SCR system automatic control method based on ammonia spraying sensitive valve locking

Abstract

The present invention discloses a SCR system automatic control method based on ammonia spraying sensitive valve locking. The method comprises three steps: firstly, performing comprehensive analysis of varying load condition operation characteristics of the SCR system based on a field test and a CFD numerical simulation technology to obtain flue gas 'NOx flow' regional continuous distribution characteristics matching an AIG type; then determining the weight of each ammonia spraying branch pipe valve, locking a certain number of sensitive valves according to a preset sensitive valve locking principle, and installing an automatic regulating valve at a corresponding ammonia spraying region; finally, developing an ammonia spraying logic controller and corresponding main control and sub-control logics, realizing multistage optimization setting of parameters of the control system, and realizing the accurate automatic control of the main ammonia spraying regulating valve of the SCR system and the locking sensitive valves. The SCR system automatic control method based on ammonia spraying sensitive valve locking is able to overcome the problems of characteristics of the SCR system such as nonlinearity, large delay and the like so as to realize the accurate automatic control of the ammonia spraying of the SCR system, substantially enhance the SCR denitration reaction efficiency, save the dosage of ammonia, reduce the ammonia escape and effectively inhibit the generation of ABS.

Description

technical field [0001] The invention relates to an automatic control method of an SCR system based on ammonia injection sensitive valve locking, and belongs to the technical field of air pollutant control of coal-fired boilers. Background technique [0002] Selective Catalyst Reduction (SCR) technology has become the most widely used flue gas denitration technology for coal-fired units at home and abroad based on its advantages of high technology maturity, high denitration rate, good reliability and low secondary pollution. The denitrification efficiency of SCR flue gas denitrification reaction directly depends on the NO in the flue gas x with NH 3 In theory, the ideal ammonia-nitrogen equivalence ratio can be well controlled in a stable state. However, the actual operation of the SCR system will be affected by factors such as coal quality, boiler load and combustion conditions. The system It presents the characteristics of nonlinearity and large hysteresis, which directly...

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Problems solved by technology

The denitrification efficiency of SCR flue gas denitrification reaction directly depends on the NO in the flue gas x with NH 3 In theory, the ideal ammonia-nitrogen equivalence ratio can be well controlled in a stable state. However, the actual operation of the SCR system will be affected by factors such as coal quality, boiler load and combustion conditions. The system It presents the characteristics of nonlinearity and large hysteresis, which directly makes it difficult to ensure the ideal ammonia-nitrogen equivalent ratio in the flue gas flow field with a single fixed ammonia injection method.

[0003] In this regard, the SCR denitrification system of some domestic coal-fired units has developed the automatic control technology of ammonia injection, but this kind of automatic control belongs to the "black box" control, and at most some feedforward predictive control is added, and the operation of the SCR system has not really been established. The good match between the characteristics and the ammonia injection control characteristics cannot guarantee that the SCR system will maintain the ideal mixed equivalent ratio of ammonia and nitrogen in the flue gas during actual operation, which directly leads to low catalytic denitrification reaction efficiency, high ammonia injection volume, increased ammonia slip, and a large amount of ABS. A series of issues such as production

[0004] The published Chinese invention patent CN105126616A proposes an optimization method for ammonia injection in SCR systems based on weight valve control, which realizes the comprehensive trade-off of the valve openings of each ammonia injection branch pipe under variable load conditions. The opening of the ammonia valve is fixed, so it is difficult to ensure the real-time and accurate matching between the system operating characteristics and the ammonia injection characteristics under variable load conditions; in addition, this method proposes that the data collection of the system operating characteristics is only through direct on-site testing. Factors such as load condition test time requirements and manpower requirements directly lead to fewer samples of constant load condition data that can be collected, which is not conducive to finding out the real operating characteristics of the system

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