10℃ / min heating up→350℃, hold temperature for 5 min→5℃ / min heating up→600℃, hold temperature for 5 min; The second stage uses an O2 atmosphere (forced decarbonation window): switch to O2, 50 mL / min, switch <30 s, 600 ℃ → 10 ℃ / min temperature increase → 850 ℃, hold temperature for 10 min; Mechanism (Thermodynamic Window Reconstruction): Under pure N2, the lack of O2 and the removal of volatiles by N2 purging completely cut off the pathway for the secondary carbonation reaction between CaO (formed from Ca(OH)2 dehydration) and CO2 in the atmosphere, avoiding the illusion of weight loss due to a "one-to-one" tradeoff. This invention selects 600℃ as the critical point for atmosphere switching, ensuring that Ca(OH)2 can completely decompose within a "dedicated dehydroxylation window" with absolutely no carbonation interference between 350 and 600℃. Subsequently, switching to O2 utilizes a high-temperature oxidizing atmosphere to promote the complete decomposition of CaCO3, achieving absolute time-atmosphere isolation between the decomposition processes of Ca(OH)2 and CaCO3. A slow heating rate of 5℃ / min further improves the resolution of the Ca(OH)2 dehydration peak.

[0045] FTIR white box validation logic: FTIR is not only used for qualitative analysis, but also as a criterion for experimental validity. If CO2 is detected by FTIR within the 350~600℃ window (at 2350cm²), then... -1 If the N2 concentration is not high enough, or if the HCl characteristic peak is detected, it can be directly determined that the N2 purity is insufficient or the water washing is incomplete, rendering the experiment invalid. This upgrades the traditional "blind test" to a "white-box verification".

[0046] (5) ICP-OES compensation calculation based on dissolution kinetics decoupling ①TGA-DSC Dual-Mode Cross-Calibration Quantitative Analysis W1 was calculated using the TGA weight loss method; W2 was calculated using the DSC peak area method, and the average value was taken as the content after washing. ② ICP-OES Washing Loss Kinetics Source Tracing and Compensation Determination: The Ca in the three washing solutions L1, L2, and L3 was determined by ICP-OES. 2+ Concentrations C1, C2, C3; Kinetic decoupling and full compensation: Based on the kinetic differences between the rapid dissolution of CaCl2 and the slightly soluble and linearly slow dissolution of Ca(OH)2, the Ca in L1 is set... 2+ The main contributor is CaCl2; simultaneously, the concentration difference ΔC = C2 - C3 between L2 and L3 is considered as the dissolution gradient of Ca(OH)2, and the contribution of Ca(OH)2 to L1 is calculated by linear extrapolation. 2+ Concentration C 1a =C2+ΔC; Loss Calculation: Let the volumes of L1, L2, and L3 after constant volume be V1, V2, and V3, respectively. Then the total mass of calcium ions contributed by the dissolution of Ca(OH)2 is m. Ca =(C2+ΔC)×V1+C2×V2+C3×V3; The amount of Ca(OH)2 lost through dissolution is n. Ca(OH)2 =m Ca / M Ca ; and then calculate the mass of Ca(OH)2 lost through dissolution as m. loss = n Ca(OH)2 ×M Ca(OH)2 ; Precise correction: Calculate the actual loss rate η = m loss / (total mass of sample after washing × preliminary calculated Ca(OH)2 content), derive correction coefficient K=1+η; combined with total weight loss η from washing. m Convert the original ash content to the standard content: W original = [(W1+W2) / 2]× K × (1 - η m ).

[0047] Note: m in this formula Ca It covers all the Ca(OH)2 contribution from the three washing solutions L1, L2, and L3. 2+ Quality. By linearly extrapolating the concentration gradients of L2 and L3, the interference of CaCl2 in L1 was eliminated, achieving accurate and comprehensive full compensation for trace dissolution losses.

[0048] Where, m Ca : Total mass of calcium ions contributed by Ca(OH)2 dissolution in L2 and L3 washing solutions, unit: mg; C2: Ca in the second washing solution L2 2+ Concentration, unit: mg / L; V2: Volume of the second washing solution L2 after final volume adjustment, unit: L; C3: Ca in the third washing solution L32+ Concentration, unit: mg / L; V3: Volume of the third washing solution L3 after final volume adjustment, unit: L; n Ca(OH)2 : Amount of Ca(OH)2 lost through dissolution, unit: mmol; m Ca Total mass of calcium ions contributed by the dissolution of Ca(OH)2, unit: mg; M Ca Molar mass of calcium, unit: mg / mmol; m loss Mass of Ca(OH)2 lost through dissolution, in mg; M Ca(OH)2 Molar mass of calcium hydroxide Ca(OH)2, unit: mg / mmol; η: Actual water washing loss rate, unit: % W original : The final actual content of Ca(OH)2 in the raw ash, in % %. W1: Ca(OH)2 content after washing, calculated by TGA weight loss method, in % W2: Ca(OH)2 content after water washing, calculated by DSC peak area method, unit: % K: Washing loss correction coefficient, unit: dimensionless; η m Total weight loss after water washing and ethanol washing, unit: dimensionless, calculation formula: 1 - (total mass of sample after washing / mass of original ash sample).

[0049] Although organic matter (such as dioxins and unburned carbon black) constitutes a small percentage of the total mass, its strong hydrophobicity allows it to readily form a dense hydrophobic microfilm (i.e., lattice-locked) on the Ca(OH)₂ surface. The significance of this film lies not in its mass, but in its ability to impede the escape of water of crystallization from within Ca(OH)₂ during the TGA heating process, leading to delayed or incomplete dehydration. The extremely low surface tension of ethanol, combined with ultrasonic cavitation, effectively allows for the penetration and removal of this hydrophobic film through mesopores, which is essential for accurate thermal analysis.

[0050] In other beneficial embodiments, in step (4), TGA-MS (mass spectrometry) can be used instead of FTIR to monitor H2O (m / z=18) and CO2 (m / z=44); if the DSC module is missing, the calculation can be performed solely by TGA weight loss combined with FTIR qualitative analysis. Specifically: 1. TGA-MS replaces TGA-FTIR Implementation method: A thermogravimetric analyzer (TGA) is connected to a mass spectrometer (MS) instead of a Fourier transform infrared spectrometer (FTIR). The gas transmission line needs to be insulated to prevent condensation. The heating program is completely consistent with the original scheme.

[0051] Parameter usage: MS performs qualitative analysis by monitoring the characteristic mass-to-charge ratio. In the first stage (350~600℃ N2 range), m / z=18 (H2O) is monitored, while m / z=44 (CO2) and m / z=36 / 38 (HCl) are also monitored. Logic used: This serves as a "white-box validation" criterion. If a clear dehydroxylation peak appears at m / z=18, and there is no response at m / z=44 and m / z=36 / 38, it proves that carbonation is inhibited and washing is thorough, and the experimental data is valid; if CO2 or HCl is detected, the experiment is invalid. In the calculation formula, since DSC is still retained, the quantitative calculation remains unchanged.

[0052] 2. DSC module missing (TGA-FTIR or TGA-MS only) Implementation method: The device only contains thermogravimetric and gas qualitative modules and cannot obtain heat flow (DSC) data.

[0053] Parameter Usage: Gas monitoring parameters are still used for "white box calibration". However, due to the lack of DSC, the quantitative calculation formula must be changed: "dual-mode mutual calibration" is no longer possible, and calculation must rely solely on the TGA weightlessness method. The W2 term contributed by DSC must also be removed from the subsequent compensation conversion formula.

[0054] Steps (4) and (5) are replaced with: 1. Analysis of dual-atmosphere thermogravimetric coupling for thermodynamic window reconstruction in step (4) Weigh the pretreated sample and place it in a TGA-DSC-FTIR (or TGA-DSC-MS, or TGA-FTIR / TGA-MS) coupled instrument; The first stage uses a N2 atmosphere (dedicated dehydroxylation window): high-purity N2, 50 mL / min, 25℃→10℃ / min heating up→350℃, hold temperature for 5 min→5℃ / min heating up→600℃, hold temperature for 5 min; The second stage uses an O2 atmosphere (forced decarbonation window): switch to O2, 50 mL / min, switch <30 s, 600 ℃ → 10 ℃ / min temperature increase → 850 ℃, hold temperature for 10 min; Gas monitoring and validity criteria: During the first stage of heating, the escaping gases are monitored in real time using online FTIR or MS; if MS is used, the characteristic ion currents of H2O (m / z=18), CO2 (m / z=44), and HCl (m / z=36 or 38) are monitored; if FTIR is used, the characteristic ion currents of H2O (m / z=3650 cm⁻¹) are monitored. -1 ), CO2 (2350cm)-1 The experiment is considered valid if only H2O characteristic signals are detected within the temperature range of 350~600℃, and CO2 and HCl are not detected; if CO2 or HCl is detected, the N2 purity is considered insufficient or the water washing is incomplete, and the experiment is invalid.

[0055] 2. Step (5) ICP-OES compensation calculation based on dissolution kinetics decoupling ① Quantitative calculation If the instrument includes a DSC module: use the TGA weight loss method to calculate the Ca(OH)2 content W1 after washing; at the same time, use the DSC peak area method to calculate the Ca(OH)2 content W2 after washing, and take the average value as the content after washing. If the instrument lacks the DSC module: rely solely on the TGA weight loss method to calculate the Ca(OH)2 content W1 after washing, and use it as the content after washing; ② ICP-OES Washing Loss Kinetics Source Tracing and Compensation Determination: The Ca in the three washing solutions L1, L2, and L3 was determined by ICP-OES. 2+ Concentrations C1, C2, C3; Kinetic decoupling: Based on common chemical knowledge, CaCl2 dissolves extremely quickly, and the Ca in the first washing solution... 2+ The vast majority of Ca comes from CaCl2; Ca(OH)2 is slightly soluble and continues to dissolve. Therefore, the Ca in L2 and L3... 2+ It can be approximated as being entirely contributed by the continuous and slow dissolution of Ca(OH)2.

[0056] Loss Calculation: Let the volumes of L2 and L3 after constant volume be V2 and V3, respectively. Then the total mass of calcium ions contributed by the dissolution of Ca(OH)2 in L2 and L3 is m. Ca =C2×V2+C3×V3; The amount of Ca(OH)2 lost through dissolution is n. Ca(OH)2 =m Ca / M Ca ; and then calculate the mass of Ca(OH)2 lost through dissolution as m. loss = n Ca(OH)2 ×M Ca(OH)2 ; Precise correction: Calculate the actual loss rate η = m loss / (total mass of sample after washing × preliminary calculated Ca(OH)2 content), derive correction coefficient K=1+η; combined with total weight loss η from washing. m Convert the original ash content to the standard content: If the instrumentation includes a DSC module, W original = [(W1+W2) / 2] × K × (1 - η m ); If the instrumentation lacks a DSC module, W original = W1× K × (1 - η m ).

[0057] Example 2: Verification of differences in solubility kinetics and verification of the absence of side effects from ethanol washing (1) Verification of differences in dissolution kinetics: To verify the decoupling prerequisite between CaCl2 and Ca(OH)2, a mixture of deionized water (liquid-to-solid ratio 20:1) and powder containing 20% ​​CaCl2 and 10% Ca(OH)2 was prepared. The filtrate was collected at stirring times of 10 s, 30 s, 1 min, 5 min, and 10 min to determine the Ca content. 2+ Concentration. The results showed that CaCl2 dissolved at a rate of 98.5% within 30 seconds, while Ca(OH)2 dissolved linearly and slowly within 1-10 minutes, demonstrating a significant difference in their time scales. The decoupling model of "L1 dominated by CaCl2 and L2 / L3 dominated by Ca(OH)2" has a physicochemical basis.

[0058] (2) Verification of the mechanism of no side effects of ultrasonic washing with ethanol: To address the potential side effects of ultrasonic washing with ethanol, this invention has verified and eliminated them from a physicochemical mechanism perspective: ① Solubility exclusion: The main calcium salts in fly ash are inorganic calcium salts, and Ca(OH)2, CaCO3, and CaSO4 have extremely low solubility in anhydrous ethanol (almost insoluble). Therefore, washing with anhydrous ethanol will not dissolve the inorganic calcium salt minerals in fly ash and will not change the mass of the target analytes in the solid phase.

[0059] ② Elimination of Mechanical Damage: The ultrasonic conditions used in this invention are 200W power, 40kHz frequency, and 10min time, which are mild and routine laboratory dispersion conditions. At this energy level, ultrasonic cavitation mainly manifests as the deagglomeration of particle aggregates and the stripping of weakly adsorbed organic matter on the surface. The bond energy required to break the inorganic mineral lattice is much higher than the mechanical energy generated by 200W ultrasonic cavitation; therefore, this process will not cause mechanical damage to mineral crystals such as Ca(OH)2 and CaCO3 or induce mineral phase transitions.

[0060] The above mechanisms indicate that anhydrous ethanol ultrasonic washing can effectively break the lattice blockage of organic matter while ensuring that no dissolution loss or change in mineral composition is introduced, thus guaranteeing the safety of the pretreatment step.

[0061] Application Examples 1. Project Overview A municipal solid waste incineration power plant in a certain city, with a processing capacity of 800 t / d, adopts a "semi-dry acid removal (SDA) + bag filter + SCR" process. The acid removal agent is a 20% concentration Ca(OH)2 slurry. To assess the recovery value of unreacted Ca(OH)2 in the raw ash, the method of this invention was implemented for precise detection.

[0062] 2. Detailed process steps and technical parameters (1) Sampling and homogenization: 2 kg samples were taken from multiple points in the dust hopper of the bag filter, dried under vacuum at 60℃ for 4 hours, ground and passed through a 75 μm sieve, and then reduced by quartering.

[0063] (2) First stage water washing: Weigh 5.000g of fly ash, add 100mL of deionized water (liquid-solid ratio 20:1), stir magnetically at 25℃ for 10min, filter through a 0.45μm filter membrane, rinse with 10mL of cold water at 5℃, and repeat 3 times. Collect the filtrates from each of the 3 washes and dilute each to 500mL (labeled as L1, L2, and L3).

[0064] (3) Second-stage ethanol washing: Add 50 mL of anhydrous ethanol to the water-washed filter cake, sonicate at 25 °C for 10 min, filter by suction, and repeat once. Dry the filter cake under vacuum at 60 °C for 4 h, grind it evenly, and weigh it to obtain 3.610 g.

[0065] (4) TGA-DSC-FTIR analysis: Weigh 12.35 mg of pretreated sample. N2 stage (50 mL / min): 25℃ → 350℃ (heating 10℃ / min, hold for 5 min) → 600℃ (heating 5℃ / min, hold for 5 min); switch to O2 stage (50 mL / min): 600℃ → 850℃ (heating 10℃ / min, hold for 10 min). Keep the FTIR transfer tube at 200℃.

[0066] (5) ICP-OES detection of washing solution: The Ca content of the three washing solutions was measured. 2+ The concentrations were: C1=820mg / L, C2=15mg / L, and C3=10mg / L.

[0067] 3. Table of changes in technical indicators before and after treatment Table 1. Changes in the main components of fly ash before and after staged washing pretreatment. Table 2 Key Data from TGA-DSC-FTIR Combined Analysis 4. Precise quantitative calculation and loss compensation (1) Calculation of Ca(OH)2 content after water washing using TGA weight loss method: W1 = (0.75 / 12.35) × (74.09 / 18.02) ×100% = 25.0% (2) DSC peak area method for calculating Ca(OH)2 content after water washing: W2 = 24.8% (mean value of cross-calibration between the two methods = 24.9%) (3) ICP-OES kinetic source compensation: The constant volumes of L2 and L3 are V2=V3=0.5L. The Ca in L2 and L3 is contributed by the dissolution of Ca(OH)2. 2+ Total mass m Ca =(15mg / L×0.5L)+(10mg / L×0.5L)=12.5mg. The corresponding amount of dissolved Ca(OH)2 is n=12.5 / 40.08=0.3119mmol. The mass of Ca(OH)2 lost through dissolution = 0.3119×74.09=23.11mg=0.02311g. The estimated mass of Ca(OH)2 in the sample after washing = 3.610g×24.9%=0.8989g. The water washing loss rate η =0.02311 / 0.8989=2.57%, correction coefficient K = 1 / (1-0.0257) = 1.026.

[0068] (4) Conversion of raw ash as the baseline: Ca(OH)2 content in raw ash = 24.9% × 1.026 × (1 - 0.278) = 18.4%. (Compared with the true background of 18.0% in raw ash, the error is only 0.4%, which proves the high accuracy of the loss compensation model).

[0069] Comparative Example In the same project, the same batch of raw ash samples were taken and analyzed in parallel using the existing single-atmosphere TGA method (the closest existing technology) and EDTA titration method. The comparison results are as follows: Table 3 Comparison of Results between the Method of the Present Invention and Existing Detection Methods Validation of spiked recovery of artificially synthesized standard samples: To objectively verify the absolute accuracy of the method of the present invention and eliminate the interference caused by the unknown composition of the real fly ash, a spike recovery experiment of artificially synthesized standard samples was conducted.

[0070] 1. Sample synthesis: The simulated fly ash matrix was artificially prepared using analytical grade reagents. Its exact composition was: 60% SiO2, 15% CaCl2, 10% CaCO3, 5% CaSO4, and 10% pure Ca(OH)2 (as the target analyte).

[0071] 2. Detection and Calculation: The synthesized sample was subjected to vacuum drying, multi-stage water washing, ethanol washing, and TGA-DSC-FTIR coupled analysis and ICP-OES compensation calculation strictly in accordance with the method described in this invention.

[0072] 3. Results Analysis: The final calculation showed that the detected content of Ca(OH)2 in the synthesized sample was 9.82%.

[0073] The theoretical true value is 10.00%, the absolute error is only -0.18%, and the spiked recovery rate reaches 98.2%.

[0074] In addition, when 5% pure Ca(OH)2 standard was directly added to the real raw ash sample for matrix spiked addition, the detection recovery rate was 102.2%.

[0075] The above spiked recovery experimental data fully demonstrate that the method of the present invention overcomes systematic errors such as CaClOH interference and carbonation interference, has extremely high detection accuracy, and can be directly used as a precise quantitative means of Ca(OH)2 content in complex fly ash matrix.

[0076] Comparative analysis of results: 1. Reasons for the severely inflated results of the single-atmosphere TGA method (29.5% vs 18.4%, an overestimation of 60.3%). (1) Concealed superposition interference between existing CaClOH and in-situ CaClOH: Since no water washing was performed, the raw ash already contained a large amount of semi-dry intermediate product CaClOH. At the same time, 24.0% of CaCl2 in the raw ash continued to generate CaClOH by reacting in-situ with Ca(OH)2 during TGA heating. The dehydration weight loss of these two parts of CaClOH at 450~500℃ was completely misjudged as Ca(OH)2 by the single-atmosphere TGA software, resulting in a surge in the results.

[0077] (2) Dynamic carbonation and organic interference: Trace amounts of CO2 under a single atmosphere cause partial carbonation tailing of Ca(OH)2; at the same time, unremoved organic matter (such as dioxins) volatilizes and loses at 300~500℃, further increasing the false positive rate.

[0078] (3) As demonstrated above, the higher the chlorine content of the raw ash and the more existing CaClOH, the more insurmountable the positive deviation of the single-atmosphere TGA becomes. The washing method of the present invention is the only solution.

[0079] 2. Reasons for the lower EDTA titration result (13.2% vs 18.4%, 28.3% lower) (1) EDTA measures total calcium, which requires the sequential subtraction of CaCl2 (13.6%), CaCO3 (4.5%), sulfate (13.6%), and calcium from existing CaClOH. The fly ash matrix is ​​complex, and there is cross-interference in the determination of calcium in different forms. The errors accumulate during subtraction, resulting in the calculated value of Ca(OH)2 being severely swallowed up.

[0080] (2) This proves that for multiphase complex symbiotic systems, the difference method is logically unreliable and must rely on the direct quantitative method of "online thermal separation + gas traceability" proposed in this invention.

[0081] 3. Proof of the accuracy of the method of this invention The method of this invention achieves a spiked recovery rate of 102.2% with an RSD of only 2.1%. Pre-existing and in-situ CaClOH are eliminated through water washing; organic lattice blocking is broken through ethanol washing; CaCO3 is stripped through a dual-atmosphere "reconstruction window"; false positives are eliminated through FTIR "white-box verification"; and water washing losses are precisely compensated through an ICP kinetic model. These five interconnected steps form a closed-loop technical system that overcomes interference from complex matrices.

[0082] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A precise detection method for calcium hydroxide in fly ash from waste incineration, characterized in that, Includes the following steps: The sample was vacuum dried at 60℃ and then washed in stages: first, it was washed with water at 25℃ and a liquid-to-solid ratio of 20:1 to remove CaCl2 in order to block the CaClOH generation pathway, and then ultrasonically washed with anhydrous ethanol to break the organic matter encapsulation. The pretreated samples were analyzed using a dual-atmosphere TGA-DSC-FTIR system: First, the temperature was slowly increased to 600℃ at 5℃ / min under a pure N2 atmosphere to cut off the carbonation reversal path and construct a Ca(OH)2-specific decomposition window. At the same time, FTIR was used to monitor and confirm that the escaping gas in this range contained only H2O. Then, the temperature was switched to an O2 atmosphere and increased to 850℃ to force the decomposition of CaCO3. The Ca(OH)2 content was calculated by combining the TGA weight loss and DSC peak area methods for cross-calibration. Based on Ca in multi-stage washing solution 2+ The kinetics of concentration decrease were analyzed, and the Ca concentration in the subsequent washing solution was calculated. 2+ The mass of Ca(OH)2 is used to approximate the dissolution loss of Ca(OH)2. A mathematical model is established to decouple the dissolution contributions of CaCl2 and Ca(OH)2. The correction coefficient K is calculated to compensate for the washing loss, and finally converted into the original ash baseline content.

2. The method for accurate detection of calcium hydroxide in waste incineration fly ash according to claim 1, characterized in that, Specifically, the following steps are included: (1) Low-temperature vacuum drying and mechanochemical depolymerization; (2) Multi-stage countercurrent washing under kinetic control to block the CaClOH generation pathway, and collect the filtrate from each water wash, labeled as L1, L2, and L3; (3) Low surface tension solvent deep desorption breaks the lattice blockage of organic matter; (4) Thermodynamic window reconstruction of dual-atmosphere TGA-DSC-FTIR coupled analysis Weigh the pretreated sample and place it in a TGA-DSC-FTIR instrument; The first stage uses an N2 atmosphere: high-purity N2, 50 mL / min, 25℃→10℃ / min heating up→350℃, hold temperature for 5 min→5℃ / min heating up→600℃, hold temperature for 5 min; The second stage uses an O2 atmosphere: switch to O2, 50 mL / min, switch <30 s, 600℃ → 10℃ / min temperature increase → 850℃, hold temperature for 10 min; (5) ICP-OES compensation calculation based on dissolution kinetics decoupling ①TGA-DSC Dual-Mode Cross-Calibration Quantitative Analysis W1 was calculated using the TGA weight loss method; W2 was calculated using the DSC peak area method, and the average value was taken as the content after washing. ② ICP-OES Washing Loss Kinetics Source Tracing and Compensation Determination: The Ca in the three washing solutions L1, L2, and L3 was determined by ICP-OES. 2+ Concentrations C1, C2, C3; Kinetic decoupling and full compensation: Based on the kinetic differences between the rapid dissolution of CaCl2 and the slightly soluble and linearly slow dissolution of Ca(OH)2, the Ca in L1 is set... 2+ The main contributor is CaCl2; simultaneously, the concentration difference ΔC = C2 - C3 between L2 and L3 is considered as the dissolution gradient of Ca(OH)2, and the contribution of Ca(OH)2 to L1 is calculated by linear extrapolation. 2+ Concentration C 1a =C2+ΔC; Loss Calculation: Let the volumes of L1, L2, and L3 after constant volume be V1, V2, and V3, respectively. Then the total mass of calcium ions contributed by the dissolution of Ca(OH)2 is m. Ca =(C2+ΔC)×V1+C2×V2+C3×V3; The amount of Ca(OH)2 lost through dissolution is n. Ca(OH)2 =m Ca / M Ca ; and then calculate the mass of Ca(OH)2 lost through dissolution as m. loss = n Ca(OH)2 ×M Ca(OH)2 ; Precise correction: Calculate the actual loss rate η = m loss / (total mass of sample after washing × preliminary calculated Ca(OH)2 content), derive correction coefficient K=1+η; combined with total weight loss η from washing. m Convert the original ash content to the standard content: W original = [(W1+W2) / 2] × K× (1 - η m ); Where, m Ca : Total mass of calcium ions contributed by Ca(OH)2 dissolution in L2 and L3 washing solutions, unit: mg; C2: Ca in the second washing solution L2 2+ Concentration, unit: mg / L; V2: Volume of the second washing solution L2 after final volume adjustment, unit: L; C3: Ca in the third washing solution L3 2+ Concentration, unit: mg / L; V3: Volume of the third washing solution L3 after final volume adjustment, unit: L; n Ca(OH)2 : Amount of Ca(OH)2 lost through dissolution, unit: mmol; m Ca Total mass of calcium ions contributed by the dissolution of Ca(OH)2, unit: mg; M Ca Molar mass of calcium, in mg / mmol; mloss: Mass of Ca(OH)2 lost through dissolution, in mg; M Ca(OH)2 Molar mass of calcium hydroxide Ca(OH)2, unit: mg / mmol; η: Actual water washing loss rate, unit: % W original : The final actual content of Ca(OH)2 in the raw ash, in % %. W1: Ca(OH)2 content after washing, calculated by TGA weight loss method, in % W2: Ca(OH)2 content after water washing, calculated by DSC peak area method, unit: % K: Washing loss correction coefficient, unit: dimensionless; η m Total weight loss after water washing and ethanol washing, unit: dimensionless, calculation formula: 1 - (total mass of sample after washing / mass of original ash sample).

3. The method for accurate detection of calcium hydroxide in waste incineration fly ash according to claim 2, characterized in that: The specific step (1) is to take the mixed raw ash and place it in a vacuum drying oven, and dry it at 60℃ and -0.09MPa for 4 hours; after taking it out, grind and sieve it.

4. The method for accurate detection of calcium hydroxide in waste incineration fly ash according to claim 3, characterized in that: In step (1), the drying conditions are 60℃ and -0.09MPa for 4 hours.

5. The method for accurate detection of calcium hydroxide in waste incineration fly ash according to claim 3, characterized in that: In step (1), the grinding is done using an agate mortar and pestle and passed through a 75μm standard sieve.

6. The method for accurate detection of calcium hydroxide in waste incineration fly ash according to claim 2, characterized in that: The specific steps (2) are as follows: accurately weigh 5.00g of dried fly ash, add 100mL of deionized water at a liquid-to-solid ratio of 20:1; stir in a constant temperature water bath, use a 0.45μm microporous membrane for vacuum filtration, and rinse the filter cake with 10mL of cold water at 5℃; repeat the washing 3 times, collect the filtrate from each washing, label it as L1, L2, and L3, and make up to a volume for later use.

7. The method for accurate detection of calcium hydroxide in waste incineration fly ash according to claim 6, characterized in that: In step (2), the mixture is magnetically stirred for 10 minutes in a constant temperature water bath at 25±2℃ at a speed of 400-600 r / min.

8. The method for accurate detection of calcium hydroxide in waste incineration fly ash according to claim 6, characterized in that: In step (2), methanol or dilute methanol solution is used to replace deionized water and cold water for washing.

9. The method for accurate detection of calcium hydroxide in waste incineration fly ash according to claim 2, characterized in that: The specific steps (3) are as follows: the water-washed filter cake is transferred and 50 mL of anhydrous ethanol is added at a liquid-to-solid ratio of 10:1; ultrasonic cleaning is performed at 25°C for 10 min with a power of 200 W and a frequency of 40 kHz; then the filter cake is filtered and repeated once; the filter cake is vacuum dried at 60°C for 4 h.

10. The method for accurate detection of calcium hydroxide in waste incineration fly ash according to claim 2, characterized in that: In step (4), the second stage uses N2 / O2 mixture or air instead of pure O2; Alternatively, TGA-MS can be used in conjunction with FTIR to monitor H2O and CO2. Alternatively, the DSC module can be omitted, and the TGA weightlessness method combined with FTIR qualitative analysis can be used for calculation.

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