US3179379A - Apparatus for treatment of powdered and granular material - Google Patents

Description

April 20, 1965 e. GRUN ETAL 3,179,379

APPARATUS FOR TREATMENT OF POWDERED AND GRANULAR MATERIAL Filed Jan. 9, 1963 2 Sheets-Sheet 1 l 0 605777 Y GEUIV *4 FQA/v 2 L BN6 INVENTORS BY M April 20, 1965 G. GRUN ETAL 3,179,379

APPARATUS FOR TREATMENT OF POWDERED AND GRANULAR MATERIAL Filed Jan. 9, 1965 2 Sheets-Sheet 2 III. I 21 47a @usTA V GIG/# R Z A. 9N6 INVENT United States Patent Ofiice 3,179,379 Patented Apr. 20, 1965 3,179,379 APPARATUS FOR TREATMENT OF POWDERED AND GRANULAR MATERIAL Gustav Griin, 73 Ortenherger Strasse, and Franz Lang, 1 Schui Strasse, both of Lissberg, Germany Filed Jan. 9, 1963, Ser. No. 250,367 2 Claims. (Cl. 259-4) V This invention relates to apparatus for mixing predetermined batches of powdered or granular substances, and is directed to improvements in the apparatus disclosed in the co-pending application of Gustav Grun, Serial No. 809,404 filed April 28, 1959, now Patent No. ,097, dated July 16, 1963.

While it has heretofore been proposed to mix granular materials in a container by utilizing continuous or intermittent air blasts, nevertheless, the maximum mixing efiiciency has not been obtained for several reasons. Among others, for example, the mixing chamber into which air is forced is more often than not so constructed so as to produce dead air spaces in which improperly mixed materials collect and ultimately drop down into the bed of the otherwise adequately mixed batch. Consequently, this defeats the primary purpose of the operation. Also, it has been generally customary where air jets are employed to use nozzles discharging air in narrow concentrated jet streams, as distinguished from expanding gusts of air, thereby creating a multiplicity of turbulent areas between them. In other words, in the prior use of air'jets, irregular air currents are set up with resulting lack of uniformity in the finally mixed batch. Thus, where numerous separate air current paths are established within the mixing chamber, the inevitable result is the presence of vagrant sub-currents which are beyond the control of the mixing medium.

Moreover, the length of time heretofore needed for mixing has been governed chiefly by the size of the particles, their properties, adherence, and bulk weight. Normally, this time is too slow for eflicient commercial operations, because it usually appears in the range of from twenty minutes to two hours, depending on the above characteristics of the material, the size of the apparatus, amount of charge, or the type and velocity of air currents.

Thus, air-operated mixing processes and devices heretofore used are open to various objections, such for example, as follows:

(1) They require relatively long periods of time for mixing, hence considerable expenditure of power;

(2) Their design must be adapted to the composition and nature of the material to be mixed;

(3) They produce dead areas in the receptacle, which are increased by structural obstacles in the interior, or by unscientific placement of nozzles;

(4) All of the material is not uniformly mixed because the character of the mixing chamber prevents all of the material near the bottom portion from being completely processed;

(5) The means and devices for intake, distribution, and filtering of the actuating gas, and the means for operating the discharge device are not readily accessible, and in some cases are partly inside the filled receptacle. Also, where corrosive substances are involved, there is danger that sliding parts, wipers, etc. become directly attacked by chemicals;

(6) Large mixing installations, especially for granular substances, present the risk that the force of the airstream will not be sufficient to produce uniform mixing in a short period of time;

(7) Air entrained particles have not been adequately prevented from escaping with the mixing gas.

Accordingly, a primary object of the invention is to minimize or eliminate the foregoing objections; and also advantageously obtain thorough mixing in a receptacle by eliminating unmixed portions of a batch due to dead spots in the receptacle; to reduce the mixing time to a fraction of what it has heretofore been; and also to standardize the design of apparatus to be more generally usable and accessible regardless of the properties of the mixed material, so that it can be used without exception for all dry mixing of powdered substances. In that connection, the invention contemplates a construction which permits the use of a single vortical air blast of considerable magnitude, for example a blast theoretically equal to the velocity of sound, but in fact somewhat less, or a succession of such air blasts depending on the volume, weight, density, or other characteristics of the material or materials to be thoroughly mixed.

A further object of the invention is to provide a new and efiicient arrangement of special nozzles in'relation to the bottom of the material bed to produce a homogeneous vortical ascending air stream which is a composite of many overlapping and upwardly deploying diifused air currents in the container which insure fast and positive mixing of the material which then descends in the axial vacuum induced by the vortex.

With the above and other objects in view which will more readily appear as the nature of the invention is better understood, the invention consists in the novel construction, combination, and arrangement of parts, hereinafter more fully described, illustrated, and claimed.

A preferred and practical embodiment of the invention is shown in the accompanying drawings, in which:

FIGURE 1 is a vertical sectional view through the vertical axis of the entire apparatus.

FIGURE 1 is an enlarged sectional detail view of the circulating chamber.

FIGURE 2 is a longitudinal section of the mixing head, shown in a larger scale.

FIGURE 3 is a plan view of the mixing head, and partly in a section through its right-hand half along the line III--III in FIG. 2.

FIGURE 4 is a sectional view through the ring of nozzles, taken on the line IVIV of FIGURE 1, on a still larger scale.

FIGURE 5 is a sectional view taken on the line VV of FIG. 4.

FIGURE 6 is a further type of the air-vent element, on a. larger scale.

Similar reference characters designate corresponding parts throughout the several figures of the drawings.

The mixing receptacle includes a vertical cylindrical shell 1 having an inverted conical bottom wall 2 whose lower end rests on the outer edge portion of the conical surface 30 of an integrated compressed air-ring assembly AR which sub-tends a central discharge trap 4.

The junction between the wall 2 and trap 4 is closable, by a material collecting cone 3 which may be raised and lowered in a manner to later appear, to first collect the mixed material and then permit its release. This cone also aids the upward and downward movement of the material in the vortical cycle.

The discharge trap 4 is surrounded by a circular air manifold chamber 5 which is connected through 'feed pipe 6, controllable by valve 7, to a compressed air tank T. The air ring assembly AR includes a circular manifold chamber 5 having bore holes 8 radiating therefrom, each being connected to a Laval type nozzle 9 as shown in FIGS. 4 and 5 and whose inlet is of less diameter than its Outlet, so that, in eflfect, the nozzle passage expands outwardly into the chamber and close to the inner face of the conical bottom 2.

These nozzles have their axes set substantially parallel W e3 to the wall of a V-shaped or substantially conical bottom 2, so that the edge of expanding air stream scavenges the inner surface of the wall 2, and also slant upward obliquely to the axis of the receptacle (FIGS. 4 and 5) to cause the material to follow the outer ascending vortical path A adjacent the inner surface of the shell and also creating an'axial vacuum to induce the material to follow the inner descending path B (FIG. 1). The ring of nozzles during operation emit overlapping streams of individual compressed air helices expanding as they whirl upward in volute fashion and in overlapping relation to provide a single concentrated massive composite vortex of great magnitude and consequent maxim-um mixing power.

The arrangement of the outwardly flaring nozzles 9 makes it possible to step up the velocity of the compressed air-stream, even if the mixing time should last only a few seconds, thereby securing the maximum mixing efiect. For example, the air "blasts may be produced by pressure at the source of twenty-five atmospheres, While at the jets, the pressure would be approximately fifteen atmospheres.

The receptacle is closed by a slightly curved top wall or cover 19 carrying a vent pipe 11, for the purpose of exhausting the spent compressed air taken in during the mixing procedure. This pipe is substantiallyL-shaped as shown in FIG. 1 of the drawing.

' Fastened to the inner side of the outer face plate of vent pipell is a vertically mounted bushing 12. Inside this bushing, shaft 13 turns fan 14 driven by motor 16 mounted on outer face plate 15. This fan contains numerous vertically-arranged blades 19, as shown in elevation in FIG. 1, radially disposed with respect to shaft 13, and secured between the upper and lower spaced plates 17 and l8.- Upper plate 18 is annular in form and has a flange 20 which provides an upwardly directed neck which fits into the vent pipe.

The fan 14 goes into action briefly ahead of each blast of compressed air which constitutes a mixing cycle and is turned off when the air blast stops. Its primary function is to intercept and throw back by centrifugal force into the receptacle any particles of material entrained in the exhaust air stream, while its secondary function is to slow down the escape of compressed air from the receptacle, thereby to enable the fan to operate at maximum intercepting capacity.

As a result, the compressed air discharges through the vent pipe virtually free of any dust particles, since the fan 14 acts as a filter.

The modification shown in FIG. 6 depicts fan 14 between the two plates 17a and 18a, containing a number of spaced horizontally disposed annular discs 19a held at equal distances between face plates 17a and 185: by studs 21. In this modification, too, the compressed air, after being slowed down, can escape through vent pipe 11, while any entrained particles of material are thrown back into the mixing receptacle by centrifugal force.

When handling particularly fine-grained material with a high percentage of extreme fineness, a fine filter 17a (FIG. 1) may be inserted behind the fan. 7

The mixing head consists of an annular member 23 (FIGS. 2 and 3) firmly integrated with V-shaped bottom 2, and contains a central passage 22 with the aforesaid chamber 5. This chamber is firmly closed by the superposed annular lid 23. A tapped bore 24 provides connection with the intake feed line for compressed air.

In each bore hole 8 of annular member 28, there is a filter element 25 which'extends radially across circular chamber 5. These filters may be removed and cleaned V by taking out the plug 29 which closes radial holes 26 in outer wall 27 of member 28. The inner wall 30' of cylindrical member 28 is oblique o the inner face of passage 22 and widens at its upper art to conform to the angle of V-shaped bottom 2. This ping surface contains the outlets of bore holes 31 d at an angle tocommunicating bore holes 8, and

amas /a 4,. having threads 32 to receive mating threads of nozzles 9 which are screwed into these taps.

The Laval nozzles have an orifice whose wall portion diverges outwardly at an angle of about 13. Bore holes 31 for the nozzles, and the nozzles seated in them are pointed upward (FIG. 4) and obliquely (FIG. 5) to the surfaces 2 and 31 (FIGS. 1 and 5 Compressed gas blasts issuing from the Laval nozzles 9 thus are directed obliquely upward so that the material being mixed in the receptacle is eddied upward as shown by arrows A (FIG. 1) in an outer spiraling vortex along the walls of receptacle 1 and carried freely up to lid ll), Where the particles become suspended. From this state of suspension the particles of material then drop into the center of receptacle 1, likewise in an inner descending vortex, as shown by arrows B, while compressed gas escapes through vent ll. 1

Near the upper portion of receptacle 1, there is a filling port 34 for the intake of material, closable by gate 33. This filling port '34 is surrounded by funnel 35 fastened to the wall of receptacle 1, through which funnel the material is fed in by means of measuring devices of known design, not shown in the drawing.

Gate 33 is mounted on piston rod 36 of piston 37, moving inside cylinder 38. This cylinder is fastened to the funnel, and piston 37 may, as desired, be connected through a check valve '39 and feed lines 40 and 41 mounted on either side of cylinder 38 to a compression intake while either branch line, 40 or 41, whichever is not at the particular time registered with the intake, is connected with vent line 43.

As mentioned at the outset, the effectiveness of the above-described apparatus rests on the fact that the material introduced in receptacle 1 is agitated, by a sharp but very-brief blast of compressed gas, into a spinning motion until it reaches a state of suspension. Depending on the type of material, one blast of suflicient magnitude may be sufficient, but, on the other hand, the blasts may proceed intermittently at intervals which permit the material to settle back to fluent state between any two successive agitations. The important thing about the application of the blast of gas to receptacle 1 is therefore to project a sudden blast at full force into receptacle 1 through Laval nozzles 9 and cut off the blast with equal suddenness.

For this purpose, feed line 6, between the main check valve '7 and mixing head 28, 5, contains a control valve 44. This valve is encased in a housing 45 which is subdivided into three chambers 48, 49 and 50 by panels 46 and 47. Panel 46 is centrally apertured and around this passageway, there is a seat 51 for valve unit 52. Valve unit 52 projects into chamber 48 communicating with inlet line 6a extending from main valve 7, and is mounted on piston rod 53 which is carried by a packing through panel 47 into chamber 50. At its lower extremity, which projects into chamber 59, piston rod 53 carries a piston 55' which moves with airtight fit against the walls of chamber 50. Chamber 49 communicates with feed line 6 through which the compression medium is introduced.

Chamber 48 is traversed at right angles to its axis by a cam shaft '56 bearing cam 57 which acts upon valve 52 and piston 53. This cam 57 may be phase-set by lever 53 operated from outside the valve casing.

Chamber 5t) registers through its floor with feed line 59, which serves the intake of a compression gas. Feed line 59 is controlled by valve oil which may alternately join line 59 to compression-gas intake 61 or outlet 62. Arm 63 of valve is coupled with setting lever 58 that controls cam 56 by means of a guide link 64 in such a way that when cam 56 depresses valve head 52, feed line 59 registers through valve 60 with outlet 62, shutting off intake 61, whereas when valve head 52 is released by the nev. position of cam 56, feed line 59 registers through valve 663 with intake line 61 and the compression medium presses upward on iston 55 and piston rod 53 and thus lifts valve head 52 from its seat 51; thus the flow of compression medium from supply tank T to the mixing head can be rapidly turned on and off.

The above-described apparatus affords a considerable reduction in the time for mixing, as compared with known apparatus.

Test measurements made for purposes of comparison with known mixing devices have resulted in the following data.

Example 1 A receptacle 1 with a net capacity of 0.6 cu. meter (approximately 21 cu. ft.) was filled with material of the following consistency:

17 percent having a screen size of 0.5 mm. 11 percent having a screen size of 0.4 mm. 14 percent having a screen size of 0.3 mm. 19 percent having a screen size of 0.2 mm. 25.8 percent having a screen size of 0.1 mm. 13.2 percent having a screen size of 0.1 mm.

Bulk weight was 635 gms. per liter, with a specific weight of 1.35 gms. per cu. cm.

To the mixture were added 3 gms. of an indicator substance and a vitamin-A preparation. The indicator substance had a specific weight of 1.52 and the vitamin preparation 1.22. The screen size of the indicator substance was less than 0.2 mm., that of the vitamin preparation was between 0.2 and 0.4 mm.

Mixing proceeded with seven blasts of gas, lasting two seconds each, with one-second intervals between blasts. The total mixing time was 20 seconds, using 4,500 liters of compression agent.

Tests made on 18 different samples, each of 50 gms., showed an average mixing rate of 1:100,000.

Example 2 A mixing receptacle 1 with a net capacity of 2,000 liters was filled with 1,000 kilograms of a mixture of varying consistency having a total bulk weight of 0.5 g./cm.

The process was controlled in such a way that four compression blasts of four seconds each were applied to the receptacle at intervals of three seconds. Following a total mixing time of 25 seconds, i.e., four 4-second blasts and three 3-second intervals, a completely uniform mixture was found, with less than l:100,000 deviation.

Example 3 Test material Cellulose derivatives. Test mixer 42 m. of useful capacity. Filling 23.5 tons of cellulose derivatives.

Character of the raw Variations of the viscosity* rangproduct. ing from 130 to 214.

Water contents 3 to'l6%.

Common salt contents 19.0 to 22.0%.

A continuous blast of sec. was applied. The air consumption amounted to 50 normal=m.

The analysis produced the following results:

Viscose contents Between 160 and 180.* Water contents 6 to 8%. 7 Common salt contents 21.2 to 21.4%.

*These values are taken for a 5% aqueous solution by means of a ball type viscosimeter.

The limits of the variations of the mixture are within the limits of error of the measuring devices so that the mixture may be considered unobjectionable.

It will of course be understood that in all cases batch mixing proceeds while the cone 3 is seated as in FIGS. 1 and 2, but when the batch is complete, the piston rod 65 in cylinder 66 is moved upwardly by compressed air admitted to the bottom of piston 67 through inlet passage 63. As the cone rises, material passes over surface 30 around support 69 for the piston into discharge trap 4. As the cone moves upwardly, the flexible diaphragm or shroud 70 having its upper end connected to the related end of the cylinder and its lower end connected to the inner side of the skirt of the cone, keeps material from lodging behind the cone and collecting on the piston rod, while at the same time directing the material fully into the trap. When lifting pressure in passage 68 ceases, the piston 67 and cone will descend by gravity because air will be admitted to the inner side of the piston through passage 71.

From the foregoing, it will be now be seen that a closed vertical cylindrical chamber is provided with a closable material intake and air outlet in its upper portion and a bottom portion in form of an inverted cone having a circular opening controlled by a cone valve to establish communication with a discharge trap. In immediate proximity to this opening a ring or nozzles each of which is disposed obliquely to both the vertical and horizontal axes of the cylinder, said nozzles discharging substantially in line with the V-shaped bottom. After filling the receptacle to approximately 70 per cent of its capacity with the material, compressed air is introduced.

Many materials are efiiciently mixed by a single blast of from one to fifteen seconds duration. Other materials (particularly those in the 0-5 0 micron particle size range) are most effectively mixed by a series of pulsating blasts. The lengths of the blasts and quiescent periods are empirically determined for each material; with the total treatment time being less than twenty-five seconds in practice, although up to forty seconds of treatment is possible utilizing the automatic controls provided. Accordingly, this apparatus is effective to intermix materials from a particle size of approximately one micron to approximately three millimeters. The materials intermixed can have a weight ratio as high as twenty to one.

The doubly oblique position of the special nozzles positively prevents dead areas and causes an ascending vortex around the periphery of the receptacles walls and a descending vortex in its center. The ascending and descending vortices form a connected movement pattern, the V-shaped form of the bottom providing the proper transition between the two movements.

The Laval jet type nozzles effect a maximum energy transfer from air compression to kinetic energy, and thereby provide an extraordinary mixing ratio.

We claim:

1. An apparatus for effecting uniform controlled mixing of powdered granular material, comprising, in combination,

a mixing container having a top wall, a circular side wall, and an inverted conical bottom wall,

a compressed air assembly below said bottom wall including an air pressure manifold communicating with a discharge passage,

an annular series of angularly spaced nozzles in said pressure manifold, said nozzles having their discharge axes disposed obliquely to said inverted conical bottom wall and substantially parallel thereto with their narrow inlet ends communicating with said air pressure manifold and their outlet ends of larger diameter directed upwardly into the container toward the the inner face of the said side wall,

a material collecting cone whose lower marginal edge normally engages the conical bottom wall to close the container and receive mixed material,

piston and cylinder means for raising and lowering said cone,

a shroud connected at one end to said cylinder and the other end connected to the bottom of the cone to conceal the said means from the mixed material descending from the container and also to direct said material through said discharge passage,

means for supplying air under pressure to said manifold,

and vent means on the top wall of the container to effect escape of air and also forcibly return entrained solid particles to the container.

2. An apparatus for effecting uniform controlled mixregulating valve and having an external phase setting ing of powdered granular material, comprising, in comlever for setting said valve, bination, and means connected with said lever to actuate said a miXl'ng contaillel having p wall, a circular Side valve to rapidly turn the compressed air on and oil wall, and an inverted conical bottom wall, 5 from said Source an annular series of angularly spaced nozzles disposed 7 adjacent to the inverted conical bottom wall, said I References (lited by the Examiner nozzles having their discharge axes disposed obliquely UNITED STATES PATENTS to said side wall and substantially parallel to said conical bottom wall, 10 2,273,341 2/42 Vollmer 55-408 X a compressed air assembly unit below said inverted 2,569,567 10/51 Kern 55408 X conical bottom wall and communicating with said 2,884,230 4/59 Pyle et al. 259---4 nozzles to supply air under high pressures, 7 3,029,000 4/62 Kobee 222-195 a pressure feed pipe connected with a source of com- 3,053,642 9/62 Huntley et a1. 259-4 X pressed air through a feed line and a regulating 15 3,097,823 7/63 G 259 4 valve assembly including a housing having a chamber controlled by a valve operated by a piston device, WALTER A. SCHEEL, Primary Examiner. a cam within the chamber in operative relation to said

Claims (1)

1. AN APPARATUS FOR EFFECTING UNIFORM CONTROLLED MIXING OF POWDERED GRANULAR MATERIAL, COMPRISING, IN COMBINATION, A MIXING CONTAINER HAVING A TOP WALL, A CIRCULAR SIDE WALL, AND AN INVERTED CONICAL BOTTOM WALL, A COMPRESSED AIR ASSEMBLY BELOW SAID BOTTOM WALL INCLUDING AN AIR PRESSURE MANIFOLD COMMUNICATING WITH A DISCHARGE PASSAGE, AN ANNULAR SERIES OF ANGULARLY SPACED NOZZLES IN SAID PRESSURE MANIFOLD, SAID NOZZLES HAVING THEIR DISCHARGE AXES DISPOSED OBLIQUELY TO SAID INVERTED CONICAL BOTTOM WALL AND SUBSTANTIALLY PARALLEL THERETO WITH THEIR NARROW INLET ENDS COMMUNICATING WITH SAID AIR PRESSURE MANIFOLD AND THEIR OUTLET ENDS OF LARGER DIAMETER DIRECTED UPWARDLY INTO THE CONTAINER TOWARD THE THE INNER FACE OF THE SAID SIDE WALL,

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