Release of nitrogenous products and the catalytic characteristics of metal ions during coal pyrolysis

The influence of metal ions on the release characteristics of nitrogenous pollutants from pyrolysis of 3 typical coals with different ranks were studied by demineralization and adding metal salts of Fe, Ca and Na. The interactions of coal type and temperature during coal pyrolysis were explored. The results show that yields of HCN and NH₃ from the demineralized coals are lower than that from the raw coals. The yield of HCN increases gradually with the increase of temperature, while the yield of NH₃ increases first and then decreases, with a maximum value at 800 ℃. Catalytic effects of metal ions on nitrogenous pollutants release from different ranks of coals are different. Fe and Na restrain HCN release from medium rank coals, but promote that from low rank coals, while Ca facilitates the HCN release from all coals to some extent. Three metal ions all inhibit the release of NH₃ from medium rank coals, but promote that for low rank coals. Catalysis of each metal ion on yield of HCN and NH₃ has its own range of effectiveness. Release of nitrogenous pollutants during coal pyrolysis is influenced by the interactions of many kinds of inherent metal ions in coals.