Comprehensive evaluation on product characteristics of fast hydrothermal liquefaction of sewage sludge at different temperatures

Hydrothermal liquefaction (HTL) can chemically convert sewage sludge (SS) into a crude bio-oil (biocrude) and other by-products. This work systematically elucidates how the yields and compositions of different products (e.g., gases, biocrude and solids) vary with temperature (260350 degrees C) in SS HTL with 10min of residence time. The results show that increasing temperature improved the biocrude quality and the gas yield, declined the water-soluble substance yield, the solid yield, and the TOC (total organic carbon) content in aqueous phase, while the biocrude yield and the NH3-N (ammonia nitrogen) content in the aqueous phase first raised and then decreased, and reached the maximum values at 340 degrees C. After SS HTL at 340 degrees C, light biocrude, light solids, water-soluble organic matters accounted for about 54.4, 50.5, 88.9wt% of total biocrude, solids and water-soluble substances, respectively. The N and S contents in the light biocrude almost halved compared with those in the heavy biocrude. The light solids contained a higher C content but lower Al, Si, Ca and Fe contents than did the heavy solids. >93.0wt% of Cu, Zn and Cr remained in the solids in contrast to 0.51.0wt% in the aqueous phase and 0.24.7wt% in the biocrude. (C) 2018 Elsevier Ltd. All rights reserved.