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

A technology of feedback control and induced draft fan, applied in various fluid ratio control, etc., can solve problems such as heavy maintenance workload, poor quality of SCR ammonia injection control, and poor accuracy of single-point measurement values

Pending Publication Date: 2021-04-16
浙江兴核智能控制技术有限公司
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  • Summary
  • Abstract
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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

Method used

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

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Experimental program
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Effect test

Embodiment 1

[0022] Such as figure 1 As shown, the structure based on rapid measurement and feedback of NOx concentration at the outlet of the induced draft fan to control the amount of SCR ammonia injection includes the sequentially connected SCR denitration device, air preheater, dust collector, induced draft fan and chimney. Both the outlet of the SCR denitrification device and the inlet of the chimney are installed With CEMS, NOx concentration rapid measuring instrument is installed at the outlet of induced draft fan, NOx concentration rapid measuring instrument T 90 The response time is less than 30s, and the signal output adopts redundant design, at least two NOx measurement signals can be output at the same time, as disclosed in the patent "A Flue Gas Pretreatment System for NOx Rapid Measurement Instrument" (Patent No. 2020201861282) NOx concentration rapid measuring instrument; the NOx concentration at the outlet of the induced draft fan is used as the feedback signal for the cont...

Embodiment 2

[0025] Basically the same as Embodiment 1, the difference is: after obtaining the feedback signal (NOx concentration at the outlet of the induced draft fan), the control loop is as follows figure 2 As shown, the differential calculator in the DCS control system obtains the total amount of ammonia injection required, and the comprehensive calculation results in the DCS control system combined with parameters such as operating load and total air volume are used as the feedforward amount in the total amount of ammonia injection control system , after the NOx concentration set value is compared with the NOx deviation at the outlet of the induced draft fan, it is calculated and calculated with the introduced feed-forward value as the set value of the ammonia injection total controller, and the SCR area is controlled by the inlet flue ammonia injection master valve. The total amount of ammonia injection is precisely controlled. Through the above control strategies, on the premise t...

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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...

Claims

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Application Information

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IPC IPC(8): G05D11/13
Inventor 韦红旗石伟伟
Owner 浙江兴核智能控制技术有限公司
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