December 1947
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
reflux ratio. As sh0n.n in Figure 9, for those systems which produce a two-phase overhead product, facilitics arc provided for continuous recycle of one phase to the extraction tower. The rate of recycle is controlled in a positive, sensitive, and reproducible manner by means of a bellow pump connected t o a Flexopulse timer controlling the pump motor current source. The time is set to deliver current, over most of the pumping cycle in order t o produce as nearly continuous pumping as possible. The use of the Flexopulse timer is far more satisfactory t,han attempting to adjust the pump stroke. The reboiler, mounted at, the bottom of the column, is shon-n in Figure 12. The electrically wound "boiling leg" Tyas made 10 inches long and 2 inches in diameter to provide maximum heat input with minimum liquid holdup. Estract is removed from the bottom of the leg (shown a t the bottom right-hand side in Figure 12) through a small conventional glass condenser acting as a cooler. The rate of withdrawal is controlled by means of a flesibly connected inverted U-tube which provides gravity overflon- and control of t,he liquid level in the reboiler. .I Hoke needle valve in the overflow line prevents pressure surges from producing irregular flo~v. -4balance line from the top of t'he inverted U-tube to the extract receiver prevents siphoning. h very small stream of inert gas, such as nitrogen, is bled continuously into t.he bottom of the reboiler. This stream of gas passes
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up through the annular space b e t w e n the hi:ated boiling leg and an inner concentric t,ube open a t the top. Thc inner tube is open a t the bottom only at the sides. This arrangement ensures even, continuous boiling by initiating vapor butlbles and enhancing natural convection. The operating procedure is as follows: The reflux ratio is set on the automatic timer and the napht,ha feed started into the t,on-er a t t,he predetermined rate. The feed preheater is adjusted t,o give the desired feed temperature. After a liquid level has been built up in the reboiler, the reboiler heat. is adjusted slowly to give approximately the desired overhead rate. Too rapid application of heat to t,he reboiler may result in flooding. Solvent feed is then s a l t e d into the tower, while the overhead rate is maintained by appropriate adjustments in reboiler heat. During this period the toFver jacket heaters are adjusted to maintain approximately adiabatic conditions. The solvent feed preheater is adjusted t>ocorrespond to the toiver temperature at, t,hc solvcnt inject,ion point. The reboiler heat. is finally readjusted to give the exact overhead yield desired. The tower is usually operated slightly below the flooding rate t o ensure high efficiency of tower operation and time utilization. Typical operating conditions and results obtained iyitli this equipment are shown in Table I. I n this case high purity toluene was extracted from a hydroformed naphtha of 80" t o 250" F. boiling range which contained about 27% t.oluene. R E C E I V EMarch D 1 3 . 1947.
END OF SECTION ON BENCH SCALE EQUIPMENT AND TECHNIQUES
ION EXCHANGE Operation of Commercial Scale Plant f o r Demineralization of Cane Sirups ai2d Molasses EAIAXUEL BLOCH .iND RICHdRD J. RITCHIE Pepsi-Cola C o m p a n y , Long Island C i t y , 9.I;.
EVERAL report,s have been A plant scale ion exchange demineralization unit was put into operation in published describing t,he order to purify cane sirups and invert molasses. The demineralizing system pilot plant' operation of various consists of a cation exchange unit, a granular carbon bed, and an anion exchange ion exchange syst'ems in treatunit. Four such batteries were used to treat 1,500,000 gallons of a blend of ing sugar juices. These plants partially inverted commercial cane sirup and a first run molasses, and for the have been used t o remove elecprocessing of 713,000 gallons of poorly defecated invert molasses. The main probtrolytes from sugar juices in order lems encountered w-ere formation of a gummy film over the cation exchange bed to obtain a higher yield of sucrose which prevented passage of the liquor, and large sugar losses due to bacterial and a minimum yield of molasses. infection in the upper layers of the cation exchange bed. With the present capaciT-ery little work on a commercial ties of exchange materials it is doubtful that blackstrap molasses can be ecoscale has been done on the purifinomically converted to an edible sirup. However, consideration should be given cation of cane sirups and molasses, to the recovery- of organic acids from the anion exchanger, and the application and, except for two beet camof this process in the demineralization of raw sugars and of partially refined sugars. paigns, no extended operation of any full scale commercial plant has DEMINERALIZING PROCESS been reported. I n 1944 this laboratory institut,ed studies in the utilization of ion exchangers for the purification of various grades Since a number of able t,heoretical presentations of ion exchange of sirups and molasses. h number of exchangers were tested in theory have been recently published, only a brief presentation of bot,h laboratory scale and pilot plant scale operations. The rethe underlying principles will be given here (6-5). Basically a sults from this work justified undertaking a full scale commercial demineralizing system consisis of two steps. I n t'he first step a operation. This plant was put into operation in January cationexchanger removes such ions as Na+, K*, Ca++,and M g + + 1946 and was operated until August of that year. It' is the from their salts in solution by replacing them with hydrogen ions. This results in the production of the corresponding acidspurpose of this paper to describe the production methods and hydrochloric, sulfuric, carbonic, and various organic acids. This indicate some of the problems and possibilities of using ion exchangers. highly acidic solution is then brought in contact with an anion
S
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 39, No. 12
mid for the introduction i ) f watcxr for backn-ashing (Figure 1). The top of the tanks have a laundcr, as ,sliox~nin Figure 2 , for ciirrying off tho water. D l ~ \ I I S I ~ R . ~ L I Z . ~ TOF I ~ SR L C S D E l ) S I R I T . The f h t typt. of sirup trvated during this oper:it ion n-as 1,300,000 gallons of a, tiionti of partially inverted voninicrcial cane birup with a first-run inol Tlic tiI(1nd \vas recrivetl at 76" Brix and had to be tlilutcd itiitl fi1ti:retl heforc. entrxring the tlr:niiricralplant. The extent of dilution and rate of ge through the rxcliangc~rs tlrpcritl largely the ash content of ttie m:itcsrisll twing processid I n this operation 5000 g:illons of 33' b i x ,sirup tr(5:iti.d a t a flov rate of 100 t o 125 gitllons per minute gave an end product containing the desired properties of loiv ash anti 6.25 t o 6.5OcO nnnsugar .liter filtration t h e sii,up passed ange cell. Thr. w i t i i c effliient than entered the bed of activated r a r h n . Froni this cell Figure 1. Flow Sheet thcefflui~ntpassed into the Anex tied, which reinovcd the iwiciic compoiient~from the liquid. Th(. initial .4. N-ater .V. Soft water for hackwash 0. Usedsoda B. i(j3Brix sirup cffluvnt irom the ion exchanger \mi highl>- alkaline, P. Blending tank C . 3lixing tank hut with the gradual exhumion of the Iicd the D. 33' Brix sirup tank Q. Triple-effect evaporators E . Filter press R . Activated carbon mixing tank pH kept dropping until tliv final sn-cet wntw ran 9. Filter press F. Cater .'l Pan evaporator G . Darco . ~ O \ l ~ f E R ~ ~ I( '.. % % SLE S I R U P T O O S E P.iRT TABLE I. THREE this ~ v o r kLYas started \vas built a t the Isabclla Sugar Company, FIRST ~I~L.~w:s Mount Pleasant, Nich., in 1941 and v a s used during tn-o camInfluent Final paigns t o demineralize beet juice (I, 6). This dmiincralizing (before Dilution) Product system consists of four batteries of demineralizing units. Each 75 40 i6.62 Brix, degrees 30 40 53.03 o'L Sucrose, battery is composed of. three cells n-ith a hydrogen exrh2tnge cell 12.74 20 19 Invert, 7 i o 59 0$,77 located on the top floor, a granular activated carbon i x ~ dplaced 4 81 10.91 on t,he floor beneath, and belolv this the anion cxchangci cell. 0 38 14.27 0 58 3 $2 The cells are rubber-lined, and all lines connecting the cells 2s as SaCi 3.50 4 SO .i 90 are of hard rubber. -111 other surfaces coming in contiict with Ilolnises, m r l t y Bland acidic or alkaline material are painted with r Taste IrIolns>es Sone Odor The cation exchange cell has a diameter of 11 fwt 6 iiichrs and a height of 11 feet, and contains 610 cubic fcvt of Catex, a sulfo:OOO-G.ALL~SCYCLEAT 3 3 O BRIS nated coal. The granular carbon bed has a dia1iictt.r of 10 feet and (InSuent: 3?.S0 Brix; pH 4.90; Golu-Bridge, 230 grainsigal. as SaC1) a height of 10 feet, and contains 340 cubic feclt of 12-20 mesli Catex Effluent Darco. The .Inex or anion exchange bvd hap a clianietrr of 10 SoluBridge, feet and a height of 10 feet,, and cont,ains 370 cubic feet of .Inex. grains: 1-01, of gal. as Time Degrees .I11 cells have a 1-foot underlying bed of graded anthracite. InEWuent, Brix pH SsCl Gal. (P.\l.) cluded in this installation are a nuii1iic.r of tank.:for thc prepara500 0.7 11 95 16 4:25 0 . 1 3.30 2,000 tion of regenerants, and the storage of soft Tyater and sweet Tl-ater. 11 85 120 0.2 1.30 500 25 6 4,000 4343 11.75 100 0.2 1.20 500 4:55 38.9 5,000 Gravity flow is used to send the liquids through the batt,ery. All materials enter the bed through a conimnn line and strike Sweetening Off Began with Sweet \Vater Followed by Raw Viater a bafRe plate placed 8 inches above t,he lied level. The liquid is 0.2 11,65 70 1.20 500 29.0 1,000 5:os 16.8 9.60 30 1.9,5 22j 18 5 3,000 5:l.i distributed in a spreading fan over the surface of the bed. On 3.85 18 27.2 2.95 26 3:30 3.2 5,000 3 40 21 22 1 9 . 4 1 . 9 3.30 7,000 5:13 the bottom of the tank is a di ibutiiig system. This consists 3.30 15 18 16.3 1.2 3.30 9,000 5:55 of a 6-inch header line n i t h branching ll/,-inch perforated lines. 13,000 6:30 0.0 3.90 14 0.3 2.90 12 These lines serve t o collect the liquid when it reaches ttie bottom 3
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December 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
The beds rvere sn-eetened off b? passing whatever high Brix sweet n-ater (5.0-2.0" Brix) was available from previous swetening on and off into thc, heds first, followxi by raw n-ater. The low Bris sweet n-ater (2.0-0.2c Brix) was used t o dilute fresh batches of sirup. Thc total sn-eetening off required ahout 15,000 gallons of water. -liter this the beds n-ere backn-ashed until t h baclmash conwmed 10,000 to 15,000 gallons of water per bed. The anion exchange bed 1%-asbackn-ashed n-it11 soft Tvater. This watcr as obtaiiicd during the sweetening oil process and consistctl of the rwidunl Lf-ater left in the. beds from rinsing during regeneration. I n addiTion, a zrolite softener \vas used to obtain furt1it.r quantities of soft n-atc'r. This n-as done to avoid the gelatinous iron and magnesium hydroxide precipitates which could foul the beds. For regenerating the Catex the quantitj- of acid needed was made up t o 1 . 5 c c solution. The anion exchange material was rcgcncrated by making the necdrd aniount of caustic into a 1 . 8 5 solution. Excess caustic (0.6-l.OC,) n-ashcd from the anion e\-ehangt)bed during thc regeneration process \vas collected, heated to 160" F., and used for the regeneration of the carbon bed. The carbon bed n-as then acidified by using the acidic rinse n-ater obtained from the regeneration of the Catex bed. D C M I S E R . i L I Z A T I O 4 O F I S V E R T ~ I O L A S S EThe S . second type of molasses processed was 715,000 gallons of poorly defecated invert molasses, which had been prepared originally for use in alcohol production and stored at Port Everglades, Fla. When received, this molasses contained large quantities of bagacillo, gums, and dextrins. I t had previously been observed that unfiltered molasses tended t,o decrease the efficiency of the &ion eschanger by 50 t o 75'7. TKOfactors were held to be primarily responsible for this drop in capacity: ( a ) Large colloid and gum particles apparently formed a coating around the granules, preventing contact vr-ith the ions in solution; because of this, no exchange took place. .Is a result,, t,he solution passed through substantially unchanged. ( b ) ;in inpenetrable gummy film formed over the surface of the cation exchanger bed, which prevented the passage of the liquor. Khenever this occurred, normal regenerative procedures proved ineffective, and drastic treatment of the cation bed had to be undertaken. This consisted of treating the bed with hot caustic solution and then regenerating with double strength acid. T o prevent the occlusion of the particles and of matting, the molasses n-as first filtered through a bed of fine anthracite. (Sand can be used effcctivrly for the same purpose.) This re-
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moved a substantial quantity of thc undesirable material and gave a fairly cleai molasses. The data of a typical demineralization on invert molasses are shonn in Table II. INSTALLATIOS OF h-EW ANION E,XCHANGER
Before processing this latter type of mol:zsses, a n important change in the equipment was made. Tests had indicatcd that the cation eschariger beds were only about exhausted during a 5000-gallon cycle, whereas the anion eschange material was conipletell- exhausted a t t,he end of the cycle. In order t o utilize more fully the entire capacity of the system, the four beds of -inex n-ere replaced by tlvo beds of Deacidite, each having a volume of 320 cubic feet. By using two beds of Catex in parallel follon-ed bj- one bed of Deacidite, satisfactory treatment, of a 30,000-gallon cycle of 33" Brix sirup lvas possible [Table 11). This decreased markedly the amount of regenerant chemicals needed with substantial saving of time and miiterial (Table 111). CAP4CITY LOSSES O F EXCHAhGE hlATERIALS
It is not possible to enter into a discussion of the exact cost figures, since equipment and mateiial had t o be used as found, with slight modification for our o m use, and efficiency and cost n ere fiequently sacrificed to increase production. K i t h improved types of cells and exchangers, operating costs can be sharply reduced. One of the more important cost considerations is the extent of exchanger deterioration andloss of capacity. &Itthe beginning of the first run the cation exchanger had a capacity of 9900 grains per cubic foot as calcium (arbonate. h i the
T ~ B L11. E EVERGL~D ~ IEOSL A S S E P Brix, degrees Sucrose, "a Invert, yo Total sugars, % Sonsugar solids. ""0 5 . S . S . (dry basis), Yo Ash (conductivity), % Solu-Bridge, grainsigal. as S a c 1 $%e Odor
Influent (before Dilution) Final Product 83.40 75.60 24.50 20.71 48.82 49,87 73.32 70.58 5.02 10.08 G 64 12.09 0 6.5 2.49 26 350 5.1 5.0 Bland Molasses Very slight molassea hIolasses
3 0 , 0 0 0 - G a ~ ~CYCLE o ~ OF 33' B R I XMC"LASSEJ (Influent: 32.9' Brix; p H 5.0; Solu-Bridge, 275 graindgnl. as SaCI) Catex Effluent Dearidite Effluent SoluSoluBridge. Bridge. Yol. of gAlnlj grainls/' gal. aa Effluent, Time Degrees gal. as Degrees Gal. (A.K) Brix pH NaCl Brir pH SaCl 0.:2 11.8 85 3.0 20 7:30 0.2 2,000 11.6 GO 300 0.1 1.3 7:50 16.4 4,000 11.2 60 300 2.5 16 8 1.3 6,000 8:lO 290 16.8 10.7 35 25 3 1.3 8,000 8:30 10.0 25 280 27.6 28.6 1.2 10,000 8:52 29.8 10.0 21 15 250 9:lO 30 4 12,000 9.4 I8 160 29.8 2.1 9:29 30.4 14,000 29.8 9.1 16 2.5 100 9:40 30.2 15,000 Euirched to Second Catex Bed, llerging the Sweet Water Bed with t h a t of :he X e w Bed 17.0 300 9.0 1.3 4.000 10:30 300 9.8 18.7 1,4 6,000 10:50 290 22.; 1.3 11:lO 26.3 8,000 28.r 250 29.8 1.2 10.000 11:35 (P.bI.j 200 29.5 1.2 30.0 12,000 12:05 190 29.f~ 30.1 1.9 14,000 12325 170 29.6 2.4 12345 30.0 15,000
from the First 9 7 8.6 7.8 6.5
70 35 25 12
5 9 5.1 4.8
6 9
Sweetening Off Began with Sweet Water Followed by Raw K a t e r . Requirement, 11,000 Gallons of Water Juice (30,000 gal.) Sweetenihg off (11,000 gal.) Backwash and rinse Regeneration time
Anion Exchanger Bed Being Backwashed
Total
TOT.AL TIME/CYCLE. 311%. 330 63 130 100
Total
Figure 2.
7
625
-
101,'~ hours (approx.)
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 39, No. 12
WATER REQUIRERIEKTS
TABLE 111. ~ I A T E R USED I A L IN PROCES~IXG Material
Quantity, Lb.
Lb./Lb. of Solids Kemored
XaOH His04
5000 Gal. of 33' Brix Sirupa i66 1011 282 71
0 59 0.79 0 22
Hyflo Darco
0 0.55
30,000 Gal. of 33' Brix Everglades Molassesa SaOH 766 0 12 HgSO4 0 32 2022 1692 Hyflo 0 25 426 Darco 0.068 a Nonsugar solids removed per 5000-gallon cycle, 1282 pounds. b Iionsugar solids removed per 30,000-gallon cycle, 6287 pounds.
completion of 223 cycles the capacity was reduced to 8900 grains The Anex showed a far per cubic foot, a capacity loss of 11%. greater reduction in exchange capacity and a secondary loss in volume due t o the increase in fines caused by the nearing down of the resin. However, this particular type of anion exchange material is no longer used, because improved anion exchangers are available. The Deacidite showed a capacity loss of 8yoafter the completion of 123 cycles. No definite evidence is available which would indicate whether the loss in capacity of exchange materials is due t o a coating of the ion exchange material or t o its taking up a n ion which is not easily regenerated off. Undoubtedly a part of the relatively high loss in capacity experienced in these operations can be attributed t o the fact that proper clarification of the raw material was difficult. It can be assumed that in processing sugar solutions generally, the capacity losses experienced will be higher than in m t e r treatment, for large amounts of colloids and organic substances have totally different effects than do solutions containing only mineral salts. Therefore, before a n exchanger resin is selected, determination should be made of its ability t o stand up under the impact of impure sugar solutions for many cycles.
The water requirements in sirup or molasses dcmincralizstion arc high. Sirup and Inolasjes are usually oht ained in a concentration of 75" t o BO" Brix. As previously stated, thcsc high Brix matcrials must be diluted. In addition the follon-ing anioun:s of nster vert required per battery: preparation of regenerating solutions, 13.000; rinse water, 10,000: backn-ash water 40,000; the t,otal n-ater per battery, 63,000 gallons. DISCUSSION
The operation of this plant on a commercial scale has indicated t,he possibilities of demineralizing cane sirups and molasses by ion c%xchangers. The authors have not discussed the production costs because this operation n-as carried on under unusual conditions, and many of the costs met at, Mount Pleasant would normally not be encountered. The cost of demineralization will be based on the following: 1. Amount of nonsugars t o be removed. The greater the amount of nonsugars, the more frequent the regeneration, with resulting increase in cost of regenerants. 2 . Capacity of resins for the specific ash, organic, and colloid materials found in sugars 3 . Per cent resin replacement -4. Cost of regenerants in area where plant is located 5. Cost of filtering sirups before they enter the demineralizing system. If a press is used the cost of filter aids must be considered 6. Cost of treating demineralized sirups Lyith activated carbons and filter aids t o obtain clarification 7 . Evaporation costs 8. Labor
In addition a n adequate water supply must be assured. From the experience obtained during this operation it also appears improbable that complete demineralization can be obtained by one passage through the beds. The Solu-Bridge readings in Tables I1 and I11 shorn that a t no time was the sirup free of mineral matter. To obtain a completely ash-frte sirup it would be necessary to pass the liquor through at least two batteries.
SUGAR LOSSES
At times large sugar losses were sustained because of bacterial infection. The cation exchange bed appeared t o offer an extremely fertile medium for this growth. Examination showed that the infection was concentrated in the upper two inches of the bed. This is attributed t o the conditions offered for growth. The beds are always slightly acidic; the juice enters at a temperature of 70-80" F.; and the proximity t o the air provides the oxygen necessary for growth. Addition of small quantities of formaldehyde during regeneration seemed t o retard the bacterial growth, but some infection was present at all times. There were many other sugar losses, The over-all loss in the operation was 15.0y0of the total sugars. Some of this loss may be attributed t o the difficulty encountered in sweetening off the filter presses. The degradation of invert sugar under the influence of a highly alkaline or acidic media must also be considered.
COSCLUSIONS
Under normal conditions it is doubtful whether blackstrap could be economically converted to an edible sirup. The high ash and colloid content of that material would result in extremely short cycles and a corresponding increase in the amount of regenerative material. However, it appears t o the authors that this process should a t this time be considered as a possible method for reducing losses from frozen cane. In this connection the recovery of aconitic acid from the anion exchanger may prove to be a valuable by-product. The application of this process in the demineralization of raw sugars and washed raws may also prove to be fruitful. ACKNOWLEDGMENT
Grateful acknowledgment is made for the advice and assistance offered in this rork by T. Elmezzi, A. Sieland, C. Fischer, and Laurence Roberts of the Pepsi-Cola Company, and A. B. Llindler of the Permutit Corporation.
DILUTION
Dilution of the sirup entails consideration of an adequate water supply and increased evaporation costs. All sirups must be diluted t o a point where they will diffuse through the beds a t a maximum rate of flow. This would mean the addition of 0.48 gallon of water to every gallon of 75" Brix sirup in order t o obtain a 33" Brix solution. By the time the sirup reached the blending tanks the dilution by sweet water had reduced the solution t o 14" Brix. With increased exchanger capacities the bed dilution would be decreased; this would result in a composite sirup of higher concentration than that obtained in this operation.
LITERATURE CITED
(1) Gutleben, D., and Harvey, F., Intern. Sugar J . , 47, 11-13 (1945). (2) Haagenson, E. A , , Sugar, 41, KO.4, 36-41 (1946). (3) Rawlings, F. W., and Shafor, R. W., Ibid., 37, No. 1, 26-8; No. 3, 30 (1942). (4) Sussman, S., and hlindler. A. B., Chem. Inds., 56,789-95 (1945). (5) Tiger, H. L., and Sussman, S.,IND.ENG.CHEM.,35, 186-92 (1943). (6) Weits, F. Tc'., Sugar, 38, KO.1, 26 (1943). RECEIVED M a y 21, 1947. Presented before the Division of Sugar Chemistry and Technology a t the 111th Xeeting of the AMERICAN CHEMICAL SOCIETY, Atlantic City, N. J.
