Limestone-based cement raw material pre-homogenization method

Abstract

The invention relates to a limestone-based cement raw material pre-homogenization method in the technical field of cement production, which comprises the following steps: S1, crushing limestone into particles, removing impurities, drying, detecting the chemical components of the limestone particles, and recording; s2, dividing the limestone into 3-5 grades according to the content of CaO in the limestone, storing the limestone into warehouses of corresponding grades, and then calculating the ratio of the limestone of each grade to the auxiliary materials; s3, the raw materials are conveyed to a stacker according to the proportion, and stacking is conducted in a fan-shaped material distribution and layered stacking mode; s4, the raw materials at different positions of the material pile are scraped through reverse rotation of the double-spiral material taking machine; s5, feeding the raw materials obtained in the step S4 into a homogenizing silo, performing fluidized stirring with compressed air, and then performing mechanical stirring at a rotating speed of 30-50r / min for 10-15min; and S6, detecting the homogenized raw materials in the step S5, entering a grinding procedure after the raw materials are qualified, and returning the raw materials to a homogenizing silo for re-homogenization if the raw materials are unqualified. According to the scheme, the problem that the cement production quality is influenced by poor homogenization effect of the existing limestone processed cement raw material is solved.

Description

Technical Field

[0001] This invention relates to the field of cement production technology, and more specifically to a method for pre-homogenizing cement raw materials based on limestone. Background Technology

[0002] The degree of homogenization of cement raw meal is one of the key factors affecting the quality, calcination efficiency, and energy consumption of cement clinker. Limestone, as the main raw material for cement (usually accounting for more than 70%), can cause an imbalance in raw meal composition due to fluctuations in its chemical composition (CaO content). This can lead to problems such as under-burning and over-burning during clinker calcination, reducing clinker strength and increasing energy consumption and pollutant emissions.

[0003] Existing cement raw meal pre-homogenization technologies mainly include two types: stockpile pre-homogenization and silo pre-homogenization. Stockpile pre-homogenization often employs long stackers for "layered stockpiling and lateral material removal," achieving component mixing through multi-layer stacking. Silo pre-homogenization utilizes mixing devices or airflow agitation to achieve material homogenization. However, existing technologies have the following drawbacks: First, they lack adaptability to the characteristics of limestone raw materials; large differences in limestone particle size distribution and fluctuations in moisture content easily lead to segregation during stockpiling, resulting in poor homogenization effects. Second, the energy consumption for material transportation and mixing during homogenization is high, and dust pollution is easily generated. Third, homogenization parameters are mostly fixed settings, unable to be dynamically adjusted according to real-time monitoring of limestone composition fluctuations, leading to unstable homogenization accuracy and difficulty in meeting the requirements of high-quality cement production.

[0004] Therefore, it is necessary to develop a cement raw material pre-homogenization method that is adapted to the characteristics of limestone, has low energy consumption, high homogenization accuracy, and can be dynamically controlled, in order to improve the quality of cement production and reduce production costs. Summary of the Invention

[0005] The present invention aims to provide a limestone-based cement raw meal pre-homogenization method to solve the problem of poor homogenization effect of current limestone-processed cement raw meal, which affects the quality of cement production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for pre-homogenizing cement raw materials based on limestone, comprising the following steps: S1, crush the limestone raw material into particles with a diameter of 5~50mm, remove impurities and dry until the moisture content is ≤1.5%, then test and record the chemical composition of the limestone particles; S2, according to the CaO content in the limestone, is divided into 3 to 5 grades and stored in the corresponding grade storage silos. Then, the proportion of limestone and auxiliary materials for each grade is calculated by computer. S3, according to the proportion, the raw materials are transported to the stacker, and the material is stacked in a fan-shaped and layered manner. The thickness of the stack layer is 20~30cm and the height is less than 15m. S4 uses a twin-screw feeder rotating in opposite directions to scrape raw materials from different positions in the stockpile, with a scraping speed of 0.5~1.2m / s. 3 / min; S5. The raw material obtained in S4 is sent to the homogenization chamber. First, it is fluidized and stirred with compressed air at 0.3~0.5MPa for 15~25min, and then mechanically stirred at 30~50r / min for 10~15min until the composition deviation is ≤±0.5%. S6 involves testing the homogenized raw materials from S5. If the raw materials pass the test, they proceed to the grinding process; otherwise, they are returned to the homogenization chamber for re-homogenization.

[0007] Preferably, as an improvement, when crushing limestone in step S1, two-stage crushing is adopted. The first stage uses a jaw crusher to crush the limestone to ≤100mm, and the second stage uses an impact crusher to crush the limestone to 5-50mm.

[0008] Preferably, as an improvement, the width adjustment range of the stacker in step S3 is 3-8m.

[0009] Preferably, as an improvement, the air inlet of the airflow stirring device used for compressed air fluidization stirring in step S5 is evenly distributed at the bottom of the homogenization chamber, and the air inlet direction forms an angle of 30~45° with the bottom of the chamber.

[0010] Preferably, as an improvement, the stirring blade of the mechanical stirring device in step S5 is a propeller structure, and the distance between the stirring blade and the bottom of the tank is 50-80cm.

[0011] The advantages of this solution are: 1. Adapting to the characteristics of limestone and improving homogenization accuracy: This invention addresses the characteristics of limestone, such as large differences in particle size distribution and easy segregation. It adopts graded crushing and drying pretreatment, combined with a "fan-shaped material distribution and layered stacking" stacking method, which effectively avoids the segregation of limestone during the stacking process. At the same time, the double-helix material handling achieves mixing of materials at different depths, and the secondary homogenization is achieved by the dual stirring of airflow and machinery in the silo, so that the fluctuation of raw material composition is controlled within ±0.5%, and the homogenization accuracy is significantly improved.

[0012] 2. Low energy consumption and good environmental performance: The drying temperature and time in the pretreatment stage are precisely controlled to avoid energy waste caused by over-drying; the material stacking and unloading process adopts quantitative conveying and stable unloading speed to reduce material loss; the combined effect of airflow agitation and mechanical agitation reduces energy consumption by 20-30% compared with single agitation method, while reducing dust generation and environmental pollution.

[0013] 3. Each step in this plan uses mature equipment and processes, and the process design is simple and reasonable. It does not require complicated equipment modifications and can be directly applied to the upgrading and transformation of existing cement production lines, showing good prospects for industrialization. Detailed Implementation

[0014] Example 1 A method for pre-homogenizing cement raw materials based on limestone, comprising the following steps: S1. Limestone Raw Material Pretreatment and Composition Detection: The mined limestone is fed into a jaw crusher for primary crushing to obtain particles with a diameter ≤100mm; then fed into an impact crusher for secondary crushing to obtain limestone particles with a diameter of 5-50mm; impurities with a diameter greater than 50mm are removed by a screening device, and the screened limestone particles are sent to a drying device and dried at 110℃ to a moisture content of 1.2%; X-ray fluorescence spectrometry is used to detect the limestone composition: CaO 63.5%, SiO2 22.3%, Al2O3 5.1%, Fe2O3 2.8%, and the data is transmitted to the central control system.

[0015] S2. Raw material zoning and proportioning planning: According to the test results, the limestone belongs to the medium CaO content grade and is stored in raw material storage silo No. 2. The central control system calculates the theoretical proportion based on the target composition of the raw material (CaO 64%, SiO2 22%, Al2O3 5.5%, Fe2O3 3%), combined with the composition test data of clay (SiO2 62%, Al2O3 25%), iron powder (Fe2O3 65%), and sandstone (SiO2 85%): limestone 75%, clay 15%, iron powder 4%, and sandstone 6%.

[0016] 3. Dynamic Layered Stacking: Raw materials in each storage silo are transported to the stacker by a quantitative feeder according to the theoretical ratio. The stacker adopts a fan-shaped material distribution method with a distribution width of 5m. The material is stacked in layers with a thickness of 25cm, and the stacking height is 12m. During the stacking process, the central control system collects data from the quantitative feeder in real time. If the limestone CaO content fluctuates to 64.6% (exceeding ±1%), the limestone feed rate is automatically adjusted from 75% to 74%, and the clay feed rate is adjusted to 16% to ensure that the composition of each layer of material meets the requirements.

[0017] 4. Double-helix material handling and primary homogenization: After the material is piled up, start the double-helix material handling machine at the bottom of the pile, with a material handling speed of 0.8m. 3 / min, the two spiral shafts rotate in opposite directions, scraping and mixing materials at different depths to achieve primary homogenization.

[0018] 5. Secondary homogenization in the silo: The material after primary homogenization is sent into the homogenization silo. First, compressed air at a pressure of 0.4 MPa is introduced through the evenly distributed air inlets at the bottom, with the airflow direction at a 40° angle to the bottom of the silo, and fluidized and stirred for 20 minutes. Then, the mechanical stirring device is started, with the stirring paddle speed at 40 r / min and the stirring time at 12 minutes. The material composition deviation is detected by the component detection probe in the silo, which is 0.3%, meeting the requirements.

[0019] 6. Finished product conveying and testing: The material after secondary homogenization is sent to the raw material mill and its composition is tested again: CaO 63.9%, SiO2 22.1%, Al2O3 5.4%, Fe2O3 2.9%, with deviations within ±0.5%. After passing the test, it enters the grinding process.

[0020] Testing showed that the cement raw meal homogenization effect obtained by the method in this embodiment was good. The clinker obtained by subsequent calcination had a 3-day strength of 32.5 MPa and a 28-day strength of 56.8 MPa. Compared with the clinker produced by the existing technology, the strength was increased by 5-8%, and the calcination energy consumption was reduced by 25%.

[0021] Example 2 A method for pre-homogenizing cement raw materials based on limestone, comprising the following steps: S1. Limestone raw material pretreatment and composition detection: The mined limestone is crushed to ≤100mm by a jaw crusher, then crushed to 5-50mm by an impact crusher. After screening to remove impurities, it is sent to a drying device and dried at 105℃ to a moisture content of 1.0%. The composition is detected by X-ray fluorescence spectrometry: CaO 65.2%, SiO2 20.5%, Al2O3 4.8%, Fe2O3 2.2%. The data is transmitted to the central control system.

[0022] S2. Raw material zone storage and proportioning planning: This limestone is of high CaO content grade and is stored in raw material storage silo No. 3. The central control system calculates the theoretical proportion based on the target composition of raw materials (CaO 65%, SiO2 21%, Al2O3 35%, Fe2O3 2.5%) and the composition of auxiliary raw materials: limestone 78%, clay 13%, iron powder 3%, sandstone 6%.

[0023] S3. Dynamic Layered Stacking: The stacker has a material distribution width of 4m, a layer thickness of 20cm, and a stacking height of 10m. During the stacking process, if the CaO content of limestone drops to 64.0%, the central control system will automatically adjust the limestone feed rate to 79% and the sandstone feed rate to 5% to ensure accurate proportioning.

[0024] S4. Twin-helix feeding and primary homogenization: The twin-helix feeder has a feeding speed of 0.5m / s. 3 / min, reverse rotation to pick up and mix materials.

[0025] S5. Secondary homogenization in the storage chamber: 0.3MPa compressed air is introduced and fluidized stirring is performed for 15 minutes; the mechanical stirring paddle speed is 30r / min and the stirring time is 10 minutes; the component deviation is detected to be 0.2%, which meets the requirements.

[0026] S6. Finished Product Conveying and Testing: After the composition is tested again and found to be qualified, the product enters the grinding process. The clinker after subsequent calcination has a 3-day strength of 33.2 MPa and a 28-day strength of 57.5 MPa, reducing energy consumption by 28%.

[0027] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for pre-homogenizing cement raw materials based on limestone, characterized in that, Includes the following steps: S1, crush the limestone raw material into particles with a diameter of 5~50mm, remove impurities and dry until the moisture content is ≤1.5%, then test and record the chemical composition of the limestone particles; S2, according to the CaO content in the limestone, is divided into 3 to 5 grades and stored in the corresponding grade storage silos. Then, the proportion of limestone and auxiliary materials for each grade is calculated by computer. S3, according to the proportion, the raw materials are transported to the stacker, and the material is stacked in a fan-shaped and layered manner. The thickness of the stack layer is 20~30cm and the height is less than 15m. S4 uses a twin-screw feeder rotating in opposite directions to scrape raw materials from different positions in the stockpile, with a scraping speed of 0.5~1.2m / s. 3 / min; S5. The raw material obtained in S4 is sent to the homogenization chamber. First, it is fluidized and stirred with compressed air at 0.3~0.5MPa for 15~25min, and then mechanically stirred at 30~50r / min for 10~15min until the composition deviation is ≤±0.5%. S6 involves testing the homogenized raw materials from S5. If the raw materials pass the test, they proceed to the grinding process; otherwise, they are returned to the homogenization chamber for re-homogenization.

2. The method for pre-homogenizing cement raw materials based on limestone according to claim 1, characterized in that: In step S1, when crushing limestone, a two-stage crushing process is adopted. The first stage uses a jaw crusher to crush the limestone to ≤100mm, and the second stage uses an impact crusher to crush the limestone to 5-50mm.

3. The method for pre-homogenizing cement raw materials based on limestone according to claim 2, characterized in that: In step S3, the width of the stacker's material distribution machine can be adjusted from 3 to 8 meters.

4. The method for pre-homogenizing cement raw materials based on limestone according to claim 3, characterized in that: In step S5, the air inlets of the airflow mixing device used for compressed air fluidization mixing are evenly distributed at the bottom of the homogenization chamber, and the air inlet direction forms an angle of 30~45° with the bottom of the chamber.

5. The method for pre-homogenizing cement raw materials based on limestone according to claim 4, characterized in that: In step S5, the stirring blade of the mechanical stirring device is a propeller-type structure, and the distance between the stirring blade and the bottom of the tank is 50-80cm.