INDUSTRIAL AND ENGINEERING CHEMISTRY
800
k!KNOWLEDGhlENT
The bacteria used in the experiments were kindly furnished by C. H. Werkman of the Department of Bacteriology, Iowa State College.
LITERATURECITED Breden, C. R., with Fulmer, E. I., Iowa State COX J . Sci., 5, 133-53 (1931).
Burkey, L. A., Ibid., 3, 57-160 (1928). Desmots, H., Compt. rend. SOC. biol., 56,383-6 (1904j. Elion, L., Biochem. Z., 169,471-7 (1926). Fulmer, E. I., Nelson, V. E., and Sherwood, F. F., J. Am. C h m . SOC.,43,191-9 (1921). Grimbert, L., Compt. rend., 132,706-9 (1901). Harden, A., and Norris, O., Proc. Roy. SOC.(London), B85, 73-8 (1913). Harden, A., and Norris, S. G., Ibid., B84,492 (1912). Harden, A., and Walpole, G. S., Ibid., B77,399-405 (1906). Kluyver, A. J., and Donker, H. J. L., Veerslag. Akad. Wetensch. Amsterdam.,33,915-19 (1924).
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(11) Kluyver, A. J., Donker, H. J. L., and Hooft, F. v’t, Biochem. Z., 161, 361-78 (1926). (12) Lemoigne, hi., Ann. inst. Pasteur, 27,856-85 (1913). (13) Lemoigne, M., Compt. rend.. 157,653-5 (1913). (14) Ibid., 170,131-2 (1920). (15) Ibid., 177,6 6 2 4 (1923). (16) Lemoigne, M., Compt. rend. SOC. b i d , 82,984-6 (1919). (17) Lemoigne, M., and Pettit, A.,Ibid., 88,467-8 (1923). (18) Neuberg, A., and Gorr, C., Biochem. Z., 154,495-502 (1924). (19) Neuberg, C., and Reinfurth, E., Ibid., 106, 281-91 (1920). (20) Neuberg, C., and Rosenthal, O., Ber., 57, 1436-41 (1924). (21) Neuberg, C., and Simon, E., Biochem. Z., 156,374-8 (1926). (22) PBr6, A . , Ann. Inst. Pasteur, 10,417-48 (1896). (23) Shaffer, P. A , and Hartmann. A. F., J . Bid. Chem., 45, 371 (1920). (24) Sherwood, F. F., and Fulmer, E. I., J. Phys. Chem., 30,738-56 (1926). (25) Verhave, T. H., British Patents 335,280 and 337,025 (June 26, 1929). (26) Walpole, G. S., Proc. Roy. SOC.(London), B83,272-86 (1911). R E C ~ I Y EDecember D 10, 1932.
Foaming and Priming of Boiler Water Peculiar Behavior in an Experimental Boiler C. W. FOULK AND KERMITGROVES,Department of Chemistry, The Ohio State University, Columbus, Ohio
I
N B E G I S S I K G this in-
follows: Inside diameter The experimental steel boiler described is of v e s t i g a t i o n , i t w a s inof drum, 10.2 cm. (4 inches), such design that pure water and salt solutions l e n g t h of d r u m , 168 c m . (5 tended to use t h e w a t e r when boiled in it exhibit in every respect a foamf e e t , 6 inches), and inside ditube boiler described below for ing and priming behavior that is the direct opameter of water tube, 2.5 cm. repeating the work of Joseph and posite of that usually found in steam boilers. (1 inch). The boiler was f i e d Hancock (6) and of Hancock (4). by gas. These investigators had found These results are due entirely to the design of that, in t h e i r e x p e r i m e n t a l the boiler and are in no sense to be ascribed to PROCEDURE.The s a l t s o l u boiler [a simple steel drum 48 any abnormal behavior of the water or salt solutions used were prepared from em. (18 inches) long and 31 cm. distilled w a t e r and salt of the tions. Water was thrown into the steam line be(12 inches) in diameter], finely grade employed i n a n a l y t i c a l cause of waves moving through the steam drum. chemistry. Before the beginning divided s o l i d m a t t e r h a d n o of the work the boiler had been W h e n a wave crest reached the steam outlet, a effect on the priming,’ that is, opened and thoroughly cleaned. t h e p a s s i n g of l i q u i d JTater slug of water went over. The height of these Since the capacity of the pump into the steam line. These ret h a t c a m e w i t h the boiler was waves was determined by the size of the steam not sufficient to maintain a consults were so contrary to popular bubbles emerging f r o m the water tube. Because stant water level during a run, belief and t o published laborathe practice of b e g i n n i n g each steam bubbles are smaller in salt solutions than in tory experiments in glass vessels experiment at the same water level water, the waves were at their highest when the (2) that it s e e m e d d e s i r a b l e v-as adopted. The w a t e r i n t h e s t e a m was to repeat the work, particularly boiler was charged with pure water, and consemeasured by a chemical method. in a different t y p e of b o i l e r . quently there was more priming with pure water The total ejectate-that is, the I n order to have an appropriate mixture of steam and water-was than with strong salt solutions. b a c k g r o u n d for the proposed passed through a condenser and c o l l e c t e d in p o r t i o n s , usually experiments with solid matter, a series of runs was made with salt solutions alone. The of 250 cc. each. These portions were then titrated for chlorides, the amount of chloride found being obviously proportional to the results of this preliminary work were more perplexing than liquid boiler water that had gone over with the steam. When a those of Joseph and Hancock. The experiments indicated salt other than a chloride was used, about 100 p. p. m. of sodium that the throwover of water became less as the concentration chloride were added. In making the calculations, account of the dissolved salt increased. This was so unexpected and was taken of the increasing concentration resulting from the so out of accord with existing knowledge on foaming and evaporation. priming that the question of solid matter was dropped for Since close agreement among quantitative results in the time being, and the study of this peculiar behavior of the foaming and priming experiments is not t o be expected, five salt solutions was taken up. runs were made as a rule for each condition investigated, and the results averaged. Each curve, therefore, is the average EXPERIhIEKTAL BOILER of a number of experiments. Figures 1 and 2 describe the general construction and Because the results were so contrary t o what was expected, appearance of the boiler. Its essential dimensions were as it was desirable to have a mass of evidence in their support, and accordingly four different compounds, each a t various 1 The word “priming” is used in this paper merely to indicate the water concentrations, were used. Runs were also made a t other in the steam. No special meaning other than this is intended.
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It is exactly tlic opposite of the priming eflect of the same salts as observed by Joseph and Hencock (6) in their cylindrical boiler. These authors 2nd also made experiments with snit. solutions alone, and for purposes of comparison some of their resnits are shown in Figure 5. The outstanding point, liowerer, in coriiparing tlie results is that in Joseph arid flancock's boiler an increase in salt ccritration caused an increase in the water in the steam giire 5 ) wliile in the experiments with tlre water tube boiler shown liere the opposite was the case. These water tube h i l e r results witre the opposite of what was to be expected or! ttie basis of ticeepted knowledge of the foaming and priming of boiler water. The authors decided that some way should be found for ob:erving the hehavior of water in their boiler, or in a similar ainiaratus. It liad been found that tlie steel boiler sliowed the iiiine relative effects a t pressures around 10 or 15 pounds per r(,,,nre irlcll ((1.7 or I kg. per sq. cm.). Therefore, a glass geelned practical, sirice it cooid be operated at such
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pressures than 80 pounds per square indl (%5.(jkg. Per sil. em.) but these did not differ essentially fro111 tile others. The rapid drop in the percentage of priming seen in all the curves mas due to tlie falling water Ieml in tile !)oiler md must not be confused with tlre effect of salt concentration, This effeot of eoncent,ration is to he seen o n l y o n c o m p a r i n g the curves among tliemsclvt?s. The increase in priiiiiiig from tire first to t.he second ejectate was undonhtedly due to boiling c o n d i t i o n s . E a c h r u n was started with cold water and tlie procession of waves through the drum required time to establish itself. I t E S T i L T t i O u ' T A l X E l > WI'TII
Srmi. 13011,m. The experitncnts with the steel boiler are summarized in Figure 3. Some inconsistencies will be uliserved, particularly i n the regiiins of lower c o n c e n t r a t i o n , bot the most ensual observation d l show that a marked increase in concentration of salt in t,he boiler water is accompanied hy a decrease in ttie amount of water iii the steam. This is brought out morc Zlearly in Figure 4, in whiclr the results of Figure 3 are winliiicd, with tlie percentage of water in the ejectate plotted against concentration, tlie water level in all cases being cnnst.ant. It will also be observed from Figure 4 that the nature of the dissolved salt play? an important role, the order of the effect heing the opposite of that usually attributed to these salts.
'I'lie design of the glass boiler is s l i o ~ nin Figures 6 a.nd 7 . Its d r u m was 130 cm. (51 inches)
kmg atid 7.15 cm. (2.8 inches) inside diameter. The water tube Iiad an inside diameter of 3 em. (1.2 inch). OII top of the drum \\.ere two outlets-one on the left for steam, and the other on the riglit for comiccting a mnnometcr. The source of heat was a large combust,ion furnace. This glass boiler approached in size the steel boiler and was of tho Same design. The first few runs inade witli tlre glass hailer showed conclus i v e l y why an increase in salt concentration caused a decrease in water throm into the steam. Wavcs uwe propagated along the length of the drum, and, when tlie crent of one of these n-ayes r e a c h e d t h e s t e a m outlet. a qiiaiitit,y (if watw wodd be tlirown over. Experiments sliuiscd that with t,tie Iiiglier salt concent.rations these waves were flatter, and consequently not so many crests hit the out,let. This difference in the hriglit of the waves is Ehowrl in the instirntnneous photographs, Figures 6 and 7 . I+i'gure 8 is a close-up view of a ilrlive about to hit the outlet.
m
c.c F,ecrare
F i c u n ~3. EFFECT OF V I H I O USALTS ~ ox PninrsG Preasuie. 80 pounds per nyusro in& LS.6 kg. per J ( I . c a , . ) .
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1h;untr 4. EFFECTOF CORCENTRATIOX .mi)
N . ~ T ~ OF R ESALTON PRIMING water level. 10.2 om. Lieior steam outlet.
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T l i e flow tlirongli t h e w a t e r t.uiie was iiiucli faster tliiiri through the drum, and in the case of the s t , r o n g s a l t s o l u b i o n s there was a great deai of foam at the end of the drum where steam and water entered from the water tube. The bubbles of this
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All stcam bubbles at the moriient of tlieir formation are necessarily very small, but they $ increase in size as they move upward through $ tlie liquid. Tlie main cause of this increase f o a m w e r e short-lived, liomver, ax is the bJ in size is the nicrging together of s m a l l e r case wit.11 salt solirt,ions, and, in the one or $ bubbles to form larger ones. This coalescence two seconds spent in reaching the steam outof smaller bubbles decreases as tlie salt conlet,, all had burst. Thereforc, no foam u a s P' centration increases. In o t h e r w o r d s , the steam bubbles in a boiling salt solution are From watching tlie glass boiler, F smaller than in pure vater. The explanation of this is given by the balanced layer theory of film formation (8). surges or pulsations produced by the emerkllNCOCK-s B ~ , , . ~ (5) ,, According to this theory the coalescence gence of st,eam bubbles from the water tube; 160 ner of bubbles is prevented in solutions because fiirtl~crmore,it seemed reasonable to assume that the larger tlierc steam lruhhles were, m m e i n (11.2 ~ kK. per BO. the thin liquid wall between two b o b b l e s the higher would be the tvaves. The next "'")' when very close to each other acquires a step was to prove the presence of large bubbles certain degree of r e s i s t a n c e and does not in thc distilled water and small ones in the salt s~ilut~ioii.'This liresk through on crowding the bubbles together. Furthercould not. he done by visuiLl observation or by ordinary more, the resistance of this liquid film between k1ubbles in phot,ographic snapshots because the hulibles were nioving a solution i8 determined by the nature of tlie solute and by too fast through the water tube. Tho priiblem r a s finally the concentration. Z
Since castor oil prevents the formation of liquid films in most salt solutions, the experiment of adding it to a boiling salt solution in tire steel tioiler WRS tried. The resiilts are showii in Figure 11. W i t h a s o l u t i o n of 30,000 p. p. m. of sodium sulfate there was scarcely any priming hut, on the addition of 60 p. 51. m. castor oil, the throw-over of water began immediately. This effect of castor oil is also contrary to all recorded experience since this oil is the best a n t i f o a m k n o w n . It is, however, in accord with the balanced layer theory of films. The cartor oil destroyed or prevented tlie formation of permanent filiris betmeeii hulibles under the surface and thus permitted the coalescence of small bubbles to form large one?. I n other words, the salt solution then b e h a v e d like distilled water.
w i v e d by rising a Canma with a focal plane
s h n t k r marked to give an exposure of oiie sixIiiindredtli of a second. The trigger of this shiitt,er mas connerted hy a small wire to the linndle of an electric s ~ i t c hthe , closing of wliich fired a charge of flashlight ponrr; the lengtli of o adjiisted that the trigger of the shutter was p u l l e d i m i n e d i a t e l y after the pmider was ignited. Figiircs 9 and 10 made in t,liis way prove beyond douht that the steam bubbles in the sak aolubion are smaller than those in vater. Incidentally, these ghotogrsplis uf the steam l ~ i b b l e sin the water tiihe may Ire considered experimental evidence of the rate at which such b i i l h l e s move in a boiler. A flash-light cxposure, for cxamplc, failed to show the outlines of t.he buliblcs iiecause they were inoviiig too fast. The more rapid e x p o s u r e of the focal plane shutter mas required to catch t,hem.
FIGURE; 7. W ~ v e sIS DIWM01'GLIBS BO~LEW WHENCONTAINING 30.000 P. P. \I. Soorulr SULPATP: SOLUTION
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eRects of c e r t a i i i f e a t u r e s in desigii upon priining. The remarkahle results ohtained with t h i s Imiler suggest possilile new features in design of boilers and of equipment for evaporating foariry liquids. The slow movement of water along the druin gives time for foam bubbles to collapsc, and, if tlie steam outlet. had been on top of a donre, there would have been 110 liriiiiing even, with distilled TTater. I n short, liere is an experimeiital boiler in wliiclr it has lieen proved that salt solutions prime less than pure wat,er. and there is offered a coninlete exnlanatiorr, practical and theoretical, of this behavior. Finally, it would be wrong to suppose that differences in design in cross-drum lioilcrs h a m no effect on priming. Eberle ( I ) has recorded a series of experiments with such a small experimental lioiler in which the position of the opening of the water tube into the cross drum was the nlost important condition af* i i "a ar,-,+./s"Las.h-m ~~~~
I)racuas~osOF 1tEsuirTs The casual reader may think that the uiiusual behavior 01 the experimental boiler described in this paper is nrerely a freak occurrence, and, though interesting, is hardly worthy of a lengthy account because it could never happen in practice. &it anything can happen in practice! I h r i n g the last few years the scnior author has listened to dozens of accounts of freakish 1,ehavior of boiler water-cases of foarning and priming that vere inexplicable on the basis of any recorded knowledge. Most of these accounts have been of boilers that should not Iiave primed, but did. The opposite also occurs. h hoiler does not prime though conditione indicate that it should. Thwe instances are rarely reported liecause they do not drive the engineer to seek lrelp from the outside. Their study is, however, of great importa~icesince it is sure to tlirow light on the probieni from a new angle.
__
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jo
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fecting tlie prirning. si. u~s,mp.#.m,, Readers are \.iariied iiot $? \rcdp.m a,/ri0,7 t o assume f r o m t h e $$' ...__ anouialnus results of the *$ '!~wo~.wm. ---.-__ priming of the water tube 5- IMO uw 2c c LdSC 7a r e boiler that the water in Iuc~~~sn:~.vPmnm it heha.ied in any sense FIWREII. BY CASTOR On. c o n t r a r y to a c c e p t e d Piesaure. 150 pounds per a w a r e inch physico-chemical princi- (10.5 kg. per SR. ch,.). ples. It did not. ha increase in salt concentration iiicreased the amount of foam or filiri formation, and castor oil, as should be expected, destroyed this foam. The water behaved in a perfectly nomial manner. It was the design of the boiler that caused a complete reversal of tlie usual effect of foam. ACKKOTSLEnQ.lrENT
Thc authors wisli to thank the I'aige-Jones Company and the Kational Aluminate Cornpaiiy of Chicago for the gift of the experiincmtal boiler used in this investigation. Especial thailkE are also due the Engineering Experiment Station of The Ohio State University for generous financial assistance. Tlri? invest.igation was part of Project 103 of the station's activitie.. FIGUI~E 10. S ~ m a BUHXLES ts SALT SOLUTLON (l/GOO second expoeure)
The peculiar result of tlic design ol this eqieriiiieirtnl boiler (tliough accidentally discovered) should be looked iipoii as a rase of the rTell-kiiown research princ,iple of exaggerating conditions in order to increase suspectcd efSects-in this case the
