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Home | Alpha Telephone | Domain Names | Web Hosting | Get Traffic | xrEvidence | xrSoccer United States Patent
METHOD AND APPARATUS FOR MATRIX-EFFECT-COMPENSATED CONTINUOUS X-RAY ANALYSIS OF STREAMS OF SOLID PARTICLES A method and apparatus for X-ray fluorescence spectrographic analysis of streams of solid particles, wherein a matrix-effect-compensated, chemical analysis readout is obtained by separating the stream into fine and coarse component streams, sensing the mass-flow of the component streams to provide respective signals representative of such mass-flows, comparing the signals and feeding a resultant signal to an X-ray fluorescence spectrographic analyzer as a corrective factor in its operation, and passing a corrected signal to the readout means of such analyzer.
Primary Examiner: Lawrence; James W. Assistant Examiner: Dixon; Harold A. I claim: 1. A method for automatically producing a continuous, matrix-effect-compensated, output signal from a standard X-ray fluorescence spectrographic analyzer having control circuitry and a density channel, which comprises dividing a sample stream, that is substantially identical in consistituency to the sample stream being analyzed, into relatively coarse and relatively fine streams; sensing the relative mass-flows of the respective coarse and fine streams; comparing such relative mass flows with each other to obtain a resultant signal; applying said resultant signal to the control circuitry of said analyzer as a correction factor; and feeding only one of said fine and coarse streams to the density channel of said analyzer. 2. A method in accordance with claim 1, but including maintaining both a constant density and a constant static head on the sample stream which is subsequently divided into relatively coarse and relatively fine sample streams. 3. A method in accordance with claim 2, wherein both the constant density and constant static head are maintained by the addition of make-up water to the sample stream. 4. In combination with an X-ray fluorescence spectrographic analyzer having control circuitry and a density channel, apparatus for automatically producing a continuous matrix-effect-compensated, output signal from said analyzer, comprising means for dividing a sample stream into two separate streams that are substantially identical in constituency, means for sending one of said sample streams through said analyzer for analysis, means for separating the other of said sample streams into relatively coarse and relatively fine sample streams; means for sensing the mass flows of the said coarse and said fine sample streams respectively, and for producing respective signals representative thereof; means for comparing with each other the said signal representations of such mass flows and for producing a resultant signal indicative of the ratio of one to the other; means for feeding said resultant signal to the control circuitry of said analyzer as a correction factor; and means for feeding only one of the relatively coarse and relatively fine streams to the density channel of said analyzer. 5. A combination in accordance with claim 4, wherein the means for sensing the relative mass flows of the coarse and fine sample streams are flow meters. 6. A combination in accordance with claim 4, wherein the means for comparing the signals representative of the mass flows of the coarse and fine sample streams and for producing the resultant signal is an electronic comparator. 7. A combination in accordance with claim 4, wherein means are provided for maintaining a constant density and constant static head in the sample stream to be divided into two separate streams. 8. A combination in accordance with claim 7, wherein the means for maintaining a constant density and constant static head comprise a mixing vessel, and means for adding make-up water to said mixing vessel. 9. A combination in accordance with claim 8, wherein the means for adding make-up water comprises an electrically operated valve responsive to electrical signals from the density channel of the X-ray analyzer. BACKGROUND OF THE INVENTION 1. Field The invention is in the field of X-ray fluorescence spectrographic analysis of streams of solid particles, especially slurry streams, to provide readout of the chemical composition of the materials making up such streams. 2. State of the Art X-ray analysis of metallurgical and other materials to provide information as to the chemical composition of such materials by comparison of observed fluorescence spectrographic data with standard fluorescence spectrographic data previously obtained from known samples is a common technique, and well known apparatus is employed for the purpose. However, in dealing with such streams, as made up of fine and coarse solid particles usually carried in a liquid vehicle as a slurry, compensating adjustments in the readout data must be made to take care of the so-called "matrix effect," i.e., the fluorescence intensity (secondary emission) differences encountered when particles subjected to X-ray analysis are of different sizes. Normally, an X-ray fluorescence spectroscope is calibrated for a specific particle size and the sample of material subjected to analysis is as close as possible to that size. In the handling of streams of solid particles that are sampled on a continuous basis, where the maintaining of predetermined particle size is not possible or practical, it is customary to apply correction factors mathematically to the readout data obtained. Such correction factors are obtained from calibration curves prepared for different particle sizes, and are applied mathematically on a statistical basis after a separate screen analysis of the sample stream has been make. OBJECTIVE In the making of the present invention, it was a primary object to provide automatic compensation for the matrix effect in X-ray fluorescence spectrogaphic analysis of a continuously flowing sample stream of the material concerned and to provide a matrix-effect-compensated readout. SUMMARY OF THEINVENTION In accordance with the invention, the sample stream of solid particles to be subjected to analysis is separated into a relatively fine fraction and a relatively coarse fraction, advantageously by means of a particle size classifier such as a cyclone, and the separate streams are sensed to provide respective continuous signals representative of rate of flow. These signals are compared with each other, as by means of a standard electronic comparator, to provide a resultant continuous signal for feeding into the control circuitry of the X-ray analyzer as a corrective factor for the matrix effect. Corrected in this manner, the readout from the X-ray analyzer provides substantially accurate information as to chemical constituency of the material concerned. THE DRAWING The single FIGURE of the drawing is a flowsheet showing the best mode presently contemplated of carrying out the invention. DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT In the particular system illustrated, a sample stream of slurry is split off in any suitable manner from a main stream of a slurry to be continuously analyzed by X-ray fluorescence spectrographic techniques and is flowed into a mixing vessel 10, where it is subjected to moderate agitation along with any make-up water that may be required to maintain uniform density of the slurry and a substantially constant static head. A flowing stream 11 of mixed coarse and fine solid particles in liquid suspension is supplied continuously to the analyzing, i.e., assay, channel of a standard X-ray spectroscopic analyzer, as by means of any suitable piping or other conduit means, and a similar stream 12 is supplied continuously to a classifier, preferably a standard cyclone 13. The latter stream 12 is separated into a fines fraction 14 and a coarse fraction 15, which fractions are then passed through respective flow meters 16. Only one of these fractions, preferably the fines fraction 14, is passed through the density channel of the X-ray analyzer before being returned to the process, and this is advantageously accomplished by means of a pump 17 pulling a constant flow from a sump 18 and discharging into an agitation vessel 19 which discharges directly into the density chanel of the analyzer. The flow meters 16 may be of any suitable type. A very satisfactory meter for the purpose is of electro-magnetic type, e.g., as manufactured by Fischer & Porter Co., utilizing voltage induced in the slurry when flowing in a non-magnetic tube placed in a magnetic field, the voltage induced being proportional to the flow rate and the field intensity. One of the flow meters 16 delivers a continuous electrical signal, representative of the rate of flow of the fines fraction, to an electronic comparator, which may be of any suitable type, e.g., Type 19-501 manufactured by the Control Products Division of Bell & Howell, and the other delivers to such comparator a similar electrical signal representative of the rate of flow of the coarse fraction. A resultant continuous electrical signal, representative of the ratio of the flow rates of fine and coarse fractions, is transmitted to standard X-ray analyzer control circuitry 20, which is customarily part of the X-ray analyzer as purchased commercially. The operating unit of the X-ray analyzer includes a scintillometer for obtaining X-ray fluorescence information from the X-rayed sample stream passing through the assay channel of the X-ray analyzer and for providing an electrical signal proportional to the emissions given off by the excited sample. The electrical signal from the scintillometer is fed to an amplifier in control circuitry 20 where it is amplified and given a bias level by reason of the connection to the amplifier of separate bias networks (designated for sake of convenience "first" and "second," respectively), which supply voltages proportional to the density of the sample stream and to the ratio of the flow rates of the coarse and fine fractions, respectively. The resulting signal is then applied to read-out means, such as an analog or digital indicator, which indicates the percent of desired particular metal present in the sample. The density of the sample stream being fed to the density channel of the X-ray analyzer is measured by the density gauge of the X-ray analyzer. An electrical signal proportional to the measured density is applied to the first bias network in control circuitry 20, which, in turn, provides a bias signal to the amplifier. The second bias network, also provides within the standard control circuitry 20, is provided with terminals to receive external connections. The resultant output signal from the electronic comparator is fed directly to such second bias network by way of these terminals (not specifically shown), and a second bias signal is fed into the amplifier from such second bias network. The signal from the scintillometer is thus provided with a bias level, which is effectively the sum of the first and second bias signals. To recapitulate, the first bias signal is proportional to the measured density of the fines fraction 14, which is the stream that is fed to the density channel of the X-ray analyzer. The second bias signal is proportional to the electronic comparator output signal, which is itself proportional to the relative flow rates of the fines and coarse fractions from the classifier. The final bias level, which is essentially the sume of the first and second bias signals, therefore takes into account the different particle sizes present in the analyzed sample. The application of this bias level to the signal from the scintillometer provides a signal that is corrected for the matrix effect of the analyzed sample, and, when applied to the read-out means, produces a substantially accurate indication of the chemical consistituency of the sample. The density gauge of the X-ray analyzer operating unit also delivers an electrical signal representative of density of the fines fraction to the density controller in the control circuit 20. Such controller, in turn, provides a signal to a make-up water control valve 21 so an amount of water required to maintain a constant slurry density and constant hydraulic head is added to the sample stream. This makes for optimum performance of the classifier. Whereas this invention is illustrated and described herein with respect to a certain preferred form thereof, it is to be understood that many variations are possible without departing from the inventive concepts particularly pointed out in the claims. For U.S. patent law, rules, and procedures see MPEP. Disclaimer. Information presented on this page while believed to be reliable, is provided "as is" with no warranties of its accuracy or timeliness. For legal advice seek help of a licensed professional. |