CHEM ICAL
Cr M E T A L L U R G I C A L
ENGINEERING
v o l u m e 4 0 Es t a b l is h e d 1902 n u m b e r o
M C G R A W -H ILL PUBLISHING COM PANY, INC.
S. D. KIRKPATRICK, Editor
JUNE, 1933
PLANS + ACTION = RESULTS
A C A D E M I C I A N S — ed ito rs as well as col
lege p ro fe sso rs— o fte n reg a rd a th in g accom plished once th e problem is analyzed an d its solution p u t dow n in the fo rm of a plan. It is n o t su rp risin g , th e re fo re , th a t m uch of the recen t p ro g re ss we have been m aking in W a sh in g to n is still in th e plan stage, even though som e of these p lan s have becom e the law of the land w hile o th ers continue in the th ro es of con
tro v e rsy a n d debate. P e rh a p s all of us have w asted to o m uch tim e in the details o f p lan ning, fo rg e ttin g th a t success depends on the w ay the p lan s a re ad m in istered an d th u s tra n s lated into actual achievem ent.
T h e P re s id e n t’s p ro g ra m of industrial recov
ery is a case in point. I ts opponents— an d at one tim e o r an o th e r th ey have included som e of th e recognized leaders of chemical in d u stry — reg ard the plan as an attem p t to w rite into a single s ta tu te all of th e social rem edies neces
sa ry to cu re o u r in d u strial ills. T hey tell us it m eans th e s u rre n d e r of th e trad itio n al p rin ciples o f in d u strialism . T h ey say th a t its licensing fe a tu re holds the th re a t of com m er
cial exile, th a t its labor provision will kill the open shop, th a t w ith o u t tariff protection our h ig h er prices will m ake us the shining ta rg e t o f u n fa ir com petition from abroad. T hey fear th a t in d u stry will be gro u n d betw een the mill
stones of in creasin g w ages and fixed prices.
F o rg e ttin g the g ro u n d w o rk of ex p erim en t and research on w hich in d u stry itself is founded, th ey d is tru s t the sam e approach to th e all inclu
sive problem o f in d u strial coordination.
T h ese critics, it seem s to us, lose sight of
the fact th a t th e m o tiv atin g sp irit behind the national recovery plan is to give em ploym ent, to raise w ages and th ereb y to rebuild th e p u r chasing pow er of A m erica. In d u stry has be
come confused by its ow n constantly re c u rrin g references to production quotas, price fixing and other bugaboos it has read into th e w o rd ing of the m easure. O bviously m any of th e traditional view points of in d u stry m u st go, ju s t as we are th ro w in g aside the passive resistance th a t has already proved ineffective in stem m ing the tide of the depression. B u t the sooner we, accept the ex p erim en tal sp irit in which the legislation w as conceived, the quicker will be our real progress.
W h a t does all o f this m ean fo r chemical engineers an d fo r executives in chem ical in d u s
try ? F o rtu n ately , we have n o t suffered to the same ex ten t as o th er in d u stries fro m the p articu lar ills which this legislation, as a by
product o f its principal fu nction, w as designed to rem edy. W ith the exception, perhaps, of insecticides and fertilizers, o u r tra d e practices have not been open to serious criticism . T h e alkali and alcohol p roducers early ta u g h t us the b itter lesson o f price w ars. O ver-capacity is n o t a m a jo r problem , especially w hen we elim inate obsolete plan ts and equipm ent.
T h e re fo re, it w ould seem th a t the g reatest gains are to be m ade in the indirect benefit th a t will come fro m in d u strial recovery on a national scale.
Chemical executives, if they do n o t already know it, will have to learn again th e value o f cooperative effort.
E D I T O R I A L S
Business Is Better
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R O D U C T I V E activity increased m ore rap id ly in A p ril and M ay th a n in any com parable p eriod in the h isto ry o f th e U n ite d S tates. T h e F e d e ra l R eserve index, w hich stood a t 60 in M arch, ro se to 67 in A p ril an d has been given a prelim in ary figure o f 76 fo r M ay.B u t w h at about p rices? In an sw er to this question a w ell-know n econom ist told th e executives of chem ical in d u stry on J u n e 1, th a t w e a re en te rin g a long sw ing of m o unting com m odity prices an d b a rrin g d rastic m o n etary a d ju stm en ts, th e n e x t fifteen m onths will see a continued and rap id rise. C hem . & M e t.’s price in dexes given elsew here in th is issue w ould seem to con
firm th e econom ist’s prediction.
One Promising Prospect For the Tennessee Valley
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E S S I M I S T S forecast no th in g b u t fa ilu re fo r the efforts of the new ly established T ennessee V alley A u th o rity . P essim ism will not, how ever, d eter th e able g ro u p o f th re e leaders nam ed to organize the developm en t o f this g re a t m id-continental ex p erim en t. A n d chem ical en gineering offers a t least one a ttra c tiv e p ro s
pect fo r th e ir study.
T h e U n ite d S tates is sh o rt o f pulpw ood. D epletion o f o u r g re a t co n ifero u s te rrito ry o f th e N o rth e a ste rn states has reduced p ro d u ctio n fa r below consum ption.
H e re is an in creasin g o p p o rtu n ity fo r th e T ennessee V alley A u th o rity .
O n e specific p ro ced u re can be suggested. O n M ay 1 rep resen tativ es of th e pu lp an d p a p e r in d u strie s of th is co u n try and C anada visited th e G eorgia ex p erim en tal p lan t in S avannah, w h ere th ey saw th e successful p ro duction on a sem i-com m ercial scale o f g ro u n d wood, sulphite pulp and n e w sp rin t fro m th e slash an d o th e r species of y o u n g S o u th e rn pines. T h e se studies o f D r. C harles H . H e rty , if tra n s fe rre d fro m G eorgia scrub pine to T en n essee V alley w eed w ood, m ig h t affo rd ex trem ely im p o rta n t re su lts in a com paratively sh o rt tim e. B ased on such scientific know ledge, a new type o f fo restatio n w ould be practiced. I n fa c t it m ight not be re fo re sta tio n at all. I t m ig h t re q u ire the encouragem ent of th e w eed ty p e o f p re se n t tim b e r g ro w th an d certain ly new siv icu ltu ral m ethods w ould be expected. T h e practical re su lts looked fo r w ould be q u ick -g ro w in g tim b er supplies w ith sh o rt re fo re sta tio n cycle an d pulpw ood m a n u fa c tu rin g on an econom ic basis in te rrito ry now m arg in al o r su b -m arg in al fro m the sta n d p o in t o f ag ricu ltu re.
Illinois Must Tax To Build Sewage Works
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U P R E M E C O U R T decisions m u st be observed.T h is, in substance, is th e m eaning o f th e ru lin g on M ay 22 d irectin g Illinois to proceed w ith p ro p e r sew age disposal w o rk s in C hicago a n d environs, even th o u g h th e S ta te L e g isla tu re m ay n o t find it politically ex p ed i
ent to raise tax es fo r th a t purpose.
" T h e question, then, com es dow n to th e p ro c u rin g o f the m oney necessary to effect th e p ro m p t com pletion of the sew age tre a tm e n t w o rk s an d th e com plem entary facilities. T o p ro v id e the needed m oney is th e special responsibility of th e S ta te o f Illinois. . . . T h a t re sponsibility th e S ta te should m eet. D esp ite ex istin g econom ic difficulties, th e S ta te h as adeq u ate resources, and w e find it im possible to conclude th a t th e S ta te ca n n ot devise a p p ro p ria te an d ad eq u ate financial m easures.
. . . th e S ta te o f Illin o is is hereb y req u ired to take all n ecessary steps . . .”
I t is clear th a t th e C o u rt m ean t including im posing o f new ta x e s if necessary. I t is a strik in g case, in w hich a F e d e ra l au th o rity com pels sta te ta x a tio n . A n d it is a case in w hich chem ical engineers w ill be p a rtic u larly in te re ste d because m uch new technology is certain to develop in th e needed C hicago sew age-disposal enterprise.
Is Deferred M aintenance Responsible for This?
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N I T S A N N U A L re p o rt on accidental in ju ry rates in the chem ical in d u stry th e N atio n al S a fe ty Council calls atte n tio n to a th o u g h t-p ro v o k in g condition th a t has becom e increasin g ly evident d u rin g th e la tte r y ears o f the depression. T h is is the g ro w in g divergence b etw een the tre n d s o f accident freq u en cy a n d severity.
W h ile th e freq u en cy ra te has fallen considerably and c o ntinuously since 1926, the sev erity ra te d ro p p ed to a low point in 1929, b u t has ag ain rise n sh arp ly until, in 1932, it h ad alm ost reached th e 1926 level. A ccidents a re m ost fre q u en t, it appears, in fe rtiliz e r p lants, and m ost severe in explosives m a n u fa c tu re. H ig h severity ra te s a re also fo u n d in p lan ts m aking dyes, in d u strial gases, chlorine an d alkalis, p h arm aceu ticals an d fine chem icals, and vegetable oils.
C auses fo r th e accidents a re n o t given, b u t it is an open question w h eth er a t least a c o n trib u tin g cause fo r the in creasin g sev erity m ay n o t be th e slackening in m aintenance an d th e g ro w th o f u n sa fe conditions. I t is a fa c t th a t m uch m aintenance has been d e fe rre d an d th a t th is co u rse does in tro d u c e h a z a rd s. W ith r e tu r n ing business optim ism th e re is no longer an excuse fo r fu rth e r delay in this im p erativ e function.
Chemical Engineering’s Quarter of a Century
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N J U N E 22, 1908 fo rty m en m et in th e E n g in e e rs ’ Club in P h ilad elp h ia an d fo u n d ed th e A m erican I n s titu te o f Chem ical E n g in e e rs. L a s t w eek te n tim es th a t m any m et in C hicago fo r th e tw e n ty -fifth sem ian n u al m eetin g o f th e o rganization. I t is only a coin
cidence th a t th e la tte r m eeting should occur a t a tim e w hen th e w o rld is h elping C hicago celebrate its first
“ C e n tu ry o f P ro g re s s .” B u t it is m ore th a n a coin
cidence th a t chem ical en g in eerin g in its first q u a rte r of a ce n tu ry should n o t only have co n trib u ted so m uch to th e advance o f in d u stry b u t is to d a y on th e th re sh - hold o f a m uch g re a te r developm ent.
282 C h em ic a l & M eta llu rg ic a l E n g in e erin g — V ol.40,N o.6
M A K I N G P H O S P H O R IC A C ID in the
B L A S T FU R N A C E
By HENRY W. EASTERWOOD
V idor Chemical Works Chicago, III.
An abridgm ent o i th e paper presented by th e au th o r, under th e title of “M anufacture of Phosphoric Acid by the B last F u rn ace M ethod,"
before th e Chicago m eeting of the American In stitu te of Chemical Engineers, Ju n e 14-16. 1933.
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H O S P H O R I C A C ID is one of the w o rld ’s m ost im p o rta n t acids. V ic to r C hem ical W o rk s has fo r the p ast 30 y ears been in terested in p ro d u cin g pu re phosp h ate com pounds largely fo r food purposes. T h u s it can be readily seen th a t every possible effo rt has been m ade to increase the p u rity o f o u r pro d u cts. T h is aim is responsible fo r o u r u n d e rta k in g th e developm ent of the b last fu rn ace process fo r m aking phosphoric acid.U s e o f th e b last fu rn a c e fo r p hosphoric acid w as first advocated by B riso n s ( B .P . 3,515) in 1868. T h is m ethod ap p aren tly did not prove com m ercially attractiv e a t th a t tim e, and we find th a t d u rin g th e n e x t 30 to 40 y ears th e developm ent w as largely confined to electric fu rn a c e processes.
F ro m 1917 to 1923, how ever, th e re w ere the investi
g atio n s of the B u reau of Soils in th e U . S. D ep artm en t
B last furnace now in use a t N ashville
o f A g ric u ltu re on the volatilization of pho sp h o ru s and the p roduction o f phosphoric acid f o r co n cen trated phos
phate fertilizers. D etails o f this w ork are show n in D e p artm en t B ulletin N o. 1179, published in 1923. S ev eral types of oil-fired fu rn aces w ere b u ilt an d operated experim entally fo r sh o rt periods w ith prom ising results.
T h ese exp erim en ts w ere based on th e p rin cip le th a t S iO a a t high tem p eratu res acts as a stro n g acid, and is capable of replacing the P 2O 5 in the n o rm al tricalcium p hosphate w hich is th e m a jo r co n stitu en t o f th e n atu ra l p hosphate rock used. C arbon w as intro d u ced to reduce th e P2O5 to elem ental phosphorus as soon as it w as lib
erated, so th a t th e reaction betw een C aO an d S i 0 2 could proceed to com pletion w ith th e liberation o f substantially all of th e P->05. T h e reaction considered w a s :
C a3P 20 8 + 3 S i 0 2 + 5C = 3 C a S i0 3 + P ? _+ 5CO O n a w eight basis th is corresponds to a silica-to-lim e ratio o f ap p ro x im ately 1.07. I n the G overnm ent e x p erim en ts a n excess of silica w as used a n d th e silica- to-lim e ratio s ran g ed fro m ab o u t 1.40 u p to a p p ro x i
m ately 1.70. L a b o ra to ry ex p erim en ts fully confirm ed the fact th a t the h ig h er silica ratio s gave h ig h e r volatili
zation o f th e pho sp h o ru s in a s h o rte r p eriod of tim e th an th e low er silica ratios. I have p u rposely m entioned these ratios, based on p erfectly sound reasoning, as they have since cost the V ic to r Chem ical W o rk s, w ho a t th is tim e (1 9 2 4 ) u n d erto o k th e com m ercial develop
m ent of th e blast fu rn ace m ethod, larg e sum s of m oney in th eir efforts to o p erate w ith highly silicious slags.
I n 'o u r investigation a sm all blast fu rn ace w ith an overall h eight of ap p ro x im ately 25 ft. w as built a t the Chicago H eig h ts p lan t in th e early p a rt of 1924. T h e au x iliary equipm ent consisted of a conventional type d u st catcher, and gas m ains leading to th re e h ot-blast stoves o f th e usual tw o pass or “ C ow per” type. T h e stove off-gas m ain led th ro u g h a b an k o f cooling and h y d ra tin g tubes to a 60-pipe C ottrell electrical precip
itato r. T h e a ir blast w as fu rn ish ed by a m o to r-d riv en C onnersville blower. A sizable stock o f ch arg e m aterial w as m ade up by b riq u ettin g finely g ro u n d m ix tu re s of p hosphate rock, silica sand an d coke breeze, correspond-
June, 1933 — C h em ica l & M e ta llu rg ica l E n g in eerin g 283
m g ap p ro x im ately to the b riq u ets used in th e g overnm ent exp erim en ts except th a t due allow ance w as m ade fo r the silica content o f the fuel coke.
T h e stage w as now set f o r o u r first cam paign. T h e fu rn a c e w as blow n in on M ay 10, 1924, an d blow n out again on M ay 15— o u r first failu re. S everal th o u san d p ounds o f P 2O 5 had been charged an d only a few h u n d red pounds recovered as acid. Sufficient u n b u rn ed gas an d elem ental phosphorus h ad passed th ro u g h the system to set fire to the p recip itato r stru c tu re , causing th e s h u t
dow n. T h e acid produced h ard ly deserved the nam e, since th e im purities p re se n t re n d e re d it u n fit fo r any com m ercial purpose.
A f te r re p airin g th e electrical p re c ip ita to r and cleaning out the w hole system o u r second cam paign w as sta rte d on M ay 26, 1924, and ended on J u n e 2. T h e fu rn ace w as th en sh u t dow n because w e could not b u rn the gases produced. T h e re w asn ’t enough com bustion space in the th re e stoves. N o r w as the op eratio n of the f u r nace satisfacto ry . T h e d u st catcher, m ains, stoves, coolers, an d even the p recip itato rs w ere p artially stopped up w ith solid residues o r accum ulations. T h e silica-to- lime ratio d u rin g th is ru n w as 1.11 an d th e P 2O 5 con
te n t o f the slags v aried fro m 1 to 12 p e r cent.
T h e th ird cam paign w as s ta rte d on A u g u st 20, a f te r a fo u rth stove and tw o horizo n tal fire-tube boilers had been installed to increase th e gas b u rn in g capacity. A second blow er and additional coolers w ere also installed and the p recip itato r w as changed fro m a suction to a p ressu re type by placing the d r a f t fa n s betw een the coolers an d the p recip itato r. T h e fan -co n n ectin g m ains w ere of w ooden co nstruction, and leaked gas so badly th a t a f te r about seven days the fu rn a c e w as sh u t dow n and re p airs m ade.
T h e fo u rth blast w as sta rte d ab o u t a w eek a f te r the above shut-dow n, and also lasted fo r seven days. T h ese w ere seven days of co n stan t difficulty in g e ttin g the slag o u t of th e fu rn ace hearth . A f te r sh u ttin g dow n, it w as fo u n d th a t the cooling w a te r on th e bosh h ad leaked into the fu rn ace. F u rth e r, we had com pletely ru in ed the tw o boilers in these tw o seven-day ru n s. T h e expected p rotective coating of d u st h ad n o t developed in th e boiler tu b es as it did in all o th e r pieces o f equipm ent.
U p to this tim e all of o u r ex p erim en tal cam paigns had been com plete failu res, an d w e had m ade little p ro g ress to w ard o u r objective. O u r fifth cam paign w as s ta rte d on N ov. 3, an d lasted a fu ll 30 days. C leaning
of gas and d r a f t m ains an d poor com bustion of the gases w ere continual sources o f trouble. D u rin g the first w eek a sufficiently high p ro p o rtio n of coke w as ch arg ed to keep the fu rn a c e v e ry h o t an d no difficulty w as had in flushing out the slag. B ecause o f th e large am o u n t of fum e-like d u st produced, w e increased the b riq u et b u rd en , w hich cooled the h e a rth dow n to a p oint w here it w as ju s t possible to rem ove the slag. T h is slag ra n ab o u t 6 to S p e r cent P 20 5 and rep resen ted about 30 p e r cent of the P 20 5 charged. T h e fum e p ro d u c tion w as noticeably decreased, b u t w as still sufficiently high to give us considerable tro u b le in keeping th e m ains open. A typical d u st of th e type w hich collected in the fu rn a c e dow ncom er an d gas m ains analyzed C aO , 3.5 p e r c e n t; S i 0 2, 17.0; P 20 3, 6 0 .0 ; F e 20 3, 2 .0 ; A I2 O 3, 4 .0 ; a n d carbon, etc., 13.5 p e r cent.
T h is m aterial o r th e m a jo r p o rtio n o f it w as probably volatilized in the fu rn a c e h e arth and passed up th ro u g h th e charge an d into th e dow ncom er, d u st catcher, and gas m ains w h ere it condensed to a sintered, sponge-like m ass w hich w as v ery difficult to clean out. A s a te m p o ra ry expedient, a ir w as in tro d u ced into the m ains so th a t p artial com bustion of the gases k ep t the fum e residue m oving until it reached a cleanout point. N e e d less to say, larg e p o rtio n s of th is fum e c a rrie d into the stoves, plugging up the checkers, and into th e precip
itato rs, a d d in g im p u rities to th e acid collected. A t the en d of the 30 days, practically all of the stove checkers w ere stopped up. I t w as necessary to use an a ir drill to rem ove these deposits. T h e average silica-lim e ratio of the c h a rg e d u rin g this ru n w as 1.14 w hile a ratio of 1.03 w as obtained in th e slag, in d icatin g a selective volatilization o f th e silica.
A f te r installing n u m ero u s cleanout doors and a h o t
plate d ry e r fo r d ry in g the b riq u ets, an d in su latin g the fu rn ace h e a rth , w e sta rte d B last N o. 6 on F e b . 2, 1925.
T h is ru n lasted 12 days, and w hile show ing m ore p ro m ising re su lts th a n any o f the prev io u s ru n s, d em o n strated the fu tility o f o p eratin g w ith o u t som e m eans of con
tro llin g the fu m e problem .
P r io r to o u r seventh ru n , M ay 4 to 14, w e added 10 ft.
ad ditional heig h t to th e fu rn ace, increased th e size of th e dow ncom er, and p u t in a la rg e r d u stcatch er. S u b stan tial im p ro v em en t w as noted, an d w e w ere able to keep the dow ncom er, d u stcatch er, and m ains open. C om b u stio n a t th e stoves w as m uch b etter, alth o u g h not com plete. W e w ere able to m ain tain a b last tem p e ra tu re
Flow ch art of V ictor Chem ical "Works’ phosp h o ric acid process
284 C h em ica l & M e ta llu rg ica l E n g in eerin g — V0IAOJN0.6
Slag handling at the base of the blast furnace
of 675 cleg. C. an d obtained a volatilization o i 83 per cent of th e P 2O 5 ch arg ed w ith a total recovery of 45 per cent. T h e acid show ed 1.6 p e r cent o f iro n an d alum inum phosphate as its m a jo r im purities. I t w as decided to shut dow n, an d m ake extensive changes in the equipm ent.
T h e silica-lim e ra tio of the b riq u ets had been 1.07, and th a t of the slag, 0.96, d u rin g this blast, still show ing the selective v olatilization of silica.
In o rd e r to in su re com plete com bustion of the gases, a central com bustion cham ber w as provided in w hich the gas an d p h o sp h o ru s v a p o r could b u rn continuously and efficiently at a co n stan tly high tem p eratu re. T h e hot pro d u cts o f com bustion w ere th en led th ro u g h suitable valves to the h o t-b last stoves. In addition to th is p ro v i
sion, w e p u t in a larg e sp ra y to w er as a su b stitu te fo r the bank o f c a st-iro n cooling and h y d ra tin g tubes. A n additional C o ttrell p re c ip ita to r w as installed fo r m ore efficient collection of the acid. A new b riq u e t p lan t was built w ith a con tin u o u s d ry er.
W ith these im provem ents installed, we en tered on our eighth cam paign w hich lasted fro m D ec. 10 to 19, 1925, w hen a b lo w n -o u t tu y e re flooded the h e a rth w ith w ater and caused th e m ass o f slag an d sem i-fu sed charge in the bosh to freeze up. I t w as necessary to stop a n d dig out the charge. T h e nine days of u n in te rru p te d o p era
tion show ed u s a n av erag e volatilization of 84.7 p er cent, and a to tal yield of 52.5 p e r cent. T h e b riq u ets had an av erag e silica-lim e ratio o f 1.13 ancl contained 75 p er cen t carbon in excess o f th a t theoretically req u ired fo r red u ctio n of th e P2O5. T h e silica-lim e ratio of the slag w as 0.92.
In an effo rt to co n tro l the selective volatilization of
did n o t elim inate the fum e problem . T h e fu rn ace w as sh u t dow n to clean the stove checkers.
T h e stoves w ere cleaned and th e te n th blast sta rte d on Feb. 18, and lasted th ro u g h M arch 30, a to tal of 40 days. A total of 491,000 lb. of P2O5 was charged.
T h e average volatilization w as 79 p er •cent and the yield w as 75 p e r cent. T h u s we learned th a t b e tter yields of a p u re r acid could be obtained by using silica-lim e ratios below 0 .9 0 ; an d th a t a h ig h er phosphate b u rd en w ith its resu ltan t low er h e a rth tem p eratu re m aterially reduced the fum e volatilization. A blast te m p eratu re o f 610 deg.
C. w as used, and the excess carb o n w as -m aintained around 50 p er cent. I n spite of th e reduction in fum e production, we collected sufficient am ounts in th e stove checkers to cause us to sh u t dow n a fte r 40 days.
W e installed an additional d u st collector in series w ith the previous collector and sta rte d B last N o. 11 on Ju ly 15. T h is blast lasted th ree w eeks, and w as purely e x p e ri
m ental in natu re. E x c e p t fo r a few days a t th e end of the previous ru n , this w as th e first tim e w e h a d used ru n -o f-m in e phosphate rock. T h is rock analyzed 24.2 p e r cent P2O5. S ulphite liquor w as used as th e briquet binder. T h e am ount of carbon included in th e b riq u ets
Storage silos fo r ground and unground phosphate rock
silica, the b riq u ets f o r o u r n in th cam paign, w hich sta rte d Ja n . 16, 1926, an d lasted 25 days, w ere m ade up w ith a silica-lim e ra tio o f 0.95. W e also used pulverized P o cah o n tas coal as th e red u cin g agent, instead o f coke breeze as w as used in the fo rm e r cam paigns. E xcess carbon in th e b riq u ets w as v aried fro m 50 p e r cen t up to 150 p e r cen t of th a t th eo retically req u ired . T h e av e r
age volatilization obtained w as 85 p e r cent, an d th e yield w as ab o u t 67 p e r cent of th e P2O5 charged. T h e silica- lim e ra tio o f the slag w as 0.89, show ing a m arked im pro v em en t in th e excess silica volatilization, alth o u g h it
w as varied betw een 50 p er cent above theoretical, and no carbon. Som ew hat irre g u la r results w ere obtained, b u t in general it w as show n th a t b e tte r volatilization and yields w ere obtained w ith the h igher carbon contents.
F o r six days w ith the carbon content averaging ab o u t 40 p e r cent above theoretical, we showed an 81 p e r cent volatilization w ith a 76 p er cent yield. T h e silica-lim e ratio of the slag w as 0.84, th e blast te m p e ra tu re 700 deg. C. and the iron and alum inum phosphate in th e acid am ounted to 2.18 p er cent. T h e second d u st collector rem oved sufficient of the fum e d u st to enable u s to
June, 1933 — C h em ica l & M e ta llu rg ica l E n gin eerin g 285
operate th e full th re e w eeks w ith o u t loss of stove heat and w ith o u t having to clean the p recip itato rs.
D u rin g each o f these cam paigns w e obtained ju s t sufficient encouragem ent fro m one angle o r a n o th e r to cause u s to tr y again, so on S ept. 7, 1926, w e launched th e tw e lfth cam paign w hich lasted 45 days. A low silica- lime ratio w as used in an effo rt to control fu rth e r the volatilized fum es. T h e av erag e ratio in th e slag w as 0.78. T h e volatilization av erag ed 82.7 p e r cen t an d the yield 67.0 p e r cent w ith an average daily p ro d u ctio n of 12,450 lb. o f P 2O 5, w hich w as the h ig h est p ro d u ctio n obtained so fa r. A b last te m p e ra tu re of 665 deg. C.
w as m aintained th ro u g h o u t th e ru n . T h e fu m e collection in the stove checkers w as not sufficient to in te rfe re w ith the heat absorption. F u r th e r evidence of th e reduction in fum e volatilization w as show n in th e acid, w hich contained only 1.4 p e r cent iro n and alum inum ph o s
phates. B u t p roduction costs w ere still too high, and p u rity of p ro d u ct too low, so operatio n s ceased.
A carefu l an d th o ro u g h analysis w as now m ade o f all the resu lts obtained and the question of th e com m ercial possibilities o f the process w as m ost c a re fu lly studied.
A lth o u g h close to th re e -q u a rters of a m illion do llars had been sp en t on this research, it w ould have been inadvis
able to continue the w ork, unless th e re w as a reasonable chance o f th e developm ent of a pro cess a t least equal to any o th er know n process. A f te r consid erin g all the facts in the m atter, M r. K ochs, th e p resid en t o f o u r com pany, au th o rized a continuance o f th e w o rk , so on O ct. 10, 1927, th e th irte e n th an d lucky cam paign w as started .
T h e p lan t w as th o ro u g h ly overhauled, a new lining w as p u t in the fu rn ace, th e stoves w ere rep aired , tw o additional d u st collectors w ere installed, the p recip itato rs w ere retiled, an d several im provem ents w ere m ade in the b riq u et plant.
R u n -o f-m in e rock w as used, an d w as b riq u e tte d w ith 66 p e r cen t excess carb o n over th a t th eo retically req u ired . Sufficient additional silica w as ch arg ed to m ain tain a silica-lim e ra tio of 0.85 in th e slag. L e ss h an g in g of stock in the fu rn ace s h a ft w as noted, an d less rod d in g dow n w as req u ire d to b reak u p arches of stock n e a r the top. T h is im provem ent w as due no d o u b t to th e use o f b riquets w ith less th a n th e req u ire d am o u n t of silica, th e needed silica being charged separately, th u s p re v e n t
in g p re m a tu re so fte n in g of the b riq u ets in th e u p p er p a rt of the sh aft.
A n average volatilization of 78 p e r cen t an d a yield of 62 p e r cent w as obtained ov er th e e n tire 67 days o f the blast. T h e av erag e iro n and alum inum p h o sp h ate in th e acid w as 0.85 p e r cent fo r th e last 30 days. A b last te m p e ra tu re o f 680 deg. C. w as m ain tain ed w ith o u t any d r a f t o r com bustion tro u b le a t the stoves. F u m e tro u b les w ere m inim ized. T h e ru n p roved th a t an im proved q u al
ity o f acid could be obtained, th a t h o t b last stoves could be m ade to fu n ctio n ov er long periods w ith efficiency, th a t p re c ip ita to r m aintenance cost could be reduced by the use of carb o n tile, an d th a t n u m ero u s difficulties in m echanical op eratio n could be overcom e.
T h is closes th e ch ap ter on th e C hicago H e ig h ts f u r nace operations. T h e th irte e n th b last h ad show n us com m ercial possibilities f o r a fu rn ace, if operated in the p ro p e r geographical location, an d co n stru ctio n a t N a s h ville w as decided upon.
H ot-blast stoves fo r heating furnace a ir
N a sh v ille F urnace O peration
I t req u ired 13 m o n th s to design an d build th e N a sh ville fu rn ace plant. T h is p la n t w as laid o u t to fu n ctio n in connection w ith o u r ex istin g p h o sp h ate p lan t, and of such capacity as to su pplem ent th e p ro d u ctio n of acid by an efficient D o rr p lan t a lread y o p e ra tin g a t N ashville.
T h e fu rn a c e h ad an overall h e ig h t o f ab o u t 75 ft. T h e p ro d u cin g capacity w as 75,000 lb. of P 2O 5 p e r day com p ared w ith a m ax im u m of 13,000 lb. p e r d ay a t C hicago H eig h ts.
T h e re w ere n u m ero u s problem s in design to be m et in ch an g in g fro m th e C hicago H e ig h ts fu rn a c e to th e la rg e r fu rn a c e , as w e h ad only o u r earlier experience to guide us. Som e m istakes w ere m ade, b u t on th e w hole, w e had a fa irly well balanced p lan t, the cost o f w hich w as ap p ro x im ately $ 2,0 0 0 ,0 0 0 .
O p eratio n w as sta rte d in F e b ru a ry , 1929, an d in less th a n a m o n th we fo u n d by sad experience th a t th e con
clusions reached a t C hicago H e ig h ts in re g a rd to excess briq u et carbon w ere in e rro r. T h e b riq u e ts initially used a t N ashville co ntained ap p ro x im ately 50 p e r cen t excess carb o n ov er th a t theoretically req u ired . A f te r th e f u r nace h ad been o p eratin g ab o u t th re e w eeks, and ev ery body w as feeling optim istic, the tu y e re s su d d en ly w en t black, w e could n o t obtain an y slag fro m th e h e a rth , the blast p re ssu re ju m p ed to double th e n o rm al am ount, and it w as n ecessary to sh u t off th e blast. A larg e hole w as cut in th e side of the h e a rth ja c k e t ju s t above th e tu y eres, an d an oil b u rn e r supplied w ith ta n k oxygen fo r com bustion w as u sed to m elt back an d u p into th e bosh.
A ch a rg e o f d ynam ite w as placed u p into th is hole, and exploded to b re a k a passage so th a t w e could p u t th e
286 C h em ical & M e ta llu rg ica l E n g in e erin g — V ol.40,N o.6
blast on again. N e a rly tw o carloads of red -h o t dust poured out'.
N o m ore excess carb o n w as used in the b riquets. W e did not q u ite learn o u r lesson, as we cu t off only the 50 per cent excess of carbon, leaving the theoretical am ount of carb o n in c o rp o ra te d in th e b riquets, and a f te r six weeks m ore of op eratio n , th is sam e experience w as re
peated. W e th en cu t off h a lf of the rem ain in g briquet carbon leaving 50 p e r cent less th a n the theoretical am ount in the b riquets. N o fu rth e r tro u b le fro m d u st in the f u r nace w as noted. S tra n g e to relate, th e volatilization, yield, and p u rity of acid w ere considerably increased by this red u ctio n in b riq u e t carbon. T h is discovery resulted in U . S. P a te n t 1,867,241.
T h is fu rn a c e w as o p erated a little ov er a y e a r w hen it w as decided th a t w e w ould discontinue o p eratin g our w et-process p lan t an d m ake o u r full req u irem en t of acid by the fu rn a c e m ethod. W e th en dism antled the old f u r nace and erected the p resen t one. B y th o ro u g h p rep aratio n an d planning, th is job w as com pleted in the re m arkably sh o rt tim e o f six w eeks.
P resen t P la n t and Process
T h e p re se n t fu rn a c e has an ap p ro x im ate overall h eight o f 95 ft., an d has inside lines specifically adapted to o u r ex p erien ce in sm elting phosphates. T h e m ax i
m um capacity o f th is fu rn a c e is in excess o f 250,000 lb.
of PoOn p e r day. A m odel o f the com plete fu rn ace plant is on ex h ib it a t “A C e n tu ry o f P ro g re s s .”
A special g ra d e o f m uck phosphate rock fro m the M t. P le a sa n t d istric t o i T ennessee, about 50 m iles south o f N ashville, is used. T h is rock is shipped d ry in box cars to avoid pay in g fre ig h t on m oisture. T h e rock is unloaded by p o w er shovels into a skip hoist an d dum ped in a concrete silo fro m w hich it discharges into tw o mills located a t th e bottom o f th e silo. T h e pulverized rock fro m the m ills is carrie d by a pneum atic conveyor to the top o f th e m illed rock silo fro m w hich it discharges on a belt conveyor w ith sufficient pulverized coal to fu rn ish ap p ro x im a te ly h a lf o f th e carbon f o r theoretical reduc
tion o f th e P 2O 5 p resen t. T h e conveyor belt discharges into a m ix e r w h ere a suitable b in d er is added. T h is m ix tu re feeds into a set o f b riq u e t rolls w here the b riq u ets a re fo rm ed u n d e r a p re ssu re of ap p ro x im ately 5,000 lb. p er sq.in. T h e b riq u ets a re d rie d to a m oisture co n ten t o f less th a n 1 p e r cen t in a con tin u o u s d ry er, and discharged into b riq u et sto rag e bins.
Coke is shipped fro m th e C h attan o o g a o r B irm in g ham d istrict, a n d is sto red in bins sim ilar to the briquet bins. Silica g rav el is h andled in a n o th e r bin.
A n electrically d riv en scale car w ith tw o bell-bottom buckets passes u n d e r the stock bins and collects one bucket o f coke an d one bucket o f b riquets, an d a w eighed am o u n t of silica gravel, depen d in g on th e b riq u et silica an d lim e analyses. T h e se buckets a re carried up the skipw ay and dum ped into th e fu rn ace.
S lag is tapped fro m th e fu rn a c e h e a rth once an h o u r, an d the fe rro p h o sp h o ru s form ed fro m th e iron im purities in th e ro ck an d coke is tap p ed every 12 h o u rs.
T h e slag co n tain s less th an 2 p e r cent of P 2O 0 and is sold fo r railro ad ballast o r m ade in to a special cellular pro d u ct w ith th e tra d e nam e o f “ T uffiite” w hich is used fo r in sulating, and lig h t-w eig h t concrete ag g reg ate.
T h e fe rro p h o sp h o ru s, co n tain in g over 24 p e r cent
phosphorus, is converted into trisodium p hosphate by a special patented process.
T o get back to the fu rn ace, we have th e volatilized phosphorus, carbon m onoxide, an d n itro g en gases leav
ing the furn ace top, an d carry in g d u st an d fu m e p a r ticles sim ilar to those described in th e review of o u r Chicago H eig h ts experim ents. T h is gas passes th ro u g h a large du st catcher an d a series of cyclone d u st col
lectors and special fum e collectors. T h e cleaned gas stream is th en split th ree w ays, one p o rtio n going to the phosphorus condensing p lan t w here elem ental phosphorus and an h y d ro u s pho sp h o ru s p entoxide a re p repared. A second p o rtio n is passed into special boilers fo r th e generation of steam , and th e th ird p o rtio n is b u rn ed in the fo u r h ot-blast stoves fo r heating th e air blast supplied to the fu rn ace h e a rth fo r com bustion of the fuel coke.
T h e gaseous p ro d u cts o f com bustion from th e boilers and stoves, containing P 2O 5 in fum e form , are led into h y d ratin g cham bers w here they are cooled and h y d rated . T h ese cooled gases are th en draw n th ro u g h a series of d ra ft fans and d istrib u ted to the C ottrell electrical p re cipitators w here condensation o f th e liquid phosphoric acid takes place. T h e acid condensed in these units ranges in stren g th fro m 85 to above 90 p e r cen t o rth o phosphoric acid, and has only to be diluted, treated fo r arsenic and filtered b efo re it is ready fo r the m ark et, o r fo r use in m aking phosphatic salts o r com pounds. A large proportion of the acid produced is condensed in the h y d ratin g cham bers and at the fans. T h is acid is of about the sam e p u rity as the p re cip itato r acid.
I t is in terestin g to note th a t th e acid now produced is alm ost a chem ically p u re p ro d u ct, fa r su rp assin g in quality ou r acid p rio r to the in tro d u ctio n of th e furn ace process. T h is is show n by th e tabulated analyses.
Com parison of Blast-Furnace and W et-Process Acid B l a s t F u r n a c e W e t D e c o m p o -
P r o c e s s s itio n P ro c e s s G r a v ity , D e e . B£
H ,P O (, %
PaOc, %
F e a n d A I P O4, % SO2, %
M n, % T o ta l b a s e s , %
54.2 75 .6 5 54.88 0.13 0 .0 1
0.001
0.60
51.0 64.8 8 48 .2 0 1.35 0.52 0.18 5.00
I t is also in terestin g th a t th e pho sp h o ru s volatilization d u rin g the p ast y ear has averaged as high as 95 p e r cen t and th e P 20 5 yield above 90 p e r cent of th e P 20 5 charged.
In conclusion, I w ould like to m ention the nam es of M essrs. A u g u st K ochs, R o th e W eigel, an d the late H . F . N oyes, w hose u n tirin g efforts and fa ith in th e process have been largely responsible fo r its success.
Shipping finished acid in rubber-lined cars
June, 1933 — C h em ica l & M e ta llu rg ic a l E n g in eerin g 287
Burton pressure stills of about 1920 in a refinery of the Standard Oil Co. of Indiana
C h e m i c a l E n g in e e r i n g
P e t r o l e u m
A
B O O K m ig h t w ell a n d should be w ritte n on th e chem ical en g in eerin g advances m ade in the p e tro leum in d u stry d u rin g th e d epression y ears. N o o th er field, outside of th e stric tly chem ical in d u stries, has accepted the chem ical eng in eer on a com parable basis, o r m ade b e tte r use o f his ability. O n th e o ther h and, few o th er in d u strie s offer th e w id esp read o f o p p o rtu n ity , n o t only in the application of th e u n it o p erations b u t in th e developm ent o f chem ical processes a f fectin g such a v arie ty o f raw m aterials an d finished pro d u cts. T h e re fo re , in a b rie f re fe re n ce here, w e can give only a few scattered h ig h lig h ts to reflect the s trik ing p ro g ress being m ade on so m any fro n ts.
E v e n in the oilfields, the chem ical eng in eer has fo u n d a place fo r him self in solving co rro sio n problem s an d in developing new chem ical an d physical m ethods of in creasin g th e recovery o f oil fro m th e gro u n d . C onservation is a t once a re su lt and a cause fo r stim u latin g this g re a te r activity.
In the refineries, chem ical en g in eerin g a tten tio n has cen tered largely in im provem ents in crack in g and o th er distillatio n practices, in recovery of byproducts, in de
veloping and ap plying radically new refining processes such as hyd ro g en atio n , in utilizin g new ag en ts and m ethods in chem ical tre a tm e n t, and in a ttack in g and solving the m u ltitu d e o f co rro sio n problem s.
T h e p h o to g r a p h s i l l u s t r a t i n g t h i s e d i t o r ia l s u m m a r y w e r e s u p p lie d t h r o u g h th e c o u r te s y o f H . W . S h e ld o n , c h ie f c h e m ic a l e n g in e e r o f th e r e s e a r c h a n d d e v e lo p m e n t d e p a r t m e n t o f S o c o n y - V a c u u m . H is c h a p t e r o n p e tr o le u m r e fin in g a p p e a r s In th e S ilv e r A n n iv e r s a r y V o lu m e o f A .I.C h .E . j u s t p u b lis h e d b y D. V a n N o s tr a n d & Co.
A Foster-W heeler 5,000-bbl., two-stage atm ospheric vacuum p ip e still
288 C h em ical & M eta llu rg ic a l E n g in eerin g -— V ol.40,N o.6
This com bination cracking un it is the largest in opera
tion today and w ill produce several times as m uch gaso
line as all the B urton stills shown on the opposite page
A c h ie v e m e n t s in
R e f in i n g
A few exam ples will serve to recall som e o f the o u t
stan d in g d e v e lo p m e n ts: S ta n d a rd o f In d ia n a in 1932 built the larg est com m ercial crack in g u n it in th e w orld, capable of com pletely p rocessing 19,000 bbl. o f c h a rg ing stock p e r day. I t is in te re stin g to note th a t this is ju s t ab o u t 100 tim es th e size of D r. B u rto n ’s largest cracking u n its of tw en ty y ears ago. T h e V acu u m O il Co. o f P au lsb o ro , N . J., first applied the pipe heater to vacuum d istillatio n on a com m ercial scale in 1927 o r 1928. T h e ir tw o -stag e atm ospheric-vacuum u nit had a daily capacity of 2,000 bbl. T o d ay , m ost of the la rg e r lu b ricatin g oil refineries have sim ilar units b u t daily capacities have m o u n ted to as high as 14,000 bbl. of cru d e oil processed.
V ap o r-p h ase cracking, stim ulated by th e necessity f o r p ro d u cin g high an ti-k n o ck gasoline, has had its m ost rap id p ro g re ss w ithin th e p a st tw o years. T he G yro process o f P u re O il, D e F lo re z used by T e x a s a n d G u lf and the P r a tt u n it of th e L u b rite R efining C orp. a re p erh ap s o u tsta n d in g exam ples. I n all p ro c esses, h eat conservation th ro u g h im provem ents in f u r nace co n stru ctio n an d equipm ent design have been re flected in im p o rta n t fuel econom ies.
H y d ro g e n a tio n of petro leu m m ade its first public bow in A m erica th ro u g h th e pages of C hem . & M e t.
in Ju n e , 1929, a f te r tw o y ears of chem ical engineering research a t B aton R ouge, L a. T h e rem ark ab le results achieved in th e ex p erim en tal an d sem i-w orks plant th ere led the S ta n d a rd O il Co. ( N . J . ) to erect tw o large-scale h y d ro g en atio n p lants. In 1930, a 5,000-bbl.
A D eFlorez vapor-phase crack
ing un it in p lan t of the Standard Oil Co. of New Y ork
Battery of th ree 10,000-bbl. K ellogg pipe stills w hich p roduce gasoline, naphtha, kerosene, gas oil, paraffin distillate and
fuel oil continuously
June, 1 9 3 3 — C h em ica l & M eta llu rg ica l E n gin eerin g 289
per day u n it com m enced operatio n s a t B ayw ay, N . J., to be follow ed a y e a r later by a sim ilar p lan t a t B aton R ouge. A h y d ro -refin ed lu b ricatin g oil, E ssolube, w as the first p ro d u ct to be w idely m ark eted b u t th e process has d em o n strated its utility in p ro d u cin g special g rad es of kerosene, a sa fety airp lan e fuel, an d a w ide range of petro leu m and chem ical pro d u cts. H e re , it would seem , is a chem ical en g in eerin g achievem ent o f real m erit.
E th y l gasoline p u t a quality and p e rfo rm a n c e ques
tio n -m ark in the m inds of th e m otorist. T h e oil in d u stry learned th a t its b est cu sto m er w as w illing to pay a p rem ium fo r a b e tter p ro d u ct. So the sam e philosophy w as sh ifte d to lu b rican ts an d in recent y ears every pro g ressiv e oil refin ery in th e co u n try has been a t w o rk im proving th e q uality of its m o to r oils.
N ew processes an d p ro d u cts have a p p eared in p ro fusion. P ro b ab ly S ta n d a rd o f In d ia n a led the w ay w ith its Iso -V is, b u t it continued its research an d has ju s t announced tw o radically new processes. T h e first know n as “ p ro p an e d ew ax in g ” uses liquefied petroleum hyd ro carb o n s a t p re ssu res u p to 200 lb. p er sq.in. T h e p ressu re is g rad u ally reduced and by adiabatic evapo
ratio n of p a rt of th e solvent, th e solution is se lf
re frig e ra te d to ab o u t — 40 deg. F . w hich forces all of the w ax to crystallize. T h is is rem oved by settlin g or filter pressing. T h e second process know n as “ chlo rex e x tra c tio n ” utilizes a new selective solvent, dichloroethyl ether, fo r rem oving un d esirab le co n stitu en ts fro m th e base stock. O th e r com parable an d p erh ap s equally im p o rta n t ex tractiv e processes include th e use of n itro - benzol by A tla n tic R efining, o f phenol by Im p erial O il, L td;, and trich lo reth y len e by S ta n d a rd O il o f N . J .
T e x a s Pacific Coal & O il Co. w as one of th e first to a tta c k the problem o f p ro d u cin g th e ex trem ely low
Natural Gas Technology
P
R O G R E S S in this im p o rta n t field so closely allied to petroleum w as recently review ed b e fo re the T h ird P etro leu m an d N a tu ra l G as C o n feren ce of P en n sy lv an ia S ta te College by G eorge A . B u rre ll an d N elson C. T u rn e r o f th e B u rre ll-M a se E n g in e e rin g Co.T h e a u th o rs paid p a rtic u la r atte n tio n to the rem oval of h y d ro g en sulphide, w hich alth o u g h n o t g en erally p re se n t in A ppalachian n a tu ra l gas, except fro m deep horizons, m ay reach a m ax im u m of 10 p e r cent in c e rtain T e x a s fields. M eth o d s o f rem oval m ost generally used include the old iro n -o x id e process, the lim e process, th e G ird ler process em ploying a m ix tu re o f di- a n d trieth an o lam in e an d th e S eaboard process o f the K o p p ers Co., in w hich th e hy d ro g en sulphide is rem oved w ith soda ash solution.
I n one refinery ab o u t 98 p er cent rem oval is effected by th is process fro m still gases co n tain in g 1,000 g ra m s o f H 2S p e r 100 c u .ft. and the soda re q u irem en t is only 0.07 lb. p e r 1,000 c u .ft. o f gas purified.
T h e m ost recen t developm ent is ih e K o p p e rs hot activation process, in w hich th e H ^S is w ashed o u t o f the gas w ith sodium p h enolate solution m ade fro m caus-
cold test lu b ricatin g oils req u ire d fo r a irp lan es flying a t high altitu d es o r fo r m o to rin g u n d e r severe w in ter conditions. B y a p aten ted distillation process, D r. E . R.
L e d e re r p roduced a heavy bodied lu b rican t substantially fre e fro m w a x an d h av in g a cold te st below zero deg.
F . an d w hich w ith o u t b lending w o u ld rem ain fluid a t te m p e ra tu res as low as — 30 deg. F . A tta c k in g the p roblem fro m a n o th e r angle, th e research lab o rato ries of S ta n d a rd O il o f N . J . developed a new viscous sy n th etic h y d ro carb o n m aterial o f a paraffinic n a tu re know n as P araflow . W h e n blended, even in sm all percentages w ith w a x -b e a rin g oils, it g re a tly reduces the p o u r-p o in t of th e final p ro d u ct. B y th e end o f 1932 it h ad been ad o p ted by 90 p er cent o f the P e n n sylvania refineries, an d 80 p e r cent of those in th e M id -C o n tin en t.
In the field o f chem ical tre a tm e n t, m ention should be m ade o f the E d elean u process utilizin g liquid sul
p h u r dioxide, th e G ray v ap o r-p h ase process utilizing fu llers e a rth and, m o re recently, th e L ach m an process in w hich a zinc chloride so lution is em ployed. T h e b ru cite sw eetening process a n d th e in creasin g use of sodium hypochlorite have been recent developm ents.
O f th e b y p ro d u cts th a t to an e x te n t have become m ain pro d u cts, leading place m u st be given to th e liquefied petro leu m h y d ro carb o n s, w hose o u tp u t m o u n ted fro m 1,091,005 gal. in 1927 to 33,630,236 gal. in 1932. T o d a y 134 m unicipalities in 28 states a re being served w ith th is convenient fuel, w hile th ere are countless th o u san d s of individual in stallatio n s in hom es an d p lants. T h e K now les process o f coking heavy refin ery resid u u m , developed ab o u t th re e y ears ago in th e refin ery of the T id e w a te r O il Co. a t B ayonne an d since ra th e r w idely adopted solves a v ery real problem and produces as u sefu l b y p ro d u cts, coke, gas, fuel oil and gasoline.
tic soda an d ta r acids. T h e foul so lution is p re h e a te d in a heat ex ch an g er an d sen t to the actifier, w h ere th e H 2S is d riv en off by boiling w ith steam . I t can be recovered in su b stan tially p u re fo rm an d m ay b e read ily b u rn e d to su lp h u r dioxide fo r su lp h u ric acid p roduction.
N o radical im provem ents have been m ade in n a tu ra l gasoline p la n ts in recen t y e a rs ; th e g re a te st single a d vance is the in tro d u ctio n o f re c tify in g colum ns (s ta b il
iz e rs) to rem ove w ild fra c tio n s fro m th e finished p ro d u ct. C o n tro l eq uipm ent has also been im proved.
R efin ery gases a re p ro d u ced in a volum e o f close to 600,000,000 cu .ft. p e r day, m ainly fro m crack in g stills in refineries. I n c o n tra st to n a tu ra l gas th ey contain both u n sa tu ra te d an d s a tu ra te d h y d ro carb o n s, and som e h y drogen. A f te r tre a tm e n t to e x tra c t th e gasoline th e y are g en erally b u rn e d u n d e r refin ery stills. S ta n d a rd O il Co.
o f N ew J e rs e y produces isopropyl alcohol fro m th is gas, a n d C arbide an d C arbon C hem icals Co. p u rp o sely crack oil in the v a p o r phase to p ro d u ce a gas rich in u n sa tu rated com pounds fro m w hich glycols, ethyl alcohol, and o th e r chem icals a re m ade. A ro m atics can be p roduced fro m n a tu ra l gas a t high te m p e ra tu re an d w ith s h o rt tim e fo r h eatin g — a crack in g reaction sim ilar to th a t used to m ake gasoline fro m h eav ier oils.
290 C h em ica l & M eta llu rg ic a l E n g in eerin g — V ol.40,N o.6
Problems in Processing of
Cottonseed Meats
By W. R. WOOLRICH
a n dE. L. CARPENTER
Respectively, Professor and Assistant Professor of Mechanical Engineering, University of Tennessee, Knoxville
M odern ex p eller m ill installation
F
O U R M E T H O D S a re available fo r the com m ercial p ro d u ctio n o f cottonseed oil : H y d ra u lic p ress
in g o f th e oil fro m th e m eats ; expelling o f th e oil w ith the p re ssu re e x p e lle r; solvent e x tra c tio n ; and finally release of th e oil fro m th e seeds by bacterial fe rm e n ta tion. A lm o st 100 p e r cent o f the A m erican production, w hich am o u n ts n o rm ally to m ore th a n 1^ billion lb. a n nually, is sep arated e ith e r by m echanical com pression o r by expelling m ethods. T h is is rem ark ab le w hen it is con
sidered th a t even th e best m echanical m ethods recover only 85 p e r cent of th e available oil, as com pared w ith a 95 p e r cent recovery readily obtainable w ith chemical e x tractio n . T h e m echanical details of the chem ical and ferm e n ta tio n m ethods have n ev er been developed to a p o in t to a ttra c t A m erican oil m illers.
F ro m several stan d p o in ts it is desirable to e x tra c t a h ig h er p ercen tag e of oil. T h e m eal w ould keep longer w ith a lesser oil c o n te n t; b e tte r e x tra c tio n w ould yield m ore oil a t no g re a te r m illing c o s t; an d th e resu ltin g b y p ro d u ct m eal w ould be palatable, sw eet an d n u tritio u s an d desirable fo r hum an consum ption, especially w h ere a h ig h -p ro tein , alm ost sta rc h -fre e flour is d esired fo r the balancing o f diets.
C ottonseed oil w as p roduced com m ercially by cooking, follow ed by pressing, p rio r to 1830. H ence, the problem of o b tain in g h ig h oil recovery is m ore th a n 100 y ears old.
M an y reasons have been assigned fo r poor and v ary in g results, b u t th e p rin cip al cause has been a lack of carefu l stu d y o f th e conditioning, rolling an d cooking o f the m eats. C o n tro l m ethods have been ru le-o f-th u m b , the processes largely em pirical an d the fu n d am en tals o f good cooking an d pro cessin g n o t fu lly know n.
A bstracted and prep rin ted by perm ission irom a paper to be presented before the process in d u stries proup of the A.S.M.E. a t Chicagro, Ju n e 29, 1933. under the title of "F a c to rs and Problem s in Conditioning:, Cook
ing- and Pressing- Cottonseed M eats.”
P ro b ab ly the m ost im p o rta n t step in the p rep aratio n fo r cooking is the rolling operation. In a typical set of
“ five-high” rolls such as those illu strated , the cleaned m eats are fed d o w nw ard th ro u g h succeeding p a irs of rolls, in each pass o f w hich they receive the com bined w eight of all the rolls above. F o r a n u m b er o f g e n e ra tions, it has been a generally accepted th eo ry th a t rolling actually crushed the oil cell to set free th e oil. H o w ev er, several score o f rolled specim ens exam ined by the a u th o rs u n d er the m icroscope indicate th a t seldom is a cell ru p tu re d in the rolling process. E v e n w hen the m eats have passed th ro u g h a second series of rolls, a p ractice fo l
lowed in som e plants, th e re is no evidence of a general b reaking dow n of th e cell stru ctu re.
G rin d in g to a very fine m esh has been su b stitu ted fo r rolling in some plants, b u t n ev er w ith any u n ifo rm accept
ance. E x p erim en ts indicate th a t th e p re se n t rolling m ethods give oil yield equivalent to g rin d in g even w hen th e m eats are g ro u n d to pass th ro u g h a 50-m esh sieve.
M icroscopic ex am ination in- E nd section of cottonseed dicates th a t the g rin d in g
m eat rolls operation is no m ore suc
cessful in b reak in g the oil cells th a n is rolling. C onse
quently, it ap p ears th a t the real fu n ctio n of rolling is to expose a g re a te r a re a o f the m eat to th e subsequent tre a tm e n ts in th e m illing process.
A f te r th e m eats have been rolled to a given fine
ness, th e tem p erin g w ith m oisture, o r w hat the oil m iller term s “ h u m id ify in g ,”
m ust be p erfo rm ed . I n com m ercial p ractice th e m eats are conditioned to contain about 12 p e r cent m oisture w hen en te rin g th e cooker.
W h e n and how this m o istu re should be added and ju s t w h at its function
June, 1933 — C h em ica l & M e ta llu rg ica l E n g in eerin g 291
is, is one of the debated qu estio n s in the in d u stry . O n e school expresses the opinion th a t the m o istu re should be added in th e seed house, w hile a second g ro u p proposes th a t the m o istu re should be added ju s t a f te r com pletion of the hulling op eratio n and p rio r to rolling. B u t the general p ractice is to ad d th e m o istu re ju s t b e fo re the m eats e n te r the cooker or to ad d w ater in th e cooker itself. T h e first tw o m ethods cu t dow n the d u st loss b u t introduce problem s in u n ifo rm m o istu re d istrib u tio n . T h e last is evidently preferab le.
Steam for C onditioning
E x p e rim e n ts by the a u th o rs indicate th a t if m o istu re is add ed ju s t b efo re cooking and th e seed b ro u g h t u p to 210 cleg. F . w ith steam , the tim e req u ire d in the cooker itself can be reduced to a fractio n o f th e p re se n t schedule.
T h e steam used should be free fro m w a te r as it en ters the conditioning a p p aratu s to in su re a u n ifo rm p ro d u ct.
O b serv atio n s based on th e p re se n t state o f o u r research indicate th a t the cooking o p eratio n has several functions.
In the first place, it should be recognized as a d ry in g process. H ence, the m o istu re ad d itio n should precede th e cooking. T h e early belief th a t cooking assisted by m ak in g th e oil “ m ore lim pid’' is only p a rtia lly tru e . Its viscosity is o f course low ered, b u t th e oil cannot ru n fro m the seed un til the cell w all is broken. H o w ev er, if the cells a re p ro p erly processed w ith m oisture, th e walls become porous, th u s o ffering a b e tte r o u tlet fo r the oil.
U n d e r certain conditions, it ap p ears th a t th e cell w all m ay even d isin teg rate in the presence of m oisture. F u r th e r m ore, if th e cells a re heated rap id ly to 230 deg. F . a f te r p rocessing w ith m oisture, the steam g en erated w ith in the cell will ru p tu re its w alls, p e rm ittin g escape o f th e oil.
T h e h eatin g process congeals the p ro tein s of the cell, assistin g in the later filtering o p eratio n a t th e presses.
C ooking is accom plished in large steam -jack eted kettles stacked th re e to six cham bers high. F o r th e e n tran ce and discharge of the m eats, each cham ber has openings equipped w ith g ates in the top and bottom , an d is p ro vided w ith a p air of p o w er-d riv en s tirrin g a rm s fo r ag itatio n an d discharge. M eats are first fed into the to p
m ost cham ber fro m which, a f te r an interval, they d is
charge to the n e x t one below, and so on. T h e steam jack ets com prise both th e cylindrical side w alls and the p a rtitio n s betw een cham bers.
B ecause o f the high in su latin g c h a ra c ter of cottonseed m eats, ra p id heat tra n s fe r cannot tak e place w ith o u t effi
cient stirrin g . W ith o u t ag itatio n , tests m ade in a m inia
tu re cooker in o u r E n g in e e rin g E x p e rim e n t S tatio n show ed v ery slow heat tr a n s f e r from th e ja c k e t wall held a t 210 deg. F . W ith th e m eats a t an initial tem p e ra tu re o f 80 deg., th e te m p e ra tu re a f te r 30 m in. a t a p o in t 1 in. inside the jack et w as 158 deg., an d a t 6 in.
only 82 deg. H o w effective p re se n t s tirrin g a rm s a re is a m atte r fo r fu rth e r research. I t has been show n th a t a period of 10 to 20 m in. a t 230 deg. F . w ould suffice fo r the cooking if all the m eats w ere m ain tain ed a t th a t tem p e ra tu re , b u t p re se n t p ractice is to hold th e m eats in the cooker fro m 1 to 2 h o u rs. E v e n w ith this, m icroscopic ex am in atio n of the m eal reveals som e cells u nbroken.
T o speed up cooking, m any plan ts m ain tain a jack et te m p eratu re as high as 287 deg. H o w ev er, since th e oil d ark en s a t te m p e ra tu res above 230 deg., it is a d o u b tfu l p rocedure to em ploy a te m p e ra tu re of 287 cleg, w ith a
m aterial th at is a v ery good in su lato r, and w ith s tirrin g th a t is only p artially effective.
T w o m ethods m ay be u sefu l in im p ro v in g cooking.
O ne is to condition th e m eats w ith d ry steam , raisin g th e ir tem p e ra tu re to 210 deg. in th e te m p erin g process.
T h e o th e r is deliver th e m eats to th e to p cooking cham ber w ith sufficient m o istu re, b u t a t room te m p eratu re, a n d to em ploy such effective ag itatio n in th is cham ber th a t th e te m p e ra tu re is raised to 220-230 deg. so th a t th e re m a in ing cham bers need only to ho ld th e te m p e ra tu re gained in the first. In c ith er case, th e to tal tim e in th e cooker an d the am o u n t o f heat req u ired to ru p tu re th e cells, d ry the m eats and coagulate the p ro tein s w ould be sm all.
O ff-h an d it m ig h t ap p e a r th a t continuous ro ta ry cookers w ould solve the problem . D ue to balling up and consequent incom plete cooking w ith th e p resen t variable conditioning pro ced u re, rev o lv in g cookers have n o t been satisfacto ry . H o w ev er, w ith positive control o f th e co n d itioning process, such equipm ent m ig h t be a success. If these principles could be successfully in troduced, o u r ex p erim en ts have show n th a t the cooking tim e could be reduced to 10 m in.
It is generally accepted th a t a m o istu re co n ten t of 12 p e r cent on the to tal w eight o f th e m eats is m ost desirable fro m the sta n d p o in t of both cru d e oil p ro d u ctio n and of refining loss. T h e p relim in ary te s t in o u r lab o rato ries show s this to be som ew hat low, b u t consideration m u st also be given to the increase in refining loss if the m o istu re co n ten t is m ade too high. W e a re a t p resen t d eterm in in g the effect o f v a ry in g m o istu re content, u sing a continuous cooker an d special co nditioning cham ber and holding all o th er conditions constant.
E x p eller M ill Processing
P re lim in a ry m illing operatio n s in an ex p eller mill are identical w ith those in a h y d rau lic com pression plant.
M eats a re hulled, course g ro u n d and dried, fo r u n i
fo rm ity , to 3 p e r cent m o istu re. In a tem p erin g conveyor they a re slightly heated and m oistened w ith enough w a te r to act as a lu b rican t in the expeller. T h e y a re th e n con
veyed by a vertical w o rm feeder, equipped w ith a solid w orm flight, to a horizo n tal p ressin g cylinder in w hich a re in te rm itte n t w o rm s of p ro g ressiv ely sm aller pitch, all on the sam e sh a ft. T h e enclosing cylinder is m ade up of heavy bars betw een w hich the oil is expressed. T h e cake, w hich is readily g ro u n d into m eal, is fo rced fro m the end o f the cylinder. E ach expeller will rem ove the oil fro m 10 to 15 tons o f m eats p er 24 h o u rs.
T h e m a jo r unsolved problem to d ay in th e m echanical pro d u ctio n of cottonseed oil is th e im p ro v em en t of oil yield and o f m eal qu ality by b e tte r p rocessing m ethods an d control. W h e n it is considered th a t th e value o f a n o rm al y e a r’s m illing app ro ach es a q u a rte r m illion dol
lars, th e im p o rtan ce of th e p ro je c t is com m anding. In solvent production, th e m a jo r unsolved problem s a re lik e
w ise m echanical ra th e r th a n chem ical, con sistin g in the lack o f com m ercially developed continuous e x tra c to rs, lim itatio n s o f p resen t filtering m ethods, an d th e u n sa tis
facto ry distillation an d recovery o f solvents. N e v e rth e less, such are the in h eren t ad v an tag es o f the solvent process th a t m echanical m ethods m u st be th e su b ject of a decade o f v ig o ro u s research if th ey a re to retain the n ear-m onopoly they have enjoyed in the past.
292 C h em ica l & M e ta llu rg ica l E n g in eerin g — V ol.40,N o.6
