US 3561273 A
Description (OCR text may contain errors)
Feb. 9, 1971 A. J. TANILA 3,561,273
METHOD FOR CONTINUOUS SAMPLING OF A SLURRY FLOW Filed Nov. 8, 1968 /N VENTOR A IMO JUHA M 74 N/L ,4
ATTORNEY United States Patent 3,561,273 METHOD FOR CONTINUOUS SAMPLING OF A SLURRY FLOW Aimo Juhani Tanila, Pyhakumpu, Finland, assignor to Outokumpu Oy, Helsinki, Finland, a corporation of Finland Filed Nov. 8, 1968, Ser. No. 774,408 Claims priority, application Finland, Apr. 17, 1968, 1,055/ 68 Int. Cl. G01n 1/20 US. Cl. 73-423 3 Claims ABSTRACT OF THE DISCLOSURE A continuous sample of a slurry flow to be analyzed is obtained by continuously swinging the slurry flow back and forth in order to change the direction of the slurry flow so that the slurry flow only momentarily hits a sampling funnel. The portion of the slurry flow passing into and through the sampling funnel into a sample feeder for analysis is the sample flow. The level of the sample flow is maintained constant within the sample feeder by automatically regulating the opening of the inlet port of the sampling funnel by sensing the level in the sample feeder.
BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a method for continuous sampling of a slurry flow by separating a portion of the slurry flow to form a separate sample flow and passing it as a continuous flow to be analyzed.
Description of the prior art Samples from suspensions of solids in water, or slurries, are taken for chemical analysis and for other purposes. This involves a certain portion of the slurry which is entirely removed from the slurry flow subjected to sampling. Various different methods are prior known for this so called batch sampling, a common feature of all of them being that the taken sample represents the total slurry flow during a short time interval. In other words the sample is a cross section of the total slurry flow at the moment of sampling.
With the development of continuously operating analyzers, sampling has undergone a substantial change. Depending on the type of analyzer utilized, additional requirements of varying degree are made on sampling over those made on batch sampling.
A very exacting analyzer with respect to sampling is the on line X-ray fluorescence analyzer which makes the following requirements on the sample.
(1) The sample must be representative, not only with respect to the contents of the various metals, and the particle size distribution, but also with respect to the weight per volume of the slurry.
(2) The sample flow must be continuous and of constant quantity, independently of variations in the process flow it represents, and must be controllable as to its quan tity.
(3) The sample must be free from solid impurities and air bubbles.
The development of the on line X-ray fluorscence analyzer has been greatly impaired by the difliculty of sampling, with the resultant, at least partial, failure to meet the above requirements. The sampling method presently to be described will meet all the said requirements and is applicable not only for X-ray fluorescence analyzers but also, either as it is, or partially, for sample pretreatment, to continuously operating analyzers of the type ana- 3,561,273 Patented Feb. 9, 1971 "ice SUMMARY OF THE INVENTION This invention relates to a method and an apparatus for continuous sampling of a slurry flow e.g. for a continuously operating analyzer of mineral slurries, and the object of the invention is to provide a method and an apparatus by means of which a representative sample is obtained and which excellently meets all known requirements generally made on the same, and which furthermore is reliable in operation.
The method according to the invention is characterized by continuously swinging the said slurry flow back and forth in order to change the direction of the said slurry flow, so that said slurry flow only momentarily hits a sampling funnel, in which the so formed sample flow is passed for analysis, and regulating the opening of the inlet port of the said sampling funnel in order to maintain the slurry level constant in the said sampling by means of a control apparatus.
BRIEF DESCRIPTION OF THE DRAWING The method according to the invention and an apparatus applicable for carrying out said method are described more particularly in the following with reference to the accompanying drawing, which by way of an example schematically illustrates an apparatus applicable for carrying out the method of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, slurry is shown flowing continuously in line 1, the downwardly extending end of which is suitably flexible so that it can be put into reciprocating swinging movement above a sampling funnel 3 by means of an actuating device 2, the swinging movement being of an amplitude large enough to cause a major portion of the slurry discharged from the line 1, to fall down outside the sampling funnel. The slurry flow leaves the line 1 as a generally downward flowing stream, the direction of which stream is changed by the swinging motion of the end of the line 1. In this manner portions of batch sample character are continuously cut from the original slurry flow, said portions being combined to form a continuous sample flow, while the rest of the original slurry flow makes up a residual flow. The quantity of the sample generally is small compared with the residue, which falls outside of the funnelfi as shown by the arrows in the drawing.
The sample flows from the sampling funnel 3 as a continuous flow through an inclined screen 4 into a feeding pipe 5, where the slurry level is maintained constant by a control apparatus comprising a level sensing transmitter 6, a control instrument 7, and a regulating device 9 controlling an adjustable port opening 8. From the sample feeding pipe 5, preferably at its lower portion, the sample flow is passed further for analysis, e.g. into the cell of an X-ray analyzer.
By virtue of the cooperative effects of the above mentioned functions, the apparatus can be tuned into a condition of equilibrium so that the sample flow from the feeding pipe 5 is constant. In order to achieve such a constant sample flow, the level of slurry in the feeding pipe 5, indicated by H H in the drawing has to be kept steady, since it is the hydrostatic head which determines the flow, according to well-known principles.
The aforementioned level sensing transmitter 6, control instrument 7, and regulating device 9 cooperate to control the adjustable port opening 8 to provide a constant rate of sample flow through the pipe 5. If not controlled, the sample flow into the sample funnel 3 would vary with the process flow being sampled, and fluctuations in the sample flow through pipe 5 would result. This is avoided by control of the opening 8. Any increase in the process flow which causes a rise in the liquid level in the pipe 5 will be sensed and a signal will be transmitted by the level sensing transmitter 6 to the control instrument 7. The instrument 7 will then actuate the regulating device 9 to decrease the opening 8. The closing of opening 8 will slow down the flow rate by limiting the amount of slurry entering the funnel 3, until the liquid level in the pipe 5 is lowered to the desired level. This arrangement for controlled equilibrium has the following advantages:
(1) The sample is a representative portion of the slurry flow.
(2) The sample flow is maintained constant as to its quantity. The effect on the pressure P of variations in the weight per volume of the sample can be neglected, since said variations even in the slurry flow generally are minor, and when necessary can be compensated for.
(3) Discontinuation of the sample flow causes the adjustable port 8 to close, whereby the slurry flow totally by-passes the apparatus. The residual flow then equals the slurry flow.
(4) By virtue of the screen 4 the sample is free from impurities which otherwise could adhere to the throughflow cell 10.
(5) Since the sample is taken to the through-flow cell from the lower portion of the inlet pipe 5, the sample n free also from air bubbles.
What is claimed is:
1. Method for continuous sampling of a slurry flow by separating a portion of the said slurry flow to form a separate sample fiow and passing the sample flow as a continuous flow to be analyzed, comprising continuously swinging said slurry flow back and forth in order to change the direction of the said slurry flow so that said slurry flow only momentarily hits a sampling funnel, collecting only a portion of the slurry flow as a sample fiow through the funnel, passing said sample flow on through sample feeding means for analysis, and automatically regulating the opening of an inlet port of said sampling funnel for maintaining the slurry level constant in said sample feeding means by means of a control apparatus.
2. Method according to claim 1 wherein said sample feeding means is a feeding pipe, comprising passing said sample flow from a lower portion of the pipe as a continuous flow for analysis and said slurry level is maintained constant in the pipe by sensing the level in the pipe and regulating the opening of the inlet port in response to the slurry level sensed in the pipe.
3. Method according to claim 2, comprising screening said sample flow before passing the sample flow to the feeding pipe for removing coarser impurities from said sample flow.
References Cited UNITED STATES PATENTS 2,738,679 3/1956 Senkowski 73--423 3,110,183 11/1963 Logue 73-423 3,279,260 10/ 1966 Huntington 73-423 3,464,272 9/ 1969 Griffith et a1. 73423 LOUIS R. PRINCE, Primary Examiner H. C. POST, III, Assistant Examiner