CN-122006437-A - Accurate ammonia injection control method and system for low-temperature SCR denitration system

CN122006437ACN 122006437 ACN122006437 ACN 122006437ACN-122006437-A

Abstract

The invention discloses a precise ammonia injection control method and system for a low-temperature SCR denitration system, and belongs to the technical field of flue gas denitration control. The method comprises the steps of collecting real-time operation data of flue gas, calculating an absolute NOx amount and a theoretical ammonia spraying amount, determining a baseline ammonia spraying flow based on the theoretical ammonia spraying amount, ammonia water concentration and evaporation efficiency, predicting the concentration of the outlet NOx by a multi-dimensional dynamic prediction model integrating Kalman filtering and a neural network, generating a feedforward correction amount, generating a feedback correction amount according to the deviation between the actual concentration of the outlet NOx and a set value, and obtaining the final ammonia spraying flow by integrating the baseline flow, the feedforward correction amount and the feedback correction amount. The invention is also provided with a self-learning optimization module, which can dynamically correct the ammonia nitrogen molar ratio and cooperatively adjust the liquid-gas ratio according to the SO 2 concentration at the outlet of the desulfurizing tower. The method realizes the transition from passive response to active prediction of ammonia injection control, improves denitration precision and system stability, gives consideration to desulfurization cooperation, and is suitable for optimizing and upgrading a low-temperature SCR denitration system.

Inventors

CHENG FENG
CAO XINCHUANZHOU
LIU ZIMIN
YU LEI
ZHANG JIAQI
SHAO FULIANG

Assignees

马鞍山钢铁有限公司

Dates

Publication Date: 20260512
Application Date: 20260127

Claims (10)

1. The accurate ammonia injection control method for the low-temperature SCR denitration system is characterized by comprising the following steps of: collecting real-time operation data of a sintering flue gas system; Calculating an absolute amount of NOx based on the inlet NOx concentration and the flue gas flow; Calculating theoretical ammonia injection amount based on the absolute NOx amount and a set ammonia nitrogen molar ratio; calculating a baseline ammonia injection flow based on the theoretical ammonia injection amount, ammonia concentration, and ammonia water evaporator efficiency; Predicting the concentration of NO x at the outlet at the future moment by using a multidimensional dynamic prediction model fused by Kalman filtering and a neural network to generate an ammonia injection feedforward correction quantity; generating an ammonia injection feedback correction amount according to the deviation between the actual concentration of the outlet NO x and the set target value; And determining the final ammonia injection flow by combining the baseline ammonia injection flow, the feedforward correction and the feedback correction, so as to realize the accurate control of ammonia injection.
2. The method for precisely spraying ammonia for a low temperature SCR denitration system according to claim 1, wherein the real-time operation data further comprises at least one of flue gas temperature, sintering machine load, catalyst layer pressure difference, SCR outlet NOx concentration, outlet ammonia slip concentration, and desulfurizing tower outlet SO 2 concentration.
3. The method for controlling the precise ammonia injection of the low-temperature SCR denitration system according to claim 1, wherein, The formula for calculating the absolute amount of NOx is: ; The formula for calculating the theoretical ammonia injection amount is as follows: ; the formula for calculating the baseline ammonia injection flow is as follows: ; Wherein, the The absolute amount of NOx in the flue gas, The concentration of the ammonia water is adopted, Is ammonia water evaporator efficiency.
4. The precise ammonia injection control method for a low-temperature SCR denitration system according to claim 1, wherein the expression of the multidimensional dynamic prediction model is: ; Wherein, the To predict future The outlet NOx concentration is at the moment, For the kalman filter prediction module, For the neural network nonlinear correction module, For the adaptive weighting coefficients to be used, For the inlet NOx concentration, The flow of the flue gas, the temperature of the flue gas, the load of the sintering machine, As a pressure difference of the catalyst layer, To be at present Before the moment of time by Historical time series data of the outlet NOX concentration formed by the end point and forward backtracking n sampling moments.
5. The method for controlling the precise ammonia injection of the low-temperature SCR denitration system according to claim 4, wherein the ammonia injection feedforward correction amount is calculated by: ; Wherein, the Feed-forward correction for ammonia injection As a feed-forward scaling factor, Is at present The actual concentration of NO x at the time outlet.
6. The method for controlling the precise ammonia injection of the low-temperature SCR denitration system according to claim 1, wherein the ammonia injection feedback correction amount is calculated by: ; Wherein, the For the ammonia injection feedback correction amount, For feedback scaling factor, cset sets a target value for the outlet NO x concentration, Is at present The actual concentration of NO x at the time outlet.
7. The method for controlling the precise ammonia injection of the low-temperature SCR denitration system according to claim 1, wherein the calculation formula for determining the final ammonia injection flow rate is as follows: ; Wherein, the For the determined future The final ammonia injection flow rate at the moment, For the baseline ammonia injection flow rate, For the ammonia injection feedforward correction amount, For the ammonia injection feedback correction amount, The ammonia slip correction amount.
8. The method for controlling the precise ammonia injection of the low-temperature SCR denitration system according to claim 1, further comprising a self-learning optimization step of dynamically correcting the ammonia nitrogen molar ratio according to the change of the denitration efficiency, wherein the correction formula is as follows: ; Wherein, the In order to correct the molar ratio of ammonia nitrogen, Is at present The ammonia nitrogen molar ratio at the moment, Is at present The denitration efficiency is improved at all times, Is the learning rate.
9. The method for controlling the precise ammonia injection of the low-temperature SCR denitration system according to claim 1, further comprising a desulfurization cooperative control step of dynamically adjusting the liquid-gas ratio based on the concentration deviation of SO 2 at the outlet of the desulfurization tower, wherein the adjustment formula is as follows: ; Wherein, the Is a liquid-gas ratio, and is characterized by that, For the desulfurization adjustment coefficient, A target value is set for the concentration of SO 2 at the outlet of the desulfurizing tower, Is the concentration of SO 2 at the outlet of the desulfurizing tower.
10. A precision ammonia injection control system for a low temperature SCR denitration system for implementing the precision ammonia injection control method of any one of claims 1-9, comprising: The data acquisition module is used for acquiring real-time operation parameters of the flue gas denitration system; The calculation module is used for calculating the absolute amount of NO x , the theoretical ammonia injection amount and the baseline ammonia injection flow; The prediction module is internally provided with a multi-dimensional dynamic prediction model fused by Kalman filtering and a neural network and is used for predicting the concentration of the NO x at the outlet and generating a feedforward correction amount; The feedback adjustment module is used for generating a feedback correction amount according to the concentration deviation of the outlet NO x ; the control module is used for fusing the baseline ammonia injection flow, the feedforward correction and the feedback correction and outputting a final ammonia injection control instruction; and the execution module is used for adjusting the ammonia spraying flow according to the control instruction.

Description

Accurate ammonia injection control method and system for low-temperature SCR denitration system Technical Field The invention relates to the technical field of flue gas denitration accurate ammonia injection control, in particular to an accurate ammonia injection control method and system for a low-temperature SCR denitration system. Background Nitrogen oxides (NOx) are one of the main pollutants in flue gas of coal-fired power plants, sintering plants and steel industry, and the emission to the atmosphere can cause environmental problems such as photochemical smog, acid rain, ozone layer destruction and the like, so that the national and local emission standards are continuously tightened. In the prior art, a sintering machine generally adopts SDA+SCR technology to desulfurize and denitrate or adopts CFB+SCR technology to desulfurize and denitrate, and the SCR denitration technology uses ammonia water with concentration of 20% as a reducing agent to reduce NOx in sintering flue gas into N 2+H2 O under the action of a catalyst so as to realize the aim of denitration. At present, after ammonia water is evaporated by an ammonia water evaporator, ammonia is uniformly injected into flue gas by an ammonia spraying grid, and is reacted with NO x under the action of a catalyst to generate nitrogen and water, so that the denitration efficiency can reach more than 90%, and the ultra-low emission requirement is met. However, in the actual operation process, the existing ammonia injection control mode still mainly depends on single-loop feedback control or manual adjustment, so that the denitration system has the defects that the concentration and flow rate of NO x in sintering flue gas are changed frequently, the influence of load, temperature and raw material fluctuation on the inlet NO x is large, the problem of response delay exists in the traditional single-loop feedback control, the condition of ammonia injection lag or excessive injection easily occurs, the concentration fluctuation of outlet NO x is large, the manual adjustment is difficult to respond to the change of working conditions in time, and an operator is often required to adjust the ammonia injection amount by experience, so that the system operation stability is poor. In order to improve the accuracy and response speed of ammonia injection control, some technical improvements have been made in the related art. For example: Patent CN119425377a discloses a nitrous oxide emission reduction control system and method for an SCR denitration device, and the reaction conditions are optimized to reduce nitrous oxide emission by monitoring and adjusting parameters such as flue gas temperature, ammonia injection flow, etc., but the control strategy does not involve short-term prediction of NOx concentration, does not adopt a dynamic feedforward mechanism, and still belongs to passive response control. Patent CN116651203a proposes an SCR denitration control method adapted to frequent fluctuation of unit load, which adjusts the ammonia injection amount through multi-parameter feedforward such as inlet NOx concentration, SCR reaction temperature, flue gas baffle opening, etc., and limits the ammonia injection change rate when the temperature decrease rate is large, but the method does not introduce a nonlinear dynamic prediction model, has limited adaptability to complex working condition coupling effect, and cannot realize active intervention in a true sense. Patent CN117679930a relates to a flue gas coupling denitration accurate ammonia spraying method, which adopts modes of coupling SNCR and SCR, layering ammonia spraying and the like to promote denitration efficiency and control ammonia escape, but the technical key point is that the process structure is optimized, a data-driven NOx concentration prediction model is not established, and real-time feedforward correction of ammonia spraying flow is not realized. In summary, although the prior art is improved in the aspect of ammonia injection control, the prior art still has the defects that short-term accurate prediction capability of NOx concentration change trend is lacking, the control mode is mainly passive feedback, the ammonia injection amount cannot be actively regulated before the working condition changes, and meanwhile, the prior art does not consider the cooperative optimization of a denitration and desulfurization system, and the overall flue gas purification efficiency still has room for improvement. Therefore, a need exists for an accurate ammonia injection control method capable of realizing short-term prediction of NOx concentration, feed-forward feedback composite control and self-learning and multi-system collaborative optimization capability, so as to improve the stability, economy and environmental protection performance of a low-temperature SCR denitration system. Disclosure of Invention In order to solve the technical problems, the invention provides the accurate ammonia injection control