Abstract
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 by recovering both of latent heat of vaporization of water kept in the fuel and part of 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. Experimental investigation to determine the correlation between a specific coal properties originated from geological background and its drying characteristics is thus the major concern in this paper. The investigated lignite is a representative of Turoszow deposit in Poland. Experimental attempts unveiling drying kinetics were carried out for 5 mm and 10 mm diameter spherical samples in the superheated steam atmosphere in the temperature range of 110 °C–170 °C. Simultaneous and continuous measurements of changes in weight, surface and interior temperatures and appearance on each tested sample were carried out for describing drying behavior. Analytical investigation was applied to explain the drying characteristics, which are strongly affected by the individual properties of coal and the inherent ash composition.
Highlights
Lignite (brown coal or low-rank coal (LRC)) deposits occupy one-fourth of widespread coal resources in the entire world and play significant role economically and politically in countries where its share in energy mix becomes a dominative level [1]
The sample was set in the test section, where lignite was dried in a superheated steam atmosphere
The superheated steam was sent into the top of the test section, to which a baffle plate was attached to disperse the supplied steam into the entire test section, and exhausted from the bottom by a fan
Summary
Lignite (brown coal or low-rank coal (LRC)) deposits occupy one-fourth of widespread coal resources in the entire world and play significant role economically and politically in countries where its share in energy mix becomes a dominative level [1]. Unfavorable limitation of lignite for transportation or storage, due to high moisture content (typically 40%–70% of water in mass), precludes the enhancement of lignite utilization. An appropriate treatment is needed for coke production and the limited utilization in power generation sector. High moisture content deteriorates the thermal efficiency of power generation sector, in particular combustion process, due to the heat loss originated from the vaporization of large amount of water contained within this fuel carrier. Water removal technology for lignite has been attended. Energies 2016, 9, 371 as a solution for efficient utilization. Among various types of proposed drying systems by means of mechanical, thermal or chemical methods [2], superheated steam fluidized bed drying (SSFBD)
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