Disc Filter: Engineering Aspect in Solid Liquid Separation

Disc filter is famous in heavy-duty operations and other beneficiation processes

Disc filter is in use for many years in the industrial sector and chemical processing plants. It eventually belongs to the side-feed group. The filter thereby makes an essential component in the chemical processes.

All the major applications involving solid-liquid separation carry these disc filters as an important component. Furthermore, the processes that revolve around flow scheme in chemical industries, pharmaceutics, Food and water management authorities, and Ore beneficiation makes the most use of it.

These processes hence involve separation and the techniques used in these processes are diverse. The ultimate objective of this article is to provide a sustainable platform to engineers and researchers to ponder over the applications and processes. It will surely help all the stakeholders to practice and explore new ways and developments in unit processing. Read More

What is Disc Filter?

Disc filter as we have discussed above belongs to the side feed group and in use for many years. The major applications involve heavy-duty industrial applications such as dewatering of iron ore taconite, the concentration of copper, coal, hematite, and other beneficiation processes. This, therefore, demands the disc filter as an all-time high component. However, this high time period was at its peak in the 1960s. it is because at that time the metallurgical industry was experiencing a major boom. Eventually, calling for large filters of sizes 300 meters square and even larger.

In addition to this, a single filter comprises more than one disc. It consequently contains several discs. One can estimate the size of the large filter by the number of discs it contains. For the sake of example, a large filter carries 15 discs. Each disc in using sectors that are clamped together hence making a whole disc filter. All these sectors are directional towards the neck and are thereby suitable for draining at high-capacity rates.

The most striking feature of these disc filters is that they are capable to utilize minimal space. Eventually making the cost per meter square for the filtration process at the lowest. This cost is in fact the lowest when we compare it with other vacuum filters.

How Disc Filter Operates?

The working or operational mechanism of the disc filter is very interesting. At every moment, each sector of the disc enters the section of submergence. In this process, cake appears on the faces of the disc in a large amount. The disc eventually passes through the drying zone. In this zone, the liquid that is left in the filter drains out using the central barrel to vacuum the receiver. The process is guided in such a way that as soon as the sector leaves the drying zone, it simultaneously is ready for discharging the cakes.

In the next section, there are large blades on each side of the disc that helps the cake to discharge. However, one important aspect is the distance of chutes that are wide enough to make any possible clogging. In the last, a paddle agitator is the one that carries the slurry in suspension which most of the time carries the high specific gravity. These characteristics are usually fast at settling and also are abrasive in nature.

Selection Criteria for Disc Filters

There are many factors and things to consider while choosing the best quality disc filter. Amongst these some of the considerations are:

• The form-to-dry ratio of any filter makes an integral criterion for any process. Therefore, for the best filters, the form to dry time ratio must be between ½ to 1.
• A good filter always eliminates the need to have a cake washing requirement.
• Next comes the separation of the cake. Eventually, for a good filter, the separation of a cake must be smooth. By this, it means that cake that form must come of easily from the cloth.
• A good quality filter contains a good cloth that prevents itself from getting clogged.
• One of the issues that a disc filter faces is the replacement. It happens when one of the clothes of the section tear, one consequently needs to replace the whole section within a short span of time.
• However, there is an advantage of using a disc filter which allows adding more cloth and sections to expand the filtration area.
• Last but not least is the cost-effective property that allows filtration using minimum space with maximum efficiency at the lowest price.

Operational Sequence

The operation sequence of the disc filter works exactly the same as that of drum filters. However, it is different and not feasible for washing purposes. The working mechanism of the disc filters involves the passing of sectors from one zone to another. Eventually, there involves many changes and steps during this passing-by phase. Therefore, we will discuss the detail below by following each sector:

• The vacuum section process happens when the whole sector submerges into the slurry. In this whole process, the dead zone bridge receives the passing of the ports of the rotatory barrel.
• The formation of the cake happens after the leading edges of the sectors pass from the slurry. Hence, after that, the drying process commences on its own.
• After that, the process of drying out of the cakes continues to work under the vacuum section. Until we notice the ports of the rotatory barrel fully cover themselves under the dead zone bridge in the valve. The bridge ultimately separates the vacuum section from the blow compartment.
• As soon as the ports of the barrel pass the bridge and simultaneously a low-pressure air blow falls on the cakes that eventually forces it to fall off from the discharge chute.

Maintenance Of the Disc Filter

Maintenance is extremely important when it comes to disc filters. It is because these filters are prone to high wear. The wearing happens because of the presence of a high number of abrasive substances. This happens due to the various processes of slurries. Therefore, it is requested to keep a careful look at the following subassemblies.

• One of the critical components to look at is the agitator, stuffing boxes, and its bearings.
• The seals against the valve's face as well as the wear plates which are mounted on the barrel also need careful monitoring for timely maintenance.
• Cloth of the disc filter or also famous as mesh screens also require regular monitoring as they get easily susceptible to wearing and tearing.

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