Dear Dave,

Dense phase pneumatic conveying has not yet reached it's apex. This year Chicago Conveyor received a new patent on its high pressure rotary valve. This new patented design includes a proprietary "zero leakage" peripheral sealing system, as well as, other enhancements.

Customers should be looking toward new technologies that offer proven value added features. However, customers should also avoid the common pitfall of having there plants used as test labs. Hydraulic conveying (as a breakthrough) sounds a lot like a technology called super dense sold as "the latest and greatest technological breakthrough" by a German company about 6 years ago. Super dense worked in the lab, but left a lot of customers in the field "holding the bag". As far as I know super dense never worked and was never sold again.

Unless you have the resources to absorb the potential delays and additonal costs in start up and are willing to accept a system that may perform below your expectations, I would stay with the pneumatic systems.

We would be happy to present a quote for your system that you could then compare with a hydraulic system. Please visit our website or email me directly. ■

Dave,

I must completely agree with the reply from Michael Stogdill of Chicago Conveyor Corp. "...I would stay with the pneumatic systems".

Reimelt will also be glad to quote on your specifics. ■

Dave, I know it has been some time since you posted your question. However, I wanted to inject my thoughts into this discussion.

I too have seen the presentations of Waeschle about their Conticon system. It has been in development for several years. I don't know anyone who is using it now but if I wanted to consider it, I would look for some experience at a user.

In my mind, the reason to select this system should not be based on using "leading edge" technology only. I see the Conticon system coming into play as a viable option when the distances are great. When great distances are involved, of course, dilute phase becomes problematic unless it is broken into pieces where it becomes expensive.

Then you look at dense phase. Its' primary focus to me is gentle treatment of the material. You don't comment on that aspect of your material as to whether that is an issue or not. Dense phase is an expensive system due to use of compressors vs blowers and the wear of piping and support components.

We are in the Polyethylene business and we have used dilute phase and dense phase and we have decided to use dilute phase wherever possible as it is simpler and much better known. I view it as a strength that it is a well developed technology, not a weakness. ■

When distance and thruput are great hydraulic conveying must be considered as a cost effective solution. Although the technology of hydraulic conveying is a more recent development than that of dense-phase, it is none-the-less proven and already has a history of successful installations.

Even where distance and thruput are minumal there are special cases, e.g. optical grade plastics, where hydraulic conveying has been successfully applied.

Dennis Hauch ■

Dennis,

Can you please provide a list of referances or installations? ■

no ■

Dear Mr. Meyers,

Since some years we are using a typical kind of pneumatical transport at low air velocity. If you are investigating a new installation this application might be of your interrest.

At this low air velocity the behavior is a bit different from high velocity transports. Because of air viscosity a laminar air sheet is formated and almost no contact between the material and pipes will occur. The velocity of the material is the same velocity as the air velocity and thermic influences are almost 0. We even use this method to transport milk powders with increased amount of fat which is extremely sensitive to temperature influences.

Technical specs:

Starting velocity of the system is about 2-3 m/s at 2-2,5 bars overpressure, end velocity is about 6-9 m/s at 0 bars overpressure. Loading degree is about 100-300 kg material / kg air. The amount of air needed can be produced by a normal 6 bar compressor and pipe dimensions are less then traditional transport systems, 2 bars effective air consumption or . Maintenance costs are in your case about 25-50% related to traditional systems. Obstructions in the pipes, caused for example by power drops, are automatically pulled back to the sending vessel, prohibiyting the necessity to take apart the piping.

If this is of your interest, please contact me. ■

Wes,

In my earlier reply I had indicated that hydraulic already had a history of successful installations. These are the ones that I know of:

GE - Spain - 7 tph - 90 m - PC pellets - commissioned Apr 2000

GE - Spain - 7 tph - 90 m - PC pellets - commissioned May 2001

SPC - China - 35 tph - 650 m - PP pellets - commissioned Feb 2002

SPC - China - parallel 40 tph systems - 700 m - PE pellets - commissioned Mar 2002

Bayer - Germany - 40 tph - 500 m - PC pellets - not yet commissioned

Regards,

Dennis Hauch ■

Dave,

If you would like more information on a novel pneumatic conveying system with rates of up to 100 tons/hour with 6" pipe, please see our website. ■