Rapid coal quality analysis using laser-induced breakdown spectroscopy with suction-restraint particle flow method

Abstract

Real-time and accurate coal quality analysis is imperative for optimizing combustion efficiency and minimizing environmental pollution. Laser-induced breakdown spectroscopy (LIBS) analysis of particle flow offers substantial potential for online monitoring, but suffers from signal instability caused by inherent spatial dispersion. To address this fluid dynamic challenge, a novel suction-restraint particle flow LIBS (SPF-LIBS) method was developed. By utilizing active negative-pressure suction, this method aerodynamically confines the particle stream, effectively enhancing localized particle density and laser ablation efficiency. Compared to conventional free-fall particle flow LIBS (FPF-LIBS), the SPF-LIBS configuration completely eliminates invalid spectra, elevating validity rates from 65% to 100%. Furthermore, it improved the signal-to-noise ratio (SNR) of the C I 247.86 nm line from 28.01 to 41.59, and suppressed the air breakdown ratio by a factor of 3 to 4. High-speed imaging and spatiotemporal analysis confirmed that this confinement mitigates inter-pulse laser interference, reducing the average plasma pulse-to-pulse RSD by 60%. For quantitative evaluation, a Particle Swarm Optimization-Support Vector Regression (PSO-SVR) model was utilized. The system achieved excellent precision, yielding mean absolute errors of prediction (MAEP) of 0.268 MJ kg⁻¹, 0.736%, 0.522%, and 0.986% for heat value, carbon content, volatile, and ash, respectively. These findings establish SPF-LIBS as a robust solution for continuous industrial particulate monitoring.