US2368699A - Apparatus and method for treating material in a pneumatic current - Google Patents

Description

G. D. ARNOLD Feb. 6, 1945.

APPARATUS AND METHOD FOR TREATING MATERIAL IN A PNEUMATIC CURRENT Filed March 23, 1942 INVENTOR 652/740 Qflxwoao BY QM AMYAM, ATTORNEYS.

Patented Feb. c, 1945 APPARATUS AND METHOD FOR TREATING MATERIAL IN A PNEUMATIC CURRENT Gerald D. Arnold, Wauwatosa, Wis.

Application March 23, 1942, Serial No. 435,762

13 Claims. (01. 34-10) This invention relates to improvements in apparatus and'methods for treating material in a pneumatic current. The purpose of the treatment is broadly immaterial to the invention. It may conveniently comprise heating, refrigerating, or dehydrating, by way of examples. application is a companion to my application entitled Apparatus and methods for treating pneumatically borne material, filed April 4, 1941, Serial No. 386,788. I

As in my companion application, it is broadly a primary object of the present invention to provide, without baflles, for the movement of a pneumatic current and material borne thereby upon a predetermined path through a treating chamber in a manner which may involve complete change of direction in the chamber but which will nevertheless enable substantially the entire capacity of the chamber to be used and will enable the effect of the treatment upon the materialto be predetermined with accuracy such as would be impossible if the material did not move upon a well defined path for a well defined distance during treatment.

It is a further object of the invention to assure complete delivery of all material from the treating chamber upon the completion of the proper period of treatment and to tend to prevent any of such material from lodging or sticking to any portions of the walls of the chamber.

As in my companion application above identifled, further objects of the invention include the provision without baflles and in compact form, of means for inducing a change in rate as well as a change in direction of flow of the gas currents and material borne thereby, whereby automatically to provide some regulation for the movement through the chamber of particles of differing weight and, moreover, to provide relatively high velocity currents for hearing such particles into the chamber, and currents of lesser velocity acting upon the particles in thechamber.

A further object is generally tosimplify and improve the construction, arrangement and operation of devices for the purposes mentioned. Other objects will be apparent from the following disclosure of the invention.

In the drawing:

Fig. 1 is a view in vertical axial section device embodying my invention.

Fig. 2 is a view of the device as it appears in horizontal transverse section on the line 22 of Fig. l.

Figs. 3 and 4 are views similar to Fig. 1 showing modified embodiments of the invention.

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Like parts are identified by the same reference I characters throughout the several views.

The present The mode of operation of the devices herein illustrated is similar in most respects to the devices illustrated in the companion application above identified, the chief difference being that in the device herein disclosed the inlet and outlet are at the same end of the treating chamber so that the vortices formed in the ingress and egress of gas are concentric, one vortex being located within the other. The several devices herein disclosed are believed to represent improvements in that the movement of the gases and the pneumatically conveyed particles of material to be treated can be more accurately predetermined and the discharge of such particles from the treating chamber can be more accurately assured at the termination of the desired treating period.

Referring to the device shown in Fig. 1, the enclosed chamber 5 of suitable height receives through pipe 6 a pneumatic current and pneumatically borne particles of material to be treated, such material preferably being finely subdivided and delivered in pipe 6 through the rotary charging valve 1 driven by motor 8. The pipe 6 communicates through fitting 9 tangentially with chamber 5 near the bottom of the chamber. The fitting 9 preferably leads into the lowermost point of chamber 5, merging with the beveled wall Ill which comprises one end wall of the chamber and which has a helical upward pitch sufllcient in 360 degrees to clear the inlet fitting so that in one circuit of chamber 5 the incoming current of gas and the material pneumatically borne thereby will advance axially of chamber 5 for a distance equalto the axial dimension'of the current. The wall l0 connects the outer cylindrical side wall of chamber 5 with a central tub'e II which comprises a part of the treating space and extends into chamber 5 a substantial distance and also extends beneath the bottom wall In for a substantial distance as shown in Fig. 1.

By reason of the tangential admission of gases through fitting 9 to chamber 5 a whirling vortex or current of such gases is established in chamber 5 between the tube II and the outer wall of gential outlet so disposed as to cause opposite a rotation of the gases approaching the outlet, or it may be done, as suggested in Fig. 1, by the pro-' 'drlcal wall of chamber 50 with the tube 0. In

. this instance the tube has a bottom closure 2i establish the direction of the vortex or whirling rotation of gases leaving the chamber, but it is also sufiicient to establish the convection current through the apparatus. no fan at the inlet being essential in this device. Fig. 2 clearly shows how the fan It, rotating in a clockwise direction, establishes a clockwise vortex rotation in the tube H, while the tangential inlet fitting 8 establishes a counter-clockwise vortex in the vicinity of the outer wall of the chamber 5.

At some point above the upper end of tube II, the exact location depending on the relative dimensions of the parts, the two vortices established at the inlet and outlet respectively, will interact and merge with the result that near the top of chamber the incoming current moving upwardly and counter-clockwise will cease its upward movement as well as its counter-clockwise movement and will gradually assume helical movement downwardly in a clockwise direction -of vortex rotation. Due to the change in direction there will be a decrease in current velocity at the top of the chamber and any pneumatically borne material entrained with the gases will tend to fall. The heavier material will not move toward the center of the chamber as rapidly as the lighter material and therefore will tend to fall back into the ascending pneumatic stream while the lighter material, more readily changed in its direction, will move centrally and out. This factor tends to keep the heavier material in the air stream for a longer period than the lighter material, this being an advantage in automatically controlling the conditioning of the material. Where dehydration is the object, the greater weight of the heavier material is generally due to a greater proportion of moisture carried thereby, and the longer the tension of the heavy material in the air stream will tend to dehydrate it to the same extent as is accomplished in a shorter period in the case of the lighter material. Where the object is either heating or cooling, the diflerence in weight will usually be attributable merely to diflerence in size of the particles and the automatic tendency to retain the heavier particles for a longer period will automatically tend to equalize the introduction or extraction of heat by giving a longer exposure to the air stream in the case of the heavy particles requiring such prolonged exposure.

The device is not only adapted to handle solids such as chopped alfalfa, fertilizer, meal, and comminuted kelp, any one of which would normally be introduced through a charging valve such as that shown at I, but the device may also be used either concurrently or separately to operate on liquids such as may be introduced through the pressure supply line it and delivered through the spray nozzle It in a finely atomized form into the vortex in which the pneumatic current has already been established within the chamber 5.

The top of the chamber, to minimize the possibility of lodgment of material. is preferably spherically rounded as indicated at 20, but in practice, this being difilcult and expensive to make, some compromise may be necessary as suggested in the devices of Figs. 3 and 4.

The device shown in Fig. 3 hasa chamber I0 provided with a modified top 200 and a beveled upon which I provide a cone 22 carrying a helical false bottom 23 for guiding the whirling current tangentially admitted near the bottom of tube lit through the inlet pipe 6.. This current, admitted tangentially between the cone 22 and the helical false bottom 23, is constrained to rotate counter-clockwise and at the same time to advance axially by reason of the pressure diflerentials in the apparatus, assisted ,by the helical pitch of the false bottom 23. The charging valve 1 for admitting finely divided particles of solid material to the pneumatic current in the inlet pipe 80, may be identical with that shown in Fig. 1. Likewise, the pressure tube l8 and spray nozzle I 8 are identical with those previously disclosed with the exception of location, the spray nozzle in this instance preferably being located at the apex of the cone 22 which, together with the false bottom 23, comprises the actual bottom of tube 0.

In this construction the vortex established at the inlet is the inner vortex, and the vortex established at the outlet is the outer vortex of the two concentric vortices in chamber 50. The outlet occurs through the same fitting 8 described in connection with Fig. i, from which outlet pipe I'III leads to the eyecf a centrifugal 'blower fan lit for establishing the necessary convection current through the apparatus. The mere fact that the outlet is tangential is sufiicient to set up the desired clockwise rotation of gases in an exit vortex which annularly surrounds the counterclockwise inlet vortex. The two vortices react upon each other above thetop of tube H0 in substantially the manner already described, the one vortex gradually retarding the other until the air currents reach a substantially static condition near the top of the treating chamber 50, at.

device is suitable may include milk, molasses and eggs. Especially when the material is adhesive,

as in the case of eggs, it is an advantage to have a plurality of well defined currents of gas intervening between the spray nozzle l9 and the first point at which the material sprayed can contact a metallic surface.

Note that in tube iii! the vortex of gases at the inlet is established in advance of the introductlon of the spray from nozzle l9. Before the spray can diffuse itself through the whirling gas currents rising upwardly along the wall of tube H0, such currents will be free within the chamber 50 and encircled by an opposite vortex descending along the cylindrical outer wall of the chamber. The rotative velocity of the respective currents will rapidly diminish through their frictional engagement with each other, so that near the top of the chamber there will be no general movement either upwardly or downwardly or rotatively but only radial movement from the ascending path to the descending path. Therefore the material will be quite materially dehydrated before it can possibly contact any surface, and before it picks up any substantial rotative motion in the descending path such as With respect to eggs and fruit juices and other sired axial length of chamber may be employed in any of the devices disclose'di It is a phenomenon of the disclosed apparatusv that in a circular chamber closed at one end, a vortex current established at a point remote from such end will continue substantially to the top of the chamber, giving a period of treatment which may be controlled as desired. Moreover, while reference has been made to the top of thechamber, for convenience, the fact is that fortreating light finely divided material the cham-' ber may 'be horizontal.

Not only are the devices herein disclosed adapted to treat ether solids or liquids, but they are adapted to treat liquids and solids concurrently as, for example, in the dehydration of green produce such as comminuted alfalfa, hay or kelp or cannery refuse, in which case the air or gases admitted through the inlet may be previously heated to a high temperature and the liquid may constitute molasses or the like for admixture with the dried produce to enrich the same for use as a stock food. In the device shown in Fig. 4 the treating chamber 5| is generally similar to the treating chamber 50 of Fig. 3, having a cylindrical wall and a top 2! with a beveled side margin. In this instance, however, that portion of the tube III which, in Fig. 3, was extended into the interior of chamber 50, is here omitted, tube Ill being merely an extension of the chamber which is of smaller diam-.

eter than the main portion of the chamber.

Tube III is provided at its bottom with a closure 2| and with a false bottom comprising a cone 22 and a helically pitched wall 23 exactly as described in connection with Fig. 3. In this instance, however, the outlet is at this point and the pipe I'H leads to the eye of the blower fan IGI to establish convection currents through the apparatus.

As in Fig. 1, the inlet occurs through a pipe BI and a fitting 9 which admits the gas tangentially near the outer periphery of the larger diameter chamber portion 5|, fitting 9 merging with the beveled and helical wall H] which gives the incoming vortex an axially upward pitch.

Solids to be treated may be introduced in comminuted form through one or both of the charging valves 1, one of which is provided on the inlet conduit BI and the other of which is located on the top 2M of the treating chamber 5|. The top may have a conical surface at 22! in the apex of which the spray nozzle l9, supplied byv pressure pipe l8, may be downwardly directed. This modification is included to exemplify a construction in which no tube such as that shown at H in Fig. l and at I10 in Fig. 2 intervenes between the two vortices. The incoming vortex, by reason of the tangential introduction of gases, forms on the outer cylindrical wall of the treating chamber 5i. while the exit vortex, formed by the tangential withdrawal of gases from the tubular extension III of the chamber, is formed within the tube but extends upwardly into the treating chamber the parts and the velocity of the fan. At some point near the upper part of'the chamber II the two -v'ortices will neutralize each other through their relative interaction so that there rotatively.

In all forms of the invention it is preferred that the treatment be automatically controlled thermostatically by incorporating a thermostat 25 in the path of the gases near the point where they are discharged from the treating apparatus. In Fig. 1 this thermostat is located in the exhaust pipe II. In Fig. 3 it is located in the outer wall of chamber ,50, while in Fig. 4 it is located in the wall of the reduced extension III of the treating chamber. Incidentally, whether or not the tube is wholly outside of the treating chamber as in Fig. 4, or whether it extends into the treatingchamber as in Figs. 1 and 3, it may be regarded as a reduced extension of the chamber. As disclosed in the com-.

panion application above identified, the thermostat, in any case, will be governed by the temperature of the discharged gases to vary either the rate at which material is admitted to the chamber or the temperature of the gases or both of these factors, in a manner to compensate for chamber not only rotatively but axially without ,7

contacting any baflle or chamber while at the point where the change in direction occurs. A better automatic control is achieved and a much better purging of all treated material from the chamber with little or no tendency to lodge therein, since all bottom surfaces are swept by high velocity currents either entering or leaving the chamber, and the currents are not able to deposit material conveyed thereby on any top surface of the apparatus.

While it is important to the preferred embodiment of the invention that the vortices established by the inlet and outlet means should be opposite in their direction of rotation, in some aspects of the invention this is unnecessary since many of the advantages of having the inlet and outlet at the same end of the chamber and having a continuous and well defined path of circulation through the chamber, can be realized without the feature of opposite vortex rotation.

Where the vortex continues in a single direction of rotation throughout the treatment, the inlet should preferably be on the outside and the discharge end of the vortex should be at the inside. This is especially true when relatively heavy or coarse material is being-treated and, in fact, whenever solids are being treated the constructionsof Figs. 1 and 4 with the tangential admission port at the outer periphery of the. treatment chamber are to be preferred to the disclosure of Fig. 3 where the" admission port is at the interior. The reason for this lies in the fact that the heavier solids tend to be maintained centrifugally at the outside of the vortex. Hence if the admission vortex is on the outside, the heavier particles'will continue up the outside of the chamber to its very top before their momento an extent determined by the dimensions of.

It will be understood that in all mm of the invention the nature of the gas admitted to the apparatus will vary according to the type of treatment desired. The gas used to establish the desired convection current may, for example, be air either at atmospheric temperatures or heated or chilled. Or it may be the inert products of combustion, mainly carbon dioxide or any other gas. For instances where the desired treatment is chemical in its nature, the gas constituting the convection current may be active chem ially. An arrangement for heating gas is disclosed in my Patent No. 1,988,677, and an arrangement for chilling gas is disclosed in my Patent No. 2,241,654.

It is further to be understood that various changes may be made in the devices disclosed, particularly with reference to the points at which the controls are located or the material to be treated is supplied. or with reference to the specific locations of inlet and outlet ports for the convection current, or with reference to other matters relating to relative dimensions or positions of parts.

It is believed that the method of treatment has been fully disclosed in connection with the discussion of the apparatus. However, it may be 1 briefly summarized to point out that the method herein disclosed involves the preparation of the material to be treated in a form suillciently light and finely divided so that it may be pneumatically conveyed by the treating current. The treating current is thereupon established,- preferably in a chamber substantially closed at its end, by directing the current successively upon two substantially concentric helical vortex paths throughout at least a portion of which the porj tions of the current upon the respective paths are in mutual communication and contact. The material to be treated is introduced into the current at a point where it will be carried by the current through the two helical and concentric paths consecutively. Thereafter, by any usual means (not shown here) the treated material will be separated from the treating gas in any desired manner as, for example, in the conventional settling chamber or the conventional cyclone separator.

Broadly, the method and apparatus is as claimed in the companion application above identified, and specifically the improvements herein disclosed are claimed as follows.

I claim: l. The combination with a treatment chamber 01 generally circular cross section and axially elongated and substantially closed peripherally and transversely at its upper end, said chamber [being interiorly open and unobstructed at and near said end of an inlet duct communicating peripherally and tangentially with the chamber an outlet duct communicating tangentially with the chamber at a point nearer its axis than the point of peripheral communication of the inlet duct therewith, both points of communication of the respective ducts ,with the chamber being reascents end, in combination with a chamber extension portion of reduced cross. section disposed at the other end of the chamber and opening substantially axially therefrom, inlet and outlet pipes communicatingrespectively with the end of the chamber adjacent said extension and with the end of the chamberextension, the points of communication of both of-said pipes with the chamber being remote from the closed end of the chamber, and at least one of the pipes including means for inducing rotation in the chamber, and comprising a blower fan casing having a tangential outlet pipe leading therefrom and having an inlet opening leading centrally from the extension portion of'said chamber and remote from the closed end of the chamber and a rotor operable in said casing and adapted to produce a vortex, said fan casing opening communicating said vortex to said chamber.

3. The combination with a treatment chamber of axially elongated form and generally circular cross section having an end wall and a substantially coaxial extension portion extending at least outwardly from said end wall, of inlet and outlet pipes respectively communicating with said chamber immediately adjacent the end wall thereof and with the said extension, and means for feeding to the inlet pipe material to be treated each of said pipes comprising means for inducing vortex rotation and the respective vortex producing means being opposite as to the direction of vortex rotation induced thereby.

4. The combination with a treatment chamber of generally circular cross section and elongated axis, said chamber being substantially closed peripherally and transversely at one end and provided with an apertured wall at its other end, of a tubular chamber extension portion extending through said wall and projecting for a material distance axially of said chamber both interiorly and exteriorly thereof, inlet and outlet pipes one of which communicates tangentially with said chamber immediately within said wall to occasion vortex rotation in the chamber and the other with said extension at a point exteriorly of said wall and tangentially in an opposite sense to occasion opposite vortex rotation in said extension.

5. The combination with a treatment chamber axially elongated and of generally circular crosssection, of a tube constituting an extension portion of said chamber, said tube being of smaller cross section than the chamber and extending axially into the chamber and axially away therefrom, a wall for said chamber extending about an intermediate portion of said tube,- inlet and outlet pipes communicating with said chamber, one of said pipes communicating with the chamber proper, the interior of said chamberbeing open and unobstructed adjacent said tube and the pipe communicating with the chamber proper opening thereto at a point adjacent the outside of the chamber immediately adjacent said wall, the other of said pipes communicating with said tube outside of the chamber first mentioned, said pipes having a tangential disposition with regard to the chamber and tube respectively and opening oppositely in the sense of the vortex rotations tending respectively to be established, means for establishing a convection current through said pipes, chamber, and tube, and means for introducing into said current material for treatment in said chamber.

6. The combination with a vertically elongated chamber of generally circular cross section substantially closed peripherally and transversely at its top, said chamber having a lower end wall and a central opening therein of smaller area than the cross section of the chamber proper, an extension of said chamber communicating with the chamber through said opening an inlet pipe communicating with said chamber tangentially in immediate proximity to said wall, an outlet pipe communicating with said extension tangentially at a point below said wall, fan means associated with one of said pipes for establishing a convection current through said pipes and chamber and extension, and means for introducing into said current adjacent its point of tangential admission to said chamber a material to be treated therein.

'7. The combination with an open and unobstructed treatment chamber substantially closed at one end and of generally circular cross section, said chamber being adapted to facilitate the propagation of a vortex current therein of an outlet port leading tangentially from the periphery of said chamber at a point adjacent the end of the chamber opposite its closed end and providing means for finally discharging said current and treated material. an inlet port communicating with said chamber closer to its axis than said outlet port and also remote from its closed end, means for establishing a convection current through said chamber between said ports whereby to establish at least one vortex in the chamber. and means for introducing into said current in the vicinity of the inlet port a material to be conveyed and treated by said current in said chamher.

8. A method of treating material in the course of its pneumatic propulsion, which method comprises subdividing the material in a form sufficiently fine to be pneumatically propelled by the treating current, establishing a convection current of treating gas in a chamber substantially closed at one end, introducing such gas into said chamber and discharging it from the chamber at a point remote from said end While directing said gas in an inner vortex path helically of said chamber toward its closed end and upon a co-axial concentric outer helical path away from said closed end toward the point of discharge, introducing the material to be treated into the current for traversing portions of the concentric helical paths consecutively, the current portions in the respective helical aths being exposed to each other for at least a substantial part of their extent for the transfer of material and gas from one path to the other, and removing the materialfrom the chamber remote from the closed end of the chamber after the material has traversed at least a portion of both of said paths, and. removing the material from the gas.

9. The combination with art open and unobstructed treatment chamber of generally cylindrical form substantially closed at its top end, of a generally cylindrical axial extension of said chamber of materially smaller diameter than said chamber and opening from its bottom end, ports communicating tangentially with the bottom portion of the chamber and chamber extension respectively whereby both of said ports are located remote from the closed top end of the chamber,

means for establishing a convection current through the chamber between said ports, whereby to establish at least one vortex in the chamber, and means for introducin into the current in the vicinity of one of said ports material to be conveyed by said current in a vortex path through said chamber for treatment by-the current in the course of pneumatic convection of such material, the path of the material being initially in an upward helical direction in said chamber.

10. The method recited in claim 8, in which the inner vortex moves in an upward direction centrally of said chamber and the outer vortex moves in a downward direction along the periphery of said chamber.

11. A method of treating material in the course of its pneumatic propulsion, which method comprises establishing a convection current of treating gas in a chamber substantially closed at its upper end, introducing such gas into the chamber and discharging it from the chamber tangentially at different radial distances from the axis of the chamber whereby to establish concentric vortices in the chamber traversed consecutively by said current moving first in an upward direction through one of said vortices and then in a downward direction through the other, introducing material to be treated into the current to traverse at least portions of the concentric vortices consecutively, while exposing to each other for at least a. substantial part of their extent the current portions in the respective helical paths of the respective vortices, to facilitate the transfer of material and gas from one of said vortices to the other, followed by the removal of the material from the gas after it has traversed at least a portion of both vortices.

12. The method recited in claim 8 in which the inner and outer vortices rotate in opposite directions.

13. A method of treating material in the course of its pneumatic propulsion, which method comprises establishing in a confined space a pneumatic current of treating gas comprising concentric inner and outer vortices through which said current passes consecutively in opposite directions of axial and rotative movement, introducing into the outer vortex of said current the material to be treated in suificiently finely divided form to be pneumatically propelled, passing such material forth in one axial direction in the outer vortex and back in an opposite axial direction in the inner vortex, and exposing the gases of the respective vortices to each other for mutual interaction throughout substantial portions of the axial length of the vortices, whereby to transfer gas and material from one vortex to the other.

GERALD D. ARNOLD.

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