Evolution of nitrogen functionalities and their relation to NOx precursors during pyrolysis of antibiotic mycelia wastes

On the basis of rapid pyrolysis of two antibiotic mycelial wastes (AMWs), viz., penicillin mycelia waste (PMW) and terramycinmycelial waste (TMW), in a horizontal tubular quartz reactor, evolution of nitrogen functionalities and their relation to NOx precursors were investigated with the help of XPS and chemical absorption-spectrophotometry methods.The results indicate that inorganic-N (N-IN) and amide-N/amine-N/amino-N (N-A) are two kinds of nitrogen functionalities in the raw AMWs samples, determining the predominance of NH3-N among NOx precursors. N-A is found to be the main one with the proportion of 81.1% and 59.0% for PMW and TMW, respectively. At low temperatures, the decomposition of N-IN and the conversion of N-A mainly occur at 150-250℃ and 250-450℃, respectively, which are two routes for most NH3-N with yields of 20.9% (PMW) and 25.6% (TMW). While HCN-N is produced with a small amount less than 2%, having no relationship with the characteristics of nitrogen functionalities in fuels. Besides, pyridinic-N (N-6) and pyrrolic-N (N-5) are also formed and then converted with peak values at 350-400℃. At high temperatures, the conversion of N-6 and N-5 is prevailing, leading to the basically equal increments on NH3-N and HCN-N. Simultaneously, a minor amount of more stable quaternary nitrogen (N-Q) and N-oxide (N-X) is produced. Typically, due to the rapid decomposition of N-IN and labile N-A at low-temperature pyrolysis, nitrogen removal can reach up to 40% while energy loss can be controlled within 25% when pyrolyzing at 250-300℃. As a result, low-temperature pyrolysis could be an effective method for nitrogen removal whereas preserving the energy in AMWs. © 2017, Science Press. All right reserved.