Energy-saving type quick start method for supercritical unit or ultra-supercritical unit

Abstract

The invention discloses an energy-saving type quick start method for a supercritical unit or an ultra-supercritical unit. According to the method, steam from another resource is used for heating supplied water so that a boiler can be indirectly heated, and the thermal stress of a heated surface is reduced when the boiler is started so that the heating rate of the boiler can be improved; meanwhile, the heated high-temperature supplied water is converted into steam-liquid two-phase flow through throttling and pressure reduction, the flowing scouring action of the steam-liquid two-phase flow is far superior to the effect of thermal-state washing, and in other words, the boiler can complete thermal-state washing under the non-ignition condition, and can preheat the whole heated surface before ignition till certain pressure is reached. After ignition of the boiler, due to the fact that enthalpy of subcooling on an inlet of a water wall is eliminated, the problem of water power can be readily solved and the input speed of fuel can be increased. Meanwhile, by adjusting the open degree of a turbine bypass valve, the flow, the temperature rising speed and the pressure rising speed of main stream and reheat steam are controlled, and the temperature rising speed of the heated surface of the boiler is increased; when the temperature of the main steam and the temperature of the reheat steam are larger than the temperature of a turbine heating valve, valve heating is started, and a main machine can early satisfy the impulse starting condition.

Description

technical field [0001] The invention relates to an energy-saving quick start method for a super (super) critical unit, which belongs to the field of thermal coal-fired generating units. Background technique [0002] With the increasingly mature technology of coal-fired power plants and the continuous improvement of environmental protection requirements such as energy conservation and emission reduction, supercritical and ultra-supercritical parameters have been generally adopted for large thermal power units. At present, there are mainly two starting methods for these units: drain expansion type and boiler water circulation pump type. In these two start-up methods, the deaerator needs to be heated before the boiler enters the water, and the feed water is heated to the feed water temperature required by the boiler (generally around 105°C, different boiler manufacturers have different regulations on this), and then the boiler Water supply: while the boiler is being supplied w...

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Problems solved by technology

In fact, if the adjacent steam heating method is not used, at the initial stage of boiler ignition, due to the low temperature of the working medium in the water wall, the thermal stress of each component of the boiler is relatively large; at this time, the superheater and reheater will still be in the "dry burning " state, in order to reduce the thermal stress of various parts of the boiler and reduce the damage caused by "dry burning" to the boiler, the heating and pressure raising speed of the boiler can only be very slow, so when this method is used to start the unit, the time it takes for the unit to start is still very long. Fuel and plant power consumption are still huge

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