Lactic Acid from Fermentation of Sulfite Waste Liquor '
REID H. LEONARD, W. H. PETERSON, AND M. J. JOHNSON Department of Biochemistry, university of Wisconsin, Madison, Wis.
T h e production of lactic acid from sulfite waste liquor by fermentation is possible. Waste liquor was prepared by steam-stripping followed by precipitation of the sulfite a t pH 8.5. After filtration and neutralization with carbon dioxide, the liquor was inoculated with Lactobacillus pentosus 124-2. Of several nitrogen-supplying nutrients, malt sprouts were preferable. The malt sprouts were incorporated into a mash with blackstrap molasses and used as the inoculum medium. The fermentatioli required 40 to 48 hours a t 30' C. for completion and during this time the pH of the medium was controlled by addition of calcium carbonate or calcium hydroxide. Fermented liquor was concentrated to 3oqo of the initial volume, acidified, and extracted with a solvent. Distribution coefficients
were determined for 50 solvents and 19 were tested on waste liquor. Amyl alcohols and isophorone were good solvents. The lactic acid was readily extracted from the concentrate a t 90" C. and the extract was washed free of acids with water. Purity of the acid depended upon the solvent employed; with amyl alcohol the final aqueous phase after concentration yielded lactic acid of 90% strength, containing about 8% impurity and 270 water. Sulfite waste liquor (2000 gallons) corresponding to a ton of pulp made from spruce wood yielded about 285 pounds of lactic acid and 75 pounds of acetic acid after recovery. Costs for raw materials, with no credit for sulfite waste liquor, are estimated as between 2.0 and 3.5 cents per pound of pro'duct, depending on whether or not the lignin residue is used for fuel.
T
Since the majority of the sulfite waste liquor samples contained 10 to 11% solids, the figure of 2000 gallons of waste liquor per ton of pulp was used to calculate yields on the basis of pulp. Grams per 100 ml. are converted to pounds per 2000 gallons by multiplying by 167. SELECTION OF CULTURE. Some information was available on cultures suitable for wood sugar substrates but none for sulfite waste liquor substrates. Marten et al. (19 ) fermented wood sugar still bottoms to lactic acid and Allgeier et al. ( 1 ) fermented wood sugar worts to lactic acid. Both groups of authors selected and obtained successful results with Lactobacillus pentosus 124-2. Since wood sugar worts are less easily fermented than sulfite waste liquor, i t was almost certain that L. pentosus would ferment sulfite waste liquor. Lactic culture E (15), L. delbrilclcii, L. pentoaceticus (9),.L. arabinosus (8),L. pentosus (8),and one new isolate were tested for their ability to ferment sulfite waste liquor. The results given in Table I show that L. pentosus 124-2 excels the other cultures in its ability to form lactic acid. It is a hardy culture, capable of rapid growth and acid production under proper conditions.
HE utilization of sulfite waste liquor (SWL) is one of the pressing problems of the paper industry (81). The sugars, which compose about one fifth of the solids in the liquor, are readily fermentable by yeast and bacteria. A partial solution to t h e problem is utilization of the liquor for the production of ethyl alcohol (2, 18) and yeast (17); another is fermentation of the liquor with lactic acid-producing bacteria. If the cost of producing lactic acid were balanced by the returns, the process would provide another method for utilization of the waste as well as furnish a large supply of tKe chemical. Numerous aspects of this problem have been investigated and a r e reported in this paper. Data are presented on treatment df the liquor before fermentation, fermentation operations, and recovery of the lactic and acetic acids from the fermented material. METHODS
ANALYTICAL METHODS. Reducing sugars were determined by the method of Shaffer and Somogyi (19). However, a large error in the determination arises from the action of nonsugar reducing substances and slowly reacting sugars. Since sugar determinations were not satisfactory, lactic acid determinations were used as a means of following the progress of the fermentations. The determination of lactic acid has an advantage over that for sugar in its freedom from interference by substances in the sulfite waste liquor,
TREATMENT OF SULFITE WASTE LIQUOR BEFORE FERMENTATION
I n the industrial alcohol fermentation of sulfite waste liquor there are two methods of preparing the acid liquor for fermentation. The older is aeration combined with neutralization of sulfite with lime to p H 6.0 (18). Recently, steam stripping of sulfur dioxide has been introduced (9). For bacterial fermentation,
For the lactic acid determination, ether extractions of acidified 2-ml. samples were made with a battery of small extractors. A layer of powdered talc on the surface of the sulfite waste liquor underneath the ether impeded foaming. Lactic acid was determined in the extracts by the method of Friedemann and Graeser (10). Analytical results were expressed in grams per 100 ml. of sulfite waste liquor. For the determination of volatile acids, a steam-distillation apparatus was employed in which 25 ml. of steam distillate could be obtained from a 2-ml. acidified sample in about 3 minutes. Total acid was determined in a n ali uot of the distillate by adding a drop of 30% hydrogen peroxije t o oxidize the dissolved sulfur dioxide and then titrating with 0.1 N barium hydroxide t o the phenol red end point. On a second aliquot the dissolved sulfur dioxide was separate1 determined by titration with 0.02 N iodine, Formic acid $terminations by the T.A.P.P.I. method (16)indicated that only about 5% of the volatile organic acid was formic acid. The volatile acid corrected for sulfur dioxide was expressed as grams of acetic acid per 100 ml. of sulfite waste liquor.
TABLE I. COMPARISON OF CULTURES Name of Culture Lactic culture E L. delbrfickii L. wantoaceticus 118-1
Incubation Temp., O
c.
45 45
Yield of Lactic Acid=, G. per 100 M1. 48 hr. 72 hr. 0.08 0.17
24 hr.
0.07
Medium. SWL prepared by sulfite precipitation method, 1% malt sprouts and CsCOa; heated 10 min. a t 100' C.; inoculated with 5 volume % of culture. Q
57
58
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 40,
Tail Rare, Showing Waktr Lignin Pollution
tiir sulfii,t>waste liquw was adjusted to about pl1 8.5 n dc in pH with increased prceipittltion pcriods wns observed. wise, tht. yidd of lactic acid decreased with the longcr pn? Lion pcriods. The decline in yield may be related to the c in pH, since bisulfite addition cornpourids of inlrihitory subs ,my be hydrdyaed. At 36" C . ~tperiod of 20 minutes ap: suRicient for preaipit.&tiuiiof cltleium sulfilo. Attempts t o eonduet, tho fermt-ntation iviihout filtrat,ioil unsatisfsctory, as the yields oi lactic acid RCIC reduced to half. Prepared liquor could not lie s i o w d longer than a aithout giving lower yidds. STEAMSTRIP PIN^ T ~ E A T '1's. M bVheo sulfite wml,e IiG h i l c d , sulfur dioxide is e v d d uot,il iL nearly collstant about 4 is aitaiocd. I n f.hc laboratory t,hrec methods w e ) ployed and essentinlly the samc results \vwc obtained from
Liquor wzu hitilcd until n o t,est for sulfur dioxide in tlie , obtitiried with starch iodine pwpcr, niter which the Y was correet.r:d BR given bclon. Liquor was coneentratcd vaauum and Lhc volume adjusted. Iflor large volumes a 811. d u n m was uscd. A 1.75 X 36 inch c o l u m ~fillcd ~ with 0. It%+chigrings was operated w i t h 8 parts of rr4ox to 1 part tiilato Itt atmospheric piessuie. Slciam w&sgmerat,cd from waste liquor by an alurnirmm heating coil placed in tho bot1 l.ho coluinn and preheakd liquor was fed in a t tlie tog). 2 slant-level dcvier was used to mniot,ain n constant liquid IC glass stopcock seived 8s xn xdjustsble orifiec EOT flow c< e . I hc prehm1,i.r consisted swcrel t.urosof 6-mm. s t ~ i t mchitmbt:r. Thc supply of steam WBS thro liliriilm opcCt1,ion yidded 100 mi. of distillatc fur feed. Approximately 2.5 t,hcoictieal pl:it,cs wcrc obtained theac conditions. Thore was no perecptiblc sulfur dionidc discharged liquor. WNY
Tile industrial slripping opcrat,ion is followed by VBCUUIF cooling of the strippcd liquor (L). \Vit,h this typ" o l cooling lo?;, of tlir liquid is cvaporaird. This eonemtrttliorr is imp, with wr:& sugar x,lntions such as sulfite wastr: iiquor. I Isborainrp, tire volume of tlrc liquor prcpsrrd by strippin irdjustcd to 10% less than the original. Estimation of ire: sulfur dioxide in strippid liquor siroir.e< usually 0.03 gram of sulfur dioxide per 100 mi. remained in tion. Kllicn sodium bisulfite was added t o sulfite waste : fwrnerrt&ons, tlie equivalent of 0.06 grain o f sulfur dinrk
INDUSTRIAL AND ENGINEERING CHEMISTRY
January 1948
59
TABLE 11. EFFECT OF TREATMENT OF SULFITEWASTELIQUOR ON LACTICACIDYIELD
+
Passed through stripping column of Puget Sound Pulp and Timber Co. Unstripped, Puget Sound Pulp and
Stripped sulfite pptn. /Industrial strip \Industrial strip sulfite pptn. [Stripped
+
0.8% malt sprouts, steeped a t 45' C . for 12 hours, 0.3% molasses, CaCOa
'1.48 1.48 0.81 '0.81 0.31
1.81 1.92 1.06 1.06 0.47
1.90 2.12 1.14 1.46 0.61
TARLE111. CALCIUMHYDROXIDE CONSUMPTION A N D SULFURRECOVERY BY STRIPPING Lb. of Ca(0H)z Apparent was not removed in the stripping. Batches of Preparative Initial __ per 2000 Gal. Sulfur sulfite waste liquor acidified with acetic or sulType of Liquor Treatment pH p H 4.5 p H 6.5 p H 8.5 Removedd 199 furic acid before stripping gave more favorable Mitscherlich, sprucea None 1 80 68 7 Stripped 164 75 54 results. 4,.% rn $7. W^"^ Direct, sprucea I I* e.%" Stripped 2.70 2; ii 97 6 Since laboratory stripping was done a t atmosIndirect, spruce'" None 2.55 42 2: ? I: 93 Cltl4nnC.d m 17 pheric pressure and 100" C., ~t sample of liquor ..==-. . D'rect, None 2 80 30 63 94 which had been stripped a t 112' C. was obtained Stripped 3 35 25 50 80 6 from the alcohol plant of the Puget Sound Pulp Direct, poplar5 None 2.40 68 174 205 Stripped 4 25 12 86 119 37 and Timber Company. This material was comDirect, hemlockb None 2 15 37 72 115 87 12 pared with laboratory preparations of a sample of 3 65 2? 48 Direct, fir, spruceC ?$ripped the unstripped liquor. 112O stripped 3.70 13 37 57 21 In Table 11 are compiled the average results of a Sample from Rhinelander Paper Co. two t o five fermentations of liquors from different 6 Magnesium base liquor from Pulp Division, Weyerhaeuser Timber Go. Sample from Puget Sound Pulp 4nd Timber Co. treatments. Neutralization or laboratory stripd Calculated from difference between no treatment and stripping a t p H 8.5. ping does not produce readily fermentable material. Addition of acid Drevious to striminlr is a favorable procedure although not industrially desirable. Stripping after sulfite precipitation is not helpful, but stripping cipitations is important from the economic viewpoint. Stripping before sulfite precipitation gives a small yet definite increase in reduces the calcium hydroxide consumption. I n Table I11 are final yield. Liquor stripped a t 112" C. ferments much better presented the calcium hydroxide requirements of various samples than that stripped a t 100" C. Sulfite precipitation following required to attain a p H of 4.5, 6.5, or 8.5. From 57 to 205 pounds 112 O C. stripping improves the yield with longer fermentation. of calcium hydroxide per 2000 gallons were required t o reach p H The superiority of industrial stripping over laboratory strip8.5. The amount of calcium hydroxide saved by stripping varied ping was believed to be due to the higher temperature of operafrom 14 to 124 pounds and this saving would make the stripping tion. It is possible that decomposition of inhibitory sulfur comoperation worth while under most circumstances. pounds takes place a t the higher temperature. Analysis of laboThe preparation of the liquor influences slightly the amount ratory preparations compared to industrial preparations showed of acid required for acidification of fermented liquor preceding the t h a t the free sulfur dioxide was removed to the same extent, but recovery of the products. It was found t h a t about 50 pounds of that the laboratory material had a greater lime requirement than sulfuric acid per 2000 gallons were consumed by unidentified the other (see Table 111). This indicated the 112' C. stripping substances in the fermentation beer. Use of 30 pounds of acid removes or destroys lime-consuming materials that are not afpreceding stripping reduced the consumption in the beer by only fected by the 100" C. treatment. 10 pounds. Significant changes in the acid consumption by the COMBINED TREATMENTS. A suitable preparative treatment beer from other treatments were not found. cannot be selected on the hasis of fermentation and operation The best treatment found consists of stripping followed by suldata alone. The consumption of calcium hydroxide in the prefite precipitation. After filtration the liquor is acidified to p H 7 or lower with carbon dioxide. I t may be possible to eliminate the sulfite precipitation by high temperature stripping, but this point is more easily investigated in a pilot plant than in a laboratory. , , A
I."'Lr
I "
I
-.
"-
.--
",.
._.
-"
-
FERMENTATION OF SULFITE WASTE LIQUOR
L.pentosus 124-2 forms nearly 2 moles of lactic acid from a mole
-
2 4 HR. Q.07
8
I 9
I
IO
II
It
pH OF PRECIPITATION Figure 1. Effect of pH of Lime Precipitation on Lactic Acid Yield Medium. Liquor held a t alkaline p H for 20 min. (30° C.) filtered, neutralized with COz, 1% ma!t sprouts added, and pasteurized; 5% inoculation used. Yields shown after fermentation for 24 and 48 hours.
of hexose and nearly one mole each of lactic and acetic from a mole of pentose (8). The lactic acid is the d,l form. The optimum fermentation temperature is 30" C. These bacteria require a relatively rich medium and usually malt sprouts have been proposed as one of the better nutrient sources ( l a ) . Fermentations are conducted anaerobically. FERMENTATIONS OF MIXTURES OF PURE SUGARS.Marten el al. ( l a ) obtained complete fermentation of mixtures of glucose and xylose after 10 days. They did uot give data on fermentation of mixtures for shorter periods. Although the amount of pentose in sulfite waste liquor is low, usually pentose sugar did not seem to ferment. Production of acetic acid was taken as a n index of xylose fermentation, since
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
60
this acid is produced from xylose but not from glucose by L. pentosus. Solutions of individual sugars fermented well, although xylose was consumed a t a slower rate than glucose. With mixtures of glucose and xylose, the glucose fermented first. At 48 to 72 hours no xylose had been fermented, but after 10 days both were fermented and gave close to the theoretical yields of lactic
I
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I
I -
g. PER
100 mi.
-
~
OO
IO 20 30 40 50 G R A M S OF CA(OH)2 PER LITER
Figure 2. Precipitation with Ca(OH)* Sample for filtrate splids taken 90 min. after lime addition (30' C.)
and acetic acids. If, after the glucose was nearly all fermented, at about 2 days, a fresh supply of supplementary nutrients was added, the xylose fermented immediately. Addition of fresh inoculum produced on media containing either gluco$e or xylose did not induce immediate xylose fermentation unless fresh nutrients were added simultaneously. Fermentation of pentoses in sulfite waste liquor took place only when the amount of nutrient materials was large compared to the available sugar. Attempts to acclimatize the organism through 200 transfers on xylose medium were not successful. On the basis of the data it appeared that under usual conditions of fermentation very little of the pentose sugar WEE fermented. FERMENTATION TEMPERATURE. The optimum temperature for L.penlosus 124-2 in synthetic media is not necessarily the best for sulfite waste liquor. It was thought that if the fermentation could be conducted a t a higher temperature or if the inoculum were grown at a lower temperature, the fermentation rate might increase. Temperature data are collected in Table IV. The best results were obtained below 37" C. Under the conditions of the experiments, the temperature of inoculum growth did not affect the fermentation. An additional factor will be the nature of the heat economy problems for the entire process. 14
I I
E
-
I
pH 11.7
z
(residue from molasses-butanol fermentation), corn steep liquor, distiller's dried solubles (wheat-alcohol), Vacatone (molassesalcohol residue), hexane-extracted soybean oil meal, hydrolyzed casein, barley malt, cane blackstrap molasses, glutamic acid mother liquor, green barley malt, and autolyzed yeast (Basamin Busch). The preliminary evaluation of these materials showed that molasses, casein, Vacatone, and glutamic acid liquor were of little value. Curbay BG was valuable as a supplementary material to corn steep liquor. Nutrients should not be sterilized in the presence of sulfite waste liquor. Lignin substances precipitate and bind some of the nutritive materials-for example, malt sprouts and sulfite waste liquor when sterilized together (121 O C. for 15 minutes) gave 1.48 grams of lactic acid after fermentation, but when sterilized separately they gave 1.69 grams. Several alternatives were devised to avoid sterilization of nutrients in the presence of sulfite waste liquor. Addition of unsterilized nutrients to the medium followed by immediate fermentation was used successfullv, since sulfite waste liquor media are not conducive to the development of most extraneous organisms. The mixtures of nutrients and liquor were heated a t 100 C. for 10 minutes in many cases. All the nutrients were, in some fermentations, placed in the inoculum medium and added to the sulfite waste liquor via the inoculum. 1.6 [
Rate of Lignin Precipitation at 30" C.
SELLCTIONOF NUTRIENTS.Addition of a suitable auxiliary nutrient source is the most important factor in determining the success of the fermentation. Nutrients, more than any other factor, influence the rate and extent of the fermentation. The nutrient materials should be effective with minimum quantity, commercially available, inexpensive, conveniently handled, and harmless to recovery. Malt sprouts are well known as a source of nutrients for lactic acid bacteria (1.2,16). Other materials tried were Curbay BG
I
I
~
YIELD
9.0
8.5%
MINUTLS
Figure 4. Effect of Period of Sulfite Precipitation on Yield and Alkaline pH Sample (36' C.) filtered, neutralized with CO1, 1% malt sprouts added, and pasteurized: 5% inoculation used
The most promising materials were tested on media inoculated immediately after the nutrients were added. Liquor for these comparisons was prepared by, stripping, sulfite precipitation, and neutralization, After addition of various amounts of nutrients the mixtures were inoculated with 5% of a culture grown on 3% malt sprouts and 3% glucose. Some of the nutrients contained sugar which fermented to lactic acid and on the dry weight basis the following amounts of acid were obtained: from malt sprouts, 6%; corn steep liquor solids, 14'%; mashed dr,y malt (70" C., 1 hour), 35 to 50%; mashed green malt, 50 to 557,; autolyzed yeast, 1%; and cane blackstrap molasses, 50%. The malts were mashed at 40% concentration a t 70" C. for 1 hour. The malt sprouts were used in an untreated condition, after hcating (10 minutes a t 100' C.), and after steeping (20% malt sprouts in water) at 45O C. for 10 hours. Comparison of nutrients was
TABLEIV. EFFECTOF TEMPERATURE OK LACTIC
MlNUTeS
Figure 3.
Vol. 40, No. 1
FERYEKTATION OF SULFITE WASTELIQUOR
Volume of Fermentation, LMI.
165 165 165 165 1100 7700 7700 7700 7700
Inoculum Growth Tzmp.,
Fermentation T$mp.,
37 37 37 37 37 37 37 30 30
25 30 37 45 37 37 30 30 37
C.
C.
Yield of Lactic Acida, G. per 100 hll. 48 hr. 72 hr. 96 hr. 1.57 1.93 ,. 1.56 1.81 ,. 1.52 1.74 ,. 0.34 0.33 1.51 1.74 l.?4 1.48 1.74 1.80 195 2.15 1.39 1.50 1.91 2.24 1.34 1.72 1.95
24 hr. 0.97 1.13 1.07 0.31 1.13 1.07 0.87 0.98 0.87
Medium: Mitscherlich digester, spruce wood, stripped, sulfite precipitration, 0.8% steeped malt sprouts, 0.3% blackstrap molasses, and CaCOz. Q
INDUSTRIAL AND ENGINEERING CHEMISTRY
January 1948
better if it was made on the basis of crude protein content (N X 6.25). Malt sprouts contsined 23% crude protein; corn steep liquor solids, 45%; barley malts, 14%; and autolyzed yeast, 72%. The yields shown in Figure 5 were corrccted for acid added with the inoculum, but not for the acid produced irom the nutrient,s. On t,he uniform basis of 0.2570 added crude protein the yields of 1sct.k acid (grams per 1W ml.) obtained after ferinentation for 48 hours and corrected for acid obtained from the nutrient material u.em computed as follows: green malt, 2.0; dried malt, 1.2; corn steep liquorsolids, 0.8; autolyzed yeast, 2.0; untrcated malt, sprouts, 1.2; steeped malt sprouts, 1.5; and heated mall sprouts, 1.0. The niaximum yield of acid obtainable irom the SUIfite waste liquor used in these comparisons was 2.10 grams per 100 mi. Malt sprouts appeared to he thc nimt promising material u i t w consideration of cost and availebili . The improvcment, i n tile act,ion of malt sprouts obrained by oeping was of special iofcrest. Concent,rittions of 16 to 20% sprouts whiel, were steewd at, 45" C. for 8 to 12 hours gave slightly better yields than concentrations of 8 to 127*. After steeping, about 32% of t.he weight ot the dry sprouts could be removed as a cloudy solution. The favorable action resulted when sprouts were steeped in the presence of toluene, but not when they were heated before steeping. The rosults indicate a n eneymatio action on essential nutrients. The enzymatic process was active in the steeping operation and in the iermentations where untreated sprouts were added directIy to the iermontation, although in the iatfer esse the action was less pronounced. It wns desirable t.o sterilize the malt sprout,s partially and, sinre
0.4 "J
a M
OO
I
2
3
4 0
I
2
3
4
61
Wood Entering Wood Preparation Room ai Pulp Mill this could not he done in the presence of sulfite waste liquor, it wa decided Lo nlacc d l tho sprouts in the inoculum medium and to ad enough inoculum to the sulfite waste liquor to produce a satisfat tory fermentation. Sulfite waste liquor was omitted from th inoculum medium and tho necessary sugar was supplied by molar SOE or malt. The data shown in Tables IV, V, VI, VII, and VI1 were obtained from fermentat,ions t,o which all the nutrients wer added vis the inoculum. Barley malt contributes nutrients 8 8 well as sugar and niixturi with sprouts g a x cumulative resuits with respect to nutrientsthat is, the yield obtained by addition of 0.4% malt sprouts an 0.47, malt was equivalent to the sum of the yields obtained b each alone. Malt was a siightly better source of nutrients whe mitshrd at 45" C. for I0 hours than when maqhed at 70"C. for 00 hour. Correction WAS made for the sugar supplied by the malt. Heat treatment of malt sprouts, in addition to hindering t b enzymatic process. destroys heat-lstbile subatanees in the sprout, A hca!.-labile growth factor in mslt sprout,s was demonstrated b Pan et al. (i5). The retarding effect of heat sterilization wz
TABLE v. E F F E ~OFT HEATTKEATMENT O F >I.laLT SPROUT@ UBEDIN SEED MASHON FERMENTATION YIELDS* 24
12
08 04
24 HR
,
Treatment of SDrouts 121° C.. 10 mi". 100' C..10 min. None 121" C., 10 min. 100" C.. 10 mi& 121O C.. 10 mi". l0OD C.. 10 min. Nome 121' C., 10 min. 100' C..10 A n . None
Souroe Of
Yield of Lactic h i d . G . per in0 MI. 24 hr. 48 hr. 7 2 h; 1.47 1. 4 0.95 1.87 1.QS 1.53
Liauorb. Mitsoheriich. spzuce Mitecherlieh, epmce Mitecherlieh, ~ p i u o e 1.47 Mitsoherlioh, spmoe' 0.96 Mitroherlich. ~ ~ r u c 1.19 e ~ Indireat. ~prnoe 0.79 Indirect. spmm 1.27 Indirect. spruce 1.40 Direet. spruse 0.80 Direct epruoe 1.24 Direct spruce 1.32
1.82
1.88
1.43 1.68 1.28 1.37 1.60 1.12 1.41
1.58 1.80
1.38
1.56 1.72 1.71 1.16 1.62 1.37
INDUSTRIAL AND ENGINEERING CHEMISTRY
62 2.2
I
I
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I
Figure 6. Effect .of Agitation on pK and Yield A.
Not agitated
E. Agitated
Conditions. Sulfite precipitation, 10% inoculation from 8% malt sprouts and 57& molasses mash (pasteurized), excess CaCOa, 30" C.
Vol. 40, No. I.
the medium was shaken or stirred the p H would drop to as low as 4.5. Addition of fresh carbonate to an active fermentation gives rapid gas evolution for a few minutes. Fermentations with added calcium carbonate were best if they were stirred continuously and fresh calcium carbonate was added every few hours. The effect of continuous agitation on yield is shown in Figure 6. I n view of the possible conversion from the calcium to the magnesium-base cooking process (11), some information was necessary on the use of magnesium carbonate as a neutralizing material. When magnesium carbonate was added to fermentations, if they were shaken the p H would rise above neutrality and the fermentation would stop. The percentages of lactic acid obtained from fermentations with various carbonates were as follows: calcium, 1.12; barium, 1.25; zinc, 0.32; and magnesium, 1.16. The logical method of industrial operation would be to use automatic p H control by calcium hydroxide addition. The control of p H is an important factor in fermentation and very little is known about the critical limits. An apparatus was constructed to add either sodium or calcium hydroxide to a fermentation and to maintain the p H a t *O.l unit for a 48-hour period. The hydroxide was added by means of an electric valve actuated by an electronic relay and this in turn was controlled by a glass electrode in the fermenting medium. The presence of carbon dioxide did not appear to affect the fermentation in any way. The data in Table VI1 indicate that, with constant p H throughout the fermentation period, the optimum yield was obtained a t about p H 5.8. However, the maintenance of a constant p H in the medium does not necessarily mean that it is the optimum p H for the best yields. It is possible that a high p H in the initial stages followed by a low p H in the last stages would be more beneficial. In sulfite waste liquor p H 4.8 is the lowest level attained by fermentation in the absence of a neutralizing agent. .4t this p H the production of lactic acid stops. FERMENTATIOK OF CONCENTRATED LIQUOR. Concentration of the liquor is a necessary step before recovery. If concentrated liquor could be fermented, higher concentrations of nutrients and a saving in size of equipment could be effected. About 50 fermentations were attempted on concentvated liquors. Doublestrength material showed a few good results, but in general the fermentations were slow and irregular. The concentration of
easily shown with malt sprouts in sulfite waste liquor. Three mashes were prepared, one of which waspheld for 10 minutes at 121" C., one was held a t 100" C. for 10 minutes, and one was given no tkatment. These mashes were cooled, seeded, and after 8 hours' incubation were used to inoculate the sulfite waste liquor. The fermentation yields are shown in Table V. Steaming was not harmful but sterilization reduced the yield8 aboutl8%. Soybean oil meal and distiller's dried solubles were used as added protein sources in the steeping experiments (Table VI). Small amounts of these substances inconsistently caused large increases in yield. After acid hydrolysis both materials were more stimulatory to the fermentation. Although the hydrolyzed materials did not give good results when used as the sole source of nutrients, they stimulated acid production when they were added t o malt sprouts and malt inoculum mashes. Numerous attempts were made to obtain utilization of ammonium salts and urea. Various acclimatizations both on glucose and on sulfite waste liquor were unsuccessful. It is necessary to supply most of the nitrogen as amino acids. OF SOYBEAK OIL MEALA N D DISTILLER'S TABLEVI. EFFECT The liquor and nutrients apparently contained sufficient inorSOLUBLES AS SUPPLEMENTARY NUTRIENTS ganic elements for the fermentation, since no increases in yield Nutrients in Medium Yield of Lactic Acidb, G. per 100 MI. Supplementary % % % were obtained by addition of different salts. Nutrients" malt sprouts supplement 24 hr. 48 hr. 72 hr. INCUBATION OF INOCULUM. On the types of inoculum media 0.65 0.87 1.03 None 0 4 0.4 0.0 1.13 1.50 . . discussgd, the growth of L.penlosus was rapid. The inoculum Soybean, 0 4 0.4 0.2 1.14 1.44 0.4 0.2 Distiller s solubles 0.4 could be used a t an age of 8 hours. On a malt and malt sprouts 0:66 0.21 . . 0.0 0.4 Hydrolyzed soybean 0.0 0.27 0.61 0.0 0.4 Hydrolyzed solubles 0 0 mash or on a molasses and malt sprouts mash, lactic acid forma0.87 i:ia 1.15 0.4 0.06 Hydrolyzed soybean 0.4 tion has been observed at the rate of 0.20 to 0.25 gram per 100 ml. 1.11 1.49 1.57 0.06 0.4 Hydrolysed solubles 0.4 per hour. The inoculum may be suitable at ages greater than 8 a Hydrolyzed with 1 N HC1 for 2 hours a t 121' C. b Fermentation conditions: SWL prepared by sulfite precipitation hours but beyond 10 hours the results were ermethod; 10% (vol.) inoculation; CaC03. ratic. I n order to avoid depletion of the sugar supply, 2.5 to 3.0% fermentable sugar was used in TABLE VII. EFFECTOF pH OK LACTIC ACID YI.ELD IN CONSTANT pH the medium. FERMENTATIOXS The use of a n 8-hour inoculum would permit Yield of Lactic Acida, industrial equipment to handle both mashing and G. per 100 MI. Neutralizing PH Material 1 hr. 10 hr. 20 hr. 30 hr. 40 hr. 10 hr. 20 hr. 30 hr. 40 hr. inoculum production in a 24-hour period. 5 N NaOH 6.0 6.6 6.0 6.0 6 . 1 0 . 7 6 1 . 1 6 1.36 1.48 Excess precipitated calcium CONTROL OF pH. 5,6 5.1 5.1 5.1 5.1 0 , 3 7 0 . 4 8 0 . 5 4 0 . 5 9 carbonate was added t o all the laboratory fer5.6 5.6 5.6 5.6 0.95 1.48 1.50 1.51 5.4 mentations. The fermentations were initiated in 15% Ca(0H)z 5.8 6.0 5.7 5.6 5.6 0.78 1.34 1.49 1.51 5.7 5.8 6.0 0.72 1.27 1.44 1.50 5.8 5 7 the liquor at about p H 6.5 and in 2 or 3 hours 5.6 5.4 5.4 5.4 5.4 0.72 1.35 1.49 .. the p H fell to 5.6, which was normally main10% Ca(OH)%and 5% CaCOa 5.4 5.4 5.6 5.5 5.5 0.66 1.08 1.28 .. tained by excess calcium carbonate with frea Fermentation conditions: sulfite precipitation, 10% inoculation from 8% sprouts and quent shaking and addition of fresh carbonate. 5% molasses mash (pasteurized). p H regulated automatically by addition of Ca(OH)z Lignin in sulfite waste liquor seemingly coated slurry. the surface of the calcium carbonate and unless
INDUSTRIAL AND ENGINEERING CHEMISTRY
January 1948
63
TABLE VIII. YIELDSOF LACTICAND ACETICACIDSFROM DIFFERENT LIQUORS Sample Wood Diluted liquorsb Spruce Spruce Spruce Hemlock Poplar Hemlock Fir, spruce Undiluted liquors Spruce Spruce Spruce Hemlock Poplar Hemlock Fir, spruce (Inoculum)
Digester
Cooks=
Mitsch. Indir. Direct Direct Direct Direct Direct
110
Mitsch. Indir. Direct Direct Direct Direct Direct
11: 10 10; 7 2c 11 io
..
100 10; 7 2= 11 1Q
..
Strength, % SWL
Ferm. Time, Hr.
Concn. of Acids Acetic Lactic g./100 mi. g./100 mi.
Initial sugar, lb.
60d 80d 60d 8Od 70d 604 60d
48 48 48 48 48 72 72
0.45 0.45 0.37 0.39 0.72 0.21 0.36
1.14 1.21 0.92 0.97 0.78 1.27 1.09
390 330 330 180 260
1ooe
48 72 48 48 96 72 48
0.56 0.50 0.48 0.42 0.93 0.18 0.48 0.17
1.85 1.71 1.55 1.30 1.13 0.88 1.60 2.50
435 375 375 225 305
100 e loon 100 * 100~ 100: 100 06
*.
.. ..
.. .. ..
Yield per Ton of Pulp Initial Final acetic, acetic, lb lb.
63 52 57 60 92 33 55
125 94 103 81 172 58 100
Lactic, Ib.
318 253 255 202 185 372 303 340 314 285 239 189 147 294 42
Number of separate cooks represented b y sample. SWL in diluted liquors is given in column 4. Zornposite samples from Rhinelander Paper Co., 12.9,11.0, 11.1, 10.6,9.4% solids, respectively. d Concentrations and yields corrected for materials added with inoculum. e Concentrations and'yields include materials fron inoculum: 0.5% blackstrap.molasses and 0.8% malt sprouts. f Sample of magnesium base liquor from Weyerhaeuser Timber Co., 13.7% solids. 0 Sample from Puget Sound Pulp and Timber Co., 11.0% solids. a b C
toxic substances or salts may have been too high. Yields of over 3.0% lactic acid were'obtained in Borne cases. Concentration of liquor before fermentation did not appear to be feasible. EFFECT OF WOODSPECIESAND COOKING PROCEDURE. Some data on various wood spepies and cooking procedures are presented in Tables I11 and V. When a series of dilutions was made and fermented in the presence of large amounts of nutrients, the yields represented the greatest quantities that could be obtained from the samples of sulfite waste liquor. Table VI11 shows the maximum yield from diluted sulfite waste liquor only (corrected for dilution and added inoculum) as well as the yield normally obtained when no correction was made for inoculum in the full-strength liquor. Hemlock and poplar wood did not give good results. The cooking procedure affects the yields from composite samples slightly, but this could be erroneous since 2000 gallons of waste were assumed for all samples. Spruce yields about 300 pounds of lactic acid and 80 pounds of acetic acid per ton of pulp. The poor fermentability of magnesium-base liquor was largely due to inability to remove sulfur dioxide by the procedures which were developed for calcium-base liquor. No attempts were made to develop special preparative treatments for the magnesium-base liquor. Most of the acetic acid was present in the original liquor and only a small part came from fermentation. Very little of the pentose sugar appears to be fermented.
tained from fermented media adjusted to p H 2.5, but adjustment to p H 2.0 was done as a precautionary measure. Acid consump-
RECOVERY OF LACTIC ACID FROM SULFITE WASTE LIQUOR
The solids content of fermented sulfite waste liquor is about 12% by weight. Lactic and acetic acids are present as calcium salts totaling about 2.5% of the liquor by weight. Lactic acid may be recovered by a t least two methods: crystallization and solvent extraction. Although calcium lactate did crystallize in the concentrated liquors, crystallization is obviously unsuitable in the presence of such large amounts of impurity. Solvent extraction may be done on at least three kinds of fermented material: ( I ) acidification and extraction of the fermented liquor directly; (2) concentration, fermentation, acidification, and extraction; (3) fermentation, concentration, acidification, and extraction. The second procedure fails because concentrated sulfite waste liquor cannot be fermented. The success of the first and third, schemes depends upon the properties of the solvents available. ACIDIFICATION.Acid consumption of the fermented liquor is determined by the quantity of organic salts and other constituents of the medium. Complete extraction of lactic acid was ob-
SO LVE-NT
Figure 7. Limiting Solubility Curves Obtained on Pure Components at 27" and 90" C.
INDUSTRIAL AND ENGINEERING CHEMISTRY
64
TABLEIX. DISTRIBUTION COEFFICIENTSFOR LACTIC A N D ACETIC ACIDSBETWEEN WATERAND VARIOUS SOLVENTS Tpp.,
c.
Solvent n-Butyl alcohol n-Amyl alcohol n-Hexyl alcohol n-Octyl alcohol Isobutyl alcohol Isoamyl alcohol sec-Butyl carbinol Diethyl carbinol
Amyl alcohols (Pentasol) 2-Ethyl butanol Octanol-2 2-Ethvl hexanol Benzil alcohol Phenyl ethyl alcohol Phenyl cellosolve Cyclohexanol Amylcyclohexanol Phenol Eugenol Tetpineol Ethyl acetate Butyl acetate Amyl acetate (fusel oil) Amyl acetate (pentacetate) Cyclohexyl acetate Butyl carbitol acetate Butyl oellosolve acetate Diethyl carbonate n-Butyl lactate Isobutvl lactate n-Amy"l lactate Ethyl ether Isopropyl ether n-Butyl ether n-Amyl ether Methyl isobutyl ketone Methyl n-amyl ketone Diisobutyl ketone Mesityl oxide Phorone Isophorone Acetophenone Cyclohexanone
'
Furfural Furan Limonene Pinene i%?EetnU~pentine Chloroform Nitroethane
K
31 31 28 28 28 31 2s 26 26 90 90 26 26 100 28 28 28 28 28 28 26
too
26 26 28 28 31 28 28 26 28 28 28 28 28
-" 100 96
28 27 28 28 28 28 26 26 100 26 100 28 28 100 28 28 26 100 28 27 100 27 26 2s 28 28 28 28 28
Lactic Acid K 1.34 1.37 1.65 2.45 1.79 3.40 1.62 5.2 1.60 1.41 2.22 1.59 2.46 1.68 2.03 3.18 1.95 8.42 1.77 2.00 1.64 10,oo 2.30 3.07 2.01 8.79 2.83 1.84 3.64 1.81 5.2 2.03 1.98 6.8 2.33 1.63 2.36 1.73 2.41 1.68 1.74 2.60 1.40 2.82 7.0 2.71 1.35 2.56 1.80 14.7 1.82 3.84 4.07 1.77 2.00 8.2 2.15 11.0 2.80 8.8 2.08 13.0 1.79 4.1 2.78 9.3 2.12 21.0 2.56 1.88 8.38 1.61 3.54 1.82 1.61 1.86 1.87 2.88 1.88 9.8 2.27 35. 2.23 73. 2.20 100. 3.55 7.9 7.5 11.06 5.6 3.76 9.7 3.18 4.08 6.8 2.22 36.0 1.84 3.76 3.56 2.74 4.80 15.7 2.38 2.33 8.42 2.13 3.30 2.28 2.04 8.8 2.26 1.87 2.92 1.75 1.84 3.32 3.04 80. 1.83 280. 1.87 80. 1.86 600. 1.87 loo. 1.87 100. 1.81 11.0
Acetic Acid
C7D
CW
K
0.49 0.58 0.64 0.74 0.50
0.89 1.10 1.37 1.98 0.85
0:54 0.51
1.01 0.87
..
..,
..
... ...
0:57
..
i:05
0:63 0.69 0.74
1.52 1.63 1.97
0:66
1.19
..
.. .. ..
..
... ...
... ...
...
...
... ... ...
0:62
1.24
0:73 0.79
2.03 2.47
0:64
1.36
b:s6 0.58
3:53 0.98
0 : 59
0.65 0.74
1.02 1.26 2.07
1:03 1.03 0.75
11.8 14,2 2.07
0: 79
2.48
0:is
7.0
..
..
..
.. , .
0: 52
..
.. 0:50
0:65
.. .. ..
1:09
.. ..
...
... ...
... ...
...
... ...
...
... ... ... 0.87 ... ... ... 0.83 ... 1.30 ... ... I
.
.
...
70.
... ...
= CW/Cs; Cm = concentration of acid in aqueous phase, g. per 100 ml. Cs = Concentration of acid in solvent phase, g. per 100 ml.
TABLE X.
tion by unidentified substances in the liquor was found to be from 35 to 50 pounds of sulfuric acid per ton of pulp; in other words, 14 to 20% more acid was required than was calculated on the basis of organic acid content. PRELIMINARY SELECTIOX OF SOLVENTS. Solvents were selected by first determining the distribution coefficients of pure lactic acid between water and different solvents. Monomeric lactic acid must be used for the determination of distribution coefficients. Filachione and Fisher (6) have reviewed the subject of lactic acid polymers and have given data on equilibrium solutions in which lactic acid exists largely as the monomeric form. Solutions of 4 to 15y0monomeric lactic acid were obtained by autoclaving diluted 85% acid overnight a t 121 c. I n addition to monomeric acid, it is important to use a solvent that is free of acid impurity. Each sample was checked for acidity and purified if necessary. The lactic acid was determined by titrating both the water and solvent phases with 0.1 N barium hydroxide to the phenol red end point. In some cases it was necessary to distill off the solvent before titration. The coefficient K was obtained by dividing the concentration in the water phase by the concentration in the solvent phase, K = C,/C, (4). The distribution coefficients determined for lactic acid and acetic acid are given in Table IX. Solvents whfch possessed interesting properties were used at different acid concentrations and different temperatures. Since fermented sulfite waste liquor could not be concentrated beyond about 10'$0 lactic acid content without becoming a viscous mass, the extractions were limited to solutions of 2 to 10% lactic acid. No appreciable differences were found in coefficients within this range of concentration. However, high temperatures lowered the coefficients, and to a greater extent for those solvents with high initial coefficients than for the others. In general the alcohol group contained the best extractants. Lactate esters were not so good as the corresponding alcohol and were more difficult to recover. Ketones varied in ability to extract acid. Members of the acetate ester group and of the ether group were generally poor extractants. I n view of the viscous nature of sulfite waste liquor concentrate it appeared that extraction of hot liquor would be advantageous. Limiting solubility curves were established by Othmer's method (14) at both 27' and 90" C. The 90" C. point wm chosen because it was below the boiling point temperature of the constant-boiling mixtures. Limiting solubility curves of five solvents are shown in Figure 7. The decrease in the two-phase region was found to be small. The greatest changes were in the
EXTRACTION OF LACTICAND ACETIC ACIDSFROM SULFITEWASTELIQUOR(34.8y0SOLIDS) Second Stage, Solvent to Water
First Stage, Sulfite Liquor to Solvent Nonvolatile Acetic Acid impurity,
Lactic AcidQ Solvent
CW
n-Butyl alcohol %-Amyl alcohol Isobutyl alcohol Diethyl carbinol sec-Butyl carbinol Amyl alcohol (Pentasol) Cyclohexanol Phenyl cellosolve Terpineol Ethyl acetate Butyl acetate n-Butyl lactate n-Amyl lactate Ethyl ether Methyl isobutyl ketone Mesityl oxide Isophorone Cyclohexanone Furfural
4.35 4.98 4.43 5.17 5.18 5.51 4.60 5.18 5.93 5.68 6.69 5.34 5.18 5.72 5.96 5.48 5.42 4.36 5.43
a
Vol. 40, No. 1
K
% of lactic
1.28 1.51 1.41 1.75 1.96 2.07 1.41 2.26 3.14 3.12 6.3 1.62 2.13 5.0 5.5 3.01 1.98 1.57 2.51
59 39 52 28 44 37 50 119 70 35
Units for CWand K given in Table IX.
.. w.
63 57 40 44 51 40 86 81
Cw
1.35 1.40 1.35 1.38 1.38 1.45 1.37 1.37 1.26 1.36 1.54 1.36 1.49 1.71 1.61 1.42 1.34 1.12 1.12
Lactic Acid
K 1.4 1.6 1.4 1.5 1.6 1.7 1.6 1.8 1.6 1.6 2.4 1.5 1.8 2.2 2.3 1.5 1.6 1.1 1.4
C W
?;onvolatile impurity,
K
Acetic -4cid
% of lactic
CW
K
2:96
2:33
9:2
0:67
1:io
2:94
2:01
8:2
0:59
0:SS
2:98 3.07
2:24 1.68
1 19.7
0:63 0.62
1:07 0.97
2:ig
3 :42
15:s
0:59
1:34
..
3:35 2.88 1.93 1.66 2.61 2.89 2.85
..
1:87 2.34 6.9 7.5 3.45 2.54 1.76
s:
.. 3i:o
15.9 1.0 2.1 5.7
6.8
16.0
I .
.o: 65
0.69 0.94 0.69 0.69 0.59 0.62
..
0:96 1.25 2.00 2.03 1.I1 0.88 0.82
January 1948
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
mutual solubilit.ies of solvent xiid r u t e r ILL 1iwo acid r:oocentration E. WASTE I n m n ~A generttl dizeussion insny oi irhicli can be applied to sulfite waste iiquor. tias been published by Elgin (6). In the case of sulfite x m t e liquor the selrction of b solvent is complicated b.y the high ratio of impurities to lactic acid, the low concentration of recovorablc acids, and unfavorable coefficients. Prelimiiiary erpcriments and calculation indicated that the most favorable oourse of opwation would be to conacntrate the liquor RS much as pcssihlr, acidify, filter, extract wiih solvent (first stagc), and wash the acids from the solvent with water (second stage). Representative fermentation liquor was earreent.ratt:d sn that after acidification and filtration it contained 34.8% solids (dry weight). This materid was u.%d for thr dvti:rniination of diutrihutian coefficients for different solvents. Aft.er the liquor had been mixed with 1,hesolvent and nttaincd equilibrium, Samples of the riqueous and solvent layers were rcmoved and steam-distilled. T h o &due rras used for lactic acid determinat.ion and the distillate for volstilr! acid determination. Distiibution coefficients w e presented in Table X. It wm necessary to measure the amount of impurity in the extract (first stage). This w m accomplished by steam-distilling a sample free of solvent and volatile acid, titrating tho nonvalstile acid with barium hydroxide, drying to eonstsnt weight at 110" C., and weighing. The dry residue was dissolved arid lactic acid determined by the Fiicdemann and Grseser method. The impurity wiu expressed &s percentage of the lactic acid. These data are also given in Tiltile X. Another necessary determination was the amount, of impurity present io the final aqueous phase (second stage). NonvoliLtile impurity w&s the most troublesome material from thc refining viewpoint. Debrminatious werc made on samples from the water phase of the second stage. These dctkrminations were based on the fact that monomeric 1aet.ic acid will volatilize io it vileuim oven. Samples were dried until most of the lactic Reid u'as romoved and then wriglicd. Lactic acid was determined in thcsr residues by hydrolysis and titration. Impurity was expressed as percentage of the total lactic acid present in the initial sample. The dist,ribution coefficients of lit& acid betsoen concentrated liquor and solvent were more favorable than in pure Bystems (Table 1x1. The coefficients for the second stage extractions w w e very close to the true coefficients.
SOLIOS,-WT PERCENT
Figure 8. Viscosity Isothermsof Fermented. Acidified, and Filtered SulfiteWaste liquor at Different Solidi Contents
The coefficients for lactic seid were lowered in concent,rated fite wasto liquor by the presence of other dirsolvcd substance high amounts. The coefficients for volatile acids were consistel higher than for pure mixtures of acetic acid, because sulfur d ide was present in the aqueous phase. The coeffieient,s for ' second stage agree with values obtained on pure mixtures. solvents vary widely in the amount of impurity which they tract from the liquor, Application of the second extrnotion st results in appreciable purification of the lactic acid. Final la acid whioh contains from 1.0 to 10.0% impurity WBS obtainec evsporatition of tile final aqueous solution. Viscosity is known to affoct diffufiion (S), and solvent ext tions have been proposed whieli utilize higher operation t peratures (IS). The viscosity of fermented; concentrated, acidified sulfite waste liquor is shown in Figure 8 for diffe temporatwe and solids contents. At 100" C . a viscosity centipoise can be obtaincd in liquor with 30% solids and a eosity of 2 centipoise8 in liquor with 40% solids. Some countercurrent extraotions were conducted in a I; ratory apparalus. Eslritctions of liquor with 40% soli& I mkde a i t h Peot,asol, isophorone, and cyclohexanone in a 5: 0.25 iireh tube. Droplets of 3- to 4-mm. dihmeter were UE Different outflow ratios of solvont and liquor were used at 85 95" C. The results indicated that when solvent was empk as t,he continuous phase the extraction was only about 804 eoniplete as when the solvent was the dispersed phase. Ar planation may be that a drop of high viscosity liquid in the persed phase does not receive much agitation internally from drag on the surface w i d e falling through the solvent; whim t,he high viscosity liquid is the continuous phase, it. is hcing tinually agitated by the passage of solvent drops. Drop cyclohoxanone fused when collisibn occurred, but drops of Pc sol and iaophorone carried films of solidified msteriel. amount of lactic acid ertractcd in the 53-inch column varied I 50 to 70% with rat,ios of 1 to 3 volumes of solvent per volun sulfite ~ v a s t eliquor. More foaming occurred at 30" than at OC and WRS a minor problem at the high temprrature. ~LEFININQ OF LACTIC ACID. The problem of refining the b acid produced from sulfite waste liquor depends upon the m e of recovery. Distillation, methylation, and solvcnt cxtrat are possible procedures. Pilachione and Fislrer ( 7 ) II:LVC viewed purification steps and presented data on the methyls
66
INDUSTRIAL AND ENG
January 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
mentation is about 95% of the weight of the sugar fermented] while yeast is obtained a t about 4 5 % yield. Twice as much lactic acid as yeast can be obtained and, in addition, a n appreciable quantity of acetic acid is recovered. A mill of average size producing 100 tons of pulp daily per 300day year could produce 9,000,000 pounds of lactic acid annually. To utilize such large production new uses for lactic acid would be necessary, which might be found in the paper industry or in the field of acrylate plastics, adhesives, and elastomers. ACKNOWLEDGMENT
This work was initiated a t the request of Karl W. Fries of the Rhinelander Faper Company, who had already undertaken some experimental work on fermentation at the time this project was started. The authors are indebted to Dr. Fries for his fine cooperation in supplying most of the sulfite waste liquor and information about the samples. They owe thanks to D. L. Reed and R. S. Hatch for other samples of liquor. Miss E. McCoy of the Department of Agricultural Bacteriology supplied the culture stocks. The work was supported in part by a fellowship established by the Rhinelander Paper Company. LITERATURE CITED (1) Allgeier, R. H., Peterson, W. H., and Fred, E. B., IND.ENQ. CHEM.,21, 1039 (1929). (2) Anon., Pulp & PaperInd., 19, No. 6, 18 (1945). (3) Arnold, J. H., J . Am. Chem. SOC.,52, 3937 (1930). (4) Coolidge, A. S., Inter. Crit. Tables, Vol. 3, p. 398 New York. McGraw-Hill Book Co., 1929.
67
(5) Elgin, J. C., Chem. Met. Eng., 49, No. 5, 110 (1942). (6) Filachione, E. M., and Fisher, C. H., IND.ENG.CHEM.,36, 23 ( 1944). (7) Ibid., 38, 228 (1946).
Fred, E. B., Peterson, W. H., and Anderson, J. A., J . B i d . Chem., 48, 385 (1921).
Fred, E. B., Peterson, W. H., and Davenport, A,, Ibid., 39, 347 (1919).
Friedemann, T. E., and Graeser, J. B., Ibid., 100, 291 (1933). Hatch, R. S.. Paper Trade J.. 122.54 (1946). Marten, E. A., Sherrard, E. C., Peterson, W. H., and Fred, E. B., IND. ENG.CHEM.,19, 1162 (1927). Othmer, D. F., Bergen, W. S., Shlechter, N., and Bruins, P. F., Ibid., 37, 890 (1945).
Othmer, D. F., White, R. E., and Trueger, E., Ibid., 33, 1240 (1941).
Pan, S. C., Peterson, W. H., and Johnson, M. J., Ibid., 32, 709 (1940).
Partansky, A. M., and Benson, H. K., Paper Trade J . , 102, No. 7, 29 (1936).
Saeman, J. F., Locke, E. G., and Dickerman, G. K., F I A T Final Report 499, Joint Intelligence Objectives Agency, Washington, D. C., 1945. Sankey, C. A., and Rosten, M. M., P u l p & Paper Mag. Can., 45, 171 (1944).
Shaffer, P. A., and Somogyi, M., J . Biol.Chem., 100, 695 (1937). Wiley, A. J., Johnson, M. J., McCoy, E., and Peterson, W. H., IND. ENQ.CHEM.,33, 606 (1941). Wise, L. E., “Wood Chemistry,” A.C.S. Monograph 97, New York, Reir\hold Publishing Corp., 1944. R E ~ I V ESeptember D 16, 1946. Presented before the Division of Bugar Chemistry at the 110th Meeting of the AMERICAN CHEMICAL SOCIETY, Chicago, Ill. Published with the approval of the director of the Wisconsin Agricultural Experiment Station.
Atomization of Liquids in High Velocitv Gas Streams J N
H. C. LEWIS’, D. G. EDWARDS2, M. J. GOGLIA3, R. I. RICE4, AND L. W. SMITH University of Illinois, Urbana, I l l . Despite the important uses of atomization in the chemical industry, the technical literature contains little quantitative information on the performance of gas-atomizing and liquid spray nozzles. Attention is called to the general usefulness, for purposes of design and control, of the empirical equations recently published by Nukiyama and Tanasawa (11-16). The mathematics of the equations is discussed, and it is shown that drop size distribution data can be expressed in terms of a simple straight-line relation. In the case of gas-atomizing nozzles, analysis of the data in the literature reveals substantial agreement with the equations. In the case of liquid spray nozzles the agreement of the equations is more qualitative. Experiments on gas-atomizingnozzles are described. These corroborate and extend the work of Nukiyama and Tanasawa and give an indication of the effects of gas density, gas viscosity, heat transfer from gas to liquid, and the scale of the apparatus on the performance of gas-atomizing nozzles.
T
HE following article gives a n outline of the general principles that govern the atomization of liquids in a Venturi
throat, and describes the application of these principles to several devices for military use. It was pointed out that the action 1 9
8
4
Present address, Georgia School of Technology, Atlanta, Ga. Present address, California Reeearch Corporation, Richmond, Calif. Present address, Purdue University, West Lafayette, Ind. Present address, American Coating Mills, Elkhart, Ind.
in a typical device of this kind is quite complex and often involves simultaneous atomization, heat transfer, and evaporation, as well as a n unsteady-state process. For this reason the development of useful munitions could not wait upon the relatively slow procedure of a study of fundamental mechanisms and had t o be based on the qualitative methods described in the following article. I n the present article a report is made of the initial experiments in a program intended t o throw light on fundamental mechanisms and lead t o improved designs. The primary concern in this paper is with atomization. I n all the experiments reported, evaporation is kept a t a minimum by the use of nonvolatile liquids. I n one of the sets of experiments heat transfer is minimized by using both liquid and gas in the range of atmospheric temperature; and in the other runs the effect of heat transfer is measured only in so far as i t modifies the degree of atomization obtained. Because of widespread use of atomizing nozzles in chemical industry, the results reported here should be of general interest. Atomization is a practical method of obtaining intimate contact between a gas and a liquid, and is frequently employed in operations involving chemical reaction, absorption, evaporation, etc. Familiar examples are oil burners, burners for liquid sulfur, and t h e nozzles used in spray chambers for evaporation, absorption, and air conditioning. Most of the published information on pneumatic and hydraulic spray nozzles has come from five groups of investigators. First, there are articles by physicists and others interested in liquid
