Temperature measurement and control method for electric heating rotary kiln

Abstract

The application discloses a temperature measurement and control method of an electric heating rotary kiln, relates to the technical field of rotary kilns, and aims to accurately monitor and control the temperature of the electric heating rotary kiln, thereby improving product quality. The technical scheme adopted by the application is as follows: the temperature measurement and control method of the electric heating rotary kiln is characterized in that a plurality of temperature measuring points are arranged on the inner wall of the rotary kiln, temperature measuring devices are respectively arranged at the temperature measuring points, the average temperature of each temperature measuring section is calculated according to the temperatures of the plurality of temperature measuring points of each temperature measuring section, and the actual heating power of the corresponding section of the rotary kiln is adjusted according to the average temperature of each temperature measuring section. The inner cavity of the rotary kiln is provided with a plurality of temperature measuring points, so that the temperature of the inner cavity of the rotary kiln can be comprehensively and accurately obtained. The actual heating power of the corresponding section of the rotary kiln is adjusted according to the average temperature of each temperature measuring section, so that the accuracy is improved. The application is suitable for producing titanium dioxide and extracting titanium tailings.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rotary kiln, in particular to a method for monitoring and controlling the temperature of an electric heating rotary kiln. BACKGROUND

[0002] In order to obtain the calcination temperature of the material inside the rotary kiln, many enterprises use methods such as measuring the temperature of the heat carrier outside the kiln, manually observing the fire at the kiln head, and manually observing the material reaction at the kiln tail to determine the internal temperature of the rotary kiln. These methods are difficult to accurately obtain the internal temperature and have little significance for production guidance. In the prior art, there is also a method of measuring the internal temperature of the rotary kiln using infrared rays, but this method has a short distance and is severely disturbed, resulting in large measurement error. There is also a method of measuring the internal temperature of the rotary kiln using a thermocouple with a slip ring, which can accurately measure, but the installation and maintenance are relatively troublesome, and the reliability is not high. The current latest wireless measurement method is to drill holes at different temperature measurement positions of the rotary kiln and insert thermocouples for measurement. This measurement method can only measure the temperature near the hole position and cannot measure the temperature of other positions, and is not suitable for electric heating rotary kilns.

[0003] The external part of the electric heating rotary kiln is a heating cover, and the deviation between the external temperature and the internal temperature is large. At the same time, due to the continuous movement of the material, after adjusting the heating power, the external temperature lags behind the internal temperature, and the internal temperature is prone to be too high, resulting in unstable product quality of the electric heating rotary kiln. SUMMARY

[0004] The present application provides a temperature measurement and control method for an electric heating rotary kiln, which aims to accurately monitor and control the temperature of the electric heating rotary kiln, thereby improving product quality.

[0005] The technical solution adopted by the present application is as follows: a temperature measurement and control method for an electric heating rotary kiln, comprising the following steps:

[0006] S1, arranging a plurality of temperature measurement points on the inner wall of the rotary kiln.

[0007] The inner wall of the rotary kiln is sequentially divided into m temperature measurement sections along the axial direction of the rotary kiln, and n temperature measurement points are sequentially arranged in each temperature measurement section along the circumferential direction of the rotary kiln, and each temperature measurement point is marked as D ij , wherein m and n are positive integers and ≥2, i=1, 2…m, j=1, 2…n.

[0008] In the axial direction and the circumferential direction of the rotary kiln, each temperature measurement point is preferably uniformly arranged on the inner wall of the rotary kiln. The spacing of the temperature measurement points in the two directions is determined comprehensively according to the diameter of the rotary kiln, the processed material, and the processing process. For example, the size of each temperature measurement section in the axial direction of the rotary kiln is 1-3 meters, and 3-5 temperature measurement points are uniformly arranged in each temperature measurement section.

[0009] S2, a temperature measurer is installed at each temperature measuring point of the inner wall of the rotary kiln, and the temperature measured at each temperature measuring point is denoted as T ij .

[0010] In order to improve the stability and accuracy of the temperature measurer after installation, further, the temperature measuring point of the inner wall of the rotary kiln is welded with a clamping block, the material of the clamping block is the same as that of the inner wall of the rotary kiln, the clamping block is provided with a mounting hole, and the temperature measurer is fixed in the mounting hole of the clamping block; the rotary kiln is provided with a wire outlet hole, and the wires of each temperature measurer are connected to the wire outlet hole and led out to the outside of the rotary kiln, and then connected to the data acquisition transmitter fixed outside the rotary kiln.

[0011] In order to optimize the arrangement of the wires of each temperature measurer and avoid the temperature of the data acquisition transmitter being too high, further, the wire outlet hole is arranged at the feeding end of the rotary kiln, and the data acquisition transmitter is wrapped with a high-temperature-resistant material. For example, the high-temperature-resistant material is high-temperature-resistant asbestos felt.

[0012] In order to improve the accuracy of the temperature measurer, specifically, the temperature measurer is a thermocouple.

[0013] In order to fully protect the thermocouple and its wires, further, a protective tube is arranged outside the thermocouple and its wires, the protective tube is an alloy tube, and the components of the alloy tube are as follows in terms of mass: Cr 15-35%, Ni 14-20%, Co 20-35%, and the balance is Fe.

[0014] S3, the average temperature T i .

[0015] In order to improve the accuracy of T i , further, in step S2, among the n temperature measurers of the same temperature measuring section, at least one temperature measurer has a measuring point on the inner wall of the rotary kiln, and at least one temperature measurer has a measuring point in the inner cavity of the rotary kiln; in step S3, the weighted average value of the n temperatures of the same temperature measuring section is taken as the average temperature T i of the temperature measuring section, the weight of the temperature measured by the temperature measurer with the measuring point on the inner wall of the rotary kiln is equal, the weight of the temperature measured by the temperature measurer with the measuring point in the inner cavity of the rotary kiln is equal, and the weight of the temperature measured by the temperature measurer with the measuring point in the inner cavity of the rotary kiln is greater than the weight of the temperature measured by the temperature measurer with the measuring point on the inner wall of the rotary kiln.

[0016] For example, four temperature measuring devices are evenly arranged in one temperature measuring section, three of which have measuring points on the inner wall of the rotary kiln, and one has a measuring point in the inner cavity of the rotary kiln, and the distance between the measuring point and the inner wall of the rotary kiln is 10-300 mm, the weight of the temperature measured by the three temperature measuring devices with measuring points on the inner wall of the rotary kiln is 0.2, and the weight of the temperature measured by the one temperature measuring device with a measuring point in the inner cavity of the rotary kiln is 0.4.

[0017] S4, adjusting the actual heating power of the i-th section of the rotary kiln according to the average temperature T i Adjusting the actual heating power of the i-th section of the rotary kiln in the following manner:

[0018] If T i <T i下 , the percentage of the actual heating power of the i-th section of the rotary kiln to the rated heating power is 100%;

[0019] If T i下 ≤T i ≤T i上 , the percentage of the actual heating power of the i-th section of the rotary kiln to the rated heating power is (T i上 -T i ) ÷ (T i上 -T i下 ) × 100%;

[0020] If T i >T i上 , the percentage of the actual heating power of the i-th section of the rotary kiln to the rated heating power is 0%;

[0021] Wherein, T i下 is the lower limit of temperature control of the i-th section of the rotary kiln, and T i上 is the upper limit of temperature control of the i-th section of the rotary kiln.

[0022] Steps S3 and S4 can be automatically operated by PLC. Specifically: the temperatures measured by each temperature measuring device are sent to the PLC by the data acquisition transmitter through the wireless network, the PLC automatically calculates the average temperature T i of each temperature measuring section, and automatically adjusts the actual heating power of the i-th section of the rotary kiln.

[0023] The period of temperature acquisition by the temperature measuring device is consistent with the period of adjustment of the actual heating power of each section of the rotary kiln, and is related to the processed material and its processing process. For example, further: the period of temperature acquisition by the temperature measuring device is 1-100 seconds.

[0024] The beneficial effects of the present application are: the inner cavity of the rotary kiln is provided with multiple temperature measuring points, which can comprehensively and accurately obtain the temperature of the inner cavity of the rotary kiln. The average temperature T iThe temperature of each temperature measuring section is calculated according to the temperature of the n temperature measuring points, so that the problem of inaccuracy of using a single temperature measuring point as the temperature of the temperature measuring section is avoided, and the temperature measuring accuracy is improved. According to the average temperature of each temperature measuring section and the upper and lower temperature control limits of each section of the rotary kiln, the actual heating power of the section of the rotary kiln is dynamically adjusted in real time, the temperature of the material in different physical sections and regions is accurately controlled, energy-saving production is realized, and more importantly, the product quality is improved. The present application is especially suitable for producing titanium dioxide and extracting titanium tailings. DETAILED DESCRIPTION

[0025] The temperature measuring and control method of the electric heating rotary kiln mainly includes monitoring the internal temperature of the rotary kiln and adjusting the actual heating power of the rotary kiln accordingly to realize the measurability and controllability of the internal temperature of the rotary kiln, and specifically includes the following steps S1-S4.

[0026] S1, arranging a plurality of temperature measuring points on the inner wall of the rotary kiln.

[0027] The inner wall of the rotary kiln is sequentially divided into m temperature measuring sections along the axis direction of the rotary kiln, m is a positive integer and ≥2, the size of each temperature measuring section along the axis direction of the rotary kiln is equal or unequal, generally equal, for example, the size of the temperature measuring section along the axis direction of the rotary kiln is 1-3 meters, if the production process requires high temperature measuring accuracy, the size of the temperature measuring section along the axis direction of the rotary kiln can also be less than 1 meter. Each temperature measuring section is sequentially arranged with n temperature measuring points along the circumferential direction of the rotary kiln, wherein n is a positive integer and ≥2, each temperature measuring point is preferably uniformly arranged on the inner wall of the rotary kiln, and each temperature measuring point is marked as D ij , wherein i=1, 2, …, m, j=1, 2, …, n. The number of temperature measuring points in the same temperature measuring section is preferably not less than three, and at least one temperature measuring point is located in the material regardless of the state of the rotary kiln. Each temperature measuring point is preferably uniformly arranged on the inner wall of the rotary kiln along the axis direction and the circumferential direction of the rotary kiln, so that the temperature measuring points are distributed in a grid pattern. The spacing of the temperature measuring points in the above two directions is determined comprehensively according to the diameter of the rotary kiln, the processed material and its processing process. Generally, the size of the temperature measuring section along the axis direction of the rotary kiln is 1-3 meters, and 3-5 temperature measuring points are uniformly arranged in each temperature measuring section.

[0028] S2, installing a temperature measuring device at each temperature measuring point on the inner wall of the rotary kiln, and the temperature measured at each temperature measuring point is recorded as T ij .

[0029] The temperature measuring device is used for monitoring temperature. In order to improve the accuracy of the temperature measuring device, the temperature measuring device is preferably a thermocouple. In view of the impact, abrasion and other effects of the material on the temperature measuring device, in order to improve the stability and accuracy of the temperature measuring device after installation, the temperature measuring points of the inner wall of the rotary kiln are welded with clamping blocks, the inner wall of the rotary kiln and the clamping blocks are preferably seamlessly welded, the material of the clamping blocks is the same as that of the inner wall of the rotary kiln, the welding quality is ensured, and the heat conduction between the clamping blocks and the inner wall of the rotary kiln is facilitated. The spacing of the clamping blocks can ensure the stability of the temperature measuring device, for example, the spacing of the clamping blocks is 5 meters. The clamping blocks are provided with mounting holes, and the temperature measuring device is fixed in the mounting holes of the clamping blocks, for example, the temperature measuring device is welded with the clamping blocks. The temperature measuring device is connected with a wire, in order to optimize the arrangement of the wire, the rotary kiln is provided with a wire outlet hole, the wire outlet hole is preferably arranged at the feeding end of the rotary kiln, that is, the low temperature end, the wires of the temperature measuring devices are connected to the wire outlet hole and led out to the outside of the rotary kiln, and then connected with a data acquisition transmitter fixed outside the rotary kiln. The data acquisition transmitter is used for collecting temperature data and sending temperature signals. In order to avoid the temperature of the data acquisition transmitter being too high, the data acquisition transmitter is wrapped with high-temperature-resistant material, for example, the data acquisition transmitter is wrapped with high-temperature-resistant asbestos felt. The outside of the thermocouple and its wire is provided with a protective tube, which plays a protective role in isolation and insulation. In order to fully protect the thermocouple and its wire, the protective tube is an alloy tube, and the components of the alloy tube are as follows: Cr contains 15-35%, Ni contains 14-20%, Co contains 20-35%, and the balance is Fe. The alloy tube has the advantages of acid and alkali resistance, high temperature resistance, abrasion resistance and the like. In order to protect the thermocouple, the protective tube of the thermocouple head part (hot electrode) is thickened, for example, the protective tube with a length of 1-3 meters from the thermocouple head part is thickened, and the thickness of the thickened protective tube is 0.5-3.0 mm, for example, the thickness of the thickened protective tube is 1.5 mm.

[0030] S3、According to the temperature of the n temperature measuring points of each temperature measuring section, the average temperature T of each temperature measuring section is calculated i .

[0031] The average temperature T i is the average temperature of the i-th temperature measuring section. The average temperature can be an arithmetic mean or a weighted mean. The temperatures of the n temperature measuring points of the i-th temperature measuring section are taken as the average temperature T i , and the sum of the weights of the temperatures of the n temperature measuring points is 1. In order to improve the accuracy of T i , n≥3 in the n temperature measuring devices of the same temperature measuring section, at least one temperature measuring device is located on the inner wall of the rotary kiln, and at least one temperature measuring device is located in the inner cavity of the rotary kiln. The measuring point of the temperature measuring device refers to the position of the temperature measuring device, and the position of the thermocouple head part (hot electrode) of the thermocouple is the measuring point. The weighted average of the n temperatures of the same temperature measuring section is taken as the average temperature T iWhen the average temperature T of each temperature measuring section is equal to the temperature measured by the temperature measuring device with the measuring point located at the inner wall of the rotary kiln, the average temperature T of each temperature measuring section is equal to the temperature measured by the temperature measuring device with the measuring point located at the inner cavity of the rotary kiln, and the average temperature T of each temperature measuring section is greater than the temperature measured by the temperature measuring device with the measuring point located at the inner wall of the rotary kiln. For example, four temperature measuring devices are evenly arranged in one temperature measuring section, three of which have the measuring point located at the inner wall of the rotary kiln, for example, the three thermocouples are directly welded on the inner wall of the rotary kiln, and the other one has the measuring point located at the inner cavity of the rotary kiln, for example, the hot electrode of the thermocouple is tilted by 10-300 mm and extends into the inner cavity of the rotary kiln. The weight of the temperature measured by the three temperature measuring devices with the measuring point located at the inner wall of the rotary kiln is 0.2, and the weight of the temperature measured by the one temperature measuring device with the measuring point located at the inner cavity of the rotary kiln is 0.4.

[0032] S4, adjusting the actual heating power of the i-th section of the rotary kiln according to the average temperature T of each temperature measuring section. i adjusting the actual heating power of the i-th section of the rotary kiln.

[0033] The way of adjusting the actual heating power of the i-th section of the rotary kiln is that if T i <T i下 , that is, the average temperature T i is lower than the lower limit T i下 of the temperature control of the i-th section of the rotary kiln, the percentage of the actual heating power to the rated heating power of the i-th section of the rotary kiln is 100%, that is, the heating device of the i-th section is completely opened; if T i下 ≤T i ≤T i上 , that is, the average temperature T i is equal to the lower limit T i下 or the upper limit T i上 of the temperature control of the i-th section of the rotary kiln, or is between the lower limit T i下 and the upper limit T i上 of the temperature control of the i-th section of the rotary kiln, the percentage of the actual heating power to the rated heating power of the i-th section of the rotary kiln is (T i上 -T i )÷(T i上 -T i下 )×100%, that is, the heating device of the i-th section is partially opened; if T i >T i上 , that is, the average temperature T i is higher than the upper limit T i上 of the temperature control of the i-th section of the rotary kiln, the percentage of the actual heating power to the rated heating power of the i-th section of the rotary kiln is 0%, that is, the heating device of the i-th section is completely closed.

[0034] In order to realize automatic operation, steps S3 and S4 can be realized by PLC. The temperature measured by each temperature measurer is sent to the PLC by a data acquisition transmitter through a wireless network, which is generally WiFi, and the PLC automatically calculates the average temperature T of each temperature measuring section i , and automatically adjusts the actual heating power of the i-th section of the rotary kiln accordingly.

[0035] In the present application, the temperature measurer acquires temperature, and the actual heating power of each section of the rotary kiln is adjusted in real time to realize precise control. Therefore, the period of acquiring temperature by the temperature measurer is consistent with the period of adjusting the actual heating power of each section of the rotary kiln. This period is related to the processed material and its processing technology. For example, the period of acquiring temperature by the temperature measurer is 1-100 seconds.

[0036] A titanium dioxide factory with an annual output of 30,000 tons of titanium dioxide adopts an electric heating rotary kiln. The outer wall of the rotary kiln is inserted with a thermocouple to measure the outer wall temperature and infer the temperature inside the kiln. The deviation between the inferred temperature inside the kiln and the actual temperature is 100-300℃, and the unqualified rate of titanium dioxide is 5%. According to the present application, the temperature of the rotary kiln is precisely and real-time collected and controlled, and the unqualified rate of titanium dioxide is reduced to 2.1%. According to the average price of 21,000 yuan per ton of qualified titanium dioxide and 10,000 yuan per ton of unqualified titanium dioxide, the contribution of the project is 0.6, and the annual income is 5,742,000 yuan.

Claims

1. A temperature measurement and control method for an electrically heated rotary kiln, characterized in that: The steps include: S1. Arrange multiple temperature measuring points on the inner wall of the rotary kiln; The inner wall of the rotary kiln is divided into m temperature measurement sections along the axis of the rotary kiln. Each temperature measurement section is arranged with n temperature measurement points along the circumference of the rotary kiln. Each temperature measurement point is marked as D. ij , where m and n are both positive integers and ≥ 2, i = 1, 2...m, j = 1, 2...n; S2. Install temperature detectors at each temperature measuring point on the inner wall of the rotary kiln. The temperature measured at each temperature measuring point is recorded as T ij ; S3. Calculate the average temperature T of each temperature measurement section based on the temperature of n temperature measurement points in each temperature measurement section. i ; S4, according to the average temperature T of each temperature measurement section i Adjust the actual heating power of the i-th section of the rotary kiln by: If T i <T i下 , then the percentage of the actual heating power of the rotary kiln section i to the rated heating power is adjusted to 100%; If T i下 ≤T i ≤T i上 , then the percentage of the actual heating power of the rotary kiln section i to the rated heating power is (T i上 -T i )÷(T i上 -T i下 )×100%; If T i >T i上 , then adjust the percentage of the actual heating power of the rotary kiln section i to the rated heating power to 0%; Among them, T i下 is the lower limit of temperature control of the i-th section of the rotary kiln, T i上 It is the upper limit of temperature control of the i-th section of the rotary kiln.

2. The temperature measurement and control method of an electrically heated rotary kiln according to claim 1, wherein: In step S1, the size of each temperature measuring section in the axial direction of the rotary kiln is 1 to 3 meters, and 3 to 5 temperature measuring points are evenly arranged in each temperature measuring section.

3. The temperature measurement and control method of the electrically heated rotary kiln according to claim 1, wherein: In step S2, a card block is welded to the temperature measuring point on the inner wall of the rotary kiln. The material of the card block is the same as that of the inner wall of the rotary kiln. The card block is provided with a mounting hole, and the temperature detector is fixed in the mounting hole of the card block; the rotary kiln is provided with a wire outlet hole, and the wires of each temperature detector are connected to the wire outlet hole and led out to the outside of the rotary kiln, and then connected to the data acquisition transmitter fixed on the outside of the rotary kiln.

4. The temperature measurement and control method of an electrically heated rotary kiln according to claim 3, wherein: In step S2, the wire outlet is set at the feed end of the rotary kiln, and the data acquisition transmitter is wrapped with a high-temperature resistant material.

5. The temperature measurement and control method of the electrically heated rotary kiln according to claim 3, characterized in that: The temperature detector is a thermocouple.

6. The temperature measurement and control method of an electrically heated rotary kiln according to claim 5, wherein: A protective tube is provided outside the thermocouple and its wires. The protective tube is an alloy tube. The composition of the alloy tube is as follows: 15-35% Cr, 14-20% Ni, 20-35% Co, and the balance Fe.

7. The temperature measurement and control method of an electrically heated rotary kiln according to any one of claims 1 to 6, characterized in that: In step S2, among the n temperature detectors in the same temperature measuring section, the measuring point of at least one temperature detector is located on the inner wall of the rotary kiln, and the measuring point of at least one temperature detector is located in the inner cavity of the rotary kiln; in step S3, the weighted average of the n temperatures in the same temperature measuring section is taken as the average temperature T of the temperature measuring section. i The weights of the temperatures measured by the thermometer located at the inner wall of the rotary kiln are equal, the weights of the temperatures measured by the thermometer located at the inner cavity of the rotary kiln are equal, and the weight of the temperature measured by the thermometer located at the inner cavity of the rotary kiln is greater than the weight of the temperature measured by the thermometer located at the inner wall of the rotary kiln.

8. The temperature measurement and control method of an electrically heated rotary kiln according to claim 7, wherein: Four temperature sensors are evenly arranged in a temperature measuring section, of which the measuring points of three temperature sensors are located on the inner wall of the rotary kiln, and the measuring point of one temperature sensor is located in the inner cavity of the rotary kiln, and the distance between the measuring point and the inner wall of the rotary kiln is 10 to 300 mm. The weights of the temperatures measured by the three temperature sensors whose measuring points are located on the inner wall of the rotary kiln are all 0.2, and the weight of the temperature measured by the one temperature sensor whose measuring point is located in the inner cavity of the rotary kiln is all 0.

4.

9. The temperature measurement and control method of an electrically heated rotary kiln according to any one of claims 3 to 6, characterized in that: The temperature measured by each thermometer is sent to the PLC via the wireless network by the data acquisition transmitter, and the PLC automatically calculates the average temperature T of each temperature measurement section. i , and automatically adjust the actual heating power of the i-th section of the rotary kiln.

10. The temperature measurement and control method of an electrically heated rotary kiln according to any one of claims 1 to 6, characterized in that: The cycle of the temperature detector obtaining the temperature is consistent with the cycle of adjusting the actual heating power of each section of the rotary kiln, and the cycle of the temperature detector obtaining the temperature is 1 to 100 seconds.