Once the chambers are full, the cycle is complete and the filter cakes are ready to be released. In many higher capacity filter presses, fast action automatic plate shifters are employed, speeding cycle time. Some filter presses are specifically designed for fully automatic, hour operation in a harsh environment such as mines or chemical manufacturing plants. Filter presses can be built in a wide range of sizes, from small, lab-scale mm presses, to those with much larger capacities, such as those with and mm filter plates.
Design of a filter press depends on a host of factors such as filtration cycle time, cake dryness required, cloth life, whether manual or automated plate shifting is desired, and many other factors.
Or we may have just the right standard or used filter press in-stock to meet your needs today. Contact Micronics, Inc. Filter Media The efficiency of the filtration process is heavily dependant on two things, the characteristics of the solids in the slurry, and the filter media that is used.
The type of filter media selected will determine the type of filtration that will occur. Surface filtration works by stopping particles larger than the pore size of the media; as particles build on the surface the filter cake develops. Most of the filtration is performed by the developed filter cake. As the filter cake continues to build the efficiency of filtration increases and finer particles are captured in the matrix of the filter cake. Because filtration occurs on the surface of the filter cloth , the media can be used throughout many filtration cycles without needing to be replaced.
Depth filters work through several steps for particle capturing including: sieving, interception, adsorption, and absorption. Similarly to surface filtration the developed cake offers additional filtration.
Depth media becomes saturated with solids through the filtration cycle as interstitial spaces become filled with particulates. Once fully saturated the depth media is replaced with a new sheet and the filtration process can begin again. The Filtration Cycle The filtration cycle can be broken into the following steps: filling, dewatering solid-liquid separation , cake wash and air blow, membrane if applicable , and finally emptying.
Dewatering processes are performed using filter cloth or paper media and high pressure processes. Depth media is generally used for polishing or more refined filtration with low pressure processes.
Filling During the filling process solids laden slurry is pumped under pressure into the filter press chambers through the piping at the stationary head of the filter press. Solids within the slurry will flow to the area of cake development with the lowest pressure differential, resulting in a filter cake which builds uniformly over the drain-field on either side of the chamber walls. As each cake chamber fills with slurry, the liquid passes through the filter cloth , filter paper , or depth meda , across the drain-field, through the drain ports and exits via gravity out of the corner discharge eyes.
With a gravity drain on the filtrate side of the press, a pressure differential between the feed pressure and the gravity discharge is created across the media and the filter cake solids as they build in thickness.
It is the existence of this pressure differential, not just the feed pump pressure, which causes the filtering action to occur. The filter press works thanks to a series of porous plates, covered with drain fabric. The thick fluid or sludge is pumped between the plates and pressed, so that the liquid part passes through the fabric and the solid part is retained by the plates. At the end of the operation, the latter are opened to allow the unloading of the panel that they have formed.
Thus the filter pressing process works by leading to a volumetric reduction of fluid substances that contain suspended solid particles. This process allows us to obtain very dry sludge. It can be discontinuous therefore not very productive and require a lot of assistance, with an impact on labor costs. In order to optimize the process and improve the work performance of the plate filter press, it is very important to choose the best pumps for the suction and introduction of sludge and dense fluids inside the filter press.
The PEMO Pumps range offers a wide choice of vertical, horizontal, submersible or multistage pumps, which are adaptable to the needs of each sector.
It is also necessary to carry out a preventive treatment of the sludge, which usually takes place by using ferric chloride and aluminum hydrochloride or polyelectrolytes.
If we analyze all filter press models by components , we see that they can differ in the level of automation required and other details, but they mainlly share the same basic structure, which determines how a plate filter press works.
Optional components can be added to this basic structure, depending on the type of process in which the plate filter press works and on the desired degree of automation. The collection of the sludge takes place through a feed pump for filter press. To understand which type of pump to choose, it is necessary to understand well how the plate filter press works.
The pump plays a crucial role in the filtration and sludge collection process, even more crucial than that of the filter press itself. In fact, if a gasket breaks or if some automatic function is defective, it is still possible to complete the filtration, perhaps with a greater waste of time.
Instead, there is no way to proceed with filtration if the pump is not working properly. In dewatering and sludge collection plants, the applications of filter press feed pumps can be performed by:. In the first case, the collection and transit of sludge are managed by a centrifugal pump in the filling phase and a volumetric one for the final filtration phase. The former are particularly suitable in the initial stage, which requires a high flow rate with low pressure values.
The main advantage of the second option is given by having to manage a single element, with a possible reduction in management costs. It begins with the closure of the filter press through an oleodynamic system, which is composed of one or more thrust cylinders that align the plates support of the filter cloths and keep them close to each other by exerting a very strong pressure.
This also guarantees tightness and counterthrust against the one exerted by the feed pump. The sludge is pumped into the chambers that form between the plates.
The liquid in which it is suspended is pushed through a series of cloths, which cover them and perform the filtration action.
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