Influence of coal properties on the release of HCN during rapid pyrolysis of Chinese coals

Six Chinese coals were pyrolyzed in a semi-entrained flow/semi-fixed bed reactor to investigate HCN release from coal nitrogen in temperature range from 600 to 1000°C. Experimental results show that HCN release is independent on nitrogen content in coal, while pyrolysis temperature, hydrogen content in coal and ash content in coal are three major factors influencing the HCN release from coal nitrogen. As pyrolysis temperature increases, the HCN conversion increases remarkably. The more the hydrogen content in coal, the more the HCN conversion is. It shows that coal donated H is an important factor for HCN to release. The more the ash in coal, the less the HCN conversion is due to the catalysis of ash to HCN decompose or restrain to HCN formation. Catalysts of NaCl, CaCO₃ and Fe(C₅H₅)₂ were also investigated to illustrate the ash composition influence on HCN formation. Results show that Fe can reduce HCN release, while Ca and Na have little impact on HCN formation.