Bio-Crude Production through Recycling of Pretreated Aqueous Phase via Activated Carbon

Abstract

The management and optimization of the aqueous phase are the major challenges that hinder the promotion of hydrothermal liquefaction (HTL) technology on a commercial scale. Recently, many studies reported about the accumulation of the N-content in the bio-crude with continuous recycling of the aqueous phase from high protein-containing biomass. In the present study, sewage sludge was processed at 350 °C in an autoclave. The produced aqueous phase was treated with activated carbon, and its subsequent recycling effect on the properties of the bio-crude and aqueous phase was investigated. By contacting the aqueous phase with activated carbon, 38–43% of the total nitrogen was removed from the aqueous phase. After applying the treated aqueous phase recycling, the energy recovery of the bio-crude increased from 50 to 61% after three rounds of recycling. From overall carbon/nitrogen recoveries, 50 to 56% of the carbon was transferred to the bio-crude phase and more than 50% of the nitrogen remained in the aqueous phase. The aqueous phase contained mostly of N&O-heterocyclic compounds, small chain organic acids, and amides. ICP-AES analysis showed that more than 80% of the inorganic elements were concentrated into the solid phase.

Process Analysis of Main Organic Compounds Dissolved in Aqueous Phase by Hydrothermal Processing of Açaí (Euterpe oleraceae, Mart.) Seeds: Influence of Process Temperature, Biomass-to-Water Ratio, and Production Scales

“…[18,40,43], and BTEX (benzene, toluene, xylenes, and ethylbenzene) [41]. In these studies, the above compounds were dissolved in the process water by hydrothermal carbonization of biomass, including the hydrothermal processing of corn stover [14,18]; Tahoe mix, pinyon/juniper, loblolly pine wood, sugar bagasse, and rice hulls [18]; wheat straw, wheat straw digestate, poplar, garapa, massaranduba, pine wood, α-Cellulose, and D-(+)-xylose [39]; wheat straw, poplar, and α-Cellulose [40]; wheat straw, wheat straw digestate, poplar, garapa, massaranduba, and pine wood [41]; Tahoe mix [43]; and biodegassed pellets [49]. Recently, Poerschmann et al [44] investigated the distribution of medium molar mass compounds dissolved in process water by hydrothermal carbonization of glucose, fructose, and xylose by GC-MS and IC, identifying more than 50 compounds, the most abundant being carboxylic acids (formic, acetic, glycolic, lactic, and levulinic acids) and aromatic-ring compounds (furfural, 5-(Hydroxymethyl)-2-furfural).…”