Study of Light Gas Generation Behavior during the Thermal Chemistry Conversion Process of Cattle Manure

To investigate the thermal chemistry conversion behavior of cattle manure as a biomass fuel, the effect of three reaction ambiences (N₂, air, and CO₂) and four temperatures (350, 550, 750, and 950 °C) was studied on a fixed-bed reactor. The tested final products were divided into three categories: nitrogen-containing species (NO, NO₂, HCN, NH₃), carbon-containing species (HCN, CH₄, CO, CO₂), and others (SO₂, HCl). As the temperature increased, HCN and NO always increased, while NH₃ and NO₂ increased first and then decreased. This tendency was the same in all three ambiences. HCN was found to be the major component among the four measured nitrogen-containing species, with a maximum mass ratio of 17% under N₂ ambience at 950 °C. CO₂ and CO are the two major carbon-containing species. The oxygen for CO₂ or CO formation can be from either cattle manure itself or the surrounding air. As the temperature increased, the contribution to CO₂ formation from the internal oxygen became larger than that from the external oxygen in both N₂ and air ambiences. At 950 °C, the CO₂ mass ratio in N₂ ambience was 55%, while it was only 35% from the external oxygen. Under CO₂ ambience, the presence of CO₂ can boost CO formation by gasification. The SO₂-S and HCl-Cl mass ratios present no apparent relation with ambience. As the temperature increased, the SO₂-S and HCl-Cl mass ratios decreased in all three ambiences. The sulfur in cattle manure is mainly organic, while the chlorine exists mainly in inorganic forms, such as NaCl and KCl.