US 3190470 A
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Description (OCR text may contain errors)
United States Patent O 4 Claims. (Ci 21 4-1838 The present invention relates to an apparatus for distributing dusty to pulverulent or granular solids or mixtures of such solids in uniform thin layers, for example l-grain layers.
Chemical processes carried out with one or more solid reaction Components which must be applied in a fairly thin layer in order to enable the absorption of further reaction Components or the supply of energy require dis tributng apparatus which ensure the achievng of anappropriate thin and uniform layer. The common and known distrbuting apparatus are based on the principle of stripping. This principle, however, cannot be applied to reaction masses that cannot be moved. Rotary plates which distribute the solids over large circular areas by centrifugal force are also widely used. These plates have the disadvantage of having a very great indefinite scattering angle in the flight path of the solids at a constant rotational speed so that too great a classification of the different grain sizes takes place. This undesirable separation into Components is particularly pronounced when two or more solids of different specific gravity are distributed.
The present invention provides a process for distributing solids in thin layers, for example l-grain layers, which enables the aforesaid disadvantages to be overcome.
According to the process of this invention, dusty to pulverulent or granular solids or mixtures of such solids are introduced through a tube which is disposed above the center of 'a circular curved or plane receiving surface and is at a certain distance from said center and rotates about its vertical longitudinal axis at a periodically variable rate of revolutions. The tube is charged from above. The lower end of the tube is defiected or curved. The direction in which the solids are introduced as well as the distance between the point of introduction and the center of the receiving surface are thus continually and periodically varied, whereby the material is distributed in extremely thin layers.
into the straight part of the upright rotary tube a stationary tube of smaller diameter may be inserted from above and used for feeding the solids to the lower defiected end of the outer rot-ary tube.
The apparatus of this invention may be used, for example, in the following manner: the rotary tube is inserted from above into a Chemical reaction furnace, in which case it is used for charging the reaction furnace with the material to be reacted. In the zone Where the rotary tube enters the reaction furnace, the rotary tube may be surrounded with at least one cooling jacket and/ or an insulating layer. The devices for inserting and supporting the rota'y tube into the reaction furnace may be vacuum-tght if desired and are advantageously con structed in a manner such that the rotary tube can be easily exchanged.
The following remarks are made with regard to execution of the process of the invention:
When the rotary tube which is used as feeding device in the process of the invention is charged from above with solids, the latter are distributed at a scattering angle of about 5 to 6 over a circular ring surface. By causing the tube to rotate at a periodically varying rate of revolutions, the solids are distributed in layers of uniform thickthe &lh-?h Patented June 22, 1965 ness over circula' ring areas which accurately adjoin one another so that a circular area is obtained which is uni formly covered with the material with the exception of the center directly beneath the distributing tube. This small uncovered center may then be directly covered with the material without distribution.
To distribute the solids over adjoining circular ring areas is especially advantageous when two or more solids of different specific gravity are used. The undesired separation of different solids is masked and neutralized by continuously adjoining to one another several circular ring areas in accordance with the invention.
In order to avoid formation of undesired centrifugal forces in tubes of large diameters, for example of an inside diameter exceeding millimeters, which centrifugal forces prevent the solids from falling down, a stationary tube may be axially inserted in the straight part of the rotary tube as already mentioned above, the stationary tube extending from above to the lower curved end of the rotary tube. i
The present invention enables the distribution of solids in layers having a thickness ranging from the grain size in a given case to a multiple thereof. It is even possible to proceed in a manner such that not the whole surface over which the solids are to be distributed is covered in each period with an uninterrupted unform layer but that only a part of this surface is covered with fresh solids in each period so that several periods are required for covering the whole surface with one layer, that is to say, the rate of revolutions rnay be varied so rapidly and controlled in a manner such that the receiving surface is completely covered only after several periods.
The distributing tube of this invention can be used for the uniform distribution of solids in open or closed ap- -paratus at temperatures up to about +2500 C. under normal pressure, superatmospheric pressure or reduced pressure. Processes in which a great amount of energy has to be supplied at high temperatures to heat-insulating reaction mixtures which are in the solid state, can only be carried out at the rapid speed of Conversion necessary in industry when the reaction mixture is applied in uniform and fairly thin layers without separation taking place. The thinner the layer, the greater is the energy absorption per unit of surface. The apparatus of the present invention enables thisidefined distribution to be realized in an excellent manner.
An apparatus suitable for use in carrying out the process of this invention is illustrated diagrammatically by way of example in the acconpanying drawing wherein:
FIG. l is a sectonal view of one embodiment of this invention; and
FIG. 2 is an enlarged view of a portion of the embodiment shown in FIG. 1.
Reterring to the drawing, a reaction and vacuum furnace is designated by 1. The material to be reacted is in the lower part of the reaction chamber of the furnace 1, while the electrodes 12 project into the upper part thereof. The reaction chamber is connected with the vacuum pump by outlet pipe 13. Slot 16 surrounding the zone in which the electrodes are led through the wall of the furnace serves for the introduction of hydrogen. The material that has been reacted is removed by way of movable grate 7 provided at the bottom of the reac tion furnace.
The solids to be reacted which may be in a dusty, pulverulent or granular form are supplied through a feeding device ntroduced at the head of the reaction furnace 1. This feeding device consists of a rotatable feed tube 8 into which the material is introduced from above (arrow lt?) through inner tube 10' which is shown in FIG 2. The lower end 3 of the tube is curved and provided with an outlet 2 through which the material to be reacted leaves the tube in order to be finely distributed over the circular surface of material 6 lying beneath.
The rotary tube 8 is surrounded with a double cooling jacket 9 which is bent at its one end to conform to elbow 3 of tube 8. At a certain distance therefrom, a stationary double cooling jacket is disposed which is surrounded with an insulating layer 4 in the zone where the rotary tube 8 enters the hot reaction chamber. The rotary tube 8 is led through the bearings 11. It is introduced into the reaction chamber through the aperture 14 forrned by the short connecting pipe 15 and can also be removed through this aperture 14 in an upward direction.
The following example serves to illustrate the invention but it is not intended to limit it thereto:
Example Into a reaction furnace 1 for the manufacture of magnesium vapor from burnt dolomite of a grain size of 1 to millimeters and granular ferrosilicon of strength having a grain size of 0.5 to 5 millimeters at a temperature of 1500 to 1700 C. under a redueed pressure of about 1 to 100 millimeters of mercury, the reaction Components are continuously distributed in a thin layer over the mixture that has already reacted. The material is distributed in accordance with the invention through the rotary tube 8 which is disposed vertically above the center of the reaction surface and the lower end of which is deflected. The tube has an inside diameter of about millimeters and a length of 3 meters. The lower end of the tube is defiected over a length of 20 centimeters through an angle of about C. in a curve. The rotary tube 8 is provided over its entire length with a double cooling jacket 9 for cooling water.
The rotary tube is insulated against the heat prevailing in the furnace by a stationary heat insulating jacket 4 which is cooled at its inside wall by a double cooling jacket 5 through which a cooling liquid ows.
The rotary tube 8 is driven :at a speed which is continuously varied in predetermined periods and passes in about 2 minutes through all numbers of revolutions in the range of 40 revolutions per minute to revolutions per minute, the rate of revolutions increasing and deereasing. The increase and decrease of the rate of revolutions is controlled by a control disk in a manner such that per period of time of 2 minutes only one fifth of the circular reaction surface 6 having a diameter'of 5.5 meters is covered with fresh material. In the following periods of time of 2 minutes each the remaining portions of the surface are covered so that in a prolonged time the reaction mixture grows absolutely uniformly and a maximum energy is consequently transmitted by the electrodes 12.
To obtain particularly high yields of material, the process is advantageously carried out in such a manner that after a period of time of about 10 minutes a complete l-grain layer has just been distributed.
The mixture that has been reacted is removed in a downward direction by means of a movable grate 7, the removal taking place gradually as fresh reaction mixture is introduced.
It should be emphasized that when a mixture of dolomite and ferrosilicon is distributed the dolomite and ferrosilicon have a pronounced tendency to separate due to their different specific gravity. Only by the fact that the separation is masked and neutralized by the continuous adjoining of several circular ring areas in accordance with the process of the invention is it ensured that no losses occur in the reaction of the costly reducing agent.
In the preceding example the dolomite flies farther to the wall of the furnace than the ferrosilicon which is simultaneously introduced. Owng to this fact, a narrow marginal zone poor in ferrosilicon is formed whereby the reaction mixture is prevented in an advantageous manner from caking on the walls of the furnace.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. lt is, therefore, to be understood that within the scope or" the appended claims the invention may be praeticed otherwise than as specifically described.
1. An apparatus for distributing solids uniformly in thin layers onto and over the entire surface of a circular shaped area of a reaction furnace chamber which comprises a tube arranged substantially vertically and monnted for rotation about its longitudinal axis, the lower discharge end of said tube being curved outwardly away from its vertical aXis, a stationary tube disposed within the rotatable tube and extending the length of the straight part thereof, the upper end of the stationary tube being adapted to receive granular or pulverulent materials, and means to rotate the rotatable tube at varying rates over a predetermined period of time.
2. An apparatus as claimed in claim 1 wherein the rotary tube is introduced from above into a furnace reaction chamber. I
3. An apparatus as claimed in claim 2 wherein the rotary tube is surrounded with at least one cooling jacket and an insulating layer in the zone where the rotary tube enters the reaction furnace chamber.
4. An apparatus as claimed in claim 2 wherein the rotary tube is provided with bearings including a vacuumtight seal.
References Cited by the Examiner UNITED STATES PATENTS 2,2l5,736 9/40 Jones 193--3 2,320,206 5/43 Engel et al. 266-27 2,654,594 10/53 Somogyi 266-27 2,713,408 7/55 Tench 193-3 i FOREIGN PATENTS 738,584 8/43 Germany.
749,557 11/44 Germany.
777,266 6/ 57 Great Britain.
MORRIS O. WOLK, Primary Examiner.
RAY K, WINDHAM, MARCUS U. LYONS Examiners.