Metal chloride influence on syngas component during coal pyrolysis in fixed-bed and entrained flow drop-tube furnace

Pyrolysis was carried out in an entrained flow drop-tube furnace（DTF） and tube furnace（TF） using Pingzhuang lignite coal with various catalyst concentrations（2 wt%, 4 wt%, and 6 wt%） of KCl and CaCl2 for the syngas component at 800°C–1200°C. Five catalysts（KCl, CaCl2, NiCl2, MnCl2, and ZnCl2） at 6 wt% were chosen for DTF at 800°C–1200°C. An online gas chromatograph analyzer and the Fourier transform infrared spectra were used for the analysis of the syngas and char structure. Results showed that the overall CO2 and CH4 content in DTF was lower than that in TF, mainly due to the CH4 carbon reaction at high temperature. Moreover, the CO% in DTF was higher than in the TF experiment, as char reacts with carbon dioxide to form carbon monoxide. In DTF experiment, the maximum and minimum CO2 content was 15.20% with 6 wt% Mn at 800°C and 0.33% with 6 wt% K at 1100°C, respectively. The maximum CO% was found in raw coal. Concentrations of Mn2+, Zn2+, and K+can significantly increase H2%, whereas Ca2+ and Ni2+ have a minor effect on H2%; however, the overall presence of catalyst has a positive impact on the H2 content.