Design and operational performance evaluation of an integrated hydrothermal carbonization waste heat recovery and solar energy collection system

Ruikun Wang, Yukun Wu, Jiandong Jia, Jichao Wei, Lichao Ge, Yue Zhang and Peng Gao

Energy, 2025, vol. 321, issue C

Abstract: Hydrothermal carbonization is a promising technology to convert sludge into solid fuel. However, a high energy consumption is required because the hydrothermal carbonization is operated at high temperature. Therefore, an integrated system of hydrothermal carbonization waste heat recovery and solar energy collection was proposed. This system recovered energy from the slurry product through a two-stage flash evaporation process, in which the steam from the first stage and the second stage were used for drying the semi-dry hydrochar and heating the raw sludge material, respectively. In addition, solar energy was collected to heat the sludge material. When 1 ton of sludge was treated under an hydrothermal carbonization temperature of 220 °C, 49.6 kg steam with energy of 127.31 MJ was recovered in the first stage flash evaporation, which could cover the heat required for drying the semi-dry hydrochar. Moreover, 147.3 kg of steam with energy of 426.97 MJ was recovered at the second stage flash evaporation, which was used to heat the raw sludge material, as well as the collected solar energy of 302.80 MJ. The exergy efficiency of the system was 54.84 %, and the exergy loss was caused mainly due to filtrate discharge, which accounted for 72.2 % of the total exergy loss.

Keywords: Sludge; Hydrothermal carbonization; Waste heat recovery; Solar energy; Exergy (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:321:y:2025:i:c:s0360544225011144

DOI: 10.1016/j.energy.2025.135472

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