Ammonia injection uniformity adjusting method for SCR (Selective Catalytic Reduction) flue gas denitration system

Abstract

The invention relates to an ammonia injection uniformity adjusting method for an SCR (Selective Catalytic Reduction) flue gas denitration system. The ammonia injection uniformity adjusting method comprises the following steps: (1) adjusting the valve opening degrees of an ammonia injection grid to make the valve opening degrees identical; (2) adjusting the inlet content of diluent air; (3) calculating the target diluent air quantity of each single branch pipe; (4) calculating the target differential pressure on the two sides of a throttle orifice plate; and (5) adjusting the opening degrees of the single branch pipes of the ammonia injection grid in sequence so as to reach the target differential pressure on the two sides of the throttle orifice plate in the step (4). The adjusting method disclosed by the invention is high in degree of accuracy, simple in structure and reliable in result; the uniformity of concentration of NOx at a denitration outlet can be effectively improved, the ammonia escape is alleviated, and thus the safety and stability in operation of the system are improved.

Description

Technical field [0001] The invention relates to the field of SCR flue gas denitration, in particular to a method for adjusting the uniformity of ammonia injection of an SCR flue gas denitration system. Background technique [0002] Nitrogen oxides (NOx) are one of the main flue gas pollutants of thermal power plants. Their large emissions will not only cause acid rain and photochemical smog, but also cause greater harm to human health. According to the regulations in "Emission of Air Pollutants from Thermal Power Plants" (GB13223-2011), the NOx concentration of coal-fired power plants will be 100mg / Nm 3 Emission limits. According to this requirement, most power plants need to install selective catalytic reduction (SCR) denitration devices. [0003] The principle of SCR technology is that in the presence of a catalyst and oxygen, in a lower temperature range (280~420℃), a reducing agent (usually ammonia) is sprayed into the flue gas, and the flue gas is selectively injected. NOx i...

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Problems solved by technology

However, the number of ammonia injection grid valves at the inlet of the SCR reactor is 20 to 30. Due to the different positions of each ammonia injection branch pipe and the outlet main pipe of the mixer, the resistance along the route of the diluted ammonia gas passing through each ammonia injection branch pipe is different. , even if the openings of the ammonia injection grille valves of each channel are the same, the ammonia supply flow rate of each pipeline is also very different