US 3600818 A
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Description (OCR text may contain errors)
United States Patent lnventors Franz Lang Lissberg;
Gustav Gruen, Eckartsborn; Kurt Schwahn, Lebach; Franz Josef Juchem, Lebach, all of, Germany 816,930
Apr. 17, 1969 Aug. 24, 1971 Gebruder Grun KG Maschinentabrik (Oberhesen), Germany Appl. No. Filed Patented Assignee METHOD OF AND APPARATUS FOR TREATING POWDERY OR GRANULAR MATERIALS WITH GASEOUS, LIQUID OR SOLID AGENTS 0R STABILIZERS 8 Claims, 3 Drawing Figs.
US. Cl 34/10, 99/56, 99/201, 23/313 Int. Cl F26b 3/10 Field of Search 34/10, 57,
References Cited UNITED STATES PATENTS 2/1946 Alther 2/1949 Stephanoff.. 9/1959 Skoglund FORElGN PATENTS 5/1955 GreatBritain................ 4/1965 GreatBritain Primary Examiner-Frederick L. Matteson Assistant Examiner- Robert A. Dua Attorney-Edwin E. Greigg 34/10 X 34/57AX 34/57 A X ABSTRACT: A system including a conically upwardly extended treating chamber into which granular dry material is fed that descends against a rising cold gas stream while being sprayed by a liquid and cold gas mixture. The sufficiently wetted and thus heavy particles leave the chamber through an outlet in its base while the lighter particles are reintroduced by the airstream into the spraying region of the chamber. The cold airstream is divided into a plurality of part streams, one part stream serves as carrier for said dry material and one part stream constitutes said rising stream.
PATENTEUAUB24|97| I 3, 00 18 sum 1UF 2 FRANZ LAM eusmv cnum Kum scnwnm FIG] ATTORNEY FRANZ JOS JlKHEM BY 4% PATENTEU AUG24I97I 3.600.818
sum 2 OF 2 mvsmoas FRANZ urge eusmv enusn KURT scnwnm FRANZ JOSEF JUCHEM ATTORNEY BACKGROUND OF THE INVENTION This invention relates to an improvement of a known method of and an apparatus for treating powdery or granular materials with other powdery, liquid or gaseous materials wherein in the treating chamber a cloud of the dry material (i.e. a material-air mixture) is generated which is sprayed with additional liquid or powdery materials injected by nozzles through openings arranged in a circular array along the circumference of the treating chamber. At each opening, by virtue of the nozzle pressure, an injection-type effect appears which draws into the treating chamber the gas from around the nozzle to which the gas may be delivered by conduit means. As a result, inside the treating chamber a surface motion of the dispersed liquid particles and powder particles occurs. By the interaction of the admitted, pretreated (heated or cooled) air agglomerates are formed which have the desired properties. The aforedescribed process is disclosed in German Pat. application G 41,164 We, filed July 23, 1964.
In the apparatus for performing this process the powdery materials are introduced into the treating chamber from above through a separator which, in turn, receives the material from a dosing device, a scale, a centrifugal device and a pneumatic conveyor which operates in the system of recirculated air. Thus, in this apparatus the products move helically downward and, at the exit, may be seized by an entering gas flow in order to be carried into the spraying range of the nozzles. The gas stream is adjusted in such a manner that only those particles may pass through the exit which have a determined sinking speed, whereas the finer, not yet sprayed powdery particles are carried by the rising gas stream and are continuously reintroduced into the spraying range. Fine particles which rise with the gas are separated by two separators and are reintroduced to the spraying area by means of an appropriate blower whereas the carrier gas is released into the atmosphere through a filter.
As part of the above process, it has also been known to direct the gas in a circulating flow and to cool or heat the same according to requirements. It is further known to dry the products floating in a suitable gravity-type shaft drier after they leave the treating chamber and to heat the required drymg gas.
Further, it was found that when powdery materials are used which consist of several components that have to be premixed, it is significant how this mixing is performed. It has been found that a pneumatic mixing by means of a gas, particularly according to the Airmix process, results in a substantially more homogeneous structure and thus leads to constant friction and flow conditions which may be of decisive significance as far as the accuracy and the operational safety of the process are concerned.
Using the aforedescribed process for manufacturing, for example, milk substitutes which are materials that require extensive cooling and which contain liquids of an increased tendency to agglomerate, it is possible to obtain a milk substitute powder having a fat content as high as 30 percent, but it is not possible to obtain highly concentrated milk substitutes having a fat content of 60 or 80 percent, or a fat concentrate of 98 percent or more. This deficiency is particularly significant because by means of spraying towers where the increase of fat content is effected during the dispersion of low fat milk, it is possible to produce a concentrate of over 60 percent even though with relatively high operating costs and with the disadvantage that temperature-sensitive additional materials, such as vitamins or lecithins, could not precedingly be added to the milk.
It has also been attempted to produce with known processes a low fat milk concentrate of 55 percent fat. It was found, however, that the product thus manufactured did not entirely satisfy the requirements concerning its capability to be stored, its agglomeration and resistance to changes in temperature.
OBJECT OF THE INVENTION, SUMMARY OF THE IMPROVEMENTS AND THEIR ADVANTAGES It is an object of the invention to provide an improved method of treating material in an environment as set forth hereinbefore and an apparatus for performing the method to obviate the aforenoted disadvantages.
The process according to the invention incorporates the following changes:
1. The heat exchange is increased by dividing the heat-conditioned gases into two or more partial flows which are reunited in the spraying tank or downstream thereof and which are returned to the cooling apparatus through a main filter.
2. One of the partial cooling streams is used to carry the powdery material from the dosing station to the treating chamber (spraying tank) whereby the flow rate of air used for this operation equals or is larger than 30 mF/min.
3. After dosing, the powdery material (such as milk powder) is drawn by a dry blower, conveyed with turbulence by a conveyor blower, accelerated and carried to the treating chamber through a connecting conduit by means of a cooled gas having a temperature of less than 2 C.
4. Downstream of the treating chamber there is arranged a sieve device closed at all sides through which the finished product is passed and then delivered in a conveying device, also closed, to a weighing station and during such transportation the material is exposed to a temperatureconditioned (mostly cooled) gas stream.
5. The cooling of the gas stream is performed in two stages whereby the required vaporizer of the first stage cools the gas to slightly above the freezing point and the vaporizers of the second stage are of double surface design and are made of two interchangeably operative parts in which the gas is brought to the desired final temperature.
6. Between the cooling gas inlet into, and its outlet from, the spraying tank, there is provided a connecting conduit that includes a regulating device. Y
7. At the outlet of the spraying tank there is provided a dosing device with a closable inlet.
8. Between the main filter and the cooling device there is provided a safety filter.
9. The dust accumulated in the main separator may be either bagged or recirculated through a pneumatic conveyor whereby the conveying or carrier gas is drawn from the temperature-conditioned gas conduit.
10. The parts of the apparatus are isolated.
11. The liquid to be dispersed is, shortly before spraying, brought to the exact required temperature by directing it through a counterflow cooler.
12. The spray openings provided in the treating tank are shielded and are connected with the main blower through a controllable gate and through flexible tubes branching off an annular conduit surrounding the treating tank,
13. The supply container for the dry material is formed as a fluid bed and is exposed to a temperature-conditioned gas flow.
14. For the substantial increase of the heat exchange, the upper portion of the spraying tank is upwardly conically extended so that the gas quantity passing therethrough may be increased whereby simultaneously the dwell time of the obtained agglomerates is substantially increased without an increase of the dust formation.
All of the aforenoted modifications in the known process effect a stabilization of the agglomerate so that it will be form retaining, classifiable, and, when affected by the cooled gas stream, may crystallize in a satisfactory manner. From these several advantages result: the liquid particles are not larger than 5-15, or maximum 30 microns; in lieu of carrier materials, separating materials may be used; the finished product may be freely shaken, is dust free and does not tend to agglomerate; it has a high degree of wettability and an increased capability of being store. With the method according to the invention it is possible to obtain, when proper fats and separating materials are used, fat concentrates of over 98 percent. A precondition for the latter is a certain requirement concerning the treatment of the fats, the temperature conditioning of the gases as well as a thorough distribution of the dry materials and the liquids during the spraying step.
The invention will be better understood as well as further objects and advantages will become more apparent from the ensuing detailed specification taken in conjunction with the drawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic ,elevational view of a system for making milk substitute of up to 80 percent fat content;
FIG. 2 is a schematic elevational view showing a part of the system of FIG. 1 with additional devices, and
FIG. 3 is a greatly enlarged sectional elevational view of a detail of FIG. 2.
DESCRIPTION OF THE EMBODIMENT The material'mixture which, for example, may be a milk substitute consisting of various dry components, is introduced in a mixed state into the container 1 from which the material is forwarded to dosing elements 2 which, in turn, deliver the premix uniformly to the suction tube of the conveyor blower 3. From there the materials travel in conduit 4 to separator 5 and then through hopper 5a and terminal opening 5b they are introduced into the treating chamber (spraying tank) 6 in such a manner that in its lower portion a material cloud is generated which is characterized by a rising central column and into which liquid is sprayed by a plurality of nozzles c across openings 10d arranged circumferentially in the chamber 6. The upper third of the latter consists of an upwardly widening conical enlargement 6a. As may be observed in FIG. 1, the hopper opening 5b is disposed within the conical enlargement 6a. The said liquid is drawn by a pump 7 from a supply container 9 and is driven through a counterflow cooler 8. Each spray opening 10 d is shielded by a closure or housing 10 and the space enclosed thereby is connected by a flexible conduit 10a with an annular collector conduit 10b which surrounds tank 6 and which receives gas forced by blower 14 through conduit 10c and gate or throttle device 10f The agglomerates forming in the spraying space fall against the rising gas stream, pass through a cooled sieve 11, and are conveyed to the bagging scale 13 through a cooled conveyor device 12. The cold air drawn through blower 14 from the cooling device 15, through the conveyor blower 3, the conveyor device 12, the sieve 11, and the conduit 16 is passed through two separators 17. The dust separated thereby is introduced to the outlet of the main separator 5 by means of a blower 18. The air emerging from the two separators 17 is directed through the blower 14 into the main filter l9 wherefrom it is introduced dust free into the cooling device through a safety filter 21. The dust accumulating in filter 19 is collected in bags 20.
The cooled air subsequent to leaving the cooling device 15 is divided into two or more partial streams of which one partial stream proceeds, as a main stream 16, directly to the spraying tank and is controllable by means of the gate 30. As the air streams upwardly in the chamber 6, it loses speed in the range of the hopper outlet 5b by virtue of the gradual enlargement 6a of the chamber 6. As a result of this arrangement, the material introduced into the chamber dwells slightly above the spray openings 10d and floats slowly downwardly against the upwardly proceeding air current. A second stream proceeds through the control gate 27 to the conveyor blower 3 and a third stream flows through the control gate 28 to the conveyor device 12 and proceeds in a direction opposite to that of the treated material which travels towards the bagging scale 13.
This third partial stream passes through sieve ll, enters the treating chamber 6 and is recombined with the aforenoted main stream passing through gate 30. All the air streams are in a circulating flow in a closed conduit system. Stated differently, and as may be observed in FIG. 1, no air inlets for drawing air into conduits from the outside are provided. Between the safety filter 21 and the cooling device 15 there are disposed a pressure control valve 36 having an outlet nipple which opens to the free atmosphere. By means of this nipple the air that enters the circulating airflow at difi'erent locations due to imperfections in the seals is discharged dust free in order to maintain the pressure conditions in the entire system at a constant value. The flow resistances are overcome by means of the conveyor blower 3 and the mean pressure blower 14. Gates 31 and 32 serve to set the characteristics of the two blowers.
The preparation of the liquid is performed in the container 9 which is provided with a stirring mechanism (not shown) and which is provided with a heatable jacket (also not shown). The liquid is drawn from container 9 through two filters 34 and 35, having upstream and downstream valves, by a suitable pump 26 and is continuously forced across a counterflow cooler 8 into the liquid tank 22, also provided with a jacket (not shown) which may be maintained by a control valve 23 at a proper constant temperature. The liquid from the tank 22 is drawn by the pump 7 and is delivered through the membrane valves 33 to the spraying nozzles 100. The container 22 is provided with an overflow which leads through the conduit 24 to the suction tube of the pump 26 or to the tank 9. In the manufacture of milk substitutes, the dust accumulating in the separators 17 is, by means of blower 18, returned to the outlet of the' main separator 5 through the injector disposed downstream of the blower. At said outlet the dust is mixed with the admitted dry materials.
The system as shown in FIG. 1 complemented with devices according to FIG. 2 may serve for the manufacture of fat concentrates up to or even above 98 percent. In this process the dry material is admitted as separating material through the additional dosing device 37 to the gas stream, whereby the liquid fat is, in a known and already described manner, drawn from the storage containers 9 and 22 by pump 7, driven through membrane valves 33 and introduced into the treating tank 6 across the openings 10d by the spray nozzles 100. By virtue of the intensively cooled gas stream introduced from below and slowly rising in treating chamber 6, the sprayed fat particles crystallize and sink towards the outlet while they are mixed with the cloud of separating material introduced with the gas stream and leave the treating chamber as a fine granular substance. Subsequently the latter is delivered to the bagging station through a sieve and a conveying means. During the entire process, from the spraying step to the bagging step, the granular material is exposed to the effect of an intensively cooled gas stream. In this system of gas circulation, the gas streams are divided difierently from what was described hereinbefore. The conveyor blower 3 has the function of a suction pump and, by means of a substantially full closing of the gate 27, one part of the powder-containing gas stream is drawn from the container 6 through the sieve 11 and the conveyor device 12, so that the fat-stiffened into granules-is, during the entire process and during its transportation to the bagging station, exposed without interruption to a powder-containing partial gas stream such as cold air. The dust separated by the two separators 17 is directly introduced into bags through the bagging nipples or is, by an alternate setting of the gate 180, introduced into the circulating flow. The powder-containing gas stream, after having traveled together with the granular material in the conveyor device 12, leaves the latter through gate 28 and is recombined with the gas stream arriving directly from the conditioning device 15 through gate 27. The two gas streams then pass through blower 3 and, carrying the powdery material picked up from the dosing device 2, pass through the separator S where the powdery material is introduced into the treating chamber 6. The two recombined gas streams are now further combined with the gas stream that passed through the chamber 6 from the gate 30.
FIG. 3 illustrates the shielding of spray nozzle 10c by means of a cap 10 and further shows a flexible conduit 10a with the annular collector conduit 10b. With this arrangement it is achieved that the entire apparatus is independent of the ambient atmosphere so that constant manufacturing conditions may be achieved. The covering of the spraying openings 10d prevents drawing of atmospheric air into the system and in the summer, in case of elevated ambient temperatures and corresponding high humidity, it prevents the collapse of the calorific balance of the system.
The aforedescribed method is also adapted for the manufacture of detergents. Thus, for example, the dry powdery material, such as tripolyphosphate, is sprayed with water which contains dissolved therein the usual soluble materials.
What we claim is:
1. In a method of treating powdery materials by spraying them with fluid in a treating chamber, said method including the known steps of introducing said powdery material with an auxiliary gas stream at the upper part of said chamber and allowing said material to proceed downwardly in said chamber, introducing into said chamber radially inwardly directed fluid streams to spray the particles of said powdery material with fluid, introducing through the lower portion of said chamber an upwardly directed gas stream adapted to create a turbulent cloud of said powdery material and forcing nonsprayed particles thereof to travel upwardly and return to the zone of radial fluid injection, said upwardly directed gas stream allowing the heavier, sprayed particles of said powdery material to exit through the base of said chamber, the improvement comprising the steps of treating a gas stream in a conditioning device to obtain the required temperature and humidity therefor, dividing said gas stream into a first, second and third partial stream, introducing said first partial stream into the lower portion of said chamber to form said upwardly directed gas stream, causing said second partial stream to carry said powdery material from a metering device into said chamber and thus forming said auxiliary gas stream, exposing the sprayed powdery material downstream of said chamber to said third partial stream, recombining said first, second and third partial streams, and introducing the recombined stream into said conditioning device, circulating all of said streams without admitting gas from any external source to provide a closed conduit system and venting into the atmosphere part of said gas stream through a pressure control valve upstream of said conditioning device for maintaining constant the gas pressure in said closed conduit system.
2. A method as defined in claim 1, wherein said recombined stream, prior to its introduction into said conditioning device, is filtered by a preliminary filter, a main filter and a safety filter.
3. A method as defined in claim 2 wherein said pressure control valve is disposed between said safety filter and said conditioning device.
4. A method as defined in claim 1, wherein said fluid, prior to its introduction into said chamber, is passed through a cooling device.
5. A method as defined in claim 1, including the steps of dividing out said third partial stream from said second partial stream upstream of said metering device; directing said third partial stream in a counterflow against said sprayed powdery material exposing the latter to said third partial stream and recombining said third partial stream with said first partial stream in said chamber.
6. A method as defined in claim 1, including the steps of dividing outsaid third partial stream from said first partial stream in said chamber; directing said third partial stream in a concurrent flow with said sprayed powdery material exposing the latter to said third partial stream and recombining said third partial stream with said second partial stream upstream of said metering device.
7. In an apparatus for treating powdery materials, the improvement comprising,
A. a vertically disposed cylindrical treating chamber having an upwardly widening conical enlargement constituting the upper third of said chamber,
B. an inlet hopper extending downwardly from the top of said chamber and terminating within said conical enlargement, said powdery material being introduced into said chamber through said hopper,
C. means for introducing an upwardly directed gas stream into said chamber,
D. a plurality of openings in the wall of said chamber, said openings being arranged peripherally in a circumferential array below the terminus of said hopper,
E. a plurality of nozzles each in registry with a separate one of said openings to introduce fluid into said chamber for spraying said powdery material,
F. an annular conduit circumferentially surrounding said chamber, each of said nozzles being connected to said annular conduit for receiving said fluid therefrom, and
G. an outlet provided at the base of said chamber to discharge therefrom material exposed to said fluid.
8. An improvement as defined in claim 7, wherein each said opening together with its associated nozzle is covered by a separate, easily removable housing attached to the outside wall of said chamber, the space within each housing is connected with said common annular conduit by means of a flexible hose, said common annular conduit communicates with a blower through a connecting conduit including a throttle device.