Experimental study on supercritical water gasification of oily sludge using a continuous two-step method

Gaoyun Wang; Jiasunle Li; Xujun Li; Jiajing Kou; Zhiwei Ge; Linhu Li; Pai Peng; Liejin Guo

doi:10.1016/j.jhazmat.2023.131619

Experimental study on supercritical water gasification of oily sludge using a continuous two-step method

J Hazard Mater. 2023 Aug 5:455:131619. doi: 10.1016/j.jhazmat.2023.131619. Epub 2023 May 12.

Authors

Gaoyun Wang¹, Jiasunle Li¹, Xujun Li¹, Jiajing Kou², Zhiwei Ge¹, Linhu Li¹, Pai Peng¹, Liejin Guo³

Affiliations

¹ State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, No. 28 Xianning West Road, Xi'an 710049, China.
² School of Vehicles and Energy, Yanshan University, Qinhuangdao 066004, China.
³ State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, No. 28 Xianning West Road, Xi'an 710049, China. Electronic address: lj-guo@mail.xjtu.edu.cn.

PMID: 37207484
DOI: 10.1016/j.jhazmat.2023.131619

Abstract

Supercritical water gasification (SCWG) technology can convert oily sludge into hydrogen-rich gas. To achieve high gasification efficiency of oily sludge with a high oil concentration under mild conditions, a two-step method involving a desorption process and a catalytic gasification process using Raney-Ni catalyst was investigated. High oil removal efficiency (99.57%) and carbon gasification efficiency (93.87%) were achieved. The lowest wastewater total organic carbon, oil content, and carbon content in the solid residues were 4.88 ppm, 0.08% and 0.88%, respectively, using a gasification temperature of 600 °C, treatment concentration of 1.11 wt%, gasification time of 70.7 s, and the optimal desorption temperature of 390 °C. The main organic carbon component in the solid residues was cellulose, which is environmentally safe. As the treatment concentration increased, the two-step method outperformed the single-step method. The mechanism for the two-step SCWG of oily sludge was revealed. In the first step, supercritical water is used in the desorption unit to achieve a high oil removal efficiency with few liquid products generated. In the second step, the Raney-Ni catalyst promotes efficient gasification of high-concentration oil at a low temperature. This research provides valuable insights into the effective SCWG of oily sludge at a low temperature.

Keywords: Oily sludge; Supercritical water gasification; Two-step method.