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Witbank area of South Africa were specifically chosen with a range of maceral content. Previous studies investigating the effect of inorganic additives on devolatilization have found that several additives affect the amount of volatiles derived from the studied coal (Liu et al., 2004; Ahmad et al., 2009; Wu, Sugimoto, and Kawashima, 2003). Studies investigating the effect of operational conditions (temperature, pressure, and heating rate) on the devolatilization product composition have found that changing these conditions will also influence the product yield and composition (Juntgen and van Heeck, 1977; Rennhack, 1964; Peters and Bertling, 1965). The importance of studying coals from South Africa becomes apparent when comparing coals from this region to coals that are mined in other regions. Coals from North America are spread between anthracite, bituminous, sub-bituminous, and lignite ranks (vitrinite-rich); this wide variety of rank is also the case with many of the world’s other top producers of coal, as reported by the World Coal Institute (2008). As a result, most previous studies (especially those done outside of South Africa) are not applicable to the highinertinite, high-ash bituminous coals from this region. Previous studies performed in South Africa were not focused on the devolatilization products, but investigated the process of devolatilization with regard to South African coals (Beukman, 2009). Due to the potential for the production of high-value chemicals from coal, it is deemed appropriate to investigate the effect of extraneous additives on the quantity and composition of the tars that can be derived from South African coal when pyrolised at a slow heating rate in the presence of an alkali metal catalyst. Should the tar yield be reduced due to additive addition, and lighter products be formed, then this could be seen as a positive step toward the production of valuable chemicals from coal.

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