| Due to our country’s rich coal resources,coal-fired power plant has become the main force in the power industry through long-term development.However,the flue gas produced by coal combustion contains pollutants such as NO_X and dust,which brings great pressure to environmental pollution control.In response to the national ultra-low emission policy,power plants have effectively controled NO_X emissions through low-nitrogen combustion technology.But this technology will increase the CO concentration,resulting in slagging and corrosion in the furnace.Unreasonable combustion conditions will reduce combustion efficiency and waste coal resources.Monitoring the amount of oxygen in the flue gas can only provide a reference for parameter adjustments such as the ratio of air to coal.CO monitoring can further reflect the degree of incomplete combustion in the furnace,thereby reflecting the mixing of air and coal.Therefore,in view of the above-mentioned reasons,in response to the technical problems faced by the existing CO measurement principles,this paper conducted theoretical experiments and application research on CO online measurement.The main research contents as follows:1.CO measurement research was based on tunable diode laser absorption spectroscopy technology(TDLAS),which has the characteristics of high sensitivity,high precision and fast response.The characteristics of the direct absorption method and the wavelength modulation method were analyzed.The theoretical formulas of the second harmonic method and calibration-free 2f/1f method were derived.2.After analyzing the characteristics of the background environment for CO measurement,we simulated and analyzed the absorption spectrums of CO molecules near 1570nm and 2327nm from the aspects of line intensity and absorbance.Finally,the absorption spectrum at 2326.823nm was selected,which can avoid the interference of background gas absorption.3.The 4f/1f method was selected for CO experiment measurement research.We designed and built a CO experimental measurement system,calibrated the laser parameters,and used the direct absorption method to calibrate the optical path of the gas chamber.We verified the accuracy of this method through the concentration measurement experiment.The long optical path absorption spectroscopy technology was researched to effectively extend the absorption optical path and improve measurement accuracy.Based on the above studies,the CO engineering prototypes were developed,and the measurement accuracy of the prototypes were debugged and calibrated.4.By analyze the current application status of the existing power plant flue gas measurement methods,we designed a multi-point zone synchronous wheel measurement system to deal with the uneven distribution of CO concentration in the flue gas.We researched high-precision constant current dilution sampling pretreatment technology to make the flue gas have a constant dilution ratio,and reduce the dew point of flue gas.This technology does not require heat tracing for sampling pipes and measuring chambers.The concentration simultaneous comparison test was carried out between engineering prototypes and Testo 350 on site,and the partition system was debugged and calibrated.Finally,continuous online flue gas measurement was performed and the measurement results were analyzed.Based on the TDLAS technology,this paper has conducted a measurement research on CO in the power plant flue gas,which provides a reference for boiler air distribution and combustion condition adjustment,so as to effectively optimize boiler combustion. |
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