SCR denitration external hanging type intelligent ammonia spraying closed-loop control method and device

Abstract

The invention discloses an SCR denitration external hanging type intelligent ammonia spraying closed-loop control method and device, and the method comprises the steps: S100, obtaining the operation data of a boiler system and a denitration system, and building a database through the connection with an OPC communication protocol, S200, processing the operation data; S300, constructing a time-varying feedforward prediction model for the nitrogen oxide concentration at the inlet of the SCR denitration reactor, and predicting the nitrogen oxide concentration at the inlet of the SCR denitration reactor in real time; S400, constructing an SCR denitration ammonia injection amount feedback correction model by adopting a classification algorithm with a time-varying function, calculating an ammonia consumption correction coefficient of the SCR denitration reactor, and correcting an ammonia injection amount calculation value output by the feedforward prediction model according to a final calculation result; and S500, transmitting to a DCS (Distributed Control System) through a communication module of the external hanging type control system, and finally adjusting an ammonia spraying adjusting valve in real time through the DCS to control the ammonia spraying amount, thereby realizing intelligent ammonia spraying closed-loop control. According to the invention, the total ammonia spraying amount is reduced, the ammonia escape rate is reduced, and intelligent ammonia spraying closed-loop control is realized.

Description

technical field [0001] The invention belongs to the technical field of thermal power denitrification, and more specifically relates to an SCR denitrification plug-in intelligent ammonia injection closed-loop control method and equipment. Background technique [0002] In the ultra-low emission standards for pollutants from coal-fired power plants, NO X The emissions are one of the important environmental indicators. At present, in order to remove NO in the flue gas of coal-fired power plants, X The commonly used technologies are selective catalytic reduction technology (SCR), selective non-catalytic reduction technology (SNCR) and technology combining selective and selective catalytic reduction (SNCR / SCR hybrid method). Among them, the devices with mature domestic technology generally adopt selective catalytic reduction technology (SCR), that is, in a certain temperature range, the NO in the flue gas X Under the action of a catalyst, with a reducing agent (usually NH 3 ) ...

AI Technical Summary

Problems solved by technology

However, there are still many problems in the traditional SCR denitrification ammonia injection control: (1) The process principle of the denitrification reaction process is simple, but there are many influencing factors, such as flue gas temperature, smoke dust, SO2 concentration, inlet NOx concentration, denitrification efficiency, flue gas The form of the flow field and the catalyst have a great influence on the performance of the denitrification reactor; (2) parameters such as NOx at the inlet and outlet of the SCR denitrification reactor are important measurement parameters in the control of the amount of ammonia injection in the SCR denitrification system, which need to be continuously monitored through flue gas discharge. Monitoring System (CEMS) Acquisition Measurements

The hysteresis of NOx measurement at the inlet and outlet makes the ammonia injection amount control process of the denitrification system a long-term delay link, which makes it difficult for automatic control to achieve good results

In addition, the existing CEMS must intermittently purge the sampling line to ensure that the line is not blocked

Normal measurement cannot be achieved during CEMS purging, and the measured value needs to be kept in the state before purging, which reduces the effective time of measurement, resulting in an almost uncontrolled state during purging

In addition, the large dead zone of the ammonia supply control valve, idle travel and severe nonlinearity, and equipment problems such as impurities deposited in the ammonia flowmeter and inaccurate measurement will all affect the denitrification control effect

(3) At present, most of the traditional SCR denitrification closed-loop control strategies are designed as a fixed molar ratio control method. This control method is too simple and only considers the static characteristics of the object, lacks an adaptive mechanism, and often occurs due to the unevenness of the flow field. Cause local excess of ammonia, ammonia escape often exceeds the standard, and the operation of the control system is overly dependent on the accuracy of all measuring point values

(4) Considering the denitrification system monitoring equipment and the deterioration of the denitrification reactor operating conditions caused by the non-linear changes in catalyst activity. With the increase of the denitration reactor operating time, the denitration reactor operating conditions deteriorate. The deviation between the calculated ammonia injection amount and the actual required ammonia injection amount is getting bigger and bigger, and cannot be corrected automatically, so the traditional intelligent ammonia injection control system has poor adaptability

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