Effects of CaO on nitrogen transformation during pyrolysis of soybean protein

To elucidate the effects of CaO on nitrogen transformation during sludge pyrolysis, transformation behavior from char N into NO_x precursors during pyrolysis of soybean protein (SP) with CaO at 600–700°C was investigated. Results showed that CaO inhibited the transformation of pyridine N and quaternary N into HCN and promoted HCN conversion into NH₃ at 600–700°C. CaO inhibited the conversion of protein N and tar N into NH₃ at 600°C but promoted it at 700°C. NO_x precursor yield was the lowest when SP was pyrolyzed with CaO/N of 5.5 at 600°C (reduced by 11.66% compared with raw SP pyrolysis).