A fuel particle size and process optimization method

Abstract

This invention discloses a fuel particle size and process optimization method, belonging to the field of metallurgical technology, including: S1, fuel crushing: crushing fuel with a particle size not greater than 20 mm; S2, fuel screening: obtaining fine fuel with a particle size less than 1 mm, coarse fuel with a particle size greater than 3 mm, and medium fuel with a particle size between 1 and 3 mm; S3, particle size optimization: secondary crushing of coarse fuel; mixing and pelletizing medium fuel with iron ore powder, flux, return ore, and dust in a mixer to obtain a sintering mixture for sintering; S4, process optimization: mixing fine fuel with biomass carbon, adding 5% to 6% atomized water for mixing, crushing, compressing, and pelletizing into 3 mm biomass carbon particles, which are then fed into the sintering machine feeding stage. The amount of mixed fuel particles accounts for 5% to 15% of the total fuel ratio. The mixed fuel particles are fed to the front end of the hopper outlet, so that the mixed fuel particles can be fed to the upper part of the material layer.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for optimizing fuel particle size and process. Background Technology

[0002] In the iron and steel metallurgical industry, sintering is a process in which various powdered iron-containing raw materials are mixed with suitable fuels and fluxes, and an appropriate amount of water is added. After mixing and pelletizing, the mixture is sintered in a sintering machine, causing a series of physicochemical changes in the materials to form sintered ore. However, the fuel used in this process often has uneven particle size, with a high proportion of fuel particles larger than 3mm or smaller than 1mm. This results in low fuel utilization and also reduces the permeability of the sintering bed, leading to uneven carbon distribution and thus affecting the quality and yield of the sintered ore.

[0003] The crushing and processing of sintering fuel is typically affected by fluctuations in the particle size of the incoming material, making it difficult to effectively control the particle size composition of the sintering fuel. This results in a significant impact on fuel particle size fluctuations due to the influence of the incoming material particle size, with particles larger than 20mm accounting for more than 5%, and particles larger than 3mm accounting for more than 30% after crushing. The higher the proportion of fuel particles larger than 3mm, the more adversely it affects the yield, strength, and particle size composition of sintered ore, leading to higher fuel consumption and increased environmental pressure. Sintering requires fuel with a particle size of 0.5-3mm comprising 75-80% to meet production needs. The less of the other parts (smaller than 0.5mm and larger than 3mm), the more beneficial it is for sintering production, quality, and fuel consumption. Production practice shows that optimizing the particle size composition of solid fuel can improve the fuel distribution in the mixture. Furthermore, process intervention during the material distribution process, and secondary optimization of fuel allocation based on the fuel requirements of the sintering bed, can improve combustion conditions during sintering and increase fuel utilization.

[0004] In conventional sintering production processes, fuel is typically added in a single step through a batching bin. This requires the fuel particle size to meet the production process requirements. If this requirement cannot be met, the fuel ratio needs to be adjusted during production, resulting in longer reaction times and increased fuel consumption. Furthermore, because the fuel particle size is not addressed, large solid fuel particles can easily replace recycled ore during mixing, becoming the core of the pelletizing mixture. This causes fuel segregation between different pellets, resulting in slower combustion compared to normal fuel, a thicker combustion layer, and deteriorated fuel-air contact conditions, thus reducing the combustion rate and consequently decreasing the vertical sintering speed and ultimately reducing sintering production efficiency. Moreover, fuel particles smaller than 1mm, due to their small size, burn directly as fuel at a rapid rate. However, during ignition and blast sintering, they are affected by wind pressure and drawn away from the sintering layer, failing to achieve proper combustion. This worsens the permeability of the sintering layer, increases fuel consumption, and negatively impacts sintering quality.

[0005] In addition, there is an automatic heat storage effect during the sintering process. The lower part of the sintering material layer has a higher heat. The lower layer of material does not need a high fuel content, but it cannot be adjusted. Larger solid fuel particles are easily distributed to the lower part of the sintering material layer through material segregation, resulting in a high carbon content in the lower layer, which in turn increases fuel consumption.

[0006] In existing technologies, to address the aforementioned problems, some methods strictly control the particle size requirements of the fuel; others involve first screening the solid fuel, then further grinding the smaller-diameter fuel particles that pass through the screen and mixing them with iron ore powder to form mixed pellets, while the larger-diameter fuel particles on the screen are mixed with other materials to form a first mixture. This first mixture is then blended with the mixed pellets to obtain the final sintering mixture, thereby reducing segregation during sintering and improving the quality of the sinter, while also ensuring the full utilization of the smaller-diameter fuel particles. However, since the smaller-diameter fuel particles still need further grinding after screening, the cost is high. Furthermore, because the fuel particles in the mixed pellets are even smaller after grinding, and these smaller-diameter fuel particles burn quickly during sintering, poor heat transfer in the sintering material can lead to… The combustion rate of the fuel is insufficient to reach the high temperature and the time required for the material layer to melt, resulting in insufficient time for the high-temperature reaction to proceed. This leads to a decrease in the sintering temperature, a reduction in the binder phase of the sinter, a decrease in the drum strength, and an increase in the amount of powder, which in turn increases the amount of returned ore. At the same time, fine-particle fuel can easily clog the voids in the mixed pellets, hindering airflow and reducing the yield of sinter. In addition, when large-diameter fuel is mixed with other materials to form pellets, the large-diameter fuel tends to become the core of other materials. After pelleting, a thick adhesion layer easily forms around the large-diameter fuel, which hinders the contact between the fuel and the air, leading to a deterioration of hot permeability during sintering. Furthermore, it can also lead to an increase in the content of molten magnetite and a decrease in the content of calcium ferrite in the sinter, resulting in a decline in reducibility. Summary of the Invention

[0007] The purpose of this invention is to meet practical needs by providing a fuel particle size and process optimization method to solve the problem of low fuel utilization caused by sintering fuel particle size being too large or too small, while also meeting the different fuel consumption requirements of the sintering feeding process.

[0008] This invention provides a method for fuel particle size and process optimization, comprising:

[0009] S1. Fuel crushing: Crushing fuel with a particle size of no more than 20mm;

[0010] S2. Fuel screening: The fuel is screened using sieves with apertures of 3mm and 1mm to obtain fine fuel with a particle size of less than 1mm, coarse fuel with a particle size of more than 3mm, and medium fuel with a particle size between 1 and 3mm.

[0011] S3, Particle Size Optimization: Coarse fuel is returned to the fuel crushing system for secondary crushing and reuse; medium fuel is fed into a mixer with iron ore powder, flux, returned ore, and dust from the sintering raw materials to form pellets, and the resulting sintering mixture is then sintered.

[0012] S4. Process optimization: Fine fuel and biomass carbon are mixed, and 5% to 6% atomized water is added for mixing. Then, the mixture is crushed, compressed and granulated into 3mm biomass carbon particles. The particles are then transported to the sintering machine for feeding. The amount of mixed fuel particles in the sintering feeding process accounts for 5% to 15% of the total fuel ratio. The mixed fuel particles are fed to the front end of the hopper outlet so that they can be fed to the upper part of the material layer.

[0013] Preferably, the crushing process in S1 is as follows: First, the fuel is crushed into particles smaller than 10mm by an upper roller with a gap of 10mm, and then the fuel particles smaller than 10mm are crushed into particles smaller than 3mm by a lower roller with a gap of 3mm.

[0014] Preferably, in S3, coarse fuel accounts for 20% to 30% of the total fuel and is returned to the fuel crushing system via a belt for secondary crushing, so that all coarse fuel is ultimately controlled at 0% to 5%.

[0015] Preferably, in step S4, the biomass carbon includes fruit shells and wheat straw, and the mixing time with atomized water is 1 to 3 minutes.

[0016] Preferably, in S4, 2% to 10% of fine fuel and biomass carbon are mixed in a 1:1 ratio to form mixed biomass fuel, which is then crushed into 3mm biomass carbon particles.

[0017] Preferably, in S4, the thickness of the material layer is controlled at 800-950mm. The 0-50mm part from the bottom is the base material, the 50-800mm part is the sintering mixture, and the part above 800mm is the sintering mixture and mixed biomass fuel. Then, it is appropriately compacted and flattened by the pressing rod, and finally sintered.

[0018] Compared with the prior art, the advantages and positive effects of this application are:

[0019] This invention solves the problem of low fuel utilization caused by sintering fuel with excessively large or small particle size, while meeting the different fuel consumption requirements of the sintering feeding process.

[0020] 1. The sintering process of this invention is simple, requires minimal changes to traditional sintering procedures, and is highly practical;

[0021] 2. Under the same conditions, compared with traditional sintering, the sintering method with fuel grading and process optimization of this invention reduces the solid fuel consumption of sintered ore by 0.5 kg / t.

[0022] 3. The sintering method of this invention reduces the emissions of CO2, SO2 and NOx, thus improving air quality and having social benefits. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a preferred embodiment of the present invention. Detailed Implementation

[0025] 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] Please see Figure 1 A method for optimizing fuel particle size and process, including fuel crushing, screening, biomass carbon crushing and pelletizing, and distribution, with specific process steps as follows:

[0028] a. Fuel crushing: Fuel (coke particles and coal particles) no larger than 20mm is crushed by four rollers. The upper roller has a gap of 10mm and crushes into parts smaller than 10mm. The lower roller has a gap of 3mm and crushes into parts smaller than 3mm.

[0029] b. Fuel screening: The sintered fuel is screened using sieves with apertures of 3mm and 1mm to obtain fine fuel with a particle size of less than 1mm, medium fuel with a particle size of 1-3mm, and coarse fuel with a particle size of more than 3mm.

[0030] c. Particle size optimization: Fuel particles larger than 3mm are returned to the fuel crushing system via a return belt for secondary crushing and reuse. The medium-sized fuel particles (1-3mm) are directly included in the sintering batching, and are fed into the mixer along with iron ore powder, flux, return ore, dust, etc., from the sintering raw materials for pelletizing, resulting in a sintering mixture for sintering.

[0031] d. Process Optimization: Fuel particles smaller than 1mm are mixed with biomass carbon (fruit shells, wheat straw, etc.), with 5-6% atomized water added for thorough mixing. The mixture is then crushed, compressed, and granulated into 3mm biomass carbon particles using a crusher and pelletizer. These particles are then directly fed into the sintering machine's feeding stage via an auxiliary belt system. The mixed fuel particles account for 5%-15% of the total fuel mix in the sintering feeding process. The mixed fuel particles are fed to the front end of the hopper outlet to ensure they reach the upper part of the material layer.

[0032] In step c, fuel with a particle size greater than 3mm constitutes 20-30% of the total fuel. This is returned to the fuel crushing system via conveyor belt for secondary crushing and reuse. Ultimately, the particle size greater than 3mm in all fuel is controlled to 0-5%.

[0033] In step d, fine fuel particles smaller than 1 mm are mixed with biomass carbon (fruit shells, wheat straw, etc.), 5-6% atomized water is added and mixed for 1-3 minutes, then crushed, compressed and granulated into 3 mm biomass carbon particles, which are then fed into the sintering process.

[0034] In step d, the fine fuel particles smaller than 1 mm (accounting for 2-10%) are mixed with biomass carbon produced from fruit shells, wheat straw, etc., in a 1:1 ratio to form mixed biomass fuel, which is then crushed to produce 3 mm biomass carbon particles.

[0035] In step d, the mixed biomass fuel is crushed and pelletized into 3mm mixed fuel pellets, which are then directly fed into the sintering machine feeding stage via an auxiliary belt system.

[0036] In step d, the thickness of the material layer is controlled between 800 and 950 mm. The 0-50 mm part from the bottom is the base material, the 50-800 mm part is the sintering mixture, and the part above 800 mm is the sintering mixture plus mixed biomass fuel. Then, it is appropriately compacted and flattened by the pressing rod, and finally sintered.

[0037] In step d, the amount of the mixed fuel pellets used in the sintering and feeding process accounts for 5%-15% of the total fuel mix. The mixed fuel pellets are fed to the front end of the silo outlet to ensure that the mixed fuel pellets are fed to the upper part of the material layer.

[0038] In the fuel pelleting process, the moisture content of the fuel mixture—biomass carbon pellets—is controlled at 5-6%.

[0039] The portion of fuel exceeding 3mm in the sintering process should be controlled within 0-5%.

[0040] The sintering fuels are coke powder and anthracite.

[0041] The fuel is screened and graded using bar screens with gaps of 3mm and 1mm.

[0042] During the fabric sintering process, the negative pressure generated by the main sintering exhaust fan is -14.0 to -18.0 kPa.

[0043] In the fabric sintering process, the ignition temperature range is 1000-1150℃.

[0044] The principle of this invention is as follows: By separating the coarse and fine fuel particles, the coarse fuel is re-crushed to ensure optimal fuel particle size (the portion larger than 3mm is reduced to less than 5%). The fine fuel is further optimized to prevent large fuel particles from becoming the core of the fine fuel, thus avoiding fuel segregation between different pellets. This also improves the contact conditions between fuel and air, increasing the combustion rate and consequently improving the vertical sintering speed and sintering production efficiency. Secondly, by optimizing the process of distributing the mixed biomass-derived carbon pellet fuel cloth to the upper part of the fuel layer, sufficient fuel is ensured for sintering in the upper part. Simultaneously, the automatic heat storage function of the fuel layer is fully utilized to gradually reduce the amount of fuel in the lower part of the fuel layer, thereby reducing fuel consumption.

[0045] This invention comprises three parts obtained by crushing coke powder and coal powder and then screening them twice: fine fuel (less than 1 mm), medium fuel (1-3 mm), and coarse fuel (greater than 3 mm). The first screen has a gap of 3 mm, and the material remaining on the screen is the coarse fuel (greater than 3 mm), which is returned to the fuel crushing system via a return belt for secondary crushing. The medium fuel (1-3 mm) is directly included in the sintering batch, and is fed into a mixer along with iron ore powder, flux, return ore, dust, etc., from the sintering raw materials for mixing and pelletizing to obtain a sintering mixture for sintering. The fine fuel (less than 1 mm) is mixed with biomass carbon (fruit shells, wheat straw, etc.), with a small amount of water added for homogenization, and then crushed into 3 mm biomass carbon particles. These particles are then directly fed into the sintering machine's feeding stage via an auxiliary belt system, reaching the top of the material layer. This invention optimizes the combustion process of the mixture, improves fuel combustion conditions, and allows the mixture to quickly enter the raw material sintering process. Then, the upper layer combustion is driven by a bottom exhaust system to achieve vertical combustion during sintering, reducing the amount of solid fuel consumed, improving the fuel combustion mechanism, creating conditions for low-temperature combustion, eliminating the reducing atmosphere, and creating conditions for calcium ferrite formation. By adopting the above scheme, this invention can effectively reduce sintering fuel consumption during the sintering process, thereby achieving the goals of carbon reduction and energy saving.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for optimizing fuel particle size and process, characterized in that, include: S1. Fuel crushing: Crushing fuel with a particle size of no more than 20mm; S2. Fuel screening: The fuel is screened using sieves with apertures of 3mm and 1mm to obtain fine fuel with a particle size of less than 1mm, coarse fuel with a particle size of more than 3mm, and medium fuel with a particle size between 1 and 3mm. S3, Particle Size Optimization: Coarse fuel is returned to the fuel crushing system for secondary crushing and reuse; medium fuel is fed into a mixer with iron ore powder, flux, returned ore, and dust from the sintering raw materials to form pellets, and the resulting sintering mixture is then sintered. S4. Process Optimization: Fine fuel and biomass carbon are mixed, and 5%–6% atomized water is added for homogenization. Then, the mixture is crushed, compressed, and granulated into 3mm biomass carbon particles. These particles are then transported to the sintering machine's feeding stage via a conveyor. The amount of mixed fuel particles in the sintering feeding process accounts for 5%–15% of the total fuel mix. The mixed fuel particles are fed to the front end of the hopper outlet to ensure they reach the upper part of the material layer. The biomass carbon includes fruit shells and wheat straw, and the mixing time with atomized water is 1–3 minutes. 2%–10% of fine fuel and biomass carbon are mixed in a 1:1 ratio to form mixed biomass fuel, which is then crushed into 3mm biomass carbon particles.

2. The fuel particle size and process optimization method according to claim 1, characterized in that, The crushing process in S1 is as follows: First, the fuel is crushed into particles smaller than 10mm by the upper roller with a gap of 10mm, and then the fuel with a particle size smaller than 10mm is crushed into particles smaller than 3mm by the lower roller with a gap of 3mm.

3. The fuel particle size and process optimization method according to claim 1, characterized in that, In S3, coarse fuel accounts for 20% to 30% of the total fuel and is returned to the fuel crushing system via a belt for secondary crushing. Ultimately, all coarse fuel is controlled at 0% to 5%.

4. The fuel particle size and process optimization method according to claim 1, characterized in that, In S4, the thickness of the material layer is controlled between 800 and 950 mm. The 0-50 mm part from the bottom is the base material, the 50-800 mm part is the sintering mixture, and the part above 800 mm is the sintering mixture and mixed biomass fuel. Then, it is appropriately compacted and flattened by the pressing rod, and finally sintered.

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