660 MW. Vol. 31 No. 3 Mar NO x N /600 /620 45% 40% Fig. 1 Diagram of a principle thermal system for low temperature economizers 660 MW

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1 JOURNAL OF ENGINEERING FOR THERMAL ENERGY AND POWER Vol. 31 No. 3 Mar MW MW g / kwh / Nm / kg TK A DOI /j. cnki. rndlgc N /600 /620 45% % 1 ~ HG / YM7 Π NO x 1 Fig. 1 Diagram of a principle thermal system for low temperature economizers

2 H = Q η 1 72 Q 1 kg kj /kgη 6 ΔH 6 = α 6 h 6 - h 7 2 α 6 6 h 6 6 kj /kgh 7 kj /kg 6 2 Δη = ΔH 6 /H + ΔH H 1 kg 1 kj /kg Tab. 1 Main parameters of the unit at the full load /% /g kwh MW kpa 1 100% 0. 04% THA GGH 70 t /h 5 5% % /% /t h kg /kj kg /kj kg % g /kwh MW kw % THA 75% THA 50% THA 3 3

3 3 660 MW kw 120 ~ GGH 0. 5% ~ 0. 7% 1. 5 ~ 2. 1 g /kwh GGH Fig. 3 Comparison of the operating condition points of the draft fan when a low-temperature economizer and a gas-gas heater is additionally installed 2 Fig. 2 Variation values of the power generation 4 efficiency and coal consumption rate under various operating conditions /GGH ~ MW GGH GGH GGH 2 GGH 800 kw 3 3 GGH GGH 4

4 MW 0. 85% g /kwh 3 37 GGH 1. J LU Hai-jun WEN Gao. Research of seawater desalination by utilizing waste heat from power plants J. Journal of Green Science and Technology sion caused by flue gases from boilers J. Journal of Power Engi-. neering J WANG Li-biao LI Ran-shengWANG Bin et al. Applications of the absorption type heat pump-based circulating water waste heat utilization technology in the cogeneration production made by largesized steam extraction and condensing type steam turbine units J. Steam Turbine Technology J MW NI Ying-chun. Analysis of the causes and countermeasures for YE Xue-min TONG Jia-lin WU Jie et al. Cost-effectiveness analysis of the utilization of waste heat from a supercritical 660 MW u- nit J. Thermal Power Generation J LI Jian-feng ZHU Chao LENG Jie et al. Comparison of the two modes for reducing the temperature of flue gases from a boiler J. China Electric Power J LIU He-zhong LIAN Zheng-quan. Exploratory study of the application of low temperature economizers in thermal power plants J. Electric Power Survey & Design MW J SHI Yan LIANG Xiu-jin. Energy-saving analysis of a system for a 300 MW unit additionally installed with a low temperature economizer J. Huadian Technology J REN Yan ZHAO Ning CHEN Xiao-feng. Study of the energy-saving effectiveness of a low pressure economizer system in a thermal power plant J. Journal of Engineering for Thermal Energy and Power J ZHANG Ji-biao HAO Wei ZHAO Zhi-jun et al. Theoretical study and engineering practice of the low temperature corrosion and ero- J YAN Wei-ping DONG Jing-lan. Exploratory study of the causes for the fact that the temperature of the exhaust gases from a boiler during its operation is excessively high J. Thermal Power Generation GGH J. dust deposition and fouling in a gas-gas heater in a power plant J. Electric Power Science and Engineering

5 3 141 ly from Class-I and Class-II ports increasing the charging quantity from Class-II port is the key to the increase of L- valve returning flow rate. Compared with the increase of charging quantity from Class-II port more stable system operation can be achieved by increasing the charging quantity from Class-I port and the best system operation stability can be got when the charging quantity is of 15 m 3 /h. The L-valve resistance will increase with the increase of charging quantity from Class-I port but will decrease with the increase of charging quantity from Class-II port so increasing the charging quantity from Class-II port will become the effective way for reducing the valve resistance. With air charged jointly from Class-I and Class-II ports compared with the L-valve returning capability achieved as the air charging quantity from air charging port g in horizontal section being of 10 m 3 /h greater L-valve returning capability can be achieved as the air charging quantity from air charging port b in vertical section being of 5 m 3 /h. Increasing the charging quantity from Class-I port can achieve more stable system operation. When the charging quantity being of 15m3 /h the best system operation stability can be reached. Key wordshigh density circulating fluidized bed HDCFB L-valve air distribution mode returning characteristics 660 MW = Economic Analysis for 660 MW Unit Added with Low-temperature EconomizerTONG Jia-lin WENG Jing Electric Power Research Institute of State Grid Zhejiang Electric Power Company Hangzhou Zhejiang Province China Post Code310014/ /Journal of Engineering for Thermal Energy & Power The heat loss of the exhaust gas is the greatest loss in all kinds of the boiler heat loss. The major influence factor on the heat loss of the exhaust gas is the exhaust gas temperature. Adding a low-temperature economizer into the rear duct of power station boiler and utilizing the waste heat of the exhaust gas to heat condensate water can decrease the inlet flue gas temperature of desulfurization system. Taking a domestic 660MW ultra-supercritical unit as the study object the paper uses the equivalent enthalpy drop method for the calculation and analysis on the energy-saving effect of low-temperature economizer. The calculation results show that the coal consumption rate for power generation can be decreased by g / kwh after low-temperature economizers put into operation and the significant energy-saving effect can be achieved. Compared to the domestic same-type Gas-Gas-Heater units the specific pressure of induced draft fan can drop about 1000 NM /kg and the operating point can be improved remarkably. Key words low-temperature economizer waste heat utilization coal consumption rate for power generation induced draft fan = Study on Calculating Method for Air Leakage Rate of