Life Cycle Assessment On Iron And Steel Processes

Life cycle assessment is a powerful tool in the evaluation of the environmental impact of manufacturing processes and environmental management. However, there hasn't been a methodology that can be widely accepted. On the basis of the life cycle approach in combination with iron and steel processes, the purpose of the study and the system boundaries are defined and the indexes for life cycle assessment of iron & steel processes are set up. The life cycle inventory of resources and energy uses and environmental releases are complied. The integrated index of environmental impact is defined and an integrated comparative model is established. The indexes are compared with each other for several production routes of iron & steel process. The results of the life cycle assessment are analyzed and the improvement countermeasures are given for iron & steel process. In this paper, the resource consumptions and environmental conditions in the steel industry have been discussed in detail. As a large amount of natural resources and energy is consumed in steel-making and a great many pollutants are generated, pollution problems resulting from steel-making stand out. It is also pointed out that it is necessary to reduce the quantity of waste generation and emission by improving the raw material and energy structure, and reinforcing the waste control and management. Furthermore, the total emissions of waste gas, wastewater and waste solid are forecast during the next decade. Up to now the standard and control model for environmental discharge of iron & steel production have not been set up in China. According to the characteristics of complex system and the requirement of environmental assessment, a gray model for integrated assessment is introduced in this paper. It is important and beneficial for the set up of classification and the control standard of waste-discharge per ton steel for Chinese steel industry. The correspondence analysis is one of the methods in statistics. With this method, the environmental factors are analyzed for key iron & steel companies in the present thesis. The co-relativities among environmental factors and the classification of iron & steel Co. can be reasonably obtained. At the same time, it is clarified that each steel Co. is affected and controlled by different crucial factors. Based on the characteristics of the iron and steel processes in China, Integrated relative environmental index (IREI) is defined and a new accumulative comparative model for life cycle assessment is established, which is applied to the assessment of several typical iron and steel processes, such as DRI/EAF process and BF/BOF process. In addition, the concepts of dynamic correlated weighting and statistical correlated weighting are defined. It is shown that the results from this method could be quantitatively compared with each other. The case studies show that the environmental performance of the DRI/EAF process is superior to that of the BF/BOF process. Furthermore, the production of EAF-steel made from scraps has obviously more environmental advantages than that of BF/BOF process. After Tokyo greenhouse prevention conference (COP3 )a lot of countries and governments are struggling to reduce CO2 emissions. From the viewpoint of LCA, the life cycle inventories of CO2 emissions for several flows of iron and steel making are studied, and the results are shown as follows: the accumulative CO2 emissions per ton DRI are more than those of BF-iron and molting reduction iron; the accumulative CO2 emissions per ton crude steel for BF/BOF process are more than those of DRI/EAF process and EAF process; the CO2 emissions concentrate on the processes before iron-making, therefore how to reduce energy consumption before iron-making is the key to reducing CO2 emissions. From the viewpoint of sustainable development, the optimization to product structure and the complete manufacturing process, which is environment friendly, will be one of the strategic goals in Chinese steel industry. A whole procedure of cleaner production is the main measure for "Green manufacture". The paper presents the results of environmental impact assessment on cleaner production of iron and steel processes, and moreover the model of fuzzy multiple criteria decision for environmental impact improvement. It provides the reference for improving assessment. With the economic benefits as optimal goal and environmental impact as constraints, optimal programming for structure of iron & steel products is performed. Based on combining the environmental impact assessment with integrated economic benefits, it helps to apply the results of environmental impact assessment to the practical use. According to the methods of ISO14040 and《ECO-indicator 99 methodology report》, the damages to mineral and fossil resources, to ecosystem quality, and to human health of Chinese steel industry are discussed in this thesis. The results show that these damages have decreased obviously since 1990. In terms of the relationship of mineral resource consumption, energy consumption, environmental performance and technical economy for Chinese steel industry, the assessment index and its index system for sustainable development are presented. The results show that the efficiency of resources-economy, environmental-economy and sustainable development are non-steadily increasing. In the end, conclusions of the thesis and further clues for research are given.