Nitrogen conversion during rapid pyrolysis of coal and petroleum coke in a high-frequency furnace

Rapid pyrolysis of three typical Chinese coals, lignite from Inner Mongolia, bituminous from Shenfu coalfield, and anthracite from Guizhou, as well as a petroleum coke were carried out in a drop-style high-frequency furnace. The reactor was induction coil heated and had a very small high-temperature zone, which could restrain secondary conversions of nitrogen products. The effects of temperature and coal rank on conversions of fuel-N to primary nitrogen products (char-N, HCN–N, NH3–N and (tar+N2)–N) have been investigated. The results showed that, the increasing temperature reduced the yields of char-N and promoted the conversion of fuel-N to N2. Char-N yields increased, while volatile-N yields decreased as the coal rank increased. In most of the conditions, NH3–N yields were higher than HCN–N yields during rapid pyrolysis of coal. In the case of petroleum coke, NH3–N yields increased gradually with the increasing temperature, but no HCN was detected. We argue that NH3–N can be formed directly through the primary pyrolysis without secondary reactions. Although volatile-N yields of lignite were higher than those of bituminous, yields of (HCN+NH3)–N in volatile-N of lignite were lower than those of bituminous. While the (HCN+NH3)–N yields of anthracite were the lowest of the three coals. Both of the (HCN+NH3)–N yields and (HCN+NH3)–N proportions in volatile-N of petroleum coke were lower than the three coals.