ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT The electrical sensitivity required of the analyzer is low. Therefore, the usual howl.. automatic standardization to compensate for environmental effects is not rpquired to maintain an analytical accuracy of &0.01 weight % ’ water. Manual standardization based 011 daily laboratory infrared analyses is used Automatic standardization of this analyzer would be difficult because of sample handling problems. To check the analytical performance of the & , I - 201i! I I analyzer after installation, a laboratory inflared analysis for water based on the above spectral data mas developed and used a t the 10 , refinery. This 1s a base line technique using 0 IO 20 .30 PERCENT WATER (BY WEIGHT) 20 2 5 30 3 5 40 4 5 the 2.72-micron water absorotion band. WAVELENGTH -MICRONS Figure 7. Calibration for This liquid phase infrared analyzer has been Figure 6. Transmission CharacterWater in Sulfur Dioxide in continuous operation for several months a t istics of Analyzer Beams i t a present location in a sulfur dioxide-gas oil Phillips Infrared Analvzer extraction unit a t a refinery. Refinery personnel are using the analyzer as a guide for operating the extraction unit. During this period, manual tics of the quartz be checked before use in this analyzer. Since standardization based on the laboratory analyses has been rethe sensitivity of the analyzer depends upon the ratio of the transquired only a few times. mission of the sensitive radiation path to that of the reference path in the 2.7- to 2.8-micron region, this absorption is significant.
31
1
,ii b\,
--
References
Perfor ma nce h sample of liquid sulfur dioside from the extraction unit containing some hydrocarbon was analyzed for water by the Karl Fischer method and blended with known amounts of water for calibration of the analyzer. Figure 7 is the calibration curve obtained lvith these miutures.
(1) Renning, A. F..Ana2. Chem., 19,867 (1917) (2) Kratochvil, K. V., Petroleum Engr., 25, C13-15 (July 1953). (3) Mitchell, J., a n d Smith, D. &I., “.lquarnetry,” pp. 1-444, London, Interscience Publishers, 1948. (4) Pleskov, T. d.,Zavodskaya Lab., 5, 1319 22 (1936). RECEIVED f o r rryiew September 7 , 1933.
ACCEPTED
l r B r e i x 20, 1954
Continuous Infrared Analyzers GLENN
E. SMITH
Process Confrols Division, Baird Associates, Inc., Cambridge 38, Mass,
The negative filtering-type continuous infrared analyzer i s described operationally for both gas and liquid operations. Details of sensitization, calibration, and sensitivity to several specific gas phase applications are discussed. Sensitivity obtainable in the measurement of water in various organic compounds i s given. The application to determine monochlorobenzene in o-dichlorobenzene, acetic acid in acetic anhydride, and toluene in benzene i s described with discussion of sample flow rates and other operation parameter.
D
URING the past several years the negative filter-type, continuous infrared analyzw has proved its versatility and practicality in the successful monitoring of a lvide variety of gas streams in industry. Kithin the past 3 years this instrument has demonstrated its suitability for many liquid phase applications, both in the laboratory and in the plant.
Description The operating principle and the design (Figure 1) except for the cell thickness, remain as described by Patterson ( 1 ) . I n general, for liquid applications either component of any binary system may he monitored in the range, zero to loo%, with a sensitivity of, a t least, +~l$?’~. Limiting factors determining the minimum amount measurable may be small energy absorption of the compound sought and/or large energy absorption of the ve-
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hicle. Some fortuitous cases esist where the vehicle-dichlorodifluoromethane-has so litt,le absorption that sample cell lengths of several centimeters may be utilized, thus obtaining in the system a correspondingly large amount of the minor component sought. In general, however, sample cell lengths on the order of 0.5 mm. are indicated. For tertiary and more comples systems, success is dependent upon removal of spectral interferences, as it is for gas syatems. I n liquid applications the instrument is appreciably more critical of sample conditions than for gases. It is imperative that the combinations of t’emperature, pressure, and flow rate be such that no vapor is formed in the sample cell. This dictates low temperatures, high pressuree, and high flow rates for low boiling liquids. Primarily because of the relatively high specific heats of liquids, changes in sample temperat’ure and flow rate cause comparatively large deviat’ions from t,hermal equilibrium.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 7
PROCESS INSTRUMENTATION reading after a total of 8 hours. The above implies that rapid small changes and/or large changes over long time periods could be tolerated. The values found by test were 1' C. per 15 minutes for the continuous change and & 2' C. for the rapid fluctuations. I n conclusion, a number of tests of potential liquid applications are listed in Table I.
FILTER CELL
Table 1. Compound Measured
COMPENSATOR CELL
Figure 1.
H20
HzO H20 Ha0 Hz0 HCHO CHsCOOH CHsCOOH CnHsCHi C6HfiC1
Negative Filter Type Continuous Infrared Analyzer
For example, in monitoring a benzol flow in the laboratory a t approximately 5% toluol, a sample containing dissolved air was syphoned through the sample cell, This resulted in vapor formation in the cell (at 40' C.) a t flow rates to 20 ml. per minute with sample temperatures as low as 20' C. When the sample was degassed (by boiling) and subject to 1 pound per square inch gage flow rates as low as 5 ml. per minute and sample temperatures up to 50' C. could be used in a cell at 80 ' C. Subsequently, in monitoring 0 to 500 parts per million, water in circulating stream, extensive tests were made to determine more precisely the effects of varying temperature and flows. The effects were, in fact, long time transients. To illustrate: a dry benzol stream a t 30' C. was rapidly (15 minutes) brought to 70" C. Within this interval, the instrument made nearly a 100% scale excursion. With the sample held a t 70' C. the instrument recovered 90% in the ensuing 2 hours and returned to the correct
a
laboratory Tests of Liquid Analyses Vehicle CHsOH CHsCHOHCHi CHXCOCIH~ CsHe CClaFi Hi0 (CHsC0)iO CeHe CeHe oCeHG9
Length Cell, Mm. 10 10 0 2 2 0 20 0 0 0 0 0
0 2 2 2 5 5
Range Tested, %
Sensitivity,
40- 55 0-100 0- 2 0-,5000 0-100a
=tO.O05 10.01 10.01
38- 39 0-100 0- 50 0- 10 0- 10
%
A55
rir0.1n 10.01 fO.O1 f0.2
fO.l
=to,1
Parts per million.
~~
Summary
The negative filter-type, continuous infrared analyzer is applicable to a variety of liquid phase plant stream analyses. In monitoring liquids, variations in stream temperature, pressure, and flow are more critical than for gas streams. literature Cited (1) Patterson, W. A,, Chem. Eng., 59, 132-6 (September 1952). RECEIVED for review September 7, 1923
ACCEPTED May 11, 1954.
Application of Infrared Nondispersion Analyzer Refinery Process Streams L. HOLLANDER, G. A. MARTIN, AND C. W. SKARSTROM Standard Oil Developmenf Co., Linden, N. 1.
This paper deals with the application of commercially available nondispersion infrared analyzers to refinery process streams. The application work involves determining how to sensitize and calibrate a particular type nondispersion infrared instrument for an analysis, specifying the analyzer and associated sampling equipment, installing, operating, and maintaining the equipment. A specific application is presented, involving the measurement of 0 to 10% isobutane in a C4-C6 hydrocarbon stream.
T
HE petroleum industry is actively interested at the present
time in the application of continuous analyzers to refinery stream services. This interest stems from the high return on investment for this class of equipment due to decreased deviation from product quality specifications, increased efficiency of process unit operations, and reduction of storage capacity requirements. It is not uncommon for many of these applications to result in 1000% return on investment per year. Continuous analyzers are differentiated from conventional instruments (flow, temperature, pressure, and level) in that they July 1954
can be sensitized to measure specifically the concentration of a product or product contaminant in a flowing stream. Dielectric constant, pH, infrared absorption, and ultraviolet absorption measurements are a few of the methods that have been used for continuous analysis of refinery streams. Because plant-type infrared analyzers are versatile in that they have been sensitized to detect a single hydrocarbon in many complex hydrocarbon streams, they currently enjoy a favorable position in the continuous analyzer class of equipment. Infrared analyzers are either of the dispersive or nondispersive
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