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Process energetics for the hydrothermal carbonisation of human faecal wastes

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journal contribution
posted on 16.10.2015 by Eric Danso-Boateng, Richard Holdich, Simon Martin, Gilbert Shama, Andrew D. Wheatley
Hydrothermal carbonisation (HTC) has the capability to convert wet biomass such as sewage sludge to a lignite-like renewable solid fuel of high calorific value. However, to date assessment of the energy efficiency of the HTC process has not been fully investigated. In this work, mass and energy balances of semi-continuous HTC of faecal waste conducted at 200 °C and at a reaction time of 30 min are presented. This analysis is based on recovering steam from the process as well as energy from the solid fuel (hydrochar) and methane from digestion of the liquid product. The effect of the feedstock solids content and the quantity of feed on the mass and energy balance were investigated. The heat of reaction was measured at 200 °C for 4 h using wet faecal sludge, and the higher heating value was determined for the hydrochar. The results indicated that preheating the feed to 100 °C using heat recovered from the process would significantly reduce the energy input to the reactor by about 59%, and decreased the heat loss from the reactor by between 50% and 60%. For feedstocks containing 15–25% solids (for all feed rates), after the process is in operation, energy recycled from the flashing off of steam and combustion of the hydrochar and would be sufficient for preheating the feed, operating the reactor and drying the wet hydrochar without the need for any external sources of energy. Alternatively, for a feedstock containing 25% solids for all feed rates, energy recycled from the flashing off of steam and combustion of the methane provides sufficient energy to operate the entire process with an excess energy of about 19–21% which could be used for other purposes.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Chemical Engineering

Published in

Energy Conversion and Management

Volume

105

Citation

DANSO-BOATENG, E. ...et al., 2015. Process energetics for the hydrothermal carbonisation of human faecal wastes. Energy Conversion and Management, 105, pp. 1115-1124

Publisher

© Elsevier

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Publication date

2015

Notes

This paper was accepted for publication in the journal Energy Conversion and Management and the definitive published version is available at http://dx.doi.org/10.1016/j.enconman.2015.08.064.

eISSN

0196-8904

Language

en

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