Method for realizing ultra-low temperature ignition by using biomass fuel in sintering process

Abstract

The application discloses a method for realizing ultra-low temperature ignition by using biomass fuel in a sintering process, which comprises the following steps: uniformly laying biomass charcoal on the surface of a sintering material layer, and igniting under the conditions of micro-negative pressure formed by downward air draft perpendicular to the sintering material layer and a temperature of 450-700 DEG C. In the method, the biomass charcoal is used as a low-temperature ignition agent of a sintering ignition system and a trigger agent for igniting traditional fuels such as coke powder or semi-coke in the sintering raw material, and a gas fuel such as biomass gas or hot flue gas is used as an ignition heat source, so that the ignition task of the iron ore sintering can be completed at ultra-low temperature. Since the biomass is used as a renewable fuel with zero carbon emission in the sintering ignition process, the number of gas pollutants generated by the combustion of fossil fuels is significantly reduced.

Description

A method for achieving ultra-low temperature ignition using biomass fuel during sintering Technical Field

[0001] This invention relates to an ignition method in the iron ore sintering process, and particularly to a method for achieving ultra-low temperature ignition using biomass fuel in the sintering process, belonging to the field of iron ore sintering technology in iron and steel metallurgy. Background Technology

[0002] The steel industry is a typical material- and energy-intensive process industry with high pollutant emissions. With societal development, energy conservation and emission reduction have become the biggest challenges facing steel companies. Currently, the blast furnace burden structure in my country is still dominated by basic sintered ore, accounting for approximately 70% of the burden. This results in a significant energy consumption during the iron ore sintering process. Because gaseous fuels have low ignition points, high exothermic intensity, and flexible combustion control, high-calorific-value fuels such as natural gas and coke oven gas are generally used internationally for ignition in iron ore sintering. However, these high-calorific-value fuels are all fossil fuels and are relatively expensive. Therefore, adopting efficient and low-polluting ignition methods for sintering processes has become an important research topic for many metallurgists.

[0003] Biomass energy is the fourth largest energy source after coal, oil, and natural gas. The CO2 released during the combustion of this renewable energy source originates from the CO2 absorbed during its growth, thus biomass fuels have net-zero CO2 emissions. Furthermore, due to their lower ignition temperature and higher combustion intensity, biomass fuels exhibit combustion characteristics closer to gaseous / liquid fuels, making them particularly suitable for low-temperature ignition solid fuels in iron ore sintering processes. Given the current situation where the burning of agricultural and forestry biomass waste is prohibited, and excessive straw return to the fields leads to straw disposal problems, severe pest and disease infestations, and crop lodging, using biomass energy as fuel in iron ore sintering can effectively alleviate environmental pollution and energy shortages caused by burning gas in the iron ore sintering process, while also effectively realizing the resource utilization of agricultural and forestry waste.

[0004] Regarding the use of biomass fuel in iron ore sintering, Chinese patent CN102352273B discloses a type of biochar for iron ore sintering, its preparation, and its application. The biochar is prepared using a two-stage carbonization process, combining low-temperature and high-temperature carbonization, and enhanced by the addition of pitch, to achieve a density of 1.1–1.4 g / cm³. 3Biomass char with a fixed carbon content of 75-90%, volatile matter of 5-15%, and calorific value of 25-32 MJ / kg is crushed into a suitable particle size distribution. Applying biomass char to iron ore sintering can replace 0-60% of fossil fuels, achieving sintering performance comparable to using only coke powder, and significantly reducing COx, SOx, and NOx emissions during the sintering process. Chinese patent CN114935264A discloses a low-carbon sintering method based on coupled injection of biomass char and hydrogen-rich fuel gas. This method divides the sintering material surface from the initial ignition to the sintering endpoint into four zones. Heat is supplemented by injecting biomass char powder into the front sintering material surface, while hydrogen-rich fuel gas is injected into the middle and rear sintering material surfaces to maintain high temperatures. This significantly reduces the amount of solid fossil fuels used and decreases pollutant emissions. Regarding reducing ignition energy consumption in the sintering process, Chinese patent CN109556407B discloses a method for reducing ignition energy consumption in iron ore sintering. This method reduces ignition energy waste and improves ignition effect by optimizing the reasonable distribution of the temperature field in the ignition furnace.

[0005] While the aforementioned methods have positive effects on the application of biomass fuel in iron ore sintering and reducing ignition energy consumption in the sintering process, there is currently almost no research or report on using biomass fuel as ignition fuel in the iron ore sintering process to achieve low-temperature ignition. The biomass charcoal used is mostly expensive high-quality wood charcoal, and straw charcoal cannot be used. Furthermore, excessive mixing of biomass charcoal into the sintering raw materials can lead to excessively fast movement speed of the sintering front, deterioration of sinter quality, and impact on subsequent production. Therefore, in order to develop low-temperature ignition biomass fuel for iron ore sintering and further alleviate the dependence of the sintering process on fossil energy, it is necessary to control the physicochemical properties and combustion characteristics of the biomass ignition fuel used to achieve smooth ignition in the sintering process. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a method for achieving ultra-low temperature ignition using biomass fuel during the sintering process. This method promotes the use of biomass fuel in iron ore sintering while simultaneously achieving low-temperature ignition in the iron ore sintering process, thereby alleviating the problems of high dependence on fossil fuels, high ignition energy consumption, and high pollutant emissions in the sintering process. Biomass fuel possesses characteristics such as a low initial combustion temperature, fast combustion speed, and high combustion intensity, as well as concentrated exothermic processes and high heat flow during combustion. Applying it as ignition fuel in the iron ore sintering process can solve the problems of high temperature, high energy consumption, and high pollutant emissions in traditional sintering ignition processes. It also reduces the consumption of fossil fuels in the iron ore sintering process and significantly reduces flue gas pollutants and CO2 emissions from fossil fuel combustion during iron ore agglomeration. Furthermore, the sintering ignition fuel can be obtained from the carbonization of agricultural and forestry waste biomass, enabling the resource utilization of agricultural and forestry biomass waste. The process is simple, easy to implement, and low-cost, facilitating large-scale promotion and application.

[0007] To achieve the above-mentioned technical objectives, the present invention provides a method for achieving ultra-low temperature ignition using biomass fuel during sintering. The method involves uniformly spreading biomass char on the surface of the sintering material layer, and then completing ultra-low temperature ignition under the micro-negative pressure conditions formed by downward air extraction vertically through the sintering material layer and at a temperature of 450–700°C.

[0008] The key to this invention lies in utilizing the characteristics of biomass char, which has a low initial combustion temperature and a high combustion intensity, allowing it to undergo combustion at a relatively low ignition temperature. With the suction effect of the sintering blower, heat and some biomass ash can be transferred to the lower sintering material layer. Under the dual effects of high temperature and biomass ash catalysis, the coke powder or semi-coke in the sintering raw material quickly ignites and begins the iron ore sintering process. Since the biomass fuel only acts as a low-temperature igniter for the sintering ignition temperature and a trigger for the combustion of coke powder or semi-coke during the entire sintering process, it does not participate in the subsequent sintering process and has minimal impact on the quality of the sintered ore. This reduces the sintering ignition temperature and pollutant emissions without affecting normal production.

[0009] As a preferred method, biochar is evenly spread on the surface of the sintering material, and mechanical means are used to mix the biochar with the surface sintering material. The surface of the sintering material layer is then smoothed. The mixing only needs to ensure that there is no obvious boundary layer between the biochar and the surface sintering material; complete homogeneity is not required. Mechanical means achieve initial mixing between the biochar and the surface sintering material, creating a "coke-mineral, mineral-coke" transition zone in the contact area between the biochar and the surface sintering mixture, without a clear boundary layer. This increases the contact area between the biochar and the sintering material surface, ensuring that the combustion zone generated in the biochar can smoothly transition into the sintering mixture, successfully completing the entire ignition process.

[0010] As a preferred embodiment, the biochar should contain at least 70% particles with a size less than 3 mm and less than 2 mm, with an ash content of less than 15%, a volatile matter content of 10-50%, a calorific value of 25-32 MJ / kg, and a comprehensive combustion characteristic index between (0.50-1.50)×10⁻⁶. -12 s -2 ·℃ -3 Between these values, the combustion intensity is not less than 4.8 × 10⁻⁶. -4 s -1 The initial combustion temperature should be below 400℃. For biochar, if the particle size is too large, the fuel is difficult to ignite, the combustion heat release rate is low, and it is difficult to form a high-temperature ignition zone. If the particle size is too small, it will worsen the permeability of the sintering bed. A lower volatile matter content in biochar can reduce emissions of gaseous pollutants such as NOx. Controlling the calorific value of biomass fuel to above 25 MJ / kg can reduce the thickness of the biomass fuel on the bed surface and minimize the negative impact on sintering permeability.

[0011] As a preferred embodiment, the density of the biochar is 0.3–0.7 g / cm³. 3 If the density is too high, the biochar pellets will have a compact structure, resulting in poor ignition. If the density is too low, the fabric will be too thick, affecting breathability.

[0012] As a preferred embodiment, the thickness of the biochar layer on the surface of the sintering material can be determined by the following formula:

[0013]

[0014] in,

[0015] h and H represent the thickness of the biochar and sintering material layer, respectively, in cm;

[0016] ρ s and ρ c These represent the densities of the sinter and biochar, respectively, in g / cm³. 3 ;

[0017] E i This represents the ignition energy consumption of the sintering machine, in kJ / t.

[0018] Q c The lower heating value of biomass solid fuel, kJ / kg;

[0019] C1 and C2 are the specific heat capacities of air before and after ignition, in kJ / (m³). 3 ·℃);

[0020] T1 and T2 are the ultra-low temperature ignition temperature and the actual hot air temperature in contact with the sintering material surface, respectively, in °C.

[0021] The formula assumes that the temperature of the hot air contacted by the sintering material surface remains constant before and after ultra-low temperature ignition. If the biomass char layer is too thin, it will be difficult to meet the ignition heat requirements; if the biomass char layer is too thick, it will affect the sintering permeability. Therefore, controlling the biomass char layer thickness within an appropriate range is crucial to meeting the ignition requirements without affecting sintering.

[0022] As a preferred embodiment, the ignition uses gaseous fuel or high-temperature flue gas as the ignition heat source. As a more preferred embodiment, the gaseous fuel includes at least one of biomass fuel gas, coke oven gas, blast furnace gas, converter gas, natural gas, or hydrogen. As a more preferred embodiment, the high-temperature flue gas includes high-temperature flue gas from the annular cooling stage 1, or hot flue gas generated during the heating process of a hot blast stove or coke oven.

[0023] As a preferred embodiment, the proportion of solid fossil fuels in the sintering material is reduced compared to the conventional proportion, by a reduction of 2 to 4 times the mass of biochar laid on the sintering material surface. The heat generated by the biochar can replace part of the solid fossil fuels, thereby effectively reducing carbon dioxide or pollutant emissions.

[0024] The biochar and biogas produced in this invention are both derived from biomass raw materials. Biochar and biogas can be obtained through the pyrolysis of biomass raw materials, or through a hydrothermal process. Biomass raw materials include agricultural waste such as corn, rice, wheat, and soybeans, and forestry waste such as leaves, branches, and fruit pits; they can be one type or any combination of two or more. The calorific value of the biogas should not be lower than 18 MJ / m³. 3 The ash content of biochar should be less than 15%, the volatile matter 10-50%, the calorific value 25-32 MJ / kg, and the comprehensive combustion characteristic index between (0.50-1.50)×10⁻⁶. -12 s -2 ·℃ -3 Between these values, the combustion intensity is not less than 4.8 × 10⁻⁶. -4 s -1 .

[0025] As a preferred option, considering the significant differences between biochar and traditional gas-ignition fuels in terms of combustion speed and heat release rate, in order to accelerate the combustion speed and heat release rate of biochar and maintain a reasonable sintering ignition thermal regime, the combustion air in the ignition process can be selectively enriched with oxygen according to the actual ignition conditions.

[0026] As a preferred embodiment, the micro-negative pressure ranges from 0.1 to 5 kPa. Under appropriate micro-negative pressure conditions, the heat and some ash from the biomass char are facilitated to be transferred to the lower sintering bed, rapidly igniting the coke powder or semi-coke in the sintering raw materials and initiating the iron ore sintering process.

[0027] The present invention provides a method for achieving ultra-low temperature ignition using biomass fuel during sintering, comprising the following steps:

[0028] S1: Spread biomass char evenly on the surface of the sintering material layer in the sintering machine; wherein, the particle size of the biomass char is less than 3mm, and the proportion of particles smaller than 2mm should not be less than 70%. The thickness of the biomass char covering the surface of the sintering material layer can be determined by the following formula:

[0029]

[0030] in,

[0031] h and H represent the thickness of the biochar and sintering material layer, respectively, in cm;

[0032] ρ s and ρ c These represent the densities of the sinter and biochar, respectively, in g / cm³. 3 ;

[0033] E i This represents the ignition energy consumption of the sintering machine, in kJ / t.

[0034] Q c The lower heating value of biochar is kJ / kg;

[0035] C1 and C2 are the specific heat capacities of air before and after ignition, in kJ / (m³). 3 ·℃);

[0036] T1 and T2 are the ultra-low temperature ignition temperature and the actual hot air temperature in contact with the sintering material surface, respectively, in °C.

[0037] The premise of the formula is that the temperature of the hot air that the sintering material surface comes into contact with remains unchanged before and after the ultra-low temperature ignition.

[0038] S2: The biochar and surface sintering material are initially mixed using a mechanical mixing device (such as a roller sled), and the material is then fed into the sintering machine ignition furnace after the surface material is leveled by a leveling plate.

[0039] S3: Under slightly negative pressure conditions, high-temperature hot exhaust gas or gaseous fuels, including biomass gas, are used as ignition fuels. The ignition temperature range is 450-700℃. Considering the significant differences between biomass solid fuels and traditional ignition fuels in terms of combustion speed and heat release rate, in order to accelerate the combustion speed and heat release rate of biomass solid fuels and maintain a reasonable sintering ignition regime, the combustion air in the ignition process can be selectively enriched with oxygen according to the actual working conditions. For example, the oxygen content of the ignition air can be controlled between 21% and 40%.

[0040] Compared with the prior art, the beneficial effects of the technical solution of this invention are as follows:

[0041] 1) This invention provides a method for achieving ultra-low temperature ignition using biomass fuel during sintering. This method scientifically and rationally spreads solid biomass fuel on the surface of the sintering material layer, rather than mixing it into the sintering raw materials. It serves as a low-temperature igniter for the sintering ignition system and a trigger for igniting fossil fuels such as coke powder or semi-coke. It does not participate in the subsequent sintering process of the sintering material layer. Therefore, compared with existing research and methods on using biomass as fuel in the field of iron ore sintering, this method will not lead to the problem of excessively fast movement speed of the sintering front and significant deterioration of the sinter quality during the sintering process.

[0042] 2) This invention provides a method for achieving ultra-low temperature ignition using biomass fuel during the sintering process. While agricultural biomass waste has abundant reserves, its high content of harmful substances limits its use in the steel industry. In sintering ignition processes involving solid fuels, the solid fuels are required to have a low initial combustion temperature to ensure high ignition efficiency, a fast combustion reaction rate to quickly heat and ignite the coke or semi-coke powder in the sintering layer, and the ash produced by the combustion of solid fuels should not adversely affect the ignition and combustion of the lower coke or semi-coke. Biomass fuels meet all these conditions. Furthermore, the ash produced by biomass fuel combustion has a catalytic effect on the ignition and combustion of traditional fuels such as lower coke or semi-coke. Since the solid fuels do not participate in the subsequent sintering process of the sintering layer, they have no significant impact on the iron ore sintering process after ignition. Therefore, there is no need for pre-treatment of the biomass for decontamination before use, and it can accept all available biomass resources, including agricultural straw, demonstrating strong adaptability to different types of biomass fuels.

[0043] 3) This invention provides a method for achieving ultra-low temperature ignition using biomass fuel during the sintering process. Biomass solid fuel serves as the low-temperature igniter in the sintering ignition system and the trigger for igniting traditional fuels such as coke powder and semi-coke in the sintering raw materials. The ignition task of iron ore sintering can be completed at a relatively low ignition temperature. The ignition heat source in the sintering ignition process can be the high-temperature flue gas of metallurgy, including the flue gas from the first stage of the sintering ring cooler, or the heat released by the combustion of gaseous fuels, including biomass gas generated in the biomass char preparation process. This significantly reduces the ignition energy consumption in the iron ore sintering process while effectively alleviating the dependence of the sintering ignition process on high-calorific-value fossil-based fuels. It also reduces the amount of pollutants and carbon emissions caused by the combustion of fossil fuels in the sintering ignition process. This is a low-energy-consumption and green ignition method. Attached Figure Description

[0044] Figure 1 shows the schematic diagrams of cryogenic ignition (left) and conventional ignition (right) technologies for biomass fuels.

[0045] Figure 2 shows the combustion weight loss curve (left) and weight loss rate curve (right) of biochar in Example 1.

[0046] Figure 3 shows the combustion weight loss curve (left) and weight loss rate curve (right) of biochar in Example 3. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0049] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0050] The sintering raw materials and proportions in the following examples and comparative examples were carried out under the following conditions:

[0051] Main chemical composition of iron ore and iron-bearing impurities / %

[0052]

[0053]

[0054] Main chemical components of flux, fuel and return ore / %

[0055]

[0056] Industrial analysis of fuels (dry basis) / %

[0057]

[0058] Raw material ratio

[0059]

[0060]

[0061] Moisture content of iron ore and iron-containing impurities

[0062]

[0063] Flux, fuel and moisture in returned ore

[0064]

[0065]

[0066] Example 1:

[0067] The Xianggang sintering machine has a capacity of 360m. 2 The utilization coefficient is 1.35t / (m 2 The sintering rate is 97%. The ignition temperature is 1150℃, using coke oven gas with a calorific value of 17756 kJ / m³. The plant's sintering ignition gas consumption is 0.08 GJ / t, and the coke oven gas air-fuel ratio is 1:5. Currently, biomass fuel is being used for cryogenic ignition, with an ignition hot air temperature of 600℃. Without changing the original air-fuel ratio, the hot air volume is 22.52 m³ / h. 3 The composition of the biochar is shown in Table 1, with a lower heating value of 26.85 MJ / kg. The combustion weight loss curve of the biochar heated from room temperature to 800℃ at a heating rate of 10℃ / min is shown in Figure 2. The combustion characteristic parameters are shown in Table 2. The density of the biochar is 4.2 g / cm³. 3 The density of the sintered material is 1.6 g / cm³. 3 The heat capacity of hot air at 600℃ is taken as 1.13 kJ / (m³). 3 The heat capacity of hot air at 1150℃ is taken as 1.19 kJ / (m³).3 According to Formula 1, after uniformly spreading a 0.58cm thick layer of this type of biochar on the surface of the sintering material, a roller plow is used to initially mix the biochar with the surface sintering material, so that there is no obvious stratification interface between the biochar and the surface sintering material. Under a slight negative pressure of 5kPa, the normal sintering temperature can be reached to start sintering. That is, 1.51kg of this type of biochar is needed per ton of sintered ore to complete the task of reheating the ignition hot air. If gas is used to achieve secondary heating of the ignition hot air, this process requires 2.28m³ of biochar. 3 The amount of coal gas produced is approximately 25,796 m³ / t. Therefore, it can be concluded that the sintering machine, using this type of biochar for sintering with low-temperature ignition, can replace approximately 25,796 m³ / t of coal gas per day. 3 The amount of coal gas used is reduced, while the amount of biochar consumed is only 17.08 t / d. The amount of coke added in the sintering mixture can be reduced by up to 68.16 t / d, which greatly reduces the environmental pollution caused by the combustion of fossil fuels.

[0068] Table 1. Industrial and elemental analysis results of biochar.

[0069]

[0070]

[0071] Table 2 Combustion characteristic parameters of biochar

[0072]

[0073] Example 2

[0074] The Xianggang sintering machine has a capacity of 360m. 2 The utilization coefficient is 1.35t / (m 2 The plant operates at a rate of 97%. The sintering ignition temperature is 1150℃, using coke oven gas with a calorific value of 17756 kJ / m³. The plant's sintering ignition gas consumption is 0.08 GJ / t, and the coke oven gas air-fuel ratio is 1:5. Currently, biomass fuel is being used for cryogenic ignition. The ignition heat source is the hot air from the first stage of the sintering ring cooler, with an ignition hot air temperature of 450℃. Without changing the original air-fuel ratio, the hot air volume is 22.52 m³ / h. 3 The composition of the biochar is shown in Table 1, with a lower heating value of 26.85 MJ / kg. The combustion weight loss curve of the biochar heated from room temperature to 800℃ at a heating rate of 10℃ / min is shown in Figure 2. The combustion characteristic parameters are shown in Table 2. The density of the biochar is 0.42 g / cm³. 3 The density of the sintered material is 1.6 g / cm³. 3The heat capacity of hot air at 450℃ is taken as 1.10 kJ / (m³). 3 The heat capacity of hot air at 1150℃ is taken as 1.19 kJ / (m³). 3 According to Formula 1, after uniformly spreading a 0.73cm thick layer of this type of biochar on the surface of the sintering material, a roller plow is used to initially mix the biochar with the surface sintering material, so that there is no obvious stratification interface between the biochar and the surface sintering material. Under a slight negative pressure of 5kPa, the normal sintering temperature can be reached to start sintering. That is, 1.91kg of this type of biochar is needed per ton of sintered ore to complete the task of reheating the ignition hot air. If gas is used to achieve secondary heating of the ignition hot air, this process will consume 2.86m³ of biochar. 3 The amount of coal gas produced is approximately 132,358 m³ / t. Therefore, it can be concluded that the sintering machine, using this type of biochar for sintering with low-temperature ignition, can replace approximately 132,358 m³ / t of coal gas per day. 3 The amount of coal gas used is reduced, while the consumption of biochar is only 21.61 t / d. The amount of coke added to the sintering mixture can be reduced by up to 86.44 t / d, which greatly reduces the environmental pollution caused by the combustion of fossil fuels.

[0075] If the thickness of the biomass ignition fuel layer differs significantly from the result calculated by formula (1) under otherwise unchanged conditions, it will change the hot air temperature that the surface sintered ore comes into contact with, affecting the normal progress of subsequent sintering. For example, if the thickness of the biomass fuel layer is 0.5 cm, the hot air temperature that the surface of the sintered material layer comes into contact with is about 928°C, which is significantly lower than the normal sintering ignition temperature of 1150°C, resulting in a poor ignition effect. If the thickness of the biomass material layer is 1 cm, the hot air temperature that the surface of the sintered material layer comes into contact with is far higher than 1150°C. Such a high hot air temperature will cause the surface sintered ore to be overburned, affecting normal production.

[0076] Example 3

[0077] The Xianggang sintering machine has a capacity of 360m. 2 The utilization coefficient is 1.35t / (m 2 The plant operates at a rate of 97%. The sintering ignition temperature is 1150℃, using coke oven gas with a calorific value of 17.76 MJ / m³. The plant's sintering ignition gas consumption is 0.08 GJ / t, and the coke oven gas air-fuel ratio is 1:5.

[0078] Currently, ultra-low temperature ignition is performed using biomass fuel, with biomass pyrolysis gas as the ignition heat source. The main components of the pyrolysis gas are shown in Table 3, and its pyrolysis calorific value is 12.27 MJ / m³. 3 The ignition hot air temperature is 700℃, and the hot air volume is 22.52m³ without changing the original air-fuel ratio. 3 Based on the original energy utilization efficiency of the sintering machine, it is estimated that approximately 3.69m³ / t is required. 3The biomass pyrolysis gas can produce 22.52m³ of gas. 3 The air was heated from 25°C to 700°C. During this stage, the use of biomass pyrolysis gas was equivalent to 2.55m³ of gas. 3 / t of coal gas.

[0079] The composition of biochar is shown in Table 4, its lower heating value is 25.79 MJ / kg, the combustion weight loss curve of biochar is shown in Figure 3, the combustion characteristic parameters are shown in Table 5, and the density of biochar is 0.38 g / cm³. 3 The density of the sintered material is 1.6 g / cm³. 3 The heat capacity of hot air at 700℃ is taken as 1.15 kJ / (m³). 3 The heat capacity of hot air at 1150℃ is taken as 1.19 kJ / (m³). 3 According to Formula 1, after uniformly spreading a 0.53cm thick layer of this type of biochar on the surface of the sintering material, a roller plow is used to initially mix the biochar with the surface sintering material, so that there is no obvious stratification interface between the biochar and the surface sintering material. Under a slight negative pressure of 5kPa, the normal sintering temperature can be reached to start sintering. That is, 1.24kg of this type of biochar is needed per ton of sintered ore to complete the task of reheating the ignition hot air. If gas is used to achieve secondary heating of the ignition hot air, this process will consume 1.86m³ of biochar. 3 The amount of coal gas produced is approximately 21,044 m³ / t, indicating that the sintering machine using this type of biochar for low-temperature ignition can replace approximately 21,044 m³ / t of coal gas per day. 3 The amount of coal gas used is reduced, while the amount of biochar consumed is only 14.03 t / d. The amount of coke added in the sintering mixture can be reduced by up to 56.12 t / d, which greatly reduces the environmental pollution caused by the combustion of fossil fuels.

[0080] Table 3 Main components of biomass gas

[0081]

[0082] Table 4. Industrial and elemental analysis results of biochar.

[0083]

[0084] Table 5 Combustion characteristic parameters of biochar

[0085]

Claims

1. A method for achieving ultra-low temperature ignition using biomass fuel during sintering, characterized in that: Biomass char is evenly spread on the surface of the sintering material layer, and then ultra-low temperature ignition is completed under the micro-negative pressure conditions created by downward air extraction perpendicular to the sintering material layer and at a temperature of 450~700℃. The biomass char should contain at least 70% particles smaller than 3mm and at least 2mm in size, with an ash content of less than 15%, a volatile matter content of 10~50%, a calorific value of 25~32 MJ / kg, and a comprehensive combustion characteristic index between (0.50~1.50)×10⁻¹⁰. -12 s -2 ·℃ -3 Between these values, the combustion intensity is not less than 4.8 × 10⁻⁶. -4 s -1 The initial combustion temperature should be below 400℃; the ignition uses gaseous fuel or high-temperature flue gas as the ignition heat source.

2. The method for achieving ultra-low temperature ignition using biomass fuel during sintering according to claim 1, characterized in that: Biochar is evenly spread on the surface of the sintering material, and mechanical means are used to mix the biochar with the surface sintering material. Then the surface of the sintering material layer is smoothed.

3. A method for achieving cryogenic ignition using biomass fuel during sintering according to claim 1 or 2, characterized in that: The density of the biochar is 0.3~0.7 g / cm³. 3 .

4. A method for achieving cryogenic ignition using biomass fuel during sintering according to claim 1 or 2, characterized in that: The thickness of the biochar layer on the surface of the sintering material can be determined by the following formula:

5. The method for achieving ultra-low temperature ignition using biomass fuel during sintering according to claim 1, characterized in that: The gaseous fuel includes at least one of biomass gas, coke oven gas, blast furnace gas, converter gas, natural gas, or hydrogen.

6. The method for achieving ultra-low temperature ignition using biomass fuel during sintering according to claim 1, characterized in that: The proportion of solid fossil fuels in the sintering material is reduced relative to the conventional proportion, and the reduction is 2 to 4 times the mass of biochar laid on the sintering material surface.

7. The method for achieving ultra-low temperature ignition using biomass fuel during sintering according to claim 1, characterized in that: The range of the micro-negative pressure is 0.1~5kPa.

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