Influence of lignite petrographic properties for drying characteristics in superheated steam atmosphere

Polish lignite from Turow mine was experimentally investigated to determine the correlation between specific coal properties originated from geological background and its drying characteristics in the superheated steam atmosphere. A superheated steam fluidized bed dryer (SSFBD) in a self-heat recuperative configuration has a great potential of improving thermal efficiency of a lignite-fired power plant. This configuration enables to reduce heat losses in combustion process of lignite by recovering both of latent heat of vaporization of water inherently kept in the fuel and sensible heat during the fuel processing. However, the optimal design of the dryer requires the fundamental knowledge of drying characteristics in respect to the individual properties of the utilized fuel. The investigated lignite is a representative of Turoszow deposit situated in the extreme south-western part of Poland. The samples represent two different seams which currently are under exploitation and have industrial value: Seams I and II. The proximate and ultimate analyses were conducted for all the samples. Experimental attempts unveiling fundamental drying kinetics were carried out for 5 and 10 mm diameter spherical samples in the superheated steam atmosphere in the temperature range 110-170 oC. Simultaneous and continuous measurements of changes in weight, surface and core temperatures and appearance on each tested sample were carried out for describing drying behavior: moisture content, drying rate and temperature profiles. The time and efficiency of the superheated steam drying depending on the lignite particle size and steam temperature were estimated for all types of investigated samples and shown in the form of average results and individual drying curves. The fundamental studies on correlation between physical properties and drying behavior will be the basis for proposing the innovative and universal design methodology for the industrial lignite pre- Treatment system.