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5 Factors to Consider In a Custom Decanter Centrifuge Design

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Today's centrifuge market offers many standardized solutions that may best suit your separation needs.

However, it's important to recognize that sometimes standard solutions do not fit your process requirements and needs. With so many variables involved in the separation process, finding the right centrifuge for your project may be challenging.

Here are a few factors to consider when seeking a custom decanter centrifuge design.

1- Material Make-up and process

It's important to recognize the type of material that will be fed to the centrifuge and the process that needs to be completed.

For example:

Are the materials fed biosolids, wastewater, or drilling fluid?

Is your process dewatering, sludge thickening, or solids/barite recovery? 

Centrifugation is used for both thickening and dewatering of sewage sludge, where dewatered sludge has a higher dry solids (DS) concentration, the centrifuge technologies used for each are almost identical. The key operational differences between the two functions are:

  • The rotation speed employed
  • The throughput
  • The nature of the concentrated solids product generated

Dewatering typically demands more energy than thickening, due to the fact that more water must be removed to achieve higher solids concentrations.

The dewatered product, whose dry solids (DS) content may be as high as 50%, takes the form of a cake: a deformable semi-solid which forms lumps rather than a free-flowing fluid. It can therefore only be conveyed using a conveyor belt, whereas a thickened product retains the fluid properties of the feed and can be pumped.

Centrifuges are sized on the basis of the weight or volume of material to be processed. To determine the number and size of centrifuges needed, the following is needed:

  • Amount of primary solids flowing through the plant per day
  • Amount of waste activated sludge produced per day
  • Seasonal variation in the number of solids produced
  • The volume of thickened solids to be dewatered per day
  • Estimate of the range of solids concentration in the feed solids
  • The hours per day and number of days per week of operation

2-Bowl size, diameter, and pitch

Centrifugal sludge dewatering technology, solid bowl: sludge enters the bowl at one end and is fed along the inside of the centrifuge by a rotary screw while the outer bowl rotates, extracting water from the sludge through the action of a centrifugal force.

Credit: Judd Water & Wastewater Consultants

Bowl diameters are generally in the range of 10 to 100 cm and are cylindrical with a conical end (a few designs have wholly conical bowls.

The bowl centrifuge design can be modified to provide greater dewatering capacity (or a drier solids product), by:

  1. Extending the length of the solids outlet (also known as the centrifuge beach)
  2. Reducing the centrifuge differential velocity (the difference in velocity between the screw conveyor and the bowl)
  3. Modifying the screw to provide pressing of the solid sludge (also known as the cake) in the beach area.

Both, options (1) and (2), extend the residence time in the centrifuge. On the other hand, option (3) provides additional dewatering of the cake.

Solid bowl centrifuges also form the basis of a hybrid dewatering−drying process, where the bowl is adapted to allow it to be heated with a sweep gas. DS concentrations of up to 90% are apparently possible from this process from an unthickened sludge starting material, implying that dewatering and drying of raw sludges can be carried out in a single stage.

3- Unit Parts

Horizontal decanter centrifuges may be comprised of parts developed by different sources.  In most cases, centrifuge manufacturers either outsource the centrifuge parts or develop the centrifuge parts in-house.

Centrifuge manufacturers with in-house part machining capabilities have the ability to develop precise and accurate machined parts. Using CNC Machines, machinists produce highly accurate parts and products in a timely manner.

4- Mounting and Layout Arrangements

Horizontal decanter centrifuges may have different mounting options and layout arrangements.  Mounting options include

  • Skid mount
  • Base mount

Note: The skid/base layout arrangements may vary to accommodate the unit's place of installation. 

In addition, the paint applied to the skid or base mount may vary depending on the end user's paint specification requirements (if any).

5- Electrical and controls options 

Decanter centrifuges may be designed to adapt to a large spectrum of power requirements and electrical control options.

Power Requirements

Power requirements are defined by the end user's main power source in terms of voltage, frequency, and phase.  The main power source is what will determine the type of electrical motor that will be used in the custom decanter centrifuge design.

Typical motor power requirements include:

  • 120/208 Volts
  • 120/240/240 Volts
  • 277/480 Volts

These motors may be configured to satisfy a given power phase.

The frequency of the motors may vary between 50 or 60 Hz.

Control Requirements

Control requirements are defined by the end user's need to operate the custom decanter centrifuge.

Some control options include

  • Local On/Off
  • Local VFD Operations
  • Local and Remote VFD Operations

Smart control options like Vision View, allow users to have full remote control of their custom decanter centrifuge.

Smart Control Options

Smart control options (like Vision View) allow users to monitor and troubleshoot their centrifuge(s) remotely, via mobile access or computer.

  • Bowl, conveyor, and pump VFD status screens provide invaluable real-time information for on-demand viewing.
  • Continuous monitoring of electronics and machines coupled with predefined safe operating limits make the smart control options consistent and reliable.

YOU CENTRIFUGE EXPERTS

If you want to know more about our products, features, pricing, or anything at all, we are here to answer your questions.

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References

Centrifugal sludge dewatering
https://www.sludgeprocessing.com/sludge-dewatering/centrifugal-dewatering/

Centrifuges - https://thermopedia.com/content/620/

Biosolids Technology Fact Sheet Centrifuge Thickening and Dewatering - https://www.epa.gov/sites/production/files/2018-11/documents/centrifuge-thickening-dewatering-factsheet.pdf


About Vision Machine

Vision Machine Inc. specializes in the manufacturing and repair of horizontal decanter centrifuges and has been doing so since 2004.

At Vision Machine, Inc., we pride ourselves on providing our customers with the highest value, lowest total cost of ownership and easiest to operate separation systems available. All proudly made in America at our Spring, TX facility.