A control method of ammonia injection branch pipe in scr system based on flow rate and nox concentration monitoring

Abstract

The invention discloses a method for controlling ammonia injection branch pipes of an SCR system based on flow velocity and NOx concentration monitoring. According to the flue gas flow velocity characteristics of each sub-area in the grid area, the flow velocity inertia factor of the sub-area is determined; according to the measured flue gas NOx concentration characteristics of each sub-area in the flue grid area, the NOx concentration inertness factor of the sub-area is determined; based on the flow rate Inertness factor and NOx concentration inertness factor determine the inert area and non-inert area of ​​NOx flux change; the valve opening of the ammonia injection branch corresponding to the inert area is a fixed value; the valve opening of the ammonia injection branch corresponding to the non-inert area is a change value, the changing valve opening of the ammonia injection branch is determined by the fuzzy rule base after setting. The method of the invention can realize the real-time matching optimization of the ammonia-smoke equivalent ratio in the SCR system, effectively improve the ammonia utilization rate and reduce the ammonia escape.

Description

technical field [0001] The invention relates to an automatic control method for an ammonia injection branch pipe of an SCR system based on the on-line monitoring of flue gas "flow rate-NOx concentration", and belongs to the technical field of thermal power engineering. Background technique [0002] Selective Catalyst Reduction (SCR) technology is currently the mainstream application technology for flue gas denitrification of large-scale coal-fired equipment, and its operating performance directly depends on the ammonia injection characteristics of the SCR system. The ammonia injection equipment of the SCR system involves two aspects: the total amount of ammonia injection control and the distribution control of ammonia injection. With the advancement of ultra-low emission transformation of coal-fired equipment, ammonia injection distribution control of SCR system has attracted a lot of attention in the industry. The traditional manual control of ammonia injection control meth...

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Problems solved by technology

Generally speaking, the existing SCR system ammonia injection distribution control technology schemes mainly fall into three categories, which can be elaborated as follows: 1) Completely ignore the fluctuation of the flue gas operating characteristics in the unit flue, and adopt a fixed method extensively based on a single data monitoring result. Unchanged ammonia injection distribution method (such as patent CN201810146615.3), after the application of this method, the ammonia-nitrogen mixing degree of the SCR system is extremely poor, and cannot meet the strict requirements of ultra-low emission transformation; 2) Obtained through offline data monitoring The operating characteristics of the flue gas in the SCR system under various working conditions, and then formulate a corresponding dynamic ammonia injection distribution control strategy (such as patent CN201610102338.7). This method improves the mixing and matching degree of ammonia nitrogen in the SCR system to a certain extent, but it is difficult To overcome the deviation of flue gas characteristic parameters with the running time, the adaptive ability of dynamic ammonia injection logic is poor; 3) choose to realize the online monitoring of flue gas characteristic parameters at the outlet flue section of the SCR system, and then feedback dynamic ammonia injection Control (such as patent CN202010295306.X), when this method is applied, there is a problem of poor correspondence between the front-end ammonia injection unit and the outlet measurement unit (affected by factors such as flue turning and diameter change), and the uniformity of outlet NOx concentration is excessively pursued May lead to greater ammonia slip, which violates the reaction mechanism of the SCR system

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