In the pulp production process, the multi disc filter is an important solid-liquid separation device. Its core components include the multi disc filter plates, filter bags, central shafts, and water legs, and they are widely used in white water recovery, pulp concentration, and fiber recovery.
In actual production, the filtration efficiency and filtrate quality of a multi disc filter largely depend on whether a stable and properly formed filter cake can be developed on the filter plate surface.
Therefore, the structure and operation of multi disc filter plates directly affect the efficiency, quality, and stability of the filtered slurry.
Working Principle of Multi Disc Filter
Multi disc filter is an important solid liquid separation device in the slurry production line. During operation, the multi disc filter plates rotate slowly under the drive of a motor reducer and are immersed in the slurry to be treated.
Thus, under the combined action of the plate and the vacuum pump, the water in the white water is discharged. At the same time, solid substances such as fibers remain on the surface of the filter plate, gradually forming a filter cake of essentially uniform thickness.
Subsequently, the filter cake on the multi disc filter plate surface is peeled off by the combined action of the spray nozzles and doctor blades in the multi disc, thereby completing one filtration cycle.
In fact, the filtration effect of a multi disc filter is not fixed but gradually changes as the filter cake forms on the surface of the filter plates.
Factors Affecting Multi Disc Filter Plate Filtration Efficiency
White Water Fiber Quality
The efficiency of multi disc filtration of slurry mainly depends on whether a suitable filter cake can be formed on the filter plate screen. Therefore, during white water recovery, a certain amount of long fiber raw material needs to be added to the white water to facilitate the formation of the filter cake on the multi disc filter plate and the peeling of the slurry layer.
Filter Cake Thickness
In the initial stage of filtration, the filter cake layer on the surface of the multi disc filter plates is relatively thin, so pulp water can quickly pass through this filter medium.
However, during this initial filtration stage, the filter cake has not fully developed. So, more fine fibers and fillers may pass through the multi disc filter plate surface and enter the filtrate, leading to lower filtrate quality.
As the multi disc filter plates continue to rotate in the filter, more and more fibers are trapped on the surface of the plates, and the filter cake gradually thickens and becomes denser. This will further improve the retention of fine fibers and fillers, thus improving the quality of the filtrate.
Other Influencing Factors
Of course, the filtration efficiency is also significantly affected by factors such as the number of filter plates, pulp throughput, vacuum level, pulp consistency, and the rotational speed of the multi disc filter.
The Multi Disc Filter Plate Plays An Important Role In Pulp Quality
Currently, Sun Hong offers two main types of multi disc filter plates: filter bag type and non filter bag type.
The multi disc filter plate with filter bag mainly consists of a filter disc frame and an external filter screen. Its fan filter plates adopt a grid structure, and the overall structural stability is improved by reinforcing ribs.
Its outer composite material filter bag is the main filtration area, while the internal steel plate structure is used to guide the filtrate flow to the collection chamber.
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The multi disc filter plate without a bag eliminates the external filter structure and is usually formed by directly combining two stainless steel plates with micropores to form the filtration area and the internal liquid collection chamber.
During the operation of the multi disc filter, the bottom of the liquid collection chamber inside the multi disc filter plate gradually contracts to form a funnel shaped structure. The structure is connected to the liquid collection port on the central main shaft, so that the filtered liquid can be smoothly collected and discharged.
Therefore, for both the two types of filter plates, their filtration performance, structural stability, and operating status directly affect the processing efficiency, filtrate quality, and fiber recovery effect of the multi disc filter.