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T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
It is much more difficult to automatically control the variable factors affecting time and rate of heating or cooling than to control the factors affecting temperature, except in continuous furnaces, the use of which is limited to conditions that permit a steady flow of material uniform in character.
Vol. 14, No. 11
industrial chemists. The reason for this is that gases are much more difficult to collect, handle, transport, and work with in the laboratory than solids or liquids. The compositions of gases evolved in many industrial reactions are still quite unknown.
THEHUMAN ELEMENT The great variety of chemicals subjected to the action of heat in the process of production, and the still greater variety in plant conditions requiring the use of different types of furnaces and forms of fuel or electricity, and the ever-changing methods resulting from development of the art make it difficult to indicate how these variable factors may be controlled without dependence upon the human element in' the conduct of such operations. The human element cannot be eliminated by automatic devices to control temperature, except in rare cases where the manufacturing routine does not vary in essential detail. Vaqiations in size, shape, weight, quantity, rate of flow, time of exposure, rate of heating, composition of material, or nature of the heating or cooling process, call for the exercise of skill and judgment on the part of the furnace operative, in order that the charge may be properly placed and heated. As long as the many variable factors governing production of heat-treated products call for the exercise of judgment, just so long will the human element be the ultimate controlling factor. The need of the moment is for operatives or supervisors qualified to understand and properly apply the principles that govern correct heating. It is in order to suggest, in view of the ever-increasing demand for better and cheaper products, that it is advisable for those concerned with the conduct of industrial heating operations to consider the importance of these variable factors and intangible values, and the simple principles affecting their control, because of their bearing upon the result sought in the form of finished product. The needs of the future can only be met with better methods of heating and handling, better equipment, and, above all, men properly qualified to select and use the equipment that is such an essential part of the means to the end.
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Most, if not all, automatic-recording gas-anaiysis instruments on the market in the United States are designed specifically for carbon dioxide in flue gas. The principle upon which they all operate is to measure a quantity of the gas, absorb the carbon dioxide, and measure the unabsorbed residue. When this principle is applied to gases for constituents averaging 1 per cent of the total, obviously, obtaining the result by the method of differences of relatively large numbers may lead to serious errors. For example, a difference in temperature of 3' C. between the two measuring vessels of an instrument operating on the volume change principle, occurring after the instrument has been adjusted. would cause an error of 100 per cent in the record of the amount of constituent present at a concentration of 1 per cent. In this paper we will describe an instrument adapted for direct determination of carbon monoxide or dioxide a t low concentrations, but which is also applicable, when suitably
Automatic Volumetric Analysis Carbon Monoxide Recorder By Guy B. Taylor and Hugh S. Taylor E I.DU PONTDE NEMOURS & Co , EXPERIMENTAL STATION, DEL. HSNRYCLAY,
HEMIOAL industry has been singularly backward in
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encouraging the development of automatic devices for control of operations. It has preferred in most cases to spend its energies on the development of rapid analytical methods which, when carried out in the works control laboratory, interfere with production to the minimum extent. There are no doubt many cases where routine analyses might be made by machines instead of by men, furnishing results more cheaply and quickly, or even recording them continuously. Often such machines might be capable of actually performing work in the plant, resulting in considerable labor saving as well as tending toward uniformity and high quality of product. Undoubtedly, gas analysis offers the simplest case for development of automatic analysis and control devices. On the other hand, manual gas analyses seem to be avoided by
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modified, to other gases and other concentrations. In principle it consists of mixing continuously measured volumes of gas with a liquid reagent and measuring the resulting electrolytic conductivity change of the solution. The novelty
Nov., 1922
THE JOURNAL OF INDUSTRIAL AND ENGINEERING
CHEMISTRY
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GAS ANALYSIS APPARATUS itOR
of the apparatus consists ,in the method of securing accurate control of the volume of the two fluids mixed. This method of mixing two or more fluids (gas and liquid, or liquid and liquid) makes it possible to make and record continuously any volumetric chemical analysis, if the resultant chemical or physical change can be recorded automatically. Among the chemical and physical changes which may be so recorded are electrolytic conductivity, hydrogen-ion concentration, temperature, density, thermal conductivity, etc. E. K. Rideal and H. S. Taylor' published the first account of gas analysis on the electrolytic principle. Their apparatus was designed for the determination of traces of carbon monoxide in hydrogen. The gas was passed over a preferential oxidation catalyst which converted carbon monoxide to the dioxide. The gas stream then met standard limewater in a glass tower packed with glass wool. The less concentrated limewater then flowed to an electrolytic cell, the electrodes of which were connected with a source of e. m. f. and a recording milammeter. K. von Haken2 developed a similar apparatus for carbon dioxide in flue gas. The accuracy of this type of apparatus obviously depends upon maintaining a constant ratio of gas and reagent flow. In the Rideal and Taylor apparatus, liquid was delivered through a capillary under a constant head and the gas flow controlled by a capillary flowmeter. Von Haken controlled his flows by acomplicated system of manometers and floats. These methods may be satisfactory for short periods and for clean dry gas. For most industrial gases, variation in pressure a t the point of sampling and dust in the gas make them inapplicable. The ratio device developed by us consists of two piston pumps driven from a common shaft and thus stroking together. One pump delivers gas and the other, reagent. The volume ratio of the two is independent of variations in the speed of pumping. Piston pumps require valves, and 1
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Analyst, 44 (1918), 89. angew. Chern., 8s (1920), 188.
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CARBON
MONOXIDB
in this case vaIves that never fail in their action and never slip. Mechanically closing valves of the ordinary types cannot be depended upon, especially when the bore of the pump cylinder is only a small fraction of an inch in diameter. This dificulty was overcome by the use of mercury traps as valves (Figs. 1 and 2). DESCRIPTION OF CARBON MONOXIDE RECORDER The recorder described below was developed for the control of a gas-fired furnace. Fig. 3 is a diagrammatic sketch of the original apparatus, which may be used to illustrate the working of the instrument. Gas from the furnace is aspirated by 1 and enters through pipe 2, which just dips under water in bottle 3. A continuous rapid bubbling is maintained. Pipe 5 is a safety tube where air may enter if any obstruction occurs in the line to the furnace. A portion of the gas drawn from the furnace bubbles through potassium hydroxide in 4 to absorb carbon dioxide. Carbon monoxide is burned to dioxide by hot copper oxide in quartz tube 6, heated by electric furnace 7. Device 8 contains concentrated sulfuric acid for partial drying of the gas to avoid condensation of water in the pump and valve trap. The ratio pumps are indicated in the figure by 9 and 10; 15 is the pulley wheel on the gear reduction operating the pumps, and 16 an electric motor. Tenth normal ammonium hydroxide in 12 is pumped to spiral 11 and there meets gas pumped by 9. In flowing down the glass spiral, carbon dioxide is absorbed, which absorption increases the conductivity of the ammonia solution directly proportional to the amount absorbed. This solution runs through, cell 17 and wastes through 19. Water in bucket 18 maintains the cell at a fairly constant temperature, and is supplied continuously by aspirator 1, RATIOPUMP-A plan and end elevation of the ratio mechanism are shown in Figs. 1 and 2. The bore of the solution pump is 3/16 in. and that of the gas pump in, The pins 31 are movable dong the diameter of the crank
