All working condition standard emission control method for thermal power unit denitration system

Abstract

The invention provides an all working condition standard emission control method for a thermal power unit denitration system. The method comprises the steps that a main ring PID controller, a sub-ringPID controller and a feedforward controller are arranged in a denitration control system; the main ring PID controller calculates an ammonia injection control signal according to an outlet NOx concentration set value and an outlet NOx concentration feedback signal; the feedforward controller calculates an ammonia injection feedforward control signal according to the purge correction NOx concentration, the NOx estimated concentration, the inlet NOx concentration and the flue gas flow; and the sub-ring PID controller controls the opening of an ammonia injection valve according to the ammonia injection control signal, the ammonia injection feedforward control signal and an ammonia flow feedback signal. According to the invention, a gain scheduling model and an hour mean model are added intoa main ring to realize automatic control of the variable working condition of the denitration system; an inlet concentration purge correction model is introduced into a sub-ring to realize dynamic ammonia injection correction; the ammonia injection is accurately controlled; and a technical support is provided for whole process robustness and all working condition standard emission.

Description

technical field [0001] The invention relates to a control method that can effectively improve the robustness of the whole process of the denitrification system of a thermal power generating set and realize discharge up to the standard in all working conditions, and belongs to the technical field of power generation. Background technique [0002] At present, environmental pollution has become an important factor that plagues social development and human life and health. With the rapid development of the electric power industry, the parameters and capacity of coal-fired power generation units continue to increase, and the pollution caused by NOx emitted by coal-fired power plants to the atmosphere It is becoming more and more serious, photochemical smog has appeared in many areas, and its pollution is still increasing. Controlling the emission of nitrogen oxides has become a key pollution control task, and realizing ultra-low and near-zero emissions of nitrogen oxides is an im...

AI Technical Summary

Problems solved by technology

[0004] In engineering practice, thermal power plants mostly rely on manual adjustment of valve opening or traditional PID controllers to control the amount of ammonia injection. The control effect is not ideal. The NOx concentration at the SCR outlet of some power plants exceeds the national emission limit for air pollutants. value, and cannot ensure that the NOx concentration at the SCR outlet is stable at the set value while realizing the optimal control of the amount of ammonia injection

Due to problems such as imperfect control strategy design, unclear control objectives, and poor on-site measurement conditions, the SCR denitrification control of some thermal power units has a large lag. When the SCR inlet NO X When the concentration measuring point is purged, the value of the measuring point is in a distorted state. At this time, the amount of ammonia injection cannot be timely aimed at the NO at the SCR inlet. X Changes in concentration are adjusted accordingly, resulting in poor automatic input rate and input effect of the system, which significantly affects the operating performance of the entire denitrification system

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