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Economic Trend in the Chemical Industry’ Herbert H. Dow2 T H E D O WCHEMICAL COMPAXY, MIDLAXD,M I c I r
OR several thousand years civilization had its ups and downs depending largely on the number of slaves that were constructively employed. About one hundred and fifty years ago a new type of slave-the steam enginebegan to be a factor in the world’s progress. It was not evolved suddenly by James Watt. Steam engines had been used t o pump -water out of coal mines before James Watt -was born, but he improved the economy enormously and in many other ways made the engine so practical that it began to be used extensively, and laid the foundation for the great commercial expansion that made the British E m p i r e the manufacturer for the whole world. I think we can safely say that the old era was eclipsed by the new when manufactured products made by steam poner replaced the manually made necessities of life.
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Interchange System
States was the pioneer in big-scale operations on the interchange plan also tended to make us the pioneer in manufacturing the machine tools that would produce this extreme accuracy, and for many years we have been exporters of tools of this class. The application of this process soon made the United States an exporter of clocks, watches, sewing machines, and later of typewriters and adding machines. All s u c h manufactured products were of a character adapted for exploitation of the interchange plan to the greatest advantage, and today this advantage is best exemplified in the manufacture of automobiles. As a nation we still hold the lead that was initiated with the sewing m a c h i n e a n d Springfield rifle; it is this advantage in manufacture that has made us.a creditor nation and enabled us to be a large factor in introducing another great innovation that is destined to go down in h i s t o r y as the creator of the third great epoch in the march of c i v i l i z a t i o n . I refer t o h i g h wages.
The next epoch that revolutionized methods of manufacture and shortened the hours of labor was the method of manufacturing on the inPholo b y Blank-Sloller. Inc. terchange plan, whereby each part Development of Labor Savers in Herbert H. Dow a Chemical Plant of a coordinated m e c h a n i s m was made with such extreme accuracy Here again no one individual or that it would fit its companion part exactly without the use 01a file or other method of individual nation can claim the sole honor of making this great step hand treatment. Like the evolution of the steam engine, forward in the world’s progress; Switzerland and Japan, as the use of interchangeable parts did not come suddenly into well as Detroit, are conspicuous examples. High wages were the world a full-fledged process, capable of immediately forced more or less unwillingly on the manufacturer, and ousting its competitor, the hand-fitting process. Its great t o avoid too high costs he was compelled t o adopt every advantage existed only where thousands of pieces exactly labor-saving device possible. These improvements invariably alike were required, but there were no such cases a century had the ultimate effect of lowering costs, even if accompanied ago. When the sewing machine came into extensive use the with higher wages, but many of these labor-savers are justified opportunity presented itself and several New England manu- only in large-scale operations, and consequently are applicable facturers introduced the system. A little later, when the in greatest extent to the nation with the greatest market and Civil War made a demand for many thousands of pieces ex- to the firm with the most customers. The most conspicuous labor-savers in a chemical plant actly alike for the Springfield rifle, the great opportunity arose for a full development of the interchange system. Con- are: (1) larger equipment, to cut down the expense of chemitrary to the expectation of most of the authorities, an ac- cal control and operating labor per unit of product; (2) curate comparison with the hand-fitting system showed a automatic analysis, to save the labor expense of chemists marked reduction in cost, and the whole manufacturing world making routine analytical tests a t regular intervals and to beheld the dawn of the second great epoch that was destined secure results more quickly and more exactly, with the to put the United States in the lead as a manufacturing nation chance of error due to the personal factor reduced; (3) autoand incidentally give the average workman more to be thank- matic operation of the equipment, which is governed by the ful for than any of his ancestors. automatic analyzer, all leading to the final desideratum; For a time the interchange plan was handicapped by the (4) a continuous process which is both automatically confact that the machine tools employed were not, sufficiently trolled and operated. There are, of course, other means accurate to make a nice fit, and in order that there would be for labor-saving, such as the economic application of human no hand fitting the various parts were machined so that motion study, the coordination of supplies, and other ways the joints would be $1 little loose normally, in which case the for increasing the effectiveness of the human element, but off-size pieces could still be used. such measures are less important in operating large-sized This led to a long train of refinements in methods of manu- chemical equipment having a very large output per man facture, and the end is not yet, but the fact that the United employed as direct labor than in the case of machine processes involving manual operations. We shall consider here, thereReceived December 30, 1929. * President, The Dow Chemical Company. fore, only the large factors in labor-saving which make it
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Bromide P l a n t of Midland Chemical C o m p a n y
Vol. 22, No. 2
(August 31, 1900)
This photograph also accurately represents the Midland Chemical Company in 1893.
possible to pay higher wages and a t the same time give the consumer more for his money and also increase dividends. The one most important way to lower the labor cost of manufacture in a chemical plant is, doubtless, to increase the capacity of the individual apparatus unit wherever practicable. This is usually accomplished by first increasing the size of the units; then substituting a continuous process when the size is large enough to justify it, provided quick methods of analysis and control have been developed; and finally substituting automatic control for manual control. I n a product made on any ordinary machine tool it becomes necessary to increase the number of tools in proportion to the output, then to increase the number of operators in proportion to the number of tools emp!oyed, except that expensive automatic machinery can be used for very large scale production. In the case of chemical manufacturing marly of the steps involved are capable of being handled in enormously larger units than is now customary without m y increased cost of plant per unit of output and with no increase in labor costs, irrespective of the amount turned out. This is a great advantage that a chemical process has over a mechanical one, and applies to containers, mixers, fractionating columns, vacuum pans, gravity types of filters, and practically every continuous process. Let us suppose we are treating a 100-gallon tank with the proper cliemicals to carry out a certain chemical process. A small laboratory and a chemist are necessary in order to know the amount of treating material to be added. If the size of the tank were increased from 100 gallons to 1000 gallons, tlie same chemist and the same laboratory would accomplish tliat same end, but the unit labor cost of doing the treating would only be about one-tenth what it was with the smaller container, and yet even 1000-gallon tanks are puny compared with the 4,000,000-gallon tanks used fur oil storage. Why stop even with the practice of the oil m m . The waterworks reservoir is infinitely larger than an u;l tank. Apparently the size is limited only by the amount of material it is desired to produce, which in turn is limited by the demands of the market. Of course, it would be entirely feasible for a man to agitate the contents of a 100-gallon tank by hand. It is obvious that the 1000-gallon tank should require a mechanical agitator, and as the size goes up to that of the largest oil tank and then to reservoir dimensions, real engineering of a different order would have to be employed, but probably a continuous process would supersede
the big containers and reaction vessels long before the larger dimensions were attained. Brine and Bromine Plant Development a t Midland
A concrete example of the evolution of the oldest process of the Dow Chemical Company will illustrate the development that is going on in all of our methods of manufacture. The brine that is pumped from the ground consists of a saturated solution of calcium, sodium, and magnesium chlorides containing less than 0.2 per cent of bromine as bromide. It also contains a small amount of ferrous chloride and other reducing agents. The old method was to evaporate the brine, remove the salt, and then add the proper amount of oxidizing agent and distil the bromine. The objection to this method is that the salt made from this type of brine is very impure and is not salable a t the market price for good salt and ran only be made profitably where fuel of no vdne is available, such as waste from a lumber mill. In the late eighties such cheap fuel was to be found adjacent to the supply of bromine brine in Midland County. A new process that would use little or no fuel had an advan t a p that it did not possess in the boom lumber days. It was a t this time that the Dow process entered the field. This process in outline is as follows: The brine is oxidized to set the bromine free. The brine then has a light orange color, a strong odor of bromine, and is corrosive. Tliis brine, without heating, is passed down through a tower i n contact with an air current that removes the bromine by blowing out. The bromine-laden air is then broiight iiito contact with iron or an alkali solution and the bromine is thereby extracted from the air. This made a big saving in fuel required for evaporating the brine, which was the prillcipal expense item by the old process. In the first plant started in 1889 bleaching powder was used as the oxidizing agent. The brine was treated in large containers until analysis showed that the bromine was wbstantially all set free, and was then drawn off to a blowingout tower that worked continuously. The next step was to eliminate the big containers and make the whole process continuous and simultaneously substitute electrolytic oxidation for the bleaching powder and acid. This was accomplished by passing the brine through electrolytic cells located a t a higher level than the top of the blowing-out towers, whereby the bromine-laden corrosive brine would not have to be pumped and would
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INDUSTRIAL AND ENGINEERING CHEMlSTRY
flow by gravity through the towers as its bromine was being removed. It is a very simple matter to make an analysis for free halogen in brine, and if the determination showed too much oxidation, either the flow of brine was increased or the current used by the cells was decreased. The first method was to vary the amount of brine in accordance with the indications of the titrations, but later it was found more convenient and reliable to vary the electric current. This was most easily accomplished hy changing the speed of the engine driving the electric generritor, and for many years thereafter the operator changed the weights on the governor each half hour in accordance with the indications given by the brine analysis. In 1893 the bromide plant had absorption ton-ers that did not completely absorb all the bromine except when alkali had been recently added, and if there was too much conversion of the alkali into bromide and bromate there would be a big loss of bromine into the escaping air. In order to know whether the night shift had gone to sleep and let the alkali get too near saturation before replenishing it, the following device was installed: A very fine iron wire was stretched across the air outlet. If the bromine came through in abnormal amounts it would corrode the wire thus reducing its cross section enough to increase materially the electrical resistance, and it was the intention to devise instruments that would record this resistance. (This was before the days when good and cheap automatic recording apparatus was available.) However, it was found that the resistance would change only very slightly under some circumstances and under others the wire would be eaten entirely through, thereby preventing any further
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the absorption equipment was made so large and contained such a volume of alkali that it could not go far wrong between quitting time and morning, even if it were neglected; consequently the corroding wire was abandoned. In 1894 a laboratory equipment was so arranged as to give galvanometer indications of the amount of free chlorine in the bromine in this brine. The operation of this apparatus was based on the fact that chlorine in solution would produce a higher voltage than bromine. Designs were worked up for utilizing these variations in voltage to vary the speed of the engine automatically, thereby controlling the amount of oxidation of the brine; but it was not until many years afterwards that equipment was finally perfected that would accomplish this purpose in an entirely satisfactory way. Reliable equipment now on the market greatly facilitates the working out of such problems. This oxidation-potential equipment now appears to have found quite general application; in fact, i t is comparable with equipment for hydrogen-ion control. In retrospect, the bromine plant development consisted of substituting a continuous process for large containers in the first step of oxidation. The second step was changed from a batch blowing to a continuous process on the drafting board before the first plant was built. Then followed the substitution of automatic, continuous analysis for periodic titrations, and its application to suitable mechanism to make the analyzer automatically control the oxidation. The details of working this out are somewhat difficult to explain, but the principle involved can better be illustrated by a corresponding, although not altogether similar, process now operating continuously in our Epsom salt plant.
Airplane View of Dow Chemical Company
record being made. So the plans were changed and, instead of using an elaborate equipment, the wire simply supported a weight; then, if bromine came out a t any time during the night in a sufficient volume to weaken the wire materially, it would break off and drop the Q-eight and thereby prove that the operators were not attending to their business. This piece of apparatus was in use for some time, but later
Epsom Salt Plant
Magnesium hydroxide for many years had been a byproduct, and much thought was given to possible means for utilizing it. The process finally adopted is as follows: Sulfur dioxide gas is absorbed in magnesium hydroxide t o form magnesium sulfite or magnesium acid sulfite. This
e
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mixture is then oxidized to sulfate by blowing with air. We found that the acidity or alkalinity-or in other words, the hydrogen-ion concentration-of the magnesium sulfite solution was of utmost importance in carrying out the oxidation. It is well known that the oxidations of salts of lime, magnesium, iron, manganese, etc., are most easily attained in an alkaline medium, as in the re-oxidation of manganese salts in the Weldon process. I n the present case, however, although an alkaline condition would be desirable for effecting the oxidation, the magnesium sulfite unfortunately is almost insoluble in an alkaline solution and consequently would escape oxidation at a satisfactory rate when the suspension was blown with air. On the other hand, magnesium acid sulfite is readily soluble, but the acidity of the solution retards and may even stop the oxidation completely. In this dilemma we were finally led to a solution of the problem by the discovery that a mixture of normal sulfite and acid sulfite within a narrow range of composition could be oxidized a t a sufficiently rapid rate to make the process commercially feasible. It was important, however, to maintain the composition of mixture within the prescribed limits, if the oxidation were to be effected successfully. At this point the question arose-how to maintain the correct ratio of normal sulfite to bisulfite, when the proportions were constantly changing as the oxidation proceeded. Chemical analysis and control were hopeless. I n the first place, the mixture was of a muddy consistency, hard to filter, and incapable of showing a good end point with any known indicator. Then again, if a suitable indicator could have been found which would have made possible a sufficiently accurate titration, the usual methods of chemical analysis would have been too slow. Before the results could have been obtained, the composition of the mixture would have changed materially. However, the optimum ratio of normal sulfite to acid sulfite corresponds to a certain definite acidity of the solution-that is, to a definite hydrogen-ion concentration. By devising an instrument which would record almost instantaneously the hydrogen-ion concentration of the mixture in the oxidation tank, it became possible to follow the progress of the reaction closely and to maintain the correct hydrogen-ion concentration by suitable additions of magnesium hydroxide. Although the development of a satisfactory recorder required more time than was anticipated, the object was successfully accomplished. Now it has been so far improved that the recorder is caused to actuate a motor-operated valve which controls the feed of magnesium hydroxide added to the liquor. The whole operation of controlling the progress of the oxidation and the proper additions of hydroxide to maintain the correct acidity is carried out automatically. When the batch is finished, requiring about 8 hours, a workman opens a valve to empty the tank and then refills with fresh mixture t o start the next batch. At other times no operating labor is required except for occasional inspection. The automatic recorder functions accurately and without sleeping. It is not going too far t o say that this process would have been a failure but for the creation of automatic recording and control means, which have proved to be indispensable for maintaining the uniform conditions required for successful operation. Each one of the four vital factors in labor-saving in a chemical plant is well exemplified in the Epsom salt process. We use equipment of such size that it can run for an 8-hour period before dumping the batch. The analysis of the batch is automatically recorded continuously, presenting on a chart a clear history of the progress of the reaction. The automatic analyzer is employed to actuate valves to control the flow of materials added to the batch. Finally, the complete cycle of the process is carried out continuously and automatically without manual operation of any kind except
Vol. 22, No. 2
to open a valve to dump the finished batch. I n fact, it would no doubt require the exercise of but a little more ingenuity to contrive means to control the valves for emptying and refilling the tank, thus dispensing entirely with manual labor or operation. Perhaps we will come to that, but we are still old-fashioned enough to believe that a process should have some one to look after it, a t least once in every 8 hours. Brine Evaporation
We can now get a clearer view of the trend which development is taking by switching from the Epsom salt plant t o the much larger operations that accompany the evaporation of brine. It was not until a demand arose for calcium and magnesium chlorides that modern engineering was applied to this problem. The evolution was somewhat as follows: I n 1897 our company organized a regular engineering department with a civil engineer in charge. As these men were trained to design monumental structures, they had a hard time to think in terms of test tubes and beakers. This organization put us in shape to devise' large-scale evapora-' tors, and development on a large scale then began. The state of the art is now developed to such a point that evaporators are in use that will vaporize 20 tons of water per hour in single effect, from saturated solutions, with an available heat head of only 20" F., or more than 1000 pounds per minute if the heat head is raised to 30" F. Engineering conditions, as we analyze them, do not indicate the possibility of increasing this size or decreasing the heat head economically. Already the size is far ahead of present-day practice. However, if heating tubes can be made that are more uniform in texture and composition, so that when one tube begins to leak all are near the leaking point and ready for replacement, it may then be economically possible to make still larger evaporating pans and reduce the heat head. The principle involved may best be defined by examples, of which the following is typical: If the diaphragm of an electrolytic caustic soda-chlorine cell plays out only in one corner, the entire cell must be repaired. Our repair records for individual cells and our experience in operating the cells have shown that there is a limit to the size of cell which it is economical to build, taking into consideration the average frequency of repairs and the cost of disassembling a cell, repairing, and reassembling it ready for service. If diaphragms could be made so that they would wear out uniformly, there would be no such limit, because the cell could be operated "to destruction" and then discarded, while repair costs would be practically eliminated. In Midland this limit has been found to be 300 kilowatts per unit cell, each such unit comprising about 90 bipolar cells in a single assembly working a t 3.3 volts per cell and requiring but two electrical connections. One single brine feed, one hydrogen outlet, and one chlorine outlet suffice for each such 300kilowatt unit assembly. Fundamentally there is no essential difference between such a cell assembly and a single cell taking 300 kilowatts. The same principle limits the size of apparatus employed for many other purposes. Conclusion
Modern chemical processes are primarily the result of recent achievements in engineering practice. The chemical reactions involved in the Solvay process, as well as those involved in the blast-furnace reduction of iron ore, are today practically identical with those of fifty years ago, but the present equipment for carrying out these reactions differs enormously from that of the early period. The immediate developments before us point more and more toward the installation of continuous processing wherever possible. The examples described decidedly emphasize this trend.
