Press filters are used more frequently each time, despite the discontinuous character of their operation and their high investment cost. Their development is explained by the following reasons,
1.-Increasingly mechanization of the appliances up to the point to need a mimimum of manpower or supervision for the tortas discharge operations or for the washing of fabrics. (In situ automatic washing).
2.-Necessity to obtain tortas of great dryness, to allow:
– La autocombustion of sludges in their incineration.
– The reduction if the fuel consumption in the case of thermal dry.
– A more confortable discharge.
– The use of sludges as acarreo material.
– A limitation in the transportation costs of the dehydratated sludges.
The press filter is the only equipment which guarantees very high effective pressures (16 bars and above), with which maximum dryness of torta is achieved. (Generally above 30 %).
Press filters usually used to dry sludge are of the easy mechanization plaques type for the discharge of the tortas.
A filter is usually constituted by a battery of vertical plates strongly supported between them.
Over the two faces of these plaques, filtrating fabrics are applied. Sludges arrive a presión to the cámaras created between two adjacent plaques.
The filtrado recovered by the channels, in the back part of the fabrics, is evacuated by means of conduits arranged through the plaques.
Such plaques also consist of orifices whose alignment constitutes the sludge feeding ducts. These orifices are arranged at the center or at the periphery of the plaques. With the central feeding a better distribution across all the plaque is achieved, of caudal, of pressure and hence, of drainage.
The fabrics generally are tejidos of synthetic fibers. The careful selection of the quality of the fabric has great influence in the yield of filtración a presión installation.
The space that exists between two plaques, in its central hollow part, corresponds to the thickness of the torta. The thickness can oscillate between 30 and 20 mm, depending on the specific resistance, more or less elevated from the sludge and the fixed duration of the cycle.
Filling.- during this phase of relatively short duration (3 to 10 % of total cycle), the filtration cámaras, limited by the outside faces of the fabrics of two adjacent plaques, are filled with sludge to filter. The filling time depends on the caudal of the feeding bomb.
Filtration.- once the cámaras are filled, the continuous introduction of the suspension raises the pressure inside the cámaras due to the closure of the sludge’s pores, which concentrates.
Discharge.- this operation consists in opening the filter. The plaques are separated one from another and the tortas formed between two plaques are successively expelled
Among the possible models and manufacturing combinations, we find an assembly of equipments of different dimensions and specifications, which we focus next,
Fp = press filter.
H = hydraulic powering / M = manual powering.
Tl = lateral transfer / Ts = superior transfer.
R = Retruc (discharge with vibration).
Lt = torta wash.
Sp = Soplado.
Also, the standard manufactured sizes are:
– 250 x 250 mm
– 300 x 300 mm
– 470 x 470 mm
– 630 x 630 mm
– 800 x 800 mm
– 1.000 x 1.000 mm
– 1.200 x 1.200 mm
– 1.500 x 1.500 mm
If we needed a press filter with hydraulic powering, lateral transfer of plaques, with retruc and torta wash,
Fp-hTl/r-Lt 470 x 470
Its powering is completely hydraulic or manual, la concepción de utilización esta destinada a laboratorios de ensayos y pilot plants, being prepared to realize any type of operation, washing, filter, etc…
They can be built in St-37carbon steel or in Aisi-304 or 316 stainless steel, operation pressure up to 20 Kg/cm2.
Press filters with lateral transfer of plaques sizes between 630 mm and 1.200 mm:
Equipped with maneuver electrical board, which powers and automatizes its operation.
From origin, they are supplied with an elongation that allows its future expansion in 15% of its capacity. They can be supplied with plaques and frames, plaques with incorporated camera and membrana plaques built in polipropileno.
Prepared for working pressures up to 20 Kg/Cm2
Press filters with lateral transfer of plaques sizes between 1.000 mm and 1.500 mm:
Constant pressure hydraulic closing, normalized filtrating pressure between 6 Kg/cm2 and 16 Kg/cm2.
Labor racionalization, only one workman for filter discharge.
Minimum discharge times.
Transfer of plaques by an only point.
Autofrenado of the plaques that do not se trasladan.
Transfer of plaques in two tiempos, in order to facilitar the worksman equipment control time.
Total elimination of maintenance.
Total access to plaques, al desaparecer largueros laterales.
Filters of Fp-h (Tl or Ts) series, are considered automatic equipment, without manual intervention. They do not need surveillance, they can be programmed to work outside normal schedule including permanent 24 hour service.
The control cabinet is provided with selectors and pulsadores with indicators to realice all functions, in manual as well as in automatic.
With the program the filtrating times can be modified, as well as the intervention sequences of the various elements with enclavamiento devices, disposed so the filter can not be oponed without having completed a filtrating cycle or at express will because of the need due to an anomaly in the installation, giving complete security in it.
All the elements are controlled from the cabinet, filter closing, opening, automatic valve, start the feeding bomb, control of the filtrating cycle, filter despresurización through the feeding pipes, soplado del colector, opening of the filtrating package and finally, start of a new cycle.
A command selector of positions I-0-II, allows us to place it in position I, begin the filtration cycle in automatic process.
Placing it in position 0, it stops the cycle, at any point.
Placing in position II, we proceed to open the filter and its discharge.