Research On Fundamental And Technology Of Heat-Homogenizing Sintering Of Iron Ores

With the rapid development of Chinese steel industry, the total energy consumption of the steel industry continues to rise. In the system of whole steel production, energy consumption of sintering process accounts for15%of the total energy consumption of steel production. It has a great significance to study basic theory and new technology of reducing the energy consumption of sintering process for reducing the comprehensive energy consumption of steel production, saving the cost of production and improving the competitiveness of enterprises.The consumption of solid fuel accounts for75%-80%of the energy consumption of sintering process. Taking the iron raw materials and fuel from Baosteel and sintering process as research objects in this thesis, the law of the accumulation of heat in sinter layer is revealed through the study of gas kinetics and heat transfer. The new technologies of segregation feeding and airflow feeding which realize the heat-homogenizing sintering by the heat of accumulation are developed, reducing fuel consumption significantly. Particularly, the technology of heat-homogenizing sintering of airflow feeding has been applied into industrial production in Baosteel.From the study of the accumulation of heat, it can be found that the amount of accumulated heat increases from top to bottom in the material layer during sintering. If the sinter layer with height of700mm is averagely divided into seven units, the total ratios of accumulation of heat from the second to seventh layer are40.37%.54.07%.61.39%.66.60%.70.30%,72.99%successively.Due to the different heat states of each unit from top to bottom when the sinter cakes leave the sinter machine, it is hard to ascertain the reasonable distribution of fuel for the material layers according to the total accumulation of heat, so the concept of available accumulation of heat is first put forward in this study. The available accumulation of heat is the surplus amount of accumulated heat after deducting the physical heat taken away by the sinter cake, and it is the basis of heat-homogenizing sintering by accumulating heat. Through the study of heat state of every unit and calculation of physic heat, the available accumulations of heat from the second to the seventh unit are38.18%、50.80%.56.84%.60.33%.60.92%.58.39%successively, and therefore the reliable basis is provided for the development of new heat-homogenizing sintering.On the basis of theory study, the heat-homogenizing sintering technology of distribution feeding is developed firstly. Taking the advantage of distribution feeding, the solid fuel consumption can be reduced significantly on the premise of guaranteeing the output and quality of agglomerate. The results of sintering experiment show that if the mixed material is divided into three layers and the dosage of coke breeze of the upper layer is4.9%, middle layer is4.3%, lower layer is3.3%and the average amount is4.2%, the quality indicators of agglomerate will be as follows:the drum strength of agglomerate62.13%, the yield80.02%, the utilization coefficient1.85t/(m2-h), and solid fuel consumption53.85kg/t-s. The solid fuel consumption of heat-homogenizing sintering is3.69kg/t-s less than the ordinary sintering.Taking into the consideration that the production application of distribution feeding is limited by the plant layout, the heat-homogenizing sintering technology of airflow feeding is further researched and developed in this thesis.Through the study of motion character of sinter mixture in the gas flow field, the diversities of motion trails among different particles are found out and the basic theory on segregation of particle size and fuel is established. Combining with the present sintering process, the test device of airflow feeding is designed and manufactured in the laboratory. The influence of airflow speed, nozzle structure, injection position and angel on the distribution of fuel and particle size of mixture is found out by making use of this feeding device and the optimized parameters of segregation feeding process are obtained. The new heat-homogenizing sintering technology of airflow feeding to realize the segregation of particle size and fuel distribution is developed.Taking the raw material from Baosteel as research object, the fuel proportion of mixture can be reduced by8.7%(from4.6%to4.2%) in the laboratorial sintering experiment by adopting the sintering technology of airflow feeding. In addition, the yield of agglomerate is improved from73.26%to78.26%and the utilization coefficient is raised from1.40t·(m2·h)-1to1.46t·(m2·h)-1.The results of experiments show that efficient utilization of the accumulated heat of sinter layers can be realized by the sintering technology of airflow feeding, so not only the consumption of solid fuel is significantly reduced, but also the output and quality of sinter product are both raised obviously. The new method and technology are provided in this thesis. The heat-homogenizing sintering technology of airflow feeding has been applied into industry in sintering plant of Baosteel, and the benefit of602.85million yuan can be achieved by single sintering machine every year.