Denitration operation optimization method for SCR (Selective Catalytic Reduction) system of tangential firing pulverized coal boiler

Abstract

The invention discloses a denitration operation optimization method for an SCR (Selective Catalytic Reduction) system of a tangential firing pulverized coal boiler. The denitration operation optimization method comprises the special steps of using a numerical simulation method; obtaining a velocity of flue gas, an NOx concentration distribution uniformity and a deviation of an outlet of the boiler by means of considering the structure and the operation condition of the boiler as a boundary condition of an inlet of the SCR system; obtaining the velocity of the flue gas, an NH3 / NOx distribution uniformity and a deviation inside the SCR reactor; optimizing and adjusting an ammonia spraying flow of an ammonia spraying nozzle on a flue of the SCR system according to the velocity of the flue gas and the NH3 / NOx; increasing the ammonia spraying flow of the ammonia spraying nozzle corresponding to an area with the larger velocity of the flue gas, and decreasing the ammonia spraying flow of the ammonia spraying nozzle corresponding to an area with the smaller velocity of the flue gas; and increasing the ammonia spraying flow of the ammonia spraying nozzle corresponding to an area with the smaller NH3 / NOx, and decreasing the ammonia spraying flow of the ammonia spraying nozzle corresponding to an area with the larger NH3 / NOx. The denitration operation optimization method provided by the invention can be used for optimizing and adjusting by comprehensively considering the structures and the operation conditions of the boiler and the SCR system, so that the denitration efficiency of the SCR system is improved; the spraying amount and the release rate of ammonia can be reduced; the security, the economical efficiency and the environmental friendliness of the operation of the boiler unit can be improved.

Description

technical field [0001] The invention belongs to the technical field of pulverized coal combustion denitrification, and in particular relates to a denitrification operation optimization method for an SCR system of a tangentially fired pulverized coal boiler, and is especially suitable for four-corner tangentially circular and wall-type tangentially fired pulverized coal boilers. Background technique [0002] China's primary energy consumption is dominated by coal, accounting for more than 70% of primary energy consumption, and this coal-based energy structure will not change in the future. Nitrogen oxides (NO, NO 2 and N 2 O, collectively referred to as NO x ) emission is one of the main sources of air pollutants. NO x It will directly endanger human health, and also lead to the formation of acid rain and photochemical smog and cause the atmospheric greenhouse effect. The new "Emission Standards of Air Pollutants for Thermal Power Plants" (GB13223-2012), the NOx (in NO ...

AI Technical Summary

Problems solved by technology

When its molar ratio is small, NO x with NH 3 Incomplete response, NO x low conversion rate

When the molar ratio exceeds a certain range, NO x The conversion rate no longer increases, causing the reducing agent NH 3 The waste of ammonia slip increases

[0011] (4) Ammonia escape rate

[0012] If NH 3 If the quantity is not well controlled, it will not only increase the cost, but also cause two main problems: corrosion of the heat exchange surface of the air preheater and pollution of fly ash

[0017] However, in actual operation, the following problems exist in the operation of the SCR system: (1) The denitrification efficiency is lower than the design value, and the NO x The emission cannot meet the environmental protection standard; (2) Incomplete reaction leads to some NH 3 escape, and the operating cost increases; (3) NH 3 Escaping causes secondary pollution, leading to corrosion and blockage of air preheaters and other equipment, which poses hidden dangers to the safe and stable operation of boilers

In response to these factors, if the operation is not adjusted in time, the denitrification efficiency of the system will decrease, the emission will exceed the standard, the ammonia escape rate will increase, and the secondary pollution will be aggravated, which will seriously affect the safety, economic and environmental performance of the entire boiler unit system operation.

However, the influence of these factors has not been considered in the current operation adjustment.

(3) For the inlet section of the SCR system described in (2) and the flow and NO in the reactor x Uneven distribution of properties and deviations, lack of effective NH 3 Injection control optimization methods and means, including NH 3 The determination method of injection position and flow rate and the simple and easy injection of NH 3 adjustment controls

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