DEXTRQS FROM CORNSTARCH ROBERT H. ROGGE Chemical Division, Corn Products Re$ning Company, Argo, I l l .
T h e evolution of a process from laboratory work to a manufacturing plant for the production of dextrose froni cornstarch is described. By means of ion-exchange refining in a large pilot plant, yields in excess of 90% were obtained in contrast to yields of approximately 829’0 produced in existing commermial installations. The design, materials of con-
D
EXTROSE manufacture from cornstarch has been a commercial process since 1922. The procedure for crystalline monohydrate dextrose production was established by W. B. Newkirk (Y),and since that time the industry has reached a high degree of refinement (3). Cornniercial yields of the order of 82% have been realized. With the advent of ion-exchange refining, the way was opened for greater yields and improved quality ( 1 , 2 ) . A large pilot plant constructed fcr the purpose of testing the ionexchange process successfully produced dextrose with yields over 90%.
In the manufacture of commercial dextrose, washed cornstarch is converted to dextrose in the presence of acid at high temperatures according to the following simplified equation:
+
( C B H I O O ~ )XHt0 ~ e z C6Hi206 8tarch Dextrose Approximately 85% of tLe resultant hydrolyzate dry subStance i s dextrose. After convcrsion the acid is neutralized with soda ash, and the impurities and degradation products in the hydrolyzate are removed to a sufficient degree to permit the dextrose to be crystallized from solution. Generally, bone char and activated vegetable carbon are employed for the refining of the hydrolyzate. The mother liquor from the first crystallization is reconverted to produce additional dextrose. After further refining and decolorization, the mother liquor is again crystallized. The second crop of crystals, after separation from the second mother liquor, is redissolved in water and recycled t o the first crystallization step. Second mother liquor is sold as a by-product. For the pilot plant under discussion, ion-exchange materials were used in place of soda-ash neut’ralization and bone-char refining. Furthermore, the use of ion-exchange materials made it possible to eliminate some of t,heprocessing steps, improve the quality of the sugar, and increase the process yield. Research work on this new process was carried out in the usual small scale laboratory equipment. Starch conversions in 25-ml. tantalum bombs established conditions for sulfuric acid conver;sions in contrast with commercial operations with hydrochloric acid. Later, a 5-gallon glass-lined autoclave was used for conversions to furnish hydrolyzate for ion-exchange material evalua-
2070
struction, personnel organization, mechanical problems, and operating results of the pilot plant are reported. Included are equipment layout and schematic drawings showing points of instrument measurement and control. The value of the pilot plant work, in leading to the design and construction of a large manufacturing plant, is described,
tions. Ion-exchange tests vzere performed in 2-cm. diameter glass tubes with a bed depth of 6 inches. After concentration in glass apparatus, the dextrose was crystallized from 1-quart battery jar crystalhers. The crystallizer temperature was controlled by a surrounding water bath, and a slow moving, vertical, helical ribbon agitated the mass in the crystallizer. Pure dextrose was used to seed the massecuite for crystallization. The mother liquor from several crystallizations was saved for further processing, refining, and a final crystallization. A laboratory centrifugal machine with 20-ml. cups was used to spin the cake. The basic steps of the process developed in the research laboratory are the same as shown in Figure 1. Results of the research work were promising. Yields of 81% were obtained without reconversion of mother liquor and the quality of both sugars was excellent. Because of the limitations of small scale work, extended study of the ion-exchange resin life, the effect of recycling sweet waters, the effect of repeated crystallizations on seed left from previous batches, and other factors could not conveniently be investigated. A pilot plant was constructed, therefore, to test these unknown factors and to obtain information for the design of a manufacturing plant. Also, it was desired to test the enticing possibility of a “near 100%’’ yield process through the use of ion-exchange materials. DESCRIPTION OF PILOT PLANT
The pilot plant was designed to handle a nominal capacity of 5000 pounds of dextrose a day. Complete processing steps, from handling the raw starch to packaging the finished dextrose, were included in the plant. Some refinements of the process were omitted-for example, washing filter cakes (sweetening off), where information mas already available to the industry. Sufficient flexibility was provided and extra space allowed in the building for installing and operating auxiliary equipment to cope with forseeable prccess modifications. A flowsheet of one of the process arrangements is shown in Figure 1. This arrangement of the equipment together with measuring and control instrumentation is shown schematically in Figure 2 (A and B). Because the pilot plant was constructed within an existing warehouse and manufacturing building, offsets
INDUSTRIAL AND ENGINEERING CHEMISTRY
September 1949
P
x
in the floor plans as shown in Figure 2 (A, B, C, and D) were necessary t o avoid confliction with existing plant equipment. I n the pilot plant, triple-washed, reslurried starch is automatically diluted from 23" t o 10' BB. and acidified with sulfuric acid t o approximately 0.035 N . Figure 4 shows the raw materials supply station consisting of starch, water, and acid supply tanks. Converter controls, panel board, and working tank are shown in Figure 5. This station was operated over a wide range of operating conditions: starch concentration = 2 " t o 18" BB.; acid normality = 0.01 t o 0.045 N ; converter temperature = 290" t o 340 " F.; and pumping rate = 1 t o 5 gallons per minute. From the converter working tank, the acidified starch is pumped t o an entry chamber where the starch slurry is instantaneously heated t o 315" F. by means of a steam-jet heater. The starch is converted t o dextrose as the liquor flows through a continuous-converter coil consisting of 340 feet of 2-inch diameter Herculoy pipe housed in a n insulated box. The linear velocity of the liquid in the pipe is approximately 0.32 foot per second. The converted liquor discharges t o a small flash chamber where the liquor is cooled t o 212' F. by flashing a t atmospheric pressure. After removing insoluble converter residue and colloidal material with the aid of a coagulating type bentonite followed by plate-and-frame filters, the brilliantly clear liquor is fed t o the ion-exchange station. The battery of ion-exchange columns shown in Figure 6 is the heart of the process. Rubber-lined columns, 18 inches in diameter and 7 feet high, are filled with ion-exchange material to give a bed depth of approximately 3 feet. The columns are arranged in series, alternately spacing anion and cation columns. Six columns are used on stream, and two columns are off stream for regeneration with dilute acid and dilute alkali. By cutting out of service an exhausted pair of columns and putting in service a freshly regenerated pair, through interconnecting piping, the removal of acid from the sugar liquor and the refining operation are performed in a continuous fashion. The flow of liquor through the columns is essentially countercurrent; the raw liquor entering the nearly exhausted pair of columns and the refined liquor leaving the recently regenerated pair of columns. All input waters, feed liquor, and regenerants are measured through rotameters by manual oontrol. A recording pH meter is used on either the
*
LCENTRIFUGING--LDRY)NG t BY-PRODUCT SIRUP M e LB. OS
Figure 1.
+
-1518
2071
treated liquor or on continuous sampling from the individual columns. Following the ion-exchange operation, the liquor is usually given a light carbon treatment with an activated vegetable carbon t o remove residual colored substances. Carbon treating tanks are arranged for either batch or continuous contacting. Flow rate, temperature, holding time, and carbon dosage are varied as required. The carbon is filtered in plate-and-frame filter presses, and the clear, refined liquor is fed t o the evaporator station for concentration t o crystallizing density. An automatically controlled, long tube, forced-circulation evaporator constructed of Herculoy is used t o concentrate the liquor from about 8" t o 38.5" BB. (60"/60" F.). Twelve tubes, 1,120 inches inside diameter and 12 feet long, give the unit a capacity of about 1500 pounds of vapor per hour with an average heat transfer coefficient of 160 B.t.u. per hour per square foot per F. at a n estimated inlet liquor velocity to the tubes of 15 feet per second. The evaporator operates a t 28 inches of mercury vacuum with a normal steam temperature requirement in the steam chest of 330" F. Figure 7 shows a view of the lower half of the evaporator with the automatic controls. The heavy liquor, ready for crystallizing out the dextrose, is pumped t o overhead storage tanks. After the accumulation of 500 gallons of the heavy liquor, held a t a carefully controlled temperature, the charge is dropped t o batch crystallizers. A portion of the previous crystallizer batch is left in the crystallizer for seeding the new batch. The crystallizers are furnished with water jackets and a specially designed internal coil and agitator ribbon. Flexible piping arrangements permit several different cooling water flows, operating each unit independently or in series with other crystallizers. A separate variable speed motor drive is used t o motivate the agitator of each crystallizer. Figure 8 shows a front view of a few of the twelve crystallizers. Temperature recorders and flow measuring instruments are provided. Usually 72 hours are required to crystallize the dextrose cooling from about 120" to 70 " F. The massecuite a t the final temperature is a viscous, doughlike mass. Conveyers carry the massecuite t o a mixing box which accumulates a charge sufficient to load a 40-inch diameter, vertically suspended, basket centrifugal machine. This machine is the same size used in the manufacturing plants of the company, and although oversize for the average throughput of the pilot plant, data obtained from operation of the machine are directly applicable t o commercial operations. Water power is used to operate the centrifuge over a wide acceleration schedule or maximum speed up to the capacity of the machine of 2200 r.p.m. The wet cake in the centrifuge basket, after separation from the mother liquor, is water-washed t o give a white cake containing about 13 t o 16% moisture. (Dextrose monohydrate contains 9% water.) The cake is manually cut out of the basket and dropped t o a conveyer which discharges uniformly t o a rotary dryer. After cooling t o room temperature in a rotary cooler, the sugar is picked up by a Redler conveyer and carried t o a screen and packing hopper. Mother liquor and wash liquor from the centrifugal separation is given a carbon treatment to remove color, concentrated in a second evaporator, and crystallized in a second set of crystallizers. The centrifugal machine, dryers, and auxiliary equipment used for the first-sugar production are also used for the second-sugar production by scheduling the operations, O
SUGAR
LB.DS
Process Flow for Dextrose Pilot Plant
3257 1368 X 100 = 80.4%; organic dry substance (DS) Yield = 6o08 for 24 hours; cake and losses partially recoverable by usual factory practice
MATERIALS OF CONSTRUCTION AND MECHANICAL PROBLEMS
Construction of a pilot plant of this size during a period of hard-to-get materials necessitated compromising at a number of points in selecting equipment. The acid end of the process before ion exchanging offered some particularly severe conditions.
2072
All of the proce>s tanks were fabricated froin Type 304 stainless steel. T h e e n t r y chamber, the converti n g coils, t h e flash chamber, and the evaporators were constructed of 420 Herculoy. Filter presses were made from an acid resistant bronze of 85-5-5-5 9% (copperzinc-lead-tin) composition, P r o c e s s p i p i n g was of copper with acid resistant bronze fittings and valves. For severe s ervi c e c o n d i t i o n 9 , rubber-lined pipe and hard rubber cocks were used. Copper piping gave the most trouble with complete failure a t some points after 14 months' service. Stainless steel Type 304 pitted sevcrely for bome service conditions, particularly where acidified starch qlurries were handled. Pump maintenance a t the converter and filter press stations was the most scrious mechanical problem. P u m p requirements of 50 t o 100 pounds per square inch head a t 2 to 4 g a l l o n s per minute for h o t , acidified, abrasive-bearing solutions m-ere stringent c o n d i t i o n s . For this work, a RLoyno p u m p , of T y p e 3 1 6 stainless steel construction for all parts in contact with the solution except for a rubber stator, was the most suitable. Gear pumps of acid resistant bronze failed quickly; centrifugal pumps suitable for these operating conditions were not available and duplex steam pumps were not applicable because of pulsations where flow control instruments were used. Steam-jet heaters for heating the starch slurry for conversion were a source of trouble. Acid resistant bronze (85-5-5-5oJo) and Everdur heaters lasted on the average of 500
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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
2074 EVAPORATORS
PRESSES,
CONVERTER:
shown in Figure 1 was modified to include a third crystallization step, preceded by necessary reconversion and refining operations. This was accomplished b y storing process liquor in tanks and crystallizers and re-using the regular process equipment. Rubber hose connections were used where necessary for carrying out the additional process steps in the regular equipment. A number of strategically located holes in the floor were provided during construction for running temporary connections.
EXCHANGER
TABLE I. CLASSAND AREAOF RESPONSIBILITY FOR
lkLA==A
NONTECHNICAL OPERATORS
LOCKERS EVAPORATORS 7
SUPPLIES?
Supervisor (day shift) Shift foreman
Class A oDerators Converter operator
i""
*"L SCREEN?
CRYSTALLIZER&
Ion-exchange operator Evaporator operator Class B operators Crystallizer operator Centrifugal operator Utility operators (2) Clerk (day shift)
r-iI
Vol. 41, No. 9
Instrument mechanic (day shift)
Responsibility Coordinates and checks operation of all shiftsrequests, checks, and approves needed main: tenznce work Coordinates and maintains smooth operation of pilot plant according to specified procedures; checks information and data collected for accuracy and completeness; trains employees for new jobs Operation of converter and clarification station (all operators collect samples and data a t their area of activity and keep station clean) Operation of ion-exchange station Operation of both evaporators (one manual) Filling and dropping crystallizers and adjusting cooling water rates t o maintain desired cooling schedule Operation of sugar centrifugal and sugar drying system Operation of carbon-treating stations, pulling and cleaning filter presses, and bagging sugar Assembles operating data and averages in a form more easily handled by the supervisor and technical men Assigned by instrument maintenance section t o pilot plant for minor repairs chart changing, inking, and instrument adjusiment
i"' PACKER,
CRYSTALLIZERS
CENTRIFUGE2 '3D)
SECTION 'D-D* LOOKING WEST
Figure 3.
General Equipment Arrangement i n Dextrose Pilot Plant
operating hours. A heater of type 316 stainless steel construction lasted approximately 5000 hours with minor replacements, A porous carbon heating tube of special design was satisfactory. SPECIAL DESIGN FEATURES
Basic equipment to meet the process conditions shown in Figure 1 was installed. I n addition, where alternate process variations were well conceived, special piping and equipment also was provided at the start. Free floor area, extra motor starters, extra electrical services, and other provisions were allowed-for example, plate-and-frame filter presses were installed to carry out basic operations, but where studies were needed a t separation steps, a portable rotary vacuum filter was temporarily installed or process liquor was transported from the pilot plant t o equipment in other buildings for special studies. B s an example of the flexibility provided, t h e flow diagram
Another variation of the general arrangement of equipment is shown in Figure 9. This arrangement required the installation of additional converting equipment. Basically, the process shown in Figure 9 was made feasible by the use of ion-exchange materials. I n this process, the mother liquor from the first crystallization step is returned t o the converting station. On reconverting the mother liquor (first greens), some of the by-products of the initial starch-to-dextrose reaction are shifted to dextrosein the equilibrium reaction. The reconverted hydrolyzate is blended directly with the primary starch hydrolyzate. Impurities are removed from the process a t the clarification step, the ion-exchange station, and the carbon treating operations. Because the arrangement is essentially a closed system, yields of over 90% art obtained. The balance of the yield (loss) is recoverable as byproduct materials other than dextrose. A closed system, such as shown in Figure 9, is a primary objective of the industry. OPERATION AND PROJECT PERSONNEL
The normal operating schedule for the dextrose pilot plant is 24 hours a day, 7 days a week. I n a plant of this size, handling fermentable liquor, the inconveniences caused by shutting down on week ends are great. Two operations in the pilot plant are usually evaluated over extended periods of operation-namely, ion-exchange performance and crystallization. Interruption of these operations generally gives misleading results. For example, the triple-pass, ion-exchange station is conditioned before shutting down t o prevent fermentation in the columns. On starting up subsequently, i t takes several days to get the system in balance. Results obtained before equilibrium is established are usually over optimistic. Crystallization data, on the other hand, are usually poor after an extended shutdown because of mechanical fracturing of crystals and color build-up while the full crystallizer or seed is held over a week end. From an operating point of view, i t is relatively easy to start up or shut down the plant, but i t takes about 16 hours before all
September 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
2075
or revised for greater clarity. The general areas of responsibility of the various operators are shown in Table I. COLLECTION O F DATA
Figure 4.
L
d
Raw Materials Supply Station
stations are operating. It is the desired technical information that is abused over a period of frequent interruptions. Operating problems a t the ion-exchange station and the converting station are aovered in more detail in other papers (4, b, 6). The pilot plant was designed by the development engineering group, with the cooperation of the instrumentation planning group and mechanical engineering department. Start-up operations were performed by the personnel of the operating group with technical assistance from the development group. Fundamentally, the development group was primarily concerned with evaluating the process, correlating information, planning operations to obtain necessary design data, and in general was responsible for all technical information required. The piIot plant personnel were responsible for smooth operation of the plant according to the plans laid out. Mechanical repair, maintenance, and all the usual operating problems and procedures were the responsibility of the pilot plant group. There was close cooperation between these two groups and the research department. The operating force was composed of nontechnical men. On night shifts, the shift foremen and operating men were on their own; on day shifts, the coordination of the work was handled by the project leader, a chemical engineer, through his assistants. Minor mechanical repair and adjustment were handled on the day shift by a handyman and an instrument mechanic. On night shifts, the shift foreman doubled as a handyman. I n addition to the operating force, special departments of the company made their services available. Mechanical work, other than the minor jobs, was performed by the mechanical section. Instrument maintenance, adjustment, calibration, and installation were handled by the instrumentation section. Because of the complexity of instruments used in the pilot plant, it was mandatory to have specialized group directly handle instrumentation problems. For operating the plant, a detailed, technical operating manual prepared by the development group was broken down by the pilot plant group for assignment to the various operators. Cards were posted at each of the operating stations outlining the work to be performed. As experience dictated, the cards were renewed with more complete instructions
Collection of data was divided into two classes: routine and special. For the routine operating data, mimeographed tables were made up for each station and it was the operators responsibility to fill in these data sheets each shift. These sheets supplemented information that was automatically recorded. On a number of the tables, readings were recorded from indicating instruments for checking the automatically recorded information. This system was modified later as the operators became better acquainted with their jobs. The information thus assembled was compiled by the clerk or was directly uaed by the develop ment engineers. Where special tests were run, the operating information was recorded in project notebooks or on special tables prepared for the job. Samples of process liquors were taken regularly on each shift. Generally, a large volume was collected from drip samplers and an aliquot portion of the large sample was submitted each shift to a chemical analytical section for analyses. Depending on the nature of the work, special samples were also taken. I n general, the only samples taken and analyzed by the pilot plant operators were those required for immediate operating needs. The normality of the converter starch, for example, was checked hourly and compared with the automatic control results. Operations a t the ion-exchange station (regeneration and rinsing) were largely guided by the operators’ analyses. For parts of the process operated semicontinuously, a sample was taken of each batch. Feed liquor t o the crystallizers, for example, was sampled for each batch dropped to the crystallizer. In a few cases, special samplers were devised. To take a sample directly from the converter coil, a small stream was discharged continuously through a cooling coil to prevent loss of vapor by flashing from approximately 70 pounds per square inch to atmospheric pressure.
Figure 5.
Converter Supply Tank and Controls
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Vol. 41, No. 9
substance, and dextrose equivalent. Key operatling data from the midnight to 8-o’clock shift were available by noon the following day. The time required to reach steady-state conditions and the normal duration of a given set of test conditions varied widely depending on the nature and scope of the test. For a process change that was expected to affect crystallization results, three crystallizer cycles under the new conditions were required to mask fully the effect of the seed used on the first cycle. Thus, a t least 9 days elapsed for first sugar and 21 days for second sugar before the information could be considered reliable. Another example of work requiring long operating periods were tests on new ion-exchange resins. Results obtained when using new ion-exchange resins were always much better than after the resins were used for a t least 50 cycles (fifty regenerations of each column). RESULTS OF PILOT PLANT OPERATIOK
Figure 6.
Ion-Exchange Columns
Despite precautions taken some phases of the opeiation occasionally would get out of control. These problems were recognized when analytical results were completed and the quality of the product could be studied. Since a lag of 2 or 3 days sometimes existed between sampling and reporting the analytical results, the damage done by incorrect operation was sometimes appreciable. A system was devised, therefore, t o have certain key analyses reported promptly. At the converter station, for example, such analyses consisted of normality, percentage dry
T4BLE
11.
QUALITY
Material
rator Feed t o first crystallizer Centrifugal cake Dried sugar (dextrose)
RESCLTS O F ?vfAhTFACTCRR FROM CORXSTARCH
A process was developed of sufficient merit to justify the construction of a plant about sixty times the capacity of the pilot plant,. Progress of construction and pict,ures of this new factory a t Corpus Christi, Tex., were published in a recent articlc ( 8 ) . Iiicluded in this plant was the new process, such as shown in Figure 9, for the manufacture of dextrose. The commercial plant was designed while development work was still in progress, but the basic steps were worked out satisfactorily before construction started. Over-all small scale predictions were verified by the pilot plant operation and gave results such as the averages for 1 month of operation shown in Table 11. But problems not encountered in earlier work were troublesome in the pilot plant. One of the major problems, discussed in previous papers ( 6 , 6 ) ,concerned the ion-exchange station where it was found that the initial performance of new resins was over optimistic as compared to results obtained after 300 cycles of continuous operat’ion. The problems were solved by t,he use of resins of suitable properties for the job and by special operating procedures developed in cooperation with the research group and the manufacturers of the resins. The process arrangement shown in Figure 1 brought out problems at, t,he second-sugar crystallization operation which were not
OF n E X T R O 5 t
(Process arrangement as in Figure 1) Dextrose Ash Equiv., bulfated), Colo~, Acidity, Moisture, % D.B.Q (-% D.B. Lovibondb PI€ 7%
...
...
42
0.20
44
1.9
...
0.05
9
3.4
...
, . .
0.13
0.6
4.4
92.3
0.13
0 7c
4.9
... ...
... ...
.
.,
White solid
..,
.,
White solid
. ..
...
16 8.5
Dry basis, ash-free. b As is Baume at 5 p H ; except as noted. C 2O BB. as is pH.
a
Figure 7.
Evaporator and Controls
September 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
encountered in the small scale work. By means of the pilot plant, repeated crystallizations, that showed effects not apparent in single crystallization trials, were possible. These problems were accentuated by recycled centrifugal wash water, condition of the seed used, dextrose content of the first-sugar mother liquor, and other conditions not easily controlled in small scale work. Adjustment of the over-all operating conditions did result in practicable second-sugar crystallization.
2077
Pilot plant operations also showed the value of automatic instrumentation-for example, continuous conversion of starch was made possible through the use of automatic controls. Test installations also were made that demonstrated advantages of one means of instrumentation over that of another and special problems of design and installation were investigated and solved.
STARCH r-ACID k-WATER
ACID-WATER-
CONV&TINC
RE CON~ERTING ~~N~~~iTi+-----------, SWEET ,j-D--$YlNG
+ + I-
WATER FILT
ING----------,
-I-----ION-EXCHANCF REFINING------, ;" "FYLCOL RlZlNG
ALKALI CARBON---
I
I
CAKE WASTE
%
WATER CRYSTALLIZING
YIELD=> 90%
M O T ~ ~ ~ ~ + . Q IRc - C E N , T & G i N C
h DRYING-SUGAR
Figure 9.
Process Flow for Alternate Dextrose Process
Cake and losses partially recoverable by usual factory practices
I n addition, the pilot plant was also used as a training ground for potential operators of the Texas plant. Company plants in this country and abroad are considering modernization of their processes and are installing or contemplating the installation of the new process or portions thereof. No cost comparison figures, other than estimates, are available on the savings to be realized by the new dextrose process. The most significant advance is the increased yield figure from approximately 82 to greater than 90%. Figure 8.
Pilot Plant Sugar Crystallizers ACKNOWLEDGMENT
1
d
A third problem encountered in the pilot plant operation that had a severe effect on t h e quality of the finished product was one of turbidity in process liquors. Grease from pump bearings and agitator bearings entered the process liquor stream; and although the quantity of turbid material was small, 1.5 grams per 600 pounds of dry substance in the liquor, the quality of the finished sugar was seriously impaired. This source of contamination was eliminated by using water seals on rapidly moving bearings and dry bearings on slow moving agitator shafts such as a t the crystallizers. Proper precoating technique on prove-up filtrations and an improved procedure a t the clarification station also aided in reducing the quantity of turbid material in the plant liquors.
Acknowledgment is made t o the following men who contributed t o the project: W. G. Burk, P. IC. Carrel], J. E. Dlouhy, W. L. Faith, R. C. Gardner, M. Handelman, W. E. Hill, H. Hinds, Jr., S. W. Kapranos, M. E. Kaufman, E. E. Klicker, A. Kott,and R. C. Swanson of the engineering group; S. M. Cantor, G. R. Dean, J. I. Frazier, J. B. Gottfried, and T. H. Newkirk of the research group; and the personnel of other departments of the Corn Products Refining Company, who contributed to this project. LITERATURE CITED
Cantor, 5.M., U. S. Patent 2,328,191 (Aug. 31, 1943). Ibid., 2,389,119 (Nov. 20, 1945). Copland, C., I b i d . , 2,109,585 (March 1, 1938). Dlouhy, J. E., and Kott, A . , Chem. Eng. Progress, 44, 399-404 (1948).
DISCUSSION
Value of the pilot plant in' the general development work on this process is shown by the nature of the pilot plant problems encountered. Problems of ion exchanging and crystallizing, if not solved in the pilot plant and carried over into the design of the large plant, would have caused considerable delay and inefficient operation. For this industry, new problems of corrosion and materials of construction were brought out by the pilot plant operations. Field corrosion tests in the pilot plant and equipment performance records kept by the operating group gave valuable information for use in designing the large plant.
Handelman, M., and Rogge, R. H., Ibid., 583-587. Newkirk, T. H., and Handelman, M., IND.ENG. CHEM.,41, 452-457 (1949).
Newkirk, W. B., U. S. Patent 1,471,347 (Oct. 23, 1923). Whitney, F. L., Chem. Eng., 55, 99-101 (1948). RECEIVED June 20, 1949. Presented a6 a part of the Pilot Plant Symposium before the Division of Industrial and Engineering Chemistry at the 115th Meeting of the AMERICAN CHEMICAL SOCIETY, San Francisco, Calif.
