US2244195A - Apparatus and process for fluidifying and mixing by means of compressed air - Google Patents

Description

June 3; 1941., A. HASSELBACH 2,244,195

APPARATUS AND PROCESS FOR FLUIDIFYING AND MIXING BY MEANS OF COMPRESSED AIR Filed April 18, 1939 2 Sheets-Sheet 1 J1me A. HASSELBACH 3,

APPARATUS AND PROCESS FOR FLUIDIFYING AND MIXING BY MEANS OF COMPRESSED AIR Filed April 18, 1939 2 Sheets-Sheet 2 w "mam"mnmmmmmw q;

Patentedilune 3,- 1941 a arrmrns ANn'rnocEss FOR mummyme AND mxmc BY MEANS or comrnnssnn Am Alexander Hasselbach, Dessan,

.to G. Polysins Aktiengesellschatt, Dessan, Ger- Gcrmany, assignor V Application April 18, 1939, Serial No. 268,582

In Germany December 30,1935

4 Claims. Y.

This invention relates to processes of mixing bulky pulverulent materials, such as cement raw materials, coaldust, flour, and the like, and to apparatus for efiecting such processes. Among the objects ,of'the inventionthe reduction 01' the time and expense required for mixing large masses of such materials, and an increase of emciency whereby a moreco'mpletely homogeneous mass may be obtained than by prior methods of mixing. 1 a

The application is a continuationinpart of my prior application Serial No. 118,027, filed December 28, 1936, wherein isdisclosed a method of mixing which involves discharging the material into a mixing bin ortank while simultaneously introducing a limited-quantity of air under pressure into the material, and subsequently intensively the material by the introduction therein of much larger quantities of air under pressure. By introducing a'lrelatively small quantity of air into the materialduring the filling period, I am enabled to cushion the iall of the material into the tank so as to prevent the packing which would otherwise inevitably occur, the subsequent intensive mixingof the material being thereby facilitated. I have found that this treatment of the material during the filling of the tank results in the establishment of a substantially fluid condition, the air thus introduced sufiusing the material so that the mass is of relatively low density; this aeration of the 'material effectively prevents the formation of a dense mass which would otherwise result from the discharge of the material intothe'tank. Consequently, when the filling is completed, the mixing may be promptly and efficiently initiated, and the larger quantities of air then introduced create a state of turbulence, the material boiling violently in much the same manner as a liquid. subjected to excessive heating, with the result that complete mixing can be rapidly eflfected.

Not only is the efliciency of the mixing operation improved materially by this procedure and the time required for mixing decidedly shortened, but there is a very substantial saving effected in the amountof compressed air required by reason of the fact that the larger quantities of air are introduced only after the filling is completed and are immediately effective in creating the desired turbulent condition owing to the absence of densely packed material.

The process is preferably carried out by introducing the air in an extremely fine state of division, such as may be established by forcing the air through porous stone or the like. I have found, however, that for eflfective mixing -by finely divided air particles it is essential that the air be admitted into the tank over a rather large area, a very considerable volume of air being required if the desired condition of turbulence is to be imparted to the material. Thus, if the tank is of" cylindrical shape, air should be admitted over substantially the entire area of the bottom of the tank; if the tank is of varying horizontal sectional area, the areavof air admission should be comparable to the mean horizontal sectional area of the tank.

Onefonn of apparatus for carrying out the process is'illustrated in the accompanying drawings, in which:

Figure 1 is a horizontal sectional View of a tank or silo provided with suitable devices for admitting air or other gaseous medium under pressure and in finely divided form;

Figure 2 is a vertical sectional view of the tank shown in Figure 1;

Figure 3 is a plan view of a preferred form of air admitting unit;

Figure 4 is an elevation, partly in section of the structure shown in Figure 3;

Figures 5 and 6 aretransverse sectional views taken on the lines 5-5 and 6-6 respectively of Figure 3; and

Figure '7 is an enlarged fragmentary sectional view of the air inlet for the unit shown in Figure 3.

For convenience in describing the invention, reference is made to the preferred form of apparatus illustrated in the drawings and specific language is employed to describe the same. It will nevertheless be understood that variation of this structure within reasonable limits is contemplated and that the invention includes within its scope such alterations and modifications of the structure described herein as would occur to one skilled in the art to which the invention relates.

In Figure 1 is illustrated the lower end of a tank or silo of generally cylindrical shape, the peripheral wall of the tank being indicated at I 0. Substantially the entire bottom wall I5 of the tank is covered by a plurality of individually formed devices I I, the major portion of the upper surface, of each of which, indicated at I2, is of porous material and forms a support for the material to be mixed. Each of the devices H is supplied with air or other gaseous medium under pressure from a main supply conduit l3 through a plurality of smaller pipes M, the a'rangement being such that the gaseous medium is forced upwardly through the porous surface to suifuse the material supported thereon. The material to be mixed is introduced into the upper portion of the tank through a supply conduit I 8, a vent l9 being provided to permit discharge of excess gaseous medium from the tank. The devices H are so arranged as to leave uncovered a plurality of outed as shown more elusive, and includes a generally dish-shaped rectangular member 28, preferably cast of metal. This casting is formed to provide inwardly directed horizontal flanges 21 about the periphery thereof, on which are received flat lates II of porous material, such as stone, porous caoutchouc or the like. The upper perlph edgesotthe castingareturnedinwardlyasindicated at I! and metal oi. a low melting point, cement orthe like, indicated at 3|, ispouredinposition beneath these flanges and about the periphery of the plates-20 to secure the latter in Lateraliy extending strengthening ribs wallsoithecasting 2t todenneelosedspacesll lying beneath the plates 28, and extending within these casting 2' are extensions 36 of the pipes ll, these extensions being perforated at spaced points. The point of entrance of the pipes ll intothe castings It may be sealed by packing as indicated at 31. The castings are provided with openings 3| extending therethrough by means or which they may be bolted or otherwise secured in position.

Whena gaseousmediumunder ressure issupplied to the system of pipes ll. the medium will be uniformly distributed within the closed spaces immediately below the porous plates II, and will be forced upwardly through the latter. Owing to the fact that practically the entire bottom the tank is covered and constituted by these porous plates 20, a very tremely divided form, may be introduced into thelowerendofthetankinthismanner.

. ltwillbeimderstoodthatthesystemotpipes it is so controlled by suitable valves that during the introduction of the materials to be mixed into the upper end of the tank, air is admitted through a limited number only of the plates II, a s'uihcient quantity of air being thus introduced to maintain the materials in a light and substantially fluid condition so as to prevent packing as the result of the fall thereof through the entire length of the tank. When the tank has been filled, it is preferred that alr shall then be admitted over substantially the entire area of the bottom of the tank, and thematerial having already acquired a generally fluid state, the quantity 01' air thus admitted is sufflcient to agitate the material violently, a condition approximating the boiling I of the liquid being maintained until the mixing is completed.

Obviously a similar result can be achieved by admitting, for the purpose of fluidifying the material, a relatively small amount of air under pressure through all or a major portion of the porous plates, the supply pipes for the same being suitably throttled to materially reduce the flow. The flow is thereafter increased by opening the control valves to eiiect thorough mixing of the material.

It will be appreciated that by the use of individual air admitting units, such as those illustrated herein, the expense of installation may be materially reduced, replacement simplified, and accurate measured regulation of the amount of air admitted may be readily effected.

substantial volume of air, in eursothat lesagitationis ei'iected than isrequired for complete and intimate mixing. when the enclosed spaces and longitudinally oi the V tankistobedlscharged,andduringdlscharge tocompletethemixingduringtheperiodoithe discharge 0! the material.

It is round that such procedure aiiords very eflidentiinalmixingofthematerlalsandisextremely economical since the maximum amount of air is not admitted until the operation is substantially completed and the material is ready-for delivery from the tank. Stratification of the material in layers 0! diflerent density, or 0! diflerent chemical or physical properties, is eiiectively avoided by this method.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A structural unit for use in the formation 0! gas pervious walls for the suflusion oi pulverulent materials with gas. said unit including a generally flat, dished member formed of material substantially impervious to gas, a generally flat element formed of porous material pervious to gas received within and serving as a closure member for said dished member, and means including a pipe extending within said dished member and having perforations at longitudinally spaced points for introducing gas under pressure in the latter.

2. In a process of iiuidifying and mixing farinaceous or powdered bulky materials by means of compressed air, the successive steps oi! delivering the material to a'container and-maintaining the material thus delivered in a condition oi substantial fluidity by simultaneously introducing therein a relatively small quantity of compressed air, and subsequently introducing a greater quantityo fcompressed'airtostirandmixthematerial after filling o! the container.

3. In a processof iiuidifylng and mixing farinaceous or powdered bulky materials by means of gas under ressure, the successive steps 01 delivering the material to a container and maintaining the material thus delivered in a condition of substantial fluidity by simultaneously introducing therein a relatively small quantity of gas in a finely divided state, and subsequently introducing a greater quantity of gas in a nnely divided state to stir and mix the material after filling of the container.

4. Ina process of fluidfying and mixing farinaceous or powdered bulky materials by means of gas under pressure, the successive steps of delivering the material to a container and suflusing the materials thus deliveredwith compressed gas in a finely divided state and in quantity suiiicient to effect preliminary mixing of the materials, subsequently discharging the materials from the container and simultaneously suflusing the materials with a substantially greater quantity of the finely divided gas to complete the mixing.

ALEXANDER HASSELBACH.

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