Method for whitening and upgrading of limestone

Abstract

The application discloses a method for whitening and upgrading limestone, which comprises the following steps: raw material preparation: treating limestone raw material, processing the limestone into limestone with a certain particle size, and obtaining the mass of the limestone; pretreatment: selecting and weighing a fluxing agent, mixing the fluxing agent with the limestone, and stirring uniformly to form a limestone mixture; adding the fluxing agent into a furnace: putting the limestone mixture into a muffle furnace to prepare for calcination; calcination: adjusting the temperature of the muffle furnace to control the process of the calcination, wherein the process of the calcination comprises temperature rising, temperature keeping and temperature falling, and the target temperature interval of the temperature rising is 730-1200 DEG C; product treatment: taking out the limestone cooling material after the completion of the calcination process from the muffle furnace, and processing the limestone cooling material into limestone powder; and quality detection: detecting the whiteness, calcium oxide content and silicon dioxide content of the limestone powder. According to the above technical scheme, the whiteness of the limestone and the calcium oxide content can be improved by combining the fluxing agent and the temperature control of the muffle furnace, so that the effect of whitening and upgrading can be achieved.

Description

Technical Field

[0001] This invention relates to the field of limestone calcination, and more specifically, to a method for whitening and improving the quality of limestone. Background Technology

[0002] Limestone is a widely used mineral resource with diverse applications across many industrial sectors. For example, it is an important component of building materials, used in the manufacture of lime and cement. Cement, in particular, is made by mixing limestone and clay, and then calcining it at high temperatures (800–1300℃), making it an indispensable material in the construction industry.

[0003] Calcination of limestone includes traditional lime kiln calcination technology and some newer calcination methods. Traditional lime kiln calcination technology typically involves placing limestone blocks into a lime kiln for preheating, decomposition, and cooling. First, the limestone is heated to a suitable temperature for preheating; then it is heated to a higher temperature for decomposition and calcination, breaking it down into calcium oxide and carbon dioxide; finally, the decomposed lime is cooled. This method uses simple equipment but consumes a large amount of fuel and produces significant amounts of carbon dioxide and soot, negatively impacting the environment. Some newer calcination methods use muffle furnaces for high-temperature calcination. Muffle furnace calcination offers advantages such as high calcination temperature but long duration, uniform calcination, and stable product quality. However, in controlling the calcination process, variations in temperature, duration, and the addition of flux can all affect the whiteness and quality of the limestone. Therefore, a technical solution is needed to control the limestone processing to achieve whitening and quality improvement effects. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides a method for whitening and improving limestone, comprising the following steps:

[0005] Raw material preparation: Process limestone raw materials to produce limestone of a certain particle size, and obtain the mass of the limestone;

[0006] Pretreatment: Select and weigh the flux, mix it with limestone, stir evenly to form a limestone mixture;

[0007] Adding flux and loading the furnace: The limestone mixture is put into the muffle furnace in preparation for calcination;

[0008] Calcination: The process of controlling the calcination process by adjusting the temperature of the muffle furnace. The calcination process includes heating, holding, and cooling. The target temperature range for heating is 730 to 1200°C.

[0009] Product processing: The cooled limestone material after calcination is removed from the muffle furnace and processed into limestone powder;

[0010] Quality inspection: The whiteness, calcium oxide and silica content of the limestone powder are tested.

[0011] Furthermore, the calcination process takes 4 to 8 hours; when the calcination process takes 8 hours, the process time is controlled as follows: heating for 2 hours, holding for 4 hours, and cooling for 2 hours; wherein, heating for 2 hours means that the muffle furnace rises from room temperature to a specified temperature within the target temperature range within 2 hours, and cooling for 2 hours means that the muffle furnace drops from the specified temperature to a set platform temperature within 2 hours.

[0012] Furthermore, the flux includes one or more of ammonium bifluoride, boric acid, or barium chloride.

[0013] When weighing the flux, the mass of the flux is 0.3-3% of the mass of the limestone, and further, the mass of the flux is 0.5% of the mass of the limestone.

[0014] When the muffle furnace reaches a heating range of 730–1200℃, quality testing reveals that the limestone powder has a whiteness of 55%–81%, a calcium oxide content of 70%–92%, and a silica content of 4%–8%.

[0015] When the muffle furnace is heated in the range of 950–1200℃, the quality test results show that the whiteness of the limestone powder is 65%–81%, the calcium oxide content is 82%–92%, and the silica content is 4%–8%.

[0016] Furthermore, the particle size of limestone is less than or equal to 6 cm. Among them, particles with a particle size of less than or equal to 1 cm are considered small particles, particles with a particle size greater than 1 cm but less than or equal to 3 cm are considered medium particles, and particles with a particle size greater than 3 cm are considered large particles.

[0017] According to the method provided by this invention, limestone is calcined in a muffle furnace. Different fluxes and temperature controls during the limestone upgrading and whitening process can yield varying degrees of whitening and quality, which can be applied to different environments. However, excessively low temperatures or unsuitable fluxes can lead to a decrease in calcium oxide content, thereby reducing the whiteness and quality of the limestone. Attached Figure Description

[0018] Figure 1 This is a flowchart of limestone whitening and upgrading process according to an embodiment of the present invention. Detailed Implementation

[0019] The specific implementation of the present invention will now be described in detail with reference to the accompanying drawings.

[0020] like Figure 1 As shown, the limestone whitening and upgrading method provided by the present invention includes the following steps:

[0021] S100 Raw Material Preparation: In this invention, limestone of a certain particle size and mass is selected. To ensure complete combustion of the limestone, the prepared limestone particle size is less than or equal to 6 cm. Particles less than or equal to 1 cm are considered small particle sizes, particles greater than 1 cm but less than or equal to 3 cm are considered medium particle sizes, and particles greater than 3 cm are considered large particle sizes. In the embodiments provided by this invention, the mass of the limestone used in the experiment is 210–1000 g. The mass is weighed during the preparation process for subsequent flux preparation.

[0022] In practical applications, the total mass of limestone fed into the furnace for calcination is determined by the actual specifications of the muffle furnace.

[0023] S110 pretreatment: Add flux and mix with the prepared limestone, stir evenly to form a limestone mixture; after stirring, the flux can adhere to the surface layer of the limestone.

[0024] Fluxes include one or more of ammonium bifluoride, boric acid, or barium chloride.

[0025] The flux mass is 0.3-3% of the limestone mass.

[0026] S120 Flux Addition and Furnace Loading: The limestone mixture is fed into the muffle furnace in preparation for calcination;

[0027] S130 Calcination: This refers to the process of controlling the calcination process by adjusting the temperature of the muffle furnace. The calcination process includes heating, holding, and cooling. The target temperature range for heating is 730–1200℃. The calcination process lasts 4–8 hours, during which the duration of heating, holding, and cooling is allocated. For example, if the entire calcination process lasts 8 hours, the time for each step is controlled as follows: 2 hours for heating, 4 hours for holding, and 2 hours for cooling. Specifically, 2 hours of heating means the muffle furnace rises from room temperature to a specified temperature within the target temperature range within 2 hours, and 2 hours of cooling means the muffle furnace drops from a specified temperature to a set platform temperature within 2 hours. The set platform temperature can be set and determined for the muffle furnace.

[0028] After calcination and heating, the target temperature range of the muffle furnace is set at 730–1200℃, and the calcination process takes 8 hours. The temperature of the muffle furnace can significantly affect the whiteness of the limestone. At the same time, by adding 0.3–3% flux by mass of limestone, limestone with a whiteness of 55%–81%, a calcium oxide content of 70%–92%, and a silica content of 4%–8% can be obtained.

[0029] Controlling the temperature between 730 and 950℃ and between 950 and 1200℃ will produce different effects. When the temperature is controlled between 950 and 1200℃, the whiteness of limestone can be significantly improved. After adding an appropriate flux, limestone with a whiteness of 65% to 81%, a calcium oxide content of 82% to 92%, and a silica content of 4% to 8% can be obtained.

[0030] Meanwhile, keeping the food warm for four hours is a crucial step that can effectively prevent it from not being fully cooked.

[0031] S140 Product Processing: The limestone cooled material after calcination is removed from the muffle furnace and processed into limestone powder;

[0032] S150 Quality Inspection: The whiteness, calcium oxide content, and silica content of the processed limestone powder are tested, with a whiteness of 55%–81%, a calcium oxide content of 70%–92%, and a silica content of 4%–8%.

[0033] The present invention provides specific embodiments as follows:

[0034] Group 1: Four examples are provided, using limestone raw materials with similar compositions calcined at 730°C:

[0035] Example 1: Using small-diameter limestone, without flux:

[0036] The raw material is 210g of limestone. The limestone is put into a fluoropolymer furnace for calcination. The target temperature for heating is 730℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The whiteness of the resulting limestone is 65.6%, the calcium oxide content is 80.3%, and the silicon dioxide content is 4.6%.

[0037] Example 2: Using small-particle-size limestone, with the flux boric acid added:

[0038] The raw material consists of 400g of limestone and 2g of boric acid (ratio: 0.5%) to form a limestone mixture. The limestone mixture is put into a fluoropolymer furnace for calcination. The target temperature for heating is 730℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The resulting limestone has a whiteness of 62.5%, a calcium oxide content of 71.2%, and a silicon dioxide content of 5.2%.

[0039] Example 3: Using small-particle-size limestone, with the flux ammonium bifluoride added:

[0040] The raw material consists of 300g limestone and 1.5g ammonium bifluoride (ratio: 0.5%) to form a limestone mixture. The limestone mixture is put into a fluoropolymer furnace for calcination. The target temperature for heating is 730℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The resulting limestone has a whiteness of 55.2%, a calcium oxide content of 70%, and a silicon dioxide content of 6.4%.

[0041] Example 4: Using small-particle-size limestone, barium chloride flux was added:

[0042] The raw materials consist of 350g limestone and 1.75g ​​barium chloride (ratio: 0.5%) to form a limestone mixture. The limestone mixture is put into a fluoropolymer furnace for calcination. The target temperature for heating is 730℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The resulting limestone has a whiteness of 57.1%, a calcium oxide content of 73.1%, and a silicon dioxide content of 5.2%.

[0043] Quality testing of the first group of examples shows that if the temperature is too low or the flux is different, the calcium oxide content will decrease, thereby reducing the whiteness and quality of the limestone.

[0044] Group 2: Four examples are provided, using limestone raw materials with similar compositions calcined at 950°C:

[0045] Example 5: Using medium-sized limestone, with the flux ammonium bifluoride added:

[0046] The raw material consists of 440g of limestone and 2.2g of ammonium bifluoride (ratio: 0.5%) to form a limestone mixture. The limestone mixture is put into a fluoropolymer furnace for calcination. The target temperature for heating is 950℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The resulting limestone has a whiteness of 81.7%, a calcium oxide content of 92%, and a silicon dioxide content of 4.3%.

[0047] Example 6: Using medium-sized limestone, with the addition of barium chloride flux:

[0048] The raw materials consist of 410g of limestone and 2.05g of barium chloride (ratio: 0.5%) to form a limestone mixture. The limestone mixture is put into a fluoropolymer furnace for calcination. The target temperature for heating is 950℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The resulting limestone has a whiteness of 74.6%, a calcium oxide content of 89.7%, and a silicon dioxide content of 4.5%.

[0049] Example 7: Using large-particle-size limestone, with the flux ammonium bifluoride added:

[0050] The raw material consists of 610g of limestone and 3.05g of ammonium bifluoride (ratio: 0.5%) to form a limestone mixture. The limestone mixture is put into a fluoropolymer furnace for calcination. The target temperature for heating is 950℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The resulting limestone has a whiteness of 64.1%, a calcium oxide content of 90.57%, and a silicon dioxide content of 4.7%.

[0051] Example 8: Using large-particle-size limestone and adding barium chloride as flux:

[0052] The raw material consists of 520g of limestone and 2.6g of barium chloride (ratio: 0.5%) to form a limestone mixture. The limestone mixture is put into a fluoropolymer furnace for calcination. The target temperature for heating is 950℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The resulting limestone has a whiteness of 66%, a calcium oxide content of 86.08%, and a silicon dioxide content of 5.2%.

[0053] The quality tests conducted in the second set of examples show that the smaller the particle size, the better the whiteness and quality of the limestone after calcination under the same environmental conditions.

[0054] Group 3: Four examples are provided, using limestone raw materials with similar compositions calcined at 1000°C:

[0055] Example 9: Using large-particle-size limestone and adding ammonium bifluoride as flux:

[0056] The raw material consists of 510g of limestone and 2.55g of ammonium bifluoride (ratio: 0.5%) to form a limestone mixture. The limestone mixture is put into a fluoropolymer furnace for calcination. The target temperature for heating is 1000℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The resulting limestone has a whiteness of 68.5%, a calcium oxide content of 90.3%, and a silicon dioxide content of 4.4%.

[0057] Example 10: Using large-particle-size limestone, with the addition of fluxes boric acid, barium chloride, and ammonium bifluoride:

[0058] The raw material consisted of 460g of limestone, 2.3g of boric acid, barium chloride, and ammonium bifluoride (ratio: 0.5%), forming a limestone mixture. The limestone mixture was calcined in a fluoropolymer furnace with a target temperature of 1000℃, a heating time of 2 hours, a holding time of 4 hours, and a cooling time of 2 hours. The resulting limestone had a whiteness of 72.2%, a calcium oxide content of 86.1%, and a silicon dioxide content of 4.2%.

[0059] Example 11: Using large-particle-size limestone, with the addition of barium chloride as flux:

[0060] The raw materials consist of 450g of limestone and 2.25g of barium chloride (ratio: 0.5%) to form a limestone mixture. The limestone mixture is put into a fluoropolymer furnace for calcination. The target temperature for heating is 1000℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The resulting limestone has a whiteness of 70.1%, a calcium oxide content of 84.6%, and a silicon dioxide content of 5%.

[0061] Example 12: Compared with using large-particle-size limestone without adding flux:

[0062] The raw material is 760g of limestone. The limestone particles are put into a fluoropolymer furnace for calcination. The target temperature for heating is 1000℃, the heating time is 2 hours, the holding time is 4 hours, and the cooling time is 2 hours. The whiteness of the resulting limestone is 70.3%, the calcium oxide content is 87.77%, and the silicon dioxide content is 4.9%.

[0063] The processing results of the above embodiments are compared, and the comparison results are shown in the table below:

[0064]

[0065]

[0066]

[0067] As can be seen from the above examples, the use of different fluxes and the temperature control of calcined limestone are key parameters affecting the upgrading and whitening process. If the temperature is too low or different fluxes are added, the calcium oxide content will decrease, thereby reducing the whiteness and quality of the limestone. With the use of fluxes and temperature control, the whiteness of the limestone is 64%–82%, the calcium oxide content is 82%–92%, and the silica content is 4%–8%. Furthermore, the temperature control of the muffle furnace can significantly affect the whiteness of the limestone; specifically, temperature control between 950 and 1200°C can significantly improve the whiteness of the limestone.

[0068] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the present invention is not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for whitening and improving the quality of limestone, characterized in that, Includes the following steps: Raw material preparation: Process limestone raw materials to produce limestone of a certain particle size, and obtain the mass of the limestone; the certain particle size refers to: the particle size of limestone is less than or equal to 6cm, wherein the particle size is less than or equal to 1cm and is considered small particle size, the particle size is greater than 1cm and less than or equal to 3cm and is considered medium particle size, and the particle size is greater than 3cm and is considered large particle size. Pretreatment: Select and weigh flux, mix with limestone, and stir evenly to form a limestone mixture; the flux includes one or more of ammonium bifluoride, boric acid, or barium chloride; when weighing the flux, the mass of the flux is 0.3-3% of the mass of the limestone; Adding flux and loading the furnace: The limestone mixture is fed into a muffle furnace in preparation for calcination; Calcination: The process of controlling the calcination process by adjusting the temperature of the muffle furnace. The calcination process includes heating, holding, and cooling. The target temperature range for heating is 730~1200℃, and the calcination time is 4~8 hours. Product processing: The limestone cooled material after calcination is removed from the muffle furnace and processed into limestone powder; Quality inspection: The whiteness, calcium oxide and silicon dioxide content of the limestone powder are tested.

2. The method for whitening and upgrading limestone according to claim 1, characterized in that, If the calcination process takes 8 hours, the process time control of the calcination process is as follows: heating for 2 hours, holding for 4 hours, and cooling for 2 hours; wherein, the heating for 2 hours means that the muffle furnace rises from room temperature to a specified temperature within the target temperature range within 2 hours, and the cooling for 2 hours means that the muffle furnace drops from the specified temperature to a set platform temperature within 2 hours.

3. The method for whitening and upgrading limestone according to claim 1, characterized in that, The flux is 0.5% of the mass of the limestone.

4. The method for whitening and upgrading limestone according to claim 1 or 3, characterized in that, When the muffle furnace is heated to 730-1200℃, the quality test shows that the whiteness of the limestone powder is 55%-81%, the calcium oxide content is 70%-92%, and the silicon dioxide content is 4-8%.

5. The method for whitening and upgrading limestone according to claim 4, characterized in that, When the muffle furnace is heated to 950-1200℃, the quality test shows that the whiteness of the limestone powder is 65%-81%, the calcium oxide content is 82%-92%, and the silicon dioxide content is 4-8%.

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