研究目的
To improve the measurement on quantitative analysis of coal properties using laser-induced breakdown spectroscopy (LIBS) by selecting appropriate spectral pre-processing methods coupled with regression models for each index.
研究成果
The selection of appropriate spectral pre-processing coupled with calibration strategies for each indicator can effectively improve the accuracy and precision of the measurement on coal properties. WTD coupled SVR can be well estimated calorific value and ash, coupling WTD and PLSR performed best for the measurement of volatile content, and normalization with the whole spectral area combined with SVR can get better measurement results for carbon and hydrogen.
研究不足
The study is limited by the complexity of coal composition and the inherent fluctuations in LIBS signal due to factors such as laser energy. The accuracy and precision of quantitative analysis of coal properties still need to be improved for meeting the industrial needs.
1:Experimental Design and Method Selection:
The study compared different normalization methods (channel normalization and normalization with the whole spectral area) combined with two regression algorithms (PLSR and SVR) to select the appropriate calibration method for each indicator. The influence of de-noising by wavelet threshold de-noising (WTD) on quantitative analysis was further studied.
2:Sample Selection and Data Sources:
44 coal samples from different mines in China were used. The coal properties were determined by standard off-line methods based on dry basis.
3:List of Experimental Equipment and Materials:
A Q-switched Nd: YAG laser at a wavelength of 1064nm, 6ns pulse width, repeated at 1Hz. The plasma signal is collected through the optical fiber to a double-channel spectrometer with two CCD detectors.
4:Experimental Procedures and Operational Workflow:
For each coal pellet, the emission spectra were collected spectral signals from 6 locations, 50 pulses per position. Averaged the spectra at two different locations for each sample to reduce unintended measurement fluctuations.
5:Data Analysis Methods:
The performances of models were assessed by the coefficient of determination (R2), root mean square error of prediction (RMSEP), absolute error (AE), average absolute error (AAE), average relative error (ARE) and relative standard deviation (RSD).
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