Structure and method for controlling SCR ammonia spraying amount based on rapid measurement and feedback of NOx concentration at outlet of induced draft fan

Abstract

The invention discloses a method and a structure for controlling SCR (Selective Catalytic Reduction) ammonia spraying amount based on rapid measurement and feedback of NOx concentration at an outlet of an induced draft fan. The method for controlling the SCR ammonia spraying amount based on rapid measurement and feedback of the NOx concentration at the outlet of the induced draft fan takes the NOx concentration at the outlet of the induced draft fan as a feedback signal for controlling the SCR ammonia spraying amount. According to the method for controlling the SCR ammonia spraying amount based on rapid measurement and feedback of the NOx concentration at the outlet of the induced draft fan, the NOx emission concentration can be accurately and reliably reflected in real time, the obtained NOx concentration serves as a feedback signal for controlling the SCR ammonia spraying amount, the ammonia spraying control quality is improved, the ammonia escape rate is reduced, so that the adverse effect of ammonia escape on downstream equipment of the SCR denitration device is reduced or even eliminated.

Description

technical field [0001] The invention relates to a method and structure for fast measurement and feedback control of SCR ammonia injection amount based on the NOx concentration at the outlet of an induced draft fan, and belongs to the field of flue gas denitrification of large coal-fired power stations. Background technique [0002] At present, large coal-fired power plants generally use SCR denitrification devices to reduce the concentration of NOx emissions in flue gas. SCR utilizes NH 3 The reduction characteristics of NOx, under the action of the catalyst, NOx is reduced to N which is harmless to the environment 2 and H 2 O. In the actual operation process, the control of the amount of ammonia injection is particularly critical. Increasing the amount of ammonia injection is beneficial to reduce the concentration of NOx emissions, but the ammonia slip rate will increase accordingly, which will easily cause the downstream air preheater to be blocked and corroded due to t...

AI Technical Summary

Problems solved by technology

However, single-point measurement of NOx concentration is generally used at the SCR outlet at present. Due to the uneven distribution of NOx concentration at the SCR outlet, the accuracy of single-point measurement is poor; the chimney inlet also uses single-point measurement of NOx concentration, because the flue gas has flowed through Longer flue and more equipment, better uniformity of NOx concentration, so the measurement accuracy is higher, but the measurement lag time is too long, generally as long as more than 2min

In addition, the current SCR outlet NOx concentration measurement generally adopts CEMS measurement technology, and CEMS itself has problems such as long measurement lag time (generally as long as more than 1min) and heavy maintenance workload (common problems include the use of negative pressure system air leakage affecting normal measurement, Arranged in the high dust area, it has higher requirements for the analysis of flue gas pretreatment, etc.)

[0004] In short, the key feedback signal of SCR ammonia injection control, the existing technology can not take into account its accuracy, real-time and reliability, resulting in poor quality of SCR ammonia injection control

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