Zhundong coal; Sodium; Alkali metal; Sorbent additives; LIBS;INDUCED BREAKDOWN SPECTROSCOPY; FIXED-BED REACTOR; ATOMIC SODIUM; BROWN-COAL; ALKALI REMOVAL; COMBUSTION; PYROLYSIS; SORBENTS; GASIFICATION; TEMPERATURE

The retention performance of 5 different sorbent additives, including 2 pure additives, i.e., silica and alumina, and 3 typical natural mineral additives, i.e., kaolin, mica and pyrophyllite, on the release of sodium during the combustion of Zhundong coal is investigated via a combination of online multi-point Laser-Induced Breakdown Spectroscopy (LIBS) technique and offline measurements including inductively coupled plasma atomic emission spectrometer (ICP-AES), X-ray diffraction, and ash fusion temperatures (AFTs). The online and offline measurement results for the sodium release of Zhundong coal/additives mixtures are compared and verified with each other. Ternary phase diagram simulations are performed to further substantiate the impact of different additives on liquidus temperatures of Zhundong coal ash. All the five sorbent additives show a significant sodium retention effect, while alumina and kaolin are better additives considering the effects on AFTs.

LIBS instrument design; Liquid steel analysis; On-line process monitoring; Vacuum alloys production; Laser-induced breakdownspectroscopy;LIBS; STEEL

Laser-induced breakdown spectroscopy (LIBS) utilizing an echelle spectrograph-ICCD system is employed for online analysis of elements concentration in a vacuum induction melting workshop. Active temperature stabilization of echelle spectrometer is implemented specially for industrial environment applications. The measurement precision is further improved by monitoring laser parameters, such as pulse energy, spatial and temporal profiles, in real time, and post-selecting laser pulses with specific pulse energies. Experimental results show that major components of nickel-based alloys are stable, and can be well detected. By using internal standard method, calibration curves for chromium and aluminum are obtained for quantitative determination, with determination coefficient (relative standard deviation) to be 0.9559 (<22%) and 0.9723 (<2.8%), respectively. (C) 2017 Elsevier B.V. All rights reserved.

Laser induced plasma; Spectral line profile; Continuum intensity; Full width at half maximum (FWHM); Spectral line shift;INDUCED BREAKDOWN SPECTROSCOPY; INDUCED PLASMA DYNAMICS; ABLATION

There are many methods to characterize plasma parameters for laser-induced plasma, optical emission spectra method is a very important one to diagnose laser-induced plasma parameters. In this paper, Nd:YAG solid state laser which output 1064 nm wavelength interact with aluminum alloy sample, the temporal evolution of spectral line profile, spectral line intensity, continuum intensity, line to background intensity ratio, spectral line broadening and spectral line shift were investigated in detail for laser induced aluminum alloy plasma. The results show that the interaction of electrons between atoms and ions are very intense, which leads to electrons production of laser induced plasma at the early stage. Stark broadening effect of spectra lines are distinct and multiple spectral lines are overlapped. With temporal evolution, the electron density and electron temperature decreased quickly, the multiple spectral lines are separated slowly, and the spectral line profile is becoming thinner and symmetric. For Mg I 285.2126 nm characteristic spectral line, the intensity increased with temporal evolution at first, the intensity reached maximum value about 100 ns, and then the intensity decreased with temporal evolution, which is due to the fact that electron and ion are dominated at early stage of laser-induced plasma, atomic spectral line is very weak, with temporal evolution, the process of recombination between electrons dominated and the atomic number density increased, when the atomic number density reached maximum value, the spectral line intensity decreased with temporal evolution because excitation temperature decreased quickly. Taking wavelength in NIST database as reference wavelength, the spectral line shift for Mg I 285.212 7 nm and Zn II 206.200 4 nm take place red shift at early stage of laser induced plasma, the continuum intensity decreased dramatically by power law with temporal evolution, on the contrary, comparing with continuum intensity and spectral line intensity, continuum intensity attenuate sharply, the line to background intensity ratio increase with temporal evolution. This early phenomenon of laser inducedaluminum alloy plasma were discussed in detail from theoretical perspective.