And driving SCR denitration ammonia spraying targeted control loop based on model

Abstract

The invention relates to an SCR denitration ammonia spraying targeted control loop based on model driving. The system comprises an SCR steady-state model, a dynamic prediction model, a targeting control model, an SCR inlet NOx concentration soft measurement model and an SCR ammonia escape soft measurement model. Adding the NOx concentration at the outlet of the SCR denitration system to the outputvalue of the dynamic prediction model; wherein the signal is used as an input signal of the SCR steady-state model; the SCR steady-state model gives a reference instruction according to the directionand the size of an input signal and the deviation degree in a front period and a rear period so as to be adjusted by the targeting control model; and meanwhile, the reference instruction also servesas signal input values of the dynamic prediction model, the SCR inlet NOx concentration soft measurement model and the SCR ammonia escape soft measurement model, and signal outputs of the SCR inlet NOx concentration soft measurement model and the SCR ammonia escape soft measurement model are fed back to the dynamic prediction model. The ammonia spraying amount can be effectively reduced, and the operation economy of the unit is improved.

Description

technical field [0001] The invention relates to the technical field of ammonia injection regulation for an SCR denitrification system of a coal-fired unit, in particular to a model-driven SCR denitrification ammonia injection targeted control loop. Background technique [0002] At present, there are two main ways to adjust the ammonia injection in the SCR denitrification system of coal-fired units in my country: one is the constant mole ratio of ammonia nitrogen (Constant Mole Ratio Control), and the other is the fixed outlet NO x Setpoint control mode (Constant Outlet NO x Control), where: [0003] Fixed ammonia nitrogen molar ratio method: This control method is widely used and is a typical control strategy. It mainly determines the fixed ammonia nitrogen molar ratio based on the denitrification capacity and denitrification efficiency of the catalyst, so as to remove NO in the flue gas x , the control strategy is a single-loop control system, the setting value can be ad...

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Problems solved by technology

[0004] The disadvantages of this control strategy are: ①Since the combustion process of the boiler is dynamic, the nitrogen oxides in the flue gas will change in real time, and it is easy to cause excessive deamination after the ammonia-nitrogen molar ratio is fixed; ②Excessive ammonia injection will not be able to Accurately control the amount of ammonia escape; ③Increased operating costs and secondary environmental pollution; ④Only considering the denitrification efficiency, the inlet NO x When the concentration is relatively low, it is easy to over-spray ammonia, which increases operating costs

This control method is also a single-loop control system, only considering the outlet NO x Concentration changes at the inlet NO x When the concentration is too high, the outlet concentration setting value is too low, which will exceed the denitrification capacity of the catalyst, and it is easy to over-spray ammonia, which will also increase the operating cost

[0006] The above control methods all need to be controlled according to the export NO x concentration and denitrification efficiency to obtain the required amount of ammonia. The injection amount of ammonia gas is adjusted through the on-site regulating valve. If the amount of ammonia injection is small, the denitrification efficiency will be too low. If the amount of ammonia injection is too small, the ammonia escape rate will increase, resulting in ash accumulation in the tail flue. Corrosion, economically it is also a waste of ammonia supply

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