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    Home > Active Ingredient News > Drugs Articles > Discussion on the application of horizontal centrifuge in alumina sintering process

    Discussion on the application of horizontal centrifuge in alumina sintering process

    • Last Update: 2009-12-08
    • Source: Internet
    • Author: User
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    The Graduate School of Central South University, Changsha 410083, Hunan; 2 Shandong Aluminum Industry Co., Ltd., Shandong Zibo 255052 [Abstract] introduces the structure and working principle of lw350 × 1550ny centrifuge, as well as the test results and discussion of its application in the production of alumina by sintering [Key words] centrifuge; alumina; rapid separation [Chinese classification No.] TH311 [document identification code] B [Article No.] 1003-8884 (2005) 04-0006-04 in the design of ordinary horizontal screw centrifuge, in order to ensure the slag conveying, the half angles of all cones in the slag conveying section should be within a certain range, However, there is a cone angle change point (as shown in Figure 1) near the liquid level below the liquid level of the double cone angle horizontal screw centrifuge, which makes the sediment stably move on the gentle slope after being output to the liquid pool However, the large cone angle is adopted under the liquid pool because the centrifugal force in the liquid pool is small, so the reflux force is naturally small, so the sediment reflux phenomenon is also very small [1] Because of the large cone angle of the * cone section, the axial distance of the * cone section becomes shorter When the total length of the centrifuge remains the same, the second cone section correspondingly becomes longer Therefore, the liquid pool depth of the horizontal spiral centrifuge with double cone angle can be properly increased without shortening the drying distance of the drum At the same time, the settlement area of the drum increases with the increase of the depth of the liquid pool According to the production capacity is proportional to the settlement speed and the settlement area, and the gravity settlement speed is constant, so the production capacity of the double cone angle horizontal screw centrifuge increases Because the double cone structure can not only ensure the smooth transportation of sediment, but also has higher production capacity than the traditional structure of single cone, the structure of domestic large horizontal screw centrifuge is improved However, the centrifuge drum is a high-speed rotating part, which has relatively high requirements for strength, and the deformation cannot be too large [2] Therefore, it is necessary to check the strength and rigidity of the improved double cone angle drum to prevent accidents In the strength standards of centrifuges in various countries, only the membrane stress of the drum is given [3], but not the detailed stress of the whole drum Therefore, the finite element method is recommended to calculate the stress of the drum in the strength standards of centrifuges in China [4] In this paper, ANSYS software is used to calculate and analyze the stress and deformation of the double cone angle drum of the 1200 mm horizontal screw centrifuge 1 The establishment of the finite element model 1 1 The geometric model of the finite element Because the structure of the drum is axisymmetric, the load (centrifugal force, material reaction force) and constraints are also axisymmetric, so on the basis of not reducing the calculation accuracy, the axisymmetric model of the drum is simplified as a 2D model In this analysis, 4-node axisymmetric element plane42 is adopted The specific finite element model is shown in Figure 2 The inner diameter of drum is 1.2m, the wall thickness is 0.22m, the large cone angle is 15 °, the small cone angle is 8 °, the total number of elements is 1044, and the total number of nodes is 1285 The load and restraint of 1.2 drum 1) the load drum is mainly subjected to the following two kinds of loads in the working process [2] ① the centrifugal force caused by the mass of the drum itself under high-speed rotation, the centrifugal force generated by the mass of the drum body metal itself is applied to the finite element model of the drum in the form of angular velocity ω in the analysis The centrifugal pressure of the material is the pressure formed by the radial movement of the material under the action of the centrifugal force on the drum wall, and the direction is perpendicular to the inner surface of the drum The centrifugal pressure produced by the fluid material in the cylinder under high-speed rotation is, where ρ C is the density of the material in the cylinder, 1085kg / m3; R is the radius at any place in the fluid material layer, m; R0 is the free surface radius of the fluid when the cylinder rotates, 0 525M It can be seen from formula (1) that the centrifugal pressure generated by the material layer changes with the radius, and its value is equal on the same radius, and its value Zui is large on the cylinder wall, that is to say, the material pressure at any radius of the cone section cylinder wall and the large end cover of the drum is also calculated by formula (1), and the direction is perpendicular to the inner surface of the acting area Strictly speaking, the drum should also have its own weight, but because the drum has a very high separation factor, that is, the centrifugal force on the drum is far greater than its own gravity, so the influence of the self weight on the strength and rigidity of the drum is ignored 2) the restraint of the drum is determined according to the specific structure Because the finite element model of the drum is axisymmetric, a symmetrical constraint is applied on the center line of the big and small end covers of the drum, that is, UX and UZ are constrained, and then uy is constrained at a point outside the center line of the big end covers of the drum, Zui 2 Finite element calculation and analysis the static analysis of double cone angle drum is mainly to investigate its strength and rigidity, that is, under a certain working load, to investigate whether it has enough strength and small radial and axial deformation The radial and axial deformation of the double cone angle drum during operation is shown in Fig 3 and Fig 4 It can be seen from Fig 3 and Fig 4 that the large radial displacement of the double cone angle drum is 0 118mm, and the large axial displacement of the drum is - 0 141mm Obviously, the Zui large axial displacement and Zui large radial displacement of the drum are very small, which meet the stiffness requirements In this analysis, stress intensity Sint is used to describe the stress state of the drum, and is compared with the design stress intensity sm of the material The drum material is 0Cr19Ni9, and its design stress intensity is SM = 137mpa When checking, for the average stress intensity along the wall thickness direction, the allowable value is taken as twice of the design stress intensity, that is SM; for the Zui large stress intensity along the wall thickness direction, because it contains the bending stress part with less harm, the allowable value is taken as 1.5 times of the design stress intensity, that is, 1.5sm [5] It can be seen from Fig 5 that the stress level on the double cone angle drum is relatively low, and the maximum value of Zui on the drum is only 72.9mpa, while the maximum stress intensity of Zui on the drum is 109mpa, which appears at a point outside the center line of Zui on the big end cover of the drum This is different from the single cone angle drum, the Zui large stress of single cone angle drum appears on the cylinder, and its value is only 39Mpa (see Fig 6 cloud chart of stress intensity distribution of single cone angle drum) It can be seen that the stress state of single cone angle drum is better than that of double cone angle drum However, due to the fact that the Zui large stress intensity of the double cone angle drum is also less than the allowable stress of the material 1.5sm, the strength of the double cone angle drum is safe The Zui dangerous point of the double cone angle drum is not on the cylinder but on the outside of the center line of the large end cover This is because the large cone angle has a large number of degrees When the material reaction acts on the * cone section, a large bending moment will be generated at the center line of the large end of the drum, which makes the stress Zui large Therefore, the selection of the material and thickness should be fully considered in the design In order to further study the stress distribution of two special sections along the wall thickness direction of the drum, that is, the stress distribution of the sintzui large value section and the transition section of the drum cone, the following path operation is carried out Path 1: cone transition section, node491 → node591; path 2: Zui value section, node1 → node70, path operation location is shown in Figure 7 Fig 8 and Fig 9 show the change rule of stress intensity of membrane, MEM + bend and total along path 1 and path 2, and M represents displacement It can be seen from Fig 8 and Fig 9 that the membrane stress of path 1 is 3578mpa, and that of path 2 is 5985mpa, both of which are smaller than the allowable stress sm of the material It is also found that the large stress intensity (SMX) of Zui only appears on the straight section cylinder under the action of centrifugal force, and the value is 30 1MPa The value at this point is 11.9mpa only under the reaction of material, which indicates that the stress of drum is mainly caused by centrifugal force Conclusion: a reasonable two-dimensional finite element model of biconical angle drum is established in this paper The strength and rigidity of the drum under normal working condition are checked, and the improved structure is proved to be safe It is found that the dangerous position of the double cone angle drum is the outside of the center line of the large end cover, where there is a high bending stress, so the selection of the material and thickness should be fully considered in the design
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