Nadipuram,

The discontinuous nature of dense-phase conveying is synonymous with the pipe forces / pipe movement that you are experiencing. These can be accommodated, however, by a properly designed pipe support system.

It is imperative that the support system allows for a controlled movement of the pipe. Pipe that is rigidly supported will certainly be broken as will the supports, primary and secondary.

Coperion Waeschle has done a great deal of research with regard to the dynamic loads that are involved. This research has resulted in a design program that now has a proven record of success. Please contact Hans Schmidt at Coperion.

Research / experience has established the relationship between slug length and the length of the horizontal run preceding the bend, i.e. the longer the run the longer the slug. Imagine the momentum of a slug 20 feet long, which in not impossible.

There are numerous designs for devices to split slugs, some are very effective, and some are not. The Coperion designs have proven to be very effective. I would not recommend the nozzle approach that you are considering. It offers little hope of splitting or even softening the slug. On the other hand, it could very easily add to the velocity / momentum of the slug.

These are my thoughts.

Dennis Hauch ■

Nadipuram,

Yes, the dense-phase conveying process can be optimized.

A key parameter here is the gas velocity at the pickup point. The gradual minimization of this parameter will cause the system pressure to rise. This can continue until the pressure rises to, say, 80% of the supply pressure, or until conveying becomes unstable, whichever is first.

The above describes a very basic control philosophy. A highly refined process controller called Intacon is now offered by Coperion Waeschle, it is one of their featured attractions at their booth at Achema ’03. The advantages of automatic control are many, e.g. stable conveying, minimized pipe forces, maximized solids loading, maximized throughput, accommodation of varying product types and conveying distances.

Some allowance for movement of the conveying pipe is needed at every change in direction. This becomes increasingly critical as the terminal end of the system is approached, this, because the velocities are higher and the forces are greater.

As to slug lengths, you can get a “feel” for the length by hugging the conveying pipe upstream of a bend. Or you can actually measure the slug length with light beams, but this falls in the area of research which is expensive to do in operating plants. Again, Coperion Waeschle has done extensive research in this area which led directly to the development of the Intacon air control system. Check it out.

Regards,

Dennis Hauch ■

Nadipuram,

Installation of additional nozzles without understanding the nature of flow in the lines is not a good idea.

I suggest that you first try to optimize the conveying velocity in the line. The conveying velocity at each of the locations in the line should be maintained such that you do not land up in the unstable zone. This can be achieved by adjusting the gas inlet flow & may be stepping the lines. The test data from your conveying trials (if done) should be handy here.

If your conveyeying rate varies widely, you can still have problem in optimization. The gas flow rate must be adjusted as a function of conveying rate to keep the system in stable conveying region. A number of smart dense phase air control systems (mainly by Coperion and Neu Transfair) are commercially available.

Additionally, you should look at the possiblity of supporting the lines properly. Coperion, Zeppelin and Neu Transfair have done substantial work in figuring out the dynamic loads. Do not take the "rough calculation" method to guess these loads.

Plug breaking or conditioning is also a possiblity. There are plug conditioning concepts available from these vendors.

Just curious, who designed your system ? Was any tests done ? At what scale were the tests done ? What is the current scale of your system ?

Regards,

Jack ■