Automatic control method for ammonia injection regulation in thermal power plant denitrification system

Abstract

The invention provides an ammonia spraying regulation automatic control method for a denitrification system of a thermal power plant. The method comprises the following steps of 1, using a DCS to conduct circular blowing control on sampling channels of CEMS (Continuous Emission Monitoring System) analyzers on an inlet and an outlet of each flue according to the number of flues of a same boiler; 2, acquiring the analysis values of the CEMS analyzers on the inlet and the outlet of the current flue in the process of blowing control, and adjusting the opening degree of an ammonia spraying door of the current flue according to a preset specific value relation; and 3, if the CEMS analyzers on the inlet and the outlet of the current flue are maintained or blown, replacing with the analysis values of CEMS analyzers on an inlet and an outlet of another flue. According to the provided CEMS analyzer blowing control method, the CEMS analyzers of the denitrification system can be automatically and orderly blown; besides, an automatic control strategy for ammonia spraying is designed for the blowing control method, and the blowing of the CEMS analyzers is controlled; and through the set logic switch, the ammonia spraying door is guaranteed to be constantly controllable, the undisturbed switching is guaranteed after blowing is finished, and the adjusting effect is improved.

Description

technical field [0001] The invention relates to the field of power generation, in particular to an automatic control method in which the adjustment of ammonia injection in a denitrification system of a thermal power plant is not affected by the maintenance of a flue analysis device. Background technique [0002] At present, under the requirements of energy saving and environmental protection in thermal power plants, the exhaust gas needs to be desulfurized and denitrified. The denitrification system is generally installed inside the flue, and the emitted ammonia gas reacts with the nitrate in the flue gas to reduce the exhaust gas. nitrate content in. The amount of ammonia injection is automatically adjusted by the DCS system according to the content of sulfur and nitrate in the flue gas, and the content of nitrate in the flue gas is obtained by the CEMS analyzer installed at the entrance and exit of the flue. [0003] The existing CEMS analyzer needs to be maintained after...

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Problems solved by technology

[0003] The existing CEMS analyzer needs to be maintained after a period of use. After the maintenance, the sampling pipeline of the analyzer must be purged. During maintenance and purging, the content of sulfur and nitrate in the flue gas cannot be obtained.

[0004] The existing DCS adjusts the ammonia injection door of the denitrification system in the following way: use the data of the CEMS analyzer at the tail of the flue to determine whether the nitrate content in the exhausted flue gas is within the predetermined value, and if it deviates from the predetermined value, it is appropriate Increase or decrease the opening and closing amount of the ammonia injection door. Therefore, once the CEMS analyzer is maintained or purged, it will affect the control of the DCS on the ammonia injection door.

[0005] In addition, the flue of an existing boiler is divided into two, A and B, and CEMS analyzers are installed at the inlet and outlet of each flue, and the DCS automatically controls the blowing time and sequence of the CEMS analyzers in each flue. Control, when the CEMS analyzer breaks down and requires manual maintenance, the maintenance personnel will restart the purge program of the current CEMS analyzer. At this time, the purge setting of the CEMS analyzer will conflict with the automatic control of the DCS. Causes DCS alarm

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