A low carbon sintering method, process and system

Abstract

The present application belongs to the technical field of low-carbon sintering, and aims at the problem of large sintering carbon emission caused by large fossil energy consumption in the existing sintering process.The present application discloses a low-carbon sintering method, which can significantly improve the utilization efficiency of biomass and greatly reduce the consumption of fossil energy while ensuring the sintering quality by crushing, screening and grading biomass for different particle sizes to make biomass particles participate in the sintering process.In particular, combustible gas and gasification slag are obtained by gasifying medium-particle biomass, the gasification slag can be used as a sintering raw material for batching, and the combustible gas is blown onto the surface of the sintering mixture for roasting;large-particle biomass is arranged on the surface of the sintering material to assist ignition and roasting of the sintering material;and small-particle biomass is used as ignition fuel.This method can utilize all biomass after special pretreatment in the sintering process, effectively improve the utilization rate of biomass, significantly reduce the consumption of fossil energy in the sintering process, and realize low-carbon sintering.

Description

Technical Field

[0001] This invention relates to a sintering method, process, and system, specifically to a low-carbon sintering method, process, and system based on biomass fractionation, belonging to the field of sintering technology. Background Technology

[0002] Sintering is a common method for iron ore agglomeration in the steelmaking process. Currently, China's annual sinter production exceeds 1 billion tons. The main fuel used in sintering is coke powder. Based on the current energy consumption of 40-50 kgce per ton of sinter, the sintering industry emits over 100 million tons of CO2 annually, making it a significant source of CO2 emissions for the steel industry and even the entire nation. Given the national dual-carbon strategy, carbon reduction in the sintering process is particularly important. The current mainstream sintering process uses draft sintering, with key equipment including belt sintering machines, ignition and holding furnaces, material feeders, and annular coolers. Due to its high single-machine output and high degree of mechanization and automation, the belt sintering machine has become the absolute mainstream in global sintering production.

[0003] Domestic and international researchers have conducted numerous studies and experiments on low-carbon aspects of the sintering process, such as using biomass sintering and gas injection. Due to the inherent limitations of biomass fuels, biomass sintering is currently only a laboratory research project and cannot yet be widely promoted in industry. Gas injection is a method that has emerged in recent years to reduce coke usage by injecting gas into the sintering material surface. However, the gas used for injection is still mainly coke oven gas and natural gas, which are essentially derived from fossil fuels, and its effect on reducing CO2 emissions is still limited.

[0004] Existing sintering process production flow such as Figure 5 As shown, the sintering raw materials mainly consist of iron ore, flux, and fuel. The sintering fuel is primarily fossil fuel coke powder, accounting for approximately 3-5% of the raw materials. After thorough mixing and granulation, the various components of the sintering raw materials are evenly spread onto the sintering trolley by a distributor. The trolley moves at a constant speed from left to right. When the trolley enters the ignition and holding furnace, combustion gas and air are introduced through the ignition burners to ignite the raw materials. The coke powder on the surface of the raw materials is ignited. Subsequently, under the negative pressure of the exhaust fan under the trolley, air above the trolley is continuously drawn into the material layer, and the combustion zone in the material layer is transferred from top to bottom, completing the entire sintering process. The high-temperature flue gas is drawn by the main exhaust fan into the large flue below the trolley, where the temperature reaches over 900℃. After waste heat utilization and desulfurization and denitrification, it is discharged into the atmosphere.

[0005] Traditional sintering processes still primarily use fossil fuels, with coke powder added to the raw materials. The coke oven gas and blast furnace gas used for ignition are essentially derived from coal, and the production of sintered ore requires the emission of large amounts of CO2. Currently, some low-carbon sintering methods have emerged on the market, partially incorporating biomass to replace fossil fuels. These typically involve directly mixing biomass fuel with iron ore before sintering. However, due to the significant density difference between biomass fuel and other sintering raw materials like iron ore, biomass segregation easily occurs during mixing, leading to uneven heat distribution in the sintering bed. Furthermore, a large amount of volatile matter in the biomass is drawn away by the flue gas before combustion, resulting in insufficient heat in the bed and excessive levels of combustible gases in the flue gas. Directly blending biomass into the raw materials has limited carbon reduction effects on sintering and also affects the quality of the sintered ore. Summary of the Invention

[0006] To address the problems in existing low-carbon sintering methods for biomass as a substitute for fossil fuels, such as segregation during mixing leading to uneven heat distribution in the sintering bed and insufficient heat due to unburned volatiles, this invention proposes a low-carbon sintering method, process, and system. This involves crushing and screening the biomass, classifying it by particle size, and then sending biomass fuel particles of different sizes to different sintering processes, thereby achieving full utilization of biomass and low-carbon sintering. Based on the different fundamental characteristics of biomass particles of different sizes, the inventors studied the characteristics of different biomass properties and the requirements of the sintering process, coupling biomass with different properties with different sintering processes to improve the utilization efficiency of biomass in the sintering process, thereby reducing the use of fossil fuels and lowering carbon emissions, achieving low-carbon sintering.

[0007] According to a first embodiment of the present invention, a low-carbon sintering method is provided.

[0008] A low-carbon sintering method, comprising the following steps:

[0009] 1) Biomass pretreatment: The biomass is crushed and screened to obtain large-particle biomass, medium-particle biomass, and small-particle biomass; the medium-particle biomass is then gasified to obtain combustible gas and gasification residue;

[0010] 2) Sintering batching and spreading: After batching the sintering raw materials, the sintering material is obtained. The sintering material is first spread on the sintering machine trolley, and then drying is optional. Finally, large particles of biomass are spread on the surface of the sintering material to obtain sintering material containing biomass.

[0011] 3) Sintering treatment: The sintering material containing biomass moves forward with the sintering trolley and undergoes ignition, roasting and cooling treatment in sequence to obtain the sintered finished material; In the ignition process: small particles of biomass are sent to the ignition burner as ignition fuel for ignition; In the roasting process, combustible gas is injected onto the surface of the sintering mixture to participate in roasting.

[0012] Preferably, in step 1), the particle size of the large-particle biomass is [a, b], the particle size of the medium-particle biomass is [c, a), and the particle size of the small-particle biomass is (0, c).

[0013] Where a ranges from 1 to 3 mm; b ranges from 4 to 8 mm; and c ranges from 0.3 to 0.7 mm.

[0014] Preferably, ultra-large biomass particles with a particle size > b are returned to the crushing process for re-crushing.

[0015] Preferably, the gasification slag obtained in step 1) is used as one of the sintering raw materials in the batching process.

[0016] Preferably, in step 1), the gasification process specifically involves placing medium-sized particulate biomass in a mixed atmosphere containing water vapor and oxygen for thermal gasification to obtain combustible gas and gasification slag; wherein the temperature of the thermal gasification process is not lower than 700°C, preferably not lower than 800°C.

[0017] Preferably, the total mass ratio of water vapor and oxygen to the gas-solid mass ratio of biomass is 0.4 to 0.8:1, more preferably 0.5 to 0.7:1.

[0018] Preferably, in the mixed atmosphere, the volume ratio of water vapor to oxygen is 1 to 2:1, more preferably 1.2 to 1.5:1.

[0019] Preferably, the gasification process is carried out in a slurry bed reactor or a fixed bed reactor.

[0020] Preferably, the heat source in the gasification process is the high-temperature flue gas in the sintering flue. More preferably, the heat exchange between the high-temperature flue gas and the biomass is indirect heat exchange.

[0021] Preferably, all or part of the water vapor and oxygen in the gasification process are sourced from the hot and humid air discharged from the drying section of the sintering process, and fresh water is used as a supplementary source of water vapor.

[0022] Preferably, the other sintering raw materials mentioned in step 2) are iron ore, quicklime, coke powder, and optionally gasification slag.

[0023] Preferably, the drying process in step 2) is: introducing hot air at a temperature of not less than 300°C into the sintering trolley to contact the sintering material to achieve heat exchange drying; preferably, the hot air at a temperature of not less than 300°C is the hot air generated during the cooling process and / or the flue gas obtained from the gasification process.

[0024] Preferably, the method further includes: 4) after the gasification slag obtained in step 1) is shaped, the shaped slag is obtained, and the shaped slag is used as one of the sintering raw materials in the batching.

[0025] Preferably, the molding process specifically involves: extruding and degassing the obtained gasified slag and then crushing it.

[0026] Preferably, the extrusion pressure during the extrusion degassing process is 15–30 MPa, and more preferably 20–28 MPa.

[0027] Preferably, the particle size of the slag obtained after crushing is 2-7 mm, and more preferably 3-5 mm.

[0028] According to a second embodiment of the present invention, a biomass fractionation process for a low-carbon sintering method is provided.

[0029] A biomass fractionation process for a low-carbon sintering method includes: a) controlling gasification reaction parameters according to the properties of the biomass, such that the volatile matter content in the gasification slag does not exceed a set value. Further optimization also ensures that the carbon content in the gasification slag is not lower than a set value.

[0030] Preferably, the volatile matter content in the gasification slag is not higher than the set value: the volatile matter content in the gasification slag is not higher than 8%, preferably not higher than 5%; the carbon content in the gasification slag is higher than the set value: the carbon content in the gasification slag is not lower than 20%, preferably not lower than 25%.

[0031] Preferably, the gasification process is carried out in a fixed-bed reactor, and the parameters for controlling the gasification reaction are:

[0032] At a given gasification temperature, the theoretical gasification time required to equalize the carbon content in the gasification residue to a set value is:

[0033]

[0034] In the formula, C0 is the initial carbon content in the medium-sized particulate biomass, %; C1 is the set value of carbon content in the gasification residue, %; L is the particle size of the medium-sized particulate biomass, mm; M is the moisture content in the biomass, %; T1 is the gasification temperature, ℃; t ′1 represents the time required for the carbon reaction in biomass to reach the desired temperature; α and η are both adjustment coefficients, where α ranges from 0.20 to 0.30 and η ranges from 0.10 to 0.20.

[0035] At the same gasification temperature, the theoretical gasification time required to calculate the volatile matter content in the gasification residue to equal the set value is:

[0036]

[0037] In the formula, V0 is the initial volatile matter content in the medium-sized particulate biomass, %; V1 is the set value of volatile matter content in the gasification residue, %; L is the particle size of the medium-sized particulate biomass, mm; M is the moisture content in the biomass, %; T1 is the gasification temperature, ℃; t ′ 2 represents the time required for the volatile matter in biomass to react; γ and μ are both adjustment coefficients, where γ ranges from 0.08 to 0.15 and μ ranges from 0.10 to 0.20.

[0038] The actual vaporization time is then controlled as follows:

[0039] When t2≤t1, the temperature satisfies the vaporization condition. According to (Equation 1) and (Equation 2), the actual vaporization time t at this temperature is controlled as: t2≤t≤t1; when t2>t1, the actual vaporization time t at this temperature is controlled as: t≥t2.

[0040] Preferably, the process further includes: b) detecting the volatile matter content and carbon content in the gasification slag, and returning the gasification slag with excessively high volatile matter content and carbon content to the gasification process of medium-sized particulate biomass for regasification.

[0041] Preferably, the process further includes: c) controlling the mass distribution ratio of large, medium, and small biomass particles during the biomass crushing and screening process, thereby reducing carbon emissions while meeting the normal operation requirements of the sintering process; specifically including:

[0042] (ci) To reduce carbon emissions while meeting the normal operation requirements of the sintering process, a dynamic mathematical model of the mass distribution ratio of large-particle biomass, medium-particle biomass, and small-particle biomass is established:

[0043]

[0044] In Equation 3, A is the proportion of small-particle biomass to the total biomass mass (%); B is the proportion of medium-particle biomass to the total biomass mass (%); C is the proportion of large-particle biomass to the total biomass mass (%); where A+B+C<1; δ is a dimensionless correction coefficient, ranging from 1 to 3; Q is the proportion of the mass of gasification slag to the mass of medium-particle biomass after gasification (%); P is the proportion of the mass of gasified biomass to the mass of medium-particle biomass during gasification (%); T2 is the ignition temperature (°C); F is the iron ore grade (%); and Y is the carbon-saving ratio after adopting the biomass graded and graded treatment coupled with sintering process.

[0045] cii) Based on the relationship curve between the mass change of large-particle biomass laid on the sintering surface and the ignition temperature, establish the relationship between the amount of large-particle biomass laid and the ignition temperature:

[0046] T2 = 1050 - β*(0.5 + 5*D) 0.1 *In(1+5*D)……(Equation 4)

[0047] In Equation 4, β is a coefficient related to the type of ore raw material, with a value range of 50 to 600, preferably 200 to 600, and more preferably 300 to 600; D is the percentage of the mass of large-particle biomass laid on the sintering surface to the total mass of the sintering material, with a value range of 1% to 15%, preferably 2% to 10%, and more preferably 3% to 8%; the minimum ignition temperature under the target working condition is calculated based on Equation 4; combining Equation 3 and Equation 4, the mass of small-particle biomass required for the optimal energy consumption condition of sintering ignition at this ignition temperature is first calculated, then the mass distribution ratio of large-particle biomass and the mass distribution ratio of small-particle biomass are obtained, and finally, the mass distribution ratio of medium-particle biomass is calculated under the premise of satisfying the mass distribution ratio of large-particle biomass and the mass distribution ratio of small-particle biomass. Preferably, the percentage of the mass of large-particle biomass laid on the sintering surface to the total mass of the sintering material has an optimal range, that is, the optimal value of D is 1% to 15%, preferably 2% to 10%, and more preferably 3% to 8%.

[0048] Preferably, the total mass of biomass is 1% to 2.6% of the mass of sinter, the value of A is 5% to 12%, the value of B is 55% to 75%, the value of C is 18% to 28%, and A+B+C≤1; the value of P is 60% to 75%, the value of Q is 25% to 40%, and P+Q=1.

[0049] According to a third embodiment of the present invention, a low-carbon sintering system is provided.

[0050] A low-carbon sintering system includes a sintering machine, a batching device, a feeding device, an ignition burner, a crushing device, a screening device, a gasification device, an annular cooler, and a jetting device. The sintering machine is divided into a drying section, a preheating section, and a calcining section according to its operating direction. The ignition burner is located in an ignition furnace situated above and downstream of the preheating section. The material outlet of the batching device is connected to the material inlet of the feeding device. The material outlet of the feeding device is located at the feed end of the sintering machine. The jetting device is positioned above the calcining section. The discharge end of the sintering machine is connected to the feed end of the annular cooler.

[0051] The material outlet of the crushing device is connected to the material inlet of the screening device. The large particle material outlet of the screening device is connected to the material inlet of the feeding device, the medium particle material outlet of the screening device is connected to the material inlet of the gasification device, and the small particle material outlet of the screening device is connected to the material inlet of the ignition burner. The gas outlet of the gasification device is connected to the fuel inlet of the injection device. The length of the sintering machine is 1–2000 m, preferably 2–1500 m, and more preferably 3–1000 m. The length of the annular cooler is 1–800 m.

[0052] Preferably, the screening device is further provided with an oversize material outlet, which is connected to the material inlet of the crushing device.

[0053] Preferably, the system also includes a forming device, wherein the solid outlet of the gasification device is connected to the material inlet of the forming device, and the material outlet of the forming device is connected to the material inlet of the batching device.

[0054] Preferably, the gas inlet of the drying section is connected to the high-temperature gas outlet of the annular cooler or the low-temperature medium outlet of the gasification device via a pipeline.

[0055] Preferably, the ignition burner includes a combustion air duct and a biomass duct. The inlet end of the combustion air duct is connected to an oxygen-containing gas source, and the outlet end of the combustion air duct is connected to the furnace of the ignition furnace. The feed end of the biomass duct is simultaneously connected to the fine particle material outlet of the screening device and the carrier gas source, and the discharge end of the biomass duct is connected to the furnace of the ignition furnace. The bottom of the furnace is connected to the upper downstream side of the preheating section.

[0056] Preferably, the discharge section of the biomass pipeline includes a gas discharge channel and a solid discharge channel sleeved outside the gas discharge channel.

[0057] Preferably, the combustion air duct includes a central air duct and a secondary air duct that are not interconnected. The inlet ends of both the central and secondary air ducts are connected to an oxygen-containing gas source. The central air duct is fitted inside the cavity of the gas discharge channel along its axis, while the secondary air duct is fitted outside the solid discharge channel. The outlet ends of both the central and secondary air ducts are connected to the furnace chamber of the ignition furnace.

[0058] Preferably, the ignition burner further includes a swirl mechanism, which is disposed at the outlet end of the secondary air duct and / or the gas discharge channel. Preferably, the swirl mechanism is a swirl blade.

[0059] Preferably, the carrier gas source is the gas outlet of the drying section.

[0060] Preferably, the gasification device includes a kiln body and a heat exchange device extending into the kiln body but not communicating with it. The kiln body comprises a kiln head, a kiln body, and a kiln tail connected in series. The kiln head and kiln tail are fixedly arranged, while the kiln body can rotate along its axis. A gas-solid inlet is provided at the upper part of the kiln head, which is connected via pipes to both the medium-particle material outlet of the screening device and a high-humidity oxygen-containing gas source. A gas outlet is provided at the upper part of the kiln tail, which is connected via pipes to the fuel inlet of the injection device. A solid outlet is provided at the lower part of the kiln tail, which is connected via a conveyor belt to the material inlet of the forming device or the material inlet of the batching device. Preferably, the high-humidity oxygen-containing gas source is the gas outlet of the drying section.

[0061] Preferably, the heat exchange device includes an outer cylinder and an inner cylinder. The outer cylinder passes through the kiln head, kiln body, and kiln tail sequentially along the axial direction. An inner cylinder is inserted into each end of the outer cylinder, and the inserted end of the inner cylinder extends along the axis of the outer cylinder to the middle of the inner cylinder cavity. High-temperature medium inlets are provided at both ends of the outer cylinder located outside the kiln body, and medium return ports are provided at the ends of the inner cylinder located inside the outer cylinder. The inner cylinder is connected to the outer cylinder through the medium return ports. Low-temperature medium outlets are provided on the inner cylinder located outside the outer cylinder. Preferably, the high-temperature medium inlets are connected to the sintering flue. Preferably, a blind plate is also provided in the middle of the outer cylinder cavity, which divides the outer cylinder cavity into two non-communicating sections. The two inner cylinders are located in the two non-communicating sections respectively.

[0062] Preferably, there are 1 to 8 heat exchange devices evenly distributed inside the kiln body.

[0063] Preferably, the gasification device further includes a water supply pipe, the inlet end of which is connected to a new water source, and the outlet end of which extends through the kiln head and into the kiln body. Multiple atomizing nozzles are provided on the outlet section of the water supply pipe.

[0064] Preferably, the kiln body is inclined with a higher kiln head and a lower kiln tail. Preferably, the inclination angle of the kiln body is 2 to 8°, and more preferably 3 to 6°.

[0065] In existing technologies, woody plants from urban landscaping solid waste, such as pine and camphor, are preferred for biomass addition to sintering, followed by agricultural straw. A common characteristic of these materials is their high volatile matter content, typically reaching around 70%. Furthermore, biomass raw materials are irregularly shaped, while sintering requires fuel with low volatile matter content (<5%) and strong exothermic properties. Therefore, biomass cannot be directly added to the sintering process. Directly mixing biomass into the sintering raw materials does not meet the low volatile matter requirement, easily leading to uneven heat distribution or insufficient heat in the sintering bed.

[0066] In this invention, biomass is crushed and screened into three grades. Large-particle biomass fuel is arranged on the surface of the sintering bed, replacing part of the coke powder. Medium-particle biomass fuel has a moderate particle size and high reactivity, and is used for gasification to produce combustible gas. Small-particle biomass fuel has a high specific surface area, low specific gravity, and fast combustion speed, and is fed into the ignition burner as ignition fuel. This invention classifies biomass into multiple grades according to particle size and adds biomass fuel of different particle sizes to the sintering process using different processes, which can effectively improve the utilization rate of biomass and achieve low-carbon sintering. In addition, biomass with excessively large particle size (i.e., ultra-large-particle biomass fuel) can be returned to the crushing step for re-crushing, further improving the utilization rate of biomass.

[0067] In this invention, based on extensive experiments, a general range for classifying biomass fuel particle size grades was obtained, as follows. Since the particle size of coke powder in the sintering raw material is approximately 2–5 mm, the particle size of large-particle biomass fuel is set to a relatively close [a, b]. Biomass fuel within this particle size range, when laid on the surface of the sintering material layer, exhibits better reactivity than coke powder and is easier to ignite. It can be rapidly ignited after entering the preheating section, improving ignition efficiency and reducing ignition energy consumption. Furthermore, biomass with a particle size range of [c, a) has moderate reactivity and is suitable for gasification to produce combustible gases. The remaining biomass fuel with a particle size of (0, c) is used as ignition fuel for the burner. Here, a is 1–3 mm; b is 4–8 mm; and c is 0.3–0.7 mm. In practical applications, the specific values ​​of a, b, and c are determined based on the specific properties of the biomass.

[0068] Through experimental research, the inventors discovered that medium-sized particulate biomass (e.g., biomass with a particle size in the range [c, a)) has a moderate particle size and good reactivity, making it most suitable for gasification to produce combustible gas (controlling the volatile matter and carbon content in the treated material). In this invention, the gasification temperature of the medium-sized particulate biomass fuel is above 700℃ (preferably 800℃). Theoretically, the higher the gasification temperature, the higher the gasification reaction rate and the higher the carbon conversion rate. The gasification reaction uses steam and oxygen as gasifying agents, and the main reactions are as follows:

[0069] C + H₂O = CO + H₂

[0070] C + O₂ = 2CO

[0071] The combustible gas obtained from gasification mainly consists of H2, CO, and other combustible gases. Injecting this gas into the sintering material layer provides supplemental heating to the sintering surface, effectively reducing the consumption of solid carbon in the sintering material layer and achieving low-carbon sintering. Preferably, the heat required for the gasification reaction comes from the high-temperature flue gas in the sintering flue, with a temperature >700℃, and indirect heat exchange (such as a partition wall heat exchange) is used. Alternatively, the water vapor and oxygen can be sourced from the high-humidity hot air dried in other processes (e.g., the high-humidity hot air generated in the drying section), which contains abundant water vapor and air and has a high temperature. Utilizing readily available high-humidity hot air reduces the consumption of new water and improves the waste heat utilization rate of the high-humidity hot air. If the moisture content in the high-humidity hot air is insufficient, additional new water needs to be added.

[0072] In this invention, to ensure sufficient H2 in the combustible gas and to place the medium-sized particulate biomass fuel in an atmosphere of H2 and CO, the gas-solid mass ratio of the total mass of water vapor and oxygen to the residual biomass is limited to 0.4–0.8:1. Furthermore, by adjusting the water vapor content in the high-humidity hot air and the amount of fresh water replenishment, the volume ratio of water vapor to oxygen during the gasification reaction is maintained within the range of 1–2:1. Ensuring sufficient H2 content in the combustible gas improves the cleanliness of the combustion products, while also increasing the heat released by hydrogen combustion, thereby improving the energy utilization efficiency of the combustible gas.

[0073] In this invention, the reaction vessel for the gasification process can optionally be a suspended bed reactor or a fixed bed reactor.

[0074] In this invention, after gasification, medium-particle biomass fuel yields combustible gas and gasification slag. The main component of the gasification slag is unreacted carbon from the biomass, with a carbon content generally of 20-30% and volatile matter <5%. Compared to the biomass raw materials, the volatile matter and carbon content of the gasification slag are significantly reduced, resulting in relatively low reactivity, allowing it to participate in the sintering process. Preferably, since the gasification slag still has a well-developed porous structure, to further reduce its reactivity and improve biomass utilization, this invention employs an extrusion molding method and further limits parameters such as time and pressure during the extrusion molding process to eliminate the porosity of the gasification slag, forming dense gasification slag shaped fuel carbon. After crushing, carbon fuel is obtained. The obtained carbon fuel has low volatile matter, slow exothermic reaction, and high density, meeting the requirements for sintering fuel. It can be directly mixed with sintering raw materials to replace part of the coke powder, reducing the amount of fossil fuel used.

[0075] In this invention, to achieve a carbon content of no less than 20% and a volatile matter content of no more than 5% in the gasification slag, the invention calculates the gasification time t1 and the volatile matter content t2 at the critical points based on parameters such as particle size, moisture content, and carbon content of the particulate biomass. If t2 ≤ t1, it indicates that there exists a gasification time at this temperature that simultaneously satisfies the requirements for carbon content and volatile matter content, and the actual gasification time t is set to satisfy t2 ≤ t ≤ t1. When t2 > t1, since a volatile matter content below the set value is a mandatory requirement and a carbon content above the set value is a preferred requirement, t must be greater than or equal to t2. Therefore, the actual gasification time t at this temperature should be t ≥ t2.

[0076] In this invention, a dynamic mathematical model for the mass distribution ratio of large-particle biomass, medium-particle biomass, and small-particle biomass is further proposed. Simultaneously, based on the relationship curve between the mass of large-particle biomass laid on the sintering surface and the ignition temperature, a formula for the relationship between the amount of large-particle biomass laid and the ignition temperature is established. According to (Equation 4), the minimum ignition temperature under the target operating condition can be calculated. Combining (Equations 3) and (Equations 4), the mass of small-particle biomass required for the optimal energy consumption condition of sintering ignition at this ignition temperature is first calculated. Then, the mass distribution ratios of large-particle biomass and small-particle biomass are obtained. Finally, under the premise of satisfying the mass distribution ratios of large-particle biomass and small-particle biomass, the mass distribution ratio of medium-particle biomass is calculated. Furthermore, regarding the values ​​of P and Q: According to (Equation 3), the larger the value of P, the greater the carbon saving ratio. Increasing P can be achieved by increasing the gasification temperature and residence time, but P cannot be increased indefinitely. When the temperature and residence time reach a certain level, P will not increase further, at which point P reaches its maximum value. Preferably, the total mass of biomass is 1% to 2.6% of the mass of sinter, the value of A is 5% to 12%, the value of B is 55% to 75%, the value of C is 18% to 28%, and A+B+C<1; the value of P is 60% to 75%, the value of Q is 25% to 40%, and P+Q=1.

[0077] In this invention, while meeting the requirements of the ignition process, the maximum carbon saving of the technical solution is achieved by controlling the mass distribution ratio of large, medium, and small biomass particles. Through iterative calculations, the mass distribution ratio of these three particles that achieves the maximum carbon saving is obtained; then, the crushing, screening, and grading processes are controlled to obtain the required specific mass distribution ratio of these three particles.

[0078] In this invention, a drying section is set up upstream of the preheating section according to the running direction of the sintering trolley, and ambient air (preferably hot air discharged from the annular cooler or low-temperature flue gas discharged from the sintering flue and used for gasification hydrogen production) is introduced to dry the sintering raw materials, remove the moisture added to the sintering raw materials during the mixing and granulation process, reduce the energy consumed in the subsequent process, and at the same time avoid the formation of an overly wet zone in the sintering material layer, which would affect the air permeability of the sintering material layer.

[0079] This invention also proposes an ignition burner structure, which delivers gas to the sintering material surface and ignites it for heating via a combustion air duct and a biomass duct. Preferably, since biomass undergoes pyrolysis at temperatures above 300°C, and the burner is located below the high temperature (850°C~1050°C) of the sintering furnace, the internal temperature of the burner is very likely to exceed 300°C, causing the biomass to pyrolyze. This invention sets the biomass duct as an inner solid discharge channel and a gas discharge channel surrounding the solid discharge channel. After the biomass powder undergoes pyrolysis, it enters the burner tangentially, generating a swirling flow. Due to the density difference between the gas and the solid, the solid biomass powder moves towards the outer center and enters the solid discharge channel, while the gas moves closer to the center, thus generating a certain amount of swirling separation. The gas enters the gas discharge channel, enters the ignition furnace, mixes with the combustion gas, and then burns. The gas is connected to the bottom of the ignition furnace and the upper downstream side of the preheating section, completing the sintering ignition. Preferably, the combustion air duct is divided into a central air duct and a secondary air duct. The outlet of the central air duct is located inside the gas discharge channel, and the outlet of the secondary air duct is fitted outside the solid discharge channel. Under the combined action of the central and secondary air, the combustion air can be fully mixed with the biomass powder and pyrolysis gas. Furthermore, a swirling mechanism is installed in the gas discharge channel and / or the secondary air duct. The swirling combustion air entrains the biomass powder, pyrolysis gas, and internal combustion air, causing them to mix intensely, thereby achieving efficient combustion.

[0080] This invention also proposes a gasification device structure, which includes a kiln body and a heat exchanger. Indirect heat exchange provides heat for biomass gasification, increasing the gasification temperature. Biomass and high-humidity oxygen-containing gas enter through the gas-solid inlet. After the reaction is completed inside the kiln, the generated gasified gas (i.e., combustible gas) exits through the gas outlet. The gasified slag moves towards the kiln tail under the rotation of the kiln body and is finally discharged through the solid outlet. Alternatively, the kiln body can be designed with an inclined configuration, higher at the kiln head and lower at the kiln tail, combined with a rotatable kiln body, which facilitates the discharge of gasified slag. Preferably, the heat exchanger is a sleeve-type structure, with hot flue gas entering through the outer cylinder, indirectly contacting the biomass, and exiting through the inner cylinder after heat exchange, reducing the contact between biomass and low-temperature flue gas. More preferably, in addition to the high-humidity oxygen-containing gas carrying a large amount of water vapor, a water supply pipe is also provided. Water enters the kiln and undergoes a secondary reaction with the biomass, facilitating control of the water vapor to oxygen ratio, increasing the gasification intensity, and simultaneously increasing the H2 production in the gasified gas.

[0081] In this invention, the formulas are obtained by the inventors based on experimental and engineering applications. All calculations are numerical values ​​converted according to the prescribed units. The converted values ​​are substituted into the formulas to obtain the results (after converting the units of each parameter, only the numerical values ​​are substituted into the formulas for calculation, not the units; the units are only used to adjust the magnitude of the numerical values).

[0082] Compared with the prior art, the present invention has the following beneficial effects:

[0083] 1. The present invention provides a low-carbon sintering method, which crushes and screens biomass into multiple grades, and adds different processes according to different particle sizes for utilization, effectively improving the utilization rate of biomass and realizing low-carbon sintering.

[0084] 2. The present invention provides a biomass fractionation process for low-carbon sintering. Based on the properties of biomass, the gasification time is calculated to ensure that the carbon content and volatile matter content in the gasification slag meet the requirements. In addition, by controlling the mass distribution ratio of large, medium and small biomass particles, the process can meet the normal operation requirements of sintering supply and demand while achieving refined control, thereby reducing carbon emissions and fossil fuel consumption.

[0085] 3. The low-carbon sintering system provided by this invention has a simple structure and can realize the separate utilization of biomass after crushing according to different particle sizes. At the same time, the structure of the ignition burner enables the combustion gas and fuel to be mixed quickly and evenly, achieving efficient combustion. Furthermore, the gasification device increases the gasification intensity and the H2 production in the gasified gas, making it highly practical. Attached Figure Description

[0086] Figure 1 This is a schematic diagram of a low-carbon sintering system provided by the present invention.

[0087] Figure 2 This is another structural schematic diagram of a low-carbon sintering system provided by the present invention.

[0088] Figure 3 This is a schematic diagram of the structure of an ignition burner in a low-carbon sintering system provided by the present invention.

[0089] Figure 4 This is a schematic diagram of the gasification device in a low-carbon sintering system provided by the present invention.

[0090] Figure 5 This is a flowchart of the existing sintering process.

[0091] Figure reference numerals: 1: Sintering machine; 101: Drying section; 102: Preheating section; 103: Calcination section; 2: Batching device; 3: Material distribution device; 4: Ignition burner; 401: Combustion air duct; 4011: Central air duct; 4012: Secondary air duct; 402: Biomass duct; 4021: Gas discharge channel; 4022: Solid discharge channel; 403: Cyclone mechanism; 5: Crushing device; 6: Screening device; 7: Gasification device; 701: Kiln body; 70 11: Kiln head; 7012: Kiln body; 7013: Kiln tail; 7014: Gas-solid inlet; 7015: Gas outlet; 7016: Solid outlet; 702: Heat exchanger; 7021: High-temperature medium inlet; 7022: Low-temperature medium outlet; 7023: Outer cylinder; 7024: Inner cylinder; 7025: Medium return port; 7026: Blind flange; 7027: Water supply pipe; 7028: Atomizing nozzle; 8: Circular cooler; 9: Spraying device; 10: Molding device. Detailed Implementation

[0092] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0093] A low-carbon sintering system includes a sintering machine 1, a batching device 2, a feeding device 3, an ignition burner 4, a crushing device 5, a screening device 6, a gasification device 7, an annular cooler 8, and a jetting device 9. The sintering machine 1 is divided into a drying section 101, a preheating section 102, and a calcining section 103 according to its operating direction. The ignition burner 4 is located in an ignition furnace situated above and downstream of the preheating section 102. The material outlet of the batching device 2 is connected to the material inlet of the feeding device 3. The material outlet of the feeding device 3 is located at the feed end of the sintering machine 1. The jetting device 9 is located above the calcining section 103. The discharge end of the sintering machine 1 is connected to the feed end of the annular cooler 8.

[0094] The material outlet of the crushing device 5 is connected to the material inlet of the screening device 6. The large particle material outlet of the screening device 6 is connected to the material inlet of the feeding device 3, the medium particle material outlet of the screening device 6 is connected to the material inlet of the gasification device 7, and the small particle material outlet of the screening device 6 is connected to the material inlet of the ignition burner 4. The gas outlet of the gasification device 7 is connected to the fuel inlet of the injection device 9.

[0095] Preferably, the screening device 6 is further provided with an oversize material outlet, which is connected to the material inlet of the crushing device 5.

[0096] Preferably, the system further includes a forming device 10, the solid outlet of the gasification device 7 is connected to the material inlet of the forming device 10, and the material outlet of the forming device 10 is connected to the material inlet of the batching device 2.

[0097] Preferably, the gas inlet of the drying section 101 is connected to the high-temperature gas outlet of the annular cooler 8 or the low-temperature medium outlet of the gasification device 7 via a pipeline.

[0098] Preferably, the ignition burner 4 includes a combustion air duct 401 and a biomass duct 402. The inlet end of the combustion air duct 401 is connected to an oxygen-containing gas source, and the outlet end of the combustion air duct 401 is connected to the furnace of the ignition furnace. The feed end of the biomass duct 402 is simultaneously connected to the fine particle material outlet of the screening device 6 and a carrier gas source, and the discharge end of the biomass duct 402 is connected to the furnace of the ignition furnace.

[0099] Preferably, the discharge section of the biomass pipeline 402 includes a gas discharge channel 4021 and a solid discharge channel 4022 sleeved outside the gas discharge channel 4021.

[0100] Preferably, the combustion air duct 401 includes a central air duct 4011 and a secondary air duct 4012 that are not interconnected. The inlet ends of both the central air duct 4011 and the secondary air duct 4012 are connected to an oxygen-containing gas source. The central air duct 4011 is sleeved within the cavity of the gas discharge channel 4021 along its axis, and the secondary air duct 4012 is sleeved outside the solid discharge channel 4022. The outlet ends of both the central air duct 4011 and the secondary air duct 4012 are connected to the furnace chamber of the ignition furnace.

[0101] Preferably, the ignition burner 4 further includes a swirl mechanism 403, which is disposed at the outlet end of the secondary air duct 4012 and / or the gas outlet channel 4021. Preferably, the swirl mechanism 403 is a swirl blade.

[0102] Preferably, the carrier gas source is the gas outlet of the drying section 101.

[0103] Preferably, the gasification device 7 includes a kiln body 701 and a heat exchange device 702 extending into the kiln body 701 but not communicating with it. The kiln body 701 includes a kiln head 7011, a kiln body 7012, and a kiln tail 7013 connected in series. The kiln head 7011 and kiln tail 7013 are fixedly arranged, while the kiln body 7012 can rotate along its axis. A gas-solid inlet 7014 is provided at the upper part of the kiln head 7011, and the gas-solid inlet 7014 is simultaneously connected to the medium-particle material outlet of the screening device 6 and a high-humidity oxygen-containing gas source via a pipe. A gas outlet 7015 is provided at the upper part of the kiln tail 7013, and the gas outlet 7015 is connected to the fuel inlet of the injection device 9 via a pipe. A solid outlet 7016 is provided at the lower part of the kiln tail 7013, and the solid outlet 7016 is connected to the material inlet of the forming device 10 or the material inlet of the batching device 2 via a conveyor belt. Preferably, the high-humidity oxygen-containing gas source is the gas outlet of the drying section 101.

[0104] Preferably, the heat exchange device 702 includes an outer cylinder 7023 and an inner cylinder 7024. The outer cylinder 7023 sequentially passes through the kiln head 7011, the kiln body 7012, and the kiln tail 7013 along the axial direction. An inner cylinder 7024 is inserted into each end of the outer cylinder 7023, and the inserted end of the inner cylinder 7024 extends along the axis of the outer cylinder 7023 to the middle of the inner cylinder cavity. High-temperature medium inlets 7021 are provided at both ends of the outer cylinder 7023 located outside the kiln body 701, and medium return ports 7025 are provided at the ends of the inner cylinder 7024 located inside the outer cylinder 7023. The inner cylinder 7024 is connected to the outer cylinder 7023 through the medium return ports 7025. Low-temperature medium outlets 7022 are provided on the inner cylinder 7024 located outside the outer cylinder 7023. Preferably, the high-temperature medium inlet 7021 is connected to the sintering flue. Preferably, a blind plate 7026 is provided in the middle of the outer cylinder 7023 cavity, which divides the outer cylinder 7023 cavity into two non-communicating sections, and the two inner cylinders 7024 are located in the two non-communicating sections respectively.

[0105] Preferably, one to eight heat exchange devices 702 are evenly distributed inside the kiln body 701.

[0106] Preferably, the gasification device 7 further includes a water supply pipe 7027, the inlet end of which is connected to a new water source, the outlet end of which extends through the kiln head 7011 and into the kiln body 7012, and multiple atomizing nozzles 7028 are provided on the outlet section of the water supply pipe 7027.

[0107] Preferably, the kiln body 701 is inclined with the kiln head 7011 higher and the kiln tail 7013 lower. Preferably, the inclination angle of the kiln body 701 is 2 to 8°, and more preferably 3 to 6°.

[0108] Example 1

[0109] A low-carbon sintering system, such as Figure 1-4 As shown, the sintering system includes a sintering machine 1, a batching device 2, a feeding device 3, an ignition burner 4, a crushing device 5, a screening device 6, a gasification device 7, an annular cooler 8, and a jetting device 9. The sintering machine 1 is divided into a drying section 101, a preheating section 102, and a calcining section 103 according to its operating direction. The ignition burner 4 is located in an ignition furnace located above and downstream of the preheating section 102. The material outlet of the batching device 2 is connected to the material inlet of the feeding device 3. The material outlet of the feeding device 3 is located at the feed end of the sintering machine 1. The jetting device 9 is located above the calcining section 103. The discharge end of the sintering machine 1 is connected to the feed end of the annular cooler 8.

[0110] The material outlet of the crushing device 5 is connected to the material inlet of the screening device 6. The large particle material outlet of the screening device 6 is connected to the material inlet of the feeding device 3, the medium particle material outlet of the screening device 6 is connected to the material inlet of the gasification device 7, and the small particle material outlet of the screening device 6 is connected to the material inlet of the ignition burner 4. The gas outlet of the gasification device 7 is connected to the fuel inlet of the injection device 9.

[0111] Example 2

[0112] The embodiment 1 is repeated, except that the screening device 6 is also provided with an oversize material outlet, which is connected to the material inlet of the crushing device 5.

[0113] The system also includes a molding device 10, the solid outlet of the gasification device 7 is connected to the material inlet of the molding device 10, and the material outlet of the molding device 10 is connected to the material inlet of the batching device 2.

[0114] The gas inlet of the drying section 101 is connected to the high-temperature gas outlet of the annular cooler 8 via a pipeline.

[0115] Example 3

[0116] The embodiment 2 is repeated, except that the ignition burner 4 includes a combustion air duct 401 and a biomass duct 402. The inlet end of the combustion air duct 401 is connected to an oxygen-containing gas source, and the outlet end of the combustion air duct 401 is connected to the furnace of the ignition furnace. The feed end of the biomass duct 402 is simultaneously connected to the fine particle material outlet of the screening device 6 and the carrier gas source, and the discharge end of the biomass duct 402 is connected to the furnace of the ignition furnace.

[0117] The discharge section of the biomass pipeline 402 includes a gas discharge channel 4021 and a solid discharge channel 4022 sleeved outside the gas discharge channel 4021.

[0118] Example 4

[0119] The embodiment 3 is repeated, except that the combustion air duct 401 includes a central air duct 4011 and a secondary air duct 4012 that are not interconnected. The air inlet ends of both the central air duct 4011 and the secondary air duct 4012 are connected to an oxygen-containing gas source. The central air duct 4011 is sleeved within the cavity of the gas discharge channel 4021 along its axis, while the secondary air duct 4012 is sleeved outside the solid discharge channel 4022. The air outlet ends of both the central air duct 4011 and the secondary air duct 4012 are connected to the furnace chamber of the ignition furnace.

[0120] Example 5

[0121] The embodiment 4 is repeated, except that the ignition burner 4 further includes a swirl mechanism 403, which is disposed at the outlet end of the secondary air duct 4012 and the gas discharge channel 4021. The swirl mechanism 403 consists of swirl blades.

[0122] The carrier gas source is the gas outlet of the drying section 101.

[0123] Example 6

[0124] The embodiment 5 is repeated, except that the gasification device 7 includes a kiln body 701 and a heat exchange device 702 that extends into the kiln body 701 but is not connected to it. The kiln body 701 includes a kiln head 7011, a kiln body 7012, and a kiln tail 7013 connected in series. The kiln head 7011 and kiln tail 7013 are fixedly arranged, while the kiln body 7012 can rotate along its axis. A gas-solid inlet 7014 is provided at the upper part of the kiln head 7011, and the gas-solid inlet 7014 is simultaneously connected to the medium-particle material outlet of the screening device 6 and a high-humidity oxygen-containing gas source via a pipe. A gas outlet 7015 is provided at the upper part of the kiln tail 7013, and the gas outlet 7015 is connected to the fuel inlet of the injection device 9 via a pipe. A solid outlet 7016 is provided at the lower part of the kiln tail 7013, and the solid outlet 7016 is connected to the material inlet of the forming device 10 via a conveyor belt. The high-humidity oxygen-containing gas source is the gas outlet of the drying section 101.

[0125] Example 7

[0126] The embodiment 6 is repeated, except that the heat exchange device 702 includes an outer cylinder 7023 and an inner cylinder 7024. The outer cylinder 7023 passes through the kiln head 7011, kiln body 7012, and kiln tail 7013 sequentially along the axial direction. An inner cylinder 7024 is inserted into each end of the outer cylinder 7023, and the inserted end of the inner cylinder 7024 extends along the axis of the outer cylinder 7023 to the middle of the inner cylinder cavity. High-temperature medium inlets 7021 are provided at both ends of the outer cylinder 7023 located outside the kiln body 701, and medium return ports 7025 are provided at the ends of the inner cylinder 7024 located inside the outer cylinder 7023. The inner cylinder 7024 is connected to the outer cylinder 7023 through the medium return ports 7025. Low-temperature medium outlets 7022 are provided on the inner cylinder 7024 located outside the outer cylinder 7023. The high-temperature medium inlets 7021 are connected to the sintering flue. A blind plate 7026 is also provided in the middle of the outer cylinder 7023 cavity. The blind plate 7026 divides the outer cylinder 7023 cavity into two non-communicating sections. The two inner cylinders 7024 are located in the two non-communicating sections respectively.

[0127] Example 8

[0128] Example 7 is repeated, except that two heat exchange devices 702 are evenly distributed inside the kiln body 701.

[0129] The gasification device 7 also includes a water supply pipe 7027. The inlet end of the water supply pipe 7027 is connected to a new water source. The outlet end of the water supply pipe 7027 extends through the kiln head 7011 and into the kiln body 7012. Five atomizing nozzles 7028 are installed on the outlet section of the water supply pipe 7027.

[0130] The kiln body 701 is inclined with the kiln head 7011 higher and the kiln tail 7013 lower. The inclination angle of the kiln body 701 is 5°.

[0131] Application Example 1

[0132] A low-carbon sintering method, using the system described in Example 8, includes the following steps:

[0133] 1) Biomass Pretreatment: 1000 kg of biomass was crushed and screened to obtain 270.1 kg of large-particle biomass with a particle size of [2 mm to 5 mm], 529 kg of medium-particle biomass with a particle size of [0.5 mm to 2 mm], and 149.7 kg of small-particle biomass with a particle size less than 0.5 mm. The medium-particle biomass was gasified at 900°C for 5.5 min to obtain approximately 111.1 kg of gasification residue and combustible gas. In addition, screening and classification yielded 51.2 kg of ultra-large-particle biomass with a particle size greater than 5 mm, which was returned to the crushing process for re-crushing.

[0134] 2) Sintering batching and distribution: 9200kg of iron ore powder, 250kg of flux and 210kg of coke powder are batched to obtain 9850kg of sintering material. The sintering material is first distributed on the sintering trolley, and then high-temperature hot air at 400℃ is introduced for drying. Finally, 270.1kg of large-particle biomass is placed on the surface of the sintering material to obtain mixed sintering material.

[0135] 3) Sintering treatment: The mixed sintering material is moved forward at a constant speed by the sintering trolley and passes through ignition, roasting and cooling treatment in sequence to obtain the sintered finished material; During the sintering process: the 149.7kg small particle biomass is fed into the ignition burner as ignition fuel, and the combustible gas is sprayed onto the surface of the sintering mixture to participate in the roasting treatment.

[0136] 4) Exhaust the gasification residue by pressing at 25 MPa and pass it through a mold to form 111.1 kg of shaped residue with a particle size of 3-5 mm; then add 111.1 kg of shaped residue to the batching process in step 2).

[0137] Application Example 2

[0138] A biomass fractionation process is provided for applying the sintering method described in Example 1:

[0139] a) Based on the properties of biomass, control the reaction process to ensure that the volatile matter content in the gasification residue is no higher than 8%, and the carbon content in the gasification residue is no less than 20%; the gasification process is carried out in a fixed-bed reactor, and at a given gasification temperature, the time required for the carbon content in the gasification residue to equal the set value is:

[0140]

[0141] In the formula, C0 is the initial carbon content in the medium-sized pellet biomass, taken as 50%; C1 is the set value of the carbon content in the medium-sized pellet biomass, taken as 20%; L is the particle size of the medium-sized pellet biomass, taken as 1.2 mm; M is the moisture content in the biomass, taken as 8%; T1 is the gasification temperature, taken as 900℃; t ′ 1 represents the time required for the carbon reaction in biomass to reach the target temperature, which is 0.5 min; α and η are both adjustment coefficients, where α is 0.45 and η is 0.1.

[0142] At the same gasification temperature, the time required to ensure that the volatile matter content in the gasification residue does not exceed a set value is:

[0143]

[0144] In the formula, V0 is the initial volatile matter content in the medium-sized pellet biomass, taken as 70%; V1 is the set value of the volatile matter content in the medium-sized pellet biomass, taken as 6%; L is the particle size of the medium-sized pellet biomass, taken as 1.2 mm; M is the moisture content in the biomass, taken as 8%; T1 is the gasification temperature, taken as 900℃; t ′ 2 represents the time required for the volatile matter in biomass to react, which is 0.5 min; γ and μ are both adjustment coefficients, where γ is 0.20 and μ is 0.10.

[0145] According to Equations 1 and 2, the vaporization time t at this temperature should be: t2≤t≤t1, that is, 4.61min≤t≤5.45min. Therefore, t can be controlled to be 5min.

[0146] The gasification process described in step 1) is changed to: placing 529 kg of particulate biomass in a mixed atmosphere containing water vapor and oxygen, and thermally gasifying it at 900°C for 5 min to obtain approximately 132.3 kg of gasification residue and combustible gas.

[0147] b) The volatile matter content in the gasification residue was found to be 5.98%, and the carbon content was 21.13%, so there was no need to return it to the gasification process.

[0148] c) During the biomass crushing and screening process, control the mass distribution ratio of the resulting large, medium, and small biomass particles to reduce carbon emissions while meeting the normal operation requirements of the sintering process. Specifically, this includes: ci) Establishing a dynamic mathematical model for the mass distribution ratio of large, medium, and small biomass particles to reduce carbon emissions while meeting the normal operation requirements of the sintering process.

[0149]

[0150] Where A is the proportion of small-particle biomass to the total biomass mass (%); B is the proportion of medium-particle biomass to the total biomass mass (%); C is the proportion of large-particle biomass to the total biomass mass (%); δ is a dimensionless correction coefficient, with a value of 2.3; Q is the proportion of the mass of gasification residue after gasification to the mass of medium-particle biomass, with a value of 25%; P is the proportion of the mass of gasified biomass during gasification to the mass of medium-particle biomass, with a value of 75%; T2 is the ignition temperature (°C); and F is the iron ore grade, with a value of 60%.

[0151] cii) Based on the relationship curve between the mass change of large-particle biomass laid on the sintering surface and the ignition temperature, establish the relationship between the amount of large-particle biomass laid and the ignition temperature:

[0152] T2 = 1050 - β*(0.5 + 5*D)0.1 *In(1+5*D)……(Equation 4)

[0153] Wherein, β is a coefficient related to the type of ore raw material, with a value of 550; D is the percentage of the mass of large-particle biomass laid on the sintering surface material to the total mass of the sintering surface material, with a value of 5.6%, and the ignition temperature T2 is calculated to be 917.5℃ according to (Equation 4). Based on D and the total mass of the sintering surface ore, the proportion C of large-particle biomass to the total mass of biomass is further calculated to be 28%.

[0154] The required mass A of small biomass under the optimal energy consumption conditions for sintering ignition is 5%. Finally, under the premise of satisfying the minimum mass distribution ratio of large biomass (i.e., C≥28%) and the minimum mass distribution ratio of small biomass (i.e., A≥5%), the mass distribution ratio B of medium biomass is calculated to be [55%, 62%]. According to Equation 3, the larger B and C are, the smaller A is, and the larger the value of Y is. Since the mass proportion of ultra-large biomass is 5.1%, the mass distribution ratios of large, medium, and small biomass are modified as follows: A is set to 5%, B to 61.9%, and C to 28%. Furthermore, according to Equation 3, the value of Y is calculated to be 11.82%.

[0155] Using the same method as in Application Example 1, the vaporization temperature in step 1) and the volume ratio of water vapor to oxygen during the vaporization process were adjusted to conduct parallel experiments. The specific experimental parameters are shown in Table 1.

[0156] Table 1 Comparison of Gasification Reaction Parameters

[0157]

[0158]

[0159] Using the same method as in Application Example 2, the mass distribution ratio among large, medium, and small biomass particles in step 1), the mass ratio of medium biomass particles that become gasification slag and combustible gas during gasification, and the ignition temperature were adjusted to conduct parallel experiments. Specific experimental parameters are shown in Table 2. The carbon saving ratio is defined as the difference between the fossil fuel consumption after adding biomass and the fossil fuel consumption before adding biomass, expressed as a percentage of the fossil fuel consumption before adding biomass.

[0160] Table 2 Comparison of mass distribution parameters and corresponding energy consumption of biomass pellets

[0161]

[0162]

[0163] Comparative Example 1

[0164] 9200 kg of iron ore powder, 250 kg of flux, and 210 kg of coke powder were mixed to obtain 9850 kg of sinter. The sinter was first placed on a sintering trolley, then dried with 400°C hot air. Finally, 1000 kg of crushed biomass was placed on the surface of the sinter to obtain a mixed sinter. The mixed sinter moved at a constant speed along with the sintering trolley and successively underwent ignition, roasting, and cooling processes to obtain the finished sinter.

[0165] Comparative Example 2

[0166] 9200 kg of iron ore powder, 250 kg of flux, 210 kg of coke powder, and 1000 kg of crushed biomass were mixed to obtain 10850 kg of sintering material. This sintering material was first placed on a sintering trolley, then dried with 400°C hot air. Finally, the 1000 kg of crushed biomass was placed on top of the sintering material to obtain a mixed sintering material. The mixed sintering material moved at a constant speed along with the sintering trolley and successively underwent ignition, roasting, and cooling processes to obtain the finished sintered material.

[0167] The sintered finished products obtained from Application Examples 1, 3-18 and Comparative Examples 1 and 2 were tested, and the results of sintered coke powder consumption and CO and CO2 concentration in flue gas are shown in Table 3.

[0168] Table 3 Comparison of Energy Consumption and Carbon Emissions

[0169]

[0170]

[0171] Based on the above experimental results, the present invention provides a low-carbon sintering method, process and system that divides biomass into multiple grades after crushing and screening, and adds different processes according to different particle sizes for utilization. The gasification time is limited according to the properties of the biomass for fine control, which effectively improves the utilization rate of biomass and realizes low-carbon sintering.

Claims

1. A low-carbon sintering method, characterized in that: The method includes the following steps: 1) Biomass pretreatment: The biomass is crushed and screened to obtain large-particle biomass, medium-particle biomass, and small-particle biomass; the medium-particle biomass is gasified to obtain combustible gas and gasification residue; the particle size of the large-particle biomass is [a, b], the particle size of the medium-particle biomass is [c, a), and the particle size of the small-particle biomass is (0, c); where a is 1-3 mm, b is 4-8 mm, and c is 0.3-0.7 mm. 2) Sintering batching and spreading: After batching the sintering raw materials, the sintering material is obtained. The sintering material is first spread on the sintering machine trolley, and then drying is optional. Finally, large particles of biomass are spread on the surface of the sintering material to obtain sintering material containing biomass. 3) Sintering process: The sintering material containing biomass moves forward with the sintering trolley and undergoes ignition, roasting and cooling processes in sequence to obtain the sintered finished material; In the ignition process: small particles of biomass are sent to the ignition burner as ignition fuel for ignition; In the roasting process: combustible gas is injected onto the surface of the sintering mixture to participate in roasting.

2. The sintering method according to claim 1, characterized in that: Large biomass particles with a diameter greater than b are returned to the crushing process for re-crushing.

3. The sintering method according to claim 1, characterized in that: The gasification slag obtained in step 1) is used as one of the raw materials for sintering.

4. The low-carbon sintering method according to any one of claims 1-3, characterized in that: In step 1), the gasification process specifically involves placing medium-sized biomass in a mixed atmosphere containing water vapor and oxygen for thermal gasification to obtain combustible gas and gasification slag; wherein the temperature of the thermal gasification process is not lower than 700°C.

5. The sintering method according to claim 4, characterized in that: The temperature of the thermal vaporization treatment shall not be lower than 800℃.

6. The sintering method according to claim 4, characterized in that: The total mass ratio of water vapor and oxygen to the gas-solid mass ratio of biomass is 0.4 to 0.8:

1.

7. The sintering method according to claim 6, characterized in that: The total mass ratio of water vapor and oxygen to the gas-solid mass ratio of biomass is 0.5 to 0.7:

1.

8. The sintering method according to claim 4, characterized in that: In the mixed atmosphere, the volume ratio of water vapor to oxygen is 1 to 2:

1.

9. The sintering method according to claim 8, characterized in that: In the mixed atmosphere, the volume ratio of water vapor to oxygen is 1.2 to 1.5:

1.

10. The low-carbon sintering method according to claim 4, characterized in that: The gasification process takes place in a suspended bed reactor or a fixed bed reactor.

11. The sintering method according to claim 10, characterized in that: The heat source for the gasification process is the high-temperature flue gas in the sintering flue.

12. The sintering method according to claim 11, characterized in that: The heat exchange method between the high-temperature flue gas and biomass is indirect heat exchange.

13. The sintering method according to claim 10, characterized in that: The water vapor and oxygen in the gasification process are all or partly derived from the hot and humid air discharged from the drying section of the sintering process, and fresh water is used as a supplementary source of water vapor.

14. The low-carbon sintering method according to claim 4, characterized in that: The sintering raw materials mentioned in step 2) are iron ore, quicklime, coke powder, and optionally gasification slag; and / or Step 2) The drying process is as follows: hot air at a temperature of not less than 300°C is introduced into the sintering trolley to contact the sintering material and achieve heat exchange drying.

15. The low-carbon sintering method according to claim 14, characterized in that: The high-temperature hot air of not less than 300°C refers to the hot air generated during the cooling process and / or the flue gas obtained from the gasification process.

16. The low-carbon sintering method according to any one of claims 1-3 and 5-15, characterized in that: The method also includes: 4) after the gasification slag obtained in step 1) is shaped, the shaped slag is obtained, and the shaped slag is used as one of the raw materials for sintering.

17. The low-carbon sintering method according to claim 16, characterized in that: The molding process specifically involves: extruding and degassing the obtained gasified slag and then crushing it.

18. The low-carbon sintering method according to claim 17, characterized in that: The extrusion pressure during the extrusion venting process is 15–30 MPa; and / or The particle size of the shaped slag obtained after crushing is 2-7 mm.

19. The low-carbon sintering method according to claim 18, characterized in that: The extrusion pressure during the extrusion venting process is 20–28 MPa; and / or The particle size of the shaped slag obtained after crushing is 3-5 mm.

20. The low-carbon sintering method according to any one of claims 1-3, 5-15, and 17-19, characterized in that: Control the gasification reaction parameters so that the volatile matter content in the gasification residue is not higher than 8% and the carbon content in the gasification residue is not lower than 20%.

21. The low-carbon sintering method according to claim 20, characterized in that: Control the gasification reaction parameters so that the volatile matter content in the gasification residue is not higher than 5% and the carbon content in the gasification residue is not lower than 25%.

22. The low-carbon sintering method according to claim 20, characterized in that: The gasification process is carried out in a fixed-bed reactor, and the parameters for controlling the gasification reaction are as follows: At a given gasification temperature, the theoretical gasification time required to equalize the carbon content in the gasification residue to a set value is: In the formula, C0 is the initial carbon content in the medium-sized particulate biomass, %; C1 is the set value of carbon content in the gasification residue, %; L is the particle size of the medium-sized particulate biomass, mm; and M is the moisture content in the biomass, %; T1 is the vaporization temperature, in °C; t ′ 1 represents the time required for the carbon reaction in biomass to reach the desired temperature; α and η are both adjustment coefficients, where α ranges from 0.20 to 0.30 and η ranges from 0.10 to 0.

20. At the same gasification temperature, the theoretical gasification time required to calculate the volatile matter content in the gasification residue to equal the set value is: In the formula, V0 is the initial volatile matter content in medium-sized particles of biomass, %; V1 is the set value of volatile matter content in gasification residue, %; L is the particle size of medium-sized particles of biomass, mm; and M is the moisture content in biomass, %; T1 is the vaporization temperature, in °C; t ′ 2 represents the time required for the volatile matter in biomass to react; γ and μ are both adjustment coefficients, where γ ranges from 0.08 to 0.15; and μ ranges from 0.10 to 0.

20. The actual vaporization time is then controlled as follows: When t2≤t1, the temperature satisfies the vaporization condition. According to (Equation 1) and (Equation 2), the actual vaporization time t at this temperature is controlled as: t2≤t≤t1; When t2 > t1, the actual vaporization time t at this temperature is controlled as: t ≥ t2.

23. The low-carbon sintering method according to claim 22, characterized in that: The process also includes: detecting the volatile matter content and carbon content in the gasification residue, and returning the gasification residue with excessively high volatile matter content and carbon content to the gasification process of medium-sized particulate biomass for regasification.

24. The low-carbon sintering method according to claim 20, characterized in that: The process also includes controlling the mass distribution ratio of large, medium, and small biomass particles during the biomass crushing and screening process, thereby reducing carbon emissions while meeting the normal operation requirements of the sintering process; specifically including: (ci) To reduce carbon emissions while meeting the normal operation requirements of the sintering process, a dynamic mathematical model of the mass distribution ratio of large-particle biomass, medium-particle biomass, and small-particle biomass is established: In Equation 3, A is the proportion of small-particle biomass to the total biomass mass (%); B is the proportion of medium-particle biomass to the total biomass mass (%); C is the proportion of large-particle biomass to the total biomass mass (%); where A+B+C<1; δ is a dimensionless correction coefficient, ranging from 1 to 3; Q is the proportion of the mass of gasification slag to the mass of medium-particle biomass after gasification (%); P is the proportion of the mass of gasified biomass to the mass of medium-particle biomass during gasification (%); T2 is the ignition temperature (°C); F is the iron ore grade (%); and Y is the carbon-saving ratio after adopting the biomass graded and graded treatment coupled with sintering process. cii) Based on the relationship curve between the mass change of large-particle biomass laid on the sintering surface and the ignition temperature, establish the relationship between the amount of large-particle biomass laid and the ignition temperature: T2 = 1050 - β * (0.5 + 5 * D) 0.1 *In(1 + 5 * D)……(Equation 4) In Equation 4, β is a coefficient related to the type of ore raw material, with a value range of 50 to 600; D is the percentage of the mass of large-particle biomass laid on the sintering surface to the total mass of the sintering material, with a value range of 1% to 15%; the minimum ignition temperature under the target working condition is calculated based on Equation 4; combining Equations 3 and 4, the mass of small-particle biomass required for the optimal energy consumption condition of sintering ignition at this ignition temperature is first calculated, then the mass distribution ratio of large-particle biomass and the mass distribution ratio of small-particle biomass are obtained, and finally, the mass distribution ratio of medium-particle biomass is calculated under the premise of satisfying the mass distribution ratio of large-particle biomass and the mass distribution ratio of small-particle biomass.

25. The low-carbon sintering method according to claim 24, characterized in that: The value of β ranges from 200 to 600; the value of D ranges from 2% to 10%.

26. The low-carbon sintering method according to claim 25, characterized in that: The value of β ranges from 300 to 600; the value of D ranges from 3% to 8%.

27. A sintering system for the low-carbon sintering method as described in any one of claims 1-26, characterized in that: The sintering system includes a sintering machine (1), a batching device (2), a feeding device (3), an ignition burner (4), a crushing device (5), a screening device (6), a gasification device (7), an annular cooler (8), and a jetting device (9). The sintering machine (1) is divided into a drying section (101), a preheating section (102), and a calcining section (103) according to its operating direction. The ignition burner (4) is located in an ignition furnace situated above and downstream of the preheating section (102). The material outlet of the batching device (2) is connected to the material inlet of the feeding device (3). The material outlet of the feeding device (3) is located at the feed end of the sintering machine (1). The jetting device (9) is located above the calcining section (103). The discharge end of the sintering machine (1) is connected to the feed end of the annular cooler (8). The material outlet of the crushing device (5) is connected to the material inlet of the screening device (6); the large particle material outlet of the screening device (6) is connected to the material inlet of the feeding device (3); the medium particle material outlet of the screening device (6) is connected to the material inlet of the gasification device (7); the small particle material outlet of the screening device (6) is connected to the material inlet of the ignition burner (4); the gas outlet of the gasification device (7) is connected to the fuel inlet of the injection device (9).

28. The system according to claim 27, characterized in that: The screening device (6) is also provided with an oversize material outlet, which is connected to the material inlet of the crushing device (5).

29. The system according to claim 27, characterized in that: The system also includes a molding device (10), the solid outlet of the gasification device (7) is connected to the material inlet of the molding device (10), and the material outlet of the molding device (10) is connected to the material inlet of the batching device (2).

30. The system according to claim 27, characterized in that: The gas inlet of the drying section (101) is connected to the high-temperature gas outlet of the annular cooler (8) or the low-temperature medium outlet of the gasification device (7) via a pipeline.

31. The system according to claim 27, characterized in that: The ignition burner (4) includes a combustion air duct (401) and a biomass duct (402); the inlet end of the combustion air duct (401) is connected to an oxygen-containing gas source, and the outlet end of the combustion air duct (401) is connected to the furnace of the ignition furnace; the feed end of the biomass duct (402) is simultaneously connected to the fine particle material outlet of the screening device (6) and the carrier gas source, and the discharge end of the biomass duct (402) is connected to the furnace of the ignition furnace.

32. The system according to claim 31, characterized in that: The discharge section of the biomass pipeline (402) includes a gas discharge channel (4021) and a solid discharge channel (4022) sleeved outside the gas discharge channel (4021).

33. The system according to claim 32, characterized in that: The combustion air duct (401) includes a central air duct (4011) and a secondary air duct (4012) that are not interconnected; the air inlet ends of the central air duct (4011) and the secondary air duct (4012) are both connected to an oxygen-containing gas source; the central air duct (4011) is sleeved in the cavity of the gas discharge channel (4021) along the axis of the gas discharge channel (4021), and the secondary air duct (4012) is sleeved on the outside of the solid discharge channel (4022); the air outlet ends of the central air duct (4011) and the secondary air duct (4012) are both connected to the furnace of the ignition furnace.

34. The system according to claim 33, characterized in that: The ignition burner (4) also includes a swirl mechanism (403), which is located at the outlet end of the secondary air duct (4012) and / or the gas discharge channel (4021).

35. The system according to claim 34, characterized in that: The swirl mechanism (403) is a swirl blade.

36. The system according to claim 33, characterized in that: The carrier gas source is the gas outlet of the drying section (101).

37. The system according to claim 27, characterized in that: The gasification device (7) includes a kiln body (701) and a heat exchange device (702) extending into the kiln body (701) but not connected to it; wherein, the kiln body (701) includes a kiln head (7011), a kiln body (7012), and a kiln tail (7013) connected in series; the kiln head (7011) and the kiln tail (7013) are fixedly arranged, and the kiln body (7012) can rotate along its axis; a gas-solid inlet (7014) is provided at the upper part of the kiln head (7011), and the gas-solid inlet... The inlet (7014) is connected to the medium particle material outlet of the screening device (6) and the high humidity oxygen-containing gas source through a pipeline; a gas outlet (7015) is provided at the upper part of the kiln tail (7013), and the gas outlet (7015) is connected to the fuel inlet of the injection device (9) through a pipeline; a solid outlet (7016) is provided at the lower part of the kiln tail (7013), and the solid outlet (7016) is connected to the material inlet of the forming device (10) or the material inlet of the batching device (2) through a conveyor belt.

38. The system according to claim 37, characterized in that: The high-humidity oxygen-containing gas source is the gas outlet of the drying section (101).

39. The system according to claim 37, characterized in that: The heat exchange device (702) includes an outer cylinder (7023) and an inner cylinder (7024). The outer cylinder (7023) passes through the kiln head (7011), kiln body (7012), and kiln tail (7013) sequentially along the axial direction. An inner cylinder (7024) is inserted into each end of the outer cylinder (7023), and the inserted end of the inner cylinder (7024) extends along the axis of the outer cylinder (7023) to the middle of the cavity of the inner cylinder (7024). 701) High-temperature medium inlets (7021) are provided at both ends of the outer cylinder (7023) and medium return ports (7025) are provided at the ends of the inner cylinder (7024) located inside the outer cylinder (7023). The inner cylinder (7024) is connected to the outer cylinder (7023) through the medium return ports (7025). Low-temperature medium outlets (7022) are provided on the inner cylinder (7024) located outside the outer cylinder (7023).

40. The system according to claim 39, characterized in that: The high-temperature medium inlet (7021) is connected to the sintering flue.

41. The system according to claim 39, characterized in that: A blind plate (7026) is also provided in the middle of the outer cylinder (7023) cavity. The blind plate (7026) divides the outer cylinder (7023) cavity into two non-communicating sections. The two inner cylinders (7024) are located in the two non-communicating sections respectively.

42. The system according to claim 37, characterized in that: The kiln body (701) is equipped with 1 to 8 evenly distributed heat exchange devices (702).

43. The system according to claim 42, characterized in that: The gasification device (7) also includes a water supply pipe (7027), the inlet end of which is connected to a new water source, and the outlet end of which extends through the kiln head (7011) and into the kiln body (7012). Multiple atomizing nozzles (7028) are provided on the outlet section of the water supply pipe (7027).

44. The system according to claim 37, characterized in that: The kiln body (701) is inclined with the kiln head (7011) higher and the kiln tail (7013) lower.

45. The system according to claim 44, characterized in that: The kiln body (701) has an inclination angle of 2 to 8°.

46. ​​The system according to claim 45, characterized in that: The kiln body (701) has an inclination angle of 3 to 6°.

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