Drying of coal

All electrical property values are strongly dependent on water content for water, the dielectric constant is approximately 81 and resistivity is about 106 2 cm. The dielectric constant has been used as a measure of moisture in coal (Speight, 1994, and references cited therein). However, it should be noted that the effect is not considered to be additive due to the different electrical properties of physically and chemically bound water. With an increase in moisture content, electrical conductivity and dielectric constant increase, whereas resistivity and dielectric strength decrease. Hence, except for special purposes (e.g., dielectric strength measurements of underground coal blocks), electrical measurements require the meticulous drying of coal prior to experiments. 

Air drying process of partial drying of coal to bring its moisture near to equilibrium with ambient conditions in me laboratory or me room in which further reduction and division of me sample will take place (ASTM D-2013 ASTM D-2234). 

In recent years, fluid-bed dryers with a central fountain (spouted) bed have become popular for drying of coal. The fountain bed is achieved in a conical-cylindrical apparatus (Figure 51.13). The hot gas stream supplied to the dryer by tube (3) carries away the coal grains supplied by screw (2) and moves them upward. The lifted coal grains fall aside and move downward along the annulus. 

In this case study, a simple drying flowsheet was initially simulated for drying of coal based on the assumed parameters. Most of the parameters such as initial moisture content, final expected moisture content, and drying temperature are selected based on reported values in the literature the throughput is an individual choice. Coal with initial moisture content of 50% wet basis at 30°C... 

For instance, the semi-direct system shown in Fig.46 is suitable for the grinding and drying of coal with a high moisture content [14]. It is more particularly advantageous when the quantity of hot gas that has to be passed through the mill in order to drive out the moisture is greater than thequantity of primary air that the kiln burner can accept. The surplus exhaust gas from the mill is discharged into the... 

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