A detection system and method for the thickness of the ringed material of an iron ore oxidized pellet rotary kiln

Abstract

The application discloses a kind of iron ore oxidized pellet rotary kiln ring formation object thickness detection system and method, belong to steel metallurgy field.The detection system of the present application, including kiln shell and refractory layer, several linear temperature sensors are intervally embedded in the circumferential direction along the rotary kiln in refractory layer, the length of linear temperature sensor extends and covers the head of rotary kiln to kiln tail position;Kiln shell outside is also provided with pulsed light source, pulsed light source is used to provide pulsed light source to linear temperature sensor.The present application can carry out real-time detection to ring formation growth thickness, provide operation reference for site, delay ring formation growth rate, timely remove ring, improve rotary kiln equipment utilization.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and more specifically, relates to a system and method for detecting the thickness of rings in a rotary kiln for iron ore oxide pellets. Background Technology

[0002] Ore pellets, as a crucial component of modern blast furnace feedstock, are characterized by high grade, good strength, uniform particle size, and excellent metallurgical properties, while also offering significant environmental and energy-saving advantages. In 2018, China's ore pellet production was approximately 159 million tons, with an average feed ratio of about 13.91%. It is projected that both ore usage and feed ratio will further increase in the future. The production processes for oxidized pellets mainly include three types: chain grate-rotary kiln, belt roaster, and vertical shaft furnace. The chain grate-rotary kiln is the dominant process in China's oxidized pellet production, accounting for over 70% of pellet production. It features large-scale, continuous, and enclosed production, strong adaptability to raw materials, and stable product quality. However, it also commonly suffers from ring formation in the rotary kiln, which has been a major factor affecting normal rotary kiln production for many years, severely restricting the further development of this process.

[0003] In the production process of rotary kilns for oxidizing pellets, due to the rough surface of the refractory material on the inner surface of the kiln, powder and low-melting-point substances that detach from the pellet surface under high-temperature conditions easily adhere to the refractory material surface. With the rotation of the kiln, a ring of adhesive material forms along the circumference inside the kiln, known as a ring. In rotary kilns heated by coal gas, the formation of rings is mainly due to the continuous accumulation of solid-phase diffusion adhesion and liquid-phase adhesion of powder on the kiln wall, with solid-phase diffusion adhesion being dominant and liquid-phase adhesion promoting solid-phase diffusion adhesion. In rotary kilns for oxidizing pellets heated by pulverized coal, ring formation is mainly caused by excessively high temperatures, low-melting-point substances introduced by coal ash, and a reducing atmosphere.

[0004] Ring formation is a difficult-to-treat ring-shaped substance that adheres to the refractory material inside a rotary kiln during the production of oxidized pellets. In the early stages of ring formation, it has little impact on normal production. However, as the ring thickness gradually increases, it reduces the cross-sectional area inside the kiln, increasing the obstruction of airflow and material flow, thus affecting the pellet roasting effect. To maintain the kiln tail temperature, it is necessary to increase the heat supply, inevitably leading to severe energy waste and exacerbating ring formation. Simultaneously, the increased kiln filling rate increases the equipment load, reduces capacity, and enters a period of unhealthy operation for the rotary kiln. As the ring thickness continues to increase, it gradually enters a severely hazardous stage, with kiln conditions further deteriorating. At this point, pellet output and quality drop sharply, and the equipment is severely overloaded. To maintain production, it is necessary to begin treating the ring. However, frequent shutdowns for ring removal not only reduce pellet output and quality but also cause the solid solution layer formed on the refractory surface to detach along with the ring, continuously thinning the refractory bricks and reducing their wear resistance and heat resistance, making them more prone to ring formation and damage, thus creating a vicious cycle. Therefore, the ring formation problem in rotary kilns has become a bottleneck for the efficient and low-consumption production of oxide pellets, and the detection of ring thickness has become an important reference factor for subsequent ring removal operations.

[0005] A search revealed several publicly available technical solutions for detecting ring thickness in rotary kilns. For example, Chinese invention patent CN102305614B discloses a method for detecting and predicting the thickness of rings in a rotary kiln for iron ore oxide pellets. This method uses a specific formula as a model to calculate the ring thickness: utilizing historical curves of kiln outer wall temperature changes, the ring thickness is then predicted using the ring thickness model.

[0006] For example, Chinese invention patent CN103322960B discloses a method and device for detecting the thickness of the ring layer in a rotary kiln. The rotary kiln wall has holes extending from the outside in but not penetrating the refractory layer inside the kiln. The method includes: when kiln caking occurs: acquiring the flue gas temperature inside the rotary kiln, and acquiring the inner surface temperature of the rotary kiln based on the flue gas temperature and a first model; measuring the temperature at the bottom of the holes; acquiring the remaining thickness of the refractory layer, where the remaining thickness is equal to the total thickness of the refractory layer minus the hole depth; acquiring the thermal conductivity of the ring layer, the thermal conductivity of the refractory layer, and the heat flux density at the bottom of the holes; and acquiring the thickness of the ring layer based on the above parameters and a second model. When kiln caking occurs, by acquiring the flue gas temperature inside the rotary kiln in real time, measuring the temperature at the bottom of the holes on the kiln wall in real time, and combining the acquired parameters such as the remaining thickness of the refractory layer and the thermal conductivity of the ring layer with the preset second model, the thickness of the ring layer can be obtained in a timely and accurate manner.

[0007] The above methods all have certain shortcomings. The main ones are that obtaining the inner surface temperature of the ring is cumbersome and differs significantly from the actual production situation on site. In addition, it is difficult to obtain complete information on the ring formation inside the rotary kiln. Summary of the Invention

[0008] 1. The technical problem that the invention aims to solve

[0009] The technical problem to be solved by the present invention is to provide a system and method for detecting the thickness of rings in a rotary kiln for oxidized pellets. This system can detect the thickness of ring growth in real time, provide operational reference for the field, slow down the ring growth rate, remove rings in a timely manner, and improve the utilization rate of rotary kiln equipment.

[0010] 2. Technical Solution

[0011] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0012] The present invention discloses a rotary kiln ring thickness detection system for oxidized pellets, comprising a kiln shell and a refractory material layer. Several linear temperature sensors are embedded at intervals along the circumference of the rotary kiln in the refractory material layer, and the length of the linear temperature sensors extends to cover the kiln head to the kiln tail position. A pulse light source is also provided on the outside of the kiln shell, which is used to provide pulse light to the linear temperature sensors.

[0013] Furthermore, the rotary kiln is equipped with a kiln head temperature detector and a kiln tail temperature detector, respectively, to detect the flue gas temperature at the kiln head and kiln tail.

[0014] Furthermore, linear temperature sensors can be flexibly embedded in any location.

[0015] Furthermore, three linear temperature sensors are evenly embedded in the refractory material layer along the circumference of the rotary kiln.

[0016] Furthermore, the linear temperature sensor adopts the laser-fiber linear temperature measurement principle, utilizing spontaneous Raman scattering and optical time-domain reflectometry when the laser propagates in the optical fiber to obtain spatial temperature distribution information.

[0017] The present invention provides a method for detecting the ring thickness in a rotary kiln for oxidized pellets, which obtains the relationship between the inner surface temperature of the rotary kiln and the temperature of the combustion flue gas, and then determines the thickness δ2 of the ring layer.

[0018] The relationship between the inner surface temperature and the combustion flue gas temperature is as follows:

[0019] When 0 < L′ ≤ L1

[0020] When L1<L′≤L

[0021] In the formula: L′ is the distance from any point along the length of the rotary kiln to the kiln head 0m point, in meters; L1 is the distance from the point with the highest flue gas temperature to the kiln head 0m point, in meters; T 窑头 The temperature measured at the kiln head is in K; T.窑尾 The temperature measured at the kiln tail is in K; T. 燃 T1 is the corrected kiln combustion temperature, K; T2 is the inner surface temperature at any given location, K.

[0022] The thickness δ2 of the ring layer is:

[0023]

[0024] δ2 is the thickness of the ring layer, in meters; T1 is the inner surface temperature at any given location, in kilometer; T 线传 δ1 is the temperature detected by the linear sensor at any given location, in K; δ2 is the radial distance of the linear temperature sensor from the inner surface of the refractory layer, in m; λ1 is the thermal conductivity of the refractory layer, in W / (m·K); λ2 is the thermal conductivity of the ring layer, in W / (m·K); q is the heat flux density at the linear sensor, in W / m³. 2 .

[0025] Furthermore, the theoretical combustion temperature is calculated based on the gas flow rate and combustion air flow rate of the burner at the rotary kiln head, and then corrected by the actual flue gas temperature measured on-site to obtain the corrected combustion temperature T in the kiln. 燃 .

[0026] Furthermore, based on the burner's equipment parameters, installation location, and combustion air flow rate, the length of the burner flame and the spatial distance along the length direction of the highest point temperature of the flue gas in the kiln are obtained, that is, the location information corresponding to the highest point temperature of the flue gas in the kiln with a length of L1 at 0m away from the kiln head in the length direction of the rotary kiln is obtained.

[0027] 3. Beneficial effects

[0028] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0029] The ring thickness detection method of this invention uses the detection of kiln head temperature, kiln tail temperature and theoretical combustion temperature to fit the flue gas temperature distribution law inside the rotary kiln, thereby obtaining the inner surface temperature of the ring material in the rotary kiln. Combined with the obtained parameters such as the retained thickness of the refractory layer, the thermal conductivity of the ring layer, the thermal conductivity of the refractory layer, and the heat flux intensity, the ring layer thickness can be obtained in a timely and accurate manner. It can also obtain the ring thickness distribution along the length and radial distribution points of the rotary kiln, which facilitates timely maintenance or treatment. For example, by using thermal operation to rapidly cool or heat a certain part of the kiln, the service life of the furnace lining can be extended and the economic benefits of the enterprise can be improved. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the detection system of the present invention along the axial direction of the rotary kiln;

[0031] Figure 2 This is a schematic diagram of the detection system of the present invention along the radial direction of the rotary kiln.

[0032] Explanation of the labels in the diagram:

[0033] 1. Kiln shell; 2. Refractory material layer; 3. Kiln head temperature detector; 4. Kiln tail temperature detector; 5. Ring layer; 6. Thickness of refractory material layer corresponding to the measuring point position; 7. Linear temperature sensor; a. Kiln head area; b. Kiln middle area; c. Kiln tail area; A. Combustion air direction; B. Rotary kiln axial direction; C. Discharge direction; D. Rotary kiln radial direction. Detailed Implementation

[0034] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings.

[0035] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] The present invention will be further described below with reference to embodiments.

[0037] Example 1

[0038] like Figure 1 and Figure 2 As shown, this embodiment of a rotary kiln ring thickness detection system for oxidized pellets includes a kiln shell 1 and a refractory material layer 2. When kiln caking occurs, a ring layer 5 will adhere to the refractory material layer 2. In this embodiment, several linear temperature sensors 7 are embedded at intervals along the circumference of the rotary kiln in the refractory material layer 2. These linear temperature sensors 7 can be flexibly embedded according to production needs and cover the entire length of the rotary kiln, i.e., as shown in the figure. Figure 1As shown, the entire rotary kiln can be divided into three regions: kiln head region a, kiln middle region b, and kiln tail region c. Starting from the kiln head location (0m), the kiln tail location is Lm in length; the linear temperature sensor 7 covers the area from 0 to Lm. Specifically, in this embodiment, three linear temperature sensors 7 are embedded at three equidistant points along the circumference of the rotary kiln. These linear temperature sensors 7 are embedded at a radial distance δ1 from the inner surface of the refractory material layer 2, meaning the measuring point corresponds to a distance δ1 from the thickness 6 of the refractory material layer. Kiln head temperature detectors 3 and kiln tail temperature detectors 4 are respectively installed at the kiln head and kiln tail locations to detect the flue gas temperature at the kiln head and kiln tail.

[0039] In this embodiment, the linear temperature sensor 7 adopts the laser-fiber linear temperature measurement principle, enabling continuous temperature measurement and positioning. It utilizes spontaneous Raman scattering and optical time-domain reflectometry (OTDR) techniques during laser transmission in the optical fiber to obtain spatial temperature distribution information. When a pulsed light source of a certain energy is injected into the optical fiber, the pulsed light source interacts with the fiber optic molecules. As the light propagates forward, it continuously generates backward Raman scattered light. This Raman scattering, due to the thermal vibration of the fiber optic molecules, produces an anti-Stokes light with a wavelength shorter than the light source. The intensity of the anti-Stokes light signal is temperature-dependent, allowing the acquisition of temperature information at any point. The temperature location can be precisely determined based on the speed of light and the feedback time. The data can be wirelessly transmitted to a data processor. Correspondingly, the pulsed light source is fixed to the outside of the rotary kiln shell 1, allowing it to rotate with the kiln and providing pulsed light to the linear temperature sensor 7.

[0040] In this embodiment, the direction of the combustion air in the rotary kiln is as follows: Figure 1 As shown in Figure A, the axial direction of the rotary kiln is as follows: Figure 1 As shown in B; the discharge direction is as follows Figure 1 As shown in C, the radial direction of the rotary kiln is as follows: Figure 1 As shown in Figure D, the theoretical combustion temperature is calculated based on the gas flow rate and combustion air flow rate of the burner at the rotary kiln head, and then corrected against the actual flue gas temperature detected on-site. Simultaneously, based on the burner's equipment parameters, installation location, and combustion air flow rate, the spatial distance along the length of the burner flame and the highest point temperature of the flue gas in the kiln is obtained, i.e., the location information corresponding to the highest point temperature of the flue gas in the kiln at a distance of L1 from 0m along the length direction of the rotary kiln head is obtained. A kiln head temperature detection device 3 and a kiln tail temperature detection device 4 are respectively installed at the kiln head (0m along the length direction) and the kiln tail (Lm along the length direction) of the rotary kiln to acquire the flue gas temperature at the kiln head and kiln tail in real time.

[0041] The detection method in this embodiment obtains information representing the distribution of the inner surface temperature along the length direction based on the inner surface temperature obtained under different operating conditions, which corresponds to the flue gas temperature. The relationship between the obtained inner surface temperature and the flue gas temperature is as follows:

[0042] When 0 < L′ ≤ L1

[0043] When L1<L′≤L

[0044] In the above formula: L′ is the distance from any point along the length of the rotary kiln to the kiln head 0m point, in meters; L1 is the distance from the point with the highest flue gas temperature to the kiln head 0m point, in meters; T 窑头 The temperature measured at the kiln head is in K; T. 窑尾 The temperature measured at the kiln tail is in K; T. 燃 T1 is the corrected combustion temperature, K, and T1 is the inner surface temperature at any given location, K.

[0045] Furthermore, the distance δ1 between the linear temperature sensor 7 and the inner surface of the refractory material layer 2 is obtained radially; the thermal conductivity λ2 of the ring layer 5 is obtained through testing; the thermal conductivity λ1 of the refractory material layer 2 is obtained through testing; the heat flux density q at the linear sensor 7 is obtained through measurement by the detection element; based on the inner surface temperature, the detection temperature of the linear sensor, the remaining thickness, the thermal conductivity of the ring layer, the thermal conductivity of the refractory material layer, and the heat flux density, the thickness δ2 of the ring layer can be obtained.

[0046]

[0047] Where: δ2 is the thickness of the ring layer, m; T1 is the inner surface temperature at any location, K; T 线传 δ1 is the temperature detected by the linear sensor at any given location, in K; δ2 is the radial distance of the linear temperature sensor from the inner surface of the refractory layer, in m; λ1 is the thermal conductivity of the refractory layer, in W / (m·K); λ2 is the thermal conductivity of the ring layer, in W / (m·K); q is the heat flux density at the linear sensor, in W / m³. 2 .

[0048] The location and temperature information of any point obtained from the linear temperature sensor 7 are processed in the data processor to determine the distance of that point from the kiln head to 0m, and the ring layer thickness δ2 at the corresponding location is calculated according to equations 1-3 above. Similarly, the ring thickness distribution along the length of the three embedded linear temperature sensors can be obtained.

[0049] The present invention and its embodiments have been described above illustratively. This description is not restrictive and is merely one embodiment of the present invention, and is not actually limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A system for detecting the ring thickness in a rotary kiln for oxidizing pellets, comprising a kiln shell (1) and a refractory material layer (2), characterized in that: Several linear temperature sensors (7) are embedded at intervals along the circumference of the rotary kiln in the refractory material layer (2). The length of the linear temperature sensors (7) extends to cover the kiln head to the kiln tail of the rotary kiln. A pulse light source is also provided on the outside of the kiln shell (1). The pulse light source is used to provide pulse light to the linear temperature sensors (7). The rotary kiln is equipped with a kiln head temperature detector (3) and a kiln tail temperature detector (4) at the kiln head and kiln tail positions, respectively, to detect the flue gas temperature at the kiln head and kiln tail.

2. The system for detecting the ring thickness in a rotary kiln for oxidizing pellets according to claim 1, characterized in that: The linear temperature sensor (7) can be flexibly embedded in any location.

3. The system for detecting the ring thickness in a rotary kiln for oxidizing pellets according to claim 1, characterized in that: Three linear temperature sensors (7) are evenly spaced along the circumference of the rotary kiln in the refractory material layer (2).

4. A system for detecting the ring thickness in a rotary kiln for oxidizing pellets according to any one of claims 1-3, characterized in that: The linear temperature sensor (7) adopts the laser-fiber linear temperature measurement principle and uses spontaneous Raman scattering and optical time-domain reflectometry when the laser is transmitted in the optical fiber to obtain spatial temperature distribution information.

5. A method for detecting the ring thickness in a rotary kiln for oxidizing pellets according to any one of claims 1-4, characterized in that: The thickness δ2 of the ring layer (5) is determined based on the relationship between the inner surface temperature of the rotary kiln and the temperature of the combustion flue gas. The relationship between the inner surface temperature and the combustion flue gas temperature is as follows: When 0 < ≤ hour ; when < ≤ hour ; In the formula: Let m be the distance from any point along the length of the rotary kiln to the kiln head 0m. The distance in meters (m) is the distance from the point of highest flue gas temperature to the kiln head (0m). The kiln head temperature reading is in K; The temperature at the kiln tail is measured in K. The corrected kiln combustion temperature, K; Let K be the temperature of the inner surface at any given location. The thickness δ2 of the ring layer (5) is: ； The thickness of the ring layer is in meters (m). Let K be the temperature of the inner surface at any given location. Let K be the temperature detected by the linear sensor at any given location. The distance in meters is the radial distance of the linear temperature sensor from the inner surface of the refractory material layer. The thermal conductivity of the refractory layer is W / (m·K); q is the thermal conductivity of the coil layer, W / (m·K); q is the heat flux density at the linear sensor, W / m 2 .

6. The method for detecting the ring thickness in a rotary kiln for oxidizing pellets according to claim 5, characterized in that: The theoretical combustion temperature is calculated based on the gas flow rate and combustion air flow rate of the burners at the rotary kiln head, and then corrected by comparing it with the actual flue gas temperature measured on-site to obtain the corrected combustion temperature inside the kiln. .

7. The method for detecting the ring thickness in a rotary kiln for oxidizing pellets according to claim 5, characterized in that: The length of the burner flame and the spatial distance along the length direction of the highest point temperature of the flue gas in the kiln are obtained based on the burner's equipment parameters, installation location, and combustion air flow rate. In other words, the location information corresponding to the highest point temperature of the flue gas in the kiln with a length of L1 at 0m away from the kiln head is obtained.

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