Large-section flue SCR-CEMS (selective catalytic reduction-continuous emission monitoring system) flue gas multi-point equal-mixing two-stage ejecting rapid sampling device and method thereof

Abstract

The invention discloses a large-section flue SCR-CEMS (selective catalytic reduction-continuous emission monitoring system) flue gas multi-point equal-mixing two-stage ejecting rapid sampling device,and self-ejection is formed under the static pressure difference of flue gas at both ends of an inlet first stage sampling pipeline and an outlet first stage sampling pipeline, the flue gas flows intothe inlet first stage sampling pipeline and the outlet first stage sampling pipeline respectively and is mixed by mounting an inlet flue gas sampling branch pipe and an outlet flue gas sampling branch pipe, and then the flue gas flows into the outlet flue of an air preheater rapidly and automatically under the action of the static pressure difference ejection of the flue gas, the inlet first stage sampling pipeline and the outlet first stage sampling pipeline pass through a SCR-CEMS instrument cubicle, and flue gas samples are extracted from the inlet first stage sampling pipeline and the outlet first stage sampling pipeline respectively and transported to an inlet CEMS analyzer and an outlet CEMS analyzer after pretreatment respectively to form a second stage flue gas sampling pipeline.The large-section flue SCR-CEMS (selective catalytic reduction-continuous emission monitoring system) flue gas multi-point equal-mixing two-stage ejecting rapid sampling device can improve the representativeness of the flue gas sampling of the CEMS analyzer, shorten the measurement lag time, improve the load followability of the unit of the total SCR ammonia ejecting adjustment and reduce the fluctuation range of NOx emission concentration.

Description

technical field [0001] The invention relates to the technical field of SCR flue gas denitrification, in particular to a large-section flue SCR-CEMS flue gas multi-point equal-volume mixing secondary injection rapid sampling device and a method thereof. Background technique [0002] At present, domestic coal-fired units generally use SCR flue gas denitrification devices to control NOx to an ultra-low emission limit of 50mg / m 3 . Usually, a set of online CEMS analyzers are arranged at the inlet and outlet flues of the SCR reactor to measure NO / O 2 Concentration, using feedforward (load, inlet NOx concentration and outlet NOx set value to calculate ammonia injection amount) + feedback (measured outlet NOx concentration to correct ammonia injection amount) method to automatically adjust ammonia injection amount as needed. However, in the actual operation process, there are two problems and phenomena related to measurement: [0003] 1) Low representativeness of CEMS sampling m...

AI Technical Summary

Problems solved by technology

Large flue cross-section and uneven distribution of NOx concentration reduce the representativeness of single-point sampling and CEMS analysis values

The CEMS of some units adopts 3-point flue gas sampling or distributed multi-point flue gas sampling, but the former has too few sampling points and the latter does not ensure equal sampling at each point, which affects the improvement of sampling representativeness

[0005] 2) CEMS takes a long time to measure the delayed combustion condition

This method can control the fluctuation range of outlet NOx concentration to be less than ±10mg / m 3 , but when the corresponding relationship between combustion conditions and NOx changes greatly, it is necessary to reset the preset amount

2) Shorten the distance between the flue gas sampling point and the CEMS instrument, and reduce the measurement lag time to within 2 minutes as much as possible. However, for units whose NOx concentration at the SCR inlet fluctuates sharply with the combustion conditions, the NOx concentration at the SCR outlet still fluctuates greatly

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