Decanter centrifuges are more cost-effective, but traditional filtration also has advantages in solid-phase water content. If flexibility and high capacity are a great concern to you, a decanter is an excellent choice. If you have ample space and want drier solids, then you might pick traditional filtration.
The bottom line is businesses must decide according to the actual situation when choosing.
Decanter Centrifuges Defined
Decanter centrifuges separate solids from liquid in a slurry by way of great centrifugal forces to cause sedimentation. The slurry gets into the decanter centrifuge through a feed pipe that goes in a circling screw conveyor that has a tapered end. The slurry is then discharged into a bowl encircling the screw conveyor that is spinning at a higher speed than the conveyor.
Great G-forces make the solid particles in the slurry be thrown to the walls of the bowl where the screw conveyor propels them toward the discharge end. The screw’s end that is tapered lets the solids dewater as it moves toward the discharge. The water easily moves to the other end of the machine and gets out through the ports.
Decanter centrifuges generate a solid cake material that is right for mechanical handling as well as instantly recyclable process water. They release a solid material at some point between a filter press and a thickener. Decanter centrifuges are completely automated and encompassed for cleaner operation.
Benefits of Using a Decanter Centrifuge
Ease of Operation
Decanter centrifuges operate continually. Unlike traditional filtration, workers don’t need to shut off the equipment every couple of hours to take out the sediment manually.
From a labor viewpoint, a decanter centrifuge is easier to run since it requires less manual labor and attention. Furthermore, decanter centrifuges are less costly and take up a small amount of floor space, making them easy to fit into an operation.
Limitations of Using a Decanter Centrifuge
Particle Size
The greatest downside of using a decanter centrifuge is that it just gets rid of particles down to five microns in size, so it’s vaguely less effective than filtration. Tinier sediments remain in the oil, which can still contain a small percentage of solids by weight after it departs the decanter. A few tenths of the percentage might not seem significant, but based on your target markets, this little difference could substantially affect the value of your oil.
Maintenance Costs
Because of the speed at which it rotates, the parts of a decanter centrifuge can wear down way quicker than a filter. These heavyweight parts can be costly to replace, especially bearings, which usually wear out within a couple of years. Although decanting machinery costs less money upfront than oil filtration systems, these continuing maintenance costs can add up fast.
Energy Usage
Decanter centrifuges necessitate motors to keep the shaft rotating. The system uses more electric energy than oil filtration, which expends around 60-75% less energy. For any given situation, traditional filtration will deliver a greater footprint than a decanter centrifuge.
Traditional Filtration Defined
Traditional filtration delivers the highest level of mechanical dewatering without the need for chemicals. They contain many recessed plates enfolded with filter cloths. When the plates are fastened, the niches produce chambers. The filter press will soon contain slurry, filling the chambers. The liquid in the slurry moves through the cloth and out the filtrate pipes at the bottom of the plates to collect in a trough at the base of the filter press. The solids are held on the filter cloth. When no more slurry can be pressed into the filter press, the pump is stopped, and the plates open to release the solid cakes.
These solid cakes are drip-free and stackable and can be easily managed by loading or hauling equipment. Contingent on the material, it can possibly be sold as a backfill or a pond lining. The recouped water is available for use right away.
Examples of Traditional Filtration Machines
Belt Filter Press
A belt filter press (BFP) offers sludge dewatering by compressing the sludge to push the water through a permeable medium. The advantages of using a belt filter press include:
- Easy management and continuous operation
- The water content of the sludge cake is low
- Low energy consumption
There are also some limitations:
- Bigger footprint
- Not fit for organic sludge
- Rough working setting – The equipment is badly sealed
- Complicated Structure – Must use the air compressor and other supporting equipment
- Huge maintenance cost – If there are sharp pollutions in the sludge, the filter belt can get damaged easily which is costly to fix
- Filter press is a batch process in contrast to a decanter centrifuge which is a continuous process
After operating, the filter belt must be cleaned with a considerable amount of water at high pressure, creating secondary pollution.
Plate and Frame Type Filter Press
The working norm of plate-and-frame type filter presses is that slurry is propelled into the machine so that solids are dispersed evenly during the filling cycle. Solids amass on the cloth part, shaping the filter cake. The excess departs the filter plates via the ports in the corner. They make their way inside the manifold, generating clean filtered water. The advantage of using a plate and frame type filter press is the very low water content of sludge cake. However, there are limitations:
- Not fit for organic sludge
- The power of the equipment is hydraulic
- When the sludge content is low, the efficiency is lower.
- High cost due to the quick wear and tear of equipment and machine
- Low automation
When the sludge viscosity is high, the parting result will be poor and the filter cloth must be replaced immediately, which is expensive.
Advantages of Using Traditional Filtration Machines
Energy Consumption and Costs
Traditional filtration has a lower energy consumption compared to the decanter centrifuge for the following reasons:
- The hydraulic motor runs on opening, discharging, and closing with occasional operation on pressure sustain whereas decanter centrifuges’ motors run continuously during the process.
- A filter press has a way lower energy necessity resulting in decreased running costs.
Maintenance Costs and Downtime
A decanter centrifuge, because of its high-speed rotating parts, is open to much greater degrees of wear on more abrasive feed streams. Therefore, bigger operational costs are experienced than when using traditional filtration.
The assembly and access to a decanter centrifuge are more complicated than that of the filter presses used in traditional filtration.
With a decanter, many problems stem from the rotational bearings and parts. Access is based on the decanter centrifuge’s origin and typically requires specialist equipment and tools to take out the internal parts. A filter press has lesser moving parts and is easily accessible and is usually simpler to upkeep than a decanter centrifuge.
Processing
With traditional filtration, a filter press will create a dryer filter cake for the same product because a filter press can be given a higher pressure instead of relying on the G Force generated by a decanter centrifuge. Therefore, the resultant filter cake has a greater solid content and less moisture content.
Which one is the Best?
When it comes to which one is better, a decanter centrifuge or traditional filtration, the best equipment for one site might be different than the best equipment for another site. Decanter centrifuges or traditional filtration (filter presses) are good options. So, the best one depends on the goals of the job site.
The main thing to consider is the material type being dewatered. A decanter centrifuge is an industrial machine created to separate liquids from solids continually. This process is referred to as sludge thickening or dewatering. A decanter centrifuge works best with material that has a bigger particle size distribution and is more easily dewatered. They also work best for materials with low clay content, and they are less sensitive to changing feeds.
Traditional filtration can be used to dewater an assortment of various slurries in a vast range of applications, but they don’t work well with changing feed conditions. For example, a filter press is perfect for dewatering tailings from mineral concentrates, aggregate, and mineral wash plants, and any underflow slurry moving from a clarifier or thickener.
However, the percentage of solids and particle size allocation do influence the complete dewatering effectiveness of a filter press.
Summary
A decanter centrifuge could manage fluids with high sludge content with big particle sizes. They are the first line of defense in any industrial fluid separation application with thick sludge.
Additionally, a decanter centrifuge could separate fine solids with adequate retention time. In other words, a small flow rate. However, the flow rate to reach that level of division defeats the purpose of the decanter centrifuge.
Contact Diamond T Services to consult with our specialists to discuss your dewatering needs. We are ready to respond appropriately and help you make the best choice.