Weighing scales – Processes
Patent
1986-10-08
1988-06-07
Miller, Jr., George H.
Weighing scales
Processes
177165, 177245, 73 76, 364568, G01G 1314, G01G 2300, G01N 2556
Patent
active
047490543
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for measuring the quantity of the periodically dried product, and particularly the quantity of a concentrate dried in a pressure filter. The method comprises the following, periodically repeated stages: inserting the product to be dried in the drying apparatus, carrying out the successive drying stages, and discharging the dried product from the drying apparatus.
The present invention is particularly well suited to be employed in connection with concentrate drying, but naturally its scope is not limited to this one exemplary case only.
Such pressure filters that are suited for drying conentrates are manufactured for example by Larox Oy. When drying a concentrate in this type of a pressure filter, problems arise, on one hand as regards the accuracy when measuring the quantity of the conentrate, and on the other hand as regards the optimal adjusting of the drying operation. This is mainly due to the periodical nature of the operation of the pressure filter.
Generally the drying operation consists of three stages. During the filtering stage, the slurry is conducted through the filter cloth, so that the cloth separates the solid particles of concentrate from the slurry. After filtration, the slurry flow is interrupted, and the layer of concentrate formed on the filter cloth is squeezed in order to reduce the volume of the filter cake and to remove liquid therefrom. After squeezing, the filter cake is further dried by blowing air through the cake. Thereafter the filter cake is discharged from the pressure filter. The dried concentrate is further transported, preferably by means of a belt conveyor, to the desired location.
A customary method for measuring the concentrate quantity during transport in the belt conveyor is to employ a belt weigher. The belt weigher, however, does not function accurately enough owing to the periodical nature of the operation of the pressure filter.
In order to avoid this drawback, the present invention is characterized by the novel features presented in the patent claims. By employing the method of the invention, the concentrate quantity can be measured quickly and accurately and without interfering with the process itself. The capacity of the above described pressure filter is dependent on the length of the respective filtering, squeezing, air-blow drying and discharge stages. The method of the invention also makes it possible to run the pressure filter at optimum readings, in which case the capacity of the pressure filter is utilized more efficiently.
In the following, the invention is explained in more detail with reference to the appended drawing, which is a diagrammatic illustration of an advantageous application of the method of the invention.
The diagram of the drawing illustrates the drying of concentrate by employing a pressure filter manufactured by Larox Oy, and to be more precise, it illustrates one drying cycle of the pressure filter. The drying of the concentrate is started in the filtering stage 1, where the concentrate, in liquid suspension, is filtered by means of the filter cloth. In practice the length of the filtering stage may vary accoridng to the material to be filtered. As an example, the chosen filtering time may be a minute.
After filtration, the concentrate flow is interrupted, and the layer of concentrate which is accumulated on the filter cloth undergoes the squeezing stage 2. Squeezing is carried out by means of a rubber film and by utilizing liquid pressure. In practice the length of the squeezing stage may vary as well, and it can be for instance a minute.
After squeezing, the filter cake undergoes air-blow drying 3. The length of the air-blow drying stage is dependent on the qualities of the material in question, but in practice a suitable duration is for example five minutes.
After air-blow drying, the drying phase proper is completed, and the filter cake is ready to be discharged from the press. Before discharging, however, the whole press is weighed along with the concentrate contained therein. The weighin
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Reijonen Seppo
Virtanen Markku
Miller Jr. George H.
Outokumpu Oy
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