| The modern iron & steel joint enterprise is a complicated iron-coal chemical system, and the steel production process is, in essence, the dynamic operation of the material flow under the drive and effect from energy flow following the definite rules. Analysis on the influencing factors of the energy intensity of Bao Steel, An Steel and Shouqin metal material company indicates that the research on material flow, energy flow and the relationship between them will benefit the construction of a resource saving and environment-friendly enterprise. Based on the theory of Metallurgical process Engineering and methodology of Systems Energy Conversion, the physical essence of the steel production process is reobserved, and the steel production system is decomposed into two parts:materials transformation process and energy transformation process. The operating behavior and effectiveness of material flow and energy flow and the interacting mechanism between them are analyzed in order to find out the new direction of energy conservation in an iron and steel enterprise. The main contents of this paper are as follows:1. The material flow is formed when the material runs along its life cycle trace in an enterprise. Based on the 5 material flows including those from the anterior producing unit or process and those recycled through a unit or process, the material-flow diagrams for a production unit, a process and a production flow are constructed, the material input-output model is established; the influence that the material flow of a process has on the metal yield ratio is described, and so is the influence of the parameters on the resource efficiency of a production flow and the product ratios of each process. It is indicated that the main approach to increase the metal yield ratio is to reduce the defective index; the measure to improve the resource efficiency is to reduce the defective index of the flow sheet, increase the recycle rate and the material flow from out of the flow sheet per product; the path to reduce the product ratios of each process is to increase the material flow from out of the upstream processes, reduce the discharged material flow from the downstream processes, and reduce the recycled material flow.The network of flow sheet in a steel mill is classified into two sorts:connection in series & series and parallel, and the parameter of time increasing and that of channel blocking are introduced in to discuss the influence of the disturbance of cross flow and the block of channel on the time cycle and the extent of serialization of material running. Thus, the optimizing principle of the network of flow sheet is put forward:reducing the material stream, realizing the one-one corresponding relationship between the units of the processes, so as to shorten the time for transportation and waiting. Furthermore, this method is used to analyze the material flow in the typical enterprises.2. The energy flow is formed when the energy runs along the route of conversion, usage, recovery and emission. The energy flow through an energy conversion unit or a process, such as the converted energy and the energy of the product, is discomposed into 6 parts, and the energy-flow diagrams for a conversion unit, a process, and a network are designed and energy input-output model established. The influence that the flux of each energy flow, the largening extent of equipments and the recovery of residual heat (or energy) have on the energy value of the product is analyzed. The influence that the weight factor of each conversion mode, the amount of the units, the efficiency of each unit and that of energy transportation have on the energy value of final product is discussed. It is indicated that there are two methods to reduce the energy value of an energy product:largening the related equipments, adopting the advanced energy conversion modes, and recovering the residual heat and energy rationally and in the certain order. For an energy conversion network, some measure must be taken to improve the conversion efficiency and reduce the energy value of an energy product. They are: increasing the weight factors of the energy conversion modes whose efficiency is higher; reducing the amount of the conversion units, optimizing the transportation mode of energy, and shortening the distance of transportation. This method is used to analyze the energy flow in the typical enterprises, especially the influence that the conversion network has on the conversion efficiency of off-gases and the energy value of electricity.3. Material flow and energy flow cooperate with each other on a steel production process: the energy flow drive the material flow to transform, and surplus energy moves to the next steel production process or departs from the material flow to form an independent conversion network. Some measure can be used to enhance the synergetic effect between material flow and energy flow, so as to reduce the energy intensity of the processes concerned:recovering much more residual heat and energy, bringing much more energy carried by the process to the next process. Measures to reduce energy consumption per ton steel of an enterprise based on the optimization of running mode of the two sorts of flows are indicated:â‘ increasing the large extent of equipment in a process, reducing the density of the flow between the processes, reducing the channel block, therefore optimizing the interface between the processes, strengthening the hot linkup between the processes and utilizing the energy carried by the material flow farthest;â‘¡optimizing the energy conversion network, and decreasing the energy value of the main energy product;â‘¢recovering the residual heat and energy rationally and in the definite order, so as to reuse the surplus energy out of the steel production process farthest.4. Several important issues concerned with material flow and energy flow in an iron and steel enterprise, including the interface between the processes, generating electricity with residual off gases, and recovery of residual heat are discussed by the analyzing method concerned with material flow and energy flow. The temperature predicting models of hot iron between BF and BOF and billet steel between Conticaster and Mill are constructed, and the models are used to analyze the influence of interface mode and running time of material flow on the temperature fall of hot iron and billet steel, so that the optimal interface is put forward. Why the off gases are surplus is discussed, and the method of calculating the quantity of residual off gases based on the flux per hour is put forward; the electricity generating modes with residual gases are analyzed. Based on this, the optimizing principle of generating electricity with residual gases is indicated. Furthermore, the energy saving effectiveness of co-generation of heat and electricity is discussed, the viewpoint "using all the residual gases to generating electricity" is disproved, and the viewpoint "Buying only coal and no electricity" is proved. The recovery of residual heat and energy in China steel industry is summed up, base on which, the limitations of heat balance analysis, exergy analysis, energy level analysis and related efficiency indicators are discussed; exergy efficiency and variation of energy consumption per ton product have been used as the evaluating indicators to analyze the current technologies for recovery of typical residual-heat in steel industry, and the reasonable mode of residual-heat recovery and its energy saving effect are indicated.5. For a large-sized joint enterprise, An Steel, which produces all sorts of products with complicated network of flow sheet and a medium and small-sized enterprise, Shouqin, which produces special product with simple network of flow sheet, the analyzing method of material flow and energy flow is applied to discuss the influence of the running mode of material flow and energy flow on the energy intensity of the two enterprise. It is indicated that the time cycle of material flow running in the network of flow sheets in An Steel is longer, the serialization extent is lower, and the efficiency of energy flow running is lower, too. This results in the much higher energy intensity of An Steel. At the same time, the lower efficiency of energy flow running is the main reason that results in the higher energy intensity of Shouqin. It is also indicated that energy intensity of the joint enterprise, An Steel, can be reduced to 670kgce/t, and that of the medium and small-sized enterprise, Shouqin,640kgce/t if taking some optimization measure concerned with material flow and energy flow.
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