Renewable nitrogen-containing products by Maillard reaction of sewage sludge and glucose. Part II. Fixed-bed co-pyrolysis of sewage sludge and glucose

Abstract

Sewage sludge (SS) are extremely promising sustainable feedstock for fuels and chemicals. However, their high nitrogen content may result in nitrogen emissions during the pyrolysis. In this study, the fixed-bed co-pyrolysis (FBCP) of SS and glucose was carried out to obtain N-containing chemicals and N-doped bio-char. The transformation and production of nitrogen-containing compounds (NCCs) by Maillard reaction were investigated. Additionally, strategies to optimize experimental conditions were studied. Results show that keeping 50.0 wt% glucose in blended feedstock with the gas flow rate of 0.75 L/min and the final temperature of 450 °C is beneficial to maximize heterocyclic amines yield in bio-oil and limit the NH3 and NOx release. With the addition of glucose, carbonyl groups of glucose reacted with the amino groups of dried sewage sludge (DSS). A large number of amine/amide-N, pyridinic-N, pyrrolic-N, and quaternary-N enriched in bio-oil and surfaces of bio-char (over 95 wt% of total nitrogen) were generated, while significantly decreasing the nitrogen content in gas products (from 49.3 % to 3.9 %). Based on experiment results, the mechanism of nitrogen transformation during FBCP of DSS and glucose was finally proposed.