Heat Flow Field Analysis Of The Vertical Preheater And The Cooler

The high quality active lime is mainly produced by the active lime rotary kiln. The vertical preheater and cooler which are the main structure of the rotary kiln could not only improve the productivity effect, but also save energy sources and reduce pollution by getting full use of the afterheat of the off gas and the lime. So it has a directive function to improve the design of the rotary kiln by the research of the heat flow fields of the vertical preheater and the cooler.According to the structural features and working principles of the vertical preheater and the cooler belonged to the rotary kiln, the 2-dimention plane finite element model for the section of the preheater with different arrangement or different diameter and the cooler for the limestone grains. The gas-solid two-phase flow mode for the situation between the limestone grains and the hot air in the preheater and the cooler is simulated by the discrete particle model. Based on the heat transfer theory, the convection heat transfer coefficient between the limestone grains and the hot air is deduced with the experimental correlation of the air cross-flow tube bundles. On the simulation calculation of the 2-dimention finite element model of the vertical preheater and the cooler based on the FLOTRAN module of ANSYS, the temperature field, pressure field, velocity field and the temperature rising curves of the limestone grains is obtained. Then the contract and analysis is done after the calculation.The result shows that the main parameter which influences the temperature rising of the limestone is the convection heat transfer coefficient. Changing the arrangement or the diameter of the limestone grains could only improves the effect of the temperature rising a little through the slightly rising of the convection heat transfer coefficient. The convection heat transfer coefficient between the limestone grains which are ordered arranged and the hot air is a little larger than that the arrangement of limestone grains is crossed. The smaller the diameter of the limestone grain is, the larger the gap between the grains is. And the convection heat transfer coefficient is larger; the temperature of the limestone rises more quickly.According to the result mentioned above, the structure of the vertical preheater is changed to three different types: the first one is only the high temperature area being increased; the second one is only the low temperature being decreasing; the last one is the combination of the first two types. The temperature field of the new structural preheater shows that with the changing of the structure, the limestone could be warmed easily. As a result, the heat transfer efficiency of the vertical preheater is improved. The cooling effect of the girder cooler is a little better than that of the vertical cooler. The number of active lime with low temperature could be effectively enlarged by increasing the supply air rate of the girder cooler, but the temperature of the air which is sent to the rotary kiln to burn is lowered.