Temperature measurement and control method for electric heating rotary kiln

Abstract

The invention discloses a temperature measurement and control method for 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 so as to improve the product quality. According to the technical scheme, the temperature measurement and control method for the electric heating rotary kiln comprises the steps that a plurality of temperature measurement points are arranged on the inner wall of the rotary kiln, temperature detectors are installed at the temperature measurement points respectively, and then the average temperature of all temperature measurement sections is calculated according to the temperatures of the temperature measurement points of all the temperature measurement sections; and finally adjusting the actual heating work of the corresponding section of the rotary kiln according to the average temperature of each temperature measurement section. And a plurality of temperature measuring points are arranged in the inner cavity of the rotary kiln, so that the temperature of the inner cavity of the rotary kiln can be comprehensively and accurately obtained. The actual heating work of the corresponding sections of the rotary kiln is adjusted on the basis of the average temperature of all the temperature measuring sections, and accuracy is improved. The method is suitable for producing titanium dioxide and titanium extraction tailings.

Description

Technical Field

[0001] The invention relates to the technical field of rotary kilns, in particular to a method for monitoring and controlling the temperature of an electrically heated rotary kiln. Background Art

[0002] In order to obtain the calcination temperature of the material inside the rotary kiln, many companies use methods such as measuring the temperature of the heat carrier outside the kiln, or manually observing the fire at the head of the kiln and the reaction of the material at the tail of the kiln to judge the internal temperature of the rotary kiln. These methods are difficult to accurately obtain the internal temperature and are of little significance for production guidance. There is also a method of measuring the internal temperature of the rotary kiln using infrared in the prior art, but the distance of this method is short, and it is seriously interfered with, and the measurement result has a large error. There is also a method of measuring the internal temperature of the rotary kiln using a thermocouple with a slip ring in the prior art. This method can accurately measure, but the installation and maintenance are relatively troublesome, and the reliability is not high. The latest wireless measurement method is to open holes in different temperature measurement parts of the rotary kiln and insert thermocouples for measurement. This measurement method can only measure the temperature near the hole position but cannot measure the temperature of other parts. It is not suitable for electrically heated rotary kilns.

[0003] The outside of the electric heating rotary kiln is a heating hood, and the deviation between the outer wall 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 outer wall temperature lags behind the internal temperature, and the internal temperature is prone to be too high, resulting in unstable quality of the products produced by the electric heating rotary kiln. Summary of the invention

[0004] The invention provides a temperature measurement and control method for an electric heating rotary kiln, the purpose of which is 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 invention is: a temperature measurement and control method for an electrically heated rotary kiln, comprising the following steps:

[0006] S1. Arrange multiple temperature measuring points on the inner wall of the rotary kiln.

[0007] 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.

[0008] It is best to evenly arrange the temperature measuring points on the inner wall of the rotary kiln along the axial direction and circumferential direction of the rotary kiln. The spacing between the temperature measuring points in both directions is determined comprehensively based on the diameter of the rotary kiln, the processed materials and their processing technology. For example, 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.

[0009] S2. Install temperature measuring devices 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 .

[0010] In order to improve the stability and accuracy of the temperature detector after installation, further steps are as follows: a card block is welded at 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.

[0011] In order to optimize the arrangement of the wires of each temperature detector and avoid the data acquisition transmitter from being overheated, further: the outlet hole is arranged at the feed 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 a high temperature resistant asbestos felt.

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

[0013] In order to fully protect the thermocouple and its wires, further: a protective tube is provided on the outside of the thermocouple and its wires, the protective tube is an alloy tube, and the composition of the alloy tube is calculated by mass: Cr contains 15-35%, Ni contains 14-20%, Co contains 20-35%, and the balance is Fe.

[0014] S3, calculate the average temperature T of each temperature measuring section according to the temperature of n temperature measuring points in each temperature measuring section i .

[0015] In order to improve T i The accuracy of the temperature measurement section is further: in step S2, among the n temperature measuring devices in the same temperature measuring section, the measuring point of at least one temperature measuring device is located on the inner wall of the rotary kiln, and the measuring point of at least one temperature measuring device is located in the inner cavity of the rotary kiln; in step S3, the weighted average value 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 temperatures measured by the thermometer located at the inner cavity of the rotary kiln is greater than the weight of the temperatures measured by the thermometer located at the inner wall of the rotary kiln.

[0016] For example, 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 weights of the temperatures measured by the one temperature sensor whose measuring point is located in the inner cavity of the rotary kiln are all 0.4.

[0017] 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:

[0018] 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%;

[0019] 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%;

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

[0021] 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.

[0022] Steps S3 and S4 can be automatically operated by PLC. Specifically: the temperature measured by each temperature detector is sent to PLC by the data acquisition transmitter via the wireless network, and 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.

[0023] The cycle of the temperature measurement device to obtain the temperature is consistent with the cycle of adjusting the actual heating power of each section of the rotary kiln, and is comprehensively related to the processed materials and their processing technology. For example, further: the cycle of the temperature measurement device to obtain the temperature is 1 to 100 seconds.

[0024] The beneficial effect of the present invention is that 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 of each temperature measuring section iThe temperature of n temperature measuring points in each temperature measuring section is calculated to avoid the problem of inaccurate temperature of the temperature measuring section using a single temperature measuring point, thereby improving the accuracy of temperature measurement. According to the average temperature of each temperature measuring section and the upper and lower limits of the temperature control of each section of the rotary kiln, the actual heating power of the rotary kiln section is adjusted in real time and dynamically, and the temperature of the material in different physical sections and regions is accurately controlled to achieve energy-saving production, and more importantly, improve product quality. The present invention is particularly suitable for the production of titanium dioxide and titanium tailings. DETAILED DESCRIPTION

[0025] The temperature measurement and control method of the electrically heated rotary kiln of the present invention mainly includes monitoring the internal temperature of the rotary kiln and adjusting the actual heating power of the rotary kiln accordingly, so as to achieve measurable and controllable internal temperature of the rotary kiln, and specifically includes the following steps S1 to S4.

[0026] S1. Arrange multiple temperature measuring points on the inner wall of the rotary kiln.

[0027] The inner wall of the rotary kiln is divided into m temperature measurement sections along the axis of the rotary kiln, where m is a positive integer and ≥2. The sizes of each temperature measurement section along the axis of the rotary kiln are equal or unequal, and are generally equal. For example, the size of the temperature measurement section in the axis of the rotary kiln is 1 to 3 meters. If the production process requires high temperature measurement accuracy, the size of the temperature measurement section in the axis of the rotary kiln can also be less than 1 meter. Each temperature measurement section is arranged with n temperature measurement points in sequence along the circumference of the rotary kiln, where n is a positive integer and ≥2. It is best to evenly arrange the temperature measurement points on the inner wall of the rotary kiln, and each temperature measurement point is marked as D. ij , where 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. Regardless of the state of the rotary kiln, at least one temperature measuring point is guaranteed to be located inside the material. Along the axial direction and circumferential direction of the rotary kiln, the temperature measuring points are preferably evenly arranged on the inner wall of the rotary kiln so that the temperature measuring points are distributed in a grid shape. The spacing between the temperature measuring points in the above two directions is determined comprehensively based on the diameter of the rotary kiln, as well as the processed materials and their processing technology. Generally, the size of the 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.

[0028] S2. Install temperature measuring devices 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 .

[0029] The thermometer is used to monitor the temperature. In order to improve the accuracy of the thermometer, the thermometer is preferably a thermocouple. Considering that the material may have impact, abrasion and other effects on the thermometer, in order to improve the stability and accuracy of the thermometer after installation, the temperature measuring point of the inner wall of the rotary kiln is welded with a card block. The inner wall of the rotary kiln and the card block are preferably seamlessly welded. The material of the card block is the same as that of the inner wall of the rotary kiln to ensure the welding quality and facilitate the heat conduction between the card block and the inner wall of the rotary kiln. The spacing of the card blocks can ensure the stability of the thermometer, for example, the spacing of the card blocks is 5 meters. The card block is provided with a mounting hole, and the thermometer is fixed in the mounting hole of the card block, for example, the thermometer is welded and connected to the card block. The thermometer 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 feed end of the rotary kiln, that is, the low temperature end. The wires of each thermometer are connected to the wire outlet hole and led to the outside of the rotary kiln, and then connected to the data acquisition transmitter fixed to the outside of the rotary kiln. The data acquisition transmitter is used to collect temperature data and send out temperature signals. In order to avoid the temperature of the data acquisition transmitter being too high, the data acquisition transmitter is wrapped with a high temperature resistant material, such as a high temperature resistant asbestos felt. A protective tube is provided on the outside of the thermocouple and its wires, and the protective tube plays a protective role such as isolation and insulation. In order to fully protect the thermocouple and its wires, the protective tube is an alloy tube, and the components of the alloy tube are calculated by mass: Cr contains 15-35%, Ni contains 14-20%, Co contains 20-35%, and the remainder is Fe. The alloy tube has the advantages of acid and alkali resistance, high temperature resistance, and abrasion resistance. In order to protect the thermocouple in a targeted manner, the protective tube of the thermocouple head (thermal electrode) is thickened, for example, the 1-3 meter long protective tube away from the thermocouple head is thickened, and the thickness after thickening is 0.5-3.0 mm, for example, the thickened thickness is 1.5 mm.

[0030] S3, calculate the average temperature T of each temperature measuring section according to the temperature of n temperature measuring points in each temperature measuring section i .

[0031] Average temperature T i The average temperature of the i-th temperature measurement section can be the arithmetic mean or the weighted average. The weighted average of the n temperature measurement points in the i-th temperature measurement section is taken as the average temperature T i When T i The accuracy of the temperature measurement is that among the n temperature sensors in the same temperature measurement section, n≥3, at least one temperature sensor has a measuring point located on the inner wall of the rotary kiln, and at least one temperature sensor has a measuring point located in the inner cavity of the rotary kiln. The measuring point of the temperature sensor refers to the position where the temperature is measured by the temperature sensor. When the temperature sensor is a thermocouple, the position of the thermocouple head (hot electrode) is the measuring point. The weighted average of the n temperatures in the same temperature measurement section is taken as the average temperature T of the temperature measurement section. iWhen the weight of the temperature measured by the thermometer whose measuring point is located on the inner wall of the rotary kiln is equal, the weight of the temperature measured by the thermometer whose measuring point is located in the inner cavity of the rotary kiln is equal, and the weight of the temperature measured by the thermometer whose measuring point is located in the inner cavity of the rotary kiln is greater than the weight of the temperature measured by the thermometer whose measuring point is located on the inner wall of the rotary kiln. For example, four thermometers are evenly arranged in one temperature measuring section, of which the measuring points of three thermometers are located on the inner wall of the rotary kiln, such as the three thermocouples are directly welded on the inner wall of the rotary kiln, and the measuring point of another thermometer is located in the inner cavity of the rotary kiln, such as the thermocouple's thermocouple is tilted 10 to 300 mm and extends into the inner cavity of the rotary kiln, the weights of the temperatures measured by the three thermometers 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 thermometer whose measuring point is located in the inner cavity of the rotary kiln is all 0.4.

[0032] 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.

[0033] The method of adjusting the actual heating power of the i-th section of the rotary kiln is: if T i <T i下 , which is the average temperature T i Lower than the lower temperature limit T of the i-th section of the rotary kiln i下 , the percentage of the actual heating power of the i-th section of the rotary kiln to the rated heating power is adjusted to 100%, that is, the heating device of the i-th section is fully opened; if T i下 ≤T i ≤T i上 , which is the average temperature T i Equal to the lower limit of temperature control T of the i-th section of the rotary kiln i下 Or the upper temperature limit T of the i-th section of the rotary kiln i上 , or between the lower temperature limit T of the rotary kiln section i i下 and the upper temperature limit T of the i-th section of the rotary kiln i上 When the actual heating power of the rotary kiln section i is adjusted to the percentage of the rated heating power (T i上 -T i )÷(T i上 -T i下 )×100%, that is, the heating device of the i-th section is partially turned on; if T i >T i上 , which is the average temperature T i Higher than the upper temperature limit T of the i-th section of the rotary kiln i上 When , the percentage of the actual heating power of the i-th section of the rotary kiln to the rated heating power is adjusted to 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 detector is sent to PLC by data acquisition transmitter through wireless network, which is usually WiFi. 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 accordingly.

[0035] In the present invention, after the temperature detector obtains the temperature, the actual heating power of each section of the rotary kiln is adjusted in real time to achieve precise control. Therefore, 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 is comprehensively related to the processed material and its processing technology. For example, the cycle of the temperature detector obtaining the temperature is 1 to 100 seconds.

[0036] A titanium dioxide factory produces 30,000 tons of titanium dioxide annually and uses an electrically heated rotary kiln. A thermocouple is inserted into the outer wall of the rotary kiln to measure the outer wall temperature and estimate the kiln temperature. The estimated kiln temperature deviates from the actual temperature by 100 to 300°C, and the titanium dioxide unqualified rate is 5%. According to the present invention, the rotary kiln temperature can be accurately and real-timely collected and controlled, and the titanium dioxide unqualified rate is reduced to 2.1%. According to the average price of qualified titanium dioxide of 21,000 yuan / ton and the average price of unqualified titanium dioxide of 10,000 yuan / ton, the project contribution is 0.6, and the annual revenue is 5.742 million 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 measuring devices 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 measuring section according to the temperature of n temperature measuring points in each temperature measuring 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 the percentage of the actual heating power of the i-th section of the rotary kiln to the rated heating power is adjusted 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 the electrically heated rotary kiln according to claim 1, characterized in that: 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, characterized in that: In step S2, a card block is welded on the temperature measuring point of 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 sensor 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 sensor 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 the electrically heated rotary kiln according to claim 3, characterized in that: In step S2, the wire outlet hole 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 the electrically heated rotary kiln according to claim 5, characterized in that: A protective tube is arranged outside the thermocouple and its wires. The protective tube is an alloy tube. The components of the alloy tube are as follows: 15-35% Cr, 14-20% Ni, 20-35% Co, and the balance Fe, according to mass.

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 measuring devices in the same temperature measuring section, the measuring point of at least one temperature measuring device is located on the inner wall of the rotary kiln, and the measuring point of at least one temperature measuring device is located in the inner cavity of the rotary kiln; in step S3, the weighted average value 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 temperatures measured by the thermometer located at the inner cavity of the rotary kiln is greater than the weight of the temperatures measured by the thermometer located at the inner wall of the rotary kiln.

8. The temperature measurement and control method of the electrically heated rotary kiln according to claim 7, characterized in that: Four temperature sensors are evenly arranged in one 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 10-300 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 weights of the temperatures measured by the one temperature sensor whose measuring point is located in the inner cavity of the rotary kiln are 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 temperature detector is sent to the PLC through 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.