Document ByMGQrLgXBQDVk47a8by31ODw

S' "mu!5;, I03'"'<,i' Vy?""' "i> I<.000 opm of ofduon, W bl"-|u,,'c-01 K~bbOM. loaded with woihod-ouf llutdu.f solid! Steel Mills Continued Water treatment of b lasMu rn ace-gas scrubber output can ---- ---- ----" QAVSCftU&fiEfl wash woie* enters the thickeners, above, through o center dittrlbu- fbn welt; clarified woler. then Ienvoi at turfoee by woy of the two ring weir* stop stream pollution ILUOOE-RAKfNO ARMS at bottom of thickener! scrape the settled-cut lollds from the 4Crubber effluent to the thickener center fbr their final removal by pumps ! -- - duced et a rate of approximately 65 ten* in eight hours (wet basis), goes to sintering plant with a rated capacity of 100 tons per eight hours. The original dust-collection system consisted of gravity Row ol wash water from the blast-furnace area 10 a large IMype settling lagoon where a large percentage ol the solids settled out before (he water overflowed Into the plant sewer. This method was exp1* live In that U required continual clain shelling of the muck from the Itgoofl and loading it info railroad ears for the trip to the sintering plant, where i) we* dumped wet with oilier iintering-.plafii oro. The completely new plant, designed by ^Drtvo Carp in cooperation with Jones JV.ii Lsughlin's engineering dept, has two ^h.vWalker Process Clariftow thickeners, y. .v.phetos, left, p 96, sludge-pumping fa* k^i'it'cilitiei, vacuum filter plant, and dryly-^eake-hsndling facilities. The plant util* the existing gravity-flow system t^fdrom the washers at the blast furnace, which eliminates tho need of a booster #I#.',pumping .station for handling the dirty ^'5?; water from the washer stage. a*/*' Heart of the plant, iwo 105-fi-dia ;.* talker Process thickeners, handles 0 *Vv 16,000-gpm Row. One important feature b the intake arrangemenf: Influent en> ','Tlt ,cr* an annular ring around the large V'.y eenter well and then Rows to the center V't* welt through multiple tangential dlltu* II NOVEMBER lOjJ VACUUM PUMPS produce the required vocuum lot the disk-typo fillers shown above; some 1690 elm each at 20 in. vocuum s'ton ports that produce a pronounced rotational movement. This diffusion energy causes a circular motion in the large center well, which displaces down ward and enters the tonk's Roor region. Such a radially flowing current, with equal-acting vectors of flow displace ment, gives balance and lateral distribu tion in the tank. Further, it serves to concentrate the solids within the liquid. This denser mass, leaving the bottom of the center well with s circular motion, fans out along the tank floor. In turn, clarified water--that is, water free of seifleable solids--displaced above this strong, moving current, rises upward and flows over into a multiple, balanced overflow weir ayatem. This weir system runs uniformly around the entire surface area of the clarification zone. Velocity of approach 10 tho weirs, though, is low because of the mass of water displaced. The low-velocity level prevent! reaching back and drawing up previously sen led solids into the weir, system. Velocity is so k>w and uniform, in fact, that previously settled precipi tate particles, introduced near the over flow weir, settle back countercurrent to the flow and do not overflow into the ' weirs to cause any clogging. Recirculation of previously precipi tated solids, by withdrawing them from the sludge hopper end pumping them back to the center well of the thickener, {Corutruitd on page 218) ENGINEERING AND MANAGEMENT SECTION m li