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ties into one department has been agitated and it is hoped that some day it may be accomplished.
Literature Cited (1) -\In.Public Health ASSOC. and d m . Water Works Assoc., Standard Methods for Examination of Water and Sexage, i t h ed.,
863
(3) Collins, TI-. D., Ibid., 12, 1181-3 (1920); E. S. Geol. Survey, T a t e r S u p p l y P a p e r 496 (1923). (4) Jackson, D. D., U. 8.Geol. Survey, Water S u p p l y and Irrigation P a p e r 144 (1908). ( 5 ) Massachusetts State Board of Health ReDort, 1890. (6) wrolman, -4beL and German, -1.E., J . Am. T a t e r w o r k s A s s o c . , 23,171-3 (1931).
1933. ( 2 ) Black, .1. P., Rice, Owen, and Bartow, Edward, ISD. ESG.
25, 811-18 (1933: ; Bartow, Edward, Black. -1.P., and Sanshurs, IT-. E.. Ibid., 25, 898-903 (1933). CHExf.,
RECEIVED April 16, 1935. Presented before the Division of Water, Sewage, and Sanitation Chemistry a t t h e 89th Meeting of t h e American Chemical Society, h-ew York, S . Y., .Ipril 22 t o 26, 1935.
How We Use Our Semi-Works CHARLES J. DARLINGTON E. I. du Pont de Nemours & Company. W l m i n g t o n , Del. *++2-
Since the main purpose of the semi-works is the development to a financially profitstage Of those processes which have been initiated in the laboratory, frequent detailed cost estimates by the semi-works staff are essential. There must be the closest co6peration between the research staff and the semi-works staff. Best results have been obtained by making the research chemist responsible for the development until the operation is on its can be feet, at which time the
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HIS paper is equipment to m a n u f a c t u r e many p r o d u c t s on s(;ales as devoted to a discussion of widely varied as those just menthe semi-works plants connected tioned. with the Jackson Laboratory, General Method the research laboratory Of the Employed Organic Chemicals Department of E, I. du Pant de Kernours &The m a i n f u n c t i o n of the Company. Least emphasis will semi-works is to attempt to debe placed on the physical set-up velop to a stage where they will b e c o m e financially profitable of the plants, because du l’ont those processes which have been problems are so widely diversiworked out in the laboratory. fied that a group of structures turned o,er to the semi-works operating 411 purposes for which the semiof quite varied character grown up around the original staff to handle until there is Some change works is used go back ultimately in its status. Finally, the frequent changes to this beginning. buildings. As a need for more \\-orking space has arisen, the occurring during the semi-works developThere are several subdiviment of most processes the presence sions under thib main purpose. n e w e r b u i l d i n g s hare been adapted to the problems which Semi-works procedure includes and advice Of an t h e p r e p a r a t i o n of srnall have been of importance a t that particular time. Looking back engineer a necessity. BY following these batches for sale, the testing on principles, the semi-worlis has proved its a larger s c a l e of p r o c e s s e s a t these Constructions from a later date, it is always posqible value to such an extent that now it WTould developed satisfactorily on a small s e m i - a o r k s scale, the to think that a much more suitbe imprlldent and recliless to retesting of p r o c e s s e s w h i c h able building should have been erected. Experience has shown, a process without have given satisfactory results however, t h a t i t is imposthe aid of the semi-works. previously on a s e m i - w o r k s scale but which have not funcsible to give a general out>line for semi-works construction to suit all circumstances. The tioned properly on a plant-size scale, the continued production type of building will always depend upon the specific service of materials needed only in small amounts, and such other required of it. operations as varying conditions cause to be presented to the The same comments apply equally well to the equipment semi-works from time to time. I n general, however, all contained in the buildings. Although much of the equipthese apparently different procedures can be grouped under the one heading described above. Therefore, semi-works ment is of standard types which are useful for a variety of work really begins in the laboratory. Our organization and operations, many of the pieces have been installed for special purposes. Accordingly, just as in the case of the buildings, procedure are set up on this basis. A point, that should be emphasized is the phrase “financially profitable.” Because it is impossible to state definitely that a semi-works should include any specific pieces of equipment. The size and kind of the paramount importance of profit in every n e ~ vventure, of equipment installed will always depend upon the use to great emphasis is laid on frequent studies of the economics of which it is to be put. -4wide variety of equipment needs the problem being developed. has been developed; sometirnes it has been desired to produce The operating staff consists of a chemical engineer in charge, batches on a 5-pound scale and a t other times to produce a group of chemically trained supervisors, and a force of exbatches on a 2000-pound scale. Our semi-works includes perienced foremen and operators. This staff is responsible
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for maintaining equipment and buildings in operating condition and for conducting the various operations in the manner to be described. I n close cooperation with this organization is an experimental mechanical engineer of wide experience, whose advice and help are a necessary part of the development of all processes. A force of maintenance mechanics and a group of control chemists are additional parts of the organization.
Functioning of the Semi-works When a decision has been reached by the management to look into the development of a new product, and when a preliminary laboratory survey has shown satisfactory prospects, the first step is the making of a preliminary cost estimate which will give an idea as to the probable cost of production. It is the job of the semi-works chemical engineer to provide this cost estimate on the basis of whatever information the research laboratory can furnish. This estimate covers the probable future plant manufacturing cost, based on the estimated sales of the product. In some cases the estimate is rather a routine affair because the desired product is similar in method of manufacture to some other product being produced in one of the existing manufacturing plants. In such a case the estimate can be provided simply by consulting the cost records and then by determining whether there ia sufficient capacity in existing equipment for its production. If additional equipment is needed, its cost can be determined easily from the cost of the existing unit. I n many cases, however, the process does not resemble any process already in operation. The preliminary cost estimate is somewhat more difficult and the consulting mechanical engineer begins to function. It is his job to furnish a probable cost of building and equipment. This figure must be quite tentative a t this stage, but it is sufficiently accurate to indicate whether or not the costs would be prohibitive. With the cost figure thus provided, the chemical engineer then completes the preliminary estimate. Provided the outlook is satisfactory, the research chemist then undertakes the laboratory development of the process. I n addition to determining material ratios and conditions of time, temperature, and pressure, it is one of his important duties to furnish data on materials of construction, on types of agitation, on thermodynamic studies, on possible hazards of operation, and on similar problems which will be encountered as soon as a larger scale production is started. With the information made available by the chemist’s research. a new cost estimate is now made bv the semiworks chemical engineer. This estimate includes both the probable cost of producing a small preliminary lot in the semi-works and also the probable cost of future plant manufacture. In all cases the advice of the experimental mechanical engineer is used in estimating equipment costs for these productions. No clear-cut line can be drawn between the completion of the laboratory research and the future semi-works developments. In many cases it is necessary for the chemist to make a number of larger scale runs in semi-works equipment before he can write a satisfactory operating procedure. If such is the case, these runs are considered part of the laboratory development. When the chemist’s preliminary work is finished and the cost estimates are made, there is usually a period of n-aiting while this information is being digested by the management and by the sales department. If the commercial possibilities of the new product appear favorable, a preliminary order is placed and the real troubles of the semi-works organization begin. The responsibility for the satisfactory production of this preliminary order lies with the research chemist. Although
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a semi-works supervisor is assigned to the operation to familiarize himself with it, and although operating labor and other facilities are provided from the semi-works operating force, nevertheless, the burden of proof for the successful production of the preliminary order lies upon the shoulders of the research chemist. Naturally this situation does not entirely release the operating semi-works supervisor from all responsibility. He must see that the equipment is prepared as desired and that the mechanics of operation are smoothed out. Also he must learn the process. Thus there must be very close cooperation between the research chemist and the semi-works supervisor, providing a double control over the operation. If the desired results are not obtained with the completion of the preliminary lot, the course to be followed depends somewhat upon the nature of the difficulty. If further laboratory work is indicated, the research chemist takes up this investigation, and semi-works operation is suspended until new results are obtained. The semi-works production is resumed then under the same dual control. When a successful lot has been produced, the operation is turned over to the semi-works supervisor for future production, and from that point he carries the main responsibility, the research chemist serving in an advisory capacity. With continued production the rough edges of the operation are smoothed off, and finally it settles down to a standard procedure. The chemical engineer then prepares a final standard cost estimate which is used until there is some change in the status of the operation. Such a change may consist of an increase in the scale of semi-works operation or it may consist of a transfer of the operation to a full plant-size operation, provided the demand for the product is sufficiently great. If the increase is in the semi-works unit, frequently additional units of the original small size are added, although a t times the installation of larger equipment is justified. And if the operation happens to fit into existing equipment, the transfer to a different scale is quite simple. This holds true also if the operation is removed from the semi-works to full plant-scale manufacture. But if a new installation is necessary, the procedure is more complicated. In such an event the design of the ne\\plant equipment is worked out in conference by the design engineers, the experimental mechanical engineer, the research chemist. and the semi-works staff. When the new plant equipment is ready for operation, it is often customary for the plant supervisor to follow the semi-works production for a Deriod in order that he mav become thoroughly familiar n-kh the operating peculiarities of the product. rind when the plant production is started, the research chemist follows: it in detail until satisfactorv oDeration is obtained. At times an operation which has been conducted satiifactorily on a plant scale suddenly runs into unexpected difficulties, and further extensive experimental study is needed. In this event semi-works operation is sometimes resumed. The conduct of such an investigation depends somewhat upon circumstances. If the plant supervisor has time, he follow the semi-works study, sometimes providing all the supervision needed. But just as often the operation is turned over directly to the semi-works staff again, and it is their responsibility in cooperation with the research chemist to find the trouble. Once in satisfactory shape again, the process is returned to plant operation as before. The responsibility for the conduct of a n operation which has been turned over to plant-size operation lies entirely with the production management. The semi-works assumes no responsibility for such an operation unless the production department makes a specific request for further semi-works study. NIost of the control and further research work on processes which have graduated, eo to speak, from the semi-
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works are conducted in the plant control laboratories, and actually it is rather a rare occurrence for a process to be returned t o the semi-works from the production plant. Thus far only the bare outline has been given of the procedure employed for handling our semi-works, and the procedure seems reasonably simple. But anyone with experience in the development of chemical processes knows that no outline can be followed 100 per cent. Circumstances alter cases here as elsewhere. Such an outline as has been given makes no mention of the dozens of details which must be settled in every process and of the scores of headaches which must be experienced before these details are developed satisfactorily.
Specific Cases The period of incubation in a semi-works plant is a most uncertain factor. With products of a fairly standardized type, such as azo dyes, ordinarily three or four batches in the semi-works unit are sufficient t o establish a satisfactory recipe for larger scale production. With some of the more complicated products, such as anthraquinone vat dyes, however, the period of semiworks development has sometimes run into several years before satisfactory conditions have been established. Much of this time has been consumed in the development of satisfactory conditions for intermediates as well as for the finished colors, and frequent process changes involving radical changes in equipment have lengthened out these developments. Severtheless, the net result has been the long period of elapsed time before it has seemed safe to make definite recommendations for expensive plant equipment. I n such cases the semi-works plant has been developed to a scale sufficiently large to take care of all current orders. In one case of a catalytic oxidation the experimental semiworks unit was used for over ten years before development had progressed sufficiently to warrant the construction of a plant unit. During such long periods of development, the contacts between the semi-works operating staff and the research chemist must necessarily remain very close. When unexpected difficulties are encountered, it is customary for the research chemist to follow the semi-works work for long periods. And when the difficulties have been of a serious nature, frequently changes in process have been found necessary to overcome the troubles. In recent years the development of hydrogenation operations has been another similar case. Because of the expensive equipment involved, it has seemed wise to install experimental semi-works equipment of a size sufficiently large to produce all the material needed during the period of introduction to the trade. I n this way it is anticipated that the operating details of the hydrogenation processes will be fairly well established before it is necessary to construct plant-size equipment. An experience in connection with hydrogenation equipment tends to illustrate the point that the difference between success and failure is often very slight. rls is frequently the case in high-temperature reactions involving high pressures, much difficulty was experienced in preventing leaks through the packing boxes. Apparently no packing would supply the service required. Finally the comparatively simple plan of water-cooling the packing boxes was adopted. Following that change, there was relatively little trouble with leaky packing boxes. One of the factors in recent years which have made a good semi-works development job more desirable than in previous years has been the growing tendency toward more pure products in all lines. A more detailed study of corrosion-resisting
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materials has become necessary in order that contamination from scale and other materials from the equipment may be reduced to a minimum; and similarly a more careful study of ways of removing contamination has become necessary. It is truly remarkable how grit from so many sources will turn up to make a dyestuff unsuitable for printing purposes. Bnd when the manufacture of rubber accelerators and antioxidants is undertaken, it appears a t times that the very air must be laden with copper, because this metal appears myssteriously from nowhere, apparently, and is found in the finished products in quantities sufficient to render them useless for rubber work. With a copper tolerance of the magnitude of 0,001 per cent for these products, increasing care must be exerted to obtain materials that will pass sperifications. In one case a paper chemical of high purity was desired. In order to avoid contamination from the salt used for salting it out, a salt of good grade was purchased for the operation. Upon final isolation of one of the early lots, however, the product was found to contain small floating particles and was rejected. A c a r e f u l e x a m i n a t i o n s h o w e d t h a t t h e contamination consisted of small particles of lint from the bags in which the salt was packed. This trouble was overcome easily by purchasing salt directly from the dealer in barrels instead of in bags. Similar difficulties have been encountered in the use of mill bags containing excess lint for grinding certain products of high purity. I n these cases great care in shaking the bags is necessary. I n addition to the problems involved in developing maqufacturing details and technic, many problems appear after the semi-works organization believes that it has finished with the material. A complaint was received from a customer to the effect that a product which should have given a clear solution gave a turbid solution. Since file samples of the lot in question appeared satisfactory, the customer was asked to return samples of the product. When these samples arrived, they were found to be packed in small bottles containing paraffined wafers under the caps. An investigation showed that sufficient paraffin had migrated from the cap t o the product to give the undesired turbidity. CORROSION AND EQUIPMENT PROBLEMS.Examples of some of the corrosion and equipment problems encountered in our semi-works will tend to emphasize the value of ironing out these details on a relatively small scale. One experience with lead equipment stands out vividly. A lead-lined autoclave heated with a lead steam coil was being used for an acid reaction under pressure. After continuous operation for some months, the coil failed and a new coil was inserted. This coil lasted for only a few weeks before it failed. This was the beginning of a period of real grief. Coil after coil failed in rapid succession without any reason being uncovered. Finally, a statement was found in an inorganic textbook to the effect that lead containing as much as 0.04 per cent bismuth is not very resistant toward sulfuric acid. Analysis of the faulty lead pipe indicated approximately 0.03 per cent bismuth. But when lead pipe containing only 0.005 per cent bismuth mas used, the failures stopped. Seedless to say, bismuth determinations became an important part of the analytical control on that operation. Another problem involving materials of construction was the case of a thionation in semi-works equipment. Laboratory data had indicated that the use of an iron condenser was satisfactory. But with such a condenser on the experimental semi-works thionator, very poor results were obtained, due apparently to particles of rust that had not been present in the laboratory equipment. When a stainless steel condenser was used in the semi-works, however, results were satisfactory.
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iin interesting situation developed a t one time in connection with a chlorination conducted in an enameled kettle. Results in the first runs made in the semi-works duplicated the chlorination time of approximately 18 hours found necessary in the laboratory. The operation was then suspended in the semi-works, and the enameled kettle was used for other purposes over a period of about 6 months. Then the original chlorination operation was resumed. The somewhat puzzling discovery was made that the chlorination could be completed satisfactorily in only 6 hours. While a number of these short-period chlorinations were being completed in the semi-works, the laboratory study was reopened in an effort to determine the reason for the difference. After some weeks of concentrated investigation it was determined that during the 6-month period of intermission the enameled pot had become chipped, and efforts had been made to patch it with a type of cement. When the chlorination was resumed, just enough of the cement came loose in each charge to act as a catalyst for that particular operation, and the speed of chlorination was accelerated. Future chlorinations were accelerated purposely by the introduction of small quantities of that ingredient of the cement which Jyas found to exert the catalytic action. An experience quite the reverse of that just mentioned developed in a chlorination of a different type being conducted in a brick-lined tub. In this case the chlorination refused to proceed. It was determined that the cement between the bricks was the cause of the difficulty since it acted as an inhibitor to the chlorination. When a cement of a different kind was used, the chlorination proceeded normally. Some years ago a laboratory investigation of an autoclave reaction was completed, and results in a 2-liter autoclave
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indicated that the use of the recommended conditions would give the desired yield and quality with a maximum pressure of approximately 100 to 150 pounds per square inch. Since a large batch was needed for further development work and since there was a t that time no suitable intermediate sized autoclave, it was decided to make one run in a 100-150 gallon autoclave which mas available in the works. This run mas started without any thought of possible trouble. When the temperature of the charge in the gas-fired autoclave was still about 50" C. below the desired reaction temperature, a sudden reaction occurred rvhich caused the temperature to rise approximately 125" C. in less than 5 minutes. During this period the pressure increased to about 1400 pounds, a t which point the operating force hurriedly opened a release valve and emptied part of the charge on the ground. Fortunately nothing worse occurred than a good fright for the operators and the loss of part of the charge. We might add parenthetically that with present mechanical arrangements such an occurrence mould work out quite differently, because, instead of the old type of blow-off valve to safeguard pressure vessels, metallic disks which rupture when the safe limit is reached have been used exclusively for a number of years. However, the point of the story is that a trial of this reaction on an intermediate scale would have uncovered this trigger reaction, and steps could have been taken to handle it p r o p erly. Once it was found, the difficulty was overcome by adding one of the reacting materials in small portion. Following that experience, no further arguments were needed in favor of progressing by intermediate stages from laboratory to plant-size operation. RECEIVED April 8,
1935. Presented before the meeting of the American Institute of Chemical Engineers, Wilmington, Del, M a y 13 to 15, 1935
GENERATING ST.4TIOIv OF THE
BROOKLYX EDISONC O M P A S Y
Courtesy, New York Edison Co
A large part of New York City's electricity supply comes from this, the most powerful steam-electric plant in the world, which has a capacity of 770.000 kilowatts, or more t h a n 1,000,000 horsepower. Opened in 1927, the station reached its present enormous capacity in 1932 with the placing into service of two 160,000-kilowatt turbine
generators, which appear a t the far end of t h e illustration. T h e photograph shows a view of t h e generating room taken from t h e east end. T h e installation of these two units, totaling 320,000 kilowatts, was hailed by the technical press a s one of t h e outstanding developments of the year in the electric light and power industry.
