SYMPOSIUM ON AUTOMATIC CONTROL Presented before the Division of Industrial and Engineering Chemistry at the 94th Meeting of the American Chemical Society, Rochester, N. Y.,September 6 t o 10, 1937.
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ODERN industrywith its increasing demand for greater precision is turning more and more to robot control. In this field our country is leading the way, and this development is creating a special branch of chemical science. The application of automatic control to industry generally brings about (a) more fundamental knowledge of the problem, (b) a better product, and (c) a reduction in cost of labor. The result of our thinking in terms of automatic control is having a profound effect in the industry. We used to believe that a specialized organic chemist should not think in terms of automatic control but should leave that as a refinement f,or the chemical engineer. We have all seen examples of a chemist who causes a difficult reaction to take place in the laboratory and is asked to write a report on his process. This report is given to a second chemist who follows it precisely but fails to obtain the same results. Nothing is wrong with the second chemist, but with the report or with the first chemist who does not consciously recognize the fundamental factors involved in the reaction. If he were asked to think in terms of automatic control for his process, oftentimes these fundamental factors would be forced into the open. This point is well brought out in the beginning of Grebe’s paper with an example of a person accurately adjusting the temperature of a thermostat on an oil burner in his own home. Such a person consciously or unconsciously goes through the processes of analyzing the automatic control problem. He deals with time lags. If one is never called upon to analyze these factors, he may not recognize them. It is a constructive sign that chemists are thinking more in ternis of automatization. There is a wide divergence of fields in which the principles of automatic control are applied, and the branches of industry which are served are too numerous to list. Temperature and pressure controllers are used to regulate steam boxes for setting the twist in silk, t o regulate the flow of water into gas condensers in gas works, and in cracking units and all kinds of distilling operations in the oil industry. Pyrometers of ingenious design are used for galvanizing, for carburizing steel, for gas-fired and oil-fired heat-treating furnaces, in the blast furnace in the steel mills, in core ovens in the foundry, in annealing furnaces, and in other numerous high-temperature operations. I n the field of synthesis, regulators are employed for carrying out chemical reactions such as nitration, sulfonation, and reduction. High-pressure syntheses usually require combination time and pressure instruments which have been evolved and are used with great success. So one can go through the gamut of industries and find that supplanting automatic instrumentation for the personal equation results in a smoother, steadier operation and greater yield of a more uniform product with a reduction in cost. Better products usually result when more fundamental
factors are realized and dealt with. I n fact, some syntheses and processes would not have been possible if the personal equation of operators had to be considered in the minute control necessary. The late Herbert Dow aptly pointed out this factor with an example of the oxidation of magnesium sulfite to magnesium sulfate, a reaction which had to be performed within narrow hydrogen-ion concentrations. Without automatic instrumentation this process might not have been possible as it is performed today. Economic advantages obtained by the adoption of automatic control is apparent when a few actual results are cited. I n the dyeing of wool the following benefits have been claimed : 1. Production was stepped up. In one plant production was increased from six runs per vat per day to ten to twelve runs per day. This increase was brought about without adding additional men or increasing hours. 2. The control system increased the tensile strength of the wool as much as 17 per cent because it was possible to hold the temperature at the scheduled point. 3. Uniform color was obtained throughout the vat without assistance from the dyer or floor men. 4. Steam saving was effected. The steam pressure was reduced from 80 to 40 pounds per square inch after a control system had been installed. 5. The control system freed the floor men and dyer for other work. 6. The control s stem made it possible €or the dye master to duplicate results Jay after day. The recovery of solvents has always been a vital factor in the economic soundness in any process employing them. It is interesting to note that a fully automatic process operation has made possible the recovery of over 98 per cent of acetone and hexane, solvents used by manufacturers in the impregnation of a felted fabric with a base mixture of Vinylite, rosin, and other ingredients. This solvent recovery plant is completely automatic in operation and control. The operation is turned on a t the beginning of the day and turned off a t the end of the shift in the evening. No attendants are required, but one man is usually kept in the building as a safety measure. He also supervises the refining of the recovered acetone. I n a casual inspection of European chemical plants, one is impressed with the number of men required for an operation as compared with American practice. Undoubtedly one of the reasons for this is the cheaper labor in Europe. However, Europe is aware of this new development. Particularly in England and Germany numerous examples can be cited of ingenious application of the principles of automatic control. J t is therefore timely that we hold this symposium under the CHEMICAL SOCIETY, on this new auspices of the AMERICAN field of development which is progressing so rapidly.
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CIIARLESALLENTHOMAS, Symposium Chairman
