Infrared auxiliary heating method for rotary hearth furnace

Abstract

The invention discloses a rotary hearth furnace infrared auxiliary heating method which comprises an annular structure arranged in a rotary hearth furnace and used for auxiliary heating, the annular structure is composed of infrared radiation lamp tubes, the infrared radiation lamp tubes are arranged on the inner side of a furnace wall to form the annular structure, and the distance between the circle center of the annular structure and the height of a furnace bottom is 1 / 5-1 / 3 of the height of a hearth; raw materials treated by the rotary hearth furnace process are obtained, and raw material components are analyzed; obtaining the infrared absorption characteristics of the raw materials according to the raw material components, and setting the temperature or power of a radiation source according to the infrared absorption characteristics of the raw materials; calculating the thickness of a pellet layer according to a pelletizing process of the raw materials; and the heat generated by the fuel in unit time is calculated, so that the heat generated by infrared auxiliary heating and the heat generated when the fuel is reduced are consistent in total quantity. The infrared heating mode is adopted to partially replace existing coal gas to conduct auxiliary heating on the rotary hearth furnace, the energy utilization rate is high, carbon emission is not generated in the using process, the carbon emission in the production process of the rotary hearth furnace is reduced, the hearth space utilization rate is increased, and the development target of energy conservation and carbon reduction in the steel industry is achieved.

Description

Technical Field

[0001] The present invention relates to the field of metallurgical industry smelting, and particularly to a method for realizing energy conservation and emission reduction by an infrared-assisted heating rotary hearth furnace. Background Art

[0002] Iron and steel dust sludge is the solid waste after dry dust removal, wet dust removal, etc. of the soot generated in the iron and steel production process. The dust sludge contains relatively high-valued metal elements such as iron and zinc, and has the value of resource utilization. Properly treating and efficiently utilizing this resource is of great benefit. At present, the research on the resource utilization of iron and zinc-containing dust sludge is relatively in-depth, and the treatment methods are very diverse, mainly including wet processes, pyrometallurgical processes, and physical processes. Among them, the rotary hearth furnace process of the pyrometallurgical process has the advantages of simple process, reliable operation, flexible operation, flexible requirements for fuels and reducing agents, etc., and is one of the most promising processes for iron and steel enterprises to treat iron and zinc-containing dust sludge.

[0003] The main treatment process of the rotary hearth furnace process is as follows: various dust sludges, binders, and reducing agents are proportioned, mixed and pelletized, and after screening and drying, they enter the rotary hearth furnace. In the rotary hearth furnace, the high temperature generated by the combustion of gas is radiated to the carbon-containing pellet layer through the furnace wall. The iron, zinc and other oxides in the carbon-containing pellets are reduced by the carbon therein at high temperature. After the iron oxide is reduced, direct reduced iron is obtained, and the zinc oxide is reduced to gaseous zinc and then enters the flue gas, and is captured by the dust removal system. Although the rotary hearth furnace for treating iron and zinc-containing dust sludge has the advantages of high dezincification rate, high metallization rate, large treatment capacity, etc., its carbon emissions are relatively high, the utilization rate of the furnace chamber space is relatively low, and generally only 1-3 layers of materials can be laid. These problems restrict the further development and application of the rotary hearth furnace. At present, the research on reducing carbon emissions mainly starts from carbon-based reducing agents. For example, Chinese patents: CN117448511A and CN117327857A propose a method for producing direct reduced iron by a closed rotary hearth furnace using biomass carbon as a reducing agent to achieve near-zero emissions. These patents are basically centered around carbon-based reducing agents. However, the carbon emissions of the rotary hearth furnace come more from the CO and CO2 emissions generated by the combustion of gas in addition to the carbon-based reducing agent, and the problem of low utilization rate of the furnace chamber space of the rotary hearth furnace cannot be solved.

[0004] After the pellets enter the rotary hearth furnace, the temperature rise is mainly achieved by the heat radiated from the combustion of gas to the pellets. In this way, there is easily a problem that the proportion of the heat carried away by the flue gas after the combustion of gas is too large, and the heat generated by the combustion of gas cannot be fully utilized, and the thickness of the pellet layer that can be heated is not high. Summary of the Invention

[0005] In view of the above problems existing in the rotary hearth furnace at present, the purpose of the present invention is to provide a method for heating and reducing zinc-containing dust pellet by infrared-assisted rotary hearth furnace. The method is used for reducing iron-zinc-containing dust pellet in the rotary hearth furnace. By adopting the infrared heating method, compared with the traditional rotary hearth furnace, it has high heating efficiency and uniform heating, can heat a relatively thick pellet layer at the same time, effectively reduces the use of gas, reduces carbon emissions, and improves the utilization rate of the hearth space of the rotary hearth furnace.

[0006] To achieve this purpose, the present invention adopts the following technical solutions: 1. A method for infrared-assisted heating of a rotary hearth furnace, including a rotary hearth furnace, characterized in that: an annular structure for auxiliary heating is arranged in the rotary hearth furnace, and the annular structure is composed of infrared radiation lamps. The infrared radiation lamps are arranged on the inner side of the furnace wall to form an annular structure, and the distance from the center of the annular structure to the bottom of the furnace is 1 / 5 to 1 / 3 of the hearth height;

[0007] Obtain the raw materials for the process treatment of the rotary hearth furnace and analyze the raw material components; according to the raw material components, query the infrared absorption spectra of different chemical components of the raw materials to obtain the infrared absorption characteristics of the raw materials, and set the radiation source temperature or power according to the infrared absorption characteristics of the raw materials; select the filament material of the infrared radiation lamp according to the required temperature of the radiation source;

[0008] Calculate the pellet layer thickness according to the pelletizing process of the raw materials:

[0009]

[0010] In the formula: V1 is the volume of the ellipsoidal pellet, and a, b, and c respectively represent the semi-major axis length, semi-minor axis length, and semi-focal length of the shaped pellet, with the unit of mm. Generally, ellipsoidal pellets are used in actual production, and it is difficult to simulate ellipsoidal pellets in Fluent. Therefore, it is converted into a sphere with the same volume, and 2r is the pellet layer thickness, which is convenient for calculation and simulation. Therefore, the pellet layer thickness is the diameter of the spherical pellet after equal-volume conversion.

[0011] Calculation formula for the volume of spherical pellets:

[0012]

[0013] In the formula: V2 is the volume of the spherical pellet, r is the radius of the spherical pellet, with the unit of mm, and 2r is the pellet layer thickness.

[0014] Calculate the heat generated by the fuel per unit time so that the heat used for infrared-assisted heating is consistent with the heat generated by the fuel in total.

[0015] Assume that the fuel gas composition includes hydrogen, methane, carbon monoxide, etc. The heat Q (unit: J) generated per unit time and unit volume by the combustion of the mixed gas is:

[0016] Q = V1q1 + … + V i q i + … + V n q n

[0017] where, V i represents the volume percentage of the i-th component in the fuel gas, q i represents the calorific value corresponding to the i-th component in the fuel gas (unit: J / m 3 ³).

[0018] The heat used for infrared-assisted heating is consistent with the heat generated by the fuel in total, which means that after adding infrared heating, there are two heat sources in the rotary hearth furnace, one is infrared heating and the other is gas combustion heating. The heat provided by these two together is consistent with the heat provided before infrared heating was not added. When they are consistent, according to the law of conservation of energy, the fuel consumption can be reduced after introducing infrared heating.

[0019] Set the radiation source temperature or power according to the infrared absorption characteristics of the raw materials: After obtaining the infrared absorption wavelength ranges of different components of the raw materials, the most suitable radiation source temperature corresponding to the main infrared absorption wavelength of the components in the raw materials can be calculated through Wien's displacement law, so that the infrared rays radiated by the radiation source during heating can be absorbed by the raw materials to the greatest extent, thereby realizing the rapid heating and temperature rise of the object. Wien's displacement formula is as follows:

[0020] λ(m)T = b

[0021] In the formula: λ(m) is the wavelength corresponding to the maximum value of the blackbody radiation emissivity; T is the Kelvin temperature, unit: K; b is Wien's constant, b = 0.002897 m·K. Since the heat utilization rate of gas combustion is relatively low, nearly 50% of the heat carried away by the flue gas after combustion is not absorbed at all, and a waste heat recovery device needs to be added in the subsequent process. After adding infrared heating for auxiliary heating, the heat carried away by the flue gas, that is, the unused heat in the rotary hearth furnace, can be reduced, thereby improving the energy utilization rate of the rotary hearth furnace. According to theoretical calculation, after adding infrared heating, for every 10% reduction in gas consumption, the heat absorbed by the pellets can be increased by about 4%.

[0022] Impact of auxiliary heating used simultaneously with fuel on the process: After adding auxiliary heating and using it simultaneously with fuel, the heating efficiency of the rotary hearth furnace can be improved. Since infrared heating has the advantages of fast heating speed and easy absorption by objects, under the original fuel heating conditions, the rotary hearth furnace process for treating pellets is to heat up to about 1250 °C within 25 minutes; under the condition of only using infrared heating to heat up and reduce the pellets, this process can be completed within 15 minutes by infrared heating; from this perspective, using infrared heating and fuel simultaneously can greatly improve the process treatment efficiency of the rotary hearth furnace. In addition, infrared heating also has penetrability. Originally, the rotary hearth furnace could only treat 1 - 2 layers of pellets. After adding infrared heating, the simulation results show that under the condition of 3 layers of pellet layers, the temperatures of each pellet layer are not much different, indicating that the rotary hearth furnace can treat multiple layers of pellets without affecting normal production under infrared heating conditions, increasing the utilization rate of the furnace chamber space by about 50%.

[0023] It can be known from the Wien displacement law formula that in an industrial environment (1200 - 2000K), most of the energy radiated by an object is concentrated in the infrared band. Therefore, when considering radiative heating, it is necessary to start from infrared thermal radiation. When an infrared radiation lamp tube generates infrared rays and the object to be heated generates infrared absorption, according to the matching absorption principle, when the frequency of the infrared rays is consistent with the natural frequency of the object to be heated, a "resonance" phenomenon will occur. Microscopically, it is manifested as the acceleration of the molecular vibration of the object to be heated, and macroscopically, it is manifested as the rise in temperature.

[0024] Furthermore, the infrared radiation lamp tube is cylindrical, and its diameter can be set to 30 - 50 mm. Specifically, the diameter can be selected as 30 mm, 40 mm, or 50 mm.

[0025] Furthermore, the thickness of the pellets in the rotary hearth furnace is 20 - 80 mm. Specifically, the thickness can be selected as 20 mm, 40 mm, 60 mm, or 80 mm.

[0026] The heating rate of the infrared radiation lamp tube can reach a maximum of 1000 °C / min according to the different characteristics of the object to be heated for infrared heating.

[0027] A method for an infrared-assisted heating rotary hearth furnace to achieve energy conservation and emission reduction is as follows: Obtain the raw materials for the existing rotary hearth furnace process and analyze their components; according to the components of the existing raw materials, obtain their main infrared absorption characteristics and set appropriate radiation source temperatures or powers; according to the radiation source temperature, set the appropriate filament material for the infrared radiation lamp tube; calculate the thickness of the pellet layer according to the existing raw material pelletizing process; calculate the heat generated by the existing fuel per unit time to make the heat generated by the infrared-assisted heating consistent with the heat generated by the fuel in total amount.

[0028] Infrared heating is a type of electric heating, which features high energy utilization efficiency, high electro-thermal conversion rate, no carbon emissions during use, and can achieve simultaneous heating inside and outside the pellet layer; using infrared heating can effectively reduce gas consumption, lower carbon emissions in the rotary hearth furnace process, and increase the processing thickness of the pellet layer, thereby improving the utilization rate of the rotary hearth furnace hearth space.

[0029] The present invention proposes to use infrared-assisted rotary hearth furnace heating to treat carbon-containing pellets. Infrared heating has strong penetrability, high energy utilization efficiency, and good heating effect. As an auxiliary heating means, it can reduce the gas consumption during the production process of the rotary hearth furnace, thereby reducing carbon emissions and improving the utilization rate of the hearth space.

[0030] The present invention simulates the radiative heat transfer behavior of infrared heating in the rotary hearth furnace, and determines the feasibility of using infrared heating for rotary hearth furnace production by comparing the temperature fields of the rotary hearth furnace under different pellet layer thicknesses.

[0031] Compared with the existing process, the present invention has at least the following advantages:

[0032] 1. Adopting infrared heating to partially replace the existing gas for auxiliary heating of the rotary hearth furnace, it has high energy utilization efficiency, no carbon emissions during use, can reduce carbon emissions in the production process of the rotary hearth furnace, improve the utilization rate of the hearth space, and achieve the development goal of energy conservation and carbon reduction in the iron and steel industry.

[0033] 2. Infrared heating can achieve penetrative heating, increase the thickness of the pellet layer processed by the rotary hearth furnace process, and greatly enhance the dust sludge treatment capacity.

[0034] 3. There is a correlation between parameters such as the diameter of the infrared radiation lamp, the setting position, and the pellet thickness. The setting of the diameter of the infrared radiation lamp mainly refers to the national standard GB / T18497.2-2019 "Characteristics of Electric Infrared Emitters for Industrial Heating - Part 2: Medium and Long Wave Electric Infrared Emitters". According to different diameters, the power of the infrared radiation lamp tube is also different. The larger the diameter, the higher its rated power and the faster the heating rate; the setting position is mainly based on not affecting the original equipment structure of the rotary hearth furnace. The closer the setting position is to the pellet layer, the faster the pellet layer temperature rises, resulting in a relatively large temperature difference inside the pellet. A higher radiation power can alleviate this problem. It is necessary to set a reasonable placement position of the lamp tube according to the selected diameter of the infrared radiation lamp. The pellet thickness will be affected by these two factors. When the pellet thickness increases, a higher heating efficiency is required, otherwise it may lead to too large a temperature difference between the upper and lower parts of the pellet. Considering comprehensively, the diameter of the infrared radiation lamp tube and the placement position of the lamp tube should be reasonably selected, and the corresponding pellet layer thickness should be set accordingly.

[0035] 4. Analysis of the unexpected technical effects produced by the combination of the rotary hearth furnace and infrared radiation heating:

[0036] (1) Reduction efficiency. Infrared radiation heating can achieve faster and more uniform heating as well as a higher reduction reaction rate. This means that under the same operating conditions, a higher metal recovery rate can be obtained. At the same time, radiation heating may also lead to some catalytic effects at the microscopic level, resulting in a better reduction effect.

[0037] (2) Energy consumption reduction. Compared with traditional gas heating, infrared heating not only has a high heating efficiency but also does not produce carbon emissions. Roughly estimated, for every 10% of gas heating replaced by infrared-assisted heating, nearly 5% of carbon emissions can be reduced, the heat absorbed by the pellets can be increased by 4%, and the space utilization rate of the pellets can also be improved. This not only increases the processing capacity of the rotary hearth furnace but also shortens the process time. Description of the Drawings

[0038] Figure 1 It is a model diagram of the rotary hearth furnace.

[0039] Figure 2 It is a structural diagram inside the rotary hearth furnace under infrared-assisted heating conditions.

[0040] Figure 3 It is a distribution diagram of the median diameter temperature in the cross-section of the pellets under the condition that the heat source is set at 1800K.

[0041] Figure 4 It is a distribution diagram of the median diameter temperature at the interface of the pellets under the condition that the height of the lamp tube is set at 1 / 4 of the furnace height. Detailed Implementation Modes

[0042] The present invention conducts experiments using a numerical simulation method. To demonstrate the effectiveness of the method of the present invention and more comprehensively display the method and advantages of the present invention, the following will provide an in-depth and detailed description of the relevant simulation processes and results.

[0043] S1: First, a model is built and appropriately simplified in ANSYS SpaceClaim according to the actual rotary hearth furnace model. The main structural parameters of its furnace body are consistent with the actual size parameters of a certain iron and steel plant. Among them, the whole rotary hearth furnace in the present invention is divided into six segments, namely the preheating segment, reduction segment 1, reduction segment 2, reduction segment 3, reduction segment 4, and reduction segment 5. The feeding segment and the discharging segment are omitted during modeling. In actual production, the flue gas outlet is connected to the device for recovering zinc vapor, making the structure of the flue gas outlet relatively complex. At the same time, the subsequent reaction of the flue gas has no significant impact on the overall temperature of the rotary hearth furnace. Therefore, these reactions are omitted in the whole simulation. For these reasons, the flue gas outlet is simplified to a cylindrical hole, and various components of the furnace body are simplified. After the rotary hearth furnace model is established, infrared radiation lamps and pellets are added to the rotary hearth furnace model. Among them, the infrared radiation lamps are placed on the inner sides of the two furnace walls. The lamps are cylindrical, with a diameter that can be set to 30 - 50 mm, and the height of the center of the circle from the furnace bottom is 1 / 5 - 1 / 3 of the furnace height. The pellets are located at the bottom of the rotary hearth furnace model, and the thickness can be set to 20 - 80 mm.

[0044] S2: After the geometric model is established, the above model is meshed using Fluent mashing. The structure of the rotary hearth furnace is complex, especially after adding infrared lamps and pellets, which poses a great challenge to the setting of numerical simulation calculations. In addition, the burner size is relatively small, which requires high control of the mesh size during mesh generation. When generating the mesh, the smallest burner is used as the benchmark for mesh generation, and relevant parameters are set. Compared with other mesh generation forms, polyhedral meshes can obtain a lower number of meshes and better mesh quality. Therefore, this simulation divides it into polyhedral meshes, and finally the number of meshes is about 1 million, and the mesh quality is good.

[0045] S3: The meshed result is imported into the solver in Fluent. The models mainly used in the simulation are: the energy equation, the κ-ε turbulence model, and the DO radiation model. Among them, the DO radiation model can solve radiation problems in all optical depth intervals, and can be used to calculate both the radiation of semi-transparent media and the situation where the medium participates in radiation, such as flue gas, water vapor, etc. Its application range is very wide, and the calculation cost is moderate. Therefore, this model is selected.

[0046] The boundary conditions for radiation simulation are set as follows: the temperature of the radiation heat source (infrared lamp) is set to 1600 - 2000 K, the absorption coefficient of the pellets for the infrared wavelength ranges of 2 - 5 μm and 6 - 10 μm is set to 10 - 30 m -1 , the internal emissivity is set to 0.5 - 1, the external emissivity of the rest of the region is set to 1, it is default that only the infrared heating lamp is used for heating, and the air in the furnace space hardly absorbs infrared radiation. Then, initialization is carried out. After 1000 iterations, the calculation result of the model has basically converged.

[0047] By statistically analyzing the temperature distribution of the cross-section of the pellet layer, the average temperature at the bottom of the pellet can be calculated. By analyzing the temperature distribution at the median diameter of the cross-section, the variation of the temperature at the median diameter of the pellet cross-section with the angle can be obtained.

[0048] Example 1: The heat source temperature was set to 1800K for simulation.

[0049] S1: First, a model was built and appropriately simplified in ANSYS SpaceClaim according to the actual rotary hearth furnace model. The main structural parameters of its furnace body were consistent with the actual size parameters of a certain iron and steel plant. Among them, the present invention divides the entire rotary hearth furnace into six sections, namely the preheating section, reduction section 1, reduction section 2, reduction section 3, reduction section 4, and reduction section 5. The feeding section and the discharging section were omitted during modeling. In actual production, the flue gas outlet is connected to the device for recovering zinc vapor, making the structure of the flue gas outlet relatively complex. At the same time, the subsequent reaction of the flue gas has no significant impact on the overall temperature of the rotary hearth furnace. Therefore, these reactions were omitted in the entire simulation. For these reasons, the flue gas outlet was simplified to a cylindrical hole, and various components of the furnace body were simplified. After the rotary hearth furnace model was established, infrared radiation lamps and pellets were added to the rotary hearth furnace model. Among them, the infrared radiation lamps were placed inside the two side furnace walls. The lamps were cylindrical, with a diameter that could be set to 50mm, and the height of the center of the circle from the furnace bottom was 1 / 3 of the furnace height. The pellets were located at the bottom of the rotary hearth furnace model, and the thickness could be set to 20mm.

[0050] S2: After the geometric model was established, the above model was meshed using Fluent mashing. The structure of the rotary hearth furnace is complex, especially after adding infrared lamps and pellets, which poses a great challenge to the settings of numerical simulation calculations. In addition, the burner size is relatively small, which requires very high control of the mesh size during mesh generation. When generating the mesh, the smallest burner was used as the benchmark for mesh generation, and relevant parameters were set. Compared with other mesh generation forms, polyhedral meshes can obtain a lower number of meshes and better mesh quality. Therefore, this simulation divided it into polyhedral meshes, and finally the number of meshes was about 1 million, and the mesh quality was good.

[0051] S3: The result of the mesh generation was imported into the solver in Fluent. The models mainly used in the simulation were: the energy equation, the κ-ε turbulence model, and the DO radiation model; among them, the DO radiation model can solve radiation problems in all optical depth intervals, and can be used not only for calculating the radiation of semi-transparent media, but also for calculating the situation where the medium participates in radiation, such as flue gas, water vapor, etc. Its application range is very wide, and the calculation cost is moderate. Therefore, this model was selected.

[0052] The boundary conditions for radiation simulation were set as follows: the temperature of the radiation heat source (infrared lamp) was set to 1800K, and the infrared absorption coefficient of the pellet was set to 10m -1, the internal emissivity is set to 1, and the external emissivity of the remaining areas is set to 1. By default, only the infrared heating lamps are used for heating, and the air in the furnace space hardly absorbs infrared radiation. Then, initialization is performed. After 1000 iterations, the model calculation results have basically converged.

[0053] The temperature distributions of different cross-sections of the pellet layer are statistically analyzed. The average temperature of the pellet layer cross-section is calculated to be 1126K. From the radiation simulation results, it can be seen that infrared heating can heat the pellet layer both inside and outside simultaneously, with a small temperature difference and good heating uniformity. By analyzing the temperature distribution of the median diameter of the pellet cross-section, the variation of temperature with the angle can be obtained, as Figure 3 shown. It can be seen from Figure 3 that the temperature in the preheating section is relatively low, with an average temperature of 950K. After entering Reduction Section 1, the temperature rises rapidly and remains at a relatively high temperature in the subsequent reduction sections, basically exceeding 1100K.

[0054] Example 2: The height of the lamp tube is set to 1 / 4 of the furnace height for simulation.

[0055] S1: First, a model is built in ANSYS SpaceClaim according to the actual rotary hearth furnace model and appropriately simplified. The main structural parameters of its furnace body are consistent with the actual size parameters of a steel plant. Among them, the present invention divides the entire rotary hearth furnace into six sections, namely the preheating section, Reduction Section 1, Reduction Section 2, Reduction Section 3, Reduction Section 4, and Reduction Section 5. The feeding section and the discharging section are omitted during modeling. In actual production, the flue gas outlet is connected to the device for recovering zinc vapor, making the structure of the flue gas outlet relatively complex. At the same time, the subsequent reaction of the flue gas has no significant impact on the overall temperature of the rotary hearth furnace. Therefore, these reactions are omitted in the whole simulation. For these reasons, the flue gas outlet is simplified to a cylindrical hole, and various components of the furnace body are simplified. After the rotary hearth furnace model is established, infrared radiation lamp tubes and pellets are added on the basis of the rotary hearth furnace model. The infrared radiation lamp tubes are placed inside the two side furnace walls. The lamp tubes are cylindrical, with a diameter that can be set to 50mm, and the center of the circle is at a height of 1 / 4 of the furnace height from the furnace bottom. The pellets are located at the bottom of the rotary hearth furnace model, with a thickness set to 20mm.

[0056] S2: After the geometric model is established, the above model is meshed using Fluent mashing. The structure of the rotary hearth furnace is complex, especially after adding the infrared lamp tubes and pellets, which poses a great challenge to the settings of numerical simulation calculations. In addition, the burner size is relatively small, which requires a high control requirement for the mesh size during mesh generation. When generating the mesh, the smallest burner is used as the benchmark for mesh generation, and relevant parameters are set. Compared with other mesh generation forms, polyhedral meshes can obtain a lower number of meshes and better mesh quality. Therefore, this simulation divides it into polyhedral meshes, and finally the number of meshes is about 1 million, with good mesh quality.

[0057] S3: Import the result after grid division into the solver in Fluent. The models mainly used for simulation are: energy equation, κ-ε turbulence model, and DO radiation model. Among them, the DO radiation model can solve radiation problems in all optical depth intervals, and can be used not only for calculating radiation of semi-transparent media, but also for calculating cases where the medium participates in radiation, such as flue gas, water vapor, etc. Its applicable range is very wide and the calculation cost is moderate, so this model is selected.

[0058] The boundary conditions for radiation simulation are set as follows: the temperature of the radiation heat source (infrared lamp tube) is set to 1800K, the infrared absorption coefficient of the pellet is set to 10m -1 , the internal emissivity is set to 1, the external emissivity of the remaining areas is set to 1. By default, only the infrared heating lamp tube is used for heating, and the air in the furnace space hardly absorbs infrared radiation. Then initialize, and after 1000 steps of iteration, the calculation results of the model have basically converged.

[0059] Statistically analyze the temperature distribution of different cross-sections of the pellet layer. The calculated average temperature of the pellet layer cross-section is 1337K. From the radiation simulation results, it can be seen that infrared heating can achieve simultaneous internal and external heating of the pellet layer, with a small temperature difference and good heating uniformity. Analyze the temperature distribution of the median diameter of the pellet cross-section, and the change of temperature with angle can be obtained, as Figure 4 shown. As can be seen from Figure 3 , the temperature in the preheating section is relatively low, with an average temperature of 1150K. After entering Reduction Section 1, the temperature rises rapidly and remains at a relatively high temperature in the subsequent reduction sections, basically exceeding 1300K. It can be seen that as the height of the lamp tube decreases, the pellet layer receives more radiation heat, and the temperatures of each reduction section and the preheating section have increased.

Claims

1. A method for infrared-assisted heating of a rotary hearth furnace, comprising a rotary hearth furnace, characterized in that: It comprises an annular structure arranged in a rotary hearth furnace for auxiliary heating, the annular structure is composed of infrared radiation lamp tubes, the infrared radiation lamp tubes are arranged on the inner side of the furnace wall to form an annular structure, and the distance between the center of the annular structure and the furnace bottom height is 1 / 5 to 1 / 3 of the furnace height; Obtain the raw materials processed by the rotary hearth furnace process and analyze the raw material composition; obtain the infrared absorption characteristics of the raw materials based on the raw material composition, and set the radiation source temperature or power based on the infrared absorption characteristics of the raw materials; According to the pelletizing process of the raw materials, calculate the pellet layer thickness 2r: Spherical pellet volume calculation formula: Where: V2 is the volume of the spherical pellet, r is the radius of the spherical pellet; Calculate the heat generated by the fuel per unit time so that the heat used by infrared auxiliary heating is consistent with the heat generated by the fuel in total; The heat Q generated per unit volume per unit time by the combustion of mixed gas is: Q=V1q1+…+V i q i +…+V n q n Among them, V i represents the volume percentage of the i-th component in the fuel gas, q i Indicates the calorific value corresponding to the i-th component in the fuel gas.

2. The method for infrared-assisted heating of a rotary hearth furnace according to claim 1, characterized in that: The infrared radiation lamp tube is cylindrical, and the diameter can be set to 30-50 mm.

3. The method for infrared-assisted heating of a rotary hearth furnace as claimed in claim 1, characterized in that: The thickness of the pellets in the rotary hearth furnace is 20 to 80 mm.

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