Subcritical hydrothermal liquefaction uses high temperatures (270-350°C) and high pressures (80-173 bar) to produce bio-crude oils that can be upgraded to liquid transportation fuels. In this study, two strains of Galdieria sulphuraria, an acidophilic, mixotrophic red microalgae, were cultivated on effluent from primary settling tanks at a municipal wastewater treatment plant. Samples were concentrated to 5 and 10 wt.% slurries after harvest and converted by hydrothermal liquefaction in a 1.8 L batch reactor. Reaction conditions included temperatures of 310, 330 and 350°C, and hold times of 5, 30 and 60 minutes. Yields and product properties were compared to those of hydrothermal liquefaction of Galdieria sulphuraria grown on media. Total oil yields were low (11-18 wt.%) and char yields were high (28-36 wt.%) compared to those from HTL of the algae grown on media (27-35 wt.% oil and 10-13 wt.% char), likely due to the higher ash content and lower lipid content of the algae grown on wastewater. The bio-crude oil, char, and aqueous phase samples were characterized to complete mass, energy and nutrient balances to characterize the tradeoffs in the algae growth and conversion systems for energy and nutrient recovery.
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Effect of Acidic Hydrochar on Plastic Crude Oil Produced from Hydrothermal Liquefaction of Waste PVC
In this study, the effect of hydrothermal liquefaction (HTL) of waste PVC was investigated in the presence of acidic hydrochar. The hydrochar was prepared by hydrothermal carbonization of pineapple waste at 250 °C and at 1 h in the presence of citric acid. Hydrochar was acidic, stable, and porous and contained acidic functional groups. Hydrochar was co-fed with PVC during HTL to enhance HTL conversion and quality of the plastic crude oil. HTL experiments were performed at 300–350 °C, 0.25–4 h of reaction times, and 0–20 wt% hydrochar-to-PVC ratio. The plastic crude oil was separated from the solid residue to evaluate HTL conversion and to analyze elemental compositions, boiling point distribution, alteration of chemical bonds, and chemical compositions. The results showed that acidic hydrochar enhances HTL conversion with a maximum value of 28.75 at 5 wt% hydrochar content at 350 °C and 0.5 h. Furthermore, plastic crude oils contained no chloride but contained significantly high carbon and hydrogen, resulting in a higher heating value of up to 36.43 MJ/kg. The major component of the plastic crude oil was 3, 5 dimethylphenol produced ranging from 61.4 to 86.4% (percentage of total identified area) according to gas chromatography mass spectroscopy (GCMS) data.
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- Award ID(s):
- 2123495
- NSF-PAR ID:
- 10475667
- Publisher / Repository:
- MDPI
- Date Published:
- Journal Name:
- Processes
- Volume:
- 10
- Issue:
- 12
- ISSN:
- 2227-9717
- Page Range / eLocation ID:
- 2538
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/pr10122538
