Method for detecting content of calcium hydroxide in calcium-based desulfurized fly ash

Abstract

The invention relates to the technical field of chemical analysis and detection, and discloses a method for detecting the content of calcium hydroxide in calcium-based desulfurized fly ash. The method comprises the following steps: S1, drying and grinding a calcium-based desulfurization ash sample, and sieving with a 200-mesh sieve to obtain a pretreated sample; s2, the pretreated sample with the mass being W0 is placed in a thermogravimetric analyzer and heated to T at the heating rate of 5-15 DEG C / min in the nitrogen atmosphere, W0 is larger than or equal to 30 mg, and T is larger than or equal to 550 DEG C; s3, the weight loss ratio delta W1 in the interval of 400-550 DEG C is obtained, and the content W1 of calcium hydroxide in the calcium-based desulfurized fly ash is calculated according to a formula. According to the method, the calcium-based desulfurized fly ash is heated to 550 DEG C by utilizing a thermogravimetric analysis method, the weight loss at the interval of 400-550 DEG C is the weight of water lost when calcium hydroxide is decomposed into calcium oxide and water, and the content of the calcium hydroxide can be calculated according to a chemical equation for decomposing the calcium hydroxide and the weight of the lost water. The method is simple to operate and high in accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical analysis and detection, and in particular to a method for detecting the content of calcium hydroxide in calcium-based desulfurization ash. Background Art

[0002] During the calcium-based desulfurization process of coking or sintering flue gas, calcium-based desulfurization byproducts are produced, commonly known as calcium-based desulfurization ash. Its main components include calcium hydroxide, calcium carbonate, calcium sulfite, and calcium sulfate. Accurately measuring the calcium hydroxide content in calcium-based desulfurization ash is of great significance for evaluating desulfurization effects, optimizing process parameters, controlling product quality, and resource utilization of calcium-based desulfurization ash.

[0003] The chemical industry standard HG / T 4120-2009, "Industrial Calcium Hydroxide," specifies a method for detecting industrial calcium hydroxide. Using phenolphthalein as an indicator, it is titrated with a standard hydrochloric acid solution until the solution becomes colorless. The consumed hydrochloric acid solution is used to calculate the calcium hydroxide content. However, this method is susceptible to interference from other metal ions, particularly desulfurization ash, which contains more impurities such as calcium sulfite, which can significantly affect the test results and lead to inaccurate results.

[0004] Chinese patent application CN119827573A discloses a device for detecting calcium oxide in slaked lime and its application. The device includes a display screen, a controller, a reaction vessel, a temperature probe, and an operation panel. The application method includes: calcining calcium oxide at 580°C, placing calcium oxide and calcium hydroxide with gradient concentrations in a reaction vessel, detecting the temperature with a temperature probe, and drawing a standard curve for calcium oxide content; placing a sample to be tested in the reaction vessel, recording the temperature change data Δt1, and calculating the corresponding calcium oxide content based on the standard curve for calcium oxide content. The present invention eliminates the influence of calcium hydroxide content detection by accurately detecting the calcium oxide content in slaked lime, thereby ensuring the accuracy of the calcium hydroxide content detection structure in slaked lime and avoiding the problem of calcium hydroxide content detection data being biased high due to the presence of calcium oxide when using the sucrose method to detect calcium hydroxide content. This method is limited to the detection of slaked lime containing calcium oxide impurities and cannot achieve accurate detection of slaked lime containing impurities such as calcium carbonate and calcium sulfite.

[0005] Currently, common methods for detecting calcium hydroxide include hydrochloric acid titration and XRD diffraction, but this method requires comparison with standard samples and has low quantitative accuracy. There is also infrared spectroscopy, but it is significantly affected by matrix effects and has an error rate of over 15%.

[0006] It can be seen that the existing detection methods for detecting the content of calcium hydroxide in calcium-based desulfurization ash have problems such as large errors and low accuracy. It is urgent to provide a new detection method for detecting the content of calcium hydroxide in calcium-based desulfurization ash. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of large errors and low accuracy in existing detection methods for detecting the content of calcium hydroxide in calcium-based desulfurization ash, and provide a method for detecting the content of calcium hydroxide in calcium-based desulfurization ash. The method directly utilizes the thermal decomposition behavior of calcium hydroxide to achieve quantitative analysis of calcium hydroxide in desulfurization ash. The operation process is simple, the error is small, and the accuracy is high.

[0008] In order to achieve the above object, the present invention provides a method for detecting the content of calcium hydroxide in calcium-based desulfurization ash, which comprises the following steps: S1. Dry, grind, and pass the calcium-based desulfurization ash sample to be tested through a 200-mesh sieve to obtain a pretreated sample; S2. Place the pretreated sample with a mass of W0 in a thermogravimetric analyzer and heat the pretreated sample to T at a heating rate of 5-15°C / min under a nitrogen atmosphere, where W0 ≥ 30 mg and T ≥ 550°C. S3. Obtain the weight loss rate ΔW1 in the range of 400-550°C, and calculate the content of calcium hydroxide W1 in the calcium-based desulfurization ash according to the formula, wherein the units of ΔW1 and W1 are wt%.

[0009] Preferably, in step S1, the calcium hydroxide content in the calcium-based desulfurization ash sample is 10-80wt%, the calcium carbonate content is 5-50wt%, the calcium sulfite content is 0.1-30wt%, the calcium sulfate content is 0.1-30wt%, the calcium oxide content is 1-20wt%, and the content of other components is 0.1-5wt%.

[0010] Preferably, in step S1, the drying conditions include: a temperature of 100-110°C and a time of 1-5 hours.

[0011] Preferably, in step S2, W0 is 30-50 mg.

[0012] Preferably, in step S2, the purity of nitrogen is ≥99.5% by volume, and the flow rate of nitrogen is 40-60 mL / min.

[0013] Preferably, in step S2, T≥800°C.

[0014] Preferably, in step S3, the formula for calculating the calcium hydroxide content W1 in the calcium-based desulfurization ash is: W1=74×ΔW1 / 18 Formula (1).

[0015] Preferably, the method further comprises: S4. Obtain the weight loss rate ΔW2 in the range of 600-800°C, and calculate the calcium carbonate content W2 in the calcium-based desulfurization ash according to the formula, wherein the units of ΔW2 and W2 are wt%.

[0016] Preferably, the formula for calculating the calcium carbonate content W2 in calcium-based desulfurization ash is: W2=100×ΔW2 / 44 equation (2).

[0017] Preferably, the method further comprises: repeating step S2 and step S3 multiple times, and taking an average value of the calcium hydroxide content as a calculation result.

[0018] Preferably, the method further comprises: repeating steps S2 to S4 multiple times, and taking the average value of the calcium hydroxide content and the calcium carbonate content as the calculation result.

[0019] Compared with the prior art, the present invention has at least the following technical effects: Through research, the inventors discovered that using thermogravimetric analysis, the weight loss of complex calcium-based desulfurization ash in the 400-550°C temperature range, measured by heating it at a relatively high temperature rate from room temperature to 550°C or above, can be calculated based on the thermogravimetric curve of the ash. The weight loss represents the weight of water lost when calcium hydroxide decomposes into calcium oxide and water. The calcium hydroxide content can be calculated based on the chemical equation for calcium hydroxide decomposition and the weight of the lost water. This method, which directly utilizes thermal decomposition behavior to quantitatively analyze calcium hydroxide in desulfurization ash, offers a simple operational process, minimal error, and high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the method for detecting the calcium hydroxide content in calcium-based desulfurization ash provided by the present invention. DETAILED DESCRIPTION

[0021] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0022] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0023] Since calcium-based desulfurization ash contains a large number of impurities in addition to calcium hydroxide, such as calcium carbonate, calcium sulfite, calcium sulfate, etc., it is difficult to avoid the influence of impurities with a simple chemical detection method. The inventors have found through research that due to the complex composition of calcium-based desulfurization ash and the presence of multiple calcium compounds, the decomposition temperature of calcium hydroxide and other calcium compounds has changed. After continuous experiments, it was found that by using thermogravimetric analysis, the calcium-based desulfurization ash with complex composition was heated from room temperature to 550°C or above at a specific heating rate. The weight loss in the temperature range of 400-550°C is exactly the weight of water lost when calcium hydroxide decomposes into calcium oxide and water, thereby avoiding the influence of calcium carbonate and calcium sulfate, etc. through temperature zone separation.

[0024] like Figure 1 As shown, the method for detecting the content of calcium hydroxide in calcium-based desulfurization ash provided by the present invention comprises the following steps: S1. Dry, grind, and pass the calcium-based desulfurization ash sample to be tested through a 200-mesh sieve to obtain a pretreated sample; S2. Place the pretreated sample with a mass of W0 in a thermogravimetric analyzer and heat the pretreated sample to T at a heating rate of 5-15°C / min under a nitrogen atmosphere, where W0 ≥ 30 mg and T ≥ 500°C; S3. Obtain the weight loss rate ΔW1 in the range of 400-550°C, and calculate the content of calcium hydroxide W1 in the calcium-based desulfurization ash according to the formula, wherein the units of ΔW1 and W1 are wt%.

[0025] As previously mentioned, the calcium-based desulfurization ash to be tested in the present invention contains components such as calcium hydroxide, calcium carbonate, calcium sulfite, and calcium sulfate. Preferably, in step S1, the calcium hydroxide content in the calcium-based desulfurization ash sample is 10-80wt%, the calcium carbonate content is 5-50wt%, the calcium sulfite content is 0.1-30wt%, the calcium sulfate content is 0.1-30wt%, the calcium oxide content is 1-20wt%, and the content of other components is 0.1-5wt%. When the content of each component in the calcium-based desulfurization ash sample is within the aforementioned range, the decomposition temperature of calcium hydroxide is closer to the 400-550°C range, and the detection result of the calcium hydroxide content is more accurate.

[0026] In the present invention, the drying temperature can be a conventional choice in the art, as long as the water in the calcium hydroxide can be dried without decomposing the calcium compound therein. In some embodiments, in step S1, the drying conditions include: a temperature of 100-110°C and a drying time of 1-5 hours; preferably, the drying temperature is 105°C and the drying time is 2 hours.

[0027] Furthermore, the dried sample was placed in a desiccator and cooled to room temperature before being ground and sieved to avoid moisture absorption affecting the detection accuracy.

[0028] In the present invention, the purpose of grinding and passing through a 200-mesh sieve is to obtain a sample with a smaller particle size, to ensure that the calcium-based desulfurization ash to be tested can be fully decomposed, and to improve the accuracy of the test results.

[0029] To improve the accuracy of the test results, the amount of sample placed in the thermogravimetric analyzer for testing each time cannot be too small, and the sample amount W0 required for testing is required to be ≥ 30 mg; preferably, the sample amount W0 is 30-50 mg. Furthermore, the pretreated sample needs to be evenly spread on the thermogravimetric analyzer sample tray to ensure the uniformity of thermal decomposition and improve the accuracy of the test results. The sample tray of the thermogravimetric analyzer can be made of ceramic material, and a blank sample tray is used to perform baseline zeroing before each test to improve the accuracy of the test results.

[0030] In step S2, the pretreated sample is placed in a thermogravimetric analyzer and heated to 400-550°C. The calcium hydroxide in the sample is decomposed into calcium oxide and water, and the water is lost by evaporation. By reading the weight loss rate in the range of 400-550°C, the calcium hydroxide content in the calcium-based desulfurization ash sample can be calculated based on the chemical equation of calcium hydroxide decomposition and the weight loss rate.

[0031] In the present invention, the purpose of decomposing the sample in a nitrogen atmosphere is to prevent oxygen from decomposing the calcium-based desulfurization ash and affecting the accuracy of the test results. In a preferred embodiment, in step S2, the nitrogen purity is ≥99.5% by volume, and the nitrogen flow rate is 40-60 mL / min. Limiting the nitrogen flow rate to this range avoids nitrogen waste and excessive airflow that affects weight loss.

[0032] In order to control the time of a single test within an appropriate range, to ensure complete decomposition of calcium hydroxide and to avoid simultaneous decomposition of other calcium compounds and calcium hydroxide, which would affect the accuracy of the test results, the present invention heats the pretreated sample to the target temperature T at a heating rate of 5 to 15°C. In some embodiments, the heating rate can be 5°C, 10°C, or 15°C.

[0033] In the present invention, the temperature T can be determined based on the calcium compound being tested. When testing the calcium hydroxide content in calcium-based desulfurization ash, T ≥ 500°C. Since the decomposition temperature of calcium hydroxide in calcium-based desulfurization ash is 400-550°C, it is preferred that, if only the calcium hydroxide content is being tested, the pretreated sample be heated to a temperature of 550°C to better avoid the influence of other calcium-containing compounds.

[0034] Furthermore, in step S3, the formula for calculating the calcium hydroxide content W1 in the calcium-based desulfurization ash is: W1 = 74 × ΔW1 / 18 (Equation (1)). After reading the weight loss rate ΔW1 in the range of 400-550°C, the calcium hydroxide content in the calcium-based desulfurization ash can be more accurately calculated based on Equation (1).

[0035] In the present invention, in order to further improve the accuracy of the calcium hydroxide detection result, the method further includes: repeating steps S2 and S3 multiple times, taking the average value of the calcium hydroxide content as the calculation result. Preferably, in order to save test time, improve detection efficiency, and ensure the accuracy of the test results, steps S2 and S3 are repeated twice, that is, a total of three tests are performed, and the average value of the calcium hydroxide content calculated according to the formula after the three tests is used as the final calculation result.

[0036] Furthermore, the method also includes calibrating the test results: using a standard sample with a known Ca(OH)2 content to establish a weight loss rate-content relationship curve and verify the accuracy of the formula; or, cross-validating the thermogravimetric analysis results with the X-ray diffraction (XRD) quantitative analysis results, and re-testing when the error exceeds 5%.

[0037] Through research, the inventors found that when the calcium-based desulfurization ash contains components such as calcium hydroxide, calcium carbonate, calcium sulfite and calcium sulfate and the aforementioned contents, the weight loss in the temperature range of 400-550°C in thermogravimetric analysis is the weight of water lost when calcium hydroxide is calcium oxide and water, and the weight loss in the temperature range of 600-800°C is the weight of carbon dioxide lost when calcium carbonate decomposes into calcium oxide and carbon dioxide. The weight loss temperature zones of calcium hydroxide and calcium carbonate are well separated, avoiding mutual interference between the two and circumventing the influence of other calcium-containing compounds. Therefore, in addition to detecting the content of calcium hydroxide in calcium-based desulfurization ash, the method of the present invention can also simultaneously detect the content of calcium carbonate in calcium-based desulfurization ash.

[0038] Furthermore, when calcium hydroxide and calcium carbonate in calcium-based desulfurization ash are detected simultaneously, in step S2, T≥800°C. Preferably, in order to further eliminate the influence of other calcium-containing compounds, T=800°C.

[0039] In one embodiment, in order to detect the content of calcium carbonate in calcium-based desulfurization ash, the method further comprises: S4. Obtain the weight loss rate ΔW2 in the range of 600-800°C, and calculate the calcium carbonate content W2 in the calcium-based desulfurization ash according to the formula, wherein the units of ΔW2 and W2 are wt%.

[0040] Furthermore, the formula for calculating the calcium carbonate content W2 in the calcium-based desulfurization ash is: W2 = 100 × ΔW2 / 44 (Equation (2)). After reading the weight loss rate ΔW2 in the 600-800°C range, the calcium carbonate content in the calcium-based desulfurization ash can be more accurately calculated based on Equation (2).

[0041] In the present invention, in order to further improve the accuracy of the calcium hydroxide and calcium carbonate test results, the method further includes: repeating steps S2 to S4 multiple times, taking the average value of the calcium hydroxide content and the calcium carbonate content as the calculation result. Preferably, in order to save test time, improve detection efficiency, and ensure the accuracy of the test results, steps S2 to S4 are repeated twice, that is, the test is performed three times in total, and the average value of the calcium hydroxide content and the calcium carbonate content calculated according to the formula after the three tests is used as the final calculation result.

[0042] In a preferred embodiment, the method comprises: S1. Dry, grind, and pass the calcium-based desulfurization ash sample to be tested through a 200-mesh sieve to obtain a pretreated sample; S2. Place the pretreated sample with a mass of W0 in a thermogravimetric analyzer and heat the pretreated sample to T at a heating rate of 5-15°C / min under a nitrogen atmosphere, where W0 ≥ 30 mg and T = 800°C. S3. Obtain the weight loss rate ΔW1 in the range of 400-550°C, and calculate the content of calcium hydroxide W1 in the calcium-based desulfurization ash according to the formula, where the units of ΔW1 and W1 are wt%; S4. Obtain the weight loss rate ΔW2 in the range of 600-800℃, and calculate the content of calcium carbonate W2 in the calcium-based desulfurization ash according to the formula, where the units of ΔW2 and W2 are wt%; S5. Repeat steps S2 to S4 multiple times, and take the average value of the calculated calcium hydroxide content and calcium carbonate content as the calculation result.

[0043] The method of the present invention can accurately detect the contents of calcium hydroxide and calcium carbonate in calcium-based desulfurization ash with complex components, and the operation process is simple.

[0044] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto.

[0045] In the following examples, it is known that the content of calcium hydroxide in the calcium-based desulfurization ash sample is 54.5wt%, the content of calcium carbonate is 24.8wt%, the content of calcium sulfite is 2.4wt%, the content of calcium sulfate is 1.7wt%, the content of calcium oxide is 14.5wt%, and the content of other components is 2.1wt%.

[0046] Example 1 (1) Take 50g of calcium-based desulfurization ash sample, place it in an oven at 105℃ and dry it for 2 hours, grind it through a 200-mesh sieve to obtain a pretreated sample; (2) Accurately weigh 30 mg of the pretreated sample, evenly spread it on a ceramic sample plate and place it in a thermogravimetric analyzer. A nitrogen atmosphere with a purity of 99.5% and a flow rate of 40 mL / min was introduced. The pretreated sample was heated from room temperature to 550 °C at a heating rate of 10 °C / min under a nitrogen atmosphere. (3) After the heating is completed, read the weight loss rate ΔW1 in the range of 400-550°C; calculate the calcium hydroxide content W1 according to the formula W1=74×ΔW1 / 18; (4) Repeat steps (2) and (3) twice to obtain three weight loss rate ΔW1 data; according to the formula W1=74×ΔW1 / 18, the calcium hydroxide content W1 of the three times is calculated to be 55.95%, 55.62%, and 53.04%, respectively. The average value of the three times is taken, and the calcium hydroxide content in the desulfurization ash is 54.87%.

[0047] In this embodiment, the detection error of the calcium hydroxide content in the calcium-based desulfurization ash is: (54.87-54.5) / 54.5 x100% = 0.68%.

[0048] Example 2 (1) Take 50g of calcium-based desulfurization ash sample, place it in an oven at 108℃ and dry it for 3 hours, grind it through a 200-mesh sieve to obtain a pretreated sample; (2) Accurately weigh 40 mg of the pretreated sample, evenly spread it on a ceramic sample plate and place it in a thermogravimetric analyzer. A nitrogen atmosphere with a purity of 99.5% and a flow rate of 50 mL / min was introduced. The pretreated sample was heated from room temperature to 550 °C at a heating rate of 15 °C / min under a nitrogen atmosphere. (3) After the heating is completed, read the weight loss rate ΔW1 in the range of 400-550°C; calculate the calcium hydroxide content W1 according to the formula W1=74×ΔW1 / 18; (4) Repeat steps (2) and (3) twice to obtain three weight loss rate ΔW1 data; according to the formula W1=74×ΔW1 / 18, the calcium hydroxide content W1 of the three times is calculated to be 53.22%, 55.16%, and 54.39%, respectively. The average value of the three times is taken, and the calcium hydroxide content in the desulfurization ash is 54.26%.

[0049] In this embodiment, the detection error of the calcium hydroxide content in the calcium-based desulfurization ash is: (54.26-54.5) / 54.5 x100% = -0.44%.

[0050] Example 3 (1) Take 50g of calcium-based desulfurization ash sample, place it in an oven at 110℃ and dry it for 2 hours, grind it through a 200-mesh sieve to obtain a pretreated sample; (2) Accurately weigh 50 mg of the pretreated sample, evenly spread it on a ceramic sample plate and place it in a thermogravimetric analyzer. A nitrogen atmosphere with a purity of 99.5% and a flow rate of 60 mL / min was introduced. The pretreated sample was heated from room temperature to 550 °C at a heating rate of 8 °C / min under a nitrogen atmosphere. (3) After the heating is completed, read the weight loss rate ΔW1 in the range of 400-550°C; calculate the calcium hydroxide content W1 according to the formula W1=74×ΔW1 / 18; (4) Repeat steps (2) and (3) twice to obtain three weight loss rate ΔW1 data; according to the formula W1=74×ΔW1 / 18, the calcium hydroxide content W1 of the three times is calculated to be 54.18%, 54.58%, and 53.47%, respectively. The average value of the three times is taken, and the calcium hydroxide content in the desulfurization ash is 54.08%.

[0051] In this embodiment, the detection error of the calcium hydroxide content in the calcium-based desulfurization ash is: (54.08-54.5) / 54.5 x100% = -0.77%.

[0052] Example 4 The method of Example 1 was followed, except that the contents of calcium hydroxide and calcium carbonate were detected simultaneously.

[0053] The method includes: (1) Take 50g of calcium-based desulfurization ash sample, place it in an oven at 105℃ and dry it for 2 hours, grind it through a 200-mesh sieve to obtain a pretreated sample; (2) Accurately weigh 30 mg of the pretreated sample, evenly spread it on a ceramic sample plate and place it in a thermogravimetric analyzer. A nitrogen atmosphere with a purity of 99.5% and a flow rate of 40 mL / min was introduced. The pretreated sample was heated from room temperature to 800 °C at a heating rate of 10 °C / min under a nitrogen atmosphere. (3) After the heating is completed, read the weight loss rate ΔW1 in the range of 400-550℃, and calculate the content of calcium hydroxide W1 in the calcium-based desulfurization ash according to the formula W1=74×ΔW1 / 18, where the units of ΔW1 and W1 are wt%; (4) Read the weight loss rate ΔW2 in the range of 600-800℃, and calculate the calcium carbonate content W2 in the calcium-based desulfurization ash according to the formula W2=100×ΔW2 / 44, where the units of ΔW2 and W2 are wt%; (5) Repeat steps (2) to (4) twice to obtain three weight loss rate ΔW1 and ΔW2 data; According to the formula W1=74×ΔW1 / 18, the calcium hydroxide content W1 in the three calcium-based desulfurization ash is calculated to be 54.67%, 55.64%, and 54.23% respectively. Taking the average of the three times, the calcium hydroxide content in the desulfurization ash is 54.85%; According to the formula W2=100×ΔW2 / 44, the calcium carbonate content W2 in the three calcium-based desulfurization ash is calculated to be 24.51%, 25.51%, and 24.68% respectively. Taking the average of the three times, the calcium carbonate content in the desulfurization ash is 24.9%.

[0054] In this embodiment, the detection error of the calcium hydroxide content in the calcium-based desulfurization ash is: (54.85-54.5) / 54.5 x 100% = 0.64%; the detection error of calcium carbonate is: (24.9-24.8) / 24.8 x 100% = 0.40%.

[0055] Comparative Example 1 The method of Example 1 was followed, except that nitrogen was not introduced in step (2).

[0056] The specific operation process includes: (1) Take 50g of calcium-based desulfurization ash sample, place it in an oven at 105℃ and dry it for 2 hours, grind it through a 200-mesh sieve to obtain a pretreated sample; (2) Accurately weigh 30 mg of the pretreated sample, spread it evenly on a ceramic sample plate and place it in a thermogravimetric analyzer; heat the pretreated sample from room temperature to 550°C at a heating rate of 10°C / min; (3) After the heating is completed, read the weight loss rate ΔW1 in the range of 400-550°C; calculate the calcium hydroxide content W1 according to the formula W1=74×ΔW1 / 18; (4) Repeat steps (2) and (3) twice to obtain three weight loss rate ΔW1 data; according to the formula W1=74×ΔW1 / 18, the calcium hydroxide content W1 of the three times is calculated to be 50.79%, 53.40%, and 52.74%, respectively. The average value of the three times is taken, and the calcium hydroxide content in the desulfurization ash is 52.31%.

[0057] In this comparative example, the detection error of the calcium hydroxide content in the calcium-based desulfurization ash is: (52.31-54.5) / 54.5 x100% = -4.02%.

[0058] Comparative Example 2 The method of Example 1 was followed, except that the amount of pretreated sample added in step (2) was smaller.

[0059] The specific operation process includes: (1) Take 50g of calcium-based desulfurization ash sample, place it in an oven at 105℃ and dry it for 2 hours, grind it through a 200-mesh sieve to obtain a pretreated sample; (2) Accurately weigh 20 mg of the pretreated sample, evenly spread it on a ceramic sample plate and place it in a thermogravimetric analyzer. A nitrogen atmosphere with a purity of 99.5% and a flow rate of 40 mL / min was introduced. The pretreated sample was heated from room temperature to 550 °C at a heating rate of 10 °C / min under a nitrogen atmosphere. (3) After the heating is completed, read the weight loss rate ΔW1 in the range of 400-550°C; calculate the calcium hydroxide content W1 according to the formula W1=74×ΔW1 / 18; (4) Repeat steps (2) and (3) twice to obtain three weight loss rate ΔW1 data; according to the formula W1=74×ΔW1 / 18, the calcium hydroxide content W1 of the three times is calculated to be 49.46%, 49.24%, and 48.55%, respectively. The average value of the three times is taken, and the calcium hydroxide content in the desulfurization ash is 49.08%.

[0060] In this comparative example, the detection error of the calcium hydroxide content in the calcium-based desulfurization ash is: (49.08-54.5) / 54.5 x100% = -9.94%.

[0061] Comparative Example 3 The method of Example 1 was followed, except that the heating rate in step (2) was 2°C / min.

[0062] The specific operation process includes: (1) Take 50g of calcium-based desulfurization ash sample, place it in an oven at 105℃ and dry it for 2 hours, grind it through a 200-mesh sieve to obtain a pretreated sample; (2) Accurately weigh 30 mg of the pretreated sample, evenly spread it on a ceramic sample plate and place it in a thermogravimetric analyzer. A nitrogen atmosphere with a purity of 99.5% and a flow rate of 40 mL / min was introduced. The pretreated sample was heated from room temperature to 550 °C at a heating rate of 2 °C / min under a nitrogen atmosphere. (3) After the heating is completed, read the weight loss rate ΔW1 in the range of 400-550°C; calculate the calcium hydroxide content W1 according to the formula W1=74×ΔW1 / 18; (4) Repeat steps (2) and (3) twice to obtain three weight loss rate ΔW1 data; according to the formula W1=74×ΔW1 / 18, the calcium hydroxide content W1 of the three times is calculated to be 50.67%, 51.64%, and 51.75%, respectively. The average value of the three times is taken, and the calcium hydroxide content in the desulfurization ash is 51.35%.

[0063] In this comparative example, the detection error of the calcium hydroxide content in the calcium-based desulfurization ash is: -5.78%.

[0064] Comparative Example 4 The method of Example 4 was followed, except that the amount of pretreated sample added in step (2) was smaller.

[0065] (1) Take 50g of calcium-based desulfurization ash sample, place it in an oven at 105℃ and dry it for 2 hours, grind it through a 200-mesh sieve to obtain a pretreated sample; (2) Accurately weigh 20 mg of the pretreated sample, evenly spread it on a ceramic sample plate and place it in a thermogravimetric analyzer. A nitrogen atmosphere with a purity of 99.5% and a flow rate of 40 mL / min was introduced. The pretreated sample was heated from room temperature to 800 °C at a heating rate of 10 °C / min under a nitrogen atmosphere. (3) After the heating is completed, read the weight loss rate ΔW1 in the range of 400-550℃, and calculate the content of calcium hydroxide W1 in the calcium-based desulfurization ash according to the formula W1=74×ΔW1 / 18, where the units of ΔW1 and W1 are wt%; (4) Read the weight loss rate ΔW2 in the range of 600-800℃, and calculate the calcium carbonate content W2 in the calcium-based desulfurization ash according to the formula W2=100×ΔW2 / 44, where the units of ΔW2 and W2 are wt%; (5) Repeat steps (2) to (4) twice to obtain three weight loss rate ΔW1 and ΔW2 data; According to the formula W1=74×ΔW1 / 18, the calcium hydroxide content W1 in the three calcium-based desulfurization ash is calculated to be 50.45%, 50.14%, and 52.31% respectively. Taking the average of the three times, the calcium hydroxide content in the desulfurization ash is 50.97%; According to the formula W2=100×ΔW2 / 44, the calcium carbonate content W2 in the three calcium-based desulfurization ash is calculated to be 20.05%, 22.36%, and 21.54% respectively. Taking the average of the three times, the calcium carbonate content in the desulfurization ash is 21.32%.

[0066] In this comparative example, the detection error of the calcium hydroxide content in the calcium-based desulfurization ash is: -6.48%; the detection error of calcium carbonate is: -8.60%.

[0067] It can be seen from the above examples and comparative examples that the method described in the present invention is used to detect the contents of calcium hydroxide and calcium carbonate in calcium-based desulfurization ash, and the detection results are more accurate, and the error can be controlled within ±1%.

[0068] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0069] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for detecting the content of calcium hydroxide in calcium-based desulfurization ash, characterized in that: The method comprises the following steps: S1. Dry, grind, and pass the calcium-based desulfurization ash sample to be tested through a 200-mesh sieve to obtain a pretreated sample; S2. Place the pretreated sample with a mass of W0 in a thermogravimetric analyzer and heat the pretreated sample to T at a heating rate of 5-15°C / min under a nitrogen atmosphere, where W0 ≥ 30 mg and T ≥ 550°C; S3. Obtain the weight loss rate ΔW1 in the range of 400-550°C, and calculate the calcium hydroxide content W1 in the calcium-based desulfurization ash according to the formula, wherein the units of ΔW1 and W1 are wt%.

2. The method according to claim 1, characterized in that In step S1, the calcium hydroxide content in the calcium-based desulfurization ash sample is 10-80wt%, the calcium carbonate content is 5-50wt%, the calcium sulfite content is 0.1-30wt%, the calcium sulfate content is 0.1-30wt%, the calcium oxide content is 1-20wt%, and the content of other components is 0.1-5wt%.

3. The method according to claim 1, characterized in that In step S1, the drying conditions include: a temperature of 100-110°C and a time of 1-5 hours.

4. The method according to claim 1 or 2, characterized in that In step S2, W0 is 30-50 mg; And / or, in step S2, the purity of nitrogen is ≥99.5% by volume, and the flow rate of nitrogen is 40-60 mL / min.

5. The method according to claim 1, wherein In step S2, T≥800°C.

6. The method according to claim 1 or 2, characterized in that In step S3, the formula for calculating the calcium hydroxide content W1 in the calcium-based desulfurization ash is: W1=74×ΔW1 / 18 Formula (1).

7. The method according to claim 5, characterized in that The method further includes: S4. Obtain the weight loss rate ΔW2 in the range of 600-800°C, and calculate the calcium carbonate content W2 in the calcium-based desulfurization ash according to the formula, wherein the units of ΔW2 and W2 are wt%.

8. The method according to claim 7, characterized in that The formula for calculating the calcium carbonate content W2 in calcium-based desulfurization ash is: W2=100×ΔW2 / 44 equation (2).

9. The method according to claim 1, characterized in that The method further includes: repeating step S2 and step S3 multiple times, and taking an average value of the calcium hydroxide content as a calculation result.

10. The method according to claim 7, characterized in that The method further includes: repeating steps S2 to S4 multiple times, and taking the average value of the calcium hydroxide content and the calcium carbonate content as a calculation result.

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