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<br />r.---. <br />C') <br />w <br />(\:, <br /> <br />compres~ion evapora~ion is used to treat cooling tower blowdQ~n. A vapor <br /> <br />compression evaporator is used when the waste stream is large ~id dilute so <br /> <br />that sc~le formation is not a problem. The ~lowdown from the vapor compression <br /> <br />evaporators is discharged to lined evaporation ponds while the distillate is <br /> <br />used as makeup to the boilers. A cost estimate for a forced evaporation <br /> <br />vapor-compression evaporator is: <br /> <br />Minimum capital cost <br /> <br />Maximum capital cost (allowing for <br />slurry formation) <br /> <br />~4,500/IIOOO gals) (day) <br /> <br />$9,000/(1000 gals) (day) <br /> <br />Amortization and maintenance <br />(20\ of capital cost) <br /> <br />Electricity @ 85 kw-hr/1000 gal <br />@ 3~/kw-hr <br /> <br />$3.0 - 6.0/1000 gals <br /> <br />Labor and che:n.icals <br /> <br />~2. 6/1000 gals <br />~1.0 - 2.5/1000 gals <br /> <br />TOTAL AMORTIZATION ~,D OPERATI~G COSTS: <br /> <br />~6.6 - 11.1/1000 gals <br />(~2,333 - 3,620/acre-ft) <br /> <br />or, for the example shown in Figure 2-2, ~~e costs are 1.S-2.5~/106 Btu product <br /> <br />output. <br /> <br />When using a forced evaporator, ~~ere is a credit of about $1(1000 <br /> <br />gals for the distilled water ~ecovered. <br />!f large, lined ponds are not envi=or~en~al1y acceptable, then an addi~ional <br />cost of $2 to 6/1000 gals must be incurred to use =orced evaporation to t~e <br />maximum extent. However, the volt.;me of dry salt. re...-naining is not a.ltered by <br />the choice of evaporator. <br /> <br />2.5 Quantities and Qualities of Process Condensate <br />All processes to convert coal to other gas cause the release of a wastewa~e~ <br />stream whic~ is condensed out of the product fuel process lines. This water <br />is derived from the hydrogenation of oxygen in the coal, from moisture in ~~e <br />coal and from unreacted steam put through the coal conversion reactor. Some <br />quantities of process condensa~e are shown on ~able 2-5. There is a lot of <br />variation. A middle of ~~e range value of 70 lb/106 Btu product gives, for a <br />250 x 106 sef/day pipeline gas plant, a flow of 700 x 103 Ib/hr (= 1.400 gals/rnin = <br />2,250 acre-ft/yr). This is a large stream to treat. <br />The water contains coal reaction products, coal deccrnposi~ion produc~s, <br />coal pyrolysis products ~~C varling ~ounts of soluble inorganic produc~s f~crn <br /> <br />27 <br />