Pyrolysis of high-ash sewage sludge in a circulating fluidized bed reactor for production of liquids rich in heterocyclic nitrogenated compounds

A circulating fluidized bed reactor was used for pyrolyzing sewage sludge with a high ash content to produce liquids rich in heterocyclic nitrogenated compounds. GC/MS and FTIR analyses showed that heterocyclic nitrogenated compounds and hydrocarbons made up 38.5–61.21% and 2.24–17.48% of the pyrolysis liquids, respectively. A fluidized gas velocity of 1.13 m/s, a sludge feed rate of 10.78 kg/h and a particle size of 1–2 mm promoted heterocyclic nitrogenated compound production. Utilizing heterocyclic nitrogenated compounds as chemical feedstock could be a way for offsetting the cost of sewage sludge treatment.

► A circulating fluidized bed reactor was used for pyrolysis of sewage sludge with a high ash content. ► The pyrolysis liquid contained large amounts of heterocyclic nitrogenated compounds. ► Hydrocarbon cracking was promoted by long solid retention times and high ash contents. ► Heterocyclic nitrogenated compounds could be refined as chemical feedstock.