Flue gas denitration system of thermal power generating unit and control method

Abstract

The flue gas denitration system of the thermal power generating unit comprises a flue, an ammonia spraying grid, a mixer, a flow guiding device, a rectifying device, a catalyzing device and a NOx measuring device, and a control device is electrically connected with a proportioning valve of the ammonia spraying grid, the NOx measuring device, a coal quality measuring device and a unit load measuring device; according to the control method, feedback control can be carried out on the opening degree of the proportioning valve according to the concentration of NOx, and feedforward control can be carried out on the opening degree of the proportioning valve according to the quality of coal as fired and the load of a unit, so that the technical effect of automatically controlling the ammonia spraying amount according to different loads and different working conditions is achieved; according to the control method, the ammonia spraying amount can be adjusted in advance, the ammonia spraying effectiveness is high, the utilization rate is high, the ammonia escape amount is small, the environmental protection requirement can be met, according to the control method, the unit characteristics which do not fall into the database are subjected to feedback adjustment and supplemented into the database, continuous improvement and correction can be achieved, and therefore the accuracy of pre-adjustment is improved.

Description

technical field [0001] The invention relates to the technical field of flue gas denitration, in particular to a flue gas denitrification system and a control method of a thermal power unit. Background technique [0002] Nitrogen oxides (NOx) are a class of major air pollutants and one of the main factors that form acid rain, photochemical smog and PM2.5 pollution. In industrial flue gas treatment, common NOx emission control technologies include selective catalytic reduction (SCR), Selective Non-Catalytic Reduction (SNCR) and SCR-SNCR hybrid technologies, Selective Catalytic Reduction (SCR) technology has the characteristics of high efficiency, no secondary pollution, and mature technology, and is widely used in large coal-fired units . [0003] With the large-scale grid-connection of photovoltaic power generation and wind power generation, thermal power units have changed from bearing basic loads to flexible operation. Operations such as frequent start-up and shutdown of u...

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Problems solved by technology

[0003] With the large-scale grid-connection of photovoltaic power generation and wind power generation, thermal power units have changed from bearing basic loads to flexible operation. Operations such as frequent start-up and shutdown of units and rapid load reduction have brought adverse effects on the flue gas denitrification system, and ammonia injection is prone to occur. If the amount of ammonia injection is too large, the amount of ammonia escaped from the flue gas denitrification system will be large, and the operating cost will be high, which will easily lead to clogging and corrosion of the air preheater, dust accumulation and jamming of the rotor blades of the induced draft fan, etc., affecting The load capacity of the unit threatens the safe and stable operation of the unit. If the amount of ammonia injection is insufficient, the concentration of nitrogen oxides in the flue gas will be high, which cannot meet the environmental protection requirements.

[0004] Under different loads, the distribution of the flue gas flow field is different. It is difficult to adapt to the current unit operation requirements by manually adjusting the amount of ammonia injection. There is an urgent need for an automatic control of the amount of ammonia injection according to different loads and different working conditions. A thermal power unit flue gas denitrification system and control method with high effectiveness of ammonia injection, high utilization rate, and less ammonia escape, which can meet environmental protection requirements

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