669 ACKNOWLEDGMENT
The authors wish to express their appreciation to Daniel S. Prezorski, Marshall Turner, and Paul B. Ostendorf for their aid in the preparation of this paper.
TV = dry weight of slab z = length of the diffusion path e = time, hours K = 3-14 radians x = latent heat of evaporation
NOMENCLATURE
LITERATURE CITED ( 1 ) Rateman, Hohf, and Stamm, IND.ENG.CHEM.,31, 1150 (1939). (2) Besser and Piret,, Universit,y of Minnesota, private communica-
= area normal t o diffusion An,an = Fourier series constants
4
d ’ = effective area for diffusion A” = effective area for heat transfer C = water concentration, weight of water per unit weight of solid C = average water concentration Co = original water concentration C, = moisture concentration a t surface D = dsusivity, length squared per unit time e = base of natural logarithm h = heat transfer coefficient in Equation 16 H = humidity, absolute percentage k’ = proportionality constant in Equation 4 k” = proportionality constant in Equation I T k , = mass transfer coefficient in Equation 16 TD2 k = constant equal to 4L2 = total effective thickness of the slab R plus D / k = constant in Equation 19 n = exponent in Equation 19, a number P = exponent in Equation 18, a number P. = vapor pressure a t the surface of the slab Pi = vapor pressure of water in the air stream = thickness of t t e slab ‘f“ l = temperature, F. V = velocity of air, feet per minute
Eng:nyring Process development
tion. (3) Byerly, R. E., “Fourier Serieg and Spherical Hormonics,” pp. 105-6, Boston, 1895. (4) Carslaw, H. S., “The Conduction of Heat,” 2nd ed., pp. 22-3, London, 1921.
(4A) Cheng and Griffith, “Drying of Balsa Kood,” unpublished M.S. theses, Illinois Institute of Technology (1948). (5) Kamei, S., and Siomi, S., J. SOC.Chem. Ind. (Japan),43,325-37, 366-74 (1937). (6) Muller, H. I T . , and Peck, R. E., IKD. ENG. CHEM.,35. 46-8 (1 943). (7) Newman, A. B., Trans. Am I n d Chem Engrs., 27, 203-16 (1931). ( 8 ) Ibid., pp. 310-33. (9) Rohsenow. W. M . , Avonstein, >I. J , and Frank, A. C., Trans Am. SOC.Mech. Engrs., 68, 1135 (1946). (10) Sherwood, T.K., IND. ENG.CHEM.,21, 12-113 (1929). (11) Ibid., pp. 976-80. (12) Sherwood, T. K., Trans din. Inst. Chem. Enors., 23, 28-44 (1929). (13) Ibid., 27, 190-202 (1931). (14) Stout, L. E., Caplan, K. J., Raird, W. G., Ihid.. 41, 283-314 (1945). (15) Van Arsdel, W. B., Ibid., 43, 13-23 (1947).
RECEIVED for review December 9 , 1950
ACCEPTEDSovernber 15, 1981.
Operation of Pilot Plant Vinegar Generators EFFECT OF VARIOUS TYPES OF DILUTION WATER
RUDOLPH J. ALLGEIER, REUBEN T. WISTHOFF,
AND
FRANK M. HILDEBRANDT
U. S. INDUSTRIAL CHEMICALS CO., DIVISION OF NATIONAL DISTILLERS PRODUCTS CORP., BALTIMORE, MD.
T
H E quality of water used for industrial fermentations has become a problem of major interest in the past few decades. This factor of water quality is obviously an important one, if only for the reason that water constitutes such a large proportion of the solutions used for growth. Furthermore, in certain types of fermentations the water in the growing solutions becomes a part of the product. This is the case with beer, ale, and similar beverages and is also true in the case of distilled vinegar production with which this paper deals. I n early times river, pond, well, and spring waters were preferred by the fermentation industries, They yielded in most cases a soft, more or less organically pure water containing some salts necessary to the growth of organisms. However, as population increased, springs were not available and pollution problems forced the employment of treated water from municipal systems. Wells are still used by some plants. Even here, the water may be affected in unpredictable ways by changes in level of the water table which may in turn carry with it chemical alterations in the water itself.
Many studies have been made of the type of water suited for the production of beers and ales. Indeed, the quality of such beverages is, in some cases, determined largely by the type of water used, For manufacturers of vinegar, especially the socalled white or distilled vinegars, such studies have not been made or they have been inconclusive and not readily applicable to generator operation. One attempt to evaluate water was made by Wiistenfeld (3) who describes the type he considers best suited to vinegar manufacture. It has, therefore, seemed worth while to do some preliminary experimentation with the object of obtaining helpful information for the users of the modern Frings-type generators. GENERAL PLAN OF EXPERIMENTAL WORK
The first requirement in such a study is an experimental technique which will give information applicable t o large scale generators. A type of small scale generator has been described by Hildebrandt ( I ) with operation characteristics sufficiently close to those of the Frings generator to meet this requirement. Given
610
INDUSTRIAL AND ENGINEERING CHEMISTRY
such apparatus, the first approach t o the problem is to run a series of maters obtained from various parts of the country in order t o demonstrate what differences, if any, exist between them. If differences exist, it may then be possible t o correlate them xith some characteristic of the n ater determinable by chemical analysis or otherwise.
Vol. 44, No.
3
sired for vinegar production. Bact. schuetzenbachii or Bact. c u m u m produce acetic acid from ethyl alcohol in the quick vinegar process. Acetobacter aceti, A. pasteurianum, A. xylinum, A . ascendens, and A . acetigenum may be isolated from vinegar (9). Very dilute solutions of alcohol and a nutrient containing inorganic salts and malt or yeast extract are added after the warm vjiirgar has h w n pumped through the packing. This is done to develop :I. good population of organisins and the generator is ready for use If 110 complications arise the same shavings and backrial flora may be in production almost indefinitely. It is known that some generators have been ih use for more than fifty years with the same packing. I n order t o help the reader vixualize the operational procedure, Table I gives the principal factors involved in rudning the generators,
\-diii!,i> o f iliavings (packing), C I I . i t . ltnti, of p u i w gal.ihr./100 c i i . Et. (packing) .iir flow, r i i . Ct./'hr./100 C I I . it. (parking) Itate of produriion of acetic acid, Ibs>/24 hr. '100 Oxygen content at outlet, volume t C .\rerage temperature (upper), (~7 .\verage temperature (lower), ' C . Average tempei,atiire (feed), O C. Volume of charge, gallons I otal vinpgar content, gallons M'eekly s~ithdrawal,gallons
0 61 CII
12 5; i t . (packing) 11 14-16 29
I /
30-32
18 0.BU
1.P 0,5a
Approximate.
With the helpful coopcration of a number of manufacturcre of vinegar, the authors were able to secure samples of water from widely separated part,s of the country. These samples, their geographical locations and type, are listed below: Baltimoie XId. S o r t h e r n 'California Central Noi t h Carolina Northern Texas Central Kansas-, Southeastern Tc isconsin
City water P l a n t well water City mater City water City water Plant well water
EQUIPMENT U S E D
Small generators described in the paper by Hildebrandt ( 1 ) were
ing the conversion period by nieans of a special type of pump made of rubber, glass, and stainless steel. These units were operated in a battery in a basement, rooin where the temperature was relatively steadir alt'hough subject,t o variat,ionsdue to general weather conditions. Iluring the period of the experiment the temperature variation IT-^ € 3 " F. The operating te,inperature x a s approximately 85' E'. Since the generators mere small, theyassumed the approximate t,einperaturc of t.he room. Figure 1 shows the battery. For details of coiistruction and operation reference may be made t o publication ( I ) . The conditions of liquid and air flow a,rcsirnilax t,o those nixint,ained i n conventional practice. Cycle time on these generators was 7 days. This period was chosen as a result of previous studies on the effect of cycle time on yield and efficiencies. It was shown that the cycle time could not be reduced t o less than 0 days without loss and that 7 days gave the desired conversions and efficiencics. The usual procedure to start a vinegar generator is to obtain a quantity of unpasteurized vinegar, called warm vinegar, from :L generator in production. This is pumped through the bed of shavings until a film of organisms develops on the packing. The organisms commonly employed are a strain of Acelobacter suitable t,o conditions. iilthough there are a large number of bacteria and other microorganisms capable of producing acetic acid in small amounts, relat,ively few bacteria possess the characteristics de-
The collection of data involved the use of Ytandard equipment for titration of acid, alcohol distillation, and determination of nlcohol by specific gravity. IIAKE-UP OF TIIE CIIARGE
The alcohol employed in these experiments was 35A denatured by the addition of 5 parts of 85 t o 88% ethyl acetate t o 100 part6 of 190-proof alcohol by volume. This was diluted with the water under test, t o a concentration of 9 grams of alcohol per 100 ml. of feed. A ferment,ed solution of Diamalt, a malt concentrate manufactured by Standard Brands, was added as a nutrient. This nutrient,, which has proved very satisfactory, is made by fermenting a solution of Diamalt (15 grams per 100 ml.), filtering through a coarse pa er, and adding 25 ml. of the filtered solution t o the 2000 nil. of $luted 35A charged. The charges are introduced weekly into the generators following withdrawal of such an aniount of finished product as will hold the volume of liquid in the gcrierator system steady. T h e miters under test were shipped by express and immediately mixed Ivith 35'4 in order t o inhihit batterial growth. Charges were then analyzed for alcohol content,. AXALYSES AND CALCULATIONS OF WATEHS.These analyses were made upon receipt and were limited t o the usual tests. Iron content was determined, because it r a ? felt this might correlate with generator performance. .%SALYSES OF FEED . ~ N D DRAWOFF.These analyses were limited t o determinations of ethyl alcohol and acetic acid. Alcohol \vas analyzed for by distillation and determination of the specific gravity of the distillate. Two hundred ml. of the feed or product nere neutralized with strong sodium hydroxide t o a deep pink end point, wing phenolphthalein as an indicat,or. A little less than 100 nil. of this was dist.illed int,o a 100-nil. volumetric flask. After making up to volume, thedistillate was weighed a t 25' C. on an analytical b:ala.nce in a vacuum-jacketed pycnometer and th[x results were reported as grams per 100 ml. of alcohol. The acidity i n the drawoff was determined by titration with 0.75 S sodium hydroxide, accurately standardized against Bureau of Standards benzoic acid. Results were reported as grams per 100 nil. of acetic acid. CALCCLATIOSG. Performance of the generators is expressed as an efficiency figure. This is the ratio of the amount' of acetic acid
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1952
671
OBTAINING T H E FIGURES FOR FINAL INTERPRETATION OF R E S U L T S
NOR THERN GAL IFORNIA
90I
I
3-8
2-1
l
l
1
4-6
5.4
6-1
I 7-6
I 8-3
r I
I 6-31
9-27 I19501
4 4-6 5-4 6-1 7-6 9-27(1950)
90 2-1
3-8
8-3
8-31
PER100
TEXAS
3-8
2-1
%
95
-
4-6
5-4 6-1
8-3
7-6
8-31
CENTRAL
9-27 (1950)
PERIOD
KANSAS
90
I
3-8
2-1
l
4-6
l
I
1
5-4 6-1
.
7-6
CONTROL
1
8-3
There are two principal sources of variability in the week-toweek figures of generator performance. One source lies in slight variations in the amount of drawoff, and other uncontrollable factors associated with any given generator which produce plus and minus differences of approximately equal magnitude. The other is due to variables that affect the battery as a whole. Unusually high room temperatures, slight changes in air pressure, and the like may give rise to variations of this class. In order to minimifie the effect of the first class of variables, the eficienc)? figures sh0n.n in the curves in Figure 2 represent a moving average of four neelcly determinations. This smooths out the week-to-week changes which are not significantly related to the conditions of the experiment. In order to eliminate the battery fluctuations, all of the test generator efficiencies are expressed in twins of the performance of the contiol generator. The control generator iii this case is the one using the Maryland water.
I 8-31
I
9-27 (1950)
RESULTS
The analyses of the water samples used are given in Table 11. Table I11 gives monthly averages of acetic acid produced and residual alcohol left in the drawoff. Table IV gives the efficiency figures averaged by months. These are obtained from the weekby-week readings on which the curves are based. Figure 2 shows the performance of the generators on various water samples expressed in terms of the rontrol generator taken as 100.
- - - -.- D1 SCUSSlON
I
3-8
2-1
I
4-6
l
l
5-4 6-1 CONTROL
I
I
,I
7-6
8-3
8-31
I
9-27(1950)
- -- -- -
WISCONSIN m e c a j
PERIOD
90
2-1
3-8
4-6
5-4 6-1
7-6
8-3
8-31
9-27 (1950)
Figure 2. Comparative Performance of Various Waters in Pilot Plant Frings-Type Vinegar Generators
produced to the amount theoretically expected from the chemical equation of transformation of alcohol to acetic acid. The formula is
All the waters showed variations from the control and certain samples were significantly lower. I n the case of California water and the two samples of Wisconsin water, this lowering amounted to about 8% as a maximum. The residual alcohol does not explain this as may be seen from reference to Table 111. North Carolina, Texas, and Kansas waters vary above and below the control, with a tendency to recover from an initial lowering of performance as the generator operation continues. This may be due to some acclimatization of the organisms to these waters. Also, when the test waters are discontinued and the generators put on the control water (Maryland), they begin to approach the 100 line which indicates recovery from the water factor responsible for the lowered performance. Performance on water samples from North Carolina, Texas, and Kansas are not markedly differept from the control. Generators on both samplcs of Wisconsin waters rccovered when put on the Maryland water, but the generator on California water
A , X ' p X loo= efficiency in per cent 1.3 X CA X V A where A , = grams acetic acid produced per ml. of drawoff, V , = volume of drawoff in ml., C A = concentration of alcohol in ,charge, in grams per ml., and V A = volume of alcohol charged, ml. The constant, 1.3, is the grams of acetic acid theoretically obtainable from 1 gram of alcohol. It is derived from the equation C2H60H
+
__
. _ .
1/202
+
CHBCHO
ZCHaCHO
+ HzO
TABLE 11. ANALYSES OF
~~${~~:~6Bs
Total hardness as CaCOa Cations Calcium as CaCOa Magnesium as CaCOa Sodium a s CaCOs Anions Chloride as CaCOa Sulfate as CaCOt Bicarbonate as CaCOa Alkalinitv &feth$l orange, CaCOa Phenolphthalein. CaCOa Iron (Fe) PH
ll'TATEH6 ( P a r t s per Million) RId. Calif. i 3 .C Tex. 93 485 71 214 182 25 70 50 1733 22 75 59
47 32 D 13
12 44 44 None 0.30 7 6
302 346
72 3 48
"65 80 323
492 127 32
8
26
I
57 None
274 108 239
18 434 198
39 25 0.14 10 3
232 None 0.14 7.6
108 Nonr 0.27 7.4
Wells
Plant wells None
l: 11
86 48 22
11
Source
11
None 0 10
7 4
d
1/202
atment
MP, municipal purification, treatment varied.
lated for each charge period.
Wis. 765 600 61')
166 0 06
232 8 0 17 7 8
Kans. 855
Chlorinated only, ;\$Pa
6'12
INDUSTRIAL AND ENGINEERING CHEMISTRY
3Iaryland, California North Carolina, Texas, G./100 MI.G./100 3Ii. G . / I O O hll. Q./100 X I . Date Acetic Residual Acetic Residual Acetic Residual' kcetic Residual 1950 acid alcohol acid alcohol acid alcohol acid alcohol February 10,60 0.15 10.36 0. I9 10 66 10.52 0.06 0.14 March 10.43 0.22 10.36 0.21 10 51 0.96 0.11 0.21 April I O 31 10.40 0.09 0.10 10.03 0.06 10.14 0.20 May 10.37 0.06 9.71 0.11 9.69 10 03 0.17 0.22 June 10.24 9.65 0.06 0.08 0.22 9 96 9.80 0.05 July 10.06 0 07 9.65 0.40 0.12 9 86 0.13 0.06 August 0.23 0.32 9.97 0.14 10 02 9.81 0.07 0.06 September 0.13 0.0Il 9.61 0.07 9.89 10.01 10 0 5 0.11 Octobei C 0.12 9.95 0,39 9.94 0.10 0.11 10 00 0.08 a Rased o n inontlilr averaoes. h m-isconsin-2 is a 2-week ~ v e r w v for ;\Inrch and is a r c c l i ~ c kon the Tl'iscon3in s:tiniil(~ C The month of October in all u"aees is a Z-Tveek a\-erage. \Vaten
shov cd no recovery i n the s n 11 celcs on Alarylancl ivatcr after the former was discontinued This suggests that sonic permanent injury to the organisms v a s produced by this water. If an attempt is made to correlate the generator perforniance n-ith the chemical analyses of the water, only very general relationships can be observed. Apparently no one chemical characteristic of the waters is related definitely to their performance in the generators Hon ever, both of the w i t e r e that tippressed the
Kansas G./lOO i l l . Acetic Residual acid alcohol 10.69 0.13 10.11 0.33 SO. 13 0.18 10.01 0.17 10.04 0 08 9.89 0.23 10.03 0.14 10,08 n 11 0,94 0 0!1
Vol. 44 No. 3
Wisconsin, G./IOO bll. Acetic Residual acid alcohol 10.18 0.07 0.12 9.98 9.82 0.09 0.23 9.60 9.73 0.14 9.63 0.14 0.26 9.66 0.21 9.95 0.10 10.07
..
\\-isconsin-2, G./100hI Acetic Residual acid alcohol
.
10.13 9.83 9.59 9.51 $1, 66 $1.53 9.83 9 01
0.05fl 0.09 0.21
n is
0.11 0.39 0 18 0 20
good, depending perhaps on the ratio of the mineral constitucnt s of the waters rat'her than on t8heirabsolutc amounts. A question may be raised as to the significance of the variations shown in comparison to those met with in commercial operat,ions. It is true that large plants do vary in both efficiency and yield. Ilowever, in these experiments thc effect of factors ot,her than water is ruled out by comparing the experiments wit,h a control run under the same condit,ions. ThiFi method of cgpressing the results ma,kes it, possible to attach significance to variations much smaller than would otherivisc br the cam. The exGerimcnts descpribed should bc considered Kis.-2 as constituting a preliminary study designed to compare tho performance of various waters in February 89.40 88,.54 90.11 90.29 (10.07 87.92 Frings-t'ype generators operated under the eamr March 88.15 88.64 88.92 87.02 86.76 86.51 87.736 conditions. Under such conditions, it, is apparent .4pril 87.26 87.27 85.27 85.39 89.33 88.61 87.33 May 89.19 84.64 86.42 85.25 86.89 82.B5 83.17 that there is a significant difference in the suitJune 88.48 84.20 86.77 86.33 88.24 84.32 84.0.5 ,July 87.98 81.77 86.59 85.25 85,79 83.42 83.61 ability of various wat.ers for generator operation. August 82.44 82.36 86.36 80.22 86.31 86.56 84.88 The study euggesk the desirability of more deSepteniher 87.73 81.38 87.94 86.48 87.50 85.60 86.20 Octobcr C 86.85 79.81 87.76 87.(i(i 87.23 86.67 86.39 tailed work, the object of n-hich would be to bring Rased on inontlily avcragcs. out the reasons for water differcnccs. It would he 11 Wisconsin-2 is a 2-wcck averaxe for ;\larch a n d is a rcchrck on the \Tiscansin sample. possible, for instance, i o modify the ivaters n-hich C The month of Octcbcr in all casos is a %week [ L ~ - c I ~ ~ E . give lower performance by suitable ion exchange treatment and such a modification might improve them for this particular frrmentation use. Also, a study of the trace metal content, the ionic balance, deyields came from plant wells and were not treated. I t may bc gree of rhlorination (in treated waters), and prcsence of salts of that the treating process which involves chemical preripitation, aeration, and chlorination improves the water for use in vinegar common metals, such as iron, zinc, lead, etc., r o u l d all bc worthy generators. If the location is considered, it may bc stated that thc of attention in this connection. Work along some of the lines suggested is in progress. It n1.o best waters are from castern seaboard municipal supplies and have a low hardness and chlhiide content. Waters from northern has been planned to condurt bacteriological studics on water@rmploved in vinegar production. Texas and central Kansas municipal sources did not have a materially adverse affect on thc cfficiency of the generators. Plant well water from southeastern STisconsin containing high LITERATURE CITED calcium and sulfate values lowered efficiency as much as 8%. (1) Hildebranclt. F. M,, Food I?&., 13,'Ko. 8 , 47-8 (1941). However, no permanent harm was done to the generators as they (2) Prescott, S. C., and Dum. C. G., "Industrial hfiorobiology," 211d recovered steadily to 99% of the control within six weeks when ed., p. 372, Kew York, PvIcGrrrw-Hill Book Co., IIIC., 1949. ( 3 ) Wiistenfeld, H., "Lehrbuch der Essigfabrikation," PI?. 135--fj. fed with water from Baltimore municipal supply. Water from Berlin, Paul Parey, 1930. plant wells in the San Francisco Bay area caused a slower, more marked and more permanent Iomring of efficiency. Generally RLCEIVED for reviciv M a y 25, 1951. A c c ~ ~ October r ~ o 5, 1B:l. speaking, thc better waters are those that have low solids, hardPresented before the Division of Agricultural and Food Chemistry a t t l l v ness, and chloride content. Other watrrs may or may not bc 119th hleoting of t h o . ~ V E R I ~ A Csr.moar, X SOCIZTY, Clavcland, Ohio. ~~
