Primary Slurry Dewatering via Screen Basket Centrifuges for the Aggregate, Minerals and Coal Industries

Today’s mining, aggregates and coal markets provide for a myriad of options when it comes to selecting the appropriate dewatering centrifuge.    Each option requires careful consideration relative to its geometric configuration, drive system architecture, feed limitations and operating costs.   Though the following discussion focuses on screen scroll and vibratory screen centrifuges, we can’t overlook solid bowl decanter centrifuge and screen bowl centrifuges.   However, it is important to note that screen bowl and solid bowl decanter centrifuges are not considered primary dewatering devices due to the respective particle size distribution limitations.   In fact, solid bowl decanter centrifuges have a practical limit of 0.5 mm (500 microns or 0.02”).   Feeding solid bowl decanter centrifuges with solids larger than 0.5 mm would result in excessive abrasion wear, making the application uneconomic.    As such, both screen bowl centrifuges and solid bowl centrifuges are considered secondary, or polishing dewatering technologies, outside of the scope of this discussion.     

Turning our attention back to screen basket centrifuges, their inherent advantages are found within the screen media utilized.   Screen basket centrifuges traditionally deploy a stainless-steel profile wire screen basket.   The most durable screens are chrome hardened to extend screen life.   Regardless of the screen used, original equipment manufacturers (“OEM’s”) have the ability to provide screen apertures (i.e. “screen openings” or “slot sizes”) as small as 0.01 inches (250 microns).   Screen selection is dictated based on the particle size distribution of the feed slurry, the feed rate, and the level of dewatering desired.    However, when it comes to selecting the right screen basket centrifuge, there are a number of considerations.

As highlighted in the below table, each screen basket centrifuge has its own set of advantages and disadvantages.   Based on those advantages and disadvantages, there are three key take-aways:

  1. Horizontal dryers provide for lower ceiling height installations. However, they do tend to require an impact plate or other abrasion resistant device within the feed chutes and can require special rigging to remove wet-end sub-assemblies.    
  2. Horizontal vibratory centrifuges use vibration to assist in the movement of the solids and to improve fluid conductance through the screen. Though this allows for larger feed diameters, it does tend to lower the dewatering capability of the centrifuge.   In contrast, screen scroll centrifuges (both horizontal and vertical configurations) deploy flites, operating at a differential speed to the screen basket, to maximize the G-force input.  Though this maximizes the dewatering capability of the machine, it limits the maximum size of solids that can be fed into the centrifuge.  
  3. Though it was common for dewatering centrifuges to deploy complicated oil lubrication systems to properly lubricate the gearbox gears, product enhancements over the last few years have allowed both vertical and horizontal dewatering centrifuges to deploy fully sealed multi-stage gearboxes that maximize the G-force output potential, while minimizing operating costs.

Regardless of the nature of your application, it is best to reach out to an OEM applications engineer who can lead you through each products nuances in order to make the best selection.   

Contact Elgin's Mineral Division to Find the Perfect Solution for Your Dewatering Application