Enrichment characteristic and leaching risk of harmful elements in carbon-ash separation products of coal gasification fine slag

ABSTRACT

Carbon-ash separation is a prerequisite for efficiently utilizing coal gasification fine slag (CGFS), but the enrichment characteristics of harmful elements (HEs) in the separation process are not fully understood. This paper uses gravity separation to prepare different samples, and four typical HEs (Se/Cd/Pb/Cr) in separated products were investigated. The results showed that samples with an ash yield of 28.72%–98.86% and a specific surface area of 12.90 m²/g-389.51 m²/g were obtained through gravity separation. The highly volatile element Se was enriched in the C-C/C-H structure of residual carbon under the catalysis of acidic gases. The nonvolatile element Cr was encapsulated by low-melting-point minerals and remained in the minerals. The semi-volatile element Cd/Pb was easily enriched in a particle with a high specific surface area/large pore volume, especially in porous residual carbon, with an enrichment factor as high as 7.0 and 4.0, respectively. The leaching risk analysis of sorted products indicates that the products were not suitable for direct landfill; however, besides honeycomb porous carbon, other highly specific surface area products can be safely used for soil improvement. The results of this study are expected to provide a reference for the classification and utilization of CGFS and the control of HE pollution.

KEYWORDS:

• Coal gasification fine slag
• gravity separation
• harmful elements
• enrichment characteristic
• leaching risk

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15567036.2024.2303380

Additional information

Funding

National Natural Science Foundation of China (grant number 51974323)National Key R&D Program of China (grant number 2022YFF1303304)

Notes on contributors

Xu Shi

Xu Shi experimental design, experimental execution, data analysis and manuscript writing.

Mo Chu

Mo Chu experimental design and manuscript check.

Jianfei Dong

Jianfei Dong microwave digestion test execution.

Feiyong Lyu

Feiyong Lyu investigation and partial data analysis.

Xingbo Sun

Xingbo Sun investigation and partial data analysis.

Yanyu Liu

Yanyu Liu partial data analysis and plot.