Flotation of oxidized coal using coal tar as a new collector

ABSTRACT

In this study, coal tar, an industrial by-product of the carbonization/gasification of coal, was adopted as an economical flotation collector for recovering clean oxidized coal. The characteristics of high-temperature coal tar (HTCT), its performance as a flotation collector, and the interaction mechanism between HTCT and oxidized coal were analyzed by gas chromatography/mass spectrometry, flotation experiments, X-ray photoelectron spectroscopy, and dynamic contact angle measurements. The results revealed that HTCT has a strong selective collection ability because it contains a large number of aliphatic and aromatic compounds with oxygen-containing functional groups. At HTCT dosage of 3000 g/t, 79.23% of combustible matter with an ash content of 9.99% was obtained. The major mechanism responsible for the enhanced oxidized coal separation is that, with the adsorption of HTCT onto oxidized coal, the C–O hydrophilic functional groups were covered and an increased amount of the C–C/C–H hydrophobic functional groups of the oxidized coal surface was exposed, resulting in improved surface hydrophobicity and floatability of the oxidized coal. This study provides valuable guidelines for the re-utilization of coal tar and the flotation upgradation of oxidized coal.

KEYWORDS:

• Collector
• flotation
• high-temperature coal tar
• interaction mechanism
• oxidized coal

Additional information

Funding

This work was supported by the National Key R&D Program of China (2018YFC0604702), Jiangsu Province Science Fund for Distinguished Young Scholars (BK20180032), the National Nature Science Foundation of China (Grant no. 51922106, 21978318, 51904300, 51774286, and 51920105007), China Postdoctoral Science Foundation funded project (2018M642369, 2019T120482), Jiangsu Natural Science Fund-Youth Fund (BK20190639), and Young Elite Scientists Sponsorship Program by CAST (2018QNRC001).

Notes on contributors

Zili Yang

Zili Yang majored in mineral processing engineering at China University of Mining and Technology. He is mainly engaged in flotation research.

Qi He

Qi He is a master student majoring in minerals processing engineering at China University of Mining and Technology.

Guohui Chang

Guohui Chang is a master student at China University of Mining and Technology. She is mainly studies the fine coal flotation.

Yangchao Xia

Yangchao Xia majored in mineral processing engineering at China University of Mining and Technology. He is mainly engaged in molecular simulation research.

Ming Li

Ming Li majored in mineral processing engineering at China University of Mining and Technology. She is mainly engaged in the research of fine coal flotation.

Yaowen Xing

Yaowen Xing is currently a professor of China University of Mining and Technology, majoring in mineral processing engineering, mainly studying fine coal flotation.

Xiahui Gui

Xiahui Gui is working Professor in Chinese National Engineering Research Center of Coal Preparation and Purification, China University of Mining and Technology. He researches area includes mineral processing, coal preparation and colloid and interfacial chemistry in flotation.