US1964858A - Method and apparatus for treatment of nongaseous materials - Google Patents

Description

July 3, 1934. D. D. PEE'IBLES Filed June 10. 1931 .36 6

4 Sheets-Sheet l Eur/woe 4 METHOD AND APPARATUS FOR TREATMENT OF NONGASEOUS MATERIALS IN V ENTOR. Dawn 2 fise es w ATTON Y.

, July 3, 1934. D. PEEBLEs 1,964,858

METHOD AND APPARATUS FOR TREATMENT OF NONGASEOUS MATERIALS FlEl 4; INVENTOR.

AT'M 'Y.

Patented July 3, 1934 UNlTED STATES METHOD AND APPARATUS FOR TREATMENT OF NONGASEOUS MATERIALS David D. Peebles, Eureka, Calif.

Application June 10, 1931, Serial No. 543,315 In the Netherlands January 12, 1931 9 Claims. (01. 159 4) This invention relateslgenerally to methods and apparatus for effecting desiccation or other treatment of non-gaseous materials by contacting the material, while in suspension in divided con- 5 dition, with a suitable gaseous medium. The treatment 'may be for any one of a variety of purposes, and may in general be any treatment in which it is desired to effect intimate and prolonged contact between the non-gaseous material and the gaseous medium.

A particularly advantageous application of this invention is in the desiccating of non-gas eous materials consisting of solid or liquid materials contained in solution or suspension in an aqueous or other liquid material, and especially in cases where the solid or liquid consists in part or wholly of organic material or material susceptible to injury by heat, for example in the desiccation of milk, or of-milk products, such as whey. The terfi Tlesiccatio n as used herein is to be understood as including the partial or complete evaporation of Water or other liquid from any such material, and while it is customary in many operations to remove sufficient liquid to produce a substantially dry solid product, the term desiccation as used herein is not to be understood as so restricted, as the liquid may be only partially removed so as to effect merely a concentration rather than an actual complete drying of the material.

The invention in its broadest aspects is not restricted to the treatment of organic materials nor to the desiccating of material, as it may also be used to good advantage for many other purposes.

This application is a continuation in part of my application Serial No. 375,640, filed July 3, 1929.

Certain features of the preferred form of the invention herein disclosed are shown and claimed in my copending applications Serial Numbers 164,991 (now Patent No. 1,830,174) and 293,198 (now Patent No. 1,914,895). In application No. 164,991, I have disclosed a novel form of desiccating apparatus utilizing a plurality of nested vortexes or cyclonic movements of gas within an inclosed treatment chamber. Application No. 293,198 discloses a somewhat similar apparatus in which one of the vertexes or cyclonic movements of air is maintained by recirculating a gaseous medium into the treatment chamber. It is characteristic of the apparatus and methods disclosed in those applications that desiccation of organic material can be carried out with a relatively small compact apparatus, and without deleterious effect on certain organic material subject to injury by prolonged heat treatment. In operating apparatus of this character for the dehydration of certain organic materials, as for example milk, I have observed that the dehy- 0 drated product frequently contains dark particles which have apparently been carbonized by heat. Dark particles of this kind are frequently objectionable, particularly where the product is used as a food for human consumption. I have discovered that the formation of these carbon ized particles is due to the contact or accumulation of a certain amount of the material being desiccated, upon surfaces or parts of the dehydrating apparatus which are heated to relatively 7 high temperatures.

It is an object of the present invention to devise a dehydrating apparatus and method which can be used in the dehydration or other treatment of milk, or other material susceptible to 7 injury by heat, by contact with a gaseous medium at relatively high temperature without the formation of carbonized, burned or otherwise injured particles.

A further object of the invention is to provide for treating the divided non-gaseous material with a gaseous medium at a relatively high temperature, while preventing detrimental contact or accumulation of non-gaseous material being treated on surfaces or parts which are of necessity heated to a relatively high temperature by such gaseous medium.

It is a further object of this invention to provide for desiccation of materials subject to injury by heat, by means of a gaseous drying medium at relatively high temperature into which such material is introduced in divided or atomized condition, while at the same time providing means for cooling of interior surfaces of parts of the apparatus which are subject to heating by said gaseous drying medium.

A further object is to provide for desiccation of materials susceptible to injury by heat, by introducing such materials in divided or atomized condition into a gaseous drying medium at relatively high temperature in a central zone within a desiccating chamber, while maintaining an outer zone of gaseous medium at relatively low temperature serving to blanket the walls of said chamber and to prevent heating thereof by the relatively high temperature drying medium, the gas in said outer zone being maintained at a sufficiently low temperature to keep the peripheral wall of said chamber at a temperature below that at which injury would be caused to particles of said material coming in contact therewith. The central high temperature zone and the outer low temperature zone are preferably maintained by causing swirling movement of the gas therein, and the swirling movement is preferably in opposite directions in the respective zones.

It is a further object of this invention to devise an apparatus for the above-mentioned purpose having novel means for actuating a mechanical scraping or cleaning mechanism thereon.

Other objects of the invention will be pointed out hereinafter or will be evident from the following description.

According to this invention, the non-gaseous material to be treated is delivered in atomized or finely divided condition into the central portion of a treatment chamber, and a quantity of gaseous medium is delivered into a position adjacent the center of said chamber so as to receive the non-gaseous material so delivered and cause the same to become suspended therein, while one or more additional zones or gaseous medium are also maintained within said treater chamber and in nested or concentric arrangement about said first named gaseous medium, and the non-gaseous material is caused to pass outwardly and progressively through the gaseous zones thus defined, so as to effect the desired treatment by contact of the gaseous medium with such non-gaseous material, the resulting non-gaseous product being retained in divided condition and being preferably removed from the chamber in suspension in a portion of the gaseous medium and conveyed thereby to any suitable collecting means. The non-gaseous material is preferably delivered into the treatment chamber with an initial outward component of motion, for example, by means of centrifugal atomizing means, and the gaseous medium in the respective zones is also preferably caused to whirl or to have a vortical motion so as to impart a further centrifugal action to the suspended non-gaseous material therein, whereby the outward motion of the non-gaseous material is caused to be effected by means of centrifugal action.

Furthermore, the gaseous medium in adjacent concentric zones is preferably caused to whirl in opposite directions, in order to provide certain advantages in operation, as hereinafter pointed out.

In the preferred embodiment of this invention, the whirling motion of the gaseous medium in the outer zone is maintained by continually removing a portion of the gas from a point in said outer zone and continually re-introducing the same with a substantially tangential component of direction adjacent the periphery of the treatment chamber. The portion of gas thus utilized for recirculation may be removed separately from the portion of gas which is continually removed for the purpose of eventually conveying the treated non-gaseous material in suspension out of the treatment chamber to suitable means for collecting such material, or both of these portions of gas may be removed together and then divided by suitable means. Furthermore, if desired, a portion of the gas removed from the chamber may be passed through collecting means for removing suspended material therefrom and may then be returned to the treating chamber for recirculation.

When the invention is applied for the purpose of desiccation, the gaseous medium introduced adjacent the central portion of the chamber, and with which the introduced non-gaseous material first comes into contact, is at a relatively high temperature, while the gaseous medium in the outer zone is maintained at a relatively low temperature for reasons fully explained hereinafter. The incoming high temperature gaseous medium tends to cause the adjacent parts of the apparatus, and particularly the walls defining the passage through which it is introduced, to become heated to a relatively high temperature. Furthermore, the introduction of this gaseous medium, together with the whirling motion of the gas in the concentric zones, tends to cause eddy currents of gas. As a result, it has been found that, in the drying of organic materials or other substances susceptible to injury by heat, portions of such material tend to be moved by such eddy currents into contact with these heated walls or other parts adjacent the hot gas inlet passage, thus causing burning, discoloration, or other injury to the product, such as to either render the same unsaleable or of an inferior quality. This is particularly true, for example, in the case of milk or milk products. According to this invention these injurious effects are eliminated by introducing air or other gas at relatively low temperature, in relatively small amounts, adjacent the hot gas inlet passage and in such positions as to prevent contact of the divided non-gaseous material with walls or other parts of dangerously high temperature. Furthermore, the relatively low temperature gas thus introduced at these points serves to cool the adjacent parts of the apparatus and to somewhat reduce the temperature to which such parts are heated by the high temperature drying medium.

Further features of the method and apparatus of this invention may be better understood by reference to the accompanying drawings which illustrate, by way of example only, certain specific embodiments of said invention. Referring to these drawings:

Fig. 1 is a vertical section of a desiccating or treating chamber and certain apparatus associated therewith, adapted particularly for treatment of liquid containing material, taken on line 1--1 in Fig. 2, but partially in elevation.

Fig. 2 is a plan view of said treating chamber together with one form of means for supplying gaseous medium thereto and for removing the same therefrom, and for effecting recirculation of gaseous medium in the outer zone.

Fig. 3 is an enlarged vertical section of the upper portion of the treating chamber, showing the means for introducing non-gaseous material to be treated and for introducing the gaseous medium into said chamber.

Fig. 4 is a horizontal section on line 4-4 in Fig. 3.

Fig. 5 is a section on line 5-5 in Fig. 4.

Fig. 6 is a partial view of the lower portion of the treating chamber showing a modified form of the means which may be provided for removing any material which may be deposited on the sides and bottom of the treating chamber.

Fig. 7 is a plan view of an installation showing a modified means of heating the gaseous medium delivered to the treating chamber and also a modification in the means for effecting circulation and removal of gaseous medium therefrom.

Figs. 8 and 9 are plan and elevation views respectively of another form of installation embodying this invention.

Fig. 10 is a vertical section of the treatment chamber shown in Figs. 8 and 9.

of said chamber.

Fig. 11 is a horizontal section on line 11--11 in Fig. 10.

Fig. 12 is a detail of the atomizing means and adjacent parts, of the apparatus shown in Figs. and 11.

Referring to the form of apparatus shown in Figs. 1 to 5 inclusive, a treating chamber is indicated at 1, said chamber being of substantially circular horizontal cross-section, for example a cylindrical vessel having a substantially vertical axis, and being provided with top and bottom walls 2 and 3 respectively. This particular apparatus is intended especially for the drying or desiccation of divided non-gaseous materials, and for this purpose means are shown for supplying a hot gaseous medium to the chamber 1 adjacent the axis thereof, such means comprising a furnace 4 of any suitable type and fired with any suitable form of fuel, a flue or conduit 5 for conducting hot combustion gases therefrom, a branched distribution conduit 6 connected to flue 5 and extending over the top wall 2 adjacent the central portion thereof, a distribution chamber '7 formed between the top wall 2 and a frustoconical partition 8 and communicating with the conduit 6 by means of a suitably shaped opening 9 in said top wall, and helically inclined vanes 11 located in the annular opening 12, of considerably small diameter than chamber l, leading from the distribution chamber 7 into the interior The vanes 11 extend substantially radially as shown in Fig. 4, and are preferably inclined downwardly in one direction circumferentially, as shown in Fig. 5, so as to provide inclined passages 13 therebetween through which the gaseous medium is introduced downwardly and with a whirling or vortical motion into the chamber 1.

A cylindrical or other suitably shaped conduit 15 extends centrally through the distributing chamber 7, communicating at its upper end with an opening 16 in the top wall 2 and having an opening 1'? at its lower end leading into the chamber 1. Suitable means are provided for introducing non-gaseous material to be desiccated through the conduit 15 and for delivering the same outwardly in atomized or divided condition into the whirling gaseous medium delivered into the treating chamber as above described. Such means are shown as comprising a centrifugal atomizer 18 of any suitable type mounted at the lower end of a shaft 19 which extends through and is rotatably supported on an inner housing 20 and which is provided at its upper end with suitable driving means such as pulley 21 mounted on said shaft. Said pulley may be driven at suitable speed for effecting the desired atomization, by means of an electric motor 22 operatively connected thereto by means of pulley 23 and belt 24. The housing 20 together with the shaft 19 and atomizer 18 may be supported by means of a plate 25 secured upon the top wall 2 or to any other suitable fixed supporting means. The material to be desiccated may be delivered to the atomizing device 18 in any suitable manner, for example, by means of a pipe 26 extending through plate 25 and between the housing 15 and 20 and communicating at its lower end with the interior of said atomizing device, for example through the enlarged housing portion 27. The centrifugal atomizer 18 may, for example, be of the type shown and described in the patent application of David D. Peebles and Arthur E. Barlow, Serial No. 527,730, filed April 4, 1931, but it will be understood that the present invention is not restricted to the use of any particular type of atomizer.

It will be evident that the introduction of hot gaseous medium through distributing chamber 7 and through the annular opening 12 will cause the adjacent walls or surfaces, such as partition 8 and conduit 15, as well as the vanes 11, to tend to become heated to a relatively high temperature, and means are therefore shown for introducing relatively cool air or other gaseous medium adjacent these walls or surfaces so as to reduce the heating of certain of these surfaces and also prevent the non-gaseous particles within the treating chamber from coming in contact therewith. For this purpose the plate 25 may be mounted in such manner as to be spaced somewhat above the top wall 2, for example by means of washers or spacers 28, so as to provide a space 29 establishing communication between the outside air and the interior of conduit 15, thus permitting air at relatively low temperature to be drawn in through this space and through the conduit 15 and opening 17. Furthermore, additional air or other gas at relatively low temperature may be admitted through an annular passage 31 between partition 8 and an auxiliary partition 32, said annular passage communicating at its upper end with the surrounding atmosphere (or other gas source) as by means of pipes 33 and opening into the chamber 1 at its lower end through the annular opening 34 which directly surrounds the opening 12 and whose outside diameter is considerably less than that of said chamber. Means such as dampers 36 may be provided for controlling the inflow of air through the passage 31. In case the introduction of air through conduit 15 and through passage 31 would be objectionable, the upper ends thereof may be closed off from the atmosphere and may be connected by suitable piping to any suitable means for supplying a relatively cool gas of the desired nature.

For effecting circulation of gaseous medium in the outer portion of the treating chamber there is shown a flue or conduit 38 communicating with said chamber adjacent the periphery thereof, said flue preferably opening substantially tangentially through the side wall of the chamber and leading to the inlet side of a fan or blower 39 whose outlet is connected to flue or conduit 41 which also opens substantially tangentially through the side wall of the chamber 1 in a reverse direction to the flue 38, so that recirculation of gaseous medium through said flues and fan tends to set up a whirling or vortical motion of the gas in the outer portion of the chamber 1, preferably in a direction opposite to that of the gas delivered to the central portion of the chamber through the vanes 11. As shown in the drawings, for example, the vanes 11 are so disposed as to cause the hot gaseous medium delivered therethrough to whirl in a clockwise direction as indicated by the arrow at A in Fig. 2, while flues 38 and 41 are so connected as to cause whirling motion inthe outer zone in a counter-clockwise direction, as in dicated by the arrow at B in said figure. The flue 88 is shown as connected adjacent the bottom of the chamber 1 and the flue 41 is shown as connected to the chamber at a level adjacent or just below the position of the centrifugal atomizer 18, but it will be understood that the invention is not restricted to the location of these flues in these exact positions.

The means for removing from the treating chamber a portion of the gaseous medium together with the treated non-gaseous material suspended therein, is shown as comprising a conduit 43 opening substantially tangentially through the said wall of chamber 1 in the same direction as the flue 38 and at any suitable height, for example, adjacent the lower end of said chamber, a fan or blower 44 having its inlet connected to said flue, and a fiue 45 connected to the outlet of said fan or blower and adapted to deliver such gaseous medium to any suitable collecting means for separating or collecting the treated non-gaseous material from such gaseous medium. Such collecting means may be of any suitable type adapted for the collection of the particular material produced in the operation of the apparatus. For example, if such material consists of a finely divided dry solid product, such apparatus may consists of cyclone separating apparatus bag filters, or settling chambers.

Means are also shown for removing from the side and bottom walls of chamber 1 any solid materials which may tend to momentarily deposit thereon during the operation of the apparatus, such means comprising flexible cleaning members such as chains 47 connected at 48 and 49 to a supporting frame-work 50 which is rotatably supported for movement about the axis of the chamber 1. In Fig. 1 said framework is shown as mounted upon a shaft 51 rotatably mounted in bearing means 52 and 53 and driven by means of suitable mechanism such as gears 54. In. Fig. 6, on the other hand, there is shown a possible modification in which the supporting framework 5-0 is provided with vanes 56, whereby said framework is adapted to be rotated by the action of the whirling gaseous medium on said vanes. Due to the fact that chains 4'7 are connected to the rotatable supporting frame 50 at only certain points, as at 48 and i9, and to the flexible nature thereof, they are free to swing outwardly trifugal force into close engagement with the side walls of the chamber, and exert a flailing or jarring action thereon, to dislodge particles of material which may momentarily be deposited thereon, before such material has an opportunity to stick or accumulate in any quantity.

The desiccation of non-gaseous material in accordance with this invention may be carried out in the above described apparatus as follows. Hot gaseous drying medium is continually delivered through the inclined vanes 11 into the upper central portion of the chamber 1 and adjacent the centrifugal atomizer 18, whereby such gas is caused to swirl or move about in an inner zone in the general direction indicated at A and to also pass downwardly in such zone. At the same time, a certain amount of gaseous medium is continually withdrawn from said chamber through conduit 43, the amount of gas so withdrawn including a quantity of the gaseous drying medium at a relatively low temperature and augmented by a quantity of water vapor or other vapor liberated from the non-gaseous material as hereinafter described. Furthermore, a certain portion of the gaseous medium is continually caused to recirculate in an outer zone, in the direction indicated at B, by the action of fan 39 which continually withdraws gas through conduit 38 and delivers the same through conduit 41 back into the chamber with a tangential component of direction and adjacent the periphery thereof. Thus a compound movement of the gaseous medium is maintained, that is, nested zones of gas are formed in which the gas is preferably caused to swirl in opposite directions.

The relatively high velocity of swirling movement of the gaseous medium in the outer zone, together with the continual introduction of hot gas into the inner zone, causes these zones to remain fairly well defined, although the limits of the respective zones, and the relative size thereof, may vary considerably in different cases. Furthermore, since gas is continually introduced into the inner zone and continually withdrawn from the outer zone, it is evident that gas must continually pass from the inner zone to the outer swirling zone, and that in so doing the gas must gradually lose its velocity of swirling in the direction of the inner zone and then gradually acquire a velocity of swirling in the opposite direction, so that in certain portions of the chamber there may be regions of relatively little swirling movement. However, the gas moves fairly rapidly through such regions and enters the outer swirling zone, and the absence, or substantial absence, of settling of non-gaseous material within the chamber gives evidence that the movement of the gaseous medium, throughout the entire chamber, is sufiiciently active to prevent such settling from taking place to any large extent.

The material to be desiccated, consisting, for example of milk or a milk product such as whey, is also delivered to the process continually, being introduced through pipe 26 and housing 2'7 to the centrifugal atomizing device 18, by which it is thrown outwardly, by centrifugal force, in atomized or finely divided condition, direcly into the downwardly swirling hot drying gas in the inner zone. This hot gas quickly heats the particles suffieiently to cause rapid evaporation of liquid therefrom. The centrifugal atomizer is preferably rotated in the direction of swirling movement of the gas in the inner zone, for example clockwise in the present case, and thus tends to induce or increase the swirling movement of the gas in such zone and directly surrounding the atomizer. The atomized particles of material are carried along with the whirling gas and the centrifugal force thus created on said particles causes the same to continue their outward movement and to pass outwardly through the inner zone of high temperature gas. While in this zone the small size of the particles and the movement of the gas and particles relative to one another both serve not only to effect a rapid transfer of heat from the gas to the particles, but also to promote escape of vapors therefrom.

The centrifugal force then causes the particles to progress outwardly through the region of transition between the two swirling zones and into the outer zone, and in this movement, the particles are decelerated in one direction and then accelerated in the other direction, and are thus subjected to considerable agitation and the outward progress thereof is somewhat arrested. As the particles take up the direction of the swirling gas in the outer zone they are again subjected to centrifugal force which prevents reentry of the particles into the high temperature gas.

It may be pointed out here that by the time the gas reaches the outer zone it has been cooled to a relatively low temperature, by utilization of its heat in heating the particles and in evaporating liquid therefrom, so that it is no longer hot enough to injure the material being treated. The atomized particles are, therefore, initially brought into contact with a gas at a relatively high temperature which, in the case of milk or other heatsensitive organic materials, would be sufficient to injure the dried material, but the particles are maintained in contact with this high temperature gas for only a limited period of time, and only during the time when their liquid content is sufiiciently high to prevent burning or injury thereof. By the time the particles are heated and partially dried to such an extent that contact with such high temperature might be injurious they have passed out of this high temperature zone and into the outer zone of relatively lower temperature. Furthermore, since the particles are subjected substantially continually to the action of centrifugal force, they are prevented from subsequently re-entering the high temperature zone.

While the gas in the outer zone is at a relatively low temperature as compared to the inner zone, it is still warm enough and of sufiiciently low humidity to effect further evaporation of liquid from the suspended particles, and an important feature of this invention is that the particles are caused to remain in suspension in this outer zone and to swirl about with the gas therein for a sufficient period of time to complete the desiccation thereof. course, carried along with the gas recirculated through conduits 38 and 41 and back into the chamber. An important function of the recirculation is to maintain a high velocity of swirling movement of gas in the outer zone and to increase the time during which the particles are kept therein.

A portion of the gaseous medium containing desiccated particles in suspension therein is also continually withdrawn from the chamber 1 through conduit 43 by the action of fan 44. Since this portion of the gaseous medium is removed from the outer zone it is evident that the particles removed therewith will have been subjected to the action both of the high temperature gas in the inner zone and also of the relatively low tem perature gas in the outer zone, and the rate of flow of gas through the apparatus is so regulated, in proportion to the rate of feed of non-gaseous material thereto, that the particles so removed will have been dried or desiccated to the desired extent. In the apparatus shown in the drawings the rate of flow of gas through the apparatus is determined by the operation of fan 44, but it will be understood that any other suitable means may be used for controlling such rate of flow. From the fan 44 the gas and desiccated particles removed from the desiccating chamber are delivered through conduit 45 to any suitable means for separating the desiccated particles from the gas and collecting the same. In the case of dried milk or whey, such separating and collecting means may consist for example of cyclone separating apparatus or bag filters or both.

In the above described operation it will be seen that the introduction of hot gaseous drying medium through the distributing chamber '7 and annular passage 12 will cause the conduit 15 and the partition 8 to become heated to such an extent that if the suspended particles of milk or whey or other organic material, or the dried or partially dried product thereof, were permitted to come into contact with these heated surfaces, such materials would be burned, discolored or otherwise injured. Furthermore, if the incoming hot drying medium were permitted to directly contact the means for introducing the material to be dried, including the housing means 27 and atomizer 18, so as to heat these parts, and the suspended particles were permitted to come into contact therewith, similar injury would result.

Some of the suspended particles are, of

However, since the fan 44 operates to always maintain a certain reduced pressure within the chamber 1, a current of relatively cool air from the surrounding atmosphere, or other cool gaseous medium if necessary, is continually drawn in through the space 29 and through the annular space between conduit 15 and housing 20, and enters the chamber 1 through the opening 17 at the lower end of said conduit, thus serving not only to cool the walls of said conduit and the housing 27 and atomizer 18, but also to maintain suificient pressure below the opening 17 to prevent formation of eddy currents and to force the suspended particles away from, instead of toward the above mentioned parts. Furthermore, said incoming relatively cool air may in some cases serve to maintain the feed pipe 26 at a relatively low temperature so as to prevent undue localized heating of the material to be desiccated before it is delivered in atomized condition into the desiccating chamber. Similarly, a current of relatively cool air from the surrounding atmosphere, or other cool gaseous medium if necessary, is drawn in through the annular passage 31 between the partitions 8 and 32 and is delivered through opening 34 into the chamber 1 just outside the incoming current of hot drying gas and at a position removed from the side wall of the chamber, and serves to prevent heating of the partition 32 and maintain a sufiicient pressure in an intermediate zone below the opening 34, between the position of introduction of hot gas through the inlet opening 12 and the outer portion of the chamber, so as to prevent creation of eddy currents and to cause suspended particles to be continually forced away from rather than toward said partition. It will be understood that the amounts of cold air or other gas drawn in as above described are relatively small as compared to the inflow of hot drying gas, so that they do not materially reduce the temperature and drying efficiency thereof, as it has been found that the introduction of relatively cool gas at these points, even in relatively small amounts, is decidedly advantageous in connection with the desiccation or treatment of organic materials such as milk or whey. The amount of air drawn in through the annular passage 31 may be controlled by adjustment of dampers 36. In the construction shown, the amount of air drawn in through the conduit 15 is restricted by the relatively narrow space 29 between the plate 25 and the top wall 2 of the chamber, but it will be understood that suitable means may be provided if desired for adjustably controlling the inflow of air at this point also.

The present invention is not to be understood as restricted to the use of drying gas at any particular temperature, nor to the maintenance of any specific temperatures in the inner and outer whirling zones, but it may be stated by way of example that in the desiccation of milk the temperature of the incoming drying medium may be about 400 or 500 F. or even higher, while the temperature of the gaseous medium in the outer zone and of the gaseous medium withdrawn from the desiccating chamber may be in the neighborhood of 180 to 200 F. The temperature of gas in the inner zone may, therefore, be high enough to burn or otherwise injure the solids contained in milk or other organic material being desiccated, but injury to such material does not occur due to the short time of treatment of the material in this inner zone and the relatively large initial moisture content of the particles, and

also because of the means above described which reduces the temperature of certain surfaces of the apparatus and prevents contact of the material with certain heated surfaces. The gas in the outer zone, on the other hand, is below the temperature at which the desiccated or partially desiccated particles are susceptible to burning or injury within the time such particles remain in the desiccating chamber, so that no such burning or injury can occur in either the inner or outer zone. Furthermore, the lower temperature outer zone of gas keeps the side walls of the chamber at a temperature sufliciently low to prevent injury to desiccated particles which come in contact therewith. It may be pointed out that unduly prolonged subjection of heat-sensitive desiccated material, such as dried milk or whey, to temperature even as high as those which may prevail in the outer zone of the desiccating chamber, may cause injury thereto, and it is therefore of particular advantage that the dried material is not allowed to accumulate or collect within the desiccating chamber but is removed therefrom, after a certain length of time, and carried by the spent drying medium to the collecting apparatus above mentioned.

It will be understood that the apparatus may be operated under different conditions of pressure within the desiccating chamber, to meet varying requirements. For example, instead of operating at a pressure slightly below atmospheric as above described, pressures equal to or somewhat greater than atmospheric pressure may be used, it being understood that in such cases suitable means may be provided for delivering the gaseous drying medium and also the cooling gas under suitable pressure.

In many cases hot combustion gases from a suitable furnace may be used as gaseous drying medium, as in the apparatus above described. Such gases may, for example, be used in the drying of milk provided the fuel and the conditions of combustion are such as to avoid the presence in such gases of a prohibitive amount of unburned carbon, ash, or other foreign matter which would tend to contaminate or injure the desiccated material. In certain cases, however, it may be necessary or advantageous to provide other means for heating a supply of air or other gas for utilization as the drying or treating medium. For example as shown in Fig. '7, the gases from a furnace 61 may be conducted by flue 62 to a heat exchanging apparatus 63 in which said combustion gases are passed in heat interchanging relationship with a stream of air or other gas delivered through inlet flue 64, the air or other gas so heated being then drawn through flue 65 and delivered into the desiccating or treating chamber in the same manner as above described. Any suitable form of heat exchanging apparatus may be: used but there is shown in the drawing a form of apparatus comprising a chamber or housing through which the air or gas to be heated is caused to pass, while the hot combustion gases are caused to pass repeatedly and in reverse directions through sets of tubes or pipes 66 extending across said chamber, suitable return chambers 67 being provided for receiving the combustion gases from one set of pipes and delivering the same to the next set. A fan or blower 69 may also be connected at any suitable point in the path of the combustion gases, in order to induce the desired flow thereof through the heat exchanging apparatus. From the heat exchanging apparatus, the combustion gases which have given up a portion of their heat,

may be conducted through conduit 71 to a stack '72 or other suitable means for disposal thereof. It has been found, however, that, in certain cases at least, advantageous results may be secured by recirculating a portion of the partially cooled combustion gases back through the heat exchanger, and for this purpose there is shown a by-pass flue 73 leading from flue 71 back to the furnace 61, and a damper '74 for causing any desired proportion of the gases to be diverted through said flue 73.

In Fig. '7 there are also shown means whereby the removal of gaseous medium from the treating chamber 1 is effected solely through a single flue 75 and a single fan or blower 76 connected thereto, and by which the gas so withdrawn is divided, a portion thereof passing from fan 76 through flue '77, controlled by damper 78, back into the treating chamber with a tangential component of motion, and another portion thereof passing from said fan or blower through flue 79, controlled by damper 81, to any suitable means for separating and collecting suspended non-gaseous material therefrom. By adjustment of dampers 78 and:81 the proportional amount of gaseous medium recirculated, in comparison with the total amount passed through the apparatus, may be regulated as desired so as to give the most advantageous result.

It will be understood that there is no particular reason for combining the means shown in Fig. 7 for eifecting recirculation and withdrawal of gas from the treating chamber with the means shown in said figure for supplying the hot gaseous medium, and that either of these modifications may be applied separately to the system shown in Figs. 1 and 2.

Another form of apparatus in accordance with this invention is shown in Figs. 8 to 12 inclusive. This form of apparatus comprises a treatment chamber 110, preferably substantially circular in horizontal cross-section and having its axis extending in a general vertical direction. The lower wall 111 of said chamber preferably has a raised central portion, being for example conical in shape, as shown. A gaseous medium at relatively high temperature is introduced through conduit 112 which communicates with the chamber through a wall thereof, in this case the upper wall 113. Conduit 112 is shown as arranged in alignment with the axis of chamber 110 and depending for a substantial distance downwardly into said chamber. In communication with the outer end of conduit 112 there is an auxiliary chamber 114 of greater cross-sectional area into which hot gas can be discharged through conduit 116.

Means are also provided in this case for introducing a certain amount of relatively cool gas adjacent and around the periphery of the inner discharge end of conduit 112, such means being shown as comprising a compartment 117 formed about the outer periphery of conduit 112 and communicating with an external conduit 118 through which cool gas may be introduced by induced draft or by suitable means. Said conduit 118 may be connected to any suitable source of relatively cool gas at suitable pressure. Said conduit is also preferably provided with valve means 118' for regulating the amount of gas supplied therethrough. Gas from compartment 117 can flow into the treatment chamber 110 through an annular orifice 119 immediately surrounding the lower end of conduit 112.

The means for continually cleaning the inner walls of the chamber to prevent accumulation hollow shaft 139.

' ber upon said walls of material being treated, is shown in this case as comprising chains 121 carried by suitable supporting rods 122, said chains hanging down along the side walls of treatment chamber 110 and extending inwardly along the bottom wall 111 and connected to a central pivoted member 124. Vanes 125 are provided on the supporting rod 122 for causing rotation of said cleaning means by the swirling gas currents. A pipe 126 extends downwardly and centrally within chamber 114 and conduit 112, and is rotatably journaled and supported upon the top wall of chancber 114 in any suitable manner. The lower end of said pipe 126 is connected to supporting rods 122 by means of a pair of concentric rings 131 and 132 secured together by suitable spacer members 133, the outer ring 131 being connected to rods 122 and the inner ring 132 being connected to pipe 126 by means of a plurality of spaced radial inclined vanes or louvers 136. The annular space 137 between rings 131 and 132 is adjacent and aligned with the annular orifice 119, and in effect serves as a continuation of the same.

Means are also provided for introducing material to be treated into the treatment chamber near the central axis thereof and adjacent the lower end of conduit 112, such means being shown as comprising a rotary or centrifugal atomizing nozzle comprising a disc 138 secured to a rotatable Shaft 139 is preferably journaled within a pipe 141 which extends concentrically within and through the pipe 126. The pipe 141 is preferably spaced somewhat from pipe 126 so as to minimize direct conduction of heat from the chamber 114 and conduit 112 to shaft 139 and the atomizing nozzle connected thereto.

Upon the upper face of disc 138 are a plurality of circumferentially spaced bars 142 having their upper ends interconnected by a reenforcing ring 143. Fluid material to be treated is introduced into the hollow shaft 139 through external pipe 144 and coupling 145 and flows through said hollow shaft and upon the disc 138 through ports 146. Shaft 139 is connected externally to any suitable driving means such as a steam turbine,

so that it may be rotated at a relatively high speed. The fluid material discharged through ports 146 is thrown outwardly along the upper face of disc 138 by centrifugal force and is finally atomized by impact with the bars 142. It is desirable that disc 133 should not be of greater diameter than the pipe 126. and in practice I prefer that said disc should be of slightly less diameter than said pipe. so that said disc is out of the direct path of the swirling gaseous medium delivered between the louvers 136.

The circulating system for maintaining the outer swirling or vortical movement of gase ous medium within the treatment charmis shown as comprising a conduit 14'? commrmicating tangentially with the lower portion of said chamber and connected to the inlet side of a suitable fan or blower 148, and a conduit 149 leading from the discharge side of said fan or blower and communicating tangentially with the upper portion of said chamber. The tangential relationship of conduits 147 and 149 with respect to chamber 110 is such as to maintain a swirling motion in the gaseous medium in the outer portion of said chamber by recirculation of gas therethrough, in a direction opposite to that of the swirling movement of hot gaseous medium introduced through conduit 112 and louvers 136.

The hot gas conduit 116 is shown as connected to the discharge side of a fan or blower 150,

through a suitable heat exchange device 151 which serves to heat the gas delivered by fan or blower 150 to the desired temperature.

portion of the gaseous medium, with treated material in suspension therein, is continually removed from treatment chamber 110 by means of a discharge conduit 152 communicating with the lower portion of chamber 110 near the outer periphery of said chamber, said conduit preferably communicating with said chamber tangentially and in the same rotative direction as the conduit 147 above mentioned. Said discharge conduit leads to a separator 153 for separating suspended treated material from the discharge gas. If desired, the inlet of fan or blower 150 may be connected to the exhaust of separator 153 so as todraw gaseous medium through the desiccator and recirculate the same.

In the operation of this form of the invention the gaseous medium delivered by fan or blower 150 is heated by heat exchanger 151 to a suitable temperature and is delivered through conduit 116, chamber 114, and conduit 112. Said gaseous medium is introduced between the inclined vanes or louvers 136 and is thereby given a whirling motion which serves to maintain an inner swirling zone of high temperature gas adjacent the central portion of chamber 110 and adjacent the centrifugal atomizer. As before, the rotation of the atomizer is preferably in the same direction as the whirling motion produced by vanes 136, and may thus serve to enhance such whirling motion. The operation of fan or blower 148 also serves to maintain an outer zone of swirling gas in the outer portion of the chamber, the motion of which is in a direction opposite to that of the swirlin movement in the inner zone. As in the previously described forms of apparatus, the gas passes from the inner zone to the outer zone and is eventually discharged through conduit 152.

The material to be treated. for example milk to be desiccated. is introduced through pipe 144 and hollow shaft 139. and is finely divided or atomized by the centrifugal nozzle and thrown outwardly into the inner swirling zone of high temperature gas. Such material is carried along in suspension in thegas and is subjected to the successive action of the high temperature gas in the inner zone and the relatively low temperature gas in the outer zone substantially as above described and is discharged through conduit 152 separated and collected in separator 153.

The introduction of relatively cool gas into the treatment chamber through annular orifice 119 serves to materially reduce the operating temper ature of rings 131 and 132 and also serves to in crease the pressure at this point sufficiently to prevent or minimize the formation of eddy currents which would otherwise tend to carry particles of partially desiccated material into contact with the heated surfaces near the lower end of conduit 112.

As in the preceding forms of the invention, the gas introduced into the inner zone A may be heated to a temperature which would be capable of burning or injuring such material, for example to 400 or 596 F. or. even. higher in the case of milk, as the material remains in this inner zone such a short time that it is uninjured even at this high temperature and then enters the relatively cool gas in the outer zone where the treatment is completed without injury. The relatively cool gas in the outer zone also serves as before to main tain the walls of the treatment chamber 110 at a sufficiently low temperature to prevent burning or injury of particles of suspended material coming into contact with such walls.

I claim:

1. In methods of eifecting treatment of material in suspension in a gaseous medium, the steps which comprise continually introducing gaseous medium at relatively high temperature from a conduit into a chamber and causing said gaseous medium to swirl within said chamber about the axis thereof, introducing non-gaseous material to be treated into said gaseous medium in said chamber, and introducing additional gaseous medium at a temperature lower than that of the first-named gaseous medium into an intermediate zone immediately surrounding the position of introduction of said first-named gaseous medium and removed from the side wall of the cham her, so as to increase the static pressure of gas in said intermediate zone.

2. In an apparatus of the class described, a treatment chamber, means for causing a compound whirling movement of gas within the chamber, the inner zone of whirling movement being at a relatively higher temperature than the outer zone, means for introducing non-gaseous material into contact with the gas in said inner zone, and means for introducing a relatively cool gas into the chamber between the inner and outer zones of whirling movement.

3. In an apparatus of the character described, a treatment chamber, an inflow conduit communicating with said chamber and having an inner discharge opening, means for introducing a swirling current of relatively hot gas into said chamber through said conduit, means for producing a swirling current of gas in said chamber about said first named current and in the opposite direction, and means for introducing a relatively cool gas into the chamber adjacent the periphery of said opening.

4. In a desiccator, a treatment chamber, an inflow conduit extending into said chamber, means for causing drying gas introduced through said conduit to swirl about within an inner zone in said chamber, means for causing gas in said chamber to swirl around said inner zone and in an opposite direction, and means for introducing relatively cool air into said chamber adjacent the inner end of said conduit.

5. The method of treating non-gaseous material in suspension in a gaseous medium which comprises introducing gaseous medium at relatively high temperature into the central portion of a treatment chamber, and producing whirling movement of said gaseous medium in an inner zone about the axis of said chamber, maintaining whirling movementof gaseous medium at relatively low temperature within said chamber, in an outer zone surrounding said inner zone and in a direction opposite to the whirling movement of said inner zone, introducing non-gaseous material in divided condition into contact with the gaseous medium in said inner zone and causing such material to pass outwardly through said zones by centrifugal force so as to be brought successively into contact with the gaseous medium in the inner and outer zones, and continually introducing ad; ditional gaseous medium at relatively low temperature in an annular region between the inner and outer zones and immediately surrounding the position of introduction of said high temperature gaseous medium.

6. In an apparatus for treating non-gaseous material in suspension in a gaseous medium, a chamber, means for introducing non-gaseous material in divided condition, with an outward component of motion into said chamber adjacent the central portion thereof, gas inlet conduit means extending into said chamber to a position adjacent the position of introduction of said nongaseous material and provided at its inner end with an opening of considerably less diameter than said chamber, means for directing a current of hot gas through said conduit means and through said opening into contact with said nongaseous material, means for maintaining swirling movement of gas and non-gaseous material in the outer portion of said chamber, partition means extending within said chamber and surrounding and spaced from said conduit means so as to define an annular opening surrounding said first-named opening, the external diameter of said annular opening being considerably less than the diameter of said chamber, and means for introducing gas at a temperature lower than said first-named gas between said conduit means and said partition means and through said an-' nular opening into said chamber.

eous material in suspension in a gaseous medium, a chamber, means for introducing non-gaseous material in divided condition with an outward component of motion into said chamber adjacent the central portion thereof, gas inlet conduit means extending within said chamber to a position adjacent the position of introduction of said non-gaseous material and provided at its inner end with an opening of considerably less diameter than said chamber, means for introducing gas at relatively high temperature through said conduit means and through said opening into said chamber, means for continually removing gas from said chamber at a position outwardly of said opening and for continually reintroducing such gas into the outer portion of the chamber in a tangential direction so as to maintain whirling movement in the outer portion of the chamber and about the axis thereof, partition means extending within said chamber surrounding and spaced from said inlet conduit means and defining an annular opening surrounding said first-named opening and of considerably less diameter than said chamber, and means for introducing gas at a temperature lower than that of said first-named gas between said conduit means and said partition means and through said annular opening into said chamher.

8. In an apparatus for treating non-gaseous material in suspension in a gaseous medium, a chamber, gas inlet conduit means extending substantially axially into said chamber and provided at its inner end with an opening of considerably less diameter than said chamber, means for directing a current of hot gas through said conduit means and through said opening into said chamber, a centrifugal atomizer mounted within said chamber somewhat beyond the inner end of said conduit means and so disposed as to deliver atom-- ized material outwardly across the stream of hot gas delivered through said opening, means for maintaining swirling movement of gas and nongaseous material in the outer portion of said chamber, partition means extending within said chamber and surrounding and spaced from said conduit means so as to define an annular opening surrounding said first-named opening and having an external diameter considerably less than the diameter of said chamber, and means for introducing gas at a temperature lower than said first-named gas between said conduit means and said partition means and through said annular opening into said chamber.

9. In an apparatus for treatment of non-gaseous material in suspension in a gaseous medium, a chamber, gas inlet conduit means extending substantially axially within said chamber and provided at its inner end with an opening of considerably less diameter than said chamber, means for introducing gas at relatively high temperature through said conduit means and through said opening into said chamber, a centrifugal atomizer disposed within said chamber and somewhat beyond the inner end of said conduit means and mounted for rotation in such manner as to deliver non-gaseous material in divided condition outwardly and with a whirling motion in a plane substantially perpendicular to the axis of said chamber and across the stream of gas introduced through said opening, means for continually removing gas from said chamber at a position outwardly of said opening and for continually reintroducing such gas into the outer portion of the chamber in a tangential direction so as to maintain whirling movement in the outer portion of the chamber and about the axis thereof, and additional means for continually removing another portion of gas from said chamber at a position outwardly of said opening and for separating suspended particles from said last-named portion of gas after removal thereof from said chamber.

DAVID D. PEEBLES.

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