US2212819A - Apparatus for separating powdered materials - Google Patents

Description

Aug. 27, 1940. N. AHLMANN APPARATUS FCR SEPARATING POWDERED MATERIALS Filed June 18, 1938 l- Immun M ATTORN EYS Patented Aug. 27, i940 T@ S-'TES FTENT @Fi Nikolai Ahlmann, Copenhagen, lhenmark, as-

signor to F. L. Smidth &' Co., New York, N. Y., a corporation oi New Jersey Application .lune i8, 1938, Serial No. 214,500 En Great Britain July l, 1937 1 Claim.

This invention relates to apparatus for separating powdered materials from one another.

When it is desired to separate the materials in a powdered mixture, the mixture is often suspended in air and delivered to a centrifugal separator in which the heavier particles move outwards under the action of centrifugal force, and the lighter particles are carried by an air current towards the axisl of rotation of the separator.

The essentiai idea underlying the present invention is the avoidance of the necessity for mov- .ing the coarser particles from the middle to the outside of the separator, with a consequent sav-n ing of work and increase in eiciency. According to the invention the powder mixture is moved in a thin layer in a helical path along the inner lsurface of a wall of a container, internally cir- Lcular in cross-section, and air is blown in a numbei' of iets through the layer to carry the fine powder particlestowards the axis. The heavier particles, under the influence of centrifugal force, remain on the wall and are discharged separately from the lfine particles. The powder mixture is not suspended in air before the separation takes place although some air may be entrained and travel-with it, and the coarser particles remain on or close to the wall of the separator throughout. Naturally the coarse and 30, ne particles cannot be completely separated from one another in a single treatment, but excellent results are obtained if some 30 or more air nozzles are provided around the wall.

The powder mixture may advantageously be whirled around the wall mechanically and it may be caused to move upwards in a container with a vertical axis. means for causing the powder mixture to whirl around its inner wall may be constructed in sub- 40 `stantially the same way as in the cooler described 'in my copending application, Serial No. 79,837, med May 15, 1936, that is to say, the container may increase in diameter upwards and the material may be whirled around, moving vhelically upwards, by means of'vanes rotating at high speed. .v In order that the invention may be clearly understood and readily carried into eiect a pn"- 50 matic separator constructed in accordance with the invention will now be described by way of example with reference to the accompanying drawing, in which:

Figure 1 is a vertical section through the pneufr matic separator; and

'I'he container and the Figure 2 is a horizontal cross-section on the line 2 2 of Figure 1. v

The container has a cylindrical part 2a and a conical part 9a. The powder mixture is supplied at the bottom of the container by worm la. The mixture is set into rotation by a. system of vanes 6a carried by a shaft 55a through spiders 2| and 22 and is moved upwards as a result of the reaction of the wall 9a. The shaft 55a is mounted in bearings i60, and lla and rotated by a pulley i8a. At the top of the conical part 9a there is a steeper part of the wall lying Within the cylindrical part 2a and provided with slots la through which air passes from an annular chamber 6a. The coarse particles move upwards over this part of the wall and are discharged through a tangential discharge outlet ida, and the une particles are carried inwards by the air past perforated vanes I9a, rotating with the vanes la and through tangential slots 23 into a cyclone. 'I'his cyclone is bounded by conical walls 24 and 25 and a top plate 26 which is provided with a central discharge opening 2l. Vanes 28 secured to a. hollow shaft 29 rotate along the conical wall 25. The shaft 29 surrounds the shaft i5a and is carried in bearings 30 and 3| and driven independently of the shaft la by a pulley 36. 'I'he ne particles separated in the cyclone are flung out through a. tangential discharge outlet 32 and pass through a pipe a. A wall 33 is provided inside the cyclone to force the air to remain on the periphery of the cyclone. l

The clean air that passes through the outlet 21 is driven by a fan ita in a space 34 to the annular chamber 6a.

The perforated vanes i9a referred to above control the speed of rotation of the air and prevent the formation of a vortex. 'I'he speed of the air is maintained such that coarse particles carried inwardly by the air can move outwardly again under the influence of centrifugal force.

Some materials, and in particular cement from a cement mill, need to be cooled as well as separated. For cooling purposes 'a pipe 35 is arranged around the part 9a of the container and sprays/water on the` outside of the container. Thus the apparatus illustrated acts as a cooler,

separator, cyclone and fan, and as it lifts the material? it may also render an elevator unnecessary.

I claim:

-A pneumatic separator comprising a container having a vertical axis and having'a wall which is internally circular in cross section, 'means at the bottom of the container for feeding a powder mixture in bulk form to the interior of the container, a rotatable structure within the container having elements moving close to the inner surface of the container for mechanically imparting to the material a whirling motion to bring it into a. semi-liquid state and to move it upwardly in athin layer along said inner surface and to tend to keep the particles near such surface by centrifugal force, means for passing air transversely through the layer while it is moving upwardly over a portion of said inner surface, a discharge outlet at the inner surface of the container wall for the heavier particles, and a. discharge outlet for the air and ne particles picked up by it.

. NIKOLAI AHLMANN.

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