Hydrothermal liquefaction of spirulina with aqueous phase recirculation

Yi, Shuqi

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https://hdl.handle.net/2142/110767 Copy

Description

Title

Hydrothermal liquefaction of spirulina with aqueous phase recirculation

Author(s)

Yi, Shuqi

Issue Date

2021-02-19

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

Zhang, Yuanhui

Committee Member(s)

• Sharma, Brajendra Kumar
• Akdeniz, Neslihan

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)

• HTL
• aqueous phase recirculation

Abstract

Hydrothermal liquefaction (HTL), an efficient thermochemical conversion technology, can produce biofuels from biomass, but also a large amount of processing wastewater. This study mainly focuses on the recirculation of the aqueous phase from HTL in order to effectively address the aqueous phase treatment problems. Spirulina, a kind of high protein content microalgae, is chosen as a promising feedstock in this study for bio-crude oil production. In the present work, the conditions for the HTL of Spirulina are optimized before the aqueous phase recirculation is performed. The first section of this study investigates different operating parameters in the HTL of Spirulina. Specifically, in order to maximize the yield of bio-crude oil, Taguchi method is performed to optimize the HTL operating conditions of Spirulina, which lays the foundation for subsequent aqueous phase recirculation. The effects of different parameters on HTL are investigated, including the temperature, residence time, ethanol content and solid content. Based on the Taguchi design concept, an L9 orthogonal array is chosen for the experiments. The results show that the best HTL operating conditions for maximum yield of the oil are a temperature of 320 ℃, a retention time of 60 min, ethanol content of 15 wt.%, and a solid ratio of 20 wt.%. The effective sequence of different parameters on HTL oil yield is ethanol content, residence time, temperature and solid ratio. This study also explores a relatively novel area of aqueous phase recirculation, the addition of ethanol. The ethanol addition during aqueous phase recirculation deals with the increase of nitrogen content caused by the re-polymerization of nitrogenous compounds during aqueous phase recirculation in the water solvent. Thus, the aqueous phase from the HTL of Spirulina is recycled as the intermediate reactant in water and ethanol-water solvents. And its effects on the product yield and quality from the HTL of Spirulina are investigated. The results reveal that the addition of ethanol could further improve bio-oil yield during aqueous phase recirculation. The elemental analysis and gas chromatography-mass spectrometry (GC-MS) analysis indicates that the ethanol addition can inhibit the re-polymerization of nitrogenous compounds in the aqueous phase, resulting in lower nitrogen content in bio-crude oil. The final portion of this study involves providing a comparison of the effects of the aqueous phase and ethanol. From the first two portions of this study, the ethanol addition and aqueous phase recirculation can both increase the yield of bio-crude oil. Thus, an additional set of experiments are conducted in this portion using different concentrations of ethanol and the aqueous phase (AP) and a mixture of the two to determine which is more influential. Some findings are also obtained as follows: (1) The 75/25 wt/wt ethanol-water solvent is the best choice for maximum bio-crude yield, 68.4 wt.%, in the HTL of Spirulina. (2) The oil yield from HTL of Spirulina increases from 34.6 to 43.7 wt.% gradually with recycling aqueous phase concentration increasing. (3) For the bio-crude yield, the aqueous phase is more influential than the addition of ethanol in the HTL of Spirulina.

Graduation Semester

2021-05

Type of Resource

Thesis

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http://hdl.handle.net/2142/110767

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Copyright 2021 Shuqi Yi

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