Denitrification operation optimization method of SCR (selective catalytic reduction) system of W flame boiler

Abstract

The invention discloses a denitrification operation optimization method of a SCR (selective catalytic reduction) system of a W flame boiler. The denitrification operation optimization method particularly comprises the following steps: acquiring the smoke flow speed and the NOx concentration distribution uniformity and deviation at an outlet of a boiler by considering the structure and the running working condition of a W flame boiler so as to act as inlet boundary conditions of a rear-stage SCR system; adjusting the ammonia spraying flow rate corresponding to the region at which the flue flow speed is slightly high and the NH3 / NOx is slightly low to be low, increasing the number of ammonia spraying nozzles, and adjusting the ammonia spraying flow rate corresponding to a region at which the flue flow speed is slightly slow and the NH3 / NOx is slightly high to be low when the standard criterion that the ammonia spraying flow rate at the upper layer is higher than that at the lower layer, and the ammonia spraying flow rate at the middle is higher than that at two sides is met. According to the invention, the structures and the running situation of the boiler and the SCR system are optimized and adjusted, the denitrification efficiency of the SCR system is improved; the spraying-in quantity and the escape rate of ammonia are reduced.

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 coal-fired boiler, and is especially suitable for W-type flame coal-fired 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. W flame boiler is especially suitable for the combustion of low-volatile low-quality coal, but the NOx emission is relatively large. The new "Emission Standard of Air Pollutants for Therm...

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 the determination method of NH3 injection position and flow rate and the simple and easy adjustment and control means of NH3 injection

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