Study On Plasma Characteristics Of Fly Ash Particle Flow And Measurement Method Of Unburned Carbon Content

The unburned carbon in fly ash is one of the main indicators of coal-fired power plant operation,it directly reflects the incomplete combustion heat loss of boiler units and influences the emission of the Nox.Real-time monitoring of unburned carbon in fly ash can help to guide the adjustment of a reasonable degree of fineness of coal and the ratio between wind and coal to improve the control levels of boiler combustion.However,traditional measurement methods are offline detection by manual sampling,the sampling time is long and the analysis lagged,which can't satisfy the demand of real-time management of boiler operation.Current online measurement methods have the disadvantage of measuring cavity ash plugging and poor coal adaptability.Therefore,achieving online measurement of unburned carbon in fly ash particle flow without sampling has broad research prospects,it can provide real-time data for selfadaptive combustion optimization system.In this thesis,atomic emission spectroscopy is introduced into the measurement of particle flow samples.Based on the review of the measurement methods of unburned carbon in fly ash,the background and significance of this paper were expounded,and the laser induced breakdown spectroscopy(LIBS)method was introduced.The reaserch contents of this thesis were expounded in detial based on the reasearch of LIBS in unburned carbon in fly ash and particle flow.A set of atomic emission spectroscopy experiment device which can applied to particle flow measurement was set up.The interaction mechanism between laser and particle flow was mastered to exlpore the true source of the invalid spectrum in the particle flow.The influences of particle size and mass flow on laser induced plasma characteristics were also studied.As the measurement of particle flow by LIBS has deficiency,a novel analytical scheme for particle flow spark induced breakdown spectroscopy(PF-SIBS)was proposed,the influence of electrode materials and size effect on plasma characteristics were studied to evaluate its advantage.PF-SIBS was then applied to the measurement of unburned carbon in fly ash.After line interference correction of W and Fe line,the carbon content analysis model was established by multivariate regression method,which improved the measurent accuracy and precision of unburned carbon.The results satisfy the demand of field application and demonstrate the feasibility of PF-SIBS.At last,the full essay is summed up and look ahead to the later study of the application of PF-SIBS to online measurement of unburned carbon in fly ash particle flow.