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<br />• <br />Wash Plant Data <br />The thickener underflow was measured at flow rates of 225 to <br />250 gal/min. The normal solids concentration of this stream <br />during steady wash plant operation ranged between 24 to 31 percent <br />solids. This equates to a 12 to 14 ton/hr production of fine <br />refuse solids. Solids concentrations as low as 11.5 percent was <br />measured during wash plant start-up. The specific gravity- <br />percent solids relationship for the thickener underflow samples <br />obtained during this visit is presented in Figure 9. A size <br />distribution and ash analysis of the thickener underflow is <br />presented in Table 4. <br />The polymer study conducted on the thickener underflow in- <br />dicated that centrifuge centrate clarity can be obtained with <br />Allied Colloids Percol 725 at polymer dosages of 0.25 to <br />0.50 lb/ton of fine refuse solids. <br />The production of coarse refuse over the past 3 months <br />(June through August) is presented in Table 5. Assuming wash <br />plant operation for 10 hr/day, the wash plant production of <br />coarse refuse equals 87 ton/hr. <br />Conclusions and Potential Problem Areas <br />Present wash plant production rates are 16 percent for the <br />coarse refuse and 62 percent for the fine refuse higher than the <br />wash plant design. These values will probably change with the <br />introduction of a long~vall operation scheduled for November/ <br />December 1980. <br />Any additional formation of fines generated by coarse slurry <br />transport may overburden the already overloaded static thickener. <br />The present coarse refuse crusher (Jeffrey Hammermill) is <br />not acceptable due to its generation of high levels of fines. <br />Fines loading to the thickener may be reduced by recovering <br />the +100 mesh refuse. This material is 45.6 percent of the total <br />fine refuse and contains 83 percent coal with a Btu o•alue of <br />12,000 Btu/lb. Recovery of this material would significantly <br />reduce the static thickener loading, thereby permitting present <br />equipment handling of the fines generated by coarse slurry <br />transport. <br />• <br />