Boots – shoes – and leggings
Patent
1995-12-07
1998-08-25
Elmore, Reba I.
Boots, shoes, and leggings
364166, 241 33, 241 34, G05B 1302, B02C 432
Patent
active
057989176
DESCRIPTION:
BRIEF SUMMARY
SUBJECT OF THE INVENTION
The subject of the invention is a control process for closed-circuit, dry-method grinding installations which essentially comprise a batching device for the feeding of raw materials, a grinder, an adjustable-speed dynamic separator, means for bringing to the separator the matter coming from the grinder, means for returning to the grinder the insufficiently ground coarse matter and means for conveying the finished product to the exit of the separator.
The present invention also relates to the applications of the control process.
State of the Art
The present invention is intended for closed-circuit, dry-method grinding installations, and preferably for installations comprising a rotary ball mill used for the manufacture of cement. Such, grinders have ever greater capacities, some of them expending more than 8000 kW. The installations required to rotate such grinders are extremely costly in terms of investment and energy. For them to be cost-effective, demands:
It is generally recognized that, for modern grinding installations, the most cost-effective investment is a good control device which regularises the fineness of the finished product and thereby makes it possible to reduce the safety margin between the average quality produced and the required quality. By reducing this margin the capacity of the installation is increased; a few per cent gained in flow rate achieves a very sizable saving in the costs of operation and recouping of the investment.
Modern closed-circuit, dry-method grinding installations essentially include a batching device for the feeding of raw materials, a grinder, an adjustable-speed dynamic separator, means of transport (generally including an elevator) for conducting the ground matter from the grinder to the dynamic separator, means of transport for returning the coarse matter (oversize from the separator) to the grinder and means of transport for conveying the finished product.
In order to avoid expelling dust and in order to cool the installation, the grinder is moreover provided with a ventilating device.
Dynamic separators operate through the combined effects of the rotation of a distributing plate, of a selection device and of a current of ventilating air passing through the separator
This current of ventilating air within the separator can be created by a fan internal or external to the said separator.
When the fan is internal to the separator, the separating of the air and of the finished product takes place fully inside the separator.
When the fan is external, the separating of the air and the finished product takes place in one or more cyclones outside the separator and/or in a device for removing dust in bags. The separators with external fan exhibit better efficiency and allow better cooling of the treated product. At present, modern installations are generally provided with this type of separator.
Some installations having a separator with internal fan are furnished with a complementary external fan for cooling the system but which is however inefficient and hence this solution is no longer used in recent installations.
It should be noted that a grinding installation is subject to numerous disturbances, including: the latter's grinding capacity;
Any disturbance or lack of stability in a grinding installation can cause a variation in the quality of the finished product and in the yield of the grinder bringing about a downgrading of a certain quantity of product and consequently a loss in production.
To eliminate or reduce these disturbances, grinding installations must be controlled as efficiently as possible.
The principal object of a control process for grinding installations is to ensure the greatest possible constancy of the quality of the finished product. This quality depends essentially, on the one band, on the chemical composition of the product, which must be ensured by proper batching of the constituents, and on the other hand, on the fineness of the finished product, that is to say on the efficiency of the dynamic separator.
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patent: 5269468 (1993-12-01), Graenicher et al.
patent: 5454520 (1995-10-01), Folsberg
Proceedings of the Eight Triennial Congress of the International Federation of Automatic Control. vol. 5, 08-24-81; Japan, pp. 2851-2857; J. Koudstaal et al; The Application of a Multivariable Controller to an Industrial Grinding Circuit.
Nouvel Automatisme, No. 34, Dec. 1982, Paris pp. 71-74. J. Rajot Surveillance en Temps Reel D'Un Atelier de Broyage et classification.
Brown Thomas E.
Elmore Reba I.
Slegten Societe Anonyme
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