Pyrolysis experiments of Pingliang coal

wheat straw and their blends were carried out in a tube furnace in CO_2 and Ar atmosphere at 700～900 ℃

to investigate the nitrogen transformation characteristics during coal-biomass co-pyrolysis in CO_2 atmosphere. The results show that

at high temperatures

gasification occurs in CO_2 atmosphere

which promotes the nitrogen release from the fuel and enter the volatile matters

which reduces the nitrogen content in char

so the NH_3 and N_2 yield of Pingliang coal and wheat straw as well as the HCN yield of wheat straw rises. Interactions which occur in co-pyrolysis suppress the HCN and NH_3 yield but promote production of N_2 at 700 ℃.