System Extension
Conveying velocity influences product degradation, in this case the allowed shift in bulk density is limited to a specific range.
Your system is described as being "low velocity" i.e. one whose terminal velocity is in the range of 6 to 8 m/s, give or take. The low terminal velocity must be maintained if the conveyed product is to remain "in spec".
Primary and secondary air quantities, therefore, must be carefully controlled. Increasing the length of the conveying line may be possible only if the added secondary air does not put the terminal velocity out of range.
A better solution. Your conveying application is an ideal candidate for a "smart" bypass system, rather than the straight primary / secondary air system that you now have. Bypass systems are synonymous with velocity control, which is what you need if the conveying distance must be increased.
Also, your post mentions a high pressure nozzle. I understood that to mean a solids eductor is being used to introduce the material to the conveying system. If that is indeed the case it would have a significant and detrimental impact on product degradation. Here the better solution might be a blow-through rotary valve.
The short answer your original question is yes, an extension of the system is possible, if the points above are taken into account.
Dennis Hauch ■
Material Flow Rate Problem
If you are extending your pipeline from 100 m to 225 m you must expect a significant reduction in material flow rate with the longer pipeline, if you make no other changes to the conveying system. If you maintain the same air supply pressure and pipeline bore, so that there is no change in energy input to the system, material flow rate will reduce approximately in proportion to conveying distance. This means that if you convey at say 10 tonne/h over 100 m this will reduce to about 4 tonne/h over 225 m. With such a marked reduction in material flow rate I suspect that you will need to increase the bore of your pipeline, and consequently the volumetric flow rate of the air used.
For the longer distance your air flow rate will not change (for the same bore of pipeline) but if you are injecting air over 225 m of pipeline rather than 100 m you must ensure that you do not have a high velocity dilute phase conveying system at the end of the pipeline. If your material is friable it could suffer severe degradation in passing through bends towards the end of the pipeline if it is conveyed at high velocity.
If your material is granular, so that it has no air retention properties, so that it can not be conveyed in dense phase, and hence at low velocity, in a conventional pneumatic conveying system, I would go along with Dennis Hauch's "better solution". There is no addition of air along the length of the pipeline and so the increase in volumetric flow rate of the air is only due to the reduction in pressure as the air expands along the length of the pipeline. ■
Re: Maximum Allowable Lenth Of Transport Lines Agglomerated Pow…
For "smart" bypass system, go to www.q-engineering.com
Regards C.van Dorst ■
Maximum allowable lenth of transport lines agglomerated powders.
My dear bulkoholics,
This is a nice one:
Our pneumatic conveying lines are of the type: primary air at the start en secondary air to maintain the low velocity bij injecting compressed air with nozzles in the line. I want to extend the line with approximately 125 meters, I.e. a total of 225m. The idea is to allow for a breakdown of no more than 7 points (56 to 63gram/100ml, method: Yell 1000 taps)).
Product: agglomerated infant formula, high pressure nozzle, with fines return. Is such an extention possible?
Your contribution to this problem is much appreciated.
Thank you, Dirk van der Galien. ■