Type of vacuum filter and principle of cylindrical external filter vacuum filter
The vacuum filter can be basically divided into four types, namely, a cylindrical external filter type vacuum filter, a cylindrical internal filter type vacuum filter, a cylindrical magnetic vacuum filter, and a disc type vacuum filter. They work the same way.
The structure of the cylindrical outer filter type vacuum filter is as shown in the figure below. The barrel is the main body of the filter. The barrel of the large filter is made of steel plate welded, the small size is made of cast cylinder, and some old-fashioned filter cylinders are made of thick wood. The outer surface of the cylinder is divided into a plurality of axially penetrating filtering chambers in the circumferential direction by the spacers, and the chamber and the chamber are tightly sealed and are not ventilated. A filter plate is placed in the filter chamber to form communication for the flow of the filtrate on the one hand and to support the filter cloth on the other hand. The section of the filter chamber is shown below.
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A filter cloth is wrapped around the entire barrel. In order to ensure the seal between each chamber, the filter cloth is embedded in the rope groove of the spacer by a strip, a hemp rope or a brown rope. Then, a plurality of wires are wound around the outside of the cylinder at a pitch of 50 to 80 mm in the axial direction by a winding mechanism, and the filter cloth is fixed on the cylinder.
At one end of the barrel there is a throat having the same number of channels as the filter chamber, each of which is connected to a corresponding one of the filter chambers via a tube.
The transmission mechanism drives the barrel to rotate and can change several speeds.
The dispensing head is an important part of the filter and its position is fixed. One side of the tube is in close contact with the throat and the other side has a tube connected to the vacuum pump and the blower. Through it, each filter chamber of the filter is controlled to perform filtration, filter cake dewatering, unloading, and cleaning of the filter cloth.
Inside the dispensing head, there are several cavities arranged on the same circumference and spaced apart from each other to form several zones, the schematic of which is shown in the following figure.
1. Filter zone I The filter chambers in the zone are connected to the vacuum pump through a pipe. The cylinder is immersed in the slurry. The pressure difference caused by the vacuum is filtered. The filtrate is filtered through the filter cloth and then sucked into the filter chamber. The medium is discharged, and the filter residue is deposited on the filter cloth.
2. Suction dry dehydration zone II In this zone, as the vacuum pump continues to pump, the remaining liquid is sucked out to further reduce the moisture of the filter cake.
3. Blowing and unloading zone IV Each filter chamber in the zone is connected by a pipeline and a pressure blower, so that the filter chamber is changed from negative pressure to positive pressure, compressed air sucks the filter cake, and the filter cake is scraped by means of a scraper. Discharge outside the machine.
4. Filter cloth cleaning area VI In this area, the pressure fan continues to blow the filter chamber (or the blast and the water supply) to clean the filter cloth and restore its gas permeability.
The zones III, V, and VII are non-operating zones, and they do not allow each other to communicate with each other when the filter chamber is changed from one zone to another zone. [next]
During the rotation of the barrel, the barrel is transferred from zone I to zone VII to complete a filtration cycle. Each filter chamber works in such a manner that at each moment the filter chamber is forming a filter cake, blotting the filter cake, discharging the material, and cleaning the filter cloth. So the work of the filter is continuous.
The filter cake of the cylindrical external filter type vacuum filter is discharged, and is peeled off by a scraper mounted in the discharge area. This method of unloading tends to damage the filter cloth, and compressed air must be introduced into the discharge zone during operation. In order to improve the cleaning cloth and the discharge mode, recently developed a tape off the cylindrical vacuum filter, has been successfully used in the production of gold, which is configured as illustrated.
The filter cloth of the belt-type vacuum filter is wound around the filter drum, the roller, the adjustment roller like a conveyor belt, and is driven by the cylinder. After the filter cake passes through the dewatering zone, the filter cloth is taken out of the cylinder by a set of rollers for unloading and cleaning, and the cleaned filter cloth is returned to the cylinder for re-operation. The belt-type vacuum filter does not use blast discharge, thus avoiding the increase of filter cake moisture caused by backwater. Folding belt vacuum filter will take out the filter cloth out of the cylinder, and it can have enough time and take effective measures to clean the filter cloth. Generally, the two sides of the filter cloth are washed with pressurized water, and the device can be more thoroughly used with brushes and cloths. The cleaning is to ensure the permeability of the filter cloth and reduce the blockage. Folding belt filters are suitable for filtering fine, sticky pulp.
