Study On Power System And Optimization In Integrated Iron And Steel Corporation

Iron and steel industry is not only the basic industry to support national economy and industrialization, but also high energy-consuming industry. As an important energy source next only to coal, electricity including self-generation and purchased is involved in almost all steel-making processes. Iron and steel corporation is centered on pyrotic melting and machining, accompanied a large amount of waste heat, waste energy and by-product gas. How to efficiently recover this part of resources to generate electricity, and improve the proportion of self-generation and the electricity utilization efficiency of equipment, is not only the effective measure to decrease power shortage in iron and steel corporation, but also the important method of energy conservation and generation costs reduction. Based on this background, the paper systematically studies the generation process, consumption characteristics and development process of power system of the long process in iron and steel corporation; and the special input-output model of generating system, the model of power consumption cost of per metric ton steel, and the decision-making platform of power system in iron and steel corporation; meanwhile, combined the generating condition of Ansteel Anshan site with Bayuquan site, the paper proposes concrete measures for optimization of power system and the expected results. The main contents are as follows:(1) According to the characteristics of the long process in most integrated iron and steel corporations in China, the paper analyzes the generation process, consumption characteristics and the development of waste heat, waste energy, surplus gas utilization and coal-fired self-generating power plant in the power system.(2) The paper builds the input-output model fit for the power generation system in the iron and steel corporations, and analyzes the fuel consumption condition, the energy value of power products and the cost of power generating system in Ansteel Anshan site and Bayuquan site in detail. According to energy value of power generation, the paper puts forward the optimum principle of generating electricity for steel companies. According to power generation cost and the purchased electricity price, the paper proposes the best scheme of power consumption:?during the period of power peak or power flat time, in order to decrease purchased electricity, the corporations self-generation system should operate at full load to achieve the biggest ability of power generation.?during the period of power valley time, power generating units by using waste heat and waste energy and surplus gas should operate at full load, the coal-fired plants electricity generation load should be reduced, purchased electricity should be increased.(3) The paper establishes electricity consumption and the cost model of per ton steel power consumption. Comparison has been done to power consumption between Ansteel Anshan site and Bayuquan site, the results shows that:the electricity consumption and cost per ton steel in Ansteel Anshan site are higher than Bayuquan site by 23% and 36.7% respectively, ignoring cold rolling process,7.1% and 20.6% accordingly. From the view on reducing power consumption and the per ton steel cost, the main measures include:? Reducing the power consumption of each process, mainly the rolling, the energy processing and conversion process, as well as sintering process and steel-making process;?Improving the efficiency of equipment electricity consumption, and carrying out equipment energy-saving;?Improving the generation efficiency of waste heat and waste energy and surplus gas resources of the corresponding processes, and the self-generating power.(4) Choosing Ansteel as the representative for China's steel companies, the paper analyzes how power systems in Ansteel change with corporation generation scale, depth of processing and energy generation technologies at past ten years. Based on generation data in 2010, the paper elaborates technological process, technical characteristics and the amount of power changing with the seasons of generating unit of electricity generation system in Ansteel Anshan site and Bayuquan site. Meanwhile, the paper analyzes power consumption system of Ansteel power consumption units, and points out the problems of power system in Ansteel, mainly including:?Seasonal imbalance in power system. As a result of the impact of climate in the north, most of waste heat and waste energy is used for heating during the heating period and power generation systems stop running;?Ansteel has a large gap with the advanced iron and steel corporations in TRT power generation technology, effected by gas temperature, furnace top pressure and gasmenge;?Leakage of blast furnace gas and high calorific value gas consumption;?Generation and consumption of power systems are unbalanced and the strategy of electricity purchasing should be improved.(5) Combined the practical data with decision-making platform for power system in Ansteel Anshan site and Bayuquan site, the paper predicts the self-generating electricity potential of Chinese 15 million tons and 5 million tons integrated iron and steel works. The results show that, no regard to the coal-fired power plant generation electricity, the 15 million tons integrated iron and steel works can afford 91% electricity consumption, at the same time purchasing 9% electricity. The 5 million tons steel works, not only afford the power consumption, but also 2% electricity can be transfered to grid. For 15 million tons integrated iron and steel works, the improvement of one percent of the ratio of coke to steel, iron to steel and LDG recovery could lead to 1.51%,0.99% and 0.09% self-generating increase respectively. That means two measures could be used to recovery more gas and get more electricity:increasing the recovering ratio of LDQ adjusting the ratio of coke to steel and iron to steel according to the price of coke, coal, scrap and pig iron.(6) Based on practical data in Ansteel Anshan sie and Bayuquan site, the paper puts forward to the optimization methods combined with power decision-making platform. Results show that self-generating rate in Ansteel Anshan site can be improved by 5.25% and per ton steel cost of power consumption can be reduced 22 RMB,12% and 35 RMB for Bayuquan site respectively.