Document NDmMY33KnrReyBvj2zkN3J08

LIAC9C 5c LEAD INDUSTRIES Ai. SCIATDi 4 4*0 UC8M4TON SVSMU3 law romx r, n . r. s s t au j c utAO ms o o w c t * ornutom Soptetshsr IS, 1??0 c " ' -- ' 1* sr-gx The Rarnfacturo of phosphoric acid 1* an integral part of the pro 'r ctica of phosphate fertilisers. ttanifocturin* phosphoric *eid frea pherphata rwLs involve* corrosive condition* vhdeh ere boil i^t through the use cf lcc-i protect ed eycipnor.t. Cocparatiwu corrosion data <m load d cc rural types cf *taiciesa stool indicated that Iced 1* a cost practical tutorial to uro in proceisins qulpeant duo both to It* xeoll*nt oorrosien reslstano* end the fact that It 1* ooonosical to lnatoll sod naintoin. j u manta ffcosphato Plant, The Cocuolidstod Hitting Ltd., trail, B. C. SBolting Cc^**r of Cased*, 3. Btocess Phosphate rock a* nine! ii ere*hod end voWrouni 1a pebble Bill* 1a the frecaeo of phosphoric arid. The Bill direbarge together with dry, fine ground phooph-.to rock Is reacted In five agitators In *crle*. Sulphuric acid 1* fod to tho last agitator*. Sluny 1* rwclreulaU.1 fren there two agita tors to toj hood of tho circuit. Cenlltlens of terrperoture, free sulphuric acid and phosphorus pontenilo (phosphoric oeld) are carefully controlled In tho agi i tator to produco ronilly filterable oprA (CaS-> 2 B-0). IfVr tic gypjva Is filtered off, repulping, agitation and filtration follow In tvs successive togos with counter-current washing of CTff^ on th: filter. Production acid overages 32 Vo 33 percent phosphorus pontoxllo (about IS percent phespicrle ocid) and washod o~pcvo contains about 1 percent picspicrus pontojcldo. - flew diagrea of tho process cccoopanios this bulletin. U cyr.TRtmcm prr/.nj Th> Phosphate Plant wrs tieeL.Tcd by th> t**T f -*; ry, ;-c,, s v 'ift, I. T,. tho patentee of those proccisvs, Construction *Vi.i ef t ro > w~.it* In which load it usod are indicated below. 0 tvs m cmaciL Bouxrnr . >6 -2- SoptoRber 15, 155 J i. go action Aritotcr* and Hr Coalers All agitator* of th* first rtsur# circuit consist of tank* ppresda*taly 12 ft. 6 In* In disaster by U ft. in height constructed either of wood lined with 10-lb, bird ehc-t load (5 to 6 percent antiacry) and luro bride, or 10-lb. hard load, br.de lined, with a auppertirg skeleton of steel band* on tho outside. The cor.-ra cro 3 In. wood decking. The agitator* arc istercowiected at ths top by herd lead launder* and each la aquippM with IE I try* 316 *Ulr3s steel abaft aM propeller driven through tex pulleys. To air cooling baae* eat*, street*! of botvy herd load plate ara submerged under eevwral inches of *lurr7 In oach of the latter three agitator* of the flr*t stag* circuit. Air la blown Into these boxss and through tha alurry to control the teeperaure of the alurx7 by evaporation Second and third stage reaction agitator* are of aladlar else and coo. atraction as tha repulp agitators. g. Hepulp tritetor* Tha repulp agitator* serve to nix the prprja cake with filtrate phoaphordo acid to produce a pulp which can be readily peeped into tha agitator* of th* accord or third stage reaction circuit*. BeUntlon tin* 1* approxleutaly 20 sin. Theso units are 12 ft. 6 in. in diear ter by U ft. high of wood atavo construction and lined vlth hard lead sheet and Duro acid proof brick. Agitation 1* prorldod by a 20 h,p. notor with stainlass steel agitator shaft and propellers siiiilar to ths oquipaint used in the reaction agitator. The jxtl? froa the first stage ropulp agitator avnrejea 39 porcent solids by weight, 20 porcent phosphoric add and 2.5 percent sulphuric tciu, while that froa tho second stage unit average* 37 percent solid* vlth the acid in t<v> pulp containing 3.5 percent phosphorus pontoxlds and 2.5 percent sclptoric add. 0. niter Slurry is carried to the filter* by gravity in hard lead, Duro brieklinod lsundoro fitted with hard leal launder covers. Filtration of the first stage slurry (Li5 percent crpm, phosphoric and sulphuric acid* and fiuo silicatea) is dono in two 12 x 12 ft. Ourrco vacuus filter* in parallel. Ths filter shells are of slid steel lined with 20-lb. hard lead both on barrel and ends, Tbo panel* twenty in nuntx.r, arc dlrldod froa each other by herd lead bars plaoci longitudin ally and burned to ths ahoct load lining on tho shell. Porta fer rcaovol of f 11trato and air aro cut in tho bottca and at the cer.t.r of each pencl. Production acij (32 to 33 pore or.t phosphoroj pentozide) drains out of the ports through 2-in. hard load pip a running longitudinally on tho outside of tho shell around th* dlschnr'o end of tho filter aM into the head valve, drainage of acid froa the head valve is through a rubber hoso into a filtrate receiver, thence through bnrosvitric lens of hard lead pipe into purp maps situated bo low the filter. Tie filter barrels are separated by lorgltudlnal lead bars bonded through th* sheet lead lining and stool filter shell. Second stajo filtration 1* aeeoepllehei in two slnllarly constructed 12 x l?-ft. .erreo vacuus flit-rs in paralloi while third stagv filtration Is done In throe 10 x 6-f t Uonrco vacuus filters, also of alxtlar ron* trustinn. w ib i wpwinii.waL ii i-.iwp.il mmrnmmmm^mmmmmm LIa o q c 61 IWWWWPW^WI. Hi WU-I-11 o I 9 c b e ic s x ratera* * 3$ - - 3 ---------------------- *?** Us i$$o---------- fc, Ac id Pi- >, Piping arid Stera-a Tanks icld flows fr:>a tho brronctrie legs of the filbert into hard load seal boxes arvi ii pir/rid to v*>od *t<'va Ica-i-lincd storage tanks by centrifugal jxsgj* constructed cf 1151 typo 316 etsinlc:* stool. 111 acid linos ars of hard load (5 to 6 pcrc nt an-.im-gr) flfcr.rsJ every 10 ft Discharge lines froa th* UEI typo 316 stainless stjol pun;-3 hs.'vlli.-.s first stage slurry consist of 6-Ij u dicactor herd lead pipe flar --d every 10 ft. and lined tlwougbcait with wediai hard rubber lining, a rather unirua ccrbtnatlcn wBployed to re-i-be swsLa froa the slurry, U1 woodon storage tanks are lined with hard lead ehoot. Be Other rrj'uinwgr.t Fbotpborlc acid (20 percent P?0e) la weasured by a feward bcckeb-type feeder which consist* of a hard load uihed stel tank containing a east herd lead trunnion and cast hard lead buriesto. This acid and $4 format eulpLurlo acid flew to a hard lead lined fluorine strippor vburo air la blown into the sdxture to evolve fluorine (as which la then exhausted to a recovery unite Production phosphoric acid (3? to 33 percent P,(V) la avaporsted to a ceneontratlon cf 36 percent P25 *or **d the acconiuh phosphate fcrtiliaea* aectioa cf tho plant. Swenson traperater* of the low (teas prossuro horiioctal tubo typo arc usod. These arc constructed of cast hard lead sections bolted together and equipped with 1$>6 Iartsto (graphite bonded by plastic) atesn tabs*. Evaporators are not shoi<n oa tbs flow diaprac. 5. CCRROSIVa R JTL23 Rard lead (5 to 6 percent antiaory) auccoiafully handles the following corrosives encountered at various stages in ths manufacture of phosphoric add tgr ths Dorroo Procoss, a. rhornhrrlc acid - containing up to 36 percent P20j which roughly coTTcsp'-nis to a*50 p.rc.r.t ccr.ser.tratien cf phosphoric acid iH.FO^). (Lead bo csod '.ith all cone-r.tratisn of fhPCS4 op to 6C percent below 200 C (3?2 F),) A typical analysis of production phosphoric acids I& To Fluorine ffeO 33*0 percent 2.0 percent 2.0 pvreont 3.3 percent balance b. ?!lxrd arils - corrosion rate data for nixod acids arc (iven In ths tabic unior a. ciior.1 6. ' The cixod acids In sett casos consisted of a slimy containing an averago of 33 percent solids by weight, largely cal dun sulphate (lypeun) crystals. Tho slurry also contains both dissolved and undlssolved fluosillcatos. ( 6, PlTJ-yil'.trH Through tho court* sy of Tho Conaolidatod 13nlr< k 5** 1 ting Cocip.uy of Canada, Ltd., e are ailo to inrludo a socially prepared report of coanvatlvs data on th* crro*ion rsih'-uvi of load am other material* in their phosphate plant eperatioi^i, T.vt following corrosion rates were deterainvd Igr wxpcslng corrosion spools In acid section solutions. LIAC^C6 2 !f*B mm CMXICXL KJUJEm M3. 36 -bOorrosicm 1st* Data September 1$, l&O Conditions of Exposure Osrrosian Rate, la. Par Tosr Sec tion V* TsJfp. tine, C tor* fcrd Lead Soft lead Stair,lacs Steel >7 JUS 313 iA 3 BO* 75 33 n. Osin vt, ocia eOQCb .0006 eOXd] B 20* BO* 60 33 Vt. Pain Vt. Oata ,003. .0001 .oxa o 1B-I5f 2-3* 60 32 Wt. Pain Vt. Oaia .cca coca .CXI vt. vt. Vi, i1j >10* lW)f 60 30 Vt. Oeln Vt. Oais Pain Osin Odia i a-W Ki* 65 30 Vt. Pain Vt. Pain eOOCa .0001 .coca A) Production Add BJ Pint mtroto C) Socond Filtrate S) Third Filtrate l) fourth Filtrate ZB general tho corrosion resistance cf led Is excellent in solutions short sulphuric sell and phosphoric sell ore present In sufficient quantities to fora s pcrtoetlse flla of Iced sulphite and phosphate] tho presence of suLphurle eeld bo try; probably acre critical then that of phosphoric sold. Although ell throe types of stainless steel appear about equal to each other in the short i tore tests recorded above, experience has shorn that AISI typo Jl6 Is to bo pre ferred to AXSZ typo 3L7 for general corrosion resistance and that AISZ type JlB should bo used whenever welding Bust bo carried out in the field. Experience has shown that acid proof brick laid directly on atild steel Is tt satlsfactsry slneo losVj inv-j-iably develop in tho brick work ad result in corrosion of the stool. Tho problem was solved by using an istpervlous lining f lead botaaocn the brick and steel. Repair work on lead Is easily accomplished in the field, but is usually nocos;ai7 only in those locations where temperature is hi;h and croep because a factor, such as in tho first stare filters. 7. cordis!o> Production of phosphoric acid and phosphate fertilisers by The Consol idated Kinin* t Snoltlnf Cocpa/y of Canada, Ltd., Trail, B, C., ocesaonced in 1931. Tho lspctus to this dovulopoor.t was (Ivon In tho late l??3's by tho noed to recover sulphur dioxide, a by-product of tho rcaatln^ and raoltlni operations of lead and tine. To avoidps;eltlo daaago to a t 1cultural areas adjacont to tho irtimitlonal boundary, tho decision was tuvlo to build oxtonslvu contact rul.'h-rle acid plants and sulphur recovery units capable of absorbing and fixing th> rUpixir dioxide gaois. At tho sane tlnj plants capable of utilising the 0 sulphuric setd for the production of fortUiters wore constructed* LI AC 9C63 cmczxL Kuera . 36 -5- Scptoobcr 15, 1950 *Chelical Engine*rice* oa'-eetno report* that PgOf oonanoptlon haa li>* creased steadily froa about 1/2 dllion ton* 1a 1933 to noro than 21 million ton* In 19,19 anu the capacity of plants oaLcinj high concentration aupcrphosphata fcrtllij.tr la continuing to gror algnificantly. Zn tho ojeirr-srtt In there instillatIona usod for handling aithar aulphar* lc acid, aulpto- diciriia or phocpbasric acid load waa ehoscn on a coopotlfeivo bast* a* a practical material for protection against contains attack, It* ut In tho superphosphate fortillter industry of which phosphoric acid asrnfctr* la an integral pert will uaioubtodly oontlnuo to parallel tha atoa^r Inaxaao In duaand for fcrtlllxer*. 8. KOrffiSMCSS Additional detail* of tho production of phosphoric acid aro described In a paper tjr Jaose Atwell ontitlod 'PtoEphsto Processes at Trail, B C*s la tho July, 19L9, isrua of Industrial and tt^inoorinf Choaiati7*a Tho corrosion rata data given above la haaod on a private eocnunieatioo with Tho Research and Dorolopaont Division of The Consolidated Wnlng and Soolting Ccwpaiy of Canada, Ltd, Construction detail* wwo obtained through tha cooperation of tho above cocpary and Tho Dorr Coopery, Stanford, Coon* Tho reaction of load with phosphoric acid la doacrlbod In Cheoleal 0 Bulletin So, 5, a reprint froc Chcoical Engineering.* 0 V" LIAC9G64