The invention concerns a machine interface between a grinding pan of a vertical grinding mill and a drive of the grinding pan, a drive and a vertical grinding mill.
DE 2703535 A1 (Loesche), published Aug. 3, 1978, shows in FIG. 1 a roller mill having a grinding pan 7 rotating around the vertical axis and grinding rollers 4 running thereon. The grinding pan is driven by way of a transmission 9. Such mills, which are employed in a variety of applications, including cement manufacture, are also referred to as vertical grinding mills.
DE 10013097 C2 (Hitachi), published Sep. 27, 2001, describes a coal grinding mill having a number of pulverizing rollers and a pulverizing ring on which rolling surfaces for the pulverizing rollers are embodied. In this arrangement, coal guided between the pulverizing rollers and the pulverizing rings is pulverized. The mill additionally comprises a reduction gear which transmits the power for rotating the pulverizing rings from a motor to the pulverizing rings. Also provided in this configuration are a cooling fan, disposed in an input shaft of the reduction gear connected to the motor, and a radiator for cooling lubricating oil that lubricates the reduction gear. The radiator is arranged therein on the downstream side of the cooling fan.
In cement manufacture, a hot-gas generator is utilized during the grinding process for directly drying the mill feed in a vertical grinding mill. As a result a temperature of 80° C. to 130° C. is reached in the grinding chamber. Heat flows out from the grinding chamber to the drive via the interface between the grinding pan and its associated drive. Owing to this continuous flow of heat from the grinding chamber, the oil coolers used for cooling the drive, i.e. for cooling the gear teeth and the bearings, must be dimensioned for providing a greater capacity than would be necessary in the absence of a heated grinding chamber.
It is the object of the present invention to provide an improved machine interface between a grinding pan of a vertical grinding mill and a drive of the grinding pan, as well as a drive and a vertical grinding mill.
The object is achieved by means of a machine interface as claimed in claim 1, a drive as claimed in claim 3, and a vertical grinding mill as claimed in claim 4. Preferred developments of the invention are described in the dependent claims.
The machine interface according to the invention is located between a grinding pan of a vertical grinding mill and a drive of the grinding pan. In this arrangement, the machine interface is embodied in such a way that the grinding pan and the drive are thermally decoupled. Compared with conventional machine interfaces in vertical grinding mills, a flow of heat directed from the grinding pan to the drive is substantially reduced as a result.
The invention is based on the knowledge that the heat flow rate dQ/dt at which thermal energy is transferred through the machine interface between the grinding pan rotating in the grinding chamber to the drive can be described by means of the formula
dQ/dt=(λ/d)·A·ΔT
where
dQ=heat quantity,
dt=time interval,
λ=thermal conductivity
d=thickness,
A=surface area, and
ΔT=temperature difference.
A reduction in said heat flow rate can therefore be achieved by a reduction in the thermal conductivity λ and/or the surface area A of the machine interface.
The present machine interface constitutes a particularly cost-effective and robust solution because it is very simple in terms of its mechanical design. With the present invention, the oil coolers of vertical grinding mills can be dimensioned smaller than in the prior art. A rough estimation has yielded a potential cost saving of approx. 25% in comparison with conventional mills. This also leads to lower operating and running costs for the plant operator, e.g. a saving in power costs on account of the smaller oil supply system.
According to a preferred development of the invention, a heat-insulating material with respect to metal is arranged between the grinding pan and the drive. In addition or alternatively thereto, a contact surface between the grinding pan and the drive can be embodied as small as possible for a predetermined load-bearing capacity.
A thermal insulating layer is therefore arranged between components of the vertical grinding mill that are arranged in the grinding chamber and components that are cooled by means of a lubricant. Preferred heat-insulating materials fulfill the requirements in terms of mechanical loading capacity (load-bearing capacity, shear strength, etc.) to be met by the machine interface and exhibit low thermal conductivity in comparison with metal. Preferred heat-insulating materials have a thermal conductivity λ<1 W/(m·K), further preferably λ<0.5 W/(m·K). Suitable materials are e.g. ceramic or plastic in the form of disks or a surface coating. The greater the thickness d of the insulation material, the greater is its insulating effect, and consequently the reduction in the heat flow.
The machine interface between the grinding pan and the drive must satisfy specific requirements in terms of loading capacity that are to be defined by the mill operator and that arise during the operation of the mill, e.g. requirements in terms of load-bearing capacity, shear strength, elasticity, breaking resistance, etc. The bearing surface is reduced as far as possible within the scope of said requirements. The heat flow through the machine interface is reduced in proportion to the reduction in size of the bearing surface.
A preferred development of the invention is a drive, in particular a gearing mechanism, having a flange that is suitable for connecting a grinding pan, the flange being embodied as a machine interface as described hereinabove.
A further preferred development of the invention is a vertical grinding mill having a machine interface as described hereinabove.
The invention is explained hereinbelow with reference to the attached schematic drawings, which are not true to scale and in which:
The grinding pan 2 is arranged in a grinding chamber 9 which is delimited by an enclosure 8. The heating of the grinding chamber 9 causes a heat flow 10 to be produced which transfers heat energy from the grinding pan 2 via the machine interface 1 to the drive 4. According to the invention, the machine interface 1 is now embodied in such a way that the heat flow 10 directed from the grinding pan 2 to the drive 4 is substantially impeded.
Although the invention has been illustrated and described in greater detail on the basis of the preferred exemplary embodiments, the invention is not limited by the disclosed examples.
Number | Date | Country | Kind |
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10 2013 213 005.8 | Jul 2013 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2014/063046 | 6/20/2014 | WO | 00 |