Fixation of Atmospheric Nitrogen - Ernst

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Industrial Chemical M onographs

Fixa t ion o fA T M O S P H E R I C N I T R O G E N


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Industrial Chem ical M onographs

Fixation ofATMOSPHERIC NITROGEN

ByFRAME A. E IRNST

Fixed Nitrogen Research Laboratory^ U.S. Dept, Agric; Formerly withthe Nitrate Division^ Army Ordnance; American Qyanam id Compan y

LONDONC H A P M A N & H A L L , L T D .

ELEVEN HENRIETTA STBEET, W.C.2


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C O P Y R I G H T , 1 9 2 8 3 B Y D . V A N N O S T R A N D , I N C .A L L R I G H T S R E S E R V E D , I N C L U D I N G T H A T O F T R A N S L A T I O N I N TOT H E S C A K D I N A V - I A N A N D O T H E R F O R E I G N L A N G U A G E S

P R I N T E D I N T H E U N I T E D S T A T E S O F A M E R I C Aft Y T H E P L I M P T O N P R E S S N O R W O O D - M A S S ,


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F O R E W O R DA L T H O U G H s e v e r a l b oo k s and a l a r g e nu m b e r of p am ph le ts o r a r t ic le s have been wr i t ten on var ious phases o fthe f ixa t ion of a tmospher ic n i t rogen , these have been forthe mos t par t wr i t ten by and for the sc ien t i s t o r technic ianin t ima te l y in te r e s te d in o r a s s oc ia te d wi th th e wor k .F r o m t h e l a r g e n u m b e r o f q u e s ti o n s a n d t h e n a t u r e o f theques t ions asked a t the var ious technica l soc ie ty mee t ingsand f rom the number o f l e t te r s which have come to me inmy off ic ia l capaci ty on the s taff of the Fixed Nitrogen Res e a r c h L ab o r a to r y , it w as v e r y ev id e n t th a t th e s e b oo k s andp a m p h l e t s h a d no t s e r v e d a ll r e q u i r e m e n ts . I t w as th e n inan endeavor to f i l l a need as was indicated by inquir ies bothp e r s o na l and b y l e t t e r th a t th i s s ma l l v o l u m e w as w r i t t e n .T h i s b o ok is no t , t h e r e fo r e , i n t e n d e d fo r th e s c ie n t is t o rtechnic ian famil iar with the subjec t of the f ixat ion of a tmospher ic n i t rogen , bu t i s in tended for the technica l man ofo the r walks o f l i fe , fo r the teacher and s tudent , fo r the bus i ness m an and the ba nk er . I t is ho pe d th a t th is sm al l cont r ib u t ion wi l l g iv e th e g e ne r a l in fo r ma t ion ne c e s s a r y toinf luence i t s r eader to become more deep ly in te res ted in thesub jec t and seek the o the r and more technica l wr i t ings on thesubject.

In th i s v o l u me an a t t e mp t was mad e to s h ow th e ne c e s s i tyfor n i t rogen , and i t s sources ; to g ive some h is to r ica l fac tslead ing up to tint* pr es en t in du st ry ; to g ive a ge n er al des cr ip t ion , ne i the r whol ly chemica l nor whol ly eng inee r ing , o f the


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C H A P T E R IN I T R O G E N

N I T R O G E N , th e supply of which in u t i l iza ble fo rm s is nowen ga g in g th e a t t e n t i on o f a ll o f the im po r ta n t an d p rog res s ive c o u n t r ie s o f the w or ld , is one of the mo s t p len t ifu lo f t h e e l e m e n t s -

Al though the u l t ima te sou rce o f p rac t i ca l l y a l l n i t rogen i sp r o b a b l y t h e a t m o s p h e r e , t h e r e a r e t o d a y f o u r g e n e r a l l y a c cep ted commerc ia l sources , v iz , , the organics , the depos i t s o fna tu ra l n i t r a t e s , t he depos i t s o f coa l and pea t , and thea t m o s p h e r e .F o r t h o u s a n d s o f y e a r s t h e u s e o f n i t r o g e n c o m p o u n d swas conf ined to the fe r t i l i z ing of the l and by the re tu rn to i to f a n im a l an d veg e tab le re fuse- Ju s t w he n such prac t icewas ac tu a l l y s t a r t e d by m an is no t kn ow n . I t is r epo r t ed ,ho w ev er , t h a t a s ea r ly as the fou r th cen tu ry EX. the E gyp t i ans u t i l i zed camel dung wh ich they dug f rom the L ibyanD e s e r t n e a r t h e t e m p l e o f t h e i r g o d " A m m o n . 1 1 I t issupposed tha t a s a l t comparab l e w i th ou r p resen t " s a l amm o n i a c J1 w as a l so p ro du ce d f rom th is m a t er ia l . In add i t ion to such m anu res , t he o rgan ic n i t ro gen m a t e r i a l s oftoday inc lude d r i ed b lood and t ankage f rom the s l augh te rhou se , c o t t o n se e d m ea l f ro m the o il m i ll s , fish sc r ap , l ea the rsc rap , wa s te p roduc t s o f the cocoa f ac to ry , and o the r s imi l a r m a t e r i a l s .

The u se o f ino rgan ic n i t rogen s t a r t ed w i th the d i s cove ryof the n a t u r a l s a l tpe te r depos i ts o f I nd ia and fo r yea r s a

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2 F IX A T IO N O F A T M O S P H E R IC N IT R O G K Nlive ly t r a d e in th i s m a te r i a l wi th th e o th er c ou nt r ies of t hew or ld w as en joyed . W i t h the d i scovery o f b lack po w de r ,t h e m an u fac t u r e o f wh i c h d e p e n d e d u p o n p o t a s s i u m n i t r a t e ,these Ind ian depos i t s immedia te ly assumed a pos i t ion o fe v e n g r e a t e r i m p o r t an c e . T h e n a t i o n s of t h e w o r ld w e r en o w d e p e n d e n t u p o n In d i a fo r t h e m a t e r i a l n e c e ssa r y fo rn a t i o n a l d e fe n se an d p r e se r v a t i o n .

T h e d e m a n d f o r n i t r o g e n c o m p o u n d s r a p i d l y i n c r e a s e dwith th is in t roduct ion of mi l i tary explosives and f inal ly ledin 1830 to the d iscovery of the vast deposi ts of sodiumn i t r a t e in Ch i le . A l t h o u g h these C h i lean dep os i t s a lm os timmedia te ly assumed a pos i t ion o f impor tance i t was wi ththe d i scovery of a m e th o d of m a n u fa c t u r in g n i t r ic acid, thebas i s of our present smokeless powder and h igh explos ives ,f rom th i s sod ium n i t r a t e tha t t he i r r ea l va lue was r ecogniz ed . Chi le fo r ye ars w as alm os t the sole so urce of su pplyof th e w o r ld ' s i n o r g an i c n i t r o g e n d e m an d s fo r b o t h p e ac ean d war .To war d t h e e n d o f t h e n i n e t e e n t h c e n t u r y , an o t h e r so u r c eof ava i l ab le inorgan ic n i t rogen was in t roduced wi th thebr ing ing in to op era t io n o f by-p ro duc t coke ovens- C ok ingcoals conta in combined n i t rogen in vary ing quant i t i es up toabou t 40 poun ds pe r ton . In p ro du c in g coke in the beeh ivetype of oven a l l th i s n i t rogen , as wel l as many o ther va luablecon st i tuents of the coa l , a re los t- In th e by -pro du ct oven s ,ho w ev er , a p a r t o f th i s n i t ro ge n is d r iv en off du r in g t hecoking process and 4 to 5 pounds per ton of coal coked arer e c o v e r e d a s a m m o n i a .


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N I T R O G E N 3o u t t hi s s o u r c e o f s u p p l y t h e W o r l d W a r w o u l d n e v e r h a v econ t inue d for fo ur y ea rs . G e rm a n y , because of an insuffic ien t supp ly o f exp los ives , wou ld undoub ted ly have beenfo rced to ab a n d o n ho s t i l i t i e s a t an ea r ly pe r io d . Y e t eventho ug h her fleet wa s h e l d inac t ive she ta u g h t th e w o r l d ava luab le l e s son . A t the ve ry ou t se t o f the w a r , G e rm a n yw i th bu t a f ew co n v er te d f r e igh t and pa ssa ge sh ips , p re v e n t e d t h e e x p o r t a t i o n o f n i t r a t e f r o m Ch i le f o r s e v e r a lm on ths . T h i s b lo ck ad e w as so com ple te a s to cause a ve rya l a r m i n g s i t u a t io n b e f o r e It w a s b r o k e n . I t d e m o n s t r a t e dthe poss ib le he lp lessness of a na t ion re ly ing for i t s na t iona ldefense , In fac t fo r i ts p re se rv a t i o n , on a fo re ig n so urc e ofsupp ly fo r i ts in o rg an ic n i t ro ge n- In t ime o f w a r g r ea t lyinc reased quan t i t i e s o f n i t rogen a re necessa ry no t on ly fo rexp los ives b u t fo r ag r ic u l tu re a s we l l . T h e a rm ies in thef ie ld mus t be wel l f ed whi le the hea l th and hence conten tmentof t h e p e o p l e a t h o m e is a l s o o f p a r a m o u n t I m p o r t a n c e .Jus t as an army cannot be expected to l ight ef fect ively on ane m p ty s t o m a c h , s o a h u n g r y n a t i o n c a n n o t b e e x p e c t e d t osu p p o rt it s a rm ie s . I f th e n i t ro g e n supp ly is suffic ient sotha t the a rmies a re v ic tor ious , bu t insuf f ic ien t to p rov ide a l sofo r the needs o f the r ema in ing popu lace , then the causew ill u n d o u b te d l y m e e t d e f e a t f r o m w i th in .

I t is v e r y e v id e n t t h a t t h e c o n s u m p t io n o f w a r - t i m e a g r i cu l tu ra l n i t ro g en sh ou ld b e a t l ea s t equ iva l en t to , an d if a ta ll p o s sib le , g r e a t e r t h a n t h e p e a c e -t im e c o n s u m p t io n .N i t r o g e n f o r e x p l o s iv e s m u s t b e a d d i t i o n a l . I f t h e n i t r o gen is im p o r t e d f ro m a fo re ig n sou rce of supp ly , th e neces s i ty f o r In c r e a s e d t r a n s p o r t i n g c a p a c i ty f o r th i s w a r d e m a n d


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4 FIXATION OF ATMOSPHERIC NITROGENtained by G erm an y for a perio d at the beg inn ing of theWor ld War and was ma in ta ined aga ins t Germany dur ingthe whole w a r i s effected, and the country is depen den tupon this source, then that country is almost inevitablydoomed to defeat through lack of munit ions or s tarvat ion,or both.

By increasing the consumption of agricultural nitrogen,lar ge r yields pe r acre m ay be expec ted. T h is w ill resultin e i ther a greater total production or an equivalent production from sm aller ac rea ge , and hence w ith less la b o r. Suchincreased use of nitrogen might be a remedy for some peacetim e as well as w ar -tim e ag ric ul tu ra l difficulties-

I t is qui te general ly believed that Germany declared warin 19T4 only after assuring herself that she had a suitablesource of fixed ni tro ge n w ithin her own bo rd er s . T h e ra teof consumption of nitrogen in explosives during this warwas undoubtedly far beyond the expectations of any individual or na tio n . In or de r to m eet this dem an d it was necessary, even with the enormous expansion of the ratheryoung atmospheric nitrogen fixation industry, to st int agriculture. H o w gr e a t an effect this h a d on th e ev en tua l result is ra th e r difficult to app ra ise , bu t th ere Is no do ub t th a tthe people of severa l of the w ar rin g na tion s suffered m aterially and still show the effects of malnutrition.

Although agriculture in peace t ime and agriculture andmilitary explosives in times of war are the large consumersof nitrogen, It is being used in rapidly increasing quantitiesin many ind ustries . A gric ultu re is responsible for app rox imately 80 per cent of the world's inorganic consumption.


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NITROGEN 5E xp l os iv e s a r e no l ong e r t o h e a s s oc i a t e d on l y w i th

w ar . T h e u s e o f p e ac e - t im e e xp l os iv e s h as g r o w n t r e m e n dous ly un t i l today the re i s consumed in such pur su i t s a sm i n i n g , q u a r r y i n g , r o a d b u i ld i n g a n d t h e c l e a n i n g o f l a n df o r c u l t iv a t i o n , a b o u t 5 0 0 , 0 0 0 , 0 0 0 p o u n d s a n n u a l l y o fh ig h e xp l os iv e s . T h e c h e m ic a l u s es of n i t r o g e n , l a r g e l y inth e fo r m o f n i t r i c ac id , a r e in t h e m a n u fa c t u r e o f p h o to graphic f i lms , a r t i f ic ia l l ea ther , a r t i f ic ia l s i lk , imi ta t ion ivoryan d d ye s- I n t h e fo r m o f am m on ia , n i t r o g e n is u s e d in t h er e f r i g e r a t i o n i n d u s t r y fo r t h e m an u f ac tu r e o f a r ti f ic i a l iceand in t h e o p e r a t i o n o f c o l d - s to r ag e p l a n t s ; i t h a s a w id ed om e s t i c u s e a s h ou s e h o l d am m onia , and i s u s e d i n t h e m anu f a c t u r e o f s o d a a s h , o n e o f o u r m o s t i m p o r t a n t s t a p l echemica l s .

T h e p r ov i s ion o f an ad e q u a t e s u p p l y o f s u c h a v i t a lm a t e r i a l m u s t r e c e i v e t h e g r e a t e s t c o n s i d e r a t i o n o f t h e v a r i ous na t ions o f the wor ld , bo th ind iv idua l ly and co l l ec t ive ly -F ou r s ou r c e s o f s u p p l y w e r e m e n t ione d e a r l i e r and a s i th a s b e e n s h ow n t h a t a n u n l im i t e d s u p p l y is v i t a l l y ne c e ssa ry , it w i l l he w el l to co ns id er th e ex te n t of th es esources .S inc e s o i l n i t r og e n , o r w h a t m ay b e c ons id e r e d t h e na tu r a ln i t ro ge n o f th e so i l, i s a l m o s t whol ly confined to th e su r fac ep or t i on and s inc e t h e im w c a th e r e d , u nd e r l y ing r oc k i s d e v o ido f n i t r o g e n , i t is e v id e n t l y o f a tm os p h e r i c o r ig in . T h eacc um ula t io ns o f so il n i t r o g en a re th e r e su l t s o f r e s idu es o fm a n y g e n e r a t i o n s o f p l a n t s . T h i s n a t u r a l c o m b i n e d n i t r o gen is l a r ge ly a co ns t i tu en t o f o rga n ic m a t te r a n d as such isu n av a i l a b l e fo r p l a n t u s e . I t m u s t h e c o nv e r t e d i n to s im p l ew a t e r -s o l u b l e c o m p o u n d s . T h e d e c o m p o s i t i o n o f such o r g an i c m a te r i a l s r e s u l t s in t h e c on v e r s ion o f t h e c om b ine d


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6 F I X A T IO N O F A T M O S P H F R I C N I T RO G K Nth e so il ba c te r i a to n i t r i t e s , which a r e fu r the r ox id ize d ton i t r a tes , which a re qu ick ly t aken up by the g rowing p l an t .Such accumula t ions o f the so i l n i t rogen canno t be cons ide redas a source of our fu ture supply of n i t ro g en .

T h e fixa tion of n i t ro ge n is a l so acc om pl ish ed by the bac t e r i a w i th in t he t ube r c le s o f t he p l a n t s . P r o f e s s o r I l a b c ronc e re m ar k e d th a t the f ixa tion of n i t ro ge n in th e fu ture fors o i l f e r t i l i z a t i o n u s e w o u l d n o t be t h r o ugh g r e a t i n dus t r i a lp l a n t s , bu t r a th e r t h r o ug h p l a n t a n d s oil ba c t e r i a . S o d c on di t i on s rea di ly inf luence n i t ro ge n fixation by leg um ino usvege ta t ion , pa r t i cu l a r ly the supply o f l ime , and o rgan ic ma t t e r u n d t h e a e r a t i o n o f t h e s o d . T e s t s h a v e s h o w n t h u t LOOto 200 pounds o f n i t rogen can be ga the red in a good c rop o fl e gum in o us p l a n t s pe r a c r e . A t t he p r e s e n t t im e , ho w e v e r ,th i s m e th od o f n i t ro ge n fixation ca nn o t be dep end ed upo n tos upp l y o u r n i t r o ge n de m a n ds .

"While the na tu ra l m an ur es a r e wid e ly used a s f e r t i l i z e r ,y e t the i r ava i labi l i ty is pra c t ica l ly l imi ted to th is use . Sw.lim an ur es a re a by -pro duc t an d the sup ply can no t be in cre as ed a t w i l l . T h e sam e is t ru e of fish scrap, dr ie d blo od ,t a n ka ge , c o t t o n s e e d m e a l , c oc oa w a s t e , e tc . A pp r o x i m a te l y70 pe r cen t o f the combined tonnage o f these ma te r ia l s i sused for ca t t l e feed, whi le the remainder i s consumed inm ixe d f e r t i l i ze r s . Such m a te r ia l s can no t then be con s ide re das a p r im ar y source of supp ly of n i t ro ge n , b ut m u st be supp lemen ta l to some o the r source .

I n 1 898 , t he w o r l d w a s r a the r r ude l y a w a ke n e d by as t a t e m e n t by S ir W i l l i a m C r o o k e s , a n e m in e n t a u th o r i t y , t oth e effect th a t the w or ld was f ac ing u l t im a te s t a r v a t io n b e cause o f i t s dependence upon the na tura l n i t e r beds o f Chi l ef o r i ts n i t r o ge n s upp l y . W hi l e l a t e r i n ve s t i ga t i o n s ha veg iven a ssurance tha t the exhaus t ion o f these depos i t s would
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NITROGEN 7p r o b a b l y h a v e b e e n f u r t h e r d i s t a n t t h a n w a s f e a r e d f r o mSir W i l l i a m ' s s t a t e m en t , ye t h is w a rn i n g w as we ll f ou nd edand t imely .

A t th i s t im e it a p p e a rs ce r t a in th a t Ch i le could supply t h eto ta l d em an d s o f the w o r l d fo r a t l ea s t 100 ye ar s in to th efu t u re . I t is i nev i t ab l e t h a t exh aus t i on m us t occur , how ev e r ,an d wi sdo m w as sho w n in an t i c i p a t i n g t h i s cond i t ion a n dg u a r d i n g a g a i n s t i t s c o n se q u e nc e s- A l t h o u g h t h e 2 2 4 0square mi l e s o f n i t r a t e -bea r i ng g round whi ch has been ex am i ne d and p r o ve n is b u t 3 pe r cen t o f t he t o t a l n i t r a t e a re a ,yet th e re is no as su ra nc e th a t the re m ai n in g 9 7 per cen t is o fp r o p o r t i o n a t e l y e q u a l v a l u e . I t m i g h t b e a s s u m e d t h a t t h em o re l ike ly a re a s h a v e been w or k ed first. O n the o th e rhand , fu t u re work i ng o f t h i s a rea mi gh t show t hese unex p l o r e d r e g i o n s to b e v a s t l y m o r e v a l u a b l e t h a n t h e p r e s e n tw o r k i n g s -

T h e r e is s ti ll an econo m i c ques t i on t o be con s i de red- T h ew o r l d , in c o n s u m i n g s o m e 2 , 0 0 0 , 0 0 0 t o n s o f C h i l e n i t r a t e ,h a s c o n t r i b u t e d t o t h a t c o u n t r y ' s s u p p o r t t h r o u g h t h e ex p o rt:t a x n e a r l y $ 2 5 , 0 0 0 , 0 0 0 f o r t h e y e a r 1 9 2 6 . O f t h is a m o u n t ,t h e c o n s u m e r in t h e U n i t e d S t a t e s p a i d a p p r o x i m a t e l y$ 1 2 , 0 0 0 , 0 0 0 . If n i t r o g e n e q u i v a l e n t t o t h a t s u p p li ed byt h is m a t e r i a l cou ld be s ecured w i t h i n t h e b o rd e r s o f t heUn i t ed S t a t e s , even t hough a t t he s ame cos t t o t he con s u m e r a s C h i l e n i t r a t e , the country a s a w h o l e w< ndd benefitt o t h e ex t en t o f $ 1 2 ,0 0 0 ,0 0 0 , the t ax w hi ch wo uld h av ebeen pa i d t o C h i l e . I f, on t he o t h e r ha nd , p r od uc t i on cos t sare such as to permi t reduc t ion in cos t to the consumer , thedual benef i t can be immedia te ly seen .

T h i s source o f su pp ly in C hi le , w hi le o f g r e a t ex ten t a n d


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8 FIXATION OF ATMO SPHERIC NIT RO GE Nalso because of the possibi l i ty of a nat ion being shut offfro m this supply w hen i t is m o st n ee d ed .

The th i rd source of supply , coal by-products , i s a lso l imi ted . W hi l e coa l, un l ike sod ium n i t r a t e , is co m m on in l a r g edepos i t s to many par t s o f the wor ld , i t s by-product s canno tbe re li ed upon to furn i sh a na t io n ' s ino rga n ic n i t ro ge n . T h eni t rog en f rom this source m ust be a by -pr od uc t and h e n c eits p rodu ct ion will no t be de pe nd en t u po n the d em an d f o rn i t rogen bu t r a ther upon the demand fo r coke . An increaseddemand fo r n i t rogen might be met by a decreased supplyfrom this source because of con di t ions which m ig h t h av e affec ted the coke marke t which in tu rn depends upon the i ronand s teel industr ies .

These th ree sources o f supply then mus t be cons idered aswhol ly inad equ a te . N o na t ion can to d ay a f fo rd to p lace en t i re depen dence u pon any one, or even a l l o f these t h r e ecombined . T h es e sources m us t be con s idere d as su p p le m en ta l to some o th er pr inc ipa l source- T h i s pr in c ip a lsource is the a tm os ph er e .

The fo u r t h s o urce o f s upp ly , t he a t m o s phere , m us t t henbe the answe r to the im p o r ta n t ques t ion of an un l im i te ds upp ly . N o n a t i o n is m o re ad va n t a ge o u s ly s i t ua t ed a sreg ard s th is source tha n any o ther - I t fo rm s , a s was p re v ious ly s t a t ed , nea r ly 80 pe r cen t o f th e a i r we b r e a t h e .O v e r e ve ry s q u a r e m i le o f t h e e a r t h t h e r e is s o m e 2 0 , 0 0 0 , 0 0 0tons - In fac t, the a tm os ph ere furn i shes an in ex ha us t ib lesupply . I t is ap p ar en t then th a t d ifficulties which p r e v e n te di t s use were presen t and were on ly recen t ly overcome.

N i t ro ge n is one o f the m o re re m a rk a b le o f a ll o f t h eninety e lemen ts so fa r d iscov ered . I n th e f ree fo rm a s i t occurs in the a tm os ph er e i t can be u t i l i ze d ne i th er by the b o d i l ym echa nism no r in explos ives or fer t i l ize rs - In th e f ree s t a t e


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NITR O GEN , . .. . : ' 9i t is a comparatively inert gas, but once i t enters. into combination i t displays the greatest act ivi ty both in the organicand ino rga nic fields. O w in g to th e slight affinity be tw eennitrogen and the other elements with which i t enters intocombination, many of i ts compounds are unstable and canbe decomposed with the almost ins tantaneous evolut ion ofh ea t an d g as . B ecau se of this slight affinity, m il ita ry explosives a lmost wi thout except ion are ni t rogen compounds.

In order to render this free ni trogen available for useother than as a diluent for the oxygen of the air, i t must becombined with oth er elemen ts. In this fo rm i t Is kn ow n asfixed nitro ge n. T h e nitro ge n of the org an ics, of C hile nit r a t e , and of by-product coke oven ammonia is alreadyfixed. In th es e cases th e fixation has be en ac co m plis he d byslow natural processes . In the rapid fixation processes nowemployed, the natural independence of the element has beenovercom e by the ingenuity of 'm an. [f oxidized and a bso rbe din w ate r, it is fixed as nitric acid. T h i s is the A r c Pr o ce ss fo ratmospheric ni t rogen f ixat ion. Calc ium carhide at red heatwill absorb free ni tr og en as a sponge will w a ter , thu sfixing the nitrogen in the form of calcium cyanamide by theCy anam ide Pro cess . N i t r o ge n will combine direct ly w ithhydrogen under certain condit ions, result ing in the fixing ol:the ni trogen in the form of ammonia, according to the Direct Synthet ic Ammonia Process .

N it r o ge n f ixed in these forms can be readi ly co nv ertedto oth er m at er i a l s . Pra ct ical ly a ll m od ern explosives aremade by treat ing various substances with ni tr ic acid; for ins tance, smokeless powder from cot ton and ni t r ic acid; n i t ro


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i o F IX A T IO N O F A T M O S P H E R I C N I T R O G E Ncury f rom mercury and ni t r ic acid; and ammonium ni t ra tefrom am mo nia and nitric acid. Calcium cy an am ide givesup i ts ni t rogen in the form of ammonia when treated withsteam in an autoclave. A m m on ia m ay be ox idized a nd abso rbe d in w ater to form nitric acid. I t m ay also be used toneutral ize sulphuric acid to form ammonium sulphate; orphosphoric acid to form ammonium phosphatej or carbonicacid to form urea, or ni t r ic acid to form ammonium ni trate.


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C I I A P T E R I JA T M O S P H E R I C N I T R O G E N F I X A T I O N

T H E c h e m i s t h a s k n o w n f o r m a n y y e a r s h o w t o c o n v e r t t h ei n e r t f r e e n i t r o g e n o f t h e a t m o s p h e re i n t o c o m p o u n d s o fn i t r o g e n i n h i s l a b o ra t o ry - As ea r ly a s 1774 P r i e s t ly i so l a t ed ammonia , wh ich in 1777 was shown by Schec lc t oc o n t a i n n i t r o g e n . F u r t h e r w o r k b y B c r t h e l o t s h o w e d it t ob e c o m p o s e d o f o n e v o l u m e o f n i t r o g e n t o t h r e e v o l u m e s o fh y d r o g e n . I n 1 7 8 1 , C a v e n d i s h n o t e d t h e f o r m a t i o n of n it ri c ac id w he n hy d ro g e n was b u rn e d in a i r an d in 18 00S ir H u m p h r e y D a v y m a d e n it ri c o x i d e b y p a s s i n g a i r o v e r aw i re he a t e d by an e l ec t r i c cu r re n t . In 1865 D ev i l l e p as se da n i t r o g e n - h y d r o g e n m i x t u r e t h r o u g h a p o r c e l a i n tu b e a n df o u n d t h a t a m m o n i a w a s p r o d u c e d w h e n t h e t u b e w a sh e a t e d t o a b o u t i 3 0 O C . A l t h o u g h th e s e a n d o t h e r r e a c t i o n s o f n i t r o g e n w e re k n o w n , t h e r e l u c t a n c e o f t h i s e l e m e n tt o e n t e r in t o c o m b i n a t i o n l im i t e d p r o g r e s s f o r y e a r s t o t h ee x p e r i m e n t a l l a b o r a t o r y . T h e q u a n t i ti e s o f p r o d u c t o b t a in ed in t h is ea r ly w o rk we re d i s t r e s s ing ly sm a l l .T h e w a r n i n g o f S ir W i l l i a m C r o o k e s In t B 9 8 , h o w e v e r ,g a v e i m p e t u s t o t h e w o rk l o o k i n g t o w a rd c o m m e rc i a l f i x a t i o n o f t h e n i t r o g e n o f t h e a t m o s p h e r e . I n 1 9 0 2 , t h e a p p l i ca t i on on an i ndus t r i a l s ca l e o f t he combined resu l t s o f


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12 KIXATION OF A T M O S P H E R I C N I T R O G K NR . L o v q o y , a n d e r e ct e d a l a r g e w o r k s a t N i a g a r a F a l l s ,N e w Y or k . T h e i nd u s t r i a l fixation of a t m os p h e r i c n i t r o ge n thus ha d it s b i r th in the U n i t e d S ta t e s .

T h e p rocess o f Brad ley and Lo ve jo y e i iec ts t he d i re c tco m bin a t io n o f the n i t roge n and oxygen o f the a i r t o fo rmn i t r i c ox ide . By fu r the r ox ida t ion and ab so rp t io n of theox ide s by w a t e r , n i t r i c ac id o f ap pr ox im ate ly 35 pe r cen tc on c e n t r a t i on is f o r m e d . T h i s m e t h o d o f f ixa ti on is k n ow nas the arc process .

Al though th is f i r s t p lant might wel l be ca l led a technica lsuccess i t was not an economical success and c losed downin 190 4 , a f t e r le ss than two yea rs of o p e r a t io n . T h e y ie ldof 948 pounds of n i t r ic ac id per k i lowat t year of power employed proved insuf f ic ient and the equipment bes ides be ingcos t ly was ra th e r f rag il e , r equ i r ing f requen t r ep a i r s .

The commerc ia l poss ib i l i t i e s for the d i rec t ox ida t ion o fthe n i t rogen o f the a tmosphe re fo r the p roduc t ion o f n i t r i ca c i d h a d h e e n d e m on s t r a t e d . H e r e w a s a p oss i b l e m e a n sof avo id ing the se r ious s i tua t ion ind ica ted by S i r Wi l l i amC r o o k e s , E v e n b e f o r e t h e p l a n t a t N i a g a r a F a l l s h a dd i sc on t i nu e d op e r a t i o ns , a f u r na c e w a s d e v e l op e d in N o r w a y b y Prof. C h r i s t i a n B i r k e l a nd a nd E ng i ne e r Sa m u e lH y d e , w h ic h p r o v e d t o b e b o t h a m e c h a n i c a l a nd e c onom i ca l success . Ivx per im cnts w i th th i s furn ace us in g 3 h o rs ep o w er were ca r r i ed on ea r ly in 190 3 , a n d in O c to be r oft h a t yea r a sm a l l c om m c e r c ia l p l a n t e m p l oy i ng 1 5 0 h o r s e p o w e r w a s s t a r t e d in o p e r a t i o n a t A n k e r l o k k e n , n e a r O s l o ,Th i s p lan t p roved so success fu l t ha t t he fo l lowing yea ra p lan t o f 1 ,000 horsepower capac i ty was e rec ted nea rA r e n d a h

Tn 1 9 0 5 , t h e p r e se n t w o r k s a t N o t o d d c n w e r e s t a r t e dI n t o op e r a t i o n w i t h a c a p a c i ty o f 2 , 5 0 0 h o r se p o w e r . Su b -


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ATM OSPHERIC NITRO GEN FIXATION i s equen t en l a rgem en t s b ro ugh t t he capac i t y o f t h i s p l an t t o4 0 , 0 0 0 h o r s e p o w e r in 1 9 0 7 , 5 5 , 0 0 0 in 1 9 1 1 , a n d 6 0 , 0 0 0in 1 9 1 9 . I n 1 9 1 1 , t h e o p e r a t i n g c o m p a n y , t h e N o r w e g i a nH y d r o -E l e c t r i c N i t r o g e n C o m p a n y ( N o r s k H y d r o ) s t a r t e da s econ d w o r ks a t R juk an , fo r a co n s u m pt i o n o f 13 0 ,0 00ho rse p ow er a n d ad d e d a second un i t o f s im i la r s i ze in1 9 1 5 . T h e N o t o d d e n a n d R j u k a n p l a n t s a r c s till in o p e r a t io n w i t h a c o m b i n e d c o n s u m p t i o n of 3 2 0 , 0 0 0 h o r s e p o w e r ,an d an o u t pu t o f 38 ,000 t o n s o f n i t r o gen f i x ed pe r y ea r .

O t h e r a r c p r o c e s s f u r n a c e s d e v e l o p e d a n d p u t i n t o c o m m e r c i a l o p e r a t i o n a r e t h o s e of S c h o n h e r r , M o s c i c k i , P a u l in g , G u y e , a n d W i e l g o l a s k i . T h e i n s t a l l a t i o n s o t h e r t h a nt h o s e a t N o t o d d e n a n d R j u k a n h a v e b e e n r e l a t i v e l y s m a l l ,so t h a t t h e t o t a l i n s t a l l e d c a p a c i t y Is a p p r o x i m a t e l y 4 5 , 0 0 0tons o f n i t rogen per yea r .

T w o f u r t h e r a t t e m p t s h a v e b e en m a d e t o e s t a b l is h t h ea rc p ro ces s in t he U n i t e d S t a t e s . In 1 913 , t h e S o u t h e r nE l e c t r o - C h e m i c a l C o m p a n y , a s u b s i d i a r y of t h e S o u t h e r nP o w e r C o m p a n y , i n c o r p o r a t e d u n d e r t h e l aw s o f t h e S t a t eo f N e w Y o r k , e r e c t e d a p l a n t a t N i t r o l c e , S o u t h C a r o l i n a .T h i s p l a n t e m p l o y e d t h e P a u l i n g f u r n a c e a nd w a s e q u i p p e df o r n i t r i c a c i d c o n c e n t r a t i o n a n d a m m o n i u m n i t r a t e p r o duc t ion . T h e p la n t a s en la rg ed in 19 15 was o f a c ap ac i tyt o u t i l ize s o m e 7 ,0 00 e l ec t r ica l h o r s e p o w er . I ts t o t a l con s u m p t i o n f o r t h e m o n t h of M a r c h 1 9 1 5 , t h e b e s t p e r i o d ofo p e ra t i o n , w as a t t he r a t e o f le ss t h a n ha l f t h a t am o u n t ,h o w e v e r .

D u r i n g t h is m o n t h , t he eq u i v a l en t o f 42 .5 t o n s o f 100per cen t n i t r i c ac id was produced , whi le 32 tons was concent r a t e d , 2 0 .5 t o n s pack ed a n d so ld an d 10 t o n s co n s um ed ina m m o n i u m n i t r a t e m a n u f a c t u r e . T h e m a n u f a c t u r i n g c o st ,$9 0 p er ton o f co n ce n t ra te d ac id exc lusive o f cap i t a l


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14. FIXATION OF ATMOSPHERIC NITRO GE Nc harge s , an d r e c kon i n g po w e r a t $ 10 pe r ho r s e p o w e r y e a rw as h i gh . T h i s po w e r r a t e of $ 10 pe r ho r s e po w e r y e a r w asfar be low th e pre va i l ing ra te for th a t local i ty . T h e consumpt ion o f over th ree horsepower years pe r ton o f n i t r i cac id was too h igh , an d rend ere d o pe ra t io n uneconom ica l, sotha t thep lan t was c losed down ear ly in 1916 , and opera t ionhas never been resumed.

In the fo l lowing year , t he th i rd a t t empt a t e s t ab l i sh ingthe arc process in this country was made, and the fr*st permanent p lan t for the f ixat ion of a tmospher i c n i t rogen in theU ni t e d S ta t es was s t a r t ed- T hi s p la n t , e rec ted and ope ra t ed by the A m er ica n Nitrogen P ro du c t s C o m pan y , w asof about one ton of n i t rogen per day capaci ty and was loc a te d a t Lc G ra n d e , W as h i n g t o n . A f t e r e n jo y i ng n e a r l y t e nyea rs of op era t io n , the p la n t wa s de s t ro ye d by fire in th espring of 1927, and i t i s bel ieved i t wi l l not be rebui l t .

The search for means of f ixing ni t rogen in the form ofalkal i cyanides for gold ex t rac t ion led to the work of Frankand Caro , two eminen t German chemis t s , dur ing the c loseof the n ine teen th cen tury . T h e pa ten t s g r an te d these inves t ig at or s in 18 9 5 -9 8 fo rm ed th e bas is of a proce ss for th ef ixat ion of a tmospher ic n i t rogen known as the cyanamideprocess , in which calc ium carbid e is pr od uc ed th ro u g h th erea ct io n betw een l ime and coke in an electr ic furn ace . Bythe in terac t ion of calc ium carbide and pure n i t rogen a t ared he at , th e ni t ro ge n is fixed in the fo rm of calcium cyan ami de .

The f i rs t commercia l p lan t u t i l i z ing th is process was puti n t o o pe ra t i o n a t We s t e re gc l n nt^r M a g d e b u r g , G e r m a n y ,in 19 05 , T h is plan t was not a com m ercia l success and wasaban don ed in 19 08 . Some 800 tons of cyanam ide ha dbeen pro du ced the fi rs t ye ar . A second an d successful p la n t


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ATMOSPHERIC NITROGEN FIXATION 15was s ta r te d in to op era t ion in 1905 , a t P ian o d 'O r t a , I t a ly .The ini t ial capaci ty of this I tal ian plant was 4,000 tons ofcyanam ide pe r ye ar . F ro m this sm all beg innin g, the industry enjoyed a ra th e r ra p id gro w th to i ts pe ak in 1 918 of 35plants of a ra ted capaci ty of 350,000 tons of n i t rogen peryear . A large part of this capaci ty was erected for the waremergency, so that af ter the war there fo l lowed a cur ta i l ment of product ion and even a d ismant l ing of some plants .

The f i rs t cyanamide plant erected on this cont inent and infact the first successful plant for the fixation of atmos

a t N ia g a ra Fa l l s , C an ad a . T h i s compan y was incorporated in 1907 under the laws of the Sta te of Maine andin 1909 s tar ted in to operat ion a p lant for the annual production of 5,000 tons of cyan am ide . Subsequent en lar ge 120,000 tons of cyanamide per year , equivalent to 25 ,000tons of ni t rogen.

When in 1917, due to the urgency caused by war, i t became apparent that a large and posi t ive source of f ixed

cyanam ide process . T h is p la n t of a ra te d cap aci ty of

I t is know n as U . S. N i t ra te P la n t N o . 2 , an d except for atwo months ' tes t run i t has never operated .

Al though a t tempts to p roduce ammonia d i rec t ly f rom n i t rogen and hydrogen date back to 1807, commercia l Interest was not aroused unt i l af ter the publicat ion by Prof.


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16 FIXATION OF ATMOSPHERIC NITROGENto o k an active inte res t in th e po ssibil it ies of this m etho dfor the commercial f ixation of atmospheric nitrogen and in1913 started in successful operation a plant of a capacity of7 ,000 tons of n i t rog en per year . F ro m th is s ta r t , w orldcapaci ty of direct synthet ic ammonia process plants hasrapidly increased to an operat ing and under-construct ioncapaci ty today of 97 9,0 00 tons of n i t rogen per yea r . T hisis m o r e th an double the installed capa city of the cyanam ideand arc processes combined.

T h e W o rld W a r p rov ed a g re a t s timulus to the a tmosph eric nitro ge n ind ustry . A t the close of the ye ar 1913,or ju st pri o r to th e o utb rea k of the w a r, there w ere in. operation seven arc plants of a capacity of 20,000 tons of nitrogen per year, 15 cyanamide plants of a capacity of 66,000tons of ni t rogen and one direct synthet ic ammonia plant ofa cap aci ty of 7 ,000 tons of ni t r og en per ye ar. Five ye arsla ter , the close of the year 1918, there were operat ing orbui ldin g a nd la ter put into op era t io n, 12 arc plants of acapacity of 40,000 tons of nitrogen, 35 cyanamide plants ofa capaci ty of 350,000 tons, and three direct synthet ic ammonia p lants of 330,000 tons .

T h e per io d fol lowing the w ar has app aren t ly favoredthe dire ct synthet ic am m on ia proc ess. T h e capacit ies intons of ni t ro ge n instal led and bui lding for the various processes a t this t ime are: arc, 5 plants of 44,750 tons; cyanamide, 28 p lants of 315,500 tons; d i rect synthet ic ammonia ,51 p lants of 979,000 tons .T h e f irst plan t of this process erected in the U nite dSta tes w as the U . S. N it r a te P la n t N o . 1 a t Sheffield, A laba m a. T h e imm inence of w ar led to the passage in Congress of Sect ion 124 of the Nat ional Defense Act of June 3,1916 . T h is section m ad e $2 0,0 00 ,00 0 avai lable to the


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A T M O S P H E R I C N I T R O G E N F I X A T I O N 17Pres ident for an invest igat ion of the var ious methods forthe product ion of " n i t ra te an d o the r pro du ct s f or munit ions of war and useful in the manufacture of fert i l izers- 1 1

There fo l lowed the appointment of a commit tee of sc ient is ts and engineers of the Nat ional Academy of Sciences inco-operat ion with the American Chemical Society at therequest of the Se cre tary of W a r . In ad di t io n , tw o invest igators were sent abroad to s tudy and repor t on condi t ionsin Eu rope . In the m ean t im e the G en era l Che m ica l Company had worked up and patented a modif ica t ion of thedi rec t synthet ic ammonia process as operated in Germany,and m ade pr ep ar a t io n s for the e rec tion of a p lan t - T h isplant of 7 .5 tons of ammonia per day capaci ty was to beerec ted a t Shadyside , New York.

The resul t of the var ious invest igat ions made for theGo vernm en t was the r ecom m enda t ion tha t t he W a r D epar tment take over the process of the General ChemicalCompany and erec t a p i lo t p lant to tes t the process . Accord ing ly , U . S. N i t r a te P la n t N o . 1 w as e rec ted a t Sheffie ld, A la. T h is p la n t of a cap aci ty of 3 0 to n s of am m on ia,including the 7.5 ton unit which was to have been erectedat Shadyside, w as n ev er com pleted. O nly one un i t of 7-5tons of ammonia per day capaci ty was ready for t r ia l operat ion prior to the s igning of the armist ice . Continuousoperat ion of this uni t was never real ized, and only a smallamount of ammonia was produced.

In addi t ion to these three processes , a great amount ofinvest igat ional work was done on other processes , and alarge number of methods have been proposed f rom t ime totime for the co m m ercia l fixation of nitro ge n- V e ry few of


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i 8 F IX A T IO N O F A T M O S P H E R I C N I T R O G E Nm ents in ou r kno w ledg e , o r chan ges in the indu s t r i a l s i tu a t ion due to new de m an ds o r suppl ies , m ay in th e fu tu remake poss ible the commercia l success of processes a t presen t en t i r e ly imprac t icab le .

In the cyan ide p rocess a mix ture o f sod ium ca rbona te andcoke wi th i ron in smal l quant i t ies i s hea ted in a s t ream ofp u r e n i t ro g e n t o a t e m p e r a t u r e of a p p r o x i m a t e l y i o o o C*T h i s o pe r a t i o n r e s u l t s in t he f o r m a t io n o f s o d ium c y a n ide ,w h ic h m a y be de c o m po s e d w i th s t e a m to y i e ld a m m o n ia .

T he c o m m e r c i a l de ve l o pm e n t o f t h i s s o d ium c y a n ide p r o c ess w a s un de r t a ke n i n t he U n i t e d S t a t e s by t he N i t r o g e nP r o d u c t s C o m p a n y a c c o r d i n g t o t h e p a t e n t s o f Prof. J . E .Buche i \ E x pe r im en ta l p l a n t s we re e rec te d a t Sa l tv i l le , V i r g in ia and Greene , Rhode I s l and , whi l e In 1918 the Govern m e n t un de r to o k the e r e c ti o n of U n i t e d S t a t e s C he m ic a lP la n t N o- 4 a t Sa l tv i l l e , V i rg i n ia , f o r the p ro du c t io n o f 10tons of sod iu m cyan ide pe r da y by th i s p roc ess . O p e ra t i o nof th i s p l an t s t a r t e d In Se p tem ber o f th a t yea r , r e su l t in g In a .p ro du c t ion o f som e four ton s o f sod iu m cyan ide . As op er a t ing cos t s p roved to be too h igh to r ender the p l an t commerc ia l ly p rac t icab le fo r the p roduc t ion o f e i the r cyan ideo r a m m o n ia , o pe r a t i o n w a s d i sc o n t in ue d in D e c e m be r , a n dthe p l an t was l a te r d i sposed o f th rough sa lvage .

Of the va r ious n i t r ide p rocesses , pe rhaps the one bes td e v e l o p e d is t h a t f o r m a k i n g a l u m i n u m n i t r i d e f r o m c r u d ea l um in um o x ide ( ba ux i t e ) , c o ke a n d n i t r o ge n , he a t e d i n a ne lec tr ic fu rnace to a t e m pe ra tu re o f ab ou t 1800 C T h ea l um in um n i t r i de m a y be de c o m po s e d w i th s t e a m o r d i lu te caust ic so lu t ion to y ie ld am m on ia an d r eg en er a t e th ea lumina .

Var ious sma l l sca l e exper imen ta l p l an t s o f th i s p rocessha ve be en c o n s t r uc t e d a n d o pe r a t e d in F r a n c e , G e r m a n y


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A T M O S P H E R I C N I T R O G E N F IX A T I O N 19an d the U n i t e d S ta te s . T h e chief d if ficulty in a l l cases is ins e c u r in g e c o n o m i c a l l y t h e h i g h t e m p e r a t u r e s n e c e s s a r y f ort h e r e a c t i o n , a n d i n o b t a i n i n g m a t e r i a l s of c o n s t r u c t i o nc a p a b l e o f r e s i s t i n g t h e se t e m p e r a t u r e s in c o n t i n u o u s o p e r a t ion.

T h e e x p l o s i o n , o r H a u s s e r , p r o c e s s d e p e n d s f o r t h e fixa t i o n of n i t r o g e n u p o n t h e f a c t t h a t b y e x p l o d i n g a m i x t u r eo f c o m b u s t i b l e g a s w i t h a i r o r o x y g e n u n d e r p r o p e r c o n d i t io n s h i g h e n o u g h t e m p e r a t u r e s c an b e r e a c h e d t o b r i n ga b o u t t h e c o m b i n a t i o n o f a s m a l l a m o u n t o f t h e n i t r o g e na n d o x y g e n p r e s e n t . By t h i s m ea ns it is a t t e m p t e d t o b r i n ga b o u t t h e s a m e d i r e c t c o m b i n a t i o n o f n i t r o g e n a n d o x y g e nt h a t o c c u r s i n t h e a r c p r o c e s s w i t h o u t i t s e n o r m o u s e x p e n d i ture o f e lec t r i ca l energy .

E x p e r i m e n t a l p l a n t s in w h i c h o p e r a t i o n s h a v e b e en co nd u c t e d in s t a t i o n a r y b o m b s w i t h m e c h a n i c a l l y o p e r a t e dv a l v e s h a v e b e e n r u n a t H c e r i n g e n a n d N e u r e r n b e r g , ( G e r m a n y , T h e m e c h a n i c a l s t r a i n s t o w h ic h t h e a p p a r a t u s issub jec ted l i mi t t he d ev e l o p m en t s . I n its p re se n t s t a t e o fde ve lop m en t t h i s p ro ces s ca nn o t com pe e succes s fu l ly w i t ho t he r p roces ses fo r t he f i xa t i on o f a t mosphe r i c n i t rogen .

O f t h e s e p r o c e s s e s , t h e a r c p r o c e s s r e q u i r e s t h e g r e a t e s tex pe nd i t u re o f e l ec tr i ca l en e rg y , t li e cy a na m i d c an d n i t r i d eproces ses r ank nex t , wh i l e f l i c d i r ec t syn t he t i c ammon i a , cya n i d e and H a u s s e r p r o c e ss e s r e q u i r e o n l y small am ounts ornone a t a i l .

I t is i n t e r e s t i n g t o n o t e t h a t c o m m e r c i a l d e v e l o p m e n t o ft h e t h r e e p r o c e s s e s n o w in c o m m e r c i a l o p e r a t i o n s t a n d s ina p p r o x i m a t e l y i n v e r se p r o p o r t i o n t o t h e u n i t p o w e r co nsum pt ion o f ea ch . F o r ins t an ce , on ly s ix p e r cen t o f th e a t


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20 FfXATJON OF ATM OSPHERIC NIT RO GE Nh o u r s p e r ton . T h e c yan am id e p r oc e s s r e q u i r e s an av e r a g eo f 1 4 , 0 0 0 ( s om e p l an t s a s l ow as 1 2 , 0 0 0 ) k i l o w a t t h ou r s ,o r l ess th a n on e- fo ur th th a t o f the a rc p rocess , and w asacco unta b le fo r 24 pe r cen t o f the ye ar ' s p ro du c t io n . T h eremain ing 70 pe r cen t p roduc t ion was by means of the d i r e c t s yn th e ti c am m on ia p roc e s s , w ith an av e r a g e p o w e rc ons u m p t ion o f 4 , 0 0 0 k i l o w a t t h o u r s p e r ton o f n i t r o g e nfixed.

T h e 6 p e r c en t o f n i t r o g e n p r od u c e d b y th e a r c p r oc e s sconsumed 37 per cent of the to ta l power used in f ix ing nit rog en , the 24 pe r cen t by the cy an am ide p rocess con sum ed35 per cent , while the 70 per cent by the d irec t synthe t ic ammonia p rocess consumed on ly 28 pe r cen t o f the to ta l power .

Th e av e r ag e p owe r c ons u mp t ion a t th i s t ime fo r th e th r e ef ixat ion processes combined is 10 ,000 k i lowatt hours perton o f n i t r og e n a s c omp ar e d wi th 7 0 , 0 0 0 k i l owa t t h ou r sp e r ton 25 ye a r s ag o . T h e to ta l p o w e r c ons u m p t ion n ow ,h ow e v e r , is a t th e r a t e o f 7 , 0 0 0 , 0 0 0 , 0 0 0 k i l o w a t t h o u r sper year , as compared wi th l e ss than 1,000,000 then .


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C H A P T R R IIIT H E A R C P R O C E S S

Tru e comm ercial dev elo pm en t of the arc proce ss was theresult of the at t em pts of m an to em ulate natu re- I t is estim ate d th at thro ug h the l ightn ing disch arge of electr icalstorms 100,000,000 tons of ni trogen are f ixed annually andcarr ied to the ear th 's surface by the precipi ta t ion of rain,snow and hail . U n fo rtu n at el y this f ixed ni tro ge n is no t returned, to the ear th at the t ime and place most convenient to

'man and he must resor t to methods more under h is control .In the commercial operat ion of this process, a ir is passed

rapid ly through a zone of exceedingly h igh tempera ture produced in an electric arc furnace. T h e hea t of th e gase s containing the ni tric oxide produ ced is rec ov ere d in w aste -he atboilers , while the ni trogen dioxide formed on cooling the nitr ic oxide in the presence of the accompanying oxygen is absorbed in w ate r , pro du cin g di lute ni tr ic acid. T hi s is thedirect product 'of the arc process.

The fundamental chemical react ion involved, is expressedby the equationN 2 + 0 2 ^ 2 N O - 43,200 gram calor ies .

F ro m this equa tion it can be calculated th at the chem icalenergy absorbed in fixing one ton of nitrogen is the equivalent of bu t 1,630 ki lo w at t ho ur s of electrical energy - T h ischemical energy equivalent , however , represents less than 3per cent of the total electr ical energy requirements, 61,000


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22 FIXATION OF ATMOSPHERIC NITRO GE Nki lo w at t ho urs pe r to n n i t ro ge n fixed . O ve r 97 pe r cent ofthe to ta l energy exp end ed is w aste d so far as ac tua l n i t r icox ide fo rm at io n i s conce rn ed , and is necessa ry fo r p re p a r i n ga nd m a i n t a i n i ng c ond i t i ons f a v o r a b l e t o t h e f o r m a t i on o fthe oxide.

N i t r i c ox ide ex i st s in equ i l ib r ium qua n t i t i e s w i th h ea te da i r . F o r ins t ance , t he equ i l ib r ium am ou nt a t 2 3 0 0 0 C is 2pe r cent , whi le at 33 00 C it is 6 pe r cent by vo lum e. A sthe re na tu ra l ly is a he a t g rad ien t o f dec reas ing in t ens i tyaway f rom the cente r of the arc but a re la t ive ly smal l quant i t y o f the a i r a t t a ins a t empera tu re o f a s h igh as 3300 0 C ,Ye t even tho ug h i t w ere assum ed t ha t a i l t he a i r p as sedt h r ou g h t h e f u r na c e a t t a i n e d t h is t e m p e r a t u r e , s ti ll t h eg re a t excess of to ta l ap pl ie d energy for he a t in g ov er th echemical energy rece ived in re turn can be readi ly rea l ized .Ac tua l ly the gases l eav ing the a rc fu rnace con ta in an ave r -age of 1.2 pe r cent of n i t r ic ox ide . I t is th er e f o re ne ces sa ryto hand le 175 tons o f th i s gas mix tu re pe r t on o f n i t rogenfixed as n i t r i c ac id . A s th e r e is a t e m p er a tu re g ra d ie n tbe tw een the arc f i lam ent and t he su rro un di ng g as , ic is ob vi ous th a t th i s gr ad ie n t sh ou ld be as s teep as pos s ib le . Inaddi t ion to the saving of e lec t r ica l energy which wouldo the rwise be used fo r hea t ing the gas i f t he g rad ien t weref l a t t e r , t he con le r gas su r round ing the a rc ass i s t s ma te r i a l lyi n r e d u c i ng t h e t e m p e r a t u r e o f t h e n i t r i c ox i d e c on t a i n i nggases as they leave the arc f i lament .

A fa c tor w or kin g aga ins t an e fficient u t i l i za t ion of th een erg y input is the ra p i d decom po si t ion of n i t r ic oxid e a th i g h t e m p e r a t u r e s - A l t h ou g h m e a ns h a v e b e e n d e v i se d t oeffect ra pi d coo l ing of th e gase s, ye t i t is be l iev ed th a t con s ide rab le deco m pos i t ion ac tua lly t akes p lace . I t i s bymeans o f the ope ra t ion o f coo l ing the gases tha t some of the


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T H E ARC PROCESS 23s e e m i n g l y w a s t e d e n e rg y i n p ut is r e c o v e r e d . T h e g a se sl e a v i n g t h e f u r n a c e a t a p p r o x i m a t e l y 1 i o o " C a r e p a s s e dd i r ec t ly t o w a s t e h e a t b o i l e r s w h er e t h e h ea t g iv en u p in ad r o p o f t e m p e r a t u r e t o 3 5 0 C a nd f u r t h e r d r o p t o 2O O0 Cin c c r m o m i z c r s is u t il iz e d f o r t he g e n e r a t i o n of s t e a m . T h i ss t e a m b e s i d e s b e i n g u s e d f o r p u r p o s e s o( so lu t i ons a nd ev a p o r a t i o n s i s u s e d f o r t h e o p e r a t i o n of t u r b o - g e n e r a t o r s f o r t h eg e n e r a t i o n o v r e g e n e r a t i o n of e le c tr ic a l e n e r g y . A l t h o u g hd e c o m p o s i t i o n of t h e o x id e t a ke s p la c e a t t h e s e l o w e r t em p e r a t u r e s , t h e r a t e of s uc h d e c o m p o s i t io n is e x t r e m e l y s l o w .

I h e o x i d a t i o n of n i t r ic o x i de r e p r e s e n t e d b y t h e e q u a t i o n2 N O + 0-,^ 2 N 0 3 + 27 ,800 g ra m calo r ies

p r o c e e d s v e r y s lo w ly , s o t h a t th e v e l o c it y of t h e g a s m u s tb e l o w w h i l e t h e o x i d a t i o n c h a m b e r s m u s t b e v e r y l a r g e .

'I lie o x i d e l e a v i n g t h e e c o n o m i z e rs a t a b o u t 2 0 0 0 C isf u r t h e r c o o l e d in c o o li n g t o w e r s t o a b o u t 5 0 0 C be fo re i ten t e r s t h e s e r i e s of t ow er s o f t h e a b s o r p t ion sys t em, s incet he c o m p l e t e n e s s o f t h e a b s o r p ti o n d ec r ea s es r a p i d l y w i t hi n c r e a s i n g t e m p e r a t u r e . I n t h e first t o w e r o f t h e s y s t e m ,t h e o x y g e n o f t h e a c c o m p a n y i n g a i r r e a c t s w i t h t h e n i t r icuxhlc t o f o r m n i t r o g e n d i o x i d e . T h e g a s e s p a s s in s e r ie st h r o u g h t h e f o l lo w i n g t o w e r s of t h e a b s o r p t i o n s y s te mw h e r e t h e y a r e b r o u g h t i n to i n t im a t e c o n t a c t w i t h w a t e rby which the. n i t r o g e n d iox id e is a b so r b ed forming n i t r i cacid- T i n s r e a c t i o n o c c ur s a c c o rd i n g t o t h e e q u a t i o n

3 NO s + H a O ^ 2 HN O3 + N Ow h ic h i s s h o w n in o n e s t e p a l t h o u g h a c t u a l l y t a k i n g p l a c ein two.f t wi l l b e n o t e d th a t n i t r i c ox ide is aga in l ib er a t ed by th i sa b s o r p t i o n o p e r a t i o n . I n fa ct , one t h i r d o f t h e ox id i zed


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2 4 F IX A T I O N O F A T M O S P H E R I C N I T R O G E Nn i t r i c ox ide rea c t ing w i th w at e r in the ab so rp t io n sys temrev er t s to n i t r i c ox ide which m us t be reo x id ized . T h e re -oxidat ion of th is n i t r ic ox ide , l ike the or ig inal ox idat ion , i sa s low process . Because o f th i s the ab so rp t io n tow ers m us tbe ve ry l a rge in o rder to pe rmi t t ime fo r the l ibe ra ted gasto be oxidized and reoxidized unt i l i t i s eventual ly prac t ical lycomp le te ly abso rbed . T h e resu l t ing pr od uc t is a n i t r i c ac idof 30 pe r cent s t re n gt h .

In commerc ia l opera t ion , on ly about 80 pe r cen t o f theni t rogen oxides are obta ined in the form of n i t r ic ac id , s incei t is no t p rac t i cab le to ob ta in be t t e r ab so rp t io n . Som e 17per cent of these oxides then are absorbed in subsequent a l kal ine tow ers ov er wh ich flows a so lut ion of sod a as h. T h eabsorp t ion o f the n i t rogen ox ides by th i s a lka l ine so lu t ionresul t s in the product ion of sodium ni t r i te or a mixture ofsod ium n i t r i t e and sod ium n i t ra te , depending upon such cond i t io n s of o p e ra t i o n a s t e m pe ra t u r e an d de g re e of o x i d a t i o nof the n i tr ic ox ide . T h e equa t ions fo r these two rea c t io nsa r e , respec t ive ly :

N O -f N 0 3 + 1 N a O H = 1 N a N 0 2 + H 8 0 , an d a N 0 2 + 1 N a O H = N a N 0 2 + N a N O a + H * 0 .

Eve n wi t h t he s e a lka l i n e t o we rs , c o m ple t e abs o rp t i o n o fthe n i t ro ge n oxides is n o t ach ieved an d som e 3 pe r cente sc ape s t o t he a t m o s ph e re . I f s o d i um n i t r i t e r a t h e r t h a nni t r ic ac id i s des i red, a lkal ine towers a lone should be usedfo r the absorp t ion o f the n i t rogen ox ides .

Al though f ive di f feren t arc furnaces were ment ioned in ap re v i o us c hap t e r a s hav i n g be e n us e d i n c o m m e rc i a l o pe ra t ion , on ly th re e of these ha ve en joyed la rge -sca le o pe ra t io n .T he s e a re t he B i rke l a n d -Ey de , t he S c h o n h e r r , an d the P au l ing furnaces .


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THK ARC PROCESS 25in the B irk e l an d -E y d e furnace , ad va nta ge is take n of the

ph en om en on of th e deflection of an ar c by m ea ns of a m ag netic held a t r i g h t angles to it in o rd er to sp re a d the ar cthrou gh the g a s . T h e Sch onh err furnace is bui l t up on analtogether different principle, the object here being to securea s teady an d ve ry long s lender arc . T h e Pa ul in g furnacem ore near ly resem bles the B irke land -E ydc , in th a t it operates on the p rin ci p le of a sp re ad arc. In this furn ace, how ever, this spread of the arc is obtained by a blast of air directed against i t .The Bi rke land-Eyde and the Schonher r fu rnaces bo thare in o pe ra t io n a t the Rjukan p lan t of the N o rs k H y d roC om pan y. Th is pla n t is real ly the only larg e insta l la t ionof the arc pro ce ss . I t s ra ted capac ity of ap pro xim ate ly30 ,000 tons of n i t rogen per year represents over 70 percent of (he world capacity.

This plant is in two units , of equal size, Plant I , completed in if) 12, a n d P lan t II , com pleted in 19 16 . E a c hplant is se rv ed by an individual hydro-electric po w er s ta t io nof 140,000 e le ctr ica l ho rsep ow er capaci ty . T h e w a te r forPo w er H o u s e I is b ro u g h t to the turbines from a lake highup in the mountains and three miles dis tant from the powerhouse, through a number of s teel tubes or condui ts in para l le l T h e s p e n t w at er f rom th is s ta tion is then led thro ug ha rock tunnel cut in the m ou nta in , a d is tance of 3 ^ m iles toPo w er H o u se I I . In addi t ion to the hydro-e lec t ric genera t ing equipment , each power s ta t ion opera tes three s teamdriven tu rb o -g en er a t o rs of a ra ted capac ity of 13 ,000 e lectr ical h o rs ep o w er each . T h e s team for these ge ne ra to rsis supplied by the waste heat boilers for cooling the ni trogen


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2 6 FIXATION OF ATMOSPHERIC NITROG ENSc ho nh er r furnaces of 1 ,000 k i lo w at ts capa c i ty each , a n d s ixof the ea r l i e r B i rke land-Eyde type o f 3 ,500 k i lowat t s capac i ty each . A t P la n t I I a r e 36 B t r k e l a n d - E y d e f u r n a c e s .The Schonhe r r fu rnaces , to s a t i s fy the demands fo r the longs lender arc , a re 30 inches in d iameter by 25 fee t in length . Inthe new B i rke landEyde fu rnaces , a s o f P lan t I I , an a l t e rna t ing cu r r en t a r c is m a in ta in ed be tw een w a te r - co o led cop pe re lec t rodes which are p laced be tween the poles of an e lec t ro-

ir. i. 7. ^ M et f

DIAGRAMMATIC SKETCH OV BHIKELANDEDGE FURNACEm agn et , so th a t th e d i rec t io n of the arc is a t r igh t a ngles totha t of cons tant magnet ic f ie ld- This furnace i s inc losedw ithin a s teel cyl in dr ica l case , 12 feet in d ia m et er by 5feet betw een th e f ia t en ds . T h e inn er surfa ce of this cas ingis l ined wi th fire bri ck le av in g a cy lin dric al space 6 feet ind ia m ete r by 6 inches th ick in which the arc expa nds- T h e


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T H E ARC PROCESS 27a i r en te rs th i s a rc reg ion through perfora t ions In the br ickwal l and leaves through open ings a long the c i rcumferenceof this region. T h e cap aci ty of these furna ces is 4 , 00 0 kw .each.Al though the furnace rooms of the two p lan t s a re about ami le apar t the absorpt ion bui ldings are adjacent and in theim m edia te vic in i ty of the furnace ro o m of P la n t I . T h ismakes i t necessary to convey the gases as they leave theecono m izers of P la n t I I a dis tance of ne ar ly a m i le . Int rave l ing th i s d i s tance through 5 a luminum tubes , each 3fee t in d iamete r , the gases a re coo led f rom 200 0 C to about5 0 0 C, ob via t ing the necess ity of a cool ing to w er . F u rt h e r ,upon cooling, oxidat ion of the ni t r ic oxide takes place sotha t the gases upon reaching the absorpt ion bui ld ing a redrawn d i rec t ly in to the absorpt ion sys tem.

T h e a bso rpt ion to w ers wh ich a re of gra n i t e a r e 22 feet india m ete r by 70 feet high an d are ar r a n g e d in se ts of foureach . T h e furnace gases en te r ing the base o f tow er N o . 4pass up through th i s tower to the base o f tower No . 3 , andso on th ro ug h th is tow er and th ro ug h to w ers N o . 2 andN o . 1. F ro m the exi t of to w er N o . 1 th e ga ses pa ss In seriesth rough two a lka l ine t owers f rom which the unabso rbedn i t rogen ox ides pass t o t he a tm os ph e re . T h e abso rb ingl iqu id f lows th rough these t owers coun te r -cur ren t ly . Wate rspr ay ed f rom the top of tow er N o . 1 abso rbs som e of th eni t ro ge n oxides on i ts descent . T h e w ea k n i t r ic ac id f romthe base of th is tow er is pu m pe d to the top of tow er N o . 2and so on , through tower No. 4 , where the ac id reaches 30per cen t s t rength .

A product of th is plant , but not necessar i ly a product of


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28 FIXATION OF ATMOSPHERIC NITR OG ENA use for some of the steam of the waste heat boilers isp resen ted here fo r evapora t ion to concen t ra te the so lu t ion

*'.:.. .,.GRANITE TOWERS AT RJUKAN PLANT FOR ABSORPTION or NITROGEN OXIDES

to 13 pe r cent n i t ro ge n. Calc ium n i t ra te is used for fer t i l izer purposes .

The Paul ing furnace is opera ted in a p lant of 1 ,000 tonsof n i t rogen ann ua l capac i ty a t Pa t sch , n e a r In nsbruck ,A us t r ia . In th is fu rnace the a rc passes be tw een two wate r -cooled, cast-steel tubular electrodes, which are set perpen-


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C H A P T E R I VT H E C Y A N A M I D E P R O C E S S

IN the cyanamide process gaseous nitrogen is fixed bybringing it into contact with finely powdered calcium carbidehea ted to io o o C. T h is form atio n of calcium cyana m ide isrepresented by the equation

C a C 2 + N 2 = CaCN T2+ C.In producing the two react ing mater ials , extremes of tem

pera tures are em ployed. Calcium carbide is pro duc ed bymeans of the intense heat of the electric furnace, while thenitrogen is secured thro ug h th e fract io natio n of a ir whichhas been liquefied a t a te m pe rat ur e of 190 C below z e ro .

The production,ol calcium cyanamide involves four steps,-(1) T he product ion of lime from l im eston e; (2 ) T h e production of calcium carb ide; (3 ) T h e pro duc tion of gaseo usnitrogen; and (4) The ni tr i f icat ion of the carbide.

In the first step, crushed limestone is burned in a kiln ata t empera tu re of n o o 0 C until the carbon diox ide has beendriven oft, T h is proce ss is rep res en ted by the eq ua tion

C a C 0 3 - CaO + C 0a - 42,900 gra m , calo ries.and may be carr ied out in ei ther a rotary or ver t ical ki ln.In the rotary kiln the limestone rock is fed into one end ofthe kiln which is so inclined that upon rotation the limestoneflows slowly dow n its len gth . T h e fuel, dr ied a n d finelypulverized coal for instance, is intro du ced t hr o ug h a bu rn er

3


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T H E C Y A N A MI D E PRO C ESS 3 1at th is lower end. T h e rock is gra du al ly deco m po sed andthe l iberated carbon diox ide is carr ied aw ay wi th the furnace gases, by m ean s of a stack. T h e bu rn t l ime is discharged at ixoo C to a cooler from which i t is conveyed tosto rag e. In this coo ler, which m ay be a ro ta ry ki ln usuallyof smal ler diameter and length, the temperature i s reducedto about 200 0 C . Since for the pro du ct ion o( calcium carbide limestone of one inch d iam eter lump is pr ef er re d , the reis a lar ge q ua ntity of fines, pe rh a p s as much as 25 pe r cen tof the tota l . T h e se f ines ar e w as te so fa r as the cy an am ideprocess is concerned, but may have a value as agriculturalor building lime.The product ion of calcium carbide Is the power consuming ope rat ion of the cyan am ide process . T h e car bide isform ed by fusing a ch arg e of a m ixtu re of l ime an d ca rbo nin the rat io of ap pro xim ate ly 1,000 po und s of ca rbo n to 600pounds of coke in an electric fu rnace . T h e reaction is asexpressed by the equat ion

CaO + 3 C = CaC H 4- CO 121,000 g ra m calo rics.T h e carbon m ay be in t roduc ed as an thra c i t e coa l , char

coal or coke. T h e la t t e r has pro ved pre fer ab le , h ow eve r ,and is by far of wid est use in this ind us try . I t sh ou ld be asof t burned ra ther than metal lurgical coke and of aboutthree-fou rths inch in size. I t shou ld co nta in a t a m ax im um6 per cent ash and 0.5 per cent moisture.

The carbon monoxide formed, which amounts to about735 pound s pe r ton of crude carbid e, is no t rec ov ere d, although it has a he a t in g va lue of 4 ,380 B .T .U . per po un d.

T h e furnaces ar e usually rec tan gu lar in sha pe , 5 feet or 6feet deep, with the depth below the operat ing f loor, so thatthe carbide m ay be tapp ed f rom the furnace a t the low er


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32 FIXATION OF ATMOSPHERIC NITROGENfloor. T h e carb on elec trod es, usually tw o feet square each,are clamped three together in such a way as to give the appea ranc e of one big elec trod e 2 feet by 6 feet. T he se electrodes six feet long are suspended above the furnace insuch a manner that their depth in the charge is automatical lyregulated by a solenoid which controls a motor-driven hoist .After the current to the electrodes has been turned on, themixed charge of lime and coke is shoveled around the electrodes, the depth of charge being such that the top or visiblelayer is nev er th or ou gh ly fused. In the fused state , thelime reacts with the carbon to produce molten carbide.The furnace is tapped at intervals of perhaps 35 minutes byfusing the ta p plug w ith a need lelike carb on electro de. A sthe carbide issues from the furnace at a temperature of2200 0 C, it is run into iron chill cars where it is allowed tocool for from one day to a day and ahalf.

The material is an 80 per cent to 85 per cent carbide, consuming in product ion about 3,000 ki lowatt hours per ton,equivalent to approximately 3,600 ki lowatt hours per tono f ' io o pe r cent carbide, when produ ced in a furnace approximately 22 feet by 13 feet by 6 feet deep.

The 99.8 per cent pure ni t rogen necessary for the ni t r i f i cat ion of the carbide is separated from the atmospherethrough a l iquefaction an d dist il la tion pro cess. E i th er oneof two systems is general ly used, the Claude or the Linde.The cost of the nitrogen is exceedingly small as comparedwith its fixation cos t. W he n nitroge 'n fixation Is spoken of,the accent should be on the fixation, father than the nitrogenfrom a cost considerat ion.

When air or a gas is compressed the air heats up, due toits compression, necessitating intercoolers and aftercoolerson the com pressor. W h en this a ir expan ds, the reverse


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TH E CYANAMIDE PROCESS 33natural ly happens and the expanding air gives up heat or ischilled. N o w if the inte rco ole rs on th e co m pre sso r havecooled the a i r a f ter compress ion to the same tempera ture asit was origina lly, a coo ling effect can be p ro d u c e d . T h i s isthe principle of the air liquefier.

In the Lin de process the a i r is com pressed to 3 ,000 po un dsand simply expanded, while the cold expanded air passes inheat exchange cont igui ty wi th the w ar m e r incom ing a i r ,thereby reducing i ts te m p er a t u re . In the C laude processthe compressed air is expanded in an expansion engine thusob taining a .cooling effect du e to ex ter na l w o rk as w ell asto the simple exp ansio n o r Jo u le -T h o m p so n effect of theLind e process . B ecause of this , the a ir in the C laud e pro cess is com pressed to only 45 0 p ou nd s or igina l ly , an da sh or ter t ime is consum ed in reac hin g the l iquefact iontempera ture .

In the op er at io n of the C laud e l ique fact io n system , a irwhich has been washed in caust ic soda towers for the removal of carbon dioxide and passed through separa tors forthe remo val of caustic soda spray , is co m presse d to 4 5 0pounds and cooled in an af tercooler to the temperature ofthe cool ing water , perhaps 20 0 C. I t is then passe d th ro u g htwo heat exchangers in ser ies , where i ts temperature is lowered through exchange of hea t wi th colder outgoing a i r .M o st of the m ois tu re of the a ir is con den sed o ut he re andcol lected in a purge bott le while any remaining togetherwith any carbon dioxide which may not have been scrubbedout is deposited as a snow on the tubes of the second exchanger . W h e n this snow dep osi t ion is g re a t eno ug h to interfere with the free flow of air through it, the flow is auto


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34 FIXATION OF ATMOSPHERIC NITR OG ENce ives the a i r a t t he co o l in g w a te r t em pera tu re , w h ich i sh igh en o ugh to tha w o u t t he f ro zen tubes .

F r o m th e second exc han ge r , 80 p e r cen t o f th e a i r is expa n d ed in t he ex p a n s io n en g in e a n d 2 0 pe r cen t i n to th el i q u e f i e r s . T h e t e m p e r a t u r e o f t h e a i r d r o p s f r o m 1 0 80 Ca t the en t rance to the expans ion engine to 1 4 5 0 C a t th eo u t l e t va lv e . T h e 2 0 pe r cent o f t h e a i r w h ich en te re d th el iqueEer i s coo led b y guses f ro m t he rec t i fy in g co lu m n tothe l ique fy in g t e m p er a t u r e . T h es e tw o pa r t s o f a i r , 80 pe rcen t a s a gas and 20 per cen t a s a l iqu id , a re bo th admi t tedto the bo t tom of the rec t i fy ing co lumn which cons is t s o f ase ri es o f ve r t i ca l t ubes ca l led va po r i z e r t ubes , t h e lo w erends o f which a re su bm erg ed in th e l iqu id . D u e to th e diff e ren ce in p r e s s u re a t t he bo t to m o f t he r ec t i f y in g co lu m na n d t h e s p a c e s u r r o u n d i n g t h e t u b e s p a r t i a l v a p o r i z a t i o n ofthe l iqu id tak es p lace caus ing a l ique fac t io n o f th e a i r in t h etubes . T h i s l iqu id f ro m the ba se o f t h e r ec t i f y in g co lu m nis r e in t ro d uced in to the co lum n a b o u t m idw a y be tw ee n en d s .T h i s l iqu id is r i che r in o x y gen th a n the o r ig in a l a i r . T h euncond ensed gas r ich in n i t ro ge n passes th r o u g h th e condens ing co i l submerged in the l iqu id which i s co ld enough toliquefy the n i t ro gen . T h i s n ea r ly pu r e l i qu id n i t ro ge n ispa ssed to t he t o p o f t he r ec t if y in g co lum n f ro m w hic h n i t ro gen gas of 99-99 pe r cen t pur i ty com es off a t a t e m p e r a tu reo f 1 9 0 C a n d , a f t e r p a s s i n g b a c k t h r o u g h t h e l iq u e fi er a n do u t t h ro ugh the tubes o f t he hea t ex cha n ge r s , i s a va i l a b le fo rthe n i t r i f ica t ion of the carbide.

NOMENCLATURE FORCLAUDE PROCESS FOR PRODUCTION OF PURE NITROGEN GAS x1. Con trol valve of a i r enter in g exchanger .2. Gauge fo r the pressure of the compressed a ir suppl ied to the ap pa ra tus .3. Valve foi inv ertin g t in; compressed air c irculation in the ex cha ng er.

1 Fro m Fixat ion and Uti lization of Ni t rog en, Re port # 2 0 4 . 1 .


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THE CYANAMIDE PROCESS 354 . V a l v e f o r i n v e r t i n g t h e o x y g e n a n d n i t r o g e n c i r c u l a t i o n in t h e e x

c h a n g e r ,5. Va l v e f o r i nv e r t i ng - the- com p res s ed a i r a t t h e ex i t f r o m t h e ex ch a n g e r .6 . E x c h a n g e r f o r c o o li n g - t h e i n e o m m g a i r .6 a . D r a i n v a l v e o r p u r g e b o t t l e o f e x e l u m g c x7. E x c h a n g e r f o r c o o l i n g t h e i n c o m i n g a i r .7 a, D r a i n v a l v e f o r p u r g e b o t t l e o f e x c h a n g e r *8 . G aug e f o r the p re ssu re o f the com press ed a i r at1 t h e e x p a n s i o n e n g i n e

in le t .9 . C o n t r o l v a l v e f o r t h e e x p a n s i o n e n g i n e .10 . E x p a n s i o n e n g i n e f o r c o o l i n g a i r b y e x t e r n a l w o r k ,I I < L i q u ef ie r f o r l i q u e f a c t i o n o f a i r .1 1 a . J > a i n v a l v e f o r t h e l i q u e f i e r .12 , Va l v e f o r t h r o t t l i n g t h e l i q u i d - a i r s u p p l y t o fram e p re s s u re a s en g i ne

exh a u s t .13- L o w e st c o m p a r t m e n t o f r e c t i f y i n g c o l u m n .1 3 a. D r a i n v a l v e f o r lo w e s t c o m p a r t m e n t o f r e c t i f y i n g c o l u m n .1 3 b , W a t e r l e v e l f o r t h e l i q u i d r i c h I n o x y g e n .1 3 a G a u g e f o r t h e b a c k p r e s s u r e in t he l o w e s t c o m p a r t m e n t o f r e c t i f y i n g

c o l u m n .14-. V a p o r i z e r t u b es f o r l i q u e f a c t i o n o f a i r .1 4 a . M e r c u r y l e v e l o f t h e v a p o r i z e r .14b , O x y g e n p r e s s u r e g a u g e .15 . Vrd ve f o r c o n t r o l l i n g t h e i rp f lour o f t h e l i q u i d r ich i n o xy g e n .i 6 \ Va l v e f o r t h e ou t l e t o f t h e i m p u re ox yg en g a ^1 6a . C o c k f o r s a m p l i n g w a s t e o x y g e n ,17 . C o il s u b m e r g e d i n c o o l i n g l i q u i d f o r l i q u c f u e fi o n o f n i t r o g e n .1 7 a . C o c k f o r t e s t i n g t he p u r i t y o f n i t - o g e n l e a v i n g (lie v a p o r i z e r a n d g o i n gt o t h e cond ens i ng co i l ,1 8 . I n l e t t o t h e r e c t i f y i n g co l u m n o f t h e l i q u i d r i ch in ox yg en ,1 9 . V a l v e t o c o n t r o l t h e flo w o f l i q u i d n i t r o g e n t o t h e t o p o f t h e c o l u m n *2 0 . T o p o f t h e r e c t i f y i n g c o l u m n .20 a . W a t e r l ev e l f o r t h e l i q u i d p oo r i n oxyg en .2 0 b . N i t r o g e n p r e s s u r e g a u g e .2 0 c . Cock f o r t h e n i t rog en t e s t .

Before ni tr i f icat ion the carbide must be f inely pulvcrziedso th at at lea st 85 pe r cent of i t passe s th ro u g h 2 00 m eshscreen- T h is nece ss i ta tes a series of gr in di n g o pe ra t io n sfollowing th e b re ak in g up on the carb ide pig. In this pulver ized s ta te carbide readi ly reac ts wi th the mois ture of theai r to ge n era te acetylene g as which form s exp los ive m ix


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CLAUDE PROCESS FOR PRODUCTION OF PURE NITROGEN GABp h e re of n i t r og e n . F re q u e n t ana ly se s a r e ne c e s sa ry , t h e r e f o r e , t o g u a r d a g a i n s t g r e a t e r c o n c e n t r a t i o n s o f o x y g e n a n dace ty lene th an 2 pe r cen t an d 1 pe r cen t , r e spe c t ive ly .

T h e r e a r e two t yp e s o f n i t r i f y ing ov e n s in op e ra t i o n , ac on ti nu ous and a d i s c on t i nu ou s o r b a t c h t yp e . O p e ra t i o n1


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T H E CYANAMTDE PROCESS 39A s a f e r t i l i z e r , c y a n a m i d e h a s s e v e r a l d i s a d v a n t a g e s .

( 1 ) I t is a ve ry d i s ag ree ab le subs tance w i t h w hi ch t o w o rkd is so m ew h a t tox ic t o hu m an be i n gs if t h e m a t e r i a lt s i n t o t h e sk i n ; ( 2 ) I t c ann o t be used in l a rg e q ua n t i

e s in m i xed f e r t i l i z e r con t a i n i ng ac id p h o sp h a t e ow i ngt h e n a t u r a l r e a c t i o n b e t w e e n t h e a c i d p h o s p h a t e a n d

cya nam i de whi ch causes t he ac id p h o sp h a t e t o r e v e r td a ls o m a y l e a d t o t h e f o r m a t i o n o f t h e a g r i c u l t u r a l l y

e s i r a b l e s u b s t a n c e , d i c y a n o d i a m i d e ; a n d ( 3 ) I t h a s a ni z e r m a t e r i a l s . T h i s is p a r t i c u l a r l y n o t i c e a b l e in d r y

f o r m s of n i t r o g e n - c o n t a i n i n g s u b st an c e s-T h r o u g h a p r o c e s s o f a u t o c l a v i n g c y a n a m i d e m a y b e c o n r t e d in to a m m o n i a . T h e c y a n a m i d e , o r l i m e n i t r o g e n , is

i n t r o d u c e d i n t o a n a u t o c l a v e w i th w a t e r in t h e a p p r o x i m a t ero p o r t i o n s of f our p a r t s of cy an am i de by w e i g h t to livea r t s of w a t e r p lus a sma l l a m o un t o f s t r on g a lka l i n e l i quo r ,

caus t i c sod a , to a id the chem ica l rea c t io n . T h e m ix tur e ist hen t r ea t ed w i t h s t eam, and ammon i a gas i s r e l eased ac co rd i ng t o t he equa t i on

C a C N , + 3 H 2O = 2 N H 3 H- CaCO*.I n ope ra t i on , an au t oc l a ve o f 6 f eet d i a m e t e r by 21 f ee t

t a l l i s cha rged wi t h a f i l t r a t e l i quo r o f approx i ma t e ly 2 pe rc en t s o d iu m h y d r o x i d e ( N a O H ) to 9 f ee t d e p t h . T h i s isa p p r o x i m a t e l y 1 9 , 0 0 0 p o u n d s o f liq u o r- T o t h is Is a d d e d3 00 po un ds of soda a sh t o b r i n g t he a lka l i ne s t r e n g t h t o 3p e r c e n t s o d i u m h y d r o x i d e , a n d 8,000 p o u n d s o f c y a n a m i d e .T h e c h a r g e is a e r a t e d f o r 1 5 m i nu t e s t o e l i m i na t e ace t y l ene ,


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4o FIXATION OF ATMOSPHERIC NITROGENsteam turned on to s ta r t the react ion. W he n the pressu rewithin the autoclave rises to 60 pounds as recorded on thegauge the steam is turned off and the reaction continues unaided. T he amm onia outlet is then opened and am m oniawith large volumes of steam is drawn off continuously forapproxim ately three ho urs . D uring this t ime the pressureremains rather constant, but i t finally drops to atmosphericpres sure . T h e ou tlet valve is then closed and the steamonce more turned into the autoclave for about 20 minutes,when the pressure will have reached 120 pounds per squareInch within th e au toc lav e. T h e steam is aga in shu t off andthe amm onia discharge opened. T h e react ion and consequent release of ammonia now continues for an hour and ahalf. T h e sludge rem aining in the autoc lave is discha rgedto the slurry troughs which feed the filters.

This ammonia may then be oxidized to nitr ic acid, whichmay be neutral ized w ith addit ional amm onia to form ammonium ni trat e. Such is the pro po sed op eratio n of theU . S. N i t ra te Plan t N o . 2 a t M uscle Shoals, A labam a. Inorder to give a clearer picture of the cyanamide process,there follows an equipment description of this plant, theonly cyanamide plant in the United States.

T h e U . S. N i t r a t e P la n t N o . 1was erec ted as a w ar em ergency m easu re for the an nu al fixation of 40 ,00 0 ton s ofnitrogen in the form of 110,000 tons of ammonium nitrate.

The manufactur ing plant occupies an area rectangularin shape 5,310 feet by 2,860 feet with the long dimensionrunning no rth and south . W ith the exception of the liquidair production, the sequence of manufacture is from northto sou th. T h e ra w m ate ria ls limeston e, coal and. coke ar cunload ed from a trest le at the no rth end of the m anu factur ing area and sta r ted into the process. A ll m ater ia ls


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42 FIXATION OF ATMOSPHERIC NITROGENfrom the unloading of the raw materials from the carsto the discharge of the f inished ammonium nitrate fromthe gramers are mechanically handled by belt and screwconveyers, bucket elevators, electr ic traveling cranes andpumps.The lime-burning plant consists of 7 rotary kilns each 8feet in diameter by 125 feet long from which the calcinedlime is fed to 7 rotary coolers each 5 feet in diameter by 50feet long . T h e ra te d capac ity of the se is 70 0 ton s of calcined lime per day (24 hours) which is stored in four similarconc rete silos of 25 0 ton s cap acity . F u el for the lime kilnsis pre pa red in tw o F ull er indirect-f ired ro ta ry dri ers , 42inches by 42 feet , and four Fulle r-L ehig h mills . T h is pla nthas a rated capacity of 336 tons of dried and pulverizedcoal per day.

Coke for carbide production is crushed in two crushingunits of three sets of double crusher rolls each, and dried infour ro ta ry driers 5^2 feet diam eter by 40 feet long . T h isprepared coke is stored in four concrete silos of 160 tonscapacity.

C arbide is pro du ced in 12 furnaces 22 feet by 13 feet by6 feet deep of 60 ton s of carbide capac ity pe r day each .Each furnace has three electrodes 16 by 4S by 80 incheseach, which weigh together with the cooling head 3,000pou nds. T h e carbide is crushed and pu lveriz ed in thre e 30by 42 inch Buchanan jaw c rushers, thre e 10 feet dia m eter by48 inch Hardingc ball mills , and three 7 feet diameter by24 feet Smidth mills.

The l iquid air plant of a rated capacity of 12,800,000cubic feet or 300 tons of nitrogen per 24 hours receives itsair thro ug h two 36 inch spiral-r iveted intake pipes. T h eair is washed In 8 sets of scrubb ers of two to a set. T h e r e


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44 FIXATION OF ATMOSPHERIC NITROGENare 15 three-stage compressors of about 1,200 cubic feet perm inute displacement and a discharge pressure of 600 p ound spe r square inch. In op era tio n the air is com pressed to 45 0po un ds and is delivered to 3 0 nitro ge n column equipm entsfrom which the nitrogen produced is delivered to the cyanamide ovens, one-quarter of a mile to the west, through a 30inch spiral-riveted pipe.

In the cyanamide plant there are 1,536 nitrifying ovens,each of 2,000 pounds finished product capacity, arranged in16 rows of 96 ovens each. T h e m axim um ra te d capacity ofthis plant is 750 tons of crude calcium cyanamide per 24hou rs. T h e cyanamide ingots after being rem oved fromthe ovens by electric cranes ar e cooled, and then bro ke n bybeing dropped upon the inclined platform which serves thecrushing equipm ent. A fte r being crushed an d pu lve rize din a plant exactly similar to the carbide crushing plant,the cyanamide is hydrated In three 36 inch by 36 feet longhydrators of a capacity of 2,160 tons of hydrated cyanamideper 24 hours.

The si lo building between the cyanamide plant and theammonia plant contains nine concrete silos of a capacity of475 tons of cyanamide each.

The ammonia plant for the autoclaving of cyanamide isof a rated capacity of 166^4 tons of ammonia gas per 24hours and consists of 56 autoclaves arranged in 14 rows of 4each. T he se autoclaves are 6 feet in dia m ete r by 21 feethigh and are constructed of welded steel plate of one inchthickness for the side walls and 1% inches for the domedtops and bo ttom s. E ac h autoclave is f itted with an ag itat orwhich revolves at }4 r .p.m., each set of 4 agitators beingdriven by one 40-h ors epo w er squirrel-cage induction m o to r.

Stea'm for the autoclaves and for heating the plant build-


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L I M E N I T R O G E N O V E N S I N W H I C H C A L C I U M C A R B I D E IS N I T R I F I E D


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A U T O C L A V E S I N W H I C H A M M O N I A G A S IS P R O D U C E D


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T H E CYANAMIDK PROCESS 47ings

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Fixation of Atmospheric Nitrogen - Ernst