Deep recovery study for coking coal washery rejects using a comprehensive process

ABSTRACT

Washery reject is a by-product discharged during coal preparation, in which there are still certain amount of valuable combustibles. The recovery of clean coal from washery rejects is of great significance for protecting China’s scarce coking coal resources. The main purpose of this work was to design a deep process that can maximize the recovery of clean coal from a coking coal washery rejects with about 50% ash and test the technical feasibility of the process. Based on fundamental analyses, the high ash fractions of +0.2 mm and +1.80 kg/cm³ were firstly removed from the raw coal sample via hydrocyclone and spiral separator. Then, the remained parts having an ash of 27.57% were ground, pre-conditioned, and separated by flotation. The results showed that, under the optimum process parameters, a maximum yield of 24.47% clean coal with 12.23% ash can be recovered from this washery rejects. The ash content of the washery rejects increased from 50.10% to 62.37% after this treatment. This study indicated that it was technically feasible to achieve deep recovery of clean coal from washery rejects, which was of significance for the treatment of coking coal tailings.

KEYWORDS:

• Resource recycle
• clean coal
• coal tailings
• grinding
• flotation

Additional information

Funding

This project was supported by the National Natural Science Foundation of China (No. 51904239 and 51904240), the Basic Research Plan of Shaanxi Natural Science (No. 2019JQ-409 and 2019JQ-310), and the Postdoctoral Science Foundation of China (No. 2020M673445).

Notes on contributors

Yuexian Yu

Yuexian Yu earned his Ph.D. degree in mineral processing from China University of Mining and Technology (Beijing) and is currently engaged in research on mineral processing and solid waste resource utilization.

An-ning zhou

An-ning zhou is currently a professor at Xi'an University of Science and Technology. His main research areas include coal sub-processing and poly-generation conversion, coal-based materials, and carbon dioxide conversion and utilization.

Zhen Li

Dr. Zhen Li graduated from China University of Mining and Technology with a major in mineral processing. Now his main research interests are coal quality improvement/ separation processing and comprehensive utilization of secondary resources.

Ningning Zhang

Ningning Zhang, an associate professor of Xi'an University of Science and Technology, is engaged in the research of mineral processing. His main study interests are the basic theory of flotation and the deep cleaning of coal.

Jinzhou Qu

Dr. Jinzhou Qu is currently a lecturer at Xi'an University of Science and Technology, and his main research interests are low-rank coal flotation and macerals enrichment.