Cake filtration: A clever filtration technology for the finest particles
Cake filtration - what sounds like an unusual baking technique is a popular filtration technology in industry for the treatment of process liquids. It makes use of an automatic process in the filtration process to separate even fine particles from liquids. But how exactly do industrial cake filters work? And which filter types are suitable for which filtration tasks? We give you an overview of cake filtration and its areas of application.
What is cake filtration?
Cake filtration, also known as cake-forming filtration, is one of the mechanical solid-liquid separation processes. The last of these is a purely mechanical process for separating solids from a liquid using a filter medium. A special characteristic of cake filtration is the formation of a filter cake during the process.
The simplest example of a cake filter is the standard household coffee filter. The way industrial cake filtration works is not quite so far away. But how exactly does the process work in industry?
How cake filters work
In cake filtration, the suspension to be filtered is passed through a porous filter medium. The solids settle on the medium. The particle sizes retained by the filter medium at this point depend on the filter fineness of the filter medium. In cake filtration, however, this only plays an initial role.
This is because the accumulation of solid particles on the filter medium forms a porous layer, the so-called filter cake. This layer is the basic prerequisite for cake filtration and must remain filterable. The filter cake continues to build up as it takes over the filtration process and further solid particles constantly accumulate. However, the filter cake must be rinsed out after a while, as the pressure loss and flow resistance also increase over time.
If these become too large, regeneration occurs in most industrial cake filters. This involves the liquid being passed through the filter in the opposite direction. Alternatively, the filter layer can also be scraped off or discarded. The process then starts again. If a filter belt is used as the medium, the filter cake is removed by transporting the belt further.
The benefits of the filter cake
The structure of the filter cake ensures that successively smaller and smaller particles can be retained. As a result, very fine filter finenesses can be achieved. In addition, the pressure difference between the inlet and outlet sides is the driving force behind the filtration process. The filter cake is therefore the central filter medium in cake filtration.
But the cake itself can also be of value. Depending on its composition, it can be prepared and further processed. Filter cakes with a metallic composition can be briquetted, for example. Metal shavings are a valuable material and can be recycled again and again. With the help of screw presses and briquetting presses, the filter cake is dehumidified and pressed into briquettes. These can either be fed back into your own production cycle or sold to disposal companies. You can find out all about this recycling process in our articles on how screw presses and briquetting presses work.
Frequently used cake filters
A variety of filter types make use of the filter cake build-up process. Depending on the application, different solutions are best suited to fulfill the filtration task. We present a few popular filter systems below.
Belt filters
Typical cake filter solutions include our various types of belt filters. These include pressure belt, folding belt, vacuum belt, inclined belt and gravity belt filters. All these cake filter types work in a similar way: The liquid to be cleaned reaches a filter fleece or belt, where the solids are retained and form the filter cake. As soon as the pressure loss becomes too high, the cake is transported away by the belt and clean filter belt is drawn in. This ensures continuous filtration.
Cartridge filters and cartridge filter systems
Our cartridge filters and cartridge filter systems also make use of filter cake for the filtration process. No filter aids are therefore required here either. The liquid to be cleaned flows through the filter candle from the outside to the inside – the cake therefore builds up on the outside of the candle. If the permissible limit pressure is reached here, regeneration is automatically activated in our solutions. In this area, for example, we offer innovative systems for microfiltration with filter finenesses of up to 5 µm, also in the compact version if space is limited. Our backflush filters are particularly flexible and adaptable cake filters for filtration capacities from 250 l/min to 20,000 l/min.
Precoat filters
Precoat filters are used when the dirt particles are too small to produce their own filter cake. The filter cake is created by means of a precoated filter aid on the filter cartridge. The fine particles are filtered out through this precoat layer, i.e. the filter cake. When the maximum dirt holding capacity of the filter cake is reached, it is rinsed off the filter cartridge.
Automatic filters
Our slot-type filters are particularly suitable for extreme conditions and special requirements, such as high temperatures or adhering dirt particles. They offer an exceptionally robust solution. With a variety of modules and options for customizing the materials, controls and sealing systems, we also tailor them to the specific filtration task.
Our automatic module filters are also highly customizable. They are preferably used in downstream processes in the oil and gas industry. The filter cake accumulates on the outer surface of the filter medium in both the module and slot-type filters. Our module filters have an automatic backflush function, while the filter cake is scraped off the slot-type filter.
Cake filtration for every application
Our cake filters are an efficient solution for the treatment of your cooling lubricants and other process fluids. Find out everything about our exceptional filter types here.
Typical areas of application for cake filtration
Cake filters are used in various industries and processes, for example in the metalworking and automotive industries. Here they are used to clean grinding, cutting and rolling oils, among other things. Other process fluids can also be treated using cake filtration, for example after drilling and milling. They are most frequently used in the treatment of cooling lubricants.
However, cake filters are also used in the water industry and in the treatment of highly viscous liquids. In principle, cake filtration can be used in all industries in which liquids need to be cleaned of solid contaminants. We will be happy to advise you on whether this filtration method is suitable for your application.
Conclusion: When to use cake filtration?
Even if filter cakes are difficult to eat, cake filtration is an efficient and popular filtration method in various industries. In many contexts of liquid processing, the use of a cake filter is worthwhile, especially for high throughput rates. Depending on the task, belt, cartridge or more specialized filter systems can be used in this context. The filter fineness and filtration performance differ depending on the filter type and the individual design. We will be happy to find out which system is best suited for your liquid treatment in a non-binding consultation.
