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Centrifuges are classified into industrial centrifuges and laboratory centrifuges.
GlanLab just mainly develops, manufactures and sells laboratory centrifuges. Many customers come to consult us the industrial centrifuge. Based on years of deep cultivation in the field of centrifuges, let us give a brief introduction about the industrial centrifuge.
1. What is the laboratory centrifuge?
Centrifugation is a basic laboratory procedure that uses a centrifuge to separate the components of a complex mixture.
By centrifuging experimental samples at extremely high speeds, the components in the mixture are affected by centrifugal force, causing denser particles to move away from the axis and less dense particles to move towards the axis.
These particles settle to the bottom of the tube, forming a so-called precipitate, so that the separated sample, or residual liquid called supernatant, can be used for further processing or analysis.
2.What is the industrial centrifuge?
An industrial centrifuge is a separation machine that uses centrifugal force to separate solids from liquids.
A centrifuge exerts a centrifugal force thousands of times greater than the force of gravity. This force causes the solid to separate instantly from the liquid. Moreover, it can also separate fluids in the case of immiscible liquids of different densities. You can think the industrial centrifuge as a scaled-up version of a laboratory centrifuge, but on a larger scale with a flow-through design. This means that the solids and liquids are constantly separated and leaving the centrifuge.
2.1. Types of industrial centrifuges
Industrial centrifuges fall into two main categories: filtration and sedimentation.
a. the filtration type centrifuge
Porous media allows fluid to leave the screen while retaining solids in a filter centrifuge. The separated liquid collects in the screen and drains. For filter centrifuges, relatively low rotational speeds (low centrifugal forces) are sufficient. They are suitable for separating large volumes of coarse solids from liquids. An example is the separation of crystalline sugars from syrups or chemical precipitates from supernatants. There are various mechanisms to collect the separated solids. Some of these methods are described in the following sections. There are a variety of filter centrifuges. Peel-off centrifuges have cloth media that the user "peels" with solids.
b. decanter centrifuge
Decanter centrifuges do not use flow-through or perforated screens or media. This centrifuge uses a solid drum, also known as "solid drum centrifuge". Centrifugal force causes denser solids to collect along the drum wall. The lighter liquid thus separates from the solid. A liquid passage allows separated fluid to exit the drum.
The same centrifugal force will also result in different settling of the two immiscible liquids. In this case, the centrifuge separates all three phases, liquid, liquid and solid. This type of separator is called a three-phase centrifuge. Solid drum centrifuges are further subdivided into two types, namely decanter centrifuges and disc centrifuges.
2.2. Difference between filtration and decanter centrifuge
2.2.1 Drum design
The main difference between a filter centrifuge and a decanter centrifuge is the drum design. Filter centrifuges have a pass-through screen that allows liquids to pass through and retains solids. A decanter centrifuge has a solids screen that separates solids from liquids using differential settling.
2.2.2 Separation efficiency
The particle size efficiency of industrial centrifuges varies depending on the centrifuge design and other operating parameters such as flow rate, fluid viscosity, centrifugal force, etc. The media or mesh size in a filter centrifuge defines the particle size efficiency. Thus, filter centrifuges separate particles that are larger than the size of the perforations in the bowl wall or screen. This separation capability limits the application of filter centrifuges to a preset size of screen media or mesh size. However, decanter centrifuges use centrifugal force to separate. The spool pushes all separated solids out of the centrifuge bowl, regardless of size. Therefore, a solids drum or decanter centrifuge can separate a wide range of particle sizes from liquids. In general, decanter centrifuges have a higher particle size efficiency than filter centrifuges.
2.2.3 Gravity or centrifugal force
Decanter centrifuges use the difference between the specific gravity of solids and liquids to affect separation. Therefore, these centrifuges exert a high centrifugal force (RCF) for efficient separation. Filter centrifuges require lower g-forces to push liquid through the bowl holes. Typically a decanter centrifuge has a centrifugal force from 3,000 Gs to 10,000 Gs, while a filter centrifuge has a centrifugal force of less than 2,000 Gs.
2.2.4 Extraction of isolated solids
A decanter centrifuge continuously discharges the separated solids during the settling process. A rotating vortex (auger) within the bowl pushes the separated solids out. The filter centrifuge accumulates separated solids, which are periodically scraped from the mesh by the scraper.
2.2.5 Separation liquid discharge
The flow screen of the filter centrifuge allows the liquid to flow out of the screen. The separated fluid is drained from the centrifuge vessel by gravity. The separated fluid in a decanter centrifuge spins at high speed. A built-in pump converts rotational energy into pressure, under which the separated liquid is expelled.
2.2.6 Removable media
As the name implies, filter centrifuges typically use replaceable filter media. This media change increases labor and material costs. A solids net decanter centrifuge uses amplified gravity to separate liquids from solids. This type of centrifuge does not require media changes, saving cost and time.
2.3 Centrifuge Design
Decanter centrifuges and filter centrifuges are essentially different in design. Following are the key differences between these centrifuges.
2.3.1 Moving parts
Moving parts in this section refer to those inside the centrifuge. The rotating screen is a standard moving part of all centrifuges. Filter-type centrifuges typically have articulated scrapers or blades that periodically scrape separated solids off the inside surface of the bowl. The scraped solids then fall out of the net by gravity. The rotating vortex within the settling centrifuge bowl pushes the separated solids out. This solids ejection is a continuous process in which solids are ejected from the rotating web due to centrifugal force.
2.3.2 Network structure
A filter centrifuge has a mesh with holes to separate the liquid from the solids and to pass the separated liquid through. The size of these perforations determines the size of the separated particles. A decanter centrifuge has a solid mesh; hence, it is also known as a solid mesh centrifuge. No perforations make the solid mesh centrifuge more durable and last longer.
2.3.3 Erosion protection
Certain areas of the centrifuge bowl are susceptible to erosion due to contact with moving abrasive particles. The application of an anti-corrosion coating is critical to the durability of the centrifuge. Solid particles passing through the mesh in a filter centrifuge wear down the pores, expanding their size over time. Erosion protection of these pores is not always feasible. Solids scrapers or plows in filter centrifuges are prone to wear and tear. Hard surface coating on plow blades ensures wear resistance. The rotating vortex in the bowl of the settling centrifuge pushes the solids out. Scroll threads are constantly in contact with solids and are subject to erosive wear. The application of corrosion-resistant materials such as tungsten carbide protects the scroll vanes from wear.
