Effects of Na/Ca/Fe intermetallic interactions on nitrogen transformations in high-alkali coal pyrolysis

LIU Yiwen; WEI Lihong; ZHOU Yanling; ZHAO Yonghao; SHANG Jifeng; LOU Kunkun

doi:10.13225/j.cnki.jccs.2024.0103

Abstract：China Xinjiang high-alkali low-rank coal has the characteristics of low ash,high sodium content and high react-ivity.Developing clean and efficient conversion technology for high alkali coal into high-value chemicals will have im-portant strategic significance for solving its resources utilization and helping to achieve the"dual carbon"goal.The miner-al components Na,Ca and Fe in high-alkali coal have catalytic activity in coal pyrolysis,which has a significant influence on nitrogen transformation.There is still a lack of research on the effects of interactions between mineral components on the thermal conversion mechanisms of fuel-N.This study aims to elucidate the effects of intermetallic interactions on ni-trogen transformation during pyrolysis of high-alkali coal.The results have significant implications for formulating con-trol strategies of nitrogen distribution in gas,liquid and solid phases during the cascade utilization of high-alkali coal.Na,Ca,Fe mono-metal and poly-metals were added to deashed coal by equal volume impregnation and sequential impregna-tion methods,and nitrogen transformation was studied in fixed-bed pyrolysis of high-alkali coal.GC-MS,XPS and solu-tion absorption method were used to quantitatively analyze the effects of mono-metals and polymetals on the distribution of nitrogen-containing products in coal pyrolysis,and interactions between them were analyzed by comparing the results of experiments results with theoretical calculations results.The effect of poly-metals on the pathway of N transformation in pyrolysis of high-alkali coal was studied by analyzing yield/residual rate of nitrogen-containing products.The results in-dicate that poly-metals usually exhibit an intermetallic antagonism on the migration of nitrogen into the gas phase,with stronger inhibition of HCN,NH3 than monometallic.The synergistic effects of Na/Ca and Fe/Ca significantly enhance the conversion of N-6 and N-5 in char to heterocyclic nitrogen and amine-N in tar,which demonstrates stronger promotion of nitrogen-containing compound formation in tar compared to mono-metallic systems.Furthermore,Na/Fe and Na/Fe/Ca play a synergistic role for conversion of N-6 to N-Q in char though intermetallic interaction,thus promoting the fixation of nitrogen in char.