Method for utilizing ring forming material of rotary kiln in pelletizing workshop of iron and steel plant

Abstract

The invention relates to an iron and steel plant pelletizing workshop rotary kiln ring forming material utilization method which comprises the following steps: step 1, screening rotary kiln ring forming materials by using an 80mm sieve to obtain 80mm oversize products and 80mm undersize products; step 2, crushing the 80mm oversize product, then screening the crushed rotary kiln ring forming material by using a 80mm sieve to obtain 80mm undersize product, and if the 80mm oversize product still exists, crushing the 80mm oversize product again until all the rotary kiln ring forming material passes through the 80mm sieve; 3, the 80 mm undersize product is screened through a 5 mm sieve, 5 mm oversize product and 5 mm undersize product are obtained, and the 5 mm oversize product is the rotary kiln ring forming material with the particle size ranging from 5 mm to 80 mm; and fourthly, the 5-80 mm rotary kiln ring forming material obtained in the third step serves as a cooling agent to be put into a converter for use, and the 5 mm undersize product obtained in the third step is returned to the material mixing procedure of a pelletizing workshop to serve as a mother ball in the pelletizing procedure.

Description

Technical Field

[0001] This invention relates to the field of iron-containing waste recycling technology in pellet production, and in particular to a method for utilizing ring-forming material in a rotary kiln of a steel plant pellet workshop. Background Technology

[0002] The chain grate rotary kiln is the dominant process in the production of oxidized pellets, mainly consisting of a chain grate machine, a rotary kiln, and an annular cooling unit. In oxidized pellet production, ring formation in the rotary kiln is a common problem. This refers to the ring-shaped material adhesion phenomenon that forms on the inner wall of the high-temperature zone, primarily caused by the enrichment of low-melting-point substances forming a liquid phase that leads to adhesion. The chemical composition of the ring-forming material is similar to that of normal pellets, with a dense structure, high hardness, low porosity, and slightly lower reducibility than normal pellets. Ring formation can lead to obstructed ventilation and thermal imbalance within the kiln, causing equipment overload, increased energy consumption, and damage to refractory materials. In severe cases, kiln shutdown and ring removal are necessary.

[0003] Currently, in order to avoid wasting ring-forming material, steel plants usually return all the cleaned-out ring-forming material to the pellet batching system for recycling or feed the ring-forming material directly into the blast furnace.

[0004] However, after the ring-forming material is crushed into powder and returned to the pelletizing batching system, due to the poor pelletizing properties of the ring-forming material, it is necessary to increase the binder ratio in order to meet the pelletizing rate requirements of the production line, which in turn leads to increased pelletizing process costs and decreased iron content of finished pellets.

[0005] Directly feeding large ring-shaped feedstock into the blast furnace is more economical than recycling it into the pelletizing system. However, this direct feeding may negatively impact the furnace charge structure, smelting operation, and equipment. Ring-shaped feedstock has a dense structure and low porosity, resulting in a potentially higher reduction expansion rate compared to normal pellets. Furthermore, its softening and melting zone is narrower, making it prone to forming a "binding layer" in the softening zone after being fed into the furnace. This reduces the permeability of the furnace charge and increases the risk of pressure differential fluctuations in the blast furnace. The reducibility of ring-shaped feedstock is slightly lower than that of normal pellets, potentially prolonging the reduction path of iron oxides and increasing coke consumption. If the composition of the liquid phase generated after melting is incompatible with the slag system, it may affect slag fluidity and interfere with slag-iron separation efficiency. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a method for utilizing rotary kiln ring-forming material in a steel plant's pelletizing workshop. This method uses the rotary kiln ring-forming material as a coolant in steelmaking production, which fully utilizes the physicochemical properties of the material and meets the coolant requirements of converter steelmaking.

[0007] This invention is achieved through the following technical solution, providing a method for utilizing ring-forming material in a rotary kiln of a steel plant pelletizing workshop, comprising the following steps: Step 1: Use an 80mm sieve to screen the rotary kiln ring-forming material to obtain the material that passes through the 80mm sieve and the material that passes through the 80mm sieve. Step 2: Crush the material on the 80mm sieve, and then use the 80mm sieve to screen the crushed rotary kiln ring-forming material to obtain the material under the 80mm sieve. If there is still material on the 80mm sieve, crush the material on the 80mm sieve again until all the rotary kiln ring-forming material passes through the 80mm sieve. Step 3: Use a 5mm sieve to sieve the material that passes through the 80mm sieve to obtain the material that passes through the 5mm sieve and the material that passes through the 5mm sieve. The material that passes through the 5mm sieve is rotary kiln ring-forming material with a particle size of 5mm~80mm. Step 4: Use the 5mm~80mm rotary kiln ring material obtained in Step 3 as a coolant in the converter, and return the 5mm undersize material obtained in Step 3 to the mixing process in the pelletizing workshop as mother pellets in the pelletizing process.

[0008] This scheme separates the rotary kiln ring-forming material into 5mm undersize material (with a particle size of less than 5mm) and 5mm oversize material (with a particle size of 5mm to 80mm) through screening and crushing. The 5mm undersize material serves as the mother ball in the pelletizing process, which helps to improve the pelletizing speed. The 5mm to 80mm rotary kiln ring-forming material is used as a coolant in the converter, avoiding the adverse effects of directly feeding it into the blast furnace on the stable operation of the blast furnace.

[0009] As an optimization, when using 5mm~80mm rotary kiln ring-forming material as a coolant, it should be used in conjunction with sinter, and the mass ratio of 5mm~80mm rotary kiln ring-forming material to sinter should be 1:3~1:0.5. This optimized scheme can reduce the coolant reaction rate, prolong the reaction time, and increase the dephosphorization efficiency.

[0010] As an optimization, the moisture content of the 5mm~80mm rotary kiln ring-forming material used as a coolant is less than 2% by mass. This optimized moisture content control scheme avoids introducing excessive moisture into the converter.

[0011] As an optimization, the crushing and screening operations in steps one and three are all carried out indoors. This optimized scheme ensures that the converter ring-forming material and its crushing and screening processes remain dry.

[0012] As an optimization, the mass of the 5mm undersize material obtained in step three should not exceed 2% of the total mass of the rotary kiln ring material screened in step one. This optimization scheme reduces the proportion of ring material returned to the pelletizing workshop mixing process and uses more ring material as a coolant, significantly reducing the adverse effects of increased pelletizing process costs and decreased iron content in the finished pellets caused by the return of all or a high proportion of rotary kiln ring material to the pelletizing batching system.

[0013] The beneficial effects of this invention are as follows: It fully utilizes the characteristics of rotary kiln ring material, such as high iron content, no or very little water, dense and hard structure, and few impurities, to use the rotary kiln ring material as a coolant in the steelmaking process, controlling the temperature of the molten pool and preventing overheating. At the same time, it absorbs heat through slag reaction and protects the equipment. Furthermore, it produces less powder during the transfer and feeding of the rotary kiln ring material as a coolant into the converter. Using the rotary kiln ring material as a coolant in the converter avoids the adverse effects of directly feeding it into the blast furnace on the stable operation of the blast furnace, and also has higher economic value. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the process of the present invention; Detailed Implementation To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0015] like Figure 1 The process shown in this embodiment, a method for utilizing ring-forming material in a rotary kiln of a steel plant pellet workshop, includes the following steps: Step 1: Primary screening. The rotary kiln ring-forming material is screened using an 80mm sieve to obtain 80mm oversize and 80mm undersize. An 80mm sieve refers to a sieve with an aperture of 80mm. 80mm oversize refers to the material that is blocked by the 80mm sieve and cannot pass through the sieve apertures, while 80mm undersize refers to the material that falls through the sieve apertures.

[0016] Step 2: Crush the material on the 80mm sieve, and then use the 80mm sieve to screen the crushed rotary kiln ring-forming material to obtain the material under the 80mm sieve. If there is still material on the 80mm sieve, crush it again until all the rotary kiln ring-forming material passes through the 80mm sieve.

[0017] Step 3: Secondary screening. Use a 5mm sieve to screen the material under the 80mm sieve, obtaining 5mm oversize and 5mm undersize. The 5mm oversize is the rotary kiln ring-forming material with a particle size of 5mm~80mm. The mass of the 5mm undersize obtained in this step is no more than 2% of the total mass of the rotary kiln ring-forming material screened in Step 1. The 5mm oversize is the 5mm~80mm rotary kiln ring-forming material steelmaking coolant.

[0018] A 5mm sieve refers to a sieve with a mesh size of 5mm. Material that passes through a 5mm sieve is material that is blocked by the 5mm sieve and cannot pass through the 5mm sieve mesh. Material that passes through a 5mm sieve mesh is material that falls through the sieve mesh of an 80mm sieve.

[0019] Step 4: The 5mm~80mm rotary kiln ring material obtained in Step 3 is used as a coolant in the converter for the steelmaking process. The 5mm undersize material obtained in Step 3 is returned to the mixing process in the pelletizing workshop for use as mother pellets in the pelletizing process.

[0020] When 5mm~80mm rotary kiln ring feedstock is used as a coolant, it is used in combination with sinter, and the mass ratio of 5mm~80mm rotary kiln ring feedstock to sinter is 1:3~1:0.5. The composition of rotary kiln ring feedstock is similar to that of pellets, with high TFe and Fe2O3 content. The mass ratio of rotary kiln ring feedstock to sinter is designed to be 1:3~1:0.5 to avoid slag splashing caused by violent reaction when the rotary kiln ring feedstock is added to the hearth. This reduces the reaction rate of the coolant, prolongs the reaction time, and increases the dephosphorization efficiency.

[0021] The moisture content of the 5mm~80mm rotary kiln ring-forming material used as a coolant is less than 2% of its mass percentage. To prevent the converter ring-forming material from getting damp, the crushing and screening operations in steps one and three, as well as the storage of the rotary kiln ring-forming material, are all carried out indoors to keep the material dry and prevent rain and moisture.

[0022] After the 5mm undersize material is returned to the pelletizing workshop mixing system, it is mixed evenly with other commonly used materials in the mixer before going to the pelletizing machine to make pellets. The 5mm undersize material acts as the mother pellet, which helps to improve the pelletizing speed.

[0023] The rotary kiln ring-forming coolant production process provided in this embodiment involves screening, crushing, and screening again, which can effectively reduce the proportion of material under 5mm screens, and the 5mm to 80mm portion can reach more than 98%; only the portion above 80mm is crushed, which greatly reduces crushing energy consumption.

[0024] This invention fully utilizes the characteristics of rotary kiln ring material, such as high iron content, no or very little water, dense and hard structure, and few impurities. It produces less powder during the transfer and feeding process into the converter. The rotary kiln ring material can be used as a steelmaking coolant. Compared with scrap steel, which is also used as a coolant, rotary kiln ring material is cheaper and melts faster. Compared with dust collector ash pelletizing coolant, it has higher iron content, fewer impurities, lower moisture, higher strength, less powder, and is cheaper. Compared with pellets and sinter, it produces less powder and is cheaper.

[0025] This invention uses the rotary kiln ring-forming material as a coolant in the converter, avoiding the adverse effects of directly feeding it into the blast furnace on the stable operation of the blast furnace, and also has higher economic value.

[0026] Rotary kiln ring binder is a type of clinker that is entirely or largely returned to the pelletizing workshop. It must be crushed to a fineness of 200 mesh and a purity of over 85%. Its dense and hard structure increases the burden on ball mills and grinding mills, raising power consumption and equipment wear in the pelletizing process. Furthermore, its poor pelletizing shape leads to increased binder usage, resulting in lower iron content in the finished pellets and higher raw material costs. However, rotary kiln ring binder is used as a steelmaking coolant, with only a very small portion returned to the pelletizing workshop. It only needs to be mixed with other raw materials and can be used as a mother pellet for pelletizing, effectively increasing the pelletizing speed.

[0027] Using rotary kiln ring feedstock as a steelmaking coolant can significantly reduce the adverse effects of increased pelletizing costs and decreased iron content in finished pellets caused by the complete return of rotary kiln ring feedstock to the pelletizing batching system. It also avoids the negative impacts of directly feeding rotary kiln ring feedstock into the blast furnace on the furnace charge structure, smelting operation, and equipment. Rotary kiln ring feedstock used as a steelmaking coolant offers better quality and a lower price than coolants made from sinter or pellets. This invention achieves highly efficient and economical use of rotary kiln ring feedstock, resulting in significant economic benefits. For example, the pelletizing process cost is 100-150 yuan / ton, and the blast furnace process cost is 200-250 yuan / ton. Using rotary kiln ring feedstock as a steelmaking coolant eliminates the need for pelletizing and blast furnace processes, saving 300-400 yuan / ton in process costs, demonstrating substantial economic benefits.

[0028] Of course, the above description is not limited to the examples above. Technical features not described in this invention can be implemented by or using existing technology, and will not be repeated here. The above embodiments and drawings are only used to illustrate the technical solutions of this invention and are not intended to limit this invention. This invention has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention do not depart from the spirit of this invention and should also fall within the scope of protection of the claims of this invention.

Claims

1. A method for utilizing ring-forming material in a rotary kiln of a steel plant pelletizing workshop, characterized in that, Includes the following steps: Step 1: Use an 80mm sieve to screen the rotary kiln ring-forming material to obtain the material that passes through the 80mm sieve and the material that passes through the 80mm sieve. Step 2: Crush the material on the 80mm sieve, and then use the 80mm sieve to screen the crushed rotary kiln ring-forming material to obtain the material under the 80mm sieve. If there is still material on the 80mm sieve, crush the material on the 80mm sieve again until all the rotary kiln ring-forming material passes through the 80mm sieve. Step 3: Use a 5mm sieve to sieve the material that passes through the 80mm sieve to obtain the material that passes through the 5mm sieve and the material that passes through the 5mm sieve. The material that passes through the 5mm sieve is rotary kiln ring-forming material with a particle size of 5mm~80mm. Step 4: Use the 5mm~80mm rotary kiln ring material obtained in Step 3 as a coolant in the converter, and return the 5mm undersize material obtained in Step 3 to the mixing process in the pelletizing workshop as mother pellets in the pelletizing process.

2. The method for utilizing ring-forming material in a rotary kiln of a steel plant pellet workshop according to claim 1, characterized in that: When 5mm~80mm rotary kiln ring-forming material is used as a coolant, it is used in combination with sinter, and the mass ratio of 5mm~80mm rotary kiln ring-forming material to sinter is 1:3~1:0.

5.

3. The method for utilizing ring-forming material in a rotary kiln of a steel plant pellet workshop according to claim 1, characterized in that: The moisture content of the 5mm~80mm rotary kiln ring-forming material used as a coolant is less than 2% of its mass percentage.

4. A method for utilizing ring-forming material in a rotary kiln of a steel plant pellet workshop according to claim 3, characterized in that: The crushing and screening operations in steps one and three are all carried out indoors.

5. A method for utilizing ring-forming material in a rotary kiln of a steel plant pellet workshop according to claim 1, characterized in that: The mass of the 5mm sieve undersize obtained in step three shall not exceed 2% of the total mass of the rotary kiln ring-forming material screened in step one.

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