Cyclones: Three Ways to Maintain High Performance
Mineral processing can be tricky and expensive. That’s why your product should perform at the highest possible level.Do you know how to increase your cyclone’s performance?
Here are three ways to do it!
1. Water pressure
Let’s start by busting a myth.
Too many people in the industry think that a cyclone operated at high pressure is more efficient. But this isn’t necessarily always true.
High pressure also means a higher rate of wear. A cyclone with a bigger head is particularly efficient at low pressure, and the wear rate is lower too. In other words, operating a cyclone at lower pressure can boost efficiency and reduce costs!
2. Keeping alpha water low
Did you ever notice that a cyclone partition curve obtained from raw data never reaches zero on the recovery axis, and that this point changes from one application to another?
This difference is commonly called “alpha” water (or bypass water) and is defined by the proportion of water in the feed reporting to the underflow. More practically, it represents the percentage of feed material that will short-circuit to the underflow with water, therefore bypassing the classification process.
How to keep it low?
Dilute your feed or increase your underflow density. Diluting the feed is likely to be a difficult task when the sump and the pump are already operating at maximum capacity, and adding more water can cause problems with water supply and balance. This is why, especially in closed-circuit cyclone and milling operations, it is crucial to maintain cyclone underflow density at as high value as possible without roping and affecting cyclone performance!
Two reasons why high underflow density is important
The maximum classification efficiency attainable in a cyclone is 100% - w and it excludes the inherent efficiency of the cyclone. Therefore, if the underflow is extremely wet, a large amount of water reports to the underflow and, associated with it, a considerable quantity of fines.
A significant amount of feed thus reports to the underflow without being classified. An increase in underflow density reduces the amount of water reporting to the spigot and reduces short-circuiting, which in turn leads to a higher attainable cyclone operating efficiency.
All milling operations have an optimal mill density at which grinding can be achieved. If the cyclone underflow is too wet, solids will be washed through the mill, reducing the rate of grinding that can be achieved. By ensuring consistently high underflow density, optimized control of mill density can be achieved with the addition of dilution to the mill feed.
3. The spigot, a key component
Inspect the cyclone discharge into the underflow launder
A quick way to assess cyclone performance on a daily basis is to inspect the cyclone discharge into the underflow launder. If the discharge looks too dilute, your spigot (apex) might be too large, and short-circuiting of feed solids is unnecessarily increased. In contrast, if the discharge looks too thick and sausage-like, a situation known as roping, your spigot might be too small.
In this case, classified coarse material that belongs in the cyclone underflow is reported to the overflow since the spigot cannot discharge all the solids. Try to maintain discharge in between these states to be on the optimal side!
Make sure you have the right size
Spigot size is a difficult parameter to predict when sizing a cyclone, as process conditions will greatly affect this result in operation. This is why, as part of any Multotec cyclone supply, commissioning spigots always include polyurethane/rubber spigots that are one size larger and one size smaller.
Once the optimum size has been determined, we strongly recommend you switch to ceramic or silicon carbide spigots to optimize the life span of your component!
The photo below shows a 45mm diameter spigot in PU on the left and its ceramic equivalent from our 120-HS line on the right. You can expect ceramic spigots to last approximately 3 times longer on average than a PU spigot.
Contact us if you need help with your cyclones, whether they are ours or not! We engineer and manufacture our own products, and our experts are more than qualified to advise and support you in your mineral processing. Let’s reduce your mineral processing costs together!