Research On Fast NO_x Measurement Technology Based On DOAS

Nitrogen oxides are currently the largest pollutant gas emitted by coal-fired power plants.With the increasingly stringent requirements of the Ministry of Environmental Protection on the emission of pollutant gases,the emission at the general outlet of the power plant cannot be higher than 50mg/m³.Selective Catalytic Reduction（SCR）is currently the best way to remove NO_x.In order to cooperate with the peak and frequency regulation of the power grid,the boiler load of thermal power plants is often in a state of constant change,resulting in inaccurate control of ammonia injection under the SCR method,resulting in fluctuations in the NO_x value at the SCR outlet,affecting the overall economic benefits and safe operation of the power plant.It can be seen that the optimization of ammonia injection is a problem that needs to be solved urgently in the current power plant.The main logic of ammonia injection is to first give the main controller a set value,and then calculate the amount of ammonia injection by measuring the NO_x value at the SCR inlet and outlet.Therefore,the CEMS measuring instrument for NO_x must not only ensure the accuracy of the measurement,but also need to ensure a certain measurement speed.This research group investigated some CEMS instruments in the current domestic and foreign markets,and designed a measurement instrument for near-position sampling analysis based on DOAS technology.The main work includes:comparing and selecting the main components measured by DOAS method;completing the prototype assembly of the near-position instrument;in the laboratory,testing the single-component measurement and mixed gas measurement under different concentrations of NO and SO₂;The power plant has completed on-site installation,and compared with the original two foreign imported instruments of the power plant for comparative measurement and analysis.The experimental data show that the measuring instrument designed by the research group has verified the stability and accuracy of the instrument’s measurement in the laboratory.During the field experiment,the data measured by the instrument of the research group is consistent with the data measured by the imported instrument;The measurement speed is more than 60s faster than that of an imported instrument.