Kinetic Research For Reduction Of High Phosphorus Iron Ore Based On Thermal Analysis And Time Series Analysis

The resources of high-phosphorus iron ore are very abundant in Yunnan Province, the reserves such as the Huimin, Luoci iron ore, etc. have over2billion tons. Because of high phosphorus content, it is difficultly to be employed with large scale by the iron making industry. The Huimin iron ore is one kind of high phosphorus and Limonite, due to its some embedded features, such as rich crystallization water, the small proportion, and the weak magnetic flotability, the iron grade of ore is difficult to be improved by physical beneficiation approaches. The development of the traditional blast furnace iron production is recently constrained by resources and environmental protection consideration, in the meanwhile, our country not only has to continue to refine and improve iron making process of blast furnace, but also should moderately develop the technology of direct reduction and smelting reduction, particularly for the technology of non-blast furnace iron making focusing on taking iron ore fines or pink-coal as raw material directly. In order to reveal the kinetic behaviors and heat and mass transfer law for reduction of high-phosphorus iron ore fines, the combination methods of mathematical modeling and experimental are employed to study the kinetic behaviors in reduction process of the Huimin iron ore with the ordinary coal at high temperature. The thermal analysis and time series analysis approaches are applied to stage modeling, feature extraction slag and investigation of the behavior of heat and mass transfer process for reduction process non-equilibrium. From experimental verification of the analysis and testing technology, it can provide the theoretical application of Hismelt smelting reduction for Kunming Iron and Steel company.In this paper, the weight loss method is used to the kinetic process for coal reduction of the Huimin high phosphorus iron ore fines with the conditions from40℃to1400℃. Firstly, the TG-DSC curve of smelting reduction process is obtain by the iron ore experiment of Huimin reduction in TGA, and the change or peak of the curve characteristics is then used to explore the chemical reaction rule of various stages in the process of smelting reduction. The whole process is divided into six stages or segments:(1) crystalline water removal stage;(2) hematite pre-reduction stage;(3) melting transition phase;(4) Fe2O3complete conversion segment;(5) Fe3O4transformed to FeO phase;(6) FeO transformed to Fe phase. Secondly, the integration method of the Thermal analysis is employed to build the apparent kinetic model of the main stage from experience mechanism model, including the calculation of the kinetic parameters such as the apparent activation energy, frequency factor and infer the most probable mechanism function (E, A,f(α)). It is found the fact that as the temperature rises, the apparent activation energy of the key stage shows the increasing trend, in the other words, the reaction has the descending order. The longitudinal compensation effect analysis shows that the interdependence and synergy between E and lgA change significantly, the degree of difficulty and the probability of collision with each other significantly affect for all kinds of reaction during the reduction process. The apparent activation energy is got by the derivation and numerical fitting with the distribution function of the temperature and heating rate as follow:as the fitting function curve appears right tailling, the activation energy presents the sparse distribution and fast changes in the high-temperature section, the need is consistent with for energy supply in smelting reduction. After fitting process, the frequency factor expression of the reduction process can be obtained, the inflection point of the curve reveals the number of collisions between the activation of molecular significantly increase during the process in the molten state, it is helpful reduction.The apparent reaction rate (DTG data) of physical quantities in the system is extracted, and it can reflect the whole reduction process and details for comprehensive consideration. The physical quantity can not only reflect the dynamic behavior of the smelting system, but also can reflect the behavior for process of heat and mass transfer. The specific contents are as follows.(1) the phase reconstruction technique of dynamical systems theory is employed to reconstruction analysis, the evolution of the characteristics of the apparent reaction rate reveals the dynamic behavior in the smelting reduction process, the results show that the dynamic behavior of the sequence of a first-order time delay and two-dimensional embedding was accurate for system. it is found that the complex uncertainty smelting system which belongs to the random discrete dynamical system has the chaotic attractor structure, and the structure shows the graphic feature of double ’∞’ it is so-called iron reduction attractor. The points inside ’∞’ within the curve of double ’∞’ characterize that the smelting reduction system comes into the stage of interfacial chemical reaction control; it can be inferred that points outside ’∞’ characterize the system comes into the stage of diffusion-controlled while the points are scattered around the curve characterized the stage of the mixed control. The recurrence plot of DTG sequence, Poincare section, the calculation of the correlation dimension and the largest Lyapunov index calculation process all show that reduction of Huimin iron ore is provided with weak chaos, and the behavior is caused by the reduction of iron, so we determine the chaotic behavior as useful process, strengthen contribute to the smelting.(2) The iron reduction attractor is different from the Lorenz system, Rossler system and logistic map system, and the chaotic behavior is completely different from them, then the equation can not refer to the type. The universal equation calculation results show that there are many factors influencing the DTG, it is difficult to apply the usual differential equations to solve. Thus the predictive modeling methods in the analysis of time series is employed, the locally weighted linear prediction perfonnance reflects the reaction within the system appear the short-range correlation (local) as well as the differences of primary and secondary (weighted), In further the EMD-wAR model can accurately express the frequency distribution characteristics of the energy transfer process (EMD), also reflects that there is the short-range correlation (AR) as well as primary and secondary difference in nature (golded weighted) within the reaction system, the EMD-wAR declined an order of magnitude error than the locally weighted, the establishment of the EMD-wAR-CPSO-SVR model made errors again declined an order of magnitude, the expression of DTG is more accurate, so that it is helpful the establishment of the attractor equation in the reduction process.(3)The power spectral analysis was employed to the DTG signal and it is found the frequency concentrated in the low during energy transfermamtion of the reduction process for pure iron oxide, the ore reduction process is concentrated in the middle and high frequency. It can be appropriate to strengthen heating method in the process of smelting furnace, it will also help in the strengthening of the smelting process.Finally, the reduction experiment with key temperature ranges of high phosphorus iron ore by vertical electric stove were carried out, the reaction process and kinetic behavior characteristics were speculated through the phase morphology changes of various stages in slag, so as to verify the characteristics of the redcution process.