Journal of the Southern African Institute of Mining and Metallurgy
On-line version ISSN 2411-9717
TOPOROV, D. and ABRAHAM, R.. Gasification of low-rank coal in the High-Temperature Winkler (HTW) process. J. S. Afr. Inst. Min. Metall. [online]. 2015, vol.115, n.7, pp. 589-597. ISSN 2411-9717. http://dx.doi.org/10.17159/2411-9717/2015/V115N7A5.
Gasification is a process of thermal conversion of solid carbonaceous materials into a gaseous fuel called syngas. Coal gasification is an efficient technology for a range of systems for producing low-emission electricity and other high-value products such as chemicals, synthetic fuels, etc. The paper presents the High-Temperature Winkler (HTW) gasification process, which is designed to utilize low-rank feedstock such as coals with high ash content, lignite, biomass etc. The process is characterized by a bubbling fluidized bed, where coal devolatilization and partial oxidation and gasification of coal char and volatiles take place, and by a freeboard where partial combustion and gasification of coal char take place. The recent development of the high-pressure HTW process is reviewed. Gasification of low-rank, high-ash coals with respect to gasification temperatures, conversion rates, and syngas quality is also discussed. The main HTW design steps required for an industrial-scale design are presented. Special attention is given to the process modelling, including global thermodynamic calculation as well as detailed CFD-based simulation of a reacting fluidized bed. Three-dimensional numerical results of the HTW process are also provided and discussed.
Keywords : coal gasification; high-temperature Winkler process; HTW; reacting fluidized bed simulation; high-ash coal; low-rank coal; biomass; peat; municipal solid waste.