00/01754 Dewatering/reconstitution of fine clean coal slurry

Abstract

This paper describes an innovative approach for in-situ dewatering/hardening of fine clean coal slurry. The technique uses various fibrous waste materials added to coal slurry before dewatering process to obtain a dewatered product with lower cake moisture as well as sufficient strength to facilitate its handling. The study was conducted on both vacuum and pressure bench scale apparatus for dewatering and reconstitution of fine clean coal slurry. The fibrous waste materials investigated included plastic, newspaper, carpet, mixed office waste, raw paper and wood fibers. The effects of several surfactants and flocculants; on final moisture content of the filter cakes were also determined. The results showed that using the vacuum filter, addition of 10 Kg/ton of mixed office waste fibers decreased the filter cake moisture from 41.3 to 34.8 percent by weight, a 16 percent moisture reduction over the baseline data. The addition of fibers showed moisture reduction as well as large improvement in solids loading as much as 2 fold over those observed in the absence of fibers. For the pressure filtration, the addition of plastic fibers provided a filter cake containing 21.4 percent moisture which is about 2.1 percent lower than that of the untreated filter cake. The averagemore » final cake moisture reduction of 1.5 percent was achieved for the tested fibers using the pressure filter. It was also found that fiber addition in pressure filtration led to shorter cake formation time thus increasing the filtration rate of the coal slurry. The hardening properties of the dried filter cakes with fibers improved significantly such that the cake compression strength improved from 0 to 4.5 Kg/cm{sup 2}, impact resistance from 0 to 4, abrasion resistance from 0 to 70 percent, and dust reduction efficiency from 0 to 75 percent.« less