DE2551457C2 - Device for separating dust into coarse and fine material in a centrifugal field - Google Patents

Description

35

The invention relates to a device for separating dusts into coarse and fine material in a centrifugal field, consisting of a cylindrical hollow body, the cylinder wall of which at one end has a feed pipe for the sifted material carried by a gas flow and at the other end a tangentially opening outlet pipe for the coarse material and with at least one an axially arranged outlet pipe for the fine material is attached to one of its two end walls

The separation of dusty, granular or fibrous Goods according to certain grain sizes, densities or shapes is necessary for the separation of unwanted components or for fractionation of mixtures.

Various devices are known for this

In the countercurrent sifter, the mixture falling under gravity or centrifugal force flows against a gas stream, which separates the light particles and transports them away. The flow is not uniform and causes an unclean separation. In addition, economic separation can only take place in the coarse range (d> 100 μΐπ), because the smaller the particles, the lower the limit load, which is known to indicate the state in which all particles of a given separation grain size are just being transported away. As a result, only a low gas velocity is then possible, which in turn results in a low throughput.

With the cross-flow separator, the mixture introduced into an air flow from the side is fanned out under the action of air and inertial forces Air flow then transports the fine material away, while the coarse material falls downwards due to gravity The goods remain in the viewing zone for a short time, so the performance is low when the load is high (Product flow to gas flow) the selectivity decreases, especially an unfavorable one Good accumulation can occur on the opposite wall of the feed point.

In a spiral sifter, a mixture of air flow introduced into a round body is drawn into the Coarse material thrown outwards by centrifugal force and into it inwards with the air flow flowing fine material is broken down. The disadvantage is the high air throughput and the low overload capacity Overload. The mixture is slowed down by friction on the wall, which changes the Centrifugal force and thus the separation grain size. The separation time is long, since the product as strands on the Wall transported along and thereby the fine material is hindered at the drain. With abrasive A high level of wear and tear is to be expected on the product.

There are also classifiers in which fine particles are separated from a fluid that is kept in a vortex Mixing takes place in a container with a lower perforated plate. Batch operation limits the output. Because of the long sight paths in the mixture, this process is energy-consuming, because it has to be Sufficient air flow through the mix at the appropriate pressure. The size is opposite other classifiers with the same throughputs many times larger.

The invention has for its object to find a device that is within a large Grain size range a mixture flow of dust quickly without significant overlap of the two Separate grain size ranges by sifting into coarse and fine material, whereby the wear and the added The amount of gas should be as small as possible.

This task is carried out with a? Device according to the type mentioned initially according to the invention thereby solved that the cylinder wall is surrounded by a gas acted upon distribution chamber and upper their area has a large number of through-holes for the sifting gas

The advantages achieved by the invention are, in particular, that the continuously progressing flat mixture of material belt at each point of the cylindrical circumference, the amount of gas required for the classifying process is supplied in a targeted manner can be. This makes it possible to run the device in streak or fluidized bed operation, with the the latter leads to shorter viewing times because of the agitated, loose packing structure. Allowed at the same time the adjustable classifying gas metering without loss of selectivity an adaptation of the device to different grain sizes or densities. The material to be viewed is at Sifting treated gently so that the device can also be used for sensitive materials

The energy requirement is low because only a small amount of classifying gas is consumed, which is particularly important for recovered, cleaned, cooled or heated sifting gases is advantageous.

The construction is simple and can easily be adapted to the operating requirements by means of axial expansion. In addition, the device can be used in any Position to be installed. The wear that would otherwise lead to destruction in the shortest possible time with an abrasive mixture

the wall of the sifter is through what is in between Sight gas cushion low.

According to a special embodiment of the device according to the invention, the through bores in the cylinder wall for the sifting gas at an angle of 2 to 30 °, preferably 5 to 15 °, to Tangent to the cylinder wall inclined with the help of the rectified through holes can with appropriate classifying gas supply, the ratio of the drag force inwards to the centrifugal force downwards must be kept the same on the outside so that the cut size does not vary over the entire working area changed This advantage is particularly efficient with small particles <10 μm

According to a further embodiment, a helical rising helix for the Mixture arranged in the cylindrical hollow body The advantage of this construction is based on the fact that Due to the more precise guidance of the mixture to be sifted, the separation conditions in the sifter are more even will. A reflux of the mixture or an accumulation is avoided. The dwell time each single particle in the classifier is the same;,. One It is easier to adhere to the specified separating grain size.

In a further embodiment of the invention, several classifiers of different separating grain sizes are so connected in series that the coarse material outlet pipe of the preceding classifier is the same as the material feed pipe the following sifter is special advantages are that when dividing a Mixture stream in several fractions the metering of the mixture only once, namely at The first sifter has to be carried out. In this way, a preparative separation can also be carried out quickly and safely as well as a grain size analysis.

In the drawing is the device according to the invention shown purely schematically and their mode of action explained below using two examples

example 1

A classifying air supply pipe 1 (diameter 25 mm) is classifying air with a volume flow of 90 m ³ / h in

ίο a distribution chamber 2 formed between two nested tubes and passes through the through-holes 3, which are at an angle of 11 ° to the perpendicular of the radius and 9 ° to the axis with a diameter of 1 mm and an occupancy density of 10 through-holes per 4 cm ² are arranged in a cylindrical hollow body 5, which has a length of 140 mm and a diameter of 100 mm. A silicon dust of approx. 60 kg / h is introduced with air via the material feed pipe 6 tangentially to the helical spiral 7 and pneumatically The fine material (about 25%) leaves the cylindrical hollow body 5 axially via fine material outlet pipes 8, while the coarse material (about 75%) falls in the coarse material outlet pipe 9. The cut size is 21 μm.

Example 2

When using an air volume of 180 mVh, the The streak of mixed material that then sets in is 20% fine material and 80% coarse material at the points indicated. The separation size is 16 μίτι.

1 sheet of drawings

Claims (4)

Patent claims: !, Device for separating dust into coarse and fine material in a centrifugal field, consisting of a cylindrical hollow body (5), the cylinder wall (4) of which at one end is tangential in a helical feed pipe (6) for the cut material carried by a gas flow and at the other end a tangentially opening outlet pipe (9) for the coarse material carries and with the to at least on one of its two end walls an axially arranged outlet pipe (8) for the fine material is attached, characterized in that the cylinder wall (4) of one with classifying gas acted upon distribution chamber (2) is surrounded and is distributed over its area a plurality of Has through-holes (3) for the classifying gas 2. Apparatus according to claim 1, characterized in that the through bores (3) in the Cylinder wall (4) for the sifting gas at an angle of 2 to 30 °, preferably 5 to 15 °, to Tangent to the cylinder wall are arranged inclined. 3. Apparatus according to claim 1 and 2, characterized in that a helical steep 2s Low guide helix (7) for the mixture in the cylindrical hollow body (5) is arranged 4. Apparatus according to claim 1, 2 and 3, characterized in that several separators of different separating grain size so one behind the other geschaitet are that the coarse material outlet pipe (9) of the previous classifier is the same as the material feed pipe (6) of the following classifier