Classifying – separating – and assorting solids – Fluid suspension – Gaseous
Patent
1995-07-24
1997-04-29
Bollinger, David H.
Classifying, separating, and assorting solids
Fluid suspension
Gaseous
B04B 512
Patent
active
056240392
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a separator for sorting particulate material suspended in a conveying gas into a fine fraction and a coarse fraction. The separator comprises a rotor with a substantially vertical shaft, a housing encasing the rotor, and having an inlet for a material/gas suspension and outlets for fine and coarse fractions, respectively.
It is a recognized fact that the gap between the top of the separator rotor and the top of the separator housing or a stationary top plate above the rotor is of crucial importance for the attainable steepness of the particle size distribution (PSD) curve of the finished material (percentage sieve residue of a weighed sample as a function of particle diameter). The underlying explanation is that the greater or smaller gap is the main determinant of the size of the material quantities which can be conveyed past the rotor and directly into the fine material.
For cement grinding, it was previously very important, particularly for separators deployed in tube mill circuits, to ensure minimization of the gap in order to achieve the steepest possible particle size distribution curve.
By contrast, the principal objective in connection with finish grinding of cement in vertical mills and roller presses is to obtain a less steep PSD curve than can normally be achieved in these mills, given that very steep finished material PSD curves for cement, which means that the cement consists of a narrow, i.e. uniform, particle fraction, will require more water when the mortar and concrete, of which the cement is a constituent ingredient, is to be brought to a state of normal consistency.
A numbers of methods have previously been proposed for changing the PSD curve for finished material so that it comprises a more varied particle size distribution. It is thus known practice from the Danish patent specification No. 161810 to provide a separator with several different sets of rotor blades with different sorting parameters and incorporating control means for regulating the relative gas streams passing through the different sets of rotor blades. As a result, it is possible to influence the particle size distribution of the finish-separated product. One method suggested for regulating the gas flow rate involves the use of an axially displaceable elongation of the outlet duct whereby the gap width between the rotor top and the outlet duct (FIG. 3) is regulated. However, it is rather difficult to achieve precise control during operation with this separator since the diameter of the outlet channel is often about 2.5 metres or more and since the vertical adjustment is approximately 20-50 mm. This would make it necessary to regulate the vertical position of the elongation of such an outlet duct at, as a minimum, three points on the circumference of the duct.
It is the object of the present invention to increase the possibilities of controlling the amount of gas suspension which is directed past the rotor, thereby regulating the PSD curve for the finished material, while simultaneously eliminating the aforementioned disadvantages associated with the prior art.
According to the invention this is achieved with the aid of a regulating means for adjusting the axial position of the rotor shaft, and hence of the rotor, relative to the housing. As a result, the distance between the rotor and the top of the casing or a top plate between the inlet area of the rotor and the outlet area for the fine fraction can be adjusted. The vertical adjustment of the rotor is performed in a relatively simple manner, owing to the relatively small dimensions of the shaft and its bearing housing.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be described in further detail by means of an example of a separator constructed in accordance with the invention and illustrated in the accompanying drawing, which is diagrammatical, and shows an axial sectional view through the separator.
DETAILED DESCRIPTION OF THE INVENTION
The separator illustrated on the drawing has a rotor 1 which is rotatable about a ve
REFERENCES:
patent: 4689141 (1987-08-01), Folsberg
Bollinger David H.
F. L. Smidth & Co. A/S
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