Thermal state purging method and system for supercritical boiler system

Abstract

The invention relates to a thermal state purging method for a supercritical boiler system. Heat of a neighbor machine is used for heating a plate heat exchanger, high-pressure heaters and a deaeratorof a native machine, and thermal state purging of a boiler under the state of misfiring is achieved. The invention further relates to a thermal state purging system for the supercritical boiler system. The thermal state purging system comprises a steam extraction pipe set and a conveying pipe, the inlet of the steam extraction pipe set is connected with a native machine auxiliary steam header anda neighbor machine second high-pressure heater, and the outlet of the steam extraction pipe set is connected with the native machine deaerator, the native machine first high-pressure heater and the native machine second high-pressure heater; the inlet of the conveying pipe is connected with the outlet of a neighbor machine low temperature economizer, and the outlet of the conveying pipe is connected with the native machine plate heat exchanger; and the steam extraction pipe set and the conveying pipe extract heat of a neighbor machine in running to heat supply water of the native machine. By means of the thermal state purging method and system, before the boiler is started, heating and thermal state purging on a water cooling heated face of the boiler are achieved, the service life of thesupercritical boiler is prolonged, and the method and system can be widely applied to the technical field of power plant energy conservation and environmental protection and technological process optimization methods.

Description

technical field [0001] The invention relates to the technical field of power plant energy saving and environmental protection and process flow optimization methods, in particular to a hot flushing method and system for a supercritical boiler system. Background technique [0002] At present, the start-up stage of the supercritical boiler needs to undergo hot flushing to heat the steam temperature of the separator to 190°C. Conventionally, heating the temperature of the separator to 190°C is generally achieved through the following process: heating the boiler feed water to about 80°C through the auxiliary steam header to the deaerator, and then extracting the exhaust steam from the high-pressure cylinder of the adjacent steam turbine to No. 2 The high-pressure heater further increases the temperature of the feed water to about 120°C, and then further heats the temperature to 190°C after the boiler is ignited. [0003] However, the feed water temperature is low at the initial ...

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Problems solved by technology

[0003] However, the temperature of the feed water at the initial stage of boiler ignition is low, the steam production of the boiler is insufficient, the heating surface of the superheater and reheater generally has problems of dry burning and insufficient cooling capacity, and the temperature change rate of the heating surface is relatively large, and the steam temperature is high

In order to reduce the steam temperature change rate, it is necessary to spray desuperheating water, which will easily cause the scale to peel off and block the heating surface

Due to the small steam flow rate at the beginning of the start-up, the peeled off oxide belt cannot be taken away quickly. When the flow rate is large, the oxide scale will form a blockage at the elbow with a small diameter, causing the heating surface to overheat and aggravate the formation of oxide scale; When the grid-connected load of the unit increases, insufficient steam cooling will further cause the heating surface to overheat or even burst the tube. The peeled off scale may accumulate on the main steam valve and regulating valve of the steam turbine, causing the valve to jam, threatening the safe and stable operation of the unit.

[0004] Therefore, the temperature rise rate and temperature of the heating surface during the start-up stage of the unit are high, and the steam temperature often deviates from the design value when the steam turbine is running, which is not conducive to the start-up of the steam turbine; the temperature of the feed water at the initial stage of the unit grid connection is low, and the feed water absorbs less heat in the economizer Too much, resulting in low flue gas temperature at the outlet of the economizer, which cannot reach the reaction temperature of flue gas denitrification for a long time, and the denitrification and ammonia injection cannot be put into use, resulting in excessive emissions, so that the flue gas denitrification system is generally put into operation 3 to 4 hours after grid connection. Causes flue gas emission pollutants to exceed the standard and pollutes the atmospheric environment

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