US2714453A

US2714453A - Apparatus for fractionating finely divided material

Info

Publication number: US2714453A
Application number: US241376A
Authority: US
Inventors: James F Miller
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-08-10
Filing date: 1951-08-10
Publication date: 1955-08-02
Anticipated expiration: 1972-08-02

Description

J. F. MILLER Aug. 2, 1955 2 Sheets-$heet 2 APPARATUS FOR FRACTIONATING FINELY DIVIDED MATERIAL Filed Aug. 10 1951 INVENTOR \JQmeJ an /b9 M715,

APPARATUS FOR FRACTIONATING FINELY DIVIDED MATERIAL James F. Miller, Pittsburgh,

States of America as the Army Application August 10, 1951, Serial No. 241,376 2 Claims. (Cl. 2tl9-142) Pa., assignor to the United represented by the Secretary of This invention relates to apparatus for separating or fractionating finely divided or powdered material. Such apparatus is sometimes termed an elutriator.

Among the insecticide dusts which have had large scale military usage are those composed of DDT in a diluent consisting of pyrophyllite (aluminum silicate) and 10% DDT in talc as a diluent. Diluents, of course, are used for providing the most economical distribution of the active ingredient. As a rule, the physical performance characteristics of an insecticide dust are principally those of the diluent, and the biological activity of the insecticide is a function of the physical performance characteristics of the dust. These characteristics depend on various factors, one of the most important being particle size. The particle size distribution of a dispersed dust has a great influence on such properties as fall rate, degree of agglomeration of the dispersed particles, ease of dispersion, adhesion to dry surfaces, and flotation on water. These facts make it desirable to fractionate diluents by particle size in order to study the effect of particle size on the toxicity and other properties of the dust.

Elutriation equipment available on the market is considered to be too large and too expensive, one wellknown particle size analyzer, complete with accessory equipment, being priced at about one thousand dollars in 1946. Another type of classifier employing a cyclonic separation of powdered materials was tested carefully, and small samples of the fractions obtained were suspended in alcohol and examined microscopically, using a calibrated filar micrometer eyepiece or a regular eyepiece containing a calibrated Whipple disc; but under the best operating conditions, satisfactory separation of the fractions was not obtained.

The present invention provides an elutriation system which permits continuous operation, which is relatively simple in construction and inexpensive to manufacture, and which effects a satisfactory separation of the fractions, e. g., below 5 microns, 5-10 microns, lit-20 microns, 20-30 microns, 30-45 microns, 45-65 microns, and above 65 microns. Another general object is to provide an elutriation apparatus which requires little attention from the operator, once a run starts. More specific objects are to provide apparatus which makes a given run without change in the air velocity, and which separates the largest particles first, then the next largest particles, and so on. Other objects will be apparent from the following description of the preferred embodiment of the invention shown in the accompanying drawings forming a part of this specification.

In said drawings,

Fig. l is a sectional elevation of the assembly of elutriator tubes and certain associated parts, showing diagrammatically the tube-vibrating means;

Fig. 2 is a cross section on line 2-2 of Fig. 1;

Fig. 3 is a detail in vertical section, showing a joint in one of the tubes;

Fig. 4 is a vertical section through end of one of the elutriator tubes;

Fig. 5 is a cross section on line 5-5 of Fig. 4;

Fig. 6 is a cross section on line 6-6 of Fig. 4; and

Pig. 7 is a cross section on line 7-7 of Fig. 4.

In general, the air elutriation apparatus includes a plurality of vertical elutriator tubes or settling chambers of increasing diameter connected in series, a source of compressed gas, preferably air, means for feeding a charge into the apparatus, and filtering means placed at the outlet of the largest tube. Between the source of compressed air and the elutriation apparatus an air control and cleaning system is interposed, but as the latter system forms no part of the present invention, it is not shown. The air control and cleaning system may include, for example, a Nullmatic Pressure Regulator, Air Filter and Flow Controller, manufactured by the Moore Products Co., Philadelphia, Pennsylvania, and a Flowrator, such as is sold by the Fischer and Porter Co, Hatboro, Pennsylvania, all assembled and mounted on a fiat upright panel. With such a system, the elutriator tubes are assured a supply of clean air under con stant pressure.

While various arrangements of elutriator tubes may be employed, jointed metallic tubes are preferred for ease of assembly and disassembly. Referring to the drawings, i prefer to have the smallest tube 11 of one inch outside diameter, the second 12 of 1 /2 in. outside diameter, the third tube 13 of 2 in. outside diameter, the fourth tube 14- or" 3 in. outside diameter, the fifth tube 15 of 6 in. inside diameter, and the sixth tube 16 of 12 in. inside diameter. All six tubes may be about 46 long and preferably are cylindrical except at their upper and lower ends, which are frusto-conical, with vertex angles of about 45". However, the smallest tube it does not have a frusto-conical lower end.

The joint of the largest tube 16, which is representative of all the tube joints, is shown in Figs. 2 and 3. As there seen, tube 16 comprises an upper section 16a and a lower section 16b whose edges are abutted together, the two sections being held by bolts it) passed through annular flanges 2i and 22 secured respectively to said upper and lower sections and extending outwardly therefrom at right angles. The lower flange 22 is welded to a circular collar or band 23 which encloses the abutted edges of the joint and is in turn welded to the lower section 16b. Other joint constructions may, of course, be used; whatever the construction, it should permit easy disassembly of each tube and yet assure a tight joint.

Each of the tubes has its upper frusto-conical end con nected with a short pipe 25 whose upper end is coupled by a union 26 to a bent pipe 27, the latter pipe being welded at its upper end to a Y-coupling 28. A cap 29 is screwed or welded on the upper end of each Y- coupling to close the same. The other arm of each Y-coupling is welded or otherwise secured to the upper end of a vertical pipe 3t) which extends down between two of the elutriator tubes to a fitting (to be described) discharging into the lower end of the larger of the two elutriator tubes. The intake or feed pipe for the smallest tube 11 is indicated at 32, and a small dust receptacle or hopper is shown diagrammatically at 33 (Fig. l) to permit manual or other dumping into the system of the charge of dust to be fractionated. A continuous feed charging device may be used if large samples are continually run. At the upper and discharge end of the largest tube 16, a vertical pipe 34 is coupled by a union 35 to an inclined pipe 36, a Y-coupling 37 is secured to the upper end of pipe 36, a cap 38 closes the top of the Y-coupling, and a downwardly extending straight the lower or inlet pipe 39 receives the discharge from Y-coupling 37.

Pipes

34 and 36, union 3S, Y-coupling 37, cap 38 and pipe 39 are all larger than the corresponding parts coupled to the small tubes 11-15. If pipes and connected parts are one-fourth inch tubes, I prefer that pipe 34 and connected parts be of the %1 in. size. It will be noted that the described arrangement of pipes and Y- couplings provides conduit means coupling the top of each tube with the bottom of the next larger tube of the series, and that no surfaces are provided for the collection of dust, the nearly vertical pipes rising from the tops of the elutriator tubes and the Y-couplings insuring a flow of dust-laden air without collecting dust at any particular point. The Y-couplings also facilitate disassembling the conduit means for cleaning.

At the lower end of pipe 39 filtering means in the form of an extraction thimble 40 is secured, for example by a rubber stopper (not shown) fitting on the end of pipe 39, and masking tape (not shown) securing and sealing the thimble on the rubber stopper. tion thimble is made of a special porous paper, known as fat free filter paper, seamless, of single or double thickness, or it can be made of alundum or other airpermeable materials with pore diameters of less than one one-hundredths of a micron. The very finest particles obviously will collect on the inner walls of the extraction thimble, while the air, substantially free of all particles, will pass out through the walls of the thimble to the atmosphere.

Now referring to Figs. 4, 5, 6 and 7, the lower end of each elutriation tube is connected with an intake pipe 30 by means of a two-part fitting having a horizontal air passageway 46 leading to the underside of a nozzle 47 located in the extreme lower end of the elutriation tube, said nozzle having a plurality of ports 48 arranged in a circular series. There may be eight such ports each one-sixteenth of an inch in diameter, equally spaced in the nozzle, all the ports being disposed at the same angle as the walls of the frusto-conical lower end of the elutriation tube (preferably 22 /2 degrees). The two parts of fitting 45 may be temporarily secured together as by screws (not shown), and a sealing compound 50 may seal the fitting on the elutriation tube and on the end of intake pipe 30.

To obviate corrosion of the inner surfaces of the apparatus which would retain some of the dust, all the described parts may be made of stainless steel or a similar metal or alloy. Such a material will also facilitate grounding the apparatus to remove electrostatic charges. :2

As shown in Fig. 1, each elutriator tube has a wire connecting it with a ground, for example a water pipe not shown. The pipe connections coupling each pair of tubes may be separately grounded. To vibrate the elutriator tubes to prevent adherence of dust to their inner walls, a small electric vibrator 57 is located adjacent each tube, each vibrator being illustrated as an electric bell whose bell has been removed so that its clapper 58 will hammer the walls of the tube. Another form of vibrator which may be used is shown in the P. S. Roller Patent No. 2,019,507 dated Nov. 5, 1935. Because of the unpleasant noise of the vibrators, the entire assembly preferably is housed in a box or casing (not shown) having sound-absorbing walls. In lieu 3 of vibrators, a Boerner shaker (not shown) may be connected to the bottoms of all the tubes to shake them and thus prevent channeling of the air through the sample being fractionated and through the fractions collecting in the tubes.

In a calibration run of the described apparatus, using industrial fly ash (which contains, in general, about spherical particles in the size range of from less than one micron to about 300 microns) the following results were obtained:

The extrac- (1. TABLE I Percentage by weight of a given particle size found in each tube Particle Size Tube Tube Tube Tube Tube Tube Range (mu) 11 12 13 14 15 1e Thlmble Above 65 100.00

An inexperienced operator us1ng industrial fly ash obtained the following results:

TABLE 11 Percent of Recovered Material Fraction (microns) Usually 50 gm. samples were charged and the apparatus was then run about 72 hours. However, it is possible to charge 50 gm. of dust, and start elutriation, then after two hours or so, shut off the apparatus, feed another 50 gm. of dust, and resume elutriation for another two hours, and so on until the desired amount of dust 7 had been charged, concluding the run by about hours fat of elutriation. In this way several pounds of dust may be included in one run. The above referred to analyzer of the prior art, on the other hand, handles only about 15 gm. of dust in each run, separates only one fraction at a time, may require an adjustment of air flow between each fraction, and demands almost constant attention of the operator during fractionation (2 /2 hours). With this prior art apparatus, the total time for fractionation of a one pound sample will be about 10 eight hour days, including setting up and. cleaning; and during all that time, almost constant attention of an operator is required. The present apparatus requires the attention of the operator only when charging and during occasional checking of air flow and replacing thimbles; a total running time of 72l20 hours is all that is needed (the one pound charge requiring about 120 hours), following which.

about eight hours time is necessary for removing fractions, cleaning, reassembling, recharging, and readjustment of air flow for a new run. Furthermore, the described apparatus may be run 24 hrs. a day since usually no attention is required during a run. Finally, no prefractionation run is necessary, whereas with each new material the prior art apparatus must be run about five hours, under constant supervision, to determine the proper running time for complete separation of each fraction.

While particular mention has been made of diluents and insecticide dusts, the described apparatus may be used in connection with the analysis of cements, volcanic ash,- diatomaceous earth, Cottrell precipitator dust, pulverized coal, carbon, limestone, gypsum, quartz, shale, feldspar, mica, flint, salt, silica gel, talc, flake alumina, kaolin, China clay, magnetite, pigments, diatomite, battery lead oxide, organic dyes, wood flour, free-flowing sulphur, and other materials.

Obviously changes may be made in the dimensions, proportions, and number of parts, and their relative positions, without departing from the invention as defined in the appended claims.

What I claim is:

1. A continuous run apparatus for fractionating finely divided material consisting of a plurality of vertical elutriation tubes of different diameters arranged in ascending order, conduit means connecting the several tubes in series with the top of each tube connected through the conduit means with the bottom of the next larger tube of the series, a source of compressed gas coupled to the bottom of the smallest tube of the series, means for introducing the material to be fractionated into the apparatus near the connection with the source of compressed gas, a gas discharge outlet with filtering means connected with the upper end of the largest tube of the series, the several tubes each consisting of two separable abutted parts, flanges being secured to and projecting outwardly from each of said parts, the flanges being separated when the parts are abutted, and bolts passing through the flanges to secure the separable parts together, a collar or band being fixed to one of the parts of each pair and enclosing the abutted edges of the joint so as to aid in sealing the same.

2. A continuous run apparatus for fractionating finely divided material comprising a plurality of elongated verti cal elutriation tubes of difierent diameters but of the same height and arranged in ascending order, the lower ends of all the elutriation tubes except the smallest tube being frusto-conical, conduit means connecting the several tubes in series with the top of each tube connected through the conduit means with the lower end of the next larger tube of the series, a source of compressed gas coupled to the lower end of the smallest tube of the series, means for introducing the finely divided material into the apparatus near the coupling of the source of compressed gas with the smallest tube of the series, a gas discharge outlet with filtering means connected with the upper end of the largest tube of the series, each of said conduit means including a fitting secured to the extreme lower end of the next larger elutriation tube of the series, each fitting having a gas passageway and having its upper part surrounding the extreme lower end of the elutriation tube and forming a gas-tight joint therewith, a nozzle located inside the elutriation tube at the extreme lower end and having a plurality of ports arranged in a circular series and directed upwardly at the same angle as the walls of the frusto-conical lower end of the elutriation tube; the upper ends of said ports being located very close to the lower end of the frusto-conical end of the elutriation tube.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Bulletin 2055 of American Instrument Co., Inc., 8010 8020 Georgia Avenue, Silver Spring, Md., October 1937. Four pages. (Copy in Div. 55.)

Taggart: Handbook of Mineral Dressing, pp. 19-116, pp. 19-111. 1945. (Copy in Div. 55).

Taggart: Handbook of Mineral Dressing, pp. 19-112. J. Wiley & Sons, Inc., N. Y. 1945. (Copy in Div. 55.)

pp. 19-115, J. Wiley & Sons, Inc., N. Y.

Claims

1. A CONTINUOUS RUN APPARATUS FOR FRACTIONATING FINELY DIVIDED MATERIAL CONSISTING OF A PLURALITY OF VERTICAL ELUTRIATION TUBES OF DIFFERENT DIAMETERS ARRANGED IN ASCENDING ORDER, CONDUIT MEANS CONNECTING THE SEVERAL TUBES IN SERIES WITH THE TOP OF EACH TUBE CONNECTED THROUGH THE CONDUIT MEANS WITH THE BOTTOM OF THE NEXT LARGER TUBE OF THE SERIES, A SOURCE OF COMPRESSED GAS COUPLED TO THE BOTTOM OF THE SMALLEST TUBE OF THE SERIES, MEANS FOR INTRODUCING THE MATERIAL TO BE FRACTIONATED INTO THE APPARATUS NEAR THE CONNECTION WITH THE SOURCE OF COMPRESSED GAS, A GAS DISCHARGE OUTLET WITH FILTERING MEANS CONNECTED WITH THE UPPER END OF THE LARGER TUBE OF THE SERIES, THE SEVERAL TUBES EACH CONSISTING OF TWO SEPARABLE ABUTTED PARTS, FLANGES BEING SECURED TO AND PROJECTING OUTWARDLY FROM EACH OF SAID PARTS, THE FLANGES BEING SEPARATED WHEN MECHANISM FOR SHIFTING SAID CLOSURE MEMBER, RELEASABLE ACTIVATING MEANS PRESET BY SAID TESTING MEANS MANIFESTING A PREDETERMINED CLASS OF ARTICLE OF A GIVEN SAID FORM, HOLDING MEANS PRESET IN COORDINATION WITH MOVEMENT OF SAID GIVEN FORM AWAY FROM THE TESTING MEANS AND OPERABLE FOR RELEASING SAID ACTIVATING MEANS IN READINESS FOR A NEXT SUCCEEDING OPERATION THEREON, MEANS OPERABLE THROUGH SAID PRESET HOLDING MEANS IN COORDINATION WITH FURTHER MOVEMENT OF SAID GIVEN FORM INTO ARTICLE EJECTING POSITION WITH RESPECT TO SAID RECEPTACLE FOR ACTUATING SAID MECHANISM AND THEREBY TO SHIFT SAID CLOSURE MEMBER TO CLOSE ONE SAID CHAMBER INLET OPENING AND TO OPEN THE OTHER FOR RECEIVING AN ARTICLE EJECTED FROM THE GIVEN FORM INTO SAID MOUTH.