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Minerals 2018, 8(5), 202; https://doi.org/10.3390/min8050202

Changes and Distribution of Modes of Occurrence of Seventeen Potentially-Hazardous Trace Elements during Entrained Flow Gasification of Coals from Ningdong, China

1
College of Geoscience and Surveying Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
2
Department of Geosciences, The University of Texas at Dallas, 800 West Campbell Rd, R0C21, Richardson, TX 75080-3021, USA
*
Authors to whom correspondence should be addressed.
Received: 16 March 2018 / Revised: 17 April 2018 / Accepted: 24 April 2018 / Published: 8 May 2018
(This article belongs to the Special Issue Toxic Mineral Matter in Coal and Coal Combustion Products)
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Abstract

In order to reveal the migration of trace elements from coal to gasification residues, the modes of occurrence of potentially-hazardous trace elements (Be, V, Cr, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, Ba, Hg, Tl, Pb, and U) were determined by a five steps sequential chemical extraction procedure. Samples were collected from a coal-to-methanol plant (GE water-slurry coal gasification, formerly Texaco) and a coal-to-olefins plant (Gaskombimat Schwarze Pumpe pulverized coal gasification, GSP) in the Ningdong Energy and Chemical Industry Base, China. Concentrations of As and Se were determined using atomic fluorescence spectrometry (AFS). The content of Hg was determined using a DMA-80 mercury analyzer. Other trace elements (Be, Cr, Co, Ni, Cu, Zn, Mo, Cd, Sb, Ba, Tl, Pb, and U) were analyzed using inductively-coupled plasma mass spectrometry (ICP-MS). XRD and SEM-EDX were employed to determine the minerals or other inorganic phases in samples. The modes of occurrence of trace elements in feed coals can influence their behavior, including their volatility during coal gasification and, ultimately, the element’s mode of occurrence in the gasification residues. Knowing an element’s mode of occurrence in the feed coal may aid in anticipating which components the elements are likely to combine with during liquid slag cooling. Based on the relative enrichment of trace elements in the residues, elements Be, V, Cu, Mo, Ba, and Hg showed volatility during the GE and GSP gasification processes; As and Se showed volatilization-condensation behavior during the GE and GSP gasification processes; Cr, Ni, Zn, Cd, Sb, Tl, Pb, and U showed volatility during the GE gasification process; Zn, Cd, Sb, Pb, and Tl in the GSP samples, as well as Co in the GE samples, showed volatilization-condensation behavior; and Cr, Co, Ni, and U showed less volatility during the GSP gasification process. In the gasification residues, quartz, calcite, and Al–Si glass were the main inorganic phases, carbonates and iron and manganese oxides (likely recrystallized calcite) were the main hosts of most trace elements in the residues, including Be, V, Cr, Co, Ni, Zn, As, Cd, Ba, Hg, Tl, Pb, and U. Copper, Zn, Se, Cd, and Sb tended to stay in the Al–Si glass. Molybdenum is likely precipitated with the sulfides in the residues. View Full-Text
Keywords: coal gasification residues; hazardous trace elements; sequential extraction; modes of occurrence coal gasification residues; hazardous trace elements; sequential extraction; modes of occurrence
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Tang, Y.; Guo, X.; Pan, X.; Finkelman, R.B.; Wang, Y.; Huan, B.; Wang, S. Changes and Distribution of Modes of Occurrence of Seventeen Potentially-Hazardous Trace Elements during Entrained Flow Gasification of Coals from Ningdong, China. Minerals 2018, 8, 202.

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