Research On Measurement Of Gas Concentration Distribution In The Furnace Of Power Plant

Real-time detection of the concentration distribution of crucial gas components in the controllable furnace makes a contribution to the accurate adjustment of combustion, the increase of combustion efficiency and the effective control of harmful substances generation. Tunable diode laser absorption spectroscopy is a new kind of spectroscopic measurement technology of gas components, which has been an effective means of monitoring atmospheric trace gases, industrial gas leakage, high temperature and high exhaust plume with the characteristics of high spectral resolution, high accuracy, fast response, high sensitivity, and less susceptible to interference of other gases. We found it’s technically feasible for the non-contact and real-time online imaging measurement of gas components in power plant furnace basing on the TDLAS combined with tomography technique. However we still faced with some problems such as the lineshape is affected by the high temperature and negative pressure environment, the measurement accuracy is determined by the number of beams and the optical path arrangements, the laser absorption and transmission is limited by dust and other particulate matters and so on.Basing on tunable diode laser absorption spectroscopy, the methods and the techniques for the crucial gas component concentration distribution measurement in power plant furnace is studied, which is filled with many different kinds of gas components and solid particles. Firstly, the gas concentration and temperature calculation formula was deduced theoretically based on the Beer-Lambert law combining with tunable laser absorption spectroscopy technology. The scanning wavelength direct absorption method was selected as a preferred method of concentration measurement. We built a single and short optical path gas concentration measurement system in the laboratory and calibrated the laser and other key equipment of the system. In addition a single optical path direct-transmit gas absorption pool was also designed. We have completed a series of tests on different concentrations of CO₂ gas on the experimental platform. The results showed that the test system can accurately measure the CO₂ gas with the concentration of 20%-100% concentration. The main measurement error comes from the interference of adjacent lines and the limitation of wavelength scanning range. Finally, the effects of the number and arrangement of projected paths to the imaging measurement was studied by simulation based on the two-dimensional numerical simulation models built by the computer. The results showed that the distribution characteristics of field objects, the arrangement and number of projection paths were interrelated. They affect the image reconstruction results together with some preferably certain rules, which are significant to the research of two-dimensional imaging measurement of the gas distribution.