A control method for improving the flexibility of coal-fired units through high steam extraction and throttling

Abstract

The invention discloses a control method for improving the flexibility of a coal-fired unit through high-pressure steam extraction and throttling. After receiving a load increase command, the coal-fired unit closes the opening of the high-power steam extraction valve, and the load command reaches the target load. Finally, the closed extraction valve is fully opened; at the same time, the heat absorption change of the feed water caused by the reduction of the opening of the extraction valve in the transient process is compared with the low calorific value of the fuel entering the furnace, as the fuel quantity control Feed-forward value, add the feed-forward value to the fuel quantity command to obtain the new value of the fuel quantity; when the change of feedwater heat absorption caused by the decrease of the opening of the extraction valve in the transient process and the change of the unit flue gas recirculation quantity The change in heat transfer of the water-cooled wall is used as the feed-forward value of the flue gas recirculation control, and the feed-forward value is added to the command of the flue gas recirculation amount to obtain a new value of the flue gas recirculation amount; thereby completing the steam temperature control optimization. The invention improves the steam temperature control effect and improves the flexibility of the unit through the method of high steam extraction and throttling.

Description

technical field [0001] The invention belongs to the technical field of thermal control in thermal power plants, and in particular relates to a control method for improving the flexibility of a coal-fired unit through high steam extraction and throttling. Background technique [0002] The improvement of the flexibility of coal-fired units is of great significance to the consumption of renewable energy. The easy overheating of reheated steam is the main factor limiting the load changing rate in the process of increasing load of coal-fired units. On the one hand, the boiler command caused by the main steam pressure deviation is too large, resulting in fuel overburning. On the other hand, during the load increase process, due to the excessive heat storage at the economizer and the water wall, the temperature of the working medium at the outlet of the water wall is too low, which intensifies the phenomenon of fuel overcombustion. The increase of flue gas flow rate caused by fue...

AI Technical Summary

Problems solved by technology

On the one hand, the boiler command caused by the main steam pressure deviation is too large, resulting in fuel overburning

On the other hand, during the process of load increase, due to the excessive heat storage between the economizer and the water wall, the temperature of the working medium at the outlet of the water wall is too low, which intensifies the phenomenon of fuel overcombustion

The increase of flue gas flow caused by fuel overcombustion is the main reason for the overheating of reheat steam

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