Method for detecting content of calcium oxide in fly ash

Abstract

The invention discloses a method for detecting the content of calcium oxide in fly ash, which comprises the following steps: S1, grinding a fly ash sample in a planetary ball mill to form a fine fly ash material, and putting part of the fine fly ash material in a crucible; s2, weighing an ion exchanger, placing the ion exchanger in the crucible, and uniformly mixing the fine fly ash with the ion exchanger to form a mixture; s3, the crucible is placed in a high-temperature furnace, and the mixture is fully melted and reacted to form a solid mixture; and S4, after the high-temperature furnace is heated and shut down for cooling, the solid mixture in the crucible is taken out and placed in a planetary ball mill to be ground into powder. According to the method, the content of calcium oxide in the fly ash can be accurately detected under the condition that controlled medicine reagents are not used, so that an engineering laboratory can carry out detection on site, a detection result can be quickly and timely obtained, and time delay caused by entrusting a rear or external laboratory for detection is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of fly ash detection, and in particular to a method for detecting calcium oxide content in fly ash. Background Art

[0002] Fly ash refers to the powder collected from the flue gas of the pulverized coal furnace of a power plant, and does not include the powder collected when burning urban garbage or other wastes together with coal, or when burning industrial or urban garbage in an incinerator, or from the combustion of a circulating fluidized bed boiler. The national standard "Fly Ash for Cement and Concrete" divides fly ash into Class F fly ash and Class C fly ash according to the type of coal burned. Class C fly ash is collected by burning lignite or sub-bituminous coal, and the calcium oxide content is generally greater than or equal to 10%.

[0003] The chemical composition of ash of typical coal types in my country is obviously different. From the analysis of elemental composition, the chemical composition of ordinary fly ash is SiO2>Al2O3>Fe2O3>CaO>MgO>K2O>Na2O. From the analysis of mineral composition, fly ash is mainly composed of glass, mineral crystals and unburned carbon. According to field investigations and literature reports, most of the fly ash produced by coal-fired power plants in some parts of my country is Class C fly ash, which has obvious characteristics of high calcium and high alkali. The specificity of chemical composition, especially calcium oxide content, will have an important impact on the physical and chemical properties and hydration properties of fly ash, and may further affect the mechanical properties, deformation properties, thermal properties and durability of the concrete prepared therefrom. In order to ensure the quality and safety of concrete buildings, it is necessary to control the calcium oxide content of high calcium fly ash.

[0004] Therefore, the detection method of calcium oxide content in fly ash is particularly important. The calcium element in fly ash generally exists in the form of crystalline phases such as grossamite, feldspar, pyroxene, calcite, levofloxacin, etc. It is insoluble in water and has a low leaching rate. The calcium in the crystal must be converted into free calcium before it can be detected. The current method for detecting calcium oxide content in fly ash is the "Cement Chemical Analysis Method". The principle of this test method is to melt the fly ash sample, dissolve the sintered block with hydrochloric acid and nitric acid, and then filter, treat with sulfuric acid and hydrofluoric acid to destroy the calcium-containing crystal structure, and then titrate with EDTA standard titration solution in a strong alkaline solution with triethanolamine as a masking agent and calcein-methylthymol blue-phenolphthalein mixed indicator (referred to as CMP mixed indicator) in a pH>13 strong alkaline solution. The test process of this method is complicated, and it is necessary to use controlled drugs such as hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid that are easy to make drugs and explosives. The drugs are difficult to obtain and have certain toxic risks. As for the on-site inspection and quality control of fly ash at the construction site, the laboratory does not have the ability to use this method to carry out calcium oxide content testing. If the samples are entrusted to a rear laboratory, there will be a problem of insufficient timeliness in the test.

[0005] Other methods for detecting calcium ions in water, such as ion selective electrode method, atomic absorption method, flame photometry, etc., all require the conversion of crystalline calcium in fly ash into free calcium in aqueous solution, and therefore cannot avoid the aforementioned controlled drugs that are easy to make drugs and explosives.

[0006] In addition, colleges and research institutions also use XRD (X-ray diffraction) method to detect the mineral components in cement and fly ash. On this basis, they have developed advanced Q-XRD quantitative methods. The content of various mineral components can be calculated by least squares fitting, and the calcium oxide content can be further calculated according to the content of calcium-containing minerals. This method directly detects crystals, so strong acid treatment is not required. However, the problems with this method are: 1. The instruments and equipment are expensive, costing several million yuan per unit, and the test environment conditions are high. The scientific literacy and operation level of the personnel are high, so a lot of resources need to be invested; 2. The existing quantitative methods are based on the fitting results of the proposed mineral composition, not the measured values, so the accuracy varies greatly for different samples, and the test results are affected by the test personnel's cognitive ability of the samples; 3. Since there are a lot of glass in fly ash, on the one hand, it will interfere with the calculation results of Q-XRD, and on the other hand, the calcium content in the glass cannot be accurately determined, which will lead to inaccurate test results. In general, the Q-XRD method can be used as a research method to detect the calcium oxide content in fly ash, but the current method is not mature and the test results are not accurate.

[0007] In summary, the current method for detecting calcium oxide content in fly ash has the following technical problems:

[0008] 1. Traditional chemical detection methods must use controlled drugs such as hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid that are easy to make drugs and explosives. They are not available in the on-site laboratory of the project and there are toxic and harmful risks;

[0009] 2. The advanced Q-XRD detection method has high requirements on equipment and personnel and is not suitable for on-site detection. In addition, due to the presence of glass, the accuracy of this method in detecting the calcium oxide content of fly ash is not high.

[0010] In order to meet the requirements of on-site inspection and quality control of fly ash for engineering, a new method for detecting calcium oxide content in fly ash is needed. The requirements are as follows:

[0011] 1. It is not necessary to use controlled drugs that are easy to make drugs or explosives, such as hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid;

[0012] 2. The cost of the instrument and equipment is controllable, the operation is simple, and the repeatability and reproducibility of the method are good;

[0013] 3. Suitable for rapid testing at construction sites. Summary of the invention

[0014] The present invention provides a method for detecting the calcium oxide content in fly ash, which does not require the use of controlled drugs such as hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid that are easy to make drugs and explosions, and is suitable for rapid detection at engineering sites.

[0015] The technical solution of the present invention is achieved in this way:

[0016] A method for detecting calcium oxide content in fly ash, comprising:

[0017] S1. The fly ash sample is ground in a planetary ball mill to form fine fly ash material, and a portion of the fine fly ash material is placed in a crucible;

[0018] S2, weighing an ion exchanger, placing it in the above-mentioned crucible, and uniformly mixing the fine fly ash and the ion exchanger to form a mixture;

[0019] S3, placing the above crucible in a high temperature furnace to allow the above mixture to fully melt and react to form a solid mixture;

[0020] S4, after the high temperature furnace is heated and stopped for cooling, the solid mixture in the crucible is taken out and placed in a planetary ball mill for grinding to form a powder material;

[0021] S5. Place the collected powder in a 250 mL dry conical flask, add 30 mL of ethylene glycol-ethanol solution (2+1) to the conical flask, then place a magnetic bar in the conical flask, install a condenser, stir the solution at a speed of 30-100 r / min, and heat it for 3 minutes until it boils;

[0022] S6. After the conical flask is heated, condense it. When the condensed ethanol begins to drip continuously, continue to boil slightly for 5 minutes, remove the conical flask, and immediately titrate it with benzoic acid-anhydrous ethanol standard titration solution using phenolphthalein as an indicator until the reddish color disappears, and calculate the total calcium content using the total calcium content calculation formula;

[0023] S7, weigh about 1g of fly ash sample, execute steps S5 and S6, and calculate the free calcium oxide content in the fly ash using the free calcium oxide content calculation formula;

[0024] S8. Use the calcium oxide content calculation formula to calculate the calcium oxide in fly ash.

[0025] Preferably, the fly ash sample in step S1 weighs 10 g, the grinding time of the planetary ball mill is 10 min, and the weight of the intercepted fine fly ash material is 1.0000 g.

[0026] Preferably, the ion exchanger in step S2 is a metal salt, which can be one or a mixture of sodium carbonate, potassium carbonate, sodium chloride, magnesium oxide, and magnesium chloride. The amount of the ion exchanger is 30% to 100% of the mass of the fine fly ash in step S2.

[0027] Preferably, the high temperature of the high temperature furnace in step S3 is 900-1000° C., and the constant temperature time of the high temperature furnace is 30 minutes-3 hours.

[0028] Preferably, the grinding time of the planetary ball mill in step S4 is 10 min.

[0029] Preferably, the ethanol concentration in step S5 needs to be greater than or equal to 99.5% by volume.

[0030] Preferably, the total calcium content calculation formula in step S6 is:

[0031]

[0032] Where w(Ca) is the total calcium content, T cao is the titration degree of calcium oxide, m1 is the mass of the intercepted fine fly ash, and V1 is the volume of the consumed standard titration solution, accurate to 0.01 mL.

[0033] Preferably, the benzoic acid-anhydrous ethanol standard titration solution in step S6 needs to use calcium oxide burned by calcium carbonate reference reagent to determine its titer for calcium oxide. The specific operation of determining the titer for calcium oxide is:

[0034] Weigh about 0.04g of newly burned and cooled calcium oxide, accurate to 0.0001g, and place it in a 250mL dry conical flask, add 30mL of ethylene glycol-ethanol solution (2+1), put in a magnetic rod, install a condenser, stir the solution at an appropriate speed, and heat it to boil. When the condensate begins to drip continuously, continue to boil slightly for 5 minutes, remove the conical flask, use phenolphthalein as an indicator, and immediately titrate with benzoic acid-anhydrous ethanol standard titration solution until the reddish color disappears. Use the titration formula of calcium oxide to calculate the titration of benzoic acid-anhydrous ethanol standard titration solution to calcium oxide. The calculation formula is:

[0035]

[0036] Where, T cao is the titration degree of calcium oxide, V is the volume of the consumed standard titration solution, m is the mass of the intercepted fine fly ash material, and 1000 is the conversion coefficient from mg / mL to g / mL.

[0037] Preferably, the free calcium oxide content calculation formula in step S7 is:

[0038]

[0039] Where w(f-CaO) is the free calcium oxide content, T CaO is the titration degree of calcium oxide, V2 is the volume of the consumed standard titration solution, and m2 is the mass of the fly ash sample, accurate to 0.0001g.

[0040] Preferably, the calcium oxide content calculation formula in step S8 is:

[0041] w(CaO)=w(Ca)-w(f-CaO)

[0042] Wherein, w(CaO) is the calcium oxide content, w(Ca) is the total calcium content, and w(f-CaO) is the free calcium oxide content.

[0043] Beneficial effects:

[0044] The present invention can convert the calcium compound in the fly ash in the form of crystals, which can only be dissolved in inorganic strong acid (concentrated nitric acid, concentrated hydrochloric acid) but not in aqueous solution, into free calcium oxide through ion (element) replacement and measure it.

[0045] The present invention can accurately detect the calcium oxide content in fly ash without using controlled pharmaceutical reagents, so that engineering laboratories can carry out on-site testing and obtain test results quickly and timely, avoiding time delays caused by entrusting the testing to a rear or external laboratory.

[0046] This method has low requirements on equipment, concise steps, simple operation, good repeatability and reproducibility of results, and is suitable for rapid detection at engineering sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 The present invention is a process flow chart of a method for detecting calcium oxide content in fly ash according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0050] According to an embodiment of the present invention, a method for detecting calcium oxide content in fly ash is provided.

[0051] like Figure 1 As shown, in this optional embodiment, the method for detecting calcium oxide content in fly ash according to an embodiment of the present invention includes:

[0052] Step S1, placing a fly ash sample in a planetary ball mill and grinding it to form fine fly ash material, and taking a portion of the fine fly ash material and placing it in a crucible;

[0053] Step S2, weighing an ion exchanger, placing it in the above-mentioned crucible, and uniformly mixing the fine fly ash and the ion exchanger to form a mixture;

[0054] Step S3, placing the crucible in a high temperature furnace to allow the mixture to fully melt and react to form a solid mixture;

[0055] Step S4, after the high temperature furnace is heated and stopped for cooling, the solid mixture in the crucible is taken out and placed in a planetary ball mill for grinding to form a powder material;

[0056] Step S5, placing the collected powder material in a 250 mL dry conical flask, adding 30 mL of ethylene glycol-ethanol solution (2+1) into the conical flask, then placing a magnetic bar into the conical flask, installing a condenser, stirring the solution at a speed of 30 to 100 r / min, and heating the solution for 3 minutes until boiling;

[0057] Step S6, after the conical flask is heated, condense it, and when the condensed ethanol begins to drip continuously, continue to boil slightly for 5 minutes, remove the conical flask, and immediately titrate it with a benzoic acid-anhydrous ethanol standard titration solution using phenolphthalein as an indicator until the reddish color disappears, and calculate the total calcium content using the total calcium content calculation formula;

[0058] Step S7, weighing about 1g of fly ash sample, executing steps S5 and S6, and calculating the free calcium oxide content in the fly ash using the free calcium oxide content calculation formula;

[0059] Step S8, calculating the calcium oxide content in the fly ash using a calcium oxide content calculation formula.

[0060] In this optional embodiment, the temperature for the mixed reaction of the granular aluminum-containing material and the sodium hydroxide solution is 50-70° C., the reaction time is 1-4 hours, and the mixing and stirring speed is 100-500 r / min.

[0061] In this optional embodiment, the weight of the fly ash sample described in step S1 is 10g, the grinding time of the planetary ball mill is 10min, and the weight of the intercepted fine fly ash material is 1.0000g. The purpose of step S1 is to partially crush the surface of the fly ash micro-beads, which can accelerate the melting reaction of S3. Other weighing quantities or crushing methods can achieve this purpose, such as weighing 1g of sample and grinding it manually with an agate mortar.

[0062] In this optional embodiment, the ion exchanger in step S2 is a metal salt, which can be one or a mixture of sodium carbonate, potassium carbonate, sodium chloride, magnesium oxide, and magnesium chloride. The amount of the ion exchanger is 30% to 100% of the mass of the fine fly ash in step S2. The type of ion exchanger can also be other types of metal salts. The amount of the ion exchanger can also vary within other appropriate ranges. Changing the type and amount of the ion exchanger will result in different replacement efficiency of the crystalline phase calcium element in the fly ash.

[0063] In this optional embodiment, the high temperature of the high temperature furnace described in step S3 is 900-1000°C, and the constant temperature time of the high temperature furnace is 30 minutes to 3 hours. The purpose of step S3 is to allow the calcium element existing in the crystalline phase (such as calcium aluminum feldspar, feldspar, pyroxene, calcite, white asperity, etc.) in the fly ash to be exchanged by the metal element in the ion exchanger and converted into a free calcium compound. Other suitable temperature ranges and constant temperature times can also be used.

[0064] In this optional embodiment, the grinding time of the planetary ball mill in step S4 is 10 minutes. The purpose of grinding in step S4 is to increase the specific surface area of ​​the solid product so that it can react faster in step S5. Other crushing methods can also be used.

[0065] In this optional embodiment, the ethanol concentration volume fraction in step S5 needs to be greater than or equal to 99.5%. If it is less than 99.5%, it needs to be distilled before use. The ethylene glycol-ethanol solution needs to be neutralized with 0.1 mol / L sodium hydroxide-anhydrous ethanol to a slightly reddish color, and it needs to be sealed and stored to prevent the absorption of water and carbon dioxide. The slightly reddish color of the ethylene glycol-ethanol solution will fade or become lighter after long-term storage, and at this time, it is neutralized with 0.1 mol / L sodium hydroxide-anhydrous ethanol to a slightly reddish color.

[0066] In this optional embodiment, the total calcium content calculation formula in step S6 is:

[0067]

[0068] Where w(Ca) is the total calcium content, T cao is the titration degree of calcium oxide, m1 is the mass of the intercepted fine fly ash, and V1 is the volume of the consumed standard titration solution, accurate to 0.01 mL.

[0069] In this optional embodiment, the benzoic acid-anhydrous ethanol standard titration solution in step S6 needs to use calcium oxide burned by calcium carbonate reference reagent to determine its titer for calcium oxide. The specific operation of determining the titer of calcium oxide is:

[0070] Weigh about 0.04g of newly burned and cooled calcium oxide, accurate to 0.0001g, and place it in a 250mL dry conical flask, add 30mL of ethylene glycol-ethanol solution (2+1), put in a magnetic rod, install a condenser, stir the solution at an appropriate speed, and heat it to boil. When the condensate begins to drip continuously, continue to boil slightly for 5 minutes, remove the conical flask, use phenolphthalein as an indicator, and immediately titrate with benzoic acid-anhydrous ethanol standard titration solution until the reddish color disappears. Use the titration formula of calcium oxide to calculate the titration of benzoic acid-anhydrous ethanol standard titration solution to calcium oxide. The calculation formula is:

[0071]

[0072] Where, T cao is the titration degree of calcium oxide, V is the volume of the consumed standard titration solution, m is the mass of the intercepted fine fly ash material, and 1000 is the conversion coefficient from mg / mL to g / mL.

[0073] In this optional embodiment, the free calcium oxide content calculation formula in step S7 is:

[0074]

[0075] Where w(f-CaO) is the free calcium oxide content, T CaO is the titration degree of calcium oxide, V2 is the volume of the consumed standard titration solution, and m2 is the mass of the fly ash sample, accurate to 0.0001g.

[0076] In this optional embodiment, the calcium oxide content calculation formula in step S8 is:

[0077] w(CaO)=w(Ca)-w(f-CaO)

[0078] Wherein, w(CaO) is the calcium oxide content, w(Ca) is the total calcium content, and w(f-CaO) is the free calcium oxide content. In step S8, the non-free calcium oxide content in the fly ash is calculated by deducting the free calcium oxide content from the total calcium content (free plus non-free). The free calcium oxide can be measured directly, and the total calcium content is measured by converting the calcium element into free calcium oxide.

[0079] In order to facilitate understanding of the above technical solution of the present invention, the above technical solution of the present invention is further described below:

[0080] 1. Method Summary:

[0081] After the fly ash is ground, the surface of the micro-beads is broken, making the subsequent melting reaction easier to occur; an ion exchanger is added to make the mixture undergo a eutectic reaction at high temperature, so that the calcium compounds in the fly ash that exist in the form of crystals and can only be dissolved in strong inorganic acids (concentrated nitric acid, concentrated hydrochloric acid) but not in aqueous solutions are converted into free calcium oxide through ion (element) replacement; the solid product after the eutectic reaction is ground, and the total calcium content in the solution is detected using a benzoic acid-anhydrous ethanol standard titration solution; then a fly ash sample is taken to directly determine the free calcium oxide content; according to the conservation of mass of the calcium element, the calcium oxide (non-free) content in the fly ash is the total calcium content minus the free calcium oxide content.

[0082] 2. Equipment and reagents:

[0083] Main instruments and equipment: planetary ball mill (or mortar), electronic analytical balance, high temperature resistance furnace, basic burette, distillation glass device;

[0084] Main reagents: ion exchanger, 0.1 mol / L sodium hydroxide-anhydrous ethanol solution, ethylene glycol-anhydrous ethanol solution (2+1), 0.1 mol / L benzoic acid-anhydrous ethanol solution, phenolphthalein indicator, etc.

[0085] 3. Analysis steps

[0086] (1) Reagent preparation: prepare a benzoic acid-anhydrous ethanol standard titration solution [c(C6H5COOH)=0.1 mol / L], and determine the titration degree of the benzoic acid-anhydrous ethanol standard titration solution against calcium oxide. The operation is as follows:

[0087] Weigh about 0.04g of newly burned and cooled calcium oxide mg, measured 0.0404g, put it in a 250mL dry conical flask, add 30mL of ethylene glycol-ethanol solution (2+1), put in a magnetic rod, install a condenser, stir the solution at a speed of 300r / min, and heat and boil at the same time. When the condensate begins to drip continuously, continue to boil slightly for 5min, remove the conical flask, use phenolphthalein as an indicator, and immediately titrate with benzoic acid-anhydrous ethanol standard titration solution until the reddish color disappears, and the volume of the standard titration solution consumed is V=14.21mL. The titer of benzoic acid-anhydrous ethanol standard titration solution to calcium oxide is calculated by the calcium oxide titer calculation formula to obtain 2.843mg / mL;

[0088] (2) Grinding: Take about 10g of a representative fly ash sample and grind it in an agate mortar for 10 minutes. Weigh about 0.5g of the ground fly ash, with a mass of m1 and an actual weight of 0.5023g, and place it in a crucible;

[0089] (3) Add ion exchangers, using sodium carbonate and sodium chloride as ion exchangers, fly ash: sodium carbonate: sodium chloride = 1:1:0.5, actually weigh 0.5015g of sodium carbonate and 0.2504g of sodium chloride, add them to the crucible of step (2), and mix the fly ash and ion exchanger evenly;

[0090] (4) high temperature eutectic reaction, placing the crucible of step (3) in a high temperature resistance furnace, setting the temperature to 950° C., and keeping the temperature constant for 60 minutes, so that the mixture melts and reacts together;

[0091] (5) The product is cooled and ground. After the high-temperature furnace is shut down and cooled, the solid mixture in the crucible is taken out and ground in an agate mortar for 30 minutes to collect the powder;

[0092] (6) Ethylene glycol azeotropy: the powder collected in step (5) is placed in a 250 mL dry conical flask, the small amount of residue in the crucible is ground and transferred to a 250 mL conical flask with anhydrous ethanol, 30 mL of ethylene glycol-ethanol solution (2+1) is added, a magnetic bar is placed, a condenser is installed, and the solution is stirred at a speed of 50 r / min, while the temperature is raised and heated to boil;

[0093] (7) When the condensate starts to drip continuously, continue to boil slightly for 5 minutes, remove the conical flask, and immediately titrate with benzoic acid-anhydrous ethanol standard titration solution using phenolphthalein as an indicator until the reddish color disappears, and the volume of the standard titration solution consumed is V1 = 28.24 mL. The total calcium content in the fly ash is calculated by the total calcium content calculation formula = 15.98%;

[0094] (8) Weigh about 1 g of fly ash sample, with a mass of m2 = 1.0022 g. Grinding and eutectic treatment are not required. Steps (6) and (7) are directly performed. The volume of standard titration solution consumed is V2 = 2.40 mL. The free calcium oxide content in the fly ash is calculated by the calcium oxide content to be = 0.68%;

[0095] (9) The calcium oxide (non-free) content in fly ash is calculated by the calcium oxide content calculation formula: w(CaO)=w(Ca)-w(f-CaO)=15.98%-0.68%=15.30%.

[0096] The present invention aims to achieve accurate detection of the calcium oxide content (non-free) in fly ash without using controlled drugs such as hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid that are easy to make drugs and explosions, thereby solving the technical problem of rapid detection of calcium oxide content in fly ash at the construction site.

[0097] In order to facilitate understanding of the above technical solutions of the present invention, the above technical solutions of the present invention are further described below through a number of specific embodiments.

[0098] Embodiment 1

[0099] like Figure 1 As shown, in specific applications, the method for detecting the calcium oxide content in fly ash can be as follows:

[0100] 10g of fly ash sample was placed in a planetary ball mill and ground for 10min to form fine fly ash material. 1g of the fine fly ash material was placed in a crucible.

[0101] Weigh 30% of the mass of the ion exchanger, put it in the above crucible, and mix the fine fly ash and the ion exchanger evenly to form a mixture;

[0102] The crucible is placed in a high temperature furnace to allow the mixture to fully melt and react to form a solid mixture. The high temperature of the high temperature furnace is 900° C. and the constant temperature time of the high temperature furnace is 30 minutes.

[0103] After the high-temperature furnace is heated and stopped to cool, the solid mixture in the crucible is taken out and placed in a planetary ball mill for grinding for 10 minutes to form a powder material;

[0104] The collected powder material was placed in a 250 mL dry conical flask, 30 mL of ethylene glycol-ethanol solution (2+1) was added to the conical flask, a magnetic rod was then placed in the conical flask, a condenser was installed, the solution was stirred at a speed of 30 r / min, and the temperature was raised and heated for 3 minutes until boiling;

[0105] After the conical flask is heated, condense it. When the condensed ethanol begins to drip continuously, continue to boil slightly for 5 minutes, remove the conical flask, and immediately titrate it with benzoic acid-anhydrous ethanol standard titration solution using phenolphthalein as an indicator until the reddish color disappears, and calculate the total calcium content using the total calcium content calculation formula;

[0106] Weigh about 1g of fly ash sample, perform steps S5 and S6, and calculate the free calcium oxide content in the fly ash using the free calcium oxide content calculation formula;

[0107] The calcium oxide content calculation formula is used to calculate the non-free calcium oxide content in fly ash.

[0108] Embodiment 2

[0109] like Figure 1 As shown, in specific applications, the method for detecting the calcium oxide content in fly ash can be as follows:

[0110] 10g of fly ash sample was placed in a planetary ball mill and ground for 10min to form fine fly ash material. 1g of the fine fly ash material was placed in a crucible.

[0111] Weigh 70% of the mass of the ion exchanger, put it in the above crucible, and mix the fine fly ash and the ion exchanger evenly to form a mixture;

[0112] The crucible is placed in a high temperature furnace to allow the mixture to fully melt and react to form a solid mixture. The high temperature of the high temperature furnace is 950° C. and the constant temperature time of the high temperature furnace is 1.5 hours.

[0113] After the high-temperature furnace is heated and stopped to cool, the solid mixture in the crucible is taken out and placed in a planetary ball mill for grinding for 10 minutes to form a powder material;

[0114] The collected powder material was placed in a 250 mL dry conical flask, 30 mL of ethylene glycol-ethanol solution (2+1) was added to the conical flask, a magnetic rod was then placed in the conical flask, a condenser was installed, the solution was stirred at a speed of 70 r / min, and the temperature was raised and heated for 3 minutes until boiling;

[0115] After the conical flask is heated, condense it. When the condensed ethanol begins to drip continuously, continue to boil slightly for 5 minutes, remove the conical flask, and immediately titrate it with benzoic acid-anhydrous ethanol standard titration solution using phenolphthalein as an indicator until the reddish color disappears, and calculate the total calcium content using the total calcium content calculation formula;

[0116] Weigh about 1g of fly ash sample, perform steps S5 and S6, and calculate the free calcium oxide content in the fly ash using the free calcium oxide content calculation formula;

[0117] The calcium oxide content calculation formula is used to calculate the non-free calcium oxide content in fly ash.

[0118] Embodiment 3

[0119] like Figure 1 As shown, in specific applications, the method for detecting the calcium oxide content in fly ash can be as follows:

[0120] 10g of fly ash sample was placed in a planetary ball mill and ground for 10min to form fine fly ash material. 1g of the fine fly ash material was placed in a crucible.

[0121] Weigh 100% of the mass of the ion exchanger, place it in the above crucible, and mix the fine fly ash and the ion exchanger evenly to form a mixture;

[0122] The crucible is placed in a high temperature furnace to allow the mixture to fully melt and react to form a solid mixture. The high temperature of the high temperature furnace is 1000° C. and the constant temperature time of the high temperature furnace is 3 hours.

[0123] After the high-temperature furnace is heated and stopped to cool, the solid mixture in the crucible is taken out and placed in a planetary ball mill for grinding for 10 minutes to form a powder material;

[0124] The collected powder material was placed in a 250 mL dry conical flask, 30 mL of ethylene glycol-ethanol solution (2+1) was added to the conical flask, a magnetic bar was then placed in the conical flask, a condenser was installed, the solution was stirred at a speed of 100 r / min, and the temperature was raised and heated for 3 minutes until boiling;

[0125] After the conical flask is heated, condense it. When the condensed ethanol begins to drip continuously, continue to boil slightly for 5 minutes, remove the conical flask, and immediately titrate it with benzoic acid-anhydrous ethanol standard titration solution using phenolphthalein as an indicator until the reddish color disappears, and calculate the total calcium content using the total calcium content calculation formula;

[0126] Weigh about 1g of fly ash sample, perform steps S5 and S6, and calculate the free calcium oxide content in the fly ash using the free calcium oxide content calculation formula;

[0127] The calcium oxide content calculation formula is used to calculate the non-free calcium oxide content in fly ash.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting calcium oxide content in fly ash, characterized in that: include: S1. The fly ash sample is ground in a planetary ball mill to form fine fly ash material, and a portion of the fine fly ash material is placed in a crucible; S2, weighing an ion exchanger, placing it in the above-mentioned crucible, and uniformly mixing the fine fly ash and the ion exchanger to form a mixture; S3, placing the above crucible in a high temperature furnace to allow the above mixture to fully melt and react to form a solid mixture; S4, after the high temperature furnace is heated and stopped for cooling, the solid mixture in the crucible is taken out and placed in a planetary ball mill for grinding to form a powder material; S5. Place the collected powder in a 250 mL dry conical flask, add 30 mL of ethylene glycol-ethanol solution (2+1) to the conical flask, then place a magnetic bar in the conical flask, install a condenser, stir the solution at a speed of 30-100 r / min, and heat it for 3 minutes until it boils; S6. After the conical flask is heated, condense it. When the condensed ethanol begins to drip continuously, continue to boil slightly for 5 minutes, remove the conical flask, and immediately titrate it with benzoic acid-anhydrous ethanol standard titration solution using phenolphthalein as an indicator until the reddish color disappears, and calculate the total calcium content using the total calcium content calculation formula; S7, weigh about 1g of fly ash sample, execute steps S5 and S6, and calculate the free calcium oxide content in the fly ash using the free calcium oxide content calculation formula; S8. Use the calcium oxide content calculation formula to calculate the non-free calcium oxide content in fly ash.

2. The method for detecting calcium oxide content in fly ash according to claim 1, characterized in that: The fly ash sample in step S1 weighs 10 g, the grinding time of the planetary ball mill is 10 min, and the weight of the intercepted fine fly ash material is 1.0000 g.

3. The method for detecting calcium oxide content in fly ash according to claim 1, characterized in that: The ion exchanger in step S2 is a metal salt, which can be one or a mixture of sodium carbonate, potassium carbonate, sodium chloride, magnesium oxide, and magnesium chloride. The amount of the ion exchanger is 30% to 100% of the mass of the fine fly ash in step S2.

4. The method for detecting calcium oxide content in fly ash according to claim 1, characterized in that: The high temperature of the high temperature furnace described in step S3 is 900-1000° C., and the constant temperature time of the high temperature furnace is 30 minutes-3 hours.

5. The method for detecting calcium oxide content in fly ash according to claim 1, characterized in that: The grinding time of the planetary ball mill described in step S4 is 10 min.

6. The method for detecting calcium oxide content in fly ash according to claim 1, characterized in that: The ethanol concentration volume fraction in step S5 must be greater than or equal to 99.5%.

7. The method for detecting calcium oxide content in fly ash according to claim 1, characterized in that: The total calcium content calculation formula in step S6 is: Where w(Ca) is the total calcium content, T cao is the titration degree of calcium oxide, m1 is the mass of the intercepted fine fly ash, and V1 is the volume of the consumed standard titration solution.

8. The method for detecting calcium oxide content in fly ash according to claim 7, characterized in that: The benzoic acid-anhydrous ethanol standard titration solution in step S6 needs to use calcium oxide burned by calcium carbonate reference reagent to determine its titer for calcium oxide. The specific operation for determining the titer of calcium oxide is: Weigh about 0.04g of newly burned and cooled calcium oxide, accurate to 0.0001g, and place it in a 250mL dry conical flask, add 30mL of ethylene glycol-ethanol solution (2+1), put in a magnetic rod, install a condenser, stir the solution at an appropriate speed, and heat it to boil. When the condensate begins to drip continuously, continue to boil slightly for 5 minutes, remove the conical flask, use phenolphthalein as an indicator, and immediately titrate with benzoic acid-anhydrous ethanol standard titration solution until the reddish color disappears. Use the titration formula of calcium oxide to calculate the titration of benzoic acid-anhydrous ethanol standard titration solution to calcium oxide. The calculation formula is: Where, T cao is the titration degree of calcium oxide, V is the volume of the consumed standard titration solution, m is the mass of the intercepted fine fly ash material, and 1000 is the conversion coefficient from mg / mL to g / mL.

9. The method for detecting calcium oxide content in fly ash according to claim 1, characterized in that: The free calcium oxide content calculation formula in step S7 is: Where w(f-CaO) is the free calcium oxide content, T CaO is the titration degree of calcium oxide, V2 is the volume of the consumed standard titration solution, and m2 is the mass of the fly ash sample.

10. The method for detecting calcium oxide content in fly ash according to claim 1, characterized in that: The calculation formula of calcium oxide content in step S8 is: w(CaO)=w(Ca)-w(f-CaO) Wherein, w(CaO) is the calcium oxide content, w(Ca) is the total calcium content, and w(f-CaO) is the free calcium oxide content.

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