| Air pollution in China is typical coal smoke pollution from coal burning; and among the pollutants, dust and acid rain are most harmful. In fact, acid rain is direct result of SO2 pollution. Limestone-gypsum wet flue gas desulfurization (FGD) system is widely used in coal-fired power plant for SO2 removal. With its great environmental benefits, it is also a complex equipment system with high energy consumption. Therefore, saving operation power is of great significance to economic performance improvement of existing FGD system.In a FGD system, booster fan, circulating slurry pump, oxidation fan and limestone wetgrinding are the four major energy consumption devices; and their operation modes will affect the system's desulfurization performance and energy consumption. This paper analyzes the main energy-wasteful equipments by thermodynamic analysis, mathematical modeling and data fitting; establishes a mathematical relationship between energy consumption, unit loads, coal parameter variation and FGD performance; and makes a curve graph of the equipments performance characteristics. Then, with 1000MW plant operating data, it analyzes FGD's energy consumption characteristics quantitatively and proposes an optimal operation program for the major energy consumption devices. Without changing the existing equipments and their structures, the program could reduce power consumption of 5,246,400kWh every year via proper change of operation mode; it also could maintain its high desulfurization efficiency. The optimization program could save energy greatly.In China, coal-fired power plants are main suppliers of electricity. Producing electricity, they also consume a large number of coals and plenty of water, and emit pollutants like SO2 and NOX. If only net coal consumption rate is took as evaluation criteria in power plant performance evaluation, then neither unit's comprehensive performance nor unit which equips with environmental protection equipments will be assessed fairly. Such a situation is not conducive to guide power plant to improve its environment protection and control its pollution. That's why a scientific, reasonable, feasible and comprehensive evaluation system which could lead coal-fired power plant to achieve multi-optimization of its thermal, environmental and economical performances should be established.This paper discusses the multi-objective evaluation methods of power plants, and it proposes the methods of Gray Relational Degree Analysis which based on Analytic Hierarchy Process (AHP) to assess power plant performance. This paper takes the emission impact on environment as an independent design variable in evaluation system for the first time; while in the original power plants performance evaluation, coal consumption is taken as basic indicator. In this paper, AHP is used to determine the evaluation index weights and Grey Relational Degree Analysis is used to evaluate the performance of power plants. Based on the new evaluation methods, this paper carries out a case study on sup-critical 600MW unit which reveals the relevancy rules between power plant resource consumption, pollutant emissions and operation performance. The research achievements of this paper offer new ideas and methods for power plants comprehensive performance evaluation.
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