Influence of additives on the devolatilization product yield of typical South African coals, and effect on tar composition

N.C Bean,B.B Hattingh,J.R Bunt,H.W.J.P Neomagus,D Van Niekerk,C.A Strydom

doi:10.17159/2411-9717/2018/v118n4a10

Abstract

Influence of additives on the devolatilization product yield of typical South African coals, and effect on tar composition

Highlights

South African coal is mainly used for electricity generation by means of pulverized fuel combustion and liquid fuels production via indirect gasification technology and Fischer-Tropsch synthesis
Due to the potential for the production of high-value chemicals from coal, a study of this nature represents a significant insight into the devolatilization behaviour of typical South African coal, and could serve as a precursor for the development of a technology capable of producing high-value chemicals as well as a coal-derived char suitably catalysed for gasification to produce synthesis gas
Studies investigating the effect of operational conditions on the devolatilization product composition have found that changing these conditions will influence the product yield and composition (Juntgen and van Heeck, 1977; Rennhack, 1964; Peters and Bertling, 1965)

Summary

BTX Alicyclics Aliphatics

Radical reactions are the main reactions in the mechanism of tar decomposition and the formation of methane. Valuable compounds obtainable from the tar of coal pyrolysis include many one- to four-ring aromatic and polar compounds Some of these include phenol, naphthalene, phenanthrene, pyrene, biphenyl, cresol, and pyridine (Schobert and Song, 2002; Speight, 1994). In a study by Liu et al (2004), in which coal was selectively demineralized and devolatilized in order to determine the effect of inorganic material on devolatilization, it was found that the addition of inorganic additives (K2CO3 and Al2O3) to demineralized coal increased the yield of liquid products by up to 11%. In several other studies to determine the effect of inorganic material on devolatilization (without direct loading onto the coal matrix), it was found that magnesium was catalytically active; sodium, calcium, and potassium, were ineffective.

Table III

Boiling point

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Findings

Table X