Method for preparing fine calcium oxide

Abstract

This invention discloses a method for preparing fine calcium oxide, comprising the steps of raw material pretreatment, primary low-temperature calcination, digestion and deep impurity removal, composite modification and drying, secondary low-temperature calcination, and post-treatment. Limestone is pulverized, activated, and magnetically separated for impurity removal. Primary calcium oxide is obtained by calcination under a specific mixed gas and segmented temperature control. High-purity calcium hydroxide is obtained through hot water digestion, composite impurity removal with sodium citrate and disodium EDTA, and vacuum filtration. This is then composite-modified with sodium stearate, polyvinyl alcohol 124, and silane coupling agent KH-550, spray-dried, and subjected to a secondary low-temperature calcination under an inert gas atmosphere. Fine calcium oxide is then obtained through air-jet pulverization and sieving. This invention, through the synergistic effect of segmented calcination, deep impurity removal, and composite modification, produces a product with high purity, fine particle size, and good dispersibility. The process is stable and controllable, with mild conditions, suitable for industrial production, and can meet the application requirements of fine calcium oxide in high-end materials fields.

Description

Technical Field

[0001] This invention relates to the field of inorganic compound preparation technology, and in particular to a method for preparing fine calcium oxide. Background Technology

[0002] Calcium oxide (CaO), a basic inorganic chemical raw material, commonly known as quicklime, possesses excellent alkalinity, adsorption, and reactivity, playing an irreplaceable role in various fields such as environmental protection, building materials, chemicals, and new energy. With the rapid development of high-end manufacturing industries, the market demand for refined calcium oxide is increasingly urgent, requiring it to possess characteristics such as high purity (CaO content ≥ 99.0%), narrow particle size distribution (D50 ≤ 500nm), good dispersibility, and low impurity content to meet the stringent application requirements of emerging fields such as new energy and electronics.

[0003] Currently, the preparation methods for fine calcium oxide are mainly divided into three categories: traditional calcination, wet precipitation-calcination, and mechanical grinding. Traditional direct limestone calcination requires calcination at high temperatures of 900-1200℃, resulting in extremely high energy consumption. Furthermore, the prepared calcium oxide particles exhibit poor dispersion, uneven particle size, and difficulty in controlling impurity content, with CaO purity typically below 98.5%, failing to meet the demands of high-end applications. While the wet precipitation-calcination method improves dispersibility by adding modifiers, the modifier formulation is limited, resulting in insufficient precise particle size control. Additionally, the calcination process easily generates carbide residues, requiring an additional impurity removal process, leading to a cumbersome production process and increased costs. Mechanical grinding, due to its low particle size control precision and ease of impurity introduction, is gradually being phased out by the market and is only suitable for low-end product production. Moreover, most processes suffer from high energy consumption per unit product and high CO2 emissions.

[0004] Therefore, there is an urgent need to develop a fine calcium oxide preparation method that combines high purity, narrow particle size, good dispersibility, energy saving, environmental protection, and low cost. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing fine calcium oxide, which solves the defects of existing technologies such as low purity, wide particle size distribution, poor dispersibility, high energy consumption, insufficient environmental protection and high cost, so as to achieve efficient, green and large-scale preparation of fine calcium oxide and meet the needs of high-end application scenarios.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing refined calcium oxide includes the following steps:

[0008] S1. Raw material pretreatment: The raw limestone is crushed into particles with a particle size of 0.8~1.2cm, placed in an activation furnace, activated at 300~350℃ under inert gas protection for 20~30min, cooled to room temperature, and then magnetically separated to remove impurities to obtain pretreated limestone particles.

[0009] S2. Low-temperature calcination: Pretreated limestone particles are fed into a vertical calcining furnace, and a mixed gas preheated to 200~250℃ is introduced and calcined to obtain primary calcium oxide;

[0010] S3. Digestion and deep purification: Primary calcium oxide is mixed with deionized water at 85-90℃ at a mass ratio of 1:7-9 and stirred at 180-220 rpm for 30-40 min, then allowed to stand and age for 18-24 h to obtain a calcium hydroxide suspension; a composite purification agent is added to the suspension and stirred at 40-50℃ for 40-60 min, then vacuum filtered to obtain a high-purity calcium hydroxide solution;

[0011] S4. Composite Modification and Drying: Place high-purity calcium hydroxide solution in a reaction vessel, add 1.0~1.5% of its mass of composite modifier, control the reaction temperature at 40~50℃ and the stirring rate at 160~200rpm, and react for 80~100min; after the reaction is completed, spray dry to obtain modified calcium hydroxide solid;

[0012] S5. Secondary low-temperature calcination and post-treatment: The modified calcium hydroxide solid is fed into a calcination furnace, protected by inert gas, and the calcination temperature is controlled at 700~780℃ for 1.5~2.5h. Then it is cooled to room temperature and fed into an air jet mill for pulverization. After pulverization, it is screened by a vibrating screen to obtain fine calcium oxide product.

[0013] As a preferred embodiment of the present invention, the inert gas in S1 is nitrogen or argon.

[0014] In a preferred embodiment of the present invention, the mixed gas in S2 is obtained by mixing air and CO2 at a volume ratio of 7:3, and the introduction rate is 0.8~1.2m. 3 / h; the calcination process adopts segmented temperature control, raising the temperature to 650℃ in the first 30 minutes, and then continuing to raise the temperature to 700~750℃, and calcining at this temperature for 20~40 minutes.

[0015] As a preferred embodiment of the present invention, in step S3: the composite impurity remover is obtained by mixing sodium citrate and disodium EDTA at a mass ratio of 2:1, and the amount added is 0.3~0.5% of the mass of the calcium hydroxide suspension; the filter membrane of the vacuum filtration has a pore size of 0.1μm.

[0016] As a preferred embodiment of the present invention, in step S4: the composite modifier is obtained by mixing sodium stearate, polyvinyl alcohol 124 and silane coupling agent KH-550 in a mass ratio of 1:0.4:0.1; the spray drying adopts a centrifugal spray dryer with an atomization pressure of 0.3~0.5MPa, an inlet temperature of 180~200℃, and an outlet temperature of 80~90℃.

[0017] In a preferred embodiment of the present invention, the inert gas in step S5 is nitrogen, and the introduction rate is 1.0~1.5m. 3 / h.

[0018] As a preferred embodiment of the present invention, the grinding pressure of the airflow pulverizer in S5 is 0.7~0.9MPa, the feeding pressure is 0.4~0.6MPa, the CO2 concentration is monitored in real time during the calcination process, and the calcination is stopped when the CO2 concentration is lower than 0.5%.

[0019] As a preferred embodiment of the present invention, the mesh size of the vibrating screen in S5 is 300 mesh.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. This invention breaks through the limitations of traditional raw materials that are simply crushed. It adds an inert gas activation step at 300~350℃, combined with magnetic separation to remove impurities, which greatly improves the reactivity of the raw materials and removes magnetic impurities in advance. The first calcination adopts a low-temperature segmented temperature control of 700~750℃, combined with a mixture of air and CO2 gas, which not only solves the problem of high energy consumption in traditional high-temperature calcination, but also avoids excessive grain growth, laying the foundation for subsequent particle size control.

[0022] 2. By designing a composite impurity remover of sodium citrate and disodium EDTA, soluble impurities and tiny particulate impurities in the raw materials are specifically removed. Combined with vacuum filtration of a filter membrane with a pore size of 0.1μm, the pain points of existing technologies, such as the difficulty in completely removing impurities and insufficient purity, are solved. This significantly improves the purity of CaO and reduces the total content of harmful metals, meeting the requirements of electronic and new energy products.

[0023] 3. By designing a composite modification system of sodium stearate, polyvinyl alcohol 124 and silane coupling agent KH-550, the three work synergistically to not only precisely control the crystal form and particle size of calcium hydroxide and improve dispersibility, but also to form a protective film on the surface of calcium oxide to prevent it from reacting with CO2 and H2O in the air and extend the shelf life of the product.

[0024] 4. By using a secondary low-temperature calcination at 700~780℃, combined with inert gas protection, the calcium hydroxide is fully decomposed while avoiding secondary pollution from calcium oxide. The entire process emits no harmful gases, and CO2 emissions are significantly reduced compared to traditional processes. Attached Figure Description

[0025] Figure 1 This is a flowchart of a method for preparing fine calcium oxide according to the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The synergistic innovation of raw material pretreatment and primary calcination enhances the reactivity of raw materials through inert gas activation, removes magnetic impurities in advance through magnetic separation, and combines low-temperature segmented temperature-controlled calcination. This not only significantly reduces energy consumption per unit product but also avoids excessive grain growth, laying a solid foundation for precise particle size control in the future. It solves the problems of high energy consumption and uneven grain size in traditional processes.

[0028] The innovative sodium citrate and disodium EDTA composite impurity removal system, combined with high-precision vacuum filtration membrane, can thoroughly remove soluble impurities and microparticle impurities from raw materials, significantly improving product purity and achieving a CaO content of over 99.5%, meeting the stringent purity requirements of high-end applications such as electronic and new energy applications.

[0029] The innovative composite modification of sodium stearate, polyvinyl alcohol 124, and silane coupling agents not only precisely controls product particle size and improves dispersibility, but also forms a protective film on the calcium oxide surface to prevent moisture absorption and carbonization, extending product shelf life. This addresses the pain points of existing technologies, such as easy agglomeration and poor stability. The integration of multiple technologies makes the entire process clear and highly operable, significantly reducing equipment investment and production costs, facilitating large-scale industrial production, effectively filling the gap in the domestic high-end fine calcium oxide market, and enhancing product market competitiveness.

[0030] like Figure 1As shown, a method for preparing fine calcium oxide includes the following steps: S1. Raw material pretreatment: The raw material limestone is crushed into particles with a particle size of 0.8~1.2cm, placed in an activation furnace, activated at 300~350℃ under inert gas protection for 20~30min, cooled to room temperature, and then magnetically separated to remove impurities to obtain pretreated limestone particles; S2. First-stage low-temperature calcination: The pretreated limestone particles are fed into a vertical calcination furnace, a mixed gas preheated to 200~250℃ is introduced, and calcination is carried out to obtain primary calcium oxide; S3. Digestion and deep impurity removal: The primary calcium oxide is mixed with deionized water at 85~90℃ at a mass ratio of 1:7~9 and stirred at 180~220rpm for 30~40min, then allowed to stand and age for 18~24h to obtain a calcium hydroxide suspension; Add to the suspension S4. Composite modification and drying: Place the high-purity calcium hydroxide solution in a reaction vessel, add 1.0-1.5% of its mass of composite modifier, control the reaction temperature at 40-50℃ and the stirring rate at 160-200 rpm, and react for 80-100 minutes; after the reaction is completed, spray dry to obtain modified calcium hydroxide solid; S5. Secondary low-temperature calcination and post-treatment: Send the modified calcium hydroxide solid into a calcination furnace, introduce inert gas for protection, control the calcination temperature at 700-780℃, calcination time at 1.5-2.5 h, then cool to room temperature, send to an air jet mill for pulverization, and after pulverization, screen with a vibrating screen to obtain fine calcium oxide product.

[0031] All raw materials used in this invention are commercially available.

[0032] Example 1:

[0033] A method for preparing refined calcium oxide includes the following steps:

[0034] S1. Raw material pretreatment: The raw limestone is crushed into particles with a particle size of 0.8 cm, placed in an activation furnace, activated at 350°C under nitrogen protection for 30 min, cooled to room temperature, and then magnetically separated to remove impurities to obtain pretreated limestone particles.

[0035] S2. Primary Low-Temperature Calcination: Pretreated limestone particles are fed into a vertical calcining furnace, and a mixed gas (air and CO2 mixed at a volume ratio of 7:3) preheated to 250°C is introduced at a rate of 1.2 m / s. 3 / h, during the calcination process, the temperature is raised to 650℃ in the first 30 minutes, then raised to 750℃, and calcined at this temperature for 40 minutes to obtain primary calcium oxide;

[0036] S3. Digestion and deep impurity removal: Primary calcium oxide and deionized water at 90℃ are mixed at a mass ratio of 1:9 and stirred at 220 rpm for 40 min, then allowed to stand and age for 24 h to obtain a calcium hydroxide suspension; 0.5% of the mass of the calcium hydroxide suspension is added to the suspension as a composite impurity remover (sodium citrate and disodium EDTA mixed at a mass ratio of 2:1), and the mixture is stirred at 50℃ for 60 min. Then, the mixture is vacuum filtered using a filter membrane with a pore size of 0.1 μm to obtain a high-purity calcium hydroxide solution.

[0037] S4. Composite Modification and Drying: A high-purity calcium hydroxide solution was placed in a reaction vessel, and 1.5% of its mass of a composite modifier (sodium stearate, polyvinyl alcohol 124, and silane coupling agent KH-550 mixed in a mass ratio of 1:0.4:0.1) was added. The reaction temperature was controlled at 50℃, the stirring speed at 200 rpm, and the reaction was carried out for 100 min. After the reaction was completed, the modified calcium hydroxide solid was obtained by spray drying. The spray drying was carried out using a centrifugal spray dryer with an atomization pressure of 0.5 MPa, an inlet temperature of 200℃, and an outlet temperature of 90℃.

[0038] S5. Secondary Low-Temperature Calcination and Post-Treatment: The modified calcium hydroxide solid is fed into a calcination furnace, and nitrogen gas is introduced for protection at a rate of 1.5 m / s. 3 The calcination temperature was controlled at 780℃ and the calcination time was 2.5h. The CO2 concentration was monitored in real time during the calcination process. When the CO2 concentration was lower than 0.5%, the calcination was stopped. Then, the mixture was cooled to room temperature and fed into an air jet mill for pulverization. The pulverization pressure was 0.9MPa and the feed pressure was 0.6MPa. After pulverization, the mixture was screened using a 300-mesh vibrating screen to obtain fine calcium oxide product.

[0039] Example 2:

[0040] A method for preparing refined calcium oxide includes the following steps:

[0041] S1. Raw material pretreatment: The raw limestone is crushed into particles with a particle size of 1.2 cm, placed in an activation furnace, activated at 300°C under nitrogen protection for 20 min, cooled to room temperature, and then magnetically separated to remove impurities to obtain pretreated limestone particles.

[0042] S2. Primary Low-Temperature Calcination: Pretreated limestone particles are fed into a vertical calcining furnace, and a mixed gas (air and CO2 mixed at a volume ratio of 7:3) preheated to 200°C is introduced at a rate of 0.8 m / s. 3 / h, during the calcination process, the temperature is raised to 650℃ for the first 30 minutes, then raised to 700℃, and calcined at this temperature for 20 minutes to obtain primary calcium oxide;

[0043] S3. Digestion and deep impurity removal: Primary calcium oxide and deionized water at 85℃ are mixed at a mass ratio of 1:7 and stirred at 180 rpm for 30 min, then allowed to stand and age for 18 h to obtain a calcium hydroxide suspension; 0.3% of the mass of the calcium hydroxide suspension is added to the suspension as a composite impurity remover (sodium citrate and disodium EDTA mixed at a mass ratio of 2:1), and the mixture is stirred at 40℃ for 40 min. Then, the mixture is vacuum filtered using a filter membrane with a pore size of 0.1 μm to obtain a high-purity calcium hydroxide solution.

[0044] S4. Composite Modification and Drying: A high-purity calcium hydroxide solution was placed in a reaction vessel, and 1.0% of its mass of a composite modifier (sodium stearate, polyvinyl alcohol 124, and silane coupling agent KH-550 mixed in a mass ratio of 1:0.4:0.1) was added. The reaction temperature was controlled at 40℃, the stirring speed at 160 rpm, and the reaction was carried out for 80 min. After the reaction was completed, the modified calcium hydroxide solid was obtained by spray drying. The spray drying was carried out using a centrifugal spray dryer with an atomization pressure of 0.3 MPa, an inlet temperature of 180℃, and an outlet temperature of 80℃.

[0045] S5. Secondary Low-Temperature Calcination and Post-Treatment: The modified calcium hydroxide solid is fed into a calcination furnace, and nitrogen gas is introduced for protection at a rate of 1.0 m / s. 3 The calcination temperature was controlled at 700℃ and the calcination time was 1.5h. The CO2 concentration was monitored in real time during the calcination process. When the CO2 concentration was lower than 0.5%, the calcination was stopped. Then, the mixture was cooled to room temperature and fed into an air jet mill for pulverization. The pulverization pressure was 0.7MPa and the feed pressure was 0.4MPa. After pulverization, the mixture was screened using a 300-mesh vibrating screen to obtain fine calcium oxide product.

[0046] Example 3:

[0047] A method for preparing refined calcium oxide includes the following steps:

[0048] S1. Raw material pretreatment: The raw limestone is crushed into particles with a particle size of 1.0 cm, placed in an activation furnace, activated at 325℃ under nitrogen protection for 25 min, cooled to room temperature, and then magnetically separated to remove impurities to obtain pretreated limestone particles.

[0049] S2. Primary Low-Temperature Calcination: Pretreated limestone particles are fed into a vertical calcining furnace, and a mixed gas (air and CO2 mixed at a volume ratio of 7:3) preheated to 225°C is introduced at a rate of 1.0 m / s. 3 / h, during the calcination process, the temperature is raised to 650℃ for the first 30 minutes, then raised to 725℃, and calcined at this temperature for 30 minutes to obtain primary calcium oxide;

[0050] S3. Digestion and deep impurity removal: Primary calcium oxide and deionized water at 87℃ were mixed at a mass ratio of 1:8 and stirred at 200 rpm for 35 min, then allowed to stand and age for 21 h to obtain a calcium hydroxide suspension; 0.4% of a composite impurity removal agent (sodium citrate and disodium EDTA mixed at a mass ratio of 2:1) was added to the suspension, and the mixture was stirred at 45℃ for 50 min. Then, the mixture was vacuum filtered using a filter membrane with a pore size of 0.1 μm to obtain a high-purity calcium hydroxide solution.

[0051] S4. Composite Modification and Drying: A high-purity calcium hydroxide solution was placed in a reaction vessel, and 1.25% by mass of a composite modifier (sodium stearate, polyvinyl alcohol 124, and silane coupling agent KH-550 mixed in a mass ratio of 1:0.4:0.1) was added. The reaction temperature was controlled at 45℃, the stirring speed at 180 rpm, and the reaction was carried out for 90 min. After the reaction was completed, the modified calcium hydroxide solid was obtained by spray drying. The spray drying was carried out using a centrifugal spray dryer with an atomization pressure of 0.4 MPa, an inlet temperature of 190℃, and an outlet temperature of 85℃.

[0052] S5. Secondary Low-Temperature Calcination and Post-Treatment: The modified calcium hydroxide solid is fed into a calcination furnace, and nitrogen gas is introduced for protection at a rate of 1.2 m / s. 3 The calcination temperature was controlled at 740℃ and the calcination time was 2.0h. The CO2 concentration was monitored in real time during the calcination process. When the CO2 concentration was lower than 0.5%, the calcination was stopped. Then, the mixture was cooled to room temperature and fed into an air jet mill for pulverization. The pulverization pressure was 0.8MPa and the feed pressure was 0.5MPa. After pulverization, the mixture was screened using a 300-mesh vibrating screen to obtain fine calcium oxide product.

[0053] Comparative Example 1:

[0054] The difference from Example 1 is that the limestone particles crushed in step S1 are directly fed into a vertical calcining furnace for a single low-temperature calcination.

[0055] Comparative Example 2:

[0056] The difference from Example 1 is that the composite impurity remover in S3 is replaced with sodium citrate alone.

[0057] Comparative Example 3:

[0058] The difference from Example 1 is that the modified calcium hydroxide solid is directly fed into an air jet mill for crushing and screening, eliminating the need for secondary calcination treatment.

[0059] The fine calcium oxide prepared in Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3 were tested and analyzed to determine their product performance, calcium oxide content, specific surface area, and D50 (median particle size) of the powder particles. The results are shown in Table 1.

[0060] Table 1: Detection of relevant indicators for fine calcium oxide prepared in the examples and comparative groups

[0061]

[0062] As can be seen from Table 1, the fine calcium oxide prepared in the example group has higher purity, narrower particle size, and better dispersion compared with the fine calcium oxide prepared in the comparative example group.

[0063] Raw material pretreatment enhances limestone reactivity through inert gas activation, while magnetic separation removes magnetic mineral impurities in advance, reducing residual impurities during subsequent calcination. This ensures the basic purity of calcium oxide while preventing impurities from hindering grain growth, resulting in finer particles and laying the foundation for optimizing D50 particle size and increasing specific surface area. The composite impurity remover uses a combination of sodium citrate and disodium EDTA, which efficiently chelates and removes soluble trace metal impurities and fine inorganic impurities. Combined with high-precision filtration for further purification, this significantly increases the calcium oxide content of the final product. Simultaneously, it prevents impurity agglomeration that leads to uneven particle size, reduces D50 particle size, improves particle size uniformity, and indirectly increases particle specific surface area. Secondary low-temperature calcination, under inert gas protection, allows modified calcium hydroxide to fully decompose and completely transform into calcium oxide, preventing excessive sintering of grains. This further improves calcium oxide purity, precisely controls particle size, and retains internal pores, effectively increasing the product's specific surface area. These three processes work synergistically to achieve a high-purity, narrow-particle-size, and high-specific-surface-area premium fine calcium oxide product.

[0064] In summary, the fine calcium oxide preparation method of the present invention has controllable process and excellent product performance. The prepared fine calcium oxide has high purity, uniform particle size distribution and meets the specific surface area standard. It solves the core pain points of existing methods such as low purity, uneven particle size, poor dispersibility and insufficient stability, and provides a reliable solution for the green, large-scale and high-quality preparation of high-end fine calcium oxide.

[0065] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A method for producing fine calcium oxide, characterized by, Includes the following steps: S1. Raw material pretreatment: The raw limestone is crushed into particles with a particle size of 0.8~1.2cm, placed in an activation furnace, activated at 300~350℃ under inert gas protection for 20~30min, cooled to room temperature, and then magnetically separated to remove impurities to obtain pretreated limestone particles. S2. Low-temperature calcination: Pretreated limestone particles are fed into a vertical calcining furnace, and a mixed gas preheated to 200~250℃ is introduced and calcined to obtain primary calcium oxide; S3. Digestion and deep impurity removal: Primary calcium oxide is mixed with deionized water at 85~90℃ at a mass ratio of 1:7~9 and stirred at 180~220rpm for 30~40min. Then it is allowed to stand and age for 18~24h to obtain calcium hydroxide suspension. Add a composite impurity remover to the suspension, stir and react at 40-50℃ for 40-60 min, and then filter under vacuum to obtain a high-purity calcium hydroxide solution. S4. Composite Modification and Drying: Place high-purity calcium hydroxide solution in a reaction vessel, add 1.0~1.5% of its mass of composite modifier, control the reaction temperature at 40~50℃ and the stirring rate at 160~200rpm, and react for 80~100min; after the reaction is completed, spray dry to obtain modified calcium hydroxide solid; S5. Secondary low-temperature calcination and post-treatment: The modified calcium hydroxide solid is fed into a calcination furnace, and an inert gas is introduced for protection. The calcination temperature is controlled at 700~780℃ and the calcination time is 1.5~2.5h. Then it is cooled to room temperature and fed into an air jet mill for pulverization. After pulverization, it is screened by a vibrating screen to obtain fine calcium oxide product. The composite impurity remover is obtained by mixing sodium citrate and disodium EDTA at a mass ratio of 2:1, and the amount added is 0.3~0.5% of the mass of the calcium hydroxide suspension; The composite modifier is obtained by mixing sodium stearate, polyvinyl alcohol 124 and silane coupling agent KH-550 in a mass ratio of 1:0.4:0.

1.

2. The method for preparing refined calcium oxide according to claim 1, characterized in that, The inert gas in S1 is nitrogen or argon.

3. The method for preparing refined calcium oxide according to claim 1, characterized in that, The mixed gas in S2 is air mixed with CO2 at a volume ratio of 7:3, and the flow rate is 0.8-1.2 m 3 / h; in S2, the calcination is performed by using a staged temperature control, the temperature is raised to 650 DEG C in the first 30 min, then the temperature is continuously raised to 700-750 DEG C, and the calcination is performed at the constant temperature for 20-40 min.

4. The method for preparing refined calcium oxide according to claim 1, characterized in that, The filter membrane in S3 has a pore size of 0.1 μm.

5. The method for preparing refined calcium oxide according to claim 1, characterized in that, The spray drying in S4 uses a centrifugal spray dryer with an atomization pressure of 0.3~0.5MPa, an inlet temperature of 180~200℃, and an outlet temperature of 80~90℃.

6. The method for preparing refined calcium oxide according to claim 1, characterized in that, The inert gas in S5 is nitrogen, and the flow rate is 1.0-1.5 m 3 / h.

7. The method for preparing refined calcium oxide according to claim 1, characterized in that, The airflow pulverizer in S5 has a pulverizing pressure of 0.7~0.9MPa and a feeding pressure of 0.4~0.6MPa. The CO2 concentration is monitored in real time during the calcination process, and calcination is stopped when the CO2 concentration is lower than 0.5%.

8. The method for preparing refined calcium oxide according to claim 1, characterized in that, The vibrating screen in S5 has a mesh size of 300.

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