英语写作论文

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　　Experimental Study on Transport

　　Characteristics of Vibrated Discrete Particle

　　Zhan YaQuan

　　School of metallurgy, Northeastern University, P. R. China

　　Abstract: When conveying high temperature particles with vibratory conveyor，Not only can we recover most of the heat in the particulate matter, but also prevent the equipment from being damaged by the high temperature through cooling down the system. However, the vibration parameters of the vibratory conveyor and the particle diameter of the conveying material would cause varying degrees of effects on the conveying process and the waste heat recovery process. So, in this paper, the velocity curve of particle motion was obtained by tracing the trajectory of tracer particles. Based on this, the effect of the vibration frequency, the particle diameter and the thickness of the material on the particle motion had been studied.

　　Key words:Vibratory conveyor; Particle tracking; Waste heat recovery; Linearvibration system

　　Introduction

　　Metallurgical industry often produces a large number of metallurgical slag containing rich waste heat resources, and the discharge temperature is about 1300℃. Blast furnace slag takes about 2.7108GJ of sensible heat per year, equivalent to 9.2106 tons of standard coals. Compared with the wet process with low energy utilization and environmental pollution, the dry process has been paid more and more attention. After dry granulation, particles still have hundreds of degrees Celsius, or even thousands of degrees Celsius. When they were sent to the treatment facility for the recovery of the waste heat, the high temperature slag particles will cause different degrees of wear and tear on the conveying equipment. At the same time, the high temperature of the slag particles can cause the liquid core particles to melt two times, and that will also affect the heat recovery of waste heat boiler. Therefore, it is considered that the linear vibrating conveyor with circulating cooling water is used to transfer the high temperature particles.

　　People began to study the granular materials very early. In 1980, Grochowski was used to establish the model of the conveying of bulk material on the vibrating conveyor, and the influence of the throwing coefficient and the vibration angle on the average velocity was analyzed. In 2005, M. Rouijaa surveyed three kinds of vibration system vibration form of transport: straight line, circle and ellipse, solved the problem of how to establish the model structure and the influence of particle material on the conveying performance of vibrating surface.In 2009, China University of Mining and Technology, L-L. Zhao using three-dimensional discrete element method, in the low frequency range of the straight line, carried out numerical simulation of particle separation process, and analyzed the physical mechanism of separation behavior of particles of various vibration modes.In 1992, Taguch used numerical simulation to analyze the effect of vibration acceleration on particle convection. It can be concluded that the harmonic vibration of the vibrating bed can not only promote the relative motion between the slag particles, but also strengthen the heat transfer process, and can prevent the high temperature slag particles from being accumulated in the process of conveying. However, the slag particle size and the operating parameters of the

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　　vibration conveying will affect the recovery of the waste heat and relative motion of the high temperature particles. So, in this paper, the vibration test platform is designed to study the influence of particle diameter, vibration frequency, and the thickness of accumulation on the movement of material.

　　1. Experimental

　　The experimental equipment and experimental materials used in this experiment are as follows: linear vibrating bed, frequency conversion governor, computer host, Motion Pro Y3 high speed camera, black and transparent glass balls. The vibration motor used in the shaking table is YZD-03-4, the rated speed is 1400rpm, the vibration direction is 30 degrees with the vibration bed. At the top of the shaking table is a material storage container, the vibration table is symmetrically arranged on both sides of the vibration motor, the two motors are connected to the same frequency converter, the use of organic glass containers to transport particulate materials.

　　Specific experimental steps are shown in Figure 1. When the material from the storage container flows into the container, inclined upward force were decomposed into horizontal vibration and vertical vibration and the horizontal vibration makes the material move forward, while the vertical vibration strengthens the relative motion between the different layers. In the experiment, the vibration frequency changes in 12~20Hz, 3mm, 5mm and 7mm particles were used as the experimental object.

　　1-Computer，2-Power Supply，3-Storage container，4-Experimental container， 5-Variable frequency speed governor，

　　6-Two vibration motors，7-High-speed camera，8-Tungsten lamp

　　Fig 1：Flow chart of experiment

　　2. Results and Discussion

　　2.1 The Effect of Vibration Frequency on Material Movement

　　The experimental results are shown in figure 2.1.1. It can be found that with the increase of the vibration frequency, the horizontal displacement of the tracer particles increases continuously, and the particles continue to shrink in the vertical direction and converge in the lower layer. At the same time, it is found that when the vibration frequency increases, near the upper black ball began sliding opposite to the direction of movement, which allows the vertically aligned black ball to

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　　begin to bend backward when the lower layer is converging.

　　Fig. 2.1.1 Moving image of particle at different frequencies

　　In order to study the movement mechanism of the particle material, the vibration curve of the particle movement was obtained by tracking the particle trajectory, as shown in figure 2.1.2 and figure 2.1.3, and the velocity change curve, as shown in figure 2.1.4. It can be found that the vibration frequency of the vibrating table has different influence on the movement of the material in different directions. In the horizontal direction, with the increase of the vibration frequency, the velocity of the material increases and the amplitude of the vibration velocity increases; In the vertical direction, with the increase of the vibration frequency, the vibration velocity and amplitude of the material increases obviously, but it is less than that in the horizontal direction. The experimental results show that the movement of the material in the horizontal direction is the main mode of motion, and the conveying process is realized by controlling the horizontal velocity. Meanwhile, the increase of vibration frequency can increase the amplitude of vibration in two directions, especially in the vertical direction, which confirms the feasibility of cooling and waste heat recovery. And the vibration frequency has little influence on the vibration velocity in the vertical direction, which results in the accumulation of particles in the vertical direction at high frequency.

　　f=12hz f=12hz

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　　f=14hz f=14hz

　　f=16hz f=16hz

　　f=18hz f=18hz

　　f=20hz f=20hz

　　Fig. 2.1.2 Horizontal velocity of particles Fig. 2.1.3 Vertical velocity of particles

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　　Fig 2.1.4 Particle velocity change curve

　　2.2 The Effect of Particle Diameter on Material Movement

　　The experimental results are shown in figure 2.2.1, as can be seen from the same frequency of different diameter particles, at the same moment, the tilt angle of the tracer particles is approximately the same, and the conveying position is roughly the same. However, the large diameter particles in the vertical direction began to appear more obvious stack thickness, tracer particles show a short and coarse state, but generally the tracer particles at the same time to complete the transport process.

　　Fig. 2.2.1 Moving image of particle with different diameters at different time

　　Similarly, the velocity and velocity change curves of the particles were obtained, as shown in figure 2.2.2~2.2.4. It can be seen that at the same frequency, although the diameter of the particle material is different, but the mean value of vibration velocity in the two directions is not changed a lot, the maximum deviation is not more than 2mm/s. It can be seen that particle diameter is not the main factor affecting the vibration velocity, at the same time, if the vibration frequency is 18Hz, when the particle diameter increases from 5mm to 7mm, the amplitude of vibration velocity of particles in the two directions are obviously increased. The results show that when the particle diameter is large, it will be beneficial to the relative motion between the materials and enhance the heat transfer between the particles, but at the same time, when the particle diameter is larger, the heat transfer area between the material and the material or the material and wall-cooling surface will be reduced. Therefore, when using vibration to convey granular materials, particle diameter should be considered from many aspects.

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　　d=3mm d=3mm

　　d=5mm d=5mm

　　d=7mm d=7mm

　　Fig. 2.2.2 Horizontal velocity of particles Fig. 2.2.3 Vertical velocity of particles

　　Fig 2.2.4 Particle velocity change curve

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　　2.3 The Effect of Stacking Thickness on Material Movement

　　As can be seen from the figure 2.3.1, when the thickness of the stack is reduced to 65mm, the horizontal conveying process is slowed down, the horizontal displacement is reduced, and the particle material is slowly compressed and accumulated in the vertical direction.

　　Fig 2.3.1 Moving image of particle at different stacking thickness：65mm and 100mm

　　Next, the velocity and velocity change curves of the particles were obtained, as shown in figure

　　2.3.2~2.3.4. When the packing thickness is reduced to 65mm, the vibration velocity of particles in the horizontal and vertical direction is reduced by more than 50%, which directly cause horizontal displacement of material movement decreased obviously. The increase of horizontal vibration amplitude makes the arrangement between the material layer and the layer become loose. Although the amplitude of the vibration in the vertical direction has been reduced, it will eventually lead to the aggregation of particles in the vertical direction, and also reduce the horizontal displacement.

　　h=65mm h=65mm

　　h=100mm h=100mm

　　Fig. 2.3.2 Horizontal velocity of particles Fig. 2.3.3 Vertical velocity of particles

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　　Fig 2.3.4 Particle velocity change curve

　　Conclusions

　　As a byproduct of industrial production, metallurgical slag has high recovery value. After the dry granulation, residual heat can be recovered by using waste heat boiler. In order to transfer the medium and high temperature particles more economically and reasonably, the vibrating conveyor with circulating cooling water is used. In this paper, the vibration transfer experiments of glass beads under different conditions were carried out. Draw the following conclusions:

　　1. In the process of vibration transmission, the horizontal movement is the main movement of

　　the material. The average velocity of particle vibration is mainly related to the vibration frequency, with the increase of frequency, the vibration velocity in the horizontal direction is increasing, but the vibration velocity in the vertical direction is almost no change. At the same time, the increase of vibration frequency can increase the amplitude of vibration velocity in two directions, the change of the vibration velocity in the horizontal direction can meet the different transportation demand, while the increase of the amplitude strengthens the relative flow of the material, which is helpful for cooling and heat recovery.

　　2. The particle diameter is also one of the factors that affect the movement of the material, but

　　the change of the diameter mainly affects the amplitude of the particle vibration velocity, which has little effect on the mean of the particle vibration velocity.

　　3. The increase of the thickness of the material to a certain extent is also conducive to the

　　optimization of the transport process, the larger stacking thickness can not only improve the vibration velocity in two directions, but also can reduce the amplitude of the horizontal vibration velocity, and prevent the accumulation of the material layer from being loose, which simultaneously improve the conveying efficiency. However, the increase of thickness means the increase of the conveying quality, but the exciting force of the vibrating motor is limited. So only the better vibration parameters and material parameters can be chosen to maximize the efficiency of the vibration conveyor, and also to obtain the objective value of waste heat recovery.

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　　References

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