Abstract
Additional moisture added in coal stockpiles due to rain and other climatic processes causes a significant problem worldwide, which leads to not only decrease in the heating value of the coal but also creates an extra efficiency penalty. Therefore, it is important to make some predictions for control of coal moisture within stockpiles after the rainfall. When the rain falls on the stockpile, it either runs off the surface or infiltrates the stockpile. The infiltrated water may evaporate from the surface, drain or stay within the stockpile. The aims of this study (parts 1 and 2) are to describe and compare the changes in coal moisture content following rainfall events. The mechanisms of runoff, infiltration and drainage after rainfall were described in the first paper of this series. In part 2 the influence of coal particle size and ambient conditions on the rate and depth of moisture evaporation within the stockpile is investigated. The laboratory experiments showed cyclic events of adsorbing moisture overnight and desorbing this moisture during the day as part of the coal surface evaporation process. The rate of evaporation from the surface of the fine coal stockpile was faster than the coarse stockpile; however, the coarse stockpile experienced a more efficient evaporation process because of its porous structure. Fine coal beds experienced evaporation only near the surface, while the maximum influencing layer of evaporation is a depth of 0.4 cm below the surface in coarse coal beds.
Highlights
Part 2 of this study is to evaluate the influences of coal particle size and ambient conditions on the rate and depth of moisture evaporation within the stockpile that was not investigated in part A of this paper
The aim of this study is to investigate the effect of coal stockpile bed particle size and weather conditions on the rate and depth of moisture evaporation
Stockpiling of coal for a long time causes the coal to be exposed to atmospheric conditions and rainfall
Summary
As many thermal power plants are placed far away from coal mines and concentrators, for balanced operations, storage of coal in an open stockpile for a month of electricity generation is essential to dealing with any problems in coal mines or transport networks. Similar actions are considered for coast-based utilities which depend on imported or exported coal. Depending on the fluctuations in the international prices of coal, big plants purchase large amounts of coal when the price is low and store it for a long time (120 days). Coal stockpiles are generally left uncovered due to the need for frequent loading and unloading [1]. Coal stockpiling for a long period causes the coal to be exposed to atmospheric conditions such as rainfall
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