GB1577802A - Crushing plant for the crushing of mineral material - Google Patents

Description

(54) A CRUSHING PLANT FOR THE CRUSHING OF MINERAL MATERIAL (71) We, VEB ZEMENTANLAGENBAU DE SSAU, a body corporate organised and existing under the laws of the German Democr-atic Republic, of 13 Brauereistrasse, 45 Dessau, German Democratic Republic, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a crushing plant for the drying and crushing of minerals, preferably bulk materials such as the raw materials for cement.

According to the present invention there is provided a crushing plant for the crushing of mineral material, comprising a pre-crusher, a rolling mill having a rotatable grinding plate over which grinding bodies roll, a sifter for sifting the ground material from the rolling mill, means for returning material not removed in the sifter to the rolling mill, and means for supplying hot gas to the precrusher and sifter for drying the material, said pre-crusher and sifter being connected in series with the hot gas supply so that material carried in the gas flow from the pre-crusher is separated in the sifter with material ground in the rolling mill.

Some embodiments of the invention will now be described, by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a diagram of an embodiment ofa crusher plant having a hammer mill/drier and sifter with external ambient air; Figure 2 is a diagram of another embodiment of a crusher plant having a hammer mill/ drier and crossflow sifting arrangement; and Figure 3 shows a section through the pulverising zone and crossflow sifting arrangement of Figure 2.

In the drawings, the solid lines denote the flow of materials, the broken lines the gas flow and the dash-dotted lines the gas flows which are laden with solid matter.

In the embodiment of Figure 1, quarry damp cement raw material is fed in measured quantities to a drying and coarse pulverising apparatus 1, preferably a heated hammer mill/drier, where it is pre-comminuted and the pre-comminuted material is then fed to the rotating grinding plate of a rolling mill 2.

On the rotating grinding plate of the mill 2, and under the influence of centrifugal forces, the material flows to the preferably small grinding bodies, roller-like bodies or balls disposed in dense sequence of the periphery of the grinding plate, is substantially reduced by them and the ground material falls into a catching means or container 3 located be neath the rotating grinding plate and from which the ground material is fed mechanically and/or pneumatically, via a suitable vertical conveyor 4, to a sifter 5. Such a sifter 5 is sup plied with gas from a conduit 6, connected in series with the hammer mill/drier 1, to which the hot gas flow 7 may be supplied from a hot gas generator or the hot gas may comprise the waste gas from a furnace plant functioning on the dryer principle.The material not removed in the sifter 5 is re-circulated back to the mill 2 and the material removed in the sifter 5 passes to a separator 10 where the air is removed by a blower 11. The pulverising chamber of the rolling mill 2 is easily acces sible and is dust-tightly enclosed by a housing which is hinged to open. The con tainer 3 has an inclined and aerated bottom.

In Figure 2, the material is precomminuted and dried in the apparatus 1 in the same manner as in Figure 1 and after being finely pulverised in the rolling mill 2 is thrown by the high peripheral speed of the grinding plate of mill 2 directly into the flow duct 8 of a cross flow sifter disposed coaxially around the grinding plate. In this flow duct 8, a directed gas and/or air current is produced which may be fed obliquely to or parallel with the axis of the grinding plate from below and upwards or vice versa. The grit or particles which are not carried away by the gas and/or air current are caught in containers 9 which are arranged around the duct 8 and connected to the flow duct 8, the grit or particles in the containers 9 being recycled and fed back to the rolling mill 2.The finished product carried away in the stream of gas and/or air in the duct 8 is separated in cyclone separators 10 arranged singly or in pairs. Vacuum extraction of air from the cyclone separators 10 is provided by one or more symmetrically disposed blowers 11.

The supply of gas to the crossflow sifter duct 8 and hammer mill/drier 1 is effected as in Figure 1, in a series connected arrangement 6 between drier 1 and sifter 8.

Figure 3 shows the rolling mill 2 and the crossflow sifter arrangement of Figure 2 in cross-section. The pre-comminuted material to be ground is fed to the centre of a grinding plate 12 and for better distribution over the periphery of the grinding plate, by means of a fixed or movable feeder 13. By having adjustable knife-edge plates 14 between the flow duct 8 and the grit catching containers 9, any desired mesh size can be adjusted from the outside. In order to prevent coarse particles being carried out of the grit catching containers 9 due to the vacuum extraction system, it may be advantageous to feed an air supply through an annular gap 15 provided between the container 9 and the flow duct 8.

In order to ensure that the flow from the grinding plate 12 into the duct 8 is in the form of a thin layer of material travelling at high speed, the peripheral edge 16 of the plate 12 is made flat and it has a slight upwards or downwards inclination, in Figure 3 it is 'shown with a downward inclination.

WHAT WE CLAIM IS: 1. A crushing plant for the crushing of mineral material, comprising a pre-crusher, a rolling mill having a rotatable grinding plate over which grinding bodies roll, a sifter for sifting the ground material from the rolling mill, means for returning material not removed in the sifter to the rolling mill, and means for supplying hot gas to the precrusher and sifter for drying the materials, said pre-crusher and sifter being connected in series with the hot gas supply so that the material carried in the gas flow from the precrusher is separated in the sifter with material ground in the rolling mill.

2. A crushing plant as claimed in claim 1, in which the rolling mill and sifter are partially separated from one another and the rolling mill is provided with a collecting means disposed beneath the grinding plate and material is conveyed from the collecting means to the sifter by a conveying means.

3. A crushing plant as claimed in claim 1, in which the sifter is a transverse flow sifter having a gas flow passage disposed coaxially around the grinding plate of the rolling mill, said passage being surrounded by containers connected to the passage for receiving material to be returned to the rolling mill and separators for separating ground material from the gas flow.

4. A crushing plant as claimed in claim 3, in which the edge region of the grinding plate has an upwards or downwards inclination depending upon the direction of gas flow of the gas in the sifter.

5. A crushing plant as claimed in any preceding claim, in which the pre-crusher comprises a combined hammer mill and dryer.

6. A crushing plant as claimed in claim 2, in which the collecting means has an inclined and aerated bottom.

7. A crushing plant for the crushing of mineral material substantially as hereinbefore described with reference to and as illustrated in Figure 1 or Figures 2 and 3 ofthe accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. are caught in containers 9 which are arranged around the duct 8 and connected to the flow duct 8, the grit or particles in the containers 9 being recycled and fed back to the rolling mill 2. The finished product carried away in the stream of gas and/or air in the duct 8 is separated in cyclone separators 10 arranged singly or in pairs. Vacuum extraction of air from the cyclone separators 10 is provided by one or more symmetrically disposed blowers 11. The supply of gas to the crossflow sifter duct 8 and hammer mill/drier 1 is effected as in Figure 1, in a series connected arrangement 6 between drier 1 and sifter 8. Figure 3 shows the rolling mill 2 and the crossflow sifter arrangement of Figure 2 in cross-section. The pre-comminuted material to be ground is fed to the centre of a grinding plate 12 and for better distribution over the periphery of the grinding plate, by means of a fixed or movable feeder 13. By having adjustable knife-edge plates 14 between the flow duct 8 and the grit catching containers 9, any desired mesh size can be adjusted from the outside. In order to prevent coarse particles being carried out of the grit catching containers 9 due to the vacuum extraction system, it may be advantageous to feed an air supply through an annular gap 15 provided between the container 9 and the flow duct 8. In order to ensure that the flow from the grinding plate 12 into the duct 8 is in the form of a thin layer of material travelling at high speed, the peripheral edge 16 of the plate 12 is made flat and it has a slight upwards or downwards inclination, in Figure 3 it is 'shown with a downward inclination. WHAT WE CLAIM IS:

1. A crushing plant for the crushing of mineral material, comprising a pre-crusher, a rolling mill having a rotatable grinding plate over which grinding bodies roll, a sifter for sifting the ground material from the rolling mill, means for returning material not removed in the sifter to the rolling mill, and means for supplying hot gas to the precrusher and sifter for drying the materials, said pre-crusher and sifter being connected in series with the hot gas supply so that the material carried in the gas flow from the precrusher is separated in the sifter with material ground in the rolling mill.

2. A crushing plant as claimed in claim 1, in which the rolling mill and sifter are partially separated from one another and the rolling mill is provided with a collecting means disposed beneath the grinding plate and material is conveyed from the collecting means to the sifter by a conveying means.

3. A crushing plant as claimed in claim 1, in which the sifter is a transverse flow sifter having a gas flow passage disposed coaxially around the grinding plate of the rolling mill, said passage being surrounded by containers connected to the passage for receiving material to be returned to the rolling mill and separators for separating ground material from the gas flow.

4. A crushing plant as claimed in claim 3, in which the edge region of the grinding plate has an upwards or downwards inclination depending upon the direction of gas flow of the gas in the sifter.

5. A crushing plant as claimed in any preceding claim, in which the pre-crusher comprises a combined hammer mill and dryer.

6. A crushing plant as claimed in claim 2, in which the collecting means has an inclined and aerated bottom.

7. A crushing plant for the crushing of mineral material substantially as hereinbefore described with reference to and as illustrated in Figure 1 or Figures 2 and 3 ofthe accompanying drawings.