Isil,

There are three factors that, when combined, would say that you are looking at a high-pressure (10 bar) system that will have several steps the conveying pipeline:

1) the instantaneous conveying rate. An average glass processing rate of 500 t/d translates into an instantaneous conveying rate of, say, 30 t/h or more.

2) the bulk density of the conveyed material. It wasn’t stated in your thread but I would estimate it to be something in the area of 2,600 kilograms / cubic meter, very heavy indeed.

3) the horizontal and vertical conveying distance. Though not great in pneumatic conveying terms, it is significant in view of the rate and bulk density of the conveyed material.

It would be important to work with a supplier who is able to conduct pneumatic conveying trials. These trials will determine, for example, if the system must be designed as an external bypass system.

Lastly, this product is likely very abrasive so the system design must be based on minimizing / controlling conveying velocity. Anticipated wear will be a factor when selecting the pipeline material.

These are my thoughts.

Kind regards,

Dennis Hauch ■

I strongly urge you to consider other conveying options. Pneumatic transfer of a glass batch is difficult and prone to leaving material in the pipe and segregation, especially for container type batch that is granular (greater than 60 mesh), has a high bulk density, is not easily fluidizable, and contains cullet.

My company has experienced problems with pneumatic conveying of glass batches from the weighing process to the mixing process at the furnace. The problems are all those stated above. Only for our glass batches that use fine, easily fluidizable materials (all less than 100mesh) does pneumatic conveying work satisfactorily.

Completeness of batch transfer becomes acceptable only with large amounts of compressed air and long purge times. However, once we achieve acceptably complete material transfer, the wear rate of pipes and elbows increases causing rapid failures and leaks.

My preference for mixtures or combinations of materials that are handled on a batch basis is to not use pneumatic conveying. ■

We also mix the batch after transporting weighed batch. The problem we've identified is leaving portions of the weighed batch in the transport lines. The material left in the line is not the same as the overall batch composition and the resulting batch does not make the same glass.

The amount of batch remaining in the line ranges from an unacceptable 400 pounds from a 4000 pound batch to an acceptable 40 pounds from a 4000 pound batch. Your acceptable limits may differ from ours. The amount remaining in the line varies with available compressed air, raw material changes, and transport system settings. For us, the batch house is at the end of the compressed air line and only gets what all the other processes don't use.

Perfect designs of all systems could make pneumatic conveying or weighed batch acceptable. You'll also need very good control of raw materials and system settings.

It seems to me that more conventional transport systems are more forgiving for changes, easier to control, and will give more complete transports all the time. ■

This will be an issue even without cullet.

One thing we could do for you would be to measure the erosiveness of the batch, using a sample, then make predictions of the bends lives with various different options of wear resistant materials. This enables you to select an economic option or indeed rule out pneumatics if it is going to be a problem.

Mike Bradley

The Wolfson Centre for Bulk Solids Handling Technology ■

The reasons of choosing the pneumatic system are often following: no dust, no spillage, minimal space requirement, protection of the load and the environment. When conveying products by a pneumatic system there will occur three major problems; high energy costs, wear and segregation. Something that can be avoided by using well proven enclosed belt systems such as pipe conveyor or the Sicon Roulunds system. The initial investment is often lower for pneumatic systems but in the long run the costs are higher than for belt systems. I.e. Sicon have replaced several pneumatic systems in Sweden, Denmark and Norway and can show good results. Visit Internet page www.sicon-roulunds.com for more information.

Best Regards

Robert Olsson ■

I have some experience handling glass batch and cullet in pneumatic lines. The ingredients are highly abrasive, so you need to handle them as slow as possible in a dense phase system and use hardened pipe and elbows.

A company that supplies such equipment and has experience with these materials is:

J.D.B. Dense Flow

800-822.3569

Mr. Cam Boothe ■

Dear Sir, If you are considering an enclosed belt system as an alternative for the pneumatic system, you can also choose for the Enerka Becker System of Fenenr Dulop. Our comapny is the licencee for this system.

TYou can find more information of www.enclosedbulk.com

The english version will be on line soon.

Best regrads

Frans van der Zee

Enclosed Bulk Systems bv ■