Research On Energy Efficiency Assessment Method Of Iron And Steel Production Process Based On Exergy Analysis

Energy is the survival and development base for human society, and is of an important status in development of national economy. The energy consumption of the iron and steel industry is very huge, and accounts for about15%of the country’s total energy consumption. On one hand, it is because iron and steel industry is energy-intensive industry itself. On the other hand, our country has very big iron and steel production, accounting for about half of the world’s total production, but domestic production technology levels are spotty, resulting in very serious waste of energy. Therefore, the energy-saving of iron and steel production process (IASPP) has always been focused on. The energy efficiency assessment of the IASPP is the basis of energy conservation. Comprehensive, correct and feasible assessment results can scientifically display energy use structure, explain energy loss reasons, and provide ideas and theoretical basis for the further tapping of energy saving potential. For engineering application, exergy analysis method can not only analyze the process inside the system, but also can reflect the interactions between the energy flow and the material flow of the system and the external system, as well as the state of the environment (temperature, pressure, etc.). Therefore, this study chooses exergy analysis method as the basic theory of energy efficiency, using exergy efficiency to comprehensively measure the energy efficiency of the IASPP.Iron and steel enterprise’s production line is very long and complex, which bring great difficulty for the energy efficiency assessment of the whole IASPP. For this reason, this paper conducts an in-depth analysis on the IASPP, and based on witch, divides the IASPP into two kinds of processes, manufacturing process (MP) and connection part between manufacturing processes (CPBMP). So it decomposes the energy efficiency assessment of the whole IASPP into the energy efficiency assessment of MP and CPBMP respectively. After that, this paper discusses the delimitation method of the energy-using boundary. The energy-using boundary is found by a four-step procedure of determining the study object, designating the production related equipment, establishing materials within the energy-using boundary, and delineating the energy boundary.In order to assess the energy efficiency of MP, this paper establishes an MP model based on exergy analysis, partitions all the MP related exergy flows into materials exergy input, energy exergy input, production exergy output, internal exergy loss, external exergy loss and exergy recovery, and then elaborates the energy range and exergy value calculation methods of each part. After that, taking the steel-making process of a certain iron and steel enterprise as an example, the study calculates the exergy efficiency of the steel-making process by using the MP model. The analysis of the result shows the energy structure of this steel-making process and points out the methods to improve exergy efficiency from the perspective of energy quality.In order to assess the energy efficiency of the CPBMP, this paper establishes a CPBMP model based on exergy analysis, partitions all the CPBMP related exergy flows into production exergy input, energy exergy input, raw material exergy output, internal exergy loss, external exergy loss and exergy recovery, and then elaborates the energy range and exergy value calculation methods of each part. At last, taking the connection part between iron-making process and steel-making process in a certain iron and steel enterprise as an example, the study calculates the exergy efficiency by using the CPBMP model. The analysis of the result reveals the root cause of energy loss of the CPBMP from the perspective of energy quality.