Research On System Analysis And Optimization Of Boiler Flue Gas Waste Heat Utilization

Currently the total installed capacity of coal-fired power generation unit occupies over 70% of country’s total, and relatively huge heat loss is a common issue when it comes to energy consumption, among which the power plant boiler takes 70%～80% of the major energy loss. Therefore the flue gas waste heat recycling of boiler rear area not only can improve the economic performance of the power plant, also it can reduce the coal consumption rate while realizing environment protection.In recent years, analysis on flue gas waste heat utilization both at home and abroad is digging deeper and deeper, accompanied by more and more utilization methods. Among them, adding a low-temperature economizer at the boiler rear area to use the waste heat to heat the condensed water is the most widely applied method, it is of actual significance to improve the economic performance and the energy conservation of the power plant. Waste heat utilization measures on intermediate and high temperature are relatively mature, and low temperature flue gas waste heat utilization is thus the research hotspot. Compared to other industries, low temperature flue gas waste heat utilization in the power sector is far more advanced, so other high energy consumption industries are in urgent need for effective waste heat utilization method.In this paper, in-depth analysis on the energy-saving potential of the flue gas waste heat in blast furnace gas station boiler is conducted, by comparing various kinds of flue gas waste heat utilization methods and applying the energy cascade utilization principle, as well as combing the heat transfer area optimization, primary optimization idea and system analysis of efficient flue gas waste heat utilization are proposed. With the proposed measures, not only the exhausting flue gas temperature of the blast furnace boiler is reduced, also it lays a firm foundation for the design and optimization of the waste heat utilization in blast furnace gas station boiler.Finally, consulting the thermodynamic and economic benefits brought by the waste heat utilization measures, it is suggested that the appliance of flue gas waste heat utilization system to blast furnace gas station boiler should consider the specific unit parameter, especially the characteristics of the steel plant. In other words, on one hand, the flue gas waste heat retrofitting scheme should be determined in terms of the thermodynamic analysis; on the other hand, its techno-economic performances such as the investment cost, economic benefit should be taken into consideration, so as to further explore the energy-saving potential of the waste heat utilization system.Since various production processes are different, the key issue of waste heat utilization is how to efficiently combine the waste heat resource with the original producing craft. In this paper, by selecting the typical blast furnace gas station boiler in the steel industry as the reference case, its waste heat utilization and power generation engineering design are analyzed and proposed, the research result of this paper may provide valuable ideas for the flue gas waste heat utilization in other industries to some extent.