Torrefaction of Sewage Sludge: Kinetics and Fuel Properties of Biochars

Date
2019-01-01
Authors
Pulka, Jakub
Manczarski, Piotr
Koziel, Jacek
Białowiec, Andrzej
Journal Title
Journal ISSN
Volume Title
Publisher
Altmetrics
Authors
Research Projects
Organizational Units
Journal Issue
Series
Abstract

We propose a ‘Waste to Carbon’ thermal transformation of sewage sludge (SS) via torrefaction to a valuable product (fuel) with a high content of carbon. One important, technological aspect to develop this concept is the determination of activation energy needed for torrefaction. Thus, this research aimed to evaluate the kinetics of SS torrefaction and determine the effects of process temperature on fuel properties of torrefied products (biochars). Torrefaction was performed using high ash content SS at six (200~300 °C) temperatures and 60 min residence (process) time. Mass loss during torrefaction ranged from 10~20%. The resulting activation energy for SS torrefaction was ~12.007 kJ·mol−1. Initial (unprocessed) SS higher heating value (HHV) was 13.5 MJ·kg−1. However, the increase of torrefaction temperature decreased HHV from 13.4 to 3.8 MJ·kg−1. Elemental analysis showed a significant decrease of the H/C ratio that occurred during torrefaction, while the O/C ratio fluctuated with much smaller differences. Although the activation energy was significantly lower compared with lignocellulosic materials, low-temperature SS torrefaction technology could be explored for further SS stabilization and utilization (e.g., dewatering and hygienization).

Description

This article is published as Pulka, Jakub; Manczarski, Piotr; Koziel, Jacek A.; Białowiec, Andrzej. "Torrefaction of Sewage Sludge: Kinetics and Fuel Properties of Biochars." Energies 12, no. 3 (2019): 565. DOI: 10.3390/en12030565. Posted with permission.

Keywords
waste to carbon, sewage sludge, kinetics, torrefaction, biochar, activation energy, fuel properties
Citation
DOI
Collections