Fast pyrolysis of pulverized coal at high temperatures and fuel nitrogen migration characteristics in a wire mesh reactor

Pulverized coal (PC) pyrolysis is an indispensable process for coal thermal conversion and utilization. The transformation of fuel-N into fast pyrolysis is a basis for the investigation of nitrogen migration in coal combustion. In this paper, a wire mesh reactor was used to study the initial decomposition processes and to reveal the final pyrolysis yield and composition distribution during the fast pyrolysis process. Furthermore, the initial pyrolysis characteristics of PC with different ash contents were presented and compared. The results showed that both Huangling coal (with higher volatile) and Wuhai coal (with higher ash content) showed a similar trend, and the pyrolysis ratio increased with the increased pyrolysis final temperature. The pyrolysis ratio at the high heating rate was estimated to exceed that at the low heating rate by 2%-10%. With the temperature increased, the char-N yield decreased first and then tended to be stable, and most of nitrogen remained in the char (more than 55%). An increase in heating rate made the pyrolysis zone to shift toward higher temperature, and it enhanced the yields of volatile and tar as well as the proportion of tar in volatile. Besides, the heating rate increased from 10 degrees C center dot s(-1) to 1500 degrees C center dot s(-1), the yield of tar-N increased from 4% to 14% and gas-N decreased from 28% to 19%. Overall, NH3 yielded was higher than HCN, which became more apparent at high heating rates. The content of the N-6 was positively related to the coal pyrolysis ratio.

Automated summary

Pulverized coal (PC) pyrolysis plays a crucial role in coal thermal conversion and utilization. The investigation of nitrogen migration in coal combustion is based on the transformation of fuel-N into fast pyrolysis. In this study, a wire mesh reactor was used to analyze the initial decomposition processes and understand the final pyrolysis yield and composition distribution. Additionally, the initial pyrolysis characteristics of PC with different ash contents were compared. The results revealed that the pyrolysis ratio increased with the temperature and the high heating rate led to a higher pyrolysis ratio compared to the low heating rate. The char-N yield decreased initially with the increase in temperature and then reached stability, with the majority of nitrogen remaining in the char. Furthermore, an increase in heating rate resulted in a shift of the pyrolysis zone towards higher temperatures and increased yields of volatile and tar, as well as the proportion of tar in volatile. The NH3 yield was higher than HCN, especially at high heating rates. The content of N-6 showed a positive correlation with the coal pyrolysis ratio.