Facilities involved in treating oil-contaminated sludge employ a centrifuge in most cases to improve the efficacy of SAS chemicals. The decanter centrifuge is custom designed to cope with a wide range of fluctuations in the feeding material while delivering excellent dewatering and clarification performance on several processing applications.

Let’s take a look at the two commonly used centrifuge types for solid-liquid separation:

Two-Phase Decanter Centrifuge: Functioning and Features

When used for solid-liquid separation, this specific model helps save tremendous dilution water which is not only economical but also eco-friendly. It also delivers the best quality oil by retaining its highest possible content of polyphenol for an exceptionally long shelf life. The two-phase decanter centrifuge comprises a rotating bowl fitted with a screw conveyor that rotates at a slightly different speed from the solid bowl.

The feed enters the chamber assembly through a stationary tube and gets discharged through the feed ports. The slurry then falls into the large end of the rotating chamber where the gravitational force causes the solids to settle down and form a blanket against the bowl wall. The accumulated solids are then pushed up an incline and ultimately out of the liquid. The clarity of the liquid discharged from the decanter is influenced by various factors including the g-force, differential speed, polymer addition, rate of flow and pond setting.

The Process Technology Features of Two-Phase Decanter Centrifuge

• The length ratio is typically 1:4:2 or greater depending on the model
• Depending on the diameter of the bowl, the acceleration force varies between 3,000 – 5,200 x “G”
• Advanced models also feature scroll back-drive systems for faster reaction times and highest possible torques
• It features multiple bowl and scroll wear protection systems for extended service life
• All the contact parts are made using stainless steel or carbon steel for high tensile strength
• Designs are customized for 2 phase separation that meets individual sludge requirements
• Highest cake dryness brings down the disposal cost significantly
• The power consumed is relatively lower for every unit product that is processed

Three-Phase Decanter Centrifuge: Functioning and Features

The three-phase decanter centrifuge for oil waste treatment features a solid bowl engineered for highly efficient solid-liquid separation. The feed enters the rotating bowl of the decanter through a tube where it is thrown outwards by the conveyor hub containing radial ports. It employs the centrifugal force for solid liquid separation.

The solid particles settle down at the wall of the bowl from where they are discharged through the conveyor while the cleared liquid accumulates above the solids. The liquid phases are then discharged at the opposite end of the decanter. Different decanter designs employ different means to discharge the liquid phases including overflow weirs, pressure pumps or dip tubes that work under the effect of gravity.

The Process Technology Features of Three-Phase Decanter Centrifuge

• Large diameter ratio of 1:4:2 and greater in certain machines
• Acceleration forces of 3,000 – 5,200 x “G”
• Externally adjustable pump with the option of dip-tube for light discharge.
• Explosion proof design
• Flexibility of 2-phase processes as and when required
• Seamless operation even at high temperatures
• Dynamically optimized fluid design
• Stainless steel construction
• Service-friendly design

According to field experts, there are some trade tricks that can efficiently boost the sludge-splitting capacity of these centrifuges. Below are 7 tried-and-tested ways that oil waste treatments plants can employ to boost decanter performance dramatically:

1. The waste feedstock should be pre-screened using small scale equipment and then if found necessary, the treatment approach should be altered accordingly
2. Heat should be employed in the process if available
3. The content of solids, oil and water should be determined before the operations can commence. This will enable the centrifuge operators to better handle the loading of solids.
4. Instead of adding water to heavier waste, it can be mixed with lighter slops to facilitate smooth blending
5. Key variables like chemical dosing, g-force, scroll depth and speed, stock throughput, and centrifuge speed and feed stock throughput should be measured accurately. The results can then be used for fine-tuning the system for the best solid-liquid separation.
6. The operating variables should be reduced wherever possible. This is a major reason operators prefer using a decanter for solid liquid separation instead of a tricanter.
7. The solids loading should not exceed 30% because if it does, chances are high that the centrifuge will get plugged.

Using centrifuge for oil waste treatment has several benefits that range from maximum separation precision, shorter process times, full torque, rapid amortization, low energy consumption and maximum product yield.

Author Bio:

Jigar Patel is the director of Oriental Manufacturers. He believes in the power of good functional designs and its ability to boost productivity and drive growth. Fueled by his passion for innovative designs and all things EPC, Jigar took to blogging about all the information and technical know-how he has amassed over the years. He writes on topics related to process machinery production, turnkey solutions, best industry practices and his personal insights.