INFRARED ANALYZER FOR MONITORING WATER CONTENT 374 F. W. Karasek and E. C. Miller CONTINUOUS INFRARED ANALYZERS 376 Glenn E. Smith APPLICATION OF INFRARED NONDiSPERSlON ANALYZER 377 L. Hollander, G. A. Martin, and C. W. Skarstrom APPLICATION OF BICHROMATOR INFRARED DISPERSION ANALYZER 382 Abraham Savitzky and Donald R. Bresky FIELD APPLICATION OF INFRARED ANALYZERS R. F. Wall, A. L. Giusti, J. W. Fitzpatrick, and C. E. Woad 1387 INSTALLATION OF CONTINUOUS INFRARED ANALYZERS S. H. Waiters. 1390 INFRARED GAS ANALYZER FOR BUTANE SPLITTER CONTROL 1393 R. L. Martin and B. W. Thomas SENSlTiZlNG NONDISPERSIVE INFRARED ANALYZER Elliot H. Woodhull, E. H. Siegler, and Harold Sobcov 1396 PROCESS MONITOR MASS SPECTROMETER J. K. Walker, A. P. Gifford, and R. H. Nelson 1400 ION RESONANCE MASS SPECTROMETER W. A. Morgan, G. Jernakoff, and K. P. Lanneau 1404 RECORDING DIFFERENTIAL REFRACTOMETER D. N. Campbell, C. G. Fellows, S. 8. Spracklen, and C. F. Hwang 1409
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HE field of process instrumentation has become a complex mixture of new scientific applications and well-designed instrumental arrangements, both of which employ many long established basic principles of simple instrumentation and process engineering. In reviewing the more recent activities in instrumentation that are of major interest to the petroleum chemist and industrial engineer, attention is directed a t new, improved, and expanded analytical tools and applications. By successful use of continuous automatic control instruments processing costs are lowered, product quality is raised, hazards to operating per-
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ULTRAVIOLET SPECTROPHOTOMETERFOR AUTOMATIC CONTROL G. G. Campbell and J. B. Godin AUTOMATiC SEDIMENT AND MOISTURE RECORDER E. 8. Delgass, J. M. Brocks, S. Kleinheksel, and A. E. Traver POTENTIOMETRIC INSTRUMENT FOR SULFUR DETERMINATION Henry Landsberg and Edward E. Escher AUTOMATIC INSTRUMENTATION FOR BENCH SCALE UNITS E. R. Rath BECKMAN FLOW COLORIMETER John F. Bishap and Ralph S. White
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ENGINEERING, DESIGN, A N D PROCESS DEVELOPMENT sonnel are reduced, and capacity for specification products is increased. iiutomatic control instruments perform their functions more often and with greater dependability and consistency than can be expected from human operators.
Infrared Analyzers and Spectrometers Most popular in the field of continuous recording analytical instruments are infrared nondispersion analyzers for both gaseous and liquid process streams. With few exceptions these instruments make use of the entire region of infrared energy and are sensitized to detect, measure, and record compositional changes for only one component in the mixture under test. Optical systems commonly consist of single sources with two emitted beams passing through various arrangements of filter, interference, compensator, and sample cells. Nonselective detectors such as bolometers and thermopiles depend upon filtration in these cells for sensitization to a specific component. Acoustical detectors are made selective by gaseous filling with the key component and depend upon a highly sensitive microphonic system to detect and measure pressure changes in the gas. These pressure changes in the detection gases result from compositional changes svithin the gas being analyzed. In general, nonselective detector instruments can be sensitized to single components in more complex mixtures than can be handled by selective detector instruments. On the other hand, selective detector analyzers usually have greater sensitivity to minute changes in key components. These infrared instruments are highly useful in both plant and pilot unit operations and in a few applications are employed for automatic control of a profess. During the past year three new-type continuous infrared instruments have made their appearance on the American market. One of these, in addition to having the double-beam characteristics with conventional sensitizing, possesses a third radiation beam in which a sprvodriven trimmer has been added to achieve a true radiation null a t the gas filled detector. The second is a dispersion instrument in which quantitative analysis for a given component is achieved by continuous measurement of the ratio of transmission at two preselected wave lengths. The third instrument is a multicomponent analyzer in which sequential measurements are made a t six predetermined wave-length positions. Applications that have been made with nondispersion analyzers include measurement of carbon monoxide or carbon dioxide in catalyst regeneration flue gases, ethylene in ethane, methane in propylene, isobutane in normal butane and isopentane, water in sulfur dioxide, nTater in freon, acetylene in methane-ethylene mixLures, and water in liquid hydrocarbons. Manufacturers of continuous type infrared analyzers and spectrometers include Baird ASROC.,Cambridge, Mass., Mine Safety Appliance, Pittsburgh, Pa., Phillips Petroleum Co., Bartlesville, Okla., Applied Physics Corp., Pasadena, Calif., Leeds and Northrup Co., Philadelphia, Pa., the Perkin-Elmer Corp., Xorwalk, Conn., and Liston-Becker Instrument Co., Inc., Stamford, Conn.
Mass Spectrometers In many chemical and pilot unit streams monitoring of a single component is not sufficient to permit rapid study of major operational variables or evaluation of more than one quality characteristic of a product. Because of the ever-increasing complexitv of today's industrial and engineering processes brought about by public demand for greater volumes and wider varieties of high purity products, it is often advantageous to know compositional values for mixtures containing as many as five to ten components. Most appropriate for this type continuous analytical task is the process monitor mass spectrometer. There are several reasons, however, why rather extreme caution has been exercized in the development and application of process mass spectrometers. These are: high cost, specialized maintenance, difficulty of ex-
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plosion-proofing, and absence to date of automatic computing facilities. I n spite of these uncertainties developmental work i c nearing completion on process mass analyzers and testing p: cgrams under continuous operating conditions are well advanced. Three different types of mass instruments are being built C U I rently Operational principles by means of which separation of positively charged masses is accomplished in these instruments 111clude: crossed magnetic field, ion resonance and linear radiofrequency sorting. Upon motion of constant energy particles a t right angles to a magnetic field, the mass groups experience a path curvature inversely proportional to their molecular weight. MasF selection of focusing for measurement depends upon either the ion accelerating voltage or crossed magnetic field strength. I n the ion iesonance instrument a spiraling motion caused by the intLraction of a periodically varying electric field, and crossed magnetic field permits one mass group only to reach a peripheral target. Mass selection depends on frequency adjustment of the 81ternating electric field. Operating without a magnet, separation of masses in the radio-frequency instrument results from the relationship of particle velocity and an electric field frequency. Xass selection may be accomplished by varying either particlc velocities (ion accelerating voltjage) or frequency of voltages a i applied to alternate grids along the linear path of moving particles. -4pplications for process monitor type mass spectrometers include analysis of such mixtures as: C: and lighter hydrocarbon., flue gas streams from reforming, hydroforming or catalytic CI aching operations, type analysis of hydrocarbon groups, plus deki minations for hydrogen, helium, oxygen, carbon monoxide, and c a -~ bon diovide An instrument built at Ohio State University hz. been used successfully for continuous recording on parent mas for carbon monoxide, carbon dioxide, and oxygen. Separate colleetois in a 60" crossed magnetic field tube were employed to 011erate three amplifiers, each with galvanometer and recorder asseinblies to measure the three components continuously. Instrument manufacturers associated with the development of process mointor mass instruments include: Consolidated Engineering Corp Pasadena, Calif., General Electric Go., Schenectady, N. Y , Phillips Petioleum Co., Bartlesville, Okla., Beckman Instrumenti, Inc., Pasadena, Calif., and Metropolitan-Vickers Electrical Cu Ltd , Manchester, Eng.
Ultraviolet Spectrophotometers Fiist used more than 10 yeais ago as n continuous recording instrument the ultraviolet spectrophotometer has not enjoyed the diverse applications experienced by other analytical plant instruments. Use of the ultraviolet spectrophotometer has been simple and straightforward. If a particular component or compounii type absorbs heavily at a particular wave length at which other romponents in the mixture do not absorb, the ultraviolet spectrophotometer can be applied readily and with confidence. Wavelength changing facilities are locked in position for the approplmtP absorption position, and the amplifier output or recorder respoiilr can be calibiated in terms of per cent or other appropriate units. Snalyses that may be performed by the ultraviolet analyzer include: butadiene in CI mixtures, isoprene in Cd and Cs mixtuic=, CQand Cl0 aromatics in gasolines, total aromatics in crude petioleum fractions: metallic elements in gasoline and oil may be niencured R ith the flame photometer attachment. Ultraviolet 111struments available for continuous recording a t a given nave length are manufactured by Beckman Instrument Go., Pasadena, Calif., .Spplied Physics Corp., Pasadena, Calif., and Process a n d Instruments Corp., Brooklyn, Y. Y .
Recording Refractometers Refractive index is a widely used physical characteristic b) means of which chemical and petroleum compounds or compound
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 7
PROCESS INSTRUMENTATION types may be identified and/or measured in simple mixtures. Use of this physical property is well established as an analgtical laboratory tool, but application of apparatus for continuous measurement and control of refractive index is still rather limited. A fairly wide variety of refractometer instruments and techniques are available. Refractometers for operation on liquids are of two general types-transmission and reflection. Transmission instruments require transparent samples and depend on direction of refracted ray whereas reflection or nontransmission refractometers operate on clear, semitransparent, or opaque samples and depend only on light intensity measurements. Transmission instruments make use of the critical angle, the hollow prism, and the differential refraction at an interface betwcen two liquids. Nontransmission refractometry depends upon intensity of light reflected inside a prism a t the prism-sample interface. In the critical angle instrument refractive index is measured in ternis of the critical angle a t which an emergent light beam passes from a sample prism interface. Total deviation of the emergent beam away from the entrance beam direction is a measure of the refractive index for samples flowing through a prism-shaped or hollow sample cell. Right angle prism-shaped sample cells separated by a diagonal film or interface provide a means for measurement of refractive inden difference between two samples. Deviation of a beam of light upon passing through the interface serves as a measure or comparison of refractive index between a flowing sample in one cell and a reference material in the other cell. Intensity of light reflected into the prism at a prism-sample interface a t an incident angle slightly less than the critical angle affords a means of measuring refractive index of nontransparent samples. Either photoelectric cells in bridge circuits or photomultiplier tubes may be used for converting light beam positions and intensities into electrical signals for monitoring and controlling refractive index of a process. Applications for recording rclfractometers include: total aromatics in paraffin naphthene mixtures, naphthenes in paraffins, styrene in Cs aromatic mixtures, butadiene product quality, and separation efficiency on chromatographic columns. Continuous recording refractometers have been built by Precision Scientific Co., Chicago, Ill., Phillips Petroleum Co., Bartlesville, Okla., Carbide and Carbon Chemicals Co., South Charleston, W. Va., Monsanto Chemical Co., Texas City, Tex., and Esso Standard Oil Co., Baton Rouge, La.
Viscosity Recorders Viscosity is an important physical property of fluids that may be eniployed for control of many chemical and petroleum refining processes. It is especially useful for monitoring the distillation of crude, for control of extraction or blending of lube oil fractions, and for evaluation of finished chemicals and high quality lubricants. Rate of flow and/or pressure drop upon passage of fluids through capillary tubes under controlled conditions of temperature have long been used as laboratory methods for determination of viscosity. Employing somewhat different principles three new viscosity measuring instruments have appeared on the market during the past 5 years. Operation of these instruments depends on the position of a float in a vertical flow line, rate of fall of an object through the fluid, and rate a t which energy is absorbed from a high-frequency vibrating metal strip. Each of these instruments operate under pressure, accommodate a wide range of viscosity, and can be arranged for continuous recording and/or controlling. Either temperature control or temperature compensating units may be purchased with each of these viscometers. Continuous viscosity instruments have been built by Shell Development Co., Emeryville, Calif., Fischer and Porter Co., Hatboro, Pa., Norcross Corp., Newton, Mass., and Bendix Aviation Corp., Cincinnati, Ohio. July 1954
Dielectric Properties and Meters Use of the dielectric property of fluids is gaining favor as an analytical tool in many present-day chemical and industrial processes. Like refractive index, its measurement is useful for monitoring only one component or one type of component in simple mixtures. On the other hand, dielectric constant effects are more easily measured electrically than are the optical phenomena associated with refractive index. For many hydrocarbons dielectric constants are proportional to the square of refractive indices, but for most compounds that contain atoms of oxygen, nitrogen, chlorine, or bromine, dielectric properties are much higher than refractive index values. Dielectric ronstant is measured in terms of the capacitance effect on an electrical condenser element in or around which the fluid is placed for test. Capacitance elements for more precise measurement of dielectric constant may be two or more insulated plates or cylinders in a closed container through vhich the test fluid flows under pressure. Capacitance changes in the sample (Bells resulting from dielectric constant changes in the filling fluid are measured by means of high-frequency oscillating circuits and frequency meters. Applications in which dielectric constant phenomena are bases for the measurement include: reaction kinetics, chromatography, thickness of plastic plates, solvents in oil, water in alcohols, aromatics in paraffin-naphthene mixtures, level measurement and control for liquids, and granular solids. Manufacturers of equipment associated with dielectric constant measurements are: The Foxboro Co., Foxboro, Mass., Robertshaw-Fulton Controls Co , Philadelphia, Pa., General Electric Co., Schenectady, X. V.,and Instruments, Inc., Tulsa, Okla
Miscellaneous Process Control Equipment and Techniques Closed-circuit industrial television may be extended lrom current uses in the heavy metal industries to chemical and petroleum process operations. It offers excellent advantages for remote and multiple viewing of hazardous and inaccessible operations or conditions. Application of radioactivity in measuring thickness of metal pipe and plates or thinness of plastic coatings on moving sheet material, in detecting corrosion or liquid level inside closed vessels, and in following flow of products through pipelines has been made during the past few years. With increased production, lo&er cost, and ever-expanding varieties of radioisotopes resulting from government atomic energy research, this field of measurement may find many applications in process instrumentation. Availability of automatic titration and polarographic equipment for laboratory spot sample analysis appears to be adequate a t present, but development and manufacture of instruments for continuous operation on flowing liquid streams has been somewhat neglected. One apparatus for measurement and recoiding of total or individual sulfur compounds in a flowing gas stream is being marketed. No doubt many other valuable titration applications exist in both chemical manufacturing and petroleum treating operations. Designed primarily for spot sample analysis, an x-ray abtiorption apparatus is available for rapid quantitative measurement of tetraethyllead in gasoline. rlutomatic control of a gasoline-tetraethyllead blending process could be achieved through use of this equipment. Precise temperature control has long been a serious obstacle in obtaining satisfactory and dependable operation of process stream analyzers. This is especially true for viscoeity, refractive index, and dielectric constant instruments. During the past 2 years much progress has been made in overcoming the problem of temperature control through use of temperature compensation elements as a part of measuring units.
INDUSTRIAL AND ENGINEERING CHEMISTRY
B. W. THOMAS
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