| Current, our country power generating units’s capacity is bigger, the thermal power generating units are the main force, but also will be the main force in power grid for long time. In the thermal power plant, boiler feed water pump driving working fluid to cycle. With the thermal power plant unit capacity increase, pump power is also increasing. Boiler feed water pump is about the big turbine power2-4%.Such as a boiler feed water pump’s shaft power of100%capacity in a1000MW advanced uni is30670kW, pump power accounts for about3%of main turbine power, if the standard coal consumption rate of power supply is300g/kW· h, and if the pump group average efficiency can be increased by10%by the new driving scheme, then the efficiency of entire unit is to high about0.3%, that can reduce the standard coal consumption rate of power supply is about0.9g/kW· h. If annual utilization hours is5000h,so that can save4500t of standard coal. We can annual save Y3,600,000to purchase the standard coal,if we purchase the standard coal by￥800/T.Conclusively,there are two driving schemes in china’s traditional large thermal power unit:one is the boiler feed water pump driven by a small turbine (referred to as the steam scheme), other is the boiler feed water pump driven by the motor through a hydraulic coupler (referred to as the electric scheme), the electric scheme is a small amount.The two driving schemes’s heat economy although have certain expressions by predecessors, but the content is relative to aging, especially with the development of modern thermal power generation technology, especially the big turbine, high efficient motor, high efficiency hydraulic coupler, large frequency conversion technology development, water pump driving scheme will become more diversification.This paper takes large coal-fired generating unit with the big turbine and small turbine can cool by warter as the object of study, first analyzed the shortage in boiler feed water pump driving schemes thermal study by predecessors.Mainly include:one-sidedly emphasized to reduce the power consumption rate, ignored actual energy consumption index of the generating set; one-sidedly emphasized the small steam turbine high efficiency under the rated condition, ignored the small engine low efficiency under variable condition; that efficiency of pipelines and other power consumption for steam scheme is not considered; boiler feed pump capacity and driving device capacity actually is too large, there are not fully analysis capacity large influence on thermal economy.This paper comprehensively consider the chain of the actual situation, combined with modern drive technology, to establish five kinds of drive schemes physical model of boiler feed water pump:the traditional efficiency hydraulic coupler scheme; the steam scheme;high efficiency hydraulic coupler scheme; the large frequency conversion scheme;the big turbine’s shaft scheme, further establishing the mathematical model of the five driving schemes by the constant flow analysis method, then we can calculate the internet net power of each drive scheme. It can compare various driving scheme by comparing internet net power of the five drive schemes.We developed a calculation software with program as the core, good user interface, convenient operation according to the five driving scheme of the physical model and mathematical model. Then we selected typical300MW,600MW,1000MW grade unit, and we did the corresponding calculation.We discussed the topic of the power consumption rate and the thermal economy of thermal power generating units influence by the five driving schemes, and we analysed if only to reduce the power consumption rate, there may be a phenomenon that saving quantity of electricity but not saving energy in fact.At the end, on the basis of detailed calculation, we discussed the topic of the boiler feed pump capacity and driving equipment capacity is too large, it is a problem when our country boiler feed pump capacity and driving equipment capacity choice at present. |
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