Oversized cyclone

 

Outline of this blog post

• Introduction
•  Comparison of Standard and Oversized cyclone performances (calculations by Airvate)
• Recommended applications of oversized cyclone
• Summary and conclusions

Introduction

Cyclone separators are widely used in many industrial applications where it is necessary to remove the dust or particles from gasses. These devices are simple with no moving parts and are easy to maintain. Although the construction of these devices is simple, the physics governing the flow process in them is complex.

Normally cyclone designers follow two procedures to size a cyclone.

• Classical Cyclone Design process, and

• Texas A&M Cyclone Design method

The results from these procedures are usually called standard cyclones, while an oversized cyclone is the one from the same family but with a bigger body diameter and, consequently, with a lower inlet velocity at the same air flowrate.

Normally, an oversized cyclone can have a lower pressure loss at the same level as that of a dropout box, lint basket, or a horizontal classifier, if the inlet velocity is low enough. The inlet velocity for an oversized cyclone can go as low as half of the recommended inlet velocity for a standard cyclone or even lower, should dust settlement not be a problem at the inlet of a cyclone.

Comparison of Standard and Oversized cyclone performances (calculations by Airvate)

1D3D cyclones, both standard and oversized versions, are selected to separate three dusts which have different particle size distributions (PSD).

Dust 1 is coarse and has a 713.85 microns quadratic mean.

Dust 3 is fine and has an 8.76 microns quadratic mean.

Dust 2 is in the middle in terms of coarse and fine, and has a 21.04 microns quadratic mean.

A standard cyclone has an inlet velocity of 3200 FPM, while an oversized cyclone was sized based on the inlet velocity of 1600 FPM, half of that for the standard cyclone.

Pressure loss was calculated by the Casal-Martinez model. The oversized cyclone generated a much lower pressure loss, which is only 25.1% of that by the standard cyclone.

Overall collection efficiency was calculated by the Barth model. Generally the oversized cyclone works with a lower efficiency than its standard counterpart does. However, as shown by the calculation results, while collecting finer dust, the collection efficiency drops dramatically, while collecting coarser dust, the efficiency drop is insignificant.

The calculation results by Airvate are similar to those reported by other researchers through experiments and theoretical calculations.

Recommended applications of oversized cyclone

In some cases, an oversized cyclone is strongly recommended,

1. To add a pre-cleaner just ahead of a dust-collector, i.e. baghouse, or even a high efficiency cyclone, especially when the existing dust collection system has a static pressure limitation;
2. To replace an existing low efficiency pre-cleaner with low static pressure available;
3. To work with or protect an axial fan which normally generates low static pressure around or even below 1” wg.
4. Oversized cyclones have a bigger dust outlet diameter than its standard counterpart, so the “choking” problem usually does not happen. When in applications with a high dust loading, an oversized cyclone can work perfectly as a pre-cleaner of a standard cyclone.
5. When in applications with abrasive dust, oversized cyclones with low inlet velocity can work with a standard cyclone in series to reduce the abrasion problem. Oversized cyclones remove the large particles in a low velocity style, while small particles, which are less abrasive, enter the following standard cyclone with a high velocity and get collected.

Summary and conclusions

This blog post tries to tell what is an oversized cyclone and its most significant characteristic, which is low pressure loss, and also recommends some applications that are suitable for it.

The oversized cyclone has its advantages in industrial applications. Not all the applications require a high efficiency, or even a super-high efficiency cyclone.

Of course, an oversized cyclone costs more and occupies more space; but sized correctly, it is worth the money and effort.

Cyclone services by Airvate that you/ your customers can afford

Whether you are sizing a cyclone or using one now, if you need any services listed below, feel free to contact Airvate at info@airvate.com.

1. Have to change dimensions of inlet, gas outlet, and/or dust outlet, and want to know how the changes affect cyclone performance.
2. Need a new cyclone that has to meet the specified requirement.
3. Need a new cyclone with the best available performance in a limited space.
4.  Want to avoid or reduce the wear-out or blockage that always happens to your cyclone.
5. Want to reuse an existing cyclone and know its performance in a new process.
6. Want to optimize the performance of an existing low-efficiency cyclone.
7. The existing cyclone collection efficiency is too high for the process and you want to lower it.
8. The existing cyclone has either too high or too low of a pressure drop
9.  Want to optimize the performance or solve any problem of the combo of an existing cyclone (as a pre-cleaner) and a baghouse.
10.  Want to solve the uneven dust distribution problem in applications of dual-cyclone, quad-cyclone, or multi-barrel cyclone; with this issue, one or two cyclone barrels get more dust, and consequently, it causes wear-out in their inlet section and cone bottom more quickly than on others.
11. Existing cyclones in series don’t work as expected.

Keywords

Oversized cyclone, over-sized cyclone, oversize cyclone, standard cyclone, classical cyclone design, Texas A&M Cylone Design method, low Pressure Loss cyclone, low differential pressure cyclone, dropout box, lint basket, horizontal classifier, low pressure drop cyclone