Abstract:
An NIR sampling system designed to provide a stable gasoline sample stream to an NIR analyzer. Preferred design elements include a temperature-controlled stream moving through an inverted coalesce whereby gas bubbles are removed through an overhead stream. Elevated pressure is used to reduce degassing as well. Two or more prototype fuels can be injected to calibrate the instrument over a range and prove accuracy before and/or after analysis of a sample.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of USSN07/800,788 filed Nov. 27, 1991 now abandoned. 
     U.S. patent application Ser. No. 506,391, filed Apr. 9, 1990, now U.S. Pat. No. 5,751,819, relates to the general field of the present invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of on-stream analysis, particularly to sampling systems designed to provide stable samples; e.g. of gasoline to an analyzer; e.g., a near-infrared analyzer, commonly class 250, subclass 343 or 341. 
     2. Description of the Prior Art 
     U.S. Pat. Nos. 4,575,488 and 3,961,898 each use an on-line analysis instrument with a debubbler upstream to separate bubbles deliberately added between sequential samples. 
     U.S. Pat. No. 4,963,745 to Maggard et al. determines research, motor, and pump octane by infrared absorbance. 
     SUMMARY OF THE INVENTION 
     1. GENERAL STATEMENT OF THE INVENTION 
     An NIR sampling system designed to provide a stable gasoline sample stream to an NIR analyzer. Preferred design elements include a temperature-controlled stream moving through an inverted coalescer whereby gas bubbles are removed through an overhead stream. Elevated pressure is used to reduce degassing as well. Prototype fuels are a central feature of the present invention and can be injected to calibrate the instrument and to demonstrate or improve accuracy before and/or after analysis of a sample. 
     2. Utility of the Invention 
     The present invention is useful for the preferred NIR fiberoptic probes and other NIR probes, but can also be used for salt plates, quartz curettes, transmission cells, and heavy metal fluoride fiberoptic materials; e.g., zirconium fluorides and for other methods of analysis; e.g., colorimetry and infrared, as well as Fourier Transfer Infrared (FTIR). Fourier Transform near infrared can be used. The invention can also be used with multivariate spectrophotometers that are calibrated by developing a correlation between their spectral data and a physical or chemical property by some other primary reference method, e.g. such as a knock engine, GC PIANO, etc. Details of multivariate spectrophotometric calibration techniques for NIR, mid-IR, FT-NIR, and FT-IR spectrophotometers can be found in U.S. Pat. No. 4,963,745 to Maggard; U.S. Pat. No. 5,243,546 to Maggard, and in the references cited therein. 
     Essentially these techniques involve obtaining spectral data and developing a correlation using a statistical technique such as PLS, principle component regression, or multiple linear regression to develop the correlation between the spectral data and the physical or chemical property data of the samples obtained by some other analytical reference method. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of a preferred sample conditioning system according to the present invention. 
     FIG. 2 is a typical gasoline blending system showing various components and particularly showing line  30  leading to analyzer  25  which line  30  is also shown in FIG.  1 . 
     FIG. 3 is an elevation view of the rack and closed cabinet showing the components of the invention in place and also shown in side view in FIG.  3 A. 
     FIG. 4 is a side view of the rack and open cabinet showing the interior elements in place. 
     FIG. 5 is a detail of the inner cabinet of FIG.  4 . 
     FIG. 6 is a detail of the NIR sample assembly and connection to the fiberoptic cable. 
     FIG. 7 is a correlation curve of real octane (ASTM/2699/2700) versus octane measured by NIR octane, showing a lower line correlating only a single point and an upper line correlating at two points and hence over an entire range.) 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In preferred embodiments, the apparatus of the present invention consists of the following major components: 
     Sample supply means  20  comprising an adduction probe, a control valve and relatively small diameter (for minimum hold-up) tubing (preferably stainless steel) for withdrawing the sample from the stream to be analyzed. 
     Optional purge means  50  comprising an inward gas (preferably nitrogen) supply and valves and pressure gauges for permitting the purging of the entire system to clear liquids from the system for maintenance purposes. 
     Optional sample filter means  70  for removing particulates from the sample, said means preferably comprising a self-cleaning, continuous filter means, such as “Swirlklean”, Model No. II, manufactured by Collins Products Company of Livingston, Tex., together with suitable pressure gauges, flow indicators, valving and tubing. 
     Sample temperature controller means  90  comprising an inlet temperature indicator, a temperature controller, such as Filtrine, Model No. PC-50AXP-1LH, manufactured by Filtrine Manufacturing Company of Harrisville, N.H. for controlling the temperature of the sample to the preferred temperature range preferably in the room-temperature range, most preferably approximately 18°-25° C. (65°-75° F.) and additionally comprising suitable drain valves, outgoing temperature indicator, pressure indicator, and the like. 
     Degassing means  110  comprising a coalesscer, such as the Balston Model No. 45S6, manufactured by Balston Inc. of Lexington, Mass. and suitable flow indicators for rationing the flow through the analysis probe means  130  or back to the sample return means  150 . (Alternatively, heating in temperature controller means  90  can precede degassing, and cooling in temperature controller means  90  can be after degassing.) 
     Analysis probe means  130 , manufactured by NIRSystems Division of Perstorp Analytical, Inc., Model OL-5050 of Silver Springs, Md., comprising a chamber for introducing an analytical probe, preferably a near-infrared fiberoptic probe, pressure indicating means, back pressure regulator valve, and the like. 
     Optional, but preferred sample return means  150  comprising means for collecting both streams from the degasser means and from the degasser means and from the sample filter into a header, which in turn feeds to the stream from which the sample was originally taken by sample supply means  20 , but at a point having lower pressure. 
     Prototype fuel (protofuel) supply means  85  which preferably comprises a plurality of standardized hydrocarbons A and B, etc. analyzed by several different laboratories or matched to a “golden protofuel” so analyzed (by ASTM D2885). More preferably, two or more fuels having different octane (or cetane, etc.) are used as prototypes A, B, etc. The automatic valve  86  opens periodically to inject prototype A and then B sequentially to the NIR analyzer probe  131  (while automatic valve  84  is closed) and calculations are performed and results are automatically logged by the computer, then optionally, the calibrations are adjusted if necessary. 
     According to the invention, the probe sees a clean, degassed sample of controlled temperature and pressure free from particulate matter. Use of small diameter tubing, preferably less than one inch, more preferably less than one-half inch, and most preferably less than one-quarter inch insures timely delivery of the sample with minimum hold up because of fast flow through the entire sample conditioning system. 
     FIG. 2 shows the location of the sample conditioning system. The sample conditioning system is installed along with the “at-line” or “on-line” analyzer  25 , also described in U.S. Pat. No. 4,963,745, to S.M. Maggard and assigned to the assignee of the present invention. 
     EXAMPLE I 
     Invention According to FIGS.  1 ,  3  and  4   
     Referring to FIG. 1, sample supply means  20  includes eduction probe  29  which removes a sample from the approximate midpoint of the main process line and delivers it through sample block valve  34  into line  30 , also shown in FIG.  2 . Line  30  continues through purge supply means  50  which comprises a nitrogen source, a nitrogen control valve  54 , a sample block valve  56 , pressure indicator  58 , and enters sample filter means  70  which comprises a “Swirlklean” filter  72  (described above) having a capacity of about one gallon/minute. After this sample filter  72 , the sample flows through a bypass filter  72  to remove solids from liquid using a small pore membrane on the filtrate side, along with a high speed bypass to provide continuous self-cleaning. After this filter  72  having removed particles larger than one micron, preferably 0.45 micron, the sample flows past pressure indicator  74  and continues on to sample temperature control means  90  with particulates being removed at the bottom via line  76  which flows through flow indicator  78 , flow control valve  80  and process block valve  82 . 
     Continuing with the filtered stream  84  flowing into the sample temperature controller means  90 , the stream flows past block valve  92 , temperature indicator  94  into sample temperature controller  96  which is a prepackaged sample heater/chiller utilizing a high speed single pass flow design for heating/cooling liquids, Model No. PC50AXP-1LH, manufactured by Filtrine Manufacturing Co., and having a capacity of approximately 5 liters/minute, and set for a set point of approximately 24° C. (75° F.), and exits through block valve  98 , pressure indicator  102 , temperature indicator  104 , which is provided with suitable drain valves for maintenance. 
     The stream flowing from sample temperature controller means  90  into degasser means  110  continues into the degasser  112 , a stainless steel filter with replaceable filter elements for removing high solids content from liquids, and exits as a bypass stream  114  which contains most or all of the bubbles entrained into the stream entering the degasser and which flows through flow indicator  118 , needle flow control valve  120 , block valve  122  into sample return  150 . 
     Because of flammability and explosion hazard in gasoline service, all flow meters are preferably armored, rather than glass or plastic. Particularly preferred is a metallic rotated with a magnetic follower for flow indication. The other stream from degasser  112  is the debubbled stream  116  which flows through pressure indicator  124 , flow control valve  126 , flow indicator  128 , and through analytical probe chamber  131 . The NIR probe chamber  131 , manufactured by NIRSystems is a 3″×3″×2″ block of  304  series stainless steel with ½″  316  series stainless steel Swagloc tube fittings for sample inlet and outlet, and a ¾″  316  series stainless steel Swagloc tube fitting to attach the fiberoptic holder. The analytical probe chamber  131  contains a conventional fiberoptic or other probe for near-infrared or other analytical instrument and permits clean, temperature controlled, particle fee, debubbled flow past that probe for accurate consistent measurement of the analytical properties being measured. The stream continues through pressure indicator  132 ,back pressure regulator valve  134 , block valve  136 , and into sample return header  138  which has pressure indicator  139  and block valve  142  (located directly on the main process line) and flows back into the process line at a point somewhat downstream from sample supply means  20  and at a lower pressure than at the sample supply means. 
     The protofuel injection system  85  comprises automatic valve  86  and protofuel sources A and B, which can be alternatively injected into the sample feed line in place of the sample taken through automatic valve  84  (closed during protofuel injection) from the sample supply  32 . Protofuel is a suitable fuel of carefully determined octane (analyzed by ASTM 2699 and/or 2700, preferably by a number of different labs so that the average can be used). By injecting protofuel into the system periodically, the calibration of the system can be checked and standardized for exact accuracy. Stability can also be checked by repeated injection of protofuels. Preferably, two or more separate protofuels are made available so that protofuel A can be injected and then followed sequentially by injection of protofuel B. This provides two points of different octane as shown in FIG.  7 . Note that the lower correlation line shows a correlation only at a single point as determined by only a single prototype, whereas the upper correlation line shows a correlation at all points over the entire range as determined by two or more prototype fuels being injected, a substantial improvement over the one-point correlation line because it fixes the correlation curve so that it correlates with values obtained by the ASTM standard knock-engine method, over the entire octane range. More preferably, three or more prototype fuels are analyzed, so the correlation curve need not be a straight line; although a straight line has been found to often be an excellent approximation, based on extensive commercial use. 
     Unknown prior to this work was that it was possible to adjust a multivariate calibration equation derived from correlating tens to hundreds of samples of known chemical or physical properties to their corresponding spectra data by using as few as two or more readings on precisely characterized hydrocarbons, such as prototype fuels or protofuels described in ASTM D2885 or pure hydrocarbon compounds. 
     The adjustment used is the so called slope and bias adjustment taught in U.S. Pat. No. 5,243,546, Example 3. 
     Referring to FIG. 3, the external appearance of a preferred commercial embodiment of the invention for Division II, Class 2, Area Specification For Flammable Hydrocarbon Service, depicts stainless steel cabinet  300  displaying internal temperature on thermometer  302  with temperature being controlled by air conditioner/heater  304  and conduit connections  306  being provided for RS232 connection (direct or via modem) to a personal computer (PC—not shown) displaying the octane and other variables measured by NIR. External power enters through conduit  308  to the interior of the box. (This system can readily be upgraded to a Division I, Class 1 rating by providing fail-safe automatic shutdown in case of failure of air conditioning, cabinet purging or other critical components.) 
     Z-Purge pressure regulators  310  and  312  regulate the purge air pressure and flow into the cabinet as required by National Electrical Code, Class I, Division 2, for the electronics box  400  and for the lamp source box  402 , respectively. Bypass flow meter  118  and  128  measure the flow as shown schematically in FIG.  1 . Degasser  112  eliminates bubbles as also shown schematically in FIG.  1 . Sample temperature controller  90  houses the components shown under that number in FIG.  1 . 
     FIG. 4 shows cabinet  300  with its door open revealing inner NIR instrument cabinet  400  shown in further detail in FIG. 5, lamp  402  which provides illumination through fiberoptic reference cable  404  and fiberoptic sample cable  406 . Auxiliary power  408  protects the system electrically and provides and internal voltage regulator plus uninterruptable power supply. Auxiliary power  408  provides a steady 110 volts to transformer  410  which in turn provides 200 volt power supply to the NIR instrument and to auxiliary 12 volt power supply for the lamp  402 . The lamp enclosure  402  also includes a solenoid-operated shutter which alternates illumination through the reference fiberoptic cable  404  and then sequentially, through the sample fiberoptic cable  406 . 
     Cables  406  and  404  are held respectively by machined metal block alignment holders  428  and  430  which direct their beams fixedly into monochromator which disperses the light into different orders of the spectrum and into different wavelengths. Thus the monochromator  432  receives, first, the sample fiberoptic light beam  434  and then the reference fiberoptic light beam  436 . The sample fiberoptic light beam is conducted by a cable to the sample, and thence reflected back through cable  406  before entering monochromator  432 . This instrument arrangement is called “Post Dispersive Transflectance Measurement”. (The sampling system could, of course, operate with other types of NIR, infrared, colorimetric or other instrument schemes.) 
     The order sorter filter  438  also contains a new set of wavelength standards and functions to determine the order in which the wavelengths from the diffraction envelope focus on the detector  440  which outputs an electrical signal to transmission amplifier  442  which passes through various electrical circuits to the housed in  444  and  446 , and thence to motherboard  450  which outputs a signal to the PC and/or the process control computer (not shown). This signal preferably meets the standards of RS232 for compatibility with other equipment. 
     Probe chamber  130 , Model DL-6500 or OL-5000, and the connected NIR Analyzer are manufactured by NIRSystems, of Silver Springs, Md. The PIONIR analysis system by Perkin-Elmer can also be suitable for this invention. 
     EXAMPLE II 
     Invention Using FTIR 
     Apparatus similar to Example I, but constructed by substituting an Analect FTIR for the NIR spectrophotometer provides good accuracy in analyzing gasoline and diesel fuels for octane and cetane respectively and functions accurately in a controlled blend system similar to that shown in FIG.  2 . 
     EXAMPLE III 
     Invention Using a Diode Array Near Infrared Spectrophotometer 
     Apparatus similar to Example I, but constructed by substituting a Perkin-Elmer infrared spectrophotometer for the NIR spectrophotometer provides good accuracy in analyzing gasoline and diesel fuels for octane and cetane respectively and functions accurately in a controlled blend system similar to that shown in FIG.  2 . 
     EXAMPLE IV 
     Invention Using Mass Spectrophotometer 
     Apparatus similar to Example I, but constructed by substituting a Hewlett-Packard mass spectrophotometer for the NIR spectrophotometer provides good accuracy in analyzing gasoline and diesel fuels for octane and cetane respectively and functions accurately in a controlled blend system similar to that shown in FIG.  2 . 
     EXAMPLE V 
     Invention Using RAMEN Spectroscope 
     Apparatus similar to Example I, but constructed by substituting RAMEN spectroscope for the NIR spectrophotometer provides good accuracy in analyzing gasoline and diesel fuels for octane and cetane respectively and functions accurately in a controlled blend system similar to that shown in FIG.  2 . 
     EXAMPLE VI 
     Invention Using GC Mass Spectrophotometer 
     Apparatus similar to Example I, but constructed by substituting a GC Mass Spectrophotometer for the NIR spectrophotometer provides good accuracy in analyzing gasoline and diesel fuels for octane and cetane respectively and functions accurately in a controlled blend system similar to that shown in FIG.  2 . 
     Modifications 
     Specific compositions, methods, or embodiments discussed are intended to be only illustrative of the invention disclosed by this specification. Variations of these compositions, methods, or embodiments are readily apparent to a person of skill in the art based upon the teachings of this specification and are therefore intended to be included as part of the inventions disclosed herein. For example, the order of debubbler and temperature control is not critical, though debubbling is preferably downstream of temperature controller. Also, the techniques of copending USSN 698,411 (6379AUS) can be used in conjunction with the protofuel injection by utilizing as at least one of the protofuels a mixture of known amounts of pure hydrocarbon components having octane values calculated from results obtained from a calibrated NIR instrument so that the numbers previously determined for said components can be compared with the numbers obtained by analysis by the system under calibration. 
     Reference made in the above specification is intended to result in such patents or literature being expressly incorporated herein by reference including any patents or other literature references cited within such references.