Staslndustry ollaborative Repori
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Boron I;nemicais trom Searles lake brines
the concentrate, mostly in foreign markeg, for processing into refined borax and boric acid. The balance of the ox is shimxd to the company’srefinery at Wil>on, calif., where various refined products arc made, including borax, anhydrous borax, and boric acid. pCB is putting finishing touch- to an $18,000,000 expansion and mode&tion program. part of the tab is for shifting from underground to o p p i t mining, but a large portion is for a new conantrating plant and a new refinery at Boron to replace existing units. At the new r e h a y expected to start in the sewnd half of this year, PCB will open-pit mine born ore, dissolve it in mcyding refinery end liquor, remove paa of the insoluble shale in gigantic thickeners, and filter the resulting borax solution. Borax will then k -talked from this solution as sodium tetraborate decahydrate or pcntahydrate by controlling temperature in vacuum m / ~ tallizcrs. Dried borax will serve as feed mataial for further proccaring to boric acid and anhydrolk borax. The third producer, West End Chemical, u ~ e 8carbonation on Searles Lake brines in a pmces similar to American
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2! VOL. 4V. NO. S
MARCH 1957
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1873
Borax
Borax Lake Mining District* organized ivith borax recovered by leaching surface scrapings
1878
Borax
John \V, Searles formed San Bernardino Borax Mining Co. Process was leaching surface scrapings follolved by simple crystallizing
Since the mid-l940’s, A4mericanPotash has spent over $1,000,000 a year to modernize and expand plant facilities. T h e Trona plant, incidentally, has run since 1916, except for 10 months in 1921 when then owner American Trona revised the plant in light of brttrr phase rule data.
SBBhl sold to Pacific Coast Borax, which closed plant and concentrated on Death Valley deposits
Chemicals from Searles l a k e Brines
Table I. Date
Chronology a t Searles Lake“ Remarks
Product
1895 Soda ash
California Trona Co. formed to recover S a l C O a from brines and solid reefs. Company never got started, went into receivership in 1909
914
Potash, borax, sodium sulfate
Original American Trona plant completed but failed to operate properly and \vas abandoned
916
Potash
American Trona Go. process for qetting potash from brines pans out and continuous production begins a t present Trona, Calif., site
1916
Potash
Pacific Coast Borax and Solvay Process start a joint operation at Borosolvay. Plant closed 1920
1919
Borax
Added to American Trona product line
908
American Trona Co. takes over California Trona assets
912
1926
.American Trona merged into American Potash ti Chemical Corp.
1927
Boric acid
Both terhnical and U.S.P. grades produced
1934
Sodium carbonate, sodium sulfate
Se\\ plant section built to recover these
1935
Anhydrous borax
First of a series of upgrading-s of a basic product into a more “concentrated” form
1936
Potassium sulfate
Produced from KCI, burkeite ( 2 S a & 0 4 S a z C 0 3 ) , or sodium sulfate
1938
Lithium concentrate (LiNaPOc)
Prior to recovery, this \\as an anno\ing impurity that scaled heat transfer surfaces
1940
Chemical grade KCI. bromine
Bromine extracted from agricultural grade K r l to make chemical crncle KC1
1946
Borax, sodium carbonate
S6,000,000plant addition finished brines and boost basic capacity
1951
Lithium carbonate
Cpqrading of crude lirhiurn concentrate
1951
Pliosphoric acid
By-product of Li2C03 plant
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process lower structure
&illproducts a n d procrszes tIio.-e of .Imeric.nn Potash except whew noted. X o t to be confused w i t h Borax Lake. Lake C o u n t y , Calif., where several hundred tons of tincal crystals were rerovered froin niutl about 1870. a
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Potash’s, where carbon dioxide precipitates sodium bicarbonate. This is filtered off, calcined, and recrystallized as sodium carbonate. Borax is recovered from the filtrate by cooling. lt’esc End also recovers sodium sulfate. History of Searles Lake, its formation and “phase rule” recovery of chemicals from its brines, has been dealt \vith by many writers, including Teeple ( 2 ) . Briefly, therefore, Searles Lake covers 34 square miles, about 12 of r\hich is exposed salt bed in the cenrer (mud washed down from surrounding hills covers lake edges). T h e bed actually consists of two separate salt structures, a n upper one 70 to 90 feet thick and a lower one 25 to 40 feet thick. .4n impervious mud parting layer 13 feet thick divides the two. Both salt structures are porous (40 to 50% voids) and filled completely with a concentrated brine. Llpper structure brine is rich in potash, ivhile the lower structure is rich in carbonate and borate.
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Chemical recovery at Searles Lake started in 1873 ~ v h e n tlic first simple borax works reclaimed solid phase material (Table I). I n 1916 chemists succeeded in getting chemicals from the brine itself. T h e first potash product s u p plied the critical needs during ll‘orld lt’ar I: and the present American Potash operation a t ‘Trona began that year. ilmerican Potash has added to its product line a t Trona in t \ v o \vays--by getting neiv chemicals from tht, brinrs and by upgrading chemicals already produced. A move to anhydrous borax in 1935 typifies the latter. Boras is nearly 50y0 w’ater, and makin? a n anhydrous form obviously saves shipping costs. A swing from crude lithium concentrate to lithium carbonatc in 1951 is another example. 4 s to nebv chemicals from the brines, the biggest single addition came in 1946 when the company completed a neiv plant which uses a flue gas carbonation process to recover soda ash and borax from loiver lake structure brines.
INDUSTRIAL AND ENGINEERING CHEMISTRY
.4 so-called “main plant carbonation plant make u p the two basic sections a t Trona. In thr main plant cycle: oldest a t Trona: :\nirrican Potash evaporates and fractionally crystallizes upper structure brinc 10 rccover eight primary chemicals in a series of plants in scqucncc (eight rnorc clicrnicals stem from the primary ones, to give a total count at Trona of 16). ‘I’hc carbonation plant processes lo\vcr structure brine to add to production o f tivo cliernicals, sodium carbonate and borax. T h e tivo sections are tird togrther in that the carbonation plant furnishes a crude sodium bicarbonate -borax mixture to the main plant cyclc. American Potash orvns 4 square miles in the center of thc lakc and 1c:iscs an additional 10. In the ulp1)cr su‘ucturr, richest brinc lies at tlic bottoni near the parting nilid laycr, so \\TIIS arc’ drilled and cased to \vitliin a l‘civ [ret of the mud laycr. Purnt)s pull Iirine from each \vel1 ar i 0 gallons ii rninutc. Floiv t o the main plant cyclr is 2200 gallons a minute. Kaiv hriilt. enters tht. niain plant c>.clv a t thc Evaporation Plant. Here. three triple effect evaporators conct,nir;itr 3.100.000 gallons o f brine a day to 1.40(1.000 gallons (eq~ial 10 7 1011s of ivater evaporated ever>- minutc). Sodium chloridr. sodium carbonatc. and burkeirc (doulilt, salt o f sodium cai.t)onatc and sodiiirn sulfatc.) crystallize during evaporation and arc sc1)aratc.d and coni,cyed ofr‘ the cyclr to tlic Soda Products Plant. I n this plant. thti salts are separated into sodiurn carbonatt.. sodium sulfate. ; r i d dcsiccated sod iuni sulfate . .2 d ilithiu i n sodium phosphate h y - p r o d ~ ~ cfroill t thcsr S I P ~ S is furthrr procfssed i n a separate ~ ’ l a n t to prodticc. lithium carbonair and phosIihoric acid. Sodiuin cliloridc irom
Chemicals from Searles l a k e Brines PIi n i r i i p Sodium carbonate Sodium sulfate Lithium carbonate Phosphoric acid Potassium chloride, agricultural grade Potassium sulfate Bromine Borax decahydrate
Tlerir cvl Sodium sulfate, desiccated Potassium chloride, chemical grade Borax pentahydrate Boric acid Anhydrous borax Sodium pentaborate
BORON CHEMICALS the evaporators is dissolved in brackish well water and returned to the lake. Meanwhile, in the main plant cycle, the evaporator effluent, which is a concentra ted potash-borax liquor, goes to the b Potash Crystallization Plant. Borax crystallizes slowly, so operators cool the solution rapidly to get a crop of potassium chloride crystals and leave a solution supersaturated in borax. Part of the potassium chloride is dried and sold directly as crude, agricultural grade potash, part is converted to potassium sulfate, and the balance is refined to chemical grade potassium chloride. I n the latter step, bromine is removed by chlorination and steam stripping. Some of the product is marketed, and the rest is used to make organic bromides a t a subsidiary plant. Residual liquor from the potash crystallization plant goes to the b Borax Plant. There, seeding and slow crystallization produce a crude sodium tetraborate pentahydrate. T h e crude pentahydrate is filtered out, redissolved, and then recrystallized, producing either sodium tetraborate decahydrate (borax) or the pentahydrate. Refined borax serves as feed to the other two borax plant sectionsboric acid and anhydrous borax. Anhydrous borax is made by heating borax to its melting point-about 1370' E'.-in large fusion furnaces. This drives off all water of hydration and leaves Na2B4O7. Residual liquor from the borax plant then goes to the evaporation plant where it joins raw brine entering the cycle. This mixture becomes evaporator house feed stock. At the carbonation plant, carbon dioxide bubbled through lower lake structure brine produces sodium bicarbonate. This is filtered off, calcined, and recrystallized as sodium carbonate monohydrate. T h e filtrate, rich in borax, is neutralized with uncarbonated lake brine and is then refrigerated to crystallize the borax. T h e crude borax is separated and goes to the main cycle borax plant for refining, and the filtrate returns to the lake.
Crystallization T h e borax plant a t Trona consists of two sections-crude borax crystallization, where the crude sodium tetraborate pentahydrate is removed from main plant cycle liquors, and borax refining. In the latter step the crude material is redissolved, crystallized either as the penta- or decahydrate', and dried for storage. Some is sold, and the rest serves as feed for the boric acid and anhydrous borax plants. The borax process (Figure 1) actu-
First step in the borax plant is recovery of a crop of crude borax crystals in two crystallizers (background). The thickener (forebround) recovers fine crystals washing out in the overflow from the settling cone a t the top of crystallizers VOL. 49, NO. 3
MARCH 1957
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BORON CHKMICALS can P o m - u c a p ~cyuyyc .eparatoq one for each crjmpllizer. T o sfart de.. wa-g crude borax, the nystallizcrs; cyclones, and thickener work togaher. ' It is dFuable to keep a 'heavy seed bed in the aystallizcm, to make m' ' as much bow aynallizds as hedce, cone settlus at the top of each , a y s t a k e r . Since crystals~atay in the cryatallizrm as long as possible, they grow W I y l a r g t l l p to a b u t 12 mesh. This means the sludge can be M e d economically in cvclone separators before being ?ed to. filters for 6nal dewatering. Sludge is thus drawn from the aystallieer settling cone and fed .to a cyclone. The Cyclone thickens f 60-mesh Wstatp to 70 to 80% settled s o l i by volume,' and the thickened sludge then flow to the filter feed tank. Liquor and --6o-mesh crystals return m the crystollizns. Meanwhile, exceed liquor in the UYStaker &ma over the launder at the settling m e tip, eam/ing vay fine p t a h y d r a t e crystals with it. Overflows from both crystallii fud the thickener where thex small crude 'aystals are thickened. Part of the underffow horn the W q e r is fed to the crystalkem an seed, while the ' balance pues to the filter feed tank. &&low fmm the nystalksa n? malll,'~mta~ina6.to 8% satled solids by-'mlume, &d.thc thickener KWV&S most of t h e fine c+atals. However, if MGl hah not h e e r ' d ~ u a t e dproperly, prccm e&icncy dmps an fine float out of the thickener and -de to the evaporation plant. not lost, mycling borax means m W & t opation, M good deaeration is a muat. Dewaarieg of the crude borax'altury " takes place in two hoti4ontal, 13-fo0t flat hd .6lm, with an older drum 6lta being hdd in atand-by em. ~iltiate from. thc dewaming' sap' joins thick'overffow. The bmbin@ stream is mother liquor 2 (having produced a second m p of crynalborax).. -ML-Z cfabl~11) is' atill 'rich in horax-atmt 7% and po* 12%='it is blended with raw brine entaing the main-' plant 'cycle. T& mixturr bccomu, feed Nuof. &tax in -2 a b p v e s as a pmeess' , int, with the contpl range < Z$>%toT.s%. IfbocaxinMG2ia . ,/ over 7.5% ather p"eMing* '"mpm-. *s.haheen toohigh,-mquanti-' ties nf mmpcnded,6ne c r y s w borax arc present, 6r tod much m e r a t e has . fd. If the taw ODZV% the plant oroperatom a& that mbrt biitmf+ate.:be durriep &&e &.I slip atream to the carbonatim plant. I
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ReRned Borax Crude sodium tetraborate pentahy-
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Clean-up and Maintenance
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The Trona process is mainly crystallization, and most clean-up is based on removing salt buildups, either to let equipment work well or to stop contamination products. T h e Trona process is also larg!y cyclic, with one section getting “raw materials” from the preceding one a n d in turn sending end liquors to the following. Thus, regular maintenance and clean-up times in one section depend on those in another. T h e borax plant coordinates with the potash plant for scheduled cleanup. The anhydrous borax plant does not handle solutions, so its maintenance is primarily mechanical. T h e potash plant washout comes three times a week, and the borax plant schedules washouts at the same time. Potash plant washout takes about 4 hours, but borax takes about 6, mainly because the borax refinery sections must be cleaned thoroughly. Because the crude and refined borax processes a l e independent, neither the potash nor carbonation plants must surge their feeds to borax while borax completes the clean-up program. However, carbonation surges to a borax thickener in its plant during washouts at the potash plant. Main washout points in the borax plant are crude coolers, crude filters, centrifuge feed cone, concentrated borax liquor filter, vacuum crystallizers, centrifuges, a n d feed piping systems. Liquor storage tanks-concentrated borax liquor and ML-3-are hardly ever washed out, for high temperatures prevent build-ups at these points. Crude pentahydrate crystallizer washout are scheduled when needed because of build-ups. T h e thickener is cleaned about every 6 months, a 14-hour job. ML-2 a t 200’ F. is used to wash crude filters a n d is then sent to process streams. Hot condensate or filtered “ditch” water is used to wash the centrifuge feed cone, centrifuges, a n d miscellaneous lines. Hot concentrated borax liquor is used to wash the refinery crystallizers a n d is then rerouted to process. T h e anhydrous borax plant has no regular clean-up schedule for the entire plant, but sections are cleaned as needed.
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drare is contarninatcd Lrith entrained mother liquor and a t titnrs Trith sinall amounts (0.3 to 0,796) of potassium chloride Lvhich pass through the potash plant filter screens. This c r u d e material is dissolved in a cycling filtrntc ( A X - 3 ) from the refining process irsclf to make a concentrawl boras liquor (CBL). Refined boras is then obtained from CBL b!. vacuum crystallizing. follo\rrd by dewatering and drying. T h e material is subsequently scrcrned and stored for shipping-. I t can also IX used for fced to the boric acid arid a n 1il;drous sodium tctraborate plants. Besidrs the refined boras. .\mcrican Potash makes a refined sodium tetraborate peiitahydrak in thr same cr)-srallizing equipment as tliaL used for produciiig refined borax, dependinq on sales needs. Special precautions iire necessary in producing the prntahydratr. since a drop in tcmperaturc belair the transition point to the decahydrate causes the cake to ”set up.” Change-over from prnta- to decahydratr runs takes place betiveen normal \rashout prriods i n the refinery. Crude borax from the liorizotital. flat-bed filters is conveyed continuously to a repulper ~ v h e r eit dissolves in hot (160’ F.) mother liquor 3 from tlw end of the borax rcfininq process. Repulped borax is then pumped t o a hot dissolver. ivhere steam injected dircctl!. inro thc tank raises the temperature ti-] 200’ F.. and all borax goes into solution. Pachuca ivalls and agitation give proper mixing. T h e crude boras solution is polished i n pressure filters and p ~ t t ~ p e d to the CBI, storage tank. S c s t step is crystallizing refined borax. Teinpcrature of the crystallizrrs determinrs Tvhethrr pentah>-dratc ( i t ‘ decahvdrate conies doivn. Slurry from stallizers flo\rs by gravity through a seal leg and into a centrifugal feed cone (10 feet high, 16 feet in diameter a t the top) for thickening beforr criitrifuging. Final deivarering of refined boras rakes place in scvrn centrifuges. five Sharples niachinrs and t\vo Cresson-1Iorris ones. I n pentahydrare runs: slurry temperature must br high to prevent the prntahydratr from changing to decahydrate. 11pcritahydrate cake which is undergoing a phase transition to the decahydrate rapidly sets to a concretelike consistency, a n d t l i c s centrifuges \vould be badly darnaged when unloaded. Settling cone overHow and centrifuge filtrate and irashings are combined as mother liquor 3 and pumped to storage. hiL-3 goes from storage as required to the rrpulper to dissolve a fresh crop of crude pentahydrate. It is also the purity control stream in borax refining. Centrifuges dump to conveyors o n the floor dircct1)- beneath, and m o i s t tioras goes either to dryers or directly to t h t .
INDUSTRIAL AND ENGINEERING CHEMISTRY
boric acid and a n h y d i ~ o u sborax ~ i I c i i i t s . 1Ioist Ijoras runs i I O 6 (, ; frcv \ v < i t r r from tlic Cresson-Xlorris niachines! atiort t 3.57; f r m i the Sharples. ‘I‘ivo douI,le drum dryers and a tray dryer :ire u s d for dr)-ing the p r ~ i d u c t s . ‘L’lie double rotar!. d r u m d r y r r s a r c actually t\co d r u m tiryrrs su~icriinp~~sed. \ v i ~ l i the discliargr cnd o f d r u m SCJ, 1 immcdiatcl~. ab()\.? the feed (.rid o f drum So. 2 . This rnrans inoist tioras rntcrs t h c f c w l cncl of No. 1. flo\rs dl)\\Il through i t . and t h e n drops into thr feed chute t o the high cmd of So. 2 . H r r r . partiall!. dried boras rewrscs tlirectioii 180’ t o Ho\v do\rtt So. 2 druill. Hot air, rnc~an\vliile~ rwds t o hot11 drutns a t their closi*st point- riainrly. thr clischarqc end o f Yo. 1 and thr feed end of s o . 2 . .iir thus f l o \ r s collntt’l’cllrrc~lll1(J 11orax i t 1 So.1 and c o n c u i ’ t ~ nin t So. 2. Dry borax discharges f i o r n all clt~yc~t~s a t ahout 1 2 0 ” 1 , here\\. feeders 111c~1.t. d r y borax froin the d r w r s t o i t t i c~lcvatoi. for conveying to upper I t ~ v r l sfor s v w r n ing. iiiiig. t1in.r iiiaqiirseparators opcratinq in ~ ~ a i ~ a l l r l rernovr iron. A11 rrfinrd boras 1)roducts a r r su)rcti i n bins \\.it11 a cotnbincd capai,ity (11 roughl! 26,600 tons. Products a r r sliipprd in bulk. bags. and druins. dc.penclirig o n custoinrr prcl’c~rcncc,.
tic
Table It.
Analysis of Borax Plant Liquors
(‘hcrniral
Potassium Borax [NanBaOil chloride Sodium chloride Sodium carbonate Sodium sulfate Sodium sulfide Potassium bromide Phosphorus (as PlOs) Iodine
RIL-1 9.77 11.67 6.77 6.57 1.93 1.00 0.96 0.46 0.070
AII,-2 7.16 11.82 7.38 7.55 1.99 1.01 0.99 0.49 0.071
BORON CHEMICALS Calciners are 8 feet in diameter and 70 feet long. While there is no pronounced wet end as is often found in calciners and dryers, each calciner has two knockers to stop any build-ups. Hot exhaust gases from the fusion furnaces supply heat to the calciners, with the two larger furnaces “heating” one calciner each. Gas, a t 1300’ to 1500’ F., is drawn into the calciners by direct induction fans. Flow is concurrent with the calcine. Coarse granular borax from storage or moist borax from borax plant centrifuges is conveyed from the borax plant to the anhydrous borax plant across a weigh feeder to storage in two calciner storage bins, one for each calciner. A variable speed chain feeder moves borax from the calciner storage bin
Refined borax is dried prior to being conveyed to storage. In addition to dryer shown, American Potash also uses two double rotary drum dryers
Anhydrous borax is made in this large fusion furnace. Feed hoppers (top center, behind guard rail) continuously circle the furnace and distribute calcined borax into the furnace bed. Large diameter flue (lower left) supplies hot gases to calciners
to a calciner feed screw which charges the calciner. Some puffing and dusting will inevitably occur during calcining, despite the best of feeds. Therefore, dust-laden exhaust gases from each calciner pass through a cyclone separator and then into wet scrubbers. Dust collected by the cyclone joins calciner discharge. Water in the wet scrubber recirculates and is continuously bled off and piped to the borax plant where it is used as process water. Scrubber water is made up with brackish well water. Water remaining in the material leaving the calciners is then removed during fusion. Calcine is sent via a cross conveyor belt and a n inclined conveyor to a distributing system of conveyors where it can be diverted to any one of the calcine storage bins for each of the three fusion furnaces. Operating principle of each of the fusion furnaces is identical, though furnaces differ in construction detail.
Each has an inverted firebox surrounded by a cylindrical air box (Figure 2). Firing is by natural gas a t the top of each. T h e furnace bottom into which calcine feeds for fusion is bowl-shaped and water-jacketed. There is a gap of about 8 inches between the outer, bottom edge of the firebox and the top, inner edge of the furnace bottom. Directly above this gap is the furnace feed ring. Three feed hoppers continuously circle the furnace on the feed ring and distribute calcine into the furnace bed so that it completely fills the gap between firebox and bottom. As each traveling feed hopper passes beneath the furnace calcine storage bin, a cam opens the gates and calcine refills the traveling feed hopper. At the bottom center of the borax bed is a water-jacketed lip ring. Molten borax flows down the calcine bed, over the lip ring, and into the furnace nozzle. Exhaust gases from the furnace exit in a VOL. 49, NO. 3
MARCH 1957
329
BORON CHEMICALS
AnhydraK borox dischorger from one of the furnaces into bucket conveyor. By the time buckets reoch the discharge point, the borox has cooled to
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4-foot-diameter flue leading off the furnace node. Flues on the furnaces carry hot gases to the two ,calciners. Anhydmus borax may he d e either as an amorphous glasa .or a nystaUine solid. The glass is very hard to grind, and it abrades grinding equipment badly. The crystalline material, by c o n w t , grinds easily. To crystallize d t e n anhydruu borax, it may be s t i m d , seeded, or allowed to retain amall amounts of water when molten. I t must also 0001 dowly. Am&n Potash makes use of the last , .two coditions to operate furnaces No. 1 and 2 to make a crystdine pmduct, while furnace No.' 3 makes a glass. The design of the furnace bed .is such that the borax Bo- off of the bed surface and out of the furnace as m n as it is , liquid enough todo so, and sodium tetraborate at its melting temperature of about 1370" F. loem the last traces of hydration water slowly. Molten borax. attacks all known refractories rapidly, ' eyen the zircons. With surface melfing, borax actually lies on a bed.of borax rather rhan against the furnace shell. Furnace temperature may hit WOOo to 2600' F. at the top .of tht firebox, while down at the fusion zone temperature. is about 18W0F., some 430' F. above fusion point of borax. 'Asfiring ,., is usually constant, furnace operators '. ':are concaned mostly with seeing that .. the hvnace has a.gocd borax bed. If &e bed gets too thick, unmelted borax &E out the nozzle: If it gets too thin,
steel water jackets will oyerheat 'and be damaged or blow steam. Too, furnaces operate at a slight pressure-0.5-inch water--and the calcine bed seals the gap between firebox and bottom. If the calcine bed gets too thin, the seal will "blow aut." By adjusting feed hopper speed, furnace tenders keep a proper bed in the furnace. Molten borax dineharges from furMCCS No. l and 2 to mglding machines
where slow cooling promotes crystal formation. Molding machines are actually continuous bucket conveyors whose buckets serve as molds for casting q s talline anhydrous borax into ingots. Buckets move at about 22 feet a minute, and by the time any given bucket reaches the end of the conveyor where ingots discharge, borax has cooled and crystallized (ingots actually contain about 5% amorphous glass that comeskom sudden
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Materials of Construction..
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Most of the plant sections are made with standard materialsmild steel for tanks, pipes, and pumps; rubber for conveyors; wood for storage silos. Both the boric acid and anhydrous borax sections use special materials because of erosion, corrosion, or high temperatures. In the anhydrous borax plant, furnaces No, 2 and 3 have fireboxes of monolithic fire brick, and furnace No. 1 uses standard, super duty fire brick. Furnace shells are mild steel, and flues and thermocouple wells are Inconel and Type 446 stainless steel. Abrasion causes lots of trouble in the anhydrous borax plant. Armor plate protects a number of chutes, and “cushion boxes” are placed at impact points on gravity handling equipment. Shape of these latter gives a recess at impact points. Recesses fill with product, and impact takes place on the product to reduce wear.
Borate ester i s filtered in a specially-designed drybox as a step in developing new boron products
chilling as the first borax flows into individual molds). Borax ingots discharge to a tooth crusher where size is reduced to about - 11!2 inches. Crushed material is conveyed to a crusher storage bin. Furnace No. 3 operates exactly like No. 1 and 2. However, instead of molten borax discharging to molding machines, it discharges to two large, water-cooled rolls. Here it chills rapidly to the amorphous state as it is rolled into sheets about ‘,,‘IS inch thick. Although the material is amorphous and therefore very abrasive, it is easier to
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crush since it has been rolled into shcets. T h e material is then crushed, screened. and stored (Figure 2). Boric O x i d e Boric oxide (B203) is groiving rapidly in its use as a starting material for various organo-borons as w d l as inorganic borons such as elemental boron. boron trichloride, and boron carbide. Boric oxide is produced by the dehydration of boric acid in a gas-fired furnace. T h e melt discharging from the furnace is passed over a chilling roll and is subsequently crushed and screened.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Last step in development of new product in American Potash’s research laboratories i s conducted with large scale equipment, so constructed to confirm information obtained on previous small scale research. If results are satisfactory, pilot plant is then constructed to duplicate actual production on restricted scale
BORON C H E M I C A L S one of the hardest man-made materials known. Although some uses for elemental boron are classified under government restrictions, it is being used in fuses for rockets and flares and also as propellants for missiles and rockets. I n atomic reactor shields, elemental boron combined with plastics provides effective protection from radiation and eliminates the need for weighty lead or concrete shields. I t may plqy a vital role in a successful atomic reactor for aircraft. The products described so far are in the inorganic field, and there are numerous others that the company is studying. Although the uses for these inorganic products are important, American Potash sees perhaps greater potential in organo-borons. These organo-borons were experimented on from about 1840 to 1890, but little industrial application was found for them a t the time. Renewed research indicates they will find extensive use in the petroleum, plastics, glass, and other industries. The company’s organo-borons fall into three general classes-borate esters, boroxines, and miscellaneous. I n the borate esters group are methyl borate and isopropyl borate, two of the
What’s in the Future? As the world’s second largest producer of borax, American Potash & Chemical Corp. is engaged in research to find new boron products and new methods to make existing boron products. This interest in boron products is a part of the company’s long-range development and diversification program started shortly after World War 11. Since then, the company has spent an amount equal to about 3.5% of annual net sales for research. This compares with an over-all industry average of 1% for research and exceeds the chemical industry average of 3%. The bulk of American Potash sales still rests with the company’s “big five” -potash, soda ash, salt cake, borax, and lithium-but a steadily-increasing contribution to the company’s annual income is being made by upgraded products, including new boron chemicals. Boric oxide is being used in the manufacture of metallic borides. Small amounts of boron, usually in the form of ferro-boron because of cost, increase the strength of steel and reduce requirements for alloying elements such as nickel, chromium, and molybdenum. Another use is in making boron carbide,
Typical Analyses of American Potash’s Boron Products in Per Cent
Coarse Granular
Fine Granular
Powdered
101 .24 0.16 0.03 0.001
102* 2” 0.20 0.05 0.0007
103.89” 0.31 0.09 0.001
NazBdOT. 10H~0 (equivalent) NaCl NazSO4 FelOa
Standard V-Bor 101.8’ 0.08 0.019 0.0007
NazBdOl. 5H~0 NaCl NazSO, Fe
Fine V-Bor, ReGned Pentahydrate Borax 101.90 0.11 0.039 0.0007
Pyrobor Dehydrated Borax Standard 99.49 0.00006 0.0017
Na&Or Magnetic iron Acid insol.
so1
0.05
Fine 99.48 0.0004 0.0010 0.053
/
Boric Acid Granular Technical HiBOs Na,SO& Standard 7J.S.P.-XIV and B.P. (1953)tests
100.0 0.08
.*.
Dehydration during drying reflected in figures in excess of 100%.
most important organo-boron products in American Potash & Chemical Corp.’s program. I n addition there are butyl borate, cresyl borate, cyclohexyl borate, tetradecyl borate, plus some 20 lesser borate esters. Information on many of the uses for borate is restricted. Outside the restricted classification, however, experiments are being conducted with methyl borate a6 a fungicide for citrus fruit. A small amount of the borate put in sealed shipping containers lowers spoilage by permeating the carton and combining with moisture from a bruise to seal off the bruise, thus preventing mold from forming. Isopropyl borate, too, is important in the company’s program. Nearly all borate esters eventually will probably be made from isopropyl borate because of higher yields and lower over-all cost. Vital to the company’s plans for isopropyl borate is that, as far as is known, no other producer has been able to manufacture this ester on a commercially practical basis. The second organo-boron group is boroxines which include a number of compounds with a high boron content. Some organo-boron compounds have less than 1% boron, although generally they contain 3 to 4y0. The boroxines, however, may have a boron content of more than 17%. With 17y0 boron, these boroxines are viscous liquids instead of solids, and comprise a n entirely new group of boron compounds. The group is so new that few specific uses have been found as yet, but they will probably find widespread use in industrial processes where high boron content in liquid form is desired. American Potash’s third organo-boron group-miscellaneous-includes boronphosphorus polymers, boranes, and boron-carbon compounds. Although most of these compounds still are in the research or market develoment state, the effect of some are already being felt in the consumer market. One industrial application of boron chemicals was the development by Standard Oil of Ohio of the recentlyintroduced Boron Supreme gasoline, in which boron compounds provide added power for high compression automobile engines. This is one of the first commercial applications but it is not difficult to foresee the expanding effect throughout the petroleum industry.
U.S.P. 100.0
...
Pas5
literature Cited (1) Dub, George D., Am. Inst. Mining Met. Engrs., Mining Technol. 11, No. 5,
Tech. Publ. 2235 (1947). (2) Teeple, John E., “The Industrial Development of Searlcs Lakc Brines,” ACS monograph, Chemical Catalog, New York, 1929. VOL. 49, NO. 3
MARCH 1957
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