An on-line humidity ECT measurement and control device and method for a rotary dryer

Abstract

The present invention discloses an on-line humidity ECT measurement and control device and method for a rotary dryer, which is provided with an ECT imaging system; the electrode array is arranged along the inner wall of the cylinder body for one week, facing the inner cavity of the cylinder body and relatively stationary; the angular displacement sensor is fixed to the rotary dryer and can measure the angle between the ECT sensor and the vertical direction; the electrode array, the capacitance detection circuit of the angular displacement sensor, the encoder circuit of the angular displacement sensor, the wireless transmission module and the microprocessor MCU are all fixed to the cylinder body to achieve relative static position with the cylinder body; the MCU transmits the capacitance between the electrodes and the angular displacement data of the angular displacement sensor to the computer through the wireless transmission module to realize the internal image correction of the cylinder body; the computer sends control instructions to the rotary dryer according to the humidity of the imaging to realize the control of the internal humidity of the cylinder body. The present invention realizes the measurement of the humidity acquisition of the material through ECT imaging and realizes the real-time and accurate control of the moisture of the dryer material.

Description

Technical Field

[0001] The present invention relates to the application field of ECT imaging technology, and particularly relates to an on-line humidity ECT measurement and control device and a control method for a rotary dryer. Background Art

[0002] As a widely used material drying device, the rotary dryer has the advantages of high drying efficiency, greater safety, not easy to carry dust, and simple drying for material drying problems. However, the detection of the dehumidification effect of the rotary dryer is not convenient, and the humidity of the material must be detected after drying.

[0003] Capacitance tomography technology (Electrical Capacitance Tomography, abbreviated as ECT) measures the capacitance between electrodes arranged on the contour of the imaging area, and reconstructs the dielectric constant distribution of the imaging area according to the sensor sensitive field characteristics and the inversion algorithm, and can realize non-contact imaging of the dielectric constant inside any shape structure, which is an ideal non-contact measurement technology.

[0004] Applying the ECT technology to the rotary dryer can change the current situation of the existing dryer that samples and detects the water content of the dried material and then adjusts the feed rate and rotation speed during drying. The prior art with the publication number CN201721773373.8 discloses a secondary humidity adjustment type dryer; this solution has a drying chamber and a humidity adjustment chamber inside the dryer. The material dried in the drying chamber enters the humidity adjustment chamber for humidity detection and adjustment according to the humidity level, so as to ensure that the material coming out of it can be within the preset humidity range. The device for this solution requires humidity detection after drying, which is time-consuming and laborious. And because the prior art does not perform on-line monitoring of the drying process of the dryer, the adjustment of the drying process is seriously lagged and cannot guarantee the product quality. This prior art lacks a measurement technology for real-time monitoring of the water content of the material during the drying process of the rotary dryer.

[0005] Based on the ECT technology, the detection of humidity can be realized. Since the dielectric constant of water is 80, while the dielectric constant of particulate matter is less than 5, and the dielectric constant of water is much larger than that of particulate matter, the moisture content of particulate matter has a great influence on the dielectric constant of the particles, which in turn affects the capacitance value of the ECT sensor for measurement. And capacitance tomography measures the dielectric constant distribution of the material, so the moisture content distribution of the material can be measured. By obtaining the dielectric constant distribution inside the dryer through ECT imaging, the real-time measurement of the material flow state, moisture content, and material concentration can be achieved, and at the same time, the rotary dryer can be controlled based on these parameters. In actual use, it is found that there are the following problems when using the ECT technology to improve the rotary dryer: (1) After installing the humidity measurement and control device of the ECT sensor, there are many and complex circuits on the surface of the dryer, and the wires are installed on the surface of the cylinder wall and will rotate with the rotation of the cylinder wall of the rotary dryer. When the wires are connected to the external imaging computer device, it further increases the complexity of the wires. Therefore, the problem of wire rotation caused by the rotation of the rotary dryer around the axis needs to be solved; (2) Since the electrodes are installed on the cylinder wall of the dryer, and the cylinder wall rotates with the rotating shaft, when the humidity is measured during the operation of the dryer, the measured image will be the image presented in real-time rotation along with the tube wall. As a result, the detected cross-sectional image is an image in rotation. Such an image cannot be used for the observation of the flow state. Therefore, the problem of reconstructing image correction needs to be solved. Summary of the Invention

[0006] 1. Technical problems to be solved:

[0007] In view of the above technical problems, the present invention provides an on-line humidity measurement and control device and control method for a rotary dryer based on ECT imaging, which can collect the humidity of the material through ECT imaging technology and can control the rotation speed of the dryer and the temperature of the heating system according to the humidity of the material.

[0008] 2. Technical solutions:

[0009] An on-line humidity ECT measurement and control device for a rotary dryer, characterized in that: an ECT imaging system is arranged on the cylinder body of the rotary dryer; the ECT imaging system includes an ECT electrode array, a capacitance detection circuit, an angular displacement sensor, a wireless transmission module, a microprocessor MCU and a computer for imaging; the ECT electrode array is arranged around the inner wall of the cylinder body for one week; and each ECT electrode is directly opposite to the inner cavity of the cylinder body and is relatively stationary when the rotary dryer rotates; the angular displacement sensor is fixed to the rotary dryer to measure the included angle between the ECT imaging area and the vertical direction; the capacitance detection circuit of the ECT electrode array, the encoder circuit of the angular displacement sensor, the wireless transmission module and the microprocessor MCU are all fixed on the cylinder body to achieve relative static position with the cylinder body; the microprocessor MCU transmits the received capacitance data between the ECT electrodes and the angular displacement data of the angular displacement sensor to the computer through the wireless transmission module to realize the imaging picture of the inside of the cylinder body; the computer sends a control instruction to the rotary dryer to realize the control of the humidity inside the cylinder body.

[0010] Further, the rotating device of the rotary dryer includes a rotating shaft and a rotating motor; the rotating motor drives the rotating shaft to rotate, and the rotating shaft drives the cylinder body to rotate around the line where the rotating shaft is located; the control circuit of the rotating motor is connected to the computer; inside the cylinder body, the front surface of each ECT electrode is directly opposite to the rotating shaft; the angular displacement sensor is fixedly installed on the surface of the rotating shaft and rotates with the rotating shaft to collect the rotation angle data of the cylinder body.

[0011] Further, the cylinder body of the rotary dryer extends along the horizontal plane and has a preset included angle with the horizontal plane; the material inlet is located at one end of the higher cylinder body; the material outlet is located at one end of the lower cylinder body; the material inlet and outlet are both controlled by solenoid valves to realize the inlet and outlet control of the material.

[0012] Further, support columns are arranged at both ends of the rotating shaft; bearings are arranged between the support columns and the rotating shaft; the rotating motor is located on one side of the support column at the higher end.

[0013] Further, the rotary dryer further includes a heating system for heating the materials inside the cylinder body.

[0014] An on-line humidity ECT measurement and control method for a rotary dryer includes the following steps:

[0015] Step 1: System preset: Establish the corresponding relationship between the water content of the materials in the imaging area and the image gray level;

[0016] Use the two-point calibration method to perform empty tube calibration and full tube calibration on the humidity of the cylinder body; that is, empty the cylinder body as the imaging area and measure the capacitance of all ECT electrodes in this state to obtain the empty tube capacitance value matrix C empty; Fill the imaging area with the material under the preset high water content mc, and measure the capacitance matrix C of all electrodes in this state full ; Normalize the measured capacitance matrix C according to the capacitance normalization formula (1) m Normalize:

[0017] λ = (C m - C empty ) / (C full - C empty ) (1)

[0018] The normalized capacitance matrix λ is all 0 when the tube is empty, and all 1 when the tube is full; reconstruct the image according to the image reconstruction algorithm, and the reconstruction formula is as follows:

[0019] G = S T λ (2)

[0020] In formula (2), S is the normalized sensitivity matrix, and its elements are also all normalized values; S T is the matrix transpose of the sensitive field S; λ is the matrix of normalized capacitance values detected by the capacitors composed of any two ECT electrodes; G is the reconstructed image gray matrix. When the tube is empty, λ is all 0, and according to formula (2), the image gray level is all 0. When the tube is full, λ is 1, and G is also all 1;

[0021] Sample the material with high water content mc calibrated for full tube, and use the drying method to obtain its actual water content mc. Since the image gray level under full tube is all 1, the corresponding relationship between the water content in the imaging area and the image gray level is established;

[0022] Step 2: Transmit the capacitance data obtained by the ECT electrode array to the computer for imaging; the computer obtains the original image Π in the state of the θ rotation angle according to the preset image construction algorithm; the point where the central axis of the dryer rotation axis projects in the original image Π is used as the origin, and the vertical line passing through the origin is used as the X-axis to establish a rectangular coordinate system; then each pixel point in the original image Π is represented as F ij (x i , y j , g ij ), i = 1, 2, 3, 4..., j = 1, 2, 3, 4...; F ij That is, it represents the pixel point with coordinates (x i , y i ) and the gray value size of g ij . During the coordinate rotation calculation process of F ij , the gray value g ij of each point does not change with the change of coordinates; the image gray matrix G is expressed as follows:

[0023]

[0024] The original image Π is regarded as a set composed of pixel points F ij The relationship between the original image Π and the pixel point F ij is as follows:

[0025]

[0026]

[0027] Step 3: Correct the positions corresponding to each pixel point F in the original image Π, record the rotation angle Δθ value of the device through the angular displacement sensor, and convert the coordinates of each pixel point in the imaging area in the rectangular coordinate system into the change of θ in the polar coordinate system as follows; ij The coordinates of each pixel point in the imaging area in the rectangular coordinate system are converted into the change of θ in the polar coordinate system as follows;

[0028]

[0029] Then the pixel point F ij (x i ,y j ,g ij ) is converted to f ij (ρ i ,θ j ,g ij );

[0030] Step 4: Substitute the rotation angle θ’ j =θ j +Δθ to obtain the rotated pixel point f’, and calculate the coordinate points in the polar coordinate system and the rectangular coordinate system through the conversion formula f’ ij =F’ ij ·J ij (x1,...,x F ); where J n (x1,...,x F ) is the covariant matrix of the Jacobian matrix, (ρ n ,θ’ i ,g’ j ) is the coordinate of the rotated pixel point f’ ij in the polar coordinate system, g’ is the gray value of the pixel point in Π1; θ ij is the angle where each pixel point is located on the image when it is stationary, θ’ j is the angle where each pixel point is located on the image during the rotation process; θ j 、θ’ j 、θ’ jThey are all the angles between the lines connecting the pixel points and the origin and the positive half-axis of the X-axis in the counterclockwise direction. The rotation angle Δθ of the device recorded by the angular displacement sensor is the angle by which the pixel point rotates around the coordinate origin. The conversion formula between polar coordinates and rectangular coordinates is used to obtain the rectangular coordinates of each pixel point under rotation. The conversion formula is as follows

[0031] f’ ij = F’ ij ·J F (x1,...,x n ) (6)

[0032] The modified pixel point F’ at any rotation angle is obtained through formula (6) ij (x’,y’,g’ ij ). Then, the image gray matrix G’ at this rotation angle is obtained, and the image gray matrix G’ is mapped into the new image Π1, thus realizing the overall rotation of the image;

[0033] Step Five: Identify the blank points in the new image Π1; the blank points are the blank points formed when the pixel points that appear during rotation fail to be correctly mapped to the new image. The bilinear interpolation method is used to make the image transition smoothly, which specifically includes: First, traverse all the pixel points in the image Π1, and through reverse, use the inverse matrix of the converted matrix to find the coordinates of the corresponding pixel points in the original image Π to complete the assignment of all pixel points; after this process, all the rotated points have been assigned values;

[0034] Step Six: Identify the gray level of the material in the image Π1 and compare it with the gray value corresponding to the preset humidity, then the humidity inside the cylinder at this time can be obtained;

[0035] Step Seven: If the humidity inside the cylinder is greater than the preset humidity, reduce the rotation speed of the dryer cylinder and / or adjust the opening of the feed valve until the humidity inside the cylinder is equal to or less than the preset humidity.

[0036] Furthermore, the PID control of the opening of the feed valve is also included in Step Seven; when the humidity inside the cylinder is greater than the preset humidity, the feed flow is reduced by lowering the opening of the feed valve, and vice versa, the opening of the feed valve is increased.

[0037] 3. Beneficial effects:

[0038] (1) An on-line humidity ECT measurement and control device for a rotary dryer proposed by the present invention uses ECT imaging to obtain the distribution of the dielectric constant inside the dryer, realizing the real-time measurement of the material flow state and water content inside the cylinder. Through real-time detection, the humidity of the material inside the dryer can be detected on-line without the help of other external devices, so as to solve the problem of lag in the regulation of the water content of traditional dryer products. Thus, the rotation speed and feed rate of the dryer can be directly controlled according to the humidity situation, ensuring the best heat exchange efficiency between the material and the heat source, achieving the best drying efficiency, and improving the product quality.

[0039] (2) In the on-line humidity ECT measurement and control device for a rotary dryer of the present invention, in actual application, the ECT data acquisition instrument is fixed on the pipe wall of the dryer, and the angular displacement sensor is fixed on the rotating shaft. The data is transmitted to the computer for imaging in a wireless transmission form, and at the same time, the control signal can be transmitted to the control device of the material valve and the rotating shaft speed control device, and the feed rate and rotation speed of the material are adjusted through the on-line imaging result, which greatly facilitates the work of the operator.

[0040] (3) In the on-line humidity control method for a rotary dryer based on ECT imaging of the present invention, the two-point calibration method is used to calibrate the corresponding images obtained for different known humidities in the imaging area, realizing the correspondence between the image gray value of ECT imaging and the humidity value of the material. In actual operation, a certain time interval is preset, and the image inside the cylinder is collected through the ECT imaging system, and the humidity data of the cylinder at that moment is collected by analyzing the average gray value of the image.

[0041] (4) In this method, the rotation angle data collected by the angular displacement sensor is used to correct the rotation angle of the image following the rotation of the dryer cylinder. The rotation pixel point positioning in polar coordinates ensures that the highest point of the current cylinder is always located directly above the image, and the correction of the image ensures that the corrected image can be accurately and clearly observed by people. Description of the Drawings

[0042] Figure 1 It is a schematic structural diagram of a rotary dryer based on ECT imaging;

[0043] Figure 2 It is a control system diagram of a rotary dryer based on ECT imaging;

[0044] Figure 3 They are the ECT imaging images of the cylinder before and after correction in the specific embodiment;

[0045] Figure 4 It is a flow chart of an on-line humidity ECT measurement and control method for a rotary dryer.

[0046] Description of the drawings: Support column 1; Angular displacement sensor 2; Feed valve 3; ECT electrode array 4; Display screen 5; Rotating shaft 6. Detailed implementation manners

[0047] The present invention will be specifically described below with reference to the drawings. Specific embodiments:

[0049] As shown in the Figure 1-2 drawings, an on-line humidity ECT measurement and control device for a rotary dryer, characterized in that: an ECT imaging system is provided on the cylinder body of the rotary dryer; the ECT imaging system includes an ECT electrode array 4, a capacitance detection circuit, an angular displacement sensor, a wireless transmission module, a microprocessor MCU, and a computer for imaging; the ECT electrode array is arranged around the inner wall of the cylinder body for one week; and each ECT electrode is directly opposite to the inner cavity of the cylinder body and is relatively stationary when the rotary dryer rotates; the angular displacement sensor is fixed to the rotary dryer and can measure the included angle between the ECT imaging area and the vertical direction; the capacitance detection circuit of the ECT electrode array, the encoder circuit of the angular displacement sensor 2, the wireless transmission module, and the microprocessor MCU are all fixed to the cylinder body to realize relative static position with the cylinder body; the microprocessor MCU transmits the received capacitance data between the ECT electrodes and the angular displacement data of the angular displacement sensor to the computer through the wireless transmission module to realize the imaging picture of the inside of the cylinder body; the computer sends a control instruction to the rotary dryer to realize the control of the humidity inside the cylinder body.

[0050] As shown in the Figure 2 drawings is a structural schematic diagram of the measurement and control system of the present device. The capacitance detection circuit converts the signals of the sensor electrodes E1-E8 into electrical signals and then transmits them to the MCU. The MCU transmits the detected capacitance data to the computer through the wireless transmission circuit for imaging; in actual working conditions, the MCU and the circuits connected thereto, instrument devices such as the display screen 5, etc. are all fixed on the surface of the bracket outside the dryer cylinder body and rotate with the cylinder body, and these circuit components are powered by the built-in lithium battery.

[0051] Furthermore, the rotating device of the rotary dryer includes a rotating shaft 6 and a rotating motor; the rotating motor drives the rotating shaft to rotate, and the rotating shaft drives the cylinder body to rotate around the line where the rotating shaft is located; the control circuit of the rotating motor is connected to the computer; inside the cylinder body, the front surface of each ECT electrode is directly opposite to the rotating shaft; the angular displacement sensor is fixedly installed on the surface of the rotating shaft and rotates with the rotating shaft to collect the rotation angle data of the cylinder body.

[0052] Furthermore, the cylinder body of the rotary dryer extends along the horizontal plane and has a preset included angle with the horizontal plane; the material inlet is located at one end of the higher cylinder body; the material outlet is located at one end of the lower cylinder body; the material inlet and outlet are both controlled by solenoid valves to realize the inlet and outlet control of the material.

[0053] Further, support columns 1 are provided at both ends of the rotating shaft; bearings are provided between the support columns and the rotating shaft; the rotating motor is located on one side of the support column at the higher end.

[0054] Further, the rotary dryer further includes a heating system for heating the materials inside the cylinder.

[0055] As shown in the appendix Figure 4 A method for on-line humidity ECT measurement and control of a rotary dryer includes the following steps:

[0056] Step 1: System presetting: Establish the correspondence between the water content of the materials in the imaging area and the image gray level;

[0057] The two-point calibration method is used to perform empty-tube calibration and full-tube calibration on the humidity of the cylinder; that is, the cylinder as the imaging area is emptied, and the capacitance of all ECT electrodes in this state is measured to obtain the empty-tube capacitance value matrix C empty ; the imaging area is filled with materials under a preset high water content mc, and the capacitance matrix C of all electrodes in this state is measured full ; according to the capacitance normalization formula (1), the measured capacitance matrix C m is normalized:

[0058] λ = (C m - C empty ) / (C full - C empty ) (1)

[0059] The normalized capacitance matrix λ is all 0 in the empty-tube state and all 1 in the full-tube state; the image is reconstructed according to the image reconstruction algorithm, and the reconstruction formula is as follows:

[0060] G = S T λ (2)

[0061] In formula (2), S is the normalized sensitivity matrix, and its elements are also all normalized values; S T is the matrix transpose of the sensitive field S; λ is the normalized capacitance value matrix detected by the capacitors composed of any two ECT electrodes; G is the reconstructed image gray level matrix, λ is all 0 under the empty-tube state, and according to formula (2), the image gray level is all 0, λ is 1 under the full-tube state, and G is also all 1;

[0062] Samples are taken from the materials under the high water content mc of the full-tube calibration, and the actual water content mc is obtained by the drying method. The image gray level under the full-tube state is all 1, so as to establish the correspondence between the water content in the imaging area and the image gray level;

[0063] Step 2: Transmit the capacitance data obtained by the ECT electrode array to a computer for imaging; the computer obtains the original image Π in the θ rotation angle state according to a preset image construction algorithm, as shown in the left figure in the appendix Figure 3 ; the point where the central axis of the dryer rotating shaft projects in the original image Π is used as the origin, and the vertical line passing through the origin is used as the X-axis to establish a rectangular coordinate system; then each pixel point in the original image Π is represented as F ij (x i , y j , g ij ), i = 1, 2, 3, 4..., j = 1, 2, 3, 4...; F ij That is, it represents the pixel point with coordinates (x i , y i ) and a gray value of g ij . During the coordinate rotation calculation process of F ij , the gray value g ij of each point does not change with the change of coordinates; the image gray matrix G is expressed as follows:

[0064]

[0065] The original image Π is regarded as a set composed of pixel points F ij . The relationship between the original image Π and the pixel point F ij is as follows:

[0066]

[0067]

[0068] Step 3: Correct the positions corresponding to each pixel point F ij in the original image Π. Record the rotation angle Δθ value of the device through the angular displacement sensor, and convert the coordinates of each pixel point in the imaging area in the rectangular coordinate system into the change of θ in the polar coordinate system as follows;

[0069]

[0070] Then the pixel point F ij (x i , y j , g ij ) is converted to f ij (ρ i , θ j , g ij );

[0071] Step 4: Substitute the rotation angle θ’ j = θ j + Δθ to obtain the rotated pixel point f’ ij, through the transformation formula between the polar coordinate system and the rectangular coordinate system, f’ ij = F’ ij ·J F (x1,...,x n ) calculates the coordinate points in the polar coordinate and the rectangular coordinate; where J F (x1,...,x n ) is the covariance matrix of the Jacobian matrix, (ρ i , θ’, j , g’ ij ) is the coordinate of the rotated pixel point f’ ij in the polar coordinate system, and g’ is the gray value of the pixel point in Π1; θ j is the angle of each pixel point on the image formed at rest, and θ’ j is the angle of each pixel point on the image formed during the rotation process; θ j , θ’ j are both the counterclockwise angles between the line connecting the pixel point and the origin and the positive half-axis of the X-axis. The rotation angle Δθ of the device recorded by the angular displacement sensor is the rotation angle of this pixel point centered on the coordinate origin; the rectangular coordinates of each pixel point under rotation are obtained using the transformation formula between the polar coordinate and the rectangular coordinate. The transformation formula is as follows

[0072] f’ ij = F’ ij ·J F (x1,...,x n ) (6)

[0073] By using formula (6), the modified pixel point F’ ij (x’, y’, g’ ij ) at any rotation angle is obtained, and then the image gray matrix G’ at this rotation angle is obtained. Mapping the image gray matrix G’ to the new image Π1 realizes the overall rotation of the image;

[0074] Step Five: Identify the blank points in the new image Π1; the blank points are the blank points formed when the pixel points that appear during rotation fail to be correctly mapped to the new image; the bilinear interpolation method is used to make the image transition smoothly, specifically including: First, traverse all the pixel points under the image Π1, and through reverse, use the inverse matrix of the transformed matrix to find the corresponding pixel point coordinates of the original image Π to assign values to all the pixel points; after this process, all the rotated points have been assigned values; the corrected image is as shown in the attached Figure 3 right figure.

[0075] Step Six: Identify the gray level of the material in the image Π1 and compare it with the gray value corresponding to the preset humidity to obtain the humidity inside the cylinder at this time;

[0076] Step Seven: If the humidity inside the cylinder is greater than the preset humidity, reduce the rotation speed of the dryer cylinder and / or adjust the opening degree of the feed valve until the humidity inside the cylinder is equal to or less than the preset humidity.

[0077] Further, in Step Seven, it also includes PID control of the opening degree of the feed valve 3; when the humidity inside the cylinder is greater than the preset humidity, the feed flow rate is reduced by lowering the opening degree of the feed valve, and vice versa, the opening degree of the feed valve is increased.

[0078] Although the present invention has been disclosed above with preferred embodiments, they are not used to limit the present invention. Any person skilled in this art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the protection scope of the claims of this application.

Claims

1. An on-line humidity ECT measuring and controlling device for a rotary dryer, characterized in that: The cylinder of the rotary dryer is provided with an ECT imaging system; the ECT imaging system includes an ECT electrode array, a capacitance detection circuit, an angular displacement sensor, a wireless transmission module, a microprocessor MCU, and a computer for imaging; the ECT electrode array is arranged around the inner wall of the cylinder for one week; and each ECT electrode faces the inner cavity of the cylinder and is relatively stationary when the rotary dryer rotates; the angular displacement sensor is fixed to the rotary dryer and can measure the angle between the ECT imaging area and the vertical direction; the capacitance detection circuit of the ECT electrode array, the encoder circuit of the angular displacement sensor, the wireless transmission module, and the microprocessor MCU are all fixed to the cylinder to achieve relative static position with the cylinder; the microprocessor MCU transmits the received capacitance data between the ECT electrodes and the angular displacement data of the angular displacement sensor to the computer through the wireless transmission module to realize the imaging picture of the inside of the cylinder; the computer sends a control instruction to the rotary dryer to realize the control of the humidity inside the cylinder; The rotating device of the rotary dryer includes a rotating shaft and a rotating motor; the rotating motor drives the rotating shaft to rotate, and the rotating shaft drives the cylinder to rotate around the line where the rotating shaft is located; the control circuit of the rotating motor is connected to the computer; inside the cylinder, the front surface of each ECT electrode faces the rotating shaft; the angular displacement sensor is fixedly installed on the surface of the rotating shaft and rotates with the rotating shaft to collect the rotation angle data of the cylinder; The cylinder of the rotary dryer extends along the horizontal plane and has a preset angle with the horizontal plane; the material inlet is located at one end of the higher cylinder; the material outlet is located at one end of the lower cylinder; the material inlet and outlet are both controlled by solenoid valves for the inlet and outlet of materials.

2. The on-line humidity ECT measuring and controlling device for a rotary dryer according to claim 1, characterized in that: Support columns are arranged at both ends of the rotating shaft; bearings are arranged between the support columns and the rotating shaft; the rotating motor is located on one side of the support column at the higher end.

3. An on-line humidity ECT measuring and controlling device for a rotary dryer according to claim 1, characterized in that: The rotary dryer further includes a heating system for heating the materials inside the cylinder.

4. An on-line humidity ECT measurement and control method for a rotary dryer, which is used for an on-line humidity ECT measurement and control device of a rotary dryer as described in any one of claims 1-3; characterized in that: Including the following steps: Step 1: System preset: Establish the correspondence between the moisture content of the materials in the imaging area and the image grayscale; The humidity of the cylinder is calibrated for empty tube and full tube using a two-point calibration method; that is, the cylinder as the imaging area is emptied, and the capacitance of all ECT electrodes in this state is measured to obtain the empty tube capacitance value matrix C empty ; The imaging area is filled with materials under a preset high water content mc, and the capacitance matrix C of all electrodes in this state is measured full ; According to the capacitance normalization formula (1), the measured capacitance matrix C m is normalized: λ=(C m -C empty ) / (C full -C empty ) (1) When the tube is empty, the normalized capacitance matrix λ is all 0, and when the tube is full, the normalized capacitance matrix λ is all 1; the image is reconstructed according to the image reconstruction algorithm, and the reconstruction formula is as follows: G = S T λ (2) (2) In the formula, S is the normalized sensitivity matrix, and its elements are also all normalized values; S T is the matrix transpose of the sensitive field S; λ is the matrix of normalized capacitance values detected by the capacitors formed by any two ECT electrodes; G is the reconstructed image gray level matrix. Under the condition of an empty tube, λ is all 0, and according to formula (2), the image gray level is all 0. Under the condition of a full tube, λ is 1, and G is also all 1; Samples are taken from the materials with a high moisture content mc calibrated when the tube is full, and the actual moisture content mc is obtained by the drying method. The image grayscale when the tube is full is all 1, so as to establish the correspondence between the moisture content and the image grayscale in the imaging area; Step 2: Transmit the capacitance data obtained by the ECT electrode array to a computer for imaging; the computer obtains the original image Π in the θ rotation angle state according to a preset image construction algorithm; the point where the central axis of the dryer rotating shaft projects in the original image Π is used as the origin, and a vertical line passing through the origin is used as the X-axis to establish a rectangular coordinate system; then each pixel point in the original image Π is represented as F ij (x i , y j , g ij ), i = 1, 2, 3, 4... n, j = 1, 2, 3, 4... n; F ij That is, it represents the pixel point with coordinates (x i , y i ) and its gray value is g ij . During the coordinate rotation calculation process of F ij , the gray value g ij of each point does not change with the change of coordinates; the image gray matrix G is expressed as follows: The original image Π is regarded as a set composed of pixel points F ij The relationship between the original image Π and the pixel point F ij is as follows: Step Three: Correct each pixel point F in the original image Π ij at the corresponding position, record the value of the rotation angle Δθ of the device through the angular displacement sensor, and convert the coordinates of each pixel point in the imaging area in the rectangular coordinate system into the change of θ in the polar coordinate system as follows; Then the pixel point F ij (x i ,y j ,g ij ) is converted to f ij (ρ i， θ j ,g ij ); Step 4: Substitute the rotation angle θ’ j = θ j + △θ to obtain the rotated pixel point f’ ij , and calculate the coordinate points in polar coordinates and rectangular coordinates through the transformation formula f’ ij = F’ ij ·J F (x1,...,x n ); where J F (x1,...,x n ) is the covariant matrix of the Jacobian matrix, (ρ i , θ’, j , g’ ij ) are the coordinates of the rotated pixel point f’ ij in polar coordinates, and g’ ij is the gray value of the pixel point in Π1; θ j is the angle where each pixel point is located on the image formed at rest, and θ’ j is the angle where each pixel point is located on the image formed during the rotation process; θ j 、 θ’ j are both the angles between the lines connecting the pixel points to the origin and the positive X-axis in the counterclockwise direction. The rotation angle Δθ of the device recorded by the angular displacement sensor is the angle by which the pixel point rotates around the coordinate origin. The rectangular coordinates of each pixel point under rotation are obtained using the conversion formula between polar coordinates and rectangular coordinates. The conversion formula is as follows f’ ij = F’ ij · J F (x1,...,x n ) (6) The modified pixel point F’ at any rotation angle is obtained through formula (6). ij (x’ i , y’ j , g’ ij ), and then the image gray matrix G’ at this rotation angle is obtained. Mapping the image gray matrix G’ into the new image Π1 realizes the overall rotation of the image; Step 5: Identify the blank points in the new image Π1; the blank points are the blank points formed by the pixel points that fail to be correctly mapped to the new image when rotating; the bilinear interpolation method is used to make the image transition smoothly, specifically including: first traverse all pixel points in the image Π1, and through reverse, use the inverse matrix of the transformed matrix to find the coordinates of the corresponding pixel points in the original image Π to realize the assignment of all pixel points; after this process, all the rotating points have been assigned; Step 6: Identify the grayscale of the materials in the image Π1 and compare it with the grayscale value corresponding to the preset humidity, and then the humidity inside the cylinder at this time can be obtained; Step Seven: If the humidity inside the cylinder is greater than the preset humidity, reduce the rotation speed of the dryer cylinder and / or adjust the opening degree of the feed valve until the humidity inside the cylinder is equal to or less than the preset humidity.

5. An on-line humidity ECT measurement and control method for a rotary dryer according to claim 4, characterized in that: PID control of the opening degree of the feed valve is also included in Step Seven; when the humidity inside the cylinder is greater than the preset humidity, the feed flow is reduced by lowering the opening degree of the feed valve, and vice versa, the opening degree of the feed valve is increased.

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