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Comparative energy and techno-economic analyses of two different configurations for hydrothermal carbonization of yard waste

Akbari, Maryam, Oyedun, Adetoyese Olajire, Kumar, Amit
Bioresource technology reports 2019 v.7 pp. 100210
biocoal, biomass, energy, heat, heat exchangers, hydrochars, hydrothermal carbonization, models, production costs, separators, steam, yard wastes
Hydrothermal carbonization (HTC) includes conversion of wet biomass to hydrochar, a coal-like product, eliminating the need for biomass pre-drying. There has been limited focus on the techno-economic assessment of the HTC process in the literature. In this study, techno-economic models were developed to assess the economics of bio-coal production from yard waste for two different HTC plant configurations. In configuration A, heat is recovered by steam using several flash separators while in configuration B special heat exchangers are used. Process models were developed for the two configurations and then further used to estimate bio-coal production costs. The bio-coal cost and the net energy ratio (NER, or ratio of energy output to the energy input in the system) indicate that configuration A is preferable in terms of energy (NER of 5.2 versus 1.4 for configuration B) but less desired economically because it costs 3.3 $/GJ more than configuration B.