Preparation and Rheological Characterization of Lignite−Water Slurries

• Published in: Energy & fuels 2010-01, Vol.24 (1), p.496-502
• Main Authors: Goudoulas, Thomas B, Kastrinakis, Eleftherios G, Nychas, Stavros G
• Format: Article
• Language: English
• Subjects: Fossil Fuels
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef900865m

This paper reports the preparation of lignite−water slurries (LWS) and critical characteristics affecting their rheology. The slurries were prepared using wet grinding in a ball mill, having particle size distributions up to 300 μm and concentrations up to 50 wt % in solids. Surfactants and polyelectrolytes were used as additives in the slurryfication process to achieve acceptable rheological behavior and stability. Rheological measurements were performed using parallel disks geometry, and the typical shear rates were on the order from 10−2 to 103 s−1. The effect of the particle size distribution was investigated, and the apparent viscosity of the slurries, for the same solids volume fraction, was found to be lower for broad multimodal distributions. In addition, oscillatory rheological measurements were carried out to investigate the microstructure of the slurries, and it was observed that, for dense LWS (ϕ > 0.40), the viscoelastic behavior was controlled by the elastic contribution than the viscous one. When the experimental results of the lignite slurries were compared to rheological models of viscosity, satisfactory agreement was found, although relatively low values of ϕmax were observed, attributed to the physicochemical properties and the shape of the lignite particles. The results of the present study point out that, with an adequate protocol of measurement and, in turn, reproducible data, the apparent viscosity curves of LWS can be effectively described, qualitatively as well as quantitatively, by a well-established model.