Centrifuge Optimization—one of the many uses of the British £1!

There are many aspects surrounding the smooth operation of a batch-operated Vertical Basket Filtration Centrifuge that need to be addressed before it can be regarded as being fully optimized.

Many believe that a centrifuge that is producing an acceptable solid-liquid separation, runs continuously without frequent operator intervention, must surely be fully optimized. Unfortunately this is often proven not to be the case.

A basket centrifuge is essentially a high-speed filtration device which accepts a mechanical mix (or ‘slurry’) of solids in a liquid (or ‘mother liquor’) during a part of the overall cycle known as ‘feeding’. The idea here is to introduce the slurry onto a filter media that lines the rotating perforated ‘basket’ so as to catch the solid particles on the filter media. The solids collect as a ‘cake’ inside the basket and much of the mother liquor passes through and exits the centrifuge. Depending upon the slurry characteristics, feeding may be done with the feed valve open all the way, or gradually with the feed valve throttled back, or may be with multiple openings and closings of the feed valve. Once feed is complete, a ‘wash’ cycle may follow, during which another liquid (usually water) is introduced that will displace out the mother liquor in the cake. Once washing is complete, since a dry cake is usually the desired product, the centrifuge enters the ‘spin’ cycle at up to 2000 times the force of gravity (or G’s), to squeeze out any excess liquid in the cake. Then the centrifuge is slowed or stopped, and the cake is removed either manually or automatically. Summarized below is the overall filtration centrifuge cycle:

[if !supportLists]1. [endif]Feed

[if !supportLists]2. [endif]Wash

[if !supportLists]3. [endif]Spin-dry

[if !supportLists]4. [endif]Discharge

While each and every aspect of the cycle described above is important (and they will be covered in future blogs), the ‘feeding’ phase, is unquestionably the most crucial aspect of the whole centrifuge processing cycle that must be fully understood. Get this right and you are well on your way to eventually claiming you have a fully optimized centrifuge operation.

Operating vibration levels, especially at spin speed, are key here. Most centrifuge OEMs have the first high vibration level warning alarm set at around 20 mm/sec. Anything less than this and the centrifuge will continue operating without troubling the plant operation or operators.

The lower the vibration levels the better it will be for the mechanical wear and tear of the centrifuge and the more likely you will be able to gain a fully optimized centrifuge operation.

A fully optimized vertical basket centrifuge operates at maximum spin speed with a vibration level of <10 mm/sec, or below half that of the centrifuge OEM’s first alarm set point. The vast majority of vertical basket filtration centrifuges operating out in the field are not equipped with detailed vibration monitoring systems.

Without such detailed monitoring systems it makes centrifuge optimization almost impossible for plant operators. However, there is a way and this is where the importance of the British £1 coin comes into play. Unless you can replicate what is shown in the video you will not be in a position to claim you have a fully optimized centrifuge operation.

If you can get the £1 coin to stay up and turn slowly counterclockwise, you are almost certainly on your way to attaining the following (and maybe even a May 2018 wedding invitation to Windsor Castle!):

[if !supportLists]• [endif]Optimum net capacity solids volume

[if !supportLists]• [endif]Perfectly parallel cake formation

[if !supportLists]• [endif]Perfectly concentric cake formation

[if !supportLists]• [endif]Optimum time cycle

[if !supportLists]• [endif]Maximum throughput

[if !supportLists]• [endif]Optimum cake washing efficiency

[if !supportLists]• [endif]Optimum filtrate quality

[if !supportLists]• [endif]Optimum final solids quality

[if !supportLists]• [endif]Optimum product yields

[if !supportLists]• [endif]Reduced maintenance and operating costs

[if !supportLists]• [endif]Greater up-time of the centrifuge

All this for just £1!!!

If you have any doubts regarding the extent of optimization of your vertical basket centrifuge(s) and cannot replicate the British £1 challenge, then please don’t hesitate to reach out to us and discuss your requirements in more detail.

www.aumprocess.com