| With the rapid development of economy, the trend of the depletion of petroleum has brought a serious challenge for the chemical energy industry, which based on the petrochemical. At the same time, for the protection of the ecological environment, it is necessary to develop and utilize clean energy. Therefore, quickening the development of natural gas industry is an effective way to abate the lack of petroleum resource in China, and in the future it will occupy an important position in the chemical energy development pattern. For the chemical enterprises of natural gas, they need the production process flexibility to maintain the competitiveness in the market. Also, modern chemical process system engineering requires the environmental friendly of products during their whole life cycle. Nowadays, environmental performance will not be treated as a constraint condition, but looked as an objective function, which parallels with the economic performance. This pays a stricter requirement to the exploitation and usage of natural gas resource, the selection of products, and the design of process. In this dissertation, the life cycle cost analysis (LCCA) is studied in terms of concept, methodology, and application, then, the method of systematic analysis and the framework of systematic design of chemical energy products of natural gas are put forward.Based on the comparison and analysis of the different researchers'knowledge about environmental cost, the concept of environmental cost is re-defined again. Against the characteristics of chemical production, using the idea of life cycle, the concept and model of life cycle cost are brought forward. In this dissertation, the new assessment index and the framwork of LCCA are built, which perfect the theory and methodology of LCCA. In regard to the estimation of life cycle external cost, combining with the method of result-reference, the estimation model of environmental cost of per unit pollutant is built by using least-squares method.Based on the analysis of the trend of energy in China and the relationship between energy usage and environmental impact, using life cycle cost analysis, the framework of LCCA of energy usage is proposed, through comprehensive and objective comparison of environmental and economic performance of energy utilization in each phase. Taking natural gas power generation and coal-based power plant as case objects, the environmental benefit of the former is discussed and the ways to improving the life cycle performance of the latter are pointed out through comparing their respective life cycle cost.In view of the current environmental issues and natural gas chemical industry business conditions, in order to enhance the marketing competitiveness, the idea of extension of natural gas chemical product chain is conceived. Then, starting from the analysis of the economic and environmental performance of product chain, an analysis model of product chain is created. The proposed methodology is applied to evaluate three pieces of assumed product chain, which take acetylene as the core, and the factors, which affect the integrated performance of product chain, are discussed. Then, the thinking of life cycle design is adopted in the design of product chain and the framework of life cycle design of natural gas chemical product chain is constructed.With the deepening of the thinking of sustainable development, poly-generation system of chemical products, electricity, and clean fuel, etc, got a widely attention. At the end of this dissertation, a novel natural gas polygeneration system for olefin and power production is proposed, which achieves the organic coupling of hydrocarbon system and combined cycle power generation system. Through Aspen Plus simulation and thermodynamic analysis, exergy destruction biggest segment, its causes, and measures for improvement are distinguished. To invest the influence of unreaction syngas recycle on the exergy efficiency and profit of polygeneration, its thermoeconomic optimization model is built by combining economic with thermodynamic analysis.
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