Research progress on online in-furnace monitoring techniques during high-alkali coal combustion based on spontaneous emission radiation analysis
High-alkali coal such as Zhundong coal has huge reserves in Xinjiang,in which rich alkali metal elements can easily lead to fouling and slagging problem on heating surface of the furnace,thus to decrease the safety of boiler.It is of great significance to develop efficient and clean combustion power generation technology for high-alkali coal to achieve the"double-carbon"goal.The research progress of the online monitoring technology in high-alkali coal combustion furnace based on spontaneous emission radiation analysis is summarized.The development trend and dynamics are discussed focusing on the research status and application of emission spectrum technology and spontaneous emission radiation imaging and image processing technology in high-alkali coal combustion monitoring.Emission spectroscopy can obtain the temperature and component concentration by processing the spectral radiation signal emitted by the flame at different wavelengths.Recently,it has been widely used to measure the combustion temperature and the gaseous alkali metal concentration in the industrial furnace and judge the slagging trend in the furnace qualitatively.Different from emission spectroscopy technology,spontaneous emission radiation imaging and image processing technology has the ability to analyze the spatial distribution of signals.The technology obtains the spontaneous radiation image in the furnace via CCD,CMOS and other surface array sensors.Based on image processing technology and thermal radiation imaging theory,the temperature distribution of the combustion field in three-dimensional space can be obtained combining with solving radiation inverse problem,which makes it possible to monitor the three-dimensional visual of slagging formation.In the future,monitoring of the fouling and slagging on the heating surface in two or three dimensions should be carried out based on emission spectroscopy technology,spontaneous emission radiation imaging and image processing technology.Combined with the distribution of parameters such as combustion temperature and gaseous alkali metal concentration in the furnace,a quantitative judgmental index of fouling and slagging on the heating surface of high-alkali coal combustion should be established to achieve the goal of online prediction of fouling and slagging on the heating surface.