# Analysis of Key Factors Affecting the Coke Pushing Stability of Coke Pusher

Authors: Jin Xiang
Journal: Shock and Vibration
 (2022)

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## Abstract

In order to find out the key factor affecting the stability of coke pusher, the structural deformation and vibration mode parameters of the coke pusher are obtained by thermal-structural coupling simulation and thermal-modal coupling simulation, and the vibration signals in the process of coke pushing are collected for time-domain analysis and time-frequency analysis. The results show that the coke pusher vibrates after being affected by the friction, and the vibration frequencies are close to the natural frequencies; that is, the friction has a great influence on the stability of the coke pushing rod. In addition, affected by the friction, the deformation of the bottom of coke pusher is the largest, resulting in unstable contact between the bottom of coke pusher and the ground of carbonization chamber, which is very easy to cause vibration.


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## Body

## 1. Introduction

Coke oven production is beneficial for the comprehensive utilization of coal and plays an important role within the metallurgical industry. Coke pusher is the key equipment of coke oven production. Its function is to push the coke out of the carbonization chamber with a temperature of up to 1000°C [1]. However, during the coke pushing process, the coke pusher vibrates violently, resulting in the coke not being able to pull out of the carbonization chamber normally. In order to find out the reasons affecting the coke pushing stability of the coke pusher, firstly, the temperature field of its structure is analyzed by ANSYS, and the concentration points of stress and vibration modal parameters are found out by thermal-structural coupling analysis and thermal-modal coupling analysis, respectively. The vibration signals of coke pusher are collected at the coke pushing site. By the time-domain analysis and the time-frequency analysis, the time period of vibration and vibration frequency of the coke pusher are obtained. Combined with the results of finite element analysis, the key factor affecting the stability of the coke pushing rod is found out.


## 2. Working Characteristics of Coke Pusher

From Figure1, the coke pusher pushes the coke under the gear drive (F), and the coke pusher pushes the coke to generate coke pushing resistance (F2). After the slipper enters the carbonization chamber, it contacts the ground of the carbonization chamber to generate friction (f).Figure 1
Structure of coke pusher. (a) Coke pushing device. (b) Coke pusher. (c) Stress analysis of coke pusher.
(a)(b)(c)According to the structure and working characteristics of coke pusher, the coke pusher contacts and pushes the coke; the coke pushing resistance reaches the maximum at 2 s. Then, the coke pushing resistance decreases gradually with the coke being pushed out. At 10 s, the slipper enters the carbonization chamber; around 40 s, the coke is completely pushed out of the carbonization chamber. The difference of coke pushing stage is that, after the slipper enters the carbonization chamber, the coke pusher is affected by friction.


## 3. Equation of Finite Element Analysis of Coke Pusher

The finite element solution equation of temperature field of coke pusher can be expressed as(1)KT+CT•=Q,where K is the heat conduction matrix, T is the node temperature array, C is the heat capacity matrix, and Q is the temperature load array [2].The balance equation of the structure of the coke pusher can be expressed as(2)Kδ=F,where K is the stiffness matrix, δ is the node displacement of the structure, and F is the equivalent node force.According to (1) and (2), the basic equation of thermal mechanical coupling of coke pusher is obtained as follows:(3)Ku=F,CT˙+KTT=Q,where K is the stiffness matrix, u is the displacement vector of the node, F is the force vector, C is the specific heat capacity matrix, T˙ is the temperature change rate; KT is the heat conduction matrix, T is the temperature, and Q is heat flow [3, 4].The modal parameters of the coke pusher can be solved by the following formula:(4)K−ω2Mϕ=0,where K is the total stiffness matrix of the structure, M is the mass matrix, and ϕ is the array vector.When the temperature affects the structure, the stiffness matrix of the structure can be expressed asKT=∫ΩBTDTBdΩ, the stiffness matrix of the thermal stress of the structure can be expressed as Kσ=∫ΩGTΓGdΩ, and then the total stiffness matrix of the structure can be expressed as K=KT+KΩ.


## 4. Finite Element Analysis of the Structural of Coke Pusher

### 4.1. Finite Element Analysis of Temperature Field

Material parameters of temperature field is shown in Table1, the initial ambient temperature outside the carbonization chamber is 20°C, and the temperature in the carbonization chamber is 1000°C. After the coke pusher enters the carbonization chamber, the convective heat transfer coefficient is 125 (W·m−2·k−1), the time of coke pushing is 40 s, and the analysis time is 40 s. The finite element result of temperature field by ANSYS is shown in Figure 2.Table 1
Material parameters of temperature field.
MaterialSpecific heat capacity (J·kg−1·k−1)Thermal conductivity (W·m−1·k−1)Density (kg·m−3)Coefficient of thermal expansion (1 k−1)Carbon structural steel46550783517.6Figure 2
Temperature distribution of coke pusher.From Figure2, it can be seen that the temperature at the head of coke pusher is the highest, up to 353.81°C, and the temperature decreases gradually along the structural axis.


### 4.2. Test Verification

The noncontact infrared thermal imager (model: LTP_7) is selected to test the temperature of the coke pusher to verify the overall temperature distribution of the coke pusher during the coke pushing process. During the test, the positions of the rod, slipper, and head are selected along the axis of coke pusher for comparative analysis. The infrared thermal image is shown in Figure3.Figure 3
Test results of infrared thermal imager. (a) Test position and temperature of rod. (b) Test position and temperature of slipper. (c) Test position and temperature of head.
(a)(b)(c)From Figure3, it can be seen that difference between the test results and the simulation results is very small, but the overall test results are lower than the simulation results, which is related to the temperature test of coke pusher after it comes out of the carbonization chamber. However, on the whole, the error is very small, indicating the correctness of the simulation results. It can be loaded on the structure of coke pusher as a temperature load for the overall deformation analysis of the structure.


### 4.3. Thermal-Structure Coupling Simulation of Coke Pusher

Load the results of the temperature field on the structure of coke pusher, and the set material parameters are shown in Table2.Table 2
Material parameters of structure.
Poisson ratioElastic modulus (GPa)Density (kg·m−3)0.2752107835Boundary conditions are as follows:(1)
Coke pushing resistance:F=380/0.4590t−50,0s≤t≤2s380/0.45137−3.825t,2s≤t≤36s(2)
The friction coefficient between the bottom of the slipper and the ground of the carbonization chamber is 0.8(3)
Set gravity and support(4)
SetZ displacement constraint to the slipper of coke pusherAs shown in Figure4, it can be found that the deformation at the bottom of slipper is the largest. Combined with the working characteristics of coke pusher, it shows that, after the slipper enters the carbonization chamber, the bottom of slipper contacts with the ground of carbonization chamber to generate friction; affected by the friction, the bottom of slipper is greatly deformed.Figure 4
Deformation of coke pusher.


### 4.4. Modal Analysis of Coke Pusher

The temperature field of the structure of coke pusher is analyzed, and the modal analysis is carried out based on the results of temperature field. The first 24 orders’ natural frequencies are shown in Table3, and some vibration modes shown in Figure 5 are taken for analysis according to the experimental results.Table 3
The first 24 natural frequencies of structure of coke pusher.
OrderFrequencyOrderFrequencyOrderFrequencyOrderFrequency10.55874714.2221332.8271955.18121.85814.9731436.5042061.93135.2076917.9671541.0452163.310410.0411020.8031645.9422266.374511.2221126.3801749.0152368.891611.6811229.2671850.8282476.301Figure 5
Vibration modes of coke pusher. (a) 13th mode shape; (b) 14th mode shape; (c) 16th mode shape; (d) 19th mode shape; (e) 20th mode shape; (f) 24th mode shape.
(a)(b)(c)(d)(e)(f)


## 4.1. Finite Element Analysis of Temperature Field

Material parameters of temperature field is shown in Table1, the initial ambient temperature outside the carbonization chamber is 20°C, and the temperature in the carbonization chamber is 1000°C. After the coke pusher enters the carbonization chamber, the convective heat transfer coefficient is 125 (W·m−2·k−1), the time of coke pushing is 40 s, and the analysis time is 40 s. The finite element result of temperature field by ANSYS is shown in Figure 2.Table 1
Material parameters of temperature field.
MaterialSpecific heat capacity (J·kg−1·k−1)Thermal conductivity (W·m−1·k−1)Density (kg·m−3)Coefficient of thermal expansion (1 k−1)Carbon structural steel46550783517.6Figure 2
Temperature distribution of coke pusher.From Figure2, it can be seen that the temperature at the head of coke pusher is the highest, up to 353.81°C, and the temperature decreases gradually along the structural axis.


## 4.2. Test Verification

The noncontact infrared thermal imager (model: LTP_7) is selected to test the temperature of the coke pusher to verify the overall temperature distribution of the coke pusher during the coke pushing process. During the test, the positions of the rod, slipper, and head are selected along the axis of coke pusher for comparative analysis. The infrared thermal image is shown in Figure3.Figure 3
Test results of infrared thermal imager. (a) Test position and temperature of rod. (b) Test position and temperature of slipper. (c) Test position and temperature of head.
(a)(b)(c)From Figure3, it can be seen that difference between the test results and the simulation results is very small, but the overall test results are lower than the simulation results, which is related to the temperature test of coke pusher after it comes out of the carbonization chamber. However, on the whole, the error is very small, indicating the correctness of the simulation results. It can be loaded on the structure of coke pusher as a temperature load for the overall deformation analysis of the structure.


## 4.3. Thermal-Structure Coupling Simulation of Coke Pusher

Load the results of the temperature field on the structure of coke pusher, and the set material parameters are shown in Table2.Table 2
Material parameters of structure.
Poisson ratioElastic modulus (GPa)Density (kg·m−3)0.2752107835Boundary conditions are as follows:(1)
Coke pushing resistance:F=380/0.4590t−50,0s≤t≤2s380/0.45137−3.825t,2s≤t≤36s(2)
The friction coefficient between the bottom of the slipper and the ground of the carbonization chamber is 0.8(3)
Set gravity and support(4)
SetZ displacement constraint to the slipper of coke pusherAs shown in Figure4, it can be found that the deformation at the bottom of slipper is the largest. Combined with the working characteristics of coke pusher, it shows that, after the slipper enters the carbonization chamber, the bottom of slipper contacts with the ground of carbonization chamber to generate friction; affected by the friction, the bottom of slipper is greatly deformed.Figure 4
Deformation of coke pusher.


## 4.4. Modal Analysis of Coke Pusher

The temperature field of the structure of coke pusher is analyzed, and the modal analysis is carried out based on the results of temperature field. The first 24 orders’ natural frequencies are shown in Table3, and some vibration modes shown in Figure 5 are taken for analysis according to the experimental results.Table 3
The first 24 natural frequencies of structure of coke pusher.
OrderFrequencyOrderFrequencyOrderFrequencyOrderFrequency10.55874714.2221332.8271955.18121.85814.9731436.5042061.93135.2076917.9671541.0452163.310410.0411020.8031645.9422266.374511.2221126.3801749.0152368.891611.6811229.2671850.8282476.301Figure 5
Vibration modes of coke pusher. (a) 13th mode shape; (b) 14th mode shape; (c) 16th mode shape; (d) 19th mode shape; (e) 20th mode shape; (f) 24th mode shape.
(a)(b)(c)(d)(e)(f)


## 5. Test Verification

### 5.1. Collection of Test Data

Collect the vibration signals generated during the coke pushing process of coke pusher at the coke oven production site, and explore the vibration characteristics of the coke pusher by the test. During the process of data acquisition, in order to avoid the loss of energy in the process of signal transmission, the shortest transmission path of signals “coke pusher-front support-sensor” shown in Figure6 is designed, and the collection of test data is shown in Table 4.Figure 6
Diagram of data acquisition.Table 4
Test equipment.
Equipment for collecting dataVibration sensorINV306SINV9822


### 5.2. Analysis of Test Data

The time-domain signal generated during the coke pushing process of coke pusher is collected by the vibration sensors, as shown in Figure7.Figure 7
Time-domain signals of the vibration of coke pusher. (a)X-direction. (b) Y-direction. (c) Z-direction.
(a)(b)(c)By analyzing the time-domain signals of vibration of coke pusher inX, Y, and Z directions, it can be concluded that, in the whole coke pushing process, the vibration of coke pusher mainly occurs in the interval of 10–40 s. Combined with the working characteristics of coke pusher, it shows that the vibration of coke pusher occurs after the slipper enters the carbonization chamber, that is, after the coke pusher is subjected to friction force [5].Due to the nonstationary and nonlinear time-varying characteristics of coke pusher, the short-time Fourier transform is selected to analyze the time-frequency characteristics of the signals [6], and the time-frequency results are shown in Figure 7.According to Figure8, the strength of the vibration of coke pusher is characterized by the strength of the vibration energy in the time-frequency results. It can be found that the coke pusher remains stable in the interval of 0–10 s. The slipper enters the carbonization chamber, and the coke pusher begins to vibrate, and the vibration is continuous, which is consistent with the time-domain analysis results; that is, after the slipper contacts the ground of the carbonization chamber to generate friction, the coke pusher begins to vibrate, and the vibration frequencies mainly include 31.5 Hz, 37.8 Hz, 47.8 Hz, 55.2 Hz, 60.2 Hz, and 70.1 Hz, which are very close to the natural frequencies of coke pusher; it shows that the friction has a great influence on the stability of coke pusher. In addition, affected by the friction, the deformation of the bottom of slipper is the largest, resulting in unstable contact between the bottom of slipper and the ground of carbonization chamber, which is very easy to cause vibration [7, 8].Figure 8
Results of time-frequency analysis. (a)X-direction (b) Y-direction. (c) Z-direction.
(a)(b)(c)


## 5.1. Collection of Test Data

Collect the vibration signals generated during the coke pushing process of coke pusher at the coke oven production site, and explore the vibration characteristics of the coke pusher by the test. During the process of data acquisition, in order to avoid the loss of energy in the process of signal transmission, the shortest transmission path of signals “coke pusher-front support-sensor” shown in Figure6 is designed, and the collection of test data is shown in Table 4.Figure 6
Diagram of data acquisition.Table 4
Test equipment.
Equipment for collecting dataVibration sensorINV306SINV9822


## 5.2. Analysis of Test Data

The time-domain signal generated during the coke pushing process of coke pusher is collected by the vibration sensors, as shown in Figure7.Figure 7
Time-domain signals of the vibration of coke pusher. (a)X-direction. (b) Y-direction. (c) Z-direction.
(a)(b)(c)By analyzing the time-domain signals of vibration of coke pusher inX, Y, and Z directions, it can be concluded that, in the whole coke pushing process, the vibration of coke pusher mainly occurs in the interval of 10–40 s. Combined with the working characteristics of coke pusher, it shows that the vibration of coke pusher occurs after the slipper enters the carbonization chamber, that is, after the coke pusher is subjected to friction force [5].Due to the nonstationary and nonlinear time-varying characteristics of coke pusher, the short-time Fourier transform is selected to analyze the time-frequency characteristics of the signals [6], and the time-frequency results are shown in Figure 7.According to Figure8, the strength of the vibration of coke pusher is characterized by the strength of the vibration energy in the time-frequency results. It can be found that the coke pusher remains stable in the interval of 0–10 s. The slipper enters the carbonization chamber, and the coke pusher begins to vibrate, and the vibration is continuous, which is consistent with the time-domain analysis results; that is, after the slipper contacts the ground of the carbonization chamber to generate friction, the coke pusher begins to vibrate, and the vibration frequencies mainly include 31.5 Hz, 37.8 Hz, 47.8 Hz, 55.2 Hz, 60.2 Hz, and 70.1 Hz, which are very close to the natural frequencies of coke pusher; it shows that the friction has a great influence on the stability of coke pusher. In addition, affected by the friction, the deformation of the bottom of slipper is the largest, resulting in unstable contact between the bottom of slipper and the ground of carbonization chamber, which is very easy to cause vibration [7, 8].Figure 8
Results of time-frequency analysis. (a)X-direction (b) Y-direction. (c) Z-direction.
(a)(b)(c)


## 6. Conclusion

(1)
The temperature field analysis of coke pusher shows that the temperature at the head of coke pusher is the highest, up to 353.81°C, and the temperature gradually decreases along the axis of coke pusher.(2)
The results of time-domain analysis and time-frequency analysis show that the coke pusher vibrates after being affected by the friction, and the vibration frequencies are close to the natural frequencies; that is, the friction has a great influence on the stability of coke pusher. In addition, affected by friction, the deformation of the bottom of coke pusher is the largest, resulting in unstable contact between the bottom of coke pusher and the ground of carbonization chamber, which is very easy to cause vibration.



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*Source: 3259533-2022-05-12.xml*