Hydrothermal liquefaction of wastewater algae mixtures into bio-crude oil

Chen, Wan-Ting

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Description

Title

Hydrothermal liquefaction of wastewater algae mixtures into bio-crude oil

Author(s)

Chen, Wan-Ting

Issue Date

2013-08-22T16:48:53Z

Director of Research (if dissertation) or Advisor (if thesis)

Zhang, Yuanhui

Department of Study

Engineering Administration

Discipline

Agricultural & Biological Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Bio-crude oil
• Hydrothermal liquefaction
• Wastewater algae mixtures
• Characterization
• Environment-Enhancing Energy
• Swine Manure

Abstract

With the goal of incorporating bio-crude oil production and bio-waste treatment, an innovative Environmental-Enhancing Energy (E2-Energy) process was used during which mixed-cultured algal biomass from wastewater treatment system (AW) were converted into bio-crude oils. This study assesses the feasibility of converting AW, which was directly harvested from the wastewater environments, into bio-crude oil. The products distribution as well as their composition, reaction pathways and nutrient recovery via hydrothermal liquefaction (HTL) were investigated. HTL was conducted at temperatures scan of 260 to 320 ˚C between 0 to 1.5 hour retention time at 0.7 MPa N2 initial pressures. The highest bio-crude oil yield, 49 %, produced from AW (based on dry volatile matter) was obtained at 300 ˚C with 1 hour retention time, which also had the highest energy recovery ratio. The highest higher heating value (HHV) is 30.4 MJ/kg, occurred at 320 °C for 1 hour. Yet, the energy recoveries indicate 320 °C with 1 hour is an unfavorable reaction condition. Elemental analysis revealed that the decarboxylation and denitrification may be dominant at 260 to 300 °C following repolymerization governing at higher temperature; endured retention time may lead to decomposition of the bio-crude oil. TG analysis showed that approximately 60 % distilled bio-crude products were in the range of 200-550 °C. These distillates can be further upgraded for transportation fuels. We also found that there were 4-5 MJ/kg in the solid residue and TG analysis suggested that solid residue could be used as asphalt and roofing materials. GC-MS results indicated that the bio-crude oil contains a large portion of hydrocarbons, cyclic hydrocarbons and fatty acids while the aqueous phase product is rich in organic acids and cyclic amine derivatives. It is potential to apply the aqueous product to pharmaceutical synthesis or algae/microorganism culture. Reaction pathways concerning the conversion of various major bio-molecules along with reaction temperature and kinetic factor were elucidated. The lowest nitrogen recovery (NR) and the highest energy recovery (ER) distributed into bio-crude oil are about 9.54 % and 47.6 % respectively. Compared to previous similar studies resulting in NR to bio-crude oil about 25-70%, the NR to bio-crude oil presented in this work has been the lowest value so far as we know. With the goal of improving the bio-crude oil yields converted from AW, which contains relatively abundant of ash, 25%, 50% and 75% swine manure (SW) were added into AW as a co-liquefaction system with 25 % solids content in a 100 ml batch reactor. Reaction was operated at 300 ˚C with 1 hour. By combining 75% SW with 25 % AW, the bio-crude oil yield could be improved by about 9.2 % and the highest bio-crude oil yield (35.7 %, based on dry matter of feedstock) was achieved; by mixing 50% SW plus 50% AW, the highest HHV (27.35 MJ/kg) was accomplished and the H/C and O/C atomic ratios of the bio-crude oil could be improved to closer in nature to heavy crude oil.

Graduation Semester

2013-08

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Copyright 2013 Wan-Ting Chen

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