Kinetics of Sewage Sludge Pyrolysis and Air Gasification of Its Chars

Abstract

Optimal management and utilization of sewage sludge require innovative technological solutions. One of the prospective and novel concepts for the utilization of this waste, targeted at energy production, is the two-stage process combining pyrolysis and gasification. The paper presents the kinetic analysis of sewage sludge pyrolysis and air gasification of “hot” chars with the application of the thermogravimetric analyzer SDT Q600. The pyrolysis was performed below 1173 K in the inert gas atmosphere and with various heating rates of 1, 10, 50, and 100 K/min. The air gasification of chars was performed at 973, 1073, or 1173 K. The lumped model, which encompasses six first-order parallel reactions, was indicated as the most appropriate for the interpretation of the kinetics of sewage sludge pyrolysis. For the description of the char gasification stage, the Avrami–Erofeev model (A3) was proposed. The kinetic parameters estimated on the basis of the experimental data are the first published for sewage sludge “...