Precise proportioning method for producing high basicity pellets by chain return loop
By using precise pre-mixing and high-pressure roller milling processes, the problems of low pelleting rate and short ring-forming cycle in the production of alkaline pellets by chain grate-rotary kiln have been solved, achieving stable production of high-alkalinity pellets and improving production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TAIYUAN IRON & STEEL (GRP) CO LTD
- Filing Date
- 2026-04-16
- Publication Date
- 2026-06-26
Smart Images
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Figure FT_2 
Figure QLYQS_1
Abstract
Description
Technical Field
[0001] This invention belongs to the field of low-carbon technology of metallurgical pelleting, and particularly relates to a precise batching method for producing high-basicity pellets through chain loop production. Background Technology
[0002] In recent years, the pellet production technology of chain grate machine-rotary kiln-ring cooler has developed rapidly in my country. Many steel plants have successively put into operation chain grate machine-rotary kiln-ring cooler production lines with an annual output of more than one million tons. For example, Taiyuan Iron & Steel Group's Yuanjiacun Iron Mine built and put into operation a 2 million-ton acidic pellet production line in 2012 and a 2 million-ton alkaline pellet production line in 2022. Due to energy structure constraints and production cost constraints, both production lines use pulverized coal as the heat source for the rotary kiln. The pellet production line uses a mixed concentrate with hematite as the main component and containing a small amount of magnetite and limonite as the iron raw material. Due to the complex ore belt and diverse ore samples, the iron grade of the beneficiated ore is 64%-65.5%, and the SiO2 content is about 4.0%±0.5%, which fluctuates greatly. The production process adopted by the pellet production line is: various raw materials are mixed according to a set ratio, and then pelletized and roasted to produce pellets.
[0003] Through production comparison, when using this process to produce acidic pellets, the rotary kiln ring-forming cycle can reach 50-60 days, and the continuous production cycle of chain grate-rotary kiln pellets is long. However, when using this process to produce basic pellets, due to the large fluctuations in the composition of the iron concentrate raw material, it is difficult to stabilize the feed composition, the proportions are unstable, the amount of water added to CaCO3 powder is uneven, affecting the mixing effect, the alkalinity of the raw material varies greatly, the contact between material particles is loose, the surface is prone to peeling, the quality of green pellets is poor, the pelleting rate is low, and the powder content of the raw material entering the rotary kiln increases. When raw materials containing a large amount of iron powder enter the rotary kiln, the suspended mineral powder is easily oxidized into FeO, which combines with SiO2 in the feed to form low-melting-point ferrosilicon. At a temperature of 1050-1100℃, it softens and adheres to the kiln wall. When a large amount of low-melting material is formed, the viscosity increases and kiln skin is formed, resulting in ring formation. This causes the ring formation cycle in the rotary kiln to be only 20-22 days in the production of alkaline pellets. Consequently, the production cycle of alkaline pellets produced by the chain grate rotary kiln is short, and the kiln must be frequently stopped to deal with the ring formation, which seriously affects production efficiency. Summary of the Invention
[0004] The purpose of this invention is to provide a precise batching method for producing high-basicity pellets using a chain loop, thereby solving the problems of low pelletizing rate and short ring-forming cycle when producing alkaline pellets.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: A precise batching method for producing high-basicity pellets using a chain loop, comprising the following steps: Step 1: Pre-mixing of concentrate powder Pre-mixing is added during the concentrate powder batching stage. Based on the on-site production situation, the content of TFe and SiO2 in the iron concentrate is tested, and the concentrate is temporarily stored in batches in the storage silo according to the content. During pre-mixing, the industrial process data of the background computer is used to accumulate and calculate to generate a fine batching method, and the iron concentrate powder with stable composition is prepared. Step 2: Limestone powder preparation The amount of limestone powder to be added is automatically calculated based on the SiO2 content of the concentrate powder after pre-mixing, the set basicity of the pellets, and the amount of bentonite added, and then automatically added. Step 3: Roller milling After mixing iron concentrate powder and limestone powder, a roller milling process is added. The high pressure of the high-pressure roller mill causes the limestone powder particles to be embedded in the iron concentrate powder particles in an extremely fine droplet-like structure, generating tetrahedral agglomerates of iron concentrate powder. The iron concentrate powder particles and limestone powder particles are in close contact while maintaining interparticle gaps, which improves the uniformity and stability of the batching. The generation of relatively stable tetrahedral agglomerates enhances the strength of the green pellets in subsequent pelletizing. Sufficient gap space is also reserved between the particles to allow enough space for the volatilization and overflow of CO2 gas during the heating process, reducing the bursting of green pellets, increasing the pelletizing rate, and reducing the powder content during the roasting process. Step 4: Adding bentonite The appropriate amount of bentonite to be added is determined based on the quality of the green pellets to ensure the strength and bursting temperature of the green pellets.
[0006] Preferably, the specific calculation process for generating the refined ingredients in step 1 is as follows: Total ingredients TFe = (Batch 1) TFe *Ingredient quantity 1 + batch 2 TFe *Ingredient quantity 2 + ...) / Batch number Total ingredients SiO2 = (Batch 1) SiO2 *Ingredient quantity 1 + batch 2 SiO2 *Ingredient quantity 2 + ...) / Batch number Based on the TFe and SiO2 content of each batch of concentrate powder, after setting the total batching amount, and under the condition that the total batching amount of concentrate powder TFe content is 64.8%±0.1% and the SiO2 content is 4.0%±0.1%, the required batching amount of concentrate powder for each batch is calculated, and the concentrate powder is output by the quantitative feeder according to the calculated value.
[0007] Preferably, the specific formula for calculating the amount of limestone powder added in step 2 is as follows: .
[0008] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: By setting precise pre-mixing to form iron concentrate powder with stable composition, the CaCO3 powder is added with uniform water content, resulting in good mixing effect. Combined with the high-pressure roller milling process after mixing iron concentrate powder and limestone powder, the material particles are in close contact, the surface is not easy to peel off, the pelleting rate is improved, the powder rate during the roasting process is reduced, the formation of rings in the rotary kiln is prevented, and the production cycle is extended. Attached Figure Description
[0009] Figure 1 These are tetrahedral agglomerated particles of iron concentrate powder and limestone powder in the embodiments of the present invention; Figure 2 This is a schematic diagram of the contact between iron concentrate powder particles and limestone powder particles in an embodiment of the present invention. Detailed Implementation
[0010] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.
[0011] A precise batching method for producing high-basicity pellets using a chain loop, comprising the following steps: Step 1: Pre-mixing of concentrate powder During the concentrate batching stage, pre-mixing materials are added. Based on the on-site production situation, the content of TFe and SiO2 in the iron concentrate is tested, and the concentrate is temporarily stored in batches in the storage silo according to the content. The batch composition is as follows: Batch 1: TFe: 64%, SiO2: 5%; Batch 2: TFe: 65%, SiO2: 3.5%; Batch 3: TFe: 64.5%, SiO2: 3.8%; Batch 4: TFe: 65.5%, SiO2: 4%; Batch 5: TFe: 64.2%, SiO2: 3.8%. The total batching rate is set at 500 t / h. During pre-batching, the industrial process data from the background computer is used to accumulate and calculate the fine batching method to prepare iron concentrate powder with stable composition, calculated according to the following formula: Total ingredients TFe = (Batch 1) TFe *Ingredient quantity 1 + batch 2 TFe *Ingredient quantity 2 + ...) / Batch number Total ingredients SiO2 = (Batch 1) SiO2 *Ingredient quantity 1 + batch 2 SiO2 *Ingredient quantity 2 + ...) / Batch number Calculations show that the concentrate usage for batch 1 is 80 t / h, for batch 2 it is 120 t / h, for batch 3 it is 80 t / h, for batch 4 it is 150 t / h, and for batch 5 it is 70 t / h, with a total batching amount of 500 t. The concentrate after batching has a TFe content of 64.80% and a SiO2 content of 3.98%, which meets the usage requirements. At the same time, the quantitative feed scales 1-5 start outputting concentrate at rates of 80 t / h, 120 t / h, 80 t / h, 150 t / h, and 70 t / h, respectively.
[0012] Step 2: Limestone powder preparation The amount of limestone powder to be added is automatically calculated based on the SiO2 content of the pre-mixed concentrate powder, the set basicity of the pellets, and the amount of bentonite added, and then automatically added. The specific calculation formula is as follows: ,
[0013] Based on the batching conditions, the total amount of mineral powder is 500 t / h, with mineral powder grades of TFe: 64.80%, SiO2: 3.98%, calcium oxide content of 0.5%, and moisture content of 10%; bentonite has SiO2 of 58%, calcium oxide content of 1%, and moisture content of 13%; limestone powder has SiO2 of 1.5%, calcium oxide content of 50%, and moisture content of 1%. When the bentonite ratio is set at 1.9% and the pellet basicity is 0.29-0.3, the limestone powder usage is calculated to be 9 t / h and the bentonite usage is 10 t / h, resulting in a pellet basicity of 0.294.
[0014] Step 3: Roller milling After mixing iron concentrate powder and limestone powder, a roller milling process is added. The high pressure of the high-pressure roller mill causes the limestone powder particles to be embedded in the iron concentrate powder particles in an extremely fine droplet-like structure, generating tetrahedral agglomerated particles of the iron concentrate powder. Figure 1-2 As shown, the iron concentrate powder particles and limestone powder particles are in close contact while maintaining interparticle gaps, which improves the uniformity and stability of the batching and generates relatively stable tetrahedral agglomerated particles, thereby enhancing the strength of the green pellets in subsequent pelletizing. Sufficient gap space is also reserved between the particles to allow for the volatilization and overflow of CO2 gas during the heating process, reducing the bursting phenomenon of green pellets, increasing the pelletizing rate, and reducing the powder content during the roasting process.
[0015] Step 4: Adding bentonite With the bentonite ratio set at 1.9%, the screw feeder outputs 9t / h of bentonite according to the set parameters. After the mineral powder, limestone powder and bentonite are evenly mixed by the high-pressure mixer, they enter the pelletizing system to produce pellets.
[0016] Using this method, the kiln only needs to be shut down to deal with the ring buildup inside the kiln after an average of more than 35 days of production, which significantly reduces the frequency of downtime caused by ring buildup in the rotary kiln. This provides strong technical support for achieving continuous production of alkaline pellets using a chain grate and rotary kiln, and ensuring production efficiency.
[0017] Working principle: The main function of adding limestone powder in production is to act as a pelletizing flux, completely decomposing CaCO3 in limestone into CaO, which reacts with iron concentrate powder. The reaction mechanism is that limestone powder begins to decompose at about 670℃, and the weight loss accelerates with increasing temperature between about 670-860℃, with the maximum weight loss rate at 834.3℃. The strongest endothermic peak generated by the decomposition of limestone powder is at 838.7℃, which should be the boiling decomposition temperature. After about 860℃, the mass of limestone powder remains unchanged with increasing temperature, indicating that the limestone powder is completely decomposed. A large amount of CO2 gas is generated during the decomposition of limestone, and the volatilization and overflow of the gas also accelerates the formation of powder. The high pressure of the high-pressure roller mill causes limestone powder particles to be embedded in the iron concentrate powder particles in an extremely fine droplet-like structure. Under high pressure, the iron concentrate powder forms tetrahedral agglomerates, and the iron concentrate powder particles and limestone powder particles are in close contact while maintaining interparticle gaps. This improves the uniformity and stability of the batching, generates more stable tetrahedral agglomerates, enhances the strength of green pellets in subsequent pelletizing, and leaves sufficient gap space between particles to allow for the volatilization and overflow of CO2 gas during the heating process, reducing the bursting of green pellets, increasing the pelletizing rate, reducing the powder content during the roasting process, preventing ring formation in the rotary kiln, and extending the production cycle.
Claims
1. A precise batching method for producing high-basicity pellets using a chain loop, characterized in that, The specific steps are as follows: Step 1: Pre-mixing of concentrate powder Pre-mixing is added during the concentrate powder batching stage. Based on the on-site production situation, the content of TFe and SiO2 in the iron concentrate is tested, and the concentrate is temporarily stored in batches in the storage silo according to the content. During pre-mixing, the industrial process data of the background computer is used to accumulate and calculate to generate a fine batching method, and the iron concentrate powder with stable composition is prepared. Step 2: Limestone powder preparation The amount of limestone powder to be added is automatically calculated based on the SiO2 content of the concentrate powder after pre-mixing, the set basicity of the pellets, and the amount of bentonite added, and then automatically added. Step 3: Roller milling After mixing iron concentrate powder and limestone powder, a roller milling process is added. The high pressure of the high-pressure roller mill causes the limestone powder particles to be embedded in the iron concentrate powder particles in an extremely fine droplet-like structure, generating tetrahedral agglomerates of iron concentrate powder. The iron concentrate powder particles and limestone powder particles are in close contact while maintaining interparticle gaps, which improves the uniformity and stability of the batching. The generation of relatively stable tetrahedral agglomerates enhances the strength of the green pellets in subsequent pelletizing. Sufficient gap space is also reserved between the particles to allow enough space for the volatilization and overflow of CO2 gas during the heating process, reducing the bursting of green pellets, increasing the pelletizing rate, and reducing the powder content during the roasting process. Step 4: Adding bentonite The appropriate amount of bentonite to be added is determined based on the quality of the green pellets to ensure the strength and bursting temperature of the green pellets.
2. The precise batching method for producing high-basicity pellets using a chain loop according to claim 1, characterized in that, The specific calculation process for generating the refined ingredients in step 1 is as follows: Total ingredients TFe = (Batch 1) TFe *Ingredient quantity 1 + batch 2 TFe *Ingredient quantity 2 + ...) / Batch number Total ingredients SiO2 = (Batch 1) SiO2 *Ingredient quantity 1 + batch 2 SiO2 *Ingredient quantity 2 + ...) / Batch number Based on the TFe and SiO2 content of each batch of concentrate powder, after setting the total batching amount, and under the condition that the total batching amount of concentrate powder TFe content is 64.8%±0.1% and the SiO2 content is 4.0%±0.1%, the required batching amount of concentrate powder for each batch is calculated, and the concentrate powder is output by the quantitative feeder according to the calculated value.
3. The precise batching method for producing high-basicity pellets using a chain loop according to claim 1, characterized in that, The specific formula for calculating the amount of limestone powder added in step 2 is as follows: 。