A red kiln early warning method for rotary kiln

Abstract

The present invention discloses a red kiln early warning method for a rotary kiln, comprising the following specific steps: measuring the kiln body surface temperature of the rotary kiln in real time, corresponding to the position coordinates, in two stages: when the refractory material is intact and when the refractory material is damaged, and establishing a corresponding relationship between the real-time kiln body surface temperature and the real-time position coordinates of the kiln shell surface; establishing a functional relationship between the change in refractory material thickness and the change in kiln body surface temperature; establishing a functional relationship between the real-time refractory material thickness and the real-time kiln body surface temperature based on the kiln body surface temperature and the initial thickness of the refractory material in the initial production stage of the rotary kiln, as well as the functional relationship between the change in refractory material thickness and the change in kiln body surface temperature; and calculating the time required for the real-time kiln body surface temperature to reach a red kiln early warning value based on the rate of change of the kiln body surface temperature and the functional relationship between the real-time refractory material thickness and the real-time kiln body surface temperature. The present invention effectively predicts the occurrence time of a red kiln in a rotary kiln.

Description

Technical Field

[0001] The invention belongs to the technical field of rotary kilns, and in particular relates to a red kiln early warning method for a rotary kiln. Background Art

[0002] A rotary kiln is a cylindrical reactor used to heat bulk or slurry materials. It is a thermal process equipment used to dry and calcine materials. It is widely used in processes across various industries, including nonferrous metallurgy, steelmaking, chemicals, cement, alumina, building materials, and refractory materials. The refractory bricks within the rotary kiln are in direct contact with the material, subjecting them to constant friction, vibration, alternating hot and cold temperatures, and various chemical attacks, creating extremely harsh operating conditions. Overheating in the rotary kiln can cause partial damage, wear, and melting of the refractory bricks, leading to brick shedding and crusting. Damage and shedding of the rotary kiln's refractory materials directly impacts normal operation, and improper maintenance can lead to serious production accidents. Therefore, timely warnings of "red kiln" conditions are crucial to guiding rotary kiln process operation and control.

[0003] In the prior art, the main methods for detecting refractory materials inside rotary kilns are: (1) Installing thermocouples on the rotary kiln cylinder and using the thermocouples to measure the temperature changes inside the rotary kiln to estimate the wear state of the refractory materials. However, this method requires drilling holes in the rotary kiln to install thermocouples, as well as installing slip rings and brush systems. During the rotation of the rotary kiln, the slip rings and brushes are severely worn, affecting the stability of the signal. In addition, the impact, wear and corrosion of the thermocouple protection tube by the material at high temperature causes the life of the thermocouple protection tube to be very short. A thermocouple can only detect a certain temperature inside the kiln. If the combustion conditions of all axial sections of the entire rotary kiln need to be understood, more thermocouples and more slip rings need to be installed, which will greatly increase the investment cost. (2) Observing the state of the refractory materials inside the kiln through the monitoring video at the kiln head. However, this method has a limited range of observation and is easily interfered by the flame, dust and gas inside the kiln. It cannot accurately estimate the wear state of the refractory materials. (3) Using an infrared thermal imager to penetrate into the kiln from the kiln head and observe the preset detection points. However, this method has major disadvantages. First, the kiln needs to be stopped for detection, which results in poor real-time performance and low efficiency. Second, it is affected by temperature differences, distance, and dust and gas in the kiln, resulting in low accuracy. (4) Holes are drilled in the kiln body and temperature sensors are installed. The temperature of the temperature sensors is measured by infrared thermometers to deduce the temperature inside the kiln, obtain the flue gas temperature and the kiln body temperature, and obtain the thermal conductivity of the refractory material to establish a heat transfer model to deduce the wear state of the refractory material. However, this method also requires drilling holes in the kiln body, and a temperature sensor can only obtain one temperature inside the kiln. If the entire temperature inside the rotary kiln needs to be mastered, more temperature sensors and infrared thermometers need to be installed, increasing the investment cost. (5) Manual handheld portable thermometers are used to measure the temperature of the kiln body at a fixed point, and the wear state of the refractory material is estimated based on the change in the kiln body temperature. However, the disadvantage is that temperature data cannot be obtained in a timely manner. It cannot participate in related automatic control and is affected by equipment performance and the quality level of operators. The timeliness, accuracy, and reliability of the measurement are difficult to guarantee. Summary of the Invention

[0004] The purpose of the present invention is to address the shortcomings of the above-mentioned background technology and provide a red kiln early warning method for a rotary kiln. By measuring the surface temperature of the kiln outside, the thickness of the refractory material in the kiln is calculated, and the position and thickness of the refractory material in the kiln are monitored in a timely and accurate manner, thereby realizing the visualization of the refractory material in the kiln.

[0005] The technical solution adopted by the present invention is: a red kiln early warning method for a rotary kiln, comprising the following specific steps: constructing a site coordinate database of the rotary kiln body surface, measuring and recording in real time the kiln body surface temperature set of each point on the rotary kiln body surface in two stages: the refractory material is not damaged and the refractory material is damaged, and constructing a correspondence between the real-time surface temperature of the kiln body and the real-time site coordinates of the kiln shell surface; constructing a functional relationship between the change in refractory material thickness and the change in kiln body surface temperature; constructing a functional relationship between the real-time thickness of the refractory material and the real-time temperature of the kiln body surface based on the kiln body surface temperature and the initial thickness of the refractory material in the initial production stage of the rotary kiln, as well as the functional relationship between the change in refractory material thickness and the change in kiln body surface temperature; calculating the time required for the real-time temperature of the kiln body surface to reach the red kiln early warning value based on the change rate of the real-time temperature of the kiln body surface and the functional relationship between the real-time thickness of the refractory material and the real-time temperature of the kiln body surface.

[0006] The beneficial effects of the present invention are as follows: in the stable initial production process, the surface temperature of the kiln body is measured by an infrared scanning thermometer, the temperature is recorded in a database, and the site coordinates of the kiln surface are recorded to establish a synchronous three-dimensional stereogram of the kiln body surface temperature and the site coordinates outside the kiln; on the basis of the determined outer surface temperature of the rotary kiln, the thermal conductivity of the refractory material is obtained by a thermal conductivity detector and recorded in a database, and then the thickness of the refractory material is calculated by using the heat conduction equation, the thickness of the refractory material has a corresponding relationship with the temperature change outside the kiln, and the functional relationship between the thickness of the refractory material and the temperature outside the kiln is used; by retrieving the site coordinates in the three-dimensional stereogram, the position and thickness of the refractory material at the site coordinates are obtained; by observing the thickness of the refractory material The temperature of the rotary kiln is measured by the infrared thermometer, which not only does not require drilling holes in the kiln body, but also does not require the installation of thermocouples or other temperature sensing elements, thus reducing costs and facilitating the monitoring of changes in refractory materials in the kiln during the production process of the rotary kiln. This gives an early warning of the occurrence of a "red kiln" and avoids the impact of a "red kiln" on production and equipment. This enables visualization of the thickness of the refractory materials in the kiln, reduces labor intensity, reduces production costs, and improves the economic benefits of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a schematic diagram of the application of the present invention;

[0008] Figure 2 It is a three-dimensional schematic diagram of the present invention.

[0009] Among them, 1-infrared thermometer, 2-kiln shell, 3-refractory material, and the arrow is the rotation direction of the kiln body. DETAILED DESCRIPTION

[0010] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but they do not constitute a limitation to the present invention.

[0011] like Figure 1 As shown, the present invention provides a red kiln early warning method for a rotary kiln, comprising the following specific steps: constructing a surface site coordinate database of the kiln shell 2, measuring and recording the kiln surface temperature of the rotary kiln in two stages when the refractory material is not damaged and when the refractory material is damaged, corresponding to the site coordinates of the kiln shell 2 surface, by an infrared thermometer 1 in real time, and constructing a corresponding relationship between the real-time surface temperature of the kiln body and the real-time site coordinates of the kiln shell 2 surface; constructing a functional relationship between the thickness change of the refractory material 3 and the change of the kiln surface temperature; constructing a functional relationship between the real-time thickness of the refractory material 3 and the real-time surface temperature of the kiln body according to the kiln surface temperature and the initial thickness of the refractory material in the initial production stage of the rotary kiln, as well as the functional relationship between the thickness change of the refractory material 3 and the change of the kiln surface temperature; calculating the time required for the real-time thickness of the refractory material to reach the red kiln early warning value according to the rate of change of the real-time surface temperature of the kiln body and the functional relationship between the real-time thickness of the refractory material and the real-time surface temperature of the kiln body.

[0012] The device for measuring the kiln surface temperature is an infrared scanning thermometer or a high-temperature probe thermometer. The device for measuring the thermal conductivity of the kiln shell and refractory material is a thermal conductivity tester. A reduction in the thickness of the rotary kiln's refractory material will cause an increase in the kiln's outer surface temperature. The occurrence of reddening in a rotary kiln can be predicted by changes in the kiln's outer temperature. Generally, a rise of approximately 50-80°C in outer kiln temperature may lead to a reddening event.

[0013] Specifically, in the initial stage of the stabilization of the rotary kiln, that is, when the rotary kiln is replaced with new refractory materials and put into normal production, the surface temperature of the kiln body remains stable.

[0014] Use an infrared scanning thermometer to measure the kiln surface temperature T0 and record this temperature in the database. This temperature is the temperature when the refractory material in the kiln is not damaged.

[0015] Record the coordinates of the site on the surface of the kiln shell (θ, l), where θ is the circumferential angle of the kiln body and l is the axial distance from the kiln surface to the kiln head.

[0016] After the rotary kiln has been in normal production for a period of time, the surface temperature of the kiln body begins to rise.

[0017] Use an infrared scanning thermometer to measure the kiln surface temperature T1 and record this temperature in the database. This temperature is the temperature at which the refractory material in the kiln is damaged. Use a thermal conductivity coefficient detector to obtain the thermal conductivity coefficient λ of the kiln shell. 1， and the thermal conductivity of the refractory material λ2;

[0018] First, the temperature T2 of the refractory material and the temperature T3 of the contact surface of the kiln shell can be calculated using the formula:

[0019] T2=T0+qδ1 / λ1, T3=T1+qδ1 / λ1

[0020] Where q is the heat flux density, δ1 is the kiln shell thickness, and λ1 is the thermal conductivity of the kiln shell.

[0021] Then, using the heat conduction equation, we can know that the thickness of the refractory material changes with its temperature. ΔL=β(T2-T3)λ2+b

[0022] Where β and b are constants;

[0023] Finally, using the above relationship, we can establish the corresponding relationship between the thickness change of the refractory material ΔL and the surface temperature of the kiln body T0, T1, which can be specifically expressed as ΔL = f(T0, T1, λ2)

[0024] Substitute T0, T1 and λ2 into formula (1);

[0025] ΔL=β(T0-T1)λ2+b (1)

[0026] The thickness change of the refractory material is calculated as ΔL;

[0027] The original thickness of the refractory material is L, that is, when the surface temperature of the kiln body is T1, the thickness of the refractory material in the rotary kiln is δ=L-ΔL;

[0028] The thickness δ of the refractory material calculated above is recorded in the database, and a corresponding relationship between the thickness δ of the refractory material and the coordinates of the site on the outer surface of the kiln (θ, l) is established, which can be specifically expressed as δ = f(θ, l). The software is used to draw a three-dimensional stereogram of the thickness δ of the refractory material, the coordinates of the site on the outer surface of the kiln (θ, l) and the temperature T; in the three-dimensional stereogram, the X / Y axis is the coordinates of the site on the kiln surface, the Z axis is the thickness of the refractory material, and the grayscale value of the color represents the corresponding temperature.

[0029] By observing the above 3D graph, the specific distribution of the refractory material thickness δ on the rotary kiln can be observed. By retrieving the coordinates of a point in the 3D graph and the relationship δ = f(θ, l), the position and thickness of the refractory material at that point can be obtained. By observing the relationship between the kiln's outer surface temperature and the refractory material thickness δ in the 3D graph, the time of red kiln occurrence can be effectively predicted.

[0030] Specific embodiment 1 is an oxidation pellet rotary kiln with an inner diameter of 5.0m for the steel plate. At a distance from the kiln head (90°, 7.463m), a 70mm thick high-quality calm steel plate (thermal conductivity of 45.36W / (m·K)) and the original 250mm high-alumina brick (thermal conductivity of 1.75+0.00045TW / (m·K)) were used. Through an infrared thermometer, the temperatures outside the kiln from May 4, 2021 to May 8, 2021 were 260°C, 265°C, 269°C, 273°C and 276°C, respectively. The linear fitting calculation shows that the temperature rise rate outside the kiln here is 3.2°C / day. As shown in Table 1. Generally, the thickness of the refractory material is about 100mm when the red kiln occurs in the rotary kiln. According to the data in Table 1, it can be calculated that the refractory material reduction rate is 2.53mm / degree. When the thickness of the refractory material is 100mm, that is, when the thickness of the refractory material is reduced by 150mm, when the red kiln occurs, according to the refractory material reduction rate, it can be calculated that when the thickness of the refractory material is reduced by 150mm, the temperature outside the kiln will rise by about 60°C compared with the temperature outside the kiln in the stage where the refractory material is not damaged.

[0031] Table 1 Variation of refractory material thickness at characteristic sites

[0032]

[0033] According to the straight line fitting in the table above, the temperature rise rate at 90° and 7.463m is 3.2℃ per day. According to the difference between the temperature outside the kiln when the red kiln is expected to occur and the temperature outside the kiln in the stage where the refractory material is not damaged, divided by the temperature rise rate, the time required for the last time point of the refractory material not damaged stage to develop into the red kiln is obtained. The calculated time is subtracted from the time when the refractory material enters the stage of damage to obtain the estimated time of the red kiln. That is, the temperature difference outside the kiln is 60 divided by the temperature rise rate of 3.2, and the time required for the outer wall temperature of the kiln to rise from 260℃ to 320℃ is 18.75 days. Subtract 5 days from the time when the refractory material enters the stage of damage (May 4th to 8th), and the estimated time point of the red kiln is 13.75 days from 0:00 on the 8th. Therefore, it is predicted that the time required for the red kiln to occur from 0:00 on May 8, 2021 is 13.75 days.

[0034] After adjusting and optimizing the on-site operating parameters, the temperature rise rate outside the kiln was effectively reduced, and the time required for the red kiln was predicted to be extended to 20 days.

[0035] Specific Example 2 is an oxidation pelletizing rotary kiln with a steel plate inner diameter of 5.0m. At a distance of 8.428m from the kiln head, a 70mm thick high-quality killed steel plate (thermal conductivity of 45.36W / (m·K)) and an original 250mm high-alumina brick (thermal conductivity of 1.75+0.00045TW / (m·K)) were used. The infrared thermometer showed that the kiln external temperatures from June 4, 2021 to June 8, 2021 were 258°C, 262°C, 267°C, 271°C, and 275°C, respectively. According to the linear fitting calculation in Table 2, the temperature rise rate outside the kiln here was 3.4°C / day.

[0036] Table 2 Variation of refractory material thickness at characteristic sites

[0037]

[0038] Generally, the thickness of the refractory material is about 100mm when the red kiln of a rotary kiln occurs. According to the data in Table 2, it can be calculated that the reduction rate of the refractory material is 2.63mm / degree. Therefore, when the thickness of the refractory material is reduced by 150mm, the temperature outside the kiln will rise by about 60°C when the red kiln occurs. That is, the temperature difference outside the kiln is 60 divided by the temperature rise rate of 3.4, and the time required for the outer wall temperature of the kiln to rise from 258°C to 318°C is 17.65 days. Minus the time when the refractory material enters the damage (June 4th to 8th) for 5 days, it is calculated from 0:00 on the 8th, and the estimated time point of the red kiln is 12.65 days later. Therefore, it is predicted that the time required for the red kiln to occur from 0:00 on June 8, 2021 is 12.65 days. After the on-site operation parameter adjustment and optimization, the temperature rise rate outside the kiln is effectively reduced, and the time required for the red kiln is predicted to be extended to 25 days.

[0039] The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

Claims

1. A red kiln early warning method for a rotary kiln, characterized by: The method comprises the following specific steps: constructing a database of site coordinates of the surface of a rotary kiln body, measuring and recording in real time the surface temperature of the rotary kiln body at each point on the surface of the rotary kiln body in two stages: when the refractory material is not damaged and when the refractory material is damaged, and constructing a corresponding relationship between the surface temperature of the kiln body and the real-time site coordinates of the kiln shell surface; constructing a functional relationship between the change in thickness of the refractory material and the change in the surface temperature of the kiln body; constructing a functional relationship between the real-time thickness of the refractory material and the surface temperature of the kiln body based on the surface temperature of the kiln body and the initial thickness of the refractory material in the initial production stage of the rotary kiln, as well as the functional relationship between the change in thickness of the refractory material and the change in the surface temperature of the kiln body; calculating the time required for the surface temperature of the kiln body to reach a red kiln warning value based on the rate of change of the surface temperature of the kiln body and the functional relationship between the real-time thickness of the refractory material and the surface temperature of the kiln body; The red kiln warning value is calculated by adding the kiln surface temperature of the rotary kiln when the refractory material is not damaged to the set temperature value; After the rotary kiln is operating normally, if the surface temperature of the kiln body remains stable for a period of time, it is determined that the rotary kiln is in the stage of no damage to the refractory material during this period; if the surface temperature of the kiln body remains stable for a period of time and then begins to rise, it is determined that the rotary kiln has entered the stage of damage to the refractory material; The functional relationship between the change in refractory material thickness and the change in kiln surface temperature is: ΔL=β(T0-T1)λ2+b; Wherein, ΔL represents the thickness change of the refractory material; β and b are constants; T1 is the real-time kiln surface temperature; T0 is the kiln surface temperature of the rotary kiln in the initial production stage when the refractory material is intact; λ2 is the thermal conductivity of the refractory material; The functional relationship between the real-time thickness of the refractory material δ and the kiln surface temperature T1 is: δ=L-ΔL=L-β(T0-T1)λ2-b; Wherein, L is the initial thickness of the refractory material; Based on the historical data of the kiln surface temperature and the real-time thickness of the refractory material during the stage of refractory material damage, the rate of change of the kiln surface temperature and the reduction rate of the refractory material during the stage of refractory material damage are calculated; the reduction rate of the refractory material is used to characterize the mathematical relationship between the thickness change of the refractory material and the change of the kiln surface temperature, and the unit is mm / degree; the thickness of the refractory material when the rotary kiln red kiln occurs is 100mm; the change value of the kiln surface temperature when the refractory material thickness reaches 100mm is calculated based on the difference between the initial thickness of the refractory material and the thickness of the refractory material when the rotary kiln red kiln occurs and the reduction rate of the refractory material; the time required for the kiln surface temperature to reach the red kiln warning value is calculated based on the change value of the kiln surface temperature and the rate of change of the kiln surface temperature.

2. The red kiln early warning method of a rotary kiln according to claim 1, characterized in that: The following steps are also included: Based on the functional relationship between the real-time thickness of the refractory material and the surface temperature of the kiln body, as well as the corresponding relationship between the surface temperature of the kiln body and the real-time position coordinates of the kiln shell surface, a three-dimensional stereogram of the real-time thickness of the refractory material and the position coordinates of the outer surface of the kiln body is drawn; the three-dimensional stereogram is used to characterize the relationship between the position coordinates of the outer surface of the kiln body and the real-time thickness of the refractory material.

3. The red kiln early warning method of a rotary kiln according to claim 1, characterized in that: According to the correspondence between the surface temperature of the kiln body and the real-time coordinates of the kiln shell surface, and the functional relationship between the real-time thickness of the refractory material and the surface temperature of the kiln body, the correspondence between the thickness of the refractory material δ and the coordinates of the kiln outer surface (θ, l) is established: δ=f(θ, l), where θ is the circumferential angle of the kiln body and l is the axial distance from the kiln surface to the kiln head.

4. The red kiln early warning method of a rotary kiln according to claim 1, characterized in that: The kiln surface temperature is measured by an infrared scanning thermometer or a high temperature probe thermometer.

5. The red kiln early warning method of a rotary kiln according to claim 1, characterized in that: The thermal conductivity of the refractory material is measured by a thermal conductivity tester.

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