Research On Structures And Kinetic Parameters Of Charging Test System For Rotary Hearth Furnaces

According to the direct reduction process to produce sponge irons of high quality by rotary hearth furnace (RHF), pellets containing carbon should be charged evenly onto a flat annulus rotary hearth in order to make temperature gradient and reduction rate within reasonable ranges. Zhongye Changtian International Engineering Company designed a new vibrating feeder for rotary hearth furnace, and its performance should be verified by test. As a result of limits of test site, fees and so on, a charging modal test have to be done on a small engineering test platform, and the test results reverse to the prototype by similitude criteria. In this paper, the main research contents and research results are as follows:(1)The article analyzes the industrial rotary hearth furnace prototype and the charging process, applies the similitude theory to devise similitude criteria that the charging test system and the prototype must satisfy based on key parameters.(2) Based on the industrial rotary hearth furnace prototype and the similitude criteria, structure gallery and motion parameters’control are proposed. According to the key geometric dimensions, the modals of rotary hearth furnace and vibrating feeder are designed by1/3of their prototypes. The rotary hearth furnace modal is driven by a motor at its center and the speed can be control independently. The amplitude of vibrating feeder can be changed by exciting force. A star charge valve whose flow can be control is also designed.(3) The Finite element model of rotary hearth furnace is established in the software ANSYS. Then, the modal is solved to obtain reaction forces based on analysis of deformation, so its driving power can be computed by the analysis results. At the same time, the cases are analyzed when the rotary hearth furnace runs under the conditions of different weights in bob-weight box. The results show that the structure of rotary hearth furnace satisfies the strength and stiffness; the maximum equivalent stress and strains appeared at shaft hole of the arm, and the maximum sum displacements appeared at the outsides of rotary hearth ends. The maximum equivalent stress at the shaft hole can be greatly reduced when a reasonable value of the bob-weight is used.(4) Three kinetic parameters need control independently in the charging test. They are amplitude of vibrating feeder, rotate speeds of star charge valve and rotary hearth modal. The amplitude can be change by adjusting the exciting force, so analyzing their relationship is useful for the charging test. The other two parameters are control by U/f frequency conversion, and their characteristics must be researched when stator voltages are compensated or not. The results show that, the starting torques of the two motors fell when no stator voltage compensation; but their starting torques between frequency conversation and base frequency have few differences.(5)The true rotary speeds of star charge valve and rotary hearth furnace are tested, and the strains at6points are obtained by electric test. Comparing the test results and the simulation results, the difference between the test and the simulation is very small. It shows the finite element model of rotary hearth furnace structure is right.