Boiler denitration control method based on outlet NOx content control and system thereof

Abstract

The invention discloses a boiler denitration control method based on outlet NOx content control and a system thereof. Two PID controllers are used to adjust an ammonia spraying amount so as to finally control a NOx content of a boiler outlet. During a control process, an inlet flue gas NOx flow E needs to be determined in real time and the E satisfies the following equation: E=DFGA*D, wherein the D is the NOx content (concentration) of the boiler inlet; the DFGA is an inlet flue gas amount; and the DFGA satisfies the following equation: DFGA=x*F(x). An output signal of a second PID controller is u2. The u2 expresses an opening degree of an ammonia spraying regulating valve. The opening degree of the ammonia spraying regulating valve is adjusted according to the u2 and the boiler denitration control is realized. The boiler denitration control method based on the outlet NOx content control and the system are easy to perform. Liquid ammonia consumption and a chimney NOx concentration can be greatly reduced.

Description

technical field [0001] The invention relates to a method based on export NO x A content-controlled boiler denitrification control method and system. Background technique [0002] Existing large-scale thermal power units (such as "W" type flame boiler supercritical units), the boiler combustion is difficult to control, and because of the mixed combustion of multiple coals, the inlet NO x Concentrations often exceed 1300mg / Nm 3 , so that the original denitrification and ammonia injection automatic system based on the fixed molar ratio control method cannot meet the needs of operation. [0003] In the existing control method, the automatic control of denitrification and ammonia injection is based on the inlet NO x Concentration and flue gas volume, calculation of denitrification ammonia gas flow, can be called a fixed molar ratio control method. This control method is based on the denitration efficiency and catalyst denitrification ability. Under this control method, the sy...

AI Technical Summary

Problems solved by technology

This control method is based on the denitration efficiency and catalyst denitrification ability. Under this control method, the system removes NO from the flue gas according to a fixed ammonia nitrogen molar ratio. x , this control method is a single-loop control system with adjustable set value. The control loop is simple and easy to debug and adjust. Its disadvantage is that it will cause excessive denitrification and increase operating costs. The specific performance is:

[0004] 1. After the denitrification and ammonia injection are automatically put in, the controlled SCR (Selective Catalytic Reduction, that is, selective catalytic reduction technology) exports NO x The concentration adjustment quality is very poor, especially in the process of changing the load, the outlet NOX fluctuates too much, exceeding the NO allowed by the environmental assessment x Emission value standard

[0005] 2. Excessive denitrification occurs, resulting in a high ammonia escape rate at the SCR outlet, causing damage to downstream main equipment, and at the same time consumes a lot of ammonia, increasing operating costs

Images