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 “hot” char air gasification. The impact of the sewage sludge pyrolysis process parameters on the reactivity of chars in the in situ air gasification was also analyzed.

Characteristic and kinetics of corn stalk pyrolysis in a high pressure reactor and steam gasification of its char

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“…4 Arrhenius equation can be used for pyrolysis of formula (1), the kinetics of reactions in solid-state are described by the following equation [33]:…”

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“…Recently, over 3080 municipal wastewater treatment plants are being operated in China, and they are producing about 20 million tons of sewage sludge every year (Hu et al, 2016). However, sewage sludge is being considered as a raw renewable energy source benefiting in zero-CO 2 -emission (Urych and Smolinski, 2016).…”

“…Based on biomass pyrolysis characteristics, co-pyrolysis of sewage sludge with biomass is a valuable technique to improve the energy utilization of sewage sludge, such as the improvement of pyrolysis airflow and the higher heating value of bio-oil (Urych and Smolinski, 2016). Also, the co-pyrolysis of sewage sludge with biomass in an appropriate proportion may improve the mechanical and physicochemical characteristics.…”

Numerical Study on the Efficiency of Biomass and Municipal Waste Fixed-Bed Co-Gasification

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