I
V. F. PFEIFER, V. E. SOHNS, H. F. CONWAY, E. B. LANCASTER, S. DABIC, and E. L. GRIFFIN, Jr. Northern Regional Research Laboratory, U. S. Department of Agriculture, Peoria, 111.
Two-Stage Process for
Dialdehyde Starch Using Electrolytic Regeneration of Periodic Acid Production of dialdehyde starch on an industrial scale requires a simple, economical, and reliable process. This process has given excellent pilot-plant results and should be suitable for commercial adaptation
D I A L D E H Y D E starch, a derivative applicable in such fields as leather tanning, paper coating, and tobacco binding, can be produced readily by reacting starch with periodic acid. Jackson and Hudson (5)studied the oxidation rate of starch and cellulose at 70' to 72' F.; they showed that the reaction with starch was quite specific in producing dialdehydetype oxidation. After investigating the effects of pH and temperature upon rate and specificity of the oxidation, Grangaard, Cladding, and Purves ( 3 ) concluded that a p H from 2 to 5 and a temperature not above 77' F. were the most suitable. The simultaneous oxidation of starch by periodic acid to dialdehyde starch and regeneration of the resulting iodic acid to periodic acid in an electrolytic cell have been described (2, 7, 9). These workers found that the oxidation required only about 0.1 mole of periodic acid per mole of starch treated, and was practically complete in 48 hours. Current efficiency was 56% at a reasonable anode current density. A cell in which starch oxidation and electrolytic regeneration of periodic acid occur simultaneously has been described (7). In this work, a two-stage process was developrd for the production on a pilotplant scale of periodate oxidized staich (dialdehyde starch) of over 90% dialdehyde starch content. The process employs iodic acid prepared electrolytically from Chilean crude iodine, as described by Mehltretter (8). Periodic acid is generated electrolytically from iodic acid, and the solution is mixed with corn starch to be oxidized in a separate vessel. After the reaction is complete, dialdehyde starch is removed and washed while the spent oxidant solution is recycled through the cells for regeneration to periodic acid. Cost estimates indicate that dialde-
hyde starch of high oxidation and alkali solubility can be produced to sell a t a price that will permit its use in many fields provided a reasonable sales volume is attained. Experimental Electrolytic Cell. Iodic acid was converted to periodic acid in an electrolytic cell equipped with six lead anodes and 14 cathodes. The cathodes were mounted inside porous ceramic thimbles. The anodes and cathodes were mounted in a wooden support and immersed in a poly(viny1 chloride) tank holding approximately 10 gallons of anolyte. Cell construction was similar to that described by Conway and Sohns (71, except that no provision was made for flushing the thimbles. Effluent from the cathode chambers dripped back into the anolyte solution so that very little change in p H of the anolyte liquor occurred. The anodes of 1% silver-lead alloy were '/s-inch thick, G inches wide, 11 inches long, and were submerged approximately 9 inches in the anolyte. Anode current density was about 0.15 ampere per square inch (0.024 ampere per square centimeter) so that about 100 amperes at 4.5 to 5.0 volts were required for the cell. Two types of porous ceramic thimbles of silicate bonded aluminas-Alundum (grade RA 84) and Burundite (1-micron pore size)-were used successfully. A selenium rectifier operating on 208-volt, 3-phase, 60-cycle a x . and delivering up to 150 amperes at a variable voltage up to 15 volts provided direct current. An air-driven agitator with Type 316 stainless-steel blades and shaft agitated the cell contents, and temperature was controlled by passing cold water through a lead cooling coil as needed. T o electrolyze a large quantity of liquor for pilot-plant scale starch oxida-
tions, a 55-gallon polyethylene tank served as a supply reservoir. The iodic acid solution was pumped at about 1 gallon per minute into one end of the cell; the overflow from the other end was returned to the reservoir. Oxidation Tanks. Small-scale starch oxidations were carried out in 3.5-gallon polyethylene buckets provided with lead cooling coils and stainless-steel airdriven agitators. I n large oxidations a 100-gallon open tank of Type 304 stainless-steel coated with corrosionresistant paint was used. The agitator was driven by a 0.25-hp. electric motor. Temperature control was obtained by a spray ring mounted around the outside top of the tank. Procedure for Starch Oxidation. The used oxidant solution from a previous run was electrolyzed in the cell at a p H in the range of 0.7 to 2.0 to regenerate periodic acid to the desired level. The oxidant, after settling hour to remove suspended lead dioxide, was pumped to the oxidation tank. 'Temperature of the oxidant was adjusted to the desired level, agitation was begun, and corn starch to be oxidized was added rapidly. The flow of cooling water was controlled to maintain the desired temperature. After the reaction was completed, agitation was stopped, the starch was allowed to settle about 1 hour, and the clear supernatant liquor containing up to 75y0of the iodic acid was pumped to the cell system for re-use. The remaining slurry was filtered or centrifuged, and the clear effluent containing most of the remaining iodic acid was returned to the cell system, usually with some wash water. Starch Recovery. Dialdehyde starch from small-scale experiments was recovered by settling and decanting most of the iodic and periodic acids. The VOL. 52, NO. 3
MARCH 1960
201
starch, filtered in 10-inch Buchner funnels, washed with water, and dried in a circulating hot-air oven at about 120" F. for 16 hours, was ground in a small hammer mill provided with a 0.020-inch screen. In large-scale experiments dialdehyde starch was concentrated by settling and decanting, rentrifuged in a suspended basket-centrifuge (26-inch perforated basket), washed with water in the basket, spun-dry (50 to 5470 solids), dried in forced-air ovens at 120" to 125" F. for 24 to 40 hours, and ground in a hammer mill equipped with a 0.033-inch screen. Preparation a n d Purification of Periodic Acid. Periodic acid prepared from Chilean crude iodine was used for starch oxidations with and without purification. The previously described cell was used to convert the crude iodine to iodic acid, then to periodic acid, employing the procedure of Mehltretter (8), except that a caustic catholyte was used throughout the electrolysis. During oxidation of iodine to iodic acid, anode current density was kept at about 0.4 ampere per square inch, and the temperature a t 90" F. The iodic acid was then converted to periodic acid at the usual anode current density of 0.15 ampere per square inch. The final filtered solution contained iodic and periodic acids equivalent to 93% of the crude iodine charged. Periodic acid prepared in the pilotplant cells, in which there was some contact with Type 316 stainless steel, required purification to remove traces of chromium by alkali precipitation of the paraperiodate at pH 11.5. The precipitate was washed by resuspending, settling, and decanting, and finally water and technical grade sulfuric acid were added to obtain the desired content of periodic acid at p H 1.0 to 1.5. When this procedure was carried out properly, loss of iodine amounted to 2% of the iodine treated. Methods of Analysis. The amount of dialdehyde starch in dried products was measured by the alkali-consumption method of Hofreiter, Alexander, and Wolff (4) employing a reaction time of 3 minutes at 70" C. and by the sodium borohydride method of Rankin and Mehltretter (70). Amounts of iodic and periodic acid in reaction solutions were determined by methods described by Mehltretter, Rankin, and Watson (9). Moisture in the solid materials was determined as the weight loss when 10-gram samples were heated at 120' C. for 1 hour in a forced circulation air oven. Because ready solubility in very dilute alkaline solutions is a necessary property in some known and potential applications for dialdehyde starch, it was a matter of concern to produce dialdehyde starch in a form soluble in dilute alkali. The behavior of dialdehyde starch when
202
: /
-
i
Renition Time, Hours
Figure 2. Oxidations conducted at 95" to 100" F. were sufficiently rapid for a commercial process
heated with water and dilute alkali is complex and has been reported previously (4, 6, 77). I n the course of laboratory studies of the properties of dialdehyde starch, Sloan and others (72) devised a simple method for determining solubility in dilute alkali. In this method, 1.5 ml. of 0.1N sodium hydroxide are added to 1 gram of dry dialdehyde starch, ground to pass an 80-mesh screen, in a 10-ml. beaker. The two are mixed at room temperature for 2 minutes, and the absorption of the liquid by the solid is rated from A to D as the first stage of the test-A for absorption to a dry crumbly mixture in less than 1 minute, D for an unchanged slurry. The beaker is then placed on a steam bath and heated for 2 minutes, and the solubility is rated from A to D as the second stage of the test-A for a clear solution, D for n o change except darkening. An alkali-solubility rating of AA indicates a product of excellent solubility, whereas a rating of DD indicates a preparation of low solubility.
investigated. The term "oxidation efficiency" referred to hereafter is the ratio of the actual oxidation produced, as determined by borohydride reduction, to the theoretical oxidation as calculated from the quantity of periodic acid reduced. Purity of Periodic Acid from Crude Iodine. Periodic acid solution free from metal ion contamination is essential to the efficient production of dialdehyde starch of high alkali solubility. Contact with all metals except the lead anodes should be carefully avoided in the iodine oxidation cells. When oxidation of crude iodine to periodic acid was carried out in a metal-free cell (except for lead anodes), the filtered solution without purification oxidized starch efficiently and yielded dialdehyde starch of high oxidation and alkali solubility. Periodic acid solutions contaminated with chromium by contact with the small amounts of Type 316 stainless steel used in the cells oxidized starch inefficiently, yielding products with low alkali SOIUbility. Small amounts of chromium dissolved from the stainless-steel components of the cell by the alkaline iodideiodate solution seem to be chiefly responsible for these difficulties. This could be only partially corrected by electrolysis over a long period to 99% conversion to periodic acid. Adequate purification of the 99% conversion solution was accomplished by the sodium paraperiodate precipitation procedure. Results of starch oxidations
Factors Affecting Starch Oxidation
Factors that affect oxidation of starch with periodic acid solutions were investigated : purity of periodic acid, temperature and p H of reaction, mole ratio of periodic acid to starch, and concentration of periodic acid. Methods for treating recycled iodic acid solutions for satisfactory re-use in the process were
Table 1.
Starch Oxidation Was Satisfactory When Purified Oxidant Solution W a s Employed"
Periodic Acid Solution Total eauiv. Conversion to HIOa, -% HI& %
Oxidation Efficiency,
%
6.2
74
74
7.5 5.8
99
88
loo*
93
Dried Product Dialdehyde Alkali starch, % solubility
82 92 93
a 18-hour oxidations a t pH 1.0, 8 7 O F., 1.2 HIO,/starch mole ratio. periodate precipitation.
INDUSTRIAL AND ENGINEERING CHEMISTRY
AD BD AA Purified by para-
D I A L D E H Y D E STARCH
3 1
1
1.4
Figure 3. Specificity of oxidation is difficult to control when mole ratio of periodic acid to starch exceeds 1.2
with periodic acid prepared from crude iodine in cells containing stainless-steel components and with purified periodic acid are listed in Table I. Reduction of periodic acid during the Oxidations is shown in Figure 1. Reaction Temperature. Results of experiments in which the reaction temperature was varied are given in Table 11, and the periodic acid reduction during these experiments is shown in Figure 2. Oxidation below 75' F. is probably too slow for comniercial use. At 104 F. the specificity of the reaction is impaired. These tests indicated that starch can be oxidized to over SOYo dialdehyde starch content in 2 to 4 hours by using a reaction temperature in the range of 95" to 100" F. Periodic Acid to Starch Mole Ratio. Table I11 lists results obtained when the mole ratio of periodic acid to starch was varied from 1.0 to 1.6, and Figure 3 shows the reduction of periodic acid during the oxidations. For a conimercia1 process a suitable mole ratio of periodic acid to starch is in the range of 1.05 to 1.20. When the ratio is above 1.2, oxidation efficiency decreases below 9070, indicating reaction beyond that of dialdehyde production.
Table II. Temperatures Ranging from 75" to 100" F. W e r e Suitable for
ReQCliOll Time, H O U r l
Figure 4. Rate of oxidation decreases with reduction of pH
Reaction pH. Table IV lists results of experiments in which the reaction p H was varied in the range of 0.7 to 4.2, and Figure 4 shows the periodic acid reduction. In these experiments the rate of oxidation was somewhat low at p H below 1.0. Handling properties of materials from runs carried out in the p H range 0.7 to 1.5 were superior to those carried out at p H above 1.5. These included ease of filtration, washing, drying, and grinding. The wet cake remaining after vacuum filtration retained excessive amounts of moisture when the p H of the reaction was above 1.5, and the dried product from this cake was usually somewhat horny and hard to grind. When dewatering and washing were carried out in a centrifuge, the moisture content of the wet cake could be reduced below 60y0, and the material could then be dried without becoming horny. When oxidation was carried out a t p H 4.2 with a total equivalent iodic acid content of 6.570, the finished reaction mixture contained appreciable quantities of crystalline sodium iodate. From these considerations it would appear that the p H should be kept low enough to prevent separation of iodate or periodate, but not so low as to affect the oxidation rate adversely. A p H in the range of 1.O
Starch Oxidation Dried Product r)ialdehyde starch, Alkali yo solubilitl 70" 96 89 ABb 80a 93 91 ABb 8Qa 93 94 ABb 8SC 100 96 AA 96c 98 97 AA 104c 93 98 AA Oxidant: 4.4% tot.al equiv. HIOS: 85% conversion: 1.2 HI04/starch mole ratio; pH 0.8. Product washed with hard water. Oxidant: 7.0% total equiv. HIOs; 77% conversion; 1.2 HIOJstarch mole ratio; pH 1.2. Starch Oxidation Oxidation Temp., efficiency, ' F. %
Table 111. Mole Ratio of Periodic Acid to Starch Ranging from 1 .O to 1.2 Was Satisfactory" Starch Oxidation Dried P r o d u c t HI04 Dialdestarch Oxidation hyde mole efficiency, starch, Alkali % solubilityb ratio % 1.0 95 92 AB 1.1 95 94 AB 1.2 93 94 AB 87 1.4 93 AB 1.6 81 92 AB a 20-hour oxidations at pH 1.0, 8 6 O F., 4.6% total equiv. HIOa, 82% conv. to HIO,. * Products washed with hard water.
to 1.5 appears suitable for a commercial process. Concentration of Periodic Acid. Experiments were conducted in which the concentration of periodic acid in the oxidation liquor was varied in the range of 4 to loyo, while keeping the mole ratio of periodic acid to starch constant. No significant differences were observed in the rates of oxidation with solutions containing from 6 to 10% periodic acid, and the reaction was only slightly slower at the 4y0level. A level of 7y0 total equivalent iodic acid was chosen for most pilot-plant work to prevent the separation of sodium iodate at 90' F. from spent oxidant solutions containing appreciable sodium sulfate. This concentration of oxidant is sufficiently low to allow good sedimentation of starch sluiries. If oxidant solutions are made with minimum amounts of sulfate or no sulfate, or if the p H of the oxidant is maintained below 1.O, considerably higher concentrations can be employed. Purification of Spent Oxidant Solutions for Re-use. After repeated recycling of oxidant solution or its use under improper operating conditions, it may become contaminated with metal ions and/or excessive amounts of soluble reaction products of the oxidation reaction. The alkali solubility of successive products tends to decrease, and at some point purification of the solution may be required, Trisodium paraperiodate precipitation is one satisfactory purification method, although it is rather wasteful of chemicals and usually rcsults in a loss of at least 2y0of the total equivalent iodic acid treated. Table V lists attempts at purification of a contaminated oxidant solution by heating, treatment with adsorbents, and precipitation of the paraperiodate. Heating the oxidant solution to 185' F. and maintaining this temperature for 1 hour was unsatisfactory. Treatment with fine or granular carbons was satisfactory; Fuller's earth was somewhat less satisfactory. Recycled oxidant solutions can be purified batchwise by contact filtration using carbon or similar industrial adsorbents. I t may be possible to adapt the purification to a continuous percolation method, although this has not as yet been successful. Some success was also attained in evaporating whole liquors and separating purified oxidant by crystallization. Pilot-Plant Process
Based on the results of the studies described above: a suitable set of operating conditions was selected for a pilotplant process which embodied good VOL. 52, NO. 3
MARCH 1960
203
Table IV. Best Over-all Results W e r e Obtained When Starch Oxidation Was Carried Out at pH 1.0 to 1.5 Starch Oxidation ~ ~ o i s t u r e Oxidain Dried Product tion Product DialdeeffiBefore hyde Alkali ciency, Drying, starch, solu% bility % PH % 90 50 92 ABb 0.7a 92 55 95 ABb 1.5" 2.55 87 65 91 CCb 0.7= 95 45 92 AAd 1.20 94 49 95 AAd 4.2e 96 56 98 AAd a Oxidations at 8 5 O F. with HIOd/starch mole ratio 1.2, 4.9% total equiv. HIOs, 80% conversion. Filtered on Buchner funnel and washed with hard water before drying. Oxidations at 85' F. with HIOd/starch mole ratio 1.1, 6.8% total equiv. HIOa, 80% conversion. Centrifuged and washed in centrifuge with distilled water before drying. ~
process control, simplicity of operation, excellent product quality, low lead contamination, and minimum loss of oxidant. The process starts with periodic acid, purified by the sodium paraperiodate precipitation procedure and produced from Chilean crude iodine. (The periodic acid solution should be prepared in a metal-free cell so that the filtered solution need not be purified before use.) Starch was oxidized at pH 1.2 to 1.4, a temperature of 100' F. for about 3 hours, and a mole ratio of periodic acid to starch of 1.1. The total equivalent iodic acid concentration was about 7%, and conversion of iodic acid to periodic acid was about 85%. Batches of starch oxidized ranged from 25 to 35 pounds. After oxidation about two thirds of the iodic acid was recovered by settling and decanting, and the starch was recovered and washed in a 26-inch perforated basket centrifuge. The centrifuge was loaded at 500 r.p.m. (approximately 100 X G), washed with distilled or deionized water a t 1 to 2 gallons per minute, and spun a t 1800 r.p.m. (appioximately 1200 X G) to a 50 to 54% solids content. Centrifugal force during loading and washing was kept sufficiently low so that no cracking of the cake surface occurred even though liquid drained well from the solids, and the cake could then be washed satisfactorily. Water required for washing free of residual iodate and acid amounted to about 15 pounds per pound of starch, of which the first 4 pounds were concentrated at 100' to 120° F. in an evaporator constructed of Type 316 stainless steel and re-used. After transfer to trays the wet cake was dried in a forced-air dryer for 24 hours at 120' to 125' F., and the dried product was ground in a hammer mill, using a 0.033inch screen.
204
Results of 11 consecutive oxidations carried out as described were extremely uniform: dialdehyde starch content after 1 hour of oxidation was 90%, after 2 hours 9475, after 3 hours 95%; recovery of product was above 98% of theoretical; oxidation efficiency was 99%. No purification of the oxidant solution was required under these conditions to maintain high alkali solubility of the product. Product from these pilot-plant operations had the following properties and characteristics :
and small amounts of metals were dissolved by the oxidant solution. The loss of iodic acid measured during 20 consecutive runs in the above series was less than 1 pound per 100 pounds of starch processed, about half of which occurred during evaporation of wash waters. Periodate oxidized starches having low contents of dialdehyde starch were also readily prepared. The process was carried out as described, but the ratio of periodic acid to starch was decreased to obtain the desired degree of oxidation. An excess of 2 to 20y0 periodic acid was used over that theoretically required, depending upon the particular conditions selected.
Dialdehyde starch content,
%
Moisture, % Residual acid, ml. Ar/4 NaOH per 5 grams pH, 5 grams per 100 ml. distilled water Residual iodate, ml. N / l O NaAOa per 5 grams Lead, p.p.m. Alkali solubility Screen analysis : On 100-mesh, % Through 100-mesh, %
95 (dry basis) 11
0.72 3.8
Discussion
0.04 65 AA
Dialdehyde starch of high oxidation and alkali solubility can be prepared by this two-stage process. Operating conditions for each stage minimize side reactions and maintain a uniform product, and recovery is carried out so as to prevent the loss of oxidant. The process has been demonstrated to be straightforward, reproducible, and efficient, and it yields a highly reactive material. Advantages of this "out-cell" process over the "in-cell'' process in which starch oxidation and electrolytic regeneration occur simultaneously in the cell include : improved control of process and product; lower production cost because of simpler cell construction and less critical diaphragm and agitation requirement; lower lead contamination of product by clarification of oxidant before use, thereby eliminating particles of lead dioxide shed by anodes; and higher current efficiency. I n addition there is much less possibility of lost
7.5 92.5
The reduced solutions resulting from the starch oxidations were returned to the electrolytic cell and were regenerated to 85% periodic acid conversion at a current efficiency in the range of 60 to 70y0 (anode current density of 0.15 ampere per square inch). Over 30 consecutive oxidations were made before contamination of recycled oxidant solution required its purification to maintain high alkali solubility of the dialdehyde starch. By using a metalfree cell and plastic, rubber-lined, or glass equipment throughout the processing, the number of possible recycles would undoubtedly have been greater. However, considerable stainless-steel equipment was used in the pilot plant,
Table V.
Recycled Oxidant Solutions W e r e Purified by Treatment with Adsorbents
Liquor contained 6.68% total equivalent H103, 90% conversion to H104, pH 1 .O Treatment of Solution ConverDried Product sion to Loss of OxidaHI04 total tion after equivaeffitreatlent ciency, Alkali Type of Treatment ment, % HI03, % % Acidity" solubility 96 2.8 AD None 88 98 2.8 AD Heated to 185' F., held 1 hr., cooled Agitated at 75O F. for 15 minutes with Nuchar C-l90N, filtered, and washed, 69 0 99 0.9 AA 1% Nuchar 86 0.1 97 1.4 AA A s above, 0.5% Nuchar 88 0 AA As above, 0.2% Nuchar Columbia activated carbon, Grade G, 10-24 29 6 mesh, 6% carbon used as above 84 1.2 AA As above, 1.0% carbon 89 0.4 AB 4As above, 0.2% carbon Fuller's earth, Florex XXF, 1% earth used 87 0 AA as above 91 0.5 AB 4As above, 0.2% Precipitation of sodium paraperiodate, 100 11 95 0.9 AA decant, redissolve
INDUSTRIAL AND ENGINEERING CHEMISTRY
...
... ...
..
...
....
... ... ... ...
..
.. *.
0
M1. N/4 NaOH/bgram sample shaken in 100 ml. distilled water.
...
... -
-
D I A L D E H Y D E STARCH in a metal-free cell so that no purification of the make-up oxidant is required, and the iodic acid loss is calculated at 1.570 of the weight of starch processed.
+ - + - + - t - + -
Table VI. Estimated Fixed Capital Investment of Dialdehyde Starch Plant Annual capacity 10,000,000 pounds product at 1 170moisture, 9570 oxidation Estimahed Delivered
cost
Item
I I
$
176,000 300,000 150,000 6,000
30,000 15,000
60,000 50,000 5,000 2,000
I+ 51 Warr Wash
I
I I I
n
I
ti. .. ..... I
I
m
m
I
I
Dialdehyde Starch A commercial process for producing dialdehyde starch can b e carried out in a continuous fashion
product or oxidant such as occurs in the "in-cell" process because of diaphragm failure, excessive temperatures, or the formation of free iodine from starch and oxidant in stagnant cell pockets. The two-stage process can be continuous by passing the oxidant-containing liquor through the cells with series flow to produce the solution of periodic acid, then mixing the oxidant solution continuously with starch or starch slurry, and passing the mixture through a series of tanks to provide 3- to 4-hour retention, concentrating the starch slurry in a continuous centrifuge, and finally separating the dialdehyde starch product in a bank of basket centrifuges operated in a manner to approximate continuous centrifugation.
Rectifiers, 1600-kv.-amp., at $1 lO/kv.-amp. 100 electrolytic cells Bus bars, accessories, distribution, switch gear, etc. Heat exchangers, 150 sq. ft., two at $3,000 Mixing tanks for starch oxidation, 4,000-gal., jacketed, agitated, 5 hp. each, vinyl clad, four at $7,500 Continuous centrifuge, nozzle type, 15 hp. Basket centrifuges, 48411. diameter baskets X 24 inches high, rubber lined, 15 hp., four at $15,000 Rotary dryer, Type 304 stainless steel Hammer mill, 20 hp. Bagger Evaporator, triple effect, 600 sq. ft. Deionizing installation, 2,000 gal. /hr. Strainers for centrifuges and iodine oxidation unit, four at $2,000 Paraperiodate precipitation tank, 15,000 gal., agitated and jacketed, 20 hp., vinyl clad Pumps, 25 required Instruments Conveyors Storage bins Feed tank for cellhouse feed, 12,000-gal., agitated, 10 hp., vinyl clad Feed tank for starch oxidation, 4,000-gal., vinyl clad Starch slurry feed tank, 4,000gal., agitated, 5 hp., vinyl clad Feed tank for concentrating centrifuge, 4,000-gal., agitated, 5 hp., vinyl clad Feed tank for basket centrifuges, 1,000 gal., agitated, 2 hp., vinyl clad Feed tank for evaporator, 4,000 gal., agitated, 5 hp., vinyl clad Iodine solution tank, jacketed, agitated, 2 hp., vinyl clad, 500-gal. Storage tank for finished periodic acid, 1,000-gal., agitated, 2 hp., vinyl clad Equipment, delivered
Costs.
A flow sheet for estimating
costs of production on a commercial scale by use of this "out-cell" process, employing operating conditions as described in the pilot-plant process, is shown above. I t is assumed that the plant will produce periodate oxidized starch of high alkali solubility having 95% dialdehyde starch content and containing llyomoisture in a continuous process and that operations will be conducted 24 hours per day 350 days per year, with allowance for repairs and other contingencies. The starch will be supplied from an adjacent com starch plant in the form of a slurry containing 3570 starch at an assumed cost of 5 cents per pound of dry starch, make-up iodic acid will be prepared from crude iodine
Installation of equipment Piping, wiring Other construction costs Contingencies, engineering, and contracting fees Building, 265,000 cu. ft. Land and improvements Fixed capital investment
VOL. 52, NO. 3
90,000
25,000
8,000
22,000 25,000 25,000 5,000
5,000 12,000 4,000 6,000 6,000
2,500
6,000 2,000 2,500 -$1,040,000 260,000 300,000 300,000
500,000 200,000 50,000 $2,650,000
MARCH 1960
205
~~
Table VII.
Estimated Production Cost for Manufacturing Dialdehyde Starch
Annual production 10,000,000 pounds of product at 1 1 % moisture, 95% oxidation; 24 hours/doy, 350 dayslyear; 24-hour operation = 28,600 pounds of product
Daily Cost
Cents per Pound of Product
Raw Materials Starch slurry, 26,100 Ib. dry starch at 5.0% Crude iodine, 283 lb. at 956 NaOH, 800 lb. at 66 NazS04, 65 lb. at lob HzSO~, 700 Ib. at 2.56 Total cost of raw materials
$1,305.00 268.85 48.00 6.50 17.50 $1,645.85
5.75
Utilities 100,000 lb. at 75 t/ 1000 lb. Steam Water 900,000 gal. at 7.5d/1000 gal. Electricity 38,400 kw.-hr. at 0.7k/kw.-hr. Total cost for utilities
75.00 67.50 268.80 411.30
1.44
75.00
0.26
$
Miscellaneous Factor Supplies and Expenses Labor and Supervision Operators 6/shift at $2.50/hr. Helpers 3/shift at $2.00/hr. Foreman l/shift at $2.75/hr. Laboratory technician, 820.00/day Superintendent, %38.40/day Overhead (Social Security, pensions, vacations, etc.) Total labor cost Maintenance Building and land, 2%/yr. of $250,000 Equipment, 5%/yr. of $2,400,000 Total maintenance cost Fixed Charges Depreciation Building 5%/yr. of $250,000 Equipment 10%/yr. of $2,400,000 Taxes and insurance, 3%/yr. of $2,650,000 Total fixed charges Working capital charge, 5%/yr. on $192,000 Replacement of diaphragms three times/yr. at $22,500 Replacement of anodes one time/yr. at $14,000 Total production cost
I t is assumed that the oxidant will be purified each 30 days by the paraperiodate precipitation procedure, although experience may show that purification is not required this frequently. In view of the impurities introduced by contact of the solution with stainless steel a n d the advantages of using nonmetallic equipment, metal-free cells a n d plastic, rubber-lined, o r glass equipment a r e used throughout the plant to prevent contamination of oxidant with metals. A detailed list of the land, building, and equipment (exclusive of steam generating facilities) required for a plant with an annual capacity of 10,000,000 pounds is given in T a b l e VI. T h e estimated fixed capital investment for such a plant is $2,650,000. Estimated production costs for this plant as reported in detail in T a b l e VI1 show a production cost of 15.6 cents per pound of product. This production cost does not include interest on the investment, profits, income tax, or selling a n d administrative expenses. For comparison the fixed capital a n d processing costs for producing 2,100,000
206
Annual Production, Lb. of Product 10,000,000 2,100,000 Land and improvements $ 50,000 $ 18,000 Building 200,000 55,500 Equipment, delivered 1 ,040,000 267,500 Installation of equipment 260,000 67,000 Piping and wiring 300,000 84,000 Other construction costs 300,000 84,000 Contingencies, engineering, and contracting fees 500,000 132,000 Fixed capital investment $2,650,000 $708,000 e
$
360.00 144.00 66.00 60.00 38.40 99.30 767.70
$
14.30 342.90 357.20
96
35.70 685.70 227.10 948.50 27.40 193.00 40.00
2.68
1.25
3.32 0.10 0.67 0.14 15.61
pounds per year of dialdehyde starch in a smaller plant are also summarized in Tables VI11 a n d IX. A production cost of 20.4 cents per pound of product and a fixed capital requirement of $708,000 a r e estimated for this capacity. T h e operations of the two plants are basically the same, and only minor differences occur in the charges for most items, b u t the charge for labor per pound of product is considerably more in the smaller plant. In small-scale production the production costs would, of course, be much higher.
Acknowledgment
The authors are grateful to L. A. Pope, J. C. Code, L. T. Black, a n d J. R. Langdon for their assistance in carrying o u t the described work. T h e advice of C. L. Mehltretter of the cereal crops laboratory of this division is gratefully acknowledged. literature Cited (1) Conway, H. F., Sohns, V. E., IND. ENG.CHEW51, 637 (1959).
INDUSTRIAL AND ENGINEERINGCHEMISTRY
Table VIII. Comparison of Estimated Fixed Capital Investment with Smaller Plant Costs for Producing Dialdehyde Starch-
95% oxidation, 11% moisture content.
Table IX. Comparison of Estimated Plant Production Cost with Smaller Plant Costs for Producing Dialdehyde Starch.
Raw materials Utilities Miscellaneous factory supplies and expenses Maintenance Fixed charges Labor and supervision Working capital charge Replacement of diaphragms and anodes Total production cost
Annual Production, Lb. of Product 10,000,000 2,100,000 Cents/lb. Cents/lb. 5.75 5.75 1.44 1.63 0.26 1.25 3.32 2.68 0.10
0.81 15.61
0.32 1.58 4.11 6.04 0.14 0.81 20.ss
95% oxidation, 11% moisture content.
(2) Dvonch W., Mehltretter, C. L. (to U.S.A., Secretary of Agriculture), U. S. Patent 2,648,629 (Aug. 11, 1953). (3) Grangaard, D. H., Gladding, E. K., Purves, C. B., Pafier Trade J . 115, No. 7, 41 (1942). (4) Hofreiter, B. T., Alexander, B. H., Wolff, I . A,, Anal. Chem. 27, 1930 (1955). ( 5 ) Jackson, E. L., Hudson, C. S., J . A m . Chem. SOC. 59, 2049 (1937). (6) Levine, S., Griffin, H. L., Senti, F. R., J . Polymer SLi. 35, 31 (1959). (7) Mehltretter, C. L. (to U.S.A., Secretary of Agriculture), U. S. Patent 2,713,553 (July 19, 1955). (8) Zbid.,2,830,941 (April 15, 1958). (9) Mehltretter, C. L., Rankin, J . C., Watson, P. R., IND.ENG.CHEM.49, 350 (1957). (10) Rankin, J. C., Mehltretter, C . L., Anal. Chem. 28, 1012 (1956). (11) Sloan, J. W., Hofreiter, B. T., Mellies, R . L., Wolff, I. A., IND. ENC. CHEM.4 8 , 1 1 6 5 (1956). (12) Sloan, J. W., Rankin, J. C., Hamerstrand, G. E., Mehltretter, c. L., Northern Regional Research Laboratory, Peoria, Ill., unpublished results (1958). RECEIVED for review September 4, 1959 ACCEPTED December 1, 1959 Mention of firm names or commercial products does not constitute an endorscment by the U. S. Department of Agriculture,
