FINE COAL DEWATERING USING PH-SENSITIVE AND TEMPERATURE-SENSITIVE SUPERABSORBENT POLYMERS

Water is a necessary medium in most coal preparation processes, but it s presence in the final product has a negative impact on transporation costs, handling and specific energy value. A major contribution to th e total moisture content may be attributed to the proportion of fine c oal in the total product, which presents the greatest dewatering probl em. This paper describes a novel process that seeks to reduce the mois ture content of fine coal cakes to a level comparable to that achieved by thermal drying. In this process, superabsorbent polymers, which ar e granular highly crosslinked synthetic copolymers with excellent wate r-absorbing properties, are employed to draw water from moist fine coa l. The drying or dewatering process is characterized by three main sta ges: (a) contacting of superabsorbents with high-moisture fine coal; ( b) separation of dried fine coal from superabsorbents by screening; an d (c) regeneration of used superabsorbent polymer, taking advantage of its response to changes in such conditions as pH, temperature or elec tric field. Depending on the polymer type, the dosage and the polymer/ coal contact time, the moisture content of coal filter cake can readil y be reduced from, say, 25% to 10% by mass or less. The results of lab oratory and pilot scale tests conducted using pH-and temperature-sensi tive superabsorbent polymers are discussed in this paper. (C) 1997 by John Wiley & Sons, Ltd.