A Method for Optimizing Circulating Water Flow of Two-speed Pumps in Double-Back-pressure Cold End System of Thermal Power Units

Abstract

The invention provides a method for optimizing a circulating water flow rate of a two-speed pump of a double back-pressure cold end system of a thermal power generating unit. The method comprises the following steps of obtaining unit operating data at a given moment; computing exhaust steam moisture of a low pressure cylinder, and computing inlet exhaust steam mass flow rates, specific enthalpies of inlet exhaust steam, specific enthalpies of condensed water and saturated steam temperatures of a high-pressure condenser and a low-pressure condenser at the given moment under a given condition of a stream extraction portion; computing an actual circulating water mass flow rate, a circulating water outlet temperature of the low-pressure condenser and a current end difference of the high-pressure condenser; changing a two-speed pump operation mode and computing a circulating water outlet temperature of the low-pressure condenser, and the saturated steam temperatures and the specific enthalpies of inlet exhaust steam of the high-pressure condenser and the low-pressure condenser, which are corresponding to the two-speed pump operation mode; and defining a difference between a micro-increment power of the unit after the change of the two-speed pump operation mode and a power consumption increment of a circulating water pump as a benefit function, and taking the two-speed pump operation mode as a to-be-optimized variable to optimize the benefit function in order to obtain an optimal two-speed pump operation mode. The method can provide a technical support for thermal power energy saving and efficiency improvement.

Description

technical field [0001] The present invention relates to the technical field of thermal power optimization control, in particular, to a method for optimizing the mass flow rate of circulating water in a double back pressure cold end system, especially a dual back pressure cooling system for thermal power units based on maximizing the net power increase of the unit. A method for optimizing the mass flow rate of circulating water in a system equipped with a two-speed pump (that is, the mass flow rate of circulating water is non-continuously adjustable). Background technique [0002] The cold end system is an important part of the thermal power unit. With the expansion of unit capacity, the exhaust steam volume and the number of exhaust outlets of the steam turbine increase. In order to improve the efficiency of the unit, most power plants adopt a double back pressure or multi back pressure cold end system. The working status of each equipment in the cold end system not only af...

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Problems solved by technology

[0004] However, the above-mentioned invention needs to use the overall heat transfer coefficient in the process of calculating the expected value of the condenser, and needs to use the unit power correction curve when calculating the slightly increased power. The fitting curve obtained from the test, under the condition that most units can only be tested once a year, obviously cannot reflect the dynamic changes in the performance of the equipment, so it cannot guarantee that the circulating water flow in the cold end system is actually optimal

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