Method for preparing high-activity calcium hydroxide through ultrasonic-microwave coupling enhanced lime digestion

Abstract

The invention belongs to the technical field of inorganic material preparation, and particularly relates to a method for preparing high-activity calcium hydroxide through ultrasonic-microwave coupling reinforced lime digestion. According to the invention, quicklime and water are used as raw materials, water is used as a solvent to obtain a lime-water mixed system, and through three-stage regulation and control of pre-ultrasonic activation, ultrasonic-microwave coupling accelerated reaction kinetics and high-frequency ultrasonic post-treatment, pore structure optimization and particle refinement of the product are realized; the high-activity calcium hydroxide particles with the specific surface area of more than 45m < 2 > / g and the porous structure are obtained. According to the preparation method provided by the invention, the specific surface area of the calcium hydroxide can be further increased through the decomposition of the pore-forming agent and the ultrasonic-microwave coupling synergistic effect, the accurate regulation and control of the pore structure of the calcium hydroxide are realized, the desulfurization activity of the product is improved, and the obtained product can be widely applied to the fields of flue gas purification, soil remediation and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic material preparation, and particularly relates to a method for preparing highly active calcium hydroxide by enhancing lime digestion through ultrasound-microwave coupling. Background Art

[0002] Lime, a core industrial raw material in metallurgy, construction, and other fields, reached approximately 300 million tons in my country in 2020, representing a significant industry scale. Lime slaking (also known as slaking or digestion) is the chemical process by which quicklime (calcium oxide, CaO) reacts with water to produce slaked lime (calcium hydroxide, Ca(OH)2). This process is widely used in the construction, chemical, and environmental protection sectors.

[0003] Although the traditional lime digestion process combined with mechanical stirring and hydrothermal reaction has improved compared with natural digestion, it still has significant technical bottlenecks: low reaction efficiency, usually taking 4-6 hours; insufficient specific surface area of the product, usually less than 30m 2 / g, as well as serious particle agglomeration problems, lead to poor dispersion of calcium hydroxide, which directly affects the application performance of the product in high-end fields such as environmental adsorption and nanomaterials.

[0004] Among the existing technological improvements, some technical approaches focus on optimizing a single performance or fail to balance the requirements of reaction rate and product homogenization. In particular, there is a lack of systematic solutions for the structural control and dispersion stability of micro-nano calcium hydroxide. For example, patent CN101654339B discloses an ultrasonically enhanced lime smelting and emulsification device. By utilizing the ultrasonic effect to break up initial particles, the lime milk particles can be suspended in the solution for a long time. Although this shortens some reaction times, it still takes more than two hours due to the attenuation of ultrasonic energy. Furthermore, the scale-up of the reaction system is difficult, making it difficult to achieve industrial production of highly active calcium hydroxide.

[0005] Therefore, there is an urgent need to develop innovative processes to break through the limitations of traditional processes and existing patented technologies and meet the urgent demand for high-performance calcium hydroxide in new energy, fine chemicals and other fields. Summary of the Invention

[0006] In view of the above shortcomings, the present invention aims to provide a method for preparing highly active calcium hydroxide by enhancing lime digestion through ultrasonic-microwave coupling. The calcium hydroxide particles prepared by the method of the present invention have a specific surface area of 45-100 m 2 / g, the desulfurization activity is improved compared with the traditional process, and the SO2 adsorption rate exceeds 98% within 30 seconds. It can be widely used in flue gas purification, soil remediation and other fields.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing highly active calcium hydroxide by using ultrasonic-microwave coupling to enhance lime digestion comprises the following steps: subjecting a lime-water mixed system to ultrasonic pretreatment, then enhancing the lime digestion reaction in a coupled field of microwave radiation and ultrasonic cavitation, and performing post-treatment to obtain a product; the lime-water mixed system is a mixture of quicklime and water, and the post-treatment comprises high-frequency ultrasonic particle refinement.

[0009] Optionally, the CaO content in the quicklime is ≥95%.

[0010] Optionally, the quicklime has a particle size of 50-200 μm.

[0011] Optionally, the water-lime ratio of water to quicklime in the lime-water mixing system is 3:1-6:1.

[0012] As a preferred embodiment of the method of the present invention, the lime-water mixture system further contains a pore-forming agent and an optional dispersant.

[0013] As a preferred embodiment of the method of the present invention, the lime-water mixture system further contains a pore-forming agent and an optional dispersant, wherein the pore-forming agent is a thermal decomposition type pore-forming agent with a content of 1-5% by mass of quicklime.

[0014] As a preferred embodiment of the method of the present invention, the lime-water mixture system further contains a pore-forming agent and an optional dispersant, and the pore-forming agent is a combination of any one or more of ammonium bicarbonate, urea, and citric acid.

[0015] As a preferred embodiment of the method of the present invention, the lime-water mixture system further contains a pore-forming agent and an optional dispersant, and the pore-forming agent is used in combination with the dispersant sodium hexametaphosphate.

[0016] As a preferred embodiment of the method of the present invention, the lime-water mixture system further contains a pore-forming agent and an optional dispersant, and the mass ratio of the pore-forming agent to the dispersant is 2:1-5:1.

[0017] As a preferred method of the present invention, ultrasonic pretreatment is performed with a frequency of 20-40 kHz and a power density of 1-3 W / cm 3 Ultrasonic pretreatment for 5-15 minutes can make the lime-water mixture more uniform and allow the pore-forming agent to evenly coat the lime particles.

[0018] As a preferred method of the present invention, the enhanced lime digestion reaction in the coupled field of microwave radiation and ultrasonic cavitation is achieved by microwave heating and simultaneous application of ultrasonic waves with a frequency of 28-60 kHz for 20-40 minutes. The microwave heating can induce the decomposition of the pore-forming agent to generate gas.

[0019] As a preferred method of the present invention, the high frequency ultrasonic refining of particles in the post-processing is to apply a frequency of 40-100 kHz and a power density of 2-5 W / cm 3High-frequency ultrasonic particle refinement can break down some macropores into mesopores with a pore size of 2-50nm after 15-20 minutes of treatment.

[0020] As a specific embodiment of the method of the present invention, the method for preparing highly active calcium hydroxide comprises the following steps:

[0021] S1: Apply a frequency of 20-40kHz and a power density of 1-3W / cm to the lime-water mixture. 3 Ultrasonic pretreatment for 5-15 minutes to obtain a premix;

[0022] S2: The premix is microwave-heated in a coupled field of microwave radiation and ultrasonic cavitation and ultrasonic waves with a frequency of 28-60 kHz are simultaneously applied to enhance the lime digestion reaction for 20-40 minutes, and the reaction is stopped;

[0023] S3: Switch to a frequency of 40-100kHz and a power density of 2-5W / cm 3 The particles were refined by high-frequency ultrasonic treatment for 15-20 minutes and dried to obtain a product.

[0024] As a preferred embodiment of the method of the present invention, after high-frequency ultrasonic refining of the particles, centrifugal separation is performed and the precipitate is vacuum dried at 60-80° C. to obtain the product, thereby retaining the pore structure of the product.

[0025] As a specific embodiment of the method of the present invention, the method for preparing highly active calcium hydroxide comprises the following steps:

[0026] S1: mixing quicklime having a CaO content of ≥95% with water to obtain a mixed solution; the quicklime has a particle size of 50-200 μm; and the water-to-lime ratio is 3:1-6:1;

[0027] S2: mixing the mixed solution with a pore-forming agent and an optional dispersant to obtain a lime-water mixed system;

[0028] S3: Apply a frequency of 20-40kHz and a power density of 1-3W / cm to the lime-water mixture system. 3 Ultrasonic pretreatment for 5-15 minutes to obtain a premix;

[0029] S4: heating the premix in a microwave-heated coupled field of microwave radiation and ultrasonic cavitation and simultaneously applying ultrasonic waves with a frequency of 28-60 kHz to enhance the lime digestion reaction for 20-40 minutes, and then stopping the reaction;

[0030] S5: Switch to a frequency of 40-100kHz and a power density of 2-5W / cm 3 The particles were refined by high-frequency ultrasonic treatment for 15-20 minutes, and the mixture was centrifuged. The precipitate was vacuum-dried at 60-80° C. to obtain the product.

[0031] As a preferred embodiment of the method of the present invention, the frequency of microwave heating in the coupled field of microwave radiation and ultrasonic cavitation is 2.45 GHz, the temperature is controlled at 80-95°C, and the microwave power is 500-800 W; so as to induce the decomposition of the pore-forming agent to produce gaseous CO2 and / or NH3. The decomposition temperature of the pore-forming agent matches the microwave heating temperature, so that the gas produced by the decomposition forms through-holes under the action of ultrasonic cavitation.

[0032] Furthermore, the heating rate of microwave heating is preferably 10-15° C. / min, so as to promote concentrated gas release from the pore-forming agent.

[0033] Furthermore, it is preferred that the microwave power be gradient-decreased from an initial value of 800W to a final value of 500W.

[0034] Furthermore, it is preferred that the microwave power be gradient-decreased controlled with a decrease of 50-100 W / 5 min.

[0035] Furthermore, it is preferred that the microwave power be gradient-decreased controlled with a reduction of 100 W / 5 min.

[0036] As a preferred method of the present invention, the power density of the ultrasonic wave applied in the coupled field of microwave radiation and ultrasonic cavitation is 2-5W / cm 3 The ultrasonic cavitation effect can be used to amplify the bubbles generated by the pore-forming agent. Furthermore, it is preferred that the synchronization rate between ultrasonic cavitation and pore-forming agent decomposition in the coupled field of microwave radiation and ultrasonic cavitation is greater than 70%, which is more conducive to bubble generation. This synchronization rate can be monitored by thermogravimetric-gas chromatography-mass spectrometry to monitor the peak period of pore-forming agent decomposition for ≥50% and by high-speed video or acoustic emission to detect ultrasonic cavitation power ≥2W / cm 3 The specific surface area of the product can be measured by BET method ≥ 65m 2 / g, and the nitrogen adsorption method was used to measure the proportion of mesopores at 50-60%, which indirectly verified the synchronization rate.

[0037] As a preferred embodiment of the method of the present invention, the ultrasonic frequency applied in the microwave radiation and ultrasonic cavitation coupling field and the high-frequency ultrasonic frequency applied during the high-frequency ultrasonic particle refinement in the post-processing are dynamically matched; preferably, the initial frequency of the ultrasonic wave applied in the microwave radiation and ultrasonic cavitation coupling field is 40 kHz, and the dynamic matching can switch the frequency of the high-frequency ultrasonic wave applied during the high-frequency ultrasonic particle refinement in the post-processing to 80 kHz.

[0038] As a preferred embodiment of the method of the present invention, the product provided by the method of the present invention has a three-level pore structure, with micropores accounting for 10-15%, mesopores accounting for 50-60%, and macropores accounting for 25-40%.

[0039] In addition, the product provided by the method of the present invention can also be used in desulfurization.

[0040] The above technical solution in the embodiment of the present invention has at least the following technical effects:

[0041] The invention provides a method for preparing highly active calcium hydroxide by using ultrasonic-microwave coupling to enhance lime digestion. The method comprises the following steps: using quicklime and water as raw materials and water as a solvent to obtain a lime-water mixed system; performing ultrasonic pretreatment on the lime-water mixed system to cause an activation reaction; then enhancing the lime digestion reaction in a coupled field of microwave radiation and ultrasonic cavitation; and finally performing high-frequency ultrasonic post-treatment to achieve product pore structure optimization and particle refinement, thereby obtaining highly active calcium hydroxide particles with a porous structure, increasing the specific surface area of the calcium hydroxide, and improving the desulfurization activity of the calcium hydroxide.

[0042] Compared with the prior art, the advantages and beneficial effects of the present invention include:

[0043] This invention revolutionizes the traditional lime digestion process through ultrasound-microwave coupling technology, achieving efficient, high-quality calcium hydroxide production. Compared to the traditional process, which requires a digestion reaction time of at least four hours, this invention uses ultrasound-microwave coupling to enhance lime digestion, shortening the reaction time to 40 minutes. Furthermore, the invention provides a method for adjusting the microwave power gradient and dynamically matching the ultrasonic frequency, significantly reducing energy consumption and facilitating the efficient, industrialized production of highly active calcium hydroxide.

[0044] The present invention achieves a breakthrough improvement in the performance of the product obtained by three-stage regulation of pre-ultrasonic activation, ultrasonic-microwave coupling to accelerate reaction kinetics, and high-frequency ultrasonic post-treatment. The specific surface area of calcium hydroxide is less than 30m2 in the traditional process. 2 / g increased to 45-65m 2 / g, and after further introduction of pore-forming agents, it reaches 65-100m 2 / g, and the particle size distribution of the product particles is highly uniform, reaching D90<1.5μm; the present invention can construct a through three-level pore structure through the synergistic effect of pore-forming agent decomposition and ultrasonic cavitation, in which macropores (>50nm) transmit gas, mesopores (2-50nm) provide active sites, and micropores (<2nm) enhance adsorption, thereby greatly optimizing the mass transfer and adsorption performance of calcium hydroxide particles; in terms of application, the desulfurization activity of the calcium hydroxide product obtained by the present invention is improved compared with the traditional process, and the SO2 adsorption rate exceeds 98% within 30 seconds.

[0045] The present invention introduces a pore-forming agent and is supplemented by an optional dispersant and a special reactor design, which can further enhance particle dispersibility and process stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic flow chart of a method for preparing highly active calcium hydroxide by enhancing lime digestion through ultrasound-microwave coupling in an optional embodiment of the present invention;

[0047] Figure 2 Schematic diagram of the structure of the ultrasonic-microwave coupled reactor;

[0048] Figure 3 The graph is a relationship between the specific surface area and reaction time of the products obtained by different preparation methods;

[0049] Figure 4 Schematic diagram of the mechanism of action of the pore-forming agent in an optional embodiment of the present invention;

[0050] Figure 5 This is a graph showing the relationship between the pore structure ratio and reaction time of the products obtained without and with the addition of a pore-forming agent in an optional embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0052] In this application, the use of the terms "optionally", "optional", "optional", "optional" or "any one" means that the subsequently described matter or event can or cannot occur, and that the description includes instances where the event occurs and instances where it does not.

[0053] In this application, the terms "a" or "an" are used to describe elements and components described herein. This is done for convenience only and to provide a general sense of the scope of this application. Such descriptions should be understood to include one or at least one, and the singular also includes the plural unless otherwise clearly indicated. "Multiple" means two or more.

[0054] As used herein, the terms "comprises," "including," "having," "containing" or any other variations thereof are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0055] In the present invention, the term "water-cement ratio" is the ratio of the volume of water to the mass of quicklime, where the unit of volume is mL and the unit of mass is g.

[0056] In the present invention, the pore sizes of different pores range from macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm).

[0057] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0058] Example 1

[0059] A method for preparing calcium hydroxide, comprising the following steps:

[0060] S1: Select quicklime with a CaO content of ≥95%, take 100 g of 100-mesh quicklime powder, crush it to a particle size of 50-100 μm, add 400 mL of deionized water at a water-cement ratio of 4:1, and mechanically stir to preliminarily mix to obtain a lime-water mixture;

[0061] S2: Start the ultrasonic processor during the pre-stirring stage, set the frequency to 30kHz, and the power density to 2W / cm 3 , process for 10 minutes to obtain a premix;

[0062] S3: The premix was transferred into an ultrasonic-microwave coupled reactor, the microwave frequency was set to 2.45 GHz, the initial microwave power was set to 800 W, the temperature was controlled at 90 °C, and 40 kHz ultrasonic waves were applied simultaneously with a power density of 3 W / cm 3 , the microwave power was reduced by 100 W every 5 minutes to a final value of 500 W, and the total reaction time was 30 minutes;

[0063] S4: After the reaction is completed, switch the ultrasonic frequency to 80kHz and the power density to 3W / cm 3 , continue the treatment for 15 minutes, centrifuge and collect the precipitate, place the precipitate in a vacuum drying oven, and dry it at 60°C for 12 hours to obtain white powdery calcium hydroxide.

[0064] Example 2

[0065] A method for preparing calcium hydroxide, comprising the following steps:

[0066] S1: Select quicklime with a CaO content of ≥95%, take 100 g of 100 mesh quicklime powder, crush it to a particle size of 50-100 μm, add 500 mL of deionized water at a water-cement ratio of 5:1, and mechanically stir to obtain a mixed solution;

[0067] S2: Add 3g of ammonium bicarbonate thermal decomposition type pore-forming agent to the mixed solution and mix evenly to obtain a lime-water mixed system;

[0068] S3: Start the ultrasonic processor during the pre-stirring stage, set the frequency to 30kHz, and the power density to 2.5W / cm 3 , processing for 12 minutes to allow the pore-forming agent to evenly coat the lime particles to obtain a premix;

[0069] S4: The premix was transferred into an ultrasonic-microwave coupled reactor, and microwave heating was used to induce the decomposition of the pore-forming agent to produce gas. The microwave frequency was set to 2.45 GHz, the initial microwave power was set to 800 W, the heating rate was set to 10 °C / min to the target temperature of 85 °C, and 40 kHz ultrasonic waves were applied simultaneously with a power density of 4 W / cm 3 , reduce the microwave power by 100W every 5 minutes to the final value of 500W, and the total reaction time is 25 minutes; among them, the microwave power gradient adjustment is combined with the dynamic matching of the ultrasonic frequency. In the first 5 minutes, the microwave power is 800W and the ultrasonic frequency is 40kHz. In 5-10 minutes, the microwave power is 700W and the ultrasonic frequency is 50kHz. In 10-15 minutes, the microwave power is 600W and the ultrasonic frequency is 60kHz. In the last 10 minutes, the microwave power is maintained at 500W and the ultrasonic frequency is 60kHz.

[0070] S5: After the reaction is completed, switch the ultrasonic frequency to 80kHz and the power density to 3W / cm 3 , continue the treatment for 20 minutes, centrifuge and collect the precipitate, place the precipitate in a vacuum drying oven, and dry it at 60°C for 12 hours to obtain white powdery calcium hydroxide.

[0071] Example 3

[0072] A method for preparing calcium hydroxide, comprising the following steps:

[0073] S1: Select quicklime with a CaO content of ≥95%, take 100 g of 100 mesh quicklime powder, crush it to a particle size of 50-100 μm, add 500 mL of deionized water at a water-cement ratio of 5:1, and mechanically stir to obtain a mixed solution;

[0074] S2: Add 2g of ammonium bicarbonate and 2g of urea mixed with a thermal decomposition pore-forming agent and 1g of sodium hexametaphosphate dispersant to the mixed solution, and mix them evenly at a mass ratio of pore-forming agent to dispersant of 4:1 to obtain a lime-water mixed system;

[0075] S3: Start the ultrasonic processor during the pre-stirring stage, set the frequency to 30kHz, and the power density to 2.5W / cm 3 , processing for 15 minutes to allow the pore-forming agent to evenly coat the lime particles to obtain a premix;

[0076] S4: The premix was transferred into an ultrasonic-microwave coupled reactor, and microwave heating was used to induce the decomposition of the pore-forming agent to produce gas. The microwave frequency was set to 2.45 GHz, the initial microwave power was set to 800 W, the heating rate was set to 10 °C / min to the target temperature of 85 °C, and 40 kHz ultrasonic waves were applied simultaneously with a power density of 4 W / cm 3 , the microwave power was reduced by 100 W every 5 minutes to a final value of 500 W, and the total reaction time was 25 minutes;

[0077] S5: After the reaction is completed, switch the ultrasonic frequency to 80kHz and the power density to 3W / cm 3 , continue the treatment for 20 minutes, centrifuge and collect the precipitate, place the precipitate in a vacuum drying oven, and dry it at 60°C for 12 hours to obtain white powdery calcium hydroxide.

[0078] Comparative Example 1

[0079] A method for preparing calcium hydroxide, comprising the following steps:

[0080] S1: Select quicklime with a CaO content of ≥95%, take 100 g of 100-mesh quicklime powder, crush it to a particle size of 50-100 μm, add 400 mL of deionized water at a water-cement ratio of 4:1, and mechanically stir to preliminarily mix to obtain a lime-water mixture;

[0081] S2: Start the ultrasonic processor during the pre-stirring stage, set the frequency to 30kHz, and the power density to 2W / cm 3 , process for 10 minutes to obtain a premix;

[0082] S3: The premix was transferred into an ultrasonic-microwave coupled reactor, the microwave frequency was set to 2.45 GHz, the initial microwave power was set to 800 W, the temperature was controlled at 90°C, the microwave power was reduced by 100 W every 5 minutes to a final value of 500 W, the total reaction time was 50 minutes, and no ultrasonic wave was applied during the entire reaction process;

[0083] S4: After the reaction is completed, switch the ultrasonic frequency to 80kHz and the power density to 3W / cm 3 , continue the treatment for 15 minutes, centrifuge and collect the precipitate, place the precipitate in a vacuum drying oven, and dry it at 60°C for 12 hours to obtain white powdery calcium hydroxide.

[0084] Comparative Example 2

[0085] A method for preparing calcium hydroxide by a traditional process, the steps are as follows:

[0086] S1: Select quicklime with a CaO content of ≥95%, take 100 g of 100 mesh quicklime powder, crush it to a particle size of 50-100 μm, add 400 mL of deionized water at a water-cement ratio of 4:1, and mechanically stir to obtain a mixed solution;

[0087] S2: The mixed solution was placed in a 90°C water bath with continuous mechanical stirring without applying ultrasound or microwaves for lime digestion reaction;

[0088] S3: After the reaction is completed, the precipitate is collected by direct centrifugation and dried in vacuum at 60°C for 1 hour to obtain white calcium hydroxide powder.

[0089] Comparative Example 3

[0090] A method for preparing calcium hydroxide using a single ultrasound process, comprising the following steps:

[0091] S1: Select quicklime with a CaO content of ≥95%, take 100 g of 100-mesh quicklime powder, crush it to a particle size of 50-100 μm, add 400 mL of deionized water at a water-cement ratio of 4:1, and mechanically stir to preliminarily mix to obtain a lime-water mixture;

[0092] S2: Start the ultrasonic processor during the pre-stirring stage, set the frequency to 30kHz, and the power density to 2.5W / cm 3 , process for 12 minutes to obtain a premix;

[0093] S3: In a 90°C water bath, apply a 40kHz power density of 3W / cm 3 Ultrasonic cavitation, lime digestion reaction without microwave application;

[0094] S4: After the reaction is completed, switch the ultrasonic frequency to 80kHz and the power density to 3W / cm 3 , continue the treatment for 20 minutes, centrifuge and collect the precipitate, place the precipitate in a vacuum drying oven, and dry it at 60°C for 12 hours to obtain white powdery calcium hydroxide.

[0095] Comparative Example 4

[0096] A method for preparing calcium hydroxide using a single microwave, comprising the following steps:

[0097] S1: Select quicklime with a CaO content of ≥95%, take 100 g of 100 mesh quicklime powder, crush it to a particle size of 50-100 μm, add 400 mL of deionized water at a water-cement ratio of 4:1, and mechanically stir to obtain a mixed solution;

[0098] S2: The mixed solution was placed in a microwave reactor, the microwave frequency was set to 2.45 GHz, the initial power was 800 W, the temperature was raised to 90°C, and the lime digestion reaction was carried out without applying ultrasonic waves;

[0099] S3: After the reaction is completed, switch the ultrasonic frequency to 80kHz and the power density to 3W / cm 3 , continue the treatment for 20 minutes, centrifuge and collect the precipitate, place the precipitate in a vacuum drying oven, and dry it at 60°C for 12 hours to obtain white powdery calcium hydroxide.

[0100] Test Example 1

[0101] Calcium hydroxide performance test indicators and methods:

[0102] Specific Surface Area: Specific surface area is determined using the BET nitrogen adsorption method. The total surface area per unit mass of the sample is calculated by measuring the multilayer adsorption isotherm of nitrogen on the sample surface at liquid nitrogen temperature. Prior to testing, the sample must be vacuum degassed to remove surface impurities. This method is applicable to mesoporous or microporous materials and can directly reflect the surface activity and porosity of calcium hydroxide particles, making it a key indicator for evaluating the material's adsorption performance.

[0103] Particle Size D90: This is measured using a laser particle size analyzer, utilizing the principle of laser scattering to measure the particle size distribution in a dispersion. The sample is ultrasonically dispersed to prevent agglomeration, then injected into the sample cell after instrument calibration. The particle size is calculated based on the angular distribution of scattered light. The particle size corresponding to the 90th percentile is directly read, reflecting the uniformity of the product particles.

[0104] Pore volume: The pore volume is analyzed by nitrogen adsorption-desorption method combined with BJH model. The total pore volume is calculated using the adsorption amount of nitrogen at different partial pressures, and the mesopore volume is determined by the adsorption data of the mesopore size distribution range.

[0105] Desulfurization activity: Take 0.1g of sample and place it in a fixed bed reactor. Pass 500ppm SO2 / nitrogen mixed gas at a flow rate of 100mL / min. After reacting for 30s, the outlet SO2 concentration is detected with an online SO2 analyzer and the desulfurization adsorption rate is calculated.

[0106] According to the above method, the specific surface area, particle size D90, pore volume and desulfurization activity of the calcium hydroxide of the embodiment and the comparative example were tested. The test results are shown in Table 1.

[0107] Table 1 Specific surface area, particle size, pore volume and desulfurization activity test results of calcium hydroxide

[0108]

[0109]

[0110] It can be seen that the present invention has revolutionized the traditional lime slurrying process, significantly shortening the reaction time from 4-6 hours to 20-40 minutes, and significantly improving product performance. Specifically:

[0111] (1) As can be seen from Examples 1-3, the present invention can effectively inhibit particle agglomeration by combining ultrasonic cavitation effect with microwave heating (ultrasonic-microwave coupling technology), so that the specific surface area of calcium hydroxide is reduced from less than 30 m2 in the traditional process (specifically, the preparation method of comparative example 2 with a reaction time of 6 hours). 2 / g increased to 45m 2 / g or more, the calcium hydroxide particle size D90 is controlled to be less than 1.5μm, and the desulfurization adsorption rate of calcium hydroxide exceeds 98% within 30 seconds;

[0112] (2) As can be seen from Examples 2-3, the method of the present invention also introduces a pore-forming agent (such as Figure 1 The method shown) can make the specific surface area of calcium hydroxide reach 65-100m 2 / g, the particle size distribution of calcium hydroxide particles is highly uniform, and through the synergistic effect of ultrasonic-microwave coupling technology and pore-forming agents, a three-level structure of macropores, mesopores and micropores is constructed. The macropores transmit gas, the mesopores provide active sites, and the micropores enhance adsorption, which greatly optimizes the mass transfer and adsorption performance of calcium hydroxide; at the same time, with the help of optional dispersants and Figure 2 The special reactor design shown can further enhance the dispersion of calcium hydroxide particles and the stability of the preparation process;

[0113] (3) As can be seen from Comparative Example 1, when only microwave-enhanced lime digestion is used, the specific surface area of calcium hydroxide is only 36.5 m 2 / g and the particles are severely agglomerated, and the pore volume is reduced from 0.64cm 3 / g down to 0.21cm 3 / g, a decrease of 67%, further verifying the important role of ultrasound and pore-forming agent in ultrasound-microwave coupling technology.

[0114] Test Example 2

[0115] The present invention also investigates the effects of different preparation methods and reaction times on the properties of calcium hydroxide.

[0116] In the method of Comparative Example 3, the cavitation effect easily causes the pore wall to collapse, which will destroy the mesoporous structure. Through the nitrogen adsorption-desorption method combined with the BJH model analysis, it was found that this single ultrasonic method for preparing calcium hydroxide will cause a significant decrease in the mesopore volume, which is not conducive to obtaining a highly active product.

[0117] In detail, the present invention also investigates the relationship between the specific surface area and reaction time of the products obtained by the following methods: Comparative Example 2 (traditional process), Comparative Example 3 (single ultrasound), Comparative Example 4 (single microwave), and when the microwave power and ultrasonic frequency are fixed to the initial value in the microwave radiation and ultrasonic cavitation coupling field without adopting the microwave power gradient adjustment and the ultrasonic frequency dynamic matching (synergistic effect) as in Example 2 (see Figure 3 ), it can be seen that the method of the present invention is more conducive to increasing the specific surface area of calcium hydroxide and more conducive to regulating calcium hydroxide particles.

[0118] The present invention further investigates the relationship between the pore structure ratio and reaction time of the products obtained without adding pore-forming agent and with adding pore-forming agent when the microwave power gradient adjustment and ultrasonic frequency dynamic matching are not adopted as in Example 2 (see Figure 5 ), combined with Figure 4From the mechanism of action of the pore-forming agent shown, it can be seen that the preparation method of the present invention introducing the pore-forming agent is more conducive to achieving precise control of the multi-level pores of calcium hydroxide, so that the product has a three-level pore structure, in which micropores account for 10-15%, mesopores account for 50-60%, and macropores account for 25-40%.

[0119] Furthermore, the method of the present invention provides a measure for dynamically matching microwave power gradient regulation with ultrasonic frequency, facilitating efficient energy consumption control. This invention surpasses conventional processes in terms of reaction efficiency, product performance, and potential for industrial application, providing a highly active, stable, and low-cost innovative solution for environmental protection fields such as flue gas purification.

[0120] The embodiments described above are merely optional embodiments of the present application and are not intended to limit the scope of protection of the present application. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the technical principles of the present application, and these improvements and modifications should also be regarded as within the scope of protection of the present application.

Claims

1. A method for preparing highly active calcium hydroxide by ultrasonic-microwave coupling-enhanced lime digestion, characterized in that: The method comprises the following steps: performing ultrasonic pretreatment on a lime-water mixed system, then strengthening the lime digestion reaction in a coupled field of microwave radiation and ultrasonic cavitation, and performing post-treatment to obtain a product; the lime-water mixed system is a mixture of quicklime and water, and the post-treatment comprises high-frequency ultrasonic particle refinement.

2. The method for preparing highly active calcium hydroxide according to claim 1, wherein The CaO content in the quicklime is ≥95%; and / or, the quicklime has a particle size of 50-200 μm; And / or, the water-lime ratio of water to quicklime in the lime-water mixing system is 3:1-6:

1.

3. The method for preparing highly active calcium hydroxide according to any one of claims 1 to 2, wherein The lime-water mixture system also contains a pore-forming agent and an optional dispersant; And / or, the lime-water mixture system further contains a pore-forming agent and an optional dispersant, wherein the pore-forming agent is a thermal decomposition type pore-forming agent accounting for 1-5% of the mass of quicklime; And / or, the lime-water mixture system further contains a pore-forming agent and an optional dispersant, wherein the pore-forming agent is a combination of any one or more of ammonium bicarbonate, urea, and citric acid; and / or, the lime-water mixture system further comprises a pore-forming agent and an optional dispersant, wherein the pore-forming agent is used in combination with the dispersant sodium hexametaphosphate; And / or, the lime-water mixture system further contains a pore-forming agent and an optional dispersant, and the mass ratio of the pore-forming agent to the dispersant is 2:1-5:

1.

4. The method for preparing highly active calcium hydroxide according to any one of claims 1 to 3, wherein The method comprises the following steps: S1: Apply a frequency of 20-40kHz and a power density of 1-3W / cm to the lime-water mixture. 3 Ultrasonic pretreatment for 5-15 minutes to obtain a premix; S2: The premix is microwave-heated in a coupled field of microwave radiation and ultrasonic cavitation and ultrasonic waves with a frequency of 28-60 kHz are simultaneously applied to enhance the lime digestion reaction for 20-40 minutes, and the reaction is stopped; S3: Switch to a frequency of 40-100kHz and a power density of 2-5W / cm 3 The particles were refined by high-frequency ultrasonic treatment for 15-20 minutes and dried to obtain a product.

5. The method for preparing highly active calcium hydroxide according to any one of claims 1 to 4, wherein The method comprises the following steps: S1: mixing quicklime having a CaO content of ≥95% with water to obtain a mixed solution; the quicklime has a particle size of 50-200 μm; and the water-to-lime ratio is 3:1-6:1; S2: mixing the mixed solution with a pore-forming agent and an optional dispersant to obtain a lime-water mixed system; S3: Apply a frequency of 20-40kHz and a power density of 1-3W / cm to the lime-water mixture system. 3 Ultrasonic pretreatment for 5-15 minutes to obtain a premix; S4: heating the premix in a microwave-heated coupled field of microwave radiation and ultrasonic cavitation and simultaneously applying ultrasonic waves with a frequency of 28-60 kHz to enhance the lime digestion reaction for 20-40 minutes, and then stopping the reaction; S5: Switch to a frequency of 40-100kHz and a power density of 2-5W / cm 3 The particles were refined by high-frequency ultrasonic treatment for 15-20 minutes, and the mixture was centrifuged. The precipitate was vacuum-dried at 60-80° C. to obtain the product.

6. The method for preparing highly active calcium hydroxide according to any one of claims 1 to 5, wherein The microwave heating frequency in the coupled field of microwave radiation and ultrasonic cavitation is 2.45 GHz, the temperature is controlled at 80-95°C, and the microwave power is 500-800W; Preferably, the heating rate of the microwave heating is 10-15°C / min; Preferably, the microwave power is controlled to decrease in gradient from an initial value of 800W to a final value of 500W; Preferably, the microwave power is gradient-decreased and the decrease range is 50-100 W / 5 min; Preferably, the microwave power is gradient-decreased and the decrease range is 100W / 5min.

7. The method for preparing highly active calcium hydroxide according to any one of claims 1 to 6, wherein The power density of the ultrasonic wave applied in the microwave radiation and ultrasonic cavitation coupling field is 2-5W / cm 3 ; Preferably, the synchronization rate of ultrasonic cavitation and pore-forming agent decomposition in the coupled field of microwave radiation and ultrasonic cavitation is above 70%.

8. The method for preparing highly active calcium hydroxide according to any one of claims 1 to 7, wherein The ultrasonic frequency applied in the microwave radiation and ultrasonic cavitation coupling field is dynamically matched with the high-frequency ultrasonic frequency applied during the high-frequency ultrasonic particle refinement in the post-processing; preferably, the initial frequency of the ultrasonic wave applied in the microwave radiation and ultrasonic cavitation coupling field is 40kHz, and the dynamic matching can switch the frequency of the high-frequency ultrasonic wave applied during the high-frequency ultrasonic particle refinement in the post-processing to 80kHz.

9. The method for preparing highly active calcium hydroxide according to any one of claims 1 to 8, wherein The product has a three-level pore structure, with micropores accounting for 10-15%, mesopores accounting for 50-60%, and macropores accounting for 25-40%.

10. Use of a product obtained by the method for preparing highly active calcium hydroxide according to any one of claims 1 to 9 in desulfurization.

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