A novel method for precise measurement of unburnt carbon in boiler fly ash by ECSA® based on TG-MS

Abstract

The unburnt carbon content of fly ash is an important index for evaluating the combustion efficiency of boilers. Measurement by traditional loss-on-ignition (LOI), approximate and elemental analyses causes large errors due to mixing minerals such as portlandites, carbonates, or sulfates with the unburnt carbon. In this paper a new method of Equivalent Characteristic Spectrum Analysis (ECSA®) based on Thermogravimetric Mass Spectrometry (TG-MS) was adopted to determine the unburnt carbon in fly ash. The measuring mechanism, accuracy, superiority, sensitivity, and reliability of ECSA® were discussed. The intrinsic measuring mechanism of ECSA® and its sensitivity were explored through analyzing the reaction characteristics of model compounds that were used to simulate the real fly ash. Five types of real fly ashes collected from boiler plants were used to calibrate and verify the reliability and accuracy of ECSA® method. The ECSA® was finally validated to be more precise and accurate by improving 2 to 3 orders of magnitude in error compared with the LOI and elemental analysis on determining the unburnt carbon in fly ash, and can provide reliable information to assess the operating status of boilers.