Experimental investigation on the degradation of polymer-containing oily sludge in sub-/supercritical water

ABSTRACT

Polymer-containing oily sludge (PCOS) has caused tremendous hazards with the broad application of polymer flooding technology. Traditional methods cannot meet the treatment demand due to the high-water content of PCOS. In this work, the degradation of PCOS in sub-/supercritical water is studied to explore an appropriate treatment method. The influence of residence time (15–90 min), temperature (340–700°C), catalysts (sulfates, carbonates, and alkalis), and co-solvents (methanol-water and ethanol-water) on the distribution of end products is studied in details. Results show that PCOS is hardly gasified under the subcritical conditions and the increase in residence time and temperature has positive effects on the phase conversion. The conversion rate reaches 81.77% at 60 min, 340°C, compared to 67.09% at 15 min. Supercritical water shows a great solubility for PCOS, and no solid residues are detected at supercritical conditions (400–700°C, 23 MPa). Organic matter in liquid phase is classified into nine types, and the increase in temperature greatly changes its composition. The relative proportion of ketones reaches more than 50% of the organic matter in liquid at 400°C. Ketones are proven to be the main source of CO₂ and disappear at above 500°C. Moreover, the migration of elements (carbon and nitrogen) is comprehensively studied.

KEYWORDS:

• Polymer-containing oily sludge
• end products analysis
• sub-/supercritical water
• elements migration
• degradation mechanism

Data availability statement

Due to the nature of this research, participants of this study did not agree for their data to be shared publicly, so supporting data are not available.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15567036.2023.2184001.

Additional information

Funding

This work is supported by the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China (No. 51888103).

Notes on contributors

Pai Peng

Pai Peng is currently working toward the Ph.D. degree in Power Engineering in State Key Laboratory of Multiphase Flow in Power Engineering (SKLMFPE), Xi’an Jiaotong University, Xi’an, China. His research interests are waste-to-energy and hydrogen production.

Gaoyun Wang

Gaoyun Wang is currently working toward the Ph.D. degree in Power Engineering in SKLMFPE. His research interest is hydrogen production.

Linhu Li

Linhu Li is currently working toward the Ph.D. degree in Power Engineering in SKLMFPE. His research interest is waste to energy.

Hui Ge

Hui Ge is currently working toward the Ph.D. degree in Power Engineering in SKLMFPE. His research interest is biomass.

Hui Jin

Hui Jin is currently a Professor of Power Engineering in SKLMFPE. His research interest is hydrogen production.

Liejin Guo

Liejin Guo is currently a member of the Chinese Academy of Sciences. His research interests are hydrogen production and renewable energy.