Soft measurement based ammonia injection grid partition control method

Abstract

The invention relates to a soft measurement based ammonia injection grid partition control method. An ammonia injection grid changes all original manually adjusting doors to pneumatic (or electric) control valve. The control method includes the steps of 1), acquiring and pre-processing data, wherein the data acquisition comprises the measurement of NOX and O2 at an inlet of an SCR (Selective Catalytic Reduction) reactor as well as NOX, O2 and ammonia escape rate at an outlet of an SCR reactor; 2), establishing soft measurement models according to the acquired data; 3), combining the plurality of static soft measurement models with disturbance quantity unit load and coal mill combination to generate a dynamic controller for controlling the opening size of every pneumatic control valve of the ammonia injection grid for further controlling the amount of ammonia injection of every adjustment door, thereby achieving ammonia injection in equimolar ratio of the ammonia injection grid partition. Compared with the prior art, the soft measurement based ammonia injection grid partition controlling method has the advantages of improving the denitration efficiency, reducing the ammonia escape rate and investment and operating costs and the like.

Description

technical field [0001] The present invention relates to the manufacturing technology of environmental protection equipment, in particular to a soft-sensing-based ammonia injection grid partition control method, which is used to control the selective catalytic reduction (SCR) flue gas of thermal power generation unit boilers, waste incinerators and diesel engines, etc. Denitrification device. Background technique [0002] Selective catalytic reduction method is the most common and effective method for removing nitrogen oxides in boiler tail gas. It is widely used in various industrial devices. The main principle is to use liquid ammonia or ammonia water as a reducing After mixing, it is sprayed into the flue upstream of the SCR reactor, and reacts with the nitrogen oxides in the flue gas under the action of a catalyst to form a harmless nitrogen and water discharge system, in which the mixing and distribution of ammonia and nitrogen oxides are the most important One of the k...

AI Technical Summary

Problems solved by technology

Since the layout of the ammonia injection grid cannot adapt to the change of the load of the unit and the combination of the coal mill, it will cause excessive ammonia injection and insufficient ammonia injection

It is difficult to achieve an ideal and uniform distribution of flue gas flow in the flue, and its distribution characteristics will change with factors such as boiler load and coal mill combination

If the current conventional method of equalizing the AIG ammonia injection grid is adopted, it will cause NOx / NH 3 Decreased mixing effect will lead to increased ammonia escape rate and poor denitrification effect in the reaction area

Escaping ammonia and SO in flue gas 3 reaction to form ammonium bisulfate (NH 4 HSO 3 ), because the melting point of ammonium bisulfate is around 140°C, and its freezing point is higher than the temperature of flue gas cooled after passing through the air preheater. After cooling, ammonium bisulfate is very viscous like asphalt. The combination of dust in the air preheater will cause blockage or corrosion of the air preheater, resulting in reduced efficiency and / or output of the unit, and in severe cases, it will cause unplanned shutdown of the unit

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