These devices are devices that are actively used today in industry, for example, at the Novoangarsk concentrator, which is located in the Krasnoyarsk Territory. Their main task is the enrichment of minerals. This unit is a continuous device. The basic principle of its operation is the separation of liquid heterogeneous systems under pressure. The separation occurs in two phases - solid (cake) and liquid (filtrate).
Description of tape device
One of the most common devices is a belt vacuum filter. Its peculiarity lies in the fact that in such a device the direction of movement of the filtrate will coincide with the direction of movement of the existing gravity. Also, this device is continuous in nature. In the design of the unit there is a perforated rubber band, the movement of which is ensured by the action of two drums - drive and tension.
The movement of the tape is carried out inside a closed loop. The fabric in this case plays the role of a filtering partition, which is pressed against the tape by means of rollers. The suspension that needs to be filtered using such a vacuum filter is located in a special tray, from where it is fed to the filter cloth. Due to the pressure difference, different fractions of the filtrate will be fed into the vacuum chambers, which are located directly under the tape.
After it is removed from the device. During the procedure, a precipitate will remain on the filter cloth , which must be washed off after the completion of the filtration step. Flushing is carried out using water, which is supplied from the nozzles. The tissue washing liquid is also sucked into the vacuum chambers, but of a different type, after which it is also removed from the unit.
As for the main advantages of such vacuum filters, the simplicity of the device, the possibility of sludge dewatering, and excellent washing conditions can be attributed to them. The pluses also often include the fact that the device does not have a distribution head. In such equipment (due to the presence of tissue regeneration and its cleaning), even hard-to-filter suspensions can be washed.
Description of disk design elements
Disc vacuum filters consist of a set of fairly simple elements. The main components of the device are a trough, several disks, as well as a distribution head. The disks of this device are mounted on a rotating shaft of a cell type. The filtering process is carried out due to the fact that each disk has from twelve to eighteen cells that are covered with filter cloth or mesh. As for the sectors of this vacuum filter, they are usually made of a material such as metal or polypropylene. The fastening process begins with a shaft, which has a hollow structure, two walls - internal and external, docking on thrust bearings. It is between these walls that the disk cells are located in the right amount.
General description of the device
As in the case of the tape type, filtering is carried out using a partition. In this case, it turns out that the filter material is separated into a precipitate, that is, solid particles remaining on one side of the septum, as well as into a liquid substance, that is, a filtrate. It passes through the septum and accumulates on the other side. In order to successfully carry out the process, it is necessary to achieve the condition that the pressure of the incoming suspension must exceed the pressure that is on the other side of the partition.
For this to happen, it is necessary to greatly increase the mass of the suspension before serving. To do this, it is artificially pumped, using various pumps, gas pressure or even creating a vacuum from the back of the partition.
It is also worth noting that the filter material enters this unit intermittently. In other words, a disk device (like, for example, a drum device) works in cycles. There are some limitations regarding suspension. Firstly, to use a disk filter, it must be completely safe, and secondly, the liquid phase, that is, the suspension filtrate, must not crystallize when there is a vacuum in the medium. In such filters it is impossible to process a suspension which belongs to the explosive, flammable or poisonous class.
The principle of operation of the apparatus
Disk type filtering unit works according to the following principle.
At the moment the shaft begins to rotate, all the filter cells in turn begin to communicate with the chambers of the distribution head. The filtrate in the filter zone is carried out under vacuum. It enters the cavity of the sector, that is, the cell, passing the partition. After that, the process of removing the filtrate from the unit through the shaft cells and the chamber, which communicates with the vacuum line, begins.
As for the solid part of the element, it remains on the surface of the partition. Because of this, a rather thick sediment layer is formed on the surface of the fabric in this type of filter plant in just a few minutes of operation of the equipment.
In addition, the device also has a drying zone and a dehydration zone. In these areas, the process of aspiration of moisture that remains on the sediment is carried out, after which it is also removed from the device through a special channel. The unit has another chamber, which is designed to supply compressed air to the partition in order to separate the sediment from it. The final separation is carried out manually, with a knife. To supply compressed air with one powerful impulse, the device has a blow-off valve. This vacuum filtering device , like the belt one, has the ability to regenerate tissue. To do this, it passes through a special separate chamber in which it is exposed to air or steam for cleaning.
However, there is a slight difference, which lies in the fact that the regeneration zone is used only if the precipitate clogs the partition too much, in contrast to the tape, where regeneration is required. It is worth paying attention to the trough, which is usually a welded structure with an overflow trough. The main objective of this part is to maintain a constant uniform level of suspension.
Drum device
The design of vacuum filters is quite diverse. A drum unit is another variation of such an assembly.
It is a rotating cylindrical perforated drum. The part is covered with a metal mesh, and also covered with a filter cloth on top. Most often, such devices are used in the chemical industry, especially if they have an external filtering surface. The difference between these devices from others is that they are very simple to use, their degree of filtration is quite high, and also with their help you can process a variety of suspensions. Some are difficult to design, so you have to accurately calculate a large number of parts.
The principle of operation and working areas of the drum device
It is immediately worth noting that this type of vacuum filter works on a cyclical basis, rather than on a continuous basis, in addition, it is divided into 4 working zones.
The working area number 1 is a filter, and also serves to dry the sediment. It is in it that the chambers are connected to the vacuum line. Due to the presence of a vacuum that creates pressure on the filtrate, it passes through the filter screen, perforated the drum, and then gets into the middle of the cell. After the filtrate is removed through a special pipe from the unit. At the same time, a precipitate forms on the outside of the mesh, which will partially dry at the moment the cells come out of the suspension.
This is followed by the second working area, where the washing and drying of sludge is carried out. In this zone, the cells also connect to the vacuum line. The device is configured in such a way that it delivers a special flushing fluid that passes through the filter screen, and then is removed from the device. In those places where the liquid did not enter, the precipitate will be dried.
The third working area is the sediment site. In this case, the cells will not be connected to the vacuum line, but to the compressed air line. When it is fed, it will loosen the precipitate, which simplifies the process of its removal. Then the solid filtrate is completely removed from the grid with a knife.
The last fourth zone serves to regenerate the filter mesh. To do this, compressed air is used in the drum unit, which frees the partition from any particles remaining on it.
After the work is completed, the cycle of the working area is repeated. The zones themselves operate sequentially, but they do not depend on each other. Thanks to this, it is possible to create the appearance of a continuous process of operation of the drum device, although by the nature of its work it is still considered cyclical. It is worth adding that during the rotation process, dead zones appear in which the cells are completely disconnected from the supply of both compressed air and vacuum.
General description of the stages of work
It is worth mentioning that any type of such equipment works according to a principle common to all, including, for example, hyperbaric filters. Their work includes seven sequential steps.
The first stage is the immersion of the device in suspension, the formation of a precipitate and the further removal of the filtrate, that is, the liquid component. Next comes the second stage, when air is drawn in through the sediment and the final removal of filtrate residues. The third stage is the washing of the suspension solid particles. The next stage is again drawing air through the sediment, but with the removal of the washing liquid. The fifth stage is the removal of sediment and its washing. One of the last stages is detachment, that is, the complete removal of sediment from the tissue. The last, seventh stage is the process of tissue regeneration.
General principle of steps
It is worth mentioning that the first four stages have something in common - connecting to a vacuum line. The last three stages are carried out with the connection to the line of compressed air, and not vacuum. During the purge of the fabric, a sufficiently thin and spiral wire is used. It is necessary in order to press the fabric to the surface of the drum, shaft and so on. This is done in order to avoid possible stretching of the fabric due to exposure to a strong air stream.
Filter press
Automated filters of this type are very widely used in industrial enterprises. Most often, they consist of a filter plate, which is covered with a perforated sheet on top. Between the sheet and the slab there is usually a free space that is filled with filtrate. Between the plates and frames of such devices, waterproofing diaphragms are also installed. As filter baffles in such filter presses are long pieces of fabric that are stretched between the plates using hydraulic devices.
As for the main advantages of this equipment, it is possible to distinguish automation of the cleaning process, small dimensions, sludge extraction, as well as the minimum working time for the working cycle. The approximate time, which is the execution of all operations, is several minutes.
Frame and chamber filters
Frame and chamber filter presses are popular today.
As for the frame device, it is most widely used in the chemical industry. This device consists of a set of plates of a rectangular type, which are arranged alternately in one row and suspended from a support. The plates themselves have a grooved surface, which is fitted with a filter cloth. The suspension enters the channels under pressure, where it passes through the tissue.
If we talk about chamber presses, then they are also quite well distributed in the chemical industry. However, unlike frame they are incredibly successfully used in mining metallurgy, in oil refining, in the mining industry. As for the design of the filter, it consists of a set of plates that are arranged vertically. To date, there are four types of plates that can be used: these are filter, end, pressure, and persistent.
Fastening of any type of plates is carried out on longitudinal couplers. On these screeds are guides along which the plates move. If you close the press, then the filter plate with adjacent forms a chamber for washing and filtering. The thickness of the chamber is usually 30 mm.
The use of various types of devices of this class is carried out on a large scale at a variety of enterprises, including the domestic Novoangarsk concentrator.