A new high-efficiency feedwater recuperation system for double reheat units

Abstract

The invention provides a novel efficient water supply heat recovery system for a secondary reheating unit, and relates to a novel water supply heat recovery technical scheme for the secondary reheating unit of a thermal power station, wherein the water supply heat recovery system is capable of reducing the heat consumption of the unit remarkably. A new 2 extraction component, a new 3 extraction component and a new 4 extraction component which are lower in enthalpy value and lower in the degree of superheat replace a 2 extraction component, a 3 extraction component, a 4 extraction component, a 5 extraction component and a 6 extraction component which are higher in enthalpy value and higher in the degree of superheat and arranged on a high-pressure cylinder or a middle-pressure cylinder; due to the fact that the exergy loss is reduced greatly in the water supply and heat recovery processes, the output power of a generator is increased remarkably, the heat consumption of the unit is reduced, the operation safety is improved, and obvious heat economy benefits are provided; the degree of superheat of the new 3 extraction component is reduced greatly, so that the opening of the No. 3 high-pressure steam-inlet check regulation valve is controlled to improve the transient response capacity of load increasing of a main engine; the new 2 extraction component, the new 3 extraction component and the new 4 extraction component increase the pressure stage of a 6-stage short blade in an ultrahigh pressure cylinder, the diffluent steam continuously conducts expansion acting, and extracted steam with low enthalpy value is output from connectors of the new 2 extraction component, the new 3 extraction component and the new 4extraction component.

Description

(1) Technical field: [0001] The invention relates to a novel high-efficiency feed water recuperation system for a double reheat unit, which relates to a new feed water recuperation technical scheme used in a thermal power station reheat unit, which can significantly reduce the heat consumption of the unit. (two) background technology: [0002] The double-reheat power plant boiler used in the thermal power station in the prior art is used to supply steam to the double-reheat turbine generator set. The typical steam turbine side main steam temperature / primary reheat steam temperature / second reheat steam temperature The design value is 600°C / 620°C / 620°C; the steam turbine unit for secondary reheating is usually composed of coaxial ultra-high pressure cylinders, high-pressure cylinders, medium-pressure cylinders, low-pressure cylinders and many auxiliary equipment; the primary reheater is arranged in the super Between the exhaust cylinder of the high-pressure cylinder and the pr...

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Problems solved by technology

[0004] The high-efficiency ultra-supercritical double-reheating unit has high and medium-pressure cylinder inlet steam temperatures as high as 620°C, and the enthalpy value of the 2-extraction (pre-extraction of the high-pressure cylinder) increases, and the temperature can reach above 540°C; 3-extraction (high-pressure cylinder) 4 extraction (exhaust steam of the high-pressure cylinder) is 434 °C; 5 extraction (pre-stage extraction of the medium pressure cylinder) is as high as 545 °C; 6 extraction (the rear stage extraction of the medium pressure cylinder steam) for the deaerator is still as high as 432 ℃, and even need to use a special temperature and pressure reducer to reduce the temperature and pressure before sending it into the deaerator; 2 pumping, 3 pumping, 4 pumping, 5 pumping, 6 pumping The heat-to-work ratio drops sharply, and the use of high-enthalpy, high-superheat high- and medium-pressure cylinders to extract steam to heat the feedwater will greatly increase the exergy (exergy) loss during the feedwater reheating process and increase the heat consumption of the unit

[0005] The reheat temperature gradually rises from 535°C of the subcritical unit to 620°C of the high-efficiency ultra-supercritical unit, and the evolution from primary reheating to secondary reheating makes the problem of increased exergy (exergy) loss during feedwater reheating become a problem. It is becoming more and more prominent. If it is not improved, it will seriously damage the energy saving effect brought by high parameters and double reheating when it reaches 700℃ / 720℃, 700℃ / 720℃ / 720℃ units

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