Process analysis of Pb transformation in the coal devolatilization stage

The transformation of Pb during coal devolatilization affects its emission characteristics. Herein, devolatilization experiments were conducted at 1100-1300 degrees C in a fixed-bed experimental system using four types of coal samples. The occurrences of Pb in coal and devolatilization products were characterized. The release ratio of Pb first increased and then stabilized with time. The Pb release ratio and rate were higher at higher temperatures. Pb in some coal samples was completely released at 1100 degrees C. Pb in coal was mainly in carbonate-and oxide-bound, sulfide-bound, and residual forms. During devolatilization, carbonate-, oxide-, and sulfide-bound Pb gradually disappeared. Organic-bound and residual Pb first increased and then decreased owing to the conversion of gaseous Pb into Char-Pb by char, according to further form analysis of residual Pb and the experiments of char retaining PbCl2 and PbO. The effects of different volatile components on residual Pb were compared, and H2S was found to significantly promote the release of residual Pb in coal. The transformation paths of Pb during coal devolatilization were proposed, including the release of original Pb in coal and the reversible conversion between gaseous Pb and Char-Pb. The results help understanding Pb emission and developing control techniques for coal-fired plants.

Automated summary

The transformation of Pb during coal devolatilization was studied in this research. Devolatilization experiments were conducted on four different coal samples at temperatures ranging from 1100 to 1300°C. The occurrence of Pb in coal and devolatilization products was analyzed, and the release ratio and rate of Pb were found to increase with temperature. The results also showed the different forms of Pb in coal and their changes during devolatilization. This research provides insights into Pb emission and offers guidance for developing control techniques for coal-fired plants.